JP4204331B2 - Projection exposure equipment - Google Patents

Description

【００５６】
ＳＲおよびＭｇｎ_ｐを数１に基づいて設定すると、不鮮明領域の大きさｂはｂ_ｍａｘとなる。また、ＳＲとＲ_ｘの差、およびＭｇｎ_ｐとＲ_ｙの差のいずれか大きい方の値が最小になる。マスク４の中心からＸ軸方向にｄｘ、Ｙ軸方向にｄｙ離れた位置にあるパターンの像は、プリント基板Ｂの中心からＸ軸方向にＲ_ｘ×ｄｘ、Ｙ軸方向にＲ_ｙ×ｄｙ離れた位置に投影されることが望ましい。ＳＲおよびＭｇｎ_ｐを数１に基づいて設定する場合、不鮮明領域の大きさｂを許容値ｂ_ｍａｘ以内に抑えつつ、パターンが投影される位置の、望ましい位置からのずれ量を最小にすることが可能となる。
【００５７】
また、｜Ｒ_ｘ−Ｒ_ｙ｜≦Ａの時は、ＳＲとＭｇｎ_ｐは数２を満たすよう設定される。
【００５８】
【数２】

【００５９】
ＳＲおよびＭｇｎ_ｐを数２に基づいて設定すると、不鮮明領域の大きさｂは許容値ｂ_ｍａｘ以下となる。マスク４の中心からＸ軸方向にｄｘ、Ｙ軸方向にｄｙ離れた位置にあるパターンの像は、プリント基板Ｂの中心からＸ軸方向にＲ_ｘ×ｄｘ、Ｙ軸方向にＲ_ｙ×ｄｙ離れた位置に投影される。従って、ＳＲおよびＭｇｎ_ｐを数２に基づいて設定する場合、不鮮明領域の大きさｂを許容値ｂ_ｍａｘ以内に抑えつつ、パターンが投影される位置の、望ましい位置からのずれ量を０にすることが可能となる。
【００６０】
また、（Ｒ_ｘ−Ｒｙ）＜−Ａの時は、ＳＲとＭｇｎ_ｐは数３を満たすよう設定される。
【００６１】
【数３】

【００６２】
ＳＲおよびＭｇｎ_ｐを数３に基づいて設定すると、不鮮明領域の大きさｂはｂ_ｍａｘとなる。また、ＳＲとＲ_ｘの差、およびＭｇｎ_ｐとＲ_ｙの差のいずれか大きい方の値が最小になる。マスク４の中心からＸ軸方向にｄｘ、Ｙ軸方向にｄｙ離れた位置にあるパターンの像は、プリント基板Ｂの中心からＸ軸方向にＲ_ｘ×ｄｘ、Ｙ軸方向にＲ_ｙ×ｄｙ離れた位置に投影されることが望ましい。ＳＲおよびＭｇｎ_ｐを数３に基づいて設定する場合、不鮮明領域の大きさｂを許容値ｂ_{ｍ ａｘ}以内に抑えつつ、パターンが投影される位置の、望ましい位置からのずれ量を最小にすることが可能となる。
【００６３】
図９は、基板ホルダ８およびプリント基板ＢをＹ軸負の方向から見た概略図である。基板高さ検出機構３８はプリント基板Ｂ上に塗布された感光剤と反応しない波長および強度のレーザ光ＬＢをプリント基板Ｂに向けてＸＺ平面上斜め方向に入射させるレーザ光源３８ａと、３８ａより出射した光をプリント基板Ｂ上に集光させる凸レンズ３８ｄと、プリント基板Ｂ上で反射したレーザ光ＬＢを受光する受光部３８ｂと、凸レンズ３８ｃを有する。凸レンズ３８ｃは受光部３８ｂの受光面の手前に、その光軸が反射したレーザ光ＬＢの光軸と平行になるよう配置されており、プリント基板Ｂ上で反射したレーザ光ＬＢを屈折させて受光部３８ｂの受光面内に収める。プリント基板Ｂ上の反射位置と受光部３８ｂは凸レンズ３８ｃの共役位置にあり、倍率μの関係になっている。尚、倍率μとはおよそ凸レンズ３８ｃと受光部３８ｂ間の光軸方向の長さΛ２と、プリント基板Ｂ上反射面と凸レンズ３８ｃ間の光軸方向の長さΛ１の比Λ２／Λ１である。プリント基板Ｂ上で反射した時点でのレーザ光ＬＢが凸レンズ３８ｃの光軸よりもＺ軸負の方向寄り（すなわち、プリント基板Ｂ寄り）のときは、レーザ光ＬＢは凸レンズ３８ｃの光軸よりもＺ軸正の方向寄りの位置に入射する。
