JP4376479B2

JP4376479B2 - Method for producing Si-SiC composite material

Info

Publication number: JP4376479B2
Application number: JP2001265228A
Authority: JP
Inventors: 守阿諏訪
Original assignee: Showa Denko KK
Current assignee: Showa Denko KK
Priority date: 2001-09-03
Filing date: 2001-09-03
Publication date: 2009-12-02
Anticipated expiration: 2021-09-03
Also published as: JP2003071555A

Description

【０００１】
【発明の属する技術分野】
本発明は珪素・炭化珪素セラミックス（以下、Ｓｉ−ＳｉＣとする。）の製造方法に関し、より詳しくはＳｉＣ焼成体中の空隙にＳｉを含浸させる方法に関する。
【０００２】
【従来の技術】
従来よりＳｉとＳｉＣからなるＳｉ−ＳｉＣ系材料は緻密性、高熱伝導性、および強度に優れていることから、シリコン単結晶ウエハー等の熱処理用部材、例えば半導体用熱処理用ウエハーボート、半導体用炉芯管等に用いられている。
【０００３】
Ｓｉ−ＳｉＣ複合材は、通常、ＳｉＣ粉末を単独もしくは粗粒と細粒とを配合した粉末をバインダーと混合して、それを静水圧加圧成形、鋳込み生成法等によって成形し、焼成したのち、その焼成体にＳｉを含浸処理等して製造する。
【０００４】
ＳｉをＳｉＣ焼成体中に含浸する代表的な方法として以下に示す方法が提案されている。
【０００５】
（ａ）多孔質のＳｉＣを、溶融したＳｉ浴中に入れ、ＳｉＣの細孔（内部に貫通した開気孔）によって生じる毛細管現象を利用して溶融したＳｉを含浸させる方法。
【０００６】
（ｂ）坩堝にＳｉを入れ、坩堝とＳｉＣ焼成体の間に炭素繊維等を配置し、溶融したＳｉを炭素繊維の毛細管現象を利用して焼成体に誘導し、焼成体にＳｉを含浸する方法（特開平７−８９７７８号公報、特開２０００−１１９０７９号公報）。
【０００７】
（ｃ）ＳｉをＳｉＣ粉末と混ぜて被含浸体の周辺に配置して、高周波加熱をおこない被含浸体を移動させながらＳｉを溶融含浸させる方法（特公昭５３−２９３１９号公報）。
【０００８】
（ｄ）窒化珪素（Ｓｉ₃Ｎ₄）を熱分解してＳｉ蒸気をＳｉＣ焼成体の気孔中に含浸させる方法（特公昭３６−１５１６３号公報）。
【０００９】
以上のＳｉ含浸方法の問題点としては
（ａ）毛細管現象を利用した含浸方法は一定以上の高さを超えると含浸できない領域が生じ、今日の部材の大型化に伴う要求に応えきれない。また、下部に残留したＳｉが残るため煩雑で面倒な後処理を残すことになる。
【００１０】
（ｂ）炭素繊維（ヤーン）を複数配置して一度に含浸させる場合、その事前の手間と準備が複雑である。また被含浸体の他にＳｉを入れる坩堝や炭素繊維、その他の装置が必要など複雑で、装置全体が高価にならざるを得ない。また、炭素繊維が含浸体に付着してその後処理が必要となる。
【００１１】
（ｃ）含浸に周到な準備が必要であり、また効率性に劣る。更に冷却固化後に、周辺に配置したＳｉＣ粉末を取り除くことが困難である。
【００１２】
（ｄ）Ｓｉ₃Ｎ₄の分解温度が高く、含浸に必要以上のＳｉを分解させるため非効率となり、また過剰のＳｉは炉周辺に堆積して炉の寿命を損なう。
【００１３】
【発明が解決しようとする課題】
開気孔を持つ多孔質ＳｉＣ中にＳｉを含浸する方法において、複雑な含浸機構や高価な装置を用いずに、簡便かつ容易で確実な方法によって緻密なＳｉ−ＳｉＣ複合材を得る製造方法で、溶融Ｓｉの供給速度を容易に制御できる方法とそのために必要なＳｉの坩堝を提供することを課題としている。
【００１４】
【課題を解決するための手段】
本発明者は上記課題を解決すべく鋭意努力検討した結果本発明に到達した。すなわち、本発明は下記に関する。
【００１５】
（１）ＳｉＣを主成分とする焼成体の上部にＳｉを入れた坩堝を設置し、該坩堝を加熱してＳｉを溶融状態とし、Ｓｉの融液を坩堝が有する孔を通じて焼成体表面に供給し、Ｓｉを焼成体に含浸させてＳｉ−ＳｉＣ複合材を製造するＳｉ−ＳｉＣ複合材の製造方法。
【００１６】
（２）ＳｉＣを主成分とする焼成体の上部に、Ｓｉを入れた坩堝を２個以上設置することを特徴とする（１）に記載のＳｉ−ＳｉＣ複合材の製造方法。
【００１７】
（３）坩堝が、ＳｉＣを主成分とし、密度が１．３０ｇ／ｃｍ³〜３．０２ｇ／ｃｍ³の範囲内であり、密度比が４０〜９２ＴＤ％の範囲内であり、水銀ポロシメーターで測定した平均気孔径（平均細孔径）が５０ｎｍ〜３０μｍの範囲内であることを特徴とする（１）または（２）に記載のＳｉ−ＳｉＣ複合材の製造方法。
【００１８】
（４）坩堝が、ＳｉＣを主成分とし、密度が１．７０ｇ／ｃｍ³〜２．９０ｇ／ｃｍ³の範囲内であり、密度比が５３ＴＤ％〜９０ＴＤ％の範囲内であり、水銀ポロシメーターで測定した平均気孔径が３００ｎｍ〜４０００ｎｍの範囲内であることを特徴とする（１）または（２）に記載のＳｉ−ＳｉＣ複合材の製造方法。
【００１９】
（５）坩堝が、粒度０．１μｍ〜３００μｍの範囲内のＳｉＣ粉末に、結合材を加えて鋳込み成形、または、ラバープレス成形、または、金型成形し、その後、１２００℃〜２３００℃の温度範囲内で加熱して焼成した、ＳｉＣを主成分とする坩堝であることを特徴とする（１）〜（４）の何れか１項に記載のＳｉ−ＳｉＣ複合材の製造方法。
【００２０】
（６）坩堝が、黒鉛を主成分とし、密度が１．５０ｇ／ｃｍ³〜２．０５ｇ／ｃｍ³の範囲内であり、坩堝の下部または側部に開口部を有することを特徴とする（１）に記載のＳｉ−ＳｉＣ複合材の製造方法。
【００２１】
（７）開口部が孔形状であり、孔径が０．２５〜２．０ｍｍφの範囲内であり、開口部を有する領域での孔の個数密度が０．００１個／ｃｍ³ 〜１個／ｃｍ³の範囲内であることを特徴とする（６）に記載のＳｉ−ＳｉＣ複合材の製造方法。
【００２２】
（８）ＳｉＣを主成分とする焼成体が、密度が１．３ｇ／ｃｍ³〜３．０ｇ／ｃｍ³の範囲内であり、密度比が４０ＴＤ％〜９２ＴＤ％の範囲内であり、水銀ポロシメーターで測定した平均気孔径（平均細孔径）が５０ｎｍ〜３０μｍの範囲内であることを特徴とする（１）〜（７）の何れか１項に記載のＳｉ−ＳｉＣ複合材の製造方法。
【００２３】
（９）ＳｉＣを主成分とする焼成体への坩堝からのＳｉの供給速度が、１ｇ／分〜２００ｇ／分の範囲内であることを特徴とする（１）〜（８）の何れか１項に記載のＳｉ−ＳｉＣ複合材の製造方法。
【００２４】
（１０）ＳｉＣを主成分とする焼成体への坩堝からのＳｉの供給速度が、焼成体の単位体積当たりの、Ｓｉの供給速度で０．００５ｇ／（ｃｍ³・分）〜５ｇ／（ｃｍ³・分）の範囲内であることを特徴とする（１）〜（９）の何れか１項に記載のＳｉ−ＳｉＣ複合材の製造方法。
【００２５】
（１１）坩堝１個当たりのＳｉの供給速度が、２ｇ／分〜２００ｇ／分の範囲内であることを特徴とする（１）〜（１０）の何れか１項に記載のＳｉ−ＳｉＣ複合材の製造方法。
【００２６】
（１２）焼成体を構成するＳｉＣの金属不純物の総量が５０ｐｐｍ以下であることを特徴とする（１）〜（１１）の何れか１項に記載のＳｉ−ＳｉＣ複合材の製造方法。
【００２７】
（１３）坩堝を構成するＳｉＣの金属不純物の総量が５０ｐｐｍ以下であることを特徴とする（３）〜（５）および（８）〜（１１）の何れか１項に記載のＳｉ−ＳｉＣ複合材の製造方法。
【００２８】
（１４）ＳｉＣを主成分とし、密度が１．３０ｇ／ｃｍ³〜３．０２ｇ／ｃｍ³の範囲内であり、密度比が４０ＴＤ％〜９２ＴＤ％の範囲内であり、水銀ポロシメーターで測定した平均気孔径（平均細孔径）が５０ｎｍ〜３０μｍの範囲内であることを特徴とする焼成体への融液含浸用坩堝。
【００２９】
（１５）黒鉛を主成分とし、密度が１．５０ｇ／ｃｍ³〜２．０５ｇ／ｃｍ³の範囲内であり、坩堝の下部または側部に開口部を有することを特徴とする焼成体への融液含浸用坩堝。
【００３０】
【発明の実施の形態】
本発明は、ＳｉＣを主成分とする焼成体に溶融したＳｉを含浸させ、Ｓｉ−ＳｉＣ複合材とする、例えば半導体用熱処理用部材を製造する方法において、ＳｉＣを主成分とする焼成体の上部にＳｉを入れた坩堝を設置し、該坩堝を加熱してＳｉを溶融状態とし、Ｓｉの融液を坩堝が有する孔を通じて焼成体表面に供給し、Ｓｉを焼成体に含浸させて複合材を製造するＳｉ−ＳｉＣ複合材の製造方法である。この際、あらかじめＳｉを入れる坩堝の密度（空隙量）や開気孔量、およびその細孔径を制御しておき、被含浸体へ供給する溶融Ｓｉの供給量をコントロールすることが好ましい。
【００３１】
従来では多孔質のＳｉＣを、溶融したＳｉ浴中に入れ、毛細管現象を利用して細い連続気孔へＳｉを含浸させていた。本発明では、この毛細管現象と同時に重力を利用して焼成体の上部からＳｉを滴下させて供給し、焼成体の空隙中にＳｉを充填させていく。これによって毛細管現象のみでは不可能な距離や、大きな容積、大きな含浸速度が得られる。その結果、形状、大きさの制約を受けずに複雑形状品などへの含浸が容易に達成できるようになった。
【００３２】
本発明では、焼成体の上部に設置する坩堝を、被含浸体の形状に応じて何カ所かに分けて設置することが好ましい。これにより、必要最小限度のスペースで効率的な含浸処理ができる。坩堝の材料には、例えば高純度処理をおこなったＳｉＣ多孔体や黒鉛、もしくは同質のＳｉ−ＳｉＣ複合材から選択できる。このように高純度処理を施した各材料を用いることで半導体用途に適したボートや炉芯管を製造できる。
【００３３】
Ｓｉの供給量は坩堝の開気孔量とその気孔径とに関連する。Ｓｉの供給量を多くするには気孔量か細孔径、もしくはその両方を大きくする。反対に坩堝の気孔量と細孔径を小さくすることでＳｉ供給量を制限できる。また黒鉛坩堝の場合は孔径とその数や孔の密度で調整できる。ＳｉＣやＳｉ−ＳｉＣ坩堝の開気孔量や細孔径を制御するには、その原料となるＳｉＣ粉末の粒径やその成形方法、焼成条件などを調整することで操作できる。
【００３４】
Ｓｉを入れた坩堝から被含浸体へのＳｉの供給速度は被含浸体への含浸能力（速度）を上回らないように抑える必要がある。坩堝からの供給量が多すぎるとＳｉ融液が被含浸体の外部にこぼれ落ち、被含浸体に供給されるべきＳｉ量が不足することになる。
【００３５】
一方、黒鉛は通常１０〜４０体積％と多くの気孔を持っている。この開気孔を通じてＳｉを供給すると黒鉛の一部が反応してＳｉＣを生成する。この反応により坩堝の強度低下が生ずると共に、体積膨張が生じて坩堝が割れる。このため黒鉛製坩堝を用いる場合は、気孔率が１０〜２０体積％といった比較的緻密な高純度黒鉛を用いるとＳｉの進入と反応を抑制できる。そのような坩堝の下部または側面に任意の開口部、例えば孔と、被含浸体形状に応じた位置に必要な孔数をあけてＳｉの供給量を調整することが好ましい。
【００３６】
以上のように、本発明は被含浸体の上部、もしくは被含浸体の上部に接するようにＳｉを入れた坩堝を配置する。たとえば真空下、加熱した炉内に、被含浸体の上にＳｉを入れた坩堝をセットして、炉全体をＳｉ融液温度以上に加熱して融液となったＳｉを、坩堝の開気孔や開口部を通じて被含浸体表面に供給し、含浸処理をおこなうことが好ましい。
【００３７】
