JP2007261843A

JP2007261843A - Method for manufacturing silicon carbide single crystal

Info

Publication number: JP2007261843A
Application number: JP2006087076A
Authority: JP
Inventors: Kazuhiko Kusunoki; 一彦楠; Kazuto Kamei; 一人亀井; Masanari Yashiro; 将斉矢代; Akihiro Yanai; 昭博八内; Mitsuhiro Hasebe; 光弘長谷部
Original assignee: Sumitomo Metal Industries Ltd
Current assignee: Nippon Steel Corp
Priority date: 2006-03-28
Filing date: 2006-03-28
Publication date: 2007-10-11
Anticipated expiration: 2026-03-28
Also published as: JP4645499B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a high-quality SiC single crystal at a high growth rate. <P>SOLUTION: In the liquid phase growing method for growing an SiC single crystal on a seed crystal substrate by bringing the seed crystal substrate 4 for growing SiC into contact with a melt 6 and rendering SiC dissolved in the melt at least around the seed crystal substrate into a supersaturated state by supercooling the melt, the melt contains (1) Si, C and V or (2) Si, C, V and Ti. The amount of V in the melt satisfies 0.1≤[V]/[Si]+[V]≤0.45, wherein the atomic ratio of V to Si is expressed by [V]/[Si]+[V]. If the melt further contains Ti, the atomic ratio of Ti to Si, expressed by [Ti]/[Si]+[Ti], satisfies 0.1≤[Ti]/[Si]+[Ti]≤0.25. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

本発明は、特に光デバイスおよび電子デバイスの材料として好適な炭化珪素の良質な単結晶の製造方法に関し、特に液相成長法により炭化珪素単結晶を高い成長速度で製造することのできる炭化珪素単結晶の製造方法に関する。 The present invention relates to a method for producing a high-quality single crystal of silicon carbide that is particularly suitable as a material for optical devices and electronic devices, and in particular, a silicon carbide single crystal capable of producing a silicon carbide single crystal at a high growth rate by a liquid phase growth method. The present invention relates to a method for producing a crystal.

炭化珪素（ＳｉＣ）は、熱的および化学的に安定な化合物半導体の１種であって、シリコン（Ｓｉ）に比べ、バンドギャップが約３倍、絶縁破壊電圧が約１０倍、電子飽和速度が約２倍、熱伝導率が約３倍大きいという物性的特徴を有する。このような優れた特徴から、炭化珪素はＳｉデバイスの物性的な限界を打破するパワーデバイスや、高温動作する耐環境デバイスといった電子デバイス材料としての応用が期待されている。 Silicon carbide (SiC) is one of the thermally and chemically stable compound semiconductors. Compared to silicon (Si), the band gap is about 3 times, the breakdown voltage is about 10 times, and the electron saturation rate is about It has the physical characteristics of about twice the thermal conductivity and about three times the thermal conductivity. Due to such excellent features, silicon carbide is expected to be applied as an electronic device material such as a power device that breaks the physical limitations of Si devices and an environment-resistant device that operates at high temperatures.

一方、光デバイスにおいては、短波長化を目指した窒化物系材料（ＧａＮ，ＡｌＮ）の開発が行われている。炭化珪素は窒化物系材料に対する格子不整合が他の化合物半導体材料に比べて格段に小さいので、窒化物系材料のエピタキシャル成長用の基板材料としても注目されている。 On the other hand, for optical devices, development of nitride-based materials (GaN, AlN) aimed at shortening the wavelength has been carried out. Silicon carbide is attracting attention as a substrate material for epitaxial growth of nitride-based materials because lattice mismatch with respect to nitride-based materials is much smaller than that of other compound semiconductor materials.

しかし、ＳｉＣは結晶多形（ポリタイプ）を呈する物質として有名である。結晶多形とは、化学量論的には同じ組成でありながら原子の積層様式がＣ軸方向にのみ異なる多くの結晶構造を取りうる現象である。ＳｉＣの代表的な結晶多形としては、６Ｈ型（６分子を１周期とする六方晶系）４Ｈ型（４分子を１周期とする六方晶系）３Ｃ型（３分子を１周期とする立方晶系）、１５Ｒ型（１５分子を１周期とする菱面晶系）などがある。ある一定の温度でＳｉＣ単結晶を成長させた場合にも２種類以上の結晶多形が発生することがあるが、結晶多形の混在はデバイスへの応用上好ましくない。 However, SiC is famous as a substance exhibiting a crystal polymorph (polytype). Crystal polymorphism is a phenomenon that can take many crystal structures in which the stacking mode of atoms differs only in the C-axis direction while having the same stoichiometric composition. Typical crystal polymorphs of SiC are 6H type (hexagonal system with 6 molecules as one period), 4H type (hexagonal system with 4 molecules as one period), and 3C type (cube with 3 molecules as one period). Crystal system) and 15R type (rhombohedral system with 15 molecules as one period). Even when an SiC single crystal is grown at a certain temperature, two or more types of crystal polymorphs may be generated. However, the mixture of crystal polymorphs is not preferable in terms of application to a device.

炭化珪素を電子または光デバイスに応用するには、結晶多形が単一で、欠陥が皆無または非常に少ないという意味で良質の、バルク（自立）形態または薄膜形態のＳｉＣ単結晶が必要となる。 Application of silicon carbide to electronic or optical devices requires high-quality SiC single crystals in the form of bulk (self-supporting) or thin film in the sense that they have a single crystal polymorphism and no or very few defects. .

従来より知られている炭化珪素の製造方法として、気相成長法に属する昇華再結晶化法および化学気相成長（ＣＶＤ法）と、液相成長法、とが挙げられる。
昇華再結晶化法は、原料の炭化珪素粉末を２２００〜２５００℃の高温で昇華させ、低温部に配置した炭化珪素単結晶からなる種結晶基板上に炭化珪素単結晶を再結晶化させる方法である。昇華再結晶化法では、バルク結晶が得られやすいことから、現在、ＳｉＣ単結晶ウエハーの工業的な生産は昇華再結晶化法で行われている。しかし、昇華法で成長させたＳｉＣ単結晶は、マイクロパイプ欠陥と呼ばれる中空貫通欠陥やらせん転位、積層欠陥、などの結晶欠陥を含んでおり、結晶の品質に問題がある。 Conventionally known methods for producing silicon carbide include a sublimation recrystallization method and chemical vapor deposition (CVD method) belonging to a vapor phase growth method, and a liquid phase growth method.
The sublimation recrystallization method is a method in which a silicon carbide powder as a raw material is sublimated at a high temperature of 2200 to 2500 ° C., and a silicon carbide single crystal is recrystallized on a seed crystal substrate made of a silicon carbide single crystal disposed in a low temperature portion. is there. Since bulk crystals are easily obtained by the sublimation recrystallization method, industrial production of SiC single crystal wafers is currently performed by the sublimation recrystallization method. However, the SiC single crystal grown by the sublimation method has crystal defects such as hollow penetrating defects called micropipe defects, screw dislocations, and stacking faults.

ＣＶＤ法は、原料としてシラン系ガスと炭化水素系ガスとを用い、シリコンまたは炭化珪素単結晶からなる基板上に炭化珪素単結晶をエピタキシャル成長させる方法である。ＣＶＤ法は、成長速度が比較的遅いことから、主として薄膜の炭化珪素結晶の成長に利用されている。薄膜の炭化珪素単結晶は基板の影響を受けるが、主に昇華再結晶化法で作製される基板が上記のように品質に問題があるため、薄膜の高品質化には制約がある。 The CVD method is a method in which a silane-based gas and a hydrocarbon-based gas are used as raw materials, and a silicon carbide single crystal is epitaxially grown on a substrate made of silicon or a silicon carbide single crystal. The CVD method is mainly used for the growth of a thin silicon carbide crystal because the growth rate is relatively slow. Although the thin film silicon carbide single crystal is affected by the substrate, there is a limitation in improving the quality of the thin film because the substrate produced mainly by the sublimation recrystallization method has a problem in quality as described above.

