JP2005015290A

JP2005015290A - Method for manufacturing single crystal, and single crystal

Info

Publication number: JP2005015290A
Application number: JP2003183833A
Authority: JP
Inventors: Makoto Iida; 誠飯田; Masahiro Sakurada; 昌弘櫻田; Nobuaki Mitamura; 伸晃三田村
Original assignee: Shin Etsu Handotai Co Ltd
Current assignee: Shin Etsu Handotai Co Ltd
Priority date: 2003-06-27
Filing date: 2003-06-27
Publication date: 2005-01-20

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a single crystal, in which the single crystal having a desired defect area can be efficiently manufactured in a short time at a high yield by controlling the ratio V/G by controlling change of the crystal temperature gradient G during pulling the single crystal without reducing the pulling speed V when the single crystal is grown by a Czochralski (CZ) method. <P>SOLUTION: In the method for manufacturing the single crystal by pulling it from a raw material melt in a chamber by the CZ method, when the pulling speed at the time of growing the constant diameter part of the single crystal is expressed as V (mm/min) and the crystal temperature gradient in the pulling-axis direction in the vicinity of the solid-liquid interface is expressed as G (°C/mm) when growing the single crystal, the ratio V/G (mm<SP>2</SP>/°C×min) of the pulling speed V to the crystal temperature gradient G is controlled by controlling the crystal temperature gradient G by changing the interval between the surface of the raw material melt and a heat-shielding member arranged oppositely to the surface of the melt so that the single crystal having the desired defect area can be grown. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、チョクラルスキー法による単結晶の製造方法に関し、特に所望の欠陥領域を有する単結晶を製造する方法に関する。
【０００２】
【従来の技術】
半導体デバイスの基板として用いられる単結晶には、例えばシリコン単結晶等があり、主にチョクラルスキー法（ＣｚｏｃｈｒａｌｓｋｉＭｅｔｈｏｄ、以下ＣＺ法と略称する）により製造されている。近年、半導体デバイスでは高集積化が促進され、素子の微細化が進んでいる。それに伴い、単結晶の結晶成長中に導入されるグローンイン（Ｇｒｏｗｎ−ｉｎ）欠陥の問題がより重要となっている。
【０００３】
ここで、グローンイン欠陥について図５を参照しながら説明する。
一般に、シリコン単結晶を成長させるときに、結晶成長速度Ｖ（結晶引上げ速度）が比較的高速の場合には、空孔型の点欠陥が集合したボイド起因とされているＦＰＤ（ＦｌｏｗＰａｔｔｅｒｎＤｅｆｅｃｔ）やＣＯＰ（ＣｒｙｓｔａｌＯｒｉｇｉｎａｔｅｄＰａｒｔｉｃｌｅ）等のグローンイン欠陥が結晶径方向全域に高密度に存在する。これらのボイド起因の欠陥が存在する領域はＶ（Ｖａｃａｎｃｙ）領域と呼ばれている。
【０００４】
また、結晶成長速度を低くしていくと成長速度の低下に伴いＯＳＦ（酸化誘起積層欠陥、ＯｘｉｄａｔｉｏｎＩｎｄｕｃｅｄＳｔａｃｋｉｎｇＦａｕｌｔ）領域が結晶の周辺からリング状に発生し、さらに成長速度を低速にすると、ＯＳＦリングがウエーハの中心に収縮して消滅する。一方、さらに成長速度を低速にすると格子間シリコンが集合した転位ループ起因と考えられているＬＳＥＰＤ（ＬａｒｇｅＳｅｃｃｏＥｔｃｈＰｉｔＤｅｆｅｃｔ）、ＬＦＰＤ（ＬａｒｇｅＦｌｏｗＰａｔｔｅｒｎＤｅｆｅｃｔ）等の欠陥が低密度に存在し、これらの欠陥が存在する領域はＩ（Ｉｎｔｅｒｓｔｉｔｉａｌ）領域と呼ばれている。
【０００５】
近年、Ｖ領域とＩ領域の中間でＯＳＦリングの外側に、ボイド起因のＦＰＤ、ＣＯＰ等の欠陥も、格子間シリコン起因のＬＳＥＰＤ、ＬＦＰＤ等の欠陥も存在しない領域の存在が発見されている。この領域はＮ（ニュートラル、Ｎｅｕｔｒａｌ）領域と呼ばれる。また、このＮ領域をさらに分類すると、ＯＳＦリングの外側に隣接するＮｖ領域（空孔の多い領域）とＩ領域に隣接するＮｉ領域（格子間シリコンが多い領域）とがあり、Ｎｖ領域では、熱酸化処理をした際に酸素析出量が多く、Ｎｉ領域では酸素析出が殆ど無いことがわかっている。
【０００６】
さらに、熱酸化処理後、酸素析出が発生し易いＮｖ領域の一部に、Ｃｕデポジション処理で検出される欠陥が著しく発生する領域（以下、Ｃｕデポ欠陥領域という）があることが見出されており、これは酸化膜耐圧特性のような電気特性を劣化させる原因になることがわかっている。
【０００７】
これらのグローンイン欠陥は、単結晶を成長させるときの引上げ速度Ｖ（ｍｍ／ｍｉｎ）と固液界面近傍のシリコンの融点から１４００℃の間の引上げ軸方向の結晶温度勾配Ｇ（℃／ｍｍ）の比であるＶ／Ｇ（ｍｍ^２／℃・ｍｉｎ）というパラメーターにより、その導入量が決定されると考えられている（例えば、非特許文献１参照）。すなわち、Ｖ／Ｇを所定の値で一定に制御しながら単結晶の育成を行うことにより、所望の欠陥領域あるいは所望の無欠陥領域を有する単結晶を製造することが可能となる。
【０００８】
例えば特許文献１では、シリコン単結晶を育成する際に、結晶中心でＶ／Ｇ値を所定の範囲内（例えば、０．１１２〜０．１４２ｍｍ^２／℃・ｍｉｎ）に制御して単結晶を引上げることによって、ボイド起因の欠陥及び転位ループ起因の欠陥が存在しないシリコン単結晶ウエーハを得ることができることが示されている。また、近年では、Ｃｕデポ欠陥領域を含まないＮ領域の無欠陥結晶に対する要求が高まりつつあり、Ｖ／Ｇを所望の無欠陥領域に高精度に制御しながら単結晶を引上げる単結晶の製造が要求されてきている。
【０００９】
一般的に、引上げ軸方向の結晶温度勾配Ｇは、単結晶の育成が行われる単結晶引上げ装置のＨＺ（ホットゾーン：炉内構造）により一義的に決まるものとされていた。しかしながら、単結晶引上げ中にＨＺを変更することは極めて困難であることから、上記のようにＶ／Ｇを制御して単結晶の育成を行う場合、結晶温度勾配Ｇを単結晶引上げ中に制御することは行われず、引上げ速度Ｖを調節することによってＶ／Ｇ値を制御して所望の欠陥領域を有する単結晶を製造することが行われている。
【００１０】
また、一般に結晶温度勾配Ｇは単結晶の成長が進むにつれて低下する傾向にあることが知られており、単結晶直胴部の成長開始時より成長終了時の方が小さくなる。したがって、Ｖ／Ｇを所望の値でほぼ一定に制御するためには、単結晶の成長が進むにつれて、引上げ速度Ｖを結晶温度勾配Ｇの変化（低下）に合わせて低速となるように変更していかなければならず、その結果、単結晶直胴部の育成にかかる時間が長くなるため生産性が低下するという問題が生じていた。
【００１１】
さらに、単結晶直胴部の成長終了時における引上げ速度は、その後単結晶尾部を形成するために行う丸め工程での単結晶の引上げ速度及び引上げ時間に影響を与えている。そのため、上記のように直胴部成長終了時の引上げ速度が低速になると、丸め工程における引上げ速度も低速化して引上げ時間をさらに長引かせてしまうため、単結晶製造における生産性を著しく低下させて製造コストの上昇を招くといった問題があった。
【００１２】
加えて、従来の単結晶の製造においては、単結晶の引上げ速度は、育成する単結晶の直径を制御するパラメーターの一つとしても使用されている。そのため、上記のように所望の欠陥領域で単結晶を育成する場合は、引上げ速度を調節することによりＶ／Ｇの制御を行うと同時に単結晶の直径制御も行わなければならない。したがって、例えば単結晶の引上げ中にＶ／Ｇの制御と単結晶の直径制御を行う際に、それぞれの制御で互いに異なる条件で引上げ速度を変更したい場合ではどちらか一方の制御しか行うことができず、その結果、単結晶引上げ中に単結晶直径が大きく変動したり、または欠陥領域等の結晶品質が所望領域から外れてしまい、歩留まりの著しい低下を招いていた。
【００１３】
【特許文献１】
特開平１１−１４７７８６号公報
【非特許文献１】
Ｖ．Ｖ．Ｖｏｒｏｎｋｏｖ，ＪｏｕｒｎａｌｏｆＣｒｙｓｔａｌ
Ｇｒｏｗｔｈ，５９（１９８２），６２５〜６４３
【００１４】
【発明が解決しようとする課題】
そこで、本発明は上記問題点に鑑みてなされたものであって、本発明の目的は、ＣＺ法により単結晶を育成する際に、引上げ速度Ｖを低速化させずに結晶引上げ中の結晶温度勾配Ｇの変化を制御することによりＶ／Ｇを制御して、所望の欠陥領域を有する単結晶を短時間で効率的に、かつ高い歩留まりで製造することのできる単結晶の製造方法を提供することにある。
【００１５】
【課題を解決するための手段】
上記目的を達成するために、本発明によれば、チョクラルスキー法によってチャンバ内で単結晶を原料融液から引上げて製造する方法において、前記単結晶を育成する際に、前記単結晶の直胴部を成長させるときの引上げ速度をＶ（ｍｍ／ｍｉｎ）、固液界面近傍の引上げ軸方向の結晶温度勾配をＧ（℃／ｍｍ）で表したとき、該結晶温度勾配Ｇを前記原料融液の融液面と前記チャンバ内で原料融液面に対向配置された遮熱部材との距離を変更することにより制御して、引上げ速度Ｖと結晶温度勾配Ｇの比Ｖ／Ｇ（ｍｍ^２／℃・ｍｉｎ）を所望の欠陥領域を有する単結晶が育成できるように制御することを特徴とする単結晶の製造方法が提供される（請求項１）。
【００１６】
このように、ＣＺ法によって単結晶を育成する際に、原料融液面と遮熱部材間の距離を変更することによって結晶温度勾配Ｇを制御することができ、それによって、引上げ速度Ｖを低速化させずにＶ／Ｇを制御することが可能となり、所望の欠陥領域を有する単結晶を短時間で効率的に製造することができる。そして、このように単結晶を効率的に製造することができれば、単結晶の製造における生産性を向上させて、コストの低減を図ることができる。さらに、このように融液面と遮熱部材間の距離を変更することによってＶ／Ｇを制御すれば、Ｖ／Ｇの制御を高精度で行うと同時に引上げ速度による単結晶の直径制御も高精度に安定して行うことが可能となるので、所望の結晶品質及び結晶直径を有する高品質の単結晶を高い歩留まりで安定して製造することができる。
【００１７】
このとき、前記引上げ速度Ｖを一定の値にして単結晶の引上げを行うことができる（請求項２）。
本発明の単結晶の製造方法によれば、上記のように融液面と遮熱部材間の距離を変更して結晶温度勾配Ｇを制御できるので、引上げ速度Ｖを一定の値にして単結晶の引上げを行っても、Ｖ／Ｇを所望欠陥領域の単結晶が育成できるように容易に制御することができる。したがって、引上げ速度Ｖを高速で一定に保ったまま、結晶成長軸方向で同じ欠陥領域を有する単結晶を容易に引上げることができる。尚、本発明で言う引上げ速度Ｖを一定の値にするとは、単結晶直胴部の各結晶部位におけるそれぞれの平均引上げ速度を一定にすることを意味するものであり、単結晶の各結晶部位における平均引上げ速度が一定の値となれば、単結晶の直径を所定値に精度良く制御するために、各結晶部位で平均引上げ速度に対して所定範囲内でＶを変動させることができるものである。
【００１８】
この場合、前記Ｖ／Ｇを、前記育成する単結晶の欠陥領域が径方向の全面にわたってＮ領域となるように制御することが好ましい（請求項３）。
このように、Ｖ／Ｇを単結晶の欠陥領域が径方向全面でＮ領域となるように制御することによって、ＦＰＤやＣＯＰ等のボイド起因の欠陥も、またＬＳＥＰＤ、ＬＦＰＤ等の転位ループ起因の欠陥も存在しない非常に高品質の単結晶を高生産性、高歩留まりで製造することができる。
【００１９】
また、本発明では、前記原料融液面と遮熱部材との距離を、予め試験を行って求めた変更条件に従って自動的に変更することが好ましい（請求項４）。
このように、融液面と遮熱部材間の距離を変更して結晶温度勾配Ｇを制御する際に、実際に単結晶の製造が行われる製造環境での融液面から遮熱部材までの距離と結晶温度勾配Ｇとの関係を予めシミュレーション解析、あるいは実生産等の試験を行って明らかにし、そこで得られた情報を基に融液面と遮熱部材間の距離を変更する変更条件を求めておく。そして、その求めた変更条件に従って単結晶引上げ中に融液面と遮熱部材間の距離を自動的に変更することによって、結晶温度勾配Ｇを高精度に自動制御することが可能となり、所望の欠陥領域を有する単結晶を安定して製造することができる。
【００２０】
さらに、前記原料融液面と遮熱部材との距離を変更する変更条件を、単結晶の製造バッチ間で調節することが好ましい（請求項５）。
通常、単結晶の製造を複数バッチ繰り返して行うと、単結晶引上げ装置でＨＺを構成するパーツの劣化等の原因により、単結晶の製造バッチ間で製造環境が変化してしまう場合がある。しかしながら、本発明のように融液面と遮熱部材間の距離を変更する変更条件を単結晶の製造バッチ間で調節することによって、製造環境の変化を補正することが可能となり、単結晶の製造を複数バッチ繰り返し行っても製造バッチ間で品質のバラツキが生じずに非常に安定して単結晶の製造を行うことができる。
【００２１】
この場合、前記製造する単結晶をシリコン単結晶とすることができる（請求項６）。
このように、本発明の単結晶の製造方法は、シリコン単結晶を製造する場合に特に好適に用いることができ、それにより、引上げ速度Ｖを低速化させずにＶ／Ｇを制御して、所望の欠陥領域を有するシリコン単結晶を短時間で効率的に、また高い歩留まりで製造することができる。
【００２２】
そして、本発明によれば、前記単結晶の製造方法により製造された単結晶が提供される（請求項７）。
本発明により製造された単結晶は、所望の欠陥領域を有し、結晶直径も均一な非常に高品質の単結晶とすることができる。さらに、本発明の単結晶は、短時間で効率的にまた高歩留まりで製造されたものであるので、従来に比べて安価なものとなる。
【００２３】
さらに、本発明によれば、チョクラルスキー法により原料融液から単結晶を引き上げる際に使用する単結晶引上げ装置であって、少なくとも、前記原料融液を収容するルツボと、該ルツボを昇降させるルツボ駆動機構と、前記原料融液を加熱するヒーターと、前記単結晶を回転させながら引上げる引上げ機構と、前記原料融液の融液面に対向配置された遮熱部材と、該遮熱部材の位置を上下に調節できる遮熱部材駆動手段と、前記ルツボ駆動機構及び／または遮熱部材駆動手段を調節してルツボの位置及び／または遮熱部材の位置を変える駆動制御手段とを具備することを特徴とする単結晶引上げ装置が提供される（請求項８）。
【００２４】
このような構成を有する単結晶引上げ装置であれば、原料融液面と遮熱部材との距離を容易に変更することができるようになり、単結晶引上げ中に結晶温度勾配Ｇを制御して引上げ速度Ｖを低速化させずにＶ／Ｇを所望欠陥領域を有する単結晶が育成できるように制御できる単結晶引上げ装置とすることができる。
【００２５】
【発明の実施の形態】
以下、本発明について実施の形態を説明するが、本発明はこれらに限定されるものではない。
本発明者等は、所望の欠陥領域を有する単結晶を短時間で効率的に製造する方法について鋭意実験及び検討を重ねた結果、単結晶を育成する際の原料融液の融液面とチャンバ内に原料融液面と対向するように設けられた遮熱部材との距離に注目した。
【００２６】
従来のＣＺ法による単結晶の育成では、所望の欠陥領域を有する単結晶を安定して引上げるために、単結晶引上げ中に原料融液の減少に伴いルツボを徐々に上昇させることによって原料融液の融液面を一定の高さに維持しながら引上げ速度Ｖを徐々に低速化させて育成を行っていた。また、原料融液面に対向するように設置されている遮熱部材は単結晶引上げ装置のチャンバ内で固定されていたため、単結晶の育成中に遮熱部材の位置を変化させることはなかった。そのため、従来では、単結晶を育成する際に原料融液面と遮熱部材間の距離が変化することはなく、むしろ一定の大きさとなるように維持されていた。
【００２７】
しかしながら、本発明者等は、この原料融液面と遮熱部材間の距離を単結晶引上げ中に故意に変化させることによって固液界面近傍のシリコンの融点から１４００℃の間の引上げ軸方向の結晶温度勾配Ｇを制御できること、またそれによって単結晶引上げ中に引上げ速度Ｖを低速に変更させずにＶ／Ｇの制御が可能であることを見出した。
【００２８】
ここで、総合伝熱解析ソフトＦＥＭＡＧ（Ｆ．Ｄｕｐｒｅｔ，Ｐ．Ｎｉｃｏｄｅｍｅ，Ｙ．Ｒｙｃｋｍａｎｓ，Ｐ．Ｗｏｕｔｅｒｓ，ａｎｄＭ．Ｊ．Ｃｒｏｃｈｅｔ，Ｉｎｔ．Ｊ．ＨｅａｔＭａｓｓＴｒａｎｓｆｅｒ，３３，１８４９（１９９０））を用いて、単結晶の引上げ中に原料融液の融液面とチャンバ内に設けた遮熱部材間の距離Ｌを変化させたときの引上げ軸方向の結晶温度勾配Ｇの変化についてシミュレーション解析した結果の一例を図１に示す。
【００２９】
図１に示したように、シミュレーション解析の結果、原料融液面と遮熱部材間の距離Ｌを変化させることによって結晶温度勾配Ｇが変化することが明らかとなり、例えば単結晶引上げ中に原料融液面と遮熱部材間の距離Ｌを増大させれば、結晶温度勾配Ｇを小さくすることができ、また一方上記距離Ｌを減少させれば結晶温度勾配Ｇを大きくできることがわかった。
【００３０】
本発明は、このような単結晶引上げ中の原料融液面と遮熱部材間の距離Ｌと結晶温度勾配Ｇとの関係を利用したものである。
すなわち、本発明の単結晶の製造方法は、ＣＺ法によって単結晶を育成する際に、結晶温度勾配Ｇが小さくなるような領域では原料融液面と遮熱部材間の距離Ｌを減少させるように変更し、また逆に結晶温度勾配Ｇが大きくなるような領域では原料融液面と遮熱部材間の距離Ｌを増大させるように変更して単結晶の成長を行うことにより結晶温度勾配Ｇを制御して、所望の欠陥領域を有する単結晶が育成できるようにＶ／Ｇを所望値に制御することに特徴を有するものである。
【００３１】
以下、本発明の単結晶の製造方法について図面を参照しながら詳細に説明するが、本発明はこれに限定されるものではない。
本発明の単結晶の製造方法で用いられる単結晶引上げ装置は、単結晶の引上げ中に原料融液の融液面とチャンバ内で原料融液面に対向して配置された遮熱部材間の距離Ｌの大きさを変更できるものであれば特に限定されないが、例えば図４に示すような単結晶引上げ装置を用いることができる。先ず、図４を参照しながら、本発明の単結晶の製造方法を実施する際に使用することのできる単結晶引上げ装置について説明する。
【００３２】
図４に示した単結晶引上げ装置２０は、メインチャンバ１内に、原料融液４を収容する石英ルツボ５と、この石英ルツボ５を保護する黒鉛ルツボ６とがルツボ駆動機構２１によって回転・昇降自在に保持軸１３で支持されており、またこれらのルツボ５、６を取り囲むようにして原料融液を加熱するための加熱ヒーター７と断熱材８が配置されている。メインチャンバ１の上部には育成した単結晶３を収容し、取り出すための引上げチャンバ２が連接されており、引上げチャンバ２の上部には単結晶３をワイヤー１４で回転させながら引上げる引上げ機構１７が設けられている。
【００３３】
さらに、メインチャンバ１の内部にはガス整流筒１１が設けられており、このガス整流筒１１の下部には原料融液４と対向するように遮熱部材１２を設置して、原料融液４の表面からの輻射をカットするとともに原料融液４の表面を保温するようにしている。また、ガス整流筒１１の上部には、ガス整流筒１１を昇降させて遮熱部材１２の位置を上下に調節できる遮熱部材駆動手段２２が設置されている。尚、本発明において、遮熱部材１２の形状や材質等は特に限定されるものではなく、必要に応じて適宜変更することができる。さらに、本発明の遮熱部材１２は、融液面に対向配置されたものであれば良く、必ずしも上記のようにガス整流筒の下部に設置されているものに限定されない。
【００３４】
また、引上げチャンバ２の上部に設けられたガス導入口１０からはアルゴンガス等の不活性ガスを導入でき、引上げ中の単結晶３とガス整流筒１１との間を通過させた後、遮熱部材１２と原料融液４の融液面との間を通過させ、ガス流出口９から排出することができる。
【００３５】
さらに、上記のルツボ駆動機構２１及び遮熱部材駆動手段２２はそれぞれ駆動制御手段１８に接続されている。そして、例えばこの駆動制御手段１８に、ルツボ５、６の位置、遮熱部材１２の位置、ＣＣＤカメラ１９で測定した原料融液４の融液面の位置、引上げ機構１７から得られる単結晶の引上げ長さ等の情報がフィードバックされることにより、駆動制御手段１８で例えば単結晶の引上げ長さ等に応じてルツボ駆動機構２１及び／または遮熱部材駆動手段２２を調節してルツボ５、６の位置及び／または遮熱部材１２の位置を変えることができ、それによって、原料融液４の融液面と遮熱部材１２間の距離Ｌを変更することができるようになっている。
【００３６】
このような単結晶引上げ装置２０を用いて、ＣＺ法により例えばシリコン単結晶を育成する場合、種ホルダー１５に固定された種結晶１６を石英ルツボ５中の原料融液４に浸漬し、その後回転させながら静かに引上げて種絞りを形成した後所望の直径まで拡径し、略円柱形状の直胴部を有するシリコン単結晶３を成長させることができる。
【００３７】
本発明は、このようにしてシリコン単結晶３を育成する際に、石英ルツボ５中の原料融液４の融液面と遮熱部材１２の下端との距離Ｌを変更することにより固液界面近傍の引上げ軸方向の結晶温度勾配Ｇを制御することができ、それによって、引上げ速度Ｖを低速化させずに一定の値に維持しながらＶ／Ｇを制御して、所望の欠陥領域を有する単結晶を短時間で効率的に育成することができるものである。
【００３８】
具体的に説明すると、例えばシリコン単結晶を欠陥領域が径方向の全面にわたってＮ領域となるように育成する場合、単結晶の直胴部をＮ領域で育成できるように引上げ速度Ｖを単結晶の製造が行われる製造環境（例えば、単結晶引上げ装置のＨＺ等）に応じて設定する。このとき、引上げ速度Ｖは、単結晶をＮ領域で育成できる範囲の最大値に設定することができる。
【００３９】
そして、このように設定した引上げ速度Ｖで単結晶直胴部を育成するときに、そのまま直胴部を引上げた場合に結晶温度勾配Ｇが小さくなる領域では原料融液面と遮熱部材１２間の距離Ｌを減少させるように変更し、また逆に結晶温度勾配Ｇが大きくなる領域では上記距離Ｌが増大するように変更して単結晶の育成を行うことによって、単結晶引上げ中に結晶温度勾配Ｇを制御することができ、引上げ速度Ｖに依らずにＶ／Ｇを所定値（Ｎ領域）に制御することが可能となる。
【００４０】
このとき、原料融液面と遮熱部材１２間の距離Ｌは、ルツボ駆動機構２１で石英ルツボ５及び黒鉛ルツボ６を結晶成長による融液面低下分を考慮して押し上げることによって原料融液面の高さを結晶成長軸方向で上下に調節したり、また遮熱部材駆動手段２２でガス整流筒１１を昇降させて遮熱部材１２の位置を調節したり、さらに原料融液面の高さと遮熱部材１２の位置を同時に調節することによって、容易にまた高精度で変更させることができる。
【００４１】
すなわち、例えば原料融液面と遮熱部材１２間の距離Ｌを減少させるように変更する場合であれば、ルツボ駆動機構２１でルツボ５、６を結晶成長による融液面低下分より大きく押し上げることによって原料融液面の高さを上昇させたり、及び／または、遮熱部材駆動手段２２でガス整流筒１１を下降させて遮熱部材１２の位置を下方に移動させたりすれば良い。また一方、距離Ｌを増大させるように変更する場合は、ルツボ駆動機構２１で結晶成長による融液面低下分より小さくルツボ５、６を押し上げることによって融液面の高さを下降させたり、及び／または、遮熱部材駆動手段２２で遮熱部材１２の位置を上方に移動させたりすれば良い。
【００４２】
この場合、単結晶引上げ中に変更する原料融液面と遮熱部材１２間の距離Ｌの制御範囲は、実際に製造が行われる製造環境、例えばＨＺの構造等に応じて適宜設定することができ、特に限定されるものではないが、例えば単結晶育成中に融液面と遮熱部材１２間の距離Ｌが余りに小さ過ぎたり、また大き過ぎたりすると、結晶温度勾配Ｇの結晶径方向における面内分布ΔＧが不均一となってしまったり、効果が小さくなったりして、単結晶を結晶径方向全面が所望欠陥領域となるように育成することが困難となることが有り得る。
【００４３】
したがって、原料融液面と遮熱部材間の距離Ｌは、引上げる単結晶の直径の大きさや単結晶製造を行う製造環境にもよるが、単結晶引上げ中に１〜５００ｍｍの範囲で、好ましくは１０〜３００ｍｍ、さらに好ましくは２０〜２００ｍｍの範囲で制御・変更することが望ましい。このような範囲で原料融液面と遮熱部材間の距離Ｌを制御・変更すれば、Ｖ／Ｇを非常に高精度に安定して制御できるとともに、単結晶引上げ中に結晶温度勾配Ｇの面内分布を均一にすることができ、単結晶を結晶成長軸方向の全域に渡って径方向全面が所望欠陥領域となるように安定して育成することができる。
【００４４】
このように、本発明によれば、単結晶引上げ中に原料融液面と遮熱部材間の距離Ｌを変更して結晶温度勾配Ｇを制御することにより、引上げ速度Ｖを従来のように低速化させることなく所定の値以上に、特にはその欠陥領域となる最大引上げ速度で一定に維持したまま、所望の欠陥領域、例えばＮ領域を有する単結晶が得られるようにＶ／Ｇを容易に制御することができる。もちろん、本発明は融液面と遮熱部材間の距離Ｌを変化させることにより結晶温度勾配Ｇを制御し、所望欠陥領域内で単結晶を成長させるのであれば、引上げ速度Ｖは必ずしも一定の値にする必要はないが、上記のように所望欠陥領域となる引上げ速度の最大値で一定になるようにすれば、単結晶の生産性を大幅に向上させることができる。
【００４５】
すなわち、本発明の単結晶の製造方法は、単結晶直胴部を引上げる際の平均結晶引上げ速度を向上できるので、従来よりも単結晶直胴部の育成を短時間で行うことができるし、さらに単結晶直胴部の成長終了時の引上げ速度が低速にならないので、その後の丸め工程における引上げ時間も短縮することができるため、結晶径方向の全面がＮ領域となる非常に高品質のシリコン単結晶を高い生産性で製造することができる。また、製造時間が短縮されることにより、結晶が有転位化する可能性も低減し、生産性だけでなく、歩留りをも向上させることができる。その結果、単結晶の生産性が向上して大幅なコストダウンを図ることができ、非常に安価に単結晶を提供することができる。
【００４６】
また、本発明は、上記のように引上げ速度Ｖに依らずにＶ／Ｇを所定値に制御できるため、融液面と遮熱部材間の距離Ｌを変更してＶ／Ｇの制御を高精度で行うと同時に平均引上げ速度を例えば一定にすることにより単結晶の直径を安定して制御することが可能となる。したがって、結晶成長軸方向で単結晶の直径のバラツキを低減して不良の発生を防止することができ、所望の結晶品質及び均一な結晶直径を有する非常に高品質の単結晶を高歩留まりで製造することができる。
【００４７】
さらに、単結晶を育成する際に本発明のようにして結晶温度勾配Ｇを制御することによって、Ｖ／Ｇの制御性を向上させることができる。そのため、例えば図５に示すような、Ｃｕデポ欠陥領域を含まないＮ領域中のＮｖ領域やＮｉ領域といった狭い領域にＶ／Ｇを高精度に制御して単結晶を製造することが可能となり、所望の欠陥領域を結晶成長軸方向の全域に渡って有する高品質の単結晶を非常に安定して得ることができる。
【００４８】
また、このような本発明の単結晶の製造方法では、予め、単結晶の製造を行う製造環境において結晶温度勾配Ｇの状態や結晶温度勾配Ｇと融液面から遮熱部材までの距離Ｌとの関係等を例えばシミュレーション解析、あるいは実測等の試験を行って調べておくことによって、単結晶引上げ中に融液面と遮熱部材間の距離Ｌを変更させる変更条件を詳細に求めることができる。
【００４９】
そして、このようにして予め求めた距離Ｌの変更条件を図４に示した駆動制御手段１８に入力しておき、単結晶を育成する際に例えばルツボ５、６の位置、遮熱部材１２の位置、ＣＣＤカメラ１９で測定した原料融液４の融液面の位置、引上げ機構１７から得られる単結晶の引上げ長さ等の情報が駆動制御手段１８にフィードバックされることにより、変更条件に従って駆動制御手段１８でルツボ駆動機構２１及び／または遮熱部材駆動手段２２を調節してルツボ５、６の位置及び／または遮熱部材１２の位置を変えることができ、それによって、原料融液面と遮熱部材間の距離Ｌを単結晶の引上げ長さ等に応じて自動的に変更して結晶温度勾配Ｇを高精度に制御することができる。したがって、Ｖ／Ｇの制御を自動で高精度に行うことが可能となり、所望の欠陥領域を有する単結晶の製造を容易に安定して行うことができる。
【００５０】
さらに、本発明の単結晶の製造方法において、ＣＺ法により単結晶を複数バッチ連続して製造する場合、原料融液面と遮熱部材間の距離Ｌを変更する変更条件を単結晶の製造バッチ間で調節することが好ましい。
通常、単結晶の製造を複数バッチ繰り返して行うと、単結晶引上げ装置でＨＺを構成するパーツの劣化等の原因により、単結晶の製造バッチ間でＨＺ等の製造環境が変化してしまうことがある。特に、ＨＺのパーツは黒鉛製のものが多く用いられ、その中でもヒーターは通常黒鉛ヒーターであることが多く、使用により徐々に温度分布が変化する。そして、このように単結晶の製造バッチ間で製造環境が変化すると、結晶温度勾配Ｇも製造バッチ間で変化することになる。
【００５１】
したがって、単結晶を複数バッチ製造する場合、上記のように原料融液面と遮熱部材間の距離Ｌの変更条件を単結晶の製造バッチ間で製造環境の変化等に応じて調節することによって、製造環境の変化を補正することが可能となり、製造バッチ間で品質のバラツキを生じさせずに高品質の単結晶を非常に安定して製造することができる。具体的には、前バッチにおける融液面と遮熱部材間の距離Ｌと欠陥分布の関係をフィードバックして、次バッチ以降の製造条件を調整すれば良い。
【００５２】
【実施例】
以下、実施例及び比較例を示して本発明をより具体的に説明するが、本発明はこれらに限定されるものではない。
（実施例）
図４に示した単結晶引上げ装置２０を用いて、直径２４インチ（６００ｍｍ）の石英ルツボに原料多結晶シリコンを１５０ｋｇチャージし、ＣＺ法により、方位＜１００＞、直径２００ｍｍ、酸素濃度が２２〜２３ｐｐｍａ（ＡＳＴＭ’７９）となるシリコン単結晶を育成した（単結晶直胴部の長さは約１４０ｃｍ）。
【００５３】
このとき、単結晶引上げ中の引上げ条件については、予めシミュレーション解析を行って結晶温度勾配Ｇを調べておき、その解析の結果に基づいて、単結晶引上げ中に原料融液４の融液面と遮熱部材１２間の距離Ｌ及び引上げ速度が以下の表１に示した値となるように引上げ条件を制御して、Ｃｕデポジション欠陥が検出されないＮ領域で単結晶の育成を行った。具体的には、単結晶育成中にルツボ駆動機構２１でルツボ５、６を結晶成長による融液面低下分だけ上昇させて原料融液４の融液面を一定の高さにするとともに、遮熱部材駆動手段２２で遮熱部材１２の位置を融液面と遮熱部材間の距離Ｌが表１に示した値となるように単結晶引上げ長さに応じて調節した。また、単結晶の引上げ速度は単結晶直胴部の１０ｃｍ以降で一定の値となるように制御した。尚、直胴部０ｃｍでの引上げ速度が高速であるのは、拡径部から直胴部に入るためのいわゆる肩部の引上げであるためで、肩部を形成することで直胴部の引上げに移行し、１０ｃｍ以内に引上げ速度を安定化させることができる。
【００５４】
【表１】

【００５５】
次に、上記のようにして育成した単結晶の成長軸方向１０ｃｍ毎の部位から約２ｍｍ厚のウエーハを切り出した後、平面研削及び研磨を行って検査用のサンプルを作製し、以下に示すような結晶品質特性の検査を行った。
【００５６】
（１）ＦＰＤ（Ｖ領域）及びＬＳＥＰＤ（Ｉ領域）の検査
検査用のサンプルに３０分間のセコエッチングを無攪拌で施した後、ウエーハ面内を顕微鏡で観察することにより結晶欠陥の有無を確認した。
（２）ＯＳＦの検査
検査用のサンプルにウエット酸素雰囲気下、１１００℃で１００分間の熱処理を行った後、ウエーハ面内を顕微鏡で観察することによりＯＳＦの有無を確認した。
（３）Ｃｕデポジション処理による欠陥の検査
検査用のサンプルの表面に酸化膜を形成した後、Ｃｕデポジション処理を行って酸化膜欠陥の有無を確認した。その際の評価条件は以下の通りである。
酸化膜：２５ｎｍ
電解強度：６ＭＶ／ｃｍ
電圧印加時間：５分間
（４）酸化膜耐圧特性の検査
検査用のサンプルに乾燥雰囲気中で熱酸化処理を行って２５ｎｍのゲート酸化膜を形成し、その上に８ｍｍ^２の電極面積を有するリンをドープしたポリシリコン電極を形成した。そして、この酸化膜上に形成したポリシリコン電極に電圧を印加して酸化膜耐圧の評価を行った。このとき、判定電流は１ｍＡ／ｃｍ^２とした。
【００５７】
（比較例）
上記実施例と同様の単結晶引上げ装置２０を用いて、直径２４インチ（６００ｍｍ）の石英ルツボに原料多結晶シリコンを１５０ｋｇチャージし、ＣＺ法により、方位＜１００＞、直径２００ｍｍ、酸素濃度が２２〜２３ｐｐｍａ（ＡＳＴＭ’７９）となるシリコン単結晶を育成した（単結晶直胴部の長さは約１４０ｃｍ）。
【００５８】
このとき、単結晶引上げ中の引上げ条件については、単結晶育成中にルツボ駆動機構２１でルツボ５、６を結晶成長による融液面低下分だけ上昇させて原料融液４の融液面を一定の高さにするとともに、遮熱部材１２を所定の位置で保持することによって、融液面と遮熱部材間の距離Ｌが単結晶引上げ中に常に一定になるようにした。また、引上げ速度は、単結晶育成中に以下の表２に示した値となるように制御して、Ｃｕデポジション欠陥が検出されないＮ領域で単結晶の育成を行った。
そして、得られた単結晶の成長軸方向１０ｃｍ毎の部位から約２ｍｍ厚のウエーハを切り出した後、平面研削及び研磨を行って検査用のサンプルを作製し、実施例と同様の結晶品質特性の検査を行った。
【００５９】
【表２】

