JP2007230823A - Method for manufacturing silicon carbide single crystal ingot, and silicon carbide single crystal ingot - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing an SiC single crystal ingot from which large-diameter, good-quality face ä0001} wafers almost free from dislocation defects can inexpensively be obtained with good reproducibility. <P>SOLUTION: A part or the whole of silicon carbide single crystal 12 is grown using a seed crystal 1 by a sublimation-recrystallization method in such a state as to increase the electron concentration of the growing single crystal 12 to ≥1×10<SP>19</SP>cm<SP>-3</SP>but ≤6×10<SP>20</SP>cm<SP>-3</SP>. Thereby, the dislocation defect is reduced to obtain the high-quality, large-diameter silicon carbide single crystal ingot 12. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a silicon carbide single crystal ingot and a method for manufacturing the same, and more particularly, to a high-quality and large single crystal ingot that becomes a substrate wafer for an electronic device and a method for manufacturing the same.

  Silicon carbide (SiC) has attracted attention as an environmentally resistant semiconductor material because of its physical and chemical properties such as excellent heat resistance and mechanical strength, and 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, high frequency / high voltage electronic devices, and the like 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 materials having many advantages and possibilities as described above.

  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 manufacturing 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. Also, it is not easy to control the crystal polymorphism and impurity carrier concentration of SiC. In addition, a cubic SiC single crystal is grown by heteroepitaxial growth on a heterogeneous substrate such as silicon (Si) using a chemical vapor deposition method (CVD method). In this method, a single crystal having a large area can be obtained. However, since the lattice mismatch with the substrate is about 20%, crystal defects such as stacking faults are easily generated, and it is difficult 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 (Non-Patent Document 1) and is being implemented by many research institutions. 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 to about 100 Pa to 15 kPa with an inert gas. .

  The principle of the improved Rayleigh method will be described with reference to FIG. The SiC single crystal (silicon carbide wafer) 1 used as a seed crystal and the SiC crystal powder 2 used as a raw material are stored in a crucible (usually graphite) 3 and in an inert gas atmosphere such as argon (133 to 13.3 kPa) , Heated to 2000-2400 ° C. At this time, the temperature gradient is set so that the seed crystal 1 is slightly lower in temperature than the raw material powder 2. After sublimation, the raw material (SiC crystal powder) 2 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 recrystallizing the source gas arriving at the seed crystal on the seed crystal (growth crystal 12 in the figure). At this time, the resistivity of the obtained crystal can be controlled by adding an impurity gas in an atmosphere made of an inert gas or mixing an impurity element or a compound thereof in the SiC raw material powder. Representative examples of substitutional impurities in SiC single crystals include nitrogen (n-type), boron (p-type), and aluminum (p-type). 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.) and the shape, carrier type and concentration of the SiC single crystal.

Currently, SiC single crystal wafers having a diameter of 2 inches (50.8 mm) to 3 inches (76.2 mm) are manufactured by the above-described improved Rayleigh method, and are used for epitaxial thin film growth and device fabrication. However, these SiC single crystal wafers contain about 10 ⁴ to 10 ⁵ cm ^{−2 of} dislocation defects penetrating in the growth direction (crystal c-axis direction), which hinders the production of high-performance devices.

  A threading dislocation defect that propagates substantially parallel to the c-axis direction is a plane whose inclination from the {0001} plane is 60 to 120 ° (preferably 90 °), for example, the a plane ({11-20} plane) or the m plane. Patent Document 1 discloses that it can be completely prevented by growing a SiC single crystal in the <0001> direction, that is, substantially perpendicular to the c-axis direction, using ({1-100} plane) as a seed crystal. Has been. However, with this method, dislocation defects penetrating in the c-axis direction can be completely suppressed, but basal plane dislocations existing in the direction perpendicular to the c-axis remain and a new stacking fault occurs. However, this is disclosed in Non-Patent Document 2.

