JP4733882B2 - Silicon carbide single crystal, method for producing the same, and silicon carbide crystal raw material for growing silicon carbide single crystal - Google Patents

Description

[0001]
BACKGROUND 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 high-quality and large-sized single crystal ingot that becomes a substrate wafer of a high-frequency electronic device and a method for manufacturing the same.
[0002]
[Prior art]
Silicon carbide (SiC) has excellent heat resistance and mechanical strength, and has attracted attention as an environmentally resistant semiconductor material because of its physical and chemical properties such as resistance to radiation. In recent years, the demand for SiC single crystal wafers as substrate wafers for short-wavelength optical devices from blue to ultraviolet and high-frequency high-voltage electronic devices has been increasing. However, a crystal growth technique that can stably supply a high-quality SiC single crystal having a large area on an industrial scale has not yet been established. Therefore, practical use of SiC has been hindered despite the semiconductor material having many advantages and possibilities as described above.
[0003]
Conventionally, on a laboratory scale scale, for example, a SiC single crystal was grown by a sublimation recrystallization method (Rayleigh method) to obtain a SiC single crystal of a size capable of producing a semiconductor element. However, with this method, the area of the obtained single crystal is small, and it is difficult to control its size and shape with high accuracy. Moreover, it is not easy to control the crystal polymorphism and impurity carrier concentration of SiC. Also, a cubic silicon carbide single crystal is grown by heteroepitaxial growth on a heterogeneous substrate such as silicon (Si) using chemical vapor deposition (CVD). In this method, a single crystal having a large area can be obtained, but many defects (−10⁷cm^-2Can be grown only, and it is not easy to obtain a high-quality SiC single crystal. In order to solve these problems, an improved Rayleigh method for performing sublimation recrystallization using a SiC single crystal wafer as a seed crystal has been proposed (Yu. M. Tailov and VF Tsvetkov, Journal of). Crystal Growth, vol. 52 (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 atmospheric pressure from about 100 Pa to about 15 kPa with an inert gas. The principle of the improved Rayleigh method will be described with reference to FIG. SiC single crystal as seed crystal and SiC crystal powder as raw material (usually used after cleaning and pretreatment of abrasive prepared by Acheson method) are housed in crucible (usually graphite) and argon In an inert gas atmosphere (133 Pa to 13.3 kPa) or the like, and heated to 2000 to 2400 degrees Celsius. At this time, the temperature gradient is set so that the seed crystal has a slightly lower temperature than the raw material powder. After sublimation, the raw material is diffused and transported in the direction of the seed crystal by a concentration gradient (formed by a temperature gradient). Single crystal growth is realized by recrystallization of the source gas that has arrived at the seed crystal on the seed crystal. By using the modified Rayleigh method, it is possible to grow a SiC single crystal while controlling the crystal polymorphism (6H type, 4H type, 15R type, etc.), shape, carrier type and concentration of the SiC single crystal.
[0004]
  Currently, SiC single crystal wafers having a diameter of 2 inches (50 mm) to 3 inches (75 mm) are cut out from the SiC single crystal produced by the above-described improved Rayleigh method, and are used for epitaxial thin film growth and device production. As a high frequency application of such a SiC single crystal substrate, high resistivity (10⁶ Ωcm or more) is desired. Increasing the resistivity of a substrate has become an indispensable technique for reducing parasitic capacitance and isolating elements produced on the substrate. Currently, such a high resistivity substrate is industrially obtained by adding a vanadium element to a SiC single crystal. Specifically, in the above-mentioned sublimation recrystallization method, a metal vanadium or vanadium compound (oxide, silicide, etc.) is contained in the SiC crystal powder as a raw material and added to the grown crystal by sublimation with the SiC raw material. (For example, SA Reshanov et al., Materials Science Forum, vols. 353-356 (2001) pp. 53-56). 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 an extremely limited portion in the grown crystal.
