JP3821952B2 - Pattern forming method and semiconductor device manufacturing method - Google Patents

Description

【００１５】
【化２】

【００１６】
式中Ｒ1、Ｒ2、Ｒ3、Ｒ4、Ｒ5、Ｒ6、Ｒ7、Ｒ8は、水素または炭素数１から１０のアルキル基を表し、それらのアルキル基は互いにつながって環状アルキル基を形成していても良い。
【００１７】
さらには少なくとも上記式（１）または（２）で示されるカルボン酸構造は，上記感光性組成物を構成する高分子化合物に含まれることが望ましい。
【００１８】
具体的には下記一般式（５）〜（１２）から選ばれる繰り返し構造を少なくとも含む樹脂が、上記のような構造を有しており、しかも遠紫外領域で吸収が小さく、ドライエッチ耐性を有するので望ましい。
【００１９】
【化５】

【００２０】
【化６】

【００２１】
【化７】

【００２２】
【化８】

【００２３】
【化９】

【００２４】
【化１０】

【００２５】
【化１１】

【００２６】
【化１２】

【００２７】
ここでそれぞれ式中ｎは整数を表す。
【００２８】
上記式（５）または（６）のような繰り返し構造を少なくとも有する樹脂は、５−メチレンビシクロ［２．２．１］ヘプト−２−エンのような環状脂肪族炭化水素骨格を含む化合物と無水マレイン酸をラジカル共重合体して、その無水マレイン酸部分を還元してラクトン化し、それを加水分解して変性することにより得られる。
【００２９】
また上記式（７）または（８）のような繰り返し構造を少なくとも有する樹脂は、シクロオクタ−１、５−ジエンのような環状脂肪族炭化水素骨格を含む化合物と無水マレイン酸をラジカル共重合体して、その無水マレイン酸部分を還元してラクトン化し、それをさらに加水分解して変性することにより得られる。
【００３０】
また上記式（９）または（１０）のような繰り返し構造を少なくとも有する樹脂は、５−エチレンビシクロ［２．２．１］ヘプト−２−エンのような環状脂肪族炭化水素骨格を含む化合物と無水マレイン酸をラジカル共重合体して、その無水マレイン酸部分を還元してラクトン化し、それをさらに加水分解して変性することにより得られる。
【００３１】
また上記式（１１）または（１２）のような繰り返し構造を少なくとも有する樹脂は、５−ビニルビシクロ[２．２．１]ヘプト−２−エンのような環状脂肪族炭化水素骨格を含む化合物と無水マレイン酸をラジカル共重合体して、その無水マレイン酸部分を還元してラクトン化し、それをさらに加水分解して変性することにより得られる。
【００３２】
なお、これらの樹脂の重量平均分子量は、１、０００〜３００、０００であることが望ましい。
【００３３】
上記高分子化合物のうち、側鎖に上記式（１）または（２）で示されるカルボン酸構造を有する脂環族構造の繰り返しを含むものは、主鎖に直接（１）または（２）で示されるカルボン酸構造を含むものに比べて、酸触媒反応でのラクトン化が起こりやすく、高感度になり易いのでより望ましい。
【００３４】
具体的には上記式（５）または（６）または（９）または（１０）または（１１）または（１２）で表されるような、側鎖に上記式（１）または（２）で示されるカルボン酸構造を有する脂環族構造の繰り返しを含む樹脂の方が、上記式（７）または（８）で表されるような、主鎖に直接（１）または（２）で示されるカルボン酸構造を含む樹脂の方がより高感度でパタン形成ができるので、より望ましい。
【００３５】
式（１）または（２）で表されるカルボン酸構造が、主鎖に直接含まれる場合は、立体的に式（１）または（２）中のカルボン酸部分と水酸基が遠くなる場合があり、ラクトン化の反応が起こりにくい場合がある。これに対して式（１）または（２）で表されるカルボン酸構造が、側鎖に含まれた場合は、立体的にそのカルボン酸部分と水酸基部分が遠くなりにくいので、ラクトン化が容易に起こりやすく高感度でパタン形成ができる可能性がある。
【００３６】
上記のような構造を有する樹脂は、活性化学線の照射により酸を発生する化合物を、上記樹脂に対して０．１〜３０重量部組み合わせることによりパタン形成材料となる。ここで活性化学線の照射により酸を発生する化合物としては、トリフェニルスルホニウムトリフレートなどのオニウム塩、トリフルオロメタンスルホニルオキシナフチルイミドなどのスルホニルオキシイミド、スルホン酸エステル等が挙げられるが、活性化学線、例えばＡｒＦエキシマレーザ等の照射により酸を発生するものであれば良い。
【００３７】
本発明のパタン形成方法で用いられる上記のカルボン酸構造は、下記式（３）または（４）で示される化学構造であっても良い。
【００３８】
【化３】

【００３９】
【化４】

【００４０】
式中Ｒ1、Ｒ2、Ｒ3、Ｒ4、Ｒ5、Ｒ6、Ｒ7、Ｒ8は、水素、炭素数１から１０のアルキル基を表し、それらのアルキル基は互いにつながって環状アルキル基を形成していても良い。また式中Ｘは、１−エトキシエチル基、テトラヒドロピラニル基などのアセタールやケタールを表す。この場合、Ｘにより、水酸基が保護された形になっているので、熱的により安定である。
【００４１】
さらには少なくとも上記式（３）または（４）で示されるカルボン酸構造は、上記感光性組成物を構成する高分子化合物に含まれることが望ましい。
【００４２】
また上記高分子化合物のうち、側鎖に上記式（３）または（４）で示されるカルボン酸構造を有する脂環族構造の繰り返しを含むものは、主鎖に直接（３）または（４）で示されるカルボン酸構造を含むものに比べて、酸触媒反応でのラクトン化が起こりやすく、高感度になり易いのでより望ましい。
【００４３】
式（３）または（４）で表されるカルボン酸構造が、主鎖に直接含まれる場合は、立体的に式（３）または（４）中のカルボン酸部分と保護された水酸基が遠くなる場合があり、ラクトン化の反応が起こりにくい場合がある。これに対して式（３）または（４）で表されるカルボン酸構造が、側鎖に含まれた場合は、立体的にそのカルボン酸部分と保護された水酸基部分が遠くなりにくいので、ラクトン化が容易に起こりやすく高感度でパタン形成ができる可能性がある。
【００４４】
本発明のパタン形成方法に用いるカルボン酸構造を含む感光性組成物は、さらにドライエッチング耐性を向上させるための脂環族構造を含んでもよい。脂環族構造としては、アダマンチル、ノルボルナン、トリシクロデカンやアンドロスタンの構造があげられる。これらの構造は、遠紫外領域で透明であり、ドライエッチング耐性を有する。
【００４５】
本発明に用いる活性化学線は波長２５０ｎｍ以下の遠紫外光、ＡｒＦエキシマレーザ光のような真空紫外光が挙げられる。なお電子線、ＥＵＶ、エックス線等も用いることが出来る。
【００４６】
本発明で用いる水性アルカリ現像液は、炭素数１から５のテトラアルキルアンモニウムヒドロキシド水溶液であることが望ましい。
【００４７】
上記第２の目的を達成するための本発明の半導体装置の製造方法は、半導体基板上に上記記載のいずれかのパタン形成方法によりレジストパタンを形成し、それをもとに、基板をエッチング加工する工程か、もしくは基板にイオンを打ち込む工程を含むようにしたものである。
【００４８】
本発明の半導体の製造方法で用いられるエッチング加工法としては、プラズマエッチング、反応性イオンエッチング、反応性イオンエッチング、反応性イオンビームエッチング等のドライエッチング法や、ウエットエッチング法が挙げられる。
【００４９】
本発明の半導体装置の製造方法において加工される基板としては、ＣＶＤ法や熱酸化法で形成された二酸化珪素膜、塗布性ガラス膜などの酸化膜、あるいは窒化珪素膜等の窒化膜が挙げられる。またアルミニウムやその合金、タングステンなどの各種金属膜、多結晶シリコン等が挙げられる。
【００５０】
本発明では、カルボン酸のエステル化の中でも反応性の高いラクトン化を利用することにより、露光により発生した酸による触媒反応で、効率的にカルボン酸からカルボン酸エステルへの変換を行うことができる。この反応は分子内のエステル化であるので、分子間の架橋等も起きず、単純にカルボン酸の量が露光部と未露光部で変化する。カルボン酸とアルコールが別々の分子である場合は、現実的に適用できる条件下では、酸触媒反応により膜中で数％のカルボン酸しかエステル化しない。これに対して、本発明のパタン形成方法で用いているγ−あるいはδ−ラクトン化では、露光部では、３０％以上のカルボン酸がエステル化する。そのため、溶解速度が大きく変化し、しかも架橋反応は起きていないので、従来技術の問題点であった膨潤が避けられ、微細パタンが形成できる。
【００５１】
【発明の実施の形態】
以下、実施例により本発明をさらに詳細に説明するが、本発明はこれらの実施例にのみ限定されるものではない。まず実施例に先立ち、本発明で用いた材料の合成例を示す。
【００５２】
〈合成例１〉γ―ヒドロキシカルボン酸構造を有するポリマー（１ｂ）の合成
温度計、冷却管、窒素導入管をつけた５００ｍｌ３つ口フラスコに、５−メチレンビシクロ[２．２．１]ヘプト−２−エン２１．２ｇ、無水マレイン酸１９．６ｇ、２,２’−アゾビス（イソブチロニトリル）２．５６ｇ、テトラヒドロフラン２４０ｇを入れ、窒素を導入しながら７０℃で加熱環流して、８時間重合を行った。重合後、ｎ−ヘキサン１０００ｍｌへ溶液を注ぎ、ポリマーを析出させ乾燥して５−メチレンビシクロ[２．２．１]ヘプト−２−エン−無水マレイン酸共重合体（１ａ）を３７．５ｇを得た（収率９２％）。得られたポリマーの構造は、種々の分析法から下記の構造が主であることがわかった。
【００５３】
【化１３】

【００５４】
式中、ｎは整数を表す。
【００５５】
またゲルパーミエーションクロマトグラフィー（ＧＰＣ）によりテトラヒドロフラン中で、このポリマーのポリスチレン換算の分子量を調べたところ、重量平均分子量が５、８００、数平均分子量が２、５００であった。
【００５６】
５００ｍｌ３つ口フラスコに水素化ホウ素ナトリウム１．９ｇとテトラヒドロフラン３０ｇを入れ、窒素下でアイスバスで０℃に冷却して攪拌しながら、上記のように合成した５−メチレンビシクロ[２．２．１]ヘプト−２−エン−無水マレイン酸共重合体１０ｇをテトラヒドロフラン１００ｇに溶解したものを約１時間かけて滴下した。滴下後、数時間攪拌した後、一晩放置した。
【００５７】
溶液を約３００ｍｌの水に注ぎ攪拌した後、それに約１Ｎ塩酸水溶液を徐々に加えて、弱酸性にした。この溶液に酢酸エチル約１５０ｍｌを加えて抽出を２回行い、得られた有機層を１００ｍｌの水で２回洗浄した。洗浄後、有機層を無水硫酸ナトリウムで乾燥し、乾燥後、溶媒を減圧留去して減らして、ｎ−ヘキサン５００ｍｌへ注ぎ、沈殿したポリマーを乾燥して白色粉末状のポリマー７．８ｇを得た。得られたポリマーの構造は、種々の分析法から（１ａ）の無水物の部分が還元されてラクトン化した構造及びそれがさらに開環したγ―ヒドロキシカルボン酸構造を少なくとも有するポリマー（１ｂ）であることがわかった。
【００５８】
【化１４】

