JP3571397B2 - Light source filter, projection exposure apparatus and projection exposure method using the same - Google Patents

Description

【００１０】
そこで、近年、光源の波長や投影レンズの開口数ＮＡの改良なしに解像度および焦点深度の向上を図る幾つかの方法が提案されている。
【００１１】
マスクへの加工あるいは露光装置の光学系への遮光板の設置により解像度や焦点深度などの改善を図る方法は、露光装置としてこれまでどおりの光源とレンズが適用でき、かつ、レジストなどの周辺プロセスも生かせることで、大幅なコスト増なしに展開できる。
【００１２】
たとえば、特開昭５７−６２０５２によれば、周期的なパターンを有するマスクの不透明部を挟む両側の光透過部の少なくとも一方に、隣り合う光透過部とは位相の１８０°反転する透明膜を形成することにより、同一開口数ＮＡのレンズと比較して解像度を高める方法が開示されている（第１の方法）。
【００１３】
特開昭６２−６７５１４によれば、孤立（単一）パターンの解像度向上手段として、マスクの単一光透過部の周辺に良好な解像度が得られる範囲で位相の反転した、やはり透明膜で形成された光透過部を補助パターンとして設ける方法が開示されている（第２の方法）。
【００１４】
また、Ｊｏｕｒｎａｌ ｏｆ Ｖａｃｕｕｍ Ｓｃｉｅｎｃｅ Ｔｅｃｈｎｏｌｏｇｙ Ｂ９（６） （３１１３）１９９１に、マスクパターンからの回折光の位相を制御し、多重焦点結像系を形成可能とすべく縮小投影レベルの瞳部分に光源フィルタを設置することにより、コンタクトホールパターンなどの繰返し性のない単一パターンの特性向上に有効な方法が開示されている（第３の方法）。
【００１５】
さらに、特開平４−１０１１４８では、照明光学系の瞳面かその共役面あるいは投影光学系の瞳面の少なくとも１箇所に、マスクの微細パターンから得られるフーリエ変換パターンに基づいて定めた１組以上の光透過部を有する遮光板を設け、同一開口数ＮＡのレンズに比較し繰返しパターンの解像度と焦点深度の向上を図る方法が開示されている（第４の方法）。
【００１６】
しかしながら、上記第１の方法は、規則的な繰返しパターンでなければ効果が得られない。また、シフト端部の位相反転により周期性パターンの端部にマスクパターンにないパターンを転写してしまう場合もある。さらに、実際の回路をレイアウトする場合は、複雑な回路パターン中に良好な効果が得られるようにシフタを配置する必要があり、この作業が非常に煩雑となる。さらに、回路構成によってはシフタレイアウトに矛盾を生じシフタの配置が困難な場合もあり、実用化に向けて大きな障害となっている。また、マスクの作製においても、シフタを不透明（遮光）パターンの上部、下部のどの位置に形成する場合でも、従来のマスク作製工程にない重ね合わせのプロセスを有し、高精度要求とともに工程の増加を招く。さらに、欠陥の検査・修正も、シフタが従来からの遮光膜であるＣｒ膜とは全く異なる透明膜であるため、検査・修正とも実用的な手法が得られていないのが現状である。
【００１７】
第２の方法は、第１の方法が適用できない単一パターンの特性向上に有益であるが、周囲に透過光の位相を反転した補助シフタが必要であり、パターンレイアウトは非常に煩雑で制約も増大する。また、補助パターンのサイズによっては不必要なパターンが転写されてしまうなどの問題もある。その他アライメント工程、欠陥検査・修正などのマスク作製上の問題は第１の方法と同様で実用上大きな障壁となっている。
【００１８】
第３の方法は、コンタクトホールパターンなどの周期性のない単一パターンの特性向上に有効であるが、この手法を達成するために縮小投影レンズ内にマスクパターンからの回折光の位相を制御・変調可能な光学素子を要する。さらに、この光学素子の位相変調領域は効果の得られるマスクパターンに依存があるため、適用パターンに応じて最適な変調光学素子を縮小投影レンズ内で交換しなければならない。したがって、この光学素子を含めた縮小投影レンズの透過率の確保と、光学素子の発熱などに起因する各種収差の除去は実用上極めて重大な問題である。
【００１９】
第４の方法は、シフタなどを形成しない従来どおりの通常マスクを用い、照明系へ遮光板を配置するだけで特性の向上が図れ有益であるが、パターンレイアウト方向依存を有し、限定されたレイアウト方向でしか良好な効果が得られない。また、最適化された所定の線幅より太い線幅領域では、焦点深度特性は通常の照明系で得られる特性よりも大幅に低下する。さらに、同一の線幅でもいわゆるパターンの疎密依存（近接効果）を有し、パターンピッチの違いにより良好な特性の得られる露光条件が異なる。しかも、この技術の最大の問題点は周期性のない単一パターンあるいはランダムパターンには全く改善効果が得られないことである。
【００２０】
図１２および１３は、従来の投影露光装置による簡単な結像原理を示す模式図である。図１２は通常のマスクパターンによる結像を示す図であり、図１３は露光光の回折角が大きく結像できない様子を示す図である。
【００２１】
図１２および１３において、従来の投影露光装置は、光源１とフライアイレンズ２とコンデンサレンズ４とマスク５と投影レンズ８とを含む。
【００２２】
光源１の下方にフライアイレンズ２が設けられ、フライアイレンズ２の下方にコンデンサレンズ４が設けられ、コンデンサレンズ４の下方にマスク５が設けられ、マスク５の下方に投影レンズ８が設けられている。ウエハ１０は投影レンズ８の下方に設置されている。
【００２３】
図１２を参照して、光源１からの露光光６１は、フライアイレンズ２およびコンデンサレンズ４を通りマスク５のパターンによって回折され回折光７１となって、投影レンズ８の瞳に取込まれ、０次光と回折された±１次光の３光束でウエハ１０上にマスクパターンが結像される。
【００２４】
図１３を参照して、微細なマスクパターンになるほどその回折角は大きくなり、微細さがある限界を越えると、そのパターンについては±１次回折光が投影レンズ８の有効瞳から外れ、ウエハ１０上に微細パターンを結像することができなくなる。
【００２５】
図１４は、従来の投影露光装置において遮光板１３を設けた場合の簡単な結像原理を示す模式図である。
【００２６】
光源１の下方にフライアイレンズ２が設けられ、フライアイレンズ２の下方に遮光板１３が設けられ、遮光板１３の下方にコンデンサレンズ４が設けられ、コンデンサレンズ４の下方にマスク５１が設けられ、マスク５１の下方に投影レンズ８が設けられている。ウエハ１０は投影レンズ８の下方に設置されている。
【００２７】
図１４を参照して、照明系の中心領域を遮光した遮光板１３をフライアイレンズ２の下方に設け、露光光６１の斜入射成分６５の回折光７５を利用した変形照明技術により上記の問題を改善している。この手法はマスクパターンで得られる回折角の半分を利用する２光束７５ａ，７５ｂにより結像を得るものであり（回折光７５ｃは投影レンズ８の有効瞳から外れる）、解像度の向上が望めるとともに、２光束結像であることから理想的にはそれぞれの光束で光路差がほとんどなく、位相の整合性に優れ良好な焦点深度が得られる。
【００２８】
しかしながら、通常照明はもとより、斜入射照明を利用する変形照明技術においても、結像の基本はマスクパターンで回折された露光光の干渉効果を利用している。したがって、周期性を有する繰返しパターンに対しては干渉効果は得られるが、周期性のない単一パターンでは干渉効果が全く得られず、変形照明によっても改善効果は望めない。
【００２９】
図１５は、特開平４−１０１１４８に開示された図１４に示した従来の変形照明技術に用いられている遮光板３５の構造例を示す模式図である。（ａ）および（ｃ）は遮光板３５の平面図である。（ｂ）および（ｄ）は、それぞれ（ａ）および（ｃ）の遮光板を点線ｍｍ′または点線ｎｎ′で切断した断面図である。
【００３０】
図１５において、遮光板３５は、露光光が通る開口部１１と露光光が遮光される遮光部１２とを含む。
【００３１】
図１５を参照して、２つの開口部１１からなる遮光板３５を投影露光装置に装着することにより斜入射の点形状照明系が形成される。
【００３２】
しかしながら、この方法は特性改善効果の得られるパターン（たとえば繰返しパターン）にレイアウト方向依存を有し、種々のレイアウトが施される実際の回路パターンへの適用には問題となる。また、最適化された線幅領域以上の線幅では通常照明に比較して大幅に焦点深度（ＤＯＦ）が低下する。さらに、同一の線幅でもいわゆるパターンの疎密依存（近接効果）を有し、ピッチの違いにより良好な特性の得られる露光条件が異なる。さらに、この手法の最大の問題点として、周期性のない単一パターンあるいはランダムパターンに対して全く改善効果が認められない点が挙げられる。
【００３３】
この単一パターンやランダムパターンに対しての問題は、結像特性の改善効果がマスクで回折された露光光の干渉効果に基づいているためであり、周期性を有する繰返しパターンでは改善効果が得られるものの、周期性のない単一パターンやランダムパターンでは改善効果は得られない。
【００３４】
このように従来の技術では、パターンの周期性、パターンのレイアウト、広範なパターンサイズ、パターンの疎密（近接効果）などの実用上要求される特性の改善をすべて良好に満足することができないという問題点があった。
【００３５】
本発明は以上のような問題点を解決するためになされたもので、投影露光装置の波長およびレンズの開口数ＮＡの改善なしに微細パターンの解像度ならびに広範なパターン領域における焦点深度の向上をパターンのレイアウト方向依存なく達成し、また、周期性のない単一パターンやランダムパターンの特性改善を図ることが可能な光源フィルタおよびそれを用いた露光装置を提供することを目的とする。
【００３６】
【課題を解決するための手段】
請求項１に係る光源フィルタは、露光光を透過する光源フィルタであって、露光光が透過する第１領域と、第１領域を挟んで設けられた第２領域とを設けたものであり、露光光は第１領域と第２領域の境界での反射なしに第１領域を透過する第１露光光と、上記境界で反射され第１領域を一往復して透過する第２露光光とを含み、第２露光光は第１露光光と２分の１波長の位相差を生じる。
【００３７】
請求項２に係る光源フィルタは、請求項１の光源フィルタにおいて、第２領域は露光光に対する透過率が３０％以上であり、反射率が５５％以下の薄膜である。
【００３８】
請求項３に係る光源フィルタは、請求項２の光源フィルタにおいて、薄膜はＣｒ，Ｔａ，Ｍｏ，Ａｌ，Ｔｉ，ＭｏＳｉ、あるいはＣｒ，Ｔａ，Ｍｏ，Ａｌ，Ｔｉ，ＭｏＳｉを主成分とする酸化物または窒化物からなる。
【００３９】
請求項４に係る光源フィルタは、請求項１ないし３のいずれかの光源フィルタにおいて、第１領域はＳＯＧまたはスパッタＳｉＯ_２ または光学ガラスまたは有機膜のいずれかにより形成されている。
【００４０】
請求項５に係る光源フィルタは、請求項１ないし４のいずれかの光源フィルタにおいて、露光光の一部を遮光する遮光部分を設けたものである。
【００４１】
請求項６に係る投影露光装置は、露光光を投影する投影露光装置であって、露光光を出射する光源と、光源フィルタとを設けたものであり、光源フィルタは露光光が透過する第１領域と、第１領域を挟んで第２領域とを設けたものであり、露光光は第１領域と第２領域との境界での反射なしに第１領域を透過する第１露光光と、上記境界で反射され第１領域を一往復して透過する第２露光光とを含み、第２露光光は第２露光光と２分の１波長の位相差を生じ、投影形状を有するマスクとを設けたものである。
【００４２】
請求項７に係る投影露光装置は、請求項６の投影露光装置において、光源フィルタの第２領域は露光光に対する透過率が３０％以上であり、反射率が５５％以下の薄膜である。
【００４３】
請求項８に係る投影露光装置は、請求項７の投影露光装置において、薄膜はＣｒ，Ｔａ，Ｍｏ，Ａｌ，Ｔｉ，ＭｏＳｉ、あるいはＣｒ，Ｔａ，Ｍｏ，Ａｌ，Ｔｉ，ＭｏＳｉを主成分とする酸化物または窒化物からなる。
【００４４】
請求項９に係る投影露光装置は、光源フィルタの第１領域は請求項６ないし８のいずれかの投影露光装置において、ＳＯＧまたはスパッタＳｉＯ_２ または光学ガラスまたは有機膜のいずれかにより形成されている。
【００４５】
請求項１０に係る投影露光装置は、請求項６ないし９のいずれかの投影露光装置において、光源フィルタに隣接して設けられた露光光の一部を遮光する遮光部分を設けたものである。
【００４８】
【作用】
請求項１に係る光源フィルタにおいては、第１露光光が第１領域と第２領域との境界での反射なしに第１領域と第２領域とを透過し、第２露光光が第１領域と第２領域との境界で反射され第１領域を一往復して透過し、第２露光光は第１露光光と２分の１波長の位相差を生じるので、第１露光光と第２露光光の結像焦点位置は半波長光路差分ずれる。
【００４９】
請求項２に係る光源フィルタにおいては、請求項１の光源フィルタにおいて、第２領域は露光光に対する透過率が３０％以上であり反射率が５５％以下の薄膜である。
【００５０】
請求項３に係る光源フィルタにおいては、請求項２の光源フィルタにおいて、薄膜はＣｒ，Ｔａ，Ｍｏ，Ａｌ，Ｔｉ，ＭｏＳｉ、あるいはＣｒ，Ｔａ，Ｍｏ，Ａｌ，Ｔｉ，ＭｏＳｉを主成分とする酸化物または窒化物からなる。
【００５１】
請求項４に係る光源フィルタにおいては、請求項１ないし３のいずれかの光源フィルタにおいて、第１領域はＳＯＧまたはスパッタＳｉＯ_２ または光学ガラスまたは有機膜のいずれかにより形成される。
【００５２】
したがって、第１領域と第２領域との境界での良好な多重反射が実現される。請求項５に係る光源フィルタにおいては、請求項１ないし４のいずれかの光源フィルタにおいて、露光光の一部を遮光する遮光部分があるので、露光光の必要な成分のみを取出し、位相変調して干渉させることが可能である。
【００５３】
