JP3630852B2 - Pattern formation state detection apparatus and projection exposure apparatus using the same - Google Patents

Description

となる。
【００５０】
ここでｎ１，ｎ２はそれぞれ格子のＬ（ライン部分）とＳ（スペース相当部分）の屈折率である。ライン部分Ｌとスペース部分Ｓはレジストの潜像の場合、Ｌがレジスト、Ｓが露光されたレジストであり、レジストを現像した場合、ＬがレジストでＳが空気等の気体である。
【００５１】
偏光解析のモデルはウエハ基盤上の所定の厚みの複屈折媒質の複屈折率を測定することに相当する。偏光解析法とは、このウエハ基盤上にＰ／Ｓ（Ｐ偏光／Ｓ偏光）の位相差０、振幅比１の直線偏光光を所定の角度θで入射させ、その反射光の位相差（Δ）と振幅比（Ψ）を測定し、予め測定したライン部分Ｌとスペース部分Ｓの屈折率ｎ１，ｎ２及びレジスト厚ｄを用いて屈折率ｎ‖，ｎ⊥を求めることができるものである。この偏光解析法により求まった屈折率ｎ‖，ｎ⊥の値から、上記式を用いてデューティｔを求めている。この偏光解析法は公知であるので詳細は省略する。
【００５２】
本発明の一実施形態ではこのように偏光解析法を利用してレジスト内の潜像パターン、若しくは現像後の凹凸パターンのデューティを測定している。
【００５３】
本発明の一実施形態ではＬ＆Ｓパターンを異なる露光条件で感光体面上に転写して複数の感光パターンを形成する工程と、前記複数の感光パターンに対し、順次前記光束を照射し、その反射光の偏光状態を検出し、前記偏光状態から感光パターンのデューティを算出する工程と、前記デューティが所望になる露光条件を決定する工程と、その露光条件でその後、複数のウエハに焼き付ける工程を含むことを特徴としている。
【００５４】
次に本発明の実施形態を図を用いて説明する。図１は本発明の実施形態１の要部概略図、図２〜図６は図１の一部分を抽出したときの説明図である。
【００５５】
本実施形態は感光パターンを介した入射光束の変化として偏光状態の変化を利用した場合である。
【００５６】
図１において１０１は縮小型の投影レンズであり、後述する露光用の光源１０７からの露光光で照明したレチクル１０２面上の回路パターン１０２ａをウエハ１０３上に投影している。１０４はウエハチャックであり、ウエハ１０３を吸着している。１０５は粗微動ステージ（Ｚステージ）であり、ウエハチャック１０４をＺ方向に粗微動させている。１０６はＸＹステージ（ウエハステージ）であり、ＸＹ方向にウエハチャック１０４を移動させている。１０７は露光用の光源である。１０８は構造体であり、光源１０７，レチクル１０２，投影レンズ１０１及びウエハステージ１０６等を支えている。
【００５７】
次に本実施形態で用いているウエハ１０３の投影レンズ１０１の光軸方向の位置、即ちフォーカス位置を検出する為のフォーカス位置制御装置とレチクル１０２を露光光で照明する際の露光量制御装置とを有する制御手段について図４を参照して説明する。
【００５８】
図４において２０１は半導体レーザ等の高輝度の光源である。光源２０１から出たレーザ光は折り曲げミラー２０８により方向を変えられた後、ウエハ１０３の表面に入力する。ウエハ１０３の測定点Ｐ１で反射した後、光束は折り曲げミラー２０９で方向を変えられた後、入射光束の２次元位置を検出する検出素子２０２に入射する。検出素子２０２は、例えばＣＣＤ等から成り、光束の入射位置を検知している。ウエハ１０３の表面のＺ方向（投影レンズ１０１の光軸方向）の位置変化が検出素子２０２上の入射位置の位置ずれとなるようにして検出している。この検出素子２０２からの信号に基づいてフォーカス制御装置２０３はウエハ１０３のＺ方向の位置、即ちフォーカス位置をＺステージ１０５で制御している。
【００５９】
２０６はシャッター開閉機構、２０７はハーフミラー、２０５は照度センサーであり、ハーフミラー２０７で反射した光源１０７からの光束の露光量を検出している。積算露光制御装置２０４は照度センサー２０５からの信号に基づいてシャッター開閉機構２０６を制御して光源１０７からの光束の通過量を制御している。これによりレチクル１０２を照射する露光量が予め設定した値となるように調整している。
【００６０】
本実施形態では、このような露光量制御装置とフォーカス位置制御装置より成る制御手段を利用してレチクル１０２面上のパターンをウエハ１０３面上に投影する際の露光条件を制御している。
【００６１】
次に光源１０７からの露光光で照明したレチクル１０２面上のパターンをウエハ１０３面上に投影する場合について説明する。
【００６２】
図５はレチクル１０２面上の基準パターン（以下「パターン」という）１０２ａの説明図である。パターン１０２ａはライン（Ｌ）とスペース（Ｓ）より成るＬ＆Ｓのパターン１０２１，１０２２を互いに直交させて構成している。
【００６３】
本実施形態ではＬ＆Ｓのパターン１０２１，１０２２より成るパターン１０２ａを描画したレチクル１０２をレチクルステージにセットし、レジストを塗布したウエハ１０３をウエハチャック１０４にセットし、レチクル１０２のパターン１０２ａをステップ＆リピート方式でウエハ１０３上に順次露光していく。このとき前述したフォーカス制御装置２０３及び積算露光制御装置２０４を用いて図６に示すように１ショットである領域１０３１を順次焼き付けパターン１０２１，１０２２の潜像１０３１２及び１０３１１を焼き付ける。
【００６４】
そしてＸ方向のショット位置に応じてｆｏｃｕｓオフセットを予想最適位置を中心に一定量ずつ変えながらステップ移動し、Ｙ方向のショットに対しては同様に、最適露光量（シャッター時間）を中心に露光量を変えながら露光していく。図６の例では説明の都合上、３×３のマトリックスであるが、このショット数は多い方が条件を出しやすくなる。
【００６５】
図７は、このように順次露光したときのウエハ１０３のレジストの断面の説明図である。露光後のウエハ１０３のレジストは図７に示すようにレジスト内に潜像を形成する。潜像は露光光によってレジストが化学変化等で性質が変化して構成されたもので、一般にこの斜線で示した部分は露光した部分であり、この部分は屈折率が変化している。
【００６６】
図７のマトリックス番地は図６のそれぞれに対応した位置での断面であり、（１），（２），（３）はそれぞれのチップのパターン像１０３１２の断面を表している。
【００６７】
次に露光後のウエハ１０３のレジストは図７に示すように潜像をウエハチャック１０４から外すことなく、光源部３０１，受光部３０２，ドライバー３０３，そして偏光処理装置３０４で構成される偏光解析装置３００により入射光に対する反射光の振幅比Ψと位相差Δを測定している。
【００６８】
図３は、このときの図１の偏光解析装置３００の主要部分を抽出した概略図である。図１１は図３の光路を展開した説明図である。図３，図１１において照射手段としての光源部（光束入射手段）３０１は光源３０１１（ウエハ１０３上のＬ＆Ｓピッチ以上の波長でＨｅＮｅレーザや半導体レーザばかりでなく、分光器の単色光でも良い）と偏光素子３０１２（グラムトムソン等）を有している。偏光素子３０１２はウエハ１０３に対し、Ｐ偏光成分（紙面に平行）とＳ偏光成分（紙面に垂直）が等量になるように紙面と偏光面が４５度となるように設置している。従ってこの光束Ｐ，Ｓの位相差Δは０で、振幅比Ψは１である。
【００６９】
受光部（受光手段）３０２は異方性の軸が光束３０５に直交したλ／４波長板３０２４、アナライザーであるところの偏光素子３０２２（グラムトムソン等）、光電変換素子３０２１とを有している。更にλ／４板３０２４は光束３０５方向を回転軸とする回転機構３０２３内に保持され、ドライバー３０３からの指令により一定速度で回転している。
【００７０】
今、光源部３０１からの射出光３０５がウエハ１０３上のレジスト表面とウエハ表面で反射し、その合波光束がウエハ１０３上のレジストの複屈折率ｎ１，ｎ２等に応じてＰ，Ｓ偏光の位相差Δと振幅比Ψが変化する。
【００７１】
その光束を回転するλ／４板３０２４とアナライザー３０２２を通してディテクタ３０２１で検出し、これにより処理手段３０４は位相差Δと振幅比Ψに応じた正弦波の電気信号を得て、その振幅と直流成分の大きさの正弦波の位相情報から上記Δ，Ψを求めている。
【００７２】
以上のように、偏光解析法を利用して予め測定されているレジストの未露光部分の屈折率ｎ１，被露光部分の屈折率をｎ２，レジストの厚みｄ，及び基盤の複素屈折率ｎｓを与えることによりＬ＆Ｓのレジストパターンを複屈折構造体として屈折率ｎ⊥を求めている。
【００７３】
更にデューティｔ⊥を屈折率ｎ⊥の値から以下の式で求めている。
【００７４】

