JP2004356411A - Method and apparatus for measuring position, and for exposure method and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To rapidly and accurately judge front or rear surface of a substrate. <P>SOLUTION: Sub-orientations OF1, OF2 for judging front or rear surface are formed except an orientation flat OF formed heretofore on a wafer W in a linear profile. A method for measuring the position includes first imaging the outer edge of the wafer W by using pre-alignment sensors 22a, 22b, and 22c disposed at a preset positional relationship, then extracting point group having a plurality of points along the profile of the wafer W from the imaged result of the pre-alignment sensor 22c, and linearly approximating the extracted point group by a least square method. The method also includes obtaining the positional relationship of the point group to the obtained approximate straight line, and judging whether a circular arc edge CE is disposed as a curved profile directly under the pre-alignment sensor 22c or not or sub-orientation OF1 is disposed or not to judge the front or rear surface of the wafer W. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００６７】
上記の（１）式にｎ１個の外縁点Ｐｃ_ｋのＸ座標Ｘｃ_ｋ及びＹ座標Ｙｃ_ｋのそれぞれを代入して得られる連立式を行列の形式で表すと以下の（２）式となる。
【００６８】
【数２】

【００６９】
ここで、上記（２）式を以下の（３）式の通り表すと、
【００７０】
【数３】

【００７１】
求める解（上記（３）式における行列ｐ）は最小二乗法により以下の（４）式から求められる。
【００７２】
【数４】

【００７３】
すなわち、上記（４）式を解いて得られる行列の第１行目が上記（１）式中の変数「ａ」であり、第２行目が上記（１）式中の変数「ｂ」である。なお、上記（４）式においてＡ^ｔは行列Ａの転置行列である。
【００７４】
外縁点Ｐｃ_ｋに対する近似直線が得られると、次に制御部３１の制御に従って、表裏判別部３５は以下の（５）式を用いて、ステップＳ１１で抽出した外縁点Ｐｃ_ｋとステップＳ１２で求めた近似直線との距離、すなわち近似直線に対する各外縁点Ｐｃ_ｋの残差ｄを求める。
【００７５】
【数５】

【００７６】
上記（５）式中の変数「ａ」，「ｂ」は、上記（４）式で求められた近似直線を表す変数であり、Ｘｃ_ｋ，Ｙｃ_ｋはそれぞれ外縁点Ｐｃ_ｋのＸ座標及びＹ座標である。なお、ここで求められる近似直線は、外縁点Ｐｃ_ｋの各々から近似直線までの距離の二乗の和を最小にする直交回帰直線である。外縁点Ｐｃ_ｋの全てについての残差ｄを求めると、表裏判別部３５は残差ｄの最大値、又は分散若しくは標準偏差を求める。これにより、外縁点Ｐｃ_ｋと近似直線との位置関係が求められる（ステップＳ１３）。
【００７７】
ここで、円弧エッジから抽出された外縁点と近似直線との位置関係、及びサブオリエンテーションフラットＯＦ１等の直線状の外縁から抽出された外縁点と近似直線との位置関係について考察する。図９は、円弧エッジ又は直線状の外縁と近似直線との位置関係を例示する図であり、（ａ）は円弧エッジＣＥから抽出された外縁点Ｐｃ_ｋと近似直線Ｌ１との位置関係を例示する図であって、（ｂ）はサブオリエンテーションフラットＯＦ１から抽出された外縁点Ｐｃ_ｋと近似直線Ｌ２との位置関係を例示する図である。
【００７８】
図９に示す通り、プリアライメントセンサ２２ｃが円弧エッジＣＥを撮像した場合、及びサブオリエンテーションフラットＯＦ１を撮像した場合の何れの場合であっても、近似直線Ｌ１，Ｌ２が得られることが分かる。しかしながら、図９（ａ）を参照すると、近似直線Ｌ１に対する外縁点Ｐｃ_ｋの距離のばらつきが大きいため、残差ｄの最大値又は分散若しくは標準偏差が大きくなることが推定される。これに対し、図９（ｂ）を参照するとサブオリエンテーションフラットＯＦ１と近似直線Ｌ２とはほぼ一致し、近似直線Ｌ２に対する外縁点Ｐｃ_ｋの距離のばらつきは外縁抽出時のサンプリング誤差のみとなるため、残差ｄの最大値又は分散若しくは標準偏差が小さくなることが推定される。
【００７９】
本実施形態では所定の閾値を設定し、残差ｄの最大値又は分散若しくは標準偏差が設定した閾値を越えているか否かを判断して、プリアライメントセンサ２２ｃの真下に配置されたウエハＷの外縁が円弧エッジＣＥであるのか、又はサブオリエンテーションフラットＯＦ１であるのかを判定する（ステップＳ１４）。ここで、残差ｄの最大値を用いて上記の判定を行う場合を例に挙げて説明する。図１０は、撮像した外縁部が円弧エッジＣＥであるか否かの判定を行う際に設定する閾値の一例を説明するための図である。
【００８０】
いま、図１０に示す通り、プリアライメントセンサ２２ｃの視野Ｖｃ内に円弧エッジＣＥの一部が配置されているとする。また、プリアライメントセンサ２２ｃの視野Ｖｃに対してウエハＷの中心Ｃ１が図示の位置にあるとする。更に、図１０中の破線で示した直線Ｌ１は、プリアライメントセンサ２２ｃの撮像結果から求められた近似直線であるとする。プリアライメントセンサ２２ｃの視野Ｖｃ内において円弧エッジＣＥから抽出される外縁点Ｐｃ_ｋが取りうるＸ座標の幅は、Ｅ１−Ｅ２で求められる。上記のＥ１はウエハＷの中心Ｃ１からＸ座標の値が最も小さくなる外縁点Ｐ２までのＸ方向の距離であり、Ｅ２はウエハＷの中心Ｃ１からＸ座標の値が最も大きくなる外縁点Ｐ１，Ｐ３までのＸ方向の距離である。
【００８１】
ここで、図１０中に示した近似直線Ｌ１に対して予想される最大残差ｄ_ｍａｘは、ｄ_ｍａｘ＝（Ｅ１−Ｅ２）／２と推定される。つまり、外縁点Ｐｃ_ｋが取りうるＸ座標の幅の中間位置に近似直線Ｌ１があり、この近似直線Ｌ１に対してウエハＷの中心Ｃ１からＸ座標の値が最も小さくなる外縁点Ｐ２までのＸ方向の距離、又は近似直線Ｌ１に対してウエハＷの中心Ｃ１からＸ座標の値が最も大きくなる外縁点Ｐ１，Ｐ３までのＸ方向の距離が最大残差ｄ_ｍａｘと推定される。
【００８２】
ここで、ウエハＷの半径をＲとし、プリアライメントセンサ２２ｃのＹ方向における計測視野Ｖｃの長さをｖとして、これらを用いて最大残差ｄ_ｍａｘを表すと、以下の（６）式となる。なお、プリアライメントセンサ２２ｃのＹ方向における計測視野Ｖｃの長さは、プリアライメントセンサ２２ｃで撮像された円弧エッジＣＥの弦の長さである。
【００８３】
【数６】

【００８４】
前述した通り、プリアライメントセンサ２２ｃの真下にサブオリエンテーションフラットＯＦ１が配置された場合よりも円弧エッジが配置された場合の方が残差ｄは大きくなり、また上述のように円弧エッジが配置された場合の最大残差ｄ_ｍａｘは上記（６）式で表される。このため、プリアライメントセンサ２２ｃの真下に円弧エッジが配置されているのか又はサブオリエンテーションフラットＯＦ１が配置されているのかを判定するためには、０＜ｄ_ｔｈ＜ｄ_ｍａｘを満たす閾値ｄ_ｔｈ、望ましくは（ｄ_ｍａｘ／２）＜ｄ_ｔｈ＜ｄ_ｍａｘを満足する閾値ｄ_ｔｈを設定すれば良い。
【００８５】
上記（６）式を参照すると最大残差ｄ_ｍａｘは、ウエハＷの半径及び計測視野ＶｃのＹ方向における長さのみを用いて表されており、これらはウエハＷの処理を行うに先だって予め得られている情報である。図３に示す表裏判別部３５は予めこれらの情報を制御部３１から得て閾値ｄ_ｔｈを設定している。表裏判別部３５は、算出した残差ｄの最大値が以上説明した閾値ｄ_ｔｈを越えている場合（残差ｄが閾値ｄ_ｔｈよりも大きい場合）には、プリアライメントセンサ２２ｃの真下には円弧エッジＣＥが配置されていると判断し、逆に残差ｄの最大値が以上説明した閾値ｄ_ｔｈを越えていない場合（残差ｄが閾値ｄ_ｔｈ以下である場合）には、プリアライメントセンサ２２ｃの真下にはサブオリエンテーションフラットＯＦ１が配置されていると判定する。以上、残差ｄの最大値を用いて判定する場合を例に挙げて説明したが、残差ｄの分散若しくは標準偏差又はこれらの両者を用いて判定する場合も同様に閾値を設定して判定を行う。
【００８６】
また、残差ｄの最大値ｄ_ｍａｘのみを用いる場合のみに本発明は限定されるものではない。例えば、残差の大きいものを何点か選別し、それらの合計値が所定の閾値を越えていれば円弧であるという判別手法を用いるようにしても良い。例えば、残差ｄの大きい順にｎ点抽出し、それらの点の各残差（ｄ_ｍａｘ〜ｄ_ｎ）の合計値（ｄ_ｍａｘ＋ｄ_{ｍａｘ−１}＋…＋ｄ_ｎ）と所定の閾値とを比較するようにすれば良い。あるいは、残差ｄの最大値ｄ_ｍａｘを用いるのではなく、ｎ番目（例えば、２番目）に大きい残差（ｄ_{ｍａｘ−１}）を用いて（ｎ番目の残差とｎ番目残差用の閾値とを比較することによって）、円弧かオリエンテーションフラットかを判別するようにしても良い。以上のように、残差ｄの最大値ｄ_ｍａｘのみでの判別ではなく、ｎ番目に大きい残差を用いて判別することによって、例えば、ゴミ等の影響で測定値に「飛び」があった場合に、そのゴミの影響を受けた「飛び値」を最大残差ｄ_ｍａｘと認識して、表裏を誤判別してしまうことを防止することができる。
【００８７】
図５を参照して説明した通り、プリアライメントセンサ２２ａ，２２ｂの真下にオリエンテーションフラットＯＦが配置されている状態において、プリアライメントセンサ２２ｃの真下に円弧エッジＣＥが配置されているか又はサブオリエンテーションフラットＯＦ１が配置されているかを判定することができれば、センターテーブル上に表面を上側にして又は裏面を上側にしてウエハＷが配置されているかを判別することができる。そこで、この関係を用いて表裏判別部３５は基板テーブル１４上に載置されたウエハＷの表裏判別を行う（ステップＳ１５）。ウエハＷの表裏判別結果は、制御部３１に出力される。以上の処理によりウエハＷの表裏判別が終了し、処理は図４に示したメインルーチンにリターンする。
【００８８】
処理がメインルーチンにリターンすると、ウエハＷの位置情報を算出する処理が行われる（ステップＳ５）。図１１は、ウエハＷの位置情報を算出する処理を示すフローチャートである。ウエハＷの位置情報算出処理が開始されると、まず主制御系２０に設けられた制御部３１が、表裏判別部３５の判別結果に基づいて、基板テーブル１４上のウエハＷが表面を上側にして配置されているのか否かを判断する（ステップＳ２１）。
【００８９】
表面を上側にしてウエハＷが基板テーブル１４上に配置されていると判断された場合（判断結果が「ＹＥＳ」の場合）には、従来から用いられる周知の方法（例えば、前述の特許文献１又は２に記載の方法）を用いてウエハＷの位置情報を算出する（ステップＳ２２）。ここで、ウエハＷが表面を上側にしてセンターテーブル上に載置されていると、ウエハＷはプリアライメントセンサ２２ａ，２２ｂ，２２ｃに対して図５（ａ）に示す状態で配置されていることになり、図６に示す撮像データＤ１がプリアライメントセンサ２２ａ，２２ｂ，２２ｃの各々から得られる。
【００９０】
前述した通り、ウエハＷはオリエンテーションフラットＯＦが形成された従来から用いられているものに、サブオリエンテーションフラットＯＦ１，ＯＦ２を新たに形成したものであり、オリエンテーションフラットＯＦと円弧エッジＣＥとを観察して得られた計測結果は従来のウエハＷを観察して得られる計測結果と同じものとなる。このため、表面を上側にしてセンターテーブル上に載置されているウエハＷの位置情報を算出する場合には、従来から用いられている方法を用いて位置情報の算出を行う。
【００９１】
従来から用いられている位置情報の算出方法を簡単に説明すると以下の通りである。まず、図３に示した制御部３１の制御の下で、外縁抽出部３３が撮像データ格納領域４１に格納されている撮像データＤ１を読み出してウエハＷの外縁に沿った複数の外縁点からなる点群を抽出し、それらの位置を求める。ここで、抽出する点群は、図６に示した外縁点Ｐａ_ｉ、外縁点Ｐｂ_ｊ、及び外縁点Ｐｃ_ｋである。なお、ｉは１≦ｉ≦ｎ１を満たす整数であり、ｊは１≦ｊ≦ｎ２を満たす整数である。尚、ｎ１，ｎ２は２以上の整数である。抽出された外縁点の全ては外縁情報格納領域４２に格納される。
【００９２】
次に、制御部３１の制御の下で、直線近似部３４が外縁情報格納領域４２から外縁点Ｐａ_ｉ及び外縁点Ｐｂ_ｊを読み出し、各々について最小二乗法を用いて直線近似を行い、求めた近似直線を表す情報を近似直線格納領域４３に格納する。そして、制御部３１の制御の下で回転量算出部３６が近似直線格納領域４３に格納された近似直線を読み出し、Ｘ軸に対するウエハＷの回転量を算出し、算出した回転量を回転情報格納領域４４に格納する。
【００９３】
以上の処理が終了すると、制御部３１の制御の下で位置情報算出部３７が、外縁情報格納領域４２から外縁点Ｐｃ_ｋを読み出すとともに、回転情報格納領域４４から回転量を読み出して、ウエハＷの中心位置（基準位置）を算出する。なお、ウエハＷの中心位置の算出にあたっては、ウエハＷの回転量に代えて、外縁点Ｐａ_ｉ及び外縁点Ｐｂ_ｊを用いてもよく、更にはオリエンテーションフラットＯＦの近似直線を用いても良い。また、ウエハＷの中心位置を算出する際には、外縁点Ｐｃ_ｋの少なくとも１つを用いれば良く、必ずしも全てを用いなくても良い。
【００９４】
このようにして算出されたウエハＷの中心位置は位置情報格納領域４５に格納される。以上の処理により、ウエハＷが表面を上側にしてセンターテーブル上に載置されている場合のウエハＷの位置情報を算出する処理が終了し、処理は図４に示したメインルーチンにリターンする。
【００９５】
一方、ステップＳ２１において、裏面を上側にしてウエハＷがセンターテーブル上に配置されていると判断された場合（判断結果が「ＮＯ」の場合）には、処理がステップＳ２３へ進む。ここで、ウエハＷが裏面を上側にしてセンターテーブル上に配置されている場合には、図７に示した通り、プリアライメントセンサ２２ａ，２２ｂ，２２ｃの全てにおいて直線状の外縁が観察された状態となり、上述した従来の方法を用いてはウエハＷの中心位置を求めることができない。そこで、本実施形態では以下の方法を用いてウエハＷの中心位置を算出している。
【００９６】
まず、ステップＳ２３では、オリエンテーションフラットＯＦを直線近似する処理が行われる。この処理では、図３に示す制御部３１の制御の下で、外縁抽出部３３が撮像データ格納領域４１に格納されている撮像データＤ１を読み出してウエハＷの外縁に沿った複数の外縁点からなる点群を抽出し、それらの位置を求める。ここで、抽出する点群は、図７に示した外縁点Ｐａ_ｉ及び外縁点Ｐｂ_ｊである。抽出された外縁点の全ては外縁情報格納領域４２に格納される。なお、以下の説明において、外縁点Ｐａ_ｉ（Ｘａ_ｉ，Ｙａ_ｉ）及び外縁点Ｐｂ_ｊ（Ｘｂ_ｊ，Ｙｂ_ｊ）の全てを表す場合には、外縁点Ｐｄ_ｍ（Ｘｄ_ｍ，Ｙｄ_ｍ）と記すものとする。なお、ｍは１＜ｍ≦（ｎ１＋ｎ２）を満たす整数である。
【００９７】
次に、制御部３１の制御に従って、直線近似部３４が外縁情報格納領域４２に格納された外縁点Ｐｄ_ｍを読み出し、最小二乗法を用いて直線近似を行う。求めた近似直線を表す情報は近似直線格納領域４３に格納される。
【００９８】
以上の処理が終了すると、サブオリエンテーションフラットＯＦ１を直線近似する処理が行われる（ステップＳ２４）。この処理では、図３に示す制御部３１の制御の下で、外縁抽出部３３が撮像データ格納領域４１に格納されている撮像データＤ１を読み出してウエハＷの外縁に沿った複数の外縁点からなる点群を抽出し、それらの位置を求める。ここで、抽出する点群は、図７に示した外縁点Ｐｃ_ｋである。抽出された外縁点の全ては外縁情報格納領域４２に格納される。次に、制御部３１の制御に従って、直線近似部３４が外縁情報格納領域４２に格納された外縁点Ｐｃ_ｋを読み出し、最小二乗法を用いて直線近似を行う。求めた近似直線を表す情報は近似直線格納領域４３に格納される。
【００９９】
ここで、ステップＳ２３で求められるオリエンテーションフラットＯＦの近似直線（直交回帰直線）の式を変数「ａ_１」，「ｂ_１」を用いて以下の（７）式で表し、ステップＳ２４で求められるサブオリエンテーションフラットＯＦ１の近似直線（直交回帰直線）の式を変数「ａ_２」，「ｂ_２」を用いて以下の（８）式で表す。
【０１００】
【数７】

