JP2010270000A - Silicon carbide raw material for growing silicon carbide single crystal and method for producing silicon carbide single crystal using the same - Google Patents
Silicon carbide raw material for growing silicon carbide single crystal and method for producing silicon carbide single crystal using the same Download PDFInfo
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- 239000013078 crystal Substances 0.000 title claims abstract description 223
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 title claims abstract description 161
- 229910010271 silicon carbide Inorganic materials 0.000 title claims abstract description 160
- 239000002994 raw material Substances 0.000 title claims abstract description 64
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 21
- 238000000034 method Methods 0.000 claims abstract description 54
- 239000012535 impurity Substances 0.000 claims abstract description 45
- 238000000859 sublimation Methods 0.000 claims abstract description 21
- 230000008022 sublimation Effects 0.000 claims abstract description 21
- 238000001953 recrystallisation Methods 0.000 claims abstract description 19
- 230000008569 process Effects 0.000 claims abstract description 15
- 239000000463 material Substances 0.000 claims abstract description 10
- 238000009826 distribution Methods 0.000 claims description 7
- 239000002245 particle Substances 0.000 claims description 4
- 238000005192 partition Methods 0.000 abstract description 5
- 235000012431 wafers Nutrition 0.000 description 50
- 239000000843 powder Substances 0.000 description 23
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 21
- 229910002804 graphite Inorganic materials 0.000 description 21
- 239000010439 graphite Substances 0.000 description 21
- 239000010409 thin film Substances 0.000 description 17
- 239000007789 gas Substances 0.000 description 15
- 239000000758 substrate Substances 0.000 description 12
- 239000010453 quartz Substances 0.000 description 10
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 10
- 239000012071 phase Substances 0.000 description 8
- 238000004140 cleaning Methods 0.000 description 7
- 230000007547 defect Effects 0.000 description 7
- 230000003287 optical effect Effects 0.000 description 6
- 239000007787 solid Substances 0.000 description 6
- 239000007790 solid phase Substances 0.000 description 6
- 238000005229 chemical vapour deposition Methods 0.000 description 5
- 238000010298 pulverizing process Methods 0.000 description 5
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 4
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 description 4
- BLRPTPMANUNPDV-UHFFFAOYSA-N Silane Chemical compound [SiH4] BLRPTPMANUNPDV-UHFFFAOYSA-N 0.000 description 4
- 229910052751 metal Inorganic materials 0.000 description 4
- 239000002184 metal Substances 0.000 description 4
- 238000000746 purification Methods 0.000 description 4
- 239000004065 semiconductor Substances 0.000 description 4
- 229910000077 silane Inorganic materials 0.000 description 4
- 230000009466 transformation Effects 0.000 description 4
- XCZXGTMEAKBVPV-UHFFFAOYSA-N trimethylgallium Chemical compound C[Ga](C)C XCZXGTMEAKBVPV-UHFFFAOYSA-N 0.000 description 4
- 229910052720 vanadium Inorganic materials 0.000 description 4
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 description 4
- 238000004430 X-ray Raman scattering Methods 0.000 description 3
- 238000002441 X-ray diffraction Methods 0.000 description 3
- 239000002253 acid Substances 0.000 description 3
- 239000003513 alkali Substances 0.000 description 3
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 3
- 229910003460 diamond Inorganic materials 0.000 description 3
- 239000010432 diamond Substances 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- 229910021529 ammonia Inorganic materials 0.000 description 2
- 239000010408 film Substances 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 125000004435 hydrogen atom Chemical class [H]* 0.000 description 2
- 239000011261 inert gas Substances 0.000 description 2
- 239000004570 mortar (masonry) Substances 0.000 description 2
- 239000003960 organic solvent Substances 0.000 description 2
- 239000001294 propane Substances 0.000 description 2
- 239000002002 slurry Substances 0.000 description 2
- 229910001218 Gallium arsenide Inorganic materials 0.000 description 1
- 238000001069 Raman spectroscopy Methods 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 239000003082 abrasive agent Substances 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 230000006911 nucleation Effects 0.000 description 1
- 238000010899 nucleation Methods 0.000 description 1
- 230000003071 parasitic effect Effects 0.000 description 1
- 238000005498 polishing Methods 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 239000003870 refractory metal Substances 0.000 description 1
- 229910021332 silicide Inorganic materials 0.000 description 1
- FVBUAEGBCNSCDD-UHFFFAOYSA-N silicide(4-) Chemical compound [Si-4] FVBUAEGBCNSCDD-UHFFFAOYSA-N 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000001308 synthesis method Methods 0.000 description 1
- 229910052715 tantalum Inorganic materials 0.000 description 1
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 description 1
- 150000003682 vanadium compounds Chemical class 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
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Abstract
Description
本発明は、炭化珪素単結晶育成用炭化珪素原料及びそれを用いた炭化珪素単結晶の製造方法に係わり、特に、電子デバイスの基板ウェハとなる良質で大型の単結晶インゴットの製造方法に関するものである。 The present invention relates to a silicon carbide raw material for growing a silicon carbide single crystal and a method for producing a silicon carbide single crystal using the same, and more particularly to a method for producing a high-quality and large-sized single crystal ingot to be a substrate wafer of an electronic device. is there.
炭化珪素（ＳｉＣ）は、耐熱性及び機械的強度も優れ、放射線に強い等の物理的、化学的性質から耐環境性半導体材料として注目されている。また、近年、青色から紫外にかけての短波長光デバイス、高周波高耐圧電子デバイス等の基板ウェハとしてＳｉＣ単結晶ウェハの需要が高まっている。しかしながら、大面積を有する高品質のＳｉＣ単結晶を、工業的規模で安定に供給し得る結晶成長技術は、いまだ確立されていない。それゆえ、ＳｉＣは、上述のような多くの利点及び可能性を有する半導体材料にもかかわらず、その実用化が阻まれていた。 Silicon carbide (SiC) has excellent heat resistance and mechanical strength, and has attracted attention as an environmentally resistant semiconductor material because of its physical and chemical properties such as resistance to radiation. In recent years, the demand for SiC single crystal wafers as substrate wafers for short-wavelength optical devices from blue to ultraviolet, high-frequency high-voltage electronic devices, and the like has increased. However, a crystal growth technique that can stably supply a high-quality SiC single crystal having a large area on an industrial scale has not yet been established. Therefore, practical use of SiC has been hindered despite the semiconductor material having many advantages and possibilities as described above.
