JP2003104798A - Silicon carbide single crystal, method for producing the same, and silicon carbide crystal raw material for growing silicon carbide single crystal - Google Patents

Abstract

(57) [PROBLEMS] To provide a method of manufacturing a large-diameter silicon carbide single crystal ingot having high resistivity and high quality, a silicon carbide crystal raw material for growing a silicon carbide single crystal used in the method, and silicon carbide manufactured by the method A single crystal is provided. A silicon carbide single crystal manufacturing method including a step of growing a silicon carbide single crystal on a seed crystal by a sublimation recrystallization method, wherein the concentration of vanadium as a raw material is 1 × 1.
A silicon carbide single crystal is grown using a silicon carbide crystal having a concentration of 0 ^{18 to} 6 × 10 ¹⁹ atoms / cm ³ and inevitable impurities other than vanadium being less than the vanadium concentration. Method for producing single crystal, silicon carbide crystal raw material for growing silicon carbide single crystal used in the method,
It is a silicon carbide single crystal manufactured by the method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicon carbide single crystal and a method for manufacturing the same, and more particularly to a large-sized high quality single crystal ingot which is a substrate wafer of a high frequency electronic device and a method for manufacturing the same.

[0002]

2. Description of the Related Art Silicon carbide (SiC) has attracted attention as an environment-resistant semiconductor material because of its excellent heat resistance and mechanical strength and its physical and chemical properties such as resistance to radiation. In recent years, demand for SiC single crystal wafers as substrate wafers for short-wavelength optical devices from blue to ultraviolet, high-frequency high-voltage electronic devices, etc. has been increasing. However, a crystal growth technique capable of stably supplying a high-quality SiC single crystal having a large area on an industrial scale has not yet been established. Therefore, despite the semiconductor material having many advantages and possibilities as described above, SiC has been hindered from its practical use.

Conventionally, on a scale of a laboratory, an SiC single crystal was grown by, for example, a sublimation recrystallization method (Rayleigh method) to obtain an SiC single crystal of a size capable of producing a semiconductor device. However, with this method, the area of the obtained single crystal is small, and it is difficult to control the size and shape with high accuracy. Moreover, it is not easy to control the crystal polymorphism and the impurity carrier concentration of SiC. Further, a cubic silicon carbide single crystal is also grown by performing heteroepitaxial growth on a heterogeneous substrate such as silicon (Si) using a chemical vapor deposition method (CVD method).
Although a large area single crystal can be obtained by this method, only a SiC single crystal containing many defects (~ 10 ⁷ cm ^-2 ) can be grown due to the fact that the lattice mismatch with the substrate is about 20%. It is not possible to obtain a high quality SiC single crystal. In order to solve these problems, an improved Rayleigh method in which sublimation recrystallization is performed using a SiC single crystal wafer as a seed crystal has been proposed (Yu. M. Tairo).
v and V. F. Tsvetkov, Journa
l of Crystal Growth, vol. 5
2 (1981) pp. 146-150). In this method, since the seed crystal is used, the nucleation process of the crystal can be controlled, and the growth rate of the crystal can be controlled with good reproducibility by controlling the atmosphere pressure from 100 Pa to 15 kPa with an inert gas. The principle of the modified Rayleigh method will be described with reference to FIG. SiC single crystal as a seed crystal and SiC crystal powder as a raw material (usually Acheson
The abrasive produced by the method is used after cleaning and pretreatment. It is stored in a crucible (usually graphite) and is placed in an inert gas atmosphere such as argon (133 Pa to 13.3 kP).
a), heated to 2000-2400 degrees Celsius. At this time, the temperature gradient is set so that the seed crystal is slightly lower in temperature than the raw material powder. After sublimation, the raw material is diffused and transported in the seed crystal direction by a concentration gradient (formed by a temperature gradient). Single crystal growth is realized by recrystallizing the source gas that has reached the seed crystal on the seed crystal. If the modified Rayleigh method is used, the crystal polymorph of SiC single crystal (6H type, 4H type,
Type, 15R type, etc.) and shape, carrier type and concentration can be controlled to grow an SiC single crystal.

