JP4563609B2 - Method for producing silicon carbide - Google Patents

Description

【００３９】
【表２】

【００４０】
【表３】

【００４１】
なお、反位相領域境界面の密度は、３Ｃ−ＳｉＣ表面をＡＦＭ観察して求めた。この際、３Ｃ−ＳｉＣの表面を熱酸化処理しさらに熱酸化膜を除去することにより反位相境界を顕在化させたあとに観察を行った。
表３に示すオフ角度と反位相領域境界面密度との関係から、オフ角導入による反位相領域境界面密度の減少が確認されるものの、完全な解消には至っていないことがわかる。
オフ角４°の基板上に成長させた３Ｃ−ＳｉＣ膜表面の走査型電子顕微鏡写真を図２に示し、オフ角無しの基板上に成長させた３Ｃ−ＳｉＣ膜表面の走査型電子顕微鏡写真を図３に示す。
図２及び図３から、オフ角導入によりテラス面積の拡大が確認されてステップフローモードでの３Ｃ−ＳｉＣ成長が支配的となっており、面欠陥の伝搬方位が特定の結晶面内に限定されていることがわかる。しかし、これらの欠陥伝播方位は全て平行となり、消滅する事無く残存する。したがって反位相境界面欠陥等を完全に消滅することは不可能である。
【００４２】
実施例１
直径６インチのＳｉ（００１）面を被成長基板とし、基板表面を熱酸化後、フォトリソグラフィー技術を用いて基板表面上に１．５μｍ幅、長さ６０ｍｍ、厚さ１μｍのライン＆スペースパターンをレジストにて形成した。ただし、ライン＆スペースパターンの方向は＜１１０＞方位に平行にした。この基板を表４に示す条件でホットプレートを用いて加熱することにより、ライン＆スペースレジストパターンがラインと直交する方向に広がって変形し、起伏の頂点と底が滑らかな曲線で繋がった波面状の断面のレジストパターン形状を得た。このレジストパターンの断面形状（起伏）及び平面形状（ライン＆スペース）をドライエッチングにて珪素基板に転写した。
【００４３】
レジストを過酸化水素と硫酸の混合液中で除去して基板を得た。この基板は、電子顕微鏡観察の結果、図4に示すと同様に、基板表面に略平行に延在する複数の起伏を有しており、かつこの起伏が延在する方向と直交する断面において、斜面同士が隣接する部分の形状は曲線状であった。さらに、この起伏は中心線平均粗さが１００ｎｍであり、この起伏の斜面の平均斜度は４°であった。尚、中心線平均粗さ及び起伏斜面の斜度の測定は、原子間力顕微鏡（ＡＦＭ）により行った。
【００４４】
この基板に３Ｃ−ＳｉＣの成長を実施した。３Ｃ−ＳｉＣの成長は、基板表面の炭化工程と、原料ガスの交互供給による３Ｃ−ＳｉＣ成長工程に分けられる。３Ｃ−ＳｉＣ成長工程の詳細条件を表５に示す。なお、炭化工程の詳細条件は表１と同様とした。
３Ｃ−ＳｉＣ成長工程において、原料ガスの供給サイクル数を変化させることにより、３Ｃ−ＳｉＣの膜厚を変化させて、最表面に現れる反位相領域境界面の密度を上記と同様にして測定したところ、表６に示す結果を得た。
【００４５】
【表４】

【００４６】
【表５】

【００４７】
【表６】

【００４８】
表６に示す３Ｃ−ＳｉＣ膜厚と反位相領域境界面密度との関係から、３Ｃ−ＳｉＣの成長が進むにしたがって面欠陥同士が衝突し、消滅していることがわかる。従来法である表３の数値と比較して本発明の有効性が顕著であることがわかる。また、本実施例で得られた６インチΦ３Ｃ−ＳｉＣのエッチピット密度と双晶密度を以下の如く調べた。３Ｃ−ＳｉＣを溶融ＫＯＨ（５００℃、５分）に曝した後、表面を光学顕微鏡で観察したところ、積層欠陥密度に相当するエッチピット数は６インチ全面で１，７００個以下、そして密度は１０／ｃｍ²以下であった。さらに、３Ｃ−ＳｉＣ＜１１１＞方位に対するＸ線回折ロッキングカーブ（ＸＲＤ）の極点観察を行い、双晶面に相当する｛１１５｝面方位の信号強度と通常の単結晶面｛１１１｝面方位の信号強度比から双晶密度を算出した。その結果、双晶密度は測定限界である４×１０^-4Ｖｏｌ．％以下であることが分かった。
【００４９】
実施例２
直径６インチのＳｉ（００１）面を被成長基板とし、フォトリソグラフィー技術を用いて基板表面上に１．５μｍ幅、長さ６０ｍｍ、厚さ１μｍのライン＆スペースパターンをレジストにて形成した。ただし、ライン＆スペースパターンの方向は＜１１０＞方位に平行にした。この基板を表７に示す条件でホットプレートを用いて加熱しレジストを軟化させてレジストパターンの断面形状を変化させた。このレジストパターンの断面形状（起伏）及び平面形状（ライン＆スペース）をドライエッチングにてＳｉ基板に転写した。尚、レジストパターンの加熱温度は１５０℃〜２００℃の間で変化させて、起伏の傾斜角θを表８に示すように変化させた。
レジストを過酸化水素と硫酸の混合液中で除去して基板を得た。この基板は、電子顕微鏡観察の結果、図4に示すと同様に、基板表面に略平行に延在する複数の起伏を有しており、かつこの起伏が延在する方向と直交する断面において、斜面同士が隣接する部分の形状は曲線状であった。さらに、この起伏は中心線平均粗さが１００ｎｍであり、この起伏の斜面の平均斜度は表８に示すとおりであった。尚、中心線平均粗さ及び起伏斜面の斜度の測定は、実施例１と同様に行った。
【００５０】
これらの基板に３Ｃ−ＳｉＣの成長を実施した。３Ｃ−ＳｉＣの成長は、基板表面の炭化工程と、原料ガスの交互供給による３Ｃ−ＳｉＣ成長工程に分けられる。なお、炭化工程の詳細条件は表１と同様とし、３Ｃ−ＳｉＣ成長工程の詳細条件は表５と同様とした。
各基板上にそれぞれ成長させた３Ｃ−ＳｉＣについて、最表面に現れる反位相領域境界面の密度を上記と同様にして測定したところ、表８に示す結果を得た。
【００５１】
【表７】

【００５２】
【表８】

【００５３】
表８に示す起伏の斜度と反位相領域境界面密度との関係から、起伏の傾斜角θが、特に（１１１）面のなす角である５４．７°未満であって１°以上である場合に反位相領域境界面の密度の減少が確認できる。さらに、従来法である表３の数値と比較して、同じオフ角であっても本発明の如く起伏加工基板上へ成長させた３Ｃ−ＳｉＣは反位相領域境界面密度が大幅に減少又は解消しており、本発明の有効性が顕著であることがわかる。また、本実施例で得られた起伏の傾斜角４度の起伏加工基板上に成長させた３Ｃ−ＳｉＣのエッチピット密度と双晶密度を以下の如く調べた。３Ｃ−ＳｉＣを溶融ＫＯＨ（５００℃、５分）に曝した後、表面を光学顕微鏡で観察したところ、積層欠陥密度に相当するエッチピット数は６インチ全面で１，５２８個、そして密度は８．６５／ｃｍ²であった。さらに、３Ｃ−ＳｉＣ＜１１１＞方位に対するＸ線回折ロッキングカーブ（ＸＲＤ）の極点観察を行い、双晶面に相当する｛１１５｝面方位の信号強度と通常の単結晶面｛１１１｝面方位の信号強度比から双晶密度を算出した。その結果、双晶密度は測定限界である４×１０^-4Ｖｏｌ．％以下であることが分かった。
【００５４】
実施例３
実施例１、２はいずれもＳｉ（００１）面基板上に立方晶ＳｉＣ膜を成長させたものである。実施例３では被成長基板として、直径６インチの単結晶の立方晶炭化珪素（３Ｃ−ＳｉＣ）の（００１）面上に＜１１０＞方位に平行に伸びる起伏を具備した基板、または単結晶の六方晶炭化珪素の（１，１，−２，０）面上に＜０，０，０，１＞方位に平行に伸びる起伏を具備した基板を用いて、各基板表面上に立方晶炭化珪素膜もしくは六方晶炭化珪素膜の成長を実施例１と同様の条件で行った。
尚、いずれの基板も、電子顕微鏡観察の結果、図4に示すと同様に、基板表面に略平行に延在する複数の起伏を有しており、かつこの起伏が延在する方向と直交する断面において、斜面同士が隣接する部分の形状は曲線状であった。さらに、この起伏は中心線平均粗さが１００ｎｍであり、この起伏の斜面の平均斜度は４°であった。
その結果、上記基板を用いた場合にも実施例１と同様に本発明の有効性が確認された。
【００５５】
実施例４
直径６インチのＳｉ（００１）基板表面に、＜１１０＞方向に平行に研磨処理を施す方法で、＜１１０＞方向に平行な起伏形成基板を作製することを試みた。研磨には、市販されている約φ１５μｍ径のダイヤモンドスラリー（エンギス社製：ハイプレス）と市販の研磨クロス（エンギス社製：Ｍ４１４）を用いた（表９）。 クロス上にダイヤモンドスラリーを一様に浸透させ、パッド上にＳｉ（００１）基板を置き、０．２ｋｇ／ｃｍ²の圧力をＳｉ（００１）基板全体に加えながら、＜１１０＞方向に平行にクロス上約２０ｃｍの距離を３００回往復させて一方向研磨処理を施した。Ｓｉ（００１）基板表面には＜１１０＞方向に平行な研磨傷（スクラッチ）が無数に形成された。
【００５６】
【表９】

【００５７】
一方向研磨処理を施したＳｉ（００１）基板表面に研磨砥粒などが付着しているので、ＮＨ₄ＯＨ＋Ｈ₂Ｏ₂＋Ｈ₂Ｏ混合溶液（ＮＨ₄ＯＨ：Ｈ₂Ｏ₂：Ｈ₂Ｏ＝４：４：１の割合で液温６０℃）にて洗浄し、Ｈ₂ＳＯ₄＋Ｈ₂Ｏ₂溶液（Ｈ₂ＳＯ₄：Ｈ₂Ｏ₂＝１：１の割合で液温８０℃）とＨＦ（１０％）溶液に交互に３回ずつ浸して洗浄し、最後に純水でリンスした。
洗浄した後、熱処理装置を用い、表１０に示す条件で一方向研磨処理基板上に熱酸化膜を約１μｍ形成した。そして熱酸化膜をＨＦ１０％溶液により除去した。研磨を施しただけであると、基板表面は得たい起伏以外にも細かい凹凸や欠陥が多く残存し、被成長基板としては用い難い。しかし、熱酸化膜１μｍほど形成して改めて酸化膜を除去することで、基板表面を約２０００Åエッチングし、細かい凹凸が除去されて非常にスムーズなアンジュレーション（起伏）面を得ることができた。波状断面を見ると波状凹凸の大きさは不安定で不規則であるが、密度は高い。少なくとも（００１）面は１０％以下であった。常に起伏の状態にある。平均すると、中心線平均粗さは２０ｎｍであった。また、溝の深さは３０〜５０ｎｍ、幅は０．５〜１．５μｍ程度であった。斜度は３〜５°であった。代表的なＡＦＭ像を図４に示す。
【００５８】
【表１０】

【００５９】
この基板を用いて３Ｃ−ＳｉＣ膜を基板上に作製した。３Ｃ−ＳｉＣの成長は、基板表面の炭化工程と、原料ガスの交互供給による３Ｃ−ＳｉＣ成長工程に分けられる。なお、炭化工程の詳細条件は表１と同様とし、３Ｃ−ＳｉＣ成長工程の詳細条件は表５と同様とした。
【００６０】
結果は、＜１１０＞に平行な起伏形成基板の効果が得られた。すなわち、反位相境界面の欠陥は大幅に減少することを確認した。
例えば、未研磨のＳｉ基板上に成長した３Ｃ−ＳｉＣ膜の反位相境界面密度は８×１０⁹／ｃｍ²であるのに対し、今回の一方向研磨を施したＳｉ基板上に成長した３Ｃ−ＳｉＣ膜の反位相境界面欠陥密度は０〜１／ｃｍ²となった。砥粒サイズに対しての起伏形状と反位相境界面欠陥密度は表１１に示す通りになった。また、研磨回数に対しての起伏の密度と反位相境界面欠陥密度は表１２に示す通りになった。
【００６１】
【表１１】

