JP2018118866A - Silicon carbide powders - Google Patents
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- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 title claims abstract description 98
- 239000000843 powder Substances 0.000 title claims abstract description 49
- 229910010271 silicon carbide Inorganic materials 0.000 title claims abstract description 39
- 238000000859 sublimation Methods 0.000 claims abstract description 33
- 230000008022 sublimation Effects 0.000 claims abstract description 33
- 239000002994 raw material Substances 0.000 claims abstract description 30
- 239000002245 particle Substances 0.000 claims abstract description 23
- 239000013078 crystal Substances 0.000 claims abstract description 21
- 238000001953 recrystallisation Methods 0.000 claims abstract description 15
- 238000000034 method Methods 0.000 claims description 32
- 238000010438 heat treatment Methods 0.000 description 14
- 238000010298 pulverizing process Methods 0.000 description 13
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 12
- 238000010304 firing Methods 0.000 description 12
- 238000002156 mixing Methods 0.000 description 11
- 238000011049 filling Methods 0.000 description 10
- 230000005484 gravity Effects 0.000 description 8
- 238000004519 manufacturing process Methods 0.000 description 8
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 6
- 229910052799 carbon Inorganic materials 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 4
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 4
- 239000012298 atmosphere Substances 0.000 description 4
- 229910002804 graphite Inorganic materials 0.000 description 4
- 239000010439 graphite Substances 0.000 description 4
- 230000009257 reactivity Effects 0.000 description 4
- 229910052710 silicon Inorganic materials 0.000 description 4
- 239000010703 silicon Substances 0.000 description 4
- 239000003575 carbonaceous material Substances 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- 239000007789 gas Substances 0.000 description 3
- 238000010008 shearing Methods 0.000 description 3
- 229910003481 amorphous carbon Inorganic materials 0.000 description 2
- 229910052786 argon Inorganic materials 0.000 description 2
- 239000006229 carbon black Substances 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 239000006185 dispersion Substances 0.000 description 2
- 239000011261 inert gas Substances 0.000 description 2
- 230000000007 visual effect Effects 0.000 description 2
- 229910004298 SiO 2 Inorganic materials 0.000 description 1
- 239000012300 argon atmosphere Substances 0.000 description 1
- 229910021383 artificial graphite Inorganic materials 0.000 description 1
- 238000003763 carbonization Methods 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 239000000571 coke Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 229910002026 crystalline silica Inorganic materials 0.000 description 1
- 238000010332 dry classification Methods 0.000 description 1
- 238000007580 dry-mixing Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000005684 electric field Effects 0.000 description 1
- 238000005485 electric heating Methods 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 239000011812 mixed powder Substances 0.000 description 1
- 229910021421 monocrystalline silicon Inorganic materials 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 229910021382 natural graphite Inorganic materials 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 230000000452 restraining effect Effects 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 229910021487 silica fume Inorganic materials 0.000 description 1
- 239000000741 silica gel Substances 0.000 description 1
- 229910002027 silica gel Inorganic materials 0.000 description 1
- 235000012239 silicon dioxide Nutrition 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 238000003746 solid phase reaction Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
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Abstract
Description
本発明は、昇華再結晶法（改良レーリー法）で炭化珪素の単結晶を製造する際の原料となる炭化珪素粉末に関する。 The present invention relates to a silicon carbide powder as a raw material for producing a silicon carbide single crystal by a sublimation recrystallization method (an improved Rayleigh method).
炭化珪素粉末は、その高硬度性、高熱伝導性、高温耐熱性から、成形砥石、セラミックス部品等の材料として使用されている。また、炭化珪素の単結晶は、シリコンと比較すると、バンドギャップは約３倍、絶縁破壊電界強度は約１０倍という物性を有するので、シリコンに代わるパワー半導体用基盤の材料として注目されている。 Silicon carbide powder is used as a material for molding wheels, ceramic parts and the like because of its high hardness, high thermal conductivity, and high temperature heat resistance. In addition, silicon carbide single crystal is attracting attention as a power semiconductor substrate material that replaces silicon because it has a physical property of about three times the band gap and about ten times the dielectric breakdown electric field strength compared to silicon.
炭化珪素単結晶の製造方法として、原料である炭化珪素粉末を２０００℃以上の高温条件下において昇華させ、炭化珪素を単結晶成長させる昇華再結晶法がよく知られており、工業的に広く使用されている。この昇華再結晶法における原料で炭化珪素粉末に関して、様々な工夫がなされている。 As a method for producing a silicon carbide single crystal, a sublimation recrystallization method in which silicon carbide powder as a raw material is sublimated under a high temperature condition of 2000 ° C. or higher to grow a single crystal of silicon carbide is well known and widely used industrially. Has been. Various ideas have been made regarding silicon carbide powder as a raw material in the sublimation recrystallization method.
