JP2004161512A - Low thermal expansion ceramic member, method of manufacturing the same, and member for semiconductor manufacture apparatus - Google Patents
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【０００１】
【発明の属する技術分野】
本発明は、半導体集積回路あるいは液晶集積回路などを作製する際に、半導体ウェーハあるいは液晶ガラス基板に露光処理を施す際に用いられる半導体あるいは液晶露光装置用部材、具体的には真空チャック、ステージあるいはステージ位置測定ミラーなどの半導体製造プロセスにおける治具などに適した、コーディエライト、スポジューメンまたはユークリプタイトを主体とする低熱膨張セラミックス部材およびその製造方法に関する。
【０００２】
【従来の技術】
ＬＳＩなどの高集積化に伴い、回路の超微細化が進められ、その線幅は半導体においては０．１ミクロンを切るレベルにまで到達しようとしている。そして、このような回路を形成するための露光装置に要求される精度も年々高くなってきており、それに伴い、露光装置に使用される部材として熱膨張係数の低いものが開発されてきている。たとえば、コーディエライトを８０質量％以上、望ましくは希土類元素を酸化物換算で１〜２０質量％含有し、気孔率が０．１％以下、１０〜４０℃における熱膨張係数が１×１０−６／℃以下である緻密質低熱膨張セラミックスからなる半導体製造装置用部材が開示されている（特許文献１参照）。
【０００３】
また、コーディエライトを８０質量％以上、望ましくは希土類元素を酸化物換算で１〜２０質量％含有し、気孔率が０．５％以下、カーボン含有量が０．１〜２．０質量％であり、１０〜４０℃における熱膨張係数が０．５×１０−６／℃以下である低熱膨張性黒色セラミックスおよびそのような緻密質低熱膨張セラミックスからなる半導体製造装置用部材が開示されている（特許文献２参照）。
【０００４】
さて、回路の超微細化が進むにつれて、半導体あるいは液晶ガラス基板の露光精度を確保するため、たとえば、露光装置用真空チャック、ステージ位置測定ミラー向けの材料には、低い熱膨張係数および高い剛性（ヤング率）が求められる。従来より、低熱膨張材として利用されてきた材料のうち、石英、β−スポジューメン、チタン酸アルミニウム、結晶化ガラスなどは、剛性に問題がある。一方、従来の緻密質コーディエライト材、あるいは、コーディエライトを主成分とする低熱膨張セラミックス（特許文献１、特許文献２参照）、あるいは、ユークリプタイトを主成分とする低熱膨張セラミックス（特許文献３参照）は、低い熱膨張係数および製品として使用し得るレベルの高い剛性という上記の条件を満たし得る。
【０００５】
これらのセラミックスは、一般には常圧焼結、高圧付与のホットプレス焼結あるいはＨＩＰ焼結などの手法により、焼結される。しかし、この焼結により素材には応力が残留する。また、焼結後の加工においても、加工面には応力が残留する。かかる残留応力により、製品は変形および割れなどの影響を受けることとなる。
【０００６】
たとえば、変形においては、これらのセラミックスは前述のとおり製品として使用しうるレベルの剛性を備えてはいるが、アルミナまたはＳｉＣセラミックスに比べて約１／２〜１／３程度のヤング率しか備えておらず、付加された応力により変形しやすい。また、焼結または加工工程で製品に付与された残留応力が瞬間的にあるいは長期間をかけて解放される際に、製品は変形し、たとえば、平面度が変化するなど、精度が狂いやすい。さらに、このように長期間をかけて製品平面度などの製品精度の経時変化が発生した場合、折角、初期に高精度に加工したとしても残留応力解放要因による製品精度が変化し、あらためて修正加工が必要とされるケースが生じうる。一方、割れにおいては、焼結体を所望の形状に加工する際に加工応力が素材に付与され、素材中に残留応力があれば、加工割れが発生するリスクが高まる。
【０００７】
さて、研削加工により製品表層に生じたマイクロクラックによる素材強度回復策としては、たとえば、セラミックス焼結体を所定の形状に研削加工した後、８００〜１１００℃で１〜２４時間の熱処理を施す方法があり、これにより研削加工の際に生じたミクロな鋭角状の切欠きが丸められ、機械的強度が向上することができる（特許文献４参照）。また、研削加工が施された焼結体に最後に加熱処理として１０００〜１５５０℃の温度で０．１〜６時間にわたり加熱処理する方法があり、マイクロクラックの先端部が丸みを帯びるようになり、割れ感受性が低下し、プラズマイオンの照射を受けてもセラミックス粒子の飛散を抑止することが可能である（特許文献５参照）。
【０００８】
【特許文献１】
特開平１１−２０９１７１号公報
【０００９】
【特許文献２】
特開平１１−３４３１６８号公報
【００１０】
【特許文献３】
特開２０００−２１９５７２号公報
【００１１】
【特許文献４】
特開昭６３−５５１８０号公報
【００１２】
【特許文献５】
特許３１２６６３５号公報
【００１３】
【発明が解決しようとする課題】
しかし、これらはいずれもアルミナ、窒化ケイ素、ＳｉＣなど高いヤング率を有し、応力により変形しにくいセラミックスに対するマイクロクラック対策であり、コーディエライトなどの低熱膨張セラミックスのように比較的ヤング率が低く、応力の解放により変形が生じやすいセラミックス製品について精度の向上を図るという課題認識はない。
【００１４】
本発明の課題は、コーディエライト、スポジューメンおよびユークリプタイトなどを含む低熱膨張セラミックス部材において、加工による割れを抑え、高精度に仕上げた表面の残留応力を極小にし、かつ精度の変化を極小にするための処理方法を明らかにし、高精度を維持した部材を提供することにある。
【００１５】
【課題を解決するための手段】
本発明者らは、上記課題に対し鋭意研究を重ねた結果、１０〜４０℃における熱膨張係数が０．５×１０−６／℃以下で、気孔率が０．５％以下のセラミックスの焼結後、最終の加工工程までの間に、５００〜１２００℃で０．３〜２００時間の熱処理を少なくとも１回行なうことにより、加工による割れを抑え、セラミックス部材の表面における残留応力を低減し、高精度を維持した低熱膨張セラミックス部材を製造することができることを見出した。かかる熱処理は、セラミックスの焼結後、最初の加工工程までの間に、５００〜１２００℃で０．３〜２００時間の熱処理を行ない、最終の加工工程の直前に、５００〜１１００℃で０．３〜２００時間の熱処理をさらに行なう態様が望ましい。また、熱処理においては、加熱後、６００℃以下の温度までの冷却速度を毎時２０℃以下とすることが望ましい。
【００１６】
