JP4436029B2 - Projection optical system manufacturing method and adjustment method, exposure apparatus and manufacturing method thereof, device manufacturing method, and computer system - Google Patents

Description

【０１３８】
スポット位置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、次式（４）のように展開できる。
【０１３９】
【数２】

【０１４０】
直交系であるから各項の係数Ｚ_iを独立に決定することができる。ｉを適当な値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。なお、一例として第１項〜第３７項までのｆ_iをＺ_iとともに例示すると、次の表１のようになる。但し、表１中の第３７項は、実際のツェルニケ多項式では、第４９項に相当するが、本明細書では、ｉ＝３７の項（第３７項）として取り扱うものとする。すなわち、本発明において、ツェルニケ多項式の項の数は、特に限定されるものではない。
【０１４１】
【表１】

【０１４２】
実際には、その微分が上記の位置ずれ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（５）、（６）のように表される。
【０１４３】
【数３】

【０１４４】
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つのスポット像の結像点の情報（ずれ量）はＸとＹ方向につき与えられるので、ピンホールの数をｎ（ｎは、例えば８１〜４００程度とする）とすると、上記式（２）〜（６）で与えられる観測方程式の数は２ｎ（＝１６２〜８００程度）となる。
【０１４５】
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(ｉの小さい項)は、ザイデル収差にほぼ対応する。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。
【０１４６】
上述のような原理に従って、第１プログラムの演算手順が決められており、この第１プログラムに従った演算処理により、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の情報（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３７項の係数Ｚ₃₇が求められる。
【０１４７】
以下の説明においては、上記の第１計測点〜第ｎ計測点に対応する波面（波面収差）のデータを、次式（７）のような列マトリックスＱで表現する。
【０１４８】
【数４】

【０１４９】
なお、上式（７）において、マトリックスＱの要素Ｐ₁〜Ｐ_nは、それぞれがツェルニケ多項式の第２項〜第３７項の係数（Ｚ₂〜Ｚ₃₇）から成る列マトリックス（縦ベクトル）である。
【０１５０】
このようにして、波面のデータ（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３７項の係数Ｚ₃₇）を求めると、主制御装置５０では、その波面のデータを記憶装置４２に格納する。
【０１５１】
また、主制御装置５０では、後述するように、第１通信サーバ１２０からの問い合わせに応じて、波面のデータを記憶装置４２から読み出し、ＬＡＮ１１８を介して前述した第１通信サーバ１２０に送信するようになっている。
【０１５２】
図１に戻り、第１通信サーバ１２０が備えるハードディスク等の内部には、第１〜第３露光装置１２２₁〜１２２₃で達成すべき目標情報、例えば解像度（解像力）、実用最小線幅（デバイスルール）、照明光ＥＬの波長、転写対象のパターンの情報、その他の露光装置１２２₁〜１２２₃の性能を決定する投影光学系に関する何らかの情報であって目標値となり得る情報が格納されている。また、第１通信サーバ１２０が備えるハードディスク等の内部には、今後導入する予定の露光装置での目標情報、例えば使用を計画しているパターンの情報なども目標情報として格納されている。
【０１５３】
一方、第２通信サーバ１３０が備えるハードディスク等の内部には、ツェルニケ多項式の各項の係数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(以下、便宜上「第２プログラム」と呼ぶ)、最良露光条件の設定を行う最良露光条件設定プログラム（以下、便宜上「第３プログラム」と呼ぶ）、及び第２プログラムに付属するデータベースが格納されている。
【０１５４】
次に、上記データベースについて説明する。このデータベースは、投影光学系の光学特性、ここでは波面収差の計測結果の入力に応じて、結像特性を調整するための前述した可動なレンズ素子（以下、「可動レンズ」と呼ぶ）１３₁，１３₂，１３₃，１３₄の目標駆動量（目標調整量）を算出するためのパラメータ群の数値データから成るデータベースである。このデータベースは、可動レンズ１３₁，１３₂，１３₃，１３₄を各自由度方向（駆動可能な方向）について単位調整量駆動した場合に、投影光学系ＰＬの視野内の複数の計測点それぞれに対応する結像特性、具体的には波面のデータ、例えばツェルニケ多項式の第２項〜第３７項の係数がどのように変化するかのデータを、投影光学系ＰＬと実質的に等価なモデルを用いて、シミュレーションを行い、このシミュレーション結果として得られた結像特性の変動量を所定の規則に従って並べたデータ群から成る。
【０１５５】
ここで、このデータベースの作成手順について、簡単に説明する。特定の光学ソフトがインストールされているシミュレーション用コンピュータに、まず、露光条件、すなわち投影光学系ＰＬの設計値（開口数Ｎ．Ａ．、各レンズのデータ等）や照明条件（コヒーレンスファクタσ値、照明光の波長λ、２次光源の形状等）を入力する。次に、シミュレーション用コンピュータに、投影光学系ＰＬの視野内の任意の第１計測点のデータを入力する。
【０１５６】
次いで、可動レンズの各自由度方向（可動方向）についての単位量のデータを入力する。例えば可動レンズ１３₁をＹ方向チルトの＋方向に関して単位量だけ駆動するという指令を入力すると、シミュレーション用コンピュータにより、投影光学系ＰＬの視野内の予め定めた第１計測点についての第１波面の理想波面からの変化量のデータ、例えばツェルニケ多項式の各項（例えば第２項〜第３７項）の係数の変化量が算出され、その変化量のデータがシミュレーション用コンピュータのディスプレイの画面上に表示されるとともに、その変化量がパラメータＰＡＲＡ１Ｐ１としてメモリに記憶される。
【０１５７】
次いで、可動レンズ１３₁をＸ方向チルトの＋方向に関して単位量だけ駆動するという指令を入力すると、シミュレーション用コンピュータにより、第１計測点についての第２波面のデータ、例えばツェルニケ多項式の上記各項の係数の変化量が算出され、その変化量のデータが上記ディスプレイの画面上に表示されるとともに、その変化量がパラメータＰＡＲＡ２Ｐ１としてメモリに記憶される。
【０１５８】
次いで、可動レンズ１３₁をＺ方向シフトの＋方向に関して単位量だけ駆動するという指令を入力すると、シミュレーション用コンピュータにより、第１計測点についての第３波面のデータ、例えばツェルニケ多項式の上記各項の係数の変化量が算出され、その変化量のデータが上記ディスプレイの画面上に表示されるとともに、その変化量がパラメータＰＡＲＡ３Ｐ１としてメモリに記憶される。
【０１５９】
以後、上記と同様の手順で、第２計測点〜第ｎ計測点までの各計測点の入力が行われ、可動レンズ１３₁のＹ方向チルト，Ｘ方向チルト、Ｚ方向シフトの指令入力がそれぞれ行われる度毎に、シミュレーション用コンピュータによって各計測点における第１波面、第２波面、第３波面のデータ、例えばツェルニケ多項式の上記各項の係数の変化量が算出され、各変化量のデータがディスプレイの画面上に表示されるとともに、パラメータＰＡＲＡ１Ｐ２，ＰＡＲＡ２Ｐ２，ＰＡＲＡ３Ｐ２、……、ＰＡＲＡ１Ｐｎ，ＰＡＲＡ２Ｐｎ，ＰＡＲＡ３Ｐｎとしてメモリに記憶される。
【０１６０】
他の可動レンズ１３₂，１３₃，１３₄についても、上記と同様の手順で、各計測点の入力と、各自由度方向に関してそれぞれ単位量だけ＋方向に駆動する旨の指令入力が行われ、これに応答してシミュレーション用コンピュータにより、可動レンズ１３₂，１３₃，１３₄を各自由度方向に単位量だけ駆動した際の第１〜第ｎ計測ポイントのそれぞれについての波面のデータ、例えばツェルニケ多項式の各項の変化量が算出され、パラメータ（ＰＡＲＡ４Ｐ１，ＰＡＲＡ５Ｐ１，ＰＡＲＡ６Ｐ１，……，ＰＡＲＡｍＰ１）、パラメータ（ＰＡＲＡ４Ｐ２，ＰＡＲＡ５Ｐ２，ＰＡＲＡ６Ｐ２，……，ＰＡＲＡｍＰ２）、……、パラメータ（ＰＡＲＡ４Ｐｎ，ＰＡＲＡ５Ｐｎ，ＰＡＲＡ６Ｐｎ，……，ＰＡＲＡｍＰｎ）がメモリ内に記憶される。そして、このようにしてメモリ内に記憶されたツェルニケ多項式の各項の係数の変化量から成る列マトリックス（縦ベクトル）ＰＡＲＡ１Ｐ１〜ＰＡＲＡｍＰｎを要素とする次式（８）で示されるマトリックス（行列）Ｏのデータが、上記データベースとして、第２通信サーバ１３０が備えるハードディスク等の内部に格納されている。なお、本実施形態では、３自由度方向に可動なレンズが３つ、２自由度方向に可動なレンズが１つであるから、ｍ＝３×３＋２×１＝１１となっている。
【０１６１】
【数５】

【０１６２】
次に、本実施形態における第１〜第３露光装置１２２₁〜１２２₃が備える投影光学系ＰＬの調整方法について説明する。なお、以下においては、特に区別が必要な場合の他は、第１〜第３露光装置１２２₁〜１２２₃を代表して露光装置１２２と記述する。
【０１６３】
前提として、露光装置１２２の定期メンテナンス時等に、サービスエンジニア等の計測指示に応じ、露光装置１２２の主制御装置５０により、前述した波面収差計測器８０を用いた投影光学系ＰＬの波面収差の計測が行われ、その計測された波面のデータが記憶装置４２に格納されているものとする。
【０１６４】
まず、第１通信サーバ１２０では、未だ受信していない新しい波面の計測データ（第１計測点〜第ｎ計測点に対応する波面を展開した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３７項の係数Ｚ₃₇）が露光装置１２２の記憶装置４２にあるか否かを所定のインターバルで問い合わせる。ここでは、露光装置１２２（実際には、第１〜第３露光装置１２２₁〜１２２₃のいずれか）が備える記憶装置４２内に新しい波面の計測データが格納されているものとする。そこで、その露光装置１２２が備える主制御装置５０ではＬＡＮ１１８を介して第１通信サーバ１２０にその波面の計測データを送信する。
【０１６５】
第１通信サーバ１２０では、その受信した波面の計測データを、第２通信サーバ１３０に対して、投影光学系ＰＬの自動調整の指示（あるいは投影光学系ＰＬの調整量の演算の指示）とともに送信する。これにより、これらのデータは、ＬＡＮ１１８を介して第１認証用プロキシサーバ１２４を通過し、更に公衆回線１１６を介して第２認証用プロキシサーバ１２８に至る。第２認証用プロキシサーバ１２８では、そのデータに付された送信先のアドレスを確認してそのデータが第２通信サーバ１３０に対して送信されたことを認識し、ＬＡＮ１２６を介して第２通信サーバ１３０に送る。
【０１６６】
第２通信サーバ１３０では、その送られてきたデータを受信し、その旨をデータの送信元とともにディスプレイに表示するとともに、波面の計測データをハードディスク等に記憶する。そして、次のようにして、投影光学系ＰＬの調整量、すなわち前述した可動レンズ１３₁〜１３₄の各自由度方向の調整量を算出する。
【０１６７】
まず、第２通信サーバ１３０では、ハードディスク等から第２プログラムをメインメモリにロードし、第２プログラムに従って、前述した可動レンズ１３₁〜１３₄の各自由度方向の調整量を演算する。具体的には、第２通信サーバ１３０では、次のような演算を行う。
【０１６８】
第１計測点〜第ｎ計測点に対応する波面（波面収差）のデータＱと、前述したデータベースとしてハードディスク内に格納されているマトリックスＯと、可動レンズ１３₁〜１３₄の各自由度方向の調整量Ｐとの間には、次式（９）のような関係が成立する。
【０１６９】
Ｑ＝Ｏ・Ｐ ……（９）
上式（９）において、Ｐは、次式（１０）で表されるｍ個の要素から成る列マトリックス（すなわち縦ベクトル）である。
【０１７０】
【数６】