On the other hand, Patent Document 2 includes N growth steps (N is a natural number of N ≧ 3), and in the first growth step where n = 1, the off angle ± 20 from the {1-100} plane. A SiC single crystal in a direction perpendicular to the first growth plane, using a first seed crystal whose first growth plane is a plane of less than 0 ° or a plane with an off angle of ± 20 ° or less from the {11-20} plane In the intermediate growth step where n = 2, 3,..., (N-1) time (N ≧ 3 natural number), 45% from the (n-1) growth plane. An n-th seed crystal is formed from the (n-1) -th growth crystal with a plane inclined by ~ 90 ° and a plane inclined by 60-90 ° from the {0001} plane as the n-th growth plane. An n-th growth crystal is produced in a direction perpendicular to the n-growth plane, and in the final growth step where n = N, a plane having an off angle of ± 20 ° or less from the {0001} plane of the (N-1) -th growth crystal The final seed crystal as the final growth surface is prepared from the (N-1) th growth crystal and is orthogonal to the final growth surface of this final seed crystal. By producing bulk SiC single crystal in the direction, the manufacturing method of threading dislocations and stacking faults is very small high-quality SiC single crystals.
JP-A-5-2562599 JP 2003-119097 Yu. M. Tairov and VF Tsvetkov, Journal of Crystal Growth, Vol.52 (1981) pp.146-150 J. Takahashi et al., Journal of Crystal Growth, Vol.181 (1997) pp.229-240

  However, in the method described in Patent Document 1 or 2 described above, the growth direction of the single crystal is greatly inclined from the c-axis direction (vertical direction of {0001} plane) (tilt angle: 60 ° or more). Therefore, in order to obtain a {0001} plane wafer having a large diameter, it is necessary to grow a crystal to a length substantially corresponding to the diameter. For this reason, the time required for crystal growth becomes longer, and the productivity of crystal production decreases. Furthermore, in SiC single crystal growth, it is generally difficult to maintain optimum growth conditions for a long time due to changes in the raw materials and crucibles over time. As a result, it is difficult to improve the quality of long crystals. Therefore, in the method described in Patent Document 1 or 2, the yield of crystal growth is reduced and the crystal production cost is significantly increased as the crystal growth is prolonged.

  The present invention has been made in view of the above circumstances, and a method for producing a SiC single crystal ingot for producing a high-quality large-diameter {0001} plane wafer with few threading dislocation defects at low cost with good reproducibility, and A SiC single crystal ingot is provided.

The present invention
(1) In a manufacturing method for producing a bulk SiC single crystal ingot by growing a SiC single crystal on a seed crystal made of SiC single crystal, the electron concentration of the grown SiC single crystal is 1 × 10 ¹⁹ cm ⁻³ or more A method for producing a SiC single crystal ingot characterized by growing a part or all of a single crystal in a state of 6 × 10 ²⁰ cm ⁻³ or less,
(2) The method for producing a SiC single crystal ingot according to (1), wherein the electron concentration is 3 × 10 ¹⁹ cm ⁻³ or more and 6 × 10 ²⁰ cm ⁻³ or less,
(3) The method for producing a SiC single crystal ingot according to (1) or (2), wherein an impurity is added to a growing SiC single crystal to control an electron concentration,
(4) The method for producing a SiC single crystal ingot according to (3), wherein the impurity is nitrogen,
(5) The method for producing a SiC single crystal ingot according to (1) or (2), wherein the electron concentration is controlled by irradiating light to the growing SiC single crystal,
(6) The method for producing a SiC single crystal ingot according to (5), wherein the wavelength of the light is 250 nm or more and 400 nm or less,
(7) SiC single crystal ingot obtained by the production method according to (1) to (6), wherein the ingot has a diameter of 50 mm to 300 mm, SiC single crystal ingot,
(8) The SiC single crystal ingot according to (7), wherein the total etch pit density caused by dislocations measured on a {0001} plane 8 ° off-wafer cut out from the ingot is 1 × 10 ⁴ cm ⁻ SiC single crystal ingot characterized by being ² or less,
(9) SiC single crystal substrate obtained by cutting and polishing the SiC single crystal ingot according to (7) or (8),
(10) A SiC epitaxial wafer obtained by epitaxially growing a SiC thin film on the SiC single crystal substrate according to (9),
(11) The thin film epitaxial wafer formed by epitaxially growing gallium nitride (GaN), aluminum nitride (AlN), indium nitride (InN) or a mixed crystal thereof on the SiC single crystal substrate according to (9),
It is.

