JP4229348B2

JP4229348B2 - Projection exposure method and apparatus

Info

Publication number: JP4229348B2
Application number: JP17136999A
Authority: JP
Inventors: 容三深川
Original assignee: Canon Inc
Current assignee: Canon Inc
Priority date: 1999-06-17
Filing date: 1999-06-17
Publication date: 2009-02-25
Anticipated expiration: 2019-06-17
Also published as: JP2001006993A

Description

【０００１】
【発明の属する技術分野】
本発明は、原版および投影光学系を介して基板を露光する方法および装置に関する。
【０００２】
【従来の技術】
投影露光装置は、高い像性能と重ね合わせ精度が求められるため、露光装置に使用される位置決めステージの位置計測計は、投影光学系と共に重量構造で剛性の高い本体構造体に取付けられ、計測基準ズレを生じにくいようになっている。しかしながら、本体構造体を支持する支持台から侵入する床振動によって、僅かではあるが本体構造体が弾性変形する。また本体構造体に移動するステージを搭載した場合、移動するステージの重量によって本体構造体の支持力が変化するので、本体構造体の弾性変形を生じる。このような現象から、投影レンズの露光光軸に対するステージ位置計測計の取付け位置や姿勢が変化し、ステージの位置計測誤差を生じる。
【０００３】
一方、ＩＣやＬＳＩ等の半導体集積回路のパターンが微細化するのに伴い、より高い精度が要求される傾向にあるが、従来のような本体構造体の高剛性化は著しい重量増加を招き、装置の搬出、搬入、設置等の面で非常に取り扱いにくい製品にすることから、本体構造体の高剛性化はもはや限界に近づいていた。
【０００４】
そこで、投影本体構造体の弾性変形とそれによる計測誤差が、原因となる作用力の線形和になることを利用し、これを原因とするステージ位置計測誤差をリアルタイムに補正する技術が開発された。これは、例えばステージを移動することにより本体構造体に強制的な作用力を与えながら、ＴＴＬアライメントスコープとステージ位置計測用干渉計の計測値を同時に比較する実験から、補正係数を求め、露光時は、ステージ位置に基づいて、ステージ位置計測誤差をリアルタイムに補正するものである。
【０００５】
【発明が解決しようとする課題】
本発明は、ステージの位置を計測する手段の計測値をより高精度に補正することを目的とする。
【０００６】
【課題を解決するための手段】
上記の問題を解決するための本発明の露光方法は、投影光学系と、基板を搭載して移動するステージと、該ステージの位置を計測する位置計測手段と、前記投影光学系と前記位置計測手段とを保持する構造体と、該構造体を支持する支持台とを用い、原版および前記投影光学系を介して前記基板を露光する露光方法であって、前記支持台から前記構造体を加振しながら、前記位置計測手段により前記ステージの位置を計測して前記ステージを逐次移動させながら、かつ前記構造体に作用する力を計測しながら、基準マークおよび比較マークを有するテスト用原版を介して基板を複数回露光する第１の工程と、前記支持台から前記構造体を加振しながら、前記位置計測手段により前記ステージの位置を計測して前記ステージを逐次移動させながら、かつ前記構造体に作用する力を計測しながら、前記基準マークと前記比較マークとが前記基板上で重なるように前記テスト用原版を介して前記基板を複数回露光する第２の工程と、前記基板上の前記基準マークと前記比較マークとの複数の組それぞれについての前記基準マークと前記比較マークとに関して露光中に計測された前記ステージの位置の差および前記力の差と、前記複数の組それぞれについて露光後に得られた前記基準マークと前記比較マークとの位置の差とに基づいて、前記位置計測手段により計測された前記ステージの位置を前記力に応じて補正するための係数を求める第３の工程と、前記位置計測手段により前記ステージの位置を計測しながら、前記構造体に作用する力を計測しながら、かつ計測された前記力と求められた前記係数とに基づいて前記位置計測手段により計測された前記ステージの位置を補正して前記ステージを逐次移動させながら、デバイスのパターンを有する原版を介して基板を複数回露光する第４の工程とを有することを特徴とする。