【０１７１】
従って、上式（９）より、次式（１１）の演算を行うことにより最小自乗法により、Ｐの各要素ＡＤＪ１〜ＡＤＪｍ、すなわち可動レンズ１３₁〜１３₄の各自由度方向の調整量（目標調整量）を求めることができる。
【０１７２】
Ｐ＝（Ｏ^T・Ｏ）^-1・Ｏ^T・Ｑ ……（１１）
上式（１１）において、Ｏ^Tは、行列Ｏの転置マトリックスであり、（Ｏ^T・Ｏ）^-1は、（Ｏ^T・Ｏ）の逆マトリックスである。
【０１７３】
すなわち、第２プログラムは、上式（１１）の最小自乗演算を、データベースを用いて行うためのプログラムである。従って、第２通信サーバ１３０では、この第２プログラムに従って、ハードディスク内のデータベースをＲＡＭ内に順次読み込みつつ、調整量ＡＤＪ１〜ＡＤＪｍを算出する。
【０１７４】
次に、第２通信サーバ１３０では、その算出した調整量ＡＤＪ１〜ＡＤＪｍのデータを、露光装置１２２の主制御装置５０に対して送信する。これにより、調整量ＡＤＪ１〜ＡＤＪｍのデータは、ＬＡＮ１２６を介して第２認証用プロキシサーバ１２８を通過し、更に公衆回線１１６を介して第１認証用プロキシサーバ１２４に至る。第１認証用プロキシサーバ１２４では、その調整量ＡＤＪ１〜ＡＤＪｍのデータに付されたアドレスを確認してそのデータが露光装置１２２に対して送信されたことを認識し、ＬＡＮ１１８を介して露光装置１２２に送る。なお、実際には、調整量ＡＤＪ１〜ＡＤＪｍのデータに付されたアドレスがＡＤ２である場合には、そのデータは、第１露光装置１２２₁に送られ、アドレスがＡＤ３である場合には、そのデータは、第２露光装置１２２₂に送られ、アドレスがＡＤ４である場合には、そのデータは第３露光装置１２２₃に送られる。
【０１７５】
ここで、第２通信サーバ１３０では、その算出した調整量ＡＤＪ１〜ＡＤＪｍのデータを、第１通信サーバ１２０に送ることも勿論可能である。この場合には、第１通信サーバ１２０により、先に波面データを送ってきた露光装置１２２の主制御装置５０に対してその調整量ＡＤＪ１〜ＡＤＪｍのデータが送られることとなる。
【０１７６】
いずれにしても、その調整量ＡＤＪ１〜ＡＤＪｍのデータを受信した露光装置１２２の主制御装置５０では、調整量ＡＤＪ１〜ＡＤＪｍのデータに従って、可動レンズ１３₁〜１３₄を各自由度方向に駆動すべき旨の指令値を、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。
【０１７７】
上記の説明から明らかなように、本実施形態では、可動レンズ１３₁〜１３₄、これらの可動レンズを駆動する駆動素子、結像特性補正コントローラ４８によって調整装置としての結像特性補正機構が構成されている。また、該結像特性補正機構を制御する制御装置が主制御装置５０とによって構成されている。
【０１７８】
このように、本実施形態では、露光装置の通常使用時における、投影光学系ＰＬの調整の際には、サービスエンジニア等が、波面収差計測器８０をＺチルトステージ５８に取り付け、入力装置４５を介して波面収差の計測指令を入力するだけで、ほぼ全自動で、遠隔操作により、投影光学系ＰＬの結像特性が高精度に調整されるようになっている。
【０１７９】
なお、上の説明では、投影光学系を自動調整するものとしたが、自動調整では補正が困難な収差が含まれる場合も起こりうる。このような場合を考慮して、第２通信サーバ１３０側の熟練技術者が、第２通信サーバ１３０のハードディスク内に記憶されている波面の計測データをディスプレイに表示させ、その表示内容を分析して、問題点を把握し、自動調整では困難な収差が含まれている場合には、的確な対応策の指示内容を第２通信サーバ１３０のキーボード等から入力し、通信にて露光装置１２２の表示装置４４の画面上に表示させることも可能である。メーカＡ側にいるサービスエンジニア等は、この画面の表示内容に基づいてレンズの組み付けを微調整する等により、短時間に投影光学系の調整を行うことが可能となる。
【０１８０】
次に、露光装置１２２（１２２₁〜１２２₃）の最良露光条件の設定について、第２通信サーバ１３０のＣＰＵの主要な制御アルゴリズムを示す図５のフローチャートに沿って説明する。前提として、露光装置１２２の定期メンテナンス時等に、サービスエンジニア等の計測指示に応じ、例えば第１露光装置１２２₁の主制御装置５０により、前述した波面収差計測器８０を用いた投影光学系ＰＬの波面収差の計測が行われ、その計測された波面のデータが、前述と同様の手順により、第１通信サーバ１２０のハードディスク等の内部に記憶されているものとする。なお、最良露光条件の設定の場合も、第１通信サーバ１２０あるいは露光装置１２０₁と第２通信サーバ１３０との間のデータの通信は、上述と同様にして行われるが、説明の簡略化のために、以下においては通信経路等の通信に関する説明は省略するものとする。
【０１８１】
図５のフローチャートがスタートするのは、メーカＡ側のオペレータの指示に応じて第１通信サーバ１２０から第２通信サーバ１３０に、最良露光条件の決定の対象である露光装置の指定を含む最良露光条件の決定の指示がなされ、これに応答して第２通信サーバ１３０により、第３プログラムがメインメモリにロードされたときである。従って、図５のステップ２０２以降の処理は実際には第３プログラムに従って行われる。
【０１８２】
まず、ステップ２０２では、第１通信サーバ１２０に対して条件入力を指示した後、ステップ２０４に進んで条件が入力されるのを待つ。
【０１８３】
このとき、第１通信サーバ１２０では、上記のオペレータによる最良露光条件の決定の指示に応じ、例えば露光装置１２２₁で次に使用が予定されているレチクルの情報を、例えば露光装置１２２_１〜１２２₃を管理する不図示のホストコンピュータに対して問い合わせ、そのレチクルの情報に基づいて、所定のデータベースを検索し、そのパターン情報を得ている。また、第１通信サーバ１２０では、露光装置１２２_１の主制御装置５０に対して例えば現在の照明条件等の設定情報を問い合わせ、それらの情報をメモリに記憶しているものとする。
【０１８４】
あるいは、上記のパターンの情報や、照明条件等の情報は、オペレータが入力装置を介して第１通信サーバ１２０に手入力にて入力することも可能である。
【０１８５】
いずれにしても、上で入手した、シミュレーションの対象であるパターンの情報（例えばラインアンドスペースパターンの場合、線幅、デューティ比等（あるいは実際のパターンの設計データなどであっても良い））が、予め設定された目的とする結像特性（該結像特性の指標値を含む：以下、「目的収差」と呼ぶ）の情報、例えば線幅異常値等の情報とともに、第１通信サーバ１２０によって入力されることとなる。
【０１８６】
このようにして、第１通信サーバ１２０により条件の入力がなされその入力完了の指示がなされると、図５のステップ２０６に進んで上記ステップ２０４で入力された目的収差のツェルニケ変化表を作成するための条件設定を行った後、次のステップ２０８に進む。なお、ステップ２０４で入力される目的収差の情報は、一種類とは限らない。すなわち、投影光学系ＰＬの複数種類の結像特性を同時に目的収差として指定することは可能である。
【０１８７】
ステップ２０８では、露光装置１２２₁の投影光学系ＰＬに関する情報の入力を第１通信サーバ１２０に指示した後、ステップ２１０に進んで、その情報の入力を待つ。そして、第１通信サーバ１２０により、投影光学系ＰＬに関する情報、具体的には、開口数（Ｎ．Ａ．）、照明条件（例えば照明系開口絞りの設定、あるいはコヒーレンスファクタσ値等）、波長などの情報が入力されると、ステップ２１２に進んで、その入力された情報をＲＡＭ内に記憶するとともに、与えたい収差の情報を設定する。一例として、ツェルニケ多項式の各項の係数の値を、例えば、第２項の係数Ｚ₂〜第３７項の係数Ｚ₃₇として、同一の値、例えば０．０５λを、個別に設定する。
【０１８８】
次のステップ２１４では、上記の入力されたパターンの情報及び投影光学系ＰＬに関する情報などに基づいて設定した収差の情報、例えば０．０５λに応じた１つの目的収差又はその指標値（例えばコマ収差の指標である線幅異常値など）を縦軸とし、横軸をツェルニケ多項式の各項の係数とするグラフ（例えば線幅異常値などのツェルニケ変化表（計算表））を作成した後、ステップ２１６に進む。
【０１８９】
ここで、ツェルニケ変化表とは、入力されたパターンを対象パターンとした場合の特定の収差、すなわち上記の目的収差（その指標値を含む）に対する、投影光学系ＰＬの波面を展開したツェルニケ多項式の各項の係数の感度（Zernike Sensitivity）から成るテーブルデータに他ならない。このツェルニケ変化表は、入力されたパターンの情報及び投影光学系ＰＬに関する情報、及び設定した収差の情報に基づいて、同一種類の投影光学系については、投影光学系を構成する各レンズ素子の種類や配置などを含む設計情報に基づいて一義的に定まる。従って、最良露光条件の決定の対象である露光装置の指定（例えば機種名の指定）に基づいて、メーカＢの社内のデータベース等を検索してその露光装置の投影光学系の種類を確認することにより、目的収差に対応するツェルニケ変化表を作成することができる。
【０１９０】
次のステップ２１６では、上記ステップ２０４で入力された全ての目的収差についてツェルニケ変化表を作成したか否かを判断する。そして、この判断が否定された場合には、ステップ２１４に戻り、次の目的収差について変化表を作成する。
【０１９１】
そして、全ての目的収差についての変化表の作成が終了し、ステップ２１６の判断が肯定されると、次のステップ２１８に進む。ステップ２１８では、第１通信サーバ１２０に対し、波面の計測データの入力を指示した後、ステップ２２０に進んで、その計測データが入力されるのを待つ。そして、第１通信サーバ１２０からハードディスク内に格納されている波面の計測データ（第１計測点〜第ｎ計測点に対応する波面を展開した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３７項の係数Ｚ₃₇）が入力されると、ステップ２２２に進んで、先に作成したツェルニケ変化表（計算表）を用いて、計測点毎に、次式（１２）のような演算を行って、先にステップ２０４で入力された目的収差の１つを算出し、ＲＡＭ内に記憶する。
【０１９２】
Ａ=Ｋ・{Ｚ₂・(変化表の値)+Ｚ₃・(変化表の値)+…+Ｚ₃₇・(変化表の値)} …(１２)
【０１９３】
ここで、Ａは、投影光学系ＰＬの目的収差、例えば非点収差、像面湾曲等、あるいは、目的収差の指標、例えばコマ収差の指標である線幅異常値などである。また、Ｋは、レジスト感度等に応じて定まる比例定数である。
【０１９４】
ここで、例えば、Ａが、線幅異常値である場合を考えると、例えばパターンが５本のラインを有するＬ／Ｓパターンである場合には、線幅異常値は、前述した式（１）で表せる。この式（１）から明らかなように、上式（１２）の計算は、パターンを空間像（投影像）に変換する計算に他ならない。
【０１９５】
次のステップ２２４では、全ての目的収差（条件設定された収差（結像特性））を算出したか否かを判断し、この判断が否定された場合には、ステップ２２２に戻り、次の目的収差を算出し、ＲＡＭ内に記憶する。
【０１９６】
このようにして、全ての目的収差の算出が終了すると、ステップ２２６に進んで、ＲＡＭ内に記憶されている全ての目的収差の算出結果をハードディスク等に記憶した後、次のステップ２２８に進む。
【０１９７】
ステップ２２８では、投影光学系ＰＬに関する情報、具体的には、開口数（Ｎ．Ａ．）、照明条件（例えば照明系開口絞りの設定、あるいはコヒーレンスファクタσ値等）、波長などの一部を、先にステップ２１０で入力されたものと異なる内容に変更した後、次のステップ２３０に進み、予め想定している予定回数の内容変更が終了したか否かを判断する。ここでは、１回だけ投影光学系ＰＬに関する情報を変更したのみなので、この判断は否定され、ステップ２１４に戻り、その後上記ステップ２１４以降の処理、判断を繰り返す。この際、ステップ２１４では、ツェルニケ変化表を作成するが、このとき上記ステップ２２８で変更された変更後の投影光学系ＰＬに関する情報に基づいてツェルニケ変化表を作成する。このようにして、照明条件、開口数、波長等を順次変更しながら、ステップ２１４〜ステップ２３０の処理、判断が繰り返され、予定回数の照明条件等の変更が繰り返されると、ステップ２３０における判断が肯定され、次のステップ２３２に進む。この時点では、予定数の条件設定下における目的収差の算出結果がハードディスク等の内部に記憶されている。
【０１９８】
次のステップ２３２では、ハードディスク等の内部に格納されている目的収差が最適となる（例えば、零ないし最小となる）ような投影光学系に関する条件（照明条件、開口数、波長等）を求め、その条件を最良露光条件として決定する。
【０１９９】
次のステップ２３４では、決定した最良露光条件を第１通信サーバ１２０に送信した後、本ルーチンの一連の処理を終了する。
【０２００】
上記の最良露光条件のデータを受信した第１通信サーバ１２０では、必要に応じて、最良露光条件の設定を命じる命令データを露光装置１２２₁の主制御装置５０に送り、主制御装置５０では、そのデータに応じて最良露光条件を設定する。具体的には、主制御装置５０では、照明系開口絞り板２４の開口絞りを変更することにより照明条件を変更（設定）し、あるいは、図２に示される投影光学系ＰＬの瞳開口絞り１５を調整することにより投影光学系ＰＬの開口数を調整することができる。あるいは、主制御装置５０では、制御情報ＴＳとして照明光ＥＬの波長を変更する情報を光源１６に与えることにより露光波長を設定することができる。
【０２０１】
なお、最良露光条件の設定を指示する指示データを、第２通信サーバ１３０が、直接露光装置１２２₁に与えることにより、露光装置１２２₁の最良露光条件を設定することも可能である。
【０２０２】
また、図５のフローチャートに対応する第３プログラムに僅かの変更を加えることにより、パターンの情報以外の設定情報を固定したまま、パターン情報を徐々に変更しながら、上記と同様のツェルニケ変化表の作成、及び波面の計測データに基づく目的収差（あるいは空間像）の算出を、繰り返し行うことにより、最良露光条件として最適なパターンの設定情報を決定することも可能である。
【０２０３】
同様に、図５のフローチャートに対応する第３プログラムに僅かの変更を加えることにより、与えたい収差の情報以外の設定情報を固定したまま、与えたい収差の情報を変更しながら、上記と同様のツェルニケ変化表の作成、及び波面の計測データに基づく目的収差（あるいは空間像）の算出を、繰り返し行うことにより、最良露光条件として、入力されたパターンを転写する際の投影光学系に与えるべき収差を決定することも可能である。かかる場合には、第２通信サーバ１３０は、投影光学系ＰＬにそのような収差（例えばツェルニケ多項式の第２項の係数Ｚ₂〜第３７項の係数Ｚ₃₇）が与えられるように、露光装置１２２₁の主制御装置５０を介して結像補正コントローラ４８を制御することにより結像特性を調整することができる。あるいは、第２通信サーバ１３０は、投影光学系ＰＬにそのような収差が与えられるように、第１通信サーバ１２０及び主制御装置５０を介して結像補正コントローラ４８を制御して結像特性を調整することができる。
【０２０４】
その他の露光装置１２２₂、１２２₃における最良露光条件の設定も上述と全く同様にして行われる。
【０２０５】
また、本実施形態において、例えば露光装置１２２の定期点検時等において、サービスエンジニア等が第１通信サーバ１２０側から条件設定入力、投影光学系に関する情報の入力等を行うことにより、これに応答して、第２通信サーバ１３０により、前述した第３プログラムを一部変更した別のプログラムを用いて、上述した最良露光条件の設定時におけるシミュレーションと同様の手順で同様のツェルニケ変化表が作成される。そして、露光装置１２２側でサービスエンジニア等の指示に基づき主制御装置５０により波面収差の計測が実行され、その結果得られる位置ずれのデータが第１通信サーバ１２０を介して送信されると、第２通信サーバ１３０では、上述と同様にして目的収差を算出する。そして、第２通信サーバ１３０では、その目的収差が最適（例えば零ないし最小）となるような可動レンズ１３₁〜１３₄の各自由度方向の駆動量を、別のプログラムを用いて最小自乗法により算出する。そして、第２通信サーバ１３０では、その算出した駆動量の指令値を、主制御装置５０を介して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の少なくとも１つ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の目的とする結像特性、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。この場合、必ずしも前述した第２プログラムを用いる必要はない。
【０２０６】
また、本実施形態では、ドライブ装置４６から記憶装置４２に上述した第３プログラムを一部変更した別のプログラムを予めインストールしておくことにより、定期メンテナンス時等における露光装置１２２の投影光学系ＰＬの調整時に、露光装置１２２自身による投影光学系ＰＬの結像特性の自動調整を容易に実現することができる。この場合、オペレータの指示（条件設定入力、投影光学系に関する情報の入力等も含む）に基づき、主制御装置５０内のＣＰＵにより上記のシミュレーションと同様の手順で同様の処理が行われ、同様のツェルニケ変化表が作成される。そして、波面収差の計測が実行され、位置ずれのデータが入力されると、主制御装置５０内のＣＰＵにより、上述と同様にして目的収差が算出される。その後、主制御装置５０内のＣＰＵでは、それらの目的収差が最適（例えば零ないし最小）となるような可動レンズ１３₁〜１３₄の各自由度方向の駆動量を、別のプログラムを用いて最小自乗法により算出する。そして、主制御装置５０内のＣＰＵでは、その算出した駆動量の指令値を、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の少なくとも１つ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の目的とする結像特性、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。
【０２０７】
上記の説明から明らかなように、本実施形態では、可動レンズ１３₁〜１３₄、これらの可動レンズを駆動する駆動素子、結像特性補正コントローラ４８によって結像特性調整機構が構成され、主制御装置５０によって結像特性調整機構を制御する制御装置が構成されている。
【０２０８】
ところで、上述の説明では、投影光学系ＰＬの波面収差の計測を波面収差計測器８０を用いて行う場合について説明したが、これに限らず、次に説明するような計測用レチクルＲ_T（以下、適宜「レチクルＲ_T」ともいう）を用いて波面収差を計測することも可能である。
【０２０９】
図６には、この計測用レチクルＲ_Tの概略斜視図が示されている。また、図７には、レチクルステージＲＳＴ上に装填した状態におけるレチクルＲ_Tの光軸ＡＸ近傍のＸＺ断面の概略図が、投影光学系ＰＬの模式図とともに示されている。また、図８には、レチクルステージＲＳＴ上に装填した状態におけるレチクルＲ_Tの−Ｙ側端部近傍のＸＺ断面の概略図が、投影光学系ＰＬの模式図とともに示されている。
【０２１０】
図６から明らかなように、この計測用レチクルＲ_Tの全体形状は、通常のペリクル付きレチクルとほぼ同様の形状を有している。この計測用レチクルＲ_Tは、ガラス基板６０、該ガラス基板６０の図６における上面のＸ軸方向中央部に、固定された長方形板状の形状を有するレンズ取付け部材６２、ガラス基板６０の図３における下面に取り付けられた通常のペリクルフレームと同様の外観を有する枠状部材から成るスペーサ部材６４、及びこのスペーサ部材６４の下面に取り付けられた開口板６６等を備えている。
【０２１１】
前記レンズ取付け部材６２には、Ｙ軸方向の両端部の一部の帯状の領域を除く、ほぼ全域にマトリックス状配置でｎ個の円形開口６３_i,j（ｉ＝１〜ｐ、ｊ＝１〜ｑ、ｐ×ｑ＝ｎ）が形成されている。各円形開口６３_i,jの内部には、Ｚ軸方向の光軸を有する凸レンズから成る集光レンズ６５_i,jがそれぞれ設けられている（図７参照）。
【０２１２】
また、ガラス基板６０とスペーサ部材６４と開口板６６とで囲まれる空間の内部には、図７に示されるように、補強部材６９が所定の間隔で設けられている。
【０２１３】
更に、ガラス基板６０の下面には、前記各集光レンズ６５_i,jに対向して、図７に示されるように、計測用パターン６７_i,jがそれぞれ形成されている。また、開口板６６には、図７に示されるように、各計測用パターン６７_i,jにそれぞれ対向してピンホール状の開口７０_i,jが形成されている。このピンホール状の開口７０_i,jは、例えば直径１００〜１５０μｍ程度とされている。
【０２１４】
図６に戻り、レンズ保持部材６２には、Ｙ軸方向の両端部の一部の帯状の領域の中央部に、開口７２₁、７２₂がそれぞれ形成されている。図８に示されるように、ガラス板６０の下面（パターン面）には、一方の開口７２₁に対向して基準パターン７４₁が形成されている。また、図示は省略されているが、他方の開口７２₂に対向して、ガラス板６０の下面（パターン面）に、基準パターン７４₁と同様の基準パターン（便宜上、「基準パターン７４₂」と記述する）が形成されている。
【０２１５】
また、図６に示されるように、ガラス基板６０のレチクル中心を通るＸ軸上には、レンズ保持部材６２の両外側に、レチクル中心に関して対称な配置で一対のレチクルアライメントマークＲＭ１，ＲＭ２が形成されている。
【０２１６】
ここで、本実施形態では、計測用パターン６７_i,jとして、図９（Ａ）に示されるような網目状（ストリートライン状）のパターンが用いられている。また、これに対応して、基準パターン７４₁、７４₂として、図９（Ｂ）に示されるような、計測用パターン６７_i,jと同一ピッチで正方形パターンが配置された２次元の格子パターンが用いられている。なお、基準パターン７４₁、７４₂として図９（Ａ）のパターンを用い、計測用パターンとして図９（Ｂ）に示されるパターンを用いることは可能である。また、計測用パターン６７_i,jは、これに限られず、その他の形状のパターンを用いても良く、その場合には、基準パターンとして、その計測用パターンとの間に所定の位置関係があるパターンを用いれば良い。すなわち、基準パターンは、計測用パターンの位置ずれの基準となるパターンであれば良く、その形状等は問わないが、投影光学系ＰＬの結像特性（光学特性）を計測するためには、投影光学系ＰＬのイメージフィールド又は露光領域の全面に渡ってパターンが分布しているパターンが望ましい。
【０２１７】
次に、露光装置１２２（露光装置１２２₁〜１２２₃）においてレチクルＲ_Tを用いる場合の投影光学系ＰＬの波面収差の計測について説明する。
【０２１８】
まず、計測用レチクルＲ_Tを用いて、投影光学系ＰＬの視野内の複数（ここでは、ｎ個）の計測点において、以下のようにして、波面収差を計測する。
【０２１９】
まず、入力装置４５を介してオペレータ（サービスエンジニアを含む）により波面収差の計測指令が入力されると、主制御装置５０では、不図示のレチクルローダを介して計測用レチクルＲ_TをレチクルステージＲＳＴ上にロードする。次いで、主制御装置５０では、レーザ干渉計５４Ｗの出力をモニタしつつ、ウエハステージ駆動部５６を介してウエハステージＷＳＴを移動し、基準マーク板ＦＭ上の一対のレチクルアライメント用基準マークを予め定められた基準位置に位置決めする。ここで、この基準位置とは、例えば一対の第２基準マークの中心が、レーザ干渉計５４Ｗで規定されるステージ座標系上の原点に一致する位置に定められている。
【０２２０】
次に、主制御装置５０では、計測用レチクルＲ_T上の一対のレチクルアライメントマークＲＭ１，ＲＭ２とこれらに対応するレチクルアライメント用基準マークとを、前述のレチクルアライメント顕微鏡により同時に観察し、レチクルアライメントマークＲＭ１，ＲＭ２の基準板ＦＭ上への投影像と、対応する基準マークとの位置ずれが、共に最小となるように、不図示の駆動系を介してレチクルステージＲＳＴをＸＹ２次元面内で微少駆動する。これにより、レチクルアライメントが終了し、レチクル中心が投影光学系ＰＬの光軸にほぼ一致する。
【０２２１】
次に、主制御装置５０では、不図示のウエハローダを用いて表面にレジスト（感光剤）が塗布されたウエハＷをＺチルトステージ５８上にロードする。
【０２２２】
次いで、主制御装置５０では、計測用レチクルＲ_Tの集光レンズ６５_i,jの全てが含まれ、かつ開口７２₁，７２₂が含まれず、レンズ保持部材６２のＸ軸方向の最大幅以内のＸ軸方向の長さを有する矩形の照明領域を形成するため、不図示の駆動系を介してレチクルブラインド３０の開口を設定する。また、これと同時に、主制御装置５０では、駆動装置４０を介して照明系開口絞り板２４を回転して、所定の開口絞り、例えば小σ絞りを照明光ＥＬの光路上に設定する。
【０２２３】
このような準備作業の後、主制御装置５０では、制御情報ＴＳを光源１６に与えて、レーザビームＬＢを発光させて、照明光ＥＬをレチクルＲ_Tに照射して露光を行う。これにより、図７に示されるように、各計測用パターン６７_i,jが、対応するピンホール状の開口７０_i,j及び投影光学系ＰＬを介して同時に転写される。この結果、ウエハＷ上のレジスト層には、図１０（Ａ）に示されるような各計測用パターン６７_i,jの縮小像（潜像）６７’_i,jが、所定間隔でＸＹ２次元方向に沿って所定間隔で形成される。
【０２２４】
次に、主制御装置５０では、不図示のレチクルレーザ干渉計の計測値とレチクルセンタと一方の基準パターン７４₁との設計上の位置関係とに基づいて、基準パターン７４₁の中心位置が光軸ＡＸ上に一致するように、不図示の駆動系を介してレチクルステージＲＳＴをＹ軸方向に所定距離移動する。次いで、主制御装置５０では、その移動後の開口７２₁を含むレンズ保持部材６２上の所定面積の矩形領域（この領域は、いずれの集光レンズにも掛からない）にのみ照明光ＥＬの照明領域を規定すべく、不図示の駆動系を介してレチクルブラインド３０の開口を設定する。
【０２２５】
次に、主制御装置５０では、最初の計測用パターン６７_1,1の潜像６７’_1,1が形成されたウエハＷ上の領域のほぼ中心が、投影光学系ＰＬの光軸上にほぼ一致するように、レーザ干渉計５４Ｗの計測値をモニタしつつ、ウエハステージＷＳＴを移動する。
【０２２６】
そして、主制御装置５０では、制御情報ＴＳを光源１６に与えて、レーザビームＬＢを発光させて、照明光ＥＬをレチクルＲ_Tに照射して露光を行う。これにより、ウエハＷ上のレジスト層の計測用パターン６７_1,1の潜像が既に形成されている領域（領域Ｓ_1,1と呼ぶ）に基準パターン７４₁が重ねて転写される。この結果、ウエハＷ上の領域Ｓ_1,1には、図１０（Ｂ）に示されるように、計測用パターン６７_1,1の潜像６７’_1,1と基準パターン７４₁の潜像７４’₁が同図のような位置関係で形成される。
【０２２７】
次いで、主制御装置５０では、レチクルＲ_T上の計測用パターン６７_i,jの配列ピッチと投影光学系ＰＬの投影倍率とに基づいて、ウエハＷ上の計測用パターン６７_i,jの設計上の配列ピッチｐを算出し、そのピッチｐだけ、ウエハステージＷＳＴをＸ軸方向に移動して、第２番目の計測用パターン６７_1,2の潜像が形成されたウエハＷ上の領域（領域Ｓ_1,2と呼ぶ）のほぼ中心が、投影光学系ＰＬの光軸上にほぼ一致するように、ウエハステージＷＳＴを移動する。
【０２２８】
そして、主制御装置５０では、制御情報ＴＳを光源１６に与えて、レーザビームＬＢを発光させて、照明光ＥＬをレチクルＲ_Tに照射して露光を行う。これにより、ウエハＷ上の領域Ｓ_1,2には基準パターン７４₁が重ねて転写される。
【０２２９】
以後、上記と同様の領域間ステッピング動作と、露光動作とを繰り返すことにより、ウエハＷ上の領域Ｓ_i,jに、図１０（Ｂ）と同様の計測用パターンと基準パターンとの潜像が形成される。
【０２３０】
このようにして、露光が終了すると、主制御装置５０では、不図示のウエハローダを介してウエハＷをＺチルトステージ５８上からアンロードした後、チャンバ１１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）に送る。そして、Ｃ／Ｄ内で、そのウエハＷの現像が行われ、その現像後にウエハＷ上には、マトリックス状に配列された各領域Ｓ_i,jに図１０（Ｂ）と同様の配置で計測用パターンと基準パターンとのレジスト像が形成される。
【０２３１】
その後、現像が終了したウエハＷは、Ｃ／Ｄから取り出され、外部の重ね合せ測定器（レジストレーション測定器）を用いて、各領域Ｓ_i,jについての重ね合せ誤差の測定が行われ、この結果に基づいて、各計測用パターン６７_i,jのレジスト像の対応する基準パターン７４₁に対する位置誤差（位置ずれ）が算出される。なお、この位置ずれの算出方法は、種々考えられるが、いずれにしても、計測された生データに基づいて統計演算を行うことが、精度を向上する観点からは望ましい。
【０２３２】
このようにして、各領域Ｓ_i,jについて、基準パターンに対する計測用パターンのＸ，Ｙ２次元方向の位置ずれ（Δξ’，Δη’）が求められる。そして、この各領域Ｓ_i,jについての位置ずれ（Δξ’，Δη’）のデータが、前述したサービスエンジニア等により、入力装置４４を介して主制御装置５０に入力される。なお、外部の重ね合せ測定器から、演算した各領域Ｓ_i,jについての位置ずれ（Δξ’，Δη’）のデータを、オンラインにて主制御装置５０に入力することも可能である。
【０２３３】
いずれにしても、上記の入力に応答して、主制御装置５０内のＣＰＵでは、前述した第１プログラムと同様の演算プログラムをメインメモリにロードし、位置ずれ（Δξ’，Δη’）に基づいて、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３７項の係数Ｚ₃₇を上記演算プログラムに従って演算する。
【０２３４】
このように、主制御装置５０内のＣＰＵでは、上記の位置ずれ（Δξ’，Δη’）に基づいて、所定の演算プログラムに従った演算により投影光学系ＰＬの波面を求めるのであるが、ここでは、その演算の前提となる、位置ずれ（Δξ’，Δη’）と波面との物理的な関係を、図７及び図８に基づいて簡単に説明する。
【０２３５】
図７に、計測用パターン６７_k,lについて、代表的に示されるように、計測用パターン６７_i,jで発生した回折光のうち、ピンホール状の開口７０_i,jを通過した光は、どの位置の計測用パターン６７_i,jに由来する光であるかによって、投影光学系ＰＬの瞳面を通過する位置が異なる。すなわち、当該瞳面の各位置における波面は、その位置に対応する計測用パターン６７_i,jの位置を介した光の波面と対応している。そして、仮に投影光学系ＰＬに収差が全くないものとすると、これらの波面は、投影光学系ＰＬの瞳面では、すべて符号Ｆ₁で示されるような理想波面（ここでは平面）となるはずである。しかるに、収差の全く無い投影光学系は実際には存在しないため、瞳面においては、例えば、点線で示されるような曲面状の波面Ｆ₂となる。従って、計測用パターン６７_i,jの像は、ウエハＷ上で波面Ｆ₁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。
【０２３６】
この一方、基準パターン７４₁（又は７４₂）から発生する回折光は、図８に示されるように、ピンホール状の開口の制限を受けることなく、しかも投影光学系ＰＬに直接入射し、該投影光学系ＰＬを介してウエハＷ上に結像される。更に、この基準パターン７４₁を用いた露光は、投影光学系ＰＬの光軸上に基準パターン７４₁の中心を位置決めした状態で行われることから、基準パターン７４₁から発生する結像光束は殆ど投影光学系ＰＬの収差の影響を受けることなく、光軸を含む微小領域に位置ずれなく結像する。
【０２３７】
従って、位置ずれ（Δξ’，Δη’）は、波面の理想波面に対する傾斜をそのまま反映した値になり、逆に位置ずれ（Δξ’，Δη’）に基づいて波面を復元することができる。なお、上記の位置ずれ（Δξ’，Δη’）と波面との物理的な関係から明らかなように、本実施形態における波面の算出原理は、周知のShack-Hartmannの波面算出原理そのものである。
【０２３８】
なお、計測用レチクルＲ_Tと同様の構成の特殊な構造のマスクを用い、そのマスク上の複数の計測用パターンのそれぞれを、個別に設けられたピンホール及び投影光学系を順次介して基板上に焼き付けるとともに、マスク上の基準パターンを集光レンズ及びピンホールを介することなく、投影光学系を介して基板上に焼き付けて、それぞれの焼き付けの結果得られる複数の計測用パターンのレジスト像それぞれの基準パターンのレジスト像に対する位置ずれを計測して所定の演算により、波面収差を算出する技術に関する発明が、米国特許第５，９７８，０８５号に開示されている。
【０２３９】
ところで、本実施形態の露光装置１２２₁〜１２２₃では、半導体デバイスの製造時には、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。
【０２４０】
なお、上記のレチクルアライメント、ベースライン計測等の準備作業については、例えば特開平４−３２４９２３号公報などに詳細に開示され、また、これに続くＥＧＡについては、特開昭６１−４４４２９号公報等に詳細に開示されているので、詳細な説明は省略する。
【０２４１】
その後、前述した計測用レチクルＲ_Tを用いた波面収差の計測時と同様のステップ・アンド・リピート方式の露光が行われる。但し、この場合、ステッピングは、ウエハアライメント結果に基づいて、ショット間を単位として行われる。なお、露光時の動作等は通常のステッパと異なることがないので、詳細説明については省略する。
【０２４２】
次に、露光装置１２２（１２２₁〜１２２₃）の製造の際に行われる投影光学系ＰＬの製造方法について説明する。
【０２４３】
ａ． 投影光学系の仕様の決定
この仕様の決定に際しては、まず、ユーザーであるメーカＡ側の技術者等により、不図示の入出力装置を介して第１通信サーバ１２０に、露光装置が達成すべき目標情報、例えば露光波長、最小線幅（又は解像力）、及び対象パターン等の情報が入力される。次に、上記技術者等は、入出力装置を介してその目標情報の送信を第１通信サーバ１２０に指示する。
【０２４４】
これにより、第１通信サーバ１２０では、第２通信サーバ１３０に対してデータの受信が可能であるか否かの問い合わせを行い、第２通信サーバ１３０からの受信可能である旨の回答を受けて、前記目標情報を第２通信サーバ１３０に送信する。
【０２４５】
第２通信サーバ１３０では、上記の目標情報を受信して、分析を行い、その分析結果に基づいて、後述するような７通りの仕様決定方法の中から、１つの方法を選択して、仕様を決定し、その決定した仕様をＲＡＭ内に記憶する。
【０２４６】
ここで、仕様決定方法の説明に先立って、前述した式（４）で表される、投影光学系の波面を展開したツェルニケ多項式（フリンジツェルニケ多項式）の各項の係数Ｚ_iがどのような収差に関連するかを簡単に説明する。各項は、前述した表１に示されるような、ｆ_i（ρ，θ）項、すなわちρの最高次数をｎ次とし、θに掛かる係数をｍとするｎ次ｍθ項を含む項である。
【０２４７】
０次０θ項の係数Ｚ₁は、波面のポジションを示すものであり、収差とは殆ど関係がない。
１次１θ項（の係数（Ｚ₂，Ｚ₃））は、ディストーション成分を示す。
２次０θ項（の係数Ｚ₄）は、フォーカス成分を示す。
３次以上の０θ項（の係数（Ｚ₉，Ｚ₁₆，Ｚ₂₅，Ｚ₃₆，Ｚ₃₇））は、球面収差成分を示す。
２θ項（の係数（Ｚ₅，Ｚ₆，Ｚ₁₂，Ｚ₁₃，Ｚ₂₁，Ｚ₂₂，Ｚ₃₂，Ｚ₃₃））、及び４θ項（の係数（Ｚ₁₇，Ｚ₁₈，Ｚ₂₈，Ｚ₂₉））は、非点収差成分を示す。
３次以上の１θ項（の係数（Ｚ₇，Ｚ₈，Ｚ₁₄，Ｚ₁₅，Ｚ₂₃，Ｚ₂₄，Ｚ₃₄，Ｚ₃₅））、３θ項（の係数（Ｚ₁₀，Ｚ₁₁，Ｚ₁₉，Ｚ₂₀，Ｚ₃₀，Ｚ₃₁））、及び５θ項（の係数（Ｚ₂₆，Ｚ₂₇））はコマ収差成分を示す。
【０２４８】
以下、７通りの仕様決定方法について説明するが、いずれの方法も投影光学系が満足すべき波面収差を規格値として投影光学系の仕様を決定するものである。
【０２４９】
＜第１の方法＞
これは、投影光学系の波面を展開したツェルニケ多項式の各項の係数のうち、目標情報に基づいて選択した特定の項の係数（の値）を規格値として投影光学系の仕様を決定する方法である。この第１の方法は、一例として、目標情報に例えば解像力が含まれる場合に、例えばディストーション成分に対応する係数Ｚ₂，Ｚ₃を選択し、これらの係数の値そのものを規格値として、視野内において、これらがそれぞれ所定の値以下となるように投影光学系の仕様を決定するような場合に用いられる。
【０２５０】
＜第２の方法＞
これは、投影光学系の波面を展開したツェルニケ多項式の各項の係数のＲＭＳ値（Root-means-square value：二乗平均値の平方根）を規格値とし、投影光学系の視野内全体における前記ＲＭＳ値が所定の許容値を超えないように投影光学系の仕様を決定する方法である。この第２の方法によれば、例えば像面湾曲等の視野内全体で定義される収差が抑制されることとなる。この第２の方法は、目標情報の如何によらず好適に適用できる。勿論、各項の係数の視野内におけるＲＭＳ値を規格値としても良い。
【０２５１】
＜第３の方法＞
これは、投影光学系の波面を展開したツェルニケ多項式の各項の係数の値を規格値とし、前記係数が個別に定められた各許容値をそれぞれ超えないように前記投影光学系の仕様を決定する方法である。この第３の方法では、各許容値を同一値として設定することもできるし、個別に異なる値を任意に設定することもできる。勿論、このうちのいくつかが同一値であることとすることもできる。
【０２５２】
＜第４の方法＞
この第４の方法は、投影光学系の波面を展開したツェルニケ多項式の各項の係数のうち、着目する特定の収差に対応するｎ次ｍθ項の係数のＲＭＳ値を規格値とし、前記ＲＭＳ値が所定の許容値を超えないように投影光学系の仕様を決定する方法である。この第４の方法は、例えば目標情報にパターン情報が含まれている場合に、そのパターン情報を分析してそのパターンの投影像を良好な状態で像面上に形成するためには、特に抑制しなければならないのは、どの収差であるかを推測し、その推測結果に基づいて、ｎ次ｍθ項の係数のＲＭＳ値を例えば次のように規格化する。
【０２５３】
視野内におけるＺ₂，Ｚ₃に関するＲＭＳ値Ａ₁を規格値とし、規格値Ａ₁≦許容値Ｂ₁とする。
視野内におけるＺ₄のＲＭＳ値Ａ₂を規格値とし、規格値Ａ₂≦許容値Ｂ₂とする。
視野内におけるＺ₅，Ｚ₆に関するＲＭＳ値Ａ₃を規格値とし、規格値Ａ₃≦許容値Ｂ₃とする。
視野内におけるＺ₇，Ｚ₈に関するＲＭＳ値Ａ₄を規格値とし、規格値Ａ₄≦許容値Ｂ₄とする。
視野内におけるＺ₉のＲＭＳ値Ａ₅を規格値とし、規格値Ａ₅≦許容値Ｂ₅とする。
視野内におけるＺ₁₀，Ｚ₁₁に関するＲＭＳ値Ａ₆を規格値とし、規格値Ａ₆≦許容値Ｂ₆とする。
視野内におけるＺ₁₂，₁₃に関するＲＭＳ値Ａ₇を規格値とし、規格値Ａ₇≦許容値Ｂ₇とする。
視野内におけるＺ₁₄，Ｚ₁₅に関するＲＭＳ値Ａ₈を規格値とし、規格値Ａ₈≦許容値Ｂ₈とする。
視野内におけるＺ₁₆のＲＭＳ値Ａ₉を規格値とし、規格値Ａ₉≦許容値Ｂ₉とする。
視野内におけるＺ₁₇，Ｚ₁₈に関するＲＭＳ値Ａ₁₀を規格値とし、規格値Ａ₁₀≦許容値Ｂ₁₀とする。
視野内におけるＺ₁₉，Ｚ₂₀に関するＲＭＳ値Ａ₁₁を規格値とし、規格値Ａ₁₁≦許容値Ｂ₁₁とする。
視野内におけるＺ₂₁，Ｚ₂₂に関するＲＭＳ値Ａ₁₂を規格値とし、規格値Ａ₁₂≦許容値Ｂ₁₂とする。
視野内におけるＺ₂₃，Ｚ₂₄に関するＲＭＳ値Ａ₁₃を規格値とし、規格値Ａ₁₃≦許容値Ｂ₁₃とする。
視野内におけるＺ₂₅のＲＭＳ値Ａ₁₄を規格値とし、規格値Ａ₁₄≦許容値Ｂ₁₄とする。
視野内におけるＺ₂₆，Ｚ₂₇に関するＲＭＳ値Ａ₁₅を規格値とし、規格値Ａ₁₅≦許容値Ｂ₁₅とする。
視野内におけるＺ₂₈，Ｚ₂₉に関するＲＭＳ値Ａ₁₆を規格値とし、規格値Ａ₁₆≦許容値Ｂ₁₆とする。
視野内におけるＺ₃₀，Ｚ₃₁に関するＲＭＳ値Ａ₁₇を規格値とし、規格値Ａ₁₇≦許容値Ｂ₁₇とする。
視野内におけるＺ₃₂，Ｚ₃₃に関するＲＭＳ値Ａ₁₈を規格値とし、規格値Ａ₁₈≦許容値Ｂ₁₈とする。
視野内におけるＺ₃₄，Ｚ₃₅に関するＲＭＳ値Ａ₁₉を規格値とし、規格値Ａ₁₉≦許容値Ｂ₁₉とする。
視野内におけるＺ₃₆，Ｚ₃₇に関するＲＭＳ値Ａ₂₀を規格値とし、規格値Ａ₂₀≦許容値Ｂ₂₀とする。
【０２５４】
＜第５の方法＞
この第５の方法は、投影光学系の波面を展開したツェルニケ多項式の各項の係数のうち、着目する特定の収差に対応する各項をｍθ項毎の複数のグループに分離し、各グループに含まれる各項の係数の視野内におけるＲＭＳ値を規格値とし、各グループの前記ＲＭＳ値が個別に定められた各許容値を超えないように投影光学系の仕様を決定する方法である。
【０２５５】
例えば、３次以上の０θ項の係数Ｚ₉，Ｚ₁₆，Ｚ₂₅，Ｚ₃₆，Ｚ₃₇に関する視野内におけるＲＭＳ値Ｃ₁を規格値とし、規格値Ｃ₁≦許容値Ｄ₁とする。
３次以上の１θ項の係数Ｚ₇，Ｚ₈，Ｚ₁₄，Ｚ₁₅，Ｚ₂₃，Ｚ₂₄，Ｚ₃₄，Ｚ₃₅に関する視野内におけるＲＭＳ値Ｃ₂を規格値とし、規格値Ｃ₂≦許容値Ｄ₂とする。２θ項の係数Ｚ₅，Ｚ₆，Ｚ₁₂，Ｚ₁₃，Ｚ₂₁，Ｚ₂₂，Ｚ₃₂，Ｚ₃₃に関する視野内におけるＲＭＳ値Ｃ₃を規格値とし、規格値Ｃ₃≦許容値Ｄ₃とする。
３θ項の係数Ｚ₁₀，Ｚ₁₁，Ｚ₁₉，Ｚ₂₀，Ｚ₃₀，Ｚ₃₁に関する視野内におけるＲＭＳ値を規格値Ｃ₄とし、規格値Ｃ₄≦許容値Ｄ₄とする。
４θ項の係数Ｚ₁₇，Ｚ₁₈，Ｚ₂₈，Ｚ₂₉に関する視野内におけるＲＭＳ値を規格値Ｃ₅とし、規格値Ｃ₅≦許容値Ｄ₅とする。
５θ項の係数Ｚ₂₆，Ｚ₂₇に関する視野内におけるＲＭＳ値を規格値Ｃ₆とし、規格値Ｃ₆≦許容値Ｄ₆とする。
【０２５６】
この第５の方法も、前述の各項の係数の有する意味からわかるように、例えば目標情報にパターン情報が含まれている場合に、そのパターン情報を分析してそのパターンの投影像を良好な状態で像面上に形成するためには、特に抑制しなければならないのは、どの収差であるかを推測し、その推測結果に基づいて行うことができる。
【０２５７】
＜第６の方法＞
この第６の方法は、投影光学系ＰＬの波面を展開したツェルニケ多項式の各項の係数に目標情報に応じて重み付けした重み付け後の各項の係数を規格値とし、重み付け後の前記各項の係数の視野内におけるＲＭＳ値が所定の許容値を超えないように投影光学系の仕様を決定する方法である。この第６の方法も、例えば目標情報にパターン情報が含まれている場合に、そのパターン情報を分析してそのパターンの投影像を良好な状態で像面上に形成するためには、特に抑制しなければならないのは、どの収差であるかを推測し、その推測結果に基づいて行うことができる。
【０２５８】
＜第７の方法＞
この第７の方法は、目標情報に、投影光学系の投影対象であるパターンの情報が含まれる場合にのみ用いられる方法であって、前記パターンの情報に基づいて、該パターンを投影光学系により投影した際に像面に形成される空間像を求めるためのシミュレーションを行い、このシミュレーション結果を分析してパターンが良好に転写されるために投影光学系に許容される波面収差を規格値として投影光学系の仕様を決定するものである。この場合、シミュレーションの方法として、例えば前述と同様のツェルニケ変化表を予め作成し、そのツェルニケ変化表から得られる、前記パターンを対象パターンとした場合に特定の収差（その指標値を含む）に対して前記パターンに応じて定まる、、投影光学系の波面を展開したツェルニケ多項式の各項の係数の感度（Zernike Sensitivity）と、投影光学系の波面を展開したツェルニケ多項式の各項の係数との線形結合に基づいて空間像を求めても良い。
【０２５９】
これを更に詳述すると、投影光学系の視野内のｎ個の計測点（評価点）における諸収差（その指標値を含む）、例えばｍ種類の収差から成るｎ行ｍ列のマトリックスｆと、前記ｎ個の計測点における波面収差のデータ、例えば波面を展開したツェルニケ多項式の各項の係数、例えば第２項〜第３７項の係数Ｚ₂〜Ｚ₃₇から成るｎ行３６列のマトリックスＷａと、ツェルニケ変化表のデータ（すなわち所定の露光条件下におけるｍ種類の諸収差のツェルニケ多項式の各項の係数、例えば第２項〜第３７項の係数Ｚ₂〜Ｚ₃₇の１λ当たりの変化量（Zernike Sensitivity）から成る例えば３６行ｍ列のマトリックスＺＳとの間には、次式（１３）で示される関係がある。
ｆ＝Ｗａ・ＺＳ ……（１３）
【０２６０】
ここで、ｆ、Ｗａ、ＺＳは、一例としてそれぞれ次式（１４）、（１５）、（１６）のように表すことができる。
【０２６１】
【数 ７】

