JP5614387B2 - Silicon carbide single crystal manufacturing method and silicon carbide single crystal ingot - Google Patents
Silicon carbide single crystal manufacturing method and silicon carbide single crystal ingot Download PDFInfo
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- 239000013078 crystal Substances 0.000 title claims description 144
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 title claims description 93
- 229910010271 silicon carbide Inorganic materials 0.000 title claims description 91
- 238000004519 manufacturing process Methods 0.000 title claims description 24
- 238000000034 method Methods 0.000 claims description 25
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- 238000006243 chemical reaction Methods 0.000 claims description 5
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- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
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Description
本発明は、基底面転位の少ない、結晶品質の高い炭化珪素単結晶の製造方法、及び炭化珪素単結晶インゴットに関するものである。本発明の製造方法により得られる炭化珪素単結晶から加工及び研磨工程を経て製造される炭化珪素単結晶基板は、主として各種の半導体電子デバイス、あるいはそれらの基板として用いられる。 The present invention is less basal plane dislocation, a method of manufacturing a highly crystalline quality silicon carbide single crystal, and those related to the silicon carbide single crystal ingot. A silicon carbide single crystal substrate manufactured by processing and polishing steps from a silicon carbide single crystal obtained by the manufacturing method of the present invention is mainly used as various semiconductor electronic devices or their substrates.
炭化珪素(ＳｉＣ)は２．２〜３．３ｅＶの広い禁制帯幅を有するワイドバンドギャップ半導体である。従来、ＳｉＣは、その優れた物理的、化学的特性から耐環境性半導体材料としての研究開発が行われてきたが、近年は青色から紫外にかけての短波長光デバイス、高周波電子デバイス、高耐圧・高出力電子デバイス向けの材料としてＳｉＣが注目されており、活発に研究開発が行われている。しかし、これまで、ＳｉＣは良質な大口径単結晶の製造が難しいとされてきており、それがＳｉＣデバイスの実用化を妨げてきた。 Silicon carbide (SiC) is a wide band gap semiconductor having a wide forbidden band width of 2.2 to 3.3 eV. Conventionally, SiC has been researched and developed as an environmentally resistant semiconductor material because of its excellent physical and chemical properties, but in recent years, short wavelength optical devices from blue to ultraviolet, high frequency electronic devices, SiC is attracting attention as a material for high-power electronic devices, and research and development is actively being conducted. However, until now, it has been considered difficult to produce high-quality large-diameter single crystals, which has hindered the practical application of SiC devices.
従来、研究室程度の規模では、例えば昇華再結晶法(レーリー法)で半導体素子の作製が可能なサイズのＳｉＣ単結晶を得ていた。しかしながら、この方法では得られる単結晶の面積が小さく、その寸法、形状、さらには結晶多形(ポリタイプ)や不純物キャリア濃度の制御も容易ではない。一方、化学気相成長(Chemical Vapor Deposition、CVD)を用いて珪素(Ｓｉ)等の異種基板上にヘテロエピタキシャル成長させることにより、立方晶のＳｉＣ単結晶を成長させることも行われている。この方法では大面積の単結晶は得られるが、ＳｉＣとＳｉの格子不整合が約２０％もあること等により、多くの欠陥（〜１０7/ｃｍ2）を含むＳｉＣ単結晶しか成長させることができず、高品質のＳｉＣ単結晶は得られていない。これらの問題点を解決するために、ＳｉＣ単結晶ウェハを種結晶として用いて昇華再結晶を行う改良型のレーリー法が提案されている（特許文献１）。この改良レーリー法を用いれば、ＳｉＣ単結晶のポリタイプ(６Ｈ型、４Ｈ型、１５Ｒ型等)及び形状、キャリア型及び濃度を制御しながらＳｉＣ単結晶を成長させることができる。 Conventionally, on the scale of a laboratory level, for example, a SiC single crystal having a size capable of producing a semiconductor element by a sublimation recrystallization method (Rayleigh method) has been obtained. However, in this method, the area of the obtained single crystal is small, and it is not easy to control the size, shape, crystal polymorph (polytype), and impurity carrier concentration. On the other hand, a cubic SiC single crystal is also grown by heteroepitaxial growth on a heterogeneous substrate such as silicon (Si) using chemical vapor deposition (CVD). With this method, a single crystal with a large area can be obtained, but only a SiC single crystal containing many defects (−10 7 / cm 2 ) can be grown due to the lattice mismatch between SiC and Si of about 20%. Therefore, a high-quality SiC single crystal has not been obtained. In order to solve these problems, an improved Rayleigh method for performing sublimation recrystallization using a SiC single crystal wafer as a seed crystal has been proposed (Patent Document 1). By using this improved Rayleigh method, a SiC single crystal can be grown while controlling the polytype (6H type, 4H type, 15R type, etc.), shape, carrier type and concentration of the SiC single crystal.
