JP4147574B2 - Wavefront aberration measurement method, projection optical system adjustment method and exposure method, and exposure apparatus manufacturing method - Google Patents

Description

【００７７】
位置ずれ量のみでしか与えられていない波面の傾きをそのまま積分するのは容易ではないため、面形状を級数に展開して、これにフィットするものとする。この場合、級数は直交系を選ぶものとする。ツェルニケ多項式は軸対称な面の展開に適した級数で、円周方向は三角級数に展開する。すなわち、波面Ｗを極座標系（ρ，θ）で表すと、ツェルニケ多項式をＲ_n ^m（ρ）として、次式（５）のように展開できる。
【００７８】
【数２】

【００７９】
なお、Ｒ_n ^m（ρ）の具体的な形は、周知である（例えば光学の一般的な教科書などに記載されている）ので、詳細な説明は省略する。直交系であるから各項の係数、Ａ_n ^m，Ｂ_n ^mは独立に決定することができる。有限項で切ることはある種のフィルタリングを行うことに対応する。
【００８０】
実際には、その微分が上記の位置ずれ量として検出されるので、フィッティングは微係数について行う必要がある。極座標系（ｘ＝ρｃｏｓθ，ｙ＝ρｓｉｎθ）では、次式（６）、（７）のように表される。
【００８１】
【数３】

【００８２】
ツェルニケ多項式の微分形は直交系ではないので、フィッティングは最小自乗法で行う必要がある。１つの計測用パターンからの情報（ずれの量）はＸとＹ方向につき与えられるので、計測用パターンの数をＮ（Ｎは、例えば８１〜４００程度とする）とすると、上式（３）〜（７）で与えられる観測方程式の数は２Ｎ（＝１６２〜８００程度）となる。これから例えば２７の係数を決めるため各係数の誤差はかなり小さくなる（面の傾きを表すＡ₁ ¹，Ｂ₁ ¹を除けば係数のばらつきは数ｎｍ程度に収まっている）。
【００８３】
ツェルニケ多項式のそれぞれの項は光学収差に対応する。しかも低次の項はザイデル収差にほぼ対応する。従って、ツェルニケ多項式を用いることにより、投影光学系ＰＬの波面収差を求めることができる。
【００８４】
そこで、主制御装置５０では、前述のようにして位置ずれ量（Δξ，Δη）を算出した後、所定の演算プログラムを用いて、位置ずれ量（Δξ，Δη）に基づいて、前述した原理に従って、各領域Ｓ_i,jに対応する、すなわち投影光学系ＰＬの視野内の第１計測点〜第ｎ計測点に対応する波面（波面収差）、ここでは、ツェルニケ多項式の各項の係数、例えば第２項の係数Ｚ₂〜第３６項の係数Ｚ₃₆を演算する。
【００８５】
ところで、本実施形態の露光装置１０では、定期的にメンテナンスが行われる。その際に、前述した計測用レチクルＲ_T及びＣＣＤエリアイメージセンサ４５等を用いて、前述した手順で波面収差の計測が行われ、その計測結果に基づいて、投影光学系ＰＬが調整される。この調整は、例えば、主制御装置５０が波面収差の計測結果に基づいて、非点収差、コマ収差、ディストーション、像面湾曲（又はフォーカス）、球面収差などの低次収差、すなわちザイデルの５収差等を求め、これらの収差を補正すべき旨の指令を結像特性補正コントローラ４８に与える。これにより、結像特性補正コントローラ４８により、可動レンズ１３₁〜１３₄のうちの少なくとも１つの所定の可動レンズを、少なくとも１自由度方向に駆動する所定の駆動素子に対する印加電圧が制御され、前記所定の可動レンズの位置及び姿勢の少なくとも一方が調整され、投影光学系ＰＬの結像特性、例えばディストーション、像面湾曲、コマ収差、球面収差、及び非点収差等が補正される。
【００８６】
この場合において、予め各可動レンズの各自由度方向の単位駆動量と、波面収差（ツェルニケ多項式の各項の係数）の変化量との関係を予め求め、これをデータベースとしてメモリ内に記憶しておくとともに、このデータベースとツェルニケ多項式の各項の係数とに基づいて結像特性の調整量を演算する調整量演算プログラムを準備しておくこととしても良い。このようにすると、主制御装置５０では、波面収差の計測結果（ツェルニケ多項式の各項の係数の算出値）が得られた時点で、上記のデータベースとその得られた波面収差の計測結果とを用いて上記の調整量演算プログラムに従って、可動レンズ１３₁〜１３₄を各自由度方向に駆動すべき調整量を演算し、この調整量の指令値を、結像特性補正コントローラ４８に与える。これにより、結像特性補正コントローラ４８により、可動レンズ１３₁〜１３₄をそれぞれの自由度方向に駆動する各駆動素子に対する印加電圧が制御され、可動レンズ１３₁〜１３₄の位置及び姿勢の少なくとも一方がほぼ同時に調整され、投影光学系ＰＬの結像特性、例えばディストーション、像面湾曲、コマ収差、球面収差、及び非点収差等が補正される。なお、コマ収差、球面収差、及び非点収差については、低次のみならず高次の収差をも補正可能である。
【００８７】
本実施形態の露光装置１０では、半導体デバイスの製造時には、レチクルとしてデバイス製造用のレチクルＲがレチクルステージＲＳＴ上に装填され、その後、レチクルアライメント及び不図示のウエハアライメント系のいわゆるベースライン計測、並びにＥＧＡ（エンハンスト・グローバル・アライメント）等のウエハアライメントなどの準備作業が行われる。その後、ウエハアライメント結果に基づいて、ウエハＷ上の各ショット領域をレチクルパターンの投影位置に位置決めするショット間ステッピング動作と露光動作とを繰り返す、ステップ・アンド・リピート方式の露光が行われる。なお、露光時の動作等は通常のステッパと異なるところがないので、詳細説明については省略する。
【００８８】
但し、露光装置１０では、露光に先立って、前述したメンテナンス時、あるいはその他必要なタイミングで、前述した投影光学系ＰＬの結像特性の補正（調整）が行われ、この結像特性補正後の投影光学系ＰＬを用いて、上記のステップ・アンド・リピート方式の露光が行われる。
【００８９】
次に、露光装置１０の製造方法について説明する。露光装置１０の製造に際しては、まず、複数のレンズ、ミラー等の光学素子などを含む照明光学系１２、投影光学系ＰＬ、多数の機械部品から成るレチクルステージ系やウエハステージ系などを、それぞれユニットとして組み立てるとともに、それぞれユニット単体としての所望の性能を発揮するように、光学的な調整、機械的な調整、及び電気的な調整等を行う。
【００９０】
次に、照明光学系１２や投影光学系ＰＬなどを露光装置本体に組むとともに、レチクルステージ系やウエハステージ系などを露光装置本体に取り付けて配線や配管を接続する。
【００９１】
次いで、照明光学系１２や投影光学系ＰＬについては、光学的な調整を更に行う。これは、露光装置本体への組み付け前と組み付け後とでは、それらの光学系、特に投影光学系ＰＬの光学特性が微妙に変化するからである。本実施形態では、この露光装置本体へ組み込み後に行われる投影光学系ＰＬの光学的な調整に際して、前述した計測用レチクルＲ_T及びＣＣＤエリアイメージセンサ４５等を用いて、前述した手順で、投影光学系ＰＬの波面収差の計測を行う。そして、この波面収差結果に基づいて、前述のメンテナンス時と同様にして、ザイデル収差等の補正が行われる。また、より高次の収差に基づいて必要であればレンズ等の組付けを再調整する。なお、再調整により所望の性能が得られない場合などには、一部のレンズを再加工する必要も生じる。なお、投影光学系ＰＬの光学素子の再加工を容易に行うため、投影光学系ＰＬを露光装置本体に組み込む前に前述の波面収差を計測し、この計測結果に基づいて再加工が必要な光学素子の有無や位置などを特定し、その光学素子の再加工と他の光学素子の再調整とを並行して行うようにしても良い。
【００９２】
その後、更に総合調整（電気調整、動作確認等）をする。これにより、光学特性が高精度に調整された投影光学系ＰＬを用いて、レチクルＲのパターンをウエハＷ上に精度良く転写することができる、本実施形態の露光装置１０を製造することができる。なお、露光装置の製造は温度およびクリーン度等が管理されたクリーンルームで行うことが望ましい。
【００９３】
以上説明したように、本実施形態によると、投影光学系ＰＬの波面収差の計測に際し、計測用レチクルＲ_TがレチクルステージＲＳＴ上に装填され、レチクルアライメントが行われた状態で、計測用レチクルＲ_T上の複数の計測用パターン６７_i,jが照明光で照明される。これにより、各計測用パターン６７_i,jが、個別に対応するピンホール状の開口７０_i,j及び投影光学系ＰＬを介してウエハステージＷＳＴ上に設けられた、投影光学系ＰＬの像面と共役な面に配置されたＣＣＤエリアイメージセンサ４５の撮像面に投影される。このとき、各計測用パターン６７_i,jの像は、前述の如く、投影光学系ＰＬによりそれぞれの計測用パターン６７_i,jを介した光の波面の理想波面に対する傾きに応じてずれた位置に結像される。そして、ＣＣＤエリアイメージセンサ４５によりそのずれた位置に結像された各計測用パターン６７_i,jの投影像６７’_i,jが撮像される。
【００９４】
そして、主制御装置５０により、その撮像結果に基づいて得られる各計測用パターンの投影位置の基準位置からの位置ずれ量に基づいて、所定の演算プログラムに従って投影光学系ＰＬの波面収差が算出される。
【００９５】
また、本実施形態では、各計測用パターン６７_i,jとして、Ｘ軸に対して角度θを成し所定幅を有する複数本の直線状パターンが所定ピッチで配列されたラインアンドスペースパターンと、Ｙ軸に対して角度θを成し所定幅を有する複数本の直線状パターンが所定ピッチで配列されたラインアンドスペースパターンとが、相互に直交して形成された網目状（ストリートライン状）のパターンが用いられている。そして、各計測用パターンのＸ軸方向に関する位置ずれ量は、Ｘ軸に対して角度θを成す直線状パターン部分のＸ軸方向に関する位置ずれ量を（１／ｔａｎθ）倍に拡大した量の計測結果に基づいて算出され、Ｙ軸方向に関する位置ずれ量は、前記直線状パターン部分のＹ軸方向に関する位置ずれ量を（１／ｔａｎθ）倍に拡大した量の計測結果に基づいて算出される。従って、実質的に位置ずれ量を上記拡大倍率に応じた高い分解能で計測することが可能となり、位置ずれ量の計測精度、ひいては波面収差の計測精度の向上が可能となる。
【００９６】
従って、本実施形態によると、マイクロレンズアレイを用いることなく、投影光学系の波面収差を高精度に計測することが可能となっている。
【００９７】
また、本実施形態によると、メンテナンス時等において定期的に投影光学系ＰＬの波面収差が精度良く計測され、この精度良く計測された波面収差の計測結果に基づいて投影光学系ＰＬが調整されるので、投影光学系ＰＬの光学特性を精度良く調整することができる。
【００９８】
そして、本実施形態に係る露光装置によると、露光に先立って、上述の如くして光学特性が調整された投影光学系ＰＬを用いて、レチクルＲのパターンがウエハＷ上に転写されるので、レチクルＲのパターンをウエハＷ上に精度良く転写することが可能になる。
【００９９】
さらに、本実施形態によると、露光装置１０の製造時においても、投影光学系ＰＬを露光装置本体に組み込んだ後において、前述のように投影光学系ＰＬの波面収差が計測され、その計測された波面収差に基づいて投影光学系ＰＬを調整するので、投影光学系の結像特性が精度良く調整される。従って、投影光学系の結像特性が精度良く調整された露光装置１０が製造され、該露光装置１０を用いて露光を行うことにより、レチクルパターンを投影光学系ＰＬを介してウエハ上に精度良く転写することが可能になる。
【０１００】
