JP4986342B2 - 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 that can be suitably used as a semi-insulating or insulating single crystal substrate 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.
As a method for producing the silicon carbide single crystal, an improved Rayleigh method (an improved sublimation recrystallization method) in which a graphite crucible is used to sublimate silicon carbide powder and a silicon carbide single crystal is grown on a silicon carbide single crystal seed crystal. In the periodic table of the 1989 IUPAC Inorganic Chemical Nomenclature Revision, the impurity element belongs to the group 1 to group 17 and has an atomic number of 3 or more (provided that the carbon atom, nitrogen atom, oxygen atom and silicon There are few known methods for producing silicon carbide single crystals whose content is 1.0 mass ppm or less.
On the other hand, a silicon carbide single crystal obtained using a silicon carbide powder containing a large amount of nitrogen atoms, which is not the impurity element, gives electron conductivity as a donor atom to the silicon carbide crystal. Although it can be used, it cannot be used as a semi-insulator or insulator. For this reason, in some devices such as MESFETs for high frequency applications, the use of a highly insulating substrate is desired for the purpose of suppressing the high frequency loss of the substrate, but a silicon carbide single layer suitable as such a highly insulating substrate is desired. The present condition is that the manufacturing method of a crystal is not yet provided.
[0003]
[Problems to be solved by the invention]
This invention is made | formed in view of this present condition, and makes it a subject to achieve the following objectives. That is, the present invention has a low content of the impurity element and a low content of an element such as nitrogen that is not the impurity element, and can be used as a semi-insulator or insulator. It is an object of the present invention to provide a silicon carbide single crystal that can be suitably used as a substrate and the like, and a method for producing a silicon carbide single crystal capable of efficiently producing the silicon carbide single crystal.
[0004]
[Means for Solving the Problems]
Means for solving the above problems are as follows. That is,
<1> Growing a silicon carbide single crystal by sublimating and recrystallizing a silicon carbide powder having a nitrogen content of 100 mass ppm or less and each impurity element content of 0.1 mass ppm or less. Is a method for producing a silicon carbide single crystal.
<2> The method for producing a silicon carbide single crystal according to <1>, wherein the nitrogen content of the silicon carbide powder is 50 ppm by mass or less.
<3> A method for producing a silicon carbide single crystal, wherein a silicon carbide single crystal having a nitrogen content of 0.1 mass ppm or less is sublimated and then recrystallized to grow a silicon carbide single crystal.
<4> The method for producing a silicon carbide single crystal according to any one of <1> to <3>, wherein the silicon carbide powder is obtained by firing a mixture containing at least a silicon source and a xylene-based resin.
<5> The method for producing a silicon carbide single crystal according to <4>, wherein the silicon source is an alkoxysilane compound.
<6> The method for producing a silicon carbide single crystal according to <4> or <5>, wherein the mixture is obtained by adding an acid to a silicon source and then adding a xylene-based resin.
<7> The silicon carbide according to any one of <4> to <6>, wherein a ratio of carbon contained in the xylene-based resin to silicon contained in the silicon source is 1.8 or less during firing. This is a method for producing a single crystal.
<8> The method for producing a silicon carbide single crystal according to any one of <1> to <7>, wherein the volume average diameter of the silicon carbide powder is 50 to 400 μm.
<9> The method for producing a silicon carbide single crystal according to any one of <1> to <8>, wherein the silicon carbide powder contains 30% by mass or less of silicon carbide powder whose crystal polymorph is a beta type (3C). It is.
<10> The method for producing a silicon carbide single crystal according to any one of <1> to <9>, 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.
<11> The method for producing a silicon carbide single crystal according to any one of <1> to <10>, wherein a silicon carbide crystal including the silicon carbide single crystal is grown in a substantially chevron shape.
<12> The method for producing a silicon carbide single crystal according to any one of <1> to <11>, wherein the silicon carbide crystal including the silicon carbide single crystal is composed only of the silicon carbide single crystal.
<13> A silicon carbide powder 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 silicon carbide powder 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.
<14> The silicon carbide powder is accommodated on one end side in the reaction vessel, and a silicon carbide single crystal seed 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 silicon carbide powder can be sublimated,
The second heating means arranged on the other end side forms a recrystallization atmosphere so that the silicon carbide 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 <13>, wherein the silicon carbide is recrystallized on a seed crystal of the silicon carbide single crystal.
<15> The method for producing a silicon carbide single crystal according to <14>, wherein the first heating unit and the second heating unit are coils capable of induction heating.
<16> The method for producing a silicon carbide single crystal according to <15>, 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.
<17> The silicon carbide according to <15> or <16>, 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.
<18> The temperature on one end side containing the silicon carbide powder 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 <14> to <17>, wherein is increased continuously or stepwise.
<19> A silicon carbide single crystal produced by the method for producing a silicon carbide single crystal according to any one of <1> to <18>.
<20> Non-destructive optical image detection of hollow pipe-like crystal defects of 100 / cm ² The silicon carbide single crystal according to <19>, which is the following.
<21> The silicon carbide single crystal according to <19> or <20>, wherein the total content of impurity elements is 10 ppm by mass or less.
<22> Volume resistance value is 1 × 10 ⁷ The silicon carbide single crystal according to any one of <19> to <21>, which is Ω · cm or more.
<23> The silicon carbide single crystal according to any one of <19> to <22>, wherein the nitrogen content is 0.01 mass ppm or less.
[0005]
Examples of means for solving the above-described problems further include the following. That is,
<24> Firing is heated to 1300 to 1600 ° C. at 100 to 1000 ° C./h in a non-oxidizing atmosphere, then heated to 1800 to 2100 ° C. at 50 to 300 ° C./h, and then 1800 to 2100 ° C. The method for producing a silicon carbide single crystal according to any one of <4> to <18>, wherein the method is carried out by holding within 240 minutes.
<25> The silicon carbide single crystal according to any one of <4> to <18> and <24>, wherein 1 to 5% by volume of halogen or hydrogen halide is added to the silicon source and the carbon source during firing. It is a manufacturing method.
<26> The method for producing a silicon carbide single crystal according to any one of <4> to <18> and <23> to <25>, wherein post-treatment by heating is performed after firing.
