Manufacturing method of microwave transistor with control electrode of t-shaped configuration of submicron length

FIELD: electricity.

SUBSTANCE: manufacturing method of microwave transistor with control electrode of T-shaped configuration of submicron length involves formation on the front side of semi-insulating semi-conductor plate with active layer of the specified structure of a pair of electrodes of transistor, which form ohmic contacts by means of lithographic, etching method and method of sputtering of metal or system of metals, formation of transistor channel by means of electronic lithography and etching, application of masking dielectric layer, formation in masking dielectric layer of submicron slot by means of electronic lithography and etching; at that, submicron slot is formed with variable cross section decreasing as to height from wide upper part adjacent to the head of the above control electrode to narrow lower part adjacent to transistor channel, formation of topology of the above control electrode by means of electronic lithography method, formation of the above control electrode in submicron slot by means of sputtering of metal or system of metals; at that, configuration of its base repeats configuration of submicron slot. During formation of submicron slot with variable cross section in masking dielectric layer, which decreases throughout its height, by means of electronic lithography and etching, the latter of masking dielectric layer is performed in one common production process in high-frequency plasma of hexafluoride of sulphur, oxygen and helium and discharge power of 8-10 W.

EFFECT: increasing output power and amplification factor, increasing reproducibility of the above output parametres and therefore yield ratio, simplifying and decreasing labour input for manufacturing process.

2 cl, 1 dwg, 1 tbl, 5 ex

 

The invention relates to electronic engineering microwave, and in particular to methods of manufacturing power semiconductor microwave devices, especially power transistors and monolithic microwave integrated circuits based on them.

The gain in power (the gain) and output power is one of the main parameters of the power transistors microwave.

Reduce heat and electrical resistance, reducing total internal parasitic capacitance of the transistor is one of the possible ways to improve these parameters powerful transistor microwave.

The use of the transistor control electrode with the so-called T-shaped configuration submicron length - one of the famous and widely used today for constructive solutions, which reduces electrical resistance and thereby reduce the noise factor and to increase the cutoff frequency for low noise and output power, gain and cutoff frequency for high-power microwave transistors.

A known method of manufacturing of microwave transistor with a control electrode T-shaped configuration submicron length (hereinafter control electrode), lies in the

forming on the semiconductor substrate active region of a semiconductor device,

- forming electrodes forming ohmic contacts, through the m method of lithography and etching and subsequent deposition of the metal or metals

- applying the auxiliary layer from the dielectric layer and the metal layer,

- formation of submicron cracks in this layer,

- with the subsequent formation of the crack of the control electrode by means of optical lithography,

in order to reduce the length of the control electrode submicron gap in the auxiliary layer is formed by the gap between the two masking metal layer, which is formed by selective chemical etching open from photoresistive layer sections of the first metal layer with simultaneous potroom it under photoresistive layer to the desired depth, re-deposition on the dielectric layer of the metal layer, "explosion" photoresistive layer and subsequent chemical etching of the dielectric layer through the gap,

- this T-shaped configuration of the control electrode is formed through the use of masking materials auxiliary layer and the metal control electrode [1].

As the masking metal layer, the auxiliary layer and the material of the control electrode is used the same metal is gold (AU), with a sub-layer of vanadium(V), chromium (CR) or titanium (Ti) in the first case and the combination of gold with the same material as the substrate and the upper mask layer in which the learn control electrode

Reducing the length of the control electrode in conjunction with the use of T-shaped configuration of its cross section is possible to reduce electrical resistance and, consequently, to increase the output power and the gain of the transistor microwave.

However, specific to the transistor microwave large General internal parasitic capacitance including parasitic capacitance of the control electrode, does not allow to considerably increase the output power and gain.

This method of manufacturing a transistor is difficult.

Moreover, as a result of recent low reproducibility of output parameters and a low percentage of yield.

A known method of manufacturing a powerful microwave transistor with a control electrode (gate) type of barrier of a Schottky also T-shaped configuration submicron length, consisting in

- formation on the front side of the semiconductor wafer topology of the transistor via electronic and photolithography,

the deposition of the metal or metals of the electrodes including a control electrode (gate) type of barrier of a Schottky,

the deposition and etching of the masking dielectric layer

- deposition of gold by electroplating,

- thinning semiconductor wafer to a predetermined thickness less than 30 μm,

- etching in semiconductor p is astine through ground holes for the pins of the transistor

- deposition on the back side of the semiconductor wafer of the integrated heat sink of gold given thickness by electroplating,

in order to reduce thermal resistance

before thinning semiconductor wafer on its obverse outside of the topology of the transistor form a groove of predetermined depth and width to set the size of the transistor crystal, and after thinning the semiconductor wafer to form a groove on its underside directly under the groove on the front side and with the same predetermined depth with a ratio of width 3:2, respectively, by the method of photolithography and etching [2].

