JP2006335774A - Method for producing fluorine-containing polymer for resist - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a fluorine-containing polymer for photoresist transparent in a vacuum ultraviolet region, especially F2 laser (157 nm) beams and having excellent solubility in alkali developers and to provide a photoresist composition comprising the fluorine-containing polymer. <P>SOLUTION: The method for producing the fluorine-containing polymer for the resist which is a fluorine-containing polymer having an aliphatic ring structure in the main chain, an acid reactive group reactive with an acid or a group convertible into the acid reactive group in the polymer and excellent solubility in developers is characterized as follows. A monomer mixture containing monomers affording the aliphatic ring structure in the main chain is made to coexist with a radical polymerization initiator and a chain transfer agent represented by general formula R-(X)<SB>n</SB>(wherein, R is a 1-20C hydrocarbon group that may contain an ether bond in which a part of hydrogen atoms may be substituted with fluorine atoms; X is an oxygen atom-containing functional group or a substituted or an unsubstituted amino group; and n is an integer of 1-4). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

【００４６】
（式中、Ｒ⁷、Ｒ⁸、Ｒ⁹、Ｒ¹⁰、Ｒ¹¹、Ｒ¹²、Ｒ¹⁴、Ｒ¹⁸、Ｒ¹⁹、Ｒ²⁰、Ｒ²¹、Ｒ²²、Ｒ²⁴、Ｒ²⁵、Ｒ²⁶、Ｒ²⁷、Ｒ²⁸、Ｒ²⁹は同じかまたは異なり、炭素数１〜１０の炭化水素基；Ｒ¹³、Ｒ¹⁵、Ｒ¹⁶は同じかまたは異なり、Ｈまたは炭素数１〜１０の炭化水素基；Ｒ¹⁷、Ｒ²³は同じかまたは異なり、炭素数２〜１０の２価の炭化水素基）などがあげられる。
【００４７】
上記例示のなかから、ｔ−ブトキシ基、ｔ−ブトキシカルボニル基、ｔ−ブトキシカルボニルオキシ基、メトキシメチル基、エトキシメチル基等が好ましくあげられる。
【００４８】
親水性の官能基に変換可能な基のなかでも、ヒドロキシル基、カルボキシル基に変換可能な基であることが好ましく、さらには透明性に優れる点でヒドロキシル基に変換可能な基であることが特に好ましい。
【００４９】
前記連鎖移動剤を示す式（１）中における炭化水素基Ｒは炭素数１〜２０の炭化水素基から選ばれるものであって、そのなかにエーテル結合を含んでいても良い。また、水素原子の一部がフッ素原子で置換されていても良い。
【００５０】
式（１）の連鎖移動剤における官能基Ｘはこの炭化水素基Ｒ中の同一または異なる炭素原子に１〜４個結合していることが好ましく、ラジカル重合をスムーズに進行させるためには官能基Ｘは１または２個、さらには１個が炭化水素基Ｒに結合しているものが好ましい。
【００５１】
炭化水素基Ｒは、なかでも飽和脂肪族炭化水素基（たとえば炭素−炭素二重結合や芳香族基を含まない）であることが透明性に優れる点で好ましい。
【００５２】
具体的には、炭素数１〜２０の直鎖または分岐状のアルキル基、飽和脂肪族環状構造を有するアルキル基から選ばれる。
【００５３】
なかでも、炭化水素基Ｒ中に飽和脂肪族環状構造を含む場合、ドライエッチング耐性を改善できる点で好ましい。
【００５４】
炭化水素基Ｒの炭素数は１〜２０から選ばれ、好ましくは１〜１５、より好ましくは１〜１０、さらには１〜６である。炭素数が多くなりすぎるとラジカル重合がスムーズに進行しなくなるため好ましくない。
【００５５】
直鎖状または分岐状のアルキル基として具体的には、
【００５６】
【化４】

【００５７】
などがあげられる。
【００５８】
なかでもＣＨ₃−、ＣＨ₃ＣＨ₂−、ＣＨ₃ＣＨ₂ＣＨ₂−、（ＣＨ₃）₂ＣＨ−などが好ましく、より好ましくはＣＨ₃−、（ＣＨ₃）₂ＣＨ−、さらにはラジカル重合がスムーズに進行する点で、ＣＨ₃−が最も好ましい。
【００５９】
飽和脂肪族環状構造を含むアルキル基として具体的には、
【００６０】
【化５】

【００６１】
などが好ましくあげられる。
【００６２】
本発明の製造法において用いる連鎖移動剤のなかで好ましいものは、アルコール類であり、好ましくは炭素数１〜１０のアルコール類、より好ましくは炭素数１〜１０の１価のアルコール類である。
【００６３】
具体的には、メタノール、エタノール、プロパノール、イソプロパノール、ｎ−ブタノール、ｔ−ブタノール、２−メチルプロパノール、シクロヘキサノール、メチルシクロヘキサノール、シクロペンタノール、メチルシクロペンタノール、ジメチルシクロペンタノールなどがあげられる。
【００６４】
なかでもメタノール、イソプロパノール、ｔ−ブタノール、シクロヘキサノール、メチルシクロヘキサノール、シクロペンタノール、メチルシクロペンタノールなどが好ましく、特にメタノールが好ましい。
【００６５】
つぎに式（１）の連鎖移動剤を使用してラジカル重合する各単量体について説明する。
【００６６】
まず、本発明で得られるレジスト用含フッ素重合体の必須成分である、重合体主鎖に脂肪族環構造の構造単位（Ｍ２）を与え得るフッ素原子を含んでいてもよい単量体（ｍ２）について説明する。
【００６７】
かかる単量体（ｍ２）は、レジスト用途に用いた場合ドライエッチング耐性を向上させる脂肪族環構造の構造単位（Ｍ２）を重合体主鎖中に導入することができる。この効果と上記の真空紫外領域の透明性とアルカリ現像液に対する優れた溶解性の改善効果とが合さって、本発明の製法により得られる主鎖に脂肪族環構造を有する含フッ素重合体は、Ｆ２レーザー用レジストに特に好ましいものである。
【００６８】
単量体（ｍ２）は、ラジカル重合性の炭素−炭素不飽和結合を環構造中に有する不飽和環状化合物から選ばれるものであってもよいし、ジエン化合物の環化重合により主鎖に環構造を形成させることができる非共役ジエン化合物から選ばれるものであってもよい。
【００６９】
また単量体（ｍ２）は、その単量体中に酸反応性官能基Ｙを有していてもよいし有していなくてもよい。
【００７０】
この単量体（ｍ２）を（共）重合することによって、主鎖に単環構造または複環構造の脂肪族環構造単位を有する重合体を得ることができる。
【００７１】
単量体（ｍ２）の好ましい第１は、ラジカル重合性の炭素−炭素不飽和結合を有し、ポリマー主鎖に単環または複環構造を形成できる単量体であって、かつ酸反応性官能基Ｙを有さない単量体（ｍ２−１）である。
【００７２】
具体的には、酸反応性官能基Ｙを有さない単環状の脂肪族不飽和炭化水素化合物からなる単量体（ｍ２−１ａ）、酸反応性官能基Ｙを有しない複環状の脂肪族不飽和炭化水素化合物からなる単量体（ｍ２−１ｂ）、または後述する酸反応性官能基Ｙを有しない環化重合可能な非共役ジエン化合物（ｍ２−１ｃ）から選ばれるものである。
【００７３】
酸反応性官能基Ｙを有しない単環状の単量体（ｍ２−１ａ）は環構造中にエーテル結合を含んでいてもよい３員環〜８員環構造の脂肪族不飽和炭化水素化合物であることが好ましい。
【００７４】
単量体（ｍ２−１ａ）は、具体的には、
【００７５】
【化６】

【００７６】
などが好ましくあげられる。
【００７７】
さらに、これら単量体（ｍ２−１ａ）の水素原子の一部または全部がフッ素原子で置換された単量体であってもよく、たとえば、
【００７８】
【化７】

【００７９】
などが好ましくあげられる。
【００８０】
前記、単量体（ｍ２−１）のもう一方は、重合体主鎖中に脂肪族複環構造を有する構造単位を与え、かつ酸反応性官能基Ｙを有しない脂肪族複環構造を有する単量体（ｍ２−１ｂ）であり、好ましい単量体（ｍ２−１ｂ）はノルボルネン誘導体である。
【００８１】
酸反応性官能基Ｙを有していない脂肪族複環構造を有する単量体（ｍ２−１ｂ）は、具体的には、
【００８２】
【化８】

【００８３】
などがあげられる。
【００８４】
上記例示のノルボルネン類の環構造にフッ素原子を導入したものであってもよく、フッ素原子を導入することによりドライエッチング耐性を低下させずに透明性を向上できる。
【００８５】
具体的には、式：
【００８６】
【化９】

【００８７】
（式中、Ａ、Ｂ、ＤおよびＤ’は同じかまたは異なり、いずれもＨ、Ｆ、炭素数１〜１０のアルキル基または炭素数１〜１０の含フッ素アルキル基；ｍは０〜３の整数。ただし、Ａ、Ｂ、Ｄ、Ｄ’のいずれか１つはフッ素原子を含む）で示される含フッ素ノルボルネンであり、具体的には、
【００８８】
【化１０】

【００８９】
などで示される含フッ素ノルボルネンがあげられる。
【００９０】
そのほか、
【００９１】
【化１１】

【００９２】
などのノルボルネン誘導体もあげられる。
【００９３】
単量体（ｍ２）の好ましい第２は、ラジカル重合性の炭素−炭素不飽和結合を有し、ポリマー主鎖に単環または複環構造を形成できる単量体であって、かつ酸反応性官能基Ｙを有する単量体（ｍ２−２）である。
【００９４】
詳しくは、酸反応性官能基Ｙを有する単環状の脂肪族不飽和炭化水素化合物からなる単量体（ｍ２−２ａ）、酸反応性官能基Ｙを有する複環状の脂肪族不飽和炭化水素化合物からなる単量体（ｍ２−２ｂ）、または後述する環化重合可能な非共役ジエン化合物であって酸反応性官能基Ｙを有する単量体（ｍ２−２ｃ）から選ばれるものである。
【００９５】
なかでも酸反応性官能基Ｙを有する単環状の単量体（ｍ２−２ａ）は環構造中にエーテル結合を含んでいてもよい３員環〜８員環構造の不飽和炭化水素化合物であることが好ましい。また前述と同様、単量体（ｍ２−２ａ）の水素原子の一部またはすべてがフッ素原子で置換された単量体であってもよい。
【００９６】
酸反応性官能基Ｙを有する単環状の単量体（ｍ２−２ａ）は、具体的には、
【００９７】
【化１２】

【００９８】
などの単量体があげられる。
【００９９】
前記、酸反応性官能基Ｙを有する単量体（ｍ２−２）のもう一方は、重合体主鎖中に脂肪族複環構造を有する構造単位を与え、かつ酸反応性官能基Ｙを有する脂肪族複環構造を含む単量体（ｍ２−２ｂ）であり、好ましい単量体（ｍ２−２ｂ）は酸反応性官能基Ｙを有するノルボルネン誘導体である。
【０１００】
酸反応性官能基Ｙを有している脂肪族複環構造を含む単量体（ｍ２−２ｂ）は、具体的には、
【０１０１】
【化１３】

【０１０２】
などがあげられる。
【０１０３】
さらに酸反応性官能基Ｙを有する脂肪族複環構造を含む単量体（ｍ２−２ｂ）は、環構造に結合した水素原子の一部またはすべてをフッ素原子に置換したものであってもよく、このものは重合体にさらなる透明性を付与できる点で好ましい。
【０１０４】
具体的には、
【０１０５】
【化１４】

【０１０６】
（式中、Ａ、ＢおよびＤは同じかまたは異なり、いずれもＨ、Ｆ、炭素数１〜１０のアルキル基または炭素数１〜１０のエーテル結合を有していてもよい含フッ素アルキル基；Ｒは炭素数１〜２０の２価の炭化水素基、炭素数１〜２０の含フッ素アルキレン基または炭素数２〜１００のエーテル結合を有する含フッ素アルキレン基；ａは０〜５の整数；ｂは０または１。ただし、ｂが０またはＲがフッ素原子を含まない場合はＡ、Ｂ、Ｄのいずれか１つはフッ素原子またはエーテル結合を有していてもよい含フッ素アルキル基である）で表わされる含フッ素ノルボルネン誘導体があげられる。
【０１０７】
これらのなかでも、Ａ、Ｂ、Ｄのいずれかがフッ素原子であることが好ましく、またはＡ、Ｂ、Ｄにフッ素原子が含まれない場合はＲのフッ素含有率が６０重量％以上であることが好ましく、さらにはパーフルオロアルキレン基であることが、重合体に透明性を付与できる点でさらに好ましい。
【０１０８】
具体的には、
【０１０９】
【化１５】

【０１１０】
などで示されるノルボルネン誘導体があげられる。
【０１１１】
さらに、
【０１１２】
【化１６】

【０１１３】
（式中、Ａ、ＢおよびＤは同じかまたは異なり、いずれもＨ、Ｆ、炭素数１〜１０のアルキル基または炭素数１〜１０のエーテル結合を有していもよい含フッ素アルキル基；Ｒは炭素数１〜２０の２価の炭化水素基、炭素数１〜２０の含フッ素アルキレン基または炭素数２〜１００のエーテル結合を有する含フッ素アルキレン基；ａは０〜５の整数；ｂは０または１）で表わされる含フッ素ノルボルネン誘導体があげられる。
【０１１４】
具体的には、
【０１１５】
【化１７】

【０１１６】
などのノルボルネン誘導体が好ましくあげられる。
【０１１７】
またさらに、酸反応性官能基Ｙを有する脂肪族複環構造を含む単量体（ｍ２−２ｂ）の好ましいものとして、式：
【０１１８】
【化１８】

【０１１９】
（式中、Ｒｆ¹、Ｒｆ²は同じかまたは異なり、炭素数１〜１０の含フッ素アルキル基またはエーテル結合を有する含フッ素アルキル基；Ａ、Ｂ、Ｄは同じかまたは異なり、いずれもＨ、Ｆ、Ｃｌ、炭素数１〜１０のアルキル基または炭素数１〜１０のエーテル結合を含んでいてもよい含フッ素アルキル基；ＲはＨまたは炭素数１〜１０のアルキル基；ｎは０〜５の整数）で示される含フッ素ノルボルネン誘導体があげられる。
【０１２０】
具体的には、たとえば
【０１２１】
【化１９】

【０１２２】
などがあげられる。
【０１２３】
より具体的には、
【０１２４】
【化２０】

【０１２５】
などが好ましくあげられる。
【０１２６】
その他、式：
【０１２７】
【化２１】

【０１２８】
（式中、Ｒｆ¹、Ｒｆ²は同じかまたは異なり、炭素数１〜１０の含フッ素アルキル基またはエーテル結合を有する含フッ素アルキル基；Ｂ、Ｄは同じかまたは異なり、いずれもＨ、Ｆ、Ｃｌ、炭素数１〜１０のアルキル基または炭素数１〜１０のエーテル結合を含んでいてもよい含フッ素アルキル基；ＲはＨまたは炭素数１〜１０のアルキル基；ｎは０〜５の整数）で示されるノルボルネン誘導体もあげられる。
【０１２９】
これら例示の脂肪族複環構造を含む単量体（ｍ２−１ｂ）、（ｍ２−２ｂ）は、重合体にドライエッチ耐性を付与できる点で、特にレジスト用重合体の原料として好ましい。また、本発明の製造方法により、効率的にラジカル重合法で重合体を製造でき、効果的に透明性を改善できる点でも好ましい。特にフッ素原子を複環構造に含むノルボルネン誘導体は、透明性の点で好ましくかつ本発明の製造方法により、効率的にラジカル重合法で重合体を製造でき、効果的に透明性を改善できる点でも好ましい。
【０１３０】
また、酸反応性官能基Ｙを有するノルボルネン誘導体（ｍ２−２ｂ）は重合体に効率的にレジスト用途に必要な官能基を導入でき、結果的に透明性、ドライエッチング耐性において有利となるため好ましい。
【０１３１】
単量体（ｍ２）の好ましい第３は、重合により脂肪族環構造を形成し得るフッ素原子を有していてもよい非共役のジエン化合物である。非共役ジエン化合物は、主鎖中に環構造の構造単位を有する重合体を効率よく与えることができ、前述と同様、真空紫外領域の透明性も改善できるものである。
【０１３２】
非共役ジエン化合物としては、たとえば環化重合し主鎖に単環構造を与える特定のジビニル化合物が好ましくあげられ、酸反応性の官能基Ｙを有さないもの（ｍ２−１ｃ）、または酸反応性の官能基Ｙを有するもの（ｍ２−２ｃ）である。
【０１３３】
具体例としては、たとえばフッ素原子や酸反応性官能基Ｙを有していてもよい式：
【０１３４】
【化２２】

【０１３５】
（式中、Ｚ¹およびＺ²は同じか異なり、水素原子、フッ素原子、炭素数１〜５のエーテル結合を有していてもよい炭化水素基、炭素数１〜５のエーテル結合を有していてもよい含フッ素アルキル基）で示されるジアリル化合物があげられる。
【０１３６】
このジアリル化合物をラジカル環化重合することにより、
【０１３７】
【化２３】

【０１３８】
（式中、Ｚ¹、Ｚ²は前記と同じ）で示される主鎖中に単環状の構造単位を形成することができる。
【０１３９】
これらの環化ラジカル重合においても、前記式（１）の官能基を有する連鎖移動剤を使用してラジカル（共）重合することによって効率よくポリマー主鎖に環構造を有する含フッ素重合体を得ることができ、前述と同様、現像液に対する溶解性を改善できるものである。
【０１４０】
本発明の方法で製造される構造単位Ｍ２−２を有する含フッ素重合体において、酸反応性官能基Ｙを有する構造単位Ｍ２−２はその構造単位中に式（２）：
【０１４１】
【化２４】

【０１４２】
（式中、Ｒｆ¹は炭素数１〜１０の含フッ素アルキル基またはエーテル結合を有する含フッ素アルキル基）で表される部位を有することが現像液への溶解性に優れ、かつ１５７ｎｍ光に対する透明性に優れる点で好ましい。
【０１４３】
Ｒｆ¹は、なかでも炭素数１〜１０のパーフルオロアルキル基であることが好ましく、より好ましくは炭素数１〜５のパーフルオロアルキル基、さらにはＣＦ₃であることが特に好ましい。
【０１４４】
式（２）の部位とは、含フッ素アルキル基Ｒｆ¹とＯＨ基が環構造を形成する炭素原子に同時に結合しているものであっても良いし、環構造を形成しない炭素原子に同時に結合し、式（２）の部位が環構造を形成する炭素原子に側鎖の形態で結合したものであっても良い。
【０１４５】
ここで酸反応性官能基Ｙについて説明する。酸反応性官能基Ｙは前記のとおり、酸反応性基Ｙ¹と、酸反応性基Ｙ¹に変換可能な酸反応性基変換基Ｙ²の総称である。
【０１４６】
本発明において酸反応性基Ｙ¹は、酸解離性または酸分解性の官能基および酸縮合性の官能基のことをいう。
【０１４７】
▲１▼酸解離性または酸分解性の官能基：
酸解離性または酸分解性の官能基は、酸と反応する前はアルカリに不溶または難溶であるが酸の作用により、アルカリに可溶化させることができる官能基である。このアルカリへの溶解性の変化により、ポジ型のレジストのベース重合体として利用できるものになる。
【０１４８】
具体的には、酸またはカチオンの作用により−ＯＨ基、−ＣＯＯＨ基、−ＳＯ₃Ｈ基などに変化する能力をもち、その結果、含フッ素重合体自体がアルカリに可溶になるものである。
【０１４９】
酸解離性または酸分解性の官能基は、具体的には、
【０１５０】
【化２５】

【０１５１】
（式中、Ｒ⁷、Ｒ⁸、Ｒ⁹、Ｒ¹⁰、Ｒ¹¹、Ｒ¹²、Ｒ¹⁴、Ｒ¹⁸、Ｒ¹⁹、Ｒ²⁰、Ｒ²¹、Ｒ²²、Ｒ²⁴、Ｒ²⁵、Ｒ²⁶、Ｒ²⁷、Ｒ²⁸、Ｒ²⁹は同じかまたは異なり、炭素数１〜１０の炭化水素基；Ｒ¹³、Ｒ¹⁵、Ｒ¹⁶は同じかまたは異なり、Ｈまたは炭素数１〜１０の炭化水素基；Ｒ¹⁷、Ｒ²³は同じかまたは異なり、炭素数２〜１０の２価の炭化水素基）
が好ましく利用でき、さらに具体的には
【０１５２】
【化２６】

【０１５３】
などが好ましく例示される。
【０１５４】
▲２▼酸縮合反応性の官能基：
酸縮合反応性の官能基は、酸と反応する前はアルカリ現像液（またはその他の現像用溶剤）に可溶であるが酸の作用により、重合体自体をアルカリ現像液（またはその他の現像用溶剤）に不溶にすることができる官能基である。
【０１５５】
具体的には酸またはカチオンの作用による自己縮合、重縮合あるいは架橋剤の存在下、酸の作用による架橋剤との縮合反応または重縮合反応を起こす官能基、または酸やカチオンによる転位反応（たとえばピナコール転位、カルビノール転位）などで、極性変化を起こす官能基であって、いずれにしてもその結果、重合体自体はアルカリ現像液（またはその他の現像用溶剤）に不溶となるものである。
【０１５６】
かかる不溶化によって、ネガ型のレジストのベース重合体として利用できるものである。
【０１５７】
酸縮合性の官能基としては、−ＯＨ、−ＣＯＯＨ、−ＣＮ、−ＳＯ₃Ｈ、エポキシ基などから選ばれるものが好ましい具体例である。
【０１５８】
使用する場合、架橋剤としては特に制限なく、従来ネガ型レジストの架橋剤として慣用されているものの中から任意に選択して用いることができる。架橋剤としては、たとえばＮ−メチロール化メラミン、Ｎ−アルコキシメチル化メラミン化合物、尿素化合物、エポキシ化合物、イソシアネート化合物などが好ましい具体例である。
【０１５９】
以上の酸反応性基Ｙ¹のなかでも、ＯＨ基、酸でＯＨ基に変換できる酸解離性官能基、ＣＯＯＨ基、酸で解離してＣＯＯＨ基に変化させることができる酸解離性官能基の少なくとも１種が好ましい。
【０１６０】
酸でＯＨ基に変換できる酸解離性官能基としては、
【０１６１】
【化２７】

【０１６２】
（式中、Ｒ³¹、Ｒ³²、Ｒ³³およびＲ³⁴は同じかまたは異なり、いずれも炭素数１〜５のアルキル基）で示される基が好ましくあげられる。
【０１６３】
より具体的には、
【０１６４】
【化２８】

【０１６５】
が好ましく例示でき、なかでも酸反応性が良好な点で、
【０１６６】
【化２９】

【０１６７】
が好ましく、さらに透明性が良好な点で、−ＯＣ（ＣＨ₃）₃、−ＯＣＨ₂ＯＣＨ₃、−ＯＣＨ₂ＯＣ₂Ｈ₅が好ましい。
【０１６８】
酸で−ＣＯＯＨ基に変換できる酸解離性官能基としては、
【０１６９】
【化３０】

【０１７０】
（式中、Ｒ³⁵、Ｒ³⁶、Ｒ³⁷、Ｒ³⁸、Ｒ³⁹、Ｒ⁴⁰、Ｒ⁴¹、Ｒ⁴²、Ｒ⁴⁶、Ｒ⁴⁷、Ｒ⁴⁸は同じかまたは異なり、いずれも炭素数１〜１０の炭化水素基；Ｒ⁴³、Ｒ⁴⁴は同じかまたは異なり、いずれもＨまたは炭素数１〜１０の炭化水素基；Ｒ⁴⁵は炭素数２〜１０の２価の炭化水素基）などがあげられ、より詳しくは
【０１７１】
【化３１】

【０１７２】
などが好ましくあげられる。
【０１７３】
これらの酸反応性基Ｙ¹は、通常、酸反応性基Ｙ¹を有する単量体を本発明の製造法に従って重合することで重合体に導入することができる。
【０１７４】
または酸反応性基Ｙ¹に変換できる酸反応性基変換基Ｙ²を有する単量体を本発明の製造法に従って重合し、重合体に導入した後、高分子反応によって目的の酸反応基Ｙ¹に変換することでも得られる。
【０１７５】
高分子反応によって目的の酸反応性基Ｙ¹に変換して導入する方法としては、たとえば式：
【０１７６】
【化３２】

【０１７７】
（式中、Ｘ⁵、Ｘ⁶はＨまたはＦ；Ｘ⁷はＨ、ＣＨ₃またはＣＦ₃；Ｒは炭素数１〜５のアルキル基または含フッ素アルキル基）で示されるビニルエステル化合物（酸反応性基変換基（エステル基）Ｙ²を有する単量体）を本発明の製造法によりｍ１および／またはｍ２と共重合することで酸反応性基変換基Ｙ²を有する含フッ素重合体を製造し、得られた含フッ素重合体の酸反応性基変換基Ｙ²をアルカリ加水分解させることでＯＨ基（酸反応性基Ｙ¹）に変換する方法などがあげられる。
【０１７８】
本発明はこれら高分子反応のプロセスを経由して酸反応性基Ｙ¹を有する含フッ素重合体を製造する方法も含むものである。
【０１７９】
いずれの場合においても、本発明の製造法によると酸反応性基Ｙ¹を有する含フッ素重合体を効率よく得ることができ、現像液に対する溶解性も改善できるものである。
【０１８０】
酸反応性官能基Ｙを有する含フッ素重合体は、脂肪族環構造を与え得る単量体（ｍ２）のうち酸反応性官能基Ｙを有する単量体（ｍ２−２）、つまり前述の（ｍ２−２ａ）、（ｍ２−２ｂ）または（ｍ２−２ｃ）のなかから少なくとも１種を式（１）の官能基を有する連鎖移動剤の存在下、ラジカル重合開始剤を用いてラジカル重合することで得られる。
【０１８１】
または、単量体（ｍ２）として酸反応性官能基Ｙを有さない単量体（ｍ２−１）を用いる場合、共単量体（ｎ１）のうちで酸反応性官能基Ｙを有する単量体（ｎ１−２）を単量体（ｍ２）に加えて共重合し、構造単位（Ｍ２）に加え、酸反応性官能基Ｙを有する構造単位（Ｎ１−２）を導入してもよい。
【０１８２】
任意の構造単位（Ｎ１−２）に酸反応性官能基Ｙを導入できる単量体（ｎ１−２）としては、共重合可能な酸反応性官能基Ｙを有するエチレン性単量体が好ましい。
【０１８３】
具体的には、酸反応性官能基Ｙを有するアクリル系単量体、酸反応性官能基Ｙを有する含フッ素アクリル系単量体、酸反応性官能基Ｙを有するアリルエーテル系単量体、酸反応性官能基Ｙを有する含フッ素アリルエーテル系単量体、酸反応性官能基Ｙを有するビニルエーテル系単量体、酸反応性官能基Ｙを有する含フッ素ビニルエーテル系単量体などが好ましい。
【０１８４】
より具体的には、
（メタ）アクリル酸、α−フルオロアクリル酸、α−トリフルオロメチルアクリル酸、ｔ−ブチル（メタ）アクリレート、ｔ−ブチル−α−フルオロアクリレート、ｔ−ブチル−α−トリフルオロメチルアクリレート、
【０１８５】
【化３３】