例えば、特許文献１には、炭化珪素粉末の全量中、目開き寸法Ａと目開き寸法Ｂ（ただし、ＡはＢよりも小さな値である。）の間の粒度を有する粉末の割合が、８０体積％以上であり、かつ、上記目開き寸法Ｂが、上記目開き寸法Ａの５倍以下であることを特徴とする炭化珪素粉末が開示されている。 For example, in Patent Document 1, in the total amount of silicon carbide powder, the proportion of powder having a particle size between an aperture size A and an aperture size B (where A is a value smaller than B) is 80%. There is disclosed a silicon carbide powder which is not less than volume% and has an opening size B of 5 times or less than the opening size A.
上記特許文献１は、炭化珪素粉末の粒度を調整することにより、昇華再結晶法の原料として用いた場合に、昇華速度の大きい炭化珪素粉末を提供する技術を開示しているが、炭化珪素粉末の形状については検討されていない。 Patent Document 1 discloses a technique for providing a silicon carbide powder having a high sublimation speed when used as a raw material for a sublimation recrystallization method by adjusting the particle size of the silicon carbide powder. The shape of is not studied.
したがって、本発明の目的は、炭化珪素粉末の形状を調整することにより、昇華再結晶法の原料として用いた場合に、昇華速度がより大きい炭化珪素粉末を提供することにある。 Accordingly, an object of the present invention is to provide a silicon carbide powder having a higher sublimation rate when used as a raw material for the sublimation recrystallization method by adjusting the shape of the silicon carbide powder.
上記目的を達成するため、本発明の炭化珪素粉末は、昇華再結晶法により炭化珪素の単結晶を製造する際の原料として用いられる炭化珪素粉末において、長軸径／短軸径の比が５以下であり、短軸径／厚さの比が２以上である板状粉末を４〜２６％含有し、前記炭化珪素粉末の粒度範囲をｄ〜ｄ×α（μm）としたとき、α≦６であることを特徴とする。 In order to achieve the above object, the silicon carbide powder according to the present invention is a silicon carbide powder used as a raw material for producing a silicon carbide single crystal by a sublimation recrystallization method. 4 to 26% of a plate-like powder having a minor axis diameter / thickness ratio of 2 or more, and when the particle size range of the silicon carbide powder is d to d × α (μm), α ≦ It is 6, It is characterized by the above-mentioned.
本発明の炭化珪素粉末によれば、板状粒子を特定の割合で含有することにより、昇華再結晶法により炭化珪素の単結晶を製造する際、黒鉛るつぼに充填するときの充填量のばらつきを抑制しつつ、粉末どうしの間隙を増やすことができる。また、炭化珪素粉末の粒度範囲をｄ〜ｄ×α（μm）としたとき、α≦６であることにより、粉末どうしの間隙をより効果的に増やすことができる。このため、昇華速度を向上させることができる。 According to the silicon carbide powder of the present invention, when a single crystal of silicon carbide is produced by a sublimation recrystallization method by containing plate-like particles at a specific ratio, variation in filling amount when filling a graphite crucible is achieved. The gap between the powders can be increased while suppressing. Further, when the particle size range of the silicon carbide powder is d to d × α (μm), the gap between the powders can be more effectively increased by α ≦ 6. For this reason, the sublimation speed can be improved.
以下、本発明の実施形態を挙げて、本発明について更に詳細に説明する。 Hereinafter, the present invention will be described in more detail with reference to embodiments of the present invention.
まず、炭化珪素粉末の製造方法について説明する。ここでは、固相反応を利用した方法について説明するが、液相反応などを利用した方法であってもよい。 First, a method for producing silicon carbide powder will be described. Although a method using a solid phase reaction will be described here, a method using a liquid phase reaction or the like may be used.
本発明の炭化珪素粉末の製造方法は、無機珪酸質原料と炭素質原料とを混合して焼成することにより、炭化珪素からなる塊状物を形成する焼成工程と、前記焼成工程で得られた炭化珪素からなる塊状物を衝撃式粉砕機によって粉砕して第１炭化珪素粉末を得る第１粉砕工程と、前記第１炭化珪素粉末を剪断式粉砕機によって粉砕して第２炭化珪素粉末を得る第２粉砕工程と、前記第１炭化珪素粉末と前記第２炭化珪素粉末とを混合して、長軸径／短軸径の比が５以下であり、短軸径／厚さの比が２以上である板状粉末を４〜２６％含有する炭化珪素粉末を得る混合工程とを含む。 The method for producing silicon carbide powder according to the present invention includes a firing step of forming a lump of silicon carbide by mixing and firing an inorganic siliceous material and a carbonaceous material, and a carbonization obtained in the firing step. A first pulverizing step of pulverizing a lump of silicon with an impact pulverizer to obtain a first silicon carbide powder; and 2 pulverizing step, mixing the first silicon carbide powder and the second silicon carbide powder, the ratio of major axis diameter / minor axis diameter is 5 or less, and the ratio of minor axis diameter / thickness is 2 or more. And a mixing step of obtaining silicon carbide powder containing 4 to 26% of the plate-like powder.
