JP5375783B2 - Method for producing silicon carbide single crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a silicon carbide single crystal, capable of effectively using a raw material with which a crucible is loaded, as a supply source of a sublimation gas while appropriately maintaining the temperature of the silicon carbide raw material and the surface of the growing silicon carbide single crystal. <P>SOLUTION: In the process of producing a silicon carbide single crystal by using a sublimation re-crystallization method, a heating method is employed, in which a silicon carbide single crystal is grown by moving a region to be heated to the sublimation temperature or higher at least once in a silicon carbide raw material, and thereby, the temperature of the crystal and the raw material can be appropriately maintained as well as the raw material can be effectively sublimated. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

The present invention relates to an optimal method for manufacturing a silicon carbide Tan'yui crystal to create a silicon carbide single crystal substrate is used for the substrate of electronic materials.

A silicon carbide single crystal having high thermal conductivity and a large band gap is a useful material as a substrate for electronic materials used at high temperatures and electronic materials that require high breakdown voltage. One method for producing a silicon carbide single crystal is a sublimation recrystallization method (Non-patent Document 1). In the sublimation recrystallization method, the temperature of the raw material part is heated to a temperature higher than the temperature at which silicon carbide sublimates, while in the part where crystal growth is performed, the temperature of the crystal part is lowered to a temperature lower than the raw material part to the extent that the sublimation gas recrystallizes. A single crystal is grown while recrystallizing. In general, silicon carbide crystals are grown by appropriately maintaining the temperature difference between the raw material and the crystal.

If the temperature difference between the raw material portion and the crystal portion is large, silicon precipitates or the recrystallization speed increases to such an extent that stable crystal growth cannot be performed, so that defects are introduced into the crystal during crystal growth, There is a problem that a high-quality silicon carbide single crystal cannot be obtained. In general, there is a known problem that defects caused by silicon droplets are introduced into the crystal growth surface when the temperature difference between the silicon carbide single crystal and the silicon carbide raw material powder where the sublimation gas is generated is large ( Non-patent document 2). In particular, since the thickness of the grown single crystal is small at the initial stage of crystal growth, the temperature difference between the silicon carbide single crystal and the silicon carbide raw material powder tends to increase, and defects due to silicon droplets are introduced into the grown single crystal. The inventors have found that the quality of the silicon carbide single crystal deteriorates.

When the silicon carbide raw material is sublimated, silicon carbide gas containing a large amount of silicon is generated, and carbon remains as a residue. When the same portion of the raw material is heated, the sublimation of silicon carbide proceeds, the generation amount of silicon carbide gas gradually decreases, and the raw material gas necessary for crystal growth is not supplied. At the same time, there is a problem that the grown silicon carbide crystal starts sublimation, the surface of the grown single crystal is carbonized, and a high-quality silicon carbide single crystal cannot be obtained. In order not to cause these problems, while maintaining the temperature of the growing crystal part and the temperature of the raw material part generating the sublimation gas appropriately, the crystal growth is performed while constantly supplying the raw material gas to the crystal growth surface. It is necessary to do.

However, in general, in the sublimation recrystallization method, a raw material and a grown single crystal are placed inside the same crucible, and when the raw material is heated, the grown single crystal is also heated at the same time. For this reason, when performing crystal growth, by independently controlling the temperature of the raw material part and the growing single crystal part, it is possible to effectively supply the sublimation gas while maintaining the temperature of the raw material and the growing single crystal appropriately. It is difficult to heat as a source. In order to reduce the temperature difference between the silicon carbide single crystal and the silicon carbide raw material powder, which is a desirable crystal growth condition, it is necessary to heat the raw material powder close to the single crystal to the sublimation temperature. . On the other hand, if the portion near the single crystal is continuously heated, sublimation of the raw material powder in the heated portion proceeds, and even if unsublimated raw material remains in other portions of the raw material powder, the sublimation gas necessary for crystal growth Is not supplied, and the problem arises that the crystal growth surface is carbonized. This is a problem that the loaded raw material is wasted, and at the same time, it is a problem that a crystal that requires supply of a large amount of sublimation gas cannot be enlarged.