現在、改良レーリー法で作製したＳｉＣ単結晶から、口径５１ｍｍ(２インチ)から１００ｍｍのＳｉＣ単結晶ウェハが切り出され、電力エレクトロニクス分野のデバイス作製等に供されている。ＳｉＣには２００種類以上のポリタイプがあるが、物性値及び結晶成長の安定性から、４Ｈポリタイプが電子デバイス用途として使用されることが多い。ＳｉＣ単結晶中には、マイクロパイプと呼ばれる成長方向に貫通した中空ホール状欠陥、転位欠陥（貫通刃状転位、基底面転位、らせん転位）、積層欠陥等の結晶欠陥が存在している。これらの結晶欠陥はデバイス性能を低下させるために、これらの結晶欠陥の低減がＳｉＣデバイス応用上の重要課題とされている。 At present, a SiC single crystal wafer having a diameter of 51 mm (2 inches) to 100 mm is cut out from a SiC single crystal manufactured by an improved Rayleigh method and used for device manufacturing in the field of power electronics. There are over 200 polytypes of SiC, but the 4H polytype is often used as an electronic device because of its physical properties and stability of crystal growth. In SiC single crystals, there are crystal defects such as hollow hole defects penetrating in the growth direction called micropipes, dislocation defects (penetrating edge dislocations, basal plane dislocations, screw dislocations), stacking faults, and the like. Since these crystal defects deteriorate device performance, reduction of these crystal defects is regarded as an important issue in SiC device application.
現在市販されているＳｉＣ基板中にはらせん転位は８×１０2〜３×１０3（個／ｃｍ2）、貫通刃状転位は５×１０3〜２×１０4（個／ｃｍ2）、基底面転位は２×１０3〜２×１０4（個／ｃｍ2）存在している（非特許文献１）。 In a SiC substrate currently on the market, screw dislocations are 8 × 10 2 to 3 × 10 3 (pieces / cm 2 ), threading edge dislocations are 5 × 10 3 to 2 × 10 4 (pieces / cm 2 ), The basal plane dislocations are 2 × 10 3 to 2 × 10 4 (pieces / cm 2 ) (Non-patent Document 1).
近年、結晶欠陥とデバイス性能に関する調査から、基底面転位がデバイスの酸化膜不良を生じ絶縁破壊の原因となることが報告されている。（非特許文献２）。また、バイポーラデバイスなどでは、基底面転位から積層欠陥が発生することが報告されており、デバイス特性の劣化の原因となることが知られている（非特許文献３）。高性能ＳｉＣデバイスの作製のために基底面転位の少ないＳｉＣ単結晶基板が求められている。 In recent years, studies on crystal defects and device performance have reported that basal plane dislocations cause device oxide film defects and cause dielectric breakdown. (Non-patent document 2). In bipolar devices and the like, it has been reported that stacking faults are generated from basal plane dislocations, and this is known to cause deterioration of device characteristics (Non-Patent Document 3). There is a need for a SiC single crystal substrate with few basal plane dislocations for the production of high performance SiC devices.
