JP4619567B2 - Silicon carbide single crystal and method for producing the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a silicon carbide single crystal particularly suitable as an electronic device, an optical device and the like, and a method capable of efficiently producing the silicon carbide single crystal.
[0002]
[Prior art]
Silicon carbide has a larger band gap and superior dielectric breakdown characteristics, heat resistance, radiation resistance, etc., compared to silicon, so it is excellent as an electronic device material such as a small and high-power semiconductor, and also has excellent optical characteristics. Therefore, it has been attracting attention as an optical device material. Among such silicon carbide crystals, a silicon carbide single crystal has an advantage that it is particularly excellent in uniformity of characteristics in a wafer when applied to a device such as a wafer, compared to a silicon carbide polycrystal.
[0003]
Although several methods for producing the silicon carbide single crystal have been provided in the past, any silicon carbide single crystal obtained can be mixed with polycrystals, polymorphs, or hollow pipe-like crystal defects (so-called micropipes). ) Would occur.
[0004]
Therefore, as a method for producing a silicon carbide single crystal in which such a problem is solved, for example, a method using a silicon carbide single crystal production apparatus as shown in FIG. 8 has been generally known. The silicon carbide single crystal manufacturing apparatus 80 is detachable from the container main body 12 capable of storing the sublimation raw material 40 and the container main body 12 and is stored in the container main body 12 when the container main body 12 is mounted. The graphite crucible 10 provided with the lid 11 capable of disposing the seed crystal 50 of the silicon carbide single crystal at the approximate center of the surface facing the sublimation raw material 40, and the graphite crucible 10 are fixed inside the quartz tube 30. A support rod 31 and an induction heating coil 25 arranged in a spirally wound manner at substantially equal intervals around the periphery of the quartz tube 30 where the graphite crucible 10 is located. In silicon carbide single crystal manufacturing apparatus 80, when current is passed through induction heating coil 25 to heat it, sublimation raw material 40 is heated by the heat. The sublimation raw material 40 sublimes when heated to a predetermined temperature. The sublimated raw material 40 does not recrystallize unless cooled to the recrystallization temperature. Here, since the temperature of the lid 11 side is lower than that of the sublimation raw material 40 side and the sublimation raw material 40 is in an atmosphere where it can be recrystallized, the silicon carbide is regenerated on the seed crystal 50 of the silicon carbide single crystal. Crystallize and grow silicon carbide crystals.
[0005]
At this time, the silicon carbide single crystal 60 recrystallizes and grows on the silicon carbide single crystal seed crystal 50, and the silicon carbide polycrystal 70 recrystallizes and grows on the outer peripheral edge of the silicon carbide single crystal seed crystal 50. To do. Finally, as shown in FIG. 8, a concave portion 71 that is depressed on the lid body 11 side is formed in a ring shape, and the vicinity of the concave portion 71 or the outer peripheral edge side of the lid body 11 has a foreign material such as polycrystal or polymorph. It is in a state of being mixed and present in large quantities. The entire surface of the lid 11 facing the inside of the container body 12 is covered with silicon carbide crystals, and the silicon carbide polycrystal 70 contacts the inner peripheral side surface of the container body 12 on the outer peripheral edge of the lid 11. Grows in a state that In this state, when cooling to room temperature, stress based on the thermal expansion difference is concentrated and applied from the silicon carbide polycrystal 70 side to the silicon carbide single crystal 60 side, and the silicon carbide single crystal as shown in FIG. In some cases, breakage such as cracks occurred in 60, or defects such as polycrystals, polymorphs, or micropipes occurred. In recent times when the production of large-diameter silicon carbide single crystals is required, this has become a serious problem that must be overcome.
[0006]
High-quality silicon carbide single crystals that are free from breakage such as cracks and free of defects such as polycrystals, polymorphs, and micropipes, as well as high-quality silicon carbide single crystals of such high quality As a method that can be easily and easily manufactured, the applicants of the present application subsidized silicon carbide powder and the like as a raw material for sublimation, and recrystallized on a silicon carbide single crystal seed crystal to grow a silicon carbide single crystal. In the production of a silicon single crystal, an invention was proposed in which a silicon carbide single crystal is grown while maintaining a convex shape toward the sublimation raw material side throughout the entire growth process (Japanese Patent Application No. 2000-402730).
However, in recent years, due to the development of technology, there is a demand for a method for producing a silicon carbide single crystal that can use a sublimation raw material more efficiently at a lower cost and that is excellent in production efficiency.
[0007]
[Problems to be solved by the invention]
It is an object of the present invention to solve the above-mentioned problems in the prior art, meet the demands, and achieve the following objects.
The present invention is excellent in dielectric breakdown characteristics, heat resistance, radiation resistance, etc., and is particularly suitable for electronic devices such as semiconductor wafers, optical devices such as light emitting diodes, etc. Provided are a high-quality silicon carbide single crystal having no defects, and a method capable of producing the high-quality silicon carbide single crystal at a low cost and in a large diameter easily without damage such as cracks. For the purpose.
[0008]
[Means for Solving the Problems]
Means for solving the above problems are as follows. That is,
<1> A method for producing a silicon carbide single crystal in which a sublimated sublimation raw material is recrystallized to grow a silicon carbide single crystal,
The silicon carbide single crystal is characterized in that the raw material for sublimation includes a silicon carbide sintered body, and the silicon carbide single crystal is grown while maintaining the entire growth surface in a convex shape throughout the entire growth process. It is a manufacturing method.
<2> The method for producing a silicon carbide single crystal according to <1>, wherein a silicon carbide crystal including the silicon carbide single crystal is grown in a substantially chevron shape.
<3> A sublimation raw material is housed in a reaction vessel, and a seed crystal of a silicon carbide single crystal is disposed at an end portion substantially opposed to the sublimation raw material in the reaction vessel,
The carbonization according to <1> or <2>, wherein the growth of the silicon carbide crystal including the silicon carbide single crystal is performed only in a region other than a portion adjacent to the peripheral side surface portion in the reaction vessel at the end portion. This is a method for producing a silicon single crystal.
[0009]
<4> A method for producing a silicon carbide single crystal in which a silicon carbide single crystal is grown by recrystallizing a sublimated raw material for sublimation,
The sublimation raw material includes a silicon carbide sintered body, the sublimation raw material is accommodated in a reaction vessel, and a seed crystal of the silicon carbide single crystal is provided at an end portion substantially opposed to the sublimation raw material in the reaction vessel. Place and
A method for producing a silicon carbide single crystal, wherein a silicon carbide crystal including the silicon carbide single crystal is grown only in a region of the end portion excluding a portion adjacent to a peripheral side surface portion in the reaction vessel. is there.
<5> The method for producing a silicon carbide single crystal according to any one of <2> to <4>, wherein the silicon carbide crystal including the silicon carbide single crystal is composed only of the silicon carbide single crystal.
<6> A raw material for sublimation is accommodated on one end side in the reaction vessel, a seed crystal of silicon carbide single crystal is placed on the other end side in the reaction vessel,
By a first heating means arranged on the one end side, a sublimation atmosphere is formed so that the sublimation raw material can be sublimated,
The second heating means disposed on the other end side changes the recrystallization atmosphere so that the sublimation raw material sublimated by the first heating means can be recrystallized only in the vicinity of the seed crystal of the silicon carbide single crystal. The method for producing a silicon carbide single crystal according to any one of <1> to <5>, wherein the raw material for sublimation is formed and recrystallized on a seed crystal of the silicon carbide single crystal.
[0010]
<7> The method for producing a silicon carbide single crystal according to <6>, wherein the temperature of the recrystallization atmosphere is 30 to 300 ° C. lower than the temperature of the sublimation atmosphere in the reaction vessel.
<8> The method for producing a silicon carbide single crystal according to <6> or <7>, wherein the first heating unit and the second heating unit are induction-heatable coils.
<9> The method for producing a silicon carbide single crystal according to <8>, wherein the current value of the induction heating current in the first heating unit is larger than the current value of the induction heating current in the second heating unit.
[0011]
<10> The silicon carbide according to <8> or <9>, wherein the current value of the induction heating current in the second heating means is decreased continuously or stepwise as the diameter of the growing silicon carbide single crystal increases. This is a method for producing a single crystal.
<11> The temperature on the one end side containing the sublimation raw material in the reaction vessel is T ₁ And the temperature on the other end side where the seed crystal of the silicon carbide single crystal is arranged is T ₂ And the temperature T of the adjacent portion to the inner peripheral side surface portion of the reaction vessel on the other end portion side. ₃ T ₃ -T ₂ And T ₁ -T ₂ The method for producing a silicon carbide single crystal according to any one of <6> to <10>, wherein is increased continuously or stepwise.
<12> An induction current can be passed between the first heating means and the second heating means, and interference between the first heating means and the second heating means is caused by passing the induced current. The method for producing a silicon carbide single crystal according to any one of <8> to <11>, wherein interference preventing means for preventing is arranged.
[0012]
<13> The method for producing a silicon carbide single crystal according to <12>, wherein the interference prevention unit is a coil capable of circulating cooling water.
<14> The method for producing a silicon carbide single crystal according to any one of <6> to <13>, wherein the one end is a lower end and the other end is an upper end.
<15> The method for producing a silicon carbide single crystal according to any one of <6> to <14>, wherein the reaction vessel is a crucible disposed in a quartz tube.
[0013]
<16> The region where the silicon carbide single crystal is grown at the other end, and the region located on the outer periphery of the region and adjacent to the inner peripheral side surface of the reaction vessel are formed of different members, And, in the member forming the region where the silicon carbide single crystal is grown, one end is exposed to the inside of the reaction vessel and the other end is exposed to the outside of the reaction vessel. It is a manufacturing method of the silicon carbide single crystal in any one.
<17> Production of a silicon carbide single crystal according to any one of <4> to <16>, wherein the surface of the other end portion adjacent to the inner peripheral side surface portion in the reaction vessel is glassy carbon. Is the method.
<18> A preparation process in which a silicon carbide sintered body prepares a slurry or paste by dispersing silicon carbide powder in a solvent, and calcined body formation in which the slurry or paste is molded and calcined to form a calcined body The silicon carbide single unit according to any one of <1> to <17>, obtained by a method for producing a sintered silicon carbide body, comprising: a pore sealing step of impregnating the calcined body with metal silicon. It is a manufacturing method of a crystal.
[0014]
<19> A silicon carbide sintered body comprising a mixture containing silicon carbide powder, a boron compound, and a nonmetallic sintering aid, having a temperature of 2000 to 2400 ° C. and a pressure of 300 to 700 kgf / cm. ² The method for producing a silicon carbide single crystal according to any one of <1> to <17>, obtained by a method for producing a silicon carbide sintered body including a hot pressing step of hot pressing in a non-oxidizing atmosphere.