一般に半導体用熱処理用部材には、高強度、高純度、高熱伝導性が要求される。したがってその前駆体となるＳｉＣを主成分とする焼成体は高密度で、かつ十分な粒子間結合力が必要になる。それには高密度成形体を得たのち、所定温度で焼成することが望ましい。このとき焼成温度に連動して細孔径も拡大する。これらの条件設定により、十分な強度と毛細管引力を最も引き出すように、焼成体の密度、密度比、平均気孔径を設定するのが好ましい。
【００３８】
本発明の方法によって含浸処理したＳｉ−ＳｉＣ複合材は、ポアの量が飛躍的に少なく、緻密な組織とすることができる。また、適当なＳｉ供給量を選択することで付着したＳｉや、被含浸体に巻き付けた炭素繊維を除去するといった後処理を必要としない極めて効率的な製造方法を提供する。
【００３９】
以下に本発明を更に詳しく述べる。
【００４０】
被含浸体であるＳｉＣを主成分とする焼成体の製造について例示する。ＳｉＣ焼結体はＳｉＣ粉末と有機系バインダーを用いて成形、脱バインダー処理した後、Ｓｉ含浸処理に好適な連続した開気孔の形成と、高強度含浸体を得るに十分なＳｉＣ前駆体を得るため、これらを所定の温度で焼成する。
【００４１】
ＳｉＣを主成分とする焼成体とは、主成分であるＳｉＣの他、バインダーからの炭素、含浸させるＳｉ、その他、不可避不純物を含む焼成体を意味する。
【００４２】
高純度ＳｉＣ粉末を単独、もしくは粒子径の異なる何種類かの粉末を配合し、そこにバインダーを混合して緻密な成形体を製造する。
【００４３】
ＳｉＣ原料には高純度粉末を用いるのが望ましい。特に金属不純物として混入しやすいＦｅ、Ｎｉ、Ｃｒ、Ｃａ、Ｃｕといった元素が少ない粉末を用いるのが好ましい。金属不純物量は一般に弗酸や弗酸と硝酸との混酸で繰り返し酸洗することにより低減できる。さらにハロゲン系ガス中で加熱処理すると、よりいっそう純化される。少なくともこれらの金属不純物量の総計が５０ｐｐｍ以下の粉末が好ましい。
【００４４】
ＳｉＣ粉末の粒子径は０．１μｍ〜３００μｍの範囲が好ましい。単一粒径のみで成形する場合には、その平均粒子径が０．３〜２０μｍの範囲内の粒を用いると成形性と充填性に優れた成形体が得られる。
【００４５】
また、二つの粒度以上を混合して緻密化を図る場合には粗粒の平均粒子径は５０〜３００μｍの範囲内、細粒の平均粒子径は０．１〜３０μｍの範囲内を用いるのが好ましい。その配合比率は粗粒と細粒の比率を３〜７：７〜３とするのが好ましい。より好ましくは粗粒と細粒の比率を４〜６：６〜４の範囲内で選択することにより、高い充填性が得られる。また、粉末は凝集のない単分散した粉末が好ましい。
【００４６】
ＳｉＣの結晶系は六方晶（以下α）、立方晶（以下β）、非晶質もしくはその混合物の何れでも良い。様々な粒子径を安価で容易に調達できる点から、アチソン法で得られるαＳｉＣ粉末が好適に用いることができる。
【００４７】
このＳｉＣ粉末の高純度化は、一般には粉末を酸洗処理することにより得られる。酸の種類は塩酸、弗酸、硝酸など、あるいは、その混酸が用いられている。
【００４８】
アチソン法から合成されたＳｉＣ中の金属不純物の分布は特開平５−３２４５８号公報に開示されているが、一般には粒子径が細かい方が不純物を除去しやすい。
【００４９】
ＳｉＣ粉末に分散剤、有機系バインダーを加えて攪拌混合して造粒したのち、金型、ラバープレス成形（ＣＩＰ）、もしくは混合したスラリーを石膏型を用いた鋳込み成形によって造形する。半導体熱処理部材として多様な形状や薄肉のチューブ、長尺寸法の成形品等を得るには鋳込み成形方法が優れている。
【００５０】
有機結合材には水溶性フェノール樹脂、ポリ酢酸エマルジョン、シリコーン樹脂、アクリル樹脂エマルジョン等を使用するのが好ましい。結合材の配合比率は０．２質量％〜１５質量％の範囲内でＳｉＣ粉末の粒子径によって変える。粗い粒子径の場合は少なく、細かい粒子径のときは多く添加する。フェノール樹脂を結合材として使用するときは成形体にカーボンが残留する。このカーボンはＳｉを含浸したときにＳｉＣに変わる。
【００５１】
開気孔径の測定方法は水銀ポロシメータ−により行う。すなわち、水銀を成形体中に圧入してその圧力から換算した気孔径もしくは細孔径を求める。
【００５２】
ぬれ角で90゜以上を持つ液体は表面張力のために自己自身では細孔内に入っていけない。したがって細孔へ液体を入れるためには外側から圧力を加える必要があり必要とする圧力は細孔径に関係する。
【００５３】
加えた圧力とそのとき入りうる細孔径の関係は次の式で表される。
【００５４】
Ｐｒ＝２σｃｏｓθ
Ｐ：加えられた圧力
ｒ：細孔半径
θ：接触角（ぬれ角）（水銀の場合の平均値は１４１．３度）
σ：水銀の表面張力（４８０ｍＮ／ｍ²）
【００５５】
この関係式はフォッシュボーン式として知られている。ほとんどの多孔質物質の細孔径は円筒形ではないがこの式は水銀圧入データーから細孔径分布を計算するために一般的に使用されている。
【００５６】
上記細孔を円筒と仮定し、水銀を浸透させた場合には上記値を代入すると次の式が求まる。
【００５７】
ｒ＝７５００／Ｐ
ｒ：細孔半径
Ｐ：加えられた絶対圧力
【００５８】
測定方法は試料容器に入る数ｍｍ角、長さ約３０ｍｍの長方体の質量を計る。長方体のうち５面を有機系樹脂で塗布する。試料をガラス製容器（ディラトメーター）に入れ、水銀圧入装置にセットする。真空脱気したのち水銀を充填する。水銀圧入措置からディラドメーターを外しオートクレーブにセットする。系内へ順次水銀を圧入して各圧力での圧入量を記録する。計測後、圧力と気孔径との換算をおこない気孔径分布を求める。
【００５９】
Ｓｉを含浸するには大きな毛管引力を前駆体となるＳｉＣ焼成体に付与する
一般に毛細管引力は次式で示される。含浸Ｓｉの引き上げ高さをｈとすると、
ｈ＝（２σ）／ｒ・ρ・ｃｏｓα
σ：表面張力（Ｓｉ（１５００℃）で８００ｍＮ／ｍ²）
ｒ：毛細管の半径（細孔径）
ρ：液体の比重（２．５ｇ／ｃｍ³）
ｃｏｓα：接触角（４０度未満）
【００６０】
このように、通常、細孔径が小さいほど大きな毛細管力が働くことになる。しかしながら実際の気孔形態は、三次元的に入り組んでおり、太い孔と細い孔とが交錯した不定形状の連続孔である。
【００６１】
成形体の細孔径は用いたＳｉＣ粉末の粒子径と関連する。すなわち粒子径の細かいＳｉＣ粉末を用いるほど細孔径が小さく、粒子径が大きいＳｉＣ粉末を用いるほど細孔径も大きくなる傾向を示す。たとえば、０．４μｍの平均粒子径を持つ粉末を上記バインダーに加えて、最密充填した成形体の平均細孔径は約２０ｎｍ〜３０ｎｍ前後であり、平均粒子径が０．６μｍでは約５０ｎｍ、同じく３μｍでは約７０ｎｍ〜１００ｎｍ、また５０μｍ〜１００μｍの平均粒径を持つ粗粒と十μｍ以下の細粒とを混合した粉末の平均粒子径が１５μｍ〜４０μｍの範囲では１００〜２００ｎｍの細孔径を持った成形体が得られる。５０ｎｍ以下の小さい細孔では溶融したＳｉは成形体の持つ毛管力（吸引力）より細孔の気孔形態に起因する抵抗の方が高く、表面近傍のみが含浸するだけである。そのため焼成してＳｉが入りやすいように細孔径を調整する必要がある。
【００６２】
まず成形体を所定の形状に加工した後、真空下、もしくは非酸化性雰囲気の下、脱バインダー処理をおこなう。脱脂温度は７００℃〜１１００℃の範囲で１時間〜３時間、所定温度で保持する。非酸化性ガスは窒素、アルゴン、ヘリウムガス等を用いるのが好ましい。
【００６３】
次に脱脂した成形体を焼成する。焼成温度は１２００℃〜２３００℃でおこなう。雰囲気は真空下、もしくは非酸化性雰囲気下でおこなう。非酸化性ガスは窒素、アルゴン、ヘリウムガス等を用いるのが好ましい。真空雰囲気下で焼成する場合には、炉の構成材料の耐熱性やＳｉＣの分解を考慮して２０００℃以下でおこなうのが好ましい。また、真空度は１３３Ｐａ（１Ｔｏｒｒ）以下が好ましく、より望ましくは１３Ｐａ（０．１Ｔｏｒｒ）以下が優れる。真空下で焼成をおこなった場合、常圧下に比較して不純物が除去しやすい。すなわち成形体中のＣａ、Ｆｅ、Ｃｕ等の不純物含有量を、真空下で焼成することで５０％〜８０％低減できる。
【００６４】
各焼成温度の保持時間は１時間〜５時間とする。１時間以下であると粒成長が中途半端で終わり、目的とする細孔径に安定した調整ができない。５時間以上保持しても細孔径の拡大がなく意味を持たない。
【００６５】
成形体を焼成することにより、成形体中の粒成長が進行し、細孔径は拡大していく。鋭意研究の結果、この焼成体中の細孔径が５０ｎｍ〜３０μｍの範囲内、より好ましくは３００ｎｍ〜５μｍの範囲内にあるとき、最もＳｉを吸引しやすいことを見出した。
【００６６】
もう一方の主要な要素である被含浸体にＳｉを供給する坩堝は、その細孔径または開口部の大きさや密度によりＳｉの供給速度を制御できる。
【００６７】
坩堝の形状と大きさは、被含浸体との形状的なバランスと炉空間の有効的活用の観点から決める。坩堝の形状は円筒が好ましい。肉厚は形状を最低維持するに必要な厚みとする。坩堝の表面積を多くしたいときは小さい坩堝を複数個用意する。坩堝の細孔径は被含浸体と同程度であることが好ましく、細孔径が小さいと被含浸体に対して供給量が少なく、細孔径が大きいと被含浸体に対して供給量は多くなる。細孔径が５０ｎｍより小さいと開気孔を通じてＳｉが供給されない。また、３０μｍより大きいとＳｉの供給が速過ぎて目的とする被含浸体中に含浸し切れずに、外にこぼれ落ちる場合がある。
【００６８】
ＳｉＣを主成分とする坩堝とは、主成分であるＳｉＣの他、バインダーからの炭素、含浸させるＳｉ、その他不可避元素を含む坩堝を意味する。
【００６９】
ＳｉＣを主成分とする坩堝の密度は成形の際に形状を維持する最低限の密度１．３０ｇ／ｃｍ³以上、より好ましくは１．７０ｇ／ｃｍ³以上、密度比で４０ＴＤ％以上、より好ましくは５３ＴＤ％以上で、開気孔の形態を維持できる密度の上限として３．０２ｇ／ｃｍ³以下であることが好ましい。また密度が高くなると気孔量が小さく、かつ細孔径が細くなり、結果、Ｓｉの供給量が少なくなる。このため密度は、より好ましくは２．９０ｇ／ｃｍ³以下、密度比で９２ＴＤ％以下、より好ましくは９０ＴＤ％以下のＳｉＣ焼結体が望ましい。
【００７０】
密度比ＴＤ％とは、坩堝を形成する物質の真密度（ＳｉＣが１００％の場合は３．２１ｇ／ｃｍ³である。）に対する実際の坩堝の、密度（嵩密度）の比率を表したものである。測定方法としてはアルキメデス法が例示できるが、多孔質の場合は表面をパラフィン等で覆い嵩密度を求める。また、水中で真空脱気し、空中重量（Ｗ₁）、水中重量（Ｗ₂）、包含水重量（Ｗ₃）から嵩密度、気孔率を求めることが出来る。密度、気孔率は下述式にしたがって計算する。
【００７１】
嵩密度（ρ）
ρ＝Ｗ₁／（Ｗ₃−Ｗ₂）
気孔率（Ｐｏ）
Ｐｏ＝（Ｗ₃−Ｗ₁）／（Ｗ₃−Ｗ₂）×１００
（ＪＩＳＲ２２０５による。）
【００７２】
次にＳｉＣを主成分とする坩堝や焼成体の細孔径の調整方法を示す。ＳｉＣを主成分とする成形体の焼成温度はＳｉＣ粉末粒子径毎に異なる。約０．４μｍといった微粉は１０００℃で既に粒成長が開始し、１２００℃で２００ｎｍ、１４００℃で５００ｎｍ、１６００℃には約１μｍ、２０００℃では約２μｍにまで成長する。また粗粒と微粉とを配合した場合には微粉が粗粒子中に拡散していくため著しい粒成長が起こり、その結果細孔径は２０μmに達する。したがって焼成温度の範囲は１２００℃〜１８００℃が好ましい。一方、粒子径が大きくなると焼成温度を変えても細孔径の変化は小さく、１５μｍの粒子径の場合、細孔径は約３μｍと一定の値を示す。このように細孔径は粒子径毎にそれぞれ好ましい焼成温度を適時、選択する。表１に粒子径とその成形体の細孔径、各焼成温度における細孔径の変化を示す。
【００７３】
【表１】