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ＳｉＣ単結晶を成長させ、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、得られた単結晶の面積が小さく、その寸法及び形状を高精度に制御することは困難である。また、ＳｉＣが有する結晶多形及び不純物キャリア濃度の制御も容易ではない。また、化学気相成長法（ＣＶＤ法）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、基板との格子不整合が約２０％もあること等により、多くの欠陥（〜１０７ｃｍ−２）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単結晶を得ることは容易でない。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（非特許文献１）。この方法では、種結晶を用いているため結晶の核形成過程が制御でき、また、不活性ガスにより雰囲気圧力を１００Ｐａから１５ｋＰａ程度に制御することにより、結晶の成長速度等を再現性良くコントロールできる。図１を用いて、改良レーリー法の原理を説明する。種結晶となるＳｉＣ単結晶と原料となるＳｉＣ結晶粉末（通常、アチソン法で作製された研磨材を洗浄・前処理したものが使用される）は、坩堝（通常黒鉛）の中に収納され、アルゴン等の不活性ガス雰囲気中（１３３Ｐａ〜１３．３ｋＰａ）、２０００〜２４００℃に加熱される。この際、原料粉末に比べ、種結晶がやや低温になるように、温度勾配が設定される。原料は、昇華後、濃度勾配（温度勾配により形成される）により、種結晶方向へ拡散、輸送される。単結晶成長は、種結晶に到着した原料ガスが種結晶上で再結晶化することにより実現される。改良レーリー法を用いれば、ＳｉＣ単結晶の結晶多形（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 a laboratory scale scale, for example, a SiC single crystal was grown by a sublimation recrystallization method (Rayleigh method) to obtain a SiC single crystal of a size capable of producing a semiconductor element. However, with this method, the area of the obtained single crystal is small, and it is difficult to control its size and shape with high accuracy. Moreover, it is not easy to control the crystal polymorphism and impurity carrier concentration of SiC. In addition, a cubic SiC single crystal is grown by heteroepitaxial growth on a heterogeneous substrate such as silicon (Si) using a chemical vapor deposition method (CVD method). In this method, a single crystal having a large area can be obtained, but only a SiC single crystal including many defects (−10 7 cm −2 ) is grown due to a lattice mismatch with the substrate of about 20%. It is not easy to obtain a high-quality SiC single crystal. In order to solve these problems, an improved Rayleigh method has been proposed in which sublimation recrystallization is performed using a SiC single crystal wafer as a seed crystal (Non-patent Document 1). In this method, since the seed crystal is used, the nucleation process of the crystal can be controlled, and by controlling the atmospheric pressure from about 100 Pa to about 15 kPa with an inert gas, the growth rate of the crystal can be controlled with good reproducibility. . The principle of the improved Rayleigh method will be described with reference to FIG. The SiC single crystal used as a seed crystal and the SiC crystal powder used as a raw material (usually used after cleaning and pretreatment of an abrasive produced by the Atchison method) are stored in a crucible (usually graphite) It is heated to 2000 to 2400 ° C. in an inert gas atmosphere such as argon (133 Pa to 13.3 kPa). At this time, the temperature gradient is set so that the seed crystal has a slightly lower temperature than the raw material powder. After sublimation, the raw material is diffused and transported in the direction of the seed crystal by a concentration gradient (formed by a temperature gradient). Single crystal growth is realized by recrystallization of the source gas that has arrived at the seed crystal on the seed crystal. By using the modified Rayleigh method, it is possible to grow a SiC single crystal while controlling the crystal polymorphism (6H type, 4H type, 15R type, etc.), shape, carrier type and concentration of the SiC single crystal.
現在、上記の改良レーリー法で作製したＳｉＣ単結晶から、口径２インチ（５０．８ｍｍ）から３インチ（７６．２ｍｍ）のＳｉＣ単結晶ウェハが切り出され、エピタキシャル薄膜成長、デバイス作製に供されている。しかしながら、現在市販されているＳｉＣ単結晶は、まだ品質面での問題が多く、今後ＳｉＣ単結晶及びデバイスを実用化していくためには、結晶品質の改善が必須である。 Currently, SiC single crystal wafers having a diameter of 2 inches (50.8 mm) to 3 inches (76.2 mm) are cut out from the SiC single crystal produced by the above-described improved Rayleigh method, and are used for epitaxial thin film growth and device fabrication. Yes. However, currently available SiC single crystals still have many problems in terms of quality, and in order to put SiC single crystals and devices into practical use in the future, it is essential to improve the crystal quality.
一般的に言って、良好な結晶品質の単結晶を成長するには、成長環境に可能な限り不純物がないのが好ましい。これは、結晶成長にとって望ましいステップフロー成長等の成長様式を不純物が阻害し、良好な結晶成長が実現できないためである。また、ＳｉＣ単結晶の高周波デバイス応用では、基板の高抵抗率化（１０５Ωｃｍ以上）が望まれている。基板の高抵抗率化は、その上に作製される素子の寄生容量低減と素子間分離において不可欠な技術となっている。現在、このような高抵抗率基板は、ＳｉＣ単結晶にバナジウム元素を添加する方法、あるいは、結晶を高純度化する方法により、工業的に得られている。バナジウムを添加して高抵抗率のＳｉＣ単結晶を製造する方法では、上記した昇華再結晶法において、原料となるＳｉＣ結晶粉末中に金属バナジウムあるいはバナジウム化合物（珪化物、炭化物等）を含有させ、ＳｉＣ原料と共に昇華させることにより、成長結晶中に添加している（例えば、非特許文献２）。 Generally speaking, in order to grow a single crystal of good crystal quality, it is preferable that the growth environment be as free of impurities as possible. This is because impurities inhibit the growth mode such as step flow growth desirable for crystal growth, and good crystal growth cannot be realized. Further, in application of SiC single crystal high-frequency devices, it is desired to increase the resistivity of the substrate (10 5 Ωcm or more). Increasing the resistivity of a substrate has become an indispensable technique for reducing parasitic capacitance and isolating elements produced on the substrate. At present, such a high resistivity substrate is industrially obtained by a method of adding a vanadium element to a SiC single crystal or a method of purifying a crystal. In the method for producing a high resistivity SiC single crystal by adding vanadium, in the above-described sublimation recrystallization method, the SiC crystal powder as a raw material contains metal vanadium or a vanadium compound (silicide, carbide, etc.), It is added to the grown crystal by sublimation with the SiC raw material (for example, Non-Patent Document 2).
しかしながら、この方法では、先に述べたように、不純物として導入したバナジウムが良好な結晶成長を阻害し、一般に結晶品質に多くの問題を残す。一方、結晶を高純度化する方法では、このような不純物に起因した問題は起こらないが、改良レーリー法によるＳｉＣ単結晶成長において、結晶の高純度化が極めて難しいという問題がある。この原因は、改良レーリー法によるＳｉＣ単結晶成長に適した高純度のＳｉＣ原料が存在しないことにある。従来技術の研磨材としてのＳｉＯを原料として製造されたＳｉＣ単結晶の純度は低く、結晶成長中の残留不純物によって、結晶の高品質化並びに高抵抗率化が阻害される。高純度のＳｉＣ粉末は、ＣＶＤ法、プラズマ合成法等により製造、市販されているが、結晶多形が立方晶（３Ｃ型）タイプであったり、結晶粒径が極めて小さな（１μｍ以下）微粉末であったり、と改良レーリー法に適したものではない。立方晶タイプや微粉末の原料を使用すると、原料の昇華速度の制御が極めて困難となる。このように、改良レーリー法におけるＳｉＣ単結晶の高純度化は、高純度の原料が存在しない、または得られないといった問題により、その実現が阻まれていた。 However, in this method, as described above, vanadium introduced as an impurity inhibits good crystal growth and generally leaves many problems in crystal quality. On the other hand, the method for purifying a crystal does not cause a problem due to such impurities, but has a problem that it is very difficult to purify the crystal in the SiC single crystal growth by the modified Rayleigh method. This is because there is no high-purity SiC material suitable for SiC single crystal growth by the modified Rayleigh method. The purity of a SiC single crystal manufactured using SiO as a raw material for the prior art as a raw material is low, and high quality and high resistivity of the crystal are hindered by residual impurities during crystal growth. High-purity SiC powder is manufactured and marketed by the CVD method, plasma synthesis method, etc., but the crystal polymorph is a cubic (3C type) type, or the crystal grain size is very small (1 μm or less). It is not suitable for the improved Rayleigh method. When a cubic type or fine powder raw material is used, it is extremely difficult to control the sublimation speed of the raw material. Thus, the high purity of the SiC single crystal in the modified Rayleigh method has been hindered by the problem that a high purity raw material does not exist or cannot be obtained.
