JP2005220017A - Manufacturing method of single crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a single crystal with less defects and high quality by suppressing the fluctuation of the temperature distribution in the single crystal growth and the fluctuation of Si/C ratio in the raw material gas. <P>SOLUTION: In supplying the raw material gas to the seed crystal 3 arranged in a graphite crucible 1 to grow the SiC single crystal on the seed crystal 3, the method is characterized by arranging a tubular member 4 in which the inner surface is coated with the SiC polycrystal 5 in advance so that it surrounds a single crystal growth space formed between growth surface 31 of the seed crystal 3 and a raw material powder 2 to grow the single crystal as it is. The temperature fluctuation due to the deposition of the polycrystal on the side wall of the crucible 1, the fluctuation of the compositional ratio of the raw materials and the incorporation of impurities are prevented by arranging the polycrystal 5 at the proximity of the seed crystal 3 in advance. Thus, the single crystal with less defects and high quality can be manufactured. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  In the present invention, a single crystal such as silicon carbide is formed on a seed crystal by supplying a source gas to the seed crystal using a sublimation recrystallization method or a chemical reaction method (CVD (chemical vapor deposition) or the like). It relates to the method of growing.

  As a method for producing a silicon carbide (SiC) single crystal used for a substrate of a semiconductor element or the like, a sublimation recrystallization method is widely adopted. In the sublimation recrystallization method, a graphite crucible 1 shown in FIG. 5 is usually used as a reaction vessel, and SiC raw material powder 2 is used at the bottom of the crucible 1, and a lid 12 of the crucible 1 facing the raw material powder 2 is seeded. A single crystal is grown by fixing and heating the crystal 3 and recrystallizing the sublimation gas of the raw material powder 2 on the seed crystal 3.

  Examples of vapor phase species involved in growth in the sublimation recrystallization method include Si, SiC2, Si2 C and the like. These vapor phase species have different equilibrium vapor pressures, and their proportions change depending on the growth temperature. Therefore, when trying to obtain a homogeneous high-quality single crystal with few defects, it is possible to prevent temperature fluctuations during the growth of the single crystal, fluctuations in the Si / C ratio, and mixing of fine graphite particles due to roughening of the crucible 1 surface. It is important to perform crystal growth under such conditions.

  However, when a single crystal is grown in the graphite crucible 1 by the conventional method, during the single crystal growth, (i) SiC polycrystal is deposited on the side wall of the crucible 1 in the vicinity of the seed crystal 3, and (Ii) Si or a gas phase species containing Si reacts with carbon (C), which is a crucible material, so that the temperature distribution and Si / C ratio are likely to fluctuate. It was difficult to avoid mixing of fine particles and metal impurities into the single crystal. These contaminants cause various defects and make it difficult to produce high-quality single crystals with few defects.

  On the other hand, as an example using a reaction vessel made of a material other than graphite, an example in which a SiC single crystal is grown using a tantalum crucible has been reported. (A. O. Konstantinovand PA, I. Ivanov, Inst. Phys. Conf. Ser. No. 137 (1994) 37-40). However, in this case as well, it is not possible to prevent polycrystals from being deposited on the side wall of the vessel, and the vapor phase species containing C reacts with tantalum in the reaction vessel to become tantalum carbide, resulting in fluctuations in the Si / C ratio. It is expected to cause this. Moreover, since tantalum is very expensive compared to graphite, there is a problem that the manufacturing cost is greatly increased.

Patent Documents 1 and 2 describe that crystal growth is performed in a state where silicon or silicon carbide powder is filled in the vicinity of a seed crystal placed in a graphite crucible. Patent Document 3 uses a graphite crucible by using a single crystal manufacturing apparatus having a sintering / sublimation zone for generating and sublimating a silicon carbide sintered body and a crystal growth zone for growing a single crystal. The production of high-quality silicon carbide without sublimation is described.
JP-A-6-333830 JP 7-237999 A JP-A-5-306199

  However, although these methods can slightly reduce fluctuations in the Si / C ratio, it is difficult to suppress the formation of SiC polycrystals deposited on the reaction vessel side wall in the vicinity of the seed crystal. Such SiC polycrystal deposition leads to fluctuations in the growth temperature and fluctuations in the Si / C ratio, and it is still difficult to produce a high-quality single crystal with few defects.

