JP4731766B2 - 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 an efficient manufacturing method thereof.
[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. Accordingly, the present situation is that a high-quality silicon carbide single crystal free from such defects as polycrystals, polymorphs, micropipes, and the like, and an efficient manufacturing method thereof have not yet been provided.
[0004]
[Problems to be solved by the invention]
An object of the present invention is to solve the above-described problems and achieve the following objects. That is, 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, An object of the present invention is to provide a high-quality silicon carbide single crystal having no defects such as the above, and an efficient production method thereof.
[0005]
[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 raw material for sublimation is recrystallized to grow a silicon carbide single crystal, wherein the grown silicon carbide single crystal has a major axis of the bottom surface of D (cm) And (H / D) ≧ 0.1, where H (cm) is the length of the perpendicular line connecting the bottom surface and the apex.
<2> The method for producing a silicon carbide single crystal according to <1>, wherein the curvature radius of the convex portion of the silicon carbide single crystal is 9 cm or less.
<3> A method for producing a silicon carbide single crystal in which a sublimated raw material for sublimation is recrystallized to grow a silicon carbide single crystal, wherein the curvature radius of the convex portion of the silicon carbide single crystal is 9 cm or less. It is the manufacturing method of the silicon carbide single crystal characterized.
<4> The method for producing a silicon carbide single crystal according to any one of <1> to <3>, wherein the silicon carbide crystal including the silicon carbide single crystal is composed only of the silicon carbide single crystal.
<5> The method for producing a silicon carbide single crystal according to any one of <1> to <4>, wherein the silicon carbide single crystal is grown through the entire growth process while maintaining the entire growth surface in a convex shape. It is.
<6> A raw material for sublimation is accommodated in a reaction vessel, and 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 growth of a silicon carbide crystal including a 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. It is a manufacturing method of the silicon carbide single crystal of description.
<7> A raw material for sublimation is accommodated on one end side in the reaction vessel, a seed crystal of a silicon carbide single crystal is disposed on the other end side in the reaction vessel,
By the 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 <6>, wherein the raw material for sublimation is formed and recrystallized on a seed crystal of the silicon carbide single crystal.
<8> A silicon carbide single crystal produced by the method for producing a silicon carbide single crystal according to any one of <1> to <7>.
<9> Non-destructive and 50 hollow / pipe crystal defects detected optically ² The silicon carbide single crystal according to <8>, which is the following.
<10> The silicon carbide single crystal according to <8> or <9>, wherein the total content of impurity elements is 10 ppm or less.
[0006]
In the present invention, the following means are also preferable.
<11> The method for producing a silicon carbide single crystal according to <7>, wherein the temperature of the recrystallization atmosphere is 30 to 300 ° C. lower than the temperature of the sublimation atmosphere in the reaction vessel.
<12> The method for producing a silicon carbide single crystal according to <7>, wherein the first heating unit and the second heating unit are induction-heatable coils.
<13> The method for producing a silicon carbide single crystal according to <12>, 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.
<14> The silicon carbide according to <12> or <13>, 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.
<15> 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 <7> and <11> to <14>, in which increases in a continuous or stepwise manner.
<16> 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 <7> and <11> to <15>, wherein interference preventing means for preventing is arranged.
<17> The method for producing a silicon carbide single crystal according to <16>, wherein the interference prevention unit is a coil capable of circulating cooling water.
<18> The method for producing a silicon carbide single crystal according to any one of <7> and <11> to <17>, wherein the one end is a lower end and the other end is an upper end.
<19> The method for producing a silicon carbide single crystal according to any one of <6> to <7> and <11> to <18>, wherein the reaction vessel is a crucible disposed in a quartz tube.
<20> 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, <7> and <11> from the above <7> and <11>, wherein one end of the member forming the region where the silicon carbide 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. The manufacturing method of the silicon carbide single crystal in any one of 19>.
<21> The silicon carbide single unit according to any one of <7> and <11> to <20>, wherein the surface of the other end portion adjacent to the peripheral side surface portion in the reaction vessel is glassy carbon. It is a manufacturing method of a crystal.
<22> The sublimation raw material 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. The silicon carbide single piece according to any one of <1> to <7> and <11> to <21>, wherein the silicon carbide powder is obtained by heating and firing a mixture obtained by mixing in a non-oxidizing atmosphere. It is a manufacturing method of a crystal.
<23> The method for producing a silicon carbide single crystal according to <22>, wherein the silicon source is a tetraalkoxysilane polymer and the carbon source is a phenol resin.