【０１８６】
（式中、Ｘ¹およびＸ²は同じかまたは異なり、いずれもＨまたはＦ；Ｘ³はＨ、Ｆ、ＣＨ₃またはＣＦ₃；Ｘ⁴はＨ、ＦまたはＣＦ₃；Ｒｆは炭素数１〜４０の含フッ素アルキレン基または炭素数２〜１００のエーテル結合を有する含フッ素アルキレン基；ａは０または１〜３の整数；ｂは０または１）で示される含フッ素エチレン性単量体である。
【０１８７】
なかでも式：
ＣＨ₂＝ＣＦ−ＣＦ₂Ｏ−Ｒｆ−Ｙ
（式中、Ｒｆは前記と同じ）で示される含フッ素アリルエーテル化合物が好ましい。
【０１８８】
より具体的には、
【０１８９】
【化３４】

【０１９０】
などの含フッ素アリルエーテル化合物が好ましくあげられる。
【０１９１】
また、式：
ＣＦ₂＝ＣＦ−Ｏ−Ｒｆ−Ｙ
（式中、Ｒｆは前記と同じ）で示される含フッ素ビニルエーテル化合物が好ましい。
【０１９２】
より具体的には、
【０１９３】
【化３５】

【０１９４】
などの含フッ素ビニルエーテル化合物があげられる。
【０１９５】
その他、酸反応性官能基Ｙを含有する含フッ素エチレン性単量体としては、
ＣＦ₂＝ＣＦ−ＣＦ₂Ｏ−Ｒｆ−Ｙ、 ＣＦ₂＝ＣＦ−Ｒｆ−Ｙ、
ＣＨ₂＝ＣＨ−Ｒｆ−Ｙ、 ＣＨ₂＝ＣＨ−Ｏ−Ｒｆ−Ｙ
（Ｒｆは前記と同じ）
などの単量体があげられ、より具体的には、
【０１９６】
【化３６】

【０１９７】
などがあげられる。
【０１９８】
本発明の製造法で得られる酸反応性官能基Ｙを有するレジスト用含フッ素重合体の好ましくは、式（Ｍ−１）：
−（Ｍ１）−（Ｍ２）−（Ｎ１）−（Ｎ）− （Ｍ−１）
（式中、構造単位Ｍ１は炭素数２または３のエチレン性単量体であって少なくとも１個のフッ素原子を有する含フッ素エチレン性単量体（ｍ１）由来の繰り返し単位；構造単位Ｍ２は重合体主鎖に脂肪族環構造を与え得る単量体（ｍ２）由来の繰り返し単位；構造単位Ｎ１は単量体（ｍ１）および単量体（ｍ２）と共重合可能な単量体（ｎ１）由来の繰り返し単位；構造単位Ｎは単量体（ｍ１）、単量体（ｍ２）および単量体（ｎ１）と共重合可能な単量体（ｎ）由来の繰り返し単位であって、構造単位Ｍ２またはＮ１のいずれか少なくとも一方に酸反応性基Ｙ¹または酸反応性基Ｙ¹に変換可能な基Ｙ²を有し、構造単位Ｍ２に酸反応性基Ｙ¹または酸反応性基Ｙ¹に変換可能な基Ｙ²を有する場合は構造単位Ｎ１とＮは同じであってよい）であって、構造単位Ｍ１を１〜９９モル％、構造単位Ｍ２を１〜９９モル％、構造単位Ｎ１を０〜９８モル％、構造単位Ｎを０〜９８モル％含むレジスト用含フッ素重合体である。
【０１９９】
さらに、本発明の製造法で得られるレジスト用含フッ素重合体の好ましくは、式（Ｍ−２）：
−（Ｍ１）−（Ｍ２−２）−（Ｍ２）−（Ｎ）− （Ｍ−２）
（式中、構造単位Ｍ１、Ｍ２は前記式（Ｍ−１）と同じ；構造単位Ｍ２−１は重合体主鎖に脂肪族環構造を与え得る単量体であって酸反応性基Ｙ¹または酸反応性基Ｙ¹に変換可能な基Ｙ²を有する単量体（ｍ２−２）由来の繰り返し単位；構造単位Ｎは単量体（ｍ１）、（ｍ２−２）および単量体（ｍ２）と共重合可能な単量体（ｎ）由来の繰り返し単位）であって、構造単位Ｍ１を１〜９９モル％、構造単位Ｍ２−２を１〜９９モル％、構造単位Ｍ２を０〜９８モル％、構造単位Ｎを０〜９８モル％含むレジスト用含フッ素重合体である。
【０２００】
式（Ｍ−１）、（Ｍ−２）のレジスト用含フッ素重合体において含フッ素重合体に繰り返し単位（Ｍ１）を与える単量体（ｍ１）は、重合性、特にラジカル重合性の炭素−炭素二重結合を１つ有する炭素数２または３の含フッ素エチレン性単量体であって少なくとも１個のフッ素原子を有する単量体である。
【０２０１】
かかる含フッ素エチレン性単量体（ｍ１）は重合性の炭素−炭素二重結合を１つ有するモノエン化合物であって、重合によっても主鎖中に環構造を有する繰り返し単位は形成しない。
【０２０２】
含フッ素エチレン性単量体（ｍ１）は、その単量体中に酸反応性官能基Ｙを有していても有していなくてもよいが、通常、酸反応性官能基を有していない単量体を用いた方が、ラジカル重合反応性が良好な点で、また、より透明性を効果的に改善できる点で好ましい。
【０２０３】
好ましい含フッ素エチレン性単量体（ｍ１）としては、エチレンまたはプロピレンの水素原子の少なくとも１つがフッ素原子に置換したものがあげられる。他の水素原子はフッ素原子以外のハロゲン原子に置換されていてもよい。
【０２０４】
なかでもフッ素原子が炭素−炭素二重結合を構成する炭素原子に少なくとも１個結合した単量体であることが好ましい。それによって、繰り返し単位（Ｍ１）に、つまり重合体主鎖中にフッ素原子を導入でき、真空紫外領域において特に優れた透明性を与える含フッ素重合体が効果的に得られる。
【０２０５】
具体的には、テトラフルオロエチレン、クロロトリフルオロエチレン、フッ化ビニリデン、フッ化ビニル、トリフルオロエチレン、ヘキサフルオロプロピレン、ＣＨ₂＝ＣＦＣＦ₃から選ばれる少なくとも１種の単量体が好ましくあげられる。
【０２０６】
なかでもテトラフルオロエチレン、クロロトリフルオロエチレン、フッ化ビニリデンまたはヘキサフルオロプロピレンの少なくとも１種または２種以上の混合物であることが透明性の点で特に好ましく、とりわけテトラフルオロエチレンおよび／またはクロロトリフルオロエチレンが好ましい。
【０２０７】
式（Ｍ−１）、（Ｍ−２）のレジスト用含フッ素重合体において脂肪族環構造の構造単位Ｍ２を与え得る単量体（ｍ２）、酸反応性官能基Ｙを有する脂肪族環構造のＭ２−２を与え得る単量体は前述の単量体（ｍ２）、（ｍ２−２）と同様のものが好ましく例示できる。
【０２０８】
また、式（Ｍ−１）、（Ｍ−２）のレジスト用含フッ素重合体において、任意の構造単位Ｎ１、Ｎに酸反応性官能基Ｙを有する構造単位を用いる場合、前述の酸反応性官能基Ｙを有するエチレン性単量体ｎ１−２と同様のものが好ましく例示できる。
【０２０９】
本発明の製造法では、単量体（ｍ１）、（ｍ２）、（ｍ２−２）または（ｎ１−２）に加え、さらに任意の単量体として、ラジカル重合性の単量体（ｎ１）を得られる含フッ素共重合体に別異の特性、たとえば機械的強度や塗工性などを改善する目的で共重合してもよい。
【０２１０】
そうした任意の単量体（ｎ１）としては、上記共単量体（ｎ１−２）のほか、他の構造単位（Ｍ１）を構成するための単量体（ｍ１）および（ｍ２）と共重合できるものから選ばれる。
【０２１１】
たとえば、
アクリル系単量体（ただし（ｎ１−２）で記載の単量体は除く）：
【０２１２】
【化３７】

【０２１３】
スチレン系単量体：
【０２１４】
【化３８】

【０２１５】
エチレン系単量体：
ＣＨ₂＝ＣＨ₂、ＣＨ₂＝ＣＨＣＨ₃、ＣＨ₂＝ＣＨＣｌなど
【０２１６】
マレイン酸系単量体：
【０２１７】
【化３９】

【０２１８】
アリル系単量体：
ＣＨ₂＝ＣＨＣＨ₂Ｃｌ、ＣＨ₂＝ＣＨＣＨ₂ＯＨ、ＣＨ₂＝ＣＨＣＨ₂ＣＯＯＨ、ＣＨ₂＝ＣＨＣＨ₂Ｂｒなど
【０２１９】
アリルエーテル系単量体：
【０２２０】
【化４０】

【０２２１】
その他の単量体：
【０２２２】
【化４１】

【０２２３】
などがあげられる。
【０２２４】
本発明の製造法で得られる式（Ｍ−１）、（Ｍ−２）の含フッ素重合体の分子量は、数平均分子量で１０００〜１０００００、好ましくは２０００〜５００００、より好ましくは２０００〜１００００であり、重量平均分子量で２０００〜２０００００、好ましくは３０００〜５００００、より好ましくは３０００〜１００００である。
【０２２５】
これら式（Ｍ−１）、（Ｍ−２）のレジスト用含フッ素重合体を製造する際、本発明の製造法を用いることで特に現像液に対する溶解性が改善でき、超微細加工プロセスにおいて高解像度のパターン形成が可能となるため好ましい。
【０２２６】
本発明においては、炭素数２または３のエチレン性単量体であって少なくとも１個のフッ素原子を有する単量体（ｍ１）、または重合体主鎖中に脂肪族環構造を与え得る単量体（ｍ２−１）、（ｍ２−２）、および必要に応じて、酸反応性官能基を有するエチレン性単量体（ｎ１−２）を含む共単量体（ｎ１）を、前記式（１）の官能基を有する連鎖移動剤を用いて、種々の公知の方法で（共）重合する。
【０２２７】
重合法としては、単量体を溶解させる有機溶媒中で行なう溶液重合法、水性媒体中で適当な有機溶剤の存在下または非存在下に行なう懸濁重合法、水性媒体に乳化剤を添加して行なう乳化重合法、無溶媒で行なうバルク重合法などを用いることができる。なかでも、有機溶剤を用いての溶液重合、懸濁重合が好ましい。
【０２２８】
重合溶剤としては特に制限されないが、炭化水素系溶剤、フッ素系溶剤（フロン系）、塩素系溶剤、アルコール系溶剤、ケトン系溶剤、酢酸エステル系溶剤、エーテル系溶剤などが好ましく用いられる。
【０２２９】
なかでもフッ素系溶剤、塩素系溶剤が、単量体やラジカル重合開始剤の溶解性が良好な点、また重合反応を良好に進行させることもできる点で好ましい。具体的には、ハイドロフルオロカーボン類、ハイドロクロロカーボン類、フルオロクロロカーボン類、ハイドロクロロフルオロカーボン類から選ばれる１種または２種以上であることが好ましい。
【０２３０】
重合は、重合開始剤、好ましくは有機パーオキサイドを単量体と接触させ、熱を加える（有機パーオキサイド固有の温度で）か、光または電離放射線などの活性エネルギー線を照射することによって開始する。
【０２３１】
重合開始剤としては特に制限されないが、有機パーオキサイドまたはアゾ系開始剤が好ましい。有機パーオキサイドとしてはジアシルパーオキサイド類、オキシパーエステル類、パーオキシケタール類、ジアルキルパーオキサイド類、パーオキシジカーボネート類から選ばれる１種または２種以上が好ましい。
【０２３２】
なかでもオキシパーエステル類やジアシルパーオキサイド類がより好ましく、ラジカル重合反応性を促進でき、得られる重合体の真空紫外領域での透明性をより一層改善できる点で好ましい。またさらにポリマー自体の親水性も向上し、特に酸反応性官能基Ｙを有する含フッ素重合体（露光後または保護基が脱離したもの）の現像液への溶解性が向上する点で好ましい。
【０２３３】
オキシパーエステル類としては、１，１，３−テトラメチルブチルパーオキシネオデカネート、１−シクロヘキシル−１−メチルエチルパーオキシネオデカネート、ｔｅｒｔ−ヘキシルパーオキシネオデカネート、ｔｅｒｔ−ブチルパーオキシネオデカネート、ｔｅｒｔ−ヘキシルパーオキシピバレート、ｔｅｒｔ−ブチルパーオキシピバレート、１，１，３，３−テトラメチルブチルパーオキシ−２−エチルヘキサノエート、２，５−ジメチル−２，５−ビス（２−エチルヘキサノイルパーオキシ）ヘキサン、１−シクロヘキシル−１−メチルエチルパーオキシ２−エチルヘキサノエート、ｔｅｒｔ−ヘキシルパーオキシ２−エチルヘキサノエート、ｔｅｒｔ−ブチルパーオキシ２−エチルヘキサノエート、ｔｅｒｔ−ブチルパーオキシイソブチレート、ｔｅｒｔ−ブチルパーオキシマレニックアシッド、ｔｅｒｔ−ヘキシルパーオキシイソブチルモノカーボネート、ｔｅｒｔ−ブチルパーオキシ３，５，５−トリメチルヘキサノエート、ｔｅｒｔ−ブチルパーオキシラウレート、ｔｅｒｔ−ブチルパーオキシイソブチルモノカーボネート、ｔｅｒｔ−ブチルパーオキシアセテートなどのアルキル基を有するオキシパーエステル類が好ましい。
【０２３４】
またさらには、脂肪族環状構造を有するアルキル基のパーオキシエステル類であることがドライエッチ耐性を改善できる点で好ましく、１−シクロヘキシル−１−メチルエチルパーオキシネオデカネート、１−シクロヘキシル−１−メチルエチルパーオキシ２−エチルヘキサノエートなどが好ましくあげられる。
【０２３５】
ジアシルパーオキサイド類としては、イソブチリルパーオキサイド、３，５，５−トリメチルヘキサノイルパーオキサイド、オクタノイルパーオキサイド、ラウロイルパーオキサイド、ステロイルパーオキサイド、スクシニックアシッドパーオキサイドが好ましくあげられる。
【０２３６】
パーオキシジカーボネート類の具体例としては、ジ−ｎ−プロピルパーオキシジカーボネート、ジイソプロピルパーオキシジカーボネート、ビス（４−ｔｅｒｔ−ブチルシクロヘキシル）パーオキシジカーボネート、ジ−２−エトキシメチルパーオキシジカーボネート、ジ−２−エチルヘキシルパーオキシジカーボネート、ジ−２−メトキシブチルパーオキシジカーボネート、ジ（３−メチル−３−メトキシブチル）パーオキシジカーボネートなどがあげられる。
【０２３７】
パーオキシケタール類としては、たとえば、１，１−ビス（ｔｅｒｔ−ヘキシルパーオキシ）３，３，５−トリメチルシクロヘキサン、１，１−ビス（ｔｅｒｔ−ヘキシルパーオキシ）シクロヘキサン、１，１−ビス（ｔｅｒｔ−ブチルパーオキシ）３，３，５−トリメチルシクロヘキサン、１，１−ビス（ｔｅｒｔ−ブチルパーオキシ）シクロヘキサン、１，１−ビス（ｔｅｒｔ−ブチルパーオキシ）シクロドデカン、２，２−ビス（ｔｅｒｔ−ブチルパーオキシ）バレレート、２，２−ビス（４，４−ｔｅｒｔ−ブチルパーオキシシクロヘキシル）プロパンなどがあげられる。
【０２３８】
またさらに透明性の観点から、フッ素原子を有するパーオキサイド類を用いるのが好ましく、なかでもフッ素原子を有するジアシルパーオキサイド類がより好ましい。具体的には、ペンタフルオロプロピオノイルパーオキサイド：（ＣＦ₃ＣＦ₂ＣＯＯ）₂、ヘプタフルオロブチリルパーオキサイド：（ＣＦ₃ＣＦ₂ＣＦ₂ＣＯＯ）₂、７Ｈ−ドデカフルオロヘプタノイルパーオキサイド：（ＣＨＦ₂ＣＦ₂ＣＦ₂ＣＦ₂ＣＦ₂ＣＦ₂ＣＯＯ）₂がより好ましくあげられる。
【０２３９】
アゾ系の化合物としては、ジメチル−２，２’−アゾビスイソブチレート、２，２’−アゾビス（２，４，４−トリメチルペンタン）、２，２’−アゾビス（２−メチルプロパン）、ジブチル−２，２’−アゾビスイソブチレートなどがあげられる。
【０２４０】
また、親水性の官能基を有する重合開始剤は重合末端に親水性の官能基を導入でき現像特性が改善できる点で好ましい。具体例としては、スクシニックアシッドパーオキサイド、２，２’−アゾビス｛２−メチル−Ｎ−［１，１−ビス（ヒドロキシメチル）−２−ヒドロキシエチル］プロピオンアミド｝、２，２’−アゾビス｛２−メチル−Ｎ−［２−（ヒドロキシブチル）］プロピオンアミド｝、２，２’−アゾビス［２−メチル−Ｎ−（２−ヒドロキシエチル）プロピオンアミド］、２，２’−アゾビス｛２−［１−（ヒドロキシエチル）−２−イミダゾリン−２−イル］プロパン｝ジヒドロクロリド、２，２’−アゾビス［Ｎ−（２−カルボキシエチル）−２−メチルプロピオンアミジン］、２，２’−アゾビス（２−メチルプロピオンアミドオキシム）、４，４’−アゾビス（４−シアノ吉草酸）、ジメチル−２，２’−アゾビス（２−メチルプロピオネート）、１，１’−アゾビス（１−アセトキシ−１−フェニルエタン）などが好ましくあげられる。
【０２４１】
また、本発明の含フッ素エチレン性単量体ｍ２を用いてｍ２由来の構造単位を有するポリマーを製造する際、有機パーオキサイドのなかでも１０時間半減期温度で５〜１３０℃の有機パーオキサイドを使用することが好ましく、さらに１０時間半減期温度で１５〜１００℃、特に３０〜８０℃のものを使用するのが、重合反応性が良好な点で好ましい。
【０２４２】
生成する共重合体の組成は、仕込む単量体の組成によって制御可能である。
【０２４３】
また分子量は、重合に用いる単量体の濃度や有機パーオキサイドの濃度、前記連鎖移動剤の濃度、温度によって制御することができる。
【０２４４】
使用する単量体に対する有機パーオキサイドの使用量は、使用する単量体の種類、目的とする重合体の組成や分子量によって適宜選択されるが、単量体１００重量部に対し０．００５〜１０重量部、好ましくは０．０１〜５重量部、より好ましくは０．１〜１重量部である。別の観点からみれば、使用する単量体のモル量に対して有機パーオキサイドが０．０１〜１０モル％、好ましくは０．０５〜５モル％、より好ましくは０．１〜２モル％である。
【０２４５】
有機パーオキサイドが少なすぎると、重合反応が充分に進行しにくく、未反応の単量体が残留したり、オリゴマー成分が生成し重合体の着色や透明性の低下が生じ好ましくない。有機パーオキサイドが多すぎると重合体の分子量低下を起こし、透明性を低下させたり、未反応の有機パーオキサイドが残留するため重合体の着色や透明性低下を起こし、好ましくない。
【０２４６】
本発明の製造法において、式（１）の官能基を有する連鎖移動剤の使用量は、使用する単量体の種類、目的とする重合体の組成や分子量によって適宜選択されるが、使用する単量体のモル量に対して式（１）の連鎖移動剤が０．０１〜２０モル％、好ましくは０．０５〜１０モル％、より好ましくは０．１〜５モル％、特に０．２〜２モル％である。
【０２４７】
連鎖移動剤の使用量が少なすぎると、現像液に対する溶解性の改善効果が充分にえられないことがあり、また、連鎖移動剤の使用量が多すぎると重合反応がスムーズに進行しにくく、重合反応が停止または重合反応率が低下し、その結果、低分子量成分が残留することがある。
【０２４８】
これら連鎖移動剤は重合反応初期から一括で存在させても良いし、または重合反応の進行に従って、連続的にまたは間歇的に追加導入しても良い。
【０２４９】
本発明の連鎖移動剤を用いた重合における反応温度は、たとえば使用する有機パーオキサイドのそれぞれの１０時間半減期温度に応じて、またさらに目標の反応時間に応じて適宜選択できるが、一般には０〜１５０℃、好ましくは５〜１２０℃、より好ましくは１０〜１００℃である。
【０２５０】
共重合する場合の単量体の組成は、各単量体の重合反応性、共重合反応比のほか、得られる含フッ素重合体に付与する特性に合わせて選定すればよい。各単量体が含フッ素重合体に与え得る特性は前述のとおりである。より具体的には後述する。
【０２５１】
本発明の製造法により得られる含フッ素重合体は波長２００ｎｍ以下の真空紫外領域の光に対して透明性が高く、したがってＡｒＦエキシマレーザー（１９３ｎｍ）やＦ２レ−ザー（１５７ｎｍ）を用いたフォトリソグラフィープロセスに特に有用なレジスト用重合体である。
【０２５２】
本発明は、さらに
（Ａ−１）ＯＨ基、酸でＯＨ基に変換できる酸解離性官能基、ＣＯＯＨ基または酸で解離してＣＯＯＨ基に変化させることができる酸解離性官能基の少なくとも１種の酸反応性基Ｙ¹を有する含フッ素重合体、
（Ｂ）光酸発生剤、および
（Ｃ）溶剤
からなる組成物に関し、
該含フッ素重合体（Ａ−１）が本発明の前述の製造方法で得られる重合体であるフォトレジスト組成物に関する。
【０２５３】
本発明のフォトレジスト組成物では、酸反応性官能基ＹとしてＯＨ基、酸でＯＨ基に変換できる酸解離性官能基、ＣＯＯＨ基または酸で解離してＣＯＯＨ基に変化させることができる酸解離性官能基の少なくとも１種という特定の酸反応性基Ｙ¹を有する含フッ素重合体（Ａ−１）を使用する。
【０２５４】
酸でＯＨ基に変換できる酸解離性官能基および酸で−ＣＯＯＨ基に変換できる酸解離性官能基としては、前述のものが採用できる。
【０２５５】
特定の酸反応性基Ｙ¹を有する含フッ素重合体（Ａ−１）としては、つぎの重合体が好ましい。
【０２５６】
（Ｉ）式：
−（Ｍ１）−（Ｍ２−２ａ）−
（式中、Ｍ１は炭素数２または３のエチレン性単量体であって少なくとも１個のフッ素原子を有する単量体（ｍ２）由来の構造単位；Ｍ２−２ａは単環状の脂肪族不飽和炭化水素化合物に酸反応性基Ｙ¹を有するフッ素原子を有していてもよい単量体（ｍ２−２ａ）に由来する構造単位）で示される含フッ素重合体。
【０２５７】
構造単位（Ｍ１）と（Ｍ２−２ａ）との組成割合は、通常、８０／２０〜２０／８０モル％比、好ましくは７０／３０〜３０／７０モル％比、特に好ましくは６０／４０〜４０／６０モル％比である。
【０２５８】
単量体の具体例としては、前述の単量体（ｍ１）の具体例、および単量体（ｍ２−２ａ）の具体例のうち酸反応性官能基Ｙが酸反応性基Ｙ¹であるものが好ましく例示できる。
【０２５９】
（II）式：
−（Ｍ１）−（Ｍ２−２ｂ）−
（式中、Ｍ１は前記と同じ；（Ｍ２−２ｂ）は前述の酸反応性基Ｙ¹を有する脂肪族複環構造含有単量体（ｍ２−２ｂ）、特にノルボルネン誘導体由来の構造単位）で示される含フッ素重合体。
【０２６０】
構造単位（Ｍ１）と（Ｍ２−２ｂ）との組成割合は、通常、８０／２０〜２０／８０モル％比、好ましくは７０／３０〜３０／７０モル％比、特に好ましくは６０／４０〜４０／６０モル％比である。
【０２６１】
具体的な単量体としては、前述の単量体（ｍ１）の具体例、および単量体（ｍ２−２ｂ）の具体例のうち酸反応性官能基Ｙが酸反応性基Ｙ¹であるものが好ましく例示できる。
【０２６２】
これら（Ｉ）、（II）の含フッ素重合体はその重合体自体、透明性とドライエッチング耐性に優れており、また含フッ素重合開始剤を使用する本発明の製造法によりさらに真空紫外領域の透明性が改善できる。
【０２６３】
（III）式：
−（Ｍ１）−（Ｍ２−１ａ）−（Ｎ１−２）−
（式中、Ｍ１は前記と同じ；Ｍ２−１ａは重合性の炭素−炭素不飽和結合を環構造中に有し酸反応性官能基Ｙを有していない単環状の単量体（ｍ２−１ａ）由来の構造単位；Ｎ１−２は酸反応性基Ｙ¹を有する共重合可能なエチレン性単量体（ｎ１−２）由来の構造単位）で示される含フッ素重合体。
【０２６４】
構造単位（Ｍ１）と（Ｍ２−１ａ）と（Ｎ１−２）との組成割合は、（Ｍ１）＋（Ｍ２−１ａ）＋（Ｎ１−２）＝１００モル％とし、（Ｍ１）＋（Ｍ２−１ａ）／（Ｎ１−２）が通常、９０／１０〜２０／８０モル％比、好ましくは８０／２０〜３０／７０モル％比、特に好ましくは７０／３０〜４０／６０モル％比である。
【０２６５】
具体的な単量体としては、前述の単量体（ｍ１）および（ｍ２−１ａ）の具体例、および単量体（ｎ１−２）の具体例のうち酸反応性官能基Ｙが酸反応性基Ｙ¹であるものが好ましく例示できる。
【０２６６】
（IV）式：
−（Ｍ１）−（Ｍ２−１ｂ）−（Ｎ１−２）−
（式中、Ｍ１、Ｎ１−２は前記と同じ；Ｍ２−１ｂは酸反応性官能基Ｙを有していない脂肪族複環構造含有単量体（ｍ２−１ｂ）、特にノルボルネン誘導体由来の構造単位）で示される含フッ素重合体。
【０２６７】
構造単位（Ｍ１）と（Ｍ２−１ｂ）と（Ｎ１−２）との組成割合は、（Ｍ１）＋（Ｍ２−１ｂ）＋（Ｎ１−２）＝１００モル％とし、（Ｍ１）＋（Ｍ２−１ｂ）／（Ｎ１−２）が通常、９０／１０〜２０／８０モル％比、好ましくは８０／２０〜３０／７０モル％比、特に好ましくは７０／３０〜４０／６０モル％比である。
【０２６８】
具体的な単量体としては、前述の単量体（ｍ１）および（ｍ２−１ｂ）の具体例、および単量体（ｎ１−２）の具体例のうち酸反応性官能基Ｙが酸反応性基Ｙ¹であるものが好ましく例示できる。
【０２６９】
これら（III）、（IV）の含フッ素重合体は、その重合体自体、ドライエッチング耐性に優れており、また官能基を有する連鎖移動剤を使用する本発明の製造法により真空紫外領域の透明性を維持しながら、さらに現像特性が改善できる。
【０２７０】
また、(I)〜（IV）の酸反応性基Ｙ¹含有含フッ素重合体は、本発明の製造方法によって、ポリマー末端に親水性の原子団を付与した点で従来のレジスト用含フッ素重合体と異なっており、特に現像液への溶解性に優れている。さらに、ポリマー自体の１５７ｎｍ波長での透明性にも優れている。
【０２７１】
本発明のフォトレジスト組成物において、酸反応性基Ｙ¹を有する含フッ素重合体（Ａ−１）は１５７ｎｍ波長での透明性に優れており、なかでも１５７ｎｍでの吸光係数で２．０μｍ^-1以下のもの、好ましくは１．５μｍ^-1以下のもの、特に好ましくは１．０μｍ^-1以下のもの、さらには０．５μｍ^-1以下のものが好ましく、１５７ｎｍ波長での吸光係数が低くなればなるほどＦ２フォトレジスト組成物として用いて良好なレジストパターンを形成できる点で好ましい。
【０２７２】
本発明のフォトレジスト組成物において、光酸発生剤（Ｂ）としては、国際公開公報第０１／７４９１６号パンフレットに記載の光酸発生剤（Ｂ）と同様のものが同様に好ましく例示でき、本発明でも有効に使用できる。
【０２７３】
具体的には、光を照射することによって酸またはカチオンを発生する化合物であって、たとえば有機ハロゲン化合物、スルホン酸エステル、オニウム塩（特に中心元素がヨウ素、イオウ、セレン、テルル、窒素またはリンであるフルオロアルキルオニウム塩など）、ジアゾニウム塩、ジスルホン化合物、スルホンジアジド類など、またはこれらの混合物があげられる。
【０２７４】
より好ましい具体例としては、つぎのものがあげられる。
【０２７５】
（１）ＴＰＳ系：
【０２７６】
【化４２】