[0005]
[Problems to be solved by the invention]
As described above, the vanadium-added high resistivity SiC single crystal produced by the prior art has a low crystal quality, and the crystal portion having the high resistivity is an extremely limited portion of the grown crystal. This is due to the fact that the sublimation or evaporation rate of the vanadium material is much higher than the sublimation rate of the SiC material. Since the sublimation or evaporation rate of vanadium is larger than the sublimation rate of the SiC raw material, a large amount of vanadium is taken into the growth crystal at the initial stage of growth (FIG. 2A). As a result, the amount of vanadium in the grown crystal is the solid solution limit (3 × 10¹⁷atom / cm^Three), And the crystallinity is deteriorated with the generation of precipitates (the crystallinity deterioration in the initial growth part also adversely affects the crystallinity of the SiC single crystal grown thereafter). Further, when a SiC crystal powder based on a normal abrasive is used as a raw material, the concentration of other residual impurities taken into the SiC single crystal is 1 × 10¹⁷atom / cm^ThreeAs a result, the portion where a single crystal having a high resistivity was obtained was extremely limited. As shown in FIG. 2 (a), the vanadium raw material is depleted several hours after the start of growth because the sublimation gas pressure of the vanadium raw material is high. As a result, vanadium is added in excess of the residual impurity concentration. This is because the region is a very limited portion of the grown crystal. If the concentration of vanadium in the SiC single crystal is 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.
[0006]
This invention is made | formed in view of the said situation, and provides the manufacturing method and raw material of the SiC single crystal which can manufacture it with high reproducibility and high quality large-diameter ingot.
[0007]
[Means for Solving the Problems]
  Therefore, the manufacturing method of the SiC single crystal of the present invention is:
  (1) A method for producing a silicon carbide single crystal comprising 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 × 10¹⁸~ 6 × 10¹⁹atom / cm³Inhibits the high resistivity of silicon carbide single crystals other than vanadiumRuPure product concentration is 1 × 10¹⁵atom / cm³A method for producing a silicon carbide single crystal, characterized by growing a silicon carbide single crystal in an inert gas atmosphere using only a silicon carbide crystal that is:
  (2) A method for producing a silicon carbide single crystal comprising 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 × 10¹⁹~ 6 × 10¹⁹atom / cm³Inhibits the high resistivity of silicon carbide single crystals other than vanadiumRuPure product concentration is 1 × 10¹⁶atom / cm³A method for producing a silicon carbide single crystal, characterized by growing a silicon carbide single crystal in an inert gas atmosphere using only a silicon carbide crystal that is:
  (3) Vanadium concentration is 1 × 10¹⁸~ 6 × 10¹⁹atom / cm³Inhibits the high resistivity of silicon carbide single crystals other than vanadiumRuPure product concentration is 1 × 10¹⁵atom / cm³A silicon carbide crystal raw material for growing a silicon carbide single crystal,
  (4) Vanadium concentration is 1 × 10¹⁹~ 6 × 10¹⁹atom / cm³Inhibits the high resistivity of silicon carbide single crystals other than vanadiumRuPure product concentration is 1 × 10¹⁶atom / cm³A silicon carbide crystal raw material for growing a silicon carbide single crystal,
  (5) A silicon carbide single crystal obtained by the production method according to (1) or (2), having a diameter of 50 mm or more, and covering the entire length of the silicon carbide single crystal excluding the seed crystal, vanadium Concentration of 1 × 10¹⁵~ 3x10¹⁷atom / cm³A silicon carbide single crystal, characterized in that
(6) The vanadium concentration is 1 × 10¹⁶~ 3x10¹⁷atom / cm³The silicon carbide single crystal according to (5),
  (7) Impeding high resistivity of silicon carbide single crystals other than vanadiumRuThe concentration of pure product isLess than the concentration of vanadium,1 × 10¹⁶ atom / cm ³ The silicon carbide single crystal according to (5) or (6),
  (8) A silicon carbide single crystal substrate obtained by cutting and polishing the silicon carbide single crystal according to any one of (5) to (7),
  (9) A silicon carbide epitaxial wafer obtained by epitaxially growing a silicon carbide thin film on the silicon carbide single crystal substrate according to (8),
  (10) 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 (8),
It is.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
  In the production method of the present invention, the concentration of vanadium as a raw material for silicon carbide (hereinafter also referred to as “SiC”) is 1 × 10 5 in advance.¹⁸~ 6 × 10¹⁹atom / cm³, Preferably 1 × 10¹⁹~ 6 × 10¹⁹atom / cm³And inhibits the high resistivity of SiC single crystals other than vanadium.RuThe concentration of pure substance is less than the concentration of vanadium, preferably the concentration of vanadium is 1 × 10¹⁸~ 6 × 10¹⁹atom / cm³In case of 1 × 10¹⁵atom / cm³Hereinafter, the concentration of vanadium is 1 × 10¹⁹~ 6 × 10¹⁹atom / cm³In case of 1 × 10¹⁶atom / cm³By using the following SiC single crystal, high resistivity (10⁶A high-quality large-diameter SiC single crystal ingot can be obtained.
