Field transistor

FIELD: physics, radio.

SUBSTANCE: invention is to find application in microelectronics. Concept of the invention is as follows: the proposed field transistor is composed of a source electrode, a drain electrode, a gate insulator, a gate electrode and an effective layer; the effective layer contains an amorphous oxide with an electronic media concentration less than 1018/cm3 and the electronic mobility increasing proportional to the electronic media concentration. Of the source, drain and gate electrodes at least one is visual light translucent with the current flowing between the source and the drain electrodes never exceeding 10 mA unless there is a voltage applied to the gate electrode.

EFFECT: development of a transistor enabling improvement of at least one of the following properties: translucency, thin film transistor electrical properties, gate insulation film properties, leakage current prevention and adhesiveness between the effective layer and the substrate.

21 cl, 12 dwg

 

The technical FIELD TO WHICH the INVENTION RELATES.

The present invention relates to a field effect transistor using amorphous oxide.

The LEVEL of TECHNOLOGY

In recent years, flat panel display (TTD) is widespread as a result of technological progress in the field of liquid crystals and electroluminescence (EL). TTD is driven by active matrix circuit, consisting of thin-film field-effect transistor (TFT)using as an active layer of a thin amorphous silicon film or a thin film of polycrystalline silicon, located on the glass substrate.

On the other hand, an attempt was made instead of the glass substrate to use is easy and flexible polymer substrate to further reduce the thickness of the DPP, to make it more thin and resistant to destruction. However, as for the production of the transistor using the above-described thin silicon film requires a thermal process with a relatively high temperature, it is difficult to form a thin silicon film directly on a polymer substrate with low heat resistance.

In this regard, has been actively developed (paved patent application of Japan No. 2003-298062) TFT using the semiconductor thin oxide film such as a ZnO thin film, to the which can be formed into a film at low temperature.

However, there has not been a transistor, which would have all the required properties: transparency, electrical properties of the TFT, the properties of the film, the insulating shutter, preventing leakage current and the adhesiveness between the active layer and the substrate.

DISCLOSURE of INVENTIONS

The present invention relates to a new field-effect transistor using amorphous oxide.

Additionally, the present invention relates to the production of the transistor, which has good characteristics in respect of at least one of the properties: transparency, electrical properties of the TFT, the film properties, insulating shutter, preventing leakage current and the adhesiveness between the active layer and the substrate.

According to the first variant implementation is provided a field-effect transistor containing a source electrode, a drain electrode, a gate insulator, the gate electrode and the active layer, and an active layer contains an amorphous oxide in which the concentration of electronic carriers below 1018/cm3or amorphous oxide in which the electron mobility increases with increasing concentration of electronic carriers; and

at least one of the source electrode, drain electrode and gate electrode is transparent to visible light.

Field-effect transistor preferably has a metal the second wiring, connected, at least one of the source electrode, drain electrode and gate electrode.

Amorphous oxide is preferably an oxide containing at least one of In, Zn, or Sn, or an oxide containing In, Zn and Ga.

According to the second variant implementation is provided a field-effect transistor containing a source electrode, a drain electrode, a gate insulator, the gate electrode and the active layer:

moreover, the active layer contains an amorphous oxide in which the concentration of electronic carriers below 1018/cm3or amorphous oxide in which the electron mobility increases with increasing concentration of electronic carriers; and

having a layered structure consisting of the first layer, in which at least one of the source electrode, drain electrode and gate electrode is transparent to visible light, and a second layer consisting of a metal, or

having a layered structure consisting of a first layer in which a wired connection, at least one of the source electrode, drain electrode and gate electrode is transparent to visible light, and a second layer consisting of metal.

According to a third aspect of the present invention is a field effect transistor containing a source electrode, a drain electrode, a film insulating the gate electrode sat the RA and the active layer,

moreover, the active layer consists of an amorphous oxide, transparent to visible light, and at least one of the source electrode, drain electrode and gate electrode is transparent to visible light.

The transistor is preferably a transistor normally off type, which uses the active layer.

Metal wiring is preferably connected to the electrode is transparent to visible light, which belongs to the source electrode, the drain electrode or the gate electrode.

According to a fourth aspect of the present invention is a field effect transistor containing a source electrode, a drain electrode, a film insulating the gate electrode of the gate and the active layer,

moreover, the active layer consists of an amorphous oxide in which the concentration of electronic carriers below 1018/cm3and the film, the insulating shutter is composed of the first layer that is in contact with the amorphous oxide, and a second layer, different from the first layer, layered on the first layer.

The first layer preferably is an insulating layer containing HfO2, Y2O3or a mixed crystal compound containing HfO2, Y2About3.

Amorphous oxide is preferably an oxide containing at least one of In, Zn and Sn, or OK the ID, containing In, Zn and Ga.

The first layer preferably is a layer for improving the interface to improve the properties of the interface with the active layer and the second layer is a layer for preventing current leakage to prevent leakage of electric current.

According to the fifth aspect of the present invention is a field effect transistor containing a source electrode, a drain electrode, a gate insulator, the gate electrode and the active layer,

moreover, the active layer consists of an amorphous oxide, and the gate insulator consists of a first layer in contact with the amorphous oxide, and the second layer, different from the first layer and layered on the first layer.

Amorphous oxide is preferably any one selected from the group consisting of oxide, consisting of In, Zn and Sn oxide, consisting of In and Zn; oxide consisting of In and Sn; and oxide, consisting of In.

The transistor is preferably a transistor normally off type.

According to the sixth aspect of the present invention is a field effect transistor containing a source electrode, a drain electrode, a film insulating the gate electrode of the gate and the active layer,

moreover, the active layer consists of an amorphous oxide in which the concentration of electronic carriers below 1018/cm3or AMO is mnogo oxide, in which the electron mobility increases with increasing concentration of electronic carriers; and

between the active layer and the layer insulating the gate, there is a passivating layer.

Amorphous oxide is preferably an oxide containing at least one of In, Zn and Sn, or an oxide containing In, Zn and Ga.

Passivating layer preferably is a layer for preventing current leakage, to prevent leakage of electric current.

According to the seventh aspect of the present invention is a field effect transistor containing a source electrode, a drain electrode, a gate insulator, the gate electrode and the active layer,

moreover, the active layer contains an amorphous oxide; and

between the active layer and the gate insulator provides a passivating layer.

According to the eighth aspect of the present invention is a field effect transistor containing a source electrode, a drain electrode, a film insulating the gate electrode of the gate and the active layer on the substrate:

moreover, the active layer contains an amorphous oxide in which the concentration of electronic carriers below 1018/cm3or amorphous oxide in which the electron mobility increases with increasing concentration of electronic carriers; and

between the active layer and the substrate includes a layer that covers the second surface.

Amorphous oxide is preferably an oxide containing at least one of In, Zn and Sn, or an oxide containing In, Zn and Ga.

Layer covering the surface, preferably is a layer that improves the adhesion, to improve the adhesiveness between the substrate and the active layer.

According to the ninth aspect of the present invention is a field effect transistor containing a source electrode, a drain electrode, a gate insulator, the gate electrode and the active layer,

moreover, the active layer contains an amorphous oxide; and

between the active layer and the substrate includes a layer covering the surface.

The study authors present invention the oxide semiconductor was found that the above-mentioned ZnO formed in the polycrystalline state phase, causing carrier scattering at an interface between the polycrystalline grains and thereby reducing the electron mobility. Moreover, it was found that ZnO is exposed to the occurrence in it of oxygen defects, creating electron-carriers, which make it difficult to reduce the conductivity. Thus, even if the voltage of the gate is not applied to the transistor between the source terminal and the drain terminal, there is a strong electric current that makes it impossible to create TFT off normally the CSO type and getting high on/OFF for the transistor.

The authors of the present invention investigated the oxide film

ZnxMyInzO(x+3y/2+3z/2)(M is at least one element of Al and Ga)described in Japanese laid patent application No. 2000-044236. This material contains electronic media with a concentration not lower than 1×1018/cm3and is suitable as a simple transparent electrode. However, the oxide containing electronic media with a concentration not lower than 1×1018/cm3used in the channel layer of the TFT, can not provide an effective ratio of on/OFF and is not suitable for TFT normally off type. Thus, the conventional amorphous oxide cannot provide the film with the concentration of media below

1×1018/cm3.

The authors of the present invention manufactured TFT, using as the active layer of the field effect transistor of amorphous oxide with a carrier concentration below

1×1018/cm3. It was found that the TFT has the desired properties and can be used in the display device image that is similar to the light-emitting device.

Moreover, the authors of the present invention investigated the material InGaO3(ZnO)mand conditions of formation of a film of such material and found that the carrier concentration of such material can be adjusted so that it was below 1×10 18/cm3by controlling the oxygen atmosphere during formation of the film.

According to the present invention provides a new field-effect transistor using amorphous oxide as the active layer.

BRIEF DESCRIPTION of DRAWINGS

Figure 1 is a graph showing the relationship between the concentration of electronic carriers in the amorphous oxide, an In-Ga-Zn-O type, formed in the process of deposition pulsed laser deposition at a partial pressure of oxygen during film formation.

Figure 2 is a graph showing the dependence of electron mobility on carrier concentration of the amorphous oxide, an In-Ga-Zn-O type, formed in the process of deposition pulsed laser deposition from the vapor phase.

Figure 3 is a graph showing the dependence of the conductivity of the amorphous oxide, an In-Ga-Zn-O type, formed by way of the high-frequency sputtering using gaseous argon at a partial pressure of oxygen during film formation.

Figa, 4B and 4C are diagrams showing the change in conductivity, carrier concentration and mobility of electrons depending on the values of x for film InGaO3(Zn1-xMgxO)4formed by the method of pulsed laser OS is being introduced in the atmosphere at a partial pressure of oxygen, equal to 0.8 PA;

Figure 5 represents a schematic structure of a MOS-transistor with a top gate, obtained in examples 6-10.

6 is a graph showing the voltage-current characteristic of a MOS transistor with a top gate using Y2About3as a film, the insulating shutter, obtained in example 6.

Figa, 7B, 7C, 7D, 7E and 7F show the first example of a process of manufacturing a TFT of the present invention.

Figa, 8B, 8C, 8D, 8E and 8F shows a second example of a process of manufacturing a TFT of the present invention.

Fig.9G, N, 9I, 9J, 9K and 9L shows a first example of a process of manufacturing a TFT of the present invention.

Figure 10 schematically shows the structure of a MOS transistor with a top gate, obtained in example 1.

Figure 11 schematically shows an apparatus for forming films by PLD process.

On Fig schematically shows an apparatus for forming a film coating process.

The IMPLEMENTATION of the INVENTION

The following describes the structure of the active layer of the field effect transistor according to the present invention.

The authors of the present invention have found that some types of amorphous thin films of the semi-insulating oxide have characteristics in which the electron mobility increases with the increase in the number of conduction electrons, and moreover detect and, that TFT manufactured by using such a film has superior characteristics of the transistor, such as the ratio of on/OFF, the saturation current is in the cutoff state and the switching speed.

By using transparent politology thin film as a channel layer of the thin film transistor can adjust the current between the drain terminal and the source terminal (without application of gate voltage) so that it was less than 10 microamps, preferably below 0.1 microamps, when the mobility of electrons above 1 cm2/B*s, preferably above 5 cm2/*Sec, and at a concentration of electronic carriers below 1×1018/cm3, preferably below 1×1016/cm3. Moreover, by using the thin film can be increased saturation current of 10 microamps or more after the cut-off, and on/OFF can be increased more than 1×103when the mobility of electrons above 1 cm2/*Sec, preferably 5 cm2/*Sec.

In a state of cutoff TFT to the terminal of the gate high voltage is applied and the electrons in the channel have high density. Therefore, according to the present invention, the saturation current can be increased according to the increase of electron mobility. Thus, almost all the characteristics of the transistor to improve the I, such as the ratio of on/OFF, increased saturation current, increased switching speed. In contrast, in the conventional connection, the increase in the number of electrons reduces the mobility of the electrons due to collisions between electrons.