【０２７７】
（式中、Ｘ^-はＰＦ₆ ^-、ＳｂＦ₆ ^-、ＣＦ₃ＳＯ₃ ^-、Ｃ₄Ｆ₉ＳＯ₃ ^-など；Ｒ^1a、Ｒ^1b、Ｒ^1cは同じかまたは異なり、ＣＨ₃Ｏ、Ｈ、ｔ−Ｂｕ、ＣＨ₃、ＯＨなど）
【０２７８】
（２）ＤＰＩ系：
【０２７９】
【化４３】

【０２８０】
（式中、Ｘ^-はＣＦ₃ＳＯ₃ ^-、Ｃ₄Ｆ₉ＳＯ₃ ^-、ＣＨ₃−φ−ＳＯ₃ ^-、ＳｂＦ₆ ^-、
【０２８１】
【化４４】

【０２８２】
など；Ｒ^2a、Ｒ^2bは同じかまたは異なり、Ｈ、ＯＨ、ＣＨ₃、ＣＨ₃Ｏ、ｔ−Ｂｕなど）
【０２８３】
（３）スルホネート系：
【０２８４】
【化４５】

【０２８５】
（式中、Ｒ^4aは
【０２８６】
【化４６】

【０２８７】
など）
【０２８８】
本発明のフォトレジスト組成物における光酸発生剤の含有量は、酸反応性基Ｙ¹を有する含フッ素重合体（Ａ−１）１００重量部に対して０．１〜３０重量部が好ましく、さらには０．２〜２０重量部が好ましく、最も好ましくは０．５〜１０重量部である。
【０２８９】
光酸発生剤の含有量が０．１重量部より少なくなると感度が低くなり、３０重量部より多く使用すると光酸発生剤が光を吸収する量が多くなり、光が基板まで充分に届かなくなって解像度が低下しやすくなる。
【０２９０】
また本発明のフォトレジスト組成物には、上記の光酸発生剤から生じた酸に対して塩基として作用できる有機塩基を添加してもよい。有機塩基は国際公開第０１／７４９１６号パンフレットに記載のものと同様のものが好ましく例示でき、本発明でも有効に使用できる。
【０２９１】
具体的には、含窒素化合物から選ばれる有機アミン化合物であり、たとえばピリジン化合物類、ピリミジン化合物類、炭素数１〜４のヒドロキシアルキル基で置換されたアミン類、アミノフェノール類などがあげられ、特にヒドロキシル基含有アミン類が好ましい。
【０２９２】
具体例としては、ブチルアミン、ジブチルアミン、トリブチルアミン、トリエチルアミン、トリプロピルアミン、トリアミルアミン、ピリジンなどが好ましくあげられる。
【０２９３】
本発明のフォトレジスト組成物における有機塩基の含有量は、光酸発生剤の含有量に対して０．１〜１００モル％が好ましく、さらに好ましくは、１〜５０モル％である。０．１モル％より少ない場合は解像性が低くなり、１００モル％よりも多い場合は低感度になる傾向にある。
【０２９４】
その他、本発明のフォトレジスト組成物に、必要に応じて国際公開第０１／７４９１６号パンフレットに記載の添加物、たとえば、溶解抑制剤、増感剤、染料、接着性改良剤、保水剤などこの分野で慣用されている各種の添加剤を含有させることもできる。
【０２９５】
また、本発明のフォトレジスト組成物において溶剤（Ｃ）は、国際公開公報第０１／７４９１６号パンフレットに記載の溶剤（Ｃ）と同様のものが同様に好ましく例示でき、本発明でも有効に使用できる。
【０２９６】
具体的には、セロソルブ系溶剤、エステル系溶剤、プロピレングリコール系溶剤、ケトン系溶剤、芳香族炭化水素系溶剤、またはこれらの混合溶剤が好ましくあげられる。さらに含フッ素重合体（Ａ−１）の溶解性を高めるために、ＣＨ₃ＣＣｌ₂Ｆ（ＨＣＦＣ−１４１ｂ）などの含フッ素炭化水素系溶剤やフッ素アルコール類などのフッ素系溶剤を併用してもよい。
【０２９７】
これらの溶剤（Ｃ）の量は、溶解させる固形分の種類や塗布する基材、目標の膜厚、などによって選択されるが、塗布のし易さという観点から、フォトレジスト組成物の全固形分濃度が０．５〜７０重量％、好ましくは１〜５０重量％となるように使用するのが好ましい。
【０２９８】
本発明のフォトレジスト組成物は、従来のフォトレジスト技術のレジストパターン形成方法において使用される。特にレジストパターン形成方法を好適に行なうには、まずシリコンウェハーのような支持体上にフォトレジスト組成物の溶液をスピンナーなどで塗布し、乾燥して感光層を形成させ、これに縮小投影露光装置などにより、紫外線、ｄｅｅｐ−ＵＶ、エキシマレーザー光、Ｘ線を所望のマスクパターンを介して照射するか、あるいは電子線により描画し、加熱する。ついでこれを現像液、たとえば１〜１０重量％テトラメチルアンモニウムヒドロキシド（ＴＭＡＨ）水溶液のようなアルカリ性水溶液などのアルカリ現像液を用いて現像処理する。この形成方法でマスクパターンに忠実な画像を得ることができる。
【０２９９】
半導体デバイスの微細回路パターンを形成する際、フォトリソグラフィープロセスにおける現像工程では、現像液として２．３８重量％のテトラメチルアンモニウムヒドロキシド水溶液が好ましく用いられる。
【０３００】
またさらに、レジスト被膜との塗れ性を調整するため、２．３８重量％のテトラメチルアンモニウムヒドロキシド水溶液中に界面活性剤やメタノール、エタノール、プロパノールまたはブタノールなどのアルコール類を添加しても良い。
【０３０１】
なかでも本発明のフォトレジスト組成物を用いることによって、真空紫外領域においても透明性の高いレジスト被膜（感光層）を形成できることが見出されている。それによって特に今後０．０７μｍのテクノロジーノードを目指して開発中のＦ２レーザー（１５７ｎｍ波長）を用いたフォトリソグラフィープロセスに好ましく利用できるものである。
【０３０２】
本発明のフォトレジストを塗布した被膜は、前述のフォトレジスト組成物をスピンコートなどの塗装方法によってシリコンウエハーのような支持体上に塗布し、乾燥することによって形成され、被膜中には、酸反応性基を有する含フッ素重合体（Ａ−１）、光酸発生剤（Ｂ）、その他の添加物などの固形成分が含まれている。
【０３０３】
形成するレジスト被膜の膜厚は、通常１．０μｍ以下の薄層被膜であり、好ましくは０．０１〜０．５μｍ、より好ましくは０．０５〜０．５μｍの薄膜である。
【０３０４】
さらに本発明のフォトレジスト組成物を塗布した被膜は、真空紫外領域の透明性が高いものが好ましく、具体的には１５７ｎｍ波長の吸光係数が２．５μｍ^-1以下のものであり、好ましくは２．０μｍ^-1以下、特に好ましくは１．５０μｍ^-1以下、さらには１．０μｍ^-1以下であることが好ましい。この被膜はＦ２レーザー（１５７ｎｍ）の光線を用いるリソグラフィープロセスに効果的に利用できる。
【０３０５】
なお、レジスト被膜が施される基材は、従来レジストが適用される各種基材が同様に利用できる。たとえばシリコンウェハー、有機系または無機系反射防止膜が設けられたシリコンウェハー、ガラス基板などのいずれでもよい。特に有機系反射防止膜が設けられたシリコンウェハー上での感度、プロファイル形状が良好である。
【０３０６】
本発明の第三は、現像液に対する溶解性に優れた含フッ素重合体に関するものであり、本発明の含フッ素重合体の第一はＯＨ基を有し、なおかつ現像液への溶解性を付与する官能基としてはＯＨ基のみを有する重合体主鎖に脂肪族環構造を有する含フッ素重合体であって、該重合体が式（Ｍ−３）：
−（Ｍ１）−（Ｍ２−３）−（Ｍ２）−（Ｎ）− （Ｍ−３）
（式中、構造単位Ｍ１は炭素数２または３のエチレン性単量体であって、少なくとも１個のフッ素原子を有する含フッ素エチレン性単量体（ｍ１）由来の繰り返し単位；構造単位Ｍ２−３はＯＨ基を有するフッ素原子を有していても良いノルボルネン誘導体（ｍ２−３）由来の繰り返し単位；構造単位Ｍ２は重合体主鎖に脂肪族環構造を与え得る単量体（ｍ２）由来の繰り返し単位；構造単位Ｎは単量体（ｍ１）、（ｍ２−３）および単量体（ｍ２）と共重合可能な単量体（ｎ）由来の繰り返し単位）で示され、構造単位Ｍ１を２４〜７０モル％、構造単位Ｍ２−３を１〜７０モル％、構造単位Ｍ２を０〜６９モル％、構造単位Ｎを０〜２０モル％含み、かつ（Ｍ１）＋（Ｍ２−３）＋（Ｍ２）＝１００としたとき（Ｍ１）／｛（Ｍ２−３）＋（Ｍ２）｝が３０／７０〜７０／３０モル比である数平均分子量で１０００〜５００００の含フッ素重合体であって、該含フッ素重合体の後述するＱＣＭ測定法で測定した、２．３８重量％テトラメチルアンモニウムハイドロオキサイド水溶液に対する溶解速度が５００ｎｍ／ｓｅｃ以上である現像液に対する溶解性が優れたレジスト用含フッ素重合体である。
【０３０７】
本発明者らは、含フッ素エチレン性単量体（ｍ１）とＯＨ基を有するノルボルネン誘導体（ｍ２−３）、さらに必要に応じて単量体（ｍ２）、（ｎ）を用いて共重合を鋭意検討した結果、同じ重合体組成、同じ分子量であっても、製造方法の違いによって、つまり結果的に得られる末端構造の一部の違いによって、現像液に対する溶解性に特に優れた含フッ素重合体を得ることができた。
【０３０８】
従来の方法では、現像液への溶解性を付与する官能基としてＯＨ基のみを有する上記含フッ素重合体は現像液に対して充分な溶解性が得られなかった。ＯＨ基のみを有する含フッ素重合体においても、元来溶解性の高い−ＣＯＯＨ基などを有する重合体、フッ素を含まないＡｒＦレジスト用ポリマーやＫｒＦレジスト用ポリマーと同等以上の溶解性（溶解速度）を有する含フッ素重合体を見出した。それによって、１５７ｎｍでの透明性と現像液に対する溶解性を両立する含フッ素重合体を得ることができた。
【０３０９】
さらに本発明の含フッ素重合体の第二は、上記含フッ素重合体中に有するＯＨ基の一部またはすべてを酸と反応して解離する酸解離性官能基Ｙ³で保護した形態の含フッ素重合体に関し、該ＯＨ基を保護した含フッ素重合体は、酸と反応してＯＨ基に変化した後、現像液に対する溶解性に優れた重合体となり得るものである。
【０３１０】
つまり、本発明のＯＨ基を保護した含フッ素重合体は、酸でＯＨ基に変換できる酸解離性官能基Ｙ³を有する重合体主鎖に脂肪族環構造を有する含フッ素重合体であって、該重合体が式（Ｍ−４）：
−（Ｍ１）−（Ｍ２−３）−（Ｍ２−４）−（Ｎ）− （Ｍ−４）
（式中、構造単位Ｍ１、構造単位Ｍ２−３は式（Ｍ−３）と同じ；構造単位Ｍ２−４は酸でＯＨ基に変換できる酸解離性官能基のうち少なくとも１種の官能基Ｙ³を有するフッ素原子を有していても良いノルボルネン誘導体（ｍ２−４）由来の繰り返し単位；構造単位Ｎは単量体（ｍ１）、（ｍ２−３）および単量体（ｍ２−４）と共重合可能な単量体（ｎ）由来の繰り返し単位）で示され、構造単位Ｍ１を２４〜７０モル％、構造単位Ｍ２−３を０〜６９モル％、構造単位Ｍ２−４を１〜７０モル％、構造単位Ｎを０〜２０モル％含み、かつ（Ｍ１）＋（Ｍ２−３）＋（Ｍ２−４）＝１００としたとき（Ｍ１）／｛（Ｍ２−３）＋（Ｍ２−４）｝が３０／７０〜７０／３０モル比である数平均分子量で１０００〜５００００の含フッ素重合体であって、ただし前記式（Ｍ−４）の含フッ素重合体を酸と反応させ構造単位Ｍ２−４中の酸解離性官能基Ｙ³をＯＨ基に変換させた酸反応後の含フッ素重合体において、現像液への溶解性を付与する官能基としてはＯＨ基のみを有し、なお前記酸反応後の含フッ素重合体のＱＣＭ測定法で測定した、２．３８重量％テトラメチルアンモニウムハイドロオキサイド水溶液に対する溶解速度が５００ｎｍ／ｓｅｃ以上であるレジスト用含フッ素重合体である。
【０３１１】
上記の含フッ素重合体の現像液溶解速度を示す測定法であるＱＣＭ測定法とは、水晶振動子法と呼ばれるポリマーの溶解速度を測定する方法であって、たとえば、Ｊ.Ｐｈｏｔｏｐｏｌｙｍｅｒ Ｓｃｉ．Ｔｅｃｈｎｏｌ．１２，５４５−５５１（１９９９）やＰｒｏｃ．ＳＰＩＥ４６９０，９０４−９１１（２００２）に記載された方法であり、レジスト被膜の現像液への溶解挙動について検討されている。詳しくは金などを蒸着した水晶振動子板にポリマーの被膜を形成し、その水晶振動子板を現像液などに浸せきした状態で膜厚の変化（重量の変化）を水晶振動子の振動数変化により換算し、膜厚の減少速度を測定する方法である。本発明におけるＱＣＭ法における含フッ素重合体の溶解速度は、上記記載の重合体のみを溶剤に溶解させた溶液を水晶振動子板に塗布し、加熱などにより重合体のみの膜厚で８０〜１５０ｎｍの被膜を作成し上記方法で被膜の減少速度を測定したものであり、具体的に速度は浸せき時間に対して被膜の膜厚変化をプロットし、膜の中心部分であって膜厚全体に対して６０％の部分での被膜の減少速度を算出したものである。
【０３１２】
本発明者らは目標とする５０〜７０ｎｍといった超微細なレジストパターンを形成するためには、従来の含フッ素重合体、さらには従来のレジスト用ポリマーに比べても特に高度な現像液溶解速度が必要であることを見出した。
【０３１３】
本発明によると現像液可溶性基としてＯＨ基のみを有する含フッ素重合体であっても現像液溶解性の大幅な改善がなされた含フッ素重合体を用いることで、高解像度な超微細レジストパターンが可能となるものである。
【０３１４】
また、本発明の上記含フッ素重合体は、さらに１５７ｎｍでの透明性とドライエッチ耐性に優れる点で好ましい。
【０３１５】
本発明の含フッ素重合体の現像液溶解速度は上記ＱＣＭ測定法で５００ｎｍ／ｓｅｃ以上であるが、好ましくは７５０ｎｍ／ｓｅｃ以上、より好ましくは１０００以上、特に好ましくは１５００ｎｍ／ｓｅｃ以上である。それによって更なる高解像度な超微細レジストパターンが可能となるため好ましいものである。
【０３１６】
また一方、７５０ｎｍ／ｓｅｃ以上といった現像速度の速い重合体についてＱＣＭ測定法を検討した結果、０．５９５重量％ＴＭＡＨ溶液といった低濃度の現像液を用いて上記同様のＱＣＭ測定を行うことで、より精度の高く、再現性の良好な測定が可能であることを見出し、同時に現像液溶解速度の比較を行った。
【０３１７】
その０．５９５重量％ＴＭＡＨ溶液で測定した溶解速度においては１ｎｍ／ｓｅｃ以上好ましくは２ｎｍ／ｓｅｃ以上、より好ましくは５ｎｍ／ｓｅｃ以上、さらに好ましくは１０ｎｍ／ｓｅｃ以上、特に好ましくは２０ｎｍ／ｓｅｃ以上である。
【０３１８】
本発明の式（Ｍ−３）、（Ｍ−４）のレジスト用含フッ素重合体の現像液溶解性を付与する官能基はＯＨ基のみであり、ＯＨ基は１５７ｎｍでの透明性を低下させない点で好ましく、逆に−ＣＯＯＨや−ＳＯ₃Ｈなどの導入は１５７ｎｍでの透明性を低下させる点で好ましくない。
【０３１９】
本発明の式（Ｍ−３）、（Ｍ−４）の重合体における構造単位（Ｍ１）は炭素数２または３のエチレン性単量体であって少なくとも１個のフッ素原子を有する含フッ素エチレン性単量体（ｍ１）由来の繰り返し単位であり、前記現像液溶解性に優れた重合体の製造方法で例示したものと同様のものが同様に好ましくあげられる。
【０３２０】
本発明の式（Ｍ−３）、（Ｍ−４）の重合体における構造単位（Ｍ２−３）はＯＨ基を有するフッ素原子を有していても良いノルボルネン誘導体（ｍ２−３）由来の繰り返し単位であり、ノルボルネン誘導体（ｍ２−３）は前記現像液溶解性に優れた重合体の製造方法で例示した酸反応性基Ｙを有するノルボルネン誘導体（ｍ２−２ｂ）の例示のそれぞれについて酸反応性基ＹをＯＨ基に置き換えたものが同様に好ましくあげられ、なかでも、式（３）：
【０３２１】
【化４７】

【０３２２】
（式中、Ｒｆ²は炭素数１〜１０の含フッ素アルキル基またはエーテル結合を有する含フッ素アルキル基）で表わされる構造をノルボルネン誘導体に存在することが好ましく、現像液への溶解性に優れ、かつ１５７ｎｍ光に対する透明性に優れる点で好ましい。
【０３２３】
式（３）の部位において、Ｒｆ²は、なかでも炭素数１〜１０のパーフルオロアルキル基であることが好ましく、より好ましくは炭素数１〜５のパーフルオロアルキル基、さらにはＣＦ₃であることが特に好ましい。
【０３２４】
式（３）の部位は、含フッ素アルキル基Ｒｆ²とＯＨ基がノルボルネン誘導体の環構造を形成する炭素原子に同時に結合しているものであっても良いし、環構造を形成しない炭素原子に同時に結合し、式（３）の部位が環構造を形成する炭素原子に側鎖の形態で結合したものであっても良い。
【０３２５】
本発明の式（Ｍ−４）の重合体において構造単位（Ｍ２−４）に含まれる酸解離性官能基Ｙ³は光酸発生剤から発生する酸と反応してＯＨ基に変化する官能基であり、ＯＨ基に変化した後も、同様に優れた現像液溶解性を示すものである。さらに１５７ｎｍ光での透明性にも優れている。
【０３２６】
酸解離性官能基Ｙ³は具体的には、前記例示と同様のものが好ましく、たとえば、
【０３２７】
【化４８】

【０３２８】
（式中、Ｒ³¹、Ｒ³²、Ｒ³³およびＲ³⁴は同じかまたは異なり、いずれも炭素数１〜５のアルキル基）で示される基が好ましくあげられる。
【０３２９】
より具体的には、
【０３３０】
【化４９】