本発明は、上記事情に鑑みてなされたものであり、高純度なＳｉＣ単結晶の製造方法及びそれに用いられる原料を提供するものである。 This invention is made | formed in view of the said situation, and provides the manufacturing method of a high purity SiC single crystal, and the raw material used for it.
本発明は、
（１） １回の昇華再結晶法により１３３Ｐａ〜１３．３ｋＰａの不活性雰囲気で不純物の分配係数Ｐ２が０．００１〜０．３で成長したＳｉＣ結晶の粉砕物であるＳｉＣ単結晶育成用ＳｉＣ原料、
（２） 前記ＳｉＣ結晶が、単結晶である（１）記載の炭化珪素単結晶育成用炭化珪素原料、
（３） 前記炭化珪素結晶が、４Ｈ型である（１）又は（２）に記載の炭化珪素単結晶育成用炭化珪素原料、
（４） 前記炭化珪素結晶が、単結晶又は多結晶の一方又は双方の粉砕物である（１）〜（３）のいずれかに記載の炭化珪素単結晶育成用炭化珪素原料、
（５） 前記昇華再結晶法を２回以上経てなる（１）〜（４）のいずれかに記載のＳｉＣ単結晶育成用ＳｉＣ原料、
（６） 前記粉砕物の平均粒径が１０μｍ〜３ｍｍである（１）〜（５）のいずれかに記載のＳｉＣ単結晶育成用ＳｉＣ原料、
（７） 昇華再結晶法により種結晶上にＳｉＣ単結晶を成長させる工程を包含するＳｉＣ単結晶の製造方法であって、原料として（１）〜（６）のいずれかに記載のＳｉＣ単結晶育成用ＳｉＣ原料を用いることを特徴とするＳｉＣ単結晶の製造方法、
である。
The present invention
(1) SiC for SiC single crystal growth, which is a pulverized product of SiC crystals grown in an inert atmosphere of 133 Pa to 13.3 kPa with an impurity distribution coefficient P2 of 0.001 to 0.3 by a single sublimation recrystallization method material,
(2) The silicon carbide raw material for growing a silicon carbide single crystal according to (1), wherein the SiC crystal is a single crystal,
(3) The silicon carbide raw material for growing a silicon carbide single crystal according to (1) or (2), wherein the silicon carbide crystal is 4H type,
(4) The silicon carbide raw material for growing a silicon carbide single crystal according to any one of (1) to (3), wherein the silicon carbide crystal is a pulverized product of one or both of a single crystal and a polycrystal,
(5) The SiC raw material for SiC single crystal growth according to any one of (1) to (4), wherein the sublimation recrystallization method is performed twice or more,
(6) The SiC raw material for SiC single crystal growth according to any one of (1) to (5), wherein the pulverized product has an average particle size of 10 μm to 3 mm.
(7) A method for producing a SiC single crystal comprising a step of growing a SiC single crystal on a seed crystal by a sublimation recrystallization method, wherein the SiC single crystal according to any one of (1) to (6) is used as a raw material A method for producing a SiC single crystal, characterized by using a SiC raw material for growth;
It is.
本発明によれば、種結晶を用いた改良型レーリー法により、良質且つ高純度・高抵抗率のＳｉＣ単結晶を再現性良く成長させることができる。このような結晶から切り出したＳｉＣ単結晶ウェハを用いれば、特性の優れた高周波電子デバイスを作製することができる。 According to the present invention, a SiC single crystal of high quality, high purity and high resistivity can be grown with good reproducibility by an improved Rayleigh method using a seed crystal. If a SiC single crystal wafer cut out from such a crystal is used, a high-frequency electronic device having excellent characteristics can be manufactured.
本発明の製造方法では、改良レーリー法自体が持つＳｉＣ結晶の高純度化作用を利用して、高純度のＳｉＣ原料及び単結晶を製造する。本発明は、改良レーリー法（昇華再結晶法）によりＳｉＣ単結晶を成長させる際に、別途昇華再結晶法により成長したＳｉＣ単結晶あるいは多結晶を粉砕したものを、原料として用いることを特徴とするＳｉＣ単結晶の製造方法である。 In the production method of the present invention, a high-purity SiC raw material and a single crystal are produced by utilizing the SiC crystal high-purification action of the improved Rayleigh method itself. The present invention is characterized in that, when a SiC single crystal is grown by an improved Rayleigh method (sublimation recrystallization method), a SiC single crystal or polycrystal grown separately by a sublimation recrystallization method is used as a raw material. This is a method for producing a SiC single crystal.
昇華再結晶化プロセスの過程で、固相（結晶粉末）→気相→固相（バルク単結晶あるいは多結晶）と、物質は相変態を起こすが、この過程で、不純物は各相変態過程の分配係数に応じて、固体あるいは気体中に取り込まれる。不純物の分配係数Ｐは、例えば、気相から固相への相変態を考えた場合、固体中の不純物濃度ＮＳを気体中の不純物濃度ＮＧで除した値（ＮＳ／ＮＧ）として定義される。すなわち、ある特定の不純物の分配係数が１．０以下であるということは、気相→固相の相変態過程に際して、固体中の不純物濃度ＮＳが、気体中の不純物濃度ＮＧよりも低くなることを意味している。逆に、分配係数が、１．０よりも大きい場合は、固体中の不純物濃度ＮＳが、気体中の不純物濃度ＮＧよりも高くなることを意味する。 In the course of the sublimation recrystallization process, the solid phase (crystal powder) → the gas phase → the solid phase (bulk single crystal or polycrystal) undergoes phase transformation, but in this process, impurities are in the phase transformation process. Depending on the partition coefficient, it is taken into a solid or gas. Partition coefficient P of impurities, for example, when considering the phase transformation to the solid phase from the gas phase, the impurity concentration N S in the solid as a value obtained by dividing the impurity concentration N G in the gas (N S / N G) Defined. That is, there is the fact that the distribution coefficient of a specific impurity is 1.0 or less, when the phase transformation process of gas-phase → the solid phase, the impurity concentration N S in the solid is lower than the impurity concentration N G in the gas Is meant to be. Conversely, the distribution coefficient is greater than 1.0, the impurity concentration N S in the solid, which means that higher than impurity concentration N G in the gas.