【００５９】
または
【００６０】
【化１５】

【００６１】
式中、ｌ及びｍは整数を表す。
【００６２】
得られたポリマー（１ｂ）１００重量部をシクロヘキサノン６００重量部に溶解し、孔径０．２μｍのフィルターで濾過した。それを回転塗布し、１００℃で２分間ベークしてポリマー膜を得た。シリコン基板上に塗布した膜（膜厚５７０ｎｍ）をテトラメチルアンモニウムヒドロキシド水溶液（濃度０．１１３重量％）に浸したところ、干渉色が変化しながら７．２秒で溶け、残膜が０になった。また溶解速度モニターを用いて溶解を調べたところ、膨潤せずに溶解していることがわかった。図１に溶解速度モニターを用いて得られた生データである現像時間とモニター光の強度の関係を示す。また図２にそれを解析して得られた溶解時間と膜厚の関係を示す。
【００６３】
フッ化リチウム基板上に塗布した膜の吸収スペクトルを、真空紫外分光装置（ＡＲＣ社製）で測定したところ、１９３ｎｍの吸光度が、膜厚１．０μｍで０．８０であり、吸収が小さいことがわかった。
【００６４】
〈合成例２〉γ―ヒドロキシカルボン酸構造を有するポリマー（２ｂ）の合成
合成例１で用いた５−メチレンビシクロ[２．２．１]ヘプト−２−エン２１．２ｇの代わりに、シクロオクタ−１、５−ジエン２１．６ｇを用いて同様にラジカル重合を行い、シクロオクタ−１、５−ジエン−無水マレイン酸共重合体（２ａ）を３８ｇを得た（収率９３％）。得られたポリマーの構造は、種々の分析法から下記の構造が主であることがわかった。
【００６５】
【化１６】

【００６６】
式中ｎは整数を表す。
【００６７】
このポリマーのポリスチレン換算の分子量は、重量平均分子量が１、４００、数平均分子量が１、０００であった。
【００６８】
合成例１と同様にして、水素化ホウ素ナトリウムにより無水の部分を還元、加水分解したところ、得られたポリマーの構造は、種々の分析法から（２ａ）の無水物の部分が還元されてラクトン化した構造及びそれがさらに開環したγ―ヒドロキシカルボン酸構造を少なくとも有するポリマー（２ｂ）であることがわかった。
【００６９】
【化１７】

【００７０】
または
【００７１】
【化１８】

【００７２】
式中ｌ及びｍは整数を表す。
【００７３】
〈合成例３〉γ―ヒドロキシカルボン酸構造を有するポリマー（３ｂ）の合成
合成例１で用いた５−メチレンビシクロ[２．２．１]ヘプト−２−エン２１．２ｇの代わりに、５−エチレンビシクロ[２．２．１]ヘプト−２−エン２４ｇを用いて同様にラジカル重合を行い、５−エチレンビシクロ[２．２．１]ヘプト−２−エン−無水マレイン酸共重合体（３ａ）を３７ｇを得た（収率８６％）。得られたポリマーの構造は、種々の分析法から下記の構造が主であることがわかった。
【００７４】
【化１９】

【００７５】
式中ｎは整数を表す。
【００７６】
このポリマーのポリスチレン換算の分子量は、重量平均分子量が３、３００、数平均分子量が２、０００であった。
【００７７】
合成例１と同様にして、水素化ホウ素ナトリウムにより無水の部分を還元、加水分解したところ、得られたポリマーの構造は、種々の分析法から（３ａ）の無水物の部分が還元されてラクトン化した構造及びそれがさらに開環したγ―ヒドロキシカルボン酸構造を少なくとも有するポリマー（３ｂ）であることがわかった。
【００７８】
【化２０】

【００７９】
または
【００８０】
【化２１】

【００８１】
式中ｌ及びｍは整数を表す。
【００８２】
〈合成例４〉γ―ヒドロキシカルボン酸構造を有するポリマー（４ｂ）の合成
合成例１で用いた５−メチレンビシクロ[２．２．１]ヘプト−２−エン２１．２ｇの代わりに、５−ビニルビシクロ[２．２．１]ヘプト−２−エン２４ｇを用いて同様にラジカル重合を行い、５−ビニルビシクロ[２．２．１]ヘプト−２−エン−無水マレイン酸共重合体（４ａ）を２６ｇを得た（収率５９％）。得られたポリマーの構造は、種々の分析法から下記の構造が主であることがわかった。
【００８３】
【化２２】

【００８４】
式中ｎは整数を表す。
【００８５】
このポリマーのポリスチレン換算の分子量は、重量平均分子量が２、９００、数平均分子量が１、７００であった。
【００８６】
合成例１と同様にして、水素化ホウ素ナトリウムにより無水の部分を還元、加水分解したところ、得られたポリマーの構造は、種々の分析法から（４ａ）の無水物の部分が還元されてラクトン化した構造及びそれがさらに開環したγ―ヒドロキシカルボン酸構造を少なくとも有するポリマー（４ｂ）であることがわかった。
【００８７】
【化２３】

【００８８】
または
【００８９】
【化２４】

【００９０】
式中ｌ及びｍは整数を表す。
【００９１】
〈合成例５〉
（５−１） リトコール酸ダイマー（５a）の合成
窒素気流下３００ｍｌ３つ口フラスコにリトコール酸１１．３ｇ（０．０３０ｍｏｌ）、ピリジン２．４ｇ（０．０３０ｍｏｌ）及びテトラヒドロフラン１００ｍｌを入れ、０℃に冷却しながら、テトラヒドロフラン３０ｍｌに溶解したスクシニルクロリド２．３ｇ（０．０１５ｍｏｌ）を滴下した。滴下後室温で２時間攪拌し、それをさらに２時間還流した。還流後、析出した黒色の塩をろ別し、溶液を１％塩酸水溶液１０００ｍｌに滴下した。析出した灰色の沈殿を吸引ろ過、水洗後、乾燥して１２．６ｇのリトコール酸ダイマー（５ａ）を得た。
【００９２】
【化２５】

【００９３】
なおここでは、カルボン酸を有する脂環式化合物としてリトコール酸を用いたが、それ以外にデオキシコール酸、コール酸、ウルソデオキシコール酸などを用いることができる。ただし、これらは分子内に複数個のアルコール性水酸基を有するので、ジカルボン酸クロライドとの反応では、ダイマーではなくてオリゴマーを生ずる。また、ジカルボン酸クロライドも、スクシニルクロライドだけでなく、マロン酸クロリド、１、３−アダマンタンジカルボン酸クロライドなど任意のものを用いることができる。
【００９４】
（５−２） １−（テトラヒドロピラニルオキシ）−２−ブロモエタン（５ｂ）及び１−（テトラヒドロピラニルオキシ）−３−ブロモプロパン（５ｃ）の合成２−ブロモエタノール１２．５ｇ（０．１０ｍｏｌ）、３、４−ジヒドロ−２Ｈ−ピラン１２．６ｇ（０．１５ｍｏｌ）を酢酸エチル２００ｍｌに溶解し、そこへ、ピリジニウム−ｐ−トルエンスルホネート１．０ｇを加えて、室温で４時間攪拌した。赤外吸収スペクトルで、アルコール性水酸基が消失していることを確認してから、溶液にテトラメチルアンモニウムヒドロキシド２．３８％水溶液８０ｍｌを加えて、２回洗浄し、さらに水８０ｍｌで２回洗浄した。有機層を硫酸ナトリウムで乾燥した後、減圧蒸留して１−（テトラヒドロピラニルオキシ）−２−ブロモエタン（５ｂ）１５．７ｇを得た。
【００９５】
【化２６】

【００９６】
また同様にして１−（テトラヒドロピラニルオキシ）−３−ブロモプロパン（５ｃ）を合成した。
【００９７】
【化２７】

【００９８】
（５−３） γ−ヒドロキシカルボン酸構造を有する化合物（５ｄ）及びδ−ヒドロキシカルボン酸構造を有する化合物（５ｅ）の合成
乾燥窒素気流下、リチウムジイソプロピルアミド２．０Ｍ溶液（市販品）３０ｍｌ（０．０６０ｍｏｌ）に乾燥テトラヒドロフラン１００ｍｌを加え、そこへ合成したリトコール酸ダイマー（５ａ）１１．７ｇ（０．０１４ｍｏｌ）の乾燥テトラヒドロフラン溶液を反応温度が０℃を超えないように滴下し、０℃で攪拌した。この溶液にヘキサメチルリン酸トリアミド５．４ｇ（０．０３０ｍｏｌ）を加えて０℃で攪拌した後、合成した１−（テトラヒドロピラニルオキシ）−２−ブロモエタン（５ｂ）１５．７ｇを０℃で速やかに加えた。温度が上昇するが、そのまま攪拌しながら、室温で２時間放置した。氷冷した５％塩酸水溶液２００から３００ｍｌを加えて弱酸性を確認した後、ジエチルエーテル１５０ｍｌで２回抽出した。その後、有機層を３％塩酸水溶液１００ｍｌで洗浄し、さらに１００ｍｌ水で洗浄を２回行い、有機層を硫酸ナトリウムで乾燥した。乾燥後、溶媒を減圧留去して濃縮し、ヘキサンで再沈殿してγ−ヒドロキシカルボン酸構造を有する化合物（５ｄ）を１２．１ｇを得た。種々の分析から生成物は、テトラヒドロピラニル基が一部の残った以下の構造であることがわかった。
【００９９】
【化２８】

【０１００】
式中Ｒは、水素またはテトラヒドロピラニル基を表す。
【０１０１】
また同様にして、上記で用いた１−（テトラヒドロピラニルオキシ）−２−ブロモエタン（５ｂ）の代わりに、それと等モルの１−（テトラヒドロピラニルオキシ）−３−ブロモプロパン（５ｃ）を用いて、δ−ヒドロキシカルボン酸構造を有する化合物（５ｅ）をを得た。種々の分析から生成物は、テトラヒドロピラニル基が一部の残った以下の構造であることがわかった。
【０１０２】
【化２９】