<27> The method for producing a silicon carbide single crystal according to <26>, wherein the post-treatment is performed at 2150 to 2400 ° C.
<28> The method for producing a silicon carbide single crystal according to <26> or <27>, wherein the post-treatment is performed in an argon atmosphere for 3 to 8 hours.
<29> Volume average particle diameter of silicon carbide powder (D ₅₀ ) Is 0.5 to 800 μm. The method for producing a silicon carbide single crystal according to any one of <1> to <18> and <23> to <28>.
<30> Particle size distribution of silicon carbide powder (D ₉₀ / D ₁₀ ) Is 4 or less. The method for producing a silicon carbide single crystal according to any one of <1> to <18> and <23> to <29>.
<31> In the reaction vessel, the temperature of the recrystallization atmosphere is 30 to 300 ° C. lower than the temperature of the sublimation atmosphere, and the silicon carbide single unit according to any one of <12> to <18> and <23> to <30> It is a manufacturing method of a crystal.
<32> The method for producing a silicon carbide single crystal according to any one of <12> to <18> and <23> to <31>, wherein the reaction vessel is a crucible disposed in a quartz tube.
<33> The surface of the other end portion adjacent to the peripheral side surface portion in the reaction vessel is glassy carbon according to any one of the items <12> to <18> and <23> to <32>. This is a method for producing a silicon carbide single crystal.
<34> 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 <12> to <18> and <23> to <33>, wherein interference preventing means for preventing is arranged.
<35> The method for producing a silicon carbide single crystal according to <34>, wherein the interference prevention unit is a coil capable of circulating cooling water.
<36> The method for producing a silicon carbide single crystal according to any one of <12> to <18> and <23> to <35>, wherein one end is a lower end and the other end is an upper end. .
<37> 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 inside the reaction vessel and the other end is exposed outside the reaction vessel. The method for producing a silicon carbide single crystal according to any one of <23> to <36>.
[0006]
The method for producing a silicon carbide single crystal according to <1> includes sublimating a silicon carbide powder having a nitrogen content of 100 mass ppm or less and each impurity element content of 0.1 mass ppm or less. Since the silicon carbide single crystal is grown by recrystallization from the above, the nitrogen content in the recrystallized silicon carbide single crystal is low. For this reason, the manufactured silicon carbide single crystal is suitable as a semi-insulating or insulating single crystal substrate.
[0007]
In the method for producing a silicon carbide single crystal according to <2>, since the nitrogen content of the silicon carbide powder is 50 mass ppm or less in <1>, nitrogen in the silicon carbide single crystal to be recrystallized Very low content. For this reason, the manufactured silicon carbide single crystal is particularly suitable as a semi-insulating or insulating single crystal substrate.
[0008]
In the method for producing a silicon carbide single crystal according to the above <3>, the silicon carbide single crystal having a nitrogen content of 0.1 mass ppm or less is sublimated and then recrystallized to grow the silicon carbide single crystal. The nitrogen content in the crystallized silicon carbide single crystal is very low. For this reason, the manufactured silicon carbide single crystal is particularly suitable as a semi-insulating or insulating single crystal substrate.
[0009]
In the method for producing a silicon carbide single crystal according to <4>, in any one of <1> to <3>, the silicon carbide powder is obtained by firing a mixture containing at least a silicon source and a xylene-based resin. Since the silicon carbide powder has a low nitrogen content, the nitrogen content in the produced silicon carbide single crystal is low. For this reason, the manufactured silicon carbide single crystal is particularly suitable as a semi-insulating or insulating single crystal substrate.
[0010]
In the method for producing a silicon carbide single crystal according to <5>, in the <4>, the silicon source is a tetraalkoxysilane polymer. For this reason, the silicon carbide powder can be easily obtained at low cost.
[0011]
The method for producing a silicon carbide single crystal according to <6> is obtained by adding a xylene-based resin after adding an acid to a silicon source in the above <4> or <5>. For this reason, the said mixture of a uniform state is obtained very easily, and a silicon carbide single crystal is manufactured efficiently.
[0012]
In the method for producing a silicon carbide single crystal according to <7>, in any one of <4> to <6>, the carbon contained in the xylene-based resin in the mixture and the silicon contained in the silicon source in firing The ratio is less than or equal to 1.8 and there is little free carbon in the silicon carbide powder, so that a high-quality silicon carbide single crystal can be obtained.
[0013]
In the method for producing a silicon carbide single crystal according to <8>, the volume average diameter of the silicon carbide powder is 50 to 400 μm in any one of <1> to <7>, and is produced by a CVD method or the like. It has a volume average particle size larger than that of silicon carbide powder, is easy to handle, and is excellent in production efficiency of silicon carbide single crystals.
[0014]
In the method for producing a silicon carbide single crystal according to <9>, in any one of <1> to <8>, the silicon carbide powder is a silicon carbide powder whose crystal polymorph is a beta type (3C). Since it contains less than mass%, it has a larger volume average particle size than beta-type silicon carbide powder produced by CVD method, etc., and it is easy to handle due to stable sublimation, producing silicon carbide single crystal Excellent efficiency.
[0015]
In the method for producing a silicon carbide single crystal according to <10>, in the above <1> to <9>, the entire surface of the growth surface of the silicon carbide single crystal is held in a convex shape throughout the entire growth process. Let it grow. Here, the depressed recess is not formed in a ring shape in the direction opposite to the growth direction on 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.
[0016]
In the method for producing a silicon carbide single crystal according to <11>, since the silicon carbide crystal including the silicon carbide single crystal is grown in a substantially chevron shape in <1> to <10>, the silicon carbide single crystal to be grown , There is no depressed recess at all in the direction opposite to the growth 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.
[0017]
In the method for producing a silicon carbide single crystal according to <12>, in any one of the items <1> to <11>, 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.
[0018]
In the method for producing a silicon carbide single crystal according to <13>, the silicon carbide powder is accommodated in a reaction vessel in <1> to <12>, and substantially opposed to the silicon carbide powder 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.