Currently, the S produced by the above modified Rayleigh method is used.
A SiC single crystal wafer having a diameter of 2 inches (50 mm) to 3 inches (75 mm) is cut out from the iC single crystal, and is used for epitaxial thin film growth and device fabrication. As a high frequency application of such a SiC single crystal substrate, it is desired to increase the resistivity of the substrate (10 ⁶ Wcm or more). Increasing the resistivity of the substrate has become an indispensable technique for reducing the parasitic capacitance of the devices formed thereon and separating the devices. At present, such a high resistivity substrate is industrially obtained by adding vanadium element to a SiC single crystal. Specifically, in the sublimation recrystallization method described above, S that is a raw material
Metal vanadium or a vanadium compound (oxide, silicide, etc.) is contained in the iC crystal powder and is added to the grown crystal by sublimation together with the SiC raw material (for example, SA Reshanov et al.
Materials Science Forum, v
ols. 353-356 (2001) pp. 53-5
6). However, although the SiC single crystal thus produced has a high resistivity, the crystal quality is poor, and the crystal portion having a high resistivity is a very limited portion in the grown crystal.

[0005]

As described above, the vanadium-added high-resistivity SiC single crystal produced by the conventional technique has a low crystal quality, and the crystal portion having a high resistivity is extremely limited in the grown crystal. It was the part where This is because the sublimation or evaporation rate of the vanadium raw material is much higher than the sublimation rate of the SiC raw material. Since the sublimation or evaporation rate of vanadium is higher than the sublimation rate of the SiC raw material, a large amount of vanadium is incorporated into the grown crystal at the early stage of growth (FIG. 2 (a)). As a result, the amount of vanadium in the grown crystal was limited to the solid solution limit (3 × 10 ¹⁷ ato).
m / cm ³ ) and deteriorates the crystallinity with the generation of precipitates (this crystallinity deterioration in the initial growth portion also adversely affects the crystallinity of the SiC single crystal grown thereafter). When SiC crystal powder based on an ordinary abrasive is used as a raw material, the concentration of other residual impurities taken into the SiC single crystal is as high as about 1 × 10 ¹⁷ atom / cm ³ ,
As a result, the site where a high resistivity single crystal can be obtained has been extremely limited. This is because, as shown in FIG. 2A, the vanadium raw material is depleted within a few hours after the start of growth because the sublimation gas pressure of the vanadium raw material is high, and as a result, vanadium is added to a concentration higher than the residual impurity concentration. This is because the region was a very limited part of the grown crystal. If the vanadium concentration in the SiC single crystal is equal to or lower than the residual impurity concentration, the electrical characteristics of the SiC single crystal are determined by other impurities, and a high resistivity single crystal cannot be obtained.

The present invention has been made in view of the above circumstances, and provides a large-diameter ingot with high resistivity and high quality, and a method and a raw material for producing a SiC single crystal capable of producing the ingot with good reproducibility. is there.

[0007]