【００６４】
受光部３８ｂは受光部３８ｂの受光面のどの位置にレーザ光ＬＢが入射したのかを検出可能であり、この入射位置からプリント基板Ｂの高さを検出可能である。
【００６５】
基板高さ検出機構３８を用いたプリント基板Ｂの高さの検出方法を以下に詳説する。なお、受光部３８ｂの受光面の中心（受光面と凸レンズ３８ｃの光軸とが交差する点）にレーザ光ＬＢが入射したときの基板高さＢＨ_０をあらかじめ実験によって算出する。
【００６６】
ここで、レーザ光ＬＢの入射位置が凸レンズ３８ｃの光軸と受光部３８ｂの受光面との交点からΔＬ_Ｄだけずれている場合、その時の基板高さＢＨは数４によって演算される。なお、レーザ光ＬＢの入射位置がプリント基板Ｂから遠ざかる方向に移動している場合はΔＬ_Ｄ＞０、プリント基板Ｂに近づく方向に移動している場合はΔＬ_Ｄ＜０としている。また、θはレーザ光ＬＢの入射角である。
【００６７】
【数４】

【００６８】
ここでＢＨをより精度良く検出する為にはあらかじめ実験等によりＢＨの変化に対するΔＬ_Ｄを計測しておく方法もある。
【００６９】
以上の方法にて算出したプリント基板Ｂの高さＢＨ、および折り返しミラー５の位置から、マスク４からレンズユニット６に至る光路長とレンズユニット６からプリント基板Ｂの露光面に至る光路長との和Ｄ_Ｌを演算可能となっている。
【００７０】
マスク４上に形成されたパターンがプリント基板Ｂ上にピントが合った状態で結像するようにするためにはレンズユニット６に対してマスク４とプリント基板Ｂの露光面とが共役の関係となるように配置されていなければならない。本実施形態においてはレンズユニット６は固定されており、またマスク４および基板ホルダ８はＺ軸方向には移動しない。
【００７１】
上記のような構成の露光装置１においては、折り返しミラー５をＸ軸方向に移動させることにより、マスク４とプリント基板Ｂの露光面とが共役の関係となるようにしてピント合わせが行われる。距離ＤＬがレンズユニット６の焦点距離の２倍であるとき、マスク４とプリント基板Ｂの露光面とが共役の関係となる。以下、折り返しミラー５の移動によってマスク４上に形成されたパターンがプリント基板Ｂ上に結像するようにする手順を図１０を用いて説明する。
【００７２】
図１０は、図１の投影露光装置１をＹ軸方向に投影した側面図である。図７においては、図面の簡略化のためレンズユニット６は一枚の凸レンズとして、またダハミラー７は１枚の平面鏡として記載されている。コントローラ１０は距離Ｄ_Ｌとレンズユニット６の焦点距離ｆを比較し、プリント基板Ｂの露光面とマスクのレンズユニット６による結像面との距離の差ΔＤ_Ｌ＝Ｄ_Ｌ−２ｆを求める。次いで、ΔＤ_Ｌ＞０ならばＸ軸正の方向に、またΔＤ_Ｌ＜０ならばＸ軸負の方向に折り返しミラー５を距離|ΔＤ_Ｌ|／２だけ移動させる。ここで、図７においてはΔＤ_Ｌ＞０であり、レンズユニット６による結像面の位置はプリント基板Ｂの露光面よりもＺ軸正の方向に|ΔＤ_Ｌ|だけ移動した位置（図１０中２点鎖線で図示された位置）となる。折り返しミラー５をＸ軸正の方向に距離|ΔＤ_Ｌ|／２だけ移動させたときの折り返しミラー５を破線で、またその時の光路を一点鎖線で示す。