[0019]
In the method for producing a silicon carbide single crystal according to <14>, in any one of <1> to <13>, the silicon carbide powder is accommodated on one end side in the reaction vessel, A seed crystal of the silicon carbide single crystal is disposed on the other end side of the substrate, and a sublimation atmosphere is formed by the first heating means disposed on the one end side so that the silicon carbide powder can be sublimated. The second heating means arranged on the end side forms a recrystallization atmosphere so that the silicon carbide sublimated by the first heating means can be recrystallized only in the vicinity of the seed crystal of the silicon carbide single crystal, Silicon 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 silicon carbide powder 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 free from breakage such as cracks and free from crystal defects such as polycrystals, polymorphs, and micropipes is produced.
[0020]
The method for producing a silicon carbide single crystal according to <15> is the coil according to <14>, wherein the first heating unit and the second heating unit are induction-heatable. For this reason, 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 are easily and reliably performed by induction heating by the coil. To be done.
[0021]
In the method for producing a silicon carbide single crystal according to <16>, in <15>, 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. 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.
[0022]
In the method for producing a silicon carbide single crystal according to <17>, in <15> or <16>, the current value of the induction heating current in the second heating unit is set so that the diameter of the growing silicon carbide single crystal is large. As it becomes, 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
[0023]
In the method for producing a silicon carbide single crystal according to <18>, in any one of <14> to <17>, the temperature on one end side containing the silicon carbide powder 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 If the silicon carbide single crystal continues to grow toward the one end portion over time, the crystal growth tip side of the silicon carbide single crystal is always prone to recrystallization. Maintained. On the other hand, T ₃ -T ₂ When the silicon carbide single crystal grows continuously or stepwise, 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.
[0024]
The silicon carbide single crystal according to <19> is manufactured by the method for manufacturing a silicon carbide single crystal according to any one of <1> to <18>. For this reason, the silicon carbide single crystal obtained has a low nitrogen content and is particularly suitable as a semi-insulating or insulating single crystal substrate.
[0025]
The silicon carbide single crystal according to <20> has 100 hollow crystal defects / cm in non-destructive optical image detection in the above <19>. 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. .
[0026]
The silicon carbide single crystal according to <21> has a total content of the impurity elements of 10 mass ppm or less in the <19> or <20>. For this reason, the silicon carbide single crystal has an extremely high quality.
[0027]
The silicon carbide single crystal according to <22> has a volume resistance value of 1 × 10 in any one of <19> to <21>. ⁷ Ω · cm or more. For this reason, the silicon carbide single crystal is a semi-insulator or insulator.
[0028]
The silicon carbide single crystal according to <23> has a nitrogen content of 0.01 mass ppm or less in any one of the above items <19> to <22>. The nitrogen content is very low. For this reason, the manufactured silicon carbide single crystal is particularly suitable as a semi-insulating or insulating single crystal substrate.
[0029]
In the method for producing a silicon carbide single crystal according to <24>, in any one of <4> to <18>, the firing is performed in a non-oxidizing atmosphere at 100 to 1000 ° C./h to 1300 to 1600 ° C. The temperature is raised, and then the temperature is raised to 1800 to 2100 ° C. at 50 to 300 ° C./h, and then maintained at 1800 to 2100 ° C. within 240 minutes. For this reason, a silicon carbide single crystal is efficiently manufactured.
[0030]
In the method for producing a silicon carbide single crystal according to <25>, in any one of <4> to <18> and <24>, halogen or hydrogen halide 1 is used for the silicon source and the carbon source during firing. ~ 5% by volume is added. For this reason, in the obtained silicon carbide single crystal, the amount of the impurity element is effectively suppressed to be low.
[0031]
In the method for producing a silicon carbide single crystal according to <26>, in any of the above <4> to <18> and <23> to <25>, post-treatment by heating is performed after firing. For this reason, the impurity element is removed, and a high-purity and high-quality silicon carbide single crystal is efficiently produced.
[0032]
In the method for producing a silicon carbide single crystal according to <27>, since the post-treatment is performed at 2150 to 2400 ° C. in <26>, the impurity element is removed, and the silicon carbide single crystal has high purity and high quality. Is efficiently manufactured.
[0033]
In the method for producing a silicon carbide single crystal according to <28>, the post-treatment in <26> or <27> is performed in an argon atmosphere for 3 to 8 hours. A quality silicon carbide single crystal is efficiently produced.
[0034]
The method for producing a silicon carbide single crystal according to <29> is the volume average particle diameter (D) of the silicon carbide powder in any one of the items <1> to <18> and <23> to <28>. ₅₀ ) Is 100 to 500 μm, the sublimation is efficiently performed, and the silicon carbide single crystal is efficiently manufactured.
[0035]
In the method for producing a silicon carbide single crystal according to <30>, in any one of the items <1> to <18> and <23> to <29>, the particle size distribution (D ₉₀ / D ₁₀ ) Is 4 or less, sublimation is efficiently performed, and a silicon carbide single crystal is efficiently produced.
[0036]
In the method for producing a silicon carbide single crystal according to <31>, in the above <12> to <18> and <23> to <30>, the temperature of the recrystallization atmosphere is the sublimation atmosphere in the reaction vessel. 30-300 ° C. lower than temperature. For this reason, recrystallization is performed easily and smoothly on or near the seed crystal of the silicon carbide single crystal.
[0037]
The method for producing a silicon carbide single crystal according to <32> is a crucible in which the reaction vessel is disposed in a quartz tube in any one of the items <12> to <18> and <23> to <31>. is there. For this reason, since the silicon carbide powder is sublimated and recrystallized and the silicon carbide single crystal is grown in the closed system in the quartz tube, these controls are easy.
[0038]
The method for producing a silicon carbide single crystal according to <33>, in any one of <12> to <18> and <23> to <32>, is the inner peripheral side surface of the reaction vessel at the other end The surface of the part adjacent to the part 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.
[0039]
In the method for producing a silicon carbide single crystal according to <34>, in any one of the items <12> to <18> and <23> to <33>, the first heating unit and the second heating unit In the meantime, an induction current can be applied, and an interference preventing means for preventing interference between the first heating means and the second heating means by supplying the induced current is disposed. 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.
[0040]
In the method for producing a silicon carbide single crystal according to <35>, in the <34>, 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.
