Method for preparing even-atom surface of gallium arsenide

FIELD: microelectronics, namely processes for preparing even-atom surfaces of semiconductors.

SUBSTANCE: method comprises steps of chemical-dynamic polishing of substrate surface in polishing etching agent containing sulfuric acid, hydrogen peroxide and water for 8 - 10 min; removing layer of natural oxide in aqueous solution of hydrochloric acid until achieving hydrophobic properties of purified surface of substrate; washing it in deionized water and drying in centrifuge. Then substrate is treated in vapor of selenium in chamber of quasi-closed volume while forming gallium selenide layer at temperature of substrate Ts = (310 -350)°C, temperature of chamber walls Tc = (230 - 250)°C, temperature of selenium Tsel = (280 - 300)°C for 3 - 10 min. After such procedure substrate is again placed in aqueous solution of hydrochloric acid in order to etch layer of gallium selenide. Invention allows produce even-atom surface of gallium arsenide at non-uniformity degree such as 3Å.

EFFECT: possibility for using substrates for constructing nano-objects with the aid of self-organization effects.

4 dwg

 

The invention relates to microelectronics, in particular to a method of preparing nuclear-smooth surfaces of semiconductor substrates.

Closest to the technical essence and the achieved effect to the proposed method is chemical-dynamic polishing (CDA) the surface of a semiconductor. By common polishing stain for GaAs are solutions on the basis of H2SO4:H2O2:H2O with a ratio of 3:1:1 to 30:1:1. After the CDA provide the Etchant in this sample is washed in deionized water and treated in a solution of N2O:HCl=10:1 for removing a layer of natural oxide, and then washed in deionized water and then dried in a centrifuge. (Physico-chemical methods of surface treatment of semiconductors. Bedloft, Vairuotoj, Linozelou, Iasonos, Cgimain.; Under. edit Bedloft. - M.: Radio and communication, 1982. - 136 C., Il.)

The disadvantage of this method - after polishing the CDA in a solution of N2SO4:H2A:H2Oh and treatment in a solution of N2O:HCl=10:1 on the surface of the gallium arsenide present heterogeneity with a scale of about 15 nm (figure 1), which prevents the use of GaAs as a substrate for the formation of quantum-well systems.

An object of the invention is to obtain atomic-smooth surface of the gallium arsenide masshtaba heterogeneity is less than the lattice period.

The technical problem is achieved in that in the method of obtaining atomic-smooth surface of a substrate of gallium arsenide, including chemical-dynamic polishing the semiconductor surface in the polishing provide the Etchant containing sulfuric acid, hydrogen peroxide and water, for 8÷10 min, the removal of a layer of natural oxide in aqueous hydrochloric acid solution until the symptoms of the hydrophobic properties of the pure surface of a substrate of gallium arsenide, rinsed in deionized water and drying in a centrifuge, after drying, the substrate is treated in pairs of selenium in the camera close spaced sublimation technique volume with the formation of a layer of gallium selenide at a temperature of the substrate is Tp=(310÷350)°C, the temperature of the chamber walls - Twith=(230-250)°C, the temperature of the selenium - TSe=(280÷300)°C for 3÷10 min, after which the substrate is placed again on 10÷15 min in an aqueous solution of hydrochloric acid to release the layer of gallium selenide.

Figure 1. Topology (a) and cross section of the surface (b) of gallium arsenide after the CDA in a solution of H2SO4:H2About2:H2O=5:1:1.

Figure 2. Topology (a) and cross section of the surface (b) of gallium arsenide after processing in pairs selenium and subsequent etching of layer Ga2Se3in a solution of N2O:HCl=10:1

The technical result consists in achieving its objectives, namely to obtain atomic-g is adcoy the GaAs surface with scale heterogeneity of the order of 3Å (figure 2).

The method of obtaining atomic-smooth surface of a substrate of gallium arsenide is as follows.

A substrate of gallium arsenide chemical dynamically polished in a solution of N2SO4:H2O2:H2O=5:1:1 for 8÷10 min, then a solution of N2O:HCl=10:1 remove the layer of natural oxide before the onset of hydrophobic properties clean the surface of the GaAs substrate, then the substrate is washed with deionized water and dried in a centrifuge, and then the substrate is placed in a chamber close spaced sublimation technique volume (CSO), in which processing occurs in pairs of selenium at a temperature of the substrate is Tp=(310÷350)°C, the temperature of the chamber walls - Twith=(230÷250)°C, the temperature of the selenium - TSe=(280÷300)°C for 3÷10 minutes the Temperature is measured using a chromel-aluminievyh of thermocouples installed in the appropriate areas of the chamber.