また、昇華再結晶プロセスにおいては、固相→気相→固相プロセストータルの不純物分配係数も考えることができる。この分配係数Ｐ２は、形成される固体（単結晶）中の不純物濃度ＮＳ１を原料となる固体（粉末）中の不純物濃度ＮＳ２で除した値（ＮＳ１／ＮＳ２）として定義される。表１に、ＳｉＣ単結晶において代表的な不純物の原料中と単結晶中の不純物濃度及び分配係数Ｐ２を示す。不純物により程度の差はあるが、原料中の不純物濃度に比べ、単結晶中の不純物濃度は、概ね数百分の１から数分の１程度に減少しており、分配係数Ｐ２も０．００１〜０．３となっている。 Further, in the sublimation recrystallization process, the total impurity partition coefficient of solid phase → gas phase → solid phase process can also be considered. The partition coefficient P2 is defined impurity concentration N S1 in the solid (a single crystal) formed as a solid as a starting material divided by the impurity concentration N S2 in (powder) (N S1 / N S2) . Table 1 shows the impurity concentration and distribution coefficient P2 in the raw material and the single crystal of typical impurities in the SiC single crystal. Although the degree varies depending on the impurities, the impurity concentration in the single crystal is reduced from about one hundredth to about a few compared to the impurity concentration in the raw material, and the distribution coefficient P2 is also 0.001. It is -0.3.
本発明では、まず通常の研磨材原料（アチソン法により製造されたもの）を用いて、１回の昇華再結晶法により１３３Ｐａ〜１３．３ｋＰａの不活性雰囲気で不純物の分配係数Ｐ２が０．００１〜０．３でＳｉＣ単結晶を製造する。これを第１回目の結晶成長とする。その後、このＳｉＣ単結晶を粉砕し、第２回目のＳｉＣ単結晶成長の原料とする。粉砕は、ダイヤモンド、アルミナ、金属カーバイド等の硬質材料製の工具、あるいは、これらの材料を表面にコーティングした工具を用いて行う。粉砕の程度は、最終粒度が、昇華再結晶化プロセスに適する平均粒径１０μｍ以上３ｍｍ以下になるまで行う。粉砕時に不純物が混入されることも考えられるが、これらの不純物は、製造された粉末結晶の中に取り込まれることはなく、その表面に付着している。結晶粒表面に付着した不純物は、有機洗浄、酸・アルカリ洗浄等を十分に行うことにより、除去することが可能である。 In the present invention, first, a normal abrasive material (manufactured by the Atchison method) is used, and the impurity distribution coefficient P2 is 0.001 in an inert atmosphere of 133 Pa to 13.3 kPa by a single sublimation recrystallization method. A SiC single crystal is produced at ˜0.3. This is the first crystal growth. Thereafter, the SiC single crystal is pulverized and used as a raw material for the second SiC single crystal growth. The pulverization is performed using a tool made of a hard material such as diamond, alumina, metal carbide, or a tool whose surface is coated with these materials. The degree of pulverization is performed until the final particle size becomes an average particle size of 10 μm or more and 3 mm or less suitable for the sublimation recrystallization process. Although it is conceivable that impurities are mixed during pulverization, these impurities are not taken into the produced powder crystal and are adhered to the surface thereof. Impurities adhering to the crystal grain surface can be removed by sufficiently performing organic cleaning, acid / alkali cleaning, or the like.
発明者らは、上記のプロセスに従って製造された原料を用いて、第２回目の結晶成長を行った場合に、その成長されたＳｉＣ単結晶中のほぼ全ての不純物が、第１回目の結晶成長により製造されたＳｉＣ単結晶中の不純物濃度に比べて、大幅に低減されることを数多くの実験から見出した。 When the second crystal growth is performed by using the raw material manufactured according to the above-described process, the inventors have found that almost all the impurities in the grown SiC single crystal are caused by the first crystal growth. It has been found from a number of experiments that the impurity concentration is greatly reduced compared to the impurity concentration in the SiC single crystal produced by the above method.
上記のＳｉＣ単結晶成長を利用した原料の高純度化は、その回数を重ねることにより（例えば、第２回目の結晶を原料として第３回目の結晶を製造する）、その効果を最大限に利用できる。ただし、上記高純度化プロセスの回数を重ねると、最終的には、原料以外の部分（例えば、坩堝等）からの不純物混入が主となり、それ以上の原料の高純度化は意味がなくなる。したがって、原料製造のコストも加味して考えると、通常は１回以上５回以下程度の高純度化が行われることになる。 The purification of the raw material using the SiC single crystal growth described above can be utilized to the maximum extent by repeating the number of times (for example, manufacturing the third crystal using the second crystal as a raw material). it can. However, if the number of times of the above-mentioned purification process is repeated, finally, impurities are mainly mixed from parts other than the raw material (for example, crucible etc.), and further purification of the raw material becomes meaningless. Therefore, when considering the cost of raw material production, high purity is usually performed about 1 to 5 times.
また、最終段の結晶（上記の例では、第２回目に成長した結晶）以外は、粉砕して原料にしてしまうので、特に単結晶として製造する必要がない。従って、その形態は多結晶でも構わない。上記した昇華再結晶法では、種結晶を用いない成長を行えば、容易にバルク状の多結晶も製造できる。 In addition, since the crystals other than the final stage crystals (in the above example, crystals grown in the second time) are pulverized into raw materials, there is no need to produce them as single crystals. Therefore, the form may be polycrystalline. In the sublimation recrystallization method described above, bulk polycrystals can be easily produced by performing growth without using a seed crystal.
本発明により製造されたＳｉＣ粉末原料を用いれば、高純度のＳｉＣ単結晶を製造できる。高純度なＳｉＣ単結晶は、高い抵抗率を示し、高周波デバイス用途に適している。また、その結晶成長過程で、不純物がステップフロー成長等の望ましい結晶成長様式を阻害することがないために、結晶品質も優れたＳｉＣ単結晶が製造できる。 If the SiC powder raw material manufactured by this invention is used, a high purity SiC single crystal can be manufactured. A high-purity SiC single crystal exhibits high resistivity and is suitable for high-frequency device applications. Further, in the crystal growth process, impurities do not hinder a desirable crystal growth mode such as step flow growth, so that a SiC single crystal having excellent crystal quality can be manufactured.
このようにして製造したＳｉＣ単結晶を切断、研磨してなるＳｉＣ単結晶ウェハは、５０ｍｍ以上３００ｍｍ以下の口径を有しているので、このウェハを用いて各種デバイスを製造する際、工業的に確立されている従来の半導体（Ｓｉ、ＧａＡｓ等）ウェハ用の製造ラインを使用することができ、量産に適している。特に、このウェハの結晶品質が高く、さらに、抵抗率も高いため、動作周波数の高いデバイスへの適用が可能である。さらに、このＳｉＣ単結晶ウェハ上に、ＣＶＤ法等によりエピタキシャル薄膜を成長して作製されるＳｉＣ単結晶エピタキシャルウェハ、あるいは、ＧａＮ、ＡｌＮ、ＩｎＮ及びこれらの混晶薄膜エピタキシャルウェハは、その基板となるＳｉＣ単結晶ウェハの品質が優れているために、良好な特性（エピタキシャル薄膜の表面モフォロジー、電気特性等）を有するようになる。 Since the SiC single crystal wafer obtained by cutting and polishing the SiC single crystal thus manufactured has a diameter of 50 mm or more and 300 mm or less, when manufacturing various devices using this wafer, An established production line for conventional semiconductor (Si, GaAs, etc.) wafers can be used, which is suitable for mass production. In particular, since the crystal quality of this wafer is high and the resistivity is also high, it can be applied to a device having a high operating frequency. Further, the SiC single crystal epitaxial wafer produced by growing an epitaxial thin film on the SiC single crystal wafer by CVD or the like, or GaN, AlN, InN and mixed crystal thin film epitaxial wafer thereof serve as the substrate. Since the quality of the SiC single crystal wafer is excellent, it has good characteristics (surface morphology, electrical characteristics, etc. of the epitaxial thin film).
