JP2004146702A - Method for measuring optical characteristic, exposure method and method for manufacturing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To measure an optical characteristic of a projection optical system quickly, surely, in high accuracy and reproductivity. <P>SOLUTION: According to a photographed data of an area on an entirely square wafer including a plurality of partitioned areas wherein patterns for measurement are transferred under different conditions, part of a side of an outer frame in the square area is an object to be detected, and a window area is scanned crossing almost orthogonally the side as an detection object, and then the position of the side as an object is detected during the scanning on the basis of a pixel data in the window area (steps 504 to 508). Next, the detection result on the position of the side is used to calculate part of the partitioned area in the outer frame (step 516), and the formation condition of an image in the partitioned area is detected in a short time by using the contrast of an objective and quantitative image. Then, the detected result is used to find out the optical characteristic of a projection optical system. In this case, the optical characteristic can be obtained by using such a mechanism that the exposure condition during transfer of the pattern for measurement varies depending on the partitioned areas. <P>COPYRIGHT: (C)2004,JPO

Description

【０１７４】
上記の連立方程式（１）を解けば、頂点ｐ_０’の位置（ｐ_０ｘ’，ｐ_０ｙ’）が求められる。
【０１７５】
残りの頂点ｐ_１’、ｐ_２’、ｐ_３’についても、同様の連立方程式を立て、それを解くことにより、それぞれの位置を求めることができる。
【０１７６】
図１０に戻り、次のステップ５１６では、図１５（Ｂ）に示されるように、上で求めた４頂点ｐ_０’〜ｐ_３’の座標値に基づいて、最小二乗法による長方形近似を行い、回転を含めた評価点対応領域ＤＢ_ｎの外枠ＤＢＦを算出する。
【０１７７】
ここで、このステップ５１６における処理を、図２１に基づいて詳述する。すなわち、このステップ５１６では、４頂点ｐ_０〜ｐ_３の座標値を用いて、最小二乗法による長方形近似を行い、評価点対応領域ＤＢ_ｎの外枠ＤＢＦの幅ｗ、高さｈ、及び回転量θを求めている。なお、図２１において、ｙ軸は紙面の下側が正となっている。
【０１７８】
中心ｐ_ｃの座標を（ｐ_ｃｘ，ｐ_ｃｙ）とすると、長方形の４頂点（ｐ_０，ｐ_ｌ，ｐ_２，ｐ_３）はそれぞれ次式（２）〜（５）のように表せる。
【０１７９】
【数２】

【０１８０】
上記ステップ５１４で求めた４頂点ｐ_０’，ｐ_ｌ’，ｐ_２’，ｐ_３’の各点とそれぞれ対応する上式（２）〜（５）でそれぞれ表される頂点ｐ_０，ｐ_ｌ，ｐ_２，ｐ_３との距離の総和を誤差Ｅ_ｐとする。誤差Ｅ_ｐは、次式（６）、（７）で表せる。
【０１８１】
【数３】

【０１８２】
上記式（６）、（７）を、未知変数ｐ_ｃｘ，ｐ_ｃｙ，ｗ，ｈ，θでそれぞれ偏微分し、その結果が０になるように連立方程式を立て、その連立方程式を解くことによって長方形近似結果が得られる。
【０１８３】
この結果、評価点対応領域ＤＢ_ｎの外枠ＤＢＦが求められた様子が、図１５（Ｂ）に実線にて示されている。
【０１８４】
図１０に戻り、次のステップ５１８では、上で検出した評価点対応領域ＤＢ_ｎの外枠ＤＢＦを、既知の区画領域の縦方向の数＝（Ｍ＋２）＝１５、区画領域の横方向の数＝（Ｎ＋２）＝２５を用いて、等分割し、各区画領域ＤＡ_ｉ，ｊ（ｉ＝０〜１４、ｊ＝０〜２４）を求める。すなわち、外枠ＤＢＦを基準として、各区画領域（位置情報）を求める。
【０１８５】
図１５（Ｃ）には、このようにして求められた、第１領域ＤＣ_ｎを構成する各区画領域ＤＡ_ｉ，ｊ（ｉ＝１〜１３、ｊ＝１〜２３）が示されている。
【０１８６】
図１０に戻り、次のステップ５２０では、各区画領域ＤＡ_ｉ，ｊ（ｉ＝１〜Ｍ、ｊ＝１〜Ｎ）について、ピクセルデータに関する代表値（以下、適宜「スコア」とも呼ぶ）を算出する。
【０１８７】
以下、スコアＥ_ｉ，ｊ（ｉ＝１〜Ｍ、ｊ＝１〜Ｎ）の算出方法について詳述する。
【０１８８】
通常、撮像された計測対象において、パターン部分と非パターン部分にはコントラスト差がある。パターンが消失した領域内には非パターン領域輝度をもつピクセルだけが存在し、一方、パターンが残存する領域内にはパターン領域輝度をもつピクセルと非パターン領域輝度を持つピクセルとが混在する。従って、パターン有無判別を行うための代表値（スコア）として、各区画領域内でのピクセル値のばらつきを用いることができる。
【０１８９】
本実施形態では、一例として、区画領域内の指定範囲のピクセル値の分散（又は標準偏差）を、スコアＥとして採用するものとする。
【０１９０】
指定範囲内のピクセルの総数をＳ、ｋ番目のピクセルの輝度値をＩ_ｋとすると、スコアＥは次式（８）で表せる。
【０１９１】
【数４】

【０１９２】
本実施形態の場合、前述の如く、レチクルＲ_Ｔ上で、開口パターンＡＰ_ｎ（ｎ＝１〜５）と中心を同じくする、該各開口パターンの約６０％の縮小領域部分に計測用パターンＭＰ_ｎがそれぞれ配置されている。また、前述の露光の際のステップピッチＳＰが、各開口パターンＡＰ_ｎのウエハＷ_Ｔ上への投影像の寸法とほぼ一致する約５μｍに設定されている。従って、パターン残存区画領域において、計測用パターンＭＰ_ｎは、区画領域ＤＡ_ｉ，ｊと中心を同じくし、該区画領域ＤＡ_ｉ，ｊをほぼ６０％に縮小した範囲（領域）に存在することとなる。
【０１９３】
かかる点を考慮すると、上記の指定範囲として、例えば区画領域ＤＡ_ｉ，ｊ（ｉ＝１〜Ｍ、ｊ＝１〜Ｎ）と中心を同じくし、その領域を縮小した範囲をスコア算出に用いることができる。但し、その縮小率Ａ（％）は以下のように制限される。
【０１９４】
まず、下限については、範囲が狭すぎるとスコア算出に用いる領域が、パターン部分のみになってしまい、そうするとパターン残存部でもばらつきが小さくなってパターン有無判別には利用できなくなる。この場合には、上述のパターンの存在範囲から明らかなように、Ａ＞６０％である必要がある。また、上限については、当然１００％以下だが、検出誤差などを考慮して１００％より小さい比率にすべきである。これより、縮小率Ａは、６０％＜Ａ＜１００％に定める必要がある。
【０１９５】
本実施形態の場合、パターン部が区画領域の約６０％を占めているため、スコア算出に用いる領域（指定範囲）の区画領域に対する比を上げるほどＳ／Ｎ比が上がるものと予想される。
【０１９６】
しかるに、スコア算出に用いる領域内でのパターン部と非パターン部の領域サイズが同じになれば、パターン有無判別のＳ／Ｎ比を最大にすることができる。本実施形態では、幾つかの比率を実験的に確認した結果、例えばＡ＝９０％の場合に最も安定した結果が得られたので、Ａ＝９０％という比率を採用するものとする。勿論Ａは、９０％に限定されるものではなく、計測用パターンＭＰ_ｎと開口パターンＡＰ_ｎとの関係、及びステップピッチＳＰによって決定されるウエハ上の区画領域を考慮して、区画領域に対する計測用パターンＭＰ_ｎの像が占める割合を考慮して定めれば良い。また、スコア算出に用いる指定範囲は、区画領域と中心を同じくする領域に限定されるものではなく、計測用パターンＭＰ_ｎの像が区画領域内のどの位置に存在するかを考慮して定めれば良い。
【０１９７】
ところで、ウエハＷ_Ｔ上のバークとレジストとの組み合わせによっては、上述した式（８）で表されるスコアＥが、一部の区画領域では、パターン有無判別を行うためのスコアとして必ずしも適当でない場合があり得る。そこで、パターンが消失した領域内には非パターン領域輝度をもつピクセルだけが存在することに着目し、上式（８）の一部を変更した、次式（９）で表される各区画領域の指定範囲内におけるピクセル値のばらつきの指標を、スコアＥ’として採用しても良い。
【０１９８】
【数５】

【０１９９】
上式（９）において、Ｉ^＊は、計測用パターンの像が残存しない（消失した）と予想される任意の区画領域内におけるピクセル値の平均値である。従って、上式（９）で表されるスコアＥ’は、平均値としてＩ^＊を用いて求められた、各区画領域内の指定範囲におけるピクセルデータに対応するピクセル値の分散であると言える。
【０２００】
従って、ステップ５２０では、前記撮像データファイルから、各区画領域ＤＡ_ｉ，ｊの前記指定範囲内の撮像データを抽出し、上式（８）又は（９）を用いて、各区画領域ＤＡ_ｉ，ｊ（ｉ＝１〜Ｍ、ｊ＝１〜Ｎ）のスコアＥ_ｉ，ｊ又はＥ’_ｉ，ｊ（ｉ＝１〜Ｍ、ｊ＝１〜Ｎ）を算出する。
【０２０１】
上記の方法で求めたスコアＥ又はＥ’は、パターンの有無具合を数値として表しているので、所定の閾値で二値化することによってパターン有無の判別を自動的にかつ安定して行うことが可能である。
【０２０２】
そこで、次のステップ５２２（図１１）において、区画領域ＤＡ_ｉ，ｊ毎に上で求めたスコアＥ_ｉ，ｊ又はＥ’_ｉ，ｊと所定の閾値ＳＨとを比較して、各区画領域ＤＡ_ｉ，ｊにおける計測用パターンＭＰの像の有無を検出し、検出結果としての判定値Ｆ_ｉ，ｊ（ｉ＝１〜Ｍ、ｊ＝１〜Ｎ）を図示しない記憶装置に保存する。すなわち、このようにして、スコアＥ_ｉ，ｊ又はＥ’_ｉ，ｊに基づいて、区画領域ＤＡ_ｉ，ｊ毎に計測用パターンＭＰ_ｎの像の形成状態を検出する。なお、像の形成状態としては、種々のものが考えられるが、本実施形態では、上述の如く、スコアＥ又はＥ’がパターンの有無具合を数値として表すものであるという点に基づいて、区画領域内にパターンの像が形成されているか否かに着目することとしたものである。
【０２０３】
ここでは、スコアＥ_ｉ，ｊ又はＥ’_ｉ，ｊが閾値ＳＨ以上の場合には、計測用パターンＭＰ_ｎの像が形成されていると判断し、検出結果としての判定値Ｆ_ｉ，ｊを「０」とする。一方、スコアＥ_ｉ，ｊ又はＥ’_ｉ，ｊが閾値ＳＨ未満の場合には、計測用パターンＭＰ_ｎの像が形成されていないと判断し、検出結果としての判定値Ｆ_ｉ，ｊを「１」とする。図２２には、この検出結果の一例がテーブルデータとして示されている。この図２２は、前述の図９に対応するものである。
【０２０４】
図２２において、例えば、Ｆ_{１２，１６}は、ウエハＷ_ＴのＺ軸方向の位置がＺ_１２で、露光エネルギ量がＰ_１６のときに転写された計測用パターンＭＰ_ｎの像の形成状態の検出結果を意味し、一例として、図２２の場合には、Ｆ_{１２，１６}は、「１」という値になっており、計測用パターンＭＰ_ｎの像が形成されていないと判断されたことを示している。
【０２０５】
なお、閾値ＳＨは、予め設定されている値であり、オペレータが図示しない入出力装置を用いて変更することも可能である。
【０２０６】
次のステップ５２４では、上述の検出結果に基づいて、フォーカス位置毎にパターンの像が形成されている区画領域の数を求める。すなわち、フォーカス位置毎に判定値「０」の区画領域が何個あるかを計数し、その計数結果をパターン残存数Ｔ_ｉ（ｉ＝１〜Ｍ）とする。この際に、周囲の領域と異なる値を持ついわゆる跳び領域は無視する。例えば、図２２の場合には、ウエハＷ_Ｔのフォーカス位置がＺ_１ではパターン残存数Ｔ_１＝８、Ｚ_２ではＴ_２＝１１、Ｚ_３ではＴ_３＝１４、Ｚ_４ではＴ_４＝１６、Ｚ_５ではＴ_５＝１６、Ｚ_６ではＴ_６＝１３、Ｚ_７ではＴ_７＝１１、Ｚ_８ではＴ_８＝８、Ｚ_９ではＴ_９＝５、Ｚ_１０ではＴ_１０＝３、Ｚ_１１ではＴ_１１＝２、Ｚ_１２ではＴ_１２＝２、Ｚ_１３ではＴ_１３＝２である。このようにして、フォーカス位置とパターン残存数Ｔ_ｉとの関係を求めることができる。
【０２０７】
なお、上記の跳び領域が生ずる原因として、計測時の誤認識、レーザのミスファイヤ、ゴミ、ノイズ等が考えられるが、このようにして生じた跳び領域がパターン残存数Ｔ_ｉの検出結果に与える影響を軽減するために、フィルタ処理を行っても良い。このフィルタ処理としては、例えば評価する区画領域を中心とする３×３の区画領域のデータ（判定値Ｆ_ｉ，ｊ）の平均値（単純平均値又は重み付け平均値）を求めることが考えられる。なお、フィルタ処理は、形成状態の検出処理前のデータ（スコアＥ_ｉ，ｊ又はＥ’_ｉ，ｊ）に対して行っても勿論良く、この場合には、より有効に跳び領域の影響を軽減できる。
【０２０８】
次のステップ５２６では、パターン残存数からベストフォーカス位置を算出するためのｎ次の近似曲線（例えば４〜６次曲線）を求める。
【０２０９】
具体的には、上記ステップ５２４で検出されたパターンの残存数を、横軸をフォーカス位置とし、縦軸をパターン残存数Ｔ_ｉとする座標系上にプロットする。この場合、図２３に示されるようになる。ここで、本実施形態の場合、ウエハＷ_Ｔの露光にあっては、各区画領域ＤＡ_ｉ，ｊを同一の大きさとし、かつ、行方向で隣接する区画領域間の露光エネルギの差を一定値（＝ΔＰ）とし、列方向で隣接する区画領域間のフォーカス位置の差を一定値（＝ΔＺ）としたので、パターン残存数Ｔ_ｉが露光エネルギ量に比例するものとして扱うことができる。すなわち、図２３において、縦軸は露光エネルギ量Ｐであると考えることもできる。
【０２１０】
上記のプロット後、各プロット点をカーブフィットすることによりｎ次の近似曲線（最小自乗近似曲線）を求める。これにより、例えば図２３に点線で示されるような曲線Ｐ＝ｆ（Ｚ）が求められる。
【０２１１】
図１１に戻り、次のステップ５２８では、上記曲線Ｐ＝ｆ（Ｚ）の極値（極大値又は極小値）の算出を試みるとともに、その結果に基づいて極値が存在するか否かを判断する。そして、極値が算出できた場合には、ステップ５３０に移行して極値におけるフォーカス位置を算出して、その算出結果を光学特性の一つである最良フォーカス位置とするとともに、該最良フォーカス位置を図示しない記憶装置に保存する。
【０２１２】
一方、上記ステップ５２８において、極値が算出されなかった場合には、ステップ５３２に移行して、ウエハＷの位置変化（Ｚの変化）に対応する曲線Ｐ＝ｆ（Ｚ）の変化量が最も小さいフォーカス位置の範囲を算出し、その範囲の中間の位置を最良フォーカス位置として算出し、その算出結果を最良フォーカス位置とするとともに、該最良フォーカス位置を図示しない記憶装置に保存する。すなわち、曲線Ｐ＝ｆ（Ｚ）の最も平坦な部分に基づいてフォーカス位置を算出する。
【０２１３】
ここで、このステップ５３２のようなベストフォーカス位置の算出ステップを設けたのは、計測用パターンＭＰ_ｎの種類やレジストの種類その他の露光条件によっては、例外的に上述の曲線Ｐ＝ｆ（Ｚ）が明確なピークを持たないような場合がある。このような場合にも、ベストフォーカス位置をある程度の精度で算出できるようにしたものである。
【０２１４】
次のステップ５３４において、前述のカウンタｎを参照して、全ての評価点対応領域ＤＢ_１〜ＤＢ_５について処理が終了したか否かを判断する。ここでは、評価点対応領域ＤＢ_１についての処理が終了しただけであるため、このステップ５３４における判断は否定され、ステップ５３６に進んでカウンタｎをインクリメント（ｎ←ｎ＋１）した後、図１０のステップ５０２に戻り、評価点対応領域ＤＢ_２がアライメント検出系ＡＳで検出可能となる位置に、ウエハＷ_Ｔを位置決めする。
【０２１５】
そして、上述したステップ５０４〜５３４までの処理（判断を含む）を再度行い、上述した評価点対応領域ＤＢ_１の場合と同様にして、評価点対応領域ＤＢ_２について最良フォーカス位置を求める。
【０２１６】
そして、評価点対応領域ＤＢ_２について最良フォーカス位置の算出が終了すると、ステップ５３４で全ての評価点対応領域ＤＢ_１〜ＤＢ_５について処理が終了したか否かを再度判断するが、ここでの判断は否定される。以後、ステップ５３４における判断が肯定されるまで、上記ステップ５０２〜５３６の処理（判断を含む）が繰り返される。これにより、他の評価点対応領域ＤＢ_３〜ＤＢ_５について、前述した評価点対応領域ＤＢ_１の場合と同様にして、それぞれ最良フォーカス位置が求められることとなる。
【０２１７】
このようにして、ウエハＷ_Ｔ上の全ての評価点対応領域ＤＢ_１〜ＤＢ_５について最良フォーカス位置の算出、すなわち投影光学系ＰＬに関して照明領域ＩＡＲ’と共役な被露光領域内で５つの計測用パターンＭＰ_１〜ＭＰ_５の投影位置となる前述した各評価点での最良フォーカス位置の算出がなされると、ステップ５３４での判断が肯定され、ステップ５３８に移行して、上で求めた最良フォーカス位置データに基づいて他の光学特性を算出する。
【０２１８】
例えば、このステップ５３８では、一例として、評価点対応領域ＤＢ_１〜ＤＢ_５における最良フォーカス位置のデータに基づいて、投影光学系ＰＬの像面湾曲を算出する。また、前述した被露光領域内の各評価点での焦点深度などを求めても良い。
【０２１９】
ここで、本実施形態では、説明の簡略化のため、投影光学系ＰＬの視野内の各評価点に対応するレチクルＲ_Ｔ上の領域に計測用パターンとして前述のパターンＭＰ_ｎのみが形成されていることを前提として、説明を行った。しかし、本発明がこれに限定されないことは勿論である。例えば、レチクルＲ_Ｔ上に、例えば各評価点に対応するレチクルＲ_Ｔ上の領域の近傍に、前述したステップピッチＳＰの整数倍、例えば８倍、１２倍などの間隔で複数の開口パターンＡＰ_ｎを配置し、各開口パターンＡＰ_ｎの内部に、周期方向が異なるＬ／Ｓパターンや、ピッチが異なるＬ／Ｓパターンなど複数種類の計測用パターンをそれぞれ配置しても良い。このようにすると、例えば、各評価点に対応する位置に近接して配置された周期方向が直交する１組のＬ／Ｓパターンを計測用パターンとして得られた最良フォーカス位置から各評価点における非点収差を求めることができる。さらに、投影光学系ＰＬの視野内の各評価点について、上述のようにして算出された非点収差に基づいて最小二乗法による近似処理を行うことにより非点収差面内均一性を求めるとともに、非点収差面内均一性と像面湾曲とから総合焦点差を求めることも可能となる。
【０２２０】
そして、上述のようにして求められた投影光学系ＰＬの光学特性データは、図示しない記憶装置に保存されるとともに、不図示の表示装置の画面上に表示される。これにより、図１１のステップ５３８の処理、すなわち図５のステップ４５６の処理を終了し、一連の光学特性の計測処理を終了する。
【０２２１】
次に、デバイス製造の場合における、本実施形態の露光装置１００による露光動作を説明する。
【０２２２】
前提として、上述のようにして決定された最良フォーカス位置の情報、あるいはこれに加えて像面湾曲の情報が、不図示の入出力装置を介して主制御装置２８に入力されているものとする。
【０２２３】
例えば、像面湾曲の情報が入力されている場合には、主制御装置２８は、露光に先立って、この光学特性データに基づいて、図示しない結像特性補正コントローラに指示し、例えば投影光学系ＰＬの少なくとも１つの光学素子（本実施形態では、レンズエレメント）の位置（他の光学素子との間隔を含む）あるいは傾斜などを変更することにより、その像面湾曲が補正されるように投影光学系ＰＬの結像特性を可能な範囲で補正する。なお、投影光学系ＰＬの結像特性の調整に用いる光学素子は、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ＰＬ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ＰＬの結像特性の補正方法は光学素子の移動に限られるものではなく、例えば光源１を制御して照明光ＩＬの中心波長を僅かにシフトさせる方法、又は投影光学系ＰＬの一部で屈折率を変化させる方法などを単独、あるいは光学素子の移動との組み合わせで採用しても良い。
【０２２４】
そして、主制御装置２８からの指示に応じて、不図示のレチクルローダにより転写対象となる所定の回路パターン（デバイスパターン）が形成されたレチクルＲがレチクルステージＲＳＴ上にロードされる。同様に、不図示のウエハローダにより、ウエハＷがウエハテーブル１８上にロードされる。
【０２２５】
次に、主制御装置２８により、不図示のレチクルアライメント検出系、ウエハテーブル１８上の基準マーク板ＦＰ、アラインメント検出系ＡＳ等を用いて、レチクルアラインメント、ベースライン計測などの準備作業が所定の手順で行われ、これに続いてＥＧＡ（エンハンスト・グローバル・アラインメント）方式などのウエハアライメントが行われる。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７−１７６４６８号公報（対応米国特許第５，６４６，４１３号）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（対応米国特許第４，７８０，６１７号）に詳細に開示されているので、ここではこれ以上の詳細説明は省略する。
【０２２６】
上記のウエハアライメントが終了すると、以下のようにしてステップ・アンド・スキャン方式の露光動作が行われる。
【０２２７】
まず、主制御装置２８は、レチクルＲとウエハＷ、すなわちレチクルステージＲＳＴとＸＹステージ２０とのＹ軸方向の相対走査を開始する。両ステージＲＳＴ、２０がそれぞれの目標走査速度に達し、等速同期状態に達すると、照明系ＩＯＰからの紫外パルス光によってレチクルＲのパターン領域が照明され始め、走査露光が開始される。上記の相対走査は、主制御装置２８が、前述したレーザ干渉計２６及びレーザ干渉計１４の計測値をモニタしつつ、レチクルステージ駆動部（不図示）及び駆動系２２を制御することにより行われる。
【０２２８】
主制御装置２８は、特に上記の走査露光時には、レチクルステージＲＳＴのＹ軸方向の移動速度ＶｒとＸＹステージ２０のＹ軸方向の移動速度Ｖｗとが、投影光学系ＰＬの投影倍率（１／４倍あるいは１／５倍）に応じた速度比に維持されるように同期制御を行う。また、主制御装置２８は、走査露光中に、フォーカスセンサＡＦＳによって検出されたウエハＷのＺ軸方向の位置情報に基づき、前述した光学特性補正後の投影光学系ＰＬの像面の焦点深度の範囲内にウエハＷ（ショット領域）表面の露光領域が収まるように、駆動系２２を介してウエハテーブル１８をＺ軸方向及び傾斜方向に駆動し、ウエハＷのフォーカス・レベリング制御を行う。なお、本実施形態では、ウエハＷの露光動作に先立って、前述した各評価点における最良フォーカス位置に基づいて投影光学系ＰＬの像面を算出し、この像面がフォーカスセンサＡＦＳの検出基準となるようにフォーカスセンサＡＦＳの光学的なキャリブレーション（例えば、受光系５０ｂ内に配置される平行平面板の傾斜角度の調整など）が行われている。勿論、光学的なキャリブレーションを必ずしも行う必要はなく、例えば先に算出した像面とフォーカスセンサＡＦＳの検出基準との偏差に応じたオフセットを考慮して、フォーカスセンサＡＦＳの出力に基づいてウエハＷ表面を像面に一致させるフォーカス動作（及びレベリング動作）を行うようにしても良い。
【０２２９】
そして、レチクルＲのパターン領域の異なる領域が紫外パルス光で逐次照明され、パターン領域全面に対する照明が完了することにより、ウエハＷ上の第１ショット領域の走査露光が終了する。これにより、レチクルＲのパターンが投影光学系ＰＬを介して第１ショット領域に縮小転写される。
【０２３０】
上述のようにして、第１ショット領域の走査露光が終了すると、主制御装置２８により、駆動系２２を介してＸＹステージ２０がＸ、Ｙ軸方向にステップ移動され、第２ショット領域の露光のための走査開始位置（加速開始位置）に移動される。
【０２３１】
そして、主制御装置２８により、上述と同様に各部の動作が制御され、ウエハＷ上の第２ショット領域に対して上記と同様の走査露光が行われる。
【０２３２】
このようにして、ウエハＷ上のショット領域の走査露光とショット間のステッピング動作とが繰り返し行われ、ウエハＷ上の露光対象ショットの全てにレチクルＲのパターンが順次転写される。
【０２３３】
ウエハＷ上の全露光対象ショットへのパターン転写が終了すると、次のウエハと交換され、上記と同様にアライメント、露光動作が繰り返される。
【０２３４】
以上詳細に説明したように、本実施形態に係る露光装置における、投影光学系ＰＬの光学特性計測方法によると、矩形枠状の開口パターンＡＰ_ｎと該開口パターンＡＰ_ｎの内部に位置する計測用パターンＭＰ_ｎとが形成されたレチクルＲ_Ｔを、投影光学系の物体面側に配置されたレチクルステージＲＳＴ上に搭載し、投影光学系ＰＬの像面側に配置されたウエハＷ_Ｔの投影光学系ＰＬの光軸方向に関する位置（Ｚ）とウエハＷ_Ｔ上に照射される照明光ＩＬのエネルギ量Ｐをそれぞれ変更しながら、ウエハＷ_Ｔを開口パターンＡＰ_ｎのサイズに対応する距離、すなわち開口パターンＡＰ_ｎのウエハＷ_Ｔ上への投影像のサイズ以下のステップピッチで順次ＸＹ面内で移動して計測用パターンＭＰ_ｎをウエハＷ_Ｔ上に順次転写する。これにより、ウエハＷ_Ｔ上には、マトリックス状に配置された複数の区画領域ＤＡ_ｉ，ｊ（ｉ＝０〜Ｍ＋１、ｊ＝０〜Ｎ＋１）から成る全体として矩形の評価点対応領域ＤＢ_ｎが形成される。この場合、前述した理由により、ウエハＷ_Ｔ上には、区画領域相互間の境界に従来のような枠線が存在しない複数のマトリックス状配置の複数の区画領域（計測用パターンの像が投影された領域）が形成される。
【０２３５】
そして、ウエハＷ_Ｔの現像後に、主制御装置２８が、ＦＩＡ系のアライメントセンサから成るアライメント検出系ＡＳを用いてウエハＷ_Ｔ上の評価点対応領域ＤＢ_ｎを撮像する。次いで、主制御装置２８は、取り込んだレジスト像の撮像データに基づき、評価点対応領域ＤＢ_ｎの輪郭から成る矩形の外枠ＤＢＦを構成する少なくとも１辺、例えば上辺、下辺を検出対象とし、所定大きさの窓領域ＷＤ１、ＷＤ２をそれぞれの検出対象の辺にほぼ直交する走査方向に走査し、該走査中に窓領域ＷＤ１、ＷＤ２それぞれの内部のピクセルデータの代表値、すなわちピクセル値の分散（又は標準偏差）がそれぞれ最大となる位置を、それぞれの検出対象の辺である上辺、下辺の位置として検出する。すなわち、本実施形態では、このようにして、外枠ＤＢＦの一部のラフ検出が行われる。
【０２３６】
ここで、検出領域は、検出対象の辺の設計値に基づいて、その辺が必ず含まれるように容易に設定することができる。また、外枠ＤＢＦの部分は、その他の部分と明らかにピクセル値（画素値）が異なるので、窓領域ＷＤ１、ＷＤ２内のピクセル値の分散（又は標準偏差）の大小に基づき、検出対象の辺（外枠の一部）の位置が確実に検出される。
【０２３７】
次に、主制御装置２８は、前記撮像データに基づき、前記検出対象の辺、すなわち上辺及び下辺の位置の検出結果（ラフ検出の結果）を利用して、上辺より僅かに下のピクセル列データのピクセル値に対応する波形データＰＤ１、下辺より僅かに上のピクセル列データのピクセル値に対応する波形データＰＤ２を用いて、左辺、右辺上の境界点を各２点検出することによって左辺、右辺を検出する。次いで、主制御装置２８は、検出した左辺の僅かに右側のピクセル列データのピクセル値に対応する波形データＰＤ３、右辺の僅かに左側のピクセル列データのピクセル値に対応する波形データＰＤ４を用いて、上辺、下辺上の境界点を各２点検出することによって上辺、下辺（の詳細位置）を検出する。
【０２３８】
次に、主制御装置２８は、検出した外枠部分（上辺、下辺、左辺、右辺）を基準として評価点対応領域ＤＢ_ｎを構成する複数の区画領域のうち、第２領域ＤＤ_ｎを除く第１領域ＤＣ_ｎを構成するＭ×Ｎ個の区画領域それぞれの位置を算出する。この算出は、外枠内の区画領域の数及び配置の情報に基づいて行われる。
【０２３９】
次いで、前記撮像データに基づき、第１領域ＤＣ_ｎを構成するＭ×Ｎ個の区画領域における像の形成状態を画像処理の手法、すなわち前述の各区画領域ＤＡ_ｉ，ｊのスコア（Ｅ_ｉ，ｊ又はＥ’_ｉ，ｊ）と閾値ＳＨとを比較した二値化の手法により検出する。
【０２４０】
いずれにしても、前述の如く、外枠の少なくとも１辺の位置をラフ検出し、その検出結果を利用して外枠ＤＢＦの詳細位置を検出するという、２段階の検出により外枠の少なくとも一部の位置を確実にかつ精度良く検出することができ、その検出した外枠部分を基準として設計値に基づき少なくとも一部の複数の区画領域の位置を算出するので、その複数の区画領域のほぼ正確な位置を求めることが可能となる。
【０２４１】
また、本実施形態の場合、隣接する区画領域間に枠線が存在しないので、像形成状態の検出対象である複数の区画領域（主として計測用パターンの像の残存する区画領域）において、計測用パターンの像のコントラストが枠線の干渉に起因して低下することがない。このため、それらの複数の区画領域の撮像データとしてパターン部と非パターン部のＳ／Ｎ比の良好なデータを得ることができる。従って、区画領域毎の計測用パターンＭＰ_ｎの形成状態を精度、再現性良く検出することが可能となる。しかも、像の形成状態を客観的、定量的なスコア（Ｅ_ｉ，ｊ又はＥ’_ｉ，ｊ）を閾値ＳＨと比較してパターンの有無情報（二値化情報）に変換して検出するので、区画領域毎の計測用パターンＭＰ_ｎの形成状態を、再現性良く検出することができるとともに、パターン有無の判別を自動的にかつ安定して行うことができる。従って、本実施形態では、二値化に際して、閾値は一つだけで足り、複数の閾値を設定しておいて閾値毎にパターンの有無具合を判別するような場合に比べて、像の形成状態の検出に要する時間を短縮することができるとともに、その検出アルゴリズムも簡略化することができる。
【０２４２】
また、主制御装置２８は、上述した区画領域毎の像の形成状態の検出結果、すなわち客観的かつ定量的な上記のスコア（Ｅ_ｉ，ｊ又はＥ’_ｉ，ｊ）、すなわち画像のコントラストの指標値を用いた検出結果に基づいて最良フォーカス位置などの投影光学系ＰＬの光学特性を求めている。このため、短時間で精度良く最良フォーカス位置などを求めることが可能となる。従って、この最良フォーカス位置に基づいて決定される光学特性の測定精度及び測定結果の再現性を向上させることができるとともに、結果的に光学特性計測のスループットを向上させることが可能となる。
【０２４３】
また、本実施形態では、上述の如く、像の形成状態をパターンの有無情報（二値化情報）に変換して検出するので、レチクルＲ_Ｔのパターン領域ＰＡ内に計測用パターンＭＰ_ｎ以外のパターン（例えば、比較用の基準パターンや、位置決め用マークパターン等）を配置する必要がない。また、従来の寸法を計測する方法（ＣＤ／フォーカス法、ＳＭＰフォーカス計測法など）に比べて、計測用パターンを小さくすることができる。このため、評価点の数を増加させることができるとともに、評価点間の間隔を狭くすることが可能となる。結果的に、光学特性の測定精度及び測定結果の再現性を向上させることができる。
【０２４４】
また、本実施形態では、ウエハＷ_Ｔ上に形成される隣接する区画領域間に枠線が存在しないことに鑑み、各評価点対応領域ＤＢ_ｎの外周縁である外枠ＤＢＦを基準として各区画領域ＤＡ_ｉ，ｊの位置を算出する手法を採用している。そして、各評価点対応領域ＤＢ_ｎ内の最外周部に位置する複数の区画領域から成る第２領域ＤＤ_ｎを構成する各区画領域が過露光の領域となるように露光条件の一部としてウエハＷ_Ｔ上に照射される照明光ＩＬのエネルギ量を変更している。これにより、前述の外枠ＤＢＦの検出に際してのＳ／Ｎ比が向上し、外枠ＤＢＦの検出を高精度に行うことができ、この結果、これを基準として各第１領域ＤＣ_ｎを構成する各区画領域ＤＡ_ｉ，ｊ（ｉ＝１〜Ｍ、ｊ＝１〜Ｎ）の位置を精度良く検出することができる。
【０２４５】
また、本実施形態に係る光学特性計測方法によると、統計処理による近似曲線の算出という客観的、かつ確実な方法を基礎として最良フォーカス位置を算出しているので、安定して高精度かつ確実に光学特性を計測することができる。なお、近似曲線の次数によっては、その変曲点、あるいはその近似曲線と所定のスライスレベルとの複数の交点等に基づいて最良フォーカス位置を算出することは可能である。
【０２４６】
また、本実施形態の露光装置によると、前述の光学特性計測方法により精度良く計測された投影光学系ＰＬの光学特性を考慮して最適な転写が行えるように投影光学系ＰＬが露光に先立って調整され、その調整された投影光学系ＰＬを介してレチクルＲに形成されたパターンがウエハＷ上に転写される。更に、上述のようにして決定された最良フォーカス位置を考慮して露光の際のフォーカス制御目標値の設定が行われるので、デフォーカスによる色むらの発生を効果的に抑制することができる。従って、本実施形態に係る露光方法によると、微細パターンをウエハ上に高精度に転写することが可能となる。
【０２４７】
なお、上記実施形態では、投影光学系ＰＬの光学特性の計測方法の一部として、矩形枠状の開口パターンＡＰ_ｎと該開口パターンＡＰ_ｎの内部に位置する計測用パターンＭＰ_ｎとが形成されたレチクルＲ_Ｔを、投影光学系の物体面側に配置されたレチクルステージＲＳＴ上に搭載し、投影光学系ＰＬの像面側に配置されたウエハＷ_Ｔの投影光学系ＰＬの光軸方向に関する位置（Ｚ）とウエハＷ_Ｔ上に照射される照明光ＩＬのエネルギ量Ｐをそれぞれ変更しながら、ウエハＷ_Ｔを所定のステップピッチで移動して、計測用パターンＭＰ_ｎをウエハＷ_Ｔ上に順次転写する転写工程が含まれるものとしたが、本発明がこれに限定されるものではない。すなわち、異なる露光条件下で投影光学系ＰＬを介して転写された計測用パターンの転写領域から成るマトリックス状配置の複数の区画領域を含む全体として矩形の所定の領域が予め形成されたウエハなどの物体を予め用意し、このウエハに対して、前述の実施形態と同様にアライメント検出系ＡＳによる撮像処理以後の各処理を行うことによっても、マトリックス状配置の複数の区画領域が異なる露光条件下で投影光学系ＰＬを介して転写された計測用パターンの転写領域である限り、換言すれば、区画領域に形成された像が、投影光学系ＰＬの光学特性の影響を受けた像を含む限り、上記実施形態と同様に投影光学系の光学特性を計測することができる。