[0041]
The method for producing a silicon carbide single crystal according to <36>, in any one of <12> to <18> and <23> to <35>, the one end is a lower end, and the other end Is the upper end. For this reason, the silicon carbide powder is accommodated in the lower part of the reaction vessel, and the silicon carbide powder 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.
[0042]
In the method for producing a silicon carbide single crystal according to <37>, in any one of <12> to <18> and <23> to <36>, a region in which the silicon carbide single crystal is grown; One end of the member that is located on the outer periphery of the region and that is adjacent to the inner peripheral side surface of the reaction vessel is formed of another member and that forms a region where the silicon carbide single crystal is grown. Is exposed inside the reaction vessel and the other end is exposed outside 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.
[0043]
DETAILED DESCRIPTION OF THE INVENTION
(Method for producing silicon carbide single crystal)
In the method for producing a silicon carbide single crystal of the present invention, a silicon carbide single crystal having a nitrogen content of 100 mass ppm or less is sublimated and then recrystallized to grow a silicon carbide single crystal.
[0044]
-Silicon carbide powder-
The silicon carbide powder has a nitrogen content of 100 mass ppm or less and a content of each impurity element of 0.1 mass ppm or less, or a nitrogen content of 0.1 mass ppm or less. Things.
[0045]
The nitrogen content of the silicon carbide powder needs to be 100 mass ppm or less, preferably 50 mass ppm or less, more preferably 40 mass ppm or less, and 0.1 mass ppm or less. Is particularly preferred.
When the nitrogen content is 100 mass ppm or less, 50 mass ppm or less, and 40 mass ppm or less, it is necessary that each content of the impurity element is 0.1 mass ppm or less. Resistive silicon carbide single crystal is obtained, and the silicon carbide single crystal can be suitably used as a semi-insulating or insulating single crystal substrate or the like, while the nitrogen content is 0.1 mass ppm or less Even if each content of the impurity elements is not limited to 0.1 mass ppm or less, a high-resistance silicon carbide single crystal is obtained, and the silicon carbide single crystal is a semi-insulating or insulating single crystal substrate. Etc. can be suitably used.
The nitrogen content can be measured using, for example, an oxygen-nitrogen simultaneous analyzer, a secondary ion mass spectrometer, a glow discharge mass spectrometer, a photoluminescence measuring device, or the like.
[0046]
The content of each impurity element in the silicon carbide powder is preferably 0.3 mass ppm or less, and more preferably 0.1 mass ppm or less.
When each content of the impurity element is 0.3 mass ppm or less, it is necessary that the nitrogen content is 0.1 mass ppm or less. In this case, an extremely high resistance silicon carbide single crystal The silicon carbide single crystal can be suitably used as a semi-insulating or insulating single crystal substrate or the like, and on the other hand, when each content of the impurity element is 0.1 mass ppm or less, Even if the nitrogen content is not more than 0.1 mass ppm, a semi-insulator or insulator silicon carbide single crystal is obtained, and the silicon carbide single crystal is used as a semi-insulator or insulating single crystal substrate or the like. It can be suitably used.
[0047]
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.
[0048]
Volume average particle diameter of the silicon carbide powder (D ₅₀ ) Is preferably 0.5 to 800 μm, more preferably 50 to 400 μm.
The volume average particle diameter (D ₅₀ ) Is 0.5 to 800 μm, it is advantageous in terms of excellent workability in producing a silicon carbide single crystal and good packing at the time of filling, and if it is 50 to 400 μm, it is advantageous in the CVD method or the like. Compared with the fine powder produced, it is advantageous in that the workability is further improved and the packing at the time of filling is further improved.
[0049]
Particle size distribution of the silicon carbide powder (D ₉₀ / D ₁₀ ) (Volume average particle diameter standard) is preferably 4.0 or less, and more preferably 3.5 or less, from the viewpoint of uniformity of the silicon carbide powder.
[0050]
The silicon carbide powder preferably contains 30% by mass or less of β-SiC (the crystal polymorph is “3C”) in terms of stabilization of the sublimation rate (70% by mass of α-SiC). More preferably 10% by mass or less (more preferably 90% by mass of α-SiC).
Whether it is α-SiC or β-SiC can be determined from a matching peak or the like in the ATSM library data.
[0051]
The silicon carbide powder is obtained by firing a mixture containing at least a silicon source and a xylene-based resin.
[0052]
--Silicon source--
Examples of the silicon source include silicon compounds.
The silicon compound may be liquid or solid, and these may be used in combination, but it is preferable to use at least one liquid.
[0053]
As said liquid thing, an alkoxysilane compound etc. are mentioned suitably.
Examples of the alkoxysilane compound include alkoxysilanes, alkoxysilane oligomers, and alkoxysilane polymers.
The alkoxysilane or alkoxysilane unit in the alkoxysilane, the alkoxysilane oligomer, and the alkoxysilane polymer may be any of monoalkoxysilane, dialkoxysilane, trialkoxysilane, and tetraalkoxysilane. Silane is preferred.
[0054]
Examples of the alkoxysilane include methoxysilane, ethoxysilane, propoxysilane, and butoxysilane. Among these, ethoxysilane is preferable in terms of handling.
[0055]
The alkoxysilane oligomer is a low molecular weight polymer having a degree of polymerization of about 2 to 15, and specific examples thereof include methoxysilane oligomer, ethoxysilane oligomer, propoxysilane oligomer, butoxysilane oligomer, etc. An ethoxysilane oligomer is preferable in terms of handling.
[0056]
The alkoxysilane polymer is a high molecular weight polymer having a degree of polymerization exceeding about 15, and specific examples thereof include a methoxysilane polymer, an ethoxysilane polymer, a propoxysilane polymer, a butoxysilane polymer, and the like. From this point, an ethoxysilane polymer is preferable.
[0057]
Examples of the solid material include silicon oxide such as SiO, silica sol (colloidal ultrafine silica-containing liquid, containing OH group or alkoxyl group inside), silicon dioxide (silica gel, fine silica, quartz powder), and the like. .
