JP2004226476A - Method for manufacturing pellicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a pellicle having no deposition of contaminants and high transmittance and durability to laser light at 100 to 200 nm wavelengths. <P>SOLUTION: The method for manufacturing a pellicle comprising a pellicle film made of the following fluorine-containing polymer (A), a frame and an adhesive adhering the pellicle film and the frame includes processes of: forming the pellicle film on a substrate; removing the pellicle film from the substrate; and immersing the substrate with the pellicle formed in ultrapure water at a temperature in the range from (glass transition temperature (T<SB>g,m</SB>) of the fluorine-containing polymer (A) in the pellicle film -40)°C to (T<SB>g,m</SB>-10)°C before the removing process. The fluorine-containing polymer (A) is a substantially linear polymer having chains of carbon atoms as the main chain which contains, as carbon atoms in the main chain, carbon atoms coupled with one or two hydrogen atoms and carbon atoms not coupled with hydrogen atoms but with fluorine atoms or fluorine-containing organic groups. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００２５】
上記式１〜式３においてＲ^１１〜Ｒ^１６はそれぞれ独立にフッ素原子または含フッ素有機基を表し、含フッ素有機基としてはパーフルオロアルキル基、特に炭素数１または２のパーフルオロアルキル基が好ましい。
モノマー（ｂ）とモノマー（ｃ）のコポリマーからなる含フッ素ポリマー（Ａ）としては、エチレン／テトラフルオロエチレンコポリマー、プロピレン／テトラフルオロエチレンコポリマー、プロピレン／フッ化ビニリデン／テトラフルオロエチレンコポリマー、フッ化ビニリデン／ヘキサフルオロプロピレンコポリマーなどの主鎖に含フッ素脂肪族環構造を有しないポリマーであってもよいが、これらは透明性が充分とはいえない。しかし、膜とフレームを接着するための接着剤としては有用である。好ましい含フッ素ポリマー（Ａ）はモノマー（ｂ）と上記式１〜式３で表される含フッ素脂肪族不飽和環状モノマー（ｃ）とのコポリマーである。この場合のモノマー（ｂ）としては、エチレンなどのオレフィンおよび不飽和基の炭素原子に水素原子を有するフルオロオレフィンから選ばれた少なくとの１種のモノマーが好ましい。
【００２６】
モノマー（ｂ）とモノマー（ｃ）のコポリマーにおけるモノマー（ｂ）の重合により形成されたモノマー単位（以下モノマー単位（ｂ）という。他のモノマー単位についても同様とする）とモノマー単位（ｃ）との合計に対するモノマー単位（ｂ）の割合は１０〜７０モル％が好ましい。モノマー（ｂ）がエチレンなどの２個以上の水素原子（重合性不飽和結合の炭素原子に結合した水素原子）を有するモノマーの場合は１０〜５０モル％が好ましい。特に好ましいモノマー単位（ｂ）の割合は２０〜４０モル％である。接着剤用の含フッ素ポリマー（Ａ）においてはさらにモノマー単位（ｂ）とモノマー単位（ｃ）との合計に対するモノマー単位（ｂ）の割合が４０〜８５モル％であるポリマーも好ましい。
なお、このポリマーにおける全モノマー単位に対するモノマー単位（ｂ）とモノマー単位（ｃ）の合計の割合は５０〜１００モル％が好ましく、特に８０〜１００モル％が好ましい。最も好ましいポリマーはモノマー（ｂ）とモノマー（ｃ）のみからなるコポリマー（ただし各モノマーは２種以上であってもよい）である。
【００２７】
ジエンモノマー（ｄ）としては、ＣＨ_２＝ＣＲ^７−Ｑ−ＣＲ^８＝ＣＦ_２［ただし、Ｒ^７、Ｒ^８はそれぞれ独立に水素原子、フッ素原子または１価の含フッ素有機基を表し、Ｑは２価の含フッ素有機基を表す］で表されるモノマーが好ましい。Ｒ^７としては水素原子とフッ素原子が好ましく特に水素原子が好ましい。Ｒ^８としてはフッ素原子または炭素数２以下のパーフルオロアルキル基が好ましく、特にフッ素原子が好ましい。
【００２８】
Ｑとしては、炭素数１０以下のエーテル性酸素原子を有していてもよいパーフルオロアルキレン基が好ましい。エーテル性酸素原子はパーフルオロアルキレン基の一方の末端に存在していてもよく、両末端に存在していてもよく、炭素原子間に存在していてもよい。エーテル性酸素原子を有しないパーフルオロアルキレン基の場合は炭素数２〜６、一方の末端にエーテル性酸素原子を有するまたは炭素原子間にエーテル性酸素原子を有するパーフルオロアルキレン基の場合は炭素数１〜４、両末端にエーテル性酸素原子を有するパーフルオロアルキレン基の場合は炭素数１〜３であることがより好ましい。分岐部の炭素原子を除いた炭素原子と酸素原子の合計数は２〜４であることが最も好ましい。
Ｑとしては、２，２−ジフルオロビニル基側にエーテル性酸素原子を有する炭素数４以下のパーフルオロアルキレン基、炭素原子間にエーテル性酸素原子を有する炭素数４以下のパーフルオロアルキレン基およびエーテル性酸素原子を有しない炭素数４以下のパーフルオロアルキレン基が好ましい。さらに好ましいＱは２，２−ジフルオロビニル基側にエーテル性酸素原子を有する炭素数４以下のパーフルオロアルキレン基である。
すなわち、最も好ましいジエンモノマー（ｄ）は、ＣＨ_２＝ＣＨ−Ｒ^ｆ−Ｏ−ＣＦ＝ＣＦ_２［ただし、Ｒ^ｆは炭素数１〜４のパーフルオロアルキレン基を表す］で表されるモノマーである。このモノマーは環化重合性が高く、短波長光の透過性が高く機械的強度の高いポリマーが得られる（特開昭６３−２３８１１１号公報、特開昭６３−２３８１１３号公報等参照）。Ｒ^ｆとしては分岐を除いて炭素数１〜３のパーフルオロアルキレン基が好ましい。分岐が存在する場合は、分岐はトリフルオロメチル基が好ましく、分岐の数は１〜２が好ましい。
【００２９】
なお、ＣＨ_２＝ＣＲ^７−Ｑ−ＣＲ^８＝ＣＦ_２の環化重合により通常下記式４、式５、式６などで表されるモノマー単位（以下モノマー単位（ｄ）という。）が形成される。ＣＨ_２＝ＣＲ^７−Ｑ−ＣＲ^８＝ＣＦ_２で表されるジエンモノマー（ｄ）としては、例えば以下の化合物がある。
【００３０】
【化２】

【００３１】
【化３】

【００３２】
含フッ素ポリマー（Ａ）は、ジエンモノマー（ｄ）のホモポリマー（ただし、ジエンモノマー（ｄ）の２種以上のコポリマーであってもよい）であってもよく、他のモノマーとのコポリマーであってもよい。他のモノマーとしては、モノマー（ａ）、モノマー（ｂ）、モノマー（ｃ）、ジエンモノマー（ｅ）などがある。コポリマーとしてはジエンモノマー（ｄ）とモノマー（ｃ）のコポリマーおよびジエンモノマー（ｄ）とジエンモノマー（ｅ）のコポリマーが好ましく、ジエンモノマー（ｄ）とモノマー（ｃ）のコポリマーがより好ましい。この場合のモノマー（ｃ）としては、前記の含フッ素脂肪族不飽和環状モノマー（ｃ）が好ましい。
この含フッ素ポリマー（Ａ）における全モノマー単位に対するモノマー単位（ｄ）の割合は３０〜１００モル％が適当であり、５０〜１００モル％が好ましく、１００モル％であることが最も好ましい。
ジエンモノマー（ｅ）としては、ジエンモノマー（ｄ）の重合性不飽和基の炭素原子に結合した水素原子がすべてフッ素原子またはパーフルオロアルキル基に置換されたモノマーが好ましい。より好ましくは、ＣＦ_２＝ＣＲ^９−Ｑ−ＣＲ^１０＝ＣＦ_２［Ｒ^９、Ｒ^１０はそれぞれ独立にフッ素原子または１価の含フッ素有機基を表し、Ｑは前記に同じ］で表されるモノマーが好ましい。ただし、前記したＱにおけるエーテル性酸素原子の位置や数の制約はない。具体的には下記のようなモノマーがある。
【００３３】
【化４】

【００３４】
モノマー（ｆ）としては前記モノマー（ａ）やモノマー（ｂ）を使用しうる。特にモノマー（ｂ）が好ましい。ジエンモノマー（ｅ）とモノマー（ｆ）の共重合においてはジエンモノマー（ｅ）は環化重合により含フッ素脂肪族環構造を有するモノマー単位を形成し、このモノマー単位（ｅ）とモノマー単位（ｆ）とを有するコポリマーが生成する。モノマー単位（ｅ）とモノマー単位（ｆ）とを有するコポリマーはさらに他のモノマー単位を有していてもよく、例えば前記モノマー単位（ｃ）を有していてもよい。