The structure of the above-mentioned TFT may be a checkerboard structure (top gate), in which the film insulating the gate, and the gate terminal sequentially formed on the semiconductor channel layer, or reverse checkerboard structure (bottom gate), in which the film insulating the gate, and a layer of semi-conductive channel sequentially formed on the terminal bolt.

A specific example of an amorphous oxide comprising the active layer is an oxide in the crystalline state, containing In-Ga-Zn-O, in the form of InGaO3(ZnO)m(m is a natural number less than 6). Another example is an oxide containing In-Ga-Zn-Mg-O, in the form of InGaO3(Zn1-xMgxO)m(m is a natural number less than 6, 0<x≤1), containing the electronic media with a concentration below

1×1018/cm3.

The amorphous oxide film preferably shows the electron mobility greater than 1 cm2/*Sec.

Found that by using the above film as a channel layer can be manufactured TFT, which is normally wykluczen the m with the current shutter below 0.1 increasing volume of computer in the transistor in the OFF state, related on/OFF above 1×103and which is transparent to visible light and flexible.

In the above-mentioned transparent film, the electron mobility increases with the increase in the number of conducting electrons. The substrate for forming a transparent film includes a glass plate, a plastic plate and a plastic film.

In the preferred embodiment, using the above oxide film as the channel layer, the transistor obtained by forming an electrode layer of at least a layer consisting of SnO2, In2O3, ITO, Tl2About3, TlOF, SrTiO3, EuO, TiO or VO as a transparent electrode.

In another preferred embodiment, using the above transparent oxide film as the channel layer, the transistor obtained by forming an electrode layer of at least one of the layers consisting of Au, Ag, Al or Cu as an electrode.

In another preferred embodiment, using the above transparent oxide film as the channel layer, the transistor obtained by forming the gate insulator of at least one of the layers consisting of Y2About3or HfO2or mixed crystalline compounds or SiO2 Si3N4, TiO2TA2O5, PbTiO3Vata2O6, SrTiO3, MgO or AlN, or an amorphous structure.

In another embodiment, the film formed in an atmosphere containing gaseous oxygen without intentionally adding an impurity to increase electrical resistance.

The process of manufacturing an amorphous oxide film and the process of manufacturing TFT using an amorphous oxide, explained in more detail after the description of the first-third embodiments.

Structural requirements that differ from the requirements of the active layer of the field effect transistor described in the fifth to ninth aspects of the present invention on the example of the first-third embodiments.

For the following first-third embodiments, it is preferable to use such an active layer, an electrode material for an insulator shutter, etc. as described above. However, the invention in accordance with the following implementation options are not limited to the above-mentioned active layer, etc.

First option: transparent S, D, G electrodes or layered electrodes

Field-effect transistor of the present invention belongs to the category of the above-mentioned first, second, and third aspects of the present invention.

Description "transparent ViDi the CSOs light" means a state, when the material is transparent, at least for part of the spectrum with a wavelength of visible light. Transparency means not only the condition of light absorption and permeability portions of the visible light. In the present invention, the transmittance of visible light is not less than 40%, more preferably not lower than 60%, more preferably not lower than 80%.

Thus, highly transparent device is sold through a transparency of at least part of the electrode or other element constituting the transistor.

Preferably, all of the source electrode, drain electrode, gate electrode and the film, the insulating shutter, are transparent to visible light.

Examples of electrodes are transparent to visible light, are electrodes formed from SnO2, In2O3, ITO, Tl2About3, TlOF, SrTiO3, EuO, TiO or VO.

Typically, the electrode material, transparent to visible light, has a low conductivity or high electrical resistance. Therefore, the display device which has a wiring formed entirely of such electrode material will have a high parasitic resistance. Therefore, the transaction made by the layering of the first layer formed from a material transparent to visible light, and Vtorov the layer, formed from gold, copper, aluminum or similar metal or alloy containing the metal. Essentially, for example, the first transparent layer is used around the transistor, the other part is formed by layering the first layer and the second layer, and the lead wire forming the second layer having a high conductivity, and thus can be reduced parasitic resistance. Of course, the above-mentioned source electrode, the drain electrode or the gate electrode may be formed using a layered structure.

The active layer of the field effect transistor according to a third aspect of the present invention is, as mentioned above, the amorphous oxide transparent to visible light. Such an active layer is preferably a transistor normally off type.

From the point of view of the first aspect of the present invention the active layer according to a third aspect of the present invention are formed from an amorphous oxide, which contains the media with a concentration below 1×1018/cm3while the mobility of electrons increases with increasing carrier concentration, and it is transparent to visible light, and at least one of the source electrode, drain electrode and gate electrode is transparent to visible light.

Thus, it can be obtained from trojstvo, having a large area transparent by making transparent, at least part of the electrodes or other elements of the transistor.

Second option: Multilayer gate insulator

Field-effect transistor of the present invention relates to the above fourth and fifth aspects of the present invention. The active layer of such a variant implementation preferably consists of transparent amorphous oxide comprising, at least, of the In-Ga-Zn-O presented in the crystalline state formula of the form InGaO3(ZnO)m(m is a natural number less than 6), containing a carrier concentration lower than 1×1018/cm3; or transparent amorphous oxide containing In-Ga-Zn-Mg-O presented in the crystalline state in the form of InGaO3(Zn1-xMgxO)m(m is a natural number less than 6; 0<x≤1).

The first layer consisting of a film, an insulating shutter, for example, consists of HfO2or Y2About3or mixed of these crystalline compounds. The second layer consists, for example of SiO2Si3N4, TiO2Ta2O5, PbTiO3Vata2About6, SrTiO3, MgO or AlN, or amorphous structure consisting of the above substances.

The above materials of the first layer and the second layer and the materials of the first and second layers can correspond the public to use for the first and second layers.

HfO2and Y2About3are good material, having a high ability excitation current due to their high dielectric constant. According to authors of the invention the use of HfO2or Y2About3as a film, the insulating shutter in combination with a channel layer composed InGaO3(ZnO)mor InGaO3(Zn1-xMgxO)mallows you to create TFT, showing extremely high mobility and low threshold value. The mechanism of this is unknown, but presumably HfO2or Y2About3form a good interface with

InGaO3(ZnO)mor InGaO3(Zn1-xMgxO)mthat improves the properties of the interface.

Moreover it requires film, an insulating closure to prevent leakage of the shutter. Leak stopper may occur in parts with different layers on the electrode end 6 of the source and drain electrode 5, as shown in figure 5. Therefore, the thickness of the layer 3, the insulating shutter, preferably equal to the thickness of the electrode 6 and source and drain electrode 5, or twice their thickness.

However, since Hf and Y are costly, the film thickness, the insulating shutter of HfO2or Y2About3becomes a significant factor in increasing the cost during manufacturing the TFT plate bol the large square.

On the other hand, HfO2or Y2O3is capable of forming a satisfactory interface with the amorphous oxide such as InGaO3(ZnO)mor

InGaO3(Zn1-xMgxO)m. Therefore, such a film, the insulating shutter is used only around the interface with the channel layer, and forming a second layer insulating the gate from inexpensive material such as SiO2and Al2O3with a given thickness. That is, the second gate electrode serves as a layer that prevents leakage.

Thus, leakage of the shutter can be effectively prevented by using the good properties of the interface with HfO2or Y2O3. Therefore, according to the present invention, even with a small amount of Hf or Y can be obtained TFT, which has a high mobility, low threshold value and has a high reliability without leakage of the shutter. Thus, the above construction, in particular, is suitable for the TFT plate of large area from the viewpoint of high productivity and low cost of the product.

According to authors of the invention may be a problem, if the conductive layer or the like formed or etched, is located on the surface of the channel layer, comprising the C InGaO 3(ZnO)mor InGaO3(Zn1-xMgxO)mbefore forming the layer insulating the gate, at the data link layer: the current in the TFT formed may change over time, or may occur snapping the shutter. Although the detailed mechanism of this is not known, it is possible that this phenomenon may be caused by unwanted diffusion of the impurity in the channel layer, strong roughness of the surface or the formation of particles.

On figa-7F shows the structure of the TFT and the process of manufacture so as to avoid the above problems:

(7A) the Channel layer (2701) is formed on the substrate 2700.

(7B) the Surface is covered with a mask 2702 and form the electrode 2703 drain electrode 2704 source. The mask 2702 slightly raised above the channel layer 2701 to prevent contact with the surface channel layer 2701. After removal of the mask 2702 remain electrode 2703 drain electrode 2704 source.

(7C) is Formed from a first film 2705, isolating shutter, and the second film 2706, an insulating shutter. At stages 7A-7C, the operation of attaching and detaching the mask is preferably performed without supplying external air, for example, in a vacuum.

(7D) Through the hole 2707 forms the connection with the drain electrode, and the through hole 2708 form the connection with the source electrode through films 2705, 2706, an insulating shutter.

(7E) Form the conductive layer 2709.

(7F) Navigating the th film 2709 made on the pattern for forming the wiring 2710, thus deactivating the drain electrode, a wired connection 2711, deducing it from the source electrode and electrode 2712 shutter.

In the above steps, the surface channel layer 2701 is not disturbed by the formation of a conducting layer and other films and etching, so that the TFT receive with high performance and high reliability.

On figa-8F and 9G-9L shows a more efficient structure of the TFT and its manufacture to prevent leakage of the shutter and increase the efficiency of the excitation electrode of the gate.

(8A) On the substrate 2800 form the channel layer.

(8B) is Formed from a first film 2802, an insulating shutter. At stages 8A and 8B, the operation is preferably performed without supplying external air, for example, in a vacuum.

(8C) is Applied to the photoresist 2803.

(8D) the Photoresist 2803 form a pattern.

(8E) Etched first film 2802, an insulating gate to form a box 2804 electrode for the drain and open 2805 for electrode 2805 source.

(8F) is Formed from a first conductive layer 2806.

(9G) the Unused portion of the conductive layer 2806 removed in the direction of the arrow A.

(N) Form the electrode 2807 drain electrode 2808 source.

(9I) Form the second film 2809, insulating the gate.

(9J) is Made on the pattern of the second film, the insulating gate to form a connection with the source electrode through the opening 2810 and for shaping the ia connection with the drain electrode through the hole 2811.

(9K) Form the second conductive layer 2812.

(9L) is Made on the pattern of the second conductive film 2812 for forming a wired connection 2813 to bring it out of the drain electrode, a wired connection 2814, to bring it from the source electrode, and the electrode 2815 shutter.

In the above process, the first layer 2802, isolating shutter, completely covers the channel layer 2801, but does not cover the electrode 2808 drain electrode 2809 source. Therefore, the height of the surfaces of the first film 2802, insulating the gate electrode 2808 flow and electrode 2809 source are the same. Accordingly, the difference in the level of the second film 2809, insulating the gate is so small that it does not cause any leakage of the shutter, and the second film 2809, isolating shutter, can be made thin enough to increase the capacitance of the gate electrode and increase the efficiency of excitation.

It is assumed that the structure and the processes shown in figa-7F, figa-8F and fig.9G-9L, effective for the film, the insulating shutter, consisting of a conventional insulating material. However, the foregoing structure and processes are particularly effective for the channel layer using the above-mentioned amorphous oxide containing at least an In-Ga-Zn-O presented in the crystalline state as InGaO3(ZnO)m(m is a natural num is less than 6) containing media with a concentration below 1×1018/cm3or transparent amorphous oxide containing In-Ga-Zn-Mg-O presented in the crystalline state in the form of InGaO3(Zn1-xMgxO)m(m is a natural number less than 6; 0<x≤1); and using the film, the insulating shutter consisting of HfO2or Y2O3.

Thus, according to the present invention can be obtained TFT, which shows a high mobility and a low threshold value, causing a small leak shutter, and having stable characteristics. In particular, plate large-area TFT manufactured according to the present invention has balanced characteristics with high reliability.

Third option: a Passivation layer covering the surface

This version of the implementation of the field-effect transistor refers to the above seventh, eighth and ninth aspects of the invention.