液相成長法は、シリコンまたはシリコン含有合金融液中に炭素を溶解させ、種結晶基板を融液に浸漬し、少なくとも種結晶基板の周囲に融液の過冷却によるＳｉＣ濃度の過飽和状態を創出し、種結晶基板上に炭化珪素単結晶を成長させる方法である。融液は、Ｓｉを溶媒とするＳｉＣの溶液である。 In the liquid phase growth method, carbon is dissolved in silicon or a silicon-containing compound financial solution, the seed crystal substrate is immersed in the melt, and at least around the seed crystal substrate, a supersaturated state of SiC concentration is created by supercooling the melt. In this method, a silicon carbide single crystal is grown on a seed crystal substrate. The melt is a SiC solution using Si as a solvent.

液相成長法には、融液に種結晶基板近傍の融液温度が他の部分よりも低温になるような温度勾配を設ける、いわゆる温度差法（種結晶基板の近傍の融液だけが過飽和となる）と、種結晶基板を浸漬した融液全体を冷却してＳｉＣの過飽和溶液とする、いわゆる冷却法とがある。他に、溶媒を蒸発させて溶液を過飽和にする蒸発法もある。冷却法や蒸発法はバッチ式であるため、薄膜の単結晶を得る方法として好ましく、バルク単結晶を得るには連続成長とすることができる温度差法が好ましい。 In the liquid phase growth method, the melt is provided with a temperature gradient such that the melt temperature in the vicinity of the seed crystal substrate is lower than that in the other parts, so-called temperature difference method (only the melt near the seed crystal substrate is supersaturated. Then, there is a so-called cooling method in which the entire melt immersed in the seed crystal substrate is cooled to obtain a supersaturated solution of SiC. There is also an evaporation method in which the solvent is evaporated to supersaturate the solution. Since the cooling method and the evaporation method are batch methods, it is preferable as a method for obtaining a single crystal of a thin film, and a temperature difference method capable of continuous growth is preferable for obtaining a bulk single crystal.

液相成長法では、熱的平衡状態に近い状態で結晶成長が起こるため、気相成長に比べて格段に結晶性の良好な（ＳｉＣの異なるポリタイプの混入がない）結晶が得ることができることが知られている。従って、液相成長法によれば、昇華再結晶化法に比べて良質のＳｉＣ単結晶を製造することができる。しかし、融液への炭素の溶解度が低く、従って、融液中のＳｉＣ濃度が低いため、ＳｉＣ単結晶の成長速度が遅いことが、液相成長法の実用化を阻む問題点となっていた。 In the liquid phase growth method, crystal growth occurs in a state close to a thermal equilibrium state, so that crystals with significantly better crystallinity (no contamination of different polytypes of SiC) can be obtained compared to vapor phase growth. It has been known. Therefore, according to the liquid phase growth method, it is possible to produce a SiC single crystal having a higher quality than the sublimation recrystallization method. However, since the solubility of carbon in the melt is low and, therefore, the SiC concentration in the melt is low, the slow growth rate of the SiC single crystal has been a problem that hinders the practical application of the liquid phase growth method. .

下記特許文献１には、少なくとも１種の遷移金属元素とＳｉとＣとを含む原料を加熱溶融して融液とし、この融液を冷却することによりＳｉＣ単結晶を析出成長させることが開示されている。この場合には、Ｓｉと遷移金属との合金がＳｉＣの溶媒となる。しかし、この方法は、ＳｉＣ単結晶の液相成長の原理を記述しているにすぎず、ＳｉＣ単結晶の液相成長それ自体は下記非特許文献１などにあるような公知技術をそのまま利用している。 The following Patent Document 1 discloses that a raw material containing at least one transition metal element and Si and C is heated and melted to form a melt, and this melt is cooled to precipitate and grow a SiC single crystal. ing. In this case, an alloy of Si and a transition metal serves as a solvent for SiC. However, this method only describes the principle of the liquid phase growth of the SiC single crystal, and the liquid phase growth of the SiC single crystal itself uses a known technique as described in Non-Patent Document 1 below. ing.

今日のＳｉＣ単結晶の液相成長における技術課題は、Ｓｉ−Ｃ−Ｍ（Ｍは添加金属）の３元系状態図がほとんど知られていないため、ＳｉＣ結晶成長に最適な融液組成を絞り込むことすらできないことである。特許文献１では、具体的に開示されている融液組成は、遷移金属がＭｏ、Ｃｒ、Ｃｏの場合ついてそれぞれ１つずつの組成にすぎない。 The technical problem in the liquid phase growth of today's SiC single crystal is that the ternary phase diagram of Si-C-M (M is an additive metal) is hardly known, so the optimum melt composition for SiC crystal growth is narrowed down. You can't even do that. In Patent Document 1, the melt composition specifically disclosed is only one composition for each of the transition metals Mo, Cr, and Co.

本発明者等は先に、ＳｉとＣとＴｉまたはＭｎとを含む三元系の融液を用いる液相成長法により、ＳｉＣのバルク単結晶を得ることに成功した（下記特許文献２）。Ｓｉとの合金元素としてＴｉ又はＭｎを選択し、かつその最適組成範囲を絞り込むことにより、Ｓｉのみを溶媒とする場合に比べて、数倍高い成長速度を実現できた。これはＴｉ又はＭｎとのＳｉ合金からなる溶媒の炭素溶解度が、Ｓｉに比べて極めて大きいためと考えられる。しかし、Ｓｉ−Ｍｎの場合は、Ｍｎの平衡蒸気圧が高いため、成長温度を高くしすぎると融液の蒸発が激しくなるという問題があった。 The present inventors have succeeded in obtaining a SiC bulk single crystal by a liquid phase growth method using a ternary melt containing Si, C and Ti or Mn (Patent Document 2 below). By selecting Ti or Mn as an alloy element with Si and narrowing down the optimum composition range, a growth rate several times higher than that in the case of using only Si as a solvent could be realized. This is presumably because the carbon solubility of the solvent made of a Si alloy with Ti or Mn is extremely higher than that of Si. However, in the case of Si—Mn, since the equilibrium vapor pressure of Mn is high, there is a problem that if the growth temperature is too high, the evaporation of the melt becomes intense.

ＳｉＣ単結晶の量産化を実現するには、上記従来技術より更に高速成長を可能とする、即ち、炭素溶解度のより高い、溶媒系の探索が求められている。
特開２０００−２６４７９０号公報特開２００４−２１７３号公報 J. Crystal Growth 27 (1974) p. 320-324 In order to achieve mass production of SiC single crystals, it is necessary to search for a solvent system that enables higher-speed growth than the above-described conventional technology, that is, higher carbon solubility.
JP 2000-264790 A JP 2004-2173 A J. Crystal Growth 27 (1974) p. 320-324

良質なＳｉＣ単結晶を成長させることができる液相成長法によるＳｉＣ単結晶の量産化を実現するには、高速成長を可能とするように、溶媒なるＳｉ合金について、炭素溶解度がこれまでより大きな合金の選定が求められている。本発明は、そのような合金を見出すことにより、液相成長法による良質なＳｉＣ単結晶の量産化を実現することを目指したものである。 In order to realize mass production of SiC single crystals by the liquid phase growth method capable of growing high-quality SiC single crystals, the carbon solubility of solvent Si alloys is higher than ever so as to enable high-speed growth. Selection of alloys is required. The present invention aims to realize mass production of high-quality SiC single crystals by a liquid phase growth method by finding such an alloy.

本発明によれば、Ｓｉ合金の合金元素としてＶまたはＶとＴｉを使用し、その量を特定範囲に設定することにより、上記課題を解決することができる。
本発明は、ＳｉとＣとＶまたはＳｉとＣとＶとＴｉとを含む融液に、ＳｉＣ成長用の種結晶基板を接触させ、少なくとも前記種結晶基板周辺において前記融液の過冷却により融液に溶解しているＳｉＣを過飽和状態とすることによって、前記種結晶基板上にＳｉＣ単結晶を成長させる、ＳｉＣ単結晶の製造方法である。融液の合金元素（Ｖ又はＶとＴｉ）の量は次の通りである。 According to the present invention, the above-mentioned problems can be solved by using V or V and Ti as alloy elements of the Si alloy and setting the amount within a specific range.
According to the present invention, a seed crystal substrate for SiC growth is brought into contact with a melt containing Si and C and V or Si and C and V and Ti, and at least the seed crystal substrate is melted by overcooling the melt. In this SiC single crystal manufacturing method, SiC single crystal is grown on the seed crystal substrate by bringing SiC dissolved in the liquid into a supersaturated state. The amount of alloy elements (V or V and Ti) in the melt is as follows.