【００３５】
ジエンモノマー（ｅ）とモノマー（ｆ）のコポリマーにおいて、モノマー単位（ｅ）とモノマー単位（ｆ）との合計に対するモノマー単位（ｆ）の割合は１０〜７０モル％が好ましい。エチレンなどの２個以上の水素原子（重合性不飽和結合の炭素原子に結合した水素原子）を有するモノマー（ｆ）の場合は１０〜６０モル％が好ましい。特に好ましいモノマー（ｆ）の割合は２０〜５０モル％である。なお、このポリマーにおける全モノマー単位に対するモノマー単位（ｅ）とモノマー単位（ｆ）の合計の割合は５０〜１００モル％が好ましく、特に７０〜１００モル％が好ましい。
含フッ素ポリマー（Ａ）は前記のように含フッ素脂肪族環構造を有するモノマー単位を含むポリマーであることが好ましい。含フッ素ポリマー（Ａ）における全モノマー単位に対するこの含フッ素脂肪族環構造を有するモノマー単位の割合は、２０モル％以上、特に４０モル％以上であることが好ましい。
特に好ましい含フッ素ポリマー（Ａ）は、エチレンとパーフルオロ（２，２−ジメチル−１，３−ジオキソール）とのコポリマー、ジエンモノマー（ｄ）のホモポリマー、および、含フッ素脂肪族不飽和環状モノマーであるモノマー（ｃ）とジエンモノマー（ｄ）とのコポリマーである。
【００３６】
本発明におけるペリクル膜とフレームは、含フッ素ポリマー（Ａ）を含む接着剤により接着されていることが好ましい。
ペリクル膜とフレームを接着する接着剤用の含フッ素ポリマー（Ａ）としては、例えば、含フッ素脂肪族不飽和環状モノマーであるモノマー（ｃ）とモノマー（ｂ）とのコポリマー、ジエンモノマー（ｄ）のポリマー、ジエンモノマー（ｅ）とモノマー（ｆ）とのコポリマーなどが好ましい。また、接着剤用の含フッ素ポリマー（Ａ）は必ずしも高い透明性は要求されないことより、主鎖に含フッ素脂肪族環構造を有しないポリマーであってもよい。したがって、含フッ素脂肪族不飽和環状モノマー以外のモノマー（ｃ）とモノマー（ｂ）とのコポリマー（すなわち主鎖に脂肪族環構造を有しない含フッ素ポリマー（Ａ））も好ましい接着剤として使用できる。
主鎖に脂肪族環構造を有しない含フッ素ポリマー（Ａ）としては、プロピレン／フッ化ビニリデン／テトラフルオロエチレンコポリマー、フッ化ビニリデン／ヘキサフルオロプロピレンコポリマーなどがある。このようなポリマーにおけるモノマー単位（ｃ）とモノマー単位（ｂ）の合計に対するモノマー単位（ｂ）の割合は、４０〜８５モル％が好ましく、特に５０〜８０モル％が好ましい。
【００３７】
本発明におけるフレームとしては、アルミニウム、黒化処理したアルミニウムまたは合成石英製のフレームであることが好ましい。
また、含フッ素ポリマー（Ａ）を、フレームとペリクル膜との接着剤として用いる場合、接着性向上に有効な官能基が導入された含フッ素ポリマー（Ａ）を用いることが好ましい。なお、ペリクル膜用の含フッ素ポリマー（Ａ）は光透過性の面から官能基を有しないことが好ましい。
該官能基としては、フレームやペリクル膜に対して接着性を発現しうるものであれば特に制約はなく、例えば、カルボン酸基、スルホン酸基、エステル結合を有する基、アルケニル基、加水分解性シリル基、水酸基、マレイミド基、アミノ基、シアノ基、イソシアネート基などが挙げられる。この官能基としては、フレームの材料であるアルミニウムなどに対する接着性が良好で、保存安定性に富み、比較的低温でその効果が発現できる観点より、カルボン酸基が特に好適である。
【００３８】
本発明は、ペリクル膜を基板上に製膜する工程を有する。かかる基板は、平滑かつ本発明に使用する含フッ素ポリマー（Ａ）または後述する含フッ素ポリマー（Ａ）溶液に溶解または膨潤しないものであれば何ら制限はない。好ましくはシリコン基板や石英基板が使用される。
【００３９】
好ましい基板の例としては、半導体用のシリコンウエハ、シリコン酸化膜ウエハなどのシリコン基板、合成石英、フッ素ドープ合成石英などの石英基板が例示される。これらの基板を使用する際には、事前に研磨、洗浄などの前処理を施しておくことが好ましい。例えば、シリコンウエハの場合は、極微量の有機性不純物が付着している可能性があるため、約０．５％程度の希釈したフッ化水素水溶液にて洗浄した後、超純水で洗浄し乾燥させることが好ましい。特に好ましい基板は半導体用シリコン基板および１００〜２００ｎｍにて高い透過率を示すフッ素ドープ合成石英基板である。
【００４０】
本基板上にペリクル膜を形成する方法としては、本ペリクル膜の材料となる含フッ素ポリマー（Ａ）の溶液を使用した製膜法が好ましい。溶媒としては、本発明における含フッ素ポリマー（Ａ）を溶解できるものであれば、なんでも使用できる。好ましくは含フッ素溶媒である。該溶液のポリマー濃度としては、３〜１０質量％であることが好ましい。この溶液を用いて、基板上に均一な湿潤薄膜を形成する。このときの湿潤薄膜の形成方法としては、スピンコート法、キャスト法、ディップコート法などが用いられる。これらの手法を用いてポリマー溶液の湿潤薄膜を形成した後、オーブン、ホットプレート等の加熱装置を用いて溶媒を揮発させ、好ましくは厚み０．５〜２μｍの均一な薄膜（ペリクル膜）が形成された基板を製造する。
【００４１】
本発明は、該基板から該ペリクル膜を剥離する工程、および該剥離工程の前にペリクル膜が形成された基板を、熱超純水に浸漬する工程を有する。熱超純水に浸漬する際には、後の工程を考慮して、あらかじめペリクル膜にフレームを接着させておくことが好ましい。以下、この好ましい態様について本工程を詳細に述べる。尚、本発明における超純水とは、電気抵抗が１０ＭΩ・ｃｍ以上の水を意味する。
フレームにあらかじめ接着剤のポリマー溶液を塗布し、自然乾燥したのち加熱を行う。接着剤のポリマーとしては、フレームとペリクル膜を接着できるものであれば何でも構わない。好ましくは前述した通り、含フッ素ポリマー（Ａ）であり、さらに好ましくは官能基を有する含フッ素ポリマー（Ａ）である。溶液の溶媒としては、接着剤のポリマーを溶解できるものであれば何でも構わない。接着剤が、好ましい態様である含フッ素ポリマー（Ａ）である場合は、かかる溶媒は含フッ素溶媒であることが好ましい。接着剤のポリマー溶液の濃度としては、２〜１０質量％であることが操作性が良好であるころから好ましい。
前記加熱はオーブン、ホットプレートなどを使用し、フレームに溶液を塗布した面を上にして加熱する。加熱温度は、フレームと前記基板上の膜をしっかりと接着させる観点から、接着剤のポリマーのガラス転移温度（以下、Ｔ_ｇ，ａと記す。）以上で行うことが好ましく、より具体的にはＴ_ｇ，ａ〜（Ｔ_ｇ，ａ＋５０）℃の範囲、より好ましくは（Ｔ_ｇ，ａ＋２０）〜（Ｔ_ｇ，ａ＋５０）℃の範囲である。また加熱時間は１０〜２０分程度が好ましいが、この時間についてはフレームの厚みおよび幅によって調節されることが好ましい。
【００４２】
接着剤のポリマーが柔らかくなったところで、前記基板のペリクル膜が形成された面を接着剤面側にして基板をフレーム上にのせ、さらに加熱を行い、フレームとペリクル膜を接着させる。より強固な接着を得るためにフレームを取り付けた基板ごとオーブンにて再加熱してもよい。このようにして、フレーム、接着剤、ペリクル膜および基板との一体化品が得られる。
【００４３】
次に、この基板からフレームと膜を剥離する工程について説明する。ペリクル膜の材料である含フッ素ポリマー（Ａ）のガラス転移温度をＴ_ｇ，ｍとすると、前記一体化品を（Ｔ_ｇ，ｍ−４０）〜（Ｔ_ｇ，ｍ−１０）℃の超純水に浸漬する。後記の実施例の重合体Ａについては、この温度はほぼ７０〜１００℃となる。より好ましい温度は（Ｔ_ｇ，ｍ−３０）〜（Ｔ_ｇ，ｍ−１０）℃である。
【００４４】
また、浸漬時間は１時間から４８時間の間であることが好ましい。１時間未満の場合は、熱超純水処理としては不十分であり、４８時間を超える場合は生産性が悪くなると同時に不要なＨ_２Ｏの吸着をまねき、ペリクルの透過率を悪化させるおそれがある。より好ましくは１時間〜３６時間である。
【００４５】
加熱処理を行う容器としては、有機性不純物や無機性不純物の溶出のない容器であれば特に制限はなく、種々の材質が使用可能である。しかしながら超純水は極性が高いこと、浸漬温度がポリマーによっては１００℃以上となることからフッ素樹脂容器が好ましい。なかでも溶出金属と溶出物を抑えた高純度ＰＦＡ（テトラフルオロエチレン／パーフルオロアルキルビニルエーテル共重合体）を使用した半導体用途向けの容器が好ましい。また、これらの容器を加熱する装置としては、一般的なオーブンや加湿加圧型のオーブンもしくはオートクレーブ等が好ましい装置として用いられる。
【００４６】
熱超純水に浸漬後、一体化品を取り出すと、ペリクル膜がフレームごと基板より容易に剥離することができる。この理由は以下のように考えられる。
含フッ素ポリマー（Ａ）は完全フッ素化ポリマーではなく基本骨格の一部に水素を含む含フッ素ポリマーであるため、水素とフッ素の大きな電気陰性度の差から分子内に極性が発生し、それらにより基板との相互作用がパーフルオロポリマーと比較して強くなることから、従来の方法では基板から剥離できない。
【００４７】