<20> Silicon carbide powder uses at least one selected from high-purity alkoxysilanes and alkoxysilane polymers as a silicon source, and uses a high-purity organic compound that generates carbon by heating as a carbon source, and these are mixed uniformly. This is a method for producing a silicon carbide single crystal according to <18> or <19>, wherein the mixture is a silicon carbide powder obtained by heating and firing in a non-oxidizing atmosphere.
<21> The method for producing a silicon carbide single crystal according to <20>, wherein the silicon source is a tetraalkoxysilane polymer and the carbon source is a phenol resin.
[0015]
<22> The method for producing a silicon carbide single crystal according to <20> or <21>, wherein each content of impurity elements in the silicon carbide powder is 0.5 ppm or less.
<23> A silicon carbide single crystal produced by the method for producing a silicon carbide single crystal according to any one of <1> to <22>.
<24> Non-destructive and 100 optical defects / cm of hollow pipe-like crystal defects detected optically ² The silicon carbide single crystal according to <23>, which is the following.
<25> The silicon carbide single crystal according to <23> or <24>, wherein the total content of impurity elements is 10 ppm or less.
[0016]
The method for producing a silicon carbide single crystal according to <1> is a method for producing a silicon carbide single crystal in which a sublimation sublimation raw material is recrystallized to grow a silicon carbide single crystal, wherein the sublimation raw material is A silicon carbide sintered body is included, and the silicon carbide single crystal is grown through the entire growth process while maintaining the entire growth surface in a convex shape. In this method for producing a silicon carbide single crystal, the depressed recess is not formed in a ring shape in the direction opposite to the growth direction over the entire growth surface of the growing silicon carbide single crystal. For this reason, a high-quality silicon carbide single crystal free from damage such as cracks and free from crystal defects such as polycrystals, polymorphs, and micropipes is produced.
[0017]
The sublimation raw material includes a sintered body of silicon carbide. The silicon carbide sintered body has no heat transfer between a solid and a gas as compared with a powder raw material, and heat energy at the time of heating is transmitted uniformly and efficiently in the sintered body. For this reason, the sintered body is uniformly heated in a short time, and is excellent in energy efficiency and cost. Furthermore, since there is no problem such as recrystallization of the raw material and the packing density of silicon carbide is high, the raw material including the manufacturing space can be efficiently used. Since the production is less, the silicon carbide single crystal is efficiently produced.
[0018]
In the method for producing a silicon carbide single crystal according to <2>, since the silicon carbide crystal including the silicon carbide single crystal is grown in a substantially chevron shape in <1>, the growth is performed in the growing silicon carbide single crystal. There is no depressed depression in the opposite direction. For this reason, a high-quality silicon carbide single crystal free from damage such as cracks and free from crystal defects such as polycrystals, polymorphs, and micropipes is produced.
[0019]
The method for producing a silicon carbide single crystal according to <3> is the method according to <1> or <2>, wherein the sublimation raw material is accommodated in a reaction vessel and substantially opposed to the sublimation raw material in the reaction vessel. A seed crystal of the silicon carbide single crystal is disposed at an end portion of the silicon carbide crystal, and the growth of the silicon carbide crystal containing the silicon carbide single crystal excludes a portion of the end portion adjacent to the peripheral side surface portion in the reaction vessel. Only done in the area. Therefore, in the growing silicon carbide single crystal, the depressed recess is not formed in a ring shape in the direction opposite to the growth direction, and the silicon carbide polycrystal is not formed in the reaction vessel at the end. It does not grow in contact with the peripheral side surface. 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. Defects such as cracks do not occur in the single crystal. As a result, a high-quality silicon carbide single crystal free from damage such as cracks and free from crystal defects such as polycrystals, polymorphs, and micropipes can be produced efficiently and reliably.
[0020]
The method for producing a silicon carbide single crystal according to <4> is a method for producing a silicon carbide single crystal in which a silicon carbide single crystal is grown by recrystallizing a sublimation raw material that has been sublimated. Including a silicon carbide sintered body, containing the sublimation raw material in a reaction vessel, disposing a seed crystal of the silicon carbide single crystal at an end portion substantially opposed to the sublimation raw material in the reaction vessel, and A silicon carbide crystal including a silicon single crystal is grown only in a region excluding the end portion adjacent to the peripheral side surface portion in the reaction vessel. For this reason, the said silicon carbide polycrystal does not grow in the state which contacted the surrounding side surface part in this reaction container in the said edge part. When the grown silicon carbide single crystal is cooled to room temperature, stress based on the difference in thermal expansion is not concentrated and applied from the silicon carbide polycrystal side to the silicon carbide single crystal side. Defects such as cracks do not occur. As a result, a high-quality silicon carbide single crystal free from breakage such as cracks and free from crystal defects such as polycrystals, polymorphs, and micropipes is produced.
[0021]
The sublimation raw material includes a sintered body of silicon carbide. The silicon carbide sintered body has no heat transfer between a solid and a gas as compared with a powder raw material, and heat energy at the time of heating is transmitted uniformly and efficiently in the sintered body. For this reason, the sintered body is uniformly heated in a short time, and is excellent in energy efficiency and cost. Furthermore, since there is no problem such as recrystallization of the raw material and the packing density of silicon carbide is high, the raw material including the manufacturing space can be efficiently used. Since the production is less, the silicon carbide single crystal is efficiently produced.
[0022]
In the method for producing a silicon carbide single crystal according to <5>, in any one of the items <2> to <4>, the silicon carbide crystal including the silicon carbide single crystal is composed only of the silicon carbide single crystal. For this reason, a silicon carbide single crystal having a large diameter is obtained, and it is not necessary to separate the silicon carbide single crystal from a silicon carbide polycrystal or the like.
[0023]
In the method for producing a silicon carbide single crystal according to <6>, in any one of the items <1> to <5>, the sublimation raw material is accommodated on one end side in the reaction vessel, and the reaction vessel contains A seed crystal of the silicon carbide single crystal is arranged on the other end side of the substrate, and a sublimation atmosphere is formed by the first heating means arranged on the one end side so that the sublimation raw material can be sublimated. The second heating means disposed on the end side forms a recrystallization atmosphere so that the sublimation raw material sublimated by the first heating means can be recrystallized only in the vicinity of the seed crystal of the silicon carbide single crystal, The sublimation raw material is recrystallized on the seed crystal of the silicon carbide single crystal.
In this method for producing a silicon carbide single crystal, heating for forming a sublimation atmosphere is performed by the first heating means so that the sublimation raw material can be sublimated, and only on the seed crystal of the silicon carbide single crystal. By performing formation of a recrystallization atmosphere that enables recrystallization with the second heating means, recrystallization can be selectively performed only on or near the seed crystal of the silicon carbide single crystal, Silicon carbide polycrystal does not grow in contact with the peripheral side surface in the reaction vessel at the end. When the grown silicon carbide single crystal is cooled to room temperature, stress based on the difference in thermal expansion is not concentrated and applied from the silicon carbide polycrystal side to the silicon carbide single crystal side. Defects such as cracks do not occur. As a result, 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 is produced.
[0024]
In the method for producing a silicon carbide single crystal according to <7>, in <6>, the temperature of the recrystallization atmosphere is 30 to 300 ° C. lower than the temperature of the sublimation atmosphere in the reaction vessel. For this reason, recrystallization is performed easily and smoothly on or near the seed crystal of the silicon carbide single crystal.
[0025]
In the method for producing a silicon carbide single crystal according to <8>, in the <6> or <7>, the first heating unit and the second heating unit are coils capable of induction heating. For this reason, by the induction heating by the coil, the temperature control of the first heating means for forming the sublimation atmosphere and the temperature control of the second heating means for forming the recrystallization atmosphere can be easily and reliably performed. To be done.
[0026]
In the method for producing a silicon carbide single crystal according to <9>, the current value of the induction heating current in the first heating unit is the induction heating current in the second heating unit in any one of <6> to <8>. Is larger than the current value. For this reason, the temperature of the recrystallization atmosphere in the vicinity of the seed crystal is maintained lower than the temperature of the sublimation atmosphere, and recrystallization is easily performed.
[0027]
In the method for producing a silicon carbide single crystal according to <10>, in any one of the items <6> to <9>, the current value of the induction heating current in the second heating unit As the diameter increases, it decreases continuously or stepwise. For this reason, since the heating amount by the second heating means is controlled to be small as the silicon carbide single crystal grows, recrystallization is performed only in the vicinity of the silicon carbide single crystal that continues to grow. No polycrystal is formed around
[0028]
In the method for producing a silicon carbide single crystal according to <11>, in any one of <6> to <10>, the temperature on one end side containing the raw material for sublimation in the reaction vessel is set to T ₁ And the temperature on the other end side where the seed crystal of the silicon carbide single crystal is arranged is T ₂ And the temperature T of the adjacent portion to the inner peripheral side surface portion of the reaction vessel on the other end portion side. ₃ T ₃ -T ₂ And T ₁ -T ₂ Increases continuously or stepwise. T ₁ -T ₂ When the silicon carbide single crystal grows continuously or stepwise, the crystal growth front side of the silicon carbide single crystal is always prone to recrystallization even if the silicon carbide single crystal continues to grow toward the one end. Maintained. On the other hand, T ₃ -T ₂ If the silicon carbide single crystal continuously grows in a stepwise manner, even if the silicon carbide single crystal continues to grow toward the outer peripheral direction on the other end side, the crystal growth outer peripheral end side of the silicon carbide single crystal always re-appears. A state in which crystallization is likely to occur is maintained. 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. A large-diameter silicon carbide single crystal can be obtained without contamination.
[0029]
In the method for producing a silicon carbide single crystal according to <12>, in any one of <8> to <11>, an induced current can be passed between the first heating unit and the second heating unit. And an interference preventing means for preventing interference between the first heating means and the second heating means by applying the induced current. For this reason, when induction heating by the first heating means and the second heating means is performed simultaneously, an induction current flows through the interference prevention means, and the interference prevention means minimizes and prevents interference between the two.
[0030]
In the method for producing a silicon carbide single crystal according to <13>, in the <12>, the interference prevention unit is a coil that can be cooled. Even if an induced current flows through the coil and is heated, the coil is cooled, so that the coil does not heat the reaction vessel. For this reason, temperature control of the reaction vessel is easy.
[0031]
In the method for producing a silicon carbide single crystal according to <14>, in any one of <6> to <13>, the one end is a lower end and the other end is an upper end. For this reason, the sublimation raw material is housed in the lower part of the reaction vessel, the sublimation raw material is smoothly sublimated, and the silicon carbide single crystal is directed downward, that is, in the direction of gravity. It grows with no extra load.