  An object of the present invention is to provide a method for producing a high-quality single crystal with few defects by suppressing fluctuations in temperature distribution during single crystal growth and fluctuations in the Si / C ratio in the raw material gas.

The present inventors have intensively studied in view of the above situation, supply a single crystal source gas to be produced to a seed crystal placed in a reaction vessel, and grow a single crystal on the seed crystal In the manufacturing method of
In the reaction vessel, at least an inner surface of the same type of polycrystal and sintered body that is to be produced so as to surround a single crystal growth space formed between the growth surface of the seed crystal and the raw material supply unit Alternatively, a cylindrical member made of a reaction sintered body is disposed in advance,
The cylindrical member is shaped to have an opening in which the lower end is open and the seed crystal is disposed on the upper end surface. The diameter of the seed crystal is S, and the width of the inner surface of the annular portion around the opening on the upper end surface is W. When the height of the inner surface of the side surface is H, the angle θ defined by the following formula (1) is set to be 20 ° ≦ θ ≦ 80 °,
θ = tan ⁻¹ [H / (W + S)] (1)
Thereafter, it has been found that the above problem can be solved by supplying a raw material gas from the raw material supply section to the single crystal growth space to grow a single crystal (claim 1).

  According to the method of the present invention, since a polycrystal, sintered body or reaction sintered body of the same kind as the single crystal to be manufactured is disposed in advance around the space where the single crystal grows, there are many on the side wall of the reaction vessel. Temperature fluctuations due to crystal deposition can be reduced. In addition, the reaction between the constituent elements of the reaction vessel and the raw material gas can be suppressed, and the fluctuation of the composition ratio of the raw material gas and the mixing of impurities into the single crystal can be prevented.

  In order to arrange the polycrystal, sintered body, or reaction sintered body, specifically, a cylindrical member is installed in the reaction vessel so as to surround the single crystal growth space, The surface on which the source gas is crystallized during the single crystal growth process and polycrystal deposition is expected may be covered in advance with the same type of polycrystal, sintered body, or reactive sintered body as the single crystal to be manufactured. At this time, the shape and size of the cylindrical member are set as described above, and the seed crystal is disposed in the opening on the upper end surface, thereby effectively protecting the single crystal growth space formed below the seed crystal. can do. Therefore, it is possible to manufacture a high-quality single crystal with few defects regardless of the material of the reaction vessel, and it is not necessary to use an expensive reaction vessel, so that the cost can be reduced.

  Preferably, the angle θ defined by the equation (1) is set to satisfy 30 ° ≦ θ ≦ 60 ° (Claim 2). In this way, a high-quality single crystal can be manufactured more effectively at a low cost.

  As a method of coating the surface of the cylindrical member with a polycrystal, a sintered body or a reaction sintered body, a sublimation recrystallization method or a CVD method can be employed. Here, when the sublimation recrystallization method is used, a raw material gas is supplied into the reaction vessel in advance under the same conditions as the single crystal growth conditions, and the raw material gas in the single crystal growth process of the cylindrical member is supplied. The polycrystal, sintered body, or reaction sintered body is deposited on the surface where crystallization is expected to deposit polycrystal. As a result, the surface is coated with a polycrystal, a sintered body, or a reaction sintered body. After that, the seed crystal is placed in the reaction vessel to grow a single crystal.

  At this time, the coating thickness of the cylindrical member is preferably 1 μm to 5 mm. (Claim 3). In order to obtain the above-mentioned effect by arranging a polycrystal, sintered body or reaction sintered body, the thickness of the cylindrical member should be 1 μm or more, and the cost can be reduced by setting it to 5 mm or less. Can be achieved.