しかし、本相互作用は静電的なものであり、化学的な結合ではないため基板との相互作用のより強い物質かつポリマーとの相互作用のない物質にて界面を処理すると剥離可能となると考えられる。このような物質として清浄性が高くコスト的にも安価であり、溶存有機物とイオン性不純物のレベルが最も低い超純水が選ばれる。超純水のなかでも、電気抵抗が１５ＭΩ・ｃｍ以上であることが好ましい。
【００４８】
しかも、（Ｔ_ｇ，ｍ−４０）℃以上とすることにより、基板とペリクル膜の界面内へ短時間に超純水が浸透し、ムラが発生することがなく、剥離時に膜の伸びやたるみを招くことがない。一方で、（Ｔ_ｇ，ｍ−１０）℃以下とすることにより、膜の機械的強度が低下することがなく、剥離時に伸びや破れを発生させることがない。
【００４９】
上記のようにして得られたペリクル膜には、極わずかではあるが容器からの不純物や製膜工程などで基板に付着した有機性不純物が転写付着する場合がある。また、高温化で剥離処理を施すため、ペリクル膜表面に水蒸気が溶存する場合もある。これら不純物は、例えば１５７ｎｍの光の透過率を著しく低下させ、耐久性を悪化させるため取り除くことが好ましい。
【００５０】
これら不純物の除去にはアルキルアルコールを主成分とする溶媒を用いることが好ましい。かかる溶媒は、ペリクル膜を溶解も膨潤もせず、水と相溶性が良好であり、後の工程で容易に除去できるため好ましい。具体的には、フッ素を含まないアルキルアルコールを主成分とする溶媒が好ましく、より好ましいものは炭素数４以下のアルキル基を有するアルキルアルコールを主成分とする溶媒である。具体的にはメタノール、エタノール、イソプロパノールが好ましく、メタノールが最も好ましい。これらは１種類を単独で用いても２種類以上を混合して用いてもよい。また、新たな不純物を再付着させない観点より、当然のことながら半導体グレードの溶媒を用いることが好ましい。
【００５１】
アルキルアルコールを主成分とするということは、これらアルキルアルコールを容量比で５０％以上含むことを意味する。より好ましくは６０％以上である。当然のことながら該アルキルアルコールを１００％で用いても差し支えない。アルキルアルコールが容量比で５０％以上含むことにより洗浄中にペリクル膜の伸びや破れが発生する可能性が小さい。
【００５２】
該アルキルアルコールと併用してもよい溶媒としては、極性溶媒、無極性溶媒のいずれでもよく、１種類でも数種類併用してもよい。しかしながら、ペリクル膜の破れや剥離を防止する観点から、フッ素原子を含まないものが好ましい。また、後工程にて除去を容易にするため沸点が１気圧下で１５０℃以下のものが好ましい。より好ましい溶媒を例示すればアセトン、２−ブタノン、酢酸エチル、酢酸−ｎ−ブチル、メチルイソブチルケトン、トルエン等が例示される。これらはいずれも半導体用超高純度薬品として入手可能でありこれらを使用することが好ましいことは言うまでもない。また、フレームとして耐酸性の材料、例えばニッケルやニッケルめっき品を選択した場合は、希フッ化水素酸なども選択可能である。
【００５３】
前記アルキルアルコールを主成分とする溶媒にて洗浄する場合は、溶媒中にペリクル膜をフレームごと浸漬し、暫く遥動させた後引き上げ、その後新鮮な同種溶媒にてリンスを行い、常圧下、または減圧下にて乾燥させればよい。遥動の代わりに前記溶媒の循環槽中に浸漬し洗浄する方法もとりうる。本溶媒での洗浄処理は非常に短時間でよい。浸漬時間としてはとくに制限はないが５秒〜数１０分の間で任意に選択可能である。本洗浄においては長時間の浸漬を行うより、新鮮な溶媒を用いて回数を多く洗浄する方が効果的である。また、処理温度については、常温下で行うことが好ましい。また、アルキルアルコールを主成分とする溶媒にて洗浄したのち膜表面に水分を吸着させない程度の短時間で常温の超純水にてリンスしたのち乾燥を行ってもよい。
【００５４】
本発明におけるペリクルの製造方法を適応した膜は、光透過率にてその性能を確認することが可能である。本製造法を適応した膜の光透過率は１５７ｎｍ〜２００ｎｍの範囲の光で膜厚１μｍで９５％以上の光透過率を有する。ここで、光透過率とは、山と谷の連続した透過率曲線に対しては山の透過率値をいう。
以下、本発明の具体例を、実施例をもって説明するが、本発明は何らこれらに限定されるものではない。
【００５５】
【実施例】
（例１）［含フッ素ポリマー（Ａ）の合成例］
１，１，２，４，４，５−ヘキサフルオロ−３−オキサ−５−トリフルオロメチル−１，６−ヘプタジエン［ＣＨ_２＝ＣＨＣＦ（ＣＦ_３）ＣＦ_２ＯＣＦ＝ＣＦ_２］の３０ｇおよび１Ｈ−パーフルオロヘキサン［ＣＦ_３ＣＦ_２ＣＦ_２ＣＦ_２ＣＦ_２ＣＦ_２Ｈ］の７０ｇを窒素置換した内容積１００ｍｌの耐圧ガラス製オートクレーブに入れた。
重合開始剤としてビス（ヘプタフルオロブチリル）パーオキシドの１７ｍｇを加え、系内を再度窒素で置換した後、５℃で７２時間重合を行った。その結果、主鎖に含フッ素環構造を有する非結晶性ポリマー（以下「重合体Ａ」という。）を２４ｇ得た。
重合体Ａの固有粘度［η］は、パーフルオロ（２−ブチルテトラヒドロフラン）中３０℃で０．６０ｄｌ／ｇであった。重合体Ａのガラス転移温度は１０８℃であり、室温ではタフで透明ガラス状の重合体であり、屈折率は１．３４と低かった。
一方、上記と同じ方法で得た重合体Ａを空気中３２０℃で４時間熱処理した後に水中に浸漬して変性した。変性された重合体ＡのＩＲスペクトル測定によりカルボキシル基のピークが確認され、その量は０．００５ミリモル／ｇであった。この変性された重合体Ａを以下「接着剤Ａ」という。
【００５６】
（例２）
重合体Ａの６ｇとパーフルオロトリブチルアミンの９４ｇをガラス製フラスコ中に入れて４０℃にて２４時間加熱撹拌した。その結果、無色透明で濁りのない均一な溶液を得た。シリコンウェハを基板として使用し、この溶液をシリコン基板上にスピン速度５００ｒｐｍにて１０秒、その後１０００ｒｐｍにて２０秒スピンコートを実施した後、８０℃にて１時間、さらに１８０℃にて１時間加熱処理することにより、シリコン基板上に均一で透明な膜が得られた。
一方、接着剤Ａの４ｇとパーフルオロトリブチルアミンの４８ｇ、パーフルオロオクタンの４８ｇを上記と同様に処理して得た溶液をアルミニウムフレーム上に塗布し、室温で４時間乾燥した。その後、１３０℃のホットプレート上に接着面を上にしてアルミニウムフレームを載せて１０分間加熱し、上記重合体Ａの膜が形成された基板の膜面をフレーム側にして圧着した。その状態で１３０℃で１０分間、２００℃オーブン中１時間保持して接着を完結させ、フレーム、接着剤、ペリクル膜および基板の一体化品を得た。その後、電気抵抗１６ＭΩ・ｃｍの超純水７００ｍｌを内容積１リットルの密栓可能な高純度ＰＦＡ容器中に用意し、前記一体化品を浸漬し、密栓した後、８５℃のオーブン中に２４時間保持した。オーブンからＰＦＡ容器を取り出し、一体化品を水中から取り出した。基板からフレームごとペリクル膜を容易に剥離することができ、のびやむらのない重合体Ａからなる膜厚約１μｍの均一な自立膜からなるペリクル膜がついたペリクルを得た。本ペリクルをそのまま９０℃で真空乾燥を行いペリクルＡを得た。
一方、上記重合体Ａのペリクルをそのまま真空乾燥せず、半導体用グレードのメタノール中に浸漬して、５分間左右上下に揺動し、膜面に付着した不純物や水蒸気を溶出させた。その後、９０℃で真空乾燥を行い、ペリクルＢを得た。
【００５７】
上記のようにして得たペリクルＡおよびＢの膜の表面をＸ線光電子分光分析装置をもちいて分析したところ、メタノールにて洗浄処理をしなかったペリクルＡでは剥離工程前の膜組成と比較して炭素量が多く有機不純物の付着が示唆された。一方メタノールにて洗浄処理したペリクルＢについては、剥離工程前の膜組成と同等であり、不純物などの付着がないことがわかった。
表１にＸ線光電子分光分析装置による分析結果を示す。
【００５８】
【表１】

【００５９】
ペリクルＡおよびＢを用いて光透過率を測定したところ、ペリクルＡについては１５７ｎｍでの光透過率が約９４％であり、１５７ｎｍ〜２００ｎｍの範囲内で９５％未満の透過率範囲があった。一方、ペリクルＢは１５７ｎｍの波長での光透過率は９８％以上でありかつ、波長１５７ｎｍ〜２００ｎｍの範囲でも９５％以上であった。
図１にペリクルＡ及びペリクルＢの光透過率の測定結果を示す。
【００６０】
（例３）
剥離のために超純水に浸漬する温度を６５℃にする以外は例２と同じ方法でペリクルの製造を試みたが、基板からペリクル膜をはがすことができなかった。
【００６１】
【発明の効果】
本発明を用いて製造したペリクルは波長１００〜２００ｎｍ（特に１５７ｎｍ）の短波長領域において光透過率が高く、今後のより微細な加工に使用される短波長レーザー光に対して高い耐久性を示す。また、本発明の方法により、良好な歩留まりでペリクルが得られるとともに、ペリクル表面の汚染を極力抑えることができる。
【００６２】
【図面の簡単な説明】
【図１】ペリクルＡ及びペリクルＢの透過率の測定結果を示すグラフである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a pellicle suitable for photolithography using a laser beam having a wavelength of 100 to 200 nm.
