JP3707110B2 - Method for growing compound semiconductor single crystal - Google Patents

Description

【００７８】
また、スカム（浮遊物）が発生しにくい結果、原料融液中から失われるドーパントの量が少なくなるため、この方法に従えば、ドーパントの濃度が所望の濃度に制御よく制御された化合物半導体単結晶を育成することができる。
【００７９】
また、前述の問題を解決する技術の他の例としては、日本結晶成長学会バルク成長分科会第１８回研究会資料集第１６頁ないし第２２頁に開示された方法もある。
【００８０】
この方法は、ＳｉＯ₂を含有するＢ₂Ｏ₃を封止剤として使用し、ＶＢ法またはＶＧＦ法等の縦型ボート法により、ＧａＡｓ結晶を成長させるものである。
【００８１】
この方法によれば、ドーパントとしてのＳｉの酸化によるロスが低減されるとともに、結晶中へのホウ素の混入量を減少させることができるという効果が記載されている。
【００８２】
【発明が解決しようとする課題】
しかしながら、シリコン酸化物または珪酸とＢ₂ Ｏ₃ とからなる封止剤は、Ｂ₂ Ｏ₃ に比べ、粘度が著しく高い。
【００８３】
また、シリコン酸化物または珪酸とＢ₂Ｏ₃とからなる封止剤は、Ｂ₂Ｏ₃に比べ、融点が高くなる。
【００８４】
このため、封止剤として、シリコン酸化物または珪酸とＢ₂ Ｏ₃ とからなる封止剤を用いる、化合物半導体単結晶の育成方法は、封止剤として、Ｂ₂ Ｏ₃ を用いる化合物半導体単結晶の育成方法に比べ、固体状態の、シリコン酸化物または珪酸とＢ₂ Ｏ₃ とからなる封止剤を溶融（融解）するのに時間がかかるといった問題がある。
【００８５】
また、シリコン酸化物または珪酸とＢ₂ Ｏ₃ とからなる封止剤は、溶融状態において、Ｂ₂ Ｏ₃ に比べ粘度が高いため、ＶＢ法やＶＧＦ法においてるつぼ２８の内側表面２８ｓを均一に被覆する機能が、溶融したＢ₂ Ｏ₃ に比べ、やや劣るといった問題がある。
【００８６】
また、シリコン酸化物または珪酸とＢ₂ Ｏ₃ とからなる封止剤は、製造に手間がかかり、製造コストが高いという問題がある。
【００８７】
たとえば、Ｂ₂ Ｏ₃ 中にＳｉＯ₂ を添加した封止剤は、以下に示す２つの製造方法により製造される。
【００８８】
▲１▼ 出発原料として、ホウ酸とＳｉＯ₂ の粉末を使用し、ホウ酸とＳｉＯ₂ とを共存させた後、これを加熱して、ＳｉＯ₂ とＢ₂ Ｏ₃ とからなる封止剤を製造する。
【００８９】
▲２▼ 出発原料として、Ｂ₂ Ｏ₃ とＳｉＯ₂ の固まりまたは粉末を使用し、Ｂ₂ Ｏ₃ とＳｉＯ₂ とを共存させた後、これを加熱して、ＳｉＯ₂ とＢ₂ Ｏ₃ とからなる封止剤を製造する。
【００９０】
上記▲１▼に示す、ＳｉＯ₂ とＢ₂ Ｏ₃ からなる封止剤の製造方法では、ホウ酸とＳｉＯ₂ が共存しているため、ホウ酸を高温に加熱して、Ｂ₂ Ｏ₃ を製造する際に、脱水化反応が起こりにくく、その結果、ＳｉＯ₂ とＢ₂ Ｏ₃ とからなる封止剤の製造に長時間を要する。
【００９１】
また、上記▲２▼に示す、ＳｉＯ₂ が添加されたＢ₂ Ｏ₃ の製造方法では、Ｂ₂ Ｏ₃ 中に、ＳｉＯ₂ が分散混合するのに長時間を要する。
【００９２】
また、ＳｉＯ₂ とＢ₂ Ｏ₃ からなる封止剤は、粘度が高いため、所望の形状に成形しにくく、さらにるつぼ内側表面を均一に被膜できないという問題がある。
【００９３】
以上のようなことが原因して、ＳｉＯ₂ とＢ₂ Ｏ₃ からなる封止剤の製造コストは、Ｂ₂ Ｏ₃ の製造コストに対し、３倍以上高い。
【００９４】
さらに、ＳｉＯ₂ を添加したＢ₂ Ｏ₃ は、前述のようにるつぼ内壁を均一に被覆することができないため、Ｂ₂ Ｏ₃ が被覆されていないところでは、ＧａＡｓ等の原料融液がるつぼと直接接触するため、結晶欠陥が発生し、多結晶化してしまうという問題もあった。
【００９５】
本発明は、以上のような問題を解決するためになされたものである。
すなわち、本発明は、ドーパントの濃度が所望の濃度に精度よく制御され、かつ、双晶や多結晶等の結晶欠陥の少ない高品質の、ドーパントがドープされたＩＩＩ−Ｖ族化合物半導体単結晶、ドーパントがドープされたＩＩ−ＶＩ族化合物半導体単結晶等の化合物半導体単結晶をより効率よく、より安価に製造することのできる、化合物半導体単結晶の育成方法を提供することを目的とする。
【００９６】
【課題を解決するための手段】
請求項１の発明による化合物半導体単結晶の育成方法は、るつぼ内に、第１の融点を有する化合物原料と、化合物原料にドープするためのドーパントと、化合物原料を介してドーパントと分離するように配置された第１の融点よりも低い第２の融点を有する封止剤と、化合物原料を介してドーパントと分離するように配置されたドーパントと同一材料からなる添加剤とを収容する工程と、
化合物原料、ドーパント、封止剤および添加剤が収容されたるつぼを、第２の融点以上第１の融点未満の温度に加熱して、封止剤を溶融させて、化合物原料を介して溶融した封止剤をドーパントと分離した状態を保持しつつ、溶融した封止剤と添加剤とを接触させて反応させることにより反応物を生成させて、反応物を含む溶融状態の封止剤を形成するステップと、
るつぼを、第１の融点以上の温度にさらに加熱して、化合物原料を溶融させて、反応物を含む溶融状態の封止剤によりその表面が封止された、化合物原料とドーパントとを含む原料融液を作製するステップと、
原料融液から、種結晶を用いてドーパントがドープされた化合物半導体単結晶を育成する工程とを備えている。
【００９７】
請求項２の発明による化合物半導体単結晶の育成方法は、るつぼ内に、第１の融点を有する化合物原料と、化合物原料にドープするためのドーパントと、化合物原料を介してドーパントと分離するように配置された第１の融点よりも低い第２の融点を有する封止剤と、化合物原料を介してドーパントと分離するように配置されたドーパントを構成要素として含む非還元性化合物とを収容する工程と、
化合物原料、ドーパント、封止剤および非還元性化合物が収容されたるつぼを、第２の融点以上第１の融点未満の温度に加熱して、封止剤を溶融させて、化合物原料を介して溶融した封止剤をドーパントと分離した状態を保持しつつ、溶融した封止剤と非還元性化合物とを接触させて溶融した封止剤に非還元性化合物を分散混合させることにより、非還元性化合物を含む溶融状態の封止剤を形成するステップと、
るつぼを、第１の融点以上の温度にさらに加熱して、化合物原料を溶融させて、非還元性化合物を含む溶融状態の封止剤によりその表面が封止された、化合物原料とドーパントとを含む原料融液を作製するステップと、
原料融液から、種結晶を用いてドーパントがドープされた化合物半導体単結晶を育成する工程とを備えている。
【００９８】
請求項３の発明による化合物半導体単結晶の育成方法は、第１の融点を有する化合物原料と、化合物原料にドープするためのドーパントと、化合物原料を介してドーパントと分離するように配置された第１の融点よりも低い第２の融点を有する封止剤とを、その内表面がドーパントを構成要素として含む非還元性化合物からなるるつぼ内に収容する工程と、
化合物原料、ドーパントおよび封止剤が収容されたるつぼを、第２の融点以上第１の融点未満の温度に加熱して、封止剤を溶融させて、化合物原料を介して溶融した封止剤をドーパントと分離した状態を保持しつつ、溶融した封止剤と非還元性化合物からなるるつぼの内表面とを接触させて溶融した封止剤に非還元性化合物を分散混合させることにより、非還元性化合物を含む溶融状態の封止剤を形成するステップと、
るつぼを、第１の融点以上の温度にさらに加熱して、化合物原料を溶融させて、非還元性化合物を含む溶融状態の封止剤によりその表面が封止された、化合物原料とドーパントとを含む原料融液を作製するステップと、
原料融液から、種結晶を用いてドーパントがドープされた化合物半導体単結晶を育成する工程とを備えている。
【００９９】
なお、請求項３の発明に用いられるるつぼとしては、例えば石英製のるつぼが挙げられる。
【０１００】
また、請求項１および請求項２の発明においては、るつぼの材質としては、パイロリックボロンナイトライド（ＰＢＮ）、パイロリックグラファイト（ＰＧ）、ガラス化カーボン、ＳｉＣ、窒化ホウ素（ＢＮ）、グラファイト等を好ましい材料として挙げることができる。
【０１０１】
また、るつぼとして、グラファイト等の基材からなる容器の内側表面に、パイロリックボロンナイトライド（ＰＢＮ）、パイロリックグラファイト（ＰＧ）、ガラス化カーボン、ＳｉＣ等をコーティングしたものを用いることもできる。
【０１０２】
また、化合物原料は、好ましくは、ＩＩＩ−Ｖ族化合物原料、ＩＩ−ＶＩ族化合物原料である。
【０１０３】
ＩＩＩ−Ｖ族化合物原料としては、ＧａＡｓ、ＩｎＡｓ、ＩｎＰ、ＧａＰ、ＧａＳｂ、ＩｎＳｂ等を挙げることができる。
【０１０４】
また、ＩＩ−ＶＩ族化合物原料としては、ＣｄＴｅ、ＺｎＳｅ等を挙げることができる。
【０１０５】
また、化合物原料にドープするためのドーパントとしては、Ｓｉ、Ｔｉ等を挙げることができる。
【０１０６】
また、添加剤としては、Ｓｉ、Ｔｉ等を挙げることができる。
また、非還元性化合物としては、ＳｉＯ₂ 等のシリコン酸化物、珪酸（〔（ＳｉＯ₂ ）_m ・（Ｈ₂ Ｏ）_n 〕：（ｍ、ｎは整数である））等の非還元性Ｓｉ化合物や、ＴｉＯ₂ 等のチタン酸化物、チタン酸（〔（ＴｉＯ₂ ）_p ・（Ｈ₂ Ｏ）_q 〕：（ｐ、ｑは整数である））等の非還元性Ｔｉ化合物を挙げることができる。
【０１０７】
また、封止剤として、酸化ホウ素（Ｂ₂ Ｏ₃ ）を用いる場合は、水分濃度が３００ｐｐｍ以下の酸化ホウ素（Ｂ₂ Ｏ₃ ）を用いるのが好ましい。
【０１０８】
また、添加剤として、Ｓｉを用いる場合は、反応物を含む溶融状態の封止剤中における、Ｓｉ濃度が、０．０１モル（ｍｏｌ）％以上になるように調整するのが好ましい。
【０１０９】
また、非還元性化合物として、ＳｉＯ₂ を用いる場合は、非還元性化合物を含む溶融状態の封止剤中における、Ｓｉ濃度が、０．０１モル（ｍｏｌ）％以上になるように調整するのが好ましい。
【０１１０】
また、第１の発明において、化合物原料、ドーパント、封止剤および添加剤を収容したるつぼは、真空または減圧下で加熱することが好ましい。
【０１１１】
また、第２の発明において、化合物原料、ドーパント、封止剤および非還元性化合物を収容したるつぼは、真空または減圧下で加熱するのが好ましい。
【０１１２】
以下、本願発明の作用について説明する。
請求項１の発明は、以下の構成を備える。
【０１１３】
（１） るつぼ内に、化合物原料と、化合物原料にドープするためのドーパントと、化合物原料を介してドーパントと分離するように配置された化合物原料の融点よりも低い融点を有する封止剤と、化合物原料を介してドーパントと分離するように配置されたドーパントと同一材料からなる添加剤とを収容する工程を備える。
【０１１４】
（２） 化合物原料、ドーパント、封止剤および添加剤を収容したるつぼを、封止剤の融点以上化合物原料の融点未満の温度に加熱して、
（Ａ） まず、封止剤を溶融させて、溶融した封止剤とドーパントとを化合物原料により分離した状態を保持しつつ、
（Ｂ） 溶融した封止剤と添加剤とを接触させて反応させることにより反応物を生成させて、反応物を含む溶融状態の封止剤を形成し、
（Ｃ） しかる後に、るつぼを、化合物原料の融点以上の温度にさらに加熱して、化合物原料を溶融させて、反応物を含む溶融状態の封止剤によりその表面が封止された、化合物原料とドーパントとを含む原料融液を作製する工程を備える。
【０１１５】
（３） 種結晶を用いて、原料融液から、ドーパントがドープされた化合物半導体単結晶を育成する工程を備える。
【０１１６】
第１の発明では、上記（１）に示す工程において、るつぼ内に、化合物原料にドープするためのドーパントと、封止剤およびドーパントと同一材料からなる添加剤とを、化合物原料を介して、分離するように配置している。
【０１１７】
また、封止剤として、化合物原料より低い融点を有するものが選択されている。
【０１１８】
したがって、上記（２）に示す工程において、化合物原料、ドーパント、封止剤および添加剤を収容したるつぼを加熱することにより、るつぼ内において、以下の現象を生じさせることができる。
【０１１９】
上記（２）（Ａ）に示す工程において、まず、封止剤が溶融する。
化合物原料は、封止剤に比べ、融点が高いため、溶融した封止剤とドーパントとを、化合物原料により分離した状態に保つことができる。
【０１２０】
そして、上記（２）（Ａ）に示す状態を保持しつつ、上記（２）（Ｂ）に示す工程において、溶融した封止剤と添加剤とを接触させる。
【０１２１】
すると、溶融した封止剤と添加剤とが反応し、反応物が生成され、反応物を含む溶融状態の封止剤が形成される。
【０１２２】
次に、上記（２）（Ｃ）に示す工程において、さらにるつぼを化合物原料の融点以上の温度に加熱する。
【０１２３】
すると、化合物原料が溶融し、化合物原料とドーパントとを含む原料融液が作製され、原料融液の表面が、反応物を含む溶融状態の封止剤により封止される。
【０１２４】
そして、この工程において、ドーパントが、反応物を含む溶融状態の封止剤と接触する。
【０１２５】
そして、ドーパントと封止剤との反応は、封止剤中に含まれる反応物により抑制されることになる。
【０１２６】
すなわち、請求項１の発明によれば、ドーパントは、反応物を含む溶融状態の封止剤と接触することになるため、ドーパントと封止剤との反応によるスカム（浮遊物）の発生が抑制される。
【０１２７】
したがって、請求項１の発明に従えば、原料融液からスカム（浮遊物）となって、反応物を含む封止剤側へ拡散消失するドーパントの量が少ないため、ドーパントの濃度が所望の濃度に精度よく制御された化合物半導体単結晶を効率よく育成することができる。
【０１２８】
また、請求項１の発明に従えば、ドーパントと封止剤との反応により発生するスカム（浮遊物）の発生量が、もともと少ないため、育成する化合物半導体単結晶中に、スカム（浮遊物）が付着したり、取り込まれるという現象を生じにくい結果、双晶や多結晶等の結晶欠陥の少ない高品質の化合物半導体単結晶を効率よく育成することができる。
【０１２９】
すなわち、請求項１の発明に従えば、ドーパントの濃度が所望の濃度に精度よく制御された高品質の化合物半導体単結晶を効率よく製造することができる。
【０１３０】
また、請求項２の発明は、以下の構成を備える。
（１） るつぼ内に、化合物原料と、化合物原料にドープするためのドーパントと、化合物原料に比べ、低い融点を有する封止剤と、化合物原料を介してドーパントと分離されて配置され、ドーパントを構成要素として含む非還元性化合物とを収容する工程を備える。
【０１３１】
（２） 化合物原料、ドーパント、封止剤および非還元性化合物を収容したるつぼを加熱して、
（Ａ） まず、封止剤を溶融し、溶融した封止剤とドーパントとを化合物原料により分離した状態を保持しつつ、
（Ｂ） 溶融した封止剤と非還元性化合物とを接触させ、溶融した封止剤に非還元性化合物を分散混合させることにより、非還元性化合物を含む溶融状態の封止剤を形成し、
（Ｃ） しかる後に、さらにるつぼをより高温に加熱して、化合物原料を溶融し、非還元性化合物を含む溶融状態の封止剤により、その表面が封止された、化合物原料とドーパントとを含む原料融液を形成する工程を備える。
【０１３２】
（３） 種結晶を用いて、原料融液から、ドーパントがドープされた化合物半導体単結晶を育成する工程を備える。
【０１３３】
請求項２の発明では、上記（１）に示す工程において、るつぼ内に、化合物原料にドープするためのドーパントと、ドーパントを構成要素として含む非還元性化合物とを、化合物原料を介して、分離するように配置している。
【０１３４】
また、封止剤として、化合物原料より低い融点を有するものが選択されている。
【０１３５】
したがって、上記（２）に示す工程において、化合物原料、ドーパント、封止剤および非還元性化合物を収容したるつぼを加熱することにより、るつぼ内において、以下の現象を生じさせることができる。
【０１３６】
上記（２）（Ａ）に示す工程において、まず、封止剤が溶融する。
化合物原料は、封止剤に比べ、融点が高いため、溶融した封止剤とドーパントとを、化合物原料により分離した状態に保つことができる。
【０１３７】
そして、上記（２）（Ａ）に示す状態を保持しつつ、上記（２）（Ｂ）に示す工程において、溶融した封止剤と非還元性化合物とを接触させる。
【０１３８】
すると、溶融した封止剤に非還元性化合物が分散混合し、非還元性化合物を含む封止剤が形成される。
【０１３９】
次に、上記（２）（Ｃ）に示す工程において、さらにるつぼをより高温に加熱する。
【０１４０】
すると、化合物原料が溶融し、化合物原料とドーパントとを含む原料融液が形成され、原料融液の表面が、非還元性化合物を含む溶融状態の封止剤により封止される。
【０１４１】
非還元性化合物を含む溶融状態の封止剤と接触する。
したがって、ドーパントと封止剤との反応は、封止剤中に含まれる非還元性化合物により抑制されることになる。
【０１４２】
すなわち、請求項２の発明によれば、ドーパントは、非還元性化合物を含む溶融状態の封止剤と接触することになるため、ドーパントと封止剤との反応によるスカム（浮遊物）の発生が抑制される。
【０１４３】
したがって、請求項２の発明に従えば、原料融液からスカム（浮遊物）となって、非還元性化合物を含む封止剤側へ拡散消失するドーパントの量が少ないため、ドーパントの濃度が所望の濃度に精度よく制御された化合物半導体単結晶を効率よく育成することができる。
【０１４４】