[0009]
The effect of this invention is demonstrated using FIG.2 (b). In the growth of SiC single crystal by the sublimation recrystallization method, when vanadium is added to the grown crystal using a SiC crystal raw material that contains vanadium as an intracrystalline impurity in the SiC crystal in advance, the sublimation or evaporation of vanadium from the raw material is caused by the SiC crystal. It is rate-limited by decomposition | disassembly (sublimation) of a raw material. Therefore, in this case, the sublimation or evaporation rate of vanadium is not determined by the sublimation or evaporation rate of metal vanadium or vanadium compounds 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 sublimation or evaporation rate difference between the vanadium and SiC. Thus, when the sublimation or evaporation rate of vanadium is the same as the sublimation rate of the SiC crystal, vanadium is not depleted within a few hours after the start of growth, and a constant amount of vanadium is always present during growth. Can be sublimated or evaporated. As a result, it becomes possible to always add a certain amount of vanadium into the grown crystal. 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, the amount of vanadium in the SiC crystal raw material is 2 × 10¹⁹atom / cm^ThreeAs a result, the amount of vanadium incorporated into the grown crystal is 2 × 10¹⁶atom / cm^Three~ 1x10¹⁷atom / cm^ThreeIt becomes. The vanadium concentration is lower in the grown crystal than in the raw material because the vanadium uptake 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 into the SiC crystal raw material must be determined in consideration of this fact. As described above, if the concentration of vanadium in the SiC crystal raw material is determined in consideration of the incorporation rate into the grown crystal, and the SiC single crystal is grown by the sublimation recrystallization method using this raw material, the grown SiC single crystal is obtained. Vanadium that is constant and below the solid solution limit can be added with good reproducibility over the entire crystal, and as a result, a high-quality SiC single crystal can be obtained.
[0010]
  In the method for producing a SiC single crystal according to the present invention, high resistivity of SiC single crystals other than vanadium in the SiC crystal raw material is inhibited.RuAn SiC crystal raw material having a pure substance concentration less than the vanadium concentration is used. ThisThisThe concentration of the pure material may be less than the concentration of vanadium, and preferably the concentration of vanadium is 1 × 10.¹⁸~ 6 × 10¹⁹atom / cm³In case of 1 × 10¹⁵atom / cm³Or the concentration of vanadium is 1 × 10¹⁹~ 6 × 10¹⁹atom / cm³In case of 1 × 10¹⁶atom / cm³It is as follows. In these concentration range conditions, the vanadium concentration in the grown SiC single crystal always inhibits the high resistivity of the SiC single crystal.RuThis is because the concentration of the pure material is not less than that, and a particularly preferable SiC single crystal can be manufactured under the concentration conditions of the above specific examples. In order to obtain a high resistivity with a SiC single crystal to which vanadium is added, the increase in the resistivity of the SiC single crystal in an amount exceeding the amount of the added vanadium is inhibited.RuPure products should not be present in the SiC single crystal. Inhibits higher resistivity of SiC single crystal than vanadium concentration in grown crystalRuIf the concentration of pure substance has increased, the electrical characteristics of the single crystalIncongruityHigh resistivity (10⁶Ωcm or more). Since the incorporation rate of impurities that inhibit the increase in resistivity of SiC single crystals other than vanadium is approximately 1.0 at high values, the increase in resistivity of SiC single crystals other than vanadium in the SiC crystal raw material is inhibited. The impurity concentration must be the same as or lower than that allowed in the grown crystal.
[0011]
  Inhibits high resistivity of vanadium and other SiC single crystals in SiC crystals used as raw materials for sublimation recrystallizationRuIf the pure substance concentration is set within the range of the present invention, high resistivity (10⁶It has been found by the inventors from numerous experiments that an SiC single crystal of Ωcm or more can be obtained.