[0058]
In the present invention, the silicon compound may be used alone or in combination of two or more. Among the silicon compounds, an ethoxysilane oligomer is preferable in terms of good homogeneity and handling properties. , An ethoxysilane polymer, a mixture of an ethoxysilane oligomer and fine powder silica, and the like, and an ethoxysilane dimer, an ethoxysilane polymer, and the like are more preferable.
[0059]
The silicon compound preferably has a high purity, the impurity element is preferably 20 ppm by mass or less, and more preferably 5 ppm by mass or less.
Here, the impurity element belongs to groups 1 to 17 in the periodic table of the 1989 IUPAC inorganic chemical nomenclature revised edition and has an atomic number of 3 or more (except for atomic numbers 6 to 8 and 14). Refers to an element (the same applies hereinafter).
[0060]
-Xylene resin-
The xylene-based resin has a high residual carbon ratio, a small content of the impurity element, and hardly contains nitrogen in the synthesis process. The xylene-based resin is used as a carbon source.
Examples of the xylene-based resin include a xylene homopolymer (hereinafter simply referred to as “xylene polymer”), a xylene copolymer, and the like. From the viewpoint of mixing of the impurity elements, a xylene polymer is preferable. A resol type xylene polymer is more preferable.
The xylene-based resin may be appropriately synthesized or may be a commercially available product.
[0061]
The xylene-based resin may be an oligomer or a polymer, and the degree of polymerization is not particularly limited and can be appropriately selected according to the purpose. For example, in the case of the oligomer The polymerization degree is preferably 3 to 15, and in the case of the polymer, the polymerization degree is preferably 15 to 1200.
The degree of polymerization can be measured by, for example, general gel permeation chromatography, osmotic pressure method, GC-MS and the like.
[0062]
The xylene-based resin preferably has a high purity, the impurity element is preferably 20 ppm by mass or less, and more preferably 5 ppm by mass or less.
[0063]
--Mixture--
The mixture contains the silicon source and the xylene-based resin.
[0064]
The amount ratio between the silicon source and the xylene-based resin in the mixture is not particularly limited and may be appropriately selected depending on the intended purpose. However, the amount of free carbon in the obtained silicon carbide powder decreases. As described above, it is preferable to determine the quantity ratio between the silicon source and the xylene-based resin in advance.
[0065]
The amount of the free carbon is controlled by appropriately adjusting the ratio of carbon contained in the xylene-based resin to silicon contained in the silicon source (hereinafter referred to as “C / Si ratio”) in the mixture. can do.
Here, the C / Si ratio is expressed by the following formula: C / Si = (amount of the xylene-based resin (g) × residual carbon ratio / 12.011) /0.4× (amount of the silicon source (g) (Wherein “amount of xylene-based resin” means the amount of the xylene-based resin contained in the solution when the xylene-based resin is in solution) In the case where the silicon source is a solution, the “amount of silicon source” means the amount of the silicon source contained in the solution.
The C / Si ratio can be measured by elemental analysis of a carbide intermediate obtained by carbonizing the mixture at 1000 ° C.
Stoichiometrically, the free carbon in the silicon carbide powder obtained when the C / Si ratio is 3.0 is 0%, but in practice, the C Even when the / Si ratio is a small value, the free carbon may be generated.
[0066]
The method for preparing the mixture is not particularly limited and may be appropriately selected depending on the intended purpose. However, the method of adding the xylene-based resin after adding an acid to the silicon source is particularly preferable. In this case, it is advantageous in that the silicon source and the xylene-based resin can be mixed uniformly and a phase separation state does not occur.
When a method other than the method of adding the xylene-based resin after adding an acid to the silicon source is adopted as a method of preparing the mixture, the silicon source and the xylene-based resin can be uniformly mixed. In some cases, phase separation may occur. In this case, the mixture in the phase separation state can be made uniform by heating.
[0067]
The mixture is usually prepared without adding a halogen compound. However, when obtaining ultra-high purity silicon carbide powder, 0.5 to 5% by mass of a halogen compound is added to the mixture. May be.
When the halogen compound is added to the mixture, the impurity element mixed in the mixture is halogenated and effectively removed by vaporization and scattering in the next firing, so that an ultra-high purity silicon carbide powder is obtained. It is done. Specifically, the content of each of the impurity elements in the obtained silicon carbide powder can be reduced to 0.1 mass ppm or less by adding the halogen compound.
When the halogen compound is added, the mixture is reacted for 10 to 30 minutes in the vicinity of the decomposition temperature of the added halogen compound, and the temperature is raised to the next firing temperature from the viewpoint of removing the impurity element. preferable.
[0068]
When the mixture is liquid, the halogen compound is preferably added to the mixture with a liquid halogen compound such as ammonium chloride or aqueous hydrochloric acid. When the mixture is solid (as the xylene-based resin, Solid halogen compounds such as halogen-containing polymers such as polyvinyl chloride, chlorinated polyethylene, and polychloroprene are added to the mixture. It is preferable.
[0069]
The mixture may be in a solid state or in a liquid state, but when it is in a liquid state, it may be cured to be in a solid state before the firing.
The curing method is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include a method of crosslinking by heating, a method of curing with a curing catalyst, and a method of electron beam or radiation.
[0070]
The heating is performed at a temperature of about 50 ° C. or more for a time of about 1 hour or more.
The curing catalyst is not particularly limited and may be appropriately selected depending on the purpose. Examples thereof include acids such as toluenesulfonic acid, toluenecarboxylic acid, acetic acid, oxalic acid, hydrochloric acid, and sulfuric acid. Among these, those not containing a nitrogen atom are preferable.
[0071]
The mixture is preferably heated at 500 to 1000 ° C. in a non-oxidizing atmosphere before the firing, and after heating at 500 to 600 ° C. for 10 to 30 minutes in a non-oxidizing atmosphere, the mixture is then non-oxidized. It is more preferable to heat at 800 to 1000 ° C. for 30 minutes to 2 hours in a neutral atmosphere.
There is no restriction | limiting in particular as said non-oxidizing atmosphere, According to the objective, it can select suitably, For example, atmospheres, such as nitrogen and argon, etc. are mentioned, Among these, argon is preferable.