According to the data obtained through the study of data structures in the transmission electron microscope (TEM) Hitachi H-800, it was found that when the above processing parameters on the surface of gallium arsenide is formed pseudomorphs relative to the substrate layer Ga2Se3oriented in the direction [110]. The film thickness Ga2Se3(110), estimated from ellipsometric measurements on the device LEF-3M, amounted to (7÷12) nm.

The mechanism of film growth Ga2Se3(110) surface of GaAs (100), according to the authors should be regarded under two behind each other mechanisms:

- education Ga2Se3in the heterovalent substitution of arsenic in the lattice of gallium arsenide on selenium (adsorbed on the sample surface) by the reaction:

- sverhkategorijnye for Ga2Se3the gallium atoms left after the reaction (1) are on the surface of the sample, where the "flock" in fossa, formed after the CDA gallium arsenide, and participate in education Ga2Se3directly reacting with selenium by the reaction:

This reaction provides the 2nd mechanism of formation of gallium selenide in the process of thermal annealing in GaAs pairs of selenium. Layer Ga2Se3formed under the first mechanism, grows inside the GaAs surface, while the second one out.

After processing in pairs selenium obtained sample is incubated in a solution of N2O:HCl=10:1 for 10÷15 min to bleed layer Ga2Se3. No selenide on the surface of gallium arsenide after this treatment was monitored using x-ray microanalysis, as well as to increase the height of the barrier (ϕb) diode the Schottky Al/GaAs, calculated from the volt-ampere characteristics (VAC), to the value corresponding to the value of ϕbon the original (not treated in selenium) surface.

The method is illustrated with an example.

For the experiment were chosen n - GaAs (100) grade AGC-25A (Nd˜1016cm-3), the surface of which is chemical-dynamically polished in a solution of H2SO4:H2About2:H2O=5:1:1 for 10 min, and then for 5 min was maintained in a solution of H2O:HCl=10:1, after which the substrate was rinsed in deionized water and dried in a centrifuge.

The study of the topology of the polished surface of GaAs was carried out using atomic force microscope (AFM) NT-MDT Solver Pro. The resulting image is shown in figure 1.

Then the sample was placed in a chamber close spaced sublimation technique volume (CSO), where for 5 min was processed in pairs of selenium in the following process conditions: temperature of the substrate of GaAs - Tp=330°C, the temperature of the chamber walls - Twith=235°temperatures selenium - TSe=280°C.

Formation on the surface of the investigated GaAs (100) pseudomorphs layer Ga2Se3, (110) was found by using the obtained sample mode microdiffraction in TEM Hitachi H-800 at an accelerating voltage of 200 kV, and the amount calculated from I-V characteristics of the height of the barrier (ϕbin SFOR is new on the treated selenium surface of the gallium arsenide diode Schottky Al/Ga 2Se3/GaAs to a value of 0.5 eV. The film thickness Ga2Se3(110), estimated from ellipsometric measurements on the device LEF-3M, was 10 nm.

At the last stage of film Ga2Se3(110) to be removed from the surface of the substrate GaAs (100) etch for 10 minutes in a solution of N2O:HCl=10:1. No film Ga2Se3recorded using x-ray spectral microanalysis, as well as to increase ϕbthe Schottky diode to a value of 0.75 eV, which corresponds to the case of forming the diode is not processed in sälen the GaAs surface.

The proposed method allows to obtain atomic-smooth surface of a substrate of gallium arsenide with the scale of the inhomogeneity of the order of 3Å (2)that gives the possibility to use the data base for the design of nano-objects with the effects of self-organization.

The method of obtaining atomic-smooth surface of a substrate of gallium arsenide, including chemical-dynamic polishing the substrate surface in the polishing provide the Etchant containing sulfuric acid, hydrogen peroxide and water for 8÷10 min, the removal of a layer of natural oxide in aqueous hydrochloric acid solution until the symptoms hydrophobic properties clean the surface of the substrate, rinsed in deionized water and drying in a centrifuge, wherein after drying, the substrate is treated in PA is Oh selenium in the chamber close spaced sublimation technique volume with the formation of a layer of gallium selenide at a temperature of the substrate is Tp=(310-350)°C, the temperature of the chamber walls - Twith=(230-250)°C, the temperature of the selenium - TSe=(280-300)°C for 3÷10 min, after which the substrate is placed again on 10÷15 min in an aqueous solution of hydrochloric acid to release the layer of gallium selenide.



 

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