ここで、本発明における板状粉末の定義について、図１を参照して説明する。例えば図１に示すような形状の粉末（ただしこのような形状には限られない）において、投影面積が最も広くなる方向（この例では扁平な平面に対して垂直な方向）Ａから見て、外径が最も長くなる方向（この例では対角線方向）を長軸方向Ｌとし、その方向でのサイズを長軸径とする。また、上記方向Ａから見て、外径が最も短くなる方向（この例では短辺方向）を短軸方向Ｓとし、その方向でのサイズを短軸径とする。そして、長軸方向Ｌ及び短軸方向Ｓに対して直交する方向Ｔにおける最大サイズを厚さとする。そうした場合に、長軸径／短軸径の比が５以下であり、短軸径／厚さの比が２以上であるような粉末を、本発明では板状粉末と定義する。 Here, the definition of the plate-like powder in the present invention will be described with reference to FIG. For example, in a powder having a shape as shown in FIG. 1 (but not limited to such a shape), when viewed from the direction A in which the projected area is the largest (in this example, the direction perpendicular to the flat plane) A, The direction in which the outer diameter is the longest (in this example, the diagonal direction) is the major axis direction L, and the size in that direction is the major axis diameter. In addition, the direction in which the outer diameter becomes the shortest when viewed from the direction A (the short side direction in this example) is the short axis direction S, and the size in that direction is the short axis diameter. And let the maximum size in the direction T orthogonal to the major axis direction L and the minor axis direction S be thickness. In such a case, a powder having a major axis / minor axis ratio of 5 or less and a minor axis / thickness ratio of 2 or more is defined as a plate-like powder in the present invention.
無機珪酸質原料としては、珪石などの結晶質シリカ、シリカフューム、シリカゲル等の非晶質シリカが挙げられる。これらは１種を単独で又は２種以上を組み合わせて使用してもよい。無機珪酸質原料の平均粒径は、焼成時の環境、原料の状態（結晶質、非晶質）、炭素質原料との反応性などによって、適宜選ばれる。ただし、焼成時の反応性が良く、炉の制御が容易となるので、無機珪酸質原料としては、非晶質シリカを用いることが好ましい。 Examples of the inorganic siliceous raw material include crystalline silica such as silica, amorphous silica such as silica fume and silica gel. These may be used alone or in combination of two or more. The average particle size of the inorganic siliceous material is appropriately selected depending on the environment during firing, the state of the material (crystalline or amorphous), the reactivity with the carbonaceous material, and the like. However, it is preferable to use amorphous silica as the inorganic siliceous raw material because the reactivity during firing is good and the furnace is easily controlled.
炭素質原料としては、例えば、天然黒鉛、人工黒鉛等の結晶性カーボン、カーボンブラック、コークス、活性炭等の非晶質カーボンが挙げられる。これらは１種を単独で又は２種以上を組み合わせて使用してもよい。炭素質原料の平均粒径は、焼成時の環境、原料の状態（結晶質、非晶質）、及び炭素質材料との反応性などによって、適宜選ばれる。 Examples of the carbonaceous raw material include crystalline carbon such as natural graphite and artificial graphite, and amorphous carbon such as carbon black, coke and activated carbon. These may be used alone or in combination of two or more. The average particle diameter of the carbonaceous raw material is appropriately selected depending on the environment during firing, the state of the raw material (crystalline or amorphous), the reactivity with the carbonaceous material, and the like.
無機珪酸質原料と炭素質原料とを混合して、炭化珪素粉末用の原料を調整する。この際の混合方法は任意であり、湿式混合、乾式混合の何れであってもよい。混合の際の炭素質原料と無機珪酸質原料の混合モル比（Ｃ／Ｓｉ）は、焼成時の環境、炭化珪素粉末用原料の粒径、反応性などを考慮して、最適なものを選択する。ここでいう「最適」とは、焼成によって得られる炭化珪素の収量を向上させ、且つ、無機珪酸質原料及び炭素質原料の未反応の残存量を小さくさせることを意味する。 An inorganic siliceous raw material and a carbonaceous raw material are mixed to prepare a raw material for silicon carbide powder. The mixing method at this time is arbitrary, and may be either wet mixing or dry mixing. The mixing molar ratio (C / Si) of the carbonaceous raw material and inorganic siliceous raw material during mixing is selected in consideration of the environment during firing, the particle size of the silicon carbide powder raw material, reactivity, etc. To do. The term “optimum” as used herein means improving the yield of silicon carbide obtained by firing and reducing the unreacted residual amount of the inorganic siliceous raw material and carbonaceous raw material.