このときのマスク４からレンズユニット６に至る光路長とレンズユニット６からプリント基板Ｂの露光面に至る光路長との和Ｄ_Ｌは折り返しミラー５を動かす前の距離Ｄ_Ｌよりも|ΔＤ_Ｌ|だけ短くなっており、Ｄ_Ｌ＝２ｆとなる。従ってマスク４とプリント基板Ｂの露光面とが共役の関係となり、マスク４上に形成されたパターンはプリント基板Ｂ上に結像するようになる。従って、上記のように前工程でプリント基板Ｂの高さを計測し、結像位置を調整することで、投影露光装置１は厚さの異なるプリント基板に対応可能となっている。
【００７３】
次いで、マスク４の像がプリント基板Ｂ上に結像するときの倍率を上記の演算によって求めた倍率Ｍｇｎ_ｐに設定する。倍率の設定は、コントローラ１０がダハミラー駆動機構１７を制御してダハミラー７をＸ軸方向に駆動し、さらにコントローラ１０が折り返しミラー駆動機構１５を制御して折り返しミラー５をＺ軸方向に駆動することによって行われる。
【００７４】
図１１および図１２を用いて倍率の設定の原理について説明する。図１１は、レンズユニット６およびダハミラー７をＺ軸正の方向から見た概略図である。図示の簡略のため、レンズユニット６およびダハミラー７はそれぞれ一枚の面として描写されている。また、ダハミラー７に向かう光束を２点鎖線で、ダハミラー７で反射した光束を破線で示す。
【００７５】
倍率を設定するためには、最初にダハミラー７をレンズユニット６の焦点位置７ａからＸ軸正の方向にΔＬ_１移動させる。ダハミラー７をこのように移動させると、レンズユニット６出射時の瞳位置をＸ軸正の方向に２ΔＬ_１ずらす事になる。この結果、平行光束である入射光に対して反射光はテレセン性が扇状に崩れた光束となる。
【００７６】
しかしながら、基板側焦点位置での像の大きさはテレセン性を崩しただけでは変化しない。そこで、レンズユニット６に対するマスク４およびプリント基板Ｂの露光面の相対位置を、マスク４とプリント基板Ｂの露光面とがレンズユニット６に対して共役状態を保つように光学的に移動させる。すなわち、プリント基板Ｂの露光面がレンズユニット６に対して近づけば、プリント基板Ｂの露光面状に結像されるマスクの像は拡大される。反対にプリント基板Ｂの露光面がレンズユニット６に対して遠ざかれば、プリント基板Ｂの露光面状に結像されるマスクの像は縮小される。
【００７７】
レンズユニット６に対するマスク４およびプリント基板Ｂの露光面の相対位置を、マスク４とプリント基板Ｂの露光面とがレンズユニット６に対して共役状態を保つように光学的に移動させるために、折り返しミラー５をＺ軸の方向にΔＤ_１移動させる。なお、ダハミラー７をＸ軸正の方向に移動させた場合に、像を拡大するときは折り返しミラー５をＺ軸負の方向に移動させ、像を縮小するときは折り返しミラー５をＺ軸正の方向に移動させる。また、ダハミラー７をＸ軸負の方向に移動させた場合に、像を拡大するときは折り返しミラー５をＺ軸正の方向に移動させ、像を縮小するときは折り返しミラー５をＺ軸負の方向に移動させる。
【００７８】
図１２は、マスク４、折り返しミラー５、レンズユニット６、ダハミラー７、およびプリント基板ＢをＹ軸負の方向から見たものである。図１２においては、倍率を設定する前の光束を２点鎖線で、またダハミラー７および折り返しミラー５を移動して倍率を設定した後の光束を破線で示している。なお、図１２に示した例においては倍率Ｍｇｎ_ｐ＜１とし、折り返しミラー５はＺ軸正の方向に移動する。