[0002]
[Prior art]
A pellicle is a photolithography process that is a process for manufacturing a semiconductor device or a liquid crystal display panel. A foreign substance is placed on a photomask or a reticle (hereinafter referred to as a “mask”), resulting in a pattern defect during exposure. In order to prevent this, the protective device is mounted on the mask pattern and includes a pellicle film and a frame. Usually, the pellicle attached to the frame via an adhesive has a structure in which it is installed at a certain distance from the mask surface.
[0003]
In the field of manufacturing semiconductor devices and liquid crystal display panels in which these are used, the wavelength of the light source used in photolithography is rapidly shortening as the wiring and wiring spacing become finer. In a conventional exposure technique having a minimum pattern size of 0.3 μm or more, a process using i-line (365 nm) as a light source is mainstream, and a nitrocellulose-based material has been used as a pellicle material.
[0004]
For wiring processing with a minimum pattern dimension of less than 0.3 μm, a laser beam with a wavelength of 248 nm using a KrF excimer laser as a light source and an argon fluoride excimer laser (hereinafter referred to as “ArF excimer laser”) as a light source. Light is used. In these wavelength regions, the nitrocellulose-based film material has insufficient durability, and an amorphous perfluoropolymer is used as the material for the pellicle film.
[0005]
On the other hand, a fluorine gas excimer laser (hereinafter referred to as “F” for further fine processing. ₂ Excimer laser ". ) Is used as a light source, and the use of laser light having a wavelength of 157 nm has been proposed. ArF excimer laser light with a wavelength of 100 to 200 nm or F ₂ A fluoropolymer having a specific structure has been proposed as a material for a pellicle film in which excimer laser light is used.
[0006]
However, since the laser light from these lasers has very high energy, the amorphous perfluoropolymer is not sufficiently durable. For example, “CYTOP” (trade name), which is a perfluoropolymer used therein, has a sharp decrease in light transmission and durability at wavelengths shorter than 170 nm. This perfluoropolymer has an F wavelength of 157 nm. ₂ The permeability to excimer laser light is extremely low. Therefore, F ₂ As a pellicle material that can handle excimer laser light, for example, a fluorine-containing polymer (A) or a polymer mainly composed of perfluoro-1,3-dioxole is considered useful as an adhesive between a film or a film of the pellicle and a frame. Yes.
Here, the fluoropolymer (A) is a substantially linear fluoropolymer having a chain of carbon atoms as a main chain, and one or two hydrogen atoms are bonded as the main chain carbon atoms. The fluorine-containing polymer contains a carbon atom to which a carbon atom and a fluorine atom or a fluorine-containing organic group are bonded and a carbon atom and a hydrogen atom are not bonded.
[0007]
For non-crystalline perfluoropolymers used in pellicle films for KrF excimer laser exposure and ArF excimer laser exposure, a clean pellicle film should be applied from the substrate to suppress the adhesion of contaminants that affect the light transmittance and light resistance. Various methods of obtaining are known. For example, as a method of peeling the pellicle film from the substrate, a method of peeling by applying an electric charge to the peeling portion (see Patent Document 1), a method of peeling while irradiating ions (see Patent Document 2), and soft X-ray irradiation A method of peeling while being known (see Patent Document 3) is known.
[0008]
However, F ₂ The fluorine-containing polymer (A) useful as a pellicle for excimer laser exposure contains hydrogen in the polymer and has a polarity in the polymer as compared with the non-crystalline perfluoropolymer, so that it can interact with various substrates. Even when such a conventional method is used, it is difficult to peel off from the substrate, and there has been a problem that significant elongation or tearing occurs in the peeled film.
[0009]
[Patent Document 1]
Japanese Patent Laid-Open No. 10-26821
[Patent Document 2]
Japanese Patent Laid-Open No. 10-26822
[Patent Document 3]
Japanese Patent Laid-Open No. 10-26823
[0010]
[Problems to be solved by the invention]
The problem to be solved by the present invention is to manufacture a pellicle that has no transmittance of contaminants and has high transmittance and durability against irradiation with laser light having a wavelength of 100 to 200 nm (hereinafter also referred to as short wavelength laser light). Is to provide a method.
[0011]
[Means for Solving the Problems]
The inventors diligently studied to solve this problem and found that hot ultrapure water is effective for peeling from the substrate. That is, the novel peeling method which peels a fluorine-containing polymer (A) from a board | substrate was discovered. This invention is the following invention regarding the manufacturing method of the pellicle using the fluorine-containing polymer (A) which has high permeability | transmittance and durability with respect to the short wavelength laser beam whose wavelength is 100-200 nm.
[0012]
In a method for producing a pellicle comprising a pellicle film comprising the following fluoropolymer (A), a frame, and an adhesive for bonding the pellicle film and the frame, a step of forming the pellicle film on the substrate, and the pellicle film from the substrate Before the peeling step, and before the peeling step, the substrate on which the pellicle film is formed is changed from (the glass transition temperature of the fluorine-containing polymer (A) of the pellicle film −40) ° C. (the fluorine-containing polymer (A) of the pellicle film) A method for producing a pellicle, comprising a step of immersing in ultrapure water having a glass transition temperature of −10) ° C.
Fluoropolymer (A): A substantially linear fluoropolymer having a chain of carbon atoms as the main chain, and carbon and hydrogen in which one or two hydrogen atoms are bonded as carbon atoms in the main chain A fluorine-containing polymer containing a carbon atom to which no atom is bonded and a fluorine atom or a fluorine-containing organic group is bonded.
[0013]
The pellicle manufacturing method of the present invention is particularly suitable as a method for manufacturing a pellicle for exposure processing using a laser beam having a wavelength of 100 to 200 nm. Specifically, F of 157 nm ₂ It is most suitable as a method for producing a pellicle in an exposure process using excimer laser light.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
[0015]
The pellicle membrane in the present invention is composed of the following fluoropolymer (A). The fluorine-containing polymer (A) is a substantially linear fluorine-containing polymer having a chain of carbon atoms as a main chain. The carbon chain of the main chain of this polymer is basically composed of a chain in which two carbon atoms constituting the polymerizable unsaturated bond of the monomer are connected. Therefore, in the fluoropolymer (A), “a carbon atom having one or two hydrogen atoms bonded as a carbon atom in the main chain and a carbon atom having no hydrogen atom bonded and a fluorine atom or a fluorine-containing substituent bonded” In the case of a homopolymer obtained by polymerization of a monomer having one polymerizable unsaturated group, one of the two carbon atoms constituting the polymerizable unsaturated bond of the monomer is a hydrogen atom. Is a polymer of a monomer (hereinafter referred to as “monomer (a)”) in which no hydrogen atom is bonded to the other carbon atom.