屈折率ｎ‖の値からデューティｔ‖は
ｔ‖＝（ｎ‖＊＊２−ｎ２＊＊２）／（ｎ１＊＊２−ｎ２＊＊２）
となる。この２値を次のように平均化して精度を高めている。
【００７５】
ｔ１＝（ｔ⊥＋ｔ‖）／２
通常は以上でデューティｔを求めることができるが、レジストむらや下地の構造等による測定値の変動がある場合もあるので、図２の平面図に示すように前記のｘ方向からの偏光解析測定に対し、それに直交した、つまりｙ方向からの第２の偏光解析装置を構成し、第１の偏光解析装置（３０１，３０２）が測定した測定点と略同一点を同時に測定することにより以下のようにして精度向上を図っている。
【００７６】
この場合もデューティｔ１を求めたときと同様に
ｔ２＝（ｔ⊥＋ｔ‖）／２
となり、前述したデューティｔ１を使って、
ｔ＝（ｔ１＋ｔ２）／２
と平均することにより、更にデューティｔの測定精度を高めている。
【００７７】
一方、図８はサンプルのＬ＆Ｓを偏光解析によって得られたデューティとそのサンプルを現像し、ＳＥＭで測定した値を比較することにより最適露光条件を見出す方法の説明図である。これにより偏光解析法で発生する下地の構造等で発生するデューティのオフセットを計り、以降の測定ではこのオフセット値を差し引いた値を補正された正しい測定値としている。このＳＥＭとの比較はプロセス等の条件が変わる最初に一度だけすれば良く、以後はＳＥＭは必要としない。
【００７８】
次に図９，図１０に示す露光条件の最適化のフローチャートを説明する。図９は１枚のウエハに８×６個のチップ露光をし、その偏光解析結果をΔ−Ψマップ上に表した例である。例えば、ライン４１０上の測定点は露光量が一定でｆｏｃｕｓが変化しているものであり、一方ライン４０１上の測定点は逆にｆｏｃｕｓが一定で露光量が変化している場合を示している。
【００７９】
このΔ−Ψのマップ上の四角枠ＡＸ内に示されたショットは、前述したようなＳＥＭ測定との対応により最適なデューティになっている範囲を示している。従って露光ショットを偏光解析法により測定し、Δ，Ψがこの枠ＡＸに入れば最適デューティを示していることになる。
【００８０】
以上をフロー化したのが図１０である。まず、ウエハにレジストをコートする。このときレジストの厚みが分かっていなければ、このとき測定する。次に前述したようにステージをステップ移動しながらｆｏｃｕｓと露光量（シャッター時間）を変えて試し焼きをする。
【００８１】
次にウエハをウエハチャックから取り外すことなく、同様にステージを移動しながら偏光解析法で次々にショットを変えてΔ，Ψを測定する。偏光解析結果が図９で示された所定の範囲ＡＸのΔ，Ψであれば、そのショットを焼き付けた露光条件を量産焼きの最適露光条件とする。
【００８２】
この偏光解析方法によるデューティチェックをウエハの量産焼き付け工程内の途中で随時行い、歩留を上げている。
【００８３】
本実施形態では以上のようにして最適な露光条件を設定した後にウエハを所定の現像処理工程を介して、これにより高集積度のデバイスを製造している。
【００８４】
図１２は本発明の実施形態２の説明図である。本実施形態では実施形態１に比べて露光装置上に物理的制約等がある場合に、偏光解析装置を露光装置のウエハステージ上とは別に設けている点が異なっているだけであり、その他の構成は同じである。
【００８５】
図１３は本発明の実施形態３の説明図である。実施形態１ではウエハ面上のレジストを現像しない潜像のままで偏光解析をしているのに対して、本実施形態ではレジストを現像してから偏光解析をしている点が実施形態１と異なっており、その他の構成は同じである。
【００８６】
図１４は本実施形態に係るレジスト現像後の感光パターンの断面形状の説明図である。図１４から明かのように、本実施形態は実施形態１，２の潜像方式に比べて屈折率ｎ２が略１．０の気体である為、Ｌ＆Ｓの屈折率差が大きく取れるので、デューティの測定精度が有利であり、条件が厳しい場合、この方式が向いている。
【００８７】
本実施形態では現像処理後の感光パターンを偏光解析して最適な露光条件を求めており、これにより従来のＳＥＭを用いた場合に比べて短時間で最適な露光条件を求めている。
【００８８】
図１５は本実施形態のフローチャートである。図１６は本発明の実施形態４の説明図である。本実施形態では実施形態１に比べてレジストの現像とＳＥＭを同居させている点が異なっており、その他の構成は同じである。尚、本実施形態ではＳＥＭは偏光解析法によるデューティ測定の更生用として現像したレジスト像を確認する必要が生じたときに使用している。
【００８９】
図１７は本発明の実施形態５の要部概略図である。本実施形態は感光パターンを介した入射光束の変化として、入射光束の波長を変化させた時の反射光束の強度の変化を用いた場合を示している。ここで入射光束の強度の変化としてレジスト膜の屈折率を用いて求めている。
【００９０】
図１７において図１で示した要素と同一要素には同符番を付している。同図において５０１はモノクロメーターであり、内蔵している不図示の白色光源を回折格子等で波長分散させスリットで切り出すことにより、ウエハ１０３上のレジスト膜の表裏面で干渉できる程度に短波長化した光束を放射している。５０２はレジストパターン（現像／潜像）の表裏面から反射干渉してきた光束の光量を検出する光電検出器である。５０３はモノクロメーター５０１の波長をドライブし、光電検出器５０２からの電気信号からレジストパターンの屈折率を演算し、その結果を中央処理装置１０９に送信するドライバ／処理装置である。ここで５０１は白色光源、５０２は分光反射率を求める分光器でもよい。
【００９１】
次に本実施形態の動作原理を図１８〜図２１を用いて説明する。尚、ウエハ１０３上に塗布したレジストの膜厚は予め膜厚計で測定して求めている。又レジストパターンの屈折率を求めてからパターンのデューティを算出、更にフォーカス、露光量制御をするところは実施形態１と同一であるところから説明を省略する。
【００９２】
まずレジストの屈折率ｎ_２ の測定原理について説明する。図１８において媒質の屈折率を光の入射側から順にｎ_１ ，ｎ_２ ，ｎ_３ とし、膜厚をｄとする。使用波長（真空中での波長λ_０ ）の各々の入射角をθ_１ ，θ_２ ，θ_３ とする。このときの振巾反射率γは次のようになる［参考：Ｍ．Ｂｏｒｎ ａｎｄ Ｅ．Ｗｏｌｆ 著，”Ｐｒｉｎｃｉｐｌｅｓ ｏｆ Ｏｐｔｉｃｓ” ３ｒｄ ｅｄｉｔｉｏｎ，ＰＥＲＧＡＭＯＮ ＰＲＥＳＳ，６２頁］。
【００９３】
【数２】