【０１０３】
式中Ｒは、水素またはテトラヒドロピラニル基を表す。
【０１０４】
〈実施例１〉
合成例１で合成したγ−ヒドロキシカルボン酸構造を有するポリマー（１ｂ）１００重量部、酸発生剤トリフェニルスルホニウムトリフレート２重量部をシクロヘキサノン６００重量部に溶解し、孔径０．２０μｍのテフロンフィルターを用いてろ過しレジスト溶液とした。
【０１０５】
ヘキサメチルジシラザンで処理したシリコン基板上に、上記のレジスト溶液を回転塗布し、塗布後１００℃で２分間加熱処理して、膜厚０．５４μｍのレジスト膜を形成した。この膜の吸収スペクトルを、紫外可視分光光度計で測定したところ、１９３ｎｍの透過率は２５％であった。
【０１０６】
窒素で装置内部を置換した露光実験装置に、上記のレジストを塗布した基板を入れ、その上に石英板上に形成したレベンソン型の位相シフトマスクを密着させた。そのマスクを通じてＡｒＦエキシマレーザ光を照射し、その後１００℃で２分間露光後ベークを行った。２３℃のテトラメチルアンモニウムヒドロキシド水溶液（０．１１３重量％）にレジスト膜を浸漬したところ、膜の未露光部は３０秒で溶解した。そこで現像は、その４倍の時間の１２０秒間行い、続いて６０秒間純水でリンスした。その結果、露光量２０ｍＪ／ｃｍ2で、ネガ型の０．２０μｍラインアンドスペースパタンが得られた。この際、パタンの膨潤は見られなかった。
【０１０７】
この際、得られたパタンのついた基板を、テトラヒドロフランに浸漬したところ、パタンは瞬時に溶解し、架橋が起きていないことがわかった。
【０１０８】
またこのレジスト膜をＫｒＦエキシマレーザステッパー（ＮＡ＝０．４５）を用いて、レベンソン型の位相シフトマスクを介して露光をおこなった。その後、上記のプロセス条件の露光後ベーク、及び現像を行ったところ、露光量３０ｍＪ／ｃｍ2で、ネガ型の０．１８μｍラインアンドスペースパタンが得られた。この際、パタンの膨潤は見られなかった。
【０１０９】
さらにアルミ基板上に塗布した上記レジスト膜（膜厚５４０ｎｍ）について、ＥＣＲ方式のドライエッチング装置で、下記の条件でエッチングを行った。
【０１１０】
Ｃｌ2流量 ９０ｓｃｃｍ
ＢＣｌ3流量 ６０ｓｃｃｍ
ガス圧 １．３Ｐａ
ＲＦバイアスパワー １４０Ｗ、
その結果、このレジストのエッチレートは１２３０ｎｍ／分であった。同条件下で比較したポリ（メタクリル酸メチル）のエッチレート１５８０ｎｍ／分より小さかった。
【０１１１】
ＮａＣｌ板上に塗布した上記レジストに、同様にＡｒＦエキシマ光を２０ｍＪ／ｃｍ2照射し、露光前および露光後ベーク後の赤外吸収スペクトルをパーキンエルマー社製ＦＴ−１７２０Ｘにより測定した。その結果、露光後ベーク後にカルボン酸及び水酸基に起因する３３００ｃｍ-1のピークが大きく減少していることがわかった。またカルボン酸の１７０５ｃｍ-1のピークが減少して、ラクトンに起因する１７７０ｃｍ-1のピークが増加していることがわかった。これらの吸収の強度から、露光前にあったカルボン酸のうちの約７２％が、露光後にラクトン化していることがわかった。
【０１１２】
レジスト膜は初めγ−ヒドロキシカルボン酸構造を有するポリマー（１ｂ）の構造であり、そのカルボン酸によりアルカリ可溶であった。ＡｒＦエキシマレーザ露光により、酸発生剤トリフェニルスルホニウムトリフレートからトリフルオロメタンスルホン酸が発生した。露光後ベーク中にその酸を触媒として、ポリマー中のγ―ヒドロキシカルボン酸の構造が分子内脱水してエステル化して、γ―ラクトンの構造を生じた。その結果、露光部がアルカリ現像液に不溶となり、ネガ型のパタンが形成された。この際のネガ化の機構は架橋反応ではなく、ラクトン化によるカルボン酸の量の大幅な減少であるために膨潤が避けられ微細パタンが形成できた。
【０１１３】
〈実施例２〉
実施例１で用いたγ−ヒドロキシカルボン酸構造を有するポリマー（１ｂ）の代わりに、合成例２で合成したポリマー（２ｂ）を１００重量部、合成例５で合成したγ−ヒドロキシカルボン酸構造を有する化合物（５ｄ）３０重量部、酸発生剤トリフルオロメタンスルホニルオキシナフチルイミド２重量部をシクロヘキサノン６００重量部に溶解し、孔径０．２０μｍのテフロンフィルターを用いてろ過しレジスト溶液とした。
【０１１４】
実施例１と同様にヘキサメチルジシラザンで処理したシリコン基板上に、上記のレジスト溶液を回転塗布し、塗布後９０℃で２分間加熱処理して、膜厚０．５２μｍのレジスト膜を形成した。この膜の吸収スペクトルを、紫外可視分光光度計で測定したところ、１９３ｎｍの透過率は６０％であった。
【０１１５】
実施例１と同様に位相シフトマスクを通じてＡｒＦエキシマレーザ光を照射し、その後９０℃で２分間露光後ベークを行った。２３℃のテトラブチルアンモニウムヒドロキシド水溶液（０．４０重量％）にレジスト膜を浸漬したところ、膜の未露光部は１５秒で溶解した。そこで現像は、その４倍の時間の６０秒間行い、続けて６０秒間純水でリンスした。その結果、露光量２７ｍＪ／ｃｍ2で、ネガ型の０．２２μｍラインアンドスペースパタンが得られた。この際、パタンの膨潤は見られなかった。
【０１１６】
さらにアルミ基板上に塗布した上記レジスト膜（膜厚５２０ｎｍ）について、ＥＣＲ方式のドライエッチング装置で、実施例１の条件でエッチングを行った。
【０１１７】
その結果、このレジストのエッチレートは１０９０ｎｍ／分であった。同条件下で比較したポリヒドロキシスチレンのエッチレート１０８０ｎｍ／分と同程度であった。
【０１１８】
〈実施例３〉
実施例１で用いたγ−ヒドロキシカルボン酸構造を有するポリマー（１ｂ）を１００重量部、合成例５で合成したδ−ヒドロキシカルボン酸構造を有する化合物（５ｅ）３０重量部、酸発生剤ジメチルフェニルスルホニウムトリフレート３重量部をシクロヘキサノン６００重量部に溶解し、孔径０．２０μｍのテフロンフィルターを用いてろ過しレジスト溶液とした。
【０１１９】
実施例１と同様にヘキサメチルジシラザンで処理したシリコン基板上に、上記のレジスト溶液を回転塗布し、塗布後９０℃で２分間加熱処理して、膜厚０．５４μｍのレジスト膜を形成した。この膜の吸収スペクトルを、紫外可視分光光度計で測定したところ、１９３ｎｍの透過率は６５％であった。
【０１２０】
実施例１と同様に位相シフトマスクを通じてＡｒＦエキシマレーザ光を照射し、その後９０℃で２分間露光後ベークを行った。２３℃のテトラメチルアンモニウムヒドロキシド水溶液（０．１１３重量％）にレジスト膜を浸漬したところ、膜の未露光部は１２秒で溶解した。そこで現像は、その４倍の時間の４８秒間行い、続けて６０秒間純水でリンスした。その結果、露光量３５ｍＪ／ｃｍ2で、ネガ型の０．２２μｍラインアンドスペースパタンが得られた。この際、パタンの膨潤は見られなかった。
【０１２１】
さらにアルミ基板上に塗布した上記レジスト膜（膜厚５４０ｎｍ）について、ＥＣＲ方式のドライエッチング装置で、実施例１の条件でエッチングを行った。
【０１２２】
その結果、このレジストのエッチレートは１０７５ｎｍ／分であった。同条件下で比較したポリヒドロキシスチレンのエッチレート１０８０ｎｍ／分と同程度であった。
【０１２３】
〈実施例４〉
実施例１で用いたγ−ヒドロキシカルボン酸構造を有するポリマー（１ｂ）の代わりに、合成例３で合成したγ−ヒドロキシカルボン酸構造を有するポリマー（３ｂ）を１００重量部、酸発生剤ジフェニルヨードニウムトリフレート３重量部をシクロヘキサノン６００重量部に溶解し、孔径０．２０μｍのテフロンフィルターを用いてろ過しレジスト溶液とした。
【０１２４】
実施例１と同様にヘキサメチルジシラザンで処理したシリコン基板上に、上記のレジスト溶液を回転塗布し、塗布後９０℃で２分間加熱処理して、膜厚０．５５μｍのレジスト膜を形成した。
【０１２５】
これを加速電圧５０ｋＶの電子線描画装置を用いて、ラインアンドスペースパタンの露光を行った。露光後ベークを９０℃で２分間行った後、２３℃のテトラメチルアンモニウムヒドロキシド水溶液（０．１１３重量％）にレジスト膜を浸漬したところ、膜の未露光部は２０秒で溶解した。そこで現像は、その４倍の時間の８０秒間行い、続けて６０秒間純水でリンスした。その結果、露光量１５μＣ／ｃｍ2で、ネガ型の０．２０μｍラインアンドスペースパタンが得られた。この際、パタンの膨潤は見られなかった。
【０１２６】
〈実施例５〉
実施例１で用いたγ−ヒドロキシカルボン酸構造を有するポリマー（１ｂ）の代わりに、合成例４で合成したγ−ヒドロキシカルボン酸構造を有するポリマー（４ｂ）を１００重量部、酸発生剤カンファースルホニルオキシナフチルイミド５重量部をシクロヘキサノン６００重量部に溶解し、孔径０．２０μｍのテフロンフィルターを用いてろ過しレジスト溶液とした。
【０１２７】
実施例１と同様にヘキサメチルジシラザンで処理したシリコン基板上に、上記のレジスト溶液を回転塗布し、塗布後９０℃で２分間加熱処理して、膜厚０．５２μｍのレジスト膜を形成した。
【０１２８】
このレジスト膜をＫｒＦエキシマレーザステッパー（ＮＡ＝０．４５）を用いて、レベンソン型の位相シフトマスクを介して露光をおこなった。露光後ベークを９０℃で２分間行った後、２３℃のテトラメチルアンモニウムヒドロキシド水溶液（０．１１３重量％）にレジスト膜を浸漬したところ、膜の未露光部は２５秒で溶解した。そこで現像は、その４倍の時間の１００秒間行い、続けて６０秒間純水でリンスした。その結果、露光量２０ｍＪ／ｃｍ2で、ネガ型の０．１８μｍラインアンドスペースパタンが得られた。この際、パタンの膨潤は見られなかった。
【０１２９】
〈実施例７〉
図３に公知のＭＯＳ（金属−酸化物−半導体）型トランジスタの断面図を示す。同トランジスタは、ゲート電極３８に印加する電圧により、ソース電極３６及びドレイン電極３７間に流れるドレイン電流を制御する構造となっている。
【０１３０】
ここでこのような構造を作る工程は、十数工程からなるが、それらを大きく分けるとフィールド酸化膜形成までの工程と、ゲート形成までの工程と、最終工程の３つにグループわけする事ができる。ここではじめのフィールド酸化膜形成までの工程（図４）には、窒化シリコン膜上でレジストパタンを形成する工程が含まれる。このフィールド酸化膜形成を以下の実施例の様にして行った。
【０１３１】
公知の方法により、図４（ａ）の様にｐ型シリコンウエハ４１上に５０ｎｍの酸化膜４２を形成し、その上にプラズマＣＶＤにより、２００ｎｍの窒化シリコン膜を形成し基板とする。この基板に、実施例１に示した材料、方法により０．５０μｍラインのレジストパタン４４の形成を行う（図４（ｂ））。このレジストパタンをマスクとして、公知の方法で窒化シリコン膜をエッチングした後（図４（ｃ））、このレジストを再びマスクにして、チャンネルストッパのためのホウ素のイオン打ち込みを行う。レジストを剥離後（図４（ｄ））、窒化シリコン膜をマスクとする選択酸化により、素子分離領域に１．２μｍのフィールド酸化膜を形成する（図４（ｅ））。
【０１３２】
このあと公知の方法に従い、ゲート形成の工程と、最終工程を行った。窒化シリコン膜をエッチング後、ゲートを酸化し、多結晶シリコンの成長を行う（図４（ｆ））。この基板に、実施例１に示したパタン形成方法を用いて、０．２０μｍラインのレジストパタンの形成を行う（図４（ｇ））。このレジストパタンをマスクとして、公知の方法で多結晶シリコンのエッチングを行い、ゲートを形成する（図４（ｈ））。ソース、ドレインの薄い酸化膜をエッチングし、ついで多結晶シリコンゲートとソース、ドレインにヒ素を拡散し、多結晶シリコンゲートとソース、ドレイン領域に酸化膜を形成する。ゲート、ソース、ドレインへのアルミニウム配線のためのコンタクトを開口視、アルミニウム上着とパタンニングを行い、さらに保護膜を形成し、ボンディングのためのパッドを開講する。このようにして図３のようなＭＯＳ型トランジスタが形成される。
【０１３３】
ここではＭＯＳ型トランジスタについて、特にフィールド酸化膜の形成方法を記述したが、本発明はこれに限らないのは言うまでもなく、他の半導体素子の製造方法、工程に適用できる。
【０１３４】
〈比較例１〉
合成例１で合成した５−メチレンビシクロ[２．２．１]ヘプト−２−エン−無水マレイン酸共重合体１０ｇをメタノール１５０ｍｌ、塩酸４滴とともに約１０時間、加熱環流した。はじめポリマーはメタノールに不溶であったが、加熱環流により溶けて均一になった。その後、メタノールを減圧留去した後、テトラヒドロフランに再溶解し、ｎ−ヘキサンに再沈殿して白色粉末状ポリマー（１ｃ）１０．６ｇを得た。得られたポリマーの構造は、種々の分析法からカルボン酸とカルボン酸メチルエステルを含む、下記の構造が主であることがわかった。
【０１３５】
【化３０】