本発明の低熱膨張セラミックス部材は、１０〜４０℃における熱膨張係数が０．５×１０−６／℃以下で、気孔率が０．５％以下の低熱膨張セラミックスからなり、残留応力が２０ＭＰａ以下であることを特徴とし、かかるセラミックスとしては、コーディエライトと、スポジューメンと、ユークリプタイトとからなる群より選択された少なくとも１種を含むものが好適である。また、本発明の半導体製造装置用部材は、１０〜４０℃における熱膨張係数が０．５×１０−６／℃以下で、気孔率が０．５％以下で、残留応力が２０ＭＰａ以下である低熱膨張セラミックス部材からなることを特徴とする。
【００１７】
【発明の実施の形態】
（低熱膨張セラミックス部材の製造方法）
本発明の低熱膨張セラミックス部材の製造方法は、セラミックスの焼結後、最終の加工工程までの間に、５００〜１２００℃で０．３〜２００時間の熱処理を少なくとも１回行なうことを特徴とする。かかる熱処理を施すことにより、焼結時あるいは加工時に付与された残留応力を緩和して、加工時の割れのリスクを低減し、セラミックス部材の製品精度を高く維持することができるようになる。セラミックス部材の表面における残留応力を２０ＭＰａ以下にすると、精度変化を低減することができる。部材表面の残留応力は、加工時の割れをより少なくし、製品精度をより高める点で、１５ＭＰａ以下が望ましい。ここに加工とは、セラミックスの焼結後に行なう厚み加工、外径加工、両面粗研磨加工または両面精度出し研磨加工などを指す。コーディエライト、ユークリプタイトなどの低熱膨張セラミックスは低強度材であるため、残留応力があると、加工時の加工応力により割れが生じやすい。
【００１８】
熱処理の温度は、５００〜１２００℃とする。５００℃未満では応力の解放は少なくなり、１２００℃より高温では、素材の変形が大きくなる。なお、最高温度については、たとえば、コーディエライトを主成分とする場合は、１２００℃を上限とし、スポジューメンを主成分とする場合は、１１５０℃を上限とし、また、ユークリプタイトを主成分とする場合は、１１００℃を上限とするのが望ましい。
【００１９】
熱処理の時間は、０．３〜２００時間とする。たとえば、外径３０ｍｍ程度の小型製品であれば０．３時間が最低必要で、０．３時間未満では充分な効果が望めない。また、外径３００ｍｍ以上の大型製品においては、２時間以上が望ましく、より望ましくは３時間以上である。処理時間は長い方が効果があるが、２００時間を超える処理時間は実用上困難である。
【００２０】
熱処理の回数は、少なくとも１回である。たとえば、加工毎に予め熱処理を実施するなど、製品の特性に影響を及ぼさない範囲内で、何度実施しても良い。また、製品の要求精度により、たとえば、１回だけの熱処理としてもよい。
【００２１】
熱処理の時期は、セラミックスの焼結後、最終の加工工程までの間である。焼結や加工により付与された残留応力を緩和し、割れおよび変形を抑制するためである。熱処理の時期は、セラミックスの焼結後、最初の加工工程までの間、および最終の加工工程の直前に行なうことが望ましい。セラミックスの焼結後、最初の加工工程までの間に熱処理を行なうことにより、焼結時に焼結体に残留している応力を解放し、以降の加工時に付与される加工応力による製品の割れを抑えることができる。
【００２２】
焼結後、最初の加工工程までの間に熱処理を行なうことにより、焼結体中の残留応力を緩和できるが、その後の加工工程で製品表面に応力が付与されるため、加工工程における残留応力によって、製品加工中の精度、あるいは製品化後の製品精度を高く維持することができなくなる可能性がある。そのため、製品化直前において、たとえば、最終の精度出し加工前に熱処理を行なうのが望ましい。熱処理により応力が解放し、これに伴い加工品の形状がわずかに変形するから、熱処理後に最終の精度出し加工を行なうことにより、所期の形状寸法に調整することができる。なお、最終の精度出し加工によっても製品に応力が付与されるが、かかる応力は微小であるため、影響は小さい。
【００２３】
最終の加工工程の直前に行なう熱処理は、５００〜１１００℃で０．３〜２００時間とするのが望ましい。処理温度が、５００℃未満では応力の解放は少なく、製品の変形を抑えるためには１１００℃以下とするのが望ましい。処理時間は、０．３〜２００時間とするのが望ましい。外径３０ｍｍ程度の小型製品でも０．３時間未満では充分な効果が望めない。また、外径３００ｍｍ以上の大型製品においては、２時間以上が望ましく、より望ましくは３時間以上である。処理時間は長い方が効果があるが、２００時間を超える処理時間は実用上困難である。
【００２４】
熱処理における冷却操作は、加熱後、６００℃以下の温度までの冷却速度を、毎時２０℃以下で徐冷することが望ましい。加熱により残留応力は緩和するが、冷却時の温度勾配が大きいと、製品に温度分布が大きく生じ、それにより残留応力が付与されるためである。最高温度から毎時２０℃以下の温度で徐冷する温度範囲（以下、「徐冷区間」という。）は、６００℃あるいは、それ以下の温度までとするのが望ましい。徐冷区間の下限は、６００℃以下の温度まで行なえば、残留応力が付与されるのを低減することができるが、たとえば、下記に示す転移点を下回る温度とすると、より望ましい。
【００２５】
図２に、温度変化と熱膨張係数の変化の関係を示す。図２は、純度９９％以上で平均粒径３μｍのコーディエライト粉末、平均粒径１μｍの窒化珪素粉末、平均粒径０．１μｍのカーボン粉末を、各々９６．５ｖｏｌ％、２ｖｏｌ％、１．５ｖｏｌ％となるように調合し、焼結して得たサンプル（３ｍｍ×３ｍｍ×１５ｍｍ）について、線膨張計により熱膨張係数を測定して作成したものである。測定条件は、
（１）測定区間：ＲＴ〜１３５０℃
（２）加熱速度：１０℃／分
（３）測定環境：Ｎ２ガスフロー中
コーディエライトなどの低熱膨張セラミックスの場合、図２に示すように温度の上昇に従い、熱膨張係数は直線的に増加するが、たとえば、３００〜６００℃の間でグラフに屈曲が見られる。この屈曲が生じる温度（以下、「転移点」と称する。）以下まで徐冷することが望ましい。転移点以下の温度では、徐冷による残留応力の緩和や製品平面度の抑制効果はあまり見られないため、たとえば１００℃以下の温度まで徐冷しても時間がかかるばかりであり、転移点以下で、３００〜４００℃程度の温度を徐冷区間の下限とすることが望ましい。
【００２６】
熱処理炉は、主原料以外の添加材が非酸化物である場合、または、カーボン分を添加材として使用している場合においては、窒素またはアルゴン雰囲気に置換が可能な炉を使用する。真空炉に、これらの不活性ガスを置換する手法が望ましいが、製品の導電性や膨張係数などの特性に悪影響がない範囲ならば、たとえば真空構造でなく、ガスフローのみの炉であっても使用は可能である。真空炉を使用する場合には、炉内は真空ではなく、少なくとも０．５気圧以上のガス圧がある方が望ましい。これは、真空ならば、製品への熱伝達が輻射および熱伝導に頼る必要があって、炉内の位置により温度分布が生じやすくなり、製品に温度分布が発生すると、製品の残留応力が強くなりやすいためである。一方、ガス圧があれば、熱伝達に炉内の対流が加わるため、製品への熱伝達が比較的均一に進行し、製品の温度分布を小さくし、製品の残留応力を抑えることができる。主原料以外の添加材が酸化物である場合には、大気雰囲気炉、たとえばガス炉や電気炉を使用することができる。