請求項６に係る投影露光装置においては、光源から露光光が出射され、光源フィルタにおいて第１露光光が第１領域と第２領域との境界での反射なしに第１領域を透過し、第２露光光が第１領域と第２領域との境界で反射され第１領域を一往復して透過し、第２露光光は第１露光光と２分の１波長の位相差を生じ、光源フィルタを透過した第１および第２露光光によりマスクの形状が投影されるので、第１露光光と第２露光光の焦点位置は半波長光路差分ずれ、設定された焦点位置での結像振幅は反転し、干渉して得られる結像の光強度分布は互いのサイドローブが相殺された急峻で良好なプロファイルとなる。したがって光強度分布のコントラストが改善され解像度の大幅な向上が可能となる。また、焦点方向における光強度分布のコントラストが向上し焦点深度の大幅な拡大が可能となる。さらに、繰返しパターンはもとより、単一パターンであっても半波長位相の異なる第１露光光と第２露光光とにより繰返しパターンの干渉性が付与されたのと同等の効果が得られるため解像度の大幅な改善が図れるとともに、パターンの疎密に起因する近接効果が低減される。
【００５４】
請求項７に係る投影露光装置においては、請求項６の投影露光装置において、光源フィルタの第２領域は露光光に対する透過率が３０％以上であり反射率が５５％以下の薄膜である。
【００５５】
請求項８に係る投影露光装置においては、請求項７の投影露光装置において、薄膜はＣｒ，Ｔａ，Ｍｏ，Ａｌ，Ｔｉ，ＭｏＳｉ、あるいはＣｒ，Ｔａ，Ｍｏ，Ａｌ，Ｔｉ，ＭｏＳｉを主成分とする酸化物または窒化物からなる。
【００５６】
請求項９に係る投影露光装置においては、請求項６ないし８のいずれかの投影露光装置において、光源フィルタの第１領域はＳＯＧまたはスパッタＳｉＯ_２ または光学ガラスまたは有機膜のいずれかにより形成されている。
【００５７】
したがって、光源フィルタの第１領域と第２領域との境界での良好な多重反射が実現され、解像度の大幅な向上および焦点深度の拡大が実現される。
【００５８】
請求項１０に係る投影露光装置においては、請求項６ないし９の投影露光装置において、光源フィルタに隣接して設けられた露光光の一部を遮光する遮光部分があるので、露光光の必要な成分のみを取出し、位相変調して干渉させることができ、余分な露光光の成分による結像が除去され、さらなる解像度の向上および焦点深度の拡大が可能となる。
【００５９】
請求項１１に係る投影露光方法においては、露光光が作成され、作成された露光光の一部の位相が光源フィルタにより１／２波長ずらされ、１／２波長ずれた露光光と１／２波長ずれていない元の露光光とが重ねて所定の被投影物に投影されるので、それらの露光光の焦点位置は半波長光路差分ずれ、設定された焦点位置での結像振幅が反転し、干渉して得られる結像の光強度分布は互いのサイドローブが相殺された急峻で良好なプロファイルとなる。したがって光強度分布のコントラストが改善され解像度の大幅な向上が可能となる。また、焦点方向における光強度分布のコントラストが向上するので焦点深度の大幅な拡大が可能となる。
【００６１】
【実施例】
以下、本発明による光源フィルタおよびそれを用いた投影露光装置の実施例を図面を参照しながら説明する。
【００６２】
図１は本発明の実施例の光源フィルタを設置した投影露光装置の構成およびその露光光の結像を示す模式図である。
【００６３】
図１を参照して、本発明の実施例の光源フィルタを設置した投影露光装置は、露光光６１を出射する光源１と、２次光源面であるフライアイレンズ２と、露光光６１から可干渉性に優れた２つの回折光を透過する多重反射干渉光源フィルタ３と、半導体回路のレジストパターンが設けられたマスク５と、マスク５を通って２つの露光光（回折光）６１，６２をウエハ１０に投影し結像させる投影レンズ８およびその瞳面９とを含む。
【００６４】
多重反射干渉光源フィルタ３は、さらに、フィルタ基板３１と半透過膜３２と透明領域３３とを含む。
【００６５】
図１においては、簡単のため、１フライアイレンズからの１光束のみを示している。また、多重反射干渉光源フィルタ３の一部分拡大図では、実際は露光光６１の一部は垂直に反射するが、模式的にずらして示してある。
【００６６】
光源１の下方にフライアイレンズ２が設けられ、フライアイレンズ２の下方に多重反射干渉光源フィルタ３が設けられ、多重反射干渉光源フィルタ３の下方にコンデンサレンズ４が設けられ、コンデンサレンズ４の下方にマスク５が設けられ、マスク５の下方に投影レンズ８が設けられ、投影レンズ８は瞳面９を有す。瞳面９の下方にウエハ１０が設置されている。
【００６７】
多重反射干渉光源フィルタ３においては、フィルタ基板３１の下面に半透過膜３２が形成され、その下に透明領域３３が形成され、その下に再び半透過膜３２が形成されている。
【００６８】
光源１から露光光６１が出射され、投影露光装置の２次光源面であるフライアイレンズ２から得られたコヒーレンシの高い露光光は、多重反射干渉光源フィルタ３の透過光６１と多重反射干渉光源フィルタ３内での多重反射光６２に適正な振幅で半波長位相分離された可干渉性に優れた２つの波面を有する構成となる。
【００６９】
多重反射干渉光源フィルタ３で得られる多重反射光６２は、半透過膜３２と透明領域３３との上下２つの境界での反射により得られ、まず、下側の境界で反射されて１／４波長位相がずれ、次に上側の境界で反射されさらに１／４波長位相がずれ、最終的には露光光６１と１／２波長位相差が生じる。１／２波長、すなわち１８０°の位相差は、±５°程度前後してもそれほど影響はない。また、トータルで１／２波長位相差が生じればよく、必ずしも上下の２つの境界で１／４波長ずつ位相がずれなくともよい。
【００７０】
この半波長位相の異なる２波面を有する露光光６１，６２でマスク５上のパターンを照明することにより、本来は隣接パターンとの干渉性が期待できない単一パターンであっても、マスク５で回折により得られた半波長位相の異なる２波面を有する回折光７１，７２それぞれから可干渉な結像イメージが得られ、実効的に干渉性を有する隣接パターンあるいは補助パターンを主解像単一パターンに対してマスク上に付加形成したのと同等の効果が得られる。
【００７１】
図２および３は、本発明の実施例の多重反射干渉光源フィルタ３を設置した投影露光装置による単一パターン投影時の結像原理を従来照明による結像と比較して示した図である。
【００７２】
図２（Ａ）は図１の７０に示した回折光７１，７２によるｚ方向位置における結像イメージを従来照明（回折光７１のみ）によるものと比較して示す図であり、（Ｂ）は良好な解像度が得られる焦点深度（従来：ｄ_１ ，本発明：ｄ_２ ）を示す図である。
【００７３】
図２において、回折光７１，７２の回折光強度は１：１ではなく、回折光７１の方が強い構成としているため、回折光７１と回折光７２の回折光強度比から、良好な解像度が得られる焦点深度は図２（Ｂ）に示したような領域となる。
【００７４】
図３（Ｃ）は図２に示した結像のｚ方向位置における振幅分布を示す図であり、（Ｄ）は光強度分布を示す図である。
【００７５】
図１の同一光源１から発せられ、半波長時間（位相）分離された２つの波面を有する露光光６１，６２がマスクパターン５で回折され、回折光７１，７２が得られる。この回折光７１，７２の波面がそれぞれウエハ１０面上で結像する。回折光７１，７２の波面の位相は半波長（１８０°）異なるため、従来は図３（Ｃ）の（ｂ）−１，（ｄ）−１のような振幅分布であったが、図３（Ｃ）の（ａ）−１，（ｃ）−１のように図２の各焦点位置−ｚ_１ ，ｚ_１ での結像振幅は反転し、干渉して得られる結像の光強度分布は結果として図３（Ｄ）の（ａ）−２，（ｃ）−２のように互いのサイドローブが相殺された急峻で良好なプロファイルとなる。したがって、図３（Ｄ）の（ｂ）−２，（ｄ）−２に示した従来の照明系で得られる結像の光強度分布と比較して、光強度のコントラスト（光強度の最大値Ｉｍａｘと最小値Ｉｍｉｎの比；（Ｉｍａｘ−Ｉｍｉｎ）／（Ｉｍａｘ＋Ｉｍｉｎ））が改善され解像度の大幅な向上が図れる。
【００７６】
また、焦点深度においても、前述のように半波長時間（位相）分離された２つの波面を有する回折光７１，７２は互いに半波長分の光路差のため結像焦点位置が異なる。すなわち、ウエハの焦点方向に図２（Ａ），（Ｂ）のように２つの結像焦点位置−ｚ_１ ，ｚ_１ を有し、かつ上記解像度向上効果で述べたように反転した結像振幅の重ね合わせが適用できることから、ウエハの焦点方向における光強度分布のコントラストが向上し、焦点深度も従来照明と比較して大幅に拡大する。
【００７７】
繰返しパターンでは隣接するパターン間の干渉効果があり、単一パターンと比較して従来からの結像構成においても良好な特性を有するが、本発明の光源フィルタを適用することでさらに特性の向上を図ることができる。
【００７８】
さらに、解像度や焦点深度（ＤＯＦ）向上のため、投影露光装置の光源波長や投影レンズの開口数ＮＡの改良なしに、しかも簡便な方法で低コストに良好な改善特性が得られ、かつ広範な適用（汎用性）を考えた場合、従来技術で述べた第４の方法の遮光板を投影露光装置の照明系に配置する方法、いわゆる変形照明技術が最も適しているので、これを改良し従来の任意の２次光源形状を得る変形照明技術では改善が困難であった周期性のない単一パターンあるいはランダムパターンに対して良好な改善効果を得ることとした。
【００７９】
図４は、本発明の実施例の多重反射干渉光源フィルタ３を設置した投影露光装置による直入射３光束結像の模式図である。
【００８０】
図５は、本発明の実施例の多重反射干渉光源フィルタ３を設置した投影露光装置において多重反射干渉光源フィルタ３の一部を遮光した場合の構成および斜入射３光束結像の模式図である。
【００８１】
σファクタσ＝０．６の多重反射干渉光源フィルタ３においてσ＝０．５の領域を遮光する輪帯形状照明により斜入射照明の効果を付加した構成としたときのライン＆スペースなどの繰返しパターンに対する結像イメージを示している。輪帯形状照明とは後述の図１５（ｃ）のような遮光形状である。
【００８２】
σファクタとは、投影露光装置照明光学系のコヒーレンシの度合いを示し、コヒーレントファクタと呼ばれる。照明光学系レンズ（４（図１中））の開口数ＮＡ_ｉ１１ および投影光学系レンズ（８（図１中））の開口数ＮＡ_ｏｂによりσ＝ＮＡ_ｉ１１ ／ＮＡ_ｏｂで定義される。開口径が小さいほどコヒーレンシは高い傾向にある。
【００８３】
図６は、本発明の多重反射干渉光源フィルタ３を設置した投影露光装置において繰返しパターンから得られる結像の振幅分布と光強度分布を従来照明による結像構成の投影露光装置による場合と比較した図であり、（Ａ）は図４の本発明の多重反射干渉光源フィルタ３を設置した投影露光装置による直入射３光束結像の振幅分布および光強度分布を示す図であり、（Ｂ）は図５の本発明の多重反射干渉光源フィルタ３を設置した投影露光装置による斜入射２光束結像の振幅分布および光強度分布を示す図であり、（Ｃ）は従来照明による結像の振幅分布および光強度分布を示す図である。
【００８４】
図４および５において、投影露光装置は、光源１とフライアイレンズ２と多重反射干渉光源フィルタ３とコンデンサレンズ４とマスク５１と投影レンズ８とその瞳面９とを含む。
【００８５】
光源１の下方にフライアイレンズ２が設けられ、フライアイレンズ２の下方に多重反射干渉光源フィルタ３が設けられ、多重反射干渉光源フィルタ３の下方にコンデンサレンズ４が設けられ、コンデンサレンズ４の下方にマスク５１が設けられ、マスク５１の下方に投影レンズ８が設けられ、投影レンズ８は瞳面９を有し、瞳面９の下方にウエハ１０が設置されている。
【００８６】
多重反射干渉光源フィルタの構成および構造は図１の場合と同様である。
図４を参照して、光源１から出射された露光光６１はフライアイレンズ２を通って多重反射干渉光源フィルタ３で多重反射される。この多重反射により得られる２波面を有する直入射の露光光６３は、コンデンサレンズ４を通り繰返しパターンを有するマスク５１で回折され２波面を有する回折光７３となり、投影レンズ８およびその瞳面９によりウエハ１０上に結像される。２波面を有する直入射の露光光６３の多重反射干渉光源フィルタ３での多重反射、および露光光６３から得られる繰返しパターンによる回折光７３の波面は図中では省略してある。
【００８７】
図５を参照して、光源１から出射された露光光６１は、フライアイレンズ２を通って多重反射干渉光源フィルタ３で多重反射され、遮光板３６により中心部が遮光されて２波面を有する斜入射の露光光６４となり、コンデンサレンズ４を通り繰返しパターンを有するマスク５１で回折され２波面を有する回折光７４となり、投影レンズ８およびその瞳面９によりウエハ１０上で結像される。
【００８８】
２波面を有する斜入射の露光光６４の多重反射干渉光源フィルタ３での多重反射、および露光光６４から得られるパターンの回折光７４の波面は図中では省略してある。
【００８９】
斜入射の露光光６４について、露光光６４ｘによる結像は、その０次回折光７４ｃと±１次回折光７４ｄ，７４ｂのうち−１次回折光７４ｂによる２光束結像であり、露光光６４ｙによる結像は、その０次光７４ｂと±１次回折光７４ａ，７４ｃのうち−１次回折光７４ｃによる２光束結像である。
【００９０】
このように、斜入射照明を利用した場合、図４に示した０次回折光７３ａと±１次回折光７３ｂで形成される通常照明の３光束結像に対し、０次回折光と±１次回折光の片方の１次回折光を用いる２光束結像となり、半分の回折角で結像が得られ、解像度の向上が図れるとともに２光束の良好な位相整合により焦点深度も拡大できる。
【００９１】
この露光光６１の斜入射成分から得られた半波長位相の異なる２波面を有する露光光６４で照明することにより、図６（Ｂ）の（ｂ）−１のような斜入射にて得られた反転した結像振幅（位相反転した２波面を有する露光光それぞれから得られる振幅分布）の重ね合わせにより、同一露光量で露光したときの光強度のピークＩｍａｘは、（Ａ）の（ａ）−２に示された多重反射干渉光源フィルタ３の中心部を輪帯形状などに遮光しない場合に比較して低下するものの、（ｂ）−２のような急峻な光強度分布が得られコントラストが向上する。
【００９２】
すなわち（Ｃ）の（ｃ）−１，−２に示した従来からの通常の結像構成を用いて得られる特性と比較して光強度分布のコントラストが大幅に改善され、良好な解像度と焦点深度が得られる。
【００９３】