  By using the production method of the present invention, a high-quality SiC single crystal with few dislocation defects can be grown with good reproducibility at low cost. By using a wafer and an epitaxial wafer cut out from such a SiC single crystal, it is possible to manufacture a blue light-emitting element with excellent optical characteristics and a high-frequency / high-voltage electronic device with excellent electrical characteristics.

According to the method for producing a SiC single crystal ingot of the present invention, when a SiC single crystal is grown on a seed crystal made of a SiC single crystal to produce a bulk SiC single crystal ingot, the electron concentration of the grown SiC single crystal Dislocation defects in the SiC single crystal can be reduced by growing a part or all of the single crystal in a state where is set to 1 × 10 ¹⁹ cm ⁻³ or more.

The effect of the present invention will be described with reference to FIG. In the method for producing a SiC single crystal ingot according to the present invention, as schematically shown in FIG. 2, when a bulk SiC single crystal is grown on the seed crystal 1, the electron concentration of a part or all of it is 1 ×. Crystal growth is performed at 10 ¹⁹ cm ⁻³ or more. The inventors have found from many crystal growth experiments that threading dislocation defects are terminated in the region where the crystal growth is performed with the electron concentration of 1 × 10 ¹⁹ cm ⁻³ or more. The intermediate termination of threading dislocation defects means a decrease in the dislocation density of the grown crystal, leading to higher quality of the grown crystal. In addition, in FIG. 2, the crystal growth region (high electron concentration) after the region (high electron concentration growth crystal) 13 where the crystal growth is performed with a high electron concentration of 1 × 10 ¹⁹ cm ⁻³ or more is shown. This shows that there is a difference in the dislocation density in the grown crystal between the grown crystal 14 after the region and the crystal grown region 12 before that.

  The mechanism by which threading dislocation defects are terminated will be described below. In SiC single crystal growth, it is known that when the electron concentration is increased, the laminated structure of the SiC single crystal changes. For example, when a 4H polytype crystal is grown and the electron concentration is increased, a 3C polytype stack structure (a kind of stacking fault) appears. This is because the conduction band of 3C polytype (energy band in which the existence of electrons is allowed) is lower in energy than the conduction band of 4H polytype. That is, when the electron concentration of the crystal increases, the energy of the electron system is reduced by the appearance of a 3C polytype stacked structure having a low energy position in the conduction band. At this time, dislocation groups such as threading dislocations and basal plane dislocations are the nuclei of the 3C polytype laminated structure. When threading dislocations become the generation nucleus of this 3C multilayer structure, the threading dislocations that were going to penetrate in the c-axis direction are accompanied by structural defects in the basal plane, such as base area layer defects. Convert to etc. The threading dislocations converted into structural defects in the basal plane do not propagate in the c-axis direction (crystal growth direction) in subsequent crystal growth, and as a result, crystals grown after the region grown with a high electron concentration The dislocation density is lowered at the site. The reduction rate of dislocation defects varies depending on the growth conditions, but is about 1/4 to 2/3 of the density of the seed crystal.

  There are several methods for increasing the electron concentration during crystal growth. First, there is a method of adding an impurity (donating electrons in a SiC single crystal) which becomes a donor during crystal growth. Nitrogen, arsenic, phosphorus, etc. can be considered as such impurities. The electron concentration can also be increased by irradiating the growing crystal with light. At this time, the wavelength of light is preferably 250 nm or more and 400 nm or less. When the wavelength of light is less than 250 nm, light is absorbed at the extreme surface of the crystal, and the termination effect of threading dislocation cannot be obtained over a large area. In addition, when the wavelength of light exceeds 400 nm, the energy of light becomes less than the forbidden band width of the SiC single crystal, and the electron generation efficiency is remarkably reduced.

The electron concentration causing the termination of threading dislocations is 1 × 10 ¹⁹ cm ⁻³ or more and 6 × 10 ²⁰ cm ⁻³ or less, preferably 3 × 10 ¹⁹ cm ⁻³ or more and 6 × 10 ²⁰ cm ⁻³ or less. When the electron concentration is less than 1 × 10 ¹⁹ cm ⁻³ , it is difficult to obtain the above-described effect (the 3C polytype laminated structure is not stabilized). Further, when the electron concentration exceeds 6 × 10 ²⁰ cm ⁻³ , the crystallinity of the grown crystal is significantly deteriorated, which is not preferable.