【００６０】
ここで、実施例及び比較例における単結晶の引上げ条件を比較するために、図２に、単結晶直胴部の結晶成長軸方向の長さと原料融液面と遮熱部材間の距離Ｌとの関係を表すグラフを示し、また図３に、直胴部の結晶成長軸方向の長さと引上げ速度との関係を表すグラフを示す。さらに、実施例及び比較例において単結晶直胴部を育成したときの直胴部１０ｃｍ以降の平均引上げ速度を計算して比較したところ、実施例の平均引上げ速度が比較例よりも０．０１４ｍｍ／ｍｉｎ程度大きかった。
【００６１】
また、上記のようにして実施例及び比較例で作製したシリコン単結晶にそれぞれ結晶品質特性の検査を行った結果、両シリコン単結晶とも単結晶直胴部１０ｃｍから直胴部終端までの領域において、ＦＰＤ、ＬＳＥＰＤ、ＯＳＦの何れの欠陥も検出されず、またＣｕデポジション処理による欠陥も観察されなかった。さらに酸化膜耐圧特性の評価では、酸化膜耐圧レベルは１００％の良品率であった。
【００６２】
一方、実施例及び比較例で得られたシリコン単結晶の直胴部形状を目視にて観察したところ、実施例のシリコン単結晶には結晶成長軸方向で直径のバラツキは見られず不良となる箇所は確認されなかったが、比較例のシリコン単結晶には直胴部の４０〜６０ｃｍの領域で結晶形状に変形が見られた。
【００６３】
以上の結果より、引上げ速度を一定の値にして単結晶を育成した実施例は、比較例と比べて、結晶品質が同等以上となるシリコン単結晶をより短い時間で効率的に製造できることがわかった。また、歩留まりの点においても、実施例のシリコン単結晶に不良箇所が観察されなかったことから、比較例に対して同等以上の高い歩留まりを達成できることが確認できた。
【００６４】
なお、本発明は、上記実施形態に限定されるものではない。上記実施形態は、例示であり、本発明の特許請求の範囲に記載された技術的思想と実質的に同一な構成を有し、同様な作用効果を奏するものは、いかなるものであっても本発明の技術的範囲に包含される。
【００６５】
例えば、上記実施の形態では単結晶をＮ領域で育成する場合を例に挙げて説明を行っているが、本発明はこれに限定されず、Ｖ領域またはＩ領域、あるいはＯＳＦ領域といった所望の欠陥領域で単結晶を育成することもできる。また、本発明は、シリコン単結晶を製造する場合に好適に用いることができるが、これに限定されるものではなく、化合物半導体単結晶等を製造する場合にも同様に適用することができる。
【００６６】
尚、本発明の単結晶の製造方法は、必ずしも単結晶直胴部の全長で実施する場合に限られず、一部の長さに渡って結晶温度勾配Ｇを原料融液面と遮熱部材間の距離を変更することによって制御し、所望の欠陥領域とする場合を含む。特に上記のように、直胴部の前半である肩部から１０ｃｍの領域は、引上げ速度や直径が安定しないことがあるので、これが定常状態となり易い直胴部の５ｃｍ以降あるいは１０ｃｍ以降で行うのが好ましい。
【００６７】
【発明の効果】
以上説明したように、本発明によれば、単結晶を引上げる際に原料融液の融液面とチャンバ内に設けられた遮熱部材との距離を変更することによって結晶温度勾配Ｇを制御することができ、それによって、引上げ速度Ｖに依らずにＶ／Ｇを高精度に制御することができる。したがって、引上げ速度Ｖを低速化させずに一定の値にして所望の欠陥領域を有する単結晶を育成することができ、従来よりも短時間で効率的な単結晶製造を行うことが可能となるし、また単結晶の直径のバラツキも低減できるので、単結晶の製造における生産性や歩留まりを向上させて大幅なコストダウンを図ることができる。
【図面の簡単な説明】
【図１】原料融液面と遮熱部材間の距離Ｌと結晶温度勾配Ｇとの関係の一例を示すグラフである。
【図２】実施例及び比較例において単結晶を育成するときの単結晶直胴部の成長軸方向の長さと原料融液面と遮熱部材間の距離Ｌとの関係を示したグラフである。
【図３】実施例及び比較例において単結晶を育成するときの単結晶直胴部の成長軸方向の長さと引上げ速度との関係を示したグラフである。
【図４】本発明の単結晶の製造方法を実施する際に使用することのできる単結晶引上げ装置の一例を説明する構成概略図である。
【図５】Ｖ／Ｇと結晶欠陥分布の関係を表す説明図である。
【符号の説明】
１…メインチャンバ、２…引上げチャンバ、
３…単結晶（シリコン単結晶）、４…原料融液、５…石英ルツボ、
６…黒鉛ルツボ、７…加熱ヒーター、８…断熱材、
９…ガス流出口、１０…ガス導入口、１１…ガス整流筒、
１２…遮熱部材、１３…保持軸、１４…ワイヤー、
１５…種ホルダー、１６…種結晶、１７…引上げ機構、
１８…駆動制御手段、１９…ＣＣＤカメラ、
２０…単結晶引上げ装置、２１…ルツボ駆動機構、
２２…遮熱部材駆動手段。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a single crystal by the Czochralski method, and more particularly to a method for producing a single crystal having a desired defect region.
[0002]
[Prior art]
As a single crystal used as a substrate of a semiconductor device, for example, there is a silicon single crystal or the like, and it is mainly manufactured by a Czochralski method (hereinafter abbreviated as CZ method). In recent years, high integration has been promoted in semiconductor devices, and miniaturization of elements has progressed. Accordingly, the problem of grown-in defects introduced during single crystal growth has become more important.
[0003]
Here, the grow-in defect will be described with reference to FIG.
In general, when a silicon single crystal is grown, if the crystal growth rate V (crystal pulling rate) is relatively high, FPD (Flow Pattern Defect), which is caused by voids in which hole-type point defects are gathered, is assumed. Grown-in defects such as COP (Crystal Originated Particle) and the like exist in high density throughout the crystal diameter direction. A region where defects due to these voids exist is called a V (vacancy) region.
[0004]
Further, when the crystal growth rate is lowered, an OSF (Oxidation Induced Stacking Fault) region is generated in a ring shape from the periphery of the crystal as the growth rate is lowered, and when the growth rate is further lowered, the OSF is reduced. The ring shrinks to the center of the wafer and disappears. On the other hand, when the growth rate is further reduced, defects such as LSEPD (Large Secco Etch Pit Defect) and LFPD (Large Flow Pattern Defect), which are considered to be caused by dislocation loops in which interstitial silicon has gathered, exist at low density. The region where the defect exists is called an I (Interstitial) region.
[0005]
In recent years, it has been discovered that there is an area outside the OSF ring between the V region and the I region, where there are no defects such as FPD and COP caused by voids and no defects such as LSEPD and LFPD caused by interstitial silicon. This region is called an N (neutral) region. Further, this N region is further classified into an Nv region (region with many vacancies) adjacent to the outside of the OSF ring and a Ni region (region with a lot of interstitial silicon) adjacent to the I region. In the Nv region, It is known that the amount of precipitated oxygen is large when the thermal oxidation treatment is performed, and there is almost no oxygen precipitation in the Ni region.
[0006]
Furthermore, after thermal oxidation treatment, it has been found that there is a region (hereinafter referred to as Cu deposition defect region) in which defects detected by Cu deposition treatment are remarkably generated in a part of the Nv region where oxygen precipitation is likely to occur. This has been found to cause deterioration of electrical characteristics such as oxide film breakdown voltage characteristics.
[0007]
These grow-in defects are caused by a pulling rate V (mm / min) when growing a single crystal and a crystal temperature gradient G (° C / mm) in the pulling axial direction between 1400 ° C and the melting point of silicon near the solid-liquid interface. The amount of introduction is considered to be determined by a parameter V / G (mm ² / ° C. · min) which is a ratio (see, for example, Non-Patent Document 1). That is, a single crystal having a desired defect region or a desired defect-free region can be manufactured by growing a single crystal while V / G is controlled to be constant at a predetermined value.
[0008]
For example, in Patent Document 1, when a silicon single crystal is grown, the V / G value is controlled within a predetermined range (for example, 0.112 to 0.142 mm ² / ° C./min) at the center of the crystal. It has been shown that by pulling up, a silicon single crystal wafer free from defects caused by voids and defects caused by dislocation loops can be obtained. In recent years, there has been an increasing demand for defect-free crystals in the N region that do not include the Cu deposition defect region, and production of a single crystal that pulls up the single crystal while controlling V / G to a desired defect-free region with high accuracy. Has been required.
[0009]
In general, the crystal temperature gradient G in the pulling axis direction is uniquely determined by HZ (hot zone: in-furnace structure) of a single crystal pulling apparatus in which single crystals are grown. However, since it is extremely difficult to change HZ during pulling of the single crystal, when the single crystal is grown by controlling V / G as described above, the crystal temperature gradient G is controlled during pulling of the single crystal. However, a single crystal having a desired defect region is manufactured by controlling the V / G value by adjusting the pulling rate V.
[0010]
In general, it is known that the crystal temperature gradient G tends to decrease as the growth of the single crystal proceeds, and is smaller at the end of growth than at the start of growth of the single crystal straight body. Therefore, in order to control V / G to be almost constant at a desired value, the pulling rate V is changed so as to become slower in accordance with the change (decrease) in the crystal temperature gradient G as the growth of the single crystal proceeds. As a result, the time required for growing the single crystal straight body portion becomes long, which causes a problem that productivity is lowered.
[0011]
Further, the pulling speed at the end of the growth of the single crystal straight body part affects the pulling speed and pulling time of the single crystal in the rounding step performed to form the single crystal tail part thereafter. Therefore, if the pulling speed at the end of the straight body growth is slow as described above, the pulling speed in the rounding process is also slowed down and the pulling time is further prolonged, which significantly reduces the productivity in single crystal production. There was a problem that the manufacturing cost was increased.
[0012]
In addition, in the production of a conventional single crystal, the pulling rate of the single crystal is also used as one of parameters for controlling the diameter of the single crystal to be grown. Therefore, when a single crystal is grown in a desired defect region as described above, the diameter of the single crystal must be controlled at the same time as controlling the V / G by adjusting the pulling rate. Therefore, for example, when performing V / G control and single crystal diameter control during pulling of a single crystal, only one of the controls can be performed when it is desired to change the pulling speed under different conditions. As a result, the single crystal diameter greatly fluctuates during pulling of the single crystal, or the crystal quality such as the defect region deviates from the desired region, resulting in a significant decrease in yield.
[0013]
[Patent Document 1]
JP 11-147786 A [Non-patent Document 1]
V. V. Voronkov, Journal of Crystal
Growth, 59 (1982), 625-643.
[0014]
[Problems to be solved by the invention]
Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to increase the crystal temperature during crystal pulling without reducing the pulling rate V when growing a single crystal by the CZ method. Provided is a method for producing a single crystal, which can produce a single crystal having a desired defect region efficiently in a short time and with a high yield by controlling V / G by controlling a change in gradient G. There is.
[0015]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, in a method for producing a single crystal by pulling it from a raw material melt in a chamber by the Czochralski method, when the single crystal is grown, When the pulling speed when growing the body portion is expressed as V (mm / min) and the crystal temperature gradient in the pulling axis direction near the solid-liquid interface is expressed as G (° C./mm), the crystal temperature gradient G is expressed as the raw material melt. The ratio V / G (mm ^{2) of the} pulling speed V and the crystal temperature gradient G is controlled by changing the distance between the melt surface of the liquid and the heat shield member disposed opposite to the raw material melt surface in the chamber. / ° C./min) is controlled so that a single crystal having a desired defect region can be grown (claim 1).
[0016]
Thus, when growing a single crystal by the CZ method, the crystal temperature gradient G can be controlled by changing the distance between the raw material melt surface and the heat shield member, thereby reducing the pulling rate V. V / G can be controlled without conversion to a single crystal, and a single crystal having a desired defect region can be manufactured efficiently in a short time. And if a single crystal can be manufactured efficiently in this way, the productivity in manufacturing a single crystal can be improved and the cost can be reduced. Further, if the V / G is controlled by changing the distance between the melt surface and the heat shielding member in this way, the V / G can be controlled with high accuracy and at the same time, the diameter control of the single crystal by the pulling speed can be enhanced. Since it is possible to carry out stably with high accuracy, a high-quality single crystal having a desired crystal quality and crystal diameter can be stably produced with a high yield.
[0017]
At this time, the single crystal can be pulled with the pulling speed V set to a constant value.
According to the method for producing a single crystal of the present invention, the crystal temperature gradient G can be controlled by changing the distance between the melt surface and the heat shield member as described above. Even if the pulling is performed, V / G can be easily controlled so that a single crystal of a desired defect region can be grown. Therefore, a single crystal having the same defect region in the crystal growth axis direction can be easily pulled up while keeping the pulling rate V constant at a high speed. In the present invention, the constant pulling rate V means that the average pulling rate in each crystal part of the single crystal straight body is constant, and each crystal part of the single crystal. If the average pulling rate at the point is a constant value, in order to accurately control the diameter of the single crystal to a predetermined value, V can be varied within a predetermined range with respect to the average pulling rate at each crystal part. is there.
[0018]
In this case, it is preferable to control the V / G so that the defect region of the single crystal to be grown becomes an N region over the entire surface in the radial direction.
In this way, by controlling the V / G so that the defect region of the single crystal becomes the N region over the entire radial direction, defects caused by voids such as FPD and COP are also caused by dislocation loops such as LSEPD and LFPD. A very high-quality single crystal having no defects can be produced with high productivity and high yield.
[0019]
Moreover, in this invention, it is preferable to change automatically the distance of the said raw material melt surface and a heat-shielding member according to the change conditions calculated | required by conducting the test beforehand (Claim 4).
Thus, when the crystal temperature gradient G is controlled by changing the distance between the melt surface and the heat shield member, from the melt surface to the heat shield member in the production environment where the single crystal is actually produced. The relationship between the distance and the crystal temperature gradient G is clarified by conducting simulation analysis or actual production tests in advance, and based on the information obtained there is a change condition for changing the distance between the melt surface and the heat shield member I ask for it. Then, by automatically changing the distance between the melt surface and the heat shield member during pulling of the single crystal according to the obtained change condition, it becomes possible to automatically control the crystal temperature gradient G with high accuracy, A single crystal having a defect region can be manufactured stably.
[0020]
Furthermore, it is preferable that the changing condition for changing the distance between the raw material melt surface and the heat shield member is adjusted between production batches of single crystals.
Normally, when a single crystal is manufactured repeatedly in multiple batches, the manufacturing environment may change between single crystal manufacturing batches due to deterioration of parts constituting the HZ by a single crystal pulling apparatus. However, by adjusting the change condition for changing the distance between the melt surface and the heat shield member between the single crystal production batches as in the present invention, it becomes possible to correct the change in the production environment. Even if the production is repeated a plurality of batches, the single crystal can be produced very stably without causing quality variations between the production batches.
[0021]
In this case, the single crystal to be manufactured can be a silicon single crystal.
As described above, the method for producing a single crystal according to the present invention can be particularly preferably used for producing a silicon single crystal, thereby controlling V / G without reducing the pulling speed V, A silicon single crystal having a desired defect region can be manufactured efficiently in a short time and with a high yield.
[0022]
And according to this invention, the single crystal manufactured by the manufacturing method of the said single crystal is provided (Claim 7).
The single crystal produced by the present invention can be a very high quality single crystal having a desired defect region and a uniform crystal diameter. Furthermore, since the single crystal of the present invention is produced efficiently in a short time and with a high yield, it is less expensive than the conventional one.
[0023]
Furthermore, according to the present invention, there is provided a single crystal pulling apparatus used when pulling up a single crystal from a raw material melt by the Czochralski method, and at least a crucible containing the raw material melt, and raising and lowering the crucible A crucible drive mechanism, a heater for heating the raw material melt, a pulling mechanism for pulling up the single crystal while rotating, a heat shield member disposed opposite to the melt surface of the raw material melt, and the heat shield member A heat shield member driving means capable of adjusting the position of the crucible vertically, and a drive control means for adjusting the crucible drive mechanism and / or the heat shield member drive means to change the position of the crucible and / or the position of the heat shield member. A single crystal pulling apparatus is provided (claim 8).
[0024]
With the single crystal pulling apparatus having such a configuration, the distance between the raw material melt surface and the heat shield member can be easily changed, and the crystal temperature gradient G is controlled during the pulling of the single crystal. A single crystal pulling apparatus capable of controlling V / G so that a single crystal having a desired defect region can be grown without reducing the pulling speed V can be obtained.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, although an embodiment is described about the present invention, the present invention is not limited to these.
The inventors of the present invention have conducted extensive experiments and studies on a method for efficiently producing a single crystal having a desired defect region in a short time, and as a result, the melt surface and chamber of the raw material melt when growing the single crystal Attention was paid to the distance from the heat shield member provided so as to face the melt surface of the raw material.
[0026]
In the conventional single crystal growth by the CZ method, in order to stably pull up a single crystal having a desired defect region, the melting of the raw material is performed by gradually raising the crucible as the raw material melt decreases during the pulling of the single crystal. While the melt surface of the liquid was maintained at a certain height, the pulling speed V was gradually decreased to perform the growth. Moreover, since the heat shield member installed so as to face the raw material melt surface was fixed in the chamber of the single crystal pulling apparatus, the position of the heat shield member was not changed during the growth of the single crystal. . Therefore, conventionally, when growing a single crystal, the distance between the raw material melt surface and the heat shielding member does not change, but rather is maintained to be a constant size.
[0027]
However, the present inventors have intentionally changed the distance between the raw material melt surface and the heat shield member during pulling of the single crystal, so that the pulling axial direction between the melting point of silicon near the solid-liquid interface and 1400 ° C. It has been found that the crystal temperature gradient G can be controlled, and that V / G can be controlled without changing the pulling speed V to a low speed during pulling the single crystal.
[0028]
Here, comprehensive heat transfer analysis software FEMAG (F. Dupret, P. Nicodeme, Y. Ryckmans, P. Waterers, and M. J. Crochet, Int. J. Heat Mass Transfer, 33, 1849 (1990)) was used. As a result of the simulation analysis of the change in the crystal temperature gradient G in the pulling axis direction when the distance L between the melt surface of the raw material melt and the heat shield member provided in the chamber is changed during the pulling of the single crystal. An example is shown in FIG.