（実施例１）
以下に、図２を用いて本発明の実施例を述べる。まず、この単結晶成長装置について、簡単に説明する。結晶成長は、ＳｉＣ結晶粉末２を昇華させ、種結晶として用いたＳｉＣ単結晶１上で、再結晶化させることによりに行われる。種結晶のＳｉＣ単結晶１は、高純度黒鉛製坩堝３の蓋４の内面に取り付けられる。原料のＳｉＣ結晶粉末２は、高純度黒鉛製坩堝３の内部に充填されている。このような黒鉛製坩堝３は、二重石英管５の内部に、黒鉛の支持棒６により設置される。黒鉛製坩堝３の周囲には、熱シールドのための黒鉛製フェルト７が設置されている。二重石英管５は、真空排気装置により高真空排気（１０−３Ｐａ以下）することができ、かつ内部雰囲気をＡｒガスにより圧力制御することができる。また、二重石英管５の外周には、ワークコイル８が設置されており、高周波電流を流すことにより黒鉛製坩堝３を加熱し、原料及び種結晶を所望の温度に加熱することができる。坩堝温度の計測は、坩堝上部及び下部を覆うフェルトの中央部に直径２〜４ｍｍの光路を設け、坩堝上部及び下部からの光を取りだし、二色温度計を用いて行う。坩堝下部の温度を原料温度、坩堝上部の温度を種温度とする。
Example 1
Hereinafter, an embodiment of the present invention will be described with reference to FIG. First, this single crystal growth apparatus will be briefly described. Crystal growth is performed by sublimating SiC crystal powder 2 and recrystallizing on SiC single crystal 1 used as a seed crystal. The seed crystal SiC single crystal 1 is attached to the inner surface of the lid 4 of the high-purity graphite crucible 3. The raw material SiC crystal powder 2 is filled in a high-purity graphite crucible 3. Such a graphite crucible 3 is installed inside a double quartz tube 5 by a support rod 6 made of graphite. Around the graphite crucible 3, a graphite felt 7 for heat shielding is installed. The double quartz tube 5 can be high vacuum evacuated (10 −3 Pa or less) by a vacuum evacuation device, and the internal atmosphere can be pressure controlled by Ar gas. In addition, a work coil 8 is provided on the outer periphery of the double quartz tube 5, and the graphite crucible 3 can be heated by flowing a high-frequency current to heat the raw material and the seed crystal to a desired temperature. The crucible temperature is measured using a two-color thermometer by providing an optical path having a diameter of 2 to 4 mm at the center of the felt covering the upper and lower parts of the crucible, extracting light from the upper and lower parts of the crucible. The temperature at the bottom of the crucible is the raw material temperature, and the temperature at the top of the crucible is the seed temperature.
次に、この結晶成長装置を用いたＳｉＣ単結晶の製造について、実施例を説明する。まず、種結晶として、口径５０ｍｍの（０００１）面を有し４Ｈ型のＳｉＣ単結晶ウェハを用意した。次に、種結晶１を黒鉛製坩堝３の蓋４の内面に取り付けた。黒鉛製坩堝３の内部には、アチソン法により製造したＳｉＣ結晶原料粉末２を洗浄後、充填した。次いで、原料を充填した黒鉛製坩堝３を、蓋４で閉じ、黒鉛製フェルト７で被覆した後、黒鉛製支持棒６の上に乗せ、二重石英管５の内部に設置した。そして、石英管の内部を真空排気した後、ワークコイルに電流を流し、原料温度を２０００℃まで上げた。その後、雰囲気ガスとして高純度Ａｒガスを流入させ、石英管内圧力を約８０ｋＰａに保ちながら、原料温度を目標温度である２４００℃まで上昇させた。成長圧力である１．３ｋＰａには約３０分かけて減圧し、その後約２０時間成長を続けた。この際の坩堝内の温度勾配は１５℃／ｃｍで、成長速度は約０．８ｍｍ／時であった。得られた結晶の口径は５１ｍｍで、高さは１６ｍｍ程度であった。 Next, an example will be described for the production of a SiC single crystal using this crystal growth apparatus. First, as a seed crystal, a 4H type SiC single crystal wafer having a (0001) plane with a diameter of 50 mm was prepared. Next, the seed crystal 1 was attached to the inner surface of the lid 4 of the graphite crucible 3. The inside of the graphite crucible 3 was filled with the SiC crystal raw material powder 2 produced by the Atchison method after being washed. Next, the graphite crucible 3 filled with the raw material was closed with the lid 4 and covered with the graphite felt 7, and then placed on the graphite support rod 6 and installed inside the double quartz tube 5. And after evacuating the inside of a quartz tube, the electric current was sent through the work coil and the raw material temperature was raised to 2000 degreeC. Thereafter, high-purity Ar gas was introduced as the atmospheric gas, and the raw material temperature was raised to the target temperature of 2400 ° C. while maintaining the pressure in the quartz tube at about 80 kPa. The growth pressure was reduced to 1.3 kPa over about 30 minutes, and then the growth was continued for about 20 hours. At this time, the temperature gradient in the crucible was 15 ° C./cm, and the growth rate was about 0.8 mm / hour. The diameter of the obtained crystal was 51 mm, and the height was about 16 mm.
こうして得られたＳｉＣ単結晶をＸ線回折及びラマン散乱により分析したところ、４Ｈ型のＳｉＣ単結晶が成長したことを確認できた。次に、ダイヤモンドスラリーを用いたマルチワイヤーソーにより、この結晶を切断し、厚さ０．４ｍｍの（０００１）面方位ウェハを結晶上部から２０枚切り出した。これらウェハの内、最上部（結晶端（最も種結晶から離れた位置）に相当）の１枚を除いて、残り全てを洗浄後、アルミナ製の乳鉢、乳棒を用いて粉砕し、１ｍｍ弱程度の粉末とした。 When the SiC single crystal thus obtained was analyzed by X-ray diffraction and Raman scattering, it was confirmed that a 4H type SiC single crystal was grown. Next, this crystal was cut by a multi-wire saw using diamond slurry, and 20 (0001) plane orientation wafers having a thickness of 0.4 mm were cut out from the upper part of the crystal. Of these wafers, except for the uppermost one (corresponding to the crystal edge (the position farthest from the seed crystal)), all the remaining wafers are washed and then pulverized using an alumina mortar and pestle. Of powder.