[0032]
In the method for producing a silicon carbide single crystal according to <15>, in any one of <6> to <14>, the reaction vessel is a crucible arranged in a quartz tube. For this reason, since the sublimation raw material is sublimated and recrystallized and the silicon carbide single crystal is grown in a closed system in the quartz tube, these controls are easy.
[0033]
The method for producing a silicon carbide single crystal according to <16> is any one of <6> to <15>, wherein the silicon carbide single crystal is grown and located on an outer periphery of the region. The inner peripheral side surface of the reaction vessel and the adjacent region are formed of different members, and one end of the member forming the region where the silicon carbide single crystal is grown is exposed inside the reaction vessel. The other end is exposed to the outside of the reaction vessel. A region where the silicon carbide single crystal is grown (inner region) and a region located on the outer periphery of the region and adjacent to the inner peripheral side surface portion (outer region) are formed of different members. Therefore, when heating is performed by the second heating unit, the outer region located on the second heating unit side is easily heated, but the inner region has a contact resistance with the outer region. It is not easily heated by the difference. For this reason, even if heating is performed by the second heating means, a temperature difference is generated between the outer region and the inner region, and the inner region is less likely to be heated than the outer region. It is kept low and the silicon carbide is easily recrystallized. In addition, since the side opposite to the inside of the reaction vessel in the member forming the inner region is exposed to the outside of the reaction vessel and heat is easily radiated to the outside of the reaction vessel, heating is performed by the second heating unit. In this case, the inner region is less likely to be heated than the outer region, a temperature difference occurs between the outer region and the inner region, and the inner region is maintained at a lower temperature than the outer region, Recrystallization of silicon carbide is easily performed. As a result, the silicon carbide single crystal hardly grows in the outer region, and the silicon carbide single crystal selectively recrystallizes and grows only in the inner region.
[0034]
In the method for producing a silicon carbide single crystal according to <17>, in any one of <4> to <16>, a surface of an adjacent portion of the other end portion to an inner peripheral side surface portion of the reaction vessel is It is glassy carbon. For this reason, in the said other end part, an adjacent part with the inner peripheral side part of this reaction container is less likely to recrystallize than areas other than this adjacent part. As a result, a silicon carbide crystal does not grow in the adjacent portion at the other end, and a silicon carbide single crystal selectively recrystallizes and grows only in a region other than the adjacent portion.
[0035]
In the method for producing a silicon carbide single crystal according to <18>, in any one of the items <1> to <17>, the silicon carbide sintered body disperses silicon carbide powder in a solvent to prepare a slurry or a paste. Silicon carbide firing comprising: a preparation step to form, a calcined body forming step of forming and calcining the slurry or paste to form a calcined body; and a pore sealing step of impregnating the calcined body with metal silicon It is obtained by the manufacturing method of a knot. For this reason, the silicon carbide sintered compact of a desired shape can be used as a raw material for sublimation. As a result, the sublimation raw material can be used efficiently, and the silicon carbide single crystal can be produced efficiently.
[0036]
The method for producing a silicon carbide single crystal according to <19> is the method according to any one of <1> to <17>, wherein the silicon carbide sintered body is a silicon carbide powder, a boron compound, and a nonmetallic sintering aid. And a mixture containing 2000 to 2400 ° C. and a pressure of 300 to 700 kgf / cm. ² And a method for producing a silicon carbide sintered body including a hot pressing step of hot pressing in a non-oxidizing atmosphere. For this reason, a silicon carbide sintered body having a high packing density of silicon carbide can be used as a raw material for sublimation. As a result, the sublimation raw material can be used efficiently, and the silicon carbide single crystal can be produced efficiently.
[0037]
In the method for producing a silicon carbide single crystal according to <20>, in the above <18> or <19>, the silicon carbide powder is at least one selected from high-purity alkoxysilane and alkoxysilane polymer. This is a silicon carbide powder obtained by heating and firing a mixture obtained by uniformly mixing these, using a high-purity organic compound that produces carbon by heating as a source, and mixing them uniformly. Since the silicon carbide powder has a high purity, when the silicon carbide single crystal is grown, there is no polycrystal or polymorph mixing into the silicon carbide single crystal, and the silicon carbide single crystal grows smoothly. In the produced silicon carbide single crystal, defects such as micropipes do not occur.
[0038]
In the method for producing a silicon carbide single crystal according to <21>, in the <20>, the silicon source is a tetraalkoxysilane polymer, and the carbon source is a phenol resin. For this reason, the sublimation raw material can be easily obtained at low cost.
[0039]
In the method for producing a silicon carbide single crystal according to <22>, in each of <20> or <21>, the content of each impurity element in the silicon carbide powder is 0.5 ppm or less. For this reason, the raw material for sublimation has an extremely high purity, and the occurrence of polycrystals, polymorphs, and crystal defects in the silicon carbide single crystal is effectively suppressed.
[0040]
The silicon carbide single crystal according to <23> is manufactured by the method for manufacturing a silicon carbide single crystal according to any one of <1> to <22>. For this reason, the obtained silicon carbide single crystal has no damage such as cracks, is free of crystal defects such as polycrystals, polymorphs, and micropipes, and is extremely high quality, dielectric breakdown characteristics, heat resistance, It has excellent radiation resistance and is particularly suitable for electronic devices such as semiconductor wafers and optical devices such as light emitting diodes.
[0041]
In the silicon carbide single crystal according to <24>, the hollow pipe-like crystal defects detected non-destructively and optically in 100 are described in <23>. ² It is as follows. Therefore, the silicon carbide single crystal has extremely high quality, is particularly excellent in dielectric breakdown characteristics, heat resistance, radiation resistance, etc., and is particularly suitable for electronic devices such as semiconductor wafers, optical devices such as light emitting diodes, and the like. .
[0042]
The silicon carbide single crystal according to <25> has a total content of the impurity elements of 10 ppm or less in the <23> or <24>. For this reason, the silicon carbide single crystal has an extremely high quality.
[0043]
DETAILED DESCRIPTION OF THE INVENTION
(Method for producing silicon carbide single crystal)
Hereinafter, the manufacturing method of the silicon carbide single crystal of the present invention will be described.
The method for producing a silicon carbide single crystal of the present invention is a method for producing a silicon carbide single crystal in which a sublimated raw material for sublimation is recrystallized on a seed crystal of the silicon carbide single crystal to grow a silicon carbide single crystal.
[0044]
In the method for producing a silicon carbide single crystal of the present invention, the following first to third aspects can be mentioned. Among these, the third aspect includes the first aspect and the second aspect. Is a preferred embodiment of the content.
[0045]
In the first aspect, the silicon carbide single crystal is grown through the entire growth process while the entire growth surface is held in a convex shape.
[0046]
In the second aspect, the raw material for sublimation is accommodated in a reaction vessel, a seed crystal of a silicon carbide single crystal is disposed at an end portion substantially opposed to the raw material for sublimation in the reaction vessel, and the silicon carbide The single crystal is grown only in a region excluding a portion adjacent to the peripheral side surface portion in the reaction vessel at the end portion.
[0047]
In the third aspect, the raw material for sublimation is accommodated in a reaction vessel, a seed crystal of a silicon carbide single crystal is disposed at an end portion of the reaction vessel that substantially faces the raw material for sublimation, and the silicon carbide A region (inner side) of the single crystal is maintained throughout the entire growth process, with the entire growth surface held in a convex shape, and excluding a portion (outer portion) adjacent to the peripheral side surface portion in the reaction vessel at the end portion. Only grow in (part).
[0048]
-Reaction vessel-
The reaction vessel is not particularly limited and may be appropriately selected depending on the intended purpose. However, the sublimation raw material can be accommodated therein, and the silicon carbide single unit is positioned substantially opposite the sublimation raw material. It is preferable to have an end where a crystal seed crystal can be arranged.
Although there is no restriction | limiting in particular as a shape of the said edge part, For example, it is preferable that it is a substantially planar shape.
[0049]
Although there is no restriction | limiting in particular as a site | part in which the said raw material for sublimation is accommodated, It is preferable that it is an edge part substantially opposite to the edge part which can arrange | position the seed crystal of the said silicon carbide single crystal. In this case, the inside of the reaction vessel has a cylindrical shape, and the cylindrical axis may be linear or curved, and is perpendicular to the axial direction of the cylindrical shape. The cross-sectional shape may be a circle or a polygon. Preferable examples of the circular shape include those in which the axis is linear and the cross-sectional shape perpendicular to the axial direction is circular.
When two ends exist in the reaction vessel, the sublimation raw material is accommodated on one end side, and the seed crystal of the silicon carbide single crystal is disposed on the other end side. Hereinafter, the one end portion may be referred to as a “sublimation raw material storage portion”, and the other end portion may be referred to as a “seed crystal arrangement portion”.
There is no restriction | limiting in particular as a shape of the said one end part (sublimation raw material accommodating part), A planar shape may be sufficient, and the structure (for example, convex part etc.) for promoting soaking | uniform-heating may be provided suitably.
[0050]
In the reaction vessel, it is preferable that the other end portion (seed crystal placement portion) side is designed to be detachable. In this case, it is advantageous in that the grown silicon carbide single crystal can be easily separated from the reaction vessel only by detaching the other end (seed crystal arrangement portion) side.
Examples of such a reaction container include a container main body that can store a sublimation raw material, and the sublimation that is detachable from the container main body and is stored in the container main body when mounted on the container main body. Preferable examples include a reaction vessel provided with a lid capable of disposing a seed crystal of a silicon carbide single crystal in the approximate center of the surface facing the starting material.
[0051]
The positional relationship between the one end portion (sublimation raw material storage portion) and the other end portion (seed crystal placement portion) is not particularly limited and may be appropriately selected depending on the purpose. The raw material storage part) is a lower end part, and the other end part (seed crystal placement part) is an upper end part, that is, the one end part (sublimation raw material storage part) and the other end part (seed crystal placement part). Are preferably located in the direction of gravity. In this case, it is preferable in that the sublimation raw material is smoothly sublimated, and the silicon carbide single crystal is grown in a state where no excessive load is applied downward, that is, in the direction of gravity.
[0052]
In addition, you may arrange | position the member formed with the material excellent in heat conductivity in order to perform the sublimation of the said sublimation raw material efficiently, for example in the said one end part (sublimation raw material accommodating part) side.
As the member, for example, an inverted cone shape in which the outer periphery can be in close contact with the peripheral side surface portion in the reaction vessel and the diameter gradually increases as the inside approaches the other end portion (seed crystal placement portion). A member having an inverted frustum shape or the like is preferable.
[0053]
The portion exposed to the outside of the reaction vessel may be provided with threading, a temperature measuring recess, or the like, depending on the purpose, and the temperature measuring recess has the one end side and the other end. It is preferable to be provided in at least one part on the side.