【０１３６】
または
【０１３７】
【化３１】

【０１３８】
式中ｎは整数を表す。
【０１３９】
上記ポリマー（１ｃ）１００重量部、１−ヒドロキシメチルアダマンタン３０重量部、酸発生剤トリフェニルスルホニウムトリフレート３重量部をシクロヘキサノン６００重量部に溶解し、孔径０．２０μｍのテフロンフィルターを用いてろ過しレジスト溶液とした。
【０１４０】
ヘキサメチルジシラザンで処理したシリコン基板上に、上記のレジスト溶液を回転塗布し、塗布後１００℃で２分間加熱処理して、膜厚０．５１μｍのレジスト膜を形成した。
【０１４１】
実施例１と同様にしてそのレジスト膜にＡｒＦエキシマレーザ光を照射し、その後１００℃で２分間露光後ベークを行い、テトラメチルアンモニウムヒドロキシド水溶液（０．１１３重量％）で現像した。露光量３００ｍＪ／ｃｍ2のＡｒＦエキシマレーザ光を照射しても、パタンは得られず、膜は露光部、未露光部ともに１５秒で溶解した。
【０１４２】
ＮａＣｌ板上に塗布した上記レジストに、同様にＡｒＦエキシマ光を３００ｍＪ／ｃｍ2照射し、露光前および露光後ベーク後の赤外吸収スペクトルを実施例１と同様に測定した。その結果、露光前と露光後ベーク後のスペクトルの変化は小さく、カルボン酸の約３％程度しかエステル化は起こっていないことがわかった。
【０１４３】
上記の１−ヒドロキシアダマンタンの代わりに、同量の２−アダマンタノールを用いて同条件下で実験したが、やはりネガ化は起こらず、赤外吸収スペクトルによる分析でも約３％程度しかエステル化は起こっていないことがわかった。
【０１４４】
〈比較例２〉
合成例１で合成したγ−ヒドロキシカルボン酸構造を有するポリマー（１ｂ）１００重量部，酸発生剤トリフェニルスルホニウムトリフレート３重量部をシクロヘキサノン６０００重量部に溶解し，孔径０．２０μmのテフロンフィルターを用いてろ過をし、レジスト溶液Aとした。上記ポリマー（１ｂ）の代わりに，合成例２で合成したポリマー（２ｂ）を用いてレジスト溶液を同様に調製し，レジスト溶液Bとした。さらに合成例1と同様にして，合成例１で用いた5−メチレンビシクロ［２．２．１］ヘプト−２−エンの代わりに，ビシクロ［２．２．１］ヘプト−２−エンを用いてシクロ［２．２．１］ヘプト−２−エン−無水マレイン酸共重合体を合成し，それを還元，加水分解して以下の化学式のポリマー（６ａ）を合成した。
【０１４５】
【化３２】

【０１４６】
上記ポリマー（１ｂ）の代わりに、ポリマー（６ａ）を用いてレジスト溶液を同様に調製し、レジスト溶液Ｃとした。
【０１４７】
ここでレジストAで用いたポリマー（１ｂ）は、側鎖にγ―ヒドロキシカルボン酸構造を有する脂環族構造の繰り返しを含む樹脂であり、レジストB及びCで用いたポリマー（２ｂ）、（６ａ）は、主鎖に直接γ―ヒドロキシカルボン酸構造を含む樹脂である。
【０１４８】
ヘキサメチルジシラザンで処理したシリコン基板上に、上記のレジスト溶液Ａ、Ｂ、Ｃを回転塗布し、塗布後１００℃で２分間加熱処理して、膜厚０．５０μｍのレジストＡ、Ｂ、Ｃの３種類の膜を形成した。
【０１４９】
窒素で装置内部を置換した露光実験装置に、上記のレジストを塗布した基板を入れ、ＡｒＦエキシマレーザ光を露光量を段階的に変えて照射し、その後１００℃で２分間露光後ベークを行った。２３℃のテトラメチルアンモニウムヒドロキシド水溶液（０．１１３重量％）にレジスト膜を浸漬したところ、膜の未露光部は２０から３０秒で溶解した。そこで現像は、その約４倍の時間の１２０秒間行い、続いて６０秒間純水でリンスした。
【０１５０】
その結果、レジストＡは、露光量１５ｍＪ／ｃｍ2で、ネガ化して残膜厚がほぼ１００％になった。これに対して、レジストＢは低感度であり、露光後ベークを１２０℃にした場合に８０ｍＪ／ｃｍ２で、ネガ化して残膜厚が約９０％となった。さらにレジストＣでは、露光後ベークが１２０℃の条件で、露光量２００ｍＪ／ｃｍ２でもネガ化は起こらず、ポリマー構造による感度の違いが見られた。
【０１５１】
【発明の効果】
水性アルカリ現像液で微細パタンが膨潤することなく現像でき、カルボン酸を有する樹脂のエステル化を用いた解像性能の優れたネガ型のパタン形成方法を得ることができる。
【図面の簡単な説明】
【図１】合成例１のポリマーの塗膜を水性アルカリ現像液につけた時の溶解速度モニターを用いて得られた現像時間とモニター光の強度の関係を示すグラフ。
【図２】合成例１のポリマーの塗膜を水性アルカリ現像液につけた時の溶解時間と膜厚の関係を示すグラフ。
【図３】ＭＯＳ（金属−酸化物−半導体）型トランジスタの断面図。
【図４】本発明のパタン形成方法を用いたフィールド酸化膜、及びシリコンゲートの形成方法を示す図。
【符号の説明】
３２、４５…フィールド酸化膜、３３…ソースコンタクト、３４…ドレインコンタクト、３５…多結晶シリコン、３６…ソース電極、３７…ドレイン電極、３８…ゲート電極、３９…保護膜、４２…酸化膜、４４…レジストパタン、４６…多結晶シリコン膜、４７…レジストパタン、４８…多結晶シリコンゲート。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a microlithography process using a photosensitive composition, which is a fine processing technique in a manufacturing process of a semiconductor device or the like, and a manufacturing method of a semiconductor device or the like including the microlithography process. More specifically, it is a negative type suitable for an optical lithography process using far ultraviolet rays having a wavelength of 220 nm or less, such as ArF excimer laser light, which is a radiation source having a shorter wavelength than a high-pressure mercury lamp or KrF excimer laser, which is an existing ultraviolet light source. The present invention relates to a pattern forming method and a semiconductor device manufacturing method.
[0002]
[Prior art]
Photolithography technology that produces micron or submicron fine patterns in electronic devices such as semiconductors has been at the heart of mass production microfabrication technology. Recent demands for higher integration and higher density of semiconductor devices have led to many advances in microfabrication technology. In particular, as the minimum processing size approaches the exposure wavelength, photolithography technology using a high-pressure mercury lamp g-line (436 nm), i-line (365 nm) to KrF excimer laser (248 nm) and a light source with a shorter wavelength is developed. It has been. In response to these changes in exposure wavelength, materials corresponding to the respective wavelengths have been developed for photoresists. Conventionally, photoresists suitable for these wavelengths have different photosensitizers and photosensitivity mechanisms, but aqueous alkali development utilizing aqueous alkali solubility of a resin or polymer material having a phenol structure has been used industrially. It was. These resins or polymer materials inevitably contain a lot of aromatic rings, which are chemical structural elements that increase the etching resistance in the dry etching process after forming the resist pattern.
[0003]
As the negative resists using such a resin having a phenol structure, there are a crosslinked type as disclosed in JP-A-62-164045 and a dissolution-inhibiting type as described in JP-A-4-165359. In either case, submicron fine patterns can be formed without swelling.
[0004]
In recent years, expectations for photolithography using an ArF excimer laser (193 nm) as a light source are increasing as photolithography in a region where the minimum processing dimension is smaller than 0.25 microns. However, this wavelength corresponds to the absorption maximum due to the aromatic ring, and in the photoresist material that has been used industrially in the related art, the exposure latent image can be formed only on the extreme surface of the photoresist film. It was difficult to form a fine resist pattern by aqueous alkali development.
[0005]
On the other hand, various resist materials having high transmittance in this wavelength region and high dry etching resistance have been proposed. As a chemical structure that is transparent in the far ultraviolet region including the wavelength of 193 nm of an ArF excimer laser and can impart dry etching resistance to a resist material instead of an aromatic ring, use of an adamantane skeleton is disclosed in JP-A-4-39665 and JP-A-5-265212. Similarly, use of a norbornane skeleton is disclosed in JP-A-5-80515 and JP-A-5-257284. In addition to these structures, it is disclosed in JP-A-7-28237 and JP-A-8-259626 that alicyclic structures such as tricyclodecanyl groups are effective.
[0006]
Regarding a resist material which has a transparent chemical structure in the far ultraviolet region including the wavelength of 193 nm of an ArF excimer laser and is capable of aqueous alkali developability, JP-A-4-39665, JP-A-4-184345, JP-A-4 Attempts have been made to use a carboxylic acid structure of acrylic acid or methacrylic acid, as disclosed in 226461, JP-A-5-80515, and the like. In these, the aqueous alkali solubility of the portion dissolved in the developer by aqueous alkaline development is based on the carboxylic acid structure of acrylic acid or methacrylic acid. JP-A-8-259626 discloses a polymer compound in which a carboxylic acid group is added to an alicyclic structure introduced into a methacrylic acid ester side chain.
[0007]
[Problems to be solved by the invention]
In the phenol structure conventionally used as an alkali-soluble group, pKa = 10.0 (phenol), whereas in these carboxylic acid structures, pKa = 4.8 (acetic acid) has a low value and high acidity. . Therefore, when they are used as the alkali-soluble group of the base resin, generally, at the same molar fraction, the resin having a carboxylic acid structure has a higher dissolution rate in an aqueous alkali and the resin having a phenol structure is less soluble. Even in a concentrated alkaline developer, the resin having a carboxylic acid structure is dissolved.
[0008]
When a resin having a carboxylic acid as described above is used, if a cross-linking agent such as that disclosed in JP-A-62-164045 is used, a carboxylic acid having a high acidity remains in the cross-linked portion. There was a drawback that the developer was infiltrated and swollen, and a fine pattern could not be formed. In addition, when using a compound having an inhibitory action of an acid generated by exposure, as disclosed in JP-A-4-165359, a resin having a carboxylic acid does not provide a dissolution contrast and does not become a negative resist. There was a drawback.
[0009]
It is generally known that a carboxylic acid is converted into a carboxylic acid ester by an acid-catalyzed reaction with an alcohol in solution, and this reaction is one of useful methods for synthesizing a carboxylic acid ester. However, since this reaction is an equilibrium reaction, in order to advance the reaction to the ester side, it is necessary to use a large excess of alcohol and to take out by-product water out of the system. When this reaction is applied to a radiation-sensitive composition, alcohol cannot be added in a large excess while maintaining the alkali solubility of the coating film, and it is difficult to remove water generated by the reaction out of the system. For this reason, esterification usually proceeds only a few percent. As a result, there was a drawback that the dissolution contrast was not high enough to form a pattern only by reducing the amount of carboxylic acid to that extent.
SUMMARY OF THE INVENTION A first object of the present invention is to provide a negative pattern forming method which can be developed with an aqueous alkaline developer without swelling of fine patterns and has excellent resolution performance using esterification of a resin having a carboxylic acid. There is. A second object of the present invention is to provide a semiconductor device manufacturing method using such a pattern forming method.
[0010]
[Means for Solving the Problems]
In order to achieve the first object, the pattern forming method of the present invention forms a coating film comprising a photosensitive composition containing at least a carboxylic acid structure on a predetermined substrate, and the predetermined pattern is formed on the coating film. A latent image of a desired pattern is formed in the coating film by irradiating active actinic radiation in the form of a film, the film is heated to cause the reaction to proceed, and then the desired coating is applied to the coating film using an aqueous alkaline developer. In the pattern forming method for developing the pattern, part or all of the carboxylic acid structure in the irradiated portion of the active radiation is changed to a γ-lactone structure or δ-lactone structure which is a carboxylic acid ester structure.
[0011]
The structure of these γ-lactone and δ-lactone structures is an ester produced by acid-catalyzed reaction because the alcohol that becomes the esterification ester of the carboxylic acid is generated from the γ- or δ-position of the carboxylic acid in the molecule. Occurs more easily than usual. In addition, the produced ester is not hydrolyzed by a commonly used tetraalkylammonium hydroxide aqueous solution and is stable during development.
[0012]
The structure of the carboxylic acid for producing the γ-lactone structure or δ-lactone structure as described above is preferably a γ-hydroxycarboxylic acid structure or a δ-hydroxycarboxylic acid structure. In such a structure, esterification easily occurs because a 5-membered ring or a 6-membered ring can be formed by intramolecular esterification by an acid-catalyzed reaction.
[0013]
The carboxylic acid structure used in the pattern forming method of the present invention is preferably a chemical structure represented by the following formula (1) or (2).
[0014]
[Chemical 1]

