JP3793553B2

JP3793553B2 - Black SiO2 corrosion-resistant member and method for producing the same

Info

Publication number: JP3793553B2
Application number: JP09178199A
Authority: JP
Inventors: 裕見子伊東; 等松之迫; 正博中原; 敏幸濱田
Original assignee: Kyocera Corp
Current assignee: Kyocera Corp
Priority date: 1999-03-31
Filing date: 1999-03-31
Publication date: 2006-07-05
Anticipated expiration: 2019-03-31
Also published as: JP2000281430A

Description

【０００１】
【発明の属する技術分野】
本発明は、腐食性ガス等に晒される熱処理用の耐食性部材として、特に半導体及び液晶製造の分野で有用な高純度黒色ＳｉＯ₂質耐食性部材及びその製造方法に関するものである。
【０００２】
【従来技術】
従来、半導体素子や液晶などの高集積回路形成プロセスでは不純物の混入が素子特性に影響を与えるため、比較的容易に高純度の部材を作製できる石英ガラス部材が多用されてきた。しかし、特に赤外線加熱等熱処理プロセスにおいて、透明な石英ガラス部材を利用する上でのエネルギーロスが近年注目されるようになっており、赤外線を透過しない黒色の高純度材料が求められている。
【０００３】
従来、石英ガラスの黒色化は、石英ガラス中にＶ₂Ｏ₅等、Ｖａ金属あるいはＦｅ₂Ｏ₃のような遷移金属酸化物を着色剤として添加することによって作製されている（特開昭５４−１５７１２１号公報、特開平７−１９６３３５号公報、特開平４−２５４４３３号公報等参照）。しかし、このような材料は高温熱履歴によって変色しやすい上に、半導体に対して悪影響を及ぼす恐れのある着色用金属類が比較的多量に含有されているため、特に半導体製造における熱処理プロセス用部材としては好ましいとは言えなかった。
【０００４】
これに対し、炭化けい素や炭素を添加することで不純物金属を添加することなく石英ガラスを均質に黒色化する方法が提案されている（特開平５−１７０４７７号公報、特開平５−３０６１４２号公報、特開平６−１２２５３３号公報参照）。
【０００５】
また、石英ガラス粉体に炭素成分を添加し、焼成することによって１〜５重量％の炭素含有黒色石英ガラスを作製することが特開平５−３０６１４２号公報にて提案されている。
【０００６】
さらに、炭素粉末とシリカ粉末の混合物を焼成した炭素含有石英ガラスも特開平３−２７９２０９号公報にて提案されている。
【０００７】
【発明が解決しようとする課題】
しかし、特開平５−１７０４７７号公報等に開示されるように炭化けい素を添加すると緻密化が阻害され低密度の多孔体となるため、熱間静水圧プレス等を用いて緻密化する必要があった。また、ガラス化の過程で色調が変化するため、安定した材料を得ることが困難であった。
【０００８】
また、上述した炭素含有黒色石英ガラスでは耐熱性や耐酸化性には優れるものの腐食性ガス等に対する耐食性の点では充分でなく、例えば腐食性ガスを系内に含み、加熱するような装置内にて使用するような場合においては、前記腐食性ガスにより前記炭素含有黒色石英ガラスが腐食されるとともに、パーティクルが発生することにより系内に悪影響を及ぼす等の問題があった。
【０００９】
特に、特開平５−３０６１４２号公報にて開示されるような１重量％を超える炭素を含有する石英ガラスでは、腐食性ガスに接触した場合に、腐食性しやすいという問題があった。
【００１０】
本発明は、腐食性ガス等に晒された場合においても優れた耐食性を有し、熱処理のエネルギー効率を向上できる高純度の黒色を呈し、半導体製造プロセスにおいて重大な影響を及ぼす金属不純物を含有せず、耐熱性やプラズマ特性を劣化させる水酸基の含有量を低減した緻密な黒色ＳｉＯ₂焼結体とそれを安定的に製造する製造方法を提供するものである。
【００１１】
【課題を解決するための手段】
本発明の黒色ＳｉＯ_２質耐食性部材は、炭素含有量が０．０５〜１．０重量％、密度が２．０３〜２．２１ｇ／ｃｍ^３、水酸基含有量が５ｐｐｍ以下、Ｓｉ以外の金属の総量が０．５重量％以下の非晶質焼結体からなり、厚さ１ｍｍの非晶質焼結体に対して波長２００〜１６０００ｎｍの直線透過率が１％以下であることを特徴とするものである。
【００１２】
また、本発明の黒色ＳｉＯ_２質耐食性部材の製造方法は、Ｓｉ以外の金属の総量が０．１重量％以下、水酸基含有率が２０ｐｐｍ以下および平均粒径５μｍ以下のＳｉＯ_２粉末に、２５０〜４５０℃の温度で熱処理により炭素源となりうる有機結合剤を添加して所定形状に成形し、該成形体を酸化雰囲気中にて２５０〜４５０℃の温度で熱処理して前記有機結合剤を分解して炭素を生成させた後、非酸化雰囲気中にて１１００〜１６００℃で焼成し、密度２．０３〜２．２１ｇ／ｃｍ^３、炭素含有量０．０５〜１．０重量％の焼結体を得ることを特徴とするものである。
【００１３】
【作用】
本発明の黒色ＳｉＯ_２系耐食性部材は、波長２００ｎｍから１６０００ｎｍまでの遠赤外領域までの幅広い波長領域での直線透過率が厚さ１ｍｍに対して１％以下（実質的に測定装置の検出限界以下）であることから、特に半導体製造時における熱処理用部材に用いた場合、透明石英ガラス部材に比較して熱効率の向上に有効である。また、実質的に非晶質相のみからなるために、少なくとも１４００℃の温度まで結晶化、変色することなく特性を保持することができる。