なお、上記実施形態では、計測用パターンの基準位置に対する位置ずれ量を１／ｔａｎθ倍に拡大した量を計測し、これをｔａｎθ倍して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、ＣＣＤエリアイメージセンサ４５の分解能が十分に高ければ、位置ずれ量を直接計測しても良い。かかる場合であっても、マイクロレンズアレイを用いることなく、上記実施形態と同様に、計測した位置ずれ量に基づいて投影光学系ＰＬの波面収差を精度良く求めることは可能である。この場合においても、露光装置の製造段階、及び製造後のいずれのときにおいても、波面収差を高精度に計測し、その計測結果に基づいて、投影光学系ＰＬの光学特性を高精度に調整することができる。また、この光学特性が精度良く調整された投影光学系ＰＬを用いてレチクルパターンをウエハ上に精度良く転写することができる。また、上記実施形態ではＣＣＤエリアイメージセンサ４５の画素を基準として計測用パターンの投影像の位置ずれ量を計測するものとしたが、例えばＣＣＤエリアイメージセンサ４５の撮像面に近接して基準パターンを配置し、この基準パターンに対する計測用パターンの投影像の位置ずれ量を計測するようにしても良い。また、上記実施形態において、レンズ系４３を拡大系として計測用パターンの投影位置の検出精度の向上を図るようにしても良い。ＣＣＤエリアイメージセンサ４５の撮像面に近接して基準パターンを配置する場合も同様である。
【０１０１】
なお、上記実施形態において、投影光学系ＰＬの像面とＣＣＤエリアイメージセンサ４５とを共役関係にするレンズ系４３の光学特性を計測しておき、例えばこの計測結果を用いて前述の位置ずれ量を求める、あるいは投影光学系の光学特性の計測結果を補正することが好ましい。これにより、そのレンズ系４３に起因した光学特性の計測誤差を低減することができる。
【０１０２】
なお、上記実施形態において、ＣＣＤエリアイメージセンサ４５に代えて、複数の計測用パターンの各投影位置に対応して、例えば複数の計測用パターンと対応する位置関係で、複数の撮像素子を投影光学系の像面（又はその共役面）に配置して各撮像素子により対応する計測用パターンの投影位置（すなわち各撮像素子を基準とする対応する計測用パターンの投影位置）を計測しても良い。この場合、複数の撮像素子の位置関係（間隔など）を計測しておき、例えばこの計測結果を考慮して、計測用パターン毎に前述の位置ずれ量を求める、あるいは投影光学系の光学特性の計測結果を補正することが望ましい。これにより、撮像素子の位置誤差などに起因した光学特性の計測誤差を低減することができる。同様に、ＣＣＤエリアイメージセンサ４５の各画素の配列を正確に計測しておき、この計測結果を考慮して、計測用パターン毎に前述の位置ずれ量を求める、あるいは投影光学系の光学特性の計測結果を補正することとしても良い。
【０１０３】
また、上記実施形態では、撮像素子として２次元撮像素子であるＣＣＤエリアイメージセンサを用い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、撮像素子としてＣＣＤラインセンサなどの１次元撮像素子を用い、これを画素の配列方向とは直交する方向に移動しつつ、計測用パターンの投影像の撮像を行うことにより、各投影像の投影位置の基準位置に対する位置ずれ量を計測し、この位置ずれ量に基づいて投影光学系ＰＬの波面収差を求めることも可能である。
【０１０４】
あるいは、少なくとも１つの撮像素子を第２面（投影光学系の像面又はこの共役面）内で移動して各計測用パターンの投影像を検出しても良い。この場合には、撮像素子の移動時に生じ得る位置決め誤差を例えば計測用パターンの投影位置毎に計測しておき、この計測結果を考慮して計測用パターン毎に前述の位置ずれ量を求める、あるいは投影光学系の光学特性の計測結果を補正することが望ましい。これにより、撮像素子の移動時の位置決め誤差などに起因した光学特性の計測誤差を低減することができる。
【０１０５】
なお、上記実施形態において、計測用レチクル上での複数の計測用パターンの位置関係（間隔など）を計測しておき、例えばこの計測結果をも考慮して投影光学系ＰＬの光学特性を求めることが望ましい。これにより、計測用レチクル上での計測用パターンの位置誤差（描画誤差）に起因した投影光学系ＰＬの光学特性の計測誤差を低減することができる。この場合も、上記と同様に、前述の位置ずれ量を求める際に、計測用パターンの位置誤差を考慮しても良いし、光学特性の計測結果を計測用パターンの位置誤差を用いて補正しても良い。
【０１０６】
また、上記実施形態では、投影光学系ＰＬの光学特性として波面収差を求める場合について説明したが、これに限らず、上記各計測用パターンの投影位置の所定の基準位置からの位置ずれ量に基づいて、波面収差以外の光学特性を求めることは可能である。
【０１０７】
なお、上記実施形態では、Ｚチルトステージ５８にＣＣＤエリアイメージセンサを有する撮像部４２が固定的に設けられた場合について説明したが、これに限らず、ウエハホルダの交換機構を備える場合（ウエハの搬送系がウエハホルダの搬送系を兼ねる場合を含む）には、ウエハホルダ２５に撮像素子（ＣＣＤエリアイメージセンサなど）を組み込み、そのウエハホルダを前記交換機構により非露光時にウエハステージ上に搭載し、そのウエハホルダを用いて投影光学系の波面収差を計測するようにしても良い。この場合、実際の露光に先立って、その計測に用いたウエハホルダを露光に用いるウエハホルダに再度交換するようにすれば良い。また、上記のウエハホルダには、撮像素子とともに基準照度計などを組み込むようにしても良い。
【０１０８】
また、上記実施形態では、撮像素子（ＣＣＤエリアイメージセンサ）を、投影光学系の像面の共役面に配置した状態で、投影像の撮像を行う場合について説明したが、これに限らず、投影光学系ＰＬの像面近傍の面（上記実施形態ではＺチルトステージ５８上の受光ガラスの配置面）に撮像素子を直接配置することとしても良く、撮像部４２の小型化を図ることができる。更に、投影光学系ＰＬの投影視野（照明光の照射領域）に対応して複数の計測用パターンをレチクルに形成することなく、少なくとも１つの計測用パターンをレチクルに形成するだけでも良く、この場合は投影光学系の物体面（第１面）内でそのレチクルを移動することになる。このとき、レチクルステージＲＳＴの移動時に生じ得る位置決め誤差を、例えば計測用パターンを配置すべき位置毎に計測しておき、この計測結果を用いて計測用パターン毎に前述の位置ずれ量を求める、あるいは投影光学系の光学特性の計測結果を補正することが望ましい。更に、上記実施形態では計測用レチクルを用いるものとしたが、例えばレチクルステージＲＳＴ上に少なくとも１つの計測用パターンを形成するとともに、投影光学系の光学特性の計測時にピンホールが形成されたプレートをレチクルのパターン面に近接して配置する、あるいはレチクルステージの下面にその計測用パターンに近接してピンホール板を設けても良い。すなわち、光学特性の計測に用いるマスクはマスク又はレチクルに限られるものではなく、例えばレチクルステージなどに設けられるパターン板などであっても良い。
【０１０９】
なお、上記実施形態では、本発明がステッパに適用された場合について説明したが、これに限らず、例えば米国特許第５，４７３，４１０号等に開示されるマスクと基板とを同期移動してマスクのパターンを基板上に転写する走査型の露光装置にも適用することができる。
【０１１０】
露光装置の用途としては半導体製造用の露光装置に限定されることなく、例えば、角型のガラスプレートに液晶表示素子パターンを転写する液晶用の露光装置や、薄膜磁気ヘッド、マイクロマシーン及びＤＮＡチップなどを製造するための露光装置にも広く適用できる。また、半導体素子などのマイクロデバイスだけでなく、光露光装置、ＥＵＶ露光装置、Ｘ線露光装置、及び電子線露光装置などで使用されるレチクル又はマスクを製造するために、ガラス基板又はシリコンウエハなどに回路パターンを転写する露光装置にも本発明を適用できる。
【０１１１】
また、上記実施形態の露光装置の光源は、Ｆ₂レーザ光源、ＡｒＦエキシマレーザ光源、ＫｒＦエキシマレーザ光源などの紫外パルス光源に限らず、ｇ線（波長４３６ｎｍ）、ｉ線（波長３６５ｎｍ）などの輝線を発する超高圧水銀ランプを用いることも可能である。
【０１１２】
また、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、投影光学系の倍率は縮小系のみならず等倍および拡大系のいずれでも良い。
【０１１３】
なお、半導体デバイスは、デバイスの機能・性能設計を行うステップ、この設計ステップに基づいたレチクルを製作するステップ、シリコン材料からウエハを製作するステップ、前述した実施形態の露光装置によりレチクルのパターンをウエハに転写するステップ、デバイス組み立てステップ（ダイシング工程、ボンディング工程、パッケージ工程を含む）、検査ステップ等を経て製造される。
【０１１４】
【発明の効果】
以上説明したように、本発明の波面収差計測方法によれば、マイクロレンズアレイを用いることなく、投影光学系の波面収差を高精度に計測することができるという効果がある。
【０１１５】
また、本発明の投影光学系の調整方法によれば、投影光学系の光学特性を精度良く調整することができるという効果がある。
【０１１６】
また、本発明の露光方法によれば、マスクのパターンを基板上に精度良く転写することが可能な露光方法が提供される。
【０１１７】
また、本発明の露光装置の製造方法によれば、マスクのパターンを基板上に精度良く転写することが可能な露光装置の製造方法が提供される。
【図面の簡単な説明】
【図１】一実施形態に係る露光装置の概略構成を示す図である。
【図２】図１のＺチルトステージを一部破断し、かつ一部省略して示す拡大図である。
【図３】計測用レチクルを示す概略斜視図である。
【図４】レチクルステージ上に装填した状態における計測用レチクルの光軸近傍のＸＺ断面の概略図を投影光学系の模式図とともに示す図である。
【図５】図３のガラス基板を取り出して示す底面図である。
【図６】ＣＣＤエリアイメージセンサの撮像面に形成される計測用パターンの縮小像（投影像）を示す図である。
【図７】計測用パターンの位置ずれ量を拡大して計測する方法を示す図である。
【符号の説明】
１０…露光装置、４５…ＣＣＤエリアイメージセンサ（撮像素子）、６６…開口板、６７_i,j…計測用パターン、７０_i,j…ピンホール状の開口、ＥＬ…照明光、ＰＬ…投影光学系、Ｒ…レチクル（マスク）、Ｒ_T…計測用レチクル（計測用マスク）、Ｗ…ウエハ（基板）。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wavefront aberration measuring method, a projection optical system adjustment method and an exposure method, and an exposure apparatus manufacturing method. More specifically, the present invention relates to a projection optical system that projects a pattern on a first surface onto a second surface. Wavefront aberration measurement method suitable for wavefront aberration measurement, projection optical system adjustment method for adjusting projection optical system based on measurement result of wavefront aberration measured by the method, and projection optical system adjusted by the adjustment method The present invention relates to an exposure method for transferring a mask pattern onto a substrate, and a method for manufacturing an exposure apparatus including the wavefront aberration measurement method.