Accordingly, the SiC of the present invention
The method for producing a single crystal is (1) a method for producing a silicon carbide single crystal that includes a step of growing a silicon carbide single crystal on a seed crystal by a sublimation recrystallization method, and the concentration of vanadium as a raw material is 1 × 10. ^A silicon carbide single crystal is grown using a silicon carbide crystal having a concentration of ^{18 to} 6 × 10 ¹⁹ atoms / cm ³ and an unavoidable impurity other than vanadium less than the concentration of vanadium. (2) The vanadium concentration is 1 × 10 ¹⁸ to
6 × 10 ¹⁹ atom / cm ³ , and the concentration of the unavoidable impurities is 1 × 10 ¹⁵ atom / cm ³ or less,
(1) The production method according to (1), (3) the vanadium concentration is 1 × 10 ^{19 to} 6 × 10 ¹⁹ atom / cm ³ , and the unavoidable impurity concentration is 1 × 10 ¹⁶ atom / cm ³ or less. And (4) the vanadium concentration is 1 × 10 ^{18 to} 6 × 10 ¹⁹ atom / cm ³ , and the concentration of unavoidable impurities other than vanadium is less than the vanadium concentration. Silicon carbide crystal raw material for growing silicon single crystal, (5) Vanadium concentration is 1 × 10 ^{18 to} 6 ×
10 ¹⁹ atom / cm ³ , and the concentration of unavoidable impurities other than vanadium is 1 × 10 ¹⁵ atom / cm ³ or less, a silicon carbide crystal raw material for growing a silicon carbide single crystal, (6) the concentration of vanadium is 1 × 10 ^{19 to} 6 × 10 ¹⁹ atom / c
m ³ and the concentration of unavoidable impurities other than vanadium is 1
A silicon carbide crystal raw material for growing a silicon carbide single crystal having a density of × 10 ¹⁶ atoms / cm ³ or less, and a silicon carbide single crystal obtained by the manufacturing method according to any one of (7) (1) to (3). And a vanadium concentration of 1 × 10 ^{15 to} 3 over the entire length of the silicon carbide single crystal excluding the (8) seed crystal, which has a diameter of 50 mm or more.
× 10 ¹⁷ atom / cm ³ silicon carbide single crystal, (9) The vanadium concentration is 1 × 10 ¹⁶
The silicon carbide single crystal according to (8), having a diameter of 3 × 10 ¹⁷ atoms / cm ³ , and (10) having a diameter of 50 mm or more, the silicon carbide according to (8) or (9). Single crystal, a silicon carbide single crystal substrate obtained by cutting and polishing the silicon carbide single crystal according to any one of (11), (7) to (10), and the silicon carbide single crystal according to (12) and (11). A silicon carbide epitaxial wafer obtained by epitaxially growing a silicon carbide thin film on a crystal substrate, and a gallium nitride, aluminum nitride, indium nitride or a mixed crystal thereof is epitaxially grown on the silicon carbide single crystal substrate according to (13) or (11). Thin film epitaxial wafer.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the production method of the present invention, the concentration of vanadium is previously set to 1 × 10 ^{18 to} 6 × 10 ¹⁹ atom / cm as a silicon carbide (hereinafter also referred to as “SiC”) raw material.
³ , preferably 1 × 10 ^{19 to} 6 × 10 ¹⁹ atom / cm ^3.
And the concentration of unavoidable impurities other than vanadium is less than the concentration of vanadium, preferably 1 × 10 ^{15 to} less than 1 × 10 ¹⁵ atom / cm ³ when the concentration of vanadium is 1 × 10 ^{18 to} 6 × 10 ¹⁹ atom / cm ^3. , 1 if the vanadium concentration is 1 × 10 ^{19 to} 6 × 10 ¹⁹ atom / cm ^3.
By using a SiC single crystal having a density of × 10 ¹⁶ atoms / cm ³ or less, a high-quality large-diameter SiC single crystal ingot with a high resistivity (10 ⁶ Wcm or more) can be obtained.

The effect of the present invention will be described with reference to FIG. In the growth of a SiC single crystal by the sublimation recrystallization method, when vanadium is added to a growing crystal by using a SiC crystal raw material containing vanadium as an intracrystalline impurity in the SiC crystal in advance, sublimation or evaporation of vanadium from the raw material results in the SiC crystal. The rate is limited by the decomposition (sublimation) of the raw materials. Therefore, in this case, the sublimation or evaporation rate of vanadium is not determined by the sublimation or evaporation rate of metal vanadium or a vanadium compound as in the conventional method, but is always the same as that of the SiC crystal raw material, which is a problem in the conventional method. There is no difference in sublimation or evaporation rate between vanadium and SiC. As described above, when the sublimation or evaporation rate of vanadium becomes the same as the sublimation rate of SiC crystal, vanadium is not depleted within a few hours after the start of growth, and a constant amount of vanadium is always maintained during growth. Can be sublimated or evaporated. As a result, it becomes possible to always add vanadium to the grown crystal in a constant amount. Further, if the amount of vanadium added to the SiC crystal raw material is adjusted in advance, the amount added to the grown crystal can also be adjusted. For example, if the amount of vanadium in the SiC crystal raw material is set to 2 × 10 ¹⁹ atom / cm ³ , the amount of vanadium taken into the grown crystal is 2 × 10.
¹⁶ atom / cm ³ to 1 × 10 ¹⁷ atom / cm ³ . The vanadium concentration is lower in the grown crystal than in the raw material because the vanadium incorporation rate from the raw material into the SiC single crystal (vanadium concentration in the grown crystal ÷ vanadium concentration in the crystal raw material) is 0.001 to 0. This is because it is as low as 0.005. This uptake rate depends on the growth conditions of the SiC single crystal, and the vanadium concentration charged in the SiC crystal raw material must be determined in consideration of this. In this way, taking into consideration the rate of incorporation into the grown crystal,
If the vanadium concentration in the SiC crystal raw material is determined and the SiC single crystal is grown by the sublimation recrystallization method using this raw material, vanadium that is constant and below the solid solution limit amount is reproduced throughout the grown SiC single crystal. It can be added with good properties, and as a result, a high quality SiC single crystal can be obtained.