【００１４】
さらに、水酸基含有量が５ｐｐｍ以下であるために、腐食性ガスに対して高い耐食性を示すとともに、熱処理プロセスにおける高温熱履歴に対しても高い強度を保ち、また、プラズマ処理プロセスにおいても水酸基の放出によりプラズマに悪影響を与えることはない。
【００１５】
また、上記特性の黒色ＳｉＯ_２焼結体を製造するにあたり、Ｓｉ以外の金属の総量が０．１重量％以下、水酸基の含有率が２０ｐｐｍ以下、平均粒径５μｍ以下のＳｉＯ_２粉末に、有機結合剤を添加して所定形状に成形し、該成形体を酸化雰囲気中にて２５０〜４５０℃の温度で熱処理して、２５０〜４５０℃の温度で熱処理により炭素源となりうる有機結合剤を分解させて炭素を生成せしめることにより、炭素をＳｉＯ_２ガラスネットワーク中に固溶しやすい状態に転化することができ、その後、真空あるいは非酸化雰囲気中にて１１００〜１６００℃で焼成することにより、前記優れた特性を有する部材を安定して製造することができる。
【００１６】
【発明の実施の形態】
本発明の黒色ＳｉＯ_２質耐食性部材は、ＨＦ、ＨＣ１、ＣｌＦ_３などのハロゲン含有ガスに代表される腐食性ガスと接触する、例えば半導体素子や液晶などの高集積回路形成プロセス、特にランプアニ―ル、ＣＶＤ、拡散炉等熱処理装置のベルジャー、リング、炉心管等の部材として有用であり、特に、波長２００〜１６０００ｎｍの直線透過率が厚さ１ｍｍに対して１％以下であるために、透明な石英ガラスでは光として外部に放出されていたエネルギーを逃さず利用することが可能となり、熱効率の向上に有効である。
【００１７】
本発明の黒色ＳｉＯ₂質耐食性部材は、組成上、炭素を０．０５〜１．０重量％、特に０．２〜０．８重量％含有し、残部が実質的にＳｉＯ₂からなる焼結体からなるものである。この炭素は、焼結体を黒色化する成分であるが、炭素含有量が０．０５重量％に満たない場合は、色むらが生じて均質な黒色を呈することが困難であり、光透過率が１％よりも増大してこれを部材として使用した場合、熱効率の向上に効果が認められない。
【００１８】
また、炭素含有量が１．０重量％を越えると、焼結性が急激に低下し、所定の密度が得られず多孔体となる。また、焼成温度を上げても炭素とシリカの反応によりガスが発生するために発泡体となり強度が大きく低下する。
【００１９】
また、この耐食性部材を構成する焼結体は、密度が２．０３〜２．２１ｇ／ｃｍ³、特に２．１０〜２．２０ｇ／ｃｍ³である。この密度が２．０３ｇ／ｃｍ³よりも低いと、気孔の残留により強度が低下するとともに光透過率が増加し、２．２１ｇ／ｃｍ³よりも大きいと、ＳｉＯ₂が結晶化したり、炭素がＳｉＣ化して耐熱性が低下する。
【００２０】
さらに、本発明におけるＳｉＯ₂焼結体は、実質的に非晶質のみからなるものである。ＳｉＯ₂＋Ｃ系においては、クオーツ、クリストバライトや炭化けい素などの結晶相が生成されやすいが、本発明では、Ｘ線回折測定などの既知の結晶相検出方法によっても、これらの結晶相が検出されないものである。これは、結晶相が存在すると高温熱履歴を繰り返した場合、結晶相が成長したり、非晶質相と結晶相との熱膨張差により亀裂が生じる等によって部材の寿命が低下してしまうためである。
【００２１】
本発明におけるＳｉＯ₂焼結体に含有される炭素の存在形態は、上述したように炭化けい素結晶相が確認されないこと、同程度の炭素含有量を有しながらも製造方法によっては透明体や結晶相を有する白色体となることから、本発明の焼結体では微細なＳｉＯ₂粒子間に均一に分散した炭素源となりうる結合剤が、熱処理により分解してガラスネットワーク中にとりこまれ、焼成過程で均一に固溶して黒色化しているものと考えられる。
【００２２】
また、水酸基含有量が５ｐｐｍ以下、特に１ｐｐｍ以下であることが重要である。この水酸基は、腐食性ガスと接触した場合において、ガスと反応してガラスのネットワークを切断し、さらに反応を促進するために耐食性を著しく低下させてしまう。また、高温での耐熱性が低く、高温熱履歴を繰り返すことにより部材が変形するなどの問題がある。さらに、部材をプラズマ中にて利用する場合、部材表面のプラズマに対する耐食性が低下し、部材からの水酸基の放出によりプラズマ状態に悪影響を与えてしまい、プラズマ装置内のエッチング率分布やバッチ間のばらつきが生じやすくなる。
【００２３】
なお、上記水酸基の含有率Ｃ（ｐｐｍ）は、波長２．６０μｍおよび２．７３μｍの赤外線の透過率を測定し、Ｌａｍｂｅｒｔ−Ｂｅｅｒの式に基づき、下記数１によって算出することができる。
【００２４】
【数１】

【００２５】
また、半導体素子製造時の不純物の混入防止などを考慮して、Ｓｉ以外の金属含有量が０．５重量％以下、特に０．３重量％以下、０．１重量％以下であることが必要である。
【００２６】
また、腐食性ガスとの接触時における耐食性を向上させる上で、上記のＳｉＯ₂焼結体からなる部材表面の平均表面粗さＲａが１μｍ以下、特に０．５μｍ以下、さらには０．１μｍ以下であることが望ましい。これは、表面粗さが荒いと腐食性ガスとの接触面積が大きくなり、腐食の進行を早めてしまうためである。
【００２７】
次に、上記黒色ＳｉＯ₂質耐食性部材を製造する方法としては、原料粉末として、Ｓｉ以外の金属の総量が０．１重量％以下、特に０．０５重量％以下、水酸基含有率２０ｐｐｍ以下、特に１５ｐｐｍ以下、平均粒径５μｍ以下、特に１μｍ以下の高純度のＳｉＯ₂粉末を準備する。特にこのＳｉＯ₂粉末は、天然原料よりも合成原料であることが望ましい。