【０２６２】
上記式（１３）から明らかなように、ツェルニケ変化表と波面収差のデータ（例えば波面を展開したツェルニケ多項式の各項の係数、例えば第２項〜第３７項の係数Ｚ₂〜Ｚ₃₇）とを用いることにより、任意の収差を所望の値に定めることができる。換言すれば、上式（１３）のｆに所望の収差の値を与え、既知の（予め作成した）ツェルニケ変化表のデータを用いて、上式（１３）を最小自乗法で解くことにより、特定の収差を所望の値にする投影光学系の視野内の各点におけるツェルニケ多項式の各項の係数、例えば第２項〜第３７項の係数Ｚ₂〜Ｚ₃₇を定めることができることがわかる。
【０２６３】
すなわち、この第７の方法は、上記のシミュレーションにより、特定の収差、例えばコマ収差の指標値である線幅異常値が所定の値以下となるようなパターンの空間像を求め、その空間像が得られたときの波面収差（波面を展開したツェルニケ多項式の各項の係数）を規格値として投影光学系の仕様を決定するものである。
【０２６４】
上述した第１〜第７の仕様決定方法は、いずれも露光装置が達成すべき目標情報に基づいて、投影光学系の瞳面における波面の情報、すなわち瞳面を通過する総合的な情報を規格値として投影光学系の仕様を決定するので、この仕様を満足する投影光学系を製造すれば、結果的に露光装置が達成すべき目標を確実に達成することができる。
【０２６５】
ｂ． 投影光学系の製造工程
次に、図１１のフローチャートに沿って投影光学系ＰＬの製造工程について説明する。
【０２６６】
〔ステップ１〕
ステップ１では、まず、所定の設計レンズデータによる設計値に従って投影光学系ＰＬを構成する各光学部材としての各レンズ素子、並びに各レンズを保持するレンズホルダ、レンズ素子とレンズホルダとから成る光学ユニットを収納する鏡筒を製造する。すなわち、各レンズ素子は、周知のレンズ加工機を用いて所定の光学材料からそれぞれ所定の設計値に従う曲率半径、軸上厚を持つように加工され、また各レンズを保持するレンズホルダ、レンズ素子とレンズホルダとから成る光学ユニットを収納する鏡筒は、周知の金属加工機等を用いて所定の保持材料（ステンレス、真鍮、セラミック等）からそれぞれ所定の寸法を持つ形状に加工される。
【０２６７】
〔ステップ２〕
ステップ２では、ステップ１にて製造された投影光学系ＰＬを構成する各レンズ素子のレンズ面の面形状を例えばフィゾー型の干渉計を用いて計測する。このフィゾー型の干渉計としては、波長６３３ｎｍの光を発するＨｅ−Ｎｅ気体レーザや波長３６３ｎｍの光を発するＡｒレーザ、波長２４８ｎｍに高調波化されたＡｒレーザ等を光源とするものが用いられる。このフィゾー型の干渉計によると、光路上に配置された集光レンズの表面に形成された参照面と被検面であるレンズ素子表面からの反射光の干渉による干渉縞をＣＣＤ等の撮像装置により計測することにより被検面の形状を正確に求めることができる。なお、フィゾー型の干渉計を用いてレンズ等の光学素子の表面（レンズ面）の形状を求めることは公知であり、このことは、例えば、特開平６２−１２６３０５号、特開平６−１８５９９７号等にて開示されているので、詳細な説明は省略する。
【０２６８】
上述したフィゾー型の干渉計を用いた光学素子の面形状の計測は、投影光学系ＰＬを構成する各レンズ素子の全てのレンズ面に関して行われる。そして、それぞれの計測結果をコンソール等の不図示の入力装置を介して第２通信サーバ１３０が備えるＲＡＭ等のメモリ、あるいはハードディスク等の記憶装置に記憶させる。
【０２６９】
〔ステップ３〕
ステップ２での投影光学系ＰＬを構成する各レンズ素子の全てのレンズ面の面形状の計測が完了した後、設計値に従って加工製造された光学ユニット、すなわち、レンズ等の光学素子とその光学素子を保持するレンズホルダとからそれぞれ成る複数の光学ユニットを組み上げる。この光学ユニットのうち、複数、例えば４つは、前述した可動レンズ１３₁〜１３₄をそれぞれ有しており、該可動レンズ１３₁〜１３₄を有する光学ユニットには、前述の如く、上記レンズホルダとして、二重構造のレンズホルダが用いられている。すなわち、これらの二重構造のレンズホルダは、可動レンズ１３₁〜１３₄をそれぞれ保持する内側レンズホルダと、その内側レンズホルダを保持する外側レンズホルダとをそれぞれ有し、内側レンズホルダと外側レンズホルダとの位置関係が機械式の調整機構を介して調整可能な構造となっている。また、二重構造のレンズホルダには、前述した駆動素子がそれぞれ所定の位置に設けられている。
【０２７０】
そして、上述のようにして組み上げられた複数の光学ユニットを、鏡筒の上部開口を介して順次、スペーサを介在させながら鏡筒内に落とし込むように組み上げていく。そして、最初に鏡筒内に落としこまれた光学ユニットは、鏡筒の下端に形成された突出部によってスペーサを介して支持され、全ての光学ユニットが鏡筒内に収容されることにより組み立て工程が完了する。この組み立て工程と並行して、光学ユニットと共に鏡筒内に収納されるスペーサの厚さを加味しながら工具（マイクロメータ等）を用いて、各レンズ素子の光学面（レンズ面）の間隔に関する情報を計測する。そして、投影光学系の組み立て作業と計測作業とを交互に行いながら、ステップ３の組み立て工程が完了した段階での投影光学系ＰＬの最終的な各レンズ素子の光学面（レンズ面）の間隔を求める。
【０２７１】
なお、この組み立て工程を含み、製造段階の各工程では、前述した可動レンズ１３₁〜１３₄は中立位置に固定されている。また、説明は省略したが、この組み立て工程において、瞳開口絞り１５も組み込まれる。
【０２７２】
上記の組み立て工程中または組み立て完了時での投影光学系ＰＬの各レンズ素子の光学面（レンズ面）間の間隔に関する計測結果を不図示のコンソール等の不図示の入力装置を介して第２通信サーバ１３０が備えるＲＡＭ等のメモリ、あるいはハードディスク等の記憶装置に記憶させる。なお、以上の組み立て工程に際して、必要に応じて光学ユニットを調整しても良い。
【０２７３】
このとき、例えば、機械式の調整機構を介して光学素子間の光軸方向での相対間隔を変化、あるいは光軸に対して光学素子を傾斜させる。また、鏡筒の側面を貫通する雌螺子部を通して螺合するねじ（ビス）の先端がレンズホルダに当接するように鏡筒を構成し、そのねじをねじ回し（スクリュドライバ）等の工具を介して移動させることにより、レンズホルダを光軸と直交する方向へずらし、偏心等の調整をしても良い。
【０２７４】
〔ステップ４〕
次に、ステップ４では、ステップ３にて組み上がった投影光学系ＰＬの波面収差を計測する。
【０２７５】
具体的には、投影光学系ＰＬを不図示の大型の波面計測装置のボディに取り付け、波面収差を計測する。この波面計測装置による波面の計測原理は、前述した波面収差計測器８０と異なるところがないので、詳細説明は省略する。
【０２７６】
上記の波面収差の計測の結果、波面計測装置により、投影光学系の波面を展開したツェルニケ多項式（フリンジツェルニケ多項式）の各項の係数Ｚ_i（ｉ＝１、２、……、３７）が得られる。従って、波面計測装置を第２通信サーバ１３０に接続しておくことにより、第２通信サーバ１３０のＲＡＭ等のメモリ（あるいはハードディスク等の記憶装置）に上記ツェルニケ多項式の各項の係数Ｚ_iが自動的に取り込まれる。なお、上記の説明では、波面計測装置では、ツェルニケ多項式の第８１項までを用いるものとしたが、これは、投影光学系ＰＬの各収差の高次成分も算出するためにこのようにしたものである。しかし、前述の波面収差計測器の場合と同様に第３７項までを算出することとしても良いし、あるいは８２項以上の項をも算出するようにしても良い。
【０２７７】
〔ステップ５〕
ステップ５では、ステップ４にて計測された波面収差が、先に説明した第１〜第７の仕様決定方法のうちから選択された決定方法に従って決定された仕様を満足するように、投影光学系ＰＬを調整する。
【０２７８】
まず、投影光学系ＰＬの調整に先立って、第２通信サーバ１３０は、メモリ内に記憶された各情報、すなわち上記ステップ２にて得られた各光学素子の面形状に関する情報及び上記ステップ３の組み立て工程にて得られた各光学素子の光学面の間隔に関する情報等に基づいて、メモリ内に予め記憶された光学基本データを修正して、実際に組上がった投影光学系ＰＬの製造過程での光学データを再現する。この光学データは、各光学素子の調整量を算出するために用いられる。
【０２７９】
すなわち、第２通信サーバ１３０のハードディスク内には、投影光学系ＰＬを構成する全てのレンズ素子について、各レンズ素子の６自由度方向それぞれの単位駆動量とツェルニケ多項式の各項の係数Ｚ_iの変化量との関係を、投影光学系の設計値に基づいて算出した、いわば前述したマトリックスＯを可動レンズのみならず非可動のレンズ素子をも含むように拡張した調整用基本データベースが、予め格納されている。そこで、第２通信サーバ１３０では、上述した投影光学系ＰＬの製造過程での光学データに基づいて、所定の演算により上記の調整用基本データベースを修正する。
【０２８０】
そして、例えば上述した第１〜第６の方法のいずれかを選択している場合には、第２通信サーバ１３０では、修正後の基本データベースと、波面の目標値、すなわち選択した仕様決定方法に基づきツェルニケ多項式の各項の係数Ｚ_iが満足すべき値と、上記波面計測装置の計測結果として得られたツェルニケ多項式の各項の係数Ｚ_iの実測値とに基づいて、所定の演算プログラムに従って、各レンズ素子の６自由度方向それぞれの調整量を例えば最小自乗法により算出する。
【０２８１】
そして、第２通信サーバ１３０では、ディスプレイの画面上に各レンズ素子の６自由度方向それぞれの調整量（ゼロを含む）の情報を表示する。
【０２８２】
この表示に従って、技術者（作業者）により、各レンズ素子が調整される。これにより、選択された仕様決定方法に従って決定された仕様を満たすように投影光学系ＰＬが調整される。
【０２８３】
具体的には、仕様決定方法として、第１の方法が選択されている場合には、投影光学系ＰＬの波面を展開したツェルニケ多項式の各項の係数のうち、目標情報に基づいて選択した特定の項の係数が所定値を超えないように投影光学系ＰＬが調整される。また、第２の方法が選択されている場合には、投影光学系ＰＬの視野内全体における波面を展開したツェルニケ多項式の各項の係数のＲＭＳ値が、所定の許容値を超えないように投影光学系ＰＬが調整される。また、第３の方法が選択されている場合には、投影光学系の波面を展開したツェルニケ多項式の各項の係数が個別に定められた各許容値をそれぞれ超えないように投影光学系ＰＬが調整される。また、第４の方法が選択されている場合には、投影光学系ＰＬの波面を展開したツェルニケ多項式の各項の係数のうち、着目する特定の収差に対応するｎ次ｍθ項の係数の視野内におけるＲＭＳ値が所定の許容値を超えないように投影光学系ＰＬが調整される。第５の方法が選択されている場合には、投影光学系ＰＬの波面を展開したツェルニケ多項式の各項の係数のうち、着目すべき特定の収差に対応する各項をｍθ項毎の複数のグループに分離し、各グループに含まれる各項の係数の視野内におけるＲＭＳ値が個別に定められた各許容値を超えないように投影光学系が調整される。また、第６の方法が選択されている場合には、投影光学系ＰＬの波面を展開したツェルニケ多項式の各項の係数に目標情報に応じて重み付けした重み付け後の各項の係数の視野内におけるＲＭＳ値が所定の許容値を超えないように投影光学系ＰＬが調整される。
【０２８４】
一方、第７の方法を選択している場合には、第２通信サーバ１３０では、前記目標情報に含まれるパターンの情報に基づいて、該パターンを投影光学系により投影した際に像面に形成される空間像を求めるためのシミュレーションを行い、このシミュレーション結果を分析してパターンが良好に転写されるために投影光学系ＰＬに許容される波面収差を満たすように投影光学系ＰＬを調整する。この場合において、第２通信サーバ１３０では、シミュレーションの方法として、例えば前述と同様のツェルニケ変化表を予め作成し、そのツェルニケ変化表から得られる、前記パターンを対象パターンとした場合の特定の収差（その指標値を含む）に対する、投影光学系の波面を展開したツェルニケ多項式の各項の係数の感度（Zernike Sensitivity）と、投影光学系の波面を展開したツェルニケ多項式の各項の係数との線形結合に基づいて空間像を求め、その空間像に基づいて前記着目する収差が許容値を超えないようなレンズ素子の調整量を例えば最小自乗法により算出する。
【０２８５】
そして、第２通信サーバ１３０では、ディスプレイの画面上に各レンズ素子の６自由度方向それぞれの調整量（ゼロを含む）の情報を表示する。この表示に従って、技術者（作業者）により、各レンズ素子が調整される。これにより、選択された第７の仕様決定方法に従って決定された仕様を満たすように投影光学系ＰＬが調整される。
【０２８６】
いずれにしても、投影光学系ＰＬの波面の計測結果に基づいて投影光学系ＰＬが調整されるので、低次収差のみでなく高次収差も含めて同時に調整でき、しかも従来のように調整する収差の順番を考慮する必要もない。従って、投影光学系の光学特性を高精度にかつ簡易に調整することが可能となる。このようにして、決定した仕様をほぼ満たす投影光学系ＰＬが製造されることとなる。
【０２８７】
なお、本実施形態では、ステップ４にて波面収差を計測した後、投影光学系の調整を行うことなく投影光学系を露光装置に組み込んでから投影光学系の調整を行うものとしたが、投影光学系を露光装置に組み込む前に投影光学系の調整（光学素子の再加工や交換など）を行い、この調整された投影光学系を露光装置に組み込むようにしても良い。このとき、前述の結像特性調整機構を用いることなく、例えば作業者が光学素子の位置調整などを行うことにより投影光学系を調整しても良い。また、投影光学系を露光装置に組み込んでから、前述の波面収差計測器８０又は計測用レチクルＲ_Tを用いて波面収差を再度計測し、この計測結果に基づいて投影光学系を再調整することが望ましい。
【０２８８】
なお、上記の投影光学系ＰＬの調整等に際して行われる波面収差の計測は、上述の如く、波面計測装置を用い、ピンホール及び投影光学系ＰＬを介して形成された空間像に基づいて行うこととしても良いが、これに限らず、例えば計測用レチクルＲ_Tを用い、所定の計測用パターンをピンホール及び投影光学系ＰＬを介してウエハＷ上に焼付けた結果に基づいて行うこととしても良い。また、投影光学系の光学素子の再加工又は交換が必要なときは、投影光学系を露光装置に組み込む前に再加工又は交換を行うことが好ましい。
【０２８９】
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、上述の波面計測装置を用いて波面収差を計測した際に、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。
【０２９０】
次に、露光装置１２２の製造方法について説明する。
【０２９１】
露光装置１２２の製造に際しては、まず、複数のレンズ素子、ミラー等の光学素子などを含む照明光学系１２をユニット単体として組み立てるとともに、上述のようにして投影光学系ＰＬを単体として組み立てる。また、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。そして、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。なお、この調整に際して、投影光学系ＰＬについては上述した方法により調整が行われる。
【０２９２】
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。
【０２９３】
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の結像特性が微妙に変化するからである。本実施形態では、この露光装置本体に対する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、前述した波面収差計測器８０をＺチルトステージ５８に取り付け、前述と同様にして波面収差を計測し、その波面収差の計測結果として得られる各計測点における波面の情報を、オンラインにてその製造中の露光装置の主制御装置５０から第２通信サーバ１３０に送る。そして、第２通信サーバ１３０により、上述した投影光学系ＰＬ単体の製造時における調整の際と同様にして、各レンズ素子の６自由度方向それぞれの調整量を例えば最小自乗法により算出し、その算出結果をディスプレイ上に表示させる。
【０２９４】
そして、この表示に従って、技術者（作業者）により、各レンズ素子が調整される。これにより、決定された仕様を確実に満たす投影光学系ＰＬが製造される。
【０２９５】
なお、この製造段階における最終調整を、前述した第２通信サーバ１３０からの指示に基づく、主制御装置５０による結像特性補正コントローラ４８を介した投影光学系ＰＬの自動調整により行うことは可能である。しかしながら、露光装置の製造が終了した段階では、各可動レンズを中立位置に保っておくことが、半導体製造工場への納入後に駆動素子の駆動ストロークを十分に確保するために望ましく、また、この段階で、修正されていない収差、主として高次収差は自動調整が困難な収差であると判断できるので、上記の如く、レンズ等の組付けなどを再調整することが望ましい。
【０２９６】
なお、上記の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又は交換する必要も生じる。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、前述した如く、投影光学系ＰＬを露光装置本体に組み込む前に投影光学系ＰＬの波面収差を前述の波面計測装置等を用いて計測し、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することとしても良い。また、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。
【０２９７】
また、投影光学系ＰＬの光学素子単位でその交換などを行っても良いし、あるいは複数の鏡筒を有する投影光学系ではその鏡筒単位で交換などを行っても良い。更に、光学素子の再加工では必要に応じてその表面を非球面に加工しても良い。また、投影光学系ＰＬの調整では光学素子の位置（他の光学素子との間隔を含む）や傾斜などを変更するだけでも良いし、特に光学素子がレンズエレメントであるときはその偏心を変更したり、あるいは光軸ＡＸを中心として回転させても良い。
【０２９８】
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１２２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。
【０２９９】
以上説明したように、本実施形態によると、投影光学系ＰＬの製造に際して、コンピュータシステム１０によって、露光装置１２２が達成すべき目標情報に基づいて、投影光学系ＰＬが満足すべき波面収差を規格値として投影光学系ＰＬの仕様が決定される。すなわち、投影光学系ＰＬの瞳面における波面の情報を規格値として投影光学系ＰＬの仕様が決定される。そして、投影光学系ＰＬ、ひいては露光装置の製造工程における投影光学系の調整段階では、決定された仕様を満足するように投影光学系ＰＬが調整される。この際、低次収差のみでなく高次収差も含めて調整されるので、従来のような段階的な調整が不要となるとともに、高次収差の調整のための光線追跡等も不要となる。従って、投影光学系ＰＬの製造工程を簡略化することが可能である。しかも、製造された投影光学系ＰＬにより露光装置１２２が達成すべき目標が確実に達成されることとなる。
【０３００】
また、上記の露光装置の製造工程における投影光学系の調整に際しては、投影光学系ＰＬの波面収差を計測し、その波面収差の計測結果（実測値）に基づいて、投影光学系ＰＬが前記仕様を満足するように投影光学系ＰＬを調整する。従って、仕様通りの投影光学系ＰＬを簡易かつ確実に製造することができる。
【０３０１】
また、本実施形態では、波面収差の計測を、投影光学系ＰＬが露光装置本体（光学装置の本体）に組み込まれる前及び投影光学系ＰＬが露光装置本体に組み込まれた後のいずれにおいても行われる。前者では、専用の波面収差計測装置を用いて非常に高精度に投影光学系の波面を計測することができ、また、後者により、露光装置本体に対する組み込みの前後において環境条件の変化等があっても、これに影響を受けることのない、高精度な投影光学系の光学特性の調整が可能となる。これに限らず、波面収差の計測を、投影光学系ＰＬが露光装置本体（光学装置の本体）に組み込まれる前及び投影光学系ＰＬが露光装置本体に組み込まれた後のいずれか一方のみにおいて行うようにしても良い。
【０３０２】
いずれにしても、投影光学系ＰＬの波面の計測結果に基づいて投影光学系ＰＬが調整されるので、低次収差のみでなく高次収差も含めて同時に調整でき、しかも従来のように調整する収差の順番を考慮する必要もない。従って、投影光学系の光学特性を高精度にかつ簡易に調整することが可能となる。このようにして、所望の仕様をほぼ満たす投影光学系ＰＬが製造されることとなる。
【０３０３】
本実施形態に係る露光装置１２２によると、主制御装置５０により前述の如くして波面収差計測器８０（又は計測用レチクルＲ_T）を用いて投影光学系ＰＬの波面が計測される。そして、主制御装置５０により、投影光学系の瞳面を通過する総合的な情報である、波面の計測結果を利用して結像特性調整機構（４８、１３₁〜１３₄）等が制御される。従って、波面計測の結果を利用して投影光学系ＰＬの結像特性が自動的に調整される。
【０３０４】
また、本実施形態に係る露光装置１２２によると、前述した製造方法によって製造され、製造時は勿論、その後の調整時においても、低次収差のみでなく高次収差も含めて調整された投影光学系ＰＬを露光用光学系として具備しているので、この投影光学系ＰＬによりレチクル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となる。
【０３０５】
また、本実施形態に係るコンピュータシステム１０によると、露光装置１２２が備える波面収差計測器８０により投影光学系ＰＬの波面が自己計測される。第１通信サーバ１２０では、波面収差計測器８０で計測される投影光学系ＰＬの波面の計測結果を通信路を介して第２通信サーバ１３０に送信する。第２通信サーバ１３０では、波面の計測結果を利用して結像特性調整機構（４８、１３₁〜１３₄）を制御する。従って、投影光学系の瞳面における波面の情報、すなわち瞳面を通過する総合的な情報を利用して投影光学系ＰＬの結像特性が精度良く調整される。この場合、第２通信サーバ１３０を露光装置１２２及びそれに接続された第１通信サーバ１２０から離れた位置に配置することが可能であり、かかる場合には、遠隔操作により投影光学系ＰＬの結像特性の高精度な調整が可能となる。
【０３０６】
また、上記実施形態に係るコンピュータシステム１０及び該コンピュータシステムによって行われる最良条件の決定方法によると、露光装置１２２を管理するホストコンピュータあるいはオペレータにより、第１通信サーバ１２０に所定のパターンの情報を含む露光条件の情報が入力されると、第２通信サーバ１３０では、通信路を介して第１通信サーバ１２０から受信した露光条件の情報に含まれる前記パターンの情報と投影光学系ＰＬの既知の収差情報とに基づいて、前記パターンを投影光学系ＰＬにより投影した際に像面に形成される空間像を求めるためのシミュレーションを繰り返し行い、そのシミュレーション結果を分析して最良露光条件を決定する。従って、最適な露光条件の設定をほぼ全自動で行うことが可能となる。
【０３０７】
また、本実施形態のコンピュータシステム１０によると、露光装置１２２のメンテナンス時等における投影光学系ＰＬの調整の際には、サービスエンジニア等が、波面収差計測器８０をＺチルトステージ５８に取り付け、入力装置４５を介して波面収差の計測指令を入力するだけで、ほぼ全自動で、第２通信サーバ１３０による遠隔操作により、投影光学系ＰＬの結像特性を高精度に調整することができる。あるいは、サービスエンジニア等は、計測用レチクルＲ_Tを用いて露光装置１２２の投影光学系ＰＬの波面収差の計測を前述した手順で行い、その結果得られた位置ずれ量のデータを露光装置１２２の主制御装置５０に入力することによっても、ほぼ全自動で、第２通信サーバ１３０による遠隔操作により、投影光学系ＰＬの結像特性を高精度に調整することができる。
【０３０８】
また、本実施形態の露光装置１２２によると、露光の際には、上述のようにして最良露光条件が設定され、かつ投影光学系ＰＬの結像特性が精度良く調整された投影光学系ＰＬを介してレチクルＲのパターンがウエハＷ上に転写されるので、微細パターンを重ね合せ精度良くウエハＷ上に転写することが可能になっている。
【０３０９】
なお、上記実施形態では、投影光学系ＰＬによるパターンの投影像の形成状態を調整する調整装置が、投影光学系ＰＬの結像特性を調整する結像特性調整機構によって構成された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。調整装置としては、前述の結像特性調整機構に代えて、あるいはこれとともに、例えばレチクルＲ及びウエハＷの少なくとも一方を光軸ＡＸ方向に駆動する機構や、照明光ＥＬの波長をシフトさせる機構などを用いても良い。例えば、照明光ＥＬの波長をシフトさせる機構を、前述の結像特性調整機構とともに用いる場合には、前述と同様に、照明光ＥＬの単位シフト量に対する投影光学系ＰＬの視野内の複数の計測点それぞれに対応する結像特性、具体的には波面のデータ、例えばツェルニケ多項式の第２項〜第３７項の係数がどのように変化するかのデータをシミュレーション等により予め求めておき、それを前述のデータベース内のパラメータの１つとして含めることにより、前述の各可動レンズの調整量と同様の扱いが可能となる。すなわち、前述の第２プログラムに従った最小自乗演算を、そのデータベースを用いて行うことにより、投影光学系によるパターンの結像状態の調整のための照明光ＥＬの波長の最適シフト量の算出を容易に行うことができ、この算出結果に基づく波長の自動調整が可能となる。
【０３１０】
なお、上記実施形態では、光学装置として露光装置が用いられる場合について説明したが、これに限らず、投影光学系を備えた光学装置であれば良い。
【０３１１】
また、上記実施形態では、公衆回線をその一部に含む通信路を介して第１コンピュータとしての第１通信サーバ１２０と第２コンピュータとしての第２通信サーバ１３０とが接続されたコンピュータシステム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。例えば、図１２に示されるように通信路としてのＬＡＮ１２６’を介して第１通信サーバ１２０と第２通信サーバ１３０とが接続されたコンピュータシステムであっても良い。かかる構成としては、露光装置メーカ内の研究開発部門内に設置された社内ＬＡＮシステムなどが考えられる。
【０３１２】
このような社内ＬＡＮシステムを構築する場合には、例えば、研究開発部門のクリーンルーム側、例えば露光装置の組み立て調整を行う場所（以下、「現場」と呼ぶ）に第１通信サーバ１２０を設置し、第２通信サーバ１３０を現場から離れた研究室に設置する。そして、現場側の技術者が前述した波面収差の計測や、実験段階での露光装置の露光条件の情報（パターンの情報を含む）を第１通信サーバ１２０を介して研究室側の第２通信サーバ１３０に送る。そして、研究室側の技術者は、自ら設計したソフトウェアプログラムが予めインストールされた第２通信サーバ１３０を用いて、送られてきた情報に基づいて、露光装置１２２の投影光学系ＰＬの結像特性の自動補正を、離れた場所から行い、その結像特性の調整後の投影光学系の波面収差の計測結果を受け取ることにより、その結像特性の調整の効果を確認することができ、ソフトウェアの開発段階などにも役立てることができる。
【０３１３】
あるいは、現場の技術者が、第２通信サーバ１３０に対してパターンの情報等を第１通信サーバ１２０から送信することにより、第２通信サーバ１３０によってそのパターンに最適な投影光学系の仕様を決定することが可能となる。
【０３１４】
この他、第１通信サーバ１２０と第２通信サーバ１３０とは、無線回線によって接続しても良い。
【０３１５】
また、上記実施形態及び変形例では、露光装置１２２が、複数台設けられ、第２通信サーバ１３０が、通信路を介して複数台の露光装置１２２₁〜１２２₃に共通に接続された場合について説明したが、本発明がこれに限定されることはなく、露光装置は単数であっても勿論良い。
【０３１６】
なお、上記実施形態では、投影光学系の仕様をコンピュータシステム１０を用いて決定する場合について説明したが、波面を規格値として投影光学系の仕様を決定するという技術的思想は、コンピュータシステム１０とは無関係に用いることができる。すなわち、メーカＡとメーカＢとの商談においても、メーカＡからのパターン情報等の提供を受け、メーカＢ側でそのパターンの露光に最適な投影光学系の仕様を波面を規格値として決定しても良い。かかる場合であっても、波面を規格値として決定された仕様に基づいて投影光学系を製造する場合には、前述の如く製造工程が簡略化されるという利点がある。
【０３１７】
さらに、上記実施形態では、露光装置１２２の投影光学系ＰＬの波面収差の計測結果に基づいて、第２通信サーバ１３０が第２プログラムを用いて可動レンズ１３₁〜１３₄の調整量ＡＤＪ１〜ＡＤＪｍを算出し、この調整量のデータを露光装置１２２の主制御装置５０に送信する。そして、その調整量ＡＤＪ１〜ＡＤＪｍのデータを受信した露光装置１２２の主制御装置５０が、調整量ＡＤＪ１〜ＡＤＪｍのデータに従って、可動レンズ１３₁〜１３₄を各自由度方向に駆動すべき旨の指令値を、結像特性補正コントローラ４８に与えることにより、投影光学系ＰＬの結像特性の調整を遠隔操作により行うものとした。しかし、これに限らず、露光装置１２２自らが第２プログラムと同様の演算プログラムを用いて、波面収差の計測結果に基づいて投影光学系の結像特性を自動調整するような構成とすることとしても良い。
【０３１８】
なお、例えばマイクロプロセッサなどではゲートパターンの形成時に位相シフトマスクとしての位相シフトレチクル、特に空間周波数変調型（レベンソンタイプ）の位相シフトレチクルが用いられるようになっている。この位相シフトレチクルでは小σ照明が用いられる。具体的には、コヒーレンスファクタ（σ値）が０．５よりも小さい、好ましくは０．４５程度以下となる照明条件で位相シフトレチクルが照明される。このとき、投影光学系の収差（例えば、非点収差、球面収差等）などに起因して、投影光学系の視野内で露光用照明光が照射される露光領域（投影光学系に関して照明領域と共役で、レチクルのパターン像が形成される投影領域）内でベストフォーカス位置がばらついて焦点深度が小さくなる。
【０３１９】
そこで、上記実施形態による投影光学系の製造時に、位相シフトレチクルの使用による、投影光学系の露光領域内でのベストフォーカス位置（即ち、結像面）の変動に基づいて、例えば投影光学系の収差（像面湾曲、非点収差、または球面収差など）を調整するなどして、露光領域内でベストフォーカス位置を部分的に故意にずらしておくことが望ましい。この場合、いわゆる総合焦点差を小さくするように上記収差を補正するフォーカスの事前補正を行うこととしても良い。これにより、位相シフトレチクルの使用時にベストフォーカス位置のばらつきが大幅に低減され、従来に比べて大きな焦点深度で位相シフトレチクルのパターン像をウエハ上に転写可能となる。
【０３２０】
また、デバイス製造工場に出荷された露光装置で位相シフトレチクルを用いるときも上記と同様の問題が生じる。そこで、投影光学系の結像特性の調整機構（例えば、投影光学系の少なくとも１つの光学素子をアクチュエータ（ピエゾ素子など）で駆動する機構など）を用いて収差を調整するなどして、露光領域内でベストフォーカス位置を部分的に故意にずらすことが望ましい。このとき、投影光学系の像面湾曲及び非点収差の少なくとも一方、あるいはそれに加えて球面収差を調整すると良い。この場合も、いわゆる総合焦点差を小さくするように上記収差を補正するフォーカスの事前補正を行うこととしても良い。
【０３２１】
なお、投影光学系の調整に先立ってその結像特性、主として結像面（露光領域のほぼ全面でのベストフォーカス位置）を、投影光学系の設計データなどから計算（シミュレーションなど）にて求めても良いし、あるいは結像特性を実測しても良い。
【０３２２】
前者の場合、上記実施形態で説明したツェルニケ変化表を用いる計算方法などを用いることができる。また、後者では前述の波面収差から結像特性を求めても良いが、レチクルのパターン像を、ウエハステージ上に受光面が設けられる空間像計測器で検出する、あるいはレチクルのパターンをウエハ上に転写してその転写像（潜像又はレジスト像など）を検出し、この検出結果から結像特性を求めるだけでも良い。
【０３２３】
このとき、レチクルのパターンに位相シフト部を設けて小σ照明を用いる、すなわちデバイス製造時とほぼ同一の露光条件でパターン像を形成して、投影光学系の結像特性を求めることが好ましい。
【０３２４】
また、位相シフトレチクルの使用時におけるベストフォーカス位置のばらつきが低減された投影光学系はその組立（製造）又は調整後に結像特性が再計測される。
【０３２５】
このとき、投影光学系では残留収差などに起因してベストフォーカス位置での面内線幅ばらつきが生じることがある。そして、このばらつきが許容値を越えているときは、投影光学系の収差をより小さくしなければならないので、投影光学系の少なくとも一部を交換または調整することが好ましい。
【０３２６】
このとき、投影光学系の光学素子単位でその交換を行っても良いし、あるいは複数の鏡筒を有する投影光学系ではその鏡筒単位で交換を行っても良い。また、投影光学系の少なくとも１つの光学素子を再加工しても良く、特にレンズエレメントでは必要に応じてその表面を非球面に加工しても良い。この光学素子は、レンズエレメントなどの屈折光学素子だけでなく、例えば凹面鏡などの反射光学素子、あるいは投影光学系の収差（ディストーション、球面収差など）、特にその非回転対称成分を補正する収差補正板などでも良い。さらに、投影光学系の調整では光学素子の位置（他の光学素子との間隔を含む）や傾斜などを変更するだけでも良いし、特に光学素子がレンズエレメントであるときはその偏芯を変更したり、あるいは光軸を中心として回転させても良い。この調整（交換または再加工など）は上記実施形態でも同様に行っても良い。
【０３２７】
なお、上記実施形態では、計測用レチクルＲ_Tに計測用パターンとともに、基準パターンが設けられる場合について説明したが、基準パターンは、光学特性計測用マスク（上記実施形態では計測用レチクルＲ_T）に設ける必要はない。すなわち、基準パターンを別のマスクに設けても良いし、基準パターンをマスク側に設けることなく、基板（ウエハ）側に設けても良い。すなわち、基準パターンが投影倍率に応じた大きさで予め形成された基準ウエハを用い、その基準ウエハ上にレジストを塗布し、そのレジスト層に計測用パターンを転写して、現像を行い、その現像後に得られる計測用パターンのレジスト像と基準パターンとの位置ずれを計測するようにすることにより、実質的に上記実施形態と同様の計測が可能となる。
【０３２８】
また、上記実施形態では、計測用パターン及び基準パターンをウエハＷ上に転写した後に、そのウエハを現像して得られるレジスト像の計測結果に基づいて、投影光学系ＰＬの波面収差を算出するものとしたが、これに限らず、計測用パターンの投影像（空間像）をウエハ上に投影し、その投影像（空間像）を空間像計測器などを用いて計測し、あるいはレジスト層に形成された計測用パターン及び基準パターンの潜像あるいはウエハをエッチングして得られる像を計測することとしても良い。かかる場合であっても、計測用パターンの基準位置（例えば設計上の計測用パターンの投影位置）からの位置ずれを計測すれば、その計測結果に基づいて上記実施形態と同様の手順で投影光学系の波面収差を求めることは可能である。また、計測用パターンをウエハ上に転写する代わりに、予め計測用パターンが形成された基準ウエハを準備しておき、この基準ウエハ上のレジスト層に基準パターンを転写してその位置ずれを計測しても良いし、あるいは計測用パターンに対応する複数の開口を有する空間像計測器を用いてその両者の位置ずれを計測するようにしても良い。更に、上記実施形態では前述した位置ずれを重ね合せ測定器を用いて計測するものとしたが、それ以外、例えば露光装置内に設けられるアライメントセンサなどを用いても良い。
【０３２９】
また、上記実施形態ではツェルニケ多項式の第３７項までを用いるものとしたが、第３８項以上を用いても良く、例えば第８１項までを用いて、投影光学系ＰＬの各収差の高次成分も算出しても良い。すなわち、ツェルニケ多項式で使用する項の数や番号は任意で構わない。更に、照明条件などによっては、投影光学系ＰＬの収差を積極的に発生させることもあるので、上記実施形態では目的収差を常に零ないし最小とするだけでなく、目的収差を所定値となるように投影光学系ＰＬの光学素子を調整しても良い。
【０３３０】
なお、上記実施形態では、第１通信サーバ１２０が、例えば露光装置１２２₁で次に使用が予定されているレチクルの情報を、例えば露光装置１２２_１〜１２２₃を管理する不図示のホストコンピュータに対して問い合わせ、そのレチクルの情報に基づいて、所定のデータベースを検索し、そのパターン情報を得る、あるいはパターン情報をオペレータが入力装置を介して第１通信サーバ１２０に手入力にて入力するものとした。しかし、これに限らず、露光装置内に図２中に仮想線で示されるバーコードリーダ等の読取装置ＢＲを設け、この読取装置ＢＲを用いて主制御装置５０を介して第１通信サーバ１２０が、レチクルステージＲＳＴに搬送される途中のレチクルＲに付されたバーコード又は２次元コードなどを読み取って、そのパターン情報を自ら得るようにしても良い。
【０３３１】
また、波面収差の計測に例えば前述の計測用レチクルを用いる場合には、ウエハ上のレジスト層に転写され形成された計測用パターンの潜像の基準パターンの潜像に対する位置ずれを、例えば露光装置が備えるアライメント系ＡＬＧによって検出することとしても良い。また、波面収差の計測に例えば波面収差計測器を用いる場合に、その波面収差計測器として全体形状がウエハホルダと交換可能な形状を有する波面収差計測器を用いても良い。かかる場合には、この波面収差計測器は、ウエハ又はウエハホルダの交換を行う搬送系（ウエハローダなど）を用いて自動搬送することが可能である。このような種々の工夫により、前述の投影光学系ＰＬの結像特性の自動調整や、最良露光条件の設定を、オペレータやサービスエンジニアを介在させることなくコンピュータシステム１０によって全て自動的に行うようにすることも可能である。なお、上記実施形態では、ウエハステージに対して波面収差計測器８０が着脱自在である場合について説明したが、波面収差計測器８０は、ウエハステージに常設されていても良い。このとき、波面収差計測器８０の一部のみをウエハステージに設置し、残りをウエハステージの外部に配置しても良い。また、上記実施形態では波面収差計測器８０の受光光学系の収差を無視するものとしたが、その波面収差を考慮して投影光学系の波面収差を決定しても良い。
【０３３２】
さらに、上記実施形態で説明した第１〜第３プログラムの全て及びこれらに付属するデータベースを露光装置１２２のドライブ装置４６にセットされた情報記録媒体又は記憶装置４２に予め格納しておいて、露光装置１２２単独で、前述の投影光学系ＰＬの結像特性の自動調整や、最良露光条件の設定を行うようにすることも可能である。また、メーカＡの工場内にＬＡＮなどにより露光装置と接続される専用サーバ（前述の第２通信サーバ１３０に相当）を設置し、この専用サーバに第１〜第３プログラムなどを格納しても良い。要は、本発明は、図１の構成に限られるものではなく、第１〜第３プログラムを格納するコンピュータ（サーバなど）の設置場所などは任意で構わない。
【０３３３】
なお、上記実施形態では、露光装置としてステッパを用いる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を用いても良い。
【０３３４】
この場合の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、及び電子線又はイオンビームなどを用いる荷電粒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。
【０３３５】
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、連続光源、例えば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。
【０３３６】
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及び拡大系のいずれでも良い。また、投影光学系としては、屈折系に限らず、反射光学素子と屈折光学素子とを有する反射屈折系（カタッディオプトリック系）あるいは反射光学素子のみを用いる反射系を用いても良い。なお、投影光学系ＰＬとして反射屈折系又は反射系を用いるときは、前述した可動の光学素子として反射光学素子（凹面鏡や反射鏡など）の位置などを変更して投影光学系の結像特性を調整する。また、照明光ＥＬとして、Ｆ₂レーザ光、Ａｒ₂レーザ光、又はＥＵＶ光などを用いる場合には、投影光学系ＰＬを反射光学素子のみから成るオール反射系とすることもできる。但し、Ａｒ₂レーザ光やＥＵＶ光などを用いる場合にはレチクルＲも反射型とする。
【０３３７】
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。このデバイス製造方法によると、リソグラフィ工程で、前述した実施形態の露光装置を用いて露光が行われるので、対象パターンに応じて結像特性が調整された、あるいは波面収差の計測結果に基づいて結像特性が高精度に調整された投影光学系ＰＬを介してレチクルＲのパターンがウエハＷ上に転写されるので、微細パターンを重ね合せ精度良くウエハＷ上に転写することが可能となる。従って、最終製品であるデバイスの歩留まりが向上し、その生産性の向上が可能となる。
【０３３８】
【発明の効果】
以上説明したように、請求項１〜１４にそれぞれ記載の投影光学系の製造方法によれば、製造工程を簡略化できるとともに、結果的に光学装置が達成すべき目標を確実に達成することを可能とするという効果がある。
【０３３９】
また、請求項１５〜請求項１７にそれぞれ記載の投影光学系の製造方法によれば、製造された投影光学系を用いることにより、高精度な露光が可能となるという効果がある。
【０３４０】
また、請求項１８〜２１に記載の各露光装置によれば、投影光学系を用いてパターンを基板上に精度良く転写することができるという効果がある。
【０３４１】
請求項２２に記載の露光装置の製造方法によれば、投影光学系を用いてパターンを基板上に精度良く転写することができる露光装置を製造できる。
【０３４２】
また、請求項２３〜３３にそれぞれ記載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高精度にかつ簡易に調整することができるという効果がある。
【０３４３】
また、請求項３４〜３６にそれぞれ記載の投影光学系の調整法法によれば、その調整の結果、高精度な露光が可能となるという効果がある。
【０３４４】
また、請求項３７に記載のデバイス製造方法によれば、高集積度のマイクロデバイスを歩留まり良く製造することができるという効果がある。
【０３４５】
また、請求項３８〜４７に記載の各コンピュータシステムによれば、露光装置が備える投影光学系の結像特性を通信路を介して高精度に調整することができるという効果がある。
【図面の簡単な説明】
【図１】本発明の一実施形態に係るコンピュータシステムの構成を示す図である。
【図２】図１の第１の露光装置１２２₁の構成を概略的に示す図である。
【図３】波面収差計測器の一例を示す断面図である。
【図４】図４（Ａ）は、光学系に収差が存在しない場合においてマイクロレンズアレイから射出される光束を示す図であり、図４（Ｂ）は、光学系に収差が存在する場合においてマイクロレンズアレイから射出される光束を示す図である。
【図５】露光装置の最良露光条件の設定に際し、第２通信サーバ内のＣＰＵによって実行される制御アルゴリズムを示すフローチャートである。
【図６】計測用レチクルを示す概略斜視図である。
【図７】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８】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−Ｙ側端部近傍の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９】図９（Ａ）は、本実施形態の計測用レチクルに形成された計測用パターンを示す図であり、図９（Ｂ）は、本実施形態の計測用レチクルに形成された基準パターンを示す図である。
【図１０】図１０（Ａ）は、ウエハ上のレジスト層に所定間隔で形成される計測用パターンの縮小像（潜像）を示す図であり、図１０（Ｂ）は、図１０（Ａ）の計測用パターンの潜像と基準パターンの潜像の位置関係を示す図である。
【図１１】投影光学系の製造工程を概略的に示すフローチャートである。
【図１２】変形例に係るコンピュータシステムの構成を示す図である。
【符号の説明】
１０…コンピュータシステム、１３₁〜１３₄…可動レンズ（調整装置としての結像特性調整機構の一部、）、４８…結像特性補正コントローラ（調整装置としての結像特性調整機構の一部）、５０…主制御装置（制御装置）、８０…波面収差計測器（波面計測装置）、１２０…第１通信サーバ（第１コンピュータ）、１２２₁〜１２２₃…露光装置（光学装置）、１３０…第２通信サーバ（第２コンピュータ）、ＰＬ…投影光学系（露光用光学系）、Ｗ…ウエハ（基板）、Ｒ…レチクル（マスク）。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a projection optical system manufacturing method and adjustment method, an exposure apparatus and manufacturing method thereof, a device manufacturing method, and a computer system, and more particularly, a projection optical system manufacturing method and adjustment method included in the optical apparatus, The present invention relates to an exposure apparatus including a projection optical system manufactured by the manufacturing method, a manufacturing method thereof, a device manufacturing method using the exposure apparatus, and a computer system that adjusts imaging characteristics of the projection optical system included in the exposure apparatus.
[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, with the high integration of semiconductor elements and the like, a step-and-repeat reduction projection exposure apparatus (so-called stepper) capable of forming 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 accurately, the optical characteristics of the projection optical system are accurately measured, and this is measured in a desired state (for example, a magnification error of a transfer image of a reticle pattern with respect to a shot area (pattern) on a substrate). It is necessary to adjust and manage to correct. Even when the first layer reticle pattern is transferred to each shot area on the substrate, the imaging characteristics of the projection optical system are used to accurately transfer the second and subsequent reticle patterns to each shot area. It is desirable to adjust.
[0004]
Conventionally, as a method for measuring optical characteristics (including imaging characteristics) of a projection optical system, exposure is performed using a measurement reticle on which a predetermined measurement pattern that significantly reacts to a specific aberration is formed, and the measurement pattern A method of calculating optical characteristics based on a measurement result obtained by measuring a resist image obtained by developing a substrate on which the projected image is transferred (hereinafter referred to as “baking method”) is mainly used.
[0005]
Conventional exposure apparatuses measure low-order aberrations such as so-called Seidel's five aberrations, such as spherical aberration, coma aberration, astigmatism, field curvature, and distortion (distortion), by the above-mentioned printing method. Based on this, it has been mainly performed to adjust and manage the various aberrations of the projection optical system.
[0006]
For example, when measuring distortion of a projection optical system, a measurement reticle in which, for example, a 100 μm square inner box mark and a 200 μm square outer box mark are formed is used as a measurement mark. After the transfer onto the wafer having the resist coated on the surface via the system, the wafer stage is moved to transfer the other mark on the wafer via the projection optical system. If the projection magnification is 1/5, for example, after developing this wafer, a resist image of a box-in-box mark in which a 20 μm square box mark is arranged inside a 40 μm square box mark is formed. Become. Then, the distortion of the projection optical system is measured based on the positional relationship between the marks and the amount of deviation from the reference point of the stage coordinate system.
[0007]
For example, when measuring coma aberration of a projection optical system, as a measurement mark, for example, a line and space having five line patterns with a line width of 0.9 μm (hereinafter referred to as “L / S”). Using a measurement reticle on which a pattern is formed, this mark is transferred via a projection optical system onto a wafer whose surface is coated with a resist. If the projection magnification is, for example, 1/5, a resist image having an L / S pattern having a line width of 0.18 μm is formed after developing the wafer. Then, for example, the line widths of the line patterns at both ends are set to L1 and L5, and the line width abnormal value represented by the following equation (1) is obtained to measure the coma aberration.
Line width abnormal value = (L1−L5) / (L1 + L5) (1)
[0008]
Further, for example, the best focus position of the projection optical system is measured by moving the wafer to a plurality of positions with respect to the optical axis direction of the projection optical system at a predetermined step pitch, and transferring the L / S pattern at each position via the projection optical system. The wafer is sequentially transferred to different areas on the wafer, and the wafer position at which the line width of the resist image formed after development is maximized is measured as the best focus position.
[0009]
When measuring spherical aberration, the above-mentioned best focus position is measured using a plurality of types of L / S patterns having different duty ratios, and the spherical aberration is measured based on the difference between the best focus positions. .
[0010]
For the measurement of the field curvature, the above-mentioned best focus position is measured for each of a plurality of measurement points in the field of view of the projection optical system, and the field curvature is calculated by the least square method based on the measurement result.
[0011]
Further, for example, astigmatism of the projection optical system, the above-mentioned best focus position is obtained for each of two types of periodic patterns whose periodic directions are orthogonal, and astigmatism is calculated based on the difference between the two.
[0012]
[Problems to be solved by the invention]
However, semiconductor devices are highly integrated year by year, and accordingly, exposure apparatuses are required to have higher precision exposure performance. In recent years, low-order aberrations are measured by the above-described method. It is not sufficient to adjust the optical characteristics of the projection optical system based on the measurement result. The reason is as follows.
[0013]
That is, in the case of a measurement pattern, for example, an L / S pattern, the aerial image has a spatial frequency component (natural frequency component) of a fundamental wave and its harmonics corresponding to the period of L / S, and these spatial frequency components. The information passing through the pupil plane of the projection optical system is determined by the pattern. On the other hand, various patterns exist on the reticle used for actual device manufacture, and the aerial image includes innumerable spatial frequency components. Therefore, in the above conventional aberration measurement method, the aberration is specified and adjusted based on limited information passing through the pupil plane, but this achieves the exposure accuracy required at present or in the future. Because it is difficult.
[0014]
In this case, in order to detect the missing information, it is necessary to measure a reticle pattern having a natural frequency that compensates for that part, but the measurement takes a very large amount of measurement, so the measurement time also becomes enormous. , Is almost unrealistic.
[0015]
In addition, since the measurement target is a resist image, measurement accuracy, inherent characteristics of the resist, etc. are involved, and it is necessary to establish measurement data after establishing a correlation between the resist image and the optical image (aberration) in advance. .
[0016]
If the aberration is large, the resist image loses linearity with respect to the aerial image of the pattern, and accurate aberration measurement becomes difficult. In such a case, correct aberration can be achieved by gradually changing the pitch, line width, etc. (spatial frequency) of the measurement pattern on the reticle to a level where the inherent characteristics of the resist described above can be measured (linearity is maintained). It was also necessary to be able to measure.
[0017]
Further, as described above, when an aberration (non-linear aberration) that causes the resist image to lose its linearity with respect to the aerial image of the pattern occurs, the order of the aberrations to be adjusted is taken into consideration. It was also necessary to make adjustments. For example, when coma is large, the pattern to be formed is not resolved, and accurate data cannot be obtained even if distortion, astigmatism, and spherical aberration are measured. Therefore, when adjusting the projection optical system, the coma aberration is first measured using a pattern that can measure the coma aberration correctly, and after adjusting the projection optical system so that the coma aberration becomes sufficiently small, distortion, non- It is necessary to adjust the projection optical system based on the measurement of the point aberration and the spherical aberration and the measurement result. Thus, the definition of the order of aberrations to be adjusted means that selection of lenses and lens groups used for adjustment is limited.
[0018]
Furthermore, in the conventional method for manufacturing a projection optical system, it is necessary to adjust the high-order aberrations by adjusting the high-order aberrations after correcting the low-order aberrations by the above-described procedure. For this purpose, it was necessary to perform a task of several days even if calculation was performed using a high-speed computer called ray tracing.
[0019]
Conventionally, measurement patterns (patterns that react significantly to each aberration), which are considered to be optimal for measuring each aberration, are used as target patterns regardless of the user of the exposure equipment that is the delivery destination. The specification of the projection optical system and the management of optical characteristics have been performed.
[0020]
However, the influence of each aberration of the projection optical system on the imaging characteristics of various patterns is not uniform. For example, contact hole patterns are particularly problematic due to the effects of astigmatism. In addition, the line-and-space pattern with a narrow line width is greatly affected by coma aberration. Further, for example, the best focus position differs between the isolated line pattern and the line and space pattern.
[0021]
Therefore, the required optical characteristics (such as aberration) of the projection optical system and other performances of the exposure apparatus are actually different for each user (more precisely, for each pattern).
[0023]
  First of the present invention1An object of the present invention is to provide a projection optical system adjustment method capable of easily and easily adjusting the optical characteristics of the projection optical system.
[0024]
  First of the present invention2An object of the present invention is to provide an exposure apparatus and an exposure method capable of accurately transferring a mask pattern onto a substrate using a projection optical system.
[0025]
  First of the present invention3An object of the present invention is to provide a device manufacturing method capable of manufacturing a highly integrated microdevice with a high yield.
[0033]
[Means for Solving the Problems]
  In this specification,“Adjusting the projection optical system” means changing the position (including the distance from other optical elements) or the inclination of at least one optical element constituting the projection optical system, and in particular the optical element. When the lens element is a lens element, the eccentricity of the lens element is changed, or rotation about the optical axis is also included. In addition, the replacement is performed in units of optical elements of the projection optical system, or in the case of a projection optical system having a plurality of lens barrels, replacement is performed in units of the lens barrels, and at least one optical element of the projection optical system is reworked. In particular, the lens element includes processing the surface of the lens element into an aspherical surface as necessary. In this specification, expressions such as adjusting the projection optical system or adjusting the projection optical system are used in this sense.
[0038]
  This specification“Zernike Sensitivity” means the imaging performance of the projection optical system under a predetermined exposure condition, for example, each of the Zernike polynomials of various aberrations (or their index values). It means the amount of change per 1λ of the term. In this specification, the term “Zernike Sensitivity” is used in this sense for each term of the Zernike polynomial.
[0051]
  According to a first aspect of the present invention, there is provided a method for adjusting a projection optical system used in an exposure apparatus, wherein the specification is determined using wavefront aberration as a standard value.Imaging characteristicsA measurement result, a Zernike change table corresponding to a pattern to be transferred onto the object via the projection optical system and its exposure condition, and an imaging state of the pattern image on the object Based on the relationship between the adjustment amount of the device for adjusting the coefficient and the coefficient of the predetermined term of the Zernike polynomial.The objective aberration of the projection optical system is zero to minimum or a predetermined value.A second step of determining an adjustment amount in the adjustment device and adjusting the projection optical system using the determined adjustment amount.
[0052]
  According to this, the projection optical system whose specifications are determined with the wavefront aberration as a standard value is used.Imaging characteristicsThat adjusts the measurement result, the Zernike change table corresponding to the pattern to be transferred onto the object via the projection optical system and the exposure condition thereof, and the imaging state of the pattern image on the object Data on the relationship between the adjustment amount in the Zernike polynomial and the coefficient of the predetermined term of the Zernike polynomialThe objective aberration of the projection optical system is zero to minimum or a predetermined value.An adjustment amount in the adjustment device is determined, and the projection optical system is adjusted using the determined adjustment amount. For this reason, the optical characteristics of the projection optical system can be easily adjusted with high accuracy.