In the case of a copolymer, a monomer in which a hydrogen atom is bonded to at least one of two carbon atoms constituting the polymerizable unsaturated bond (hereinafter referred to as “monomer (b)”) and a polymerizable unsaturated bond. It may be a copolymer with a monomer in which a hydrogen atom is not bonded to any of the two carbon atoms (hereinafter referred to as “monomer (c)”). The monomer (b) includes the monomer (a) in its category.
Furthermore, the fluorine-containing polymer (A) may be a copolymer of two or more of the monomer (a), or may be a copolymer of the monomer (a) and another monomer. Similarly, it may be a copolymer of the monomer (b), the monomer (c) and other monomers.
[0016]
The fluorine-containing polymer (A) may be a polymer obtained by cyclopolymerization of a monomer having two polymerizable unsaturated bonds (hereinafter referred to as “diene monomer”). Usually, in the case of this polymer, four carbon atoms of two polymerizable unsaturated bonds form the main chain of the polymer. Therefore, in this fluoropolymer (A), one or more carbon atoms out of four carbon atoms of two polymerizable unsaturated bonds have hydrogen atoms and one or more carbon atoms contain hydrogen atoms. It is a polymer obtained by cyclopolymerization of a monomer that does not have (hereinafter referred to as “diene monomer (d)”).
In the case of a copolymer, a diene monomer in which none of the four carbon atoms has a hydrogen atom (hereinafter referred to as “diene monomer (e)”) and a monomer having a hydrogen atom on a polymerizable unsaturated bond carbon atom (this monomer) May be a cycloene-polymerizable diene monomer having two polymerizable unsaturated bonds or a monomer having one polymerizable unsaturated bond) (hereinafter referred to as “monomer (f)”). It may be a copolymer. Further, the fluorine-containing polymer (A) may be a copolymer of a diene monomer (d) and another monomer, or may be a copolymer of a diene monomer (e), a monomer (f) and other monomers. Good.
[0017]
Since the fluorine-containing polymer (A) is a polymer having fluorine, the monomer (a), the monomer (c), the diene monomer (d) and the diene monomer (e) have a fluorine atom at the carbon atom of the polymerizable unsaturated bond. Alternatively, it is necessary that a fluorine-containing organic group is bonded. It is not essential that the monomer (b) and the monomer (f) have a fluorine atom or a fluorine-containing organic group bonded to a carbon atom of a polymerizable unsaturated bond, but they may be bonded.
As the fluorine-containing organic group, a monovalent group and a divalent group are preferable. Two bonds of the divalent fluorine-containing organic group are bonded to each of two carbon atoms of the polymerizable unsaturated bond (to form a ring containing two carbon atoms) and two carbon atoms May bond to only one of them (form a ring containing one carbon atom, and the other carbon atom becomes a carbon atom outside the ring).
The monomer (a) to the monomer (f) may have an organic group such as a hydrogen atom, a fluorine atom or an alkyl group, or other substituents on the carbon atom of the polymerizable unsaturated group within the range satisfying the above definition. . However, in a polymer having a large number of organic groups such as alkyl groups in the side chain, hydrogen atoms bonded to carbon atoms are likely to cause a decrease in durability, and it is preferable that the number of such substituents is small.
As the monovalent fluorine-containing organic group, a fluorine-containing alkyl group and a fluorine-containing alkoxy group are preferable. These groups preferably have 10 or less carbon atoms, particularly 4 or less. These groups preferably do not contain hydrogen atoms, and groups containing only fluorine atoms are preferred.
The divalent fluorine-containing organic group is preferably a polyfluoroalkylene group having 10 or less (particularly 6 or less) carbon atoms which may contain an etheric oxygen atom. The polyfluoroalkylene group is preferably a perfluoroalkylene group. The etheric oxygen atom may be present at one end of the polyfluoroalkylene group, may be present at both ends, or may be present between carbon atoms. The divalent fluorine-containing organic group is not limited to a linear one, and may have a branch.
Examples of the monovalent organic group include the monovalent fluorine-containing organic group and a monovalent organic group having no fluorine. As the monovalent organic group having no fluorine, an alkyl group and an alkoxy group having 10 or less carbon atoms, particularly 4 or less carbon atoms are preferable. As the monovalent organic group having no fluorine, a methyl group is particularly preferable.
[0018]
Since the polymer having crystallinity causes a decrease in transmittance due to light scattering and distortion of the reticle image, the degree of crystallinity of the fluorine-containing polymer (A) is preferably 30% or less, particularly 20% or less. Is preferred. By introducing a bulky structure into the polymer molecule, the crystallinity of the polymer can be lowered. Therefore, it is preferable that an aliphatic ring having a bulky structure is present in the main chain of the polymer to suppress crystallization of the polymer and to make the polymer highly amorphous and transparent. Therefore, the fluorine-containing polymer (A) is particularly preferably a fluorine-containing polymer having an aliphatic ring structure in the main chain.
“Having an aliphatic ring structure in the main chain” means that one or more carbon atoms in the main chain are carbon atoms constituting the aliphatic ring. This aliphatic ring is preferably a fluorinated aliphatic ring in which a fluorine atom or a fluorinated organic group is bonded to one or more carbon atoms constituting the aliphatic ring. Further, some of the atoms constituting the aliphatic ring may be atoms such as oxygen atoms and nitrogen atoms other than carbon atoms. A preferred aliphatic ring is a 5- to 8-membered fluorine-containing aliphatic ring having 1 to 2 oxygen atoms.
[0019]
By using a monomer having a polymerizable unsaturated group in the aliphatic ring, a polymer having an aliphatic ring structure in the main chain can be obtained. The diene monomer (d) and the diene monomer (e) form a polymer having an aliphatic ring structure in the main chain by cyclopolymerization. The term “having a polymerizable unsaturated group in the aliphatic ring” means that there is a polymerizable unsaturated group between carbon atoms constituting the aliphatic ring, or a carbon atom constituting the ring and a carbon atom outside the ring. It means having a polymerizable unsaturated group. The aliphatic ring is preferably a fluorine-containing aliphatic ring, and may have an oxygen atom as an atom constituting the ring as described above.
Hereinafter, a monomer having a polymerizable unsaturated group in the fluorinated aliphatic ring is referred to as a fluorinated aliphatic unsaturated cyclic monomer. The atoms constituting the ring of the fluorinated aliphatic unsaturated cyclic monomer may have 1 to 2 oxygen atoms in addition to the carbon atom. The monomer (c) is preferably a fluorine-containing aliphatic unsaturated cyclic monomer. Monomer (a), monomer (b) and monomer (f) may be fluorine-containing aliphatic unsaturated cyclic monomers.
[0020]
The monomer (a) is preferably vinylidene fluoride, 1,2-difluoroethylene, vinyl fluoride or trifluoroethylene. However, homopolymers of these monomers are often crystalline and tend to have low transparency.
[0021]
As the monomer (b), CHR ¹ = CR ² R ³ [R ¹ , R ² , R ³ Are each independently a hydrogen atom, a fluorine atom or a monovalent organic group]. As described above, the monomer (b) includes the monomer (a). R ¹ , R ² Is preferably a hydrogen atom or a fluorine atom, and R ³ Is preferably a hydrogen atom, a fluorine atom or an alkyl group having 4 or less carbon atoms (particularly a methyl group). Specific examples include olefins such as ethylene and propylene, and fluoroolefins in which hydrogen atoms are bonded to carbon atoms of polymerizable unsaturated groups such as vinyl fluoride, 1,2-difluoroethylene, vinylidene fluoride, and trifluoroethylene. . As a monomer (b), a C2-C3 olefin and a C2-C3 fluoroolefin are preferable. Particularly preferred monomers (b) are olefins selected from ethylene and propylene and fluoroolefins selected from vinyl fluoride, 1,2-difluoroethylene and vinylidene fluoride.
[0022]
As the monomer (c), CFR ⁴ = CR ⁵ R ⁶ [R ⁴ , R ⁵ , R ⁶ Each independently represents a fluorine atom or a monovalent fluorine-containing organic group, or R ⁴ And R ⁵ Together represent a divalent fluorine-containing organic group and R ⁶ Represents a fluorine atom or a monovalent fluorine-containing organic group, or R ⁵ And R ⁶ Together represent a divalent fluorine-containing organic group and R ⁴ Represents a fluorine atom or a monovalent fluorine-containing organic group]. Of these, R ⁴ And R ⁵ Together represent a divalent fluorine-containing organic group and R ⁶ Represents a fluorine atom or a monovalent fluorine-containing organic group, and R ⁵ And R ⁶ Together represent a divalent fluorine-containing organic group and R ⁴ Represents a fluorine atom or a monovalent fluorine-containing organic group, the monomer (c) is one of fluorine-containing aliphatic unsaturated cyclic monomers, and this monomer is hereinafter referred to as a fluorine-containing aliphatic unsaturated cyclic monomer (c). That's it.
[0023]
Specific examples of the monomer (c) include polyfluoroolefins having no hydrogen atom, such as tetrafluoroethylene and hexafluoropropylene, perfluoro (alkyl vinyl ether), and the following formulas 1, 2 and 3. And fluorinated aliphatic unsaturated cyclic monomer (c). Particularly preferred monomers (c) are perfluoro (2,2-dimethyl-1,3-dioxole) [ie R ¹¹ And R ¹² Is a compound represented by Formula 1 wherein all are trifluoromethyl groups.
