JP2010030828A - Production method of silicon carbide single crystal and apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for producing silicon carbide single crystals which can provide the silicon carbide single crystals being reduced in micro pipe defects compared with conventional ones. <P>SOLUTION: The production method of silicon carbide single crystals comprises receiving a raw material 40 for sublimation in a first end part in a reaction vessel 10, arranging seed crystals 50 of the silicon carbide single crystals in a second end part nearly facing to the raw material 40 for sublimation in the reaction vessel 10, and recrystallizing the sublimed raw material 40 for sublimation on the seed crystal 50, to grow the silicon carbide monocrystal. The seed crystals 50 are arranged in the second end part so as to be adhered to a graphite thin plate 51. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method and apparatus for producing a silicon carbide single crystal, and more particularly, a method for producing a silicon carbide single crystal for obtaining a high-quality and large-sized silicon carbide single crystal ingot that becomes a substrate wafer for blue light-emitting diodes and electronic devices. And a manufacturing apparatus.

  Silicon carbide single crystal has a larger band gap than silicon and is superior in dielectric breakdown characteristics, heat resistance, radiation resistance, etc. Therefore, it has attracted attention as an optical device material.

However, when producing such a silicon carbide single crystal, the obtained silicon carbide single crystal has about 50 to 200 / cm ² of pinhole defects (micropipe defects) having a diameter of about several μm that penetrate in the growth direction. In order to solve this problem, various studies have been conducted so far.

  As a method for producing a silicon carbide single crystal for the purpose of reducing micropipe defects, for example, there is a method using a silicon carbide single crystal production apparatus as shown in FIG. 2 (see, for example, Patent Document 1). The illustrated manufacturing apparatus includes a reaction vessel main body 12 that can contain a sublimation raw material 40, and is detachable from the reaction vessel main body 12, and faces the sublimation raw material 40 when the reaction vessel main body 12 is mounted. A reaction vessel 10 provided with a lid 11 capable of disposing a seed crystal 50 of a silicon carbide single crystal substantially at the center of the surface to be supported, a support rod 31 for fixing the reaction vessel 10 inside the quartz tube 30, and a quartz tube 30 and an induction heating coil 20 to 22 arranged in a spirally wound state around a portion where the reaction vessel 10 is located. In this case, the seed crystal 50 is bonded to a thick reaction vessel (crucible) made of graphite or the like to grow the crystal.

  In the manufacturing apparatus shown in the figure, when current is passed through the induction heating coils 20 to 22 to heat the reaction vessel body 12, the sublimation raw material 40 is heated by the heat, and the sublimation raw material 40 is heated to a predetermined temperature. Sublimated by being done. On the other hand, since the temperature of the lid 11 side where the seed crystal 50 is arranged is lower than that of the sublimation raw material 40 side, the sublimated raw material 40 is in an environment where it can be recrystallized. Therefore, the sublimation raw material 40 sublimated in the apparatus is recrystallized as silicon carbide on the seed crystal 50 on the lid portion 11 side, thereby growing a silicon carbide single crystal.

Moreover, as a technique related to the improvement of the micropipe defect, for example, Patent Document 2 includes a soaking member having higher thermal conductivity than the sublimation raw material, and includes at least a central portion in the radial direction of the reaction vessel. There is disclosed a method for producing a silicon carbide single crystal that is arranged near the surface of the substrate and promotes soaking of the surface of the opposing seed crystal.
International Patent Publication WO 02/053813 JP 2006-69851 A (Claims etc.)

  As described above, various studies have been made in the past in order to reduce micropipe defects in a silicon carbide single crystal, but this is not sufficient, and a high-quality silicon carbide single crystal with fewer defects is obtained. There was a need to establish technology for this.

  Accordingly, an object of the present invention is to provide a technique for obtaining a silicon carbide single crystal in which micropipe defects are further reduced as compared with the prior art by improving a manufacturing process or an apparatus configuration.

  As a result of intensive studies, the present inventor has found that the above problem can be solved by adopting the following configuration, and has completed the present invention.

That is, in the method for producing a silicon carbide single crystal of the present invention, a sublimation raw material is accommodated in a first end portion in a reaction vessel, and a silicon carbide single crystal is disposed in a second end portion substantially opposed to the sublimation raw material in the reaction vessel. In the method for producing a silicon carbide single crystal in which a seed crystal of crystal is arranged and the sublimation raw material that has been sublimated is recrystallized on the seed crystal to grow a silicon carbide single crystal.
The seed crystal is arranged at the second end in a state of being bonded to a graphite thin plate.

  In the production method of the present invention, it is preferable to use a graphite thin plate having a diameter of 1.2 to 1.4 times the diameter of the seed crystal, and 1.5 to 1.5 times the thickness of the seed crystal. It is also preferable to use one having a thickness of 2.0 times and a thickness of 0.5 mm or more.