[0072]
--Baking--
The firing is not particularly limited with respect to the method, conditions, and the like, and can be appropriately selected depending on the particle size of the silicon carbide powder to be obtained. From the viewpoint of more efficient production of the silicon carbide powder. The temperature of the mixture was raised to 1300-1600 ° C. at 100 to 1000 ° C./h in a non-oxidizing atmosphere, then raised to 1900 to 2100 ° C. at 50 to 300 ° C./h, and then 1900 to 2100 ° C. It is preferable to carry out by holding within 240 minutes.
[0073]
In addition, the said carbide | carbonized_material is obtained by heating the said mixture at 800-1000 degreeC. At this time, although there is no restriction | limiting in particular as a yield with respect to the said mixture of the said carbide | carbonized_material, it is so preferable that it is high and it is preferable that it is 50 mass% or more.
[0074]
The non-oxidizing atmosphere is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include an atmosphere of an inert gas such as nitrogen or argon, but it is non-reactive even at high temperatures. And an argon atmosphere is preferred.
[0075]
In the firing, the inert gas is preferably introduced into a reaction vessel containing the mixture. In this case, it is advantageous in that the SiO gas, CO gas, and the like containing the impurity element generated during the firing can be discharged or removed out of the reaction vessel.
[0076]
In the firing, 1 to 5% by volume of halogen or hydrogen halide is added to the silicon source and the xylene-based resin to suppress the amount of the impurity element contained in the obtained silicon carbide powder. It is preferable in that
[0077]
The C / Si ratio at the time of firing can vary depending on the pressure at the time of firing, so it cannot be defined unconditionally, but the generation of the free carbon can be effectively suppressed, It is preferably 1.85 or less, and more preferably 1.55 or less.
[0078]
-Other processing-
There is no restriction | limiting in particular as another process, Although it can select suitably according to the objective, For example, the following post-processing etc. are mentioned suitably.
[0079]
The post-treatment is preferably performed at 2000 ° C. or higher after the firing, more preferably performed at 2100 ° C. or higher, and particularly preferably performed at 2150 to 2400 ° C.
There is no restriction | limiting in particular as time of the said post-processing, Although it can select suitably according to the objective, Usually, it is 5 minutes or more, about 3 to 8 hours are preferable, and about 4 to 6 hours are more preferable.
The post-treatment is preferably performed in the non-oxidizing atmosphere, and among the non-oxidizing atmospheres, an argon atmosphere is preferable in that it is non-reactive even at high temperatures.
The post-treatment is advantageous in that the impurity element is removed, high purity, large particle size, narrow particle size distribution, and high quality silicon carbide powder can be obtained.
[0080]
There is no restriction | limiting in particular about the apparatus etc. which are used for manufacture of the said silicon carbide powder, According to the objective, it can select suitably.
The production of the silicon carbide powder may be performed in a continuous processing mode or a batch processing mode. Moreover, the said baking and the said post-processing may be performed by continuous processing in one heating furnace, and may be performed by batch processing in a separate heating furnace.
[0081]
The silicon carbide powder is as described above. In the present invention, instead of the silicon carbide powder, a mixture of the silicon carbide powder and a sintered body of the silicon carbide powder, or the silicon carbide A powdered sintered body may be used.
[0082]
Sublimation and recrystallization of the silicon carbide powder can be performed in a reaction vessel.
The reaction vessel is not particularly limited and may be appropriately selected depending on the intended purpose. However, the silicon carbide powder can be accommodated therein, and the silicon carbide single-piece can be provided at a position substantially opposite to the silicon carbide powder. 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.
[0083]
Although there is no restriction | limiting in particular as a site | part in which the said silicon carbide powder 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 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 are present inside the reaction vessel, the silicon carbide powder 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 “silicon carbide powder containing 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 (silicon carbide powder 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.
[0084]
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).
As such a reaction container, for example, a container main body that can store silicon carbide powder, and the carbonization powder 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 substantially at the center of the surface facing the silicon powder.
[0085]
The positional relationship between the one end portion (silicon carbide powder containing portion) and the other end portion (seed crystal placement portion) is not particularly limited and may be appropriately selected depending on the purpose. A mode in which the silicon powder accommodating portion is a lower end portion and the other end portion (seed crystal arranging portion) is an upper end portion, that is, the one end portion (silicon carbide powder accommodating portion) and the other end portion (seed crystal arranging portion). Are preferably located in the direction of gravity. In this case, the silicon carbide powder is preferably sublimated smoothly, 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.
[0086]
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 silicon carbide powder efficiently, for example in the said one end part (silicon carbide powder 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.
[0087]
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.
[0088]
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 in that polycrystals and polymorphs due to the generation of impurities are few, and the sublimation and recrystallization of the silicon carbide powder are easy to control.
[0089]
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.
[0090]
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.
[0091]
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.
[0092]
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.
[0093]
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 (silicon carbide powder containing 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 (silicon carbide powder containing portion), a graphite cover member or the like is further provided to prevent the heat insulating material powder from falling. It is preferable.
[0094]
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 silicon carbide powder 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.
[0095]
-Sublimation-
The sublimation of the silicon carbide powder may be performed using the same heating means as the heating means for performing the heating necessary for performing recrystallization, but the heating means is performed using a separate heating means. This is preferable in terms of precision control, independent control, interference prevention and the like. 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 that allows the silicon carbide powder to be sublimated is the first heating means, and the sublimated silicon carbide is a seed of the silicon carbide single crystal. The heating means for forming the recrystallization atmosphere that allows recrystallization only in the vicinity of the crystal is the second heating means.
[0096]
The first heating means is disposed on one end portion (silicon carbide powder containing portion) side of the reaction vessel, forms a sublimation atmosphere so that the silicon carbide powder can be sublimated, and heats the silicon carbide powder. 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.
[0097]
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.
[0098]
-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.
[0099]
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 silicon carbide powder sublimes, and the sublimated silicon carbide powder 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.
[0100]
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 silicon carbide powder sublimated by the first heating means is near the seed crystal of the silicon carbide single crystal. A recrystallization atmosphere is formed so as to allow recrystallization only, and the silicon carbide powder is recrystallized on the seed crystal of the silicon carbide single crystal.
