JPWO2002061505A1 - Mask, optical property measurement method, exposure apparatus adjustment method and exposure method, and device manufacturing method - Google Patents

Abstract

The first pattern and the second pattern are sequentially projected onto the projection object via the projection optical system while changing the position of the projection object with respect to the optical axis of the projection optical system at predetermined intervals. Then, a line width value corresponding to the line width of the image of each pattern is measured using the electrical resistance of the transferred pattern, and the line width value corresponding to the image of the first pattern and the optical axis of the projection optical system are measured. The correlation between the position of the projection target (curve A) and the correlation between the line width value corresponding to the image of the second pattern and the position of the projection target with respect to the optical axis of the projection optical system (curve B). The optical characteristics of the projection optical system are measured based on the measured values.

Description

ここで、上記（１）式における「Ｌｎ２」は、２の自然対数を意味している。上記（１）式を用いて算出されたシート抵抗値ρ_ｓは、コントローラ５２０の記憶部５２５に保存される。
次に、計測部５２１は、各線幅計測用エッチング像における対象パターンの線幅を求める。なお、本実施形態では、線幅計測用エッチング像におけるＬ／Ｓパターンの周期方向の両端に位置する２本のエッチング像が対象パターンである。そこで、以下においては、Ｌ／Ｓパターンの周期方向における対象パターンの位置を区別するため、エッチング像２２１ａＷ，２３１ａＷ，２４１ａＷ，２５１ａＷ，２６１ａＷ，２７１ａＷ，２８１ａＷ，２９１ａＷを「第１の対象パターン」、エッチング像２２１ｂＷ，２３１ｂＷ，２４１ｂＷ，２５１ｂＷ，２６１ｂＷ，２７１ｂＷ，２８１ｂＷ，２９１ｂＷを「第２の対象パターン」と総称する。なお、第１の対象パターンは前記第１のラインパターンの像に対応するエッチング像であり、第２の対象パターンは前記第２のラインパターンの像に対応するエッチング像である。
一般的に、線状体に電流Ｉｐを流した時の電圧降下をＶｐとすると、該線状体の電気抵抗値Ｒｐは、次の（２）式で求められる。

また、この電気抵抗値Ｒｐは、該線状体の長さをＬ、線幅をｗ、及びシート抵抗値をρ_ｓとすると、次の（３）式の関係にあることが知られている。

従って、（２）式と（３）式とから、線状体の線幅ｗを算出する次の（４）式が得られる。

そこで、第１の対象パターンの線幅値ｗ^Ｌは、第１の対象パターンの長さをＬ^Ｌ、電流Ｉｐを流した時の電圧降下をＶｐ^Ｌとすると、次の（５）式から算出される。

また、第２の対象パターンの線幅値ｗ^Ｒは、第２の対象パターンの長さをＬ^Ｒ、電流Ｉｐを流した時の電圧降下をＶｐ^Ｒとすると、次の（６）式から算出される。

そこで、計測部５２１は、前記線幅計測用エッチング像２２０Ｗの場合は、図１０に示されるように、電極パッド２２２ａＷと電極パッド２２２ｄＷを介してエッチング像２２１ａＷとエッチング像２２１ｂＷに電流Ｉｐを流す。そして、電極パッド２２２ｂＷと電極パッド２２２ｃＷを介してエッチング像２２１ａＷでの電圧降下Ｖｐ^Ｌを、また電極パッド２２２ｅＷと電極パッド２２２ｆＷを介してエッチング像２２１ｂＷでの電圧降下Ｖｐ^Ｒを測定する。そして、計測部５２１は、初期条件として入力されているエッチング像２２１ａＷの長さＬ^Ｌとエッチング像２２１ｂＷの長さＬ^Ｒと先に測定した前記シート抵抗値ρ_ｓとを記憶部５２５から読み出し、上記（５）式を用いて前記ラインパターン２２１ａの転写像の線幅に対応するエッチング像２２１ａＷの線幅値ｗ^Ｌを算出し、上記（６）式を用いて前記ラインパターン２２１ｂの転写像の線幅に対応するエッチング像２２１ｂＷの線幅値ｗ^Ｒを算出する。この算出結果は記憶部５２５に保存される。なお、符号の右肩に付されているＬは第１の対象パターンを示し、Ｒは第２の対象パターンを示している。
続いて、計測部５２１は、上述した線幅計測用エッチング像２２０Ｗの場合と同様にして、他の１４個の対象パターン２３１ａＷ，２３１ｂＷ，２４１ａＷ，２４１ｂＷ，２５１ａＷ，２５１ｂＷ，２６１ａＷ，２６１ｂＷ，２７１ａＷ，２７１ｂＷ，２８１ａＷ，２８１ｂＷ，２９１ａＷ，２９１ｂＷの線幅値をそれぞれ順次求める。
計測部５２１は、上述のような計測を、ウエハＷ上の全てのショット領域内の対応するエッチング像２００Ｗについて行う。そして、すべてのエッチング像２００Ｗの対象パターンの線幅値の計測が終了すると、計測部５２１はデータ処理を行う。
計測部５２１は、投影光学系ＰＬの光軸方向に関するウエハＷの位置毎（すなわち、ショット領域毎）に、第１の対象パターンの線幅値ｗ^Ｌと、第２の対象パターンの線幅値ｗ^Ｒについて整理する。すなわち、計測部５２１は、８つの第１の対象パターン２２１ａＷ，２３１ａＷ，２４１ａＷ，２５１ａＷ，２６１ａＷ，２７１ａＷ，２８１ａＷ，２９１ａＷの線幅値の平均値を算出し、第１のラインパターンの転写像の線幅に対応する第１の線幅値ｗ^Ｌとする。また、計測部５２１は、８つの第２の対象パターン２２１ｂＷ，２３１ｂＷ，２４１ｂＷ，２５１ｂＷ，２６１ｂＷ，２７１ｂＷ，２８１ｂＷ，２９１ｂＷの線幅値の平均値を算出し、第２のラインパターンの転写像の線幅に対応する第２の線幅値ｗ^Ｒとする。
次に、計測部５２１は、図１３に示されるように、最小二乗法を用いた近似処理により、投影光学系の光軸方向に関するウエハＷの位置と第１の線幅値ｗ^Ｌとの相関関係である第１の相関関係を求める。なお、図１３では、投影光学系ＰＬの光軸方向に関する所定基準位置に対するウエハＷの位置をフォーカス位置として横軸にとっている。この結果は計測部５２１の指示により、印字部５２４から自動的にプリント出力される。
同様にして、計測部５２１は、図１４に示されるように、投影光学系の光軸方向に関するウエハＷの位置と第２の線幅値ｗ^Ｒとの相関関係である第２の相関関係を求める。なお、図１４では、図１３と同様に、投影光学系の光軸方向に関する所定基準位置に対するウエハＷの位置をフォーカス位置として横軸にとっている。この結果は計測部５２１の指示により、印字部５２４から自動的にプリント出力される。
さらに、計測部５２１は、投影光学系の光軸方向に関するウエハＷの位置毎に、第１の線幅値ｗ^Ｌと第２の線幅値ｗ^Ｒとの平均値を求める。そして、この平均値と投影光学系の光軸方向に関するウエハＷの位置との相関関係について、図１５に示されるように最小二乗法を用いた近似処理を行い、最も誤差の少ない近似式を求める。そして、計測部５２１は、この近似式から線幅値の平均値が最大となる時の投影光学系ＰＬの光軸方向に関するウエハＷの位置を算出し、該ウエハＷの光軸方向の位置（Ｚ位置）を上述したエッチング像２００Ｗに対応する投影光学系ＰＬの視野内の評価点（計測点）における最良フォーカス位置とする。なお、この結果も計測部５２１の指示により、印字部５２４から自動的にプリント出力される。
さらに、計測部５２１は、投影光学系ＰＬの視野内の他の評価点においても同様にして最良フォーカス位置を求め、それらの結果を印字部５２４からプリント出力する。
なお、第１の線幅値ｗ^Ｌと第２の線幅値ｗ^Ｒとの平均値と投影光学系の光軸方向に関するウエハＷの位置との相関関係について、最小二乗法を用いた近似処理を行い、最も誤差の少ない近似式（あるいは近似曲線）を求めた場合に、この近似曲線が明確なピークを持たない場合もあり得る。このような場合を考慮して、ウエハＷの位置変化に対応する前記平均値の変化量が最も小さいウエハＷの位置を最良フォーカス位置とすることとしても良い。上述の最大値（極大値）あるいは最小値（極小値）などを最良フォーカス位置とする方法と、平均値の変化量が最も小さい位置を最良フォーカス位置とする方法とを、パターン種別、レジスト種類などの露光条件に応じて選択できるようにしておいても良い。
上記説明では、８つの線幅計測用パターンをすべて用いて最良フォーカス位置を求めるものとしたが、これに限らず、例えば８つの線幅計測用パターンの少なくとも１つを用いて最良フォーカス位置を求めても良い。例えば、線幅計測用パターンを個別に用いて最良フォーカス位置をそれぞれ求めると、８つの最良フォーカス位置を得ることができる。そして、例えば、周期方向が異なる４つの線幅計測用パターン（一例として、２２０、２４０、２６０、２８０）について求められた最良フォーカス位置に基づいて周期方向の違いによる最良フォーカス位置の違いを計測することができる。
また、少なくとも２つの線幅計測用パターンを用いるときはその線幅値の平均値を用いるのではなく、各線幅計測用パターン毎にフォーカス位置を求め、その平均値を最良フォーカス位置としても良い。特に、少なくとも２つの線幅計測用パターンとして、周期方向が異なる線幅計測用パターンを選択することが望ましく、このとき例えば、周期方向に応じた重みを与えて各線幅計測用パターンの線幅値を平均化し、その平均の線幅値に基づいて最良フォーカス位置を求める、あるいは、各線幅計測用パターン毎に求めたフォーカス位置に周期方向に応じた重みを与えて最良フォーカス位置を決定しても良い。
また、周期方向毎に形成条件（線幅等）が異なる複数の線幅計測用パターンをレチクル上に配置し、周期方向が同じで線幅が異なる複数の線幅計測用パターンでそれぞれ最良フォーカス位置を求めても良く、あるいはそれらの平均値（又は加重平均値）を最良フォーカス位置としても良い。例えば、本実施形態では、線幅計測用パターン２２０と２３０、線幅計測用パターン２４０と２５０、線幅計測用パターン２６０と２７０、線幅計測用パターン２８０と２９０とで線幅を変えることにより、線幅計測用パターン２２０と２３０とから第１方向での最良フォーカス位置が求められ、線幅計測用パターン２４０と２５０とから第２方向での最良フォーカス位置が求められ、線幅計測用パターン２６０と２７０とから第３方向での最良フォーカス位置が求められ、線幅計測用パターン２８０と２９０とから第４方向での最良フォーカス位置が求められる。すなわち、本実施形態において、線幅計測用パターン２２０を第１方向で第１の線幅を有するＬ／Ｓパターンとし、線幅計測用パターン２３０を第１方向で第４の線幅を有するＬ／Ｓパターンとし、線幅計測用パターン２４０を第２方向で第２の線幅を有するＬ／Ｓパターンとし、線幅計測用パターン２５０を第２方向で第５の線幅を有するＬ／Ｓパターンとし、線幅計測用パターン２６０を第３方向で第３の線幅を有するＬ／Ｓパターンとし、線幅計測用パターン２７０を第３方向で第６の線幅を有するＬ／Ｓパターンとし、線幅計測用パターン２８０を第４方向で第７の線幅を有するＬ／Ｓパターンとし、線幅計測用パターン２９０を第４方向で第８の線幅を有するＬ／Ｓパターンとすることにより前述と同様にして、周期方向毎に最良フォーカス位置を求めることが可能となる。
これにより、異なる線幅のラインパターンに対応する像の線幅計測結果と、方向の異なるラインパターンに対応する像の線幅計測結果とをほぼ同時に得ることができ、線幅の違いや方向の違いを利用した投影光学系の光学特性の計測を短時間で行うことが可能となる。そして、結果として投影光学系の光学特性計測に関するスループットを向上させることが可能となる。
繰り返しになるが、本実施形態では、少なくとも１つの線幅計測用パターンを設けるだけで良いが、形成条件（周期方向、線幅、パターンピッチ、及びデューティ比等の少なくとも１つを含む）が異なる複数の線幅計測用パターンを設けておくことが望ましい。
また、同様にして、互いに対をなす２種類の線幅計測用パターンのエッチング像（例えば、エッチング像２２０Ｗとエッチング像２３０Ｗ）の線幅値に着目し、これらの線幅値と投影光学系の光軸方向に関するウエハＷの位置との相関関係に基づいて、周期方向毎に最良フォーカス位置を求めることもできる。すなわち、エッチング像２２０Ｗとエッチング像２３０Ｗからは、第１方向における最良フォーカス位置が求められ、エッチング像２４０Ｗとエッチング像２５０Ｗからは、第２方向における最良フォーカス位置が求められ、エッチング像２６０Ｗとエッチング像２７０Ｗからは、第３方向における最良フォーカス位置が求められ、エッチング像２８０Ｗとエッチング像２９０Ｗからは、第４方向における最良フォーカス位置が求められる。これにより、４つの周期方向について、それぞれ最良フォーカス位置が求められ、Ｌ／Ｓパターンの周期方向による最良フォーカス位置の違いを求めることができる。また、４つの周期方向について求められた最良フォーカス位置の平均値（又は加重平均値）を算出し、該平均値（又は加重平均値）を各評価点での最良フォーカス位置としても良い。
なお、上記説明では、投影光学系の視野内に設定される複数の評価点の１つにおける光学特性としての最良フォーカス位置の計測について述べたが、残りの評価点についても同様に光学特性が決定される。
続いて、計測部５２１は、最良フォーカス位置でのエッチング像２２１ａＷの線幅値ｗ^Ｌとエッチング像２２１ｂＷの線幅値ｗ^Ｒとを用いて、次の（７）式により線幅異常値を算出し、投影光学系の光学特性の一つであるコマ収差を求める。

