JPH06124863A - Gaas compound semiconductor substrate - Google Patents

Abstract

PURPOSE:To improve the yield of the manufacture of a semiconductor device, to make a pretreatment such as etching useless at the time of an epitaxial growth by MBE apparatus, etc., and to thin a buffer layer to improve productivity by using a substrate satisfactory in the crystalline property and stability of surface. CONSTITUTION:In the title GaAs compound semiconductor substrate, the difference between the ratio GaAs of the number of atoms of gallium to that of arsenic within 10nm from the surface and the ratio (Ga/As)c of the number of atoms of gallium to that of arsenic in the cleavage plane of a GaAs single crystal (110) is within + or -0.2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a GaAs compound semiconductor, and more particularly to a substrate provided with a surface layer such that the atomic ratio Ga / As of gallium and arsenic on the cleaved surface and the surface layer is substantially equal.

[0002]

2. Description of the Related Art Generally, a GaAs compound semiconductor substrate (hereinafter abbreviated as GaAs substrate) manufacturing process is carried out in the order of lapping, etching, polishing and final cleaning after slicing a single crystal ingot. In the semiconductor device manufacturing process, after the GaAs substrate is subjected to pretreatments such as etching and cleaning, processes such as ion implantation and epitaxial growth are performed. In the conventional GaAs substrate, the atomic number ratio of gallium to arsenic should be theoretically 1: 1 in the surface layer due to the difference in the dissociation rate of gallium and arsenic in processing such as polishing, etching, and cleaning. It was very different from. This was clear, for example, by comparing the Ga / As ratio of the cleaved surface obtained by cleaving the same GaAs substrate surface with an arbitrary measurement method.

[0003]

Since the composition ratio of gallium and arsenic on the surface is different from the stoichiometric composition ratio,
There is a problem that the crystallinity of the surface becomes poor and the stability of the surface also becomes low. For this reason, a pretreatment such as etching was performed before actually laminating other layers for forming an element on the GaAs substrate, but this time there is a problem that the surface becomes rough due to the pretreatment. , Improvement was desired.

[0004]

As a result of intensive studies, the present inventors have found that such a problem is caused by the fact that a large amount of either gallium or arsenic is eluted by a cleaning solution or the like, and The present inventors have found that such problems can be solved by carrying out final cleaning using the same, and reached the present invention. That is, an object of the present invention is to provide a GaAs compound semiconductor substrate having high crystallinity and stability, and an object thereof is to provide an atomic ratio Ga / As of gallium to arsenic within 10 nm from the surface and a GaAs single crystal (110 ) The final polished GaAs compound semiconductor substrate, and the final polished Ga, characterized in that the difference between the atomic number ratio (Ga / As) _C of gallium and arsenic on the cleavage plane is within ± 0.2.
In the method of manufacturing an As compound semiconductor substrate, the atomic number ratio (Ga / As) of gallium and arsenic on the substrate surface is measured immediately before the final cleaning step, and the value of (Ga / As) is G
When the atomic number ratio (Ga / As) _C of gallium to arsenic on the cleavage plane of the aAs single crystal (110) is larger than _C , an alkaline solution is used for the final cleaning, and when it is smaller, a polar organic solvent is used for the final cleaning. This can be easily achieved by a method of manufacturing a final polished GaAs compound semiconductor substrate, which is characterized in that the difference between (Ga / As) and (Ga / As) _C is ± 0.2 or less. The present invention will be described in more detail below.

The final polished GaA used in the present invention
s compound semiconductor substrate (hereinafter referred to as GaAs compound semiconductor substrate) is manufactured by lapping, etching, polishing, and final cleaning steps of a single crystal ingot made by an arbitrary method and sliced by an arbitrary method. . However, depending on the conditions, some of the lapping, etching, and polishing steps may be omitted.

In the GaAs compound semiconductor substrate of the present invention, after performing lapping, etching, and polishing by arbitrary methods, and before the final cleaning, the atomic number ratio (Ga / As) of gallium and arsenic within 10 nm from the surface is set. The amount of gallium was measured by an arbitrary method and compared with the atomic number ratio (Ga / As) _C of the (110) cleavage plane of the GaAs single crystal by the same method as that for measuring (Ga / As). If the amount is large, an alkaline solution is used, and if the amount of arsenic is large, a polar organic solvent is used for the final cleaning. The present inventors have surprisingly found that when an alkaline solution is used for this final cleaning, a large amount of gallium and a large amount of arsenic are eluted in the organic polar solvent (Ga
/ As) Ga close to _C , that is, close to stoichiometric composition ratio
They have found that an As compound semiconductor substrate can be obtained. As the alkaline solution used in the present invention, various known ones can be used, but ammonia water is preferable, and ammonia water of 1 to 30% is particularly preferable. Various known polar organic solvents can be used, but acetone, methyl ethyl ketone, methanol, ethanol and isopropyl alcohol are preferable, and isopropyl alcohol is particularly preferable.

The method for measuring (Ga / As) and (Ga / As) _C used in the present invention is also (Ga / As).
There is no particular limitation as long as As) and (Ga / As) _C are measured by the same measuring method, but X-ray photoelectron spectroscopy (XPS) is preferable. As a specific example, when the measurement method using XPS is given, the analysis depth is set to 10 nm or less, and Ga
There is a method of obtaining from the area intensity ratio of the narrow spectrum of −3d and As-3d. Needless to say, when the method of the present invention is used, it is clear that it is not necessary to measure the atomic ratio of gallium to arsenic for each substrate, and the measurement may be performed once under certain conditions.