【００７９】
図１１、１２に示すように、ダハミラー７を位置７ａから７ｂへＸ軸正の方向にΔＬ_１移動させ、さらに折り返しミラー５をＺ軸正の方向にΔＤ_１移動させることにより、マスク４を通過した光束が収縮してプリント基板Ｂ上で結像する。このとき、ΔＬ_１およびΔＤ_１は数５を満たす値に設定される。なお、この倍率補正においては、光軸の中心位置は変化しない。
【００８０】
【数５】

【００８１】
図１３は、上記倍率の設定原理によって像の拡大処理が行われた後の光源２、マスク４およびプリント基板ＢをＸ軸正の方向から見たものである。なお、実際の投影露光装置においては、コリメータレンズ３、折り返しミラー５、レンズユニット６およびダハミラー７を介してマスク４のパターンがプリント基板Ｂ上に結像する構成であるが、図１３においては結像状態を明確に示すため光源２、マスク４およびプリント基板Ｂのみ記載するものとする。図１３に示すように、像の拡大処理が行われると、個々の光源２による像のそれぞれは拡大されるものの、それぞれの像のＹ軸方向の結像位置は変化しない。このため、各光源による像がプリント基板Ｂ上で重なり合って、正確にマスク４のパターンがプリント基板Ｂ上に転写されない。従って、各像のＹ軸方向の結像位置を、像同士が重ならないようにそれぞれＹ軸方向にシフトさせるＹシフト処理が行われる。
【００８２】
図１４および図１５は、マスク４、プリント基板Ｂ、レンズユニット６およびダハミラー７をＺ軸正の方向から見た概略図である。図示の簡略のため、レンズユニット６はそれぞれ一枚の面として描写され、さらに折り返しミラー５を省略して基板面およびマスク面の位置はＸＹ平面上に投影されている。
【００８３】
図１４は、Ｙシフト処理を行う前のマスク４、プリント基板Ｂ、レンズユニット６およびダハミラー７の状態を示したものである。この時、マスク４およびプリント基板Ｂは共にレンズユニット６の焦点距離ｆだけレンズユニット６から離れている。また、ダハミラー７はレンズユニット６の焦点位置Ｏ_Ｍに配置されている。なお、光束を２点鎖線で示す。
【００８４】
この時の光束は、図１４のようなマスク４とプリント基板ＢをＸＹ平面上に投影した図においては、入射光と反射光との光路が等しくなる。
【００８５】
Ｙシフト処理は、コントローラ１０がダハミラー駆動機構１７を制御してダハミラー７をＹ軸方向に駆動し、さらにコントローラ１０が折り返しミラー駆動機構１５を制御して折り返しミラー５をＺ軸方向に駆動することによって行われる。
【００８６】
図１５は、Ｙシフト処理を行ってプリント基板Ｂ上の結像位置をＹ軸負の方向にΔＹ移動させたときのマスク４、プリント基板Ｂ、レンズユニット６およびダハミラー７の状態を示したものである。なお、図１５においては、ダハミラー７によって反射する前の光束を２点鎖線で、また反射後の光束を破線で示す。図１４に示すように、ダハミラー７をＯ_Ｍの位置にあるときは、レンズユニット６からダハミラー７に向かう光束の瞳位置はＯ_Ｍである。一方、ダハミラー７をＯ_ＭからＹ軸正の方向に距離ΔＬ_２だけ移動させると、図１５に示すように上記瞳位置はＯ_ＭからＹ軸正の方向に距離２ΔＬ_２だけ移動する。なお、ダハミラー７をＯ_ＭからＹ軸負の方向に移動させると、上記瞳位置もＯ_ＭからＹ軸負の方向にダハミラー７の移動距離の２倍だけ移動する。
