JP2000034198A - Silicon carbide single crystal and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a large, high purity, high-quality single crystal hardly containing grain boundary, micropipe defect, etc. SOLUTION: This single crystal is produced by preparing a complex M in which a β-SiC polycrystalline layer 2 is formed on the surface of a β-SiC single crystal substrate 1 by the thermal CVD method, by heat-treating the complex M at 2,100-2,400 deg.C to recrystallize a polycrystal of the layer 2 and to transform it into a single crystal and by making single crystals, including the above single crystal and α-SiC single crystal substrate 1, in a state that their crystal axes are oriented in the same direction, grow a lot in a unified state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single crystal SiC and a method of manufacturing the same, and more particularly, to a single crystal SiC used as a light emitting diode or a substrate wafer of an electronic device, and a method of manufacturing the same.

[0002]

2. Description of the Related Art SiC (silicon carbide) is not only excellent in heat resistance and mechanical strength, but also resistant to radiation. In addition, it is easy to control valence electrons and holes by adding impurities. Has a wide forbidden band (By the way, 6H type S
about 3.0 eV for an iC single crystal and 3.26 eV for a 4H type SiC single crystal), such as Si (silicon) or GaAs.
(Gallium arsenide) and other materials that can not be realized with existing semiconductor materials, can achieve high capacity, high frequency, withstand voltage and environmental resistance, and are attracting attention and expected as next-generation semiconductor materials for power devices I have.

As a method of growing (manufacturing) this kind of SiC single crystal, conventionally, a raw material SiC powder is sublimated in a graphite crucible, and the sublimation gas is diffused and transported in a closed space, and is placed in a low-temperature portion of the crucible. Sublimation recrystallization method (improved Rayleigh method) in which recrystallization is performed on the seed crystal, or cubic crystal is formed by epitaxial growth using a chemical vapor deposition method (CVD method) on a Si (silicon) substrate at a high temperature. A high temperature epitaxial method or the like for growing a SiC single crystal is known.

[0004]

However, among the above-mentioned conventional manufacturing methods, the improved Rayleigh method has the following disadvantages.
Although the growth rate of crystal growth and the growth of large single crystals have become possible, micro-pipe defects with a diameter of several microns that penetrate the crystal in the direction of crystal growth that cause leakage current when manufacturing semiconductor devices 10 pinholes
About 0 to 1000 / cm ^2, single crystal SiC which easily remains in the grown crystal and has a quality sufficient to satisfy the requirements as a semiconductor device has not been obtained. In addition, the high-temperature epitaxial method requires a high substrate temperature, a large amount of re-evaporation due to the high temperature of the substrate, and it is necessary to create a high-purity reducing atmosphere. Therefore, the crystal growth rate is naturally limited,
There is a problem that productivity of single crystal SiC is very poor,
Although this has many excellent features as compared with existing semiconductor materials such as Si and GaAs as described above, it is a factor that hinders its practical use.

In view of the above circumstances, the present applicant has proposed α-Si
Β-S on the surface of C single crystal substrate by thermochemical vapor deposition
By heat-treating the composite formed with the iC layer,
A completely new method for producing single-crystal SiC, in which a polycrystalline body of the β-SiC layer is converted into α-SiC and a single crystal oriented in the same direction as the crystal axis of the α-SiC single crystal base material is integrally grown. Has been developed and has already been proposed as a patent application. According to this already proposed manufacturing method, simply performing high-temperature heat treatment without requiring special equipment,
A high-quality single crystal SiC having very few crystal grain boundaries and micropipe defects can be manufactured with high productivity, and the technology has reached a technical level where practical application as a semiconductor material can be promoted.

As a result of further research on the above-mentioned manufacturing method which has been already proposed, the applicant has found that when an α-SiC single crystal base material is used as a single crystal base material serving as a seed crystal,
The single crystal base material itself is limited in film thickness and area, and it is difficult to obtain a large single crystal SiC as a final product. In addition, since α-SiC single crystals are grown at high temperatures, it is difficult to obtain high purity due to impurities and the like during the growth process, and there is room for improvement in quality. did.