A significant reduction in thermal resistance of the transistor, the order of ten percent, allowed, as a consequence, to increase the gain and power output.

However, inherent in this transistor, as described in the first analogy, most common internal parasitic capacitance including parasitic capacitance of the control electrode T-shaped configuration, do not allow more significantly increase the output power and the gain of the transistor microwave.

A known method of manufacturing of microwave transistor with a control electrode is also T-shaped configuration submicron length, consisting in

- formation of individuals who howl side politology semiconductor wafer with the active layer of the specified structure, a pair of electrodes of the transistor, forming ohmic contacts, through the lithography and etching and subsequent deposition of the metal or metals

- formation of the channel of the transistor through the gradual etching:

in the first liquid chemical etching in order to remove damaged surface layer,

the second dry etching in a high-frequency plasma gas mixture boron trichloride and sulfur hexafluoride,

- applying a masking dielectric layer of silicon nitride,

- the formation of the masking dielectric layer submicron gaps for subsequent forming in her founding of the control electrode by electronic lithography and etching,

- formation of the topology of the control electrode by electron lithography

forming in each of submicron cracks of the control electrode by a sputtering system of the metals titanium - platinum - gold, and the configuration of its Foundation the same as the configuration of submicron cracks [3 - prototype],

in order to reduce the stray capacitance of the control electrode specified sub-micron slit shape with a variable cross-section, decreasing its height from the wide upper part adjacent to the cap of the control electrode, to a narrow lower portion, adjacent to the transistor channel.

This ASU is estlat through the gradual etching of the masking dielectric layer of silicon nitride:

on the first exercise of liquid chemical etching in buffered oxide provide the Etchant, which provides an implementation of only isotropic etching, resulting in lateral leakage at a depth of about 30-40 percent of the initial thickness of the masking dielectric layer of silicon nitride, and thus provides a significant expansion of the cross-section of the upper part of submicron gap relative to a set of electronic lithography,

on the second dry etching in a high-frequency plasma cetarehhloristam carbon, which provides the implementation of anisotropic etching and vertical according to the specified e-lithography.

The result is a sub-micron gap and consequently the basis of the control electrode (gate) of the T-shaped configuration submicron length, has a cross-section of the wide upper portion, adjacent to the hat T-shaped configuration of the control electrode, and a narrow lower portion, adjacent to the transistor channel.

The ability of this method to form submicron gap with a variable cross-section and, respectively, and the base of the control electrode, thereby significantly reducing its parasitic capacitance, on the order of twenty percent, and thus reduce the overall vnutrenniy the parasitic capacitance of the transistor and, as a consequence, to increase the output power and the gain of the transistor microwave.

However, this method of manufacturing of microwave transistor with a control electrode T-shaped configuration submicron length and first of all from the point of view of the implementation of the proposed design of the control electrode, namely the gradual formation of variable cross section submicron cracks and these technological modes:

firstly, it is not possible to ensure the smoothness of the geometrical sizes of submicron gap height and smoothness of the geometric dimensions of the height of the base of the control electrode and, consequently, limits the further reduction of the parasitic capacitances mentioned control electrode and accordingly the total internal parasitic capacitance of the transistor and the output power and gain;

secondly, is quite complex, which defines the low reproducibility of output parameters and correspondingly low percentage of yield.

In addition, has a low mechanical strength - stability.

The technical result of the claimed method of manufacturing of microwave transistor with a control electrode T-shaped configuration submicron length is to increase power output and factor is selenia, improving the reproducibility of these output parameters and, consequently, yield, simplifying and reducing the complexity of manufacture.

The specified technical result is achieved by the claimed method of manufacturing of microwave transistor with a control electrode T-shaped configuration submicron length, including

- formation on the front side politology semiconductor wafer with the active layer of the specified structure, a pair of electrodes of the transistor, forming ohmic contacts, through the method of lithography, etching and subsequent deposition of the metal or metals

- formation of a channel of the transistor by electronic lithography and etching,

- applying a masking dielectric layer

- the formation of the masking dielectric layer of submicron gap by electronic lithography and etching, with submicron gap is formed with a variable cross-section, decreasing its height from the wide upper part adjacent to the cap mentioned control electrode to a narrow lower portion, adjacent to the transistor channel,

- formation of a topology referred to the control electrode of the electron lithography

- the formation of submicron gap mentioned control electrode by sputtering the metal is or metals, when this configuration is its Foundation the same as the configuration of submicron cracks.