【０２４８】
従って、第２領域、すなわち矩形枠状の領域、あるいはその一部の領域を形成する方法は、上記実施形態で説明した計測用パターンを過露光の状態でウエハ上に転写する、ステップ・アンド・リピート方式の露光方法以外の方法を採用しても良い。例えば、露光装置１００のレチクルステージＲＳＴ上に例えば矩形枠状の開口パターン（第２領域ＤＤ_ｎと同様の形状のパターン）、あるいはその一部のパターンなどが形成されたレチクルを搭載し、そのレチクルのパターンを１回の走査露光で、投影光学系ＰＬの像面側に配置されたウエハ上に転写して、過露光の第２領域をウエハ上に形成することとしても良い。この他、前述した開口パターンＡＰ_ｎと同様の開口パターンが形成されたレチクルをレチクルステージＲＳＴ上に搭載して、ステップ・アンド・リピート方式又はステップ・アンド・スキャン方式で、その開口パターンを過露光の露光エネルギ量でウエハ上に転写することにより、過露光の第２領域をウエハ上に形成することとしても良い。また、例えば上記の開口パターンを用いてステップ・アンド・スティッチ方式で露光を行い、ウエハ上に開口パターンの複数の像を隣接してあるいは繋ぎ合わせて形成することによって、過露光の第２領域をウエハ上に形成しても良い。この他、レチクルステージＲＳＴを静止させた状態でそのレチクルステージＲＳＴ上に搭載されたレチクルに形成された開口パターンを照明光で照明しながらウエハＷ（ウエハテーブル１８）を所定方向に移動して過露光の第２領域を形成しても良い。いずれにしても、上記実施形態と同様に、過露光の第２領域の存在により、その第２領域の外縁をＳ／Ｎ比の良好な検出信号に基づいて精度良く検出することが可能となる。
【０２４９】
これらの場合において、マトリックス状に配置された複数の区画領域ＤＡ_ｉ，ｊから成る全体として矩形の第１領域ＤＣ_ｎをウエハＷ_Ｔ上に形成する工程と、第１領域の周囲の少なくとも一部のウエハ上の領域に過露光の第２領域（例えばＤＤ_ｎなど）を形成する工程とは、上記実施形態の場合と反対であっても良い。特に、像形成状態の検出の対象となる第１区画領域の形成のための露光を、後で行うようにした場合には、例えば感光剤として、化学増幅型レジストなどの高感度レジストを用いる場合に、計測用パターンの像の形成（転写）から現像までの時間を短くできるので、特に好適である。
【０２５０】
なお、上記実施形態では、評価点対応領域ＤＢ_ｎの外枠ＤＢＦの概略位置検出に際して、窓領域ＷＤ１，ＷＤ２内のピクセルデータの代表値として、例えばそれぞれの窓領域ＷＤ１、ＷＤ２内のピクセルデータに対応するピクセル値の分散（又は標準偏差）、又は２つの窓領域ＷＤ１、ＷＤ２を同時にスキャンする場合には、それらの加算値を用いる場合について説明した。しかし、これに限らず、前記ピクセルデータの代表値は前記窓領域内の中心を含む一部の領域内のピクセルデータに対応するピクセル値の分散又は標準偏差、又は２つの窓領域ＷＤ１、ＷＤ２を同時にスキャンする場合には、それらの加算値であっても良い。あるいは、上記各場合において、ピクセル値の分散又は標準偏差に代えて、ピクセル値の加算値又は微分総和値を用いても良い。加算値又は微分総和値などを用いる場合、ピクセル値の定義の仕方に応じて、その加算値又は微分総和値が最大又は最小となる位置を、外枠の概略位置として検出することになる。いずれにしても、窓領域内のピクセルデータに基づいて、外枠の概略位置を検出すれば良い。
【０２５１】
なお、上記実施形態では、計測用パターンＭＰ_ｎの像の形成状態を、スコア（Ｅ_ｉ，ｊ又はＥ’_ｉ，ｊ）と閾値ＳＨとを比較してパターンの有無情報（二値化情報）に変換して検出する場合について説明したが、本発明がこれに限定されるものではない。上記実施形態では、評価点対応領域ＤＢ_ｎの外枠ＤＢＦを精度良く検出し、この外枠を基準として各区画領域ＤＡ_ｉ，ｊを演算により算出するので、各区画領域の位置を正確に求めることができる。従って、この正確に求められた各区画領域に対してテンプレートマッチングを行うこととしても良い。このようにすれば、短時間にテンプレートマッチングを行うことができる。この場合、テンプレートパターンとして、例えば像が形成された区画領域あるいは像が形成されなかった区画領域の撮像データを用いることができる。このようにしても、客観的、定量的な相関値の情報が区画領域毎に得られるので、得られた情報を、所定の閾値と比較することにより、計測用パターンＭＰ_ｎの形成状態を二値化情報（像の有無情報）に変換することにより、上記実施形態と同様に像の形成状態を精度、再現性良く検出することができる。
【０２５２】
また、上記実施形態では、評価点対応領域ＤＢ_ｎを構成する第２領域が正確な矩形枠状である場合について説明したが、本発明がこれに限定されるものではない。すなわち、第２領域は、その外縁が少なくとも第１領域を構成する各区画領域の位置算出の基準にできれば良いので、矩形枠状の区画領域の一部の例えばコ字状（Ｕ字状）部分、あるいはＬ字状部分であっても良い。この場合、第１領域とその外側の第２領域とで構成される評価点対応領域は、全体として矩形の領域となる。
【０２５３】
また、過露光の第２領域は、必ずしもなくても良い。かかる場合であっても、第１領域の輪郭が矩形の外枠となり、第１領域内の最外周部に位置する区画領域（以下、「外縁部区画領域」と呼ぶ）の一部には、パターン像が形成されない領域が存在するので、上記実施形態と同様の手法により、その外枠の一部、すなわち第１領域とその外側の領域の境界線をＳ／Ｎ比良く検出することが可能となり、その境界線を基準として設計値に基づき他の区画領域（第１領域を構成する各区画領域）の位置を算出することができ、他の区画領域のほぼ正確な位置を求めることが可能である。同様に、過露光の第２領域は、上記実施形態のような矩形枠状あるいはその一部のような形状に限定されるものではない。例えば、第２領域の形状は、第１領域との境界線（内縁）のみが矩形枠状の形状を有し、外縁は任意形状であっても良い。かかる場合であっても、第１領域の外側に過露光の第２領域（パターン像が形成されない領域）が存在するので、外縁部区画領域の像の形成状態の検出の際に、隣接する外側の領域のパターン像の存在によりその外縁部区画領域の像のコントラストが低下するのが防止される。従って、前記外縁部区画領域と第２領域の境界線をＳ／Ｎ比良く検出することが可能となり、その境界線を基準として設計値に基づき他の区画領域（第１領域を構成する各区画領域）の位置を算出することができ、他の区画領域のほぼ正確な位置を求めることが可能である。
【０２５４】
従って、これらの場合にも、第１領域内の複数の区画領域それぞれの位置をほぼ正確に知ることができるので、例えばそれぞれの区画領域に対して、上記実施形態と同様のスコア（像のコントラストの指標値）を用いた方法、あるいはテンプレートマッチング法を適用して像の形成状態を検出することにより、上記実施形態と同様に、パターン像の形成状態を短時間で検出することが可能になる。
【０２５５】
そして、その検出結果に基づいて投影光学系の光学特性を求めることにより、客観的かつ定量的な像のコントラスト又は相関値を用いた検出結果に基づいて光学特性を求めることができる。従って、上記実施形態と同等の効果を得ることができる。
【０２５６】
また、上記実施形態では、各区画領域の検出の基準となる外枠ＤＢＦの検出、及び各区画領域の像の形成状態の検出にＦＩＡ系のアライメントセンサを用いるものとしたが、本発明がこれに限定されるものではない。すなわち、外枠ＤＢＦあるいは上述した前記外縁部区画領域と第２領域の境界線の検出、及び各区画領域の像の形成状態の検出の少なくとも一方に、ＳＥＭ（走査型電子顕微鏡）などの他の撮像装置（画像計測装置）を用いても良い。かかる場合であっても、第２領域の外枠又は内縁部を基準として、第１領域内の各区画領域の位置を精度良く求めることが可能である。
【０２５７】
また、上記実施形態と同様に、各評価点対応領域を第１領域とその周囲の第２領域とで形成する場合には、前述のステップピッチＳＰを、前述した開口パターンＡＰ_ｎの投影領域サイズ以下に必ずしも設定しなくても良い。その理由は、これまでに説明した方法で、第２領域の一部を基準として、第１領域を構成する各区画領域の位置がほぼ正確に求まるので、その位置の情報を用いることにより、例えばテンプレートマッチングや、上記実施形態の場合を含むコントラスト検出をある程度の精度でかつ短時間で行うことができるからである。
【０２５８】
一方、前述のステップピッチＳＰを、前述した開口パターンＡＰ_ｎの投影領域サイズ以下に設定する場合において、第１領域の外側に前述の第２領域を必ずしも形成しなくても良い。かかる場合であっても、上記実施形態と同様にして第１領域の外枠を検出することが可能であり、この検出した外枠を基準として第１領域内の各区画領域の位置を正確に求めることが可能だからである。そして、このようにして求められた各区画領域の位置の情報を用いて、例えばテンプレートマッチングや、上記実施形態のようなスコアを用いた検出（コントラスト検出）により像形成状態を検出する場合に、枠の干渉に起因するパターン部と非パターン部のコントラスト低下のないＳ／Ｎ比の良好な画像データを用いて像形成状態を精度良く検出することが可能となる。
【０２５９】
但し、この場合には、第１領域内の最外周の区画領域でパターンが残っている区画領域が並ぶ辺上では境界の誤検出を起こし易くなる。このため、誤検出を起こし難い境界の検出情報を用いて、誤検出を起こし易い境界の検出範囲を限定することによって対処することが望ましい。上記実施形態に則して説明すれば、誤検出を起こし難い区画領域が並ぶ右辺で検出した境界の情報を基に、誤検出を起こし易い区画領域が並ぶ左辺上の境界位置の検出範囲を限定する。また、第１領域の上下辺上の境界検出では、誤検出を起こし難い右側の検出情報を用いて左側の境界位置の検出範囲を限定することとすれば良い（図９参照）。
【０２６０】
また、この場合、８ビットの撮像データの内の例えば最上位２ビット以外の下位ビットのデータを０クリアしたデータ（又は全て「１」にしたデータ）を前記ピクセルデータとして用いて、前述の実施形態と同様の手法により外枠を検出しても良い。例えば、外枠の上辺及び右辺を検出対象の辺とする場合を考えると、例えば図９の第１領域ＤＣ_１を見るとわかるように、検出対象の辺近傍の外枠の内側はパターンの像が残存していない露光済みの領域であるのに対し、検出対象の辺近傍の外枠の外側はレジストがそのまま残存する未露光領域となる。従って、外枠内の各区画領域のピクセル値は、零に近い一定値以下であり、外枠の外側の領域のピクセル値はある一定値以上となっている。従って、これら２つの領域の撮像データにおける最上位２ビット以外の下位ビットのデータを０クリアしたデータは、外枠内の各区画領域の画素のピクセル値が零、外部の領域では全ての画素のピクセル値が２^７＋２^６＝１９２となる。このため、外枠を境界として、外側と内側でピクセル値が大きく異なるので、前述と同様の窓領域のスキャンその他の方法により、外枠を構成する検出対象の辺の概略位置検出をより確実に行うことが可能となる。
【０２６１】
同様に、上述の実施形態においても、８ビットの撮像データの内の例えば最上位２ビット以外の下位ビットのデータを０クリアしたデータを前記ピクセルデータとして用いて、前述と同様の手法により外枠を検出しても良い。この場合には、図９から明らかなように、外枠ＤＢＦの全周に渡ってその内側に過露光の第２領域ＤＤ_１が存在するので、外枠のいずれの辺を検出対象の辺とする場合にも、外枠内の各区画領域の画素のピクセル値が零、外部の領域では全ての画素のピクセル値が１９２となる。このため、外枠のいずれの辺を検出対象の辺としてもその概略位置を確実に検出することができる。
【０２６２】
また、上記実施形態では、全体として矩形の第１領域を構成するＮ×Ｍ個の区画領域を全て露光するものとしたが、Ｎ×Ｍ個の区画領域の少なくとも１個、すなわち曲線Ｐ＝ｆ（Ｚ）の決定に明らかに寄与しない露光条件が設定される区画領域（例えば、図９で右上隅及び右下隅に位置する区画領域など）についてはその露光を行わなくても良い。すなわち、計測用パターンＭＰ_ｎを転写すべき複数の区画領域（ショット領域）は全体として矩形（マトリックス）となっていなくても良い。このとき、第１領域の外側に形成される第２領域はその形状が矩形でなくその一部に凹凸を持つ、換言すればＮ×Ｍ個の区画領域のうち露光された区画領域のみを囲む、あるいはその周囲の一部のみに第２領域を形成しても良い。
【０２６３】
なお、上記実施形態では、ウエハＷ_ＴのステップピッチＳＰを、通常より狭く設定することにより、ウエハＷ_Ｔ上に形成された評価点対応領域を構成する区画領域間に枠が残存しないようにして、枠の干渉によるパターン部のコントラスト低下を防止する場合について説明した。しかし、枠の存在によるパターン部のコントラスト低下は、以下のようにしても防止することができる。
【０２６４】
すなわち、前述の計測用パターンＭＰ_ｎと同様にマルチバーパターンを含む計測用パターンが形成されたレチクルを用意し、該レチクルをレチクルステージＲＳＴ上に搭載し、ステップ・アンド・リピート方式などで前記計測用パターンをウエハ上に転写し、これにより、隣接する複数の区画領域から成り、各区画領域に転写されたマルチバーパターンとこれに隣接するパターンとが、マルチバーパターンの像のコントラストが前記隣接するパターンによる影響を受けない距離Ｌ以上離れている所定の領域をウエハ上に形成することとしても良い。
【０２６５】
この場合、各区画領域に転写されたマルチバーパターンとこれに隣接するパターンとが、マルチバーパターンの像のコントラストが隣接するパターンによる影響を受けない距離Ｌ以上離れているので、前記所定の領域を構成する複数の区画領域の少なくとも一部の複数の区画領域における像の形成状態を、画像処理の手法、テンプレートマッチング、あるいはスコア検出を含むコントラスト検出などの画像処理手法により検出する際に、それぞれの区画領域に転写されたマルチバーパターンの像のＳ／Ｎ比が良好な撮像信号を得ることができる。従って、この撮像信号に基づいて、テンプレートマッチング、あるいはスコア検出を含むコントラスト検出などの画像処理手法により各区画領域に形成されたマルチバーパターンの像の形成状態を精度良く検出することができる。
【０２６６】
例えば、テンプレートマッチングによる場合には、客観的、定量的な相関値の情報が区画領域毎に得られ、コントラスト検出の場合には、客観的、定量的なコントラスト値の情報が区画領域毎に得られるので、いずれにしても、得られた情報を、それぞれの閾値と比較することにより、マルチバーパターンの像の形成状態を二値化情報（像の有無情報）に変換することにより、各区画領域毎のマルチバーパターンの形成状態を精度、再現性良く検出することが可能となる。
【０２６７】
従って、かかる場合にも上記実施形態と同様に、上記の検出結果に基づいて投影光学系の光学特性を求めることにより、客観的かつ定量的な相関値、コントラストなどを用いた検出結果に基づいて光学特性が求められる。従って、従来の方法と比較して光学特性を精度及び再現性良く計測することができる。また、評価点の数を増加させることができるとともに、各評価点間の間隔を狭くすることができ、結果的に光学特性計測の測定精度を向上させることが可能となる。
【０２６８】
なお、上記実施形態では、レチクルＲ_Ｔ上の計測用パターンＭＰ_ｎとして開口パターンＡＰ_ｎ内の中央部に配置された１種類のＬ／Ｓパターン（マルチバーパターン）を用いる場合について説明したが、本発明がこれに限定されないことは言うまでもない。計測用パターンとしては、周期方向が異なる少なくとも２種類のＬ／Ｓパターンや、孤立線やコンタクトホールなどを用いても良い。計測用パターンＭＰ_ｎとしてＬ／Ｓパターンを用いる場合には、デューティ比及び周期方向は、任意で良い。また、計測用パターンＭＰ_ｎとして周期パターンを用いる場合、その周期パターンは、Ｌ／Ｓパターンだけではなく、例えばドットマークを周期的に配列したパターンでも良い。これは、像の線幅等を計測する従来の方法とは異なり、像の形成状態をスコア（コントラスト）で検出しているからである。
【０２６９】
また、上記実施形態では、１種類のスコアに基づいて最良フォーカス位置を求めているが、これに限らず、複数種類のスコアを設定しこれらに基づいて、それぞれ最良フォーカス位置を求めても良く、あるいはこれらの平均値（あるいは重み付け平均値）に基づいて最良フォーカス位置を求めても良い。
【０２７０】
また、上記実施形態では、ピクセルデータを抽出するエリアを矩形としているが、これに限定されるものではなく、例えば、円形や楕円形、あるいは三角形などであっても良い。また、その大きさも任意に設定することができる。すなわち、計測用パターンＭＰ_ｎの形状に合わせて抽出エリアを設定することによりノイズを減少させ、Ｓ／Ｎ比を高くすることが可能である。
【０２７１】
また、上記実施形態では、像の形成状態の検出に１種類の閾値を用いているが、これに限らず、複数の閾値を用いても良い。複数の閾値を求める場合、それぞれの閾値を、スコアと比較することで、区画領域の像の形成状態を検出することとしても良い。この場合、例えば第１の閾値での検出結果から最良フォーカス位置が算出困難な場合に、第２の閾値での形成状態の検出を行い、その検出結果から最良フォーカス位置を求めることなどが可能となる。
【０２７２】
また、予め複数の閾値を設定しておき、閾値毎に最良フォーカス位置を求め、それらの平均値（単純平均値あるいは重み付け平均値）を最良フォーカス位置としても良い。例えば、各閾値に応じて、露光エネルギ量Ｐが極値を示すときのフォーカス位置を順次算出する。そして、各フォーカス位置の平均値を最良フォーカス位置とする。なお、露光エネルギ量Ｐとフォーカス位置Ｚとの関係を示す近似曲線と適当なスライスレベル（露光エネルギ量）との２つの交点（フォーカス位置）を求め、両交点の平均値を、各閾値毎に算出し、それらの平均値（単純平均値あるいは重み付け平均値）を最良フォーカス位置としても良い。
【０２７３】
あるいは、各閾値毎に最良フォーカス位置を算出し、閾値と最良フォーカス位置との関係において、閾値の変動に対して、最良フォーカス位置の変化が最も小さい区間における最良フォーカス位置の平均値（単純平均値あるいは重み付け平均値）を最良フォーカス位置としても良い。
【０２７４】
また、上記実施形態では、予め設定されている値を閾値として用いているが、これに限定されるものではない。例えば、ウエハＷ_Ｔ上の計測用パターンＭＰ_ｎが転写されていない領域を撮像し、得られたスコアを閾値としても良い。
【０２７５】
さらに、例えば前述の第１領域と第２領域とで、アライメント検出系ＡＳによる画像の取り込み回数を異ならせても良く、このようにすることにより計測時間の短縮などを図ることができる。
【０２７６】
なお、上記実施形態の露光装置１００では、主制御装置２８は、図示しない記憶装置に格納されている処理プログラムに従って、前述した投影光学系の光学特性の計測を行うことにより、計測処理の自動化を実現することができる。勿論、この処理プログラムは、他の情報記録媒体（ＣＤ−ＲＯＭ、ＭＯ等）に保存されていても良い。さらに、計測を行う時に、図示しないサーバから処理プログラムをダウンロードしても良い。また、計測結果を、図示しないサーバに送付したり、インターネットやイントラネットを介して電子メール及びファイル転送により、外部に通知することも可能である。
【０２７７】
なお、上記実施形態では、計測用パターンＭＰ_ｎをウエハＷ_Ｔ上の各区画領域ＤＡ_ｉ，ｊに転写した後、現像後にウエハＷ_Ｔ上の各区画領域ＤＡ_ｉ，ｊに形成されるレジスト像をアライメント検出系ＡＳによって撮像し、その撮像データに対して画像処理を行う場合について説明したが、本発明に係る光学特性の計測方法はこれに限定されるものではない。例えば、撮像の対象は、露光の際にレジストに形成された潜像であっても良く、上記像が形成されたウエハを現像し、さらにそのウエハをエッチング処理して得られる像（エッチング像）などに対して行っても良い。また、ウエハなどの物体上における像の形成状態を検出するための感光層は、フォトレジストに限らず、光（エネルギ）の照射によって像（潜像及び顕像）が形成されるものであれば良い。例えば、感光層は、光記録層、光磁気記録層などであっても良く、従って、感光層が形成される物体もウエハ又はガラスプレート等に限らず、光記録層、光磁気記録層などが形成可能な板等であっても良い。
【０２７８】
また、オペレータなどが介在することなく、前述の計測結果（最良フォーカス位置など）に基づいて投影光学系ＰＬの光学特性を調整することができる。すなわち、露光装置に自動調整機能を持たせることが可能となる。
【０２７９】
また、上記実施形態では、パターンの転写の際に変更される露光条件が、投影光学系の光軸方向に関するウエハＷ_Ｔの位置及びウエハＷ_Ｔの面上に照射されるエネルギビームのエネルギ量（露光ドーズ量）である場合について説明したが、本発明がこれに限定されるものではない。例えば、照明条件（マスクの種別を含む）、投影光学系の結像特性など露光に関連する全ての構成部分の設定条件などの何れかであれば良く、また、必ずしも２種類の露光条件を変更しながら露光を行う必要もない。すなわち、一種類の露光条件、例えば投影光学系の光軸方向に関するウエハＷ_Ｔの位置のみを変更しながら、計測用マスクのパターンを感光物体上の複数の領域に転写し、その転写像の形成状態を検出する場合であっても、上記実施形態と同様のスコアを用いたコントラスト計測、あるいはテンプレートマッチングの手法により、その検出を迅速に行うことができるという効果がある。
【０２８０】
また、上記実施形態において、最良フォーカス位置とともに最良露光量を決定することができる。すなわち、露光エネルギ量を低エネルギ量側にも設定して、上記実施形態と同様の処理を行い、露光エネルギ量毎に、その像が検出されたフォーカス位置の幅を求め、該幅が最大となるときの露光エネルギ量を算出し、その場合の露光量を最良露光量とする。
【０２８１】
また、上記実施形態では、一例として、区画領域内の指定範囲のピクセル値の分散（又は標準偏差）を、スコアＥとして採用するものとしたが、本発明がこれに限定されるものではなく、区画領域内又はその一部（例えば、前述の指定範囲）のピクセル値の加算値、微分総和値をスコアＥとしても良い。また、上記実施形態中で説明した外枠検出のアルゴリズムは一例であって、これに限らず、例えば前述した境界検出と同様の手法により、評価点対応領域ＤＢ_ｎの４辺（上辺、下辺、左辺及び右辺）でそれぞれ少なくとも２点を検出することとしても良い。このようにしても、検出された少なくとも８点に基づいて例えば前述と同様の頂点検出、長方形近似などが可能である。また、上記実施形態では、図３に示されるように、開口パターンの内部に遮光部によって計測用パターンＭＰ_ｎが形成された場合について説明したが、これに限らず、図３の場合と反対に、遮光部内に光透過性のパターンから成る計測用パターンを形成しても良い。さらに、上記実施形態ではレチクルのパターン領域ＰＡを遮光部としたが、パターン領域ＰＡは光透過部でも良く、この場合は前述の計測用パターンＭＰ_ｎを設けるだけでも良いし、あるいは計測用パターンＭＰ_ｎを囲む遮光性の枠状パターンを一緒に形成しても良い。また、ウエハに塗布するレジストはポジ型に限られるものではなくネガ型でも良い。
【０２８２】
また、上記実施形態では、各区画領域ＤＡ_ｉ，ｊの計測用パターンの像の有無を、スコアを閾値と比較することで検出するものとしたが、この代わりに、次のようにして、前述の図２３の曲線Ｐ＝ｆ（Ｚ）と同様の近似曲線を算出しても良い。
【０２８３】
すなわち、前述の外枠検出及びその検出結果を利用した各区画領域の位置の算出により、撮像データ上における第１領域ＤＣ_ｎの範囲を容易に求めることができる。そして、この第１領域ＤＣ_ｎに対応する撮像データの所定方向、例えば前述のマトリックスの行方向（Ｘ軸方向）のピクセル列毎のピクセルデータの加算値（Ｘ軸方向の走査線上の輝度値の積算信号）の分布状況を検出する。図２４には、このようにして得られた図９の第１領域ＤＣ_１の撮像データにおけるピクセル列毎のピクセルデータ（ピクセル値）の加算値Ｇの分布曲線Ｇ＝ｇ（Ｚ）の一例が示されている。そこで、この曲線Ｇ＝ｇ（Ｚ）における各ピーク点（図２４中に●で示される）を、カーブフィットすることによりｎ次の近似曲線（最小自乗近似曲線）を求める。これにより、例えば図２４に点線で示されるような曲線Ｇ＝ｈ（Ｚ）が求められる。この曲線Ｇ＝ｈ（Ｚ）と前述の曲線Ｐ＝ｆ（Ｚ）とを比べると明からなように、両者はほぼ同様の形状をしていることがわかる。この場合、所定方向のピクセル列毎のピクセルデータの加算値の分布状況を算出するという簡単な画像処理により、前述の区画領域毎の像の形成状態（例えば有無検出）の検出結果と実質的に等価な分布状況のデータを得ることができる。従って、客観的かつ定量的な撮像データを用いて、前述の区画領域毎の像の形成状態（例えば有無検出）の検出結果を得る場合と同程度の検出精度及び再現性で、より簡易な手法により像の形成状態を検出することができる。
【０２８４】
そして、上記の曲線Ｇ＝ｈ（Ｚ）を用いて、上記実施形態と同様の処理を行うことにより、投影光学系ＰＬの光学特性、例えばベストフォーカス位置などを求めることとすれば良い。このようにしても、上記実施形態と同様に、客観的かつ定量的な撮像データを用いた検出結果に基づいて光学特性が求められるため、従来の方法と比較して光学特性を精度及び再現性良く計測することができる。
【０２８５】
さらに、上記実施形態では、結像特性補正コントローラを介して投影光学系ＰＬの結像特性を調整するものとしたが、例えば、結像特性補正コントローラだけでは結像特性を所定の許容範囲内に制御することができないときなどは、投影光学系ＰＬの少なくとも一部を交換しても良いし、あるいは投影光学系ＰＬの少なくとも１つの光学素子を再加工（非球面加工など）しても良い。また、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。このとき、露光装置１００のアライメントセンサを用いてレジスト像などを検出する場合、主制御装置２８はディスプレイ（モニタ）への警告表示、あるいはインターネット又は携帯電話などによって、オペレータなどにアシストの必要性を通知しても良いし、投影光学系ＰＬの交換箇所や再加工すべき光学素子など、投影光学系ＰＬの調整に必要な情報を一緒に通知すると良い。これにより、光学特性の計測などの作業時間だけでなく、その準備期間も短縮でき、露光装置の停止期間の短縮、すなわち稼働率の向上を図ることが可能となる。また、本実施形態では計測用パターンを静止露光方式でウエハに転写するものとしたが、静止露光方式の代わりに、あるいはそれに加えて走査露光方式で、上記実施形態と全く同様に少なくとも１つの露光条件を変えながら計測用パターンをウエハに転写することでダイナミックな光学特性を求めるようにしても良い。
【０２８６】
さらに、本発明が適用される露光装置の光源は、ＫｒＦエキシマレーザやＡｒＦエキシマレーザに限らず、Ｆ_２レーザ（波長１５７ｎｍ）、あるいは他の真空紫外域のパルスレーザ光源であっても良い。この他、露光用照明光として、例えば、ＤＦＢ半導体レーザ又はファイバーレーザから発振される赤外域、又は可視域の単一波長レーザ光を、例えばエルビウム（又はエルビウムとイッテルビウムの両方）がドープされたファイバーアンプで増幅し、非線形光学結晶を用いて紫外光に波長変換した高調波を用いても良い。また、紫外域の輝線（ｇ線、ｉ線等）を出力する超高圧水銀ランプ等を用いても良い。この場合には、ランプ出力制御、ＮＤフィルタ等の減光フィルタ、光量絞り等によって露光エネルギの調整を行えば良い。また、ＥＵＶ光、Ｘ線、あるいは電子線及びイオンビームなどの荷電粒子線を露光ビームとして用いる露光装置に本発明を適用しても良い。
【０２８７】
なお、上記実施形態では、本発明がステップ・アンド・スキャン方式の縮小投影露光装置に適用された場合について説明したが、本発明の適用範囲がこれに限定されないのは勿論である。すなわち、ステップ・アンド・リピート方式、ステップ・アンド・スティッチ方式又はプロキシミティ方式などの露光装置、あるいはミラープロジェクション・アライナー、及びフォトリピータなどにも好適に適用することができる。
【０２８８】
さらに、投影光学系ＰＬは、屈折系、反射屈折系、及び反射系のいずれでもよいし、縮小系、等倍系、及び拡大系のいずれでも良い。
【０２８９】
さらに、本発明は、半導体素子の製造に用いられる露光装置だけでなく、液晶表示素子、プラズマディスプレイなどを含むディスプレイの製造に用いられる、デバイスパターンをガラスプレート上に転写する露光装置、薄膜磁気へッドの製造に用いられる、デバイスパターンをセラミックウエハ上に転写する露光装置、撮像素子（ＣＣＤなど）、マイクロマシン、及びＤＮＡチップなどの製造、さらにはマスク又はレチクルの製造に用いられる露光装置などにも適用することができる。
【０２９０】
《デバイス製造方法》
次に、上記説明した露光装置及び方法を使用したデバイスの製造方法の実施形態を説明する。
【０２９１】
図２５には、デバイス（ＩＣやＬＳＩ等の半導体チップ、液晶パネル、ＣＣＤ、薄膜磁気ヘッド、ＤＮＡチップ、マイクロマシン等）の製造例のフローチャートが示されている。図２５に示されるように、まず、ステップ３０１（設計ステップ）において、デバイスの機能・性能設計（例えば、半導体デバイスの回路設計等）を行い、その機能を実現するためのパターン設計を行う。引き続き、ステップ３０２（マスク製作ステップ）において、設計した回路パターンを形成したマスクを製作する。一方、ステップ３０３（ウエハ製造ステップ）において、シリコン等の材料を用いてウエハを製造する。
【０２９２】
次に、ステップ３０４（ウエハ処理ステップ）において、ステップ３０１〜ステップ３０３で用意したマスクとウエハを使用して、後述するように、リソグラフィ技術によってウエハ上に実際の回路等を形成する。次いで、ステップ３０５（デバイス組立ステップ）において、ステップ３０４で処理されたウエハを用いてデバイス組立を行う。このステップ３０５には、ダイシング工程、ボンディング工程、及びパッケージング工程（チップ封入）等の工程が必要に応じて含まれる。
【０２９３】
最後に、ステップ３０６（検査ステップ）において、ステップ３０５で作製されたデバイスの動作確認テスト、耐久性テスト等の検査を行う。こうした工程を経た後にデバイスが完成し、これが出荷される。
【０２９４】
図２６には、半導体デバイスの場合における、上記ステップ３０４の詳細なフロー例が示されている。図２６において、ステップ３１１（酸化ステップ）においてはウエハの表面を酸化させる。ステップ３１２（ＣＶＤステップ）においてはウエハ表面に絶縁膜を形成する。ステップ３１３（電極形成ステップ）においてはウエハ上に電極を蒸着によって形成する。ステップ３１４（イオン打込みステップ）においてはウエハにイオンを打ち込む。以上のステップ３１１〜ステップ３１４それぞれは、ウエハ処理の各段階の前処理工程を構成しており、各段階において必要な処理に応じて選択されて実行される。
【０２９５】
ウエハプロセスの各段階において、上述の前処理工程が終了すると、以下のようにして後処理工程が実行される。この後処理工程では、まず、ステップ３１５（レジスト形成ステップ）において、ウエハに感光剤を塗布する。引き続き、ステップ３１６（露光ステップ）において、上記各実施形態の露光装置及び露光方法によってマスクの回路パターンをウエハに転写する。次に、ステップ３１７（現像ステップ）においては露光されたウエハを現像し、ステップ３１８（エッチングステップ）において、レジストが残存している部分以外の部分の露出部材をエッチングにより取り去る。そして、ステップ３１９（レジスト除去ステップ）において、エッチングが済んで不要となったレジストを取り除く。
【０２９６】
これらの前処理工程と後処理工程とを繰り返し行うことによって、ウエハ上に多重に回路パターンが形成される。
【０２９７】
以上のような、本実施形態のデバイス製造方法を用いれば、露光ステップで、上記実施形態の露光装置及び露光方法が用いられるので、前述した光学特性計測方法で精度良く求められた光学特性を考慮して調整された投影光学系を介して高精度な露光が行われ、高集積度のデバイスを生産性良く製造することが可能となる。
【０２９８】
【発明の効果】
以上説明したように、本発明に係る光学特性計測方法によれば、短時間で、精度及び再現性良く投影光学系の光学特性を求めることができるという効果がある。
【０２９９】
また、本発明に係る露光方法によれば、高精度な露光を実現できるという効果がある。
【０３００】
また、本発明に係るデバイス製造方法によれば、高集積度のデバイスを製造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の露光装置の概略構成を示す図である。
【図２】図１の照明系ＩＯＰの具体的構成の一例を説明するための図である。
【図３】投影光学系の光学特性の計測に用いられるレチクルの一例を示す図である。
【図４】光学特性の計測方法を説明するためのフローチャート（その１）である。
【図５】光学特性の計測方法を示すフローチャート（その２）である。
【図６】区画領域の配列を説明するための図である。
【図７】ウエハＷ_Ｔ上に第１領域ＤＣ_ｎが形成された状態を示す図である。
【図８】ウエハＷ_Ｔ上に評価点対応領域ＤＢ_ｎが形成された状態を示す図である。
【図９】ウエハＷ_Ｔを現像後にウエハＷ_Ｔ上に形成された評価点対応領域ＤＢ_１のレジスト像の一例を示す図である。
【図１０】図５のステップ４５６（光学特性の算出処理）の詳細を示すフローチャート（その１）である。
【図１１】図５のステップ４５６（光学特性の算出処理）の詳細を示すフローチャート（その２）である。
【図１２】図１０のステップ５１０の詳細を示すフローチャートである。
【図１３】図１２のステップ７０２の詳細を示すフローチャートである。
【図１４】図１４（Ａ）は、ステップ５０８の処理を説明するための図、図１４（Ｂ）は、ステップ５１０の処理を説明するための図、図１４（Ｃ）はステップ５１２の処理を説明するための図である。
【図１５】図１５（Ａ）は、ステップ５１４の処理を説明するための図、図１５（Ｂ）は、ステップ５１６の処理を説明するための図、図１５（Ｃ）は、ステップ５１８の処理を説明するための図である。
【図１６】窓領域の評価点対応領域ＤＢ_１の外枠に対するスキャン方向の他の例を簡略化して示す図である。
【図１７】図１７（Ａ）は、１つの評価点対応領域ＤＢ_ｋの外枠の４辺を検出するためにそれぞれ設定された４つの検出領域を示す図、図１７（Ｂ）は、一組の窓領域を図１７（Ａ）中の右から左に、図１７（Ｃ）は一組の窓領域を図１７（Ａ）中の上から下に、同時に設定された検出領域内でスキャンした際に得られたピクセル値の分散信号の和信号をそれぞれ示す図である。
【図１８】また、図１８（Ａ）は、外枠の上辺を検出対象として、窓領域を図１７（Ａ）中の下から上に、図１８（Ｂ）は、外枠の下辺を検出対象として、窓領域を図１７（Ａ）中の下から上に、図１８（Ｃ）は、外枠の右辺を検出対象として、窓領域を図１７（Ａ）中の右から左に、図１８（Ｄ）は、外枠の左辺を検出対象として、窓領域を図１７（Ａ）中の左から右に、設定された検出領域内でスキャンした際に得られたピクセル値の分散信号を、それぞれ示す図である。