【００７４】
次に黒鉛を主成分とする坩堝について説明する。黒鉛を主成分とする坩堝とは、主成分である黒鉛以外に不可避不純物や他の添加元素を含む坩堝、また表面改質を行った黒鉛を主成分とする坩堝を含む意味である。
【００７５】
黒鉛坩堝の開気孔を経由してＳｉを供給しようとすると黒鉛粒子と溶融したＳｉとの反応によって黒鉛の一部がＳｉＣ化して坩堝が膨潤し、坩堝に亀裂や破損が起こる。このため黒鉛坩堝は気孔率が１０〜２０％の高密度品が好ましい。この際の密度は、１．５０ｇ／ｃｍ³〜２．０５ｇ／ｃｍ³の範囲内となる。密度が高いと細孔径が小さくなり、気孔中にＳｉが浸透しないで表面がＳｉでコーティングされる。
【００７６】
黒鉛坩堝を繰り返し使用するといった観点から坩堝の肉厚は２０ｍｍ以上が好ましい。坩堝の側面、もしくは底部に任意の孔を空け、そこから溶融したＳｉを被含浸体に供給する。孔径は０．２５ｍｍφ〜２．０ｍｍφの範囲内が好ましい。
【００７７】
高密度黒鉛に０．２５ｍｍφより小さい孔を空けることは実質上困難であり経済的ではない。また、２．０ｍｍφ以上の大きな孔を空けることは溶融したＳｉを常に一定量供給するといった目的に対して、初期と終期とではＳｉ浴の圧力が変化するためＳｉの供給量が不安定となり含浸には不都合となる。したがって孔径は０．２５ｍｍφ〜２．０ｍｍφの孔が好ましい。黒鉛坩堝を用いた場合のＳｉの供給量は孔径と孔の数とで制御する。本発明の黒鉛坩堝では、開口部を有する領域での孔の個数密度で、０．００１個／ｃｍ³〜１個／ｃｍ³の範囲内が好ましく、０．０１個／ｃｍ³〜０．１個／ｃｍ³の範囲内であることがより好ましい。なお、開口部を有する領域での孔の個数密度とは、黒鉛坩堝の外表面で、開口部を形成していない領域を除いて孔の個数密度を算出する意味である。
【００７８】
坩堝と被含浸体（ＳｉＣを主成分とする焼成体）の位置関係としては、焼成体の上部に坩堝を配置した位置関係であり、坩堝の外周のみが被含浸体と接する構造としても良い。また坩堝の表面の全体が接するのではなく、坩堝の表面に櫛の刃状に溝を入れて接触面積を抑える構造とするのがより好ましい。ＳｉＣ坩堝は１度含浸に使用すればＳｉ−ＳｉＣ組成となり、Ｓｉを供給する坩堝として繰り返して使用できる。同じく黒鉛坩堝も同様に何度でも使用できる。
【００７９】
坩堝や焼成体は、Ｃｌ₂、ＨＣｌなどのハロゲン系ガスを流通しながら純化処理を行うのが好ましい。純化処理温度は１１００℃〜１７００℃範囲内で行うのが好ましい。加熱温度が１１００℃以下では純化が不十分でＳｉＣ表面に拡散してきた不純物を十分に除くことが困難である。また、１７００℃以上になるとＳｉＣ粒子と塩素との反応による塩化物の形成が著しくなり好ましくない。ハロゲン系ガスによる純化によって坩堝や成形体中のＦｅ，Ｎａ，Ｃｕ等の不純物量が低減する。この他に湿式酸洗、たとえば弗酸もしくは弗酸と硝酸、弗酸と塩酸等との混酸中に坩堝や焼成体を浸漬して金属不純物を酸中に溶解したのち、純水等で酸基を除去することでも同等な純化が得られ好ましい。
【００８０】
焼成、純化した各部材を組み合わせてボートやチューブ等を組み立てることもできる。この際は、部材同士の接着性や基材との馴染みを良好とするような配慮が必要である。
【００８１】
接合工程は成形体、もしくは焼成体の何れの場合で行っても良い。接着剤としては組成が同質のスラリーを用いるのが好ましいが、必ずしも同質スラリーである必要はなく、例えば加熱後に残炭して、それがＳｉ含浸時においてＳｉＣ反応生成を起こすフェノール系バインダーを添加したＳｉＣスラリー等が接合剤として好適に使用できる。
【００８２】
焼成体へのＳｉの含浸処理は、焼成体の密度から含浸に必要なＳｉ量を割り出し、加熱時に揮散するＳｉ量を補正したＳｉ量を、坩堝に入れる。このときＳｉＣを主成分とする坩堝の場合にはその空隙量に必要なＳｉ量も加える。Ｓｉを入れた坩堝を被含浸体の上に置き、炉内にセットする。被含浸体は、例えば純化した黒鉛板、カーボンフェルトや純化した黒鉛粒子の上に設置する。また炉内物全体を高純度製の密閉した黒鉛容器に入れるのが好ましい。減圧にしたのち、１５００℃〜１８００℃に加熱する。１時間〜３時間、同温度で保持したのち冷却する。
【００８３】
炉内の真空度は１３３Ｐａ（１Ｔｏｒｒ）以下が好ましく、より好ましくは１Ｐａ（０．０１Ｔｏｒｒ）以下が望ましい。含浸温度はＳｉの融点以上であれば良いが、Ｓｉの粘度が十分に下がる１５００℃以上とするのが好ましい。また、１８００℃以上になると炉内へのＳｉのベーパーライズが多くなり、いたずらに炉を汚し好ましくない。保持時間はＳｉを入れた坩堝からのＳｉの供給速度に依存することになるが、Ｓｉが十分に被含浸体全体に行き渡るには１時間〜３時間が好ましい。
【００８４】
このとき、Ｓｉの供給量は１ｇ／分〜２００ｇ／分の範囲内が好ましい。
１ｇ／分以下であると含浸に時間がかかり過ぎ、揮散するＳｉ量が多くなるため不経済となる。また、２００ｇ／分を越えると被含浸体へのＳｉ供給量が多すぎて一部のＳｉが含浸されずに落下する。
【００８５】
供給するＳｉ流量は被含浸体の形状やその空隙量に影響を受ける。毛細管力と重力によって吸引、落下するＳｉの供給量を被含浸体の単位体積（ｃｍ³）当たりに換算した場合、０．００５ｇ／（ｃｍ³・分）〜５ｇ／（ｃｍ³・分）の範囲内、より好ましくは０．０１ｇ／（ｃｍ³・分）〜１ｇ／（ｃｍ³・分）の範囲内で供給するのが好適である。供給量が０．００５ｇ／（ｃｍ³・分）より少ないと含浸に時間がかかり過ぎ非効率になる。また５ｇ／（ｃｍ³・分）より早いと被含浸体のＳｉ吸収能を上回り、Ｓｉが被含浸体から外に流れ落ちる。
【００８６】
坩堝を取り外した被含浸体をブラスト処理により一部に付着している突起状Ｓｉを除く。また溝等の部分はダイヤモンドブレード等を用いて溝切り加工をおこなう。その後、弗酸もしくは弗酸と塩酸の混酸を用いて表面洗浄する。酸濃度はＨＦ：Ｈ₂Ｏが１：１０〜１：５の範囲内が好ましい。次いで純水を用いた高圧水洗浄と超音波洗浄をおこない酸成分と表面に付着している不純物を完全に除く。その後、約５００℃で乾燥をおこなう。
【００８７】
乾燥後の被含浸体を１１００℃〜１６００℃の温度範囲内でシラン系ガスとメタン系ガスを主体とした雰囲気に置き、ＣＶＤ法により表面にＳｉＣ膜を形成させＳｉ−ＳｉＣ複合材を製造する。
【００８８】
【実施例】
（実施例１）
αＳｉＣ粉末（＃１５０）と平均粒子径が２μｍのαＳｉＣ粉末とを弗酸と硝酸（１：１）の混酸で酸洗処理し、Ｆｅがそれぞれ２．１ｐｐｍと１．２ｐｐｍの粉末を得た。αＳｉＣ（＃１５０）と２μｍのαＳｉＣ粒子を１：１（質量比）で配合し、そこへ純水と水溶性フェノール樹脂を加えて混合し、固形分濃度８０質量％のスラリーを得た。次にこのスラリーを石膏型（横３０ｍｍ、縦４０ｍｍ、長さ１ｍの角棒型）に流し込み、固形鋳込みした。同様にスラリーを径２３０ｍｍφの石膏型に流し込み、肉厚が１０ｍｍの円盤状となるように成形した。
【００８９】
同じく径が１４０ｍｍφ、高さ１００ｍｍの円筒石膏型にスラリーを流し込み、肉厚が４ｍｍの円筒容器となるように成形し坩堝を作製した。
【００９０】
上記成形体を乾燥、加工後、１１００℃で脱脂したのち、真空雰囲気下、１８００℃、２時間保持して焼成した。このときの焼成体の気孔率は１９％、焼成体の細孔径は約８００ｎｍであった。フェノール樹脂を含んだ同質スラリーを用いて角棒と円盤との接合を行いボート形状とし、２００℃で乾燥した。
【００９１】
上記の焼成体とＳｉＣ坩堝との気孔量に必要な高純度Ｓｉ量、１．１ｋｇを計り取り、ＳｉＣ坩堝に入れた。気孔率２０％、細孔径が６００ｎｍのＳｉＣ坩堝をボート上に乗せて含浸炉にセットした。この組み合わせを計５セット用意し、炉内に全て並べた。
【００９２】
全体を密閉した高純度黒鉛容器に入れ、真空中、１６５０℃で１時間保持してＳｉを含浸した。含浸したボートからＳｉＣ坩堝を取り外し、被含浸体をブラスト処理し、表面の一部に付着している突起状Ｓｉを取り除いた。ボートの溝切り加工はダイヤモンドブレードを用いて切り込み加工をおこない、２ｍｍ幅の溝を形成した。次に弗酸と純水を用いて洗浄した。その後、純水を用いて高圧水洗浄と超音波洗浄をおこなってＳｉ−ＳｉＣ複合材によるウエハーボートを製造した。複合材は空隙にＳｉが含浸した気孔のない緻密な組織であった。
【００９３】
（実施例２）
αＳｉＣ粉末（＃１８０）と平均粒子径が２．５μｍのαＳｉＣ粉末を弗酸と硝酸との混酸で酸洗処理をおこない、Ｆｅがそれぞれ２．４ｐｐｍと２ｐｐｍの粉末を得た。αＳｉＣ粉末（＃１８０）と２．５μｍのαＳｉＣ粒子とを４：６（質量比）で配合し、そこへ純水とアクリル樹脂エマルジョンを加えて混合し、固形分濃度８２質量％のスラリーを得た。次にこのスラリーを円筒形の石膏型に流し込み、約４ｍｍの肉厚を確認したのちスラリーを排泥した。（これを排泥鋳込み成型法という。）これにより、外径３５０ｍｍφ、内径３４１ｍｍφ、長さ１．５ｍの円筒形の成形体を得た。
【００９４】
同様に曲率Ｒ５００ｍｍφのキャップを排泥鋳込み法によって作製し、円筒の一端に接合した。
【００９５】
上記成形体を１１００℃で脱脂したのち、真空雰囲気下、焼成温度２０００℃、２時間保持して焼成した。このときの焼成体の気孔率は１９％、同焼成体細孔径は約１μｍであった。焼成体とＳｉＣ坩堝との気孔量に必要な高純度Ｓｉ量３．４ｋｇを計り取り坩堝に入れた。気孔率２３％、細孔径が９００ｎｍのＳｉＣ坩堝を均熱管の上に乗せ、それを含浸炉にセットし、全体を密閉した高純度黒鉛容器に入れて準備を終了した。
【００９６】
上記含浸炉内を真空にし、１７００℃で２時間保持してＳｉを含浸した。被含浸体からＳｉＣ坩堝を取り外し、混酸と純水で酸洗浄をおこなったのち、高圧水洗浄と超音波洗浄をおこなって半導体用均熱管を得た。複合材は空隙にＳｉが含浸した気孔のない緻密な組織であった。
【００９７】
（実施例３）
αＳｉＣ粉末（＃２４０）と平均粒子径が１μｍの高純度αＳｉＣ粉末（Ｆｅ不純物濃度：０．６ｐｐｍ）を３：７の質量比で配合し、そこへ純水、可塑剤としてグリセリン、バインダーとしてセルロースを加えて混合し、固形分濃度７７質量％の可塑性を持った混練物を得た。
【００９８】
テフロン樹脂でコーティングしたシリンダーとプランジャーを有する押し出し成型機を使用して、外径６ｍｍ、内径４ｍｍの細管を得た。同質材で一端を塞いで保護管を製造した。
【００９９】
上記保護管を乾燥、加工後、７００℃で脱脂したのち、アルゴン雰囲気下、１６００℃、１時間保持して焼成した。このときの焼成体の気孔率は２１％、同焼成体細孔径は約７００ｎｍであった。
【０１００】
数十本の上記焼成体を、塞いだ一端が下になるように黒鉛板上に立てて並べた。その上にＳｉＣ坩堝を置き、焼成体と坩堝の気孔を含浸するに必要な高純度Ｓｉ量２３０ｇを計り取り、坩堝に入れた。坩堝の気孔率は２０％、細孔径は６００ｎｍであった。真空中、１６５０℃で１時間保持して焼成体にＳｉを含浸した。その後、被含浸体を１２００℃、大気中で加熱して被含浸体表面に酸化膜を形成させてＳｉ−ＳｉＣ複合材による保護管を製造した。複合材は空隙にＳｉが含浸した気孔のない緻密な組織であった。
【０１０１】
（実施例４）
実施例１と同一のαＳｉＣ粉末を４：６の質量比で配合し、そこへ純水とポリビニルアルコールを加えて混合し、固形分濃度８２質量％のスラリーを得た。次にこのスラリーを円筒形の石膏型に流し込み肉厚が約２５ｍｍとなるように固形鋳込みをし、外径３５０ｍｍφ、内径３００ｍｍφ、長さ３００ｍｍの成形体を製造した。
【０１０２】
上記成形体を乾燥、加工後、１１００℃で脱脂し、アルゴン雰囲気下、１９００℃、２時間保持して焼成した。このときの焼成体の気孔率は２０％、同焼成体の細孔径は約９００ｎｍであった。
【０１０３】
高純度黒鉛を用いた外径２００ｍｍφ、内径１５０ｍｍφ、高さ１００ｍｍの坩堝の側面下部に１ｍｍφの孔を均等に八箇所あけた。黒鉛坩堝に被含浸体の気孔量に見合った高純度Ｓｉ、１．４ｋｇを入れた。被含浸体を高密度黒鉛板に乗せ、その上に坩堝をセットし、全体を密閉した高純度黒鉛容器に入れ、真空中、１７５０℃で２時間保持してＳｉを含浸した。被含浸体から黒鉛坩堝を取り外し、ブラスト処理で突起状Ｓｉを除いたのち、研削加工、酸洗浄をおこなったのち、高圧水洗浄と超音波洗浄をおこなってＳｉ−ＳｉＣ複合材のベルジャー管を製造した。複合材は空隙にＳｉが含浸した気孔のない緻密な組織であった。
【０１０４】
（実施例５）
αＳｉＣ粉末（＃１８０）と平均粒子径が１５μｍの高純度αＳｉＣ粉末を１：１の質量比で配合し、そこへ純水とポリビニルアルコールを加えて混合し造粒した。次に造粒粉末を、静水圧加圧成形法（ＣＩＰ成形）で１．５トン／ｃｍ²の圧力で成形して、横３５０ｍｍ、縦１２５ｍｍ、厚さ８ｍｍの平板を得た。
【０１０５】
上記成形体を１１００℃で脱脂したのち、アルゴン雰囲気下、２１００℃、２時間保持して焼成した。このときの焼成体の気孔率は１８％、同焼成体細孔径は約３μｍであった。この焼成体を横長になるように立て、各焼成体との間隔を約１０ｍｍ空けて複数枚を列べた。その上に角形に鋳込み成形で作製した、横２００ｍｍ、長さ３００ｍｍ、高さ５０ｍｍで、気孔率２０％、細孔径が６００ｎｍの角状のＳｉＣ坩堝を乗せた。ＳｉＣ坩堝と成形体の気孔量に必要な高純度Ｓｉ量７．１ｋｇを計り取り、ＳｉＣ角坩堝に入れた。この組み合わせを計６セット用意し、炉内に全て並べ、全体を密閉した高純度黒鉛容器に入れて、真空中、１６００℃で２時間保持してＳｉを含浸した。含浸した平板から角坩堝を取り外し、被含浸体をブラスト処理により一部に付着している突起状Ｓｉを除いた。この被含浸体をさらに研削加工してＳｉ−ＳｉＣ複合体による４インチウエハーのトレイを製造した。複合材は空隙にＳｉが含浸した気孔のない緻密な組織であった。
【０１０６】
（実施例６）
αＳｉＣ細粒（＃１２００）をさらに粉砕、酸洗、ＨＣｌガスを流通して純化処理をおこない、Ｆｅが０．２ｐｐｍｍ、最大粒子径が１５μｍ未満、平均粒子径１．８μｍの高純度αＳｉＣ細粒を得た。この粉末に純水とアクリル樹脂エマルジョンを加えて混合し、固形分濃度７８質量％のスラリーを得た。次にこのスラリーを石膏型に流し込み、ウエハーボート搬送用のフォーク形状成形体を得た。
【０１０７】
この成形体を乾燥後、１１００℃で脱脂したのち、真空雰囲気下、１９００℃、２時間保持して焼成した。このときの焼成体の気孔率は２１％、同焼成体平均細孔径は約５μｍであった。含浸は一度含浸処理に使用したＳｉ−ＳｉＣ坩堝を用いて、横長に列べた焼成体の上に坩堝を乗せ行った。被含浸体の気孔量に必要な高純度Ｓｉ量１．２ｋｇを計り取り坩堝の中に入れ、全体を密閉した高純度黒鉛容器に入れ、真空中、１６００℃で２時間保持してＳｉを含浸した。被含浸体から坩堝を取り外し、被含浸体表面をブラスト処理により付着している突起状Ｓｉを除いた。
【０１０８】
この含浸体をさらに研削加工してウエハー搬送用フォーク形状Ｓｉ−ＳｉＣ複合材を製造した。複合材は空隙にＳｉが含浸した気孔のない緻密な組織であった。
【０１０９】
（実施例７）
ＳｉＯ₂と炭素からβＳｉＣを合成して粉砕、酸洗して平均粒子径１．５μｍのβＳｉＣ粉末を得た。純水とデキストリンを加えてスラリーとし、実施例１の石膏型に鋳込んだ。固形後、脱型して円盤と角棒を得た。同じく径１４０ｍｍφ、高さ１００ｍｍの円柱石膏型にスラリーを流し込み、厚みが４ｍｍとなるように着肉させたのちスラリーを排泥してＳｉを入れる坩堝を製造した。
【０１１０】
上記成形体を、乾燥、加工後、脱脂したのち、真空雰囲気下、１９００℃、１時間保持して焼成した。このときの焼成体と坩堝の気孔率は２１％、同焼成体細孔径は約４μｍであった。焼成体とＳｉＣ坩堝との気孔量に必要な高純度Ｓｉ量１．２ｋｇを計り取り、ＳｉＣ坩堝に入れ、ＳｉＣ坩堝を接合したボート上に乗せて含浸炉内にセットし、密閉した高純度黒鉛容器に入れ、真空中、１６５０℃で１時間保持してＳｉを含浸した。含浸したボートからＳｉＣ坩堝を取り外し、Ｓｉ−ＳｉＣ複合材によるボート形状品を製造した。ボート形状品は空隙にＳｉが含浸した気孔のない緻密な組織であった。
【０１１１】
（実施例８）
実施例７で合成したβＳｉＣ粉末をさらに水分級して平均粒子径が０．３μｍの粉末を得た。純化処理を施したのち、ポリビニルアルコールを加えて造粒した。金型成形で成形体密度１．５ｇ／ｃｍ³、気孔率５３％、１００ｍｍ角、高さ８０ｍｍの角鉢を成形した。これを１２００℃で焼成して細孔径３００ｎｍの気孔を持つ多孔体を得た。
【０１１２】
このＳｉＣ角鉢と実施例１と同条件で別途焼成した被含浸体との気孔量に必要な高純度Ｓｉ量１．３ｋｇを計り取りＳｉＣ角鉢に入れた。それを被含浸体の上に乗せて含浸炉内にセットし、密閉した高純度黒鉛容器に入れ、真空中、１６００℃で２時間保持してＳｉを含浸した。含浸したボートからＳｉＣ坩堝を取り外し、ボート形状品を得た。ボート形状品は空隙にＳｉが含浸した気孔のない緻密なＳｉ−ＳｉＣ複合材であることを確認した。
【０１１３】
（実施例９）
実施例２で配合したαＳｉＣ粉末へ、炭素源として水溶性フェノール樹脂を１２％添加し、そこへ純水を加えて固形分濃度８０質量％のスラリーを得た。これを実施例１で用いた石膏型に流し込みＳｉＣ坩堝を成形した。これを加工したのち、乾燥、脱脂し、真空雰囲気下、１９００℃、１時間保持して焼成した。このときのＳｉＣ坩堝の気孔率は２１％、同焼成体細孔径は約９００ｎｍであった。この焼成体にＳｉ含浸処理をおこない、残存している炭素をＳｉＣ化してＳｉ−ＳｉＣ複合材を得た。その密度は３．１ｇ／ｃｍ³となった。この一部を切り出し、酸によりＳｉを除去したＳｉＣ基体の密度は２．９ｇ／ｃｍ³、開気孔量１０％、細孔径３５０ｎｍであった。
【０１１４】
ＳｉＣを主成分とする焼成体の気孔量に必要な高純度Ｓｉ量０．８ｋｇを計り取り、坩堝に入れ、接合したボート上に同坩堝を乗せて含浸炉内にセットし、密閉した高純度黒鉛容器に入れ、真空中、１６５０℃で２時間保持してＳｉを含浸した。含浸後の複合材は織観察から気孔のない緻密体であることを確認した。
【０１１５】
（比較例１）
実施例５において作製した平板を同条件で焼成して、焼成体が横長になるよう、各焼結体との間隔を約１０ｍｍにして並べた。その間に、焼成体の含浸に必要なＳｉ量７．４ｋｇと約５ｍｍφの高純度黒鉛と３ｍｍ径のＳｉＣとを同容量混ぜたものを充填した。全体を密閉した高純度黒鉛容器に入れ、真空中、１６００℃で２時間保持してＳｉを含浸した。被含浸体である平板を剥離する際に、過剰なＳｉとＳｉＣ粒子および黒鉛粒子との混在相が下部に堆積しているため、平板の数枚が破損し、また平板に固着した含浸物を取り除くのに多く時間を要した。
【０１１６】
（比較例２）
実施例１で焼成したＳｉＣ焼成体の周辺に、粒状Ｓｉをフェノール樹脂で一様に塗布固定し、その周りを炭素繊維で覆い、粒状Ｓｉの脱落を防止した。これを真空中、１６５０℃で１時間保持してＳｉを含浸した。被含浸体の表面は過剰のＳｉと炭素繊維とが固着し、それを隔離するのに多くの時間を費やし、また、焼成体の表面には未含浸相が生じたため、再度、含浸処理を施す必要があった。
【０１１７】
（比較例３）
実施例２で作製した焼成体を炉中央に設置し、焼成体に炭素繊維を巻き付け、黒鉛坩堝に入れたＳｉが炭素繊維の毛細管現象により供給されるよう配置した。これらを密閉した高純度黒鉛容器内に入れ、真空下、１８００℃、２時間保持してＳｉを含浸した。
【０１１８】
被含浸体は一部に気孔を残した組織であり、均一なＳｉ−ＳｉＣ複合材を得ることはできなかった。
【０１１９】
【発明の効果】
本発明により、従来行われてきた含浸法に比べ、炭素繊維の巻き込みやＳｉの塗布、充填といった煩雑で人手の掛かる準備が不用となり、極めて簡単で、効率的な製造方法が提供可能となった。特に、製品形態の異なる複数個の製品の一括処理が可能となり生産効率が著しく高まった。
【０１２０】
また本発明の製造方法を用いることによって製造したＳｉ−ＳｉＣ複合材は、高純度で緻密な組織を有し、特に半導体用冶具の分野で、製品の歩留まりを高める信頼性の高い冶具を提供可能となった。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing silicon / silicon carbide ceramics (hereinafter referred to as Si—SiC), and more particularly to a method for impregnating Si in voids in a SiC fired body.
[0002]
[Prior art]
Conventionally, Si-SiC materials composed of Si and SiC are excellent in denseness, high thermal conductivity, and strength. Therefore, heat treatment members such as silicon single crystal wafers, for example, semiconductor heat treatment wafer boats, semiconductor furnaces. It is used for core tubes.
[0003]
The Si-SiC composite is usually obtained by mixing SiC powder alone or a mixture of coarse and fine particles with a binder, molding it by hydrostatic pressure molding, casting production method, etc., and firing it. The fired body is manufactured by impregnating Si.
[0004]
As a typical method for impregnating Si into a SiC fired body, the following method has been proposed.
[0005]
(A) A method in which porous SiC is placed in a molten Si bath and impregnated with molten Si by utilizing a capillary phenomenon generated by SiC pores (open pores penetrating inside).
[0006]
(B) Si is put into the crucible, carbon fibers are arranged between the crucible and the SiC fired body, the molten Si is guided to the fired body using the capillary action of the carbon fiber, and the fired body is impregnated with Si. Method (JP-A-7-89778, JP-A-2000-119079).
[0007]
(C) A method in which Si is mixed with SiC powder and disposed around the object to be impregnated, and high-frequency heating is performed to melt and impregnate Si while moving the object to be impregnated (Japanese Patent Publication No. 53-29319).
[0008]
(D) Silicon nitride (Si _Three N _Four ) Is impregnated into the pores of the SiC fired body (Japanese Patent Publication No. 36-15163).
[0009]
The problems of the above Si impregnation method
(A) When the impregnation method using the capillary phenomenon exceeds a certain height, a region that cannot be impregnated is generated, and it cannot meet the demands associated with the increase in the size of today's members. Further, since Si remaining in the lower portion remains, complicated and troublesome post-processing is left.
[0010]
(B) In the case where a plurality of carbon fibers (yarns) are arranged and impregnated at a time, the prior labor and preparation are complicated. In addition to the impregnated body, a crucible for putting Si, carbon fiber, and other devices are complicated and the entire device must be expensive. Further, the carbon fiber adheres to the impregnated body and requires subsequent treatment.
[0011]
(C) Thorough preparation for impregnation is required and the efficiency is poor. Furthermore, it is difficult to remove the SiC powder disposed around after cooling and solidification.
[0012]
(D) Si _Three N _Four The decomposition temperature of the silicon is high, so that the silicon more than necessary for the impregnation is decomposed, resulting in inefficiency, and excessive Si is deposited around the furnace and impairs the life of the furnace.
[0013]
[Problems to be solved by the invention]