昇華再結晶法によって所定の成長圧力及び基板温度でおよそ２００μｍのＳｉＣ単結晶を初期成長層として成長させた後、基板温度及び圧力を徐々に減じながら結晶成長を行うことで、マイクロパイプやらせん転位の極めて少ない高品質なＳｉＣ単結晶を得る方法が報告されている（特許文献２参照）。しかしながら、基底面転位密度については言及されておらず、ＳｉＣデバイスへの応用を考えると基底面転位密度の低減化が必要である。同じく、所定の成長圧力及び基板温度で同程度のＳｉＣ単結晶を初期成長層として成長させた後、基板温度はそのままで減圧して成長速度を高めて結晶成長させて、マイクロパイプの発生を抑えて、かつ、らせん転位等の転位密度を少なくさせる方法が報告されているが（特許文献３参照）、この場合も高性能ＳｉＣデバイスの作製のために基底面転位密度の低減化が必要である。 After growing a SiC single crystal of about 200μm as an initial growth layer at a predetermined growth pressure and substrate temperature by sublimation recrystallization method, crystal growth is carried out while gradually decreasing the substrate temperature and pressure, so that micropipes and screw dislocations can be obtained. There has been reported a method for obtaining a high-quality SiC single crystal with very little (see Patent Document 2). However, there is no mention of the basal plane dislocation density, and it is necessary to reduce the basal plane dislocation density in consideration of application to SiC devices. Similarly, after growing a SiC single crystal of the same degree as the initial growth layer at a predetermined growth pressure and substrate temperature, the substrate temperature is kept as it is and the growth rate is increased to grow the crystal, thereby suppressing the occurrence of micropipes. In addition, a method for reducing the dislocation density such as screw dislocation has been reported (see Patent Document 3), but in this case as well, it is necessary to reduce the basal plane dislocation density in order to produce a high-performance SiC device. .
なお、化学気相成長法（ＣＶＤ法）でのＳｉＣ薄膜のエピタキシャル成長において、鏡像力によって基底面転位が刃状転位に変換すること（非特許文献４）や、溶液成長法においてもほぼ同様の構造変換が起こること（非特許文献５）が報告されている。また、昇華再結晶法での報告例として、Ohtaniらは貫通刃状転位が基底面転位に変換することを報告している（非特許文献６）。しかしながら、これら先行技術において、ＳｉＣ単結晶を工業的に製造する上で、基底面転位を構造変換させて減らすための制御方法やその条件等については一切述べられていない。 In the epitaxial growth of a SiC thin film by chemical vapor deposition (CVD), the basal plane dislocation is converted into edge dislocation by mirror image force (Non-Patent Document 4), and the solution growth method has almost the same structure. It has been reported that conversion occurs (Non-Patent Document 5). As a report example in the sublimation recrystallization method, Ohtani et al. Report that threading edge dislocations are converted to basal plane dislocations (Non-patent Document 6). However, in these prior arts, there is no mention of a control method and its conditions for reducing the basal plane dislocations by structural conversion in industrial production of SiC single crystals.
本発明は、上記事情に鑑みてなされたものであり、昇華再結晶法による炭化珪素単結晶の成長において、基底面転位が少なく、結晶品質の高く、抵抗率が制御されたＳｉＣ単結晶を得ることができる製造方法を提供するものである。 The present invention has been made in view of the above circumstances, and in the growth of a silicon carbide single crystal by a sublimation recrystallization method, obtains a SiC single crystal having few basal plane dislocations, high crystal quality, and controlled resistivity. The manufacturing method which can be provided is provided .