Yu. M.M. Tailov and V.M. F. Tsvetkov, Journal of Crystal Growth, 52 (1981) p. 146 R. V. Drachev et al. , Journal of Crystal Growth, 233 (2001) p. 541

The present invention provides a method for producing a silicon carbide single crystal using a heating method capable of effectively utilizing the silicon carbide raw material powder while at the same time maintaining the temperatures of the silicon carbide single crystal and the silicon carbide raw material powder appropriately. It is.

A method of growing a silicon carbide single crystal having a diameter of 50 mm to 300 mm using a sublimation recrystallization method, filling a graphite crucible with a silicon carbide raw material to a height of at least 30 mm, and supplying a sublimation gas during crystal growth. When heating a part of the silicon carbide raw material to a temperature equal to or higher than the temperature, the region having the highest temperature of the silicon carbide raw material part is at least in the lower direction of the raw material part away from the growing single crystal from the raw material part close to the growing single crystal. It is moved once at a moving speed of 10 mm / hour or less and 0.1 mm / hour or more, and the temperature of the region having the highest temperature of the raw material part is set to be higher than when there is a region having the highest temperature in the raw material part close to the grown single crystal. The temperature difference between the region having the highest temperature of the raw material part and the surface of the growing single crystal is increased in the growing single crystal by increasing the value when the region having the highest temperature is located under the raw material part far from the growing single crystal. close Than when there is a region having the highest temperature in the postal unit, and characterized in that while maintaining such it is greater when there is a region having the highest temperature in the lower portion of the raw material portion, sublimation of substantially all of the silicon carbide material This is a method for producing a silicon carbide single crystal.

This is a method for producing a silicon carbide single crystal, wherein the height of the silicon carbide crystal exceeds 6 mm .

In the method of manufacturing a silicon carbide single crystal, the movement is divided into a plurality of steps and moved a plurality of times during crystal growth.
Moreover, the silicon carbide single crystal ingot having a diameter of 50 mm to 300 mm produced by the above manufacturing method is a high-quality for electronic devices by forming a silicon carbide single crystal substrate having a diameter of 50 mm to 300 mm by cutting and polishing the ingot. It becomes possible to provide a silicon carbide single crystal substrate.

According to the present invention, the improved Rayleigh method using a seed crystal suppresses the occurrence of defects at the initial stage of crystal growth, enables stable growth of the polytype, and at the same time, the loaded silicon carbide powder raw material is not sublimated. A growth method capable of performing crystal growth without leaving the state is obtained. By using this method, a good quality silicon carbide single crystal can be obtained with good reproducibility.

It is drawing explaining the principle of an improved Rayleigh method. Drawing showing an example of the contour lines of the temperature inside the crucible obtained by numerically analyzing the temperature distribution inside the crucible when the graphite crucible is heated using the induction heating method using the finite element method (the numerical value attached to the isotherm is the temperature (° C)). Drawing showing other examples of temperature contours inside crucible, numerical analysis of temperature distribution inside crucible when heating graphite crucible using induction heating method (numerical values attached to isotherm) Is temperature (° C.). Drawing showing another example of temperature contours inside crucible obtained by numerical analysis of temperature distribution inside crucible when graphite crucible is heated using induction heating method (numerical values attached to isotherm) Is temperature (° C.). Drawing showing other examples of temperature contours inside crucible obtained by numerically analyzing the temperature distribution inside the crucible when the graphite crucible is heated using the induction heating method using the finite element method (values attached to the isotherm) Is temperature (° C.). It is drawing explaining the single crystal growth apparatus of a present Example.