[0053]
  According to a second aspect of the present invention, there is provided an exposure method for transferring a pattern onto an object via a projection optical system, wherein the projection optical system is adjusted using the projection optical system adjustment method of the present invention, A first exposure method is characterized in that a pattern image is generated on the object through the adjusted projection optical system under the exposure conditions.
According to this, it becomes possible to accurately transfer the pattern onto the object.
[0054]
  According to a third aspect of the present invention, in an exposure apparatus for transferring a pattern onto an object, a projection optical system whose specifications are determined using a wavefront aberration as a standard value, and an imaging state of the pattern image on the object An adjusting device for adjusting the projection optical system;Imaging characteristics measurement resultsAnd saidShould be transferred onto the object via the projection opticsBased on the Zernike change table corresponding to the pattern and its exposure conditions, and the data regarding the relationship between the adjustment amount in the adjustment device and the coefficient of the predetermined term of the Zernike polynomial,The objective aberration of the projection optical system is zero to minimum or a predetermined value.A control system for controlling an adjustment device using the determined adjustment amount in order to determine an adjustment amount in the adjustment device and transfer the pattern onto the object via the projection optical system; An exposure apparatus characterized by that.
[0055]
  According to this, since the pattern is transferred onto the object via the projection optical system by the control system, the optical characteristics of the projection optical system are easily adjusted with high accuracy. Therefore, the pattern can be accurately transferred onto the object.
[0056]
  According to a fourth aspect of the present invention, in an exposure method for transferring a pattern onto an object, a projection optical system in which specifications are determined using wavefront aberration as a standard value.Imaging characteristics measurement resultsAnd saidShould be transferred onto the object via the projection opticsBased on the Zernike change table corresponding to the pattern and its exposure condition, and the data relating to the relationship between the adjustment amount in the apparatus for adjusting the imaging state of the pattern image on the object and the coefficient of the predetermined term of the Zernike polynomial,The objective aberration of the projection optical system is zero to minimum or a predetermined value.In order to determine an adjustment amount in the adjustment device and transfer the pattern onto the object via the projection optical system, an image formation state of the pattern image by the adjustment device using the determined adjustment amount The second exposure method is characterized by performing the above adjustment.
  According to this, it becomes possible to accurately transfer the pattern onto the object.
[0057]
  According to a fifth aspect of the present invention, in a device manufacturing method including a lithography process, in the lithography process, a pattern is formed on an object using any one of the first and second exposure methods of the present invention. A device manufacturing method characterized by the following.
[0071]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
[0072]
FIG. 1 shows the overall configuration of a computer system according to an embodiment of the present invention.
[0073]
A computer system 10 shown in FIG. 1 includes a lithography system 112 in a semiconductor factory of a device manufacturer (hereinafter referred to as “manufacturer A” as appropriate) that is a user of a device manufacturing apparatus such as an exposure apparatus, and the lithography system 112. A computer system 114 of an exposure apparatus manufacturer (hereinafter referred to as “manufacturer B” as appropriate) connected to a part thereof via a communication path including a public line 116 is provided.
[0074]
The lithography system 112 includes a first communication server 120 as a first computer and a first exposure apparatus 122 as an optical apparatus that are connected to each other via a local area network (LAN) 118.₁, Second exposure apparatus 122₂, Third exposure apparatus 122_Three, And the first authentication proxy server 124 and the like.
[0075]
First communication server 120 and first to third exposure apparatuses 122₁~ 122_ThreeIt is assumed that addresses AD1 to AD4 for identification are respectively assigned to.
[0076]
The first authentication proxy server 124 is provided between the LAN 118 and the public line 116, and functions as a kind of firewall here. That is, the first authentication proxy server 124 prevents communication data flowing on the LAN 118 from leaking to the outside, passes only information from the outside with addresses AD1 to AD4, and passes other information. This prevents the LAN 118 from being illegally entered from the outside.
[0077]
The computer system 114 includes a second authentication proxy server 128 and a second communication server 130 as a second computer connected to each other via a LAN 126. Here, it is assumed that the address AD5 for identification is assigned to the second communication server 130.
[0078]
Similar to the first authentication proxy server 124 described above, the second authentication proxy server 128 prevents the communication data flowing on the LAN 126 from leaking to the outside and protects the LAN 126 from unauthorized entry from the outside. Has the role of a firewall.
[0079]
In the present embodiment, the first to third exposure apparatuses 122 are used.₁~ 122_ThreeThe data is transmitted from the outside to the outside via the first communication server 120 and the first authentication proxy server 124, and the first to third exposure apparatuses 122 from the outside.₁~ 122_ThreeThe data is transmitted directly to the authentication server 124 via the first authentication proxy server 124 or via the first authentication proxy server 124 and the first communication server 120.
[0080]
FIG. 2 shows the first exposure apparatus 122.₁The schematic structure of is shown. This exposure apparatus 122₁Is 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.
[0081]
Exposure device 122₁Is a reticle stage RST and a reticle R as a mask stage for holding a reticle R as a mask illuminated by an illumination light EL for exposure as an energy beam from the illumination system, and an illumination system comprising a light source 16 and an illumination optical system 12. A wafer stage on which a projection optical system PL as an exposure optical system for projecting the exposure illumination light EL emitted from the light beam onto a wafer W (image surface) as a substrate and a Z tilt stage 58 for holding the wafer W are mounted. WST and these control systems are provided.
[0082]
Here, the light source 16 is F.₂A pulsed ultraviolet light source that outputs pulsed light in the vacuum ultraviolet region such as a laser light source (output wavelength 157 nm) or an ArF excimer laser light source (output wavelength 193 nm) is used. The light source 16 may be a light source that outputs pulsed light in the ultraviolet region, such as a KrF excimer laser light source (output wavelength 248 nm).
[0083]
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. In this light source 16, based on the control information TS from the main controller 50, an internal controller turns on / off the output of the laser light LB, the energy per pulse of the laser light LB, the oscillation frequency (repetition frequency), The center wavelength and the half width of the spectrum (wavelength width) are controlled.
[0084]
The illumination optical system 12 includes a beam shaping / illuminance uniformizing optical system 20 including a cylinder lens, a beam expander (all not shown), an optical integrator (homogenizer) 22, and the like, 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 bending an optical path, a condenser lens 32, and the like. As the optical integrator, a fly-eye lens, a rod integrator (an internal reflection type integrator), a diffractive optical element, or the like can be used. In the present embodiment, since a fly-eye lens is used as the optical integrator 22, it is also referred to as a fly-eye lens 22 below.
[0085]
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”.
[0086]
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.
[0087]
In place of or in combination with the aperture stop plate 24, for example, a plurality of diffractive optical elements exchanged in the illumination optical system, a prism (conical prism, polyhedron, movable along the optical axis of the illumination optical system) An optical unit including at least one of a prism and the zoom optical system is disposed between the light source 16 and the optical integrator 22, and when the optical integrator 22 is a fly-eye lens, illumination light on an incident surface thereof When the optical integrator 22 is an internal reflection type integrator, by changing the incident angle range of the illumination light with respect to the incident surface, the light intensity distribution (2 of illumination light on the pupil plane of the illumination optical system) The size and shape of the next light source), that is, it is desirable to suppress the light amount loss accompanying the change in the illumination condition of the reticle R. In the present embodiment, a plurality of light source images (virtual images) formed by the internal reflection type integrator are also called secondary light sources.
[0088]
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.
[0089]
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.
[0090]
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 Kohler illumination system.
[0091]
The operation of the illumination system configured in this way will be briefly described. After the laser beam LB pulsed from the light source 16 is incident on the beam shaping / illuminance equalizing optical system 20 and the cross-sectional shape is shaped, The light enters the fly eye lens 22. Thereby, the secondary light source described above is formed on the exit-side focal plane of the fly-eye lens 22.
[0092]
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.
[0093]
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). 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.
[0094]
The material used for the reticle R needs to be properly used depending on the light source used. That is, when an ArF excimer laser or a KrF excimer laser is used as a light source, a fluoride crystal such as synthetic quartz or fluorite, or fluorine-doped quartz can be used.₂When using a laser, it is necessary to form with a fluoride crystal such as fluorite or fluorine-doped quartz.
[0095]
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).
[0096]
As the projection optical system PL, as shown in FIG. 2, a refraction system including only a plurality of, for example, about 10 to 20 refractive optical elements (lens elements) 13 is used. Among the plurality of lens elements 13 constituting the projection optical system PL, a plurality of lens elements 13 on the object plane side (reticle R side) (here, four elements 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 element 13₁~ 13_FourAre held by the lens barrel through respective lens structure holders (not shown). Of these, the lens element 13₁, 13₂, 13_FourAre held by an inner lens holder that holds them, and this inner lens holder is supported with respect to the outer lens holder at three points in the direction of gravity by a driving element (not shown) such as a piezoelectric element. Then, by independently adjusting the voltage applied to these drive elements, the lens element 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 element 13_ThreeIs held by an inner lens holder (not shown), and driving elements such as piezo elements are arranged at intervals of approximately 90 ° between the outer peripheral surface of the inner lens holder and the inner peripheral surface of the outer lens holder. The lens element 13 is obtained by adjusting the voltage applied to each drive element, with two drive elements facing each other as a set._ThreeIs configured to be capable of two-dimensional shift driving in the XY plane.
[0097]
The other lens elements 13 are held by the lens barrel via a normal lens holder. The lens element 13₁~ 13_FourNot limited to this, a lens disposed near the pupil plane of the projection optical system PL or on the image plane side, or an aberration correction plate (optical plate) that corrects aberrations of the projection optical system PL, particularly non-rotationally symmetric components, is driven. You may comprise. Furthermore, the freedom degree (movable direction) of these drivable optical elements is not limited to two or three, and may be one or four or more.
[0098]
Further, a pupil aperture stop 15 capable of continuously changing the numerical aperture (NA) within a predetermined range is provided in the vicinity of the pupil plane of the projection optical system PL. As this pupil aperture stop 15, for example, a so-called iris stop is used. The pupil aperture stop 15 is controlled by the main controller 50.
[0099]
When ArF excimer laser light or KrF excimer laser light is used as the illumination light EL, each lens element constituting the projection optical system PL is composed of fluoride crystals such as fluorite and the above-described fluorine-doped quartz. Quartz can also be used, but F₂When laser light is used, the material of the lens used in the projection optical system PL is all fluoride crystals such as fluorite and fluorine-doped quartz.
[0100]
Wafer stage WST is freely driven in an XY two-dimensional plane by a wafer stage driving unit 56 including a linear motor and the like. On the Z tilt stage 58 mounted on the wafer stage WST, the wafer W is held by electrostatic chucking (or vacuum chucking) or the like via a wafer holder (not shown).
[0101]
The Z tilt stage 58 is positioned on the wafer stage WST in the XY direction, and can be moved in the Z-axis direction and tilted with respect to the XY plane by a drive system (not shown). Thereby, the surface position (Z-axis direction position and inclination with respect to the XY plane) of the wafer W held on the Z tilt stage 58 is set to a desired state.
[0102]
Further, a movable mirror 52W is fixed on the Z tilt stage 58, and an X-axis direction, a Y-axis direction, and a θz direction (rotation direction about the Z axis) of the Z tilt stage 58 are performed by a wafer laser interferometer 54W arranged outside. The position information measured by the interferometer 54W is supplied to the main controller 50. Main controller 50 determines wafer stage WST via wafer stage drive unit 56 (including all of the drive system of wafer stage WST and the drive system of Z tilt stage 58) based on the measurement value of interferometer 54W. (And Z tilt stage 58) is controlled.
[0103]
A reference mark plate FM on which a reference mark such as a so-called baseline measurement reference mark is measured is fixed on the Z tilt stage 58 so that the surface thereof is substantially the same height as the surface of the wafer W. Yes.
[0104]
A wavefront aberration measuring instrument 80 as a detachable portable wavefront measuring device is attached to the side surface of the Z tilt stage 58 on the + X side (the right side in the drawing in FIG. 2).
[0105]
As shown in FIG. 3, the wavefront aberration measuring instrument 80 includes a hollow casing 82 and a light receiving optical system 84 including a plurality of optical elements arranged in a predetermined positional relationship inside the casing 82. And a light receiving portion 86 disposed at the + Y side end portion inside the housing 82.
[0106]
The housing 82 is made of a member having an L-shaped YZ cross section and a space formed therein, and light from above the housing 82 is exposed to the internal space of the housing 82 at the uppermost portion (the end in the + Z direction). An opening 82a having a circular shape in plan view is formed so as to be incident toward the top. A cover glass 88 is provided so as to cover the opening 82 a from the inside of the housing 82. On the upper surface of the cover glass 88, a light shielding film having a circular opening in the center is formed by vapor deposition of a metal such as chromium, and the light shielding film is unnecessary from the surroundings when measuring the wavefront aberration of the projection optical system PL. Light is blocked from entering the light receiving optical system 84.
[0107]
The light receiving optical system 84 is arranged in order from the top to the bottom below the cover glass 88 inside the housing 82, and is placed on the + Y side of the folding mirror 84c. The objective lens 84a, the relay lens 84b, the folding mirror 84c are arranged. A collimator lens 84d and a microlens array 84e are sequentially arranged. The folding mirror 84c is obliquely inclined at 45 °, and the optical path of light incident on the objective lens 84a vertically downward from above is bent by the folding mirror 84c toward the collimator lens 84d. . Each optical member constituting the light receiving optical system 84 is fixed to the inside of the wall of the housing 82 via a holding member (not shown). The microlens array 84e is configured by arranging a plurality of small convex lenses (lens elements) in an array in a plane orthogonal to the optical path.
[0108]
The light receiving unit 86 is composed of a light receiving element such as a two-dimensional CCD and an electric circuit such as a charge transfer control circuit. The light receiving element has a sufficient area to receive all of the light beams incident on the objective lens 84a and emitted from the microlens array 84e. Note that the measurement data obtained by the light receiving unit 86 is output to the main controller 50 via a signal line (not shown) or by wireless transmission.
[0109]
By using the wavefront aberration measuring instrument 80 described above, the wavefront aberration of the projection optical system PL can be measured on-body. A method for measuring the wavefront aberration of the projection optical system PL using the wavefront aberration measuring instrument 80 will be described later.
[0110]
Returning to FIG. 2, the exposure apparatus 122 of the present embodiment.₁Includes a light source that is controlled to be turned on and off by the main controller 50, and forms an imaging light beam for forming images of a large number of pinholes or slits toward the imaging surface of the projection optical system PL on the optical axis. Incident light type multi-point focal position detection system (hereinafter referred to as an irradiation system 60a that irradiates AX from an oblique direction) and a light receiving system 60b that receives a reflected light beam of the imaging light beam on the surface of the wafer W. Simply referred to as a “focus detection system”). As this focus detection system (60a, 60b), for example, one having the same configuration as that disclosed in JP-A-6-283403 is used.
[0111]
The main controller 50 tilts the wafer W with respect to the Z position and the XY plane so that the focus shift becomes zero based on a defocus signal (defocus signal) from the light receiving system 60b, for example, an S curve signal, during exposure or the like. Are controlled via the wafer stage drive unit 56, thereby performing autofocus (automatic focusing) and autoleveling. In addition, the main controller 50 measures and aligns the Z position of the wavefront aberration measuring instrument 80 using the focus detection system (60a, 60b) when measuring the wavefront aberration described later. At this time, the inclination measurement of the wavefront aberration measuring instrument 80 may be performed as necessary.
[0112]
Further, the exposure apparatus 122₁Includes an off-axis alignment system ALG used for position measurement of the alignment mark on the wafer W held on the wafer stage WST and the reference mark formed on the reference mark plate FM. ing. As this alignment system ALG, for example, the target mark is irradiated with a broadband detection light beam that does not sensitize the resist on the wafer, and the target mark image formed on the light receiving surface by the reflected light from the target mark and an index (not shown) An image processing type FIA (Field Image Alignment) type sensor that captures the image of the image using an image sensor (CCD) or the like and outputs the imaged signals is used. In addition to the FIA system, the target mark is irradiated with coherent detection light to detect scattered light or diffracted light generated from the target mark, or two diffracted lights (for example, of the same order) generated from the target mark. Of course, it is possible to use an alignment sensor for detecting the interference by using them alone or in combination as appropriate.
[0113]
Furthermore, the exposure apparatus 122 of the present embodiment.₁Although not shown in the figure, light having an exposure wavelength for observing simultaneously the reticle mark on the reticle R and the corresponding reference mark on the reference mark plate via the projection optical system PL above the reticle R. There is provided a pair of reticle alignment microscopes comprising a TTR (Through The Reticle) alignment optical system. As these reticle alignment microscopes, for example, those having the same configuration as that disclosed in JP-A-7-176468 are used.
[0114]
The control system is mainly configured by the main controller 50 in FIG. The main controller 50 includes a so-called workstation (or microcomputer) including a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. In addition to performing the above control operation, the entire apparatus is controlled in an integrated manner. Main controller 50 controls, for example, step-to-shot stepping of wafer stage WST, exposure timing, and the like so that the exposure operation is performed accurately.
[0115]
The main controller 50 includes, for example, a storage device 42 composed of a hard disk, an input device 45 including a pointing device such as a keyboard and a mouse, a display device 44 such as a CRT display (or liquid crystal display), and a CD. A drive device 46 for an information recording medium such as a ROM, DVD-ROM, MO or FD is connected externally. Further, the main controller 50 is connected to the LAN 118 described above.
[0116]
The positional deviation amount measured by using the wavefront aberration measuring instrument 80 as described later is recorded on an information recording medium (hereinafter referred to as a CD-ROM for convenience) set in the drive device 46 as each term of the Zernike polynomial. A conversion program (hereinafter referred to as “first program” for convenience) for conversion into coefficients is stored.
[0117]
The second and third exposure apparatuses 122₂122_ThreeIs the first exposure apparatus 122 described above.₁It is configured in the same way.
[0118]
Next, the 1st-3rd exposure apparatus 122 performed at the time of a maintenance etc.₁~ 122_ThreeA method for measuring wavefront aberration will be described. In the following description, for simplification of description, it is assumed that the aberration of the light receiving optical system 84 in the wavefront aberration measuring instrument 80 is negligibly small.
[0119]
It is assumed that the first program in the CD-ROM set in the drive device 46 is installed in the storage device 42.
[0120]
During normal exposure, the wavefront aberration measuring instrument 80 is removed from the Z tilt stage 58. Therefore, when measuring the wavefront, a service engineer or an operator (hereinafter referred to as “service engineer or the like” as appropriate) firstly sets the Z tilt stage. An operation of attaching the wavefront aberration measuring instrument 80 to the side surface of 58 is performed. At the time of mounting, a bolt or a magnet or the like is provided on a predetermined reference surface (here, the surface on the + X side) so that the wavefront aberration measuring device 80 is within the moving stroke of the wafer stage WST (Z tilt stage 58) during wavefront measurement. Fixed through.
[0121]
After completion of the above attachment, in response to an input of a measurement start command by a service engineer or the like, main controller 50 sets wafer stage driving unit 56 so that wavefront aberration measuring instrument 80 is positioned below alignment system ALG. Through which wafer stage WST is moved. Then, main controller 50 detects an alignment mark (not shown) provided on wavefront aberration measuring instrument 80 by the alignment system, and performs alignment based on the detection result and the measured value of laser interferometer 54W at that time. The position coordinates of the mark are calculated, and the exact position of the wavefront aberration measuring instrument 80 is obtained. Then, after measuring the position of the wavefront aberration measuring instrument 80, the main controller 50 measures the wavefront aberration as follows.
[0122]
First, main controller 50 loads a measurement reticle (not shown) on which a pinhole pattern is formed by a reticle loader (not shown) (hereinafter referred to as “pinhole reticle”) onto reticle stage RST. This pinhole reticle is a reticle in which pinholes (pinholes that generate a spherical wave as an almost ideal point light source) are formed at a plurality of points in the same area as the illumination area IAR of the pattern surface.
[0123]
It should be noted that the pinhole reticle used here is provided with a diffusion surface on the upper surface, etc., so that all N.D. A. So that the wavefront of the light beam passing through the projection optical system PL can be obtained. A. It is assumed that the wavefront aberration over the range is measured.
[0124]
After loading the pinhole reticle, main controller 50 uses a reticle alignment microscope (not shown) to detect a reticle alignment mark formed on the pinhole reticle and, based on the detection result, to detect the pinhole reticle in a predetermined manner. Align to position. Thereby, the center of the pinhole reticle and the optical axis of the projection optical system PL substantially coincide.
[0125]
Thereafter, the main controller 50 gives the control information TS to the light source 16 to emit laser light. Thereby, the illumination light EL from the illumination optical system 12 is irradiated to the pinhole reticle. Then, light emitted from a plurality of pinholes of the pinhole reticle is condensed on the image plane via the projection optical system PL, and an image of the pinhole is formed on the image plane.
[0126]
Next, the main controller 50 sets the opening 82a of the wavefront aberration measuring instrument 80 at an image formation point where an image of any pinhole on the pinhole reticle (hereinafter referred to as a pinhole of interest) is formed. Wafer stage WST is moved via wafer stage drive unit 56 while monitoring the measurement value of wafer laser interferometer 54W so that the centers substantially coincide. At this time, in the main controller 50, based on the detection result of the focus detection system (60a, 60b), the upper surface of the cover glass 88 of the wavefront aberration measuring instrument 80 should be aligned with the image plane on which the pinhole image is formed. The Z tilt stage 58 is slightly driven in the Z-axis direction via the wafer stage drive unit 56. As a result, the image light beam of the pinhole of interest enters the light receiving optical system 84 through the central opening of the cover glass 88 and is received by the light receiving element constituting the light receiving unit 86.
[0127]
More specifically, a spherical wave is generated from a focused pinhole on the pinhole reticle, and this spherical wave forms an objective lens constituting the projection optical system PL and the light receiving optical system 84 of the wavefront aberration measuring instrument 80. 84a, relay lens 84b, mirror 84c, and collimator lens 84d are converted into parallel light fluxes to irradiate the microlens array 84e. Thereby, the pupil plane of the projection optical system PL is relayed to the microlens array 84e and divided. Then, each lens element of the microlens array 84e condenses each light on the light receiving surface of the light receiving element, and a pinhole image is formed on the light receiving surface.
[0128]
At this time, if the projection optical system PL is an ideal optical system without wavefront aberration, the wavefront on the pupil plane of the projection optical system PL becomes an ideal wavefront (here, a plane), and as a result, a microlens array. The parallel light flux incident on 84e becomes a plane wave, and its wavefront should be an ideal wavefront. In this case, as shown in FIG. 4A, a spot image (hereinafter also referred to as “spot”) is formed at a position on the optical axis of each lens element constituting the microlens array 84e.
[0129]
However, since there is usually wavefront aberration in the projection optical system PL, the wavefront of the parallel light beam incident on the microlens array 84e is deviated from the ideal wavefront. As shown in FIG. 4B, the imaging position of each spot is shifted from the position on the optical axis of each lens element of the microlens array 84e. In this case, the position shift from the reference point of each spot (the position on the optical axis of each lens element) corresponds to the inclination of the wavefront.
[0130]
Then, the light (spot image light flux) incident on each light condensing point on the light receiving element constituting the light receiving unit 86 is photoelectrically converted by the light receiving element, and the photoelectric conversion signal is transmitted to the main controller 50 via the electric circuit. The main controller 50 calculates the imaging position of each spot on the basis of the photoelectric conversion signal, and further uses the calculation result and the position data of the known reference point to calculate the position shift (Δξ, Δη ) Is calculated and stored in the RAM. At this time, the main controller 50 includes a measured value (X_i, Y_i) Is supplied.
[0131]
As described above, when the measurement of the positional deviation of the spot image by the wavefront aberration measuring device 80 at the focusing point of one focused pinhole image is completed, the main controller 50 forms the next pinhole image. Wafer stage WST is moved so that the substantially center of opening 82a of wavefront aberration measuring instrument 80 coincides with the point. When this movement is completed, laser light is emitted from the light source 16 by the main controller 50 in the same manner as described above, and the imaging position of each spot is calculated by the main controller 50 in the same manner. Thereafter, the same measurement is sequentially performed at other imaging points of the pinhole image. Note that, for example, for each pinhole, the reticle blind 30 is used at the time of measurement so that only the focused pinhole on the reticle or at least a partial region including the focused pinhole is illuminated with the illumination light EL. The position and size of the illumination area on the reticle may be changed.
[0132]
In this way, at the stage where necessary measurement is completed, the RAM of the main controller 50 stores the above-described positional deviation data (Δξ, Δη) at the image formation point of each pinhole image and the coordinates of each image formation point. Data (measurement value of laser interferometer 54W when measurement is performed at the image point of each pinhole image (X_i, Y_i)) And are stored.
[0133]
Next, in the main controller 50, the first program is loaded into the main memory, the positional deviation data (Δξ, Δη) at the image formation point of each pinhole image stored in the RAM, and the image of each image formation point. Based on the coordinate data, the wavefront (wavefront aberration) corresponding to the imaging point of the pinhole image according to the principle described below, that is, corresponding to the first to nth measurement points in the field of the projection optical system PL. Here, the coefficient of each term of the Zernike polynomial of equation (4) described later, for example, the coefficient Z of the second term₂~ Coefficient Z of the 37th term₃₇Is calculated according to the first program.
[0134]
In the present embodiment, the wavefront of the projection optical system PL is obtained by calculation according to the first program based on the above-described positional deviation (Δξ, Δη). That is, the positional deviation (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 (Δξ, Δη). As is clear from the physical relationship between the positional deviations (Δξ, Δη) and the wavefront, the wavefront calculation principle in this embodiment is the well-known Shack-Hartmann wavefront calculation principle.
[0135]
Next, a method for calculating the wavefront based on the above positional deviation will be briefly described.
[0136]
As described above, the positional deviation (Δξ, Δη) corresponds 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 (wavefront deviation from the reference plane) is W (x, y) and the proportionality coefficient is k, the following relational expressions (2) and (3) are established.
[0137]
[Expression 1]