<24> The method for producing a silicon carbide single crystal according to <22> or <23>, wherein each content of impurity elements in the silicon carbide powder is 0.5 ppm or less.
[0007]
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 silicon carbide single crystal is grown by recrystallizing a sublimated raw material for sublimation. A single crystal satisfies (H / D) ≧ 0.1 when the major axis of the bottom surface is D (cm) and the length of the perpendicular connecting the bottom surface and the apex is H (cm). For this reason, a high quality silicon carbide single crystal free from the above-mentioned problems, i.e., breakage such as cracks, and free from crystal defects such as polycrystals, polymorphs, and micropipes is produced.
[0008]
In the method for producing a silicon carbide single crystal according to <2>, the curvature radius of the convex portion of the silicon carbide single crystal is 9 cm or less in <1>. For this reason, a high quality silicon carbide single crystal free from the above-mentioned problems, i.e., breakage such as cracks, and free from crystal defects such as polycrystals, polymorphs, and micropipes is produced.
[0009]
The method for producing a silicon carbide single crystal according to <3> 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. The curvature radius in the convex portion is 9 cm or less. For this reason, a high quality silicon carbide single crystal free from the above-mentioned problems, i.e., breakage such as cracks, and free from crystal defects such as polycrystals, polymorphs, and micropipes is produced.
[0010]
In the method for producing a silicon carbide single crystal according to <4>, 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.
[0011]
The method for producing a silicon carbide single crystal according to <5> above is the method according to any one of <1> to <4>, wherein the entire surface of the growth surface of the silicon carbide single crystal has a convex shape throughout the entire growth process. Grow while holding on. 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, high-quality silicon carbide single crystals that do not have various problems in the past, that is, breakage such as cracks, and that do not contain polycrystals, polymorphs, or crystal defects such as micropipes are produced.
[0012]
<6> The method for producing a silicon carbide single crystal according to <6>, wherein the sublimation raw material is contained in a reaction vessel in any one of <1> to <5>, and the sublimation material in the reaction vessel A seed crystal of the silicon carbide single crystal is arranged at an end portion substantially facing the raw material, and the growth of the silicon carbide crystal containing the silicon carbide single crystal is formed with the peripheral side surface portion in the reaction vessel at the end portion. It is performed only in the area excluding the adjacent part. 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, the above-mentioned problems in the prior art, that is, there is no breakage such as cracking, and high-quality silicon carbide single crystals free from crystal defects such as polycrystals, polymorphs, and micropipes are efficiently and reliably produced. .
[0013]
In the method for producing a silicon carbide single crystal according to <7>, in any one of <1> to <6>, 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 does not have the above-described problems, that is, breakage such as cracks, and does not contain polycrystals, polymorphs, or crystal defects such as micropipes is produced.
[0014]
The silicon carbide single crystal according to <8> is manufactured by the method for manufacturing a silicon carbide single crystal according to any one of <1> to <7>. 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.
[0015]
In the silicon carbide single crystal according to <9>, the hollow pipe-like crystal defect detected non-destructively and optically in 50 in the above <8> / cm. ² It is as follows. For this reason, the silicon carbide single crystal is extremely high quality, 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. .
[0016]
In the <8> or <9>, the silicon carbide single crystal according to <10> has a total content of the impurity elements of 10 ppm or less. For this reason, the silicon carbide single crystal has an extremely high quality.
[0017]
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.
A method for producing a silicon carbide single crystal according to the present invention is a method for producing a silicon carbide single crystal in which a sublimation material that has been sublimated is recrystallized to grow a silicon carbide single crystal. When the major axis of the bottom surface is D (cm) and the length of the perpendicular connecting the bottom surface and the apex is H (cm), (H / D) ≧ 0.1 is satisfied.
[0018]
The value of (H / D) is preferably 0.13 or more.
When the value of (H / D) satisfies the above numerical range, the above-mentioned problems, that is, there is no breakage such as cracks, and there are no crystal defects such as polycrystals, polymorphs, and micropipes. A high quality silicon carbide single crystal is produced.
The major axis D of the bottom surface includes a sphere having a radius of curvature (R) defined so as to substantially overlap the convex portion of the grown silicon carbide single crystal and the bottom surface of the seed crystal, as shown in FIG. It refers to the length of the diameter D of the intersection circle with the plane. Moreover, the length H of the said perpendicular shows the length of H in the silicon carbide single crystal 60 shown in FIG.
[0019]
The curvature radius of the convex portion of the silicon carbide single crystal is preferably 9 cm or less, and more preferably 7 cm or less.
