JP4182303B2 - Distortion measuring method for projection optical system and method for manufacturing semiconductor device by correcting distortion - Google Patents

Description

【００３３】
特開昭６１−４４４２９号(USP4,780,617)公報に詳述されているＥＧＡ計算に則り、ショット設計位置（ＳＸi，ＳＹi）と、その位置でのショットの設計位置からの理想的なずれ（αMi，βMi）の間には以下の関係があるものとする。
【００３４】
【数２】

【００３５】
上式において、Ｘ方向のウエハスケーリングγx、Ｙ方向のウエハスケーリングγy、Ｙ軸のウエハ回転φ、Ｘ軸のウエハ回転θ、Ｘ方向のウエハシフトＯx、Ｙ方向のウエハシフトＯyである。なお、当該座標測定器２００のウエハステージ２３０は、Ｘ軸モータとＹ軸モータにより互いに直交する方向に移動可能になっているが、実際には係るモータの送り込み方向は正確には直交しておらず、僅かながら直交度誤差ｗを含んでいる。式（２）では、この直交度誤差ｗはＹ軸のウエハ回転成分φに含まれているため、Ｙ軸のウエハ回転成分φとＸ軸のウエハ回転成分θとの間には、φ＝ｗ＋θなる関係が成立している。
簡単のために各行列の成分をアルファベット一文字に置き換える。
【００３６】
【数３】

【００３７】
理想的なずれ（αMi，βMi）と実際の計測値（αi，βi）との違いは、本当にずれてマークが作られているのと、計測誤差との両方が含まれている。実際に得られるのは実際の計測値（αi，βi）であるから、六つの変換パラメータＡ、Ｂ、Ｃ、Ｄ、Ｅ、Ｆを最小二乗法で求める。理想的なずれ（αMi，βMi）と実際の計測値（αi, βi）との差を各ｉ毎に取り二乗し、全てのｉについて和を求める。
【００３８】
【数４】

【００３９】
（εx，εy）をそれぞれＡ、Ｂ、Ｃ、Ｄ、Ｅ、Ｆで微分し、＝０と置いて連立方程式を求めることによりＡ、Ｂ、Ｃ、Ｄ、Ｅ、Ｆが求められる（図１、工程１３０）。
【００４０】
【数５】

【００４１】
次に、基準ウエハＷ１の計測値を保存する。先に述べたように、基準ウエハＷ１を座標測定機２００で測定して得られた測定値（ΔＸij，ΔＹij）は、各マークの設計座標に対して実際のマーク位置がどれだけずれているかを表わしている。同じウエハを何度も測定する場合、ウエハが測定機に載せられた姿勢によりウエハ回転成分は異なるし、測定時の環境温度が変わればウエハのスケーリング成分も異なる。
【００４２】
測定機の計測再現精度は仕方ないが、そうでないウエハの回転やウエハのスケーリングなどの変動の影響を受けない形で、基準ウエハＷ１の測定結果を保存しておくのがよい。具体的には以下の計算式によって求められる（ＣＸij，ＣＹij）を計測値として保存する（図１、工程１３０）。
【００４３】
【数６】

【００４４】
例えば、前記したとおりＡ＝γx−１である。γxはほぼ１に等しく、例えばウエハ温度が１度高くなるとＳｉウエハは約２．６ｐｐｍだけ膨張する。１ショットの大きさが、２０ｍｍ×２０ｍｍとして、ショット周辺では５２ｎｍもの位置ずれになる。
しかしながら、同時にウエハ全体の伸びを表わすγxも２．６ｐｐｍだけ大きくなり、前式により求められる保存計測値（ＣＸij，ＣＹij）は膨張前後で変化しない。ウエハが計測機に載せられる姿勢により変化するウエハシフト、ウエハ回転分も同様の効果が得られ、前式によれば保存される計測値は、計測時の条件に左右されない。図８に、以上の関係をベクトル表示する。
【００４５】
以上で事前準備は終了して、次にディストーション測定に入る。図の被測定露光装置１００には基準ウエハＷ１を搭載するための不図示のウエハホルダがあって、その平面度は重要である。なぜなら、ウエハＷが曲がると、（ウエハ厚さ）×（傾き）で与えられる量だけウエハ表面のパターンが横ずれを起こすからである。基準レチクルＲ１を載せるためのレチクルホルダも同様の理由から平面度を良くしておく必要がある。
【００４６】
基準レチクルＲ１を投影露光装置１００にセットするとともに、基準ウエハＷ１にレジストを塗布し、投影露光装置１００にローディングする（図１、工程１４０）。投影露光装置１００ではウエハアライメント顕微鏡２０によりウエハＷ１上の位置合わせマークＡwを測定、ウエハＷ１が投影露光装置１００のウエハステージ座標に対してどのような位置、姿勢になっているかを求める。具体的には前述のＥＧＡと呼ばれる方法により定める（図１、工程１４０）。
【００４７】
このとき、ウエハスケーリング量γxEGA、γyEGA、ウエハ回転量φEGA、θEGA、ウエハシフト量ＯxEGA、ＯyEGAが求められ、基準レチクルＲ１を露光する位置にフィードバックされる。なお、このアライメント工程において、ウエハスケーリング量γxEGAは、ショット間隔の設計値ａｘに対する測定されたショット間隔ａｘＭの比（ａｘＭ／ａｘ）で与えられ、γyEGAは、ショット間隔の設計値ｂｘに対する測定されたショット間隔ｂｘＭの比（ｂｘＭ／ｂｘ）で与えられる。ただし、ウエハスケーリング量γxEGA、γyEGは、各アライメントマークＡＷの測定された間隔と設計値から求めてもよい。
【００４８】
１ｓｔ露光において基準ウエハＷ１に形成された主尺パターン上に、２ｎｄ露光として基準レチクルＲ１の副尺パターンの露光が行われる（図２、工程１５０）。
露光終了後基準ウエハＷ１を現像し、出来上がった主尺パターンと副尺パターンを、重ねあわせ測定機（レジストレーション測定器）によって測定する（図２、工程１５０）。全部でｍショットあり、各ショットにはｎ点の測定点がある。主尺と副尺のずれ量は、例えば（株）ニコン製のレジストレーション測定器により測定可能であり、特開平6-168320号公報にその構成が詳述されている。図１１は、相対的なずれ量の測定を説明するための概念図であり、この図におけるレジストレーション測定機３００は、ホルダ３０８に保持された基準ウエハＷ２に光を照明する照明光学系と、基準ウエハＷ２からの反射光を集光する対物レンズ３０６と、この対物レンズ３０６を出た反射光を結像する結像光学系３０９と、結像光学系３０９により結像した像を観察するＣＣＤカメラ３１０を備えている。また、照明光学系を構成する光源３０１の光は、コンデンサレンズ３０２、照明絞り３０３、投影レンズ３０４、及びハーフミラー３０５を経て対物レンズ３０６の瞳面に結像し、基準ウエハＷ２をケーラー照明する。
【００４９】
続いて、ショット内各点毎に全ショット分の平均を求める。その値にはウエハの膨張分が残留している。この重ね合わせ測定器で測定された値は（ＲｅｇＸij，ＲｅｇＹij）として保存される。
最後に校正を行う。即ち、測定値からウエハ膨張分、ウエハ回転分などの残留誤差を取り除く。先の露光前のＥＧＡ計測において、ウエハＷ１のスケーリングなど各成分が求められている。その求められている値の分は当然残留誤差となっているので、計算により取り除いてやることが許される。また、ＥＧＡ測定自身に誤差が含まれていることも予想されるので、重ねあわせ測定機によって求められる残留ウエハスケーリング誤差も一緒に補正するのがよい。
【００５０】
結局、被測定露光装置１００を通して基準ウエハＷ１の主尺に重ねて基準レチクルＲ１の副尺を投影露光し、重ね合わせ測定器、例えば（株）ニコン製のレジストレーション測定器で測定したそれら主尺と副尺のずれ（ＲｅｇＸij，ＲｅｇＹij）及び、基準ウエハの主尺の実際の位置（（ＣＸij，ＣＹij）で与えられた）、基準レチクルの副尺の実際の位置、露光時のウエハの伸縮、に基づきディストーションを求めることになる。
【００５１】
ウエハスケーリングのＸ成分について整理すると、ＥＧＡ計測値γxEGA、重ねあわせ測定機による測定結果より最小二乗法で求めたウエハ残留スケーリング値γxRとすれば、露光時の実際のウエハのスケーリング量は（γxEGA−γxR＋１）で表わされる。なお、ウエハ残留スケーリング値γxRは、測定結果（ＲｅｇＸｉｊ，ＲｅｇＹｉｊ）、そのショット内平均等から、上述された計算（式（１）〜式（５））と同様の手順で求められるパラメータＡ〜Ｆより得られる。
したがって、ｉ番目のショットにおける各マークの重ねあわせ測定値を（Ｒxij,Ｒyij）とすれば、そのマークのショット内相対位置座標（ＭＸj，ＭＹj）から次の式７で表される補正計算により正しいディストーションが求められる。
【００５２】
【数７】