[0101]
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.
[0102]
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.
[0103]
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 silicon carbide powder is sublimated, and recrystallization is easily performed.
[0104]
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.
[0105]
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.
[0106]
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.
[0107]
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.
[0108]
The pressure of the recrystallization atmosphere formed by the second heating means is preferably 10 to 100 Torr (1330 to 13300 Pa). In the case of this pressure condition, it is preferable that the pressure condition is adjusted so as to be within the predetermined numerical range by heating to the set temperature and then reducing the pressure, not at a low temperature.
The recrystallization atmosphere is preferably an inert gas atmosphere such as argon gas.
[0109]
In the present invention, controlled by the first heating unit, the temperature on the one end (sublimation raw material storage unit) side containing the silicon carbide powder in the reaction vessel, and controlled by the second heating unit, 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 silicon carbide powder 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 at the other end portion adjacent to the inner peripheral side surface of the reaction vessel is T ₃ T ₃ -T ₂ And T ₁ -T ₂ Is preferably controlled to increase continuously or stepwise.
[0110]
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.
[0111]
In the present invention, the silicon carbide single crystal is preferably recrystallized and grown according to the first to third aspects.
[0112]
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.
[0113]
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.
[0114]
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.
[0115]
As the shape of the silicon carbide single crystal to be grown, the entire growth surface is preferably convex in the growth direction side, and the one end (silicon carbide powder containing portion) and the other end (seed crystal arrangement) Part) is preferably convex toward the silicon carbide powder side, that is, toward the one end (silicon carbide powder containing 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.
[0116]
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.
[0117]
Further, the shape of the silicon carbide crystal including the silicon carbide single crystal is preferably a substantially chevron shape toward the silicon carbide powder side, that is, toward 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.
[0118]
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.
[0119]
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.
[0120]
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.
[0121]
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.
[0122]
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.
[0123]
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.
[0124]
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.
[0125]
As described above, according to the method for producing a silicon carbide single crystal of the present invention, silicon carbide having a low nitrogen content, high quality, a semi-insulator or insulator, and suitable as a semi-insulator or insulator single crystal substrate or the like A single crystal can be produced efficiently.
[0126]
(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.
[0127]
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.
[0128]
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.
[0129]
The volume resistivity of the silicon carbide single crystal of the present invention is 1 × 10 ⁰ It is preferably Ω · cm or more, 1 × 10 ³ More preferably Ω · cm or more, 1 × 10 ⁷ It is especially preferable that it is Ω · cm or more.
When the volume resistance value is within the above range, the silicon carbide single crystal is semi-insulating or insulating, which is advantageous in that it is suitable as a semi-insulating or insulating single crystal substrate.
[0130]
The nitrogen content of the silicon carbide single crystal is preferably 0.1 mass ppm or less, and more preferably 0.01 mass ppm or less.
When the nitrogen content is within the numerical range, the silicon carbide single crystal is advantageous in that it is particularly suitable as a semi-insulating or insulating single crystal substrate.
The nitrogen content can be measured using, for example, an oxygen-nitrogen simultaneous analyzer, a secondary ion mass spectrometer, a glow discharge mass spectrometer, a photoluminescence measuring device, or the like.
[0131]
The total content of the impurity elements in the silicon carbide single crystal is preferably 10 mass ppm or less.
[0132]
The silicon carbide single crystal of the present invention has a low nitrogen content, is of high quality, is a semi-insulator or insulator, and can be particularly suitably used as a semi-insulator or insulator single crystal substrate.
[0133]
【Example】
Examples of the present invention will be described below, but the present invention is not limited to these examples.
[0134]
Example 1
A silicon carbide single crystal was manufactured using the silicon carbide single crystal manufacturing apparatus 1 shown in FIG. The silicon carbide single crystal manufacturing apparatus 1 is detachable by screwing to the container body 12 that can contain the silicon carbide powder 40 and the container body 12. 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 silicon carbide powder 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 on the outer periphery of the quartz tube 30 and the portion of the graphite crucible 10 containing the silicon carbide powder 40, 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).
[0135]
The silicon carbide powder 40 was prepared as follows. That is, SiO ₂ After adding 34 g of high-purity maleic acid as a catalyst to 212 g of high-purity tetraethoxysilane having a content of 40% by mass, a 50% by mass high-purity liquid resol-type xylene resin (manufactured by Mitsubishi Gas Chemical Co., Ltd., Nikanol PR- 1440M) When 127 g was mixed, a highly viscous bowl-like mixture was obtained. This cage-like mixture was heat-cured at 70 ° C. to obtain a homogeneous resinous solid. 300 g of this resinous solid was carbonized at 900 ° C. under vacuum for 1 hour to obtain 129 g of carbide (43% yield). In addition, the said C / Si ratio in the said resin-like solid substance is a calculated value, (127g * 0.5 * 0.4 / 12.011) / (0.4 * 212g / 60.0843) = 1.5 The result of elemental analysis was 1.52.
129 g of this carbide is placed in a carbon container, heated to 1600 ° C. at 800 ° C./hour, then heated to 1900 ° C. at 100 ° C./hour, and then held at 1900 ° C. for 2 hours for firing. SiC was obtained. The yield at this time was 35% by mass. Further, this powder was heated to 2350 ° C. in an argon atmosphere and held for 6 hours to obtain a high-purity silicon carbide powder (100% by mass α-SiC). The obtained silicon carbide powder 40 was light green gray. Further, no impurity element exceeding 0.1 mass ppm was detected even when a glow discharge mass spectrometer or the like was used.
[0136]
When the nitrogen content in the silicon carbide powder 40 was measured using an oxygen-nitrogen simultaneous analyzer (manufactured by LECO, TC436), it was less than 40 ppm by mass.
Further, the impurity element in the silicon carbide powder 40 is analyzed by pressure pyrolysis of the silicon carbide powder 40 with a mixed acid containing hydrofluoric acid, nitric acid and sulfuric acid, and then by ICP-mass spectrometry and flameless atomic absorption. As a result, the contents of B, Na, K, Al, Cr, Fe, Ni, Cu, W, Ti, and Ca as the impurity elements were each 0.1 ppm by mass or less.