[0054]
The material for the reaction vessel is not particularly limited and may be appropriately selected depending on the intended purpose. However, it is preferably formed of a material excellent in durability, heat resistance, heat transfer property, and the like. Further, it is particularly preferable that it is made of graphite from the viewpoint that there are few polycrystals and polymorphs due to the generation of impurities, and that sublimation and recrystallization of the sublimation raw material are easy to control.
[0055]
The reaction vessel may be formed of a single member, or may be formed of two or more members, and can be appropriately selected according to the purpose, but is formed of two or more members. In some cases, the other end portion (seed crystal placement portion) is preferably formed of two or more members, and the central portion of the other end portion (seed crystal placement portion) and the outer peripheral portion thereof are separate members. It is more preferable that a temperature difference or a temperature gradient can be formed. Specifically, a region (inner region) where silicon carbide single crystal is grown as the central portion, and the outer periphery are formed. As a part, a region (outer region) adjacent to the inner peripheral side surface portion of the reaction vessel located on the outer periphery of the inner region is formed of another member, and one end of the member forming the inner region is a reaction vessel The other end is exposed to the outside of the reaction vessel It is particularly preferred.
[0056]
In this case, when the other end portion (seed crystal arrangement portion) is heated from the outside, the outside region is easily heated, but the inside region is hardly heated due to contact resistance with the outside region. A temperature difference occurs between the outer region and the inner region, and the inner region is maintained at a slightly lower temperature than the outer region, so that the inner region is more silicon carbide than the outer region. Can be easily recrystallized. Further, since the other end of the member forming the inner region is exposed to the outside of the reaction vessel, the inner region easily dissipates heat to the outside of the reaction vessel. Silicon carbide can cause recrystallization more easily than the outer region.
[0057]
In addition, the aspect in which the other end of the member forming the inner region is exposed to the outside of the reaction vessel is not particularly limited. Examples include a shape whose diameter changes discontinuously (increases or decreases).
Specifically, as such a shape, a columnar shape having a bottom surface in the inner region (a cylindrical shape, a prismatic shape, etc. are preferable, and a columnar shape is preferable), and a frustum shape having a bottom surface in the inner region (conical shape) A trapezoidal shape, a truncated pyramid shape, an inverted truncated cone shape, an inverted truncated pyramid shape and the like, and an inverted truncated cone shape is preferable.
[0058]
The reaction vessel is located on the outer periphery of the region (inner region) where the silicon carbide single crystal is grown in the other end portion (seed crystal arrangement portion) and is adjacent to the inner peripheral side surface portion (outer side) of the reaction vessel The surface of the region is preferably glassy carbon or amorphous carbon. In this case, the outer region is preferable in that recrystallization is less likely to occur than the inner region.
[0059]
The reaction vessel is preferably surrounded by a heat insulating material or the like. In this case, the heat insulating material or the like is provided in the approximate center of the one end portion (sublimation raw material storage portion) and the other end portion (seed crystal placement portion) in the reaction vessel for the purpose of forming a temperature measuring window. Preferably not. In addition, when the temperature measuring window is provided at substantially the center of the one end (sublimation raw material storage), a graphite cover member or the like is further provided to prevent the heat insulating material powder from falling. It is preferable.
[0060]
The reaction vessel is preferably arranged in a quartz tube. In this case, it is preferable in that the loss of heating energy for sublimation and recrystallization of the sublimation raw material is small.
In addition, the said quartz tube can obtain a high purity product, and when a high purity product is used, it is advantageous at the point with few mixing of a metal impurity.
[0061]
-Raw material for sublimation-
The sublimation raw material includes a silicon carbide sintered body, specifically, an embodiment in which the silicon carbide sintered body is used alone, and an embodiment in which the silicon carbide sintered body and the silicon carbide powder are used in combination. Can be mentioned.
As the silicon carbide sintered body, a preparation process in which silicon carbide powder is dispersed in a solvent to prepare a slurry or paste, and a calcined body forming process in which the slurry or paste is molded and calcined to form a calcined body. And a pore sealing step of impregnating the calcined body with metallic silicon, and a silicon carbide sintered body obtained by a method for producing a silicon carbide sintered body (hereinafter referred to as “reactive sintered body”). And a mixture containing silicon carbide powder, boron compound and non-metallic sintering aid is used at 2000-2400 ° C., pressure 300-700 kgf / cm. ² A silicon carbide sintered body obtained by a method for producing a silicon carbide sintered body including a hot pressing step of hot pressing in a non-oxidizing atmosphere (hereinafter sometimes referred to as “hot press sintered body”), and the like. Particularly preferred.
[0062]
If the reaction sintered body is used, a silicon carbide sintered body having a desired shape can be used as a raw material for sublimation. As a result, the sublimation raw material can be used efficiently, and the silicon carbide single crystal can be produced efficiently.
If the said hot press sintered compact is used, the silicon carbide sintered compact with a high packing density of silicon carbide can be used as a raw material for sublimation. As a result, the sublimation raw material can be used efficiently, and the silicon carbide single crystal can be produced efficiently.
[0063]
In the method for producing the reaction sintered body, examples of the solvent used in the preparation step include water, lower alcohols such as ethyl alcohol, ethyl ether, acetone, and the like. In the preparation step, it is preferable to add an organic binder or the like as appropriate. Further, nitrogen or aluminum can be introduced for the purpose of imparting conductivity to the obtained reaction sintered body. For example, after dissolving and dispersing an organic substance composed of a nitrogen source and an aluminum source in the solvent, silicon carbide powder It is preferable to sufficiently stir and mix with.
[0064]
The organic substance comprising the nitrogen source is preferably a substance that generates nitrogen by heating, such as a polymer compound (specifically, polyimide resin, nylon resin, etc.), organic amine (specifically, hexamethylene). And various amines of tetramine, ammonia, triethylamine, and the like, and their compounds and salts). 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 the organic substance composed of the nitrogen source. These organic substances 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 said aluminum source, According to the objective, it can select suitably.
[0065]
In the reaction sintered body manufacturing method, in the calcined body forming step, the slurry or paste is formed into a desired shape and calcined. As temperature of this calcination, 1200-2300 degreeC is preferable and 1500-2000 degreeC is preferable.
In the reaction sintered body manufacturing method, the calcined body is impregnated with metallic silicon in the pore sealing step. In the impregnation, pores inside the calcined body are impregnated with high-melting high-purity metal silicon, and in the pores, the high-purity metal silicon reacts with carbon contained in the calcined body to form silicon carbide. To fill the pores. The form of the high-purity metal silicon may be any of powder, granule, and bulk, and bulk metal silicon having a particle diameter of 2 to 5 mm is preferably used. The impregnation is preferably performed in a vacuum atmosphere or an inert gas atmosphere.
[0066]
In the method for producing a hot press sintered body, boron compounds used in the hot press step include BN, B ₂ O ₃ Etc. are preferable.
Examples of the non-metallic sintering aid include a substance that generates carbon by heating, an organic compound that generates carbon by heating, or a silicon carbide powder whose surface is coated with these (particle size: 0.01 to 1 μm) is particularly preferable, and the former is more preferable from the viewpoint of the effect.
[0067]
Specific examples of the organic compound that generates carbon by heating include coal tar pitch, pitch tar, phenol resin, furan resin, epoxy resin, phenoxy resin, monosaccharides such as glucose, sucrose, and the like with a high residual carbon ratio. Various sugars such as oligosaccharides such as oligosaccharides, celluloses and starches can be mentioned. For the purpose of homogeneously mixing with silicon carbide powder, these are liquid at room temperature, those that dissolve in a solvent, those that soften or become liquid when heated, such as thermoplastic or heat-meltable, etc. Among them, a phenol resin having a high strength of the obtained molded product, particularly a resol type phenol resin is preferable.
[0068]
As the silicon carbide sintered body, one of the reaction sintered body and the hot press sintered body may be used alone, or two or more kinds may be used in combination.
[0069]
--Silicon carbide powder--
There are no particular restrictions on the production of the reactive sintered body and the hot-press sintered body, and the polymorphism, amount used, purity, and production method of the silicon carbide powder used in the sublimation raw material. It can be appropriately selected depending on the case.
[0070]
Examples of the crystal polymorph of the silicon carbide powder include 4H, 6H, 15R, and 3C. Among these, 6H is preferable. These are preferably used alone, but may be used in combination of two or more.
[0071]
The amount of the silicon carbide powder 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.
[0072]
The purity of the silicon carbide powder is preferably high from the viewpoint of preventing polycrystals and polymorphs from being mixed into the silicon carbide single crystal to be produced as much as possible. Each content is preferably 0.5 ppm or less.
[0073]
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 homogeneous in the silicon carbide single crystal. The evaluation differs depending on whether the distribution is locally distributed or locally distributed. Here, the “impurity element” refers to 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 silicon) Element excluding atoms). In addition, in order to impart n-type or p-type conductivity to the growing silicon carbide single crystal, when a dopant element such as nitrogen or aluminum is intentionally added, these are also excluded.
[0074]
The silicon carbide powder is, for example, dried by dissolving in a solvent at least one silicon compound as a silicon source, at least one organic compound that generates carbon by heating, and a polymerization catalyst or a crosslinking catalyst as a carbon source. It is obtained by firing the powder obtained in this manner in a non-oxidizing atmosphere.
[0075]
As the silicon compound, a liquid one and a solid one can be used together, but at least one kind is selected from a liquid one.
[0076]
As the liquid, an alkoxysilane and an alkoxysilane polymer are preferably used.
[0077]
Examples of the alkoxysilane include methoxysilane, ethoxysilane, propoxysilane, and butoxysilane. 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 silicate polymer.
[0078]
Examples of the solid include silicon oxide such as SiO, silica sol (liquid containing colloidal ultrafine silica, containing OH group or alkoxyl group inside), silicon dioxide (silica gel, fine silica, quartz powder).
[0079]
The said silicon compound may be used individually by 1 type, and may use 2 or more types together. Among the silicon compounds, an oligomer of tetraethoxysilane, a mixture of an oligomer of tetraethoxysilane and fine powder silica, and the like are preferable in terms of good homogeneity and handling properties.
[0080]
The silicon compound preferably has a high purity, and the content of each impurity in the initial stage is preferably 20 ppm or less, and more preferably 5 ppm or less.
[0081]
As the organic compound that generates carbon by heating, a liquid one may be used alone, or a liquid one and a solid one may be used in combination.
[0082]
The organic compound that generates carbon by heating is preferably an organic compound that has a high residual carbon ratio and is polymerized or cross-linked by a catalyst or heating, 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.