The silicon carbide single crystal production apparatus of the present invention is a silicon carbide single crystal production apparatus for growing a silicon carbide single crystal by recrystallizing a sublimated raw material for sublimation on a seed crystal, In an apparatus for producing a silicon carbide single crystal comprising at least a reaction vessel comprising a reaction vessel main body capable of containing a raw material, and a lid body detachably provided to the reaction vessel main body and capable of arranging the seed crystal,
A graphite thin plate for carrying the seed crystal and fixing it to the lid is provided.

  According to the present invention, by adopting the above-described configuration, it is possible to realize a silicon carbide single crystal manufacturing method and manufacturing apparatus capable of obtaining a silicon carbide single crystal in which micropipe defects are further reduced as compared with the prior art. became.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the drawings.
In the method for producing a silicon carbide single crystal of the present invention, a silicon carbide single crystal production apparatus 1 having a configuration as shown in FIG. 1 can be used. The manufacturing apparatus 1 shown in the figure includes a reaction vessel 10 including a reaction vessel main body 12 that can store a sublimation raw material 40 and a lid 11 that is detachably provided on the reaction vessel main body 40 and on which a seed crystal 50 can be placed. The sublimation raw material 40 is accommodated in the reaction container main body 12 serving as the first end in the reaction container 10, and the silicon carbide single crystal is formed on the lid 11 serving as the second end substantially opposite to the sublimation raw material 40. A seed crystal 50 is disposed, and the sublimated raw material 40 is recrystallized on the seed crystal to grow a silicon carbide single crystal. In the following, the first end portion in which the sublimation raw material 40 in the reaction vessel 10 is accommodated is referred to as “sublimation raw material accommodation portion”, and the second end portion in which the seed crystal in the reaction vessel 10 is disposed is referred to as “seed crystal”. Also referred to as “arrangement part”.

  In the present invention, when manufacturing a silicon carbide single crystal using such a manufacturing apparatus, it is important to dispose the seed crystal 50 at the second end in a state of being bonded to the graphite thin plate 51. The seed crystal 50 is not directly attached to the container body 10 but arranged in the container body 10 through the graphite thin plate 51, so that the seed crystal 50 is compared with the thermal stress received from the thick crucible material. Since the thermal stress received from the graphite thin plate is small, it is possible to reduce the generation of micropipe defects due to distortion of the seed crystal due to the thermal stress, and a high quality crystal can be obtained. In addition, since the back surface of the seed crystal is bonded to the graphite thin plate 51, the problem of macro defects generated by sublimation of the back surface of the seed crystal can be avoided. In addition, it is preferable to use the graphite thin plate 51 having a thermal expansion coefficient substantially the same as that of the seed crystal.

  The graphite thin plate 51 used in the present invention is not particularly limited as long as it can support the seed crystal 50 and can be fixed to the lid body 11. A material having a diameter of 2 to 1.4 times, 1.5 to 2.0 times the thickness of the seed crystal 50 and having a thickness of 0.5 mm or more can be suitably used. The adhesion between the seed crystal 50 and the graphite thin plate 51 can be performed using, for example, a phenol resin mixed with carbon powder, but is not particularly limited.

  In the present invention, the point other than the arrangement of the seed crystal 50 bonded to the graphite thin plate 51 is not particularly limited, and can be appropriately carried out according to a conventional method. It is.

(Silicon carbide single crystal manufacturing equipment)
There is no restriction | limiting in particular as a crucible used for the reaction container 10, A well-known thing can be used. The inside of the illustrated reaction vessel 10 has a cylindrical shape. In this case, the cylindrical axis may be linear or curved, and a cross-sectional shape perpendicular to the axial direction of the cylindrical shape. May be circular or polygonal. A preferable shape of the reaction vessel 10 is a cylindrical shape having a straight axis and a circular cross section perpendicular to the axial direction.

  The shape of the reaction vessel main body 12 forming the first end of the reaction vessel 10 (sublimation raw material storage unit) is not particularly limited as long as it has a function capable of storing the sublimation raw material, and a known one is used. It may be a planar shape, or a structure (for example, a convex portion) for promoting soaking may be provided as appropriate.

  In addition, the lid body 11 forming the second end (seed crystal placement portion) of the reaction vessel 10 is designed to be detachable from the first end portion, whereby the second end (seed crystal placement portion) is designed. The grown silicon carbide single crystal can be easily separated from the reaction vessel 10 simply by removing the lid 11 attached to the container. Here, the reaction vessel main body 12 and the lid body 11 may be designed to be detachable by fitting, screwing or the like, but those by screwing are preferred.

  The lid 11 that forms the second end portion (seed crystal placement portion) can also be formed of two or more members. In particular, the central portion of the second end portion and the outer peripheral portion thereof can be formed of different members. The formation is preferable in that a temperature difference or a temperature gradient can be formed. More preferably, the lid 11 is formed of separate members for the inner region adjacent to the region where the silicon carbide single crystal is grown and the outer region located on the outer periphery thereof, thereby constituting the inner region. With respect to the above, at least a part is exposed to the outside of the reaction vessel.