【０００７】
上記の問題を解決するための本発明の露光装置は、投影光学系と、基板を搭載して移動するステージと、該ステージの位置を計測する位置計測手段と、前記投影光学系と前記位置計測手段とを保持する構造体と、該構造体を支持する支持台とを有し、原版および前記投影光学系を介して前記基板を露光する露光装置であって、前記支持台に設けられて前記構造体を加振する加振手段と、前記支持台から前記構造体に作用する力を計測する力計測手段と、を有し、前記加振手段により前記構造体を加振しながら、前記位置計測手段により前記ステージの位置を計測して前記ステージを逐次移動させながら、かつ前記力計測手段により前記構造体に作用する力を計測しながら、基準マークおよび比較マークを有するテスト用原版を介して基板を複数回露光し、前記加振手段により前記構造体を加振しながら、前記位置計測手段により前記ステージの位置を計測して前記ステージを逐次移動させながら、かつ前記力計測手段により前記構造体に作用する力を計測しながら、前記基準マークと前記比較マークとが前記基板上で重なるように前記テスト用原版を介して前記基板を複数回露光し、前記基板上の前記基準マークと前記比較マークとの複数の組それぞれについての前記基準マークと前記比較マークとに関して露光中に計測された前記ステージの位置の差および前記力の差と、前記複数の組それぞれについて露光後に得られた前記基準マークと前記比較マークとの位置の差とに基づいて、前記位置計測手段により計測された前記ステージの位置を前記力に応じて補正するための係数を求め、前記位置計測手段により前記ステージの位置を計測しながら、前記力計測手段により前記構造体に作用する力を計測しながら、かつ計測された前記力と求められた前記係数とに基づいて前記位置計測手段により計測された前記ステージの位置を補正して前記ステージを逐次移動させながら、デバイスのパターンを有する原版を介して基板を複数回露光することを特徴とする。
【０００８】
本発明の一つの実施態様は、例えば、ＩＣやＬＳＩ等の半導体素子を製造する際に、レチクル面上の電子回路パターンを投影光学系を介し、ウエハ面上に順にステップアンドリピートして投影露光する露光装置（いわゆるステッパ）や、同様に、レチクル面上の電子回路パターンを投影光学系を介し、ウエハ面上に順にステップアンドスキャンして投影露光する露光装置（いわゆるスキャナ）において、本体構造体を支持する力や本体構造体の振動を制御する力などが変化することによって生じる本体構造体の弾性変形によって、ステージの位置を計測するステージ位置計測計の取付位置にズレが生じても、本体構造体に作用する力を常に計測することによって、そのズレによる計測誤差をリアルタイムに算出して補正を行なうので、
本体構造体の変形に影響されにくい投影露光装置を実現できる。
【００１５】
【発明の実施の形態】
本発明の好ましい実施の形態では、ステージ位置計測値ｘ（ｔ）と本体構造体に作用する主たる力またはこれらに比例した物理量ｐ（ｔ）を連続的に計測記録した状態で、レチクル上の基準マークを投影露光して、ウエハ表面にこれを描画する。物理量ｐ（ｔ）としては、例えば支持台から受ける支持力を計測するロードセル、支持台との接点に空気バネ除振機構を設けた場合は当該空気バネの圧力、または支持台との接点付近に設置された歪ゲージなどの計測値を用いることができる。そしてステージを逐次移動させながらこの動作をＮ回繰り返し、ウエハ全面に複数の基準マークを描画する１次露光過程を実施する。次に、同じレチクル上の比較マークを、ウエハ全面に描画された基準マークと重なるようステージを移動させながら２次露光動作を実施する。なお、１次露光過程と２次露光過程のいずれの場合でも、露光中であることを示す信号、例えばシャッタの開閉指令信号や、露光レーザの発光に伴う信号などを計測記録する。
これらの露光過程を経た後、ウエハに描画された基準マークと比較マークの相対位置差Ｙ（ｉ）を顕微鏡等で観察記録する。
【００１６】
連続的に計測したステージ位置計測値ｘ（ｔ）と本体構造体に作用する主たる力またはこれらに比例した物理量ｐ（ｔ）のうち、露光中であった時間帯だけの計測値を露光回毎に平均値を求め、１次露光過程と２次露光過程で区別すると、基準マークと比較マークの相対位置差と同数のデータＸ₁ （ｉ）、Ｘ₂ （ｉ）、Ｐ₁ （ｉ）、Ｐ₂ （ｉ）が得られる。
このとき、基準マークと比較マークの相対位置差Ｙ（ｉ）は（１）式で表わされる。
【００１７】
【数１】