また、請求項２の発明に従えば、ドーパントと封止剤との反応により発生するスカム（浮遊物）の発生量が、もともと少ないため、育成する化合物半導体単結晶中に、スカム（浮遊物）が付着したり、取り込まれるという現象を生じにくい結果、双晶や多結晶等の結晶欠陥の少ない高品質の化合物半導体単結晶を効率よく育成することができる。
【０１４５】
すなわち、請求項２の発明に従えば、ドーパントの濃度が所望の濃度に精度よく制御された高品質の化合物半導体単結晶を効率よく製造することができる。
【０１４６】
また、請求項３の発明は、請求項２の発明において、非還元性化合物を別途加えるのではなく、その内表面がたとえば石英（ＳｉＯ₂ ）等の非還元性化合物からなるるつぼを用いることを特徴としている。
【０１４７】
請求項３の発明によれば、るつぼの内表面自身が非還元性化合物からなるため、別途に添加剤または非還元性化合物を加えなくても、請求項２の発明と同様の作用効果が得られる。
【０１４８】
なお、本願発明においては、化合物原料を溶融する前に、添加剤もしくは非還元性化合物と封止剤とを、十分に反応させておく必要がある。
【０１４９】
そのため、添加剤または非還元性化合物の表面積が、できるだけ大きいことが好ましい。また、添加剤もしくは非還元性化合物と封止剤とを反応させる温度はできるだけ高いことが好ましく、一方、反応させる時間はできるだけ長いことが好ましい。
【０１５０】
具体的には、添加剤または非還元性化合物の粒径は、粉末で用いる場合、好ましくは直径５００μｍ以下、より好ましくは直径１００μｍ以下、最も好ましくは直径１０μｍ以下であるとよい。
【０１５１】
また、たとえば化合物原料としてＧａＡｓを、封止剤としてＢ₂ Ｏ₃ を使用する場合、添加剤もしくは非還元性化合物と封止剤との反応温度は、好ましくは６００℃以上１２００℃以下、より好ましくは８００℃以上１２００℃以下、最も好ましくは１０００℃以上１２００℃以下であるとよい。
【０１５２】
反応温度が６００℃より低くなると、反応性が低下してしまうからである。
一方、添加剤もしくは非還元性化合物と封止剤との反応時間は、好ましくは２時間以上、より好ましくは４時間以上、最も好ましくは６時間以上であるとよい。ただし、反応時間をあまり長くすると、生産性が低下してしまう。
【０１５３】
また、図９は、この発明において、添加剤もしくは非還元性化合物と封止剤とを反応させる際の昇温プロファイルの例を示す図である。図９（ａ）および（ｂ）において、横軸は反応経過時間を示し、縦軸は反応温度を示している。
【０１５４】
この発明において、添加剤もしくは非還元性化合物と封止剤とを十分に反応させるためには、たとえば図９（ａ）に示すように、封止剤の融点以上化合物原料の融点未満のある一定温度に保持することが好ましいが、必ずしも一定温度に保持する必要はなく、たとえば図９（ｂ）に示すように、封止剤の融点以上化合物原料の融点未満の温度範囲内に一定時間保持するようにしてもよい。
【０１５５】
【実施例】
以下、実施例を用いて説明するが、本発明は、以下の実施例によって何ら限定されていることはない。
【０１５６】
実施例１
図５は、本発明に従う化合物半導体単結晶の育成方法を概略的に示す縦断面図である。
【０１５７】
図５を参照して、本発明に従う化合物半導体単結晶の育成装置４１は、図１に示す化合物半導体単結晶の育成装置１と同様であるので、相当する部材については、相当する参照符号を付して、その説明を省略する。
【０１５８】
そして、本発明に従う化合物半導体単結晶の育成方法は、るつぼ８内に、化合物原料１４を介して、封止剤１５およびドーパント１３と同一材料からなる添加剤５１もしくはドーパント１３を構成要素として含む非還元性化合物５１を、ドーパント１３と分離して配置している点において、従来の化合物半導体単結晶の育成方法と、特に異なっている。
【０１５９】
次に、より具体的なデータに基づいて説明する。
実験例１
実験例１は、本発明に従う化合物半導体単結晶の育成方法の一具体例であり、ＬＥＣ法の改良に関するものである。
【０１６０】
より詳しくは、請求項２の発明に従って、ＳｉドープＧａＡｓ単結晶を育成した例を示す。
【０１６１】
すなわち、図５に示す化合物半導体単結晶の育成装置４１を用い、直径３インチのＳｉドープＧａＡｓ単結晶の育成を行なった。
【０１６２】
図５を参照して、るつぼ８として、直径が１５０ｍｍのＰＢＮ製のるつぼを使用した。
【０１６３】
また、化合物原料１４として、ＧａＡｓ多結晶を６ｋｇ使用した。
また、ドーパント１３として、固体Ｓｉを３００ｍｇ使用した。
【０１６４】
また、封止剤１５として、水分濃度２００ｐｐｍのＢ₂ Ｏ₃ を５００ｇ使用した。
【０１６５】
また、非還元性化合物５１として、粒径５０μｍのＳｉＯ₂ 粉末を５０ｇ使用した。
【０１６６】
本実験例では、図５に示すように、ドーパント１３が軟化（溶融）した封止剤１５と直接反応しないように、化合物原料１４の上に、ドーパント１３を載置した。
【０１６７】
より詳しくは、まず、るつぼ８内の底部周辺部８ｂに、非還元性化合物５１を収容した。次に、化合物原料１４を非還元性化合物５１を覆うように収容した。そして、本実験例では、化合物原料１４を用いて、上方に起立する周壁１４ｗを形成した。
【０１６８】
なお、本実験例では、化合物原料１４として、ブロック体の集合物を用いているが、化合物原料１４としては、粉状体集合物、粒状体集合物、ブロック体集合物、一体成形体であってもよいことを付記しておく。
【０１６９】
次に、化合物原料１４の表面上の周壁１４ｗの内部に、ドーパント１３を収容した。
【０１７０】
また、化合物原料１４の表面上の周壁１４ｗの外側に、封止剤１５を収容した。
【０１７１】
次に、化合物原料１４、ドーパント１３、封止剤１５および非還元性化合物５１を収容したるつぼ８を、気密容器２内の所定の位置に収容した。
【０１７２】
次に、気密容器２の挿通孔２ｈ₁ から、気密容器２内に挿入した引き上げ軸（上軸）４下方先端部４ｅに種結晶１０を取り付けた。
【０１７３】
次に、気密容器２を密閉し、しかる後に、気密容器２内を真空に引きながら、ヒーター６を用いて昇温し、気密容器２部材および封止剤１５中の含有水分を除去した。
【０１７４】
その後、気密容器２内に窒素（Ｎ₂ ）ガスを導入し、気密容器２内を窒素（Ｎ₂ ）ガスで加圧し、かつ、ヒータ６を用いて、るつぼ８を封止剤の融点以上化合物原料の融点未満の温度に加熱した。
【０１７５】
るつぼ８内では、まず、封止剤１５が軟化（溶融）して下方へ移動し、非還元性化合物５１と接触し、溶融した封止剤に非還元性化合物５１が分散混合して非還元性化合物５１を含む溶融状態の封止剤が形成された。なお、非還元性化合物５１の封止剤への分散混合を十分行なわせるため、８００℃に４時間保持した。
【０１７６】
しかる後に、るつぼ８を化合物原料の融点以上の温度にさらに加熱することにより、化合物原料１４が溶融し、非還元性化合物５１を含む溶融状態の封止剤によりその表面が封止された、化合物原料１４とドーパント１３とを含む原料融液（図示せず）が形成された。
【０１７７】
この工程において、原料融液（図示せず）の表面が、非還元性化合物５１を含む溶融状態の封止剤（図示せず）により液封された。
【０１７８】
その際、スカム（浮遊物）は、全く観察されなかった。
【０１７９】
次に、容器駆動手段５を用い、容器（サセプタ）３を所定の回転速度で回転させつつ、引上げ軸（上軸）駆動手段（図示せず）を用い、原料融液（図示せず）に種結晶１０を浸漬し、しかる後に、原料融液（図示せず）から種結晶１０を所定の回転速度で、かつ、所定の引上げ速度で引上げることにより、直径が約８５ｍｍで、長さが約２２ｃｍのＳｉドープＧａＡｓ単結晶（図示せず）を成長させた。
【０１８０】
なお、ドーパント（Ｓｉ）１３と封止剤（Ｂ₂ Ｏ₃ ）１５との反応はごく僅かであり、育成したＳｉドープＧａＡｓ単結晶中のＳｉ含有量は、Ｓｉ含有量の設計値からのずれが３％以下であった。
【０１８１】
実験例２
実験例１とは、非還元性化合物５１の代わりに、Ｓｉ１ｇを用いる以外は、実験例１と同様にして、ＳｉドープＧａＡｓ単結晶の育成を行なった。
【０１８２】
その結果、実験例１と同様の効果を奏することが明らかになった。
実施例２
図６は、他の実施例としての本発明に従う化合物半導体単結晶の育成方法を概略的に示す縦断面図である。
【０１８３】
図６を参照して、本発明において用いる化合物半導体単結晶の育成装置２１は、図３に示す化合物半導体単結晶の育成装置２１と同様であるので、相当する部材については、相当する参照符号を付して、その説明を省略する。
【０１８４】
そして、本発明に従う化合物半導体単結晶の育成方法は、るつぼ２８内に、化合物原料３４を介して、封止剤３５およびドーパント３３と同一材料からなる添加剤７１もしくはドーパント３３を構成要素として含む非還元性化合物７１を、ドーパント３３と分離して配置している点において、従来の化合物半導体単結晶の育成方法と特に異なっている。
【０１８５】
次に、より具体的なデータに基づいて説明する。
実験例３
実験例３は、本発明に従う化合物半導体単結晶の育成方法の他の具体例であり、ＶＧＦ法の改良に関するものである。
【０１８６】
より詳しくは、第２の発明に従って、ＳｉドープＧａＡｓ単結晶を育成した例を示す。
【０１８７】
すなわち、図６に示す化合物半導体単結晶の育成装置２１を用い、直径２インチのＳｉドープＧａＡｓ単結晶の育成を行なった。
【０１８８】
図６を参照して、るつぼ２８として、直径が５５ｍｍのＰＢＮ製のるつぼを使用した。
【０１８９】
また、化合物原料３４として、ＧａＡｓ多結晶を１．５ｋｇ使用した。
また、ドーパント３３として、固体Ｓｉを２５０ｍｇ使用した。
【０１９０】
また、封止剤３５として、水分濃度１００ｐｐｍのＢ₂ Ｏ₃ を５０ｇ使用した。
【０１９１】
また、非還元性化合物７１として、粒径１０μｍのＳｉＯ₂ 粉末を１０ｇ使用した。
【０１９２】
本実験例では、図６に示すように、ドーパント３３が軟化（溶融）した封止剤３５と直接反応しないように、化合物原料３４の上にドーパント３３を載置した。
【０１９３】
より詳しくは、まず、るつぼ２８内の下端２８ｅ内に、種結晶３０を取付けた。
【０１９４】
次に、種結晶３０の上に、非還元性化合物７１を収容した。
次に、化合物原料３４を、非還元性化合物７１を覆うように収容した。
【０１９５】
そして、本実験例では、化合物原料３４を用いて、上方に起立する周壁３４ｗを形成した。
【０１９６】
なお、本実験例でも、化合物原料３４として、ブロック体の集合物を使用しているが、化合物原料３４としては、粉状体集合物、粒状体集合物、ブロック体集合物、一体成形体であってもよいことを付記しておく。
【０１９７】
次に、化合物原料３４の表面上の周壁３４ｗの内部に、ドーパント３３を収容した。
【０１９８】
また、化合物原料３４の表面上の周壁３４ｗの外側に、封止剤３５を収容した。
【０１９９】
次に、化合物原料３４、ドーパント３３、封止剤３５および非還元性化合物７１を収容したるつぼ２８を、気密容器２２内の所定の位置に収容した。
【０２００】
次に、気密容器２２を密閉し、しかる後に、気密容器２２内を真空に引きながら、ヒーター２６ａ、２６ｂ、２６ｃ、２６ｄ、２６ｅを用い昇温し、気密容器２２部材および封止剤（Ｂ₂ Ｏ₃ ）３５中の含有水分を除去した。
【０２０１】
その後、気密容器２２内に、アルゴン（Ａｒ）を導入し、チャンバ２２内をアルゴン（Ａｒ）ガスで加圧し、かつ、ヒーター２６ａ、２６ｂ、２６ｃ、２６ｄ、２６ｅを用い、るつぼ２８内を、封止剤の融点以上化合物原料の融点未満の温度に加熱した。
【０２０２】
るつぼ２８内では、まず、封止剤３５が軟化（溶融）し、下方へ移動しながら石英るつぼ内側表面を被覆した。さらに、非還元性化合物７１と接触して、溶融した封止剤に非還元性化合物７１が分散混合し、非還元性化合物７１を含む溶融状態の封止剤（図示せず）が形成された。なお、非還元性化合物７１の封止剤への分散混合を十分に行なわせるため、６００℃から１２００℃まで、１００℃／時の速度で、約６時間かけてゆっくり昇温した。
【０２０３】
しかる後に、さらにるつぼ２８を、化合物原料の融点以上の温度に加熱することにより、化合物原料３４が溶融し、非還元性化合物７１を含む溶融状態の封止剤（図示せず）によりその表面が封止された、化合物原料３４とドーパント３３とを含む原料融液（図示せず）が形成された。
【０２０４】
この工程において、原料融液（図示せず）の表面が、非還元性化合物７１を含む溶融状態の封止剤（図示せず）により液封された。
【０２０５】
その際、スカム（浮遊物）は全く観察されなかった。
次に、ヒーター２６ａ、２６ｂ、２６ｃ、２６ｄ、２６ｅにより、気密容器２２内の温度分布を適正化した後、ヒーター２６ａ、２６ｂ、２６ｃ、２６ｄ、２６ｅの温度を変化させて、低温部を、ヒーター２６ａ、２６ｂ、２６ｃ、２６ｄ、２６ｅの順に徐々に上方に移動させ、種結晶３０の側から、原料融液（図示せず）を固化させることによって、直径が５５ｍｍで、長さが約１４ｃｍのＳｉドープＧａＡｓ単結晶を成長させた。
【０２０６】
ドーパント（Ｓｉ）３３と封止剤（Ｂ₂ Ｏ₃ ）３５との反応はごく僅かであり、ＳｉドープＧａＡｓ単結晶中のＳｉ含有量は、Ｓｉ含有量の設計値からのずれが３％以下であった。
【０２０７】
実験例４
実験例３とは、非還元性化合物７１の代わりに、ドーパント３３と同一材料からなる添加剤７１、すなわち、固体Ｓｉ５００ｍｇを用いる以外は、実験例３と同様にして、ＳｉドープＧａＡｓ単結晶を育成した。
【０２０８】
その結果、実験例４は、実験例３と同様の効果を奏することが明らかとなった。
【０２０９】
実験例５
図６に示す化合物半導体の育成装置２１を用い、直径２インチのＳｉドープＧａＡｓ単結晶の育成を行なった。
【０２１０】
るつぼ２８として、直径が５５ｍｍの石英製のるつぼを使用した。また、化合物原料３４として、ＧａＡｓ多結晶を１．５ｋｇ使用した。さらに、ドーパント３３として、固体Ｓｉを２００ｍｇ使用した。また、封止剤３５として、水分濃度１００ｐｐｍのＢ₂ Ｏ₃ を５０ｇ使用した。
【０２１１】
なお、非還元性化合物および添加剤７１は、使用しなかった。
本実験においても、ドーパント３３が、軟化（溶融）した封止剤３５と直接反応しないように、化合物原料３４の上に、ドーパント３３を載置した。
【０２１２】
より詳しくは、まず、るつぼ２８内の下端２８ｅ内に、種結晶３０を取付けた。次に、種結晶３０の上に、化合物原料３４を収容した。そして、本実験例では、化合物原料３４を用いて、上方に起立する周壁３４ｗを形成した。
【０２１３】
なお、本実験例でも、化合物原料３４として、ブロック体の集合物を使用しているが、化合物原料３４としては、粉状体集合物、粒状体集合物、ブロック体集合物、一体成形体であってもよいことを付記しておく。
【０２１４】
次に、化合物原料３４の表面上の周壁３４ｗの内側に、ドーパント３３を収容した。また、化合物原料３４の表面上の周壁３４ｗの外側に、封止剤３５を収容した。
【０２１５】
次に、化合物原料３４、ドーパント３３および封止剤３５を収容したるつぼ２８を、気密容器２２内の所定の位置に収容した。
【０２１６】
次に、気密容器２２を密閉し、しかる後に、気密容器２２内を真空に引きながら、ヒーター２６ａ、２６ｂ、２６ｃ、２６ｄ、２６ｅを用い昇温し、気密容器２２部材および封止剤（Ｂ₂ Ｏ₃ ）３５中の含有水分を除去した。
【０２１７】
その後、気密容器２２内に、アルゴン（Ａｒ）を導入し、チャンバ２２内をアルゴン（Ａｒ）ガスで加圧し、かつ、ヒーター２６ａ、２６ｂ、２６ｃ、２６ｄ、２６ｅを用い、るつぼ２８内を、封止剤の融点以上化合物原料の融点未満の温度に加熱した。
【０２１８】
るつぼ２８内では、まず、封止剤３５が軟化（溶融）し、下方へ移動しながら石英るつぼの内側表面を被覆した。
【０２１９】
石英るつぼに含まれる非還元性化合物（ＳｉＯ₂ ）の封止剤（Ｂ₂ Ｏ₃ ）への分散混合を十分に行なわせるため、１０００℃に４時間保持し、非還元性化合物（ＳｉＯ₂ ）を含む封止剤（Ｂ₂ Ｏ₃ ）を形成した。
【０２２０】
しかる後に、さらにるつぼ２８を、化合物原料の融点以上の温度に加熱することにより、化合物原料３４が溶融し、るつぼに含まれる非還元性化合物を含む溶融状態の封止剤によりその表面が封止された、化合物原料３４とドーパント３３とを含む原料融液が形成された。
【０２２１】
この工程において、原料融液の表面が、非還元性化合物を含む溶融状態の封止剤により液封された。
【０２２２】
その際、スカム（浮遊物）は全く観察されなかった。
次に、ヒーター２６ａ、２６ｂ、２６ｃ、２６ｄ、２６ｅにより、気密容器２２内の温度分布を適正化した後、ヒーター２６ａ、２６ｂ、２６ｃ、２６ｄ、２６ｅの温度を変化させて、低温部を、ヒーター２６ａ、２６ｂ、２６ｃ、２６ｄ、２６ｅの順に徐々に上方に移動させ、種結晶３０の側から、原料融液（図示せず）を固化させることによって、直径が５５ｍｍで、長さが約１４ｃｍのＳｉドープＧａＡｓ単結晶を成長させた。
【０２２３】
ドーパント（Ｓｉ）３３と封止剤（Ｂ₂ Ｏ₃ ）３５との反応はごくわずかであり、ＳｉドープＧａＡｓ単結晶中のＳｉ含有量は、Ｓｉ含有量の設計値からのずれが３％以下であった。
【０２２４】
上記した実施例１、２では、ドーパント１３、３３として添加したＳｉＯ₂ またはＳｉが、封止剤（Ｂ₂ Ｏ₃ ）１５、３５と反応する前に、ドーパント１３、３３と同一材料からなる添加剤（Ｓｉ）５１、７１、または、ドーパント１３、３３を構成要素として含む非還元性化合物（ＳｉＯ₂ ）５１、７１の効果によって、ドーパント１３、３３として添加したＳｉと封止剤（Ｂ₂ Ｏ₃ ）１５、３５との反応が抑制される。
【０２２５】
このため、ドーパント（Ｓｉ）１３、３３を、効果的に育成する化合物半導体単結晶にドープすることができ、キャリア濃度制御性が向上する。
【０２２６】
また、無添加Ｂ₂ Ｏ₃ を使用した場合に問題となる、育成するＳｉドープＧａＡｓ単結晶中のＢ（ボロン）濃度の増加が抑えられる。したがって、特に低ボロン濃度が要求されるような品種に対しても、対応可能となる。
【０２２７】
また、低水分濃度のＢ₂ Ｏ₃ を使用し、さらにＢ₂ Ｏ₃ および化合物半導体単結晶の育成装置、すなわち炉内部品の脱水処理を十分施すことにより、スカムの発生を防止でき、双晶（ツイン）の発生や、多結晶化（ポリ化）を効果的に防止することができる。
【０２２８】
また、本発明に従えば、スカム（浮遊物）の発生量がもともと少ないため、育成する化合物半導体単結晶中に、スカム（浮遊物）が付着したり、取り込まれるという現象を生じにくい結果、双晶や多結晶等の結晶欠陥の少ない高品質の化合物半導体単結晶を効率よく育成することができる。
【０２２９】
また、実施例１、２に示したＳｉＯ₂ がドープされたＢ₂ Ｏ₃ は、粘度が高く、所望の形状に成形し難いという問題も、解決することができる。
【０２３０】
すなわち、本発明の方法によれば、ＳｉＯ₂ を予めＢ₂ Ｏ₃ に添加しておくのではなく、化合物原料１４、３４およびドーパント（Ｓｉ）１３、３３および封止剤（Ｂ₂ Ｏ₃ ）１５、３５とともに、過剰のＳｉまたはＳｉＯ₂ として、るつぼ８、２８内に入れ、ドーパント（Ｓｉ）１３、３３が封止剤（Ｂ₂ Ｏ₃ ）１５、３５と反応する前に、予めるつぼ８、２８内に入れた過剰のＳｉまたはＳｉＯ₂ によって、ＳｉをＢ₂ Ｏ₃ に添加している。
【０２３１】
したがって、本発明によれば、ＳｉＯ₂ をドープしたＢ₂ Ｏ₃ を用いるのではなく、Ｂ₂ Ｏ₃ を用いている結果、特公平３−５７０７９号公報に記載の方法において問題となる、封止剤を所望の形状に成形しにくいという問題が解消される。
【０２３２】
また、本発明によれば、特公平３−５７０７９号公報に記載の方法に比べ、ＶＢ法やＶＧＦ法においてるつぼ２８の内側表面２８ｓを均一に被覆する機能がすぐれていたことを付記しておく。
【０２３３】
また、本発明によれば、無添加のＢ₂ Ｏ₃ を使用することができるので、ＳｉＯ₂ をドープしたＢ₂ Ｏ₃ を用いる、特公平３−５７０７９号公報に記載の方法に比べ、Ｓｉドープ化合物半導体単結晶の製造コストを極端に低くできるという効果もある。
【０２３４】
さらに、バルク成長分科会第１８回研究会資料集に開示された方法においては、Ｂ₂ Ｏ₃ は封止剤として使用されているのに対し、本願発明においては、Ｂ₂ Ｏ₃ は封止剤としてだけでなく、るつぼ内表面の被覆のためにも使用されている。
【０２３５】
本発明においては、このようにるつぼ内表面がＢ₂ Ｏ₃ で被覆されるため、ＧａＡｓ等の原料融液がるつぼと直接接することによる、結晶欠陥の発生や、多結晶化を効果的に防止できる。
【０２３６】
なお、るつぼ内に、化合物原料と、化合物原料にドープするためのドーパントと、化合物原料を介してドーパントと分離するように配置された化合物原料の融点よりも低い融点を有する封止剤と、化合物原料を介してドーパントと分離するように配置されたドーパントと同一材料からなる添加剤またはドーパントを構成要素として含む非還元性化合物とを収容する方法は、図５、図６に示される方法に限定されるものではないことは言うまでもない。
【０２３７】
この工程においては、種々の変形例が考えられる。
そのような変形例の代表的な収容方法を、図７および図８に示す。
【０２３８】
図７を参照して、図７（ａ）〜図７（ｃ）は、それぞれ、実施例１の変形例を示しており、るつぼ内に、化合物原料と、ドーパントと、封止剤と、ドーパントと同一材料からなる添加剤またはドーパントを構成要素として含む非還元性化合物とを収容した状態を模式的に示す断面図である。
【０２３９】
図７（ａ）を参照して、図７（ａ）では、るつぼ８内に、まず、ドーパント１３と同一材料からなる添加剤５１またはドーパント１３を構成要素として含む非還元性化合物５１を収容し、添加剤５１または非還元性化合物５１に近接するように、封止剤１５を収容し、封止剤１５の上に、化合物原料１４を収容し、化合物原料１４の上にドーパント１３を収容している。
【０２４０】
また、図７（ｂ）では、るつぼ８内に、まず、化合物原料１４を収容し、しかる後に、化合物原料１４を用い、上方に起立する周壁１４ｗを形成し、周壁１４ｗの内側にドーパント１３を収容し、周壁１４ｗの外側にドーパント１３と同一材料からなる添加剤５１またはドーパント１３を構成要素として含む非還元性化合物５１を収容し、添加剤５１または非還元性化合物５１に近接するように、封止剤１５を収容している。
【０２４１】
また、図７（ｃ）では、るつぼ８内に、まず、ドーパント１３と同一材料からなる添加剤５１またはドーパント１３を構成要素として含む非還元性化合物５１を収容し、添加剤５１または非還元性化合物５１の上に、化合物原料１４ａを収容し、そして、化合物原料１４ａ上に、化合物原料からなる上方に起立する柱状体１４ｐを形成し、るつぼ８、化合物原料１４ａおよび柱状体１４ｐにより形成される空隙部Ｂ内に、封止剤１５を収容し、さらに、柱状体１４ｐおよび封止剤１５をともに覆うように、さらに、化合物原料１４ｂを収容し、化合物原料１４ｂの上にドーパント１３を収容している。
【０２４２】
また、図８を参照して、図８（ａ）〜図８（ｂ）は、それぞれ、実施例２の変形例を模式的に示しており、るつぼ内に、化合物原料と、ドーパントと、封止剤と、ドーパントと同一材料からなる添加剤またはドーパントを構成要素として含む非還元性化合物とを収容した状態を模式的に示す断面図である。
【０２４３】
図８（ａ）を参照して、図８（ａ）では、るつぼ２８内に、まず、種結晶３０を取付けた後、種結晶３０の近傍に、ドーパント３３と同一材料からなる添加剤７１またはドーパント３３を構成要素として含む非還元性化合物７１を収容し、添加剤７１または非還元性化合物７１上に、化合物原料３４ａを収容し、化合物原料３４ａ上に、化合物原料からなる柱状体３４ｐを形成し、るつぼ２８、化合物原料３４ａおよび柱状体３４ｐにより形成される空隙部Ｂ内に封止剤３５を収容し、封止剤３５および柱状体３４ｐをともに覆うように、さらに、化合物原料３４ｂを収容し、化合物原料３４ｂ上にドーパント３３を収容している。
【０２４４】
また、図８（ｂ）では、るつぼ２８内に、種結晶３０を取付けた後、種結晶３０上に化合物原料３４ａを収容し、化合物原料３４ａ上に化合物原料からなる柱状体３４ｐを収容し、るつぼ２８、柱状体３４ｐおよび化合物原料３４ａにより形成される空隙部Ｂ内に、ドーパント３３と同一材料からなる添加剤７１またはドーパント３３を構成要素として含む非還元性化合物７１を収容し、添加剤７１または非還元性化合物７１に近接するように、封止剤３５を収容し、封止剤３５および柱状体３４ｐをともに覆うように、さらに化合物原料３４ｂを収容し、化合物原料３４ｂ上に、ドーパント３３を収容している。
【０２４５】
なお、これらは、単に具体例を図示したに過ぎず、他にも種々の方法が可能である。
【０２４６】
たとえば、化合物原料で溝を作り、その中に、ドーパント（固体Ｓｉ）を保持したり、あるいは、予めドーパント（Ｓｉ）を含有する化合物原料を使用し、化合物原料が融解するまで、ドーパント（Ｓｉ）が封止剤（Ｂ₂ Ｏ₃ ）と、直接反応することがないように、収容すればよい。
【０２４７】
また、Ｂ₂ Ｏ₃ 中の水分や雰囲気の水分によって、スカムは発生するので、スカムの発生を防止するためには、使用するＢ₂ Ｏ₃ の水分濃度を３００ｐｐｍ以下にすることが望ましく、また結晶成長を行なう前に、真空または減圧下で加熱昇温し、炉内部品と酸化硼素（Ｂ₂ Ｏ₃ ）の脱水処理を施すことが望ましいことを付記しておく。
【０２４８】
また、炉内部品は、水分を吸収しないように、炉開放時に、炉内部品を乾燥した雰囲気に保持することが望ましいことを付記しておく。
【０２４９】
【発明の効果】
以上詳細に説明したように、本発明は、上記した構成を有する結果、以下の効果を奏する。
【０２５０】
すなわち、請求項１の発明によれば、ドーパントは、反応物を含む溶融状態の封止剤と接触することになるため、ドーパントと封止剤との反応によるスカム（浮遊物）の発生が抑制される。
【０２５１】
したがって、請求項１の発明に従えば、原料融液からスカム（浮遊物）となって、反応物を含む封止剤側へ拡散消失するドーパントの量が少ないため、ドーパントの濃度が所望の濃度に精度よく制御された化合物半導体単結晶を効率よく育成することができる。
【０２５２】
また、請求項１の発明に従えば、ドーパントと封止剤との反応により発生するスカム（浮遊物）の発生量がもともと少ないため、育成する化合物半導体単結晶中に、スカム（浮遊物）が付着したり、取り込まれるという現象を生じにくい結果、双晶や多結晶等の結晶欠陥の少ない高品質の化合物半導体単結晶を効率よく育成することができる。
【０２５３】
すなわち、請求項１の発明に従えば、ドーパントの濃度が所望の濃度に精度よく制御された高品質の化合物半導体単結晶を効率よく製造することができる。
【０２５４】
また、請求項２の発明によれば、ドーパントは、非還元性化合物を含む溶融状態の封止剤と接触することになるため、ドーパントと封止剤との反応によるスカム（浮遊物）の発生が抑制される。
【０２５５】
したがって、請求項２の発明に従えば、原料融液からスカム（浮遊物）となって、非還元性化合物を含む封止剤側へ拡散消失するドーパントの量が少ないため、ドーパントの濃度が所望の濃度に精度よく制御された化合物半導体単結晶を効率よく育成することができる。
【０２５６】
また、請求項２の発明に従えば、ドーパントと封止剤との反応により発生するスカム（浮遊物）の発生量がもともと少ないため、育成する化合物半導体単結晶中に、スカム（浮遊物）が付着したり、取込まれるという現象を生じにくい結果、双晶や多結晶等の結晶欠陥の少ない高品質の化合物半導体単結晶を効率よく育成することができる。
【０２５７】
すなわち、請求項２の発明に従えば、ドーパントの濃度が所望の濃度に精度よく制御された高品質の化合物半導体単結晶を効率よく製造することができる。
【０２５８】
また、請求項３の発明によれば、ドーパントは、非還元性化合物を含む溶融状態の封止剤と接触することになるため、ドーパントと封止剤との反応によるスカム（浮遊物）の発生が抑制される。
【０２５９】
したがって、請求項３の発明に従えば、原料融液からスカム（浮遊物）となって、非還元性化合物を含む封止剤側へ拡散消失するドーパントの量が少ないため、ドーパントの濃度が所望の濃度に精度よく制御された化合物半導体単結晶を効率よく育成することができる。
【０２６０】
また、請求項３の発明に従えば、ドーパントと封止剤との反応により発生するスカム（浮遊物）の発生量がもともと少ないため、育成する化合物半導体単結晶中に、スカム（浮遊物）が付着したり、取込まれるという現象を生じにくい結果、双晶や多結晶等の結晶欠陥の少ない高品質の化合物半導体単結晶を効率よく育成することができる。
【０２６１】
すなわち、請求項３の発明に従えば、ドーパントの濃度が所望の濃度に精度よく制御された高品質の化合物半導体単結晶を効率よく製造することができる。
【０２６２】
さらに、本願発明によれば、封止剤として、たとえばＳｉＯ₂ を添加していないＢ₂ Ｏ₃ が用いられる。このようなＢ₂ Ｏ₃ は粘度が低く、成形が容易であるため、所望の形状を有するＢ₂ Ｏ₃ の使用が可能となる。
【０２６３】
以上説明したように、本発明に従えば、結晶歩留りの向上と低コスト化が実現できるという効果があり、産業上有用である。
【図面の簡単な説明】
【図１】ＬＥＣ法に用いられる、従来の単結晶の育成装置の一例を概略的に示す縦断面図である。
【図２】るつぼ８内において生じる現象を模式的に示す断面図である。
【図３】ＶＢ法に用いられる、従来の単結晶の育成装置の一例を概略的に示す縦断面図である。
【図４】るつぼ２８内において生じる現象を模式的に示す断面図である。
【図５】本発明に従う化合物半導体単結晶の育成方法を概略的に示す縦断面図である。
【図６】本発明に従う化合物半導体単結晶の育成方法を概略的に示す縦断面図である。
【図７】実施例１の変形例を模式的に示しており、るつぼ内に、化合物原料と、ドーパントと、封止剤およびドーパントと同一材料からなる添加剤またはドーパントを構成要素として含む非還元性化合物を収容した状態を模式的に示す断面図である。
【図８】実施例２の変形例を模式的に示しており、るつぼ内に、化合物原料と、ドーパントと、封止剤およびドーパントと同一材料からなる添加剤またはドーパントを構成要素として含む非還元性化合物を収容した状態を模式的に示す断面図である。
【図９】この発明において、添加剤もしくは非還元性化合物と封止剤とを反応させる際の昇温プロファイルの例を示す図である。
【符号の説明】
１、２１、４１、５１ 化合物半導体単結晶の育成装置
２、２２ 気密容器
３、２３ 容器（サセプター）
４ 引上げ軸（上軸）
４ｅ 下方先端部
５ 容器駆動手段
６、２６ａ〜２６ｅ ヒーター
７、２７ 断熱材
８、２８ るつぼ
９、２９ 下軸
１０、３０ 種結晶
１１、３１ 原料融液
１２、３２ 化合物半導体単結晶
１３、３３ ドーパント
１４、３４ 化合物原料
１５、３５ 封止剤
１６、３６ 溶融状態の封止剤
５１、７１ 添加剤または非還元性化合物[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for growing a compound semiconductor single crystal such as a III-V group compound semiconductor single crystal or a II-VI group compound semiconductor single crystal, and in particular, a high concentration of a dopant is controlled to a desired concentration with high precision. The present invention relates to a method for growing a compound semiconductor single crystal capable of efficiently producing a quality compound semiconductor single crystal.
[0002]
[Prior art]
Compound semiconductor single crystals such as III-V group compound semiconductor single crystals such as GaAs, GaP, GaSb, InP, InAs and InSb, and II-VI group compound semiconductor single crystals such as CdTe, CdMnTe, CdZnTe, HgCdTe, ZnSe and ZnSSe Conventionally, various breeding methods have been proposed.
[0003]
As a typical method for growing such a compound semiconductor single crystal, a Czochralski method (hereinafter simply referred to as “CZ method”), a liquid encapsulated Czochralski method (hereinafter simply referred to as “Czochralski method”). Pull-up method such as “LEC method”, horizontal Bridgman method (hereinafter simply referred to as “HB method”), temperature gradient method (hereinafter referred to simply as “GF method”) Vertical Bridgman method (hereinafter, simply referred to as “VB method”), Vertical Gradient Freezing method (hereinafter, “Gradient Freezing method”) , Has simply been known, etc.) that "the VGF method".
[0004]
These compound semiconductor single crystal growth methods are to grow a compound semiconductor single crystal from a raw material melt contained in a crucible using a seed crystal.
[0005]
When growing a compound semiconductor single crystal such as a group III-V compound semiconductor single crystal or a group II-VI compound semiconductor single crystal, it is a volatile component from the raw material melt and / or the growing compound semiconductor single crystal. Sealants are used for the purpose of preventing dissociation and decomposition of group V elements or group VI elements.
[0006]
For example, in the LEC method, the VB method, the VGF method, etc., for the purpose of preventing dissociation and decomposition of the volatile component group V element or group VI element from the raw material melt and / or the growing compound semiconductor single crystal, sealing is performed. Boron oxide (B₂ O_Three ) Is usually used.
[0007]
Further, for example, in the HB method, GF method, VB method, VGF method, etc., dissociation and decomposition of group V elements or group VI elements, which are volatile components, from the raw material melt and / or the growing compound semiconductor single crystal are prevented. Boron oxide (B) as a sealant for the purpose and to prevent wetting of the crucible wall and the compound semiconductor single crystal₂ O_Three ) Is used.
[0008]
Next, a specific example of the LEC method will be described in more detail.
FIG. 1 is a longitudinal sectional view schematically showing an example of a conventional single crystal growth apparatus used in the LEC method.
[0009]
Referring to FIG. 1, a single crystal growth apparatus 1 is an airtight container (also referred to as a high pressure container, an outer container or a chamber; hereinafter simply referred to as “airtight container”) 2 and a container (susceptor or support base). (Also referred to as) 3, a lifting shaft (upper shaft) 4, and a lifting shaft (upper shaft) drive means (not shown) for driving the lifting shaft (upper shaft) 4 to be rotatable and vertically movable up and down. ), A container driving means 5 for driving the container (susceptor) 3 to be rotatable and vertically movable, a heater 6, and a heat insulating material 7.
[0010]
The container (susceptor) 3, the heater 6, and the heat insulating material 7 are accommodated in the airtight container 2.
[0011]
Further, in this single crystal growing apparatus 1, a crucible 8 is accommodated upward so as to be inscribed in a container (susceptor) 3, and a raw material melt 11 is contained in the crucible 8. It is to be accommodated.
[0012]
Further, in this single crystal growth apparatus 1, the insertion holes 2h are provided in the upper surface 2a and the lower surface 2b of the hermetic vessel 2, respectively.₁ 2h₂ Is provided.
[0013]
The container driving means 5 includes a lower shaft 9.
The lower shaft 9 is an insertion hole 2h in the lower surface 2b of the airtight container 2.₂ Are inserted into the airtight container 2 and connected to the center 3c of the bottom surface of the container (susceptor) 3.
[0014]
The container (susceptor) 3 is supported by the lower shaft 9 so as to be rotatable and vertically movable up and down.
[0015]
A seed crystal 10 is attached to a lower end portion 4 e of the pulling shaft (upper shaft) 4.
[0016]
The pulling shaft (upper shaft) 4 is inserted into the insertion hole 2h on the upper surface 2a of the airtight container 2.₁ From the raw material melt 11 inserted into the airtight container 2 and accommodated in the crucible 8, the seed crystal 10 can be pulled up by a pulling shaft (upper shaft) driving means (not shown). Yes.
[0017]
The heater 6 is provided so as to surround the container (susceptor) 3, and prepares the raw material melt 11 by heating the compound raw material accommodated in the crucible 8 accommodated in the container (susceptor) 3. When the compound semiconductor single crystal 12 is grown, it is provided to give an appropriate temperature gradient to the single crystal 12 to be pulled up.
[0018]
The heat insulating material 7 is provided so as to surround the heater 6.
FIG. 2 is a cross-sectional view schematically showing a phenomenon that occurs in the crucible 8.
[0019]
Referring to FIG. 2, FIG. 2A is a cross-sectional view schematically showing a state in which the compound raw material 14, the dopant 13, and the sealant 15 are accommodated in the crucible 8. FIG. 2B shows the compound raw material 14 and dopant in which the crucible 8 containing the compound raw material 14, dopant 13 and sealant 15 is heated and its surface 11s is sealed by the molten sealant 16. 13 is a cross-sectional view schematically showing a state in which a raw material melt 11 containing 13 is prepared.
[0020]
Next, the conventional LEC method will be described below with reference to FIGS. 1 and 2 by taking the case of growing a Si-doped GaAs single crystal as an example.
[0021]
First, in the crucible 8, as a compound raw material 14, a group III-V compound, more specifically, a GaAs compound such as GaAs polycrystal, a dopant 13, solid Si, and a sealant 15, boron oxide ( B₂ O_Three ).
[0022]
In this step, the dopant 13 is usually accommodated in the bottom 8 b of the crucible 8, the compound raw material 14 is accommodated on the dopant 13, and the sealing agent 15 is formed on the compound raw material 14.TheAccommodate.
[0023]
Next, the crucible 8 containing the compound raw material 14, the dopant 13 and the sealant 15 is accommodated upward in the container (susceptor) 3 accommodated in the airtight container 2.
[0024]
Next, the insertion hole 2h of the airtight container 2₁ The seed crystal 10 is attached to the lower end portion 4e of the pulling shaft (upper shaft) 4 inserted into the hermetic container 2 from above.
[0025]
Next, an inert gas such as Ar or N in the airtight container 2₂ Gas or the like is introduced to adjust the inside of the airtight container 2 to a predetermined pressure.
[0026]
Next, the temperature of the heater 6 is raised, the crucible 8 containing the compound raw material 14, the dopant 13 and the sealant 15 is heated, the sealant 15 is melted, the compound raw material 14 is melted, and the melted sealing A raw material melt 11 containing a compound raw material 14 and a dopant 13 whose surface 11s is sealed with a stopper 16, that is, a raw material melt 11 containing a GaAs compound and Si is prepared.
[0027]
In this step, the surface 11 s of the raw material melt 11 is liquid-sealed with the molten sealant 16.
[0028]
Next, using the container driving means 5 and rotating the container (susceptor) 3 at a predetermined rotational speed, the pulling shaft (upper shaft) driving means (not shown) is used to place the seed crystal 10 in the raw material melt 11. The compound semiconductor single crystal 12 doped with the dopant 13, more specifically, by immersing and then pulling up the seed crystal 10 from the raw material melt 11 at a predetermined rotational speed and at a predetermined pulling speed. Then, Si-doped GaAs single crystal is grown.
[0029]
Next, a specific example of the VB method will be described in more detail.
FIG. 3 is a longitudinal sectional view schematically showing an example of a conventional single crystal growth apparatus used in the VB method.
[0030]
Referring to FIG. 3, this single crystal growing apparatus 21 includes an airtight container (also referred to as a high-pressure container, an outer container or a chamber; hereinafter, simply referred to as “airtight container”) 22 and a container (susceptor or support base). 23, a container driving means 25 for driving the container (susceptor) 23 so as to be movable up and down, heaters 26a, 26b, 26c, 26d, and 26e, and a heat insulating material 27.
[0031]
The container (susceptor) 23, the heaters 26 a, 26 b, 26 c, 26 d, 26 e, and the heat insulating material 27 are accommodated in the airtight container 22.
[0032]
Further, in this single crystal growing apparatus 21, the crucible 28 is accommodated upward in a container (susceptor) 23 so as to be inscribed therein.