【００２８】
このＳｉＯ₂原料粉末のＳｉ以外の金属の総量が０．１重量％よりも多いと、最終的に焼結体中のＳｉ以外の金属総量を０．５重量％以下とすることが困難となり、部材から半導体素子への不純物の混入や不純物のパーティクル化を生じる以外に、焼結体内部で不純物金属を結晶核とした結晶化が進行して白色化したり、耐熱性の低下、熱履歴による変質等の問題が発生し目的とする非晶質焼結体が得られないためである。
【００２９】
なお、原料の平均粒径が５μｍよりも大きいと、焼結に必要な温度が融点近くまで上昇し、粉末が溶融して炭素とシリカの反応によりガスが発生し、発泡体となるため目的の焼結体が得られない。従って、平均粒径５μｍ以下の原料粉末を使用することにより、融点よりも１００℃以上低い温度にて溶融することなく緻密な焼結体を作製することができる。
【００３０】
また、原料粉末の水酸基含有率が２０ｐｐｍを越えると、焼結体中に残留する水酸基を５ｐｐｍ以下とすることが困難となる。原料中の水酸基は合成後の処理によって除去することが困難なため、水酸基含有率の低い焼結体を得るためには、原料中の水酸基量を極力無くする必要がある。この水酸基含有率を低減するには、例えば酸化可能な珪素化合物をレーザー加熱により酸素ガスと反応させる方法（特公昭５３−２４４３号）、水素雰囲気で加熱処理する方法（特開平５−２５４８５９号公報）等を行えばよい。
【００３１】
原料の合成法としては、結果として先にあげた特性を有するＳｉＯ₂粉末を得られるのであればどのような方法でも構わないが、水酸基含有率の少ない微粉末を得るという点からすると、ＳｉＣｌ₄の高温加水分解法、酸素或いは酸素、Ａｒ混合プラズマ中で反応させるプラズマ法、高純度金属Ｓｉ粉末を酸化気流中で燃焼させる方法が望ましい。珪酸アルコキシドを原料とするゾルゲル法は化学吸着水を多量に含有する場合が多いため、本発明の焼結体を作製する原料としては好ましいとは言えない。
【００３２】
次に上記粉末に、炭素源となりうるワックス、ポリビニルアルコール等の有機結合剤をイソプロピルアルコールや水などの溶媒とともに添加し均一に混合する。所望により解砕、粉砕処理を別途あるいは同時に施すことも可能である。
【００３３】
その後、この混合原料を所定形状に成形する。成形法としては、目的とする部材の形状に合わせ適当な成形方法を選択して構わない。具体的には金型プレス成形、等方静水圧プレス成形等の乾式成形法、鋳込み成形、押し出し成形、射出成形等の湿式成形法のいずれを利用しても構わない。
【００３４】
なお、湿式にて解砕、粉砕等を行う場合、溶媒は特に限定しないが、例えば水を利用しても焼結体の水酸基含有率には何ら影響しない。
【００３５】
このようにして成形したＳｉＯ₂成形体を、酸化雰囲気中にて２５０〜４５０℃の温度で熱処理することにより、脱脂及び分解処理を行う。このとき、真空あるいは非酸化雰囲気で処理を行うと、結合剤が分解しないまま蒸発し、黒色化に必要な残炭量が得られない。また、熱処理温度が２５０℃より低い場合は未分解のまま残留した結合材が焼成中に分解することなく脱脂され、焼結体が均一に黒色化されない。また、４５０℃を超えると炭素の酸化が顕著となり炭素含有量は０．０５重量％未満となるため黒色の焼結体が得られない。
【００３６】
また、この段階で分解し残留した炭素は焼成によってもほとんど量的に変化しないため、熱処理温度は本発明にて指定した温度範囲内で、添加した結合剤等の分解温度に応じて適宜選択し、必要な炭素量を調整しても構わない。
【００３７】
このようにして処理したＳｉＯ₂成形体を、真空或いは窒素ガス、アルゴンガス、水素とアルゴンとの混合ガス等による非酸化雰囲気中で１１００〜１６００℃、より好ましくは１２５０〜１４５０℃の温度範囲で焼成することにより、焼結の過程で成形体中に均一に分散している炭素が反応することなくガラスネットワーク中に取り込まれ緻密で均一に黒色化したＳｉＯ₂焼結体からなる部材を得られる。
【００３８】
また、焼結体中の水酸基含有率を低減する上では、真空焼成の方が望ましいが、前記非酸化雰囲気中でも水酸基含有率５ｐｐｍ以下は達成可能である。なお、真空焼成時の真空度は、０．２Ｔｏｒｒ以下が望ましい。
【００３９】
これに対し、空気中等の酸化雰囲気中で焼成した場合には、先の熱処理過程と同様な理由で黒色化ができないことに加え、焼結体中の水酸基含有率が１００ｐｐｍ以上となり目的とする黒色のＳｉＯ₂焼結体を作製できない。
【００４０】
また、焼成温度が１１００℃より低いと、焼結性が低下するため緻密な焼結体が得られず、炭素の固溶も不充分なために白色または灰色あるいは色むらのある焼結体となる。さらに、１６００℃より高いと、原料粒径が微細なため溶融を開始し、全体がガラス化して形状を保てないだけでなく、炭素とＳｉＯ₂の反応によりガスが生じ、多量の気泡を含有した発泡体となり、黒色化に必要な炭素が消費されるため目的の黒色のＳｉＯ₂焼結体が得られない。
【００４１】
このようにして得られた黒色のＳｉＯ₂焼結体は、適用する部材形状に応じて、そのままあるいは研削加工などによって所望の形状の部材を作成できる。また、腐食性ガスと接触する部材の目的によりそのまま洗浄して使用することも可能だが、適宜研削、研磨して所望の形状に加工することもできる。
【００４２】
【実施例】
金属Ｓｉ微粉末を酸素気流中で燃焼させて製造した、Ｓｉ以外の金属量が０．０１〜０．２重量％、水酸基含有率１０〜２５ｐｐｍ、平均粒径０．２〜１５μｍのＳｉＯ₂原料粉末を用いて焼結体を作製し物性を評価した。
【００４３】