【図１９】外枠検出における境界検出処理を説明するための図である。
【図２０】ステップ５１４の頂点検出を説明するための図である。
【図２１】ステップ５１６の長方形検出を説明するための図である。
【図２２】検出結果の一例を示すテーブルデータ形式の図である。
【図２３】パターン残存数（露光エネルギ量）とフォーカス位置との関係を示す図である。
【図２４】図９の第１領域ＤＣ_１の撮像データにおけるピクセル列毎のピクセルデータ（ピクセル値）の加算値Ｇの分布曲線の一例を示す図である。
【図２５】本発明に係るデバイス製造方法の実施形態を説明するためのフローチャートである。
【図２６】図２５のステップ３０４における処理のフローチャートである。
【符号の説明】
ＭＰ_ｎ…計測用パターン、ＤＢ_ｎ…評価点対応領域（所定領域）、ＤＣ_ｎ…第１領域、ＤＤ_ｎ…第２領域、ＰＬ…投影光学系、Ｗ…ウエハ（物体）、Ｗ_Ｔ…ウエハ（物体）。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical property measuring method, an exposure method, and a device manufacturing method, and more particularly, to an optical property measuring method for measuring optical properties of a projection optical system, and taking into account optical properties measured by the optical property measuring method. The present invention relates to an exposure method for performing exposure using a projection optical system adjusted by the method, and a device manufacturing method using the exposure method.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in a lithography process for manufacturing a semiconductor element, a liquid crystal display element, or the like, a resist or the like is applied to a pattern formed on a mask or a reticle (hereinafter, collectively referred to as a “reticle”) via a projection optical system. 2. Description of the Related Art An exposure apparatus is used for transferring an image onto a substrate such as a wafer or a glass plate (hereinafter, also appropriately referred to as a “wafer”). In recent years, as this type of apparatus, from the viewpoint of emphasizing throughput, a step-and-repeat type reduced projection exposure apparatus (so-called “stepper”) or a step-and-scan type scanning type apparatus which is an improvement on this stepper has been used. 2. Description of the Related Art A sequentially moving type exposure apparatus such as an exposure apparatus is relatively frequently used.
[0003]
In addition, semiconductor elements (integrated circuits) and the like are becoming highly integrated year by year. Accordingly, projection exposure apparatuses, which are apparatuses for manufacturing semiconductor elements and the like, require higher resolution, that is, transfer of finer patterns with high precision. It has come to be required. In order to improve the resolving power of a projection exposure apparatus, it is necessary to improve the optical characteristics of the projection optical system. Therefore, it is necessary to accurately measure and evaluate the optical characteristics (including the imaging characteristics) of the projection optical system. Is important.
[0004]
The accurate measurement of the optical characteristics of the projection optical system, for example, the image plane of the pattern, is based on the premise that the optimum focus position (best focus position) at each evaluation point (measurement point) in the field of view of the projection optical system can be accurately measured. Become.
[0005]
As a method of measuring the best focus position in a conventional projection exposure apparatus, mainly the following two methods are known.
[0006]
One is a measurement method known as a so-called CD / focus method. Here, a predetermined reticle pattern (for example, a line and space pattern) is used as a test pattern, and the test pattern is transferred to the test wafer at a plurality of wafer positions in the optical axis direction of the projection optical system. Then, the line width value of the resist image (transferred pattern image) obtained by developing the test wafer is measured using a scanning electron microscope (SEM) or the like, and the line width value and the projection optical system are measured. The best focus position is determined based on a correlation with the wafer position in the optical axis direction (hereinafter, also appropriately referred to as “focus position”).
[0007]
The other is a measurement method known as a so-called SMP focus measurement method. Here, a resist image of a wedge-shaped mark is formed on the wafer at a plurality of focus positions, and a change in the line width value of the resist image due to the difference in the focus position is amplified and replaced by a change in the longitudinal dimension, and is replaced on the wafer. The length of the resist image in the longitudinal direction is measured using a mark detection system such as an alignment system for detecting a mark. Then, the vicinity of the maximum value of the approximate curve indicating the correlation between the focus position and the length of the resist image is sliced at a predetermined slice level, and the middle point of the obtained focus position is determined as the best focus position.
[0008]
For various test patterns, astigmatism, field curvature, and the like, which are optical characteristics of the projection optical system, are measured based on the best focus position obtained in this manner.
[0009]
However, in the above-described CD / focus method, for example, in order to measure the line width value of a resist image by SEM, it is necessary to strictly adjust the focus of SEM, and the measurement time per point is extremely long. It took several hours to several tens of hours to perform the measurement at. Further, it is expected that a test pattern for measuring the optical characteristics of the projection optical system will be miniaturized, and the number of evaluation points in the field of view of the projection optical system will also increase. Therefore, the conventional measurement method using the SEM has a disadvantage that the throughput until a measurement result is obtained is significantly reduced. In addition, higher levels of measurement errors and reproducibility of measurement results have been required, and it has been difficult to cope with the conventional measurement methods. Further, as an approximation curve indicating the correlation between the focus position and the line width value, an approximation curve of the fourth order or higher is used to reduce the error. There was a constraint that a width value had to be determined. The difference between the line width value at the focus position (including both the + direction and the − direction with respect to the optical axis direction of the projection optical system) deviated from the best focus position and the line width value at the best focus position is an error. Is required to be 10% or more in order to reduce the value, but it has become difficult to satisfy this condition.
[0010]
In addition, in the above-described SMP focus measurement method, since the measurement is usually performed with monochromatic light, the influence of interference varies depending on the shape of the resist image, which may lead to a measurement error (dimensional offset). Furthermore, in order to measure the length of the resist image of the wedge-shaped mark by image processing, it is necessary to capture in detail information up to both ends in the longitudinal direction where the resist image becomes thinnest. However, there is a problem that the resolution of a camera or the like is not yet sufficient. In addition, since the test pattern is large, it has been difficult to increase the number of evaluation points in the field of view of the projection optical system.
[0011]
In addition, as a measure for improving the above-mentioned drawbacks of the CD / focus method, the position of the measurement-sensitive substrate (hereinafter, referred to as a wafer) in the optical axis direction of the projection optical system or the amount of exposure energy is changed. The pattern is sequentially transferred onto the wafer to form a rectangular area in which a plurality of partitioned areas on which the image of the measurement pattern is transferred are arranged in a matrix, and after developing the wafer, the rectangular area is formed on the wafer. There is known an invention which captures a resist image of a measurement pattern to be measured, performs pattern matching with a predetermined template using the captured data, and determines the best exposure condition such as the best focus position based on the result. (See Patent Document 1, Patent Document 2, etc.). According to the inventions disclosed in these patent documents, it is difficult to increase the number of evaluation points in the field of view of the projection optical system due to insufficient resolution of the current image capturing device (such as a CCD camera) such as the SMP measurement method. There is no inconvenience.
[0012]
[Patent Document 1]
JP-A-11-233434
[Patent Document 2]
WO 02/29870 pamphlet
[0013]
[Problems to be solved by the invention]
When a template matching method is adopted and automated, a frame (pattern) serving as a reference for matching is usually formed on a wafer together with a pattern in order to facilitate the template matching.
[0014]
However, in the method for determining the best exposure condition using the template matching as described above, the presence of a frame serving as a reference for template matching formed in the vicinity of the pattern in the various process conditions causes When an image is captured by a wafer alignment system of a processing method, for example, an alignment sensor of a FIA (field image alignment) system or the like, the contrast of a pattern portion is significantly reduced, and measurement may not be performed.
[0015]
As a method for improving such inconvenience, an image formation state (for example, the presence or absence of an image, etc.) of each partitioned area is determined based on a representative value (for example, a contrast value) of image data of each partitioned area without using template matching. , It may be conceivable to determine the optical characteristics of the projection optical system or the best exposure conditions. In this case, it is important to accurately detect the position of each partitioned area. One method for that is to detect the contour of the above-described rectangular area and determine the position of the required partitioned area based on a part of the contour. A method of calculating based on a design value may be adopted. By doing so, it is possible to obtain the position of an arbitrary partitioned area if only the above-described contour is detected.
[0016]
Incidentally, as the above-mentioned sensitive substrate for measurement, a wafer in which an antireflection film (ARC: Antireflection Coating) is formed as a base on the surface of bare silicon and a resist (photosensitive agent) is applied thereon is generally used. I have. However, in reality, there is a combination of various kinds of resists and an antireflection film (BARK (Bottom ARC); hereinafter, referred to as “bark”) formed as a base of the resist, and in all cases of these combinations. It is not easy to obtain the ideal signal and detect the above-mentioned outer frame accurately and reliably. As a result, depending on the combination of resist and bark, the optical characteristics of the projection optical system can be accurately measured. The probability of being unable to do so is increasing.
[0017]
The present invention has been made under such circumstances, and a first object of the present invention is to provide an optical characteristic measuring method capable of measuring the optical characteristics of a projection optical system reliably, accurately, and reproducibly in a short time. Is to provide.
[0018]
A second object of the present invention is to provide an exposure method capable of realizing highly accurate exposure.
[0019]
A third object of the present invention is to provide a device manufacturing method capable of improving the productivity of a highly integrated device.
[0020]
[Means for Solving the Problems]
The invention according to claim 1 is an optical characteristic measuring method for measuring an optical characteristic of a projection optical system (PL) for projecting a pattern on a first surface onto a second surface, wherein the projection is performed under different exposure conditions. Object (W _T ) Are divided into a plurality of divided areas (DAs) _{i, j} ) And at least a part of the outline is a straight line (DB) _n A) capturing an image of the window area (WD1, WD1, WD2) in a scanning direction substantially orthogonal to the linear portion to be detected, and detecting the position of the linear portion to be detected based on pixel data in the window area during the scanning; Utilizing the detection result of the position of the linear portion of the detection target in the second step, detecting a formation state of an image in at least a part of the plurality of divided areas using the imaging data. An optical characteristic measuring method comprising: three steps; and a fourth step of obtaining optical characteristics of the projection optical system based on a detection result in the third step.
[0021]
In this specification, “exposure conditions” include all conditions related to exposure, such as illumination conditions (including the type of mask), exposure conditions in a narrow sense such as an exposure dose on an image plane, and optical characteristics of a projection optical system. This means a broadly defined exposure condition including a setting condition of a component.
[0022]
According to this, a predetermined pattern in which at least a part of the outline includes a plurality of divided regions including a transfer region of the measurement pattern transferred onto the object via the projection optical system under different exposure conditions, and at least a part of the outline is a linear portion An area is imaged (first step).
[0023]
Then, based on the imaging data obtained by the imaging, the linear portion forming the outer frame formed by the contour of the predetermined region is set as a detection target, and the window region having a predetermined size is set in a scanning direction substantially orthogonal to the detection target linear portion. And the position of the linear portion to be detected is detected based on the pixel data in the window area during the scanning (second step).
[0024]
Here, the pixel data of the outer frame portion clearly has a different pixel value (pixel value) from the pixel data of the other portions, and thus, for example, a window corresponding to a change in the position of the window region in the scanning direction by one pixel. Based on the change in the pixel data in the area, the position of the linear portion (part of the outer frame) to be detected is reliably detected.
[0025]
Next, using a detection result of the position of the linear portion to be detected in the second step, an image formation state in at least a part of the plurality of divided areas of the plurality of divided areas is detected using imaging data. (3rd process). In this case, the design positional relationship between an arbitrary straight line portion forming the outer frame and a plurality of partitioned areas (hereinafter, also referred to as “detection target areas”) in which an image formation state is to be detected is known. By considering the positional relationship, the detection target area can be found, and for each of the found detection target areas, the image formation state is detected by performing image processing using the imaging data. can do.