得られた混合粉末（炭化珪素製造用の原料）を２２００℃以上、好ましくは２５００℃以上で焼成して、塊状の炭化珪素を得る。 The obtained mixed powder (raw material for silicon carbide production) is fired at 2200 ° C. or higher, preferably 2500 ° C. or higher to obtain bulk silicon carbide.
焼成方法は、特に限定されないが、外部加熱による方法、通電加熱による方法等が挙げられる。外部加熱の方法としては、例えば、流動層炉、バッチ式の炉などを用いる方法が挙げられる。通電加熱による方法としては、例えば、アチソン炉を用いる方法が挙げられる。本発明においては、板状結晶が得られやすいことから、アチソン炉を用いて焼成を行うことが好ましい。 The firing method is not particularly limited, and examples thereof include a method using external heating and a method using current heating. Examples of the external heating method include a method using a fluidized bed furnace, a batch type furnace, and the like. Examples of the method using electric heating include a method using an Atchison furnace. In the present invention, since it is easy to obtain plate crystals, it is preferable to perform firing using an Atchison furnace.
焼成雰囲気は、還元雰囲気であることが好ましい。還元性が弱い雰囲気下で焼成すると、炭化珪素の収率が低下するためである。 The firing atmosphere is preferably a reducing atmosphere. This is because the yield of silicon carbide is reduced when fired in an atmosphere having low reducing ability.
なお、本明細書中、「アチソン炉」とは、上方が開口した箱型の間接抵抗加熱炉をいう。ここで、間接抵抗加熱とは、被加熱物に電流を直接流すのではなく、電流を流して発熱させた発熱体によって炭化珪素を得るものである。また、このようなアチソン炉の具体的構成の一例は、特開２０１３−１１２５４４号公報に記載されている。 In the present specification, the “Atchison furnace” refers to a box-type indirect resistance heating furnace having an open top. Here, the indirect resistance heating does not directly flow an electric current to an object to be heated, but obtains silicon carbide by a heating element that generates heat by flowing an electric current. An example of a specific configuration of such an Atchison furnace is described in Japanese Patent Laid-Open No. 2013-112544.
このような炉を用いることにより、下記式（１）に示した反応が生じ、炭化珪素（ＳｉＣ）からなる塊状物が得られる。
ＳｉＯ２＋３Ｃ→ＳｉＣ＋２ＣＯ …（１）
By using such a furnace, the reaction shown in the following formula (1) occurs, and a lump made of silicon carbide (SiC) is obtained.
SiO 2 + 3C → SiC + 2CO (1)
アチソン炉の発熱体の種類は、電気を通すことができるものであれば特に限定されるものではなく、例えば、黒鉛粉、カーボンロッド等が挙げられる。 The type of the heating element of the Atchison furnace is not particularly limited as long as it can conduct electricity, and examples thereof include graphite powder and carbon rod.
発熱体を構成する物質の形態は、特に限定されず、例えば、粉状、塊状等が挙げられる。発熱体は、アチソン炉の通電方向の両端に設けられた電極芯を結ぶように全体として棒状の形状になるように設けられる。ここでの棒状の形状とは例えば、円柱状、角柱状等が挙げられる。 The form of the substance constituting the heating element is not particularly limited, and examples thereof include powder and lump. The heating element is provided so as to have a rod-like shape as a whole so as to connect the electrode cores provided at both ends in the energizing direction of the Atchison furnace. Examples of the rod shape here include a columnar shape and a prismatic shape.
通電後、炉内に炭化珪素からなる塊状物が生成する。 After energization, a lump made of silicon carbide is generated in the furnace.
炉内が常温になるまで、アルゴンガス等の不活性ガスを導入して空冷を行う。そして、得られた炭化珪素からなる塊状物（インゴット）を粉砕する。 Air cooling is performed by introducing an inert gas such as argon gas until the temperature inside the furnace reaches room temperature. And the lump (ingot) which consists of obtained silicon carbide is grind | pulverized.
本発明では、上記塊状物の粉砕を、衝撃式粉砕機によって粉砕して第１炭化珪素粉末を得る第１粉砕工程と、第１炭化珪素粉末を剪断式粉砕機によって粉砕して第２炭化珪素粉末を得る第２粉砕工程とで行う。 In the present invention, the lump is pulverized by an impact pulverizer to obtain a first silicon carbide powder, and the first silicon carbide powder is pulverized by a shear pulverizer to obtain a second silicon carbide. And a second pulverization step to obtain a powder.