[0012]
  The SiC crystal raw material for growing SiC single crystal used in the present invention is, for example, high-purity silicon dioxide (SiO 2).₂) And graphite at a high temperature. SiO₂In the reaction at a high temperature (2000 ° C. or more), oxygen contained in is discharged out of the system as carbon monoxide and does not remain in the SiC crystal. Vanadium is the above-mentioned SiO.₂+ Added to graphite in the form of high purity metal vanadium and incorporated into SiC crystals during the reaction. The vanadium concentration in the SiC crystal varies depending on the growth site, but is uniformized when the crystal is crushed and adjusted in particle size (powdered) after growth. The vanadium concentration in the SiC crystal raw material is 1 × 10¹⁹~ 6 × 10¹⁹atom / cm³Or 1 × 10¹⁸~ 6 × 10¹⁹atom / cm³SiO in a molar ratio of 1: 1₂+ High purity vanadium having a molar ratio with respect to Si of 4 to 24% or 0.4 to 24% may be added to graphite. At this time, however, the remaining metal vanadium that has not been incorporated into the SiC crystal is attached around the produced crystal grains. Therefore, in order to obtain an SiC crystal raw material having a desired vanadium concentration, the crystal is crushed and the particle size is adjusted. Before this is done, it is necessary to remove this adhesion layer by acid cleaning. Moreover, the high resistivity of the SiC single crystal in the SiC crystal raw material manufactured in this way is inhibited.RuPure substance concentration is less than the vanadium concentration, preferably 1 × 10¹⁶atom / cm³Or 1 × 10¹⁵atom / cm³To make the following, the starting SiO₂In graphite, vanadiumIncongruityThe pure substance concentration must be 0.2 ppm or less or 0.02 ppm or less in terms of atomic concentration.
[0013]
  The SiC single crystal ingot produced by the production method of the present invention can be characterized by having a large diameter of 50 mm or more, high resistivity, and few crystal defects due to vanadium precipitates. Further, the vanadium concentration is 1 × 10 6 over the entire length of the silicon carbide single crystal excluding the seed crystal.¹⁵~ 3x10¹⁷atom / cm³, Preferably 1 × 10¹⁶~ 3x10¹⁷atom / cm³If so, the high resistivity of SiC single crystal is hindered.Ru10 without being affected by pure products⁶High resistivity of Ωcm or higher is shown. 3 × 10¹⁷atom / cm³A vanadium concentration exceeding 1 is not preferable because vanadium precipitates in the SiC single crystal.
[0014]
Since the SiC single crystal substrate obtained by cutting and polishing the SiC single crystal ingot thus manufactured has a diameter of 50 mm or more, it is industrially established when manufacturing various devices using this substrate. A conventional production line for semiconductor (Si, GaAs, etc.) wafers can be used, which is suitable for mass production. In particular, since the resistivity of the substrate is high, it can be applied to a device having a high operating frequency. Furthermore, an 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 a thin film epitaxial wafer formed by epitaxially growing a mixed crystal of GaN, AlN, InN and these, Since the SiC single crystal substrate as the substrate has very few crystal defects due to vanadium precipitates, the SiC single crystal substrate has good characteristics (surface morphology, electrical characteristics, etc. of the epitaxial thin film).
[0015]
【Example】
(Example)
An embodiment of the present invention will be described below with reference to FIG. First, this 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. The seed crystal SiC single crystal 1 is attached to the inner surface of a graphite crucible lid 4 of a high-purity graphite crucible 3. The SiC crystal powder raw material 2 is filled in the crucible 3. Such a crucible 3 is installed inside a double quartz tube 5 by a support rod 6 made of graphite. Around the crucible 3, a graphite felt 7 for heat shielding is installed. The double quartz tube 5 is subjected to high vacuum exhaust (10^-3Pa or less) and the internal atmosphere can be pressure controlled by Ar gas. In addition, a work coil 8 is provided on the outer periphery of the double quartz tube 5, and the crucible 3 can be heated by flowing a high-frequency current to heat the raw material and the seed crystal to a desired temperature. The temperature of the crucible is measured using a two-color thermometer by providing an optical path having a diameter of 2 to 4 mm at the center of the felt covering the upper and lower parts of the crucible and extracting light from the upper and lower parts of the crucible. The temperature at the bottom of the crucible is the raw material temperature, and the temperature at the top of the crucible is the seed temperature.