ここでγ_１２は媒質１と２の境界でのフレネルの反射係数で、γ_２３は媒質２と３の境界でのフレネルの反射係数であり、βはβ＝（２π／λ_０ ）・ｎ_２ ・ｄ・ ｃｏｓθ_２ である。
【００９４】
実際測定可能な量は、反射強度すなわちＲ＝｜γ｜^２ （通常反射率と呼ぶ）であり、次のようになる。
【００９５】
【数３】

（２）式より、いま測定しようとする屈折率ｎ_２ は次のようになる。
【００９６】
【数４】

ここでＮは整数である。
【００９７】
使用波長λ_０ を変化させたときの反射率Ｒとｎ_２ は図１８（Ｂ）及び図１８（Ｃ）のようになる。従って各波長での屈折率ｎ_２ の平均値ｎ_２ＡＶ を屈折率とすることにより、再現性の良い高精度な測定ができる。
【００９８】
屈折率を高精度に測定するには、反射率の測定精度を挙げることが肝要である。本実施形態は反射率の測定精度向上を目的としている。
【００９９】
測定精度の劣化原因として、以下のことが挙げられる。
【０１００】
イ．迷光
ロ．光量検出器の変動
ハ．経時変化
本実施形態は、これらを自動的に補正することにより、測定精度を向上している。
【０１０１】
図１９，図２０，図２１は測定原理の説明図である。図１９は構成を、図２０は処理プロセスを、図２１は図２０の処理プロセスの各プロセスでの信号を示したものである。
【０１０２】
図１９において５００１は分光器、５００２は分光器での試料面からの各波長の反射率相当の出力信号を記憶するＲＡＭ１、５００３はこの出力信号を計算処理するＣＰＵ１、５００４は所定の膜の理想の反射率を計算し、その計算値をデータ処理するＣＰＵ２、５００５はＣＰＵ２の処理後のデータを記憶するＲＡＭ２、５００６はＣＰＵ１とＲＡＭ２の処理データからＲＡＭ１のデータを補正し更に膜厚計算をするＣＰＵ３、そして５００７は膜厚計算結果を出力する出力機器から成り立つ。
【０１０３】
次にその作用について図２０，図２１を使って以下説明する。
【０１０４】
まず分光器からの各波長の反射率測定（図２０のステップ５０１３）のデータすなわちＲＡＭ１のデータを、ＣＰＵ１で高速フーリエ変換等によりデータの平滑化（図２０のステップ５０１４）を行う。すなわち図２１（Ａ）の×印が測定値であり実線のｆ（λ）で示したのが平滑化した曲線である。
【０１０５】
ここでｆは波長λの関数である。次のこのｆ（λ）の極大、極小値及びその中間レベルを求める（図２０のステップ５０１５）。その方法は、まず極大点の点列を結び曲線ｍａｘ（λ）そして極小点の点列を結び曲線ｍｉｎ（λ）を求めそして、その中間レベル
【０１０６】
【数５】

を求める。
【０１０７】
一方、予め、測定対象の膜の反射率の理論値すなわち各波長の理想反射率をＣＰＵ２で計算（図２０のステップ５０１６）し、その曲線Ｆ（λ）から、極大値を結んだ曲線ＭＡＸ（λ）、極小値を結んだ曲線ＭＩＮ（λ）、そして中間レベルＡＶＥ（λ）を算出しておく（図２０のステップ５０１７）。ＭＡＸ（λ），ＭＩＮ（λ），ＡＶＥ（λ）はＲＡＭ２に入れる。
【０１０８】
以上からＣＰＵ３によってｆ（λ）を次のように修正し、ｆ′（λ）とする。
【０１０９】
【数６】

前記測定精度劣化原因によって生ずる反射率データのゲイン変動を（４）式第１項で修正し（図２０のステップ５０１８）、バイアス変動（図２１（Ｃ）参照）を第２項で修正する（図２０のステップ５０１９）。
【０１１０】
更にこの修正されたｆ′（λ）をＲとして前記（３）式により屈折率ｎ_２ を算出する（図２０のステップ５０２０）ことにより、反射率の測定を行っている。
【０１１１】
また同様の試料を繰り返し測定する場合は、図２１（Ｄ）に示すように毎回ｍａｘ（λ），ｍｉｎ（λ）そしてａｖｅ（λ）を算出するには時間のロスとなるから、初回に測定した試料のデータを使い、修正することも可能である。
【０１１２】
第Ｎ回目の試料測定ｆ′_Ｎ （λ）を次式で計算する。なお添字１又はＮは初回測定又はＮ回目の測定での値を示す。
【０１１３】
【数７】