あるいは、計測部５２１は、（線幅値ｗ^Ｌ−線幅値ｗ^Ｒ）をコマ収差の指標値とし、この指標値に基づいて、投影光学系の光学特性の一つであるコマ収差を求めることもできる。この他、計測部５２１は、（線幅値ｗ^Ｌ−線幅値ｗ^Ｒ）とＬ／Ｓパターン２２１のピッチとの比を、コマ収差の指標値とし、該指標値に基づいてコマ収差を求めることもできる。
これらの結果は、計測部５２１の指示により、印字部５２４から自動的にプリント出力される。
さらに、計測部５２１は、他のエッチング像及び投影光学系ＰＬの視野内の他の評価点においても同様にして線幅異常値などを算出し、それらの結果を印字部５２４からプリント出力する。
また、本実施形態で求められた最良フォーカス位置に基づいて、次のようにして投影光学系の光学特性である非点収差、像面湾曲、及び総合焦点差を求めることができる。
非点収差は、周期方向が直交する周期パターン（評価点が光軸上にあるときは、例えば、エッチング像２２０Ｗと２４０Ｗ）から得られる最良フォーカス位置の差に基づいて算出することができる。すなわち、投影光学系ＰＬの視野内で任意の像高位置にある評価点に配置されたサジタル方向とメリジオナル方向とを周期方向とする、周期パターンの線幅値に基づいて求められる最良フォーカス位置の差に基づいて非点収差を算出することができる。さらに、投影光学系の視野内の複数の評価点について算出された非点収差に基づいて最小二乗法による近似処理を行うことにより非点収差面内均一性を求めることができる。
また、投影光学系の視野内の複数の評価点について計測された最良フォーカス位置に基づいて最小二乗法による近似処理を行うことにより像面湾曲を算出することができる。
さらに、非点収差面内均一性と像面湾曲とから総合焦点差を求めることができる。
また、投影光学系の視野内の複数の評価点について、最良フォーカス位置での第１の線幅値ｗ^Ｌと第２の線幅値ｗ^Ｒとの少なくとも一方あるいはその平均値に基づいて最小二乗法による近似処理を行うことにより、投影光学系の光学特性の一つである投影光学系の視野内での線幅均一性を求めることができる。
本実施形態では、上述した計測と同一の計測を、実験的に複数のウエハＷについて行ったところ、計測された線幅値の標準偏差をσとすると、３σ≦０．５ｎｍであり、良好な再現性を確認することができた。また、１計測点当たりの線幅計測に要した時間は０．５秒以下であり、短時間で計測できることを確認した。
計測部５２１が行った上記処理は、その手順が記憶部５２５にプログラムとして記憶されており、計測部５２１は、その手順に従って自動的に処理を行っている。すなわち、ウエハＷがウエハボックス５１０に固定され、オペレータが初期条件を入力し、測定開始を指示した後は、自動的に処理が行われる。
このようにして求められた投影光学系の光学特性データは、露光装置の主制御装置２８に入力され、図示しない記憶装置に保存される。そして、主制御装置２８は、この光学特性データに基づいて、図示しない結像特性補正コントローラに指示し、投影光学系ＰＬの複数のレンズエレメントを制御することにより投影光学系ＰＬのコマ収差や像面湾曲などを調整する。
また、本実施形態の露光装置１００では、前述した投影光学系ＰＬの光学特性を計測するためのパターンの転写像を形成する動作と同様の手順で、上述の如く、結像特性が調整された投影光学系ＰＬを用いて露光（感光物体へのデバイスパターンの転写）が行われる。
以上説明したように、本実施形態によれば、像の線幅を電気抵抗計測で求めているために、ほぼ同時に複数の像の線幅を測定でき、光学特性計測のスループットを低下させることなく評価点を増やすことが可能となる。これは、結果的に、測定精度の向上や、測定結果の再現性の向上に寄与することになる。
また、本実施形態によれば、非点収差、像面湾曲、総合焦点差といった光学特性を評価するための最良フォーカス測定と、投影光学系の重要な光学特性の一つであるコマ収差を評価するための線幅異常値の測定と、露光領域内の線幅均一性を評価するためのΔＣＤ測定とを短時間で、精度よく、しかも自動的に行うことが可能となる。
さらに、本実施形態によれば、ラインパターンが第１方向と第２方向に伸びている線幅計測用パターンをパターン領域ＰＡ内に配置した後の隙間領域に、ラインパターンが第３方向と第４方向に伸びている線幅計測用パターンを配置している。このため、面積が限られているパターン領域ＰＡを有効に利用することができるとともに、１回の露光で多数の計測値を得ることができる。
また、本発明に係るマスクを用いて、最良露光量を計測することも可能である。すなわち、最良フォーカス位置において、ウエハＷ上に照射される露光光のエネルギ量（露光ドーズ量）を変えながら、パターンを転写することにより、像の線幅値と露光ドーズ量との間の相関関係から最良露光量を求めることができる。あるいは、投影光学系の光軸に関するウエハ位置及び、ウエハＷ上に照射される露光光のエネルギ量（露光ドーズ量）を変えながら、パターンを転写することにより、露光ドーズ量と像の線幅値と投影光学系の光軸に関するウエハ位置との間の相関関係から最良フォーカス位置及び最良露光量を求めることができる。
さらに、本実施形態によれば、電気抵抗測定装置５００における線幅計測及びデータ処理は、その手順が記憶部５２５にプログラムとして記憶されており、計測部５２１は、その手順に従って自動的に処理を行っている。すなわち、ウエハＷがウエハボックス５１０に固定され、オペレータが初期条件を入力し、測定開始を指示した後は、自動的に処理が行われるため、省力化を図ることができる。
また、本実施形態に係る露光方法によると、前述のようにして計測された投影光学系ＰＬの光学特性に基づいて、投影光学系ＰＬが調整され、この調整後の投影光学系を介してレチクルＲのパターンがウエハＷの各ショット領域に転写されるので、微細パターンを高精度に転写することができる。
なお、上記実施形態では、パターン２００は、ラインパターンが４方向（第１〜第４方向）に伸びる８種類の線幅計測用パターンから構成されているがこれに限定されるものではない。すなわち、パターン２００は、ラインパターンが４方向（第１〜第４方向）に伸びる少なくとも４種類の線幅計測用パターンから構成されても良い。あるいは、パターン２００は、ラインパターンが３方向（第１〜第３方向）に伸びる少なくとも３種類の線幅計測用パターンから構成されていても良い。
また、上記実施形態では、パターン２００における線幅計測対象のパターン線幅は、すべて同一であるがこれに限定されるものではない。すなわち、パターン２００を構成する各線幅計測用パターンにおける線幅計測対象のパターン線幅が２種類以上あっても良い。
なお、上記実施形態では、シート抵抗計測用パターンを挟んで、対称な線幅計測用パターンが配置されているが、これに限らず、例えばシート抵抗計測用パターンを挟んで、線幅のみが異なるラインパターンを含む線幅計測用パターンが配置されても良く、あるいは、ラインパターンの方向のみが異なる線幅計測用パターンが配置されても良い。また、シート抵抗計測用パターンは、必ずしもパターン２００の中央部に配置されなくても良い。
さらに、上記実施形態では、パターン２００は、ウエハＷのシート抵抗値を計測するためのパターンとして、ファン・デア・パウ（ｖａｎ ｄｅｒ Ｐａｕｗ）構造のパターンを含んでいるが本発明がこれに限定されるものではない。また、パターン２００は、シート抵抗計測用パターンを含まなくても良い。
なお、上記実施形態では、線幅計測用パターンにおけるＬ／Ｓパターンとして、５本のラインパターンが周期的に配列されたＬ／Ｓパターンが用いられているが、５本に限定されるものではないし、Ｌ／Ｓパターンのような密集パターンではなく孤立パターン、すなわち１本のラインパターンでも良い。また、上記実施形態では、Ｌ／Ｓパターンの周期方向の両端に位置する２本のラインパターンを線幅計測の対象パターンとしているがこれに限定されるものではない。すなわち、Ｌ／Ｓパターンの周期方向の中心に最も近い位置にあるラインパターンを線幅計測の対象パターンとしても良い。また、Ｌ／Ｓパターンの周期方向の両端に位置する２本のラインパターンを線幅計測の対象パターンとする線幅計測用パターンと、Ｌ／Ｓパターンの周期方向の中心に最も近い位置にあるラインパターンを線幅計測の対象パターンとする線幅計測用パターンとが混在しても良い。さらに、１つの線幅計測用パターンにおいて、Ｌ／Ｓパターンの周期方向の両端に位置する２本のラインパターンとＬ／Ｓパターンの周期方向の中心に最も近い位置にあるラインパターンとを線幅計測の対象パターンとしても良い。
また、上記実施形態では、各線幅計測用パターンにおけるＬ／Ｓパターンのパターンピッチ及びデューティ比は同一としているが、計測目的や計測手法に応じて変更しても良い。
なお、各線幅計測用パターンのＬ／Ｓパターンにおける周期方向の両端に位置する２本のラインパターンで挟まれているラインパターン（ダミーパターン）が複数本の場合には、図７に示されるように、各ダミーパターンの隣接する端部同士の一部を線状のパターンで連通し、１本のラインパターン３００が折り畳まれた形状となるようにしてもよい。また、ダミーパターンを含まなくても良い。すなわち、相互に隣接するラインパターンが、線幅計測の対象パターンであっても良く、この場合、それ以外のパターンが存在しなくても良い。すなわち、相互に隣接する２本のラインパターンから成るマルチラインパターンを線幅計測用パターンの前述のＬ／Ｓパターンの代わりに用いても良い。
なお、上記実施形態では、パターン２００を構成する線幅計測用パターンのすべてに電気抵抗計測用電極パッドパターンを含んでいるがこれに限定されるものではない。すなわち、パターン２００は、電気抵抗計測用電極パッドパターンを含まない線幅計測用パターンを含んでいても良い。
さらに、電気抵抗測定装置５００には、複数のウエハを連続して測定するために、複数のウエハをストックする図示しないウエハストック部と、このウエハストック部から自動的にウエハを取り出して固定部５１１にセットする図示しないローダ部とを備えることも可能であり、これにより更なる省力化、短時間化が図られる。
なお、電気抵抗測定装置５００のコントローラ５２０は、一般のパーソナルコンピュータにＡＤボード、ＤＡボード、及びＤＩＯボードを備えたものでも良い。
さらに、電気抵抗測定装置５００のコントローラ５２０で求められた光学特性データを、主制御装置２８に自動的に転送することも可能である。
《第２の実施形態》
次に、本発明の第２の実施形態を図１６〜図２４に基づいて説明する。この第２の実施形態では、本発明に係る投影光学系の光学特性計測方法及び露光方法が、前述の第１の実施形態と同一若しくは同等の露光装置を用いて行われる。また、後述するエッチング像の線幅計測には、前述の第１の実施形態と同一若しくは同等の電気抵抗測定装置が用いられる。従って、以下においては、重複記載を防止する観点から、これらの装置及びそれぞれの構成各部については第１の実施形態と同一の符号を用いるとともに、光学特性計測方法及び露光方法を中心として説明する。なお、本実施形態では、投影光学系ＰＬの投影倍率βが１／４であるものとする。
図１６には、本第２の実施形態において、投影光学系の光学特性の計測に用いられるレチクルＲ_Ｔ’の一例が示されている。この図１６は、レチクルＲ_Ｔ’を、パターン面側（図１における下面側）から見た平面図である。このレチクルＲ_Ｔ’は、ほぼ正方形のガラス基板４２’の中央に、パターン領域ＰＡ’が設けられ、そのパターン領域ＰＡ’内に、後述するような複数のパターンが配置されている。また、パターン領域ＰＡ’の中心、すなわちレチクルＲ_Ｔ’の中心（レチクルセンタ）を通るパターン領域ＰＡ’のＸ軸方向の両側には、一対のレチクルアライメントマークＲＭ３，ＲＭ４が形成されている。
ここで、前記パターン領域ＰＡ’内に配置されている投影光学系の光学特性を計測するためのパターン７００の構成について、図１７〜図１９を用いて説明する。
パターン７００は、図１７に示されるように、基板としてのウエハＷのシート抵抗値を計測するためのファン・デア・パウ構造のシート抵抗値計測用パターン７１０と、線幅を計測するための８個の線幅計測用パターン７２０，７３０，７４０，７５０，７６０，７７０，７８０，７９０とから構成されている。
パターン７００の中央部に配置されている前記シート抵抗値計測用パターン７１０は、前述したシート抵抗値計測用パターン２１０（図５参照）と同様に、正方形の形状を有する計測領域パターン７１１と、正方形の形状を有する４個の電極パッドパターン７１２ａ，７１２ｂ，７１２ｃ，７１２ｄとから構成されおり、該電極パッドパターンは、それぞれ線状のパターンを介して前記計測領域パターン７１１と接続されている。なお、図１７においては、電極パッドパターンについては、引き出し線を省略し、各電極パッドパターンの位置に符号を記している。
前記シート抵抗値計測用パターン７１０の図１７における紙面上側（−Ｙ側）には、線幅計測用パターン７２０が配置されている。線幅計測用パターン７２０は、図１８に示されるように、５本のラインパターンが周期的に配列されたラインアンドスペース（以下、「Ｌ／Ｓ」と略述する）パターンと、正方形の形状を有する４個の電極パッドパターン７２２ａ，７２２ｂ、７２２ｃ，７２２ｄとから構成されている。そして、電極パッドパターン７２２ａ，７２２ｃは、それぞれ線状のパターンを介して前記Ｌ／Ｓパターンの周期方向における中央のラインパターン７２１の長手方向における一端と接続されており、電極パッドパターン７２２ｂ，７２２ｄは、それぞれ線状のパターンを介して前記ラインパターン７２１の長手方向における他端と接続されている。
図１７に戻り、前記シート抵抗値計測用パターン７１０の図１７における紙面下側（＋Ｙ側）には、線幅計測用パターン７３０が配置されている。この線幅計測用パターン７３０は、前記線幅計測用パターン７２０と互いに対をなすパターンであり、Ｌ／Ｓパターンのデューティ比が異なる以外は同一の形状を有している。すなわち、線幅計測用パターン７３０は、Ｌ／Ｓパターンと４個の電極パッドパターン７３２ａ，７３２ｂ、７３２ｃ，７３２ｄとから構成されている。そして、電極パッドパターン７３２ａ，７３２ｃは、それぞれ線状のパターンを介して前記Ｌ／Ｓパターンの周期方向における中央のラインパターン７３１の長手方向における一端と接続されており、電極パッドパターン７３２ｂ，７３２ｄは、それぞれ線状のパターンを介して前記ラインパターン７３１の長手方向における他端と接続されている。
なお、前記２種類の線幅計測用パターン７２０，７３０におけるＬ／Ｓパターンのピッチは同一であり、本実施形態では、一例として、図１９Ａに示されるように、前記線幅計測用パターン７２０におけるＬ／Ｓパターンのライン部の幅を５８０ｎｍ、図１９Ｂに示されるように、前記線幅計測用パターン７３０におけるＬ／Ｓパターンのライン部の幅を６２０ｎｍとし、前記２種類の線幅計測用パターン７２０，７３０におけるＬ／Ｓパターンのデューティ比を変えている。
図１７に戻り、前記シート抵抗値計測用パターン７１０の図１７における紙面左側（−Ｘ側）には、線幅計測用パターン７４０が配置されている。この線幅計測用パターン７４０は、前記線幅計測用パターン７２０を図１７における紙面内で反時計回りに９０度回転させた形状を有している。すなわち、線幅計測用パターン７４０は、Ｌ／Ｓパターンと４個の電極パッドパターン７４２ａ，７４２ｂ、７４２ｃ，７４２ｄとから構成されている。そして、電極パッドパターン７４２ａ，７４２ｃは、それぞれ線状のパターンを介して前記Ｌ／Ｓパターンの周期方向における中央のラインパターン７４１の長手方向における一端と接続されており、電極パッドパターン７４２ｂ，７４２ｄは、それぞれ線状のパターンを介して前記ラインパターン７４１の長手方向における他端と接続されている。
前記シート抵抗値計測用パターン７１０の図１７における紙面右側（＋Ｘ側）には、線幅計測用パターン７５０が配置されている。この線幅計測用パターン７５０は、前記線幅計測用パターン７４０と互いに対をなすパターンであり、前記線幅計測用パターン７３０を図１７における紙面内で反時計回りに９０度回転させた形状を有している。すなわち、線幅計測用パターン７５０は、Ｌ／Ｓパターンと４個の電極パッドパターン７５２ａ，７５２ｂ、７５２ｃ，７５２ｄとから構成されている。そして、電極パッドパターン７５２ａ，７５２ｃは、それぞれ線状のパターンを介して前記Ｌ／Ｓパターンの周期方向における中央のラインパターン７５１の長手方向における一端と接続されており、電極パッドパターン７５２ｂ，７５２ｄは、それぞれ線状のパターンを介して前記ラインパターン７５１の長手方向における他端と接続されている。
前記線幅計測用パターン７２０の図１７における紙面左側（−Ｘ側）には、線幅計測用パターン７６０が配置されている。この線幅計測用パターン７６０は、図１７に示されるように、前記線幅計測用パターン７２０のＬ／Ｓパターンを図１７における紙面内で反時計回りに４５度回転させたＬ／Ｓパターンと、正方形の形状を有する４個の電極パッドパターン７６２ａ，７６２ｂ、７６２ｃ，７６２ｄとから構成されている。そして、電極パッドパターン７６２ａ，７６２ｃは、それぞれ線状のパターンを介して前記Ｌ／Ｓパターンの周期方向における中央のラインパターン７６１の長手方向における一端と接続されており、電極パッドパターン７６２ｂ，７６２ｄは、それぞれ線状のパターンを介して前記ラインパターン７６１の長手方向における他端と接続されている。
前記線幅計測用パターン７３０の図１７における紙面右側（＋Ｘ側）には、線幅計測用パターン７７０が配置されている。この線幅計測用パターン７７０は、前記線幅計測用パターン７６０と互いに対をなすパターンであり、前記線幅計測用パターン７３０のＬ／Ｓパターンを図１７における紙面内で反時計回りに４５度回転させたＬ／Ｓパターンと、正方形の形状を有する４個の電極パッドパターン７７２ａ，７７２ｂ、７７２ｃ，７７２ｄとから構成されている。そして、電極パッドパターン７７２ａ，７７２ｃは、それぞれ線状のパターンを介して前記Ｌ／Ｓパターンの周期方向における中央のラインパターン７７１の長手方向における一端と接続されており、電極パッドパターン７７２ｂ，７７２ｄは、それぞれ線状のパターンを介して前記ラインパターン７７１の長手方向における他端と接続されている。
さらに、前記線幅計測用パターン７２０の図１７における紙面右側（＋Ｘ側）には、線幅計測用パターン７８０が配置されている。この線幅計測用パターン７８０は、前記線幅計測用パターン７６０を図１７における紙面内で時計回りに９０度回転させた形状を有している。すなわち、線幅計測用パターン７８０は、Ｌ／Ｓパターンと４個の電極パッドパターン７８２ａ，７８２ｂ、７８２ｃ，７８２ｄとから構成されている。そして、電極パッドパターン７８２ａ，７８２ｃは、それぞれ線状のパターンを介して前記Ｌ／Ｓパターンの周期方向における中央のラインパターン７８１の長手方向における一端と接続されており、電極パッドパターン７８２ｂ，７８２ｄは、それぞれ線状のパターンを介して前記ラインパターン７８１の長手方向における他端と接続されている。
前記線幅計測用パターン７３０の図１７における紙面左側（−Ｘ側）には、線幅計測用パターン７９０が配置されている。この線幅計測用パターン７９０は、前記線幅計測用パターン７８０と互いに対をなすパターンであり、前記線幅計測用パターン７７０を図４における紙面内で時計回りに９０度回転させた形状を有している。すなわち、線幅計測用パターン７９０は、Ｌ／Ｓパターンと４個の電極パッドパターン７９２ａ，７９２ｂ、７９２ｃ，７９２ｄとから構成されている。そして、電極パッドパターン７９２ａ，７９２ｃは、それぞれ線状のパターンを介して前記Ｌ／Ｓパターンの周期方向における中央のラインパターン７９１の長手方向における一端と接続されており、電極パッドパターン７９２ｂ，７９２ｄは、それぞれ線状のパターンを介して前記ラインパターン７９１の長手方向における他端と接続されている。
前記各線幅計測用パターンにおけるＬ／Ｓパターンの中央のラインパターンを延長した線は、前記シート抵抗値計測用パターン７１０の計測領域パターン７１１の中央部で交差するように配置されている。すなわち、前記シート抵抗値計測用パターン７１０を挟んで、Ｌ／Ｓパターンのデューティ比のみが異なる同一形状の線幅計測用パターンを対称的に配置することにより、Ｌ／Ｓパターンのデューティ比の違いを利用した計測を精度良く行うことが可能となる。
また、同一デューティ比を有するＬ／Ｓパターンがそれぞれ異なった方向を向いているために、方向に依存する影響を平均化する、あるいは方向毎に光学特性の計測を行うことができる。
また、レチクルＲ_Ｔ’のパターン面上には、レチクルＲ_Ｔ’のアライメントが行われた状態で、投影光学系ＰＬの視野内の各評価点毎に対応する位置にパターン７００がそれぞれ配置されている。このため、各評価点毎に８つの線幅データが計測されることになる。
なお、本実施形態では、レチクルＲ_Ｔ’上のパターン部分は、遮光部となっているものとする。但し、これに限らず、パターン部分を光透過部としたり、あるいは半透過部としたりすることは可能である。
ウエハＷは、前述した第１の実施形態と同様に、シリコン基板、絶縁膜、導電膜、感光層としてのフォトレジスト層が順次積層された構成となっている（図８Ａ参照）。なお、本実施形態においても、レチクルＲ_Ｔ’のパターン部分が遮光部となっているために、フォトレジストにはポジ型の化学増幅型レジストが用いられている。
本第２の実施形態では、投影光学系ＰＬの光学特性を計測する際には、露光装置１００を用いて、前述した第１の実施形態と全く同様にして、ウエハテーブル１８のＺ位置を所定ピッチΔＺずつ変化させながら、ウエハＷ上の複数のショット領域にステップ・アンド・リピート方式でレチクルＲ_Ｔ’のパターンが転写される。これにより、ウエハＷの各Ｚ位置に対応するパターン７００の縮小像がウエハＷ上の各ショット領域の複数点にそれぞれ形成される。なお、この複数点は、投影光学系ＰＬの視野内でその光学特性（本実施形態では主として最良フォーカス位置）を検出すべき複数の評価点に対応している。
その後、ウエハＷは、露光装置１００にインラインにて接続されている不図示のコータ・デベロッパ（以下、「Ｃ／Ｄ」と略述する）に搬送され、現像される。そして、この現像後のウエハＷは、ドライエッチング装置に送られ、ドライエッチングが施され、このエッチングにより、フォトレジスト層が除去された部分のみの導電膜が除去され、絶縁膜が露出する。その後、ウエハＷは洗浄後、すべてのフォトレジスト層が除去される。これにより、ウエハＷ上のレジスト像は、同一形状の導電性を有するパターンに置き換えられ、パターン像のサイズ、本実施形態では、線幅の計測用の試料となる。なお、この導電性を有するパターンを、以下では、第１の実施形態と同様に「エッチング像」と呼ぶものとする。
次に、上述のようにして、ウエハＷ上に形成されるエッチング像７００Ｗについて、図２０及び図２１を用いて説明する。
エッチング像７００Ｗは、図２０に示されるように、シート抵抗値計測用エッチング像７１０Ｗと、８種類の線幅計測用エッチング像７２０Ｗ，７３０Ｗ，７４０Ｗ，７５０Ｗ，７６０Ｗ，７７０Ｗ，７８０Ｗ，７９０Ｗとから構成されている。
前記シート抵抗値計測用エッチング像７１０Ｗは、前述したシート抵抗値計測用エッチング像２１０Ｗ（図１０参照）と同様に構成されている。すなわち、シート抵抗値計測用エッチング像７１０Ｗは、図２０に示されるように、中央部に位置する正方形の形状を有する計測領域７１１Ｗと、この周囲に位置する正方形の形状を有する４個の電極パッドとから構成される。
また、図２０における線幅計測用エッチング像７２０Ｗは、前記線幅計測用パターン７２０のエッチング像であり、図２１に示されるように、Ｌ／Ｓパターンと４個の電極パッド７２２ａＷ，７２２ｂＷ，７２２ｃＷ，７２２ｄＷとから構成される。ここで、電極パッド７２２ａＷと電極パッド７２２ｂＷは、前記Ｌ／Ｓパターンの周期方向における中央のラインパターン７２１Ｗ（線幅計測の対象となるパターン）に所定の電流を流すための電極パッドであり、電極パッド７２２ｃＷと電極パッド７２２ｄＷは、前記ラインパターン７２１Ｗにおける電圧降下を計測するため電極パッドである。
図２０に戻り、線幅計測用エッチング像７３０Ｗは、前記線幅計測用パターン７３０のエッチング像であり、Ｌ／Ｓパターンと４個の電極パッドとから構成される。そして、線幅計測の対象となるパターンは、前記Ｌ／Ｓパターンの周期方向における中央のラインパターン７３１Ｗである。
線幅計測用エッチング像７４０Ｗは、前記線幅計測用パターン７４０のエッチング像であり、Ｌ／Ｓパターンと４個の電極パッドとから構成される。そして、線幅計測の対象となるパターンは、前記Ｌ／Ｓパターンの周期方向における中央のラインパターン７４１Ｗである。
線幅計測用エッチング像７５０Ｗは、前記線幅計測用パターン７５０のエッチング像であり、Ｌ／Ｓパターンと４個の電極パッドとから構成される。そして、線幅計測の対象となるパターンは、前記Ｌ／Ｓパターンの周期方向における中央のラインパターン７５１Ｗである。
線幅計測用エッチング像７６０Ｗは、前記線幅計測用パターン７６０のエッチング像であり、Ｌ／Ｓパターンと４個の電極パッドとから構成される。そして、線幅計測の対象となるパターンは、前記Ｌ／Ｓパターンの周期方向における中央のラインパターン７６１Ｗである。
線幅計測用エッチング像７７０Ｗは、前記線幅計測用パターン７７０のエッチング像であり、Ｌ／Ｓパターンと４個の電極パッドとから構成される。そして、線幅計測の対象となるパターンは、前記Ｌ／Ｓパターンの周期方向における中央のラインパターン７７１Ｗである。
線幅計測用エッチング像７８０Ｗは、前記線幅計測用パターン７８０のエッチング像であり、Ｌ／Ｓパターンと４個の電極パッドとから構成される。そして、線幅計測の対象となるパターンは、前記Ｌ／Ｓパターンの周期方向における中央のラインパターン７８１Ｗである。
線幅計測用エッチング像７９０Ｗは、前記線幅計測用パターン７９０のエッチング像であり、Ｌ／Ｓパターンと４個の電極パッドとから構成される。そして、線幅計測の対象となるパターンは、前記Ｌ／Ｓパターンの周期方向における中央のラインパターン７９１Ｗである。
次に、前記線幅計測用エッチング像における線幅計測の対象となるパターン（以下、「対象パターン」と略述する）の線幅を計測する方法について簡単に説明する。
上記対象パターンの線幅を求める方法は、種々の方法が考えられるが、本実施形態では、対象パターンの電気抵抗値から対象パターンの線幅を求める手法が採用される。すなわち、本実施形態では、対象パターンの電気抵抗値を計測する装置として前述と同一（若しくは同等）の電気抵抗計測装置５００（図１２参照）が用いられる。
本第２の実施形態においては、前述した第１の実施形態と同様の手順で、電気抵抗計測装置５００にセットされたウエハＷ状のエッチング像７００Ｗに対する線幅計測が行われる。但し、本第２の実施形態では、計測対象となるパターンは、レチクルＲ_Ｔ’上の各Ｌ／Ｓパターンの周期方向の中央に位置するラインパターン（例えばラインパターン７２１など）のエッチング像であるラインパターン（例えばラインパターン７２１Ｗなど）となっている。また、線幅計測に当たっては、前述の（４）式が用いられる。
上記の線幅計測により、ウエハＷ上のショット領域毎に、ショット領域内の複数点の各々におけるエッチング像について対象パターン７２１Ｗ、７３１Ｗ，７４１Ｗ，７５１Ｗ，７６１Ｗ，７７１Ｗ，７８１Ｗ，７９１Ｗの線幅値が、計測部５２１によってそれぞれ求められ、記憶部５２に保存される。
計測部５２１は、すべてのエッチング像の対象パターンの線幅値の計測が終了すると、以下のようにしてデータ処理を行う。なお、以下においては、説明の簡略化のため、投影光学系ＰＬの視野内の複数の評価点の１つで投影光学系の光学特性を求める場合で、その１つの評価点に対応するウエハＷ上の各ショット領域内の所定点に形成されるパターン７００のエッチング像７００Ｗの線幅計測結果を用いるものとして説明する。
計測部５２１は、投影光学系ＰＬの光軸方向に関するウエハＷの位置毎（すなわちショット領域毎）に、レチクルパターンにおけるＬ／Ｓパターンのライン部の幅が５８０ｎｍの場合（第１パターン）と、６２０ｎｍの場合（第２パターン）について線幅値を整理する。すなわち、計測部５２１は、第１パターンのエッチング像である４つの対象パターン７２１Ｗ，７４１Ｗ，７６１Ｗ，７８１Ｗの線幅値の平均値を算出し、第１パターンの像の線幅値（第１の線幅値）とする。また、計測部５２１は、第２パターンのエッチング像である４つの対象パターン７３１Ｗ，７５１Ｗ，７７１Ｗ，７９１Ｗの線幅値の平均値を算出し、第２パターンの像の線幅値（第２の線幅値）とする。
次に、計測部５２１は、最小二乗法を用いた近似処理により、投影光学系ＰＬの光軸方向に関するウエハＷの位置と前記第１の線幅値との相関関係である第１の相関関係を求める。第１の相関関係は、図２２に示されるように、ウエハＷの投影光学系ＰＬの光軸方向の位置に関する前記第１の線幅値が極大値を有する曲線Ａとなる。また、計測部５２１は、同様にして、投影光学系ＰＬの光軸方向に関するウエハＷの位置と前記第２の線幅値との相関関係である第２の相関関係を求める。第２の相関関係は、図２２に示されるように、ウエハＷの投影光学系ＰＬの光軸方向の位置に関する前記第２の線幅値が極小値を有する曲線Ｂとなる。なお、図２２では、投影光学系の光軸方向に関する所定基準位置に対するウエハＷの位置をフォーカス位置として横軸にとっている。この結果は、計測部５２１の指示により、印字部５２４から自動的にプリント出力される。
さらに、計測部５２１は、投影光学系ＰＬの光軸方向に関するウエハＷの位置毎に、第１の線幅値と第２の線幅値との差分、すなわち、図２２における曲線Ａと曲線Ｂとの差を求める。そして、この線幅値の差と投影光学系ＰＬの光軸方向に関するウエハＷの位置との相関関係について、図２３に示されるように最小二乗法を用いた近似処理を行い、最も誤差の少ない近似式を求める。そして、計測部５２１は、この近似式から線幅値の差が最小となる時の投影光学系ＰＬの光軸方向に関するウエハＷの位置を算出し、該ウエハＷの光軸方向の位置（Ｚ位置）を上述したエッチング像７００Ｗに対応する投影光学系ＰＬの視野内の評価点（計測点）における最良フォーカス位置とする。なお、この結果も計測部５２１の指示により、印字部５２４から自動的にプリント出力される。
さらに、計測部５２１は、投影光学系ＰＬの視野内の他の評価点においても同様にして最良フォーカス位置を求め、それらの結果を印字部５２４からプリント出力する。
上記説明では、Ｌ／Ｓパターンのデューティ比が同一の４つの対象パターンの線幅値の平均値をそれぞれ用いて最良フォーカス位置を求めているが、これに限らず、互いに対をなす２種類の線幅計測用パターンのエッチング像（例えば、パターン７２０Ｗとパターン７３０Ｗ）の線幅値に着目し、これらの線幅値と投影光学系ＰＬの光軸方向に関するウエハＷの位置との相関関係に基づいて、最良フォーカス位置を求めることもできる。これにより、４つの周期方向について、それぞれ最良フォーカス位置が求められ、Ｌ／Ｓパターンの周期方向による最良フォーカス位置の違いを求めることができる。また、４つの周期方向について求められた最良フォーカス位置の平均値を算出し、該平均値を各評価点での最良フォーカス位置としても良い。
また、Ｌ／Ｓパターンのデューティ比が同一の４つの対象パターンの少なくとも２つ（例えば７２１Ｗ、７４１Ｗ）と、これと対をなしＬ／Ｓパターンのデューティ比が異なる少なくとも２つの対象パターン（例えば７３１Ｗ、７５１Ｗ）とでそれぞれ線幅値を求め、周期方向が同一の対象パターン７２１Ｗと７３１Ｗの線幅値の差と投影光学系ＰＬの光軸方向に関するウエハＷの位置との相関関係から最良フォーカス位置を求め、同様に周期方向が同一の対象パターン７４１Ｗと７５１Ｗの線幅値の差と投影光学系ＰＬの光軸方向に関するウエハ位置との相関関係から最良フォーカス位置を求めることで、Ｌ／Ｓパターンの周期方向による最良フォーカス位置の違いを求めることができる。同様に、対象パターン７６１Ｗと７７１Ｗの線幅値の差と投影光学系ＰＬの光軸に関するウエハ位置との相関関係から求められる最良フォーカス位置と、対象パターン７８１Ｗと７９１Ｗの線幅値の差と投影光学系の光軸に関するウエハ位置との相関関係から求められる最良フォーカス位置とから、Ｌ／Ｓパターンの周期方向による最良フォーカス位置の違いを求めることができる。
このようにして求められた最良フォーカス位置に基づいて、次のようにして投影光学系の光学特性である非点収差、像面湾曲、及び総合焦点差を求めることができる。
非点収差は、周期方向が直交する２対の周期パターンから得られる最良フォーカス位置の差に基づいて算出することができる。例えば、上述のように、対象パターン７２１Ｗと７３１Ｗの線幅値に基づいて求められる最良フォーカス位置と対象パターン７４１Ｗと７５１Ｗの線幅値に基づいて求められる最良フォーカス位置との差に基づいて非点収差を算出することができる。また、対象パターン７６１Ｗと７７１Ｗの線幅値に基づいて求められる最良フォーカス位置と対象パターン７８１Ｗと７９１Ｗの線幅値に基づいて求められる最良フォーカス位置との差に基づいて非点収差を算出することができる。すなわち、投影光学系ＰＬの視野内で任意の像高位置にある評価点に配置されたサジタル方向とメリジオナル方向とを周期方向とする、それぞれ対をなす対象パターンの線幅値に基づいて求められる最良フォーカス位置の差に基づいて非点収差を算出することができる。
さらに、投影光学系ＰＬの視野内の複数の評価点について、上述のようにして算出された非点収差に基づいて最小二乗法による近似処理を行うことにより非点収差面内均一性を求めることができる。
また、投影光学系の視野内の複数の評価点について計測された最良フォーカス位置に基づいて最小二乗法による近似処理を行うことにより像面湾曲を算出することができる。
さらに、非点収差面内均一性と像面湾曲とから総合焦点差を求めることができる。
なお、本実施形態では、レチクルパターンにおけるＬ／Ｓパターンのデューティ比を変えることによって、像の線幅値と投影光学系の光軸に関するウエハ位置との間の複数の相関関係を求めているが、レチクルパターンにおけるＬ／Ｓパターンのデューティ比を一定にし、ウエハＷ上に照射される露光光のエネルギ量（露光ドーズ量）を変えることによって、像の線幅値と投影光学系の光軸に関するウエハ位置との間の複数の相関関係を求めてもよい。これにより、第１の露光条件として露光ドーズ量が標準値よりも大きい場合は図２２の曲線Ａと同様に上に凸の近似曲線が得られ、第２の露光条件として露光ドーズ量が標準値よりも小さい場合は図２２の曲線Ｂと同様に下に凸の近似曲線が得られるため、上述と同様にして最良フォーカス位置を求めることができる。
露光ドーズ量の調整は、主制御装置２８により、照明系ＩＯＰ内のエネルギ粗調器３あるいは光源１を制御して行われる。すなわち、第１の方法として、パルスの繰り返し周波数は一定に維持しエネルギ粗調器３を用いてレーザビームＬＢの透過率を変化させ像面（ウエハ面）に与えられる露光光のエネルギ量を調整する。第２の方法として、パルスの繰り返し周波数は一定に維持し光源に指示を与えてレーザビームＬＢの１パルス当たりのエネルギを変化させることにより像面（ウエハ面）に与えられる露光光のエネルギ量を調整する。第３の方法として、レーザビームＬＢの透過率及びレーザビームＬＢの１パルス当たりのエネルギを一定に維持し、パルスの繰り返し周波数を変更することによって、像面（ウエハ面）に与えられる露光光のエネルギ量を調整する。また、これら３つの方法を適宜組み合わせることも可能である。
２本の近似曲線から得られた最良フォーカス位置は、従来の１本のみの近似曲線から得られた最良フォーカス位置に比較してバラツキが少ない。これは、測定条件の変数が１種類（レチクルパターンの線幅又は露光ドーズ量）のみであるため、その条件下で得られた測定結果の差を利用することにより、上記変数に依存しない種々の影響を打ち消すことができるためである。
また、線幅計測用パターンにおいて、複数本のラインパターンが周期的に配列されたＬ／Ｓパターンを用い、しかもＬ／Ｓパターンの周期方向における中央のラインパターンを線幅計測の対象とすることにより、コマ収差の影響を小さくすることができ、測定精度を更に向上させることができる。
なお、上述した計測と同一の計測を、実験的に複数のウエハＷで行ったところ、計測された線幅値の標準偏差をσとすると、３σ≦０．５ｎｍであり、良好な再現性を確認することができた。
次に、計測部５２１は、最良フォーカス位置におけるレチクルパターンでのライン部の幅とそれに対応する像の線幅との関係を最小二乗法を用いた近似処理により求める。例えば、図２４に示されるように、第１の線幅値の平均値が１４０ｎｍであり、第２の線幅値の平均値が１６０ｎｍであれば、レチクルパターンの線幅と像の線幅との関係は、次の（８）式で示される。