In the method for producing a SiC single crystal of the present invention, S
The SiC crystal raw material is characterized in that the concentration of unavoidable impurities other than vanadium in the iC crystal raw material is less than the concentration of vanadium. Concentration of the inevitable impurities may be less than the concentration of vanadium, preferably, the concentration of vanadium 1 × 10 ¹⁵ atom / cm ³ or less in the case of ^{1 × 10 18 ~6 × 10 19} atom / cm 3, or , the concentration of vanadium ^{1 × 10 1 9 ~6 × 10} 19 atom / cm 3
In the case of, it is 1 × 10 ¹⁶ atoms / cm ³ or less. The conditions of these concentration ranges are so that the vanadium concentration in the grown SiC single crystal is always higher than the inevitable impurity concentration, and particularly preferable SiC single crystals can be manufactured under the concentration conditions of the above specific examples. In order to obtain a high resistivity in the SiC single crystal with vanadium added, the amount of unavoidable impurities exceeding the amount of vanadium added is Si.
It must not be present in the C single crystal. When the unavoidable impurity concentration becomes higher than the vanadium concentration in the grown crystal, the electrical characteristics of the single crystal are determined by the unavoidable impurities, and the high resistivity (10 ⁶ Wcm or more)
It cannot be. Since the rate of incorporation of impurities other than vanadium is about 1.0 at a high level, the concentration of impurities other than vanadium in the SiC crystal raw material should be set to the same level as or lower than the concentration allowed in the grown crystal. There must be.

A SiC crystal used as a raw material for the sublimation recrystallization method.
Concentration of inevitable impurities other than vanadium and vanadium in crystals
If the degree is set within the range of the present invention, high reproducibility and high resistivity
(10 ⁶A SiC single crystal of Wcm or more) can be obtained.
The present inventors have found out from many experiments.

S for growing SiC single crystal used in the present invention
The iC crystal raw material is, for example, high-purity silicon dioxide (SiO 2).
₂) And graphite at high temperature.
SiO₂The oxygen contained in is high temperature (2000 degrees Celsius
In the above reaction, carbon monoxide is discharged to the outside of the system.
And does not remain in the SiC crystal. Vanadium is the above SiO
₂+ Added to graphite in the form of high-purity metal vanadium,
It is incorporated into the SiC crystal during the reaction. In the SiC crystal
Vanadium concentration varies depending on the growth site, but
After that, when the crystals are crushed and the particle size is adjusted (powdered), they are made uniform.
Be done. The vanadium concentration in the SiC crystal raw material is set to 1 × 10.¹⁹
~ 6 × 10¹⁹atom / cm³, Or 1 × 10¹⁸~
6 x 10¹⁹atom / cm³To the range of the molar ratio
1: 1 mixed with SiO₂+ Si in graphite
High purity of 4 to 24% or 0.4 to 24% in terms of molar ratio
Vanadium may be added once. However, at this time,
Around the crystal grains that were formed, the SiC crystal remained without being incorporated.
The desired vanadium is
To obtain a SiC crystal raw material with a high um concentration, crush the crystal
・ Remove this adhesion layer by acid cleaning before adjusting the particle size.
It is needed. Moreover, the SiC crystal manufactured in this way
The unavoidable impurity concentration in the raw material is less than the vanadium concentration,
Preferably 1 × 10¹⁶atom / cm³Below,
Is 1 × 10¹⁵atom / cm³To depart,
Raw material SiO₂Unavoidable impurities in graphite, graphite and vanadium
The atomic concentration is 0.2 ppm or less, or 0.0
It should be 2 ppm or less.