このとき初回の試料は、第Ｎ回目の試料と全く同一である必要はない。すなわちｆ_Ｎ （λ）にゲインとバイアスを与えることができれば良く、測定精度劣化原因の各項目が変動していない範囲であれば良い。
【０１１４】
【発明の効果】
本発明によれば以上のように、露光によるレジストの感光状態（潜像）あるいは現像後のＬ＆Ｓ等の感光パターンの形成状態を入射光束の変化，例えば反射光の強度の変化や偏光状態の変化を利用して測定し、その測定値から最適な露光条件を決定し、その最適露光条件でウエハを量産露光していくことにより短時間で最適な露光条件を設定することができ、高集積度の投影パターンが容易に得られるパターン形成状態検出装置及びそれを用いた投影露光装置を達成することができる。
【０１１５】
特に従来のＳＥＭを用いる方法に比べて、周期性を持つパターン、例えばＬ＆Ｓパターンをレチクルに構成した露光条件測定用のレチクルを用いて、このパターンのレジスト像（現像する場合、若しくは現像しない潜像の場合）のデューティを反射光の情報を用いることにより最適露光条件を、高精度でしかも短時間で得られるという効果がある。
【図面の簡単な説明】
【図１】本発明の実施形態１の要部断面図
【図２】本発明の実施形態１の部分の平面図
【図３】図１の偏光解析装置の一部分の説明図
【図４】露光装置におけるｆｏｃｕｓ検出と露光量制御の一部分の概略図
【図５】露光条件測定用のレチクルパターンの説明図
【図６】露光条件を振って焼いたウエハ上のレジスト潜像の説明図
【図７】図６のウエハのレジスト潜像の断面図
【図８】偏光解析装置による測定値のＳＥＭによる更生の説明図
【図９】Δ−Ψマップ
【図１０】偏光解析法を露光条件設定に適用した場合のフローチャートの説明図
【図１１】偏光解析法構成の説明図
【図１２】偏光解析装置を別置きした実施形態２の説明図
【図１３】レジスト現像工程を入れた実施形態３の説明図
【図１４】レジスト現像後の断面形状の説明図
【図１５】現像工程を入れたフローチャートの説明図
【図１６】ＳＥＭと隣接させた実施形態４の説明図
【図１７】本発明の実施形態５の要部断面図
【図１８】本発明に利用した分光反射率から膜厚を求める基本原理説明図
【図１９】本発明の実施形態の構成を示すブロック図
【図２０】本発明の実施形態の処理プロセスを示す説明図
【図２１】本発明の実施形態の信号状態を示す説明図
【符号の説明】
１０１ 縮小型の投影レンズ
１０２ レチクル
１０３ ウエハ
１０４ ウエハチャック
１０５ 粗微動チルトＺステージ
１０７ 光源
１０８ フレーム
１０９ 中央処理装置
２０１ フォーカス検知用光源
２０２ フォーカス検知用光電変換器
２０３１ フォーカス制御装置
２０４１ 積算露光量検出回路
２０４２ 積算露光量制御回路
３０１ 偏光解析光源部
３０２ 偏光解析受光部
３０３ 回転ステージドライバー
３０４ 偏光解析処理装置
５０１ 光束入射手段
５０２ 受光手段
５０３ 処理手段[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pattern formation state detection apparatus and a projection exposure apparatus using the same, for example, a process for manufacturing a semiconductor device such as an IC or LSI, an imaging device such as a CCD, a display device such as a liquid crystal panel, or a device such as a magnetic head. Among these, the exposure state of a projection exposure apparatus used in the lithography process is measured, and the optimum exposure conditions are determined in real time or quickly, which is suitable for exposure.
[0002]
[Prior art]
In recent years, higher integration of semiconductor devices such as ICs and LSIs has been accelerated, and the progress of microfabrication technology for semiconductor wafers accompanying this has been remarkable. As this fine processing technology, various reduction projection exposure apparatuses (steppers) that form circuit pattern images of a mask (reticle) on a photosensitive substrate by a projection optical system (projection lens) and expose the photosensitive substrate by a step-and-repeat method are proposed. Has been.
[0003]
In this stepper, the circuit pattern on the reticle is reduced and projected to a predetermined position on the wafer surface via a projection optical system having a predetermined reduction magnification, and after one projection transfer is completed, the wafer is The entire surface of the wafer is exposed by repeating the step of moving the stage placed by a predetermined amount and transferring again.
[0004]
In general, in order to transfer a fine circuit pattern using a stepper having a projection optical system, the exposure conditions such as the exposure amount on the wafer surface and the focus position of the wafer (position in the optical axis direction of the projection optical system) are appropriately set. Setting is important.
[0005]
For this reason, in the conventional stepper, after printing on the photosensitive substrate while changing at least one of the exposure conditions, that is, the focus position and the exposure amount (shutter time) for each shot in the trial printing process (send head) before entering the mass production process. The optimal exposure conditions are determined by developing the photosensitive substrate and measuring the line width of the pattern on a straight line with an optical microscope or a line width measuring device.
[0006]
For example, in the horizontal direction of the shot area array on the wafer, exposure is performed by changing the exposure amount (shutter time) by a constant amount while keeping the focus value constant, and the exposure amount is constant in the vertical direction of the shot array. Exposure is performed by changing the value by a certain amount.
[0007]
Then, the line width of the resist pattern (L & S pattern) of the line (L) & space (S) in each shot formed after development is measured and detected by a scanning electron microscope (SEM). The optimum focus position and the optimum exposure amount are calculated.
[0008]
[Problems to be solved by the invention]
In order to set the optimum exposure conditions (exposure amount and focus position) in a conventional stepper, the line width of the resist pattern formed on the wafer is measured with an SEM or the like, which requires a long processing time. It was.
[0009]
The present invention measures the exposure state (latent image) of a resist by exposure or the formation state of a photosensitive pattern such as L & S after development using changes in incident light flux, for example, changes in intensity of reflected light and changes in polarization state. The optimum exposure conditions are determined from the measured values, and the wafers are mass-produced and exposed under the optimum exposure conditions, so that the optimum exposure conditions can be set in a short time, making it possible to easily project highly integrated projection patterns. It is an object of the present invention to provide a pattern formation state detection apparatus and a projection exposure apparatus using the pattern formation state detection apparatus.
[0010]
[Means for Solving the Problems]
The pattern formation state detection apparatus according to the first aspect of the present invention is an apparatus for detecting a formation state of a photosensitive pattern formed by exposing a photosensitive member applied to an object to a periodic pattern via an optical system.
Irradiating means for irradiating the photosensitive pattern with a luminous flux;
A light receiving means for receiving a light beam from the photosensitive pattern;
And processing means for detecting a change in the polarization state of the light beam received by the light receiving means and obtaining the formation state of the photosensitive pattern based on the detection result.
[0011]
According to a second aspect of the present invention, in the first aspect of the present invention, the formation state of the photosensitive pattern is a duty of the photosensitive pattern.
[0012]
According to a third aspect of the present invention, in the first aspect of the invention, the wavelength of the incident light beam is different from the wavelength of the exposure light.
[0013]
According to a fourth aspect of the present invention, there is provided a pattern formation state detection apparatus for detecting a formation state of a photosensitive pattern formed by exposing a photosensitive member applied to an object to a periodic pattern via an optical system.
Irradiating means for irradiating the photosensitive pattern with a luminous flux;
A light receiving means for receiving a light beam from the photosensitive pattern;
And processing means for detecting a change in reflectance for each wavelength of the light beam received by the light receiving means and determining the formation state of the photosensitive pattern based on the detection result.
[0014]
According to a fifth aspect of the present invention, a projection exposure apparatus projects and exposes a periodic pattern on a first object surface illuminated with exposure light onto a second object surface coated with a photosensitive member by a projection optical system, thereby forming a photosensitive pattern. The projection exposure apparatus includes the pattern formation state detection device according to any one of claims 1 to 4 for detecting a formation state of the photosensitive pattern.
[0015]
According to a sixth aspect of the present invention, in the fifth aspect of the present invention, the pattern formation state detection device detects the formation states of a plurality of photosensitive patterns formed under a plurality of different exposure conditions.
[0016]
A seventh aspect of the invention is characterized in that, in the fifth or sixth aspect of the invention, the photosensitive member is a resist, and the photosensitive pattern is a latent image or an uneven step of a resist formed after development processing.
[0017]
The invention of claim 8 is the invention of any one of claims 5 to 7, wherein the exposure condition is an exposure amount on the second object plane or / and an optical axis direction of the projection optical system of the second object. It is characterized by the focus position.
[0018]
The projection exposure method of the invention of claim 9 detects the formation state of a plurality of photosensitive patterns formed under a plurality of different exposure conditions using the pattern formation state detection device according to any one of claims 1 to 4, A pattern on the first object plane is projected and exposed onto the second object plane via the optical system using the detection result.
[0019]
According to a tenth aspect of the present invention, in the ninth aspect of the invention, the different exposure conditions are different in at least one of an exposure amount for exposing the second object plane and a position in the optical axis direction of the optical system. It is said.
[0020]
A device manufacturing method according to an eleventh aspect of the invention is a method of projecting and exposing a pattern on a reticle surface onto a photoconductor on a wafer surface by the optical system using the projection exposure method according to the ninth or tenth aspect, and the wafer. And a developing process.
[0038]
DETAILED DESCRIPTION OF THE INVENTION
First, the characteristics of the optimum exposure condition setting method when the pattern on the first object (reticle) surface is projected and exposed to the second object (wafer) in the present invention will be described.
[0039]
In the present invention, when the L & S pattern (periodic pattern) is transferred to the resist,
(I). Optimal focus position
(B). Optimal exposure
The principle in which the duty ratio (the sum of the width of the resist remaining portion and the portion without the resist, that is, the ratio of the width of the remaining portion of the resist to the pitch) is 2: 1 is used.
[0040]
Therefore, in the present invention, a mask in which a reticle (R) has a cycle in one direction, for example, a reference pattern (periodic pattern) for measuring exposure conditions with an L & S duty ratio of 2: 1 is formed, and an image of the reference pattern is transferred to the wafer. The wafer is sequentially exposed to (W) while changing at least one of the exposure amount and focus conditions.
[0041]
Then, the light beam is incident on the latent image in the resist on the wafer formed by this exposure (image formed by a portion where the refractive index is changed by causing a chemical change or the like by exposure) or a photosensitive pattern such as an uneven pattern after development. An incident light beam is irradiated from the means, and a signal light beam from the photosensitive pattern is received by the light receiving means. Changes in the incident light beam (changes in the polarization state of the incident light beam, changes in intensity, etc.) are detected using a signal from the light receiving means, and the formation state of the photosensitive pattern is obtained by the processing means. Based on the signal from the processing means, the control means controls the exposure conditions (such as the exposure amount and the position of the wafer in the optical axis direction) on the wafer surface.
[0042]
Next, the case where the change in the polarization state of the incident light beam is used as the change in the incident light beam will be described as an example.
[0043]
A light beam having a predetermined wavelength and a predetermined polarization state is incident on the resist at a predetermined incident angle with respect to the photosensitive pattern.
[0044]
Measure the polarization state of the light beam that is transmitted through the resist, reflected on the wafer substrate, and combined with the light beam that has been transmitted through the resist again and reflected directly on the resist surface. ing.
[0045]
In general, it is known that a phase-type diffraction grating composed of a concavo-convex pattern does not generate diffracted light at a wavelength longer than the pitch and has birefringence characteristics.
[0046]
In the embodiment of the present invention, the case where the reflected light is detected is mainly shown, but when the resist pattern pitch is larger than the wavelength, diffracted light is generated, and the same measurement can be performed with this diffracted light.
[0047]
Next, the ellipsometric method used in the present invention will be described.
[0048]
Assume that the grating thickness is d, the duty ratio is t, and a laser beam having a wavelength longer than the period is perpendicularly incident on the birefringent element. At this time, it is known that the refractive indexes n‖ and n⊥ at the periodic structure portion of the birefringent element are given by the following equations depending on whether the polarization state of the incident light is parallel or perpendicular to the groove of the grating. (Principle of optics III: by Born Wolff). Now, if the refractive index for light parallel to the grooves of the grating is n‖ and the refractive index for perpendicular light is n⊥,
[0049]
[Expression 1]

It becomes.
[0050]
Here, n1 and n2 are the refractive indexes of L (line portion) and S (space equivalent portion) of the lattice, respectively. The line portion L and the space portion S are a resist latent image, L is a resist, and S is an exposed resist. When the resist is developed, L is a resist and S is a gas such as air.
[0051]
The ellipsometry model corresponds to measuring the birefringence of a birefringent medium of a predetermined thickness on the wafer substrate. In the ellipsometry, linearly polarized light having a P / S (P-polarized / S-polarized) phase difference of 0 and an amplitude ratio of 1 is incident on the wafer substrate at a predetermined angle θ, and the phase difference (Δ ) And the amplitude ratio (ψ), and the refractive indexes n‖ and n⊥ can be obtained using the refractive indexes n1 and n2 of the line portion L and space portion S and the resist thickness d measured in advance. From the values of the refractive indexes n 率 and n⊥ obtained by this ellipsometry, the duty t is obtained using the above formula. Since this ellipsometry is known, the details are omitted.
[0052]
In one embodiment of the present invention, the duty of the latent image pattern in the resist or the concavo-convex pattern after development is measured using the ellipsometry as described above.
[0053]
In one embodiment of the present invention, a process of forming a plurality of photosensitive patterns by transferring an L & S pattern onto a photoreceptor surface under different exposure conditions, and sequentially irradiating the plurality of photosensitive patterns with the light flux, Detecting a polarization state, calculating a duty of a photosensitive pattern from the polarization state, determining an exposure condition where the duty is desired, and thereafter baking the wafer on a plurality of wafers under the exposure condition It is a feature.
[0054]
Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram of a main part of Embodiment 1 of the present invention, and FIGS. 2 to 6 are explanatory views when a part of FIG. 1 is extracted.
[0055]
In this embodiment, the change in the polarization state is used as the change in the incident light beam through the photosensitive pattern.
[0056]
In FIG. 1, reference numeral 101 denotes a reduction type projection lens, which projects a circuit pattern 102 a on the surface of a reticle 102 illuminated with exposure light from an exposure light source 107 described later onto a wafer 103. A wafer chuck 104 adsorbs the wafer 103. 105 is a coarse / fine movement stage. (Z stage) The wafer chuck 104 is coarsely and finely moved in the Z direction. 106 is an XY stage (Wafer stage) The wafer chuck 104 is moved in the XY directions. Reference numeral 107 denotes a light source for exposure. Reference numeral 108 denotes a structure, which is a light source 107, a reticle 102, Projection lens 101 and the wafer stage 106 are supported.
[0057]
Next, a focus position control device for detecting the position in the optical axis direction of the projection lens 101 of the wafer 103 used in this embodiment, that is, a focus position, and an exposure amount control device for illuminating the reticle 102 with exposure light, The control means having the above will be described with reference to FIG.
[0058]
In FIG. 4, reference numeral 201 denotes a high-luminance light source such as a semiconductor laser. The direction of laser light emitted from the light source 201 is changed by the bending mirror 208 and then input to the surface of the wafer 103. After being reflected at the measurement point P <b> 1 of the wafer 103, the light beam is changed in direction by the bending mirror 209 and then incident on the detection element 202 that detects the two-dimensional position of the incident light beam. The detection element 202 is composed of, for example, a CCD and detects the incident position of the light beam. Detection is performed such that a change in the position of the surface of the wafer 103 in the Z direction (the optical axis direction of the projection lens 101) becomes a displacement of the incident position on the detection element 202. Based on the signal from the detection element 202, the focus control device 203 controls the position of the wafer 103 in the Z direction, that is, the focus position by the Z stage 105.
[0059]
Reference numeral 206 denotes a shutter opening / closing mechanism, 207 a half mirror, and 205 an illuminance sensor, which detect the exposure amount of the light beam from the light source 107 reflected by the half mirror 207. The integrated exposure control device 204 controls the shutter opening / closing mechanism 206 based on the signal from the illuminance sensor 205 to control the passage amount of the light beam from the light source 107. As a result, the exposure amount for irradiating the reticle 102 is adjusted to a preset value.
[0060]
In the present embodiment, the exposure condition at the time of projecting the pattern on the reticle 102 surface onto the wafer 103 surface is controlled using the control means including the exposure amount control device and the focus position control device.
[0061]
Next, a case where a pattern on the surface of the reticle 102 illuminated with exposure light from the light source 107 is projected onto the surface of the wafer 103 will be described.
[0062]
FIG. 5 is an explanatory diagram of a reference pattern (hereinafter referred to as “pattern”) 102 a on the surface of the reticle 102. The pattern 102a is configured by making L & S patterns 1021 and 1022 including lines (L) and spaces (S) orthogonal to each other.
[0063]
In the present embodiment, a reticle 102 on which a pattern 102a composed of L & S patterns 1021 and 1022 is drawn is used. Reticle stage Then, the wafer 103 coated with resist is set on the wafer chuck 104, and the pattern 102a of the reticle 102 is sequentially exposed on the wafer 103 by the step & repeat method. At this time, using the focus control device 203 and the integrated exposure control device 204 described above, the latent images 10312 and 10311 of the printing patterns 1021 and 1022 are sequentially printed on the area 1031 which is one shot as shown in FIG.
[0064]
Then, the focus offset is changed by a certain amount around the predicted optimum position according to the shot position in the X direction, and the exposure amount around the optimum exposure amount (shutter time) is similarly applied to the shot in the Y direction. Change the exposure. In the example of FIG. 6, for convenience of explanation, a 3 × 3 matrix is used. However, the larger the number of shots, the easier the condition is set.
[0065]
FIG. 7 is an explanatory view of a resist cross section of the wafer 103 when sequentially exposed in this way. The exposed resist on the wafer 103 forms a latent image in the resist as shown in FIG. The latent image is formed by changing the properties of the resist by chemical change or the like by exposure light. Generally, the hatched portion is an exposed portion, and the refractive index of this portion is changed.
[0066]
The matrix addresses in FIG. 7 are cross sections at positions corresponding to those in FIG. 6, and (1), (2), and (3) represent cross sections of the pattern image 10312 of each chip.
[0067]
Next, as shown in FIG. 7, the resist on the wafer 103 after exposure has a light source unit 301, a light receiving unit 302, a driver 303, and a polarization processing device 304 without removing the latent image from the wafer chuck 104. 300 measures the amplitude ratio Ψ and the phase difference Δ of the reflected light with respect to the incident light.
[0068]
FIG. 3 is a schematic diagram in which main parts of the ellipsometer 300 in FIG. 1 are extracted. FIG. 11 is an explanatory diagram in which the optical path of FIG. 3 is developed. 3 and 11, a light source unit (light beam incident means) 301 as an irradiating means is a light source 3011 (not only a HeNe laser or a semiconductor laser but a monochromatic light of a spectroscope at a wavelength equal to or larger than the L & S pitch on the wafer 103). A polarizing element 3012 (Gram Thomson or the like) is included. The polarizing element 3012 is installed with respect to the wafer 103 so that the P-polarization component (parallel to the paper surface) and the S-polarization component (perpendicular to the paper surface) are equal to each other with the paper surface and the polarization surface being 45 degrees. Accordingly, the phase difference Δ between the light beams P and S is 0, and the amplitude ratio Ψ is 1.
[0069]
The light receiving unit (light receiving means) 302 includes a λ / 4 wavelength plate 3024 whose anisotropy axis is orthogonal to the light beam 305, a polarizing element 3022 (Gram Thompson or the like) as an analyzer, and a photoelectric conversion element 3021. . Further, the λ / 4 plate 3024 is held in a rotation mechanism 3023 having the light beam 305 direction as a rotation axis, and is rotated at a constant speed by a command from the driver 303.
[0070]
Now, the emitted light 305 from the light source unit 301 is reflected by the resist surface on the wafer 103 and the wafer surface, and the combined light flux is P or S-polarized light depending on the birefringence indices n1, n2, etc. of the resist on the wafer 103. The phase difference Δ and the amplitude ratio Ψ change.
[0071]
The light beam is detected by a detector 3021 through a rotating λ / 4 plate 3024 and an analyzer 3022, whereby the processing means 304 obtains a sinusoidal electric signal corresponding to the phase difference Δ and the amplitude ratio Ψ, and the amplitude and DC component. [Delta] and [Psi] are obtained from the phase information of a sine wave of the size.
[0072]
As described above, the refractive index n1 of the unexposed portion of the resist, the refractive index n2 of the exposed portion, the thickness d of the resist, and the complex refractive index ns of the substrate, which are measured in advance using ellipsometry, are given. Thus, the refractive index n⊥ is obtained using the L & S resist pattern as a birefringent structure.
[0073]
Further, the duty t⊥ is obtained from the value of the refractive index n⊥ by the following formula.
[0074]