ここで、ｉは基準マークと比較マークの相対位置差Ｙの順番を示す添え字で、ｉ＝ｌ〜Ｎ、Ｋは本体構造体に作用する主たる力またはこれらに比例した物理量による位置誤差を補正する係数、ｅは顕微鏡観察などの誤差である。
（１）式より、補正係数Ｋは最小自乗法によって容易に求められる。
【００１８】
本発明は、本体構造体に作用する主たる力またはこれらに比例した物理量ｐ（ｔ）に適切なる係数Ｋを乗じることによって、レチクル投影画像とステージ位置計測計との相対位置誤差を補正する投影露光装置を提案するものである。
【００１９】
従来の補正技術では、本体構造体に作用する主たる作用力によって生じるレチクル投影画像と干渉計基準との相対位置誤差補正値を、ＴＴＬアライメントスコープと干渉計基準との相対位置誤差の補正値で代用していたため、僅かではあるが補正残差を生じていた。
【００２０】
しかし、本実施形態によれば、レチクル投影画像と干渉計基準との相対位置誤差を直接的に計測できるので、当該誤差と本体構造体に作用する主たる作用力との関係を正確に実験で求められるため、投影露光時のステージ位置補正精度を向上させることが可能となる。
【００２１】
【実施例】
以下、図面を用いて本発明の実施例を説明する。
実施例１
図１は、本発明が適用される投影露光装置の全体構成を示し、図２、図３および図４は図１の装置各部のより詳細な構成を示す。
図１において、１は投影レンズ、２は本体構造体、３はウエハステージ用レーザ干渉計、４は照明系、５はレチクル、６はウエハ、７はＸ軸用レーザ干渉計ミラー、８はウエハステージ天板、９はＹ軸用レーザ干渉計ミラー、１４はＸＹステージ、２１はウエハステージ定盤、２２はロードセル、２３は支持台である。
【００２２】
図２において、１７はＸ軸スライダ、１８はＹ軸スライダ、１９はＹ軸駆動リニアモータ可動子、２０はＹ軸駆動リニアモータ固定子である。
【００２３】
図３において、１０はＺチルトアクチュエータ、１１はθ_z ステージ、１２はθ_z ガイド、１３はθ_z アクチュエータ、１５はＸ軸駆動リニアモータ可動子、１６はＸ軸駆動リニアモータ固定子である。
【００２４】
図１の装置において、所定の位置までステージ１４を移動させ、レチクル原版５上のパターンをウエハ基板６上に投影露光する場合を考える。
このとき、本体構造体２に一切の変形が生じなければ、ステージ位置と投影露光光軸との相対位置は一定である。
【００２５】
逆に、本体構造体を支持する力を変動させることで、本体構造体に顕著な弾性変形を発生させ、ステージ位置計測計と投影露光光軸の相対位置を変化させれば、このステージ位置計測値の変動分は本体構造体の支持力変動の線形和になる。つまり、本体構造体を支持する全ての点において計測された支持力に何らかの係数行列を乗じれば、ステージ位置計測誤差を予測できる。
【００２６】
次に、この係数行列を求める方法について述べる。
ステージを位置決めした状態で各支持台２３の支持力を１つずつ変動させる。加振波は低周波成分が多く含まれるような加振波が好ましい。例えば、ピンクノイズやランダムノイズの累積和などを与えるとよい。
【００２７】
具体的な例として、投影露光装置の支持台によく用いられる空気バネ式除振脚を用いた加振方法について述べる。
図４は、図１における支持台（空気バネ式除振脚）２３の詳細を示す。この支持台は、互いに対向して取付けられた水平方向空気バネ２４と水平方向平衡バネ２６、垂直方向空気バネ２５を介して支持脚４１に取付けられたハウジング２７で構成され、各空気バネ２４、２５に供給する空気量は、ハウジング２７のレベルや空気バネの圧力などの計測値をフィードバック信号３３とする制御弁コントローラ２９が出力した制御信号３２によって制御弁２８を制御し、供給空気３５から各空気バネ２４、２５に供給される空気量を制御する。以上のような空気バネ式除振脚において、各空気バネの支持力を変動させるには、ウェーブジェネレータ３０から出力した加振信号３１を切り替えスイッチ３４などで分岐させ、各制御信号３２に加える。
【００２８】
なお、各支持台の支持力を同時に加振しても構わないが、その場合、各制御信号に加えられる波形は互いに独立なものでなくてはならない。
【００２９】
このような状態で、ＸＹステージ１４を順次移動させ、図５（ａ）に示す順序で、ウエハ全面に複数のショットを投影露光する。なお、１回の投影露光で描画されるショット内には図６のように基準マーク（■）３６と比較マーク（□）３７が同時に描画される。この過程を１次露光過程と呼ぶ。但し、１次露光過程で描画される比較マーク３７は使用しない。
【００３０】
続いて、図５（ｂ）に示す順序で、先に描画した基準マーク３６に比較マーク３７が重なるように複数のショットを投影露光する。この過程を２次露光過程と呼ぶ。但し、２次露光過程で描画される基準マーク３６は使用しない。
【００３１】
なお、露光装置が一括式露光型の場合、テスト用レチクルは固定した状態のままである。
一方、露光装置が走査式露光型の場合は、レチクルステージを一定の位置に静止させた状態にする。
【００３２】
また、加振方法に関係なく全ての支持力とステージ位置制御偏差、および投影露光中であることを判別できる信号、例えばシャッタ開閉信号や露光用レーザ光の発振信号なども同時に計測する。
【００３３】
また、支持力計測には、ロードセル２２を用いて各方向の支持力を計測するのが好ましいが、各空気バネの圧力を計測する圧力計（不図示）を用いても支持力変動に比例した計測値が得られるので、これを代用しても構わない。
【００３４】
このようにして投影された基準マーク３６と比較マーク３７の重心間距離データと、投影露光していた時間内で平均した各除振脚の支持力、位置決め制御残差を用いることでレチクル画像を投影露光する時のステージ位置計測誤差補正係数を求めることができる。
【００３５】
実施例２
実施例２は、１回の露光で複数の基準マーク（■）３６と比較マーク（□）３７を同時に投影露光する場合である。θ軸のステージ位置計測誤差も補正する場合には、図７に示すように十分に離れた少なくとも２つの基準マーク３６と比較マーク３７を同時に投影露光することによってθ軸のステージ位置計測誤差の補正係数を求めることができる。
【００３６】
実施例３
実施例３は、基準マーク（■）３６を投影露光するショット順序と、比較マーク（□）３７を投影露光するショット順序を不規則にした場合である。実施例１や２のように、規則的な順序で投影露光を行なうと、図８のように重なりあう基準マーク３６と比較マーク３７が投影露光されるショット間隔は概ね一定となる。このショット間隔は概ねショットの時間間隔に比例するので、この時間間隔が強制的に与えた作用力３８の周期に近い場合、基準マーク３６と比較マーク３７を投影露光したときの作用力の差が小さくなり、強制的な作用力を与えた意味を失う恐れがある。
【００３７】
したがって、図９のように、重なりあう基準マーク３６と比較マーク３７を投影露光する時間間隔が適当にバラツクよう、露光順序を乱すことで、この問題を解決することができる。
【００３８】
実施例４
実施例４は、環境温度や気圧が比較的に短い周期（連続する投影露光の時間間隔とほぼ等しい周期）で変動し、これらを原因とする計測誤差が無視できない場合に適した投影露光順序である。この場合、図１０のように、基準マーク（■）３６を投影露光した次のショットで、これに重なる比較マーク（□）３７を投影露光する。このとき、両者を投影露光する時の環境温度や気圧はほぼ等しいので、環境温度や気圧の影響をほぼキャンセルすることができる。
【００３９】
【デバイス生産方法の実施例】
次に上記説明した露光装置または露光方法を利用したデバイスの生産方法の実施例を説明する。
図１１は微小デバイス（ＩＣやＬＳＩ等の半導体チップ、液晶パネル、ＣＣＤ、薄膜磁気ヘッド、マイクロマシン等）の製造のフローを示す。ステップ１（回路設計）ではデバイスのパターン設計を行なう。ステップ２（マスク製作）では設計したパターンを形成したマスクを製作する。一方、ステップ３（ウエハ製造）ではシリコンやガラス等の材料を用いてウエハを製造する。ステップ４（ウエハプロセス）は前工程と呼ばれ、上記用意したマスクとウエハを用いて、リソグラフィ技術によってウエハ上に実際の回路を形成する。次のステップ５（組み立て）は後工程と呼ばれ、ステップ４によって作製されたウエハを用いて半導体チップ化する工程であり、アッセンブリ工程（ダイシング、ボンディング）、パッケージング工程（チップ封入）等の工程を含む。ステップ６（検査）ではステップ５で作製された半導体デバイスの動作確認テスト、耐久性テスト等の検査を行なう。こうした工程を経て半導体デバイスが完成し、これが出荷（ステップ７）される。
【００４０】
図１２は上記ウエハプロセスの詳細なフローを示す。ステップ１１（酸化）ではウエハの表面を酸化させる。ステップ１２（ＣＶＤ）ではウエハ表面に絶縁膜を形成する。ステップ１３（電極形成）ではウエハ上に電極を蒸着によって形成する。ステップ１４（イオン打込み）ではウエハにイオンを打ち込む。ステップ１５（レジスト処理）ではウエハに感光剤を塗布する。ステップ１６（露光）では上記説明した露光装置によってマスクの回路パターンをウエハに焼付露光する。ステップ１７（現像）では露光したウエハを現像する。ステップ１８（エッチング）では現像したレジスト像以外の部分を削り取る。ステップ１９（レジスト剥離）ではエッチングが済んで不要となったレジストを取り除く。これらのステップを繰り返し行なうことによって、ウエハ上に多重に回路パターンが形成される。
【００４１】
本実施例の生産方法を用いれば、従来は製造が難しかった高集積度のデバイスを低コストに製造することができる。
【００４２】
【発明の効果】
本発明によれば、ステージの位置を計測する手段の計測値をより高精度に補正することができる。
【図面の簡単な説明】
【図１】本発明の一実施例に係る投影露光装置の構成説明図である。
【図２】図１の装置に搭載されたステージの構成説明図である。
【図３】図２のステージの断面図である。
【図４】図１の装置で用いられる除振機能付支持台の構成図である。
【図５】実施例１および２における投影露光順序の説明図である。
【図６】実施例１において投影露光されるショット内の図である。
【図７】実施例２において投影露光されるショット内の図である。
【図８】実施例１および２における各ショット位置の投影間隔一覧を示す図である。
【図９】実施例３における投影露光順序の説明図と各ショット位置の投影間隔一覧を示す図である。
【図１０】実施例４における投影露光順序の説明図と各ショット位置の投影間隔一覧を示す図である。
【図１１】微小デバイスの製造の流れを示す図である。
【図１２】図１１におけるウエハプロセスの詳細な流れを示す図である。
【符号の説明】
１：投影レンズ、２：本体構造体、３：ステージ位置決め用レーザ干渉計、４：照明系、５：レチクル、６：ウエハ、７：Ｘ軸用レーザ干渉計ミラー、９：Ｙ軸用レーザ干渉計ミラー、８：ウエハステージ天板、１０：Ｚチルトアクチュエータ、１１：θ_z ステージ、１２：θ_z ガイド、１３：θ_z アクチュエータ、１４：ＸＹステージ、１５：Ｘ軸駆動リニアモータ可動子、１６：Ｘ軸駆動リニアモータ固定子、１７：Ｘ軸スライダ、１８：Ｙ軸スライダ、１９：Ｙ軸駆動リニアモータ可動子、２０：Ｙ軸駆動リニアモータ固定子、２１：ウエハステージ定盤、２２：ロードセル、２３：支持台、２４：水平方向空気バネ、２５：垂直方向空気バネ、２６：水平方向平衡バネ、２７：ハウジング、２８：制御弁、２９：制御弁コントローラ、３０：ウェーブジェネレータ、３１：加振信号、３２：制御信号、３３：フィードバック信号、３４：切り替えスイッチ、３５：供給空気、３６：基準マーク、３７：比較マーク。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for exposing a substrate through an original and a projection optical system.
[0002]
[Prior art]
Since the projection exposure system requires high image performance and overlay accuracy, the position measuring instrument for the positioning stage used in the exposure system is attached to a highly rigid main body structure together with the projection optical system. It is difficult to cause deviation. However, the main body structure is elastically deformed by a small amount due to floor vibration entering from the support base that supports the main body structure. In addition, when a moving stage is mounted on the main body structure, the supporting force of the main body structure changes depending on the weight of the moving stage, which causes elastic deformation of the main body structure. From such a phenomenon, the mounting position and posture of the stage position measuring instrument with respect to the exposure optical axis of the projection lens change, and a stage position measurement error occurs.
[0003]
On the other hand, as the pattern of semiconductor integrated circuits such as ICs and LSIs becomes finer, higher accuracy tends to be required. However, the increase in rigidity of the main body structure as in the past causes a significant increase in weight, Since the product is very difficult to handle in terms of device unloading, loading, installation, etc., the increase in rigidity of the main body structure has already approached its limit.
[0004]
Therefore, a technology has been developed that uses the fact that the elastic deformation of the projection body structure and the measurement error resulting from it become the linear sum of the acting forces causing it, and corrects the stage position measurement error caused by this in real time. . This is because, for example, a correction coefficient is obtained from an experiment in which the measured values of the TTL alignment scope and the stage position measuring interferometer are simultaneously compared while applying a forcible acting force to the main body structure by moving the stage. Is for correcting the stage position measurement error in real time based on the stage position.
[0005]
[Problems to be solved by the invention]
An object of this invention is to correct | amend the measured value of the means which measures the position of a stage more highly accurately.
[0006]
[Means for Solving the Problems]
An exposure method of the present invention for solving the above-described problems includes a projection optical system, a stage on which a substrate is mounted, a position measuring unit that measures the position of the stage, the projection optical system, and the position measurement. An exposure method for exposing the substrate through an original plate and the projection optical system using a structure holding the means and a support table that supports the structure, and adding the structure from the support table While shaking, measuring the position of the stage by the position measuring means and sequentially moving the stage, and measuring the force acting on the structure, through a test master plate having a reference mark and a comparison mark A first step of exposing the substrate a plurality of times, and while oscillating the structure from the support base, the position of the stage is measured by the position measuring means and the stage is moved sequentially. And while measuring the forces acting on the structure, a second step of the reference mark and said comparing mark is exposed a plurality of times the substrate through the test plate precursor so as to overlap on said substrate, A difference in position of the stage and a difference in force measured during exposure with respect to the reference mark and the comparison mark for each of a plurality of sets of the reference mark and the comparison mark on the substrate; A coefficient for correcting the position of the stage measured by the position measuring unit according to the force is obtained based on the position difference between the reference mark and the comparison mark obtained after exposure for each set. While measuring the position of the stage by the third step and the position measuring means, measuring the force acting on the structure, and determining the measured force. Wherein while coefficient and to correct the position of the stage measured by said position measuring means on the basis by sequentially moving the stage, a fourth step of exposing a plurality of times a substrate through an original having a pattern of the device was It is characterized by having.
[0007]