  In this case, when the second end portion is heated from the outside, the outer region is easily heated, but the inner region is hardly heated due to contact resistance with the outer region. Therefore, a temperature difference is generated between the outer region and the inner region, and the temperature in the inner region is kept slightly lower than that in the outer region, and silicon carbide is easily recrystallized in the inner region. In addition, since a part of the member forming the inner region is exposed to the outside of the reaction vessel 10, the inner region easily radiates heat to the outside of the reaction vessel 10. Silicon recrystallization can easily occur.

  Here, the form of exposure of the other end of the member forming the inner region to the outside of the reaction vessel 10 is not particularly limited, and the inner region is a bottom surface and is continuously or discontinuously toward the outside of the reaction vessel 10. Examples include a shape whose diameter changes, that is, a shape that increases or decreases. Specific examples of such a shape include a columnar shape and a frustum shape having an inner region as a bottom surface. Examples of the columnar shape include a columnar shape and a prismatic shape, and a columnar shape is preferable, and the frustum shape includes, for example, a truncated cone shape, a truncated pyramid shape, an inverted truncated cone shape, and an inverted truncated pyramid shape. An inverted frustoconical shape is preferable.

  The positional relationship between the first end portion (sublimation raw material storage portion) and the second end portion (seed crystal placement portion) is not particularly limited and can be appropriately selected according to the purpose. It is preferable that the part is the lower end part and the seed crystal arrangement part is the upper end part, that is, the sublimation raw material storage part and the seed crystal arrangement part are located in the direction of gravity. In this case, the sublimation of the raw material for sublimation is performed smoothly, and the growth of the silicon carbide single crystal is performed in a state where no additional load is applied downward, that is, in the direction of gravity.

  In addition, on the first end portion (sublimation raw material storage portion) side, for example, a member formed of a material having excellent heat conductivity may be disposed for the purpose of efficiently sublimating the sublimation raw material. As such a member, for example, the outer periphery can be intimately contacted with the peripheral side surface portion 13 in the reaction vessel 10, and the inside has an inverted weight shape or a reverse shape in which the diameter gradually increases as the second end portion is approached. A member having a frustum shape is preferable. Further, the portion exposed to the outside of the reaction vessel 10 may be provided with threading, a temperature measuring recess, or the like according to the purpose. Such a temperature measuring recess can be provided in at least one of the first end portion side and the second end portion side.

  The material of the reaction vessel 10 is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably formed of a material excellent in durability, heat resistance, heat transfer properties, and the like. It is particularly preferable that it is made of graphite from the viewpoint that there is little mixing of polycrystals and polymorphs due to the occurrence of, and control of sublimation and recrystallization of the sublimation raw material is easy. In particular, it is preferable that at least the inner surface of the lid 11 constituting the second end portion is made of glassy carbon or amorphous carbon, whereby recrystallization of silicon carbide on at least the inner surface of the lid 11 is performed. Can be prevented.

  Moreover, it is preferable that the reaction vessel 10 is surrounded by a heat insulating material or the like. However, a substantially central portion of the first end portion (sublimation raw material storage portion) and the second end portion (seed crystal placement portion) in the reaction vessel 10 is covered with a heat insulating material or the like in order to form a temperature measurement window. It is preferred not to. In this case, if a temperature measuring window is provided in the approximate center of the first end (sublimation raw material storage), a graphite cover member is provided to prevent the insulation powder from falling. It is preferable to do.

  Furthermore, it is preferable to arrange the reaction vessel 10 in a quartz tube, whereby the loss of heating energy for sublimation and recrystallization of the sublimation raw material can be reduced. The quartz tube is easily available as a high-purity product, and a high-purity product is advantageous in that it contains less metal impurities.

  The heating means for heating each of the first end and the second end is preferably performed using separate heating means from the viewpoints of precision control, independent control, interference prevention, and the like of the heating means. In this case, as shown in the drawing, first heating means (first induction heating coil) 20 that is arranged at the first end portion (sublimation raw material storage unit) and forms a sublimation atmosphere for enabling sublimation of the sublimation raw material. And a second heating means (second induction heating coil) 21 for forming a recrystallization atmosphere for enabling recrystallization of the sublimation raw material arranged at the second end (seed crystal arrangement portion). It is preferable to provide two heating means.

  In this case, the first heating means is not particularly limited and may be appropriately selected depending on the purpose. Examples thereof include induction heating means and resistance heating means, but induction heating is preferable because temperature control is easy. Means are preferable, and among the induction heating means, a coil capable of induction heating is preferable. When the first heating means is a coil capable of induction heating, the number of wound turns is not particularly limited, and the heating efficiency and temperature efficiency are optimal depending on the distance from the second heating means, the material of the reaction vessel, etc. Can be determined. Also, the second heating means is not particularly limited and can be appropriately selected according to the purpose. Examples thereof include induction heating means, resistance heating means, etc. Induction heating means in terms of easy temperature control. Among them, a coil capable of induction heating is preferable. When the second heating means is a coil capable of induction heating, the number of windings is not particularly limited, and the heating efficiency and temperature efficiency are optimal depending on the distance from the first heating means and the material of the reaction vessel. Can be determined.