[0015]
[Chemical 2]

[0016]
In the formula, R 1, R 2, R 3, R 4, R 5, R 6, R 7 and R 8 represent hydrogen or an alkyl group having 1 to 10 carbon atoms, and these alkyl groups may be connected to each other to form a cyclic alkyl group. .
[0017]
Furthermore, it is desirable that at least the carboxylic acid structure represented by the formula (1) or (2) is included in the polymer compound constituting the photosensitive composition.
[0018]
Specifically, a resin containing at least a repeating structure selected from the following general formulas (5) to (12) has the above-described structure, and has low absorption in the far ultraviolet region and has dry etch resistance. So desirable.
[0019]
[Chemical formula 5]

[0020]
[Chemical 6]

[0021]
[Chemical 7]

[0022]
[Chemical 8]

[0023]
[Chemical 9]

[0024]
[Chemical Formula 10]

[0025]
Embedded image

[0026]
Embedded image

[0027]
Here, n in the formula represents an integer.
[0028]
The resin having at least a repeating structure such as the above formula (5) or (6) includes a compound containing a cyclic aliphatic hydrocarbon skeleton such as 5-methylenebicyclo [2.2.1] hept-2-ene and anhydrous resin. It can be obtained by radically copolymerizing maleic acid, reducing the maleic anhydride portion to lactonize, and hydrolyzing and modifying it.
[0029]
A resin having at least a repeating structure such as the above formula (7) or (8) is a radical copolymer of a compound containing a cyclic aliphatic hydrocarbon skeleton such as cycloocta-1,5-diene and maleic anhydride. Thus, the maleic anhydride moiety is reduced to lactonize, and it is further hydrolyzed and modified.
[0030]
The resin having at least a repeating structure such as the above formula (9) or (10) includes a compound containing a cyclic aliphatic hydrocarbon skeleton such as 5-ethylenebicyclo [2.2.1] hept-2-ene. It can be obtained by radically copolymerizing maleic anhydride, reducing the maleic anhydride portion to lactonize, and further hydrolyzing and modifying it.
[0031]
The resin having at least a repeating structure such as the above formula (11) or (12) includes a compound containing a cyclic aliphatic hydrocarbon skeleton such as 5-vinylbicyclo [2.2.1] hept-2-ene. It can be obtained by radically copolymerizing maleic anhydride, reducing the maleic anhydride portion to lactonize, and further hydrolyzing and modifying it.
[0032]
In addition, as for the weight average molecular weight of these resin, it is desirable that it is 1,000-300,000.
[0033]
Among the above polymer compounds, those containing a repeating alicyclic structure having a carboxylic acid structure represented by the above formula (1) or (2) in the side chain are directly (1) or (2) in the main chain. Compared to those containing the carboxylic acid structure shown, lactonization is likely to occur in an acid-catalyzed reaction, which is more desirable because it tends to be highly sensitive.
[0034]
Specifically, the side chain as represented by the above formula (5) or (6) or (9) or (10) or (11) or (12) is represented by the above formula (1) or (2). The resin containing a repeating alicyclic structure having a carboxylic acid structure is a carboxylic acid directly represented by (1) or (2) in the main chain as represented by the above formula (7) or (8). A resin containing an acid structure is more desirable because it can form a pattern with higher sensitivity.
[0035]
When the carboxylic acid structure represented by the formula (1) or (2) is directly contained in the main chain, the carboxylic acid moiety in the formula (1) or (2) may be sterically separated from the hydroxyl group. In some cases, the reaction of lactonization hardly occurs. On the other hand, when the carboxylic acid structure represented by the formula (1) or (2) is included in the side chain, the carboxylic acid portion and the hydroxyl portion are hardly separated sterically, so that lactonization is easy. There is a possibility that a pattern can be formed with high sensitivity.
[0036]
The resin having the above structure becomes a pattern forming material by combining 0.1 to 30 parts by weight of a compound that generates an acid upon irradiation with active actinic radiation with respect to the resin. Examples of compounds that generate an acid upon irradiation with active actinic radiation include onium salts such as triphenylsulfonium triflate, sulfonyloxyimides such as trifluoromethanesulfonyloxynaphthylimide, and sulfonic acid esters. For example, any acid may be used as long as it generates acid upon irradiation with an ArF excimer laser or the like.
[0037]
The carboxylic acid structure used in the pattern forming method of the present invention may be a chemical structure represented by the following formula (3) or (4).
[0038]
[Chemical 3]

[0039]
[Formula 4]