【０３３１】
が好ましく例示でき、なかでも酸反応性が良好な点で、
【０３３２】
【化５０】

【０３３３】
が好ましく、さらに透明性が良好な点で、−ＯＣ（ＣＨ₃）₃、−ＯＣＨ₂ＯＣＨ₃、−ＯＣＨ₂ＯＣ₂Ｈ₅が好ましい。
【０３３４】
さらには上記式（３）の構造をノルボルネン誘導体中に含むものが好ましい。
【０３３５】
本発明の式（Ｍ−３）の重合体において、構造単位Ｍ２は重合体主鎖に脂肪族環構造を与え得る単量体（ｍ２）由来の繰り返し単位であり、前記現像液溶解性に優れた重合体の製造方法で例示したもののうち、前述の構造単位（Ｍ２−２）以外のものであり、任意の構造単位である。
【０３３６】
好ましくは、官能基を含まない単環または複環構造を重合体主鎖に有する構造単位、たとえば前述の単量体（ｍ２−１ａ）、（ｍ２−１ｂ）由来の繰り返し単位であることが好ましい。主に、溶剤との溶解性や基材との塗れ性、重合体のガラス転位温度、機械的特性を調整する目的で導入される。
【０３３７】
本発明の式（Ｍ−３）、（Ｍ−４）の重合体において、構造単位Ｎは任意の構造単位であり、前述の重合体の製造方法で例示した構造単位Ｎと同様エチレン性単量体由来の構造単位から選ばれ、溶剤との溶解性や基材との塗れ性等を調整する目的で導入される。さらには、現像液溶解性を付与するような官能基は含まないか、含んでもＯＨ基または酸で反応してＯＨ基に変化する酸解離性官能基を有するものである。それによってさらに現像液溶解性を改善することができ、好ましい。ただし、重合体全体に対し２０モル％以下であり、好ましくは１５モル％以下であり、より好ましくは１０モル％以下、本発明の現像液溶解性に優れた重合体においては、５モル％以下、構造単位Ｎを含まない重合体で充分な現像液溶解性を有する場合、構造単位Ｎは特には含まい方がよい。
【０３３８】
任意成分であるエチレン性単量体由来の構造単位Ｎが多くなりすぎるとドライエッチ耐性が低下するため好ましくない。
【０３３９】
本発明の式（Ｍ−３）の重合体における含フッ素エチレン性単量体由来の構造単位（Ｍ１）と主鎖に環構造を形成する構造単位の合計、つまり｛（Ｍ２−３）＋（Ｍ２）｝の存在比率は（Ｍ１）＋（Ｍ２−３）＋（Ｍ２）＝１００としたとき（Ｍ１）／｛（Ｍ２−３）＋（Ｍ２）｝が３０／７０〜７０／３０モル比であり、好ましくは３５／６５〜６５／３５モル比、より好ましくは４０／６０〜６０／４０モル比、さらに好ましくは４０／６０〜５０／５０モル比である。
【０３４０】
構造単位（Ｍ１）の比率が大きすぎると現像液溶解性が低下し、構造単位（Ｍ１）比率が小さすぎると１５７ｎｍ光での透明性が低下するため好ましくない。
【０３４１】
環構造を形成する構造単位｛（Ｍ２−３）＋（Ｍ２）｝の比率が大きすぎると１５７ｎｍ光での透明性が低下し、構造単位｛（Ｍ２−３）＋（Ｍ２）｝の比率が小さすぎるとドライエッチ耐性が低下するため好ましくない。
【０３４２】
本発明の式（Ｍ−４）の重合体においても同様に、含フッ素エチレン性単量体由来の構造単位（Ｍ１）と主鎖に環構造を形成する構造単位の合計、つまり｛（Ｍ２−３）＋（Ｍ２−４）｝の存在比率は（Ｍ１）＋（Ｍ２−３）＋（Ｍ２−４）＝１００としたとき（Ｍ１）／｛（Ｍ２−３）＋（Ｍ２−４）｝が３０／７０〜７０／３０モル比であり、好ましくは３５／６５〜６５／３５モル比、より好ましくは４０／６０〜６０／４０モル比、さらに好ましくは４０／６０〜５０／５０モル比である。構造単位（Ｍ１）の比率が大きすぎると酸解離後の現像液溶解性が低下し、構造単位（Ｍ１）比率が小さすぎると１５７ｎｍ光での透明性が低下するため好ましくない。
【０３４３】
環構造を形成する構造単位｛（Ｍ２−３）＋（Ｍ２−４）｝の比率が大きすぎると１５７ｎｍ光での透明性が低下し、構造単位｛（Ｍ２−３）＋（Ｍ２−４）｝の比率が小さすぎるとドライエッチ耐性が低下するため好ましくない。
【０３４４】
本発明の式（Ｍ−３）、（Ｍ−４）の重合体の分子量は共に数平均分子量で１０００〜５００００であり、好ましくは１５００〜３００００、より好ましくは２０００〜２００００、さらに好ましくは２０００〜１００００である、分子量が低すぎると、透明性が低下したり、ドライエッチ耐性が低下するため好ましくない。また、分子量が高すぎると、現像液溶解性が低下するため好ましくない。
【０３４５】
本発明の式（Ｍ−３）、（Ｍ−４）の重合体自体、１５７ｎｍ光での透明性に優れたものであり、具体的には１５７ｎｍ波長の吸光係数が１．５μｍ^-1以下のものであり、好ましくは１．０μｍ^-1以下、特に好ましくは０．６μｍ^-1以下であることが好ましい。これら含フッ素重合体はＦ２レーザー（１５７ｎｍ）の光線を用いるリソグラフィープロセスに効果的に利用できる。
【０３４６】
本発明は、さらに
（Ａ−２）ＯＨ基または酸でＯＨ基に変換できる酸解離性官能基の少なくとも１種の酸反応性基Ｙ⁴を有する含フッ素重合体、
（Ｂ）光酸発生剤、および
（Ｃ）溶剤
からなる組成物に関し、
該含フッ素重合体（Ａ−２）が本発明の前記式（Ｍ−３）および／または式（Ｍ−４）の重合体であるフォトレジスト組成物に関する。
【０３４７】
本発明のフォトレジスト組成物において、含フッ素重合体（Ａ−２）は前記式（Ｍ−３）、（Ｍ−４）の重合体の例示と同様のものが好ましくあげられる。
【０３４８】
本発明のフォトレジスト組成物において、光酸発生剤（Ｂ）の種類や使用比率は前述の新規な製造方法で得られた含フッ素重合体（Ａ−１）を含むフォトレジスト組成物で例示した光酸発生剤（Ｂ）と同様のものが好ましくあげられる。
【０３４９】
本発明のフォトレジスト組成物において、溶剤（Ｃ）の種類や使用比率は前述の新規な製造方法で得られた含フッ素重合体（Ａ−１）を含むフォトレジスト組成物で例示した溶剤（Ｃ）と同様のものが好ましくあげられる。
【０３５０】
本発明のフォトレジスト組成物において、光酸発生剤（Ｂ）、溶剤（Ｃ）以外の添加物においても前述の含フッ素重合体（Ａ−１）を含むフォトレジスト組成物で例示したものと同様なものが好ましく利用できる。
【０３５１】
本発明のフォトレジスト組成物は、従来のフォトレジスト技術のレジストパターン形成方法において使用される。特にレジストパターン形成方法を好適に行なうには、まずシリコンウェハーのような支持体上にフォトレジスト組成物の溶液をスピンナーなどで塗布し、乾燥して感光層を形成させ、これに縮小投影露光装置などにより、紫外線、ｄｅｅｐ−ＵＶ、エキシマレーザー光、Ｘ線を所望のマスクパターンを介して照射するか、あるいは電子線により描画し、加熱する。ついでこれを現像液、たとえば１〜１０重量％テトラメチルアンモニウムヒドロキシド水溶液のようなアルカリ性水溶液などを用いて現像処理する。この形成方法でマスクパターンに忠実な画像を得ることができる。
【０３５２】
半導体デバイスの微細回路パターンを形成する際、フォトリソグラフィープロセスにおける現像工程では、現像液として２．３８重量％のテトラメチルアンモニウムヒドロキシド水溶液が好ましく用いられる。
【０３５３】
またさらに、レジスト被膜との塗れ性を調整するため、２．３８重量％のテトラメチルアンモニウムヒドロキシド水溶液中に界面活性剤やメタノール、エタノール、プロパノールまたはブタノールなどのアルコール類を添加しても良い。
【０３５４】
なかでも本発明のフォトレジスト組成物を用いることによって、真空紫外領域においても透明性の高いレジスト被膜（感光層）を形成できることが見出されている。それによって特に今後０．０７μｍのテクノロジーノードを目指して開発中のＦ２レーザー（１５７ｎｍ波長）を用いたフォトリソグラフィープロセスに好ましく利用できるものである。
【０３５５】
本発明のフォトレジストを塗布した被膜は、前述のフォトレジスト組成物をスピンコートなどの塗装方法によってシリコンウェハーのような支持体上に塗布し、乾燥することによって形成され、被膜中には、ＯＨ基および／または酸でＯＨ基に変換できる酸解離性官能基を有する含フッ素重合体（Ａ−２）、光酸発生剤（Ｂ）、その他の添加物などの固形成分が含まれている。
【０３５６】
形成するレジスト被膜の膜厚は、通常１．０μｍ以下の薄層被膜であり、好ましくは０．０１〜０．５μｍ、より好ましくは０．０５〜０．５μｍの薄膜である。
【０３５７】
さらに本発明のフォトレジスト組成物を塗布した被膜は、真空紫外領域の透明性が高いものが好ましく、具体的には１５７ｎｍ波長の吸光係数が２．０μｍ^-1以下のものであり、好ましくは１．５μｍ^-1以下、特に好ましくは１．０μｍ^-1以下、さらには０．６μｍ^-1以下であることが好ましい。この被膜はＦ２レーザー（１５７ｎｍ）の光線を用いるリソグラフィープロセスに効果的に利用できる。
【０３５８】
なお、レジスト被膜が施される基材は、従来レジストが適用される各種基材が同様に利用できる。たとえばシリコンウェハー、有機系または無機系反射防止膜が設けられたシリコンウェハー、ガラス基板などのいずれでもよい。特に有機系反射防止膜が設けられたシリコンウェハー上での感度、プロファイル形状が良好である。
【０３５９】
【実施例】
つぎに本発明を実施例などにより説明するが、本発明はこれらの実施例などに限定されるものではない。
【０３６０】
実験例１（メタノールを用いたＴＦＥとＯＨ基含有含フッ素ノルボルネン（ＮＢ−１）との共重合体の合成）
バルブ、圧力ゲージ、攪拌器および温度計を備えた５００ｍｌのオートクレーブを窒素で数回置換した後に真空にして、ＯＨ基含有含フッ素ノルボルネン（ＮＢ−１）：
【０３６１】
【化５１】

【０３６２】
の３９．０ｇとＨＣＦＣ−１４１ｂの２５０ｍｌの溶液を仕込んだ。ついでバルブよりＴＦＥ５８．０ｇを仕込み、ペンタフルオロプロピオノイルパーオキサイド：（ＣＦ₃ＣＦ₂ＣＯＯ）₂の１０．０重量％パーフルオロヘキサン溶液１０.５ｇ、メタノール０．２２ｇを入れ、３５℃にて３時間、攪拌して反応させた。
【０３６３】
未反応モノマーを放出したのち、重合溶液を取り出し、濃縮後ヘキサンで再沈殿させ、共重合体を分離した。恒量になるまで真空乾燥を行ない、共重合体３．２ｇを得た。
【０３６４】
この共重合体の組成比は、¹Ｈ−ＮＭＲおよび¹⁹Ｆ−ＮＭＲ分析の結果より、ＴＦＥ／前記ＯＨ基含有含フッ素ノルボルネン誘導体（ＮＢ−１）が５０／５０モル％の共重合体であった。
ＧＰＣ分析により数平均分子量は３６００であった。
【０３６５】
実験例２（メタノールを用いたＴＦＥとＯＨ基含有含フッ素ノルボルネン（ＮＢ−１）との共重合体の合成）
実験例１において、連鎖移動剤としてメタノールを０．１１ｇ使用した以外は実験例１と同様にして反応を行ない、共重合体３．７ｇを得た。
【０３６６】
この共重合体の組成比は、¹Ｈ−ＮＭＲおよび¹⁹Ｆ−ＮＭＲ分析の結果より、ＴＦＥ／前記ＯＨ基含有含フッ素ノルボルネン誘導体（ＮＢ−１）が５０／５０モル％の共重合体であった。
ＧＰＣ分析により数平均分子量は３７００であった。
【０３６７】
実験例３（ＴＦＥとＯＨ基含有含フッ素ノルボルネン誘導体（ＮＢ−１）との共重合体の合成）
実験例１において、連鎖移動剤を使用しなかった以外は実験例１と同様にして反応を行ない、共重合体３．５ｇを得た。
【０３６８】
この共重合体の組成比は、¹Ｈ−ＮＭＲおよび¹⁹Ｆ−ＮＭＲ分析の結果より、ＴＦＥ／前記ＯＨ基含有含フッ素ノルボルネン誘導体（ＮＢ−１）が５０／５０モル％の共重合体であった。
ＧＰＣ分析により数平均分子量は３７００であった。
【０３６９】
実験例４（ＴＦＥとＯＨ基含有含フッ素ノルボルネン（ＮＢ−１）との共重合体の合成）
実験例１において、連鎖移動剤を使用せず、ＯＨ基含有含フッ素ノルボルネン誘導体（ＮＢ−１）を３０．６ｇ、重合開始剤としてパーロイルＴＣＰ（ビス（４−ｔ−ブチルシクロヘキシル）パーオキシジカーボネート）を６．５ｇ用いた以外は実験例１と同様にして４０℃で反応を行ない、共重合体３．９ｇを得た。
【０３７０】
この共重合体の組成比は、¹Ｈ−ＮＭＲおよび¹⁹Ｆ−ＮＭＲ分析の結果より、ＴＦＥ／前記ＯＨ基含有含フッ素ノルボルネン誘導体（ＮＢ−１）が５０／５０モル％の共重合体であった。
ＧＰＣ分析により数平均分子量は３７００であった。
【０３７１】
実験例５（連鎖移動剤としてメタノールを用いたＴＦＥ、ＯＨ基含有含フッ素ノルボルネン誘導体（ＮＢ−１）とＯＣＨ₂ＯＣＨ₂ＣＨ₃基含有含フッ素ノルボルネン誘導体（ＮＢ−２）との共重合体の合成）
実験例１において、（ＮＢ−１）を２３．５ｇとＯＣＨ₂ＯＣＨ₂ＣＨ₃基含有含フッ素ノルボルネン誘導体（ＮＢ−２）：
【０３７２】
【化５２】

【０３７３】
を１８．９ｇ使用した以外は実験例１と同様にして反応を行ない、共重合体３．０ｇを得た。
【０３７４】
この共重合体の組成比は、¹Ｈ−ＮＭＲおよび¹⁹Ｆ−ＮＭＲ分析の結果より、ＴＦＥ／前記ＯＨ基含有含フッ素ノルボルネン誘導体（ＮＢ−１）／前記ＯＣＨ₂ＯＣＨ₂ＣＨ₃基含有含フッ素ノルボルネン誘導体（ＮＢ−２）が５０／３０／２０モル％の共重合体であった。
ＧＰＣ分析により数平均分子量は３０００であった。
【０３７５】
実験例６（ＯＣＨ₂ＯＣＨ₂ＣＨ₃基の脱保護反応）
還流管を備えた５０ｍｌナスフラスコに実験例５で得られたポリマーを１．０ｇとり、ここにジクロロメタン２０ｍｌとトリフルオロ酢酸を０．５ｇ加え、撹拌しながらジクロロメタンが還流する温度で３時間反応させた。反応終了後、ジクロロメタン溶液を水洗、無水硫酸ナトリウムで乾燥後、エバポレーターにてジクロロメタンを留去した後、恒量になるまで６０℃で真空乾燥し、０．７ｇの白色固体を得た。¹Ｈ−ＮＭＲおよび¹⁹Ｆ−ＮＭＲ分析より、ＴＦＥ／前記ＯＨ基含有含フッ素ノルボルネン誘導体（ＮＢ−１）／前記ＯＣＨ₂ＯＣＨ₂ＣＨ₃基含有含フッ素ノルボルネン誘導体（ＮＢ−２）が５０／４９．５／０．５モル％の共重合体であった。
【０３７６】
実験例７（ＴＦＥとＯＨ基含有含フッ素ノルボルネン誘導体（ＮＢ−１）との共重合体の合成）
実験例１において、連鎖移動剤を使用せず、ＯＨ基含有含フッ素ノルボルネン誘導体（ＮＢ−１）を２３．５ｇ、ＯＣＨ₂ＯＣＨ₂ＣＨ₃基含有含フッ素ノルボルネン誘導体（ＮＢ−２）を１８．９ｇ用いた以外は実験例１と同様にして反応を行ない、共重合体２．９ｇを得た。
【０３７７】
この共重合体の組成比は、¹Ｈ−ＮＭＲおよび¹⁹Ｆ−ＮＭＲ分析の結果より、ＴＦＥ／前記ＯＨ基含有含フッ素ノルボルネン誘導体（ＮＢ−１）／前記ＯＣＨ₂ＯＣＨ₂ＣＨ₃基含有含フッ素ノルボルネン誘導体（ＮＢ−２）が５０／２９／２１モル％の共重合体であった。
ＧＰＣ分析により数平均分子量は３０００であった。
【０３７８】
実験例８（ＯＣＨ₂ＯＣＨ₂ＣＨ₃基の脱保護反応）
還流管を備えた５０ｍｌナスフラスコに実験例７で得られたポリマーを１．０ｇとり、実験例６と同様にしてトリフルオロ酢酸と反応および単離を行ない、０．８ｇの白色固体を得た。¹Ｈ−ＮＭＲおよび¹⁹Ｆ−ＮＭＲ分析より、ＴＦＥ／前記ＯＨ基含有含フッ素ノルボルネン誘導体（ＮＢ−１）／前記ＯＣＨ₂ＯＣＨ₂ＣＨ₃基含有含フッ素ノルボルネン誘導体（ＮＢ−２）が５０／５０／０モル％の共重合体であった。
【０３７９】
実験例９（現像液に対する溶解性の測定）
実験例１〜８で得られた含フッ素重合体およびパラヒドロキシスチレン（ＰＨＳ）の重合体を用いて、以下のようにして水晶振動子法（ＱＣＭ法）により溶解速度を測定した。
【０３８０】
（１）試料の作製：金で被覆された直径２４ｍｍの水晶振動子板に膜厚８０ｎｍ反射防止膜（ＳＨＩＰＬＥＹ社製、ＡＲ１９）を形成し、その上に実験例１〜７で得た含フッ素重合体およびパラヒドロキシスチレンの重合体（ＰＨＳ、アルドリッチ社製 重量平均分子量８０００）をＰＧＭＥＡに溶解させた溶液（重合体濃度：１〜１０％）を塗布し１１０℃で９０秒乾燥後、１００ｎｍの被膜を作製した。
【０３８１】
（２）溶解速度の測定：膜厚は水晶振動子板の振動数から換算して算出し測定する。
【０３８２】
上記、含フッ素重合体を塗布した水晶振動子板を標準現像液である２．３８重量％濃度のテトラメチルアンモニウムヒドロキサイド（ＴＭＡＨ）水溶液に浸し、浸漬させた時点から時間に対する被膜の膜厚変化を、振動数の変化により測定し、単位時間あたりの溶解速度（ｎｍ／ｓｅｃ）を算出した。（参考文献：Advances in Resist Technology and Proceedings of SPIE Vol. 4690, 904(2002)）。
【０３８３】
さらに、０．５９５重量％濃度のＴＭＡＨ水溶液を用いて同様に溶解速度を測定した。結果を表１に示す。
【０３８４】
実験例１０（１５７ｎｍ波長での透明性の測定）
（１）塗布用組成物の作製
実験例１〜５、７で製造した各種含フッ素重合体およびＰＨＳをＰＧＭＥＡに１〜１０％濃度となるように溶解して塗布用組成物を調製した。
【０３８５】
（２）コーティング
▲１▼透明性測定用基材（ＭｇＦ₂）への塗布
ＭｇＦ₂の基板上に、各塗布用組成物をスピンコーターを用い、室温で１０００回転の条件でコートした。塗布後１００℃で１５分間焼成し、透明な被膜を作製した。
【０３８６】
▲２▼膜厚測定
ＭｇＦ₂基板に代えてシリコンウエハーを用いた以外は上記と同じ条件でそれぞれの塗布用組成物を用いてシリコンウエハー上に被膜を形成した。
【０３８７】
ＡＦＭ装置（セイコー電子（株）ＳＰＩ３８００）にて各被膜の厚さを測定した。
【０３８８】
（３）真空紫外領域の透明性測定
▲１▼測定装置
・瀬谷−波岡型分光装置（高エネルギー研究機構：ＢＬ−７Ｂ）
・スリット ７／８−７／８
・検出器 ＰＭＴ
・グレーティング（ＧＩＩ：ブレーズ波長１６０ｎｍ、１２００本／ｍｍ）
光学系は、Ｈ．ＮａｍｂａらのＲｅｖ．Ｓｉｃ．Ｉｎｓｔｒｕｍ．，６０（７）、１９１７（１９８９）を参照。
【０３８９】
▲２▼透過スペクトルの測定
各塗布用組成物から（２）▲１▼の方法で得たＭｇＦ₂基板上に形成した被膜の２００〜１００ｎｍの透過スペクトルを上記の装置を用いて測定した。
【０３９０】
１５７ｎｍにおける透過率と被膜の膜厚から分子吸光度係数を算出した。結果を表１に示す。
【０３９１】
実験例１１（フォトレジスト用組成物の作製とレジスト被膜の透明性測定）
（１）フォトレジスト用組成物の調製
実験例５で製造した含フッ素重合体（Ａ−２）と重合体（Ａ−２）に対して５重量％の光酸発生剤（Ｂ）を溶剤（Ｃ）としてＰＧＭＥＡに溶解させ重合体濃度５重量％に希釈した。
【０３９２】
なお光酸発生剤としてＳ−（トリフルオロメチル）−ジベンゾチオフェニウムトリフルオロメタンスルホネート
【０３９３】
【化５３】

【０３９４】
を用いた。
【０３９５】
（２）コーティング
上記フォトレジスト用組成物を用い、Ｓｉ基板状に膜厚１００ｎｍとなるようにスピンコーターで塗布し、乾燥させた。
【０３９６】
（３）真空紫外領域の透明性の測定
実験例１０と同様にして行なった。１５７ｎｍにおける分子吸光度係数を表１に示す。
【０３９７】
【表１】