【０１０１】
【数８】

【０１０２】
上記の（７）式に（ｎ１＋ｎ２）個の外縁点Ｐｄ_ｍのＸ座標Ｘｄ_ｍ及びＹ座標Ｙｄ_ｍのそれぞれを代入して得られる連立式を行列の形式で表すと以下の（９）式となる。
【０１０３】
【数９】

【０１０４】
同様に、上記の（８）式にｎ３個の外縁点Ｐｃ_ｋのＸ座標Ｘｃ_ｋ及びＹ座標Ｙｃ_ｋのそれぞれを代入して得られる連立式を行列の形式で表すと以下の（１０）式となる。
【０１０５】
【数１０】

【０１０６】
ここで、上記（９）式を以下の（１１）式の通り表し、上記（１０）式を以下の（１２）式の通り表す。
【０１０７】
【数１１】

【０１０８】
【数１２】

【０１０９】
求める解（上記（１１）式における行列ｐ_１及び上記（１２）式における行列ｐ_２）は最小二乗法により以下の（１３）式及び（１４）式からそれぞれ求められる。
【０１１０】
【数１３】

【０１１１】
【数１４】

【０１１２】
すなわち、上記（１３）式を解いて得られる行列の第１行目が上記（７）式中の変数「ａ_１」であり、第２行目が上記（７）式中の変数「ｂ_１」である。また、上記（１４）式を解いて得られる行列の第１行目が上記（８）式中の変数「ａ_２」であり、第２行目が上記（８）式中の変数「ｂ_２」である。なお、上記（１３）式においてＡ_１ ^ｔは行列Ａ_１の転置行列であり、上記（１４）式においてＡ_２ ^ｔは行列Ａ_２の転置行列である。
【０１１３】
以上の処理により、オリエンテーションフラットＯＦの近似直線Ｌ１１及びサブオリエンテーションフラットの近似直線Ｌ１２が求まり、これら近似直線Ｌ１１，Ｌ１２を表す情報が近似直線格納領域４３に格納される。
【０１１４】
次に、これらの近似直線Ｌ１１，Ｌ１２を用いてウエハＷの中心位置（基準位置）を求める処理が行われる。図１２は、オリエンテーションフラットＯＦの近似直線Ｌ１１とサブオリエンテーションＯＦ１の近似直線Ｌ１２とを用いてウエハＷの中心位置を求める処理を説明するための図である。図１２において、Ｇ１はウエハＷの中心位置に対するオリエンテーションフラットＯＦの距離を示しており、Ｇ２はウエハＷの中心位置に対するサブオリエンテーションフラットＯＦ１の距離を示している。これら距離Ｇ１，Ｇ２は予め設計値から求められている。
【０１１５】
このため、本実施形態では、図１２に示す通り、ステップＳ２３で得られた近似直線Ｌ１１をウエハＷの中心方向に向けて距離Ｇ１だけ平行移動するとともに、ステップＳ２４で得られた近似直線Ｌ１２をウエハＷの中心方向に向けて距離Ｇ２だけ平行移動する。そして、平行移動させた近似直線（以下、移動後直線という）の交点Ｃ２を算出し（ステップＳ２５）、この交点Ｃ２をウエハＷの中心位置として推定して（ステップＳ２６）、ウエハＷの中心位置を求めている。なお、図１２においては、ウエハＷの回転量を誇張して図示している。
【０１１６】
上記ステップＳ２５においては、図３に示した制御部３１の制御の下で、回転量算出部３６が近似直線格納領域４３に格納された近似直線Ｌ１１に関する情報を読み出し、所定の基準としてのＸ軸に対する近似直線Ｌ１１の傾きθ（ウエハＷの回転量）を算出し、算出した傾きθを回転情報格納領域４４に格納する。次に、制御部３１の制御の下で、位置情報算出部３７が近似直線格納領域４３に格納された近似直線Ｌ１１，Ｌ１２に関する情報を読み出すとともに、回転情報格納領域４４から近似直線Ｌ１１の傾きθを読み出し、これらを用いてウエハＷの中心位置と推定される交点Ｃ２を算出する。
【０１１７】
オリエンテーションフラットＯＦの近似直線Ｌ１１は前述した（７）式で表されており、サブオリエンテーションフラットＯＦ１の近似直線Ｌ１２は前述した（８）式で表されている。近似直線Ｌ１１をウエハＷの中心に向けて距離Ｇ１だけ平行移動させた移動後直線は以下の（１５）式で表され、近似直線Ｌ１２をウエハＷの中心に向けて距離Ｇ２だけ平行移動させた移動後直線は以下の（１６）式で表される。
【０１１８】
【数１５】

【０１１９】
【数１６】

【０１２０】
上記（１５）式と（１６）式を用いれば交点Ｃ２を算出することができる。
【０１２１】
なお、以上説明した方法においては、近似直線Ｌ１１，Ｌ１２を共にウエハＷの中心に向けて平行移動させて交点Ｃ２を算出したが、近似直線Ｌ１１，Ｌ１２の何れか一方のみをウエハＷの中心に向けて平行移動させるだけでも上記の交点Ｃ２を算出することができる。この方法においては、例えば、近似直線Ｌ１１のみをウエハＷの中心に向けて移動させ、この移動後直線と平行移動を行っていない近似直線Ｌ１２との交点Ｃ３（図１２参照）を求めてから交点Ｃ２を算出する。
【０１２２】
近似直線Ｌ１１をウエハＷの中心に向けて平行移動させた移動後直線は上記（１５）式で表される。この移動後直線を平行移動を行っていない近似直線Ｌ１２（（８）式の近似直線）に代入して求められる交点Ｃ３の座標（Ｘ_３，Ｙ_３）は、以下の（１７）式で表される。
【０１２３】
【数１７】

【０１２４】
上記（１７）式で表される交点Ｃ３の座標（Ｘ_３，Ｙ_３）から求められる交点Ｃ２の座標（Ｘ_２，Ｙ_２）は、以下の（１８）式で表される。
【０１２５】
【数１８】