【００２７】
本発明の低熱膨張セラミックス部材の製造方法において使用するセラミックスは、１０〜４０℃における熱膨張係数が０．５×１０−６／℃以下であり、気孔率が０．５％以下である。１０〜４０℃における熱膨張係数を０．５×１０−６／℃以下と限定しているのは、高精度が要求される部材においては使用時の温度変化による精度への影響が無視できないからである。たとえば、露光装置用真空チャックまたはステージ位置測定ミラー向け材料では、１０〜４０℃における熱膨張係数が０．５×１０−６／℃以下、より望ましくは０．３×１０−６／℃以下である。一方、気孔率を０．５％以下と限定しているのは、０．５％より大きくなると、強度およびヤング率などの特性が低下するためであり、また、たとえば、製品をＳｉウェーハ搭載用の治具として使用した場合においては、気孔へのパーティクル付着によるウェーハ自体の精度変化、および製品の吸水による精度変化が問題となるからである。
【００２８】
かかるセラミックスは、コーディエライト、スポジューメン、ユークリプタイトまたはそれらの組合せを主材とするものが好適である。低熱膨張材として知られているチタン酸アルミニウムは、緻密化が困難であり、緻密化できたとしても剛性が低く使用に耐えることができない。前述したとおりスポジューメンは、それ自体剛性が比較的低いが、比較的高い剛性を有するコーディエライトまたはユークリプタイトとともに焼結体を構成することにより、剛性の高いセラミックス材料をもたらすことができる。
【００２９】
かかるセラミックスには、必要な特性に応じて、４ａ族元素、５ａ族元素もしくは６族の炭化物、窒化物、硼化物、珪化物、ＳｉＣ、Ｂ４Ｃ、窒化珪素またはカーボン源を、低熱膨張性を阻害しない程度に添加しても良い。また、セラミックスは、希土類元素を含んでいても、含まなくともよい。希土類元素の化合物、典型的には希土類元素酸化物を使用しなくとも、下記に示すような製造方法により十分緻密な低熱膨張セラミックスを得ることができる。
【００３０】
かかるセラミックスは、具体的には、つぎの方法により焼結する。主材としては、平均粒径が１０μｍ以下、たとえば、２〜３μｍのコーディエライト粉末、β−スポジューメン粉末、β−ユークリプタイト粉末のうちの少なくとも１種を使用する。特性上、必要に応じて、４ａ族元素、５ａ族元素もしくは６族の炭化物、窒化物、硼化物、珪化物、ＳｉＣ、Ｂ４Ｃ、窒化珪素またはカーボン源を低熱膨張性を阻害しない程度に添加する。これらは市販されているが、カーボン源については粉末カーボンでもフェノール樹脂やフラン樹脂などを使用しても良い。
【００３１】
熱処理前の焼結体の調製方法には、たとえば、つぎの３種の方法がある。第１の方法としては、常圧で焼結する方法がある。まず、原料を調合し、アルコールまたは水などの溶媒を加え、必要に応じて、ＰＶＡやアクリル樹脂などの樹脂バインダを配合してボールミル混合し、乾燥させて、原料粉末を得る。得られた粉末から、金型プレス成形あるいはＣＩＰ成形などの手法によって、成形体を得る。その成形体を所望の形状に生加工し、焼結を実施する。
【００３２】
焼結は、大気雰囲気、不活性雰囲気または非酸化性雰囲気下で実施し、たとえば、コーディエライト主材においては１３００〜１４５０℃、β−スポジューメン主材においては１２００〜１３５０℃、β−ユークリプタイト主材においては１１５０〜１３００℃などの焼結温度が適している。得られた焼結体は、研削や研磨などにより所望の製品形状に機械加工することができる。
【００３３】
焼結体の別の調製方法としては、ホットプレス焼結をする方法がある。この方法は、まず、原料を調合し、アルコールや水などの溶媒でボールミル混合する。それを乾燥させて、原料粉末を得、この原料粉末を窒素やアルゴンなどの不活性雰囲気下でホットプレスにより焼結する。たとえば、コーディエライト主材においては１３００〜１４５０℃で４．９〜４９ＭＰａ、β−スポジューメン主材においては１２００〜１３５０℃で４．９〜４９ＭＰａ、β−ユークリプタイト主材においては１１５０〜１３００℃で４．９〜４９ＭＰａなどの条件が適している。得られた焼結体は、研削や研磨などにより所望の製品形状に機械加工することができる。
【００３４】
焼結体の別の調製方法としては、高温等方加圧焼結（ＨＩＰ）をする方法がある。この方法によれば、たとえば、常圧で焼結したコーディエライト主材の焼結体を、窒素やアルゴンなどの不活性雰囲気下、１２５０〜１４００℃、雰囲気圧力が２０〜２００ＭＰａなどの条件で焼結する。得られた焼結体は、研削や研磨などにより所望の製品形状に機械加工することができる。
【００３５】
（低熱膨張セラミックス部材）
本発明の低熱膨張セラミックス部材は、１０〜４０℃における熱膨張係数が０．５×１０−６／℃以下で、気孔率が０．５％以下のセラミックスからなり、残留応力が２０ＭＰａ以下であることを特徴とする。焼結時または加工時に付与された残留応力が緩和されているため、セラミックス部材の製品精度を高く維持することができる。セラミックスとしては、コーディエライトと、スポジューメンと、ユークリプタイトとからなる群より選択された少なくとも１種を含むものが好適である。
【００３６】
（半導体製造装置用部材）
本発明の半導体製造装置用部材は、１０〜４０℃における熱膨張係数が０．５×１０−６／℃以下で、気孔率が０．５％以下のセラミックスで、残留応力が２０ＭＰａ以下である低熱膨張セラミックス部材からなることを特徴とする。かかる半導体製造装置用部材は、表面の残留応力が低いため変形が少なく、精度の経時変化も小さい。したがって、特に、高精度が要求される露光装置用真空チェック、ステージ部材などの半導体製造装置用部材あるいは液晶製造装置用部材、加えて、光学精密部品や精密測定治具類など幅広い分野に適用することができる。
【００３７】
【実施例】
実施例１
純度９９％以上で平均粒径３μｍのコーディエライト粉末、平均粒径１μｍの窒化珪素粉末、平均粒径０．１μｍのカーボン粉末を、各々９６．５ｖｏｌ％、２ｖｏｌ％、１．５ｖｏｌ％となるように調合した後、溶媒としてエタノールを使用し、ボールミルで２４時間混合した。得られた混合物を乾燥した後、１３８０℃で窒素雰囲気下、４９ＭＰａの圧力下でホットプレス焼結した。得られた焼結体のサイズは外径３２０ｍｍ×高さ２３ｍｍであり、気孔率は０．１％以下であり、１０〜４０℃における熱膨張係数は０．１×１０−６／℃であった。
【００３８】
焼結体の気孔率は、外径３２０ｍｍ×高さ２３ｍｍの試料について、アルキメデス法により測定した。また、焼結体の熱膨張係数は、３ｍｍ×３ｍｍ×１５ｍｍの試料について、レーザ干渉法により測定した。レーザ干渉法は、レーザ熱膨張計を用いて、ヘリウム中、温度１０〜４０℃、昇温速度１℃／分で測定した。