An exposure apparatus of the present invention for solving the above problems includes a projection optical system, a stage on which a substrate is mounted and moved, position measurement means for measuring the position of the stage, the projection optical system, and the position measurement. An exposure apparatus that exposes the substrate through an original plate and the projection optical system, the exposure apparatus being provided on the support base and having the structure that holds the structure and the support base that supports the structure. A vibration means for vibrating the structure, and a force measuring means for measuring a force acting on the structure from the support base. While measuring the position of the stage by measuring means and sequentially moving the stage, and measuring the force acting on the structure by the force measuring means, via a test master plate having a reference mark and a comparison mark Duplicate substrates It is applied to the structure by the force measuring means while performing the double exposure and vibrating the structure by the vibrating means, measuring the position of the stage by the position measuring means and sequentially moving the stage. The reference mark and the comparative mark on the substrate are exposed a plurality of times through the test master so that the reference mark and the comparative mark overlap on the substrate while measuring the force to be The difference in the position of the stage and the difference in force measured during exposure with respect to the reference mark and the comparison mark for each of the plurality of sets, and the reference mark obtained after exposure for each of the plurality of sets Based on the position difference from the comparison mark, a coefficient for correcting the position of the stage measured by the position measuring unit according to the force Therefore, while measuring the position of the stage by the position measuring means, measuring the force acting on the structure by the force measuring means, and based on the measured force and the obtained coefficient The substrate is exposed a plurality of times through an original having a device pattern while correcting the position of the stage measured by the position measuring means and sequentially moving the stage.
[0008]
In one embodiment of the present invention, for example, when manufacturing a semiconductor device such as an IC or LSI, a projection exposure is performed by stepping and repeating an electronic circuit pattern on a reticle surface sequentially on a wafer surface via a projection optical system. Main body structure in an exposure apparatus (so-called stepper) that performs projection exposure by step-and-scanning an electronic circuit pattern on a reticle surface sequentially on a wafer surface via a projection optical system. Even if the mounting position of the stage position meter that measures the position of the stage shifts due to elastic deformation of the main body structure caused by changes in the force that supports the body or the force that controls vibration of the main body structure, the main body By constantly measuring the force acting on the structure, the measurement error due to the deviation is calculated and corrected in real time.
A projection exposure apparatus that is not easily affected by deformation of the main body structure can be realized.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
In a preferred embodiment of the present invention, the stage position measurement value x (t) and the main force acting on the main body structure or the physical quantity p (t) proportional to these are continuously measured and recorded, and the reference on the reticle. The mark is projected and exposed and drawn on the wafer surface. As the physical quantity p (t), for example, a load cell for measuring the supporting force received from the support base, or if an air spring vibration isolation mechanism is provided at the contact point with the support base, the pressure of the air spring or near the contact point with the support base Measurements such as installed strain gauges can be used. This operation is repeated N times while sequentially moving the stage, and a primary exposure process for drawing a plurality of reference marks on the entire surface of the wafer is performed. Next, a secondary exposure operation is performed while moving the stage so that the comparison mark on the same reticle overlaps the reference mark drawn on the entire wafer surface. In both the primary exposure process and the secondary exposure process, a signal indicating that exposure is in progress, for example, a shutter open / close command signal, a signal associated with light emission of the exposure laser, and the like are recorded.
After these exposure processes, the relative position difference Y (i) between the reference mark drawn on the wafer and the comparison mark is observed and recorded with a microscope or the like.
[0016]
Of the continuously measured stage position measurement value x (t) and the main force acting on the main body structure or the physical quantity p (t) proportional to these, the measurement value only for the time zone during the exposure is used for each exposure time. When the average value is obtained and the primary exposure process and the secondary exposure process are distinguished, the same number of data X ₁ (i), X ₂ (i), P ₁ (i), the relative position difference between the reference mark and the comparison mark, P ₂ (i) is obtained.
At this time, the relative position difference Y (i) between the reference mark and the comparison mark is expressed by equation (1).
[0017]
[Expression 1]