【０１２６】
以上説明した処理を行って求められた交点Ｃ２の座標座標（Ｘ_２，Ｙ_２）は、位置情報として位置情報格納領域４５に格納される。以上の処理によりウエハＷが裏面を上側にしてセンターテーブル上に載置されている場合のウエハＷの位置情報を算出する処理が終了し、処理は図４に示したメインルーチンにリターンする。
【０１２７】
処理がメインルーチンにリターンすると、上記サブルーチンＳ５で算出されたウエハの回転量を補正するようにセンターテーブルを回転させながら下降させて、ウエハを基板ホルダ１５上に吸着保持させる。なお、サブルーチンＳ５で求めたウエハ中心は、オフセット情報として保持しておき、各ショット領域の位置合わせを行う際のオフセットとして使用される。次に、制御部３１は、上記で求めたウエハＷの形状測定以外の露光準備用計測を行う（ステップＳ６）。すなわち、制御部３１は、基板テーブル１４上に配置された不図示の基準部材を使用したレチクルアライメント、及びアライメント検出系ＡＳのベースライン量の測定等の準備作業を行う。なお、上記のレチクルアライメント、ベースライン計測等の準備作業については、例えば特開平４−３２４９２３号公報及びこれに対応する米国特許第５，２４３，１９５号に詳細に開示されている。
【０１２８】
また、ウエハＷに対する露光が、第２層目以降の露光であるときには、既にウエハＷ上に形成されている回路パターンと、重ね合わせ精度良く回路パターンを形成するため、上述のウエハＷの位置情報計測結果に基づいて、前述した基準座標系における、ウエハＷ上の回路パターンの配列、すなわちショット領域の配列に関する配列座標位置情報が、アライメント検出系ＡＳを使用して高精度で検出される。
【０１２９】
以上の処理が完了すると、ウエハＷに対する露光が行われる（ステップＳ７）。この露光動作にあたっては、まず、ウエハＷのＸＹ位置がウエハＷ上の最初のショット領域（ファースト・ショット）の露光のための走査開始位置となるように、基板テーブル１４が移動される。この移動は、位置情報格納領域４５から読み出された上述のウエハＷの位置情報計測結果（主にサブルーチンＳ５で求めたウエハ中心位置情報（オフセット情報））、及びウエハ干渉計１９からの位置情報（速度情報）等（第２層目以降の露光の場合には、基準座標系上での配列座標位置情報の検出結果及びウエハ干渉計１９からの位置情報（速度情報）及び上記オフセット情報等）に基づき、主制御系２０によりステージ制御系２１及びウエハ駆動装置１７等を介して行われる。同時に、レチクルＲのＸＹ位置が、走査開始位置となるように、レチクルステージＲＳＴが移動される。この移動は、主制御系２０によりステージ制御系２１及び不図示のレチクル駆動部等を介して行われる。
【０１３０】
次に、ステージ制御系２１が、主制御系２０からの制御命令に応じて、多点フォーカス位置検出系によって検出されたウエハＷのＺ位置情報、レチクル干渉計１３によって計測されたレチクルＲのＸＹ位置情報、ウエハ干渉計１９によって計測されたウエハＷのＸＹ位置情報に基づき、不図示のレチクル駆動部及びウエハ駆動装置１７を介して、ウエハＷの面位置の調整を行いつつ、レチクルＲとウエハＷとを相対移動させて走査露光を行う。
【０１３１】
こうして、最初のショット領域の露光が終了すると、次のショット領域の露光のための走査開始位置となるように、基板テーブル１４が移動されるとともに、レチクルＲのＸＹ位置が、走査開始位置となるように、レチクルステージＲＳＴが移動される。そして、このショット領域に関する走査露光が上述の最初のショット領域と同様にして行われる。以後、同様にして各ショット領域について走査露光が行われ、露光が完了する。ウエハＷの露光が完了すると、ウエハステージＷＳＴがアンロード位置に移動された後、不図示のウエハアンローダにより、ウエハＷが基板テーブル１４からアンロードされる（ステップＳ８）。こうして、ウエハ１枚についての露光処理が終了する。
【０１３２】
なお、以上の露光処理が第１層目の走査露光である場合は、前述の位置計測結果に基づいて、ウエハＷ上におけるショット領域の位置が補正され、結果としてショット領域の配列座標系は設計上の座標系に対する座標原点のシフト量や回転量がほぼ零となるが、ウエハＷの中心位置のずれ量（シフト量）及び回転量が小さいときは、その位置情報計測結果に基づくショット位置の補正は行わなくともよい。また、上記露光処理が第２層目以降の走査露光である場合は、走査露光に先立ってファインアライメントが行われるので、走査露光におけるレチクルステージＲＳＴ及びウエハステージＷＳＴの同期移動で前述の位置情報計測結果を用いる必要はなく、ファインアライメント時におけるウエハステージＷＳＴの移動のみでその位置情報計測結果が用いられることになる。
【０１３３】
さらに、第１層目ではその走査露光、第２層目ではファインアライメントに先立ち、前述の位置情報計測結果に基づいて、例えばウエハＷ又はウエハホルダ１５を回転させるようにしてもよい。この場合は、第１層目の走査露光や第２層目以降のファインアライメントにおいて、前述の位置情報計測結果すなわち回転量を用いる必要がなくなる。このとき、ウエハＷの回転量の代わりに、又はそれに加えて、前述の位置計測により得られたウエハＷの中心位置を示す情報に基づいてウエハホルダ１５上におけるウエハＷの位置を微調整することにより、以降の動作で中心位置を示す情報を用いる必要がなくなる。
【０１３４】
以上説明したように、本実施形態によれば、プリアライメントセンサ２２ｃの撮像結果に基づいて、プリアライメントセンサ２２ｃの真下に円弧エッジＣＥが位置しているのか、又はサブオリエンテーションフラットＯＦ１が位置しているのかを判定し、この判定結果に基づいてウエハＷの表裏判断を行っているため、高速且つ正確にウエハＷの表裏判別を行うことができる。この結果、例えばウエハＷの表面に転写すべきパターンがウエハＷの裏面に転写されるといった事態を防止することができ、高い歩留まりでデバイスを製造することができる。
【０１３５】
また、オリエンテーションフラットＯＦの近似直線及びサブオリエンテーションフラットＯＦ１の近似直線を求め、これらをウエハＷの中心に向かって平行移動し、移動後直線の交点をウエハＷの中心と推定しているため、プリアライメントセンサ２２ａ，２２ｂの真下にオリエンテーションフラットＯＦが位置し、プリアライメントセンサ２２ｃの真下にサブオリエンテーションフラットＯＦ１が位置する場合のように、プリアライメントセンサ２２ａ，２２ｂ，２２ｃの全てが直線状の外縁を観察するような状況においてもウエハＷの位置情報を求めることができる。
【０１３６】
なお、以上説明した実施形態は、本発明の理解を容易にするために記載されたものであって、本発明を限定するために記載されたものではない。したがって、上記の実施形態に開示された各要素は、本発明の技術的範囲に属する全ての設計変更や均等物をも含む趣旨である。
【０１３７】
例えば、上記実施形態では、図４に示したウエハＷの表裏判別を行うステップＳ４とウエハＷの位置情報を算出するステップＳ５とにおいて、説明の便宜上、個別に外縁に沿った点群を抽出して近似直線を求めていた。しかしながら、ステップＳ３の撮像を行って得られた撮像データＤ１（プリアライメントセンサ２２ａ，２２ｂ，２２ｃの撮像データ）各々に対して一括して点群抽出処理及び直線近似処理を行って、図３に示す外縁情報格納領域４２及び近似直線格納領域４３に各々の処理結果を格納しておき、必要になったときに必要な情報を読み出すようにすることで、処理の効率化を図ることができる。
【０１３８】
また、上記実施形態においては、プリアライメントセンサ２２ｃの真下に円弧エッジＣＥが配置されているのか又はサブオリエンテーションフラットＯＦ１が配置されているのかを判定し、この判定結果のみに基づいてウエハＷの表裏判別を行っていたが、プリアライメントセンサ２２ａ，２２ｂ，２２ｃの全てについて各々の真下に位置しているのが直線状輪郭であるのか曲線状輪郭であるのかを判定し、これらの判定結果に基づいて表裏判定を行うようにしても良い。
【０１３９】
また、上述した実施形態においては、露光装置で用いる場合を例に挙げて説明したが、本発明は露光装置のみならず、ウエハに形成されたパターンの重ね合わせ精度を検査する検査装置、ウエハに形成されたパターンの線幅を検査する検査装置、ウエハに形成されたパターンのマクロ的（巨視的）な欠陥を検査する検査装置、その他の検査装置にも検査対象のウエハを所定の精度で位置合わせするために用いることができる。
【０１４０】
なお、上述した実施形態では、ウエハ（基板）を検査対象として説明したが、検査対象としては、円弧状の輪郭と直線上の輪郭とをあわせ持つ物体であれば、ウエハに限られるものではない。
【０１４１】
また、上記実施形態においては、本発明をステップ・アンド・スキャン方式の露光装置に適用した場合を例に挙げて説明したが、ステップ・アンド・リピート方式の露光装置（ステッパー）にも適用することができる。また、上記実施形態では、照明光ＩＬとしてＡｒＦエキシマレーザ等から射出されるレーザ光を用いていたが、レーザプラズマ光源、又はＳＯＲから発生する軟Ｘ線領域、例えば波長１３．４ｎｍ、又は１１．５ｎｍのＥＵＶ（Ｅｘｔｒｅｍｅ Ｕｌｔｒａ Ｖｉｏｌｅｔ）光を用いるようにしてもよい。さらに、電子線又はイオンビームなどの荷電粒子線を用いてもよい。また、投影光学系は、反射光学系、屈折光学系、及び反射屈折光学系のいずれを用いてもよい。
【０１４２】
また、ＤＦＢ半導体レーザ又はファイバーレーザから発振される赤外域、又は可視域の単一波長レーザを、例えばエルビウム（又はエルビウムとイットリビウムの両方）がドープされたファイバーアンプで増幅し、非線形光学結晶を用いて紫外光に波長変換した高調波を用いてもよい。
【０１４３】
さらに、半導体素子の製造に用いられるデバイスパターンをウエハ上に転写する露光装置だけでなく、液晶表示素子などを含むディスプレイの製造に用いられるデバイスパターンをガラスプレート上に転写する露光装置、薄膜磁気ヘッドの製造に用いられるデバイスパターンをセラミックウエハ上に転写する露光装置、撮像素子（ＣＣＤなど）、マイクロマシン、及びＤＮＡチップなどの製造に用いられる露光装置等にも本発明を適用することができる。
【０１４４】
ところで、ＥＵＶ光を用いる露光装置では反射型マスクが用いられ、電子線露光装置などでは透過型マスク（ステンシルマスク、メンブレンマスク）が用いられるので、マスクの原版としてはシリコンウエハなどが用いられる。
【０１４５】
複数のレンズから構成される照明光学系、投影光学系を露光装置本体に組み込み光学調整をするとともに、多数の機械部品からなるレチクルステージや基板ステージを露光装置本体に取り付けて配線や配管を接続し、さらに総合調整（電気調整、動作確認等）をすることにより本実施形態の露光装置を製造することができる。なお、露光装置の製造は温度及びクリーン度等が管理されたクリーンルーム内で行うことが望ましい。
【０１４６】
半導体素子は、デバイスの機能・性能設計を行うステップ、この設計ステップに基づいて、レチクルを製造するステップ、シリコン材料からウエハを製造するステップ、上述した実施形態の露光装置等によりレチクルのパターンをウエハに露光転写するステップ、デバイス組み立てステップ（ダイシング工程、ボンディング工程、パッケージ工程を含む）、検査ステップ等を経て製造される。
【０１４７】
【発明の効果】
本発明によると、撮像した物体の輪郭の一部に沿って点群を抽出し、抽出した点群に対して直線近似を行って近似直線を算出し、この近似直線と点群との位置関係に応じて上記輪郭の一部が直線状輪郭であるのか又は曲線状輪郭であるのかを判定しているため、撮像した物体の輪郭の一部が直線状輪郭であるのか又は曲線状輪郭であるのかを高速且つ正確に判定することができるという効果がある。
【０１４８】
また、本発明によると、所定の位置に配設された撮像装置の撮像結果について直線状輪郭であるのか又は曲線状輪郭であるのかを高速且つ正確に判定し、これらの判定結果に基づいて物体の表裏を判別しているため、物体の表裏判別を高速且つ正確に行うことができるという効果がある。
【０１４９】
さらに、本発明によると、物体としての基板の表裏判別が高速且つ正確に行われた上で、計測された基板の位置情報及び回転位置情報に基づいて基板の位置制御を行いつつ基板上にパターンを転写しているため、例えば基板の表面に転写すべきパターンが基板の裏面に転写されるといった事態を防止することができ、高い歩留まりでデバイスを製造することができるという効果がある。
【図面の簡単な説明】
【図１】本発明の実施形態に係る露光装置の全体構成の概略を示す図である。
【図２】プリアライメント検出系の周辺の構成を概略的に示す平面図である。
【図３】本発明の実施形態に係る露光装置が備える主制御系の内部構成を示すブロック図である。
【図４】本発明の実施形態に係る露光装置の露光時の動作の概略を示すフローチャートである。
【図５】プリアライメントセンサの撮像位置へウエハが配置された状態を示す上面図である。
【図６】ウエハが表面を上側にして配置されているときのプリアライメントセンサの撮像結果の一例を示す図である。
【図７】ウエハが裏面を上側にして配置されているときのプリアライメントセンサの撮像結果の一例を示す図である。
【図８】ウエハの表裏判別処理を示すフローチャートである。
【図９】円弧エッジ又は直線状の外縁と近似直線との位置関係を例示する図である。
【図１０】撮像した外縁部が円弧エッジであるか否かの判定を行う際に設定する閾値の一例を説明するための図である。
【図１１】ウエハの位置情報を算出する処理を示すフローチャートである。
【図１２】オリエンテーションフラットの近似直線とサブオリエンテーションの近似直線とを用いてウエハの中心位置を求める処理を説明するための図である。
【符号の説明】
１…露光装置
１４…基板テーブル（ステージ）
１６…ウエハステージ装置（ステージ装置）
２０…主制御系（制御装置、制御用コンピュータ）
２２ａ〜２２ｃ…プリアライメントセンサ（撮像装置）
３３…外縁抽出部（点群抽出部）
３４…直線近似部
３５…表裏判別部（判定部）
ＣＥ…円弧エッジ（曲線状輪郭）
ＯＦ…オリエンテーションフラット（直線状輪郭）
ＯＦ１…サブオリエンテーションフラット（直線状輪郭）
ＯＦ２…サブオリエンテーションフラット（直線状輪郭）
ＲＡＳ…プリアライメント検出系（撮像装置）
Ｗ…ウエハ（基板）[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a position measurement method and apparatus, an exposure method and apparatus, and a program, and in particular, a position measurement method and apparatus for measuring position information of an object such as a substrate, an exposure method using the position measurement method, and the position measurement apparatus And a program for causing a control computer of the exposure apparatus to measure positional information of an object such as a substrate.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in a lithography process for manufacturing a semiconductor element, a liquid crystal display element, a thin film magnetic head, and other devices, a pattern formed on a mask or reticle (hereinafter, collectively referred to as a “mask”) is used. 2. Description of the Related Art There is used an exposure apparatus that transfers a photosensitive agent such as a resist onto a substrate such as a wafer or a glass plate via a projection optical system. As the exposure apparatus, a static exposure type projection exposure apparatus such as a so-called stepper and a scanning exposure type projection exposure apparatus such as a so-called scanning stepper are mainly used. In such an exposure apparatus, it is necessary to perform high-precision alignment (alignment) between the reticle and the wafer prior to exposure. In order to perform this high-accuracy alignment, it is necessary to measure the position of the wafer with high accuracy. For this purpose, various position measurement techniques have been proposed.
[0003]
In the above-described exposure apparatus, an alignment method called enhanced global alignment (hereinafter, referred to as “EGA”) is used in order to ensure high overlay accuracy between the reticle and the mask. This EGA measures the arrangement coordinate position of each shot area on a wafer on a reference coordinate system (movement coordinate system of the wafer stage) defining the movement of the wafer with high accuracy while the wafer is placed on the wafer stage. The positioning (detailed (fine) alignment) is performed based on the measurement result. More specifically, several fine alignment marks (detailed alignment marks transferred together with the circuit pattern) in the wafer are measured, and a processing such as least square approximation is performed on the measurement result to arrange each shot area. Find coordinates. Then, at the time of exposure, the wafer stage is stepped and moved according to the obtained arrangement coordinates, and the position of the wafer stage is adjusted depending on the accuracy of the wafer stage.
[0004]
For the above-mentioned EGA, it is necessary to observe a fine alignment mark formed at a predetermined position on a wafer at a high magnification, but when observing at a high magnification, the observation field of view is necessarily narrowed. However, if the wafer is loaded on the wafer stage in a state where the wafer is largely displaced from the wafer stage, there is a problem that the fine alignment mark on the wafer does not enter the observation field. Therefore, in order to reliably capture the fine alignment mark in a narrow observation field (to load the wafer to a desired position (orientation) on the wafer stage), observe the position of the outer edge of the wafer prior to fine alignment. Then, a reference position (for example, a center position) of the wafer and a rotation amount around the center axis of the wafer are measured based on the observation result, and based on the measurement result, the wafer is aligned on the wafer stage with predetermined accuracy. The pre-alignment for loading into is performed.
[0005]
A V-shaped notch (notch) or a linear notch (orientation flat) is formed at a part of the outer edge of the wafer. In pre-alignment, these are observed to measure the reference position and the amount of rotation of the wafer. ing. This pre-alignment is performed not only by the exposure apparatus, but also by an inspection apparatus for inspecting the overlay accuracy of the pattern formed on the wafer, an inspection apparatus for inspecting the line width of the pattern formed on the wafer, and the pattern formed on the wafer. In an inspection apparatus for inspecting a macro (macroscopic) defect and other inspection apparatuses, the inspection apparatus is used to align a wafer to be inspected with a predetermined accuracy. For details of the conventional pre-alignment method, refer to, for example, Patent Documents 1 and 2 below.
[0006]
[Patent Document 1]
WO 02/061367 pamphlet
[0007]
[Patent Document 2]
WO 02/033352 pamphlet
[0008]
[Problems to be solved by the invention]
In recent years, in the manufacture of devices, exposure processing (pattern transfer processing) has been performed not only on the front surface of a wafer but also on the back surface of the wafer, mainly for high integration or high functionality. Was. In the above-described prior art, since only the pattern transfer to the surface of the wafer is assumed, in the pre-alignment, it is sufficient to measure the reference position and the rotation amount of the wafer using the above-described notch or orientation flat.
[0009]
However, in a situation where the pattern is transferred to the front and back surfaces of the wafer, it is necessary to determine not only the reference position and the rotation amount of the wafer but also the front and back of the wafer. In a conventional wafer having an orientation flat formed only at one position of the outer edge, the external shape is symmetrical with respect to a straight line passing through the center of the wafer and orthogonal to the orientation flat. Cannot be determined.
[0010]
Therefore, in recent years, a wafer having another orientation flat (sub-orientation flat) formed at one or two places other than the conventionally formed orientation flat for discrimination between front and back has been used. The plurality of orientation flats formed on one wafer are set to different lengths, and the outer shape is asymmetric with respect to an arbitrary line included in the wafer surface, so that the front and back can be distinguished.
[0011]
When such a wafer is used, the reference position and the amount of rotation of the wafer are measured using the pre-alignment method described above, but the front and back of the wafer are imaged by a pre-alignment imaging device (camera). The operator visually determines the outer edge image. As described above, the length of each of the orientation flats formed on the wafer is set to be different from each other, but the length is not extremely long and the difference is slight. Further, since the image obtained by the camera has a detection range not so large, it is easy to determine whether the image portion is an arc portion of the wafer or an orientation flat portion only by looking at the image. Not that. For this reason, there is a problem that the discrimination between the front and the back by the visual inspection of the operator may be erroneous, and skill is required to reduce the erroneous discrimination.
[0012]
The present invention has been made in view of such a problem of the related art, and based on an imaging result of a part of a contour of a substrate having a linear contour and a curvilinear contour, a part of the imaged part is formed into a linear shape. An object of the present invention is to enable high-speed and accurate discrimination between a contour and a curvilinear contour, and to perform high-speed and accurate discrimination between front and back of a substrate.
[0013]
[Means for Solving the Problems]
Hereinafter, in the description given in this section, the present invention will be described in association with member numbers shown in the drawings representing the embodiments, but each constituent requirement of the present invention is limited to the members shown in the drawings with these member numbers. It is not done.
[0014]
In order to solve the above problem, according to a first aspect of the present invention, position measurement for measuring position information of an object (W) having a linear contour (OF, OF1, OF2) and a curved contour (CE). An imaging step (S3) of imaging a part of an outline of the object, and a point group including a plurality of points along the part of the outline of the object based on an imaging result of the imaging step. A point group extraction step (S11) of extracting the point group, a straight line approximation step (S12) of linearly approximating the point group, and the contour according to a positional relationship of the point group with respect to the approximate straight line obtained in the line approximation step. A determination step (S14) of determining whether a part of is a straight-line contour or a curved-line contour.
[0015]
According to the present invention, a point group is extracted along a part of the contour of the imaged object, a straight line approximation is performed on the extracted point group to calculate an approximate straight line, and a positional relationship between the approximate straight line and the point group is calculated. It is determined whether a part of the contour is a linear contour or a curvilinear contour according to the above. Therefore, a part of the contour of the imaged object is a linear contour or a curvilinear contour. Can be quickly and accurately determined.
[0016]
In the position measurement method according to the first aspect of the present invention, the imaging step is a step of imaging a part of the contour of the substrate as the object by an imaging device disposed in a predetermined position in advance, and the imaging result The method may further include a front / back discrimination step (S15) of discriminating between front and back of the substrate based on a result of the above-described determination. By doing so, it is possible to quickly and accurately determine whether or not the imaging location is a linear contour or a curved contour based on the imaging results at a plurality of locations on the contour of the substrate. Since the front and back sides of the board are determined based on the determination result, the front and back sides of the board can be quickly and accurately determined.
[0017]
To solve the above problem, according to a second aspect of the present invention, position measurement for measuring position information of an object (W) having a linear contour (OF, OF1, OF2) and a curved contour (CE). An imaging device (RAS, 22a, 22b, 22c) for imaging a part of an outline of the object; and a plurality of imaging devices along the part of the outline of the object based on an imaging result of the imaging device. A point group extraction unit (33) for extracting a point group consisting of points, a straight line approximation unit (34) for linearly approximating the point group, and a positional relationship of the point group with respect to an approximate line obtained by the straight line approximation unit. And a controller having a determination unit (35) for determining whether a part of the contour is the linear contour or the curved contour.