[0033]
A lower portion 28b of the crucible 28 is formed in an inverted conical shape, and a seed crystal 30 is attached in a lower end 28e of the crucible 28.
[0034]
Further, the raw material melt 31 is accommodated in the crucible 28.
Further, in the single crystal growing apparatus 21, the insertion hole 22h is formed in the lower surface 22b of the airtight container 22.₂ Is provided.
[0035]
The container driving unit 25 includes a lower shaft 29.
The lower shaft 29 is an insertion hole 22h in the lower surface 22b of the airtight container 22.₂ Are inserted into the airtight container 22 and connected to the bottom center part 23 c of the container (susceptor) 23.
[0036]
The container (susceptor) 23 is supported by the lower shaft 29 so as to be vertically movable.
[0037]
The heaters 26a, 26b, 26c, 26d, and 26e are provided outside the container (susceptor) 23 so as to surround the container (susceptor) 23, and are accommodated in a crucible 28 in the container (susceptor) 23. It is provided to heat the raw material to prepare the raw material melt 31 and to give an appropriate temperature gradient to the single crystal 32 to be grown when the compound semiconductor single crystal 32 is grown.
[0038]
More specifically, the temperature T of the heater 26a_26aThe temperature T of the heater 26b_26bThe temperature T of the heater 26c_26cThe temperature T of the heater 26d_26dThe temperature T of the heater 26e_26eT_26a≦ T_26b≦ T_26c≦ T_26d≦ T_26eIt has been adjusted to satisfy.
[0039]
The heat insulating material 27 is provided so as to surround the heaters 26a, 26b, 26c, 26d, and 26e.
[0040]
FIG. 4 is a cross-sectional view schematically showing a phenomenon that occurs in the crucible 28.
[0041]
Referring to FIG. 4, FIG. 4A is a cross-sectional view schematically showing a state in which the compound raw material 34, the dopant 33, and the sealant 35 are accommodated in the crucible 28. 4B, the crucible 28 containing the compound raw material 34, the dopant 33, and the sealing agent 35 is heated, and the surface 31s thereof is sealed by the molten sealing agent 36, and the inside of the crucible 28. It is sectional drawing which shows typically the state by which the raw material melt 31 containing the compound raw material 34 and the dopant 33 with which the surface 28s was coat | covered with the fuse | melting sealing agent 36 was prepared.
[0042]
FIG. 4B is a cross-sectional view schematically showing a state in which the compound semiconductor single crystal 32 is formed in the crucible 28.
[0043]
Next, referring to FIG. 3 and FIG. 4, an example of growing a Si-doped GaAs single crystal using the single crystal growth apparatus 21 as a method for growing a compound semiconductor single crystal by the conventional VB method will be described. As will be described below.
[0044]
First, a seed crystal 30 is mounted in the crucible 28, and then a III-V group compound, more specifically, a GaAs compound such as GaAs polycrystal, as a compound raw material 34, solid Si as a dopant 33, Boron oxide (B₂ O_Three ).
[0045]
In this step, usually, first, the seed crystal 30 is mounted in the crucible 28, then the dopant 33 is accommodated, the compound raw material 34 is accommodated on the dopant 33, and the compound raw material 34 is sealed. A stop agent 35 is accommodated.
[0046]
Next, the crucible 28 containing the compound raw material 34, the dopant 33, and the sealing agent 35 is accommodated in the container (susceptor) 23.
[0047]
Next, an inert gas such as Ar or N in the airtight container 22₂ Gas or the like is introduced to adjust the inside of the airtight container 22 to a predetermined pressure.
[0048]
Next, using the container driving means 25, the container (susceptor) 23 is moved upward in the airtight container 22 and fixed near the heater 26d.
[0049]
Next, the temperature of the heater 26d is raised and the sealing agent 35 is melted (melted).
In this step, the inner surface 28 s of the crucible 28 is covered with the molten sealant 36.
[0050]
Next, the crucible 28 is heated to a higher temperature to melt (melt) the compound raw material 34, that is, the GaAs compound, and prepare a raw material melt 31 containing the compound raw material 34 and the dopant 33.
[0051]
Next, after the temperature distribution in the hermetic container 22 is optimized by the heaters 26a, 26b, 26c, 26d, and 26e, the lower shaft 29 is lowered downward using the container driving means 25, so that the crucible 28 is cooled to a low temperature. The compound semiconductor single crystal 32, that is, the Si-doped GaAs single crystal is grown by moving to the side and solidifying the raw material melt 31 from the seed crystal 30 side.
[0052]
The VGF method is substantially the same as the VB method except for the following points.
That is, the VGF method is particularly different from the VB method in the step of growing a compound semiconductor single crystal.
[0053]
More specifically, in the case of the VGF method, the temperature of the heaters 26a, 26b, 26c, 26d, and 26e is changed without changing the position (height) of the crucible 28 when the compound semiconductor single crystal 32 is grown. Then, the low temperature portion is gradually moved upward in the order of the heaters 26a, 26b, 26c, 26d, and 26e, and the raw material melt 31 in the crucible 28 is solidified from the seed crystal 30 side, so that the compound semiconductor single crystal 32 Cultivate
[0054]
3 shows an example in which the hermetic container 22 is used, but the VB method and the VGF method both contain the seed crystal 30, the raw material 34, the dopant 33, and the sealant 35 without using the hermetic container 22. A compound semiconductor single crystal can be grown in the atmosphere by vacuum-sealing the crucible 28 together with a quartz tube.
[0055]
In this case, the heat insulating material 27, the heaters 26a, 26b, 26c, 26d, and 26e need to be configured so that they can be used in the atmosphere.
[0056]
Each of the conventional methods for growing a compound semiconductor single crystal described above includes the following steps.
[0057]
(1) The crucibles 8 and 28 include a step of containing the compound raw materials 14 and 34, dopants 13 and 33 for doping the compound raw materials 14 and 34, and sealants 15 and 35.
[0058]
(2) The crucibles 8 and 28 containing the compound raw materials 14 and 34, the dopants 13 and 33 and the sealants 15 and 35 are heated, and the surfaces 11s and 31s are sealed by the melted sealants 16 and 36. A step of forming raw material melts 11 and 31 including stopped compound raw materials 14 and 34 and dopants 13 and 33 are provided.
[0059]
(3) A step of growing the compound semiconductor single crystals 12 and 32 doped with the dopants 13 and 33 from the raw material melts 11 and 31 using the seed crystals 10 and 30 is provided.
[0060]
In the conventional compound semiconductor single crystal growth method for growing a compound semiconductor single crystal doped with a dopant as described above, both of the sealing agents 15 and 35 are boron oxide (B₂ O_Three ), More specifically, additive-free boron oxide (B₂ O_Three ) Resulted in the following problems.
[0061]
In the following description, for ease of explanation, the description will focus on the case where a Si-doped GaAs single crystal is grown according to a conventional method for growing a compound semiconductor single crystal.
[0062]
(1) When the melted sealants 16 and 36 come into contact with the dopants 13 and 33, they react with each other, the dopants 13 and 33 are oxidized, and the dopants 13 and 33 are lost from the raw material melts 11 and 31. The phenomenon that occurs.
[0063]
More specifically, molten boron oxide (B₂ O_Three ) And Si react with each other to oxidize Si, and from the raw material melts 11 and 31 containing GaAs compound and Si, the oxide of Si is melted boron oxide (B₂ O_Three ) Causes the phenomenon of diffusion and disappearance on the side.
[0064]
And since the quantity of the dopants 13 and 33 lost by oxidation is not constant, the compound semiconductor single crystal doped with the dopant grown according to the conventional compound semiconductor single crystal growth method has a dopant concentration ( There arises a problem that variation in carrier concentration becomes large.
[0065]
More specifically, since the amount of Si lost due to oxidation is not constant, the Si-doped GaAs single crystal grown according to the conventional method for growing a compound semiconductor single crystal has a large variation in Si concentration between lots. This causes a problem.
[0066]
{Circle around (2)} By the oxidation of the dopants 13 and 33, the sealing agents 16 and 36 are reduced, and the reduced products of the sealing agents 16 and 36 are taken into the compound semiconductor single crystals 12 and 32 to be grown.
[0067]
More specifically, boron oxide (B₂ O_Three ) Is reduced, and the boron (B) concentration in the grown Si-doped GaAs single crystal becomes abnormally high.
[0068]
(3) Referring again to FIG. 2 and FIG. 3, according to the conventional method for growing a compound semiconductor single crystal, at the liquid-liquid interface between the melted sealant 16, 36 and the raw material melt 11, 31, A large amount of scum (floating matter) 100 is generated. In particular, in the LEC method, the scum (floating matter) 100 is easily attached or taken into the compound semiconductor single crystal 12 to be grown, and the scum (floating matter) 100 is attached or taken into the growing compound semiconductor single crystal 12. However, it causes generation of twins appearing in the compound semiconductor single crystal 12 to be grown and crystal defects such as polycrystallization.
[0069]
Further, in order to grow a compound semiconductor single crystal whose dopant concentration (carrier concentration) is controlled to a desired concentration, the loss of the dopants 13 and 33 lost from the raw material melts 11 and 31 is taken into consideration. When an excessive amount of dopant more than the desired amount of dopant is added to the liquids 11 and 31, a scum (floating) that floats at the liquid-liquid interface between the melted sealants 16 and 36 and the raw material melts 11 and 31 is added. The amount of generation 100) increases.
[0070]
For this reason, the scum (floating matter) 100 is easily attached or taken into the compound semiconductor single crystals 12 and 32 to be grown, and as a result, twin crystals, polycrystals, and the like are added to the compound semiconductor single crystals 12 and 32 to be grown. The crystal defect is likely to occur, and the yield is reduced.
[0071]
As an example of a technique for solving such a problem, there is a method described in Japanese Patent Publication No. 3-57079.
[0072]
The method for producing a Si-doped n-type GaAs single crystal described in Japanese Examined Patent Publication No. 3-57079 is an improvement of the LEC method and has the following configuration.
[0073]
(1) In a crucible, a compound raw material, a dopant for doping the compound raw material, and B as a sealant₂ O_Three In advance, B₂ O_Three Silicon oxide or silicic acid and B to which silicon compound in the form of silicon oxide or silicic acid is added by a method that does not reduce₂ O_Three A step of accommodating a sealant comprising:
[0074]
(2) Compound raw material, dopant and silicon oxide or silicic acid and B₂ O_Three A crucible containing a sealant consisting of the following is heated to melt silicon oxide or silicic acid and B₂ O_Three A step of forming a raw material melt containing a compound raw material and a dopant, the surface of which is sealed with a sealant containing
[0075]
(3) A step of growing a compound semiconductor doped with a dopant from a raw material melt using a seed crystal is provided.
[0076]
According to this prior art, silicon oxide or silicic acid and B₂ O_Three As a result of using a sealant consisting of: scum (floating matter) is less likely to occur because the chemical reaction shown below can be prevented from proceeding in the right direction. It has been shown that crystal defects such as twin (twin) and polycrystallization (poly) are less likely to occur in a single crystal.
[0077]
[Chemical 1]

[0078]
In addition, since the amount of dopant lost from the raw material melt is reduced as a result of the difficulty of generating scum (floating matter), according to this method, a compound semiconductor unit in which the concentration of the dopant is controlled to a desired concentration with good control. Crystals can be grown.
[0079]
As another example of the technique for solving the above-mentioned problem, there is a method disclosed on pages 16 to 22 of the 18th meeting of the Japanese Society for Crystal Growth Bulk Growth Section.
[0080]
This method uses SiO₂Containing B₂O_ThreeIs used as a sealant, and by a vertical boat method such as VB method or VGF method,GaAs crystal is grown.
[0081]
According to this method, there is described an effect that loss due to oxidation of Si as a dopant can be reduced and the amount of boron mixed into the crystal can be reduced.
[0082]
[Problems to be solved by the invention]
However, silicon oxide or silicic acid and B₂ O_Three The sealant consisting of₂ O_Three The viscosity is significantly higher than
[0083]
Also silicon oxide or silicic acidWhenB₂O_ThreeThe sealant consisting of₂O_ThreeThe melting point is higher than that.
[0084]
For this reason, as a sealant, silicon oxide or silicic acid and B₂ O_Three The method for growing a compound semiconductor single crystal using a sealant comprising:₂ O_Three Compared with a method for growing a compound semiconductor single crystal using silicon, solid-state silicon oxide or silicic acid and B₂ O_Three There is a problem that it takes time to melt (melt) the sealant consisting of
[0085]
Also, silicon oxide or silicic acid and B₂ O_Three The sealing agent consisting of₂ O_Three Since the viscosity is higher than that of the melted B, the function of uniformly coating the inner surface 28s of the crucible 28 in the VB method or the VGF method is₂ O_Three There is a problem that it is slightly inferior to.
[0086]
Also, silicon oxide or silicic acid and B₂ O_Three However, there is a problem in that the sealant consisting of is time-consuming to manufacture and high in manufacturing cost.
[0087]
For example, B₂ O_Three SiO in₂ The sealant to which is added is produced by the following two production methods.
[0088]
(1) Boric acid and SiO as starting materials₂ Boric acid and SiO₂ And coexisting, and heating this, SiO 2₂ And B₂ O_Three The sealing agent which consists of these is manufactured.
[0089]
(2) B as a starting material₂ O_Three And SiO₂ Use lump or powder of B₂ O_Three And SiO₂ And coexisting, and heating this, SiO 2₂ And B₂ O_Three The sealing agent which consists of these is manufactured.
[0090]
SiO shown in (1) above₂ And B₂ O_Three In a method for producing a sealant comprising boric acid and SiO₂ Coexist, so boric acid is heated to high temperature and B₂ O_Three In the production of dehydration reaction, and as a result, SiO₂ And B₂ O_Three It takes a long time to produce a sealant consisting of
[0091]
In addition, SiO shown in (2) above.₂ B with added₂ O_Three In the manufacturing method of B,₂ O_Three Inside, SiO₂ Takes a long time to disperse and mix.
[0092]
In addition, SiO₂ And B₂ O_Three Since the sealing agent made of is highly viscous, there is a problem that it is difficult to form into a desired shape and the inner surface of the crucible cannot be uniformly coated.
[0093]
Due to the above reasons, SiO₂ And B₂ O_Three The manufacturing cost of the sealant consisting of₂ O_Three 3 times higher than the manufacturing cost.
[0094]
Furthermore, SiO₂ B added with₂ O_Three Can not uniformly coat the inner wall of the crucible as described above.₂ O_Three Where the coating is not coated, since the raw material melt such as GaAs is in direct contact with the crucible, there is a problem that crystal defects occur and polycrystallizes.
[0095]
The present invention has been made to solve the above problems.
That is, the present invention provides a high-quality dopant-doped group III-V compound semiconductor single crystal in which the dopant concentration is accurately controlled to a desired concentration and has few crystal defects such as twins and polycrystals. An object of the present invention is to provide a method for growing a compound semiconductor single crystal, which can produce a compound semiconductor single crystal such as a II-VI group compound semiconductor single crystal doped with a dopant more efficiently and at a lower cost.