The sublimation recrystallization method is a method for producing a silicon carbide crystal by sublimating silicon carbide powder at a high temperature exceeding 2000 ° C. and recrystallizing the sublimation gas into a low temperature part. In this method, a method of manufacturing a silicon carbide single crystal using a seed crystal composed of a silicon carbide single crystal is called an improved Rayleigh method (Non-Patent Document 1), and is used for manufacturing a bulk silicon carbide single crystal. It's being used. The modified Rayleigh method uses seed crystals, so the nucleation process of the crystals can be controlled,
Moreover, by controlling the atmospheric pressure to about 10 Pa to 15 kPa with an inert gas,
The growth rate of crystals can be controlled with good reproducibility. The principle of the improved Rayleigh method will be described with reference to FIG. A silicon carbide single crystal used as a seed crystal and a silicon carbide crystal powder used as a raw material (usually used after cleaning and pretreatment of an abrasive prepared by the Acheson method) are crucibles (usually made of graphite) In an inert gas atmosphere such as argon (13.3 Pa).
˜13.3 kPa) and heated to 2000 ° C. or higher in order to sublimate the raw material. On this occasion,
The temperature gradient is set so that the seed crystal is slightly cooler than the raw material powder. The raw material is sublimated
It is diffused and transported in the direction of the seed crystal by the concentration gradient (formed by the temperature gradient). Single crystal growth is realized by recrystallization of the source gas that has arrived at the seed crystal on the seed crystal.

The temperature distribution inside the graphite crucible when the graphite crucible was heated using a high frequency induction heating apparatus was numerically calculated using a finite element method. The frequency for induction heating was set to 7 kHz, and the heat generation due to Joule heat when an appropriate constant heating power was used was calculated. Based on the heat generation amount, the temperature distribution inside the graphite crucible was calculated from the heat conduction equation. In this calculation, the following two assumptions were made to simplify the calculation. As a first assumption, the sublimation recrystallization process is not considered. That is, the process of subliming the raw material silicon carbide powder and recrystallizing on the silicon carbide single crystal in a gas flow was ignored. For this reason, the temperature of the silicon carbide powder is calculated to be higher than when the sublimation process is taken into consideration. As a second assumption, the physical property values used in the calculation are assumed to be axially symmetric and do not consider the crystal anisotropy. The purpose of this calculation is to investigate the tendency of the temperature distribution change inside the graphite crucible, so that sufficient consideration can be given to the present invention even with these assumptions.
The physical property values used for the calculation are shown in Table 1.

In this calculation, the height of the grown silicon carbide single crystal was changed at the same time as the positions of the high-frequency induction heating coil and the graphite crucible were changed. FIGS. 2A to 2D show contour diagrams of the temperature inside the graphite crucible, which is the calculation result. In FIG. 2, the contour map of the temperature inside the crucible at one side portion from the central axis is shown by utilizing axial symmetry. Table 2 shows the thickness of the silicon carbide single crystal used for the calculation and the relative positional relationship between the crucible and the high-frequency induction heating coil. The positional relationship between the graphite crucible and the high-frequency induction heating coil is based on the case where 0 is the reference arrangement, and when it is +20 mm, the graphite crucible is moved 20 mm upward with respect to the high-frequency induction heating coil.

2 (a) and 2 (c), it can be seen that when the graphite crucible is moved upward by +20 mm with respect to the coil, the region having the highest temperature moves to the lower side of the graphite crucible. The temperature difference between the single crystal and the raw material powder is smaller in FIG. 2A than in FIG. Comparing FIG. 2 (b) and FIG. 2 (d) as a result of calculating the temperature distribution at the stage of crystal growth, FIG. 2 (a) and FIG. 2 (c)
As in the case of), when the relative positional relationship of the graphite crucible with respect to the high-frequency induction heating coil is changed, the region having the highest temperature moves. In FIG. It is heated strongly. The temperature difference between the single crystal and the raw material powder is smaller in FIG. 2D than in FIG. This is thought to be due to the fact that the surface of the single crystal and the raw material powder approach each other as the thickness of the single crystal increases, so that the temperature difference is reduced.