[0018]
According to the present invention, the control device extracts a point group along a part of the contour of the imaged object, calculates a straight line by performing linear approximation on the extracted point group, and calculates the approximate straight line and the point group. It is determined whether a part of the contour is a linear contour or a curved contour in accordance with the positional relationship with, and thus, a part of the contour of the imaged object is a linear contour or a curved part. It is possible to quickly and accurately determine whether the contour is a contour without human intervention.
[0019]
In the position measurement device according to the second aspect of the present invention, as the imaging device, using a device that images a part of the contour of the substrate as the object at a plurality of locations having a predetermined positional relationship set in advance, The control device may further include a front / back discrimination unit (35) for discriminating between the front and back of the board based on the determination result of the determination unit for each of the imaging results obtained at the plurality of locations. With this configuration, it is possible to quickly and accurately determine whether or not the imaging location is a linear contour or a curved contour based on the imaging results at a plurality of locations on the board contour without manual intervention. In addition, since the control device determines the front and back of the board based on these determination results, the front and back of the board can be quickly and accurately determined without manual intervention.
[0020]
According to a third aspect of the present invention, there is provided an exposure method for transferring a predetermined pattern onto a substrate (W) as an object, wherein the position measurement method according to the first aspect of the present invention uses the position information of the substrate, A substrate measuring step (S4, S5) for obtaining rotation position information and information indicating front and back; and a method for measuring the position of the substrate, the rotation position information, and information indicating front and back obtained in the substrate measurement step. And a transfer step (S6, S7) of transferring the pattern onto the substrate while controlling the position of the substrate.
[0021]
According to the present invention, the pattern is transferred onto the substrate while performing the position control of the substrate based on the measured position information and rotational position information of the substrate after the front / back discrimination of the substrate is performed quickly and accurately. Therefore, for example, a situation in which a pattern to be transferred to the front surface of the substrate is transferred to the back surface of the substrate can be prevented, and the device can be manufactured with a high yield.
[0022]
According to a fourth aspect of the present invention, there is provided an exposure apparatus (1) for transferring a predetermined pattern onto a substrate (W) as an object, wherein position information, rotational position information, and information indicating front and back of the substrate are obtained. An exposure apparatus is provided, comprising: a position measuring device according to the second aspect of the present invention; and a stage device (16) having a stage (14) on which the substrate measured by the position measuring device is mounted.
[0023]
According to the present invention, similarly to the exposure method according to the third aspect of the present invention, for example, it is possible to prevent a situation in which a pattern to be transferred to the front surface of the substrate is transferred to the back surface of the substrate, and to achieve a high yield. Devices can be manufactured.
[0024]
According to a fifth aspect of the present invention, a computer for controlling an exposure apparatus (1) for transferring a predetermined pattern onto a substrate (W) having a linear contour (OF, OF1, OF2) and a curved contour (CE). (20) A capturing step, which is a program for measuring positional information of the substrate, wherein the capturing result is obtained by capturing a part of an outline of the substrate at a plurality of locations having a predetermined positional relationship set in advance. (S3) and a determining step (S14) of determining, for each of the imaging results captured in the capturing step, whether a part of the contour is the linear contour or the curved contour. A program is provided for causing the control computer to execute a front / back discrimination step (S15) of discriminating between front and back of the substrate according to a result of the judgment in the judgment step.
[0025]
According to the present invention, a computer is made to quickly and accurately determine whether a part of a contour of a board imaged is a linear contour or a curved contour, and based on the result of the determination, it is possible to quickly determine front / back of a board. In addition, it is possible to provide a function of performing the operation with high accuracy.
[0026]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram schematically illustrating an overall configuration of an exposure apparatus including a position measuring device according to an embodiment of the present invention. The exposure apparatus shown in FIG. 1 moves a reticle R as a mask and a wafer W as a substrate relative to the projection optical system PL in FIG. This is a step-and-scan exposure apparatus that manufactures semiconductor elements by sequentially transferring.
[0027]
In the following description, the XYZ rectangular coordinate system shown in FIG. 1 is set, and the positional relationship of each member will be described with reference to the XYZ rectangular coordinate system. The XYZ orthogonal coordinate system is set so that the X axis and the Y axis are parallel to the wafer W, and the Z axis is set in a direction orthogonal to the wafer W. In the XYZ orthogonal coordinate system in the figure, the XY plane is actually set to a plane parallel to the horizontal plane, and the Z axis is set vertically upward. In the present embodiment, the direction in which the reticle R and the wafer W are synchronously moved (hereinafter, referred to as a scanning direction) is set in the Y direction.
[0028]
An exposure apparatus 1 shown in FIG. 1 holds an illumination system 10 for emitting illumination light for exposure, a reticle stage RST as a mask stage for holding a reticle R as a mask, a projection optical system PL, and a wafer W as a substrate. A wafer stage device 16 as a stage device on which a substrate table 14 as a stage that moves in the XY plane in the XY two-dimensional directions is mounted; a pre-alignment detection system RAS as an imaging device for imaging the outer edge shape of the wafer W; It is configured to include an alignment detection system AS for observing marks formed on a wafer W mounted (loaded) thereon, a control system thereof, and the like.
[0029]
The illumination system 10 includes a light source unit, a shutter, an optical integrator, a beam splitter, a condenser lens system, a reticle blind, and an imaging lens system (all not shown). Details of the configuration of the illumination system 10 are disclosed in, for example, Japanese Patent Application Laid-Open Nos. 9-320956, 6-349701, and U.S. Pat. No. 5,534,970 corresponding thereto. In the present embodiment, a case where a fly-eye lens is provided as an optical integrator will be described as an example. However, the present invention is not limited to this, and a rod integrator (internal reflection type integrator), a diffractive optical element, or the like can be used.
[0030]
Here, as the light source unit, an excimer laser light source such as a KrF excimer laser light source (oscillation wavelength 248 nm) or an ArF excimer laser light source (oscillation wavelength 193 nm), or F₂Laser light source (oscillation wavelength: 157 nm), Ar₂A laser light source (having an oscillation wavelength of 126 nm), a copper vapor laser light source, a harmonic generator of a YAG laser, an ultra-high pressure mercury lamp (g-line, i-line, or the like) can be used.
[0031]
The operation of the illumination system 10 thus configured will be briefly described. Illumination light emitted by the light source unit enters the optical integrator when the shutter is open. When illumination light is incident on a fly-eye lens as an optical integrator, a surface light source composed of a large number of light source images, that is, a secondary light source is formed on the emission-side focal plane.
[0032]
Illumination light emitted from a fly-eye lens as an optical integrator reaches a reticle blind via a beam splitter and a condenser lens system. The illumination light having passed through the reticle blind is emitted toward the mirror 11 via the imaging lens system. Thereafter, the optical path of the illumination light IL is bent vertically downward (−Z direction) by the mirror 11 to illuminate a rectangular illumination area IAR on the reticle R held on the reticle stage RST.
[0033]
A reticle R is fixed on the reticle stage RST by, for example, vacuum suction. The reticle stage RST is two-dimensionally (X direction and orthogonal thereto) in a plane perpendicular to an optical axis IX of the illumination system 10 (coincident with an optical axis AX of a projection optical system PL described later) for positioning the reticle R. (In the rotation direction about the Z axis orthogonal to the Y direction and the XY plane).
[0034]
The reticle stage RST can be moved on a reticle base (not shown) at a scanning speed designated in a scanning direction (Y direction) by a reticle driving unit (not shown) composed of a linear motor or the like. . The reticle stage RST has a movement stroke that allows the entire surface of the reticle R to cross at least the optical axis IX of the illumination system 10.
[0035]
A movable mirror 12 that reflects a laser beam from a reticle laser interferometer (hereinafter, referred to as a “reticle interferometer”) 13 is fixed on the reticle stage RST, and the position of the reticle stage RST in the stage movement plane is reticle interference. The total 13 is always detected at a resolution of, for example, about 0.5 to 1 nm. Here, actually, the movable mirror (or at least one corner cube type mirror) having a reflecting surface orthogonal to the scanning direction (Y direction) on the reticle stage RST is orthogonal to the non-scanning direction (X direction). A movable mirror having a reflecting surface is provided, and a reticle interferometer 13 is provided for one or more axes for each movable mirror. In FIG. 1, these are typically the movable mirror 12 and the reticle interferometer 13. Respectively.
[0036]
The position information (velocity information) RPV of the reticle stage RST from the reticle interferometer 13 is sent to the stage control system 21 and the main control system 20 via the stage control system 21, and the stage control system 21 responds to an instruction from the main control system 20. The reticle stage RST is driven via a reticle driving unit (not shown) based on the position information of the reticle stage RST.
[0037]
The projection optical system PL is arranged below (in the −Z direction) of the reticle stage RST in FIG. 1, the direction of its optical axis AX (coinciding with the optical axis IX of the illumination system 10) is the Z direction, and is predetermined by telecentric on both sides. (For example, 1/5, 1/4, or 1/6) is used. Therefore, when the illumination area IAR of the reticle R is illuminated by the illumination light IL from the illumination system 10, the illumination light IL passing through the reticle R causes the reticle R in the illumination area IAR to pass through the projection optical system PL. Is projected onto an exposure area IA on a wafer W having a surface coated with a photoresist (photosensitive agent).
[0038]
Wafer stage WST is driven by, for example, a two-dimensional linear actuator on base BS in the Y direction (left-right direction in FIG. 1), which is the scanning direction, and in the X direction orthogonal to the Y direction (a direction orthogonal to the plane of FIG. 1). It has become. Substrate table 14 is provided on wafer stage WST. A wafer holder 15 is placed on the substrate table 14, and the wafer W is held by the wafer holder 15 by vacuum suction. The wafer stage WST, the substrate table 14, and the wafer holder 15 constitute a wafer stage device 16.
[0039]
Substrate table 14 is mounted on wafer stage WST in a state where it is positioned in the XY directions and allowed to move and tilt in the Z direction. The substrate table 14 is supported by three shafts (not shown) at three different support points, and these three shafts are independently driven in the Z direction by a wafer driving device 17 as a driving mechanism. As a result, the surface position (the position in the Z direction and the inclination with respect to the XY plane) of the wafer W held on the substrate table 14 is set to a desired state. Further, the wafer holder 15 can rotate around the Z axis. Therefore, the wafer holder 15 is driven in the direction of six degrees of freedom by the two-dimensional linear actuator and the driving mechanism. In FIG. 1, the two-dimensional linear actuator and the driving mechanism are representatively shown as the wafer driving device 17.
[0040]
At a substantially central position of the substrate table 14 (wafer holder 15), a center table (not shown) for receiving or transferring a wafer from a wafer loader is provided. The center table is provided with a suction mechanism by vacuum, and can hold a wafer by suction. In addition, the center table has a structure capable of vertically moving (moving in the Z direction) and rotating (about the Z axis) while holding the wafer. When receiving the wafer, the center table moves up to receive the wafer, and then moves down to hold the wafer on the wafer holder 15 (substrate table 14).
[0041]
A movable mirror 18 for reflecting a laser beam from a wafer laser interferometer (hereinafter, referred to as “wafer interferometer”) 19 is fixed on the substrate table 14, and the XY of the substrate table 14 is controlled by a wafer interferometer 19 arranged outside. The position in the plane is always detected with a resolution of, for example, about 0.5 to 1 nm. Here, actually, on the substrate table 14, a moving mirror 18Y having a reflecting surface orthogonal to the scanning direction Y direction and a moving mirror 18X having a reflecting surface orthogonal to the non-scanning direction X direction are provided. The wafer interferometers 19X and 19Y are provided for one or a plurality of axes for each movable mirror (see FIG. 2). However, in FIG. 1, these are typically shown as moving mirror 18 and wafer interferometer 19, respectively.
[0042]
The position information (or speed information) WPV of the substrate table 14 is sent to the stage control system 21 and the main control system 20 via the stage control system 21, and the stage control system 21 receives the position information (or speed information) in response to an instruction from the main control system 20. Information) The wafer stage WST is controlled via the wafer driving device 17 based on WPV. Also, on the substrate table 14, various reference marks for baseline measurement and the like for measuring a distance from a detection center of an off-axis type alignment detection system AS described later to an optical axis AX of the projection optical system PL are formed. A reference member (not shown) is fixed.
[0043]
The pre-alignment detection system RAS is held by a holding member (not shown) at a position separated from the projection optical system PL above the base BS. The pre-alignment detection system RAS includes three pre-alignment sensors 22a, 22b, and 22c that detect the positions of three outer green portions of the wafer W held by the wafer loader (not shown) and held by the wafer holder 15. Here, the configuration of the pre-alignment detection system RAS will be described. FIG. 2 is a plan view schematically showing a configuration around the pre-alignment detection system RAS.
[0044]
First, the outer edge shape of the wafer W will be described with reference to FIG. As shown in FIG. 2, the wafer W has an orientation flat OF and sub-orientation flats OF1 and OF2 formed as straight notches (linear contours). The orientation flat OF is an orientation flat conventionally formed on the wafer W as a linear notch, and the sub-orientation flats OF1 and OF2 are newly formed linear flats for discriminating the front and back of the wafer W. It is a notch. That is, in the present embodiment, the exposure processing is performed on both the front surface and the back surface of the wafer W. The lengths of the orientation flat OF and the sub-orientation flats OF1 and OF2 are set to different lengths, and the orientation flat OF and the sub-orientation flat OF1 are in a relationship orthogonal to each other.