  Hereinafter, the method of the present invention will be described in detail by taking the production of a silicon carbide (SiC) single crystal as an example. FIG. 1 is a schematic view of an apparatus used for producing a single crystal in the present invention. In the figure, 1 is a graphite crucible as a reaction container, and the crucible 1 is composed of a container body 11 and a lid body 12. A SiC raw material powder 2 is accommodated in the bottom of the container 11 of the crucible 1, and a seed crystal 3 is disposed in the center of the back surface of the lid 12 facing the raw material powder 2. The seed crystal 3 is a single crystal manufactured by the Atchison method or a sublimation recrystallization method in advance, and is processed into, for example, a disk shape according to the shape of the graphite pedestal 13 provided integrally with the lid 12. The base 13 is joined using an adhesive or the like.

  In the method of the present invention, when a SiC single crystal is produced by the sublimation recrystallization method using the crucible 1, the growth surface 31 of the seed crystal 3 (the surface on which the single crystal grows) and the raw material supply section A polycrystal of the same kind as the single crystal to be manufactured, that is, a SiC polycrystal is arranged so as to surround a single crystal growth space formed between the powder 2 and a single crystal is grown in that state. Or a SiC sintered compact or a SiC reaction sintered compact can also be arranged instead of SiC polycrystal.

  Among these, as a specific example for arranging the SiC polycrystal, in the method shown in FIG. 1, the inner surface is previously coated with the SiC polycrystal 5 so as to surround the single crystal growth space formed below the seed crystal 3. The cylindrical member 4 is installed. The cylindrical member 4 is fixed to the inner wall of the crucible 1 so that the seed crystal 3 is located in the opening of the upper end surface, and the upper end surface and the inner surface of the side surface, that is, the source gas is crystallized in the single crystal growth process. The surface on which polycrystalline deposition is expected is covered with SiC polycrystalline 5. The cylindrical member 4 has an opening at the lower end, and the sublimation gas of the raw material powder 2 is introduced into the single crystal growth space through the opening at the lower end and reaches the growth surface 31.

  In the present invention, the cylindrical member 4 whose inner surface is previously coated with the SiC polycrystal 5 is installed, so that the source gas is crystallized in the single crystal growth process around and below the seed crystal 3 to deposit the polycrystal. The region where the potential is expected is covered with the SiC polycrystal 5 to solve the problem caused by the deposition of the polycrystal during the single crystal growth. Here, the size of the cylindrical member 4 is set as follows in order to protect the region where the source gas is crystallized and the polycrystalline deposition is expected in the single crystal growth process and to obtain a sufficient effect. Good.

2A, the diameter of the seed crystal 3 is S, the width of the annular portion (inner surface) around the opening of the upper end surface of the tubular member 4 is W, and the side surface of the tubular member 4 (inner surface) ) When the height is H, the following formula (1):
θ = tan −1 [H / (W + S)] (1)
The width W and the height H are set so that the angle θ defined by the following formula is 20 ° ≦ θ ≦ 80 °, preferably 30 ° ≦ θ ≦ 60 °. Here, when the angle θ is smaller than the above range, Si or a gas phase species containing Si reacts with graphite as the crucible material, and the Si / C ratio is affected, and good growth cannot be expected. On the other hand, when the angle θ is larger than the above range, the region covered with the SiC polycrystal increases, and the manufacturing cost increases. Preferably, the angle θ is in a range of 30 ° ≦ θ ≦ 60 °.