Conventionally, it is known that when the temperature difference between the raw material powder and the growth single crystal surface is large during crystal growth, silicon droplets are formed and defects are easily introduced. Also, if the temperature difference between the raw material powder and the growth single crystal surface is small during crystal growth, or the raw material powder has already been heated to a high temperature for a long time and sublimation has progressed, it is necessary for growth from the raw material powder to the single crystal. If no gas is supplied,
It is known that the surface of a single crystal sublimates and carbonizes.

From these findings and the numerical calculation result of the temperature distribution inside the crucible, the temperature distribution of FIG. 2 (a) is preferable to FIG. 2 (c) at the initial stage of crystal growth where the single crystal is thin. However, FIG.
When the growth is continued with the arrangement of (a), the temperature distribution of FIG. 2 (b) is shown when the single crystal grows and the thickness of the crystal increases. In this temperature distribution, only the upper part of the raw material powder is heated for a long time from the start of heating. As a result, the sublimation of the upper part of the raw material powder proceeds and the function as the raw material becomes smaller, while the silicon carbide powder loaded in the lower part of the raw material powder is not effectively used as the raw material, and the raw material powder remains at the bottom of the crucible. The problem arises that the sublimation gas is not supplied to the growing single crystal and the surface of the growing single crystal is carbonized. Therefore, as shown in FIG. 2 (d), it is desirable to heat the lower portion of the raw material portion to heat the non-sublimated raw material portion so that the supply of sublimation gas is not interrupted. In this case, the temperature difference between the crystal growth surface and the raw material is smaller than that in FIG. 2C, and the temperature difference between the growth crystal surface and the raw material powder is not too large. In the sublimation recrystallization method, the sublimation gas recrystallizes on the crystal surface at a lower temperature than the sublimation gas, so crystal growth proceeds. Compared to the temperature difference between the crystal and the raw material during crystal growth and changes in temperature gradient,
It is important that the sublimation gas having a temperature higher than that of the growth surface is supplied to the crystal growth surface without interruption, and a method of heating the raw material portion that has not been sublimated by moving the heated portion of the raw material is useful.

Here, as shown in FIG. 2 (a), the raw material powder in the portion close to the crystal is heated to the sublimation temperature at the initial stage of growth, and the crystal growth by recrystallization proceeds to sublimate the raw material in the portion close to the single crystal. However, as the function of the raw material is not fulfilled, a crystal growth method is used in which the part for heating the raw material powder is moved to a part far from the single crystal where the unsublimated raw material remains as shown in FIG. The present inventors have found a method for realizing good crystal growth conditions that can suppress the introduction of defects and prevent carbonization of the crystal growth surface while keeping the temperature of the single crystal and the raw material powder appropriately. By moving the region having the highest temperature in the raw material powder, the non-sublimated raw material portion that has not been included in the region having the highest temperature so far is newly added to at least a part of the region having the highest temperature, and sublimation gas is generated. By newly generating, the growth gas can be supplied to the crystal growth surface without interruption. As a method of moving the region having the highest temperature in the raw material powder, for example, before the raw material powder is sublimated during crystal growth and no longer functions as a raw material,
Move the region having the highest temperature at least once and heat the newly sublimated raw material powder part, and crystal growth is greatly divided into the early, middle and late stages,
There is a method of moving the region having the highest temperature in the raw material powder to a different part. There is also a method of dividing a region having the highest temperature in the raw material powder by dividing a large number of steps from the initial stage to the late stage of growth or continuously. The present invention relates to these movement methods and the number of movements,
The moving distance and moving speed are not specified as specific ones. However, when moving the region having the highest temperature in the raw material powder, the temperature distribution inside the crucible performing crystal growth changes,
Since the crystal growth is disturbed and defects may be introduced into the grown single crystal, the moving speed of the region having the highest temperature is more preferably 10 mm / hour or less. If the moving speed is too low, the raw material of the heated portion is sublimated before the effect of moving the region having the maximum temperature is obtained, and the effect of the present invention cannot be obtained. Speed over time is desirable.