[0016]
  Next, an example of manufacturing a SiC single crystal using this crystal growth apparatus will be described. First, a hexagonal SiC single crystal wafer having a (0001) face with a diameter of 50 mm was prepared as a seed crystal. Next, the seed crystal 1 was attached to the inner surface of the graphite crucible lid 4 of the crucible 3. The inside of the crucible 3 was filled with SiC crystal raw material powder 2. The SiC crystal used as the raw material powder is SiO prepared at a molar ratio of 1: 1.₂It was prepared by adding 8% of high-purity vanadium in a molar ratio with respect to Si in + graphite and reacting in a high temperature furnace. SiO used at this time₂In graphite, vanadiumIncongruityPure substance concentration is 1 × 10¹⁶atom / cm³It was the following. The vanadium concentration in the obtained SiC crystal powder was 2 × 10.¹⁹atom / cm³Met. Other than vanadiumIncongruityPure substance concentration is 1 × 10¹⁶atom / cm³It was the following. Next, the crucible 3 filled with the raw material was closed with a graphite crucible lid 4, covered with a graphite felt 7, placed on a graphite support rod 6, and installed inside the double quartz tube 5. Then, 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. Thereafter, high purity Ar gas is introduced as atmospheric gas through the high purity Ar gas pipe 9 while being controlled by the mass flow controller 10 for high purity Ar gas, and the raw material temperature is set to the target temperature while maintaining the pressure in the quartz tube at about 80 kPa. It was raised to 2400 degrees Celsius. The growth pressure was reduced to 1.3 kPa over about 30 minutes, and then the growth was continued for about 20 hours. At this time, the temperature gradient in the crucible was 15 degrees Celsius / cm, and the growth rate was about 0.8 mm / hour. The diameter of the obtained crystal was 51 mm, and the height was about 16 mm.
[0017]
  When the silicon carbide single crystal thus obtained was analyzed by X-ray diffraction and Raman scattering, it was confirmed that a hexagonal SiC single crystal was grown. For the purpose of measuring the impurity concentration of crystals, nine wafers having a thickness of 1 mm were cut out from the grown single crystal ingot. The plane orientation of the wafer was 3.5 degrees off from the (0001) plane in the <11-20> direction. When the impurity concentrations in the wafers corresponding to the upper, middle, and lower portions (near the seed crystal) of the grown crystal (the ninth, fifth, and second wafers from the seed crystal, respectively) were examined, the vanadium concentration was 6 × 10 for any wafer¹⁶atom / cm³Degree, otherwiseIncongruityThe concentration of pure substances is 1 × 10¹⁶atom / cm³It was the following. Further, when the obtained wafer was observed with a microscope, no defect that might be caused by vanadium precipitates was observed. Further, when the resistivity of each wafer was examined by electrical measurement, every wafer was found to be 10⁶The resistivity was as high as Wcm or more.
[0018]
Next, the SiC single crystal wafer thus manufactured was polished to produce a SiC single crystal mirror wafer having a thickness of 300 microns and a diameter of 51 mm.
[0019]
Further, SiC was epitaxially grown using this 51 mm diameter SiC single crystal mirror wafer as a substrate. The growth conditions of the SiC epitaxial thin film are as follows: the growth temperature is 1500 degrees Celsius, and silane (SiH_Four), Propane (C_ThreeH₈), Hydrogen (H₂) Flow rate of 5.0 × 10 respectively^-9m^Three/ Sec, 3.3 × 10^-9m^Three/ Sec, 5.0 × 10^-Fivem^Three/ Sec. The growth pressure was atmospheric pressure. The growth time was 2 hours, and the film thickness was about 5 μm.
[0020]
After the epitaxial thin film was grown, the surface morphology of the obtained epitaxial thin film was observed with a Nomarski optical microscope. It turns out that a thin film is growing.
[0021]
In addition, a (0001) plane wafer having an off angle of 0 degrees 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). Epitaxially grown. The growth conditions are as follows: growth temperature 1050 degrees Celsius, trimethylgallium (TMG), ammonia (NH_Three), Silane (SiH)_Four) 54 × 10 respectively^-6Mol / min, 4 liters / min, 22 × 10^-11Mol / min flowed. The growth pressure was atmospheric pressure. The growth time was 60 minutes, and n-type gallium nitride was grown to a thickness of 3 μm.