  Here, in FIG. 2, the seed crystal 3 is illustrated so as to be positioned substantially in contact with the opening edge of the cylindrical member 4, but this is for easy understanding of the relationship of the above formula (1). The positional relationship between them is not limited to the case where they are arranged in contact with each other as shown in the figure. The opening part of the cylindrical member 4 should just be the magnitude | size beyond the diameter of the seed crystal 3, Preferably, it forms slightly larger than the seed crystal 3. FIG. This forms a slight gap between the outer peripheral edge of the seed crystal 3 and the inner peripheral edge of the opening of the cylindrical member 4, thereby preventing the growing single crystal from uniting with the polycrystal on the inner surface of the cylindrical member 4. It is to do. In order to enhance this effect, it is preferable to provide a temperature gradient in the radial direction in the growth surface of the seed crystal 3 (a slight temperature gradient that decreases toward the center of the seed crystal 3) in the growth process of the single crystal. More preferable.

  1 schematically shows the arrangement of the seed crystal 3 and the cylindrical member 4, the gap between the two is shown large. However, if the gap is too large, the crystal quality deteriorates. The distance between the outer peripheral edge and the inner peripheral edge of the opening of the cylindrical member 4 is preferably about 5 mm or less, for example. Preferably, the distance between the outer peripheral edge of the seed crystal 3 and the inner peripheral edge of the opening of the cylindrical member 4 is preferably about 1 mm, for example. As described above, even if the seed crystal 3 and the cylindrical member 4 are not in contact with each other, the gap is very small. Therefore, the angle θ defined by the equation (1) based on FIG. 2 is within the predetermined range. As long as the width W and the height H of the cylindrical member 4 are set as described above, the same effects can be obtained.

  Furthermore, it is desirable that the width W of the annular portion of the upper end surface of the cylindrical member 4 is 0 ≦ W ≦ 5S, preferably 0 ≦ W ≦ 2S. If the width W is 0, it is not possible to increase the diameter of the grown crystal. Therefore, when it is desired to increase the diameter of the grown crystal, the width W is preferably made larger than 0. When there is no need to increase the diameter, the width W may be zero. However, depending on the arrangement, the SiC polycrystal 5 arranged around the seed crystal 3 and the grown crystal collide with each other, resulting in stress at the contact portion. May accumulate and cause cracking and distortion in the grown crystal. In order to avoid this, as described above, a slight gap is formed between the outer peripheral edge of the seed crystal 3 and the inner peripheral edge of the opening of the cylindrical member 4, and more preferably, in the single crystal growth process, It is preferable to provide a temperature gradient in the radial direction in the growth surface of the seed crystal 3 (a slight temperature gradient that decreases toward the center of the seed crystal 3). On the other hand, when the width W is larger than the above range, the area covered with the SiC polycrystal 5 increases, resulting in an increase in cost.

  When the side wall of the cylindrical member 4 is inclined as shown in FIG. 2B, the height H is lowered from the upper end surface (inner surface) of the cylindrical member 4 toward the lower end surface. It becomes the height of the perpendicular.

  As a method for coating the surface of the cylindrical member 4 with the SiC polycrystal 5, any known method such as a sublimation recrystallization method or a CVD method may be employed. When the sublimation recrystallization method is used as the coating method, the raw material gas is supplied under the same conditions as the actual single crystal growth conditions with the cylindrical member 4 installed in the crucible 1 and the seed crystal 3 not installed. Thus, the polycrystal 5 can be deposited on the surface of the tubular member 4 where polycrystal is expected to be deposited at the time of actual single crystal production. In this case, at the time of actual single crystal production, the crucible 1 is filled again with a sufficient amount of the raw material powder 2, and the lid 12 is replaced with one to which the seed crystal 3 is attached. A single crystal is grown.

  If the said cylindrical member 4 is comprised as mentioned above, the area | region where the volume of a single crystal is anticipated can be protected by coat | covering the inner surface with the SiC polycrystal 5. FIG. Further, the surface other than the inner surface may be coated with SiC polycrystal 5.

  The coating thickness of the tubular member 4 is preferably 1 μm to 5 mm. When the coating thickness is smaller than the above range, the SiC polycrystal coated in advance is sublimated in the setting (initial stage of growth) stage of growth temperature, atmospheric pressure, etc., and the cylindrical shape coated with the SiC polycrystal The effect of installing the member 4 cannot be expected. On the other hand, if the coating thickness is larger than the above range, the amount of SiC polycrystal used for coating increases, which is undesirable because the cost increases.