同様にして、成長した複数個のＳｉＣ単結晶を粉砕することにより、第２回目のＳｉＣ単結晶成長に必要な量の粉末原料を準備した。その後、この粉末を有機溶剤洗浄及び酸・アルカリ洗浄することにより、粉砕プロセス中に混入した不純物を除去し、第２回目のＳｉＣ単結晶成長の原料とした。 Similarly, a plurality of grown SiC single crystals were pulverized to prepare an amount of powder raw material necessary for the second SiC single crystal growth. Thereafter, the powder was subjected to organic solvent cleaning and acid / alkali cleaning to remove impurities mixed during the pulverization process, and used as a raw material for the second SiC single crystal growth.
第２回目のＳｉＣ単結晶成長も、第１回目と同様な条件の下に行い、第１回目に成長したＳｉＣ単結晶から得た粉末原料を用いて、口径５１ｍｍ、高さ１５ｍｍのＳｉＣ単結晶を得た。得られたＳｉＣ単結晶をＸ線回折及びラマン散乱により分析したところ、４Ｈ型のＳｉＣ単結晶が成長したことを確認できた。次に、この結晶をマルチワイヤーソーにより切断し、厚さ０．４ｍｍのウェハを結晶上部より９枚切り出した。ウェハの面方位は（０００１）面から＜１１−２０＞方向に８°オフとした。これら９枚のＳｉＣ単結晶ウェハを、第１回目に成長した結晶から切り出した最上部のウェハ１枚と共に研磨して、厚さ３００μｍ、口径５１ｍｍのＳｉＣ単結晶鏡面ウェハを作製した。第１回目及び第２回目の結晶の最上部から切り出したウェハの不純物濃度を調べたところ、第２回目に成長したＳｉＣ単結晶中の不純物濃度は、第１回目に成長したＳｉＣ単結晶中の不純物濃度に比べ、数千分の１から数十分の１になっていることが分かった。また、この２つのウェハの欠陥密度を、顕微鏡観察により調べたところ、第２回目の結晶成長により製造したウェハの方が、第１回目に製造したものに比べ、マイクロパイプ等の欠陥密度が低いことが分かった。 The second SiC single crystal is grown under the same conditions as in the first, and the SiC single crystal having a diameter of 51 mm and a height of 15 mm is obtained using the powder raw material obtained from the SiC single crystal grown in the first time. Got. When the obtained SiC single crystal was analyzed by X-ray diffraction and Raman scattering, it was confirmed that a 4H type SiC single crystal was grown. Next, this crystal was cut by a multi-wire saw, and nine wafers having a thickness of 0.4 mm were cut from the upper part of the crystal. The plane orientation of the wafer was 8 ° off from the (0001) plane in the <11-20> direction. These nine SiC single crystal wafers were polished together with one uppermost wafer cut from the first grown crystal to produce a SiC single crystal mirror wafer having a thickness of 300 μm and a diameter of 51 mm. When the impurity concentration of the wafer cut out from the top of the first and second crystals was examined, the impurity concentration in the SiC single crystal grown in the second time was found in the SiC single crystal grown in the first time. It was found that the concentration was 1 / several thousand to several tenths compared to the impurity concentration. Further, when the defect density of the two wafers was examined by microscopic observation, the defect density of the micropipe and the like was lower in the wafer manufactured by the second crystal growth than that manufactured in the first time. I understood that.
次に、第２回目に成長したＳｉＣ単結晶から切り出した残り８枚のウェハの電気抵抗率を調べたところ、ウェハによって値がばらついていたものの、全てウェハにおいて１０３〜１０１０Ωｃｍという高い抵抗率を示した。 Next, when the electrical resistivity of the remaining eight wafers cut out from the SiC single crystal grown at the second time was examined, all the wafers had a high resistance of 10 3 to 10 10 Ωcm although the values varied. Showed the rate.
さらに、この５１ｍｍ口径のＳｉＣ単結晶鏡面ウェハを基板として用いて、ＳｉＣのエピタキシャル成長を行った。ＳｉＣエピタキシャル薄膜の成長条件は、成長温度１５００℃、シラン（ＳｉＨ４）、プロパン（Ｃ３Ｈ８）、水素（Ｈ２）の流量が、それぞれ５．０×１０−９ｍ３／ｓｅｃ、３．３×１０−９ｍ３／ｓｅｃ、５．０×１０−５ｍ３／ｓｅｃであった。成長圧力は大気圧とした。成長時間は２時間で、膜厚としては約５μｍ成長した。 Further, SiC was epitaxially grown using this 51 mm diameter SiC single crystal mirror wafer as a substrate. The growth conditions of the SiC epitaxial thin film are as follows: the growth temperature is 1500 ° C., and the flow rates of silane (SiH 4 ), propane (C 3 H 8 ), and hydrogen (H 2 ) are 5.0 × 10 −9 m 3 / sec, 3 It was .3 × 10 -9 m 3 /sec,5.0×10 -5 m 3 / sec. The growth pressure was atmospheric pressure. The growth time was 2 hours, and the film thickness was about 5 μm.
エピタキシャル薄膜成長後、ノマルスキー光学顕微鏡により、得られたエピタキシャル薄膜の表面モフォロジーを観察したところ、ウェハ全面に渡って非常に平坦で、ピット等の表面欠陥が少ない良好な表面モフォロジーを有するＳｉＣエピタキシャル薄膜が成長されているのが分かった。 After the epitaxial thin film growth, the surface morphology of the obtained epitaxial thin film was observed with a Nomarski optical microscope. I found it growing up.
また、同様にして作製した別のＳｉＣ単結晶（上記第２回目の結晶成長により製造したＳｉＣ単結晶に相当）から、オフ角度が０°の（０００１）面ウェハを切り出し、鏡面研磨した後、その上にＧａＮ薄膜を有機金属化学気相成長（ＭＯＣＶＤ）法によりエピタキシャル成長させた。成長条件は、成長温度１０５０℃、トリメチルガリウム（ＴＭＧ）、アンモニア（ＮＨ３）、シラン（ＳｉＨ４）をそれぞれ、５４×１０−６モル／ｍｉｎ、４Ｌ／ｍｉｎ、２２×１０−１１モル／ｍｉｎ流した。また、成長圧力は大気圧とした。成長時間は６０分間で、ｎ型のＧａＮを３μｍの膜厚で成長させた。 In addition, from another SiC single crystal produced in the same manner (corresponding to the SiC single crystal produced by the second crystal growth), a (0001) plane wafer having an off angle of 0 ° was cut out and mirror-polished, A GaN thin film was epitaxially grown thereon by metal organic chemical vapor deposition (MOCVD). The growth conditions, the growth temperature of 1050 ° C., trimethylgallium (TMG), ammonia (NH 3), silane (SiH 4), respectively, 54 × 10 -6 mol / min, 4L / min, 22 × 10 -11 mol / min Washed away. The growth pressure was atmospheric pressure. The growth time was 60 minutes, and n-type GaN was grown to a thickness of 3 μm.
得られたＧａＮ薄膜の表面状態を調べる目的で、成長表面をノマルスキー光学顕微鏡により観察した。ウェハ全面に渡って非常に平坦なモフォロジーが得られ、全面に渡って高品質なＧａＮ薄膜が形成されているのが分かった。 For the purpose of examining the surface state of the obtained GaN thin film, the growth surface was observed with a Nomarski optical microscope. It was found that a very flat morphology was obtained over the entire wafer surface, and a high-quality GaN thin film was formed over the entire surface.