[0002]
[Prior art]
Conventionally, in lithography processes for manufacturing semiconductor elements (CPU, DRAM, etc.), imaging elements (CCD, etc.), liquid crystal display elements, thin film magnetic heads, etc., various exposure apparatuses for forming device patterns on a substrate have been used. Yes. In recent years, along with the high integration of semiconductor elements and the like, a step-and-repeat reduction projection exposure apparatus (so-called stepper) that can form a fine pattern on a substrate such as a wafer or a glass plate with high throughput and high accuracy. Projection exposure apparatuses such as a step-and-scan type scanning exposure apparatus (so-called scanning stepper) obtained by improving the stepper are mainly used.
[0003]
By the way, when manufacturing a semiconductor element or the like, it is necessary to stack different circuit patterns on the substrate in layers, so that a reticle (or mask) on which the circuit pattern is drawn and each shot on the substrate are used. It is important to accurately overlay the pattern already formed in the region. In order to perform such superposition with high accuracy, it is necessary to accurately measure the optical characteristics of the projection optical system, and to adjust and manage it in a desired state.
[0004]
Conventionally, as a method for measuring the optical characteristics of a projection optical system, a resist obtained by performing exposure using a measurement mask on which a predetermined measurement pattern is formed and developing a substrate onto which the projection image of the measurement pattern is transferred A method of calculating optical characteristics based on a measurement result obtained by measuring an image (hereinafter referred to as “baking method”) is mainly used. In addition to this, without actually performing exposure, the measurement mask is illuminated with illumination light, and a spatial image (projected image) of the measurement pattern formed by the projection optical system is measured. Based on the measurement result, the optical characteristics are measured. A calculation method (hereinafter referred to as “aerial image measurement method”) is also performed.
[0005]
In conventional exposure apparatuses, low-order aberrations such as so-called Seidel's five aberrations, spherical aberration, coma, astigmatism, field curvature, distortion, and distortion are measured by the printing method or the aerial image measurement method. Based on the measurement results, the above-mentioned various aberrations of the projection optical system are mainly adjusted and managed.
[0006]
However, semiconductor devices are highly integrated year by year, and accordingly, exposure apparatuses are required to have higher precision exposure performance. In recent years, it is not possible to adjust only the low-order aberrations. It is enough. Therefore, not only when assembling the exposure apparatus in the manufacturing factory, but also after installation in the clean room of the device manufacturing factory, the wavefront aberration of the projection optical system is measured to include the higher order aberrations. There is a need to maintain properties.
[0007]
As a wavefront aberration measuring apparatus for measuring wavefront aberration after manufacturing an exposure apparatus, a Shack-Hartmann wavefront aberration measuring apparatus using a microlens array is disclosed in, for example, International Publication WO99 / 60361.
[0008]
[Problems to be solved by the invention]
However, it is difficult to manufacture a microlens array that is as accurate and small as required for a wavefront aberration measuring instrument with current manufacturing techniques. For this reason, in the type of wavefront aberration measuring instrument using a microlens array, downsizing as well as improvement in the measurement accuracy has become a major issue in the present and the future. Further, in this type of wavefront aberration measuring instrument, an optical system must be arranged between the image plane of the projection optical system and the microlens array, and it is difficult to reduce the size of the measuring instrument. In some cases, the influence of aberrations cannot be ignored.
[0009]
The present invention has been made under such circumstances, and a first object thereof is a wavefront aberration measuring method capable of measuring the wavefront aberration of a projection optical system with high accuracy without using a microlens array. It is to provide.
[0010]
A second object of the present invention is to provide a projection optical system adjustment method capable of accurately adjusting the optical characteristics of the projection optical system.
[0011]
A third object of the present invention is to provide an exposure method capable of accurately transferring a mask pattern onto a substrate.
[0012]
A fourth object of the present invention is to provide a method of manufacturing an exposure apparatus that can accurately transfer a mask pattern onto a substrate.
[0013]
[Means for Solving the Problems]
  The invention according to claim 1 is a wavefront aberration measuring method for measuring a wavefront aberration of a projection optical system (PL) that projects a pattern on a first surface onto a second surface, and is predetermined on the first surface. Arranged in a positional relationshipAnd a linear pattern portion having a predetermined width that forms a predetermined angle θ (0 ° <θ <45 °) with respect to a specific direction.Multiple measurement patterns (67_{i, j}) With illumination light, and each of the plurality of measurement patterns is provided with a pinhole-like opening (70) provided corresponding to each measurement pattern._{i, j}And projecting onto the second surface via the projection optical system; imaging a projected image of each measurement pattern with an imaging device disposed on the second surface; Obtained based onBased on the result of enlarging (1 / tan θ) times at least one of the positional deviation amount from the reference position in the specific direction of the linear pattern portion and the positional deviation amount from the reference position in the direction orthogonal to the specific direction. AndDetermining a wavefront aberration of the projection optical system.
[0014]
  According to this, it is arranged in a predetermined positional relationship on the first surface.And includes a linear pattern portion having a predetermined width with respect to a specific direction.A plurality of measurement patterns are illuminated with illumination light, and each of the plurality of measurement patterns is provided through the pinhole-shaped opening provided corresponding to each measurement pattern and the projection optical system. Project onto two sides. As a result, a projected image of each measurement pattern is formed on the second surface. This projected image is picked up by an image pickup device arranged on the second surface.
[0015]
In this case, the projection image of each measurement pattern is imaged on the second surface at a position shifted according to the inclination of the wavefront on the pupil plane of the projection optical system with respect to the ideal wavefront. The projected image formed on the image is picked up.
[0016]
The positional deviation amount of each measurement pattern in the specific direction can be calculated based on a measurement result of an amount obtained by enlarging the positional deviation amount of the linear pattern portion in the specific direction by (1 / tan θ) times. The positional deviation amount in the direction orthogonal to the specific direction is calculated based on the measurement result of the amount obtained by enlarging the positional deviation amount of the linear pattern portion in the direction orthogonal to the specific direction by (1 / tan θ) times. be able to.AndThis calculation result, that is,The wavefront aberration of the projection optical system is obtained based on the amount of positional deviation from the reference position of the projection position of each measurement pattern. Therefore, according to the present invention, the wavefront aberration of the projection optical system can be measured with high accuracy without using a microlens array.
[0017]
  In this case, when a projection image arranged in a two-dimensional plane is picked up, a one-dimensional image pickup device such as a CCD line sensor is used as the image pickup device, and this is picked up while moving in a direction orthogonal to the pixel arrangement direction. You can do that. However, the present invention is not limited to this. For example, as in the wavefront aberration measuring method according to claim 2, the imaging device is a two-dimensional imaging device in which pixels are arranged in a matrix in orthogonal two-axis directions.Specific directionIs in either of the orthogonal biaxial directionsCan be.
[0018]
According to a third aspect of the present invention, there is provided a step of measuring the wavefront aberration of the projection optical system using the wavefront aberration measuring method according to the first or second aspect; and the projection optical system based on the measurement result of the wavefront aberration. Adjusting the projection optical system.
[0019]
According to this, since the wavefront aberration of the projection optical system is measured using the wavefront aberration measurement methods described in claims 1 and 2, the wavefront aberration of the projection optical system is accurately measured. Since the projection optical system is adjusted based on the measurement result of the wavefront aberration measured with high accuracy, the optical characteristics of the projection optical system can be adjusted with high accuracy.
[0020]
According to a fourth aspect of the present invention, there is provided an exposure method for transferring a pattern of a mask (R) onto a substrate (W) via a projection optical system (PL), wherein the projection is performed by the adjustment method according to the third aspect. An exposure method comprising: adjusting an optical system; and transferring the pattern onto the substrate through the adjusted projection optical system.