本発明は以下の構成より成るものである。
（１）（０００１）面を主面としてオフ角が＜１１−２０＞方向に４度傾いた４Ｈ型の炭化珪素単結晶基板からなる種結晶を用いた昇華再結晶法による炭化珪素単結晶の製造方法において、成長雰囲気圧力を３．９ｋＰａ以上３９．９ｋＰａ以下、成長温度を２１００℃以上２３００℃未満にして、成長中の炭化珪素単結晶に存在する基底面転位の少なくとも一部を貫通刃状転位に構造変換させることを特徴とする炭化珪素単結晶の製造方法。
（２）前記構造変換の手段が、成長雰囲気圧力を３．９ｋＰａ以上１３．３ｋＰａ未満、成長温度を２１００℃以上２３００℃未満にすることである（１）に記載の炭化珪素単結晶の製造方法。
（３）（０００１）面を主面としてオフ角が＜１１−２０＞方向に４度傾いた４Ｈ型の炭化珪素単結晶基板からなる種結晶を用いた昇華再結晶法による炭化珪素単結晶の製造方法において、成長雰囲気圧力を１．３ｋＰａ以上３．９ｋＰａ未満、成長温度を２１００℃以上２２００℃未満にして、成長中の炭化珪素単結晶に存在する基底面転位の少なくとも一部を貫通刃状転位に構造変換させることを特徴とする炭化珪素単結晶の製造方法。
（４）（１）〜（３）のいずれか１項に記載の方法で作製した炭化珪素単結晶インゴットであって、種結晶に比べて基底面転位密度が少なく、かつ、種結晶に比べて貫通刃状転位の多い炭化珪素単結晶が結晶成長していることを特徴とする炭化珪素単結晶インゴット。
（５）基底面転位密度が１０００個／ｃｍ2以下の部位を有する（４）に記載の炭化珪素単結晶インゴット。
（６）基底面転位密度が５００個／ｃｍ2以下の部位を有する（４）に記載の炭化珪素単結晶インゴット。
（７）基底面転位密度が２５０個／ｃｍ2以下の部位を有する（４）に記載の炭化珪素単結晶インゴット。
（８）前記インゴットのポリタイプが４Ｈ型、６Ｈ型又は３Ｃ型のいずれかの単一ポリタイプである（４）〜（７）のいずれか１項に記載の炭化珪素単結晶インゴット。
（９）前記インゴットの口径が５０ｍｍ以上３００ｍｍ以下である（４）〜（８）のいずれか１項に記載の炭化珪素単結晶インゴット。
The present invention has the following configuration.
(1) A silicon carbide single crystal formed by a sublimation recrystallization method using a seed crystal composed of a 4H type silicon carbide single crystal substrate having a (0001) plane as a main surface and an off-angle of 4 ° in the <11-20> direction . In the manufacturing method, the growth atmospheric pressure is set to 3.9 kPa or more and 39.9 kPa or less, the growth temperature is set to 2100 ° C. or more and less than 2300 ° C., and at least a part of the basal plane dislocations existing in the growing silicon carbide single crystal is threaded. A method for producing a silicon carbide single crystal, wherein the structure is converted into dislocations.
(2) The method for producing a silicon carbide single crystal according to (1), wherein the means for the structural conversion is that the growth atmosphere pressure is 3.9 kPa or more and less than 13.3 kPa, and the growth temperature is 2100 ° C. or more and less than 2300 ° C. .
(3) A silicon carbide single crystal formed by a sublimation recrystallization method using a seed crystal composed of a 4H type silicon carbide single crystal substrate having a (0001) plane as a principal plane and an off angle of 4 degrees in the <11-20> direction . In the manufacturing method, the growth atmosphere pressure is set to 1.3 kPa or more and less than 3.9 kPa, the growth temperature is set to 2100 ° C. or more and less than 2200 ° C., and at least a part of the basal plane dislocations existing in the growing silicon carbide single crystal is formed as a penetrating edge. A method for producing a silicon carbide single crystal, wherein the structure is converted into dislocations.
(4) A silicon carbide single crystal ingot produced by the method according to any one of (1) to (3), wherein the basal plane dislocation density is lower than that of the seed crystal and is higher than that of the seed crystal. A silicon carbide single crystal ingot characterized by crystal growth of a silicon carbide single crystal with many threading edge dislocations .
(5) The silicon carbide single crystal ingot according to (4), having a basal plane dislocation density of 1000 / cm 2 or less.
(6) The silicon carbide single crystal ingot according to (4), which has a portion having a basal plane dislocation density of 500 pieces / cm 2 or less.
(7) The silicon carbide single crystal ingot according to (4), wherein the basal plane dislocation density has a site of 250 pieces / cm 2 or less.
(8) polytype of the ingot 4H type, 6H type or any single polytype of 3C type (4) to (7) single-crystal silicon carbide ingot according to any one of.
(9) The silicon carbide single crystal ingot according to any one of (4) to (8), wherein a diameter of the ingot is 50 mm or greater and 300 mm or less.