【００３９】
得られた焼結体を、図１の製法１に示す方法で処理した。すなわち、焼結体に、第１回目の熱処理を施した後、厚み加工、外径加工、両面粗研磨加工、第２回目の熱処理をし、最後に両面精度出し加工を行なった。また、第１回目の熱処理は、１１００℃で５時間、４００℃までの冷却速度１５℃／時とした。厚み加工は、ロータリ平面研削盤により、素材の厚さ２０．１ｍｍ、平面度１０μｍ程度になるように粗加工を実施した。平面度は、接触型真直度測定機（測定子は電気マイクロメータを使用した。）を用いて評価した。
【００４０】
外径加工は、万能研削盤により、外径３００ｍｍに仕上げた。両面粗研磨加工は、両面研磨機で平均粒径１０μｍのダイヤモンド砥粒を使用し、素材の両面を同時に研磨をした。加工後の両面の平面度は２〜３μｍであった。第２回目の熱処理は、１０００℃で２０時間、３５０℃までの冷却速度１５℃／時とした。最後の両面精度出し加工は、片面研磨機により、平均粒径４μｍのダイヤモンド砥粒を使用し、素材の片面ずつ研磨した。加工後の両面の平面度は、０．５〜１．０μｍであり、加工後、外径３００ｍｍ×高さ２０ｍｍの円板状になるようにした。
【００４１】
得られたセラミックス部材について、平面度の変化と残留応力を測定した。平面度の変化は、最終加工日から１日後と、１０日後の平面度を測定し、両面の平面度の平均値を計算し、最初の平面度からの変化量で表した。残留応力は、表１に示す条件で測定し、最終加工直後の表面の残留応力を、表、裏の各面について、外周部２方向（箇所）、中心部２方向（箇所）測定し、表裏全８方向（箇所）の平均値を計算し、この絶対値をもって残留応力とした。平面度の変化と残留応力の測定結果を表２に示す。
【００４２】
【表１】
【表２】
実施例２
実施例１における第１回目の熱処理条件を、９００℃で４０時間、４００℃までの冷却速度１０℃／時とし、また、第２回目の熱処理条件を、４００℃で１００時間、３５０℃までの冷却速度１０℃／時とした以外は、実施例１と同様にして、セラミックス部材を製造し、平面度変化および残留応力を測定した。その結果を表２に示す。
【００４５】
実施例３
実施例１で実施した製造方法を、図１における製法２とし、第１回目の熱処理時間を８時間とした以外は、実施例１と同様にして、セラミックス部材を製造し、平面度変化および残留応力を測定した。その結果を表２に示す。
【００４６】
実施例４
実施例３で実施した熱処理条件を、８００℃で１００時間、４００℃までの冷却速度１０℃／時とした以外は、実施例３と同様にして、セラミックス部材を製造し、平面度変化および残留応力を測定した。その結果を表２に示す。
【００４７】
比較例１
実施例１で実施した製造方法を、図１における製法３とし、熱処理を一切行なわなかった以外は、実施例１と同様にして、セラミックス部材を製造し、平面度変化および残留応力を測定した。その結果を表２に示す。
【００４８】
比較例２
実施例１における第１回目の熱処理を、２５０℃で２００時間、１５０℃までの冷却速度１０℃／時とし、また、第２回目の熱処理を、２５０℃で２００時間、１００℃までの冷却速度１０℃／時とした以外は、実施例１と同様にして、セラミックス部材を製造し、平面度変化および残留応力を測定した。その結果を表２に示す。
【００４９】
比較例３
実施例３で実施した熱処理を、２５０℃で２００時間とした以外は、実施例３と同様にして、セラミックス部材を製造し、平面度変化および残留応力を測定した。その結果を表２に示す。
【００５０】
表２の結果から明らかなとおり、実施例１〜実施例４においては、最終加工日から１日後の平面度変化は０．０〜０．１５μｍであり、また、最終加工から１０日後の平面度変化はいずれも０．３μｍ以下であり、精度が高く維持されていた。これに対して、比較例１〜比較例３においては、１０日後の平面度変化が１．５〜２μｍであり、本発明の実施例と比較して精度の維持が困難であることがわかった。
【００５１】
また、残留応力については、実施例１〜実施例４では５〜１５ＭＰａであるのに対して、比較例１〜比較例３では２５〜４０ＭＰａであり、本発明の実施例では熱処理により製品表面の残留応力が十分に緩和されていることがわかった。また、セラミックス部材の表面の残留応力を２０ＭＰａ以下とすることにより、精度変化を低減できることがわかった。
【００５２】
今回開示された実施の形態および実施例はすべての点で例示であって制限的なものではないと考えられるべきである。本発明の範囲は上記した説明ではなくて特許請求の範囲によって示され、特許請求の範囲と均等の意味および範囲内でのすべての変更が含まれることが意図される。
【００５３】
【発明の効果】
本発明の低熱膨張セラミックス部材は、焼結時または加工時に付与された残留応力が緩和されているため、セラミックス部材の製品精度を高く維持することができる。かかる低熱膨張セラミックス部材は、セラミックスの焼結後、最終の加工工程までの間に、５００〜１２００℃で０．３〜２００時間の熱処理を少なくとも１回行なうことにより製造することができる。本発明の半導体製造装置用部材は、表面の残留応力が低いため変形が少なく、精度の経時変化も小さい。したがって、特に、高精度が要求される半導体製造装置用部材、液晶製造装置用部材、光学精密部品および精密測定治具類などに適用することができる。
【図面の簡単な説明】
【図１】焼結後、最終加工工程が終了するまでの、低熱膨張セラミックス部材の製造方法を示す工程図である。
【図２】温度変化と熱膨張係数の変化の関係を示す図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor or liquid crystal exposure apparatus member used when a semiconductor wafer or a liquid crystal glass substrate is subjected to an exposure process when producing a semiconductor integrated circuit or a liquid crystal integrated circuit, specifically a vacuum chuck, a stage or The present invention relates to a low thermal expansion ceramic member mainly composed of cordierite, spodumene or eucryptite suitable for a jig in a semiconductor manufacturing process such as a stage position measuring mirror, and a method for manufacturing the same.