Here, i is a subscript indicating the order of the relative positional difference Y between the reference mark and the comparison mark, and i = 1 to N and K are corrections of position errors due to main forces acting on the main body structure or physical quantities proportional to these. The coefficient to be used, e is an error such as microscopic observation.
From the equation (1), the correction coefficient K can be easily obtained by the method of least squares.
[0018]
The present invention is a projection exposure for correcting a relative position error between a reticle projection image and a stage position meter by multiplying an appropriate coefficient K by a main force acting on a main body structure or a physical quantity p (t) proportional thereto. A device is proposed.
[0019]
In the conventional correction technique, the relative position error correction value between the reticle projection image generated by the main acting force acting on the main body structure and the interferometer reference is substituted with the correction value of the relative position error between the TTL alignment scope and the interferometer reference. As a result, there was a slight correction residual.
[0020]
However, according to the present embodiment, since the relative position error between the reticle projection image and the interferometer reference can be directly measured, the relationship between the error and the main acting force acting on the main body structure is accurately obtained through experiments. Therefore, it is possible to improve stage position correction accuracy during projection exposure.
[0021]
【Example】
Embodiments of the present invention will be described below with reference to the drawings.
Example 1
FIG. 1 shows the overall configuration of a projection exposure apparatus to which the present invention is applied, and FIGS. 2, 3 and 4 show the detailed configuration of each part of the apparatus of FIG.
In FIG. 1, 1 is a projection lens, 2 is a main body structure, 3 is a laser interferometer for a wafer stage, 4 is an illumination system, 5 is a reticle, 6 is a wafer, 7 is a laser interferometer mirror for X axis, and 8 is a wafer. A stage top plate, 9 is a Y-axis laser interferometer mirror, 14 is an XY stage, 21 is a wafer stage surface plate, 22 is a load cell, and 23 is a support base.
[0022]
In FIG. 2, 17 is an X-axis slider, 18 is a Y-axis slider, 19 is a Y-axis drive linear motor movable element, and 20 is a Y-axis drive linear motor stator.
[0023]
In FIG. 3, 10 is a Z tilt actuator, 11 is a θ _z stage, 12 is a θ _z guide, 13 is a θ _z actuator, 15 is an X axis drive linear motor mover, and 16 is an X axis drive linear motor stator.
[0024]
In the apparatus of FIG. 1, consider a case where the stage 14 is moved to a predetermined position and the pattern on the reticle original plate 5 is projected and exposed onto the wafer substrate 6.
At this time, if no deformation occurs in the main body structure 2, the relative position between the stage position and the projection exposure optical axis is constant.
[0025]
Conversely, by varying the force that supports the main body structure, significant elastic deformation occurs in the main body structure, and this stage position measurement can be achieved by changing the relative position of the stage position meter and the projection exposure optical axis. The fluctuation of the value is a linear sum of the fluctuation of the supporting force of the main body structure. That is, the stage position measurement error can be predicted by multiplying the support force measured at all points supporting the main body structure by some coefficient matrix.
[0026]
Next, a method for obtaining this coefficient matrix will be described.
With the stage positioned, the support force of each support base 23 is varied one by one. The excitation wave is preferably an excitation wave containing many low frequency components. For example, a cumulative sum of pink noise and random noise may be given.
[0027]
As a specific example, a vibration method using an air spring type vibration isolation leg that is often used for a support base of a projection exposure apparatus will be described.
FIG. 4 shows details of the support base (air spring type vibration isolation leg) 23 in FIG. The support base is composed of a horizontal air spring 24 and a horizontal balance spring 26 which are attached to face each other, and a housing 27 which is attached to a support leg 41 via a vertical air spring 25, and each air spring 24, The amount of air supplied to 25 is controlled by a control signal 32 output by a control valve controller 29 that uses a measured value such as the level of the housing 27 and the pressure of an air spring as a feedback signal 33, and is supplied from the supply air 35. The amount of air supplied to the air springs 24 and 25 is controlled. In the air spring type vibration isolation leg as described above, in order to vary the support force of each air spring, the excitation signal 31 output from the wave generator 30 is branched by the changeover switch 34 and the like and applied to each control signal 32.
[0028]
Note that the support force of each support base may be vibrated at the same time, but in this case, the waveforms applied to the respective control signals must be independent from each other.
[0029]
In this state, the XY stage 14 is sequentially moved, and a plurality of shots are projected and exposed on the entire surface of the wafer in the order shown in FIG. In the shot drawn by one projection exposure, the reference mark (■) 36 and the comparison mark (□) 37 are simultaneously drawn as shown in FIG. This process is called a primary exposure process. However, the comparison mark 37 drawn in the primary exposure process is not used.
[0030]
Subsequently, a plurality of shots are projected and exposed in the order shown in FIG. 5B so that the comparative mark 37 overlaps the previously drawn reference mark 36. This process is called a secondary exposure process. However, the reference mark 36 drawn in the secondary exposure process is not used.
[0031]
When the exposure apparatus is a batch exposure type, the test reticle remains fixed.
On the other hand, when the exposure apparatus is a scanning exposure type, the reticle stage is brought to a stationary state at a fixed position.
[0032]
Regardless of the vibration method, all support forces, stage position control deviations, and signals that can be determined as being during projection exposure, such as shutter open / close signals and exposure laser light oscillation signals, are simultaneously measured.
[0033]
In addition, for measuring the support force, it is preferable to measure the support force in each direction using the load cell 22, but even using a pressure gauge (not shown) that measures the pressure of each air spring is proportional to the support force fluctuation. Since a measured value is obtained, this may be used instead.
[0034]