[0045]
These orientation flat OF and sub-orientation flats OF1 and OF2 correspond to the linear contour according to the present invention, and the other outer edge of the wafer W corresponds to the curved contour according to the present invention. In the following description, the outer edge of the wafer W other than where the orientation flat OF and the sub-orientation flats OF1 and OF2 are formed is referred to as an "arc edge", and is continuously connected to the orientation flat OF and the sub-orientation flat OF2. The connected arc edges are distinguished by attaching a symbol CE.
[0046]
Further, as shown in FIG. 2, the pre-alignment sensor 22a and the pre-alignment sensor 22b are respectively arranged at positions for capturing images near both ends of the orientation flat OF. Further, the pre-alignment sensor 22c is arranged at a position where an image of a part of the outer edge position of the wafer W other than the portion where the orientation flat OF is formed is taken. In the example shown in FIG. 2, the orientation flat OF and the sub-orientation flat OF2 are each parallel to the X-axis, the sub-orientation flat OF1 is parallel to the Y-axis, and the orientation flat OF is in the + Y direction with respect to the center of the wafer W. When the sub-orientation flat OF2 is located in the -Y direction and the sub-orientation flat OF is located in the + X direction, a position where a part of the arc edge CE located in the -X direction from the center of the wafer W can be imaged. Are located in The relative positional relationship between the three pre-alignment sensors 22a, 22b, 22c is a predetermined positional relationship.
[0047]
As these pre-alignment sensors 22a, 22b, 22c, sensors of an image processing system including an image sensor and an image processing circuit are used. The imaging data D1 of the outer edge of the wafer W by the pre-alignment detection system RAS having the above configuration is supplied to the main control system 20. The imaging data D1 includes imaging result data DA from the pre-alignment sensor 22a, imaging result data DB from the pre-alignment sensor 22b, and imaging result data DC from the pre-alignment sensor 22c. When measuring the outer green portion of the wafer W, the wafer W is provided at the wafer holder 15 (more precisely, at the approximate center of the wafer holder 15, and is not shown in the figure for moving the wafer up and down (Z direction)). This may be performed not after the wafer W is placed on the center table) but before the wafer W is placed on the wafer holder 15, that is, in a state where the wafer W is held by the wafer loader. In such a configuration, the measurement may be performed by the pre-alignment sensor 22 in a state where the wafer is placed on the transfer arm provided as a part of the configuration for transferring the wafer to the wafer holder. Since this arm is known in, for example, JP-A-2002-280288, a detailed description thereof will be omitted. Further, the above-mentioned center table is also disclosed in the above publication.
[0048]
Returning to FIG. 1, the alignment detection system AS is arranged on the side surface of the projection optical system PL, and in the present embodiment, an imaging for observing a street line and a position detection mark (fine alignment mark) formed on the wafer W. An off-axis type alignment microscope including an alignment sensor of a type is used. The detailed configuration of the alignment detection system AS is disclosed in, for example, Japanese Patent Application Laid-Open No. 9-219354 and US Pat. No. 5,859,707. Image data D2 of the wafer W observed by the alignment detection system AS is supplied to the main control system 20.
[0049]
Further, the exposure apparatus according to the present embodiment includes a measurement point Z on the surface of the wafer W at the measurement points set in the exposure area IA (the area on the wafer W optically conjugate with the illumination area IAR described above) and in the vicinity thereof. A multipoint focus position detection system (not shown), which is one of oblique incidence type focus detection systems (focus detection systems) for detecting a position in the direction (optical axis AX direction), is provided. The multi-point focus position detection system includes an irradiation optical system including an optical fiber bundle, a condenser lens, a pattern forming plate, a lens, a mirror, and an irradiation objective lens, a condenser objective lens, a rotational diaphragm, an imaging lens, It comprises a light receiving slit system, a light receiving optical system including a light receiving device having a large number of photo sensors, and a light receiving optical system (both are not shown). The detailed configuration and the like of this multipoint focus position detection system are disclosed in, for example, Japanese Patent Application Laid-Open No. Hei 6-283403 and U.S. Pat. No. 5,448,332 corresponding thereto.
[0050]
Next, the main control system 20 will be described. FIG. 3 is a block diagram showing an internal configuration of the main control system 20 included in the exposure apparatus according to the embodiment of the present invention. As shown in FIG. 3, the main control system 20 includes a main control device 30 and a storage device 40. The main control device 30 includes a control unit 31, an imaging data collection unit 32, an outer edge extraction unit 33, a straight line approximation unit 34, a front / back discrimination unit 35, a rotation amount calculation unit 36, and a position information calculation unit 37. The control unit 31 supplies the stage control data CD to the stage control system 21 based on the position information (speed information) RPV of the reticle R and the position information (speed information) WPV of the wafer W to operate the exposure apparatus 1. Take control of the whole.
[0051]
The imaging data collection unit 32 collects the imaging data D1 supplied from the pre-alignment detection system RAS. The outer edge extraction unit 33 extracts the outer edge position of the wafer W based on the imaging data collected by the imaging data collection unit 32. From the outer edge position of the wafer W extracted by the outer edge extracting unit 33, the straight line approximating unit 34 obtains an approximate straight line along the outer edge. The front / back discrimination unit 35 performs front / back discrimination of the wafer W based on the approximate straight line obtained by the straight line approximation unit 34. The rotation amount calculation unit 36 as a rotation position information calculation unit calculates the rotation amount of the wafer W based on the imaging result of the orientation flat OF. The position information calculation unit 37 calculates a reference position (for example, a center position) of the wafer W based on the rotation amount of the wafer W calculated by the rotation amount calculation unit 36 and an imaging result of the outer edge of the wafer W.
[0052]
Further, the storage device 40 includes an imaging data storage area 41, an outer edge information storage area 42, an approximate straight line storage area 43, a rotation information storage area 44, and a position information storage area 45. In FIG. 3, the flow of data is indicated by solid arrows, and the flow of control is indicated by dotted arrows. The configuration of the main control system 20 has been described above, but the operation of each unit included in the main control system 20 will be described in detail later.
[0053]
Note that FIG. 3 shows an example in which each block is configured as hardware and the main control system 20 is configured by combining them. However, in terms of hardware, it is also possible to configure the main control system 20 as a computer system, and realize the function of each block constituting the main control device 30 by a program built in the main control system 20.
[0054]
When the main control device 30 is configured as a computer system, it is not necessary to previously incorporate in the main control device 30 all of the programs for realizing the functions of the above-described blocks constituting the main control device 30 which will be described later. Not necessarily required. For example, as shown by a dotted line in FIG. 1, a recording medium 26 storing a program for realizing the function of each block described above is prepared, and the program contents can be read from the recording medium 26 and recorded. A reading device 25 to which a medium 26 can be attached and detached is connected to the main control system 20, and the main control system 20 reads program contents necessary for realizing functions from the recording medium 26 loaded in the reading device 25, and reads the read program. It can be configured to perform. Further, the main control system 20 may read the program contents from the recording medium 26 loaded in the reading device 25 and install the program contents therein. Further, a configuration may be adopted in which the program contents necessary for realizing the functions are installed in the main control system 20 via the communication network using the Internet or the like.
[0055]
The recording medium 26 may be a magnetic recording medium (magnetic disk, magnetic tape, etc.), an electric recording medium (PROM, RAM with battery backup, EEPROM, other semiconductor memory, etc.), or a magneto-optical medium. Optical recording (compact disk (CD), DVD (registered trademark)), etc. What is recorded in various recording forms can be adopted. As described above, by using a recording medium on which the program contents for realizing the functions are recorded or configured so that the program contents can be installed, the program contents can be corrected later or the performance can be improved. Can be easily upgraded.
[0056]
Next, the operation at the time of exposure will be described. FIG. 4 is a flowchart showing an outline of the operation at the time of exposure of the exposure apparatus according to the embodiment of the present invention. First, a reticle R on which a pattern to be transferred is formed from a reticle library (not shown) is loaded onto a reticle stage RST using a reticle loader (not shown). Further, a wafer W to be exposed is loaded onto the above-described center table on the substrate table 14 by a wafer loader (not shown). At this time, the center table is in an up state (a state protruding from the upper surface of the wafer holder 15), and in this state, the center table sucks and holds the wafer by vacuum. That is, at this time, the wafer is still held above the wafer holder 15 (step S1). Here, in the present embodiment, since it is assumed that the exposure process is performed on both the front surface and the back surface of the wafer W, the wafer W may be loaded on the center table with the front surface facing upward. May be loaded on the center table with the upper side facing up.
[0057]
Next, main control system 20 (more specifically, control unit 31 (see FIG. 3)) outputs a control signal to stage control system 21 to control wafer stage WST via wafer drive device 17 (that is, the center table). Then, the wafer W is moved to an imaging position by the pre-alignment sensors 22a, 22b, 22c (step S2). Specifically, the orientation flat OF formed on the wafer W is positioned directly below the pre-alignment sensors 22a and 22b, and the part of the arc edge CE or the sub-orientation flat OF1 is positioned directly below the pre-alignment sensor 22c. The wafer W is moved. The wafer W can be moved so that the orientation flat OF is located directly below the pre-alignment sensors 22a and 22b because the orientation flat OF and the sub-orientation flats OF1 and OF2 are set to different lengths. Because it is.
[0058]
Here, in a state where the orientation flat OF is located directly below the pre-alignment sensors 22a and 22b, the wafer W is loaded on the center table with the front side up or on the center table with the back side up. The outer edge portion of the wafer W disposed immediately below the pre-alignment sensor 22c changes depending on whether the wafer W is loaded.
[0059]
FIG. 5 is a top view showing a state where the wafer W is arranged at the imaging position of the pre-alignment sensors 22a, 22b, 22c. As shown in FIG. 5A, when the wafer W is loaded on the center table with the front surface facing upward, a part of the arc edge CE is located immediately below the pre-alignment sensor 22c. In addition, as shown in FIG. 5B, when the wafer W is loaded on the center table with the back surface facing upward, the sub-orientation flat OF1 is located directly below the pre-alignment sensor 22c.
[0060]
When the movement of the wafer W is completed in this way, the vicinity of the outer edge of the wafer W is imaged using the pre-alignment sensors 22a, 22b, 22c (step S3). FIG. 6 is a diagram illustrating an example of an imaging result of the pre-alignment sensors 22a, 22b, and 22c when the wafer W is arranged with the front surface facing upward. FIG. 7 is a diagram illustrating an example of an imaging result of the pre-alignment sensors 22a, 22b, and 22c when the wafer W is arranged with the back surface facing upward. 6 and 7, Va to Vc indicate measurement fields of view of the pre-alignment sensors 22a, 22b, and 22c, and images of the wafer W are shown in the respective measurement fields Va to Vc.
[0061]
Referring to FIG. 6, images of the orientation flat OF formed on the wafer W are shown in the measurement visual fields Va and Vb of the pre-alignment sensors 22a and 22b, and the image of the wafer W is shown in the visual field Vc of the pre-alignment sensor 22c. A partial image of the arc edge CE is shown. On the other hand, referring to FIG. 7, an image of the orientation flat OF formed on the wafer W is shown in the measurement visual fields Va and Vb of the pre-alignment sensors 22a and 22b, as in FIG. A partial image of the sub-orientation flat OF1 is shown in the visual field Vc of 22c. As shown in FIG. 7, in a state where the wafer W is arranged with the back surface facing upward, only linear outer edges are arranged in the measurement visual fields Va, Vb, Vc of the pre-alignment sensors 22a, 22b, 22c.
[0062]
Image data D1 of the wafer W imaged by the pre-alignment sensors 22a, 22b, 22c is supplied to the main control system 20. In the main control system 20, the imaging data collection unit 32 (see FIG. 3) receives the imaging data D1, and stores the received imaging data D1 in an imaging data storage area 41 provided in the storage device 40. When the imaging of the wafer W by the pre-alignment sensors 22a, 22b, and 22c is completed and the imaging data D1 is obtained, the front and back of the wafer W are determined based on the imaging data near the outer edge of the wafer W stored in the imaging data storage area 41. A determination is made (step S4).
[0063]
Here, as described with reference to FIGS. 5 to 7, the orientation flat OF formed on the wafer W is such that the wafer W is disposed on the substrate table 14 with the front surface facing upward, or the rear surface is disposed with the rear surface facing upward. Irrespective of whether or not the pre-alignment sensors 22a and 22b are provided. On the other hand, depending on whether the wafer W is disposed on the substrate table 14 with the front surface facing upward or the rear surface facing upward, the sub-orientation flat OF1 or the arc edge CE is located immediately below the pre-alignment sensor 22c. Is arranged. In the present embodiment, the front and back sides of the wafer W are determined using the imaging result of the pre-alignment sensor 22c. Hereinafter, the front / back discrimination processing will be described in detail.
[0064]
FIG. 8 is a flowchart illustrating the front / back discrimination processing of the wafer W. When the front / back discrimination processing of the wafer W is started, the outer edge extraction unit 33 controls the imaging data stored in the imaging data storage area 41 provided in the storage device 40 under the control of the control unit 31 provided in the main control system 20. The imaging data of the pre-alignment sensor 22c is read from D1, a point group including a plurality of outer edge points along the outer edge of the wafer W is extracted, and their positions are obtained (step S11). The outer edge point thus extracted is defined as Pc_k(Xc_k, Yc_k) (See FIGS. 6 and 7). Here, k is an integer satisfying 1 ≦ k ≦ n3 (n3 is an integer of 2 or more). The extracted outer edge point Pc_kAre stored in the outer edge information storage area 42 provided in the storage device 40.
[0065]
Next, under the control of the control unit 31, the straight line approximation unit 34 stores the outer edge point Pc stored in the outer edge information storage area 42._kIs read out, and linear approximation is performed using the least squares method (step S12). Here, the equation of the approximate straight line to be obtained is expressed by the following equation (1) using the variables “a” and “b”.
[0066]
(Equation 1)