[0002]
[Prior art]
Along with the high integration of LSIs and the like, ultra-fine circuits are being advanced, and the line width is about to reach a level of less than 0.1 microns in a semiconductor. Further, the accuracy required for an exposure apparatus for forming such a circuit is increasing year by year, and accordingly, a member having a low thermal expansion coefficient has been developed as a member used in the exposure apparatus. For example, cordierite is contained in an amount of 80% by mass or more, preferably 1 to 20% by mass of a rare earth element in terms of oxide, a porosity of 0.1% or less, and a thermal expansion coefficient at 10 to 40 ° C. of 1 × 10 -6 A member for a semiconductor manufacturing apparatus made of a dense low thermal expansion ceramic having a temperature of / ° C. or lower is disclosed (see Patent Document 1).
[0003]
Further, cordierite is contained in an amount of 80% by mass or more, preferably 1 to 20% by mass of rare earth element in terms of oxide, the porosity is 0.5% or less, and the carbon content is 0.1 to 2.0% by mass. The coefficient of thermal expansion at 10 to 40 ° C. is 0.5 × 10 -6 A low thermal expansion black ceramic having a temperature of / ° C. or less and a semiconductor manufacturing apparatus member made of such a dense low thermal expansion ceramic are disclosed (see Patent Document 2).
[0004]
Now, as circuit miniaturization progresses, in order to ensure the exposure accuracy of a semiconductor or a liquid crystal glass substrate, for example, a material for a vacuum chuck for an exposure apparatus and a stage position measuring mirror has a low thermal expansion coefficient and a high rigidity ( Young's modulus) is required. Conventionally, among materials that have been used as low thermal expansion materials, quartz, β-spodumene, aluminum titanate, crystallized glass, and the like have a problem in rigidity. On the other hand, conventional dense cordierite materials, low thermal expansion ceramics mainly composed of cordierite (see Patent Documents 1 and 2), or low thermal expansion ceramics mainly composed of eucryptite (patents) Document 3) can meet the above conditions of low coefficient of thermal expansion and high level of stiffness that can be used as a product.
[0005]
These ceramics are generally sintered by a technique such as atmospheric pressure sintering, hot press sintering with high pressure, or HIP sintering. However, stress remains in the material due to this sintering. Further, in the processing after sintering, stress remains on the processed surface. The product is affected by deformation and cracking due to such residual stress.
[0006]
For example, in deformation, these ceramics have a level of rigidity that can be used as a product as described above, but only have a Young's modulus of about 1/2 to 1/3 compared to alumina or SiC ceramics. They are easily deformed by the applied stress. Further, when the residual stress applied to the product in the sintering or processing process is released instantaneously or over a long period of time, the product is deformed, and for example, the flatness changes, and the accuracy is likely to go wrong. In addition, when the product accuracy such as product flatness changes over time over such a long time, the product accuracy changes due to the residual stress release factor even if it is processed with high accuracy at the initial stage, and correction processing is performed again. There may be cases where this is required. On the other hand, in cracking, when a sintered body is processed into a desired shape, processing stress is applied to the material, and if there is residual stress in the material, the risk of processing cracking increases.
[0007]
As a material strength recovery measure due to microcracks generated on the product surface layer by grinding, for example, a method of performing a heat treatment at 800 to 1100 ° C. for 1 to 24 hours after grinding a ceramic sintered body into a predetermined shape As a result, a micro sharp notch generated during grinding is rounded, and the mechanical strength can be improved (see Patent Document 4). In addition, there is a method in which the sintered body subjected to the grinding process is finally subjected to a heat treatment at a temperature of 1000 to 1550 ° C. for 0.1 to 6 hours as a heat treatment, and the tip portion of the microcrack becomes rounded. The susceptibility to cracking is reduced, and it is possible to suppress scattering of ceramic particles even when irradiated with plasma ions (see Patent Document 5).
[0008]
[Patent Document 1]
JP-A-11-209171
[0009]
[Patent Document 2]
JP-A-11-343168
[0010]
[Patent Document 3]
JP 2000-219572 A
[0011]
[Patent Document 4]
JP-A-63-55180
[0012]
[Patent Document 5]
Japanese Patent No. 3126635
[0013]
[Problems to be solved by the invention]
However, they all have a high Young's modulus such as alumina, silicon nitride, and SiC, and are countermeasures against microcracks against ceramics that are difficult to deform due to stress, and have a relatively low Young's modulus like low thermal expansion ceramics such as cordierite. There is no recognition of the problem of improving the accuracy of ceramic products that are easily deformed by releasing stress.
[0014]
The object of the present invention is to suppress cracking due to processing in a low thermal expansion ceramic member including cordierite, spodumene, eucryptite, etc., minimize the residual stress on the surface finished with high accuracy, and minimize the change in accuracy. It is an object to provide a member that maintains a high accuracy by clarifying a processing method for achieving this.
[0015]
[Means for Solving the Problems]
As a result of intensive studies on the above problems, the present inventors have a coefficient of thermal expansion at 10 to 40 ° C. of 0.5 × 10 5. -6 By performing at least one heat treatment at 500 to 1200 ° C. for 0.3 to 200 hours after sintering of ceramics having a porosity of 0.5% or less at / ° C. or less, It has been found that it is possible to produce a low thermal expansion ceramic member that suppresses cracking due to processing, reduces residual stress on the surface of the ceramic member, and maintains high accuracy. The heat treatment is performed at a temperature of 500 to 1200 ° C. for 0.3 to 200 hours after sintering of the ceramics and before the first processing step, and at a temperature of 500 to 1100 ° C. immediately before the final processing step. An embodiment in which the heat treatment for 3 to 200 hours is further performed is desirable. In the heat treatment, it is desirable that the cooling rate to a temperature of 600 ° C. or less after heating is 20 ° C. or less per hour.