The above electron concentration is 1 × 10 ¹⁹ cm ⁻³ or more and 6 × 10 ²⁰ cm ⁻³ or less, preferably 3 × 10 ¹⁹ cm ⁻³ or more and 6 × 10 ²⁰ cm ⁻³ or less in the growing SiC single crystal. This can be realized by adding a donor impurity. For example, in the case of a nitrogen donor, it can be realized by controlling the nitrogen gas partial pressure in the atmospheric gas in the range of 170 Pa to 5.3 kPa in bulk SiC single crystal growth by the modified Rayleigh method. On the other hand, in the case of electron concentration control by light irradiation, when the light penetration length is estimated to be about 1 mm, a desired electron concentration can be realized with a light irradiation amount of 0.5 to ³ W / cm ² per unit area. Light irradiation of the SiC single crystal during crystal growth can be performed by providing a minute light irradiation window at the bottom of a sufficiently insulated crucible. As for the electron concentration, when impurities are added, it can be obtained from the donor concentration to be added, as described in the following examples. On the other hand, in the case of light irradiation, from the number of incident photons per unit area. Can be estimated.

  The end of the dislocation defect starts to appear when the thickness of the region with a high electron density is 1 mm or more, and becomes more prominent as the thickness of the region increases. Therefore, it is preferable that the high electron concentration crystal region be at least 1 mm thick in the growth direction of the single crystal. However, when the thickness of the high electron concentration region is 5 mm or more, the mechanism is not well understood, but the effect (reduction rate of dislocation defects) tends to be saturated.

In the present invention, a high-quality single crystal can be obtained by controlling the electron concentration of the growing silicon carbide single crystal. Therefore, a large-diameter silicon carbide single crystal ingot is prepared by preparing a large seed crystal. Obtainable. In particular, if a SiC single crystal substrate obtained by cutting and polishing an ingot having a diameter of 50 mm or more and 300 mm or less, a conventional semiconductor (established industrially) when manufacturing various devices using this substrate ( Si, GaAs, etc.) production lines for substrates can be used and are suitable for mass production. In addition, since the dislocation density of this substrate is as low as 1 × 10 ⁴ cm ^-2 or less in terms of etch pit density on the {0001} plane 8 ° off-wafer, when the device is fabricated on this substrate, the reverse leakage of the device The current can be reduced, and is particularly suitable for manufacturing a large current and high output device.

  Furthermore, a SiC single crystal epitaxial wafer produced by growing a SiC epitaxial thin film having a thickness of about 0.1 to 500 μm on this SiC single crystal substrate by a CVD method or the like, or GaN, AlN, InN and mixed crystal thin film epitaxial thereof. The wafer has good characteristics (such as withstand voltage and surface morphology of the epitaxial thin film) because the dislocation density of the SiC single crystal substrate as the substrate is small.

Below, the Example and comparative example of this invention are described.
FIG. 3 shows a manufacturing apparatus according to the method for manufacturing a silicon carbide single crystal ingot of the present invention, which is an example of an apparatus for growing a SiC single crystal by an improved Rayleigh method using a seed crystal.

First, this single crystal growth apparatus will be briefly described. Crystal growth is performed by sublimating and recrystallizing SiC powder 2 as a raw material on SiC single crystal 1 having an inclined surface used as a seed crystal on the growth surface. The seed crystal SiC single crystal 1 is attached to the inner surface of the lid 4 of the graphite crucible 3. The raw material SiC powder 2 is filled in a graphite crucible 3. Such a graphite crucible 3 is installed inside a double quartz tube 5 by a graphite support rod 6. Around the graphite crucible 3, a graphite felt 7 for heat shielding is attached. The double quartz tube 5 can be high vacuum evacuated (10 ⁻³ Pa or less) by the vacuum evacuation device 11, and the Ar gas pipe 9 and the Ar gas mass flow controller 10 provided in the double quartz tube 5 The internal atmosphere can be pressure controlled with Ar gas. A work coil 8 is provided on the outer periphery of the double quartz tube 5, and the graphite 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 (not shown) by providing an optical path with a diameter of 2 to 4 mm at the center of the felt covering the upper and lower parts of the crucible, taking out light from the upper and lower parts of the crucible. At this time, the temperature at the lower part of the crucible is the raw material temperature, and the temperature at the upper part of the crucible is the seed crystal temperature.