[0026]
Here, the detection of the image formation state may be performed on a latent image formed on the object without developing the object, if the object is a photosensitive object, or the image may be formed. After the object is developed, the process may be performed on a resist image formed on the object, or an image (etched image) obtained by etching the object on which the resist image is formed. Here, the photosensitive layer for detecting the formation state of the image on the object is not limited to the photoresist, and may be any as long as an image (a latent image and a visible image) is formed by irradiation of light (energy). For example, the photosensitive layer may be an optical recording layer, a magneto-optical recording layer, or the like. Therefore, the object on which the photosensitive layer is formed is not limited to a wafer or a glass plate, and the optical recording layer and the magneto-optical recording layer are formed. A possible plate or the like may be used.
[0027]
For example, when detecting the image formation state with respect to a resist image, an etching image, and the like, not only a microscope such as an SEM but also an alignment detection system of an exposure apparatus, for example, an image of an alignment mark is formed on an image sensor. An alignment sensor based on an image processing method, that is, a so-called FIA (Field Image Alignment) -based alignment sensor can be used. Further, when the formation state of an image is detected for a latent image, an FIA system or the like can be used.
[0028]
In any case, as described above, the position of at least a part of the linear portion of the outer frame is reliably detected, and the detection results are used to determine the image formation state in a plurality of divided areas to be detected. For example, by detecting the contrast or the like of the image in each of the divided areas, it is possible to detect the formation state of the pattern image in a short time.
[0029]
Then, the optical characteristics of the projection optical system are obtained based on the detection result (fourth step). Here, since the optical characteristics are obtained based on the detection result using the objective and quantitative image contrast, the optical characteristics can be measured with higher accuracy and reproducibility than the conventional method.
[0030]
Further, since the measurement pattern can be made smaller as compared with the conventional method of measuring dimensions, it is possible to arrange many measurement patterns in the pattern region of the mask. Therefore, the number of evaluation points can be increased, and the interval between each evaluation point can be narrowed. As a result, the measurement accuracy of the optical characteristic measurement can be improved.
[0031]
Therefore, according to the optical characteristic measuring method of the first aspect, the optical characteristics of the projection optical system can be measured in a short time, reliably, with high accuracy and reproducibility.
[0032]
In the optical characteristic measuring method according to the first aspect, as in the optical characteristic measuring method according to the second aspect, the scanning direction may be a direction from the inside to the outside of the outer frame. In such a case, when the peak of the pixel value corresponding to the pixel data in the above-described window area is first obtained, the position surely matches the position of the outer frame, so that the outer frame detection is more reliably performed. be able to.
[0033]
In the optical characteristic measuring method according to claim 1, as in the optical characteristic measuring method according to claim 3, when the predetermined region includes at least one set of mutually parallel linear portions in an outline thereof, In the second step, based on the imaging data, a set of window regions of a predetermined size arranged at a predetermined distance according to a design value of the outer frame is formed by a set of mutually parallel sets constituting the outer frame. Of each of the linear portions of the detection target are simultaneously scanned in a scanning direction substantially orthogonal to the linear portion of the detection target, and the linear portion of the detection target is determined based on pixel data in the set of window regions during the scanning. The position can be detected.
[0034]
In each of the optical characteristic measuring methods according to claims 1 to 3, as in the optical characteristic measuring method according to claim 4, in the second step, a representative value of pixel data in the window region is set to a maximum or a minimum. Is detected as the position of the side to be detected.
[0035]
In this case, as in the optical characteristic measuring method according to claim 5, the size of the window region is such that the difference between the outer frame on which the representative value of the pixel data is a detection target and the predetermined region is different. The size may be set to be equal to or larger than a predetermined value. For example, when the variance of the pixel values corresponding to the pixel data in the window area is used as the representative value of the pixel data, the size of the window area is set so that the variance is sufficiently large on the outer frame and the variance is small in the pattern portion. May be set.
[0036]
In each of the optical characteristic measuring methods according to claims 4 and 5, various values can be used as representative values of the pixel data. For example, as in the optical characteristic measuring method according to claim 6, the pixel data May be any of the variance, standard deviation, addition value, and differential sum value of the pixel values corresponding to the pixel data in at least a part of the area including the center in the window area. .
[0037]
In each of the optical characteristic measuring methods according to the first to sixth aspects, as in the optical characteristic measuring method according to the seventh aspect, the imaging data is data of a plurality of bits larger than 2, and in the second step, Data obtained by changing lower bit data other than the higher-order plural bits including the most significant two bits from the plural-bit data to 0 or 1 may be used as the pixel data.
[0038]
In each of the optical characteristic measuring methods according to the first to seventh aspects, as in the optical characteristic measuring method according to the eighth aspect, prior to the first step, while changing at least one exposure condition, a rectangular frame-like shape is formed. A target pattern including a pattern and the measurement pattern located inside the rectangular frame-shaped pattern is arranged on the first surface, and an object arranged on the second surface side of the projection optical system is moved to a predetermined position. The method further includes a transfer step including a step of forming a plurality of partitioned regions in a matrix arrangement on the object by sequentially moving the target pattern on the object by sequentially moving at a step pitch. Can be.
[0039]
Here, the “rectangular frame-shaped pattern” is not only a pattern having a shape like a literally rectangular frame, but also a pattern in which the outline is a rectangular frame, for example, a light-shielding pattern in which the outer edge has a rectangular shape, This is a concept including an opening pattern formed inside a light-shielding pattern having a rectangular inner edge.
[0040]
In this case, as in the optical characteristic measuring method according to the ninth aspect, the step pitch may be set to be equal to or less than a distance corresponding to the size of the rectangular frame-shaped pattern. In such a case, a plurality of divided regions (regions on which the image of the measurement pattern is projected) are formed on the object in a plurality of matrix arrangements in which there is no conventional frame at the boundary between the divided regions. Is done. Further, in this case, when detecting the image formation state in at least some of the plurality of divided areas constituting the predetermined area by an image processing method, a frame line is formed between adjacent divided areas. not exist. For this reason, in the detection target area (mainly, a section area where the image of the measurement pattern remains), the contrast of the image of the measurement pattern does not decrease due to the presence of the frame line. For this reason, it is possible to obtain good data of the S / N ratio of the pattern portion and the non-pattern portion as the imaging data of the plurality of detection target regions, and use such data to perform a contrast detection method or a template matching method. The state of image formation can be accurately detected by the image processing technique.
[0041]
In the optical characteristic measuring method according to claim 8, as in the optical characteristic measuring method according to claim 10, when the predetermined area includes only the plurality of divided areas, the predetermined area is included in the transfer step. The energy of the energy beam irradiated onto the object as a part of the exposure condition such that at least a part of the plurality of divided regions located at the outermost peripheral portion is a region of overexposure. The amount can be changed. In such a case, the S / N ratio at the time of detecting the outer frame is improved, and the outer frame can be detected with high accuracy.
[0042]
In each of the optical characteristic measuring methods according to claims 1 to 10, as in the optical characteristic measuring method according to claim 11, the measurement pattern includes a multi-bar pattern and is transferred to each of the plurality of divided regions. The multi-bar pattern and the pattern adjacent thereto may be separated by a distance L or more that does not affect the contrast of the image of the multi-bar pattern by the adjacent pattern.
[0043]
Here, the multi-bar pattern means a pattern in which a plurality of bar patterns (line patterns) are arranged at predetermined intervals. Further, the pattern adjacent to the multi-bar pattern includes both a frame pattern existing at the boundary of the divided area where the multi-bar pattern is formed and a multi-bar pattern of the adjacent divided area.
[0044]
In such a case, the multi-bar pattern transferred to each partitioned area and the adjacent pattern are separated by a distance L or more that does not affect the contrast of the image of the multi-bar pattern by the adjacent pattern. An imaging signal having a good S / N ratio of the image of the multi-bar pattern transferred to the divided area can be obtained, and based on this imaging signal, an image processing method such as contrast detection or template matching is applied to each divided area. The formation state of the formed image of the multi-bar pattern can be accurately detected.
[0045]
For example, in the case of template matching, objective and quantitative correlation value information is obtained for each sectioned area, and in the case of contrast detection, objective and quantitative contrast value information is obtained for each sectioned area. In any case, by comparing the obtained information with the respective thresholds, the formation state of the image of the multi-bar pattern is converted into binarized information (information on the presence or absence of an image). It is possible to detect the formation state of the multi-bar pattern for each area with high accuracy and reproducibility.
[0046]
In each of the optical characteristic measuring methods according to claims 1 to 11, as in the optical characteristic measuring method according to claim 12, the third step is based on a detection result of a position of the linear portion of the detection target. The method may include a step of calculating a position of each of at least some of the plurality of divided regions constituting the predetermined region with reference to the detected outer frame portion.
[0047]
In each of the optical characteristic measuring methods according to the first to twelfth aspects, as in the optical characteristic measuring method according to the thirteenth aspect, the predetermined area is an area whose contour is formed only of a linear portion. Can be.
[0048]
In the optical characteristic measuring method according to the twelfth aspect, in this case, as in the optical characteristic measuring method according to the fourteenth aspect, the predetermined area is a rectangular area whose outline is composed of four linear portions, In the third step, prior to the calculating step, based on the detection result of the position of the side that is the linear portion to be detected, each of the first to fourth sides forming the outer frame of the rectangle The method further includes an outer frame calculation step of calculating at least two points on each of the above, and calculating the outer frame based on the obtained at least eight points. In the calculating step, the outer frame is calculated using array information of a known partitioned area. The position of each of the plurality of partitioned areas constituting the predetermined area may be calculated by equally dividing the internal area of the frame.
[0049]
In this case, as in the optical characteristic measuring method according to claim 15, in the outer frame calculation step, four straight lines determined based on each of the two points on the first to fourth sides are obtained. Calculating four vertices of the predetermined area which is a rectangular area as an intersection, performing a rectangle approximation by the least squares method based on the obtained four vertices, and calculating an outer frame of a rectangle of the predetermined area including rotation. It can be.
[0050]
In each of the optical characteristic measuring methods according to any one of the first to fifteenth aspects, as in the optical characteristic measuring method according to the sixteenth aspect, the image forming state in the at least some of the plurality of divided regions in the third step is changed. The detection may be performed using a representative value regarding the pixel data of each partitioned area as the determination value.
[0051]
In this case, various representative values regarding the pixel data of each partitioned area can be considered. For example, as in the optical characteristic measuring method according to claim 17, the representative value is a pixel within at least a part of the range within each partitioned area. It can be one of the sum of the pixel values corresponding to the data, the differential sum, the variance, and the standard deviation. Alternatively, as in the optical characteristic measuring method according to claim 18, the representative value is obtained by using, as an average value, an average value of pixel values in an arbitrary partitioned area where an image of the measurement pattern is not expected to remain. The obtained variance and standard deviation of the pixel value corresponding to the pixel data in at least a part of the range within each of the divided areas may be determined.
[0052]
In the present specification, the sum of the pixel values, the differential sum, the variance, or the standard deviation of the pixel values used as the representative values will be referred to as “score” or “contrast index value” as appropriate.
[0053]
In each of the optical characteristic measuring methods according to the first to fifteenth aspects, as in the optical characteristic measuring method according to the nineteenth aspect, the image forming state in the at least some of the plurality of divided regions in the third step is changed. The detection can be performed by a template matching method.
[0054]
In each of the optical characteristic measuring methods according to any one of claims 1 to 19, as in the optical characteristic measuring method according to claim 20, the exposure condition includes the position of the object and the object in the optical axis direction of the projection optical system. It may include at least one of the energy amounts of the energy beam irradiated thereon.
[0055]
In each of the optical characteristic measuring methods according to claims 1 to 20, as in the optical characteristic measuring method according to claim 21, the exposure condition includes a position of the object with respect to an optical axis direction of the projection optical system and the object. And the energy amount of the energy beam irradiated on the object, a plurality of partitioned areas in a matrix arrangement formed on the object are sequentially formed on the object via the projection optical system while changing the exposure conditions. The detection of the state of image formation in the third step is detection of the presence or absence of the image of the measurement pattern in the detection target partitioned area, and the fourth step includes detecting the transferred area of the transferred measurement pattern. Then, the best focus is obtained based on the correlation between the energy amount of the energy beam corresponding to the plurality of divided areas where the images are detected and the position of the object in the optical axis direction of the projection optical system. It may be able to determine the scum position.
[0056]
In such a case, when transferring the measurement pattern, two exposure conditions, that is, the position of the object in the optical axis direction of the projection optical system and the energy amount of the energy beam irradiated on the object are changed while changing the measurement pattern. The image is sequentially transferred to a plurality of areas on the object. As a result, the image of the measurement pattern in which the position of the object in the optical axis direction of the projection optical system at the time of transfer and the energy amount of the energy beam irradiated onto the object are different is transferred to each region on the object. Then, when detecting the image formation state, the presence or absence of the image of the measurement pattern is detected for each of the at least some of the plurality of divided areas on the object, for example, for each position in the optical axis direction of the projection optical system. As a result, for each position of the projection optical system in the optical axis direction, the energy amount of the energy beam whose image has been detected can be obtained.
[0057]
Therefore, when obtaining the optical characteristics, an approximate curve indicating the correlation between the energy amount of the energy beam from which the image is detected and the position of the projection optical system in the optical axis direction is determined. For example, the extreme value of the approximate curve is determined. To find the best focus position.
[0058]
The invention according to claim 22 is an optical characteristic measuring method for measuring an optical characteristic of a projection optical system for projecting a pattern on a first surface onto a second surface, wherein at least one exposure condition is changed. A first step of sequentially transferring a measurement pattern arranged on the first surface to a plurality of regions on an object arranged on the second surface side of the projection optical system; and An image is captured of an area including a predetermined-shaped area composed of at least a part of a plurality of divided areas of the transferred plurality of divided areas, and pixels in a predetermined direction of the predetermined-shaped area in the imaged data are captured. An optical characteristic measuring method comprising: a second step of detecting a distribution state of an added value of pixel data for each column; and a third step of obtaining an optical characteristic of the projection optical system based on the detection result.
[0059]
According to this, the measurement pattern arranged on the first surface is sequentially transferred to a plurality of regions on the object arranged on the second surface side of the projection optical system while changing at least one exposure condition ( First step). As a result, a plurality of divided areas where the measurement pattern is transferred under different exposure conditions are formed on the object.
[0060]
Next, an image is captured of an area including a predetermined-shaped area composed of at least some of the plurality of divided areas on the object onto which the measurement pattern has been transferred under different exposure conditions. A distribution state of an added value of pixel data for each pixel row in a predetermined direction in the predetermined shape area is detected (second step). Here, the predetermined direction is determined as an arrangement direction of a part of the divided regions constituting the region of the predetermined shape, and data of a distribution curve is obtained based on, for example, a distribution situation. In this case, the detection result of the image formation state (for example, presence / absence detection) of each of the above-described divided areas is substantially obtained by a simple image processing of calculating the distribution state of the added value of the pixel data for each pixel row in the predetermined direction. Data of an equivalent distribution situation can be obtained. Therefore, a simpler method with the same level of detection accuracy and reproducibility as the case of using the objective and quantitative imaging data to obtain a detection result of the image formation state (for example, presence / absence detection) of each of the above-described divided areas. Thus, the state of image formation can be detected.
[0061]
Then, the optical characteristics of the projection optical system are obtained based on the data of the distribution state (third step). Here, since the optical characteristics are obtained based on the detection result using the objective and quantitative imaging data, the optical characteristics can be measured with higher accuracy and reproducibility than the conventional method.
[0062]
The invention according to claim 23 is an exposure method for irradiating a mask with an energy beam for exposure and transferring a pattern formed on the mask onto an object via a projection optical system. Adjusting the projection optical system in consideration of the optical characteristics measured by the optical characteristic measurement method according to any one of the preceding claims; and a pattern formed on the mask via the adjusted projection optical system. Transferring the image onto the object.
[0063]
According to this, the projection optical system is adjusted so that optimal transfer can be performed in consideration of the optical characteristics of the projection optical system measured by the optical characteristic measurement methods according to claims 1 to 22, and the adjustment is performed. Since the pattern formed on the mask is transferred onto the object via the projection optical system, the fine pattern can be transferred onto the object with high accuracy.
[0064]
An invention according to claim 24 is a device manufacturing method including a lithography step, wherein the lithography step uses the exposure method according to claim 23.
[0065]
According to this, in the lithography process, a fine pattern can be accurately transferred onto an object by the exposure method according to claim 23, and as a result, the productivity (including the yield) of a highly integrated device can be improved. It can be improved.
[0066]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
[0067]
FIG. 1 shows a schematic configuration of an exposure apparatus 100 according to an embodiment suitable for carrying out the optical characteristic measuring method and the exposure method according to the present invention. The exposure apparatus 100 is a step-and-scan type reduction projection exposure apparatus (a so-called scanning stepper (also called a scanner)).
[0068]
The exposure apparatus 100 projects an illumination system IOP, a reticle stage RST holding a reticle R as a mask, and a pattern image formed on the reticle R onto a wafer W as an object coated with a photosensitive agent (photoresist). A projection optical system PL, an XY stage 20 that holds a wafer W and moves on a two-dimensional plane (within an XY plane), a drive system 22 that drives the XY stage 20, and a control system for these components. This control system is mainly composed of a main controller 28 composed of a microcomputer (or a workstation) for controlling the whole apparatus.
[0069]
As shown in FIG. 2, the illumination system IOP includes a light source 1, a beam shaping optical system 2, an energy rough adjuster 3, an optical integrator (homogenizer) 4, an illumination system aperture stop plate 5, a beam splitter 6, a first relay. A lens 7A, a second relay lens 7B, a reticle blind 8 (including a fixed reticle blind 8A and a movable reticle blind 8B in this embodiment) as a field stop, a mirror M for bending an optical path, and the like are provided. In addition, as the optical integrator 4, a fly-eye lens, a rod type (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 4, it is also referred to as a fly-eye lens 4 below.
[0070]
Here, each component of the illumination system IOP will be described. As the light source 1, a KrF excimer laser (oscillation wavelength 248 nm), an ArF excimer laser (oscillation wavelength 193 nm), or the like is used. The light source 1 is actually installed on a floor surface in a clean room in which the exposure apparatus main body is installed, or on a room (service room) having a low degree of cleanness different from the clean room, and is connected via a drawing optical system (not shown). Connected to the incident end of the beam shaping optical system 2.
[0071]
The beam shaping optical system 2 shapes the cross-sectional shape of the laser beam LB pulsed from the light source 1 so as to efficiently enter a fly-eye lens 4 provided behind the optical path of the laser beam LB. For example, it is composed of a cylinder lens, a beam expander (both not shown), and the like.
[0072]
The energy rough adjuster 3 is disposed on the optical path of the laser beam LB behind the beam shaping optical system 2. Here, a plurality of energy rough adjusters 3 (e.g. 6), ND filters (only two ND filters 32A and 32D are shown in FIG. 2) are arranged, and the rotating plate 31 is rotated by a drive motor 33, so that the incident laser beam The transmittance for LB can be switched from 100% in geometric progression in a plurality of steps. Drive motor 33 is controlled by main controller 28.
[0073]
The fly-eye lens 4 is disposed on the optical path of the laser beam LB behind the energy coarse adjuster 3, and has a large number of point light sources (light source images) on its emission-side focal plane to illuminate the reticle R with a uniform illuminance distribution. , Ie, a secondary light source. Hereinafter, the laser beam emitted from the secondary light source is referred to as “illumination light IL”.
[0074]
An illumination system aperture stop plate 5 made of a disc-shaped member is arranged near the exit-side focal plane of the fly-eye lens 4. The illumination system aperture stop plate 5 is provided at substantially equal angular intervals, for example, an aperture stop composed of a normal circular aperture, an aperture stop composed of a small circular aperture, and a small coherence factor σ value (small σ stop); A ring-shaped aperture stop (ring-shaped stop) for annular illumination, and a modified aperture stop in which a plurality of apertures are eccentrically arranged for the modified light source method (only two of these aperture stops are shown in FIG. 2). Etc.) are arranged. The illumination system aperture stop plate 5 is configured to be rotated by a driving device 51 such as a motor controlled by the main controller 28, so that one of the aperture stops is selectively placed on the optical path of the illumination light IL. Is set to Instead of the aperture stop plate 5 or in combination therewith, for example, a plurality of diffractive optical elements that are exchangeably arranged in the illumination optical system, a prism (cone prism, polyhedron, movable along the optical axis of the illumination optical system) An optical unit including at least one of a prism and a zoom optical system is disposed between the light source 1 (specifically, the energy rough adjuster 3) and the optical integrator 4, and the optical integrator 4 is a fly-eye lens. In some cases, the intensity distribution of the illumination light IL on the incident surface is varied, and when the optical integrator 4 is an internal reflection type integrator, the incident angle range of the illumination light IL on the incident surface is variable, so that the illumination optical system is changed. Of the illumination light IL (the size and shape of the secondary light source) on the pupil plane of the pupil plane, that is, the light amount loss accompanying the change of the illumination condition. Obtaining it is desirable.
[0075]
A beam splitter 6 having a small reflectance and a large transmittance is arranged on the optical path of the illumination light IL behind the illumination system aperture stop plate 5, and the reticle blind 8 is interposed on the optical path behind the first. A relay optical system including a relay lens 7A and a second relay lens 7B is arranged.
[0076]
The fixed reticle blind 8A constituting the reticle blind 8 is disposed on a plane slightly defocused from a conjugate plane with respect to the pattern plane of the reticle R, and has a rectangular opening that defines an illumination area on the reticle R. In addition, an opening having a variable position and width in a direction corresponding to the scanning direction (in the present embodiment, the Y-axis direction, which is the horizontal direction in the drawing of FIGS. 1 and 2) is provided near the fixed reticle blind 8A. A movable reticle blind 8B is provided, and at the start and end of the scanning exposure, the illumination area is further limited via the movable reticle blind 8B, thereby preventing unnecessary portions from being exposed. Further, the width of the opening of the movable reticle blind 8B is variable also in the direction corresponding to the non-scanning direction orthogonal to the scanning direction, and the width of the opening in the non-scanning direction of the illumination area is changed according to the pattern of the reticle R to be transferred onto the wafer. The width can be adjusted.
[0077]
A bending mirror M that reflects the illumination light IL that has passed through the second relay lens 7B toward the reticle R is disposed on the optical path of the illumination light IL behind the second relay lens 7B that constitutes the relay optical system. .
[0078]
On the other hand, on the light path reflected by the beam splitter 6, an integrator sensor 53 composed of a photoelectric conversion element is disposed via a condenser lens 52. As the integrator sensor 53, for example, a PIN photodiode having sensitivity in the deep ultraviolet region and having a high response frequency for detecting pulse light emission of the light source unit 1 can be used. The correlation coefficient (or correlation function) between the output DP of the integrator sensor 53 and the illuminance (intensity) of the illumination light IL on the surface of the wafer W is obtained in advance and stored in a memory inside the main controller 28. ing.
[0079]
The operation of the illumination system IOP configured as described above will be briefly described. The laser beam LB pulse-emitted from the light source 1 enters the beam shaping optical system 2 where the laser beam LB is efficiently transmitted to the rear fly-eye lens 4. After its cross-sectional shape is shaped so as to be incident well, it is incident on the energy rough adjuster 3. Then, the laser beam LB transmitted through any of the ND filters of the energy rough adjuster 3 enters the fly-eye lens 4. Thus, the above-mentioned secondary light source is formed on the exit-side focal plane of the fly-eye lens 4. The illumination light IL emitted from the secondary light source passes through one of the aperture stops on the illumination system aperture stop plate 5 and thereafter reaches a beam splitter 6 having a large transmittance and a small reflectance. The illumination light IL transmitted through the beam splitter 6 passes through the opening of the reticle blind 8 via the first relay lens 7A, passes through the second relay lens 7B, and the optical path is bent vertically downward by the mirror M. Thereafter, a rectangular illumination area on reticle R held on reticle stage RST is illuminated with a uniform illuminance distribution.
[0080]
On the other hand, the illumination light IL reflected by the beam splitter 6 is received by an integrator sensor 53 via a condenser lens 52, and a photoelectric conversion signal of the integrator sensor 53 is transmitted to a peak hold circuit and an A / D converter (not shown). The output is supplied to the main controller 28 as an output DP (digit / pulse).
[0081]
Returning to FIG. 1, the reticle stage RST is arranged below the illumination system IOP in FIG. The reticle R is mounted on the reticle stage RST, and is held by suction via a vacuum chuck (not shown). The reticle stage RST can be finely driven in a horizontal plane (XY plane) by a reticle stage driving unit (not shown), and has a predetermined stroke in a scanning direction (here, the Y-axis direction which is the horizontal direction in FIG. 1). It is designed to be scanned in a range. The position of the reticle stage RST during the scanning is measured by an external laser interferometer 14 via a movable mirror 12 fixed on the reticle stage RST, and the measured value of the laser interferometer 14 is supplied to a main controller 28. It is supposed to be. Note that the end surface of reticle stage RST may be mirror-finished to form a reflection surface of laser interferometer 14 (corresponding to the reflection surface of movable mirror 12 described above).
[0082]
The projection optical system PL is arranged below the reticle stage RST in FIG. 1 so that the direction of the optical axis AXp is the Z-axis direction orthogonal to the XY plane. Here, as the projection optical system PL, a refracting optical system which is a double-sided telecentric reduction system and includes a plurality of lens elements (not shown) having a common optical axis AXp in the Z-axis direction is used. Specific plural lenses among the lens elements are controlled by an imaging characteristic correction controller (not shown) based on a command from the main controller 28, and optical characteristics (including imaging characteristics) of the projection optical system PL, for example, magnification. , Distortion, coma, curvature of field, and the like can be adjusted.
[0083]
The projection magnification of the projection optical system PL is, for example, 1/4 (or 1/5). For this reason, when the reticle R is illuminated with the uniform illuminance by the illumination light IL as described above, the pattern of the reticle R is reduced by the projection optical system PL and projected onto the wafer W coated with the photoresist, and A reduced image of the pattern is formed in the area to be exposed on W (the area conjugate to the illumination area).
[0084]
The XY stage 20 is actually composed of a Y stage that moves on a base (not shown) in the Y-axis direction and an X stage that moves on the Y stage in the X-axis direction. Are representatively shown as an XY stage 20. A wafer table 18 is mounted on the XY stage 20, and a wafer W is held on the wafer table 18 by vacuum suction or the like via a wafer holder (not shown).
[0085]
The wafer table 18 minutely drives a wafer holder that holds the wafer W in the Z-axis direction and the tilt direction with respect to the XY plane, and is also called a Z-tilt stage. A movable mirror 24 is provided on the upper surface of the wafer table 18, and the position of the wafer table 18 in the XY plane is measured by projecting a laser beam onto the movable mirror 24 and receiving the reflected light. A laser interferometer 26 is provided to face the reflecting surface of the movable mirror 24. Actually, the moving mirror is provided with an X moving mirror having a reflecting surface orthogonal to the X axis and a Y moving mirror having a reflecting surface orthogonal to the Y axis. Although an X laser interferometer for measuring the direction position and a Y laser interferometer for measuring the Y direction position are provided, these are representatively shown as a movable mirror 24 and a laser interferometer 26 in FIG. The X laser interferometer and the Y laser interferometer are multi-axis interferometers having a plurality of measurement axes, and in addition to the X and Y positions of the wafer table 18, rotation (yaw (θz rotation which is rotation about the Z axis)) , Pitching (θx rotation around the X axis) and rolling (θy rotation around the Y axis) can also be measured. Therefore, in the following description, it is assumed that the position of the wafer table 18 in the directions of five degrees of freedom of X, Y, θz, θy, and θx is measured by the laser interferometer 26. Further, instead of the movable mirror 24, the end surface of the wafer table 18 may be mirror-finished and used as a reflection surface.
[0086]
The measurement value of the laser interferometer 26 is supplied to a main controller 28, and the main controller 28 controls the XY stage 20 via the drive system 22 based on the measurement value of the laser interferometer 26, so that the wafer table 18 (Including θz rotation) in the XY plane is controlled.