From the value of the refractive index n‖, the duty t‖ is
t‖ = (n‖ ** 2-n2 ** 2) / (n1 ** 2-n2 ** 2)
It becomes. The two values are averaged as follows to improve accuracy.
[0075]
t1 = (t⊥ + t‖) / 2
Normally, the duty t can be obtained as described above. However, since there may be a variation in measurement values due to resist unevenness, the structure of the base, etc., the ellipsometric measurement from the x direction as shown in the plan view of FIG. On the other hand, by forming a second ellipsometer orthogonal to it, that is, from the y-direction, and measuring substantially the same point as the measurement point measured by the first ellipsometer (301, 302), the following In this way, accuracy is improved.
[0076]
In this case as well, when the duty t1 is obtained
t2 = (t⊥ + t‖) / 2
And using the aforementioned duty t1,
t = (t1 + t2) / 2
And the measurement accuracy of the duty t is further increased.
[0077]
On the other hand, FIG. 8 is an explanatory diagram of a method for finding the optimum exposure condition by comparing the L & S of the sample obtained by ellipsometry with the duty obtained by developing the sample and comparing the value measured by the SEM. As a result, the offset of the duty generated by the base structure generated by the ellipsometry is measured, and in the subsequent measurement, the value obtained by subtracting the offset value is used as a corrected correct measured value. The comparison with the SEM may be performed only once at the beginning of the change of process conditions, and thereafter, the SEM is not required.
[0078]
Next, flowcharts for optimizing the exposure conditions shown in FIGS. 9 and 10 will be described. FIG. 9 shows an example in which 8 × 6 chip exposure is performed on one wafer and the result of polarization analysis is shown on the Δ-Ψ map. For example, the measurement point on the line 410 indicates that the exposure amount is constant and the focus changes, while the measurement point on the line 401 indicates the case where the focus is constant and the exposure amount changes. .
[0079]
The shot shown in the square frame AX on the Δ-Ψ map shows the range where the optimum duty is obtained due to the correspondence with the SEM measurement as described above. Accordingly, when the exposure shot is measured by the ellipsometry, and Δ and Ψ fall within this frame AX, the optimum duty is indicated.
[0080]
FIG. 10 shows the above flow. First, a resist is coated on the wafer. If the thickness of the resist is not known at this time, it is measured at this time. Next, as described above, trial printing is performed by changing the focus and exposure amount (shutter time) while moving the stage stepwise.
[0081]
Next, without removing the wafer from the wafer chuck, Δ and Ψ are measured by changing shots one after another by ellipsometry while moving the stage in the same manner. If the result of the polarization analysis is Δ, Ψ within the predetermined range AX shown in FIG. 9, the exposure condition for printing the shot is set as the optimum exposure condition for mass production printing.
[0082]
The duty check by this ellipsometry is performed at any time during the mass production baking process of the wafer to increase the yield.
[0083]
In this embodiment, after setting the optimum exposure conditions as described above, the wafer is manufactured through a predetermined development processing step, thereby manufacturing a highly integrated device.
[0084]
FIG. 12 is an explanatory diagram of Embodiment 2 of the present invention. This embodiment is different from the first embodiment in that there is a physical restriction on the exposure apparatus, except that the polarization analyzer is provided separately from the wafer stage of the exposure apparatus. The configuration is the same.
[0085]
FIG. 13 is an explanatory diagram of Embodiment 3 of the present invention. In the first embodiment, the polarization analysis is performed with the latent image not developed on the resist on the wafer surface, whereas in this embodiment, the polarization analysis is performed after the resist is developed. They are different and the other configurations are the same.
[0086]
FIG. 14 is an explanatory diagram of a cross-sectional shape of a photosensitive pattern after resist development according to the present embodiment. As is clear from FIG. 14, the present embodiment is a gas having a refractive index n2 of approximately 1.0 as compared with the latent image systems of the first and second embodiments. This method is suitable when measurement accuracy is advantageous and conditions are severe.
[0087]
In the present embodiment, the optimal exposure conditions are obtained by performing polarization analysis on the photosensitive pattern after the development processing, thereby obtaining the optimum exposure conditions in a shorter time compared with the case where a conventional SEM is used.
[0088]
FIG. 15 is a flowchart of this embodiment. FIG. 16 is an explanatory diagram of Embodiment 4 of the present invention. The present embodiment is different from the first embodiment in that the resist development and the SEM are coexisting, and other configurations are the same. In the present embodiment, the SEM is used when it is necessary to check the developed resist image for regenerating duty measurement by ellipsometry.
[0089]
FIG. 17 is a schematic view of the essential portions of Embodiment 5 of the present invention. In the present embodiment, the change in the intensity of the reflected light beam when the wavelength of the incident light beam is changed is used as the change in the incident light beam through the photosensitive pattern. Here, the change in the intensity of the incident light beam is obtained using the refractive index of the resist film.
[0090]
In FIG. 17, the same elements as those shown in FIG. In the figure, reference numeral 501 denotes a monochromator, which has a wavelength shortened to such an extent that it can interfere with the front and back surfaces of the resist film on the wafer 103 by dispersing the wavelength of a built-in unillustrated white light source with a diffraction grating and cutting it with a slit. Radiated light flux. Reference numeral 502 denotes a photoelectric detector that detects the amount of light flux reflected and interfered from the front and back surfaces of the resist pattern (development / latent image). Reference numeral 503 denotes a driver / processing device that drives the wavelength of the monochromator 501, calculates the refractive index of the resist pattern from the electrical signal from the photoelectric detector 502, and transmits the result to the central processing unit 109. Here, 501 may be a white light source, and 502 may be a spectroscope for obtaining spectral reflectance.
[0091]
Next, the operation principle of this embodiment will be described with reference to FIGS. Note that the film thickness of the resist coated on the wafer 103 is obtained in advance by measuring with a film thickness meter. Since the refractive index of the resist pattern is obtained, the pattern duty is calculated, the focus, and the exposure amount control are the same as those in the first embodiment, and the description thereof is omitted.
[0092]
First, the refractive index n of the resist ₂ The measurement principle will be described. In FIG. 18, the refractive index of the medium is expressed as n in order from the light incident side. ₁ , N ₂ , N ₃ And the film thickness is d. Working wavelength (wavelength λ in vacuum ₀ ) For each incident angle ₁ , Θ ₂ , Θ ₃ And The amplitude reflectivity γ at this time is as follows [reference: M.M. Born and E.M. Wolf, "Principles of Optics" 3rd edition, PERGAMON PRESS, p. 62].
[0093]
[Expression 2]