The movement of the region having the maximum temperature in the silicon carbide raw material powder is moved relative to the heating work coil for heating the silicon carbide raw material by moving the crucible filled with the silicon carbide raw material along the central axis. Or a method of moving the heating work coil for heating the silicon carbide raw material along the central axis and changing the relative position with the crucible filled with the silicon carbide raw material. it can.

By using such a crystal growth method that moves the portion to heat the raw material, the diameter 50
It is possible to stably supply the source gas necessary for growing an ingot having a size of ˜300 mm. As a result, a stable crystal growth rate can be obtained, generation of defects can be suppressed, and a silicon carbide single crystal ingot having high crystallinity with uniform crystal orientation can be manufactured. In addition, a single crystal substrate obtained by cutting and polishing the silicon carbide single crystal ingot becomes a highly crystalline substrate and is highly useful as a substrate for manufacturing an electronic device.

  Examples of the present invention will be described below.

Example 1
First, a single crystal growth apparatus used in the examples will be briefly described with reference to FIG. Crystal growth is performed by sublimating silicon carbide crystal powder 2 and recrystallizing on silicon carbide single crystal 1 used as a seed crystal. The seed crystal silicon carbide single crystal 1 is attached to the inner surface of the lid 4 of the high-purity graphite crucible 3. The raw material silicon carbide crystal powder 2 is filled in a high-purity graphite crucible 3. Such a graphite crucible 3 is installed inside a double quartz tube 5 by a support rod 6 made of graphite. Around the graphite crucible 3, a graphite felt 7 for heat shielding is installed. The double quartz tube 5 can be highly evacuated (10 −3 Pa or less) by an evacuation apparatus, 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 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. In order to change the relative positional relationship between the work coil 8 and the graphite crucible 3, a mechanism 12 capable of moving the graphite crucible 3 or the like along the central axis, or the work coil 8 along the central axis. A mechanism 13 that can be moved is provided. 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, taking out 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.

Next, an example is described about manufacture of a silicon carbide single crystal using this crystal growth device.
First, a 4H polytype silicon carbide single crystal wafer having a (0001) plane with a diameter of 75 mm was prepared as a seed crystal. Next, the seed crystal 1 was attached to the inner surface of the lid 4 of the graphite crucible 3. The graphite crucible 3 was filled with high-purity silicon carbide crystal powder 2 obtained by the CVD method.
The filling amount was set so that the axial height of the silicon carbide crystal powder was 40 mm. Then
The graphite crucible 3 filled with the raw material was closed with a lid 4, covered with a graphite felt 7, placed on a graphite support rod 6, and installed inside the double quartz tube 5. And after evacuating the inside of a quartz tube, the electric current was sent through the work coil and the raw material temperature was raised to 2000 degreeC. Thereafter, high-purity Ar gas was introduced as the 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 of 1.3 kPa is about 30
The pressure was reduced over a period of time, and then crystal growth started. At the time of starting crystal growth, among the raw material silicon carbide crystal powder, so that the portion close to the growing single crystal is the region having the highest temperature,
The position of the graphite crucible 3 with respect to the work coil 8 was set. This was confirmed by separately conducting an experiment to stop heating immediately after the start of crystal growth and observing the sublimation state of the silicon carbide crystal powder 2. In this example, from 18 hours after the crystal growth started, the graphite crucible 3 was moved with respect to the work coil 8 in the upward direction at a speed of 10 mm / hour for 2 hours to perform crystal growth. After the movement for 2 hours, the work coil 8 is positioned so that the part (bottom part) farthest from the grown single crystal of the silicon carbide single crystal powder as the raw material is heated most strongly, and the maximum temperature is reached. The region having γ was the bottom portion of the silicon carbide raw material powder. Crystal growth was terminated after 40 hours from the start of crystal growth, and the current flowing through the work coil was reduced to zero.