  In the present invention, it is preferable to use an interference preventing means for preventing interference between the first heating means and the second heating means for the purpose of efficient growth of the silicon carbide single crystal. The interference prevention means is not particularly limited and may be appropriately selected depending on the types of the first heating means and the second heating means. Examples thereof include an interference prevention coil and an interference prevention plate. As shown in FIG. 2, when the first heating means and the second heating means are the coils 20 and 21 that can be induction-heated, the interference preventing coil 22 can be suitably used.

  Such an interference preventing coil preferably has a function of preventing interference between the first heating means and the second heating means by passing an induced current. By arranging it between the heating unit and the induction heating by the first heating unit and the second heating unit at the same time, a dielectric current flows through the interference prevention coil, and the interference prevention coil minimizes the interference between the two. Can be prevented.

  The interference preventing coil is preferably designed so as not to be heated by an induced current flowing through itself, more preferably cooled by itself, and particularly preferably when a cooling medium such as water can be circulated. As a result, even when an induced current from the first heating unit and the second heating unit flows through the interference prevention coil, it is possible to prevent problems such as the interference prevention coil being heated and damaged, or peripheral components causing malfunctions. it can. Further, the number of turns of the interference preventing coil is not particularly limited, and may be determined by the types of the first heating means and the second heating means, the amount of current passed through them, etc. It is enough.

  In the silicon carbide single crystal manufacturing apparatus shown in the figure, a sublimation atmosphere is formed by the first induction heating coil 20 to sublimate the sublimation raw material 40, and the sublimated raw material 40 can be recrystallized only in the vicinity of the seed crystal 50. Then, a recrystallization atmosphere is formed by the second induction heating coil 21 so that the sublimation raw material 40 is recrystallized on the seed crystal 50. For this reason, in the growing silicon carbide single crystal, the entire growth surface maintains a convex shape toward the growth direction, and the concave portion depressed on the lid 11 side is formed in a ring shape in the entire growth process. In addition, the silicon carbide polycrystal does not grow in contact with the peripheral side surface portion 13 in the reaction vessel main body 12. Therefore, when the grown silicon carbide single crystal is cooled to room temperature, stress based on the thermal expansion difference is not concentrated and applied from the silicon carbide polycrystal side to the silicon carbide single crystal side. No damage such as cracks occurs in the single crystal. As a result, it is possible to efficiently and reliably produce a high-quality silicon carbide single crystal that is free from breakage such as cracks and does not contain polycrystals, polymorphs, or crystal defects such as micropipes.

(Raw material for sublimation)
As the sublimation raw material 40, as long as it is silicon carbide, the polymorph of crystal, the amount used, the purity, the production method thereof and the like are not particularly limited, and can be appropriately selected according to the purpose. Examples of the crystal polymorph of the sublimation raw material 40 include 4H, 6H, 15R, and 3C. Among these, 6H and the like are preferable. These are preferably used alone, but may be used in combination of two or more.

  The purity of the sublimation raw material 40 is preferably high purity from the viewpoint of preventing as much as possible the mixing of polycrystals and polymorphs in the silicon carbide single crystal to be produced. Each content is 0.5 ppm or less. Here, the content of the impurity element is an impurity content by chemical analysis and has only a meaning as a reference value. In practice, the impurity element is uniformly distributed in the silicon carbide single crystal. The evaluation differs depending on whether it is localized or unevenly distributed. Here, the “impurity element” means a group 1 to group 17 element in the periodic table of the 1989 IUPAC inorganic chemical nomenclature revised edition and has an atomic number of 3 or more (however, a carbon atom, an oxygen atom and a silicon atom) Element). In addition, when a dopant element such as nitrogen or aluminum is intentionally added for the purpose of imparting n-type or p-type conductivity to the growing silicon carbide single crystal, these are also excluded.

  The amount of the sublimation raw material 40 used can be appropriately selected according to the size of the silicon carbide single crystal to be produced, the size of the reaction vessel, and the like.

  The silicon carbide powder as the sublimation raw material 40 includes, for example, at least one silicon compound as a silicon source, at least one organic compound that generates carbon by heating as a carbon source, and a polymerization catalyst or a crosslinking catalyst. The powder obtained by dissolving and drying in a solvent is obtained by firing in a non-oxidizing atmosphere.

  As a silicon compound, 1 type may be used independently, 2 or more types may be used together, a liquid thing and a solid thing can be used together, but at least 1 sort is a liquid thing Select from.

  As the liquid silicon compound, alkoxysilane and alkoxysilane polymers are preferably used. Among these, examples of the alkoxysilane include methoxysilane, ethoxysilane, propoxysilane, butoxysilane and the like, and among these, ethoxysilane is preferable in terms of handling. The alkoxysilane may be any of monoalkoxysilane, dialkoxysilane, trialkoxysilane, and tetraalkoxysilane, with tetraalkoxysilane being preferred. Examples of the alkoxysilane polymer include a low molecular weight polymer (oligomer) having a polymerization degree of about 2 to 15 and a silicic acid polymer, and specifically, for example, a tetraethoxysilane oligomer.