If the radius of curvature exceeds 9 cm, polycrystals or polymorphs may be mixed, or crystal defects such as micropipes may be easily generated.
[0020]
The radius of curvature is, for example, the limit value dω / ds of Δω / Δs at the point P, where Δω is the angle between the tangents at two points P (s) and P (s + Δs) separated by Δs. This curvature is the reciprocal of this.
In the present invention, the “curvature radius” can be specifically measured by the following measuring method.
That is, first, a cross-sectional curve of the growth end face is obtained by a stylus type surface profile measuring machine. Next, curve fitting is performed on the convex portion in the cross-section curve by the least square method, and the radius of the circular curve is set as the radius of curvature in the convex portion.
[0021]
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.
[0022]
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.
[0023]
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.
[0024]
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).
[0025]
-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.
[0026]
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 which substantially opposes 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 a cross section perpendicular to the axial direction of the cylindrical shape. The shape may be circular or polygonal. Preferable examples of the circular shape include those having a straight axis and a circular cross-sectional shape perpendicular to the axial direction.
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.
[0027]
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 by simply detaching the other end (seed crystal arrangement portion).
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.
[0028]
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.
[0029]
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.
[0030]
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.
[0031]
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.
[0032]
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.
[0033]
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.
[0034]
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.
[0035]
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.
[0036]
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 portion (sublimation raw material storage portion), a graphite cover member or the like is further provided to prevent the heat insulating material powder or the like from falling. It is preferable.
[0037]
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.
[0038]
-Raw material for sublimation-
As the sublimation raw material, as long as it is silicon carbide, the polymorph of crystal, the amount used, the purity, the production method thereof, and the like are not particularly limited, and can be appropriately selected according to the purpose.
[0039]
Examples of the polymorph of the sublimation raw material crystal 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.
[0040]
The amount of the sublimation raw material 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.
[0041]
The purity of the sublimation raw material 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.
[0042]
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 a silicon atom represent Element). 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.
[0043]
The silicon carbide powder as the sublimation raw material contains, for example, 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 in a non-oxidizing atmosphere a powder obtained by dissolving and drying in.
[0044]
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.
[0045]
As the liquid, an alkoxysilane and an alkoxysilane polymer are preferably used.
[0046]
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.
[0047]
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).
[0048]
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.
[0049]
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.
[0050]
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.
[0051]
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.
[0052]
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.
[0053]
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.
[0054]
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. .
[0055]
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.
[0056]
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.
[0057]
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.
[0058]
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 to do. 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.
[0059]
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 3C silicon carbide powder, Although what is generally marketed may be sufficient, it is preferable that it is a high purity thing.
[0060]
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
[0061]
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.
[0062]
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.
[0063]
-Sublimation-
The sublimation of the sublimation raw material is performed using a heating unit that is different from the heating unit for performing the recrystallization, such as precise control of the heating unit, independent control, prevention of interference, etc. This is preferable. 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.
[0064]
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.
[0065]
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.
[0066]
-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.
[0067]
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. A recrystallization atmosphere (in other words, an atmosphere having a temperature distribution in which the temperature becomes lower toward the center (center of the inner region) in the radial direction of the surface on which the seed crystal is arranged). Preferably formed.
[0068]
The recrystallization atmosphere can be preferably 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 that only the recrystallization is possible, and the sublimation raw material is recrystallized on the seed crystal of the silicon carbide single crystal.
[0069]
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.
[0070]
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.
[0071]
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, it is advantageous in that 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, and recrystallization is facilitated.
[0072]
Further, the current value of the induction heating current in the second heating means is preferably controlled so as to decrease continuously or stepwise as the diameter of the growing silicon carbide single crystal increases. In this case, as the silicon carbide single crystal grows, the amount of heating by the second heating means is controlled to be small, so that recrystallization is performed only in the vicinity of the silicon carbide single crystal that continues to grow. It is advantageous in that the formation of polycrystals around is effectively suppressed.
[0073]
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.
[0074]
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.
[0075]
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.
[0076]
The pressure of the recrystallization atmosphere formed by the second heating means is preferably 10 to 100 Torr (1330 to 13300 Pa). In this case, it is preferable to adjust the pressure condition so that it is within the predetermined numerical range by reducing the pressure after heating up to the set temperature without reducing the pressure at room temperature.
The recrystallization atmosphere is preferably an inert gas atmosphere such as argon gas.
[0077]
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.
[0078]
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.
[0079]
In the present invention, the silicon carbide single crystal is recrystallized and grown according to the first to third aspects.