パターンの疎密（線幅の近遠）に起因して結像振幅が変化する近接効果については、その原因が密なパターン領域では繰返しパターンと同様に干渉効果があるのに対し、疎なパターン領域では単一パターンと同様となり干渉効果が得られず、この干渉効果の違いにより同一パターンサイズであっても大きな振幅分布を生じる結果となる。しかし、本発明の多重反射干渉光源フィルタを用いれば、単一パターンすなわち疎なパターン領域においても半波長位相の異なる２波面の露光光により干渉性が付与されたのと同等の効果が得られ、密なパターン領域とバランスし、結果として近接効果を低減することができる。
【００９４】
諸特性の改善効果を本発明の多重反射干渉光源フィルタで達成するためには、露光光を半波長位相分離するための透明領域の膜厚と、分離された２つの波面を有する露光光のフィルタ透過率の比が重要である。なお、この位相変調（光路差）を得るための光源フィルタの透明領域の膜厚ｔ_１ 、ならびに光源フィルタを透過する露光光の透過率は式（３）〜（８）より求まる（透過率には、半透明領域で反射されずにフィルタを透過する露光光のものＴ_１ と半透明領域で反射され透明領域を一往復してフィルタを透過する露光光のものＴ_２ とがある）。
【００９５】
【数２】

【００９６】
この露光光のフィルタ透過率は式（７），式（８）により与えられ、半透明領域で反射されずに透過する露光光の透過率Ｔ_１ と透明領域を一往復した露光光の透過率Ｔ_２ の比Ｔ_２ ／Ｔ_１ は半透明領域の反射率ＲからＴ_２ ／Ｔ_１ ＝Ｒ^２ となる。上記のように露光光により得られる結像特性を向上させるためには、マスクで生じる回折光の１次回折光のサイドローブ振幅を相殺できる位相反転した結像振幅をもう一方の露光光で形成することが基本となる。
【００９７】
たとえば、図１において、メインの結像振幅に対してサイドローブ振幅のピークは約３０％程度と見積もられ、改善に寄与する半透明領域３２の反射率Ｒは≦５５％程度（Ｔ_２ ／Ｔ_１ ≦〜３０％）が望ましい。また、露光光６１で形成される結像光強度は、露光の処理速度を考慮すると通常照明系の〜１０％以上は必要と考えられ、半透明領域３２の透過率ＴはＴ≧３０％程度（Ｔ_１ ≧９％）を要する。
【００９８】
したがって、半透明領域を形成する材料は、これら透過率と反射率の条件を同一膜厚で同時に満足し、かつ露光装置の２次光源面開口部全面にわたって均一な膜厚分布が得られる膜厚材料がふさわしい。
【００９９】
また、透明領域３３の膜厚は式（６）により与えられるが、この透明領域３３内を一往復する露光光６２の位相は透明領域３３の膜厚にほぼ依存することから、半透明領域３２を有する基板３１上に形成しやすく、かつ均一な膜厚分布の得られる膜厚透明材料が望ましい。
【０１００】
このように本発明の多重反射干渉光源フィルタは従来の変形照明技術を用いる投影露光装置と比較して、パターンの解像度、ならびに焦点深度の良好な改善が達成できる。特に、単一パターンについては大幅に改善効果が得られる。したがって、パターンの周期性、パターンレイアウト、パターンサイズ、パターンの疎密などの依存が小さく、実用上要求されるほとんどの特性を良好に満足する。
【０１０１】
すなわち、単一パターンと繰返しパターンのどちらにも改善効果を有し、しかも広範なパターンサイズならびにパターンの疎密（近接効果）に対しても有効であることから、同一の投影露光装置でしかも光源フィルタの交換なしに、超ＬＳＩなどの実際の作製工程で要求されるほとんどすべてのパターンに適用でき、プロセスコストならびに初期設備投資の大幅な低減が図れ実用上極めて有益である。
【０１０２】
図５や図１５でも少し述べたが解像度および焦点深度などの特性のさらなる改善に、本発明の多重反射干渉光源フィルタ３の露光光透過領域３３を種々の形状に遮光することが有効である。
【０１０３】
そこで、この露光光透過領域３３の遮光について詳しく述べることにする。
図７は、本発明の実施例の多重反射干渉光源フィルタ３の露光光透過領域３３を遮光板３５により遮光する種々遮光形状を示す図である。
【０１０４】
図７において、多重反射干渉光源フィルタ３は、図１と同様の構成および構造である。
【０１０５】
図７を参照して、遮光板３５は多重反射干渉光源フィルタ３の最上部に多重反射干渉光源フィルタ３の半透過膜３２形成に用いた材料により遮光できる膜厚でパターン形成されている。
【０１０６】
図７（ａ）の遮光形状は、中心部透過領域の低減構造であり、単一パターンの改善に一層有効である。（ｂ）および（ｃ）の遮光形状は、中心部透過領域を遮光し、照明系の周辺から得られる斜入射光を有する構造であり、繰返しパターンの改善に一層有効である。（ｃ）は図５と同様の輪帯形状照明である。
【０１０７】
図８は、本発明の実施例の多重反射干渉光源フィルタ３の露光光透過領域３３を遮光板などにより遮光する種々遮光構造を示す図である。
【０１０８】
多重反射干渉光源フィルタ３の構成および構造は図１の場合と同様である。
図７および８を参照して、遮光部の形成は、少なくとも半透過膜３２形成に用いた材料を図７のように多重反射干渉光源フィルタ３の最上部または図８（ａ）のように最下部（裏面）、あるいは図８（ｂ）のように少なくとも下層、上層半透過膜３２の上下面のいずれかに遮光できる膜厚でパターン形成することが望ましいが、図８（ｃ）のように有機膜３６のパターン塗布形成あるいは遮光フィルム３６の樹脂接着などの他の材料を用いた手法であってもよい。
【０１０９】
さらに、遮光板３５と多重反射干渉光源フィルタ３を必ずしも一体形成する必要はなく、前述の図９のホルダ３７に遮光板３５と多重反射干渉光源フィルタ３とを重ね合わせて投影露光装置に装着することも、それぞれの交換が可能となるので有益である。
【０１１０】
以上のような多重反射干渉光源フィルタ３の遮光により得られるこれらの位相の高度化手法は、照明光学系を一部遮光することにより露光強度に若干の低下をきたすものの、本発明の多重反射干渉光源フィルタ３による効果に、コヒーレンシの位相の高度化による干渉性の向上、あるいは前述のような斜入射照明の効果が付加されることで適応パターンに応じて特性改善がもたらされる。
【０１１１】
次に、具体的な適用例について説明する。
図９は、本発明の多重反射干渉光源フィルタ３および遮光板３４とそのホルダ３７（片側のみ示す）とを示す斜視図である。
【０１１２】
図９において、多重反射干渉光源フィルタ３は、基板３１と半透過膜３２と透明領域３３とを含む。
【０１１３】
多重反射干渉光源フィルタ３において、石英基板などのような露光光に対して透明な基板３１が形成される。その最大開口径は投影露光装置のσファクタで表わせば、σ＝約０．７である。基板３１上に、透過率が３０％以上、反射率が５５％以下で約１５ｎｍ以下程度の膜厚からなるＣｒ，Ｔａ，Ｍｏ，Ａｌ，ＭｏＳｉなどあるいはこれらの材料を主成分とする酸化物または窒化物などからなる半透過膜３２が形成される。半透過膜３２上にＳＯＧ（Ｓｐｉｎ Ｏｎ Ｇｌａｓｓ）， スパッタ形成したＳｉＯ_２ （スパッタＳｉＯ_２ ），光学ガラス，有機膜などのような露光光が多重反射する透明領域３３が形成される。さらに、透明領域３３の上層に下層と同様な半透過膜３２が形成される。ここでは、基板３１として屈折率ｎがｎ＝１．５１が用いられ、半透過膜３２として露光光に対する透過率ＴがＴ＝約４０％、反射率ＲがＲ＝約２０％得られるＣｒ膜が膜厚約１０ｎｍでスパッタ形成されている。また、透明領域３３には屈折率ｎ＝１．４８のＳＯＧ膜が用いられ、ＳＯＧの膜厚としては半透過膜３２での位相変調も考慮して、透過する露光光の位相がトータルで１／２波長変調される膜厚とする必要があり、ここでは前述の式（６）に基づき約０．４５μｍとした。
【０１１４】
この作製においては、露光光の位相を制御するＳＯＧの膜厚とその均一性、また、２つの波面を有する露光光の透過率を制御する極薄Ｃｒ膜の膜質と膜厚の管理が極めて重要である。したがって、ＳＯＧの膜厚ならびに膜厚均一性に最も影響を及ぼすＳＯＧ粘度・塗布装置の回転数・塗布雰囲気温度・焼成温度などのプロセス条件のばらつきを設定値の≦５％に制御することで達成する。さらに、極薄Ｃｒ膜の形成においては、スパッタ製膜時初期の凝集を回避するため、比較的低圧のスパッタガス圧領域において製膜速度を制御することにより、適正な透過率と反射率を有する半透過膜を形成する。
【０１１５】
このようにして作製した多重反射干渉光源フィルタを投影露光装置の照明光学系に光軸整合を図り図９に示すように露光装置のσ値を定義する遮光板３４と重ね合わせる。そしてホルダ３７に重ねられた多重反射干渉光源フィルタと遮光板３４とを固定し、投影露光装置の照明光学系に設置する。
【０１１６】
投影露光装置にはＮＡ＝０．５、σ＝０．６のＫｒＦエキシマレーザ投影露光装置を使用し、その照明光学系（光源１直下流側）に本発明の多重反射干渉光源フィルタ３を設置する。投影露光装置の全体構成図は図１と同様である。
【０１１７】
図１０および１１は、本発明の多重反射干渉光源フィルタを設置した投影露光装置を用いた場合および光源フィルタを用いない従来の通常の投影露光装置を用いた場合の単一パターンに対する転写結果の解像特性および焦点深度特性を比較した図である。
【０１１８】
設置された多重反射干渉光源フィルタの半透明領域の透過率Ｔ＝４０％、半透明領域の反射率Ｒ＝２０％である。
【０１１９】
図１０を参照して、従来照明によれば、設計線幅が約０．３μｍ以下になると、レジストパターンが正確に投影されなくなってしまう。それに対し、本発明の投影露光装置による照明によれば、設計線幅が約０．２μｍ程度までは、それほど誤差を含まずほぼ正確にレジストパターンを投影できることがわかる。
【０１２０】
図１１を参照して、従来照明によれば、デフォーカス（焦点ぼけ）が生じない範囲が、図２に示したｚ方向において、約−０．２５μｍ以上０．２５μｍ以下と狭い範囲であった。しかし、本発明の投影露光装置による照明によれば、約−０．７５μｍ以上、１．０μｍ以下の広い範囲でデフォーカスを生じなくなる。
【０１２１】
したがって、本発明の多重反射干渉光源フィルタを設置した投影露光装置を用いることにより、従来の投影露光装置の照明系に比較して極めて良好な特性が得られることがわかる。
【０１２２】
上記と同様にＮＡ＝０．５、σ＝０．６のＫｒＦエキシマレーザ投影露光装置を用いて、多重反射干渉光源フィルタ３の透明領域３３にＳｉＯ_２ をスパッタ形成し、また、半透明膜３２にＴ＝５０％、Ｒ＝１５％が得られるＡｌ膜をスパッタ形成する。
【０１２３】
これをライン＆スペースの繰返しパターンに適用する。その際の特性は、図６（Ａ）の（ａ）−２に示したものと同様な光強度分布のコントラストが得られ、図６（Ｃ）の（ｃ）−２のような従来の通常の投影露光装置から得られる光強度分布と比較して解像度が大幅に改善される。また、焦点位置の光強度分布コントラストが従来の通常の投影露光装置から得られる値と比較して極めて良好であることから、焦点深度も大幅な拡大が見込める。
【０１２４】
以上のように、本発明の多重反射干渉光源フィルタおよびそれを用いた投影露光装置は、単一パターンと繰返しパターンのどちらにも改善効果を有し、同一光源フィルタで実際の超ＬＳＩなどの作製工程で要求されるほとんどすべてのパターンに対し良好に対応できることから、ＤＲＡＭなどの繰返しパターン中心のチッププロセス、また、ランダムパターンの多いロジックなどのチッププロセスともに有効であり、したがって、マスクのレイヤや対象チップにより光源フィルタの交換の必要がなくプロセスコストの大幅な低減が図れる。また、フィルタ全面に薄膜を形成することで得られるので、微細加工プロセスを有する位相シフトマスクなどの作製工程と比較して極めて簡便である。さらに、従来の投影露光装置の照明光学系のみの改良で、解像度や焦点深度などの特性改善効果が得られることから、投影露光装置の適応チップ世代延命に伴う初期設備投資の大幅低減に寄与する。
【０１２５】
そして、改善効果が原理的に露光光の波長に依存しないため、上記実施例で述べたＫｒＦエキシマレーザ（波長：２４８ｎｍ）に限定されるものではなく、ｇ線（波長：４３６ｎｍ）、ｉ線（波長：３６５ｎｍ）、さらにはＡｒＦエキシマレーザ（波長：１９３ｎｍ）、Ｆ_２ エキシマレーザ（波長：１５７ｎｍ）などの多世代の露光光源に対して有効であり、実用上極めて有益な露光装置を提供することができる。
【０１２６】
【発明の効果】
本発明の請求項１に係る光源フィルタは、第１露光光が第１領域と第２領域との境界での反射なしに第１領域と第２領域とを透過し、第２露光光が第１領域と第２領域との境界で反射され第１領域を一往復して透過し、第１露光光と第２露光光は２分の１波長の位相差を生じるので、第１露光光と第２露光光の焦点位置は半波長光路差分ずれる。
【０１２７】
その結果、設定された焦点位置での結像振幅は反転し、干渉して得られる結像の光強度分布は互いのサイドローブが相殺された急峻で良好なプロファイルとなる。したがって光強度分布のコントラストが改善され解像度の大幅な向上が可能となる。また、焦点方向における光強度分布のコントラストが向上するので焦点深度の大幅な拡大が可能となる。さらに、繰返しパターンはもとより、単一パターンであっても半波長位相の異なる第１露光光と第２露光光とにより繰返しパターンの干渉性が付与されたのと同等の効果が得られるため解像度の大幅な改善が図れるとともに、パターンの疎密に起因する近接効果が低減される。
【０１２８】
請求項２に係る光源フィルタにおいては、請求項１の光源フィルタにおいて、第２領域が露光光に対する透過率が３０％以上であり反射率が５５％以下の薄膜である。
【０１２９】
請求項３に係る光源フィルタにおいては、請求項２の光源フィルタにおいて、薄膜はＣｒ，Ｔａ，Ｍｏ，Ａｌ，Ｔｉ，ＭｏＳｉ、あるいはＣｒ，Ｔａ，Ｍｏ，Ａｌ，Ｔｉ，ＭｏＳｉを主成分とする酸化物または窒化物からなる。
【０１３０】
請求項４に係る光源フィルタは、請求項１ないし３のいずれかの光源フィルタにおいて、第１領域がＳＯＧまたはスパッタＳｉＯ_２ または光学ガラスまたは有機膜のいずれかにより形成されている。
【０１３１】
したがって、第１領域と第２領域との境界での良好な多重反射が実現される。その結果、光強度分布のコントラストの向上および焦点深度の拡大を実現することが可能である。