[0087]
Further, the position and the amount of tilt in the Z-axis direction of the surface of the wafer W can be determined, for example, from the oblique incidence type multi-point focal position detection system having the light transmission system 50a and the light reception system 50b disclosed in Japanese Patent Application Laid-Open No. 6-283403. Is measured by the focus sensor AFS. The measurement value of the focus sensor AFS is also supplied to the main controller 28. The main controller 28 moves the wafer table 18 via the drive system 22 in the Z direction, the θx direction, and the θy based on the measurement value of the focus sensor AFS. In the direction of the optical axis of the projection optical system PL to control the position and inclination of the wafer W.
[0088]
In this way, the position and orientation of the wafer W in the directions of five degrees of freedom of X, Y, Z, θx, and θy are controlled via the wafer table 18. The remaining error of θz (yaw) is corrected by rotating at least one of reticle stage RST and wafer table 18 based on yaw information of wafer table 18 measured by laser interferometer 26.
[0089]
On the wafer table 18, a reference plate FP whose surface is the same as the surface of the wafer W is fixed. On the surface of the reference plate FP, various reference marks including a reference mark used for so-called baseline measurement of an alignment detection system described later are formed.
[0090]
Further, in the present embodiment, an off-axis type alignment detection system AS as a mark detection system for detecting an alignment mark formed on the wafer W is provided on a side surface of the projection optical system PL. As an example of the alignment detection system AS, a kind of an image processing type alignment sensor of an image processing method of illuminating a mark with broadband (broadband) light such as a halogen lamp and measuring a mark position by processing the mark image. The FIA (Field Image Alignment) system is used, and it is possible to measure the positions of the reference marks on the reference plate FP and the alignment marks on the wafer in the X and Y two-dimensional directions.
[0091]
The alignment control device 16 performs A / D conversion of information DS from the alignment detection system AS, and performs arithmetic processing on the digitized waveform signal to detect a mark position. This result is supplied from the alignment control device 16 to the main control device 28.
[0092]
The alignment detection system AS includes, in addition to the above-described FIA system, an alignment sensor that irradiates a target with coherent detection light and detects scattered light or diffracted light generated from the target, and two diffraction lights generated from the target. Various alignment sensors such as an alignment sensor that detects light by interference with light (for example, the same order) can be used alone or in an appropriate combination.
[0093]
Further, in the exposure apparatus 100 of the present embodiment, although not shown, the reticle R is disposed above the reticle R via a projection optical system PL disclosed in, for example, JP-A-7-176468. A pair of reticle alignments composed of a TTR (Through The Reticle) alignment system using light of an exposure wavelength for simultaneously observing a reticle mark or a reference mark on the reticle stage RST (both not shown) and a mark on the reference plate FP. A detection system is provided. The detection signals of these reticle alignment detection systems are supplied to main controller 28 via alignment controller 16.
[0094]
Next, an example of a reticle used for measuring the optical characteristics of the projection optical system according to the present invention will be described.
[0095]
FIG. 3 shows a reticle R used for measuring the optical characteristics of the projection optical system. _T An example is shown. FIG. 3 shows a reticle R _T 2 is a plan view as viewed from a pattern surface side (a lower surface side in FIG. 1). As shown in FIG. 3, reticle R _T In the figure, a pattern area PA made of a light shielding member such as chrome is formed in the center of a glass substrate 42 as a substantially rectangular mask substrate. The center of the pattern area PA (that is, the reticle R _T At the four corners inside a virtual rectangular area IAR ′ located at the center of the pattern area PA in the Y-axis direction (corresponding to the reticle center), for example, a 20 μm square aperture pattern (transmission area). ) AP ₁ ~ AP ₅ Is formed, and a measurement pattern MP composed of a line and space pattern (L / S pattern) is formed at the center of each of the opening patterns. ₁ ~ MP ₅ Are formed respectively. Note that the rectangular area IAR ′ has a size and a shape that substantially match the illumination area IAR described above.
[0096]
Measurement pattern MP _n In each of (n = 1 to 5), for example, the X-axis direction is a periodic direction, and five line patterns having a line width of about 1.3 μm and a length of about 12 μm are arranged at a pitch of about 2.6 μm. It is composed of a multi-bar pattern. For this reason, in the present embodiment, the opening pattern AP _n Each opening pattern AP having the same center as _n Measurement pattern MP in a reduced area of about 60% of _n Are arranged respectively.
[0097]
A pair of reticle alignment marks RM1 and RM2 are formed on both sides of the pattern area PA passing through the reticle center in the X-axis direction.
[0098]
Next, a method for measuring the optical characteristics of the projection optical system PL in the exposure apparatus 100 of the present embodiment will be described with reference to FIGS. 4 and 5, which show simplified processing algorithms of the CPU in the main controller 28, and Description will be made with reference to other drawings as appropriate.
[0099]
First, in step 402 of FIG. 4, the reticle R is placed on the reticle stage RST via a reticle loader (not shown). _T Is loaded, and the wafer W is loaded through a wafer loader (not shown). _T Is loaded on the wafer table 18.
[0100]
In the next step 404, reticle R _T Preparatory work such as alignment with the projection optical system PL and setting of a reticle blind is performed. Specifically, first, the midpoint of a pair of fiducial marks (not shown) formed on the surface of the fiducial plate FP provided on the wafer table 18 substantially coincides with the optical axis of the projection optical system PL. The XY stage 20 is moved via the drive system 22 while monitoring the measurement result of the laser interferometer 26. Then, reticle R _T The position of reticle stage RST is adjusted via a reticle stage drive unit (not shown) based on the measurement value of laser interferometer 14 so that the center of reticle (reticle center) substantially matches the optical axis of projection optical system PL. . At this time, for example, the relative position between the reticle alignment marks RM1 and RM2 and the corresponding reference mark is detected by the reticle alignment detection system (not shown) via the projection optical system PL. A reticle stage driving unit (not shown) based on the detection result of the relative position detected by the reticle alignment detection system, so that the relative position error between the reticle alignment marks RM1 and RM2 and the corresponding reference mark is minimized. The position of the reticle stage RST in the XY plane is adjusted via. Thereby, the reticle R _T (Reticle center) exactly coincides with the optical axis of the projection optical system PL, and the reticle R _T Also accurately coincides with the coordinate axes of the rectangular coordinate system defined by the length measurement axes of the laser interferometer 26.
[0101]
In addition, for example, the irradiation area of the illumination light IL is in the reticle R _T The opening width of the movable reticle blind 8B in the non-scanning direction in the illumination system IOP is adjusted so as to substantially coincide with the pattern area PA.
[0102]
When the predetermined preparation work is completed in this way, the process proceeds to the next step 406, in which a flag F for determining the end of exposure of the first area described later is set (F ← 1).
[0103]
In the next step 408, the target value of the exposure energy amount is initialized. That is, the initial value “1” is set in the counter j and the target value P of the exposure energy amount is set. _j To P ₁ (J ← 1). In the present embodiment, the counter j sets the target value of the exposure energy amount and sets the wafer W during the exposure. _T Is also used to set the movement target position in the row direction. In the present embodiment, the wafer W _T A positive resist is applied to the surface of the substrate. For example, the exposure energy amount is set to P around a known optimum exposure amount for the positive resist. ₁ From P in ΔP increments _N (For example, N = 23) (P _j = P ₁ ~ P ₂₃ ).
[0104]
In the next step 410, the wafer W _T The target value of the focus position (position in the Z-axis direction) is initialized. That is, the initial value “1” is set in the counter i and the wafer W _T Focus position target value Z _i To Z ₁ (I ← 1). In the present embodiment, the counter i is _T The target value of the focus position is set, and the wafer W at the time of exposure is set. _T Is also used to set the movement target position in the column direction. In the present embodiment, for example, the wafer W is centered on a known best focus position (design value or the like) related to the projection optical system PL. _T The focus position of ₁ To Z in ΔZ increments _M (For example, M = 13) (Z _i = Z ₁ ~ Z _Thirteen ).
[0105]
Therefore, in the present embodiment, the wafer W in the optical axis direction of the projection optical system PL is _T Position and wafer W _T While changing the amount of energy of the illumination light IL illuminated above, the measurement pattern MP _n (N = 1 to 5) for the wafer W _T N × M (for example, 23 × 13 = 299) exposures are performed for sequential transfer to the upper side. Wafer W corresponding to each evaluation point in the field of view of projection optical system PL _T Upper area (hereinafter referred to as “evaluation point corresponding area”) DB ₁ ~ DB ₅ Of the first area DC to be described later ₁ ~ DC ₅ (See FIGS. 7 and 8) include N × M measurement patterns MP. _n Will be transferred.
[0106]
Here, the evaluation point corresponding area DB _n First area DC in (n = 1 to 5) _n In the present embodiment, each evaluation point corresponding area DB _n Is the above-mentioned N × M measurement patterns MP _n Is transferred to a rectangular first area DC _n And a rectangular frame-shaped second region DD surrounding the first region. _n (See FIG. 8).
[0107]
In addition, this evaluation point corresponding area DB _n (That is, the first area DC _n ) Correspond to a plurality of evaluation points whose optical characteristics are to be detected in the field of view of the projection optical system PL.
[0108]
Here, although the description is before and after, for convenience, the measurement pattern MP _n Wafer W to which is transferred _T Each first area DC above _n Will be described with reference to FIG. As shown in FIG. 6, in the present embodiment, M × N (= 13 × 23 = 299) virtual partitioned areas DA arranged in a matrix of M rows and N columns (13 rows and 23 columns) _{i, j} (I = 1 to M, j = 1 to N) and the measurement pattern MP _n Are transferred respectively, and these measurement patterns MP _n Are respectively transferred to the M × N divided areas DA _{i, j} 1st area DC which consists of _n Is wafer W _T Formed on top. Note that the virtual partitioned area DA _{i, j} Are arranged such that the + X direction is the row direction (j increasing direction) and the + Y direction is the column direction (i increasing direction), as shown in FIG. The subscripts i and j and M and N used in the following description have the same meaning as described above.
[0109]
Returning to FIG. 4, in the next step 412, the wafer W _T Each evaluation point corresponding area DB above _n Virtual partitioned area DA within _{i, j} (Here DA _1,1 (See FIG. 7)) _n XY stage 20 (wafer W) via drive system 22 while monitoring the measurement value of laser interferometer 26 at the positions where the images of _T Move).
[0110]
In the next step 414, the wafer W _T Target value Z at which the focus position is set _i (In this case Z ₁ The wafer table 18 is minutely driven in the Z-axis direction and the tilt direction while monitoring the measurement value from the focus sensor AFS so as to coincide with (2).
[0111]
In the next step 416, exposure is performed. At this time, the wafer W _T The target value (in this case, P ₁ The exposure amount control is performed so that As a method of controlling the amount of exposure energy, for example, the following first to third methods can be used alone or in an appropriate combination.
[0112]
That is, as a first method, the energy amount of the illumination light IL given to the image plane (wafer plane) by maintaining the pulse repetition frequency constant and changing the transmittance of the laser beam LB using the energy coarse adjuster 3 To adjust. As a second method, by maintaining the pulse repetition frequency constant and giving an instruction to the light source 1 to change the energy per pulse of the laser beam LB, the illumination light IL given to the image plane (wafer plane) is changed. Adjust the amount of energy. As a third method, the transmittance of the laser beam LB and the energy per pulse of the laser beam LB are kept constant, and the illumination light IL applied to the image plane (wafer plane) by changing the pulse repetition frequency. Adjust the energy amount of.
[0113]
As a result, as shown in FIG. _T Each first area DC above _n Area DA _1,1 Each for measurement pattern MP _n And opening pattern AP _n Is transferred.
[0114]
Referring back to FIG. 4, when the exposure in step 416 is completed, it is determined in step 418 whether the flag F is set, that is, whether F = 1. In this case, since the flag F is set in the above-described step 406, the determination here is affirmed, and the process proceeds to the next step 420.
[0115]
In step 420, the wafer W _T The target value of the focus position is Z _M By judging whether or not this is the case, it is determined whether or not exposure in a predetermined Z range has been completed. Here, the first target value Z ₁ Since the exposure in the step (b) is only completed, the process proceeds to step 422, where the counter i is incremented by one (i ← i + 1), and the wafer W _T Is added to the target value of the focus position (Z _i ← Z + ΔZ). Here, the target value of the focus position is Z ₂ (= Z ₁ + ΔZ), and then returns to step 412. In this step 412, the wafer W _T Each first area DC above _n Area DA _2,1 Measurement pattern MP _n Wafers W at the positions where the images of _T The XY stage 20 is moved in a predetermined direction (in this case, the −Y direction) within the XY plane by a predetermined step pitch SP so that is positioned. Here, in the present embodiment, the above-described step pitch SP is determined by each opening pattern AP. _n Wafer W _T The size is set to about 5 μm, which substantially matches the size of the projected image above. The step pitch SP is not limited to about 5 μm, but is 5 μm, that is, each opening pattern AP. _n Wafer W _T It is desirable that the size be equal to or smaller than the size of the above projected image. The reason will be described later.
[0116]
In the next step 414, the wafer W _T Is the target value (in this case, Z ₂ The wafer table 18 is step-moved by ΔZ in the direction of the optical axis AXp so as to coincide with the above. _T Each first area DC above _n Area DA _2,1 Measurement pattern MP _n And opening pattern AP _n Are transferred respectively. However, the step pitch SP is equal to the opening pattern AP. _n Wafer W _T Each of the first regions DC _n Area DA _2,1 And partition area DA _2,1 Pattern AP at the boundary with _n There is no frame formed by a part of the image.
[0117]
Thereafter, until the determination in step 420 is affirmed, that is, the wafer W set at that time is set. _T The target value of the focus position is Z _M Until it is determined that, the loop processing (including the determination) of steps 418 → 420 → 422 → 412 → 414 → 416 is repeated. Thereby, the wafer W _T Each first area DC above _n Area DA _{i, 1} (I = 3 to M) for the measurement pattern MP _n And opening pattern AP _n Are respectively transcribed. However, also in this case, no border line exists at the boundary between adjacent partitioned areas for the same reason as described above.
[0118]
On the other hand, the partition area DA _{M, 1} Is completed, and if the determination in step 420 is affirmative, the process proceeds to step 424 where the target value of the exposure energy amount set at that time is P _N It is determined whether or not this is the case. Here, the target value of the exposure energy amount set at that time is P ₁ Therefore, the determination in step 424 is denied, and the process proceeds to step 426.
[0119]
In step 426, the counter j is incremented by 1 (j ← j + 1), and ΔP is added to the target value of the exposure energy amount (P _j ← P _j + ΔP). Here, the target value of the exposure energy amount is P ₂ (= P ₁ + ΔP), and then returns to step 410.
[0120]
Thereafter, in step 410, the wafer W _T After the target value of the focus position is initialized, the loop processing (including the determination) of steps 412 → 414 → 416 → 418 → 420 → 422 is repeated. The processing of this loop is performed until the determination in step 420 is affirmed, that is, the target value P of the exposure energy amount. ₂ Predetermined wafer W _T Focus position range (Z ₁ ~ Z _M This is repeated until the exposure for ()) is completed. Thereby, the wafer W _T Each first area DC above _n Area DA _{i, 2} (I = 1 to M) for the measurement pattern MP _n And opening pattern AP _n Are respectively transcribed. However, also in this case, no border line exists at the boundary between adjacent partitioned areas for the same reason as described above.
[0121]
On the other hand, the target value P of the exposure energy amount ₂ Predetermined wafer W _T Focus position range (Z ₁ ~ Z _M When the exposure of ()) is completed, the determination in step 420 is affirmed, and the flow shifts to step 424 where the target value of the set exposure energy amount is P. _N It is determined whether or not this is the case. In this case, the target value of the exposure energy amount is P ₂ Therefore, the determination in step 424 is denied, and the process proceeds to step 426. In step 426, the counter j is incremented by one, and ΔP is added to the target value of the exposure energy amount (P _j ← P _j + ΔP). Here, the target value of the exposure energy amount is P ₃ After that, the process returns to step 410. Thereafter, the same processing (including determination) as above is repeated.
[0122]
Thus, the range of the predetermined exposure energy amount (P ₁ ~ P _N When the exposure of ()) is completed, the determination in step 424 is affirmed, and the flow shifts to step 428 in FIG. Thereby, the wafer W _T Each first area DC above _n As shown in FIG. 7, N × M (23 × 13 = 299 as an example) measurement patterns MP with different exposure conditions _n Is formed. In practice, as described above, the wafer W _T Measurement pattern MP on top _n When N × M (for example, 23 × 13 = 299) divided areas in which transfer images (latent images) are formed, each first area DC _n Is formed, but in the above description, the first region DC is used to make the description easy to understand. _n Is the wafer W _T An explanation method as if it is above is adopted.
[0123]
In step 428 in FIG. 5, it is determined whether the flag F has been set, that is, whether F = 0. Here, since the flag F is set in the step 406, the determination in the step 428 is denied, and the process shifts to the step 430 to increment the counters i and j by 1 (i ← i + 1, j ← j + 1). . As a result, the counters i = M + 1 and J = N + 1, and the area to be exposed is divided area DA shown in FIG. _{M + 1, N + 1} = DA _14,24 It becomes.
[0124]
In the next step 432, the flag F is lowered (F ← 0), and the process returns to step 412 in FIG. In step 412, the wafer W _T Each first area DC above _n Area DA _{M + 1, N + 1} = DA _14,24 Measurement pattern MP _n Wafers W at the positions where the images of _T And proceeds to the next step 414. However, at this time, the wafer W _T The target value of the focus position is Z _M Therefore, the process proceeds to step 416 without performing any operation, and the partition area DA _14,24 Is exposed. At this time, the exposure energy amount P is the maximum exposure amount P _N Exposure is performed.
[0125]
In the next step 418, since the flag F = 0, steps 420 and 424 are skipped, and the process proceeds to step 428. In this step 428, it is determined whether or not the flag F has been lowered. Here, since F = 0, this determination is affirmative, and the flow proceeds to step 434.
[0126]
In step 434, it is determined whether or not the counter i = M + 1 and the counter j> 0 are satisfied. At this time, since i = M + 1 and j = N + 1, the determination here is affirmed, and step 436 is performed. Then, the counter j is decremented by 1 (j ← j−1), and the process returns to step 412. Thereafter, the loop processing (including the determination) of steps 412 → 414 → 416 → 418 → 428 → 434 → 436 is repeated until the determination in step 434 is denied. Thus, the partition area DA shown in FIG. _14,23 From DA _14,0 Exposure at the maximum exposure amount described above is performed sequentially.
[0127]
And the partition area DA _14,0 When the exposure for is completed, i = M + 1 (= 14) and j = 0, so the determination in step 434 is denied, and the flow shifts to step 438. In this step 438, it is determined whether or not the counter i> 0 and the counter j = 0 are satisfied. At this time, since i = M + 1, j = 0, the determination here is affirmed, and step 440 is performed. Then, the counter i is decremented by 1 (i ← i−1), and the process returns to step 412. Thereafter, the loop processing (including the determination) of steps 412 → 414 → 416 → 418 → 428 → 434 → 438 → 440 is repeated until the determination in step 438 is denied. Thereby, the partition area DA of FIG. _13,0 From DA _0,0 Exposure is performed sequentially with the maximum exposure amount until the above.
[0128]
And the partition area DA _0,0 When the exposure for is completed, i = 0 and j = 0, so the determination in step 438 is denied, and the flow shifts to step 442. In this step 442, it is determined whether or not the counter j = N + 1. At this time, since j = 0, the determination here is denied, and the process proceeds to step 444 to increment the counter j. (J ← j + 1), and the process returns to step 412. Thereafter, the loop processing (including the determination) of steps 412 → 414 → 416 → 418 → 428 → 434 → 438 → 442 → 444 is repeated until the determination in step 442 is affirmed. Thereby, the partition area DA of FIG. _0,1 From DA _0,24 Exposure is performed sequentially with the maximum exposure amount until the above.
[0129]
And the partition area DA _0,24 Is completed, j = N + 1 (= 24), so the determination in step 442 is affirmative, and the flow shifts to step 446. In this step 446, it is determined whether or not the counter i = M. At this time, since i = 0, the determination here is denied, and the routine proceeds to step 448, where the counter i is incremented by one. (I ← i + 1), and the process returns to step 412. Thereafter, the loop processing (including the determination) of steps 412 → 414 → 416 → 418 → 428 → 434 → 438 → 442 → 446 → 448 is repeated until the determination in step 446 is affirmed. Thereby, the partition area DA of FIG. _1,24 From DA _13,24 Exposure is performed sequentially with the maximum exposure amount until the above.
[0130]
And the partition area DA _13,24 Is completed, i = M (= 23), so that the determination in step 446 is affirmative, whereby the wafer W _T Is completed. Thereby, the wafer W _T Above, a rectangular (rectangular) first area DC as shown in FIG. _n And a rectangular frame-shaped second region DD surrounding the second region DD _n Evaluation point corresponding area DB consisting of _n (N = 1 to 5) latent images are formed. In this case, the second area DD _n Are clearly overexposed (overdose).
[0131]
Thus, the wafer W _T When the exposure for is completed, the process proceeds to step 450 in FIG. In this step 450, the wafer W is transferred via a wafer unloader (not shown). _T Is unloaded from above the wafer table 18 and the wafer W is _T Is transported to a coater / developer (not shown) connected inline to the exposure apparatus 100.
[0132]
Wafer W for the above coater / developer _T After the transfer of the wafer W, the process proceeds to step 452, where the wafer W _T Wait for the development to finish. During the waiting time in this step 452, the wafer W _T Is developed. Upon completion of this development, the wafer W _T Above, a rectangular (rectangular) first area DC as shown in FIG. _n And a rectangular frame-shaped second region DD surrounding the second region DD _n Evaluation point corresponding area DB consisting of _n (N = 1 to 5) resist image is formed, and the wafer W on which the resist image is formed _T Is a sample for measuring the optical characteristics of the projection optical system PL. FIG. 9 shows the wafer W _T Evaluation point corresponding area DB formed above ₁ Is shown as an example.
[0133]
In FIG. 9, the evaluation point corresponding area DB ₁ Is (N + 2) × (M + 2) = 25 × 15 = 375 divided areas DA _{i, j} (I = 0 to M + 1, j = 0 to N + 1), and is illustrated as if a resist image of a partition frame exists between adjacent partitioned areas. This is done for clarity. However, in practice, there is no resist image of a partition frame between adjacent partitioned areas. By eliminating the frame in this manner, it is possible to prevent a decrease in the contrast of the pattern portion due to interference caused by the frame when capturing an image using an FIA-based alignment sensor, which has conventionally been a problem. For this reason, in the present embodiment, the above-described step pitch SP is set to each opening pattern AP. _n Wafer W _T The size was set to be smaller than the size of the projected image above.
[0134]
In this case, the measurement pattern MP composed of a multi-bar pattern between adjacent partitioned areas is used. _n Let L be the distance between the resist images of FIG. _n The other measurement pattern MP _n The distance is set to such an extent that the presence of the image does not affect the image. This distance L is determined by the resolution of an imaging device (in this embodiment, an alignment detection system AS (an FIA alignment sensor)) for imaging a partitioned area. _f , The contrast of the image of the measurement pattern _f , The process factor determined by the process including the reflectivity and the refractive index of the resist _f , The detection wavelength of the alignment detection system AS (the alignment sensor of the FIA system) is λ _f If, for example, L = f (C _f , R _f , P _f , Λ _f ).
[0135]
Note that the process factor P _f Affects the image contrast, so the function L ′ = f ′ (C _f , R _f , Λ _f ) May be used to define the distance L.
[0136]
Further, as can be seen from FIG. 9, the rectangular (rectangular) first region DC ₁ Frame-shaped second area DD surrounding ₁ No pattern remaining area is found. This is, as described above, the second area DD. ₁ This is because the exposure energy that causes overexposure during the exposure of each of the divided regions that constitutes. The reason for this is to improve the contrast of the outer frame portion at the time of detecting the outer frame, which will be described later, and to increase the S / N ratio of the detection signal.
[0137]
In the waiting state of the step 452, the wafer W is notified by a notification from the control system of the coater / developer (not shown). _T Is completed, the process proceeds to step 454, where an instruction is issued to a wafer loader (not shown), and the wafer W _T Is loaded onto the wafer table 18 again, and the process proceeds to a subroutine for calculating the optical characteristics of the projection optical system in step 456 (hereinafter, also referred to as an “optical characteristic measurement routine”).
[0138]
In this optical characteristic measurement routine, first, in step 502 of FIG. _T Upper evaluation point corresponding area DB _n Wafer W at a position where the resist image can be detected by alignment detection system AS. _T To move. This movement, that is, positioning, is performed by controlling the XY stage 20 via the drive system 22 while monitoring the measurement value of the laser interferometer 26. Here, it is assumed that the counter n has been initialized to n = 1. Therefore, here, the wafer W shown in FIG. _T Upper evaluation point corresponding area DB ₁ Wafer W at a position where the resist image can be detected by alignment detection system AS. _T Is positioned. In the following description of the optical characteristic measurement routine, the evaluation point corresponding area DB _n The resist image of “Evaluation point corresponding area DB” _n ".
[0139]
In the next step 504, the wafer W _T Upper evaluation point corresponding area DB _n (Here, DB ₁ ) Is captured using the alignment detection system AS, and the captured data is captured. The alignment detection system AS divides the resist image into pixels of an image pickup device (CCD or the like) of its own, and converts the density of the resist image corresponding to each pixel into 8-bit digital data (pixel data). 28. That is, the imaging data is composed of a plurality of pixel data. Here, it is assumed that the value of the pixel data increases as the density of the resist image increases (closes to black).
[0140]
In the next step 506, the evaluation point corresponding area DB from the alignment detection system AS _n (Here, DB ₁ The image data of the resist image formed in the step (1) is arranged and an image data file is created.
[0141]
In the next steps 508 to 516, the evaluation point corresponding area DB _n (Here, DB ₁ ) Is detected. FIGS. 14 (A) to 14 (C), FIGS. 15 (A) and 15 (B) show states of outer frame detection in order. In these figures, the code DB _n The rectangular area marked with is an evaluation point corresponding area DB for which an outer frame is to be detected. _n Is equivalent to
[0142]
First, in step 508, the evaluation point corresponding area DB _n Approximate positions of the upper side and lower side of are detected.
[0143]
That is, in this step 508, as shown in FIG. _n (Here, DB ₁ ) Based on the design value of the evaluation point corresponding area DB _n (Here, DB ₁ ), A detection area having a length SL in the Y-axis direction (SL is, for example, 20 μm) and a length B in the X-axis direction (B is, for example, 10 μm) including the design positions of the upper side and the lower side are set. The window regions WD1 and WD2 are scanned (scanned) in the −Y direction (direction substantially perpendicular to the upper side and the lower side of the outer frame) as indicated by arrows A1 and A2, respectively. The window regions WD1 and WD2 have a length T in the scanning direction (T is, for example, 3 μm) and a length B in the non-scanning direction. The interval LL between the window regions WD1 and WD2 is determined by the evaluation point corresponding region DB. _n It is set equal to the design distance between the upper side and the lower side.
[0144]
During the scanning of the window regions WD1 and WD2, the representative value of the pixel data in the window regions WD1 and WD2, for example, the added value of the variance (or standard deviation) of the pixel values in the window regions WD1 and WD2 is calculated. , At each predetermined sampling interval, for example, every time the position of the window area WD1 or WD2 in the scanning direction changes by one pixel, the calculation result is stored in the memory in association with the position of the window area WD1 or WD2 in the scanning direction. Remember. Then, after the end of the scan, the positions in the scanning direction (the positions in the Y-axis direction) of the window regions WD1 and WD2 in which the above-described calculation result is maximum are stored in the evaluation point corresponding region DB _n (In this case, the evaluation point corresponding area DB ₁ ) Is detected as the approximate position of the upper and lower sides. This is because, when the outer frame portion is completely included in the window regions WD1 and WD2, the variance and the standard deviation of the pixel values in each window region are the largest, and one of the window regions WD1 is in the outer frame. Since the scanning is performed from the outside to the inside and the other window area WD2 is scanned from the inside to the outside of the outer frame, the sum of the variances (or standard deviations) of the pixel values in the window areas WD1 and WD2 is maximum. This is because there is no doubt that the positions of the window regions WD1 and WD2 in the scanning direction are near the positions of the upper side and the lower side of the outer frame.