[0016]
The low thermal expansion ceramic member of the present invention has a thermal expansion coefficient of 0.5 × 10 10 at 10 to 40 ° C. -6 It is composed of a low thermal expansion ceramic having a porosity of 0.5% or less at / ° C. or less, and having a residual stress of 20 MPa or less. Such ceramics include cordierite, spodumene, and eucryptite. What contains at least 1 sort (s) selected from the group which consists of is suitable. Moreover, the member for a semiconductor manufacturing apparatus of the present invention has a thermal expansion coefficient at 10 to 40 ° C. of 0.5 × 10 -6 It is characterized by comprising a low thermal expansion ceramic member having a porosity of 0.5% or less and a residual stress of 20 MPa or less at / ° C or less.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
(Manufacturing method of low thermal expansion ceramic member)
The method for producing a low thermal expansion ceramic member of the present invention is characterized in that a heat treatment is performed at least once at a temperature of 500 to 1200 ° C. for 0.3 to 200 hours between the sintering of the ceramic and the final processing step. . By performing such heat treatment, the residual stress applied during sintering or processing can be relaxed, the risk of cracking during processing can be reduced, and the product accuracy of the ceramic member can be maintained high. When the residual stress on the surface of the ceramic member is 20 MPa or less, the change in accuracy can be reduced. The residual stress on the surface of the member is preferably 15 MPa or less from the viewpoint of reducing cracks during processing and improving product accuracy. Here, processing refers to thickness processing, outer diameter processing, double-sided rough polishing processing, double-sided precision polishing processing, etc., performed after sintering of the ceramic. Since low thermal expansion ceramics such as cordierite and eucryptite are low-strength materials, if there is residual stress, cracking is likely to occur due to processing stress during processing.
[0018]
The temperature of heat processing shall be 500-1200 degreeC. When the temperature is lower than 500 ° C., the release of stress is small, and when the temperature is higher than 1200 ° C., the deformation of the material increases. Regarding the maximum temperature, for example, when cordierite is the main component, the upper limit is 1200 ° C., when spodumene is the main component, the upper limit is 1150 ° C., and eucryptite is the main component. In this case, it is desirable that the upper limit is 1100 ° C.
[0019]
The heat treatment time is 0.3 to 200 hours. For example, a small product having an outer diameter of about 30 mm requires a minimum of 0.3 hours, and a sufficient effect cannot be expected in less than 0.3 hours. In a large product having an outer diameter of 300 mm or more, 2 hours or more is desirable, and more desirably 3 hours or more. A longer treatment time is more effective, but a treatment time exceeding 200 hours is practically difficult.
[0020]
The number of heat treatments is at least once. For example, the heat treatment may be performed before and after the processing within a range that does not affect the product characteristics. Further, depending on the required accuracy of the product, for example, only one heat treatment may be performed.
[0021]
The time for the heat treatment is between the sintering of the ceramics and the final processing step. This is because the residual stress imparted by sintering or processing is relaxed and cracking and deformation are suppressed. It is desirable that the heat treatment be performed after the ceramic is sintered until the first processing step and immediately before the final processing step. After sintering the ceramics, heat treatment is performed before the first processing step to release the stress remaining in the sintered body during sintering, and cracking of the product due to processing stress applied during subsequent processing. Can be suppressed.
[0022]
Residual stress in the sintered body can be reduced by performing heat treatment between sintering and the first processing step, but since the stress is applied to the product surface in the subsequent processing step, the residual stress in the processing step Therefore, there is a possibility that the accuracy during product processing or the product accuracy after commercialization cannot be maintained high. Therefore, it is desirable to perform the heat treatment immediately before commercialization, for example, before the final accuracy-determining process. The stress is released by the heat treatment, and the shape of the workpiece is slightly deformed accordingly. Therefore, the final shape can be adjusted after the heat treatment, so that the desired shape dimension can be adjusted. In addition, although stress is applied to the product also by the final accuracy-determining process, since the stress is minute, the influence is small.
[0023]
The heat treatment performed immediately before the final processing step is desirably performed at 500 to 1100 ° C. for 0.3 to 200 hours. When the processing temperature is less than 500 ° C., the release of stress is small, and in order to suppress deformation of the product, it is desirable that the temperature is 1100 ° C. or less. The treatment time is preferably 0.3 to 200 hours. Even for a small product having an outer diameter of about 30 mm, a sufficient effect cannot be expected in less than 0.3 hours. In a large product having an outer diameter of 300 mm or more, 2 hours or more is desirable, and more desirably 3 hours or more. A longer treatment time is more effective, but a treatment time exceeding 200 hours is practically difficult.
[0024]
As for the cooling operation in the heat treatment, it is desirable to slowly cool the cooling rate to a temperature of 600 ° C. or lower after heating at a temperature of 20 ° C. or lower per hour. This is because the residual stress is relaxed by heating, but if the temperature gradient during cooling is large, a large temperature distribution is generated in the product, thereby imparting residual stress. It is desirable that the temperature range (hereinafter referred to as “slow cooling section”) for slow cooling from the maximum temperature to 20 ° C. or less per hour is 600 ° C. or lower. If the lower limit of the slow cooling section is reduced to a temperature of 600 ° C. or lower, it is possible to reduce the application of residual stress. For example, it is more desirable to set the temperature below the transition point shown below.
[0025]
FIG. 2 shows the relationship between the change in temperature and the change in thermal expansion coefficient. 2 shows a cordierite powder having a purity of 99% or more and an average particle diameter of 3 μm, a silicon nitride powder having an average particle diameter of 1 μm, and a carbon powder having an average particle diameter of 0.1 μm, respectively, 96.5 vol%, 2 vol%, 1. The sample (3 mm × 3 mm × 15 mm) obtained by blending and sintering to 5 vol% was prepared by measuring the thermal expansion coefficient with a linear dilatometer. The measurement conditions are
(1) Measurement section: RT to 1350 ° C
(2) Heating rate: 10 ° C / min
(3) Measurement environment: N 2 During gas flow
In the case of low thermal expansion ceramics such as cordierite, the thermal expansion coefficient increases linearly as the temperature rises as shown in FIG. 2, but for example, bending is seen in the graph between 300 and 600 ° C. It is desirable to slowly cool to a temperature at which this bending occurs (hereinafter referred to as “transition point”) or lower. At temperatures below the transition point, the effects of relaxation of residual stress and product flatness due to gradual cooling are not so much seen, so it takes time even when gradual cooling to a temperature of, for example, 100 ° C. or less. Therefore, it is desirable to set the temperature of about 300 to 400 ° C. as the lower limit of the slow cooling section.
[0026]
When the additive other than the main raw material is a non-oxide, or when a carbon component is used as the additive, the heat treatment furnace uses a furnace that can be replaced with a nitrogen or argon atmosphere. A method of replacing these inert gases in a vacuum furnace is desirable, but as long as it does not adversely affect the electrical conductivity and expansion coefficient of the product, for example, a furnace with only a gas flow, not a vacuum structure. Use is possible. When a vacuum furnace is used, it is desirable that the inside of the furnace is not a vacuum but has a gas pressure of at least 0.5 atm or more. In a vacuum, it is necessary to rely on radiation and heat conduction for heat transfer to the product, and the temperature distribution is likely to occur depending on the position in the furnace. It is because it is easy to become. On the other hand, if there is a gas pressure, the convection in the furnace is added to the heat transfer, so that the heat transfer to the product proceeds relatively uniformly, the product temperature distribution can be reduced, and the residual stress of the product can be suppressed. When the additive other than the main raw material is an oxide, an air atmosphere furnace such as a gas furnace or an electric furnace can be used.