[0022]
For the purpose of examining the surface state of the obtained GaN thin film, the growth surface was observed with a Nomarski optical microscope. It was found that a very flat morphology was obtained over the entire wafer surface, and a high-quality GaN thin film was formed over the entire surface.
[0023]
(Comparative example)
As a comparative example, the production of a high resistivity SiC single crystal by a conventional method will be described. As in the above example, a hexagonal SiC single crystal wafer having a (0001) plane with a diameter of 50 mm was prepared as a seed crystal. 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 obtained by washing the abrasive. Furthermore, 0.4% of metal vanadium was added to this raw material powder in a molar ratio with respect to Si. The crucible 3 filled with the raw material was closed with a graphite crucible lid 4, covered with a graphite felt 7, placed on a graphite support rod 6, and installed inside the double quartz tube 5. Then, 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. Thereafter, high-purity Ar gas was introduced as the atmospheric gas, and the raw material temperature was raised to the target temperature of 2400 degrees Celsius while maintaining the pressure in the quartz tube at about 80 kPa. The growth pressure was reduced to 1.3 kPa over about 30 minutes, and then the growth was continued for about 20 hours. At this time, the temperature gradient in the crucible was 15 degrees Celsius / cm, and the growth rate was about 0.8 mm / hour. The diameter of the obtained crystal was 51 mm, and the height was about 17 mm.
[0024]
  When the silicon carbide single crystal thus obtained was analyzed by X-ray diffraction and Raman scattering, it was confirmed that a hexagonal SiC single crystal was grown. For the purpose of measuring the impurity concentration of crystals, nine wafers having a thickness of 1 mm were cut out from the grown single crystal ingot. The plane orientation of the wafer was 3.5 degrees off from the (0001) plane in the <11-20> direction. When the impurity concentrations in the wafers corresponding to the upper, middle, and lower portions (near the seed crystal) of the grown crystal (the ninth, fifth, and second wafers from the seed crystal, respectively) were examined, the vanadium concentration was 5 × 10 for the wafer corresponding to the lower part of the grown crystal¹⁸atom / cm³In the case of wafers corresponding to the middle and upper parts, 5 × 10¹⁶atom / cm³It was the following. All wafers except vanadiumIncongruityThe concentration of pure product is 2 × 10¹⁷atom / cm³It was about. When the obtained wafer was observed with a microscope, crystal defects thought to be caused by vanadium precipitates were observed on the wafer corresponding to the lower part of the grown crystal. Further, when the resistivity of each wafer was examined by electrical measurement, 10 wafers corresponding to the lower part of the grown crystal were found.⁶Although a high resistivity of Wcm or more was shown, wafers corresponding to the middle and upper portions showed a low resistivity of 0.4 Wcm.
[0025]
Next, among the SiC single crystal wafers manufactured in this way, those having a high resistivity (wafer corresponding to the lower part of the grown crystal) are polished, and a SiC single crystal mirror wafer having a thickness of 300 microns and a diameter of 51 mm is obtained. Produced.
[0026]
Further, SiC was epitaxially grown using this 51 mm diameter SiC single crystal mirror wafer as a substrate. The growth conditions of the SiC epitaxial thin film are as follows: the growth temperature is 1500 degrees Celsius, and silane (SiH_Four), Propane (C_ThreeH₈), Hydrogen (H₂) Flow rate of 5.0 × 10 respectively^-9m^Three/ Sec, 3.3 × 10^-9m^Three/ Sec, 5.0 × 10^-Fivem^Three/ Sec. The growth pressure was atmospheric pressure. The growth time was 2 hours, and the film thickness was about 5 μm.
[0027]
After the epitaxial thin film was grown, the surface morphology of the obtained epitaxial thin film was observed with a Nomarski optical microscope. A defect appeared.