  Examples of solid silicon compounds include silicon oxides such as SiO, silica sol (liquid containing colloidal ultrafine silica, containing OH groups and alkoxyl groups inside), and silicon dioxide (silica gel, fine silica, quartz powder). .

  Among the above silicon compounds, tetraethoxysilane oligomers, a mixture of tetraethoxysilane oligomers and fine powder silica, and the like are preferable in terms of good homogeneity and handling properties. Moreover, it is preferable that a silicon compound is highly purified, and it is more preferable that content of each impurity in an initial stage is 20 ppm or less, and especially 5 ppm or less.

  Moreover, as an organic compound which produces | generates carbon by heating, 1 type may be used independently and 2 or more may be used together, In this case, a liquid thing may be used independently, for example, a liquid A solid material and a solid material may be used in combination.

  As the organic compound that produces carbon by heating, a residual carbon ratio is high, and an organic compound that is polymerized or cross-linked by a catalyst or heating is preferable, for example, a resin monomer such as phenol resin, furan resin, polyimide, polyurethane, and polyvinyl alcohol. And prepolymers, and other liquid materials such as cellulose, sucrose, pitch, and tar. Among these, high-purity ones are preferable, phenol resins are more preferable, and resol type phenol resins are particularly preferable. The purity of the organic compound that generates carbon by heating can be appropriately selected according to the purpose. However, when high-purity silicon carbide powder is required, an organic compound that does not contain 5 ppm or more of each metal is used. It is preferable.

  The polymerization catalyst and the crosslinking catalyst can be appropriately selected according to the organic compound that generates carbon by heating. When the organic compound that generates carbon by heating is a phenol resin or furan resin, toluenesulfonic acid, toluenecarboxylic acid, acetic acid, oxalic acid is used. Acids such as acid, maleic acid and sulfuric acid are preferred, and maleic acid is particularly preferred.

  The ratio of silicon contained in the silicon compound to carbon contained in the organic compound that produces carbon by heating (hereinafter referred to as “C / Si ratio”) is a carbide obtained by carbonizing a mixture of both at 1000 ° C. Intermediates are defined by elemental analysis. Stoichiometrically, the free carbon in the silicon carbide powder obtained when the C / Si ratio is 3.0 should be 0%, but in practice, due to volatilization of the SiO gas produced simultaneously, Free carbon is generated at low C / Si ratios. It is preferable to determine the blending ratio in advance so that the amount of free carbon in the obtained silicon carbide powder becomes an appropriate amount. Usually, in firing at 1600 ° C. or higher near 1 atm, free carbon can be suppressed by setting the C / Si ratio to 2.0 to 2.5. When the C / Si ratio exceeds 2.5, free carbon increases remarkably. However, the firing is not limited to the range of the C / Si ratio when firing at a low or high atmospheric pressure.

  The silicon carbide powder can also be obtained, for example, by curing a mixture of a silicon compound and an organic compound that generates carbon by heating. Examples of the curing method include a method of crosslinking by heating, a method of curing with a curing catalyst, and a method of electron beam or radiation. The curing catalyst in this case can be appropriately selected according to the type of organic compound that produces carbon by heating. In the case of a phenol resin or furan resin, toluenesulfonic acid, toluenecarboxylic acid, acetic acid, oxalic acid Preferable examples include acids such as hydrochloric acid, sulfuric acid and maleic acid, and amine acids such as hexamine. When these curing catalysts are used, the curing catalyst is dissolved or dispersed in a solvent. Examples of the catalyst include lower alcohols (for example, ethyl alcohol), ethyl ether, acetone and the like.

  The silicon carbide powder obtained as described above is fired at 800 to 1000 ° C. for 30 to 120 minutes in a non-oxidizing atmosphere such as nitrogen and argon. By this firing, the silicon carbide powder becomes a carbide, and this carbide is fired at 1350 to 2000 ° C. in a non-oxidizing atmosphere such as argon to produce a silicon carbide powder. The firing temperature and time can be appropriately selected according to the particle size and the like of the silicon carbide powder to be obtained. From the viewpoint of more effective production of the silicon carbide powder, the firing temperature is 1600 to 1900 ° C. Is preferred. In addition, for the purpose of removing impurities and obtaining high-purity silicon carbide powder, it is also preferable to perform a heat treatment at, for example, 2000 to 2400 ° C. for 3 to 8 hours after firing.

  Since the silicon carbide powder obtained as described above is non-uniform in size, the desired particle size can be obtained by pulverization, classification, and the like. In the present invention, the average particle size of the silicon carbide powder is preferably 10 to 700 μm, more preferably 100 to 400 μm. If the average particle size is less than 10 μm, the sublimation surface area of the silicon carbide for growing the silicon carbide single crystal, that is, sintering rapidly occurs at 1800 ° C. to 2700 ° C., so that the sublimation surface area becomes small and carbonization occurs. The growth of the silicon single crystal may be slow, and when the silicon carbide powder is accommodated in the reaction vessel 10 or when the pressure of the recrystallization atmosphere is changed to adjust the growth rate, the silicon carbide powder is scattered. It becomes easy to do. On the other hand, when the average particle diameter exceeds 500 μm, the specific surface area of the silicon carbide powder itself becomes small, so that the growth of the silicon carbide single crystal may also be slow.