本発明のＳｉＣ単結晶の製造方法は、既存の製造装置に何ら改造を加えることなく、成長雰囲気圧力・温度を制御することで、簡便に基底面転位を大幅に低減した高品質のＳｉＣ単結晶を製造できる。また、本発明のＳｉＣ単結晶は、基底面転位が少なく、この単結晶から加工された基板は高品質であるため、電子デバイス向けの基板として高い性能を発揮する。 The SiC single crystal manufacturing method of the present invention is a high-quality SiC single crystal in which the basal plane dislocation is easily greatly reduced by controlling the growth atmosphere pressure and temperature without any modification to the existing manufacturing apparatus. Can be manufactured. Moreover, since the SiC single crystal of the present invention has few basal plane dislocations and the substrate processed from this single crystal is of high quality, it exhibits high performance as a substrate for electronic devices.
本発明により、ＳｉＣ単結晶中において基底面転位を貫通刃状転位へ構造変換させることで、基底面転位の少ない高品質ＳｉＣ単結晶の製造が可能となる。 According to the present invention, it is possible to manufacture a high-quality SiC single crystal with few basal plane dislocations by structurally converting basal plane dislocations to threading edge dislocations in the SiC single crystal.
本発明者らは種結晶を用いた昇華再結晶法による炭化珪素単結晶成長において、成長雰囲気圧力が３．９ｋＰａ以上３９．９ｋＰａ以下、かつ、成長温度を２１００℃以上２３００℃未満とすることで基底面転位密度が顕著に減少することを見つけた。この時、貫通刃状転位が増加していることから基底面転位が貫通刃状転位に構造変換してことが示唆された。 In the silicon carbide single crystal growth by a sublimation recrystallization method using a seed crystal, the present inventors set the growth atmosphere pressure to 3.9 kPa to 39.9 kPa and the growth temperature to 2100 ° C. or more and less than 2300 ° C. It was found that the basal plane dislocation density decreased significantly. At this time, the number of threading edge dislocations increased, suggesting that basal plane dislocations were structurally converted to threading edge dislocations.
本発明者らは、成長雰囲気圧力を３．９ｋＰａ以上３９．９ｋＰａ以下、かつ、成長温度を２１００℃以上２３００℃未満とすることで、好ましくは、成長雰囲気圧力を３．９ｋＰａ以上１３．３ｋＰａ未満、成長温度を２１００℃以上２３００℃未満にすることで、結晶成長速度をＣＶＤ法及び溶液成長法並みの低速成長（数１０μｍ／ｈ）を実現することができ、この時に基底面転位の貫通刃状転位への構造変換が起きることを発見した。成長雰囲気圧力が高い場合、原料ガスの拡散が抑えられるため、結晶成長表面へ到達する原料ガス量が減るために成長速度が小さくなることにつながっているものと考えられる。すなわち、成長雰囲気圧力を３．９ｋＰａ以上３９．９ｋＰａ以下、かつ、成長温度を２１００℃以上２３００℃未満とすることで、結晶成長速度を５０μｍ／ｈ以下に抑えて、基底面転位を貫通刃状転位に構造変換させることができるようになる。 The inventors set the growth atmosphere pressure to 3.9 kPa to 39.9 kPa, and the growth temperature to 2100 ° C. to less than 2300 ° C., preferably, the growth atmosphere pressure is 3.9 kPa to less than 13.3 kPa. By setting the growth temperature to 2100 ° C. or higher and lower than 2300 ° C., the crystal growth rate can be achieved as low as the CVD method and the solution growth method (several tens of μm / h). It has been found that structural transformation to a dislocation occurs. When the growth atmosphere pressure is high, the diffusion of the raw material gas is suppressed, and therefore the amount of the raw material gas reaching the crystal growth surface is reduced, leading to a reduction in the growth rate. That is, by setting the growth atmosphere pressure to 3.9 kPa to 39.9 kPa and the growth temperature to 2100 ° C. to less than 2300 ° C., the crystal growth rate is suppressed to 50 μm / h or less, and the basal plane dislocation is threaded. It becomes possible to convert the structure into dislocations.