[0028]
Further, a high resistivity (0001) plane wafer having an off angle of 0 degree was cut out from another SiC single crystal ingot produced in the same manner (cut out from a region in the vicinity of the seed crystal), mirror-polished, and then GaN thereon The thin film was epitaxially grown by metal organic chemical vapor deposition (MOCVD). The growth conditions are as follows: growth temperature 1050 degrees Celsius, trimethylgallium (TMG), ammonia (NH_Three), Silane (SiH)_Four) 54 × 10 respectively^-6Mol / min, 4 liters / min, 22 × 10^-11Mol / min flowed. The growth pressure was atmospheric pressure. The growth time was 60 minutes, and n-type gallium nitride was grown to a thickness of 3 μm.
[0029]
For the purpose of investigating the surface state of the obtained GaN thin film, the growth surface was observed with a Nomarski optical microscope. As a result, the portion grown on the wafer where defects due to vanadium precipitates existed was found to be pit-like. A surface defect occurred.
[0030]
【The invention's effect】
As described above, according to the present invention, a high-resistivity, high-quality SiC single crystal can be grown with good reproducibility by an improved sublimation recrystallization method (Rayleigh method) using a seed crystal. 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 price.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining the principle of an improved Rayleigh method.
FIGS. 2A and 2B are diagrams for explaining the effects of the present invention, in which FIG. 2A shows vanadium and residual impurity concentration distribution in a SiC single crystal manufactured by a conventional method, and FIG. 2B shows the effect of the present invention. 2 shows vanadium and residual impurity concentration distribution in a SiC single crystal.
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 insulation)
8 Work coil
9 High purity Ar gas piping
10 Mass flow controller for high purity Ar gas
11 Vacuum exhaust system

Claims (10)

A method for producing a silicon carbide single crystal comprising 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 × 10 ^{18 to} 6 × 10 ¹⁹ atoms / cm ^3. , and the concentration of non neat you inhibit high resistivity of the silicon carbide single crystal other than vanadium using only is 1 × 10 15 ^{atom /} cm ³ or less silicon carbide crystals in an inert gas atmosphere A method for producing a silicon carbide single crystal, comprising growing a silicon carbide single crystal. A method for producing a silicon carbide single crystal comprising 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 × 10 ^{19 to} 6 × 10 ¹⁹ atoms / cm ^3. , and the concentration of non neat you inhibit high resistivity of the silicon carbide single crystal other than vanadium using alone is silicon carbide crystals below ^{1 × 10 16 atom / cm 3} , in an inert gas atmosphere A method for producing a silicon carbide single crystal, comprising growing a silicon carbide single crystal. The concentration of vanadium is that ^{1 × 10 18 ~6 × 10 19} atom / cm 3, the concentration of non neat you inhibit high resistivity of the silicon carbide single crystal other than vanadium 1 × ¹⁰ 15 atom / cm ³ The silicon carbide crystal raw material for silicon carbide single crystal growth which is the following. The concentration of vanadium is that ^{1 × 10 19 ~6 × 10 19} atom / cm 3, the concentration of non neat you inhibit high resistivity of the silicon carbide single crystal other than vanadium 1 × ¹⁰ 16 atom / cm ³ The silicon carbide crystal raw material for silicon carbide single crystal growth which is the following. A silicon carbide single crystal obtained by the production method according to claim 1, wherein the concentration of vanadium is 1 × over the entire length of the silicon carbide single crystal having a diameter of 50 mm or more excluding the seed crystal. A silicon carbide single crystal characterized by being 10 ^{15 to} 3 × 10 ¹⁷ atoms / cm ³ . The silicon carbide single crystal according to claim 5, wherein the vanadium concentration is 1 × 10 ^{16 to} 3 × 10 ¹⁷ atoms / cm ³ . Is not neat concentration you inhibit high resistivity of the silicon carbide single crystal other than vanadium, less than the concentration of vanadium carbide according to claim 5 or 6 is 1 × 10 16 ^{atom /} cm ³ or less Silicon single crystal.   A silicon carbide single crystal substrate obtained by cutting and polishing the silicon carbide single crystal according to any one of claims 5 to 7.   A silicon carbide epitaxial wafer obtained by epitaxially growing a silicon carbide thin film on the silicon carbide single crystal substrate according to claim 8.   A thin film epitaxial wafer formed by epitaxially growing gallium nitride, aluminum nitride, indium nitride or a mixed crystal thereof on the silicon carbide single crystal substrate according to claim 8.

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