[0145]
However, it is not always necessary to scan two window regions at the same time, and the detection regions similar to those in FIG. 14A may be individually set, and the window regions WD1 and WD2 may be separately scanned. In this case, for each of the window regions WD1 and WD2, the position in the scanning direction (the position in the Y-axis direction) of the window regions WD1 and WD2 in which the variance (or standard deviation) of the pixel values in the region is maximum is evaluated. Point corresponding area DB _n (In this case, the evaluation point corresponding area DB ₁ ) May be detected as approximate positions of the upper side and the lower side. In this case, in this embodiment, as described above, the evaluation point corresponding area DB _n Overexposed second area DD _n Considering the existence of a region (that is, a region where no pattern remains), both of the window regions WD1 and WD2 are converted to the evaluation point corresponding region DB as shown in FIG. _n (In this case, the evaluation point corresponding area DB ₁ The scanning may be performed from inside to outside with respect to the outer frame of ()). In this way, the position where the peak of the variance (or standard deviation) of the pixel value is first detected during the scan can be detected as the approximate position of the upper side and the lower side of the outer frame. The reason is that immediately after the start of scanning, both the window areas WD1 and WD2 have the overexposed second area DD. _n , The variance (or standard deviation) of the pixel values in the window region is almost zero, and then remains until the window region is overlaid with the outer frame. This is because the variance (or standard deviation) increases when the window region reaches the outer frame, and the variance (or standard deviation) peaks when the outer frame is completely included in the window region. By doing so, the time required for detecting the position of the outer frame can be reduced.
[0146]
Further, as shown in FIG. 16, a window region WD3, which is the same size as the window regions WD1 and WD2 and is rotated by 90 °, is scanned from left to right in FIG. 16 as indicated by an arrow A3. The evaluation point corresponding area DB ₁ May be detected in the same manner as described above. In addition, upon detecting the approximate position of at least one of the upper side, the lower side, and the right side of the outer frame, the window area is scanned at a plurality of points on the side in the same manner as described above, and a plurality of points on the same side are detected. Of course, it is also possible to detect the approximate position.
[0147]
In any case, the size of the window regions WD1 and WD2 is determined by the variance (or standard deviation) of the pixel values in the window region during the scan, and the evaluation point corresponding region DB. ₁ It is important to determine the difference based on a simulation or an experiment or the like so that the difference between the outer frame and the other place becomes a predetermined value or more. In the present embodiment, the above-described size is determined in this manner. In the present embodiment, the window regions WD1 to WD3 whose longitudinal directions are substantially parallel to the respective sides of the outer frame are set. However, these window regions WD1 to WD3 correspond to directions substantially orthogonal to the respective sides. It may be a rectangular area that is set in the longitudinal direction.
[0148]
FIGS. 17A to 18D show examples of the results of experiments performed by the inventor. FIG. 17A shows one evaluation point corresponding area DB _k 4 shows four detection areas set to detect the four sides of the outer frame.
[0149]
FIG. 17B shows pixels obtained by scanning a set of window regions from the right to the left in FIG. 17A (from the + X side to the −X side) within the simultaneously set detection regions. The sum signal of the variance signals of the values is shown with the horizontal axis as the X position. Also, in FIG. 17C, similarly to the present embodiment, a set of window regions is set in a detection region set simultaneously from top to bottom (from + Y side to −Y side) in FIG. 17A. , The sum signal of the variance signals of the pixel values obtained when scanning is performed is shown with the horizontal axis as the Y position.
[0150]
In FIG. 18A, with the upper side of the outer frame as a detection target, the window area is set from bottom to top (from −Y side to + Y side) in FIG. The variance signal of the pixel value obtained at the time of scanning is shown with the horizontal axis as the Y position. Similarly, in FIG. 18B, the window area is set from the bottom to the top (from −Y side to + Y side) in FIG. The variance signal of the pixel value obtained when scanning is performed is shown with the horizontal axis as the Y position.
[0151]
Also, in FIG. 18C, the window area is set from the right side to the left side (from + X side to −X side) in FIG. The variance signal of the pixel value obtained at the time of scanning is shown with the horizontal axis as the X position. Similarly, FIG. 18 (D) shows the window region from left to right (from −X side to + X side) in FIG. 17 (A) with the left side of the outer frame as a detection target, The variance signal of the pixel value obtained when scanning is performed is shown with the horizontal axis as the X position.
[0152]
For example, in the case of FIG. 18A, since the scanning direction is set to the direction in which the window region moves from the inside to the outside of the outer frame, the position of the first peak of the dispersion signal is set to the outside. Since the position substantially matches the position of the frame, this position can be detected as the approximate position of the outer frame. On the other hand, in the case of FIG. 18B, since the scanning direction is set to the direction in which the window region moves from the outside to the inside of the outer frame, the position of the first peak of the dispersion signal is set. Does not match the approximate position of the outer frame, the position cannot be detected as the approximate position of the outer frame. As described above, from the actual experimental results, as described above, both of the window regions WD1 and WD2 are set in the evaluation point corresponding region DB. _n It is supported that scanning from the inside to the outside with respect to the outer frame can detect the approximate position of the outer frame in a shorter time.
[0153]
The inventor of the present invention has formed an evaluation point corresponding area on various wafers having different combinations of a bark formed as a base on a wafer and a resist applied thereon, in the same procedure as described above, and then formed the window described above. An experiment was performed on the approximate position detection (rough detection) of the outer frame of the evaluation point corresponding area using the area scanning method. In almost all cases, it was confirmed that the approximate position of the outer frame of the evaluation point corresponding area could be detected without any problem. Was done.
[0154]
As described above, the evaluation point corresponding area DB _n (In this case, the evaluation point corresponding area DB ₁ When the approximate positions of the upper and lower sides are detected, the process returns to step 510 in FIG. In this step 510, as shown in FIG. 14B, a pixel row on a horizontal line LH1 in a horizontal direction (direction substantially parallel to the X-axis direction) slightly lower than the upper side obtained in step 508, and Boundary detection is performed using the pixel row on the horizontal straight line LH2 slightly above the lower side thus obtained, and the evaluation point corresponding area DB _n A subroutine process for obtaining a total of four points, two points each on the left side and the right side, is performed. In FIG. 14B, waveform data PD1 corresponding to the pixel value of the pixel row data on the straight line LH1 and pixel value of the pixel row data on the straight line LH2 used for the boundary detection in step 510 are shown. Are respectively shown.
[0155]
In the subroutine 510, first, in step 701 of FIG. 12, based on the approximate position of the upper side obtained in step 508, a pixel row slightly lower than that position, for example, a straight line LH1 shown in FIG. After determining the linear pixel row along the pixel row as the first boundary detection pixel row, the process proceeds to a subroutine for performing the process of determining the threshold value t in step 702.
[0156]
In this subroutine 702, first, in step 802 of FIG. 13, the data of the linear pixel row (pixel row data) along the straight line LH1 determined in step 701 is extracted from the above-described imaging data file. Thus, for example, it is assumed that pixel row data having a pixel value corresponding to the waveform data PD1 in FIG. 14B is obtained.
[0157]
In the next step 804, the average value and standard deviation (or variance) of the pixel values (pixel data values) of the pixel row are obtained.
[0158]
In the next step 806, the swing width of the threshold (threshold level line) SL is set based on the obtained average value and standard deviation.
[0159]
In the next step 808, as shown in FIG. 19, the threshold value (threshold level line) SL is changed at a predetermined pitch with the swing width set above, and the waveform data PD1 and the threshold value (threshold level line) SL are changed for each change position. And the information of the processing result (the value of each threshold value and the number of intersections) is stored in a storage device (not shown).
[0160]
In the next step 810, the number of intersections obtained based on the information of the processing result stored in the step 808 is set to the target pattern (in this case, the evaluation point corresponding area DB _n ), A threshold value (referred to as a provisional threshold value) t that matches the number of intersections ₀ Ask for.
[0161]
In the next step 812, the provisional threshold value t ₀ And a threshold range in which the number of intersections is the same.
[0162]
In the next step 814, after a predetermined value (for example, in the present embodiment, for example, the center) of the threshold range determined in step 812 is determined as the optimum threshold t, the process returns to step 704 in FIG.
[0163]
Here, the threshold value is discretely changed (at a predetermined step pitch) based on the average value and the standard deviation (or variance) of the pixel values of the pixel row for the purpose of speeding up. Is not limited to this, and may be, for example, continuously changed.
[0164]
In step 704 of FIG. 12, an intersection between the threshold value (threshold level line) t determined above and the above-described waveform data PD1 (that is, a point where the threshold value t crosses the waveform data PD1) is obtained. Note that this intersection is actually detected by scanning the pixel row from outside to inside as indicated by arrows A and A 'in FIG. Therefore, at least two intersections are detected.
[0165]
Returning to FIG. 12, in the next step 706, a pixel row is bidirectionally scanned from the obtained position of each intersection, and the maximum value and the minimum value of the pixel values near each intersection are obtained.
[0166]
In the next step 708, the average value of the obtained maximum value and minimum value is calculated, and this is set as a new threshold value t '. In this case, since there are at least two intersections, a new threshold value t 'is also obtained for each intersection.
[0167]
In the next step 710, the intersection between the threshold value t 'and the waveform data PD1 between the maximum value and the minimum value for each intersection point obtained in step 708 (that is, the point at which the threshold value t' crosses the waveform data PD1) Are obtained, and the positions of the obtained two points (pixels) are defined as boundary points. That is, the boundary point (in this case, the evaluation point corresponding area DB _n After calculating the points on the left side and the right side, the process proceeds to step 712 to determine whether four boundary points have been detected. In this case, since only two boundary points have been detected, the determination here is denied, and the process proceeds to step 718, and based on the approximate position of the lower side obtained in step 508, a pixel slightly above the position is determined. After determining a column, for example, a linear pixel column along the straight line LH2 shown in FIG. 14 (B) as the second pixel line for boundary detection, the process returns to the subroutine of step 702. In this subroutine 702, first, in 802 of FIG. 13, the data of the linear pixel row (pixel row data) along the straight line LH2 determined in the step 718 is extracted from the above-described imaging data file. Thus, for example, it is assumed that pixel row data having a pixel value corresponding to the waveform data PD2 in FIG. 14B is obtained. After that, the processing of the above-described steps 804 to 814 is performed using the pixel column data having the pixel value corresponding to the waveform data PD2, and the optimum threshold value t is determined. Thereafter, the processing of steps 704 to 710 is performed in the same manner as described above, and the intersection of two points of the threshold value t 'and the waveform data PD1 (that is, the point at which the threshold value t' crosses the waveform data PD2) is obtained. The positions of the two points (pixels) are defined as boundary points.
[0168]
In the next step 712, it is determined again whether or not four boundary points have been detected. Here, since four boundary points have been detected, the determination here is affirmative, and the process returns to step 510 in FIG. . In FIG. 14B, the four boundary points Q obtained in step 510 are shown. ₁ ~ Q ₄ Are also shown.
[0169]
Returning to FIG. 10, in the next step 512, as shown in FIG. 14C, the two points Q ₁ , Q ₂ A pixel row on the vertical straight line LV1 slightly to the right and two points Q on the right side obtained ₃ , Q ₄ Using a pixel row on the vertical straight line LV2 slightly to the left, boundary detection is performed in the same manner as in step 508 described above, and the evaluation point corresponding area DB _n The boundary points on the upper side and the lower side are each 2 points, that is, 4 points in total are obtained. In FIG. 14C, waveform data PD3 corresponding to the pixel value of the pixel row data on the straight line LV1 and pixel value of the pixel row data on the straight line LV2 used for the boundary detection in this step 512 are shown. Are shown, respectively. Also, in FIG. 14 (C), the boundary point Q obtained in step 512 ₅ ~ Q ₈ Are also shown.
[0170]
By the way, the evaluation point corresponding area DB _n (In this case DB ₁ ), The boundary point on the low dose (low exposure amount) side, for example, the boundary point Q ₅ , Q ₇ When detecting the wafer W _T Depending on the combination of the above bark and resist, the boundary point Q ₅ , Q ₇ May be detected at each of a plurality of candidate points. In such a case, in the present embodiment, the evaluation point corresponding area DB _n (In this case DB ₁ ), The approximate positions (pixel units) of the upper side and the lower side of the outer frame are detected by scanning the window regions WD1 and WD2, and the point closest to this value is selected from the candidate points. By selecting, the boundary point Q ₅ , Q ₇ Can be reliably detected. In this sense, in step 508, at least one of the left side and the right side of the outer frame, for example, the evaluation point corresponding area DB _n (In this case DB ₁ ), The approximate position (pixel unit) of the left side corresponding to the low dose side may be obtained by scanning the window area in the same manner as described above. In this case, the pattern remains in the resist image, and in some cases, a plurality of candidate points are expected to appear. ₁ , Q ₂ Can be reliably detected in the same manner as described above.
[0171]
Returning to FIG. 10, in the next step 514, as shown in FIG. 15A, the evaluation point corresponding area DB obtained in the above steps 510 and 512, respectively. _n Two points (Q on the left, right, upper, and lower sides of ₁ , Q ₂ ), (Q ₃ , Q ₄ ), (Q ₅ , Q ₆ ), (Q ₇ , Q ₈ ), An intersection between straight lines determined by two points on each side is an evaluation point corresponding area DB which is a rectangular area (rectangular area). _n 4 vertices p of the outer frame of ₀ ', P ₁ ', P ₂ ', P ₃ Ask for '. Here, regarding the method of calculating the vertex, the vertex p ₀ 'Will be described as an example with reference to FIG.
[0172]
As shown in FIG. ₀ 'Is the boundary position Q ₂ To Q ₁ Α (α> 0) of the vector K1 toward ₅ To Q ₆ Assuming that it is at a position β times (β <0) of the vector K2 heading toward, the following simultaneous equation (1) holds. (Here, the subscripts x and y represent the x and y coordinates of each point, respectively.)
[0173]
(Equation 1)

[0174]
Solving the above simultaneous equation (1) gives the vertex p ₀ 'Position (p _0x ', P _0y ') Is required.
[0175]
Remaining vertex p ₁ ', P ₂ ', P ₃ With regard to ', the same system of equations can be established and solved to find the respective positions.
[0176]
Returning to FIG. 10, in the next step 516, as shown in FIG. ₀ '~ P ₃ Based on the coordinate value of ', a rectangle approximation by the least squares method is performed, and the evaluation point corresponding area DB including the rotation _n Is calculated.
[0177]
Here, the processing in step 516 will be described in detail with reference to FIG. That is, in this step 516, four vertices p ₀ ~ P ₃ Is approximated by the least squares method using the coordinate values of _n The width w, the height h, and the rotation amount θ of the outer frame DBF are obtained. In FIG. 21, the y-axis is positive on the lower side of the paper.
[0178]
Center p _c Coordinates of (p _cx , P _cy ), The four vertices of the rectangle (p ₀ , P _l , P ₂ , P ₃ ) Can be expressed as the following equations (2) to (5).
[0179]
(Equation 2)

[0180]
Four vertices p obtained in the above step 514 ₀ ', P _l ', P ₂ ', P ₃ 'And vertices p corresponding to the above equations (2) to (5), respectively. ₀ , P _l , P ₂ , P ₃ Error E _p And Error E _p Can be expressed by the following equations (6) and (7).
[0181]
[Equation 3]

[0182]
Equations (6) and (7) are converted to the unknown variable p _cx , P _cy , W, h, and θ, a simultaneous equation is established such that the result is 0, and a rectangular approximation result is obtained by solving the simultaneous equation.
[0183]
As a result, the evaluation point corresponding area DB _n 15B is shown by a solid line in FIG. 15B.
[0184]
Returning to FIG. 10, in the next step 518, the evaluation point corresponding area DB _n Is equally divided using the known number of partitioned areas in the vertical direction = (M + 2) = 15 and the number of known partitioned areas in the horizontal direction = (N + 2) = 25, and the respective partitioned areas DA _{i, j} (I = 0 to 14, j = 0 to 24) are obtained. That is, each section area (position information) is obtained based on the outer frame DBF.
[0185]
FIG. 15C shows the first area DC obtained in this manner. _n Areas DA that configure _{i, j} (I = 1 to 13, j = 1 to 23) are shown.
[0186]
Returning to FIG. 10, in the next step 520, each partitioned area DA _{i, j} For (i = 1 to M, j = 1 to N), a representative value (hereinafter, also appropriately referred to as “score”) regarding the pixel data is calculated.
[0187]
Below, score E _{i, j} The calculation method of (i = 1 to M, j = 1 to N) will be described in detail.
[0188]
Usually, in a captured measurement target, there is a contrast difference between a pattern portion and a non-pattern portion. Only the pixels having the non-pattern area luminance exist in the area where the pattern has disappeared, while the pixels having the pattern area luminance and the pixels having the non-pattern area luminance coexist in the area where the pattern remains. Therefore, as a representative value (score) for determining the presence / absence of a pattern, a variation in pixel value within each partitioned area can be used.
[0189]
In the present embodiment, as an example, the variance (or standard deviation) of the pixel values in the specified range in the defined area is adopted as the score E.
[0190]
S is the total number of pixels within the specified range, and I is the luminance value of the kth pixel. _k Then, the score E can be expressed by the following equation (8).
[0191]
(Equation 4)

[0192]
In the case of the present embodiment, as described above, the reticle R _T Above, the opening pattern AP _n (N = 1 to 5), the measurement pattern MP is placed in a reduced area portion of about 60% of each opening pattern. _n Are arranged respectively. Further, the step pitch SP at the time of the above-described exposure is different from that of each opening pattern AP. _n Wafer W _T It is set to about 5 μm, which substantially matches the size of the projected image upward. Therefore, in the pattern remaining section area, the measurement pattern MP _n Is the partition area DA _{i, j} And the center of the area DA _{i, j} Exists in a range (region) reduced to approximately 60%.
[0193]
In consideration of such a point, for example, the specified area _{i, j} (I = 1 to M, j = 1 to N), the center is the same, and a reduced area of the area can be used for score calculation. However, the reduction rate A (%) is limited as follows.
[0194]
First, as for the lower limit, if the range is too narrow, the area used for score calculation is only the pattern part, and if this is the case, the variation is reduced even in the remaining part of the pattern, making it unusable for pattern presence determination. In this case, it is necessary that A> 60%, as is apparent from the above-described pattern existence range. Although the upper limit is naturally 100% or less, the upper limit should be smaller than 100% in consideration of a detection error and the like. Thus, the reduction ratio A needs to be set to 60% <A <100%.
[0195]
In the case of the present embodiment, since the pattern portion occupies about 60% of the defined area, it is expected that the S / N ratio will increase as the ratio of the area (designated range) used for score calculation to the defined area increases.
[0196]
However, if the area size of the pattern part and the non-pattern part in the area used for score calculation become the same, the S / N ratio of the pattern presence / absence determination can be maximized. In the present embodiment, as a result of experimentally confirming some ratios, for example, the most stable result is obtained when A = 90%, the ratio A = 90% is adopted. Of course, A is not limited to 90%, and the measurement pattern MP _n And opening pattern AP _n Of the measurement pattern MP for the divided area in consideration of the relation between the pattern and the divided area on the wafer determined by the step pitch SP. _n May be determined in consideration of the ratio occupied by the image. Further, the designated range used for calculating the score is not limited to an area having the same center as the divided area, and the measurement pattern MP _n May be determined in consideration of where in the partitioned area the image is located.
[0197]
By the way, the wafer W _T Depending on the combination of the above bark and resist, the score E represented by the above equation (8) may not always be appropriate as a score for performing pattern presence / absence determination in some of the divided regions. Therefore, focusing on the fact that only pixels having the non-pattern area luminance exist in the area where the pattern has disappeared, each section area expressed by the following equation (9) is obtained by partially changing the above equation (8). May be adopted as the score E ′.
[0198]
(Equation 5)

[0199]
In the above equation (9), I ^* Is an average value of pixel values in an arbitrary partitioned area where the image of the measurement pattern is not expected to remain (disappear). Accordingly, the score E ′ represented by the above equation (9) is expressed as an average value of I ^* Can be said to be the variance of the pixel values corresponding to the pixel data in the specified range in each of the divided areas, obtained by using.
[0200]
Therefore, in step 520, the respective segment areas DA are read from the image data file. _{i, j} The imaging data within the specified range is extracted, and each partitioned area DA is extracted using the above equation (8) or (9). _{i, j} Score E of (i = 1 to M, j = 1 to N) _{i, j} Or E ' _{i, j} (I = 1 to M, j = 1 to N) are calculated.
[0201]
Since the score E or E ′ obtained by the above method expresses the presence or absence of a pattern as a numerical value, it is possible to automatically and stably determine the presence or absence of a pattern by binarizing it with a predetermined threshold. It is possible.
[0202]
Therefore, in the next step 522 (FIG. 11), the partition area DA _{i, j} Score E obtained above for each _{i, j} Or E ' _{i, j} Is compared with a predetermined threshold value SH. _{i, j} The presence or absence of an image of the measurement pattern MP in the above, and a determination value F as a detection result _{i, j} (I = 1 to M, j = 1 to N) are stored in a storage device (not shown). That is, in this way, the score E _{i, j} Or E ' _{i, j} Based on the partition area DA _{i, j} Measurement pattern MP for each _n Is detected. Note that various image forming states are conceivable. In the present embodiment, as described above, based on the point that the score E or E ′ represents the presence or absence of a pattern as a numerical value, This is to pay attention to whether or not an image of the pattern is formed in the region.
[0203]
Here, the score E _{i, j} Or E ' _{i, j} Is greater than or equal to the threshold SH, the measurement pattern MP _n Is determined to be formed, and a determination value F as a detection result is determined. _{i, j} Is set to “0”. On the other hand, score E _{i, j} Or E ' _{i, j} Is less than the threshold value SH, the measurement pattern MP _n Is not formed, and the determination value F as a detection result is determined. _{i, j} Is “1”. FIG. 22 shows an example of this detection result as table data. FIG. 22 corresponds to FIG. 9 described above.
[0204]
In FIG. 22, for example, F _12,16 Is the wafer W _T Is in the Z-axis direction ₁₂ And the exposure energy amount is P ₁₆ Measurement pattern MP transferred at the time of _n 22 indicates the detection result of the image formation state. For example, in the case of FIG. _12,16 Has a value of “1”, and the measurement pattern MP _n Is determined not to have been formed.
[0205]
The threshold value SH is a preset value and can be changed by an operator using an input / output device (not shown).
[0206]
In the next step 524, based on the above-described detection results, the number of divided areas where a pattern image is formed for each focus position is determined. That is, the number of partitioned areas having the determination value “0” is counted for each focus position, and the counting result is used as the pattern remaining number T _i (I = 1 to M). At this time, a so-called jump area having a different value from the surrounding area is ignored. For example, in the case of FIG. _T Focus position of Z ₁ Then the number of remaining patterns T ₁ = 8, Z ₂ Then T ₂ = 11, Z ₃ Then T ₃ = 14, Z ₄ Then T ₄ = 16, Z ₅ Then T ₅ = 16, Z ₆ Then T ₆ = 13, Z ₇ Then T ₇ = 11, Z ₈ Then T ₈ = 8, Z ₉ Then T ₉ = 5, Z ₁₀ Then T ₁₀ = 3, Z ₁₁ Then T ₁₁ = 2, Z ₁₂ Then T ₁₂ = 2, Z _Thirteen Then T _Thirteen = 2. Thus, the focus position and the number of remaining patterns T _i You can ask for the relationship.
[0207]
The jump area may be caused by erroneous recognition at the time of measurement, laser misfire, dust, noise, and the like. _i Filter processing may be performed to reduce the influence on the detection result. As this filter processing, for example, data of a 3 × 3 section area centered on the section area to be evaluated (judgment value F _{i, j} ) May be calculated (simple average or weighted average). Note that the filter processing is performed on the data (score E) before the formation state detection processing. _{i, j} Or E ' _{i, j} ) May be performed, and in this case, the effect of the jump area can be more effectively reduced.
[0208]
In the next step 526, an nth-order approximate curve (for example, a 4th to 6th-order curve) for calculating the best focus position from the number of remaining patterns is obtained.
[0209]
Specifically, the horizontal axis indicates the focus position, and the vertical axis indicates the pattern remaining number T, where the number of remaining patterns detected in step 524 is set as the focus position. _i Is plotted on a coordinate system. In this case, the result is as shown in FIG. Here, in the case of the present embodiment, the wafer W _T In the exposure of _{i, j} Are the same size, the difference between the exposure energies between the adjacent divided areas in the row direction is a constant value (= ΔP), and the difference between the focus positions between the adjacent divided areas in the column direction is a constant value (= ΔZ). , The remaining pattern number T _i Can be treated as being proportional to the amount of exposure energy. That is, in FIG. 23, the vertical axis can be considered to be the exposure energy amount P.
[0210]
After the above plotting, an nth-order approximate curve (least squares approximate curve) is obtained by curve fitting each plot point. Thereby, for example, a curve P = f (Z) shown by a dotted line in FIG. 23 is obtained.
[0211]
Returning to FIG. 11, in the next step 528, calculation of an extreme value (maximum value or minimum value) of the curve P = f (Z) is attempted, and it is determined whether or not an extreme value exists based on the result. I do. If the extreme value can be calculated, the process proceeds to step 530 to calculate the focus position at the extreme value, and to use the result of calculation as the best focus position, which is one of the optical characteristics. Is stored in a storage device (not shown).
[0212]
On the other hand, if the extreme value has not been calculated in step 528, the process proceeds to step 532, where the change amount of the curve P = f (Z) corresponding to the change in the position of the wafer W (change in Z) is the smallest. The range of the small focus position is calculated, the middle position of the range is calculated as the best focus position, the calculation result is set as the best focus position, and the best focus position is stored in a storage device (not shown). That is, the focus position is calculated based on the flattest part of the curve P = f (Z).
[0213]
Here, the calculation step of the best focus position such as step 532 is provided because the measurement pattern MP _n In some cases, the above-mentioned curve P = f (Z) does not have a clear peak depending on the type of the resist, the type of the resist, and other exposure conditions. Even in such a case, the best focus position can be calculated with a certain degree of accuracy.
[0214]
In the next step 534, referring to the aforementioned counter n, all the evaluation point corresponding areas DB ₁ ~ DB ₅ It is determined whether or not the processing has been completed for. Here, the evaluation point corresponding area DB ₁ Since the processing of step 534 has only been completed, the determination in step 534 is denied, the processing proceeds to step 536, and the counter n is incremented (n ← n + 1). Thereafter, the processing returns to step 502 in FIG. ₂ At a position where the wafer W can be detected by the alignment detection system AS. _T Position.
[0215]
Then, the processing (including determination) of steps 504 to 534 described above is performed again, and the above-described evaluation point corresponding area DB ₁ In the same manner as in the case of ₂ For the best focus position.
[0216]
And evaluation point corresponding area DB ₂ When the calculation of the best focus position is completed for all the evaluation point corresponding areas DB in step 534 ₁ ~ DB ₅ It is determined again whether or not the processing has been completed, but this determination is denied. Thereafter, the processing (including the determination) of steps 502 to 536 is repeated until the determination in step 534 is affirmed. Thereby, another evaluation point corresponding area DB ₃ ~ DB ₅ The evaluation point corresponding area DB described above ₁ In the same manner as in the above case, the best focus position is obtained.
[0217]
Thus, the wafer W _T All evaluation point corresponding area DB above ₁ ~ DB ₅ Calculation of the best focus position, that is, five measurement patterns MP in the exposure area conjugate with the illumination area IAR ′ with respect to the projection optical system PL. ₁ ~ MP ₅ After the calculation of the best focus position at each of the evaluation points described above, which is the projection position, the determination in step 534 is affirmed, and the flow shifts to step 538 to execute other calculations based on the best focus position data obtained above. Is calculated.
[0218]
For example, in this step 538, as an example, the evaluation point corresponding area DB ₁ ~ DB ₅ The field curvature of the projection optical system PL is calculated based on the data of the best focus position in. Further, the depth of focus or the like at each evaluation point in the above-described exposed area may be obtained.