Where γ ₁₂ Is the Fresnel reflection coefficient at the boundary between media 1 and 2, and γ ₂₃ Is the Fresnel reflection coefficient at the boundary between media 2 and 3, and β is β = (2π / λ ₀ ) ・ N ₂ ・ D ・ cosθ ₂ It is.
[0094]
The actual measurable amount is the reflection intensity, ie R = | γ | ² (Usually called reflectance) and is as follows.
[0095]
[Equation 3]

From equation (2), the refractive index n to be measured now ₂ Is as follows.
[0096]
[Expression 4]

Here, N is an integer.
[0097]
Working wavelength λ ₀ Reflectivity R and n when ₂ Is as shown in FIGS. 18B and 18C. Therefore, the refractive index n at each wavelength ₂ Average value of n _2AV By using as a refractive index, highly accurate measurement with good reproducibility can be performed.
[0098]
In order to measure the refractive index with high accuracy, it is important to raise the measurement accuracy of the reflectance. The purpose of this embodiment is to improve reflectance measurement accuracy.
[0099]
The following can be cited as causes of deterioration in measurement accuracy.
[0100]
A. Stray light
B. Variation in light intensity detector
C. change over time
In the present embodiment, the measurement accuracy is improved by correcting these automatically.
[0101]
19, 20, and 21 are explanatory diagrams of the measurement principle. FIG. 19 shows the configuration, FIG. 20 shows the processing process, and FIG. 21 shows the signals in each of the processing processes of FIG.
[0102]
In FIG. 19, reference numeral 5001 denotes a spectroscope, 5002 denotes an RAM 1 that stores an output signal corresponding to the reflectance of each wavelength from the sample surface, 5003 denotes a CPU 1 that calculates the output signal, and 5004 denotes an ideal film. The CPU 2 and 5005 for processing the calculated values of the data, and the RAM 2 and 5006 for storing the data after the processing of the CPU 2 correct the data of the RAM 1 from the processing data of the CPU 1 and the RAM 2 and further calculate the film thickness. The CPU 3 and 5007 comprise output devices that output the film thickness calculation results.
[0103]
Next, the operation will be described below with reference to FIGS.
[0104]
First, the data of the reflectance measurement of each wavelength from the spectroscope (step 5013 in FIG. 20), that is, the data in the RAM 1 is smoothed by the CPU 1 by fast Fourier transform or the like ( FIG. Step 5014) is performed. That is, the x mark in FIG. 21A is the measured value, and the solid line f (λ) is the smoothed curve.
[0105]
Here, f is a function of the wavelength λ. Next, the maximum and minimum values of f (λ) and the intermediate level are obtained (step 5015 in FIG. 20). In the method, first, a point sequence of local maximum points is connected to obtain a curve max (λ) and a point sequence of local minimum points to obtain a curve min (λ).
[0106]
[Equation 5]