The SiC single crystal ingot produced by the production method of the present invention is characterized by having a large diameter of 50 mm or more, a high resistivity, and a small number of crystal defects caused by vanadium precipitates. obtain. In addition, the vanadium concentration is 1 × over the entire length of the silicon carbide single crystal excluding the seed crystal.
10 ^{15 to} 3 × 10 ¹⁷ atom / cm ³ , preferably 1 ×
When it is 10 ^{16 to} 3 × 10 ¹⁷ atom / cm ³ , it exhibits a high resistivity of 10 ⁶ Wcm or more without being affected by unavoidable impurities. A vanadium concentration exceeding 3 × 10 ¹⁷ atom / cm ³ is not preferable because vanadium is precipitated in the SiC single crystal.

The SiC single crystal ingot manufactured by cutting and polishing the SiC single crystal ingot thus manufactured has 50
Since it has a diameter of mm or more, when manufacturing various devices using this substrate, it is possible to use a conventional industrially established manufacturing line for semiconductor (Si, GaAs, etc.) wafers. Suitable for mass production. In particular, since the substrate has a high resistivity, it can be applied to a device having a high operating frequency. Further, a SiC single crystal epitaxial wafer produced by growing an epitaxial thin film on this SiC single crystal substrate by a CVD method or the like, or Ga
A thin film epitaxial wafer obtained by epitaxially growing a mixed crystal of N, AlN, InN and these has excellent characteristics (epitaxial growth) because the SiC single crystal substrate used as the substrate has extremely few crystal defects due to vanadium precipitates. Surface morphology, electrical properties, etc.) of the thin film.

[0015]

EXAMPLE An example of the present invention will be described below with reference to FIG. First, the single crystal growth apparatus will be briefly described. Crystal growth is performed by sublimating the SiC crystal powder raw material 2 and recrystallizing it on the SiC single crystal 1 used as a seed crystal. Seed crystal SiC single crystal 1
Is attached to the inner surface of the graphite crucible lid 4 of the high-purity graphite crucible 3. The SiC crystal powder raw material 2 is filled in the crucible 3. Such a crucible 3 has a double quartz tube 5
It is installed by a graphite support rod 6 inside. Around the crucible 3, a graphite felt 7 for heat shield is installed. The double quartz tube 5 can be evacuated to high vacuum (10 ⁻³ Pa or less) by the vacuum exhaust device 11, and the internal atmosphere can be pressure-controlled by Ar gas.
Further, a work coil 8 is installed on the outer circumference of the double quartz tube 5, and the crucible 3 can be heated by passing a high-frequency current to heat the raw material and the seed crystal to a desired temperature. The temperature of the crucible is measured by using a two-color thermometer by providing an optical path with a diameter of 2 to 4 mm in the center of the felt that covers the upper and lower portions of the crucible and extracting light from the upper and lower portions of the crucible. The temperature of the lower part of the crucible is the raw material temperature, and the temperature of the upper part of the crucible is the seed temperature.

Next, an example of the production of a SiC single crystal using this crystal growth apparatus will be described. First, as a seed crystal, a hexagonal SiC single crystal wafer having a (0001) plane with a diameter of 50 mm was prepared. Next, the seed crystal 1 was attached to the inner surface of the graphite crucible lid 4 of the crucible 3. Inside the crucible 3, SiC crystal raw material powder 2 was filled. The SiC crystal that is the raw material powder is SiO that is prepared in a molar ratio of 1: 1.
High purity vanadium was added to ₂ + graphite in a molar ratio of 8% with respect to Si and reacted in a high temperature furnace. The unavoidable impurity concentration in SiO ₂ , graphite and vanadium used at this time was 1 × 10 ¹⁶ atom / cm ³ or less. The vanadium concentration in the obtained SiC crystal powder was 2 × 10 ¹⁹ at
It was om / cm ³ . The unavoidable impurity concentration other than vanadium was 1 × 10 ¹⁶ atom / cm ³ or less. Next, the crucible 3 filled with the raw material is replaced with the graphite crucible lid 4
After closing with, and covering with a felt 7 made of graphite, it was placed on a support rod 6 made of graphite and placed inside a double quartz tube 5. After evacuating the inside of the quartz tube, an electric current was passed through the work coil to raise the raw material temperature to 2000 degrees Celsius. After that, high-purity Ar gas as an atmospheric gas is introduced through the high-purity Ar gas pipe 9 while being controlled by the high-purity Ar gas mass flow controller 10, and the pressure inside the quartz tube is set to about 8
While maintaining at 0 kPa, the raw material temperature was raised to the target temperature of 2400 degrees Celsius. Growth pressure of 1.3 kP
The pressure was reduced to a in about 30 minutes, and then the growth was continued for about 20 hours. The temperature gradient in the crucible at this time is 15 degrees Celsius / cm.
The growth rate was about 0.8 mm / hour. The obtained crystal had a diameter of 51 mm and a height of about 16 mm.