[0024]
[Chemical 1]

[0025]
In the above formulas 1 to 3, R ¹¹ ~ R ¹⁶ Each independently represents a fluorine atom or a fluorine-containing organic group, and the fluorine-containing organic group is preferably a perfluoroalkyl group, particularly a perfluoroalkyl group having 1 or 2 carbon atoms.
Examples of the fluorine-containing polymer (A) comprising a copolymer of the monomer (b) and the monomer (c) include ethylene / tetrafluoroethylene copolymer, propylene / tetrafluoroethylene copolymer, propylene / vinylidene fluoride / tetrafluoroethylene copolymer, and vinylidene fluoride. / A polymer that does not have a fluorine-containing aliphatic ring structure in the main chain, such as a hexafluoropropylene copolymer, may not be sufficient in transparency. However, it is useful as an adhesive for bonding the membrane and the frame. A preferred fluorine-containing polymer (A) is a copolymer of the monomer (b) and the fluorine-containing aliphatic unsaturated cyclic monomer (c) represented by the above formulas 1 to 3. In this case, the monomer (b) is preferably at least one monomer selected from olefins such as ethylene and fluoroolefins having a hydrogen atom at the carbon atom of the unsaturated group.
[0026]
A monomer unit formed by polymerization of monomer (b) in a copolymer of monomer (b) and monomer (c) (hereinafter referred to as monomer unit (b); the same shall apply to other monomer units), monomer unit (c), The ratio of the monomer unit (b) to the total of is preferably 10 to 70 mol%. In the case where the monomer (b) is a monomer having two or more hydrogen atoms (hydrogen atom bonded to a carbon atom of a polymerizable unsaturated bond) such as ethylene, 10 to 50 mol% is preferable. The proportion of the monomer unit (b) is particularly preferably 20 to 40 mol%. In the fluorine-containing polymer (A) for an adhesive, a polymer in which the ratio of the monomer unit (b) to the total of the monomer unit (b) and the monomer unit (c) is 40 to 85 mol% is also preferable.
In addition, 50-100 mol% is preferable and, as for the ratio of the sum total of the monomer unit (b) and monomer unit (c) with respect to all the monomer units in this polymer, 80-100 mol% is especially preferable. The most preferred polymer is a copolymer consisting only of the monomer (b) and the monomer (c) (however, each monomer may be two or more types).
[0027]
As the diene monomer (d), CH ₂ = CR ⁷ -Q-CR ⁸ = CF ₂ [However, R ⁷ , R ⁸ Each independently represents a hydrogen atom, a fluorine atom or a monovalent fluorinated organic group, and Q represents a divalent fluorinated organic group]. R ⁷ Are preferably a hydrogen atom and a fluorine atom, particularly preferably a hydrogen atom. R ⁸ Is preferably a fluorine atom or a perfluoroalkyl group having 2 or less carbon atoms, particularly preferably a fluorine atom.
[0028]
Q is preferably a perfluoroalkylene group which may have an etheric oxygen atom having 10 or less carbon atoms. The etheric oxygen atom may be present at one end of the perfluoroalkylene group, may be present at both ends, or may be present between carbon atoms. In the case of a perfluoroalkylene group not having an etheric oxygen atom, the number of carbons is 2 to 6, and in the case of a perfluoroalkylene group having an etheric oxygen atom at one end or having an etheric oxygen atom between carbon atoms, the number of carbons In the case of a perfluoroalkylene group having 1 to 4 and etheric oxygen atoms at both ends, it is more preferably 1 to 3 carbon atoms. Most preferably, the total number of carbon atoms and oxygen atoms excluding the carbon atoms in the branched portion is 2 to 4.
Q is a perfluoroalkylene group having 4 or less carbon atoms having an etheric oxygen atom on the 2,2-difluorovinyl group side, a perfluoroalkylene group having 4 or less carbon atoms having an etheric oxygen atom between carbon atoms, and ether. A perfluoroalkylene group having 4 or less carbon atoms that does not have a reactive oxygen atom is preferred. Further preferred Q is a perfluoroalkylene group having 4 or less carbon atoms having an etheric oxygen atom on the 2,2-difluorovinyl group side.
That is, the most preferred diene monomer (d) is CH. ₂ = CH-R ^f -O-CF = CF ₂ [However, R ^f Represents a perfluoroalkylene group having 1 to 4 carbon atoms]. This monomer has a high cyclopolymerizability, a polymer having high short wavelength light transmittance and high mechanical strength (see JP-A-63-238111, JP-A-63-238113, etc.). R ^f Is preferably a perfluoroalkylene group having 1 to 3 carbon atoms excluding branching. When there is a branch, the branch is preferably a trifluoromethyl group, and the number of branches is preferably 1 to 2.
[0029]
CH ₂ = CR ⁷ -Q-CR ⁸ = CF ₂ In general, a monomer unit represented by the following formula 4, formula 5, formula 6 or the like (hereinafter referred to as monomer unit (d)) is formed. CH ₂ = CR ⁷ -Q-CR ⁸ = CF ₂ Examples of the diene monomer (d) represented by the following include:
[0030]
[Chemical 2]

[0031]
[Chemical 3]

[0032]
The fluorine-containing polymer (A) may be a homopolymer of the diene monomer (d) (however, it may be a copolymer of two or more of the diene monomers (d)), and is a copolymer with other monomers. May be. Examples of other monomers include monomer (a), monomer (b), monomer (c), and diene monomer (e). As the copolymer, a copolymer of diene monomer (d) and monomer (c) and a copolymer of diene monomer (d) and diene monomer (e) are preferable, and a copolymer of diene monomer (d) and monomer (c) is more preferable. As the monomer (c) in this case, the fluorine-containing aliphatic unsaturated cyclic monomer (c) is preferable.
30-100 mol% is suitable for the ratio of the monomer unit (d) with respect to all the monomer units in this fluoropolymer (A), 50-100 mol% is preferable and it is most preferable that it is 100 mol%.
The diene monomer (e) is preferably a monomer in which all hydrogen atoms bonded to the carbon atoms of the polymerizable unsaturated group of the diene monomer (d) are substituted with fluorine atoms or perfluoroalkyl groups. More preferably, CF ₂ = CR ⁹ -Q-CR ¹⁰ = CF ₂ [R ⁹ , R ¹⁰ Each independently represents a fluorine atom or a monovalent fluorine-containing organic group, and Q is the same as defined above. However, there is no restriction on the position or number of etheric oxygen atoms in Q described above. Specifically, there are the following monomers.
[0033]
[Formula 4]

[0034]
As the monomer (f), the monomer (a) and the monomer (b) can be used. Monomer (b) is particularly preferable. In the copolymerization of the diene monomer (e) and the monomer (f), the diene monomer (e) forms a monomer unit having a fluorine-containing aliphatic ring structure by cyclopolymerization, and the monomer unit (e) and the monomer unit (f ) Is produced. The copolymer having the monomer unit (e) and the monomer unit (f) may further have another monomer unit, for example, the monomer unit (c).
[0035]
In the copolymer of the diene monomer (e) and the monomer (f), the ratio of the monomer unit (f) to the total of the monomer unit (e) and the monomer unit (f) is preferably 10 to 70 mol%. In the case of the monomer (f) having two or more hydrogen atoms (hydrogen atom bonded to a carbon atom of a polymerizable unsaturated bond) such as ethylene, 10 to 60 mol% is preferable. A particularly preferable ratio of the monomer (f) is 20 to 50 mol%. In addition, 50-100 mol% is preferable and, as for the ratio of the sum total of the monomer unit (e) and monomer unit (f) with respect to all the monomer units in this polymer, 70-100 mol% is especially preferable.
The fluorine-containing polymer (A) is preferably a polymer containing monomer units having a fluorine-containing aliphatic ring structure as described above. The ratio of the monomer unit having the fluorine-containing aliphatic ring structure to the total monomer units in the fluorine-containing polymer (A) is preferably 20 mol% or more, particularly preferably 40 mol% or more.
Particularly preferred fluorine-containing polymer (A) is a copolymer of ethylene and perfluoro (2,2-dimethyl-1,3-dioxole), a homopolymer of diene monomer (d), and a fluorine-containing aliphatic unsaturated cyclic monomer. A copolymer of the monomer (c) and the diene monomer (d).
[0036]
In the present invention, the pellicle membrane and the frame are preferably bonded with an adhesive containing the fluorine-containing polymer (A).
Examples of the fluorine-containing polymer (A) for the adhesive that bonds the pellicle membrane and the frame include, for example, a copolymer of a monomer (c) and a monomer (b), which are fluorine-containing aliphatic unsaturated cyclic monomers, and a diene monomer (d). And a copolymer of diene monomer (e) and monomer (f) are preferred. Further, the fluorine-containing polymer (A) for adhesive does not necessarily require high transparency, and may be a polymer having no fluorine-containing aliphatic ring structure in the main chain. Therefore, a copolymer of the monomer (c) and the monomer (b) other than the fluorine-containing aliphatic unsaturated cyclic monomer (that is, the fluorine-containing polymer (A) having no aliphatic ring structure in the main chain) can also be used as a preferable adhesive. .