Ask for.
[0107]
On the other hand, the theoretical value of the reflectance of the film to be measured, that is, the ideal reflectance of each wavelength is calculated in advance by the CPU 2 (step 5016 in FIG. 20), and the curve MAX ( λ), a curve MIN (λ) connecting the minimum values, and an intermediate level AVE (λ) are calculated (step 5017 in FIG. 20). MAX (λ), MIN (λ), and AVE (λ) are stored in the RAM 2.
[0108]
From the above, the CPU 3 corrects f (λ) as follows to obtain f ′ (λ).
[0109]
[Formula 6]

The gain fluctuation of the reflectance data caused by the cause of the deterioration of the measurement accuracy is corrected by the first term of the equation (4) (step 5018 in FIG. 20), and the bias fluctuation (see FIG. 21C) is corrected by the second term (see FIG. 21C). Step 5019 in FIG.
[0110]
Further, this modified f ′ (λ) is R, and the refractive index n is given by the above equation (3). ₂ Is calculated (step 5020 in FIG. 20) to measure the reflectance.
[0111]
When the same sample is repeatedly measured, as shown in FIG. 21 (D), since it is a time loss to calculate max (λ), min (λ) and ave (λ) every time, the first measurement is performed. It is also possible to make corrections using the sample data.
[0112]
Nth sample measurement f ′ _N (Λ) is calculated by the following equation. The subscript 1 or N indicates a value in the first measurement or the Nth measurement.
[0113]
[Expression 7]

At this time, the first sample need not be exactly the same as the Nth sample. That is, f _N It suffices if a gain and a bias can be given to (λ) as long as each item causing measurement accuracy deterioration does not vary.
[0114]
【The invention's effect】
According to the present invention, as described above, the photosensitive state (latent image) of the resist by exposure or the photosensitive pattern formation state such as L & S after development changes the incident light flux, for example, the change in the intensity of the reflected light or the change in the polarization state. The optimum exposure condition can be set in a short time by determining the optimum exposure condition from the measured value and mass-producing exposure of the wafer under the optimum exposure condition. A pattern formation state detection apparatus and a projection exposure apparatus using the same can be achieved.
[0115]
In particular, compared with a method using a conventional SEM, a resist pattern (a latent image that is developed or not developed) of a pattern having a periodicity, for example, a reticle for measuring exposure conditions in which an L & S pattern is configured on a reticle. In this case, it is possible to obtain the optimum exposure condition with high accuracy and in a short time by using the reflected light information.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an essential part of Embodiment 1 of the present invention.
FIG. 2 is a plan view of a portion of the first embodiment of the present invention.
3 is an explanatory view of a part of the ellipsometer of FIG.
FIG. 4 is a schematic diagram of a part of focus detection and exposure amount control in the exposure apparatus;
FIG. 5 is an explanatory diagram of a reticle pattern for measuring exposure conditions.
FIG. 6 is an explanatory diagram of a latent resist image on a wafer baked under different exposure conditions.
7 is a cross-sectional view of a latent resist image on the wafer of FIG. 6;
FIG. 8 is an explanatory diagram of rehabilitation by SEM of measured values by an ellipsometer
FIG. 9 Δ-Ψ map
FIG. 10 is an explanatory diagram of a flowchart when the ellipsometry is applied to the exposure condition setting.
FIG. 11 is an explanatory diagram of the ellipsometry configuration.
FIG. 12 is an explanatory diagram of Embodiment 2 in which an ellipsometer is installed separately.
FIG. 13 is an explanatory diagram of Embodiment 3 in which a resist development process is performed.
FIG. 14 is an explanatory diagram of a cross-sectional shape after resist development.
FIG. 15 is an explanatory diagram of a flowchart including a developing process.
FIG. 16 is an explanatory diagram of a fourth embodiment adjacent to an SEM.
FIG. 17 is a cross-sectional view of main parts of Embodiment 5 of the present invention.
FIG. 18 is an explanatory diagram of the basic principle for obtaining the film thickness from the spectral reflectance used in the present invention.
FIG. 19 is a block diagram showing the configuration of the embodiment of the present invention.
FIG. 20 is an explanatory diagram illustrating a processing process according to the embodiment of this invention.
FIG. 21 is an explanatory diagram showing signal states according to the embodiment of the present invention.
[Explanation of symbols]
101 Reduction type projection lens
102 reticle
103 wafers
104 Wafer chuck
105 Coarse / Fine Tilt Z Stage
107 Light source
108 frames
109 Central processing unit
201 Light source for focus detection
202 Photoelectric converter for focus detection
2031 Focus control device
2041 Integrated exposure amount detection circuit
2042 Integrated exposure amount control circuit
301 Ellipsometric light source
302 Ellipsometric light receiving unit
303 Rotating stage driver
304 ellipsometry processor
501 Light beam incident means
502 Light receiving means
503 processing means

Claims (11)

In a device for detecting the formation state of a photosensitive pattern formed by exposing a periodic pattern to a photoreceptor applied to an object via an optical system,
Irradiating means for irradiating the photosensitive pattern with a light beam ;
And a light-receiving means for receiving the light beam from the photosensitive pattern,
A pattern formation state detection apparatus comprising: processing means for detecting a change in polarization state of a light beam received by the light receiving means and obtaining a formation state of the photosensitive pattern based on the detection result . 2. The pattern formation state detection apparatus according to claim 1, wherein the formation state of the photosensitive pattern is a duty of the photosensitive pattern. 2. The pattern formation state detection apparatus according to claim 1, wherein the wavelength of the incident light beam is different from the wavelength of the exposure light. In a device for detecting the formation state of a photosensitive pattern formed by exposing a periodic pattern to a photoreceptor applied to an object via an optical system,
Irradiating means for irradiating the photosensitive pattern with a luminous flux;
A light receiving means for receiving a light beam from the photosensitive pattern;
A pattern forming state comprising: processing means for detecting a change in reflectance for each wavelength of the light beam received by the light receiving means, and obtaining the formation state of the photosensitive pattern based on the detection result Detection device. In a projection exposure apparatus for projecting and exposing a periodic pattern on a first object surface illuminated with exposure light onto a second object surface coated with a photosensitive member by a projection optical system, and forming a photosensitive pattern, the formation state of the photosensitive pattern A projection exposure apparatus comprising: the pattern formation state detection apparatus according to claim 1. 6. The projection exposure apparatus according to claim 5, wherein a formation state of a plurality of photosensitive patterns formed under a plurality of different exposure conditions is detected by the pattern formation state detection device. 7. The projection exposure apparatus according to claim 5, wherein the photosensitive member is a resist, and the photosensitive pattern is a latent image or an uneven step of a resist formed after development processing. 8. The exposure condition according to claim 5, wherein the exposure condition is an exposure amount on the second object plane and / or a focus position of the projection optical system of the second object in the optical axis direction. The projection exposure apparatus described . The pattern formation state detection device according to any one of claims 1 to 4 detects a formation state of a plurality of photosensitive patterns formed under a plurality of different exposure conditions, and uses the detection result on the first object plane. A projection exposure method characterized by projecting and exposing the pattern of the pattern onto the second object plane through the optical system. 10. The projection exposure method according to claim 9 , wherein the plurality of different exposure conditions are different in at least one of an exposure amount for exposing the second object plane and a position in the optical axis direction of the optical system . A projection exposure method using the projection exposure method according to claim 9 or 10, wherein the optical system projects and exposes a pattern on a photoreceptor on a wafer surface, and develops the wafer. Device manufacturing method.

Images