  As described above, the silicon carbide powder may be any of 4H, 6H, 15R, 3C, a mixture thereof, etc., but the same polymorph as the single crystal to be grown is preferable and has high purity. It is preferable.

  For the purpose of imparting n-type or p-type conductivity to a silicon carbide single crystal grown using silicon carbide powder, nitrogen or aluminum can be introduced, respectively. In the case of introduction at the time of production, first, an organic substance composed of a nitrogen source or an aluminum source may be uniformly mixed together with the aforementioned silicon source, carbon source, polymerization or crosslinking catalyst. At this time, for example, when an organic substance composed of a carbon source such as a phenol resin and a nitrogen source such as hexamethylenetetramine and a polymerization or crosslinking catalyst such as maleic acid are dissolved in a solvent such as ethanol, tetraethoxysilane is dissolved. It is preferable to sufficiently mix with a silicon source such as an oligomer of

  The organic material comprising the nitrogen source is preferably a material that generates nitrogen by heating, such as a polymer compound (specifically, polyimide resin, nylon resin, etc.), organic amine (specifically, hexamethylenetetramine). , Ammonia, triethylamine and the like, and compounds and salts thereof). Among these, hexamethylenetetramine is preferable. A phenol resin synthesized using hexamine as a catalyst and containing 2.0 mmol or more of nitrogen derived from the synthesis step with respect to 1 g of the resin can also be suitably used as an organic substance composed of a nitrogen source. These organic materials composed of nitrogen sources may be used alone or in combination of two or more. In addition, there is no restriction | limiting in particular as an organic substance which consists of aluminum sources, According to the objective, it can select suitably.

  The addition amount of the organic substance composed of the nitrogen source is preferably such that when the silicon source and the carbon source are added at the same time, 1 mmol or more of nitrogen is contained per 1 g of the silicon source, and 80 to 1000 μg per 1 g of the silicon source. preferable.

  More specific sublimation raw materials that can be used in the production of silicon carbide single crystals include, for example, (1) High purity alkoxysilane and / or high purity alkoxysilane polymer is used as a silicon source, and carbon is generated by heating. Silicon carbide powder obtained by heating and firing a mixture obtained by uniformly mixing these compounds with a high-purity organic compound as a carbon source, and (2) high-purity methoxysilane, high-purity High purity that produces carbon by heating at least one selected from the group consisting of ethoxysilane, high purity propoxysilane, high purity butoxysilane and polymers having a polymerization degree of 2 to 15 Silicon carbide powder obtained by heating and firing a mixture obtained by uniformly mixing these organic compounds with a carbon source as a carbon source, (3) high At least one selected from the group consisting of monoalkoxysilanes having a high degree of purity, dialkoxysilanes having a high purity, trialkoxysilanes having a high purity, tetraalkoxysilanes having a high purity, and polymers having a polymerization degree of 2 to 15 A silicon carbide powder obtained by heating and calcining a mixture obtained by uniformly mixing a high-purity organic compound that produces carbon by heating as a carbon source, under a non-oxidizing atmosphere, (4) A silicon carbide powder obtained by heating and firing a mixture obtained by uniformly mixing a silicon source as a tetraalkoxysilane polymer and a carbon source as a phenol resin in a non-oxidizing atmosphere.

(Growth of silicon carbide single crystal)
The growth of the silicon carbide single crystal is performed on the seed crystal of the silicon carbide single crystal disposed at the second end of the reaction vessel. As described above, in order to recrystallize and grow a silicon carbide single crystal on a seed crystal, the sublimation raw material is set to a temperature higher than the sublimation temperature, and the sublimated raw material is recrystallized only in the vicinity of the seed crystal. It is necessary to form a recrystallization atmosphere that can be made possible, but in particular, the temperature decreases as it approaches the center (center of the inner region) in the radial direction of the surface on which the seed crystal is arranged. It is preferable to form an atmosphere having a temperature distribution.

  The recrystallization atmosphere can be formed by the second heating means described above, and by this second heating means, the sublimation raw material sublimated by the first heating means is recrystallized only in the vicinity of the seed crystal of the silicon carbide single crystal. A recrystallization atmosphere is formed so as to be possible, and the raw material for sublimation is recrystallized on the seed crystal of the silicon carbide single crystal.

  Here, the amount of the induction heating current energized to the second heating means can be appropriately determined in relation to the amount of the induction heating current energized to the first heating means. It is preferable that the current value of the induction heating current in is set to be larger than the current value of the induction heating current in the second heating means. In this case, the temperature of the recrystallization atmosphere in the vicinity of the seed crystal is maintained lower than the temperature of the atmosphere in which the sublimation raw material is sublimated, which is advantageous in that recrystallization is easily performed.