また、成長雰囲気圧力１．３ｋＰａ以上３．９ｋＰａ未満、かつ、成長温度が２１００℃以上２２００℃未満での結晶成長中にも基底面転位の貫通刃状転位の構造変換が起きることを見出した。これは、成長温度を２１００℃以上２２００℃未満にすることで、原料ガスの昇華量が少なくなるために成長速度が数１０μｍ／ｈ程度に低速化されるため、先の場合と同様にこの構造変換が起きると考えられる。 It was also found that structural transformation of threading edge dislocations of basal plane dislocation occurred during crystal growth at a growth atmosphere pressure of 1.3 kPa to less than 3.9 kPa and a growth temperature of 2100 ° C. to less than 2200 ° C. This is because when the growth temperature is set to 2100 ° C. or higher and lower than 2200 ° C., the sublimation amount of the source gas is reduced, so that the growth rate is reduced to about several tens of μm / h. Conversion is expected to occur.
本発明によって作製されたＳｉＣ単結晶インゴットは基底面転位が少ないため、インゴットから切り出した基板からは、基底面転位起因のデバイス性能の劣化の少ない、高性能デバイスの作製が可能である。また、基底面転位はデバイス作製時の酸化膜不良を起こし、デバイス作製歩留りが低下する原因となると考えられるため、その密度は１０００個／ｃｍ2以下、更には５００個／ｃｍ2以下、更に望ましくは２５０個／ｃｍ2以下であることが好ましい。 Since the SiC single crystal ingot produced by the present invention has few basal plane dislocations, it is possible to produce a high-performance device with little deterioration in device performance due to basal plane dislocations from a substrate cut out from the ingot. In addition, since basal plane dislocation is considered to cause an oxide film defect during device fabrication and cause a decrease in device fabrication yield, the density is 1000 / cm 2 or less, more preferably 500 / cm 2 or less, and more desirably. Is preferably 250 pieces / cm 2 or less.
本発明は、転位の構造変換を利用した基底面転位の低減化であることから、特にポリタイプによる制限はなく、代表的なポリタイプである４Ｈ型、６Ｈ型および３Ｃ型のＳｉＣ単結晶に適用可能である。特にパワーデバイス応用として有力視されている４Ｈ型にも適用可能である。 Since the present invention is a reduction of basal plane dislocations utilizing structural transformation of dislocations, there is no particular limitation on polytypes, and typical polytypes such as 4H-type, 6H-type and 3C-type SiC single crystals are used. Applicable. In particular, the present invention can also be applied to the 4H type, which is regarded as a promising power device application.
本発明のらせん転位の低減は、成長雰囲気圧力および成長温度を制御することで行われるため、適用範囲で結晶口径の制限は無く、口径５０ｍｍ以上、３００ｍｍ以下の結晶成長プロセスへの適用が可能である。 Since the screw dislocation reduction of the present invention is performed by controlling the growth atmosphere pressure and growth temperature, there is no limitation on the crystal diameter in the applicable range, and it can be applied to a crystal growth process with a diameter of 50 mm or more and 300 mm or less. is there.
本発明のＳｉＣ単結晶の製造方法では、高純度ガス配管やマスフローコントローラ等を用いてＳｉＣ単結晶の成長雰囲気中に供給する窒素ガス量を制御することで、結晶中への窒素ドープが可能である。これによって結晶から得られる単結晶基板の抵抗率を制御することができる。 In the method for producing a SiC single crystal according to the present invention, nitrogen can be doped into the crystal by controlling the amount of nitrogen gas supplied into the growth atmosphere of the SiC single crystal using a high purity gas pipe or a mass flow controller. is there. Thus, the resistivity of the single crystal substrate obtained from the crystal can be controlled.
以下、本発明を実施例に基づき具体的に説明する。 Hereinafter, the present invention will be specifically described based on examples.