焼結体の作製方法は、まず超純水を溶媒としてボールミルにて上記原料粉末を湿式解砕し、有機結合剤として表１の種々の化合物を添加してスラリーを作製した。湿式解砕時のメディアとしては高純度ＳｉＯ₂ボールを用いた。このスラリーを造粒した原料粉体を０．８ｔｏｎ／ｃｍ²の荷重で金型プレスにて成形し、これを表１の条件で脱脂した。
【００４４】
このようにして作製した脱脂体を、表１の焼成条件で焼成し、得られたＳｉＯ₂焼結体について以下の特性を測定した。
【００４５】
特性評価として、焼結体密度は、嵩密度をアルキメデス法にて測定した。焼結体の色調は、焼結体の中心付近を切り出し１ｍｍの厚さに加工したものを目視にて判断した。光の直線透過率は、１ｍｍの厚さに加工したものを、２００〜１６０００ｎｍの波長にて光透過率を測定し、その最大値を示した。水酸基含有率は、ＩＲ（赤外線吸収スペクトル）測定を行い、前記数１に基づき算出した。
【００４６】
焼結体の結晶相は、焼結体の中心部を切り出してを粉砕し、粉末Ｘ線回折法にて測定した。材料強度は、焼結体から４ｍｍ×３ｍｍ×５０ｍｍの試験片を切り出し、ＪＩＳＲ１６０１に基づき４点曲げ試験によって抗折試験を行った。
【００４７】
耐熱性は、焼結体を１４００℃で２時間保持し、重量、寸法、色調の変化や亀裂の有無を評価した。
【００４８】
さらに、耐食性は、直径が２００ｍｍの焼結体を作製し、その表面を平均表面粗さＲａが０．０８μｍとなるように鏡面研磨した後、これをＲＩＥ（反応性イオンエッチング）装置にてＨＦのプラズマに室温で曝し、エッチングレートを測定した。
【００４９】
【表１】

【００５０】
【表２】

【００５１】
表１、表２の結果によれば、空気中にて脱脂した試料Ｎo.１〜１０のうち、焼成を空気中で行った試料Ｎo.８は焼成過程で炭素成分が酸化されて脱離し、焼結体中の炭素量が不足したため透明な焼結体となった。また、多量の水酸基が焼結体中に残存していたため高温で粘性が低下し変形した。
【００５２】
試料Ｎo.９は脱脂温度が低く、結合剤の分解が進まず遊離炭素を核として結晶化が生じて半透明の焼結体となった。高温では、内在した微細な結晶が成長し、マイクロクラックが発生したため部分的に白濁してしまった。
【００５３】
試料Ｎo.１０は脱脂温度が高く、炭素に分解した結合剤が酸素と反応して脱離し、炭素含有量が少ない透明体となった。試料Ｎo.１１は脱脂処理を行わず成形体をそのまま焼成した結果、焼成中に、結合剤が酸化分解することなく除去されたため透明体となった。
【００５４】
試料Ｎo.１２、１３は酸化雰囲気でないため脱脂中に、結合剤が分解しないまま融解、脱離し、炭素含有量の少ない透明な焼結体となった。これらの透明な焼結体は、高温で熱処理すると、特に不純物金属を含有しない限り表面から結晶化が進行し、白濁して使用に耐えない。
【００５５】
焼成温度をかえた試料１４〜１７のうち、試料Ｎo.１４は焼成温度が低すぎるため緻密化せず、試料Ｎo.１７は逆に焼成温度が高すぎるためＳｉＯ₂と炭素が反応してＳｉＣ結晶を形成して暗緑色となり、さらに反応時に発生したガスにより内部に気泡が生じて密度が低下した。
【００５６】
原料の純度をかえた場合、試料Ｎo.１９はＳｉ以外の金属量が０．１重量％よりも多いために焼結体中のＳｉ以外の金属量が増加し暗褐色に着色するとともにその不純物を核として結晶化がおこり高温ではさらにそれが進んで白濁した。
【００５７】
原料中の水酸基含有率については、２０ｐｐｍを越える試料Ｎo.２１では焼成工程にて水酸基が除去しきれず残留し、高温での変形の原因となっている。
【００５８】
原料の平均粒径に関しては、５μｍを越える試料Ｎo.２５、２６では炭素がＳｉＯ₂と反応しない温度では緻密化が困難であった。
【００５９】
また、炭素源としてグラファイトを添加した試料Ｎo.２８では炭素含有量が１％を越えているため焼結が阻害され、さらに結晶化が生じて目的とする黒色ＳｉＯ₂焼結体を得ることができなかった。また、試料Ｎo.２９のように炭素源となる結合剤等を添加しなかった場合には黒色化できなかった。
【００６０】
それに対し、本発明におけるＳｉＯ₂焼結体である試料Ｎo.１〜７、１５、１６、１８、２０、２２〜２４、２７では、密度２．０３〜２．２１ｇ／ｃｍ³、直線透過率が２００〜１６０００ｎｍの波長で最大１％以下であった。また、水酸基含有率が５ｐｐｍ以下であり、結晶相を持たないことから１４００℃にて熱処理を行っても変形、変色を起こさない耐熱性を有し、しかも、エッチングレート５０ｎｍ／ｍｉｎ以下の優れた耐食性を示した。
【００６１】
【発明の効果】
以上詳述したように、本発明によれば、金属不純物を含有せず、耐熱性やプラズマ特性を劣化させる水酸基含有量を低減し、腐食性ガスとの接触においても高い耐食性を有する緻密な焼結体を耐食性部材として用いることにより、半導体製造プロセスにおいて、部材の長寿命化とともに、重大な影響を及ぼす金属不純物の混入がなく、熱処理のエネルギー効率を向上させることが可能となる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a high-purity black SiO ₂ corrosion-resistant member useful as a corrosion-resistant member for heat treatment exposed to a corrosive gas or the like, particularly in the field of semiconductor and liquid crystal production, and a method for producing the same.