[0083]
The organic compound which produces carbon by the heating may be used alone or in combination of two or more.
The purity of the organic compound that generates carbon by heating can be appropriately selected according to the purpose, but when a 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.
[0084]
The polymerization catalyst and the crosslinking catalyst can be appropriately selected according to the organic compound that generates carbon by heating, but when the organic compound that generates carbon by heating is a phenol resin or a furan resin, toluenesulfonic acid, toluenecarboxylic acid, Acids such as acetic acid, oxalic acid, maleic acid and sulfuric acid are preferred, and maleic acid is particularly preferred.
[0085]
The ratio of carbon contained in the organic compound that produces carbon by heating and silicon contained in the silicon compound (hereinafter abbreviated as “C / Si ratio”) is obtained by carbonizing a mixture of both at 1000 ° C. Carbide 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 it is reduced by volatilization of the simultaneously generated SiO gas. Free carbon is generated at the C / Si ratio. The blending ratio is preferably determined in advance so that the amount of free carbon in the obtained silicon carbide powder is 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, the free carbon increases remarkably. However, when the atmospheric pressure is fired at a low pressure or a high pressure, the C / Si ratio for obtaining pure silicon carbide powder varies, and in this case, it is not necessarily limited to the range of the C / Si ratio. .
[0086]
The silicon carbide powder can also be obtained, for example, by curing a mixture of the silicon compound and an organic compound that produces carbon by heating.
Examples of the curing method include a method of crosslinking by heating, a method of curing with a curing catalyst, a method of electron beam and radiation, and the like.
The curing catalyst can be appropriately selected according to the type of organic compound that produces carbon by heating, and in the case of 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 amines such as hexamine. When these curing catalysts are used, the curing catalyst is dissolved or dispersed in a solvent. Examples of the solvent include lower alcohols (eg, ethyl alcohol), ethyl ether, acetone and the like.
[0087]
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 or argon.
The silicon carbide powder becomes a carbide by the firing, and the carbide is fired at 1350 to 2000 ° C. in a non-oxidizing atmosphere such as argon to produce a silicon carbide powder.
[0088]
The firing temperature and time can be appropriately selected according to the particle size of the silicon carbide powder to be obtained, and the temperature is 1600 to 1900 ° C. in terms of more efficient production of the silicon carbide powder. preferable.
In addition, after the said baking, it is preferable to heat-process at 2000-2400 degreeC for 3 to 8 hours in order to remove an impurity and to obtain a high purity silicon carbide powder, for example.
[0089]
Since the silicon carbide powder obtained as described above is non-uniform in size, it can be made into a desired particle size by pulverization, classification, and the like.
As an average particle diameter of the said silicon carbide powder, 10-700 micrometers is preferable and 100-400 micrometers is more preferable.
When the average particle size is less than 10 μm, sintering occurs rapidly at the sublimation temperature (1800 to 2700 ° C.) of silicon carbide for growing a silicon carbide single crystal, so that the sublimation surface area becomes small, and silicon carbide. The growth of the single crystal may be slow, and the silicon carbide powder is scattered when the silicon carbide powder is accommodated in the reaction vessel or when the pressure of the recrystallization atmosphere is changed to adjust the growth rate. It becomes easy. On the other hand, when the average particle size exceeds 500 μm, the specific surface area of the silicon carbide powder itself is decreased, and thus the growth of the silicon carbide single crystal may be slowed.
[0090]
The silicon carbide powder may be any of 4H, 6H, 15R, 3C, a mixture thereof, and the like. In addition, there is no restriction | limiting in particular as a grade of the said silicon carbide powder, Although what is generally marketed may be sufficient, It is preferable that it is a high purity thing.
[0091]
Nitrogen or aluminum can be introduced into the silicon carbide single crystal grown using the silicon carbide powder for the purpose of imparting n-type or p-type conductivity, and the nitrogen or aluminum is introduced into the silicon carbide. In the case of introducing at the time of producing the powder, first, the silicon source, the carbon source, an organic substance composed of a nitrogen source or an aluminum source, and the polymerization or crosslinking catalyst may be uniformly mixed. 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
[0092]
The organic material consisting of the nitrogen source and the organic material consisting of the aluminum source are the same as the organic material consisting of the nitrogen source and the organic material consisting of the aluminum source.
[0093]
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 simultaneously, 1 mmol or more of nitrogen is contained per 1 g of the silicon source, with respect to 1 g of the silicon source. 80 to 1000 μg is preferable.
[0094]
-Sublimation-
The sublimation of the sublimation raw material is not particularly limited, but it is performed using a heating unit separate from the heating unit for performing heating necessary for performing recrystallization. This is preferable in terms of independent control. In such an embodiment, the number of heating means is two or more, but two is preferable in the present invention.
When the heating means is two preferred embodiments, the heating means for forming a sublimation atmosphere enabling the sublimation raw material to be sublimated is the first heating means, and the sublimated raw material is the silicon carbide single crystal. The heating means for forming the recrystallization atmosphere that allows recrystallization only in the vicinity of the seed crystal is the second heating means.
[0095]
The first heating means is disposed on one end (sublimation raw material storage unit) side of the reaction vessel, forms a sublimation atmosphere so that the sublimation raw material can be sublimated, and heats the sublimation raw material. Sublimate.
The first heating means is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include induction heating means and resistance heating means. However, induction heating means is preferable in terms of easy temperature control. Among the induction heating means, a coil capable of induction heating is preferable.
[0096]
In the case where the first heating means is a coil capable of induction heating, the number of turns wound around the first heating means is not particularly limited, and the heating efficiency and temperature efficiency depend on the distance from the second heating means, the material of the reaction vessel, and the like. Can be determined to be optimal.
[0097]
-Growth of silicon carbide single crystals-
The growth of the silicon carbide single crystal is performed on a seed crystal of the silicon carbide single crystal disposed at the other end (seed crystal disposition portion) of the reaction vessel.
As the seed crystal of the silicon carbide single crystal, the polymorph, size, etc. of the crystal can be appropriately selected according to the purpose, but the polymorph of the crystal is usually the carbonization to be obtained. The same polymorph as the polymorph of the silicon single crystal is selected.
[0098]
In order to recrystallize and grow the silicon carbide single crystal on the seed crystal, the temperature is lower than the temperature at which the sublimation raw material sublimates, and the sublimated raw material can be recrystallized only in the vicinity of the seed crystal. (In other words, in the radial direction of the surface on which the seed crystal is arranged, an atmosphere having a temperature distribution in which the temperature decreases as it approaches the center (center of the inner region)) is formed. It is preferable to do this.
[0099]
The recrystallization atmosphere can be suitably formed by the second heating means. Such second heating means is arranged on the other end (seed crystal arrangement part) side of the reaction vessel, and the sublimation raw material sublimated by the first heating means is in the vicinity of the seed crystal of the silicon carbide single crystal. A recrystallization atmosphere is formed so as to allow recrystallization only, and the sublimation raw material is recrystallized on the seed crystal of the silicon carbide single crystal.
[0100]
There is no restriction | limiting in particular as said 2nd heating means, According to the objective, it can select suitably, For example, although an induction heating means, a resistance heating means, etc. are mentioned, an induction heating means is a point with easy temperature control. Among the induction heating means, a coil capable of induction heating is preferable.
[0101]
When the second heating means is a coil that can be induction-heated, the number of turns wound around the second heating means is not particularly limited, and the heating efficiency and temperature efficiency depend on the distance from the first heating means, the material of the reaction vessel, and the like. Can be determined to be optimal.
[0102]
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, and the relationship between the two includes 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.
[0103]
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, since the heating amount by the second heating means is controlled to be small as the silicon carbide single crystal grows, recrystallization is performed only in the vicinity of the silicon carbide single crystal that continues to grow. It is advantageous in that the formation of polycrystals around is effectively suppressed.
[0104]
In addition, the current value of the induction heating current in the second heating means is controlled to be small when the diameter of the seed crystal of the silicon carbide single crystal is large, and is large when the diameter is small. There is a tendency to favor control.
[0105]
In the present invention, since the second heating means can be controlled independently of the first heating means, the heating amount of the second heating means is set according to the growth rate of the silicon carbide single crystal. By appropriately adjusting, a preferable growth rate can be maintained throughout the entire growth process of the silicon carbide single crystal.
[0106]
The temperature of the recrystallization atmosphere formed by the second heating means is preferably 30 to 300 ° C., and 30 to 150 ° C. lower than the temperature of the sublimation atmosphere formed by the first heating means. More preferred.
[0107]
The pressure of the recrystallization atmosphere formed by the second heating means is preferably 10 to 100 Torr (1330 to 13300 Pa). In addition, when setting it as this pressure condition, it is preferable to adjust pressure conditions so that pressure reduction may be performed in the state heated to preset temperature, and it may become in the said predetermined numerical range.
The recrystallization atmosphere is preferably an inert gas atmosphere such as argon gas.
[0108]
In the present invention, controlled by the first heating means, the temperature on one end (sublimation raw material storage part) side containing the sublimation raw material in the reaction vessel, and the second heating means, The temperature of the central portion on the other end portion (seed crystal disposing portion) side where the seed crystal of the silicon carbide single crystal is disposed in the reaction vessel and the inner peripheral side surface portion of the reaction vessel located outside the central portion Control of the temperature of the adjacent portion with the following relationship is preferable from the viewpoint of obtaining a large-diameter silicon carbide single crystal. That is, the temperature on one end side containing the sublimation raw material is T ₁ And the temperature on the other end side where the seed crystal of the silicon carbide single crystal is arranged is T ₂ And the temperature T of the adjacent portion to the inner peripheral side surface portion of the reaction vessel on the other end portion side. ₃ T ₃ -T ₂ And T ₁ -T ₂ Is preferably controlled to increase continuously or stepwise.
[0109]
In this case, T ₁ -T ₂ Since the size of the silicon carbide single crystal continues to grow continuously or stepwise, even if the silicon carbide single crystal continues to grow toward the one end, the crystal growth tip side of the silicon carbide single crystal is always easily recrystallized. Maintained in a state. On the other hand, T ₃ -T ₂ Therefore, even if the silicon carbide single crystal continues to grow toward the outer peripheral direction on the other end side over time, the crystal growth outer peripheral end side of the silicon carbide single crystal is always The state where recrystallization is likely to occur is maintained. 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 without contamination.
[0110]
In the present invention, the silicon carbide single crystal is recrystallized and grown according to the first to third aspects.
[0111]
In the first aspect, the silicon carbide single crystal is grown through the entire growth process while the entire growth surface is held in a convex shape. In this case, the concave portion depressed on the other end portion (seed crystal arrangement portion) side is not formed in a ring shape over the entire growth surface of the silicon carbide single crystal.