図１は、本発明の実施例の結晶を製造するために用いた改良レーリー法による単結晶成長装置である。結晶成長は、昇華原料２を誘導加熱により昇華させ、種結晶１上に再結晶させることにより行われる。種結晶１は黒鉛蓋４の内面に取り付けられており、昇華原料２は黒鉛坩堝３の内部に充填される。この黒鉛坩堝３及び黒鉛蓋４は、熱シールドのために黒鉛製フェルト７で被膜され、二重石英管５内部の黒鉛支持棒６の上に設置される。石英管５の内部を真空排気装置１１によって真空排気した後、高純度Ａｒガスおよび窒素ガスを、配管９を介してマスフローコントローラ１０で制御しながら流入させ、石英管内圧力（成長雰囲気圧力）を真空排気装置１１で調整しながらワークコイル８に高周波電流を流し、黒鉛坩堝を加熱することで結晶成長を行った。成長温度は炭化珪素種結晶温度とした。
FIG. 1 shows an apparatus for growing a single crystal by an improved Rayleigh method used for producing a crystal according to an embodiment of the present invention. Crystal growth is performed by sublimating the sublimation
(実施例１)
予め成長しておいたＳｉＣ単結晶インゴットから、口径５０ｍｍの（０００１）面を主面とした、オフ角が〈１１−２０〉方向に４度傾いた４Ｈ型のＳｉＣ単結晶基板を切り出し、研磨後、種結晶とした。成長雰囲気圧力１３．３ｋＰａ、成長温度２２００℃の条件で結晶成長を行った。なお、得られた結晶の高さと成長時間から成長速度を算出すると、結晶成長速度は２０μｍ／ｈであった。
(Example 1)
A 4H type SiC single crystal substrate having a (0001) plane with a diameter of 50 mm as a main surface and an off angle inclined by 4 degrees in the <11-20> direction is cut out from a previously grown SiC single crystal ingot and polished. Thereafter, a seed crystal was obtained. Crystal growth was performed under conditions of a growth atmosphere pressure of 13.3 kPa and a growth temperature of 2200 ° C. When the growth rate was calculated from the height of the obtained crystal and the growth time, the crystal growth rate was 20 μm / h.
得られた結晶より（０００１）面４度オフウェハを切り出し、鏡面研磨の後に、溶融ＫＯＨエッチングを行い、光学顕微鏡によって基底面転位密度および貫通刃状転位密度を計測した。ここではJ. Takahashi et al., Journal of Crystal Growth, 135, (1994), 61-70に記載されている方法に従って、５３０℃の溶融ＫＯＨに試料を１０分間浸漬し、貝殻型ピットを基底面転位、小型の６角形ピットを貫通刃状転位、中型・大型の６角形ピットをらせん転位として、エッチピット形状から転位欠陥を分類した。基底面転位密度が４．８×１０2（個／ｃｍ2）、貫通刃状転位密度が６．５×１０3（個／ｃｍ2）であった。成長に使用した種結晶の基底面転位密度は２．５×１０3（個／ｃｍ2）、貫通刃状転位密度は４．４×１０3（個／ｃｍ2）であった。これらの増減より結晶成長中に基底面転位が貫通刃状転位に構造変換しているものと示唆される。 A (0001) plane 4 degree off-wafer was cut out from the obtained crystal, and after mirror polishing, melted KOH etching was performed, and the basal plane dislocation density and threading edge dislocation density were measured with an optical microscope. Here, according to the method described in J. Takahashi et al., Journal of Crystal Growth, 135, (1994), 61-70, the sample was immersed for 10 minutes in molten KOH at 530 ° C. Dislocation defects were classified based on etch pit shape, with dislocations, small hexagonal pits as threading edge dislocations, and medium and large hexagonal pits as screw dislocations. The basal plane dislocation density was 4.8 × 10 2 (pieces / cm 2 ) and the threading edge dislocation density was 6.5 × 10 3 (pieces / cm 2 ). The seed crystal used for growth had a basal plane dislocation density of 2.5 × 10 3 (pieces / cm 2 ) and a threading edge dislocation density of 4.4 × 10 3 (pieces / cm 2 ). From these increases and decreases, it is suggested that the basal plane dislocations are structurally converted to threading edge dislocations during crystal growth.
(実施例２)
予め成長しておいたＳｉＣ単結晶インゴットから、口径５０ｍｍの（０００１）面を主面としたオフ角が〈１１−２０〉方向に４度傾いた４Ｈ型のＳｉＣ単結晶基板を切り出し、研磨後、種結晶とした。成長雰囲気圧力１３．３ｋPaで成長温度は２１５０℃の条件で結晶成長を行った。なお、このときの成長速度は１５μｍ／ｈであった。
(Example 2)
After a SiC single crystal ingot grown in advance, a 4H type SiC single crystal substrate having an off angle of 4 degrees in the <11-20> direction with a (0001) plane of 50 mm in diameter as the main surface is cut and polished. A seed crystal was obtained. Crystal growth was performed under the conditions of a growth atmosphere pressure of 13.3 kPa and a growth temperature of 2150 ° C. The growth rate at this time was 15 μm / h.