[0029]
As shown in FIG. 1, as a result of the simulation analysis, it becomes clear that the crystal temperature gradient G changes by changing the distance L between the raw material melt surface and the heat shield member. It has been found that the crystal temperature gradient G can be reduced by increasing the distance L between the liquid surface and the heat shield member, and the crystal temperature gradient G can be increased by decreasing the distance L.
[0030]
The present invention utilizes such a relationship between the distance L between the raw material melt surface during the pulling of the single crystal and the heat shield member and the crystal temperature gradient G.
That is, in the method for producing a single crystal of the present invention, when the single crystal is grown by the CZ method, the distance L between the raw material melt surface and the heat shield member is reduced in a region where the crystal temperature gradient G is small. On the contrary, in a region where the crystal temperature gradient G is large, the crystal temperature gradient G is obtained by growing the single crystal by changing the distance L between the raw material melt surface and the heat shield member to be increased. And V / G is controlled to a desired value so that a single crystal having a desired defect region can be grown.
[0031]
Hereinafter, although the manufacturing method of the single crystal of this invention is demonstrated in detail, referring drawings, this invention is not limited to this.
A single crystal pulling apparatus used in the method for producing a single crystal according to the present invention is provided between a melt surface of a raw material melt and a heat shielding member disposed in the chamber so as to face the raw material melt surface during pulling of the single crystal. Although it will not specifically limit if the magnitude | size of the distance L can be changed, For example, a single crystal pulling apparatus as shown in FIG. 4 can be used. First, a single crystal pulling apparatus that can be used when carrying out the method for producing a single crystal of the present invention will be described with reference to FIG.
[0032]
In the single crystal pulling apparatus 20 shown in FIG. 4, a quartz crucible 5 for containing a raw material melt 4 and a graphite crucible 6 for protecting the quartz crucible 5 are rotated and moved up and down by a crucible driving mechanism 21 in a main chamber 1. A heater 7 and a heat insulating material 8 for heating the raw material melt are disposed so as to surround the crucibles 5, 6. A pulling chamber 2 for accommodating and taking out the grown single crystal 3 is connected to the upper part of the main chamber 1, and a pulling mechanism 17 for pulling up the single crystal 3 while rotating it with a wire 14 is connected to the upper part of the pulling chamber 2. Is provided.
[0033]
Further, a gas rectifying cylinder 11 is provided inside the main chamber 1, and a heat shield member 12 is installed at the lower part of the gas rectifying cylinder 11 so as to face the raw material melt 4. The radiation from the surface of the material is cut and the surface of the raw material melt 4 is kept warm. Further, on the upper part of the gas rectifying cylinder 11, a heat shielding member driving means 22 that can adjust the position of the heat shielding member 12 up and down by raising and lowering the gas rectifying cylinder 11 is installed. In the present invention, the shape, material, and the like of the heat shield member 12 are not particularly limited, and can be changed as appropriate. Furthermore, the heat shield member 12 of the present invention may be any member as long as it is disposed so as to face the melt surface, and is not necessarily limited to the member installed at the lower portion of the gas rectifying cylinder as described above.
[0034]
Further, an inert gas such as argon gas can be introduced from the gas inlet 10 provided in the upper part of the pulling chamber 2, and after passing between the single crystal 3 being pulled and the gas rectifying cylinder 11, It can be passed between the member 12 and the melt surface of the raw material melt 4 and discharged from the gas outlet 9.
[0035]
Further, the crucible driving mechanism 21 and the heat shield member driving means 22 are respectively connected to the drive control means 18. For example, the position of the crucibles 5 and 6, the position of the heat shield member 12, the position of the melt surface of the raw material melt 4 measured by the CCD camera 19, and the single crystal obtained from the pulling mechanism 17 are added to the drive control means 18. When the information such as the pulling length is fed back, the crucibles 5 and 6 are adjusted by adjusting the crucible driving mechanism 21 and / or the heat shield member driving means 22 according to the pulling length of the single crystal by the drive control means 18. And / or the position of the heat shield member 12 can be changed, whereby the distance L between the melt surface of the raw material melt 4 and the heat shield member 12 can be changed.
[0036]
For example, when growing a silicon single crystal by the CZ method using such a single crystal pulling apparatus 20, the seed crystal 16 fixed to the seed holder 15 is immersed in the raw material melt 4 in the quartz crucible 5, and then rotated. The silicon single crystal 3 having a substantially cylindrical straight body portion can be grown by gently pulling up and forming a seed drawing and then expanding to a desired diameter.
[0037]
In the present invention, when the silicon single crystal 3 is grown in this manner, the distance L between the melt surface of the raw material melt 4 in the quartz crucible 5 and the lower end of the heat shield member 12 is changed to change the solid-liquid interface. It is possible to control the crystal temperature gradient G in the direction of the pulling axis in the vicinity, thereby controlling V / G while maintaining the pulling speed V at a constant value without reducing the pulling speed V, thereby having a desired defect region. A single crystal can be efficiently grown in a short time.
[0038]
More specifically, for example, when a silicon single crystal is grown so that the defect region is an N region over the entire surface in the radial direction, the pulling rate V is set so that the straight body of the single crystal can be grown in the N region. It is set according to the manufacturing environment in which the manufacturing is performed (for example, HZ of a single crystal pulling apparatus). At this time, the pulling rate V can be set to the maximum value within a range where the single crystal can be grown in the N region.
[0039]
When the single crystal straight body portion is grown at the pulling speed V set in this way, when the straight body portion is pulled as it is, the region between the raw material melt surface and the heat shield member 12 is small in the region where the crystal temperature gradient G becomes small. The distance L of the crystal is decreased, and conversely, in the region where the crystal temperature gradient G is increased, the distance L is increased so that the single crystal is grown to increase the crystal temperature during the pulling of the single crystal. The gradient G can be controlled, and V / G can be controlled to a predetermined value (N region) regardless of the pulling speed V.
[0040]
At this time, the distance L between the raw material melt surface and the heat shield member 12 is determined by raising the quartz crucible 5 and the graphite crucible 6 by the crucible driving mechanism 21 in consideration of the melt surface decrease due to crystal growth. Or the height of the raw material melt surface is adjusted by adjusting the position of the heat shield member 12 by moving the gas rectifying cylinder 11 up and down by the heat shield member driving means 22. By simultaneously adjusting the position of the heat shield member 12, the heat shield member 12 can be easily changed with high accuracy.
[0041]
That is, for example, when changing so as to reduce the distance L between the raw material melt surface and the heat shield member 12, the crucible drive mechanism 21 pushes up the crucibles 5 and 6 more than the melt surface decrease due to crystal growth. Accordingly, the height of the raw material melt surface may be increased and / or the gas rectifying cylinder 11 may be lowered by the heat shield member driving means 22 to move the position of the heat shield member 12 downward. On the other hand, when changing to increase the distance L, the crucible drive mechanism 21 lowers the height of the melt surface by pushing the crucibles 5 and 6 smaller than the melt surface decrease due to crystal growth, and Alternatively, the heat shield member driving means 22 may move the position of the heat shield member 12 upward.
[0042]
In this case, the control range of the distance L between the raw material melt surface to be changed during the pulling of the single crystal and the heat shield member 12 can be appropriately set according to the manufacturing environment where the manufacturing is actually performed, for example, the structure of HZ. Although not particularly limited, for example, if the distance L between the melt surface and the heat shield member 12 is too small or too large during single crystal growth, the crystal temperature gradient G in the crystal diameter direction is too large. The in-plane distribution ΔG may become non-uniform or the effect may be reduced, and it may be difficult to grow the single crystal so that the entire surface in the crystal diameter direction is a desired defect region.
[0043]
Therefore, the distance L between the raw material melt surface and the heat shield member is preferably in the range of 1 to 500 mm during the pulling of the single crystal, although it depends on the diameter of the single crystal to be pulled and the manufacturing environment in which the single crystal is manufactured. Is preferably controlled and changed within a range of 10 to 300 mm, more preferably 20 to 200 mm. By controlling and changing the distance L between the raw material melt surface and the heat shield member in such a range, V / G can be stably controlled with very high accuracy, and the crystal temperature gradient G can be controlled during the pulling of the single crystal. The in-plane distribution can be made uniform, and the single crystal can be stably grown over the entire region in the crystal growth axis direction so that the entire radial direction becomes a desired defect region.
[0044]
Thus, according to the present invention, during the pulling of the single crystal, by changing the distance L between the raw material melt surface and the heat shield member and controlling the crystal temperature gradient G, the pulling speed V is reduced as in the conventional case. V / G can be easily adjusted so that a single crystal having a desired defect region, for example, an N region can be obtained while maintaining a constant value at a maximum pull-up rate that is the defect region, in particular, at a predetermined value or more without being converted Can be controlled. Of course, in the present invention, if the crystal temperature gradient G is controlled by changing the distance L between the melt surface and the heat shield member, and the single crystal is grown in the desired defect region, the pulling rate V is not necessarily constant. Although it is not necessary to make it a value, if it is made constant at the maximum value of the pulling rate that becomes the desired defect region as described above, the productivity of the single crystal can be greatly improved.
[0045]
That is, the method for producing a single crystal of the present invention can improve the average crystal pulling speed when pulling up the single crystal straight body part, so that the single crystal straight body part can be grown in a shorter time than before. Furthermore, since the pulling speed at the end of the growth of the single crystal straight body portion does not become low, the pulling time in the subsequent rounding process can also be shortened, so that the entire surface in the crystal diameter direction becomes an N region, which is very high quality. A silicon single crystal can be manufactured with high productivity. In addition, since the manufacturing time is shortened, the possibility that the crystal is dislocated is reduced, and not only the productivity but also the yield can be improved. As a result, the productivity of the single crystal can be improved and the cost can be greatly reduced, and the single crystal can be provided at a very low cost.
[0046]
Further, according to the present invention, V / G can be controlled to a predetermined value without depending on the pulling speed V as described above. Therefore, the distance L between the melt surface and the heat shield member is changed to increase the control of V / G. It is possible to stably control the diameter of the single crystal by making the average pulling speed constant, for example, while maintaining the accuracy. Therefore, it is possible to prevent the occurrence of defects by reducing the variation in the diameter of the single crystal in the direction of the crystal growth axis, and manufacture a very high quality single crystal having a desired crystal quality and a uniform crystal diameter with a high yield. can do.
[0047]
Furthermore, when the single crystal is grown, the controllability of V / G can be improved by controlling the crystal temperature gradient G as in the present invention. Therefore, for example, as shown in FIG. 5, it is possible to manufacture a single crystal by controlling V / G with high precision in a narrow region such as an Nv region or an Ni region in an N region that does not include a Cu deposit defect region, A high-quality single crystal having a desired defect region over the entire region in the crystal growth axis direction can be obtained very stably.
[0048]
In the method for producing a single crystal of the present invention, the state of the crystal temperature gradient G, the crystal temperature gradient G, and the distance L from the melt surface to the heat shield member in advance in the production environment for producing the single crystal, For example, a change condition for changing the distance L between the melt surface and the heat shield member during pulling of the single crystal can be obtained in detail by examining the relationship of the above by performing a simulation analysis or a test such as actual measurement. .
[0049]
And the change condition of the distance L calculated | required beforehand in this way is input into the drive control means 18 shown in FIG. 4, and when growing a single crystal, for example, the position of the crucibles 5 and 6 and the heat shield member 12 Information such as the position, the position of the melt surface of the raw material melt 4 measured by the CCD camera 19 and the pulling length of the single crystal obtained from the pulling mechanism 17 is fed back to the drive control means 18 to drive according to the changing conditions. The position of the crucibles 5 and 6 and / or the position of the heat shield member 12 can be changed by adjusting the crucible drive mechanism 21 and / or the heat shield member drive means 22 with the control means 18. The crystal temperature gradient G can be controlled with high accuracy by automatically changing the distance L between the heat shield members according to the pulling length of the single crystal. Therefore, V / G control can be performed automatically and with high accuracy, and a single crystal having a desired defect region can be easily and stably manufactured.
[0050]
Furthermore, in the method for producing a single crystal of the present invention, when a plurality of single crystals are continuously produced by the CZ method, the change condition for changing the distance L between the raw material melt surface and the heat shielding member is changed to a single crystal production batch. It is preferable to adjust between.
Usually, when a single crystal is manufactured repeatedly in multiple batches, the manufacturing environment of HZ and the like may change between single crystal manufacturing batches due to deterioration of parts constituting the HZ by a single crystal pulling apparatus. is there. In particular, HZ parts are often made of graphite. Among them, the heater is usually a graphite heater, and the temperature distribution gradually changes with use. When the production environment changes between production batches of single crystals in this way, the crystal temperature gradient G also changes between production batches.
[0051]
Therefore, when manufacturing multiple batches of single crystals, as described above, by adjusting the change condition of the distance L between the raw material melt surface and the heat shield member according to changes in the manufacturing environment between the single crystal manufacturing batches, etc. Thus, it becomes possible to correct a change in the manufacturing environment, and it is possible to manufacture a high-quality single crystal very stably without causing quality variations between manufacturing batches. Specifically, the relationship between the distance L between the melt surface and the heat shield member in the previous batch and the defect distribution may be fed back to adjust the manufacturing conditions for the next batch and subsequent batches.
[0052]
【Example】
EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not limited to these.
(Example)
Using a single crystal pulling apparatus 20 shown in FIG. 4, 150 kg of raw material polycrystalline silicon is charged into a quartz crucible having a diameter of 24 inches (600 mm), and an orientation <100>, a diameter of 200 mm, and an oxygen concentration of 22 to A silicon single crystal to be 23 ppma (ASTM '79) was grown (the length of the single crystal straight body portion was about 140 cm).
[0053]
At this time, with respect to the pulling conditions during pulling of the single crystal, simulation analysis is performed in advance to examine the crystal temperature gradient G, and based on the result of the analysis, the melt surface of the raw material melt 4 during pulling of the single crystal The pulling conditions were controlled so that the distance L between the heat shield members 12 and the pulling speed were the values shown in Table 1 below, and single crystals were grown in the N region where no Cu deposition defect was detected. Specifically, during the growth of the single crystal, the crucible drive mechanism 21 raises the crucibles 5 and 6 by the amount corresponding to the decrease in the melt surface due to crystal growth to keep the melt surface of the raw material melt 4 at a certain height and to block the melt. The position of the heat shield member 12 was adjusted by the heat member driving means 22 in accordance with the single crystal pulling length so that the distance L between the melt surface and the heat shield member became the value shown in Table 1. Further, the pulling rate of the single crystal was controlled to be a constant value after 10 cm of the single crystal straight body part. Note that the pulling speed at the straight body portion of 0 cm is high because the so-called shoulder portion is pulled up from the enlarged diameter portion to enter the straight body portion, and the straight body portion is lifted by forming the shoulder portion. The pulling speed can be stabilized within 10 cm.
[0054]
[Table 1]