[0219]
Here, in the present embodiment, for simplicity of description, the reticle R corresponding to each evaluation point in the field of view of the projection optical system PL. _T The above pattern MP is used as a measurement pattern in the upper area. _n The description has been made on the assumption that only the first electrode is formed. However, it goes without saying that the present invention is not limited to this. For example, reticle R _T Above, for example, the reticle R corresponding to each evaluation point _T In the vicinity of the upper region, a plurality of opening patterns AP are provided at intervals of an integral multiple of the step pitch SP, for example, 8 times, 12 times, or the like. _n And arrange each opening pattern AP _n , A plurality of types of measurement patterns such as L / S patterns having different periodic directions or L / S patterns having different pitches may be arranged. In this way, for example, a set of L / S patterns arranged in close proximity to the position corresponding to each evaluation point and having a periodic direction orthogonal to each other is obtained from the best focus position obtained as a measurement pattern and the non- Point aberration can be determined. Further, for each evaluation point in the field of view of the projection optical system PL, an astigmatism in-plane uniformity is obtained by performing an approximation process by the least square method based on the astigmatism calculated as described above, It is also possible to obtain the total focus difference from the astigmatism in-plane uniformity and the field curvature.
[0220]
The optical characteristic data of the projection optical system PL obtained as described above is stored in a storage device (not shown) and displayed on a screen of a display device (not shown). As a result, the process of step 538 in FIG. 11, that is, the process of step 456 in FIG. 5, ends, and a series of optical characteristic measurement processes ends.
[0221]
Next, an exposure operation by the exposure apparatus 100 of the present embodiment in the case of device manufacturing will be described.
[0222]
It is assumed that the information on the best focus position determined as described above or the information on the curvature of field in addition to the information is input to the main controller 28 via an input / output device (not shown). .
[0223]
For example, when information on the curvature of field is input, the main controller 28 instructs an imaging characteristic correction controller (not shown) based on the optical characteristic data before the exposure, for example, before the exposure. By changing the position (including the distance from another optical element) or the inclination of at least one optical element (lens element in the present embodiment) of the PL, the projection optics is corrected so that its field curvature is corrected. The imaging characteristics of the system PL are corrected within a possible range. The optical elements used for adjusting the imaging characteristics of the projection optical system PL are not only refractive optical elements such as lens elements, but also reflective optical elements such as concave mirrors, or aberrations (distortion, spherical aberration, etc.) of the projection optical system PL. ), Especially an aberration correction plate for correcting the non-rotationally symmetric component may be used. Further, the method of correcting the image forming characteristics of the projection optical system PL is not limited to the movement of the optical element. For example, the method of controlling the light source 1 to slightly shift the center wavelength of the illumination light IL, or the method of correcting the projection optical system PL The method of changing the refractive index in a part of the method may be used alone or in combination with the movement of the optical element.
[0224]
Then, in response to an instruction from main controller 28, reticle R on which a predetermined circuit pattern (device pattern) to be transferred is formed by reticle loader (not shown) is loaded onto reticle stage RST. Similarly, the wafer W is loaded on the wafer table 18 by a wafer loader (not shown).
[0225]
Next, the main controller 28 uses a reticle alignment detection system (not shown), a reference mark plate FP on the wafer table 18, an alignment detection system AS, and the like to perform a preparation operation such as reticle alignment and baseline measurement in a predetermined procedure. Subsequently, wafer alignment such as an EGA (Enhanced Global Alignment) method is performed. The above-mentioned preparation work such as reticle alignment and baseline measurement is disclosed in detail, for example, in JP-A-7-176468 (corresponding US Pat. No. 5,646,413). Is disclosed in detail in JP-A-61-44429 (corresponding to U.S. Pat. No. 4,780,617), and will not be described in further detail here.
[0226]
When the above wafer alignment is completed, the exposure operation of the step-and-scan method is performed as follows.
[0227]
First, main controller 28 starts relative scanning of reticle R and wafer W, ie, reticle stage RST and XY stage 20, in the Y-axis direction. When the two stages RST and 20 reach their respective target scanning speeds and reach a constant speed synchronization state, the pattern area of the reticle R starts to be illuminated by the ultraviolet pulse light from the illumination system IOP, and scanning exposure is started. The relative scanning is performed by the main controller 28 controlling the reticle stage driving unit (not shown) and the driving system 22 while monitoring the measured values of the laser interferometer 26 and the laser interferometer 14 described above. .
[0228]
Main controller 28 determines that the moving speed Vr of reticle stage RST in the Y-axis direction and the moving speed Vw of XY stage 20 in the Y-axis direction particularly at the time of the scanning exposure described above are the projection magnification (倍率) of projection optical system PL. (Or 1/5 times). The main controller 28 also determines the depth of focus of the image plane of the projection optical system PL after the above-described optical characteristic correction based on the position information in the Z-axis direction of the wafer W detected by the focus sensor AFS during the scanning exposure. The wafer table 18 is driven via the drive system 22 in the Z-axis direction and the tilt direction so that the exposure area on the surface of the wafer W (shot area) falls within the range, and focus / leveling control of the wafer W is performed. Note that, in the present embodiment, prior to the exposure operation of the wafer W, the image plane of the projection optical system PL is calculated based on the above-described best focus position at each evaluation point, and this image plane is used as a detection reference of the focus sensor AFS. Optical calibration of the focus sensor AFS (for example, adjustment of the inclination angle of a plane-parallel plate disposed in the light receiving system 50b) is performed so as to be as follows. Of course, it is not always necessary to perform optical calibration, and for example, taking into account an offset corresponding to a deviation between the previously calculated image plane and the detection reference of the focus sensor AFS, the wafer W is output based on the output of the focus sensor AFS. A focus operation (and a leveling operation) for matching the surface to the image plane may be performed.
[0229]
Then, the different areas of the pattern area of the reticle R are sequentially illuminated with the ultraviolet pulse light, and the illumination of the entire pattern area is completed, thereby completing the scanning exposure of the first shot area on the wafer W. Thus, the pattern of the reticle R is reduced and transferred to the first shot area via the projection optical system PL.
[0230]
As described above, when the scanning exposure of the first shot area is completed, the XY stage 20 is step-moved in the X and Y axes directions by the main controller 28 via the drive system 22 so that the exposure of the second shot area is performed. Is moved to the scanning start position (acceleration start position).
[0231]
Then, the operation of each section is controlled by the main controller 28 in the same manner as described above, and the same scanning exposure as described above is performed on the second shot area on the wafer W.
[0232]
In this manner, the scanning exposure of the shot area on the wafer W and the stepping operation between shots are repeatedly performed, and the pattern of the reticle R is sequentially transferred to all the exposure target shots on the wafer W.
[0233]
When the pattern transfer to all the shots to be exposed on the wafer W is completed, the wafer is replaced with the next wafer, and the alignment and exposure operations are repeated in the same manner as described above.
[0234]
As described above in detail, according to the optical characteristic measuring method of the projection optical system PL in the exposure apparatus according to the present embodiment, the rectangular frame-shaped opening pattern AP _n And the opening pattern AP _n For measurement MP located inside _n Reticle R formed with _T Is mounted on a reticle stage RST arranged on the object plane side of the projection optical system, and a wafer W arranged on the image plane side of the projection optical system PL _T (Z) of the projection optical system PL in the optical axis direction and the wafer W _T The wafer W is changed while changing the energy amount P of the illumination light IL irradiated thereon. _T The opening pattern AP _n , That is, the opening pattern AP _n Wafer W _T The measurement pattern MP is sequentially moved in the XY plane at a step pitch equal to or smaller than the size of the projected image upward. _n The wafer W _T Transfer sequentially on top. Thereby, the wafer W _T On the top, a plurality of divided areas DA arranged in a matrix _{i, j} (I = 0 to M + 1, j = 0 to N + 1) as a whole rectangular evaluation point corresponding area DB _n Is formed. In this case, the wafer W _T On the upper side, a plurality of divided regions (regions on which the images of the measurement patterns are projected) are formed in a plurality of matrix arrangements in which no border lines exist as in the related art at boundaries between the divided regions.
[0235]
Then, the wafer W _T After the development of the wafer W, the main controller 28 uses the alignment detection system AS including an FIA-based alignment sensor to _T Upper evaluation point corresponding area DB _n Is imaged. Next, the main controller 28 determines the evaluation point corresponding area DB based on the captured image data of the resist image. _n At least one side, for example, an upper side and a lower side, which constitute a rectangular outer frame DBF having the outline of, is to be detected, and the window regions WD1 and WD2 of a predetermined size are scanned in a scanning direction substantially orthogonal to the respective sides to be detected. During the scanning, the representative value of the pixel data inside each of the window regions WD1 and WD2, that is, the position where the variance (or the standard deviation) of the pixel value is the maximum is determined by the upper side and the lower side which are the sides to be detected. Detect as position. That is, in the present embodiment, a part of the outer frame DBF is roughly detected in this manner.
[0236]
Here, the detection area can be easily set based on the design value of the side to be detected so that the side is always included. Also, since the pixel value (pixel value) of the outer frame DBF is clearly different from the other portions, the detection target edge is determined based on the magnitude of the variance (or standard deviation) of the pixel values in the window regions WD1 and WD2. The position of (part of the outer frame) is reliably detected.
[0237]
Next, based on the image data, the main control device 28 uses the detection results of the sides to be detected, that is, the positions of the upper side and the lower side (rough detection results), to obtain pixel row data slightly lower than the upper side. The left and right sides are detected by detecting two boundary points on the left and right sides, respectively, using the waveform data PD1 corresponding to the pixel values of the above and the waveform data PD2 corresponding to the pixel values of the pixel row data slightly above the lower side. Is detected. Next, the main controller 28 uses the detected waveform data PD3 corresponding to the pixel value of the slightly right pixel row data on the left side and the waveform data PD4 corresponding to the pixel value of the slightly left pixel row data on the right side. , The upper side and the lower side (detailed position) are detected by detecting two boundary points on the upper side and the lower side.
[0238]
Next, main controller 28 sets evaluation point corresponding area DB based on the detected outer frame portion (upper side, lower side, left side, right side) as a reference. _n Area DD among the plurality of divided areas constituting _n 1st area DC excluding _n Is calculated for each of the M × N divided areas. This calculation is performed based on information on the number and arrangement of the divided areas in the outer frame.
[0239]
Next, based on the imaging data, the first area DC _n The image formation state in the M × N divided areas constituting the image is determined by an image processing method, that is, the above-described divided areas DA _{i, j} Score (E _{i, j} Or E ' _{i, j} ) Is compared with the threshold value SH by a binarization method.
[0240]
In any case, as described above, the position of at least one side of the outer frame is roughly detected, and the detailed position of the outer frame DBF is detected by using the detection result. Position can be reliably and accurately detected, and the positions of at least some of the plurality of divided regions are calculated based on the design values based on the detected outer frame portion. An accurate position can be obtained.
[0241]
Further, in the case of the present embodiment, since there is no frame line between the adjacent divided areas, the plurality of divided areas (mainly the area where the image of the measurement pattern remains) for which the image forming state is to be detected are measured. The contrast of the pattern image does not decrease due to the interference of the frame lines. For this reason, it is possible to obtain, as the imaging data of the plurality of divided areas, data having a good S / N ratio between the pattern portion and the non-pattern portion. Therefore, the measurement pattern MP for each partitioned area _n Can be detected with high accuracy and reproducibility. In addition, an objective and quantitative score (E _{i, j} Or E ' _{i, j} ) Is compared with the threshold value SH and converted into the presence / absence information of the pattern (binary information) and detected. _n Can be detected with good reproducibility, and the presence or absence of a pattern can be automatically and stably determined. Therefore, in the present embodiment, when binarizing, only one threshold is sufficient, and compared to a case where a plurality of thresholds are set and the presence or absence of a pattern is determined for each threshold, the image forming state Can be shortened and the detection algorithm can be simplified.
[0242]
In addition, the main control device 28 detects the above-described detection result of the image formation state for each of the divided areas, that is, the objective and quantitative score (E _{i, j} Or E ' _{i, j} ), That is, the optical characteristics of the projection optical system PL such as the best focus position are obtained based on the detection result using the index value of the contrast of the image. For this reason, the best focus position and the like can be accurately obtained in a short time. Therefore, it is possible to improve the measurement accuracy of the optical characteristic determined based on the best focus position and the reproducibility of the measurement result, and as a result, it is possible to improve the throughput of the optical characteristic measurement.
[0243]
Further, in the present embodiment, as described above, since the image formation state is converted into the presence / absence information of the pattern (binary information) and detected, the reticle R _T Measurement pattern MP in the pattern area PA _n There is no need to arrange other patterns (for example, a reference pattern for comparison, a mark pattern for positioning, etc.). In addition, the measurement pattern can be made smaller as compared with conventional methods for measuring dimensions (CD / focus method, SMP focus measurement method, etc.). Therefore, the number of evaluation points can be increased, and the interval between the evaluation points can be narrowed. As a result, the measurement accuracy of the optical characteristics and the reproducibility of the measurement result can be improved.
[0244]
In the present embodiment, the wafer W _T In view of the fact that no frame line exists between adjacent partitioned areas formed above, each evaluation point corresponding area DB _n Area DA with respect to outer frame DBF which is the outer peripheral edge of _{i, j} The method of calculating the position of is adopted. And each evaluation point corresponding area DB _n Area DD consisting of a plurality of partitioned areas located at the outermost periphery _n Wafer W as a part of the exposure conditions so that each of the divided regions constituting _T The amount of energy of the illumination light IL irradiated upward is changed. As a result, the S / N ratio at the time of detecting the outer frame DBF is improved, and the outer frame DBF can be detected with high precision. As a result, each first region DC _n Areas DA that configure _{i, j} The position of (i = 1 to M, j = 1 to N) can be accurately detected.
[0245]
In addition, according to the optical characteristic measurement method according to the present embodiment, since the best focus position is calculated based on an objective and reliable method of calculating an approximate curve by statistical processing, stable high accuracy and reliability are ensured. Optical characteristics can be measured. Note that, depending on the order of the approximate curve, it is possible to calculate the best focus position based on the inflection point or a plurality of intersections between the approximate curve and a predetermined slice level.
[0246]
Further, according to the exposure apparatus of the present embodiment, the projection optical system PL is subjected to the exposure before the exposure so that the optimal transfer can be performed in consideration of the optical characteristics of the projection optical system PL accurately measured by the above-described optical characteristic measurement method. The adjusted pattern formed on the reticle R is transferred onto the wafer W via the adjusted projection optical system PL. Furthermore, since the focus control target value at the time of exposure is set in consideration of the best focus position determined as described above, it is possible to effectively suppress the occurrence of color unevenness due to defocus. Therefore, according to the exposure method according to the present embodiment, a fine pattern can be transferred onto a wafer with high accuracy.
[0247]
In the above embodiment, as a part of the method of measuring the optical characteristics of the projection optical system PL, a rectangular frame-shaped opening pattern AP is used. _n And the opening pattern AP _n For measurement MP located inside _n Reticle R formed with _T Is mounted on a reticle stage RST arranged on the object plane side of the projection optical system, and a wafer W arranged on the image plane side of the projection optical system PL _T (Z) of the projection optical system PL in the optical axis direction and the wafer W _T The wafer W is changed while changing the energy amount P of the illumination light IL irradiated thereon. _T Is moved at a predetermined step pitch, and the measurement pattern MP is moved. _n The wafer W _T Although a transfer step of sequentially transferring the above is included, the present invention is not limited to this. That is, such as a wafer in which a predetermined rectangular area as a whole including a plurality of divided areas in a matrix arrangement composed of transfer areas of the measurement pattern transferred via the projection optical system PL under different exposure conditions is formed in advance. By preparing an object in advance and performing each processing after the imaging processing by the alignment detection system AS on the wafer in the same manner as in the above-described embodiment, a plurality of divided areas in a matrix arrangement can be exposed under different exposure conditions. As long as it is the transfer area of the measurement pattern transferred via the projection optical system PL, in other words, as long as the image formed in the partitioned area includes the image affected by the optical characteristics of the projection optical system PL, The optical characteristics of the projection optical system can be measured as in the above embodiment.
[0248]
Therefore, the method of forming the second region, that is, the rectangular frame-shaped region or a part of the region is performed by transferring the measurement pattern described in the above embodiment onto the wafer in an over-exposed state. A method other than the repeat type exposure method may be employed. For example, a rectangular frame-shaped opening pattern (second region DD) is formed on reticle stage RST of exposure apparatus 100, for example. _n Or a reticle on which a pattern of the reticle is formed, and the reticle pattern is formed on a wafer arranged on the image plane side of the projection optical system PL by one scanning exposure. To form a second overexposed area on the wafer. In addition, the opening pattern AP _n A reticle having an opening pattern similar to that described above is mounted on a reticle stage RST, and the opening pattern is transferred onto a wafer by a step-and-repeat method or a step-and-scan method with an exposure energy amount of overexposure. By doing so, the second region of overexposure may be formed on the wafer. In addition, for example, by performing exposure by the step-and-stitch method using the above-described opening pattern and forming a plurality of images of the opening pattern adjacent to or joined to each other on the wafer, the second region of overexposure is formed. It may be formed on a wafer. In addition, while the reticle stage RST is stationary, the wafer W (wafer table 18) is moved in a predetermined direction while illuminating an opening pattern formed on the reticle mounted on the reticle stage RST with illumination light. A second region for exposure may be formed. In any case, as in the above embodiment, the presence of the overexposed second region makes it possible to accurately detect the outer edge of the second region based on a detection signal having a good S / N ratio. .
[0249]
In these cases, a plurality of partitioned areas DA arranged in a matrix _{i, j} As a whole, a first rectangular region DC _n The wafer W _T Forming an over-exposed second region (for example, DD) on at least a part of the wafer around the first region. _n ) May be opposite to the case of the above embodiment. In particular, when the exposure for forming the first partitioned area for which the image formation state is to be detected is performed later, for example, when a highly sensitive resist such as a chemically amplified resist is used as a photosensitive agent In particular, the time from the formation (transfer) of the image of the measurement pattern to the development can be shortened, which is particularly preferable.
[0250]
In the above embodiment, the evaluation point corresponding area DB _n When the approximate position of the outer frame DBF is detected, as a representative value of the pixel data in the window regions WD1 and WD2, for example, the variance (or standard deviation) of the pixel values corresponding to the pixel data in the window regions WD1 and WD2, or In the case where the two window regions WD1 and WD2 are simultaneously scanned, the case of using the added value of them has been described. However, the present invention is not limited to this, and the representative value of the pixel data is the variance or standard deviation of the pixel values corresponding to the pixel data in a part of the area including the center in the window area, or the two window areas WD1 and WD2. In the case of scanning at the same time, the sum of them may be used. Alternatively, in each of the above cases, instead of the variance or the standard deviation of the pixel values, the sum of the pixel values or the differential sum may be used. When the addition value or the differential sum is used, the position where the addition value or the differential sum is maximum or minimum is detected as the approximate position of the outer frame in accordance with the definition method of the pixel value. In any case, the approximate position of the outer frame may be detected based on the pixel data in the window area.
[0251]
In the above embodiment, the measurement pattern MP _n The formation state of the image of _{i, j} Or E ' _{i, j} ) Is compared with the threshold value SH to convert to pattern presence / absence information (binary information) for detection, but the present invention is not limited to this. In the above embodiment, the evaluation point corresponding area DB _n Is accurately detected, and each of the divided areas DA is determined based on the outer frame DBF. _{i, j} Is calculated by calculation, the position of each partitioned area can be accurately obtained. Therefore, the template matching may be performed on each of the precisely determined divided areas. By doing so, template matching can be performed in a short time. In this case, as the template pattern, for example, imaging data of a partitioned area where an image is formed or a partitioned area where no image is formed can be used. Even in this case, objective and quantitative information of the correlation value is obtained for each sectioned area. By comparing the obtained information with a predetermined threshold value, the measurement pattern MP _n Is converted to binary information (image presence / absence information), the image formation state can be detected with high accuracy and reproducibility as in the above embodiment.
[0252]
In the above embodiment, the evaluation point corresponding area DB _n Has been described in the case where the second region constituting is exactly a rectangular frame, but the present invention is not limited to this. In other words, the second region only needs to be such that its outer edge can be used as a reference for calculating the position of at least each of the divided regions constituting the first region. Therefore, for example, a U-shaped (U-shaped) portion of a part of the rectangular frame-shaped divided region Or an L-shaped portion. In this case, the evaluation point corresponding area including the first area and the second area outside the first area is a rectangular area as a whole.
[0253]
Further, the second region of overexposure is not necessarily required. Even in such a case, the outline of the first area is a rectangular outer frame, and a part of the outermost peripheral area in the first area (hereinafter referred to as “outer edge area”) includes: Since there is an area where no pattern image is formed, it is possible to detect a part of the outer frame, that is, the boundary between the first area and the area outside the area, with a good S / N ratio by the same method as in the above embodiment. Then, the position of another partitioned area (each of the partitioned areas constituting the first area) can be calculated based on the design value based on the boundary line, and an almost accurate position of the other partitioned area can be obtained. It is. Similarly, the second region of overexposure is not limited to a rectangular frame or a part thereof as in the above embodiment. For example, as for the shape of the second region, only the boundary (inner edge) with the first region may have a rectangular frame shape, and the outer edge may have an arbitrary shape. Even in such a case, since the overexposed second region (region where the pattern image is not formed) exists outside the first region, the adjacent outer region is detected when the image forming state of the outer edge section region is detected. The contrast of the image in the outer edge region is prevented from being reduced due to the presence of the pattern image in the region. Therefore, it is possible to detect the boundary between the outer edge sectioned area and the second area with a good S / N ratio, and to set another sectioned area (each area constituting the first area) based on the boundary line based on a design value. Area) can be calculated, and an almost accurate position of another sectioned area can be obtained.
[0254]
Therefore, also in these cases, since the positions of the plurality of divided regions in the first region can be almost accurately known, for example, for each of the divided regions, the same score (contrast of image as in the above embodiment) is obtained. And the template matching method is used to detect the image formation state, so that the pattern image formation state can be detected in a short time as in the above embodiment. .
[0255]
Then, by obtaining the optical characteristics of the projection optical system based on the detection result, it is possible to obtain the optical characteristics based on an objective and quantitative detection result using the image contrast or correlation value. Therefore, the same effect as in the above embodiment can be obtained.
[0256]
In the above-described embodiment, the FIA-based alignment sensor is used for detecting the outer frame DBF as a reference for detecting each of the divided areas and for detecting the image formation state of each of the divided areas. However, the present invention is not limited to this. That is, at least one of the detection of the boundary between the outer frame DBF or the outer edge section area and the second area and the detection of the image formation state of each section area is performed by another method such as SEM (scanning electron microscope). An imaging device (image measuring device) may be used. Even in such a case, it is possible to accurately determine the position of each partitioned area in the first area based on the outer frame or inner edge of the second area.
[0257]
Further, similarly to the above embodiment, when each evaluation point corresponding area is formed by the first area and the surrounding second area, the above-described step pitch SP is changed to the above-described opening pattern AP. _n May not necessarily be set to be equal to or smaller than the projection area size. The reason is that, with the method described above, the position of each of the divided regions constituting the first region can be almost accurately determined based on a part of the second region. For example, by using the position information, for example, This is because template matching and contrast detection including the case of the above embodiment can be performed with a certain degree of accuracy and in a short time.
[0258]
On the other hand, the aforementioned step pitch SP is changed to the aforementioned opening pattern AP. _n When the size is set to be equal to or smaller than the projection area size, the second area need not always be formed outside the first area. Even in such a case, it is possible to detect the outer frame of the first area in the same manner as in the above-described embodiment, and accurately determine the position of each of the divided areas in the first area based on the detected outer frame. Because it is possible to ask. Then, when the image formation state is detected by using, for example, template matching or detection using a score (contrast detection) as in the above-described embodiment using the information on the position of each of the divided areas obtained in this manner, It is possible to accurately detect an image forming state using image data having a good S / N ratio without a decrease in contrast between a pattern portion and a non-pattern portion caused by interference of a frame.
[0259]
However, in this case, erroneous detection of the boundary is likely to occur on the side of the outermost peripheral region in the first region where the region where the pattern remains remains. For this reason, it is desirable to cope with the problem by limiting the detection range of the boundary where the erroneous detection is likely to occur using the detection information of the boundary where the erroneous detection is unlikely to occur. According to the above embodiment, based on the information on the boundary detected on the right side where the erroneous detection is unlikely to occur, the detection range of the boundary position on the left side where the erroneous detection is liable is limited. I do. Further, in the boundary detection on the upper and lower sides of the first area, the detection range of the left boundary position may be limited using the right detection information that is unlikely to cause erroneous detection (see FIG. 9).
[0260]
In this case, for example, data obtained by clearing, for example, data of lower-order bits other than the most significant 2 bits of the 8-bit image data to 0 (or data in which all bits are set to “1”) is used as the pixel data. The outer frame may be detected by a method similar to the embodiment. For example, considering the case where the upper side and the right side of the outer frame are the sides to be detected, for example, the first area DC in FIG. ₁ As can be seen from the figure, the inside of the outer frame near the side of the detection target is an exposed area where the pattern image does not remain, while the resist remains as it is outside the outer frame near the side of the detection target. This is a remaining unexposed area. Therefore, the pixel value of each partitioned area in the outer frame is equal to or less than a certain value close to zero, and the pixel value of the area outside the outer frame is equal to or more than a certain value. Therefore, the data in which the lower bits of the imaging data of these two areas other than the most significant two bits are cleared to 0 is the pixel value of the pixel of each partitioned area in the outer frame is zero, and in the outer area, the pixel value of all the pixels is zero. Pixel value is 2 ⁷ +2 ⁶ = 192. For this reason, the pixel value greatly differs between the outside and the inside with the outer frame as a boundary, so that the approximate position detection of the detection target side constituting the outer frame can be performed more reliably by scanning the window area or other methods similar to the above. It is possible to do.
[0261]
Similarly, also in the above-described embodiment, data obtained by clearing, for example, lower-bit data other than the most significant 2 bits of the 8-bit imaging data to 0 is used as the pixel data, and the outer frame is formed in the same manner as described above. May be detected. In this case, as is apparent from FIG. 9, the over-exposed second region DD is provided around the entire periphery of the outer frame DBF. ₁ Therefore, when any side of the outer frame is set as the detection target side, the pixel value of the pixel in each partitioned area in the outer frame is zero, and the pixel value of all the pixels in the outer area is 192. Become. Therefore, the approximate position can be reliably detected regardless of which side of the outer frame is the detection target side.
[0262]
Further, in the above embodiment, all the N × M divided areas constituting the first rectangular area are exposed, but at least one of the N × M divided areas, that is, the curve P = f It is not necessary to perform the exposure for a section area where an exposure condition that does not clearly contribute to the determination of (Z) is set (for example, a section area located at the upper right corner and the lower right corner in FIG. 9). That is, the measurement pattern MP _n The plurality of divided areas (shot areas) to which the image is to be transferred need not be rectangular (matrix) as a whole. At this time, the second region formed outside the first region is not rectangular in shape but has irregularities in a part thereof. In other words, the second region surrounds only the exposed divided region among the N × M divided regions. Alternatively, the second region may be formed only in a part of the periphery.
[0263]
In the above embodiment, the wafer W _T Of the wafer W by setting the step pitch SP of _T The case has been described in which the frame is prevented from remaining between the divided areas constituting the evaluation point corresponding area formed above to prevent the pattern portion from lowering in contrast due to the interference of the frame. However, a decrease in the contrast of the pattern portion due to the presence of the frame can be prevented as follows.
[0264]
That is, the aforementioned measurement pattern MP _n Prepare a reticle on which a measurement pattern including a multibar pattern is formed in the same manner as above, mount the reticle on a reticle stage RST, and transfer the measurement pattern onto a wafer by a step-and-repeat method or the like. Thus, the multi-bar pattern formed of a plurality of adjacent divided areas and transferred to each divided area and the adjacent pattern are separated by a distance L at which the contrast of the image of the multi-bar pattern is not affected by the adjacent pattern. The predetermined areas separated from each other may be formed on the wafer.