[0021]
According to this, since the projection optical system is adjusted using the adjustment method according to claim 3, the optical characteristics of the projection optical system are adjusted with high precision, and the projection optical system with the optical characteristics adjusted with high precision is used. Since the mask pattern is transferred onto the substrate, the mask pattern can be transferred onto the substrate with high accuracy.
[0022]
A fifth aspect of the present invention is a method of manufacturing an exposure apparatus (10) for transferring a pattern of a mask (R) onto a substrate (W) via a projection optical system (PL). A method of measuring the wavefront aberration of the projection optical system using the wavefront aberration measurement method according to claim 1, and a step of adjusting the projection optical system based on the measurement result of the wavefront aberration. .
[0023]
According to this, since the optical characteristics of the projection optical system are accurately measured using the optical characteristic measurement methods according to claims 1 and 2, and the projection optical system is adjusted based on the measured optical characteristics, The optical characteristics (including imaging characteristics) of the projection optical system are adjusted with high accuracy. Accordingly, an exposure apparatus in which the optical characteristics of the projection optical system are adjusted with high precision is manufactured, and the mask pattern is accurately transferred onto the substrate via the projection optical system by performing exposure using the exposure apparatus. Is possible.
[0024]
The second surface includes not only the image plane of the projection optical system but also its conjugate plane. When the conjugate plane with the image plane of the projection optical system is the second plane, the image plane and the second plane are It is preferable to measure the optical characteristics of the optical system in a conjugate relationship and obtain the above-described positional deviation amount using this measurement result, or correct the measurement result of the optical characteristics of the projection optical system, for example. Thereby, the measurement error of the optical characteristic resulting from the optical system can be reduced. At this time, the optical system may be a reduction system or an equal magnification system, but may be designed to improve the detection accuracy of the projection position of the measurement pattern as an enlargement system.
[0025]
Further, for each projection position of a plurality of measurement patterns, for example, a plurality of image sensors are arranged on the second surface in a positional relationship corresponding to the plurality of measurement patterns, and the corresponding measurement is performed by each image sensor. The projection position of the pattern (that is, the projection position of the corresponding measurement pattern based on each image sensor) may be measured, or at least one image sensor may be moved in the second plane to A projected image may be detected. In the former case, the positional relationship (interval and the like) of a plurality of image sensors is measured, and for example, the above-described positional deviation amount is obtained for each measurement pattern in consideration of the measurement result, or the projection optical system It is desirable to correct the measurement result of the optical characteristics. Thereby, the measurement error of the optical characteristic due to the position error of the image sensor can be reduced. On the other hand, in the latter case, a positioning error that may occur when the image sensor is moved is measured for each projection position of the measurement pattern, for example, and the above-described positional deviation amount is calculated for each measurement pattern in consideration of the measurement result. It is desirable to obtain or correct the measurement result of the optical characteristics of the projection optical system. As a result, it is possible to reduce an optical characteristic measurement error caused by a positioning error or the like during movement of the image sensor.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a schematic configuration of an exposure apparatus 10 according to an embodiment for carrying out the wavefront aberration measuring method according to the present invention. The exposure apparatus 10 is a step-and-repeat reduction projection exposure apparatus using a pulse laser light source as an exposure light source (hereinafter referred to as “light source”), that is, a so-called stepper.
[0027]
The exposure apparatus 10 includes an illumination system including a light source 16 and an illumination optical system 12, and a reticle stage as a mask stage that holds a reticle R as a mask illuminated by exposure illumination light EL as an energy beam from the illumination system. RST, a projection optical system PL that projects the exposure illumination light EL emitted from the reticle R onto a wafer W (image surface) as a substrate, and a Z tilt stage 58 that holds the wafer W as a substrate stage Wafer stage WST and control system thereof are provided.
[0028]
Here, an ArF excimer laser light source (output wavelength 193 nm) is used as the light source 16. As the light source 16, F is used.₂A light source that outputs pulsed light in the vacuum ultraviolet region such as a laser light source (output wavelength 157 nm) or a light source that outputs pulsed light in the near ultraviolet region such as a KrF excimer laser light source (output wavelength 248 nm) may be used.
[0029]
The light source 16 is actually a clean room in which a chamber 11 in which an exposure apparatus main body including the constituent elements of the illumination optical system 12 and the reticle stage RST, the projection optical system PL, the wafer stage WST, and the like is housed is installed. It is installed in another low clean room, and is connected to the chamber 11 via a light transmission optical system (not shown) including at least a part of an optical axis adjusting optical system called a beam matching unit. Based on the control information TS from the main controller 50, the light source 16 is turned on and off by the internal controller, the output of the laser beam LB, the energy per pulse of the laser beam LB, the oscillation frequency (repetition frequency), The center wavelength, spectrum half width, etc. are controlled.
[0030]
The illumination optical system 12 includes a cylinder lens, a beam expander, a zoom optical system (all not shown), a fly-eye lens as an optical integrator (homogenizer), or an internal reflection type integrator (fly-eye lens in this embodiment) 22 and the like. Including a beam shaping / illumination uniformity optical system 20, an illumination system aperture stop plate 24, a first relay lens 28A, a second relay lens 28B, a reticle blind 30, a mirror M for folding an optical path, a condenser lens 32, and the like. .
[0031]
The beam shaping / illuminance uniformity optical system 20 is connected to a light transmission optical system (not shown) through a light transmission window 17 provided in the chamber 11. The beam shaping / illuminance equalizing optical system 20 shapes the cross-sectional shape of the laser beam LB that is pulsed by the light source 16 and incident through the light transmission window 17 using, for example, a cylinder lens or a beam expander. The fly-eye lens 22 located on the exit end side in the beam shaping / illumination uniformity optical system 20 is irradiated with a laser beam whose cross-sectional shape is shaped in order to illuminate the reticle R with a uniform illumination distribution. A surface light source (secondary light source) composed of a large number of point light sources (light source images) is formed on the exit-side focal plane arranged so as to substantially coincide with the pupil plane of the illumination optical system 12. Hereinafter, the laser beam emitted from the secondary light source is referred to as “illumination light EL”.
[0032]
An illumination system aperture stop plate 24 made of a disk-like member is disposed in the vicinity of the exit-side focal plane of the fly-eye lens 22. The illumination system aperture stop plate 24 is provided with an aperture stop (small aperture) made up of, for example, a normal circular aperture, and an aperture stop (small size) for reducing the σ value that is a coherence factor made up of a small circular aperture at substantially equal angular intervals. σ stop), an annular aperture stop for annular illumination (annular stop), and a modified aperture stop in which a plurality of openings are arranged eccentrically for the modified light source method (two of these are shown in FIG. 1). Only the aperture stop is shown). The illumination system aperture stop plate 24 is rotated by a drive device 40 such as a motor controlled by the main control device 50, whereby any aperture stop is selectively placed on the optical path of the illumination light EL. The light source surface shape in Koehler illumination, which will be described later, is limited to an annular zone, a small circle, a large circle, or the fourth. In the present embodiment, the aperture stop plate 24 is used to change the illumination light quantity distribution (the shape and size of the secondary light source) on the pupil plane of the illumination optical system, that is, the illumination condition of the reticle R. However, instead of or in combination with the aperture stop plate 24, for example, a plurality of diffractive optical elements that are exchanged on the optical path of the illumination optical system, at least one movable along the optical axis of the illumination optical system An optical unit including at least one of a prism (conical prism, polyhedral prism, and the like) and a zoom optical system is disposed between the light source 16 and the optical integrator (fly-eye lens) 22, and the optical integrator (fly-eye lens) 22 Minimize the light loss caused by changing the illumination conditions described above by making the intensity distribution of the illumination light on the incident surface or the incident angle range of the illumination light variable. It is preferable to suppress.
[0033]
A relay optical system including a first relay lens 28A and a second relay lens 28B is disposed on the optical path of the illumination light EL emitted from the illumination system aperture stop plate 24 with a reticle blind 30 interposed therebetween. The reticle blind 30 is disposed on a conjugate plane with respect to the pattern surface of the reticle R, and a rectangular opening that defines a rectangular illumination area IAR on the reticle R is formed. Here, as the reticle blind 30, a movable blind having a variable opening shape is used, and the opening is set by the main controller 50 based on blind setting information also called masking information.
[0034]
On the optical path of the illumination light EL behind the second relay lens 28B constituting the relay optical system, a bending mirror M that reflects the illumination light EL that has passed through the second relay lens 28B toward the reticle R is disposed. A condenser lens 32 is disposed on the optical path of the illumination light EL behind the mirror M.
[0035]
In the above configuration, the entrance surface of the fly-eye lens 22, the placement surface of the reticle blind 30, and the pattern surface of the reticle R are optically conjugate with each other and formed on the exit-side focal plane of the fly-eye lens 22. The light source plane (pupil plane of the illumination optical system) and the Fourier transform plane (exit pupil plane) of the projection optical system PL are optically conjugate with each other to form a Koehler illumination system.
[0036]
The operation of the illumination optical system 12 configured as described above will be briefly described. After the laser beam LB pulsed from the light source 16 enters the beam shaping / illuminance equalizing optical system and the cross-sectional shape is shaped, , Enters the fly-eye lens 22. Thereby, the secondary light source described above is formed at the exit end of the fly-eye lens 22.
[0037]
The illumination light EL emitted from the secondary light source passes through any one of the aperture stops on the illumination system aperture stop plate 24, and then passes through the rectangular opening of the reticle blind 30 via the first relay lens 28A. After passing through the second relay lens 28B, the optical path is bent vertically downward by the mirror M, and then through the condenser lens 32, the rectangular illumination area IAR on the reticle R held on the reticle stage RST is uniformly illuminated. Illuminate with.
[0038]
A reticle R is loaded on the reticle stage RST, and is held by suction via an electrostatic chuck (or vacuum chuck) (not shown). Reticle stage RST is configured to be capable of minute driving (including rotation) in a horizontal plane (XY plane) by a drive system (not shown). In addition, reticle stage RST is configured to be movable within a predetermined stroke range (about the length of reticle R) in the Y-axis direction. Note that the position of the reticle stage RST is measured by a position detector (not shown) such as a reticle laser interferometer with a predetermined resolution (for example, a resolution of about 0.5 to 1 nm), and the measurement result is sent to the main controller 50. It comes to be supplied.