Examples of the fluorine-containing polymer (A) having no aliphatic ring structure in the main chain include propylene / vinylidene fluoride / tetrafluoroethylene copolymer and vinylidene fluoride / hexafluoropropylene copolymer. The ratio of the monomer unit (b) to the total of the monomer unit (c) and the monomer unit (b) in such a polymer is preferably 40 to 85 mol%, particularly preferably 50 to 80 mol%.
[0037]
The frame in the present invention is preferably a frame made of aluminum, blackened aluminum or synthetic quartz.
Moreover, when using a fluorine-containing polymer (A) as an adhesive agent of a flame | frame and a pellicle film, it is preferable to use the fluorine-containing polymer (A) into which the functional group effective for adhesiveness improvement was introduce | transduced. In addition, it is preferable that the fluorine-containing polymer (A) for the pellicle film does not have a functional group in terms of light transmittance.
The functional group is not particularly limited as long as it can exhibit adhesiveness to the frame or pellicle membrane. For example, a carboxylic acid group, a sulfonic acid group, a group having an ester bond, an alkenyl group, hydrolyzable Examples include a silyl group, a hydroxyl group, a maleimide group, an amino group, a cyano group, and an isocyanate group. As this functional group, a carboxylic acid group is particularly preferable from the viewpoints of good adhesion to aluminum or the like as a frame material, excellent storage stability, and the effect can be exhibited at a relatively low temperature.
[0038]
The present invention includes a step of forming a pellicle film on a substrate. Such a substrate is not particularly limited as long as it is smooth and does not dissolve or swell in the fluoropolymer (A) used in the present invention or the fluoropolymer (A) solution described later. A silicon substrate or a quartz substrate is preferably used.
[0039]
Examples of preferred substrates include silicon substrates such as semiconductor silicon wafers and silicon oxide film wafers, and quartz substrates such as synthetic quartz and fluorine-doped synthetic quartz. When using these substrates, it is preferable to perform pretreatment such as polishing and cleaning in advance. For example, in the case of a silicon wafer, there is a possibility that a very small amount of organic impurities are attached, so after washing with about 0.5% diluted hydrogen fluoride aqueous solution, washing with ultrapure water. It is preferable to dry. Particularly preferred substrates are a semiconductor silicon substrate and a fluorine-doped synthetic quartz substrate exhibiting high transmittance at 100 to 200 nm.
[0040]
As a method for forming a pellicle film on the substrate, a film forming method using a solution of a fluoropolymer (A) as a material of the pellicle film is preferable. Any solvent can be used as long as it can dissolve the fluoropolymer (A) in the present invention. A fluorine-containing solvent is preferable. The polymer concentration of the solution is preferably 3 to 10% by mass. Using this solution, a uniform wet thin film is formed on the substrate. As a method for forming the wet thin film at this time, a spin coating method, a casting method, a dip coating method, or the like is used. After forming a wet thin film of the polymer solution using these methods, the solvent is volatilized using a heating device such as an oven or a hot plate to form a uniform thin film (pellicle film) preferably having a thickness of 0.5 to 2 μm. A manufactured substrate is manufactured.
[0041]
The present invention includes a step of peeling the pellicle film from the substrate, and a step of immersing the substrate on which the pellicle film has been formed before the peeling step in hot ultrapure water. When dipping in hot ultrapure water, it is preferable to adhere the frame to the pellicle membrane in advance in consideration of the subsequent steps. Hereinafter, this process will be described in detail for this preferred embodiment. The ultrapure water in the present invention means water having an electric resistance of 10 MΩ · cm or more.
An adhesive polymer solution is applied to the frame in advance, air-dried and then heated. Any polymer may be used as the adhesive polymer as long as it can bond the frame and the pellicle film. As described above, the fluorine-containing polymer (A) is preferable, and the fluorine-containing polymer (A) having a functional group is more preferable. Any solvent can be used as long as it can dissolve the adhesive polymer. When the adhesive is the fluorine-containing polymer (A) which is a preferred embodiment, the solvent is preferably a fluorine-containing solvent. The concentration of the polymer solution of the adhesive is preferably 2 to 10% by mass from the viewpoint of good operability.
The heating is performed using an oven, a hot plate or the like, with the surface on which the solution is applied to the frame facing up. From the viewpoint of firmly bonding the frame and the film on the substrate, the heating temperature is a glass transition temperature (hereinafter, T) of the polymer of the adhesive. _{g, a} . ) It is preferable to perform the above, more specifically, T _{g, a} ~ (T _{g, a} +50) ° C., more preferably (T _{g, a} +20) to (T _{g, a} +50) ° C. The heating time is preferably about 10 to 20 minutes, but this time is preferably adjusted by the thickness and width of the frame.
[0042]
When the polymer of the adhesive is softened, the substrate is placed on the frame with the surface of the substrate on which the pellicle film is formed facing the adhesive, and further heated to bond the frame and the pellicle film. In order to obtain stronger adhesion, the substrate with the frame attached may be reheated in an oven. In this way, an integrated product with the frame, the adhesive, the pellicle film and the substrate is obtained.
[0043]
Next, a process of peeling the frame and the film from the substrate will be described. The glass transition temperature of the fluoropolymer (A) that is the material of the pellicle film is T _{g, m} Then, the integrated product is (T _{g, m} −40) to (T _{g, m} -10) Immerse in ultrapure water at ℃. For polymer A in the examples described later, this temperature is approximately 70-100 ° C. A more preferred temperature is (T _{g, m} -30) to (T _{g, m} -10) ° C.
[0044]
The immersion time is preferably between 1 hour and 48 hours. If it is less than 1 hour, it is insufficient as a thermal ultrapure water treatment, and if it exceeds 48 hours, the productivity deteriorates and unnecessary H ₂ O adsorption may be caused and the transmittance of the pellicle may be deteriorated. More preferably, it is 1 hour to 36 hours.
[0045]
The container for performing the heat treatment is not particularly limited as long as it does not elute organic impurities or inorganic impurities, and various materials can be used. However, a fluororesin container is preferred because ultrapure water has high polarity and the immersion temperature is 100 ° C. or higher depending on the polymer. Among these, containers for semiconductor applications using high-purity PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer) that suppresses eluted metals and eluted substances are preferable. Moreover, as a device for heating these containers, a general oven, a humidifying and pressing oven, an autoclave, or the like is preferably used.
[0046]
When the integrated product is taken out after being immersed in hot ultrapure water, the pellicle film can be easily peeled off from the substrate together with the frame. The reason is considered as follows.
Since the fluorine-containing polymer (A) is not a fully fluorinated polymer but a fluorine-containing polymer containing hydrogen in a part of the basic skeleton, polarity is generated in the molecule due to a large difference in electronegativity between hydrogen and fluorine. Since the interaction with the substrate is stronger than that of the perfluoropolymer, the conventional method cannot be peeled from the substrate.
[0047]
However, since this interaction is electrostatic and is not a chemical bond, it can be peeled off if the interface is treated with a material that has a stronger interaction with the substrate and a material that does not interact with the polymer. It is done. As such a substance, ultrapure water is selected which has high cleanliness and low cost, and has the lowest levels of dissolved organic substances and ionic impurities. Among the ultrapure water, the electric resistance is preferably 15 MΩ · cm or more.
[0048]
Moreover, (T _{g, m} By setting the temperature to −40) ° C. or higher, ultrapure water permeates into the interface between the substrate and the pellicle film in a short time, so that unevenness does not occur and the film does not stretch or sag during peeling. On the other hand, (T _{g, m} −10) By setting the temperature to be equal to or lower than ° C., the mechanical strength of the film does not decrease, and elongation or tearing does not occur during peeling.
[0049]
In the pellicle film obtained as described above, impurities from the container or organic impurities attached to the substrate in the film forming process may be transferred and attached to the pellicle film. In addition, since the peeling process is performed at a high temperature, water vapor may be dissolved on the surface of the pellicle film. These impurities are preferably removed to significantly reduce the light transmittance of, for example, 157 nm and deteriorate the durability.
[0050]
In order to remove these impurities, it is preferable to use a solvent mainly composed of alkyl alcohol. Such a solvent is preferable because it does not dissolve or swell the pellicle film, has good compatibility with water, and can be easily removed in a later step. Specifically, a solvent mainly containing an alkyl alcohol containing no fluorine is preferable, and a solvent mainly containing an alkyl alcohol having an alkyl group having 4 or less carbon atoms is more preferable. Specifically, methanol, ethanol and isopropanol are preferable, and methanol is most preferable. These may be used alone or in combination of two or more. Of course, it is preferable to use a semiconductor grade solvent from the viewpoint of preventing redeposition of new impurities.