A layer of passivation in the first aspect includes two concepts. A layer of passivating the first concept is a separate layer located between the active layer and the layer insulating the gate, and consists of a material different from the material of the active layer or layer, the insulating shutter. This layer is the passivation of the first concept in the present description is called "pass ivireanul layer. The passivated layer is, for example, of amorphous silicon oxide, titanium oxide, aluminum oxide, magnesium oxide, etc.

The passivated layer of the second concept is the biggest part of the surface of the active layer is treated with an oxygen plasma. Processing for forming the passivation layer of the second concept in the present description is called "processing the passivation". This concept is not provided another layer consisting of a material different from the material of the active layer, and the layer insulating the gate. Essentially, after processing the passivation may be formed Passivated layer of the first concept, consisting of amorphous silica.

The passivated layer or processing the passivation prevents deterioration of the film, the insulating shutter: the passivation layer serves as a layer for preventing leakage current.

Layer covering the surface, in the FET of the sixth aspect of the present invention are formed from amorphous silicon nitride, amorphous silicon oxide, amorphous silicon nitride, titanium oxide, aluminum oxide, magnesium oxide or similar material. Layer covering the surface may consist of the same material as the above passivated layer, or other material.

Layer covering the surface of the e l e C improves the adhesiveness between the substrate and the active layer serving as a layer for improving adhesiveness to prevent exfoliation of the film, reducing the leakage current, etc. moreover, the layer covering the surface, can weaken the protrusions and depressions on the substrate to reduce leakage current and improve the ratio of transistor turned on/OFF.

In the above thin-film transistor that uses a transparent film, the film, the insulating shutter, preferably consists of Al2O3, Y2About3, HfO2or mixed crystalline compounds consisting of two or more oxides. Any defect at the interface between the thin film insulating the gate, and a thin channel layer increases the mobility of electrons and causes the hysteresis characteristics of the transistor. Leakage current mainly depends on the type of film, the insulating shutter. Therefore, the film, the insulating shutter should be chosen so that it was suitable for the channel layer.

The aforementioned problems are reduced by the introduction of the passivation layer at the interface that allows the use of an insulating layer with a high dielectric constant and to increase the electron mobility. Thus, the passivation layer boundary, which is an aspect of the present invention, the SP is capable of forming TFT, in which reduced leakage current and hysteresis and increased electron mobility. TFT can be formed either in the form of a checkerboard patterns, either in the form of inverse chess patterns, because the layer insulating the gate and the channel layer can be formed at room temperature.

Thin-film transistor (TFT) is threateningly element with the terminal gate, the source terminal and the drain terminal. TFT is an active element which uses a semiconductor film formed on an insulating substrate made of a ceramic material, glass material or plastic material as a channel layer for the transfer of electrons or holes; and regulates the current flowing through the channel layer by applying a voltage to the gate to switch the current between the source terminal and the drain terminal.

The concentration of electronic carriers can be adjusted by regulating the amount of oxygen defects, if desired.

In the above first and third embodiments, the implementation of the amount of oxygen (the number of oxygen defects in the transparent oxide film is controlled by the formation of a film in an atmosphere containing oxygen, with a given concentration. Otherwise, the number of oxygen defects can R guluronate (decrease or increase) after formation of a film by further processing of the oxygen film in the atmosphere, containing oxygen.

For effective management of the number of oxygen defects, the temperature of the atmosphere containing oxygen is maintained in the range from 0 to 300°C, preferably from 25 to 250°C., more preferably from 100 to 200°C.

Essentially, the film can be formed in the atmosphere containing oxygen, and then with further processing in an atmosphere containing oxygen. Otherwise, the film can be formed without controlling the partial pressure of oxygen and without further treatment in the atmosphere containing oxygen, to such an extent that it was possible to obtain the desired concentration of electronic carriers (below 1×1018/cm3).

The lower concentration limit of the electronic media of the present invention is, for example, 1×1014/cm3depending on the element type, scheme or device, using the obtained oxide film.

AMORPHOUS OXIDE

Described in more detail below the active layer, used above in options 1-3 implementation.

The concentration of electronic carriers in the amorphous oxide in the present invention is the value measured at room temperature. Room temperature is a temperature in the range from 0°C to about 40°C., for example 25°C. the Concentration of electronic carriers in the amorphous oxide in the present from which britanii does not have to be less than 10 18/cm3within the entire region from 0°C to 40°C. for Example, the acceptable concentration of electronic carriers less than 1018/cm3at a temperature of 25°C. At lower concentrations of electronic media, not more than 1017/cm3or not more than 1016/cm3can be obtained with a high yield of TFT normally off type.

In this specification the definition of "less than 1018/cm3" means "is preferably less than 1×1018/cm3and more preferably less than 1.0×1018/cm3". The concentration of electronic carriers can be measured by measuring the Hall effect.

Amorphous oxide of the present invention is an oxide, which detects the halo pattern and that has no characteristic diffraction lines in the x-ray diffraction spectrometry.

In amorphous oxide of the present invention, the lower limit of the concentration of electronic carriers is, for example, 1×1012/cm3, but is not limited to this limit, since it can be used as a channel layer of the TFT.

Accordingly, in the present invention the concentration of electronic carriers govern by the selection of material, composition, conditions of manufacture, etc. of amorphous oxide, for example, as described below in PR the measures so she was within, for example, from 1×1012/cm3up to 1×1018/cm3preferably from 1×1013/cm3up to 1×1017/cm3, more preferably from 1×1015/cm3up to 1×1016/cm3.

Amorphous oxide other than InZnGa oxides may be selected appropriately from In oxides, InxZn1-xoxides (0,2≤x≤1), InxSn1-xoxides (0,8≤x≤1),

Inx(Zn,Sn)1-xoxides (0,15≤x≤1). Inx(Zn,Sn)1-xthe oxide may also be an Inx(ZnySn1-y)1-x(0≤y≤1).

If In the oxide contains no Zn or Sn, then In may be partially substituted Ga: InxGa1-xoxide (0≤x≤1).

Amorphous oxide with a concentration of electronic carriers 1×1018/cm3that obtained by the authors of the present invention, described in more detail below.

One group of the above-mentioned oxides typically has a composition of In-Ga-Zn-O, presented in the form of InGaO3(ZnO)m(m: natural number less than 6) in a crystalline state, and contains the electronic media with a concentration of less than 1018/cm3.

Another group of the above-mentioned oxides typically has a composition of In-Ga-Zn-Mg-O, presented in the form of InGaO3(Zn1-xMgxO)m(m: natural number less than 6, and 0<x≤1) in the crystalline state, and contains electronic media with conc is of less than 10 18/cm3.

The film consisting of such oxide, preferably designed for receiving the electron mobility greater than 1 cm2/B*s.

Using the above film as a channel layer, can be obtained TFT normally off type with the current shutter less than 0.1 microamps and the ratio of on/off is higher than 1×103that is also transparent to visible light and flexible.

In the above film, the electron mobility increases with the conduction electrons. The substrate for forming a transparent film includes a glass plate, a plastic plate and a plastic film.

When using the above film of the amorphous oxide as a channel layer, at least one of the layers consisting of Al2About3, Y2About3and HfO2or crystal mixtures may be used as the gate insulator.

In a preferred embodiment, the film formed in an atmosphere containing gaseous oxygen, without adding in the amorphous oxide impurities to increase electrical resistance.

The authors of the present invention have found that a thin amorphous film politology oxides have characteristics, which consists in the fact that the mobility of electrons in them zoom is by increasing the number of conduction electrons, and, in addition, it was found that the TFT obtained by the use of such a film has superior characteristics of the transistor, such as the ratio of on/off, the saturation current is in the cutoff state and the switching speed. Thus, the TFT normally off type can be obtained by using an amorphous oxide.

By using a ton of film of the amorphous oxide as a channel layer of the thin film transistor can be obtained electron mobility greater than 1 cm2/B*s, preferably above 5 cm2/B*sec. The current between the drain terminal and the source terminal in the off state (no applied voltage gate) can be controlled so that it was less than 10 microamps, preferably less than 0.1 increasing volume of computer when carrier concentration lower than 1×1018/cm3, preferably lower than 1×1016/cm3. In addition, by using such a thin film saturation current after the cut-off may be increased to 10 microamps or more, and the ratio of on/off can be higher than 1×103when the electron mobility is higher than 1 cm2/*Sec, preferably higher than 5 cm2/*Sec.

In a state of cutoff TFT to the terminal of the gate high voltage is applied, and the channel electrons have a high density. Therefore, according to the present invention, the saturation current can be increased in accordance with increase of electron mobility. Thus, it can be improved characteristics of the transistor, such as the increase of the ratio on/off, increase of the saturation current and increase the speed of switching. In contrast, using conventional compounds increase the number of electrons reduces the mobility of the electrons due to collisions between electrons.

The structure of the above-described TFT may be a structure in staggered (top gate), in which the gate insulator and the terminal gate sequentially formed on the semiconductor channel layer, or structure in a reverse staggered (bottom gate), in which the gate insulator and the semiconductor channel layer sequentially formed on the terminal bolt.

The FIRST PROCESS is the formation of a FILM: PLD PROCESS

A thin film of an amorphous oxide comprising InGaO3(ZnO)m(m is a natural number less than 6) in a crystalline state is stable at high temperatures up to 800°C or above, if m is less than 6, whereas the increase in m, that is, with increase of the ratio of ZnO to InGaO3closer to the composition of ZnO, the oxide has a tendency to crystallize. Therefore, for use as a channel layer of an amorphous TFT is preferable that the value of m oxide was less than 6.

p> The formation of the film preferably is in the process of forming film in a gas phase by using a target of polycrystalline sintered compact having a composition InGaO3(ZnO)m. Suitable processes are the formation of a film in a gas phase, sputtering and pulsed laser deposition. For mass production is particularly suitable spraying.

However, when forming an amorphous film in normal conditions can occur oxygen defects so that it is impossible to obtain the concentration of electronic carriers is less than 1×1018/cm3and conductivity of less than 10 Cm/see this film cannot be created, the transistor is normally off type.

The authors of the present invention was created In-Ga-Zn-O film using pulsed laser deposition using the apparatus shown in 11.

The film formation was carried out by using such a PLD device for forming a film, as shown in figure 11.

Figure 11 reference position indicate the following: 701 - PH (rotary pump); 702 - TDS (turbomolecular pump); 703 - preparatory chamber; 704 - e-gun for RHEED; 705 - tool mounting substrate for rotation and vertical movement of the substrate; 706 - box input laser beam; 707 - substrate; 708 - target; 709 - source radicals; 710 - about the opening for gas supply; 711 - a means of fixing targets for rotation and vertical movement of the target; 712 - line bypass; 713 - main line; 714 - TDS (turbomolecular pump); 715 - PH (rotary pump); 716 - titanium gas absorbing capacity pump; 717 - blind; 718 - IM (ion gauge); 719 - FE (Pirani gauge); 720 - BCH (pressure transducer Baratron); and 721 camera growth.

The semiconductor thin film of the In-Ga-Zn-O amorphous oxide layer on SiO2a glass substrate (Corning Co.: 737) pulsed laser deposition using a KrF excimer laser. As a pre-treatment prior to deposition the substrate was washed for degreasing using ultrasound acetone, ethanol, and ultrapure water, for five minutes each, and dried at 100°C.