The silicon carbide single crystal thus obtained was analyzed by X-ray diffraction and Raman scattering. As a result, hexagonal S
It was confirmed that the iC single crystal had grown. For the purpose of measuring the impurity concentration of the crystal, nine 1 mm-thick wafers were cut out from the grown single crystal ingot. The plane orientation of the wafer was set to 3.5 degrees off from the (0001) plane in the <11-20> direction. Upper, middle and lower part of grown crystal (near seed crystal)
Wafer corresponding to (the 9th wafer from each seed crystal,
When the impurity concentration in the fifth and second wafers was examined, the vanadium concentration was 6 × 10 ¹⁶ a for all wafers.
In tom / cm ³ or so, it the concentration of inevitable impurities other than were all below ^{1 × 10 16 atom / cm 3} . Further, when the obtained wafer was observed with a microscope, no defects that were considered to be caused by vanadium precipitates were observed. When the resistivity of each wafer was examined by electrical measurement, all the wafers exhibited a high resistivity of 10 ⁶ Wcm or more.

Next, the thus-produced SiC single crystal wafer is polished to have a thickness of 300 μm and a diameter of 51 m.
m SiC single crystal mirror-finished wafer was produced.

Further, using this SiC single crystal mirror-polished wafer having a diameter of 51 mm as a substrate, SiC was epitaxially grown. The growth conditions for the SiC epitaxial thin film are as follows: growth temperature 1500 ° C., silane (SiH ₄ ), propane (C ₃ H ₈ ), and hydrogen (H ₂ ) flow rates of 5.0 × 10 ⁻⁹ m ³ / sec, respectively. 3.3 × 10 ^-9 m ³ / se
c, 5.0 × 10 ⁻⁵ m ³ / sec. The growth pressure was atmospheric pressure. The growth time is 2 hours and the film thickness is about 5
μm was grown.

After growth of the epitaxial thin film, the surface morphology of the obtained epitaxial thin film was observed by a Nomarski optical microscope. It has been found that the SiC epitaxial thin films that it has grown.

Further, a (0001) plane wafer having an off angle of 0 degree was cut out from another SiC single crystal ingot produced in the same manner, mirror-polished, and then a GaN thin film was formed thereon by metal organic chemical vapor deposition (MOCVD). ) Method was used for epitaxial growth. The growth condition is a growth temperature of 1050 degrees Celsius.
Degree, trimethylgallium (TMG), ammonia (NH
₃ ) and silane (SiH ₄ ) at 54 × 10 ⁻⁶ mol / min, 4 l / min, and 22 × 10 ⁻¹¹ mol / min, respectively.
I shed min. The growth pressure was atmospheric pressure. The growth time was 60 minutes, and n-type gallium nitride was grown to a film thickness of 3 μm.

The growth surface was observed by a Nomarski optical microscope for the purpose of examining the surface state of the obtained GaN thin film. It was found that a very flat morphology was obtained over the entire surface of the wafer and a high quality GaN thin film was formed over the entire surface.

Comparative Example As a comparative example, production of a high resistivity SiC single crystal by the conventional method will be described. As in the above example, a seed crystal (0001) with a diameter of 50 mm was used.
A hexagonal SiC single crystal wafer having a face was prepared.
Next, the seed crystal 1 was attached to the inner surface of the graphite crucible lid 4 of the graphite crucible 3, and the inside of the crucible 3 was filled with the SiC crystal raw material powder 2 having the abrasive material washed. Further, vanadium metal was added to the raw material powder in a molar ratio to Si of 0.4%. The crucible 3 filled with the raw material was closed with a graphite crucible lid 4, covered with a graphite felt 7, and then placed on a graphite support rod 6 and placed inside a double quartz tube 5. After evacuating the inside of the quartz tube, an electric current was passed through the work coil to raise the raw material temperature to 2000 degrees Celsius. After that, high-purity Ar gas was introduced as an atmosphere gas, and the raw material temperature was raised to a target temperature of 2400 degrees Celsius while maintaining the pressure in the quartz tube at about 80 kPa. Growth pressure is 1.
The pressure was reduced to 3 kPa over about 30 minutes, and then the growth was continued for about 20 hours. At this time, the temperature gradient inside the crucible was 15 degrees Celsius / cm, and the growth rate was about 0.8 mm / hour. The obtained crystal had a diameter of 51 mm and a height of about 17 mm.