（実施例２）
実施例１と同じく、黒鉛製坩堝３の内部に、研磨材を洗浄処理したＳｉＣ結晶原料粉末２を充填した。この原料を充填した黒鉛製坩堝３を、黒鉛製の蓋４（種結晶を内面に取り付けていない）で閉じ、黒鉛製フェルト７で被覆した後、黒鉛製支持棒６の上に乗せ、二重石英管５の内部に設置した。そして、石英管の内部を真空排気した後、ワークコイルに電流を流し、原料温度を２０００℃まで上げた。その後、雰囲気ガスとして高純度Ａｒガスを流入させ、石英管内圧力を約８０ｋＰａに保ちながら、原料温度を目標温度である２４００℃まで上昇させた。成長圧力である１．３ｋＰａには約３０分かけて減圧し、その後約２０時間成長を続けた。この際の坩堝内の温度勾配は１５℃／ｃｍで、成長速度は約１．１ｍｍ／時であった。同条件で成長しても、一般に多結晶の成長速度の方が、単結晶の成長速度よりも大きくなる。得られた結晶は、バルク状の多結晶であり、結晶粒の大きさは１〜数ｍｍ程度であった。多結晶の口径は５１ｍｍで、高さは２２ｍｍ程度であった。
(Example 2)
As in Example 1, the inside of the graphite crucible 3 was filled with SiC crystal raw material powder 2 obtained by washing the abrasive. The graphite crucible 3 filled with this raw material is closed with a graphite lid 4 (no seed crystal is attached to the inner surface), covered with a graphite felt 7, placed on a graphite support rod 6, and double It was installed inside the quartz tube 5. And after evacuating the inside of a quartz tube, the electric current was sent through the work coil and the raw material temperature was raised to 2000 degreeC. Thereafter, high-purity Ar gas was introduced as the atmospheric gas, and the raw material temperature was raised to the target temperature of 2400 ° C. while maintaining the pressure in the quartz tube at about 80 kPa. The growth pressure was reduced to 1.3 kPa over about 30 minutes, and then the growth was continued for about 20 hours. At this time, the temperature gradient in the crucible was 15 ° C./cm, and the growth rate was about 1.1 mm / hour. Even when grown under the same conditions, the growth rate of polycrystals is generally higher than the growth rate of single crystals. The obtained crystal was a bulk polycrystal, and the size of crystal grains was about 1 to several mm. The diameter of the polycrystal was 51 mm and the height was about 22 mm.
こうして得られたＳｉＣ多結晶をラマン散乱により分析したところ、６Ｈ型のＳｉＣ多結晶が成長したことを確認できた。次に、ダイヤモンドスラリーを用いたマルチワイヤーソーにより、この多結晶を切断し、厚さ０．４ｍｍのウェハを結晶上部から３０枚切り出した。これら全てのウェハを洗浄後、アルミナ製の乳鉢、乳棒を用いて粉砕し、１ｍｍ弱程度の粉末とした。 When the SiC polycrystal obtained in this way was analyzed by Raman scattering, it was confirmed that a 6H-type SiC polycrystal was grown. Next, this polycrystal was cut by a multi-wire saw using diamond slurry, and 30 wafers having a thickness of 0.4 mm were cut out from the upper part of the crystal. All these wafers were washed and then pulverized using an alumina mortar and pestle to obtain a powder of about 1 mm or less.
同様にして成長した複数個のバルク状ＳｉＣ多結晶を粉砕することにより、次に行うＳｉＣ単結晶成長に必要な量の粉末原料を準備した。その後、この粉末を有機溶剤洗浄及び酸・アルカリ洗浄することにより、粉砕プロセス中に混入した不純物を除去し、次のＳｉＣ単結晶成長の原料とした。 A plurality of bulk SiC polycrystals grown in the same manner were pulverized to prepare an amount of powder raw material necessary for the next SiC single crystal growth. Thereafter, the powder was subjected to organic solvent cleaning and acid / alkali cleaning to remove impurities mixed in during the pulverization process, and used as a raw material for the next SiC single crystal growth.
次に行ったＳｉＣ単結晶成長は、上記バルク状ＳｉＣ多結晶から得た粉末原料を用いて、実施例１の第２回目の単結晶成長と同様な条件の下に行った。その結果、口径５１ｍｍ、高さ１６ｍｍのＳｉＣ単結晶を得た。得られたＳｉＣ単結晶をＸ線回折及びラマン散乱により分析したところ、４Ｈ型のＳｉＣ単結晶が成長したことを確認できた。次に、この結晶をマルチワイヤーソーにより切断し、厚さ０．４ｍｍのウェハを結晶上部より９枚切り出した。ウェハの面方位は（０００１）面から＜１１−２０＞方向に８度オフとした。これら９枚のＳｉＣ単結晶ウェハを研磨して、厚さ３００μｍ、口径５１ｍｍのＳｉＣ単結晶鏡面ウェハを作製した。この内、結晶最上部から切り出したウェハ中の不純物濃度を測定し、実施例１の第１回目の結晶成長により製造したウェハ中の不純物濃度と比較したところ、ほぼ実施例１と同様な不純物濃度低減効果を確認できた。即ち、実施例２において製造したＳｉＣ単結晶ウェハ中の不純物濃度は、実施例１の第１回目の結晶成長により製造したＳｉＣ単結晶ウェハ中の不純物濃度と比較して、数千分の１から数十分の１になっていた。また、本実施例２において製造したウェハ中の欠陥密度を、顕微鏡観察により調べたところ、実施例１の第２回目の結晶成長により製造したウェハとほぼ同程度にマイクロパイプ等の欠陥密度が低いウェハが製造できていることが分かった。 The next SiC single crystal growth was performed under the same conditions as the second single crystal growth of Example 1 using the powder raw material obtained from the bulk SiC polycrystal. As a result, a SiC single crystal having a diameter of 51 mm and a height of 16 mm was obtained. When the obtained SiC single crystal was analyzed by X-ray diffraction and Raman scattering, it was confirmed that a 4H type SiC single crystal was grown. Next, this crystal was cut by a multi-wire saw, and nine wafers having a thickness of 0.4 mm were cut from the upper part of the crystal. The plane orientation of the wafer was turned off by 8 degrees from the (0001) plane in the <11-20> direction. These nine SiC single crystal wafers were polished to produce a SiC single crystal mirror wafer having a thickness of 300 μm and a diameter of 51 mm. Of these, the impurity concentration in the wafer cut out from the top of the crystal was measured and compared with the impurity concentration in the wafer produced by the first crystal growth in Example 1, and as a result, almost the same impurity concentration as in Example 1 was obtained. The reduction effect was confirmed. That is, the impurity concentration in the SiC single crystal wafer manufactured in Example 2 is from several thousandths compared to the impurity concentration in the SiC single crystal wafer manufactured by the first crystal growth in Example 1. It was a tens of minutes. Further, when the defect density in the wafer manufactured in Example 2 was examined by microscopic observation, the defect density of micropipes and the like was as low as that of the wafer manufactured by the second crystal growth in Example 1. It was found that the wafer was manufactured.