[0080]
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.
[0081]
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.
[0082]
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.
[0083]
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.
[0084]
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. Some parts may be included.
[0085]
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. It is preferable to prevent the silicon carbide polycrystals and polymorphs from being mixed because the silicon carbide crystal containing silicon carbide can be made of only a silicon carbide single crystal.
[0086]
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.
[0087]
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.
[0088]
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.
[0089]
The interference prevention coil (sometimes simply referred to as a “coil”) can be supplied with an induced current. By passing an induced current, interference between the first heating means and the second heating means is prevented. What has the function to prevent is preferable.
[0090]
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.
[0091]
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.
[0092]
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 type of the first heating means and the second heating means, the amount of current passed through them, and cannot be specified unconditionally. However, even a single layer is sufficient.
[0093]
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.
[0094]
(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.
[0095]
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.
[0096]
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.
[0097]
The total content of the impurity elements in the silicon carbide single crystal is preferably 10 ppm or less.
[0098]
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.
[0099]
<Silicon carbide single crystal manufacturing equipment, etc.>
The silicon carbide single crystal production apparatus capable of suitably producing the silicon carbide single crystal of the present invention includes, for example, recrystallizing the sublimated raw material to grow a silicon carbide single crystal and carbonizing the present invention. Examples thereof include an apparatus for producing a silicon single crystal.
[0100]
The silicon carbide single crystal manufacturing apparatus includes at least a crucible, a first induction heating coil, and a second induction heating coil, and includes other members and the like appropriately selected as necessary.
[0101]
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.
[0102]
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.
[0103]
In the silicon carbide single crystal manufacturing apparatus, the silicon carbide single crystal is generally placed 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. A seed crystal is arranged.
[0104]
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.
[0105]
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.
[0106]
In the silicon carbide single crystal manufacturing 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, in the growing silicon carbide single crystal, in the whole growth process, the entire surface of the growth surface is maintained in a convex shape toward the growth direction, and the concave portion depressed on the lid side is formed in a ring shape. 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 does not have the above-mentioned problems, that is, breakage such as cracks, and does not include polycrystals, polymorphs, or crystal defects such as micropipes. be able to.
[0107]
As mentioned above, according to the manufacturing apparatus of the said silicon carbide single crystal, the high quality silicon carbide single crystal of this invention can be manufactured efficiently in the state which does not have breakage, such as a crack, efficiently.
[0108]
【Example】
Examples of the present invention will be described below, but the present invention is not limited to these examples.
[0109]
Example 1
A silicon carbide single crystal was manufactured using the silicon carbide single crystal manufacturing apparatus 1 shown in FIG.
[0110]
The silicon carbide single crystal manufacturing apparatus 1 can be attached to and detached from the container main body 12 capable of accommodating the sublimation raw material 40 and the container main body 12 by screwing. A graphite crucible 10 provided with a lid 11 capable of disposing a seed crystal 50 of a silicon carbide single crystal at the approximate center of the surface facing the accommodated sublimation raw material 40, and the graphite crucible 10 inside the quartz tube 30. The support rod 31 to be fixed, the first induction heating coil 21 disposed in the outer periphery of the quartz tube 30 and the portion of the graphite crucible 10 in which the raw material for sublimation 40 is accommodated, and the outer periphery of the quartz tube 30 and the graphite And a second induction heating coil 20 disposed in a portion of the crucible 10 where the lid 11 is located. The graphite crucible 10 is covered with a heat insulating material (not shown).
[0111]
The sublimation raw material 40 is obtained by heating and baking a mixture obtained by uniformly mixing the above-described high-purity tetraethoxysilane polymer as a silicon source and resol type phenol resin as a carbon source in an argon atmosphere. The obtained silicon carbide powder (6H (partly including 3C), average particle size is 200 μm), and the seed crystal 50 of the silicon carbide single crystal is a 6H Rayleigh crystal.
[0112]
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.
[0113]
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.
[0114]
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.
[0115]
When the obtained silicon carbide single crystal 60 was evaluated, the major axis D (cm) of the bottom surface of the silicon carbide single crystal 60 was 8.2 cm, and the length H (cm) of the perpendicular connecting the bottom surface and the apex was 1.6 cm. And H / D was 0.17. The curvature radius of the convex portion of the silicon carbide single crystal was 6.1 cm. In the obtained silicon carbide single crystal 60, polycrystals and polymorphic crystals are not mixed, and micropipe crystal defects are 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 wafer surface, the inside of the micropipe 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.