[0040]
In the formula, R 1, R 2, R 3, R 4, R 5, R 6, R 7 and R 8 represent hydrogen and an alkyl group having 1 to 10 carbon atoms, and these alkyl groups may be connected to each other to form a cyclic alkyl group. . In the formula, X represents an acetal or ketal such as a 1-ethoxyethyl group or a tetrahydropyranyl group. In this case, since the hydroxyl group is protected by X, it is more thermally stable.
[0041]
Furthermore, it is desirable that at least the carboxylic acid structure represented by the formula (3) or (4) is included in the polymer compound constituting the photosensitive composition.
[0042]
Among the above polymer compounds, those containing a repeating alicyclic structure having a carboxylic acid structure represented by the above formula (3) or (4) in the side chain are directly contained in the main chain (3) or (4). Compared to those containing a carboxylic acid structure represented by the formula (1), lactonization by an acid-catalyzed reaction is likely to occur, and it is more desirable because it tends to be highly sensitive.
[0043]
When the carboxylic acid structure represented by the formula (3) or (4) is directly contained in the main chain, the carboxylic acid moiety in the formula (3) or (4) is sterically separated from the protected hydroxyl group. In some cases, the reaction of lactonization hardly occurs. On the other hand, when the carboxylic acid structure represented by the formula (3) or (4) is contained in the side chain, the carboxylic acid portion and the protected hydroxyl portion are not easily separated sterically. There is a possibility that a pattern can be formed with high sensitivity.
[0044]
The photosensitive composition containing a carboxylic acid structure used in the pattern forming method of the present invention may further contain an alicyclic structure for improving dry etching resistance. Examples of the alicyclic structure include adamantyl, norbornane, tricyclodecane, and androstane structures. These structures are transparent in the far ultraviolet region and have dry etching resistance.
[0045]
Examples of the active actinic radiation used in the present invention include far ultraviolet light having a wavelength of 250 nm or less, and vacuum ultraviolet light such as ArF excimer laser light. An electron beam, EUV, X-ray, or the like can also be used.
[0046]
The aqueous alkaline developer used in the present invention is preferably an aqueous tetraalkylammonium hydroxide solution having 1 to 5 carbon atoms.
[0047]
According to another aspect of the present invention, there is provided a method for manufacturing a semiconductor device, comprising: forming a resist pattern on a semiconductor substrate by any one of the pattern forming methods described above; and etching the substrate based on the resist pattern. Or a step of implanting ions into the substrate.
[0048]
Examples of the etching method used in the semiconductor manufacturing method of the present invention include dry etching methods such as plasma etching, reactive ion etching, reactive ion etching, and reactive ion beam etching, and wet etching methods.
[0049]
Examples of the substrate processed in the method for manufacturing a semiconductor device of the present invention include a silicon dioxide film formed by a CVD method or a thermal oxidation method, an oxide film such as a coating glass film, or a nitride film such as a silicon nitride film. . Moreover, various metal films, such as aluminum, its alloy, tungsten, a polycrystalline silicon, etc. are mentioned.
[0050]
In the present invention, by utilizing the highly reactive lactonization among the esterification of carboxylic acid, it is possible to efficiently convert carboxylic acid to carboxylic acid ester by catalytic reaction with acid generated by exposure. . Since this reaction is intramolecular esterification, cross-linking between molecules does not occur, and the amount of carboxylic acid simply changes between the exposed and unexposed areas. When the carboxylic acid and the alcohol are separate molecules, only a few percent of the carboxylic acid is esterified in the membrane by an acid catalyzed reaction under conditions that can be practically applied. On the other hand, in the γ- or δ-lactonization used in the pattern forming method of the present invention, 30% or more of the carboxylic acid is esterified in the exposed area. For this reason, the dissolution rate is greatly changed, and the crosslinking reaction has not occurred, so that the swelling which has been a problem of the prior art can be avoided and a fine pattern can be formed.
[0051]
DETAILED DESCRIPTION OF THE INVENTION
EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited only to these Examples. First, prior to examples, a synthesis example of materials used in the present invention will be shown.
[0052]
<Synthesis Example 1> Synthesis of polymer (1b) having γ-hydroxycarboxylic acid structure
In a 500 ml three-necked flask equipped with a thermometer, a condenser tube, and a nitrogen inlet tube, 21.2 g of 5-methylenebicyclo [2.2.1] hept-2-ene, 19.6 g of maleic anhydride, 2,2′- 2.56 g of azobis (isobutyronitrile) and 240 g of tetrahydrofuran were added, and polymerization was performed for 8 hours by heating and refluxing at 70 ° C. while introducing nitrogen. After the polymerization, the solution was poured into 1000 ml of n-hexane, the polymer was precipitated and dried to obtain 37.5 g of 5-methylenebicyclo [2.2.1] hept-2-ene-maleic anhydride copolymer (1a). Obtained (yield 92%). The structure of the obtained polymer was found to be mainly the following structure from various analysis methods.
[0053]
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[0054]
In the formula, n represents an integer.
[0055]
Moreover, when the molecular weight of polystyrene conversion of this polymer was investigated in tetrahydrofuran by gel permeation chromatography (GPC), the weight average molecular weight was 5,800 and the number average molecular weight was 2,500.
[0056]
A 500 ml three-necked flask was charged with 1.9 g of sodium borohydride and 30 g of tetrahydrofuran, cooled to 0 ° C. in an ice bath under nitrogen, and stirred while stirring the 5-methylenebicyclo [2.2.1] synthesized as described above. A solution of 10 g of hept-2-ene-maleic anhydride copolymer in 100 g of tetrahydrofuran was added dropwise over about 1 hour. After dropping, the mixture was stirred for several hours and then left overnight.
[0057]
The solution was poured into about 300 ml of water and stirred, and then about 1N aqueous hydrochloric acid was gradually added to make it weakly acidic. About 150 ml of ethyl acetate was added to this solution, extraction was performed twice, and the obtained organic layer was washed twice with 100 ml of water. After washing, the organic layer is dried over anhydrous sodium sulfate, and after drying, the solvent is distilled off under reduced pressure, poured into 500 ml of n-hexane, and the precipitated polymer is dried to obtain 7.8 g of a white powdery polymer. It was. The structure of the polymer obtained was analyzed by various analytical methods, and the polymer (1b) having at least a structure in which the anhydride part of (1a) was reduced to lactonize and a γ-hydroxycarboxylic acid structure that was further ring-opened was obtained. I found out.
[0058]
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[0059]
Or
[0060]
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[0061]
In the formula, l and m represent integers.
[0062]
100 parts by weight of the obtained polymer (1b) was dissolved in 600 parts by weight of cyclohexanone and filtered through a filter having a pore size of 0.2 μm. It was spin-coated and baked at 100 ° C. for 2 minutes to obtain a polymer film. When a film (film thickness of 570 nm) coated on a silicon substrate was immersed in an aqueous tetramethylammonium hydroxide solution (concentration: 0.113 wt%), it melted in 7.2 seconds while the interference color changed, and the remaining film became zero. became. Further, when dissolution was examined using a dissolution rate monitor, it was found that the solution was dissolved without swelling. FIG. 1 shows the relationship between the development time, which is raw data obtained using a dissolution rate monitor, and the intensity of the monitor light. FIG. 2 shows the relationship between the dissolution time and the film thickness obtained by analyzing it.
[0063]
When the absorption spectrum of the film coated on the lithium fluoride substrate was measured with a vacuum ultraviolet spectrometer (manufactured by ARC), the absorbance at 193 nm was 0.80 at a film thickness of 1.0 μm, and the absorption was small. all right.
[0064]
<Synthesis Example 2> Synthesis of polymer (2b) having γ-hydroxycarboxylic acid structure
In place of 21.2 g of 5-methylenebicyclo [2.2.1] hept-2-ene used in Synthesis Example 1, 21.6 g of cycloocta-1,5-diene was subjected to radical polymerization in the same manner. 38 g of a 1,5-diene-maleic anhydride copolymer (2a) was obtained (yield 93%). The structure of the obtained polymer was found to be mainly the following structure from various analysis methods.
[0065]
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[0066]
In the formula, n represents an integer.
[0067]
As for the molecular weight of this polymer in terms of polystyrene, the weight average molecular weight was 1,400, and the number average molecular weight was 1,000.
[0068]
When the anhydrous portion was reduced and hydrolyzed with sodium borohydride in the same manner as in Synthesis Example 1, the structure of the polymer obtained was reduced to the lactone from the various analytical methods by reducing the anhydride portion of (2a). It was found that this was a polymer (2b) having at least a converted structure and a γ-hydroxycarboxylic acid structure that was further ring-opened.
[0069]
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[0070]
Or
[0071]
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[0072]
In the formula, l and m represent integers.
[0073]
<Synthesis Example 3> Synthesis of polymer (3b) having γ-hydroxycarboxylic acid structure
The same procedure was performed using 24 g of 5-ethylenebicyclo [2.2.1] hept-2-ene instead of 21.2 g of 5-methylenebicyclo [2.2.1] hept-2-ene used in Synthesis Example 1. Was subjected to radical polymerization to obtain 37 g of 5-ethylenebicyclo [2.2.1] hept-2-ene-maleic anhydride copolymer (3a) (yield 86%). The structure of the obtained polymer was found to be mainly the following structure from various analysis methods.
[0074]
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[0075]
In the formula, n represents an integer.
[0076]
As for the molecular weight of this polymer in terms of polystyrene, the weight average molecular weight was 3,300, and the number average molecular weight was 2,000.
[0077]
When the anhydrous portion was reduced and hydrolyzed with sodium borohydride in the same manner as in Synthesis Example 1, the structure of the resulting polymer was reduced to the lactone from the various analytical methods by reducing the anhydride portion of (3a). It was found that this was a polymer (3b) having at least a converted structure and a ring-opened γ-hydroxycarboxylic acid structure.
[0078]
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[0079]
Or
[0080]
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[0081]
In the formula, l and m represent integers.
[0082]
<Synthesis Example 4> Synthesis of polymer (4b) having γ-hydroxycarboxylic acid structure
The same procedure was performed using 24 g of 5-vinylbicyclo [2.2.1] hept-2-ene instead of 21.2 g of 5-methylenebicyclo [2.2.1] hept-2-ene used in Synthesis Example 1. Was subjected to radical polymerization to obtain 26 g of 5-vinylbicyclo [2.2.1] hept-2-ene-maleic anhydride copolymer (4a) (yield 59%). The structure of the obtained polymer was found to be mainly the following structure from various analysis methods.
[0083]
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[0084]
In the formula, n represents an integer.
[0085]
As for the molecular weight of this polymer in terms of polystyrene, the weight average molecular weight was 2,900, and the number average molecular weight was 1,700.
[0086]
When the anhydrous portion was reduced and hydrolyzed with sodium borohydride in the same manner as in Synthesis Example 1, the structure of the resulting polymer was reduced to the lactone from the various analytical methods (4a). It was found that this was a polymer (4b) having at least a converted structure and a γ-hydroxycarboxylic acid structure that was further ring-opened.
[0087]
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[0088]
Or
[0089]
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[0090]
In the formula, l and m represent integers.
[0091]
<Synthesis Example 5>
(5-1) Synthesis of lithocholic acid dimer (5a)
In a 300 ml three-necked flask under nitrogen flow, 11.3 g (0.030 mol) of lithocholic acid, 2.4 g (0.030 mol) of pyridine and 100 ml of tetrahydrofuran were placed, and succinyl chloride dissolved in 30 ml of tetrahydrofuran was cooled to 0 ° C. 3 g (0.015 mol) was added dropwise. After the dropwise addition, the mixture was stirred at room temperature for 2 hours and refluxed for another 2 hours. After refluxing, the precipitated black salt was filtered off, and the solution was added dropwise to 1000 ml of 1% aqueous hydrochloric acid. The gray precipitate thus deposited was suction filtered, washed with water and dried to obtain 12.6 g of lithocholic acid dimer (5a).
[0092]
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[0093]
Here, lithocholic acid is used as the alicyclic compound having a carboxylic acid, but deoxycholic acid, cholic acid, ursodeoxycholic acid, and the like can also be used. However, since these have a plurality of alcoholic hydroxyl groups in the molecule, in the reaction with dicarboxylic acid chloride, an oligomer is formed instead of a dimer. Further, as dicarboxylic acid chloride, not only succinyl chloride but also any one such as malonic acid chloride and 1,3-adamantane dicarboxylic acid chloride can be used.
[0094]
(5-2) Synthesis of 1- (tetrahydropyranyloxy) -2-bromoethane (5b) and 1- (tetrahydropyranyloxy) -3-bromopropane (5c) 2-bromoethanol 12.5 g (0.10 mol) ) 12.6 g (0.15 mol) of 3,4-dihydro-2H-pyran was dissolved in 200 ml of ethyl acetate, 1.0 g of pyridinium-p-toluenesulfonate was added thereto, and the mixture was stirred at room temperature for 4 hours. After confirming the disappearance of the alcoholic hydroxyl group by infrared absorption spectrum, add 80 ml of a 2.38% aqueous solution of tetramethylammonium hydroxide to the solution, wash twice, and then wash twice with 80 ml of water. did. The organic layer was dried over sodium sulfate and distilled under reduced pressure to obtain 15.7 g of 1- (tetrahydropyranyloxy) -2-bromoethane (5b).
[0095]
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[0096]
Similarly, 1- (tetrahydropyranyloxy) -3-bromopropane (5c) was synthesized.
[0097]
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[0098]
(5-3) Synthesis of compound (5d) having γ-hydroxycarboxylic acid structure and compound (5e) having δ-hydroxycarboxylic acid structure
Under a dry nitrogen stream, 100 ml of dry tetrahydrofuran was added to 30 ml (0.060 mol) of lithium diisopropylamide 2.0 M solution (commercially available), and 11.7 g (0.014 mol) of dry tetrahydrofuran synthesized lithocholic acid dimer (5a). The solution was added dropwise so that the reaction temperature did not exceed 0 ° C and stirred at 0 ° C. After adding 5.4 g (0.030 mol) of hexamethylphosphoric triamide to this solution and stirring at 0 ° C., 15.7 g of synthesized 1- (tetrahydropyranyloxy) -2-bromoethane (5b) was added at 0 ° C. Added promptly. Although the temperature rose, the mixture was allowed to stand at room temperature for 2 hours while stirring as it was. After adding 300 ml of ice-cooled 5% aqueous hydrochloric acid solution 200 to confirm weak acidity, the mixture was extracted twice with 150 ml of diethyl ether. Thereafter, the organic layer was washed with 100 ml of 3% aqueous hydrochloric acid, and further washed twice with 100 ml of water, and the organic layer was dried over sodium sulfate. After drying, the solvent was distilled off under reduced pressure, and the residue was reprecipitated with hexane to obtain 12.1 g of the compound (5d) having a γ-hydroxycarboxylic acid structure. Various analyzes revealed that the product had the following structure with some remaining tetrahydropyranyl groups.
[0099]
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[0100]
In the formula, R represents hydrogen or a tetrahydropyranyl group.
[0101]
Similarly, instead of 1- (tetrahydropyranyloxy) -2-bromoethane (5b) used above, equimolar 1- (tetrahydropyranyloxy) -3-bromopropane (5c) is used. Thus, a compound (5e) having a δ-hydroxycarboxylic acid structure was obtained. Various analyzes revealed that the product had the following structure with some remaining tetrahydropyranyl groups.
[0102]
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[0103]
In the formula, R represents hydrogen or a tetrahydropyranyl group.
[0104]
<Example 1>
100 parts by weight of the polymer (1b) having a γ-hydroxycarboxylic acid structure synthesized in Synthesis Example 1 and 2 parts by weight of the acid generator triphenylsulfonium triflate are dissolved in 600 parts by weight of cyclohexanone to obtain a Teflon filter having a pore size of 0.20 μm. It was used and filtered to make a resist solution.
[0105]
The above resist solution was spin-coated on a silicon substrate treated with hexamethyldisilazane, and was heat-treated at 100 ° C. for 2 minutes after coating to form a resist film having a thickness of 0.54 μm. When the absorption spectrum of this film was measured with an ultraviolet-visible spectrophotometer, the transmittance at 193 nm was 25%.
[0106]
A substrate coated with the above resist was placed in an exposure experimental apparatus in which the inside of the apparatus was replaced with nitrogen, and a Levenson type phase shift mask formed on a quartz plate was adhered thereto. ArF excimer laser light was irradiated through the mask, and then post-exposure baking was performed at 100 ° C. for 2 minutes. When the resist film was immersed in an aqueous solution of tetramethylammonium hydroxide (0.113% by weight) at 23 ° C., the unexposed part of the film was dissolved in 30 seconds. Therefore, development was performed for 120 seconds, which is four times as long as that, and then rinsed with pure water for 60 seconds. As a result, a negative 0.20 μm line and space pattern was obtained at an exposure amount of 20 mJ / cm 2. At this time, no pattern swelling was observed.
[0107]
At this time, when the obtained substrate with the pattern was immersed in tetrahydrofuran, it was found that the pattern was instantaneously dissolved and no crosslinking occurred.
[0108]
The resist film was exposed using a KrF excimer laser stepper (NA = 0.45) through a Levenson type phase shift mask. Thereafter, after exposure bake and development under the above process conditions, a negative 0.18 .mu.m line and space pattern was obtained with an exposure dose of 30 mJ / cm @ 2. At this time, no pattern swelling was observed.
[0109]
Further, the resist film (film thickness of 540 nm) applied on the aluminum substrate was etched using an ECR dry etching apparatus under the following conditions.
[0110]
Cl2 flow rate 90sccm
BCl3 flow rate 60sccm
Gas pressure 1.3Pa
RF bias power 140W,
As a result, the etch rate of this resist was 1230 nm / min. The poly (methyl methacrylate) etch rate compared under the same conditions was less than 1580 nm / min.
[0111]
Similarly, the resist applied on the NaCl plate was irradiated with 20 mJ / cm 2 of ArF excimer light, and the infrared absorption spectra before and after exposure and after baking were measured with FT-1720X manufactured by PerkinElmer. As a result, it was found that the peak at 3300 cm @ -1 due to carboxylic acid and hydroxyl group was greatly reduced after post-exposure baking. It was also found that the peak at 1705 cm -1 of carboxylic acid decreased and the peak at 1770 cm -1 due to lactone increased. From the intensity of these absorptions, it was found that about 72% of the carboxylic acid existing before exposure was lactonized after exposure.
[0112]
The resist film initially had a polymer (1b) structure having a γ-hydroxycarboxylic acid structure and was alkali-soluble by the carboxylic acid. ArF excimer laser exposure generated trifluoromethanesulfonic acid from the acid generator triphenylsulfonium triflate. In the post-exposure bake, using the acid as a catalyst, the structure of γ-hydroxycarboxylic acid in the polymer was esterified by intramolecular dehydration, resulting in the structure of γ-lactone. As a result, the exposed portion became insoluble in the alkaline developer, and a negative pattern was formed. In this case, the mechanism of negative formation was not a cross-linking reaction, but a large decrease in the amount of carboxylic acid due to lactonization, so that swelling was avoided and a fine pattern could be formed.
[0113]
<Example 2>
Instead of the polymer (1b) having a γ-hydroxycarboxylic acid structure used in Example 1, 100 parts by weight of the polymer (2b) synthesized in Synthesis Example 2 and the γ-hydroxycarboxylic acid structure synthesized in Synthesis Example 5 were used. 30 parts by weight of the compound (5d) and 2 parts by weight of the acid generator trifluoromethanesulfonyloxynaphthylimide were dissolved in 600 parts by weight of cyclohexanone and filtered using a Teflon filter having a pore size of 0.20 μm to obtain a resist solution.
[0114]
The above resist solution was spin-coated on a silicon substrate treated with hexamethyldisilazane in the same manner as in Example 1, and heat-treated at 90 ° C. for 2 minutes to form a resist film having a thickness of 0.52 μm. . When the absorption spectrum of this film was measured with an ultraviolet-visible spectrophotometer, the transmittance at 193 nm was 60%.
[0115]
In the same manner as in Example 1, ArF excimer laser light was irradiated through a phase shift mask, followed by post-exposure baking at 90 ° C. for 2 minutes. When the resist film was immersed in an aqueous solution of tetrabutylammonium hydroxide (0.40% by weight) at 23 ° C., the unexposed part of the film was dissolved in 15 seconds. Therefore, development was performed for 60 seconds, which is four times as long as that, and then rinsed with pure water for 60 seconds. As a result, a negative 0.22 μm line and space pattern was obtained with an exposure amount of 27 mJ / cm 2. At this time, no pattern swelling was observed.
[0116]
Further, the resist film (film thickness 520 nm) applied on the aluminum substrate was etched under the conditions of Example 1 with an ECR dry etching apparatus.
[0117]
As a result, the etch rate of this resist was 1090 nm / min. The etching rate of polyhydroxystyrene compared under the same conditions was comparable to 1080 nm / min.
[0118]
<Example 3>
100 parts by weight of the polymer (1b) having a γ-hydroxycarboxylic acid structure used in Example 1, 30 parts by weight of the compound (5e) having a δ-hydroxycarboxylic acid structure synthesized in Synthesis Example 5, and dimethylphenyl acid generator 3 parts by weight of sulfonium triflate was dissolved in 600 parts by weight of cyclohexanone and filtered using a Teflon filter having a pore size of 0.20 μm to obtain a resist solution.
[0119]
In the same manner as in Example 1, the above resist solution was spin-coated on a silicon substrate treated with hexamethyldisilazane, followed by heat treatment at 90 ° C. for 2 minutes to form a resist film having a thickness of 0.54 μm. . When the absorption spectrum of this film was measured with an ultraviolet-visible spectrophotometer, the transmittance at 193 nm was 65%.
[0120]
In the same manner as in Example 1, ArF excimer laser light was irradiated through a phase shift mask, and then post-exposure baking was performed at 90 ° C. for 2 minutes. When the resist film was immersed in an aqueous solution of tetramethylammonium hydroxide (0.113 wt%) at 23 ° C., the unexposed part of the film was dissolved in 12 seconds. Therefore, development was performed for 48 seconds, which is four times as long as that, and then rinsed with pure water for 60 seconds. As a result, a negative 0.22 μm line and space pattern was obtained with an exposure amount of 35 mJ / cm 2. At this time, no pattern swelling was observed.
[0121]
Further, the resist film (film thickness 540 nm) applied on the aluminum substrate was etched under the conditions of Example 1 with an ECR dry etching apparatus.
[0122]
As a result, the etch rate of this resist was 1075 nm / min. The etching rate of polyhydroxystyrene compared under the same conditions was comparable to 1080 nm / min.
[0123]
<Example 4>
Instead of the polymer (1b) having a γ-hydroxycarboxylic acid structure used in Example 1, 100 parts by weight of the polymer (3b) having a γ-hydroxycarboxylic acid structure synthesized in Synthesis Example 3 and an acid generator diphenyliodonium 3 parts by weight of triflate was dissolved in 600 parts by weight of cyclohexanone and filtered using a Teflon filter having a pore size of 0.20 μm to obtain a resist solution.
[0124]
In the same manner as in Example 1, the above resist solution was spin-coated on a silicon substrate treated with hexamethyldisilazane, followed by heat treatment at 90 ° C. for 2 minutes to form a resist film having a thickness of 0.55 μm. .
[0125]
This was subjected to line and space pattern exposure using an electron beam drawing apparatus with an acceleration voltage of 50 kV. After the exposure, the resist film was immersed in an aqueous tetramethylammonium hydroxide solution (0.113 wt%) at 23 ° C. for 2 minutes at 90 ° C., and the unexposed portion of the film was dissolved in 20 seconds. Therefore, development was performed for 80 seconds, which is four times as long as that, and then rinsed with pure water for 60 seconds. As a result, a negative 0.20 μm line and space pattern was obtained at an exposure amount of 15 μC / cm 2. At this time, no pattern swelling was observed.
[0126]
<Example 5>
Instead of the polymer (1b) having a γ-hydroxycarboxylic acid structure used in Example 1, 100 parts by weight of the polymer (4b) synthesized in Synthesis Example 4 and the acid generator camphorsulfonyl 5 parts by weight of oxynaphthylimide was dissolved in 600 parts by weight of cyclohexanone and filtered using a Teflon filter having a pore size of 0.20 μm to obtain a resist solution.
[0127]
The above resist solution was spin-coated on a silicon substrate treated with hexamethyldisilazane in the same manner as in Example 1, and heat-treated at 90 ° C. for 2 minutes to form a resist film having a thickness of 0.52 μm. .
[0128]
This resist film was exposed using a KrF excimer laser stepper (NA = 0.45) through a Levenson type phase shift mask. After the post-exposure baking was performed at 90 ° C. for 2 minutes, the resist film was immersed in a 23 ° C. aqueous tetramethylammonium hydroxide solution (0.113 wt%). The unexposed portion of the film was dissolved in 25 seconds. Therefore, development was performed for 100 seconds, which is four times as long as that, and then rinsed with pure water for 60 seconds. As a result, a negative type 0.18 μm line and space pattern was obtained at an exposure amount of 20 mJ / cm 2. At this time, no pattern swelling was observed.
[0129]
<Example 7>
FIG. 3 shows a cross-sectional view of a known MOS (metal-oxide-semiconductor) transistor. The transistor has a structure in which a drain current flowing between the source electrode 36 and the drain electrode 37 is controlled by a voltage applied to the gate electrode 38.
[0130]
Here, the process of making such a structure is composed of more than a dozen processes. However, if these are roughly divided, they can be divided into three groups: a process up to field oxide film formation, a process up to gate formation, and a final process. it can. Here, the first process up to the formation of the field oxide film (FIG. 4) includes a process of forming a resist pattern on the silicon nitride film. The field oxide film was formed as in the following examples.
[0131]
By a known method, a 50 nm oxide film 42 is formed on a p-type silicon wafer 41 as shown in FIG. 4A, and a 200 nm silicon nitride film is formed thereon by plasma CVD to form a substrate. A 0.50 μm line resist pattern 44 is formed on the substrate by the material and method shown in Example 1 (FIG. 4B). After etching the silicon nitride film by a known method using the resist pattern as a mask (FIG. 4C), boron ion implantation for a channel stopper is performed using the resist as a mask again. After removing the resist (FIG. 4D), a field oxide film of 1.2 μm is formed in the element isolation region by selective oxidation using the silicon nitride film as a mask (FIG. 4E).
[0132]
Thereafter, a gate forming step and a final step were performed according to a known method. After etching the silicon nitride film, the gate is oxidized to grow polycrystalline silicon (FIG. 4F). A resist pattern of 0.20 μm line is formed on this substrate using the pattern forming method shown in Example 1 (FIG. 4G). Using this resist pattern as a mask, the polycrystalline silicon is etched by a known method to form a gate (FIG. 4H). A thin oxide film of the source and drain is etched, and then arsenic is diffused into the polycrystalline silicon gate, the source and the drain, and an oxide film is formed in the polycrystalline silicon gate and the source and drain regions. A contact for aluminum wiring to the gate, source and drain is viewed from the opening, aluminum coating and patterning are performed, a protective film is further formed, and a pad for bonding is provided. In this way, a MOS transistor as shown in FIG. 3 is formed.
[0133]
Although a method for forming a field oxide film has been particularly described here for a MOS transistor, the present invention is not limited to this and can be applied to other methods and processes for manufacturing semiconductor devices.
[0134]
<Comparative example 1>
10 g of 5-methylenebicyclo [2.2.1] hept-2-ene-maleic anhydride copolymer synthesized in Synthesis Example 1 was heated to reflux with 150 ml of methanol and 4 drops of hydrochloric acid for about 10 hours. At first, the polymer was insoluble in methanol, but it was dissolved by heating reflux and became uniform. Then, after depressurizingly distilling methanol, it re-dissolved in tetrahydrofuran and reprecipitated in n-hexane, and 10.6g of white powdery polymer (1c) was obtained. The structure of the obtained polymer was found to be mainly the following structure containing carboxylic acid and carboxylic acid methyl ester from various analytical methods.
[0135]
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[0136]
Or
[0137]
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[0138]
In the formula, n represents an integer.
[0139]
100 parts by weight of the above polymer (1c), 30 parts by weight of 1-hydroxymethyladamantane, and 3 parts by weight of acid generator triphenylsulfonium triflate are dissolved in 600 parts by weight of cyclohexanone and filtered using a Teflon filter having a pore size of 0.20 μm. A resist solution was obtained.
[0140]
The above resist solution was spin-coated on a silicon substrate treated with hexamethyldisilazane, and was heat-treated at 100 ° C. for 2 minutes after coating to form a resist film having a thickness of 0.51 μm.
[0141]
In the same manner as in Example 1, the resist film was irradiated with ArF excimer laser light, then subjected to post-exposure baking at 100 ° C. for 2 minutes, and developed with an aqueous tetramethylammonium hydroxide solution (0.113 wt%). Irradiation with an ArF excimer laser beam with an exposure dose of 300 mJ / cm 2 did not give a pattern, and the film dissolved in 15 seconds in both the exposed and unexposed areas.
[0142]
Similarly, ArF excimer light was irradiated at 300 mJ / cm 2 on the resist coated on the NaCl plate, and the infrared absorption spectra before and after the exposure were measured in the same manner as in Example 1. As a result, it was found that the change in the spectrum before the exposure and after the post-exposure bake was small and esterification occurred only about 3% of the carboxylic acid.
[0143]
An experiment was conducted under the same conditions using the same amount of 2-adamantanol instead of the above 1-hydroxyadamantane. However, no negative reaction occurred, and the esterification was only about 3% in the infrared absorption spectrum analysis. I knew it was not happening.
[0144]
<Comparative example 2>
100 parts by weight of the polymer (1b) having a γ-hydroxycarboxylic acid structure synthesized in Synthesis Example 1 and 3 parts by weight of the acid generator triphenylsulfonium triflate are dissolved in 6000 parts by weight of cyclohexanone, and a Teflon filter having a pore size of 0.20 μm is obtained. The resultant was filtered to obtain a resist solution A. A resist solution was prepared in the same manner using the polymer (2b) synthesized in Synthesis Example 2 instead of the polymer (1b). Further, in the same manner as in Synthesis Example 1, instead of 5-methylenebicyclo [2.2.1] hept-2-ene used in Synthesis Example 1, bicyclo [2.2.1] hept-2-ene was used. Then, a cyclo [2.2.1] hept-2-ene-maleic anhydride copolymer was synthesized and reduced and hydrolyzed to synthesize a polymer (6a) having the following chemical formula.
[0145]
Embedded image