次に、本実施例２において製造した成長したＳｉＣ単結晶ウェハの電気抵抗率を調べたところ、ウェハによって値がばらついていたものの、単結晶を粉末原料として製造したものとほぼ同様に、全てウェハにおいて１０３〜１０１０Ωｃｍという高い抵抗率を示した。 Next, the electrical resistivity of the grown SiC single crystal wafer manufactured in Example 2 was examined. Although the values varied depending on the wafer, the wafer was almost the same as that manufactured using the single crystal as a powder raw material. The resistivity was as high as 10 3 to 10 10 Ωcm.
さらに、この５１ｍｍ口径のＳｉＣ単結晶鏡面ウェハを基板として用いて、ＳｉＣのエピタキシャル成長を行った。ＳｉＣエピタキシャル薄膜の成長条件は、成長温度１５００℃、シラン（ＳｉＨ４）、プロパン（Ｃ３Ｈ８）、水素（Ｈ２）の流量が、それぞれ５．０×１０−９ｍ３／ｓｅｃ、３．３×１０−９ｍ３／ｓｅｃ、５．０×１０−５ｍ３／ｓｅｃであった。成長圧力は大気圧とした。成長時間は２時間で、膜厚としては約５μｍ成長した。 Further, SiC was epitaxially grown using this 51 mm diameter SiC single crystal mirror wafer as a substrate. The growth conditions of the SiC epitaxial thin film are as follows: the growth temperature is 1500 ° C., and the flow rates of silane (SiH 4 ), propane (C 3 H 8 ), and hydrogen (H 2 ) are 5.0 × 10 −9 m 3 / sec, 3 It was .3 × 10 -9 m 3 /sec,5.0×10 -5 m 3 / sec. The growth pressure was atmospheric pressure. The growth time was 2 hours, and the film thickness was about 5 μm.
エピタキシャル薄膜成長後、ノマルスキー光学顕微鏡により、得られたエピタキシャル薄膜の表面モフォロジーを観察したところ、表面モフォロジーに優れ、ピット等の表面欠陥の少ない良好なエピタキシャル薄膜が成長しているのが分かった。 After the epitaxial thin film growth, the surface morphology of the obtained epitaxial thin film was observed with a Nomarski optical microscope. As a result, it was found that a good epitaxial thin film having excellent surface morphology and few surface defects such as pits was grown.
また、同様にして作製した別のＳｉＣ単結晶インゴットからオフ角度が０°の高抵抗率（０００１）面ウェハを切り出し（種結晶近傍の領域から切り出した）、鏡面研磨した後、その上にＧａＮ薄膜を有機金属化学気相成長（ＭＯＣＶＤ）法によりエピタキシャル成長させた。成長条件は、成長温度１０５０℃、トリメチルガリウム（ＴＭＧ）、アンモニア（ＮＨ３）、シラン（ＳｉＨ４）をそれぞれ、５４×１０−６モル／ｍｉｎ、４Ｌ／ｍｉｎ、２２×１０−１１モル／ｍｉｎ流した。また、成長圧力は大気圧とした。成長時間は６０分間で、ｎ型のＧａＮを３μｍの膜厚で成長させた。 Further, a high resistivity (0001) plane wafer having an off angle of 0 ° was cut out from another SiC single crystal ingot produced in the same manner (cut out from a region near the seed crystal), mirror-polished, and then GaN thereon The thin film was epitaxially grown by metal organic chemical vapor deposition (MOCVD). The growth conditions were growth temperature of 1050 ° C., trimethylgallium (TMG), ammonia (NH 3 ), and silane (SiH 4 ), 54 × 10 −6 mol / min, 4 L / min, and 22 × 10 −11 mol / min, respectively. Washed away. The growth pressure was atmospheric pressure. The growth time was 60 minutes, and n-type GaN was grown to a thickness of 3 μm.
得られたＧａＮ薄膜の表面状態を調べる目的で、成長表面をノマルスキー光学顕微鏡により観察したところ、こちらの場合も、基板ウェハに欠陥が少ないことに対応して、ピット等の表面欠陥が少ない良質なエピタキシャル薄膜が成長できていることが分かった。 For the purpose of examining the surface state of the obtained GaN thin film, the growth surface was observed with a Nomarski optical microscope. In this case as well, the surface quality such as pits is small, corresponding to the fact that the substrate wafer has few defects. It was found that an epitaxial thin film could be grown.
１ 種結晶（ＳｉＣ単結晶）、
２ ＳｉＣ結晶粉末原料、
３ 坩堝（黒鉛あるいはタンタル等の高融点金属）、
４ 黒鉛製坩堝蓋、
５ 二重石英管、
６ 支持棒、
７ 黒鉛製フェルト（断熱材）、
８ ワークコイル、
９ 高純度Ａｒガス配管、
１０ 高純度Ａｒ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 SiC crystal powder raw material,
3 crucibles (refractory metals such as graphite or tantalum),
4 Graphite crucible lid,
5 Double quartz tube,
6 Support rod,
7 Graphite felt (heat insulation),
8 Work coil,
9 High purity Ar gas piping,
10 Mass flow controller for high purity Ar gas,
11 Vacuum exhaust device.
Claims (7)
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| JP2012250864A (en) * | 2011-06-01 | 2012-12-20 | Sumitomo Electric Ind Ltd | Silicon carbide crystal ingot, silicon carbide crystal wafer, and method for producing the silicon carbide crystal ingot |
| WO2013015642A2 (en) * | 2011-07-28 | 2013-01-31 | Lg Innotek Co., Ltd. | Method for growth of ingot |
| JP2013067522A (en) * | 2011-09-21 | 2013-04-18 | Sumitomo Electric Ind Ltd | Method for producing silicon carbide crystal |
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| JPS6350393A (en) * | 1986-08-20 | 1988-03-03 | Sanyo Electric Co Ltd | Growth method for sic single crystal |
| JPH09157091A (en) * | 1995-12-08 | 1997-06-17 | Nippon Steel Corp | Production of 4h type single-crystalline silicon carbide |
| JP2003002794A (en) * | 2001-06-15 | 2003-01-08 | Bridgestone Corp | Silicon carbide single crystal and method for producing the same |
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| JPS6350393A (en) * | 1986-08-20 | 1988-03-03 | Sanyo Electric Co Ltd | Growth method for sic single crystal |
| JPH09157091A (en) * | 1995-12-08 | 1997-06-17 | Nippon Steel Corp | Production of 4h type single-crystalline silicon carbide |
| JP2003002794A (en) * | 2001-06-15 | 2003-01-08 | Bridgestone Corp | Silicon carbide single crystal and method for producing the same |
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| JP2012250864A (en) * | 2011-06-01 | 2012-12-20 | Sumitomo Electric Ind Ltd | Silicon carbide crystal ingot, silicon carbide crystal wafer, and method for producing the silicon carbide crystal ingot |
| WO2013015642A2 (en) * | 2011-07-28 | 2013-01-31 | Lg Innotek Co., Ltd. | Method for growth of ingot |
| WO2013015642A3 (en) * | 2011-07-28 | 2013-04-11 | Lg Innotek Co., Ltd. | Method for growth of ingot |
| JP2013067522A (en) * | 2011-09-21 | 2013-04-18 | Sumitomo Electric Ind Ltd | Method for producing silicon carbide crystal |
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