Polycrystalline target was a InGaO3(ZnO)4sintered compact (about the size of 20 mm in diameter, 5 mm in thickness), which was obtained by wet mixing In2O3, Ga2O3and ZnO (4-normal solution of each reagent) as the source material (solvent: ethanol), firing the mixture (1000°C, 2 h), dry grinding and sintering (1550°C, 2 h). Target had a conductivity of 90 Cm/see

The film formation was carried out by maintaining the final pressure in the cell growth of 2×10-6PA and the partial pressure of oxygen during growth to 6.5 PA. Partial pressure is the oxygen in the chamber 721 growth was 6.5 PA, and the temperature of the substrate was 25°C. the distance between the target 708 and substrate 707, holding the film was 30 mm, power input via the window 706 input was in the range of 1.5-3 MJ/cm2/pulse. The pulse duration was 20 NS, repetition frequency was set to 10 Hz, and the point of exposure was represented by a square 1×1 mm In the above-described conditions, the formed film with a speed of 7 nm/min

The obtained thin film investigated by the method of small-angle x-ray (SAXS) (method of thin films, the incidence angle of 0.5°): a clear diffraction peak was not observed. Thus obtained thin film type In-Ga-Zn-O was considered to be amorphous. The coefficient of reflection of x-rays and analysis of its pattern was found root-mean-square surface roughness (Rrms), is equal to approximately 0.5 nm, and a film thickness of approximately 120 nm. From x-ray fluorescence analysis (XRF) it was found that the metal content in the film corresponds to the ratio of In:Ga:Zn = 0,98:1,02:4. The conductivity was lower than about 1×10-2Cm/see was estimated concentration of electronic carriers, which was less than 1×10-16/cm3. The electron mobility was about 5 cm2/*Sec. By analyzing the absorption of light was measured width of the forbidden zone in the optical range in the resulting amorphous thin film, the which was approximately 3 eV.

The above results show that the obtained thin film type In-Ga-Zn-O is a transparent thin film having the amorphous phase composition close to that of crystalline InGaO3(ZnO)4that has less oxygen defects and lower electrical conductivity.

The formation of the above films is due, in particular, with reference to figure 1. Figure 1 shows the dependence of the concentration of electronic carriers in the formed transparent thin film made of amorphous oxide from the partial pressure of oxygen for film composition InGaO3(ZnO)m(m is a whole number less than 6) in a prospective crystalline state in the same conditions of formation of a film, as described in the example above.

By forming the film in an atmosphere having a partial pressure of oxygen higher than 4.5 PA in the same conditions as described above, the concentration of electronic carriers can be reduced to less than 1×1018/cm3as shown in figure 1. In this film formation, the substrate can be at a temperature close to room temperature without special heating. To use a flexible plastic film as the substrate temperature of the substrate is preferably kept lower than 100°C.

The higher the partial pressure of oxygen can lead to decrease the structure of concentration of electronic carriers. For example, as shown in figure 1, thin InGaO3(ZnO)4film formed at a temperature of the substrate 25°C and a partial pressure of oxygen equal to 5 PA, had a lower concentration of electronic carriers, component 1×1016/cm3.

In the resulting thin film, the electron mobility was higher than 1 cm2/B*s, as shown in figure 2. However, the film, layered by means of pulsed laser deposition at a partial pressure of oxygen higher than 6.5 PA, as in this example, had an uneven surface that is unsuitable for the channel layer of the TFT.

Accordingly, in the above example, the transistor is normally off type can be created by using a thin transparent oxide represented by the formula InGaO3(ZnO)m(m is a whole number less than 6), in the crystalline state, is formed at a partial pressure of oxygen higher than 4.5 PA, preferably higher than 5 PA, but below 6.5 PA, by the method of pulsed laser deposition.

The obtained thin film had an electron mobility greater than 1 cm2/B*s, and the ratio of on/off could exceed 1×103.

As described above, when forming InGaZn oxide films by PLD method under the conditions shown in this example, the partial pressure of oxygen was maintained in the range from 4.5 to 6.5 PA.

To achieve conc is the electronic media 1×10 18/cm3it is necessary to control the oxygen partial pressure, the structure of the device formation film, the type and composition of the material for the formation of a film.

Then, MOS transistor with a top gate, as shown in figure 5, produced by forming an amorphous oxide using the above device at a partial pressure of oxygen, 6.5 PA. In particular, on the glass substrate 1 formed politology amorphous InGaO3(ZnO)4the film thickness of 120 nm for use as a channel layer 2 of the above-described method of forming a thin amorphous Ga-Ga-Zn-O film. In addition, it was layered InGaO3(ZnO)4film having a higher conductivity, and a gold film with a thickness of 30 nm pulsed laser deposition at a partial pressure of oxygen in the chamber is below 1 PA. Then the drain terminal 5 and terminal 6 of the source formed by the photolithography method and the method of inverse lithography. Finally Y2About3the film was formed to the insulator 3 of the shutter by deposition using electron beam evaporation (thickness of 90 nm, relative dielectric constant of about 15, the density of leakage current

1×10-3A/cm3at a voltage of 0.5 MV/cm). It was formed of a gold film, and the terminal 4 gate was sformirovannost photolithography and a method of inverse lithography.

Performance evaluation element MOS transistor

Figure 6 shows the volt-ampere characteristic element of a MOS-transistor, measured at room temperature. Given that the drain current IDSincreases with increasing voltage drain VDSit is obvious that the channel is an n-type semiconductor. This is consistent with the fact that the amorphous-type semiconductor In-Ga-Zn-O refers to n-type. IDSis saturated (clipped) at VDS=6 V, which is typical for a semiconductor transistor. Evaluation of the characteristics of the shutter, it was found that a threshold value of gate voltage VGSwhen the voltage VDS=4 is approximately -0,5 Century When VG=10 occurred In the current IDS=1,0×10-5A. This corresponds to the impact of the bias on the gate on the carriers in the semiconductor thin amorphous In-Ga-Zn-O film.

The ratio of on/off of the transistor exceeded 1×103. From the output characteristics to calculate the drift mobility, which was approximately 7 cm2/B*sec. According to similar measurements of the emission of visible light does not change the characteristics of the element.

According to the present invention can be manufactured thin-film transistor that has a channel layer containing the electronic media with a lower concentration on what I achieve higher specific resistance and achieve higher mobility of electrons.

The above amorphous oxide has good features, namely that the electron mobility increases with increasing concentration of electronic carriers, and has a degenerate case. In this example, a thin film was formed on the glass substrate. However, a plastic plate or film can also be used as a substrate, since the film formation can be carried out at room temperature. Moreover, the amorphous oxide obtained in this example, absorbs visible light only in a small amount, allowing you to create flexible transparent TFT.

(Second process of forming a film: the process of sputtering (SP))

Below is described the formation of thin films of high-frequency SP process in the atmosphere of gaseous argon.

SP process is performed using the device shown in Fig. On Fig reference position indicate the following: 807 - substrate for the formation of a film; 808 - target; 805 - tool mounting substrate equipped with a cooling mechanism; 814 - turbomolecular pump; 815 - rotary pump; 817 - blind; 818 - ion gauge; 819 - gauge Pirani; 821 - growing chamber; and 830 - valve shutter.

The substrate 807 for the formation of a film was a SiO2a glass substrate (Corning Co.: 1737), which was washed for degreasing using the trasloco acetone, ethanol and ultrapure water, for five minutes each, and dried at 100°C.

The target consisted of a polycrystalline sintered compact having a composition InGaO3(ZnO)4(20 mm in diameter, 5 mm in thickness), which was obtained by wet mixing In2About3, Ga2About3and ZnO (4-normal solution of each reagent) as the source material (solvent: ethanol), firing the mixture (1000°C, 2 h), dry grinding and sintering (1550°C, 2 h). Target 808 had a conductivity of 90 Cm/cm and was politology.

The final value of the vacuum in the cell growth 821 was 1×10-4Topp. During the growth of the total pressure of oxygen and argon was maintained in the range from 4 to 0.1×10-1PA. The ratio of the partial pressure of argon and oxygen was changed in the range of oxygen partial pressure from 1×10-3up to 2×10-1PA.

The temperature of the substrate was room temperature. The distance between the target 808 and substrate 807 for the formation of a film was 30 mm

Supplied electric power was 180 watts of RF, and the rate of formation of the film was 10 nm/min

The obtained thin film investigated by the method of small-angle x-ray (SAXS) (method of thin films, the incidence angle of 0.5°): a clear diffraction peak was not observed. Thus obtained thin film type In-Ga-Zn-O was considered Amorin the th. The coefficient of reflection of x-rays and analysis of its pattern was found root-mean-square surface roughness (Rrms), is equal to approximately 0.5 nm, and a film thickness of approximately 120 nm. From x-ray fluorescence analysis (XRF) it was found that the metal content in the film corresponds to the ratio of In:Ga:Zn = 0,98:1,02:4.

The film was formed under different partial pressures of oxygen environment, and measured the electrical conductivity of the amorphous oxide film. The result is shown in figure 3.

As shown in figure 3, the conductivity can be reduced to values less than 10 s/Cm by the process of forming the film in an atmosphere with a partial pressure of oxygen greater than 3×10-2PA. The number of electronic media can be reduced by increasing the partial pressure of oxygen.

As shown in figure 3, for example, thin InGaO3(ZnO)4film formed at a temperature of the substrate is 25°C and a partial pressure of oxygen of 1×10-1PA had lower conductivity of approximately 1×10-10Cm/see moreover, thin InGaO3(ZnO)4the film is formed at a partial pressure of oxygen of 1×10-1PA had a too high resistance, while having no measurable conductivity. This film, while n is then, the electron mobility was not measurable, the electron mobility was estimated as equal to about 1 cm2/*Sec, by extrapolation from the values of films with a higher concentration of electronic carriers.

Thus, the transistor is normally off type with respect to on/off higher than 1×103can be obtained by using a transparent thin film of an amorphous oxide containing In-Ga-Zn-O presented in the crystalline state as InGaO3(ZnO)m(m is a natural number less than 6), obtained by the method of vacuum deposition in an argon atmosphere containing oxygen with a partial pressure above 3×10-2PA, preferably higher than 5×10-1PA.

When using the device and the material used in this Example, the film formation by sputtering is carried out at a partial pressure of oxygen in the range from 3×10-2PA to 5×10-1PA. In this regard, in a thin film, obtained by pulsed laser deposition, or sputtering, electron mobility increases with the increase in the number of conductive electrons, as shown in figure 2.

As described above, by controlling the partial pressure of oxygen, it is possible to reduce the number of oxygen defects, and thus can be reduced concentration of electronic carriers. In thin am hnoi film, the electron mobility may be high, as in the amorphous state, no boundaries between grains in contrast to the polycrystalline state.

In this regard, the replacement of the glass substrate 200 μm polyethylene terephthalate (PET) film does not change the properties formed the film of the amorphous oxide InGaO3(ZnO)4.

Amorphous film InGaO3(Zn1-xMgxO)m(m is a natural number less than 6) with high resistivity can be obtained by using as a target of polycrystalline InGaO3(Zn1-xMgxO)meven at a partial pressure of oxygen below 1 PA. For example, using a target in which 80% of the Zn atoms is substituted by an Mg, you can get the concentration of electronic carriers below 1×1016/cm3(resistivity of about 1×10-2Cm/cm) using pulsed laser deposition in an atmosphere containing oxygen with a partial pressure of 0.8 PA. In this film, the electron mobility is lower than the electron mobility in the film, not containing Mg, but the reduction is insignificant: the electron mobility is about 5 cm2/B*s at room temperature, which is higher than the electron mobility in amorphous silicon by about one order of magnitude. When the film formation under the same conditions, the increase in the Mg content decreases as conductivity, so podvijnosti electrons. Therefore, the Mg content is about 20%-85% (of 0.2<x<0,85).

In the thin-film transistor using the above amorphous oxide film, the gate insulator preferably contains a complex crystalline compound composed of 2 or more Al2About3, Y2About3, HfO2and mixtures thereof.

The presence of a defect at the interface between the thin film insulating layer shutter and a thin film channel layer reduces the mobility of electrons is the cause of gasteria performance of the transistor. Moreover, the leakage current strongly depends on the type of insulator bolt. Therefore, the gate insulator should be chosen in such a way that it was appropriate for the channel layer. The leakage current can be reduced by using Al2About3film, hysteresis can be reduced by using Y2O3film, and the electron mobility can be increased using HfO2film having a high dielectric constant. TFT can be formed by using crystalline complex compounds of the above oxides, which can lead to less leakage current, a smaller hysteresis and higher mobility of the electrons. Since the process of forming the gate insulator and the process of forming the channel layer can be carried out at room Tempe is the atur, TFT can be staggered or placed in reverse staggered.