【００５３】
結局、Ｘ方向のディストーション即ちＸ方向のずれ量は、次の数８で表される。
【００５４】
【数８】

【００５５】
ここで、±の記号は座標の取り方によって変わり、（γxEGA−γxR）・（ＳＸi＋ＭＸj）の項は実施例によって変わる。また、ＣＸijは、ｉ番目のショットのj番目の主尺がウエハ内座標基準でどれくらいずれているかを示す、即ちショット（主尺）のウエハ内非線形ずれを示すものである。
Ｙ方向についても同じである。実際にはスケーリング成分だけでなくウエハ回転成分、ステージ直交度成分、シフト成分も同様に補正される。
【００５６】
このようにして求められたディストーション分だけ、投影露光装置１００の投影レンズ系を調整し（図２、工程１７０）、調整された投影露光装置１００で製品ウエハを投影露光し、半導体デバイスを製造する（図２、工程１８０）。
図３を参照して、本発明の第２実施例を説明する。第１の実施の形態と異なる点は、基準ウエハＷ１を被測定投影露光装置１００で露光する際、ＥＧＡ法により求められたウエハスケーリング値に基づいて投影レンズ系ＰＬの倍率を制御し、基準ウエハＷ１の伸縮に合わせてショット倍率を変える点である（図３、工程１４１）。したがって、真のディストーションを求めるときに倍率補正は不要となる（図３、工程１５１）。即ち、数７に対応する補正計算式は次の式９になる。
【００５７】
【数９】

【００５８】
前記パラメータＡ1〜Ｆ1の求め方を以下に説明する。
重ね合わせ測定器３００により測定されたずれ量（ＲｅｇＸij，ＲｅｇＹij）の各ショット領域ＳＡｉにおける平均のずれ量（Ｒｅｇαｉ，Ｒｅｇβｉ）を以下の式（１０）から求める。
【００５９】
【数１０】

【００６０】
そして、上記式（２）と同様に、理想的なずれ量（ＲｅｇαＭｉ，ＲｅｇβＭｉ）を以下の式（１１）で与える。
【００６１】
【数１１】

【００６２】
この式（１１）において、γxRは露光時のEGA計測誤差による残留スケーリング量、γyRは露光時のEGA計測誤差による残留スケーリング量、φRはＹ軸の露光時のEGA計測誤差による残留ウエハ回転成分、θRはＸ軸の露光時のEGA計測誤差による残留ウエハ回転成分、ＯxRはＸ方向の露光時のEGA計測誤差による残留平行シフト量（重ねあわせ測定器３００のＸ方向のオフセット量）、ＯyRはＹ方向の平行シフト量（測定器３００のＹ方向のオフセット量）である。
さらに、上記式（１１）の各行列成分を以下の式（１２）に示されたようにＡ1〜Ｆ1に置き換える。
【００６３】
【数１２】

【００６４】
そして、以下の式（１３）のように、理想的なずれ量（ＲｅｇαMi，ＲｅｇβMi）と実際の平均ずれ量（Ｒｅｇαi, Ｒｅｇβi）との差を各ｉごとに二乗し、全てのｉについて和を求める。
【００６５】
【数１３】

【００６６】
ここで、（εx，εy）をそれぞれＡ1〜Ｆ1で微分し、さらに０と置いて上述の式（５）で示された連立方程式を解くことによりパラメータＡ1〜Ｆ1が得られる。
ちなみに、基準ウエハＷ２における伸縮のＸ成分γxRは、得られたパラメータＡ1（Ａ1＝γxR−１）から容易に求められる。
【００６７】
実測された主尺・副尺間のずれ（ＲｅｇＸij、ＲｅｇＹij）からＥＧＡ誤差による残留線形成分すなわち残留スケーリング、残留回転、及び残留平行シフト成分を差し引いたもの（ＲｅｇＸ１ij、ＲｅｇＹ１ij）を求める。
【００６８】
【数１４】

【００６９】
第１実施例においては、ＥＧＡ計測により求められたウエハ伸縮量を投影光学系ＰＬの投影倍率に反映させずに露光するため、式１４で求めた（ＲｅｇＸ１ij、ＲｅｇＹ１ij）を式１５のように補正する必要がある。
【００７０】
【数１５】

【００７１】
結局、各測定点における諸誤差（基準ウエハ上の主尺位置誤差、基準レチクル上の副尺位置誤差等）を取り除いた純粋な主尺・副尺のずれ、すなわち投影光学系ＰＬのディストーションは、第１実施例については式１６となり、第２実施例においては式１７となる。
【００７２】
【数１６】