【０１３２】
請求項５に係る光源フィルタにおいては、請求項１ないし４のいずれかの光源フィルタにおいて、露光光の一部を遮光する遮光部分があるので、露光光の必要な成分のみを取出し、位相変調して干渉させることが可能である。
【０１３３】
請求項６に係る光源フィルタを用いた投影露光装置においては、第１露光光が第１領域と第２領域との境界上での反射なしに第１領域と第２領域とを透過し、第２露光光が第１領域と第２領域との境界で反射され第１領域を一往復して透過し、第１露光光と第２露光光は２分の１波長の位相差を生じ、マスクの形状が投影されるので、第１露光光と第２露光光の焦点位置は半波長の光路差分ずれ、焦点位置での結像振幅を反転し、干渉して得られる結像の光強度分布は互いにサイドローブが相殺された急峻で良好なプロファイルとなる。したがって光強度分布のコントラストが改善され解像度の大幅な向上が可能となる。また焦点方向における光強度分布のコントラストが向上し焦点深度の大幅な拡大が可能となる。さらに、繰返しパターンはもとより単一パターンであっても半波長位相の異なる第１露光光と第２露光光とにより繰返しパターンの干渉性が付与されたのと同等の効果が得られるため、解像度の大幅な改善が図れるとともに、パターンの疎密に起因する近接効果が低減される。
【０１３４】
その結果、パターンの周期性、パターンレイアウト、パターンサイズ、パターンの疎密などの依存が小さく単一パターンおよび繰返しパターンのいずれにも有効な実用上要求されるほとんどの特性を良好に満足するような投影露光装置を提供することが可能となる。
【０１３５】
請求項７に係る投影露光装置においては、請求項６の投影露光装置において、光源フィルタの第２領域が露光光に対する透過率が３０％以上であり反射率が５５％以下の薄膜である。
【０１３６】
請求項８に係る投影露光装置においては、請求項７の投影露光装置において、薄膜はＣｒ，Ｔａ，Ｍｏ，Ａｌ，Ｔｉ，ＭｏＳｉ、あるいはＣｒ，Ｔａ，Ｍｏ，Ａｌ，Ｔｉ，ＭｏＳｉを主成分とする酸化物または窒化物からなる。
【０１３７】
請求項９に係る投影露光装置においては、請求項６ないし８のいずれかの投影露光装置において、光源フィルタの第１領域がＳＯＧまたはスパッタＳｉＯ_２ または光学ガラスまたは有機膜のいずれかにより形成されている。
【０１３８】
したがって、光源フィルタの第１領域と第２領域との境界での良好な多重反射が実現され、解像度の大幅な向上および焦点深度の拡大が実現される。
【０１３９】
その結果、パターンの周期性、パターンレイアウト、パターンサイズ、パターンの疎密などの依存が小さく単一パターンおよび繰返しパターンのいずれにも有効な実用上要求されるほとんどの特性を良好に満足するような投影露光装置が実現可能となる。
【０１４０】
請求項１０に係る投影露光装置においては、請求項６ないし９の投影露光装置において、光源フィルタに隣接して設けられた露光光の一部を遮光する遮光部分があるので、露光光の必要な成分のみを取出し、位相変調して干渉させることができ、余分な露光光の成分による結像が除去され、さらなる解像度の向上および焦点深度の拡大が可能となる。
【０１４１】
その結果、パターンの周期性、パターンレイアウト、パターンサイズ、パターンの疎密などの依存が小さく単一パターンおよび繰返しパターンのいずれにも有効な実用上要求されるほとんどの特性をより良好に満足するような投影露光装置を提供することが可能となる。
【０１４２】
請求項１１に係る投影露光方法においては、露光光が作成され、作成された露光光の一部の位相が光源フィルタにより１／２波長ずらされ、１／２波長ずれた露光光と１／２波長ずれていない元の露光光とが重ねて所定の被投影物に投影されるので、それらの露光光の焦点位置は半波長光路差分ずれ、設定された焦点位置での結像振幅が反転し、干渉して得られる結像の高強度分布は互いのサイドローブが相殺された急峻で良好なプロファイルとなる。したがって光強度分布のコントラストが改善され解像度の大幅な向上が可能となる。また、焦点方向における光強度分布のコントラストが向上し焦点深度の大幅な拡大が可能となる。さらに、繰返しパターンはもとより単一パターンであっても半波長位相の異なる２つの露光光により繰返しパターンの干渉性が付与されたのと同等の効果が得られるため、解像度の大幅な改善が図れるとともに、パターンの疎密に起因する近接効果が低減される。
【０１４３】
その結果、パターンの周期性、パターンレイアウト、パターンサイズ、パターンの疎密などの依存が小さく単一パターンおよび繰返しパターンのいずれにも有効な実用上要求されるほとんどの特性を良好に満足するような投影露光方法を実現することが可能となる。
【図面の簡単な説明】
【図１】本発明の実施例の光源フィルタを設置した投影露光装置の構成およびその露光光の結像を示す模式図である。
【図２】本発明の実施例の多重反射干渉光源フィルタ３を設置した投影露光装置による単一パターン投影時の結像原理を従来照明による結像と比較した図である。
【図３】本発明の実施例の多重反射干渉光源フィルタ３を設置した投影露光装置による単一パターン投影時の結像原理を従来照明による結像と比較した図である。
【図４】本発明の実施例の多重反射干渉光源フィルタ３を設置した投影露光装置において繰返しパターンに対し多重反射干渉光源フィルタ３を設置した場合の構成および直入射３光束結像の模式図である。
【図５】本発明の多重反射干渉光源フィルタ３を設置した投影露光装置において繰返しパターンに対し一部を遮光した多重反射干渉光源フィルタ３を設置した場合の構成および斜入射３光束結像の模式図である。
【図６】本発明の多重反射干渉光源フィルタ３を設置した投影露光装置において図４の直入射３光束結像構成を用いた投影露光装置と図５の斜入射３光束結像構成を用いた投影露光装置とを繰返しパターンから得られる結像振幅分布と光強度分布を従来照明による結像構成の投影露光装置による場合とを比較した図である。
【図７】本発明の実施例の多重反射干渉光源フィルタ３の露光光透過領域３３を遮光板３５により遮光する種々遮光形状を示す図である。
【図８】本発明の実施例の遮光板３５による多重反射干渉光源フィルタ３の露光光透過領域３３を遮光する種々遮光構造を示す模式図である。
【図９】本発明の多重反射干渉光源フィルタの構造と遮光板３４と多重反射干渉光源フィルタ３と遮光板３４のホルダ３７（片側のみ示す）とを示す図である。
【図１０】本発明の多重反射干渉光源フィルタ３を設置した投影露光装置１を用いた場合および光源フィルタを用いない従来の通常の投影露光装置を用いた場合の単一パターンに対する転写結果の解像度特性を比較した図である。
【図１１】本発明の多重反射干渉光源フィルタ３を設置した投影露光装置１を用いた場合および光源フィルタを用いない従来の通常の投影露光装置を用いた場合の単一パターンに対する転写結果の焦点深度特性を比較した図である。
【図１２】従来の通常の投影露光装置による簡単な結像原理を示す模式図である。図１２は通常のマスクパターンによる結像を示す図である。
【図１３】従来の通常の投影露光装置による簡単な結像原理を示す模式図である。図１２は通常のマスクパターンによる結像を示す図である。
【図１４】特開平４−１０１１４８に開示された従来の変形照明技術に用いられている簡単な結像原理を示す模式図である。
【図１５】従来の遮光板３５の遮光形状を示す図である。
【符号の説明】
１ 光源
３ 多重反射干渉光源フィルタ
５，５１ マスク
３１ 基板
３２ 半透明領域
３３ 透明領域
１３，３４，３５ 遮光板
３６ 遮光板３５と異なる遮光板
３７ ホルダ
６１ 露光光束
６２ 多重反射した露光光束
６４ 多重反射した露光光束の斜入射成分
７１ 露光光束６１のマスク５パターンによる回折光束
７２ 露光光束６２のマスク５パターンによる回折光束
７３ 露光光束６３のマスク５１パターンによる回折光束
７４ 露光光束６４のマスク５１パターンによる回折光束
７５ 露光光束６５のマスク５１パターンによる回折光束[0001]
[Industrial applications]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light source filter and a projection exposure apparatus using the same, and more particularly, to control the phase of exposure light by interference modulation by multiple reflection on an illumination optical system (secondary light source surface) and the transmittance by a translucent film. The present invention relates to a light source filter and a projection exposure apparatus using the same.
[0002]
2. Description of the Related Art
2. Description of the Related Art In recent years, with higher integration of semiconductor elements, a circuit configuration with a finer pattern has been demanded, and a demand for further miniaturization of lithography technology has been remarkable. Accordingly, studies have been made to use a projection type exposure apparatus called a stepper to meet the demand.
[0003]
The focus of conventional studies has focused on shortening the wavelength of the light source used in the exposure apparatus and the accompanying improvements in peripheral technologies such as optical systems and registers. The g-line (wavelength: 436 nm), which is the bright line of high-pressure mercury lamps , I-line (wavelength: 365 nm), and deep UV region (wavelength: 248 nm) using a KrF excimer laser.
[0004]
However, with the rapid integration of semiconductor devices in particular, the minimum line width requirement of the circuit is 0.3 μm or less, and further 0.2 μm or less, which is approaching a value equal to or less than the wavelength of the light source.
[0005]
Here, the critical resolution R and the depth of focus (DOF) of the projection type exposure apparatus are generally given by Rayleigh's equation shown in equation (1).
[0006]
It is important to shorten the wavelength of the light source to improve the resolution and the like. However, the high performance of the entire exposure system, such as the achievement of a narrow-band light source with a shorter wavelength and the achievement of an optical system without aberration, and the construction of a peripheral process centered on a resist with a transmittance suitable for the exposure wavelength range Therefore, the optical system centering on the reduction of the wavelength of the light source or the like or the reduction projection lens is approaching its limit. In addition, as a matter of course, investment in these exposure apparatuses and exposure processes also increases, and it is difficult to reduce costs.
[0007]
Therefore, in order to improve the resolution without shortening the wavelength of the light source from Expression (1), it is necessary to increase the NA (numerical aperture) of the projection lens.