Instead of installing the cylindrical member 4 previously coated with the SiC polycrystal 5, as shown in FIG. 3 (a), the upper edge of the container body 11 of the crucible 1 is bent inward and the edge is seeded. 3 may be extended to a position close to the outer periphery of 3, and the inner surface of the upper end portion 11 a of the container body 11 including the extended portion may be covered with the SiC polycrystal 5. At this time, if the upper end portion 11a is formed of a separate member from the container body 11 to form a cylindrical member, and the inner surface thereof is previously coated with the SiC polycrystal 5, it is assembled to the container body 11 so that a necessary portion is obtained. Can be coated only, and the cost can be reduced. At this time, it goes without saying that the width W and height H of the inner surface of the annular portion of the upper end portion 11a are within the range defined by the angle θ.

  Alternatively, as shown in FIG. 3B, only a part 11b of the inner wall of the upper end portion of the container body 11 having the same shape as that of FIG. Further, as shown in FIG. 3 (c), the upper end edge of the container body 11 is extended inward as a separate member, and the extended portion 11c is bent downward at a position close to the outer periphery of the seed crystal 3. It is good also as a cylindrical member. In these cases as well, the configuration is such that the width 11 and the height H of the inner surface 11b of the upper end portion of the container 11 as a separate member and the inner surface of the annular portion of the extending portion 11c are defined by the angle θ. To do. In particular, the extension 11c in FIG. 3C corresponds to the case where W = 0. Thus, if the part covered with the SiC polycrystal 5 is made into a split type, only the target member can be covered, so that the cost required for the covering can be reduced.

  In the present invention, instead of coating the surface of the cylindrical member 4 with the SiC polycrystal 5, the cylindrical member 4 itself can be composed of a SiC sintered body or a SiC reaction sintered body. The same applies to the case where the crucible 1 having the structure shown in FIG. 3 is used. The same kind of sintered body or reaction as the single crystal to be used for manufacturing the upper end portion 11a, the part 11b of the container body 11, and the tubular member 4 ′ itself. By setting it as a sintered compact, the effect similar to arrange | positioning the member coat | covered with the polycrystal is acquired.

  When producing a single crystal using the above apparatus, the cylindrical member 4 and the seed crystal 3 previously coated with the SiC polycrystal 5 are disposed in the crucible 1, and the crucible 1 is placed in a heating apparatus. Heat to predetermined temperature. Thereby, the raw material powder 2 is sublimated, and the sublimation gas reaches the surface of the seed crystal 3 and recrystallizes to grow a single crystal.

  At this time, if the surface of the crucible 1 or the surface of the member in the vicinity of the seed crystal 3 exposed to the sublimation gas is exposed, SiC polycrystals are deposited on the surface, causing the above-described variation in the Si / C ratio, etc. In the present invention, however, the cylindrical member 4 previously coated with the SiC polycrystal 5 is installed so as to surround the single crystal growth space below the growth surface 31 of the seed crystal 3, or the surface of the crucible 1 is previously formed. Since it is coated with the SiC polycrystal 5, it is possible to suppress the deposition of the SiC polycrystal and reduce the temperature fluctuation caused by this. In addition, the reaction between the C of the crucible 1 and the gas phase species containing Si or Si can be suppressed, the fluctuation of the Si / C ratio caused by the reaction, the generation of Si droplets associated therewith, and the fine particles of graphite in the single crystal. It becomes possible to prevent mixing.