【００７３】
【数１７】

【００７４】
更に、ショット数ｍで平均することにより投影光学系ＰＬのディストーションを求めることができる。
【００７５】
【数１８】

【００７６】
このように測定されたディストーションの除去は、以上のように求められたディストーション成分だけ、図６に示された被測定露光装置１００の投影光学系ＰＬを調整系４２０により光学調整することにより、実現される。なお、該投影光学系ＰＬの具体的な調整方法は、例えば米国特許第5,117,255号に詳述されている。
また、この発明では、上記基準ウエハＷ１の伸縮成分のみならず、上述のようにＥＧＡ誤差による残留ウエハ回転成分φR，θR及び残留平行シフト量についても同時に除去することができる。
【００７７】
以上の測定方法は、マスクのパターンを投影光学系（ＰＬ）により基板（Ｗ１，Ｗ２）に露光する露光装置（１００）の投影光学系（ＰＬ）の結像誤差を測定する測定方法であって、基板（Ｗ１）上に形成された第１パターン（ＭＭｉｊ）の位置を基板（Ｗ１）の伸縮に関連して検出する第１ステップ（ステップ１２０、１３０）と、第１パターン（ＭＭｉｊ）を有した基板（Ｗ１）を露光装置（１００）に載置して、第１パターン（ＭＭｉｊ）の位置を基板（Ｗ１）の伸縮に関連して検出する第２ステップ（ステップ１４０）と、投影光学系（ＰＬ）により、第１パターン（ＭＭｉｊ）上に第２パターン（ＳＭｉｊ）を露光する第３ステップと、第１パターン（ＭＭｉｊ）と第２パターン（ＳＭｉｊ）とのずれ量と、基板（Ｗ２）の伸縮とに基づいて投影光学系（ＰＬ）の結像誤差を検出する第４ステップ（ステップ１５０、１６０）とを含んでいる。
以上の測定方法で、第１パターン（ＭＭｉｊ）が基板（Ｗ１）の複数のショット領域に形成されており、この複数のショット領域の間隔に基づいて基板（Ｗ１）の伸縮を検出するステップを含んでいる。
また、以上の測定方法で、基板（Ｗ１）に所定の間隔でアライメントマーク（Ａｗ）が形成されており、この所定の間隔で形成されたアライメントマーク（Ａｗ）の検出に基づいて、基板（Ｗ１）の伸縮を検出するステップを含んでいる。 さらに、以上の測定方法は、請求項８記載の測定方法は、第２パターン（ＳＭｉｊ）を露光する前に、第１ステップの検出結果に基づいて、投影光学系（ＰＬ）を調整するステップを含んでいる。
なお、この発明に係る半導体デバイスの製造方法は、上述のように調整された被検露光装置１００を利用し、製品ウエハ上に所定のパターン（回路パターン等）を投影露光し、半導体デバイスを製造する。
加えて、上述された第２実施例の場合についても言及すると、この第２実施例と上述された第１実施例との異なる点は、基準ウエハＷ１を被検露光装置１００で露光する前に、ＥＧＡ計測により得られた該基準ウエハＷ１のスケーリング成分（ＬＭＸ／ＬＤＸ、ＬＭＹ／ＬＤＹ）に基づいて、投影光学系ＰＬのショット倍率を調整系４２０が制御し、基準ウエハＷ１の伸縮に合わせてショット倍率を変える点である。
【００７８】
【発明の効果】
以上のように本発明によれば、各点の設計値からのずれを、座標測定機の座標系基準で求めるのでなく、ウエハ全体の伸縮を差し引いた相対座標系で求めるので、座標測定した時の雰囲気と、投影露光装置の雰囲気が一致していなくても、ほとんど誤差なくディストーションが測定でき、座標測定機と投影露光装置の温度差が未知のままであっても問題ない。またそれにより投影レンズ系を校正できるので、正確な投影露光が可能となる。また、主尺と副尺を用いて基準ウエハ上の各点の設計値からのずれを計測するので、計測そのものの迅速化が可能である。
【図面の簡単な説明】
【図１】本発明の第１の実施例の方法の前半のステップを示すフローチャートである。
【図２】図１のステップに続けて実行するステップを示すフローチャートである。
【図３】本発明の第２の実施例の方法の前半のステップを示すフローチャートである。
【図４】本発明に用いられる主尺と副尺の例を示す図である。
【図５】本発明に用いられる基準ウエハ及びその上に重ね合わせて形成された主尺と副尺の例を示す図である。
【図６】本発明に用いられる投影露光装置の概略図である。
【図７】基準レチクルと基準ウエハ上に形成された主尺と副尺の座標関係を示す図である。
【図８】基準ウエハ上の主尺の実際の測定値、設計位置からの理想的なずれ、環境条件の排除された保存計測値との関係をベクトル表示した図である。
【図９】本発明に係る測定方法を説明するための概念図である。
【図１０】座標測定器２００を示す概念図である。
【図１１】レジストレーション測定機３００を示す概念図である。
【符号の説明】
Ｌ 照明光学系
Ｒ レチクル
ＰＬ 投影レンズ系
Ｗ ウエハ
ＳＴ ウエハステージ
ＭＭｉｊ 主尺パターン
ＳＭｉｊ 副尺パターン
１０ 座標測定機（測長干渉計）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a distortion measurement method for a projection optical system and a semiconductor device manufacturing method performed by correcting the distortion, and in particular, a distortion measurement method for measuring a deviation from a design value of each point using a reference wafer and the distortion correction. The present invention relates to a method for manufacturing a semiconductor device.
[0002]
[Prior art]
Conventionally, in order to measure distortion of a projection lens in a projection exposure apparatus, a so-called reference wafer method in which measurement is performed using a reference wafer has been used. In this method, the deviation from the design value of each point on the reference wafer is obtained for each point using the coordinate reference of the coordinate measuring device.
[0003]
[Problems to be solved by the invention]
According to the prior art as described above, the reference wafer expands and contracts when the temperature changes. There is no problem if the atmosphere at the time of coordinate measurement matches the atmosphere of the projection exposure apparatus, but if it is different, the magnification component of the lens cannot be measured correctly. Further, since each point is obtained based on the coordinate reference of the coordinate measuring instrument, the distortion measurement requires a long time in units of one day. Therefore, the present invention is a method for measuring distortion of a projection lens that can be measured in a relatively short time without being affected by the ambient temperature at the time of coordinate measurement, and manufacturing a semiconductor device that is corrected after measuring distortion in this way. It aims to provide a method.
[0004]
[Means for Solving the Problems]
In order to achieve the above object, a distortion measuring method according to the first aspect of the present invention is the coordinate between the ideal design coordinates and the actual coordinates of the position of the main scale formed on the reference substrate under a predetermined measurement environment. A first step of measuring a deviation amount; a second step of measuring a position of a vernier pattern formed on the reference reticle; and the predetermined measurement based on the coordinate deviation amount measured in the first step. A third step of obtaining an ideal deviation amount of the design coordinates of the main scale determined under the environment from an ideal design coordinate, and obtaining a deviation amount difference between the ideal deviation amount and the coordinate deviation amount; A fourth step of setting the measurement exposure apparatus; a fifth step of measuring a position and orientation value of the reference substrate with respect to the exposure apparatus to be measured; projecting and exposing a vernier pattern of the reference reticle onto the reference substrate; Form a vernier over the main scale A seventh step of measuring a relative deviation amount between the main scale and the sub-scale; and a distortion of the exposure apparatus to be measured based on the deviation amount difference, the position / posture value, and the relative deviation amount. And an eighth step for obtaining.
[0005]
If comprised in this way, the relative deviation | shift amount of a main scale and a sub-scale can be measured with a registration measuring device, and a quick measurement is possible.
According to a second aspect of the present invention, there is provided a distortion measurement method for measuring a coordinate shift amount between an ideal design coordinate and an actual coordinate of a position of a main scale formed on a reference substrate under a predetermined measurement environment. A first step; a second step of measuring the position of the vernier pattern formed on the reference reticle; and a predetermined measurement environment based on the coordinate shift amount measured in the first step. A third step of obtaining an ideal deviation amount of the design coordinates of the main scale from the ideal design coordinates and obtaining a difference amount between the ideal deviation amount and the coordinate deviation amount; and setting the reference substrate on the exposure apparatus to be measured. A fourth step; a fifth step of measuring a position and orientation value of the reference substrate with respect to the exposure apparatus to be measured; and a projection optical system of the exposure apparatus to be measured based on the position and orientation value measured in the fifth step A ninth step of adjusting; on the reference substrate; A sixth step of projecting and exposing a vernier pattern of the reference reticle and forming a vernier over the main metric; a seventh step of measuring a relative displacement between the main metric and the vernier; And a tenth step of obtaining distortion of the exposure apparatus to be measured based on the difference in deviation amount and the relative deviation amount.
[0006]
If comprised in this way, since the 9th process which adjusts the projection optical system of the said to-be-measured exposure apparatus based on the position-orientation value measured at the 5th process is provided, in the 10th process which finally calculates | requires distortion. There is no need to capture position and orientation values.
In the distortion measuring method according to claim 2, as in the method according to claim 3, the eleventh step of obtaining a residual deformation amount of the reference substrate based on the relative deviation amount; and based on the residual deformation amount; The distortion obtained in the tenth step may be calibrated. In this case, the residual deformation amount of the reference substrate is obtained based on the relative deviation amount, and the distortion is calculated based on the residual deformation amount. Because it calibrates, distortion can be adjusted more accurately.
[0007]
A method of manufacturing a semiconductor device according to a fourth aspect of the present invention is obtained by a step of measuring distortion of a projection optical system using the distortion measurement method according to any of claims 1 to 3, and a step of measuring the distortion. Adjusting the magnification of the projection optical system based on the distortion, and projecting and exposing a pattern onto the photosensitive substrate by the projection optical system adjusted in the adjusting step.
[0008]
In this way, since the distortion is measured and calibrated using the above-described distortion measurement method, the distortion can be measured in a relatively short time without being influenced by the ambient temperature at the time of coordinate measurement, and the throughput of manufacturing the semiconductor device can be increased. improves.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 6 shows a schematic configuration of the projection exposure apparatus 100 used in the present invention. In the drawing, an illumination optical system L, a reticle R, and a projection lens system PL are arranged in this order, and the wafer W is placed on the wafer stage ST so that the projection lens PL is at a position conjugate with the reticle R. . A pattern (not shown) on the reticle R uniformly illuminated by the illumination optical system L is projected and exposed onto the wafer W by the projection lens system PL. A movable mirror 15 is fixed to the wafer stage ST, and a laser beam from a coordinate measuring machine (length measuring interferometer) 10 for the wafer stage ST is irradiated onto the movable mirror 15. The coordinate measuring machine (measurement interferometer) 10 receives the laser beam reflected by the movable mirror 15 and measures the position of the wafer stage ST.
[0012]
In the exposure apparatus 100 to be measured, the reticle stage RS that holds the reticle R can be moved in the X direction and the Y direction by the reticle stage drive system 410 in accordance with an instruction from the main control system 400, and the position of the reticle stage RS is , And accurately measured by the laser interferometer 30. The wafer stage ST can also be moved in the X and Y directions by the wafer stage drive system 430 in accordance with instructions from the main control system 400. As described above, the position of the wafer stage ST is accurately measured by the laser interferometer 10. Is done.
[0013]
Reference numeral 35 in the drawing also denotes a movable mirror (reflecting mirror) fixed to the reticle stage RS. The alignment process performed prior to exposure of the vernier pattern is performed via the alignment microscope 20, and the distortion that is an imaging error of the projection optical system PL is adjusted by the control of the adjustment system 420. This is performed by moving or tilting the lens constituting the PL in the optical axis direction of the projection optical system PL. A specific method for adjusting the projection optical system PL is described in detail, for example, in US Pat. No. 5,117,255.
[0014]
Here, the principle of the present invention will be described. In such an apparatus, the reference wafer method is used to measure the distortion of the projection lens system PL and calibrate it. In the reference wafer method, the distortion of the projection lens system PL is measured using the reference wafer W1 before projecting and exposing the actual pattern onto the product wafer.
The reference wafer W1 expands and contracts when the temperature changes. There is no problem as long as the atmosphere (for example, temperature) when the coordinates are measured and the atmosphere (for example, temperature) of the projection exposure apparatus match, but if they are different, the magnification component of the lens cannot be measured correctly. In the present invention, since the scaling (expansion / contraction ratio) of the entire wafer is subtracted and the residual component is used as a drawing error, even if the temperature difference between the coordinate measuring machine 200 (see FIG. 10) and the projection exposure apparatus 100 remains unknown. There is no error.
[0015]
In general, in a coordinate measuring machine (for example, “light wave interference type coordinate measuring device” manufactured by Nikon Corporation), the position of a wafer stage coordinate is measured by a length measuring interferometer 240. Normally, the mark position is measured by the interferometer standard of the coordinate measuring machine. Therefore, if the temperature of the coordinate measuring machine 200 is high, the reference wafer W1 expands, and accordingly, the shot magnification is greatly measured. However, since the entire reference wafer W1 is expanded at the same ratio, if the amount of expansion / contraction of the entire reference wafer W1 with respect to the design value is subtracted from the shot magnification, the value is stored even if the temperature is slightly different. The In the projection exposure apparatus 100, if the wafer scaling is measured by the alignment before the exposure by the wafer alignment microscope 20 and the shot magnification is changed accordingly, the temperature of the wafer itself can be any degree.
[0016]
In the conventional method, when the reference wafer W1 is rotated with respect to the coordinate system of the coordinate measuring machine 200, the rotation amount is subtracted by common sense, but the calibration for the scaling has not been performed. . In the present invention, the calibration is performed.
Specifically, in the case of measuring distortion generated by the projection optical system as an imaging error, as shown in FIG. 9, the present invention relates to the main scale MMij (on the reference wafer W1 (first reference wafer)). i is the number of shot areas SAi on the reference wafer W1, and j is the number of main scales provided in each shot area SAi) from the design position; The reference wafer W1 is set and the reference reticle R1 provided with the vernier pattern SPj (j is the number of vernier patterns provided on the reference reticle R1) is set at a predetermined position, and the reference wafer W1 and the reference wafer W1 are set. The position of the reticle R1 is adjusted (alignment process); the exposure apparatus 100 to be measured actually causes the vernier pattern SPj on the reference reticle R1 to pass through the projection optical system PL. A reference wafer W2 (second reference wafer) on which a vernier SMj is formed by being transferred onto the reference wafer W1 and superimposed on the main metric MMij is created; and the main metric MMij and the vernier SMj on the reference wafer W2. Measure the amount of relative displacement from the. In this specification, for convenience, the shot area SAi may be simply referred to as a shot, but each means an area on the reference wafer W1 or W2 where the main scale MMij is provided.
[0017]
In particular, in measuring the deviation of the main scale MMij, the position of the main scale MMij on the reference wafer W1 measured by a predetermined coordinate measuring device 200 (see FIG. 10) as the first environment, and the design position of the main scale MMij Based on the positional deviation amount, the positional deviation amount of the main scale mark MMij from which the first variation component with respect to the design value of the reference wafer W1 depending on the measurement environment is removed is calculated. The first fluctuation component includes an expansion / contraction component with respect to the design value of the reference wafer W1 depending on the ambient temperature in the measurement environment of the reference wafer W1, and a reference wafer installed on the wafer stage 230 of the coordinate measuring instrument 200. The rotation component of W1, the orthogonality error component of the wafer stage 230, and the offset amount (parallel shift amount of the reference wafer W1) of the measuring device 200 are included.
[0018]
The process of forming the vernier SMij on the main scale MMij is a process performed in the projection exposure apparatus 100 which is a second environment different from the first environment. In this step, precise alignment and measurement are performed according to a so-called EGA (Enhansed Global Alignment) as shown in, for example, US Pat. No. 4,780,617. Therefore, alignment marks AW and AR are provided on the reference wafer W1 and the reference reticle R1, respectively. On the basis of the reference in the second environment, the expansion / contraction of the reference wafer W1 is detected by measuring the distances ax and bx of the shot area SAi or by measuring the distance between the alignment marks AW.
Further, the reference wafer W2 created by the projection exposure apparatus 100 is compared with the main scale MMij on the reference wafer W2 by the overlay measuring device 300 (see FIG. 11) which is a third environment different from the first and second environments. A relative deviation amount from the vernier SMj is measured. This relative positional deviation amount is calibrated using at least the deviation amount from which the fluctuation component in the coordinate measuring instrument 200 of the main scale MMij is removed.
On the other hand, in order to enable more accurate calculation of the distortion component, it is possible to adopt a configuration in which an error component due to the installation state of the reference reticle R1 in the projection exposure apparatus 100 is removed. That is, the present invention relates to the reference reticle R1 between the position of the vernier pattern SPj on the reference reticle R1 measured in a fourth environment different from the first to third environments and the design position of the vernier pattern SPj. The method further includes a step of calculating a manufacturing positional deviation amount of the vernier SMj provided on the reference wafer W2 by the test exposure apparatus 100 on which the reference reticle R1 is installed based on the positional deviation amount caused by the sagging. May be. In this case, the relative positional shift amount is calibrated by the shift amounts of the main scale MMij and the vernier SMij. Therefore, it is preferable that the measurement process related to the reference reticle R1 is performed at least before the process of obtaining the relative deviation amount.
[0019]
Further, the distortion is removed by forming the above measured exposure apparatus (sub-scale SMj on the reference wafer W1) by using, for example, means detailed in US Pat. No. 5,117,255. This is done by adjusting the projection optical system PL of the exposure apparatus.
In the present invention, a more accurate distortion component is obtained by removing a fluctuation component that changes depending on the measurement environment from the measurement data obtained in each measurement environment. Accordingly, in order to prevent the fluctuation component in the second environment from propagating to at least the second measurement process to be performed next, the present invention is based on the design value of the reference wafer W1 measured in the alignment process in the second environment. A configuration in which the shot magnification of the projection optical system in the test exposure apparatus is adjusted in advance based on the expansion / contraction component may be employed. This magnification adjustment can also be performed by means as detailed in the above-mentioned US Pat. No. 5,117,255.