The present invention has been made based on the above-mentioned findings, and has very few crystal grain boundaries and micropipe defects, and is excellent not only in productivity but also in a very large size. It is another object of the present invention to provide a single-crystal SiC capable of significantly improving quality and a method for manufacturing the same.

[0008]

In order to achieve the above object, a single-crystal SiC according to the first aspect of the present invention comprises a β-S
By performing a heat treatment on the composite formed by forming a β-SiC polycrystalline layer on the surface of the iC single crystal base material, the polycrystalline body of the β-SiC polycrystalline layer is recrystallized and converted into a single crystal, Α-SiC single crystal whose crystal axis is oriented in the same direction including the single crystal part and the β-SiC single crystal base material are grown integrally,
Further, in the method for producing single-crystal SiC according to the invention of claim 4, after forming a β-SiC polycrystalline layer on the surface of the β-SiC single-crystal base material, the composite is converted to a non-atmospheric pressure or lower. The polycrystalline body of the β-SiC polycrystalline layer is recrystallized and converted into a single crystal by performing a heat treatment in an active gas atmosphere and under a SiC saturated vapor pressure, and the converted single crystal portion and the β-SiC polycrystalline layer are converted to a single crystal. The present invention is characterized in that an α-SiC single crystal whose crystal axes are oriented in the same direction including a SiC single crystal substrate is integrated and grown.

According to the first and fourth aspects of the present invention having the above constitutional requirements, the above-described manufacturing method which has been already proposed by the present applicant as a single crystal base material serving as a seed crystal. By using a β-SiC single crystal instead of the α-SiC single crystal used in the above, a large single crystal base material (seed) having a very large film thickness and area compared to the case of using an α-SiC single crystal As a result, it is easy to obtain a large-sized single-crystal SiC having a wide range of application as a semiconductor material even as a final product, single-crystal SiC. Further, a β-SiC single crystal can be grown at a relatively low temperature, and impurities and the like hardly enter during the growth process.
Easy to obtain high purity single crystal.

[0010] A complex formed by using such a large, high-purity β-SiC single crystal base material as a seed crystal and forming a β-SiC polycrystal layer on the surface thereof is simply subjected to high-temperature heat treatment to form a polycrystal. By recrystallization, as in the manufacturing method already proposed by the present applicant, in addition to having very few crystal grain boundaries and micropipe defects, the purity is also very high, and as a result, very high quality, In addition, large single-crystal SiC can be easily obtained with equipment and with high productivity.

Here, as the β-SiC polycrystalline layer,
As described in claims 2 and 5, 1300 to 19
By using what was formed on the surface of the β-SiC single crystal base material by the thermochemical vapor deposition method in the 00 ° C. range, the polycrystal of the β-SiC polycrystal layer was converted into a single crystal by recrystallization. At this time, diffusion of impurity atoms is suppressed, and higher quality single crystal SiC can be obtained.

Further, the single-crystal SiC according to the first aspect and the single-crystal Si according to the fourth aspect of the present invention.
In the method for producing C, as a β-SiC single crystal base material serving as a seed crystal, as described in claims 3 and 6,
Β-Si is formed on a β-SiC epitaxial layer epitaxially grown using a Si single crystal carbonized SiC layer as a substrate.
A single crystal having a large area and a large film thickness can be easily obtained by forming a C polycrystalline layer by a thermochemical vapor deposition method and using a single crystal formed by heat-treating them. At the same time, impurities do not enter during the process of producing the seed crystal, so that a β-SiC single crystal with higher purity can be easily obtained.

The single-crystal SiC according to claim 6
The heat treatment temperature of the β-SiC epitaxial layer and the β-SiC polycrystalline layer formed thereon is preferably set in the range of 2200 to 2350 ° C. in the manufacturing method of The heat treatment temperature for the composite in any one of the methods for producing single-crystal SiC described above is desirably set in the range of 2100 to 2400 ° C.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a single crystal Si according to the present invention.
FIG. 3 is a schematic diagram showing a state before heat treatment of C, in which 1 is a β-SiC single crystal base material, and 1300 is provided on the surface thereof.
Thermochemical vapor deposition method (hereinafter referred to as thermal CVD)
By forming a cubic β-SiC polycrystalline layer 2 by the method described above, the surface of the β-SiC single crystal
Forming a composite M in which the polycrystalline body 3 of SiC is grown.