[0096]
[Means for Solving the Problems]
In the method for growing a compound semiconductor single crystal according to the invention of claim 1, the compound raw material having the first melting point, the dopant for doping the compound raw material, and the dopant are separated through the compound raw material in the crucible. Containing a sealant having a second melting point lower than the first melting point disposed, and an additive made of the same material as the dopant disposed to be separated from the dopant via the compound raw material;
The crucible containing the compound raw material, dopant, sealant and additive was heated to a temperature not lower than the second melting point and lower than the first melting point to melt the sealant and melted via the compound raw material. While maintaining the state where the sealant is separated from the dopant, the molten sealant and the additive are brought into contact with each other to react to form a reactant, thereby forming a molten sealant containing the reactant. And steps to
A raw material containing a compound raw material and a dopant, wherein the crucible is further heated to a temperature equal to or higher than the first melting point, the compound raw material is melted, and the surface thereof is sealed with a molten sealant containing a reactant. Creating a melt;
And a step of growing a compound semiconductor single crystal doped with a dopant from a raw material melt using a seed crystal.
[0097]
In the method for growing a compound semiconductor single crystal according to the invention of claim 2, the compound raw material having the first melting point, the dopant for doping the compound raw material, and the dopant are separated through the compound raw material in the crucible. The process of accommodating the sealing agent which has 2nd melting | fusing point lower than 1st melting | fusing point arrange | positioned, and the non-reducing compound which contains the dopant arrange | positioned so that it may isolate | separate from a dopant through a compound raw material as a component When,
The crucible containing the compound raw material, dopant, sealant and non-reducing compound is heated to a temperature not lower than the second melting point and lower than the first melting point to melt the sealant, and through the compound raw material While maintaining the state where the melted sealant is separated from the dopant, the melted sealant and the non-reducing compound are brought into contact with each other to disperse and mix the non-reducing compound into the melted sealant, thereby reducing Forming a molten sealant containing a functional compound;
The crucible is further heated to a temperature equal to or higher than the first melting point, the compound raw material is melted, and the compound raw material and the dopant, the surface of which is sealed with a molten sealant containing a non-reducing compound, Producing a raw material melt comprising:
And a step of growing a compound semiconductor single crystal doped with a dopant from a raw material melt using a seed crystal.
[0098]
According to a third aspect of the present invention, there is provided a compound semiconductor single crystal growth method comprising: a compound raw material having a first melting point; a dopant for doping the compound raw material; and a dopant separated from the dopant via the compound raw material. Containing a sealing agent having a second melting point lower than the melting point of 1 in a crucible made of a non-reducing compound whose inner surface contains a dopant as a constituent;
The crucible containing the compound raw material, the dopant and the sealant is heated to a temperature not lower than the second melting point and lower than the first melting point to melt the sealant, and melted through the compound raw material. The molten sealing agent and the inner surface of the crucible made of a non-reducing compound are brought into contact with each other while the non-reducing compound is dispersed and mixed in the molten sealing agent while maintaining the state separated from the dopant. Forming a molten sealant comprising a reducing compound;
The crucible is further heated to a temperature equal to or higher than the first melting point, the compound raw material is melted, and the compound raw material and the dopant, the surface of which is sealed with a molten sealant containing a non-reducing compound, Producing a raw material melt comprising:
And a step of growing a compound semiconductor single crystal doped with a dopant from a raw material melt using a seed crystal.
[0099]
In addition, as a crucible used for invention of Claim 3, a crucible made from quartz is mentioned, for example.
[0100]
In the first and second aspects of the invention, the crucible may be made of pyrolytic boron nitride (PBN), pyrolytic graphite (PG), vitrified carbon, SiC, boron nitride (BN), graphite or the like. Can be mentioned as preferred materials.
[0101]
Moreover, as a crucible, what coated the inside surface of the container which consists of base materials, such as a graphite, with pyrolytic boron nitride (PBN), pyrolytic graphite (PG), vitrified carbon, SiC, etc. can also be used.
[0102]
The compound raw material is preferably a III-V group compound raw material or a II-VI group compound raw material.
[0103]
Examples of the group III-V compound material include GaAs, InAs, InP, GaP, GaSb, and InSb.
[0104]
Moreover, CdTe, ZnSe etc. can be mentioned as a II-VI group compound raw material.
[0105]
Moreover, Si, Ti, etc. can be mentioned as a dopant for dope to a compound raw material.
[0106]
Moreover, Si, Ti, etc. can be mentioned as an additive.
Non-reducing compounds include SiO.₂ Such as silicon oxide, silicic acid ([(SiO₂ )_m・ (H₂ O)_n]: (M and n are integers)) and the like, and TiO₂ Titanium oxide, titanic acid ([(TiO₂ )_p・ (H₂ O)_q]: (P and q are integers)) and the like.
[0107]
In addition, boron oxide (B₂ O_Three ) Is used, boron oxide (B₂ O_Three ) Is preferably used.
[0108]
Moreover, when using Si as an additive, it is preferable to adjust so that Si density | concentration in the sealing agent of the molten state containing a reaction material may be 0.01 mol (mol)% or more.
[0109]
Further, as a non-reducing compound, SiO₂ Is preferably adjusted so that the Si concentration in the molten sealant containing the non-reducing compound is 0.01 mol (mol)% or more.
[0110]
In the first invention, the crucible containing the compound raw material, dopant, sealant and additive is preferably heated under vacuum or reduced pressure.
[0111]
In the second invention, the crucible containing the compound raw material, the dopant, the sealant and the non-reducing compound is preferably heated under vacuum or reduced pressure.
[0112]
Hereinafter, the operation of the present invention will be described.
The invention of claim 1 has the following configuration.
[0113]
(1) In a crucible, a compound raw material, a dopant for doping the compound raw material, and a sealant having a melting point lower than the melting point of the compound raw material arranged to be separated from the dopant via the compound raw material, A step of accommodating an additive made of the same material as the dopant disposed so as to be separated from the dopant via the compound raw material.
[0114]
(2) heating the crucible containing the compound raw material, dopant, sealant and additive to a temperature not lower than the melting point of the sealant and lower than the melting point of the compound raw material;
(A) First, the sealing agent is melted and the melted sealing agent and the dopant are kept separated by the compound raw material,
(B) A reaction product is produced by bringing a molten sealant and an additive into contact with each other to form a reaction product, and a molten sealant containing the reaction product is formed.
(C) Thereafter, the crucible is further heated to a temperature equal to or higher than the melting point of the compound raw material to melt the compound raw material, and the surface of the compound raw material is sealed with a molten sealant containing a reactant. And a step of producing a raw material melt containing a dopant.
[0115]
(3) A step of growing a compound semiconductor single crystal doped with a dopant from a raw material melt using a seed crystal is provided.
[0116]
In 1st invention, in the process shown to said (1), in the crucible, the dopant for dope to a compound raw material, and the additive which consists of a sealing agent and the same material as a dopant through a compound raw material, It arranges so that it may separate.
[0117]
Moreover, what has melting | fusing point lower than a compound raw material is selected as a sealing agent.
[0118]
Therefore, in the process shown in (2) above, the following phenomenon can be caused in the crucible by heating the crucible containing the compound raw material, dopant, sealant and additive.
[0119]
In the steps shown in (2) and (A) above, first, the sealant is melted.
Since the compound raw material has a higher melting point than the sealant, the melted sealant and the dopant can be kept in a state separated by the compound raw material.
[0120]
And in the process shown to said (2) (B), the molten sealing agent and an additive are made to contact in the process shown to said (2) (B), hold | maintaining the state shown to said (2) (A).
[0121]
Then, the molten sealant and the additive react to generate a reaction product, and a molten sealant containing the reaction product is formed.
[0122]
Next, in the step shown in (2) and (C) above, the crucible is further heated to a temperature equal to or higher than the melting point of the compound raw material.
[0123]
Then, the compound raw material is melted, a raw material melt containing the compound raw material and the dopant is produced, and the surface of the raw material melt is sealed with a molten sealant containing a reactant.
[0124]
And in this process, a dopant contacts the sealing agent of the molten state containing a reaction material.
[0125]
And reaction with a dopant and sealing agent will be suppressed by the reactant contained in sealing agent.
[0126]
That is, according to invention of Claim 1, since a dopant will contact the sealing agent of the molten state containing a reaction material, generation | occurrence | production of the scum (floating matter) by reaction with a dopant and a sealing agent is suppressed. Is done.
[0127]
Therefore, according to the invention of claim 1, since the amount of the dopant that becomes a scum (floating matter) from the raw material melt and diffuses and disappears toward the sealant containing the reactant is small, the concentration of the dopant is a desired concentration. Therefore, it is possible to efficiently grow a compound semiconductor single crystal controlled with high accuracy.
[0128]
According to the invention of claim 1, since the amount of scum (floating matter) generated by the reaction between the dopant and the sealant is originally small, the scum (floating matter) is contained in the compound semiconductor single crystal to be grown. As a result, a high quality compound semiconductor single crystal with few crystal defects such as twins and polycrystals can be efficiently grown.
[0129]
That is, according to the invention of claim 1, a high-quality compound semiconductor single crystal in which the dopant concentration is accurately controlled to a desired concentration can be efficiently produced.
[0130]
The invention of claim 2 comprises the following configuration.
(1) In a crucible, a compound raw material, a dopant for doping the compound raw material, a sealant having a lower melting point than the compound raw material, and a dopant separated from the dopant via the compound raw material are disposed. A step of containing a non-reducing compound contained as a constituent element.
[0131]
(2) Heating the crucible containing the compound raw material, dopant, sealant and non-reducing compound,
(A) First, the sealing agent is melted, and the melted sealing agent and the dopant are kept separated by the compound raw material,
(B) A molten sealing agent containing a non-reducing compound is formed by bringing a molten sealing agent into contact with a non-reducing compound and dispersing and mixing the non-reducing compound in the molten sealing agent. ,
(C) Thereafter, the crucible is further heated to a higher temperature to melt the compound raw material, and the compound raw material and the dopant whose surfaces are sealed with a sealing agent in a molten state containing a non-reducing compound. A step of forming a raw material melt containing.
[0132]
(3) A step of growing a compound semiconductor single crystal doped with a dopant from a raw material melt using a seed crystal is provided.
[0133]
In the invention of claim 2, in the step shown in (1) above, the dopant for doping the compound raw material and the non-reducing compound containing the dopant as a constituent element in the crucible are separated through the compound raw material. It is arranged to do.
[0134]
Moreover, what has melting | fusing point lower than a compound raw material is selected as a sealing agent.
[0135]
Therefore, in the step shown in (2) above, the following phenomenon can be caused in the crucible by heating the crucible containing the compound raw material, the dopant, the sealant and the non-reducing compound.
[0136]
In the steps shown in (2) and (A) above, first, the sealant is melted.
Since the compound raw material has a higher melting point than the sealant, the melted sealant and the dopant can be kept in a state separated by the compound raw material.
[0137]
And in the process shown to said (2) and (B), the molten sealing agent and a nonreducible compound are made to contact, maintaining the state shown to said (2) (A).
[0138]
Then, the non-reducing compound is dispersed and mixed in the melted sealing agent to form a sealing agent containing the non-reducing compound.
[0139]
Next, in the step shown in (2) and (C) above, the crucible is further heated to a higher temperature.
[0140]
Then, the compound raw material is melted to form a raw material melt containing the compound raw material and the dopant, and the surface of the raw material melt is sealed with a molten sealant containing the non-reducing compound.
[0141]
Contact with a molten sealant containing a non-reducing compound.
Therefore, the reaction between the dopant and the sealant is suppressed by the non-reducing compound contained in the sealant.
[0142]
That is, according to the invention of claim 2, since the dopant comes into contact with the molten sealant containing the non-reducing compound, scum (floating matter) is generated by the reaction between the dopant and the sealant. Is suppressed.
[0143]
Therefore, according to the invention of claim 2, since the amount of dopant which becomes scum (floating matter) from the raw material melt and diffuses and disappears toward the sealant containing the non-reducing compound is small, the concentration of the dopant is desired. It is possible to efficiently grow a compound semiconductor single crystal that is accurately controlled to the concentration of.
[0144]
According to the invention of claim 2, since the amount of scum (floating matter) generated by the reaction between the dopant and the sealant is originally small, scum (floating matter) is contained in the compound semiconductor single crystal to be grown. As a result, a high quality compound semiconductor single crystal with few crystal defects such as twins and polycrystals can be efficiently grown.
[0145]
That is, according to the invention of claim 2, a high-quality compound semiconductor single crystal in which the dopant concentration is accurately controlled to a desired concentration can be efficiently produced.
[0146]
The invention of claim 3 is the same as that of claim 2 except that a non-reducing compound is not added separately, and the inner surface thereof is, for example, quartz (SiO 2).₂ ) Or the like, and a crucible made of a non-reducing compound is used.
[0147]
According to the invention of claim 3, since the inner surface of the crucible itself is made of a non-reducing compound, the same effect as that of the invention of claim 2 can be obtained without adding an additive or a non-reducing compound separately. It is done.
[0148]
In the present invention, it is necessary to sufficiently react the additive or the non-reducing compound and the sealing agent before melting the compound raw material.
[0149]
Therefore, the surface area of the additive or non-reducing compound is preferably as large as possible. The temperature at which the additive or non-reducing compound and the sealant are reacted is preferably as high as possible, while the reaction time is preferably as long as possible.
[0150]
Specifically, the particle size of the additive or non-reducing compound is preferably 500 μm or less, more preferably 100 μm or less, and most preferably 10 μm or less when used as a powder.
[0151]
Also, for example, GaAs as the compound raw material and B as the sealing agent₂ O_Three Is used, the reaction temperature between the additive or the non-reducing compound and the sealant is preferably 600 ° C. or higher and 1200 ° C. or lower, more preferably 800 ° C. or higher and 1200 ° C. or lower, and most preferably 1000 ° C. or higher and 1200 ° C. or lower. It is good to be.
[0152]
This is because when the reaction temperature is lower than 600 ° C., the reactivity is lowered.
On the other hand, the reaction time between the additive or the non-reducing compound and the sealant is preferably 2 hours or longer, more preferably 4 hours or longer, and most preferably 6 hours or longer. However, if the reaction time is too long, productivity will decrease.
[0153]
Moreover, FIG. 9 is a figure which shows the example of the temperature rising profile at the time of making an additive or a nonreducing compound, and a sealing agent react in this invention. 9A and 9B, the horizontal axis indicates the reaction elapsed time, and the vertical axis indicates the reaction temperature.
[0154]
In this invention, in order to sufficiently react the additive or the non-reducing compound with the sealing agent, for example, as shown in FIG. Although it is preferable to hold at a temperature, it is not always necessary to hold at a constant temperature. For example, as shown in FIG. You may do it.
[0155]
【Example】
Hereinafter, although demonstrated using an Example, this invention is not limited at all by the following Examples.
[0156]
Example 1
FIG. 5 is a longitudinal sectional view schematically showing a method for growing a compound semiconductor single crystal according to the present invention.
[0157]
Referring to FIG. 5, compound semiconductor single crystal growth apparatus 41 according to the present invention is the same as compound semiconductor single crystal growth apparatus 1 shown in FIG. 1, and accordingly, corresponding members are denoted by corresponding reference numerals. Therefore, the description is omitted.
[0158]
The method for growing a compound semiconductor single crystal according to the present invention includes a non-contained additive 51 or dopant 13 made of the same material as the sealing agent 15 and the dopant 13 in the crucible 8 via the compound raw material 14. This is different from the conventional method for growing a compound semiconductor single crystal in that the reducing compound 51 is arranged separately from the dopant 13.
[0159]
Next, description will be made based on more specific data.
Experimental example 1
Experimental Example 1 is a specific example of a method for growing a compound semiconductor single crystal according to the present invention, and relates to improvement of the LEC method.
[0160]
More specifically, an example in which a Si-doped GaAs single crystal is grown according to the invention of claim 2 is shown.
[0161]
In other words, a Si-doped GaAs single crystal having a diameter of 3 inches was grown using the compound semiconductor single crystal growth apparatus 41 shown in FIG.