[0002]
[Prior art]
Conventionally, in a highly integrated circuit formation process such as a semiconductor element or a liquid crystal, mixing of impurities affects element characteristics, and therefore, a quartz glass member that can produce a high-purity member relatively easily has been frequently used. However, particularly in heat treatment processes such as infrared heating, energy loss in using a transparent quartz glass member has recently attracted attention, and a black high-purity material that does not transmit infrared rays is required.
[0003]
Conventionally, blackening of the quartz glass, V ₂ O ₅ or the like in a quartz glass, which is produced by adding transition metal oxide, such as Va metal or Fe ₂ O ₃ as a coloring agent (JP 54 No. -157121, JP-A-7-196335, JP-A-4-254433, etc.). However, since such materials easily change color due to high-temperature thermal history and contain a relatively large amount of coloring metals that may adversely affect semiconductors, they are especially members for heat treatment processes in semiconductor manufacturing. It was not preferable.
[0004]
On the other hand, there has been proposed a method of uniformly blackening quartz glass by adding silicon carbide or carbon without adding an impurity metal (Japanese Patent Laid-Open Nos. 5-170477 and 5-306142). Gazette, JP-A-6-122533).
[0005]
JP-A-5-306142 proposes that a black component containing 1 to 5% by weight of carbon is prepared by adding a carbon component to quartz glass powder and firing it.
[0006]
Further, a carbon-containing quartz glass obtained by firing a mixture of carbon powder and silica powder is also proposed in Japanese Patent Laid-Open No. 3-279209.
[0007]
[Problems to be solved by the invention]
However, as disclosed in JP-A-5-170477 and the like, when silicon carbide is added, densification is inhibited and a low-density porous body is formed. Therefore, it is necessary to perform densification using a hot isostatic press or the like. there were. In addition, since the color tone changes in the process of vitrification, it is difficult to obtain a stable material.
[0008]
In addition, the carbon-containing black quartz glass described above is excellent in heat resistance and oxidation resistance, but is not sufficient in terms of corrosion resistance against corrosive gas, etc., for example, in a system that contains corrosive gas in the system and heats it. In such a case, the carbon-containing black quartz glass is corroded by the corrosive gas, and the generation of particles causes problems such as adversely affecting the system.
[0009]
In particular, quartz glass containing more than 1% by weight of carbon as disclosed in JP-A-5-306142 has a problem that it is easily corroded when it comes into contact with corrosive gas.
[0010]
This invention has excellent corrosion resistance even when exposed to corrosive gases, etc., exhibits a high-purity black color that can improve the energy efficiency of heat treatment, and contains metal impurities that have a significant effect on semiconductor manufacturing processes. In addition, the present invention provides a dense black SiO ₂ sintered body in which the content of hydroxyl group that deteriorates heat resistance and plasma characteristics is reduced, and a production method for stably producing it.
[0011]
[Means for Solving the Problems]
The black SiO ₂ quality corrosion-resistant member of the present invention has a carbon content of 0.05 to 1.0% by weight, a density of 2.03 to 2.21 g / cm ³ , a hydroxyl group content of 5 ppm or less, and a metal other than Si. It consists of an amorphous sintered body having a total amount of 0.5% by weight or less , and a linear transmittance at a wavelength of 200 to 16000 nm is 1% or less with respect to an amorphous sintered body having a thickness of 1 mm. Is.
[0012]
A method of manufacturing a black SiO ₂ quality corrosion resistant member of the present invention, the total amount of metal other than Si is 0.1 wt% or less, 20 ppm or less hydroxyl group content and an average particle size 5μm or less of SiO ₂ powder, 250 An organic binder that can be a carbon source is added by heat treatment at a temperature of 450 ° C. to form a predetermined shape, and the molded body is heat-treated at a temperature of 250 to 450 ° C. in an oxidizing atmosphere to decompose the organic binder. After carbon is produced, the sintered body is fired at 1100 to 1600 ° C. in a non-oxidizing atmosphere, and has a density of 2.03 to 2.21 g / cm ³ and a carbon content of 0.05 to 1.0% by weight. It is characterized by obtaining.
[0013]
[Action]
The black SiO ₂ -based corrosion-resistant member of the present invention has a linear transmittance in a wide wavelength range from 200 nm to 16000 nm in the far-infrared range of 1% or less with respect to a thickness of 1 mm (substantially the detection limit of the measuring apparatus). Therefore, when used as a member for heat treatment at the time of manufacturing a semiconductor, it is effective in improving thermal efficiency as compared with a transparent quartz glass member. Moreover, since it consists essentially of an amorphous phase, it is possible to maintain the characteristics without crystallization and discoloration up to a temperature of at least 1400 ° C.
[0014]
Furthermore, since the hydroxyl group content is 5 ppm or less, it exhibits high corrosion resistance against corrosive gases, maintains high strength against high-temperature thermal history in the heat treatment process, and also releases hydroxyl groups in the plasma treatment process. Does not adversely affect the plasma.