[0008]
However, as is apparent from equation (2), increasing the NA results in a reduction in the depth of focus, which is another important characteristic in lithography, and it is necessary to optimize the numerical aperture NA to achieve both characteristics well. is there. Further, increasing the NA involves difficulties in manufacturing technology, and at present, the so-called maximum numerical aperture NA is about 0.6. Further, with a generally used quartz lens material, it is difficult to correct chromatic aberration in a short wavelength region, and absorption is increased. Therefore, lens distortion due to heat generation becomes a problem.
[0009]
(Equation 1)

[0010]
Therefore, in recent years, several methods have been proposed for improving the resolution and the depth of focus without improving the wavelength of the light source or the numerical aperture NA of the projection lens.
[0011]
A method to improve resolution and depth of focus by processing a mask or installing a light-shielding plate in the optical system of the exposure apparatus is to use the same light source and lens as the exposure apparatus, and to use peripheral processes such as resist. Can be deployed without significant cost increase.
[0012]
For example, according to Japanese Patent Application Laid-Open No. 57-62052, at least one of the light transmitting portions on both sides of an opaque portion of a mask having a periodic pattern is provided with a transparent film whose phase is inverted by 180 ° from that of an adjacent light transmitting portion. There is disclosed a method of increasing the resolution by forming the lens as compared with a lens having the same numerical aperture NA (first method).
[0013]
According to Japanese Patent Application Laid-Open No. 62-67514, as a means for improving the resolution of an isolated (single) pattern, a transparent film is formed around the single light transmitting portion of the mask, the phase of which is inverted within a range where a good resolution can be obtained. There is disclosed a method of providing a light transmitting portion as an auxiliary pattern (second method).
[0014]
Also, in Journal of Vacuum Science Technology B9 (6) (3113) 1991, a light source filter is provided at a pupil portion of a reduced projection level so as to control the phase of diffracted light from a mask pattern and form a multifocal imaging system. There is disclosed a method that is effective for improving the characteristics of a single pattern having no repeatability such as a contact hole pattern by providing the third pattern (third method).
[0015]
Further, in Japanese Patent Application Laid-Open No. 4-101148, at least one set of a pupil plane of an illumination optical system, a conjugate plane thereof, or a pupil plane of a projection optical system is determined based on a Fourier transform pattern obtained from a fine pattern of a mask. A method is disclosed in which a light-shielding plate having a light-transmitting portion is provided to improve the resolution and depth of focus of a repetitive pattern as compared with a lens having the same numerical aperture NA (fourth method).
[0016]
However, the first method has no effect unless it is a regular repeating pattern. Further, a pattern that is not in the mask pattern may be transferred to the end of the periodic pattern due to the phase inversion of the shift end. Further, when laying out an actual circuit, it is necessary to arrange shifters so that a good effect can be obtained in a complicated circuit pattern, and this operation becomes very complicated. Furthermore, depending on the circuit configuration, inconsistency may occur in the shifter layout, making it difficult to arrange the shifters, which is a major obstacle to practical use. Also, in the mask fabrication, even if the shifter is formed at any position above or below the opaque (light-shielded) pattern, a superposition process not included in the conventional mask fabrication process is required, and the number of processes increases with the demand for high precision. Invite. Furthermore, since the shifter is a transparent film completely different from the Cr film, which is a conventional light-shielding film, a practical method for inspection and correction has not yet been obtained for defect inspection and correction.
[0017]
The second method is useful for improving the characteristics of a single pattern to which the first method cannot be applied, but requires an auxiliary shifter in which the phase of transmitted light is inverted around the pattern, and the pattern layout is very complicated and has restrictions. Increase. There is also a problem that an unnecessary pattern is transferred depending on the size of the auxiliary pattern. Other problems in mask fabrication such as alignment steps and defect inspection / correction are practically large barriers as in the first method.
[0018]
The third method is effective for improving the characteristics of a single pattern having no periodicity such as a contact hole pattern, but in order to achieve this method, the phase of the diffracted light from the mask pattern is controlled in the reduction projection lens. A modulatable optical element is required. Furthermore, since the phase modulation region of this optical element depends on the mask pattern for which the effect is obtained, the optimum modulation optical element must be replaced in the reduction projection lens according to the applied pattern. Therefore, securing the transmittance of the reduction projection lens including the optical element and removing various aberrations due to heat generation of the optical element are extremely serious problems in practical use.
[0019]
The fourth method is advantageous in that the characteristics can be improved simply by arranging a light-shielding plate in the illumination system using a conventional normal mask without forming a shifter or the like, but has a pattern layout direction dependency and is limited. Good effects can be obtained only in the layout direction. Further, in a line width region larger than the optimized predetermined line width, the depth of focus characteristic is significantly lower than the characteristic obtained by a normal illumination system. Further, even with the same line width, there is a so-called pattern density dependence (proximity effect), and the exposure conditions under which good characteristics can be obtained differ depending on the pattern pitch. Moreover, the biggest problem of this technique is that no improvement effect can be obtained for a single pattern or a random pattern having no periodicity.
[0020]
12 and 13 are schematic views showing a simple image forming principle by a conventional projection exposure apparatus. FIG. 12 is a diagram showing an image formed by a normal mask pattern, and FIG. 13 is a diagram showing a state in which the diffraction angle of exposure light is so large that an image cannot be formed.
[0021]
12 and 13, the conventional projection exposure apparatus includes a light source 1, a fly-eye lens 2, a condenser lens 4, a mask 5, and a projection lens 8.
[0022]
A fly-eye lens 2 is provided below the light source 1, a condenser lens 4 is provided below the fly-eye lens 2, a mask 5 is provided below the condenser lens 4, and a projection lens 8 is provided below the mask 5. ing. The wafer 10 is provided below the projection lens 8.
[0023]
Referring to FIG. 12, exposure light 61 from light source 1 passes through fly-eye lens 2 and condenser lens 4 and is diffracted by the pattern of mask 5 to become diffracted light 71, which is taken into the pupil of projection lens 8, A mask pattern is imaged on the wafer 10 by three light beams of the zero-order light and the diffracted ± first-order light.
[0024]
Referring to FIG. 13, the diffraction angle increases as the mask pattern becomes finer. When the fineness exceeds a certain limit, ± 1st-order diffracted light of the pattern deviates from the effective pupil of projection lens 8, and It becomes impossible to form an image of a fine pattern.
[0025]
FIG. 14 is a schematic diagram showing a simple image forming principle when a light shielding plate 13 is provided in a conventional projection exposure apparatus.
[0026]
A fly-eye lens 2 is provided below the light source 1, a light-shielding plate 13 is provided below the fly-eye lens 2, a condenser lens 4 is provided below the light-shielding plate 13, and a mask 51 is provided below the condenser lens 4. The projection lens 8 is provided below the mask 51. The wafer 10 is provided below the projection lens 8.
[0027]
Referring to FIG. 14, a light-shielding plate 13 that shields the central region of the illumination system is provided below fly-eye lens 2, and the above-described problem is caused by the modified illumination technique using diffracted light 75 of oblique incident component 65 of exposure light 61. Has been improved. In this method, an image is obtained by two light beams 75a and 75b using half of the diffraction angle obtained by the mask pattern (the diffracted light 75c deviates from the effective pupil of the projection lens 8). Ideally, there is almost no optical path difference between the respective light beams because of the two-beam image formation, and excellent phase matching is obtained and a good depth of focus is obtained.
[0028]
However, in the modified illumination technique using the oblique incidence illumination as well as the normal illumination, the image formation is based on the interference effect of the exposure light diffracted by the mask pattern. Therefore, an interference effect can be obtained for a repetitive pattern having a periodicity, but no interference effect can be obtained for a single pattern having no periodicity, and no improvement effect can be expected even with modified illumination.
[0029]
FIG. 15 is a schematic diagram showing an example of the structure of a light shielding plate 35 used in the conventional modified illumination technique shown in FIG. 14 disclosed in Japanese Patent Application Laid-Open No. 4-101148. (A) and (c) are plan views of the light shielding plate 35. (B) and (d) are cross-sectional views of the light shielding plates of (a) and (c), respectively, taken along a dotted line mm 'or a dotted line nn'.
[0030]
In FIG. 15, the light blocking plate 35 includes an opening 11 through which the exposure light passes and a light blocking portion 12 through which the exposure light is blocked.
[0031]
Referring to FIG. 15, a point-shape illumination system for oblique incidence is formed by mounting a light shielding plate 35 including two openings 11 on a projection exposure apparatus.
[0032]
However, this method has a layout direction dependence on a pattern (for example, a repetitive pattern) that can obtain a characteristic improving effect, and is problematic when applied to an actual circuit pattern on which various layouts are performed. Further, when the line width is equal to or more than the optimized line width region, the depth of focus (DOF) is significantly reduced as compared with the normal illumination. Furthermore, even with the same line width, there is a so-called pattern density dependence (proximity effect), and the exposure conditions under which good characteristics can be obtained differ depending on the pitch. Furthermore, the biggest problem of this method is that no improvement effect is recognized for a single pattern or a random pattern having no periodicity.
[0033]
The problem with single patterns and random patterns is that the effect of improving the imaging characteristics is based on the interference effect of the exposure light diffracted by the mask. However, an improvement effect cannot be obtained with a single pattern having no periodicity or a random pattern.
[0034]
As described above, according to the conventional technology, it is not possible to satisfactorily satisfy all the characteristics required in practical use such as pattern periodicity, pattern layout, a wide range of pattern sizes, and pattern density (proximity effect). There was a point.
[0035]
SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and is intended to improve the resolution of a fine pattern and the depth of focus in a wide pattern area without improving the wavelength of a projection exposure apparatus and the numerical aperture NA of a lens. It is an object of the present invention to provide a light source filter and an exposure apparatus using the same, which can achieve the characteristics of a single pattern or a random pattern having no periodicity and can achieve the characteristics without depending on the layout direction.
[0036]
[Means for Solving the Problems]
The light source filter according to claim 1 is a light source filter that transmits exposure light, and includes a first region through which exposure light transmits, and a second region provided across the first region. The exposure light is divided into a first exposure light transmitted through the first area without reflection at the boundary between the first area and the second area, and a second exposure light reflected at the boundary and transmitted through the first area one round trip. The second exposure light includes a half wavelength phase difference from the first exposure light.
[0037]
According to a second aspect of the present invention, in the light source filter according to the first aspect, the second region is a thin film having a transmittance for exposure light of 30% or more and a reflectance of 55% or less.
[0038]
The light source filter according to claim 3 is the light source filter according to claim 2, wherein the thin film is Cr, Ta, Mo, Al, Ti, MoSi, or an oxide containing Cr, Ta, Mo, Al, Ti, MoSi as a main component. Or it consists of nitride.
[0039]
The light source filter according to claim 4 is the light source filter according to any one of claims 1 to 3, wherein the first region is SOG or sputtered SiO. ₂ Alternatively, it is formed of either an optical glass or an organic film.
[0040]
A light source filter according to a fifth aspect is the light source filter according to any one of the first to fourth aspects, wherein a light-shielding portion for shielding a part of the exposure light is provided.
[0041]
A projection exposure apparatus according to claim 6, which is a projection exposure apparatus that projects exposure light, comprising a light source that emits the exposure light and a light source filter, wherein the light source filter transmits the first exposure light. A region and a second region sandwiching the first region, wherein the exposure light is a first exposure light that passes through the first region without being reflected at a boundary between the first region and the second region; A second exposure light reflected at the boundary and transmitted through the first area by reciprocating once, the second exposure light having a phase difference of a half wavelength with the second exposure light, and a mask having a projection shape; Is provided.
[0042]
In a projection exposure apparatus according to a seventh aspect, in the projection exposure apparatus according to the sixth aspect, the second region of the light source filter is a thin film having a transmittance of 30% or more for exposure light and a reflectance of 55% or less.
[0043]
The projection exposure apparatus according to claim 8 is the projection exposure apparatus according to claim 7, wherein the thin film is mainly composed of Cr, Ta, Mo, Al, Ti, MoSi, or Cr, Ta, Mo, Al, Ti, MoSi. It consists of an oxide or a nitride.
[0044]
According to a ninth aspect of the present invention, in the projection exposure apparatus according to any one of the sixth to eighth aspects, the first region of the light source filter is an SOG or sputtered SiO. ₂ Alternatively, it is formed of either an optical glass or an organic film.
[0045]
A projection exposure apparatus according to a tenth aspect is the projection exposure apparatus according to any one of the sixth to ninth aspects, wherein a light-shielding portion that shields a part of the exposure light provided adjacent to the light source filter is provided.
[0048]
[Action]
In the light source filter according to the first aspect, the first exposure light passes through the first area and the second area without being reflected at the boundary between the first area and the second area, and the second exposure light is transmitted through the first area. The second exposure light is reflected at the boundary between the first exposure light and the second exposure light and travels back and forth through the first area, and the second exposure light has a phase difference of a half wavelength with the first exposure light. The imaging focal position of the exposure light is shifted by a half wavelength optical path difference.
[0049]
In the light source filter according to the second aspect, in the light source filter according to the first aspect, the second region is a thin film having a transmittance for exposure light of 30% or more and a reflectance of 55% or less.
[0050]
In the light source filter according to the third aspect, in the light source filter according to the second aspect, the thin film is made of an oxide mainly composed of Cr, Ta, Mo, Al, Ti, MoSi, or Cr, Ta, Mo, Al, Ti, MoSi. Or nitride.
[0051]
In the light source filter according to claim 4, in the light source filter according to any one of claims 1 to 3, the first region is SOG or sputtered SiO. ₂ Alternatively, it is formed of either an optical glass or an organic film.
[0052]
Therefore, good multiple reflection at the boundary between the first region and the second region is realized. In the light source filter according to the fifth aspect, in the light source filter according to any one of the first to fourth aspects, since there is a light-shielding portion that shields a part of the exposure light, only a necessary component of the exposure light is extracted and phase-modulated. It is possible to cause interference.