The reticle image is obtained by using the distance data between the centers of gravity of the reference mark 36 and the comparison mark 37 projected in this way, the supporting force of each anti-vibration leg, and the positioning control residual averaged over the projection exposure time. A stage position measurement error correction coefficient for projection exposure can be obtained.
[0035]
Example 2
In the second embodiment, a plurality of reference marks (■) 36 and comparison marks (□) 37 are simultaneously projected and exposed in one exposure. When the θ-axis stage position measurement error is also corrected, correction of the θ-axis stage position measurement error is performed by simultaneously projecting and exposing at least two reference marks 36 and a comparison mark 37 that are sufficiently separated as shown in FIG. A coefficient can be obtained.
[0036]
Example 3
In the third embodiment, the shot order for projecting and exposing the reference mark (■) 36 and the shot order for projecting and exposing the comparison mark (□) 37 are irregular. When the projection exposure is performed in a regular order as in the first and second embodiments, the shot interval at which the reference mark 36 and the comparison mark 37 that overlap each other as shown in FIG. 8 are projected and exposed is substantially constant. Since this shot interval is approximately proportional to the shot time interval, if this time interval is close to the period of the force 38 that is forcibly applied, the difference in force when the reference mark 36 and the comparison mark 37 are projected and exposed is different. There is a risk that it will become smaller and lose its meaning given the compulsory force.
[0037]
Therefore, as shown in FIG. 9, this problem can be solved by disrupting the exposure order so that the time intervals for projecting and exposing the overlapping reference mark 36 and comparison mark 37 are appropriately varied.
[0038]
Example 4
The fourth embodiment is a projection exposure sequence suitable for a case where the environmental temperature and the atmospheric pressure fluctuate in a relatively short cycle (a cycle substantially equal to the time interval between successive projection exposures), and measurement errors caused by these fluctuations cannot be ignored. is there. In this case, as shown in FIG. 10, the reference mark (■) 36 is projected and exposed, and the comparison mark (□) 37 overlapping with the next shot is projected and exposed. At this time, since the environmental temperature and the atmospheric pressure when the both are projected and exposed are substantially equal, the influence of the environmental temperature and the atmospheric pressure can be almost canceled.
[0039]
[Example of device production method]
Next, an embodiment of a device production method using the above-described exposure apparatus or exposure method will be described.
FIG. 11 shows a flow of manufacturing a microdevice (a semiconductor chip such as an IC or LSI, a liquid crystal panel, a CCD, a thin film magnetic head, a micromachine, etc.). In step 1 (circuit design), a device pattern is designed. In step 2 (mask production), a mask on which the designed pattern is formed is produced. On the other hand, in step 3 (wafer manufacture), a wafer is manufactured using a material such as silicon or glass. Step 4 (wafer process) is called a pre-process, and an actual circuit is formed on the wafer by lithography using the prepared mask and wafer. The next step 5 (assembly) is referred to as a post-process, and is a process for forming a semiconductor chip using the wafer produced in step 4, such as an assembly process (dicing, bonding), a packaging process (chip encapsulation), and the like. including. In step 6 (inspection), inspections such as an operation confirmation test and a durability test of the semiconductor device manufactured in step 5 are performed. Through these steps, the semiconductor device is completed and shipped (step 7).
[0040]
FIG. 12 shows a detailed flow of the wafer process. In step 11 (oxidation), the wafer surface is oxidized. In step 12 (CVD), an insulating film is formed on the wafer surface. In step 13 (electrode formation), an electrode is formed on the wafer by vapor deposition. In step 14 (ion implantation), ions are implanted into the wafer. In step 15 (resist process), a photosensitive agent is applied to the wafer. In step 16 (exposure), the circuit pattern of the mask is printed onto the wafer by exposure using the exposure apparatus described above. In step 17 (development), the exposed wafer is developed. In step 18 (etching), portions other than the developed resist image are removed. In step 19 (resist stripping), unnecessary resist after etching is removed. By repeating these steps, multiple circuit patterns are formed on the wafer.
[0041]
By using the production method of this embodiment, a highly integrated device that has been difficult to manufacture can be manufactured at low cost.
[0042]
【The invention's effect】
According to the present invention, the measurement value of the means for measuring the position of the stage can be corrected with higher accuracy .
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a configuration of a projection exposure apparatus according to an embodiment of the present invention.
FIG. 2 is a configuration explanatory diagram of a stage mounted on the apparatus of FIG. 1;
FIG. 3 is a cross-sectional view of the stage of FIG.
4 is a configuration diagram of a support base with a vibration isolation function used in the apparatus of FIG. 1. FIG.
FIG. 5 is an explanatory diagram of a projection exposure order in the first and second embodiments.
FIG. 6 is a view in a shot to be projected and exposed in the first embodiment.
FIG. 7 is a view in a shot subjected to projection exposure in the second embodiment.
FIG. 8 is a diagram showing a list of projection intervals at each shot position in the first and second embodiments.
FIG. 9 is an explanatory diagram of a projection exposure order and a list of projection intervals at each shot position in Embodiment 3.
FIG. 10 is an explanatory diagram of a projection exposure order and a list of projection intervals at each shot position in Embodiment 4.
FIG. 11 is a diagram showing a flow of manufacturing a microdevice.
12 is a diagram showing a detailed flow of the wafer process in FIG. 11. FIG.
[Explanation of symbols]
1: projection lens, 2: main body structure, 3: laser interferometer for stage positioning, 4: illumination system, 5: reticle, 6: wafer, 7: laser interferometer mirror for X axis, 9: laser interference for Y axis Total mirror, 8: Wafer stage top plate, 10: Z tilt actuator, 11: θ _z stage, 12: θ _z guide, 13: θ _z actuator, 14: XY stage, 15: X axis drive linear motor mover, 16 : X-axis drive linear motor stator, 17: X-axis slider, 18: Y-axis slider, 19: Y-axis drive linear motor mover, 20: Y-axis drive linear motor stator, 21: Wafer stage surface plate, 22: Load cell, 23: support base, 24: horizontal air spring, 25: vertical air spring, 26: horizontal balance spring, 27: housing, 28: control valve, 29: control valve controller, 3 : Wave generator, 31: vibration signal, 32: a control signal, 33: a feedback signal, 34: selector switch, 35: supply air, 36: a reference mark, 37: Comparison mark.