【００６２】
【表１２】

【００６３】
砥粒サイズ１５μｍ、研磨往復回数３００回の起伏加工基板上に成長させた３Ｃ−ＳｉＣのエッチピット密度と双晶密度を以下の如く調べた。３Ｃ−ＳｉＣを溶融ＫＯＨ（５００℃、５分）に曝した後、表面を光学顕微鏡で観察したところ、積層欠陥密度に相当するエッチピット数は６インチ全面で１，４１４個、そして密度は８．００／ｃｍ²であった。さらに、３Ｃ−ＳｉＣ＜１１１＞方位に対するＸ線回折ロッキングカーブ（ＸＲＤ）の極点観察を行い、双晶面に相当する｛１１５｝面方位の信号強度と通常の単結晶面｛１１１｝面方位の信号強度比から双晶密度を算出した。その結果、双晶密度は測定限界である４×１０^-4Ｖｏｌ．％以下であることが分かった。
本実施例では、研磨剤としてダイヤモンドスラリーφ１５μｍサイズのものを用いたが、砥粒のサイズや砥粒の種類はこの限りではない。粒径を大きくすれば起伏の幅は広くなり、緩やかとなる。粒径を小さくすれば起伏の幅は狭くなる事は容易に想像できる。φ１〜３００μｍ程度の粒径であれば、効果的な起伏を形成する事が可能である。パッドも上記の限りではない。研磨時の基板とクロス間の負荷圧力、研磨速度や回数なども上記に限らない。また、実施例ではＳｉ（００１）を用いたが、立方晶、六方晶の炭化珪素を用いても、上記と同様の結果が得られることは言うまでもない。また、Ｓｉ（００１）基板上にて＜１１０＞方向に平行な方向へ伸びる起伏を形成したが、方向はこの限りではない。
【００６４】
実施例５
炭化珪素層に発生する歪みや反りを解消するために、直径６インチのＳｉ（００１）基板表面上の＜１１０＞方向に平行に研磨処理を施す方法で、＜１１０＞方向に平行な起伏形成基板を作製することを試みた。本実施例では、研磨処理回数によってＳｉ（００１）面の存在確率を制御し、本発明の効果を確認した。表９と同条件にて、研磨回数を３０回から３００回と変化させてＳｉ（００１）面上に一方向研磨処理を施した。Ｓｉ（００１）基板表面には＜１１０＞方向に平行な研磨傷（スクラッチ）が無数に形成された。
一方向研磨処理を施したＳｉ（００１）基板に研磨砥粒などが付着しているので、ＮＨ₄ＯＨ＋Ｈ₂Ｏ₂＋Ｈ₂Ｏ混合溶液（ＮＨ₄ＯＨ：Ｈ₂Ｏ₂：Ｈ₂Ｏ＝４：４：１の割合で液温６０℃）にて洗浄し、Ｈ₂ＳＯ₄＋Ｈ₂Ｏ₂溶液（Ｈ₂ＳＯ₄：Ｈ₂Ｏ₂＝１：１の割合で液温８０℃）とＨＦ（１０％）溶液に交互に３回ずつ浸して洗浄し、最後に純水でリンスした。
洗浄した後、熱処理装置を用い、表１０の条件にて一方向研磨処理基板上に熱酸化膜を約１μｍ形成した。そして熱酸化膜をＨＦ１０％溶液により除去した。
【００６５】
この基板を用いて３Ｃ−ＳｉＣ膜を基板上に作製した。３Ｃ−ＳｉＣの成長は、基板表面の炭化工程と、原料ガスの交互供給による３Ｃ−ＳｉＣ成長工程に分けられる。なお、炭化工程の詳細条件は表１と同様とし、３Ｃ−ＳｉＣ成長工程の詳細条件は表５と同様とした。Ｓｉ（００１）面の存在率と３Ｃ−ＳｉＣの内部応力ならびに反位相境界面欠陥密度の関係を表１３に示す。
【００６６】
【表１３】

【００６７】
３Ｃ−ＳｉＣ成長下地基板であるＳｉ（００１）基板上のＳｉ（００１）面が１０％以下の時、ＳｉＣ層内の内部応力は圧縮の方向で３５ＭＰａ以下という結果が得られた。Ｓｉ（００１）面が１０％以上であるときは、表を見て明らかな通り、非常に高い応力を示す結果となった。Ｓｉ（００１）面に起伏を設け、Ｓｉ（００１）面を１０％以下に制御した効果が現れたといえる。また、Ｓｉ（００１）面の割合が高くなるに連れて欠陥密度が高くなる傾向を示した。欠陥密度もＳｉ（００１）面の割合が少ないほど良いことが明らかとなった。また、Ｓｉ（００１）面を１０％以下に制御した起伏加工基板上に成長させた３Ｃ−ＳｉＣのエッチピット密度と双晶密度を以下の如く求めた。３Ｃ−ＳｉＣを溶融ＫＯＨ（５００℃、５分）に曝した後、表面を光学顕微鏡で観察したところ、積層欠陥密度に相当するエッチピット数は６インチ全面で１，５４８個、そして密度は８．７６／ｃｍ²であった。さらに、３Ｃ−ＳｉＣ＜１１１＞方位に対するＸ線回折ロッキングカーブ（ＸＲＤ）の極点観察を行い、双晶面に相当する｛１１５｝面方位の信号強度と通常の単結晶面｛１１１｝面方位の信号強度比から双晶密度を算出した。その結果、双晶密度は測定限界である４×１０^-4Ｖｏｌ．％以下であることが分かった。
尚、いずれの基板も、電子顕微鏡観察の結果、図4に示すと同様に、基板表面に略平行に延在する複数の起伏を有しており、かつこの起伏が延在する方向と直交する断面において、斜面同士が隣接する部分の形状は曲線状であった。さらに、この起伏は中心線平均粗さが２０〜４０ｎｍであり、この起伏の斜面の平均斜度は３〜５°であった。
【００６８】
本実施例では上記のようにＳｉ（００１）面で実施した。これと同様に、Ｓｉ（１１１）面では（１１１）面を３％以下とすることで、六方晶炭化珪素（１,１,−２,０）面では（１,１,−２,０）面を１０％以下とすることで、六方晶炭化珪素（０,０,０,１）面では（０,０,０,１）面を３％以下とすることで、それぞれ析出させたＳｉＣ層内の内部応力が１００ＭＰａ以下にできるという結果も得られた。
【００６９】
実施例６
炭化珪素層に発生する歪みや反りを解消するために、直径６インチのＳｉ（００１）基板表面上の＜１１０＞方向に平行に研磨処理を施す方法で、＜１１０＞方向に平行な起伏形成基板を作製することを試みた。本実施例では、研磨砥粒の粒径によってＳｉ（００１）面の中心線平均粗さを制御し、本発明の効果を確認した。表９と同条件にて研磨を行った。Ｓｉ（００１）基板表面には＜１１０＞方向に平行な研磨傷（スクラッチ）が無数に形成された。
一方向研磨処理を施したＳｉ（００１）基板に研磨砥粒などが付着しているので、ＮＨ₄ＯＨ＋Ｈ₂Ｏ₂＋Ｈ₂Ｏ混合溶液（ＮＨ₄ＯＨ：Ｈ₂Ｏ₂：Ｈ₂Ｏ＝４：４：１の割合で液温６０℃）にて洗浄し、Ｈ₂ＳＯ₄＋Ｈ₂Ｏ₂溶液（Ｈ₂ＳＯ₄：Ｈ₂Ｏ₂＝１：１の割合で液温８０℃）とＨＦ（１０％）溶液に交互に３回ずつ浸して洗浄し、最後に純水でリンスした。
洗浄した後、熱処理装置を用い、表１０の条件にて一方向研磨処理基板上に熱酸化膜を約１μｍ形成した。そして熱酸化膜をＨＦ１０％溶液により除去した。
【００７０】
この基板を用いて３Ｃ−ＳｉＣ膜を基板上に作製した。３Ｃ−ＳｉＣの成長は、基板表面の炭化工程と、原料ガスの交互供給による３Ｃ−ＳｉＣ成長工程に分けられる。なお、炭化工程の詳細条件は表１と同様とし、３Ｃ−ＳｉＣ成長工程の詳細条件は表５と同様とした。Ｓｉ（００１）面の中心線平均粗さと３Ｃ−ＳｉＣの内部応力ならびに反位相境界面欠陥密度の関係を表１４に示す。
【００７１】
【表１４】

【００７２】
中心線平均粗さが３ｎｍ以下では、内部応力は高く、面欠陥密度も高い。中心線平均粗さが３ｎｍ〜１００ｎｍの間では、内部応力も低くなり、面欠陥密度も解消される。中心線平均粗さが１００ｎｍを超えると、また面欠陥密度が高くなる傾向を示した。また、Ｓｉ（００１）面の中心線平均粗さを３０〜５０ｎｍに制御した起伏加工基板上に成長させた３Ｃ−ＳｉＣのエッチピット密度と双晶密度を以下の如く求めた。３Ｃ−ＳｉＣを溶融ＫＯＨ（５００℃、５分）に曝した後、表面を光学顕微鏡で観察したところ、積層欠陥密度に相当するエッチピット数は６インチ全面で１，６８３個、そして密度は９．５２／ｃｍ²であった。さらに、３Ｃ−ＳｉＣ＜１１１＞方位に対するＸ線回折ロッキングカーブ（ＸＲＤ）の極点観察を行い、双晶面に相当する｛１１５｝面方位の信号強度と通常の単結晶面｛１１１｝面方位の信号強度比から双晶密度を算出した。その結果、双晶密度は測定限界である４×１０^-4Ｖｏｌ．％以下であることが分かった。Ｓｉ（００１）面に起伏を設け、中心線平均粗さを３ｎｍ〜１００ｎｍへと制御したことで本発明の効果が現れたといえる。
尚、いずれの基板も、電子顕微鏡観察の結果、図4に示すと同様に、基板表面に略平行に延在する複数の起伏を有しており、かつこの起伏が延在する方向と直交する断面において、斜面同士が隣接する部分の形状は曲線状であった。さらに、この起伏の斜面の平均斜度は３〜５°であった。
【００７３】
本実施例ではＳｉ（００１）面で実施したが、Ｓｉ（１１１）面、六方晶炭化珪素（１,１,−２,０）、六方晶炭化珪素（０,０,０,１）でも同様の結果が得られることを確認している。
【００７４】
実施例７
直径６インチのＳｉ（００１）基板の表面、および裏面に起伏を設け、３Ｃ−ＳｉＣの歪みを低減する事を試みた。起伏は表９の条件により研磨で形成した。中心線平均粗さは表裏面ともに５０ｎｍ程度とした。本基板上に３Ｃ−ＳｉＣを成長した。３Ｃ−ＳｉＣの成長は、基板表面の炭化工程と、原料ガスの交互供給による３Ｃ−ＳｉＣ成長工程に分けられる。なお、炭化工程の詳細条件は表１と同様とし、３Ｃ−ＳｉＣ成長工程の詳細条件は表５と同様とした。成長した３Ｃ−ＳｉＣ内部応力は、圧縮の方向で１０ＭＰａと非常に低応力を得た。表裏面に発生する応力が相殺し、反りや歪みが小さくなり、良好な３Ｃ−ＳｉＣの成長がもたらされた。基板表裏面に起伏を形成した効果が得られたといえよう。
本実施例はＳｉ（１００）面で行ったが、Ｓｉ（１１１）面、六方晶炭化珪素（１,１,−２,０）、六方晶炭化珪素（０,０,０,１）でも同様の結果が得られることを確認している。
【００７５】
実施例８
以上の実施例では、所定の形状を有する起伏を基板表面に形成することで高品質な３Ｃ−ＳｉＣが得られる事がわかった。本実施例では、ドライエッチングにより起伏形状を作製する方法を示す。まず、図５のような石英製のマスクを作製した。本実施例のマスクに設けたラインアンドスペースパターンは100μｍ間隔である。マスクの窓の長辺を珪素基板の＜１１０＞に平行に配置する。そして、珪素基板とマスクの間隔を１ｍｍとした（図６）。これは間隔を０とすると、珪素基板には矩形のライン＆スペースパターンが転写されるからである。ドライエッチングはRIE装置を用いた。エッチングには、CF₄を４０ｓｃｃｍとO₂を１０ｓｃｃｍのガスを用いた。ＲＦ電源のパワーを２５０Ｗとし、電極間の真空度を８Ｐａとしてエッチングを４時間行った（表１５）。その結果、珪素基板表面には周期２００μｍ、深さ８μｍ（中心線平均粗さ６０ｎｍ〜１００ｎｍ）で斜度が３〜５°の安定した波状起伏が転写された。本基板上に形成した３Ｃ−ＳｉＣは、面欠陥密度が０〜１／ｃｍ²という良好な結果が得られた。また、ＲＩＥ（Reactive Ion Etching(反応性イオンエッチング)）で加工した波形起伏基板上に成長させた３Ｃ−ＳｉＣのエッチピット密度と双晶密度を以下の如く求めた。３Ｃ−ＳｉＣを溶融ＫＯＨ（５００℃、５分）に曝した後、表面を光学顕微鏡で観察したところ、積層欠陥密度に相当するエッチピット数は６インチ全面で１，２９０個、そして密度は７．３０／ｃｍ²であった。さらに、３Ｃ−ＳｉＣ＜１１１＞方位に対するＸ線回折ロッキングカーブ（ＸＲＤ）の極点観察を行い、双晶面に相当する｛１１５｝面方位の信号強度と通常の単結晶面｛１１１｝面方位の信号強度比から双晶密度を算出した。その結果、双晶密度は測定限界である４×１０^-4Ｖｏｌ．％以下であることが分かった。
【００７６】
【表１５】

【００７７】
実施例では石英のマスクを用いたが、材質はこの限りではない。また、ラインアンドスペースは１００μｍ間隔としたが、１０〜１０００μｍと任意に設定できる。より細い窓を開けるとマスクの強度が課題となるが、ラインとスペースの間隔を１：２や１：３としてマスク強度を確保し、ドライエッチングをマスクの位置をずらしながら複数回行う事によってより密度の高い起伏を形成してもよい。マスクと被パターン転写基板の間隔を１ｍｍとしたが、転写パターンを波状にするためであって、距離は必ずしもこの限りではない。転写されるパターンが波状になる程度の距離を有していれば十分である。マスクの窓の断面を台形にする事で、波状の起伏をエッチングにより転写する事も可能である。
【００７８】
実施例９
作製したアンジュレーション基板の表面形状が鋸型である場合、図７（a）のように、急峻な凹部にエッチピットなどの欠陥が時折発生し、表面まで欠陥が伝播してしまうことが問題となる。
そこで、アンジュレーションの表面形状を波形にし、この急峻な凹部を減らすことで欠陥の発生を抑制することを試みた。
鋸型のアンジュレーションは、一方向研磨により作製した。（方法は実施例の一 方向研磨と同じであるが、最後の酸化処理は行わない）直径６インチのＳｉ（００１）基板表面に、＜１１０＞方向に平行に研磨処理を施す方法で、＜１１０＞方向に平行な起伏形成基板を作製することを試みた。研磨には、市販されている約φ１５μｍ径のダイヤモンドスラリー（エンギス社製：ハイプレス）と市販の研磨クロス（エンギス社製：Ｍ４１４）を用いた（表９）。クロス上にダイヤモンドスラリーを一様に浸透させ、パッド上にＳｉ（００１）基板を置き、０．２ｋｇ／ｃｍ²の圧力をＳｉ（００１）基板全体に加えながら、＜１１０＞方向に平行にクロス上約２０ｃｍの距離を３００回往復させて一方向研磨処理を施した。Ｓｉ（００１）基板表面には＜１１０＞方向に平行な研磨傷（スクラッチ）が無数に形成された。
【００７９】
一方向研磨処理を施したＳｉ（００１）基板表面に研磨砥粒などが付着しているので、ＮＨ₄ＯＨ＋Ｈ₂Ｏ₂＋Ｈ₂Ｏ混合溶液（ＮＨ₄ＯＨ：Ｈ₂Ｏ₂：Ｈ₂Ｏ＝４：４：１の割合で液温６０℃）にて洗浄し、Ｈ₂ＳＯ₄＋Ｈ₂Ｏ₂溶液（Ｈ₂ＳＯ₄：Ｈ₂Ｏ₂＝１：１の割合で液温８０℃）とＨＦ（１０％）溶液に交互に３回ずつ浸して洗浄し、最後に純水でリンスした。
研磨直後の表面は非常に鋭利なアンジュレーション形状（鋸型）が得られた（図７（b））。
波型のアンジュレーションは、一方向研磨により鋸型のアンジュレーションを作製した後、アンジュレーション表面に対して熱酸化処理を行うことにより、表面を波形に緩和した。
研磨後のアンジュレーション基板を洗浄した後、熱処理装置を用い、表１０に示す条件で一方向研磨処理基板上に熱酸化膜を約１μｍ形成した。そして熱酸化膜をＨＦ１０％溶液により除去した。研磨を施しただけであると、基板表面は得たい起伏以外にも細かい凹凸や欠陥が多く残存し、被成長基板としては用い難い。しかし、熱酸化膜１μｍほど形成して改めて酸化膜を除去することで、基板表面を約２０００Åエッチングし、細かい凹凸が除去されて非常にスムーズなアンジュレーション（起伏）面を得ることができた。波状断面を見ると波状凹凸の大きさは不安定で不規則であるが、密度は高い。少なくとも（００１）面は１０％以下である。常に起伏の状態にある。平均すると、中心線平均粗さで２０ｎｍ。溝の深さは３０〜５０ｎｍ、幅は０．５〜１．５μｍ程度であった。斜度は３〜５°であった。代表的なＡＦＭ像を図４に示す。
【００８０】
この基板を用いて３Ｃ−ＳｉＣ膜を基板上に作製した。３Ｃ−ＳｉＣの成長は、基板表面の炭化工程と、原料ガスの交互供給による３Ｃ−ＳｉＣ成長工程に 分けられる。なお、炭化工程の詳細条件は表１と同様とし、３Ｃ−ＳｉＣ成長工程の詳細条件は表５と同様とした。
波型のアンジュレーションは、一方向研磨により鋸型のアンジュレーションを作製した後、アンジュレーション表面に対して熱酸化処理を行うことにより、表面を波形に緩和した。
波形のアンジュレーション基板を作製し、急峻な凹部は緩やかに改善された。
また、ドライエッチングにより波形のアンジュレーションも形成し、比較を行った。
波型のアンジュレーション基板上にSiCを成長した結果、鋸型アンジュレーション基板上SiCのように、急峻な凹部に発生する欠陥は観察されなかった。（図７（c））
表に欠陥の発生密度を示す。
【００８１】
【表１６】

【００８２】
また、波形アンジュレーション基板上に成長させた３Ｃ−ＳｉＣのエッチピット密度と双晶密度を以下の如く求めた。３Ｃ−ＳｉＣを溶融ＫＯＨ（５００℃、５分）に曝した後、表面を光学顕微鏡で観察したところ、積層欠陥密度に相当するエッチピット数は６インチ全面で１，７００個以下、そして密度は１０／ｃｍ²以下であった。さらに、３Ｃ−ＳｉＣ＜１１１＞方位に対するＸ線回折ロッキングカーブ（ＸＲＤ）の極点観察を行い、双晶面に相当する｛１１５｝面方位の信号強度と通常の単結晶面｛１１１｝面方位の信号強度比から双晶密度を算出した。その結果、双晶密度は測定限界である４×１０^-4Ｖｏｌ．％以下であることが分かった。一方、鋸型アンジュレーション基板上に成長させた３Ｃ−ＳｉＣのエッチピット数は６インチ全面で２８４，３５６個、密度は１６０９／ｃｍ²となり、双晶密度は６×１０^-3Ｖｏｌ．％であった。
このように、波形アンジュレーションを作製することで、基板界面に発生する欠陥の発生密度は大幅に改善することができた。本発明によれば、基板表面に発生するエッチピット密度を１０／ｃｍ²以下、双晶の混入を４×１０^-4Ｖｏｌ．％以下とすることが可能となる。さらに、直径６インチという大面積に渡って基板表面のエッチピット密度を１０／ｃｍ²以下、双晶の混入を４×１０^-4Ｖｏｌ．％以下とすることができる。
以上、実施例を挙げて本発明を説明したが、本発明は上記実施例に限定されるものではない。例えば、３Ｃ−ＳｉＣ膜の成膜条件や膜厚等は実施例のものに限定されない。実施例では直径６インチの基板について説明したが、本発明の効果は直径６インチの基板に限定されるものではなく、例えば、直径８インチ以上の大口径基板や直径４インチ以下の小口径基板においても同様に得ることができる。
【００８３】
【発明の効果】
以上説明したように本発明の炭化珪素の製造方法によれば、反位相領域境界面を効果的に低減又は消滅させ、炭化珪素層の内部応力や歪みを低減させた炭化珪素膜が得られる。
また、本発明の炭化珪素膜は、結晶境界密度が小さいため非常に優れた電気的特性を有し、各種電子素子などとして広く有用である。
【図面の簡単な説明】
【図１】炭化珪素／珪素基板界面のステップ密度の増大による反位相領域境界面１および双晶の生成の説明図。
【図２】オフ角４°の基板上に成長させた３Ｃ−ＳｉＣ膜表面の走査型電子顕微鏡写真。
【図３】オフ角無しの基板上に成長させた３Ｃ−ＳｉＣ膜表面の走査型電子顕微鏡写真。
【図４】本発明で用いる、起伏が延在する方向と直交する断面において、基板表面に存在する斜面同士が隣接する部分の形状が曲線状である基板表面の電子顕微鏡写真。
【図５】実施例８で用いた石英製のマスクの概略図。
【図６】珪素基板とマスクとき関係を示す説明図。
【図７】実施例９で得られた表面形状が鋸型であるアンジュレーション基板（ａ）、非常に鋭利なアンジュレーション形状を有する基板（ｂ）または表面形状が波型のアンジュレーション基板（ｃ）に成長させた３Ｃ−ＳｉＣ膜表面の走査型電子顕微鏡写真。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a single crystal silicon carbide film useful as an electronic material and a method for manufacturing the same. In particular, the present invention relates to a single crystal silicon carbide having a low defect density or a small crystal lattice distortion, which is preferable for manufacturing a semiconductor device, and a method for manufacturing the same.
[0002]
[Prior art]
Conventionally, the growth of silicon carbide (SiC) has been classified into bulk growth by sublimation and thin film formation by epitaxial growth on a substrate.
Bulk growth by sublimation allows growth of hexagonal (6H, 4H, etc.) silicon carbide, which is a crystalline polymorph of the high temperature phase, and the fabrication of a substrate of SiC itself has been realized. However, there are many defects (micropipes) introduced into the crystal and it is difficult to expand the substrate area.
[0003]
On the other hand, when the epitaxial growth method on a single crystal substrate is used, the controllability of impurity addition, the expansion of the substrate area, and the reduction of micropipes that have been problematic in the sublimation method are realized. However, in the epitaxial growth method, an increase in stacking fault density due to a difference in lattice constant between the substrate material and the silicon carbide film is often a problem. In particular, silicon generally used as a substrate to be grown has a large lattice mismatch with silicon carbide, so twins (Twin) and antiphase boundary (APB) in the silicon carbide growth layer. The generation of silicon is remarkable, and these damage the characteristics of silicon carbide as an electronic device.
[0004]
As a method for reducing surface defects in a silicon carbide film, for example, a step of providing a growth region on a substrate to be grown, and a thickness of a silicon carbide single crystal in the growth region is a thickness inherent to the growth surface orientation of the substrate. And a process of reducing the surface defects after the inherent thickness has been proposed (Japanese Patent Publication No. 6-41400). However, the two types of anti-phase regions contained in silicon carbide have the property of expanding in directions orthogonal to each other with respect to the increase in the thickness of the silicon carbide, so the anti-phase region boundary surface is effective. Cannot be reduced. In addition, since the orientation of the superstructure formed on the grown silicon carbide surface cannot be controlled arbitrarily, for example, when discrete growth regions are coupled with each other as they grow, a new reaction against the coupling portion is performed. There is a problem that a phase region boundary surface is formed, and electrical characteristics are impaired.
[0005]
[Problems to be solved by the invention]
As an effective method of reducing the anti-phase region boundary surface, K. Shibahara et al., Si (001) surface with the surface normal axis slightly tilted from the <001> direction to the <110> direction (with an off angle introduced) A growth method on the substrate was proposed (Applied Physics Letter, 50, 1987, 1888). In this method, since the atomic level steps are introduced at equal intervals in one direction by giving a slight tilt to the substrate, surface defects in the direction parallel to the introduced steps propagate, whereas the introduced steps are introduced. This has the effect of suppressing the propagation of surface defects in the direction perpendicular to the direction (the direction across the step). For this reason, the anti-phase region that expands in the direction parallel to the introduced step out of the two types of anti-phase regions included in the film increases in the direction orthogonal to the increase in the thickness of the silicon carbide film. Since the enlargement is preferentially performed compared to the phase region, the anti-phase region boundary surface can be effectively reduced. However, as shown in FIG. 1, this method causes unintentional antiphase region boundary surface 1 and twins to be generated due to an increase in the step density at the silicon carbide / silicon substrate interface. There is a problem that it cannot be completely resolved. In FIG. 1, 1 is an antiphase region boundary surface generated at a monoatomic step of a silicon substrate, 2 is an antiphase region boundary surface meeting point, 3 is an antiphase region boundary surface generated at a silicon substrate surface terrace, θ represents the off-angle, and φ represents the angle (54.7 °) formed by the Si (001) plane and the antiphase region boundary surface. The antiphase region boundary surface 3 generated on the silicon substrate surface terrace disappears at the antiphase region boundary surface meeting point 2, but the antiphase region boundary surface 1 generated in the monoatomic step of the silicon substrate has no associated partner, It will not disappear.
[0006]
In addition, when silicon carbide is formed on a silicon substrate, the silicon carbide layer is affected by the difference in thermal expansion coefficient between silicon and silicon carbide, the mismatch of lattice constants, defects generated in silicon carbide, or the influence of strain. Internal stress is generated. Due to the internal stress generated in the silicon carbide layer, the silicon carbide formed on the silicon substrate is warped and strained, and it is difficult to use this as a semiconductor element material.
[0007]
Accordingly, an object of the present invention is to provide a method for manufacturing silicon carbide that can effectively reduce the antiphase region boundary surface and a method for manufacturing silicon carbide that can reduce warpage and distortion associated with internal stress.
It is a further object of the present invention to provide a single crystal silicon carbide in which warpage and distortion associated with an antiphase region boundary surface and / or internal stress are reduced and / or a method for manufacturing the same.
[0008]
[Means for Solving the Problems]
  In order to achieve the above object, the present invention is as follows.
[Claim 1] In the method of manufacturing silicon carbide in which silicon carbide is deposited on at least a part of the substrate surface, the substrate surface on which the silicon carbide is deposited has a plurality of undulations extending substantially in parallel. The line average roughness is in the range of 3 to 1000 nm, the slope of the undulating slope is in the range of 1 ° to 54.7 °, and in the cross section perpendicular to the direction in which the undulation extends, the slopes are A method for producing silicon carbide, wherein the adjacent portions are curved.
[Claim 2] In the silicon carbide manufacturing method of depositing silicon carbide on at least a part of the substrate surface, the substrate surface on which the silicon carbide is deposited isOn the {001} face of silicon or silicon carbideMultiple undulations extending approximately parallelIs formedThis undulation has a centerline average roughness in the range of 3 to 1000 nm, and the slope of this undulation slope is in the range of 1 ° to 54.7 °., GroupA method for producing silicon carbide, wherein the ratio of the {001} plane in the area of the plate surface does not exceed 10%.
[Claim 3] In the method of manufacturing silicon carbide in which silicon carbide is deposited on at least a part of the substrate surface, the substrate surface on which the silicon carbide is deposited isOn the {111} face of silicon or cubic silicon carbideMultiple undulations extending approximately parallelIs formedThis undulation has a centerline average roughness in the range of 3 to 1000 nm, and the slope of this undulation slope is in the range of 1 ° to 54.7 °., GroupA method for producing silicon carbide, wherein a ratio of {111} planes occupying an area of a plate surface does not exceed 3%.
[Claim 4] In the method of manufacturing silicon carbide in which silicon carbide is deposited on at least a part of the substrate surface, the substrate surface on which the silicon carbide is deposited isOn the {1,1, -2,0} face of hexagonal silicon carbideMultiple undulations extending approximately parallelIs formedThis undulation has a centerline average roughness in the range of 3 to 1000 nm, and the slope of this undulation slope is in the range of 1 ° to 54.7 °., GroupA method for producing silicon carbide, characterized in that a ratio of {1, 1, -2, 0} plane occupying an area of a plate surface does not exceed 10%.
[Claim 5] In the method of manufacturing silicon carbide in which silicon carbide is deposited on at least a part of the substrate surface, the substrate surface on which the silicon carbide is deposited isOn the {0,0,0,1} face of hexagonal silicon carbideMultiple undulations extending approximately parallelIs formedThis undulation has a centerline average roughness in the range of 3 to 1000 nm, and the slope of this undulation slope is in the range of 1 ° to 54.7 °., GroupA method for producing silicon carbide, wherein a ratio of {0, 0, 0, 1} plane occupying an area of a plate surface does not exceed 3%.
[Claim 6] The method according to any one of claims 1 to 5, wherein the precipitation of silicon carbide is performed from a gas phase or a liquid phase.
[7] The manufacturing method according to any one of [2] to [6], wherein the shape of the portion where the inclined surfaces are adjacent to each other is a curved line in a cross section perpendicular to the direction in which the undulations of the substrate surface extend. Summary [claims8] By epitaxially growing silicon carbide precipitates while taking over the crystallinity of the substrate surfaceThe surface defect density is 1000 / cm ² The manufacturing method as described in any one of Claims 1-7 which manufactures the single crystal silicon carbide which is the following.
[Claim 9] According to any one of claims 1 to 7, single crystal silicon carbide having an internal stress of 100 MPa or less is produced by epitaxially growing silicon carbide precipitation while taking over the crystallinity of the substrate surface. The manufacturing method as described.
[10] A surface defect density of 1000 / cm can be obtained by epitaxially growing silicon carbide precipitation while taking over the crystallinity of the substrate surface. ² The manufacturing method as described in any one of Claims 1-7 which manufactures the single crystal silicon carbide which is below and an internal stress is 100 Mpa or less.
[11] An etch pit density of 10 / cm can be obtained by epitaxially growing silicon carbide precipitation while taking over the crystallinity of the substrate surface. ² And the twin density is 4 × 10 ^-Four Vol. The manufacturing method as described in any one of Claims 1-7 which manufactures the single crystal silicon carbide which is% or less.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
[Invention of Claim 1]
In the first aspect of the present invention, a substrate having a plurality of undulations extending substantially in parallel is used on the surface of the substrate on which silicon carbide is deposited. Thus, by using a substrate having a plurality of undulations on its surface, the effect of introducing an off angle shown by K. Shibahara et al. Can be obtained on each undulation slope. Further, by using a substrate having a plurality of undulations on its surface, it becomes possible to improve surface defects in silicon carbide deposited on the substrate, reduce strain, and reduce silicon carbide internal stress. .
[0010]
Note that the undulations referred to in the present invention do not require mathematically strict parallelism or mirror symmetry, and are sufficient to effectively reduce or eliminate the anti-phase region boundary surface. It suffices to have the form.
Further, the undulations referred to in the present invention are formed by repetition of peaks and valleys, and are not so-called atomic steps, but have a centerline average roughness of 3 to 1000 nm, which is macroscopic than atomic steps, as will be described later. The relief is in range. Further, the mountain portion has an inclined surface having an inclination of 1 to 54.7 ° with respect to the base surface. Furthermore, the slopes of the adjacent mountain parts are formed so as to face each other across the valley part. Preferably, when the inclination angle of the undulating surface with respect to the basal plane is integrated over the entire surface, the integrated value is formed to be substantially 0 °.
[0011]
The undulations on the substrate surface have a center line average roughness of 3 to 1000 nm. If the center line average roughness is less than 3 nm, it is difficult to obtain an effective off angle, and the generation density of surface defects is increased, which is not sufficient. On the other hand, if the center line average roughness exceeds 1000 nm, the probability that the surface defects collide with each other and are reduced is lowered, and the effect of the present invention cannot be obtained. Therefore, the center surface average roughness of the substrate surface is 3 nm or more and 1000 nm or less. In order to obtain the effect of the present invention more effectively, it is desirable that the center line average roughness is 10 nm or more and 100 nm or less.
[0012]
The center line average roughness of the substrate surface is the center line average roughness (Ra) defined in B0601-1982 (JIS Handbook 1990), and the measured length L is in the direction of the center line from the roughness curve. When the part is extracted, the center line of the extracted part is the X axis, the direction of the vertical magnification is the Y axis, and the roughness curve is expressed by y = f (x), the value expressed by the following formula is (μm) Say what you represent.
[0013]
[Expression 1]
Ra = (1 / L) ∫¹ ₀│f (x) │dx
[0014]
In the definition in the above JIS B0601-1982, the unit of the center line average roughness is μm, but nanometer (nm) is used in the present invention. Further, the roughness curve for obtaining the center line average roughness (Ra) is measured using an atomic force microscope (AFM).
[0015]
Furthermore, the slope of the undulating slope extending on the substrate surface is in the range of 1 ° or more and 54.7 ° or less.
In the method of the present invention, the effect is exerted by promoting the growth of silicon carbide in the vicinity of the atomic level step on the surface of the substrate to be grown. The present invention is realized when the slope of the (111) plane to be covered is inclined at 54.7 ° or less. Further, when the slope is less than 1 °, the step density of the undulating slope is remarkably reduced, so the slope of the undulating slope is 1 ° or more. Furthermore, from the viewpoint that the effects of the present invention are more effectively exhibited, the inclination angle of the undulating slope is preferably 2 ° or more and 10 ° or less.
In the present invention, the “undulating slope” includes all forms such as a plane and a curved surface. Further, in the present invention, “the slope of the undulating slope” means the substantial slope of the slope contributing to the effect of the present invention, and means the average slope of the slope. The average inclination means the angle (average value of the evaluation region) at which the crystal orientation plane of the substrate surface and the inclined surface intersect.
[0016]
Furthermore, in the cross section perpendicular to the direction in which the undulations extend, the shape of the portion where the inclined surfaces existing on the substrate surface are adjacent is curved. The portions where the slopes are adjacent are the undulating groove portion and the ridge portion extending on the surface, and the shape of the cross section of both the bottom portion of the groove and the top of the ridge is curved. This state can also be seen from the electron micrograph shown in FIG. That is, the cross-sectional shape of the undulation in the cross-section perpendicular to the direction in which the undulation extends extends, but the wavelength and the wave height do not need to be constant, but have a shape like a kind of sine wave. As described above, since the cross-sectional shape of both the bottom portion of the groove and the top of the ridge is curved, it is possible to reduce the surface defect density.
[0017]
As described above, by providing a plurality of undulations on the surface of the substrate to be grown of silicon carbide, it is possible to obtain the effect of introducing the off angle shown by K. Shibahara et al. The interval between the undulation tops is preferably 0.01 μm or more from the viewpoint of the limit of the microfabrication technique in producing the undulations on the growth substrate. In addition, since the frequency of association between the antiphase region boundaries extremely decreases when the interval between the undulation peaks exceeds 1000 μm, the interval between the undulation peaks is preferably 1000 μm or less. Furthermore, the distance between the undulating peaks is preferably 0.1 μm or more and 100 μm or less from the viewpoint that the effects of the present invention are sufficiently exhibited.
[0018]
The height difference and interval of the undulations influence the slope of the undulations, that is, the step density. Although the preferable step density varies depending on the crystal growth conditions, it cannot be generally stated. However, the required undulation height difference is generally the same as the undulation top interval, that is, 0.01 μm or more and 20 μm or less.
[0019]
In the present invention, the entire substrate as described above or a partial region of the substrate (however, this region has the plurality of undulations) is used as one growth region, and a silicon carbide film is continuously formed thereon. Let it form. By providing the substrate with such undulations, it is possible to associate the growing antiphase region boundary surfaces with each other between the plurality of undulations, which are generated from the steps existing on the slope according to the growth of silicon carbide. is there. Therefore, the antiphase region boundary surface can be effectively eliminated and removed, and single crystal silicon carbide with few defects can be obtained.
