JPH03187213A - Manufacture of semiconductor crystal - Google Patents

Abstract

PURPOSE:To enable epitaxial growth of semiconductor crystal having less crystal defects whose lattice constant is different from that of a semiconductor substrate on the substrate by heating and treating the semiconductor substrate at a temperature higher than an epitaxial growth temperature, by forming crystal of the same component as the substrate on the substrate, and by heating the substrate to realize an epitaxial growth temperature. CONSTITUTION:After a semiconductor substrate 1 is heated and treated in inert gas atmosphere or vacuum atmosphere at a temperature higher than an epitaxial growth temperature, a crystal 7 of the same component as the substrate 1 is formed on the substrate 1. The substrate 1 is heated to an epitaxial growth temperature and dissimilar crystal 10 of different lattice constant is formed on the substrate 1 by epitaxial growth. That is, after a surface of the GaAs substrate 1 is cleaned, the GaAs crystal 7 is further formed on the substrate 1 by epitaxial growth to fill in an area wherein arsenic atom which is evaporated by cleaning treatment is dissociated. CdTe crystal 10 is formed by epitaxial growth in this way on the crystal defect-free high quality GaAs crystalline substrate 7 wherein an area of dissociated arsenic atom is filled; thereby, crystal defect-free crystal of high quality CdTe can be acquired.

Description

[Detailed Description of the Invention] [Summary] A method of epitaxially growing a semiconductor crystal having a different lattice constant from that of the substrate on a semiconductor substrate, the method involves epitaxially growing a semiconductor crystal having a different lattice constant from that of the substrate on a semiconductor substrate in a state with few crystal defects. With the purpose of A different crystal having a lattice constant different from that of the substrate is epitaxially grown on the substrate by heating the substrate to a certain temperature.

[Industrial application field]

The present invention relates to a vapor phase epitaxial growth method, and more particularly to a method of vapor phase epitaxial growth of a semiconductor crystal having a different lattice constant from that of the substrate on a semiconductor substrate in a state where crystal defects are less likely to occur.

Mercury, cadmium, and tellurium ("gI-w"), which have a narrow energy band gap, are used as materials for forming infrared sensing elements.
A compound semiconductor crystal such as CclgTe) is used, and a vapor phase epitaxial growth method is used to obtain the crystal in a large area and in a thin layer for convenient device formation.

By the way, when epitaxially growing such a Hg+-x Cdx Te crystal, the "g+-x c
A CdTe crystal having a lattice constant close to that of a dxTe crystal is used as a substrate crystal, but a problem with this CdTe crystal is that it is difficult to manufacture and obtain a large-area single crystal.

Therefore, a gallium arsenide (GaAs) crystal, which is relatively easy to obtain a large-area single crystal, is used as a substrate for epitaxial growth, and a cadmium-zinc-tellurium (CdTe) crystal or a cadmium-zinc-tellurium (CdZnTe) crystal is grown on it. After epitaxial growth, Hg1-11 is added on top of it.
A method has been adopted in which cd and Te crystals are grown by vapor phase epitaxial growth.

[Conventional technology]

Since GaAs crystals, CdTe crystals, and CdZnTe crystals have different lattice constants, the above C
When a dTe crystal or a CdZnTe crystal is epitaxially grown, the lattice mismatch between the substrate and the epitaxial crystal (difference in lattice constant of each crystal/average value of lattice constant of each crystal) is as large as about 14%, so (100) When a CdTe crystal having a (100) crystal plane is grown on a GaAs substrate having a (100) crystal plane, a problem arises in that many dislocations occur in the epitaxially grown CdTe crystal due to lattice mismatch.

Therefore, in the past, GaA with a (100) crystal growth plane was used.
After placing the s substrate in the epitaxial growth container, the G
By heating the aAs substrate to a temperature of about 600"C and heat-treating it for 20 minutes, the GaA attached to the surface of the substrate can be removed.
After cleaning the substrate surface by removing foreign substances such as s oxides, the substrate is lowered to a temperature of 300 to 400''C, and the CdTe crystal is MOCVD (
Metal Organic Chemical Va
porDeposition method, real wall epitaxial growth method, or molecular beam epitaxial growth method.

Before growing a CdTe crystal on a GaAs substrate by vapor phase epitaxial growth, if the surface of the GaAs substrate is heat treated to clean the substrate surface, the (100) plane G
A (111)-plane CdTe crystal is epitaxially grown on an aAs substrate with few crystal defects.