[0112]
In the second aspect, the growth of the silicon carbide single crystal is performed only in a region (inner region) excluding a portion adjacent to the peripheral side surface in the reaction vessel at the end of the reaction vessel. In this case, the silicon carbide polycrystal does not grow in contact with the peripheral side surface portion in the reaction vessel at the other end portion (seed crystal arrangement portion). 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 cracking occurs in the single crystal.
[0113]
In the third aspect, the silicon carbide single crystal is kept in a convex shape throughout the entire growth process, while maintaining the entire growth surface in a convex shape, and at the end of the reaction vessel. It is performed only in the region (inner region) excluding the adjacent portion with the side surface portion.
In this case, the concave portion depressed on the other end portion (seed crystal arrangement portion) side of the reaction vessel is not formed in a ring shape over the entire growth surface of the silicon carbide single crystal, and the silicon carbide polycrystal However, it does not grow in contact with the peripheral side surface portion in the reaction vessel at the other end portion (seed crystal arrangement portion). 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 cracking occurs in the single crystal.
[0114]
As the shape of the silicon carbide single crystal to be grown, it is preferable that the entire growth surface is convex in the growth direction side, and the one end (sublimation raw material storage) and the other end (seed crystal arrangement) Part) is preferably convex toward the sublimation raw material side, that is, toward the one end (sublimation raw material storage part) side.
In this case, polycrystals and polymorphs are often mixed, and stress due to a difference in thermal expansion is considered to be concentrated, but this is preferable in that there is no recessed portion depressed on the other end portion (seed crystal arrangement portion) side.
[0115]
The shape of the growing silicon carbide single crystal is flat even if it does not have the convex shape unless the entire growth surface includes a concave shape on the opposite side of the growth direction. Part may be included in a part.
[0116]
Further, the shape of the silicon carbide crystal including the silicon carbide single crystal is preferably a substantially chevron shape toward the sublimation raw material side, that is, the one end side, and is a substantially chevron shape whose diameter gradually decreases. Is more preferable.
In addition, silicon carbide polycrystals and polymorphs may be mixed in the base portion, that is, the outer peripheral portion of the silicon carbide crystal having the approximately chevron shape, and this mixing is caused by the thickness, size, and shape of the seed crystal. Etc. and the combination of conditions of the amount of heating by the second heating means can prevent the occurrence. When mixing of the silicon carbide polycrystal and polymorphism is prevented, it is preferable in that the silicon carbide crystal containing silicon carbide can be made of only a silicon carbide single crystal.
[0117]
In the present invention, a ring-shaped plate member may be fixedly disposed substantially parallel to the other end portion (seed crystal disposing portion) on the peripheral side surface portion in the reaction vessel. In this case, when the silicon carbide single crystal is recrystallized and grown on the seed crystal, only the silicon carbide single crystal can be recrystallized and grown on the seed crystal, and no silicon carbide polycrystal is generated. Alternatively, it can be selectively deposited on the ring-shaped plate member. In this case, the diameter of the obtained silicon carbide single crystal is limited by the amount of the ring-shaped plate member.
[0118]
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.
[0119]
The interference preventing means is not particularly limited and can be appropriately selected according to the types of the first heating means and the second heating means. Examples thereof include an interference preventing coil and an interference preventing plate. In the case where the first heating unit and the second heating unit are coils capable of induction heating, an interference prevention coil or the like is preferably used.
[0120]
The interference preventing coil is preferably capable of passing an induced current and having a function of preventing interference between the first heating means and the second heating means by passing an induced current.
The interference preventing coil is preferably disposed between the first heating unit and the second heating unit. In this case, when induction heating by the first heating means and the second heating means is simultaneously performed, an induction current flows through the interference prevention coil, and the interference prevention coil can minimize and prevent interference between the two. It is preferable in that it can be performed.
[0121]
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 capable of circulating a cooling medium such as water. In this case, even if an induced current in the first heating unit and the second heating unit flows through the interference prevention coil, the interference prevention coil is not heated, and thus the reaction vessel can be heated. It is preferable in that there is no.
[0122]
There are no particular restrictions on the number of turns of the interference prevention coil, and the number of turns is different depending on the types of the first heating means and the second heating means, the amount of current induced in them, and cannot be specified unconditionally. However, even a single layer is sufficient.
[0123]
As described above, according to the method for producing a silicon carbide single crystal of the present invention, a high-quality silicon carbide single crystal of the present invention can be produced efficiently and without breakage such as cracks.
[0124]
The above-described method for producing a silicon carbide single crystal of the present invention can be suitably performed by, for example, the following apparatus.
[0125]
The apparatus includes, for example, a crucible, a first induction heating coil, and a second induction heating coil, and an interference preventing coil disposed between the first induction heating coil and the second induction heating coil. Examples of the apparatus include other members appropriately selected as necessary.
[0126]
There is no restriction | limiting in particular as said crucible, It can select suitably from well-known things, Generally, a container main body and a cover body are provided.
There is no restriction | limiting in particular as a material of the said crucible, Although it can select suitably from well-known things, It is especially preferable that it is made from graphite.
[0127]
The container body is not particularly limited as long as it has a function capable of accommodating the sublimation raw material, and a known one can be adopted.
The lid is preferably detachable from the container main body, and a known one can be adopted. The container body and the lid may be designed to be detachable by fitting, screwing or the like, but those by screwing are preferred.
[0128]
In the apparatus, usually, the seed crystal of the silicon carbide single crystal is arranged at the approximate center of the surface facing the sublimation raw material housed in the container body when the lid is mounted on the container body. Is done.
[0129]
The first induction heating coil is not particularly limited as long as the first induction heating coil can be heated by energization to form a sublimation atmosphere so that the sublimation raw material can be sublimated, and examples thereof include a coil capable of induction heating.
Said 1st induction heating coil is arrange | positioned in the state wound around the outer periphery of the part in which the said sublimation raw material was accommodated in the said crucible.
[0130]
The second induction heating coil forms a recrystallization atmosphere so that the sublimation raw material sublimated by the first induction heating coil can be recrystallized only in the vicinity of the silicon carbide seed crystal, and the sublimation raw material Is not particularly limited as long as it can be recrystallized on the silicon carbide seed crystal, and examples thereof include a coil capable of induction heating.
Said 2nd induction heating coil is arrange | positioned in the state wound around the outer periphery of the part in which the said silicon carbide seed crystal is arrange | positioned in the said crucible.
[0131]
In the apparatus, a sublimation atmosphere is formed so that the first induction heating coil can sublimate the sublimation raw material, and the sublimation raw material is sublimated. The second induction heating coil forms a recrystallization atmosphere so that the sublimation raw material sublimated by the first induction heating coil can be recrystallized only in the vicinity of the seed crystal, and the sublimation raw material is Recrystallization is performed on the seed crystal. For this reason, the silicon carbide single crystal to be grown may be formed in a ring shape in which the entire growth surface is maintained in a convex shape in the growth direction and the concave portion depressed on the lid side is formed in the entire growth process. In addition, the silicon carbide polycrystal does not grow in contact with the peripheral side surface portion in the container body. 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 cracking 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 of breakage such as cracks and does not contain polycrystals, polymorphs, or crystal defects such as micropipes.
[0132]
(Silicon carbide single crystal)
The silicon carbide single crystal of the present invention is produced by the method for producing a silicon carbide single crystal of the present invention.
The silicon carbide single crystal of the present invention has non-destructive and optically detected crystal defects (pipe defects) of 100 / cm. ² The following is preferable, 50 / cm ² More preferably, it is 10 / cm ² It is particularly preferred that
The crystal defects can be detected as follows, for example. That is, when the silicon carbide single crystal is illuminated with an appropriate amount of transmitted illumination in addition to reflected illumination, and the microscope focus is focused on the opening of a crystal defect (pipe defect) on the surface of the silicon carbide single crystal. The entire surface of the silicon carbide single crystal is scanned under a condition in which a portion continuing to the inside of the pipe defect can be observed as a shadow that is weaker than the image of the opening and connected to the opening. After obtaining the image, the microscopic image is subjected to image processing, and only the shape characteristic of the pipe defect is extracted and the number thereof is measured, whereby the pipe defect can be detected.
[0133]
In addition, according to the above detection, only the pipe defects can be accurately detected in a non-destructive manner from the presence of foreign matters, polishing scratches, void defects, and other defects attached to the surface of the silicon carbide single crystal. Moreover, even a minute pipe defect of, for example, about 0.35 μm can be accurately detected. On the other hand, conventionally, a method has been used in which the pipe defect portion is selectively etched by molten alkali and enlarged and detected. In this method, adjacent pipe defects are joined together by etching. However, there is a problem that the number of the pipe defects is detected as a result.
[0134]
The total content of the impurity elements in the silicon carbide single crystal is preferably 10 ppm or less.
[0135]
The silicon carbide single crystal of the present invention 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 suitable for optical devices such as electronic devices and light-emitting diodes.
[0136]
【Example】
Examples of the present invention will be described below, but the present invention is not limited to these examples.
[0137]
Example 1
A silicon carbide single crystal was manufactured using the silicon carbide single crystal manufacturing apparatus 1 shown in FIG. In addition, if the manufacturing apparatus 1 of a silicon carbide single crystal is implemented, the manufacturing method of the silicon carbide single crystal of this invention will also be implemented.
[0138]
The silicon carbide single crystal manufacturing apparatus 1 is detachably attached to the container main body 12 by screwing to the container main body 12 capable of accommodating the sublimation raw material (silicon carbide sintered body) 40, and the container main body 12. At this time, a graphite crucible 10 provided with a lid 11 capable of disposing a seed crystal 50 of a silicon carbide single crystal at a substantially center of a surface facing the sublimation raw material 40 accommodated in the container body 12, and the graphite crucible 10 A support rod 31 for fixing the inside of the quartz tube 30, a first induction heating coil 21 disposed in a portion of the outer periphery of the quartz tube 30 where the raw material for sublimation 40 is accommodated in the graphite crucible 10, and a quartz tube 30 and a second induction heating coil 20 disposed in a portion of the graphite crucible 10 where the lid 11 is located. The graphite crucible 10 is covered with a heat insulating material (not shown).
[0139]
As the sublimation raw material (silicon carbide sintered body) 40, the above-described high-pressure tetraethoxysilane polymer is used as the silicon carbide powder as the raw material of the hot press sintered body. Is a silicon source, a resol type phenol resin is used as a carbon source, and a mixture obtained by uniformly mixing these is heated and fired in an argon atmosphere to obtain silicon carbide powder (6H (including 3C in part), average A particle size of 200 μm) was used.
As the seed crystal 50 of the silicon carbide single crystal, a 6H Rayleigh crystal was used.