【０３９８】
【発明の効果】
本発明の製造方法によれば、真空紫外領域における透明性に優れ、しかも含フッ素重合体でありながらアルカリ現像液に対する優れた溶解性を併せもつフォトレジスト用含フッ素重合体を製造することができ、特にＦ２レジスト用として超微細パターンを形成することができる含フッ素重合体を製造することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a novel method for producing a fluoropolymer, and further to production of a fluoropolymer for a photoresist which is transparent in the vacuum ultraviolet region, particularly F2 laser (157 nm) light and has excellent solubility in an alkaline developer. The present invention relates to a method and a photoresist composition comprising the fluorine-containing polymer for photoresist.
[0002]
[Prior art]
As the need for high integration of large scale integrated circuits (LSIs) increases, fine processing techniques are required in photolithography techniques. In response to this requirement, far ultraviolet rays, KrF excimer laser light (wavelength 248 nm), and ArF excimer laser light (wavelength 193 nm) which are shorter than conventional g-line (wavelength 436 nm) and i-line (wavelength 365 nm) are used as exposure light sources. It has been tried to be used as a practical application.
[0003]
Recently, a process using an F2 laser beam (wavelength of 157 nm) in the vacuum ultraviolet region is being studied as a further ultrafine processing technique, and it is promising as an exposure technique aiming for a future technology node of 0.07 μm.
[0004]
Examples of such resist resins used in conventional photolithography include those in which part or all of the hydroxyl groups of the phenolic resin are protected with protecting groups such as acetals and ketals (KrF resists), and methacrylic acid resins. Examples include an acid dissociable ester group introduced into a carboxyl group (ArF resist).
[0005]
However, these conventional resist polymers have strong absorption in the wavelength region of vacuum ultraviolet, and have low transparency in F2 laser light having a wavelength of 157 nm, which is being studied for use as an ultrafine patterning process (the extinction coefficient is low). There is a fundamental problem. Therefore, in order to perform exposure with the F2 laser, it is necessary to extremely reduce the film thickness of the resist, and it is practically difficult to use it as a single-layer F2 resist.
[0006]
Therefore, studies have been made on resists using fluorine-containing polymers that are highly transparent to F2 laser light.
[0007]
Among them, a fluoropolymer obtained by copolymerizing a fluoroolefin having 2 or 3 carbon atoms represented by tetrafluoroethylene and / or a fluoropolymer having a ring structure in the main chain has both transparency and dry etching resistance. And is useful as a resist polymer.
[0008]
As these fluorine resists, a fluorine-containing polymer for resist having a functional group that reacts with an acid, and a resist composition using the same have been proposed (for example, see Patent Document 1, Patent Document 2, and Patent Document 3). .
[0009]
In these patent documents, a copolymer of a fluoroolefin typified by tetrafluoroethylene and an alicyclic monomer typified by norbornene (or a norbornene derivative) is specifically described. Specifically, no quantitative study has been made on the solubility in tetramethylammonium hydroxide aqueous solution (abbreviated as “TMAH aqueous solution”).
[0010]
[Patent Document 1]
International Publication No. 00/17712 Pamphlet
[Patent Document 2]
International Publication No. 00/67072 Pamphlet
[Patent Document 3]
WO 01/74916 pamphlet
[0011]
[Problems to be solved by the invention]
The present inventors have intensively studied in view of these problems, and include a fluorine-containing polymer for a resist having an acid-reactive group by radical (co) polymerizing a fluoroolefin or a monomer that forms a ring structure in the main chain. Is obtained by radical (co) polymerization using a specific chain transfer agent, and a fluorine-containing polymer for resist is efficiently obtained, and the solubility of the fluorine-containing polymer in an alkaline developer (TMAH aqueous solution) is obtained. Found a dramatic improvement.
[0012]
The first object of the present invention is excellent in transparency in F2 laser light by radical (co) polymerizing a fluoroolefin or a monomer that forms a ring structure in the main chain using a specific chain transfer agent. The object is to provide a method for producing a fluoropolymer for resist.
[0013]
The second object of the present invention is to provide transparency in F2 laser light by copolymerizing a fluoroolefin and a specific monomer having a specific functional group and forming a ring structure in the main chain by such a production method. Another object of the present invention is to provide a fluorine-containing polymer for resists excellent in solubility in an alkaline developer (TMAH aqueous solution).
[0014]
The third object of the present invention is to provide a composition for a resist, particularly an F2 resist, which contains a fluoropolymer having excellent transparency and solubility in an alkaline developer (TMAH aqueous solution).
[0015]
[Means for Solving the Problems]
As a result of diligent investigations to achieve the above object, the present inventors have used a fluorine-containing copolymer obtained by using a specific chain transfer agent as a photoresist resin, compared with a fluorine-containing polymer produced by a conventional method. It has been found that when used, the solubility in an alkaline developer (TMAH aqueous solution) is dramatically improved. Further, a specific fluorine-containing polymer having an aliphatic ring structure in the main chain having a specific functional group therein, and having a dissolution rate in a TMAH aqueous solution measured by a QCM measurement method is greater than a specific value. Thus, it has been found that it is particularly useful in that it can form a high-resolution pattern when used in an ultrafine processing process.
[0016]
The first of the present invention is a fluorine-containing polymer having an aliphatic ring structure repeating unit (M2) in the polymer main chain, and an acid-reactive group Y that reacts with an acid in the polymer.¹Or acid-reactive group Y¹Y group convertible to²In order to obtain a fluorine-containing polymer for resists having the following formula, a monomer mixture containing a monomer (m2) capable of giving an aliphatic ring structure to the polymer main chain is represented by the formula (1) in the presence of a radical polymerization initiator. :
R- (X)_n
(In the formula, R is selected from hydrocarbon groups optionally containing an ether bond having 1 to 20 carbon atoms, and a part of hydrogen atoms may be substituted with fluorine atoms; X coexists with a chain transfer agent having a specific functional group represented by a functional group containing an oxygen atom and at least one functional group selected from the group consisting of a substituted or unsubstituted amino group; n is an integer of 1 to 4) The present invention relates to a method for producing a fluorine-containing polymer for a resist excellent in solubility in an alkaline developer, characterized by radical polymerization.
[0017]
According to the production method of the present invention, the obtained fluoropolymer is excellent in transparency to light in the vacuum ultraviolet region, and is excellent in developer solubility.
[0018]
The second of the present invention is (A-1) an OH group, an acid dissociable functional group that can be converted to an OH group by an acid, a COOH group, or an acid dissociable functional group that can be dissociated by an acid to be converted to a COOH group At least one acid-reactive group Y¹A fluorine-containing polymer having
(B) a photoacid generator, and
(C) Solvent
And the fluorine-containing polymer (A-1) is a polymer obtained by the production method according to the first aspect of the present invention.
[0019]
Such a photoresist composition provides a resist film that is excellent in transparency of vacuum ultraviolet light and excellent in solubility in an alkaline developer, and enables high-resolution pattern formation when used in an ultrafine processing process. It is a particularly useful photoresist composition.
[0020]
A third aspect of the present invention is a fluorine-containing polymer having an aliphatic ring structure in a polymer main chain having an OH group and having only an OH group as a functional group that imparts solubility to a developer. The polymer is represented by the formula (M-3):
-(M1)-(M2-3)-(M2)-(N)-(M-3)
(In the formula, the structural unit M1 is an ethylenic monomer having 2 or 3 carbon atoms and is a repeating unit derived from a fluorine-containing ethylenic monomer (m1) having at least one fluorine atom; structural unit M2-3 Is a repeating unit derived from a norbornene derivative (m2-3) which may have a fluorine atom having an OH group; the structural unit M2 is derived from a monomer (m2) capable of giving an aliphatic ring structure to the polymer main chain. The repeating unit; the structural unit N is represented by the monomer (m1), (m2-3) and the repeating unit derived from the monomer (n) copolymerizable with the monomer (m2). 24 to 70 mol%, 1 to 70 mol% of the structural unit M2-3, 0 to 69 mol% of the structural unit M2-4, 0 to 20 mol% of the structural unit N, and (M1) + (M2-3 ) + (M2-4) = 100 (M1) / {(M2 3) + (M2-4)} is a fluoropolymer having a number average molecular weight of 1000 to 50000 in a 30/70 to 70/30 molar ratio, and the fluoropolymer is measured by a QCM measurement method described later. The present invention relates to a fluorine-containing polymer for a resist excellent in solubility in a developing solution having a dissolution rate in a 2.38 wt% tetramethylammonium hydroxide aqueous solution of 500 nm / sec or more.
[0021]
Such a fluoropolymer for resist provides a resist film that is particularly excellent in transparency of vacuum ultraviolet light and has excellent solubility in an alkaline developer, and can form a high-resolution pattern when used in an ultrafine processing process. Therefore, it is a particularly useful polymer.
[0022]
The fourth of the present invention is (A-2) at least one acid-reactive group Y of an acid-dissociable functional group that can be converted to an OH group with an OH group or an acid.^FourA fluorine-containing polymer having
(B) a photoacid generator, and
(C) Solvent
The photoresist composition comprising the fluorine-containing polymer (A-2) is a fluorine-containing polymer for resist obtained in the third invention of the present invention.
[0023]
Such a photoresist composition and resist film provide a resist film that is further excellent in transparency of vacuum ultraviolet light and excellent in solubility in an alkali developer, and has an ultra-fine high-resolution ultra-high resolution when used in an F2 photolithography process. Since a fine pattern can be formed, it is a particularly useful photoresist composition.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
The fluoropolymer produced by the production method of the present invention is a fluoropolymer having an aliphatic ring structure repeating unit (M2) in the polymer main chain, in other words, an aliphatic ring in the polymer main chain. The polymer has a repeating unit (M2) derived from the monomer (m2) which may contain a fluorine atom capable of giving a structure as an essential component, and the acid-reactive group Y¹Or acid-reactive group conversion group Y²(Hereinafter also referred to as “acid-reactive functional group Y”). Moreover, arbitrary repeating units (N) may further be included.
[0025]
As will be described in detail later, the fluoropolymer produced is preferably an ethylenic monomer having 2 or 3 carbon atoms in addition to the repeating unit (M2) of the aliphatic ring structure in the polymer main chain. Having a repeating unit (M1) derived from a fluorine-containing ethylenic monomer (m1) having at least one fluorine atom, and an acid-reactive group Y¹Or acid-reactive group conversion group Y²(Hereinafter also referred to as “acid-reactive functional group Y”). Moreover, arbitrary repeating units (N1, N) may further be included. (Fluoropolymer of formula (M-1))
[0026]
In addition, the fluorine atom in the fluoropolymer obtained in the present invention is not necessarily derived from the monomer (m2) (or the monomer (m1)), but any other comonomer. (N1, n, etc.) may be derived.
[0027]
The method for introducing the acid-reactive functional group Y into the polymer will be described in detail later.
(I) a method of copolymerizing a monomer (m2-2) (structural unit (M2-2)) having an acid-reactive functional group Y as a monomer (m2) that forms an aliphatic ring structure;
(II) Method of copolymerizing monomer (n1-2) other than monomer (m2) and having acid-reactive functional group Y
Etc.
[0028]
Hereinafter, the chain transfer agent will be described first, and then each monomer that undergoes radical polymerization will be specifically described.
[0029]
In the production method of the present invention, when obtaining the above-mentioned fluoropolymer, a monomer mixture containing the monomer m2 is represented by the formula (1):
R- (X)_n
(In the formula, R is selected from hydrocarbon groups optionally containing an ether bond having 1 to 20 carbon atoms, and a part of hydrogen atoms may be substituted with fluorine atoms; X is an oxygen atom-containing functional group and at least one functional group selected from the group consisting of a substituted or unsubstituted amino group; n is an integer of 1 to 4, and at least one oxygen atom-containing group in the molecule It is characterized by radical polymerization using a chain transfer agent having a substituted or unsubstituted amino group.
[0030]
By using such a chain transfer agent, the functional group X can be partially imparted to the polymer terminal, thereby improving the hydrophilicity of the polymer itself, and the inclusion of the acid-reactive functional group Y of the present invention for a resist. It is considered that the solubility of the fluoropolymer (after exposure or after removal of the protecting group) in the developer is improved.
[0031]
Conventionally, the solubility of a fluorine-containing polymer for resist in a developing solution has been dependent on the acid-reactive functional group Y (or the protecting group in Y is eliminated), but the acid-reactive functional group Y However, sufficient development characteristics (resolution) could not be obtained only by introduction of.
[0032]
As a result of intensive studies on a method for producing a fluoropolymer for resist, the present inventors use a chain transfer agent of the above formula (1) when producing a fluoropolymer having an acid-reactive functional group Y. As a result, the solubility in the developer is further greatly improved, and a high-resolution fine pattern can be formed.
[0033]
As the chain transfer agent used in the production method of the present invention, as shown in the formula (1), a chain having at least one functional group selected from the group consisting of an oxygen atom-containing group and a substituted or unsubstituted amino group in the molecule. Although it will not specifically limit if it is a transfer agent, The following are mentioned preferably.
[0034]
Examples of the oxygen atom-containing group in the functional group X contained in the chain transfer agent used in the production method of the present invention include a hydroxyl group, a carboxyl group, an acyl group, a substituted oxy group, a substituted oxycarbonyl group, a substituted or unsubstituted carbamoyl group, hydroxy Examples include imino group, substituted oxyimino group, sulfonic acid group, sulfonic acid ester group, and nitro group.
[0035]
Examples of the substituted oxy group include alkoxy groups such as a methoxy group, an ethoxy group, a propoxy group, a t-butoxy group, and a cyclohexyloxy group (particularly C_1-6Alkoxy group); aryloxy group such as phenoxy group; aralkyloxy group such as benzyloxy group; acyloxy group such as acetoxy group, propionyl group, benzoyloxy group (especially C_1-5An aliphatic acyloxy group or an aromatic acyloxy group); an alkoxycarbonyloxy group such as a methoxycarbonyloxy group, an ethoxycarbonyloxy group, or a t-butoxycarbonyloxy group (particularly C_1-4Alkoxycarbonyloxy group) and the like.
[0036]
Examples of the substituted oxycarbonyl group include alkoxycarbonyl groups such as methoxycarbonyl group, ethoxycarbonyl group, propoxycarbonyl group, t-butoxycarbonyl group (particularly C_1-4Alkoxy-carbonyl groups); aryloxycarbonyl groups such as phenoxycarbonyl groups; aralkyloxycarbonyl groups such as benzyloxycarbonyl groups and the like.
[0037]
Examples of the acyl group include aliphatic acyl groups such as formyl group, acetyl group, propionyl group and cyclohexanoyl group (particularly C_1-6Aliphatic acyl groups); aromatic acyl groups such as benzoyl groups; heterocyclic acyl groups such as pyridinecarbonyl groups.
[0038]
Examples of the substituted or unsubstituted carbamoyl group include a carbamoyl group; a mono- or dicarbamoyl group such as a methylcarbamoyl group, an ethylcarbamoyl group, a dimethylcarbamoyl group, and a diethylcarbamoyl group (particularly C_1-4Alkylcarbamoyl group); cyclic aminocarbonyl groups such as 1-pyrrolidylcarbonyl group, piperidinocarbonyl group and morpholinocarbonyl group. Examples of the substituted oxyimino group include alkoxyimino groups such as methoxyimino group and ethoxyimino group (particularly C_1-4Alkoxyoxymino groups); aryloxyimino groups such as phenoxyimino groups; aralkyloxyimino groups such as benzyloxyimino groups and the like.
[0039]
Examples of the sulfonate group include alkyl sulfonate groups such as methyl sulfonate group and ethyl sulfonate group (particularly C_1-4Alkylsulfonic acid ester group) and the like.
[0040]
The functional group X contained in the chain transfer agent used in the production method of the present invention may be a substituted or unsubstituted amino group. Specifically, for example, an amino group; a mono- or dialkylamino group such as a methylamino group, an ethylamino group, a dimethylamino group, or a diethylamino group (particularly C_1-4Monoalkylamino group); cyclic amino groups such as 1-pyrrolidinyl group, piperidino group and morpholino group.
[0041]
The functional group X contained in the chain transfer agent is preferably a hydrophilic functional group or a group that can be converted into a hydrophilic functional group in the above examples.
[0042]
As the hydrophilic functional group, a hydroxyl group, a carboxyl group, a sulfonic acid group, and an unsubstituted amino group are preferable. Among them, a hydroxyl group, a carboxyl group, and a sulfonic acid group are preferable, and a hydroxyl group and a carboxyl group are particularly preferable. Furthermore, it is most preferable that it is a hydroxyl group at the point which is excellent in transparency.
[0043]
The group that can be converted into a hydrophilic functional group is a group that can be converted into the above-mentioned hydrophilic functional group by the action of acid, base, or heat. A group that can be converted into a group is preferred.
[0044]
For example,
[0045]
[Chemical Formula 3]

[0046]
(Wherein R⁷, R⁸, R⁹, R^Ten, R¹¹, R¹², R¹⁴, R¹⁸, R¹⁹, R²⁰, R^{twenty one}, R^{twenty two}, R^{twenty four}, R^{twenty five}, R²⁶, R²⁷, R²⁸, R²⁹Are the same or different and are hydrocarbon groups having 1 to 10 carbon atoms; R¹³, R¹⁵, R¹⁶Are the same or different, H or a hydrocarbon group having 1 to 10 carbon atoms; R¹⁷, R^{twenty three}Are the same or different and are divalent hydrocarbon groups having 2 to 10 carbon atoms.
[0047]
Of the above examples, t-butoxy group, t-butoxycarbonyl group, t-butoxycarbonyloxy group, methoxymethyl group, ethoxymethyl group and the like are preferable.
[0048]
Of the groups that can be converted into hydrophilic functional groups, a group that can be converted into a hydroxyl group or a carboxyl group is preferable, and further, a group that can be converted into a hydroxyl group in terms of excellent transparency. preferable.
[0049]
The hydrocarbon group R in the formula (1) representing the chain transfer agent is selected from hydrocarbon groups having 1 to 20 carbon atoms, and may contain an ether bond therein. Moreover, a part of hydrogen atoms may be substituted with fluorine atoms.
[0050]
It is preferable that 1 to 4 functional groups X in the chain transfer agent of the formula (1) are bonded to the same or different carbon atoms in the hydrocarbon group R. In order to allow radical polymerization to proceed smoothly, the functional group X X is preferably one or two, more preferably one bonded to the hydrocarbon group R.
[0051]
In particular, the hydrocarbon group R is preferably a saturated aliphatic hydrocarbon group (for example, does not contain a carbon-carbon double bond or an aromatic group) from the viewpoint of excellent transparency.
[0052]
Specifically, it is selected from a linear or branched alkyl group having 1 to 20 carbon atoms and an alkyl group having a saturated aliphatic cyclic structure.
[0053]
Of these, when the hydrocarbon group R contains a saturated aliphatic cyclic structure, it is preferable in that the dry etching resistance can be improved.
[0054]
The carbon number of the hydrocarbon group R is selected from 1 to 20, preferably 1 to 15, more preferably 1 to 10, and further 1 to 6. If the number of carbon atoms is too large, radical polymerization will not proceed smoothly, such being undesirable.
[0055]
Specifically, as a linear or branched alkyl group,
[0056]
[Formula 4]

[0057]
Etc.
[0058]
Especially CH_Three-, CH_ThreeCH₂-, CH_ThreeCH₂CH₂-, (CH_Three)₂CH- etc. are preferred, more preferably CH_Three-, (CH_Three)₂CH-, and further, in that radical polymerization proceeds smoothly, CH_Three-Is most preferred.
[0059]
Specifically, as an alkyl group containing a saturated aliphatic cyclic structure,
[0060]
[Chemical formula 5]

[0061]
Etc. are preferred.
[0062]
Among the chain transfer agents used in the production method of the present invention, alcohols are preferable, preferably alcohols having 1 to 10 carbon atoms, more preferably monovalent alcohols having 1 to 10 carbon atoms.
[0063]
Specific examples include methanol, ethanol, propanol, isopropanol, n-butanol, t-butanol, 2-methylpropanol, cyclohexanol, methylcyclohexanol, cyclopentanol, methylcyclopentanol, dimethylcyclopentanol and the like. .
[0064]
Of these, methanol, isopropanol, t-butanol, cyclohexanol, methylcyclohexanol, cyclopentanol, methylcyclopentanol and the like are preferable, and methanol is particularly preferable.
[0065]
Next, each monomer that undergoes radical polymerization using the chain transfer agent of formula (1) will be described.
[0066]
First, a monomer (m2) that may contain a fluorine atom that can give the structural unit (M2) of the aliphatic ring structure to the polymer main chain, which is an essential component of the fluoropolymer for resist obtained in the present invention. ).
[0067]
The monomer (m2) can introduce an aliphatic ring structure unit (M2) that improves dry etching resistance into a polymer main chain when used in resist applications. Combined with this effect and the above-mentioned transparency in the vacuum ultraviolet region and the improvement effect of excellent solubility in an alkali developer, the fluoropolymer having an aliphatic ring structure in the main chain obtained by the production method of the present invention is , Especially preferred for an F2 laser resist.
[0068]
The monomer (m2) may be selected from unsaturated cyclic compounds having a radically polymerizable carbon-carbon unsaturated bond in the ring structure, and the monomer (m2) is cyclically linked to the main chain by cyclopolymerization of a diene compound. It may be selected from non-conjugated diene compounds capable of forming a structure.
[0069]
The monomer (m2) may or may not have the acid-reactive functional group Y in the monomer.
[0070]
By polymerizing this monomer (m2), a polymer having an aliphatic ring structural unit having a monocyclic structure or a multicyclic structure in the main chain can be obtained.
[0071]
The first preferred monomer (m2) is a monomer having a radical-polymerizable carbon-carbon unsaturated bond and capable of forming a monocyclic or polycyclic structure in the polymer main chain, and is acid-reactive. It is a monomer (m2-1) having no functional group Y.
[0072]
Specifically, a monomer (m2-1a) made of a monocyclic aliphatic unsaturated hydrocarbon compound having no acid-reactive functional group Y, a bicyclic aliphatic having no acid-reactive functional group Y It is selected from a monomer (m2-1b) composed of an unsaturated hydrocarbon compound, or a non-conjugated diene compound (m2-1c) capable of cyclopolymerization without the acid-reactive functional group Y described later.
[0073]
The monocyclic monomer (m2-1a) having no acid-reactive functional group Y is a 3-membered to 8-membered aliphatic unsaturated hydrocarbon compound which may contain an ether bond in the ring structure. Preferably there is.
[0074]
Specifically, the monomer (m2-1a) is
[0075]
[Chemical 6]

[0076]
Etc. are preferred.
[0077]
Furthermore, a monomer in which some or all of the hydrogen atoms of these monomers (m2-1a) are substituted with fluorine atoms may be used.
[0078]
[Chemical 7]

[0079]
Etc. are preferred.
[0080]
The other of the monomer (m2-1) has an aliphatic double ring structure that gives a structural unit having an aliphatic double ring structure in the polymer main chain and does not have an acid-reactive functional group Y. It is a monomer (m2-1b), and a preferable monomer (m2-1b) is a norbornene derivative.
[0081]
Specifically, the monomer (m2-1b) having an aliphatic polycyclic structure that does not have the acid-reactive functional group Y includes:
[0082]
[Chemical 8]

[0083]
Etc.
[0084]
A fluorine atom may be introduced into the ring structure of the norbornenes exemplified above, and the transparency can be improved without reducing the dry etching resistance by introducing the fluorine atom.
[0085]
Specifically, the formula:
[0086]
[Chemical 9]

[0087]
(In the formula, A, B, D and D ′ are the same or different, and all are H, F, an alkyl group having 1 to 10 carbon atoms or a fluorine-containing alkyl group having 1 to 10 carbon atoms; An integer, wherein any one of A, B, D and D ′ contains a fluorine atom), specifically,
[0088]
Embedded image

[0089]
And fluorine-containing norbornene represented by
[0090]
others,
[0091]
Embedded image

[0092]
And norbornene derivatives such as
[0093]
The second preferable monomer (m2) is a monomer having a radical-polymerizable carbon-carbon unsaturated bond and capable of forming a monocyclic or polycyclic structure in the polymer main chain, and is acid-reactive. It is a monomer (m2-2) having a functional group Y.
[0094]
Specifically, a monomer (m2-2a) composed of a monocyclic aliphatic unsaturated hydrocarbon compound having an acid-reactive functional group Y, a bicyclic aliphatic unsaturated hydrocarbon compound having an acid-reactive functional group Y Or a monomer (m2-2c) having an acid-reactive functional group Y, which is a non-conjugated diene compound capable of cyclopolymerization, which will be described later.
[0095]
Among them, the monocyclic monomer (m2-2a) having an acid-reactive functional group Y is an unsaturated hydrocarbon compound having a 3-membered to 8-membered ring structure which may contain an ether bond in the ring structure. It is preferable. Similarly to the above, the monomer (m2-2a) may be a monomer in which some or all of the hydrogen atoms are substituted with fluorine atoms.
[0096]
Specifically, the monocyclic monomer (m2-2a) having the acid-reactive functional group Y is:
[0097]
Embedded image

[0098]
And other monomers.
[0099]
The other monomer (m2-2) having an acid-reactive functional group Y gives a structural unit having an aliphatic polycyclic structure in the polymer main chain, and has an acid-reactive functional group Y. It is a monomer (m2-2b) containing an aliphatic bicyclic structure, and a preferred monomer (m2-2b) is a norbornene derivative having an acid-reactive functional group Y.
[0100]
Specifically, the monomer (m2-2b) containing an aliphatic polycyclic structure having an acid-reactive functional group Y includes:
[0101]
Embedded image

[0102]
Etc.
[0103]
Furthermore, the monomer (m2-2b) having an aliphatic polycyclic structure having an acid-reactive functional group Y may be one in which part or all of the hydrogen atoms bonded to the ring structure are substituted with fluorine atoms. This is preferable in that it can impart further transparency to the polymer.
[0104]
In particular,
[0105]
Embedded image

[0106]
(In the formula, A, B and D are the same or different, and all are H, F, an alkyl group having 1 to 10 carbon atoms or a fluorine-containing alkyl group optionally having an ether bond having 1 to 10 carbon atoms; R is a divalent hydrocarbon group having 1 to 20 carbon atoms, a fluorine-containing alkylene group having 1 to 20 carbon atoms, or a fluorine-containing alkylene group having an ether bond having 2 to 100 carbon atoms; a is an integer of 0 to 5; b Is 0 or 1. However, when b is 0 or R does not contain a fluorine atom, any one of A, B and D is a fluorine atom or a fluorine-containing alkyl group which may have an ether bond. And fluorine-containing norbornene derivatives represented by the formula:
[0107]
Among these, any of A, B and D is preferably a fluorine atom, or when A, B and D do not contain a fluorine atom, the fluorine content of R is 60% by weight or more. Is more preferable, and a perfluoroalkylene group is further preferable in terms of imparting transparency to the polymer.
[0108]
In particular,
[0109]
Embedded image

[0110]
Norbornene derivatives represented by the above.
[0111]
further,
[0112]
Embedded image

[0113]
(In the formula, A, B and D are the same or different and all are H, F, an alkyl group having 1 to 10 carbon atoms or a fluorine-containing alkyl group optionally having an ether bond having 1 to 10 carbon atoms; R Is a divalent hydrocarbon group having 1 to 20 carbon atoms, a fluorine-containing alkylene group having 1 to 20 carbon atoms, or a fluorine-containing alkylene group having an ether bond having 2 to 100 carbon atoms; a is an integer of 0 to 5; And fluorine-containing norbornene derivatives represented by 0 or 1).
[0114]
In particular,
[0115]
Embedded image

[0116]
Norbornene derivatives such as are preferred.
[0117]
Furthermore, as a preferable thing of the monomer (m2-2b) containing the aliphatic polycyclic structure which has the acid reactive functional group Y, Formula:
[0118]
Embedded image

[0119]
(Where Rf¹, Rf²Are the same or different and the fluorine-containing alkyl group having 1 to 10 carbon atoms or the fluorine-containing alkyl group having an ether bond; A, B, and D are the same or different, and all are H, F, Cl, and carbon atoms 1 to 10 Or a fluorine-containing alkyl group optionally containing an ether bond having 1 to 10 carbon atoms; R is H or an alkyl group having 1 to 10 carbon atoms; n is an integer of 0 to 5) Derivatives.
[0120]
Specifically, for example
[0121]
Embedded image

[0122]
Etc.
[0123]
More specifically,
[0124]
Embedded image

[0125]
Etc. are preferred.
[0126]
Other formula:
[0127]
Embedded image

[0128]
(Where Rf¹, Rf²Are the same or different and the fluorine-containing alkyl group having 1 to 10 carbon atoms or the fluorine-containing alkyl group having an ether bond; B and D are the same or different, and all are H, F, Cl, alkyl having 1 to 10 carbon atoms And a norbornene derivative represented by a fluorine-containing alkyl group optionally containing an ether bond having 1 to 10 carbon atoms; R is H or an alkyl group having 1 to 10 carbon atoms; and n is an integer of 0 to 5). .
[0129]
These exemplary monomers (m2-1b) and (m2-2b) containing an aliphatic polycyclic structure are particularly preferable as a raw material for a resist polymer in that dry etch resistance can be imparted to the polymer. The production method of the present invention is also preferable in that a polymer can be produced efficiently by radical polymerization and the transparency can be effectively improved. In particular, norbornene derivatives containing a fluorine atom in a bicyclic structure are preferable from the viewpoint of transparency, and the production method of the present invention can efficiently produce a polymer by a radical polymerization method and can effectively improve transparency. preferable.
[0130]
Further, the norbornene derivative (m2-2b) having an acid-reactive functional group Y is preferable because it can efficiently introduce functional groups necessary for resist application into the polymer, resulting in advantages in transparency and dry etching resistance. .
[0131]
The third preferable monomer (m2) is a non-conjugated diene compound which may have a fluorine atom capable of forming an aliphatic ring structure by polymerization. The non-conjugated diene compound can efficiently give a polymer having a structural unit having a ring structure in the main chain, and can improve the transparency in the vacuum ultraviolet region as described above.
[0132]
As the non-conjugated diene compound, for example, a specific divinyl compound that gives a monocyclic structure to the main chain by cyclopolymerization is preferred, and those having no acid-reactive functional group Y (m2-1c), or acid reaction Having a functional group Y (m2-2c).
[0133]
As specific examples, for example, a formula that may have a fluorine atom or an acid-reactive functional group Y:
[0134]
Embedded image

[0135]
(Where Z¹And Z²Are the same or different, hydrogen atom, fluorine atom, hydrocarbon group optionally having an ether bond of 1 to 5 carbon atoms, fluorine-containing alkyl group optionally having an ether bond of 1 to 5 carbon atoms) The diallyl compound shown by these is mention | raise | lifted.
[0136]
By radical cyclopolymerizing this diallyl compound,
[0137]
Embedded image

[0138]
(Where Z¹, Z²Can form a monocyclic structural unit in the main chain as shown above.
[0139]
Also in these cyclized radical polymerizations, a fluorine-containing polymer having a ring structure in the polymer main chain is efficiently obtained by radical (co) polymerization using a chain transfer agent having a functional group of formula (1). In the same manner as described above, the solubility in the developer can be improved.
[0140]
In the fluoropolymer having the structural unit M2-2 produced by the method of the present invention, the structural unit M2-2 having the acid-reactive functional group Y is represented by the formula (2):
[0141]
Embedded image

[0142]
(Where Rf¹Preferably has a moiety represented by a fluorine-containing alkyl group having 1 to 10 carbon atoms or a fluorine-containing alkyl group having an ether bond) in terms of excellent solubility in a developing solution and excellent transparency to 157 nm light. .
[0143]
Rf¹Is preferably a C 1-10 perfluoroalkyl group, more preferably a C 1-5 perfluoroalkyl group, and even more preferably CF._ThreeIt is particularly preferred that
[0144]
The site of the formula (2) is a fluorine-containing alkyl group Rf¹And OH group may be bonded simultaneously to a carbon atom forming a ring structure, or may be bonded simultaneously to a carbon atom not forming a ring structure, and the site of formula (2) forms a ring structure. It may be bonded to the atom in the form of a side chain.
[0145]
Here, the acid-reactive functional group Y will be described. The acid-reactive functional group Y is the acid-reactive group Y as described above.¹And acid-reactive group Y¹Acid reactive group converting group Y convertible to²It is a general term.
[0146]
In the present invention, the acid-reactive group Y¹Means an acid-dissociable or acid-decomposable functional group and an acid-condensable functional group.
[0147]
(1) Acid-dissociable or acid-decomposable functional group:
An acid-dissociable or acid-decomposable functional group is a functional group that is insoluble or hardly soluble in an alkali before reacting with an acid, but can be solubilized in an alkali by the action of an acid. This change in solubility in alkali makes it usable as a base polymer for a positive resist.
[0148]
Specifically, an -OH group, -COOH group, -SO by the action of an acid or cation._ThreeAs a result, the fluoropolymer itself becomes soluble in an alkali.
[0149]
The acid-dissociable or acid-decomposable functional group specifically includes
[0150]
Embedded image