  Further, in order to obtain the above effect to the maximum extent, in the single crystal growth process, the temperature gradient (temperature gradient at which the seed crystal side becomes a low temperature) in the initial single crystal growth space (from the raw material side to the seed crystal side) It is desirable that the temperature is 10 ° C./cm or less, preferably 1 to 5 ° C./cm. If the temperature gradient is larger than 10 ° C./cm, fluctuations in the Si / C ratio and the degree of supersaturation increase, and Si droplets and the like are generated, so that good initial growth cannot be expected. On the other hand, if the temperature is less than 1 ° C./cm, the growth end face is locally unsaturated, and the seed crystal may be partially thermally etched. Furthermore, the growth rate is extremely slow, which is not preferable for production. At 5 ° C./cm or less, it is possible to realize good initial growth by further suppressing fluctuations in the Si / C ratio and supersaturation.

  Examples of means for providing the temperature gradient include the following. In the case of the resistance heating method, for example, as shown in FIG. 6, an example in which a temperature gradient is provided by an independently controllable two-stage heating element (heater) 6 (in this example, heat insulation is provided between the two-stage heaters 6. If the material 8 is provided, it is easier to create a temperature gradient), or in the case of a one-stage heater, there is an example in which the temperature gradient is provided by setting the relative position of the heater with respect to the reaction vessel (crucible) or setting the shape and material of the crucible.

  In the case of the high-frequency heating method, as shown in FIG. 7, the number of turns per unit length of the coil (high-frequency coil) 7 is set or the shape and material of the reaction vessel (crucible) 1 is set or the coil 7 for the crucible 1 is set. There is an example in which a temperature gradient is provided by setting the relative position. A quartz double tube 10 is provided between the crucible 1 and the coil 7, and cooling water is introduced therein.

  Even in the case of the resistance heating method or the high-frequency heating method, it is also possible to cool the seed crystal part by the structure of the reaction vessel to effectively give a temperature gradient. For example, a pruning structure 9 is provided in the reaction vessel (crucible) 1 as shown in FIG. 8 to increase the cooling efficiency of the seed crystal 3, or a cooling gas (for example, He) in the reaction vessel (crucible) 1 as shown in FIG. Can be introduced so that the seed crystal 3 can be cooled. As described above, the example in which the raw material is arranged in the lower part of the crucible and the seed crystal is arranged in the upper part has been described.

  By performing growth in the range of the above-mentioned member and the above temperature gradient, generation of Si droplets, laminating fluctuations and mixing of graphite fine particles due to temperature fluctuations and Si / C ratio fluctuations that are remarkable in the early stage of growth are prevented. it can. Therefore, it is possible to prevent defects that occur mainly in the early stage of growth and to manufacture a high-quality silicon carbide single crystal with few defects with good reproducibility. As a method for growing a single crystal, in addition to the above-described sublimation recrystallization method, a method by a chemical reaction between gas phase species such as a CVD method can be applied.

  In addition to SiC, there are, for example, ZnSe, ZnS, CdS, CdSe, AlN, GaN, BN, and the like as single crystals that can be manufactured based on the present invention, and any single crystal that can be grown by sublimation recrystallization method. The same effect can be obtained regardless of which is applied.

(Example 1)
Using the graphite crucible 1 shown in FIG. 1 as a reaction vessel, a SiC single crystal growth experiment was conducted based on the method of the present invention. First, the inner surface of the cylindrical member 4 arranged in the container body 11 of the crucible 1 was previously coated with SiC polycrystal 5 using a sublimation method. At this time, the diameter S of the seed crystal 3 is 10 mm, the width W of the upper end surface (inner surface) of the cylindrical member 4 is 20 mm, and the height H of the side surface (inner surface) is 24 mm. The angle θ shown in FIG. = 38.7 ° region was covered with SiC polycrystal 5. The cylindrical member 4 and the seed crystal 3 are arranged in the crucible 1, filled with the SiC raw material powder 2, under reduced pressure of inert atmosphere gas: about 1 Torr, crucible temperature: about 2300 ° C., initial temperature gradient of 4 ° C. A single crystal was grown by heating for about 24 hours under the conditions of / cm. At that time, the temperature gradient was gradually increased in order to improve the growth rate. The growth amount was about 10 mm.