[0146]
A resist solution was prepared in the same manner using the polymer (6a) instead of the polymer (1b) to obtain a resist solution C.
[0147]
Here, the polymer (1b) used in the resist A is a resin containing a repeating alicyclic structure having a γ-hydroxycarboxylic acid structure in the side chain, and the polymers (2b), (6a) used in the resists B and C are used. ) Is a resin containing a γ-hydroxycarboxylic acid structure directly in the main chain.
[0148]
On the silicon substrate treated with hexamethyldisilazane, the above resist solutions A, B, and C are spin-coated, and after the coating, heat treatment is performed at 100 ° C. for 2 minutes to form resists A, B, and C having a thickness of 0.50 μm. These three types of films were formed.
[0149]
The substrate coated with the above resist was placed in an exposure experimental apparatus in which the inside of the apparatus was replaced with nitrogen, and irradiated with ArF excimer laser light while changing the exposure stepwise, followed by post-exposure baking at 100 ° C. for 2 minutes. . When the resist film was immersed in an aqueous solution of tetramethylammonium hydroxide (0.113% by weight) at 23 ° C., the unexposed part of the film was dissolved in 20 to 30 seconds. Therefore, development was performed for 120 seconds, which is about four times as long as that, and then rinsed with pure water for 60 seconds.
[0150]
As a result, the resist A was negative at an exposure amount of 15 mJ / cm @ 2, and the remaining film thickness was almost 100%. On the other hand, the resist B had low sensitivity, and when the post-exposure baking was performed at 120 ° C., it was 80 mJ / cm 2. Furthermore, in the resist C, negative exposure did not occur even when the post-exposure baking was 120 ° C. and the exposure amount was 200 mJ / cm 2, and a difference in sensitivity depending on the polymer structure was observed.
[0151]
【The invention's effect】
Development can be performed without swelling the fine pattern with an aqueous alkaline developer, and a negative pattern forming method having excellent resolution performance using esterification of a resin having a carboxylic acid can be obtained.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between development time and monitor light intensity obtained using a dissolution rate monitor when a polymer coating film of Synthesis Example 1 is applied to an aqueous alkaline developer.
FIG. 2 is a graph showing the relationship between dissolution time and film thickness when the polymer coating film of Synthesis Example 1 is applied to an aqueous alkaline developer.
FIG. 3 is a cross-sectional view of a MOS (metal-oxide-semiconductor) type transistor.
FIG. 4 is a view showing a method for forming a field oxide film and a silicon gate using the pattern forming method of the present invention.
[Explanation of symbols]
32, 45 ... Field oxide film, 33 ... Source contact, 34 ... Drain contact, 35 ... Polycrystalline silicon, 36 ... Source electrode, 37 ... Drain electrode, 38 ... Gate electrode, 39 ... Protective film, 42 ... Oxide film, 44 ... resist pattern, 46 ... polycrystalline silicon film, 47 ... resist pattern, 48 ... polycrystalline silicon gate.