In a method of impregnating Si in porous SiC having open pores, a manufacturing method for obtaining a dense Si-SiC composite material by a simple, easy and reliable method without using a complicated impregnation mechanism and expensive equipment, It is an object to provide a method capable of easily controlling the supply rate of molten Si and a Si crucible necessary for the method.
[0014]
[Means for Solving the Problems]
The inventor of the present invention has reached the present invention as a result of diligent efforts to solve the above problems. That is, the present invention relates to the following.
[0015]
(1) A crucible containing Si is placed on the upper part of a fired body containing SiC as a main component, the crucible is heated to bring the Si into a molten state, and a Si melt is supplied to the surface of the fired body through the holes of the crucible. And Si—SiC composite material manufacturing method for manufacturing Si—SiC composite material by impregnating a fired body with Si.
[0016]
(2) The method for producing a Si—SiC composite material according to (1), wherein two or more crucibles containing Si are installed on an upper part of a fired body containing SiC as a main component.
[0017]
(3) The crucible is composed mainly of SiC and has a density of 1.30 g / cm. ^Three ~ 3.02 g / cm ^Three The density ratio is in the range of 40 to 92 TD%, and the average pore diameter (average pore diameter) measured with a mercury porosimeter is in the range of 50 nm to 30 μm (1) or The manufacturing method of the Si-SiC composite material as described in (2).
[0018]
(4) The crucible is composed mainly of SiC and has a density of 1.70 g / cm. ^Three ~ 2.90 g / cm ^Three (1) or (2), wherein the density ratio is in the range of 53 TD% to 90 TD%, and the average pore diameter measured with a mercury porosimeter is in the range of 300 nm to 4000 nm. The manufacturing method of Si-SiC composite material of description.
[0019]
(5) A crucible adds a binder to a SiC powder having a particle size in the range of 0.1 μm to 300 μm and casts, rubber press, or molds, and then a temperature of 1200 ° C. to 2300 ° C. The method for producing a Si-SiC composite material according to any one of (1) to (4), wherein the crucible is heated and fired within a range and is composed mainly of SiC.
[0020]
(6) The crucible is composed mainly of graphite and has a density of 1.50 g / cm. ^Three ~ 2.05 g / cm ^Three The method for producing a Si—SiC composite material according to (1), wherein the crucible has an opening at a lower part or a side part of the crucible.
[0021]
(7) The opening has a hole shape, the hole diameter is in the range of 0.25 to 2.0 mmφ, and the number density of holes in the region having the opening is 0.001 / cm. ^Three ~ 1 piece / cm ^Three (6) The method for producing a Si—SiC composite material according to (6).
[0022]
(8) The sintered body containing SiC as a main component has a density of 1.3 g / cm. ^Three ~ 3.0 g / cm ^Three The density ratio is in the range of 40 TD% to 92 TD%, and the average pore diameter (average pore diameter) measured with a mercury porosimeter is in the range of 50 nm to 30 μm (1) The manufacturing method of the Si-SiC composite material of any one of-(7).
[0023]
(9) Any one of (1) to (8), wherein the supply rate of Si from the crucible to the fired body mainly composed of SiC is in the range of 1 g / min to 200 g / min. The manufacturing method of Si-SiC composite material as described in a term.
[0024]
(10) The supply rate of Si from the crucible to the fired body containing SiC as a main component is 0.005 g / (cm) as the Si supply rate per unit volume of the fired body. ^Three Min) to 5 g / (cm ^Three The method for producing a Si—SiC composite material according to any one of (1) to (9), characterized in that it is within a range of (min).
[0025]
(11) The Si-SiC composite according to any one of (1) to (10), wherein the supply rate of Si per crucible is within a range of 2 g / min to 200 g / min. A method of manufacturing the material.
[0026]
(12) The method for producing a Si—SiC composite material according to any one of (1) to (11), wherein the total amount of SiC metal impurities constituting the fired body is 50 ppm or less.
[0027]
(13) The Si-SiC composite according to any one of (3) to (5) and (8) to (11), wherein the total amount of SiC metal impurities constituting the crucible is 50 ppm or less. A method of manufacturing the material.
[0028]
(14) SiC as the main component, density 1.30 g / cm ^Three ~ 3.02 g / cm ^Three To a fired body characterized in that the density ratio is in the range of 40 TD% to 92 TD% and the average pore diameter (average pore diameter) measured with a mercury porosimeter is in the range of 50 nm to 30 μm. Crucible for impregnating melt.
[0029]
(15) Mainly composed of graphite, with a density of 1.50 g / cm ^Three ~ 2.05 g / cm ^Three A crucible for impregnating a melt into a fired body, characterized by having an opening in a lower part or a side part of the crucible.
[0030]
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a method of manufacturing a heat treatment member for semiconductor, for example, in a Si-SiC composite material by impregnating a melted Si into a fired body containing SiC as a main component. A crucible containing Si is installed, and the crucible is heated to bring Si into a molten state. The melt of Si is supplied to the surface of the fired body through the holes of the crucible, and the fired body is impregnated with Si to impregnate the composite material. It is a manufacturing method of the Si-SiC composite material to manufacture. At this time, it is preferable to control the supply amount of molten Si to be supplied to the impregnated body by controlling the density (the amount of voids), the amount of open pores, and the pore diameter of the crucible containing Si in advance.
[0031]
Conventionally, porous SiC is put in a molten Si bath, and thin continuous pores are impregnated with Si by using a capillary phenomenon. In the present invention, simultaneously with this capillary action, Si is dropped and supplied from the upper part of the fired body using gravity, and the voids of the fired body are filled with Si. As a result, a distance, a large volume, and a large impregnation speed that are impossible only by capillary action are obtained. As a result, it has become possible to easily achieve impregnation into complex shaped products without being restricted by shape and size.
[0032]
In the present invention, it is preferable that the crucible installed on the upper part of the fired body is divided and installed in several places according to the shape of the impregnated body. Thereby, an efficient impregnation process can be performed in the minimum necessary space. The material for the crucible can be selected from, for example, a high-purity SiC porous body, graphite, or a homogeneous Si—SiC composite material. By using each material subjected to high-purity treatment in this way, it is possible to manufacture boats and furnace core tubes suitable for semiconductor applications.
[0033]
The amount of Si supplied is related to the amount of open pores in the crucible and the pore diameter. In order to increase the supply amount of Si, the amount of pores and / or the pore diameter is increased. On the other hand, the amount of Si supply can be limited by reducing the pore volume and pore diameter of the crucible. In the case of a graphite crucible, it can be adjusted by the hole diameter, the number thereof and the hole density. In order to control the open pore volume and pore diameter of SiC or Si-SiC crucible, it can be operated by adjusting the particle size of SiC powder as the raw material, the molding method, firing conditions, and the like.
[0034]
It is necessary to suppress the supply rate of Si from the crucible containing Si to the object to be impregnated so as not to exceed the impregnation ability (speed) of the object to be impregnated. If the supply amount from the crucible is too large, the Si melt spills outside the impregnated body, and the amount of Si to be supplied to the impregnated body is insufficient.
[0035]
On the other hand, graphite usually has many pores of 10 to 40% by volume. When Si is supplied through the open pores, a part of the graphite reacts to generate SiC. This reaction reduces the strength of the crucible and causes volume expansion to break the crucible. For this reason, when using a graphite crucible, Si intrusion and reaction can be suppressed by using relatively dense high-purity graphite having a porosity of 10 to 20% by volume. It is preferable to adjust the supply amount of Si by opening an arbitrary opening, for example, a hole and a necessary number of holes at a position corresponding to the shape of the impregnated body in the lower part or side surface of such a crucible.
[0036]
As described above, in the present invention, the crucible containing Si is disposed so as to be in contact with the upper part of the object to be impregnated or the upper part of the object to be impregnated. For example, in a furnace heated under vacuum, a crucible containing Si is set on an object to be impregnated, and the entire furnace is heated to a temperature equal to or higher than the Si melt temperature, and the melted Si is converted into open pores It is preferable that the impregnation treatment is performed by supplying to the surface of the object to be impregnated through the openings.
[0037]
In general, a semiconductor heat treatment member is required to have high strength, high purity, and high thermal conductivity. Therefore, the fired body containing SiC as a main component as its precursor is required to have a high density and a sufficient interparticle bonding force. For this purpose, it is desirable to obtain a high-density molded body and then fire it at a predetermined temperature. At this time, the pore diameter also expands in conjunction with the firing temperature. By setting these conditions, it is preferable to set the density, density ratio, and average pore diameter of the fired body so that sufficient strength and capillary attraction can be maximized.
[0038]
The Si—SiC composite material impregnated by the method of the present invention has a remarkably small amount of pores and can have a dense structure. Further, the present invention provides an extremely efficient production method that does not require post-treatment such as removing Si adhered by selecting an appropriate Si supply amount and carbon fibers wound around an impregnated body.
[0039]
The present invention is described in further detail below.
[0040]
An example of manufacturing a fired body mainly composed of SiC, which is an impregnated body, will be described. After the SiC sintered body is molded and debindered using SiC powder and an organic binder, continuous open pores suitable for the Si impregnation treatment are formed, and an SiC precursor sufficient to obtain a high-strength impregnated body is obtained. Therefore, these are fired at a predetermined temperature.
[0041]
The fired body containing SiC as a main component means a fired body containing carbon as a main component, carbon from a binder, Si to be impregnated, and other inevitable impurities.
[0042]
A high-purity SiC powder is used alone or several kinds of powders having different particle diameters are blended, and a binder is mixed therewith to produce a dense compact.
[0043]
It is desirable to use high-purity powder as the SiC raw material. In particular, it is preferable to use a powder containing few elements such as Fe, Ni, Cr, Ca, and Cu that are easily mixed as metal impurities. The amount of metal impurities can generally be reduced by repeated pickling with hydrofluoric acid or a mixed acid of hydrofluoric acid and nitric acid. Furthermore, when the heat treatment is performed in a halogen-based gas, it is further purified. At least the total amount of these metal impurities is preferably 50 ppm or less.