[0162]
Referring to FIG. 5, a PBN crucible having a diameter of 150 mm was used as the crucible 8.
[0163]
Further, 6 kg of GaAs polycrystal was used as the compound raw material 14.
Further, 300 mg of solid Si was used as the dopant 13.
[0164]
Moreover, as sealing agent 15, B with a water concentration of 200 ppm is used.₂ O_Three 500 g was used.
[0165]
Further, as the non-reducing compound 51, SiO having a particle diameter of 50 μm.₂ 50 g of powder was used.
[0166]
In this experimental example, as shown in FIG. 5, the dopant 13 was placed on the compound raw material 14 so that the dopant 13 did not directly react with the softened (melted) sealant 15.
[0167]
More specifically, first, the non-reducing compound 51 was accommodated in the bottom peripheral portion 8 b in the crucible 8. Next, the compound raw material 14 was accommodated so as to cover the non-reducing compound 51. In the present experimental example, the compound raw material 14 was used to form the peripheral wall 14w standing up.
[0168]
In this experimental example, a block aggregate is used as the compound raw material 14, but the compound raw material 14 is a powder aggregate, a granular aggregate, a block aggregate, or an integrally molded body. It should be noted that it may be.
[0169]
Next, the dopant 13 was accommodated inside the peripheral wall 14 w on the surface of the compound raw material 14.
[0170]
Further, the sealant 15 was accommodated outside the peripheral wall 14 w on the surface of the compound raw material 14.
[0171]
Next, the crucible 8 containing the compound raw material 14, the dopant 13, the sealing agent 15 and the non-reducing compound 51 was stored in a predetermined position in the airtight container 2.
[0172]
Next, the insertion hole 2h of the airtight container 2₁ The seed crystal 10 was attached to the lower end portion 4e of the pulling shaft (upper shaft) 4 inserted into the hermetic container 2.
[0173]
Next, the airtight container 2 was sealed, and then the temperature was raised using the heater 6 while evacuating the inside of the airtight container 2 to remove moisture contained in the airtight container 2 member and the sealant 15.
[0174]
Thereafter, nitrogen (N₂ ) Introducing gas, nitrogen (N₂ ) Pressurized with gas, and using the heater 6, the crucible 8 was heated to a temperature not lower than the melting point of the sealant and lower than the melting point of the compound raw material.
[0175]
In the crucible 8, first, the sealing agent 15 softens (melts) and moves downward, comes into contact with the non-reducing compound 51, and the non-reducing compound 51 is dispersed and mixed in the molten sealing agent to perform non-reduction. The sealing compound in the molten state containing the functional compound 51 was formed. In order to sufficiently disperse and mix the non-reducing compound 51 into the sealant, the mixture was kept at 800 ° C. for 4 hours.
[0176]
Thereafter, the crucible 8 is further heated to a temperature equal to or higher than the melting point of the compound raw material, whereby the compound raw material 14 is melted and the surface thereof is sealed with a molten sealant containing the non-reducing compound 51. A raw material melt (not shown) including the raw material 14 and the dopant 13 was formed.
[0177]
In this step, the surface of the raw material melt (not shown) was sealed with a molten sealant (not shown) containing the non-reducing compound 51.
[0178]
At that time, no scum (floating matter) was observed.
[0179]
Next, using the container driving means 5 and rotating the container (susceptor) 3 at a predetermined rotational speed, using the pulling shaft (upper shaft) driving means (not shown), the raw material melt (not shown) is used. The seed crystal 10 is immersed, and then the seed crystal 10 is pulled from the raw material melt (not shown) at a predetermined rotational speed and at a predetermined pulling speed, so that the diameter is about 85 mm and the length is increased. About 22 cm of Si-doped GaAs single crystal (not shown) was grown.
[0180]
In addition, dopant (Si) 13 and sealing agent (B₂ O_Three ) The reaction with 15 was very slight, and the Si content in the grown Si-doped GaAs single crystal was 3% or less of deviation from the design value of the Si content.
[0181]
Experimental example 2
In Experimental Example 1, a Si-doped GaAs single crystal was grown in the same manner as in Experimental Example 1 except that Si1g was used instead of the non-reducing compound 51.
[0182]
As a result, it has become clear that the same effects as those of Experimental Example 1 can be obtained.
Example 2
FIG. 6 is a longitudinal sectional view schematically showing a method for growing a compound semiconductor single crystal according to the present invention as another embodiment.
[0183]
Referring to FIG. 6, the compound semiconductor single crystal growth apparatus 21 used in the present invention is the same as the compound semiconductor single crystal growth apparatus 21 shown in FIG. A description thereof will be omitted.
[0184]
Then, the method for growing a compound semiconductor single crystal according to the present invention includes, in the crucible 28, an additive 71 or a dopant 33 made of the same material as the sealing agent 35 and the dopant 33 as a constituent element through the compound raw material 34. This is different from the conventional method for growing a compound semiconductor single crystal in that the reducing compound 71 is arranged separately from the dopant 33.
[0185]
Next, description will be made based on more specific data.
Experimental example 3
Experimental Example 3 is another specific example of the method for growing a compound semiconductor single crystal according to the present invention, and relates to the improvement of the VGF method.
[0186]
More specifically, an example is shown in which a Si-doped GaAs single crystal is grown according to the second invention.
[0187]
That is, the Si-doped GaAs single crystal having a diameter of 2 inches was grown using the compound semiconductor single crystal growth apparatus 21 shown in FIG.
[0188]
Referring to FIG. 6, a PBN crucible having a diameter of 55 mm was used as the crucible 28.
[0189]
Further, 1.5 kg of GaAs polycrystal was used as the compound raw material 34.
Further, 250 mg of solid Si was used as the dopant 33.
[0190]
Moreover, as sealing agent 35, B with a water concentration of 100 ppm₂ O_Three Was used in an amount of 50 g.
[0191]
Further, as the non-reducing compound 71, SiO having a particle diameter of 10 μm₂ 10 g of powder was used.
[0192]
In this experimental example, as shown in FIG. 6, the dopant 33 was placed on the compound raw material 34 so that the dopant 33 did not react directly with the softened (melted) sealant 35.
[0193]
More specifically, first, the seed crystal 30 was attached in the lower end 28 e in the crucible 28.
[0194]
Next, the non-reducing compound 71 was accommodated on the seed crystal 30.
Next, the compound raw material 34 was accommodated so as to cover the non-reducing compound 71.
[0195]
In the present experimental example, the compound raw material 34 was used to form the peripheral wall 34w that stood upward.
[0196]
In this experimental example, a block aggregate is used as the compound raw material 34. However, the compound raw material 34 is a powder aggregate, a granular aggregate, a block aggregate, or an integrally molded body. It should be noted that this may be the case.
[0197]
Next, the dopant 33 was accommodated in the peripheral wall 34 w on the surface of the compound raw material 34.
[0198]
Further, a sealant 35 was accommodated outside the peripheral wall 34 w on the surface of the compound raw material 34.
[0199]
Next, the crucible 28 containing the compound raw material 34, the dopant 33, the sealing agent 35, and the non-reducing compound 71 was stored in a predetermined position in the airtight container 22.
[0200]
Next, the airtight container 22 is sealed, and then the temperature is raised using the heaters 26a, 26b, 26c, 26d, and 26e while evacuating the airtight container 22, and the airtight container 22 member and the sealant (B₂ O_Three ) Water contained in 35 was removed.
[0201]
Thereafter, argon (Ar) is introduced into the hermetic container 22, the interior of the chamber 22 is pressurized with argon (Ar) gas, and the crucible 28 is sealed with the heaters 26a, 26b, 26c, 26d, and 26e. It was heated to a temperature above the melting point of the stopper and below the melting point of the compound raw material.
[0202]
In the crucible 28, first, the sealing agent 35 was softened (melted), and the quartz crucible inner surface was coated while moving downward. Furthermore, in contact with the non-reducing compound 71, the non-reducing compound 71 was dispersed and mixed in the molten sealing agent, and a molten sealing agent (not shown) containing the non-reducing compound 71 was formed. . In order to sufficiently disperse and mix the non-reducing compound 71 into the sealant, the temperature was slowly raised from 600 ° C. to 1200 ° C. at a rate of 100 ° C./hour over about 6 hours.
[0203]
Thereafter, the crucible 28 is further heated to a temperature equal to or higher than the melting point of the compound raw material, whereby the compound raw material 34 is melted and the surface thereof is melted by a sealing agent (not shown) in a molten state containing the nonreducing compound 71. A sealed raw material melt (not shown) containing the compound raw material 34 and the dopant 33 was formed.
[0204]
In this step, the surface of the raw material melt (not shown) was sealed with a molten sealant (not shown) containing the non-reducing compound 71.
[0205]
At that time, no scum (floating matter) was observed.
Next, after the temperature distribution in the airtight container 22 is optimized by the heaters 26a, 26b, 26c, 26d, and 26e, the temperature of the heaters 26a, 26b, 26c, 26d, and 26e is changed, and the low temperature portion is changed to the heater. By gradually moving upward in the order of 26a, 26b, 26c, 26d, and 26e and solidifying the raw material melt (not shown) from the seed crystal 30 side, the diameter is 55 mm and the length is about 14 cm. A Si-doped GaAs single crystal was grown.
[0206]
Dopant (Si) 33 and sealant (B₂ O_Three ) The reaction with 35 was negligible, and the Si content in the Si-doped GaAs single crystal was 3% or less from the design value of the Si content.
[0207]
Experimental Example 4
Experimental example 3 is the same as experimental example 3, except that additive 71 made of the same material as dopant 33, that is, 500 mg of solid Si, is used instead of non-reducing compound 71. A Si-doped GaAs single crystal is grown. did.
[0208]
As a result, it has been clarified that Experimental Example 4 has the same effect as Experimental Example 3.
[0209]
Experimental Example 5
A Si-doped GaAs single crystal having a diameter of 2 inches was grown using the compound semiconductor growth apparatus 21 shown in FIG.
[0210]
As the crucible 28, a quartz crucible having a diameter of 55 mm was used. Further, 1.5 kg of GaAs polycrystal was used as the compound raw material 34. Furthermore, 200 mg of solid Si was used as the dopant 33. Moreover, as sealing agent 35, B with a water concentration of 100 ppm is used.₂ O_Three Was used in an amount of 50 g.
[0211]
Note that the non-reducing compound and additive 71 were not used.
Also in this experiment, the dopant 33 was placed on the compound raw material 34 so that the dopant 33 did not directly react with the softened (melted) sealant 35.
[0212]
More specifically, first, the seed crystal 30 was attached in the lower end 28 e in the crucible 28. Next, the compound raw material 34 was accommodated on the seed crystal 30. And in this experiment example, the surrounding wall 34w which stands up was formed using the compound raw material 34. As shown in FIG.
[0213]
In this experimental example, a block aggregate is used as the compound raw material 34. However, as the compound raw material 34, a powder aggregate, a granular aggregate, a block aggregate, and an integrally molded body are used. It should be noted that this may be the case.
[0214]
Next, the dopant 33 was accommodated inside the peripheral wall 34 w on the surface of the compound raw material 34. Further, a sealant 35 was accommodated outside the peripheral wall 34 w on the surface of the compound raw material 34.
[0215]
Next, the crucible 28 containing the compound raw material 34, the dopant 33 and the sealant 35 was stored in a predetermined position in the airtight container 22.
[0216]
Next, the airtight container 22 is sealed, and then the temperature is raised using the heaters 26a, 26b, 26c, 26d, and 26e while evacuating the airtight container 22, and the airtight container 22 member and the sealant (B₂ O_Three ) Water contained in 35 was removed.
[0217]
Thereafter, argon (Ar) is introduced into the hermetic container 22, the interior of the chamber 22 is pressurized with argon (Ar) gas, and the crucible 28 is sealed with the heaters 26a, 26b, 26c, 26d, and 26e. It was heated to a temperature above the melting point of the stopper and below the melting point of the compound raw material.
[0218]
In the crucible 28, first, the sealing agent 35 was softened (melted), and covered the inner surface of the quartz crucible while moving downward.
[0219]
Non-reducing compounds contained in quartz crucibles (SiO₂ ) Sealant (B₂ O_Three In order to sufficiently disperse and mix with non-reducing compound (SiO 2).₂ Encapsulant (B)₂ O_Three ) Was formed.
[0220]
Thereafter, the crucible 28 is further heated to a temperature equal to or higher than the melting point of the compound raw material, whereby the compound raw material 34 is melted and the surface thereof is sealed with a molten sealant containing the non-reducing compound contained in the crucible. Thus, a raw material melt containing the compound raw material 34 and the dopant 33 was formed.
[0221]
In this step, the surface of the raw material melt was liquid-sealed with a molten sealant containing a non-reducing compound.
[0222]
At that time, no scum (floating matter) was observed.
Next, after the temperature distribution in the airtight container 22 is optimized by the heaters 26a, 26b, 26c, 26d, and 26e, the temperature of the heaters 26a, 26b, 26c, 26d, and 26e is changed, and the low temperature portion is changed to the heater. By gradually moving upward in the order of 26a, 26b, 26c, 26d, and 26e and solidifying the raw material melt (not shown) from the seed crystal 30 side, the diameter is 55 mm and the length is about 14 cm. A Si-doped GaAs single crystal was grown.
[0223]
Dopant (Si) 33 and sealant (B₂ O_Three ) The reaction with 35 was negligible, and the Si content in the Si-doped GaAs single crystal was 3% or less of the deviation of the Si content from the design value.
[0224]
In Examples 1 and 2 described above, SiO added as dopants 13 and 33 was added.₂ Or Si is a sealing agent (B₂ O_Three ) Before reacting with 15, 35, the additive (Si) 51, 71 made of the same material as the dopant 13, 33, or the non-reducing compound (SiO) containing the dopant 13, 33 as a constituent element₂ ) 51 and 71, Si added as dopants 13 and 33 and sealant (B₂ O_Three ) Reaction with 15, 35 is suppressed.
[0225]
For this reason, the dopant (Si) 13 and 33 can be doped into the compound semiconductor single crystal to be effectively grown, and the carrier concentration controllability is improved.
[0226]
Additive-free B₂ O_Three The increase in the B (boron) concentration in the Si-doped GaAs single crystal to be grown, which becomes a problem when using Si, is suppressed. Therefore, it is possible to cope with varieties that require a particularly low boron concentration.
[0227]
In addition, low moisture concentration B₂ O_Three And then use B₂ O_Three Moreover, by thoroughly dehydrating the compound semiconductor single crystal growth equipment, that is, in-furnace parts, it is possible to prevent scum and effectively prevent twins and polycrystallization. can do.
[0228]
In addition, according to the present invention, since the amount of scum (floating matter) generated is originally small, the phenomenon that the scum (floating matter) adheres to or is taken into the compound semiconductor single crystal to be grown is less likely to occur. A high-quality compound semiconductor single crystal with few crystal defects such as crystals and polycrystals can be efficiently grown.
[0229]
In addition, SiO shown in Examples 1 and 2₂ B doped with₂ O_Three Can solve the problem of high viscosity and difficulty in forming into a desired shape.
[0230]
That is, according to the method of the present invention, SiO₂ B in advance₂ O_Three Compound raw materials 14 and 34 and dopant (Si) 13 and 33 and sealant (B₂ O_Three ) 15, 35 along with excess Si or SiO₂ And put in crucibles 8 and 28, dopant (Si) 13 and 33 are encapsulant (B₂ O_Three ) Excess Si or SiO previously placed in crucibles 8, 28 before reacting with 15, 35₂ Si to B₂ O_Three It has been added to.