第１粉砕工程で用いる衝撃式粉砕機としては、例えば、ジョークラッシャー、ボールミル、ハンマーミル等が挙げられるが、ジョークラッシャーにより粗砕し、該粗砕物を所定の粒度になるまでボールミルによって粉砕することが好ましい。このような方法で粉砕することにより、図１を参照して説明した長軸径、短軸径、厚さが近似した形状（板状でない形状）の粉末が得られやすくなる。 Examples of the impact pulverizer used in the first pulverization step include a jaw crusher, a ball mill, a hammer mill, and the like. Is preferred. By pulverizing by such a method, it becomes easy to obtain a powder having a shape (non-plate shape) in which the major axis diameter, minor axis diameter, and thickness described with reference to FIG.
その後、所望の粒度範囲になるように、粉砕物を分級することが好ましい。分級は、篩を用いた方法が最も簡便であり、好ましい。ただし、分級は、篩を用いた方法に限定されず、乾式、湿式の何れでもよい。また、乾式の分級として、気流を用いた例えば遠心式の分級方法を用いることもできる。 Thereafter, it is preferable to classify the pulverized product so as to obtain a desired particle size range. For classification, a method using a sieve is the simplest and preferable. However, classification is not limited to a method using a sieve, and may be either dry or wet. Further, as a dry classification, for example, a centrifugal classification method using an air flow can be used.
上記分級により、第１炭化珪素粉末として、篩の目開き寸法での粒度範囲がａ〜ｂのものを得る。上記粒度範囲ａ〜ｂは、ａ，ｂがいずれも３２〜４０００μｍの範囲にあって、ｂ≦ａ×６となるようにすることが好ましく、ａ×２≦ｂ≦ａ×６となるようにすることがより好ましい。なお、本発明における粒度範囲とは、粉末の８０体積％以上がその粒度範囲に入ることを意味している。 As a result of the classification, the first silicon carbide powder having a particle size range of a to b in the opening size of the sieve is obtained. In the particle size range ab, it is preferable that a and b are in a range of 32 to 4000 μm, and b ≦ a × 6, and a × 2 ≦ b ≦ a × 6. More preferably. The particle size range in the present invention means that 80% by volume or more of the powder falls within the particle size range.
第２粉砕工程で用いる剪断式粉砕機としては、例えば、ディスクミル、ローラーミル、トップグラインダー等が挙げられるが、特にトップグラインダーが好ましい。トップグラインダーを用いる場合、前記第１粉砕工程で得られる第１炭化珪素粉末の篩の目開き寸法での粒度範囲がａ〜ｂであるとき、トップグラインダーのディスクの間隔ＩはＩ＝ａで設定することが好ましい。 Examples of the shearing pulverizer used in the second pulverization step include a disk mill, a roller mill, and a top grinder, and a top grinder is particularly preferable. When a top grinder is used, when the particle size range of the first silicon carbide powder obtained in the first pulverization step is a to b, the interval I between the top grinder disks is set to I = a. It is preferable to do.
第１粉砕工程で得られる第１炭化珪素粉末を、上記のような剪断式粉砕機で粉砕することにより、炭化珪素粉末が所定の方向に剪断されて、前述した定義による板状粉末が形成される。剪断式粉砕機で粉砕された粉末中の板状粉末の割合を更に増加させるため、所定の目開き寸法の篩にかけて、該篩にオンしたものを第２炭化珪素粉末として回収することが好ましい。例えばトップグラインダーを用いて粉砕した場合、上記篩の目開き寸法Ｏは、トップグラインダーのディスクの間隔Ｉに対してＯ＝Ｉとすることが好ましい。 By pulverizing the first silicon carbide powder obtained in the first pulverization step with the above-described shearing type pulverizer, the silicon carbide powder is sheared in a predetermined direction to form a plate-like powder as defined above. The In order to further increase the ratio of the plate-like powder in the powder pulverized by the shearing pulverizer, it is preferable to collect the powder that has been turned on the sieve as a second silicon carbide powder through a sieve having a predetermined mesh size. For example, when pulverizing using a top grinder, the opening size O of the sieve is preferably O = I with respect to the interval I of the disc of the top grinder.
そして、第１粉砕工程で得られた第１炭化珪素粉末と、第２粉砕工程で得られた第２炭化珪素粉末とを所定の割合で混合することにより、前述した定義による板状粉末を４〜２６％、好ましくは７〜２３％含有する炭化珪素粉末を得る。 Then, by mixing the first silicon carbide powder obtained in the first pulverization step and the second silicon carbide powder obtained in the second pulverization step at a predetermined ratio, 4 plate-like powders as defined above are obtained. Silicon carbide powder containing ~ 26%, preferably 7-23% is obtained.
このように板状粉末を含有することにより、昇華再結晶法により炭化珪素単結晶を製造する際、黒鉛等からなるるつぼに充填したとき、板状粉末を含有しない場合に比べて粉末どうしの間隙が多くなり、昇華速度を高めることができる。 When a silicon carbide single crystal is produced by the sublimation recrystallization method by containing a plate-like powder in this way, when the crucible made of graphite or the like is filled, the gap between the powders is smaller than when no plate-like powder is contained. Can increase the sublimation speed.