[0053]
In the projection exposure apparatus according to the sixth aspect, the exposure light is emitted from the light source, and the first exposure light passes through the first area without being reflected at the boundary between the first area and the second area in the light source filter. The second exposure light is reflected at the boundary between the first area and the second area, and travels back and forth through the first area, and the second exposure light has a phase difference of a half wavelength from the first exposure light. Since the shape of the mask is projected by the first and second exposure lights transmitted through the filter, the focal positions of the first exposure light and the second exposure light are shifted by a half-wavelength optical path difference, and the imaging amplitude at the set focal position Are inverted, and the light intensity distribution of the image formed by the interference has a steep and favorable profile in which the side lobes are offset. Therefore, the contrast of the light intensity distribution is improved, and the resolution can be greatly improved. Further, the contrast of the light intensity distribution in the focal direction is improved, and the depth of focus can be greatly increased. Further, the same effect as the coherence of the repeated pattern is obtained by the first exposure light and the second exposure light having different half-wave phases even in the case of a single pattern as well as the repetition pattern. Significant improvement can be achieved, and the proximity effect due to the density of the pattern is reduced.
[0054]
In the projection exposure apparatus according to claim 7, in the projection exposure apparatus according to claim 6, the second region of the light source filter is a thin film having a transmittance of 30% or more and a reflectance of 55% or less for exposure light.
[0055]
In the projection exposure apparatus according to claim 8, in the projection exposure apparatus according to claim 7, the thin film contains Cr, Ta, Mo, Al, Ti, MoSi or Cr, Ta, Mo, Al, Ti, MoSi as a main component. Oxide or nitride.
[0056]
In the projection exposure apparatus according to the ninth aspect, in the projection exposure apparatus according to any one of the sixth to eighth aspects, the first region of the light source filter is SOG or sputtered SiO. ₂ Alternatively, it is formed of either an optical glass or an organic film.
[0057]
Therefore, good multiple reflection at the boundary between the first region and the second region of the light source filter is realized, and a significant improvement in resolution and an increase in the depth of focus are realized.
[0058]
In the projection exposure apparatus according to the tenth aspect, since the projection exposure apparatus according to the sixth to ninth aspects, there is a light shielding portion provided adjacent to the light source filter to block a part of the exposure light. Only the component can be taken out, phase-modulated and interfered, the image formed by the extra exposure light component is removed, and the resolution can be further improved and the depth of focus can be increased.
[0059]
In the projection exposure method according to the eleventh aspect, exposure light is created, and a part of the phase of the created exposure light is shifted by １ ／ wavelength by the light source filter, and the exposure light shifted by １ ／ wavelength and とSince the original exposure light having no wavelength shift is projected onto the predetermined projection object in a superimposed manner, the focus positions of those exposure lights are shifted by a half-wavelength optical path difference, and the imaging amplitude at the set focus position is inverted. The light intensity distribution of the image formed by the interference has a steep and favorable profile in which the side lobes are offset. Therefore, the contrast of the light intensity distribution is improved, and the resolution can be greatly improved. Further, the contrast of the light intensity distribution in the focus direction is improved, so that the depth of focus can be greatly increased.
[0061]
【Example】
Hereinafter, embodiments of a light source filter and a projection exposure apparatus using the same according to the present invention will be described with reference to the drawings.
[0062]
FIG. 1 is a schematic diagram showing a configuration of a projection exposure apparatus provided with a light source filter according to an embodiment of the present invention and an image of the exposure light.
[0063]
Referring to FIG. 1, a projection exposure apparatus having a light source filter according to an embodiment of the present invention includes a light source 1 that emits exposure light 61, a fly-eye lens 2 that is a secondary light source surface, and an exposure light 61. A multi-reflection interference light source filter 3 that transmits two diffracted lights having excellent coherence, a mask 5 provided with a resist pattern of a semiconductor circuit, and two exposure lights (diffraction lights) 61 and 62 passing through the mask 5 are formed. It includes a projection lens 8 for projecting and forming an image on a wafer 10 and a pupil plane 9 thereof.
[0064]
The multiple reflection interference light source filter 3 further includes a filter substrate 31, a semi-transmissive film 32, and a transparent region 33.
[0065]
FIG. 1 shows only one light beam from one fly-eye lens for simplicity. Further, in the partially enlarged view of the multiple reflection interference light source filter 3, although a part of the exposure light 61 is actually reflected vertically, it is schematically shifted.
[0066]
A fly-eye lens 2 is provided below the light source 1, a multiple reflection interference light source filter 3 is provided below the fly-eye lens 2, a condenser lens 4 is provided below the multiple reflection interference light source filter 3, and a condenser lens 4 is provided. A mask 5 is provided below, and a projection lens 8 is provided below the mask 5. The projection lens 8 has a pupil plane 9. A wafer 10 is provided below the pupil plane 9.
[0067]
In the multiple reflection interference light source filter 3, the semi-transmissive film 32 is formed on the lower surface of the filter substrate 31, the transparent region 33 is formed thereunder, and the semi-transmissive film 32 is formed therebelow.
[0068]
Exposure light 61 is emitted from the light source 1 and the exposure light with high coherency obtained from the fly-eye lens 2 which is the secondary light source surface of the projection exposure apparatus is transmitted light 61 of the multiple reflection interference light source filter 3 and multiple reflection interference light source. The multi-reflected light 62 in the filter 3 is configured to have two wavefronts excellent in coherence and separated by a half-wavelength phase with an appropriate amplitude.
[0069]
The multiple reflection light 62 obtained by the multiple reflection interference light source filter 3 is obtained by reflection at two upper and lower boundaries between the semi-transmissive film 32 and the transparent region 33, and is first reflected at the lower boundary to obtain a １ ／ wavelength. The phase is shifted, then reflected at the upper boundary, and further shifted by １ ／ wavelength, and finally, a 波長 wavelength phase difference occurs with the exposure light 61. A half wavelength, that is, a phase difference of 180 ° does not significantly affect even if it is about ± 5 °. Further, it is sufficient that a phase difference of 差 wavelength is generated in total, and the phase does not necessarily have to be shifted by ４ wavelength at the upper and lower boundaries.
[0070]
By illuminating the pattern on the mask 5 with the exposure light 61 and 62 having two wavefronts having different half-wave phases, even if a single pattern cannot be expected to have coherence with an adjacent pattern, it can be diffracted by the mask 5. A coherent imaging image is obtained from each of the diffracted lights 71 and 72 having two wavefronts having different half-wave phases obtained by the above method, and an adjacent pattern or auxiliary pattern having effective coherence is converted into a main resolution single pattern. On the other hand, the same effect as that obtained by additional formation on the mask can be obtained.
[0071]
FIGS. 2 and 3 are diagrams showing the principle of image formation when a single pattern is projected by the projection exposure apparatus provided with the multiple reflection interference light source filter 3 according to the embodiment of the present invention, in comparison with image formation by conventional illumination.
[0072]
FIG. 2A is a diagram showing an image formed by the diffracted lights 71 and 72 shown in FIG. 1 at the z-direction position in comparison with that obtained by conventional illumination (only the diffracted light 71), and FIG. Depth of focus at which good resolution is obtained (conventional: d ₁ , The present invention: d ₂ FIG.
[0073]
In FIG. 2, since the diffracted light intensity of the diffracted light 71 and 72 is not 1: 1, but the diffracted light 71 is configured to be stronger, a good resolution can be obtained from the diffracted light intensity ratio of the diffracted light 71 and the diffracted light 72. The obtained depth of focus is a region as shown in FIG.
[0074]
FIG. 3C is a diagram showing an amplitude distribution at the z-direction position of the image shown in FIG. 2, and FIG. 3D is a diagram showing a light intensity distribution.
[0075]
Exposure light beams 61 and 62 emitted from the same light source 1 in FIG. 1 and having two wavefronts separated by a half wavelength and time (phase) are diffracted by the mask pattern 5, and diffracted light beams 71 and 72 are obtained. The wavefronts of the diffracted lights 71 and 72 form images on the surface of the wafer 10, respectively. Since the phases of the wavefronts of the diffracted lights 71 and 72 are different from each other by a half wavelength (180 °), the amplitude distribution is conventionally as shown in (b) -1 and (d) -1 of FIG. As shown in (a) -1 and (c) -1 of (C), each focal position -z of FIG. ₁ , Z ₁ 3A, the light intensity distribution of the image formed by the interference is canceled out as a result, as shown in FIGS. 3D-2 (a) -2 and (c) -2. The profile is steep and good. Therefore, as compared with the light intensity distribution of the image formed by the conventional illumination system shown in (b) -2 and (d) -2 of FIG. The ratio between Imax and the minimum value Imin; (Imax-Imin) / (Imax + Imin)) is improved, and the resolution can be significantly improved.
[0076]
Also at the depth of focus, the diffracted lights 71 and 72 having two wavefronts separated by half-wavelength time (phase) as described above have different imaging focal positions due to an optical path difference of half a wavelength. That is, as shown in FIGS. 2A and 2B, two imaging focal positions -z are set in the focal direction of the wafer. ₁ , Z ₁ And, since the superposition of the inverted image amplitude can be applied as described in the resolution improvement effect, the contrast of the light intensity distribution in the focal direction of the wafer is improved, and the depth of focus is also compared with the conventional illumination. Expand significantly.
[0077]
The repetitive pattern has an interference effect between adjacent patterns, and has good characteristics even in the conventional imaging configuration as compared with a single pattern, but the characteristics are further improved by applying the light source filter of the present invention. Can be planned.
[0078]
Furthermore, in order to improve the resolution and the depth of focus (DOF), good improvement characteristics can be obtained at a low cost by a simple method without improving the light source wavelength of the projection exposure apparatus and the numerical aperture NA of the projection lens, and a wide range. Considering the application (general versatility), the method of disposing the light-shielding plate of the fourth method described in the prior art in the illumination system of the projection exposure apparatus, that is, the so-called modified illumination technique is most suitable. It was decided to obtain a good improvement effect on a single pattern or a random pattern without periodicity, which was difficult to improve by the modified illumination technique for obtaining an arbitrary secondary light source shape.
[0079]
FIG. 4 is a schematic diagram of three incident light flux images formed by a projection exposure apparatus provided with the multiple reflection interference light source filter 3 according to the embodiment of the present invention.
[0080]
FIG. 5 is a schematic diagram of a configuration in which a part of the multiple reflection interference light source filter 3 is shielded from light in the projection exposure apparatus in which the multiple reflection interference light source filter 3 according to the embodiment of the present invention is installed, and an image formation of three obliquely incident light beams. .
[0081]
A repetitive pattern such as a line & space pattern in which a multi-reflection interference light source filter 3 having a σ factor σ = 0.6 and a ring-shaped illumination for shielding an area of σ = 0.5 with the effect of oblique incidence illumination is added. 3 shows an image formed on the image. The annular illumination is a light-shielding shape as shown in FIG.
[0082]
The σ factor indicates the degree of coherency of the illumination optical system of the projection exposure apparatus, and is called a coherent factor. Numerical aperture NA of illumination optical system lens (4 (in FIG. 1)) _i11 And the numerical aperture NA of the projection optical system lens (8 in FIG. 1) _ob Σ = NA _i11 / NA _ob Is defined by The coherency tends to be higher as the opening diameter is smaller.
[0083]
FIG. 6 compares the amplitude distribution and light intensity distribution of an image obtained from a repetitive pattern in a projection exposure apparatus provided with the multiple reflection interference light source filter 3 of the present invention, as compared with the case of a projection exposure apparatus having an image formation configuration using conventional illumination. 4A is a diagram showing an amplitude distribution and a light intensity distribution of a three-beam image formed by direct projection by a projection exposure apparatus provided with the multiple reflection interference light source filter 3 of the present invention shown in FIG. 4, and FIG. FIG. 6 is a diagram showing the amplitude distribution and light intensity distribution of obliquely incident two-beam image formation by the projection exposure apparatus provided with the multiple reflection interference light source filter 3 of the present invention shown in FIG. 5, and FIG. FIG. 4 is a diagram showing a light intensity distribution.
[0084]
4 and 5, the projection exposure apparatus includes a light source 1, a fly-eye lens 2, a multiple reflection interference light source filter 3, a condenser lens 4, a mask 51, a projection lens 8, and a pupil plane 9 thereof.
[0085]
A fly-eye lens 2 is provided below the light source 1, a multiple reflection interference light source filter 3 is provided below the fly-eye lens 2, a condenser lens 4 is provided below the multiple reflection interference light source filter 3, and a condenser lens 4 is provided. A mask 51 is provided below, and a projection lens 8 is provided below the mask 51. The projection lens 8 has a pupil plane 9, and a wafer 10 is provided below the pupil plane 9.
[0086]
The configuration and structure of the multiple reflection interference light source filter are the same as those in FIG.
Referring to FIG. 4, exposure light 61 emitted from light source 1 passes through fly-eye lens 2 and is multiple-reflected by multiple reflection interference light source filter 3. The normally incident exposure light 63 having two wavefronts obtained by the multiple reflection passes through the condenser lens 4 and is diffracted by the mask 51 having a repetitive pattern to become a diffracted light 73 having two wavefronts. An image is formed on the wafer 10. The multiple reflection of the directly incident exposure light 63 having two wavefronts at the multiple reflection interference light source filter 3 and the wavefront of the diffracted light 73 by the repetitive pattern obtained from the exposure light 63 are omitted in the figure.
[0087]
Referring to FIG. 5, exposure light 61 emitted from light source 1 passes through fly-eye lens 2, is multiple-reflected by multiple reflection interference light source filter 3, is shielded at the center by light-shielding plate 36, and has two wavefronts. The light becomes obliquely incident exposure light 64, is diffracted by the mask 51 having a repetitive pattern through the condenser lens 4, becomes diffracted light 74 having two wavefronts, and is imaged on the wafer 10 by the projection lens 8 and its pupil surface 9.