[0015]
Further, in producing the black SiO ₂ sintered body of the above characteristics, the total amount of metal other than Si is 0.1 wt% or less, 20 ppm or less by hydroxyl content, the following SiO ₂ powder having an average particle size of 5 [mu] m, an organic A binder is added to form a predetermined shape, and the molded body is heat-treated in an oxidizing atmosphere at a temperature of 250 to 450 ° C., and the organic binder that can be a carbon source is decomposed by the heat treatment at a temperature of 250 to 450 ° C. By generating carbon, the carbon can be converted into a state in which it can be easily dissolved in the SiO ₂ glass network, and then calcined at 1100 to 1600 ° C. in a vacuum or non-oxidizing atmosphere. A member having excellent characteristics can be stably produced.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
The black SiO ₂ -based corrosion-resistant member of the present invention is in contact with a corrosive gas typified by a halogen-containing gas such as HF, HC1, or ClF ₃ , for example, a highly integrated circuit forming process such as a semiconductor element or a liquid crystal, particularly a lamp anneal. It is useful as a member for bell jars, rings, furnace core tubes, etc. of heat treatment apparatuses such as CVD and diffusion furnaces, and is particularly transparent because the linear transmittance at a wavelength of 200 to 16000 nm is 1% or less with respect to 1 mm in thickness. Quartz glass can be used without losing energy released to the outside as light, which is effective in improving thermal efficiency.
[0017]
The black SiO ₂ quality corrosion-resistant member of the present invention contains 0.05 to 1.0% by weight, particularly 0.2 to 0.8% by weight of carbon in terms of composition, and the balance is substantially made of SiO _2. It consists of the body. This carbon is a component that blackens the sintered body. However, when the carbon content is less than 0.05% by weight, it is difficult to produce a uniform black color due to uneven color, and light transmittance. When this is increased to more than 1% and used as a member, no effect is observed in improving thermal efficiency.
[0018]
On the other hand, if the carbon content exceeds 1.0% by weight, the sinterability is drastically lowered, and a predetermined density cannot be obtained, resulting in a porous body. Further, even if the firing temperature is raised, gas is generated by the reaction of carbon and silica, so that it becomes a foam and the strength is greatly reduced.
[0019]
Further, the sintered body constituting the corrosion-resistant member has a density of 2.03 to 2.21 g / cm ³ , particularly 2.10 to 2.20 g / cm ³ . If the density is lower than 2.03 g / cm ^{3, the} strength decreases due to residual pores and the light transmittance increases, and if the density is higher than 2.21 g / cm ³ , SiO ₂ is crystallized or carbon is reduced. It becomes SiC and heat resistance decreases.
[0020]
Furthermore, the SiO ₂ sintered body in the present invention is substantially composed only of an amorphous material. In the SiO ₂ + C system, crystal phases such as quartz, cristobalite, and silicon carbide are easily generated, but in the present invention, these crystal phases are not detected even by a known crystal phase detection method such as X-ray diffraction measurement. Is. This is because when the high-temperature thermal history is repeated in the presence of a crystal phase, the crystal phase grows or the life of the member decreases due to cracks caused by the difference in thermal expansion between the amorphous phase and the crystal phase. It is.
[0021]
The presence form of carbon contained in the SiO ₂ sintered body in the present invention is that the silicon carbide crystal phase is not confirmed as described above, and depending on the production method, the transparent body or Since it becomes a white body having a crystalline phase, in the sintered body of the present invention, the binder that can be a carbon source uniformly dispersed between the fine SiO ₂ particles is decomposed by heat treatment and taken into the glass network and fired. It is thought that the solution is uniformly dissolved and blackened in the process.
[0022]
Further, it is important that the hydroxyl group content is 5 ppm or less, particularly 1 ppm or less. When this hydroxyl group comes into contact with a corrosive gas, it reacts with the gas to break the glass network and further reduces the corrosion resistance in order to accelerate the reaction. In addition, there is a problem that the heat resistance at high temperature is low and the member is deformed by repeating the high temperature heat history. Furthermore, when the member is used in plasma, the corrosion resistance to the plasma on the member surface is reduced, and the plasma state is adversely affected by the release of hydroxyl groups from the member, resulting in the etching rate distribution in the plasma apparatus and the variation between batches. Is likely to occur.
[0023]
The hydroxyl group content C (ppm) can be calculated by the following equation 1 based on the Lambert-Beer equation after measuring the transmittance of infrared rays at wavelengths of 2.60 μm and 2.73 μm.
[0024]
[Expression 1]

[0025]
In addition, in consideration of preventing contamination of impurities during the manufacture of semiconductor elements, the metal content other than Si must be 0.5% by weight or less, particularly 0.3% by weight or less and 0.1% by weight or less. It is.
[0026]
Further, in improving the corrosion resistance at the time of contact with the corrosive gas, the average surface roughness Ra of the surface of the member made of the above-mentioned SiO ₂ sintered body is 1 μm or less, particularly 0.5 μm or less, further 0.1 μm or less. It is desirable that This is because if the surface roughness is rough, the contact area with the corrosive gas becomes large, and the progress of corrosion is accelerated.
[0027]
Next, as a method for producing the black SiO ₂ quality corrosion-resistant member, the raw material powder has a total amount of metals other than Si of 0.1% by weight or less, particularly 0.05% by weight or less, and a hydroxyl group content of 20 ppm or less. A high-purity SiO ₂ powder of 15 ppm or less and an average particle size of 5 μm or less, particularly 1 μm or less is prepared. In particular, this SiO ₂ powder is preferably a synthetic raw material rather than a natural raw material.
[0028]
If the total amount of metals other than Si in the SiO ₂ raw material powder is more than 0.1% by weight, it becomes difficult to finally make the total amount of metals other than Si in the sintered body 0.5% by weight or less, In addition to mixing impurities into the semiconductor element from the member and causing particle formation of impurities, crystallization using impurity metals as crystal nuclei progresses inside the sintered body, whitening, deterioration of heat resistance, alteration due to thermal history This is because the desired amorphous sintered body cannot be obtained.
[0029]
If the average particle size of the raw material is larger than 5 μm, the temperature required for sintering rises to near the melting point, the powder melts and gas is generated by the reaction between carbon and silica, resulting in a foam. A sintered body cannot be obtained. Therefore, by using raw material powder having an average particle size of 5 μm or less, a dense sintered body can be produced without melting at a temperature lower than the melting point by 100 ° C. or more.