なお、本実施形態では、レチクルパターンにおけるＬ／Ｓパターンのライン部の幅が２種類であるため、レチクルパターンの線幅とパターン像の線幅との関係は一次式で示されているが、レチクルパターンにおけるＬ／Ｓパターンのライン部の幅が３種類以上の場合には、レチクルパターンの線幅とパターン像の線幅との関係は二次式以上の高次式となることもある。計測部５２１は、処理結果を印字部５２４からプリント出力する。
そして、計測部５２１は、基準パターンとして例えば線幅が６００ｎｍのレチクルパターンがウエハＷ上に転写された場合に予測される像の線幅を上記（８）式から算出する。ここでは、予測される像の線幅として、１５０ｎｍという値が得られる。この値（以下、「基準パターンの転写線幅」という）は、実測値に含まれるレチクル製造誤差及びそれに起因する光学的な誤差を含めたプロセス誤差が補正されている。
計測部５２１は、投影光学系の視野内の他の評価点についても同様な処理を行い、基準パターンの転写線幅を算出する。計測部５２１は、それらの算出結果を印字部５２４からプリント出力する。
そして、最良フォーカス位置条件において、各評価点での基準パターンの転写線幅に基づいて、投影光学系ＰＬの光学特性の一つである投影光学系ＰＬの視野内の線幅均一性を求めることができる。
従来は、ある１つの評価点で求めた設計上の線幅と実際に形成される像の線幅との差をレチクル製造誤差に対する補正値とし、この補正値を他のすべての評価点についても適用していた。本発明に係る光学特性計測方法では、上述したように、評価点毎にその位置でのレチクル製造誤差を補正した線幅値を用いているため、高精度で再現性に優れた線幅均一性を求めることができる。
本実施形態では、上述した計測と同一の計測を、実験的に複数のウエハＷについて行ったところ、計測された線幅値の標準偏差をσとすると、３σ≦０．５ｎｍであり、良好な再現性を確認することができた。また、１計測点当たりの線幅計測に要した時間は０．５秒以下であり、短時間で計測できることを確認した。
計測部５２１が行った上記処理は、その手順が記憶部５２５にプログラムとして記憶されており、計測部５２１は、その手順に従って自動的に処理を行っている。すなわち、ウエハＷがウエハボックス５１０に固定され、オペレータが初期条件を入力し、計測開始を指示した後は、自動的に処理が行われるため、省力化を図ることができる。
また、複数のウエハＷを連続して計測するために、複数のウエハＷをストックする図示しないウエハストック部と、このウエハストック部から自動的にウエハを取り出して固定部５１１にセットする図示しないローダ部とを電気抵抗計測装置５００に備えることも可能であり、これにより更なる省力化、短時間化が図られる。
コントローラ５２０は、一般のパーソナルコンピュータにＡＤボード、ＤＡボード、及びＤＩＯボードを備えたものでも良い。
このようにして求められた投影光学系の光学特性データは、露光装置の主制御装置２８に入力され、図示しない記憶装置に保存される。そして、主制御装置２８は、この光学特性データに基づいて、図示しない結像特性補正コントローラに指示し、投影光学系ＰＬの複数のレンズエレメントを制御することにより投影光学系ＰＬの像面湾曲などを調整する。
なお、本実施形態では、パターン７００は８個の線幅計測用パターンを有しているがこれに限定されるものではない。また、ウエハＷのシート抵抗値を計測するためのパターンとして、ファン・デア・パウ（ｖａｎ ｄｅｒ Ｐａｕｗ）構造のパターンを用いているがこれに限定されるものではない。さらに、最良フォーカス位置の決定にあたって、Ｌ／Ｓパターンのデューティ比が同一で周期方向が異なる複数のエッチング像の線幅値の平均値を用いるものとしたが、周期方向は１つ以上であれば良く、例えば周期方向が同一でＬ／Ｓパターンのデューティ比が異なる一対のパターンのみから最良フォーカス位置を決定しても良い。
さらに、本実施形態では、線幅計測用パターンにおけるＬ／Ｓパターンとして、５本のラインパターンが周期的に配列されたＬ／Ｓパターンが用いられているが、５本に限定されるものではない。さらに、例えばコマ収差の影響が小さい、あるいは無視し得るときは、Ｌ／Ｓパターンではなく１本のラインパターンのみを用いるようにしても良い。このとき、長手方向が同一で線幅が異なる複数のラインパターンを形成しておくことは言うまでもない。また、Ｌ／Ｓパターンにおけるライン部のパターン本数を偶数にし、中央付近の２本のラインパターンについて線幅計測を行い、それらの平均値を計測値としても良い。
なお、電気抵抗計測装置５００のコントローラ５２０で求められた光学特性データを、主制御装置２８に自動的に通信により転送することも可能である。
また、本実施形態の露光装置１００では、前述した投影光学系ＰＬの光学特性を計測するためのパターン像を形成する動作と同様の手順で、上述の如く、結像特性が調整された投影光学系ＰＬを用いて露光（感光物体へのデバイスパターンの転写）が行われる。
以上説明したように、本第２の実施形態によれば、投影光学系の重要な光学特性の一つである露光領域内の線幅均一性を評価するためのΔＣＤ計測と、非点収差、像面湾曲、総合焦点差といった光学特性を評価するための最良フォーカス計測とを、短時間で、精度よく、しかも自動的に行うことが可能となる。さらに、本実施形態において、線幅計測用パターンにおけるＬ／Ｓパターンの特定のラインパターン（例えば、周期方向の両端に位置する２本のラインパターン）の線幅を計測することにより、コマ収差の計測を短時間で、精度よく行うことができる。
また、像の線幅を電気抵抗計測で求めているために、同時に複数の像の線幅を計測でき、スループットを低下させることなく評価点を増やすことが可能となる。これは、結果として、計測精度の向上や、再現性の向上に寄与することになる。
さらに、線幅計測及びデータ処理の自動化により省力化を図ることができる。
また、本第２の実施形態に係る露光方法によると、前述のようにして計測された投影光学系ＰＬの光学特性に基づいて、投影光学系ＰＬが調整され、この調整後の投影光学系を介してレチクルＲのパターンがウエハＷの各ショット領域に転写されるので、微細パターンを高精度に転写することができる。
なお、上記第２の実施形態中では、レチクルパターンにおけるＬ／Ｓパターンのデューティ比を変えて、像の線幅値と投影光学系ＰＬの光軸方向に関するウエハＷの位置との間の複数の相関関係を求める場合や、レチクルパターンにおけるＬ／Ｓパターンのデューティ比を一定にし、ウエハＷ上に照射される露光光のエネルギ量（露光ドーズ量）を変えることによって、像の線幅値と投影光学系ＰＬの光軸方向に関するウエハ位置との間の複数の相関関係を求める場合について説明した。しかし、本発明がこれらに限定されるものではない。すなわち、本発明は、投影光学系ＰＬの像面側に配置された基板（被投影物体）の投影光学系の光軸方向に関する位置を所定範囲内で所定の手順で変化させ、物体面に配置された第１パターンの投影光学系による像を各変化位置で被投影物体上にそれぞれ形成し、投影光学系の像面側に配置された被投影物体の投影光学系の光軸方向に関する位置を前記所定範囲内で前記所定の手順で変化させて、物体面上に配置された第２パターンの投影光学系による像を各変化位置で被投影物体上にそれぞれ形成する。そして、前記変化位置毎の第１パターンの像のサイズ（例えば線幅）を計測し、前記変化位置毎の第２パターンの像のサイズ（例えば線幅）を計測する。そして、被投影物体の前記光軸方向に関する位置と第１パターンの像のサイズとの相関関係である第１の相関関係と、被投影物体の前記光軸方向に関する位置と第２パターンの投影像のサイズとの相関関係である第２の相関関係とに基づいて投影光学系の光学特性を算出するものであれば良い。
換言すれば、パターンの像とその像が形成された被投影物体の投影光学系の光軸方向位置との関係である相関関係を少なくとも２種類求め、その２種類の相関関係に基づいて投影光学系の光学特性を算出すれば良い。すなわち、１種類の相関関係でなく、２種類の相関関係に基づいて光学特性を求めることにより、投影光学系の光学特性の測定精度を向上させることが可能となる。
従って、上記の２種類の相関関係を求めるために、物体面に配置されるパターンは、物体面上に同時に配置された別々のパターンでも良いし、異なる時間に物体面に配置される同一のパターンでも良い。また、第１のパターンを用いた像の形成と第２のパターンを用いて像の形成とは、同時に行われても良いし、別々の露光によって行われても良い。
なお、上記実施形態では、ウエハＷ上に形成されたエッチング像を計測することによりパターンの像に対応する線幅値を求める場合について説明したが、本発明がこれに限定されるものではない。すなわち、パターンの像に対応する線幅値の計測は、投影光学系により被投影物体上に投影されたパターンの投影像（空間像）を計測する空間像計測によって行っても良く、この場合には、空間像検出装置の受光部が被投影物体に相当することとなる。この場合、受光部には、投影光学系の像面側で空間像に対してスリット状あるいは矩形状の開口パターンが形成されたパターン板を相対的に走査し、開口を介した光を受光してその光電変換信号に基づいて空間像を検出するいわゆる空間像計測器を構成するパターン板や、投影光学系の像面側で像光束を受光する他の空間像検出装置を構成する受光素子あるいは撮像素子などの他、反射方式で空間像に対応する光を受光するタイプの空間像検出装置の場合の反射光学素子（ミラー等）なども含まれる。
さらには、上記実施形態と同様に、基板上に形成された転写像の線幅を計測する場合であってもその対象はエッチング像ではなく、現像処理後に得られるレジスト像であっても良い。この他、基板上に形成された潜像の線幅を計測しても良い。このとき、感光層はレジストに限られるものではなく、光磁気層などでも良い。また、第２の実施形態では、電気抵抗計測によりパターン像の線幅を得るものとしたが、線幅測定は電気抵抗計測に限られるものではなく、光学計測など、他のいかなる方法を用いても良い。要は、計測方法を問わず、上述の２種類の相関関係を得ることが出来れば良い。
また、上記第２の実施形態では、パターンの像のサイズとして代表的に線幅を計測する場合について説明したが、本発明がこれに限定されるものではない。すなわち、パターンの像の線幅に代えて、パターンの像の長さその他の寸法を像のサイズとして計測しても良い。また、パターンが例えば楔形パターンなどである場合、その対角線の長さを計測対象である像のサイズとしても良い。かかる像の長さその他の寸法も、ウエハのデフォーカス量や露光ドーズ量に応じて変化するので、上記実施形態と同様の相関関係が得られるからである。
なお、上記各実施形態では、ポジレジストを用いるものとしたが、その代わりにネガレジストを用いても良い。
なお、上記各実施形態では、本発明がステップ・アンド・リピート方式の縮小投影露光装置に適用された場合について説明したが、本発明の適用範囲がこれに限定されないのは勿論である。すなわち、ステップ・アンド・スキャン方式、ステップ・アンド・スティッチ方式、ミラープロジェクション・アライナー、及びフォトリピータなどにも好適に適用することができる。また、投影光学系は、屈折系のみならず、反射屈折系又は反射系でも良い。
さらに、本発明が適用される露光装置の光源は、ＫｒＦエキシマレーザやＡｒＦエキシマレーザに限らず、Ｆ_２レーザ（波長１５７ｎｍ）、他の真空紫外域、遠紫外域又は紫外域のパルス光源、あるいは連続光源であっても良い。この他、露光用照明光として、例えば、ＤＦＢ半導体レーザ又はファイバーレーザから発振される赤外域、又は可視域の単一波長レーザ光を、例えばエルビウム（又はエルビウムとイッテルビウムの両方）がドープされたファイバーアンプで増幅し、非線形光学結晶を用いて紫外光に波長変換した高調波を用いても良い。また、露光用照明光としてＥＵＶ光などのＸ線、あるいは電子線やイオンビームなどの荷電粒子線などを用いても良い。
さらに、本発明は、半導体素子の製造に用いられる露光装置だけでなく、液晶表示素子、プラズマディスプレイなどを含むディスプレイの製造に用いられる、デバイスパターンをガラスプレート上に転写する露光装置、薄膜磁気ヘッドの製造に用いられる、デバイスパターンをセラミックウエハ上に転写する露光装置、撮像素子（ＣＣＤなど）、マイクロマシン、及びＤＮＡチップなどの製造、さらにはマスク又はレチクルの製造に用いられる露光装置などにも適用することができる。
《デバイス製造方法》
次に、上記で説明した露光装置及び方法を使用したデバイスの製造方法の実施形態を説明する。
図２５には、デバイス（ＩＣやＬＳＩ等の半導体チップ、液晶パネル、ＣＣＤ、薄膜磁気ヘッド、ＤＮＡチップ、マイクロマシン等）の製造例のフローチャートが示されている。図２５に示されるように、まず、ステップ３０１（設計ステップ）において、デバイスの機能・性能設計（例えば、半導体デバイスの回路設計等）を行い、その機能を実現するためのパターン設計を行う。引き続き、ステップ３０２（マスク製作ステップ）において、設計した回路パターンを形成したマスクを製作する。一方、ステップ３０３（ウエハ製造ステップ）において、シリコン等の材料を用いてウエハを製造する。
次に、ステップ３０４（ウエハ処理ステップ）において、ステップ３０１〜ステップ３０３で用意したマスクとウエハを使用して、後述するように、リソグラフィ技術によってウエハ上に実際の回路等を形成する。次いで、ステップ３０５（デバイス組立ステップ）において、ステップ３０４で処理されたウエハを用いてデバイス組立を行う。このステップ３０５には、ダイシング工程、ボンディング工程、及びパッケージング工程（チップ封入）等の工程が必要に応じて含まれる。
最後に、ステップ３０６（検査ステップ）において、ステップ３０５で作製されたデバイスの動作確認テスト、耐久性テスト等の検査を行う。こうした工程を経た後にデバイスが完成し、これが出荷される。
図２６には、半導体デバイスの場合における、上記ステップ３０４の詳細なフロー例が示されている。図２６において、ステップ３１１（酸化ステップ）においてはウエハの表面を酸化させる。ステップ３１２（ＣＶＤステップ）においてはウエハ表面に絶縁膜を形成する。ステップ３１３（電極形成ステップ）においてはウエハ上に電極を蒸着によって形成する。ステップ３１４（イオン打込みステップ）においてはウエハにイオンを打ち込む。以上のステップ３１１〜ステップ３１４それぞれは、ウエハ処理の各段階の前処理工程を構成しており、各段階において必要な処理に応じて選択されて実行される。
ウエハプロセスの各段階において、上述の前処理工程が終了すると、以下のようにして後処理工程が実行される。この後処理工程では、まず、ステップ３１５（レジスト形成ステップ）において、ウエハに感光剤を塗布する。引き続き、ステップ３１６（露光ステップ）において、上記実施形態の露光装置及び露光方法によってマスクの回路パターンをウエハに転写する。次に、ステップ３１７（現像ステップ）においては露光されたウエハを現像し、ステップ３１８（エッチングステップ）において、レジストが残存している部分以外の部分の露出部材をエッチングにより取り去る。そして、ステップ３１９（レジスト除去ステップ）において、エッチングが済んで不要となったレジストを取り除く。
これらの前処理工程と後処理工程とを繰り返し行うことによって、ウエハ上に多重に回路パターンが形成される。
以上のような、本実施形態のデバイス製造方法を用いれば、露光ステップで、上記実施形態の露光装置及び露光方法が用いられるので、前述した光学特性計測方法で精度良く求められた光学特性に基づいて調整された投影光学系を介して高精度な露光が行われ、高集積度のデバイスの生産性を向上させることが可能となる。
産業上の利用可能性
以上説明したように、本発明のマスクは、投影光学系の光学特性の計測に用いるのに適している。また、本発明の投影光学系の光学特性計測方法は、短時間で、精度及び再現性良く投影光学系の光学特性を計測するのに適している。また、本発明の露光装置の調整方法及び露光方法は、基板上にパターンを精度良く形成するのに適している。また、本発明のデバイス製造方法は、マイクロデバイスの製造に適している。
【図面の簡単な説明】
図１は、本発明の第１の実施形態に係る露光装置の構成を概略的に示す図である。
図２は、図１の照明系の具体的構成の一例を説明するための図である。
図３は、第１の実施形態において、投影光学系の光学特性の計測に用いられるレチクルの一例を示す図である。
図４は、図３のレチクル上に形成されたパターンを説明するための図である。
図５は、ファン・デア・パウ（ｖａｎ ｄｅｒ Ｐａｕｗ）構造のシート抵抗値計測用パターンを説明するための図である。
図６は、第１の実施形態に係る線幅計測用パターンの一例を説明するための図である。
図７は、図６とは異なる線幅計測用パターンの一例を説明するための図である。
図８Ａ〜図８Ｄは、それぞれウエハ上に線幅計測用パターンを形成する工程を説明するための図である。
図９は、ウエハ上に転写された図４のパターンの転写像を説明するための図である。
図１０は、シート抵抗値計測用パターンの転写像におけるシート抵抗値の測定方法を説明するための図である。
図１１は、線幅計測用パターンにおけるラインパターンの転写像の線幅測定の方法を説明するための図である。
図１２は、電気抵抗測定装置の具体的構成の一例を説明するための図である。
図１３は、第１の線幅値とフォーカス位置との相関関係を説明するための図である。
図１４は、第２の線幅値とフォーカス位置との相関関係を説明するための図である。
図１５は、第１の線幅値と第２の線幅値の平均値とフォーカス位置との相関関係を説明するための図である。
図１６は、第２の実施形態において、投影光学系の光学特性の計測に用いられるレチクルの一例を示す図である。
図１７は、図１６のレチクル上に形成されたパターンを説明するための図である。
図１８は、第２の実施形態に係る線幅計測用パターンの一例を説明するための図である。
図１９Ａ及び図１９Ｂは、線幅計測用パターンでのデューティ比を説明するための図である。
図２０は、ウエハ上に転写された図１７のパターンの像を説明するための図である。
図２１は、線幅計測用パターン像における線幅計測の方法を説明するための図である。
図２２は、ウエハ上での線幅値とフォーカス位置との相関関係を説明するための図である。
図２３は、ウエハ上での線幅値の差とフォーカス位置との相関関係を説明するための図である。
図２４は、ウエハ上での線幅値とレチクルパターンの線幅との相関関係を説明するための図である。
図２５は、本発明に係るデバイス製造方法の実施形態を説明するためのフローチャートである。
図２６は、図２５のステップ３０４における処理のフローチャートである。Technical field
The present invention relates to a mask, an optical characteristic measuring method, an exposure apparatus adjusting method and an exposure method, and a device manufacturing method. More specifically, the present invention relates to a mask suitable for use in measuring optical characteristics of a projection optical system, The present invention relates to an optical characteristic measuring method for measuring optical characteristics, an exposure apparatus adjusting method and an exposure method using a measurement result of the optical characteristic measuring method, and a device manufacturing method using the exposure method.
Background art
2. Description of the Related Art Conventionally, in a lithography process for manufacturing a semiconductor element, a liquid crystal display element, or the like, a resist or the like is applied to a pattern formed on a mask or a reticle (hereinafter, collectively referred to as a “reticle”) via a projection optical system. 2. Description of the Related Art An exposure apparatus is used for transferring an image onto a substrate such as a wafer or a glass plate (hereinafter, also appropriately referred to as a “wafer”). In recent years, as an apparatus of this type, from the viewpoint of emphasizing throughput, a step-and-repeat type reduction projection exposure apparatus (so-called “stepper”) or a step-and-scan type scanning type apparatus which is an improvement of this stepper has been used. 2. Description of the Related Art Sequentially moving projection exposure apparatuses such as exposure apparatuses are relatively frequently used.
In this type of exposure apparatus, the accuracy of a projected image greatly changes due to a focus shift during exposure (transfer of a reticle pattern onto a wafer) or aberration of a projection optical system. And a technique for accurately measuring aberrations is required.
As a method of measuring the best focus position of the above-mentioned projection optical system, for example, after performing test printing on a wafer coated with a resist, the wafer is developed and the line width of a linear pattern is set to, for example, SEM ( A technique for measuring the best focus position by measuring using a scanning electron microscope) and comparing it with the designed line width value or utilizing the fact that the line width becomes the smallest under certain conditions is known. Have been.
Regarding the aberration of the projection optical system, the line width and the like of the pattern transferred onto the wafer are measured again at the best focus position determined as described above, and the aberration amount is measured.
However, in the conventional measurement method, for example, after a pattern formed on a test reticle is transferred to a resist layer such as a wafer, focusing of the SEM is performed in order to measure an interval between parallel edges of a resist image of the pattern by the SEM. It must be performed strictly, and the measurement time per point is very long, and several to several tens of hours are required to perform measurement at many points.
In addition, semiconductor elements (integrated circuits) and the like are becoming highly integrated year by year, and accordingly, a projection exposure apparatus which is a manufacturing apparatus for semiconductor elements and the like is required to have a higher resolution, that is, to transfer a finer pattern with high precision. Is required. From this, it is expected that the test pattern for measuring the optical characteristics of the projection optical system will be finer and the number of evaluation points (measurement points) in the field of view of the projection optical system will also increase. Therefore, in the conventional measurement method using the SEM, there is a possibility that the throughput until a measurement result is obtained may be significantly reduced. Also, higher levels of measurement error and reproducibility have been required, and it has become difficult to cope with the conventional measurement methods.
The present invention has been made under such circumstances, and a first object of the present invention is to provide a mask that can be suitably used for measuring optical characteristics of a projection optical system.
A second object of the present invention is to provide an optical characteristic measuring method capable of improving the measuring ability when measuring the optical characteristics of a projection optical system.
A third object of the present invention is to provide a method of adjusting an exposure apparatus capable of realizing highly accurate exposure.
A fourth object of the present invention is to provide an exposure method capable of realizing highly accurate exposure.
A fifth object of the present invention is to provide a device manufacturing method capable of improving the productivity of a highly integrated device.
Disclosure of the invention
According to a first aspect of the present invention, there is provided a mask used for measuring a line width using an electric resistance of a transferred pattern, wherein the mask includes at least one line pattern extending in a first direction and an electric resistance of the line pattern. At least one first pattern including a measurement electrode pad pattern, at least one line pattern extending in a second direction at an angle of 90 degrees to the first direction, and an electrical resistance measurement electrode pad pattern of the line pattern And at least one line pattern extending in a third direction that forms an angle θ1 (0 ° <θ1 <180 °, θ1 ≠ 90 °) with the first direction, and the line pattern And at least one third pattern including an electrode pad pattern for electrical resistance measurement of the above is formed on the pattern surface so as not to overlap with each other. A first mask comprising a mask substrate that is.
Here, the “angle” means a magnitude of an angle formed by the directions, and is a concept that does not include the angle direction (positive or negative). In this specification, the term “angle” is used as such a concept.
According to this, for example, the first, second, and third patterns on a mask are transferred onto a substrate via a projection optical system, and are subjected to processing such as development and etching, so that the first, second, and third patterns are formed on the substrate. And a pattern corresponding to the transferred image of the third pattern (since this pattern is formed on the substrate after etching, it is also referred to as an “etched image” hereinafter). Then, by measuring the line widths of the patterns corresponding to the line patterns constituting the first to third patterns in the etched image by electric resistance measurement, at least three lines corresponding to the transfer images of the line patterns having different directions are obtained. It is possible to obtain two line width values almost simultaneously. As a result, in the measurement method for measuring the optical characteristics of the projection optical system using the line width measurement corresponding to the line pattern image, it is possible to improve the throughput by shortening the measurement time.
In this case,
The third pattern is formed in a virtual rectangular area on the pattern surface including the line pattern forming the first pattern and the line pattern forming the second pattern on a part of each of two adjacent sides. Is arranged. In such a case, the third pattern can be easily arranged in the gap area after the first and second patterns are arranged on the pattern surface, and the pattern surface of the mask having a limited area can be effectively used. can do.
In the first mask of the present invention, each of the first, second and third patterns is provided in a pair, and each of the first, second and third patterns forming a pair is a predetermined pattern on the pattern surface. With respect to the reference point, it may be arranged on one side and the other side.
In this case, a sheet resistance measurement pattern may be arranged in a region on the pattern surface including the reference point.
In the first mask of the present invention, at least one of the first to third patterns includes a multi-line pattern in which a plurality of line patterns are arranged at predetermined intervals along a predetermined arrangement direction; And two electrode patterns of the electric resistance measurement electrode pad patterns respectively located at one end and the other end in the arrangement direction.
In the first mask of the present invention, at least one of the first to third patterns includes a multi-line pattern in which a plurality of line patterns are arranged at predetermined intervals along a predetermined arrangement direction; And at least one line pattern closest to the center in the arrangement direction in (a).
In the first mask of the present invention, the line pattern forming the first pattern has a first line width, the line pattern forming the second pattern has a second line width, The line pattern forming the third pattern has a third line width, at least one line pattern having a fourth line width different from the first line width and extending in the first direction, and the line pattern. A fourth pattern including an electrode pad pattern for measuring electrical resistance of the pattern, at least one line pattern having a fifth line width different from the second line width and extending in the second direction, and A fifth pattern including an electric resistance measurement electrode pad pattern, at least one line pattern having a sixth line width different from the third line width and extending in the third direction, and an electric resistance of the line pattern measurement A sixth pattern including an electrode pad pattern is further formed on the pattern surface on the mask substrate such that the sixth pattern does not overlap with any of the first, second, and third patterns and does not overlap with each other. Can be.
Here, the “line width” in the case of the first line width and the second line width means not only the line width of the line pattern but also a plurality of line patterns arranged at predetermined intervals along a predetermined arrangement direction. The concept also includes the duty ratio (the ratio of the width of the line portion to the width of the space portion, or the ratio of the line portion or the space portion to the pitch (period)) in a given multi-line pattern, for example, a line and space pattern. . In this specification, a vocabulary of “line width” is used for a pattern as such a concept.
In such a case, for example, a pattern on a mask is transferred to a substrate via a projection optical system, and development, etching and the like are performed to form an etching image on the substrate corresponding to a transfer image of the pattern, The line width of the etched image is measured by electric resistance measurement. At this time, patterns corresponding to transfer images of line patterns constituting line patterns having different line widths in the same direction, for example, a first pattern and a fourth pattern, a second pattern and a fifth pattern, and a third pattern and a sixth pattern, respectively. The line width measurement results of the transferred images corresponding to the line patterns having different line widths and the line width measurement results of the transferred images corresponding to the line patterns having different directions can be almost simultaneously obtained by measuring the line width of Obtainable. Therefore, it is possible to measure the optical characteristics of the projection optical system using the difference in line width and the difference in direction in a short time. As a result, it is possible to improve the throughput for measuring the optical characteristics of the projection optical system.
In this case, at least one line having a seventh line width and extending in the fourth direction at an angle θ2 (0 ° <θ2 <180 °, θ2 ≠ 90 °, θ2 ≠ θ1) with respect to the first direction. A seventh pattern including a pattern and an electrode pad pattern for measuring electrical resistance of the line pattern, and at least one line pattern having an eighth line width different from the seventh line width and extending in the fourth direction; An eighth pattern including the electrical resistance measurement electrode pad pattern of the line pattern does not overlap with any of the first to sixth patterns and also does not overlap with each other on the pattern surface. Can be formed.
In this case, the first pattern and the fourth pattern are arranged on one side and the other side of the first direction with respect to a predetermined reference point on the pattern surface, respectively, and the second pattern and the fifth pattern Are arranged on one side and the other side of the second direction with respect to the reference point on the pattern surface, and adjoin the line pattern constituting the first pattern and the line pattern constituting the second pattern The third pattern is arranged in a virtual rectangular area on the pattern surface including a part of each of the two sides, and the line pattern forming the first pattern and the line pattern forming the fifth pattern The seventh pattern is arranged in a virtual rectangular area on the pattern surface including a part of each of two adjacent sides of the second pattern. The eighth pattern is arranged in a virtual rectangular area on the pattern surface including the line pattern forming the fourth pattern and a part of each of the two sides adjacent to the fourth pattern. The sixth pattern is arranged in a virtual rectangular area on the pattern surface that includes the line pattern forming the fourth pattern and the line pattern forming the fifth pattern on a part of each of two adjacent sides. It can be said that.
In this case, a sheet resistance measurement pattern may be arranged in a region on the pattern surface including the reference point.
In the first mask of the present invention, when the first mask has the above-described first to eighth patterns, at least one of the first to eighth patterns includes a plurality of line patterns extending along a predetermined arrangement direction. And a multi-line pattern arranged at predetermined intervals, and an electric resistance measurement electrode pad pattern of two line patterns respectively located at one end and the other end of the multi-line pattern in the arrangement direction. And can be included. Alternatively, at least one of the first to eighth patterns includes a multi-line pattern in which a plurality of line patterns are arranged at predetermined intervals along a predetermined arrangement direction, and a multi-line pattern at a center of the multi-line pattern in the arrangement direction. And an electrical resistance measurement electrode pad pattern of at least one closest line pattern.
According to a second aspect of the present invention, there is provided a mask used for measuring a line width using an electric resistance of a transferred pattern, the mask including a first line pattern and a second line pattern substantially parallel to each other. A pattern for communicating the first and second line patterns at one end in the longitudinal direction of the first and second line patterns, and a respective one of the first and second line patterns in the longitudinal direction. The line width measurement pattern having the current supply electrode pad pattern at the other end is the second mask including the mask substrate formed on the pattern surface.
According to this, it is possible to reduce the number of current supply electrode pad patterns conventionally provided for each pattern whose line width is to be measured, and to effectively use a pattern surface having a limited area. it can. In addition, for example, a line width measurement pattern on a mask is transferred to a substrate via a projection optical system, and development, etching and the like are performed to form an etching image of the line width measurement pattern on the substrate, By measuring the line width value of the line pattern corresponding to the transferred image of the first line pattern and the second line pattern constituting the etched image using electric resistance measurement, the two line width values can be substantially reduced. It is possible to determine at the same time. As a result, the throughput of optical characteristic measurement of the projection optical system can be improved.
According to a third aspect of the present invention, there is provided an optical characteristic measuring method for measuring an optical characteristic of a projection optical system using a second mask according to the present invention, wherein a position of a substrate in an optical axis direction of the projection optical system is provided. A first step of sequentially transferring the pattern on the mask to different regions on the substrate via the projection optical system while changing the pattern; and forming the pattern on the substrate at each position in the optical axis direction. A second step of obtaining first and second line width values corresponding to transfer images of the first and second line patterns by electric resistance measurement, respectively; and the substrate with respect to the first line width value and the optical axis direction. The projection based on a first correlation that is a correlation with the position of the substrate and a second correlation that is a correlation between the second line width value and the position of the substrate in the optical axis direction. A third step of calculating optical characteristics of the optical system; A first optical characteristic measuring method comprising.
According to this, the pattern on the mask is sequentially transferred to different regions on the substrate via the projection optical system while changing the position of the substrate in the optical axis direction of the projection optical system. As a result, a transferred image of the first line pattern and a transferred image of the second line pattern are formed in different regions on the substrate for each position in the optical axis direction of the projection optical system (first step). . Further, first and second line width values corresponding to the transferred images of the first and second line patterns formed on the substrate at the respective positions in the optical axis direction are respectively obtained by electric resistance measurement ( 2nd process).
Then, a first correlation, which is a correlation between the first line width value and the position of the substrate in the optical axis direction, and a correlation between the second line width value and the position of the substrate in the optical axis direction. An optical characteristic of the projection optical system is calculated based on a certain second correlation (third step). Here, as the first and second correlations, for example, the correlation between the line width values of the transferred images of the first and second line patterns and the position of the substrate in the optical axis direction of the projection optical system is obtained. When each axis is a line width value and the horizontal axis is the position of the substrate in the optical axis direction of the projection optical system, each correlation is graphed to obtain two correlation curves.
That is, by comparing two correlations obtained under the same measurement conditions except for the position of the line pattern, various effects independent of the difference in the position of the line pattern on the measurement result can be canceled out. It is possible to improve the measurement accuracy of the optical characteristics and the reproducibility of the measurement results. Further, according to the optical characteristic measuring method, as described above, the number of current supply electrode pad patterns can be reduced, and a pattern surface having a limited area can be effectively used. Further, since the line width value of the transfer image of the line pattern is obtained by measuring the electric resistance, the line width value of the transfer image of the plurality of line patterns can be obtained in a short time, and as a result, the optical characteristics of the projection optical system can be obtained. Measurement throughput can be improved. That is, when measuring the optical characteristics of the projection optical system, it is possible to improve the measurement capability in both time and accuracy.
According to a fourth aspect of the present invention, there is provided a mask used for measuring a line width using an electric resistance of a transferred pattern, wherein a plurality of line patterns arranged at predetermined intervals along a predetermined arrangement direction are provided. Connected to both ends of a first line pattern located at one end in the arrangement direction and a second line pattern located at the other end in the arrangement direction of the line patterns, respectively. The line width measurement pattern including the formed electrical resistance measurement electrode pad pattern is the third mask including the mask substrate formed on the pattern surface.
According to this, for example, a line width measurement pattern on a mask is transferred onto a substrate via a projection optical system, and development, etching, and other processing are performed to form an etching image of the line width measurement pattern on the substrate. The line width value of the line pattern corresponding to the transfer image of the first line pattern and the second line pattern forming the etched image is formed using the electric resistance measurement, so that the line width value is calculated from each line width value. The coma aberration of the projection optical system can be obtained with high accuracy based on the obtained line width abnormal value. In this case, the line width values of both patterns can be measured almost simultaneously. As a result, the throughput of optical characteristic measurement of the projection optical system can be improved.
According to a fifth aspect of the present invention, there is provided an optical characteristic measuring method for measuring an optical characteristic of a projection optical system using the third mask according to the present invention, wherein the pattern on the mask is projected onto the projection optical system. A first step of transferring the first and second line width values corresponding to the line widths of the transferred images of the first and second line patterns formed on the substrate, respectively, to the electric resistance. A second step of calculating the optical characteristics of the projection optical system based on the first line width value and the second line width value, respectively; This is a characteristic measurement method.
According to this, the pattern on the mask is transferred onto the substrate via the projection optical system (first step). As a result, transfer images of the first pattern and the second pattern are respectively formed on the substrate by the projection optical system. Further, first and second line width values respectively corresponding to the line widths of the transfer images of the first and second line patterns formed on the substrate are obtained by electric resistance measurement (second step). Then, the optical characteristics of the projection optical system are calculated based on the first line width value and the second line width value (third step).
That is, by using two line width values obtained under the same measurement conditions except for the position of the line pattern, various effects independent of the difference in the position of the line pattern on the measurement result can be canceled. It is possible to improve the measurement accuracy of the optical characteristics and the reproducibility of the measurement results. In this case, for example, in the third step, the coma aberration of the projection optical system can be obtained with high accuracy based on the abnormal line width obtained from each line width value. In addition, since the line width value of the transfer image of the line pattern is obtained by measuring the electrical resistance, the line width value of the transfer image of a plurality of line patterns can be obtained in a short time, and as a result, the optical characteristics of the projection optical system can be obtained. Measurement throughput can be improved. That is, when measuring the optical characteristics of the projection optical system, it is possible to improve the measurement capability in both time and accuracy.
According to a sixth aspect of the present invention, there is provided an optical characteristic measuring method for measuring optical characteristics of a projection optical system, the method comprising: changing a position of a substrate in an optical axis direction of the projection optical system; Are multi-line patterns arranged at predetermined intervals along a predetermined arrangement direction, and two line patterns located at one end and the other end of the multi-line pattern in the arrangement direction, respectively. A first step of sequentially transferring a pattern on the mask to a different region on the substrate via the projection optical system using a mask formed on the pattern surface of the electrode pad pattern for electrical resistance measurement; The position corresponding to the line width of the transfer image of the first line pattern located at one end in the arrangement direction of the transfer image of the multi-line pattern formed on the substrate at each position in the optical axis direction. A second step of obtaining a first line width value by electric resistance measurement, respectively; a second line width value being located at the other end of the transfer image of the multi-line pattern formed on the substrate at the respective positions in the optical axis direction in the periodic direction; A third step of obtaining a second line width value corresponding to the line width of the transfer image of the second line pattern by electric resistance measurement, respectively; the first line width value and the position of the substrate with respect to the optical axis direction; And a second correlation, which is a correlation between the second line width value and the position of the substrate in the optical axis direction, of the projection optical system. And a fourth step of calculating optical characteristics.
According to this, while changing the position of the substrate with respect to the optical axis direction of the projection optical system, a multi-line pattern in which a plurality of line patterns are arranged at predetermined intervals along a predetermined arrangement direction, An electrode pad pattern for electric resistance measurement of two line patterns respectively located at one end and the other end in the arrangement direction is formed by using a mask formed on the pattern surface. The upper pattern is sequentially transferred to different regions on the substrate via the projection optical system (first step). Thereby, a transfer image of the pattern of the multi-line pattern is formed in different regions on the substrate via the projection optical system for each position in the optical axis direction of the substrate (first step). And a first line width corresponding to a line width of a transfer image of a first line pattern located at one end in the arrangement direction of the transfer image of the multi-line pattern formed on the substrate at each position in the optical axis direction. The values are respectively obtained by electric resistance measurement (second step). A second line corresponding to a line width of a transfer image of a second line pattern located at the other end in the periodic direction of the transfer image of the multi-line pattern formed on the substrate at each position in the optical axis direction. The width value is determined by measuring the electric resistance (third step). That is, the line width values of the transfer images of the line patterns located at both ends in the arrangement direction of the multi-line pattern are obtained.
Then, a first correlation which is a correlation between a first line width value and a position of the substrate in the optical axis direction, and a correlation between a second line width value and the position of the substrate in the optical axis direction. The optical characteristic of the projection optical system is calculated based on the second correlation (4th step). Here, as the first and second correlations, the correlation between the line width values of the transferred images of the first and second line patterns and the substrate position in the optical axis direction of the projection optical system is obtained. Is plotted as a line width value, and the horizontal axis is the substrate position in the optical axis direction of the projection optical system. Each correlation is graphed to obtain two correlation curves.
That is, by comparing two correlations obtained under the same measurement conditions except for the position of the line pattern in the multi-line pattern, it is possible to cancel various effects independent of the difference in the position of the line pattern on the measurement result. In addition, it is possible to improve the measurement accuracy of the optical characteristics of the projection optical system and the reproducibility of the measurement result. In addition, since the line width value of the transfer image of the line pattern is obtained by measuring the electrical resistance, the line width value of the transfer image of a plurality of line patterns can be obtained in a short time, and as a result, the optical characteristics of the projection optical system Measurement throughput can be improved. That is, when measuring the optical characteristics of the projection optical system, it is possible to improve the measurement capability in both time and accuracy.
In the third optical characteristic measuring method according to the present invention, in the fourth step, the first line width value and the second line width are based on the first correlation and the second correlation. A third correlation, which is a correlation between an average value of the values and a position of the substrate in the optical axis direction, may be obtained, and a best focus position may be calculated based on the third correlation. .
In this case, various methods of determining the best focus position can be considered, such as setting the position of the substrate where the average value corresponding to the change in the position of the substrate is maximum or minimum based on the third correlation as the best focus position. For example, in the fourth step, based on the third correlation, the position of the substrate having the smallest change in the average value corresponding to the change in the position of the substrate may be set as the best focus position. it can.
According to a seventh aspect of the present invention, there is provided an optical characteristic measuring method for measuring an optical characteristic of a projection optical system, comprising a multi-line pattern in which a plurality of line patterns are arranged at predetermined intervals along a predetermined arrangement direction. And an electrode pad pattern for electric resistance measurement of two line patterns respectively located at one end and the other end in the arrangement direction of the multi-line pattern are formed on the pattern surface. Transferring a pattern on the mask onto the substrate via the projection optical system using the mask; and positioning the pattern on one end in the arrangement direction of a transfer image of the multi-line pattern formed on the substrate. A second step of obtaining a first line width value corresponding to the line width of the transferred image of the first line pattern by measuring electric resistance; A third step of obtaining a second line width value corresponding to the line width of the transferred image of the second line pattern to be placed by measuring the electric resistance; and calculating the first line width value and the second line width value. A fourth step of calculating an optical characteristic of the projection optical system based on the fourth step.
According to this, a multi-line pattern in which a plurality of line patterns are arranged at predetermined intervals along a predetermined arrangement direction, and one end and the other end of the multi-line pattern in the arrangement direction And the electrode pad pattern for electric resistance measurement of two line patterns respectively located on the substrate, and the pattern on the mask is transferred onto the substrate via the projection optical system using the mask formed on the pattern surface. . Thus, a transfer image of the multi-line pattern is formed on the substrate by the projection optical system (first step). Then, a first line width value corresponding to the line width of the transferred image of the first line pattern located at one end in the arrangement direction of the multi-line pattern is obtained by electric resistance measurement (second step). Further, a second line width value corresponding to the line width of the transferred image of the second line pattern located at the other end in the arrangement direction of the multi-line pattern is obtained by electric resistance measurement (third step). That is, the line width values of the transfer images of the line patterns located at both ends in the arrangement direction of the multi-line pattern are obtained.
Then, the optical characteristics of the projection optical system are calculated based on the first line width value and the second line width value (fourth step). That is, by using two line width values obtained under the same measurement conditions except for the position of the line pattern in the multi-line pattern, various effects independent of the difference in the position of the line pattern on the measurement result can be canceled. In addition, it is possible to improve the measurement accuracy of the optical characteristics of the projection optical system and the reproducibility of the measurement result. In addition, since the line width value of the transfer image of the line pattern is obtained by measuring the electrical resistance, the line width value of the transfer image of a plurality of line patterns can be obtained in a short time, and as a result, the optical characteristics of the projection optical system can be obtained. Measurement throughput can be improved. That is, when measuring the optical characteristics of the projection optical system, it is possible to improve the measurement capability in both time and accuracy.
In the fourth optical characteristic measuring method according to the present invention, in the fourth step, a difference between the first line width value and the second line width value and an index value that is a ratio of a difference between the difference and the comparison reference are used. Coma can be calculated.
In this case, the comparison criterion can be considered variously. For example, the comparison criterion is the sum of the first line width value and the second line width value, 1, and the line pattern adjacent to each other in the arrangement direction. It can be one of the arrangement intervals.
According to an eighth aspect of the present invention, there is provided an optical characteristic measuring method for measuring an optical characteristic of a projection optical system that projects a pattern on a first surface onto a second surface, wherein the second characteristic of the projection optical system is measured. The position of the object to be projected arranged on the surface side in the optical axis direction of the projection optical system is changed within a predetermined range by a predetermined procedure, and the first pattern arranged on the first surface is changed by the projection optical system. A first step of forming an image on the projected object at each change position; a second step of measuring the size of the image of the first pattern at each change position; and the second surface of the projection optical system The position of the projection object disposed on the side of the projection optical system in the optical axis direction is changed in the predetermined procedure within the predetermined range, and the projection optics of the second pattern disposed on the first surface are changed. Image by the system on the object to be projected at each change position A fourth step of measuring the size of the image of the second pattern at each of the change positions; a position of the object to be projected in the optical axis direction and a size of the projected image of the first pattern And a second correlation that is a correlation between the position of the projection target object in the optical axis direction and the size of the projection image of the second pattern. And a fifth step of calculating the optical characteristics of the projection optical system.
In this specification, “image size” means the size or size of an image, and includes the line width of the image. Further, in this specification, the “line width of an image” refers to a latent image, a resist image, and an etched image formed on a projected object when the projected object is a photoconductor (this will be described later). This is a concept that includes both the line width of a transferred image and the line width of a spatial image (projected image) of a pattern. Therefore, obtaining the line width of an image includes measuring the line width of a transferred image, as well as measuring the line width by so-called aerial image measurement.
According to this, the position of the object to be projected arranged on the second surface side (image surface side) of the projection optical system in the optical axis direction of the projection optical system is changed within a predetermined range by a predetermined procedure, and the first An image of the first pattern arranged on the plane (object plane) by the projection optical system is formed on the projected object at each change position (first step), and the size of the image of the first pattern at each change position Is measured. Further, the position of the object to be projected arranged on the second surface side of the projection optical system in the optical axis direction of the projection optical system is changed in the predetermined procedure within the predetermined range, and the projection object is arranged on the first surface. An image of the second pattern by the projection optical system is formed on the projection target object at each change position (third step), and the size of the image of the second pattern at each change position is measured (fourth step). .
Then, a first correlation, which is a correlation between the position of the projection object in the optical axis direction and the size of the image of the first pattern, and the position of the projection object in the optical axis direction and the image of the second pattern. The optical characteristics of the projection optical system are calculated based on the second correlation, which is the correlation with the size (fifth step).
That is, the correlation between the size of the image and the position of the projection target in the optical axis direction of the projection optical system is determined for each pattern, and the vertical axis represents the size, and the horizontal axis represents the projection target object in the optical axis direction of the projection optical system. When the correlations are graphed as positions, two correlation curves are obtained. Then, by performing a predetermined operation (for example, averaging operation, subtraction of both, or a predetermined statistical operation) based on two correlations (for example, two correlation curves), an optical system is formed based on one correlation. The measurement accuracy can be improved as compared with the case where the characteristics are calculated. Further, depending on the setting of the pattern and the exposure condition, it is possible to accurately extract at least one of the influence of the difference in the pattern and the difference in the exposure condition on the image size. Then, based on the extraction result, the relationship between the size of the image and the optical characteristics of the projection optical system can be obtained with high accuracy, and as a result, the measurement accuracy and reproducibility of the optical characteristics of the projection optical system can be improved. It becomes possible. That is, when measuring the optical characteristics of the projection optical system, it is possible to improve the measurement capability in terms of accuracy.
In this case, the first pattern and the second pattern are separate patterns simultaneously arranged on the first surface, and the first step and the third step are performed under the same exposure condition. Can be done. In such a case, various effects that do not depend on the pattern difference can be canceled. Therefore, the calculation error of the optical characteristics of the projection optical system is reduced, and as a result, the measurement accuracy and reproducibility of the optical characteristics of the projection optical system can be improved.
In the fifth optical characteristic measuring method according to the present invention, the first pattern and the second pattern may include patterns having different line widths. In such a case, the influence of the difference in line width on the correlation can be known to some extent quantitatively.
In the fifth optical static characteristic measuring method of the present invention, the first pattern and the second pattern may include a line pattern extending in different directions. Alternatively, the first pattern and the second pattern may include a line pattern extending in the same direction. Alternatively, the first pattern and the second pattern may be the same pattern.
The same pattern may be substantially the same pattern, and the substantially same pattern includes not only the exactly same pattern but also patterns formed under mutually different forming conditions.
In the fifth optical characteristic measuring method of the present invention, the first step and the third step can be performed simultaneously. That is, the first step and the third step can be performed under the same exposure conditions. In such a case, by comparing the two correlations obtained under the same measurement conditions except for the pattern, various effects independent of the pattern on the measurement result can be reliably canceled.
In the fifth optical characteristic measuring method of the present invention, the first step and the third step can be performed separately under different exposure conditions. In such a case, by comparing the two correlations described above, it is possible to accurately extract the influence of the change in the exposure condition on the line width value. Therefore, the relationship between the line width value and the optical characteristics of the projection optical system can be accurately determined.
In this case, the first step is performed under the first condition such that the change in the size of the image of the first pattern has a minimum value, and the third step is performed under the condition that the size of the image of the second pattern is small. The change may be made under a second condition such that the change has a local maximum.
In such a case, with respect to the position of the projection target in the optical axis direction of the projection optical system, the optical characteristics are obtained from two types of correlations in which the image size has a local maximum value or a local minimum value. As compared with the case where the optical characteristic is obtained from the correlation of the above, there is less variation in the measurement result of the optical characteristic, and as a result, the measurement accuracy of the optical characteristic of the projection optical system and the reproducibility of the measurement result can be improved.
In the fifth optical characteristic measuring method of the present invention, when the first step and the third step are performed separately under different exposure conditions, the exposure amount at the time of transfer of the first pattern and the second step are different. It may be different from the exposure amount when transferring the pattern. In this case, it is desirable that the first pattern and the second pattern are substantially the same pattern. Here, the substantially identical patterns include not only identical patterns but also patterns formed similarly under different forming conditions.
In a fifth optical characteristic measuring method according to the present invention, in the fifth step, the position of the projection target object is determined for each position in the optical axis direction based on the first correlation and the second correlation. Calculating a difference between the size of the image of the first pattern and the size of the image of the second pattern, and calculating a third correlation that is a correlation between the difference and a position of the projection target in the optical axis direction; Then, the best focus position of the projection optical system can be calculated based on the third correlation.
In the fifth optical characteristic measurement method of the present invention, various methods for measuring the size of each image are conceivable. For example, the size of each image to be measured in the second and fourth steps may be different from that of each image. In the case of the line width value, the measurement of the line width value of each image can be performed by electric resistance measurement.
In the fifth optical characteristic measuring method of the present invention, at least one of the first pattern and the second pattern is arranged at a position on a predetermined mask corresponding to a plurality of evaluation points in a field of view of the projection optical system. In the third step, based on the first correlation and the second correlation, for each of the evaluation points, a mask manufacturing error at that position is corrected using the size of the image, and the optical characteristics are used. Can be calculated.
According to a ninth aspect of the present invention, there is provided an optical characteristic measuring method for measuring an optical characteristic of a projection optical system for projecting a pattern on a first surface onto a second surface, wherein the method is arranged on the first surface. Using a mask in which a plurality of measurement patterns are respectively formed at positions corresponding to a plurality of evaluation points in the field of view of the projection optical system, and displaying images of the plurality of measurement patterns by the projection optical system on a projection target object. A first step of measuring the size of each image; and correcting a mask manufacturing error for each evaluation point based on the measurement result and the mask manufacturing error for each evaluation point position. Calculating an optical characteristic of the projection optical system using the size of the image.
According to this, a plurality of measurement patterns are formed on the first surface (object surface) using a mask in which a plurality of measurement patterns are formed at positions corresponding to a plurality of evaluation points in the field of view of the projection optical system. An image of the measurement pattern by the projection optical system is formed on the projection target object, and the size of each image is measured. Then, based on the measurement result of the size of each image and the manufacturing error of the mask at each position of the evaluation point, the optical characteristics of the projection optical system are adjusted using the image size obtained by correcting the manufacturing error of the mask for each evaluation point. Is calculated. In this case, since the size of the image in which the reticle manufacturing error at that position is corrected is used for each evaluation point, optical characteristics with high accuracy and excellent reproducibility can be obtained. For example, when the image size is a line width (value), it is possible to obtain line width uniformity with high accuracy and excellent reproducibility. That is, when measuring the optical characteristics of the projection optical system, it is possible to improve the measurement capability in terms of accuracy.
According to a tenth aspect, the present invention provides a step of measuring an optical characteristic of a projection optical system by any one of the fifth optical characteristic measuring method and the sixth optical characteristic measuring method of the present invention; Adjusting the projection optical system based on the result.
Here, the adjusting step includes not only the adjusting step but also the adjusting step in the manufacturing step. That is, the adjustment method of the present invention substantially includes a method of manufacturing an exposure apparatus.
According to this, the optical characteristics of the projection optical system are measured with good measurement accuracy and reproducibility by one of the fifth optical characteristic measurement method and the sixth optical characteristic measurement method of the present invention, and the projection is performed based on the measurement result. The projection optical system is adjusted so that the optical system can perform optimal exposure (for example, transfer of a pattern to a photosensitive object). Therefore, in the exposure apparatus in which the projection optical system is adjusted by this adjustment method, highly accurate exposure can be performed.
According to an eleventh aspect of the present invention, there is provided an optical characteristic measuring method for measuring an optical characteristic of a projection optical system for projecting a pattern on a first surface onto a second surface, the method having a first line width. One pattern is arranged on the first surface, and an image of the first pattern is formed on the projection object arranged on the second surface via the projection optical system, and corresponds to a line width of the image. A first step of obtaining a first line width value to be performed; placing a second pattern having a second line width on the first surface, and projecting the image of the second pattern through the projection optical system to the second pattern. A second step of forming on a projection object arranged on two surfaces under the same conditions as the first step, and obtaining a second line width value corresponding to the line width of the image; the first line width A pattern on the first surface based on a relationship between the second line width and the first line width value, and a relationship between the second line width and the second line width value. A third step of calculating a correlation between the line width of the image and a line width value of an image formed on the projection target object; and a fourth step of calculating an optical characteristic of the projection optical system based on the correlation. And a seventh method for measuring optical characteristics.
According to this, an image of the first pattern having the first line width is formed on the projection target object by the projection optical system, and the first line width value corresponding to the line width of the image of the first pattern is obtained. Required (first step). Also, an image of a second pattern having a second line width is formed on the object to be projected by the projection optical system under the same conditions as described above, and a second line corresponding to the line width of the image of the second pattern is formed. A width value is determined (second step). Then, the pattern on the first surface is determined based on the relationship between the first line width and the first line width value and the relationship between the second line width and the second line width value. Is calculated with the line width value of the image formed on the projection target object (third step). That is, if the correlation is graphed with the vertical axis representing the line width of the pattern on the first surface and the horizontal axis representing the line width value of the image formed on the projection target, one straight line is obtained as an example. Then, the optical characteristics of the projection optical system are calculated based on the correlation (fourth step). That is, by utilizing a plurality of relationships between the line width of the pattern and the line width value of the image, various effects due to the line width error of the pattern on the measurement result can be reduced, and the projection optical system Measurement accuracy and reproducibility of optical characteristics can be improved. That is, when measuring the optical characteristics of the projection optical system, it is possible to improve the measurement capability in terms of accuracy.
In this case, in the fourth step, a new value included between the first line width and the second line width is defined as a third line width, and the third value is determined based on the correlation. The line width of the image with respect to the line width is calculated, and the optical characteristics of the projection optical system can be calculated based on the line width of the image.
In the sixth optical characteristic measuring method of the present invention, various methods can be considered for obtaining the line width value of the image. In the first and second steps, the line width values are obtained by measuring electric resistance. Can be done.
According to a twelfth aspect, the present invention provides an exposure method for irradiating a mask with an energy beam for exposure, and transferring a pattern formed on the mask onto a substrate via a projection optical system. Adjusting the projection optical system in consideration of the optical characteristics measured by any of the first to seventh optical characteristic measurement methods; and forming the projection optical system on the mask via the adjusted projection optical system. Transferring a pattern onto the substrate.
According to this, the projection optical system is adjusted so that optimal transfer can be performed in consideration of the optical characteristics of the projection optical system measured by any of the first to seventh optical characteristic measurement methods of the present invention. The pattern formed on the mask is transferred onto the substrate via the adjusted projection optical system. Therefore, it becomes possible to transfer the fine pattern onto the substrate with high accuracy.
Further, in the lithography process, by using the exposure method of the present invention, a fine pattern pattern can be formed on a substrate with high accuracy, and thereby a microdevice with a higher degree of integration can be manufactured with good productivity (including yield). Can be manufactured. Therefore, from another viewpoint, the present invention can be said to be a device manufacturing method using the exposure method of the present invention.
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<< 1st Embodiment >>
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
FIG. 1 shows an exposure apparatus 100 according to a first embodiment suitable for carrying out the optical characteristic measuring method and the exposure method of the projection optical system of the present invention. The exposure apparatus 100 is a step-and-repeat type reduction projection exposure apparatus (so-called stepper).
The exposure apparatus 100 projects an illumination system IOP, a reticle stage RST holding a reticle R as a mask, and a pattern image formed on the reticle R onto a wafer W as a substrate coated with a photosensitive agent (photoresist). A projection optical system PL, an XY stage 20 that holds a wafer W and moves on a two-dimensional plane (within an XY plane), a drive system 22 that drives the XY stage 20, and a control system for these components. The control system includes a workstation (or a microcomputer) including a CPU, a ROM, a RAM, an I / O interface, and the like, and is mainly configured by a main control device 28 that integrally controls the entire apparatus.
As shown in FIG. 2, the illumination system IOP includes a light source 1, a beam shaping optical system 2, an energy rough adjuster 3, an optical integrator (homogenizer) 4, an illumination system aperture stop plate 5, a beam splitter 6, a first relay. A lens 7A, a second relay lens 7B, a reticle blind 8 and the like are provided. As the optical integrator, a fly-eye lens, a rod type (internal reflection type) integrator, a diffractive optical element, or the like is used. In the present embodiment, since a fly-eye lens is used as an optical integrator, the fly-eye lens 4 is also described below.
Here, each component of the illumination system IOP will be described. As the light source 1, a KrF excimer laser (oscillation wavelength 248 nm), an ArF excimer laser (oscillation wavelength 193 nm), or the like is used. The light source 1 is actually installed on a floor surface in a clean room in which the exposure apparatus main body is installed, or on a room (service room) having a low degree of cleanness different from the clean room, and is connected via a drawing optical system (not shown). Connected to the entrance end of the beam shaping optical system.
The beam shaping optical system 2 shapes the cross-sectional shape of the laser beam LB pulsed from the light source 1 so as to efficiently enter a fly-eye lens 4 provided behind the optical path of the laser beam LB. For example, it is composed of a cylinder lens, a beam expander (both not shown) and the like.
The energy rough adjuster 3 is arranged on the optical path of the laser beam LB behind the beam shaping optical system 2, and here, a plurality of (for example, different) transmittances (≒ 1-dimming ratio) around the rotating plate 31 are provided. 6), ND filters (only two ND filters 32A and 32D are shown in FIG. 2) are arranged, and the rotating plate 31 is rotated by a drive motor 33, so that the incident laser beam The transmittance for LB can be switched from 100% in geometric progression in a plurality of steps. Drive motor 33 is controlled by main controller 28.
The fly-eye lens 4 is disposed on the optical path of the laser beam LB behind the energy coarse adjuster 3, and has a large number of point light sources (light source images) on its emission-side focal plane to illuminate the reticle R with a uniform illuminance distribution. , Ie, a secondary light source. The laser beam emitted from this secondary light source is hereinafter referred to as “pulse illumination light IL”.
An illumination system aperture stop plate 5 made of a disc-shaped member is arranged near the exit-side focal plane of the fly-eye lens 4. The illumination system aperture stop plate 5 is provided at substantially equal angular intervals, for example, an aperture stop composed of a normal circular aperture, an aperture stop composed of a small circular aperture, and a small coherence factor σ value (small σ stop); A ring-shaped aperture stop (ring-shaped stop) for annular illumination, and a modified aperture stop in which a plurality of apertures are eccentrically arranged for the modified light source method (only two of these aperture stops are shown in FIG. 2). Etc.) are arranged. The illumination system aperture stop plate 5 is configured to be rotated by a drive device 51 such as a motor controlled by the main controller 28, whereby one of the aperture stops is selected on the optical path of the pulse illumination light IL. Is set.
A beam splitter 6 having a small reflectance and a large transmittance is arranged on the optical path of the pulse illumination light IL behind the illumination system aperture stop plate 5, and a reticle blind 8 is interposed between the beam splitter 6 and the first relay on the optical path behind this. A relay optical system including a lens 7A and a second relay lens 7B is provided.
The reticle blind 8 is arranged on a conjugate plane with respect to the pattern surface of the reticle R, and is composed of, for example, two L-shaped movable blades or four movable blades arranged vertically and horizontally, and is surrounded by movable blades. The opening formed defines the illumination area on reticle R. In this case, by adjusting the position of each movable blade, the shape of the opening can be set to an arbitrary rectangular shape. The driving of each movable blade is controlled by the main controller 28 via a blind driving device (not shown) in accordance with the shape of the pattern area of the reticle R, for example.
A folding mirror M that reflects the pulse illumination light IL that has passed through the second relay lens 7B toward the reticle R is disposed on the optical path of the pulse illumination light IL behind the second relay lens 7B that constitutes the relay optical system. ing.
On the other hand, on the light path reflected by the beam splitter 6, an integrator sensor 53 composed of a photoelectric conversion element is disposed via a condenser lens 52. As the integrator sensor 53, for example, a PIN photodiode having sensitivity in the deep ultraviolet region and having a high response frequency for detecting pulse light emission of the light source unit 1 can be used. The correlation coefficient (or correlation function) between the output DP of the integrator sensor 53 and the illuminance (intensity) of the pulse illumination light IL on the surface of the wafer W is obtained in advance and stored in a memory inside the main controller 28. It is remembered.
The operation of the illumination system IOP configured as described above will be briefly described. The laser beam LB pulse-emitted from the light source 1 enters the beam shaping optical system 2 where the laser beam LB is efficiently transmitted to the rear fly-eye lens 4. After its cross-sectional shape is shaped so as to be incident well, it is incident on the energy rough adjuster 3. Then, the laser beam LB transmitted through any of the ND filters of the energy rough adjuster 3 enters the fly-eye lens 4. As a result, a surface light source composed of many point light sources (light source images), that is, a secondary light source is formed on the exit-side focal plane of the fly-eye lens 4. The pulsed illumination light IL emitted from the secondary light source passes through one of the aperture stops on the illumination system aperture stop plate 5 and then reaches a beam splitter 6 having a large transmittance and a small reflectance. The pulse illumination light IL as exposure light transmitted through the beam splitter 6 passes through the first relay lens 7A, passes through the rectangular opening of the reticle blind 8, then passes through the second relay lens 7B, and passes through the optical path by the mirror M. Is bent vertically downward, and illuminates a rectangular (for example, square) illumination area on the reticle R held on the reticle stage RST with a uniform illuminance distribution.
On the other hand, the pulsed illumination light IL reflected by the beam splitter 6 is received by an integrator sensor 53 composed of a photoelectric conversion element via a condenser lens 52, and a photoelectric conversion signal of the integrator sensor 53 is supplied to a peak hold circuit (not shown). The signal is supplied to the main controller 28 as an output DP (digit / pulse) via an A / D converter.
Returning to FIG. 1, the reticle stage RST is arranged below the illumination system IOP in FIG. A reticle R is fixed on the reticle stage RST via fixing means such as a vacuum chuck (not shown), and the reticle stage RST is moved in the X-axis direction (the left-right direction in FIG. 1) by a driving system (not shown). , Can be minutely driven in the Y-axis direction (the direction perpendicular to the paper surface in FIG. 1) and the θz direction (the rotation direction around the Z-axis perpendicular to the XY surface). Thus, reticle stage RST can position reticle R (reticle alignment) in a state where the center of the pattern of reticle R (reticle center) substantially matches optical axis AXp of five projection optical system PL. FIG. 1 shows a state in which the reticle alignment has been performed.
The projection optical system PL is arranged below the reticle stage RST in FIG. 1 so that the direction of the optical axis AXp is the Z-axis direction orthogonal to the XY plane. Here, as the projection optical system PL, a dioptric system (not shown) composed of a plurality of lens elements having a common optical axis AX in the Z-axis direction, which is a telecentric reduction system on both sides, is used here. A plurality of specific lens elements are controlled by an imaging characteristic correction controller (not shown) based on a command from the main controller 28, and optical characteristics of the projection optical system PL, such as magnification, distortion, coma, and The field curvature and the like can be adjusted.
As the projection optical system PL, one having a predetermined projection magnification β (β is, for example, ４, １ ／, etc.) is used. Therefore, when the reticle R is illuminated with uniform illuminance by the pulse illumination light IL in a state where the pattern of the reticle R is aligned with the shot area on the wafer W, the pattern on the pattern forming surface is Is reduced by the projection optical system PL, projected onto the wafer W coated with the photoresist, and a reduced image of the pattern is formed in each shot area on the wafer W.
The XY stage 20 is actually composed of a Y stage that moves on a base (not shown) in the Y-axis direction and an X stage that moves on the Y stage in the X-axis direction. Are representatively shown as an XY stage 20. A wafer table 18 is mounted on the XY stage 20, and a wafer W is held on the wafer table 18 by vacuum suction or the like via a wafer holder (not shown).
The wafer table 18 minutely drives a wafer holder that holds the wafer W in the Z-axis direction and the tilt direction with respect to the XY plane, and is also called a Z-tilt stage. A movable mirror 24 is provided on the upper surface of the wafer table 18, and the position of the wafer table 18 in the XY plane is measured by projecting a laser beam onto the movable mirror 24 and receiving the reflected light. A laser interferometer 26 is provided to face the reflecting surface of the movable mirror 24. Actually, the moving mirror is provided with an X moving mirror having a reflecting surface orthogonal to the X axis and a Y moving mirror having a reflecting surface orthogonal to the Y axis. Although an X laser interferometer for measuring the direction position and a Y laser interferometer for measuring the Y direction position are provided, these are representatively shown as a movable mirror 24 and a laser interferometer 26 in FIG. The X laser interferometer and the Y laser interferometer are multi-axis interferometers having a plurality of measurement axes, and in addition to the X and Y positions of the wafer table 18, rotation (yaw (θz rotation which is rotation about the Z axis)) , Pitching (θx rotation around the X axis) and rolling (θy rotation around the Y axis) can also be measured. Therefore, in the following description, it is assumed that the position of the wafer table 18 in the directions of five degrees of freedom of X, Y, θz, θy, and θx is measured by the laser interferometer 26.
The measurement value of the laser interferometer 26 is supplied to a main controller 28, and the main controller 28 controls the XY stage 20 via the drive system 22 based on the measurement value of the laser interferometer 26, so that the wafer table 18 Position.
The position of the surface of the wafer W in the Z direction is determined by oblique incidence having a light transmitting system 50a and a light receiving system 50b disclosed in, for example, Japanese Patent Application Laid-Open No. Hei 6-283403 and U.S. Pat. It is designed to be measured by a focus sensor AFS comprising a multi-point focal position detection system. The measurement value of the focus sensor AFS is also output to the main controller 28. The main controller 28 moves the wafer table 18 via the drive system 22 based on the output of the focus sensor AFS in the Z direction, the θx direction, and the θy direction. To control the position of the wafer W in the optical axis direction and the tilt direction of the projection optical system PL (so-called focus leveling control). To the extent permitted by the national laws of the designated or designated elected States in this International Application, the disclosures in the above publications and U.S. patents are incorporated herein by reference.
In this way, the position and orientation of the wafer W in the directions of five degrees of freedom of X, Y, Z, θx, and θy are controlled via the wafer table 18. The remaining error of θz (yawing) is corrected by rotating reticle stage RST based on yawing information of wafer table 18 measured by laser interferometer 26.
On the wafer table 18, a reference plate FP whose surface is the same as the surface of the wafer W is fixed. On the surface of the reference plate FP, various reference marks including a reference mark used for so-called baseline measurement of an alignment detection system described later are formed.
Further, in the present embodiment, an off-axis type alignment detection system AS as a mark detection system for detecting an alignment mark formed on the wafer W is provided on a side surface of the projection optical system PL. This alignment detection system AS has three types of alignment sensors: an LSA (Laser Step Alignment) system, an FIA (Filled Image Alignment) system, and an LIA (Laser Interferometric Alignment) system. It is possible to measure the position of the alignment mark on the wafer in the X and Y two-dimensional directions.
Here, the LSA system is the most versatile sensor that irradiates a mark with laser light and measures the position of the mark by using diffracted and scattered light, and is conventionally used for a wide range of process wafers. The FIA system is a sensor that illuminates a mark with broadband (broadband) light such as a halogen lamp and measures the mark position by processing the mark image, and is effectively used for an asymmetric mark on an aluminum layer or a wafer surface. You. The LIA system is a sensor that irradiates a diffraction grating mark with laser light whose frequency is slightly changed from two directions, interferes the two generated diffraction lights, and detects mark position information from the phase. Yes, it is effectively used for low step and rough surface wafers.
In the present embodiment, these three types of alignment sensors are properly used according to the purpose, and fine alignment or the like for performing accurate position measurement of each shot area on the wafer is performed. In addition, as the alignment detection system AS, for example, an alignment sensor that irradiates a target mark with coherent detection light and interferes and detects two diffracted lights (for example, the same order) generated from the target mark, alone or as described above. It can be used in combination with an FIA type, LSA type, LIA type, or the like as appropriate.
Information DS from each alignment sensor constituting the alignment detection system AS is A / D-converted by the alignment control device 16, and a digitized waveform signal is arithmetically processed to detect a mark position. The result is sent to the main controller 28.
Further, in the exposure apparatus 100 of the present embodiment, although not shown, it is disclosed above the reticle R, for example, in Japanese Patent Application Laid-Open No. 7-176468 and US Pat. No. 5,646,413 corresponding thereto. Light of an exposure wavelength for simultaneously observing a reticle mark on the reticle R or a reference mark (both not shown) on the reticle stage RST and a mark on the reference plate FP via the projection optical system PL is used. A pair of reticle alignment microscopes including a TTR (Through The Reticle) alignment system is provided. The detection signals of these reticle alignment microscopes are supplied to the main controller 28 via the alignment controller 16. To the extent permitted by the national laws of the designated or designated elected States in this International Application, the disclosures in the above publications and U.S. patents are incorporated herein by reference.
Next, an example of a reticle used in the method for measuring the optical characteristics of the projection optical system according to the present invention will be described.
FIG. 3 shows a reticle R used for measuring the optical characteristics of the projection optical system. _T An example is shown. FIG. 3 shows a reticle R _T FIG. 2 is a plan view as viewed from a pattern surface side (a lower surface side in FIG. 1). This reticle R _T In the figure, a pattern area PA as a pattern surface is provided in the center of a glass substrate 42 as a substantially square mask substrate, and a plurality of patterns described later are arranged in the pattern area PA. Further, the center of the pattern area PA, that is, the reticle R _T A pair of reticle alignment marks RM1 and RM2 are formed on both sides in the X-axis direction of the pattern area PA passing through the center (reticle center).
Here, the configuration of the pattern 200 for measuring the optical characteristics of the projection optical system arranged in the pattern area PA will be described with reference to FIGS.
As shown in FIG. 4, the pattern 200 includes a sheet resistance value measurement pattern 210 having a van der Pauw structure for measuring the sheet resistance value of the wafer W, and a line width. And eight line width measurement patterns 220, 230, 240, 250, 260, 270, 280, 290.
As shown in FIG. 5, the sheet resistance value measurement pattern 210 includes a square measurement area pattern 211 and four square electrode pad patterns 212a as electric resistance measurement electrode pad patterns. , 212b, 212c, and 212d, and each of the electrode pad patterns is connected to the measurement area pattern 211 via a linear pattern.
As shown in FIG. 6, the line width measuring pattern 220 is a line and space (hereinafter, referred to as “L / S”) in which five line patterns having a predetermined line width and extending in the Y direction are periodically arranged. ), And six electrode pad patterns 222a, 222b, 222c, 222d, 222e, 222f each having a square shape as an electrode pad pattern for measuring electric resistance. Each of the electrode pad patterns is, via a linear pattern, two line patterns 221a (left end of the paper in the periodic direction) and 221b (left and right in the periodic direction) located at both ends of the L / S pattern 221 in the periodic direction. (Right end of the paper). That is, the electrode pad patterns 222a and 222b are connected to the upper end (-Y side) of the line pattern 221a in FIG. 5, and the electrode pad patterns 222d and 222e are connected to the upper side of the line pattern 221b in FIG. (-Y side). The electrode pad pattern 222c is connected to the lower end (+ Y side) of the line pattern 221a in FIG. 6, and the electrode pad pattern 222f is connected to the lower side (+ Y side) of the line pattern 221b in FIG. ) Is connected to the end. Further, the electrode pad pattern 222c and the electrode pad pattern 222f are connected via a linear pattern.
Referring back to FIG. 4, the pattern 210 for measuring sheet resistance is disposed at the center of the pattern 200, and a line pattern is formed on the upper side (−Y side) of the pattern 210 for measuring sheet resistance in FIG. The line width measurement pattern 220 extending in the Y direction as one direction is arranged. In FIG. 4, for convenience of drawing, the L / S pattern is shown as three line patterns, but is actually made up of five line patterns.
A line width measurement pattern 230 is arranged below (+ Y side) the sheet resistance value measurement pattern 210 in FIG. The line width measurement pattern 230 has a shape obtained by rotating the line width measurement pattern 220 by 180 degrees in the plane of FIG. 4, and the electrode pad patterns are provided at both ends of the L / S pattern in the periodic direction. It is connected to the located line pattern 231a (left end of the paper in the periodic direction) and line pattern 231b (right end of the paper in the periodic direction). The pitch and the line width of the line portion in the L / S pattern of the line width measurement pattern 230 and the line width measurement pattern 220 are the same.
A line width measurement pattern 240 whose line pattern extends in the X direction as the second direction is arranged on the left side (−X side) of the sheet resistance value measurement pattern 210 in FIG. The line width measurement pattern 240 has a shape obtained by rotating the line width measurement pattern 220 by 90 degrees counterclockwise in the plane of FIG. 4, and the electrode pad pattern has a period of the L / S pattern. It is connected to a line pattern 241a (the lower end of the paper in the periodic direction) and a line pattern 241b (the upper end of the paper in the periodic direction) located at both ends in the direction. The pitch and the line width of the line portion in the L / S pattern of the line width measurement pattern 240 and the line width measurement pattern 220 are the same.
A line width measurement pattern 250 having a line pattern extending in the second direction is disposed on the right side (+ X side) of the sheet resistance value measurement pattern 210 in FIG. The line width measurement pattern 250 has a shape obtained by rotating the line width measurement pattern 220 clockwise by 90 degrees in the plane of FIG. 3, and the electrode pad pattern is in the periodic direction of the L / S pattern. Are connected to a line pattern 251a (lower end of the paper in the periodic direction) and a line pattern 251b (upper end of the paper in the periodic direction) located at both ends of the line. The pitch and the line width of the line portion in the L / S pattern of the line width measurement pattern 250 and the line width measurement pattern 220 are the same.
In a virtual rectangular area including the line pattern 221a and the line pattern 241b on a part of each of two adjacent sides, an angle of 45 degrees is formed with respect to the first direction in a counterclockwise direction in FIG. A line width measurement pattern 260 in which the line pattern extends in the third direction is arranged. The line width measurement pattern 260 includes an L / S pattern obtained by rotating the L / S pattern of the line width measurement pattern 220 counterclockwise by 45 degrees in the plane of FIG. 4 and six electrode pad patterns. Is done. Each of the electrode pad patterns is connected to a line pattern 261a (lower left end of the paper in the periodic direction) and a line pattern 261b (upper right end of the paper in the periodic direction) located at both ends of the L / S pattern in the periodic direction. I have. The pitch and the line width of the line portion in the L / S pattern of the line width measurement pattern 260 and the line width measurement pattern 220 are the same.
A line width measurement pattern 270 having a line pattern extending in the third direction is arranged in a virtual rectangular area including the line pattern 231b and the line pattern 251a in a part of each of two adjacent sides. ing. The line width measurement pattern 270 has a shape obtained by rotating the line width measurement pattern 260 by 180 degrees in the plane of FIG. 4, and electrode pad patterns are provided at both ends in the periodic direction of the L / S pattern. It is connected to the located line pattern 271a (lower left end of the paper in the periodic direction) and line pattern 271b (upper right end of the paper in the periodic direction). The pitch and the line width of the line portion in the L / S pattern of the line width measurement pattern 270 and the line width measurement pattern 220 are the same.
In a virtual rectangular area that includes the line pattern 221b and the line pattern 251b in a part of each of two adjacent sides, a line forming an angle of 45 degrees with the first direction clockwise in the plane of FIG. Line width measurement patterns 280 in which the line patterns extend in four directions are arranged. The line width measurement pattern 280 has a shape obtained by rotating the line width measurement pattern 260 clockwise by 90 degrees in the plane of FIG. 4, and the electrode pad pattern is formed in the periodic direction of the L / S pattern. Are connected to a line pattern 281a (upper left end of the paper in the periodic direction) and a line pattern 281b (lower right end of the paper in the periodic direction) located at both ends of the line. The pitch and the line width of the line portion in the L / S pattern of the line width measurement pattern 280 and the line width measurement pattern 220 are the same.
A line width measurement pattern 290 having a line pattern extending in the fourth direction is arranged in a virtual rectangular area including the line pattern 231a and the line pattern 241a on a part of each of two adjacent sides. ing. The line width measurement pattern 290 has a shape obtained by rotating the line width measurement pattern 280 by 180 degrees in the plane of FIG. 4, and the electrode pad patterns are provided at both ends in the periodic direction of the L / S pattern. It is connected to the located line pattern 291a (upper left corner of the paper in the periodic direction) and line pattern 291b (lower right corner of the paper in the periodic direction). The pitch and the line width of the line portion in the L / S pattern of the line width measurement pattern 290 and the line width measurement pattern 220 are the same.
That is, in the present embodiment, the L / S patterns of the eight line width measurement patterns have the same forming conditions (eg, line width, pitch, etc.) except for the periodic direction.
In the following, the line patterns 221a, 231a, 241a, 251a, 261a, 271a, 281a, and 291a are referred to as "first line patterns" to distinguish the positions of the line patterns in the periodic direction of the L / S pattern. The patterns 221b, 231b, 241b, 251b, 261b, 271b, 281b, and 291b are collectively referred to as “second line patterns”.
Also, reticle R _T The reticle R _T Are performed, the patterns 200 are respectively arranged at positions corresponding to the respective evaluation points in the field of view of the projection optical system PL.
In this embodiment, the reticle R _T The upper pattern portion is assumed to be a light shielding portion. However, the present invention is not limited to this, and the pattern portion can be a light transmitting portion or a semi-transmitting portion.
Here, the configuration of the wafer W in the present embodiment will be described.
As shown in FIG. 8A, the wafer W includes a silicon substrate 601 serving as a base, an insulating film 602 formed on the silicon substrate 601, a conductive film 603 formed on the insulating film 602, And a photoresist layer 604 as a photosensitive layer applied on the film 603. In this embodiment, the reticle R _T Since the pattern portion is a light-shielding portion, a positive chemically amplified resist is used for the photoresist layer 604.
Next, a flow of an operation of transferring a reticle pattern onto the wafer W by the exposure apparatus 100 of the present embodiment to form a transfer image of a pattern for measuring the optical characteristics of the projection optical system PL will be briefly described.
First, the wafer W is loaded on the wafer table 18 by a wafer loader (not shown), and the reticle R is placed on the reticle stage RST by a reticle loader (not shown). _T Is loaded.
Main controller 28 adjusts the center of a pair of fiducial marks (not shown) formed on the surface of fiducial plate FP provided on wafer table 18 so as to substantially coincide with the optical axis of projection optical system PL. Move the reference plate FP. This movement is performed by moving the XY stage 20 via the drive system 22 while monitoring the measurement result of the laser interferometer 26 by the main controller 28. Next, main controller 28 controls reticle R _T Is adjusted so that the center of the reticle stage (reticle center) substantially coincides with the optical axis of the projection optical system PL. At this time, for example, the relative position between the reticle alignment marks RM1 and RM2 and the corresponding reference marks is detected by the reticle alignment microscope (not shown) via the projection optical system PL. Then, main controller 28 operates a drive system (not shown) based on the detection result of the relative position detected by the reticle alignment microscope so that the relative position error between RM1 and RM2 and the corresponding reference mark is both minimized. The position of the reticle stage RST within the XY plane is adjusted through the XY plane. Thereby, the reticle R _T (Reticle center) exactly coincides with the optical axis of the projection optical system PL, and the reticle R _T Also accurately coincides with the coordinate axes of the rectangular coordinate system defined by the length measurement axes of the laser interferometer 26. That is, the reticle alignment is completed.
Next, main controller 28 adjusts the size and position of the opening of reticle blind 8 (not shown) in illumination system IOP so that the irradiation area of illumination light IL is reticle R. _T The size and position of the opening of the reticle blind 8 in the illumination system IOP are adjusted so as to match the pattern area (actually, it matches the light-shielding zone that partitions the pattern area). At the same time, main controller 28 moves wafer XY to a position below projection optical system PL by moving XY stage 20 via drive system 22 while monitoring the measurement result of laser interferometer 26. .
Exposure is performed in this state, and the reticle R _T Is transferred via the projection optical system PL. As a result, a pattern image is transferred to the photoresist layer 604 on the wafer W.
Next, main controller 28 moves XY stage 20 in the same manner as described above, for example, by one shot in the + X direction, and determines the Z position of wafer table 18 while monitoring the Z position measurement data from focus sensor AFS. It moves in the + Z direction by the pitch ΔZ. That is, the position of the wafer W in the optical axis direction of the projection optical system is changed. Exposure is performed in this state, and the reticle R _T Is transferred onto the wafer W via the projection optical system PL.
Thereafter, main controller 28 repeats exposure of the same pattern to a plurality of shot areas on wafer W in a step-and-repeat manner while changing the Z position of wafer table 18 by a predetermined pitch ΔZ in this manner. . Thus, the image of the pattern 200 is transferred to a plurality of points in each shot area. The plurality of points correspond to a plurality of evaluation points whose optical characteristics are to be detected in the field of view of the projection optical system PL.
When exposure at a predetermined number of steps within a predetermined range of the wafer table 18 in the Z-axis direction is completed, the wafer W is moved to a wafer (not shown) according to an instruction from the main controller 28. After being unloaded from above the wafer table 18 by the unloader, a coater / developer (not shown) (hereinafter simply referred to as “C / D”) connected inline to the exposure apparatus 100 by a wafer transfer system (not shown). Conveyed).
The development of the wafer W is performed in the C / D. Upon completion of the development, a resist image is formed on wafer W. In the present embodiment, since the photoresist layer 604 on the wafer W is solubilized in a developing solution when irradiated with light, as shown in FIG. 8B, only the portion of the photoresist layer 604 that has been exposed to light by the developing process. Is removed. In the measurement by the conventional SEM, the wafer W at this stage has been used as a sample for line width measurement.
Next, the wafer W is sent to a dry etching apparatus, and as shown in FIG. 8C, only the conductive film 603 where the photoresist layer 604 has been removed is removed by dry etching, so that the insulating film 602 is exposed. .
Further, after cleaning the wafer W, all the photoresist layers 604 are removed. Thus, as shown in FIG. 8D, the resist image on wafer W is replaced with a pattern having the same shape and conductivity, and becomes a sample for line width measurement. The conductive pattern is hereinafter referred to as “etched image” for convenience.
Next, an etching image 200W of the pattern 200 formed on the wafer W will be described with reference to FIGS.
As shown in FIG. 9, the etching image 200W is composed of a sheet resistance measurement etching image 210W and eight types of line width measurement etching images 220W, 230W, 240W, 250W, 260W, 270W, 280W, and 290W. Be composed.
The sheet resistance value measurement etching image 210W is an etching image of the sheet resistance value measurement pattern 210, and as shown in FIG. 10, a measurement region 211W and four electrode pads 212aW, 212bW, 212cW, 212dW. Consists of Here, the electrode pad 212aW and the electrode pad 212bW are electrode pads for flowing a predetermined current to the measurement region 211W, and the electrode pad 212cW and the electrode pad 212dW are for measuring a voltage drop in the measurement region 211W. It is an electrode pad.
The line width measurement etching image 220W in FIG. 9 is an etching image of the line width measurement pattern 220. As shown in FIG. 11, the L / S pattern 221W and the six electrode pads 222aW, 222bW, 222cW, 222dW, 222eW and 222fW. Here, the electrode pad 222aW and the electrode pad 222dW are composed of two etched images 221aW (patterns to be subjected to line width measurement) and 221bW (to be subjected to line width measurement) located at both ends of the L / S pattern 221W in the periodic direction. And an electrode pad for allowing a predetermined current to flow therethrough. The electrode pads 222bW and 222cW are electrode pads for measuring a voltage drop in the etching image 221aW, and the electrode pads 222eW and 222fW are electrode pads for measuring a voltage drop in the etching image 221bW. is there.
Returning to FIG. 9, the line width measurement etching image 230 </ b> W is an etching image of the line width measurement pattern 230, and the line width measurement target patterns are located at both ends of the L / S pattern in the periodic direction. These are the etched images 231aW and 231bW of the book. In FIG. 9, for convenience of drawing, the L / S pattern is shown as three patterns, but is actually composed of five line patterns.
The line width measurement etching image 240W is an etching image of the line width measurement pattern 240. The pattern to be subjected to the line width measurement includes two etching images 241aW located at both ends of the L / S pattern in the periodic direction. , 241 bW.
The line width measurement etching image 250W is an etching image of the line width measurement pattern 250, and the pattern to be subjected to the line width measurement includes two etching images 251aW located at both ends in the periodic direction in the L / S pattern. , 251 bW.
The line width measurement etching image 260W is an etching image of the line width measurement pattern 260, and the pattern to be subjected to the line width measurement is two etching images 261aW located at both ends in the periodic direction in the L / S pattern. , 261 bW.
The line width measurement etching image 270W is an etching image of the line width measurement pattern 270, and the pattern to be subjected to the line width measurement includes two etching images 271aW located at both ends in the periodic direction in the L / S pattern. , 271 bW.
The line width measurement etching image 280W is an etching image of the line width measurement pattern 280, and the pattern to be subjected to the line width measurement is two etching images 281aW located at both ends of the L / S pattern in the periodic direction. , 281 bW.
The line width measurement etching image 290W is an etching image of the line width measurement pattern 290, and the pattern to be subjected to the line width measurement is two etching images 291aW located at both ends of the L / S pattern in the periodic direction. , 291 bW.
Next, a method of measuring a line width of a pattern (hereinafter, abbreviated as “target pattern”) to be subjected to line width measurement in the line width measurement etching image will be described.
In the present embodiment, since a method of obtaining the line width of the target pattern from the electric resistance value of the target pattern is adopted, the electric resistance measuring device 500 shown in FIG. 12 is used as a device for measuring the electric resistance of the target pattern. Can be
Therefore, prior to the description of the method of measuring the line width of the target pattern, the configuration of the electric resistance measuring device 500 will be described with reference to FIG.
The electric resistance measuring device 500 includes a wafer box 510 and a controller 520 as shown in FIG. Here, the wafer box 510 includes a wafer box main body 510A and a lid 510B that can be opened and closed about a support shaft 550 disposed at one end near the upper surface of the wafer box main body 510A.
A fixing portion 511 for fixing the wafer W at a predetermined position is formed on a bottom surface inside the wafer box main body 510A. A large number of probes 512 urged downward by a predetermined urging force by a spring (not shown) are provided on the surface of the lid 510B on the side facing the wafer box body 510A. In this case, by setting the wafer W inside the wafer box main body 510A and closing the lid 510B, the probe 512 comes into light contact with each electrode pad on the wafer W. The probes 512 are arranged at least at positions corresponding to the respective electrode pads.
The controller 520 is connected to the wafer box 510 via a cable 530, supplies a predetermined current to the probe 512, measures a voltage drop in the target pattern via the probe 512, and A measurement unit 521 for calculating values and the like, a display unit 522 for displaying measurement results and the like, an input unit 523 for an operator to input initial values and the like, a printing unit 524 for printing the measurement results and the like, and a processing program and data. And a storage unit 525 for storing. Each probe will be described as a probe 512 without distinction.
Next, a method for obtaining the line width of the target pattern using the electric resistance measuring device 500 will be described.
When the power of the controller 520 is turned on, an input screen for initial conditions is displayed on the display unit 522. In accordance with an instruction displayed on the display unit 522, the operator uses the input unit 523 as a key to input the length data of each target pattern calculated from the design value of the reticle pattern and the projection magnification of the projection optical system PL as initial conditions. input. The initial conditions input here are stored in the storage unit 525.
After the wafer W is set on the fixing portion 511 of the wafer box main body 510A and the lid 510B is closed, and when the measurement start instruction is given by the operator, the measuring portion 521 causes the probe 512 to correctly contact each electrode pad. Check if it is.
When confirming that the probe 512 is correctly in contact with each electrode pad, the measuring unit 521 starts measuring the electric resistance as follows. In the following, for simplification of description, measurement of one corresponding etching image 200W in each shot region on wafer W will be described.
First, the measuring unit 521 calculates the sheet resistance value ρ of the wafer W from the sheet resistance value measurement etching image 210W. _s Ask for. That is, as shown in FIG. 10, the measurement unit 521 supplies the current Is to the measurement region 211W via the electrode pad 212aW and the electrode pad 212bW, and performs the measurement in the measurement region 211W via the electrode pad 212cW and the electrode pad 212dW. The voltage drop Vs is measured. Then, the sheet resistance value ρ of the wafer W is calculated using the following equation (1) known as the equation of van der Pauw. _s Ask for.

Here, “Ln2” in the above equation (1) means a natural logarithm of 2. Sheet resistance value ρ calculated using the above equation (1) _s Are stored in the storage unit 525 of the controller 520.
Next, the measurement unit 521 obtains the line width of the target pattern in each line width measurement etching image. In the present embodiment, two etching images located at both ends in the periodic direction of the L / S pattern in the etching image for line width measurement are the target patterns. Therefore, hereinafter, in order to distinguish the position of the target pattern in the periodic direction of the L / S pattern, the etched images 221aW, 231aW, 241aW, 251aW, 261aW, 271aW, 281aW, and 291aW are referred to as "first target patterns". The images 221bW, 231bW, 241bW, 251bW, 261bW, 271bW, 281bW, and 291bW are collectively referred to as "second target patterns". The first target pattern is an etching image corresponding to the image of the first line pattern, and the second target pattern is an etching image corresponding to the image of the second line pattern.
Generally, assuming that a voltage drop when a current Ip flows through a linear body is Vp, an electric resistance value Rp of the linear body is obtained by the following equation (2).

Further, the electric resistance value Rp is such that the length of the linear body is L, the line width is w, and the sheet resistance value is ρ. _s Then, it is known that the following equation (3) is established.

Accordingly, the following expression (4) for calculating the line width w of the linear body is obtained from the expressions (2) and (3).

Therefore, the line width value w of the first target pattern ^L Sets the length of the first target pattern to L ^L , The voltage drop when the current Ip flows is Vp ^L Then, it is calculated from the following equation (5).

Also, the line width value w of the second target pattern ^R Sets the length of the second target pattern to L ^R , The voltage drop when the current Ip flows is Vp ^R Then, it is calculated from the following equation (6).

Therefore, in the case of the line width measurement etching image 220W, as shown in FIG. 10, the measurement unit 521 supplies a current Ip to the etching image 221aW and the etching image 221bW via the electrode pad 222aW and the electrode pad 222dW. Then, the voltage drop Vp at the etching image 221aW via the electrode pad 222bW and the electrode pad 222cW. ^L And the voltage drop Vp at the etched image 221bW via the electrode pad 222eW and the electrode pad 222fW. ^R Is measured. Then, the measurement unit 521 calculates the length L of the etching image 221aW input as the initial condition. ^L And the length L of the etched image 221 bW ^R And the previously measured sheet resistance value ρ _s Are read from the storage unit 525, and the line width value w of the etching image 221aW corresponding to the line width of the transfer image of the line pattern 221a is obtained by using the above equation (5). ^L Is calculated, and the line width value w of the etched image 221bW corresponding to the line width of the transferred image of the line pattern 221b is calculated using the above equation (6). ^R Is calculated. This calculation result is stored in the storage unit 525. In addition, L attached to the right shoulder of the code indicates the first target pattern, and R indicates the second target pattern.
Subsequently, the measurement unit 521 performs the other 14 target patterns 231aW, 231bW, 241aW, 241bW, 251aW, 251bW, 261aW, 261bW, 271aW, and 271bW in the same manner as in the case of the line width measurement etching image 220W described above. , 281aW, 281bW, 291aW, and 291bW are sequentially obtained.
The measurement unit 521 performs the above-described measurement on the corresponding etched images 200W in all the shot regions on the wafer W. Then, when the measurement of the line width value of the target pattern of all the etched images 200W is completed, the measurement unit 521 performs data processing.
The measurement unit 521 determines the line width w of the first target pattern for each position of the wafer W in the optical axis direction of the projection optical system PL (that is, for each shot area). ^L And the line width value w of the second target pattern ^R To organize. That is, the measurement unit 521 calculates the average value of the line width values of the eight first target patterns 221aW, 231aW, 241aW, 251aW, 261aW, 271aW, 281aW, and 291aW, and obtains the line of the transfer image of the first line pattern. A first line width value w corresponding to the width ^L And Further, the measurement unit 521 calculates the average value of the line width values of the eight second target patterns 221bW, 231bW, 241bW, 251bW, 261bW, 271bW, 281bW, and 291bW, and obtains the line of the transfer image of the second line pattern. The second line width value w corresponding to the width ^R And
Next, as shown in FIG. 13, the measurement unit 521 performs an approximation process using the least squares method to determine the position of the wafer W and the first line width w in the optical axis direction of the projection optical system. ^L And a first correlation, which is a correlation with. In FIG. 13, the horizontal axis represents the position of the wafer W with respect to a predetermined reference position in the optical axis direction of the projection optical system PL as the focus position. This result is automatically printed out from the printing unit 524 according to an instruction from the measuring unit 521.
Similarly, as shown in FIG. 14, the measurement unit 521 determines the position of the wafer W in the optical axis direction of the projection optical system and the second line width value w. ^R And a second correlation, which is a correlation with. In FIG. 14, the position of the wafer W with respect to the predetermined reference position in the optical axis direction of the projection optical system is taken as the focus position on the horizontal axis, as in FIG. This result is automatically printed out from the printing unit 524 according to an instruction from the measuring unit 521.
Further, the measuring unit 521 may set a first line width value w for each position of the wafer W in the optical axis direction of the projection optical system. ^L And the second line width value w ^R And the average value. Then, the correlation between the average value and the position of the wafer W in the optical axis direction of the projection optical system is approximated using the least square method as shown in FIG. . Then, the measuring unit 521 calculates the position of the wafer W in the optical axis direction of the projection optical system PL when the average value of the line width value becomes the maximum from the approximate expression, and calculates the position of the wafer W in the optical axis direction ( (Z position) is the best focus position at the evaluation point (measurement point) in the field of view of the projection optical system PL corresponding to the above-described etched image 200W. Note that this result is also automatically printed out from the printing unit 524 according to an instruction from the measuring unit 521.
Further, the measuring unit 521 similarly obtains the best focus position at other evaluation points in the field of view of the projection optical system PL, and prints out the results from the printing unit 524.
Note that the first line width value w ^L And the second line width value w ^R When the approximation process using the least squares method is performed on the correlation between the average value of the projection optical system and the position of the wafer W in the optical axis direction of the projection optical system, and the approximation formula (or approximation curve) with the least error is obtained. In some cases, this approximation curve does not have a clear peak. In consideration of such a case, the position of the wafer W having the smallest change in the average value corresponding to the change in the position of the wafer W may be determined as the best focus position. The method of setting the above-described maximum value (maximum value) or the minimum value (minimum value) as the best focus position, and the method of setting the position where the variation of the average value is the smallest as the best focus position include a pattern type, a resist type, etc. May be selected according to the exposure conditions.
In the above description, the best focus position is obtained by using all eight line width measurement patterns. However, the present invention is not limited to this. For example, the best focus position is obtained by using at least one of eight line width measurement patterns. May be. For example, when the best focus positions are respectively obtained by individually using the line width measurement patterns, eight best focus positions can be obtained. Then, for example, based on the best focus positions obtained for four line width measurement patterns (for example, 220, 240, 260, and 280) having different periodic directions, the difference in the best focus position due to the difference in the periodic direction is measured. be able to.
When at least two line width measurement patterns are used, instead of using the average value of the line width values, a focus position may be obtained for each line width measurement pattern, and the average value may be used as the best focus position. In particular, it is desirable to select a line width measurement pattern having a different periodic direction as at least two line width measurement patterns. At this time, for example, a line width value of each line width measurement pattern is given by assigning a weight according to the periodic direction. And the best focus position is determined based on the average line width value, or the focus position determined for each line width measurement pattern may be weighted according to the periodic direction to determine the best focus position. good.
Also, a plurality of line width measurement patterns having different formation conditions (line width and the like) are arranged on the reticle for each periodic direction, and a plurality of line width measurement patterns having the same periodic direction and different line widths are each used to determine the best focus position. Or an average value (or a weighted average value) thereof may be determined as the best focus position. For example, in the present embodiment, by changing the line width between the line width measurement patterns 220 and 230, the line width measurement patterns 240 and 250, the line width measurement patterns 260 and 270, and the line width measurement patterns 280 and 290, The best focus position in the first direction is obtained from the line width measurement patterns 220 and 230, the best focus position in the second direction is obtained from the line width measurement patterns 240 and 250, and the line width measurement pattern is obtained. The best focus position in the third direction is obtained from 260 and 270, and the best focus position in the fourth direction is obtained from the line width measurement patterns 280 and 290. That is, in the present embodiment, the line width measurement pattern 220 is an L / S pattern having a first line width in the first direction, and the line width measurement pattern 230 is an L / S having a fourth line width in the first direction. / S pattern, the line width measurement pattern 240 is an L / S pattern having a second line width in the second direction, and the line width measurement pattern 250 is an L / S having a fifth line width in the second direction. The line width measurement pattern 260 is an L / S pattern having a third line width in the third direction, and the line width measurement pattern 270 is an L / S pattern having a sixth line width in the third direction. The line width measurement pattern 280 is an L / S pattern having a seventh line width in the fourth direction, and the line width measurement pattern 290 is an L / S pattern having an eighth line width in the fourth direction. , The best for each periodic direction It is possible to determine the Okasu position.
As a result, the line width measurement results of the images corresponding to the line patterns having different line widths and the line width measurement results of the images corresponding to the line patterns having different directions can be obtained almost at the same time. The measurement of the optical characteristics of the projection optical system using the difference can be performed in a short time. As a result, it is possible to improve the throughput regarding the optical characteristic measurement of the projection optical system.
Again, in the present embodiment, it is sufficient to provide at least one line width measurement pattern, but the forming conditions (including at least one of the period direction, the line width, the pattern pitch, the duty ratio, etc.) are different. It is desirable to provide a plurality of line width measurement patterns.
Similarly, focusing on the line width values of the etching images (for example, the etching image 220W and the etching image 230W) of the two types of line width measurement patterns forming a pair, these line width values and the projection optical system The best focus position can also be obtained for each periodic direction based on the correlation with the position of the wafer W in the optical axis direction. That is, the best focus position in the first direction is obtained from the etched image 220W and the etched image 230W, and the best focus position in the second direction is obtained from the etched image 240W and the etched image 250W. The best focus position in the third direction is obtained from 270W, and the best focus position in the fourth direction is obtained from the etched image 280W and the etched image 290W. Thus, the best focus position is obtained for each of the four periodic directions, and the difference between the best focus positions depending on the periodic direction of the L / S pattern can be obtained. Further, an average value (or weighted average value) of the best focus positions obtained for the four periodic directions may be calculated, and the average value (or weighted average value) may be used as the best focus position at each evaluation point.
In the above description, the measurement of the best focus position as the optical characteristic at one of a plurality of evaluation points set in the field of view of the projection optical system has been described, but the optical characteristic is similarly determined for the remaining evaluation points. Is done.
Subsequently, the measuring unit 521 determines the line width w of the etched image 221aW at the best focus position. ^L And the line width value w of the etched image 221bW ^R Is used to calculate an abnormal line width value according to the following equation (7), and obtain coma aberration which is one of the optical characteristics of the projection optical system.