Next, an example of manufacturing a SiC single crystal using this crystal growth apparatus will be described. First, from a previously grown SiC single crystal ingot, a {0001} plane 4 ° off-wafer with a diameter of 50 mm and a thickness of 1 mm is used as a seed crystal 1, and further a {0001} plane with a diameter of 50 mm and a thickness of 0.5 mm is 8 °. Each off-wafer was prepared as an etch pit density measurement wafer. Next, for the purpose of measuring the threading dislocation density and the basal plane dislocation density in the SiC single crystal ingot, the etch pit observation of the {0001} plane 8 ° off-wafer was performed. As a result, the etch pit densities due to threading dislocations and basal plane dislocations were 1.8 × 10 ⁴ cm ⁻² and 2.6 × 10 ³ cm ⁻² , respectively.

  Thereafter, the seed crystal 1 cut out from the same ingot as the evaluation wafer was attached to the inner surface of the lid 4 of the graphite crucible 3. The raw material 2 was filled in the graphite crucible 3. As the raw material 2, a commercially available SiC crystal powder (purity: 99.9% or more) obtained after acid cleaning and drying was used. Next, the graphite crucible 3 filled with the raw material is closed with the lid 4 to which the seed crystal 1 is attached, covered with the graphite felt 7, and then placed on the graphite support rod 6, and inside the double quartz tube 5 installed.

  Then, after evacuating the inside of the quartz tube 5, a current was passed through the work coil 8 to raise the raw material temperature to 2000 ° C. Thereafter, Ar gas containing 3% nitrogen was introduced as an atmospheric gas, and the raw material temperature was raised to the target temperature of 2400 ° C. 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 SiC single crystal growth was continued for about 50 hours. At this time, the temperature gradient in the crucible was 15 ° C./cm, and the average growth rate was about 0.60 mm / hour. On the way, for the purpose of crystal growth in a high electron concentration state, the nitrogen gas content in the atmospheric gas was increased from 3% to 50% from 15 hours after the start of growth, and the crystal growth was performed for 10 hours as it was. . Thereafter, the content of nitrogen gas in the atmospheric gas was returned from 50% to 3%, and the growth was continued for 25 hours to complete the crystal process.

The finally obtained crystal (ingot) had a diameter of 51.5 mm and a height of about 30 mm. The electron concentration during the crystal growth in the region where the crystal was grown in a high electron concentration state (13-18 mm from the crystal growth edge) was estimated to be 3-4 × 10 ¹⁹ cm ⁻³ . The estimation of the electron concentration during crystal growth was made such that the nitrogen element concentration in the SiC single crystal = the electron concentration at high temperature, considering that the activation rate of the nitrogen donor at high temperature was 100%. The nitrogen element concentration in the SiC single crystal was measured by secondary ion mass spectrometry.

When the SiC single crystal thus obtained was analyzed by X-ray diffraction and Raman scattering, it was confirmed that a 4H type SiC single crystal ingot had grown. Also, in order to evaluate the threading dislocation and basal plane dislocation density existing in the grown crystal, the {0001} plane 8 ° off-wafer from the latter half of the grown single crystal ingot (grown crystal after the high electron concentration region) Cut out and polished. After that, the wafer surface was etched with molten KOH at about 530 ° C., and the density of etch pits corresponding to threading dislocations and basal plane dislocations was examined with a microscope, and the average of 0.7 × 10 ⁴ cm ⁻² , 1.9 on the entire wafer surface, respectively. × 10 ³ cm ^-2 That is, the total etch pit density was 0.89 × 10 ⁴ cm ⁻² .