[0020]
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows the steps up to the measurement of the position / orientation of the reference wafer W1 with respect to the stage coordinates in the semiconductor device manufacturing method according to the present invention. FIG. 2 follows the step of FIG. It is the flowchart which showed to the place which projects and exposes a product wafer.
[0021]
In the present embodiment, first, a reference wafer W1 is created (FIG. 1, step 110). For this purpose, first, a wafer material to be the reference wafer W1 is exposed. That is, the first exposure, so-called 1st exposure. As the wafer material, a material in which a SiO2 film is uniformly formed on silicon Si or bare silicon as it is is used.
The projection exposure apparatus used to create the reference wafer W1 does not have to be highly accurate. There is no need to reduce the lens distortion. There is no strict requirement for the flatness of the wafer holder (not shown). This is because the position of the main scale formed on the reference wafer W1 will be accurately measured by the coordinate measuring instrument 200 as will be described later. However, the higher the flatness of the wafer W1, the better.
FIG. 10 is a conceptual diagram for explaining the measurement operation of the position of the main scale MMij provided on the reference wafer W1. Each main scale MMij of the created reference wafer W1 is measured by, for example, a “light wave interference type coordinate measuring device” manufactured by Nikon Corporation. As shown in FIG. 10, the coordinate measuring apparatus 200 measures the wafer stage 230 on which the created reference wafer W1 is mounted via a wafer holder (not shown) and the position of the wafer stage 230. A laser interferometer 240, a measurement system 210 (including a control system) that irradiates a reference wafer W1 placed on the wafer stage 230 with probe light 250 and receives reflected light from the reference wafer W1, and measurement optics The system 220 is provided at least. Accordingly, the obtained measurement value (position of the main scale MMij) of the reference wafer W1 is a value based on the coordinate system of the wafer stage 230. Although FIG. 10 shows a laser interferometer for measuring the position of the wafer stage 230 along the X-axis direction, the laser interferometer for measuring the position of the wafer stage 230 along the Y-axis direction is shown. Is also provided.
[0022]
4A shows an example of a main scale pattern on the reference reticle R1 for main scale formation used in this embodiment, FIG. 4B shows an example of a vernier pattern on the reference reticle R1, FIG. FIG. 5A shows an example of a shot on the reference wafer W1, and FIG. 5B shows an example of a main scale and a sub-scale formed by overlapping the shot. FIG. 5B is a partially enlarged view of one of the shots shown in FIG. Here, for example, if the diameter of the wafer W1 is 8 inches and the shot size is 25 mm × 33 mm, 30 or more shots can be formed on the wafer W1. Since the degree is expected to be low, it is preferable to form about 16 shots in the center as shown in FIG.
4A is an alignment mark provided on the reticle R, AR in FIG. 4B is an alignment mark provided on the reference reticle R1, and in FIG. 5B. AW indicates an alignment mark provided on the reference wafer W1.
[0023]
The main scale pattern MPj on the reticle R is a square frame pattern, and is arranged in a grid pattern at intervals of 1 mm, for example, in a 25 mm × 33 mm shot. Such a reticle R pattern is projected and exposed by an exposure apparatus, and then developed and etched to complete the reference wafer W1. Since the coordinate coordinates of each main scale are accurately measured later by the coordinate measuring machine 200, the reticle R used for exposing the reference wafer W1 does not need to measure the pattern position formed thereon in advance. This is as described above.
[0024]
Note that C1 in the figure indicates the center coordinate of the main scale pattern MPj, and this center coordinate is defined as the position of the main scale pattern MPij. Therefore, the position of the main scale MMij formed on the reference wafer W1 is also given by its center coordinates.
Similarly, a reference reticle R1 is created (FIG. 1, step 110). The reference reticle R1 is formed by patterning with an exposure machine such as an electron beam exposure apparatus EB. As in the case of the reference wafer W1, the drawing position accuracy of the electron beam exposure device EB does not matter.
[0025]
The reference reticle R1 thus completed is measured by the coordinate measuring instrument 200 (FIG. 1, step 120). In order to avoid an orthogonality error of the XY moving stage of the coordinate measuring machine 200, the reference reticle R1 may be measured at 0 degrees and 90 degrees and averaged.
In addition, the pattern surface of the reference reticle R1 is supported by three-point support, and the shape of the reference reticle R1 in a zero-gravity state is determined from the amount of deflection of the reference reticle R1, that is, the change in the Z direction. Similar to the projection exposure apparatus (projection exposure apparatus 100 whose distortion is measured by the method of the present invention) used when manufacturing a wafer, how is the reference reticle R1 in a holding state in which the pattern surface faces downward? And how each pattern position shifts.
[0026]
Alternatively, such a calculation is unnecessary if it is a type of measuring machine that holds the reference reticle R1 so that the pattern surface faces downward and is measured from below so as to be the same as the projection exposure apparatus 100. There are advantages. Of course, the holder is not supported at three points, and flatness and parallelism between the contact surfaces are required. The measured value of the reference reticle R1 is stored as (CRXj, CRYj) (j = 1, 2,... N).
[0027]
Note that the measurement values (CRXj, CRYj) of the reference reticle R1 are such shot magnifications when the magnification (shot magnification) of the projection lens PL in the exposure apparatus 100 to be measured is 1/4 times, 1/5 times, or the like. It is corrected. Specifically, for example, when the shot magnification of the projection lens PL is ¼, (CRXj / 4, CRYj / 4) is stored as a vernier deviation amount.
[0028]
Further, the measured value (CRXj, CRYj) of the reference reticle R1 is a deviation from the design coordinates of the jth vernier. The reference wafer W1 is subjected to an operation for removing the influence of environmental conditions, particularly temperature conditions, but is not normally performed on the reference reticle R1. This is because the material used for the wafer has a large coefficient of linear expansion and cannot be ignored even at, for example, 0.1 degrees Celsius, whereas the material used for the reticle has a low coefficient of linear expansion, such as quartz glass, and is not affected by temperature. It is. For this reason, the temperature at the time of measurement of the reference reticle R1 (CRXj, CRYj) and the temperature at the time of measurement by the projection exposure apparatus to be measured are substantially the same, or even if correction is performed, the temperature difference at that time is known. It is sufficient to correct by calculation considering the linear expansion coefficient accordingly.
[0029]
Next, the reference wafer W1 is measured (FIG. 1, step 120). Each shot, each point, that is, the position of the main scale of the reference wafer W1 is measured by the high precision coordinate measuring machine 200. At this time, the flatness of the wafer holder holding the reference wafer W1 is important, and it is desirable that the shape of the contact portion on the surface is the same as that of the projection exposure apparatus 100 (see FIG. 6) used in the subsequent 2nd exposure.
[0030]
What is measured here is the amount by which the position of the main scale at each point deviates from the design value. The design value of the formed pattern position is expressed as follows. The shot size is a × b, the shot interval is ax, bx (ax and bx are slightly larger than a and b, respectively), the number of shots is m, and the center position coordinate of each shot is the wafer center at the origin O (SXi , SYi). i is an integer from 1 to m. Further, there are n measurement patterns in each shot, and the position of each point is set to (MXj, MYj) with the shot center (SXi, SYi) as the origin Oi. j is an integer from 1 to n. In this way, the j-th mark design position of the i-th shot is expressed as (SXi + MXj, SYi + MYj) with the wafer center as the origin O. FIG. 7 shows the relationship of the above coordinates. In the drawing, R1 represents a reference reticle, and W1 represents a reference wafer. The reference wafer W1 shows a case where the number of shots i is 16.
[0031]
When measuring the reference wafer W1, each mark of each shot is sequentially positioned on the detector, and the difference (ΔXij, ΔYij) between the design coordinates and the actual coordinates is obtained.
ΔXij is given by the difference between the actually measured position coordinate XMij and the design position coordinate XDij (ΔXij = XMij−XDij), and ΔYij is the difference between the actually measured position coordinate YMij and the design position coordinate YDij ( ΔYij = YMij−YDij). However, the design position coordinates (XDij, YDij) are strictly (SXi + MXj, SYi + MYj) as described in FIG.
An actual measurement value (αi, βi) that is an average deviation from the design position of the i-th shot is defined by obtaining an average from j = 1 to n for a certain i (FIG. 1, step 120). ).
[0032]
[Expression 1]