[0067]
In the above equation (1), n1 outer edge points Pc_kX coordinate of Xc_kAnd Y coordinate Yc_kIs expressed in the form of a matrix, and the simultaneous equation obtained by substituting each of the above is given by the following equation (2).
[0068]
(Equation 2)

[0069]
Here, if the above equation (2) is expressed as the following equation (3),
[0070]
(Equation 3)

[0071]
The solution to be obtained (matrix p in the above equation (3)) is obtained from the following equation (4) by the least square method.
[0072]
(Equation 4)

[0073]
That is, the first row of the matrix obtained by solving the above equation (4) is the variable “a” in the above equation (1), and the second row is the variable “b” in the above equation (1). is there. In the above equation (4), A^tIs the transpose of matrix A.
[0074]
Outer edge point Pc_kIs obtained, the front / back determination unit 35 then uses the following equation (5) to control the outer edge point Pc extracted in step S11 according to the control of the control unit 31._kAnd the distance from the approximate straight line determined in step S12, that is, each outer edge point Pc to the approximate straight line_kIs obtained.
[0075]
(Equation 5)

[0076]
The variables “a” and “b” in the above equation (5) are variables representing the approximate straight line obtained in the above equation (4), and Xc_k, Yc_kAre the respective outer edge points Pc_kAre the X and Y coordinates. The approximate straight line determined here is the outer edge point Pc_kIs an orthogonal regression line that minimizes the sum of the squares of the distances from each to the approximate line. Outer edge point Pc_kIs obtained, the front / back determination unit 35 obtains the maximum value of the residual d, or the variance or standard deviation. Thereby, the outer edge point Pc_kThe positional relationship between the and the approximate straight line is obtained (step S13).
[0077]
Here, the positional relationship between the outer edge point extracted from the arc edge and the approximate straight line, and the positional relationship between the outer edge point extracted from the linear outer edge such as the sub-orientation flat OF1 and the approximate straight line will be considered. FIG. 9 is a diagram illustrating a positional relationship between an arc edge or a linear outer edge and an approximate straight line. FIG. 9A illustrates an outer edge point Pc extracted from the arc edge CE._kFIG. 9B is a diagram illustrating a positional relationship between the sub-orientation flat OF1 and the approximate line L1._kFIG. 9 is a diagram illustrating a positional relationship between the approximate straight line L2 and the approximate straight line L2.
[0078]
As shown in FIG. 9, it can be seen that the approximate straight lines L1 and L2 can be obtained both in the case where the pre-alignment sensor 22c has captured the arc edge CE and in the case where the sub-orientation flat OF1 has been captured. However, referring to FIG. 9A, the outer edge point Pc with respect to the approximate straight line L1 is determined._kIs large, it is estimated that the maximum value or the variance or standard deviation of the residual d increases. On the other hand, referring to FIG. 9B, the sub-orientation flat OF1 substantially matches the approximate straight line L2, and the outer edge point Pc with respect to the approximate straight line L2._kIs only a sampling error at the time of outer edge extraction, it is estimated that the maximum value or the variance or standard deviation of the residual d becomes small.
[0079]
In the present embodiment, a predetermined threshold is set, and it is determined whether or not the maximum value or the variance or the standard deviation of the residual d exceeds the set threshold, to determine whether or not the wafer W disposed immediately below the pre-alignment sensor 22c. It is determined whether the outer edge is the arc edge CE or the sub-orientation flat OF1 (step S14). Here, a case where the above-described determination is performed using the maximum value of the residual d will be described as an example. FIG. 10 is a diagram for explaining an example of a threshold value set when determining whether or not the captured outer edge is the arc edge CE.
[0080]
Now, as shown in FIG. 10, it is assumed that a part of the arc edge CE is arranged in the visual field Vc of the pre-alignment sensor 22c. It is also assumed that the center C1 of the wafer W is at the position shown in the drawing with respect to the visual field Vc of the pre-alignment sensor 22c. Further, it is assumed that a straight line L1 indicated by a broken line in FIG. 10 is an approximate straight line obtained from the imaging result of the pre-alignment sensor 22c. Outer edge point Pc extracted from arc edge CE within visual field Vc of pre-alignment sensor 22c_kCan be obtained by E1-E2. E1 is the distance in the X direction from the center C1 of the wafer W to the outer edge point P2 at which the value of the X coordinate becomes the smallest, and E2 is the outer edge point P1, at which the value of the X coordinate becomes the largest from the center C1 of the wafer W. This is the distance in the X direction to P3.
[0081]
Here, the maximum residual d expected with respect to the approximate straight line L1 shown in FIG._maxIs d_max= (E1-E2) / 2. That is, the outer edge point Pc_kThere is an approximate straight line L1 at an intermediate position of the width of the X coordinate that can be taken, and the distance in the X direction from the center C1 of the wafer W to the outer edge point P2 where the value of the X coordinate becomes the smallest with respect to the approximate straight line L1 The distance in the X direction from the center C1 of the wafer W to the outer edge points P1 and P3 where the value of the X coordinate is the largest with respect to the straight line L1 is the maximum residual d._maxIt is estimated to be.
[0082]
Here, R is the radius of the wafer W, v is the length of the measurement visual field Vc in the Y direction of the pre-alignment sensor 22c, and the maximum residual d is calculated using these._maxIs represented by the following equation (6). The length of the measurement visual field Vc in the Y direction of the pre-alignment sensor 22c is the length of the chord of the arc edge CE imaged by the pre-alignment sensor 22c.
[0083]
(Equation 6)

[0084]
As described above, the residual d is larger when the arc edge is arranged than when the sub-orientation flat OF1 is arranged immediately below the pre-alignment sensor 22c, and the arc edge is arranged as described above. Maximum residual d in case_maxIs represented by the above equation (6). Therefore, in order to determine whether the arc edge is located immediately below the pre-alignment sensor 22c or whether the sub-orientation flat OF1 is located, 0 <d._th<D_maxThe threshold d that satisfies_th, Preferably (d_max/ 2) <d_th<D_maxThe threshold d that satisfies_thShould be set.
[0085]
Referring to the above equation (6), the maximum residual d_maxAre expressed using only the radius of the wafer W and the length of the measurement visual field Vc in the Y direction, and these are information obtained in advance before the processing of the wafer W. The front / back discrimination unit 35 shown in FIG._thIs set. The front / back discrimination unit 35 determines that the maximum value of the calculated residual d is the threshold value d described above._th(Residual d is greater than threshold d_thIs larger than the pre-alignment sensor 22c, it is determined that the arc edge CE is arranged immediately below the pre-alignment sensor 22c._thIs not exceeded (residual d is equal to threshold d_thIn the following case), it is determined that the sub-orientation flat OF1 is disposed immediately below the pre-alignment sensor 22c. The case where the determination is made using the maximum value of the residual d has been described above as an example. However, when the determination is made using the variance or the standard deviation of the residual d or both, the threshold value is similarly set and the determination is performed. I do.
[0086]
Also, the maximum value d of the residual d_maxThe present invention is not limited only to the case of using only. For example, some points having a large residual may be selected, and if the total value of the points exceeds a predetermined threshold, a discrimination method of determining that the arc is an arc may be used. For example, n points are extracted in descending order of the residual d, and each residual (d_max~ D_n) (D_max+ D_max-1+ ... + d_n) May be compared with a predetermined threshold. Alternatively, the maximum value d of the residual d_max, The n-th (eg, second) largest residual (d_max-1) (By comparing the n-th residual with a threshold for the n-th residual) to determine whether the arc is an arc or an orientation flat. As described above, the maximum value d of the residual d_maxBy using the n-th largest residual instead of using only the difference, for example, if there is a “jump” in the measured value due to the influence of dust or the like, the “jump value” affected by the dust Is the maximum residual d_max, It is possible to prevent erroneous determination of the front and back.
[0087]
As described with reference to FIG. 5, in a state where the orientation flat OF is disposed immediately below the pre-alignment sensors 22a and 22b, the arc edge CE is disposed immediately below the pre-alignment sensor 22c or the sub-orientation flat OF1 is disposed. Can be determined, it is possible to determine whether the wafer W is disposed on the center table with the front surface facing upward or the back surface facing upward. Therefore, using this relationship, the front / back discrimination unit 35 discriminates the front / back of the wafer W placed on the substrate table 14 (step S15). The result of the front / back discrimination of the wafer W is output to the control unit 31. With the above processing, the front / back discrimination of the wafer W is completed, and the processing returns to the main routine shown in FIG.
[0088]
When the process returns to the main routine, a process of calculating the position information of the wafer W is performed (Step S5). FIG. 11 is a flowchart illustrating a process of calculating the position information of the wafer W. When the position information calculation process of the wafer W is started, first, the control unit 31 provided in the main control system 20 sets the front surface of the wafer W on the substrate table 14 to the upper side based on the determination result of the front / back determination unit 35. Then, it is determined whether or not they are arranged (step S21).
[0089]
When it is determined that the wafer W is placed on the substrate table 14 with the front side up (when the determination result is “YES”), a well-known method conventionally used (for example, Patent Document 1 described above) Or, the position information of the wafer W is calculated using the method described in 2) (Step S22). Here, when the wafer W is placed on the center table with the front surface facing upward, the wafer W is arranged with respect to the pre-alignment sensors 22a, 22b, and 22c in the state shown in FIG. And the imaging data D1 shown in FIG. 6 is obtained from each of the pre-alignment sensors 22a, 22b, 22c.
[0090]
As described above, the wafer W is obtained by newly forming the sub-orientation flats OF1 and OF2 on the conventional one having the orientation flat OF formed thereon, and observing the orientation flat OF and the arc edge CE. The obtained measurement result is the same as the measurement result obtained by observing the conventional wafer W. For this reason, when calculating the position information of the wafer W placed on the center table with the front surface facing upward, the position information is calculated using a conventionally used method.
[0091]
The following is a brief description of a conventionally used method for calculating position information. First, under the control of the control unit 31 shown in FIG. 3, the outer edge extracting unit 33 reads out the imaging data D1 stored in the imaging data storage area 41 and includes a plurality of outer edge points along the outer edge of the wafer W. Extract point clouds and find their positions. Here, the extracted point group is the outer edge point Pa shown in FIG._i, Outer edge point Pb_j, And the outer edge point Pc_kIt is. Here, i is an integer satisfying 1 ≦ i ≦ n1, and j is an integer satisfying 1 ≦ j ≦ n2. Note that n1 and n2 are integers of 2 or more. All of the extracted outer edge points are stored in the outer edge information storage area 42.
[0092]
Next, under the control of the control unit 31, the straight line approximation unit 34 stores the outer edge point Pa from the outer edge information storage area 42._iAnd outer edge point Pb_jAre read out, a straight line approximation is performed for each of them using the least squares method, and information representing the obtained approximate straight line is stored in the approximate straight line storage area 43. Then, under the control of the control unit 31, the rotation amount calculation unit 36 reads the approximate straight line stored in the approximate straight line storage area 43, calculates the rotation amount of the wafer W with respect to the X axis, and stores the calculated rotation amount in the rotation information. It is stored in the area 44.
[0093]
When the above processing is completed, under the control of the control unit 31, the position information calculation unit 37 stores the outer edge point Pc in the outer edge information storage area 42._kAnd the rotation amount is read from the rotation information storage area 44 to calculate the center position (reference position) of the wafer W. In calculating the center position of the wafer W, the outer edge point Pa is used instead of the rotation amount of the wafer W._iAnd outer edge point Pb_jMay be used, or an approximate straight line of the orientation flat OF may be used. When calculating the center position of the wafer W, the outer edge point Pc_kMay be used, and not all of them may be used.
[0094]
The center position of the wafer W thus calculated is stored in the position information storage area 45. With the above processing, the processing for calculating the position information of the wafer W when the wafer W is placed on the center table with the front surface facing upward is completed, and the processing returns to the main routine shown in FIG.
[0095]
On the other hand, when it is determined in step S21 that the wafer W is placed on the center table with the back surface facing upward (when the determination result is “NO”), the process proceeds to step S23. Here, when the wafer W is placed on the center table with the back surface facing upward, as shown in FIG. 7, a state in which a linear outer edge is observed in all of the pre-alignment sensors 22a, 22b, and 22c. Therefore, the center position of the wafer W cannot be obtained by using the above-described conventional method. Therefore, in the present embodiment, the center position of the wafer W is calculated using the following method.
[0096]
First, in step S23, a process of linearly approximating the orientation flat OF is performed. In this process, under the control of the control unit 31 shown in FIG. 3, the outer edge extracting unit 33 reads out the imaging data D1 stored in the imaging data storage area 41 and reads out the imaging data D1 from a plurality of outer edge points along the outer edge of the wafer W. Then, a set of points is extracted and their positions are obtained. Here, the extracted point group is the outer edge point Pa shown in FIG._iAnd outer edge point Pb_jIt is. All of the extracted outer edge points are stored in the outer edge information storage area 42. In the following description, the outer edge point Pa_i(Xa_i, Ya_i) And outer edge point Pb_j(Xb_j, Yb_j), The outer edge point Pd_m(Xd_m, Yd_m). Here, m is an integer satisfying 1 <m ≦ (n1 + n2).
[0097]
Next, under the control of the control unit 31, the straight line approximation unit 34 stores the outer edge point Pd stored in the outer edge information storage area 42._mIs read, and linear approximation is performed using the least squares method. Information representing the obtained approximate straight line is stored in the approximate straight line storage area 43.
[0098]
When the above process is completed, a process of linearly approximating the sub-orientation flat OF1 is performed (step S24). In this process, under the control of the control unit 31 shown in FIG. 3, the outer edge extracting unit 33 reads out the imaging data D1 stored in the imaging data storage area 41 and reads out the imaging data D1 from a plurality of outer edge points along the outer edge of the wafer W. Then, a set of points is extracted and their positions are obtained. Here, the extracted point group is the outer edge point Pc shown in FIG._kIt is. All of the extracted outer edge points are stored in the outer edge information storage area 42. Next, under the control of the control unit 31, the straight line approximation unit 34 stores the outer edge point Pc stored in the outer edge information storage area 42._kIs read, and linear approximation is performed using the least squares method. Information representing the obtained approximate straight line is stored in the approximate straight line storage area 43.
[0099]
Here, the equation of the approximate straight line (orthogonal regression line) of the orientation flat OF obtained in step S23 is changed to a variable “a”.₁”,“ B₁And the expression of the approximate straight line (orthogonal regression line) of the sub-orientation flat OF1 obtained in step S24 by using the variable “a”.₂”,“ B₂And is expressed by the following equation (8).
[0100]
(Equation 7)