Further, a {0001} -plane SiC single crystal substrate having a diameter of 51 mm was cut out from the latter half of the SiC single crystal growth, and used as a mirror substrate. The plane orientation of the substrate was 8 ° off in the [11-20] direction on the (0001) Si plane. SiC was epitaxially grown using this SiC single crystal substrate. The growth conditions of the SiC epitaxial thin film are as follows: the growth temperature is 1500 ° C., the flow rates of silane (SiH ₄ ), propane (C ₃ H ₈ ), and hydrogen (H ₂ ) are 5.0 × 10 ⁻⁹ m ^{3 /} sec and 3.3 × 10 respectively. ^-9 m ³ / sec, 5.0 × 10 ^-5 m ³ / sec. The growth pressure was atmospheric pressure. The growth time was 2 hours, and a silicon carbide epitaxial wafer on which a SiC thin film having a film thickness of about 5 μm was grown was obtained.

  After the epitaxial thin film was grown, the surface morphology of the obtained epitaxial thin film was observed with a Nomarski optical microscope. It was confirmed that it was growing.

Similarly, from the SiC single crystal, a (0001) Si surface SiC single crystal substrate with an off angle of 0 ° was cut out and mirror-polished, and then a GaN thin film was formed on the metal organic chemical vapor deposition (MOCVD) method. By epitaxial growth. Growth conditions are: growth temperature 1050 ° C., trimethylgallium (TMG), ammonia (NH ₃ ), silane (SiH ₄ ), 54 × 10 ⁻⁶ mol / min, 4 liter / min, 22 × 10 ⁻¹¹ mol / min, respectively. Min shed. The growth pressure was atmospheric pressure. The growth time was 20 minutes, and a thin film epitaxial wafer was obtained by growing n-type GaN with a thickness of about 1 μm.

  In order to investigate the surface state of the obtained GaN thin film, the growth surface was observed with a Nomarski optical microscope. A very flat morphology was obtained over the entire wafer surface, and it was confirmed that a high-quality GaN thin film was formed over the entire surface.

[Comparative Example 1]
A comparative example in which the nitrogen gas content in the atmospheric gas is fixed at 3% will be described. First, from a previously grown SiC single crystal ingot, a {0001} plane 4 ° off-wafer with a diameter of 50 mm and a thickness of 1 mm is used as a seed crystal 1, and further a {0001} plane with a diameter of 50 mm and a thickness of 0.5 mm is 8 °. Each off-wafer was prepared as an etch pit density measurement wafer. Next, for the purpose of measuring the threading dislocation density and the basal plane dislocation density in the SiC single crystal ingot, etch pit observation of the {0001] plane 8 ° off-wafer was performed. As a result, the etch pit densities due to threading dislocations and basal plane dislocations were 1.6 × 10 ⁴ cm ⁻² and 2.2 × 10 ³ cm ⁻² , respectively.

Thereafter, using the seed crystal 1 cut out from the same ingot as the evaluation wafer, crystal growth was performed for 50 hours in the same procedure as in the example. However, in this comparative example, the atmospheric gas nitrogen content during crystal growth was kept constant at 3% from the beginning to the end. The diameter of the obtained crystal was 51.5 mm, the average crystal growth rate was about 0.64 mm / hour, and the height was about 32 mm. The electron concentration during crystal growth was estimated in the same manner as in Example 1, and was 4 to 6 × 10 ¹⁸ cm ⁻³ .

When the SiC single crystal thus obtained was analyzed by X-ray diffraction and Raman scattering, it was confirmed that a 4H type SiC single crystal ingot had grown. Further, secondary ion mass spectrometry was performed for the purpose of measuring the concentration of nitrogen element in the single crystal, and it was 5 × 10 ¹⁸ cm ⁻³ . Further, for the purpose of evaluating the threading dislocation and basal plane dislocation density existing in the grown crystal, a {0001} plane 8 ° off-wafer was cut out from the latter half of the grown single crystal ingot and polished. After that, the wafer surface was etched with molten KOH at about 530 ° C., and the density of etch pits corresponding to threading dislocations and basal plane dislocations was examined with a microscope. The average of the entire wafer surface was 1.7 × 10 ⁴ cm ⁻² , 2.0 × 10 ³ cm ^-2