[0151]
(Wherein R⁷, R⁸, R⁹, R^Ten, R¹¹, R¹², R¹⁴, R¹⁸, R¹⁹, R²⁰, R^{twenty one}, R^{twenty two}, R^{twenty four}, R^{twenty five}, R²⁶, R²⁷, R²⁸, R²⁹Are the same or different and are hydrocarbon groups having 1 to 10 carbon atoms; R¹³, R¹⁵, R¹⁶Are the same or different, H or a hydrocarbon group having 1 to 10 carbon atoms; R¹⁷, R^{twenty three}Are the same or different and are divalent hydrocarbon groups having 2 to 10 carbon atoms)
Can be preferably used, more specifically
[0152]
Embedded image

[0153]
Etc. are preferably exemplified.
[0154]
(2) Acid condensation reactive functional group:
The functional group having acid condensation reactivity is soluble in an alkaline developer (or other developing solvent) before reacting with the acid, but the polymer itself is converted into an alkaline developer (or other developing agent) by the action of the acid. It is a functional group that can be insoluble in a solvent.
[0155]
Specifically, self-condensation by the action of acid or cation, polycondensation or functional group that causes condensation reaction or polycondensation reaction with crosslinking agent by the action of acid, or rearrangement reaction by acid or cation (for example, Functional groups that cause a change in polarity due to pinacol rearrangement, carbinol rearrangement, etc., and in any case, the polymer itself is insoluble in an alkaline developer (or other developing solvent).
[0156]
Such insolubilization can be used as a base polymer for negative resists.
[0157]
Examples of the acid condensable functional group include —OH, —COOH, —CN, —SO._ThreeWhat is selected from H, an epoxy group and the like is a preferred specific example.
[0158]
When used, the crosslinking agent is not particularly limited and can be arbitrarily selected from those conventionally used as a crosslinking agent for negative resists. Preferred examples of the crosslinking agent include N-methylol melamine, N-alkoxymethylated melamine compound, urea compound, epoxy compound and isocyanate compound.
[0159]
The above acid-reactive group Y¹Among these, at least one of an OH group, an acid dissociable functional group that can be converted to an OH group by an acid, a COOH group, and an acid dissociable functional group that can be dissociated by an acid to be converted to a COOH group is preferable.
[0160]
As an acid dissociable functional group that can be converted to an OH group with an acid,
[0161]
Embedded image

[0162]
(Wherein R³¹, R³², R³³And R³⁴Are preferably the same or different and each is preferably an alkyl group having 1 to 5 carbon atoms.
[0163]
More specifically,
[0164]
Embedded image

[0165]
Can be preferably exemplified, in particular, the acid reactivity is good,
[0166]
Embedded image

[0167]
In view of good transparency, —OC (CH_Three)_Three, -OCH₂OCH_Three, -OCH₂OC₂H_FiveIs preferred.
[0168]
As an acid dissociable functional group that can be converted to a -COOH group with an acid,
[0169]
Embedded image

[0170]
(Wherein R³⁵, R³⁶, R³⁷, R³⁸, R³⁹, R⁴⁰, R⁴¹, R⁴², R⁴⁶, R⁴⁷, R⁴⁸Are the same or different and both are hydrocarbon groups having 1 to 10 carbon atoms; R⁴³, R⁴⁴Are the same or different and both are H or a hydrocarbon group having 1 to 10 carbon atoms; R⁴⁵Is a divalent hydrocarbon group having 2 to 10 carbon atoms).
[0171]
Embedded image

[0172]
Etc. are preferred.
[0173]
These acid reactive groups Y¹Is usually an acid-reactive group Y¹Can be introduced into the polymer by polymerizing according to the production method of the present invention.
[0174]
Or acid-reactive group Y¹Acid-reactive group converting group Y that can be converted to²Is polymerized according to the production method of the present invention, introduced into the polymer, and then subjected to the target acid-reactive group Y by polymer reaction.¹It can also be obtained by converting to.
[0175]
Target acid-reactive group Y by polymer reaction¹For example, the formula can be converted into
[0176]
Embedded image

[0177]
(Where X^Five, X⁶Is H or F; X⁷Is H, CH_ThreeOr CF_ThreeR represents a vinyl ester compound (acid-reactive group conversion group (ester group) Y) represented by an alkyl group having 1 to 5 carbon atoms or a fluorine-containing alkyl group;²Monomer) having an acid-reactive group conversion group Y by copolymerizing m1 and / or m2 with the production method of the present invention.²And the acid-reactive group converting group Y of the obtained fluoropolymer.²OH group (acid-reactive group Y¹) And the like.
[0178]
In the present invention, the acid-reactive group Y is introduced through these polymer reaction processes.¹It also includes a method for producing a fluorine-containing polymer having.
[0179]
In any case, according to the production method of the present invention, the acid-reactive group Y¹Can be efficiently obtained, and the solubility in a developer can also be improved.
[0180]
The fluorine-containing polymer having an acid-reactive functional group Y is a monomer (m2-2) having an acid-reactive functional group Y among monomers (m2) capable of giving an aliphatic ring structure, that is, the above-mentioned ( radical polymerization of at least one of m2-2a), (m2-2b) and (m2-2c) using a radical polymerization initiator in the presence of a chain transfer agent having a functional group of formula (1) It is obtained by.
[0181]
Alternatively, when the monomer (m2-1) having no acid-reactive functional group Y is used as the monomer (m2), the monomer (m1) having the acid-reactive functional group Y in the comonomer (n1). The monomer (m1-2) may be added to the monomer (m2) for copolymerization, and the structural unit (N1-2) having an acid-reactive functional group Y may be introduced in addition to the structural unit (M2). .
[0182]
As the monomer (n1-2) capable of introducing the acid-reactive functional group Y into any structural unit (N1-2), an ethylenic monomer having a copolymerizable acid-reactive functional group Y is preferable.
[0183]
Specifically, an acrylic monomer having an acid reactive functional group Y, a fluorine-containing acrylic monomer having an acid reactive functional group Y, an allyl ether monomer having an acid reactive functional group Y, A fluorine-containing allyl ether monomer having an acid-reactive functional group Y, a vinyl ether monomer having an acid-reactive functional group Y, a fluorine-containing vinyl ether monomer having an acid-reactive functional group Y, and the like are preferable.
[0184]
More specifically,
(Meth) acrylic acid, α-fluoroacrylic acid, α-trifluoromethyl acrylic acid, t-butyl (meth) acrylate, t-butyl-α-fluoroacrylate, t-butyl-α-trifluoromethyl acrylate,
[0185]
Embedded image

[0186]
(Where X¹And X²Are the same or different and both are H or F; X^ThreeIs H, F, CH_ThreeOr CF_ThreeX^FourIs H, F or CF_ThreeRf is a fluorine-containing alkylene group having 1 to 40 carbon atoms or a fluorine-containing alkylene group having an ether bond having 2 to 100 carbon atoms; a is an integer of 0 or 1-3; b is a fluorine-containing group represented by 0 or 1) It is an ethylenic monomer.
[0187]
Among other things:
CH₂= CF-CF₂O-Rf-Y
A fluorine-containing allyl ether compound represented by the formula (wherein Rf is the same as described above) is preferable.
[0188]
More specifically,
[0189]
Embedded image

[0190]
Preferred examples include fluorine-containing allyl ether compounds.
[0191]
Also the formula:
CF₂= CF-O-Rf-Y
A fluorine-containing vinyl ether compound represented by the formula (wherein Rf is the same as described above) is preferable.
[0192]
More specifically,
[0193]
Embedded image

[0194]
And fluorine-containing vinyl ether compounds such as
[0195]
In addition, as the fluorine-containing ethylenic monomer containing the acid-reactive functional group Y,
CF₂= CF-CF₂O-Rf-Y, CF₂= CF-Rf-Y,
CH₂= CH-Rf-Y, CH₂= CH-O-Rf-Y
(Rf is the same as above)
And more specifically, and more specifically,
[0196]
Embedded image

[0197]
Etc.
[0198]
The fluorine-containing polymer for resist having an acid-reactive functional group Y obtained by the production method of the present invention is preferably a formula (M-1):
-(M1)-(M2)-(N1)-(N)-(M-1)
(In the formula, the structural unit M1 is a repeating unit derived from a fluorine-containing ethylenic monomer (m1) having 2 or 3 carbon atoms and having at least one fluorine atom; The repeating unit derived from the monomer (m2) capable of giving an aliphatic ring structure to the combined main chain; the structural unit N1 is a monomer (n1) copolymerizable with the monomer (m1) and the monomer (m2) Structural unit N is a repeating unit derived from monomer (n) copolymerizable with monomer (m1), monomer (m2) and monomer (n1), Acid reactive group Y on at least one of M2 and N1¹Or acid-reactive group Y¹Y group convertible to²And the structural unit M2 has an acid-reactive group Y¹Or acid-reactive group Y¹Y group convertible to²The structural unit N1 and N may be the same), the structural unit M1 is 1 to 99 mol%, the structural unit M2 is 1 to 99 mol%, the structural unit N1 is 0 to 98 mol%, It is a fluorine-containing polymer for resists containing 0 to 98 mol% of the structural unit N.
[0199]
Furthermore, the fluorine-containing polymer for resist obtained by the production method of the present invention is preferably represented by the formula (M-2):
-(M1)-(M2-2)-(M2)-(N)-(M-2)
(In the formula, the structural units M1 and M2 are the same as those in the formula (M-1); the structural unit M2-1 is a monomer capable of giving an aliphatic ring structure to the polymer main chain, and is an acid-reactive group Y.¹Or acid-reactive group Y¹Y group convertible to²A repeating unit derived from the monomer (m2-2) having the structural unit N is derived from the monomer (n) copolymerizable with the monomer (m1), (m2-2) and the monomer (m2) 1 to 99 mol% of the structural unit M1, 1 to 99 mol% of the structural unit M2-2, 0 to 98 mol% of the structural unit M2, and 0 to 98 mol% of the structural unit N. It is a fluorine-containing polymer for resist.
[0200]
In the fluorine-containing polymer for resists of the formulas (M-1) and (M-2), the monomer (m1) that gives the repeating unit (M1) to the fluorine-containing polymer is a polymerizable, particularly a radically polymerizable carbon- It is a fluorine-containing ethylenic monomer having 2 or 3 carbon atoms having one carbon double bond and having at least one fluorine atom.
[0201]
The fluorine-containing ethylenic monomer (m1) is a monoene compound having one polymerizable carbon-carbon double bond, and does not form a repeating unit having a ring structure in the main chain even by polymerization.
[0202]
The fluorine-containing ethylenic monomer (m1) may or may not have an acid-reactive functional group Y in the monomer, but usually has an acid-reactive functional group. It is preferable to use a monomer that is free from the viewpoint of good radical polymerization reactivity and more effectively improving the transparency.
[0203]
Preferred examples of the fluorine-containing ethylenic monomer (m1) include those in which at least one hydrogen atom of ethylene or propylene is substituted with a fluorine atom. Other hydrogen atoms may be substituted with halogen atoms other than fluorine atoms.
[0204]
Among these, a monomer in which at least one fluorine atom is bonded to a carbon atom constituting a carbon-carbon double bond is preferable. Thereby, a fluorine atom can be effectively obtained which can introduce a fluorine atom into the repeating unit (M1), that is, in the polymer main chain, and give particularly excellent transparency in the vacuum ultraviolet region.
[0205]
Specifically, tetrafluoroethylene, chlorotrifluoroethylene, vinylidene fluoride, vinyl fluoride, trifluoroethylene, hexafluoropropylene, CH₂= CFCF_ThreePreferred is at least one monomer selected from the group consisting of:
[0206]
Among these, tetrafluoroethylene, chlorotrifluoroethylene, vinylidene fluoride or hexafluoropropylene is particularly preferred from the viewpoint of transparency, particularly tetrafluoroethylene and / or chlorotrifluoro. Ethylene is preferred.
[0207]
Monomer (m2) capable of providing an aliphatic ring structure structural unit M2 in the fluorine-containing polymer for resists of the formulas (M-1) and (M-2), an aliphatic ring structure having an acid-reactive functional group Y Preferred examples of the monomer that can give M2-2 are the same as those of the aforementioned monomers (m2) and (m2-2).
[0208]
In addition, in the fluorine-containing polymer for resists of the formulas (M-1) and (M-2), when a structural unit having an acid-reactive functional group Y is used as an arbitrary structural unit N1, N, the above-described acid reactivity is used. The same thing as the ethylenic monomer n1-2 which has the functional group Y can illustrate preferably.
[0209]
In the production method of the present invention, in addition to the monomer (m1), (m2), (m2-2) or (n1-2), as an optional monomer, a radical polymerizable monomer (n1) The fluorine-containing copolymer obtained may be copolymerized for the purpose of improving different properties such as mechanical strength and coatability.
[0210]
As such an arbitrary monomer (n1), in addition to the above-mentioned comonomer (n1-2), copolymerization with monomers (m1) and (m2) for constituting other structural units (M1) Choose from what you can do.
[0211]
For example,
Acrylic monomer (excluding the monomer described in (n1-2)):
[0212]
Embedded image

[0213]
Styrene monomer:
[0214]
Embedded image

[0215]
Ethylene monomer:
CH₂= CH₂, CH₂= CHCH_Three, CH₂= CHCl etc.
[0216]
Maleic monomer:
[0217]
Embedded image

[0218]
Allyl monomers:
CH₂= CHCH₂Cl, CH₂= CHCH₂OH, CH₂= CHCH₂COOH, CH₂= CHCH₂Br etc.
[0219]
Allyl ether monomers:
[0220]
Embedded image

[0221]
Other monomers:
[0222]
Embedded image

[0223]
Etc.
[0224]
The molecular weight of the fluorine-containing polymer of the formulas (M-1) and (M-2) obtained by the production method of the present invention is 1000 to 100,000, preferably 2000 to 50000, more preferably 2000 to 10,000 in terms of number average molecular weight. The weight average molecular weight is 2000 to 200000, preferably 3000 to 50000, more preferably 3000 to 10000.
[0225]
When the fluoropolymer for resists of the formulas (M-1) and (M-2) is produced, the solubility in a developer can be improved by using the production method of the present invention, and it is highly effective in an ultrafine processing process. This is preferable because a resolution pattern can be formed.
[0226]
In the present invention, an ethylenic monomer having 2 or 3 carbon atoms and a monomer (m1) having at least one fluorine atom, or a single monomer capable of providing an aliphatic ring structure in the polymer main chain The comonomer (n1) containing the body (m2-1), (m2-2), and, if necessary, the ethylenic monomer (n1-2) having an acid-reactive functional group is represented by the formula ( (Co) polymerization is carried out by various known methods using the chain transfer agent having the functional group 1).
[0227]
Polymerization methods include solution polymerization in an organic solvent in which the monomer is dissolved, suspension polymerization in the presence or absence of an appropriate organic solvent in an aqueous medium, and adding an emulsifier to the aqueous medium. An emulsion polymerization method performed, a bulk polymerization method performed without a solvent, or the like can be used. Of these, solution polymerization and suspension polymerization using an organic solvent are preferred.
[0228]
Although it does not restrict | limit especially as a polymerization solvent, A hydrocarbon type solvent, a fluorine-type solvent (fluorocarbon type), a chlorine type solvent, an alcohol type solvent, a ketone type solvent, an acetic acid ester type solvent, an ether type solvent, etc. are used preferably.
[0229]
Of these, a fluorine-based solvent and a chlorine-based solvent are preferable in that the solubility of the monomer and the radical polymerization initiator is good and the polymerization reaction can be favorably progressed. Specifically, it is preferably one or more selected from hydrofluorocarbons, hydrochlorocarbons, fluorochlorocarbons, and hydrochlorofluorocarbons.
[0230]
Polymerization is initiated by bringing a polymerization initiator, preferably an organic peroxide, into contact with the monomer and applying heat (at an inherent temperature of the organic peroxide) or by irradiating with active energy rays such as light or ionizing radiation. .
[0231]
Although it does not restrict | limit especially as a polymerization initiator, An organic peroxide or an azo initiator is preferable. The organic peroxide is preferably one or more selected from diacyl peroxides, oxyperesters, peroxyketals, dialkyl peroxides, and peroxydicarbonates.
[0232]
Of these, oxyperesters and diacyl peroxides are more preferable, which are preferable in that radical polymerization reactivity can be promoted and the transparency of the obtained polymer in the vacuum ultraviolet region can be further improved. Further, the hydrophilicity of the polymer itself is also improved, and this is particularly preferable in that the solubility of the fluorine-containing polymer having the acid-reactive functional group Y (after exposure or after removal of the protecting group) in the developer is improved.
[0233]
Examples of oxyperesters include 1,1,3-tetramethylbutylperoxyneodecanate, 1-cyclohexyl-1-methylethylperoxyneodecanate, tert-hexylperoxyneodecanate, and tert-butylperoxy. Neodecanate, tert-hexylperoxypivalate, tert-butylperoxypivalate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, 2,5-dimethyl-2,5 -Bis (2-ethylhexanoylperoxy) hexane, 1-cyclohexyl-1-methylethylperoxy 2-ethylhexanoate, tert-hexylperoxy 2-ethylhexanoate, tert-butylperoxy 2-ethyl Hexanoate, tert-butyl peroxy Butyrate, tert-butylperoxymaleic acid, tert-hexylperoxyisobutyl monocarbonate, tert-butylperoxy3,5,5-trimethylhexanoate, tert-butylperoxylaurate, tert-butylperoxyisobutyl Oxyperesters having an alkyl group such as monocarbonate and tert-butyl peroxyacetate are preferred.
[0234]
Furthermore, peroxyesters of an alkyl group having an aliphatic cyclic structure are preferable from the viewpoint that dry etch resistance can be improved. 1-cyclohexyl-1-methylethylperoxyneodecanate, 1-cyclohexyl-1 -Methyl ethyl peroxy 2-ethyl hexanoate is preferred.
[0235]
Preferred examples of the diacyl peroxide include isobutyryl peroxide, 3,5,5-trimethylhexanoyl peroxide, octanoyl peroxide, lauroyl peroxide, steroyl peroxide, and succinic acid peroxide.
[0236]
Specific examples of peroxydicarbonates include di-n-propyl peroxydicarbonate, diisopropyl peroxydicarbonate, bis (4-tert-butylcyclohexyl) peroxydicarbonate, di-2-ethoxymethyl peroxydi. Examples thereof include carbonate, di-2-ethylhexyl peroxydicarbonate, di-2-methoxybutyl peroxydicarbonate, and di (3-methyl-3-methoxybutyl) peroxydicarbonate.
[0237]
Examples of peroxyketals include 1,1-bis (tert-hexylperoxy) 3,3,5-trimethylcyclohexane, 1,1-bis (tert-hexylperoxy) cyclohexane, 1,1-bis ( tert-butylperoxy) 3,3,5-trimethylcyclohexane, 1,1-bis (tert-butylperoxy) cyclohexane, 1,1-bis (tert-butylperoxy) cyclododecane, 2,2-bis ( tert-butylperoxy) valerate, 2,2-bis (4,4-tert-butylperoxycyclohexyl) propane, and the like.
[0238]
Further, from the viewpoint of transparency, it is preferable to use a peroxide having a fluorine atom, and among them, a diacyl peroxide having a fluorine atom is more preferable. Specifically, pentafluoropropionoyl peroxide: (CF_ThreeCF₂COO)₂, Heptafluorobutyryl peroxide: (CF_ThreeCF₂CF₂COO)₂7H-dodecafluoroheptanoyl peroxide: (CHF₂CF₂CF₂CF₂CF₂CF₂COO)₂Is more preferable.
[0239]
Examples of the azo compounds include dimethyl-2,2′-azobisisobutyrate, 2,2′-azobis (2,4,4-trimethylpentane), 2,2′-azobis (2-methylpropane), Examples thereof include dibutyl-2,2′-azobisisobutyrate.
[0240]
In addition, a polymerization initiator having a hydrophilic functional group is preferable in that a hydrophilic functional group can be introduced into the polymerization terminal and development characteristics can be improved. Specific examples include succinic acid peroxide, 2,2′-azobis {2-methyl-N- [1,1-bis (hydroxymethyl) -2-hydroxyethyl] propionamide}, 2,2′-azobis. {2-Methyl-N- [2- (hydroxybutyl)] propionamide}, 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) propionamide], 2,2′-azobis {2 -[1- (hydroxyethyl) -2-imidazolin-2-yl] propane} dihydrochloride, 2,2'-azobis [N- (2-carboxyethyl) -2-methylpropionamidine], 2,2'- Azobis (2-methylpropionamidooxime), 4,4′-azobis (4-cyanovaleric acid), dimethyl-2,2′-azobis (2-methylpropio) Over G), such as 1,1'-azobis (1-acetoxy-1-phenylethane) is preferably mentioned.
[0241]
Moreover, when manufacturing the polymer which has a structural unit derived from m2 using the fluorine-containing ethylenic monomer m2 of this invention, the organic peroxide of 5-130 degreeC is 10-hour half-life temperature among organic peroxides. It is preferable to use those having a 10-hour half-life temperature of 15 to 100 ° C., particularly 30 to 80 ° C., from the viewpoint of good polymerization reactivity.
[0242]
The composition of the copolymer to be formed can be controlled by the composition of the monomer to be charged.
[0243]
The molecular weight can be controlled by the concentration of the monomer used for the polymerization, the concentration of the organic peroxide, the concentration of the chain transfer agent, and the temperature.
[0244]
The amount of the organic peroxide used relative to the monomer used is appropriately selected according to the type of monomer used, the composition and molecular weight of the target polymer, and is 0.005 to 100 parts by weight of the monomer. 10 parts by weight, preferably 0.01 to 5 parts by weight, more preferably 0.1 to 1 part by weight. From another viewpoint, the organic peroxide is 0.01 to 10 mol%, preferably 0.05 to 5 mol%, more preferably 0.1 to 2 mol%, based on the molar amount of the monomer used. It is.
[0245]
If the amount of the organic peroxide is too small, the polymerization reaction does not proceed sufficiently and unreacted monomers remain, or an oligomer component is formed, resulting in coloration of the polymer and a decrease in transparency. Too much organic peroxide is not preferable because it causes a decrease in the molecular weight of the polymer and lowers the transparency, or unreacted organic peroxide remains, resulting in coloration of the polymer and a decrease in transparency.
[0246]
In the production method of the present invention, the amount of the chain transfer agent having a functional group represented by formula (1) is appropriately selected depending on the type of monomer used, the composition and molecular weight of the target polymer, and the like. The chain transfer agent of the formula (1) is 0.01 to 20 mol%, preferably 0.05 to 10 mol%, more preferably 0.1 to 5 mol%, particularly preferably 0.1 to 5 mol% with respect to the molar amount of the monomer. It is 2-2 mol%.
[0247]
If the amount of the chain transfer agent used is too small, the effect of improving the solubility in the developer may not be sufficiently obtained, and if the amount of the chain transfer agent used is too large, the polymerization reaction does not proceed smoothly, The polymerization reaction is stopped or the polymerization reaction rate is lowered, and as a result, a low molecular weight component may remain.
[0248]
These chain transfer agents may be present all at once from the initial stage of the polymerization reaction, or may be added continuously or intermittently as the polymerization reaction proceeds.
[0249]
The reaction temperature in the polymerization using the chain transfer agent of the present invention can be appropriately selected according to, for example, the 10-hour half-life temperature of each organic peroxide used, and further according to the target reaction time. It is -150 degreeC, Preferably it is 5-120 degreeC, More preferably, it is 10-100 degreeC.
[0250]
What is necessary is just to select the composition of the monomer in the case of copolymerizing according to the characteristic provided to the fluoropolymer obtained other than the polymerization reactivity and copolymerization reaction ratio of each monomer. The characteristics that each monomer can give to the fluoropolymer are as described above. More specifically, it will be described later.
[0251]
The fluorine-containing polymer obtained by the production method of the present invention is highly transparent to light in the vacuum ultraviolet region having a wavelength of 200 nm or less. Therefore, photolithography using an ArF excimer laser (193 nm) or F2 laser (157 nm). It is a resist polymer particularly useful in the process.
[0252]
The present invention further provides
(A-1) At least one acid reactivity of an OH group, an acid dissociable functional group that can be converted to an OH group by an acid, a COOH group, or an acid dissociable functional group that can be dissociated by an acid to be converted to a COOH group Group Y¹A fluorine-containing polymer having
(B) a photoacid generator, and
(C) Solvent
A composition comprising:
The fluoropolymer (A-1) relates to a photoresist composition which is a polymer obtained by the above-described production method of the present invention.
[0253]
In the photoresist composition of the present invention, the acid-reactive functional group Y is an OH group, an acid-dissociable functional group that can be converted to an OH group by an acid, an acid dissociation that can be dissociated by a COOH group or an acid and converted into a COOH group. A specific acid-reactive group Y of at least one of functional groups¹The fluorine-containing polymer (A-1) having
[0254]
As the acid dissociable functional group that can be converted to an OH group by an acid and the acid dissociable functional group that can be converted to a -COOH group by an acid, those described above can be adopted.
[0255]
Specific acid-reactive group Y¹As the fluorine-containing polymer (A-1) having the following, the following polymers are preferred.
[0256]
(I) Formula:
-(M1)-(M2-2a)-
(Wherein, M1 is a structural unit derived from a monomer (m2) having 2 or 3 carbon atoms and having at least one fluorine atom; M2-2a is a monocyclic aliphatic unsaturated group. Hydrocarbon compound with acid reactive group Y¹A fluorine-containing polymer represented by a monomer (m2-2a) optionally having a fluorine atom.
[0257]
The composition ratio of the structural units (M1) and (M2-2a) is usually 80/20 to 20/80 mol%, preferably 70/30 to 30/70 mol%, particularly preferably 60/40 to The ratio is 40/60 mol%.
[0258]
As specific examples of the monomer, the acid-reactive functional group Y is the acid-reactive group Y among the specific examples of the monomer (m1) and the specific example of the monomer (m2-2a).¹The thing which is is can illustrate preferably.
[0259]
(II) Formula:
-(M1)-(M2-2b)-
(Wherein M1 is the same as above; (M2-2b) is the acid-reactive group Y described above.¹A fluorine-containing polymer represented by an aliphatic polycyclic structure-containing monomer (m2-2b), particularly a structural unit derived from a norbornene derivative.
[0260]
The composition ratio of the structural units (M1) and (M2-2b) is usually 80/20 to 20/80 mol% ratio, preferably 70/30 to 30/70 mol% ratio, particularly preferably 60/40 to The ratio is 40/60 mol%.
[0261]
As specific monomers, the acid-reactive functional group Y is the acid-reactive group Y among the specific examples of the monomer (m1) and the specific example of the monomer (m2-2b).¹The thing which is is can illustrate preferably.
[0262]
These fluorine-containing polymers (I) and (II) are excellent in transparency and dry etching resistance, and further in the vacuum ultraviolet region by the production method of the present invention using a fluorine-containing polymerization initiator. Transparency can be improved.
[0263]
(III) Formula:
-(M1)-(M2-1a)-(N1-2)-
(Wherein M1 is the same as above; M2-1a is a monocyclic monomer having a polymerizable carbon-carbon unsaturated bond in the ring structure and no acid-reactive functional group Y (m2- 1a) derived structural unit; N1-2 is an acid reactive group Y¹A fluorine-containing polymer represented by a copolymerizable ethylenic monomer (structural unit derived from n1-2)).
[0264]
The composition ratio of the structural units (M1), (M2-1a), and (N1-2) is (M1) + (M2-1a) + (N1-2) = 100 mol%, and (M1) + (M2 -1a) / (N1-2) is usually 90 / 10-20 / 80 mol% ratio, preferably 80 / 20-30 / 70 mol% ratio, particularly preferably 70 / 30-40 / 60 mol% ratio. is there.
[0265]
As specific monomers, among the specific examples of the monomers (m1) and (m2-1a) and the specific examples of the monomer (n1-2), the acid-reactive functional group Y is an acid reaction. Sex group Y¹The thing which is is can illustrate preferably.
[0266]
(IV) Formula:
-(M1)-(M2-1b)-(N1-2)-
(In the formula, M1 and N1-2 are the same as above; M2-1b is an aliphatic polycyclic structure-containing monomer having no acid-reactive functional group Y (m2-1b), particularly a structure derived from a norbornene derivative. Unit).
[0267]
The composition ratio of the structural units (M1), (M2-1b), and (N1-2) is (M1) + (M2-1b) + (N1-2) = 100 mol%, and (M1) + (M2 -1b) / (N1-2) is usually 90 / 10-20 / 80 mol% ratio, preferably 80 / 20-30 / 70 mol% ratio, particularly preferably 70 / 30-40 / 60 mol% ratio. is there.
[0268]
As specific monomers, among the specific examples of the monomers (m1) and (m2-1b) and the specific examples of the monomer (n1-2), the acid-reactive functional group Y is an acid reaction. Sex group Y¹The thing which is is can illustrate preferably.
[0269]
These fluorine-containing polymers (III) and (IV) are excellent in dry etching resistance, and are transparent in the vacuum ultraviolet region by the production method of the present invention using a chain transfer agent having a functional group. The development characteristics can be further improved while maintaining the properties.
[0270]
In addition, the acid-reactive group Y of (I) to (IV)¹The fluorine-containing polymer is different from conventional fluorine-containing polymers for resist in that a hydrophilic atomic group is imparted to the polymer terminal by the production method of the present invention, and particularly excellent in solubility in a developer. Yes. Furthermore, the transparency of the polymer itself at a wavelength of 157 nm is also excellent.
[0271]
In the photoresist composition of the present invention, the acid-reactive group Y¹The fluorine-containing polymer (A-1) having an excellent transparency at a wavelength of 157 nm, in particular, an absorption coefficient at 157 nm is 2.0 μm.^-1The following, preferably 1.5 μm^-1The following, particularly preferably 1.0 μm^-1The following, or even 0.5 μm^-1The following are preferable, and the lower the extinction coefficient at a wavelength of 157 nm, the more preferable is the point that a good resist pattern can be formed by using as the F2 photoresist composition.
[0272]
In the photoresist composition of the present invention, as the photoacid generator (B), those similar to the photoacid generator (B) described in WO 01/74916 can be preferably exemplified. It can also be used effectively in the invention.
[0273]
Specifically, it is a compound that generates an acid or a cation by irradiating light, for example, an organic halogen compound, a sulfonate ester, an onium salt (especially when the central element is iodine, sulfur, selenium, tellurium, nitrogen or phosphorus). A certain fluoroalkylonium salt), a diazonium salt, a disulfone compound, a sulfonediazide, and the like, or a mixture thereof.
[0274]
More preferable specific examples are as follows.
[0275]
(1) TPS system:
[0276]
Embedded image