Alternatively, the measuring unit 521 calculates (the line width value w ^L -Line width value w ^R ) Is an index value of the coma aberration, and the coma aberration which is one of the optical characteristics of the projection optical system can be obtained based on the index value. In addition, the measuring unit 521 calculates the (line width value w ^L -Line width value w ^R ) And the pitch of the L / S pattern 221 as an index value of the coma aberration, and the coma aberration can be obtained based on the index value.
These results are automatically printed out from the printing unit 524 according to an instruction from the measuring unit 521.
Further, the measuring unit 521 similarly calculates an abnormal line width value and the like at other evaluation points in the field of view of the etching image and the projection optical system PL, and prints out the results from the printing unit 524.
Further, based on the best focus position obtained in the present embodiment, astigmatism, field curvature, and total focal difference, which are optical characteristics of the projection optical system, can be obtained as follows.
The astigmatism can be calculated based on the difference between the best focus positions obtained from a periodic pattern in which the periodic directions are orthogonal (when the evaluation point is on the optical axis, for example, the etched images 220W and 240W). That is, the best focus position determined based on the line width value of the periodic pattern, with the sagittal direction and the meridional direction arranged at the evaluation point at an arbitrary image height position in the field of view of the projection optical system PL as the periodic direction. The astigmatism can be calculated based on the difference. Furthermore, the astigmatism in-plane of astigmatism can be obtained by performing an approximation process by the least squares method based on the astigmatism calculated for a plurality of evaluation points in the visual field of the projection optical system.
Further, it is possible to calculate the field curvature by performing an approximation process by the least squares method based on the best focus positions measured for a plurality of evaluation points in the visual field of the projection optical system.
Further, the total focus difference can be obtained from the astigmatism in-plane uniformity and the field curvature.
Further, for a plurality of evaluation points in the field of view of the projection optical system, the first line width value w at the best focus position is obtained. ^L And the second line width value w ^R By performing an approximation process by the least square method based on at least one of the above or the average value thereof, it is possible to obtain the line width uniformity in the field of view of the projection optical system, which is one of the optical characteristics of the projection optical system. .
In the present embodiment, the same measurement as described above was experimentally performed on a plurality of wafers W. Assuming that the standard deviation of the measured line width value is σ, 3σ ≦ 0.5 nm. The reproducibility could be confirmed. In addition, the time required for measuring the line width per measurement point was 0.5 seconds or less, and it was confirmed that measurement could be performed in a short time.
The procedure of the processing performed by the measuring unit 521 is stored in the storage unit 525 as a program, and the measuring unit 521 automatically performs the processing according to the procedure. That is, the process is automatically performed after the wafer W is fixed to the wafer box 510 and the operator inputs the initial conditions and instructs the start of the measurement.
The optical characteristic data of the projection optical system obtained in this way is input to the main controller 28 of the exposure apparatus and stored in a storage device (not shown). Then, based on the optical characteristic data, main controller 28 instructs an imaging characteristic correction controller (not shown) to control a plurality of lens elements of projection optical system PL, thereby controlling coma aberration and image of projection optical system PL. Adjust surface curvature, etc.
Further, in the exposure apparatus 100 of the present embodiment, the imaging characteristics are adjusted as described above in the same procedure as the operation of forming the transfer image of the pattern for measuring the optical characteristics of the projection optical system PL described above. Exposure (transfer of a device pattern to a photosensitive object) is performed using the projection optical system PL.
As described above, according to the present embodiment, since the line width of an image is determined by electrical resistance measurement, the line widths of a plurality of images can be measured almost simultaneously, without reducing the throughput of optical characteristic measurement. Evaluation points can be increased. As a result, this contributes to improvement of measurement accuracy and improvement of reproducibility of measurement results.
Further, according to the present embodiment, the best focus measurement for evaluating optical characteristics such as astigmatism, field curvature, and total focal difference, and the coma aberration, which is one of the important optical characteristics of the projection optical system, are evaluated. The measurement of the abnormal line width for the measurement and the ΔCD measurement for evaluating the uniformity of the line width in the exposure region can be performed in a short time, accurately, and automatically.
Further, according to the present embodiment, the line pattern is formed in the third direction and the third direction in the gap area after the line width measurement pattern in which the line pattern extends in the first direction and the second direction is arranged in the pattern area PA. Line width measurement patterns extending in four directions are arranged. Therefore, the pattern area PA having a limited area can be effectively used, and a large number of measurement values can be obtained by one exposure.
It is also possible to measure the best exposure using the mask according to the present invention. That is, at the best focus position, the pattern is transferred while changing the energy amount (exposure dose) of the exposure light applied to the wafer W, thereby obtaining a correlation between the line width value of the image and the exposure dose. To obtain the best exposure. Alternatively, the pattern is transferred while changing the wafer position with respect to the optical axis of the projection optical system and the energy amount (exposure dose) of the exposure light irradiated onto the wafer W, so that the exposure dose and the line width value of the image are transferred. The best focus position and the best exposure amount can be obtained from the correlation between the position and the wafer position with respect to the optical axis of the projection optical system.
Furthermore, according to the present embodiment, the procedure of the line width measurement and the data processing in the electric resistance measuring device 500 is stored as a program in the storage unit 525, and the measuring unit 521 automatically performs the processing according to the procedure. Is going. That is, after the wafer W is fixed to the wafer box 510 and the operator inputs the initial conditions and instructs the start of the measurement, the processing is automatically performed, so that the labor can be saved.
Further, according to the exposure method according to the present embodiment, the projection optical system PL is adjusted based on the optical characteristics of the projection optical system PL measured as described above, and the reticle is adjusted via the adjusted projection optical system. Since the R pattern is transferred to each shot area of the wafer W, a fine pattern can be transferred with high precision.
In the above embodiment, the pattern 200 is composed of eight types of line width measurement patterns in which the line pattern extends in four directions (first to fourth directions), but is not limited thereto. That is, the pattern 200 may be composed of at least four types of line width measurement patterns in which the line pattern extends in four directions (first to fourth directions). Alternatively, the pattern 200 may be composed of at least three types of line width measurement patterns in which the line pattern extends in three directions (first to third directions).
In the above embodiment, the pattern line widths of the line width measurement target in the pattern 200 are all the same, but are not limited thereto. That is, there may be two or more types of pattern line widths of the line width measurement target in each line width measurement pattern configuring the pattern 200.
In the above-described embodiment, a symmetrical line width measurement pattern is arranged across the sheet resistance measurement pattern. However, the present invention is not limited to this. For example, only the line width differs across the sheet resistance measurement pattern. A line width measurement pattern including a line pattern may be arranged, or a line width measurement pattern that differs only in the direction of the line pattern may be arranged. Further, the pattern for measuring sheet resistance does not necessarily have to be arranged at the center of the pattern 200.
Further, in the above-described embodiment, the pattern 200 includes a pattern of a van der Pauw structure as a pattern for measuring the sheet resistance value of the wafer W, but the present invention is not limited to this. Not something. The pattern 200 may not include the sheet resistance measurement pattern.
In the above embodiment, an L / S pattern in which five line patterns are periodically arranged is used as the L / S pattern in the line width measurement pattern, but the number is not limited to five. Alternatively, an isolated pattern, that is, a single line pattern may be used instead of a dense pattern such as an L / S pattern. Further, in the above embodiment, two line patterns located at both ends of the L / S pattern in the periodic direction are set as the target patterns of the line width measurement, but the present invention is not limited to this. In other words, the line pattern closest to the center of the L / S pattern in the periodic direction may be set as the line width measurement target pattern. Also, the line width measurement pattern is a line width measurement target pattern with two line patterns located at both ends in the periodic direction of the L / S pattern, and the line closest to the center of the L / S pattern in the periodic direction. A line width measurement pattern having a line pattern as a line width measurement target pattern may be mixed. Further, in one line width measurement pattern, two line patterns located at both ends in the periodic direction of the L / S pattern and a line pattern located closest to the center of the L / S pattern in the periodic direction are line widths. It may be a pattern to be measured.
In the above embodiment, the pattern pitch and the duty ratio of the L / S pattern in each line width measurement pattern are the same, but may be changed according to the measurement purpose or the measurement method.
In the case where a plurality of line patterns (dummy patterns) are sandwiched between two line patterns located at both ends in the periodic direction in the L / S pattern of each line width measurement pattern, as shown in FIG. Alternatively, a part of adjacent ends of each dummy pattern may be communicated in a linear pattern so that one line pattern 300 has a folded shape. Further, the dummy pattern need not be included. That is, the line patterns adjacent to each other may be the target patterns of the line width measurement, and in this case, there may be no other patterns. That is, a multi-line pattern composed of two line patterns adjacent to each other may be used instead of the above-described L / S pattern of the line width measurement pattern.
In the above-described embodiment, all of the line width measurement patterns constituting the pattern 200 include the electrical resistance measurement electrode pad patterns, but the present invention is not limited to this. That is, the pattern 200 may include a line width measurement pattern that does not include the electric resistance measurement electrode pad pattern.
Further, in order to continuously measure a plurality of wafers, the electric resistance measuring device 500 has a wafer stock unit (not shown) for stocking a plurality of wafers, and automatically takes out the wafers from the wafer stock unit and fixes them to a fixing unit 511. It is also possible to provide a loader unit (not shown) that is set to the power supply, thereby further saving labor and time.
The controller 520 of the electric resistance measuring device 500 may be a general personal computer provided with an AD board, a DA board, and a DIO board.
Further, the optical characteristic data obtained by the controller 520 of the electric resistance measuring device 500 can be automatically transferred to the main controller 28.
<< 2nd Embodiment >>
Next, a second embodiment of the present invention will be described with reference to FIGS. In the second embodiment, the method for measuring the optical characteristics of the projection optical system and the exposure method according to the present invention are performed using the same or equivalent exposure apparatus as in the first embodiment. For the line width measurement of an etched image described later, the same or equivalent electric resistance measuring device as that of the first embodiment is used. Accordingly, in the following, from the viewpoint of preventing redundant description, the same reference numerals as those in the first embodiment will be used for these devices and their respective components, and the description will be focused on the optical characteristic measuring method and the exposure method. In the present embodiment, it is assumed that the projection magnification β of the projection optical system PL is １ ／.
FIG. 16 shows a reticle R used for measuring the optical characteristics of the projection optical system in the second embodiment. _T An example is shown. FIG. 16 shows a reticle R _T FIG. 2 is a plan view as viewed from the pattern surface side (the lower surface side in FIG. 1). This reticle R _T Is provided with a pattern area PA 'at the center of a substantially square glass substrate 42', and a plurality of patterns described later are arranged in the pattern area PA '. Further, the center of the pattern area PA ′, that is, the reticle R _T A pair of reticle alignment marks RM3 and RM4 are formed on both sides in the X-axis direction of the pattern area PA passing through the center of the '(reticle center).
Here, the configuration of the pattern 700 for measuring the optical characteristics of the projection optical system arranged in the pattern area PA 'will be described with reference to FIGS.
As shown in FIG. 17, the pattern 700 includes a sheet resistance value measurement pattern 710 having a fan-de-pau structure for measuring the sheet resistance value of a wafer W as a substrate, and an pattern 8 for measuring a line width. The line width measurement patterns 720, 730, 740, 750, 760, 770, 780, and 790.
The sheet resistance value measurement pattern 710 disposed at the center of the pattern 700 has a square measurement area pattern 711 and a square shape similarly to the above-described sheet resistance value measurement pattern 210 (see FIG. 5). , And four electrode pad patterns 712a, 712b, 712c, 712d, which are connected to the measurement region pattern 711 via linear patterns, respectively. In FIG. 17, the lead lines are omitted from the electrode pad patterns, and the positions of the respective electrode pad patterns are denoted by reference numerals.
A line width measurement pattern 720 is arranged above the sheet resistance value measurement pattern 710 in FIG. As shown in FIG. 18, the line width measurement pattern 720 includes a line and space (hereinafter abbreviated as “L / S”) pattern in which five line patterns are periodically arranged, and a square shape. And four electrode pad patterns 722a, 722b, 722c, 722d having the following. The electrode pad patterns 722a and 722c are connected to one end in the longitudinal direction of the central line pattern 721 in the periodic direction of the L / S pattern via linear patterns, respectively, and the electrode pad patterns 722b and 722d are , Are connected to the other end in the longitudinal direction of the line pattern 721 via a linear pattern.
Referring back to FIG. 17, a line width measurement pattern 730 is arranged below (+ Y side) the sheet resistance value measurement pattern 710 in FIG. The line width measurement pattern 730 is a pattern that forms a pair with the line width measurement pattern 720, and has the same shape except that the duty ratio of the L / S pattern is different. That is, the line width measurement pattern 730 includes an L / S pattern and four electrode pad patterns 732a, 732b, 732c, 732d. The electrode pad patterns 732a and 732c are connected to one end in the longitudinal direction of the central line pattern 731 in the periodic direction of the L / S pattern via linear patterns, respectively. The electrode pad patterns 732b and 732d are Are connected to the other end in the longitudinal direction of the line pattern 731 via respective linear patterns.
Note that the pitches of the L / S patterns in the two types of line width measurement patterns 720 and 730 are the same, and in the present embodiment, as an example, as shown in FIG. The width of the line portion of the L / S pattern is 580 nm, and as shown in FIG. 19B, the width of the line portion of the L / S pattern in the line width measurement pattern 730 is 620 nm. The duty ratio of the L / S pattern in 720 and 730 is changed.
Returning to FIG. 17, a line width measurement pattern 740 is arranged on the left side (−X side) of the sheet resistance value measurement pattern 710 in FIG. The line width measurement pattern 740 has a shape obtained by rotating the line width measurement pattern 720 counterclockwise by 90 degrees in the plane of FIG. That is, the line width measurement pattern 740 includes an L / S pattern and four electrode pad patterns 742a, 742b, 742c, 742d. The electrode pad patterns 742a and 742c are connected to one end in the longitudinal direction of the central line pattern 741 in the periodic direction of the L / S pattern via linear patterns, and the electrode pad patterns 742b and 742d are connected to each other. Are connected to the other end in the longitudinal direction of the line pattern 741 via respective linear patterns.
A line width measurement pattern 750 is disposed on the right side (+ X side) of the sheet resistance value measurement pattern 710 in FIG. This line width measurement pattern 750 is a pattern that forms a pair with the line width measurement pattern 740, and has a shape obtained by rotating the line width measurement pattern 730 by 90 degrees counterclockwise in the plane of FIG. Have. That is, the line width measurement pattern 750 includes an L / S pattern and four electrode pad patterns 752a, 752b, 752c, and 752d. The electrode pad patterns 752a and 752c are connected to one end in the longitudinal direction of a central line pattern 751 in the periodic direction of the L / S pattern via a linear pattern, and the electrode pad patterns 752b and 752d are Are connected to the other end in the longitudinal direction of the line pattern 751 via respective linear patterns.
A line width measurement pattern 760 is disposed on the left side (−X side) of the line width measurement pattern 720 in FIG. As shown in FIG. 17, this line width measurement pattern 760 is obtained by rotating the L / S pattern of the line width measurement pattern 720 by 45 degrees counterclockwise in the plane of FIG. , Four electrode pad patterns 762a, 762b, 762c, 762d having a square shape. The electrode pad patterns 762a and 762c are connected to one end in the longitudinal direction of a central line pattern 761 in the periodic direction of the L / S pattern via a linear pattern, and the electrode pad patterns 762b and 762d are connected to each other. Are connected to the other end in the longitudinal direction of the line pattern 761 via respective linear patterns.
A line width measurement pattern 770 is arranged on the right side (+ X side) of the line width measurement pattern 730 in FIG. The line width measurement pattern 770 is a pattern that forms a pair with the line width measurement pattern 760, and the L / S pattern of the line width measurement pattern 730 is 45 degrees counterclockwise in the plane of FIG. It is composed of a rotated L / S pattern and four electrode pad patterns 772a, 772b, 772c, 772d having a square shape. The electrode pad patterns 772a and 772c are connected to one end in the longitudinal direction of the central line pattern 771 in the periodic direction of the L / S pattern via linear patterns, respectively, and the electrode pad patterns 772b and 772d are Are connected to the other end in the longitudinal direction of the line pattern 771 via respective linear patterns.
Further, a line width measurement pattern 780 is arranged on the right side (+ X side) of the line width measurement pattern 720 in FIG. The line width measurement pattern 780 has a shape obtained by rotating the line width measurement pattern 760 clockwise by 90 degrees in the plane of FIG. That is, the line width measurement pattern 780 is composed of the L / S pattern and the four electrode pad patterns 782a, 782b, 782c, 782d. The electrode pad patterns 782a and 782c are connected to one end in the longitudinal direction of the central line pattern 781 in the periodic direction of the L / S pattern via linear patterns, and the electrode pad patterns 782b and 782d are connected to each other. Are connected to the other end in the longitudinal direction of the line pattern 781 via respective linear patterns.
A line width measurement pattern 790 is arranged on the left side (−X side) of the line width measurement pattern 730 in FIG. The line width measurement pattern 790 is a pattern that forms a pair with the line width measurement pattern 780, and has a shape obtained by rotating the line width measurement pattern 770 clockwise by 90 degrees in the plane of FIG. are doing. That is, the line width measurement pattern 790 is composed of the L / S pattern and the four electrode pad patterns 792a, 792b, 792c, 792d. The electrode pad patterns 792a and 792c are connected to one end in the longitudinal direction of a central line pattern 791 in the periodic direction of the L / S pattern via linear patterns, respectively. Are connected to the other end in the longitudinal direction of the line pattern 791 via respective linear patterns.
Lines extending from the center line pattern of the L / S pattern in each of the line width measurement patterns are arranged so as to intersect at the center of the measurement area pattern 711 of the sheet resistance value measurement pattern 710. That is, by symmetrically arranging the line width measurement patterns of the same shape that are different only in the duty ratio of the L / S pattern with the sheet resistance value measurement pattern 710 interposed therebetween, the difference in the duty ratio of the L / S pattern is obtained. It is possible to perform the measurement using the accuracy with high accuracy.
In addition, since the L / S patterns having the same duty ratio are directed in different directions, the influence depending on the direction can be averaged, or the optical characteristics can be measured for each direction.
Also, reticle R _T 'On the pattern surface _T In the state where the alignment of ′ is performed, the patterns 700 are respectively arranged at positions corresponding to each evaluation point in the field of view of the projection optical system PL. Thus, eight line width data are measured for each evaluation point.
In this embodiment, the reticle R _T 'The upper pattern portion is assumed to be a light shielding portion. However, the present invention is not limited to this, and the pattern portion can be a light transmitting portion or a semi-transmitting portion.
The wafer W has a configuration in which a silicon substrate, an insulating film, a conductive film, and a photoresist layer as a photosensitive layer are sequentially stacked as in the first embodiment (see FIG. 8A). In this embodiment, the reticle R _T Since the pattern portion of 'serves as a light shielding portion, a positive chemically amplified resist is used as the photoresist.
In the second embodiment, when measuring the optical characteristics of the projection optical system PL, the exposure apparatus 100 is used to determine the Z position of the wafer table 18 in the same manner as in the first embodiment. While changing the pitch ΔZ, the reticle R is formed in a plurality of shot areas on the wafer W by a step-and-repeat method. _T 'Pattern is transferred. Thereby, reduced images of the pattern 700 corresponding to each Z position of the wafer W are formed at a plurality of points in each shot area on the wafer W. The plurality of points correspond to a plurality of evaluation points whose optical characteristics (mainly the best focus position in the present embodiment) are to be detected in the field of view of the projection optical system PL.
Thereafter, the wafer W is transferred to a coater / developer (not shown) (hereinafter abbreviated as “C / D”) connected inline to the exposure apparatus 100 and developed. Then, the wafer W after the development is sent to a dry etching apparatus and subjected to dry etching. By this etching, only the conductive film in the portion where the photoresist layer has been removed is removed, and the insulating film is exposed. Thereafter, after cleaning the wafer W, all the photoresist layers are removed. As a result, the resist image on the wafer W is replaced by a pattern having the same shape and conductivity, and becomes a sample for measuring the size of the pattern image, in this embodiment, the line width. The pattern having this conductivity is hereinafter referred to as an “etched image” as in the first embodiment.
Next, the etching image 700W formed on the wafer W as described above will be described with reference to FIGS.
As shown in FIG. 20, the etched image 700W is composed of an etched image 710W for sheet resistance value measurement and eight types of etched images 720W, 730W, 740W, 750W, 760W, 770W, 780W, and 790W for line width measurement. Have been.
The sheet resistance value etching image 710W has the same configuration as the sheet resistance value measurement etching image 210W (see FIG. 10). That is, as shown in FIG. 20, the etching image 710W for sheet resistance measurement has a square measurement region 711W located at the center and four electrode pads having a square shape located around the measurement region 711W. It is composed of
Further, the etching image 720W for line width measurement in FIG. 20 is an etching image of the pattern 720 for line width measurement, and as shown in FIG. 21, the L / S pattern and the four electrode pads 722aW, 722bW, 722cW. , 722 dW. Here, the electrode pad 722aW and the electrode pad 722bW are electrode pads for flowing a predetermined current through a central line pattern 721W (a pattern to be measured for a line width) in the periodic direction of the L / S pattern. The pad 722cW and the electrode pad 722dW are electrode pads for measuring a voltage drop in the line pattern 721W.
Returning to FIG. 20, the etching image for line width measurement 730W is an etching image of the pattern for line width measurement 730, and includes an L / S pattern and four electrode pads. The pattern targeted for the line width measurement is the central line pattern 731W in the periodic direction of the L / S pattern.
The line width measurement etching image 740W is an etching image of the line width measurement pattern 740, and includes an L / S pattern and four electrode pads. The pattern targeted for the line width measurement is the central line pattern 741W in the periodic direction of the L / S pattern.
The line width measurement etching image 750W is an etching image of the line width measurement pattern 750, and includes an L / S pattern and four electrode pads. The pattern targeted for the line width measurement is the central line pattern 751W in the periodic direction of the L / S pattern.
The line width measurement etching image 760W is an etching image of the line width measurement pattern 760, and includes an L / S pattern and four electrode pads. The pattern targeted for the line width measurement is the central line pattern 761W in the periodic direction of the L / S pattern.
The line width measurement etching image 770W is an etching image of the line width measurement pattern 770, and includes an L / S pattern and four electrode pads. The pattern to be subjected to the line width measurement is the central line pattern 771W in the periodic direction of the L / S pattern.
The line width measurement etching image 780W is an etching image of the line width measurement pattern 780, and is composed of an L / S pattern and four electrode pads. The pattern to be subjected to line width measurement is the central line pattern 781W in the periodic direction of the L / S pattern.
The line width measurement etching image 790W is an etching image of the line width measurement pattern 790, and includes an L / S pattern and four electrode pads. The pattern to be subjected to line width measurement is the central line pattern 791W in the periodic direction of the L / S pattern.
Next, a method of measuring a line width of a pattern (hereinafter, abbreviated as “target pattern”) to be measured in the line width measurement etching image will be briefly described.
Various methods are available for obtaining the line width of the target pattern. In the present embodiment, a method of obtaining the line width of the target pattern from the electrical resistance value of the target pattern is employed. That is, in the present embodiment, the same (or equivalent) electric resistance measuring device 500 (see FIG. 12) as described above is used as a device for measuring the electric resistance value of the target pattern.
In the second embodiment, line width measurement is performed on the wafer W-shaped etching image 700W set in the electric resistance measuring device 500 in the same procedure as in the above-described first embodiment. However, in the second embodiment, the pattern to be measured is a reticle R _T 'A line pattern (eg, line pattern 721W, etc.) is an etching image of a line pattern (eg, line pattern 721, etc.) located at the center of each L / S pattern in the periodic direction. In measuring the line width, the above equation (4) is used.
By the above line width measurement, the line width value of the target pattern 721W, 731W, 741W, 751W, 761W, 771W, 781W, 791W for the etching image at each of a plurality of points in the shot region is obtained for each shot area on the wafer W. Are obtained by the measuring unit 521 and stored in the storage unit 52.
When the measurement of the line width value of the target pattern of all the etched images is completed, the measurement unit 521 performs data processing as follows. In the following, for the sake of simplicity, the case where the optical characteristic of the projection optical system is obtained at one of a plurality of evaluation points within the field of view of projection optical system PL, and wafer W corresponding to the one evaluation point is used. Description will be made on the assumption that the line width measurement result of the etched image 700W of the pattern 700 formed at a predetermined point in each of the above shot areas is used.
The measurement unit 521 determines whether the width of the line portion of the L / S pattern in the reticle pattern is 580 nm (first pattern) at each position of the wafer W in the optical axis direction of the projection optical system PL (that is, for each shot area). The line width values are arranged for the case of 620 nm (second pattern). That is, the measurement unit 521 calculates the average value of the line width values of the four target patterns 721W, 741W, 761W, and 781W, which are the etching images of the first pattern, and calculates the line width value of the image of the first pattern (first line width). Line width). The measurement unit 521 calculates the average value of the line width values of the four target patterns 731W, 751W, 771W, and 791W, which are the etching images of the second pattern, and calculates the line width value of the image of the second pattern (second line). Line width).
Next, the measuring unit 521 performs a first correlation, which is a correlation between the position of the wafer W in the optical axis direction of the projection optical system PL and the first line width value, by an approximation process using the least square method. Ask for. The first correlation is, as shown in FIG. 22, a curve A in which the first line width value with respect to the position of the wafer W in the optical axis direction of the projection optical system PL has a maximum value. The measuring unit 521 similarly obtains a second correlation, which is a correlation between the position of the wafer W in the optical axis direction of the projection optical system PL and the second line width value. As shown in FIG. 22, the second correlation is a curve B in which the second line width value at the position of the wafer W in the optical axis direction of the projection optical system PL has a minimum value. In FIG. 22, the horizontal axis represents the position of the wafer W with respect to a predetermined reference position in the optical axis direction of the projection optical system as the focus position. This result is automatically printed out from the printing unit 524 according to an instruction from the measuring unit 521.
Further, the measuring unit 521 calculates a difference between the first line width value and the second line width value for each position of the wafer W in the optical axis direction of the projection optical system PL, that is, the curve A and the curve B in FIG. And find the difference. Then, as shown in FIG. 23, an approximation process using the least-squares method is performed on the correlation between the difference between the line width values and the position of the wafer W in the optical axis direction of the projection optical system PL, and the error is minimized. Find an approximate expression. Then, the measuring unit 521 calculates the position of the wafer W in the optical axis direction of the projection optical system PL when the difference between the line width values is minimized from the approximate expression, and calculates the position (Z Is the best focus position at the evaluation point (measurement point) in the field of view of the projection optical system PL corresponding to the above-described etched image 700W. Note that this result is also automatically printed out from the printing unit 524 according to an instruction from the measuring unit 521.
Further, the measuring unit 521 similarly obtains the best focus position at other evaluation points in the field of view of the projection optical system PL, and prints out the results from the printing unit 524.
In the above description, the best focus position is obtained by using the average value of the line width values of the four target patterns having the same duty ratio of the L / S pattern. However, the present invention is not limited to this. Focusing on the line width values of the etched images (for example, the pattern 720W and the pattern 730W) of the line width measurement pattern, and based on the correlation between these line width values and the position of the wafer W in the optical axis direction of the projection optical system PL. Thus, the best focus position can be obtained. Thus, the best focus position is obtained for each of the four periodic directions, and the difference between the best focus positions depending on the periodic direction of the L / S pattern can be obtained. Alternatively, an average value of the best focus positions obtained for the four periodic directions may be calculated, and the average value may be used as the best focus position at each evaluation point.
Further, at least two (for example, 721W and 741W) of the four target patterns having the same duty ratio of the L / S pattern, and at least two target patterns (for example, 731W) which are paired with each other and have different duty ratios of the L / S pattern. , 751W), the best focus position is obtained from the correlation between the difference between the line width values of the target patterns 721W and 731W having the same periodic direction and the position of the wafer W in the optical axis direction of the projection optical system PL. Similarly, the L / S pattern is obtained from the correlation between the line width difference between the target patterns 741W and 751W having the same periodic direction and the wafer position in the optical axis direction of the projection optical system PL. The difference in the best focus position depending on the periodic direction can be obtained. Similarly, the best focus position obtained from the correlation between the difference between the line width values of the target patterns 761W and 771W and the wafer position with respect to the optical axis of the projection optical system PL, the difference between the line width values of the target patterns 781W and 791W, and the projection From the best focus position obtained from the correlation with the wafer position with respect to the optical axis of the optical system, a difference in the best focus position depending on the periodic direction of the L / S pattern can be obtained.
Based on the thus obtained best focus position, astigmatism, field curvature, and total focal difference, which are optical characteristics of the projection optical system, can be obtained as follows.
The astigmatism can be calculated based on the difference between the best focus positions obtained from two pairs of periodic patterns whose periodic directions are orthogonal. For example, as described above, the astigmatism is set based on the difference between the best focus position obtained based on the line width values of the target patterns 721W and 731W and the best focus position obtained based on the line width values of the target patterns 741W and 751W. The aberration can be calculated. In addition, astigmatism is calculated based on a difference between the best focus position obtained based on the line width values of the target patterns 761W and 771W and the best focus position obtained based on the line width values of the target patterns 781W and 791W. Can be. In other words, it is obtained based on the line width values of the target patterns forming a pair, each of which has the sagittal direction and the meridional direction arranged at the evaluation point at an arbitrary image height position in the visual field of the projection optical system PL as the periodic direction. Astigmatism can be calculated based on the difference between the best focus positions.
Further, for the plurality of evaluation points in the field of view of the projection optical system PL, the in-plane astigmatism uniformity is obtained by performing an approximation process by the least square method based on the astigmatism calculated as described above. Can be.
Further, it is possible to calculate the field curvature by performing an approximation process by the least squares method based on the best focus positions measured for a plurality of evaluation points in the visual field of the projection optical system.
Further, the total focus difference can be obtained from the astigmatism in-plane uniformity and the field curvature.
In the present embodiment, a plurality of correlations between the line width value of the image and the wafer position with respect to the optical axis of the projection optical system are obtained by changing the duty ratio of the L / S pattern in the reticle pattern. By keeping the duty ratio of the L / S pattern in the reticle pattern constant and changing the energy amount (exposure dose) of the exposure light irradiated on the wafer W, the line width value of the image and the optical axis of the projection optical system are changed. A plurality of correlations with the wafer position may be determined. As a result, when the exposure dose is larger than the standard value as the first exposure condition, an approximate upward convex curve is obtained similarly to the curve A in FIG. 22, and the exposure dose is the standard value as the second exposure condition. If it is smaller than this, a downwardly convex approximate curve is obtained as in the case of the curve B in FIG. 22, so that the best focus position can be obtained in the same manner as described above.
The adjustment of the exposure dose is performed by the main controller 28 controlling the energy rough adjuster 3 or the light source 1 in the illumination system IOP. That is, as a first method, the energy amount of the exposure light given to the image plane (wafer plane) is adjusted by changing the transmittance of the laser beam LB using the energy coarse adjuster 3 while keeping the pulse repetition frequency constant. I do. As a second method, the energy amount of exposure light given to the image plane (wafer plane) by changing the energy per pulse of the laser beam LB by giving an instruction to the light source while keeping the pulse repetition frequency constant. adjust. As a third method, by keeping the transmittance of the laser beam LB and the energy per pulse of the laser beam LB constant and changing the pulse repetition frequency, the exposure light given to the image surface (wafer surface) is changed. Adjust the amount of energy. Further, these three methods can be appropriately combined.
The best focus position obtained from the two approximate curves has less variation than the conventional best focus position obtained from only one approximate curve. This is because there is only one type of measurement condition variable (line width of reticle pattern or exposure dose), and by utilizing the difference between the measurement results obtained under that condition, various variables independent of the above variables are used. This is because the influence can be canceled.
In the line width measurement pattern, an L / S pattern in which a plurality of line patterns are periodically arranged is used, and the line pattern at the center in the period direction of the L / S pattern is used as a line width measurement target. Accordingly, the influence of coma can be reduced, and the measurement accuracy can be further improved.
Note that when the same measurement as described above was experimentally performed on a plurality of wafers W, the standard deviation of the measured line width values was σ, and 3σ ≦ 0.5 nm. I was able to confirm.
Next, the measurement unit 521 obtains the relationship between the width of the line portion in the reticle pattern at the best focus position and the line width of the corresponding image by an approximation process using the least squares method. For example, as shown in FIG. 24, when the average value of the first line width value is 140 nm and the average value of the second line width value is 160 nm, the line width of the reticle pattern and the line width of the image Is expressed by the following equation (8).

In this embodiment, since the line width of the L / S pattern in the reticle pattern is two types, the relationship between the line width of the reticle pattern and the line width of the pattern image is expressed by a linear expression. When the width of the line portion of the L / S pattern in the reticle pattern is three or more, the relationship between the line width of the reticle pattern and the line width of the pattern image may be a higher order expression than a quadratic expression. The measurement unit 521 prints out the processing result from the printing unit 524.
Then, the measuring unit 521 calculates a line width of an image predicted when a reticle pattern having a line width of, for example, 600 nm is transferred onto the wafer W as a reference pattern from the above equation (8). Here, a value of 150 nm is obtained as the line width of the predicted image. This value (hereinafter referred to as “transfer line width of the reference pattern”) is corrected for a process error including a reticle manufacturing error included in an actual measurement value and an optical error caused by the reticle manufacturing error.
The measurement unit 521 performs the same processing for other evaluation points in the field of view of the projection optical system, and calculates the transfer line width of the reference pattern. The measurement unit 521 prints out the calculation results from the printing unit 524.
Then, under the best focus position condition, the line width uniformity in the field of view of the projection optical system PL, which is one of the optical characteristics of the projection optical system PL, is determined based on the transfer line width of the reference pattern at each evaluation point. Can be.
Conventionally, a difference between a designed line width obtained at a certain evaluation point and a line width of an actually formed image is used as a correction value for a reticle manufacturing error, and this correction value is used for all other evaluation points. Had applied. In the optical characteristic measurement method according to the present invention, as described above, since the line width value corrected for the reticle manufacturing error at that position is used for each evaluation point, the line width uniformity with high accuracy and excellent reproducibility is used. Can be requested.
In the present embodiment, the same measurement as described above was experimentally performed on a plurality of wafers W. Assuming that the standard deviation of the measured line width value is σ, 3σ ≦ 0.5 nm. The reproducibility could be confirmed. In addition, the time required for measuring the line width per measurement point was 0.5 seconds or less, and it was confirmed that measurement could be performed in a short time.
The procedure of the processing performed by the measuring unit 521 is stored in the storage unit 525 as a program, and the measuring unit 521 automatically performs the processing according to the procedure. That is, after the wafer W is fixed to the wafer box 510 and the operator inputs the initial conditions and instructs the start of the measurement, the processing is automatically performed, so that labor can be saved.
Further, in order to continuously measure the plurality of wafers W, a wafer stock unit (not shown) for stocking the plurality of wafers W, and a loader (not shown) for automatically taking out the wafers from the wafer stock unit and setting them on the fixing unit 511 It is also possible to equip the electric resistance measuring device 500 with a unit, thereby further saving labor and shortening the time.
The controller 520 may be a general personal computer provided with an AD board, a DA board, and a DIO board.
The optical characteristic data of the projection optical system obtained in this way is input to the main controller 28 of the exposure apparatus and stored in a storage device (not shown). Then, based on the optical characteristic data, main controller 28 instructs an imaging characteristic correction controller (not shown) to control a plurality of lens elements of projection optical system PL to thereby control the curvature of field of projection optical system PL. To adjust.
In this embodiment, the pattern 700 has eight line width measurement patterns, but is not limited to this. Further, a pattern having a van der Pau structure is used as a pattern for measuring the sheet resistance value of the wafer W, but the pattern is not limited to this. Further, in determining the best focus position, the average value of the line width values of a plurality of etched images having the same duty ratio of the L / S pattern and different periodic directions is used. For example, the best focus position may be determined only from a pair of patterns having the same cycle direction and different L / S pattern duty ratios.
Furthermore, in the present embodiment, an L / S pattern in which five line patterns are periodically arranged is used as the L / S pattern in the line width measurement pattern, but the number is not limited to five. Absent. Further, for example, when the influence of coma is small or negligible, only one line pattern may be used instead of the L / S pattern. At this time, it goes without saying that a plurality of line patterns having the same longitudinal direction and different line widths are formed. Alternatively, the number of line portions in the L / S pattern may be set to an even number, the line width may be measured for two line patterns near the center, and the average value thereof may be used as the measured value.
Note that the optical characteristic data obtained by the controller 520 of the electric resistance measuring device 500 can be automatically transferred to the main control device 28 by communication.
Further, in the exposure apparatus 100 of the present embodiment, as described above, the projection optical system in which the imaging characteristics are adjusted is performed in the same procedure as the operation of forming the pattern image for measuring the optical characteristics of the projection optical system PL. Exposure (transfer of a device pattern to a photosensitive object) is performed using the system PL.
As described above, according to the second embodiment, ΔCD measurement for evaluating line width uniformity in an exposure region, which is one of important optical characteristics of the projection optical system, and astigmatism, The best focus measurement for evaluating optical characteristics such as curvature of field and total focal difference can be performed in a short time, accurately, and automatically. Further, in the present embodiment, by measuring the line width of a specific line pattern (for example, two line patterns located at both ends in the periodic direction) of the L / S pattern in the line width measurement pattern, the coma aberration is reduced. Measurement can be performed accurately in a short time.
Further, since the line widths of the images are obtained by measuring the electric resistance, the line widths of a plurality of images can be measured at the same time, and the number of evaluation points can be increased without lowering the throughput. As a result, this contributes to improvement in measurement accuracy and improvement in reproducibility.
Further, labor saving can be achieved by automation of line width measurement and data processing.
Further, according to the exposure method according to the second embodiment, the projection optical system PL is adjusted based on the optical characteristics of the projection optical system PL measured as described above. Since the pattern of the reticle R is transferred to each shot area of the wafer W via the reticle R, a fine pattern can be transferred with high precision.
In the second embodiment, the duty ratio of the L / S pattern in the reticle pattern is changed so that a plurality of positions between the line width value of the image and the position of the wafer W in the optical axis direction of the projection optical system PL are changed. When the correlation is obtained or the duty ratio of the L / S pattern in the reticle pattern is made constant and the energy amount (exposure dose) of the exposure light irradiated on the wafer W is changed, the line width value of the image and the projection are obtained. The case where a plurality of correlations between the wafer position and the optical axis direction of the optical system PL are determined has been described. However, the present invention is not limited to these. That is, according to the present invention, the position of the substrate (projected object) arranged on the image plane side of the projection optical system PL in the optical axis direction of the projection optical system is changed in a predetermined procedure within a predetermined range, and the substrate is arranged on the object plane. An image of the projected first pattern formed by the projection optical system is formed on the projection object at each change position, and the position of the projection object disposed on the image plane side of the projection optical system with respect to the optical axis direction of the projection optical system is determined. The image is changed by the predetermined procedure within the predetermined range, and an image of the second pattern arranged on the object plane by the projection optical system is formed on the object to be projected at each change position. Then, the size (eg, line width) of the image of the first pattern at each change position is measured, and the size (eg, line width) of the image of the second pattern at each change position is measured. Then, a first correlation, which is a correlation between the position of the projection target in the optical axis direction and the size of the image of the first pattern, a position of the projection target in the optical axis direction, and a projection image of the second pattern It is only necessary to calculate the optical characteristics of the projection optical system based on the second correlation, which is the correlation with the size of the projection optical system.
In other words, at least two types of correlations, which are relationships between the image of the pattern and the position of the projection optical system in the optical axis direction of the projection object on which the image is formed, are obtained, and the projection optical system is determined based on the two types of correlations. What is necessary is just to calculate the optical characteristics of the system. That is, it is possible to improve the measurement accuracy of the optical characteristics of the projection optical system by obtaining the optical characteristics based on not one type of correlation but two types of correlation.
Therefore, in order to obtain the above two types of correlations, the patterns arranged on the object plane may be different patterns arranged simultaneously on the object plane or the same patterns arranged on the object plane at different times. But it's fine. Further, the formation of an image using the first pattern and the formation of an image using the second pattern may be performed simultaneously or may be performed by separate exposure.
In the above embodiment, the case where the line width value corresponding to the pattern image is obtained by measuring the etching image formed on the wafer W, but the present invention is not limited to this. That is, the measurement of the line width value corresponding to the pattern image may be performed by aerial image measurement in which a projection image (aerial image) of the pattern projected on the projection target object by the projection optical system is measured. Means that the light receiving unit of the aerial image detection device corresponds to the projection target object. In this case, the light receiving unit relatively scans the pattern plate on which the slit-shaped or rectangular opening pattern is formed with respect to the aerial image on the image plane side of the projection optical system, and receives light passing through the opening. A pattern plate constituting a so-called aerial image measuring device for detecting an aerial image based on the photoelectric conversion signal, or a light receiving element constituting another aerial image detecting device for receiving an image light beam on the image plane side of the projection optical system or In addition to an image sensor, a reflection optical element (mirror or the like) in the case of a spatial image detecting device of a type that receives light corresponding to an aerial image by a reflection method is also included.
Further, similarly to the above embodiment, even when the line width of the transfer image formed on the substrate is measured, the target may be a resist image obtained after a development process instead of an etching image. In addition, the line width of the latent image formed on the substrate may be measured. At this time, the photosensitive layer is not limited to the resist, but may be a magneto-optical layer. In the second embodiment, the line width of the pattern image is obtained by measuring the electric resistance. However, the line width measurement is not limited to the electric resistance measurement, and may be performed by any other method such as optical measurement. Is also good. In short, regardless of the measurement method, it is sufficient that the above two types of correlation can be obtained.
In the second embodiment, the case where the line width is typically measured as the size of the pattern image has been described. However, the present invention is not limited to this. That is, instead of the line width of the pattern image, the length or other dimensions of the pattern image may be measured as the image size. When the pattern is a wedge-shaped pattern, for example, the length of the diagonal may be used as the size of the image to be measured. This is because the length and other dimensions of the image also change according to the defocus amount and the exposure dose of the wafer, so that the same correlation as in the above embodiment can be obtained.
In the above embodiments, a positive resist is used, but a negative resist may be used instead.
In each of the above embodiments, the case where the present invention is applied to the step-and-repeat type reduction projection exposure apparatus has been described, but the scope of the present invention is not limited to this. That is, the present invention can be suitably applied to a step-and-scan method, a step-and-stitch method, a mirror projection aligner, a photo repeater, and the like. The projection optical system is not limited to a refraction system, but may be a catadioptric system or a reflection system.
Further, the light source of the exposure apparatus to which the present invention is applied is not limited to a KrF excimer laser or an ArF excimer laser, ₂ A laser (wavelength: 157 nm), a pulsed light source in another vacuum ultraviolet region, a far ultraviolet region or an ultraviolet region, or a continuous light source may be used. In addition, a fiber doped with, for example, erbium (or both erbium and ytterbium) is used as the exposure illumination light, for example, a single-wavelength laser light in the infrared or visible range oscillated from a DFB semiconductor laser or a fiber laser. A harmonic that has been amplified by an amplifier and wavelength-converted to ultraviolet light using a nonlinear optical crystal may be used. Further, X-rays such as EUV light, or charged particle beams such as an electron beam or an ion beam may be used as the illumination light for exposure.
Further, the present invention provides an exposure apparatus for transferring a device pattern onto a glass plate, and a thin-film magnetic head used for manufacturing a display including a liquid crystal display element, a plasma display, etc., as well as an exposure apparatus used for manufacturing a semiconductor element. Apparatus used to manufacture device such as an exposure device for transferring device patterns onto a ceramic wafer, imaging device (such as CCD), micromachine, DNA chip, etc., and also to an exposure device used to manufacture a mask or reticle. can do.
《Device manufacturing method》
Next, an embodiment of a device manufacturing method using the above-described exposure apparatus and method will be described.
FIG. 25 shows a flowchart of an example of manufacturing devices (semiconductor chips such as ICs and LSIs, liquid crystal panels, CCDs, thin-film magnetic heads, DNA chips, micromachines, etc.). As shown in FIG. 25, first, in step 301 (design step), a function / performance design of a device (for example, a circuit design of a semiconductor device) is performed, and a pattern design for realizing the function is performed. Subsequently, in step 302 (mask manufacturing step), a mask on which the designed circuit pattern is formed is manufactured. On the other hand, in step 303 (wafer manufacturing step), a wafer is manufactured using a material such as silicon.
Next, in step 304 (wafer processing step), actual circuits and the like are formed on the wafer by lithography using the mask and the wafer prepared in steps 301 to 303, as described later. Next, in step 305 (device assembly step), device assembly is performed using the wafer processed in step 304. Step 305 includes processes such as a dicing process, a bonding process, and a packaging process (chip encapsulation) as necessary.
Finally, in step 306 (inspection step), inspections such as an operation confirmation test and a durability test of the device manufactured in step 305 are performed. After these steps, the device is completed and shipped.
FIG. 26 shows a detailed flow example of step 304 in the case of a semiconductor device. In FIG. 26, in step 311 (oxidation step), the surface of the wafer is oxidized. In step 312 (CVD step), an insulating film is formed on the wafer surface. In step 313 (electrode forming step), electrodes are formed on the wafer by vapor deposition. In step 314 (ion implantation step), ions are implanted into the wafer. Each of the above steps 311 to 314 constitutes a pre-processing step in each stage of wafer processing, and is selected and executed according to a necessary process in each stage.
In each stage of the wafer process, when the above-described pre-processing step is completed, the post-processing step is executed as follows. In this post-processing step, first, in step 315 (resist forming step), a photosensitive agent is applied to the wafer. Subsequently, in step 316 (exposure step), the circuit pattern of the mask is transferred to the wafer by the exposure apparatus and the exposure method of the above embodiment. Next, in Step 317 (development step), the exposed wafer is developed, and in Step 318 (etching step), the exposed members other than the portion where the resist remains are removed by etching. Then, in step 319 (resist removing step), unnecessary resist after etching is removed.
By repeating these pre-processing and post-processing steps, multiple circuit patterns are formed on the wafer.
As described above, if the device manufacturing method according to the present embodiment is used, the exposure apparatus and the exposure method according to the above embodiment are used in the exposure step, and therefore, based on the optical characteristics accurately determined by the optical characteristic measurement method described above. High-precision exposure is performed via the projection optical system adjusted in this way, and the productivity of a highly integrated device can be improved.
Industrial applicability
As described above, the mask of the present invention is suitable for use in measuring optical characteristics of a projection optical system. Further, the method for measuring the optical characteristics of a projection optical system according to the present invention is suitable for measuring the optical characteristics of a projection optical system in a short time with high accuracy and reproducibility. Further, the adjusting method and the exposing method of the exposure apparatus according to the present invention are suitable for forming a pattern on a substrate with high accuracy. Further, the device manufacturing method of the present invention is suitable for manufacturing a micro device.
[Brief description of the drawings]
FIG. 1 is a view schematically showing a configuration of an exposure apparatus according to the first embodiment of the present invention.
FIG. 2 is a diagram for explaining an example of a specific configuration of the illumination system in FIG.
FIG. 3 is a diagram illustrating an example of a reticle used for measuring the optical characteristics of the projection optical system in the first embodiment.
FIG. 4 is a diagram for explaining a pattern formed on the reticle of FIG.
FIG. 5 is a diagram for explaining a pattern for measuring a sheet resistance value having a van der Pauw structure.
FIG. 6 is a diagram for explaining an example of the line width measurement pattern according to the first embodiment.
FIG. 7 is a diagram for explaining an example of a line width measurement pattern different from FIG.
8A to 8D are diagrams for explaining a process of forming a line width measurement pattern on a wafer.
FIG. 9 is a view for explaining a transfer image of the pattern of FIG. 4 transferred onto the wafer.
FIG. 10 is a diagram for explaining a method of measuring a sheet resistance value in a transfer image of a pattern for measuring a sheet resistance value.
FIG. 11 is a diagram for explaining a method of measuring a line width of a transferred image of a line pattern in a line width measurement pattern.
FIG. 12 is a diagram for explaining an example of a specific configuration of the electric resistance measuring device.
FIG. 13 is a diagram for explaining the correlation between the first line width value and the focus position.
FIG. 14 is a diagram for explaining the correlation between the second line width value and the focus position.
FIG. 15 is a diagram for explaining the correlation between the average value of the first line width value and the second line width value and the focus position.
FIG. 16 is a diagram illustrating an example of a reticle used for measuring optical characteristics of a projection optical system in the second embodiment.
FIG. 17 is a diagram for explaining a pattern formed on the reticle of FIG.
FIG. 18 is a diagram for explaining an example of the line width measurement pattern according to the second embodiment.
FIG. 19A and FIG. 19B are diagrams for explaining the duty ratio in the line width measurement pattern.
FIG. 20 is a diagram for explaining an image of the pattern of FIG. 17 transferred onto the wafer.
FIG. 21 is a diagram for explaining a method of measuring a line width in a line width measurement pattern image.
FIG. 22 is a diagram for explaining the correlation between the line width value on the wafer and the focus position.
FIG. 23 is a diagram for explaining the correlation between the difference between the line width values on the wafer and the focus position.
FIG. 24 is a diagram for explaining the correlation between the line width value on the wafer and the line width of the reticle pattern.
FIG. 25 is a flowchart for explaining an embodiment of the device manufacturing method according to the present invention.
FIG. 26 is a flowchart of the process in step 304 of FIG.