[0020]
In the invention described in claim 1, as a material of the substrate, for example, a single crystal substrate such as silicon, silicon carbide, or sapphire can be used.
These points are common to the inventions described in other claims of the present invention.
[0021]
[Invention of Claim 2]
  In the invention according to claim 2, similarly to the invention according to claim 1, the substrate on which silicon carbide is deposited has a plurality of undulations whose surfaces extend substantially in parallel. A substrate having an average roughness in the range of 3 to 1000 nm and a slope of the undulating slope in the range of 1 ° to 54.7 ° is used. The reason for limiting the numerical value and the preferable numerical range of the center line average roughness of the undulations, the reason for limiting the numerical value and the preferable numerical range of the slope of the undulating slope, and other common points regarding the manufacturing method are described in claim 1. This is the same as the described invention. However, in the invention described in claim 2,The substrate surface on which the silicon carbide is deposited has a plurality of undulations extending substantially in parallel to the {001} surface of silicon or silicon carbide.The ratio of the {001} plane in the area of the substrate surface does not exceed 10%. In this way, by providing the undulations on the substrate surface and controlling the ratio of the smooth surface remaining on the substrate surface, it is possible to control the internal stress of silicon carbide deposited on the substrate surface.
[0022]
In the (001) plane, a crystal phase grows in the <001> direction, and stress is generated in the tensile direction with respect to the film. However, by forming undulations on the substrate surface and increasing the proportion of the (111) plane, (001) It is possible to intentionally generate a compressive stress that cancels the tensile stress of the surface, and as a result, the stress in the surface can be relaxed. For example, when the ratio of the (001) plane is controlled to 10% or less in the substrate plane, a undulating slope including the (111) plane is formed, and a undulating substrate in which the growing crystal phases collide with each other is used. A tensile stress acting in the <001> direction and a compressive stress acting in a direction perpendicular to the <001> direction are generated in the silicon carbide layer grown on the substrate, and the stresses cancel each other. Using this, stress can be controlled. The lower limit of the ratio of the {001} plane in the area of the substrate surface is ideally 0%.
[0023]
[Invention of Claim 3]
  In the invention described in claim 3, as in the invention described in claim 1, the substrate on which silicon carbide is deposited has a plurality of undulations whose surfaces extend substantially in parallel, and the undulations are center lines. A substrate having an average roughness in the range of 3 to 1000 nm and a slope of the undulating slope in the range of 1 ° to 54.7 ° is used. The reason for limiting the numerical value and the preferable numerical range of the center line average roughness of the undulations, the reason for limiting the numerical value and the preferable numerical range of the slope of the undulating slope, and other common points regarding the manufacturing method are described in claim 1. This is the same as the described invention. However, in the invention described in claim 3,The substrate surface on which the silicon carbide is deposited has a plurality of undulations extending substantially parallel to the {111} plane of silicon or cubic silicon carbide.The ratio of the {111} plane occupying the area of the substrate surface does not exceed 3%. In this way, by providing the undulations on the substrate surface and controlling the ratio of the smooth surface remaining on the substrate surface, the inside of the silicon carbide deposited and formed on the substrate surface as in the case of the invention according to claim 2 Stress can be controlled. The lower limit of the proportion of the {111} plane that occupies the area of the substrate surface is ideally 0%.
[0024]
[Invention of Claim 4]
  In the invention according to claim 4, as in the invention according to claim 1, the substrate on which silicon carbide is deposited has a plurality of undulations whose surfaces extend substantially in parallel, and the undulations are center lines. A substrate having an average roughness in the range of 3 to 1000 nm and a slope of the undulating slope in the range of 1 ° to 54.7 ° is used. The reason for limiting the numerical value and the preferable numerical range of the center line average roughness of the undulations, the reason for limiting the numerical value and the preferable numerical range of the slope of the undulating slope, and other common points regarding the manufacturing method are described in claim 1. This is the same as the described invention. However, in the invention described in claim 4,The substrate surface on which the silicon carbide is deposited has a plurality of undulations extending substantially parallel to the {1,1, -2,0} plane of hexagonal silicon carbide.The ratio of the {1,1, -2,0} plane in the area of the substrate surface does not exceed 10%. In this way, by providing the undulations on the substrate surface and controlling the ratio of the smooth surface remaining on the substrate surface, the inside of the silicon carbide deposited and formed on the substrate surface as in the case of the invention according to claim 2 Stress can be controlled. The lower limit of the ratio of the {1,1, -2,0} plane in the area of the substrate surface is ideally 0%.
[Invention of Claim 5]
  In the invention according to claim 5, similarly to the invention according to claim 1, the substrate on which silicon carbide is deposited has a plurality of undulations whose surfaces extend substantially in parallel, and the undulations are center lines. A substrate having an average roughness in the range of 3 to 1000 nm and a slope of the undulating slope in the range of 1 ° to 54.7 ° is used. The reason for limiting the numerical value and the preferable numerical range of the center line average roughness of the undulations, the reason for limiting the numerical value and the preferable numerical range of the slope of the undulating slope, and other common points regarding the manufacturing method are described in claim 1. This is the same as the described invention. However, in the invention according to claim 5,The substrate surface on which the silicon carbide is deposited is formed by forming a plurality of undulations extending substantially in parallel on the {0, 0, 0, 1} plane of hexagonal silicon carbide.The ratio of the {0, 0, 0, 1} plane in the substrate surface area does not exceed 3%. In this way, by providing the undulations on the substrate surface and controlling the ratio of the smooth surface remaining on the substrate surface, the inside of the silicon carbide deposited and formed on the substrate surface as in the case of the invention according to claim 2 Stress can be controlled. The lower limit of the ratio of the {0, 0, 0, 1} plane in the area of the substrate surface is ideally 0%.
[0025]
[Invention of Claim 6]
In the first to fifth aspects of the present invention, silicon carbide is deposited on at least a part of the substrate surface from the vapor phase or the liquid phase. As a method for depositing silicon carbide from the gas phase or the liquid phase, a known method can be used as it is.
As a silicon source gas in the method of depositing silicon carbide from the gas phase, dichlorosilane (SiH₂Cl₂), SiH_Four, SiCl_Four, SiHCl_ThreeA silane compound gas such as can be used. As the carbon source gas, acetylene (C₂H₂), CH_Four, C₂H₆, C_ThreeH₈A hydrocarbon gas such as can be used.
Examples of the liquid phase method include a method of melting polycrystalline or amorphous silicon carbide, or a method of forming silicon carbide from a silicon source and a carbon source.
[Invention of Claim 7]
The invention according to claim 7 is the invention according to any one of claims 2 to 6, wherein the shape of the portion where the slopes are adjacent to each other is curved in the cross section perpendicular to the direction in which the undulations of the substrate surface extend. It is characterized by being in a shape. The portions where the slopes are adjacent are the undulating groove portion and the ridge portion extending on the surface, and the shape of the cross section of both the bottom portion of the groove and the top of the ridge is curved. This state can also be seen from the electron micrograph shown in FIG. That is, the cross-sectional shape of the undulation does not have to be constant in wavelength and wave height, but has a shape like one kind of sine wave. As described above, since the cross-sectional shape of both the bottom portion of the groove and the top of the ridge is curved, it is possible to reduce the surface defect density.
[0026]
In order to form the undulations having the above-described shape on the surface of the substrate, for example, an optical lithography technology, a press processing technology, a laser processing, an ultrasonic processing technology, a polishing processing technology, or the like can be used. Whichever method is used, the final form of the surface of the substrate to be grown has a form sufficient to effectively reduce or eliminate the anti-phase region boundary as described in each claim. It should be.
[0027]
If an optical lithography technique is used, an arbitrary undulating shape can be transferred to a growth substrate by arbitrarily forming a mask pattern to be transferred to the substrate. The width of the undulation shape can be controlled by changing the line width of the pattern, for example, and the depth of the undulation shape and the angle of the slope can be controlled by controlling the etching selectivity between the resist and the substrate. Is possible. When forming a substrate in which the shape of the portion where the slopes adjoin each other in a cross section perpendicular to the direction in which the undulations of the substrate surface extend is curved, the resist is softened by heat treatment after pattern transfer to the resist. Thus, it is possible to form an undulating pattern having a curved cross section (wave shape).
[0028]
If a press working technique is used, it is possible to form an arbitrary undulating shape on the substrate to be grown by arbitrarily forming a pressing die. By forming molds of various shapes, various undulating shapes can be formed on the growth substrate.
[0029]
If laser processing or ultrasonic processing technology is used, the undulation shape is directly formed on the substrate, so that finer processing is possible.
If polishing is used, it is possible to control the width and depth of the undulating shape by changing the size of the abrasive grain size and the processing pressure. When it is intended to produce a substrate having a unidirectional undulation shape, polishing is performed only in one direction.
[0030]
If dry etching is used, the width and depth of the undulation shape can be controlled by changing the etching conditions and the shape of the etching mask. In the cross section orthogonal to the direction in which the undulations of the substrate surface extend, when forming a substrate in which the shape of the portion where the slopes are adjacent is a curved shape, by disposing the etching mask away from the pattern transfer substrate, Since etching is diffused between the mask and the substrate, a wavy pattern having a curved cross section can be transferred. Alternatively, the mask may have a trapezoidal shape in which the cross section of the window of the mask widens toward the pattern transfer substrate.
[0031]
  According to the present inventionThe surface defect density is 1000 / cm²Single-crystal silicon carbide characterized by(Hereinafter also referred to as “single crystal silicon carbide I”) can be manufactured.. Conventionally, single crystal silicon carbide is known. However, conventional single crystal silicon carbide has a surface defect density of 10^Four/ Cm²(For example, A.L., Syrkin et al., Inst. Phys. Conf. Ser. No. 142, p189). In contrast, the present inventionCan be manufactured bySingle crystal silicon carbide has a surface defect density of 1000 / cm.²Below, preferably 100 / cm²It is as follows. The lower limit of the surface defect density is ideally 0 / cm²In reality, 0.1 / cm²Degree. Such single crystal silicon carbide has very excellent electrical characteristics because of its low crystal boundary density, and can be suitably used as a semiconductor substrate, a crystal growth substrate (including a seed crystal), and other electronic devices.
[0032]
  According to the present inventionSingle crystal silicon carbide characterized by having an internal stress of 100 MPa or less(Hereinafter also referred to as “single crystal silicon carbide II”) can be manufactured.. Conventionally, single crystal silicon carbide is known. However, conventional polycrystalline silicon carbide has an internal stress exceeding 100 MPa (for example, T.Shoki et al., SPIE. Int. Soc. Opt. Eng. Vol. 3748 p456). In contrast, the present inventionCan be manufactured bySingle crystal silicon carbide has an internal stress of 100 MPa or less, preferably 50 MPa or less. The lower limit of the internal stress is ideally 0 MPa, and practically 50 MPa. Such single crystal silicon carbide can provide a smooth silicon carbide with less warping and distortion of silicon carbide. When silicon carbide is warped by internal stress, the silicon carbide surface is distorted. For example, when silicon carbide is newly deposited on the silicon carbide substrate, silicon carbide is deposited while taking over the strain. However, as a substrate, the internal stress is 100 MPa or less, and the present invention is smooth without distortion.Can be manufactured byWhen single crystal silicon carbide is used, such a problem can be avoided.
[0033]
  According to the present inventionThe surface defect density is 1000 / cm²And having an internal stress of 100 MPa or less(Hereinafter also referred to as “single crystal silicon carbide III”) can be produced.. As described above, the conventional single crystal silicon carbide has a surface defect density of 10%.^Four/ Cm²There was no single crystal with an internal stress of about 100 MPa. In contrast, the present inventionCan be manufactured bySingle crystal silicon carbide has a surface defect density of 1000 / cm.²Below, preferably 100 / cm²The internal stress is 100 MPa or less, preferably 50 MPa or less. The lower limit of the surface defect density is ideally 0 / cm²In reality, 0.1 / cm²Degree. Moreover, the lower limit of the internal stress is ideally 0 MPa, and practically 50 MPa. Such single crystal silicon carbide has very excellent electrical characteristics because of its low crystal boundary density, and can be suitably used as a semiconductor substrate, a crystal growth substrate (including a seed crystal), and other electronic devices. Further, it is possible to provide a smooth silicon carbide in which warpage and distortion of silicon carbide are small.
[0034]
  According to the present inventionEtch pit density is 10 / cm²And the twin density is 4 × 10^-FourVol. % Single crystal silicon carbide(Hereinafter also referred to as “single crystal silicon carbide IV”) can be manufactured.. The etch pit density affects the yield of devices using the single crystal silicon carbide of the present invention, and the etch pit density is 10 / cm.²If the device area is 0.01 cm or less²In this case, a yield of 90% or more can be obtained. Etch pit density is 1 / cm from the viewpoint of increasing device yield.²The following is preferable. The twin density is 4 × 10.^-FourVol. % Or less, the device area is 0.01 cm²Is preferable from the viewpoint that a yield of 90% or more can be obtained.^-FiveVol. % Or less is more preferable.
[0035]
[Claims8-11Invention described in]
  Claim8-11In the manufacturing method according to any one of claims 1 to 7, the invention described in (1) is performed by epitaxially growing silicon carbide while precipitating the crystallinity of the substrate surface.SaidSingle crystal silicon carbideAny of I-IVIt is a manufacturing method. The method of epitaxially growing silicon carbide precipitation while taking over the crystallinity of the substrate surface may be any method that can limit the propagation direction of defects on the inner surface of the film within a specific crystal plane, such as a chemical vapor deposition (CVD) method, A liquid phase epitaxial growth method, a sputtering method, a molecular beam epitaxy (MBE) method, or the like can be used. In the case of the CVD method, the simultaneous supply method of source gases can be used instead of the source gas alternate supply method.
[0036]
In the invention according to the twelfth aspect, since the step of orientation of the silicon carbide substrate to be grown in a mirror-symmetrical orientation is introduced at a density that is statistically balanced, it is introduced unintentionally by the step of the substrate surface to be grown. Thus, the anti-phase region boundary surfaces in the silicon carbide layer are effectively associated with each other, and a silicon carbide film in which the anti-phase region boundary surface is completely eliminated can be obtained. Furthermore, because of the effect of introducing the off-angle, the individual growth regions all become the same phase region that expands in the same direction, so even when the discrete growth regions are joined together with growth, an antiphase region boundary surface is formed at the joint. There is also an advantage that it does not occur.
That is, according to this method, the lattice constant mismatch between the silicon and silicon carbide interface, which is a problem when silicon carbide is deposited on the silicon substrate, is eliminated, the generation of defects is suppressed, and high quality carbonization is performed. Silicon can be formed.
[0037]
【Example】
Hereinafter, the present invention will be described in more detail based on examples.
Reference example
In order to confirm the effect of introducing the off-angle, the (001) plane of a 6-inch Φ silicon substrate (hereinafter referred to as Si) without an off-angle and the Si (001) plane with off-angles of 4 ° and 10 °, respectively, are grown. As a substrate, silicon carbide (hereinafter 3C-SiC) was grown. The growth of 3C-SiC is divided into a carbonization process on the substrate surface and a 3C-SiC growth process by alternately supplying source gases. In the carbonization step, the processed substrate was heated from room temperature to 1050 ° C. for 120 minutes in an acetylene atmosphere. After the carbonization step, dichlorosilane and acetylene were alternately exposed to the substrate surface at 1050 ° C. to grow 3C—SiC. Detailed conditions of the carbonization process are shown in Table 1, and detailed conditions of the 3C-SiC process are shown in Table 2, respectively.
When the density of the antiphase region boundary surface was measured for silicon carbide grown on each substrate, the results shown in Table 3 were obtained.
[0038]
[Table 1]