[0051]
Having an alkyl alcohol as a main component means that these alkyl alcohols are contained in a volume ratio of 50% or more. More preferably, it is 60% or more. As a matter of course, the alkyl alcohol may be used at 100%. By including 50% or more by volume ratio of the alkyl alcohol, the possibility that the pellicle film is stretched or broken during cleaning is small.
[0052]
The solvent that may be used in combination with the alkyl alcohol may be either a polar solvent or a nonpolar solvent, and may be used alone or in combination. However, from the viewpoint of preventing the pellicle film from being broken or peeled, a film containing no fluorine atom is preferable. Further, in order to facilitate removal in a later step, those having a boiling point of 150 ° C. or lower under 1 atm are preferable. Examples of more preferable solvents include acetone, 2-butanone, ethyl acetate, n-butyl acetate, methyl isobutyl ketone, toluene and the like. Needless to say, these are all available as ultra-high purity chemicals for semiconductors, and it is preferable to use them. Further, when an acid-resistant material such as nickel or a nickel-plated product is selected as the frame, dilute hydrofluoric acid or the like can be selected.
[0053]
When washing with a solvent containing the alkyl alcohol as a main component, the pellicle membrane is immersed in the solvent together with the frame, lifted after being shaken for a while, then rinsed with a fresh similar solvent, under normal pressure, or What is necessary is just to dry under reduced pressure. Instead of swinging, a method of immersing and washing in the solvent circulation tank may be used. The cleaning treatment with this solvent may be very short. Although there is no restriction | limiting in particular as immersion time, It can select arbitrarily between 5 second-several dozen minutes. In the main cleaning, it is more effective to perform the cleaning more frequently using a fresh solvent than to immerse for a long time. Moreover, about processing temperature, it is preferable to carry out at normal temperature. Further, after washing with a solvent containing alkyl alcohol as a main component, drying may be performed after rinsing with ultrapure water at room temperature in a short time so as not to adsorb moisture on the film surface.
[0054]
The performance of the film to which the pellicle manufacturing method of the present invention is applied can be confirmed by the light transmittance. The light transmittance of the film to which the present manufacturing method is applied has a light transmittance of 95% or more at a film thickness of 1 μm with light in the range of 157 nm to 200 nm. Here, the light transmittance means a transmittance value of a mountain for a continuous transmittance curve of a mountain and a valley.
Specific examples of the present invention will be described below with reference to examples, but the present invention is not limited to these examples.
[0055]
【Example】
(Example 1) [Synthesis example of fluoropolymer (A)]
1,1,2,4,4,5-hexafluoro-3-oxa-5-trifluoromethyl-1,6-heptadiene [CH ₂ = CHCF (CF ₃ CF ₂ OCF = CF ₂ ] Of 30 g and 1H-perfluorohexane [CF ₃ CF ₂ CF ₂ CF ₂ CF ₂ CF ₂ H] was placed in a pressure-resistant glass autoclave with an internal volume of 100 ml, which was purged with nitrogen.
As a polymerization initiator, 17 mg of bis (heptafluorobutyryl) peroxide was added, the inside of the system was again replaced with nitrogen, and polymerization was carried out at 5 ° C. for 72 hours. As a result, 24 g of an amorphous polymer having a fluorine-containing ring structure in the main chain (hereinafter referred to as “polymer A”) was obtained.
The intrinsic viscosity [η] of the polymer A was 0.60 dl / g at 30 ° C. in perfluoro (2-butyltetrahydrofuran). The glass transition temperature of the polymer A was 108 ° C., and it was a tough and transparent glassy polymer at room temperature. The refractive index was as low as 1.34.
On the other hand, the polymer A obtained by the same method as described above was heat-treated in air at 320 ° C. for 4 hours and then immersed in water for modification. The peak of the carboxyl group was confirmed by IR spectrum measurement of the modified polymer A, and the amount thereof was 0.005 mmol / g. This modified polymer A is hereinafter referred to as “adhesive A”.
[0056]
(Example 2)
6 g of the polymer A and 94 g of perfluorotributylamine were placed in a glass flask and heated and stirred at 40 ° C. for 24 hours. As a result, a colorless and transparent uniform solution without turbidity was obtained. Using a silicon wafer as a substrate, this solution was spin-coated on a silicon substrate at a spin speed of 500 rpm for 10 seconds and then at 1000 rpm for 20 seconds, then at 80 ° C. for 1 hour, and further at 180 ° C. for 1 hour. By carrying out the heat treatment, a uniform and transparent film was obtained on the silicon substrate.
On the other hand, a solution obtained by treating 4 g of adhesive A, 48 g of perfluorotributylamine and 48 g of perfluorooctane in the same manner as described above was applied onto an aluminum frame and dried at room temperature for 4 hours. Thereafter, the aluminum frame was placed on a 130 ° C. hot plate with the adhesive surface facing upward and heated for 10 minutes, and the film surface of the substrate on which the polymer A film was formed was pressure bonded with the frame side. In this state, it was held at 130 ° C. for 10 minutes and in an oven at 200 ° C. for 1 hour to complete the adhesion, thereby obtaining an integrated product of the frame, the adhesive, the pellicle film and the substrate. Thereafter, 700 ml of ultrapure water having an electric resistance of 16 MΩ · cm is prepared in a high-purity PFA container having an inner volume of 1 liter, which can be sealed, and the integrated product is immersed, sealed, and then placed in an oven at 85 ° C. for 24 hours. Retained. The PFA container was removed from the oven, and the integrated product was removed from the water. The pellicle film was easily peeled off from the substrate together with the frame, and a pellicle with a pellicle film made of a uniform free-standing film of about 1 μm thick made of polymer A having no stretch and unevenness was obtained. The pellicle was vacuum-dried at 90 ° C. as it was to obtain pellicle A.
On the other hand, the pellicle of the polymer A was not vacuum dried as it was, but was immersed in semiconductor grade methanol and swung left and right and up and down for 5 minutes to elute impurities and water vapor adhering to the film surface. Thereafter, vacuum drying was performed at 90 ° C. to obtain Pellicle B.
[0057]
When the surfaces of the pellicle A and B films obtained as described above were analyzed using an X-ray photoelectron spectrometer, the pellicle A that was not washed with methanol was compared with the film composition before the peeling process. It was suggested that organic impurities adhere due to the large amount of carbon. On the other hand, it was found that the pellicle B washed with methanol was equivalent to the film composition before the peeling process and there was no adhesion of impurities.
Table 1 shows the results of analysis using an X-ray photoelectron spectrometer.
[0058]
[Table 1]

[0059]
When the light transmittance was measured using the pellicles A and B, the light transmittance at 157 nm was about 94% for the pellicle A, and there was a transmittance range of less than 95% within the range of 157 nm to 200 nm. On the other hand, the pellicle B had a light transmittance of 98% or more at a wavelength of 157 nm, and was 95% or more even in a wavelength range of 157 nm to 200 nm.
FIG. 1 shows the measurement results of the light transmittance of pellicle A and pellicle B.
[0060]
(Example 3)
A pellicle was produced in the same manner as in Example 2 except that the temperature of immersion in ultrapure water for peeling was 65 ° C., but the pellicle film could not be peeled from the substrate.
[0061]
【The invention's effect】
The pellicle manufactured using the present invention has a high light transmittance in a short wavelength region of a wavelength of 100 to 200 nm (especially 157 nm), and exhibits a high durability against a short wavelength laser beam used for further fine processing in the future. . In addition, the method of the present invention makes it possible to obtain a pellicle with a good yield and to suppress contamination of the pellicle surface as much as possible.
[0062]
[Brief description of the drawings]
FIG. 1 is a graph showing measurement results of transmittance of pellicle A and pellicle B;

Claims (5)

In a method for producing a pellicle comprising a pellicle film comprising the following fluoropolymer (A), a frame, and an adhesive for bonding the pellicle film and the frame, the step of forming the pellicle film on a substrate, the substrate to the pellicle film And before the peeling step, the substrate on which the pellicle film is formed (glass transition temperature of the fluoropolymer (A) of the pellicle film−40) ° C. (fluorine-containing polymer (A A glass transition temperature of -10). A method for producing a pellicle, comprising the step of immersing in ultrapure water at a temperature of 10 ° C.
Fluoropolymer (A): A substantially linear fluoropolymer having a chain of carbon atoms as the main chain, and carbon and hydrogen in which one or two hydrogen atoms are bonded as carbon atoms in the main chain A fluorine-containing polymer containing a carbon atom to which no atom is bonded and a fluorine atom or a fluorine-containing organic group is bonded. The method for producing a pellicle according to claim 1, wherein the adhesive that bonds the pellicle membrane and the frame contains a fluorine-containing polymer (A). The method for producing a pellicle according to claim 1 or 2, further comprising a step of washing the surface of the pellicle film with a solvent containing alkyl alcohol as a main component after the peeling step of the pellicle film. The method for producing a pellicle according to any one of claims 1 to 3, wherein the substrate according to claim 1 is a silicon substrate or a quartz substrate. The method for producing a pellicle according to any one of claims 1 to 4, wherein the light transmittance at a film thickness of 1 µm of the pellicle film is 95% or more with light in a range of 157 to 200 nm.

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