[0044]
The particle size of the SiC powder is preferably in the range of 0.1 μm to 300 μm. In the case of molding with only a single particle size, if a particle having an average particle size in the range of 0.3 to 20 μm is used, a molded body excellent in moldability and fillability can be obtained.
[0045]
In addition, when two or more particle sizes are mixed to achieve densification, the average particle size of coarse particles is in the range of 50 to 300 μm, and the average particle size of fine particles is in the range of 0.1 to 30 μm. preferable. The blending ratio is preferably such that the ratio of coarse particles to fine particles is 3 to 7: 7 to 3. More preferably, high filling properties can be obtained by selecting the ratio of coarse particles to fine particles within the range of 4-6: 6-4. The powder is preferably a monodispersed powder without aggregation.
[0046]
The crystal system of SiC may be hexagonal (hereinafter referred to as α), cubic (hereinafter referred to as β), amorphous, or a mixture thereof. From the viewpoint that various particle sizes can be easily procured at low cost, αSiC powder obtained by the Atchison method can be suitably used.
[0047]
The high purity of the SiC powder is generally obtained by pickling the powder. As the type of acid, hydrochloric acid, hydrofluoric acid, nitric acid, or a mixed acid thereof is used.
[0048]
The distribution of metal impurities in SiC synthesized from the Atchison method is disclosed in Japanese Patent Application Laid-Open No. 5-32458, but in general, the smaller the particle diameter, the easier it is to remove impurities.
[0049]
After adding a dispersant and an organic binder to the SiC powder and stirring and mixing, the mixture is granulated, and then a mold, rubber press molding (CIP), or the mixed slurry is formed by casting using a gypsum mold. The cast molding method is excellent for obtaining various shapes, thin-walled tubes, long-sized molded products, and the like as semiconductor heat treatment members.
[0050]
As the organic binder, it is preferable to use a water-soluble phenol resin, polyacetic acid emulsion, silicone resin, acrylic resin emulsion or the like. The blending ratio of the binder varies depending on the particle size of the SiC powder within the range of 0.2% by mass to 15% by mass. In the case of a coarse particle size, the amount is small, and in the case of a fine particle size, a large amount is added. When phenol resin is used as a binder, carbon remains in the molded body. This carbon changes to SiC when impregnated with Si.
[0051]
The open pore diameter is measured by a mercury porosimeter. That is, the pore diameter or pore diameter converted from the pressure is obtained by pressing mercury into the molded body.
[0052]
Liquids with a wetting angle of 90 ° or more cannot enter the pores themselves due to surface tension. Therefore, in order to put the liquid into the pores, it is necessary to apply pressure from the outside, and the necessary pressure is related to the pore diameter.
[0053]
The relationship between the applied pressure and the pore diameter that can enter at that time is expressed by the following equation.
[0054]
Pr = 2σ cos θ
P: Applied pressure
r: pore radius
θ: Contact angle (wetting angle) (The average value for mercury is 141.3 degrees)
σ: Surface tension of mercury (480 mN / m ² )
[0055]
This relation is known as the Fochbone formula. Although the pore size of most porous materials is not cylindrical, this formula is commonly used to calculate the pore size distribution from mercury intrusion data.
[0056]
Assuming that the pore is a cylinder and penetrating mercury, substituting the above value gives the following equation.
[0057]
r = 7500 / P
r: pore radius
P: Applied absolute pressure
[0058]
The measuring method measures the mass of a rectangular body of several mm square and about 30 mm in length entering the sample container. Five sides of the rectangular parallelepiped are coated with an organic resin. Place the sample in a glass container (dilatometer) and set in a mercury intrusion device. After degassing in vacuum, fill with mercury. Remove the diradometer from the mercury intrusion measure and place it in the autoclave. Sequentially inject mercury into the system and record the amount of injection at each pressure. After the measurement, the pressure and the pore diameter are converted to obtain the pore diameter distribution.
[0059]
To impregnate Si, a large capillary attractive force is applied to the SiC fired body as a precursor.
Generally, capillary attraction is expressed by the following equation. If the height of the impregnated Si is h,
h = (2σ) / r · ρ · cos α
σ: surface tension (800 mN / m at Si (1500 ° C.)) ² )
r: radius of capillary tube (pore diameter)
ρ: specific gravity of liquid (2.5 g / cm ^Three )
cosα: Contact angle (less than 40 degrees)
[0060]
Thus, normally, the smaller the pore diameter, the greater the capillary force. However, the actual pore shape is three-dimensionally complicated, and is an indefinite shape of continuous holes in which thick holes and thin holes intersect.
[0061]
The pore size of the compact is related to the particle size of the SiC powder used. That is, the finer the particle diameter, the smaller the pore diameter, and the larger the SiC powder, the larger the pore diameter. For example, a powder having an average particle size of 0.4 μm is added to the binder, and the average pore size of the close-packed compact is about 20 nm to about 30 nm, and about 50 nm when the average particle size is 0.6 μm. In the case of 3 μm, the powder obtained by mixing coarse particles having an average particle diameter of about 70 nm to 100 nm and fine particles of 10 μm or less has a pore diameter of 100 to 200 nm in the range of 15 μm to 40 μm. A molded product is obtained. In small pores of 50 nm or less, molten Si has a higher resistance due to the pore shape of the pores than the capillary force (suction force) of the molded body, and only the vicinity of the surface is impregnated. Therefore, it is necessary to adjust the pore diameter so that Si can easily enter by firing.
[0062]
First, the molded body is processed into a predetermined shape, and then the binder is removed under vacuum or in a non-oxidizing atmosphere. The degreasing temperature is maintained at a predetermined temperature in the range of 700 ° C. to 1100 ° C. for 1 hour to 3 hours. The non-oxidizing gas is preferably nitrogen, argon, helium gas or the like.
[0063]
Next, the degreased compact is fired. The firing temperature is 1200 ° C to 2300 ° C. The atmosphere is a vacuum or a non-oxidizing atmosphere. The non-oxidizing gas is preferably nitrogen, argon, helium gas or the like. When firing in a vacuum atmosphere, it is preferable to carry out at a temperature of 2000 ° C. or lower in consideration of the heat resistance of the constituent materials of the furnace and the decomposition of SiC. The degree of vacuum is preferably 133 Pa (1 Torr) or less, and more preferably 13 Pa (0.1 Torr) or less. When firing under vacuum, impurities are easier to remove than under normal pressure. That is, the content of impurities such as Ca, Fe, and Cu in the molded body can be reduced by 50% to 80% by firing under vacuum.
[0064]
The holding time for each firing temperature is 1 hour to 5 hours. If it is less than 1 hour, the grain growth ends halfway and stable adjustment to the target pore diameter cannot be achieved. Even if it is held for 5 hours or more, the pore diameter does not increase and is meaningless.
[0065]
By firing the compact, grain growth in the compact proceeds and the pore diameter increases. As a result of intensive studies, it was found that Si is most easily sucked when the pore diameter in the fired body is in the range of 50 nm to 30 μm, more preferably in the range of 300 nm to 5 μm.
[0066]
The crucible for supplying Si to the impregnated body, which is the other main element, can control the supply rate of Si by the pore diameter or the size and density of the opening.
[0067]
The shape and size of the crucible are determined from the viewpoint of the shape balance with the object to be impregnated and the effective utilization of the furnace space. The shape of the crucible is preferably a cylinder. The wall thickness is the thickness necessary to maintain the minimum shape. If you want to increase the surface area of the crucible, prepare several small crucibles. The pore diameter of the crucible is preferably about the same as that of the object to be impregnated. When the pore diameter is small, the supply amount to the impregnated body is small, and when the pore diameter is large, the supply amount to the impregnated body is large. If the pore diameter is smaller than 50 nm, Si is not supplied through the open pores. On the other hand, if the thickness is larger than 30 μm, the supply of Si is too fast and the target impregnated body may not be completely impregnated and may spill out.
[0068]
A crucible containing SiC as a main component means a crucible containing SiC as a main component, carbon from a binder, Si to be impregnated, and other inevitable elements.
[0069]
The density of the crucible mainly composed of SiC is 1.30 g / cm, the minimum density that maintains the shape during molding. ^Three Or more, more preferably 1.70 g / cm ^Three The density ratio is 40 TD% or more, more preferably 53 TD% or more, and 3.02 g / cm as the upper limit of the density capable of maintaining the shape of open pores. ^Three The following is preferable. Further, when the density is increased, the amount of pores is decreased and the pore diameter is decreased, and as a result, the supply amount of Si is decreased. For this reason, the density is more preferably 2.90 g / cm. ^Three Hereinafter, a SiC sintered body having a density ratio of 92 TD% or less, more preferably 90 TD% or less is desirable.
[0070]
The density ratio TD% is the true density of the material forming the crucible (3.21 g / cm2 when SiC is 100%). ^Three It is. ) Represents the ratio of the density (bulk density) of the actual crucible to. The Archimedes method can be exemplified as a measuring method. In the case of a porous material, the surface is covered with paraffin or the like to determine the bulk density. In addition, vacuum degassing in water, air weight (W ₁ ), Weight in water (W ₂ ), Water content (W) _Three ) To obtain the bulk density and porosity. The density and porosity are calculated according to the following formula.
[0071]
Bulk density (ρ)
ρ = W ₁ / (W _Three -W ₂ )
Porosity (Po)
Po = (W _Three -W ₁ ) / (W _Three -W ₂ ) × 100
(According to JIS R2205.)
[0072]
Next, a method of adjusting the pore diameter of a crucible containing SiC as a main component or a fired body will be described. The firing temperature of the compact mainly composed of SiC varies depending on the SiC powder particle diameter. Grain growth of about 0.4 μm has already started at 1000 ° C., and grows to 200 nm at 1200 ° C., 500 nm at 1400 ° C., about 1 μm at 1600 ° C., and about 2 μm at 2000 ° C. In addition, when the coarse particles and the fine powder are blended, the fine powder diffuses into the coarse particles, so that remarkable particle growth occurs. As a result, the pore diameter reaches 20 μm. Therefore, the range of the firing temperature is preferably 1200 ° C to 1800 ° C. On the other hand, when the particle size is increased, the change in the pore size is small even when the firing temperature is changed. When the particle size is 15 μm, the pore size is a constant value of about 3 μm. As described above, the pore diameter is appropriately selected at a suitable firing temperature for each particle diameter. Table 1 shows the particle diameter, the pore diameter of the molded body, and the change in pore diameter at each firing temperature.
[0073]
[Table 1]