[0039]
[Table 2]

[0040]
[Table 3]

[0041]
In addition, the density of the antiphase region boundary surface was obtained by observing the 3C-SiC surface with AFM. At this time, the surface of 3C—SiC was subjected to thermal oxidation treatment, and the thermal oxide film was removed to observe the antiphase boundary, thereby observing.
From the relationship between the off-angle and the anti-phase region boundary surface density shown in Table 3, it can be seen that although the decrease of the anti-phase region boundary surface density due to the introduction of the off-angle is confirmed, it has not been completely eliminated.
A scanning electron micrograph of the surface of the 3C-SiC film grown on the substrate having an off angle of 4 ° is shown in FIG. 2, and a scanning electron micrograph of the surface of the 3C-SiC film grown on the substrate having no off angle is shown in FIG. As shown in FIG.
2 and 3, it is confirmed that the terrace area is enlarged by introducing the off-angle, and the 3C-SiC growth in the step flow mode is dominant, and the propagation direction of the plane defect is limited to a specific crystal plane. You can see that However, these defect propagation directions are all parallel and remain without disappearing. Therefore, it is impossible to completely eliminate the anti-phase boundary surface defects.
[0042]
Example 1
A silicon (001) surface having a diameter of 6 inches is used as a substrate to be grown, and after the substrate surface is thermally oxidized, a line & space pattern having a width of 1.5 μm, a length of 60 mm, and a thickness of 1 μm is formed on the substrate surface using photolithography technology. The resist was formed. However, the direction of the line & space pattern was made parallel to the <110> orientation. By heating this substrate using a hot plate under the conditions shown in Table 4, the line & space resist pattern spreads and deforms in the direction perpendicular to the line, and the wave front is formed by connecting the top and bottom of the undulation with a smooth curve The resist pattern shape of the cross section was obtained. The cross-sectional shape (undulations) and planar shape (lines & spaces) of this resist pattern were transferred to a silicon substrate by dry etching.
[0043]
The resist was removed in a mixed solution of hydrogen peroxide and sulfuric acid to obtain a substrate. As a result of electron microscope observation, as shown in FIG. 4, this substrate has a plurality of undulations extending substantially parallel to the substrate surface, and in a cross section orthogonal to the direction in which the undulations extend, The shape of the portion where the slopes are adjacent to each other was curved. Further, this undulation had a center line average roughness of 100 nm, and the average slope of this undulation slope was 4 °. The center line average roughness and the slope of the undulating slope were measured with an atomic force microscope (AFM).
[0044]
3C-SiC was grown on this substrate. The growth of 3C-SiC is divided into a carbonization process on the substrate surface and a 3C-SiC growth process by alternately supplying a source gas. Table 5 shows the detailed conditions of the 3C-SiC growth step. The detailed conditions for the carbonization step were the same as in Table 1.
In the 3C-SiC growth step, the density of the antiphase region boundary surface appearing on the outermost surface was measured in the same manner as described above by changing the film thickness of 3C-SiC by changing the number of supply cycles of the source gas. The results shown in Table 6 were obtained.
[0045]
[Table 4]

[0046]
[Table 5]

[0047]
[Table 6]

[0048]
From the relationship between the 3C-SiC film thickness and the antiphase region boundary surface density shown in Table 6, it can be seen that the surface defects collide and disappear as the growth of 3C-SiC progresses. It can be seen that the effectiveness of the present invention is remarkable as compared with the numerical values in Table 3 which are the conventional methods. Further, the etch pit density and twin density of 6 inch Φ3C—SiC obtained in this example were examined as follows. After exposing the surface of 3C-SiC to molten KOH (500 ° C., 5 minutes), the surface was observed with an optical microscope. The number of etch pits corresponding to the stacking fault density was 1,700 or less on the entire surface of 6 inches, and the density was 10 / cm²It was the following. Furthermore, pole observation of the X-ray diffraction rocking curve (XRD) with respect to the 3C-SiC <111> orientation was performed, and the signal intensity of the {115} plane orientation corresponding to the twin plane and the normal single crystal plane {111} plane orientation The twin density was calculated from the signal intensity ratio. As a result, twin density is 4 × 10 which is the limit of measurement.^-FourVol. % Or less.
[0049]
Example 2
A Si (001) surface having a diameter of 6 inches was used as a substrate to be grown, and a line and space pattern having a width of 1.5 μm, a length of 60 mm, and a thickness of 1 μm was formed on the substrate surface using a photolithography technique. However, the direction of the line & space pattern was made parallel to the <110> orientation. This substrate was heated using a hot plate under the conditions shown in Table 7 to soften the resist and change the cross-sectional shape of the resist pattern. The cross-sectional shape (undulations) and planar shape (lines & spaces) of this resist pattern were transferred to a Si substrate by dry etching. The heating temperature of the resist pattern was changed between 150 ° C. and 200 ° C., and the undulation inclination angle θ was changed as shown in Table 8.
The resist was removed in a mixed solution of hydrogen peroxide and sulfuric acid to obtain a substrate. As a result of electron microscope observation, as shown in FIG. 4, this substrate has a plurality of undulations extending substantially parallel to the substrate surface, and in a cross section orthogonal to the direction in which the undulations extend, The shape of the portion where the slopes are adjacent to each other was curved. Further, this undulation had a center line average roughness of 100 nm, and the average slope of the undulation slope was as shown in Table 8. The centerline average roughness and the slope of the undulating slope were measured in the same manner as in Example 1.
[0050]
3C-SiC was grown on these substrates. The growth of 3C-SiC is divided into a carbonization process on the substrate surface and a 3C-SiC growth process by alternately supplying a source gas. The detailed conditions for the carbonization step were the same as in Table 1, and the detailed conditions for the 3C-SiC growth step were the same as in Table 5.
For the 3C—SiC grown on each substrate, the density of the antiphase region boundary surface appearing on the outermost surface was measured in the same manner as described above, and the results shown in Table 8 were obtained.
[0051]
[Table 7]

[0052]
[Table 8]

[0053]
From the relationship between the slope of the undulation and the antiphase region boundary surface density shown in Table 8, the inclination angle θ of the undulation is particularly less than 54.7 ° which is an angle formed by the (111) plane and is 1 ° or more. In some cases, a decrease in the density of the antiphase region boundary surface can be confirmed. Furthermore, compared with the numerical values in Table 3 which are the conventional methods, 3C-SiC grown on a relief processing substrate as in the present invention has a significantly reduced or eliminated antiphase region boundary surface density even at the same off angle. It can be seen that the effectiveness of the present invention is remarkable. Further, the etch pit density and twin density of 3C-SiC grown on the undulation substrate with the undulation inclination angle of 4 degrees obtained in this example were examined as follows. After exposing 3C-SiC to molten KOH (500 ° C., 5 minutes), the surface was observed with an optical microscope. The number of etch pits corresponding to the stacking fault density was 1,528 on the entire surface of 6 inches, and the density was 8 .65 / cm²Met. Furthermore, pole observation of the X-ray diffraction rocking curve (XRD) with respect to the 3C-SiC <111> orientation was performed, and the signal intensity of the {115} plane orientation corresponding to the twin plane and the normal single crystal plane {111} plane orientation The twin density was calculated from the signal intensity ratio. As a result, twin density is 4 × 10 which is the limit of measurement.^-FourVol. % Or less.
[0054]
Example 3
In each of Examples 1 and 2, a cubic SiC film was grown on a Si (001) plane substrate. In Example 3, as a substrate to be grown, a substrate having undulations extending parallel to the <110> direction on the (001) plane of single crystal cubic silicon carbide (3C-SiC) having a diameter of 6 inches, or a single crystal Cubic silicon carbide is formed on the surface of each substrate using a substrate having undulations extending parallel to the <0,0,0,1> orientation on the (1,1, -2,0) plane of hexagonal silicon carbide. A film or a hexagonal silicon carbide film was grown under the same conditions as in Example 1.
As a result of observation with an electron microscope, each of the substrates has a plurality of undulations extending substantially parallel to the substrate surface, as shown in FIG. 4, and is orthogonal to the direction in which the undulations extend. In the cross section, the shape of the portion where the slopes are adjacent to each other was curved. Further, this undulation had a center line average roughness of 100 nm, and the average slope of this undulation slope was 4 °.
As a result, the effectiveness of the present invention was confirmed in the same manner as in Example 1 when the substrate was used.
[0055]
Example 4
An attempt was made to fabricate an undulation-formed substrate parallel to the <110> direction by a method of polishing the surface of a 6-inch diameter Si (001) substrate in parallel to the <110> direction. For polishing, a commercially available diamond slurry having a diameter of about 15 μm (manufactured by Engis Co., Ltd .: High Press) and a commercially available abrasive cloth (manufactured by Engis Co., Ltd .: M414) were used (Table 9). The diamond slurry is uniformly infiltrated on the cloth, and the Si (001) substrate is placed on the pad, and 0.2 kg / cm.²Was applied to the entire Si (001) substrate, and a one-way polishing treatment was performed by reciprocating a distance of about 20 cm on the cloth 300 times parallel to the <110> direction. Innumerable polishing scratches (scratches) parallel to the <110> direction were formed on the surface of the Si (001) substrate.
[0056]
[Table 9]

[0057]
Since polishing abrasive grains or the like are attached to the surface of the Si (001) substrate subjected to the unidirectional polishing treatment, NH_FourOH + H₂O₂+ H₂O mixed solution (NH_FourOH: H₂O₂: H₂O = 4: 4: 1 at a liquid temperature of 60 ° C.)₂SO_Four+ H₂O₂Solution (H₂SO_Four: H₂O₂= 1: 1 (liquid temperature 80 ° C.) and HF (10%) solution alternately three times each for cleaning, and finally rinsed with pure water.
After cleaning, a thermal oxide film was formed to a thickness of about 1 μm on the unidirectionally polished substrate using the heat treatment apparatus under the conditions shown in Table 10. The thermal oxide film was removed with a HF 10% solution. If only polishing is performed, the substrate surface has many fine irregularities and defects other than the undulations to be obtained, and is difficult to use as a substrate to be grown. However, by forming a thermal oxide film of about 1 μm and removing the oxide film again, the surface of the substrate was etched by about 2000 mm, fine irregularities were removed, and a very smooth undulation surface could be obtained. Looking at the wavy cross section, the size of the wavy irregularities is unstable and irregular, but the density is high. At least the (001) plane was 10% or less. There is always ups and downs. On average, the centerline average roughness was 20 nm. The depth of the groove was about 30 to 50 nm and the width was about 0.5 to 1.5 μm. The slope was 3-5 °. A typical AFM image is shown in FIG.
[0058]
[Table 10]