融液がＳｉとＣとＶを含む場合、Ｖの量は、ＳｉとＶの原子比を[Ｖ]／([Ｓｉ]＋[Ｖ])なる式で表して、次式を満たす：
０.１≦[Ｖ]／([Ｓｉ]＋[Ｖ])≦０.４５。 When the melt contains Si, C, and V, the amount of V satisfies the following formula, where the atomic ratio of Si and V is expressed by the formula [V] / ([Si] + [V]).
0.1 ≦ [V] / ([Si] + [V]) ≦ 0.45.

融液がＳｉとＣとＶとＴｉを含む場合、ＳｉとＴｉおよびＳｉとＶの原子比をそれぞれ[Ｔｉ]／([Ｓｉ]＋[Ｔｉ])および[Ｖ]／([Ｓｉ]＋[Ｖ])なる式で表して次式を満たす：
０.１≦[Ｔｉ]／([Ｓｉ]＋[Ｔｉ])≦０.２５、かつ
０.１≦[Ｖ]／([Ｓｉ]＋[Ｖ])≦０.４５。 When the melt contains Si, C, V, and Ti, the atomic ratios of Si, Ti, and Si and V are [Ti] / ([Si] + [Ti]) and [V] / ([Si] + [ V]) and satisfy the following formula:
0.1 ≦ [Ti] / ([Si] + [Ti]) ≦ 0.25, and 0.1 ≦ [V] / ([Si] + [V]) ≦ 0.45.

言うまでもないが、上の式において[Ｓｉ]、[Ｖ]、および[Ｔｉ]は、それぞれ融液中のその原子のat％での濃度（＝モル濃度）を意味する。ＳｉはＳｉＣ単結晶の成長に伴って消費されるが、その消費量は融液中のＳｉに比べてごくわずかであり、無視しうる量である。従って、融液中のＳｉとＶまたはＳｉとＶとＴｉの各金属の量は、融液形成時における各金属の添加量に等しい。 Needless to say, in the above formula, [Si], [V], and [Ti] mean the concentration in atomic percent (= molar concentration) of the atom in the melt. Si is consumed as the SiC single crystal grows, but its consumption is negligible compared to Si in the melt and is negligible. Therefore, the amount of each metal of Si and V or Si, V and Ti in the melt is equal to the amount of each metal added at the time of melt formation.

本発明は、ＳｉＣを液相から成長させる液相成長法によるＳｉＣ単結晶の製造方法に関する。本発明で用いる融液はＳｉとＣとＶ、またはＳｉとＣとＴｉとＶ、を含有し、固相のＳｉＣと熱力学的に平衡状態となり得るＳｉＣ溶液である。 The present invention relates to a method for producing a SiC single crystal by a liquid phase growth method in which SiC is grown from a liquid phase. The melt used in the present invention is a SiC solution containing Si and C and V or Si, C and Ti and V, which can be in a thermodynamic equilibrium state with solid-phase SiC.

一般に、理論的かつ実験的に信頼できる多元系融液の平衡状態図はほとんど知られておらず、添加する遷移金属元素およびその量を選定するには、高度な知識を必要とする多元系平衡状態図計算をまず行う必要がある。 In general, few theoretical and experimentally reliable equilibrium diagrams of multicomponent melts are known. Multicomponent equilibria require advanced knowledge to select transition metal elements and their amounts. The state diagram calculation needs to be done first.

また、平衡状態図は平衡状態での種々の相の出現消滅挙動を示すのみである。液相成長法では、過飽和溶液からの結晶成長という平衡状態からのズレを利用する。そのため、仮に平衡状態図から最適の融液組成が推定できても、実際の単結晶成長では、平衡状態図から予測しえないさまざまな事態が生じ、安定してＳｉＣ単結晶が得られるとは限らない。例えば、成長のための冷却中や温度勾配下で、種々の副次的な生成物を生じて、均一な単結晶が得られなかったり、種結晶基板が溶解したり、或いは融液が坩堝と反応し、坩堝を損傷するなどの可能性がある。そのため、最適な単結晶成長条件を知るには、融液組成や他の結晶成長条件を種々に変化させた実際の成長実験を行って、いかなる現象が生じるかを子細に検討する必要がある。 The equilibrium diagram only shows the appearance and disappearance behavior of various phases in the equilibrium state. In the liquid phase growth method, a deviation from an equilibrium state of crystal growth from a supersaturated solution is used. Therefore, even if the optimum melt composition can be estimated from the equilibrium diagram, various situations that cannot be predicted from the equilibrium diagram occur in the actual single crystal growth, and a SiC single crystal can be obtained stably. Not exclusively. For example, during cooling for growth or under a temperature gradient, various secondary products are generated, and a uniform single crystal cannot be obtained, a seed crystal substrate is dissolved, or a melt is melted with a crucible. It may react and damage the crucible. Therefore, in order to know the optimum single crystal growth conditions, it is necessary to examine in detail what kind of phenomenon occurs by conducting actual growth experiments with various changes in the melt composition and other crystal growth conditions.

つまり、液相成長法によるＳｉＣ単結晶の製造においては、従来技術からの知見はほとんど参考にならない。Ｓｉ溶媒への添加元素としてＶまたはＶとＴｉを使用することにより、液相成長法で高品質ＳｉＣ単結晶を高い成長速度で安定して製造することは従来技術からは容易に導き出されるものではない。 That is, in the production of SiC single crystal by the liquid phase growth method, the knowledge from the prior art is hardly helpful. By using V or V and Ti as additive elements to the Si solvent, stable production of high-quality SiC single crystals at a high growth rate by the liquid phase growth method is not easily derived from the prior art. Absent.

本発明者等は、Ｓｉ−Ｃ−Ｍ３元系状態図を、熱力学的考察により計算で求め、溶液組成の絞り込みを行うとともに、種々の溶媒組成でのＳｉＣ結晶成長実験を行った。その結果、ＭとしてＶを選択すると、Ｖ含有量が特定の範囲内では、ＭがＴｉである場合より融液のＣ溶解度が著しく高くなり、ＳｉＣ単結晶の成長速度を著しく高めることができること、およびＳｉ−Ｃ−Ｔｉ３元系にＶを添加すると、融液中のＣ溶解度、従って、ＳｉＣ成長速度は、ＭがＶまたはＴｉである場合よりさらに著しく高くなることを見出し、本発明に至った。 The present inventors obtained a Si—C—M ternary phase diagram by calculation based on thermodynamic consideration, narrowed down the solution composition, and conducted SiC crystal growth experiments with various solvent compositions. As a result, when V is selected as M, when the V content is within a specific range, the C solubility of the melt is significantly higher than when M is Ti, and the growth rate of the SiC single crystal can be significantly increased. And the addition of V to the Si—C—Ti ternary system has found that the C solubility in the melt, and hence the SiC growth rate, is significantly higher than when M is V or Ti, leading to the present invention. .

本発明において、「少なくとも前記種結晶基板周辺において前記融液の過冷却により融液に溶解しているＳｉＣを過飽和状態とする」手段は、特に制限されず、液相成長法において一般に利用可能な任意の手段を採用することができる。前述したように、そのような手段として下記が挙げられる。
（１）融液全体を実質的に一様に徐冷して過冷却状態（すなわち過飽和状態）とする冷却法（徐冷法）、
（２）融液に温度勾配を設けて、種結晶基板の周辺が低温部になるようにして、この部分だけを溶液の過冷却状態とする温度差法（温度勾配法）
（３）溶媒を蒸発させて全体を過飽和状態とする蒸発法。 In the present invention, means for “saturating SiC dissolved in the melt by supercooling the melt at least around the seed crystal substrate” is not particularly limited, and can be generally used in the liquid phase growth method. Any means can be employed. As described above, examples of such means include the following.
(1) A cooling method (slow cooling method) in which the entire melt is gradually cooled substantially uniformly to form a supercooled state (ie, a supersaturated state),
(2) A temperature difference method (temperature gradient method) in which a temperature gradient is provided in the melt so that the periphery of the seed crystal substrate becomes a low temperature portion and only this portion is in a supercooled state of the solution.
(3) An evaporation method in which the solvent is evaporated and the whole is supersaturated.