The silicon carbide single crystal thus obtained was analyzed by X-ray diffraction and Raman scattering. As a result, hexagonal S
It was confirmed that the iC single crystal had grown. For the purpose of measuring the impurity concentration of the crystal, nine 1 mm-thick wafers were cut out from the grown single crystal ingot. The plane orientation of the wafer was set to 3.5 degrees off from the (0001) plane in the <11-20> direction. Upper, middle and lower part of grown crystal (near seed crystal)
Wafer corresponding to (the 9th wafer from each seed crystal,
When the impurity concentration in the fifth and second wafers was examined, the concentration of vanadium was 5 × 10 ¹⁸ atoms / cm ³ in the lower wafer and 5 in the middle and upper wafers. It was less than or equal to × 10 ¹⁶ atom / cm ³ .
The concentration of unavoidable impurities other than vanadium was about 2 × 10 ¹⁷ atoms / cm ³ in all the wafers. When the obtained wafer was observed with a microscope, crystal defects that were considered to be caused by vanadium precipitates were observed in the wafer corresponding to the lower part of the grown crystal. When the resistivity of each wafer was examined by electrical measurement, the wafer corresponding to the lower part of the grown crystal showed a high resistivity of 10 ⁶ Wcm or more, but the wafer corresponding to the middle part and the upper part showed 0.4
It showed a low resistivity of Wcm.

Next, among the SiC single crystal wafers manufactured in this way, one having a high resistivity (wafer corresponding to the lower part of the growing crystal) is polished to have a thickness of 300 μm and a diameter of 5
A 1 mm SiC single crystal mirror-finished wafer was prepared.

Further, using this 51 mm diameter SiC single crystal mirror-finished wafer as a substrate, SiC was epitaxially grown. The growth conditions for the SiC epitaxial thin film are as follows: growth temperature 1500 ° C., silane (SiH ₄ ), propane (C ₃ H ₈ ), and hydrogen (H ₂ ) flow rates of 5.0 × 10 ⁻⁹ m ³ / sec, respectively. 3.3 × 10 ^-9 m ³ / se
c, 5.0 × 10 ⁻⁵ m ³ / sec. The growth pressure was atmospheric pressure. The growth time is 2 hours and the film thickness is about 5
μm was grown.

After growth of the epitaxial thin film, the surface morphology of the obtained epitaxial thin film was observed with a Nomarski optical microscope. As a result, it was found that pits were found at the sites where defects due to vanadium precipitates were present in the substrate wafer. -Like surface defects appeared.

Further, from another SiC single crystal ingot produced in the same manner, a high resistivity (000
1) A plane wafer was cut out (cut out from a region near the seed crystal), mirror-polished, and then a GaN thin film was epitaxially grown thereon by a metal organic chemical vapor deposition (MOCVD) method. The growth conditions are as follows: growth temperature 1050 ° C., trimethylgallium (TMG), ammonia (NH ₃ ),
Silane (SiH ₄ ) 54 × 10 ^-6 mol / m 2, respectively
in, 4 liters / min, 22 × 10 ^-11 mol / mi
flowed n times. The growth pressure was atmospheric pressure. The growth time was 60 minutes, and n-type gallium nitride was grown to a film thickness of 3 μm.

For the purpose of investigating the surface condition of the obtained GaN thin film, the growth surface was observed by a Nomarski optical microscope. As a result, it was found that the portion grown on the place where the defect caused by the vanadium precipitate was present in the wafer also showed that Pit-like surface defects had occurred.

[0030]

As described above, according to the present invention,
By the improved sublimation recrystallization method using a seed crystal (Rayleigh method), it is possible to grow a SiC single crystal having high resistivity and good quality with good reproducibility. If a SiC single crystal wafer cut out from such a crystal is used, a high frequency electronic device having excellent characteristics can be manufactured at a low cost.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the principle of an improved Rayleigh method.