Claims (12)

Forming a coating film comprising a photosensitive composition having a compound containing a γ-hydroxycarboxylic acid structure or a δ- hydroxycarboxylic acid structure and a compound capable of generating an acid upon irradiation with active actinic radiation on a substrate; Irradiating with an active actinic ray of a predetermined pattern to change the carboxylic acid structure of the irradiated portion of the active actinic ray into a γ-lactone structure or a δ-lactone structure. 2. The pattern forming method according to claim 1, wherein the carboxylic acid structure is a chemical structure represented by the following formula (1) or (2).

In the formula, R1, R2, R3, R4, R5, R6, R7, and R8 represent hydrogen or an alkyl group having 1 to 10 carbon atoms, and these alkyl groups may be connected to each other to form a cyclic alkyl group. . The pattern formation method of Claim 1 WHEREIN: The said carboxylic acid structure is a chemical structure shown by following formula (3) or (4), The pattern formation method characterized by the above-mentioned.

In the formula, R1, R2, R3, R4, R5, R6, R7, and R8 represent hydrogen and an alkyl group having 1 to 10 carbon atoms, and these alkyl groups may be connected to each other to form a cyclic alkyl group. . In the formula, X represents an acetal such as a 1-ethoxyethyl group or a tetrahydropyranyl group. 3. The pattern forming method according to claim 2 , wherein the photosensitive composition contains a polymer compound, and at least the polymer compound contains a carboxylic acid structure represented by the formula (1) or (2). Pattern forming method. 5. The pattern forming method according to claim 4 , wherein the polymer compound includes a repeating alicyclic structure having a carboxylic acid structure represented by the above formula (1) or (2) in a side chain. Pattern formation method. 4. The pattern forming method according to claim 3 , wherein the photosensitive composition contains a polymer compound, and at least the polymer compound contains a carboxylic acid structure represented by the formula (3) or (4). Pattern forming method. 4. The pattern forming method according to claim 3 , wherein the polymer compound includes a repeating alicyclic structure having a carboxylic acid structure represented by the above formula (3) or (4) in a side chain. Pattern formation method. In the pattern forming method according to any one of claims 1 to 7, the pattern forming method, which comprises a photosensitive composition further alicyclic structure containing the carboxylic acid structure. In the pattern forming method according to any one of claims 1 to 8, pattern forming method, wherein the active chemical line is less far ultraviolet light wavelength 250 nm. In the pattern forming method according to any one of claims 1 to 8, pattern forming method, wherein the active chemical line is ArF excimer laser light. In the pattern forming method according to any one of claims 1 to 10, after the step of irradiating the active chemical line, and a step of developing the pattern on the coating film with an aqueous alkaline developer, wherein the aqueous The pattern forming method, wherein the alkaline developer is an aqueous tetraalkylammonium hydroxide solution. The pattern forming method according to any one of claims 1 to 11, forming a resist pattern on a semiconductor substrate, on the basis of the resist pattern, a step of etching the semiconductor substrate, or the step of implanting ions A method for manufacturing a semiconductor device, comprising:

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