[0116]
(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 where the seed crystal of the silicon carbide single crystal is disposed as a bottom surface, and one end thereof is exposed to the outside of the graphite crucible 10. . 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.
[0117]
(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.
[0118]
Example 4
Example 1 was the same as Example 1 except for the following differences. That is, the obtained silicon carbide powder has 6H and an average particle diameter of 300 μm, and the silicon carbide single crystal seed crystal 50 is obtained by cutting the bulk silicon carbide single crystal obtained in Example 1 and mirroring the entire surface. This is a 15R wafer (diameter 40 mm, thickness 0.5 mm) obtained by polishing.
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.
[0119]
(Example 5)
Example 4 was the same as Example 4 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 silicon carbide growth crystal including the silicon carbide single crystal 60 and the silicon carbide polycrystal formed therearound is 60 mm, and the major axis D (cm) of the bottom surface of the silicon carbide single crystal 60 is 4A. 0.5 cm, the length H (cm) of the perpendicular line connecting the bottom surface and the apex is 0.7 cm, H / D is 0.16, and the curvature radius of the convex portion of the silicon carbide single crystal is 4. Except that it was 0cm Example 4 is similar to the good results same as in Example 4 were obtained.
[0120]
(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 obtained silicon carbide powder had 6H and an average particle diameter of 250 μm. 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 an estimated temperature of 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.
[0121]
(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.
[0122]
(Comparative Example 1)
A silicon carbide single crystal was produced in the same manner as in Example 1 except that the silicon carbide single crystal production apparatus 80 shown in FIG. 8 was used.
[0123]
Specifically, the first induction heating coil 21 and the second induction heating coil 20 disposed on the outer periphery of the quartz tube 30 and in the portion where the lid 11 is located in the graphite crucible 10 are arranged on the outer periphery of the quartz tube 30. Instead of the induction heating coil 25 arranged in a spirally wound state at a substantially equal interval in the portion where the graphite crucible 10 is located, the long diameter of the bottom surface of the silicon carbide single crystal is used without using the interference preventing coil 22. Is D (cm), and the length of the perpendicular line connecting the bottom surface and the apex is H (cm), and (H / D) ≧ 0.1 is not satisfied and the convexity of the silicon carbide single crystal 60 is The same procedure as in Example 1 was performed except that the curvature radius of the shape portion was not 9 cm or less.
[0124]
In Comparative Example 1, as shown in FIG. 8, 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 is formed on the outer peripheral edge of the lid 11. The container body 12 grew in contact with the inner peripheral side surface. In this state, when cooling to room temperature, stress based on the difference in thermal expansion is concentrated from the silicon carbide polycrystal 70 side to the silicon carbide single crystal 60 side, and as shown in FIG. In addition to cracks, many micropipes (84 / cm ³ ) Occurred.
[0125]
【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, etc. It is possible to provide a high-quality silicon carbide single crystal having no defects and an efficient production method thereof.
[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 (6)

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 the 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. Forming,
Recrystallizing the sublimation raw material on the seed crystal of the silicon carbide single crystal,
The sublimation material that has been sublimated is prevented from interfering between the first heating means and the second heating means by the interference prevention means provided between the first heating means and the second heating means. A method for producing a silicon carbide single crystal comprising crystallizing and growing a silicon carbide single crystal comprising:
When the grown silicon carbide single crystal has a major axis of the bottom surface of D (cm) and a length of the perpendicular connecting the bottom surface and the apex of H (cm), (H / D) ≧ 0.16, The manufacturing method of the silicon carbide single crystal characterized by satisfy | filling . Radius of curvature at the convex portion of the silicon carbide single crystal, manufacturing method of silicon carbide single crystal according to claim 1 is 9cm less.   The method for producing a silicon carbide single crystal, wherein a silicon carbide single crystal is grown by recrystallizing a sublimated raw material for sublimation, wherein the curvature radius of the convex portion of the silicon carbide single crystal is 9 cm or less. A method for producing a silicon carbide single crystal. The method for producing a silicon carbide single crystal according to any one of claims 1 to 3 , wherein the silicon carbide crystal including the silicon carbide single crystal is composed only 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 grown through the whole growth process while maintaining the entire growth surface in a convex shape. A sublimation raw material 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 sublimation raw material in the reaction vessel,
The carbonization according to any one of claims 1 to 5 , wherein the growth of a silicon carbide crystal including a silicon carbide single crystal is performed only in a region of the end portion excluding a portion adjacent to a peripheral side surface portion in the reaction vessel. A method for producing a silicon single crystal.

Images