板状粉末の含有量が、４％未満では、昇華速度を高める効果が十分に得られず、２６％を超えると、るつぼに充填する際の充填量のばらつきが大きくなって、得られる炭化珪素単結晶の品質にばらつきが生じる可能性がある。 When the content of the plate-like powder is less than 4%, the effect of increasing the sublimation rate is not sufficiently obtained. When the content exceeds 26%, the variation in filling amount when filling the crucible becomes large, and the resulting silicon carbide is obtained. There may be variations in the quality of single crystals.
第１炭化珪素粉末と、第２炭化珪素粉末との混合比（体積比）は、１：０．０４〜０．３５が好ましくい。上記のような混合比とすることにより、板状粉末の含有量を本発明で規定する範囲に調整しやすくすることができる。 The mixing ratio (volume ratio) between the first silicon carbide powder and the second silicon carbide powder is preferably 1: 0.04 to 0.35. By setting the mixing ratio as described above, the content of the plate-like powder can be easily adjusted to the range defined in the present invention.
なお、板状粉末の割合（％）は、光学顕微鏡で観察して求めることができる。具体的には、粉末が２０個以上ある視野（倍率含め）を選択し、板状結晶とそれ以外の粒子数を計測する。この様な視野を他にも計測し、合計で５視野以上行って、全体の平均値として板状粉末の割合（％）を求めることができる。 In addition, the ratio (%) of the plate-like powder can be obtained by observing with an optical microscope. Specifically, a field of view (including magnification) having 20 or more powders is selected, and the number of plate crystals and other particles is measured. Such a visual field is also measured, and a total of five or more visual fields is performed, and the ratio (%) of the plate-like powder can be obtained as an overall average value.
こうして得られる本発明の炭化珪素粉末は、その粒度範囲をｄ〜ｄ×αμmとしたとき、α≦６となるようにすることが望ましい。これによって、るつぼに充填したときに粉末どうしの間隙が良好に形成されて昇華速度を高めることができる。ただし、α＜２の場合、商用生産的に収率が落ちるため、２≦α≦６とすることがより好ましい。α＞６では、るつぼへの充填量が増えてしまい、粉末どうしの間隙が少なくなって昇華速度の低下を引き起こす傾向がある。 The silicon carbide powder of the present invention thus obtained preferably has α ≦ 6 when the particle size range is d to d × α μm. As a result, when the crucible is filled, the gap between the powders is well formed and the sublimation rate can be increased. However, in the case of α <2, it is more preferable to satisfy 2 ≦ α ≦ 6 because the yield decreases in commercial production. When α> 6, the amount of filling into the crucible increases, and the gap between the powders tends to decrease, and the sublimation rate tends to decrease.
なお、本発明の炭化珪素粉末を用いて、昇華再結晶法により炭化珪素単結晶を製造する方法は、常法に従って行えばよく、特に限定されないが、概略は下記の通りである。 In addition, the method of manufacturing a silicon carbide single crystal by the sublimation recrystallization method using the silicon carbide powder of the present invention may be performed according to a conventional method, and is not particularly limited, but the outline is as follows.
まず、原料である炭化珪素粉末を例えば黒鉛製のるつぼ内に充填し、このるつぼを加熱装置内に配設する。ただし、炭化珪素粉末が中に充填される容器は、黒鉛製のるつぼに限定されず、昇華再結晶法で単結晶炭化珪素を製造する際に使用されるものであればよい。 First, the raw material silicon carbide powder is filled into a crucible made of graphite, for example, and this crucible is disposed in a heating device. However, the container in which the silicon carbide powder is filled is not limited to a graphite crucible, and any container may be used as long as it is used when producing single crystal silicon carbide by a sublimation recrystallization method.
そして、るつぼをアルゴンガス等の不活性ガス雰囲気とした減圧下で、るつぼ内の原料が２０００〜２５００℃となるように加熱する。ただし、るつぼの蓋の下面の炭化珪素単結晶が成長する部分は、これより１００℃程度温度低くなるようにしておく。 And it heats so that the raw material in a crucible may become 2000-2500 degreeC under pressure reduction which made the crucible inert gas atmosphere, such as argon gas. However, the temperature of the portion where the silicon carbide single crystal grows on the lower surface of the lid of the crucible is about 100 ° C. lower than this.
この加熱を数時間から数十時間持続させる。これにより、原料である炭化珪素粉末が昇華して昇華ガスとなり、蓋の下面に到達して単結晶化し、この単結晶が成長することにより炭化珪素単結晶の塊状物を得ることができる。 This heating is continued for several hours to several tens of hours. Thereby, the silicon carbide powder as a raw material is sublimated to become a sublimation gas, reaches the lower surface of the lid and is single-crystallized, and this single crystal grows, whereby a lump of silicon carbide single crystal can be obtained.
本発明の炭化珪素粉末は、板状粉末を４〜２６％含有するので、るつぼに充填したときに、粉末どうしの間隙を多く形成することができ、炭化珪素の昇華速度を高めることができる。また、るつぼに充填したときの充填量のばらつきが少ないので、一定の品質の炭化珪素単結晶を得ることができる。 Since the silicon carbide powder of the present invention contains 4 to 26% of a plate-like powder, when the crucible is filled, many gaps between the powders can be formed, and the sublimation rate of silicon carbide can be increased. Moreover, since there is little dispersion | variation in the filling amount when it fills with a crucible, the silicon carbide single crystal of fixed quality can be obtained.
以下、試験例により、本発明の実施例を説明する。ただし、本発明はこれらの実施例に限定されない。 Hereinafter, examples of the present invention will be described with reference to test examples. However, the present invention is not limited to these examples.
（試験例１）
下記の方法により、板状粉末の割合が異なる炭化珪素粉末を作成し、るつぼ充填時の比重のばらつきと、昇華再結晶法での昇華速度を求めた。
(Test Example 1)
By the following method, silicon carbide powders having different plate-like powder ratios were prepared, and the variation in specific gravity during crucible filling and the sublimation rate by the sublimation recrystallization method were determined.
［使用原料］
・Ｓｉ源：非晶質シリカ
・Ｃ源：カーボンブラック（アモルファスカーボン）
［炭化ケイ素の製造］
上記原料を、２軸ミキサーを用いて炭素と珪素のモル比（Ｃ／Ｓｉ）が３．０となるように混合して、炭化珪素製造用原料を得た。混合した各原料１０００ｋｇをアチソン炉で焼成した。焼成は、中心温度２５００℃以上で１６時間行った。
[Raw materials]
・ Si source: amorphous silica ・ C source: carbon black (amorphous carbon)
[Production of silicon carbide]
The raw materials were mixed using a biaxial mixer so that the molar ratio of carbon to silicon (C / Si) was 3.0 to obtain a raw material for producing silicon carbide. 1000 kg of each mixed raw material was fired in an Atchison furnace. Firing was performed at a center temperature of 2500 ° C. or more for 16 hours.
［炭化珪素の粉砕・粒度調整］
得られた炭化珪素塊を、ジョークラッシャーで粉砕し、その後、ボールミル粉砕を行った。次いで、篩により分級して、篩の目開き寸法で１２５〜７１０μｍの粒度範囲の第１炭化珪素粉末を得た。
[Silicon carbide grinding and particle size adjustment]
The obtained silicon carbide lump was pulverized with a jaw crusher and then ball milled. Subsequently, it classified with the sieve and obtained the 1st silicon carbide powder of the particle size range of 125-710 micrometers by the opening dimension of a sieve.
上記第１炭化珪素粉末の一部を抜き取り、トップグラインダーを用いてディスク間隔１２５μｍで粉砕し、目開き１２５μｍの篩で分級し、篩上の粉末を第２炭化珪素粉末として回収した。 A part of the first silicon carbide powder was extracted, pulverized with a top grinder at a disc interval of 125 μm, classified with a sieve having an opening of 125 μm, and the powder on the sieve was recovered as a second silicon carbide powder.
次いで、第１炭化珪素粉末と、第２炭化珪素粉末との配合比を変えて２軸ミキサーで混合し、後述する表１のＮｏ．１〜７に示すように、板状粉末の割合が変化した炭化珪素粉末を作成した。なお、板状粉末の割合は、前述した方法で測定した。 Next, the mixing ratio of the first silicon carbide powder and the second silicon carbide powder was changed and mixed with a biaxial mixer. As shown to 1-7, the silicon carbide powder from which the ratio of plate-shaped powder changed was created. In addition, the ratio of plate-shaped powder was measured by the method mentioned above.
［比重のばらつき］
表１のＮｏ．１〜７の炭化珪素粉末を、それぞれカーボンるつぼに充填し、下記の方法にて、比重のばらつきを測定した。
[Specific gravity variation]
No. in Table 1 Each of 1 to 7 silicon carbide powders was filled in a carbon crucible, and the variation in specific gravity was measured by the following method.
すなわち、図２に示すように、カーボンるつぼ１に各炭化珪素粉末２を１００ｇずつ充填した。炭化珪素粉末を充填したるつぼ１をタッピングし、粉末の容積をるつぼ１の内寸から算出して、かさ比重を求めた。それぞれの試料について上記操作を１０回繰り返し、かさ比重の最大値、最小値、平均値を求め、下記計算式（２）からばらつきを算出した。
ばらつき＝｛（最大値―最小値）／平均値｝×１００（％）…（２）
That is, as shown in FIG. 2, the carbon crucible 1 was filled with 100 g of each silicon carbide powder 2. The crucible 1 filled with silicon carbide powder was tapped, and the volume of the powder was calculated from the inner dimensions of the crucible 1 to determine the bulk specific gravity. The above operation was repeated 10 times for each sample, the maximum value, the minimum value, and the average value of bulk specific gravity were obtained, and the variation was calculated from the following calculation formula (2).