[0074]
Next, a crucible mainly composed of graphite will be described. The crucible containing graphite as a main component means a crucible containing inevitable impurities and other additive elements in addition to graphite as a main component, and a crucible containing graphite as a main component subjected to surface modification.
[0075]
When Si is supplied through the open pores of the graphite crucible, a part of the graphite is converted to SiC by the reaction between the graphite particles and the molten Si, and the crucible swells, and the crucible is cracked or broken. For this reason, the graphite crucible is preferably a high-density product having a porosity of 10 to 20%. The density at this time is 1.50 g / cm. ^Three ~ 2.05 g / cm ^Three Within the range. When the density is high, the pore diameter becomes small, and Si does not penetrate into the pores, and the surface is coated with Si.
[0076]
The thickness of the crucible is preferably 20 mm or more from the viewpoint of repeatedly using the graphite crucible. Arbitrary holes are made in the side or bottom of the crucible, and melted Si is supplied to the material to be impregnated. The pore diameter is preferably in the range of 0.25 mmφ to 2.0 mmφ.
[0077]
It is practically difficult and economical to make a hole smaller than 0.25 mmφ in high-density graphite. In addition, opening a large hole of 2.0 mmφ or more is intended to always supply a fixed amount of molten Si, but the Si supply pressure becomes unstable and impregnation because the pressure of the Si bath changes between the initial and final stages. This is inconvenient. Therefore, the hole diameter is preferably 0.25 mmφ to 2.0 mmφ. The amount of Si supplied when a graphite crucible is used is controlled by the hole diameter and the number of holes. In the graphite crucible of the present invention, the number density of holes in the region having openings is 0.001 per cm. ^Three ~ 1 piece / cm ^Three Is preferably within the range of 0.01 pieces / cm ^Three ~ 0.1 / cm ^Three It is more preferable to be within the range. The number density of the holes in the region having the opening means that the number density of the holes is calculated excluding the region where the opening is not formed on the outer surface of the graphite crucible.
[0078]
The positional relationship between the crucible and the body to be impregnated (fired body containing SiC as a main component) is a positional relation in which the crucible is arranged on the upper part of the fired body, and only the outer periphery of the crucible may be in contact with the body to be impregnated. Further, it is more preferable that the crucible surface is not in contact with the entire surface of the crucible, but a groove is formed in the shape of a comb blade on the surface of the crucible to reduce the contact area. The SiC crucible has a Si—SiC composition once used for impregnation, and can be used repeatedly as a crucible for supplying Si. Similarly, a graphite crucible can be used any number of times.
[0079]
The crucible and fired body must be Cl ₂ It is preferable to perform the purification treatment while circulating a halogen-based gas such as HCl. The purification treatment temperature is preferably within a range of 1100 ° C to 1700 ° C. When the heating temperature is 1100 ° C. or lower, purification is insufficient and it is difficult to sufficiently remove impurities diffused on the SiC surface. On the other hand, if the temperature is 1700 ° C. or higher, the formation of chloride due to the reaction between the SiC particles and chlorine becomes remarkable. The amount of impurities such as Fe, Na, Cu, etc. in the crucible and the compact is reduced by purification with the halogen-based gas. In addition, wet pickling, for example, immersing a crucible or fired body in hydrofluoric acid or a mixed acid of hydrofluoric acid and nitric acid, hydrofluoric acid and hydrochloric acid, etc. to dissolve the metal impurities in the acid, It is preferable that the same purification can be obtained by removing.
[0080]
A boat, a tube, or the like can be assembled by combining the baked and purified members. At this time, it is necessary to consider such that the adhesion between members and the familiarity with the base material are good.
[0081]
The joining step may be performed in any case of a molded body or a fired body. Although it is preferable to use a slurry having the same composition as the adhesive, it is not always necessary to use a homogeneous slurry. For example, a residual carbon after heating is added, and a phenolic binder that causes a SiC reaction generation when Si is impregnated is added. SiC slurry or the like can be suitably used as the bonding agent.
[0082]
In the Si impregnation treatment into the fired body, the amount of Si necessary for impregnation is determined from the density of the fired body, and the Si amount corrected for the amount of Si volatilized during heating is placed in the crucible. At this time, in the case of a crucible containing SiC as a main component, a necessary Si amount is added to the void amount. A crucible containing Si is placed on an object to be impregnated and set in a furnace. The impregnated material is placed on, for example, a purified graphite plate, carbon felt, or purified graphite particles. Moreover, it is preferable to put the entire contents of the furnace in a high-purity sealed graphite container. After reducing the pressure, the mixture is heated to 1500 ° C to 1800 ° C. Hold at the same temperature for 1 to 3 hours and then cool.
[0083]
The degree of vacuum in the furnace is preferably 133 Pa (1 Torr) or less, more preferably 1 Pa (0.01 Torr) or less. The impregnation temperature may be not less than the melting point of Si, but is preferably not less than 1500 ° C. at which the viscosity of Si is sufficiently lowered. On the other hand, when the temperature is 1800 ° C. or higher, the vaporization of Si into the furnace increases, which undesirably contaminates the furnace. The holding time depends on the supply rate of Si from the crucible containing Si, but 1 to 3 hours is preferable for the Si to sufficiently reach the entire body to be impregnated.
[0084]
At this time, the supply amount of Si is preferably in the range of 1 g / min to 200 g / min.
If it is 1 g / min or less, it takes too much time to impregnate, and the amount of volatilized Si increases, which is uneconomical. On the other hand, if it exceeds 200 g / min, the amount of Si supplied to the material to be impregnated is too large and a part of Si falls without being impregnated.
[0085]
The supplied Si flow rate is affected by the shape of the impregnated body and the amount of voids. The supply volume of Si sucked and dropped by capillary force and gravity is the unit volume (cm ^Three ) 0.005 g / (cm ^Three Min) to 5 g / (cm ^Three Min), more preferably 0.01 g / (cm ^Three Min) to 1 g / (cm ^Three -It is preferable to supply within the range of minutes). Supply amount is 0.005 g / (cm ^Three If less than min), impregnation takes too much time and becomes inefficient. 5g / (cm ^Three ・ Min) If it is earlier, the Si absorption capacity of the impregnated body is exceeded, and Si flows down from the impregnated body.
[0086]
The impregnated body from which the crucible has been removed is removed by blasting to remove the protruding Si adhering to a part. Further, the groove portion is grooved using a diamond blade or the like. Thereafter, the surface is cleaned using hydrofluoric acid or a mixed acid of hydrofluoric acid and hydrochloric acid. Acid concentration is HF: H ₂ O is preferably in the range of 1:10 to 1: 5. Subsequently, high pressure water cleaning using pure water and ultrasonic cleaning are performed to completely remove acid components and impurities adhering to the surface. Thereafter, drying is performed at about 500 ° C.
[0087]
The impregnated body after drying is placed in an atmosphere mainly composed of a silane-based gas and a methane-based gas within a temperature range of 1100 ° C. to 1600 ° C., and a SiC film is formed on the surface by a CVD method to produce a Si—SiC composite material. .
[0088]
【Example】
Example 1
The α-SiC powder (# 150) and the α-SiC powder having an average particle diameter of 2 μm were pickled with a mixed acid of hydrofluoric acid and nitric acid (1: 1) to obtain powders with Fe of 2.1 ppm and 1.2 ppm, respectively. αSiC (# 150) and 2 μm αSiC particles were blended at a ratio of 1: 1 (mass ratio), and pure water and a water-soluble phenol resin were added thereto and mixed to obtain a slurry having a solid content concentration of 80% by mass. Next, this slurry was poured into a gypsum mold (30 mm wide, 40 mm long, 1 m long square bar type), and solid cast. Similarly, the slurry was poured into a gypsum mold having a diameter of 230 mmφ and formed into a disk shape having a thickness of 10 mm.
[0089]
Similarly, the slurry was poured into a cylindrical gypsum mold having a diameter of 140 mmφ and a height of 100 mm, and formed into a cylindrical container having a thickness of 4 mm to produce a crucible.
[0090]
The molded body was dried and processed, degreased at 1100 ° C., and then fired in a vacuum atmosphere at 1800 ° C. for 2 hours. At this time, the porosity of the fired body was 19%, and the pore diameter of the fired body was about 800 nm. A homogenous slurry containing a phenol resin was used to join a square bar and a disk to form a boat shape, which was dried at 200 ° C.
[0091]
The amount of high purity Si necessary for the pore volume of the fired body and the SiC crucible, 1.1 kg, was weighed and placed in the SiC crucible. A SiC crucible having a porosity of 20% and a pore diameter of 600 nm was placed on a boat and set in an impregnation furnace. A total of 5 sets of this combination were prepared and all were placed in the furnace.
[0092]
The whole was put in a sealed high-purity graphite container and kept at 1650 ° C. for 1 hour in a vacuum to impregnate Si. The SiC crucible was removed from the impregnated boat, the impregnated body was blasted, and the protruding Si adhering to a part of the surface was removed. The grooving of the boat was cut using a diamond blade to form a 2 mm wide groove. Next, it was washed with hydrofluoric acid and pure water. Thereafter, high-pressure water cleaning and ultrasonic cleaning were performed using pure water to manufacture a wafer boat made of a Si—SiC composite material. The composite material was a dense structure without pores in which voids were impregnated with Si.
[0093]
(Example 2)
The α-SiC powder (# 180) and the α-SiC powder having an average particle size of 2.5 μm were pickled with a mixed acid of hydrofluoric acid and nitric acid to obtain powders of 2.4 ppm and 2 ppm of Fe, respectively. αSiC powder (# 180) and 2.5 μm αSiC particles are blended at a ratio of 4: 6 (mass ratio), and pure water and an acrylic resin emulsion are added thereto and mixed to obtain a slurry having a solid content concentration of 82% by mass. It was. Next, this slurry was poured into a cylindrical gypsum mold, and after confirming a thickness of about 4 mm, the slurry was discharged. (This is referred to as a waste mud casting method.) Thus, a cylindrical molded body having an outer diameter of 350 mmφ, an inner diameter of 341 mmφ, and a length of 1.5 m was obtained.
[0094]
Similarly, a cap having a curvature of R500 mmφ was produced by a waste mud casting method and joined to one end of a cylinder.
[0095]
The molded body was degreased at 1100 ° C. and then fired in a vacuum atmosphere at a firing temperature of 2000 ° C. for 2 hours. At this time, the porosity of the fired body was 19%, and the pore diameter of the fired body was about 1 μm. A high-purity Si amount of 3.4 kg necessary for the pore volume of the fired body and the SiC crucible was measured and placed in the crucible. An SiC crucible having a porosity of 23% and a pore diameter of 900 nm was placed on a soaking tube, set in an impregnation furnace, and put into a sealed high-purity graphite container to complete the preparation.
[0096]
The impregnation furnace was evacuated and held at 1700 ° C. for 2 hours to impregnate Si. After removing the SiC crucible from the impregnated body and performing acid cleaning with mixed acid and pure water, high-pressure water cleaning and ultrasonic cleaning were performed to obtain a soaking tube for semiconductor. The composite material was a dense structure without pores in which voids were impregnated with Si.
[0097]
(Example 3)
αSiC powder (# 240) and high-purity αSiC powder (Fe impurity concentration: 0.6 ppm) with an average particle diameter of 1 μm are blended at a mass ratio of 3: 7, and pure water, glycerin as a plasticizer, and cellulose as a binder Were added and mixed to obtain a kneaded material having plasticity with a solid content concentration of 77% by mass.