[0030]
On the other hand, if the hydroxyl group content of the raw material powder exceeds 20 ppm, it is difficult to reduce the hydroxyl group remaining in the sintered body to 5 ppm or less. Since it is difficult to remove the hydroxyl group in the raw material by the treatment after synthesis, it is necessary to minimize the amount of hydroxyl group in the raw material in order to obtain a sintered body having a low hydroxyl group content. In order to reduce this hydroxyl group content, for example, a method in which an oxidizable silicon compound is reacted with oxygen gas by laser heating (Japanese Patent Publication No. 53-2443), or a heat treatment in a hydrogen atmosphere (Japanese Patent Laid-Open No. 5-254859). ) Etc.
[0031]
As a raw material synthesis method, any method can be used as long as the resulting SiO ₂ powder having the above-mentioned characteristics can be obtained. From the viewpoint of obtaining a fine powder having a low hydroxyl group content, SiCl ₄ Desirable are a high-temperature hydrolysis method, a plasma method of reacting in oxygen or oxygen, Ar mixed plasma, and a method of burning high-purity metal Si powder in an oxidizing air stream. Since the sol-gel method using silicate alkoxide as a raw material often contains a large amount of chemically adsorbed water, it is not preferable as a raw material for producing the sintered body of the present invention.
[0032]
Next, an organic binder such as wax or polyvinyl alcohol that can be a carbon source is added to the powder together with a solvent such as isopropyl alcohol or water and mixed uniformly. If desired, crushing and pulverization can be performed separately or simultaneously.
[0033]
Thereafter, the mixed raw material is formed into a predetermined shape. As a molding method, an appropriate molding method may be selected according to the shape of the target member. Specifically, any of dry molding methods such as mold press molding and isotropic hydrostatic press molding, and wet molding methods such as cast molding, extrusion molding, and injection molding may be used.
[0034]
In addition, when performing pulverization, pulverization, etc. in a wet process, the solvent is not particularly limited. For example, even if water is used, the hydroxyl group content of the sintered body is not affected at all.
[0035]
The SiO ₂ compact thus molded is heat treated at a temperature of 250 to 450 ° C. in an oxidizing atmosphere to perform degreasing and decomposition treatment. At this time, if the treatment is performed in a vacuum or a non-oxidizing atmosphere, the binder evaporates without being decomposed, and a residual carbon amount necessary for blackening cannot be obtained. When the heat treatment temperature is lower than 250 ° C., the binder remaining undecomposed is degreased without being decomposed during firing, and the sintered body is not uniformly blackened. On the other hand, if the temperature exceeds 450 ° C., the oxidation of carbon becomes remarkable and the carbon content becomes less than 0.05% by weight, so that a black sintered body cannot be obtained.
[0036]
Also, since the carbon that decomposes and remains at this stage hardly changes quantitatively even after firing, the heat treatment temperature is appropriately selected within the temperature range specified in the present invention according to the decomposition temperature of the added binder and the like. The necessary amount of carbon may be adjusted.
[0037]
The SiO ₂ molded body treated in this manner is subjected to a temperature range of 1100 to 1600 ° C., more preferably 1250 to 1450 ° C. in a non-oxidizing atmosphere such as vacuum or nitrogen gas, argon gas, or a mixed gas of hydrogen and argon. By firing, a member made of a densely and uniformly blackened SiO ₂ sintered body is obtained in which the carbon dispersed uniformly in the molded body during the sintering process is taken into the glass network without reacting. .
[0038]
In order to reduce the hydroxyl group content in the sintered body, vacuum firing is preferable, but a hydroxyl group content of 5 ppm or less can be achieved even in the non-oxidizing atmosphere. The degree of vacuum at the time of vacuum firing is preferably 0.2 Torr or less.
[0039]
On the other hand, when fired in an oxidizing atmosphere such as in the air, blackening cannot be performed for the same reason as in the previous heat treatment process, and in addition, the hydroxyl content in the sintered body is 100 ppm or more and the target black The SiO ₂ sintered body cannot be produced.
[0040]
Also, if the firing temperature is lower than 1100 ° C., a sintered compact is not obtained because the sinterability is lowered, and a sintered body with white, gray, or uneven color due to insufficient solid solution of carbon. Become. Furthermore, when the temperature is higher than 1600 ° C., since the raw material particle size is fine, melting starts and the whole is vitrified and the shape cannot be maintained. In addition, gas is generated by the reaction of carbon and SiO ₂ and contains a large amount of bubbles. Since the carbon necessary for blackening is consumed, the desired black SiO ₂ sintered body cannot be obtained.
[0041]
The black SiO ₂ sintered body obtained in this way can produce a member having a desired shape as it is or by grinding or the like according to the member shape to be applied. Moreover, although it can be used as it is depending on the purpose of the member in contact with the corrosive gas, it can be ground and polished as appropriate to be processed into a desired shape.
[0042]
【Example】
SiO ₂ raw material produced by burning metal Si fine powder in an oxygen stream and having a metal content other than Si of 0.01 to 0.2% by weight, a hydroxyl group content of 10 to 25 ppm, and an average particle size of 0.2 to 15 μm Sintered bodies were produced using the powders and the physical properties were evaluated.
[0043]
The sintered body was prepared by wet crushing the raw material powder with a ball mill using ultrapure water as a solvent, and adding various compounds shown in Table 1 as organic binders to prepare a slurry. A high-purity SiO ₂ ball was used as a medium during wet crushing. The raw material powder obtained by granulating this slurry was molded with a mold press under a load of 0.8 ton / cm ² and degreased under the conditions shown in Table 1.
[0044]
The degreased body thus produced was fired under the firing conditions shown in Table 1, and the following characteristics of the obtained SiO ₂ sintered body were measured.