[0088]
The multiple reflection of the obliquely incident exposure light 64 having two wavefronts at the multiple reflection interference light source filter 3 and the wavefront of the diffracted light 74 of the pattern obtained from the exposure light 64 are omitted in the figure.
[0089]
Regarding the obliquely incident exposure light 64, the image formed by the exposure light 64x is a two-beam image formed by the -1st-order diffracted light 74b of the 0th-order diffracted light 74c and the ± 1st-order diffracted lights 74d and 74b, and is formed by the exposure light 64y. Is a two-beam image formed by the -1st-order diffracted light 74c of the 0th-order light 74b and the ± 1st-order diffracted lights 74a and 74c.
[0090]
As described above, when the oblique incidence illumination is used, the 0-order diffracted light 73a and the ± 1st-order diffracted light 73b shown in FIG. Two light beams are imaged using one of the first-order diffracted lights, an image can be obtained with a half diffraction angle, the resolution can be improved, and the depth of focus can be increased by good phase matching of the two light beams.
[0091]
By irradiating with the exposure light 64 having two wavefronts having different half-wave phases obtained from the oblique incidence component of the exposure light 61, the oblique incidence as shown in (b) -1 in FIG. 6B is obtained. By superimposing inverted image amplitudes (amplitude distributions obtained from respective exposure lights having two phase-inverted wavefronts), the light intensity peak Imax at the time of exposure with the same exposure amount is as shown in FIG. In contrast to the case where the central portion of the multiple reflection interference light source filter 3 shown in -2 is not shaded in a ring shape or the like, the sharp light intensity distribution as shown in (b) -2 is obtained and the contrast is reduced. improves.
[0092]
That is, the contrast of the light intensity distribution is greatly improved as compared with the characteristics obtained by using the conventional ordinary imaging configuration shown in (c) -1 and (c) of FIG. Gain depth.
[0093]
As for the proximity effect in which the imaging amplitude changes due to the density of the pattern (near and far of the line width), the cause is the interference effect in the dense pattern area as in the case of the repetitive pattern. Thus, the interference effect is not obtained because of the same effect as a single pattern, and a large amplitude distribution is produced due to the difference in the interference effect even if the pattern size is the same. However, if the multiple reflection interference light source filter of the present invention is used, even in a single pattern, that is, a sparse pattern region, the same effect as that obtained by providing coherence by exposure light of two wavefronts having different half-wave phases can be obtained, It is possible to balance with a dense pattern region and to reduce the proximity effect as a result.
[0094]
In order to achieve the effect of improving various characteristics with the multiple reflection interference light source filter of the present invention, the thickness of the transparent region for half-phase separation of the exposure light and the exposure light filter having two separated wavefronts are required. The transmission ratio is important. The thickness t of the transparent region of the light source filter for obtaining this phase modulation (optical path difference) ₁ , And the transmittance of the exposure light transmitted through the light source filter can be obtained from Expressions (3) to (8) (the transmittance is represented by T of the exposure light transmitted through the filter without being reflected by the translucent region). ₁ And the exposure light T which is reflected by the translucent area and reciprocates through the transparent area and passes through the filter. ₂ There is.)
[0095]
(Equation 2)

[0096]
The filter transmittance of the exposure light is given by Expressions (7) and (8), and the transmittance T of the exposure light transmitted through the translucent area without being reflected. ₁ And the transmittance T of the exposure light that has made one round trip between the transparent region ₂ Ratio T ₂ / T ₁ Is T from the reflectance R of the translucent area. ₂ / T ₁ = R ² It becomes. As described above, in order to improve the imaging characteristics obtained by the exposure light, a phase-inverted imaging amplitude capable of canceling the side lobe amplitude of the first-order diffracted light of the diffracted light generated by the mask is formed by the other exposure light. That is the basis.
[0097]
For example, in FIG. 1, the peak of the side lobe amplitude is estimated to be about 30% with respect to the main imaging amplitude, and the reflectance R of the translucent region 32 contributing to the improvement is about ≤55% (T ₂ / T ₁ ≦ 〜30%) is desirable. Considering the processing speed of the exposure, the intensity of the image forming light formed by the exposure light 61 is considered to be required to be 10% or more of the ordinary illumination system, and the transmittance T of the translucent region 32 is about T ≧ 30%. (T ₁ ≧ 9%).
[0098]
Therefore, the material for forming the translucent region satisfies the conditions of the transmittance and the reflectance simultaneously with the same film thickness, and provides a uniform film thickness distribution over the entire opening of the secondary light source surface of the exposure apparatus. The material is suitable.
[0099]
The thickness of the transparent region 33 is given by Expression (6). Since the phase of the exposure light 62 that makes one round trip in the transparent region 33 substantially depends on the thickness of the transparent region 33, the translucent region 32 It is desirable to use a transparent film material which can be easily formed on the substrate 31 having a thickness and which can obtain a uniform film thickness distribution.
[0100]
As described above, the multiple reflection interference light source filter of the present invention can achieve better improvement in pattern resolution and depth of focus as compared with a projection exposure apparatus using a conventional modified illumination technique. In particular, for a single pattern, a significant improvement effect can be obtained. Accordingly, the dependence on the pattern periodicity, the pattern layout, the pattern size, the pattern density, etc. is small, and most of the characteristics required in practical use are satisfied well.
[0101]
That is, it has an improvement effect on both a single pattern and a repetitive pattern, and is effective for a wide range of pattern sizes and pattern density (proximity effect). It can be applied to almost all patterns required in an actual manufacturing process such as an VLSI without replacement of the LSI, and the process cost and initial equipment investment can be greatly reduced, which is extremely useful in practical use.
[0102]
As described in FIGS. 5 and 15, it is effective to shield the exposure light transmitting region 33 of the multiple reflection interference light source filter 3 in various shapes to further improve the characteristics such as resolution and depth of focus.
[0103]
Therefore, the shielding of the exposure light transmitting region 33 will be described in detail.
FIG. 7 is a view showing various light shielding shapes in which the exposure light transmitting region 33 of the multiple reflection interference light source filter 3 according to the embodiment of the present invention is shielded by the light shielding plate 35.
[0104]
7, the multiple reflection interference light source filter 3 has the same configuration and structure as in FIG.
[0105]
Referring to FIG. 7, light shielding plate 35 is formed on the uppermost portion of multi-reflection interference light source filter 3 by using a material used for forming semi-transmissive film 32 of multi-reflection interference light source filter 3 so as to have a thickness capable of blocking light.
[0106]
The light shielding shape shown in FIG. 7A is a structure for reducing the central transmission region, and is more effective for improving a single pattern. The light-shielding shapes of (b) and (c) are structures that shield the central transmission region and have oblique incident light obtained from the periphery of the illumination system, and are more effective in improving the repetitive pattern. (C) is an annular illumination similar to FIG.
[0107]
FIG. 8 is a view showing various light shielding structures for shielding the exposure light transmitting area 33 of the multiple reflection interference light source filter 3 of the embodiment of the present invention with a light shielding plate or the like.
[0108]
The configuration and structure of the multiple reflection interference light source filter 3 are the same as those in FIG.
7 and 8, at least the material used for forming the semi-transmissive film 32 is formed on the uppermost portion of the multiple reflection interference light source filter 3 as shown in FIG. 7 or the uppermost portion as shown in FIG. It is desirable to form a pattern with a film thickness capable of blocking light on either the lower (back) surface or at least the upper and lower surfaces of the lower and upper semi-transmissive films 32 as shown in FIG. 8B, but as shown in FIG. A method using another material such as pattern coating of the organic film 36 or resin adhesion of the light-shielding film 36 may be used.
[0109]
Further, it is not always necessary to integrally form the light shielding plate 35 and the multiple reflection interference light source filter 3, but the light shielding plate 35 and the multiple reflection interference light source filter 3 are mounted on the holder 37 shown in FIG. This is also beneficial because each exchange is possible.
[0110]
In the above-described technique for enhancing the phase obtained by the light shielding of the multiple reflection interference light source filter 3, the exposure intensity is slightly reduced by partially shielding the illumination optical system. By adding the effect of the light source filter 3 to the improvement of coherency by increasing the phase of coherency, or the effect of oblique incidence illumination as described above, the characteristic can be improved according to the adaptive pattern.
[0111]
Next, a specific application example will be described.
FIG. 9 is a perspective view showing the multiple reflection interference light source filter 3 and the light shielding plate 34 of the present invention and its holder 37 (only one side is shown).
[0112]
9, the multiple reflection interference light source filter 3 includes a substrate 31, a semi-transmissive film 32, and a transparent region 33.
[0113]
In the multiple reflection interference light source filter 3, a substrate 31 such as a quartz substrate transparent to exposure light is formed. If the maximum aperture diameter is represented by the σ factor of the projection exposure apparatus, σ = approximately 0.7. Cr, Ta, Mo, Al, MoSi or the like having a thickness of about 15 nm or less with a transmittance of 30% or more and a reflectance of 55% or less, or an oxide containing these materials as main components, A semi-permeable film 32 made of nitride or the like is formed. SOG (Spin On Glass), SiO formed by sputtering on the semi-transmissive film 32 ₂ (Sputter SiO ₂ ), A transparent region 33 such as an optical glass, an organic film, etc., where the exposure light is reflected multiple times, is formed. Further, a semi-transmissive film 32 similar to the lower layer is formed above the transparent region 33. In this case, the substrate 31 has a refractive index n of n = 1.51, and the semi-transmissive film 32 has a transmittance T to exposure light of about 40% and a reflectance R of about 20% for exposure light. Is formed with a thickness of about 10 nm by sputtering. In addition, an SOG film having a refractive index n = 1.48 is used for the transparent region 33, and the phase of the transmitted exposure light is 1 in total in consideration of the phase modulation in the semi-transmissive film 32. It is necessary to set the film thickness to be half-wavelength modulated. Here, it is set to about 0.45 μm based on the above-mentioned equation (6).
[0114]
In this fabrication, it is very important to control the thickness and uniformity of the SOG film for controlling the phase of the exposure light, and the quality and thickness of the ultra-thin Cr film for controlling the transmittance of the exposure light having two wavefronts. It is. Therefore, the variation in process conditions such as the SOG film thickness, the SOG viscosity, the number of rotations of the coating apparatus, the coating atmosphere temperature, and the sintering temperature, which most affects the SOG film thickness and the film thickness uniformity, is controlled to ≦ 5% of the set value. I do. Furthermore, in the formation of an ultra-thin Cr film, by controlling the film forming speed in a relatively low-pressure sputter gas pressure region to avoid initial aggregation at the time of sputtering film formation, it has appropriate transmittance and reflectance. Form a semi-permeable membrane.
[0115]
The multi-reflection interference light source filter manufactured in this manner is aligned with the illumination optical system of the projection exposure apparatus with respect to the optical axis, and is overlapped with a light-shielding plate 34 defining a σ value of the exposure apparatus as shown in FIG. Then, the multi-reflection interference light source filter and the light shielding plate 34, which are superimposed on the holder 37, are fixed and installed in the illumination optical system of the projection exposure apparatus.
[0116]
A KrF excimer laser projection exposure apparatus with NA = 0.5 and σ = 0.6 is used as the projection exposure apparatus, and the multiple reflection interference light source filter 3 of the present invention is installed in the illumination optical system (downstream of the light source 1). I do. The overall configuration of the projection exposure apparatus is the same as that shown in FIG.
[0117]
FIGS. 10 and 11 show solutions of transfer results for a single pattern when a projection exposure apparatus equipped with a multiple reflection interference light source filter of the present invention is used and when a conventional ordinary projection exposure apparatus without a light source filter is used. FIG. 4 is a diagram comparing an image characteristic and a depth of focus characteristic.
[0118]
The transmissivity T of the translucent area of the installed multiple reflection interference light source filter is 40%, and the reflectivity R of the translucent area is 20%.
[0119]
Referring to FIG. 10, according to the conventional illumination, when the design line width becomes about 0.3 μm or less, the resist pattern cannot be accurately projected. On the other hand, according to the illumination by the projection exposure apparatus of the present invention, it can be understood that the resist pattern can be projected almost accurately without much error up to a design line width of about 0.2 μm.
[0120]
Referring to FIG. 11, according to the conventional illumination, the range in which defocus (defocus) does not occur is a narrow range of about −0.25 μm or more and 0.25 μm or less in the z direction shown in FIG. 2. . However, according to the illumination by the projection exposure apparatus of the present invention, defocus does not occur in a wide range from about −0.75 μm to 1.0 μm.
[0121]
Therefore, it can be seen that by using the projection exposure apparatus provided with the multiple reflection interference light source filter of the present invention, extremely excellent characteristics can be obtained as compared with the illumination system of the conventional projection exposure apparatus.
[0122]
As described above, the transparent region 33 of the multi-reflection interference light source filter 3 is formed by using a KrF excimer laser projection exposure apparatus with NA = 0.5 and σ = 0.6. ₂ Is formed on the semi-transparent film 32 by sputtering, and an Al film capable of obtaining T = 50% and R = 15% is formed by sputtering.
[0123]
Apply this to the repeating line and space pattern. In this case, the light intensity distribution contrast similar to that shown in (a) -2 of FIG. 6 (A) is obtained, and the conventional normal light distribution as shown in (c) -2 of FIG. 6 (C) is obtained. The resolution is greatly improved as compared with the light intensity distribution obtained from the projection exposure apparatus. Further, since the light intensity distribution contrast at the focal position is much better than the value obtained from a conventional ordinary projection exposure apparatus, it is possible to greatly increase the depth of focus.