Thereafter, the whole of the composite M is inserted into a resistance heating furnace made of carbon (not shown), and an SiC mass (not shown) made by Acheson method or the like is arranged around the composite M. In addition, an inert gas stream such as Ar is injected into the furnace at about 1 atm so that the center temperature of the furnace becomes 2100-2.
An inert gas atmosphere, such as raising the temperature to reach 400 ° C., preferably 2000 to 2200 ° C., and maintaining the temperature for several hours;
By performing the heat treatment under the saturated vapor pressure of iC, the above β-S
The polycrystalline body 3 of the iC polycrystalline layer 2 is recrystallized and converted into a single crystal, and the single crystal portion and the β-SiC
The single crystal of the single crystal substrate 1 is converted into an α-SiC single crystal, and as shown in FIG. 2, a large α-SiC single crystal 5 in which the crystal axes are oriented in the same direction is integrally grown.

The α-SiC single crystal 5 grown as described above, as a single crystal substrate 1 serving as a seed crystal, is likely to be very large in both film thickness and area, and β-SiC is easy to obtain high purity. Since the SiC single crystal is used, the final product, single crystal SiC, can be made large in size. In addition to having very few crystal grain boundaries and micropipe defects, the purity is also very high. The applicability as a semiconductor material is remarkably enhanced in terms of both quality and size and quality, and practical application can be promoted.

Here, the β-SiC single crystal base material 1 used as a seed crystal for growing the α-SiC single crystal 5 is manufactured as follows. As shown in FIG. 3A, the surface of the Si single crystal 6 is carbonized by CCl ₄ or the like in an H ₂ gas flow to form a thin SiC SiC layer 7 and the SiC SiC layer 7 is used as a substrate. Β-SiC epitaxial layer 8 by epitaxial growth
Then, as shown in FIG. 3B, the Si single crystal 6 is removed by using nitric acid or the like.

Next, as shown in FIG.
On the C epitaxial layer 8, the CH _{2 is} introduced in a large excess H ₂ gas flow.
Β-SiC polycrystalline layer 9 oriented on the (111) plane by a thermal CVD method in the range of 1300 to 1380 ° C. in an atmosphere containing ₃ SiCl ₃ (monomethyltolchlorosilane).
Is formed at a rate of 150 μ / Hr. Finally, the SiC SiC layer 7, the β-SiC epitaxial layer 8, and the β-S
The whole of the composite comprising the iC polycrystalline layer 9 was subjected to an inert gas atmosphere of Ar or the like and an SiC saturated vapor pressure of 2200 to 2200.
As shown in FIG. 3 (D), each of the layers 7 to 9 is subjected to a heat treatment of heating and raising the temperature over 3 hours until the temperature reaches a temperature range of 2350 ° C. and maintaining the temperature for 3 hours. To obtain a β-SiC single crystal substrate 1 in which the single crystal is integrally crystallized.

The β-SiC single crystal base material 1 obtained as described above has not only a large area and a large film thickness, but also has very high purity because no impurities enter during the manufacturing process. It is easily understood that a single crystal SiC (final product) manufactured using such a β-SiC single crystal substrate 1 as a seed crystal is very large and of extremely high quality.

In the above-described embodiment, the cubic β-S
Although the case where the composite M is formed by forming the iC polycrystalline layer 2 is described, the β-SiC single crystal substrate 1
The composite M may be formed by simply superposing the SiC polycrystalline layers 2 and heat-treating the composite M.