[0138]
Since it is not easy to integrate the slope of the wavefront given only by the spot position as it is, the surface shape is developed into a series and fitted 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), it can be developed as the following equation (4).
[0139]
[Expression 2]

[0140]
Since it is an orthogonal system, the coefficient Z of each term_iCan be determined independently. Cutting i by an appropriate value corresponds to performing some kind of filtering. As an example, f from 1st to 37th terms_iZ_iThe following table 1 shows examples. However, the 37th term in Table 1 corresponds to the 49th term in the actual Zernike polynomial, but is treated as a term of i = 37 (the 37th term) in this specification. That is, in the present invention, the number of terms of the Zernike polynomial is not particularly limited.
[0141]
[Table 1]

[0142]
Actually, since the differentiation is detected as the above-described positional deviation, the fitting needs to be performed on the derivative. In the polar coordinate system (x = ρcos θ, y = ρsin θ), the following expressions (5) and (6) are used.
[0143]
[Equation 3]

[0144]
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 the information (deviation amount) of the image point of one spot image is given in the X and Y directions, if the number of pinholes is n (n is about 81 to 400, for example), the above formula (2) The number of observation equations given by (6) is 2n (= about 162 to 800).
[0145]
Each term in the Zernike polynomial corresponds to an optical aberration. Moreover, the low-order terms (terms with a small i) substantially correspond to Seidel aberration. By using the Zernike polynomial, the wavefront aberration of the projection optical system PL can be obtained.
[0146]
According to the principle as described above, the calculation procedure of the first program is determined, and the calculation process according to the first program corresponds to the first to nth measurement points in the field of view of the projection optical system PL. Wavefront information (wavefront aberration), here the coefficient of each term of the Zernike polynomial, for example the coefficient Z of the second term₂~ Coefficient Z of the 37th term₃₇Is required.
[0147]
In the following description, wavefront (wavefront aberration) data corresponding to the first to nth measurement points is represented by a column matrix Q as shown in the following equation (7).
[0148]
[Expression 4]

[0149]
In the above equation (7), the element P of the matrix Q₁~ P_nAre the coefficients of the second to 37th terms of the Zernike polynomial (Z₂~ Z₃₇) Is a column matrix (vertical vector).
[0150]
In this way, the wavefront data (coefficient of each term of the Zernike polynomial, for example, the coefficient Z of the second term)₂~ Coefficient Z of the 37th term₃₇), The main controller 50 stores the wavefront data in the storage device 42.
[0151]
Further, as will be described later, in response to an inquiry from the first communication server 120, the main controller 50 reads the wavefront data from the storage device 42 and transmits it to the first communication server 120 described above via the LAN 118. It has become.
[0152]
Returning to FIG. 1, the first to third exposure apparatuses 122 are provided inside the hard disk or the like included in the first communication server 120.₁~ 122_ThreeTarget information to be achieved by, for example, resolution (resolution), practical minimum line width (device rule), wavelength of illumination light EL, pattern information to be transferred, and other exposure apparatus 122₁~ 122_ThreeSome information about the projection optical system that determines the performance of the image and information that can be the target value is stored. Further, in the hard disk or the like provided in the first communication server 120, target information in an exposure apparatus scheduled to be introduced in the future, for example, information on a pattern planned to be used, is also stored as target information.
[0153]
On the other hand, inside the hard disk or the like provided in the second communication server 130, an adjustment amount calculation program (hereinafter referred to as a “second program” for convenience) that calculates the adjustment amount of the imaging characteristics based on the coefficient of each term of the Zernike polynomial. ), A best exposure condition setting program (hereinafter referred to as “third program” for convenience) for setting the best exposure conditions, and a database attached to the second program.
[0154]
Next, the database will be described. This database is the above-mentioned movable lens element (hereinafter referred to as “movable lens”) 13 for adjusting the imaging characteristics in accordance with the input of the optical characteristics of the projection optical system, here the measurement result of the wavefront aberration.₁, 13₂, 13_Three, 13_FourThis is a database composed of numerical data of parameter groups for calculating the target drive amount (target adjustment amount). This database contains the movable lens 13₁, 13₂, 13_Three, 13_FourIs driven by a unit adjustment amount in each direction of freedom (driveable direction), imaging characteristics corresponding to each of a plurality of measurement points in the field of view of the projection optical system PL, specifically, wavefront data, for example, Zernike The data on how the coefficients of the second term to the 37th term of the polynomial change are simulated using a model substantially equivalent to the projection optical system PL, and the image obtained as a result of the simulation. It consists of a data group in which the fluctuation amount of the characteristic is arranged according to a predetermined rule.
[0155]
Here, a procedure for creating this database will be briefly described. First, in a simulation computer in which specific optical software is installed, exposure conditions, that is, design values of the projection optical system PL (numerical aperture NA, data of each lens, etc.) and illumination conditions (coherence factor σ value, The wavelength λ of the illumination light, the shape of the secondary light source, etc.) are input. Next, data of an arbitrary first measurement point in the visual field of the projection optical system PL is input to the simulation computer.
[0156]
Next, unit amount data for each direction of freedom (movable direction) of the movable lens is input. For example, movable lens 13₁When a command for driving the unit by a unit amount with respect to the + direction of the Y-direction tilt is input, the simulation computer changes the first wavefront from the ideal wavefront at a predetermined first measurement point in the field of view of the projection optical system PL. The amount of change of the coefficient of each coefficient (for example, the second term to the 37th term) of the Zernike polynomial, for example, is calculated, and the change amount data is displayed on the screen of the simulation computer display. The amount of change is stored in the memory as parameter PARA1P1.
[0157]
Next, the movable lens 13₁When a command for driving the unit by a unit amount with respect to the + direction of the tilt in the X direction is input, the simulation computer calculates the second wavefront data for the first measurement point, for example, the amount of change in the coefficients of the above terms of the Zernike polynomial Then, the change amount data is displayed on the display screen, and the change amount is stored in the memory as the parameter PARA2P1.
[0158]
Next, the movable lens 13₁When a command for driving the unit by a unit amount with respect to the + direction of the Z-direction shift is input, the simulation computer calculates the third wavefront data for the first measurement point, for example, the amount of change in the coefficients of the above terms of the Zernike polynomial. Then, the change amount data is displayed on the display screen, and the change amount is stored in the memory as the parameter PARA3P1.
[0159]
Thereafter, the measurement points from the second measurement point to the nth measurement point are input in the same procedure as described above, and the movable lens 13 is input.₁Each time a command input for tilting in the Y direction, tilting in the X direction, and shifting in the Z direction is performed, data of the first wavefront, second wavefront, and third wavefront at each measurement point by the simulation computer, for example, the Zernike polynomial The change amount of the coefficient of each term is calculated, and the data of each change amount is displayed on the display screen, and is stored in the memory as parameters PARA1P2, PARA2P2, PARA3P2,..., PARA1Pn, PARA2Pn, PARA3Pn.
[0160]
Other movable lens 13₂, 13_Three, 13_FourIn the same way as above, the input of each measurement point and the command input that the unit amount is driven in the + direction for each direction of freedom are performed, and in response to this, the computer for simulation moves Lens 13₂, 13_Three, 13_FourFor each of the first to n-th measurement points when driving the unit by a unit amount in each direction of freedom, for example, the amount of change in each term of the Zernike polynomial is calculated, and parameters (PARA4P1, PARA5P1, PARA6P1,. , PARAmP1), parameters (PARA4P2, PARA5P2, PARA6P2,..., PARAmP2),..., Parameters (PARA4Pn, PARA5Pn, PARA6Pn,..., PARAmPn) are stored in the memory. Then, a matrix (matrix) O represented by the following equation (8) whose elements are column matrices (vertical vectors) PARA1P1 to PARAmPn that are formed by the change amounts of the coefficients of the terms of the Zernike polynomial thus stored in the memory. Is stored in the hard disk or the like included in the second communication server 130 as the database. In this embodiment, since there are three lenses movable in the direction of 3 degrees of freedom and one lens movable in the direction of 2 degrees of freedom, m = 3 × 3 + 2 × 1 = 11.
[0161]
[Equation 5]

[0162]
Next, the first to third exposure apparatuses 122 in the present embodiment.₁~ 122_ThreeA method for adjusting the projection optical system PL included in the above will be described. In the following description, the first to third exposure apparatuses 122 are used unless otherwise necessary.₁~ 122_ThreeThe exposure apparatus 122 is described as a representative.
[0163]
As a premise, the wavefront aberration of the projection optical system PL using the wavefront aberration measuring instrument 80 described above is controlled by the main controller 50 of the exposure apparatus 122 in response to a measurement instruction from a service engineer or the like during regular maintenance of the exposure apparatus 122 or the like. It is assumed that measurement is performed and the measured wavefront data is stored in the storage device 42.
[0164]
First, in the first communication server 120, new wavefront measurement data not yet received (coefficients of each term of the Zernike polynomial in which the wavefront corresponding to the first measurement point to the nth measurement point is expanded, for example, the coefficient of the second term) Z₂~ Coefficient Z of the 37th term₃₇) Is stored in the storage device 42 of the exposure device 122 at a predetermined interval. Here, the exposure apparatus 122 (actually the first to third exposure apparatuses 122).₁~ 122_ThreeIt is assumed that new wavefront measurement data is stored in the storage device 42 included in any of the above. Therefore, main controller 50 included in exposure apparatus 122 transmits the wavefront measurement data to first communication server 120 via LAN 118.
[0165]
The first communication server 120 transmits the received wavefront measurement data to the second communication server 130 together with an instruction to automatically adjust the projection optical system PL (or an instruction to calculate the adjustment amount of the projection optical system PL). To do. As a result, these data pass through the first authentication proxy server 124 via the LAN 118 and further reach the second authentication proxy server 128 via the public line 116. The second authentication proxy server 128 confirms the transmission destination address attached to the data, recognizes that the data has been transmitted to the second communication server 130, and receives the second communication server via the LAN 126. 130.
[0166]
The second communication server 130 receives the transmitted data, displays that fact together with the data transmission source, and stores the wavefront measurement data in a hard disk or the like. Then, as described below, the adjustment amount of the projection optical system PL, that is, the movable lens 13 described above.₁~ 13_FourThe adjustment amount in each direction of freedom is calculated.
[0167]
First, in the second communication server 130, the second program is loaded from the hard disk or the like into the main memory, and the movable lens 13 described above is loaded according to the second program.₁~ 13_FourThe adjustment amount in each direction of freedom is calculated. Specifically, the second communication server 130 performs the following calculation.
[0168]
Wavefront (wavefront aberration) data Q corresponding to the first measurement point to the nth measurement point, the matrix O stored in the hard disk as the aforementioned database, and the movable lens 13₁~ 13_FourThe following relationship (9) is established between the adjustment amount P in each direction of freedom.
[0169]
Q = O · P (9)
In the above equation (9), P is a column matrix (that is, a vertical vector) composed of m elements represented by the following equation (10).
[0170]
[Formula 6]