  Further, the current value of the induction heating current in the second heating means is preferably controlled so as to decrease continuously or stepwise as the diameter of the growing silicon carbide single crystal increases. In this case, as the silicon carbide single crystal grows, the amount of heating by the second heating means is controlled to be small, so that recrystallization is performed only in the vicinity of the silicon carbide single crystal that continues to grow, and there is a large amount around the silicon carbide single crystal. This is advantageous because the formation of crystals can be effectively suppressed. The current value of the induction heating current in the second heating means is controlled to be small when the diameter of the silicon carbide single crystal is large, and to be large when the diameter is small. Is preferred.

  In the present invention, since the second heating means can be controlled independently of the first heating means, by appropriately adjusting the heating amount of the second heating means according to the growth rate of the silicon carbide single crystal, A favorable growth rate can be maintained throughout the entire growth process of the silicon carbide single crystal.

  The temperature of the recrystallization atmosphere formed by the second heating means is preferably 30 to 300 ° C., more preferably 30 to 150 ° C. lower than the temperature of the sublimation atmosphere formed by the first heating means. Further, the pressure of the recrystallization atmosphere formed by the second heating means is preferably 5 to 100 Torr (665 to 13300 Pa), but when this pressure condition is used, the pressure is not set while heating under reduced pressure. It is preferable to adjust the pressure condition so as to be within the above predetermined range by reducing the pressure after heating to the temperature. Note that the recrystallization atmosphere is preferably an inert gas atmosphere such as argon gas.

In the present invention, the temperature on the first end portion (sublimation raw material storage portion) side containing the sublimation raw material, controlled by the first heating means, and the carbonization controlled by the second heating means in the reaction vessel. The temperature of the central part on the second end (seed crystal arrangement part) side where the seed crystal of the silicon single crystal is arranged, and the temperature of the adjacent part to the inner peripheral side part of the reaction vessel located outside the central part From the viewpoint of obtaining a large-diameter silicon carbide single crystal, it is preferable to control the following relationship. That is, when the temperature at the _first end side is T ₁ , the temperature at the center portion at the second end side is T ₂ , and the temperature T _{3 at} the adjacent portion to the inner peripheral side surface side at the second end side is T It is preferable to control such that _3- T ₂ and T ₁ -T ₂ increase continuously or stepwise.

In this case, since T ₁ -T ₂ increases continuously or stepwise, even if the silicon carbide single crystal continues to grow toward the first end portion over time, the crystal growth front side of the silicon carbide single crystal Is always maintained in a state where recrystallization is likely to occur. On the other hand, since T ₃ -T ₂ increases continuously or stepwise, even if the silicon carbide single crystal continues to grow toward the outer peripheral direction on the second end side over time, the crystal growth of the silicon carbide single crystal The outer peripheral end side is always maintained in a state where recrystallization is likely to occur. As a result, the formation of silicon carbide polycrystal is effectively suppressed, and the silicon carbide single crystal continues to grow in the direction of increasing its thickness while expanding its diameter. This is advantageous in that a large-diameter silicon carbide single crystal can be obtained.

  As the shape of the growing silicon carbide single crystal, the entire growth surface is preferably convex in the growth direction side, and the first end portion (sublimation raw material storage portion) and the second end portion face each other. In this case, the entire growth surface is preferably convex toward the sublimation raw material (first end) side. In this case, it is preferable because there is no recessed portion on the second end side where there are many polycrystals and polymorphs and stress due to the difference in thermal expansion is likely to concentrate. The shape of the growing silicon carbide single crystal does not have to be convex as a whole as long as the entire growth surface does not include a concave portion on the opposite side of the growth direction. A flat portion may be included in part.

  Further, the shape of the silicon carbide crystal including the silicon carbide single crystal is preferably substantially mountain-shaped toward the sublimation raw material (first end) side, and more preferably, the diameter gradually decreases. Yamagata. That is, it can be said that it is preferable to grow a silicon carbide crystal including a silicon carbide single crystal while maintaining a substantially chevron shape in which the diameter gradually decreases toward the sublimation raw material side throughout the entire growth process. In addition, silicon carbide polycrystals and polymorphs may be mixed in the base portion of the silicon carbide crystal having a substantially chevron shape, that is, in the outer peripheral portion. This mixing may cause the thickness, size, shape, etc. of the seed crystal. Occurrence can be prevented by a combination of the conditions of the heating amount by the second heating means.

  In the present invention, the ring-shaped plate member may be fixedly arranged on the peripheral side surface portion in the reaction vessel substantially in parallel with the second end portion (seed crystal arrangement portion). As a result, when a silicon carbide single crystal is recrystallized and grown on a seed crystal, only the silicon carbide single crystal can be recrystallized and grown on the seed crystal without generating a silicon carbide polycrystal or a ring. Can be selectively deposited on the plate member. In this case, the diameter of the silicon carbide single crystal obtained is restricted by the amount of the ring-shaped plate member.

  In the present invention, a high-quality silicon carbide single crystal can be produced efficiently and easily without breakage such as cracks by the above production steps.