in which

when forming a masking dielectric layer of submicron gap with a variable cross-section, decreasing its height, by electronic lithography and etching, the etch mask dielectric layer is carried out in a single process in a high-frequency plasma of the following composition: sulfur hexafluoride, oxygen, helium in the following ratio of components, OBC:

Sulfur hexafluoride12,0-18,0
Oxygen1,6-2,4
Helium12,0-18,0

and the discharge power 8-10 watts, with a wide cross-section of the upper part adjacent to the cap mentioned control electrode, and a narrow lower portion, adjacent to the channel of the transistor, is determined from the expression:

LB- LH=kN,

where LB- a wide cross-section of the upper part of submicron gap adjacent to the cap referred to the control electrode of the transistor

LH- cross-section of the narrow lower part of submicron gap adjacent to the channel of the transistor,

K - coefficient, Rav is the fourth (0,8-1,2),

H - the height of the sub-micron gap.

Is made, for example, field-effect transistor microwave shutter type barrier of a Schottky T-shaped configuration submicron length, as politology semiconductor wafer take a plate made of a semiconductor material of group AIIIBVsuch as gallium arsenide, a control electrode is the above-mentioned gate field effect transistor microwave.

The stated set of essential features of the method of manufacturing of microwave transistor with a control electrode T-shaped configuration submicron length will allow, namely:

first, as much as possible to optimize the cross-sectional area of the base of the control electrode and thereby to provide:

- the maximum reduction in stray capacitance of the control electrode and, hence, the total internal parasitic capacitance of the transistor and, consequently, increase the output power and gain,

- highest possible mechanical strength and, consequently, increase of the yield;

secondly, the possibility of the formation of submicron gap with a variable cross-section, decreasing its height, from the wide upper part adjacent to the cap of the control electrode, to a narrow lower portion, adjacent to the channel of the transistor, into a single technology is a logical process (in contrast to multi-stage process, used in the method prototype) and thus will provide:

- considerable simplification of the method of manufacturing,

- reducing the complexity of manufacturing,

- improving the reproducibility of output parameters and respectively to output.

The latter, primarily because of the possibility of a significant increase process control and, above all, due to the complete exclusion of the above-mentioned process is difficult controlled liquid chemical etching.

Etching the masking dielectric layer in the high-frequency plasma composition of sulfur hexafluoride, oxygen, helium is less than 12, 1,6 and 12 OBC respectively, and the discharge power less than 8 watts, as well as over 18, 2.4 and 18 OBC respectively, and a power exceeding 10 W is inefficient because it does not provide the optimal Foundation structure, the control electrode of the transistor.

It should again be emphasized the urgency of achieving the above-mentioned optimization of structural parameters of the control electrode, namely the cross-sectional height and respectively output parameters of the transistor, since on the one hand excessive reduction of the height of the control electrode leads to an increase in the total internal parasitic capacitance, and on the other hand excessive increase - decrease mechanical about the particular transistor microwave.

Thus, the set of essential features of the claimed method of manufacturing of microwave transistor with a control electrode T-shaped configuration submicron length will fully achieve the stated technical result, namely the increase of output power and gain, improving the reproducibility of these output parameters and, consequently, yield, simplifying and reducing the complexity of manufacture.

The invention is illustrated in the drawing, which is given a cut fragment topology microwave transistor with a control electrode T-shaped configuration submicron length, where

- front politology semiconductor wafer with an active layer of the given patterns - 1,

a pair of electrodes of the transistor, forming ohmic contacts 2 and 3 respectively,

- channel transistor 4,

masking dielectric layer 5,

- submicron gap 6 in the masking dielectric layer,

- the hat and the base mentioned control electrode 7, and 8, respectively.

Examples of specific performance.

Consider implementing the inventive method on the example of the manufacture of microwave transistor with a control electrode (gate) type of barrier of a Schottky T-shaped configuration submicron length.

Example 1.

The method includes the following sequence t the logical operations and their mode of implementation:

is formed on the front side politology semiconductor wafer 1 made of gallium arsenide (GaAs) active layers: GaAs n+type concentration of 5×1018the thickness of 500A, AlGaAs concentration of 2×1018the thickness of 200A, InGaAs not doped with a thickness of 30 A GaAs buffer non-alloy thickness of 4000 And the electrodes of the source 2 and drain 3, forming ohmic contacts, through the lithography and etching and subsequent spraying direct sequence system metals, such as alloy, gold - germanium, Nickel and gold;

- next, form a 4 channel transistor electronic lithography and subsequent etching in NH4OH: H2About2: H2O,

- next, put masking dielectric layer 5, for example a layer of silicon nitride,

- next, form the masking dielectric layer 5 submicron gap 6 through e-lithography and subsequent etching in a single technological process of masking dielectric layer 5 in the high-frequency plasma composition of sulfur hexafluoride, oxygen, helium at a ratio of 15:2:15, respectively, and the discharge power of 9 W,

next form the topology of the cap 7 and the base 8 of the control electrode by electron lithography

next formed into sub-micron slit 6 control electrode 7 by sputtering in a vacuum system m is for metal titanium - the aluminum - titanium, and the configuration of its Foundation 8 the same as the configuration of submicron cracks.