[0171]
Therefore, each element ADJ1 to ADJm of P, that is, the movable lens 13 is calculated by the least square method by performing the calculation of the following expression (11) from the above expression (9).₁~ 13_FourThe amount of adjustment in each direction of freedom (target amount of adjustment) can be obtained.
[0172]
P = (O^T・ O)^-1・ O^T・ Q ...... (11)
In the above formula (11), O^TIs the transpose matrix of the matrix O and (O^T・ O)^-1Is (O^T-Inverse matrix of O).
[0173]
That is, the second program is a program for performing the least square calculation of the above equation (11) using a database. Therefore, the second communication server 130 calculates the adjustment amounts ADJ1 to ADJm while sequentially reading the database in the hard disk into the RAM according to the second program.
[0174]
Next, the second communication server 130 transmits the calculated adjustment amounts ADJ1 to ADJm to the main controller 50 of the exposure apparatus 122. Thereby, the data of the adjustment amounts ADJ1 to ADJm pass through the second authentication proxy server 128 via the LAN 126 and further reach the first authentication proxy server 124 via the public line 116. The first authentication proxy server 124 checks the addresses attached to the data of the adjustment amounts ADJ1 to ADJm, recognizes that the data has been transmitted to the exposure apparatus 122, and exposes the exposure apparatus 122 via the LAN 118. Send to. Actually, when the address attached to the data of the adjustment amounts ADJ1 to ADJm is AD2, the data is stored in the first exposure device 122.₁When the address is AD3, the data is stored in the second exposure device 122.₂When the address is AD4, the data is transferred to the third exposure apparatus 122._ThreeSent to.
[0175]
Here, of course, the second communication server 130 can send the calculated adjustment amounts ADJ1 to ADJm to the first communication server 120. In this case, the first communication server 120 sends the adjustment amounts ADJ1 to ADJm to the main controller 50 of the exposure apparatus 122 that has previously sent the wavefront data.
[0176]
In any case, the main control device 50 of the exposure apparatus 122 that has received the data of the adjustment amounts ADJ1 to ADJm moves the movable lens 13 according to the data of the adjustment amounts ADJ1 to ADJm.₁~ 13_FourIs given to the imaging characteristic correction controller 48 to be driven in each direction of freedom. 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 13₁~ 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.
[0177]
As is clear from the above description, in the present embodiment, the movable lens 13 is used.₁~ 13_FourThe drive element for driving these movable lenses and the imaging characteristic correction controller 48 constitute an imaging characteristic correction mechanism as an adjusting device. A control device for controlling the imaging characteristic correction mechanism is constituted by the main control device 50.
[0178]
As described above, in the present embodiment, when adjusting the projection optical system PL during normal use of the exposure apparatus, a service engineer or the like attaches the wavefront aberration measuring instrument 80 to the Z tilt stage 58 and connects the input device 45 to the Z tilt stage 58. The image forming characteristic of the projection optical system PL is adjusted with high accuracy by a remote operation almost completely automatically just by inputting a wavefront aberration measurement command through the remote control.
[0179]
In the above description, the projection optical system is automatically adjusted. However, aberrations that are difficult to correct by automatic adjustment may be included. Considering such a case, a skilled engineer on the second communication server 130 side displays the wavefront measurement data stored in the hard disk of the second communication server 130 on the display, and analyzes the display content. If the problem is detected and aberrations that are difficult to perform by automatic adjustment are included, the instruction content of the appropriate countermeasure is input from the keyboard of the second communication server 130, etc. It is also possible to display on the screen of the display device 44. A service engineer or the like on the maker A side can adjust the projection optical system in a short time by finely adjusting the lens assembly based on the display content of the screen.
[0180]
Next, the exposure device 122 (122₁~ 122_Three) Will be described with reference to the flowchart of FIG. 5 showing the main control algorithm of the CPU of the second communication server 130. As a premise, the first exposure apparatus 122, for example, in accordance with a measurement instruction from a service engineer or the like during regular maintenance of the exposure apparatus 122, for example₁The main controller 50 measures the wavefront aberration of the projection optical system PL using the wavefront aberration measuring instrument 80 described above, and the measured wavefront data is transmitted to the first communication server in the same procedure as described above. It is assumed that it is stored in 120 hard disks or the like. The first communication server 120 or the exposure apparatus 120 is also used when setting the best exposure conditions.₁Data communication between the communication server 130 and the second communication server 130 is performed in the same manner as described above. However, for the sake of simplification of description, description of communication such as a communication path is omitted below.
[0181]
The flowchart of FIG. 5 starts with the best exposure including the designation of the exposure apparatus to be determined for the best exposure condition from the first communication server 120 to the second communication server 130 in accordance with an instruction from the operator on the manufacturer A side. This is the time when the third program is loaded into the main memory by the second communication server 130 in response to an instruction to determine the condition. Therefore, the processing after step 202 in FIG. 5 is actually performed according to the third program.
[0182]
First, in step 202, after instructing the first communication server 120 to input a condition, the process proceeds to step 204 and waits for the condition to be input.
[0183]
At this time, in the first communication server 120, for example, according to the instruction for determining the best exposure condition by the operator, for example, the exposure apparatus 122₁Then, information on the reticle to be used next is stored in, for example, the exposure apparatus 122.₁~ 122_ThreeA pattern information is obtained by searching a predetermined database based on the information of the reticle. In the first communication server 120, the exposure apparatus 122 is used.₁It is assumed that the main control device 50 is inquired for setting information such as the current lighting conditions and the information is stored in the memory.
[0184]
Alternatively, the information on the pattern and the information on the lighting conditions can be manually input to the first communication server 120 by the operator via the input device.
[0185]
In any case, information on the pattern to be simulated obtained above (for example, in the case of a line-and-space pattern, the line width, the duty ratio, etc. (or may be actual pattern design data, etc.)). The first communication server 120 together with information on preset imaging characteristics (including index values of the imaging characteristics: hereinafter referred to as “target aberration”), such as abnormal line width values, Will be entered.
[0186]
In this way, when the first communication server 120 inputs the condition and instructs the completion of the input, the process proceeds to step 206 in FIG. 5 to create the Zernike change table of the target aberration input in step 204 above. After setting the condition for this, the process proceeds to the next step 208. Note that the target aberration information input in step 204 is not limited to one type. That is, it is possible to simultaneously specify a plurality of types of imaging characteristics of the projection optical system PL as the target aberration.
[0187]
In step 208, the exposure apparatus 122.₁After instructing the first communication server 120 to input information related to the projection optical system PL, the process proceeds to step 210 and waits for input of the information. Then, by the first communication server 120, information regarding the projection optical system PL, specifically, numerical aperture (NA), illumination conditions (for example, setting of illumination system aperture stop or coherence factor σ value, etc.), wavelength When such information is input, the process proceeds to step 212, where the input information is stored in the RAM, and information on the aberration to be given is set. As an example, the value of the coefficient of each term of the Zernike polynomial is, for example, the coefficient Z of the second term.₂~ Coefficient Z of the 37th term₃₇The same value, for example, 0.05λ is set individually.
[0188]
In the next step 214, aberration information set based on the input pattern information and information related to the projection optical system PL, for example, one target aberration corresponding to 0.05λ or its index value (for example, coma aberration). After creating a graph (for example, a Zernike change table (calculation table) such as abnormal line width values) where the vertical axis is the coefficient of each term of the Zernike polynomial and the horizontal axis is the coefficient of each term of the Zernike polynomial Proceed to 216.
[0189]
Here, the Zernike change table is a Zernike polynomial in which the wavefront of the projection optical system PL is developed for a specific aberration when the input pattern is the target pattern, that is, the target aberration (including its index value). It is nothing but table data consisting of the sensitivity of each term coefficient (Zernike Sensitivity). This Zernike change table is based on the input pattern information, information on the projection optical system PL, and information on the set aberration, and for the same type of projection optical system, the type of each lens element constituting the projection optical system. It is unambiguously determined based on design information including layout and layout. Therefore, based on the designation of the exposure apparatus (for example, designation of the model name) for which the best exposure condition is determined, the in-house database of manufacturer B is searched to confirm the type of the projection optical system of the exposure apparatus. Thus, a Zernike change table corresponding to the target aberration can be created.
[0190]
In the next step 216, it is determined whether or not a Zernike change table has been created for all the target aberrations input in step 204. If this determination is negative, the process returns to step 214, and a change table is created for the next target aberration.
[0191]
When the creation of the change table for all target aberrations is completed and the determination in step 216 is affirmed, the process proceeds to the next step 218. In step 218, after instructing the first communication server 120 to input wavefront measurement data, the process proceeds to step 220 and waits for the input of the measurement data. Then, wavefront measurement data stored in the hard disk from the first communication server 120 (coefficient of each term of the Zernike polynomial in which the wavefront corresponding to the first measurement point to the nth measurement point is expanded, for example, the coefficient of the second term) Z₂~ Coefficient Z of the 37th term₃₇) Is entered, the process proceeds to step 222, and an operation such as the following expression (12) is performed for each measurement point using the Zernike change table (calculation table) created earlier. 1 is calculated and stored in the RAM.
[0192]
A = K ・ {Z₂・ (Change table value) + Z_Three・ (Change table value) + ... + Z₃₇・ (Value of change table)}… (12)
[0193]
Here, A is a target aberration of the projection optical system PL, for example, astigmatism, curvature of field, or the like, or an index of the target aberration, for example, an abnormal line width value that is an index of coma aberration. K is a proportionality constant determined according to resist sensitivity or the like.
[0194]
Here, for example, considering the case where A is an abnormal line width value, for example, when the pattern is an L / S pattern having five lines, the abnormal line width value is expressed by the above-described equation (1). It can be expressed as As is clear from the equation (1), the calculation of the above equation (12) is nothing but the calculation for converting the pattern into an aerial image (projection image).
[0195]
In the next step 224, it is determined whether or not all the target aberrations (conditional aberrations (imaging characteristics)) have been calculated. If this determination is negative, the process returns to step 222 to determine the next target aberration. The aberration is calculated and stored in the RAM.
[0196]
When the calculation of all the target aberrations is completed in this way, the process proceeds to step 226, the calculation results of all the target aberrations stored in the RAM are stored in the hard disk or the like, and then the process proceeds to the next step 228.
[0197]
In step 228, information on the projection optical system PL, specifically, numerical aperture (NA), illumination conditions (for example, setting of illumination system aperture stop or coherence factor σ value, etc.), part of wavelength, etc. Then, after changing to the contents different from those previously input in step 210, the process proceeds to the next step 230, where it is determined whether or not the contents change of the expected number of times has been completed. Here, since the information regarding the projection optical system PL has only been changed once, this determination is denied, and the processing returns to step 214, and thereafter the processing and determination after step 214 are repeated. At this time, in Step 214, a Zernike change table is created. At this time, the Zernike change table is created based on the information about the projection optical system PL after the change changed in Step 228. In this way, when the illumination conditions, the numerical aperture, the wavelength, and the like are sequentially changed, the processes and determinations of Step 214 to Step 230 are repeated. If yes, go to next Step 232. At this time, the calculation result of the target aberration under the predetermined number of condition settings is stored in the hard disk or the like.
[0198]
In the next step 232, conditions (illumination conditions, numerical aperture, wavelength, etc.) relating to the projection optical system in which the objective aberration stored in the hard disk or the like is optimal (for example, zero to minimum) are obtained. The condition is determined as the best exposure condition.
[0199]
In the next step 234, after the determined best exposure condition is transmitted to the first communication server 120, a series of processing of this routine is terminated.
[0200]
In the first communication server 120 that has received the data of the best exposure conditions, command data for instructing the setting of the best exposure conditions is sent to the exposure device 122 as necessary.₁The main control device 50 sets the best exposure conditions according to the data. Specifically, in the main controller 50, the illumination condition is changed (set) by changing the aperture stop of the illumination system aperture stop plate 24, or the pupil aperture stop 15 of the projection optical system PL shown in FIG. By adjusting the numerical aperture, the numerical aperture of the projection optical system PL can be adjusted. Alternatively, the main control device 50 can set the exposure wavelength by giving the light source 16 information for changing the wavelength of the illumination light EL as the control information TS.
[0201]
Note that the second communication server 130 directly receives the instruction data for setting the best exposure conditions.₁To the exposure apparatus 122.₁It is also possible to set the best exposure conditions.
[0202]
Further, by making a slight change to the third program corresponding to the flowchart of FIG. 5, while gradually changing the pattern information while fixing the setting information other than the pattern information, the Zernike change table similar to the above is used. It is also possible to determine the optimum pattern setting information as the best exposure condition by repeatedly creating and calculating the target aberration (or aerial image) based on the wavefront measurement data.
[0203]
Similarly, by making a slight change to the third program corresponding to the flowchart of FIG. 5, the setting information other than the information on the aberration to be given is fixed and the information on the aberration to be given is changed and the same as above. Aberration to be given to the projection optical system when transferring the input pattern as the best exposure condition by repeatedly creating the Zernike change table and calculating the target aberration (or aerial image) based on the wavefront measurement data It is also possible to determine. In such a case, the second communication server 130 adds such aberration (for example, the coefficient Z of the second term of the Zernike polynomial) to the projection optical system PL.₂~ Coefficient Z of the 37th term₃₇) Is provided so that₁The imaging characteristics can be adjusted by controlling the imaging correction controller 48 via the main controller 50. Alternatively, the second communication server 130 controls the imaging correction controller 48 via the first communication server 120 and the main control device 50 so as to give such aberration to the projection optical system PL, thereby adjusting the imaging characteristics. Can be adjusted.
[0204]
Other exposure apparatus 122₂122_ThreeThe best exposure condition is set in the same manner as described above.
[0205]
Further, in the present embodiment, for example, during periodic inspection of the exposure apparatus 122, a service engineer or the like responds by performing condition setting input, information input regarding the projection optical system, etc. from the first communication server 120 side. Then, the second communication server 130 creates a similar Zernike change table in the same procedure as the simulation at the time of setting the best exposure condition, using another program obtained by partially changing the third program. . Then, the wavefront aberration is measured by the main controller 50 based on an instruction from a service engineer or the like on the exposure apparatus 122 side, and when the positional deviation data obtained as a result is transmitted via the first communication server 120, 2 The communication server 130 calculates the target aberration in the same manner as described above. In the second communication server 130, the movable lens 13 whose objective aberration is optimum (for example, zero to minimum).₁~ 13_FourThe driving amount in each direction of freedom is calculated by the least square method using another program. Then, the second communication server 130 gives the calculated drive amount command value to the imaging characteristic correction controller 48 via the main controller 50. 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, and the target 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. In this case, it is not always necessary to use the second program described above.
[0206]
In the present embodiment, the projection optical system PL of the exposure apparatus 122 during periodic maintenance or the like is installed in advance by installing another program in which the third program described above is partially changed from the drive device 46 to the storage device 42. During the adjustment, automatic adjustment of the imaging characteristics of the projection optical system PL by the exposure device 122 itself can be easily realized. In this case, based on the operator's instructions (including condition setting input, information input related to the projection optical system, etc.), the CPU in the main controller 50 performs the same processing in the same procedure as the above simulation, A Zernike change table is created. Then, when wavefront aberration is measured and positional deviation data is input, the target aberration is calculated by the CPU in the main controller 50 in the same manner as described above. Thereafter, in the CPU in the main controller 50, the movable lens 13 whose objective aberration is optimum (for example, zero to minimum).₁~ 13_FourThe driving amount in each direction of freedom is calculated by the least square method using another program. Then, the CPU in the main controller 50 gives the calculated drive amount command value 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, and the target 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.
[0207]
As is clear from the above description, in the present embodiment, the movable lens 13 is used.₁~ 13_FourThe driving element for driving these movable lenses and the imaging characteristic correction controller 48 constitute an imaging characteristic adjustment mechanism, and the main controller 50 constitutes a control device for controlling the imaging characteristic adjustment mechanism.
[0208]
In the above description, the case where the wavefront aberration of the projection optical system PL is measured using the wavefront aberration measuring instrument 80 has been described. However, the measurement reticle R described below is not limited to this._T(Hereafter, “Reticle R_TIt is also possible to measure wavefront aberration using
[0209]
FIG. 6 shows this measurement reticle R._TA schematic perspective view of is shown. FIG. 7 shows the reticle R in a state where it is loaded on the 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. FIG. 8 shows reticle R in a state where it is loaded on reticle stage RST._TA schematic view of an XZ cross section in the vicinity of the −Y side end is shown together with a schematic diagram of the projection optical system PL.
[0210]
As is apparent from FIG. 6, this measurement reticle R_TThe overall shape is substantially the same as that of a normal reticle with a pellicle. This measuring reticle R_TIs attached to the glass substrate 60, a lens mounting member 62 having a rectangular plate shape fixed to the X-axis direction central portion of the upper surface of the glass substrate 60 in FIG. 6, and the lower surface of the glass substrate 60 in FIG. A spacer member 64 made of a frame-like member having an appearance similar to that of a normal pellicle frame, an opening plate 66 attached to the lower surface of the spacer member 64, and the like are provided.
[0211]
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. 7).
[0212]
Further, as shown in FIG. 7, reinforcing members 69 are provided at predetermined intervals in the space surrounded by the glass substrate 60, the spacer member 64, and the opening plate 66.
[0213]
Further, on the lower surface of the glass substrate 60, each condenser lens 65 is provided._{i, j}The measurement pattern 67 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.
[0214]
Returning to FIG. 6, the lens holding member 62 has an opening 72 at the center of a part of the band-like region at both ends in the Y-axis direction.₁, 72₂Are formed respectively. As shown in FIG. 8, one opening 72 is formed on the lower surface (pattern surface) of the glass plate 60.₁Opposing to the reference pattern 74₁Is formed. Although not shown, the other opening 72 is provided.₂The reference pattern 74 is formed on the lower surface (pattern surface) of the glass plate 60 so as to face the₁The same reference pattern (for convenience, “reference pattern 74₂Is written).
[0215]
Further, as shown in FIG. 6, 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.
[0216]
Here, in this embodiment, the measurement pattern 67_{i, j}As shown in FIG. 9A, a mesh (street line) pattern as shown in FIG. 9A is used. Correspondingly, the reference pattern 74₁74₂As shown in FIG. 9B, the measurement pattern 67_{i, j}A two-dimensional lattice pattern in which square patterns are arranged at the same pitch is used. Reference pattern 74₁74₂9A can be used, and the pattern shown in FIG. 9B can be used as the measurement pattern. Also, the measurement pattern 67_{i, j}However, the present invention is not limited to this, and patterns having other shapes may be used. In this case, a pattern having a predetermined positional relationship with the measurement pattern may be used as the reference pattern. In other words, the reference pattern may be a pattern that serves as a reference for the positional deviation of the measurement pattern, and its shape is not limited. However, in order to measure the imaging characteristics (optical characteristics) of the projection optical system PL, the projection pattern is used. A pattern in which the pattern is distributed over the entire image field or exposure area of the optical system PL is desirable.
[0217]
Next, exposure apparatus 122 (exposure apparatus 122₁~ 122_Three) Reticle R_TThe measurement of the wavefront aberration of the projection optical system PL when using the above will be described.
[0218]
First, measurement reticle R_TIs used to measure the wavefront aberration at a plurality of (here, n) measurement points in the field of the projection optical system PL as follows.
[0219]
First, when a wavefront aberration measurement command is input by an operator (including a service engineer) via the input device 45, the main controller 50 causes the measurement reticle R to pass 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 determines a pair of reticle alignment reference marks on reference mark plate FM in advance. Position to the specified reference position. Here, the reference position is determined, for example, at a position where the center of the pair of second reference marks coincides with the origin on the stage coordinate system defined by the laser interferometer 54W.
[0220]
Next, in the main controller 50, a measurement reticle R_TA pair of reticle alignment marks RM1 and RM2 above and the reticle alignment reference marks corresponding thereto are simultaneously observed with the above-described reticle alignment microscope, and projected images of the reticle alignment marks RM1 and RM2 onto the reference plate FM; The reticle stage RST is slightly driven in the XY two-dimensional plane via a drive system (not shown) so that the positional deviation from the corresponding reference mark is minimized. Thereby, the reticle alignment is completed, and the reticle center substantially coincides with the optical axis of the projection optical system PL.
[0221]
Next, main controller 50 loads wafer W having a resist (photosensitive agent) coated on the surface thereof onto Z tilt stage 58 using a wafer loader (not shown).
[0222]
Next, in the main controller 50, a measurement reticle R_TCondensing lens 65_{i, j}Of all and the opening 72₁, 72₂In order to form a rectangular illumination area having a length in the X-axis direction within the maximum width in the X-axis direction of the lens holding member 62, the opening of the reticle blind 30 is set via a drive system (not shown). . 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.
[0223]
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}And simultaneously transferred via the projection optical system PL. As a result, each of the measurement patterns 67 as shown in FIG._{i, j}Reduced image (latent image) 67 '_{i, j}Are formed at predetermined intervals along the XY two-dimensional direction.
[0224]
Next, in main controller 50, a measurement value of a reticle laser interferometer (not shown), a reticle center, and one reference pattern 74 are shown.₁On the basis of the design positional relationship with the reference pattern 74₁The reticle stage RST is moved in the Y-axis direction by a predetermined distance via a drive system (not shown) so that the center position of the optical axis AX coincides with the optical axis AX. Next, in main controller 50, opening 72 after the movement is provided.₁In order to define the illumination area of the illumination light EL only in a rectangular area with a predetermined area on the lens holding member 62 including this (this area does not cover any condenser lens), a reticle is provided via a drive system (not shown). The opening of the blind 30 is set.
[0225]
Next, in the main controller 50, the first measurement pattern 67_1,1Latent image 67 '_1,1The wafer stage WST is moved while monitoring the measurement value of the laser interferometer 54W so that the substantially center of the region on the wafer W on which is formed substantially coincides with the optical axis of the projection optical system PL.
[0226]
In the main controller 50, the control information TS is given to the light source 16, the laser beam LB is emitted, and the illumination light EL is sent to the reticle R._TIs exposed to light. Thereby, the measurement pattern 67 of the resist layer on the wafer W is obtained._1,1Region where the latent image of (S region_1,1Reference pattern 74₁Are transferred in layers. As a result, the area S on the wafer W_1,1As shown in FIG. 10B, the measurement pattern 67_1,1Latent image 67 '_1,1And reference pattern 74₁Latent image 74 '₁Are formed in a positional relationship as shown in FIG.
[0227]
Next, in the main controller 50, the reticle R_TUpper measurement pattern 67_{i, j}Measurement pattern 67 on the wafer W based on the arrangement pitch of the projection optical system PL and the projection magnification of the projection optical system PL._{i, j}Is calculated, the wafer stage WST is moved in the X-axis direction by the pitch p, and the second measurement pattern 67 is calculated._1,2Area on the wafer W (area S)_1,2Wafer stage WST is moved so that the approximate center of the projection optical system PL substantially coincides with the optical axis of projection optical system PL.
[0228]
In the main controller 50, the control information TS is given to the light source 16, the laser beam LB is emitted, and the illumination light EL is sent to the reticle R._TIs exposed to light. Thereby, the region S on the wafer W is_1,2Reference pattern 74₁Are transferred in layers.
[0229]
Thereafter, by repeating the inter-region stepping operation and the exposure operation similar to the above, the region S on the wafer W is repeated._{i, j}In addition, a latent image of the measurement pattern and the reference pattern similar to those in FIG. 10B is formed.
[0230]
When the exposure is thus completed, the main controller 50 unloads the wafer W from the Z tilt stage 58 via a wafer loader (not shown), and then is connected to the chamber 11 in line (not shown). This is sent to the coater / developer (hereinafter abbreviated as “C / D”). Then, the wafer W is developed in the C / D, and after the development, the regions S arranged in a matrix on the wafer W._{i, j}In addition, a resist image of the measurement pattern and the reference pattern is formed in the same arrangement as in FIG.
[0231]
Thereafter, the developed wafer W is taken out from the C / D, and is used for each region S by using an external overlay measuring device (registration measuring device)._{i, j}Is measured, and based on the result, each measurement pattern 67 is measured._{i, j}The corresponding reference pattern 74 of the resist image₁A position error (positional deviation) with respect to is calculated. There are various methods for calculating the positional deviation, but in any case, it is desirable to perform statistical calculation based on the measured raw data from the viewpoint of improving accuracy.
[0232]
In this way, each region S_{i, j}, The positional deviations (Δξ ′, Δη ′) of the measurement pattern in the X and Y two-dimensional directions with respect to the reference pattern are obtained. And each area S_{i, j}The positional deviation data (Δξ ′, Δη ′) for the above is input to the main controller 50 via the input device 44 by the service engineer described above. Each calculated region S from an external overlay measuring instrument_{i, j}It is also possible to input the data of misalignment (Δξ ′, Δη ′) on the main controller 50 online.
[0233]
In any case, in response to the above input, the CPU in the main controller 50 loads the arithmetic program similar to the first program described above into the main memory, and based on the positional deviation (Δξ ′, Δη ′). 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 coefficient of each term of the Zernike polynomial, for example, the coefficient Z of the second term₂~ Coefficient Z of the 37th term₃₇Is calculated according to the above calculation program.
[0234]
As described above, the CPU in the main controller 50 obtains the wavefront of the projection optical system PL by calculation according to a predetermined calculation program on the basis of the positional deviation (Δξ ′, Δη ′). Now, the physical relationship between the displacement (Δξ ′, Δη ′) and the wavefront, which is the premise of the calculation, will be briefly described with reference to FIGS.
[0235]
FIG. 7 shows a measurement pattern 67._{k, l}As typically shown, the measurement pattern 67_{i, j}Out of the diffracted light generated in FIG._{i, j}The measurement pattern 67 at which position the light that has passed through_{i, j}The position that passes through the pupil plane of the projection optical system PL differs depending on whether the light is derived from. That is, the wavefront at each position of the pupil plane is a measurement pattern 67 corresponding to the position._{i, j}Corresponds to the wavefront of light through the position of If there is no aberration in the projection optical system PL, these wavefronts are all 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}Is the wavefront F on the wafer W.₁The image is formed at a position shifted according to the inclination of the ideal wavefront.
[0236]
On the other hand, the reference pattern 74₁(Or 74₂As shown in FIG. 8, the diffracted light generated from (1) is directly incident on the projection optical system PL without being limited by the pinhole-shaped opening, and is incident on the wafer W via the projection optical system PL. Imaged. Further, the reference pattern 74₁In the exposure using the reference pattern 74 on the optical axis of the projection optical system PL.₁Is performed in a state where the center of the reference pattern 74 is positioned.₁The imaged light beam generated from the image is hardly affected by the aberration of the projection optical system PL, and forms an image in a minute region including the optical axis without positional deviation.
[0237]
Accordingly, the positional deviation (Δξ ′, Δη ′) is a value that directly reflects the inclination of the wavefront with respect to the ideal wavefront, and on the contrary, the wavefront can be restored based on the positional deviation (Δξ ′, Δη ′). As is clear from the physical relationship between the positional deviations (Δξ ′, Δη ′) and the wavefront, the wavefront calculation principle in this embodiment is the well-known Shack-Hartmann wavefront calculation principle itself.
[0238]
Measurement reticle R_TA mask having a special structure similar to the above is used, and each of a plurality of measurement patterns on the mask is baked on the substrate sequentially through pinholes and projection optical systems provided individually, and on the mask. The reference pattern is printed on the substrate via the projection optical system without passing through the condensing lens and the pinhole, and the resist images of the plurality of measurement patterns obtained as a result of the respective printing positions of the reference pattern with respect to the resist image An invention related to a technique for calculating a wavefront aberration by measuring a deviation and performing a predetermined calculation is disclosed in US Pat. No. 5,978,085.
[0239]
Incidentally, the exposure apparatus 122 of the present embodiment.₁~ 122_ThreeThen, at the time of manufacturing a semiconductor device, a reticle R for device manufacturing is loaded on the reticle stage RST, and thereafter, preparatory work such as reticle alignment and so-called baseline measurement, and wafer alignment such as EGA (Enhanced Global Alignment). Is done.
[0240]
Note that the above-described preparation operations such as reticle alignment and baseline measurement are disclosed in detail in, for example, Japanese Patent Laid-Open No. 4-324923, and the following EGA is disclosed in Japanese Patent Laid-Open No. 61-44429. The detailed description will be omitted.
[0241]
After that, the measurement reticle R described above_TThe same step-and-repeat exposure is performed as in the measurement of wavefront aberration using. However, in this case, stepping is performed in units of shots based on the wafer alignment result. It should be noted that the operation at the time of exposure is not different from that of a normal stepper, and detailed description thereof is omitted.
[0242]
Next, the exposure device 122 (122₁~ 122_ThreeThe manufacturing method of the projection optical system PL performed at the time of manufacturing will be described.
[0243]
a. Determination of projection optical system specifications
In determining this specification, first, an engineer on the manufacturer A side who is a user or the like sends target information to be achieved by the exposure apparatus, such as an exposure wavelength, to the first communication server 120 via an input / output device (not shown). Information such as the minimum line width (or resolving power) and the target pattern is input. Next, the engineer or the like instructs the first communication server 120 to transmit the target information via the input / output device.
[0244]
As a result, the first communication server 120 makes an inquiry to the second communication server 130 as to whether or not data can be received, and receives a reply from the second communication server 130 that data can be received. The target information is transmitted to the second communication server 130.
[0245]
In the second communication server 130, the target information is received and analyzed, and based on the analysis result, one method is selected from seven specification determination methods as will be described later. And the determined specifications are stored in the RAM.
[0246]
Here, prior to the description of the specification determination method, the coefficient Z of each term of the Zernike polynomial (Fringe Zernike polynomial) expressed by the above-described equation (4), in which the wavefront of the projection optical system is expanded._iA simple explanation will be given of what aberrations are related to. Each term is f, as shown in Table 1 above._iThis is a term including an (ρ, θ) term, that is, an n-th order mθ term in which the highest order of ρ is n-th order and a coefficient applied to θ is m.
[0247]
0th-order 0θ term coefficient Z₁Indicates the position of the wavefront and has little to do with aberrations.
The coefficient of the primary 1θ term (Z₂, Z_Three)) Indicates a distortion component.
Second-order 0θ term (coefficient Z_Four) Indicates a focus component.
Coefficient of third-order or higher 0θ term (Z₉, Z₁₆, Z_{twenty five}, Z₃₆, Z₃₇)) Indicates a spherical aberration component.
2θ term (coefficient (Z_Five, Z₆, Z₁₂, Z₁₃, Z_{twenty one}, Z_{twenty two}, Z₃₂, Z₃₃)), And 4θ term (coefficient (Z₁₇, Z₁₈, Z₂₈, Z₂₉)) Indicates the astigmatism component.
Coefficient of 1θ term (third order or higher (Z₇, Z₈, Z₁₄, Z₁₅, Z_{twenty three}, Z_{twenty four}, Z₃₄, Z₃₅)), 3θ term (coefficient (Z_Ten, Z₁₁, Z₁₉, Z₂₀, Z₃₀, Z₃₁)), And 5θ term (coefficient (Z₂₆, Z₂₇)) Indicates a coma aberration component.
[0248]
In the following, seven specification determination methods will be described. All of these methods determine the specifications of the projection optical system using the wavefront aberration that the projection optical system should satisfy as a standard value.
[0249]
<First method>
This is a method for determining the specifications of a projection optical system using the coefficient (value) of a specific term selected based on target information among the coefficients of each term of the Zernike polynomial that develops the wavefront of the projection optical system as a standard value. It is. As an example, this first method uses a coefficient Z corresponding to, for example, a distortion component when the target information includes, for example, resolving power.₂, Z_ThreeIs used, and the values of these coefficients themselves are used as standard values, and the specifications of the projection optical system are determined so that these values are not more than predetermined values within the field of view.
[0250]
<Second method>
This is based on the RMS value (Root-means-square value) of the coefficient of each term of the Zernike polynomial that develops the wavefront of the projection optical system as a standard value, and the RMS in the entire field of view of the projection optical system. This is a method of determining the specifications of the projection optical system so that the value does not exceed a predetermined allowable value. According to this second method, for example, aberration defined in the entire field of view such as field curvature is suppressed. This second method can be suitably applied regardless of the target information. Of course, the RMS value within the field of view of the coefficient of each term may be used as the standard value.
[0251]
<Third method>
This is because the values of the coefficients of each term of the Zernike polynomial that expands the wavefront of the projection optical system are used as standard values, and the specifications of the projection optical system are determined so that the coefficients do not exceed the respective allowable values. It is a method to do. In the third method, each allowable value can be set as the same value, or a different value can be arbitrarily set individually. Of course, some of them may be the same value.
[0252]
<Fourth method>
This fourth method uses the RMS value of the coefficient of the n-th order mθ term corresponding to the particular aberration of interest as the standard value among the coefficients of each term of the Zernike polynomial in which the wavefront of the projection optical system is developed, and the RMS value Is a method for determining the specifications of the projection optical system so that the predetermined allowable value is not exceeded. For example, when the target information includes pattern information, this fourth method is particularly effective for analyzing the pattern information and forming a projected image of the pattern in a good state on the image plane. It is necessary to estimate which aberration is necessary, and normalize the RMS value of the coefficient of the n-th order mθ term based on the estimated result as follows, for example.
[0253]
Z in the field of view₂, Z_ThreeRMS value A for₁Is the standard value and standard value A₁≤ Allowable value B₁And
Z in the field of view_FourRMS value A₂Is the standard value and standard value A₂≤ Allowable value B₂And
Z in the field of view_Five, Z₆RMS value A for_ThreeIs the standard value and standard value A_Three≤ Allowable value B_ThreeAnd
Z in the field of view₇, Z₈RMS value A for_FourIs the standard value and standard value A_Four≤ Allowable value B_FourAnd
Z in the field of view₉RMS value A_FiveIs the standard value and standard value A_Five≤ Allowable value B_FiveAnd
Z in the field of view_Ten, Z₁₁RMS value A for₆Is the standard value and standard value A₆≤ Allowable value B₆And
Z in the field of view₁₂,₁₃RMS value A for₇Is the standard value and standard value A₇≤ Allowable value B₇And
Z in the field of view₁₄, Z₁₅RMS value A for₈Is the standard value and standard value A₈≤ Allowable value B₈And
Z in the field of view₁₆RMS value A₉Is the standard value and standard value A₉≤ Allowable value B₉And
Z in the field of view₁₇, Z₁₈RMS value A for_TenIs the standard value and standard value A_Ten≤ Allowable value B_TenAnd
Z in the field of view₁₉, Z₂₀RMS value A for₁₁Is the standard value and standard value A₁₁≤ Allowable value B₁₁And
Z in the field of view_{twenty one}, Z_{twenty two}RMS value A for₁₂Is the standard value and standard value A₁₂≤ Allowable value B₁₂And
Z in the field of view_{twenty three}, Z_{twenty four}RMS value A for₁₃Is the standard value and standard value A₁₃≤ Allowable value B₁₃And
Z in the field of view_{twenty five}RMS value A₁₄Is the standard value and standard value A₁₄≤ Allowable value B₁₄And
Z in the field of view₂₆, Z₂₇RMS value A for₁₅Is the standard value and standard value A₁₅≤ Allowable value B₁₅And
Z in the field of view₂₈, Z₂₉RMS value A for₁₆Is the standard value and standard value A₁₆≤ Allowable value B₁₆And
Z in the field of view₃₀, Z₃₁RMS value A for₁₇Is the standard value and standard value A₁₇≤ Allowable value B₁₇And
Z in the field of view₃₂, Z₃₃RMS value A for₁₈Is the standard value and standard value A₁₈≤ Allowable value B₁₈And
Z in the field of view₃₄, Z₃₅RMS value A for₁₉Is the standard value and standard value A₁₉≤ Allowable value B₁₉And
Z in the field of view₃₆, Z₃₇RMS value A for₂₀Is the standard value and standard value A₂₀≤ Allowable value B₂₀And
[0254]
<Fifth method>
In the fifth method, among the coefficients of the terms of the Zernike polynomial in which the wavefront of the projection optical system is expanded, the terms corresponding to the particular aberration of interest are separated into a plurality of groups for each mθ term, In this method, the RMS value in the field of view of the coefficient of each term included is used as a standard value, and the specification of the projection optical system is determined so that the RMS value of each group does not exceed the individually determined allowable values.
[0255]
For example, the coefficient Z of the third order or higher 0θ term₉, Z₁₆, Z_{twenty five}, Z₃₆, Z₃₇RMS value C in the field of view₁Is the standard value and the standard value C₁≦ Allowable value D₁And
Coefficient Z of 1θ term of third order or higher₇, Z₈, Z₁₄, Z₁₅, Z_{twenty three}, Z_{twenty four}, Z₃₄, Z₃₅RMS value C in the field of view₂Is the standard value and the standard value C₂≦ Allowable value D₂And Coefficient Z of 2θ term_Five, Z₆, Z₁₂, Z₁₃, Z_{twenty one}, Z_{twenty two}, Z₃₂, Z₃₃RMS value C in the field of view_ThreeIs the standard value and the standard value C_Three≦ Allowable value D_ThreeAnd
Coefficient Z of 3θ term_Ten, Z₁₁, Z₁₉, Z₂₀, Z₃₀, Z₃₁RMS value in the field of view for standard value C_FourStandard value C_Four≦ Allowable value D_FourAnd
Coefficient Z of 4θ term₁₇, Z₁₈, Z₂₈, Z₂₉RMS value in the field of view for standard value C_FiveStandard value C_Five≦ Allowable value D_FiveAnd
Coefficient Z of 5θ term₂₆, Z₂₇RMS value in the field of view for standard value C₆Standard value C₆≦ Allowable value D₆And
[0256]
As can be seen from the meanings of the coefficients of the respective terms, the fifth method also analyzes the pattern information and obtains a good projection image of the pattern when the target information includes pattern information, for example. In order to form the image on the image surface in a state, it is possible to estimate which aberration should be particularly suppressed and perform the estimation based on the estimated result.
[0257]
<Sixth method>
In the sixth method, the coefficient of each term after weighting according to the target information is applied to the coefficient of each term of the Zernike polynomial in which the wavefront of the projection optical system PL is developed as a standard value, and This is a method for determining the specifications of the projection optical system so that the RMS value within the field of the coefficient does not exceed a predetermined allowable value. This sixth method is also particularly effective when, for example, pattern information is included in the target information, in order to analyze the pattern information and form a projected image of the pattern in a good state on the image plane. It is possible to estimate which aberration is to be performed and perform the estimation based on the estimation result.
[0258]
<Seventh method>
The seventh method is a method that is used only when the target information includes information on a pattern that is a projection target of the projection optical system, and the pattern is obtained by the projection optical system based on the pattern information. A simulation is performed to obtain the aerial image formed on the image plane when projected, and the simulation results are analyzed, and the wavefront aberration allowed for the projection optical system is projected as a standard value in order to transfer the pattern well. It determines the specifications of the optical system. In this case, as a simulation method, for example, a Zernike change table similar to that described above is created in advance, and a specific aberration (including its index value) is obtained from the Zernike change table when the pattern is the target pattern. The linearity of the coefficient sensitivity of each term of the Zernike polynomial that expands the wavefront of the projection optical system (Zernike Sensitivity) and the coefficient of each term of the Zernike polynomial that expands the wavefront of the projection optical system are determined according to the pattern. An aerial image may be obtained based on the combination.
[0259]
This will be described in more detail. Various aberrations (including index values) at n measurement points (evaluation points) in the field of view of the projection optical system, for example, an n-row m-column matrix f composed of m types of aberrations, Wavefront aberration data at the n measurement points, for example, coefficients of each term of the Zernike polynomial in which the wavefront is expanded, for example, the coefficient Z of the second to 37th terms₂~ Z₃₇N-by-36 matrix Wa and Zernike change table data (that is, coefficients of terms of Zernike polynomials of m types of aberrations under predetermined exposure conditions, for example, coefficient Z of terms 2 to 37)₂~ Z₃₇There is a relationship expressed by the following equation (13) with a matrix ZS of, for example, 36 rows and m columns, consisting of a change amount per 1λ (Zernike Sensitivity).
f = Wa · ZS (13)
[0260]
Here, f, Wa, and ZS can be represented by the following equations (14), (15), and (16), respectively, as an example.
[0261]
[Equation 7]