[Problem to be solved by the invention]

However, in the conventional method, when the surface of the GaAs substrate is cleaned, arsenic (As) atoms with high vapor pressure dissociate from the substrate due to heating of the substrate, and as a result, the arsenic atoms dissociate. Crystal defects occur at locations in the GaAs substrate, and G with such crystal defects
When a CdTe crystal is epitaxially grown on an aAs substrate, there is a problem that crystal defects are likely to occur in the formed CdTe crystal as well.

The present invention aims to solve the above problems and provide a method for epitaxially growing a high quality CdTe crystal with few crystal defects on the GaAs substrate.

[Means to solve the problem]

The above purpose is to heat-treat a semiconductor substrate at a temperature higher than the epitaxial growth temperature and in an inert gas atmosphere or a reduced pressure atmosphere, grow a crystal having the same composition as the substrate on the substrate, and then bring the substrate to the epitaxial growth temperature. This is achieved by the method of manufacturing a semiconductor crystal of the present invention, in which a heterogeneous crystal having a lattice constant different from that of the substrate is epitaxially grown on the substrate by heating the substrate so that the lattice constant is different from that of the substrate.

[For production]

In the method of the present invention, after cleaning the surface of a GaAs substrate, a GaAs crystal is epitaxially grown on the substrate to fill in the dissociated portions of arsenic atoms evaporated by the cleaning treatment. And high-quality G with no crystal defects, where the dissociated arsenic atoms are filled in.
When a CdTe crystal is epitaxially grown on an aAs crystal substrate, a high quality CdTe crystal without crystal defects can be obtained.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a cross-sectional view of a semiconductor crystal formed by the method of the present invention;
FIG. 2 is a schematic diagram of an apparatus used in the method of the present invention, and FIG. 3 is a heating temperature profile diagram of a substrate in the present invention.

As shown in FIGS. 1 and 2, a GaAs substrate 1 whose substrate surface is a (100) plane tilted 2 degrees in the <110> direction is housed in a container 2 for the epitaxial growth phase, and then bulbs 4 and 5 are installed. The inside of the container is evacuated and depressurized using a vacuum pump connected to the exhaust pipe 3, and the substrate is heated for 20 minutes at a temperature of 600° C. as shown in FIG. 3, and the substrate surface is cleaned. to remove foreign substances such as oxides adhering to the substrate surface.

Next, with valve 4 open and valve 5 closed, arsine (8sl+) is applied onto the cleaned substrate.
gas, and trimethylgallium/,% (Ga(C
Hydrogen gas was introduced into the evaporator 6 containing Il*) *, and the hydrogen gas supporting the trimethyl gallium was introduced into the container, and the temperature of the substrate was lowered to 440°C, and the temperature was maintained at this temperature for 1 hour. A GaAs crystal 7 is epitaxially grown on the substrate to a thickness of about 1 μm.

Next, valve 4 is closed, valve 5 is opened to lower the temperature of the substrate to 370° C., and the evaporator 8 containing dimethyl cadmium and the evaporator containing diisopropyl tellurium are placed on the substrate. Hydrogen gas is introduced into the epitaxial growth container 2, and the hydrogen gas supporting the components of the raw material liquid for epitaxial growth contained in these evaporators is introduced into the epitaxial growth container 2, and the CdTe crystal 1o is epitaxially grown.

In this way, since the GaAs substrate is a high quality substrate free of crystal defects, the CdT formed on it
A high quality epitaxial crystal can also be obtained from the epitaxial crystal of e.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, CdT
Because the GaAs substrate on which the e-crystal is grown is made of a high-quality substrate that does not produce crystal defects,
Since the CdTe crystal formed thereon can also be obtained with high quality, the Hgr-x Cd
x Tt3 epitaxial crystal also has the effect of obtaining high quality crystals.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a semiconductor crystal formed by the method of the present invention, FIG. 2 is a schematic diagram of an apparatus used in the method of the present invention, and FIG. 3 is a heating temperature profile diagram of a substrate in the present invention. In the figure, 1 is a GaASa plate, 2 is a container, 3 is an exhaust pipe, 4.5 is a valve, 6, 8.9 is an evaporator, 7 is a GaAs crystal, and 1o is a CdTe crystal.

Claims (1)

[Claims] After a semiconductor substrate (1) is heat-treated at a temperature higher than the epitaxial growth temperature and in an inert gas atmosphere or a reduced pressure atmosphere, a crystal (7) having the same composition as that of the substrate is grown on the substrate. Then, the substrate is heated to the epitaxial growth temperature to form a heterogeneous crystal (1) having a different lattice constant from that of the substrate.
A method for producing a semiconductor crystal, characterized in that 0) is epitaxially grown.