冷却法では、融液の冷却をその融液の固相線温度より高い温度で終了した後、融液の加熱と冷却を繰り返すことにより過冷却を繰り返し行って、種結晶基板上へのＳｉＣ単結晶の成長を続けることにより、バルクの単結晶を得ることも可能である。しかし、加熱と冷却の繰り返しは熱エネルギーの消費量が多いので、バルク単結晶の成長は温度差法で行う方が有利である。冷却法は固相線よりも高い温度までの冷却を１回だけで終了して、バッチ方式でエピタキシャル成長薄膜を得るのに適している。蒸発法も冷却法と同様に、薄膜単結晶成長に適している。 In the cooling method, cooling of the melt is finished at a temperature higher than the solidus temperature of the melt, and then supercooling is repeatedly performed by repeating heating and cooling of the melt, so that the SiC single crystal on the seed crystal substrate is obtained. A bulk single crystal can be obtained by continuing crystal growth. However, since repeated heating and cooling consumes a large amount of heat energy, it is advantageous to perform bulk single crystal growth by the temperature difference method. The cooling method is suitable for obtaining an epitaxially grown thin film by a batch method by finishing the cooling to a temperature higher than the solidus line only once. As with the cooling method, the evaporation method is suitable for thin film single crystal growth.

温度差法は、連続的に結晶成長が行われるため、バルク単結晶を得るのに適した方法であるが、温度差法でも成長時間を短時間にすることでエピタキシャル薄膜を得ることは可能である。温度差法における融液の温度勾配は、融液の上下方向、水平方向のいずれに形成してもよく、その両方を組み合わせることも可能である。上下方向の温度勾配は通常は、種結晶基板が浸漬される融液上部を低温部、下部を高温部にする。水平方向の温度勾配は、融液の液面近傍において、種結晶基板が浸漬させる中央部を低温部とし、坩堝壁面近傍を高温部にするのが普通である。 The temperature difference method is a method suitable for obtaining a bulk single crystal because crystal growth is performed continuously, but it is possible to obtain an epitaxial thin film by shortening the growth time even with the temperature difference method. is there. The temperature gradient of the melt in the temperature difference method may be formed either in the vertical direction or in the horizontal direction of the melt, or a combination of both. The temperature gradient in the vertical direction is usually such that the upper part of the melt in which the seed crystal substrate is immersed is the low temperature part and the lower part is the high temperature part. As for the temperature gradient in the horizontal direction, in the vicinity of the liquid surface of the melt, the central portion where the seed crystal substrate is immersed is usually a low temperature portion, and the vicinity of the crucible wall surface is a high temperature portion.

本発明によれば、ＳｉＣの溶媒となるＳｉ−ＶまたはＳｉ−Ｖ−Ｔｉ合金系が、炭素溶解度が大きく、かつ固相のＳｉＣと熱力学的に平衡状態となり得るＳｉＣ溶液を形成できるものであるため、副次的な生成物を生じずに、高い成長速度で、均一にＳｉＣ単結晶を安定して液相から成長させることができる。従って、本発明の方法は、電子および光デバイスにおいて求められている良質なＳｉＣバルクおよび薄膜単結晶の効率的な製造を可能にし、その量産化を実現可能にするものである。 According to the present invention, an Si-V or Si-V-Ti alloy system serving as a solvent for SiC can form a SiC solution that has a high carbon solubility and can be in thermodynamic equilibrium with solid-phase SiC. Therefore, the SiC single crystal can be stably and stably grown from the liquid phase at a high growth rate without generating a secondary product. Therefore, the method of the present invention enables efficient production of high-quality SiC bulk and thin film single crystals required for electronic and optical devices, and enables mass production thereof.

本発明に従ってＳｉＣ単結晶を製造するには、まず、ＳｉとＶとＣ、またはＳｉとＴｉとＶとＣとを含有する融液を調製する。この融液は、溶媒であるＳｉ−ＶまたはＳｉ−Ｖ−Ｔｉ合金系にＳｉＣが溶解しているＳｉＣ溶液である。融液から単結晶を成長させるには、ＳｉＣ濃度（溶解したＣ濃度）は飽和濃度か、それに近い濃度にする必要がある。 In order to produce a SiC single crystal according to the present invention, first, a melt containing Si and V and C or Si, Ti, V and C is prepared. This melt is a SiC solution in which SiC is dissolved in the solvent Si-V or Si-V-Ti alloy system. In order to grow a single crystal from the melt, the SiC concentration (dissolved C concentration) needs to be a saturation concentration or a concentration close thereto.

この融液は、例えば、黒鉛坩堝に所定の割合でＳｉとＶ、またはＳｉとＴｉとＶ、を装入し、坩堝を加熱して融液状態にし、加熱を続けて、黒鉛坩堝からＣを溶解させることにより調製することができる。すなわち、黒鉛坩堝のような炭素質坩堝からＣを供給する方法である。この方法は、ＳｉＣ析出の核となり得る未溶解のＣが融液中に残留するおそれが無い点で望ましい。但し、坩堝が消耗するので、その交換頻度が高くなる。 For example, Si and V or Si and Ti and V are charged into a graphite crucible at a predetermined ratio, and the melt is heated to a melt state. It can be prepared by dissolving. That is, it is a method of supplying C from a carbonaceous crucible such as a graphite crucible. This method is desirable in that there is no possibility that undissolved C that can be a nucleus of SiC precipitation remains in the melt. However, since the crucible is consumed, the replacement frequency becomes high.

別のＣの供給方法として、炭化水素ガスを所定組成のＳｉ−ＶまたはＳｉ−Ｖ−Ｔｉ合金の融液に吹き込んで融液中にＣを溶解させる気相経由の方法、さらには固相のＣ源を融液に投入し、溶解させる方法も可能である。この場合には、非消耗性の坩堝を使用することができる。固体の炭素源としては、黒鉛のブロックや棒、顆粒、粉体の他に、黒鉛以外の非晶質の炭素原料、さらにはＳｉＣや添加元素（Ｖ、Ｔｉ）の炭化物等も利用できる。 As another method of supplying C, a method via a gas phase in which hydrocarbon gas is blown into a melt of Si—V or Si—V—Ti alloy having a predetermined composition to dissolve C in the melt, It is also possible to add a C source to the melt and dissolve it. In this case, a non-consumable crucible can be used. As the solid carbon source, in addition to graphite blocks, rods, granules, and powders, amorphous carbon raw materials other than graphite, carbides of SiC and additive elements (V, Ti), and the like can also be used.

もちろん、これらの２以上の方法を組み合わせてＣを供給することも可能である。
加熱温度は、坩堝に装入したＳｉとＶ、またはＳｉとＴｉとＶ、の合金の液相温度以上であれば良い。加熱は、融液中のＳｉＣ濃度が飽和濃度またはそれに近い濃度になるまで、黒鉛坩堝または添加炭素源からＣが融液中に溶解するように行う。固体の炭素源、特に粉末や顆粒の炭素源を坩堝に添加した場合は、それらが未溶解で融液中に残留すると、そこにＳｉＣが析出して、ＳｉＣ単結晶の成長速度を低下させ、あるいは結晶品質を低下させることがあるので、添加した炭素源が完全に溶解するように加熱を続けることが好ましい。融液の加熱時間は、一般に１時間から１０時間程度の範囲である。 Of course, it is also possible to supply C by combining these two or more methods.
The heating temperature should just be more than the liquid phase temperature of the alloy of Si and V or Si, Ti, and V with which the crucible was charged. The heating is performed so that C is dissolved in the melt from the graphite crucible or the added carbon source until the SiC concentration in the melt reaches a saturation concentration or a concentration close thereto. When a solid carbon source, especially a powder or granular carbon source is added to the crucible, if they remain undissolved and remain in the melt, SiC precipitates there, reducing the growth rate of the SiC single crystal, Alternatively, since the crystal quality may be deteriorated, it is preferable to continue heating so that the added carbon source is completely dissolved. The heating time of the melt is generally in the range of about 1 hour to 10 hours.