[0059]
A 3C—SiC film was formed on the substrate using this substrate. The growth of 3C-SiC is divided into a carbonization process on the substrate surface and a 3C-SiC growth process by alternately supplying source gases. The detailed conditions for the carbonization step were the same as in Table 1, and the detailed conditions for the 3C-SiC growth step were the same as in Table 5.
[0060]
As a result, the effect of the relief forming substrate parallel to <110> was obtained. That is, it was confirmed that the defects on the antiphase boundary surface were greatly reduced.
For example, the antiphase boundary surface density of a 3C—SiC film grown on an unpolished Si substrate is 8 × 10.⁹/ Cm²On the other hand, the antiphase boundary surface defect density of the 3C-SiC film grown on the Si substrate subjected to the unidirectional polishing is 0 to 1 / cm.²It became. The undulation shape and the antiphase boundary surface defect density with respect to the abrasive grain size are as shown in Table 11. Further, the undulation density and antiphase boundary surface defect density with respect to the number of polishing operations are as shown in Table 12.
[0061]
[Table 11]

[0062]
[Table 12]

[0063]
The etch pit density and twin density of 3C—SiC grown on a relief processing substrate with an abrasive grain size of 15 μm and a number of polishing round trips of 300 were examined as follows. After exposing 3C-SiC to molten KOH (500 ° C., 5 minutes), the surface was observed with an optical microscope. The number of etch pits corresponding to the stacking fault density was 1,414 on the entire surface of 6 inches, and the density was 8 .00 / cm²Met. Furthermore, pole observation of the X-ray diffraction rocking curve (XRD) with respect to the 3C-SiC <111> orientation was performed, and the signal intensity of the {115} plane orientation corresponding to the twin plane and the normal single crystal plane {111} plane orientation The twin density was calculated from the signal intensity ratio. As a result, twin density is 4 × 10 which is the limit of measurement.^-FourVol. % Or less.
In this example, a diamond slurry having a diameter of 15 μm was used as an abrasive, but the size of the abrasive grains and the type of abrasive grains are not limited thereto. If the particle size is increased, the width of the undulations becomes wider and gentler. It can be easily imagined that if the particle size is made smaller, the undulation width becomes narrower. If the particle diameter is about φ1 to 300 μm, effective undulations can be formed. The pad is not limited to the above. The load pressure between the substrate and the cloth during polishing, the polishing speed and the number of times are not limited to the above. Moreover, although Si (001) was used in the examples, it goes without saying that the same results as described above can be obtained even when cubic or hexagonal silicon carbide is used. Moreover, although the undulation extending in the direction parallel to the <110> direction was formed on the Si (001) substrate, the direction is not limited to this.
[0064]
Example 5
In order to eliminate distortion and warpage generated in the silicon carbide layer, undulation formation parallel to the <110> direction is performed by performing a polishing process parallel to the <110> direction on the surface of the Si (001) substrate having a diameter of 6 inches. An attempt was made to produce a substrate. In this example, the existence probability of the Si (001) surface was controlled by the number of polishing treatments, and the effect of the present invention was confirmed. Under the same conditions as in Table 9, the unidirectional polishing treatment was performed on the Si (001) surface by changing the number of polishing times from 30 to 300 times. Innumerable polishing scratches (scratches) parallel to the <110> direction were formed on the surface of the Si (001) substrate.
Since abrasive grains and the like are attached to the Si (001) substrate that has been subjected to the unidirectional polishing treatment, NH_FourOH + H₂O₂+ H₂O mixed solution (NH_FourOH: H₂O₂: H₂O = 4: 4: 1 at a liquid temperature of 60 ° C.)₂SO_Four+ H₂O₂Solution (H₂SO_Four: H₂O₂= 1: 1 (liquid temperature 80 ° C.) and HF (10%) solution alternately three times each for cleaning, and finally rinsed with pure water.
After cleaning, a thermal oxide film was formed to a thickness of about 1 μm on the unidirectionally polished substrate using the heat treatment apparatus under the conditions shown in Table 10. The thermal oxide film was removed with a HF 10% solution.
[0065]
A 3C—SiC film was formed on the substrate using this substrate. The growth of 3C-SiC is divided into a carbonization process on the substrate surface and a 3C-SiC growth process by alternately supplying source gases. The detailed conditions for the carbonization step were the same as in Table 1, and the detailed conditions for the 3C-SiC growth step were the same as in Table 5. Table 13 shows the relationship between the abundance ratio of the Si (001) plane, the internal stress of 3C—SiC, and the antiphase boundary surface defect density.
[0066]
[Table 13]

[0067]
When the Si (001) plane on the Si (001) substrate, which is the 3C-SiC growth base substrate, was 10% or less, the internal stress in the SiC layer was 35 MPa or less in the compression direction. When the Si (001) plane was 10% or more, as shown in the table, the result showed very high stress. It can be said that undulations were provided on the Si (001) surface, and the effect of controlling the Si (001) surface to 10% or less appeared. In addition, the defect density tended to increase as the proportion of the Si (001) plane increased. It became clear that the defect density is better as the proportion of the Si (001) plane is smaller. In addition, the etch pit density and twin density of 3C—SiC grown on a relief processing substrate in which the Si (001) plane was controlled to 10% or less were determined as follows. After exposing 3C-SiC to molten KOH (500 ° C., 5 minutes), the surface was observed with an optical microscope. The number of etch pits corresponding to the stacking fault density was 1,548 over the entire surface of 6 inches, and the density was 8 .76 / cm²Met. Furthermore, pole observation of the X-ray diffraction rocking curve (XRD) with respect to the 3C-SiC <111> orientation was performed, and the signal intensity of the {115} plane orientation corresponding to the twin plane and the normal single crystal plane {111} plane orientation The twin density was calculated from the signal intensity ratio. As a result, twin density is 4 × 10 which is the limit of measurement.^-FourVol. % Or less.
As a result of observation with an electron microscope, each of the substrates has a plurality of undulations extending substantially parallel to the substrate surface, as shown in FIG. 4, and is orthogonal to the direction in which the undulations extend. In the cross section, the shape of the portion where the slopes are adjacent to each other was curved. Further, this undulation had a center line average roughness of 20 to 40 nm, and the average slope of the undulation slope was 3 to 5 °.
[0068]
In this embodiment, the Si (001) plane was used as described above. Similarly, by setting the (111) plane to 3% or less in the Si (111) plane, (1,1, -2,0) in the hexagonal silicon carbide (1,1, -2,0) plane. By making the surface 10% or less, in the hexagonal silicon carbide (0,0,0,1) surface, the (0,0,0,1) surface is made 3% or less, and each SiC layer is deposited. The result that the internal stress inside can be reduced to 100 MPa or less was also obtained.
[0069]
Example 6
In order to eliminate distortion and warpage generated in the silicon carbide layer, undulation formation parallel to the <110> direction is performed by performing a polishing process parallel to the <110> direction on the surface of the Si (001) substrate having a diameter of 6 inches. An attempt was made to produce a substrate. In this example, the center line average roughness of the Si (001) surface was controlled by the grain size of the abrasive grains, and the effect of the present invention was confirmed. Polishing was performed under the same conditions as in Table 9. Innumerable polishing scratches (scratches) parallel to the <110> direction were formed on the surface of the Si (001) substrate.
Since abrasive grains and the like are attached to the Si (001) substrate that has been subjected to the unidirectional polishing treatment, NH_FourOH + H₂O₂+ H₂O mixed solution (NH_FourOH: H₂O₂: H₂O = 4: 4: 1 at a liquid temperature of 60 ° C.)₂SO_Four+ H₂O₂Solution (H₂SO_Four: H₂O₂= 1: 1 (liquid temperature 80 ° C.) and HF (10%) solution alternately three times each for cleaning, and finally rinsed with pure water.
After cleaning, a thermal oxide film was formed to a thickness of about 1 μm on the unidirectionally polished substrate using the heat treatment apparatus under the conditions shown in Table 10. The thermal oxide film was removed with a HF 10% solution.
[0070]
A 3C—SiC film was formed on the substrate using this substrate. The growth of 3C-SiC is divided into a carbonization process on the substrate surface and a 3C-SiC growth process by alternately supplying source gases. The detailed conditions for the carbonization step were the same as in Table 1, and the detailed conditions for the 3C-SiC growth step were the same as in Table 5. Table 14 shows the relationship between the center line average roughness of the Si (001) plane, the internal stress of 3C-SiC, and the antiphase boundary surface defect density.
[0071]
[Table 14]

[0072]
When the center line average roughness is 3 nm or less, the internal stress is high and the surface defect density is also high. When the center line average roughness is between 3 nm and 100 nm, the internal stress is also reduced and the surface defect density is also eliminated. When the center line average roughness exceeds 100 nm, the surface defect density tends to increase. Further, the etch pit density and twin density of 3C—SiC grown on the undulating substrate in which the center line average roughness of the Si (001) plane was controlled to 30 to 50 nm were determined as follows. When 3C-SiC was exposed to molten KOH (500 ° C., 5 minutes) and the surface was observed with an optical microscope, the number of etch pits corresponding to the stacking fault density was 1,683 over the entire surface of 6 inches, and the density was 9 .52 / cm²Met. Furthermore, pole observation of the X-ray diffraction rocking curve (XRD) with respect to the 3C-SiC <111> orientation was performed, and the signal intensity of the {115} plane orientation corresponding to the twin plane and the normal single crystal plane {111} plane orientation The twin density was calculated from the signal intensity ratio. As a result, twin density is 4 × 10 which is the limit of measurement.^-FourVol. % Or less. It can be said that the effect of the present invention appeared by providing undulations on the Si (001) plane and controlling the center line average roughness to 3 nm to 100 nm.
As a result of observation with an electron microscope, each of the substrates has a plurality of undulations extending substantially parallel to the substrate surface, as shown in FIG. 4, and is orthogonal to the direction in which the undulations extend. In the cross section, the shape of the portion where the slopes are adjacent to each other was curved. Furthermore, the average slope of this undulating slope was 3-5 °.
[0073]
In this embodiment, the Si (001) plane is used, but the same applies to the Si (111) plane, hexagonal silicon carbide (1,1, -2,0), and hexagonal silicon carbide (0,0,0,1). It has been confirmed that the results are obtained.
[0074]
Example 7
An attempt was made to reduce the distortion of 3C—SiC by providing undulations on the front and back surfaces of a 6-inch diameter Si (001) substrate. The undulations were formed by polishing under the conditions shown in Table 9. The center line average roughness was about 50 nm on both the front and back surfaces. 3C-SiC was grown on this substrate. The growth of 3C-SiC is divided into a carbonization process on the substrate surface and a 3C-SiC growth process by alternately supplying source gases. The detailed conditions for the carbonization step were the same as in Table 1, and the detailed conditions for the 3C-SiC growth step were the same as in Table 5. The grown 3C—SiC internal stress was as low as 10 MPa in the direction of compression. The stress generated on the front and back surfaces cancels out, warping and distortion are reduced, and good 3C—SiC growth is brought about. It can be said that the effect of forming undulations on the front and back surfaces of the substrate was obtained.
Although this embodiment was performed on the Si (100) plane, the same applies to the Si (111) plane, hexagonal silicon carbide (1,1, -2,0), and hexagonal silicon carbide (0,0,0,1). It has been confirmed that the results are obtained.
[0075]
Example 8
In the above examples, it was found that high quality 3C-SiC can be obtained by forming undulations having a predetermined shape on the substrate surface. In this embodiment, a method for producing a relief shape by dry etching is shown. First, a quartz mask as shown in FIG. 5 was produced. The line and space pattern provided in the mask of this example is 100 μm apart. The long side of the mask window is arranged parallel to <110> of the silicon substrate. The distance between the silicon substrate and the mask was 1 mm (FIG. 6). This is because if the interval is set to 0, a rectangular line & space pattern is transferred to the silicon substrate. For dry etching, an RIE apparatus was used. CF for etching_Four40 sccm and O₂10 sccm of gas was used. Etching was performed for 4 hours with the power of the RF power source set to 250 W and the degree of vacuum between the electrodes set to 8 Pa (Table 15). As a result, stable wavy undulations having a period of 200 μm and a depth of 8 μm (center line average roughness 60 nm to 100 nm) and an inclination of 3 to 5 ° were transferred to the surface of the silicon substrate. 3C-SiC formed on this substrate has a surface defect density of 0 to 1 / cm.²A good result was obtained. Further, the etch pit density and twin density of 3C—SiC grown on a corrugated relief substrate processed by RIE (Reactive Ion Etching) were determined as follows. After exposing the surface of 3C-SiC to molten KOH (500 ° C., 5 minutes), the surface was observed with an optical microscope. The number of etch pits corresponding to the stacking fault density was 1,290 on the entire surface of 6 inches, and the density was 7 .30 / cm²Met. Furthermore, pole observation of the X-ray diffraction rocking curve (XRD) with respect to the 3C-SiC <111> orientation was performed, and the signal intensity of the {115} plane orientation corresponding to the twin plane and the normal single crystal plane {111} plane orientation The twin density was calculated from the signal intensity ratio. As a result, twin density is 4 × 10 which is the limit of measurement.^-FourVol. % Or less.
[0076]
[Table 15]