[0033]
In accordance with the EGA calculation detailed in Japanese Patent Application Laid-Open No. 61-44429 (USP 4,780,617), the shot design position (SXi, SYi) and an ideal deviation from the shot design position at that position (αMi , ΒMi) have the following relationship:
[0034]
[Expression 2]

[0035]
In the above equation, wafer scaling γx in the X direction, wafer scaling γy in the Y direction, wafer rotation φ in the Y axis, wafer rotation θ in the X axis, wafer shift Ox in the X direction, and wafer shift Oy in the Y direction. Although the wafer stage 230 of the coordinate measuring instrument 200 can be moved in directions orthogonal to each other by the X-axis motor and the Y-axis motor, in reality, the feeding direction of the motor is not accurately orthogonal. However, it includes a slight orthogonality error w. In Equation (2), since the orthogonality error w is included in the Y-axis wafer rotation component φ, φ = w + θ between the Y-axis wafer rotation component φ and the X-axis wafer rotation component θ. The relationship is established.
Replace each matrix component with a single letter for simplicity.
[0036]
[Equation 3]

[0037]
The difference between the ideal deviation (αMi, βMi) and the actual measurement value (αi, βi) includes both the fact that the mark is actually deviated and the measurement error. Since the actual measurement values (αi, βi) are actually obtained, the six conversion parameters A, B, C, D, E, and F are obtained by the least square method. The difference between the ideal deviation (αMi, βMi) and the actual measurement value (αi, βi) is taken for each i and squared, and the sum is obtained for all i.
[0038]
[Expression 4]

[0039]
(Εx, εy) are differentiated by A, B, C, D, E, and F, respectively, and A, B, C, D, E, and F are obtained by setting = 0 to obtain simultaneous equations (FIG. 1). Step 130).
[0040]
[Equation 5]

[0041]
Next, the measurement value of the reference wafer W1 is stored. As described above, the measurement values (ΔXij, ΔYij) obtained by measuring the reference wafer W1 with the coordinate measuring machine 200 indicate how much the actual mark position is deviated from the design coordinates of each mark. It represents. When the same wafer is measured many times, the wafer rotation component varies depending on the posture of the wafer placed on the measuring machine, and the wafer scaling component varies depending on the environmental temperature at the time of measurement.
[0042]
Although the measurement reproduction accuracy of the measuring machine is unavoidable, it is preferable to store the measurement result of the reference wafer W1 in a form that is not affected by fluctuations such as wafer rotation and wafer scaling. Specifically, (CXij, CYij) obtained by the following calculation formula is stored as a measured value (FIG. 1, step 130).
[0043]
[Formula 6]