[0124]
As described above, the multiple reflection interference light source filter and the projection exposure apparatus using the same according to the present invention have the effect of improving both a single pattern and a repetitive pattern. Since it can respond to almost all the patterns required in the process, it is effective for both chip processes centered on repeated patterns such as DRAM and chip processes such as logic with many random patterns. The chip eliminates the need to replace the light source filter, and can greatly reduce the process cost. Further, since it is obtained by forming a thin film on the entire surface of the filter, it is extremely simple as compared with a manufacturing process of a phase shift mask or the like having a fine processing process. Furthermore, by improving only the illumination optical system of the conventional projection exposure apparatus, characteristics improvement effects such as resolution and depth of focus can be obtained, contributing to a significant reduction in initial capital investment associated with extending the life of the adaptive chip generation of the projection exposure apparatus. .
[0125]
Since the improvement effect does not depend on the wavelength of the exposure light in principle, the present invention is not limited to the KrF excimer laser (wavelength: 248 nm) described in the above embodiment, but includes g-line (wavelength: 436 nm) and i-line ( Wavelength: 365 nm), an ArF excimer laser (wavelength: 193 nm), F ₂ An exposure apparatus that is effective for multi-generation exposure light sources such as an excimer laser (wavelength: 157 nm) and is extremely useful in practice can be provided.
[0126]
【The invention's effect】
In the light source filter according to claim 1 of the present invention, the first exposure light is transmitted through the first and second regions without being reflected at the boundary between the first and second regions, and the second exposure light is transmitted through the first and second regions. The first exposure light and the second exposure light are reflected at the boundary between the first area and the second area and reciprocate through the first area and pass through the first area, and a phase difference of a half wavelength occurs between the first exposure light and the second exposure light. The focal position of the second exposure light is shifted by a half-wavelength optical path difference.
[0127]
As a result, the image formation amplitude at the set focal position is inverted, and the light intensity distribution of the image obtained by interference has a steep and favorable profile in which the side lobes are offset. Therefore, the contrast of the light intensity distribution is improved, and the resolution can be greatly improved. Further, the contrast of the light intensity distribution in the focus direction is improved, so that the depth of focus can be greatly increased. Further, the same effect as the coherence of the repeated pattern is obtained by the first exposure light and the second exposure light having different half-wave phases even in the case of a single pattern as well as the repetition pattern. Significant improvement can be achieved, and the proximity effect due to the density of the pattern is reduced.
[0128]
In the light source filter according to the second aspect, in the light source filter according to the first aspect, the second region is a thin film having a transmittance for exposure light of 30% or more and a reflectance of 55% or less.
[0129]
In the light source filter according to the third aspect, in the light source filter according to the second aspect, the thin film is made of an oxide mainly composed of Cr, Ta, Mo, Al, Ti, MoSi, or Cr, Ta, Mo, Al, Ti, MoSi. Or nitride.
[0130]
A light source filter according to claim 4 is the light source filter according to any one of claims 1 to 3, wherein the first region is SOG or sputtered SiO. ₂ Alternatively, it is formed of either an optical glass or an organic film.
[0131]
Therefore, good multiple reflection at the boundary between the first region and the second region is realized. As a result, it is possible to improve the contrast of the light intensity distribution and increase the depth of focus.
[0132]
In the light source filter according to the fifth aspect, in the light source filter according to any one of the first to fourth aspects, since there is a light-shielding portion that shields a part of the exposure light, only a necessary component of the exposure light is extracted and phase-modulated. It is possible to cause interference.
[0133]
In the projection exposure apparatus using the light source filter according to claim 6, the first exposure light transmits through the first area and the second area without being reflected on the boundary between the first area and the second area, The second exposure light is reflected at the boundary between the first area and the second area and is transmitted and reciprocated once through the first area. The first exposure light and the second exposure light have a phase difference of a half wavelength, and Is projected, the focal positions of the first exposure light and the second exposure light are shifted by a half-wavelength optical path difference, the image amplitude at the focal position is inverted, and the light intensity distribution of the image obtained by interference is obtained. Has a steep and good profile in which side lobes are offset from each other. Therefore, the contrast of the light intensity distribution is improved, and the resolution can be greatly improved. Further, the contrast of the light intensity distribution in the focal direction is improved, and the depth of focus can be greatly increased. Furthermore, even if it is a single pattern as well as a repetitive pattern, the same effect can be obtained as the coherence of the repetitive pattern is given by the first exposure light and the second exposure light having different half-wave phases. Significant improvement can be achieved, and the proximity effect due to the density of the pattern is reduced.
[0134]
As a result, a projection that is less dependent on pattern periodicity, pattern layout, pattern size, pattern density, etc., and satisfies most practically required characteristics that are effective for both single patterns and repetitive patterns. An exposure apparatus can be provided.
[0135]
In the projection exposure apparatus according to claim 7, in the projection exposure apparatus according to claim 6, the second region of the light source filter is a thin film having a transmittance of 30% or more and a reflectance of 55% or less for exposure light.
[0136]
In the projection exposure apparatus according to claim 8, in the projection exposure apparatus according to claim 7, the thin film contains Cr, Ta, Mo, Al, Ti, MoSi or Cr, Ta, Mo, Al, Ti, MoSi as a main component. Oxide or nitride.
[0137]
In the projection exposure apparatus according to the ninth aspect, in the projection exposure apparatus according to any one of the sixth to eighth aspects, the first region of the light source filter may be SOG or sputtered SiO. ₂ Alternatively, it is formed of either an optical glass or an organic film.
[0138]
Therefore, good multiple reflection at the boundary between the first region and the second region of the light source filter is realized, and a significant improvement in resolution and an increase in the depth of focus are realized.
[0139]
As a result, a projection that is less dependent on pattern periodicity, pattern layout, pattern size, pattern density, etc., and satisfies most practically required characteristics that are effective for both single patterns and repetitive patterns. An exposure apparatus can be realized.
[0140]
In the projection exposure apparatus according to the tenth aspect, since the projection exposure apparatus according to the sixth to ninth aspects, there is a light shielding portion provided adjacent to the light source filter to block a part of the exposure light. Only the component can be taken out, phase-modulated and interfered, the image formed by the extra exposure light component is removed, and the resolution can be further improved and the depth of focus can be increased.
[0141]
As a result, the dependence on pattern periodicity, pattern layout, pattern size, pattern density, etc. is small, and most characteristics required for practical use that are effective for both single patterns and repetitive patterns are better satisfied. It is possible to provide a projection exposure apparatus.
[0142]
In the projection exposure method according to the eleventh aspect, exposure light is created, and a part of the phase of the created exposure light is shifted by １ ／ wavelength by the light source filter, and the exposure light shifted by １ ／ wavelength and とSince the original exposure light having no wavelength shift is projected onto the predetermined projection object in a superimposed manner, the focus positions of those exposure lights are shifted by a half-wavelength optical path difference, and the imaging amplitude at the set focus position is inverted. The high-intensity distribution of the image formed by the interference has a steep and favorable profile in which the side lobes are offset. Therefore, the contrast of the light intensity distribution is improved, and the resolution can be greatly improved. Further, the contrast of the light intensity distribution in the focal direction is improved, and the depth of focus can be greatly increased. Furthermore, even if it is a single pattern as well as a repetitive pattern, the same effect as the coherence of the repetitive pattern is provided by two exposure lights having different half-wave phases, so that the resolution can be greatly improved. In addition, the proximity effect caused by the density of the pattern is reduced.
[0143]
As a result, a projection that is less dependent on pattern periodicity, pattern layout, pattern size, pattern density, etc., and satisfies most practically required characteristics that are effective for both single patterns and repetitive patterns. An exposure method can be realized.
[Brief description of the drawings]
FIG. 1 is a schematic diagram illustrating a configuration of a projection exposure apparatus provided with a light source filter according to an embodiment of the present invention and an image of exposure light from the apparatus.
FIG. 2 is a diagram comparing the principle of image formation when a single pattern is projected by a projection exposure apparatus provided with a multiple reflection interference light source filter 3 according to an embodiment of the present invention with image formation by conventional illumination.
FIG. 3 is a diagram comparing the principle of image formation when a single pattern is projected by a projection exposure apparatus provided with a multiple reflection interference light source filter 3 according to an embodiment of the present invention to image formation by conventional illumination.
FIG. 4 is a schematic diagram of a configuration in which a multiple reflection interference light source filter 3 is provided for a repetitive pattern and a three-beam image formation of direct incidence light in a projection exposure apparatus having the multiple reflection interference light source filter 3 according to an embodiment of the present invention. is there.
FIG. 5 is a schematic view showing a configuration in which a multiple reflection interference light source filter 3 partially shielding a repetitive pattern in a projection exposure apparatus provided with the multiple reflection interference light source filter 3 of the present invention and an image of three obliquely incident light beams. FIG.
6 shows a projection exposure apparatus provided with the multiple reflection interference light source filter 3 of the present invention, using a projection exposure apparatus using the three-beam imaging system shown in FIG. 4 and an obliquely incident three-beam imaging system shown in FIG. FIG. 9 is a diagram comparing an image forming amplitude distribution and a light intensity distribution obtained from a repetitive pattern with a projection exposure apparatus and a case using a projection exposure apparatus having an image forming configuration using conventional illumination.
FIG. 7 is a view showing various light-shielding shapes in which the exposure light transmitting region 33 of the multiple reflection interference light source filter 3 according to the embodiment of the present invention is shielded by a light shielding plate 35;
FIG. 8 is a schematic diagram showing various light shielding structures for shielding the exposure light transmitting area 33 of the multiple reflection interference light source filter 3 by the light shielding plate 35 according to the embodiment of the present invention.
FIG. 9 is a view showing the structure of the multiple reflection interference light source filter of the present invention, the light shielding plate, the multiple reflection interference light source filter 3, and the holder 37 of the light shielding plate (only one side is shown).
FIG. 10 shows the resolution of a transfer result for a single pattern when the projection exposure apparatus 1 equipped with the multiple reflection interference light source filter 3 of the present invention is used and when a conventional ordinary projection exposure apparatus without a light source filter is used. It is a figure which compared the characteristic.
FIG. 11 shows the focus of the transfer result for a single pattern when using the projection exposure apparatus 1 provided with the multiple reflection interference light source filter 3 of the present invention and when using a conventional ordinary projection exposure apparatus without using a light source filter. It is the figure which compared the depth characteristic.
FIG. 12 is a schematic diagram showing a simple image forming principle by a conventional ordinary projection exposure apparatus. FIG. 12 is a diagram showing an image formed by a normal mask pattern.
FIG. 13 is a schematic diagram showing a simple image forming principle by a conventional ordinary projection exposure apparatus. FIG. 12 is a diagram showing an image formed by a normal mask pattern.
FIG. 14 is a schematic diagram showing a simple image forming principle used in a conventional modified illumination technique disclosed in Japanese Patent Application Laid-Open No. 4-101148.
FIG. 15 is a view showing a light shielding shape of a conventional light shielding plate 35.
[Explanation of symbols]
1 light source
3 Multiple reflection interference light source filter
5,51 mask
31 substrate
32 translucent area
33 Transparent area
13,34,35 Light shield
36 Light shield plate different from light shield plate 35
37 Holder
61 Exposure luminous flux
62 Exposure luminous flux with multiple reflections
64 Oblique incidence component of multiple reflected exposure light beam
71 Diffracted light beam of exposure light beam 61 by mask 5 pattern
72 Diffracted light beam of exposure light beam 62 by mask 5 pattern
73 Diffracted light beam of exposure light beam 63 by mask 51 pattern
74 Diffracted light beam of exposure light beam 64 by mask 51 pattern
75 Diffracted light beam of exposure light beam 65 by mask 51 pattern

Claims (10)

A light source filter that transmits exposure light,
A first region through which the exposure light passes;
A second region provided across the first region,
A first exposure light that transmits through the first area without reflection at a boundary between the first area and the second area;
A second exposure light reflected at the boundary and transmitted through the first region one round trip,
A light source filter for producing a phase difference of a half wavelength between the second exposure light and the first exposure light. The light source filter according to claim 1, wherein the second region is a thin film having a transmittance of the exposure light of 30% or more and a reflectance of 55% or less. The light source filter according to claim 2, wherein the thin film is made of Cr, Ta, Mo, Al, Ti, MoSi, or an oxide or nitride containing Cr, Ta, Mo, Al, Ti, MoSi as a main component. Wherein the first region is SOG, sputtering SiO _2, the light source filter according to any one of claims 1 to 3 is formed by either an optical glass or an organic film. The light source filter according to claim 1, further comprising a light-shielding portion that shields a part of the exposure light. A projection exposure apparatus that projects exposure light,
A light source that emits the exposure light,
A light source filter transmitting the exposure light, the light source filter,
A first region through which the exposure light passes;
A second region provided across the first region,
A first exposure light transmitted through the first area without reflection at a boundary between the first area and the second area;
A second exposure light reflected on the boundary and transmitted through the first region one round trip,
The second exposure light has a phase difference of a half wavelength with the first exposure light,
A mask having a shape to be projected,
A projection exposure apparatus that projects the projection shape of the mask using the first and second exposure lights transmitted through the light source filter. The projection exposure apparatus according to claim 6, wherein the second region is a thin film having a transmittance of 30% or more for the exposure light and a reflectance of 55% or less. The projection exposure apparatus according to claim 7, wherein the thin film is made of Cr, Ta, Mo, Al, Ti, MoSi, or an oxide or nitride containing Cr, Ta, Mo, Al, Ti, MoSi as a main component. The projection exposure apparatus according to any one of the first region to claims 6 formed by either SOG or sputtered SiO ₂ or an optical glass or an organic film 8. 10. The projection exposure apparatus according to claim 6, further comprising a light blocking unit provided adjacent to the light source filter and configured to block a part of the exposure light.

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