Thus formed TFT is threateningly element with the terminal gate, the source terminal and the drain terminal. Such a TFT is formed by forming a thin semiconductor film on an insulating substrate of ceramic, glass or plastic material as a channel layer for the transfer of electrons or holes and serves as an active element having a function to control the current flowing through the channel layer by applying a voltage to the terminal gate and switching current between the source terminal and the drain terminal.

In the present invention it is also important that the planned concentration of electronic carriers was achieved by controlling the amount of oxygen defects.

In the above description, the amount of oxygen in the film of the amorphous oxide is controlled by the concentration of oxygen in the atmosphere, the formation of a film. Otherwise, the number of oxygen defects can be controlled (increased or decreased), followed by treatment of the oxide film in an atmosphere containing oxygen, as in the preferred embodiment.

For effective management of the number of oxygen defects, the temperature of the atmosphere, with the holding oxygen, supported in the range from 0°C to 300°C, preferably from 25°C to 250°C, more preferably from 100°C. to 200°C.

Naturally, the film can be formed in the atmosphere containing oxygen, and further followed by treatment in an atmosphere containing oxygen. Otherwise, the film is formed without control the partial pressure of oxygen, and the subsequent processing takes place in the atmosphere containing oxygen is provided that can be achieved planned concentration of electronic carriers (less than 1×1018/cm3).

The lower limit of the concentration of electronic carriers in the present invention is, for example, 1×1014/cm3that depends on the type of the element or device used for the manufacture of the film.

A wider range of materials

After studying the materials for the system it was found that the amorphous oxide composition, of at least one oxide of the elements Zn, In and Sn can be used for the film of the amorphous oxide with a low carrier concentration and high electron mobility. Found that such a film of the amorphous oxide has a specific property, namely, that the increase in its number of conduction electrons increases the electron mobility. Using this film, can be manufactured TFT normally " off " is of type which has good properties such as the ratio of on/off, the saturation current is in the cutoff state and the switching speed.

In the present invention can be used oxide, having any one of the operating characteristics (a)to(h)below:

(a) an amorphous oxide having a concentration of electronic carriers is less than 1×1018/cm3;

(b) an amorphous oxide in which the electron mobility increases with increasing concentration of electronic carriers;

(under room temperature refers to a temperature ranging from about 0°to about 40°C. the Term "amorphous compound" means a compound that has only a halo pattern no characteristic diffraction pattern in the diffraction spectrum of x-rays. The electron mobility means mobility, measured using Hall effect)

(c) an Amorphous oxide mentioned above in paragraphs (a) and (b), in which the electron mobility at room temperature is higher than 0.1 cm2/*Sec;

(d) amorphous oxide mentioned above in paragraphs (b)-(C)with degenerate character of conductivity;

(the term "degenerate nature conductivity" means a condition in which thermal activation energy in the temperature dependence of the resistivity does not exceed 30 MeV)

(e) an amorphous oxide mentioned above is any of paragraphs (a)to(d), which as a constituent element contains at least one element of Zn, In and Sn;

(f) film of the amorphous oxide, made of an amorphous oxide described above in paragraph (e), and optionally at least one element from:

elements of group 2 M2 with atomic number less than that of Zn (Mg and CA),

elements of group 3 M3 with atomic number less than that In (In, Al, Ga and Y),

elements of group 4 M4 with atomic number less than that of Sn (Si, Ge and Zr),

elements of group 5 M5 (V, Nb and TA) and

Lu and W to reduce the concentration of electronic carriers;

Elements M2, M3, M4, respectively having a lower atomic number than that of Zn, In, Su, are selenoenzyme, thereby creating less oxygen defects and decreases the concentration of electronic carriers. Element Lu, which has a larger atomic number than Ga, has a smaller ionic radius and is selenomonas, performing the same function as the M3. M5, which is an ionisable to the plus five valence capable of firmly contact with oxygen and is less likely to create an oxygen defect. W is an ionisable to valence plus six, able to firmly contact with oxygen and is less likely to create an oxygen defect.

(g) film of the amorphous oxide, as described in any of paragraphs (a)to(f), consisting of a single connection, there is a corresponding part In 1-xM3xO3(Zn1-yM2yO)m(0≤x≤1; 0≤y≤1; m is 0 or a natural number less than 6) in a crystalline state, or a mixture of compounds with different m, for example, from M3, representing Ga, and, for example, M2 represents Mg; and

(h) film of the amorphous oxide, as described in any of paragraphs (a)to(g), formed on a plastic substrate or plastic film.

The present invention also provides a field-effect transistor, is used as the channel layer of the above amorphous oxide or a film of the amorphous oxide.

Field-effect transistor is produced using as a channel layer of a film of the amorphous oxide, which has a concentration of electronic carriers is less than 1×1018/cm3but more than 1×1015/cm3and which has a source terminal, a drain terminal and a terminal of the shutter located between the gate insulator. If between the terminals of the source and drain applied voltage of about 5 V without the application of gate voltage, electric current between the terminals of the source and drain is about 1×10-7ampere.

The electron mobility in the crystalline oxide increases with overlapping s-orbitals of the metal ions. In the crystal of the oxide of Zn, In, or Sn with large atomic numbers e podvizhnos the ü is in the range from 0.1 to 200 cm 2/*Sec.

In the oxide oxygen ions and metal bound ionic bonds that do not have orientation and having a random structure. Therefore, in the oxide in an amorphous state, the electron mobility can be comparable with the electron mobility in the crystalline state.

On the other hand, the substitution of Zn, In, or Sn elements with lower atomic numbers reduces the electron mobility. Thus, the electron mobility in amorphous oxide of the present invention is in the range from 0.01 to 20 cm2/*Sec.

In the transistor having a channel layer composed of the above-described oxide, the gate insulator is preferably formed of Al2O3, Y2About3, HfO2or a mixed crystal compound containing two or more of these oxides.

The presence of a defect at the interface between the thin film insulating the gate, and a thin film channel layer reduces the mobility of the electrons and causes hysteresis performance of the transistor. Moreover, the leakage current strongly depends on the type of insulator bolt. Therefore, the gate insulator should be chosen in such a way that it resembled for the channel layer. The leakage current can be reduced by using a film of Al2About3hysteresis can be reduced by using a film of Y2O3and the electron mobility is in can be increased, using film from HfO2having a high dielectric constant. When using a complex crystalline compound of the above oxides can be manufactured TFT, which has a smaller leakage current, less hysteresis and has a large electron mobility. Since the process of forming the gate insulator and the process of forming the channel layer can take place at room temperature, can be formed TFT having a checkerboard structure or inverse checkerboard structure.

The film of oxide In2O3can be formed by deposition from the gas phase, and the addition of water vapor with a partial pressure of approximately 0.1 PA, the atmosphere of the formation of a film does form an amorphous film.

ZnO and SnO2accordingly, cannot be easily formed as an amorphous film. For the formation of a film of ZnO in amorphous form, add In2About3in the amount equal to about 20 atom%. For the formation of a film of SnO2in amorphous form, add In2O3in the amount equal to 90 atom%. When forming an amorphous film type Sn-In-O in the atmosphere the formation of a film introducing nitrogen gas with a partial pressure of approximately 0.1 PA.

In the above film can be added to an element capable of forming a complex oxide selected from elements stored the M2 group 2 with atomic number less than Zn (Mg and CA), elements of M3 group 3 with atomic number smaller than that In (In, Al, Ga and Y), elements M4 group 4 with atomic number less than that of Sn (Si, Ge and Zr), elements M5 group 5 (V, Nb and TA), Lu and W. Adding these elements stabilizes the amorphous film at room temperature and expands the set of compositions for forming an amorphous film.

In particular, Appendix B, Si or Ge leads to the formation of covalent bonds, which is effective to stabilize the amorphous phase. Adding a complex oxide consisting of ions with very different radii of ions is effective to stabilize the amorphous phase. For example, in-Zn-O film formation, stable at room temperature, must be contained In a quantity of more than 20 atom%. However, the addition of Mg equal to In, gives the opportunity to form a stable amorphous film in composition with the content In less than 15 atom%.

When forming a film by deposition from a gas phase film of the amorphous oxide with a concentration of electronic carriers in the range of 1×1015/cm3up to 1×1018/cm3can be obtained by controlling the atmosphere, the formation of a film.

The film of the amorphous oxide can be suitably formed using a deposition process, such as process pulse the laser deposition process (PLD), the process of spraying (process SP) and a deposition process using electron beam evaporation. For processes of deposition from the gas phase process PLD is suitable from the viewpoint of easy control of the composition of the material, while the process SP is suitable from the viewpoint of mass production. However, the process of forming a thin film, it is not limited.

The formation of a film of the amorphous oxide, In-Zn-Ga-O using the PLD process

Amorphous oxide, In-Zn-Ga-O besieged on a glass substrate (Corning Co.: 1737) process PLD using a KrF excimer laser with a polycrystalline sintered compact as a target having a composition InGaO3(ZnO) or InGaO3(ZnO)4.

Used the device, shown at 11, which is mentioned above, and the conditions of film formation were the same as described above for the device.

The temperature of the substrate was 25°C.

Two of the obtained thin films are investigated by the method of small angle x-ray (SAXS) (method of thin films, the incidence angle of 0.5°): a clear diffraction peak was not observed, which showed that the obtained thin film type In-Ga-Zn-O, manufactured using two different targets were amorphous.

The coefficient of reflection of x-rays and analysis of its pattern was found RMS uneven the terrain surface (Rrms), equal to about 0.5 nm, and a film thickness of approximately 120 nm. From x-ray fluorescence analysis (XRF) it was found that the film obtained with a target of polycrystalline sintered compact InGaO3(ZnO), had a metal content with the ratio of In:Ga:Zn = 1,1:1,1:0,9, whereas the film obtained with a target of polycrystalline sintered compact InGaO3(ZnO)4had the metal content with the ratio of In:Ga:Zn = 0,98:1,02:4.

Film of the amorphous oxide formed at different partial pressures of the atmosphere for the formation of a film with a target having a composition InGaO3(ZnO)4. The formed film of the amorphous oxide was measured by the concentration of electronic carriers. The results are presented in figure 1. When forming the film in an atmosphere having a partial pressure of oxygen is higher than 4.2V PA, the concentration of electronic carriers could be reduced to a value not exceeding

1×1018/cm3as shown in figure 1. In this film formation, the substrate can be almost at room temperature without heating. At a partial pressure of oxygen lower than 6.5 PA surface of the obtained film of the amorphous oxide were flat.

At a partial pressure of oxygen equal to 5 PA, an amorphous film formed with the target InGaO3(ZnO)4the concentration of al is Tronic media was 1×10 16/cm3the conductivity was equal to 1×10-2Cm/cm, and the electron mobility was assessed approximately 5 cm2/B*sec. From the analysis of the spectrum of light absorption was measured width of the forbidden zone in the optical range in the resulting thin amorphous oxide film which was approximately 3 eV.

A higher partial pressure further reduces the concentration of electronic carriers. As shown in figure 1, in the film of the amorphous oxide, In-Zn-Ga-O, formed at the temperature of substrate 25°C. and at a partial pressure of oxygen equal to 6 PA, the concentration of electronic carriers was below 8×1015/cm3(conductivity approximately 8×10-3Cm/cm). The electron mobility in the film was estimated as equal to 1 cm2/V*sec or more. However, when using PLD at a partial pressure of oxygen, 6.5 PA or higher deposited film had a rough surface and was not suitable for use as a channel layer of the TFT.

Film of the amorphous oxide, In-Zn-Ga-O formed under different partial pressures of oxygen in the atmosphere the formation of a film with a target consisting of a polycrystalline sintered compact having a composition InGaO3(ZnO)4. In the resulting films investigated the relationship between the concentration of electronic novtel the th and electron mobility. The results are shown in figure 2. By increasing the concentration of electronic carriers from 1×1016/cm3up to 1×1020/cm3the electron mobility was increased from about 3 cm2/*Seconds to about 11 cm2/*Sec. The same trend was observed in amorphous oxide films obtained using a polycrystalline sintered InGaO3(ZnO) target.