[0021]

As described above, according to the first and fourth aspects of the present invention, a single crystal base material serving as a seed crystal is:
A β-SiC single crystal, which is very large in both film thickness and area and easy to increase in size, and does not enter impurities or the like during its growing process and is easily purified, is used.
-By simply subjecting the composite formed with the SiC polycrystalline layer to high-temperature heat treatment, it is easy to obtain a single-crystal SiC as a final product, which has a wide range of application as a semiconductor material and has a large size. As in the case of the above-mentioned proposed manufacturing method, there are very few crystal grain boundaries and micropipe defects, and the purity is very high. As a result, extremely high-quality single-crystal SiC can be easily produced with equipment. And it can be obtained with good productivity. Thereby, Si (silicon) or Ga
Compared with existing semiconductor materials such as As (gallium arsenide), it is superior in capacity, high frequency, withstand voltage, environmental resistance, and is expected to be used as a semiconductor material for power devices. This has the effect that it can be achieved.

According to the second and fifth aspects of the present invention, and according to the third and sixth aspects of the present invention, the single-crystal SiC obtained by the first aspect of the present invention is provided.
Quality can be further improved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a state before heat treatment of single crystal SiC according to the present invention.

FIG. 2 is a schematic diagram showing a state after heat treatment of single crystal SiC according to the present invention.

FIGS. 3A to 3D are explanatory diagrams of a method for producing a β-SiC single crystal base material used as a seed crystal in producing the single crystal SiC according to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 β-SiC single crystal base material 2 β-SiC polycrystal layer 3 polycrystal 5 single crystal SiC 6 Si single crystal 7 Si carbide SiC layer 8 β-SiC epitaxial layer 9 β-SiC polycrystal layer M composite

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4G050 AA03 AB02 4G077 AA03 AB02 BE08 DA01 DB05 DB09 EA01 ED05 ED06 FE02 FE11 HA12

Claims (8)

[Claims] 1. The surface of a β-SiC single crystal substrate has β-Si
By heat treating the composite formed with the C polycrystal layer, the polycrystal of the β-SiC polycrystal layer is recrystallized and converted into a single crystal, and the single crystal portion and the β-SiC A single crystal SiC, wherein an α-SiC single crystal whose crystal axes are oriented in the same direction including a crystal substrate is integrally grown. 2. The method according to claim 1, wherein the β-SiC polycrystalline layer is
The single crystal SiC according to claim 1, wherein the single crystal SiC is formed on the surface of the β-SiC single crystal base material by a thermochemical deposition method in a temperature range of 1900 ° C. 3. The β-SiC single crystal base material is formed by thermochemical vapor deposition of a β-SiC polycrystal layer on a β-SiC epitaxial layer epitaxially grown using a Si single crystal SiC layer as a substrate. 2. A film which is formed into a single crystal by heat treatment.
Or the single crystal SiC according to 2. 4. A β-SiC single crystal substrate having β-Si
After the C polycrystalline layer is formed, the composite is formed in an inert gas atmosphere at a pressure lower than the atmospheric pressure, and
By performing the heat treatment under the saturated vapor pressure of SiC, the above β-
The polycrystal of the SiC polycrystal layer is recrystallized to be converted into a single crystal, and the converted single crystal portion and the α-crystal whose crystal axis is oriented in the same direction including the β-SiC single crystal base material are included. A method for producing single-crystal SiC, comprising integrating and growing a single-crystal SiC. 5. The polycrystalline β-SiC layer according to claim 1, wherein
The method for producing single-crystal SiC according to claim 4, wherein the single-crystal SiC is formed on the surface of the β-SiC single-crystal substrate by a thermochemical vapor deposition method in a temperature range of 1900 ° C. 6. The β-SiC single crystal base material is formed by thermochemical vapor deposition of a β-SiC polycrystalline layer on a β-SiC epitaxial layer epitaxially grown using a Si single crystal SiC layer as a substrate. 5. A film which is formed into a single crystal by heat treatment.
Or the method for producing single-crystal SiC according to 5. 7. The heat treatment temperature of the β-SiC epitaxial layer and the β-SiC polycrystalline layer formed thereon is 2
The method for producing single crystal SiC according to claim 6, wherein the temperature is set in a range of 200 to 2350 ° C. 8. The heat treatment temperature for the composite is 21.
The method for producing single-crystal SiC according to any one of claims 4 to 7, wherein the temperature is from 00 to 2400 ° C.