Variation = {(maximum value−minimum value) / average value} × 100 (%) (2)
［昇華速度］
るつぼ１に蓋４を被せ（この試験では種結晶をつけない）、アルゴン雰囲気下、０．５ｋＰａの圧力下で、るつぼ１の下部（炭化珪素粉末２の周囲）の温度が２２００℃となり、るつぼ１の上部（析出する単結晶３の周囲）の温度が２０７０℃となるように加熱することにより、るつぼ１中の炭化珪素粉末２を昇華させ、蓋４の下面に炭化珪素単結晶３を析出させた。加熱時間は６時間であった。そして、下記計算式（３）から昇華速度比を求めた。
昇華速度比＝（１００［ｇ］−加熱処理後に残った重量［ｇ］）／６［時間］…（３）
[Sublimation speed]
The crucible 1 is covered with a lid 4 (no seed crystal is attached in this test), and the temperature of the lower part of the crucible 1 (around the silicon carbide powder 2) is 2200 ° C. under a pressure of 0.5 kPa in an argon atmosphere. The silicon carbide powder 2 in the crucible 1 is sublimated by heating so that the temperature of the upper part of 1 (around the deposited single crystal 3) is 2070 ° C., and the silicon carbide single crystal 3 is deposited on the lower surface of the lid 4 I let you. The heating time was 6 hours. And the sublimation speed ratio was calculated | required from the following formula (3).
Sublimation rate ratio = (100 [g] −weight remaining after heat treatment [g]) / 6 [hour] (3)
以上の結果を下記表１に示す。 The above results are shown in Table 1 below.
表１に示されるように、板状粉末の割合が本願発明で規定する範囲である試料Ｎｏ．３〜６は、るつぼ充填時のかさ比重のばらつきを比較的低く抑えつつ、昇華速度比を高めることができる。これに対して、板状粉末の割合が本願発明で規定する範囲よりも少ない試料Ｎｏ．１、２では、昇華速度比が向上しなかった。また、板状粉末の割合が本願発明で規定する範囲よりも多い試料Ｎｏ．７では、るつぼ充填時のかさ比重のばらつきが著しく大きくなることがわかる。 As shown in Table 1, a sample No. in which the ratio of the plate-like powder is within the range specified by the present invention. 3-6 can raise the sublimation speed ratio, restraining the dispersion | variation in the bulk specific gravity at the time of crucible filling comparatively low. On the other hand, Sample No. in which the ratio of the plate-like powder is less than the range specified in the present invention. In 1 and 2, the sublimation rate ratio was not improved. In addition, the sample No. in which the ratio of the plate-like powder is larger than the range specified in the present invention. 7 shows that the variation in bulk specific gravity at the time of filling the crucible becomes remarkably large.
（試験例２）
試験例１における、第１炭化珪素粉末を得るときの篩による分級を、篩の目開き寸法で１２５〜１０００μmの粒度範囲となるように行った他は、試験例１と同様にして、試料Ｎｏ．８の炭化珪素粉末を得た。この粉末について、試験例１と同様に、るつぼ充填時のかさ比重のばらつきと、昇華速度比を測定した。この結果を、試料Ｎｏ．４の結果と並記して下記表２に示す。
(Test Example 2)
Sample No. in the same manner as in Test Example 1 except that the classification with the sieve used to obtain the first silicon carbide powder in Test Example 1 was performed so that the mesh size of the sieve was 125 to 1000 μm. . 8 silicon carbide powder was obtained. About this powder, the variation of the bulk specific gravity at the time of crucible filling and the sublimation rate ratio were measured similarly to Test Example 1. The result is shown in Sample No. The results are shown in Table 2 below.
なお、粒度範囲をｄ〜ｄ×αとすると、試料Ｎｏ．４、８のαは、下記のようになる。 When the particle size range is d to d × α, the sample No. Α of 4 and 8 is as follows.
Ｎｏ．４：α＝５．６８
Ｎｏ．８：α＝８
No. 4: α = 5.68
No. 8: α = 8
表２に示されるように、粒度範囲が大きい試料Ｎｏ．８は、粒度範囲が小さい試料Ｎｏ．４に比べて、昇華速度比が低下する傾向があることがわかる。 As shown in Table 2, Sample No. Sample No. 8 with a small particle size range. It can be seen that the sublimation rate ratio tends to be lower than 4.
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