融液の組成は、
ＳｉとＣとＶの場合、ＳｉとＶの原子比を[Ｖ]／([Ｓｉ]＋[Ｖ])なる式で表して、
０.１≦[Ｖ]／([Ｓｉ]＋[Ｖ])≦０.４であり、
ＳｉとＣとＶとＴｉの場合、ＳｉとＴｉおよびＳｉとＶの原子比を、それぞれ[Ｔｉ]／([Ｓｉ]＋[Ｔｉ])および[Ｖ]／([Ｓｉ]＋[Ｖ])で表して、
０.１≦[Ｔｉ]／([Ｓｉ]＋[Ｔｉ])≦０.２５、かつ
０.１≦[Ｖ]／([Ｓｉ]＋[Ｖ])≦０.４５である。 The composition of the melt is
In the case of Si, C and V, the atomic ratio of Si and V is represented by the formula [V] / ([Si] + [V])
0.1 ≦ [V] / ([Si] + [V]) ≦ 0.4,
In the case of Si, C, V and Ti, the atomic ratios of Si and Ti and Si and V are respectively [Ti] / ([Si] + [Ti]) and [V] / ([Si] + [V]). Represented by
0.1 ≦ [Ti] / ([Si] + [Ti]) ≦ 0.25, and 0.1 ≦ [V] / ([Si] + [V]) ≦ 0.45.

上記範囲よりもＶまたはＴｉの量が少ないと、融液中のＣ濃度が（従ってＳｉＣ濃度）が低下し、ＳｉＣ結晶成長速度が低下する。また、上記範囲よりＶまたはＴｉの量が多くなると、ＶやＴｉの炭化物が初晶として晶出するため、安定したＳｉＣ結晶の成長に支障が生じる。 If the amount of V or Ti is less than the above range, the C concentration in the melt (and hence the SiC concentration) decreases, and the SiC crystal growth rate decreases. Further, if the amount of V or Ti is larger than the above range, carbides of V and Ti are crystallized as primary crystals, which hinders stable growth of SiC crystals.

上記原子比の好ましい範囲は次の通りである；
０.２≦[Ｖ]／([Ｓｉ]＋[Ｖ])≦０.４
０.１５≦[Ｔｉ]／([Ｓｉ]＋[Ｔｉ])≦０.２。 Preferred ranges of the atomic ratio are as follows:
0.2 ≦ [V] / ([Si] + [V]) ≦ 0.4
0.15 ≦ [Ti] / ([Si] + [Ti]) ≦ 0.2.

坩堝は、炭素を坩堝の溶解により供給する場合には、黒鉛坩堝に代表される炭素質坩堝を使用する。添加した炭素源から炭素を供給する場合には、ＳｉＣの成長温度域で安定な坩堝材料、例えば、Ｔａ、Ｗ、Ｍｏなどの高融点金属からなる坩堝や、黒鉛坩堝を適当な耐火材料、例えば上記高融点金属またはセラミックスで内張りした坩堝を使用することができる。所望の融液組成を実現できるならば、コールドクルーシブルやレビテーション法など、坩堝を使用しない方法も適用可能である。 The crucible is a carbonaceous crucible represented by a graphite crucible when carbon is supplied by melting the crucible. When supplying carbon from the added carbon source, a crucible material stable in the SiC growth temperature range, for example, a crucible made of a refractory metal such as Ta, W, Mo, or a graphite crucible is used as an appropriate refractory material, for example, A crucible lined with the above refractory metal or ceramic can be used. As long as a desired melt composition can be realized, a method that does not use a crucible, such as a cold crucible or a levitation method, is also applicable.

ＳｉＣが飽和濃度またはその近くまで溶解した融液（ＳｉＣ溶液）が得られたら、その融液にＳｉＣ単結晶の基板を浸漬し、少なくとも種結晶基板近傍の融液を過冷却によりＳｉＣの過飽和状態にすることによって、ＳｉＣ単結晶を種結晶基板上に成長させる。 When a melt (SiC solution) in which SiC is dissolved at or near the saturation concentration is obtained, a SiC single crystal substrate is immersed in the melt, and at least the melt in the vicinity of the seed crystal substrate is supercooled to superheat the SiC. By doing so, a SiC single crystal is grown on the seed crystal substrate.

種結晶基板は、昇華再結晶化法で得られたＳｉＣ単結晶の他に、ＣＶＤ法などの気相成長で得られたＳｉＣ単結晶でも、溶液成長法で得られたＳｉＣ単結晶でもよい。種結晶基板の結晶構造は、成長させたいＳｉＣ単結晶の結晶構造と同じものを使用するのが一般的である。種結晶基板はＳｉＣ単結晶に限られるものではない。その上でＳｉＣがヘテロエピタキシャル成長することができ、融液中で安定し存在し得る、結晶構造が同じ異種の基板、例えば、シリコン基板を種結晶基板として使用することも可能である。 In addition to the SiC single crystal obtained by the sublimation recrystallization method, the seed crystal substrate may be an SiC single crystal obtained by vapor phase growth such as a CVD method or an SiC single crystal obtained by a solution growth method. The crystal structure of the seed crystal substrate is generally the same as that of the SiC single crystal to be grown. The seed crystal substrate is not limited to a SiC single crystal. It is also possible to use a heterogeneous substrate having the same crystal structure, for example, a silicon substrate, as a seed crystal substrate, on which SiC can be heteroepitaxially grown and can exist stably in the melt.

種結晶基板は通常は、回転可能なシード軸先端の種結晶基板支持治具に取り付けて融液に浸漬する。結晶成長を均一にするために、シード軸に加えて坩堝軸も回転させることが好ましい。この際の回転は定常回転であっても、加減速回転であっても良い。また、シード軸と坩堝軸の回転方向は互いに同方向でも、逆方向でもよい。種結晶基板の浸漬位置は、温度差法では融液の自由表面（液表面）すれすれとするのが普通である。融液全体を過飽和とする冷却法や蒸発法では、種結晶基板の浸漬位置は任意である。 The seed crystal substrate is usually attached to a seed crystal substrate support jig at the tip of a rotatable seed shaft and immersed in the melt. In order to make the crystal growth uniform, it is preferable to rotate the crucible shaft in addition to the seed shaft. The rotation at this time may be steady rotation or acceleration / deceleration rotation. Further, the rotation directions of the seed shaft and the crucible shaft may be the same or opposite directions. The immersion position of the seed crystal substrate is usually a grazing free surface (liquid surface) in the temperature difference method. In the cooling method or evaporation method in which the entire melt is supersaturated, the immersion position of the seed crystal substrate is arbitrary.

ＳｉＣの過飽和状態を得る方法としては、前述したように、溶液を蒸発させて過飽和状態とする蒸発法、飽和濃度のＳｉＣ溶液に種結晶基板を浸漬後、徐冷によって過飽和状態とする冷却法、温度勾配を有するＳｉＣ溶液中に種結晶基板を浸漬し、低温部でＳｉＣ結晶を晶出させる温度差法などが可能である。 As described above, the method for obtaining the supersaturated state of SiC is an evaporation method in which the solution is evaporated to be in a supersaturated state, a cooling method in which the seed crystal substrate is immersed in a SiC solution having a saturated concentration and then is brought into a supersaturated state by slow cooling, A temperature difference method in which a seed crystal substrate is immersed in an SiC solution having a temperature gradient and SiC crystals are crystallized at a low temperature portion is possible.