(Silicon carbide single crystal)
The silicon carbide single crystal obtained as described above has a nondestructive optically detected crystal defect (pipe defect) of preferably 100 pieces / cm ² or less, more preferably 50 pieces / cm ² or less. Yes, particularly preferably 10 pieces / cm ² or less. The total content of impurity elements in the silicon carbide single crystal is preferably 10 ppm or less. Such a silicon carbide single crystal is free from crystal defects such as polycrystals, polymorphs and micropipes, and is extremely high quality. Therefore, the silicon carbide single crystal is excellent in dielectric breakdown characteristics, heat resistance, radiation resistance, etc. It is particularly preferably used for optical devices such as devices and light emitting diodes.

Hereinafter, the present invention will be described in more detail with reference to examples.
<Example>
A silicon carbide single crystal was manufactured using the silicon carbide single crystal manufacturing apparatus 1 shown in FIG. First, a sublimation raw material 40 is accommodated in a reaction vessel main body 12 that forms a first end portion in a reaction vessel (graphite crucible) 10, and carbonized at a substantially center of a lid 11 that forms a second end portion facing this. A silicon single crystal seed crystal 50 was physically arranged in a state of being bonded to the graphite thin plate 51.

  The sublimation raw material 40 is obtained by heating and baking a mixture obtained by uniformly mixing a high purity tetraethoxysilane polymer as a silicon source and a resol type phenol resin as a carbon source in an argon atmosphere. Silicon carbide powder (6H (including 3C in part), average particle size 200 μm) was used. The seed crystal 50 was a 6H atchison crystal having a seed crystal thickness of 0.9 mm and a diameter of 20 mm.

  The primary induction heating coil 20 and the first induction heating coil 20 and the second coil 11 are set so that the temperature of the lid 11 is 100 ° C. lower than the temperature of the sublimation raw material 40 (the temperature of the lid 11: 2100 ° C., the temperature of the sublimation raw material 40: 2200 ° C.). The secondary induction heating coil 21 was heated and maintained at a pressure of 5 Torr (666.5 Pa) in an argon (Ar) gas atmosphere, thereby causing crystal growth from the sublimation raw material 40 side to the seed crystal 50 side. Then, after fully cooling, the silicon carbide single crystal wafer produced | generated from the inside of the container main body 10 was taken out.

<Conventional example>
A silicon carbide single crystal wafer was obtained in the same manner as in the example except that the seed crystal 50 was arranged directly in the reaction vessel 10 without using the graphite thin plate 51.

  The wafers obtained in the examples and the conventional examples were polished to a mirror surface, and the molten KOH etching evaluation was performed on the micropipe defects. The results are shown in Table 1 below.

  As shown in Table 1 above, as a result, in the embodiment according to the present invention in which the seed crystal is disposed in the reaction vessel and adhered to the graphite thin plate, as compared with the conventional example disposed without the graphite thin plate, The micropipe density per unit area was an order of magnitude smaller, confirming that micropipe defects can be reduced by the present invention.

It is a schematic explanatory drawing which shows the manufacturing apparatus of the silicon carbide single crystal which concerns on one embodiment of this invention. It is a schematic explanatory drawing which shows the manufacturing apparatus of the conventional silicon carbide single crystal.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Silicon carbide single crystal manufacturing apparatus 10 Graphite crucible 11 Lid 10 Reaction vessel 12 Reaction vessel body 13 Circumferential side portion 20 First induction heating coil (first heating means)
21 Second induction heating coil (second heating means)
22 Interference prevention coil (interference prevention means)
30 Quartz tube 31 Support rod 40 Sublimation raw material 50 Silicon carbide single crystal seed crystal 51 Graphite thin plate

Claims (4)

The sublimation raw material is contained in the first end portion in the reaction vessel, and the seed crystal of the silicon carbide single crystal is disposed on the second end portion substantially opposite to the sublimation raw material in the reaction vessel, and is sublimated. In the method for producing a silicon carbide single crystal in which a raw material is recrystallized on the seed crystal to grow a silicon carbide single crystal,
A method for producing a silicon carbide single crystal, comprising disposing the seed crystal on the second end in a state of being bonded to a graphite thin plate.   The method for producing a silicon carbide single crystal according to claim 1, wherein the graphite thin plate having a diameter 1.2 to 1.4 times the diameter of the seed crystal is used.   3. The method for producing a silicon carbide single crystal according to claim 1, wherein the graphite thin plate is 1.5 to 2.0 times the thickness of the seed crystal and has a thickness of 0.5 mm or more. . A silicon carbide single crystal manufacturing apparatus for growing a silicon carbide single crystal by recrystallizing a sublimation raw material on a seed crystal, a reaction vessel main body capable of containing the sublimation raw material, and the reaction vessel main body In a silicon carbide single crystal manufacturing apparatus comprising at least a reaction vessel that is detachably provided with respect to the lid on which the seed crystal can be disposed,
An apparatus for producing a silicon carbide single crystal, comprising a thin graphite plate for supporting the seed crystal and fixing the seed crystal to the lid.

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