[0101]
(Equation 8)

[0102]
In the above equation (7), (n1 + n2) outer edge points Pd_mX coordinate of Xd_mAnd Y coordinate Yd_mIs expressed in the form of a matrix, and the simultaneous equations obtained by substituting each of the following equations are given by the following equation (9).
[0103]
(Equation 9)

[0104]
Similarly, in the above equation (8), n3 outer edge points Pc_kX coordinate of Xc_kAnd Y coordinate Yc_kAre expressed in the form of a matrix, and the simultaneous equations obtained by substituting each of the above are given by the following equation (10).
[0105]
(Equation 10)

[0106]
Here, the above equation (9) is represented as the following equation (11), and the above equation (10) is represented as the following equation (12).
[0107]
(Equation 11)

[0108]
(Equation 12)

[0109]
The solution to be sought (matrix p in equation (11) above)₁And the matrix p in the above equation (12)₂) Is obtained from the following equations (13) and (14) by the least square method.
[0110]
(Equation 13)

[0111]
[Equation 14]

[0112]
That is, the first row of the matrix obtained by solving the above equation (13) is the variable “a” in the above equation (7).₁, And the second line is the variable “b” in the above equation (7).₁". The first row of the matrix obtained by solving the above equation (14) is the variable “a” in the above equation (8).₂, And the second line is the variable “b” in the above equation (8).₂". Note that, in the above equation (13), A₁ ^tIs the matrix A₁, And in the above equation (14), A₂ ^tIs the matrix A₂Is the transposed matrix of.
[0113]
Through the above processing, the approximate straight line L11 of the orientation flat OF and the approximate straight line L12 of the sub-orientation flat are obtained, and information representing these approximate straight lines L11 and L12 is stored in the approximate straight line storage area 43.
[0114]
Next, a process of obtaining the center position (reference position) of the wafer W using these approximate straight lines L11 and L12 is performed. FIG. 12 is a diagram for explaining a process of obtaining the center position of the wafer W using the approximate straight line L11 of the orientation flat OF and the approximate straight line L12 of the sub-orientation OF1. 12, G1 indicates the distance of the orientation flat OF to the center position of the wafer W, and G2 indicates the distance of the sub-orientation flat OF1 to the center position of the wafer W. These distances G1 and G2 are obtained in advance from design values.
[0115]
Therefore, in the present embodiment, as shown in FIG. 12, the approximate straight line L11 obtained in step S23 is translated in parallel toward the center of the wafer W by the distance G1, and the approximate straight line L12 obtained in step S24 is The wafer W is translated in the direction of the center of the wafer W by a distance G2. Then, an intersection C2 of an approximated straight line (hereinafter, referred to as a post-movement straight line) that has been translated is calculated (step S25), and the intersection C2 is estimated as the center position of the wafer W (step S26). Seeking. In FIG. 12, the amount of rotation of the wafer W is exaggerated.
[0116]
In the above step S25, under the control of the control unit 31 shown in FIG. 3, the rotation amount calculation unit 36 reads out information on the approximate straight line L11 stored in the approximate straight line storage area 43, and sets the X-axis as a predetermined reference. Is calculated (the amount of rotation of the wafer W) of the approximate line L11 with respect to, and the calculated inclination θ is stored in the rotation information storage area 44. Next, under the control of the control unit 31, the position information calculation unit 37 reads out information on the approximate straight lines L11 and L12 stored in the approximate straight line storage area 43, and reads the inclination θ of the approximate straight line L11 from the rotation information storage area 44. And the intersection C2 estimated as the center position of the wafer W is calculated using these.
[0117]
The approximate straight line L11 of the orientation flat OF is represented by the above-described equation (7), and the approximate straight line L12 of the sub-orientation flat OF1 is represented by the above-described equation (8). The moved straight line obtained by translating the approximate straight line L11 toward the center of the wafer W by the distance G1 is expressed by the following equation (15), and the approximate straight line L12 is translated by the distance G2 toward the center of the wafer W. The straight line after the movement is represented by the following equation (16).
[0118]
(Equation 15)

[0119]
(Equation 16)

[0120]
The intersection C2 can be calculated by using the above equations (15) and (16).
[0121]
In the method described above, the intersection C2 is calculated by moving the approximate straight lines L11 and L12 together toward the center of the wafer W, but only one of the approximate straight lines L11 and L12 is positioned at the center of the wafer W. The crossing point C2 can be calculated simply by performing the parallel movement. In this method, for example, only the approximate straight line L11 is moved toward the center of the wafer W, and after this movement, an intersection C3 (see FIG. 12) between the straight line and the approximate straight line L12 that has not been translated is obtained, and then the intersection is obtained. Calculate C2.
[0122]
The moved straight line obtained by translating the approximate straight line L11 toward the center of the wafer W is represented by the above equation (15). After this movement, the coordinates (X) of the intersection C3 obtained by substituting the straight line into the approximate straight line L12 (approximate straight line of equation (8)) that has not been translated.₃, Y₃) Is represented by the following equation (17).
[0123]
[Equation 17]

[0124]
The coordinates (X₃, Y₃), The coordinates (X₂, Y₂) Is represented by the following equation (18).
[0125]
(Equation 18)