[0140]
In the silicon carbide single crystal manufacturing apparatus 1, a current was passed through the first induction heating coil 21 to heat it. The sublimation raw material 40 was heated with that heat (after heating to 2500 ° C., the pressure was maintained at 50 Torr (6645 Pa) in an argon gas atmosphere). The sublimation raw material 40 was heated to a predetermined temperature (2500 ° C.) and sublimated. The sublimated raw material 40 does not recrystallize unless cooled to the recrystallization temperature. Here, the lid 11 side is heated by the second induction heating coil 20, the temperature is lower than the sublimation raw material 40 side (the temperature of the seed crystal is 2400 ° C.), and the sublimated raw material 40 is recrystallized. Since the possible recrystallization atmosphere (pressure is 50 Torr (6645 Pa)), the silicon carbide was recrystallized only in the vicinity of the seed crystal 50 of the silicon carbide single crystal, and the silicon carbide crystal was grown.
[0141]
At this time, as shown in FIG. 2, a silicon carbide single crystal 60 recrystallizes and grows on the seed crystal 50 of the silicon carbide single crystal, and a silicon carbide polycrystal is formed on the outer periphery of the seed crystal 50 of the silicon carbide single crystal. 70 recrystallized and grew. In the growth of the silicon carbide single crystal 60, the convex shape is maintained toward the sublimation raw material 40 side in the whole growth process, and the concave portion depressed on the lid body 11 side is not formed in a ring shape. The polycrystal 70 did not grow in contact with the peripheral side surface portion 13 in the container body 12.
[0142]
As a result, as shown in FIG. 3, when the grown silicon carbide single crystal 60 is cooled to room temperature, stress based on the thermal expansion difference is concentratedly applied from the silicon carbide polycrystal 70 side to the silicon carbide single crystal 60 side. The resulting silicon carbide single crystal 60 did not break or break.
[0143]
When the obtained silicon carbide single crystal 60 was evaluated, there was no mixture of polycrystals or polymorphs, and the number of micropipe crystal defects was 4 / cm 2. ² It was extremely high quality with almost no presence.
The micropipe crystal defects are detected by cutting the obtained silicon carbide single crystal 60 into a thickness of 0.4 mm, mirror-polishing a wafer with a surface roughness of 0.4 nm, and removing foreign matter on the surface by alkali cleaning as much as possible. After removal, detection was performed as described below. That is, when the wafer subjected to the alkali cleaning is irradiated with an appropriate amount of transmitted illumination in addition to reflected illumination, and the microscope is focused on the opening of the micropipe on the surface of the wafer, the inside of the micropipe is introduced. And scanning the entire surface of the wafer to obtain a microscopic image under a condition that the following part can be observed as a shadow that is weaker than the image of the opening and connected to the opening. Thus, the micropipes were detected by extracting only the characteristic shapes of the micropipes and measuring the number of the shapes. In this detection, even a micropipe of about 0.35 μm was accurately detected without destruction.
In addition, in the production of the silicon carbide single crystal 60, it was found that the sublimation raw material 40 after a predetermined time had decreased in weight and the raw material was efficiently sublimated. Furthermore, it was found that the total amount of electrical energy required was small and the silicon carbide single crystal 60 was efficiently produced.
[0144]
(Example 2)
Example 1 was the same as Example 1 except that the graphite crucible 10 was changed to the graphite crucible 10 shown in FIG. As a result, the same result as in Example 1 was obtained. The graphite crucible 10 shown in FIG. 4 is different from the graphite crucible 10 shown in FIG. 1 used in Example 1 only in that the lid 11 is provided with an inner region forming portion 15. As shown in FIG. 4, the inner region forming portion 15 has a cylindrical shape with the inner region in which the seed crystal of the silicon carbide single crystal is disposed as a bottom surface, and one end thereof is exposed to the outside. The material of the inner region forming part 15 has a thermal conductivity of 117 J / m / s / ° C. (W / m · K), and the material of the lid 11 other than the inner region forming part 15 has a thermal conductivity of 129 J / m. m / s / ° C. (W / m · K).
In the case of Example 2, since the inner region is formed of a member (inner region forming portion 15) different from the outer region, it is difficult to be heated due to a difference in contact resistance, and the inner region forming portion. Since one end of 15 is exposed to the outside, it is easy to dissipate heat to the outside, so that the silicon carbide can be easily recrystallized.
In addition, in the production of the silicon carbide single crystal 60, it was found that the sublimation raw material 40 after a predetermined time had decreased in weight and the raw material was efficiently sublimated. Furthermore, it was found that the total amount of electrical energy required was small and the silicon carbide single crystal 60 was efficiently produced.
[0145]
(Example 3)
Example 1 was the same as Example 1 except that the graphite crucible 10 was changed to the graphite crucible 10 shown in FIG. As a result, the same result as in Example 1 was obtained. The graphite crucible 10 shown in FIG. 5 is different from the graphite crucible 10 shown in FIG. 1 used in Example 1 only in that the lid 11 is provided with the inner region forming portion 15. As shown in FIG. 5, the inner region forming portion 15 has a stepped shape in which the inner region where the seed crystal of the silicon carbide single crystal is disposed is the bottom surface and the diameter increases discontinuously in two steps toward the outside. One end of the shape is exposed to the outside. The material of the inner region forming part 15 has a thermal conductivity of 117 J / m / s / ° C. (W / m · K), and the material of the lid 11 other than the inner region forming part 15 has a thermal conductivity of 129 J / m. m / s / ° C. (W / m · K).
In the case of Example 3, since the inner region is formed of a member different from the outer region, it is difficult to be heated due to a difference in contact resistance, and one end of the inner region forming portion 15 is exposed to the outside. Therefore, since it is easy to dissipate heat to the outside, recrystallization of silicon carbide was easily performed.
In addition, in the production of the silicon carbide single crystal 60, it was found that the sublimation raw material 40 after a predetermined time had decreased in weight and the raw material was efficiently sublimated. Furthermore, it was found that the total amount of electrical energy required was small and the silicon carbide single crystal 60 was efficiently produced.
[0146]
Example 4
Example 1 was the same as Example 1 except for the following differences. That is, the silicon carbide powder used was 6H, the average particle size was 300 μm, and the silicon carbide single crystal seed crystal 50 was obtained by cutting the bulk silicon carbide single crystal obtained in Example 1 and mirror polishing the entire surface. 15R wafer (diameter 40 mm, thickness 0.5 mm) obtained in this way.
Then, a current of 20 kHz was passed through the first induction heating coil 21 to heat it, and a current of 40 kHz was passed through the second induction heating coil 20 to raise the temperature and heat it. The lower part of graphite crucible 10 (container for sublimation raw material 40) was heated to 2312 ° C., and the upper part of graphite crucible 10 (arrangement part of silicon carbide single crystal seed crystal 50 in lid 11) was heated to 2290 ° C., respectively. At this time, the power supplied to the first induction heating coil 21 is 10.3 kW, the induction heating current (supply current to the LC circuit) is 260 A, and the power supplied to the second induction heating coil 20 is 4.6 kW. And the induction heating current was 98A. When the pressure was reduced from normal pressure to 20 Torr (2658 Pa) over 1 hour and maintained for 20 hours, the silicon carbide single crystal 60 having a convex shape maintained toward the sublimation raw material 40 side as shown in FIG. Obtained. At this time, the height of the silicon carbide single crystal 60 to the tip of the convex shape is 12 mm, and the diameter of the silicon carbide growth crystal including the silicon carbide single crystal 60 and the silicon carbide polycrystal formed therearound is It was 87 mm. In the silicon carbide single crystal 60, the concave portion recessed in the direction of the lid 11 was not formed in a ring shape. In addition, the silicon carbide single crystal 60 did not grow in contact with the peripheral side surface portion 13 of the container body 12 of the graphite crucible 10. Furthermore, the silicon carbide single crystal 60 had only a few silicon carbide polycrystals 70 around it.
Furthermore, in the production of the silicon carbide single crystal 60, it was found that the raw material for sublimation 40 after a predetermined time had decreased in weight, and the raw material was efficiently sublimated. Furthermore, it was found that the total amount of electrical energy required was small and the silicon carbide single crystal 60 was efficiently produced.
[0147]
(Example 5)
Example 4 was the same as Example 1 except for the following differences. That is, the diameter of the silicon carbide single crystal seed crystal 50 is 20 mm and the thickness is 0.5 mm, and the lower part of the graphite crucible 10 (container for the sublimation raw material 40) is heated to 2349 ° C. The heating temperature of the silicon carbide single crystal seed crystal 50 in the lid 11 is 2317 ° C., the power supplied to the second induction heating coil 20 at that time is 5.5 kW, and the induction heating current is The diameter of the growth crystal of silicon carbide including the silicon carbide single crystal 60 and the silicon carbide polycrystal formed around the silicon carbide single crystal 60 is the same as that of Example 4 except that the diameter is 60 mm. Good results similar to those obtained were obtained.
In addition, in the production of the silicon carbide single crystal 60, it was found that the sublimation raw material 40 after a predetermined time had decreased in weight and the raw material was efficiently sublimated. Furthermore, it was found that the total amount of electrical energy required was small and the silicon carbide single crystal 60 was efficiently produced.
[0148]
(Example 6)
Example 1 was the same as Example 1 except for the following differences. That is, the interference preventing coil 22 that can be cooled by allowing water to flow through the interference preventing coil 22 was used. The silicon carbide powder used was 6H, the average particle size was 250 μm, and the silicon carbide single crystal seed crystal 50 was obtained by cutting the bulk silicon carbide single crystal obtained in Example 4 and mirror polishing the entire surface. This is a wafer (6H) having a diameter of 25 mm and a thickness of 2 mm.
Then, a current of 20 kHz was passed through the first induction heating coil 21 to heat it, and a current of 40 kHz was passed through the second induction heating coil 20 to heat it. The lower part of the graphite crucible 10 (accommodating part for the sublimation raw material 40) and the upper part (arrangement part of the seed crystal 50 of the silicon carbide single crystal in the lid 11) were each heated to 2510 ° C. and heated for 1 hour. The lower part of the graphite crucible 10 is at the same temperature (T ₁ ), The seed power in the lid 11 of the graphite crucible 10 is gradually reduced (from 5.8 kW, 120 A to 4.2 kW, 90 A) while the power supplied to the second induction heating coil 20 is gradually reduced. The temperature of the arrangement part is 2350 ° C. (T ₂ ) Until the temperature of the outer peripheral portion of the seed crystal arrangement portion in the lid 11 is 2480 ° C. (T ₃ ). At this time, when the pressure was reduced from normal pressure to 20 Torr (2658 Pa) over 1 hour, a silicon carbide single crystal 60 having a convex shape maintained toward the sublimation raw material 40 side was obtained as shown in FIG. It was. At this time, the height to the tip of the convex shape in the silicon carbide single crystal 60 was 18 mm. In the silicon carbide single crystal 60, the concave portion recessed in the direction of the lid 11 was not formed in a ring shape. In addition, the silicon carbide single crystal 60 did not grow in contact with the peripheral side surface portion 13 of the container body 12 of the graphite crucible 10. Further, the silicon carbide single crystal 60 did not generate or grow adjacent to the silicon carbide polycrystal 70 around it.