[0098]
Using an extrusion molding machine having a cylinder and a plunger coated with Teflon resin, a thin tube having an outer diameter of 6 mm and an inner diameter of 4 mm was obtained. A protective tube was manufactured by closing one end with the same material.
[0099]
After drying and processing the protective tube, it was degreased at 700 ° C. and then calcined by holding at 1600 ° C. for 1 hour in an argon atmosphere. At this time, the porosity of the fired body was 21%, and the pore diameter of the fired body was about 700 nm.
[0100]
Several tens of the fired bodies were arranged on a graphite plate so that one end of the fired body was down. An SiC crucible was placed thereon, and 230 g of high-purity Si necessary for impregnating the pores of the fired body and the crucible was measured and placed in the crucible. The crucible had a porosity of 20% and a pore diameter of 600 nm. The fired body was impregnated with Si by holding at 1650 ° C. for 1 hour in vacuum. Then, the to-be-impregnated body was heated at 1200 ° C. in the atmosphere to form an oxide film on the surface of the to-be-impregnated body, thereby manufacturing a protective tube made of a Si—SiC composite material. The composite material was a dense structure without pores in which voids were impregnated with Si.
[0101]
(Example 4)
The same α-SiC powder as in Example 1 was blended at a mass ratio of 4: 6, and pure water and polyvinyl alcohol were added thereto and mixed to obtain a slurry having a solid content concentration of 82 mass%. Next, this slurry was poured into a cylindrical gypsum mold and solid cast so that the wall thickness was about 25 mm to produce a molded body having an outer diameter of 350 mmφ, an inner diameter of 300 mmφ, and a length of 300 mm.
[0102]
The molded body was dried and processed, degreased at 1100 ° C., and fired in an argon atmosphere at 1900 ° C. for 2 hours. At this time, the porosity of the fired body was 20%, and the pore diameter of the fired body was about 900 nm.
[0103]
Eight holes of 1 mmφ were equally drilled in the lower part of the side of a crucible having an outer diameter of 200 mmφ, an inner diameter of 150 mmφ and a height of 100 mm using high-purity graphite. A graphite crucible was charged with 1.4 kg of high purity Si corresponding to the pore volume of the impregnated material. The object to be impregnated was placed on a high-density graphite plate, a crucible was set thereon, and the whole was placed in a sealed high-purity graphite container, and kept at 1750 ° C. in vacuum for 2 hours to impregnate Si. Remove the graphite crucible from the impregnated body, remove the protruding Si by blasting, perform grinding and acid cleaning, then perform high pressure water cleaning and ultrasonic cleaning to produce a Si-SiC composite bell jar tube did. The composite material was a dense structure without pores in which voids were impregnated with Si.
[0104]
(Example 5)
αSiC powder (# 180) and high-purity αSiC powder having an average particle diameter of 15 μm were blended at a mass ratio of 1: 1, and pure water and polyvinyl alcohol were added thereto and mixed for granulation. Next, the granulated powder is 1.5 ton / cm by hydrostatic pressure molding (CIP molding). ² Was used to obtain a flat plate having a width of 350 mm, a length of 125 mm, and a thickness of 8 mm.
[0105]
The molded body was degreased at 1100 ° C., and then fired in an argon atmosphere at 2100 ° C. for 2 hours. The porosity of the fired body at this time was 18%, and the pore diameter of the fired body was about 3 μm. The fired bodies were placed so as to be horizontally long, and a plurality of sheets were arranged with an interval of about 10 mm between each fired body. A rectangular SiC crucible having a width of 200 mm, a length of 300 mm, a height of 50 mm, a porosity of 20% and a pore diameter of 600 nm, which was produced by casting into a square, was placed thereon. A high-purity Si amount of 7.1 kg necessary for the porosity of the SiC crucible and the compact was weighed and placed in a SiC square crucible. A total of 6 sets of this combination were prepared, all arranged in a furnace, placed in a sealed high-purity graphite container, kept at 1600 ° C. for 2 hours in a vacuum, and impregnated with Si. The square crucible was removed from the impregnated flat plate, and the protruding Si adhering to a part of the impregnated material was removed by blasting. This impregnated material was further ground to produce a 4-inch wafer tray made of a Si-SiC composite. The composite material was a dense structure without pores in which voids were impregnated with Si.
[0106]
(Example 6)
αSiC fine particles (# 1200) are further pulverized, pickled, and purified by flowing HCl gas. Fe is 0.2ppmm, maximum particle size is less than 15μm, average particle size is 1.8μm, high purity αSiC fine particles Got. To this powder, pure water and an acrylic resin emulsion were added and mixed to obtain a slurry having a solid concentration of 78% by mass. Next, this slurry was poured into a gypsum mold to obtain a fork-shaped molded body for transferring a wafer boat.
[0107]
The molded body was dried, degreased at 1100 ° C., and then fired in a vacuum atmosphere at 1900 ° C. for 2 hours. The porosity of the fired body at this time was 21%, and the average pore diameter of the fired body was about 5 μm. The impregnation was performed by placing the crucible on the fired bodies arranged in a horizontally long shape using the Si-SiC crucible once used for the impregnation treatment. Weigh 1.2 kg of high-purity Si necessary for the pore volume of the material to be impregnated, put it in a crucible, place it in a sealed high-purity graphite container, and hold it in vacuum at 1600 ° C for 2 hours to impregnate Si did. The crucible was removed from the body to be impregnated, and the protruding Si adhering to the surface of the body to be impregnated by blasting was removed.
[0108]
This impregnated body was further ground to produce a fork-shaped Si-SiC composite material for wafer conveyance. The composite material was a dense structure without pores in which voids were impregnated with Si.
[0109]
(Example 7)
SiO ₂ ΒSiC was synthesized from carbon and pulverized and pickled to obtain βSiC powder having an average particle size of 1.5 μm. Pure water and dextrin were added to form a slurry, which was cast into the gypsum mold of Example 1. After solidification, the mold was removed to obtain a disk and a square bar. Similarly, a slurry was poured into a cylindrical gypsum mold having a diameter of 140 mmφ and a height of 100 mm, and after being made to have a thickness of 4 mm, the slurry was drained to produce a crucible containing Si.
[0110]
The molded body was dried, processed, degreased, and fired in a vacuum atmosphere at 1900 ° C. for 1 hour. At this time, the porosity of the fired body and the crucible was 21%, and the pore diameter of the fired body was about 4 μm. Weigh 1.2kg of high-purity Si necessary for the amount of pores between the fired body and the SiC crucible, put it in the SiC crucible, put it on the boat with the SiC crucible joined, set it in the impregnation furnace, and sealed the high-purity graphite It was put in a container and kept at 1650 ° C. for 1 hour in a vacuum to impregnate Si. The SiC crucible was removed from the impregnated boat to produce a boat-shaped product made of Si-SiC composite material. The boat-shaped product was a dense structure without pores in which voids were impregnated with Si.
[0111]
(Example 8)
The β SiC powder synthesized in Example 7 was further subjected to moisture classification to obtain a powder having an average particle size of 0.3 μm. After the purification treatment, polyvinyl alcohol was added and granulated. Molding density 1.5g / cm ^Three A square bowl having a porosity of 53%, a 100 mm square, and a height of 80 mm was molded. This was fired at 1200 ° C. to obtain a porous body having pores with a pore diameter of 300 nm.
[0112]
1.3 kg of high-purity Si necessary for the amount of pores between the SiC bowl and the impregnated body separately fired under the same conditions as in Example 1 were weighed and placed in the SiC bowl. It was placed on an object to be impregnated, set in an impregnation furnace, placed in a sealed high-purity graphite container, and kept in vacuum at 1600 ° C. for 2 hours to impregnate Si. The SiC crucible was removed from the impregnated boat to obtain a boat-shaped product. It was confirmed that the boat-shaped product was a dense Si-SiC composite material without pores in which voids were impregnated with Si.
[0113]
Example 9
To the α SiC powder blended in Example 2, 12% of a water-soluble phenol resin was added as a carbon source, and pure water was added thereto to obtain a slurry having a solid concentration of 80% by mass. This was poured into the gypsum mold used in Example 1 to form a SiC crucible. After processing this, it was dried, degreased, and fired in a vacuum atmosphere at 1900 ° C. for 1 hour. At this time, the porosity of the SiC crucible was 21%, and the pore diameter of the fired body was about 900 nm. This fired body was subjected to Si impregnation treatment, and the remaining carbon was converted to SiC to obtain a Si—SiC composite material. Its density is 3.1 g / cm ^Three It became. The density of the SiC substrate obtained by cutting out a part of this and removing Si with acid is 2.9 g / cm. ^Three The amount of open pores was 10%, and the pore diameter was 350 nm.
[0114]
Weigh 0.8kg of high-purity Si necessary for the pore volume of the sintered body containing SiC as a main component, put it in a crucible, place the same crucible on a joined boat, set it in an impregnation furnace, and seal it in high purity. It was put into a graphite container and impregnated with Si by holding at 1650 ° C. for 2 hours in a vacuum. It was confirmed that the composite material after impregnation was a dense body without pores by woven observation.
[0115]
(Comparative Example 1)
The flat plates produced in Example 5 were fired under the same conditions, and the fired bodies were arranged horizontally with a spacing of about 10 mm so that the fired bodies were horizontally long. In the meantime, 7.4 kg of Si amount necessary for impregnation of the fired body, about 5 mmφ high-purity graphite and 3 mm diameter SiC mixed in the same volume were filled. The whole was put into a sealed high-purity graphite container, and kept at 1600 ° C. for 2 hours in a vacuum to impregnate Si. When exfoliating the flat plate, which is an impregnated body, a mixed phase of excess Si, SiC particles, and graphite particles is deposited on the lower part. It took a lot of time to get rid of.
[0116]
(Comparative Example 2)
Particulate Si was uniformly applied and fixed with a phenol resin around the SiC fired body fired in Example 1, and the periphery thereof was covered with carbon fibers to prevent the particulate Si from falling off. This was kept at 1650 ° C. in a vacuum for 1 hour to impregnate Si. Excess Si and carbon fibers adhere to the surface of the body to be impregnated, and it takes a lot of time to isolate it. Also, since the surface of the fired body has an unimpregnated phase, it is impregnated again. There was a need.
[0117]
(Comparative Example 3)
The fired body produced in Example 2 was placed in the center of the furnace, and the fired body was wrapped with carbon fiber, and Si placed in a graphite crucible was arranged to be supplied by the capillary action of the carbon fiber. These were put in a sealed high-purity graphite container and kept under vacuum at 1800 ° C. for 2 hours to impregnate Si.
[0118]
The impregnated body had a structure in which pores were partially left, and a uniform Si-SiC composite material could not be obtained.
[0119]
【The invention's effect】
According to the present invention, compared with a conventional impregnation method, it is possible to provide an extremely simple and efficient production method because the complicated and manual preparation of carbon fiber entrainment, Si coating and filling is unnecessary. . In particular, batch processing of a plurality of products having different product forms is possible, and the production efficiency is remarkably increased.
[0120]
In addition, the Si-SiC composite material manufactured by using the manufacturing method of the present invention has a high-purity and dense structure, and can provide a highly reliable jig that increases the yield of products, particularly in the field of semiconductor jigs. It became.