Claims

A projection optical system, a stage on which a substrate is mounted, a position measurement unit that measures the position of the stage, a structure that holds the projection optical system and the position measurement unit, and a structure that supports the structure An exposure method that exposes the substrate through a master and the projection optical system using a support base,
While oscillating the structure from the support, the position measuring means measures the position of the stage and sequentially moves the stage, while measuring the force acting on the structure, A first step of exposing the substrate multiple times through a test master having a comparison mark;
While oscillating the structure from the support, the reference mark is measured while measuring the position of the stage by the position measuring means and sequentially moving the stage, and measuring the force acting on the structure. And a second step of exposing the substrate a plurality of times through the test master so that the comparison mark and the comparison mark overlap each other,
A difference in position of the stage and a difference in force measured during exposure with respect to the reference mark and the comparison mark for each of a plurality of sets of the reference mark and the comparison mark on the substrate; A coefficient for correcting the position of the stage measured by the position measuring unit according to the force is obtained based on the position difference between the reference mark and the comparison mark obtained after exposure for each set. A third step;
Measured by the position measuring means while measuring the position of the stage by the position measuring means, measuring the force acting on the structure, and based on the measured force and the obtained coefficient. And a fourth step of exposing the substrate a plurality of times through an original having a device pattern while correcting the position of the stage and sequentially moving the stage.

The exposure method according to claim 1, wherein a load cell is used for measuring the force.

The exposure method according to claim 1, wherein the coefficient is a coefficient of a matrix to be multiplied by a plurality of measured forces acting on the structure.

4. The exposure method according to claim 1, wherein the coefficient is obtained by a least square method in the third step.

5. The exposure method according to claim 1, wherein the exposure of the plurality of shots in the first step and the exposure of the plurality of shots in the second step are performed in an irregular order.

The shot exposure in the second step performed so that the reference mark and the comparison mark overlap on the substrate is performed following the shot exposure in the first step performed with respect to the reference mark. 6. The exposure method according to claim 1, wherein the exposure method is characterized in that:

A projection optical system, a stage on which a substrate is mounted, a position measurement unit that measures the position of the stage, a structure that holds the projection optical system and the position measurement unit, and a structure that supports the structure And an exposure apparatus that exposes the substrate through the original plate and the projection optical system,
Vibration means provided on the support base for vibrating the structure;
Force measuring means for measuring the force acting on the structure from the support, and
While the structure is vibrated by the vibration means, the position of the stage is measured by the position measurement means and the stage is moved sequentially, and the force acting on the structure is measured by the force measurement means. While exposing the substrate multiple times through a test master having a reference mark and a comparative mark,
While the structure is vibrated by the vibration means, the position of the stage is measured by the position measurement means and the stage is moved sequentially, and the force acting on the structure is measured by the force measurement means. While exposing the substrate a plurality of times through the test master so that the reference mark and the comparison mark overlap on the substrate,
A difference in position of the stage and a difference in force measured during exposure with respect to the reference mark and the comparison mark for each of a plurality of sets of the reference mark and the comparison mark on the substrate; A coefficient for correcting the position of the stage measured by the position measuring unit according to the force is obtained based on the position difference between the reference mark and the comparison mark obtained after exposure for each set. ,
While measuring the position of the stage by the position measuring unit, measuring the force acting on the structure by the force measuring unit, and measuring the position based on the measured force and the obtained coefficient An exposure apparatus for exposing a substrate a plurality of times through an original having a device pattern while correcting the position of the stage measured by means and sequentially moving the stage.

A step of exposing the substrate using the exposure method according to claim 1 or the exposure apparatus according to claim 7;
And a step of developing the substrate exposed in the step.