蒸発法は、加熱温度が高くなり、発生した蒸気の処理も煩雑になるので、量産には冷却法または温度差法が適している。結晶成長時の温度（冷却法では冷却終了時の温度、温度差法では結晶成長が起こる低温部の種結晶基板近傍の温度）は、その融液組成の液相線温度よりもやや低い温度とすることが好ましい。 In the evaporation method, the heating temperature becomes high and the treatment of the generated steam becomes complicated, so the cooling method or the temperature difference method is suitable for mass production. The temperature at the time of crystal growth (the temperature at the end of cooling in the cooling method, the temperature in the vicinity of the seed crystal substrate in the low temperature portion where the crystal growth occurs in the temperature difference method) is slightly lower than the liquidus temperature of the melt composition. It is preferable to do.

温度差法の場合、上下方向の温度勾配は、坩堝周囲に配した加熱手段の制御により達成できるが、場合により低温部となる種結晶基板が浸漬される部分の周囲に冷却手段を配置しても良い。水平方向の温度勾配については、加熱された坩堝からの伝熱により融液を加熱すると、融液の液面からは抜熱が起こるため、坩堝壁面に接する融液の周辺部の方が、融液中央部に比べて高温になる温度勾配が自然に形成される。したがって融液中央部の液面近傍に浸漬すれば、その近傍が低温部になる。種結晶基板を取り付けたシード軸を水冷すると、この水平方向の温度勾配はさらに大きくなるので、結晶成長速度が増大する。 In the case of the temperature difference method, the temperature gradient in the vertical direction can be achieved by controlling the heating means arranged around the crucible, but in some cases, cooling means are arranged around the part where the seed crystal substrate that becomes the low temperature part is immersed. Also good. Regarding the temperature gradient in the horizontal direction, when the melt is heated by heat transfer from the heated crucible, heat is removed from the melt surface, so the periphery of the melt in contact with the crucible wall surface is melted. A temperature gradient that is higher than the temperature in the liquid center is naturally formed. Therefore, if it is immersed in the vicinity of the liquid surface of the melt central portion, the vicinity thereof becomes a low temperature portion. When the seed shaft on which the seed crystal substrate is attached is water-cooled, this horizontal temperature gradient is further increased, so that the crystal growth rate is increased.

温度差法における温度勾配は、５〜１００℃／ｃｍの範囲が好ましい。５℃／ｃｍ未満では融液内の溶質であるＳｉＣの輸送の駆動力が小さく、ＳｉＣの成長速度は小さくなる。温度勾配が、１００℃／ｃｍを越えると、種結晶基板近傍で自然核発生によるＳｉＣ結晶が生じて、種結晶基板上への均一な溶質供給を阻害する。この結果、均一層成長した結晶が得られなくなる。冷却法の場合の冷却速度は１〜６℃／ｍｉｎとすることが好ましい。 The temperature gradient in the temperature difference method is preferably in the range of 5 to 100 ° C./cm. If the temperature is less than 5 ° C./cm, the driving force for transport of SiC, which is the solute in the melt, is small, and the growth rate of SiC is small. If the temperature gradient exceeds 100 ° C./cm, SiC crystals are generated by the generation of natural nuclei in the vicinity of the seed crystal substrate, and uniform solute supply onto the seed crystal substrate is hindered. As a result, crystals with uniform layer growth cannot be obtained. The cooling rate in the cooling method is preferably 1 to 6 ° C./min.

上述したように、本発明の方法は、ＳｉＣ単結晶薄膜とバルク結晶のいずれも製造可能である。蒸発法や冷却法でバルク結晶を得るには、結晶成長すなわち、Ｃ溶解と蒸発または冷却を繰り返せばよい。温度差法では、成長時間によって、薄膜単結晶とバルク単結晶を成長時間を変えることのみで作りわけることができる。ここで、炭化珪素バルク単結晶とは、厚さ２００μｍ以上の炭化珪素単結晶であることを意味し、薄膜単結晶とはそれより小さい厚みのものを指す。 As described above, the method of the present invention can produce both a SiC single crystal thin film and a bulk crystal. In order to obtain a bulk crystal by an evaporation method or a cooling method, crystal growth, that is, C dissolution and evaporation or cooling may be repeated. In the temperature difference method, a thin film single crystal and a bulk single crystal can be formed only by changing the growth time depending on the growth time. Here, the silicon carbide bulk single crystal means a silicon carbide single crystal having a thickness of 200 μm or more, and the thin film single crystal means one having a smaller thickness.

本実施例は、図１に示した結晶成長装置を用いた温度差法によるＳｉＣ単結晶の製造を例示する。図１に示した結晶成長装置は、融液６を収容した黒鉛坩堝５を備え、この坩堝は水冷ステンレスチャンバー２内に配置されている。黒鉛坩堝５の外周は断熱材７により保温されており、さらにその外周に誘導加熱用の高周波コイル３が設けられている。結晶成長装置内の雰囲気は、ガス挿入口とガス排気口（図示せず）を利用して調整される。 This example illustrates the manufacture of a SiC single crystal by the temperature difference method using the crystal growth apparatus shown in FIG. The crystal growth apparatus shown in FIG. 1 includes a graphite crucible 5 containing a melt 6, and this crucible is disposed in a water-cooled stainless steel chamber 2. The outer periphery of the graphite crucible 5 is kept warm by a heat insulating material 7, and the induction heating high-frequency coil 3 is further provided on the outer periphery thereof. The atmosphere in the crystal growth apparatus is adjusted using a gas insertion port and a gas exhaust port (not shown).

図１の装置において、坩堝の底面は、中空状の坩堝軸８を通じて放射温度計９により測温されている。黒鉛坩堝と高周波コイルとの相対的な位置関係の制御により融液に温度勾配を形成される。本例では、常法に従って、融液の上部が低温部になるように温度勾配を形成した。低温部に浸漬される種結晶基板近傍の温度勾配は、成長実験とは別に予め融液内に熱電対を挿入して温度測定を行った。 In the apparatus of FIG. 1, the bottom surface of the crucible is measured by a radiation thermometer 9 through a hollow crucible shaft 8. A temperature gradient is formed in the melt by controlling the relative positional relationship between the graphite crucible and the high-frequency coil. In this example, according to a conventional method, a temperature gradient was formed so that the upper part of the melt became a low temperature part. The temperature gradient in the vicinity of the seed crystal substrate immersed in the low temperature portion was measured by inserting a thermocouple in advance in the melt separately from the growth experiment.

黒鉛坩堝にＳｉ：０.６０−Ｖ：０.４０（[Ｖ]／[Ｖ＋Ｓｉ]＝０.４０）となる組成の合金原料を装入し、種結晶基板近傍の温度が１７００℃、温度勾配が２０℃／ｃｍになるように加熱し、合金原料を融解させた。この加熱を、生成した融液中に黒鉛坩堝からＣが十分に溶解するまで２時間保持した。 An alloy raw material having a composition of Si: 0.60-V: 0.40 ([V] / [V + Si] = 0.40) was charged into a graphite crucible, and the temperature in the vicinity of the seed crystal substrate was 1700 ° C. with a temperature gradient. Was heated to 20 ° C./cm to melt the alloy raw material. This heating was held for 2 hours until C was sufficiently dissolved from the graphite crucible in the produced melt.

その後、上記加熱を続けながら、黒鉛製の基板保持治具で保持したＳｉＣ種結晶基板［２８ｍｍ×２８ｍｍ６Ｈ−ＳｉＣ（０００１）］を融液に浸漬した。保持治具と坩堝は、逆方向に、それぞれ１０ｒｐｍ、２０ｒｐｍで加減速回転させた。加速・減速時間は５秒とした。種結晶基板浸漬後、５時間経過したところで基板保持治具を上昇させて種結晶基板を融液から引き上げた。坩堝を室温まで徐冷した後、種結晶基板を保持治具から回収した。種結晶基板上に新たに液相成長した炭化珪素単結晶の厚みを、結晶断面の光学顕微鏡観察から計測した。 Thereafter, an SiC seed crystal substrate [28 mm × 28 mm 6H—SiC (0001)] held by a graphite substrate holding jig was immersed in the melt while continuing the heating. The holding jig and the crucible were rotated in the opposite directions at 10 rpm and 20 rpm, respectively. The acceleration / deceleration time was 5 seconds. The substrate holding jig was raised after 5 hours from the immersion of the seed crystal substrate, and the seed crystal substrate was pulled up from the melt. After slowly cooling the crucible to room temperature, the seed crystal substrate was recovered from the holding jig. The thickness of the silicon carbide single crystal newly grown in the liquid phase on the seed crystal substrate was measured from an optical microscope observation of the crystal cross section.