Further, the volume average particle size (D ₅₀ ) And particle size distribution (D ₉₀ / D ₁₀ ) (Volume average particle size standard) was measured with a particle size distribution measuring device (COULTER LS230), the volume average particle size (D ₅₀ ) Is 300 μm, and the particle size distribution (D ₉₀ / D ₁₀ ) (Volume average particle size standard) was 3.4, which was a distribution of peaks.
[0137]
Next, in the silicon carbide single crystal manufacturing apparatus 1, a current was passed through the first induction heating coil 21 to heat it. The silicon carbide powder 40 was heated with the heat and heated to 2500 ° C., and then the pressure was reduced to 50 Torr (6665 Pa) and maintained in an argon gas atmosphere. Silicon carbide powder 40 was heated to a predetermined temperature (2500 ° C.) and sublimated. The sublimated silicon carbide powder 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 silicon carbide powder 40 side (the temperature of the seed crystal is 2400 ° C.), and the sublimated silicon carbide powder 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.
[0138]
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, a convex shape is maintained toward the silicon carbide powder 40 side in the whole growth process, and a 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.
[0139]
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.
[0140]
When the obtained silicon carbide single crystal 60 was evaluated, there was no mixing of polycrystals or polymorphic crystals, and the crystal defects of the micropipes were 4 / cm2. 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.
[0141]
Further, the obtained silicon carbide single crystal 60 is pressurized and thermally decomposed with a mixed acid containing hydrofluoric acid and nitric acid, and the resulting solution is concentrated 10 times or more to perform ICP-mass spectrometry and flameless atomic absorption analysis. As a result of analysis of the impurity elements, the contents of B, Na, K, Al, Cr, Fe, Ni, Cu, W, Ti, and Ca as the impurity elements are each 15 mass ppb or less. Met.
Further, when the volume resistance value of the obtained silicon carbide single crystal 60 was measured, 4 × 10 ⁷ It was Ω · cm.
In addition, it was 0.01 mass ppm when it measured about the nitrogen content of the obtained silicon carbide single crystal 60 using the photoluminescence measuring device.
[0142]
(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.
[0143]
Example 3
In Example 1, the graphite crucible 10 was changed to the graphite crucible 10 shown in FIG. 5, and the same procedure as in Example 1 was used except that the silicon carbide single crystal manufacturing apparatus 80 shown in FIG. 8 was used. 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.
[0144]
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 of silicon carbide powder 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, as shown in FIG. 6, the silicon carbide single crystal 60 having a convex shape maintained toward the silicon carbide powder 40 side was obtained. 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.
[0145]
(Example 5)
Example 4 was the same as Example 1 except for the following differences. That is, the diameter of the seed crystal 50 of the silicon carbide single crystal is 20 mm and the thickness is 0.5 mm, and the lower part of the graphite crucible 10 (container of the silicon carbide powder 40) is heated to 2349 ° C., and the upper part of the graphite crucible 10 is heated. 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.
[0146]
(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 of the silicon carbide powder 40) and the upper part (arrangement part of the seed crystal 50 of the silicon carbide single crystal in the lid 11) were respectively 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 silicon carbide powder 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.
[0147]
(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. The silicon carbide single crystal 60 in which the entire growth surface was maintained in a convex shape toward the silicon carbide powder 40 side was grown only in the center portion (circular portion having a diameter of 60 mm) that was not performed. 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.
[0148]
(Example 8)
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.
[0149]
Specifically, the first induction heating coil 21 and the second induction heating coil 20 arranged at the outer periphery of the quartz tube 30 and the portion where the lid 11 is located in the graphite crucible 10 are connected to the outer periphery of the quartz tube 30. In the same manner as in Example 1, except that the interference preventing coil 22 was not used in place of the induction heating coil 25 that was spirally wound around the portion where the graphite crucible 10 was located at substantially equal intervals. I made it.
[0150]
In Example 8, as shown in FIG. 9, the entire surface of the lid 11 on the side facing the inside of the container main 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 thermal expansion difference is concentrated and applied from the silicon carbide polycrystal 70 side to the silicon carbide single crystal 60 side, and as shown in FIG. Cracking occurred.
[0151]
(Comparative Example 1)
In Example 1, the silicon carbide powder 40 was produced in the same manner as in Example 1 except that the resol type xylene resin used in the production of the silicon carbide powder 40 was replaced with a resol type phenol resin. The nitrogen content in the obtained silicon carbide powder was 500 mass ppm or more.
When silicon carbide single crystal 60 was produced using this silicon carbide powder 40 and the same evaluation as in Example 1 was performed, the same result as in Example 1 was obtained. However, the volume resistance value of the silicon carbide single crystal 60 was 0.02 Ω · cm, and the nitrogen content was 160 mass ppm.
[0152]
【Effect of the invention】
According to the present invention, the content of the impurity element is small and the content of an element such as nitrogen that is not the impurity element is small, and the semiconductor element can be used as a semi-insulator or insulator. It is possible to provide a silicon carbide single crystal that can be suitably used as a method, and a method for producing a silicon carbide single crystal that can efficiently produce the silicon carbide single crystal.
[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 the method for manufacturing a silicon carbide single crystal of the present invention.
FIG. 9 is a schematic view of a silicon carbide single crystal produced by the method for producing a silicon carbide single crystal of the present invention.
[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 Silicon carbide powder
50 Seed crystal of silicon carbide single crystal
60 Silicon carbide single crystal
70 Polycrystalline silicon carbide
71 recess
80 Silicon carbide single crystal manufacturing equipment

Claims (3)

  A silicon carbide single crystal is grown by sublimating a silicon carbide powder having a nitrogen content of 100 mass ppm or less and each impurity element content of 0.1 mass ppm or less and then recrystallizing. A method for producing a silicon carbide single crystal.   The method for producing a silicon carbide single crystal according to claim 1, wherein the silicon carbide powder has a nitrogen content of 50 mass ppm or less.   A method for producing a silicon carbide single crystal, wherein a silicon carbide single crystal having a nitrogen content of 0.1 mass ppm or less is sublimated and then recrystallized to grow a silicon carbide single crystal.

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