[0039]
As the projection optical system PL, for example, a double telecentric reduction system is used. The projection magnification of the projection optical system PL is, for example, 1/4, 1/5, or 1/6. Therefore, as described above, when the illumination area IAR on the reticle R is illuminated by the illumination light EL, an image obtained by reducing the pattern formed on the reticle R by the projection optical system PL at the projection magnification is the surface. And projected onto a rectangular exposure area IA (usually coincident with the shot area) on the wafer W coated with a resist (photosensitive agent).
[0040]
As the projection optical system PL, as shown in FIG. 1, a refraction system including only a plurality of, for example, about 10 to 20 refractive optical elements (lenses) 13 is used. Among a plurality of lenses 13 constituting the projection optical system PL, a plurality of lenses 13 on the object plane side (reticle R side) (here, four lenses 13 are used for the sake of simplicity).₁, 13₂, 13_Three, 13_FourIs a movable lens that can be driven externally by the imaging characteristic correction controller 48. Lens 13₁, 13₂, 13_FourAre respectively held by lens holders (not shown), and these lens holders are supported at three points in the direction of gravity by driving elements (not shown) such as piezoelectric elements. Then, by independently adjusting the voltage applied to these drive elements, the lens 13₁, 13₂, 13_FourThat can be driven in the Z-axis direction, which is the optical axis direction of the projection optical system PL, and can be driven (tiltable) in the tilt direction with respect to the XY plane (that is, the rotation direction around the X axis and the rotation direction around the Y axis) It has become. The lens 13_ThreeIs held by a lens holder (not shown), and driving elements such as piezo elements are disposed at an outer peripheral portion of the lens holder at an interval of approximately 90 °, for example. The lens 13 is adjusted by adjusting the voltage applied to each drive element._ThreeIs configured to be capable of two-dimensional shift driving in the XY plane.
[0041]
Note that the reticle R and the optical element (particularly the lens element) of the projection optical system PL are appropriately selected depending on the wavelength of the illumination light EL. For example, when the wavelength of the illumination light EL is about 190 nm or more (the illumination light EL is ArF excimer laser light, KrF excimer laser light, etc.), synthetic quartz can be used. However, for example, the wavelength of the illumination light EL is about 180 nm or less (the illumination light EL is F₂In the case of laser light, etc., it is difficult to use synthetic quartz in terms of transmittance, etc., so fluoride crystals such as fluorite and synthetic quartz doped with impurities (such as fluorine) are used.
[0042]
Wafer stage WST is freely driven in an XY two-dimensional plane by wafer stage drive unit 56. On the Z tilt stage 58 mounted on the wafer stage WST, the wafer W is held via the wafer holder 25 by electrostatic adsorption (or vacuum adsorption) or the like. The Z tilt stage 58 has a function of adjusting the position of the wafer W in the Z direction (focus position) and adjusting the tilt angle of the wafer W with respect to the XY plane. Further, the X and Y positions and rotation (including yawing, pitching and rolling) of wafer stage WST are measured by an external wafer laser interferometer 54W via a movable mirror 52W fixed on Z tilt stage 58, and this wafer laser The measurement value of the interferometer 54W is supplied to the main controller 50.
[0043]
On the Z tilt stage 58, a reference mark plate FM is fixed to one side of the wafer holder 25 so that the surface thereof is substantially the same height as the surface of the wafer W. On the surface of the reference mark plate FM, a first reference mark for so-called baseline measurement of a wafer alignment system (not shown) and a pair of second reference marks used for reticle alignment at the time of exposure are formed.
[0044]
Further, on the Z tilt stage 58, an image pickup unit 42 having a CCD area image sensor 45 as an image pickup element used for measurement of wavefront aberration described later is provided on the other side of the wafer holder 25. As shown in FIG. 2, the imaging unit 42 is fixed on the Z tilt stage 58 and closes the cylindrical casing 44 whose upper and lower surfaces are open and the opening on the upper surface side of the casing 44. A light receiving glass 46 made of a fluoride crystal such as fluorite, and a lens system 43 and a CCD area image sensor 45 disposed inside the Z tilt stage 58 so as to face the light receiving glass 46 are provided. An opening 58 a is formed in the wall surface of the Z tilt stage above the lens system 43.
[0045]
On the surface of the light-receiving glass 46, a reflective film 59 that also serves as a light-shielding film made of a chromium layer is formed, and an opening serving as an optical path of light incident on the CCD area image sensor 45 is formed at the center of the reflective film 59. . The surface of the light receiving glass 46 is almost the same height as the surface of the wafer W. The imaging surface of the CCD area image sensor 45 is a surface optically conjugate with the surface of the light receiving glass 46. In addition, a pair of alignment marks (not shown) similar to the second reference mark described above are formed on the surface of the light receiving glass 46. The imaging signal P output from the CCD area image sensor 45 is supplied to the main controller 50.
[0046]
The control system of the exposure apparatus 10 is mainly configured by the main controller 50 in FIG. The main controller 50 is constituted by a so-called workstation (or microcomputer) composed of a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), etc., and performs an exposure operation. For example, step-to-shot stepping of wafer stage WST, exposure timing, and the like are integrated and controlled so as to be performed accurately.
[0047]
Next, a measurement reticle R as a measurement mask used when measuring the optical characteristics of the projection optical system PL of the exposure apparatus 10 of the present embodiment._TWill be described.
[0048]
FIG. 3 shows this measurement reticle R._TA schematic perspective view of is shown. FIG. 4 shows reticle R in a state where it is loaded on reticle stage RST._TA schematic diagram of an XZ cross section in the vicinity of the optical axis AX is shown together with a schematic diagram of the projection optical system PL.
[0049]
As is apparent from FIG. 3, this measurement reticle R_TThe overall shape is substantially the same as that of a normal reticle with a pellicle. This measuring reticle R_T3 shows a glass substrate 60 as a pattern forming member, a lens mounting member 62 having a rectangular plate shape fixed to the center of the upper surface of the glass substrate 60 in FIG. 3, and a glass substrate 60 in FIG. A spacer member 64 made of a frame-like member having the same appearance as a normal pellicle frame attached to the lower surface, an opening plate 66 attached to the lower surface of the spacer member 64, and the like are provided.
[0050]
The lens mounting member 62 has n circular openings 63 arranged in a matrix in substantially the entire region excluding some band-like regions at both ends in the Y-axis direction._{i, j}(I = 1 to p, j = 1 to q, p × q = n) are formed. Each circular opening 63_{i, j}Is a condenser lens 65 made of a convex lens having an optical axis in the Z-axis direction._{i, j}Are provided (see FIG. 3).
[0051]
Further, as shown in FIG. 4, reinforcing members 69 are provided at predetermined intervals in a space surrounded by the glass substrate 60, the spacer member 64, and the opening plate 66.
[0052]
Further, each of the condenser lenses 65_{i, j}4, the measurement pattern 67 is formed on the lower surface of the glass substrate 60 as shown in FIG._{i, j}Are formed respectively. In addition, as shown in FIG._{i, j}A pinhole-shaped opening 70 facing each other_{i, j}Is formed. This pinhole-shaped opening 70_{i, j}Is, for example, about 100 to 150 μm in diameter.
[0053]
Further, as shown in FIG. 3, a pair of reticle alignment marks RM1 and RM2 are formed symmetrically with respect to the reticle center on both outer sides of the lens holding member 62 on the X axis passing through the reticle center of the glass substrate 60. Has been.
[0054]
FIG. 5 shows a plan view (bottom view) of the glass substrate 60 taken out and viewed from the lower surface side in FIG. As shown in FIG. 5, in this embodiment, each measurement pattern 67_{i, j}As a pattern, a net-like (street line) pattern is used, which is a line pattern having a predetermined angle θ (0 ° <θ <45 °) with respect to the X-axis direction and the Y-axis direction. Each measurement pattern 67_{i, j}Is a so-called blank pattern formed by patterning the chromium layer, that is, a pattern in which light is transmitted through only a portion of the pattern.
[0055]
The measurement pattern 67_{i, j}Is not limited to this, and patterns of other shapes may be used, but a predetermined width that intersects at least a predetermined angle θ (0 ° <θ <45 °) with respect to either the X-axis direction or the Y-axis direction. It is desirable that the pattern includes a line pattern.
[0056]
Next, measurement reticle R_TA procedure for measuring the optical characteristics of the projection optical system PL will be described with reference to FIG.
[0057]
First, in main controller 50, measurement reticle R is passed through a reticle loader (not shown)._TIs loaded onto reticle stage RST. Next, main controller 50 moves wafer stage WST via wafer stage drive unit 56 while monitoring the output of laser interferometer 54W, and a pair of alignment marks (on the surface of light receiving glass 46 described above) (Not shown) is positioned at a predetermined reference position. Here, the reference position is determined, for example, at a position where the centers of the pair of alignment marks coincide with the origin on the stage coordinate system defined by the laser interferometer 54W.
[0058]
Next, in the main controller 50, a measurement reticle R_TThe pair of reticle alignment marks RM1 and RM2 and the corresponding alignment mark on the light receiving glass 46 are simultaneously observed with a pair of reticle alignment microscopes (not shown) and onto the light receiving glass 46 of the reticle alignment marks RM1 and RM2. The reticle stage RST is slightly driven in the XY two-dimensional plane via a drive system (not shown) so that the amount of positional deviation between the projected image and the corresponding alignment mark is minimized. As a result, the reticle alignment is completed, the reticle center substantially coincides with the optical axis of the projection optical system PL, and the measurement reticle R_TIs also adjusted.
[0059]
Next, the main controller 50 measures the Z position of the light receiving glass by an oblique incident light type focal position detection system (not shown), and finely drives the Z tilt stage in the Z-axis direction based on the measurement result. The surface of the light receiving glass 46 is made to substantially coincide with the image plane of the projection optical system PL.
[0060]
Next, in the main controller 50, a measurement reticle R_TCondensing lens 65_{i, j}In order to form a rectangular illumination region having a length in the X-axis direction that is within the maximum width in the X-axis direction of the lens holding member 62, the opening of the reticle blind 30 is opened via a drive system (not shown). Set. At the same time, the main controller 50 rotates the illumination system aperture stop plate 24 via the drive unit 40 to set a predetermined aperture stop, for example, a small σ stop, on the optical path of the illumination light EL. At this time, the light beam diameter (or incident angle range) of the illumination light incident on the optical integrator (fly eye lens) 22 is reduced using an optical unit (not shown) in the illumination optical system described above, for example, a zoom optical system. It is desirable to minimize light loss.