[0231]
Thus, according to the present invention, SiO₂ B doped with₂ O_Three Instead of using B₂ O_Three As a result, the problem that it is difficult to mold the sealant into a desired shape, which is a problem in the method described in Japanese Patent Publication No. 3-57079, is solved.
[0232]
In addition, according to the present invention, it is noted that the function of uniformly covering the inner surface 28s of the crucible 28 in the VB method and the VGF method was superior to the method described in Japanese Patent Publication No. 3-57079. .
[0233]
Further, according to the present invention, additive-free B₂ O_Three Can be used, so SiO₂ B doped with₂ O_Three Compared with the method described in Japanese Patent Publication No. 3-57079, the production cost of the Si-doped compound semiconductor single crystal can be extremely reduced.
[0234]
Furthermore, in the method disclosed in the 18th Annual Meeting of the Bulk Growth Subcommittee, B₂ O_Three Is used as a sealant, while in the present invention, B₂ O_Three Is used not only as a sealant but also for coating the inner surface of the crucible.
[0235]
In the present invention, the crucible inner surface is B₂ O_Three Therefore, it is possible to effectively prevent generation of crystal defects and polycrystallization due to direct contact of the raw material melt such as GaAs with the crucible.
[0236]
In the crucible, a compound raw material, a dopant for doping the compound raw material, a sealant having a melting point lower than the melting point of the compound raw material arranged so as to be separated from the dopant via the compound raw material, and a compound The method of accommodating the dopant arranged so as to be separated from the dopant via the raw material and the non-reducing compound containing the additive or dopant made of the same material as the constituent elements is limited to the methods shown in FIGS. It goes without saying that it is not done.
[0237]
In this step, various modifications can be considered.
A typical accommodating method of such a modification is shown in FIGS.
[0238]
Referring to FIG. 7, FIGS. 7 (a) to 7 (c) each show a modification of Example 1, and in the crucible, a compound raw material, a dopant, a sealant, and a dopant It is sectional drawing which shows typically the state which accommodated the nonreducing compound which contains the additive or dopant which consists of the same material as a component.
[0239]
Referring to FIG. 7 (a), in FIG. 7 (a), first, an additive 51 made of the same material as the dopant 13 or a non-reducing compound 51 containing the dopant 13 as a constituent element is accommodated in the crucible 8. The sealing agent 15 is accommodated so as to be close to the additive 51 or the non-reducing compound 51, the compound raw material 14 is accommodated on the sealing agent 15, and the dopant 13 is accommodated on the compound raw material 14. ing.
[0240]
In FIG. 7B, the compound raw material 14 is first accommodated in the crucible 8, and then the compound raw material 14 is used to form a peripheral wall 14w that stands upward, and the dopant 13 is placed inside the peripheral wall 14w. The non-reducing compound 51 containing the additive 51 or the dopant 13 made of the same material as the dopant 13 as a constituent element is accommodated outside the peripheral wall 14w, and is close to the additive 51 or the non-reducing compound 51. The sealing agent 15 is accommodated.
[0241]
In FIG. 7C, the crucible 8 first contains the additive 51 made of the same material as the dopant 13 or the non-reducing compound 51 containing the dopant 13 as a constituent element. The compound raw material 14a is accommodated on the compound 51, and a columnar body 14p standing upward is formed of the compound raw material on the compound raw material 14a, and is formed by the crucible 8, the compound raw material 14a, and the columnar body 14p. The sealing agent 15 is accommodated in the void B, and further the compound raw material 14b is accommodated so as to cover both the columnar body 14p and the sealing agent 15, and the dopant 13 is accommodated on the compound raw material 14b. ing.
[0242]
Referring to FIG. 8, FIGS. 8 (a) to 8 (b) each schematically show a modification of Example 2, in which a compound raw material, a dopant, and a seal are encapsulated in a crucible. It is sectional drawing which shows typically the state which accommodated the non-reducing compound which contains a stopper and the additive which consists of the same material as a dopant, or a dopant as a component.
[0243]
8A, in FIG. 8A, after the seed crystal 30 is first attached in the crucible 28, an additive 71 made of the same material as the dopant 33 or in the vicinity of the seed crystal 30 is provided. The non-reducing compound 71 containing the dopant 33 as a constituent element is accommodated, the compound raw material 34a is accommodated on the additive 71 or the non-reducing compound 71, and the columnar body 34p made of the compound raw material is formed on the compound raw material 34a. The sealing agent 35 is accommodated in the gap B formed by the crucible 28, the compound raw material 34a and the columnar body 34p, and the compound raw material 34b is further accommodated so as to cover both the sealing agent 35 and the columnar body 34p. The dopant 33 is accommodated on the compound raw material 34b.
[0244]
8B, after attaching the seed crystal 30 in the crucible 28, the compound raw material 34a is accommodated on the seed crystal 30, and the columnar body 34p made of the compound raw material is accommodated on the compound raw material 34a. In the void B formed by the crucible 28, the columnar body 34p and the compound raw material 34a, the additive 71 made of the same material as the dopant 33 or the non-reducing compound 71 containing the dopant 33 as a constituent element is accommodated. Alternatively, the sealing agent 35 is accommodated so as to be close to the non-reducing compound 71, the compound raw material 34b is further accommodated so as to cover both the sealing agent 35 and the columnar body 34p, and the dopant 33 is formed on the compound raw material 34b. Is housed.
[0245]
Note that these are merely specific examples, and various other methods are possible.
[0246]
For example, a groove is formed with a compound raw material, and a dopant (solid Si) is retained therein, or a compound raw material containing a dopant (Si) is used in advance, and the dopant (Si) is melted until the compound raw material is melted. Sealant (B₂ O_Three ) And may be accommodated so that they do not react directly.
[0247]
B₂ O_Three Since scum is generated by moisture in the atmosphere and moisture in the atmosphere, in order to prevent the occurrence of scum, use B₂ O_Three It is desirable that the moisture concentration of the steel be 300 ppm or less, and before crystal growth is performed, the temperature in the furnace is increased by heating under vacuum or reduced pressure, and the components in the furnace and boron oxide (B₂ O_Three It is noted that it is desirable to perform the dehydration process.
[0248]
In addition, it should be noted that it is desirable to keep the in-furnace parts in a dry atmosphere when the furnace is opened so as not to absorb moisture.
[0249]
【The invention's effect】
As described in detail above, the present invention has the following effects as a result of having the above-described configuration.
[0250]
That is, according to invention of Claim 1, since a dopant will contact the sealing agent of the molten state containing a reaction material, generation | occurrence | production of the scum (floating matter) by reaction with a dopant and a sealing agent is suppressed. Is done.
[0251]
Therefore, according to the invention of claim 1, since the amount of the dopant that becomes a scum (floating matter) from the raw material melt and diffuses and disappears toward the sealant containing the reactant is small, the concentration of the dopant is a desired concentration. Therefore, it is possible to efficiently grow a compound semiconductor single crystal controlled with high accuracy.
[0252]
According to the invention of claim 1, since the amount of scum (floating matter) generated by the reaction between the dopant and the sealant is originally small, scum (floating matter) is present in the compound semiconductor single crystal to be grown. As a result that the phenomenon of adhesion or incorporation is less likely to occur, a high-quality compound semiconductor single crystal with few crystal defects such as twins and polycrystals can be efficiently grown.
[0253]
That is, according to the invention of claim 1, a high-quality compound semiconductor single crystal in which the dopant concentration is accurately controlled to a desired concentration can be efficiently produced.
[0254]
According to the invention of claim 2, since the dopant comes in contact with the molten sealant containing the non-reducing compound, scum (floating matter) is generated by the reaction between the dopant and the sealant. Is suppressed.
[0255]
Therefore, according to the invention of claim 2, since the amount of dopant which becomes scum (floating matter) from the raw material melt and diffuses and disappears toward the sealant containing the non-reducing compound is small, the concentration of the dopant is desired. It is possible to efficiently grow a compound semiconductor single crystal that is accurately controlled to the concentration of.
[0256]
According to the invention of claim 2, since the amount of scum (floating matter) generated by the reaction between the dopant and the sealant is originally small, scum (floating matter) is present in the compound semiconductor single crystal to be grown. As a result that the phenomenon of adhering or taking in hardly occurs, a high-quality compound semiconductor single crystal with few crystal defects such as twins and polycrystals can be efficiently grown.
[0257]
That is, according to the invention of claim 2, a high-quality compound semiconductor single crystal in which the dopant concentration is accurately controlled to a desired concentration can be efficiently produced.
[0258]
According to the invention of claim 3, since the dopant comes in contact with the molten sealant containing the non-reducing compound, scum (floating matter) is generated by the reaction between the dopant and the sealant. Is suppressed.
[0259]
Therefore, according to the invention of claim 3, since the amount of dopant that becomes scum (floating matter) from the raw material melt and diffuses and disappears toward the sealant containing the non-reducing compound is small, the concentration of the dopant is desired. It is possible to efficiently grow a compound semiconductor single crystal that is accurately controlled to the concentration of.
[0260]
According to the invention of claim 3, since the amount of scum (floating matter) generated by the reaction between the dopant and the sealant is originally small, scum (floating matter) is present in the compound semiconductor single crystal to be grown. As a result that the phenomenon of adhering or taking in hardly occurs, a high-quality compound semiconductor single crystal with few crystal defects such as twins and polycrystals can be efficiently grown.
[0261]
That is, according to the invention of claim 3, a high-quality compound semiconductor single crystal in which the dopant concentration is accurately controlled to a desired concentration can be efficiently produced.
[0262]
Furthermore, according to the present invention, as a sealant, for example, SiO₂ B without adding₂ O_Three Is used. B like this₂ O_Three Has a low viscosity and is easy to mold.₂ O_Three Can be used.
[0263]
As described above, according to the present invention, there is an effect that improvement in crystal yield and cost reduction can be realized, which is industrially useful.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view schematically showing an example of a conventional single crystal growth apparatus used in an LEC method.
FIG. 2 is a cross-sectional view schematically showing a phenomenon that occurs in the crucible 8. FIG.
FIG. 3 is a longitudinal sectional view schematically showing an example of a conventional single crystal growth apparatus used in the VB method.
4 is a cross-sectional view schematically showing a phenomenon that occurs in the crucible 28. FIG.
FIG. 5 is a longitudinal sectional view schematically showing a method for growing a compound semiconductor single crystal according to the present invention.
FIG. 6 is a longitudinal sectional view schematically showing a method for growing a compound semiconductor single crystal according to the present invention.
FIG. 7 schematically shows a modified example of Example 1, in which a crucible contains a compound raw material, a dopant, and an additive or dopant made of the same material as the encapsulant and the dopant as a constituent element. It is sectional drawing which shows the state which accommodated the active compound typically.
FIG. 8 schematically shows a modification of Example 2, in which a crucible contains a compound raw material, a dopant, and an additive or dopant made of the same material as the encapsulant and the dopant as a constituent element. It is sectional drawing which shows the state which accommodated the active compound typically.
FIG. 9 is a view showing an example of a temperature rise profile when an additive or a non-reducing compound and a sealant are reacted in the present invention.
[Explanation of symbols]
1, 21, 41, 51 Compound semiconductor single crystal growth apparatus
2,22 Airtight container
3, 23 Container (susceptor)
4 Pulling shaft (upper shaft)
4e Lower tip
5 Container drive means
6, 26a-26e Heater
7, 27 Thermal insulation
8, 28 Crucible
9, 29 Lower shaft
10, 30 seed crystals
11, 31 Raw material melt
12, 32 Compound semiconductor single crystal
13, 33 dopant
14, 34 Compound raw materials
15, 35 Sealant
16, 36 Molten sealant
51, 71 Additives or non-reducing compounds

Claims (10)

In the crucible, a compound raw material having a first melting point, a dopant for doping the compound raw material, and a first lower melting point than the first melting point disposed so as to be separated from the dopant through the compound raw material Containing a sealant having a melting point of 2 and an additive made of the same material as the dopant arranged so as to be separated from the dopant via the compound raw material;
The crucible containing the compound raw material, dopant, sealant and additive is heated to a temperature not lower than the second melting point and lower than the first melting point to melt the sealant, and the compound While maintaining the state where the melted sealant is separated from the dopant via the raw material, the reaction is performed by generating a reaction product by bringing the melted sealant into contact with the additive and reacting them. Forming a molten sealant containing an object;
The compound raw material, wherein the crucible is further heated to a temperature equal to or higher than the first melting point, the compound raw material is melted, and the surface thereof is sealed with a molten sealant containing the reactant. Producing a raw material melt containing the dopant;
Growing a compound semiconductor single crystal doped with the dopant using a seed crystal from the raw material melt. In the crucible, a compound raw material having a first melting point, a dopant for doping the compound raw material, and a first lower melting point than the first melting point disposed so as to be separated from the dopant through the compound raw material Containing a sealing agent having a melting point of 2 and a non-reducing compound containing the dopant as a constituent element arranged to be separated from the dopant via the compound raw material;
The crucible containing the compound raw material, dopant, sealant and non-reducing compound is heated to a temperature not lower than the second melting point and lower than the first melting point to melt the sealant, While maintaining the state where the molten sealant is separated from the dopant via the compound raw material, the molten sealant is brought into contact with the non-reducing compound to bring the non-reducing compound into contact with the non-reduced compound. Forming a molten sealant containing the non-reducing compound by dispersing and mixing the reducing compound;
The compound, wherein the crucible is further heated to a temperature equal to or higher than the first melting point, the compound raw material is melted, and the surface thereof is sealed with a molten sealant containing the non-reducing compound. Producing a raw material melt containing the raw material and the dopant;
Growing a compound semiconductor single crystal doped with the dopant using a seed crystal from the raw material melt. A compound raw material having a first melting point, a dopant for doping the compound raw material, and a second melting point lower than the first melting point arranged to be separated from the dopant via the compound raw material A sealing agent having an inner surface contained in a crucible made of a non-reducing compound containing the dopant as a constituent element;
The crucible containing the compound raw material, dopant and sealant is heated to a temperature not lower than the second melting point and lower than the first melting point to melt the sealant, and through the compound raw material. While maintaining the state where the molten sealant is separated from the dopant, the molten sealant and the inner surface of the crucible made of the non-reducing compound are brought into contact with the molten sealant to the molten sealant. Forming a molten sealant containing the non-reducing compound by dispersing and mixing the non-reducing compound;
The compound, wherein the crucible is further heated to a temperature equal to or higher than the first melting point, the compound raw material is melted, and the surface thereof is sealed with a molten sealant containing the non-reducing compound. Producing a raw material melt containing the raw material and the dopant;
Growing a compound semiconductor single crystal doped with the dopant using a seed crystal from the raw material melt. The method for growing a compound semiconductor single crystal according to claim 2 or 3, wherein the non-reducing compound is silicon oxide . The method for growing a compound semiconductor single crystal according to claim 1, wherein a groove is formed in the compound raw material, and the dopant is accommodated therein . The method for growing a compound semiconductor single crystal according to claim 1, wherein the compound raw material contains the dopant . The method for growing a compound semiconductor single crystal according to claim 1, wherein the compound raw material is GaAs and the dopant is Si . The method for growing a compound semiconductor single crystal according to claim 1, wherein the sealant is boron oxide . The method for growing a compound semiconductor single crystal according to claim 8, wherein the water concentration of the boron oxide is 300 ppm or less . The crucible containing the compound raw material, dopant, sealant and additive or non-reducing compound is heated and heated under vacuum or reduced pressure, according to any one of claims 1 to 9. Method for growing a compound semiconductor single crystal .

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