本発明の効果を判定するため、Ｓｉ−Ｃの液相成長法として古くから知られているＳｉ−Ｃの２元系（溶媒はＳｉ単独）からＳｉＣ単結晶を成長させる、いわゆるセルフフラックス法および、上記特許文献２に記載のＳｉ−Ｔｉ−Ｃ３元系（溶媒はＳｉ−Ｔｉ合金）を比較対象とした。Ｓｉ−Ｔｉ−Ｃ３元系（後述する比較例４）に比べて、成長速度が同等（±３０％未満）を○、３０％以上増大する場合を◎、３０％以上減少する場合または他結晶の析出によりＳｉＣ単結晶が得られなかった場合を×とした。 In order to determine the effects of the present invention, a so-called self-flux method, in which a SiC single crystal is grown from a Si—C binary system (the solvent is Si alone), which has long been known as a Si—C liquid phase growth method, and The Si—Ti—C ternary system described in Patent Document 2 (the solvent is a Si—Ti alloy) was used as a comparison target. Compared to the Si-Ti-C ternary system (Comparative Example 4 to be described later), the growth rate is the same (less than ± 30%): ◯, increased by 30% or more, ◎, decreased by 30% or more, or other crystals When the SiC single crystal was not obtained by precipitation, it was set as x.

黒鉛坩堝に、Ｓｉ：０.９０−Ｖ：０.１０（[Ｖ]／[Ｖ＋Ｓｉ]＝０.１０）となる組成の合金原料を装入し、種結晶基板近傍の温度が１７００℃、温度勾配が２０℃／ｃｍになるように融解させた以外は、実施例１と同様にＳｉＣ単結晶を製造した。 An alloy raw material having a composition of Si: 0.90−V: 0.10 ([V] / [V + Si] = 0.10) was charged into a graphite crucible, and the temperature in the vicinity of the seed crystal substrate was 1700 ° C. A SiC single crystal was produced in the same manner as in Example 1 except that melting was performed so that the gradient became 20 ° C./cm.

黒鉛坩堝に、Ｓｉ：０.８０−Ｔｉ：０.１０−Ｖ：０.１０（[Ｔｉ]／[Ｔｉ＋Ｓｉ]＝０.１１、[Ｖ]／[Ｖ＋Ｓｉ]＝０.１１）となる組成の合金原料を装入し、種結晶基板近傍の温度が１７００℃、温度勾配が２０℃／ｃｍになるように融解させた以外は、実施例１と同様にＳｉＣ単結晶を製造した。 In a graphite crucible, the composition of Si: 0.80-Ti: 0.10-V: 0.10 ([Ti] / [Ti + Si] = 0.11, [V] / [V + Si] = 0.11) An SiC single crystal was produced in the same manner as in Example 1 except that the alloy raw material was charged and melted so that the temperature near the seed crystal substrate was 1700 ° C. and the temperature gradient was 20 ° C./cm.

黒鉛坩堝に、Ｓｉ：０.７０−Ｔｉ：０.２３−Ｖ：０.０７（[Ｔｉ]／[Ｔｉ＋Ｓｉ]＝０.２４、[Ｖ]／[Ｖ＋Ｓｉ]＝０.０９）となる組成の合金原料を装入し、種結晶基板近傍の温度が１７００℃、温度勾配が２０℃／ｃｍになるように融解させた以外は、実施例１と同様にＳｉＣ単結晶を製造した。 In a graphite crucible, Si: 0.70-Ti: 0.23-V: 0.07 ([Ti] / [Ti + Si] = 0.24, [V] / [V + Si] = 0.09) An SiC single crystal was produced in the same manner as in Example 1 except that the alloy raw material was charged and melted so that the temperature near the seed crystal substrate was 1700 ° C. and the temperature gradient was 20 ° C./cm.

黒鉛坩堝に、Ｓｉ：０.５２−Ｔｉ：０.０７−Ｖ：０.４１（[Ｔｉ]／[Ｔｉ＋Ｓｉ]＝０.１１、[Ｖ]／[Ｖ＋Ｓｉ]＝０.４４）となる組成の合金原料を装入し、種結晶基板近傍の温度が１７００℃、温度勾配が２０℃／ｃｍになるように融解させた以外は、実施例１と同様にＳｉＣ単結晶を製造した。 In a graphite crucible, the composition of Si: 0.52-Ti: 0.07-V: 0.41 ([Ti] / [Ti + Si] = 0.11, [V] / [V + Si] = 0.44) An SiC single crystal was produced in the same manner as in Example 1 except that the alloy raw material was charged and melted so that the temperature near the seed crystal substrate was 1700 ° C. and the temperature gradient was 20 ° C./cm.

黒鉛坩堝に、Ｓｉ：０.４８−Ｔｉ：０.１５−Ｖ：０.３７（[Ｔｉ]／[Ｔｉ＋Ｓｉ]＝０.２３、[Ｖ]／[Ｖ＋Ｓｉ]＝０.４３）となる組成の合金原料を装入し、種結晶基板近傍の温度が１７００℃、温度勾配が２０℃／ｃｍになるように融解させた以外は、実施例１と同様にＳｉＣ単結晶を製造した。 In a graphite crucible, the composition of Si: 0.48-Ti: 0.15-V: 0.37 ([Ti] / [Ti + Si] = 0.23, [V] / [V + Si] = 0.43) An SiC single crystal was produced in the same manner as in Example 1 except that the alloy raw material was charged and melted so that the temperature near the seed crystal substrate was 1700 ° C. and the temperature gradient was 20 ° C./cm.

（比較例１）
黒鉛坩堝に、Ｓｉ（[Ｖ]／[Ｖ＋Ｓｉ]＝０）を装入し、種結晶基板近傍の温度が１７００℃、温度勾配が２０℃／ｃｍになるように融解させた以外は、実施例１と同様にＳｉＣ単結晶を製造した。 (Comparative Example 1)
Example except that Si ([V] / [V + Si] = 0) was charged into a graphite crucible and melted so that the temperature near the seed crystal substrate was 1700 ° C. and the temperature gradient was 20 ° C./cm. In the same manner as in Example 1, a SiC single crystal was produced.

（比較例２）
黒鉛坩堝に、Ｓｉ：０.９５−Ｖ：０.０５（[Ｖ]／[Ｖ＋Ｓｉ]＝０.０５）となる組成の合金原料を装入し、種結晶基板近傍の温度が１７００℃、温度勾配が２０℃／ｃｍになるように融解させた以外は、実施例１と同様にＳｉＣ単結晶を製造した。 (Comparative Example 2)
An alloy material having a composition of Si: 0.95−V: 0.05 ([V] / [V + Si] = 0.05) was charged into a graphite crucible, and the temperature near the seed crystal substrate was 1700 ° C. A SiC single crystal was produced in the same manner as in Example 1 except that melting was performed so that the gradient became 20 ° C./cm.

（比較例３）
黒鉛坩堝に、Ｓｉ：０.５０−Ｖ：０.５０（[Ｖ]／[Ｖ＋Ｓｉ]＝０.５０）となる組成の合金原料を装入し、種結晶基板近傍の温度が１７００℃、温度勾配が２０℃／ｃｍになるように融解させた以外は、実施例１と同様にＳｉＣ単結晶を製造した。 (Comparative Example 3)
An alloy raw material having a composition of Si: 0.50−V: 0.50 ([V] / [V + Si] = 0.50) was charged into a graphite crucible, and the temperature near the seed crystal substrate was 1700 ° C. A SiC single crystal was produced in the same manner as in Example 1 except that melting was performed so that the gradient became 20 ° C./cm.