得られた結晶より（０００１）面４度オフウェハを切り出し、鏡面研磨の後に、溶融ＫＯＨエッチングを行い、光学顕微鏡によって基底面転位密度を計測した。基底面転位密度が１．５×１０2（個／ｃｍ2）であった。 A (0001) plane 4 degree off-wafer was cut out from the obtained crystal, and after mirror polishing, melted KOH etching was performed, and the basal plane dislocation density was measured with an optical microscope. The basal plane dislocation density was 1.5 × 10 2 (pieces / cm 2 ).
(実施例３)
予め成長しておいたＳｉＣ単結晶インゴットから、口径８０ｍｍの（０００１）面を主面としたオフ角が〈１１−２０〉方向に４度傾いた４Ｈ型のＳｉＣ単結晶基板を切り出し、研磨後、種結晶とした。成長雰囲気圧力１．３ｋＰａで成長温度は２１００℃の条件で結晶成長を行った。なお、このときの成長速度は４０μｍ／ｈであった。
Example 3
After a SiC single crystal ingot grown in advance, a 4H type SiC single crystal substrate having an off angle of 4 degrees in the <11-20> direction with a (0001) plane of 80 mm as the main surface is cut out and polished A seed crystal was obtained. Crystal growth was performed under conditions of a growth atmosphere pressure of 1.3 kPa and a growth temperature of 2100 ° C. The growth rate at this time was 40 μm / h.
得られた結晶より（０００１）面４度オフウェハを切り出し、鏡面研磨の後に、溶融ＫＯＨエッチングを行い、光学顕微鏡によって基底面転位密度を計測した。基底面転位密度は２．０×１０2（個／ｃｍ2）であった。 A (0001) plane 4 degree off-wafer was cut out from the obtained crystal, and after mirror polishing, melted KOH etching was performed, and the basal plane dislocation density was measured with an optical microscope. The basal plane dislocation density was 2.0 × 10 2 (pieces / cm 2 ).
（比較例１）
予め成長しておいたＳｉＣ単結晶インゴットから、口径５０ｍｍの（０００１）面を主面としたオフ角が〈１１−２０〉方向に４度傾いた４Ｈ型のＳｉＣ単結晶基板を切り出し、研磨後、種結晶とした。結晶成長は上記の通りに行い、真空排気装置で結晶成長中の雰囲気圧力を１．３ｋＰａに調整した。成長温度は２２５０℃になるようにコイル出力を調整した。
(Comparative Example 1)
After a SiC single crystal ingot grown in advance, a 4H type SiC single crystal substrate having an off angle of 4 degrees in the <11-20> direction with a (0001) plane of 50 mm in diameter as the main surface is cut and polished. A seed crystal was obtained. Crystal growth was performed as described above, and the atmospheric pressure during crystal growth was adjusted to 1.3 kPa with a vacuum exhaust apparatus. The coil output was adjusted so that the growth temperature was 2250 ° C.
結晶の（０００１）面４度オフウェハを切り出し、鏡面研磨の後に、溶融ＫＯＨエッチングを行い、光学顕微鏡によって基底面転位密度を計測した。基底面転位密度は２×１０3（個／ｃｍ2）であった。基底面転位の著しい低減は見られなかった。 A crystal (0001) plane 4 ° off-wafer was cut out, mirror-polished, then melted KOH etched, and the basal plane dislocation density was measured with an optical microscope. The basal plane dislocation density was 2 × 10 3 (pieces / cm 2 ). There was no significant reduction in basal plane dislocations.
１ 種結晶(ＳｉＣ単結晶)
２ 昇華原料
３ 黒鉛坩堝
４ 黒鉛蓋
５ 二重石英管
６ 支持棒
７ 黒鉛製フェルト
８ ワークコイル
９ 高純度ガス配管
１０ 高純度ガス用マスフローコントローラ
１１ 真空排気装置
1 Seed crystal (SiC single crystal)
2 Sublimation raw materials 3 Graphite crucible 4
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