[0044]
For example, as described above, A = γx-1. γx is approximately equal to 1, for example, if the wafer temperature is increased by 1 degree, the Si wafer expands by about 2.6 ppm. If the size of one shot is 20 mm × 20 mm, the position is shifted by 52 nm around the shot.
However, at the same time, γx representing the elongation of the entire wafer is increased by 2.6 ppm, and the stored measurement values (CXij, CYij) obtained by the previous equation do not change before and after the expansion. The same effect can be obtained for the wafer shift and the wafer rotation that change depending on the posture on which the wafer is placed on the measuring instrument, and the measured value stored according to the previous equation is not affected by the measurement conditions. In FIG. 8, the above relationship is displayed as a vector.
[0045]
This completes the preparatory preparations, and then starts distortion measurement. The exposure apparatus 100 to be measured has a wafer holder (not shown) for mounting the reference wafer W1, and its flatness is important. This is because when the wafer W is bent, the pattern on the wafer surface is laterally shifted by an amount given by (wafer thickness) × (tilt). The reticle holder for placing the reference reticle R1 also needs to have good flatness for the same reason.
[0046]
The reference reticle R1 is set on the projection exposure apparatus 100, a resist is applied to the reference wafer W1, and loaded onto the projection exposure apparatus 100 (FIG. 1, step 140). In the projection exposure apparatus 100, the alignment mark Aw on the wafer W1 is measured by the wafer alignment microscope 20, and the position and orientation of the wafer W1 with respect to the wafer stage coordinates of the projection exposure apparatus 100 are obtained. Specifically, it is determined by the above-described method called EGA (FIG. 1, step 140).
[0047]
At this time, wafer scaling amounts γxEGA and γyEGA, wafer rotation amounts φEGA and θEGA, and wafer shift amounts OxEGA and OyEGA are obtained and fed back to the position for exposing the reference reticle R1. In this alignment step, the wafer scaling amount γxEGA is given by the ratio (axM / ax) of the measured shot interval axM to the shot interval design value ax, and γyEGA is measured with respect to the shot interval design value bx. It is given by the ratio (bxM / bx) of the shot interval bxM. However, the wafer scaling amounts γxEGA and γyEG may be obtained from the measured intervals and design values of the alignment marks AW.
[0048]
On the main scale pattern formed on the reference wafer W1 in the first exposure, the vernier pattern of the reference reticle R1 is exposed as 2nd exposure (FIG. 2, step 150).
After the exposure is completed, the reference wafer W1 is developed, and the completed main scale pattern and sub-scale pattern are measured by an overlay measuring device (registration measuring device) (FIG. 2, step 150). There are a total of m shots, and each shot has n measurement points. The amount of deviation between the main scale and the sub-scale can be measured by, for example, a registration measuring instrument manufactured by Nikon Corporation, and its configuration is described in detail in Japanese Patent Application Laid-Open No. 6-18320. FIG. 11 is a conceptual diagram for explaining the measurement of the relative deviation amount. The registration measuring machine 300 in this figure includes an illumination optical system that illuminates the reference wafer W2 held by the holder 308, and An objective lens 306 that collects the reflected light from the reference wafer W2, an imaging optical system 309 that forms an image of the reflected light emitted from the objective lens 306, and a CCD that observes an image formed by the imaging optical system 309 A camera 310 is provided. The light from the light source 301 constituting the illumination optical system forms an image on the pupil plane of the objective lens 306 through the condenser lens 302, the illumination stop 303, the projection lens 304, and the half mirror 305, and Koehler illuminations the reference wafer W2. .
[0049]
Subsequently, an average of all shots is obtained for each point in the shot. The expansion of the wafer remains in that value. The values measured by this overlay measuring instrument are stored as (RegXij, RegYij).
Finally, calibrate. That is, residual errors such as wafer expansion and wafer rotation are removed from the measured value. In the EGA measurement before exposure, each component such as scaling of the wafer W1 is obtained. Since the calculated value is a residual error, it can be removed by calculation. In addition, since it is expected that the EGA measurement itself includes an error, it is preferable to correct the residual wafer scaling error obtained by the overlay measuring machine.
[0050]
After all, the main scale of the reference reticle R1 is projected and exposed through the exposure apparatus 100 to be superimposed on the main scale of the reference wafer W1, and measured by an overlay measuring instrument, for example, a registration measuring instrument manufactured by Nikon Corporation. And vernier misalignment (RegXij, RegYij), the actual position of the main scale of the reference wafer (given by (CXij, CYij)), the actual position of the vernier of the reference reticle, the expansion and contraction of the wafer during exposure, The distortion is calculated based on the above.
[0051]
If the X component of wafer scaling is arranged, if the EGA measurement value γxEGA and the wafer residual scaling value γxR obtained by the least square method from the measurement result by the overlay measuring machine, the actual wafer scaling amount at the time of exposure is (γxEGA− γxR + 1). The wafer residual scaling value γxR is a parameter A to F obtained by the same procedure as the above-described calculation (formula (1) to formula (5)) from the measurement result (RegXij, RegYij), the average within the shot, and the like. More obtained.
Therefore, if the overlay measurement value of each mark in the i-th shot is (Rxij, Ryij), the correction calculation represented by the following Expression 7 is correct from the relative position coordinates (MXj, MYj) in the shot of the mark. Distortion is required.
[0052]
[Expression 7]

[0053]
After all, the distortion in the X direction, that is, the shift amount in the X direction is expressed by the following equation (8).
[0054]
[Equation 8]

[0055]
Here, the symbol of ± varies depending on how to take coordinates, and the term of (γxEGA−γxR) · (SXi + MXj) varies depending on the embodiment. Further, CXij indicates how much the j-th main scale of the i-th shot is based on the in-wafer coordinate reference, that is, shows the nonlinear deviation of the shot (main scale) in the wafer.
The same applies to the Y direction. Actually, not only the scaling component but also the wafer rotation component, the stage orthogonality component, and the shift component are similarly corrected.
[0056]
The projection lens system of the projection exposure apparatus 100 is adjusted by the distortion obtained in this way (FIG. 2, step 170), and the product wafer is projected and exposed by the adjusted projection exposure apparatus 100 to manufacture a semiconductor device. (FIG. 2, step 180).
A second embodiment of the present invention will be described with reference to FIG. The difference from the first embodiment is that when the reference wafer W1 is exposed by the measured projection exposure apparatus 100, the magnification of the projection lens system PL is controlled based on the wafer scaling value obtained by the EGA method, and the reference wafer The point is that the shot magnification is changed in accordance with the expansion and contraction of W1 (FIG. 3, step 141). Therefore, no magnification correction is required when obtaining true distortion (FIG. 3, step 151). That is, the correction calculation formula corresponding to Equation 7 is the following formula 9.
[0057]
[Equation 9]

[0058]
A method for obtaining the parameters A1 to F1 will be described below.
The average shift amounts (Regαi, Regβi) of the shift amounts (RegXij, RegYij) measured by the overlay measuring instrument 300 in each shot area SAi are obtained from the following equation (10).
[0059]
[Expression 10]

[0060]
Then, similarly to the above equation (2), ideal deviation amounts (RegαMi, RegβMi) are given by the following equation (11).
[0061]
## EQU11 ##

[0062]
In this equation (11), γxR is a residual scaling amount due to an EGA measurement error during exposure, γyR is a residual scaling amount due to an EGA measurement error during exposure, φR is a residual wafer rotation component due to an EGA measurement error during Y-axis exposure, θR is the residual wafer rotation component due to the EGA measurement error during the X-axis exposure, OxR is the residual parallel shift amount due to the EGA measurement error during the X-direction exposure (the offset amount in the X direction of the overlay measuring device 300), and OyR is Y This is a parallel shift amount of the direction (an offset amount of the measuring device 300 in the Y direction).
Further, each matrix component of the above equation (11) is replaced with A1 to F1 as shown in the following equation (12).
[0063]
[Expression 12]

[0064]
Then, as shown in the following equation (13), the difference between the ideal deviation amount (RegαMi, RegβMi) and the actual average deviation amount (Regαi, Regβi) is squared for each i, and the sum is obtained for all i. Ask.
[0065]
[Formula 13]

[0066]
Here, (εx, εy) are differentiated by A1 to F1, respectively, and further set to 0, the parameters A1 to F1 are obtained by solving the simultaneous equations shown in the above equation (5).
Incidentally, the X component γxR of the expansion / contraction in the reference wafer W2 can be easily obtained from the obtained parameter A1 (A1 = γxR−1).
[0067]
A difference (RegX1ij, RegY1ij) obtained by subtracting the residual linear component due to the EGA error, that is, residual scaling, residual rotation, and residual parallel shift component, from the measured deviation between the main scale and the subscale (RegXij, RegYij) is obtained.
[0068]
[Expression 14]

[0069]
In the first embodiment, in order to perform exposure without reflecting the wafer expansion / contraction amount obtained by EGA measurement in the projection magnification of the projection optical system PL, (RegX1ij, RegY1ij) obtained by Expression 14 is corrected as shown in Expression 15. There is a need to.
[0070]
[Expression 15]

[0071]
After all, the deviation of the main scale and vernier excluding various errors at each measurement point (main scale position error on the reference wafer, vernier position error on the reference reticle, etc.), that is, distortion of the projection optical system PL is In the first embodiment, Expression 16 is obtained, and in the second embodiment, Expression 17 is obtained.
[0072]
[Expression 16]

[0073]
[Expression 17]