（比較例４）
黒鉛坩堝に、Ｓｉ：０.８−Ｔｉ：０.２（[Ｔｉ]／[Ｔｉ＋Ｓｉ]＝０.２０）となる組成の合金原料を装入し、種結晶基板近傍の温度が１７００℃、温度勾配が２０℃／ｃｍになるように融解させた以外は、実施例１と同様にＳｉＣ単結晶を製造した。 (Comparative Example 4)
An alloy raw material having a composition of Si: 0.8-Ti: 0.2 ([Ti] / [Ti + Si] = 0.20) was charged into a graphite crucible, and the temperature near the seed crystal substrate was 1700 ° C. A SiC single crystal was produced in the same manner as in Example 1 except that melting was performed so that the gradient became 20 ° C./cm.

（比較例５）
黒鉛坩堝に、Ｓｉ：０.６３−Ｔｉ：０.３０−Ｖ：０.０７（[Ｔｉ]／[Ｔｉ＋Ｓｉ]＝０.３２、[Ｖ]／[Ｖ＋Ｓｉ]＝０.１０）となる組成の合金原料を装入し、種結晶基板近傍の温度が１７００℃、温度勾配が２０℃／ｃｍになるように融解させた以外は、実施例１と同様にＳｉＣ単結晶を製造した。 (Comparative Example 5)
In a graphite crucible, the composition becomes Si: 0.63-Ti: 0.30-V: 0.07 ([Ti] / [Ti + Si] = 0.32, [V] / [V + Si] = 0.10). An SiC single crystal was produced in the same manner as in Example 1 except that the alloy raw material was charged and melted so that the temperature near the seed crystal substrate was 1700 ° C. and the temperature gradient was 20 ° C./cm.

（比較例６）
黒鉛坩堝に、Ｓｉ：０.５０−Ｔｉ：０.０７−Ｖ：０.４３（[Ｔｉ]／[Ｔｉ＋Ｓｉ]＝０.１２、[Ｖ]／[Ｖ＋Ｓｉ]＝０.４８）となる組成の合金原料を装入し、種結晶基板近傍の温度が１７００℃、温度勾配が２０℃／ｃｍになるように融解させた以外は、実施例１と同様にＳｉＣ単結晶を製造した。 (Comparative Example 6)
In a graphite crucible, the composition of Si: 0.50-Ti: 0.07-V: 0.43 ([Ti] / [Ti + Si] = 0.12, [V] / [V + Si] = 0.48) An SiC single crystal was produced in the same manner as in Example 1 except that the alloy raw material was charged and melted so that the temperature near the seed crystal substrate was 1700 ° C. and the temperature gradient was 20 ° C./cm.

以上の実施例と比較例について製造条件と結晶成長速度の測定結果を表１に示す。 Table 1 shows the production conditions and the measurement results of the crystal growth rate for the above examples and comparative examples.

実施例１、２と比較例１、２、３とを対比すると、溶媒がＳｉ−Ｖ合金であるＳ−Ｖ−Ｃ３元系融液の場合、ＳｉへのＶの添加量を適正化することによって、Ｓｉ−Ｃ２元系融液（Ｓｉ溶媒）に比べて、ＳｉＣ成長速度が１桁大きな値となることが分かる。ＳｉＣが初晶で晶出し、かつ、融液中のＣ溶解が増大するためと考察される。Ｖの添加量が多すぎた比較例３では、ＶＣが生成するため、ＳｉＣの安定成長は見込めない。 When Examples 1 and 2 are compared with Comparative Examples 1, 2, and 3, when the solvent is an S—V—C ternary melt in which an Si—V alloy is used, the amount of V added to Si should be optimized. It can be seen that the SiC growth rate is an order of magnitude greater than that of the Si—C binary melt (Si solvent). It is considered that SiC crystallizes in the primary crystal and C dissolution in the melt increases. In Comparative Example 3 in which the amount of V added is too large, since VC is generated, stable growth of SiC cannot be expected.

実施例３、４、５、６と比較例４、５、６とを対比すると、溶媒がＳ−Ｖ−Ｔｉ合金であるＳｉ−Ｖ−Ｔｉ−Ｃ４元系融液の場合、Ｓｉ−Ｔｉ溶媒へのＶの添加量を適正化することによって、Ｓｉ−Ｔｉ−Ｃ３元系融液（溶媒はＳｉ−Ｔｉ合金、比較例４）に比べてＳｉＣ成長速度が増大することが分かる。実施例５、６に示すように、ＶとＴｉを融液に添加すると、Ｖのみを添加した実施例１、２や、Ｔｉのみを添加した比較例４より成長速度が著しく高まり、ＶとＴｉの添加による相乗効果が認められた。しかし、ＶまたはＴｉの量が上限を超えると、比較例５、６に示すように、ＴｉＣまたはＶＣが生成して、ＳｉＣの安定成長が見込めなくなる。 When Examples 3, 4, 5, and 6 are compared with Comparative Examples 4, 5, and 6, when the solvent is an Si—V—Ti—C quaternary melt that is an S—V—Ti alloy, the Si—Ti solvent is used. It can be seen that, by optimizing the amount of V added to Si, the SiC growth rate is increased as compared with the Si—Ti—C ternary melt (the solvent is a Si—Ti alloy, Comparative Example 4). As shown in Examples 5 and 6, when V and Ti were added to the melt, the growth rate was significantly increased compared to Examples 1 and 2 in which only V was added and Comparative Example 4 in which only Ti was added. A synergistic effect due to the addition of was observed. However, when the amount of V or Ti exceeds the upper limit, TiC or VC is generated as shown in Comparative Examples 5 and 6, and stable growth of SiC cannot be expected.

以上に本発明を特定の実施形態および実施例により説明したが、これらはすべての点において例示にすぎず、制限的なものではないと解すべきである。本発明の範囲は、特許請求の範囲およびそれと均等な範囲内でのすべての変更を含むものである。 Although the present invention has been described above with reference to specific embodiments and examples, it should be understood that these are merely examples in all respects and are not limiting. The scope of the present invention includes all modifications within the scope of the claims and their equivalents.

本発明の実施例で使用した単結晶成長装置を示す略式断面図である。It is a schematic sectional drawing which shows the single crystal growth apparatus used in the Example of this invention.

符号の説明Explanation of symbols

１：シード軸、２：チャンバー、３：高周波コイル、４：種結晶基板、５：坩堝、６：融液、７：断熱材、８：坩堝軸 1: seed shaft, 2: chamber, 3: high frequency coil, 4: seed crystal substrate, 5: crucible, 6: melt, 7: heat insulating material, 8: crucible shaft

Claims

ＳｉとＣとＶとを含み、ＳｉとＶの原子比が、[Ｖ]／([Ｓｉ]＋[Ｖ])なる式で表して、０.１≦[Ｖ]／([Ｓｉ]＋[Ｖ])≦０.４５の関係を満たす融液に、ＳｉＣ成長用の種結晶基板を接触させ、少なくとも前記種結晶基板周辺において前記融液の過冷却により融液に溶解しているＳｉＣを過飽和状態とすることによって、前記種結晶基板上にＳｉＣ単結晶を成長させる、ＳｉＣ単結晶の製造方法。 Including Si, C, and V, the atomic ratio of Si and V is expressed by the formula [V] / ([Si] + [V]), where 0.1 ≦ [V] / ([Si] + [ V]) ≦ 0.45 is brought into contact with a seed crystal substrate for SiC growth, and at least the seed crystal substrate is supersaturated with SiC dissolved in the melt by overcooling the melt. A method for producing a SiC single crystal, wherein a SiC single crystal is grown on the seed crystal substrate by setting the state.

前記融液が更にＴｉを含み、ＳｉとＴｉの原子比が、[Ｔｉ]／([Ｓｉ]＋[Ｔｉ])なる式で表して、０.１≦[Ｔｉ]／([Ｓｉ]＋[Ｔｉ])≦０.２５の関係を満たす、請求項１記載のＳｉＣ単結晶の製造方法。 The melt further contains Ti, and the atomic ratio between Si and Ti is expressed by the formula [Ti] / ([Si] + [Ti]), where 0.1 ≦ [Ti] / ([Si] + [ The manufacturing method of the SiC single crystal of Claim 1 which satisfy | fills the relationship of Ti]) <= 0.25.