Claims

Two or more crucibles containing Si are placed on top of a sintered body containing SiC as a main component, the crucible is heated to make Si molten, and the Si melt is supplied to the surface of the sintered body through the holes of the crucible. And Si—SiC composite material manufacturing method for manufacturing Si—SiC composite material by impregnating a fired body with Si.

Crucible, a main component SiC, in the range density of ^{^{1.30g / cm 3 ~3.02g / cm 3}} , in the range density ratio of 40～92TD%, the average air measured by a mercury porosimeter The method for producing a Si—SiC composite according to claim 1, wherein the pore diameter (average pore diameter) is in the range of 50 nm to 30 μm.

Average crucible, a main component SiC, density is in the range of ^{^{1.70g / cm 3 ~2.90g / cm 3}} , the density ratio is in the range of 53TD% ~90TD%, as measured by a mercury porosimeter The method for producing a Si-SiC composite according to claim 1 or 2, wherein a pore diameter is in a range of 300 nm to 4000 nm.

A crucible adds a binder to SiC powder within a particle size range of 0.1 μm to 300 μm and casts, rubber presses, or molds, and then within a temperature range of 1200 ° C. to 2300 ° C. The method for producing a Si-SiC composite material according to any one of claims 1 to 3, wherein the crucible is heated and baked and contains SiC as a main component.

The crucible is mainly composed of graphite, has a density in a range of 1.50 g / cm ^{3 to} 2.05 g / cm ³ , and has an opening at a lower part or a side part of the crucible. The manufacturing method of Si-SiC composite material of description.

Fired material mainly composed of SiC is, the density is in the range of ^{^{1.30g / cm 3 ~3.02g / cm 3}} , the density ratio is in the range of 40TD% ~92TD%, was measured with a mercury porosimeter 6. The method for producing a Si—SiC composite according to claim 1, wherein an average pore diameter (average pore diameter) is in a range of 50 nm to 30 μm.

The Si supply rate from the crucible to the fired body containing SiC as a main component is in the range of 1 g / min to 200 g / min. -Manufacturing method of SiC composite material.

The feed rate of the Si from the crucible to the fired body mainly composed of SiC is, per unit volume of the fired product, 0.005g / (cm ³ · min) at a feed rate of Si ~5g / (cm ³ · min The method for producing a Si—SiC composite material according to claim 1, wherein the Si—SiC composite material is in a range of

The method for producing a Si-SiC composite according to any one of claims 1 to 8, wherein a supply rate of Si per crucible is in a range of 2 g / min to 200 g / min.

The method for producing a Si-SiC composite according to any one of claims 1 to 9, wherein the total amount of SiC metal impurities constituting the fired body is 50 ppm or less.

The method for producing a Si-SiC composite material according to any one of claims 2 to 4, and 6 to 10, wherein a total amount of SiC metal impurities constituting the crucible is 50 ppm or less.