[0277]
(Where X^-Is PF₆ ^-, SbF₆ ^-, CF_ThreeSO_Three ^-, C_FourF₉SO_Three ^-Etc; R^1a, R^1b, R^1cAre the same or different and CH_ThreeO, H, t-Bu, CH_Three, OH, etc.)
[0278]
(2) DPI system:
[0279]
Embedded image

[0280]
(Where X^-Is CF_ThreeSO_Three ^-, C_FourF₉SO_Three ^-, CH_Three-Φ-SO_Three ^-, SbF₆ ^-,
[0281]
Embedded image

[0282]
Etc; R^2a, R^2bAre the same or different and H, OH, CH_Three, CH_ThreeO, t-Bu, etc.)
[0283]
(3) Sulfonate type:
[0284]
Embedded image

[0285]
(Wherein R^4aIs
[0286]
Embedded image

[0287]
Such)
[0288]
The content of the photoacid generator in the photoresist composition of the present invention is the acid reactive group Y.¹0.1 to 30 parts by weight is preferable, more preferably 0.2 to 20 parts by weight, and most preferably 0.5 to 10 parts by weight with respect to 100 parts by weight of the fluoropolymer (A-1) having is there.
[0289]
When the content of the photoacid generator is less than 0.1 parts by weight, the sensitivity is lowered. When the content of the photoacid generator is more than 30 parts by weight, the amount of the photoacid generator that absorbs light increases, and the light does not reach the substrate sufficiently. The resolution tends to decrease.
[0290]
Moreover, you may add the organic base which can act as a base with respect to the acid produced from said photo-acid generator to the photoresist composition of this invention. The organic base is preferably the same as that described in International Publication No. 01/74916, and can be used effectively in the present invention.
[0291]
Specifically, it is an organic amine compound selected from nitrogen-containing compounds, such as pyridine compounds, pyrimidine compounds, amines substituted with a hydroxyalkyl group having 1 to 4 carbon atoms, aminophenols, and the like. Hydroxyl group-containing amines are particularly preferable.
[0292]
Specific examples include butylamine, dibutylamine, tributylamine, triethylamine, tripropylamine, triamylamine, pyridine and the like.
[0293]
The content of the organic base in the photoresist composition of the present invention is preferably from 0.1 to 100 mol%, more preferably from 1 to 50 mol%, based on the content of the photoacid generator. When the amount is less than 0.1 mol%, the resolution tends to be low, and when the amount is more than 100 mol%, the sensitivity tends to be low.
[0294]
In addition to the photoresist composition of the present invention, additives described in the pamphlet of International Publication No. 01/74916, for example, dissolution inhibitors, sensitizers, dyes, adhesion improvers, water retention agents, etc. Various additives conventionally used in the field can also be contained.
[0295]
In the photoresist composition of the present invention, the solvent (C) is preferably the same as the solvent (C) described in International Publication No. 01/74916, and can be used effectively in the present invention. .
[0296]
Specifically, cellosolve solvents, ester solvents, propylene glycol solvents, ketone solvents, aromatic hydrocarbon solvents, or a mixed solvent thereof are preferable. Further, in order to increase the solubility of the fluoropolymer (A-1), CH_ThreeCCl₂A fluorine-containing hydrocarbon solvent such as F (HCFC-141b) or a fluorine solvent such as fluorine alcohols may be used in combination.
[0297]
The amount of these solvents (C) is selected depending on the type of solid content to be dissolved, the base material to be applied, the target film thickness, and the like. From the viewpoint of ease of application, the total solid content of the photoresist composition is selected. It is preferably used so that the partial concentration is 0.5 to 70% by weight, preferably 1 to 50% by weight.
[0298]
The photoresist composition of the present invention is used in a resist pattern forming method of conventional photoresist technology. In particular, in order to suitably perform the resist pattern forming method, first, a solution of a photoresist composition is coated on a support such as a silicon wafer with a spinner or the like, dried to form a photosensitive layer, and a reduced projection exposure apparatus For example, ultraviolet rays, deep-UV, excimer laser light, and X-rays are irradiated through a desired mask pattern or drawn with an electron beam and heated. This is then developed using a developer, for example an alkaline developer such as an alkaline aqueous solution such as an aqueous solution of 1 to 10% by weight tetramethylammonium hydroxide (TMAH). With this formation method, an image faithful to the mask pattern can be obtained.
[0299]
When forming a fine circuit pattern of a semiconductor device, a 2.38% by weight tetramethylammonium hydroxide aqueous solution is preferably used as a developer in a development step in a photolithography process.
[0300]
Furthermore, a surfactant or alcohol such as methanol, ethanol, propanol or butanol may be added to a 2.38 wt% tetramethylammonium hydroxide aqueous solution in order to adjust the paintability with the resist film.
[0301]
In particular, it has been found that by using the photoresist composition of the present invention, a highly transparent resist film (photosensitive layer) can be formed even in the vacuum ultraviolet region. Thereby, it can be preferably used for a photolithography process using an F2 laser (157 nm wavelength) which is under development with the aim of a technology node of 0.07 μm.
[0302]
The film coated with the photoresist of the present invention is formed by applying the above-described photoresist composition onto a support such as a silicon wafer by a coating method such as spin coating, and drying. It contains solid components such as a fluorine-containing polymer (A-1) having a reactive group, a photoacid generator (B), and other additives.
[0303]
The thickness of the resist film to be formed is usually a thin film of 1.0 μm or less, preferably 0.01 to 0.5 μm, more preferably 0.05 to 0.5 μm.
[0304]
Furthermore, the film coated with the photoresist composition of the present invention preferably has high transparency in the vacuum ultraviolet region, and specifically has an extinction coefficient of 2.5 μm at a wavelength of 157 nm.^-1The following, preferably 2.0 μm^-1Below, particularly preferably 1.50 μm^-1Below, further 1.0 μm^-1The following is preferable. This coating can be effectively used in a lithography process using F2 laser (157 nm) light.
[0305]
In addition, as the base material on which the resist film is applied, various base materials to which a conventional resist is applied can be similarly used. For example, any of a silicon wafer, a silicon wafer provided with an organic or inorganic antireflection film, and a glass substrate may be used. In particular, the sensitivity and profile shape on a silicon wafer provided with an organic antireflection film are good.
[0306]
The third of the present invention relates to a fluoropolymer having excellent solubility in a developer, and the first of the fluoropolymer of the present invention has an OH group and imparts solubility to a developer. The functional group is a fluorine-containing polymer having an aliphatic ring structure in the polymer main chain having only an OH group, and the polymer has the formula (M-3):
-(M1)-(M2-3)-(M2)-(N)-(M-3)
(In the formula, the structural unit M1 is an ethylenic monomer having 2 or 3 carbon atoms and is a repeating unit derived from a fluorine-containing ethylenic monomer (m1) having at least one fluorine atom; 3 is a repeating unit derived from a norbornene derivative (m2-3) which may have a fluorine atom having an OH group; the structural unit M2 is derived from a monomer (m2) capable of giving an aliphatic ring structure to the polymer main chain The structural unit N is represented by the monomer (m1), (m2-3), and the monomer (n) -repeating unit copolymerizable with the monomer (m2), and the structural unit M1. 24 to 70 mol%, 1 to 70 mol% of the structural unit M2-3, 0 to 69 mol% of the structural unit M2, 0 to 20 mol% of the structural unit N, and (M1) + (M2-3) When (M2) = 100, (M1) / {(M2-3) (M2)} is a fluorine-containing polymer having a number average molecular weight of 1000 to 50000 in a 30/70 to 70/30 molar ratio, and the fluorine-containing polymer was measured by the QCM measurement method described later. It is a fluorine-containing polymer for resists excellent in solubility in a developing solution having a dissolution rate in a weight% tetramethylammonium hydroxide aqueous solution of 500 nm / sec or more.
[0307]
The present inventors carried out copolymerization using a fluorine-containing ethylenic monomer (m1) and a norbornene derivative (m2-3) having an OH group, and if necessary, monomers (m2) and (n). As a result of intensive studies, even with the same polymer composition and the same molecular weight, the fluorine-containing weight is particularly excellent in solubility in the developer due to the difference in the manufacturing method, that is, the difference in the resulting end structure. A coalescence could be obtained.
[0308]
In the conventional method, the fluoropolymer having only an OH group as a functional group imparting solubility to a developer cannot obtain sufficient solubility in the developer. Even in a fluorine-containing polymer having only OH groups, the solubility (dissolution rate) is equal to or higher than that of a polymer having originally high solubility, such as a -COOH group, an ArF resist polymer not containing fluorine or a KrF resist polymer. A fluorine-containing polymer having was found. As a result, a fluoropolymer having both transparency at 157 nm and solubility in a developer could be obtained.
[0309]
Further, the second of the fluoropolymer of the present invention is an acid-dissociable functional group Y that dissociates by reacting part or all of the OH groups in the fluoropolymer with an acid.^ThreeThe fluorine-containing polymer in which the OH group is protected can be converted into an OH group by reacting with an acid, and then can be a polymer having excellent solubility in a developing solution. .
[0310]
That is, the fluorine-containing polymer having an OH group protected according to the present invention has an acid-dissociable functional group Y that can be converted to an OH group with an acid.^ThreeA fluoropolymer having an aliphatic ring structure in the polymer main chain, wherein the polymer is represented by the formula (M-4):
-(M1)-(M2-3)-(M2-4)-(N)-(M-4)
(In the formula, the structural unit M1 and the structural unit M2-3 are the same as the formula (M-3); the structural unit M2-4 is at least one functional group Y among acid dissociable functional groups that can be converted to an OH group with an acid.^ThreeA repeating unit derived from a norbornene derivative (m2-4) optionally having a fluorine atom; the structural unit N is the same as the monomer (m1), (m2-3) and the monomer (m2-4). The repeating unit derived from the polymerizable monomer (n)), the structural unit M1 is 24 to 70 mol%, the structural unit M2-3 is 0 to 69 mol%, and the structural unit M2-4 is 1 to 70 mol%. %, The structural unit N is 0 to 20 mol%, and (M1) + (M2-3) + (M2-4) = 100 (M1) / {(M2-3) + (M2-4) } Is a fluorine-containing polymer having a number average molecular weight of 1000 to 50000 in a 30/70 to 70/30 molar ratio, wherein the fluorine-containing polymer of the formula (M-4) is reacted with an acid to form a structural unit M2 Acid dissociable functional group Y in -4^ThreeIn the fluorine-containing polymer after the acid reaction in which is converted into an OH group, the functional group imparting solubility to the developer has only an OH group, and the QCM measurement of the fluorine-containing polymer after the acid reaction This is a fluorine-containing polymer for a resist having a dissolution rate of 500 nm / sec or more with respect to an aqueous 2.38 wt% tetramethylammonium hydroxide solution measured by the method.
[0311]
The QCM measurement method, which is a measurement method showing the developer dissolution rate of the above-mentioned fluoropolymer, is a method for measuring the polymer dissolution rate called the quartz crystal method, and is described in, for example, J. Photopolymer Sci. Technol. 12, 545-551 (1999) and Proc. This method is described in SPIE 4690, 904-911 (2002), and the dissolution behavior of a resist film in a developing solution has been studied. Specifically, a polymer film is formed on a quartz crystal plate on which gold or the like is vapor-deposited, and the change in film thickness (change in weight) is changed with the quartz crystal plate immersed in a developer. Is a method of measuring the rate of film thickness reduction. The dissolution rate of the fluoropolymer in the QCM method in the present invention is such that the solution of only the above-mentioned polymer dissolved in a solvent is applied to a quartz resonator plate, and the film thickness of the polymer alone is 80 to 150 nm by heating or the like. The film decrease rate was measured by the above method. Specifically, the speed plotted the change in the film thickness against the immersion time, and it was the central part of the film and the total film thickness. The reduction rate of the coating at the 60% portion is calculated.
[0312]
In order to form a target ultrafine resist pattern of 50 to 70 nm, the present inventors have a particularly high developer dissolution rate as compared with conventional fluoropolymers and further conventional resist polymers. I found it necessary.
[0313]
According to the present invention, a high-resolution ultrafine resist pattern can be obtained by using a fluorine-containing polymer having greatly improved developer solubility even if it is a fluorine-containing polymer having only an OH group as a developer-soluble group. It is possible.
[0314]
Moreover, the said fluoropolymer of this invention is further preferable at the point which is excellent in transparency at 157 nm, and dry-etching tolerance.
[0315]
The developer dissolution rate of the fluoropolymer of the present invention is 500 nm / sec or more by the above QCM measurement method, preferably 750 nm / sec or more, more preferably 1000 or more, and particularly preferably 1500 nm / sec or more. This is preferable because an ultrafine resist pattern with higher resolution can be obtained.
[0316]
On the other hand, as a result of examining the QCM measurement method for a polymer having a high development speed such as 750 nm / sec or more, by performing the same QCM measurement using a low-concentration developer such as a 0.595 wt% TMAH solution, It was found that measurement with high accuracy and good reproducibility was possible, and at the same time, the dissolution rate of the developer was compared.
[0317]
The dissolution rate measured with the 0.595 wt% TMAH solution is 1 nm / sec or more, preferably 2 nm / sec or more, more preferably 5 nm / sec or more, still more preferably 10 nm / sec or more, particularly preferably 20 nm / sec or more. is there.
[0318]
The functional group that imparts developer solubility of the fluorine-containing polymer for resists of the formulas (M-3) and (M-4) of the present invention is only an OH group, and the OH group does not lower the transparency at 157 nm. In terms of point, conversely, -COOH and -SO_ThreeIntroduction of H or the like is not preferable in that the transparency at 157 nm is lowered.
[0319]
The structural unit (M1) in the polymers of the formulas (M-3) and (M-4) of the present invention is an ethylenic monomer having 2 or 3 carbon atoms and has at least one fluorine atom. The same as those exemplified in the method for producing a polymer which is a repeating unit derived from the polymerizable monomer (m1) and is excellent in the solubility of the developer is preferably exemplified.
[0320]
The structural unit (M2-3) in the polymers of the formulas (M-3) and (M-4) of the present invention is a repeat derived from a norbornene derivative (m2-3) which may have a fluorine atom having an OH group. The norbornene derivative (m2-3) is a unit and is acid-reactive with respect to each of the examples of the norbornene derivative (m2-2b) having the acid-reactive group Y exemplified in the method for producing a polymer excellent in developer solubility. Likewise preferred are those in which the group Y is replaced by an OH group, among which the formula (3):
[0321]
Embedded image

[0322]
(Where Rf²Is preferably a norbornene derivative having a structure represented by a fluorine-containing alkyl group having 1 to 10 carbon atoms or a fluorine-containing alkyl group having an ether bond, excellent in solubility in a developer, and transparent to 157 nm light. It is preferable at the point which is excellent in.
[0323]
In the site of formula (3), Rf²Is preferably a C 1-10 perfluoroalkyl group, more preferably a C 1-5 perfluoroalkyl group, and even more preferably CF._ThreeIt is particularly preferred that
[0324]
The site of the formula (3) is a fluorine-containing alkyl group Rf²And the OH group may be simultaneously bonded to the carbon atom forming the ring structure of the norbornene derivative, or may be simultaneously bonded to the carbon atom not forming the ring structure, and the site of the formula (3) It may be bonded to the carbon atom to be formed in the form of a side chain.
[0325]
The acid dissociable functional group Y contained in the structural unit (M2-4) in the polymer of the formula (M-4) of the present invention^ThreeIs a functional group that reacts with an acid generated from a photoacid generator and changes to an OH group, and similarly exhibits excellent developer solubility even after being changed to an OH group. Furthermore, the transparency at 157 nm light is also excellent.
[0326]
Acid-dissociable functional group Y^ThreeSpecifically, the same as those exemplified above are preferable, for example,
[0327]
Embedded image

[0328]
(Wherein R³¹, R³², R³³And R³⁴Are preferably the same or different and each is preferably an alkyl group having 1 to 5 carbon atoms.
[0329]
More specifically,
[0330]
Embedded image

[0331]
Can be preferably exemplified, in particular, the acid reactivity is good,
[0332]
Embedded image

[0333]
In view of good transparency, —OC (CH_Three)_Three, -OCH₂OCH_Three, -OCH₂OC₂H_FiveIs preferred.
[0334]
Furthermore, what contains the structure of the said Formula (3) in a norbornene derivative is preferable.
[0335]
In the polymer of the formula (M-3) of the present invention, the structural unit M2 is a repeating unit derived from the monomer (m2) capable of giving an aliphatic ring structure to the polymer main chain, and has excellent developer solubility. Among those exemplified in the method for producing a polymer, those other than the structural unit (M2-2) described above are arbitrary structural units.
[0336]
Preferably, it is a structural unit having a monocyclic or polycyclic structure not containing a functional group in the polymer main chain, for example, a repeating unit derived from the aforementioned monomers (m2-1a) and (m2-1b). . It is mainly introduced for the purpose of adjusting the solubility with a solvent, the coatability with a substrate, the glass transition temperature of a polymer, and the mechanical properties.
[0337]
In the polymers of the formulas (M-3) and (M-4) of the present invention, the structural unit N is an arbitrary structural unit, and the ethylenic monomer is the same as the structural unit N exemplified in the method for producing a polymer. It is selected from structural units derived from the body and is introduced for the purpose of adjusting the solubility with a solvent, the wettability with a substrate, and the like. Furthermore, it does not contain a functional group that imparts developer solubility, or has an acid-dissociable functional group that reacts with an OH group or an acid and changes to an OH group. Thereby, the solubility of the developer can be further improved, which is preferable. However, it is 20 mol% or less, preferably 15 mol% or less, more preferably 10 mol% or less, and 5 mol% or less in the polymer having excellent developer solubility of the present invention. When the polymer does not contain the structural unit N and has sufficient developer solubility, the structural unit N is particularly preferably contained.
[0338]
An excessive amount of the structural unit N derived from an ethylenic monomer as an optional component is not preferable because dry etch resistance decreases.
[0339]
The total of the structural unit (M1) derived from the fluorine-containing ethylenic monomer and the structural unit forming a ring structure in the main chain in the polymer of the formula (M-3) of the present invention, that is, {(M2-3) + ( The abundance ratio of M2)} is (M1) + (M2-3) + (M2) = 100. (M1) / {(M2-3) + (M2)} is 30/70 to 70/30 molar ratio Preferably, it is 35 / 65-65 / 35 molar ratio, More preferably, it is 40 / 60-60 / 40 molar ratio, More preferably, it is 40 / 60-50 / 50 molar ratio.
[0340]
If the ratio of the structural unit (M1) is too large, the solubility of the developer is lowered, and if the ratio of the structural unit (M1) is too small, the transparency with 157 nm light is lowered, which is not preferable.
[0341]
If the ratio of the structural unit {(M2-3) + (M2)} forming the ring structure is too large, the transparency at 157 nm light is lowered, and the ratio of the structural unit {(M2-3) + (M2)} If it is too small, the dry etch resistance is lowered, which is not preferable.
[0342]
Similarly, in the polymer of the formula (M-4) of the present invention, the total of the structural unit (M1) derived from the fluorine-containing ethylenic monomer and the structural unit forming a ring structure in the main chain, that is, {(M2- 3) When the existence ratio of + (M2-4)} is (M1) + (M2-3) + (M2-4) = 100, (M1) / {(M2-3) + (M2-4)} Is a 30/70 to 70/30 molar ratio, preferably a 35/65 to 65/35 molar ratio, more preferably a 40/60 to 60/40 molar ratio, and even more preferably a 40/60 to 50/50 molar ratio. It is. If the proportion of the structural unit (M1) is too large, the solubility of the developer after acid dissociation is lowered, and if the proportion of the structural unit (M1) is too small, the transparency with 157 nm light is lowered, which is not preferable.
[0343]
If the ratio of the structural unit {(M2-3) + (M2-4)} forming the ring structure is too large, the transparency at 157 nm light is lowered, and the structural unit {(M2-3) + (M2-4) } Is not preferable because the dry etch resistance is lowered.
[0344]
The molecular weights of the polymers of the formulas (M-3) and (M-4) of the present invention are both 1000 to 50000 in terms of number average molecular weight, preferably 1500 to 30000, more preferably 2000 to 20000, and still more preferably 2000 to 20000. If the molecular weight is too low, it is not preferable because the transparency is lowered and the dry etch resistance is lowered. On the other hand, if the molecular weight is too high, the solubility of the developer is lowered, which is not preferable.
[0345]
The polymers of the formulas (M-3) and (M-4) of the present invention are excellent in transparency at 157 nm light, specifically, the extinction coefficient at 157 nm wavelength is 1.5 μm.^-1The following, preferably 1.0 μm^-1Below, particularly preferably 0.6 μm^-1The following is preferable. These fluoropolymers can be effectively used in a lithography process using a light beam of F2 laser (157 nm).
[0346]
The present invention further provides
(A-2) At least one acid-reactive group Y of an acid-dissociable functional group that can be converted to an OH group by an OH group or an acid^FourA fluorine-containing polymer having
(B) a photoacid generator, and
(C) Solvent
A composition comprising:
The fluorine-containing polymer (A-2) relates to a photoresist composition which is a polymer of the formula (M-3) and / or the formula (M-4) of the present invention.
[0347]
In the photoresist composition of the present invention, the fluorine-containing polymer (A-2) is preferably the same as those exemplified for the polymers of the formulas (M-3) and (M-4).
[0348]
In the photoresist composition of the present invention, the type and use ratio of the photoacid generator (B) are exemplified in the photoresist composition containing the fluoropolymer (A-1) obtained by the above-described novel production method. A thing similar to a photo-acid generator (B) is mention | raise | lifted preferably.
[0349]
In the photoresist composition of the present invention, the type and use ratio of the solvent (C) are the solvents (C) exemplified in the photoresist composition containing the fluoropolymer (A-1) obtained by the above-described novel production method. ) Are preferred.
[0350]
In the photoresist composition of the present invention, additives other than the photoacid generator (B) and the solvent (C) are the same as those exemplified for the photoresist composition containing the above-mentioned fluoropolymer (A-1). Can be preferably used.
[0351]
The photoresist composition of the present invention is used in a resist pattern forming method of conventional photoresist technology. In particular, in order to suitably perform the resist pattern forming method, first, a solution of a photoresist composition is coated on a support such as a silicon wafer with a spinner or the like, dried to form a photosensitive layer, and a reduced projection exposure apparatus For example, ultraviolet rays, deep-UV, excimer laser light, and X-rays are irradiated through a desired mask pattern or drawn with an electron beam and heated. Next, this is developed using a developer, for example, an alkaline aqueous solution such as an aqueous solution of 1 to 10% by weight of tetramethylammonium hydroxide. With this formation method, an image faithful to the mask pattern can be obtained.
[0352]
When forming a fine circuit pattern of a semiconductor device, a 2.38% by weight tetramethylammonium hydroxide aqueous solution is preferably used as a developer in a development step in a photolithography process.
[0353]
Furthermore, a surfactant or alcohol such as methanol, ethanol, propanol or butanol may be added to a 2.38 wt% tetramethylammonium hydroxide aqueous solution in order to adjust the paintability with the resist film.
[0354]
In particular, it has been found that by using the photoresist composition of the present invention, a highly transparent resist film (photosensitive layer) can be formed even in the vacuum ultraviolet region. Thereby, it can be preferably used for a photolithography process using an F2 laser (157 nm wavelength) which is under development with the aim of a technology node of 0.07 μm.
[0355]
The film coated with the photoresist of the present invention is formed by applying the above-described photoresist composition onto a support such as a silicon wafer by a coating method such as spin coating and drying, and in the film, OH Solid components such as a fluorine-containing polymer (A-2) having an acid-dissociable functional group that can be converted into an OH group by a group and / or an acid, a photoacid generator (B), and other additives are included.
[0356]
The thickness of the resist film to be formed is usually a thin film of 1.0 μm or less, preferably 0.01 to 0.5 μm, more preferably 0.05 to 0.5 μm.
[0357]
Further, the film coated with the photoresist composition of the present invention preferably has a high transparency in the vacuum ultraviolet region, and specifically has an extinction coefficient of 157 nm wavelength of 2.0 μm.^-1The following, preferably 1.5 μm^-1Below, particularly preferably 1.0 μm^-1Below, further 0.6μm^-1The following is preferable. This coating can be effectively used in a lithography process using F2 laser (157 nm) light.
[0358]
In addition, as the base material on which the resist film is applied, various base materials to which a conventional resist is applied can be similarly used. For example, any of a silicon wafer, a silicon wafer provided with an organic or inorganic antireflection film, and a glass substrate may be used. In particular, the sensitivity and profile shape on a silicon wafer provided with an organic antireflection film are good.
[0359]
【Example】
Next, the present invention will be described with reference to examples, but the present invention is not limited to these examples.
[0360]
Experimental Example 1 (Synthesis of copolymer of TFE and OH group-containing fluorine-containing norbornene (NB-1) using methanol)
A 500 ml autoclave equipped with a valve, a pressure gauge, a stirrer and a thermometer was replaced with nitrogen several times and then evacuated to obtain an OH group-containing fluorine-containing norbornene (NB-1):
[0361]
Embedded image