[0055]
Next, after cutting out a wafer having a thickness of about 2 mm from a portion of the single crystal grown as described above in every 10 cm in the growth axis direction, surface grinding and polishing are performed to produce a sample for inspection, as shown below. The crystal quality characteristics were examined.
[0056]
(1) FPD (V region) and LSEPD (I region) samples were inspected and inspected for 30 minutes without stirring, and then the wafer surface was observed with a microscope to check for crystal defects. did.
(2) A sample for OSF inspection was subjected to heat treatment at 1100 ° C. for 100 minutes in a wet oxygen atmosphere, and then the presence of OSF was confirmed by observing the wafer surface with a microscope.
(3) After forming an oxide film on the surface of the sample for inspection and inspection of defects by Cu deposition treatment, the presence or absence of oxide film defects was confirmed by performing Cu deposition treatment. The evaluation conditions at that time are as follows.
Oxide film: 25nm
Electrolytic strength: 6MV / cm
Voltage application time: 5 minutes (4) Oxide film withstand voltage characteristics test Sample is subjected to thermal oxidation treatment in a dry atmosphere to form a 25 nm gate oxide film on which phosphorous having an electrode area of 8 mm ² is formed. A polysilicon electrode doped with is formed. Then, a voltage was applied to the polysilicon electrode formed on the oxide film to evaluate the oxide film withstand voltage. At this time, the judgment current was 1 mA / cm ² .
[0057]
(Comparative example)
150 kg of raw material polycrystalline silicon is charged into a quartz crucible having a diameter of 24 inches (600 mm) using the same single crystal pulling apparatus 20 as in the above example, and an orientation <100>, a diameter of 200 mm, and an oxygen concentration of 22 are obtained by CZ method. A silicon single crystal to be -23 ppma (ASTM '79) was grown (the length of the single crystal straight body portion was about 140 cm).
[0058]
At this time, with respect to the pulling conditions during pulling of the single crystal, the crucible drive mechanism 21 raises the crucibles 5 and 6 by the amount corresponding to the lowering of the melt level due to crystal growth during the growth of the single crystal, so The distance L between the melt surface and the heat shield member was always kept constant during the pulling of the single crystal by holding the heat shield member 12 at a predetermined position. Further, the pulling rate was controlled to be the value shown in Table 2 below during single crystal growth, and single crystal was grown in the N region where no Cu deposition defect was detected.
Then, after cutting out a wafer having a thickness of about 2 mm from a portion of the obtained single crystal at every 10 cm in the growth axis direction, surface grinding and polishing are performed to prepare a sample for inspection. Inspected.
[0059]
[Table 2]