[0262]
As apparent from the above equation (13), Zernike change table and wavefront aberration data (for example, coefficients of each term of the Zernike polynomial in which the wavefront is expanded, for example, the coefficient Z of the second to 37th terms)₂~ Z₃₇) Can be used to set an arbitrary aberration to a desired value. In other words, a desired aberration value is given to f in the above equation (13), and the above equation (13) is solved by the method of least squares using the data of the known (prepared) Zernike change table, The coefficient of each term of the Zernike polynomial at each point in the field of the projection optical system that makes the specific aberration a desired value, for example, the coefficient Z of the second to 37th terms₂~ Z₃₇It can be seen that
[0263]
That is, in the seventh method, a spatial image of a pattern in which an abnormal line width value, which is an index value of a specific aberration, for example, coma aberration, is equal to or less than a predetermined value is obtained by the above simulation. The specification of the projection optical system is determined using the wavefront aberration (coefficient of each term of the Zernike polynomial that expands the wavefront) obtained as a standard value.
[0264]
In any of the first to seventh specification determination methods described above, the wavefront information on the pupil plane of the projection optical system, that is, the comprehensive information passing through the pupil plane is standardized based on the target information to be achieved by the exposure apparatus. Since the specification of the projection optical system is determined as a value, if a projection optical system satisfying this specification is manufactured, the target to be achieved by the exposure apparatus can be reliably achieved as a result.
[0265]
b. Projection optical system manufacturing process
Next, the manufacturing process of the projection optical system PL will be described along the flowchart of FIG.
[0266]
[Step 1]
In step 1, first, each lens element as each optical member constituting the projection optical system PL according to a design value based on predetermined design lens data, a lens holder that holds each lens, and an optical unit that includes the lens element and the lens holder Manufactures a lens barrel that houses That is, each lens element is processed to have a radius of curvature and an axial thickness according to a predetermined design value from a predetermined optical material using a known lens processing machine, and a lens holder and lens element for holding each lens The lens barrel that houses the optical unit including the lens holder is processed into a shape having a predetermined dimension from a predetermined holding material (stainless steel, brass, ceramic, etc.) using a known metal processing machine or the like.
[0267]
[Step 2]
In step 2, the surface shape of the lens surface of each lens element constituting the projection optical system PL manufactured in step 1 is measured using, for example, a Fizeau interferometer. As this Fizeau interferometer, a light source using a He—Ne gas laser that emits light having a wavelength of 633 nm, an Ar laser that emits light having a wavelength of 363 nm, an Ar laser that is harmonicized to a wavelength of 248 nm, or the like is used. According to this Fizeau interferometer, an interference fringe due to interference of reflected light from a reference surface formed on the surface of a condensing lens arranged on an optical path and a lens element surface which is a test surface is used as an imaging device such as a CCD. The shape of the surface to be measured can be obtained accurately by measuring with It is known that the shape of the surface (lens surface) of an optical element such as a lens is obtained using a Fizeau interferometer. This is, for example, disclosed in Japanese Patent Laid-Open Nos. 62-126305 and 6-185997. The detailed description will be omitted.
[0268]
Measurement of the surface shape of the optical element using the Fizeau interferometer described above is performed on all lens surfaces of each lens element constituting the projection optical system PL. Each measurement result is stored in a memory such as a RAM provided in the second communication server 130 or a storage device such as a hard disk via an input device (not shown) such as a console.
[0269]
[Step 3]
After the measurement of the surface shapes of all the lens surfaces of each lens element constituting the projection optical system PL in step 2, the optical unit processed and manufactured according to the design value, that is, an optical element such as a lens and the optical element A plurality of optical units each composed of a lens holder for holding the lens is assembled. Among the optical units, a plurality of, for example, four are the movable lenses 13 described above.₁~ 13_FourEach having a movable lens 13.₁~ 13_FourAs described above, a double-structured lens holder is used as the lens holder in the optical unit including the lens unit. That is, these double-structured lens holders are movable lenses 13.₁~ 13_FourEach having an inner lens holder and an outer lens holder for holding the inner lens holder, and the positional relationship between the inner lens holder and the outer lens holder can be adjusted via a mechanical adjustment mechanism. It has become. The double lens holder is provided with the drive elements described above at predetermined positions.
[0270]
Then, the plurality of optical units assembled as described above are sequentially assembled through the upper opening of the lens barrel so as to be dropped into the lens barrel with a spacer interposed therebetween. Then, the optical unit first dropped into the lens barrel is supported via a spacer by a protrusion formed at the lower end of the lens barrel, and all the optical units are accommodated in the lens barrel. Is completed. In parallel with this assembly process, information on the distance between the optical surfaces (lens surfaces) of each lens element using a tool (micrometer, etc.) while taking into account the thickness of the spacer housed in the lens barrel together with the optical unit Measure. Then, while alternately performing the assembly operation and the measurement operation of the projection optical system, the distance between the optical surfaces (lens surfaces) of the final lens elements of the projection optical system PL at the stage where the assembly process of step 3 is completed is determined. Ask.
[0271]
In addition, in each process of the manufacturing stage including this assembly process, the movable lens 13 described above is used.₁~ 13_FourIs fixed in a neutral position. Although not described, the pupil aperture stop 15 is also incorporated in this assembly process.
[0272]
Measurement results relating to the distance between the optical surfaces (lens surfaces) of the lens elements of the projection optical system PL during the assembly process or at the completion of the assembly are communicated with the second communication via an input device (not shown) such as a console (not shown). The data is stored in a memory such as a RAM provided in the server 130 or a storage device such as a hard disk. In the above assembly process, the optical unit may be adjusted as necessary.
[0273]
At this time, for example, the relative distance in the optical axis direction between the optical elements is changed or the optical elements are inclined with respect to the optical axis via a mechanical adjustment mechanism. Further, the lens barrel is configured such that the tip of a screw (screw) screwed through a female screw portion that penetrates the side surface of the lens barrel comes into contact with the lens holder, and the screw is screwed through a tool such as a screw driver. By moving the lens holder, the lens holder may be shifted in a direction orthogonal to the optical axis to adjust the eccentricity.
[0274]
[Step 4]
Next, in step 4, the wavefront aberration of the projection optical system PL assembled in step 3 is measured.
[0275]
Specifically, the projection optical system PL is attached to the body of a large wavefront measuring apparatus (not shown), and wavefront aberration is measured. The principle of wavefront measurement by this wavefront measuring apparatus is not different from that of the wavefront aberration measuring instrument 80 described above, and detailed description thereof is omitted.
[0276]
As a result of the measurement of the wavefront aberration, the coefficient Z of each term of the Zernike polynomial (Fringe Zernike polynomial) in which the wavefront of the projection optical system is expanded by the wavefront measuring apparatus._i(I = 1, 2,..., 37) is obtained. Accordingly, by connecting the wavefront measuring device to the second communication server 130, the coefficient Z of each term of the Zernike polynomial is stored in a memory (or a storage device such as a hard disk) of the second communication server 130 such as a RAM._iAre automatically imported. In the above description, the wavefront measuring apparatus uses up to the 81st term of the Zernike polynomial, but this is done in order to calculate higher-order components of each aberration of the projection optical system PL. It is. However, it is possible to calculate up to the 37th term as in the case of the wavefront aberration measuring instrument described above, or to calculate more than 82 terms.
[0277]
[Step 5]
In step 5, the projection optical system so that the wavefront aberration measured in step 4 satisfies the specification determined according to the determination method selected from the first to seventh specification determination methods described above. Adjust PL.
[0278]
First, prior to the adjustment of the projection optical system PL, the second communication server 130 determines each piece of information stored in the memory, that is, information regarding the surface shape of each optical element obtained in the above step 2 and the above step 3. In the manufacturing process of the projection optical system PL actually assembled by correcting the optical basic data stored in advance in the memory based on the information about the distance between the optical surfaces of each optical element obtained in the assembling process. Reproduce the optical data. This optical data is used to calculate the adjustment amount of each optical element.
[0279]
That is, in the hard disk of the second communication server 130, for all the lens elements constituting the projection optical system PL, the unit drive amount of each lens element in the 6 degrees of freedom direction and the coefficient Z of each term of the Zernike polynomial_iThe basic database for adjustment in which the relationship with the amount of change is calculated based on the design value of the projection optical system, that is, the matrix O described above is expanded to include not only movable lenses but also non-movable lens elements, Stored. Therefore, the second communication server 130 corrects the adjustment basic database by a predetermined calculation based on the optical data in the manufacturing process of the projection optical system PL described above.
[0280]
For example, when any one of the first to sixth methods described above is selected, the second communication server 130 uses the corrected basic database and the target value of the wavefront, that is, the selected specification determination method. Based on Zernike polynomial terms Z_iAnd a coefficient Z of each term of the Zernike polynomial obtained as a measurement result of the wavefront measuring apparatus_iOn the basis of the actual measurement value, the adjustment amount of each lens element in the six degrees of freedom direction is calculated, for example, by the least square method according to a predetermined calculation program.
[0281]
Then, in the second communication server 130, information on the adjustment amount (including zero) of each lens element in each of the six degrees of freedom directions is displayed on the display screen.
[0282]
According to this display, each lens element is adjusted by an engineer (operator). Thereby, the projection optical system PL is adjusted so as to satisfy the specifications determined according to the selected specification determination method.
[0283]
Specifically, when the first method is selected as the specification determination method, the identification selected based on the target information among the coefficients of each term of the Zernike polynomial in which the wavefront of the projection optical system PL is expanded The projection optical system PL is adjusted so that the coefficient of the term does not exceed a predetermined value. Further, when the second method is selected, the projection is performed so that the RMS value of the coefficient of each term of the Zernike polynomial that develops the wavefront in the entire field of the projection optical system PL does not exceed a predetermined allowable value. The optical system PL is adjusted. In addition, when the third method is selected, the projection optical system PL is arranged so that the coefficients of the terms of the Zernike polynomial that develops the wavefront of the projection optical system do not exceed the respective allowable values. Adjusted. In addition, when the fourth method is selected, the field of view of the coefficient of the n-th order mθ term corresponding to the specific aberration of interest among the coefficients of each term of the Zernike polynomial that develops the wavefront of the projection optical system PL. The projection optical system PL is adjusted so that the RMS value does not exceed a predetermined allowable value. When the fifth method is selected, among the coefficients of the terms of the Zernike polynomial that develops the wavefront of the projection optical system PL, each term corresponding to a specific aberration to be noted is a plurality of terms for each mθ term. The projection optical system is adjusted so that the RMS value in the field of view of the coefficient of each term included in each group does not exceed the individually determined tolerances. When the sixth method is selected, the coefficients of the respective weighted terms weighted according to the target information are applied to the coefficients of the respective terms of the Zernike polynomial in which the wavefront of the projection optical system PL is expanded. The projection optical system PL is adjusted so that the RMS value does not exceed a predetermined allowable value.
[0284]
On the other hand, when the seventh method is selected, the second communication server 130 forms the pattern on the image plane when projected by the projection optical system based on the pattern information included in the target information. A simulation for obtaining the aerial image to be performed is performed, and the simulation result is analyzed to adjust the projection optical system PL so as to satisfy the wavefront aberration allowed for the projection optical system PL in order to transfer the pattern satisfactorily. In this case, in the second communication server 130, as a simulation method, for example, a Zernike change table similar to that described above is created in advance, and a specific aberration (when obtained from the Zernike change table) when the pattern is the target pattern ( The linear combination of the sensitivity of each Zernike polynomial coefficient that expands the wavefront of the projection optical system (including its index value) and the coefficient of each term of the Zernike polynomial that expands the wavefront of the projection optical system And an adjustment amount of the lens element is calculated based on the aerial image so that the noted aberration does not exceed the allowable value, for example, by the method of least squares.
[0285]
Then, in the second communication server 130, information on the adjustment amount (including zero) of each lens element in each of the six degrees of freedom directions is displayed on the display screen. According to this display, each lens element is adjusted by an engineer (operator). As a result, the projection optical system PL is adjusted so as to satisfy the specifications determined according to the selected seventh specification determination method.
[0286]
In any case, since the projection optical system PL is adjusted based on the measurement result of the wavefront of the projection optical system PL, not only low-order aberrations but also high-order aberrations can be adjusted at the same time, and the adjustment is performed as in the past. There is no need to consider the order of aberrations. Therefore, the optical characteristics of the projection optical system can be easily adjusted with high accuracy. In this way, the projection optical system PL that substantially satisfies the determined specifications is manufactured.
[0287]
In this embodiment, after the wavefront aberration is measured in step 4, the projection optical system is adjusted in the exposure apparatus without adjusting the projection optical system, and then the projection optical system is adjusted. Before the optical system is incorporated into the exposure apparatus, the projection optical system may be adjusted (such as reworking or replacement of the optical element), and the adjusted projection optical system may be incorporated into the exposure apparatus. At this time, the projection optical system may be adjusted by, for example, an operator adjusting the position of the optical element without using the above-described imaging characteristic adjusting mechanism. Further, after the projection optical system is incorporated into the exposure apparatus, the wavefront aberration measuring instrument 80 or the measurement reticle R described above is used._TIt is desirable to measure the wavefront aberration again using, and readjust the projection optical system based on the measurement result.
[0288]
Note that the wavefront aberration measurement performed when adjusting the projection optical system PL is performed based on the aerial image formed through the pinhole and the projection optical system PL using the wavefront measurement device as described above. For example, the measurement reticle R is not limited to this._TAnd a predetermined measurement pattern may be performed based on the result of printing on the wafer W via the pinhole and the projection optical system PL. Further, when reworking or replacement of the optical elements of the projection optical system is necessary, it is preferable to perform reworking or replacement before the projection optical system is incorporated into the exposure apparatus.
[0289]
In order to easily rework the optical elements of the projection optical system PL, when wavefront aberration is measured using the above-described wavefront measuring apparatus, the presence or absence of optical elements that require reworking based on the measurement results, The position or the like may be specified, and reprocessing of the optical element and readjustment of other optical elements may be performed in parallel.
[0290]
Next, a method for manufacturing the exposure apparatus 122 will be described.
[0291]
When manufacturing the exposure apparatus 122, first, the illumination optical system 12 including a plurality of lens elements, optical elements such as mirrors is assembled as a single unit, and the projection optical system PL is assembled as a single unit as described above. In addition, a reticle stage system, a wafer stage system, and the like made up of a large number of mechanical parts are each assembled as a unit. Then, optical adjustment, mechanical adjustment, electrical adjustment, and the like are performed so that each unit exhibits desired performance as a single unit. In this adjustment, the projection optical system PL is adjusted by the method described above.
[0292]
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, a wafer stage system, etc. are attached to the exposure apparatus main body to connect wiring and piping.
[0293]
Next, the illumination optical system 12 and the projection optical system PL are further optically adjusted. This is because the imaging characteristics of these 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 body, the wavefront aberration measuring instrument 80 described above is attached to the Z tilt stage 58, and the wavefront aberration is measured in the same manner as described above. The information on the wavefront at each measurement point obtained as a measurement result of the wavefront aberration is sent to the second communication server 130 from the main controller 50 of the exposure apparatus being manufactured online. Then, the second communication server 130 calculates the adjustment amount of each lens element in the 6 degrees of freedom direction, for example, by the method of least squares, in the same manner as the adjustment at the time of manufacturing the projection optical system PL described above, The calculation result is displayed on the display.
[0294]
And according to this display, each lens element is adjusted by the engineer (operator). Thereby, the projection optical system PL that reliably satisfies the determined specifications is manufactured.
[0295]
Note that the final adjustment in the manufacturing stage can be performed by automatic adjustment of the projection optical system PL via the imaging characteristic correction controller 48 by the main controller 50 based on the instruction from the second communication server 130 described above. is there. However, at the stage where the manufacture of the exposure apparatus is completed, it is desirable to keep each movable lens in a neutral position in order to ensure a sufficient driving stroke of the driving element after delivery to the semiconductor manufacturing factory. Thus, since it can be determined that uncorrected aberrations, mainly higher-order aberrations, are difficult to adjust automatically, as described above, it is desirable to readjust the assembly of the lens and the like.
[0296]
In addition, when a desired performance cannot be obtained by the above readjustment, it is necessary to rework or replace some lenses. In order to facilitate reworking of the optical elements of the projection optical system PL, as described above, the wavefront aberration of the projection optical system PL is determined using the above-described wavefront measuring device or the like before the projection optical system PL is incorporated into the exposure apparatus body. It is also possible to specify the presence or absence or position of an optical element that needs reworking based on the measurement result. Further, the reworking of the optical element and the readjustment of other optical elements may be performed in parallel.
[0297]
Further, the replacement or the like may be performed in units of optical elements of the projection optical system PL, or in the projection optical system having a plurality of lens barrels, the replacement may be performed in units of the lens barrels. Furthermore, in the reworking of the optical element, the surface may be processed into an aspherical surface as necessary. Further, in adjusting the projection optical system PL, it is only necessary to change the position of the optical element (including the interval with other optical elements), the inclination, etc. Especially when the optical element is a lens element, the eccentricity is changed. Or may be rotated about the optical axis AX.
[0298]
Thereafter, comprehensive adjustment (electric adjustment, operation check, etc.) is further performed. As a result, the exposure apparatus 122 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.
[0299]
As described above, according to the present embodiment, when the projection optical system PL is manufactured, the computer system 10 standardizes the wavefront aberration that the projection optical system PL should satisfy based on the target information that the exposure apparatus 122 should achieve. The specification of the projection optical system PL is determined as a value. That is, the specification of the projection optical system PL is determined by using the wavefront information on the pupil plane of the projection optical system PL as a standard value. In the adjustment stage of the projection optical system PL, and hence the projection optical system in the manufacturing process of the exposure apparatus, the projection optical system PL is adjusted so as to satisfy the determined specifications. At this time, since adjustment is performed including not only low-order aberration but also high-order aberration, stepwise adjustment as in the prior art becomes unnecessary, and ray tracing for adjusting high-order aberration becomes unnecessary. Therefore, it is possible to simplify the manufacturing process of the projection optical system PL. In addition, the target to be achieved by the exposure apparatus 122 is reliably achieved by the manufactured projection optical system PL.
[0300]
Further, when adjusting the projection optical system in the manufacturing process of the exposure apparatus described above, the wavefront aberration of the projection optical system PL is measured, and the projection optical system PL has the above specifications based on the measurement result (actual value) of the wavefront aberration. The projection optical system PL is adjusted so as to satisfy the above. Therefore, the projection optical system PL as specified can be easily and reliably manufactured.
[0301]
In the present embodiment, the measurement of the wavefront aberration is performed both before the projection optical system PL is incorporated into the exposure apparatus main body (the main body of the optical apparatus) and after the projection optical system PL is incorporated into the exposure apparatus main body. Is called. In the former, the wavefront of the projection optical system can be measured with very high accuracy using a dedicated wavefront aberration measuring device, and due to the latter, there are changes in environmental conditions before and after incorporation into the exposure apparatus body. However, it is possible to adjust the optical characteristics of the projection optical system with high accuracy without being affected by this. However, the measurement of the wavefront aberration is not limited to this, and is performed only before the projection optical system PL is incorporated into the exposure apparatus main body (the main body of the optical apparatus) and after the projection optical system PL is incorporated into the exposure apparatus main body. You may do it.
[0302]
In any case, since the projection optical system PL is adjusted based on the measurement result of the wavefront of the projection optical system PL, not only low-order aberrations but also high-order aberrations can be adjusted at the same time, and the adjustment is performed as in the past. There is no need to consider the order of aberrations. Therefore, the optical characteristics of the projection optical system can be easily adjusted with high accuracy. In this way, the projection optical system PL that almost satisfies the desired specifications is manufactured.
[0303]
In the exposure apparatus 122 according to the present embodiment, the wavefront aberration measuring instrument 80 (or measurement reticle R) is processed by the main controller 50 as described above._T) Is used to measure the wavefront of the projection optical system PL. Then, the main controller 50 uses the wavefront measurement result, which is comprehensive information passing through the pupil plane of the projection optical system, to form the imaging characteristic adjustment mechanism (48, 13).₁~ 13_Four) Etc. are controlled. Accordingly, the imaging characteristics of the projection optical system PL are automatically adjusted using the result of wavefront measurement.
[0304]
Further, according to the exposure apparatus 122 according to the present embodiment, the projection optics manufactured by the above-described manufacturing method and adjusted not only at the time of manufacture but also at the time of subsequent adjustment, including not only low-order aberrations but also high-order aberrations. Since the system PL is provided as an exposure optical system, the pattern of the reticle R can be accurately transferred onto the wafer W by the projection optical system PL.
[0305]
Further, according to the computer system 10 according to the present embodiment, the wavefront of the projection optical system PL is self-measured by the wavefront aberration measuring instrument 80 provided in the exposure apparatus 122. The first communication server 120 transmits the measurement result of the wavefront of the projection optical system PL measured by the wavefront aberration measuring instrument 80 to the second communication server 130 via the communication path. In the second communication server 130, the imaging characteristic adjustment mechanism (48, 13) is obtained by using the wavefront measurement result.₁~ 13_Four) To control. Therefore, the imaging characteristics of the projection optical system PL are accurately adjusted using information on the wavefront on the pupil plane of the projection optical system, that is, comprehensive information passing through the pupil plane. In this case, the second communication server 130 can be arranged at a position away from the exposure apparatus 122 and the first communication server 120 connected thereto, and in such a case, the image of the projection optical system PL is formed by remote operation. The characteristics can be adjusted with high accuracy.
[0306]
In addition, according to the computer system 10 and the best condition determination method performed by the computer system according to the above-described embodiment, the first communication server 120 includes information on a predetermined pattern by the host computer or operator who manages the exposure apparatus 122. When the exposure condition information is input, the second communication server 130 receives the pattern information included in the exposure condition information received from the first communication server 120 via the communication path and the known aberration of the projection optical system PL. Based on the information, a simulation for obtaining an aerial image formed on the image plane when the pattern is projected by the projection optical system PL is repeatedly performed, and the simulation result is analyzed to determine the best exposure condition. Accordingly, it becomes possible to set the optimum exposure condition almost fully automatically.
[0307]
Further, according to the computer system 10 of the present embodiment, when adjusting the projection optical system PL during maintenance of the exposure apparatus 122, a service engineer attaches the wavefront aberration measuring instrument 80 to the Z tilt stage 58 and inputs it. By simply inputting a wavefront aberration measurement command via the device 45, the imaging characteristics of the projection optical system PL can be adjusted with high accuracy by a remote operation by the second communication server 130 almost automatically. Alternatively, the service engineer can use the measurement reticle R_TIs used to measure the wavefront aberration of the projection optical system PL of the exposure apparatus 122 according to the above-described procedure, and the data of the positional deviation obtained as a result is input to the main controller 50 of the exposure apparatus 122. The imaging characteristics of the projection optical system PL can be adjusted with high accuracy by a remote operation by the second communication server 130 fully automatically.
[0308]
Further, according to the exposure apparatus 122 of the present embodiment, during the exposure, the projection optical system PL in which the best exposure conditions are set as described above and the imaging characteristics of the projection optical system PL are accurately adjusted is used. Since the pattern of the reticle R is transferred onto the wafer W, the fine pattern can be transferred onto the wafer W with good overlay accuracy.
[0309]
In the above embodiment, the case where the adjustment device that adjusts the formation state of the projection image of the pattern by the projection optical system PL is configured by the image formation characteristic adjustment mechanism that adjusts the image formation characteristic of the projection optical system PL has been described. However, the present invention is not limited to this. As an adjusting device, for example, a mechanism for driving at least one of the reticle R and the wafer W in the direction of the optical axis AX, a mechanism for shifting the wavelength of the illumination light EL, or the like, instead of or together with the imaging characteristic adjusting mechanism described above. May be used. For example, when the mechanism for shifting the wavelength of the illumination light EL is used together with the imaging characteristic adjustment mechanism described above, a plurality of measurements in the field of view of the projection optical system PL with respect to the unit shift amount of the illumination light EL are performed as described above. Imaging characteristics corresponding to each point, specifically, wavefront data, for example, data on how the coefficients of the second to 37th terms of the Zernike polynomial change are obtained in advance by simulation or the like. By including it as one of the parameters in the above-mentioned database, the same handling as the above-mentioned adjustment amount of each movable lens becomes possible. That is, by performing the least square calculation according to the second program described above using the database, the optimum shift amount of the wavelength of the illumination light EL for adjusting the image formation state of the pattern by the projection optical system can be calculated. This can be easily performed, and the wavelength can be automatically adjusted based on the calculation result.
[0310]
In the above embodiment, the case where the exposure apparatus is used as the optical apparatus has been described. However, the present invention is not limited thereto, and any optical apparatus including a projection optical system may be used.
[0311]
In the above embodiment, a computer system in which a first communication server 120 as a first computer and a second communication server 130 as a second computer are connected via a communication path including a public line as a part thereof. However, the present invention is not limited to this. For example, as shown in FIG. 12, a computer system in which the first communication server 120 and the second communication server 130 are connected via a LAN 126 'as a communication path may be used. As such a configuration, an in-house LAN system installed in a research and development department within an exposure apparatus manufacturer can be considered.
[0312]
When constructing such an in-house LAN system, for example, the first communication server 120 is installed on the clean room side of the research and development department, for example, a place where the exposure apparatus is assembled and adjusted (hereinafter referred to as “on-site”), The second communication server 130 is installed in a laboratory away from the site. Then, the field side engineer measures the wavefront aberration as described above and the exposure condition information (including pattern information) of the exposure apparatus at the experimental stage via the first communication server 120 in the second communication on the laboratory side. Send to server 130. Then, the technician on the laboratory side uses the second communication server 130 in which the software program designed by himself / herself is installed in advance, and based on the sent information, the imaging characteristics of the projection optical system PL of the exposure apparatus 122 Is automatically corrected from a remote location and the measurement results of the wavefront aberration of the projection optical system after adjustment of the imaging characteristics can be received, so that the effect of adjusting the imaging characteristics can be confirmed. It can also be used for the development stage.
[0313]
Alternatively, an on-site engineer transmits pattern information and the like from the first communication server 120 to the second communication server 130, and the second communication server 130 determines the specifications of the projection optical system optimal for the pattern. It becomes possible to do.
[0314]
In addition, the first communication server 120 and the second communication server 130 may be connected by a wireless line.
[0315]
In the embodiment and the modification, a plurality of exposure apparatuses 122 are provided, and the second communication server 130 is provided with a plurality of exposure apparatuses 122 via a communication path.₁~ 122_ThreeHowever, the present invention is not limited to this, and a single exposure apparatus may be used.
[0316]
In the above embodiment, the case where the specification of the projection optical system is determined using the computer system 10 has been described. However, the technical idea of determining the specification of the projection optical system using the wavefront as a standard value is the same as that of the computer system 10. Can be used independently. That is, in a business talk between manufacturer A and manufacturer B, upon receiving the pattern information from manufacturer A, the manufacturer B side determines the optimum projection optical system specifications for the exposure of the pattern as the wavefront standard value. Also good. Even in such a case, when the projection optical system is manufactured based on the specification determined with the wavefront as the standard value, there is an advantage that the manufacturing process is simplified as described above.
[0317]
Furthermore, in the above embodiment, based on the measurement result of the wavefront aberration of the projection optical system PL of the exposure apparatus 122, the second communication server 130 uses the second program to move the movable lens 13.₁~ 13_FourThe adjustment amounts ADJ1 to ADJm are calculated, and the adjustment amount data is transmitted to the main controller 50 of the exposure apparatus 122. Then, the main controller 50 of the exposure apparatus 122 that has received the adjustment amounts ADJ1 to ADJm data moves the movable lens 13 according to the adjustment amounts ADJ1 to ADJm.₁~ 13_FourThe image formation characteristic of the projection optical system PL is adjusted by remote control by giving the image formation characteristic correction controller 48 a command value indicating that the lens should be driven in each direction of freedom. However, the present invention is not limited to this, and the exposure apparatus 122 itself uses a calculation program similar to the second program to automatically adjust the imaging characteristics of the projection optical system based on the measurement result of the wavefront aberration. Also good.
[0318]
For example, in a microprocessor or the like, a phase shift reticle as a phase shift mask, particularly a spatial frequency modulation type (Levenson type) phase shift reticle is used when forming a gate pattern. This phase shift reticle uses small σ illumination. Specifically, the phase shift reticle is illuminated under an illumination condition in which the coherence factor (σ value) is smaller than 0.5, preferably about 0.45 or less. At this time, due to aberrations (for example, astigmatism, spherical aberration, etc.) of the projection optical system, the exposure area irradiated with the illumination light for exposure within the field of the projection optical system (the illumination area with respect to the projection optical system) The best focus position varies within a conjugate region (projection region where a reticle pattern image is formed), and the depth of focus is reduced.
[0319]
Therefore, at the time of manufacturing the projection optical system according to the above embodiment, based on the variation of the best focus position (that is, the imaging plane) within the exposure area of the projection optical system due to the use of the phase shift reticle, for example, the projection optical system It is desirable to intentionally shift the best focus position partially within the exposure region by adjusting aberrations (such as field curvature, astigmatism, or spherical aberration). In this case, focus pre-correction may be performed to correct the aberration so as to reduce the so-called total focal difference. As a result, the variation in the best focus position is greatly reduced when the phase shift reticle is used, and the pattern image of the phase shift reticle can be transferred onto the wafer with a greater depth of focus than in the prior art.
[0320]
Further, the same problem as described above occurs when the phase shift reticle is used in the exposure apparatus shipped to the device manufacturing factory. Therefore, an exposure region is adjusted by adjusting an aberration using a mechanism for adjusting an imaging characteristic of the projection optical system (for example, a mechanism for driving at least one optical element of the projection optical system with an actuator (piezo element, etc.)). It is desirable to deliberately shift the best focus position partially. At this time, it is preferable to adjust the spherical aberration in addition to at least one of the field curvature and astigmatism of the projection optical system. In this case as well, focus pre-correction for correcting the aberration so as to reduce the so-called total focal difference may be performed.
[0321]
Prior to adjustment of the projection optical system, its imaging characteristics, mainly the imaging plane (best focus position on almost the entire exposure area), are obtained by calculation (simulation etc.) from the design data of the projection optical system. Alternatively, the imaging characteristics may be measured.
[0322]
In the former case, the calculation method using the Zernike change table described in the above embodiment can be used. In the latter case, the imaging characteristics may be obtained from the aforementioned wavefront aberration, but the reticle pattern image is detected by a spatial image measuring device provided with a light receiving surface on the wafer stage, or the reticle pattern is detected on the wafer. The transfer image (latent image or resist image) may be detected by transfer, and the imaging characteristics may be obtained only from the detection result.
[0323]
At this time, it is preferable to provide a phase shift portion in the reticle pattern and use a small σ illumination, that is, form a pattern image under almost the same exposure conditions as in device manufacturing, and obtain the imaging characteristics of the projection optical system.
[0324]
Further, in the projection optical system in which the variation in the best focus position when using the phase shift reticle is reduced, the imaging characteristics are measured again after the assembly (manufacture) or adjustment.
[0325]
At this time, the in-plane line width variation at the best focus position may occur in the projection optical system due to residual aberration or the like. When this variation exceeds an allowable value, the aberration of the projection optical system must be made smaller. Therefore, it is preferable to replace or adjust at least a part of the projection optical system.
[0326]
At this time, the replacement may be performed in units of optical elements of the projection optical system, or in the case of a projection optical system having a plurality of lens barrels, replacement may be performed in units of the lens barrels. Further, at least one optical element of the projection optical system may be reworked, and in particular, the surface of the lens element may be aspherical as necessary. This optical element is not only a refractive optical element such as a lens element, but also, for example, a reflective optical element such as a concave mirror, or an aberration correction plate that corrects aberrations (distortion, spherical aberration, etc.) of the projection optical system, especially its non-rotationally symmetric components Etc. Furthermore, in adjusting the projection optical system, it is only necessary to change the position of the optical element (including the interval with other optical elements), the inclination, etc. Especially when the optical element is a lens element, its eccentricity is changed. Or may be rotated about the optical axis. This adjustment (such as replacement or rework) may be performed in the same manner in the above embodiment.
[0327]
In the above embodiment, the measurement reticle R is_TIn the above description, the reference pattern is provided together with the measurement pattern. However, the reference pattern is an optical characteristic measurement mask (in the above-described embodiment, the measurement reticle R)._T) Is not necessary. That is, the reference pattern may be provided on another mask, or the reference pattern may be provided on the substrate (wafer) side without being provided on the mask side. That is, using a reference wafer in which the reference pattern is formed in advance according to the projection magnification, applying a resist on the reference wafer, transferring the measurement pattern to the resist layer, developing, and developing By measuring the positional deviation between the resist image of the measurement pattern obtained later and the reference pattern, it is possible to measure substantially the same as in the above embodiment.
[0328]
In the above embodiment, the wavefront aberration of the projection optical system PL is calculated based on the measurement result of the resist image obtained by developing the wafer after the measurement pattern and the reference pattern are transferred onto the wafer W. However, the present invention is not limited to this, and a projected image (aerial image) of the measurement pattern is projected onto the wafer, and the projected image (aerial image) is measured using an aerial image measuring instrument or formed on the resist layer. It is also possible to measure a latent image of the measured measurement pattern and reference pattern or an image obtained by etching a wafer. Even in such a case, if the positional deviation from the reference position of the measurement pattern (for example, the projected position of the design measurement pattern) is measured, the projection optics can be used in the same procedure as in the above embodiment based on the measurement result. It is possible to determine the wavefront aberration of the system. Also, instead of transferring the measurement pattern onto the wafer, prepare a reference wafer on which the measurement pattern is formed in advance, and transfer the reference pattern to the resist layer on the reference wafer and measure its positional deviation. Alternatively, it is also possible to measure the positional deviation between the two using an aerial image measuring instrument having a plurality of openings corresponding to the measurement pattern. Furthermore, in the above-described embodiment, the above-described misalignment is measured using the overlay measuring device. However, other than that, for example, an alignment sensor provided in the exposure apparatus may be used.
[0329]
In the above embodiment, the Zernike polynomial up to the 37th term is used. However, the 38th term or more may be used. For example, the high order component of each aberration of the projection optical system PL using the up to the 81st term. May also be calculated. That is, the number and number of terms used in the Zernike polynomial may be arbitrary. Furthermore, depending on the illumination conditions and the like, the aberration of the projection optical system PL may be positively generated. Therefore, in the above embodiment, not only the target aberration is always zero to the minimum, but the target aberration is set to a predetermined value. In addition, the optical elements of the projection optical system PL may be adjusted.
[0330]
In the above embodiment, the first communication server 120 is, for example, the exposure apparatus 122.₁Then, information on the reticle to be used next is stored in, for example, the exposure apparatus 122.₁~ 122_ThreeThe first communication server 120 is inquired from a host computer (not shown) that manages the information, searches a predetermined database based on the information on the reticle, and obtains the pattern information, or the operator receives the pattern information via the input device. It was supposed to be entered manually. However, the present invention is not limited to this, and a reader BR such as a bar code reader indicated by a virtual line in FIG. 2 is provided in the exposure apparatus, and the first communication server 120 is provided via the main controller 50 using this reader BR. However, the pattern information may be obtained by reading a barcode or a two-dimensional code attached to the reticle R on the way to the reticle stage RST.
[0331]
Further, in the case of using, for example, the above-described measurement reticle for wavefront aberration measurement, the positional deviation of the measurement pattern latent image transferred and formed on the resist layer on the wafer with respect to the latent image of the reference pattern, for example, an exposure apparatus It is good also as detecting by alignment system ALG with which. Further, when a wavefront aberration measuring instrument is used for measuring the wavefront aberration, for example, a wavefront aberration measuring instrument having an overall shape replaceable with the wafer holder may be used as the wavefront aberration measuring instrument. In such a case, the wavefront aberration measuring instrument can be automatically transferred using a transfer system (wafer loader or the like) for exchanging the wafer or wafer holder. With such various ideas, the computer system 10 automatically performs all the automatic adjustment of the imaging characteristics of the projection optical system PL and the setting of the best exposure conditions without intervention of an operator or a service engineer. It is also possible to do. In the above-described embodiment, the case where the wavefront aberration measuring instrument 80 is detachable from the wafer stage has been described. However, the wavefront aberration measuring instrument 80 may be provided permanently on the wafer stage. At this time, only a part of the wavefront aberration measuring instrument 80 may be placed on the wafer stage, and the rest may be placed outside the wafer stage. In the embodiment described above, the aberration of the light receiving optical system of the wavefront aberration measuring instrument 80 is ignored. However, the wavefront aberration of the projection optical system may be determined in consideration of the wavefront aberration.
[0332]
Further, all of the first to third programs described in the above embodiment and the database attached thereto are stored in advance in an information recording medium or storage device 42 set in the drive device 46 of the exposure device 122, and exposure is performed. The apparatus 122 alone can automatically adjust the imaging characteristics of the projection optical system PL and set the best exposure conditions. Further, a dedicated server (corresponding to the second communication server 130 described above) connected to the exposure apparatus via a LAN or the like is installed in the factory of manufacturer A, and the first to third programs are stored in this dedicated server. good. In short, the present invention is not limited to the configuration shown in FIG. 1, and the installation location of a computer (such as a server) that stores the first to third programs may be arbitrary.
[0333]
In the above embodiment, the stepper is used as the exposure apparatus. However, the present invention is not limited to this. For example, the mask disclosed in U.S. Pat. No. 5,473,410 is moved synchronously with the substrate. A scanning type exposure apparatus that transfers the pattern onto the substrate may be used.
[0334]
The use of the exposure apparatus in this case 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 to a square glass plate, a thin film magnetic head, a micromachine, etc. In addition, it can be widely applied to an exposure apparatus for manufacturing a DNA chip or the like. Also, not only microdevices such as semiconductor elements, but also reticles or masks used in light exposure apparatuses, EUV exposure apparatuses, X-ray exposure apparatuses, and charged particle beam exposure apparatuses using electron beams or ion beams, etc. are manufactured. Therefore, the present invention can also be applied to an exposure apparatus that transfers a circuit pattern to a glass substrate or a silicon wafer.
[0335]
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, a KrF excimer laser light source, but a continuous light source, for example, an ultra-high pressure mercury lamp that emits bright lines such as g-line (wavelength 436 nm) and i-line (wavelength 365 nm) Is also possible.
[0336]
In addition, a single wavelength laser beam oscillated from a DFB semiconductor laser or fiber laser is amplified by a fiber amplifier doped with, for example, 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. Further, the magnification of the projection optical system may be not only a reduction system but also an equal magnification or an enlargement system. The projection optical system is not limited to a refraction system, and may be a catadioptric system (catadioptric system) having a reflection optical element and a refraction optical element or a reflection system using only a reflection optical element. When a catadioptric system or a reflective system is used as the projection optical system PL, the imaging characteristics of the projection optical system are changed by changing the position of the reflective optical element (such as a concave mirror or a reflective mirror) as the movable optical element described above. adjust. Moreover, as illumination light EL, F₂Laser light, Ar₂When laser light, EUV light, or the like is used, the projection optical system PL can be an all reflection system composed of only a reflection optical element. However, Ar₂When laser light, EUV light or the like is used, the reticle R is also of a reflective type.
[0337]
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. According to this device manufacturing method, since exposure is performed in the lithography process using the exposure apparatus of the above-described embodiment, the imaging characteristics are adjusted according to the target pattern, or the result is based on the measurement result of the wavefront aberration. Since the pattern of the reticle R is transferred onto the wafer W via the projection optical system PL whose image characteristics are adjusted with high accuracy, it becomes possible to transfer the fine pattern onto the wafer W with good overlay accuracy. Therefore, the yield of the device as the final product is improved, and the productivity can be improved.
[0338]
【The invention's effect】
As described above, according to the projection optical system manufacturing method described in each of claims 1 to 14, the manufacturing process can be simplified, and as a result, the optical device can reliably achieve the target to be achieved. It has the effect of making it possible.
[0339]
According to the projection optical system manufacturing method described in each of claims 15 to 17, there is an effect that high-precision exposure is possible by using the manufactured projection optical system.
[0340]
Further, according to each of the exposure apparatuses according to claims 18 to 21, there is an effect that the pattern can be accurately transferred onto the substrate using the projection optical system.
[0341]
According to the exposure apparatus manufacturing method of the twenty-second aspect, an exposure apparatus capable of accurately transferring a pattern onto a substrate using a projection optical system can be manufactured.
[0342]
In addition, according to the projection optical system adjustment methods described in claims 23 to 33, there is an effect that the optical characteristics of the projection optical system can be easily adjusted with high accuracy.
[0343]
In addition, according to the projection optical system adjustment methods described in the thirty-fourth to thirty-sixth aspects, as a result of the adjustment, there is an effect that high-precision exposure becomes possible.
[0344]
According to the device manufacturing method of the 37th aspect, there is an effect that a highly integrated micro device can be manufactured with a high yield.
[0345]
In addition, according to each of the computer systems described in claims 38 to 47, there is an effect that the imaging characteristics of the projection optical system provided in the exposure apparatus can be adjusted with high accuracy via the communication path.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a computer system according to an embodiment of the present invention.
FIG. 2 shows a first exposure apparatus 122 in FIG.₁FIG.
FIG. 3 is a cross-sectional view showing an example of a wavefront aberration measuring instrument.
FIG. 4A is a diagram showing a light beam emitted from a microlens array when there is no aberration in the optical system, and FIG. 4B is a diagram when there is aberration in the optical system. It is a figure which shows the light beam inject | emitted from a micro lens array.
FIG. 5 is a flowchart showing a control algorithm executed by the CPU in the second communication server when setting the best exposure condition of the exposure apparatus.
FIG. 6 is a schematic perspective view showing a measurement reticle.
FIG. 7 is a diagram showing a schematic view of an XZ cross section in the vicinity of 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.
FIG. 8 is a diagram showing a schematic view of an XZ cross section near the −Y side end of a measurement reticle in a state of being loaded on a reticle stage together with a schematic diagram of a projection optical system.
FIG. 9A is a diagram showing a measurement pattern formed on the measurement reticle of the present embodiment, and FIG. 9B is a reference pattern formed on the measurement reticle of the present embodiment. It is a figure which shows a pattern.
10A is a view showing a reduced image (latent image) of a measurement pattern formed at a predetermined interval on a resist layer on a wafer, and FIG. 10B is a view showing FIG. FIG. 9 is a diagram illustrating a positional relationship between a latent image of a measurement pattern and a latent image of a reference pattern.
FIG. 11 is a flowchart schematically showing a manufacturing process of the projection optical system.
FIG. 12 is a diagram illustrating a configuration of a computer system according to a modified example.
[Explanation of symbols]
10: Computer system, 13₁~ 13_Four... movable lens (part of imaging characteristic adjustment mechanism as adjustment device), 48 ... imaging characteristic correction controller (part of imaging characteristic adjustment mechanism as adjustment device), 50 ... main control device (control device) , 80... Wavefront aberration measuring instrument (wavefront measuring device), 120... First communication server (first computer), 122.₁~ 122_Three... exposure apparatus (optical apparatus), 130 ... second communication server (second computer), PL ... projection optical system (exposure optical system), W ... wafer (substrate), R ... reticle (mask).