[0061]
After such preparatory work, the main controller 50 gives the control information TS to the light source 16 to emit the laser beam LB, and sends the illumination light EL to the reticle R._TIs exposed to light. As a result, as shown in FIG._{i, j}Is the corresponding pinhole-shaped opening 70_{i, j}6 is projected onto the light receiving glass 46 simultaneously through the projection optical system PL, and each measurement pattern 67 as shown in FIG. 6 is formed on the surface of the light receiving glass 46 and the imaging surface of the CCD area image sensor 45 conjugated thereto._{i, j}Projected image (reduced image) 67 '_{i, j}Are formed at predetermined intervals along the XY two-dimensional direction.
[0062]
These projected images 67 '_{i, j}Is picked up by the CCD area image sensor 45, and the image pickup signal is supplied to the main controller 50. In the main controller 50, each measurement pattern 67 is based on this imaging signal._{i, j}Projected image 67 '_{i, j}Displacement amounts (Δξ, Δη) in the X-axis direction and the Y-axis direction from the reference position are calculated.
[0063]
Here, a method of calculating the positional deviation amounts (Δξ, Δη) will be described in detail with reference to FIG. FIG. 7 shows a measurement pattern 67._{i, j}A projection image 68 ′ (see FIG. 6) of one square frame pattern (referred to as “pattern 68” for convenience) constituting the image is extracted and shown. In FIG. 7, a white pattern image 68 ″ indicates a projected image of the pattern 68 when there is no positional deviation. That is, the position of the pattern image 68 ″ is when there is no aberration in the projection optical system PL. This is the position where the pattern 68 is to be projected, that is, the reference position of the projection image 68 ′.
[0064]
In the case of FIG. 7, the amount of displacement (Δξ, Δη) from the reference position of the projection position of the pattern 68 is as shown in FIG. However, the positional deviation amounts (Δξ, Δη) are very small amounts as is clear from each pixel of the CCD area image sensor 45 shown in FIG. Therefore, when these amounts Δξ and Δη are directly measured, there is a risk that measurement accuracy is large and sufficient measurement accuracy cannot be obtained unless an ultra-high density (a very large number of pixels) CCD image sensor is used. There is. However, an ultra-high density CCD area image sensor is either expensive or there is no real one that achieves this depending on the required measurement accuracy.
[0065]
However, as is apparent from the geometrical relationship shown in FIG. 7, the following equations (2) are used between the positional deviation amounts Δξ and ΔY in the X-axis direction and between the positional deviation amounts Δη and ΔX in the Y-axis direction. The relations 1) and (2) are established.
[0066]
ΔY = Δξ / tanθ (1)
ΔX = Δη / tanθ (2)
[0067]
In this case, for example, if θ = 10 °, 1 / tan θ = 5.67, and if θ = 5 °, 1 / tan = 11.43. Therefore, by measuring ΔY and ΔX instead of measuring Δξ and Δη, it is possible to measure an amount enlarged by 5.67 times or 11.43 times. This means that when a CCD area image sensor having the same pixel density is used as the CCD area image sensor, the resolution is 5.67 times or 11.43 times, and the measurement accuracy is improved accordingly. Means that. In other words, when measuring with the same resolution, it means that the pixel density of the CCD area image sensor should be about (1 / 5.67) or (1 / 11.43).
[0068]
Note that the enlargement magnification becomes larger as the angle θ is closer to 0. For example, when θ = 1.15 °, a resolution of about 50 times can be obtained.
[0069]
In FIG. 7, the description is given as if the pattern image 68 ″ is assumed as the reference position. However, in reality, this is not necessary, and the design of the points A, B, etc. in FIG. In this case, the representative points of the pattern projection position in the pixel of the CCD area image sensor 45 may be determined as the reference position, and in this case, the points A ′ and B ′ are obtained from the actual imaging result, The point D is obtained from the imaging result, the point C is obtained from the A ′ point and the imaging result, the point E is obtained from the B point and the imaging result, and the point F is obtained from the B ′ point and the imaging result. ΔY and ΔX can be measured based on the coordinates of the C, D, E, and F points obtained in this way.
[0070]
As described above, in the main controller 50, each measurement pattern 67 is measured._{i, j}, The amount (ΔY, ΔX) obtained by enlarging the amount of positional deviation in the X and Y directions to a predetermined magnification is measured, and by multiplying the amount (ΔY, ΔX) by tan θ, each target measurement pattern 67 is obtained._{i, j}The amount of positional deviation (Δξ, Δη) is calculated.
[0071]
The wavefront of the projection optical system PL is obtained by calculation based on the positional deviation amounts (Δξ, Δη). As a premise, the physical relationship between the positional deviation amounts (Δξ, Δη) and the wavefront is obtained. This will be briefly described with reference to FIG.
[0072]
FIG. 4 shows a measurement pattern 67._{k, l}As typically shown, the measurement pattern 67_{i, j}(67_{k, l}) Of the diffracted light generated in the step 70)._{i, j}(70_{k, l}) Passes through the measurement pattern 67._{i, j}(67_{k, l}), The position passing through the pupil plane of the projection optical system PL differs depending on where the light comes from. That is, the wavefront at each position of the pupil plane is a measurement pattern 67 corresponding to the position._{i, j}(67_{k, l}) Corresponding to the wavefront of light through the position in FIG. If there is no aberration in the projection optical system PL, these wavefronts are denoted by F in the pupil plane of the projection optical system PL.₁It should be an ideal wavefront as shown by However, since there is actually no projection optical system having no aberration, on the pupil plane, for example, a curved wavefront F as indicated by a dotted line.₂It becomes. Therefore, the measurement pattern 67_{i, j}(67_{k, l}) Is the wavefront F on the imaging surface of the CCD area image sensor 45.₂The image is formed at a position shifted according to the inclination of the ideal wavefront.
[0073]
Therefore, the positional deviation amount (Δξ, Δη) is a value that directly reflects the inclination of the wavefront with respect to the ideal wavefront, and conversely, the wavefront can be restored based on the positional deviation amount (Δξ, Δη). As is apparent from the physical relationship between the positional deviation amounts (Δξ, Δη) and the wavefront, the wavefront calculation principle in this embodiment is the well-known Shack-Hartman wavefront calculation principle itself.
[0074]
Next, a method for calculating the wavefront based on the above-described positional deviation amount will be briefly described.
[0075]
As described above, the positional deviation amounts (Δξ, Δη) correspond to the inclination of the wavefront, and by integrating this, the shape of the wavefront (strictly, the deviation from the reference plane (ideal wavefront)) is obtained. When the wavefront (deviation of the wavefront from the reference plane) is W (x, y) and the proportionality coefficient is k, the following relational expressions (3) and (4) are established.
[0076]
[Expression 1]

[0077]
Since it is not easy to integrate the slope of the wavefront that is given only by the amount of displacement, the surface shape is developed into a series and fits to this. In this case, an orthogonal system is selected as the series. The Zernike polynomial is a series suitable for expansion of an axisymmetric surface, and the circumferential direction is expanded to a triangular series. That is, when the wavefront W is expressed in the polar coordinate system (ρ, θ), the Zernike polynomial is expressed as R_n ^m(Ρ) can be expanded as shown in the following equation (5).
[0078]
[Expression 2]

[0079]
R_n ^mThe specific form of (ρ) is well known (for example, described in general textbooks for optics), and thus detailed description thereof is omitted. Since it is an orthogonal system, the coefficient of each term, A_n ^m, B_n ^mCan be determined independently. Cutting with a finite term corresponds to performing some kind of filtering.
[0080]
Actually, since the differentiation is detected as the above-described positional deviation amount, the fitting needs to be performed on the differential coefficient. In the polar coordinate system (x = ρcos θ, y = ρsin θ), the following expressions (6) and (7) are used.
[0081]
[Equation 3]

[0082]
Since the differential form of the Zernike polynomial is not an orthogonal system, the fitting must be performed by the method of least squares. Since information (amount of deviation) from one measurement pattern is given in the X and Y directions, assuming that the number of measurement patterns is N (N is about 81 to 400, for example), the above equation (3) The number of observation equations given by (7) is 2N (= about 162 to 800). Since, for example, 27 coefficients are determined, the error of each coefficient is considerably reduced (A representing the slope of the surface).₁ ¹, B₁ ¹Except for, the coefficient variation is within a few nanometers).
[0083]
Each term in the Zernike polynomial corresponds to an optical aberration. Moreover, the low order terms almost correspond to Seidel aberration. Therefore, the wavefront aberration of the projection optical system PL can be obtained by using the Zernike polynomial.
[0084]
In view of this, the main controller 50 calculates the positional deviation amounts (Δξ, Δη) as described above, and then uses the predetermined calculation program and based on the positional deviation amounts (Δξ, Δη) according to the principle described above. , Each region S_{i, j}, That is, the wavefront (wavefront aberration) corresponding to the first to nth measurement points in the field of view of the projection optical system PL, here, the coefficients of each term of the Zernike polynomial, for example, the coefficient Z of the second term₂~ Coefficient Z in the 36th term₃₆Is calculated.
[0085]
By the way, in the exposure apparatus 10 of the present embodiment, maintenance is periodically performed. At that time, the measurement reticle R described above is used._TThen, using the CCD area image sensor 45 or the like, the wavefront aberration is measured in the above-described procedure, and the projection optical system PL is adjusted based on the measurement result. For this adjustment, for example, the main controller 50 determines low-order aberrations such as astigmatism, coma aberration, distortion, field curvature (or focus), spherical aberration, etc., that is, Seidel's five aberrations, based on the measurement result of wavefront aberration. And a command to correct these aberrations is given to the imaging characteristic correction controller 48. Accordingly, the movable lens 13 is obtained by the imaging characteristic correction controller 48.₁~ 13_FourA voltage applied to a predetermined drive element that drives at least one predetermined movable lens in at least one direction of freedom, and at least one of a position and a posture of the predetermined movable lens is adjusted, and a projection optical system PL imaging characteristics such as distortion, curvature of field, coma, spherical aberration, and astigmatism are corrected.