[0126]
The coordinates of the intersection C2 (X₂, Y₂) Are stored in the position information storage area 45 as position information. With the above processing, the processing for calculating the position information of the wafer W when the wafer W is placed on the center table with the back surface facing upward is completed, and the processing returns to the main routine shown in FIG.
[0127]
When the process returns to the main routine, the center table is rotated and lowered so as to correct the rotation amount of the wafer calculated in the subroutine S5, and the wafer is suction-held on the substrate holder 15. Note that the wafer center obtained in the subroutine S5 is held as offset information, and is used as an offset when positioning each shot area. Next, the control unit 31 performs exposure preparation measurement other than the above-described measurement of the shape of the wafer W (step S6). That is, the control unit 31 performs preparation operations such as reticle alignment using a reference member (not shown) arranged on the substrate table 14 and measurement of a baseline amount of the alignment detection system AS. The above-mentioned preparation work such as reticle alignment and baseline measurement is disclosed in detail in, for example, JP-A-4-324923 and U.S. Pat. No. 5,243,195 corresponding thereto.
[0128]
When the exposure of the wafer W is the exposure of the second and subsequent layers, the circuit pattern already formed on the wafer W and the circuit pattern with high overlay accuracy are formed. Based on the measurement result, array coordinate position information on the arrangement of the circuit patterns on the wafer W, that is, the arrangement of the shot areas in the above-described reference coordinate system is detected with high accuracy using the alignment detection system AS.
[0129]
When the above process is completed, the wafer W is exposed (Step S7). In this exposure operation, first, the substrate table 14 is moved so that the XY position of the wafer W becomes a scanning start position for exposing the first shot area (first shot) on the wafer W. This movement corresponds to the position information measurement result of the wafer W (mainly the wafer center position information (offset information) obtained in the subroutine S5) read from the position information storage area 45, and the position information from the wafer interferometer 19. (Speed information) etc. (in the case of exposure of the second and subsequent layers, a detection result of array coordinate position information on the reference coordinate system, position information (speed information) from the wafer interferometer 19, and the above offset information, etc.) Is performed by the main control system 20 via the stage control system 21 and the wafer driving device 17. At the same time, reticle stage RST is moved such that the XY position of reticle R becomes the scanning start position. This movement is performed by the main control system 20 via the stage control system 21 and a reticle driving unit (not shown).
[0130]
Next, the stage control system 21 responds to a control command from the main control system 20 so that the Z position information of the wafer W detected by the multipoint focus position detection system and the XY of the reticle R measured by the reticle interferometer 13 are obtained. Based on the position information and the XY position information of the wafer W measured by the wafer interferometer 19, the reticle R and the wafer are adjusted while adjusting the surface position of the wafer W via a reticle driving unit and a wafer driving device 17 (not shown). W is relatively moved to perform scanning exposure.
[0131]
When the exposure of the first shot area is completed in this way, the substrate table 14 is moved so as to be a scanning start position for exposure of the next shot area, and the XY position of the reticle R becomes a scanning start position. Thus, reticle stage RST is moved. Then, scanning exposure for this shot area is performed in the same manner as in the first shot area described above. Thereafter, scanning exposure is performed for each shot area in the same manner, and the exposure is completed. When the exposure of the wafer W is completed, the wafer stage WST is moved to the unload position, and then the wafer W is unloaded from the substrate table 14 by a wafer unloader (not shown) (Step S8). Thus, the exposure processing for one wafer is completed.
[0132]
If the above exposure processing is the first layer scanning exposure, the position of the shot area on the wafer W is corrected based on the above-described position measurement result, and as a result, the arrangement coordinate system of the shot area is designed. Although the shift amount and the rotation amount of the coordinate origin with respect to the upper coordinate system become substantially zero, when the shift amount (shift amount) and the rotation amount of the center position of the wafer W are small, the shot position based on the position information measurement result is determined. The correction need not be performed. Further, when the exposure processing is scanning exposure for the second and subsequent layers, fine alignment is performed prior to scanning exposure, so that the above-described positional information measurement is performed by synchronous movement of the reticle stage RST and wafer stage WST in scanning exposure. There is no need to use the result, and only the movement of wafer stage WST during fine alignment uses the position information measurement result.
[0133]
Further, prior to the scanning exposure for the first layer and the fine alignment for the second layer, for example, the wafer W or the wafer holder 15 may be rotated based on the above-described position information measurement result. In this case, it is not necessary to use the position information measurement result, that is, the rotation amount, in the scanning exposure of the first layer and the fine alignment of the second and subsequent layers. At this time, instead of or in addition to the rotation amount of the wafer W, the position of the wafer W on the wafer holder 15 is finely adjusted based on the information indicating the center position of the wafer W obtained by the above-described position measurement. Therefore, it is not necessary to use information indicating the center position in subsequent operations.
[0134]
As described above, according to the present embodiment, based on the imaging result of the pre-alignment sensor 22c, whether the arc edge CE is located immediately below the pre-alignment sensor 22c, or the sub-orientation flat OF1 is located. Is determined, and the front and back of the wafer W is determined based on the result of the determination. Therefore, the front and back of the wafer W can be quickly and accurately determined. As a result, for example, a situation in which a pattern to be transferred to the front surface of the wafer W is transferred to the rear surface of the wafer W can be prevented, and devices can be manufactured with a high yield.
[0135]
Further, since the approximate straight line of the orientation flat OF and the approximate straight line of the sub-orientation flat OF1 are obtained, these are translated toward the center of the wafer W, and the intersection of the straight line after the movement is estimated as the center of the wafer W. All of the pre-alignment sensors 22a, 22b, 22c have straight outer edges as in the case where the orientation flat OF is located directly below the alignment sensors 22a, 22b and the sub-orientation flat OF1 is located immediately below the pre-alignment sensor 22c. The position information of the wafer W can be obtained even in a situation of observation.
[0136]
The embodiments described above are described for facilitating the understanding of the present invention, and are not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.
[0137]
For example, in the above embodiment, for the sake of convenience, in step S4 for discriminating the front and back of the wafer W and step S5 for calculating the position information of the wafer W shown in FIG. To find an approximate straight line. However, the point cloud extraction processing and the linear approximation processing are collectively performed on each of the imaging data D1 (imaging data of the pre-alignment sensors 22a, 22b, and 22c) obtained by performing the imaging in step S3, and FIG. By storing the respective processing results in the outer edge information storage area 42 and the approximate straight line storage area 43 and reading out the necessary information when needed, the processing efficiency can be improved.
[0138]
Further, in the above embodiment, it is determined whether the arc edge CE is disposed immediately below the pre-alignment sensor 22c or the sub-orientation flat OF1 is disposed, and the front and back of the wafer W are determined only based on the determination result. Although the discrimination has been performed, it is determined whether the pre-alignment sensors 22a, 22b, and 22c have a straight contour or a curved contour located immediately below each of them. It is also possible to make a front / back determination.
[0139]
Further, in the above-described embodiment, the case where the present invention is used in an exposure apparatus has been described as an example. However, the present invention is not limited to an exposure apparatus, but also an inspection apparatus for inspecting the overlay accuracy of a pattern formed on a wafer, a An inspection device for inspecting a line width of a formed pattern, an inspection device for inspecting a macro (macroscopic) defect of a pattern formed on a wafer, and a position of a wafer to be inspected with a predetermined accuracy in other inspection devices. Can be used to match.
[0140]
In the above-described embodiment, the wafer (substrate) has been described as an inspection target. However, the inspection target is not limited to the wafer as long as the object has both an arc-shaped contour and a linear contour. .
[0141]
In the above embodiment, the case where the present invention is applied to a step-and-scan type exposure apparatus has been described as an example. However, the present invention is also applicable to a step-and-repeat type exposure apparatus (stepper). Can be. In the above embodiment, the laser light emitted from the ArF excimer laser or the like is used as the illumination light IL. However, a soft X-ray region generated from a laser plasma light source or SOR, for example, a wavelength of 13.4 nm, or 11.3. EUV (Extreme Ultra Violet) light of 5 nm may be used. Further, a charged particle beam such as an electron beam or an ion beam may be used. Further, the projection optical system may use any one of a reflection optical system, a refractive optical system, and a catadioptric optical system.
[0142]
Further, a single-wavelength laser in the infrared or visible range oscillated from a DFB semiconductor laser or a fiber laser is amplified by, for example, a fiber amplifier doped with erbium (or both erbium and yttrium), and a nonlinear optical crystal is used. Alternatively, a harmonic converted to ultraviolet light may be used.
[0143]
Further, not only an exposure apparatus for transferring a device pattern used for manufacturing a semiconductor element onto a wafer, but also an exposure apparatus for transferring a device pattern used for manufacturing a display including a liquid crystal display element onto a glass plate, a thin film magnetic head The present invention can also be applied to an exposure apparatus for transferring a device pattern used for manufacturing a semiconductor wafer onto a ceramic wafer, an exposure apparatus used for manufacturing an imaging device (such as a CCD), a micromachine, a DNA chip, and the like.
[0144]
By the way, a reflection type mask is used in an exposure apparatus using EUV light, and a transmission type mask (stencil mask, membrane mask) is used in an electron beam exposure apparatus or the like. Therefore, a silicon wafer or the like is used as an original mask.
[0145]
The illumination optical system and projection optical system composed of multiple lenses are incorporated into the exposure apparatus body for optical adjustment, and a reticle stage and substrate stage consisting of many mechanical parts are attached to the exposure apparatus body to connect wiring and piping. The exposure apparatus according to the present embodiment can be manufactured by performing overall adjustment (electric adjustment, operation check, and the like). It is desirable that the manufacture of the exposure apparatus be performed in a clean room in which the temperature, cleanliness, and the like are controlled.
[0146]
The semiconductor element has a step of designing the function and performance of the device, a step of manufacturing a reticle based on this design step, a step of manufacturing a wafer from a silicon material, and a step of manufacturing the reticle pattern by the exposure apparatus of the above-described embodiment. It is manufactured through a step of exposing and transferring to a device, a step of assembling a device (including a dicing step, a bonding step, and a package step), an inspection step, and the like.
[0147]
【The invention's effect】
According to the present invention, a point group is extracted along a part of the contour of an imaged object, a straight line approximation is performed on the extracted point group to calculate an approximate straight line, and a positional relationship between the approximate straight line and the point group is calculated. It is determined whether a part of the contour is a linear contour or a curvilinear contour according to the above. Therefore, a part of the contour of the imaged object is a linear contour or a curvilinear contour. This has the effect that it can be determined quickly and accurately.
[0148]
Further, according to the present invention, it is possible to quickly and accurately determine whether an imaging result of an imaging device disposed at a predetermined position is a straight contour or a curved contour, and based on these determination results, Since the front and back sides are determined, there is an effect that the front and back sides of the object can be quickly and accurately determined.
[0149]
Further, according to the present invention, the front and back of the substrate as an object are quickly and accurately determined, and the pattern on the substrate is controlled while performing the position control of the substrate based on the measured position information and rotation position information of the substrate. Is transferred, for example, it is possible to prevent a situation where a pattern to be transferred to the front surface of the substrate is transferred to the back surface of the substrate, and it is possible to manufacture a device with a high yield.
[Brief description of the drawings]
FIG. 1 is a diagram schematically illustrating an overall configuration of an exposure apparatus according to an embodiment of the present invention.
FIG. 2 is a plan view schematically showing a configuration around a pre-alignment detection system.
FIG. 3 is a block diagram illustrating an internal configuration of a main control system provided in the exposure apparatus according to the embodiment of the present invention.
FIG. 4 is a flowchart illustrating an outline of an operation at the time of exposure of the exposure apparatus according to the embodiment of the present invention.
FIG. 5 is a top view showing a state where a wafer is arranged at an imaging position of a pre-alignment sensor.
FIG. 6 is a diagram illustrating an example of an imaging result of a pre-alignment sensor when a wafer is arranged with its front side facing upward.
FIG. 7 is a diagram illustrating an example of an imaging result of a pre-alignment sensor when a wafer is placed with its back surface facing upward.
FIG. 8 is a flowchart illustrating a front / back discrimination process of a wafer.
FIG. 9 is a diagram exemplifying a positional relationship between an arc edge or a linear outer edge and an approximate straight line.
FIG. 10 is a diagram for explaining an example of a threshold value set when determining whether or not the captured outer edge is an arc edge.
FIG. 11 is a flowchart illustrating a process for calculating wafer position information.
FIG. 12 is a diagram for explaining a process of obtaining a center position of a wafer using an approximate straight line of an orientation flat and an approximate straight line of a sub-orientation.
[Explanation of symbols]
1. Exposure equipment
14 ... Substrate table (stage)
16. Wafer stage device (stage device)
20: Main control system (control device, control computer)
22a to 22c: Pre-alignment sensor (imaging device)
33 ... Outer edge extraction unit (point group extraction unit)
34 linear approximation unit
35 front / back discrimination unit (judgment unit)
CE: Arc edge (curved contour)
OF: Orientation flat (straight contour)
OF1 ... Sub-orientation flat (linear contour)
OF2: Sub-orientation flat (linear contour)
RAS: Pre-alignment detection system (imaging device)
W: Wafer (substrate)

Claims (18)

A position measurement method for measuring position information of an object having a linear contour and a curved contour,
An imaging step of imaging a part of the contour of the object,
A point group extraction step of extracting a point group consisting of a plurality of points along a part of the contour of the object based on an imaging result of the imaging step;
A linear approximation step of linearly approximating the point group,
A determining step of determining whether a part of the contour is the linear contour or the curvilinear contour according to a positional relationship of the point group with respect to the approximate straight line obtained in the straight line approximating step. A position measuring method, characterized in that: The position measuring method according to claim 1, wherein the determining step performs the determination according to a distance of at least one point in the point group with respect to the approximate straight line as the positional relationship. The said determination process uses the maximum value of the distance of each point which comprises the said point group with respect to the said approximate line as the said positional relationship, and performs the said determination according to the magnitude | size of the maximum value of the said distance. 2. The position measurement method according to 1. The determination step, a threshold setting step of setting a threshold value according to the curvature of the curved contour and the length of a chord of a part of the contour imaged in the imaging step,
When the maximum value of the distance is larger than the threshold, a part of the contour is a curved contour, and when the maximum value of the distance is equal to or less than the threshold, a part of the contour is linear. 4. The position measuring method according to claim 3, further comprising a determining step of determining that the position is a contour. The determination step uses a statistical distribution of the distance of each point forming the point group with respect to the approximate line as the positional relationship, and performs the determination according to at least one of a standard deviation and a variance of the statistical distribution. The position measurement method according to claim 1. The determination step, a threshold setting step of setting a threshold value according to the curvature of the curved contour and the length of a chord of a part of the contour imaged in the imaging step,
When at least one of the standard deviation and the variance of the statistical distribution is larger than the threshold, a part of the contour is a curved contour, and when at least one of the standard deviation and the variance is equal to or less than the threshold. 6. The method according to claim 5, further comprising: determining that a part of the contour is a linear contour. The position measuring method according to claim 1, wherein the linear approximation step is a step of linearly approximating the point group using a least squares method. The image capturing step is a step of capturing an image of a part of the contour of the substrate as the object using an image capturing device disposed at a predetermined position in advance,
The position measurement according to any one of claims 1 to 7, further comprising: a front / back discrimination step of discriminating between front and back of the substrate based on a determination result obtained by performing the determination on the imaging result. Method. When it is determined that a part of the contour imaged in the imaging step is the linear contour, position information representing a part of the contour and a slope of the linear contour with respect to a predetermined reference are obtained. 8. A position information calculating step of obtaining position information representing a part of the contour when it is determined that a part of the contour imaged in the step is the curved contour. The position measurement method according to any one of the above. The imaging step is a step of imaging a part of the contour of the object at a plurality of locations having a predetermined positional relationship set in advance,
A rotation position information calculation step of obtaining rotation position information of the object based on each position information and inclination obtained by performing the determination step and the position information calculation step for each of the imaging results obtained at the plurality of locations. The position measuring method according to claim 9, further comprising: 11. The method according to claim 10, further comprising: a front / back discrimination step of discriminating between front and back of the substrate as the object based on a determination result obtained by performing the determination on each of the imaging results obtained at the plurality of locations. The position measurement method described. A position measuring device that measures position information of an object having a linear contour and a curved contour,
An imaging device for imaging a part of the contour of the object,
A point group extraction unit configured to extract a point group including a plurality of points along a part of the outline of the object based on an imaging result of the imaging device, a straight line approximation unit that linearly approximates the point group, and the straight line A control device having a determination unit that determines whether a part of the contour is the linear contour or the curved contour according to the positional relationship of the point group with respect to the approximate straight line obtained by the approximating unit. A position measuring device comprising: The imaging device is a device that images a part of the contour of the substrate as the object at a plurality of locations having a predetermined positional relationship set in advance,
13. The control device according to claim 12, wherein the control device includes a front / back determination unit configured to determine the front / back of the substrate based on a determination result of the determination unit for each of the imaging results obtained at the plurality of locations. Position measuring device. The control device includes:
For each of a part of the contour obtained at the plurality of locations, when the determination result of the determination unit is the linear contour, the position information representing a part of the contour and the linear shape with respect to a predetermined reference Calculating a slope of the contour, and a position information calculation unit for obtaining position information representing a part of the contour when the determination result of the determination unit is the curved contour;
14. The position measuring device according to claim 13, further comprising: a rotation position information calculation unit that obtains rotation position information of the substrate based on a calculation result of the position information calculation unit. An exposure method for transferring a predetermined pattern to a substrate,
A substrate measurement step of obtaining position information, rotation position information, and information indicating front and back of the substrate as the object by the position measurement method according to claim 10,
A transfer step of transferring the pattern to the substrate while controlling the position of the substrate based on the position information of the substrate obtained in the substrate measurement step, the rotational position information, and the information indicating the front and back. Exposure method characterized by the above-mentioned. An exposure apparatus that transfers a predetermined pattern onto a substrate,
The position measurement device according to claim 14, wherein position information of the substrate as the object, rotational position information, and information indicating front and back are obtained.
An exposure apparatus, comprising: a stage device having a stage on which the substrate measured by the position measurement device is mounted. A program for causing a control computer of an exposure apparatus that transfers a predetermined pattern to a substrate having a linear contour and a curved contour to measure position information of the substrate,
A capturing step of capturing an imaging result obtained by imaging a part of the contour of the substrate at a plurality of locations having a predetermined positional relationship set in advance,
For each of the imaging results captured in the capturing step, whether a part of the contour is the linear contour, or a determination step of determining whether the curved contour,
A program for causing the control computer to execute a front / back discrimination step of discriminating between front and back of the substrate in accordance with a result of the determination in the determination step. Position information calculating step of calculating the inclination of the linear outline with respect to a predetermined reference and position information representing a part of the outline according to the determination result of the determination step,
The control computer executes a rotation position information calculation step of obtaining rotation position information of the substrate based on the determination result of the determination step and the position information and the inclination obtained in the position information calculation step. The program according to claim 17, which performs the program.

Images