Claims (32)

A method for adjusting a projection optical system used in an exposure apparatus,
A first step of measuring imaging characteristics of a projection optical system whose specifications are determined using wavefront aberration as a standard value;
The measurement result, the pattern to be transferred onto the object via the projection optical system and the Zernike change table corresponding to the exposure condition, and the adjustment amount in the apparatus for adjusting the imaging state of the pattern image on the object And the data relating to the relationship between the coefficient of the predetermined term of the Zernike polynomial and the adjustment amount in the adjusting device at which the target aberration of the projection optical system is zero to the minimum or a predetermined value is determined. And a second step of adjusting the projection optical system using the adjusted amount.   The method of adjusting a projection optical system according to claim 1, wherein the adjustment amount includes a drive amount of an optical element of the projection optical system, and the adjustment of the projection optical system moves the optical element. The projection optical system adjustment method according to claim 1, wherein the imaging characteristic is expressed as a coefficient of each term of a Zernike polynomial.   The projection optical system adjustment method according to claim 1, wherein the exposure condition includes an illumination condition of the pattern.   The projection optical system adjustment method according to claim 1, wherein the exposure condition includes a numerical aperture of the projection optical system.   The method of adjusting a projection optical system according to claim 1, wherein a least square method is used in determining the adjustment amount. An exposure method for transferring a pattern onto an object via a projection optical system,
The projection optical system is adjusted using the adjustment method according to any one of claims 1 to 6,
An exposure method, wherein a pattern image is generated on the object through the adjusted projection optical system under the exposure conditions. In an exposure apparatus that transfers a pattern onto an object,
A projection optical system whose specifications are determined using wavefront aberration as a standard value;
An adjusting device for adjusting the imaging state of the pattern image on the object;
The measurement result of the imaging characteristics of the projection optical system, the Zernike change table corresponding to the pattern to be transferred onto the object via the projection optical system and the exposure conditions, the adjustment amount in the adjustment device, and the Zernike polynomial Based on the data relating to the relationship with the coefficient of the predetermined term, an adjustment amount in the adjustment device at which the target aberration of the projection optical system is zero to minimum or a predetermined value is determined, and the adjustment amount is determined via the projection optical system. An exposure apparatus comprising: a control system that controls the adjustment device using the determined adjustment amount in order to transfer the pattern onto an object.   9. The adjustment device moves an optical element of the projection optical system, and the control system controls the movement of the optical element by the adjustment device using the determined adjustment amount. The exposure apparatus described in 1.   The adjustment device is capable of adjusting the image formation state of the pattern image on the object by each of a plurality of different methods including movement of the optical element, and the control system adjusts the adjustment amounts of the plurality of methods, respectively. The exposure apparatus according to claim 9, wherein the exposure apparatus is determined.   The control system uses data relating to a relationship between each of the plurality of adjustment amounts including the driving amount of the optical element and a coefficient of a predetermined term of the Zernike polynomial in order to determine the adjustment amounts in the plurality of methods, respectively. The exposure apparatus according to claim 10.   The said adjustment apparatus moves the said object with respect to the said pattern image, The said control system controls the movement of the said object by the said adjustment apparatus, It is any one of Claims 8-11 characterized by the above-mentioned. Exposure equipment.   The said adjustment apparatus shifts the wavelength of the illumination light used for the production | generation of the said pattern image, The said control system controls the shift of the said wavelength by the said adjustment apparatus, It is any one of Claims 8-12 characterized by the above-mentioned. The exposure apparatus according to item. The exposure apparatus according to claim 8, wherein the imaging characteristic is expressed as a coefficient of each term of a Zernike polynomial. Further comprising, before Symbol measurement result exposure apparatus according to claim 14, characterized in that the coefficients of the terms of the Zernike polynomial is determined from a measuring device for measuring the wavefront aberration of the projection optical system.   16. The control system according to claim 8, wherein when at least one of the pattern and the exposure condition is changed, a Zernike change table different from the Zernike change table before the change is used for determining the adjustment amount. The exposure apparatus according to any one of the above.   The exposure apparatus according to any one of claims 8 to 16, further comprising an illumination optical system capable of changing an illumination condition of the pattern, wherein the exposure condition includes the illumination condition.   The exposure apparatus according to claim 8, wherein the projection optical system has a variable numerical aperture, and the exposure condition includes the numerical aperture of the projection optical system.   The exposure apparatus according to any one of claims 8 to 18, wherein the control system uses a least square method for determining the adjustment amount. In an exposure method for transferring a pattern onto an object,
Measurement results of imaging characteristics of the projection optical system whose specifications are determined with the wavefront aberration as a standard value, a pattern to be transferred onto the object via the projection optical system, and a Zernike change table corresponding to the exposure conditions, Based on the amount of adjustment in the apparatus for adjusting the imaging state of the pattern image on the object and data on the relationship between the coefficients of the predetermined terms of the Zernike polynomial, the objective aberration of the projection optical system is zero to minimum or predetermined Determine the amount of adjustment in the adjustment device to be a value ,
In order to transfer the pattern onto the object via the projection optical system, the adjustment state of the pattern image is adjusted by the adjustment device using the determined adjustment amount. .   21. The exposure method according to claim 20, wherein the adjustment amount includes a drive amount of an optical element of the projection optical system, and the optical element is moved in the adjustment of the imaging state.   The image forming state of the pattern image on the object is adjusted by a plurality of different methods of the adjusting device including the movement of the optical element, respectively, and the adjustment amounts in the plurality of methods are respectively determined. The exposure method according to claim 21.   The data relating to the relationship between each of the plurality of adjustment amounts including the driving amount of the optical element and a coefficient of a predetermined term of the Zernike polynomial is used to determine the adjustment amounts in the plurality of methods, respectively. Item 23. The exposure method according to Item 22.   The exposure method according to any one of claims 20 to 23, wherein the adjustment amount includes a drive amount of the object with respect to the pattern image, and the object is moved in the adjustment of the imaging state.   The exposure according to any one of claims 20 to 24, wherein the adjustment amount includes a wavelength of illumination light used for generating the pattern image, and the wavelength is shifted in the adjustment of the imaging state. Method. 26. The exposure method according to any one of claims 20 to 25, wherein the imaging characteristic is expressed as a coefficient of each term of a Zernike polynomial.   27. The exposure method according to claim 26, wherein the coefficient of each term of the Zernike polynomial is determined from the measurement result of the wavefront aberration of the projection optical system.   28. When at least one of the pattern and the exposure condition is changed, a Zernike change table different from the Zernike change table before the change is used in determining the adjustment amount. An exposure method according to 1.   The exposure method according to any one of claims 20 to 28, wherein the exposure condition includes an illumination condition of the pattern.   30. The exposure method according to any one of claims 20 to 29, wherein the exposure condition includes a numerical aperture of the projection optical system.   31. The exposure method according to claim 20, wherein a least square method is used for determining the adjustment amount. In a device manufacturing method including a lithography process,
32. A device manufacturing method, wherein, in the lithography step, a pattern is formed on an object using the exposure method according to any one of claims 7 to 20.

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