[0027]
The ceramic used in the manufacturing method of the low thermal expansion ceramic member of the present invention has a thermal expansion coefficient of 0.5 × 10 at 10 to 40 ° C. -6 / ° C. or less, and the porosity is 0.5% or less. The thermal expansion coefficient at 10 to 40 ° C. is 0.5 × 10 -6 The reason why the temperature is limited to / ° C. or less is that, in a member that requires high accuracy, the influence on accuracy due to temperature change during use cannot be ignored. For example, in a material for a vacuum chuck for an exposure apparatus or a stage position measuring mirror, the thermal expansion coefficient at 10 to 40 ° C. is 0.5 × 10 6. -6 / ° C. or less, more desirably 0.3 × 10 -6 / ° C or less. On the other hand, the porosity is limited to 0.5% or less because, when it exceeds 0.5%, properties such as strength and Young's modulus are deteriorated. This is because, when used as a jig for this, a change in accuracy of the wafer itself due to adhesion of particles to the pores and a change in accuracy due to water absorption of the product become problems.
[0028]
As such ceramics, those mainly composed of cordierite, spodumene, eucryptite, or a combination thereof are suitable. Aluminum titanate, which is known as a low thermal expansion material, is difficult to densify, and even if it can be densified, its rigidity is low and cannot be used. As described above, the spodumene has a relatively low rigidity, but by forming a sintered body with cordierite or eucryptite having a relatively high rigidity, a ceramic material having a high rigidity can be provided.
[0029]
Such ceramics include 4a group element, 5a group element or 6 group carbide, nitride, boride, silicide, SiC, B, depending on the required characteristics. 4 C, silicon nitride, or a carbon source may be added to such an extent that the low thermal expansion is not hindered. In addition, the ceramic may or may not contain a rare earth element. Even without using a rare earth element compound, typically a rare earth element oxide, a sufficiently dense low thermal expansion ceramic can be obtained by the production method shown below.
[0030]
Specifically, such ceramics are sintered by the following method. As the main material, at least one of cordierite powder, β-spodumene powder, β-eucryptite powder having an average particle size of 10 μm or less, for example, 2 to 3 μm, is used. If necessary, 4a group element, 5a group element or 6 group carbide, nitride, boride, silicide, SiC, B 4 C, silicon nitride or a carbon source is added to such an extent that the low thermal expansion is not hindered. These are commercially available, but as the carbon source, powdered carbon or phenol resin or furan resin may be used.
[0031]
For example, there are the following three methods for preparing the sintered body before the heat treatment. As a first method, there is a method of sintering at normal pressure. First, a raw material is prepared, a solvent such as alcohol or water is added, and if necessary, a resin binder such as PVA or acrylic resin is blended, ball mill mixed, and dried to obtain a raw material powder. A molded body is obtained from the obtained powder by a technique such as die press molding or CIP molding. The green body is raw-processed into a desired shape and sintered.
[0032]
Sintering is performed in an air atmosphere, an inert atmosphere, or a non-oxidizing atmosphere. For example, the cordierite main material is 1300 to 1450 ° C., the β-spodumene main material is 1200 to 1350 ° C., β-eucrypt. For tight main materials, sintering temperatures such as 1150-1300 ° C. are suitable. The obtained sintered body can be machined into a desired product shape by grinding or polishing.
[0033]
As another method for preparing the sintered body, there is a method of performing hot press sintering. In this method, first, raw materials are prepared and ball mill mixed with a solvent such as alcohol or water. It is dried to obtain a raw material powder, and this raw material powder is sintered by hot pressing under an inert atmosphere such as nitrogen or argon. For example, the cordierite main material is 4.9 to 49 MPa at 1300 to 1450 ° C., the β-spodumene main material is 4.9 to 49 MPa at 1200 to 1350 ° C., and the β-eucryptite main material is 1150 to 1300. Conditions such as 4.9 to 49 MPa at a temperature are suitable. The obtained sintered body can be machined into a desired product shape by grinding or polishing.
[0034]
As another method for preparing the sintered body, there is a method of performing high temperature isostatic pressing (HIP). According to this method, for example, a cordierite main material sintered body sintered at normal pressure is subjected to conditions such as 1250 to 1400 ° C. and atmospheric pressure of 20 to 200 MPa in an inert atmosphere such as nitrogen or argon. Sinter. The obtained sintered body can be machined into a desired product shape by grinding or polishing.
[0035]
(Low thermal expansion ceramic materials)
The low thermal expansion ceramic member of the present invention has a thermal expansion coefficient of 0.5 × 10 10 at 10 to 40 ° C. -6 It is characterized by being made of ceramics having a porosity of 0.5% or less at / ° C or less and a residual stress of 20 MPa or less. Since the residual stress applied at the time of sintering or processing is relaxed, the product accuracy of the ceramic member can be maintained high. As the ceramic, one containing at least one selected from the group consisting of cordierite, spodumene and eucryptite is preferable.
[0036]
(Semiconductor manufacturing equipment)
The member for a semiconductor manufacturing apparatus of the present invention has a thermal expansion coefficient of 0.5 × 10 at 10 to 40 ° C. -6 It is characterized by being made of a low thermal expansion ceramic member having a residual stress of 20 MPa or less and a ceramic having a porosity of 0.5% or less at / ° C or less. Such a member for a semiconductor manufacturing apparatus has little deformation due to low residual stress on the surface, and the change with time of accuracy is also small. Therefore, in particular, it is applicable to a wide range of fields such as vacuum check for exposure apparatus requiring high precision, members for semiconductor manufacturing equipment such as stage members or liquid crystal manufacturing equipment, optical precision parts and precision measuring jigs. be able to.
[0037]
【Example】
Example 1
Cordierite powder having a purity of 99% or more and an average particle diameter of 3 μm, a silicon nitride powder having an average particle diameter of 1 μm, and a carbon powder having an average particle diameter of 0.1 μm are 96.5 vol%, 2 vol%, and 1.5 vol%, respectively. Then, ethanol was used as a solvent and mixed for 24 hours by a ball mill. The obtained mixture was dried and then hot-press sintered at 1380 ° C. in a nitrogen atmosphere under a pressure of 49 MPa. The size of the obtained sintered body is an outer diameter of 320 mm × height of 23 mm, the porosity is 0.1% or less, and the thermal expansion coefficient at 10 to 40 ° C. is 0.1 × 10. -6 / ° C.