Furthermore, a {0001} plane SiC single crystal substrate having a diameter of 51 mm was cut out from the latter half of the SiC single crystal growth stage to obtain a mirror wafer. The plane orientation of the substrate was 8 ° off in the [11-20] direction on the (0001) Si plane. SiC was epitaxially grown using this SiC single crystal substrate. The growth condition of the SiC epitaxial thin film is that the growth temperature is 1500 ° C., and the flow rates of silane (SiH ₄ ), propane (C ₃ H ₈ ), and hydrogen (H ₂ ) are 5.0 × 10 ⁻⁹ m ^{3 /} sec and 3.3 ×, respectively. 10 ⁻⁹ m ³ / sec, 5.0 × 10 ⁻⁵ m ³ / sec. The growth pressure was atmospheric pressure. The growth time was 2 hours and the film thickness was about 5 μm.

  After the epitaxial thin film was grown, the surface morphology of the obtained epitaxial thin film was observed with a Nomarski optical microscope. As a result, surface defects (pits) thought to be caused by dislocation defects were observed over almost the entire wafer surface.

Similarly, from the SiC single crystal, a (0001) Si surface SiC single crystal substrate with an off angle of 0 ° was cut out and mirror-polished, and then a GaN thin film was formed on the metal organic chemical vapor deposition (MOCVD) method. By epitaxial growth. The growth conditions are a growth temperature of 1050 ° C., trimethylgallium (TMG), ammonia (NH ₃ ), and silane (SiH ₄ ), 54 × 10 ⁻⁶ mol / min, 4 liter / min, and 22 × 10 ⁻¹¹ mol, respectively. / min flowed. The growth pressure was atmospheric pressure. The growth time was 20 minutes, and n-type GaN was grown to a thickness of about 1 μm.
In order to investigate the surface state of the obtained GaN thin film, the growth surface was observed with a Nomarski optical microscope, and it was found that the surface morphology was somewhat rough.

Diagram explaining the principle of the improved Rayleigh method The figure explaining the effect of this invention 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 Raw material for SiC powder
3 Graphite crucible
4 Graphite crucible lid
5 Double quartz tube
6 Support rod
7 Graphite felt
8 Work coil
9 Ar gas piping
10 Ar gas mass flow controller
11 Vacuum exhaust system
12 Growing crystals
13 High electron concentration growth crystal
14 Grown crystals after high electron concentration region

Claims (11)

In a method for producing a bulk silicon carbide single crystal ingot by growing a silicon carbide single crystal on a seed crystal composed of a silicon carbide single crystal, the electron concentration of the grown silicon carbide single crystal is 1 × 10 ¹⁹ cm ⁻³ or more. A method for producing a silicon carbide single crystal ingot, wherein a part or all of a single crystal is grown in a state of 6 × 10 ²⁰ cm ⁻³ or less. 2. The method for producing a silicon carbide single crystal ingot according to claim 1, wherein the electron concentration is 3 × 10 ¹⁹ cm ⁻³ or more and 6 × 10 ²⁰ cm ⁻³ or less.   3. The method for producing a silicon carbide single crystal ingot according to claim 1, wherein an impurity is added to the growing silicon carbide single crystal to control an electron concentration.   4. The method for producing a silicon carbide single crystal ingot according to claim 3, wherein the impurity is nitrogen.   3. The method for producing a silicon carbide single crystal ingot according to claim 1, wherein the electron concentration is controlled by irradiating light to the growing silicon carbide single crystal.   6. The method for producing a silicon carbide single crystal ingot according to claim 5, wherein the wavelength of the light is 250 nm or more and 400 nm or less.   A silicon carbide single crystal ingot obtained by the production method according to claim 1, wherein a diameter of the ingot is 50 mm or more and 300 mm or less. 8. The silicon carbide single crystal ingot according to claim 7, wherein a total of etch pit densities caused by dislocations measured on a {0001} plane 8 ° off-wafer cut out from the ingot is 1 × 10 ⁴ cm ⁻² or less A silicon carbide single crystal ingot characterized by being:   A silicon carbide single crystal substrate obtained by cutting and polishing the silicon carbide single crystal ingot according to claim 7 or 8.   10. A silicon carbide epitaxial wafer obtained by epitaxially growing a silicon carbide thin film on the silicon carbide single crystal substrate according to claim 9.   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 claim 9.

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