FIG. 2 is a diagram for explaining the effect of the present invention, in which (a)
Shows the vanadium and residual impurity concentration distribution in the SiC single crystal produced by the conventional method, and (b) shows the vanadium and residual impurity concentration distribution in the SiC single crystal produced by the present invention.

FIG. 3 is a configuration diagram showing an example of a single crystal growth apparatus used in the manufacturing method of the present invention.

[Explanation of symbols]

1 seed crystal (SiC single crystal) 2 SiC crystal powder raw material 3 Crucible (high melting point metal such as graphite or tantalum) 4 Graphite crucible lid 5 Double quartz tube 6 Support rod 7 Graphite felt (heat insulating material) 8 work coil 9 High-purity Ar gas piping 10 Mass flow controller for high-purity Ar gas 11 Vacuum exhaust device

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Tatsuo Fujimoto             20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel shares             Company Technology Development Division (72) Inventor Hirokatsu Yashiro             20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel shares             Company Technology Development Division F-term (reference) 4G077 AA02 BE08 DA02 EB01 HA06                       SA04

Claims (13)

[Claims] 1. A method for producing a silicon carbide single crystal, which comprises a step of growing a silicon carbide single crystal on a seed crystal by a sublimation recrystallization method, wherein a vanadium concentration as a raw material is 1 × 1.
A silicon carbide single crystal is grown using a silicon carbide crystal having a concentration of 0 ^{18 to} 6 × 10 ¹⁹ atoms / cm ³ and an unavoidable impurity other than vanadium less than the concentration of vanadium. Method for producing single crystal. 2. The vanadium concentration is 1 × 10 ^{18 to} 6
The production method according to claim 1, wherein the concentration of the unavoidable impurities is × 10 ¹⁹ atoms / cm ³ , and the concentration of the unavoidable impurities is 1 × 10 ¹⁵ atoms / cm ³ or less. 3. The vanadium concentration is 1 × 10 ^{19 to} 6
The manufacturing method according to claim 1, wherein the concentration of the inevitable impurities is × 10 ¹⁹ atoms / cm ³ , and the concentration of the unavoidable impurities is 1 × 10 ¹⁶ atoms / cm ³ or less. 4. The vanadium concentration is 1 × 10.¹⁸~ 6 x 1
0¹⁹atom / cm ³And unavoidable except vanadium
If the concentration of impurities is less than the concentration of vanadium, carbonization
A silicon carbide crystal raw material for growing a silicon single crystal. 5. The vanadium concentration is 1 × 10.¹⁸~ 6 x 1
0¹⁹atom / cm ³And unavoidable except vanadium
Impurity concentration is 1 × 10¹⁵atom / cm³Below
A silicon carbide crystal raw material for growing a silicon carbide single crystal. 6. The vanadium concentration is 1 × 10.¹⁹~ 6 x 1
0¹⁹atom / cm ³And unavoidable except vanadium
Impurity concentration is 1 × 10¹⁶atom / cm³Below
A silicon carbide crystal raw material for growing a silicon carbide single crystal. 7. A silicon carbide single crystal obtained by the manufacturing method according to claim 1, wherein the silicon carbide single crystal has a diameter of 50 mm or more. 8. The vanadium concentration is 1 × 10 ^{15 to} 3 × 10 ¹⁷ at over the entire length of the silicon carbide single crystal excluding the seed crystal.
A silicon carbide single crystal characterized in that it is om / cm ³ . 9. The vanadium concentration is 1 × 10 ^{16 to} 3
The silicon carbide single crystal according to claim 8, having a density of × 10 ¹⁷ atom / cm ³ . 10. The silicon carbide single crystal according to claim 8, which has a diameter of 50 mm or more. 11. A silicon carbide single crystal substrate obtained by cutting and polishing the silicon carbide single crystal according to claim 7. 12. A silicon carbide epitaxial wafer obtained by epitaxially growing a silicon carbide thin film on the silicon carbide single crystal substrate according to claim 11. 13. A thin-film epitaxial wafer obtained by epitaxially growing gallium nitride, aluminum nitride, indium nitride, or a mixed crystal thereof on the silicon carbide single crystal substrate according to claim 11.