[0265]
In this case, the multi-bar pattern transferred to each partitioned area and the adjacent pattern are separated from each other by a distance L that does not affect the contrast of the image of the multi-bar pattern by the adjacent pattern. When detecting the image formation state in at least some of the plurality of divided areas constituting the divided areas by an image processing method such as an image processing method, template matching, or contrast detection including score detection, It is possible to obtain an imaging signal having a good S / N ratio of the image of the multi-bar pattern transferred to the divided area. Therefore, based on the image pickup signal, it is possible to accurately detect the formation state of the image of the multi-bar pattern formed in each partitioned area by an image processing method such as template matching or contrast detection including score detection.
[0266]
For example, in the case of template matching, objective and quantitative correlation value information is obtained for each sectioned area, and in the case of contrast detection, objective and quantitative contrast value information is obtained for each sectioned area. In any case, by comparing the obtained information with the respective thresholds, the formation state of the image of the multi-bar pattern is converted into binarized information (information on the presence or absence of an image). It is possible to detect the formation state of the multi-bar pattern for each area with high accuracy and reproducibility.
[0267]
Therefore, in such a case, similarly to the above-described embodiment, by obtaining the optical characteristics of the projection optical system based on the above-described detection result, an objective and quantitative correlation value, based on the detection result using the contrast, etc. Optical characteristics are required. Therefore, the optical characteristics can be measured with high accuracy and reproducibility as compared with the conventional method. In addition, the number of evaluation points can be increased, and the interval between the evaluation points can be narrowed. As a result, the measurement accuracy of the optical characteristic measurement can be improved.
[0268]
In the above embodiment, the reticle R _T Upper measurement pattern MP _n Opening pattern AP _n Although the case where one kind of L / S pattern (multi-bar pattern) arranged at the center of the inside is used has been described, it is needless to say that the present invention is not limited to this. As the measurement pattern, at least two types of L / S patterns having different periodic directions, an isolated line, a contact hole, or the like may be used. Measurement pattern MP _n When the L / S pattern is used, the duty ratio and the period direction may be arbitrary. Also, the measurement pattern MP _n When a periodic pattern is used, the periodic pattern may be not only an L / S pattern but also a pattern in which dot marks are periodically arranged, for example. This is because, unlike the conventional method of measuring the line width or the like of an image, the state of image formation is detected by a score (contrast).
[0269]
Further, in the above embodiment, the best focus position is obtained based on one type of score. However, the present invention is not limited to this. A plurality of types of scores may be set and the best focus position may be obtained based on these. Alternatively, the best focus position may be obtained based on these average values (or weighted average values).
[0270]
Further, in the above embodiment, the area from which pixel data is extracted is rectangular, but is not limited to this, and may be, for example, a circle, an ellipse, or a triangle. Also, the size can be arbitrarily set. That is, the measurement pattern MP _n By setting the extraction area in accordance with the shape of, the noise can be reduced and the S / N ratio can be increased.
[0271]
In the above-described embodiment, one type of threshold is used for detecting the state of image formation. However, the present invention is not limited to this, and a plurality of thresholds may be used. When a plurality of threshold values are obtained, each threshold value may be compared with a score to detect the image formation state of the partitioned area. In this case, for example, when it is difficult to calculate the best focus position from the detection result at the first threshold, the formation state is detected at the second threshold, and the best focus position can be obtained from the detection result. Become.
[0272]
Alternatively, a plurality of thresholds may be set in advance, the best focus position may be determined for each threshold, and their average value (simple average value or weighted average value) may be used as the best focus position. For example, the focus position when the exposure energy amount P shows an extreme value is sequentially calculated according to each threshold value. Then, the average value of each focus position is set as the best focus position. Note that two intersections (focus positions) between an approximate curve indicating the relationship between the exposure energy amount P and the focus position Z and an appropriate slice level (exposure energy amount) are obtained, and an average value of both intersection points is calculated for each threshold value. Calculated values and their average value (simple average value or weighted average value) may be used as the best focus position.
[0273]
Alternatively, the best focus position is calculated for each threshold value, and in the relationship between the threshold value and the best focus position, the average value of the best focus position in the section where the change in the best focus position is the smallest (simple average value) Alternatively, a weighted average value may be used as the best focus position.
[0274]
In the above embodiment, a preset value is used as the threshold, but the present invention is not limited to this. For example, wafer W _T Upper measurement pattern MP _n May be imaged in an area where is not transferred, and the obtained score may be used as a threshold.
[0275]
Further, for example, the number of times the image is taken in by the alignment detection system AS may be made different between the first area and the second area. By doing so, the measurement time can be reduced.
[0276]
In the exposure apparatus 100 of the above embodiment, the main controller 28 measures the optical characteristics of the projection optical system described above according to a processing program stored in a storage device (not shown), thereby automating the measurement process. Can be realized. Of course, this processing program may be stored in another information recording medium (CD-ROM, MO, etc.). Further, when performing the measurement, a processing program may be downloaded from a server (not shown). It is also possible to send the measurement result to a server (not shown), or to notify the outside of the measurement result by e-mail and file transfer via the Internet or an intranet.
[0277]
In the above embodiment, the measurement pattern MP _n The wafer W _T Upper section area DA _{i, j} To the wafer W after development. _T Upper section area DA _{i, j} Although the description has been given of the case where the resist image formed in the image is captured by the alignment detection system AS and the image data is subjected to image processing, the method for measuring the optical characteristics according to the present invention is not limited to this. For example, the object to be imaged may be a latent image formed on a resist at the time of exposure, and an image (etched image) obtained by developing the wafer on which the image is formed and further etching the wafer. It may be performed for such as. In addition, the photosensitive layer for detecting the state of image formation on an object such as a wafer is not limited to a photoresist, but may be any as long as images (latent image and visible image) are formed by irradiation of light (energy). good. For example, the photosensitive layer may be an optical recording layer, a magneto-optical recording layer, and the like. Therefore, the object on which the photosensitive layer is formed is not limited to a wafer or a glass plate, but may be an optical recording layer, a magneto-optical recording layer, or the like. It may be a plate that can be formed.
[0278]
Further, the optical characteristics of the projection optical system PL can be adjusted based on the above-described measurement results (such as the best focus position) without the intervention of an operator or the like. That is, the exposure apparatus can have an automatic adjustment function.
[0279]
Further, in the above embodiment, the exposure condition changed at the time of pattern transfer is the same as the wafer W in the optical axis direction of the projection optical system. _T Position and wafer W _T Although the description has been given of the case where the energy amount (exposure dose) of the energy beam applied to the surface is described, the present invention is not limited to this. For example, any condition such as an illumination condition (including a type of a mask), a setting condition of all components related to exposure such as an image forming characteristic of a projection optical system, or the like may be used. It is not necessary to perform exposure while performing. That is, one kind of exposure condition, for example, the wafer W in the optical axis direction of the projection optical system _T While changing only the position, the pattern of the measurement mask is transferred to a plurality of areas on the photosensitive object, and even when the state of formation of the transferred image is detected, the same score as in the above embodiment was used. There is an effect that the detection can be quickly performed by the method of the contrast measurement or the template matching.
[0280]
In the above embodiment, the best exposure amount can be determined together with the best focus position. That is, the exposure energy amount is also set on the low energy amount side, the same processing as in the above embodiment is performed, and for each exposure energy amount, the width of the focus position where the image is detected is obtained, and the width is determined as the maximum. Is calculated, and the exposure amount in that case is set as the best exposure amount.
[0281]
Further, in the above embodiment, as an example, the variance (or standard deviation) of the pixel values in the specified range in the defined area is adopted as the score E, but the present invention is not limited to this. The score E may be the sum of the pixel values in the divided area or a part thereof (for example, the specified range described above) and the differential sum. Further, the algorithm for detecting the outer frame described in the above embodiment is an example, and is not limited to this. For example, the evaluation point corresponding area DB _n At least two points may be detected on each of the four sides (upper side, lower side, left side, and right side). Even in this case, for example, vertex detection and rectangle approximation similar to those described above can be performed based on at least eight detected points. Further, in the above embodiment, as shown in FIG. 3, the measurement pattern MP _n However, the present invention is not limited to this, and a measurement pattern composed of a light-transmitting pattern may be formed in the light-shielding portion, contrary to the case of FIG. Further, in the above embodiment, the pattern area PA of the reticle is a light-shielding part, but the pattern area PA may be a light-transmitting part. In this case, the measurement pattern MP _n May be provided, or the measurement pattern MP _n May be formed together. The resist applied to the wafer is not limited to the positive type, but may be a negative type.
[0282]
Further, in the above embodiment, each partitioned area DA _{i, j} The presence or absence of the image of the measurement pattern is detected by comparing the score with a threshold value. Instead of this, the same as the curve P = f (Z) in FIG. An approximate curve may be calculated.
[0283]
That is, by detecting the outer frame and calculating the position of each partitioned area using the detection result, the first area DC on the imaging data is obtained. _n Can easily be determined. Then, the first area DC _n Is detected, for example, the distribution state of the sum of pixel data (integrated signal of luminance values on scanning lines in the X-axis direction) of each pixel column in the row direction (X-axis direction) of the above-described matrix is detected. I do. FIG. 24 shows the first region DC of FIG. 9 obtained in this manner. ₁ An example of a distribution curve G = g (Z) of an added value G of pixel data (pixel value) for each pixel column in the imaging data of FIG. Therefore, an n-th-order approximation curve (least square approximation curve) is obtained by curve fitting each peak point (indicated by ● in FIG. 24) on the curve G = g (Z). Thereby, for example, a curve G = h (Z) shown by a dotted line in FIG. 24 is obtained. When this curve G = h (Z) is compared with the above-mentioned curve P = f (Z), it is apparent that both have almost the same shape. In this case, the detection result of the image formation state (for example, presence / absence detection) of each of the above-described divided areas is substantially obtained by a simple image processing of calculating the distribution state of the added value of the pixel data for each pixel row in the predetermined direction. Data of an equivalent distribution situation can be obtained. Therefore, a simpler method with the same level of detection accuracy and reproducibility as the case of using the objective and quantitative imaging data to obtain a detection result of the image formation state (for example, presence / absence detection) of each of the above-described divided areas. Thus, the state of image formation can be detected.
[0284]
Then, by performing the same processing as in the above embodiment using the above curve G = h (Z), the optical characteristics of the projection optical system PL, such as the best focus position, may be obtained. Even in this case, similarly to the above-described embodiment, since the optical characteristics are determined based on the detection result using the objective and quantitative imaging data, the optical characteristics can be compared with the conventional method in accuracy and reproducibility. You can measure well.
[0285]
Further, in the above embodiment, the imaging characteristic of the projection optical system PL is adjusted via the imaging characteristic correction controller. However, for example, only the imaging characteristic correction controller sets the imaging characteristic within a predetermined allowable range. When the control cannot be performed, at least a part of the projection optical system PL may be replaced, or at least one optical element of the projection optical system PL may be reworked (aspherical processing or the like). In particular, when the optical element is a lens element, the eccentricity may be changed or the optical element may be rotated about the optical axis. At this time, when detecting a resist image or the like using the alignment sensor of the exposure apparatus 100, the main control device 28 displays a warning on a display (monitor) or informs the operator or the like of necessity of assistance to the operator through the Internet or a mobile phone. The notification may be made, or information necessary for adjusting the projection optical system PL, such as a replacement portion of the projection optical system PL and an optical element to be reworked, may be notified together. As a result, not only the operation time for measuring the optical characteristics and the like but also the preparation period can be shortened, and the stop period of the exposure apparatus can be shortened, that is, the operation rate can be improved. Further, in this embodiment, the measurement pattern is transferred to the wafer by the static exposure method. However, instead of or in addition to the static exposure method, at least one exposure method is used in the scanning exposure method just as in the above embodiment. Dynamic optical characteristics may be obtained by transferring the measurement pattern to the wafer while changing the conditions.
[0286]
Further, the light source of the exposure apparatus to which the present invention is applied is not limited to a KrF excimer laser or an ArF excimer laser, ₂ A laser (wavelength: 157 nm) or another pulsed laser light source in the vacuum ultraviolet region may be used. In addition, a fiber doped with, for example, erbium (or both erbium and ytterbium) is used as the illumination light for exposure, for example, a single-wavelength laser beam in the infrared or visible range oscillated from a DFB semiconductor laser or a fiber laser. A harmonic that has been amplified by an amplifier and wavelength-converted to ultraviolet light using a nonlinear optical crystal may be used. Further, an ultra-high pressure mercury lamp or the like that outputs an ultraviolet bright line (g line, i line, etc.) may be used. In this case, the exposure energy may be adjusted by lamp output control, a dimming filter such as an ND filter, a light amount aperture, and the like. Further, the present invention may be applied to an exposure apparatus that uses a charged particle beam such as an EUV light, an X-ray, or an electron beam and an ion beam as an exposure beam.
[0287]
In the above embodiment, the case where the present invention is applied to the step-and-scan type reduction projection exposure apparatus has been described, but the scope of the present invention is not limited to this. That is, the present invention can be suitably applied to an exposure apparatus such as a step-and-repeat method, a step-and-stitch method or a proximity method, a mirror projection aligner, and a photo repeater.
[0288]
Further, the projection optical system PL may be any one of a refraction system, a catadioptric system, and a reflection system, and may be any one of a reduction system, an equal magnification system, and an enlargement system.
[0289]
Furthermore, the present invention is not limited to an exposure apparatus used for manufacturing a semiconductor element, but also an exposure apparatus used for manufacturing a display including a liquid crystal display element and a plasma display, which transfers a device pattern onto a glass plate, and a thin film magnet. For exposure equipment used to manufacture device masks, such as exposure devices that transfer device patterns onto ceramic wafers, imaging devices (such as CCDs), micromachines, and DNA chips, as well as exposure devices that are used to manufacture masks or reticles. Can also be applied.
[0290]
《Device manufacturing method》
Next, an embodiment of a device manufacturing method using the above-described exposure apparatus and method will be described.
[0291]
FIG. 25 shows a flowchart of an example of manufacturing devices (semiconductor chips such as ICs and LSIs, liquid crystal panels, CCDs, thin-film magnetic heads, DNA chips, micromachines, etc.). As shown in FIG. 25, first, in step 301 (design step), a function / performance design of a device (for example, a circuit design of a semiconductor device) is performed, and a pattern design for realizing the function is performed. Subsequently, in step 302 (mask manufacturing step), a mask on which the designed circuit pattern is formed is manufactured. On the other hand, in step 303 (wafer manufacturing step), a wafer is manufactured using a material such as silicon.
[0292]
Next, in step 304 (wafer processing step), actual circuits and the like are formed on the wafer by lithography using the mask and the wafer prepared in steps 301 to 303, as described later. Next, in step 305 (device assembly step), device assembly is performed using the wafer processed in step 304. Step 305 includes processes such as a dicing process, a bonding process, and a packaging process (chip encapsulation) as necessary.
[0293]
Finally, in step 306 (inspection step), inspections such as an operation confirmation test and a durability test of the device manufactured in step 305 are performed. After these steps, the device is completed and shipped.
[0294]
FIG. 26 shows a detailed flow example of step 304 in the case of a semiconductor device. In FIG. 26, in step 311 (oxidation step), the surface of the wafer is oxidized. In step 312 (CVD step), an insulating film is formed on the wafer surface. In step 313 (electrode forming step), electrodes are formed on the wafer by vapor deposition. In step 314 (ion implantation step), ions are implanted into the wafer. Each of the above steps 311 to 314 constitutes a pre-processing step in each stage of wafer processing, and is selected and executed according to a necessary process in each stage.
[0295]
In each stage of the wafer process, when the above-described pre-processing step is completed, the post-processing step is executed as follows. In this post-processing step, first, in step 315 (resist forming step), a photosensitive agent is applied to the wafer. Subsequently, in step 316 (exposure step), the circuit pattern of the mask is transferred to the wafer by the exposure apparatus and the exposure method of each of the above embodiments. Next, in Step 317 (development step), the exposed wafer is developed, and in Step 318 (etching step), the exposed members other than the portion where the resist remains are removed by etching. Then, in step 319 (resist removing step), unnecessary resist after etching is removed.
[0296]
By repeating these pre-processing and post-processing steps, multiple circuit patterns are formed on the wafer.
[0297]
As described above, if the device manufacturing method of the present embodiment is used, the exposure apparatus and the exposure method of the above embodiment are used in the exposure step, so that the optical characteristics accurately determined by the optical characteristic measurement method described above are taken into account. High-precision exposure is performed via the projection optical system adjusted as described above, and a device with a high degree of integration can be manufactured with high productivity.
[0298]
【The invention's effect】
As described above, according to the optical characteristic measuring method of the present invention, there is an effect that the optical characteristics of the projection optical system can be obtained in a short time with high accuracy and reproducibility.
[0299]
Further, according to the exposure method of the present invention, there is an effect that highly accurate exposure can be realized.
[0300]
Further, according to the device manufacturing method of the present invention, there is an effect that a highly integrated device can be manufactured.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a schematic configuration of an exposure apparatus according to an embodiment of the present invention.
FIG. 2 is a diagram for explaining an example of a specific configuration of the illumination system IOP of FIG.
FIG. 3 is a diagram illustrating an example of a reticle used for measuring optical characteristics of a projection optical system.
FIG. 4 is a flowchart (part 1) for describing a method for measuring optical characteristics.
FIG. 5 is a flowchart (part 2) illustrating a method for measuring optical characteristics.
FIG. 6 is a diagram for explaining the arrangement of partitioned areas.
FIG. 7 shows a wafer W _T Above the first area DC _n It is a figure showing the state where was formed.
FIG. 8 shows a wafer W _T Evaluation point corresponding area DB on top _n It is a figure showing the state where was formed.
FIG. 9 shows a wafer W _T After developing _T Evaluation point corresponding area DB formed above ₁ FIG. 3 is a diagram showing an example of a resist image of FIG.
FIG. 10 is a flowchart (part 1) showing details of step 456 (processing for calculating optical characteristics) in FIG. 5;
FIG. 11 is a flowchart (part 2) showing details of step 456 (optical characteristic calculation processing) in FIG. 5;
FIG. 12 is a flowchart showing details of step 510 in FIG. 10;
FIG. 13 is a flowchart showing details of step 702 in FIG. 12;
14A is a diagram for explaining the process of step 508, FIG. 14B is a diagram for explaining the process of step 510, and FIG. 14C is a diagram for explaining the process of step 512; FIG.
15A is a diagram for explaining the process of step 514, FIG. 15B is a diagram for explaining the process of step 516, and FIG. 15C is a diagram for explaining the process of step 518. It is a figure for explaining processing.
FIG. 16 is an evaluation point corresponding area DB of a window area. ₁ FIG. 13 is a diagram schematically illustrating another example of the scanning direction with respect to the outer frame of FIG.
FIG. 17A shows one evaluation point corresponding region DB; _k FIG. 17B shows four detection areas set to detect the four sides of the outer frame of FIG. 17B. FIG. 17B shows one set of window areas from right to left in FIG. FIG. 17C is a diagram showing the sum signal of the variance signals of the pixel values obtained when scanning a set of window regions from the top to the bottom in FIG. 17A and within the detection region set at the same time. is there.
18 (A) shows the upper side of the outer frame as a detection target, and the window region from the bottom in FIG. 17 (A) to the upper side. FIG. 18 (B) shows the lower side of the outer frame. As a target, the window region is shown from the bottom to the top in FIG. 17A, and FIG. 18C is a diagram showing the window region from the right to the left in FIG. 18 (D) shows the variance signal of the pixel value obtained when the window area is scanned from left to right in FIG. 17 (A) within the set detection area with the left side of the outer frame as the detection target. , Respectively.
FIG. 19 is a diagram for describing a boundary detection process in outer frame detection.
FIG. 20 is a diagram for explaining vertex detection in step 514.
FIG. 21 is a diagram for explaining rectangle detection in step 516.
FIG. 22 is a diagram of a table data format showing an example of a detection result.
FIG. 23 is a diagram showing a relationship between the number of remaining patterns (exposure energy amount) and a focus position.
24 is a first area DC in FIG. 9; ₁ FIG. 8 is a diagram showing an example of a distribution curve of an added value G of pixel data (pixel value) for each pixel column in the imaging data of FIG.
FIG. 25 is a flowchart illustrating an embodiment of a device manufacturing method according to the present invention.
FIG. 26 is a flowchart of a process in step 304 of FIG. 25.
[Explanation of symbols]
MP _n … Measurement pattern, DB _n ... Evaluation point corresponding area (predetermined area), DC _n ... First area, DD _n ... Second region, PL: Projection optical system, W: Wafer (object), W _T ... wafer (object).

Claims (24)

An optical characteristic measuring method for measuring an optical characteristic of a projection optical system that projects a pattern on a first surface onto a second surface,
A second image capturing a predetermined area including a plurality of divided areas including a transfer area of a measurement pattern transferred onto an object via the projection optical system under different exposure conditions, at least a part of the outline of which is a linear part. One step;
On the basis of the imaging data obtained by the imaging, the linear portion forming the outer frame formed by the contour of the predetermined region is set as a detection target, and a window region having a predetermined size is scanned substantially orthogonal to the detection target linear portion. Scanning in the direction, and detecting the position of the linear portion to be detected based on the pixel data in the window area during the scanning;
Utilizing the detection result of the position of the linear portion of the detection target in the second step, detecting a formation state of an image in at least a part of the plurality of divided areas using the imaging data. Three steps;
A fourth step of obtaining optical characteristics of the projection optical system based on the detection result in the third step. 2. The method according to claim 1, wherein the scanning direction is a direction from the inside to the outside of the outer frame. The predetermined region includes at least one set of mutually parallel straight portions in the contour thereof,
In the second step, based on the imaging data, a set of window regions of a predetermined size arranged at a predetermined distance according to a design value of the outer frame are formed in parallel with each other to form the outer frame. Each of the set of linear portions is a detection target, and is simultaneously scanned in a scanning direction substantially orthogonal to the detection target linear portion. During the scanning, the detection target straight line is determined based on pixel data in the set of window regions. The method according to claim 1, wherein the position of the portion is detected. 4. The method according to claim 1, wherein, in the second step, a position where a representative value of pixel data in the window area is maximum or minimum is detected as a position of the linear portion to be detected. 5. The optical characteristic measuring method according to the paragraph. The size of the window area is set to a size such that the difference between the representative value of the pixel data on the outer frame to be detected and the predetermined area is equal to or larger than a predetermined value. The method for measuring optical characteristics according to claim 4. The representative value of the pixel data is one of a variance, a standard deviation, an addition value, and a differential sum value of a pixel value corresponding to the pixel data in at least a part of the area including the center in the window area. The optical characteristic measuring method according to claim 4 or 5, wherein The imaging data is a plurality of bits of data larger than 2,
7. The method according to claim 1, wherein the second step uses, as the pixel data, data in which low-order bit data other than high-order plural bits including the most significant two bits from the plural-bit data is set to 0 or 1. The optical characteristic measuring method according to any one of the above. Prior to the first step, while changing at least one exposure condition, a target pattern including a rectangular frame-shaped pattern and the measurement pattern located inside the rectangular frame-shaped pattern is placed on the first surface. And sequentially transferring the object pattern on the object by sequentially moving the object arranged on the second surface side of the projection optical system at a predetermined step pitch, thereby forming the plurality of partitioned areas into The method for measuring optical characteristics according to claim 1, further comprising a transfer step including a step of forming on an object. The optical characteristic measuring method according to claim 8, wherein the step pitch is set to be equal to or smaller than a distance corresponding to a size of the rectangular frame-shaped pattern. The predetermined region includes only the plurality of divided regions, and in the transfer step, at least a part of a plurality of the divided regions located at the outermost peripheral portion of the predetermined region is overexposed. 9. The optical characteristic measuring method according to claim 8, wherein the amount of energy of the energy beam applied to the object is changed as a part of the exposure condition so as to be a region of the exposure condition. The measurement pattern includes a multi-bar pattern,
The multi-bar pattern transferred to each of the plurality of divided areas and the pattern adjacent thereto are separated by a distance L or more that does not affect the contrast of the image of the multi-bar pattern by the adjacent pattern. The optical characteristic measuring method according to any one of claims 1 to 10, wherein: In the third step, based on the detection result of the position of the linear portion to be detected, the position of each of at least some of the plurality of divided regions constituting the predetermined region is determined with reference to the detected outer frame portion. The optical characteristic measuring method according to claim 1, further comprising a calculating step. The optical characteristic measuring method according to claim 1, wherein the predetermined area is an area having an outline including only a straight line portion. The predetermined area is a rectangular area whose outline is composed of four linear portions,
In the third step, prior to the calculating step, based on the detection result of the position of the side that is the linear portion to be detected, each of the first to fourth sides forming the outer frame of the rectangle Further including an outer frame calculation step of calculating at least two points above and calculating the outer frame based on the obtained at least eight points,
In the calculating step, an inner region of the outer frame is equally divided using arrangement information of a known divided region, and a position of each of the plurality of divided regions constituting the predetermined region is calculated. An optical characteristic measuring method according to claim 12. In the outer frame calculation step, four vertices of the predetermined area, which is a rectangular area, are obtained as intersections of four straight lines determined based on the two points on the first to fourth sides obtained, 15. The optical characteristic measuring method according to claim 14, wherein a rectangle approximation by the least square method is performed based on the obtained four vertices, and a rectangular outer frame of the predetermined area including rotation is calculated. 16. The method according to claim 1, wherein in the third step, the detection of an image formation state in the at least some of the plurality of divided areas is performed using a representative value regarding pixel data of each divided area as a determination value. The method for measuring optical characteristics according to any one of the preceding claims. 17. The method according to claim 16, wherein the representative value is one of an addition value, a differential sum value, a variance, and a standard deviation of a pixel value corresponding to pixel data in at least a part of a range within each of the divided areas. The described optical property measurement method. The representative value is obtained by using an average value of pixel values in an arbitrary partitioned area in which it is expected that the image of the measurement pattern does not remain as an average value. The optical characteristic measuring method according to claim 16, wherein one of the variance and the standard deviation of a pixel value corresponding to pixel data in the pixel data is included. 16. The optical device according to claim 1, wherein the detection of an image formation state in the at least some of the plurality of divided regions in the third step is performed by a template matching technique. Characteristics measurement method. 20. The exposure condition according to claim 1, wherein the exposure condition includes at least one of a position of the object with respect to an optical axis direction of the projection optical system and an energy amount of an energy beam irradiated on the object. The optical characteristic measuring method according to the paragraph. The exposure conditions include a position of the object with respect to an optical axis direction of the projection optical system and an energy amount of an energy beam irradiated on the object,
The plurality of divided areas formed on the object are formed of transfer areas of a measurement pattern sequentially transferred onto the object via the projection optical system while changing the exposure condition,
In the third step, detection of an image formation state is detection of the presence or absence of an image of the measurement pattern in the detection target partitioned area,
In the fourth step, a best focus position is determined based on a correlation between an energy amount of the energy beam corresponding to a plurality of divided areas where the images are detected and a position of the object in an optical axis direction of the projection optical system. The optical characteristic measuring method according to any one of claims 1 to 20, wherein: An optical characteristic measuring method for measuring an optical characteristic of a projection optical system that projects a pattern on a first surface onto a second surface,
A first step of sequentially transferring a measurement pattern arranged on the first surface to a plurality of regions on an object arranged on a second surface side of the projection optical system while changing at least one exposure condition; ;
The measurement pattern is imaged at a region including a region having a predetermined shape composed of a plurality of divided regions of at least a part of the plurality of divided regions on the object to which the measurement pattern has been transferred under different exposure conditions. A second step of detecting a distribution state of an added value of pixel data for each pixel row in a predetermined direction in an area having a predetermined shape;
A third step of obtaining optical characteristics of the projection optical system based on the detection result. An exposure method of irradiating a mask with an energy beam for exposure, and transferring a pattern formed on the mask onto an object via a projection optical system,
A step of adjusting the projection optical system in consideration of the optical characteristics measured by the optical characteristic measurement method according to any one of claims 1 to 22;
Transferring the pattern formed on the mask onto the object via the adjusted projection optical system. A device manufacturing method including a lithography step,
A device manufacturing method using the exposure method according to claim 23 in the lithography step.

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