The present invention will be described below with reference to examples, but the present invention is not limited to the examples as long as the gist thereof is not exceeded.

[0009]

EXAMPLE As an example of the present invention, a GaAs single crystal ingot obtained by a known method was subjected to slicing, lapping, etching, and polishing by a known method, and an ammonia water (3
%, 25 ° C., 5 minutes) immersion cleaning, followed by ultrapure water cleaning (20
(° C, 10 minutes), spin dry (5000 rpm)
As for the GaAs substrate and the GaAs substrate that was subjected to IPA immersion cleaning (25 ° C., 15 minutes) while irradiating ultrasonic waves, as the final cleaning of the above-described processing step as a comparative example, after cleaning with ultrapure water. The difference in surface condition will be described. Here, it is preferable that the concentration of the ammonia water is 1 to 30%, the temperature is 10 to 90 ° C., and the cleaning time of the ammonia water is 1 minute or more.

Table 1 shows the results of measuring the elemental composition ratio on the surface of the GaAs substrate by X-ray photoelectron spectroscopy (XPS).
The analysis depth is 5 nm. The Ga / As ratio was 1.4 in the GaAs substrate before the final cleaning, but was G in the example.
The value was 1.3 for the aAs substrate, equivalent to 1.3 for the (110) cleavage plane, and 1.6 for the GaAs substrate of the comparative example. Here, the element composition ratios are Ga-3d and As-3d.
Was obtained from the area intensity ratio of the narrow spectrum of.

Photoluminescence band edge emission (PL emission) at room temperature to evaluate the quality of surface crystals
The result of measuring the intensity of the is shown in FIG. Example GaAs
The substrate has a good semiconductor surface with a higher emission intensity than the GaAs substrate of the comparative example. In order to evaluate the crystallinity of the surface, GaA was measured by reflection high-energy electron diffraction (PHEED).
The result of observing the s substrate is shown in FIG. FIG. 2 shows a state after heating to 580 ° C. while irradiating with an As beam. Sharp spots and streak patterns were observed on the GaAs substrate (a) of the example, indicating that the GaAs substrate (a) had better crystallinity than the GaAs substrate (b) of the comparative example.

In order to evaluate the stability of the surface, the change over time in the intensity of the band edge emission of photoluminescence at room temperature was measured for the GaAs substrate of the example and the GaAs substrate of the comparative example, and the results are shown in FIG. The substrate was stored in the atmosphere. The deterioration amount of the emission intensity of the GaAs substrate of the example is
It can be seen that it is smaller than that of the GaAs substrate of the comparative example.

FIG. 4 shows the result of measurement by electron energy loss spectroscopy (EELS) in order to evaluate the oxide film thickness on the surface.
Shown in. The peak at 16.4 eV is due to the volume plasmon of GaAs and indicates the existence of a GaAs single crystal structure.
This peak is already observed on the substrate of this example at an analysis depth of 5Å. At the analysis depth of 8 Å, both the substrates of this example and the comparative example are observed, but a stronger peak is observed in the substrate of this example.

From these results, it is understood that the GaAs substrate of the embodiment has good surface crystallinity, has a thin oxide film serving as a protective film on the surface, and has good surface stability.

[0015]

[Table 1]

[0016]

Industrial Applicability By using a substrate having a good surface crystallinity and a good surface stability, the production yield of semiconductor devices is improved. Pre-treatment such as etching is not required at the time of epitaxial growth with an MBE apparatus or the like, and the buffer layer can be thinned, and productivity can be improved.

[Brief description of drawings]

FIG. 1 is a comparison diagram of PL emission intensities.

FIG. 2 is a diagram showing a crystal structure according to an RHEED pattern.

FIG. 3 is a diagram showing a temporal change in PL emission intensity.

FIG. 4 is a diagram showing a surface analysis by EELS.

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[Procedure amendment]

[Submission date] September 22, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Figure 2

[Correction method] Change

[Correction content]

FIG. 2 is a photograph showing a crystal structure according to a RHEED pattern.

Claims (2)

[Claims] 1. The difference between the atomic ratio Ga / As of gallium and arsenic within 10 nm from the surface and the atomic ratio of gallium to arsenic (Ga / As) _C on the cleavage plane of the GaAs single crystal (110) is ± 0. Final polished GaAs compound semiconductor substrate characterized by being within 0.2. 2. In the method of manufacturing a GaAs compound semiconductor substrate which has been finally polished, immediately before the final cleaning step, the atomic number ratio (Ga / As) of gallium and arsenic on the surface of the substrate is measured to obtain the (Ga / As). ) Is a GaAs single crystal (11
0) The atomic ratio of gallium to arsenic on the cleavage plane (Ga / A
s) When it is larger than _C , an alkaline solution is used for the final washing, and when it is smaller, a polar organic solvent is used for the final washing, and the difference between the (Ga / As) and (Ga / As) _C is ± 0.2. A method of manufacturing a finally polished GaAs compound semiconductor substrate, characterized in that: