JP2002012500A - Method of and device for producing silicon carbide single crystal, and silicon carbide single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problems that during the growth of a silicon carbide single crystal, many crystal defects known as micropipes occur near the boundary between the single crystal and polycrystal, a strain occurs in the single crystal and further, a penetration hole-like micropipe parallel to the growth direction of silicon carbide single crystal occurs in the crystal by the deposition of polycrystal around the single crystal. SOLUTION: A seed crystal is held on a substrate disposed so as to set a space between it and the inner wall of a crucible in the low temperature portion inside the crucible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a silicon carbide (SiC) single crystal used for hard electronics,
The present invention relates to a manufacturing apparatus and a silicon carbide single crystal manufactured using the same, and more particularly to a manufacturing method and a manufacturing apparatus for growing a high-quality silicon carbide single crystal with few crystal defects.

[0002]

2. Description of the Related Art Hard electronics is a general term for wide band gap semiconductors such as silicon carbide and diamond having physical properties exceeding silicon (Si). Among them, silicon carbide has high heat resistance, thermal conductivity or mechanical strength, and is superior to silicon in dielectric breakdown electric field and carrier saturation drift speed. Demand for use in fields such as information electronics, etc. is increasing.

Conventionally, most silicon carbide single crystals have been manufactured by a sublimation method. FIG. 6 shows an apparatus generally used for producing a silicon carbide single crystal by a conventional sublimation method. In FIG. 6, 1 is a crucible, 2 is a silicon carbide powder, 5 is a seed crystal, 1
2 is a crucible lid. In the production of a silicon carbide single crystal by a conventional sublimation method, a silicon carbide powder 2 as a raw material is placed below a cylindrical graphite crucible 1, and a flat silicon carbide single crystal is formed on an upper crucible lid 12. The seed crystal 5 is arranged, and the crucible 1 is heated from 1800 ° C. to 2500 ° C. in a reduced pressure or normal pressure atmosphere made of an inert gas such as argon by a heating means such as high-frequency induction heating or resistance heating. At this time, the heating condition of the crucible 1 is set such that the temperature of the seed crystal 5 is lower than the temperature of the silicon carbide powder 2 as a raw material in order to efficiently perform sublimation of the raw material and deposition on the seed crystal. As described above, silicon carbide powder 2 as a raw material is sublimated in the high temperature section below crucible 1, and the raw material vapor is deposited on the surface of seed crystal 5 held in crucible lid 12 in the upper low temperature section. Thereby, a silicon carbide single crystal grows.

However, when a silicon carbide single crystal is grown by the above-described method, a polycrystal of silicon carbide precipitates around the single crystal, which often hinders the growth of the single crystal. That is, when a polycrystal is deposited around the single crystal during the growth of the single crystal, there are disadvantages such as generation of many crystal defects called micropipes near the boundary with the polycrystal in the single crystal, or distortion of the single crystal. occured. In addition, the silicon carbide single crystal grown by the above-described sublimation method has a problem that a micropipe having a through-hole parallel to the crystal growth direction is easily generated, which causes a circuit defect at the time of device fabrication.

Further, the conventional method has a problem that the crystal is distorted in the plane of the grown single crystal due to the temperature distribution in the radial direction of the crucible lid holding the seed crystal. Generally, in order to grow a large silicon carbide single crystal with few defects, it is necessary to enlarge and lengthen a relatively good quality Acheson single crystal or a small single crystal obtained by the Rayleigh method. There is. In this case, in order to enlarge the diameter of the single crystal, it is desirable that there be a temperature distribution in the radial direction. However, the conventional method has a problem in that the quality of the crystal in the enlarged portion is deteriorated due to the temperature distribution in the radial direction of the crucible lid when the diameter of the single crystal is enlarged. Therefore, in order to obtain a large single crystal of good quality, there has been a demand for a method that does not degrade the quality of the crystal when the diameter of the single crystal is enlarged.

For the purpose of solving the above problems and improving the quality of the silicon carbide single crystal or efficiently increasing the diameter, various methods of producing a silicon carbide single crystal have been proposed. I was For example, JP-A-2-3069
In the invention described in Japanese Patent Publication No. 9, the mixed growth of polycrystals is reduced by placing a partition plate slightly smaller than the diameter of the seed crystal at a distance of several mm from the seed crystal and growing the single crystal. In the invention described in JP-A-5-32496,
The crystal of the (000-1) plane is used as a seed crystal, and a partition plate having an opening of 1 to 3 times the diameter of the seed crystal is attached to avoid the mixed growth of the polycrystal, and the crystal diameter is enlarged. The aims. In Japanese Patent Application Laid-Open No. 8-295595, a shielding material surrounding a seed crystal is provided so as to shield thermal radiation from a raw material and to provide a space where a single crystal can be sufficiently grown, thereby efficiently growing a single crystal. It discloses a method for causing this to occur.
Further, as an improved type of this method, JP-A-2000-443 is disclosed.
No. 83 discloses a method in which the shape of a shielding material is improved to a cone shape so as not to hinder the radial growth of crystals. In the invention described in JP-A-9-221389,
In order to prevent micropipe defects, the orientation of the seed crystal is changed so that the sublimated raw material vapor flows substantially parallel to the surface of the seed crystal, and the graphite crucible is formed so that the sublimated raw material vapor flows in the graphite crucible. A method has been proposed in which an exhaust port or a space for recrystallizing raw material vapor is provided at the top. In this method, growth is performed with a temperature difference in the radial direction in order to effectively increase the diameter. further,
To improve the efficiency of crystal growth, Japanese Patent Publication No. 7-88274
In the invention described in Japanese Patent Application Laid-Open No. H8-325099, a cone-shaped guide for concentrating the sublimated raw material vapor on the seed crystal is provided, and further, the distance between the raw material and the single crystal growth surface is kept constant. Is provided.

However, these methods individually attempt to improve the above-mentioned problems, but cannot completely solve the above-mentioned problems. The methods described in JP-A-2-30699 and JP-A-5-32496 have a problem that a single crystal comes in contact with a shielding plate during growth and a problem that polycrystal growth cannot be completely prevented. JP-A-8-29559
No. 5 and JP-A-2000-44383 have a high effect of efficiently expanding the diameter of a single crystal or preventing the growth of a polycrystal, but have a large effect in the radial direction of a substrate holding a seed crystal. Since the diameter of the crystal is enlarged by providing a temperature difference, the enlarged single crystal is likely to be distorted. Also, Japanese Patent Application Laid-Open No. 9-221
Although the method described in Japanese Patent No. 389 is considered to be effective in preventing micropipe defects, the temperature distribution in the radial direction of the single crystal is inevitable, and the shape of the grown crystal is irregular, and the diameter of the single crystal is increased. However, there are many difficulties in lengthening. Tokuhei 7-88
In the methods described in Japanese Patent No. 274 and Japanese Patent Application Laid-Open No. 8-325099, control of the sublimated raw material vapor and control of the crystal position are performed in order to efficiently produce a single crystal. It may grow around the single crystal.
The temperature distribution in the growth direction is 5 to 20 ° C./cm.
However, in this method, it is difficult to control the temperature distribution in the radial direction of the substrate due to the complicated crucible structure, and there is a problem in in-plane crystal uniformity.

[0008]

SUMMARY OF THE INVENTION According to the present invention, a large number of crystal defects called micropipes are formed near the boundary between the single crystal and the polycrystal in the single crystal by growing the polycrystal around the single crystal. It is an object of the present invention to solve the problems of generation and distortion of a single crystal. The present invention also provides
An object of the present invention is to solve the problem that a micropipe having a through hole parallel to the growth direction of a silicon carbide single crystal is formed in the single crystal. Further, according to the present invention, due to the temperature distribution in the radial direction of the crucible lid holding the seed crystal, the crystal is distorted in the plane of the grown single crystal, and when the diameter of the single crystal is enlarged, The purpose is to solve the problem of quality deterioration.

[0009]

The present invention provides: (1) a high-temperature part and a low-temperature part provided in a crucible; a raw material vapor of silicon carbide (SiC) is generated in the high-temperature part; Is deposited on the surface of the seed crystal to grow a silicon carbide single crystal, the seed crystal, the space between the crucible and the inner wall of the crucible at a low temperature portion in the crucible A method for producing a silicon carbide single crystal, comprising: holding a silicon carbide single crystal on an installed substrate. (2) The substrate is a flat plate, a gap is provided between the side surface of the substrate and the inner wall of the crucible, and the space separated by the substrate and the inner wall of the crucible allows the flow of raw material vapor. The method for producing a silicon carbide single crystal according to (1), wherein (3) The seed crystal is held on one surface of the substrate so that the surface of the seed crystal faces the raw material vapor supplied from the high temperature portion of the crucible, and the other surface of the substrate and the inner wall of the crucible are provided. Wherein the space is provided between the silicon carbide single crystal and the silicon carbide single crystal. (4) The silicon carbide single crystal according to (2) or (3), wherein the size of the gap between the side surface of the substrate and the inner wall of the crucible is 2 to 40% of the inner diameter of the crucible. Manufacturing method. (5) The method for producing a silicon carbide single crystal according to (4), wherein the size of the gap between the side surface of the substrate and the inner wall of the crucible is 1 to 10 mm. (6) The temperature of the inner wall of the crucible surrounding the space is equal to or lower than the temperature of the substrate.
Or a method for producing a silicon carbide single crystal according to (5). (7) The single piece of silicon carbide according to (2) to (6), wherein the shape of the inner wall of the crucible facing the side surface of the substrate is a cone-shaped structure that widens toward the high-temperature portion side of the crucible. Method for producing crystals. (8) The method for producing a silicon carbide single crystal according to (7), wherein a spread angle of the cone-shaped structure is 30 ° or less. (9) The method for producing a silicon carbide single crystal according to any one of (1) to (8), wherein the silicon carbide raw material vapor is generated by sublimating silicon carbide. (10) The method for producing a silicon carbide single crystal according to any one of (1) to (8), wherein the raw material vapor of the silicon carbide is generated by a reaction between carbon and silicon. (11) The atmosphere for growing a silicon carbide single crystal is an inert gas atmosphere (1) to (10).
3. The method for producing a silicon carbide single crystal according to item 1. (12) The method for producing a silicon carbide single crystal according to (11), wherein the pressure of the atmosphere is 13 to 93000 Pa. It is.

The present invention also provides: (13) a silicon carbide obtained by the method for producing a silicon carbide single crystal according to any one of (1) to (12), wherein the micropipe density is 15 / cm ² or less. Single crystal. (14) An electronic device manufactured using the silicon carbide single crystal according to (13). It is.

The present invention also provides (15) a high-temperature portion for producing a silicon carbide source vapor in a crucible, and a low-temperature portion for depositing the source vapor on the surface of a seed crystal to grow a silicon carbide single crystal. In the apparatus for manufacturing a silicon carbide single crystal provided with, a substrate holding the seed crystal is installed in a low temperature part in the crucible so as to provide a space between the substrate and the inner wall of the crucible. For producing silicon carbide single crystal. (16) The substrate is a flat plate, a gap is provided between a side surface of the substrate and an inner wall of the crucible, and the space is separated by the substrate and the inner wall of the crucible so that the raw material vapor can flow therethrough. (15) The apparatus for producing a silicon carbide single crystal according to (15). (17) The seed crystal is held on one surface of the substrate such that the surface of the seed crystal faces the raw material vapor supplied from the high-temperature portion of the crucible, and the other surface of the substrate and the inner wall of the crucible are provided. The apparatus for producing a silicon carbide single crystal according to (16), wherein the space is provided between the silicon carbide single crystal and the silicon carbide single crystal. (18) The silicon carbide single crystal according to (16) or (17), wherein the size of the gap between the side surface of the substrate and the inner wall of the crucible is 2 to 40% of the inner diameter of the crucible. Manufacturing equipment. (19) The size of the gap between the side surface of the substrate and the inner wall of the crucible is 1 to 10 mm.
An apparatus for producing a silicon carbide single crystal according to 8). (20) The silicon carbide single crystal according to (16) to (19), wherein the temperature of the inner wall of the crucible surrounding the space is equal to or lower than the temperature of the substrate facing the raw material vapor. manufacturing device. (21) The silicon carbide single piece according to (16) to (20), wherein the shape of the inner wall of the crucible facing the side surface of the substrate is a cone-shaped structure that widens toward the high-temperature portion side of the crucible. Crystal manufacturing equipment. (22) The apparatus for producing a silicon carbide single crystal according to (21), wherein a spread angle of the cone-shaped structure is 30 ° or less. (23) The apparatus for producing a silicon carbide single crystal according to any one of (15) to (22), further comprising a mechanism for rotating the substrate and / or a mechanism for adjusting a distance between the substrate and a high-temperature portion of a crucible. . It is.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors first studied the problem of formation of a micropipe having a through hole parallel to the growth direction of a silicon carbide single crystal. The present inventors have found that silicon carbide undergoes sublimation from the back surface of the seed crystal, and eventually a through-hole-shaped micropipe parallel to the growth direction of the single crystal is generated by holding the seed crystal in the conventional method. It was considered that one of the causes was that the temperature gradient in the direction from the crystal growth surface of the seed crystal to the back surface of the seed crystal (growing direction of the single crystal) was too large for the crucible lid. Therefore, in order to prevent this micropipe, a method for reducing the temperature gradient of the crucible lid holding the seed crystal was studied.

At the same time, the present inventors considered that by reducing the radial temperature distribution of the crucible lid holding the seed crystal, it was possible to reduce the in-plane distortion of the grown single crystal. Also, a method of reducing the temperature distribution in the radial direction of the crucible lid was studied.

As a result, instead of holding the seed crystal in the crucible lid as in the prior art, the present inventors put a substrate 4 for holding the seed crystal 5 in the crucible 1 as shown in FIG. It has been found that it is preferable to set the substrate 4 so that the temperature gradient in the growth direction of the single crystal and the temperature distribution in the radial direction are small or almost nonexistent. That is, according to the present invention, the seed crystal 5 is not directly held on the crucible lid as in the conventional method, but the substrate 4 for holding the seed crystal 5 is placed in the crucible 1 as shown in FIG. The space 8 is provided between the inner wall of the crucible and the seed crystal 5 is held on the substrate 4. 1 is a crucible, 2
Is a silicon carbide powder as a raw material of a silicon carbide single crystal, 3 is a column for supporting a substrate, 4 is a substrate holding a seed crystal, 5
Is a silicon carbide seed crystal, 6 is a heating crucible, 7 is a gap between the substrate and the crucible, and 8 is a space.

Since the outside of the crucible lid holding the seed crystal by the conventional method is in contact with the outside, the temperature gradient in the growth direction of the single crystal is increased due to heat radiation to the outside.
However, according to the present invention, as shown in FIG. 1, the substrate 4 holding the seed crystal 5 is installed in the crucible so as to provide the space 8 between the inner wall of the crucible and the outside. Heat radiation from the inner surface of the crucible can achieve a state in which the temperature gradient in the growth direction of the single crystal is small or almost nonexistent. It is considered that the temperature distribution also becomes smaller.

As a method for installing the substrate 4 so as to provide a space 8 between the inner wall of the crucible and the inside of the crucible, in addition to the method of suspending the substrate 4 from the crucible lid as shown in FIG. As shown in FIG. 2 and FIG. 3, a method of taking out a thin rod 11 at three or more places from the side surface of the substrate 4 and fixing it to the crucible 1 can be adopted. Here, the substrate 4 shown in FIG.
FIG. 3 shows the structure of FIG. In order to carry out the present invention, materials such as the crucible 1, the substrate 4, and the columns 3 and the rods 11 for supporting the substrate are required to have the heat resistance of the material itself and the purity of the silicon carbide single crystal as a product. From the point of influence, it is desirable to use graphite.

When the substrate 4 is hung by the column 3 as shown in FIG. 1, a mechanism for rotating the substrate 4 and a mechanism for adjusting the distance between the substrate 4 and the high temperature portion of the crucible can be provided at the same time. In this case, a motor for rotating the substrate 4 and a driving device for adjusting the position of the substrate 4 are installed outside the crucible 1, and a shaft from the motor and the driving device are connected to the column 3. The substrate may be operated.
When the silicon carbide single crystal is grown while rotating the substrate 4, a single crystal having in-plane uniform crystallinity can be grown. In addition, when the silicon carbide single crystal is grown while adjusting the distance between the substrate 4 and the high temperature part of the crucible, and the temperature of the surface of the growing silicon carbide single crystal is kept constant, fluctuation of the growth temperature is prevented and stable. Crystal growth can be performed.

As shown in FIG. 1 or FIG. 2, the present inventors provide that the substrate 4 has a flat plate shape, a gap 7 is provided between the side surface of the substrate 4 and the inner wall of the crucible 1, and the space 8 When the raw material vapor is separated by the substrate 4 and the inner wall of the crucible so as to be able to flow, the temperature gradient in the growth direction of the single crystal and the temperature distribution in the radial direction are reduced, and at the same time, the polycrystal grows around the seed crystal 5. Was found to be possible. In this case, the seed crystal is held on one surface of the substrate 4 such that the surface of the seed crystal 5 faces the raw material vapor supplied from the silicon carbide powder 2 placed in the high temperature part of the crucible. Substrate 4
If the space 8 is provided between the other surface of the crucible and the inner wall of the crucible, the raw material vapor is efficiently deposited on the seed crystal, so that the growth rate of the single crystal can be increased, which is preferable.

In the above invention, as shown in FIG. 1 or FIG. 2, by providing the gap 7 and the space 8 around the substrate 4, the flow of the raw material vapor from the raw material side to the space 8 on the back side of the substrate 5 is controlled. As a result, excess raw material vapor that has not contributed to the growth of the single crystal can be condensed in the space 8.
As a result, the growth of polycrystal around the seed crystal 5 can be suppressed. In this case, if the temperature of the inner wall of the crucible surrounding the space 8 is equal to or lower than the temperature of the substrate 4 on the side facing the material vapor, the material vapor that has not contributed to the growth of the single crystal is efficiently deposited in the space 8. Therefore, it is more convenient to suppress the growth of the polycrystal around the seed crystal. The size of the seed crystal 5 is
It is more preferable that the size of the seed crystal 5 and the substrate 4 be substantially equal, and the seed crystal 5 be held on the substrate 4 so as to cover one entire surface of the substrate.

When the gap 7 and the space 8 are provided as described above, if the gap 7 is too large, the flow of the raw material vapor to the back side of the substrate 4 becomes too large, and the single crystal growth efficiency is reduced. Further, if the gap 7 is too small, the grown single crystal comes into contact with the inner wall of the crucible, so that excess raw material vapor does not flow into the space 8. The size of the gap between the side surface of the substrate and the inner wall of the crucible is preferably about 2 to 40% of the inner diameter of the crucible.

In an actual single crystal growth apparatus, the size of the gap 7 between the side surface of the substrate 4 holding the seed crystal and the inner wall of the crucible is appropriately adjusted according to conditions such as the size of the crucible, the temperature distribution, and the growth atmosphere. . The size of the gap 7 is preferably in the range of 2 to 40% of the inner diameter of the crucible, particularly preferably about 1 to 10 mm, and more preferably 1 to 5 mm. If the gap 7 is less than 1 mm, the grown single crystal comes into contact with the inner wall of the crucible, so that excess raw material vapor does not easily flow into the space 8. On the other hand, this gap 7 is 10
If it exceeds mm, the flow of the raw material vapor into the space 8 increases, and the efficiency of the raw material vapor depositing on the seed crystal 5 on the substrate decreases, so that the growth rate of the single crystal decreases. In the present invention, it is preferable that the size of the gap 7 is controlled at 10 mm or less, and the growth rate of the single crystal is 0.5 mm or more.

As described above, according to the present invention, since the substrate holding the seed crystal is installed so as to provide a space between the substrate and the inner wall of the crucible, the temperature distribution in the radial direction of the substrate holding the seed crystal is also reduced. Become smaller. For this reason, although the strain in the radial direction of the grown single crystal is small, there is a problem that the diameter of the single crystal is difficult to increase. Therefore, in the present invention, the shape of the inner wall of the crucible 1 facing the side surface of the plate-like substrate 4 as shown in FIG. It is preferred to work on a cone-shaped structure that widens toward the end. By making the shape of the inner wall of the crucible a cone-shaped structure, a high-quality single crystal can be efficiently expanded.

When the shape of the inner wall of the crucible facing the side surface of the flat substrate is formed in a cone-type structure that becomes wider toward the high-temperature portion side of the crucible, the substrate 4 and the crucible cone 9 shown in FIG. It is preferable to set the cone portion 9 so that the gap 7 is set to 1 to 10 mm. In addition, the spread angle 10 of the cone portion with respect to the inner wall of the crucible shown in FIG. 4 (the angle between the line parallel to the inner wall of the crucible and the inclination of the cone portion 9) is 30.
When it is set to be equal to or less than 15 °, and more preferably equal to or less than 15 °, it becomes convenient to grow a single crystal having good crystallinity when the diameter of the single crystal is enlarged.

The positional relationship between the substrate 4 holding the seed crystal 5 and the crucible cone 9 is preferably such that the seed crystal 5 matches the tapered portion of the cone. If the seed crystal 5 does not enter the tapered portion, there is a problem that when the crystal grows on the seed crystal 5, the grown crystal comes into contact with the cone portion 9.
Further, when the seed crystal 5 enters inside the tapered portion of the cone portion 9 and the substrate 4 enters the tapered portion, there is a problem that polycrystal grows on the substrate 4. On the other hand, seed crystal 5
When the single crystal is grown in accordance with the tapered portion of the cone, the single crystal grows almost along the cone angle while keeping the gap constant without contacting the inner wall of the crucible cone portion 9. Go.

The present invention is not limited to a method for producing a silicon carbide single crystal by a sublimation method in which silicon carbide is sublimated to generate a raw material vapor, and a silicon carbide single crystal using a reaction gas obtained by reacting carbon and silicon as the raw material vapor. Can also be applied to the manufacturing method. In a method for producing a silicon carbide single crystal using a reaction gas obtained by reacting carbon and silicon as a raw material vapor, an apparatus for producing a silicon carbide single crystal as shown in FIG. 5 is used. In FIG. 5, 1 is a crucible, 4 is a substrate, 5 is a seed crystal, 13 is a porous carbon inner cylinder, 14 is a raw carbon particle, 15 is a silicon charging device, and 16 is a raw silicon particle. Also, the crucible 1 has a high temperature on the 18 side and a low temperature on the 17 side. In this case, carbon and silicon can be reacted by introducing raw silicon particles into raw carbon particles 14 kept at a high temperature to generate raw material vapor.

Either a method for producing a silicon carbide single crystal by a sublimation method in which silicon carbide is sublimated to generate a raw material vapor, or a method for producing a silicon carbide single crystal using a reaction gas obtained by reacting carbon and silicon as a raw material vapor. Also in this case, the generated raw material vapor is a simple gas of silicon or a mixed gas of a compound of silicon and carbon such as Si ₂ C and SiC ₂ . That is, according to the present invention, a raw material vapor composed of silicon alone or a mixed gas of a compound of silicon and carbon such as Si ₂ C or SiC ₂ is generated in a high temperature part, and the raw material vapor is deposited on the surface of a seed crystal in a low temperature part. The present invention can be used for a method for manufacturing a silicon carbide single crystal and a manufacturing apparatus.

The installation direction of the crucible used in the present invention is not particularly limited to the vertical positional relationship between the low temperature section where the seed crystal is installed and the high temperature section where the raw material vapor is generated. For example, in the case of a method of manufacturing a silicon carbide single crystal by a sublimation method, the structure is simplified by providing a high temperature part below the crucible and setting a low temperature part where the seed crystal is installed above the crucible. Further, in the case of a method for producing a silicon carbide single crystal using a reaction gas obtained by reacting carbon and silicon as a raw material vapor, a high-temperature portion where carbon and silicon react can be provided above a low-temperature portion where a seed crystal is provided. . In either case,
A high-temperature part and a low-temperature part are provided in a crucible, a raw material vapor of silicon carbide is generated in the high-temperature part, and the raw material vapor is deposited on the surface of the seed crystal in the low-temperature part to grow a silicon carbide single crystal. I just need.

In the present invention, high-frequency induction heating is preferably used as a method for heating while controlling the temperature distribution of the crucible to an appropriate state. In this case, the crucible is made of graphite, and an appropriate temperature distribution can be obtained by adjusting the positional relationship between the induction coil and the graphite crucible. Further, an appropriate temperature distribution can be obtained by using a plurality of induction coils. Further, a graphite heating element may be separately provided outside the crucible. For example, as shown in FIG. 1 and the like, an appropriate temperature distribution can also be achieved by a method in which a heating graphite crucible 6 serving as a heating element is provided between an induction coil and a crucible 1 serving as an object to be heated.

As the temperature conditions for producing the silicon carbide single crystal in the present invention, for example, when the sublimation method is used, the temperature of the silicon carbide powder as a raw material is set to 2000 ° C. to 2 ° C.
The temperature of the growing silicon carbide single crystal is in the range of 1900 ° C. to 2400 ° C., and the relationship between the temperature of the raw material and the temperature of the growing silicon carbide single crystal is as follows. Preferably, the temperature difference is set to be higher than 20 ° C. to 200 ° C. Further, the temperature gradient between the raw material and the silicon carbide single crystal in the crucible is 5 ° C./cm to 50 ° C./cm.
It is preferable to set it in the range. Providing a high-temperature portion for generating a raw material vapor of silicon carbide in the crucible under the above temperature conditions and a low-temperature portion for depositing the raw material vapor on the surface of the seed crystal,
A single crystal can be efficiently grown on the seed crystal.

The atmosphere for growing the silicon carbide single crystal is as follows:
It is preferable to use an atmosphere of an inert gas such as an argon gas or the like, and to set the pressure to normal pressure or less. In particular, in order to increase the growth rate of the single crystal and to reduce the incorporation of impurities into the single crystal, the pressure of the atmosphere is preferably in the range of 13 Pa to 93000 Pa.

In the present invention, the movement of the raw material vapor from the high temperature part to the low temperature part is caused by the diffusion or convection of the raw material vapor. The diffusion or convection of the raw material vapor can be controlled by the type and pressure of the atmospheric gas, the flow of the atmospheric gas, the structure in the crucible, the temperature distribution, and the like.

The seed crystal used in the present invention preferably has the same crystal structure as the crystal to be grown. The seed crystal growth surface can be used in any plane orientation. For example, a C-axis ({0001} plane), a plane parallel to the C-axis, or a plane in which an off-angle is introduced for those planes can be used. The surface of the seed crystal is desirably polished after surface processing and, in some cases, used after removal of processing strain by etching or sacrificial oxidation. Also, a naturally grown surface of Acheson crystal or Rayleigh crystal can be used.

[0033]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments. Example 1 In Example 1, a silicon carbide single crystal was grown using the apparatus shown in FIG. The single crystal was grown according to the following procedure by a sublimation method. First, a 100-mesh silicon carbide powder 2 that was previously washed with an acid such as hydrofluoric acid, which is a raw material of a silicon carbide single crystal, was placed under a crucible 1 made of high-purity graphite. In addition, a graphite substrate 4 was hung by a graphite cylinder 3 above the crucible, and a flat substrate 4 was set in the crucible so as to provide a space between the crucible and the inner wall of the crucible. The thickness of the substrate 4 was 5 mm, and the diameter was 22 mm.
A surface of the substrate 4 facing the raw material vapor has a diameter of 22 mm,
A seed crystal 5 of a silicon carbide single crystal having a C-axis growth surface having a thickness of 0.8 mm was attached using a resin. The inner diameter of the crucible was 25 mm, and the size of the gap 7 between the substrate 4 and the crucible 1 was 1.5 mm. A graphite crucible 6 for heating was installed outside the crucible 1 so that the lower portion of the crucible 1 was efficiently heated by high-frequency induction heating. This graphite crucible for heating
By adjusting the length, an optimum temperature distribution of the crucible can be obtained. Further, a space 8 having a height of 20 mm was provided on the upper side of the substrate 4 in the crucible 1 so that excess raw material vapor not deposited on the surface of the seed crystal 5 was recrystallized.

The above single crystal growing apparatus was covered with a heat insulating material made of carbon fiber and installed in a high frequency induction heating apparatus. Then, the output of the high-frequency induction heating device, the thickness of the heat insulating material above the crucible, and the like were adjusted so that the raw material temperature and the substrate temperature became predetermined temperatures. In Example 1, the temperature of the high-temperature portion of the crucible containing the silicon carbide powder 2 as the raw material was set to 2300 ° C., and the temperature of the low-temperature portion of the crucible on which the substrate was set was set to 2200 ° C., to grow a silicon carbide single crystal. Was. The single crystal growth atmosphere was an argon gas atmosphere at a pressure of 200 Torr.

In this manner, the growth is performed for about 30 hours.
A silicon carbide single crystal of about 20 mm was grown. The diameter of the grown single crystal was about 23.5 mm, and the diameter was slightly increased, but the grown single crystal was not in contact with the inner wall of the crucible. No polycrystal was found around the seed crystal on the substrate. No polycrystal was mixed into the grown single crystal. Further, the single crystal was cut into a thickness of about 0.7 mm, polished, and then etched in a KOH melt at 530 ° C. for 10 minutes to measure the micropipe density. The average density of the through-hole-shaped micropipes was 10 or less / cm ² in the plane. Furthermore, in this single crystal, since no polycrystal was deposited around the seed crystal on the substrate, the micropipe density did not increase at the outer periphery of the single crystal, and the in-plane distribution of the micropipes was almost uniform. there were. Further, when this single crystal was inspected by a distortion inspection machine using polarized light, almost no distortion was observed.

Comparative Example 1 For comparison, a silicon carbide single crystal was grown by a sublimation method using the conventional single crystal growth apparatus shown in FIG. In Comparative Example 1, the lid 12 on the upper part of the graphite crucible 1 having an inner diameter of 25 mm had a diameter of 20 mm and a thickness of 0.3 mm.
Single crystal silicon carbide seed crystal 5 having a C-axis growth surface of 8 mm was directly attached. Silicon carbide powder 2 as a raw material was placed below crucible 1 in the same manner as in Example 1.

This device was covered with a heat insulating material made of carbon fiber and placed in a high-frequency induction heating device to perform heating. The temperature of the raw material silicon carbide powder 2 was kept at 2300 ° C., and the temperature of the crucible lid 12 to which the single crystal was attached was kept at 2200 ° C., to grow a silicon carbide single crystal. During the growth, the pressure was kept at 200 Torr by using argon gas as the atmosphere gas.

When a silicon carbide single crystal having a thickness of about 10 mm was grown as described above, polycrystal was deposited on the outer peripheral portion of the grown single crystal and began to cover the single crystal. Therefore, the diameter of the single crystal at the tip of the growth was reduced to about 15 mm. In the vicinity of the boundary between the grown single crystal and the polycrystal deposited on the outer periphery, it was observed that a large number of micropipes, which are considered to be caused by distortion, were generated.

The micropipe density of the obtained silicon carbide single crystal was measured in the same manner as in Example 1.
At the center of the crystal (range of about 12 mm in diameter), the micropipe density was about 200 / cm ² on average, and it was confirmed that the micropipe density increased further toward the outside of the single crystal. When this single crystal was inspected with a distortion inspection machine using polarized light, it was observed that the strain was distributed from the boundary with the polycrystal toward the inside of the single crystal.

Example 2 In Example 2, a silicon carbide single crystal was grown using the apparatus shown in FIG. In Example 2, a single crystal was grown for the purpose of enlarging the diameter of the silicon carbide single crystal.

In the apparatus shown in FIG. 4, the graphite substrate 4 to which the seed crystal 5 is to be attached is suspended from the upper part of the high-purity graphite crucible 1 with the graphite column 3 in the same manner as in the first embodiment. did. The diameter of the substrate 4 was 30 mm, and a seed crystal 5 having a diameter of 30 mm was attached to a surface facing the silicon carbide powder 2 as a raw material of the substrate 4. Further, in the second embodiment, a cone portion 9 for enlarging the seed crystal 5 is provided on the inner wall of the crucible facing the side surface of the substrate. Spread angle of this cone part 10
Was 15 °. Also, a gap 7 between the substrate 4 and the cone 9
Was adjusted to be 2 mm when no single crystal was grown.

The other growth conditions were set in the same manner as in Example 1, and the silicon carbide single crystal of Example 2 was grown. As a result, the silicon carbide single crystal grew while expanding in a single crystal state at an angle of about 15 ° without contacting the graphite cone 9. When a silicon carbide single crystal having a length of about 15 mm was grown in Example 2, the maximum diameter of the single crystal was about 3 mm.
8.5 mm.

The micropipe density of the single crystal grown in the second embodiment was measured in the same manner as in the first embodiment. The micropipe density was 15 / cm ² or less on average in the plane. Further, when this single crystal was inspected by a distortion inspection machine using polarized light, almost no radial distortion was observed.

[0044]

According to the present invention, since the substrate holding the seed crystal is set in the crucible so as to provide a space between the substrate and the inner wall of the crucible, the temperature gradient in the growth direction of the single crystal is small. Alternatively, almost no state can be achieved, and the temperature distribution in the radial direction can be reduced. Further, the substrate is formed in a flat plate shape, a gap is provided between the side surface of the substrate and the inner wall of the crucible, and a space is provided between the surface of the substrate not holding the seed crystal and the inner wall of the crucible, so that the seed is formed. It is possible to suppress the growth of polycrystal around the crystal.
As a result, during the growth of the single crystal, polycrystals are precipitated around the single crystal, so that many crystal defects called micropipes occur near the boundary with the polycrystal in the single crystal, or the single crystal is distorted Problem can be solved. Further, the problem that a micropipe having a through hole parallel to the growth direction of a silicon carbide single crystal is formed in the single crystal can be solved. Further, the present invention can solve the problem that the crystal is distorted in the plane of the grown single crystal due to the temperature distribution in the radial direction of the lid of the crucible holding the seed crystal.

Further, according to the present invention, the shape of the inner wall of the crucible facing the side surface of the flat substrate is processed into a cone-shaped structure that becomes wider toward the high-temperature portion side of the crucible, so that the radial direction of the substrate can be improved. Even if the temperature distribution is reduced, the diameter of the single crystal can be efficiently enlarged while maintaining good crystal quality.

As a result, the silicon carbide single crystal manufactured using the method for manufacturing a silicon carbide single crystal of the present invention could have a micropipe density of 15 / cm ² or less on the average in-plane. Furthermore, electronic devices such as diodes and transistors manufactured using the silicon carbide single crystal have low crystal defect density, and thus have improved electrical characteristics and reliability.

[Brief description of the drawings]

FIG. 1 is a sectional view of an apparatus for producing a silicon carbide single crystal according to the present invention.

FIG. 2 is a sectional view of another apparatus for producing a silicon carbide single crystal according to the present invention.

FIG. 3 is a view showing a structure of the substrate shown in FIG. 2;

FIG. 4 is a cross-sectional view of a silicon carbide single crystal manufacturing apparatus provided with a cone on the inner wall of a crucible according to the present invention.

FIG. 5 is a sectional view of an apparatus for producing a silicon carbide single crystal using a reaction gas obtained by reacting carbon and silicon according to the present invention as a raw material vapor.

FIG. 6 is a cross-sectional view of a conventional silicon carbide single crystal manufacturing apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Crucible 2 Silicon carbide powder 3 Column 4 Substrate 5 Seed crystal 6 Heating crucible 7 Gap 8 Space 9 Cone part 10 Cone part spread angle 11 Rod 12 Crucible lid 13 Porous carbon inner cylinder 14 Raw material carbon particles 15 Silicon injection device 16 Raw silicon particles 17 Low temperature side of crucible 18 High temperature side of crucible

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kotaro Yano 1-1-1, Onodai, Midori-ku, Chiba-shi, Chiba Prefecture Inside Showa Denko KK (72) Inventor Yasuyuki Sakaguchi 1-chome Onodai, Midori-ku, Chiba-shi, Chiba No.1-1 F-term in Showa Denko KK R4 (reference) 4G077 AA02 BE08 DA01 ED04 SA11

Claims (23)

[Claims] A high temperature part and a low temperature part are provided in a crucible, a raw material vapor of silicon carbide (SiC) is generated in the high temperature part, and the raw material vapor is deposited on a surface of a seed crystal in the low temperature part to produce silicon carbide. In the method for producing a silicon carbide single crystal for growing a single crystal, the seed crystal is held on a substrate provided so as to provide a space between the inner wall of the crucible at a low temperature part in the crucible and the silicon carbide single crystal. A method for producing a silicon carbide single crystal, comprising growing a crystal. 2. The substrate has a flat plate shape, a gap is provided between a side surface of the substrate and an inner wall of the crucible, and the space separated by the substrate and the inner wall of the crucible allows a source vapor to flow therethrough. The method for producing a silicon carbide single crystal according to claim 1, wherein 3. The seed crystal is held on one surface of the substrate such that the surface of the seed crystal faces the raw material vapor supplied from the high temperature portion of the crucible, and the other surface of the substrate is in contact with the crucible. 3. The method for producing a silicon carbide single crystal according to claim 2, wherein said space is provided between said silicon carbide single crystal and said inner wall. 4. The silicon carbide single crystal according to claim 2, wherein the size of the gap between the side surface of the substrate and the inner wall of the crucible is 2 to 40% of the inner diameter of the crucible. Manufacturing method. 5. The method for producing a silicon carbide single crystal according to claim 4, wherein the size of the gap between the side surface of the substrate and the inner wall of the crucible is 1 to 10 mm. 6. The method according to claim 2, wherein the temperature of the inner wall of the crucible surrounding the space is equal to or lower than the temperature of the substrate. 7. The silicon carbide monolith according to claim 2, wherein the shape of the inner wall of the crucible facing the side surface of the substrate is a cone-shaped structure that widens toward the high temperature portion side of the crucible. Method for producing crystals. 8. The cone type structure has a spread angle of 30 °.
The method for producing a silicon carbide single crystal according to claim 7, wherein: 9. The method for producing a silicon carbide single crystal according to claim 1, wherein said silicon carbide raw material vapor is generated by sublimating silicon carbide. 10. A method according to claim 1, wherein said silicon carbide raw material vapor is produced by a reaction between carbon and silicon.
3. The method for producing a silicon carbide single crystal according to item 1. 11. The method for producing a silicon carbide single crystal according to claim 1, wherein the atmosphere for growing the silicon carbide single crystal is an inert gas atmosphere. 12. The pressure of the atmosphere is 13 to 93000P.
The method for producing a silicon carbide single crystal according to claim 11, wherein: a. 13. A silicon carbide single crystal obtained by the method for producing a silicon carbide single crystal according to claim 1, wherein the micropipe density is 15 / cm ² or less. 14. An electronic device manufactured using the silicon carbide single crystal according to claim 13. 15. A carbonization apparatus comprising a crucible provided with a high-temperature portion for producing a silicon carbide source vapor and a low-temperature portion for depositing the source vapor on the surface of a seed crystal to grow a silicon carbide single crystal. In a silicon single crystal manufacturing apparatus, a silicon carbide single crystal characterized in that a substrate holding the seed crystal is provided in a low-temperature portion in a crucible so as to provide a space between the substrate and an inner wall of the crucible. Manufacturing equipment. 16. The substrate has a flat plate shape, a gap is provided between a side surface of the substrate and an inner wall of the crucible, and the space is
The apparatus for producing a silicon carbide single crystal according to claim 15, wherein the raw material vapor is divided so as to be circulated by the inner wall of the substrate and the crucible. 17. The seed crystal is held on one surface of the substrate such that the surface of the seed crystal faces the raw material vapor supplied from the high temperature portion of the crucible, and the other surface of the substrate is in contact with the crucible. 17. The apparatus for producing a silicon carbide single crystal according to claim 16, wherein the space is provided between the silicon carbide single crystal and an inner wall of the silicon carbide single crystal. 18. The silicon carbide single crystal according to claim 16, wherein the size of the gap between the side surface of the substrate and the inner wall of the crucible is 2 to 40% of the inner diameter of the crucible. Manufacturing equipment. 19. The apparatus for producing a silicon carbide single crystal according to claim 18, wherein the size of the gap between the side surface of said substrate and the inner wall of the crucible is 1 to 10 mm. 20. A temperature of an inner wall of a crucible surrounding the space,
20. The apparatus for producing a silicon carbide single crystal according to claim 16, wherein the temperature is equal to or lower than the temperature of the substrate facing the raw material vapor. 21. The crucible according to claim 16, wherein the shape of the inner wall of the crucible facing the side surface of the substrate is a cone-shaped structure which becomes wider toward the high temperature portion side of the crucible.
0. An apparatus for producing a silicon carbide single crystal according to 0. 22. The cone-shaped structure has a spread angle of 30.
22. The apparatus for producing a silicon carbide single crystal according to claim 21, wherein the angle is equal to or less than °. 23. A silicon carbide single crystal manufacturing apparatus according to claim 15, further comprising a mechanism for rotating said substrate and / or a mechanism for adjusting a distance between said substrate and a high-temperature portion of a crucible. .