  The obtained single crystal ingot was cut and polished in parallel to the growth direction, and observed with a cross-sectional microscope. As a result of cross-sectional observation, the generation of defects frequently occurring in the early stage of growth was suppressed, and a homogeneous single crystal was obtained from the start to the end of growth. In addition, when a CVD method was employed as a coating method for the cylindrical member 4 and a single crystal growth experiment was performed under the same conditions except that, the generation of defects at the initial stage of growth was suppressed, and a uniform single crystal from the start to the end of growth was observed. Similar results were obtained that crystals were obtained. Furthermore, instead of coating the cylindrical member 4 with polycrystals, the same effect was observed when a similar single crystal growth experiment was carried out by configuring this with a SiC sintered body and a SiC reaction sintered body. .

(Example 2)
Using the same graphite crucible 1 as in FIG. 1, the inner surface of the cylindrical member 4 was previously coated with SiC polycrystal 5 using a sublimation method. The cylindrical member 4 and the seed crystal 3 are arranged in the crucible 1 and filled with the SiC raw material powder 2. Under reduced pressure of the inert gas: about 1 Torr, crucible temperature: about 2300 ° C., temperature gradient: 12 ° C./cm Single crystal growth was performed by heating for about 24 hours under certain conditions. The growth amount was about 12 mm. As a result of cross-sectional observation of the obtained single crystal, many tubular and crack-like defects were observed mainly in the early stage of growth. These defects propagated in the late growth stage, and it was impossible to obtain a homogeneous single crystal. This is because the temperature gradient was too large, and it was difficult to prevent the generation of Si droplets, laminating fluctuations and graphite fine particles due to temperature fluctuations, fluctuations in the Si / C ratio, especially in the early stage of growth. it is conceivable that.

(Example 3)
The same graphite crucible 1 as in FIG. 1 is used, and the size of the cylindrical member 4 is changed so that the range in which the angle θ in FIG. 2 is θ = 49.6 ° is covered with the polycrystal 5. did. At this time, the diameter S of the seed crystal 3 was 10 mm, the width W of the upper end surface (inner surface) of the cylindrical member 4 was 7 mm, and the height H of the side surface (inner surface) was 20 mm. An experiment was conducted to grow a single crystal on the seed crystal 3 under the same conditions as in Example 1 above, and the cross section of the obtained single crystal was observed. As a result, the occurrence of many defects at the initial stage of growth was suppressed, and a homogeneous single crystal was obtained from the start to the end of growth. In addition, when either the sublimation method or the CVD method was used as the coating method, the same effect was obtained when a SiC sintered body or a SiC reaction sintered body was used instead of coating.

Example 4
After the graphite crucible 1 similar to that used in Example 1 was used, the cylindrical member 4 and the SiC raw material powder 2 were disposed in the crucible 1, and before the seed crystal 3 was applied to the lid 12, Heating was performed under the same crystal growth conditions as in Example 1 to deposit SiC polycrystals on the surface of the cylindrical member 4 and the inner wall of the crucible 1. Thereafter, SiC seed crystal 3 was affixed, raw material powder 2 was replaced with a new one, and a single crystal was grown on seed crystal 3 under the same conditions as in Example 1 above. As a result of cross-sectional observation of the obtained single crystal, generation of defects that frequently occurred at the initial stage of growth was suppressed, and a homogeneous single crystal was obtained from the start to the end of growth.

(Comparative Example 1)
In the same graphite crucible 1 as in Example 1, an experiment was conducted in which a single crystal was grown on the seed crystal 3 under the same conditions as in Example 1 without arranging the cylindrical member 4. The growth amount was about the same as about 10 mm / 24 hours, but as a result of cross-sectional observation of the obtained single crystal, many fatal tubular and crack-like defects were observed mainly in the early stage of growth. These defects propagated in the late growth stage, and a homogeneous single crystal could not be obtained. This is due to temperature fluctuations that are conspicuous in the early stage of growth, the formation of Si droplets due to fluctuations in the Si / C ratio, the formation of carbonized layers due to the unsaturated state of vapor phase species containing SiC locally on the growth end face, and graphite. This is probably because it was difficult to prevent the mixing of fine particles. On the other hand, according to the method of the present invention, fatal defects mainly occurring at the early stage of growth can be prevented, and therefore, a high-quality silicon carbide single crystal with few defects can be produced with good reproducibility.