The film of the amorphous oxide, In-Zn-Ga-O, which was formed on a 200 μm polyethylene terephthalate (PET) film instead of the glass substrate had similar characteristics.

The formation of a film of the amorphous oxide, In-Zn-Ga-Mg-O using the PLD process

Film of InGaO3(Zn1-xMgxO)4(0<x≤1) formed on the glass substrate using PLD process, using the target InGaO3(Zn1-xMgxO)4(0<x≤1). The device used is shown in 11.

As the substrate used a glass substrate (Corning Co.: 1737). As a pre-treatment prior to deposition the substrate was washed for degreasing using ultrasound acetone, ethanol, and ultrapure water, for five minutes each, and dried at 100°C. the Target was a sintered compact InGaO3(Zn1-xMgxO)4(x=1-0) (20 mm in diameter, 5 mm in thickness). Target got wet mixing the source materials I 2About3, Ga2O3and ZnO (4-normal solution of each reagent) (solvent: ethanol), firing the mixture (1000°C, 2 h), dry grinding and sintering (1550°C, 2 h). The final pressure in the cell growth was 2×10-6PA. The oxygen partial pressure during growth was maintained equal to 0.8 PA. The temperature of the substrate was room temperature (25°C). The distance between the target and the substrate for the formation of a film was 30 mm KrF excimer laser is radiated with a capacity of 1.5 MJ/cm2/pulse with a pulse duration of 20 NS, repetition rate 10 Hz, and the point of exposure was represented by a square 1×1 mm, the Rate of formation of the film was 7 nm/min oxygen Partial pressure in the atmosphere the formation of a film was 0.8 PA. The temperature of the substrate was 25°C.

The obtained thin film investigated by the method of small-angle x-ray (SAXS) (method of thin films, the incidence angle of 0.5°): a clear diffraction peak was not observed. Thus, the obtained thin film type In-Ga-Zn-Mg-O was amorphous. The obtained film had a flat surface.

Using targets with different values of x (with different Mg content) film of the amorphous oxide type In-Ga-Zn-O formed at a partial pressure of oxygen equal to 0.8 PA, the atmosphere for the formation of a film with the purpose of studying the dependence of the conductivity, is concentratie electronic media and mobility of electrons on the value of X.

The results are shown in figa, 4B and 4C. If the magnitude of x is greater than 0,4, films made of amorphous oxide formed by a process PLD at a partial pressure of oxygen in the atmosphere, equal to 0.8 PA, the concentration of electronic carriers decreased to a value less than 1×1018/cm3. In the amorphous film with a value of x greater of 0.4, the electron mobility was greater than 1 cm2/*Sec.

As shown in figa, 4B and 4C, the concentration of electronic carriers is lower than 1×1016/cm3can be obtained in the film produced by the method of pulsed laser deposition using a target in which 80 atom.% Zn replaced by Mg, and at a partial pressure of oxygen equal to 0.8 PA (resistivity of about 1×10-2Cm/cm). In this film, the electron mobility is lower in comparison with the film not containing Mg, but not much. The electron mobility in the films is about 5 cm2/*Sec, which is higher than the electron mobility in amorphous silicon by about one order of magnitude. In the same conditions of formation of the film as the electrical conductivity and electron mobility in the film decreases with increasing Mg content. Therefore, it is preferable that the Mg content in the film was more than 20 AMTA% and less than 85 atom% (at 0.2<x<0,85), more preferably of 0.5<x<0,85.

Amorphous the film from InGaO 3(Zn1-xMgxO)4(0<x≤1)formed on a 200 μm polyethylene terphthalate (PET) film instead of the glass substrate, with similar characteristics.

The formation of a film of the amorphous oxide In2O3using the PLD process

In2About3a film was formed on a 200 μm PET film using a target consisting of In2O3polycrystalline sintered compact using the PLD process using KrF excimer laser.

The used device is shown figure 11. The substrate for the formation of a film was a SiO2a glass substrate (Corning Co.: 1737).

As a pre-treatment prior to deposition the substrate was washed for degreasing using ultrasound acetone, ethanol, and ultrapure water, for five minutes each, and dried at 100°C.

The target consisted of In2O3sintered compact (the size of 20 mm in diameter and 5 mm in thickness), which was obtained by firing the source reagent In2About3(4 - normal reagent solution) (1000°C, 2 h), dry grinding and sintering (1550°C, 2 h).

The final pressure in the cell growth was 2×10-6PA, the oxygen partial pressure during growth was equal to 5 PA, and the temperature of the substrate is 25°C.

The partial pressure of water vapor was 0.1 PA, and the oxygen radicals of generichow the responding device for generating oxygen radicals when applied power of 200 watts.

The distance between the target and the substrate for the formation of a film was 40 mm, power KrF excimer laser was 0.5 MJ/cm2/pulse with a pulse duration of 20 NS, repetition rate 10 Hz, and the point of exposure was a square of size 1×1 mm

The rate of formation of the film was 3 nm/min

The obtained thin film investigated by the method of small-angle x-ray (SAXS) (method of thin films, the incidence angle of 0.5°): a clear diffraction peak was not observed, which showed that the obtained film type In-O was amorphous. The film thickness was 80 nm.

In the obtained film of the amorphous oxide type In-O, the concentration of electronic carriers was 5×1017/cm3and the electron mobility was approximately 7 cm2/B*s.

The formation of a film of the amorphous oxide, In-Sn-O using the PLD process

Oxide film type In-Sn-O was formed on a 200 μm PET film using a target consisting of a polycrystalline sintered compact (Infor 0.9Sna 0.1)O3,1using process PLD using a KrF excimer laser. Used the device shown in 11.

The substrate for the formation of a film was a SiO2a glass substrate (Corning Co.: 1737).

As a pre-treatment prior to deposition the substrate was washed for degreasing with the use of what Finance ultrasound acetone, ethanol and ultrapure water, for five minutes each, and dried at 100°C.

The target represents the In2O3-SnO2sintered compact (the size of 20 mm in diameter and 5 mm in thickness), it got wet mixing starting materials In2O3-SnO2(4-normal reagent solution) (solvent: ethanol), firing the mixture (1000°C, 2 h), dry grinding and sintering (1550°C, 2 h).

The substrate was at room temperature. The oxygen partial pressure was 5 PA. The partial nitrogen pressure was 0.1 PA. Oxygen radicals were generated by the device for generating oxygen radicals when applied power of 200 watts.

The distance between the target and the substrate for the formation of a film was 30 mm, power KrF excimer laser was 1.5 MJ/cm2/pulse with a pulse duration of 20 NS, repetition rate 10 Hz, and the point of exposure was represented by a square with dimension equal to 1×1 mm

The rate of formation of the film was 6 nm/min

The obtained thin film investigated by the method of small-angle x-ray (SAXS) (method of thin films, the incidence angle of 0.5°): a clear diffraction peak was not observed, which showed that the obtained film type In-Sn-O was amorphous.

In the obtained film of the amorphous oxide, In-Sn-O, the concentration of electronic carriers was 8×1017/the m 3and the electron mobility was approximately

5 cm2/*Sec. The film thickness was 100 nm.

The FORMATION of a FILM OF the AMORPHOUS OXIDE TYPE In-Ga-O using the PLD PROCESS

The substrate for the formation of a film was a SiO2a glass substrate (Corning Co.: 1737).

As a pre-treatment prior to deposition the substrate was washed for degreasing using ultrasound acetone, ethanol, and ultrapure water, for five minutes each, and dried at 100°C.

The target was a sintered compact (In2O3)1-x-(Ga2About3)x(x=0-1) (size 20 mm in diameter and 5 mm in thickness). For example, when x=0.1 target is a polycrystalline sintered compact (Infor 0.9Gaa 0.1)2O3.

Target got wet mixing starting materials In2About3-Ga2About3(4-normal solution of reagents) (solvent: ethanol), firing the mixture (1000°C, 2 h), dry grinding and sintering (1550°C, 2 h).

The final pressure in the cell growth was 2×10-6PA. The oxygen partial pressure during growth was set to 1 PA.

The substrate was at room temperature. The distance between the target and the substrate for the formation of a film was 30 mm Power KrF excimer laser was 1.5 MJ/cm2/pulse with a long what inetu pulse 20 NS, repetition rate of 10 Hz. Point of exposure was represented by a square with a size of 1×1 mm, the Rate of formation of the film was 6 nm/min

The temperature of the substrate was 25°C. the oxygen Partial pressure was 1 PA. The obtained thin film investigated by the method of small-angle x-ray (SAXS) (method of thin films, the incidence angle of 0.5°): a clear diffraction peak was not observed, which showed that the obtained oxide film type In-Ga-O was amorphous. The film thickness was 120 nm.

In the obtained film of the amorphous oxide type In-Ga-O, the concentration of electronic carriers was 8×1016/cm3and the electron mobility was approximately

1 cm2/*Sec.

FABRICATION of TFT ELEMENT WITH a FILM OF the AMORPHOUS OXIDE TYPE In-Ga-Zn-O (a GLASS SUBSTRATE).

Manufactured TFT with a top shutter, shown in figure 5.

First film of the amorphous oxide type In-Ga-Zn-O manufactured on the glass substrate 1 by using the above device PLS, using a target consisting of a polycrystalline sintered compact having a composition InGaO3(Zn1O)4at a partial pressure of oxygen equal to 5 PA. Formed In-Ga-Zn-O film had a thickness of 120 nm was used as the channel layer 2.

Further, the PLD method at a partial pressure of oxygen in the chamber is below 1 PA were n is Sloane another film of the amorphous oxide type In-Ga-Zn-O with a higher electron mobility and a gold layer, each of which had a thickness of 30 nm. Then of them were formed by the drain terminal 5 and terminal 6 of the source by way of photolithography and inverse lithography.

Finally, a deposition method using electron beam evaporation was formed Y2About3film as the gate insulator (thickness of 90 nm, relative dielectric constant of about 15, the density of leakage current

1×10-3A/cm2when a voltage of 0.5 MV/cm). Then was formed the gold film, from which then the photolithography method and the method of inverse lithography was formed terminal 4 gate. The channel length was 50 μm and a width of 200 microns.

Performance evaluation of the TFT element

Figure 6 shows the current-voltage characteristic of the TFT element at room temperature. The drain current IDSincreases with increasing voltage drain VDSthat shows that the channel has a conductance of n-type.

This is consistent with the fact that the amorphous-type semiconductor In-Ga-Zn-O is a n-type semiconductor. Inssaturated (clipped) at VDS=6 V, which is typical for a semiconductor transistor. Evaluation of the performance of the shutter found that the threshold value of gate voltage VGSwhen a voltage VDS=4 is approximately -0,5 Century, the Current IDS=1,0 is 10 -5A occurs when VG=10th Century, This corresponds to the impact of the bias on the gate on the carriers in the semiconductor thin amorphous In-Ga-Zn-O film is used as the insulator.

The ratio of on/off of the transistor is higher than 1×103. Output performance calculated drift mobility, which in the region of saturation was approximately 7 cm2/B*sec. The irradiation of visible light do not change the operating characteristics of the obtained element according to the same measurement.

Amorphous oxide with a concentration of electronic carriers is lower than 1×1018/cm3can be used as a channel layer of the TFT. The preferred concentration of electronic carriers is lower than 1×1017/cm3even more preferred are lower than 1×1016/cm3.

FABRICATION of TFT ELEMENT WITH a FILM OF the AMORPHOUS OXIDE, In-Zn-Ga-O (AMORPHOUS SUBSTRATE).

Made a TFT element with the upper shutter, shown in figure 5.

First film of the amorphous oxide type In-Ga-Zn-O manufactured on plastic terphthalate (PET) substrate 1 by using the above device PLS, using a target consisting of a polycrystalline sintered compact having a composition InGaO3(ZnO) at a partial pressure of oxygen in the atmosphere, equal to 5 PA. The formed film had a thickness of 120 nm was used the Ana as a channel layer 2.