[0060]
Here, in order to compare the pulling conditions of the single crystal in the example and the comparative example, FIG. 2 shows the length in the crystal growth axis direction of the single crystal straight body part and the distance L between the raw material melt surface and the heat shield member. FIG. 3 is a graph showing the relationship between the length of the straight body portion in the crystal growth axis direction and the pulling rate. Furthermore, when the average pulling speed after the straight body portion 10 cm when the single crystal straight body portion was grown in the examples and comparative examples was calculated and compared, the average pulling speed of the example was 0.014 mm / It was about min.
[0061]
In addition, as a result of the inspection of the crystal quality characteristics of the silicon single crystals produced in the examples and comparative examples as described above, both silicon single crystals are in the region from the single crystal straight body portion 10 cm to the end portion of the straight body portion. No defects of FPD, LSEPD, and OSF were detected, and no defects due to Cu deposition treatment were observed. Further, in the evaluation of the oxide film withstand voltage characteristics, the oxide film withstand voltage level was a non-defective rate of 100%.
[0062]
On the other hand, when the straight body part shape of the silicon single crystal obtained in the examples and comparative examples was visually observed, the silicon single crystal of the example was defective because there was no variation in diameter in the crystal growth axis direction. Although the location was not confirmed, the silicon single crystal of the comparative example showed deformation in the crystal shape in the region of 40-60 cm in the straight body portion.
[0063]
From the above results, it can be seen that the example in which the single crystal was grown at a constant pulling rate can efficiently produce a silicon single crystal with a crystal quality equivalent to or higher than that of the comparative example in a shorter time. It was. Also, in terms of yield, no defective portion was observed in the silicon single crystal of the example, so that it was confirmed that a yield equal to or higher than that of the comparative example could be achieved.
[0064]
The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.
[0065]
For example, in the above embodiment, the case where a single crystal is grown in an N region is described as an example. However, the present invention is not limited to this, and a desired defect such as a V region, an I region, or an OSF region. Single crystals can also be grown in the region. Further, the present invention can be suitably used in the case of manufacturing a silicon single crystal, but is not limited to this, and can be similarly applied to the case of manufacturing a compound semiconductor single crystal or the like.
[0066]
The method for producing a single crystal according to the present invention is not necessarily limited to the case where the entire length of the single crystal straight body portion is used. The crystal temperature gradient G is applied between the raw material melt surface and the heat shield member over a part of the length. This includes the case where the desired defect area is controlled by changing the distance. In particular, as described above, in the region 10 cm from the shoulder portion, which is the first half of the straight body portion, the pulling speed and the diameter may not be stable, so this is performed after 5 cm or 10 cm after the straight body portion, which is likely to be in a steady state. Is preferred.
[0067]
【The invention's effect】
As described above, according to the present invention, the crystal temperature gradient G is controlled by changing the distance between the melt surface of the raw material melt and the heat shielding member provided in the chamber when pulling up the single crystal. Accordingly, V / G can be controlled with high accuracy regardless of the pulling speed V. Therefore, it is possible to grow a single crystal having a desired defect region at a constant value without reducing the pulling speed V, and it is possible to manufacture a single crystal more efficiently than in the past. In addition, since the variation in the diameter of the single crystal can be reduced, the productivity and yield in the production of the single crystal can be improved and the cost can be greatly reduced.
[Brief description of the drawings]
FIG. 1 is a graph showing an example of a relationship between a distance L between a raw material melt surface and a heat shield member and a crystal temperature gradient G;
FIG. 2 is a graph showing the relationship between the length in the growth axis direction of the single crystal straight body and the distance L between the raw material melt surface and the heat shield member when growing a single crystal in Examples and Comparative Examples. .
FIG. 3 is a graph showing the relationship between the length in the growth axis direction of a single crystal straight body portion and the pulling speed when growing a single crystal in Examples and Comparative Examples.
FIG. 4 is a schematic configuration diagram illustrating an example of a single crystal pulling apparatus that can be used when carrying out the method for producing a single crystal of the present invention.
FIG. 5 is an explanatory diagram showing the relationship between V / G and crystal defect distribution.
[Explanation of symbols]
1 ... main chamber, 2 ... pulling chamber,
3 ... single crystal (silicon single crystal), 4 ... raw material melt, 5 ... quartz crucible,
6 ... Graphite crucible, 7 ... Heater, 8 ... Insulating material,
9 ... Gas outlet, 10 ... Gas inlet, 11 ... Gas rectifier,
12 ... Heat shield member, 13 ... Holding shaft, 14 ... Wire,
15 ... Seed holder, 16 ... Seed crystal, 17 ... Pulling mechanism,
18 ... Drive control means, 19 ... CCD camera,
20 ... Single crystal pulling device, 21 ... Crucible drive mechanism,
22: Heat shield member driving means.