[0008]
It is.
According to this, it is possible to reduce the number of current supply electrode pad patterns conventionally provided for each pattern whose line width is to be measured, and to effectively use a pattern surface having a limited area. it can. In addition, for example, a line width measurement pattern on a mask is transferred to a substrate via a projection optical system, and development, etching and the like are performed to form an etching image of the line width measurement pattern on the substrate, By measuring the line width value of the line pattern corresponding to the transferred image of the first line pattern and the second line pattern constituting the etched image using electric resistance measurement, the two line width values can be substantially reduced. It is possible to determine at the same time. As a result, the throughput of optical characteristic measurement of the projection optical system can be improved.
In the second mask of the present invention, the pattern may be such that only the first line pattern and the second line pattern are formed close to each other.
According to a third aspect of the present invention, there is provided an optical characteristic measuring method for measuring an optical characteristic of a projection optical system using a second mask according to the present invention, wherein a position of a substrate in an optical axis direction of the projection optical system is provided. A first step of sequentially transferring the pattern on the mask to different regions on the substrate via the projection optical system while changing the pattern; and forming the pattern on the substrate at each position in the optical axis direction. A second step of obtaining first and second line width values corresponding to transfer images of the first and second line patterns by electric resistance measurement, respectively; and the substrate with respect to the first line width value and the optical axis direction. The projection based on a first correlation that is a correlation with the position of the substrate and a second correlation that is a correlation between the second line width value and the position of the substrate in the optical axis direction. A third step of calculating optical characteristics of the optical system; A first optical characteristic measuring method comprising.
According to this, the pattern on the mask is sequentially transferred to different regions on the substrate via the projection optical system while changing the position of the substrate in the optical axis direction of the projection optical system. As a result, a transferred image of the first line pattern and a transferred image of the second line pattern are formed in different regions on the substrate for each position in the optical axis direction of the projection optical system (first step). . Also formed on the substrate at each position in the optical axis direction

[0022]
Although a method is conceivable, in the first and second steps, each of the line width values can be obtained by electric resistance measurement.
According to a twelfth aspect, the present invention provides an exposure method for irradiating a mask with an energy beam for exposure, and transferring a pattern formed on the mask onto a substrate via a projection optical system. Adjusting the projection optical system in consideration of the optical characteristics measured by any of the first to seventh optical characteristic measurement methods; and forming the projection optical system on the mask via the adjusted projection optical system. Transferring a pattern onto the substrate.
According to this, the projection optical system is adjusted so that optimal transfer can be performed in consideration of the optical characteristics of the projection optical system measured by any of the first to seventh optical characteristic measurement methods of the present invention. The pattern formed on the mask is transferred onto the substrate via the adjusted projection optical system. Therefore, it becomes possible to transfer the fine pattern onto the substrate with high accuracy.
Further, in the lithography process, by using the exposure method of the present invention, a fine pattern pattern can be formed on a substrate with high accuracy, and thereby a microdevice with a higher degree of integration can be manufactured with good productivity (including yield). Can be manufactured. Therefore, from another viewpoint, the present invention can be said to be a device manufacturing method using the exposure method of the present invention.
According to another aspect of the present invention, there is provided a second mask of the present invention (including a pattern in which only the first line pattern and the second line pattern are formed close to each other). An optical characteristic measuring method for measuring an optical characteristic of a projection optical system using the method, wherein a first step of transferring the pattern of the mask onto an object via the projection optical system; and a first step formed on the object. And a second step of obtaining first and second line width values corresponding to a transferred image of the second line pattern by electric resistance measurement.
According to this, the pattern of the mask is transferred onto the object via the projection optical system. As a result, at least a transfer image of the first line pattern and a transfer image of the second line pattern are formed on the object (first step). Further, the first and second line width values corresponding to the transferred images of the first and second line patterns formed on the object are respectively obtained by electric resistance measurement (second step). Therefore, according to this optical characteristic measuring method, as described above, the number of current supply electrode pad patterns can be reduced, and a pattern surface having a limited area can be effectively used. Further, since the line width value of the transfer image of the line pattern is obtained by measuring the electrical resistance, the line width value of the transfer images of the first and second line patterns can be obtained in a short time, and as a result, the projection optical system can be obtained. The throughput of the optical characteristic measurement of the system can be improved. That is, when measuring the optical characteristics of the projection optical system, it is possible to improve the measurement capability at least in terms of time.
In this case, in the first step, the pattern may be transferred by substantially arranging the object at a best focus position of the projection optical system.
In the eighth optical characteristic measuring method of the present invention, coma aberration of the projection optical system or related information thereof can be obtained as the optical characteristic based on the first and second line width values.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram schematically showing a configuration of an exposure apparatus according to a first embodiment of the present invention.
FIG. 2 is a diagram for explaining an example of a specific configuration of the illumination system in FIG.
FIG. 3 is a diagram illustrating an example of a reticle used for measuring the optical characteristics of the projection optical system in the first embodiment.
FIG. 4 is a diagram for explaining a pattern formed on the reticle of FIG.

Claims (47)

A mask used for line width measurement using the electrical resistance of the transferred pattern,
At least one first pattern including at least one line pattern extending in a first direction and an electrode pad pattern for measuring electrical resistance of the line pattern, and extending in a second direction forming an angle of 90 degrees with the first direction; An angle θ1 (0 ° <θ1 <180 °, θ1 ≠ 90 °) with respect to the first direction, including at least one second pattern including at least one line pattern and an electrode pad pattern for measuring the electrical resistance of the line pattern. ), And at least one third pattern including at least one line pattern extending in the third direction and an electrode pad pattern for electrical resistance measurement of the line pattern is formed on the pattern surface so as not to overlap with each other. Mask provided with a mask substrate. The mask according to claim 1,
The third pattern is formed in a virtual rectangular area on the pattern surface including the line pattern forming the first pattern and the line pattern forming the second pattern on a part of each of two adjacent sides. Is disposed. The mask according to claim 1,
The first, second and third patterns are provided in pairs, respectively.
A mask, wherein each of the first, second, and third patterns forming a pair is disposed on one side and the other side with respect to a predetermined reference point on the pattern surface. The mask according to claim 3,
A mask, wherein a pattern for measuring sheet resistance is arranged in an area on the pattern surface including the reference point. The mask according to claim 1,
At least one of the first to third patterns is a multi-line pattern in which a plurality of line patterns are arranged at predetermined intervals along a predetermined arrangement direction, and one end of the multi-line pattern in the arrangement direction. And a two-line pattern electrical resistance measurement electrode pad pattern located at each of the portion and the other end. The mask according to claim 1,
At least one of the first to third patterns is a multi-line pattern in which a plurality of line patterns are arranged at a predetermined interval along a predetermined arrangement direction, and is closest to a center of the multi-line pattern in the arrangement direction. An electrode pad pattern for measuring electrical resistance of at least one line pattern. The mask according to claim 1,
The line pattern constituting the first pattern has a first line width,
The line pattern constituting the second pattern has a second line width,
The line pattern constituting the third pattern has a third line width,
A fourth pattern including at least one line pattern having a fourth line width different from the first line width and extending in the first direction, and an electrode pad pattern for measuring electrical resistance of the line pattern; A fifth pattern including at least one line pattern having a fifth line width different from the second line width and extending in the second direction and an electrode pad pattern for measuring electrical resistance of the line pattern; A sixth pattern including at least one line pattern having a sixth line width different from the line width and extending in the third direction and an electrode pad pattern for measuring electrical resistance of the line pattern, wherein 2. A mask further formed on a pattern surface on the mask substrate so as not to overlap with any of the third and third patterns and not to overlap with each other. The mask according to claim 7,
At least one line pattern extending in a fourth direction having a seventh line width and forming an angle θ2 (0 ° <θ2 <180 °, θ2 ≠ 90 °, θ2 ≠ θ1) with respect to the first direction; A seventh pattern including an electrode pad pattern for measuring electrical resistance of the pattern, at least one line pattern having an eighth line width different from the seventh line width and extending in the fourth direction, and a line pattern of the line pattern. An eighth pattern including an electric resistance measurement electrode pad pattern is further formed on the pattern surface so as not to overlap with any of the first to sixth patterns and to overlap with each other. A mask, characterized in that: The mask according to claim 8,
The first pattern and the fourth pattern are arranged on one side and the other side of the first direction with respect to a predetermined reference point on the pattern surface,
The second pattern and the fifth pattern are arranged on one side and the other side of the second direction with respect to the reference point on the pattern surface, respectively.
The third pattern is formed in a virtual rectangular area on the pattern surface including the line pattern forming the first pattern and the line pattern forming the second pattern on a part of each of two adjacent sides. Is placed,
The seventh pattern is formed in a virtual rectangular area on the pattern surface that includes the line pattern forming the first pattern and the line pattern forming the fifth pattern on a part of each of two adjacent sides. Is placed,
The eighth pattern is formed in a virtual rectangular area on the pattern surface that includes the line pattern forming the second pattern and the line pattern forming the fourth pattern on a part of each of two adjacent sides. Is placed,
The sixth pattern is formed in a virtual rectangular area on the pattern surface that includes the line pattern forming the fourth pattern and the line pattern forming the fifth pattern on a part of each of two adjacent sides. Is disposed. The mask according to claim 9,
A mask, wherein a pattern for measuring sheet resistance is arranged in an area on the pattern surface including the reference point. The mask according to claim 9,
At least one of the first to eighth patterns is a multi-line pattern in which a plurality of line patterns are arranged at predetermined intervals along a predetermined arrangement direction, and one end of the multi-line pattern in the arrangement direction. And a two-line pattern electrode pad pattern for electric resistance measurement, which is located at each of the end and the other end. The mask according to claim 9,
At least one of the first to eighth patterns is a multi-line pattern in which a plurality of line patterns are arranged at a predetermined interval along a predetermined arrangement direction, and is closest to a center of the multi-line pattern in the arrangement direction. An electrode pad pattern for measuring electrical resistance of at least one line pattern. A mask used for line width measurement using the electrical resistance of the transferred pattern,
A pattern including a first line pattern and a second line pattern substantially parallel to each other, wherein the first and second line patterns communicate with one ends of the first and second line patterns in the longitudinal direction. A mask comprising: a mask substrate on which a line width measurement pattern having a current supply electrode pad pattern at the other end in the longitudinal direction of the first and second line patterns is formed. An optical characteristic measuring method for measuring an optical characteristic of a projection optical system using the mask according to claim 13,
A first step of sequentially transferring the pattern on the mask to different regions on the substrate via the projection optical system while changing the position of the substrate in the optical axis direction of the projection optical system;
A second step of obtaining first and second line width values corresponding to transferred images of first and second line patterns formed on the substrate at respective positions in the optical axis direction by electric resistance measurement, respectively; ;
A first correlation, which is a correlation between the first line width value and the position of the substrate in the optical axis direction, and a correlation between the second line width value and the position of the substrate in the optical axis direction A third step of calculating an optical characteristic of the projection optical system based on a second correlation that is a relation. A mask used for line width measurement using the electrical resistance of the transferred pattern,
A plurality of line patterns arranged at predetermined intervals along a predetermined arrangement direction; a first line pattern located at one end of the line direction in the line direction; A mask having a mask substrate formed on a pattern surface, the line width measurement pattern including an electric resistance measurement electrode pad pattern connected to both ends of a second line pattern located at an end on the side. An optical characteristic measuring method for measuring optical characteristics of a projection optical system using the mask according to claim 15,
A first step of transferring the pattern on the mask onto an object via the projection optical system;
A second step of obtaining first and second line width values respectively corresponding to line widths of transfer images of the first and second line patterns formed on the object by electric resistance measurement;
A third step of calculating optical characteristics of the projection optical system based on the first line width value and the second line width value. An optical characteristic measuring method for measuring optical characteristics of a projection optical system,
While changing the position of the object in the optical axis direction of the projection optical system, a multi-line pattern in which a plurality of line patterns are arranged at a predetermined interval along a predetermined arrangement direction, and a multi-line pattern in the arrangement direction in the multi-line pattern An electrode pad pattern for electric resistance measurement of two line patterns respectively located at one end and the other end is formed by using a mask formed on the pattern surface to form a pattern on the mask. A first step of sequentially transferring to different regions on the object via the projection optical system;
A first line width corresponding to a line width of a transfer image of a first line pattern located at one end in an arrangement direction of the transfer image of the multi-line pattern formed on the object at each position in the optical axis direction; A second step of determining a value by electric resistance measurement, respectively;
A second line corresponding to a line width of a transfer image of a second line pattern located at the other end in the periodic direction of the transfer image of the multi-line pattern formed on the object at each position in the optical axis direction A third step of determining width values by electrical resistance measurement, respectively;
A first correlation, which is a correlation between the first line width value and the position of the object in the optical axis direction, and a correlation between the second line width value and the position of the object in the optical axis direction A fourth step of calculating an optical characteristic of the projection optical system based on a second correlation that is a relation. The optical characteristic measuring method according to claim 17,
The mask is the mask according to claim 5,
In the second step, the transfer image of the first line pattern located at one end in the arrangement direction of the transfer image of at least one specific multi-line pattern formed on the object at each position in the optical axis direction Determining a first line width value corresponding to the line width;
In the third step, a line of a transfer image of a second line pattern located at the other end in the arrangement direction of the transfer image of the specific multi-line pattern formed on the object at each position in the optical axis direction An optical characteristic measuring method, wherein a second line width value corresponding to a width is obtained. The optical characteristic measuring method according to claim 17,
The mask is the mask according to claim 11,
In the second step, the transfer image of the first line pattern located at one end in the arrangement direction of the transfer image of at least one specific multi-line pattern formed on the object at each position in the optical axis direction Determining a first line width value corresponding to the line width;
In the third step, a line of a transfer image of a second line pattern located at the other end in the arrangement direction of the transfer image of the specific multi-line pattern formed on the object at each position in the optical axis direction An optical characteristic measuring method, wherein a second line width value corresponding to a width is obtained. The optical characteristic measuring method according to claim 17,
In the fourth step, based on the first correlation and the second correlation, an average value of the first line width value and the second line width value and the optical axis direction. An optical characteristic measuring method comprising: obtaining a third correlation that is a correlation with a position of an object; and calculating a best focus position based on the third correlation. In the optical characteristic measuring method according to claim 20,
In the fourth step, based on the third correlation, a position of the object having the smallest change in the average value corresponding to a change in the position of the object is set as a best focus position. Method. An optical characteristic measuring method for measuring optical characteristics of a projection optical system,
A multi-line pattern in which a plurality of line patterns are arranged at a predetermined interval along a predetermined arrangement direction; and two lines located at one end and the other end of the multi-line pattern in the arrangement direction, respectively. A first step of transferring the pattern on the mask using the mask formed on the pattern surface and transferring the pattern on the mask to the object via the projection optical system, and ;
A second line width value corresponding to a line width of a transfer image of a first line pattern located at one end in the arrangement direction of the transfer image of the multi-line pattern formed on the object is obtained by measuring electrical resistance. Process;
A third step of obtaining a second line width value corresponding to the line width of the transfer image of the second line pattern located at the other end in the arrangement direction of the transfer image of the multi-line pattern by measuring electrical resistance;
A fourth step of calculating optical characteristics of the projection optical system based on the first line width value and the second line width value. In the optical characteristic measuring method according to claim 22,
The mask is the mask according to claim 5,
In the second step, the transfer image of the first line pattern located at one end in the arrangement direction of the transfer image of at least one specific multi-line pattern formed on the object at each position in the optical axis direction Determining a first line width value corresponding to the line width;
In the third step, a line of a transfer image of a second line pattern located at the other end in the arrangement direction of the transfer image of the specific multi-line pattern formed on the object at each position in the optical axis direction An optical characteristic measuring method, wherein a second line width value corresponding to a width is obtained. In the optical characteristic measuring method according to claim 22,
The mask is the mask according to claim 11,
In the second step, the transfer image of the first line pattern located at one end in the arrangement direction of the transfer image of at least one specific multi-line pattern formed on the object at each position in the optical axis direction Determining a first line width value corresponding to the line width;
In the third step, a line of a transfer image of a second line pattern located at the other end in the arrangement direction of the transfer image of the specific multi-line pattern formed on the object at each position in the optical axis direction An optical characteristic measuring method, wherein a second line width value corresponding to a width is obtained. In the optical characteristic measuring method according to claim 22,
In the fourth step, coma aberration is calculated based on a difference between the first line width value and the second line width value and an index value which is a ratio of the difference between the first line width value and the second line width value. Measurement method. The optical characteristic measuring method according to claim 25,
The method according to claim 1, wherein the comparison standard is a sum of the first line width value and the second line width value. . The optical characteristic measuring method according to claim 25,
The method according to claim 1, wherein the comparison criterion is 1. The optical characteristic measuring method according to claim 25,
The method according to claim 1, wherein the comparison criterion is an arrangement interval between adjacent line patterns in the arrangement direction. An optical characteristic measuring method for measuring an optical characteristic of a projection optical system that projects a pattern on a first surface onto a second surface,
The position of the object to be projected arranged on the second surface side of the projection optical system with respect to the optical axis direction of the projection optical system is changed within a predetermined range in a predetermined procedure, and the position of the object arranged on the first surface is changed. A first step of forming one image of the pattern by the projection optical system on the projection target object at each change position, and measuring the size of the image of the first pattern at each change position;
The position of the object to be projected arranged on the second surface side of the projection optical system in the optical axis direction of the projection optical system is changed in the predetermined procedure within the predetermined range, and is arranged on the first surface. A second step of forming an image of the obtained second pattern by the projection optical system on the projection target object at each change position, and measuring the size of the image of the second pattern at each change position;
A first correlation that is a correlation between the position of the projection target in the optical axis direction and the size of the image of the first pattern, and a position of the projection target in the optical axis direction and the second pattern. A third step of calculating an optical characteristic of the projection optical system based on a second correlation that is a correlation with an image size. The optical characteristic measuring method according to claim 29,
The first pattern and the second pattern are separate patterns simultaneously arranged on the first surface,
The method according to claim 1, wherein the first step and the third step are performed under the same exposure condition. The optical characteristic measuring method according to claim 29,
The method according to claim 1, wherein the first pattern and the second pattern include patterns having different line widths. The optical characteristic measuring method according to claim 29,
The method for measuring optical characteristics, wherein the first pattern and the second pattern include line patterns extending in different directions. The optical characteristic measuring method according to claim 29,
The method according to claim 1, wherein the first pattern and the second pattern include line patterns extending in the same direction. The optical characteristic measuring method according to claim 29,
The method according to claim 1, wherein the first pattern and the second pattern are the same pattern. The optical characteristic measuring method according to claim 29,
The method according to claim 1, wherein the first step and the third step are performed simultaneously. The optical characteristic measuring method according to claim 29,
The method according to claim 1, wherein the first step and the third step are performed separately under different exposure conditions. In the optical characteristic measuring method according to claim 36,
The first step is performed under a first condition such that a change in the size of the image of the first pattern has a minimum value;
The method according to claim 1, wherein the third step is performed under a second condition such that a change in the size of the image of the second pattern has a maximum value. The optical characteristic measuring method according to claim 29,
In the fifth step, based on the first correlation and the second correlation, the size of the projection image of the first pattern and the second Calculating a difference between the size of the projected image of the pattern and the position of the projected object in the optical axis direction; calculating a third correlation; Calculating a best focus position of the projection optical system. The optical characteristic measuring method according to claim 29,
The size of each image to be measured in the second and fourth steps is a line width value of each image,
The method of measuring optical characteristics, wherein the measurement of the line width value of each image is performed by electric resistance measurement. The optical characteristic measuring method according to claim 29,
At least one of the first pattern and the second pattern is arranged at a position on a predetermined mask corresponding to a plurality of evaluation points in a field of view of the projection optical system,
In the third step, based on the first correlation and the second correlation, the optical characteristics are determined by using the size of the image obtained by correcting the manufacturing error of the mask at that position for each evaluation point. An optical characteristic measuring method characterized by calculating. An optical characteristic measuring method for measuring an optical characteristic of a projection optical system that projects a pattern on a first surface onto a second surface,
Using a mask which is arranged on the first surface and has a plurality of measurement patterns formed at positions corresponding to a plurality of evaluation points in a field of view of the projection optical system, the projection optics of the plurality of measurement patterns A first step of forming an image by the system on the projection target object and measuring a size of each image;
Calculating an optical characteristic of the projection optical system using the size of the image in which the mask manufacturing error is corrected for each evaluation point based on the measurement result and the mask manufacturing error for each evaluation point position. And an optical characteristic measuring method including: 42. A step of measuring an optical characteristic of the projection optical system by the optical characteristic measuring method according to any one of claims 29 to 41;
Adjusting the projection optical system based on the measurement result of the optical characteristics. An optical characteristic measuring method for measuring an optical characteristic of a projection optical system that projects a pattern on a first surface onto a second surface,
A first pattern having a first line width is arranged on the first surface, and an image of the first pattern is formed on the projection target object arranged on the second surface via the projection optical system. Obtaining a first line width value corresponding to the line width of the image;
A second pattern having a second line width is arranged on the first surface, and an image of the second pattern is placed on the object to be projected arranged on the second surface via the projection optical system. A second step of forming under the same conditions as in the first step and obtaining a second line width value corresponding to the line width of the image;
A line of the pattern on the first surface based on a relationship between the first line width and the first line width value and a relationship between the second line width and the second line width value. A third step of calculating a correlation between the width and a line width value of an image formed on the projection target object;
A fourth step of calculating optical characteristics of the projection optical system based on the correlation. The optical characteristic measuring method according to claim 43,
In the fourth step, a new value included between the first line width and the second line width is defined as a third line width, and a new value for the third line width is determined based on the correlation. An optical characteristic measuring method comprising: calculating a line width value of an image; and calculating an optical characteristic of the projection optical system based on the line width value of the image. The optical characteristic measuring method according to claim 43,
In the first and second steps, each of the line width values is obtained by electric resistance measurement. An exposure method of irradiating a mask with an energy beam for exposure, and transferring a pattern formed on the mask onto an object via a projection optical system,
A step of adjusting the projection optical system in consideration of the optical characteristics measured by the projection optical system optical characteristic measurement method according to any one of claims 14, 16 to 41, and 43 to 45;
Transferring a pattern formed on the mask to the object via the adjusted projection optical system. A device manufacturing method including a lithography step,
47. A device manufacturing method using the exposure method according to claim 46 in the lithography step.

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