(Comparative Example 2)
In the same graphite crucible 1 as in Example 1, an experiment was conducted in which a single crystal was grown on the seed crystal 3 under the same conditions as in Example 2 without arranging the cylindrical member 4. The amount of growth was about 12 mm / 24 hours. As a result of cross-sectional observation of the obtained single crystal, many fatal tubular and crack defects were observed mainly in the early stage of growth. These defects propagated in the late growth stage, and it was impossible to obtain a homogeneous single crystal. This is because the temperature gradient was too large, and it was difficult to prevent the generation of Si droplets, stacking fluctuations and graphite fine particles due to temperature fluctuations, fluctuations in the Si / C ratio, especially in the early stage of growth. it is conceivable that. On the other hand, according to the present invention, it is possible to prevent fatal defects mainly occurring at the early stage of growth, and therefore, it is possible to manufacture a high-quality silicon carbide single crystal with few defects with good reproducibility.

FIG. 1 is an overall schematic sectional view showing a reaction vessel structure used in the method of the present invention. FIGS. 2A and 2B are diagrams for explaining regions covered with polycrystals based on the method of the present invention. 3 (a) to 3 (c) are overall schematic cross-sectional views showing other examples of the reaction vessel structure used in the method of the present invention. FIG. 4 is an overall schematic sectional view showing the reaction vessel structure used in the examples of the present invention. FIG. 5 is an overall schematic sectional view of a reaction vessel used in a conventional method. FIG. 6 is an overall schematic sectional view showing another example of a reaction vessel structure used in the method of the present invention. FIG. 7 is an overall schematic sectional view showing another example of a reaction vessel structure used in the method of the present invention. FIG. 8 is an overall schematic cross-sectional view showing another example of the reaction vessel structure used in the method of the present invention. FIG. 9 is an overall schematic cross-sectional view showing another example of a reaction vessel structure used in the method of the present invention.

Explanation of symbols

1 crucible (reaction vessel)
11 container body 12 lid body 13 base 2 raw material powder (raw material supply part)
3 seed crystal 31 growth end face 4 cylindrical member 5 SiC polycrystal

Claims (3)

In the method for producing a single crystal, the raw material gas of the single crystal to be produced is supplied to the seed crystal arranged in the reaction vessel, and the single crystal is grown on the seed crystal.
In the reaction vessel, at least an inner surface of the same type of polycrystal and sintered body that is to be produced so as to surround a single crystal growth space formed between the growth surface of the seed crystal and the raw material supply unit Alternatively, a cylindrical member made of a reaction sintered body is disposed in advance,
The cylindrical member is shaped to have an opening in which the lower end is open and the seed crystal is disposed on the upper end surface. The diameter of the seed crystal is S, and the width of the inner surface of the annular portion around the opening on the upper end surface is W. When the height of the inner surface of the side surface is H, the angle θ defined by the following formula (1) is set to be 20 ° ≦ θ ≦ 80 °,
θ = tan ⁻¹ [H / (W + S)] (1)
Thereafter, a single crystal is grown by supplying a raw material gas from the raw material supply section into the single crystal growth space.   The method for producing a single crystal according to claim 1, wherein the angle θ is set to satisfy 30 ° ≦ θ ≦ 60 °. The cylindrical member is formed of a polycrystal, sintered body, or reaction sintered body of the same type as the single crystal to be manufactured in advance. The method for producing a single crystal according to claim 1 or 2, wherein the single crystal is coated and has a coating thickness of 1 µm to 5 mm.

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