[0077]
In the embodiment, a quartz mask is used, but the material is not limited to this. Moreover, although the line and space is set to an interval of 100 μm, it can be arbitrarily set to 10 to 1000 μm. If a narrower window is opened, the strength of the mask becomes a problem. However, the mask strength is secured by setting the space between the line and the space to 1: 2 or 1: 3, and the dry etching is performed multiple times while shifting the position of the mask. High density undulations may be formed. The distance between the mask and the pattern transfer substrate is 1 mm, but this is for making the transfer pattern wavy, and the distance is not necessarily limited to this. It is sufficient that the pattern to be transferred has a distance that is wavy. By making the cross section of the mask window trapezoidal, the wavy undulations can be transferred by etching.
[0078]
Example 9
When the surface shape of the produced undulation substrate is a saw shape, defects such as etch pits sometimes occur in steep recesses as shown in FIG. 7A, and the defects propagate to the surface. Become.
Therefore, an attempt was made to suppress the occurrence of defects by making the surface shape of the undulation corrugated and reducing this steep recess.
The saw-shaped undulation was produced by unidirectional polishing. (The method is the same as the one-way polishing in the example, but the final oxidation treatment is not performed.) The surface of the Si (001) substrate having a diameter of 6 inches is subjected to a polishing treatment parallel to the <110> direction. An attempt was made to produce a relief forming substrate parallel to the 110> direction. For polishing, a commercially available diamond slurry having a diameter of about 15 μm (manufactured by Engis Co., Ltd .: High Press) and a commercially available abrasive cloth (manufactured by Engis Co., Ltd .: M414) were used (Table 9). The diamond slurry is uniformly infiltrated on the cloth, and the Si (001) substrate is placed on the pad, and 0.2 kg / cm.²Was applied to the entire Si (001) substrate, and a one-way polishing treatment was performed by reciprocating a distance of about 20 cm on the cloth 300 times parallel to the <110> direction. Innumerable polishing scratches (scratches) parallel to the <110> direction were formed on the surface of the Si (001) substrate.
[0079]
Since polishing abrasive grains or the like are attached to the surface of the Si (001) substrate subjected to the unidirectional polishing treatment, NH_FourOH + H₂O₂+ H₂O mixed solution (NH_FourOH: H₂O₂: H₂O = 4: 4: 1 at a liquid temperature of 60 ° C.)₂SO_Four+ H₂O₂Solution (H₂SO_Four: H₂O₂= 1: 1 (liquid temperature 80 ° C.) and HF (10%) solution alternately three times each for cleaning, and finally rinsed with pure water.
A very sharp undulation shape (saw shape) was obtained on the surface immediately after polishing (FIG. 7B).
In the wave-type undulation, a saw-shaped undulation was prepared by unidirectional polishing, and then the surface was relaxed into a waveform by performing a thermal oxidation treatment on the undulation surface.
After the polished undulation substrate was cleaned, a thermal oxide film was formed to a thickness of about 1 μm on the unidirectional polished substrate using the heat treatment apparatus under the conditions shown in Table 10. The thermal oxide film was removed with a HF 10% solution. If only polishing is performed, the substrate surface has many fine irregularities and defects other than the undulations to be obtained, and is difficult to use as a substrate to be grown. However, by forming a thermal oxide film of about 1 μm and removing the oxide film again, the surface of the substrate was etched by about 2000 mm, fine irregularities were removed, and a very smooth undulation surface could be obtained. Looking at the wavy cross section, the size of the wavy irregularities is unstable and irregular, but the density is high. At least the (001) plane is 10% or less. There is always ups and downs. On average, the center line average roughness is 20 nm. The depth of the groove was about 30 to 50 nm, and the width was about 0.5 to 1.5 μm. The slope was 3-5 °. A typical AFM image is shown in FIG.
[0080]
A 3C—SiC film was formed on the substrate using this substrate. The growth of 3C-SiC is divided into a carbonization process on the substrate surface and a 3C-SiC growth process by alternately supplying source gases. The detailed conditions for the carbonization step were the same as in Table 1, and the detailed conditions for the 3C-SiC growth step were the same as in Table 5.
In the wave-type undulation, a saw-shaped undulation was prepared by unidirectional polishing, and then the surface was relaxed into a waveform by performing a thermal oxidation treatment on the undulation surface.
A corrugated undulation substrate was produced, and the steep recess was improved moderately.
In addition, waveform undulation was also formed by dry etching and compared.
As a result of growing SiC on the corrugated undulation substrate, no defects were observed in the steep recess as in SiC on the saw undulation substrate. (Fig. 7 (c))
Table shows the density of defects.
[0081]
[Table 16]

[0082]
The etch pit density and twin density of 3C-SiC grown on the corrugated undulation substrate were determined as follows. After exposing the surface of 3C-SiC to molten KOH (500 ° C., 5 minutes), the surface was observed with an optical microscope. The number of etch pits corresponding to the stacking fault density was 1,700 or less on the entire surface of 6 inches, and the density was 10 / cm²It was the following. Furthermore, pole observation of the X-ray diffraction rocking curve (XRD) with respect to the 3C-SiC <111> orientation was performed, and the signal intensity of the {115} plane orientation corresponding to the twin plane and the normal single crystal plane {111} plane orientation The twin density was calculated from the signal intensity ratio. As a result, twin density is 4 × 10 which is the limit of measurement.^-FourVol. % Or less. On the other hand, the number of etch pits of 3C-SiC grown on a saw-type undulation substrate is 284,356 on the entire 6-inch surface, and the density is 1609 / cm.²The twin density is 6 × 10^-3Vol. %Met.
Thus, the generation density of the defects generated at the substrate interface could be greatly improved by producing the waveform undulation. According to the present invention, the density of etch pits generated on the substrate surface is 10 / cm.²Hereafter, twins are mixed 4 × 10^-FourVol. % Or less. Furthermore, the etch pit density on the substrate surface is 10 / cm over a large area of 6 inches in diameter.²Hereafter, twins are mixed 4 × 10^-FourVol. % Or less.
The present invention has been described with reference to the examples. However, the present invention is not limited to the above examples. For example, the film formation conditions and the film thickness of the 3C—SiC film are not limited to those of the examples. In the embodiments, a substrate having a diameter of 6 inches has been described. However, the effect of the present invention is not limited to a substrate having a diameter of 6 inches. For example, a large-diameter substrate having a diameter of 8 inches or more or a small-diameter substrate having a diameter of 4 inches or less. Can be obtained similarly.
[0083]
【The invention's effect】
As described above, according to the silicon carbide manufacturing method of the present invention, a silicon carbide film in which the antiphase region boundary surface is effectively reduced or eliminated and the internal stress and strain of the silicon carbide layer are reduced can be obtained.
Further, the silicon carbide film of the present invention has very excellent electrical characteristics because of its low crystal boundary density, and is widely useful as various electronic devices.
[Brief description of the drawings]
FIG. 1 is an explanatory view of generation of an antiphase region boundary surface 1 and twins due to an increase in step density at a silicon carbide / silicon substrate interface.
FIG. 2 is a scanning electron micrograph of the surface of a 3C—SiC film grown on a substrate with an off angle of 4 °.
FIG. 3 is a scanning electron micrograph of the surface of a 3C—SiC film grown on a substrate having no off-angle.
FIG. 4 is an electron micrograph of a substrate surface used in the present invention, in which the shape of a portion where slopes existing on the substrate surface are adjacent to each other is curved in a cross section perpendicular to the direction in which the undulations extend.
5 is a schematic view of a quartz mask used in Example 8. FIG.
FIG. 6 is an explanatory diagram showing a relationship between a silicon substrate and a mask.
7 shows an undulation substrate (a) having a saw-shaped surface, a substrate (b) having a very sharp undulation shape, or an undulation substrate having a corrugated surface (c) obtained in Example 9. FIG. Scanning electron micrograph of the surface of the 3C-SiC film grown in (1).

Claims (11)

In the method for producing silicon carbide in which silicon carbide is deposited on at least a part of the substrate surface, the substrate surface on which the silicon carbide is deposited has a plurality of undulations extending substantially in parallel. The shape of the portion where the slopes are adjacent to each other in the cross section perpendicular to the direction in which the undulations extend in the range of 3 to 1000 nm, the slope of the slopes of the undulations is in the range of 1 ° to 54.7 °. A method for producing silicon carbide, characterized in that is curved. In the method for manufacturing silicon carbide in which silicon carbide is deposited on at least a part of the substrate surface, the substrate surface on which the silicon carbide is deposited is formed with a plurality of undulations extending substantially parallel to the {001} plane of silicon or silicon carbide. are those that are, the undulations is in the range center line average roughness of 3 to 1000, inclination of the inclined surface of the undulations is in the range of 54.7 ° from the 1 °, it occupies the area of the board surface A method for producing silicon carbide, wherein the ratio of the {001} plane does not exceed 10%. In the method for manufacturing silicon carbide in which silicon carbide is deposited on at least a part of the substrate surface, the substrate surface on which the silicon carbide is deposited has a plurality of undulations extending substantially parallel to the {111} plane of silicon or cubic silicon carbide. are those but formed, the undulations is in the range center line average roughness of 3 to 1000, inclination of the inclined surface of the undulations is in the range of 54.7 ° from the 1 °, the area of the base plate surface A method for producing silicon carbide, wherein the proportion of {111} planes occupying no more than 3%. In the method for manufacturing silicon carbide in which silicon carbide is deposited on at least a part of the substrate surface, the substrate surface on which the silicon carbide is deposited extends substantially parallel to the {1,1, -2,0} plane of hexagonal silicon carbide. A plurality of existing undulations are formed , the undulations have a centerline average roughness in the range of 3 to 1000 nm, and the slopes of the undulation slopes are in the range of 1 ° to 54.7 ° , method for producing a silicon carbide {1,1, -2,0} occupying the area of the base plate surface ratio of the surface is characterized in that it does not exceed 10%. In the method for manufacturing silicon carbide in which silicon carbide is deposited on at least a part of the substrate surface, the substrate surface on which the silicon carbide is deposited extends substantially parallel to the {0, 0, 0, 1} plane of hexagonal silicon carbide. to and in which a plurality of undulations are formed, the undulations is in the range center line average roughness of 3 to 1000, inclination of the inclined surface of the undulations is in the range of 54.7 ° from the 1 °, group A method for producing silicon carbide, wherein a ratio of {0, 0, 0, 1} plane occupying an area of a plate surface does not exceed 3%. The manufacturing method of any one of Claims 1-5 by which precipitation of silicon carbide is performed from a gaseous phase or a liquid phase. The manufacturing method according to any one of claims 2 to 6, wherein in a cross section orthogonal to a direction in which the undulations of the substrate surface extend, the shape of the portion where the slopes are adjacent is curved. The single crystal silicon carbide having a surface defect density of 1000 / cm ² or less is produced by epitaxially growing silicon carbide precipitates while taking over the crystallinity of the substrate surface. Manufacturing method. The manufacturing method according to any one of claims 1 to 7, wherein single crystal silicon carbide having an internal stress of 100 MPa or less is manufactured by epitaxially growing silicon carbide precipitation while taking over the crystallinity of the substrate surface. The surface defect density is 1000 / cm by epitaxially growing silicon carbide precipitation while taking over the crystallinity of the substrate surface. ² The manufacturing method as described in any one of Claims 1-7 which manufactures the single crystal silicon carbide which is below and an internal stress is 100 Mpa or less. Silicon carbide precipitation is epitaxially grown while inheriting the crystallinity of the substrate surface, so that the etch pit density is 10 / cm. ² And the twin density is 4 × 10 ^-Four Vol. The manufacturing method as described in any one of Claims 1-7 which manufactures the single crystal silicon carbide which is% or less.

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