The diameter of the obtained crystal was about 76 mm, and the height was about 35 mm. Growth rate is about 0
. It was 9 mm / hour. When the remaining raw material was observed, the loaded silicon carbide crystal powder sublimated almost completely, and black carbon remained as a residue. When the silicon carbide single crystal thus obtained was analyzed by X-ray diffraction and Raman scattering, it was confirmed that a high-quality silicon carbide single crystal ingot consisting of a single 4H polytype with few defects was grown. When this silicon carbide single crystal ingot was cut and polished to produce a silicon carbide single crystal substrate, a high-quality silicon carbide single crystal substrate consisting of a single polytype of 4H and having few defects could be produced. When producing an electronic device on a silicon carbide single crystal substrate, since defects present in the substrate affect the characteristics of the electronic device, the high-quality silicon carbide single crystal substrate with few defects obtained by the present invention is
It is useful as a substrate for manufacturing an electronic device.

(Example 2)
In the same manner as in Example 1, first, a 6H polytype silicon carbide 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 lid 4 of the graphite crucible 3. The graphite crucible 3 was filled with silicon carbide crystal raw material powder 2 produced by the Atchison method. The filling amount was set so that the axial height of the silicon carbide raw material powder was 30 mm. Next, the graphite crucible 3 filled with the silicon carbide raw material produced by the Atchison method is closed with the lid 4 and covered with the graphite felt 7, and then placed on the graphite support rod 6. Installed inside. And after evacuating the inside of a quartz tube, the electric current was sent through the work coil and the raw material temperature was raised to 2000 degreeC. Thereafter, a high-purity Ar gas is introduced as the atmospheric gas, and the raw material temperature is set to the target temperature 2 while maintaining the pressure in the quartz tube at about 80 kPa.
The temperature was raised to 400 ° C. The growth pressure was reduced to 1.3 kPa over about 30 minutes, and then crystal growth was started. During crystal growth, the current passed through the work coil was adjusted so that the seed temperature was about 2000 ° C. At the time of starting crystal growth, the position of the graphite crucible 3 relative to the work coil 8 was set so that a portion close to the grown single crystal in the raw material silicon carbide crystal powder would be a region having the highest temperature. This was confirmed by separately conducting an experiment to stop heating immediately after the start of crystal growth and observing the sublimation state of the silicon carbide crystal powder 2. In this example, the heating part was moved in two steps as follows. First, after 15 hours from the start of crystal growth, the graphite crucible 3 is moved in the upper direction with respect to the work coil 8 at a speed of 2 mm / hour for 5 hours, and then the movement is stopped for 10 hours. 3 at a speed of 5 mm / hour
Moved for hours. When the movement of the heated part is completed, the work coil 8 is positioned so that the part (bottom part) farthest from the grown single crystal of the silicon carbide single crystal powder as the raw material is heated most strongly. The region having the temperature was made to be the bottom portion of the silicon carbide raw material powder. Crystal growth was terminated after 40 hours from the start of crystal growth, and the current flowing through the work coil was reduced to zero.

The diameter of the obtained crystal was about 51 mm and the height was about 30 mm. Growth rate is about 0
. It was 8 mm / hour. When the remaining raw material was observed, the loaded silicon carbide crystal powder sublimated almost completely, and black carbon remained as a residue. When the silicon carbide single crystal thus obtained was analyzed by X-ray diffraction and Raman scattering, it was confirmed that a high-quality silicon carbide single crystal consisting of a single 6H polytype with few defects was grown. When this silicon carbide single crystal ingot was cut and polished to produce a silicon carbide single crystal substrate, a high-quality silicon carbide single crystal substrate consisting of a single polytype of 6H with few defects could be produced. When producing an electronic device on a silicon carbide single crystal substrate, defects existing in the substrate affect the characteristics of the electronic device. Therefore, the high-quality silicon carbide single crystal substrate obtained by the present invention has few defects. It is useful as a substrate for manufacturing a device.

(Comparative example)
In the same manner as in Example 1, first, a 4H polytype silicon carbide single crystal wafer having a (0001) plane with a diameter of 75 mm was prepared as a seed crystal. Next, the seed crystal 1 was attached to the inner surface of the lid 4 of the graphite crucible 3. The graphite crucible 3 was filled with high-purity silicon carbide crystal powder 2 obtained by the CVD method. The filling amount was set so that the axial height of the silicon carbide crystal powder was 40 mm. Next, the graphite crucible 3 filled with the raw material was closed with the lid 4 and covered with the graphite felt 7, and then placed on the graphite support rod 6 and installed inside the double quartz tube 5. And
After evacuating the inside of the quartz tube, a current was passed through the work coil to raise the raw material temperature to 2000 ° C. Thereafter, high-purity Ar gas is introduced as the atmospheric gas, and the pressure in the quartz tube is about 80 k.
The raw material temperature was raised to the target temperature of 2400 ° C. while maintaining Pa. The growth pressure was reduced to 1.3 kPa over about 30 minutes, and then crystal growth was started. At the time of starting crystal growth, the position of the graphite crucible 3 relative to the work coil 8 was set so that a portion close to the grown single crystal in the raw material silicon carbide crystal powder would be a region having the highest temperature. This was confirmed by separately conducting an experiment to stop heating immediately after the start of crystal growth and observing the sublimation state of the silicon carbide crystal powder 2. In this comparative example, in order to compare with Example 1, heating was continued for 40 hours without moving the graphite crucible 3 with respect to the work coil 8, and then the current flowing through the work coil was reduced to zero. It was.

The diameter of the obtained crystal was about 75 mm and the height was about 6 mm. Sublimation progressed from the crystal surface to the inside of the ingot, the ingot was carbonized, and deterioration of the crystal quality was observed. When the remaining raw material was observed, the upper part of the raw material part (part close to the growing single crystal) was completely sublimated, and black carbon remained as a residue, and the lower part of the raw material (part far from the growing single crystal) was carbonized. Silicon was recrystallized and remained.

1 Seed crystal (silicon carbide single crystal)
2 Raw material of silicon carbide crystal powder 3 Graphite crucible 4 Graphite crucible lid 5 Double quartz tube 6 Support rod 7 Graphite felt (heat insulation)
8 Work Coil 9 High Purity Ar Gas Pipe 10 Mass Flow Controller 11 for High Purity Ar Gas Vacuum Exhaust Device 12 Crucible Movement Mechanism 13 Work Coil Movement Mechanism

Claims (3)

A method of growing a silicon carbide single crystal having a diameter of 50 mm to 300 mm using a sublimation recrystallization method, filling a graphite crucible with a silicon carbide raw material to a height of at least 30 mm, and supplying a sublimation gas during crystal growth. When heating a part of the silicon carbide raw material to a temperature equal to or higher than the temperature, the region having the highest temperature of the silicon carbide raw material part is at least 1 in the lower direction of the raw material part away from the growing single crystal from the raw material part close to the growing single crystal. 10 mm / hour or less, moving at a moving speed of 0.1 mm / hour or more, the temperature of the region having the highest temperature of the raw material part is higher than when there is a region having the highest temperature in the raw material part close to the grown single crystal, The temperature difference between the region having the highest temperature of the raw material part and the surface of the growing single crystal is close to that of the growing single crystal by increasing the value when there is a region having the highest temperature at the lower part of the raw material part far from the growing single crystal. original Than when there is a region having the highest temperature in the section, while maintaining as better when there is a region having the highest temperature in the lower portion of the material portion is increased, and wherein the sublimating almost all of the silicon carbide material A method for producing a silicon carbide single crystal.   The method for producing a silicon carbide single crystal according to claim 1, wherein a height of the silicon carbide crystal exceeds 6 mm.   3. The method for producing a silicon carbide single crystal according to claim 1, wherein the movement is divided into a plurality of steps and moved a plurality of times during crystal growth. 4.