[0086]
In this case, the relationship between the unit driving amount of each movable lens in each direction of freedom and the amount of change in wavefront aberration (coefficient of each term of the Zernike polynomial) is obtained in advance, and this is stored in a memory as a database. In addition, an adjustment amount calculation program for calculating the adjustment amount of the imaging characteristics based on the database and the coefficient of each term of the Zernike polynomial may be prepared. In this way, at the time when the measurement result of the wavefront aberration (the calculated value of the coefficient of each term of the Zernike polynomial) is obtained, main controller 50 obtains the above database and the measurement result of the obtained wavefront aberration. Using the movable lens 13 in accordance with the above-described adjustment amount calculation program₁~ 13_FourThe adjustment amount to be driven in each direction of freedom is calculated, and a command value for this adjustment amount is given to the imaging characteristic correction controller 48. Accordingly, the movable lens 13 is obtained by the imaging characteristic correction controller 48.₁~ 13_FourThe voltage applied to each drive element that drives each in the direction of freedom is controlled, and the movable lens 13 is controlled.₁~ 13_FourAt least one of the position and orientation is adjusted almost simultaneously, and the imaging characteristics of the projection optical system PL, such as distortion, field curvature, coma aberration, spherical aberration, and astigmatism, are corrected. For coma, spherical aberration, and astigmatism, not only low-order but also high-order aberrations can be corrected.
[0087]
In the exposure apparatus 10 of the present embodiment, when manufacturing a semiconductor device, a reticle R for device manufacture is loaded on the reticle stage RST as a reticle, and thereafter, reticle alignment and so-called baseline measurement of a wafer alignment system (not shown), and Preparatory work such as wafer alignment such as EGA (Enhanced Global Alignment) is performed. Thereafter, based on the wafer alignment result, step-and-repeat exposure is performed in which an inter-shot stepping operation and an exposure operation for positioning each shot area on the wafer W at the projection position of the reticle pattern are repeated. Since the operation during exposure is not different from that of a normal stepper, the detailed description is omitted.
[0088]
However, the exposure apparatus 10 corrects (adjusts) the imaging characteristics of the projection optical system PL described above at the time of maintenance described above or at other necessary timing prior to exposure. The above-described step-and-repeat exposure is performed using the projection optical system PL.
[0089]
Next, a method for manufacturing the exposure apparatus 10 will be described. When manufacturing the exposure apparatus 10, first, an illumination optical system 12 including a plurality of optical elements such as lenses and mirrors, a projection optical system PL, a reticle stage system and a wafer stage system composed of a large number of mechanical parts are respectively united. In addition, the optical adjustment, the mechanical adjustment, the electrical adjustment, and the like are performed so that each unit exhibits desired performance as a single unit.
[0090]
Next, the illumination optical system 12 and the projection optical system PL are assembled in the exposure apparatus main body, and a reticle stage system, wafer stage system, and the like are attached to the exposure apparatus main body to connect wiring and piping.
[0091]
Next, the illumination optical system 12 and the projection optical system PL are further optically adjusted. This is because the optical characteristics of those optical systems, particularly the projection optical system PL, slightly change before and after assembly to the exposure apparatus main body. In the present embodiment, when the projection optical system PL is optically adjusted after being incorporated into the exposure apparatus main body, the measurement reticle R described above is used._TThen, the wavefront aberration of the projection optical system PL is measured by the procedure described above using the CCD area image sensor 45 and the like. Based on the wavefront aberration result, the Seidel aberration and the like are corrected in the same manner as in the maintenance described above. Further, if necessary, the assembly of the lens or the like is readjusted based on higher order aberrations. In addition, when a desired performance cannot be obtained by readjustment, it is necessary to rework some lenses. In order to easily reprocess the optical elements of the projection optical system PL, the above-mentioned wavefront aberration is measured before the projection optical system PL is incorporated in the exposure apparatus main body, and the optical that requires reprocessing based on the measurement result. The presence / absence or position of an element may be specified, and reprocessing of the optical element and readjustment of another optical element may be performed in parallel.
[0092]
Thereafter, comprehensive adjustment (electric adjustment, operation check, etc.) is further performed. As a result, the exposure apparatus 10 of the present embodiment that can accurately transfer the pattern of the reticle R onto the wafer W using the projection optical system PL whose optical characteristics are adjusted with high accuracy can be manufactured. . The exposure apparatus is preferably manufactured in a clean room where the temperature, cleanliness, etc. are controlled.
[0093]
As described above, according to the present embodiment, the measurement reticle R is used when measuring the wavefront aberration of the projection optical system PL._TIs loaded on the reticle stage RST and the reticle alignment is performed._TA plurality of measurement patterns 67 above_{i, j}Is illuminated with illumination light. Thus, each measurement pattern 67_{i, j}Are individually corresponding pinhole-shaped openings 70._{i, j}Then, the light is projected onto the imaging surface of the CCD area image sensor 45 provided on the wafer stage WST via the projection optical system PL and disposed on a plane conjugate with the image surface of the projection optical system PL. At this time, each measurement pattern 67_{i, j}As described above, the image of the measurement pattern 67 is measured by the projection optical system PL._{i, j}The image is formed at a position shifted according to the inclination of the wavefront of the light via the ideal wavefront. Then, each measurement pattern 67 imaged at the shifted position by the CCD area image sensor 45._{i, j}Projected image 67 '_{i, j}Is imaged.
[0094]
Then, the main control device 50 calculates the wavefront aberration of the projection optical system PL according to a predetermined calculation program based on the positional deviation amount from the reference position of the projection position of each measurement pattern obtained based on the imaging result. The
[0095]
In the present embodiment, each measurement pattern 67_{i, j}A line and space pattern in which a plurality of linear patterns having an angle θ with respect to the X axis and a predetermined width are arranged at a predetermined pitch, and a plurality of lines having a predetermined width with an angle θ with respect to the Y axis A mesh-like (street line-like) pattern is used in which line-and-space patterns in which linear patterns of books are arranged at a predetermined pitch are orthogonal to each other. The positional deviation amount in the X-axis direction of each measurement pattern is a measurement of an amount obtained by enlarging the positional deviation amount in the X-axis direction of the linear pattern portion that forms an angle θ with respect to the X-axis by (1 / tan θ) times. The amount of displacement in the Y-axis direction is calculated based on the result, and the amount of displacement in the Y-axis direction is calculated based on the measurement result of an amount obtained by enlarging the amount of displacement in the Y-axis direction of the linear pattern portion by (1 / tan θ) times. Accordingly, it is possible to substantially measure the positional deviation amount with a high resolution corresponding to the enlargement magnification, and it is possible to improve the measurement accuracy of the positional deviation amount and hence the measurement accuracy of the wavefront aberration.
[0096]
Therefore, according to the present embodiment, it is possible to measure the wavefront aberration of the projection optical system with high accuracy without using a microlens array.
[0097]
Further, according to the present embodiment, the wavefront aberration of the projection optical system PL is periodically measured with high accuracy during maintenance or the like, and the projection optical system PL is adjusted based on the measurement result of the wavefront aberration measured with high accuracy. Therefore, the optical characteristics of the projection optical system PL can be adjusted with high accuracy.
[0098]
Then, according to the exposure apparatus of the present embodiment, prior to exposure, the pattern of the reticle R is transferred onto the wafer W using the projection optical system PL whose optical characteristics have been adjusted as described above. The pattern on the reticle R can be transferred onto the wafer W with high accuracy.
[0099]
Further, according to the present embodiment, even when the exposure apparatus 10 is manufactured, after the projection optical system PL is incorporated in the exposure apparatus main body, the wavefront aberration of the projection optical system PL is measured and measured as described above. Since the projection optical system PL is adjusted based on the wavefront aberration, the imaging characteristics of the projection optical system are adjusted with high accuracy. Therefore, the exposure apparatus 10 in which the imaging characteristics of the projection optical system are adjusted with high precision is manufactured, and exposure is performed using the exposure apparatus 10 so that the reticle pattern can be accurately formed on the wafer via the projection optical system PL. It becomes possible to transfer.
[0100]
In the above-described embodiment, a case has been described in which the amount of displacement of the measurement pattern with respect to the reference position is increased by 1 / tan θ times and obtained by multiplying it by tan θ. However, the present invention is not limited thereto. It is not something. That is, if the resolution of the CCD area image sensor 45 is sufficiently high, the amount of positional deviation may be directly measured. Even in such a case, the wavefront aberration of the projection optical system PL can be obtained with high accuracy based on the measured positional deviation amount, without using the microlens array, as in the above embodiment. Even in this case, the wavefront aberration is measured with high accuracy at any stage of manufacture of the exposure apparatus and after manufacture, and the optical characteristics of the projection optical system PL are adjusted with high accuracy based on the measurement result. be able to. In addition, the reticle pattern can be transferred onto the wafer with high accuracy using the projection optical system PL whose optical characteristics are adjusted with high accuracy. In the above embodiment, the amount of positional deviation of the projected image of the measurement pattern is measured using the pixel of the CCD area image sensor 45 as a reference. For example, the reference pattern is set close to the imaging surface of the CCD area image sensor 45. It may be arranged to measure the amount of positional deviation of the projection image of the measurement pattern with respect to this reference pattern. In the above embodiment, the lens system 43 may be used as an enlargement system to improve the detection accuracy of the measurement pattern projection position. The same applies to the case where the reference pattern is arranged close to the imaging surface of the CCD area image sensor 45.
[0101]
In the above embodiment, the optical characteristics of the lens system 43 that conjugates the image plane of the projection optical system PL and the CCD area image sensor 45 are measured. It is preferable that the measurement result of the optical characteristics of the projection optical system is corrected. Thereby, the measurement error of the optical characteristics due to the lens system 43 can be reduced.
[0102]
In the above embodiment, instead of the CCD area image sensor 45, a plurality of imaging elements are projected optically in a positional relationship corresponding to the plurality of measurement patterns, for example, corresponding to the projection positions of the plurality of measurement patterns. The projection position of the measurement pattern corresponding to each imaging element (that is, the projection position of the corresponding measurement pattern based on each imaging element) may be measured by being arranged on the image plane of the system (or its conjugate plane). . In this case, the positional relationship (interval and the like) of a plurality of image sensors is measured, and the above-described positional deviation amount is obtained for each measurement pattern in consideration of the measurement result, or the optical characteristics of the projection optical system are determined. It is desirable to correct the measurement result. Thereby, the measurement error of the optical characteristic due to the position error of the image sensor can be reduced. Similarly, the arrangement of each pixel of the CCD area image sensor 45 is accurately measured, and the above-described positional deviation amount is obtained for each measurement pattern in consideration of the measurement result, or the optical characteristics of the projection optical system are determined. The measurement result may be corrected.