[0038]
The porosity of the sintered body was measured by the Archimedes method for a sample having an outer diameter of 320 mm and a height of 23 mm. Further, the thermal expansion coefficient of the sintered body was measured by a laser interference method for a sample of 3 mm × 3 mm × 15 mm. The laser interferometry was measured using a laser thermal dilatometer in helium at a temperature of 10 to 40 ° C. and a heating rate of 1 ° C./min.
[0039]
The obtained sintered body was processed by the method shown in production method 1 in FIG. That is, after the first heat treatment was performed on the sintered body, the thickness processing, the outer diameter processing, the double-sided rough polishing processing, and the second heat treatment were performed, and finally double-sided accuracy was obtained. The first heat treatment was performed at 1100 ° C. for 5 hours and at a cooling rate of 15 ° C./hour up to 400 ° C. Thickness processing was carried out with a rotary surface grinder so that the thickness of the material was 20.1 mm and the flatness was about 10 μm. The flatness was evaluated using a contact-type straightness measuring instrument (the measuring element used an electric micrometer).
[0040]
The outer diameter processing was finished to an outer diameter of 300 mm with a universal grinder. In the double-sided rough polishing process, diamond abrasive grains having an average particle diameter of 10 μm were used with a double-side polishing machine, and both surfaces of the material were simultaneously polished. The flatness of both surfaces after processing was 2-3 μm. The second heat treatment was performed at 1000 ° C. for 20 hours and at a cooling rate of 15 ° C./hour up to 350 ° C. In the final double-sided accuracy processing, diamond abrasive grains having an average particle diameter of 4 μm were used to polish each side of the material by a single-side polishing machine. The flatness of both surfaces after processing was 0.5 to 1.0 μm, and after processing, it was formed into a disk shape having an outer diameter of 300 mm × height of 20 mm.
[0041]
About the obtained ceramic member, the change of flatness and the residual stress were measured. The change in flatness was measured by measuring the flatness 1 day and 10 days after the final processing date, calculating the average value of the flatness on both sides, and expressing the change from the initial flatness. The residual stress is measured under the conditions shown in Table 1, and the surface residual stress immediately after the final processing is measured on the front and back surfaces in two directions (outside) and two directions in the center (location). The average value in all eight directions (locations) was calculated, and this absolute value was used as the residual stress. Table 2 shows the measurement results of changes in flatness and residual stress.
[0042]
[Table 1]
[Table 2]
Example 2
The first heat treatment conditions in Example 1 were 900 ° C. for 40 hours and the cooling rate to 400 ° C. was 10 ° C./hour, and the second heat treatment conditions were 400 ° C. for 100 hours and 350 ° C. A ceramic member was produced in the same manner as in Example 1 except that the cooling rate was 10 ° C./hour, and the change in flatness and the residual stress were measured. The results are shown in Table 2.
[0045]
Example 3
A ceramic member was manufactured in the same manner as in Example 1 except that the manufacturing method performed in Example 1 was manufacturing method 2 in FIG. 1 and the first heat treatment time was 8 hours. Stress was measured. The results are shown in Table 2.
[0046]
Example 4
A ceramic member was manufactured in the same manner as in Example 3 except that the heat treatment conditions performed in Example 3 were 800 ° C. for 100 hours and the cooling rate to 400 ° C. was 10 ° C./hour. Stress was measured. The results are shown in Table 2.
[0047]
Comparative Example 1
The manufacturing method carried out in Example 1 was changed to Production Method 3 in FIG. 1, and a ceramic member was produced in the same manner as in Example 1 except that no heat treatment was performed, and the change in flatness and residual stress were measured. The results are shown in Table 2.
[0048]
Comparative Example 2
The first heat treatment in Example 1 was performed at 250 ° C. for 200 hours and the cooling rate to 150 ° C. was 10 ° C./hour, and the second heat treatment was performed at 250 ° C. for 200 hours and the cooling rate to 100 ° C. A ceramic member was produced in the same manner as in Example 1 except that the temperature was changed to 10 ° C./hour, and the change in flatness and the residual stress were measured. The results are shown in Table 2.
[0049]
Comparative Example 3
A ceramic member was produced in the same manner as in Example 3 except that the heat treatment performed in Example 3 was performed at 250 ° C. for 200 hours, and the change in flatness and residual stress were measured. The results are shown in Table 2.
[0050]
As is apparent from the results in Table 2, in Examples 1 to 4, the change in flatness after 1 day from the final processing date is 0.0 to 0.15 μm, and the flatness after 10 days from the final processing. All the changes were 0.3 μm or less, and the accuracy was maintained high. On the other hand, in Comparative Examples 1 to 3, the change in flatness after 10 days was 1.5 to 2 μm, and it was found that it was difficult to maintain accuracy compared to the examples of the present invention. .
[0051]
Further, the residual stress is 5 to 15 MPa in Examples 1 to 4, whereas it is 25 to 40 MPa in Comparative Examples 1 to 3, and in the examples of the present invention, the surface of the product is subjected to heat treatment. It was found that the residual stress was sufficiently relaxed. Moreover, it turned out that a precision change can be reduced by making the residual stress of the surface of a ceramic member 20 MPa or less.
[0052]
It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.
[0053]
【The invention's effect】
In the low thermal expansion ceramic member of the present invention, since the residual stress applied during sintering or processing is relaxed, the product accuracy of the ceramic member can be maintained high. Such a low thermal expansion ceramic member can be manufactured by performing a heat treatment at 500 to 1200 ° C. for 0.3 to 200 hours at least once after sintering the ceramic and before the final processing step. The member for a semiconductor manufacturing apparatus of the present invention has little deformation due to low residual stress on the surface, and the accuracy change with time is also small. Therefore, the present invention can be applied particularly to semiconductor manufacturing apparatus members, liquid crystal manufacturing apparatus members, optical precision parts, precision measurement jigs, and the like that require high accuracy.
[Brief description of the drawings]
FIG. 1 is a process diagram showing a method for producing a low thermal expansion ceramic member after sintering until the final processing step is completed.
FIG. 2 is a diagram showing a relationship between a temperature change and a change in thermal expansion coefficient.
Claims (6)
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| JP2007191376A (en) * | 2006-01-23 | 2007-08-02 | Fujifilm Corp | Polycrystalline material and method for heat treating the same |
| JP2009290071A (en) * | 2008-05-30 | 2009-12-10 | Ngk Spark Plug Co Ltd | Ceramic joint and its production process |
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| JP2007191376A (en) * | 2006-01-23 | 2007-08-02 | Fujifilm Corp | Polycrystalline material and method for heat treating the same |
| JP2009290071A (en) * | 2008-05-30 | 2009-12-10 | Ngk Spark Plug Co Ltd | Ceramic joint and its production process |
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