Further, the PLD method at a partial pressure of oxygen in the chamber is below 1 PA were layered one film of the amorphous oxide type In-Ga-Zn-O with a higher electron mobility and a gold layer, each of which had a thickness of 30 nm. Then of them were formed by the drain terminal 5 and terminal 6 of the source by way of photolithography and inverse lithography.

Finally, a deposition method using electron beam evaporation was formed insulator 3 shutter. Next it was formed of a gold film, from which then the photolithography method and the method of inverse lithography was formed terminal 4 gate. The channel length was 50 μm, and the width of 200 μm. Three TFT of the above-described structure is manufactured using one of three types of insulators shutter: Y2About3(thickness 140 nm), Al2O3(thickness 130 μm) and HfO2(thickness 140 μm).

Performance evaluation of the TFT element

The TFT elements formed on the PET film at room temperature had a volt-ampere characteristics similar to those shown in Fig.6. The drain current IDSincreases with increasing voltage drain VDSthat shows that the channel is n-type conductance. This is consistent with the fact that type semiconductor In-Ga-Zn-O is a n-type semiconductor. IDSsaturated (odecalc is) at V DS=6 V, which is typical for a semiconductor transistor. Current

IDS=1,0×10-8And occurs when VG=0 V, and current IDS=2,0×10-5And occurs when VG=10th Century, This corresponds to the impact of the bias on the gate on the media in the insulator, the semiconductor thin amorphous In-Ga-Zn-O film.

The ratio of on/off of the transistor is higher than 1×103. Output performance calculated drift mobility, which in the region of saturation was approximately 7 cm2/*Sec.

The elements formed on the PET film were bent to the radius of curvature of 30 mm, and in this state were measured performance characteristics of the transistor. However, in performance changes were observed. The irradiation of visible light do not change the operating characteristics of the transistor.

TFT, using as an insulator shutter Al2About3the film also had operational characteristics of the transistor, similar to those as shown in Fig.6. Current

IDS=1,0×10-8And occurs when VG=0 V, and current IDS=5,0×10-6And occurs when VG=10th Century, the Ratio of on/off of the transistor is higher than 1×102. From the output characteristics was calculated drift mobility, which in saturation is 2 cm2/*Sec.

TFT, using as an insulator shutter HfO2PL is GCC, also had operational characteristics of the transistor, similar to those as shown in Fig.6. Current

IDS=1,0×10-8And occurs when VG=0 V, and current IDS=1,0×10-6And occurs when VG=10th Century, the Ratio of on/off of the transistor is higher than 1×102. From the output characteristics was calculated drift mobility, which in saturation is 10 cm2/*Sec.

FABRICATION of TFT ELEMENT WITH a FILM OF the AMORPHOUS OXIDE In2O3TYPE using the METHOD PLD

Manufactured TFT with a top shutter, shown in figure 5.

First on plastic terphthalate (PET) substrate 1 by the PLD method has produced a film of the amorphous oxide type In2About3as the channel layer 2 with a thickness of 80 nm.

Further, the PLD method at a partial pressure of oxygen in the chamber is below 1 PA and an applied voltage of 0 V, to a device for the generation of oxygen radicals on her were layered one film of the amorphous oxide type In2O3with the greater mobility of electrons and a gold layer, each of which had a thickness of 30 nm. Then of them were formed by the drain terminal 5 and terminal 6 of the source by way of photolithography and inverse lithography.

Finally, a deposition method using electron beam evaporation was formed Y2About3the film quality of the insulator 3 for the thief. Next it was formed of a gold film, from which then the photolithography method and the method of inverse lithography was formed terminal 4 gate.

Performance evaluation of the TFT element

Studied the current-voltage characteristics of elements formed on the PET film at room temperature. The drain current IDSincreased with increasing voltage drain VDSthat showed that the channel is n-type conductance. This is consistent with the fact that the amorphous oxide film of the type In-O is a n-type semiconductor. IDSsaturated (clipped) at VDS=6 V, which is typical for a semiconductor transistor. Current IDS=2,0×10-8And occurs when VG=0 V, and current IDS=2,0×10-6And occurs when VG=10th Century, This corresponds to the impact of the bias on the gate on the carriers in the semiconductor thin amorphous In-O film.

The ratio of on/off of the transistor is higher than 1×102. Output performance calculated drift mobility, which is in the saturation region is about 1×10 cm2/*Sec. TFT element formed on the glass substrate had similar characteristics.

The elements formed on the PET film were bent to the radius of curvature of 30 mm, and in this state were measured performance characteristics of the transistor. In working ha is acteristic changes were not observed.

The fabrication of the TFT film of the amorphous oxide, In-Sn-O using the PLD process

Manufactured TFT with a top shutter, shown in figure 5.

First on plastic terphthalate (PET) film 1 by the PLD method has shaped film 2 of amorphous oxide, In-Sn-O and manufactured with a thickness of 100 nm as a channel layer.

Next on her way PLD at a partial pressure of oxygen in the chamber is below 1 PA and an applied voltage of 0 V to the device generating oxygen radicals were layered one film of the amorphous oxide, In-Sn-O with a higher electron mobility and a gold layer, each of which had a thickness of 30 nm. Then of them were formed by the drain terminal 5 and terminal 6 of the source by way of photolithography and inverse lithography.

Finally, a deposition method using electron beam evaporation was formed Y2About3the film quality of the insulator 3 of the shutter. Next it was formed of a gold film, from which then the photolithography method and the method of inverse lithography was formed terminal 4 gate.

Performance evaluation of the TFT element

Investigated the current-voltage characteristics of the TFT elements formed on the PET film at room temperature. The drain current IDSincreased with increasing voltage drain VDSthat shows that the channel has a PR the project n-type. This is consistent with the fact that the film of the amorphous oxide, In-Sn-O is a n-type semiconductor. IDSsaturated (clipped) at VDS=6 V, which is characteristic of the transistor. Current IDS=5×10-8And occurs when VG=0 V, and current IDS=5,0×10-5And occurs when VG=10th Century, This corresponds to the impact of the bias on the gate on the media in the insulator film of the amorphous oxide, In-Sn-O.

The ratio of on/off of the transistor was approximately 1×103. Output performance calculated drift mobility, which in the region of saturation was approximately 5 cm2/B*sec. TFT element formed on the glass substrate had similar characteristics.

The elements formed on the PET film were bent to the radius of curvature of 30 mm, and in this state were measured performance characteristics of the transistor. In performance changes were observed.

FABRICATION of TFT ELEMENT WITH a FILM OF the AMORPHOUS OXIDE TYPE In-Ga-O using the PLD PROCESS

Manufactured TFT with a top shutter, shown in figure 5.

First on plastic terphthalate (PET) film 1 by the PLD method shown in example 6, was shaped film 2 of amorphous oxide type In-Ga-O thickness of 120 nm as a channel layer.

Next on her way PLD at a partial pressure of oxygen in CA the ore below 1 PA and attached to the device generating oxygen radicals voltage of 0 V was layered another film of the amorphous oxide type In-Ga-O with a higher electron mobility and a gold layer, each of which had a thickness of 30 nm. Then of them were formed by the drain terminal 5 and terminal 6 of the source by way of photolithography and inverse lithography.

Finally, a deposition method using electron beam evaporation was formed Y2About3the film quality of the insulator 3 of the shutter. Next it was formed of a gold film, from which then the photolithography method and the method of inverse lithography was formed terminal 4 gate.

Performance evaluation of the TFT element

Investigated the current-voltage characteristics of the TFT elements formed on the PET film at room temperature. The drain current IDSincreased with increasing voltage drain VDSthat showed that the channel is n-type conductance. This is consistent with the fact that the film of the amorphous oxide type In-Ga-O is a n-type semiconductor. IDSsaturated (clipped) at VDS=6 V, which is characteristic of the transistor. Current IDS=1×10-8And appeared at VG=0 V, and current IDS=1,0×10-6And appeared at VG=10th Century, This corresponds to the impact of the bias on the gate on the media in the insulator film of the amorphous oxide type In-Ga-O.

The ratio of on/off of the transistor was approximately 1×102. Output performance calculated drift mobility, which is blasti saturation was approximately 0.8 cm 2/*Sec. TFT element formed on the glass substrate had similar characteristics.

The elements formed on the PET film were curved with a curvature radius of 30 mm, and in this state were measured performance characteristics of the transistor. In performance changes were observed.

Amorphous oxide with a concentration of electronic carriers is lower than 1×1018/cm3can be used as a channel layer of the TFT. The preferred concentration of electronic carriers is lower than 1×1017/cm3even more preferred are lower than 1x1016/cm3.

The examples describe above options for implementation. The present invention covers not only the invention of the first variant implementation, and the invention of the first variant of implementation together with the second invention, and the fourth, combined with the third embodiment. The present invention is not limited to the examples below.

A. an Example of the implementation of the first inventions

Example 1: manufacture of the In-Ga-Zn-O amorphous thin film

Amorphous oxide, an In-Ga-Zn-O type is applied onto a glass substrate (Corning Co.: 1737) by the method of pulsed laser deposition using a KrF excimer laser, using as a target of polycrystalline burnt casing having with the Tav InGaO 3(ZnO)4.

With this thin film is made of a MOS-transistor top type, as shown in figure 5.

First politology amorphous film InGaO3(ZnO)4the thickness of 40 nm is formed as a channel layer 2 on the glass substrate 1 using the process of forming the above-mentioned thin amorphous In-Ga-Zn-O film.

Continue to layer it In2O3the amorphous film having a higher conductivity and a gold layer, each of which has a thickness of 30 nm by a process of pulsed laser deposition. Then form the drain terminal 5 and terminal 6 of the source of the photolithography method and the method of inverse lithography.

Finally, a deposition method using electron beam deposition form Y2About3film as film 3 (thickness 100 nm, relative dielectric constant of about 15). Further on it form a gold film and then form the terminal 4 gate by the photolithography method and the method of inverse lithography.

In particular, the TFT can be manufactured locally transparent to visible light forming a gold film on at least one of the drain electrode and the source electrode to preserve the transparency. Otherwise, ITO high productivity can be used when forming the source electrode, electr is Yes drain or gate electrode, and it does not form a gold film. Can be formed TFT with such a structure, which is transparent to the visible light range. Such a TFT is preferable to actuate the display.

Preferably, the source electrode, the drain electrode and the gate electrode are transparent, and wiring for electrical connection are formed from metal with a high conductivity. With such a structure close to the source electrode, the drain electrode or the gate electrode metal wiring is applied on the transparent electrodes.

Example 2: obtain the MOS transistor

In a similar manner as in example 1 manufacture of a MOS-transistor with a top gate, shown in figure 5.

On the glass substrate 1 to form the amorphous semiconductor film of InGaO3(ZnO)4with a thickness of 30 nm as the channel layer 2.

Further it put SnO2the film thickness of 40 nm having a higher electrical conductivity, the method of pulsed laser deposition. Then form the drain terminal 5 and terminal 6 of the source by way of photolithography and inverse lithography.

Finally, a deposition method using electron beam deposition to form TiO2film as film 3, the insulating cover (thickness 110 nm, relative dielectric constant of about 11). Next on is not the form of gold foil and then forming the terminal speed by way of lithography and inverse lithography.

Thus, there is a device that is transparent to visible light in parts of the drain terminal and source terminal.

C. exemplary embodiment of the second invention

Example 3: production of In-Ga-Zn-O amorphous thin film

Amorphous oxide, In-Zn-Ga-O type is applied onto a glass substrate (Corning Co.: 1737) by the method of pulsed laser deposition using a KrF excimer laser using as a target of polycrystalline burnt body having the composition InGaO3(ZnO)4.

The TFT plate with the upper shutter is manufactured using the steps shown figa-7F.

(a) On a glass substrate 2700 form politology amorphous film InGaO3(ZnO)4a thickness of 120 nm, a size of 12 cm × 12 cm, for use as a channel layer 2701 above method for forming a thin amorphous In-Ga-Zn-O film.