[0362]
Of 39.0 g and 250 ml of HCFC-141b was charged. Next, 58.0 g of TFE was charged from the valve, and pentafluoropropionoyl peroxide: (CF_ThreeCF₂COO)₂A 10.0 wt% perfluorohexane solution (10.5 g) and methanol (0.22 g) were added and stirred at 35 ° C. for 3 hours for reaction.
[0363]
After releasing the unreacted monomer, the polymerization solution was taken out, concentrated and then reprecipitated with hexane to separate the copolymer. Vacuum drying was performed until a constant weight was obtained, to obtain 3.2 g of a copolymer.
[0364]
The composition ratio of this copolymer is¹H-NMR and¹⁹From the results of F-NMR analysis, it was a 50/50 mol% copolymer of TFE / the OH group-containing fluorine-containing norbornene derivative (NB-1).
The number average molecular weight was 3600 by GPC analysis.
[0365]
Experimental Example 2 (Synthesis of copolymer of TFE using methanol and OH group-containing fluorine-containing norbornene (NB-1))
The reaction was conducted in the same manner as in Experimental Example 1 except that 0.11 g of methanol was used as a chain transfer agent in Experimental Example 1, to obtain 3.7 g of a copolymer.
[0366]
The composition ratio of this copolymer is¹H-NMR and¹⁹From the results of F-NMR analysis, it was a 50/50 mol% copolymer of TFE / the OH group-containing fluorine-containing norbornene derivative (NB-1).
The number average molecular weight was 3700 by GPC analysis.
[0367]
Experimental Example 3 (Synthesis of copolymer of TFE and OH group-containing fluorine-containing norbornene derivative (NB-1))
In Experimental Example 1, the reaction was performed in the same manner as in Experimental Example 1 except that no chain transfer agent was used, to obtain 3.5 g of a copolymer.
[0368]
The composition ratio of this copolymer is¹H-NMR and¹⁹From the results of F-NMR analysis, it was a 50/50 mol% copolymer of TFE / the OH group-containing fluorine-containing norbornene derivative (NB-1).
The number average molecular weight was 3700 by GPC analysis.
[0369]
Experimental Example 4 (Synthesis of copolymer of TFE and OH group-containing fluorine-containing norbornene (NB-1))
In Experimental Example 1, no chain transfer agent was used, 30.6 g of OH group-containing fluorine-containing norbornene derivative (NB-1), and peroyl TCP (bis (4-t-butylcyclohexyl) peroxydicarbonate as a polymerization initiator ) Was used at 40 ° C. in the same manner as in Experimental Example 1 except that 6.5 g was used to obtain 3.9 g of a copolymer.
[0370]
The composition ratio of this copolymer is¹H-NMR and¹⁹From the results of F-NMR analysis, it was a 50/50 mol% copolymer of TFE / the OH group-containing fluorine-containing norbornene derivative (NB-1).
The number average molecular weight was 3700 by GPC analysis.
[0371]
Experimental Example 5 (TFE using methanol as chain transfer agent, OH group-containing fluorine-containing norbornene derivative (NB-1) and OCH₂OCH₂CH_ThreeSynthesis of copolymer with group-containing fluorine-containing norbornene derivative (NB-2))
In Experimental Example 1, 23.5 g of (NB-1) and OCH₂OCH₂CH_ThreeGroup-containing fluorine-containing norbornene derivative (NB-2):
[0372]
Embedded image

[0373]
Was used in the same manner as in Experimental Example 1 except that 18.9 g was used, to obtain 3.0 g of a copolymer.
[0374]
The composition ratio of this copolymer is¹H-NMR and¹⁹From the results of F-NMR analysis, TFE / the OH group-containing fluorine-containing norbornene derivative (NB-1) / the OCH₂OCH₂CH_ThreeThe group-containing fluorine-containing norbornene derivative (NB-2) was a 50/30/20 mol% copolymer.
The number average molecular weight was 3000 by GPC analysis.
[0375]
Experimental Example 6 (OCH₂OCH₂CH_ThreeGroup deprotection)
Into a 50 ml eggplant flask equipped with a reflux tube, 1.0 g of the polymer obtained in Experimental Example 5 was added, 20 ml of dichloromethane and 0.5 g of trifluoroacetic acid were added thereto, and the mixture was reacted for 3 hours at a temperature at which dichloromethane was refluxed with stirring. It was. After completion of the reaction, the dichloromethane solution was washed with water and dried over anhydrous sodium sulfate, and then the dichloromethane was distilled off with an evaporator, followed by vacuum drying at 60 ° C. until a constant weight was obtained to obtain 0.7 g of a white solid.¹H-NMR and¹⁹From F-NMR analysis, TFE / the OH group-containing fluorine-containing norbornene derivative (NB-1) / the OCH₂OCH₂CH_ThreeThe group-containing fluorine-containing norbornene derivative (NB-2) was a copolymer of 50 / 49.5 / 0.5 mol%.
[0376]
Experimental Example 7 (Synthesis of copolymer of TFE and OH group-containing fluorine-containing norbornene derivative (NB-1))
In Experimental Example 1, 23.5 g of OH group-containing fluorine-containing norbornene derivative (NB-1) without using a chain transfer agent, OCH₂OCH₂CH_ThreeA reaction was carried out in the same manner as in Experimental Example 1 except that 18.9 g of the group-containing fluorine-containing norbornene derivative (NB-2) was used, to obtain 2.9 g of a copolymer.
[0377]
The composition ratio of this copolymer is¹H-NMR and¹⁹From the results of F-NMR analysis, TFE / the OH group-containing fluorine-containing norbornene derivative (NB-1) / the OCH₂OCH₂CH_ThreeThe group-containing fluorine-containing norbornene derivative (NB-2) was a 50/29/21 mol% copolymer.
The number average molecular weight was 3000 by GPC analysis.
[0378]
Experimental Example 8 (OCH₂OCH₂CH_ThreeGroup deprotection)
In a 50 ml eggplant flask equipped with a reflux tube, 1.0 g of the polymer obtained in Experimental Example 7 was taken and reacted and isolated with trifluoroacetic acid in the same manner as in Experimental Example 6 to obtain 0.8 g of a white solid. .¹H-NMR and¹⁹From F-NMR analysis, TFE / the OH group-containing fluorine-containing norbornene derivative (NB-1) / the OCH₂OCH₂CH_ThreeThe group-containing fluorine-containing norbornene derivative (NB-2) was a 50/50/0 mol% copolymer.
[0379]
Experimental Example 9 (Measurement of solubility in developer)
Using the fluorine-containing polymer obtained in Experimental Examples 1 to 8 and a polymer of parahydroxystyrene (PHS), the dissolution rate was measured by the quartz oscillator method (QCM method) as follows.
[0380]
(1) Preparation of sample: An antireflective film having a film thickness of 80 nm (AR19, manufactured by SHIPLEY Co., Ltd.) was formed on a quartz resonator plate with a diameter of 24 mm covered with gold, and the fluorine-containing materials obtained in Experimental Examples 1 to 7 thereon A solution (polymer concentration: 1 to 10%) in which a polymer and a polymer of parahydroxystyrene (PHS, weight average molecular weight 8000 manufactured by Aldrich) were dissolved in PGMEA was applied, dried at 110 ° C. for 90 seconds, and then 100 nm A coating was prepared.
[0381]
(2) Measurement of dissolution rate: The film thickness is calculated from the vibration frequency of the crystal plate and measured.
[0382]
The above-mentioned quartz vibrator plate coated with a fluoropolymer is immersed in a 2.38 wt% tetramethylammonium hydroxide (TMAH) aqueous solution, which is a standard developer, and the film thickness changes with time from the time of immersion. Was measured by the change in frequency, and the dissolution rate per unit time (nm / sec) was calculated. (Reference: Advances in Resist Technology and Proceedings of SPIE Vol. 4690, 904 (2002)).
[0383]
Furthermore, the dissolution rate was measured in the same manner using a TMAH aqueous solution having a concentration of 0.595% by weight. The results are shown in Table 1.
[0384]
Experimental Example 10 (Measurement of transparency at a wavelength of 157 nm)
(1) Preparation of coating composition
The various fluoropolymers and PHS produced in Experimental Examples 1 to 5 and 7 were dissolved in PGMEA to a concentration of 1 to 10% to prepare coating compositions.
[0385]
(2) Coating
(1) Base material for transparency measurement (MgF₂Application to
MgF₂Each of the coating compositions was coated on the substrate at 1000 rpm at room temperature using a spin coater. After the application, it was baked at 100 ° C. for 15 minutes to produce a transparent film.
[0386]
(2) Film thickness measurement
MgF₂A coating film was formed on the silicon wafer using each coating composition under the same conditions as described above except that a silicon wafer was used instead of the substrate.
[0387]
The thickness of each film was measured with an AFM apparatus (Seiko Electronics Co., Ltd. SPI3800).
[0388]
(3) Transparency measurement in the vacuum ultraviolet region
(1) Measuring device
・ Seya-Namioka spectrometer (High Energy Research Organization: BL-7B)
・ Slit 7 / 8-7 / 8
・ Detector PMT
・ Grating (GII: blaze wavelength 160nm, 1200 lines / mm)
The optical system is H.264. Namba et al., Rev. Sic. Instrum. , 60 (7), 1917 (1989).
[0389]
(2) Measurement of transmission spectrum
MgF obtained from each coating composition by the method (2) (1)₂The transmission spectrum of 200 to 100 nm of the film formed on the substrate was measured using the above apparatus.
[0390]
The molecular absorbance coefficient was calculated from the transmittance at 157 nm and the film thickness of the coating. The results are shown in Table 1.
[0390]
Experimental Example 11 (Preparation of photoresist composition and measurement of resist film transparency)
(1) Preparation of photoresist composition
Polymer concentration by dissolving 5% by weight of photoacid generator (B) as a solvent (C) in PGMEA with respect to the fluoropolymer (A-2) and polymer (A-2) produced in Experimental Example 5 Diluted to 5% by weight.
[0392]
S- (trifluoromethyl) -dibenzothiophenium trifluoromethanesulfonate as a photoacid generator
[0393]
Embedded image

[0394]
Was used.
[0395]
(2) Coating
Using the photoresist composition, a Si substrate was applied with a spin coater to a film thickness of 100 nm and dried.
[0396]
(3) Measurement of transparency in the vacuum ultraviolet region
It carried out similarly to Experimental example 10. The molecular absorbance coefficient at 157 nm is shown in Table 1.
[0397]
[Table 1]

[0398]
【The invention's effect】
According to the production method of the present invention, it is possible to produce a fluorine-containing polymer for photoresists which is excellent in transparency in the vacuum ultraviolet region, and also has excellent solubility in an alkali developer while being a fluorine-containing polymer. In particular, it is possible to produce a fluoropolymer capable of forming an ultrafine pattern especially for F2 resist.

Claims (27)

Fluoropolymer having an aliphatic ring structure repeating unit (M2) in the polymer main chain, and convertible to acid-reactive group Y ¹ or acid-reactive group Y ¹ that reacts with acid in the polymer In order to obtain a fluorine-containing polymer for resist having such a group Y ² , a monomer mixture containing a monomer (m2) capable of giving an aliphatic ring structure to the polymer main chain in the presence of a radical polymerization initiator, Formula (1):
R- (X) _n
(In the formula, R is selected from hydrocarbon groups optionally containing an ether bond having 1 to 20 carbon atoms, and a part of the hydrogen atoms may be substituted with fluorine atoms; X is radical polymerization in the presence of a chain transfer agent represented by at least one functional group selected from the group consisting of an oxygen atom-containing functional group and a substituted or unsubstituted amino group; n is an integer of 1 to 4) A process for producing a fluorine-containing polymer for a resist excellent in solubility in a developing solution. A fluorine-containing polymer having an aliphatic ring structure repeating unit (M2) in the polymer main chain is represented by formula (M-1):
-(M1)-(M2)-(N1)-(N)-(M-1)
(In the formula, the structural unit M1 is an ethylenic monomer having 2 or 3 carbon atoms and is a repeating unit derived from a fluorine-containing ethylenic monomer (m1) having at least one fluorine atom; A repeating unit derived from the monomer (m2) capable of giving an aliphatic ring structure to the polymer main chain; the structural unit N1 is a monomer (n1) copolymerizable with the monomer (m1) and the monomer (m2) The structural unit N is a repeating unit derived from the monomer (n) that can be copolymerized with the monomer (m1), the monomer (m2), and the monomer (n1). has units M2 or acid-reactive group Y ¹ or an acid-reactive group Y ¹ can be converted into a group Y ² in at least one of N1, acid-reactive groups in the structural unit M2 Y ¹ or an acid-reactive group Y it may be the same structural unit N1 and N if having a group convertible Y ² to ¹⁾ A fluorine-containing polymer for resists containing 1 to 99 mol% of structural unit M1, 1 to 99 mol% of structural unit M2, 0 to 98 mol% of structural unit N1, and 0 to 98 mol% of structural unit N. A method for producing a fluorine-containing polymer for a resist excellent in solubility in a developer according to claim 1. The fluorine-containing polymer having an aliphatic ring structure in the polymer main chain is represented by the formula (M-2):
-(M1)-(M2-2)-(M2)-(N)-(M-2)
(In the formula, the structural units M1 and M2 are the same as those in the formula (M-1); the structural unit M2-2 is a monomer that can give an aliphatic ring structure to the polymer main chain, and is an acid-reactive group Y ^1. Or a repeating unit derived from the monomer (m2-2) having a group Y ² that can be converted into an acid-reactive group Y ¹ ; the structural unit N is the monomer (m1), (m2-2) and the monomer ( m2) is a repeating unit derived from the monomer (n) copolymerizable with the structural unit M1, the structural unit M1 is 1 to 99 mol%, the structural unit M2-2 is 1 to 99 mol%, and the structural unit M2 is 0 to 0. 2. The method for producing a fluoropolymer for resist having excellent solubility in a developing solution according to claim 1, which is a fluoropolymer for resist containing 98 mol% and 0 to 98 mol% of the structural unit N.   The repeating unit (M1) derived from the fluorine-containing ethylenic monomer (m1) is at least one monomer selected from tetrafluoroethylene, chlorotrifluoroethylene, vinylidene fluoride, vinyl fluoride and hexafluoropropylene. 4. The method for producing a fluorine-containing polymer for a resist excellent in solubility in a developer according to claim 2, wherein the resist unit is a structural unit derived from a body.   The repeating unit (M2) derived from the monomer (m2) capable of giving an aliphatic ring structure to the polymer main chain is a repeating unit derived from a norbornene derivative which may contain a fluorine atom. A method for producing a fluorine-containing polymer for a resist excellent in solubility in a developer according to any one of claims 1 to 4. The repeating unit (M2-2) derived from the monomer (m2-2) capable of giving an aliphatic ring structure to the polymer main chain can be converted into the acid-reactive group Y ¹ or the acid-reactive group Y ^1. has a group Y ^2, resist fluoropolymer excellent in solubility in the developing solution according to any one of claims 3 to 5 is a repeating unit derived from a good norbornene derivatives also include fluorine atom Manufacturing method.   The repeating unit (M2) derived from the monomer (m2) capable of giving an aliphatic ring structure to the polymer main chain is an aliphatic monocyclic structure repeating unit optionally containing a fluorine atom. The manufacturing method of the fluoropolymer for resists excellent in the solubility to the developing solution in any one of -4. The repeating unit (M2-2) derived from the monomer (m2-2) capable of giving an aliphatic ring structure to the polymer main chain can be converted into the acid-reactive group Y ¹ or the acid-reactive group Y ^1. The solubility in a developer according to any one of claims 3, 4 and 7, wherein the repeating unit is an aliphatic monocyclic structure which has a group Y ² and may contain a fluorine atom. A method for producing an excellent fluorine-containing polymer for resist. The acid-reactive group Y ¹ in the fluorine-containing polymer is an OH group, an acid-dissociable functional group that can be converted to an OH group by an acid, an acid-dissociable functional group that can be dissociated by a COOH group or an acid and converted into a COOH group The production method according to claim 1, wherein the production method is at least one kind of group. A monomer (m2-2) capable of giving an aliphatic ring structure to the polymer main chain is represented by the formula (2):

The development according to any one of claims 3 to 8, which has a site represented by (wherein Rf ¹ is a fluorine-containing alkyl group having 1 to 10 carbon atoms or a fluorine-containing alkyl group having an ether bond). A method for producing a fluorine-containing polymer for a resist excellent in solubility in a liquid. The manufacturing method according to claim 10, wherein Rf ¹ is CF ₃ .   The production method according to any one of claims 1 to 11, wherein the functional group X in the chain transfer agent of the formula (1) is an oxygen atom-containing group and contains a hydrophilic functional group.   The resist having excellent solubility in a developing solution according to claim 12, wherein the functional group X in the chain transfer agent of the formula (1) is at least one selected from the group consisting of a hydroxyl group, a carboxyl group, and a sulfonic acid group. For producing fluoropolymer for use.   The production method according to any one of claims 1 to 13, wherein the hydrocarbon group R in the chain transfer agent of the formula (1) is an alkyl group having 1 to 6 carbon atoms.   The production method according to claim 1, wherein the hydrocarbon group R in the chain transfer agent of the formula (1) is a hydrocarbon group containing an aliphatic ring structure.   The chain transfer agent of Formula (1) is a C1-C10 alcohol, The manufacturing method in any one of Claims 1-11 characterized by the above-mentioned.   The production method according to claim 16, wherein the chain transfer agent of the formula (1) is methanol. (A-1) At least one acid reactivity of an OH group, an acid dissociable functional group that can be converted to an OH group by an acid, a COOH group or an acid dissociable functional group that can be dissociated by an acid to be converted to a COOH group A fluorine-containing polymer having a group Y ¹ ;
A composition comprising (B) a photoacid generator and (C) a solvent, wherein the fluorine-containing polymer (A-1) is obtained by the production method according to claim 1. A photoresist composition that provides a resist film excellent in solubility in a developer that is a coalescence. The photoresist composition according to claim 18, wherein the fluorinated polymer (A-1) is a polymer having an extinction coefficient at a wavelength of 157 nm of 1.0 µm ^-1 or less. The functional group having an OH group and imparting solubility to a developer is a fluorine-containing polymer having an aliphatic ring structure in a polymer main chain having only an OH group, and the polymer is represented by the formula ( M-3):
-(M1)-(M2-3)-(M2)-(N)-(M-3)
(In the formula, the structural unit M1 is an ethylenic monomer having 2 or 3 carbon atoms and a repeating unit derived from a fluorine-containing ethylenic monomer (m1) having at least one fluorine atom; structural unit M2-3 Is a repeating unit derived from a norbornene derivative (m2-3) which may have a fluorine atom having an OH group; the structural unit M2 is derived from a monomer (m2) capable of giving an aliphatic ring structure to the polymer main chain. The repeating unit; the structural unit N is represented by the monomer (m1), (m2-3) and the repeating unit derived from the monomer (n) copolymerizable with the monomer (m2). 24 to 70 mol%, 1 to 70 mol% of the structural unit M2-3, 0 to 69 mol% of the structural unit M2, 0 to 20 mol% of the structural unit N, and (M1) + (M2-3) + When (M2) = 100, (M1) / {(M2-3) + M2)} is a fluorine-containing polymer having a number average molecular weight of 1000 to 50000 in a molar ratio of 30/70 to 70/30, and measured by QCM measurement method of the fluorine-containing polymer, 2.38 wt% tetra A fluorine-containing polymer for a resist excellent in solubility in a developing solution having a dissolution rate in a methylammonium hydroxide aqueous solution of 500 nm / sec or more. A fluorine-containing polymer having an aliphatic ring structure in the polymer main chain having an acid-dissociable functional group Y ³ that can be converted into an OH group by an acid, wherein the polymer has the formula (M-4):
-(M1)-(M2-3)-(M2-4)-(N)-(M-4)
(In the formula, the structural unit M1 and the structural unit M2-3 are the same as the formula (M-3); the structural unit M2-4 is at least one functional group Y among acid dissociable functional groups that can be converted to an OH group with an acid. Repeating unit derived from norbornene derivative (m2-4) which may have a fluorine atom having ³ ; structural unit N is monomer (m1), (m2-3) and monomer (m2-4) The repeating unit derived from the copolymerizable monomer (n)), the structural unit M1 is 24-70 mol%, the structural unit M2-3 is 0-69 mol%, and the structural unit M2-4 is 1-70. When (M1) + (M2-3) + (M2-4) = 100, and (M1) / {(M2-3) + (M2-4) )} Is a fluorine-containing polymerization having a number average molecular weight of 1000 to 50000 in a 30/70 to 70/30 molar ratio. A with the proviso the formula (M-4) a fluorine-containing heavy an acid dissociable functional group Y ³ in the structural unit M2-4 is reacted with an acid-containing fluoropolymer after the reaction the acid was converted to the OH group In the coalescence, the functional group imparting solubility in the developing solution has only an OH group, and the 2.38% by weight tetramethylammonium hydro hydride was measured by the QCM measurement method of the fluoropolymer after the acid reaction. A fluorine-containing polymer for a resist excellent in solubility in a developing solution having a dissolution rate in an aqueous oxide solution of 500 nm / sec or more. A monomer (m2-3) capable of giving an aliphatic ring structure to the polymer main chain is represented by the formula (3):

22. The developer according to claim 20, wherein Rf ² has a moiety represented by the formula: Rf ² is a fluorine-containing alkyl group having 1 to 10 carbon atoms or a fluorine-containing alkyl group having an ether bond. Fluoropolymer for resists with excellent solubility. Resist fluoropolymer excellent in solubility in the developing solution according to claim 22, wherein Rf ² is is CF _3.   24. The solubility in a developer according to any one of claims 20 to 23, wherein the dissolution rate of the fluoropolymer in a 2.38 wt% tetramethylammonium hydroxide aqueous solution measured by a QCM measurement method is 750 nm / sec or more. Excellent fluorine-containing polymer for resist.   The solubility in a developer according to any one of claims 20 to 23, wherein the dissolution rate of the fluoropolymer in a 2.38 wt% tetramethylammonium hydroxide aqueous solution measured by a QCM measurement method is 1000 nm / sec or more. Excellent fluorine-containing polymer for resist. The fluoropolymer for a resist having excellent solubility in a developing solution according to any one of claims 20 to 25, wherein the fluoropolymer has an extinction coefficient at a wavelength of 157 nm of 1.0 µm ^-1 or less. (A-2) a fluorine-containing polymer having at least one acid-reactive group Y ⁴ of an acid-dissociable functional group that can be converted to an OH group by an OH group or an acid,
27. A photoresist composition comprising (B) a photoacid generator and (C) a solvent, wherein the fluorine-containing polymer (A-2) is a fluorine-containing heavy for a resist according to any one of claims 20 to 26. A photoresist composition that provides a resist film excellent in solubility in a developer that is a coalescence.