[0103]
Moreover, although the case where the CCD area image sensor which is a two-dimensional image sensor was used as an image sensor was demonstrated in the said embodiment, this invention is not limited to this. That is, a one-dimensional image sensor such as a CCD line sensor is used as the image sensor, and the projected image of the measurement pattern is captured while moving in the direction orthogonal to the pixel arrangement direction. It is also possible to measure the positional deviation amount of the projection position with respect to the reference position and obtain the wavefront aberration of the projection optical system PL based on the positional deviation amount.
[0104]
Alternatively, the projection image of each measurement pattern may be detected by moving at least one image sensor within the second surface (the image plane of the projection optical system or its conjugate plane). In this case, a positioning error that may occur when the image sensor is moved is measured for each projection position of the measurement pattern, for example, and the above-described positional deviation amount is obtained for each measurement pattern in consideration of the measurement result, or It is desirable to correct the measurement result of the optical characteristics of the projection optical system. As a result, it is possible to reduce an optical characteristic measurement error caused by a positioning error or the like during movement of the image sensor.
[0105]
In the above embodiment, the positional relationship (interval and the like) of a plurality of measurement patterns on the measurement reticle is measured, and the optical characteristics of the projection optical system PL are obtained in consideration of the measurement results, for example. Is desirable. Thereby, it is possible to reduce the measurement error of the optical characteristics of the projection optical system PL due to the position error (drawing error) of the measurement pattern on the measurement reticle. In this case as well, as described above, the position error of the measurement pattern may be taken into account when obtaining the above-described positional deviation amount, or the measurement result of the optical characteristic is corrected using the position error of the measurement pattern. May be.
[0106]
In the above-described embodiment, the case where the wavefront aberration is obtained as the optical characteristic of the projection optical system PL has been described. However, the present invention is not limited thereto, and is based on the amount of positional deviation from the predetermined reference position of the projection position of each measurement pattern. Thus, it is possible to obtain optical characteristics other than wavefront aberration.
[0107]
In the above embodiment, the case where the imaging unit 42 having the CCD area image sensor is fixedly provided on the Z tilt stage 58 has been described. However, the present invention is not limited to this, and a case where a wafer holder exchanging mechanism is provided (wafer transfer). (Including the case where the system also serves as a transfer system for the wafer holder), an image pickup device (CCD area image sensor or the like) is incorporated in the wafer holder 25, and the wafer holder is mounted on the wafer stage when not exposed by the exchange mechanism. It may be used to measure the wavefront aberration of the projection optical system. In this case, prior to actual exposure, the wafer holder used for the measurement may be exchanged again with the wafer holder used for exposure. Further, a reference illuminometer or the like may be incorporated in the wafer holder as well as the image sensor.
[0108]
Further, in the above-described embodiment, the case where the image pickup device (CCD area image sensor) is picked up in the state where the image pickup device (CCD area image sensor) is arranged on the conjugate plane of the image plane of the projection optical system has been described. The imaging element may be directly arranged on a surface in the vicinity of the image plane of the optical system PL (in the above-described embodiment, the arrangement surface of the light receiving glass on the Z tilt stage 58), and the imaging unit 42 can be downsized. Furthermore, it is sufficient to form at least one measurement pattern on the reticle without forming a plurality of measurement patterns on the reticle corresponding to the projection field of view of the projection optical system PL (illumination light irradiation region). Moves the reticle within the object plane (first surface) of the projection optical system. At this time, a positioning error that may occur when the reticle stage RST is moved is measured, for example, for each position where the measurement pattern is to be arranged, and the above-described positional deviation amount is obtained for each measurement pattern using this measurement result. Alternatively, it is desirable to correct the measurement result of the optical characteristics of the projection optical system. Further, in the above embodiment, a measurement reticle is used. For example, a plate on which at least one measurement pattern is formed on the reticle stage RST and pinholes are formed when measuring the optical characteristics of the projection optical system is used. A pinhole plate may be provided close to the pattern surface of the reticle, or provided on the lower surface of the reticle stage close to the measurement pattern. That is, the mask used for measuring the optical characteristics is not limited to the mask or the reticle, and may be a pattern plate provided on a reticle stage, for example.
[0109]
In the above embodiment, the case where the present invention is applied to a stepper has been described. However, the present invention is not limited to this. For example, the mask and the substrate disclosed in US Pat. No. 5,473,410 are moved synchronously. The present invention can also be applied to a scanning exposure apparatus that transfers a mask pattern onto a substrate.
[0110]
The use of the exposure apparatus is not limited to the exposure apparatus for semiconductor manufacturing, but for example, an exposure apparatus for liquid crystal that transfers a liquid crystal display element pattern onto a square glass plate, a thin film magnetic head, a micromachine, and a DNA chip The present invention can also be widely applied to an exposure apparatus for manufacturing the above. Further, in order to manufacture reticles or masks used in not only microdevices such as semiconductor elements but also light exposure apparatuses, EUV exposure apparatuses, X-ray exposure apparatuses, electron beam exposure apparatuses, etc., glass substrates or silicon wafers, etc. The present invention can also be applied to an exposure apparatus that transfers a circuit pattern.
[0111]
The light source of the exposure apparatus of the above embodiment is F.₂Not only an ultraviolet pulse light source such as a laser light source, an ArF excimer laser light source, and a KrF excimer laser light source, it is also possible to use an ultrahigh pressure mercury lamp that emits bright lines such as g-line (wavelength 436 nm) and i-line (wavelength 365 nm). .
[0112]
In addition, a single wavelength laser beam oscillated from a DFB semiconductor laser or fiber laser is amplified by, for example, a fiber amplifier doped with erbium (or both erbium and ytterbium), and a nonlinear optical crystal is obtained. It is also possible to use harmonics that have been converted into ultraviolet light. The magnification of the projection optical system may be not only a reduction system but also an equal magnification or an enlargement system.
[0113]
For semiconductor devices, the step of designing the function and performance of the device, the step of manufacturing a reticle based on this design step, the step of manufacturing a wafer from a silicon material, and the pattern of the reticle on the wafer by the exposure apparatus of the above-described embodiment And a device assembly step (including a dicing process, a bonding process, and a packaging process), an inspection step, and the like.
[0114]
【The invention's effect】
As described above, according to the wavefront aberration measuring method of the present invention, there is an effect that the wavefront aberration of the projection optical system can be measured with high accuracy without using a microlens array.
[0115]
Moreover, according to the projection optical system adjusting method of the present invention, there is an effect that the optical characteristics of the projection optical system can be adjusted with high accuracy.
[0116]
Further, according to the exposure method of the present invention, there is provided an exposure method capable of accurately transferring a mask pattern onto a substrate.
[0117]
Moreover, according to the exposure apparatus manufacturing method of the present invention, there is provided an exposure apparatus manufacturing method capable of accurately transferring a mask pattern onto a substrate.
[Brief description of the drawings]
FIG. 1 is a view showing a schematic configuration of an exposure apparatus according to an embodiment.
FIG. 2 is an enlarged view showing the Z tilt stage of FIG. 1 with partly broken and partly omitted.
FIG. 3 is a schematic perspective view showing a measurement reticle.
FIG. 4 is a diagram showing a schematic view of an XZ cross section near the optical axis of a measurement reticle in a state of being loaded on a reticle stage together with a schematic diagram of a projection optical system.
5 is a bottom view showing the glass substrate of FIG. 3 taken out. FIG.
FIG. 6 is a diagram showing a reduced image (projected image) of a measurement pattern formed on the imaging surface of a CCD area image sensor.
FIG. 7 is a diagram illustrating a method of measuring an amount of positional deviation of a measurement pattern in an enlarged manner.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Exposure apparatus, 45 ... CCD area image sensor (imaging element), 66 ... Opening plate, 67_{i, j}... Measurement pattern, 70_{i, j}... Pin-hole opening, EL ... Illumination light, PL ... Projection optical system, R ... Reticle (mask), R_T... Measurement reticle (measurement mask), W ... wafer (substrate).

Claims (5)

A wavefront aberration measuring method for measuring a wavefront aberration of a projection optical system that projects a pattern on a first surface onto a second surface,
Rutotomoni placed in a predetermined positional relationship on the first surface, a plurality of measurement patterns including linear pattern portion of a predetermined angle θ (0 ° <θ <45 °) predetermined width forming the relative specific direction Illumination is performed with illumination light, and each of the plurality of measurement patterns is projected onto the second surface via a pinhole-like opening provided corresponding to each measurement pattern and the projection optical system. Process and;
Capturing a projected image of each measurement pattern with an image sensor disposed on the second surface;
At least one of the positional deviation amount from the reference position with respect to the specific direction of the linear pattern portion obtained based on the imaging result and the positional deviation amount with respect to the direction orthogonal to the specific direction is (1 / tan θ). And a step of obtaining the wavefront aberration of the projection optical system based on the result of enlarging the magnification twice . The image pickup device is a two-dimensional image pickup device in which pixels are arranged in a matrix in two orthogonal axes.
The specific direction, the wavefront aberration measuring method according to claim 1, wherein the one der Turkey of the orthogonal two axial directions. Measuring the wavefront aberration of the projection optical system using the wavefront aberration measuring method according to claim 1;
Adjusting the projection optical system based on the measurement result of the wavefront aberration; and adjusting the projection optical system. An exposure method for transferring a mask pattern onto a substrate via a projection optical system,
Adjusting the projection optical system by the adjustment method according to claim 3;
Transferring the pattern onto the substrate via the adjusted projection optical system. An exposure apparatus manufacturing method for transferring a mask pattern onto a substrate via a projection optical system,
Measuring the wavefront aberration of the projection optical system using the wavefront aberration measuring method according to claim 1;
Adjusting the projection optical system based on the measurement result of the wavefront aberration; and a method of manufacturing an exposure apparatus.

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