[0074]
Furthermore, the distortion of the projection optical system PL can be obtained by averaging with the number of shots m.
[0075]
[Expression 18]

[0076]
The removal of the distortion thus measured is realized by optically adjusting the projection optical system PL of the exposure apparatus 100 to be measured shown in FIG. 6 by the adjustment system 420 only for the distortion component obtained as described above. Is done. A specific method for adjusting the projection optical system PL is described in detail, for example, in US Pat. No. 5,117,255.
In the present invention, not only the expansion / contraction component of the reference wafer W1, but also the residual wafer rotation components φR and θR and the residual parallel shift amount due to the EGA error as described above can be simultaneously removed.
[0077]
The above measuring method is a measuring method for measuring an imaging error of the projection optical system (PL) of the exposure apparatus (100) that exposes the mask pattern onto the substrate (W1, W2) by the projection optical system (PL). The first step (steps 120 and 130) for detecting the position of the first pattern (MMij) formed on the substrate (W1) in relation to the expansion and contraction of the substrate (W1), and the first pattern (MMij) are provided. A second step (step 140) of placing the processed substrate (W1) on the exposure apparatus (100) and detecting the position of the first pattern (MMij) in relation to the expansion and contraction of the substrate (W1); and a projection optical system (PL), a third step of exposing the second pattern (SMij) on the first pattern (MMij), a shift amount between the first pattern (MMij) and the second pattern (SMij), and the substrate (W2) Expansion and contraction The fourth and a step (step 150, 160) for detecting a focusing error of the projection optical system (PL) based.
In the measurement method described above, the first pattern (MMij) is formed in the plurality of shot regions of the substrate (W1), and the step of detecting expansion / contraction of the substrate (W1) based on the interval between the plurality of shot regions is included. It is out.
In addition, the alignment mark (Aw) is formed at a predetermined interval on the substrate (W1) by the above measurement method, and the substrate (W1) is detected based on the detection of the alignment mark (Aw) formed at the predetermined interval. ) To detect expansion / contraction. Further, in the above measuring method, the measuring method according to claim 8 includes the step of adjusting the projection optical system (PL) based on the detection result of the first step before exposing the second pattern (SMij). Contains.
The semiconductor device manufacturing method according to the present invention uses the test exposure apparatus 100 adjusted as described above to project and expose a predetermined pattern (circuit pattern or the like) on a product wafer to manufacture a semiconductor device. To do.
In addition, referring to the case of the second embodiment described above, the difference between the second embodiment and the first embodiment described above is that the reference wafer W1 is exposed before the exposure apparatus 100 to be tested is exposed. Based on the scaling component (LMX / LDX, LMY / LDY) of the reference wafer W1 obtained by the EGA measurement, the adjustment system 420 controls the shot magnification of the projection optical system PL to match the expansion / contraction of the reference wafer W1. The point is to change the shot magnification.
[0078]
【The invention's effect】
As described above, according to the present invention, the deviation from the design value of each point is not determined by the coordinate system reference of the coordinate measuring machine, but by the relative coordinate system obtained by subtracting the expansion and contraction of the entire wafer. Even if the atmosphere in the projection exposure apparatus does not match the atmosphere in the projection exposure apparatus, distortion can be measured with almost no error, and there is no problem even if the temperature difference between the coordinate measuring machine and the projection exposure apparatus remains unknown. In addition, the projection lens system can be calibrated, thereby enabling accurate projection exposure. Moreover, since the deviation from the design value of each point on the reference wafer is measured using the main scale and the sub scale, the measurement itself can be speeded up.
[Brief description of the drawings]
FIG. 1 is a flowchart showing the first half of the method according to the first embodiment of the present invention;
FIG. 2 is a flowchart showing steps executed subsequent to the step of FIG.
FIG. 3 is a flowchart showing the first half of the method according to the second embodiment of the present invention;
FIG. 4 is a diagram showing an example of a main scale and a sub-scale used in the present invention.
FIG. 5 is a diagram showing an example of a main scale and a sub scale formed by superimposing the reference wafer used in the present invention.
FIG. 6 is a schematic view of a projection exposure apparatus used in the present invention.
FIG. 7 is a diagram showing a coordinate relationship between a main scale and a sub-scale formed on a reference reticle and a reference wafer.
FIG. 8 is a diagram showing a vector display of a relationship between an actual measurement value of a main scale on a reference wafer, an ideal deviation from a design position, and a stored measurement value from which environmental conditions are excluded.
FIG. 9 is a conceptual diagram for explaining a measurement method according to the present invention.
10 is a conceptual diagram showing a coordinate measuring device 200. FIG.
11 is a conceptual diagram showing a registration measuring machine 300. FIG.
[Explanation of symbols]
L Illumination optical system
R reticle
PL projection lens system
W wafer
ST Wafer stage
MMij main scale pattern
SMij vernier pattern
10 Coordinate measuring machine (measurement interferometer)

Claims (4)

A first step of measuring a coordinate shift amount between an ideal design coordinate and an actual coordinate of the position of the main scale formed on the reference substrate under a predetermined measurement environment;
A second step of measuring the position of the vernier pattern formed on the reference reticle;
Based on the coordinate deviation amount measured in the first step, an ideal deviation amount from the ideal design coordinates of the design coordinates of the main scale determined under the predetermined measurement environment is obtained, and the ideal deviation amount and the coordinate deviation are obtained. A third step for determining a difference in amount from the amount;
A fourth step of setting the reference substrate on the exposure apparatus to be measured;
A fifth step of measuring a position and orientation value of the reference substrate with respect to the exposure apparatus to be measured;
A sixth step of projecting and exposing a vernier pattern of the reference reticle onto the reference substrate and forming a vernier on the main scale;
A seventh step of measuring a relative deviation amount between the main scale and the vernier;
And an eighth step of obtaining distortion of the exposure apparatus to be measured based on the deviation amount difference, the position / orientation value, and the relative deviation amount;
Distortion measurement method. A first step of measuring a coordinate shift amount between an ideal design coordinate and an actual coordinate of the position of the main scale formed on the reference substrate under a predetermined measurement environment;
A second step of measuring the position of the vernier pattern formed on the reference reticle;
Based on the coordinate deviation amount measured in the first step, an ideal deviation amount from the ideal design coordinates of the design coordinates of the main scale determined under the predetermined measurement environment is obtained, and the ideal deviation amount and the coordinate deviation are obtained. A third step for determining a difference in amount from the amount;
A fourth step of setting the reference substrate on the exposure apparatus to be measured;
A fifth step of measuring a position and orientation value of the reference substrate with respect to the exposure apparatus to be measured;
A ninth step of adjusting the projection optical system of the exposure apparatus to be measured based on the position and orientation values measured in the fifth step;
A sixth step of projecting and exposing a vernier pattern of the reference reticle onto the reference substrate and forming a vernier on the main scale;
A seventh step of measuring a relative deviation amount between the main scale and the vernier;
A tenth step of determining distortion of the exposure apparatus to be measured based on the difference in displacement amount and the relative displacement amount;
Distortion measurement method. An eleventh step of obtaining a residual deformation amount of the reference substrate based on the relative deviation amount;
Calibrating the distortion obtained in the tenth step based on the residual deformation amount;
The distortion measurement method according to claim 2. Measuring distortion of the projection optical system using the distortion measurement method according to claim 1;
Adjusting the magnification of the projection optical system based on the distortion obtained in the step of measuring the distortion;
Projecting and exposing a pattern onto a photosensitive substrate by the projection optical system adjusted in the adjusting step;
A method for manufacturing a semiconductor device.

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