Claims

In a method of pulling a single crystal from a raw material melt in a chamber by the Czochralski method, when the single crystal is grown, a pulling speed when growing the straight body portion of the single crystal is V (mm / min), when the crystal temperature gradient in the pulling axis direction in the vicinity of the solid-liquid interface is expressed by G (° C./mm), the crystal temperature gradient G is expressed by the melt surface of the raw material melt and the raw material melt surface in the chamber. The ratio of the pulling speed V to the crystal temperature gradient G V / G (mm ² / ° C./min) is controlled by changing the distance to the heat shield member arranged opposite to the single crystal having a desired defect region A method for producing a single crystal, which is controlled so as to grow.

The method for producing a single crystal according to claim 1, wherein the single crystal is pulled at a constant pulling rate V.

3. The method for producing a single crystal according to claim 1, wherein the V / G is controlled so that a defect region of the single crystal to be grown becomes an N region over the entire surface in the radial direction.

4. The unit according to claim 1, wherein the distance between the raw material melt surface and the heat shielding member is automatically changed according to a change condition obtained by performing a test in advance. Crystal production method.

The single crystal according to any one of claims 1 to 4, wherein a change condition for changing a distance between the raw material melt surface and the heat shielding member is adjusted between production batches of the single crystal. Manufacturing method.

The method for producing a single crystal according to any one of claims 1 to 5, wherein the single crystal to be produced is a silicon single crystal.

The single crystal manufactured by the manufacturing method of the single crystal as described in any one of Claims 1 thru | or 6.

A single crystal pulling apparatus for use in pulling a single crystal from a raw material melt by the Czochralski method, comprising at least a crucible containing the raw material melt, a crucible drive mechanism for raising and lowering the crucible, and the raw material melt A heater for heating the liquid, a pulling mechanism for pulling up the single crystal while rotating, a heat shielding member disposed opposite to the melt surface of the raw material melt, and a shield capable of adjusting the position of the heat shielding member up and down. A single crystal pulling device, comprising: a heat member drive means; and a drive control means for adjusting the crucible drive mechanism and / or the heat shield member drive means to change the position of the crucible and / or the position of the heat shield member. apparatus.