In addition, in the production of the silicon carbide single crystal 60, it was found that the sublimation raw material 40 after a predetermined time had decreased in weight and was efficiently sublimated. Furthermore, it was found that the total amount of electrical energy required was small and the silicon carbide single crystal 60 was efficiently produced.
[0149]
(Example 7)
Example 1 was the same as Example 1 except for the following differences. That is, the second induction heating coil 20 and the first induction heating coil 21 are replaced with the induction heating coil 25 in the conventional silicon carbide single crystal manufacturing apparatus 80 shown in FIG. 8, and the container body 12 in the lid 11 of the graphite crucible. Of the surface facing the inside of the substrate (surface on which the silicon carbide single crystal is grown), only the outer region of the circle having a radius of 60 mm from the center is determined to be glassy or amorphous by X-ray diffraction. A carbon thin film having a thickness of 1 to 10 μm was formed by the following method. It installed in the vacuum chamber in the state which exposed only the said outer side area | region in the cover body 11, and adjusted the pressure in a chamber to 0.23 Pa in benzene atmosphere. Thereafter, the lid body 11 is kept at a negative potential of 2.5 kV, and positive ions generated in the plasma are decomposed at a high speed by decomposing benzene with arc discharge plasma generated at the opposed portion of the filament and the anode. The film was formed by colliding with the outer region.
In Example 7, on the surface of the lid body 11 facing the inside of the container main body 12, silicon carbide crystals do not grow on the portion where the glassy carbon or amorphous carbon film is formed, and the film is formed. Only in the center portion (circular portion having a diameter of 60 mm) that was not performed, the silicon carbide single crystal 60 in which the entire growth surface was maintained in a convex shape grew toward the sublimation raw material 40 side. For this reason, the silicon carbide single crystal 60 does not grow in contact with the peripheral side surface portion 13 of the container body 12 of the graphite crucible 10, and breakage such as cracks does not occur when cooled to room temperature. It was.
In addition, in the production of the silicon carbide single crystal 60, it was found that the sublimation raw material 40 after a predetermined time had decreased in weight and the raw material was efficiently sublimated. Furthermore, it was found that the total amount of electrical energy required was small and the silicon carbide single crystal 60 was efficiently produced.
[0150]
(Comparative Example 1)
A silicon carbide single crystal was obtained in the same manner as in Example 1 except that the hot press sintered body used as the sublimation raw material 40 in Example 1 was replaced with the silicon carbide powder. The obtained silicon carbide single crystal was of high quality with almost no crystal defects such as polycrystals, polymorphs, and micropipes.
In addition, in the production of the silicon carbide single crystal, the sublimation raw material 40 after the lapse of a predetermined time as in Examples 1 to 7 has less weight reduction than Examples 1 to 7, and sublimation of the raw material compared with Examples 1 to 7 The efficiency of was not good. Moreover, it turned out that the total amount of the electrical energy required was larger than Examples 1-7, and the manufacturing efficiency of the silicon carbide single crystal was inferior compared with Examples 1-7.
[0151]
【The invention's effect】
According to the present invention, it has excellent dielectric breakdown characteristics, heat resistance, radiation resistance, etc., and is particularly suitable for electronic devices such as semiconductor wafers, optical devices such as light emitting diodes, A high-quality silicon carbide single crystal having no defects such as, and a method capable of producing the high-quality silicon carbide single crystal at a low cost and in a large diameter and easily without breakage such as cracks. Can be provided.
[Brief description of the drawings]
FIG. 1 is a schematic view for explaining an initial state in a method for producing a silicon carbide single crystal of the present invention.
FIG. 2 is a schematic diagram for explaining a state in which a silicon carbide single crystal is produced by the method for producing a silicon carbide single crystal of the present invention.
FIG. 3 is a schematic view of the silicon carbide single crystal of the present invention produced by the method for producing a silicon carbide single crystal of the present invention.
FIG. 4 is a schematic explanatory view showing an example of a crucible used in the method for producing a silicon carbide single crystal of the present invention.
FIG. 5 is a schematic explanatory view showing another example of a crucible used in the method for producing a silicon carbide single crystal of the present invention.
FIG. 6 is a schematic view of the silicon carbide single crystal of the present invention produced by the method for producing a silicon carbide single crystal of the present invention.
FIG. 7 is a schematic view of the silicon carbide single crystal of the present invention produced by the method for producing a silicon carbide single crystal of the present invention.
FIG. 8 is a schematic diagram for explaining a state in which a silicon carbide single crystal is manufactured by a conventional method for manufacturing a silicon carbide single crystal.
FIG. 9 is a schematic view of a silicon carbide single crystal produced by a conventional method for producing a silicon carbide single crystal.
[Explanation of symbols]
1 Production equipment for silicon carbide single crystals
10 Graphite crucible
11 Lid
12 Container body
13 circumferential side
15 Inner region forming part
20 Second induction heating coil
21 First induction heating coil
22 Interference prevention coil
25 Induction heating coil
30 quartz tube
31 Support rod
40 Raw materials for sublimation
50 Seed crystal of silicon carbide single crystal
60 Silicon carbide single crystal
70 Polycrystalline silicon carbide
71 recess
80 Conventional silicon carbide single crystal production equipment

Claims (19)

A method for producing a silicon carbide single crystal in which a silicon carbide single crystal is grown by recrystallizing a sublimated raw material for sublimation,
The sublimation raw material is obtained by hot-pressing a compound containing silicon carbide powder, a boron compound, and a nonmetallic sintering aid in a non-oxidizing atmosphere at 2000 to 2400 ° C. and a pressure of 300 to 700 kgf / cm ² . A method for producing a silicon carbide single crystal, comprising: a silicon carbide sintered body, wherein the silicon carbide single crystal is grown through a whole growth process while maintaining the entire growth surface in a convex shape.   The method for producing a silicon carbide single crystal according to claim 1, wherein the silicon carbide crystal including the silicon carbide single crystal is grown in a substantially chevron shape. A raw material for sublimation is accommodated in a reaction vessel, a seed crystal of a silicon carbide single crystal is disposed at an end portion substantially opposed to the raw material for sublimation in the reaction vessel,
The silicon carbide single crystal according to claim 1 or 2, wherein the growth of the silicon carbide crystal including the silicon carbide single crystal is performed only in a region other than a portion adjacent to the peripheral side surface portion in the reaction vessel at the end portion. Manufacturing method. The method for producing a silicon carbide single crystal according to any one of claims 2 to 3, wherein the silicon carbide crystal including the silicon carbide single crystal is composed only of the silicon carbide single crystal. A raw material for sublimation is housed on one end side in the reaction vessel, a seed crystal of silicon carbide single crystal is placed on the other end side in the reaction vessel,
By a first heating means arranged on the one end side, a sublimation atmosphere is formed so that the sublimation raw material can be sublimated,
The second heating means disposed on the other end side changes the recrystallization atmosphere so that the sublimation raw material sublimated by the first heating means can be recrystallized only in the vicinity of the seed crystal of the silicon carbide single crystal. The method for producing a silicon carbide single crystal according to any one of claims 1 to 4, wherein the silicon carbide single crystal is formed and recrystallized on the seed crystal of the silicon carbide single crystal. The method for producing a silicon carbide single crystal according to claim 5, wherein the temperature of the recrystallization atmosphere is 30 to 300 ° C lower than the temperature of the sublimation atmosphere in the reaction vessel. The method for producing a silicon carbide single crystal according to claim 5 or 6, wherein the first heating means and the second heating means are coils capable of induction heating. The method for producing a silicon carbide single crystal according to claim 7, wherein the current value of the induction heating current in the first heating means is larger than the current value of the induction heating current in the second heating means. The method for producing a silicon carbide single crystal according to claim 7 or 8, wherein the current value of the induction heating current in the second heating means is decreased continuously or stepwise as the diameter of the growing silicon carbide single crystal increases. In the reaction vessel, the temperature on one end side containing the sublimation raw material is T1, the temperature on the other end side where the seed crystal of the silicon carbide single crystal is arranged is T2, and the temperature of the reaction vessel on the other end side is The method for producing a silicon carbide single crystal according to any one of claims 5 to 9, wherein T3-T2 and T1-T2 increase continuously or stepwise when the temperature is T3 adjacent to the inner peripheral side surface portion. An interference capable of passing an induced current between the first heating means and the second heating means, and preventing interference between the first heating means and the second heating means by passing the induced current. The method for producing a silicon carbide single crystal according to any one of claims 7 to 10, wherein a prevention means is arranged. The method for producing a silicon carbide single crystal according to claim 11, wherein the interference preventing means is a coil through which cooling water can flow. The method for producing a silicon carbide single crystal according to any one of claims 5 to 12, wherein the one end is a lower end and the other end is an upper end. The method for producing a silicon carbide single crystal according to any one of claims 5 to 13, wherein the reaction vessel is a crucible arranged in a quartz tube. The region where the silicon carbide single crystal is grown at the other end and the region located on the outer periphery of the region and adjacent to the inner peripheral side surface of the reaction vessel are formed of different members, and the carbonization is performed. The silicon carbide according to any one of claims 5 to 14, wherein one end of the member forming the region where the silicon single crystal is grown is exposed to the inside of the reaction vessel and the other end is exposed to the outside of the reaction vessel. A method for producing a single crystal. The method for producing a silicon carbide single crystal according to any one of claims 3 to 15, wherein a surface of the other end portion adjacent to the inner peripheral side surface portion in the reaction vessel is glassy carbon. The silicon carbide powder is obtained by using at least one selected from high-purity alkoxysilanes and alkoxysilane polymers as a silicon source, and using a high-purity organic compound that generates carbon by heating as a carbon source, and mixing them uniformly. The method for producing a silicon carbide single crystal according to any one of claims 1 to 16, which is a silicon carbide powder obtained by heating and firing the obtained mixture in a non-oxidizing atmosphere. The method for producing a silicon carbide single crystal according to claim 17, wherein the silicon source is a tetraalkoxysilane polymer and the carbon source is a phenol resin. The method for producing a silicon carbide single crystal according to claim 17 or 18, wherein each content of the impurity element in the silicon carbide powder is 0.5 ppm or less.

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