[0045]
As characteristic evaluation, the sintered compact density measured the bulk density by the Archimedes method. The color tone of the sintered body was determined by visual observation of a portion cut out near the center of the sintered body and processed to a thickness of 1 mm. The linear transmittance of light was processed to a thickness of 1 mm, and the light transmittance was measured at a wavelength of 200 to 16000 nm, and the maximum value was shown. The hydroxyl group content was calculated based on the above formula 1 by performing IR (infrared absorption spectrum) measurement.
[0046]
The crystal phase of the sintered body was measured by a powder X-ray diffraction method by cutting out the central portion of the sintered body and crushing it. For the material strength, a 4 mm × 3 mm × 50 mm test piece was cut out from the sintered body, and a bending test was performed by a four-point bending test based on JIS R1601.
[0047]
For heat resistance, the sintered body was held at 1400 ° C. for 2 hours, and changes in weight, dimensions, color tone, and cracks were evaluated.
[0048]
Furthermore, the corrosion resistance is that a sintered body having a diameter of 200 mm is prepared, the surface is mirror-polished so that the average surface roughness Ra becomes 0.08 μm, and then this is subjected to HF using a RIE (reactive ion etching) apparatus. The plasma was exposed to plasma at room temperature, and the etching rate was measured.
[0049]
[Table 1]

[0050]
[Table 2]

[0051]
According to the results of Tables 1 and 2, among the samples No. 1 to 10 degreased in the air, the sample No. 8 which was fired in the air was desorbed due to oxidation of the carbon component during the firing process, Since the amount of carbon in the sintered body was insufficient, a transparent sintered body was obtained. In addition, since a large amount of hydroxyl groups remained in the sintered body, the viscosity decreased at high temperatures and deformed.
[0052]
Sample No. 9 had a low degreasing temperature, decomposition of the binder did not proceed, and crystallization occurred with free carbon as a nucleus, resulting in a translucent sintered body. At a high temperature, the inherent fine crystals grew and microcracks were generated, which resulted in partial cloudiness.
[0053]
Sample No. 10 had a high degreasing temperature, and the binder decomposed into carbon reacted with oxygen to be eliminated, resulting in a transparent body having a low carbon content. Sample No. 11 was baked as it was without being degreased, and as a result, the binder was removed without oxidative decomposition during the calcination, so that it became a transparent body.
[0054]
Since Samples No. 12 and 13 were not in an oxidizing atmosphere, during degreasing, the binder melted and desorbed without being decomposed, resulting in a transparent sintered body with a low carbon content. When these transparent sintered bodies are heat-treated at a high temperature, crystallization proceeds from the surface unless they contain an impurity metal, and they become cloudy and cannot be used.
[0055]
Among samples 14 to 17 having different firing temperatures, sample No. 14 is not densified because the firing temperature is too low, and sample No. 17 is too high because the firing temperature is too high, and SiO ₂ reacts with carbon. Crystals formed a dark green color, and the gas generated during the reaction produced bubbles in the interior, reducing the density.
[0056]
When the purity of the raw material was changed, Sample No. 19 had more than 0.1% by weight of metal other than Si, so the amount of metal other than Si in the sintered body increased and colored dark brown and its impurities Crystallization occurred at the nuclei and further progressed at high temperatures and became cloudy.
[0057]
With respect to the hydroxyl group content in the raw material, in sample No. 21 exceeding 20 ppm, the hydroxyl group could not be completely removed in the firing step, causing deformation at high temperatures.
[0058]
Regarding the average particle diameter of the raw material, it was difficult to densify the samples No. 25 and 26 exceeding 5 μm at a temperature at which carbon did not react with SiO ₂ .
[0059]
Further, in sample No. 28 to which graphite was added as a carbon source, the carbon content exceeded 1%, so that sintering was hindered and further crystallization occurred to obtain the desired black SiO ₂ sintered body. could not. In addition, as in sample No. 29, when a binder or the like serving as a carbon source was not added, blackening could not be achieved.
[0060]
On the other hand, in samples No. 1 to 7, 15, 16, 18, 20, 22 to 24, and 27, which are SiO ₂ sintered bodies in the present invention, the density is 2.03 to 2.21 g / cm ³ , and the linear transmittance is. Was up to 1% at a wavelength of 200 to 16000 nm. In addition, since the hydroxyl group content is 5 ppm or less and does not have a crystal phase, it has heat resistance that does not cause deformation or discoloration even when heat treatment is performed at 1400 ° C., and has an excellent etching rate of 50 nm / min or less. Corrosion resistance was shown.
[0061]
【The invention's effect】
As described above in detail, according to the present invention, a dense firing that does not contain metal impurities, reduces the hydroxyl group content that degrades heat resistance and plasma characteristics, and has high corrosion resistance even in contact with corrosive gases. By using the bonded body as a corrosion-resistant member, it is possible to improve the energy efficiency of the heat treatment without increasing the life of the member and mixing metal impurities having a significant effect in the semiconductor manufacturing process.

Claims

Carbon content from 0.05 to 1.0 wt%, a density of 2.03~2.21g / cm ^3, a hydroxyl group content of 5ppm or less, the total amount of metal other than Si is 0.5 wt% or less of amorphous A black SiO ₂ quality corrosion-resistant member comprising a sintered material having a linear transmittance of 1% or less at a wavelength of 200 to 16000 nm with respect to an amorphous sintered material having a thickness of 1 mm .

An organic binder that can be a carbon source by heat treatment at a temperature of 250 to 450 ° C. is added to a SiO ₂ powder having a total amount of metals other than Si of 0.1% by weight or less, a hydroxyl group content of 20 ppm or less, and an average particle size of 5 μm or less. Then, the molded body is heat-treated at a temperature of 250 to 450 ° C. in an oxidizing atmosphere to decompose the organic binder to form carbon, and then 1100 in a non-oxidizing atmosphere. A method for producing a black SiO ₂ corrosion-resistant member obtained by firing at 1600 ° C. to obtain a sintered body having a density of 2.03 to 2.21 g / cm ³ and a carbon content of 0.05 to 1.0% by weight.