(b) Maintaining the substrate in the chamber, the channel layer 2701 cover mask 2702, and another layer InGaO3(ZnO)4a film having a higher conductivity and a gold film each having a thickness of 30 nm by the method of pulsed laser deposition at a partial pressure of oxygen below 1 PA in the chamber for forming the electrode 2703 flow and electrode 2704 source. When drawing no distinction between InGaO3(ZnO)4film and a gold film.

(C) Maintaining the substrate in the chamber, remove the mask 2702 and form Y2About3film as film 2705, an insulating shutter (thickness 10 nm, relative dielectric constant of about 15), deposition using electron beam deposition. Then as the second film 2706, an insulating shutter (thickness 80 nm, relative dielectric constant of about 3.8), form a film of SiO2deposition using electron beam deposition.

(d) Film coated with photoresist and pattern for the drain electrode form a through hole 2707, and the source electrode via hole 2708. Then the film 2705, 2706, an insulating stopper, etched through the openings 2707, 2708.

(e) it is precipitated by Al from the vapor phase method, resistant to heating for forming the conductive layer 2709 thickness of 100 nm.

(f) Conductive layer 2709 made on the pattern for forming the wiring 2710, thus deactivating the drain electrode, a wired connection 2711, deducing it from the source electrode, and the electrode 2712 shutter. Thus, the stages of finish.

Using the above steps form the TFT 100 on a matrix of size 10×10 having two layers, an insulating shutter, through the same intervals.

Example 4: Production of plates TFT

The TFT plate with the upper shutter is made under the SIP the soup stages figa-8F and 9G-9L.

(a) On the glass substrate 2800 form politology amorphous InGaO3(ZnO)4the film thickness of 120 nm, a size of 12 cm × 12 cm, for use as a channel layer 2801.

(b) Maintaining the substrate in the chamber, form Y2O3film as film 2802, an insulating shutter (thickness 30 nm, relative dielectric constant of about 15), deposition using electron beam deposition.

(c) Film coated with photoresist 2803.

(d) the Photoresist 2803 form a pattern.

(e) the First film 2802, an insulating shutter is selectively etched to form a window 2804 electrode for the drain and open 2805 electrode for the source.

(f) At it another layer InGaO3(ZnO)4a film having a higher conductivity and a gold layer, and each has a thickness of 30 nm by the method of pulsed laser deposition at a partial pressure of oxygen, for example, below 1 PA in the chamber for forming the first conductive layer 2806. In the drawing, InGaO3(ZnO)4film and a gold film are the same.

(d) the unused portion of the first conductive layer 2806 removed.

(h) Thus form the electrode 2807 drain electrode 2808 source.

(i) as a layer 2809, insulating the gate, forming a film of SiO2(thickness of 30 nm, relative dielectric constant of about 3.8).

(j) From otaplivaet second film 2809, insulating the bolt through the hole 2810 electrode for the drain and through the hole 2811 electrode for the source.

(k) it is precipitated by Al from the vapor phase method, resistant to heating for forming the conductive layer 2812 thickness of 100 nm.

(1) the Second conductive layer 2812 made on the pattern for forming the wiring 2813, thus deactivating the drain electrode, a wired connection 2814, deducing it from the source electrode, and the electrode 2815 shutter. Thus, the stages of finish.

Using the above steps form the TFT 100 on a matrix of size 10×10 having two layers, an insulating shutter, over equal intervals on the substrate.

Using the structure described in the example, prevent the formation of defects such as short circuit of the gate, and the delay time variations of the electric current. Therefore, the present invention can be used for the manufacture of TFT panels, reliable and suitable for LCD panels large area and organic EL panels.

C. exemplary embodiment of the third invention

Example 5: Production of In-Ga-Zn-O amorphous thin film

Amorphous thin oxide film In-Zn-Ga-O type is applied onto a glass substrate (Corning Co.: 1737) by the method of pulsed laser deposition using a KrF excimer laser.

Sturdy child is t MOS transistor with a top gate, as shown in figure 10.

Layer 5010 (amorphous layer of silicon nitride 300 nm), which is a layer of the present invention. Put on a plastic film (PET) 5001.

On it are politology amorphous InGaO3(ZnO)4film film thickness of 35 nm as a channel layer 5002 above method for obtaining a thin amorphous In-Ga-Zn-O film.

Further on it layer layer 5100 passivating interface (amorphous silicon layer 3 nm), which is a layer of the present invention.

Further on it layer InGaO3(ZnO)4having a higher conductivity than the above politology amorphous oxide (the above-mentioned amorphous oxide), and a gold layer, each of which has a thickness of 30 nm. Then form the terminal 5007 flow and terminal 5006 source of the photolithography method and the method of inverse lithography.

Finally, form Y2About3film as film 5003, an insulating shutter (thickness of 70 nm, relative dielectric constant of about 15), and form a gold film, and then forming the terminal 5004 shutter by way of photolithography and a method of inverse lithography.

When the above-mentioned formation of thin films, such as a layer covering the surface, can be used other material, such as amorphous cu is MNI, the titanium oxide, aluminum oxide and magnesium oxide. It is preferred for improving the adhesiveness to the substrate, reducing the surface roughness of the substrate and prevent leakage current in the element.

When the above-mentioned formation of thin films, such as the passivation layer, it is possible to use another material such as amorphous silicon nitride, titanium oxide, aluminum oxide and magnesium oxide. It is preferred for improving layer, an insulating shutter, and prevent leakage current.

In this case, can be effective simple processing of the passivation. For example, treatment with an oxygen plasma (O2: 5 cm220 W, 20 s) the largest outer side of the channel is only effective to improve the boundary layer, the insulating shutter, to prevent leakage current in the element. Preferably after processing the passivation layer, the passivation of the interface can be optionally applied to prevent leakage current in the element.

Transistor using a transparent oxide film of the present invention can be used for a switching element for LCD and display devices and organic EL. The present invention can be widely used for flexible display devices using a flexible material such as plastic square the NSV, IC card and ID card, etc.

This application claims priority on patent application of Japan No. 2004-326683, filed November 10, 2004, which is incorporated here by reference.

1. Field-effect transistor containing a source electrode, a drain electrode, a gate insulator, the gate electrode and the active layer, and an active layer contains an amorphous oxide in which the concentration of electronic carriers below 1018/cm3and in which the electron mobility increases with increasing concentration of electronic carriers; and
at least one of the source electrode, drain electrode and gate electrode is transparent to visible light,
thus the current flowing between the source electrode and the drain electrode when the gate electrode is not applied voltage, does not exceed 10 µa.

2. Field-effect transistor according to claim 1, further comprising a metal wiring that is connected at least with one of the source electrode, drain electrode and gate electrode.

3. Field-effect transistor of claim 1, wherein the amorphous oxide is an oxide containing at least one of In, Zn, or Sn, or an oxide containing In, Zn and Ga.

4. Field-effect transistor containing a source electrode, a drain electrode, a gate insulator, the gate electrode and the active layer, and an active layer contains an amorphous oxide in which con is entrace electronic media below 10 18/cm3and in which the electron mobility increases with increasing concentration of electronic carriers; and having a layered structure consisting of a first layer, in which at least one of the source electrode, drain electrode and gate electrode is transparent to visible light, and a second layer consisting of a metal, or
having a layered structure consisting of a first layer in which a wired connection, at least one of the source electrode, drain electrode and gate electrode is transparent to visible light, and a second layer consisting of a metal,
thus the current flowing between the source electrode and the drain electrode when the gate electrode is not applied voltage, does not exceed 10 µa.

5. Field-effect transistor containing a source electrode, a drain electrode, a film insulating the gate electrode of the gate and the active layer,
moreover, the active layer consists of an amorphous oxide, transparent to visible light, and at least one of the source electrode, drain electrode and gate electrode is transparent to visible light,
thus the current flowing between the source electrode and the drain electrode when the gate electrode is not applied voltage, does not exceed 10 µa.

6. Field-effect transistor according to claim 5, in which a metal wiring connected to the electrode, the transparent is typical of visible light, which belongs to the source electrode, the drain electrode or the gate electrode.

7. Field-effect transistor according to claim 5, in which the amorphous oxide selected from the group consisting of an oxide containing In, Zn and Sn; an oxide containing In and Zn; an oxide containing In and Sn; and an oxide containing In.

8. Field-effect transistor containing a source electrode, a drain electrode, a film insulating the gate electrode of the gate and the active layer, and an active layer consists of an amorphous oxide in which the concentration of electronic carriers below
1018/cm3and in which the electron mobility increases with increasing concentration of electronic carriers, the gate insulator is composed of the first layer that is in contact with the amorphous oxide, and the second layer, different from the first layer and layered on the first layer,
thus the current flowing between the source electrode and the drain electrode when the gate electrode is not applied voltage, does not exceed 10 µa.

9. Field-effect transistor of claim 8, in which the first layer is an insulating layer containing HfO2, Y2About3or a mixed crystal compound containing HfO2or Y2About3.

10. Field-effect transistor of claim 8, in which the amorphous oxide is an oxide containing at least one of In, Zn and Sn, or an oxide containing the th In, Zn and Ga.

11. Field-effect transistor of claim 8, in which the first layer preferably is a layer for improving the interface to improve the properties of the interface with the active layer and the second layer is a layer for preventing current leakage to prevent leakage of electric current.

12. Field-effect transistor containing a source electrode, a drain electrode, a gate insulator, the gate electrode and the active layer,
moreover, the active layer consists of an amorphous oxide, and the gate insulator consists of a first layer in contact with the amorphous oxide, and the second layer, different from the first layer and layered on the first layer,
thus the current flowing between the source electrode and the drain electrode when the gate electrode is not applied voltage, does not exceed 10 µa.

13. Field-effect transistor according to item 12, in which the amorphous oxide selected from the group consisting of an oxide containing In, Zn and Sn; an oxide containing In and Zn; an oxide containing In and Sn; and an oxide containing In.

14. Field-effect transistor containing a source electrode, a drain electrode, a film insulating the gate electrode of the gate and the active layer,
moreover, the active layer consists of an amorphous oxide in which the concentration of electronic carriers below 1018/cm3and in which the electron mobility increases with increasing conc is the electronic media; and
between the active layer and the layer insulating the gate, there is a passivating layer,
thus the current flowing between the source electrode and the drain electrode when the gate electrode is not applied voltage, does not exceed 10 µa.

15. Field-effect transistor according to 14, in which the amorphous oxide is an oxide containing at least one of In, Zn and Sn, or an oxide containing In, Zn and Ga.

16. Field-effect transistor according to 14, in which the passivating layer is a layer for preventing current leakage, to prevent leakage of electric current.

17. Field-effect transistor containing a source electrode, a drain electrode, a gate insulator, the gate electrode and the active layer, and an active layer contains an amorphous oxide; and
between the active layer and the gate insulator is provided a passive layer
thus the current flowing between the source electrode and the drain electrode when the gate electrode is not applied voltage, does not exceed 10 µa.

18. Field-effect transistor containing a source electrode, a drain electrode, a film insulating the gate electrode of the gate and the active layer on the substrate:
moreover, the active layer contains an amorphous oxide in which the concentration of electronic carriers below 1018/cm3and in which the electron mobility increases with increasing concentration of electronic media is; and
between the active layer and the substrate includes a layer covering the surface,
thus the current flowing between the source electrode and the drain electrode when the gate electrode is not applied voltage, does not exceed 10 µa.

19. Field-effect transistor according p, in which the amorphous oxide is an oxide containing at least one of In, Zn and Sn, or an oxide containing In, Zn and Ga.

20. Field-effect transistor according p, in which the layer covering the surface, preferably is a layer that improves the adhesion, to improve the adhesiveness between the substrate and the active layer.

21. Field-effect transistor containing a source electrode, a drain electrode, a gate insulator, the gate electrode and the active layer,
moreover, the active layer contains an amorphous oxide; and
between the active layer and the substrate includes a layer covering the surface,
thus the current flowing between the source electrode and the drain electrode when the gate electrode is not applied voltage, does not exceed 10 µa.



 

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