Examples 2-5.

Analogously to example one were made samples, but under different technological regimes, as specified in the claims, and beyond, with each type of sample includes ten field-effect transistors microwave with a control electrode (gate) type of barrier of a Schottky T-shaped configuration.

On prepared samples:

conducted a visual analysis using a microscope LEICA INM concerning the reproducibility of the geometric dimensions of the transistor,

b) measured output power transistor UHF (Po/mm)

b) measured gain (Kymax),

g) determined the yield (the yield was estimated by the reproducibility of the geometric dimensions of the control electrode).

The data are summarized in table.

As can be seen from the table, samples of field-effect transistors microwave with a control electrode (gate) type of barrier of a Schottky T-shaped configuration submicron length (examples 1-3) have

- output power of about 800 - 900 mW/mm

- gain (Kymax) of the order of 11.5-12 dB,

the reproducibility of the geometric dimensions of the transistor 90 percent (as opposed to 70 percent of the prototype).

Thus, the claimed method of manufacturing transit the RA microwave with a control electrode T-shaped configuration submicron length will provide:

first, the increase in power output up to 900 mW/mm

secondly, increasing the gain (Kymax) up to 12 dB;

thirdly, improving the reproducibility of 20 percent and, consequently, yield, including by improving mechanical strength;

fourth, a significant simplification and reduction in the complexity of the manufacturing process.

The microwave transistor with a control electrode T-shaped configuration submicron length, made according to the claimed method, will be widely used as the active element in hybrid, hybrid-monolithic and monolithic integrated circuit power amplifiers for various purposes.

Sources of information

1. RF patent №2192069 IPC H01L 21/338, priority 2000.07.10, publ. 2002.10.27.

2. RF patent №2285976 IPC H01L 21/335, priority 06.05.2005, publ.

3. Jong - Won Lim and gr. Fabrication and characteristics of 0,12 m AlGaAs/InGaAs/GaAs. pseudomorphic HEMT using a silicon nitride assisted process. Semicond. Sci. Technol. 19 (2004) 1416-1421 prototype.

1. The method of manufacturing of microwave transistor with a control electrode of the T-shaped configuration submicron length, including the formation on the front side politology semiconductor wafer with the active layer of the specified structure, a pair of electrodes of the transistor, forming ohmic contacts, through the method of lithography, etching and subsequent n is dusting metal or metals, the formation of the channel of the transistor by electronic lithography and etching, applying a masking dielectric layer, forming a masking dielectric layer of submicron gap by electronic lithography and etching, with submicron gap is formed with a variable cross-section, decreasing its height from the wide upper part adjacent to the cap mentioned control electrode, a narrow lower portion, adjacent to the channel of the transistor, forming a topology referred to the control electrode of the electron lithography, the formation of submicron gap mentioned control electrode by deposition of the metal or metals, and the configuration of its Foundation the same as the configuration of submicron gap, characterized in that when forming the masking dielectric layer of submicron gap with a variable cross-section, decreasing its height, by electronic lithography and etching the etch mask dielectric layer is carried out in a single process in a high-frequency plasma of the following composition is sulfur hexafluoride, oxygen, helium in the following ratio of components, OBC:

Sulfur hexafluoride 12,0-18,0
Oxygen1,6-2,4
Helium12,0-18,0

and the discharge power 8-10 watts, with a wide cross-section of the upper part adjacent to the cap mentioned control electrode, and a narrow lower portion, adjacent to the channel of the transistor, is determined from the expression:
LB-LH=CN,
where LB- a wide cross-section of the upper part of submicron gap adjacent to the cap referred to the control electrode of the transistor;
LH- cross-section of the narrow lower part of submicron gap adjacent to the channel of the transistor;
K - factor (0,8-1,2);
H - the height of the sub-micron gap.

2. The method of manufacturing of microwave transistor with a control electrode of the T-shaped configuration submicron length according to claim 1, characterized in that it is made, for example, a field effect transistor with a gate-type barrier of a Schottky T-shaped configuration submicron length, as politology semiconductor wafer take a plate made of a semiconductor material of group aIIIBVsuch as gallium arsenide, a control electrode is the above-mentioned gate field effect transistor.



 

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