【００８７】
この結果、テレセン性が斜めに崩れるが、マスク４およびプリント基板Ｂは共にレンズユニット６の焦点距離ｆだけレンズユニット６から離れている状態では、プリント基板Ｂ上の結像位置はシフトしない。そこで、折り返しミラー５をＺ軸負の方向にΔＤ_２移動させてマスク４とプリント基板Ｂとが共役状態を保つように両者のレンズユニット６からの光路長を変化させる。折り返しミラー５をＺ軸負の方向にΔＤ_２移動させることにより、マスク４からレンズユニット６の光路長はΔＤ_２増加し、レンズユニット６からプリント基板Ｂへの光路長はΔＤ_２減少する。このとき、ΔＬ_２およびΔＤ_２は数６を満たす値に設定される。
【００８８】
【数６】

【００８９】
ここで、数５のΔＤ_１、数６のΔＤ_２は共に折り返しミラー５のＺ軸方向の移動量を示し、「ΔＤ_１＝ΔＤ_２」を満足する状態で数５および数６の他の軸の移動量を求める。
【００９０】
なお、投影露光装置１に用いられている光源および投影光学系の数をｎ_Ｌとすると、ΔＹの値は数７を用いて求められる。
【００９１】
【数７】

【００９２】
ここで、ａは自然数であり、最もＹ軸負側の光源の場合はａ＝１であり、この隣の光源の場合はａ＝２、さらにその隣の光源の場合はａ＝３・・、というようにａ＝ａｍである光源にＹ軸正側に隣接する光源のａの値はａ＝ａｍ＋１となるように設定される。
【００９３】
また、定数Ｗは倍率補正を行なわない時の１つの投影光学系の露光幅である。
【００９４】
図１６はＹシフト処理が行われた後の光源２、マスク４およびプリント基板ＢをＸ軸正の方向から見たものである。図１６に示すように、上記の手順によってＹシフトが行われると、中央の光源２および投影光学系による像はシフトせず、その隣の光源２および投影光学系による像はそれぞれＷ（Ｍｇｎ_ｐ−１）だけ外側にシフトし、さらにその外側に隣接する光源２による像はそれぞれ２Ｗ（Ｍｇｎ_ｐ−１）だけ外側にシフトする。従って、各像のＹ軸方向の結像位置は、像同士が重ならないように配置され、マスク４のパターンが正確にプリント基板Ｂ上に転写される。
【００９５】
次いで、基板ホルダ８の駆動速度が設定される。本実施形態においてはマスク４の駆動速度は所定値Ｖ_Ｍに固定されている。また駆動速度Ｖ_Ｂを、Ｖ_Ｂ＝ＳＲ×Ｖ_Ｍとなるように設定する。
【００９６】
次いで、マスク４とプリント基板ＢとのＸ軸方向の位置合わせを行う。この位置合わせによって、露光時にマスク４のマスク部４ａの中央を通過した光束がプリント基板Ｂのパターン部Ｂ１の中央に入射されるようになる。このように位置合わせを行なうことによって、マスク４のパターンがプリント基板Ｂに転写される時のずれのばらつきを最小限に抑えることができる。
【００９７】
このようにマスク４とプリント基板Ｂとの位置合わせを行った後、光源２を点灯し、マスク４とプリント基板ＢとをＸ軸方向に移動し、マスク４にかかれたパターンをプリント基板Ｂに転写する。
【００９８】
なお、マスク４とプリント基板Ｂとの移動が開始された後も、基板高さ検出機構３８を用いてマスク４からレンズユニット６に至る光路長とレンズユニット６からプリント基板Ｂの露光面に至る光路長との和Ｄ_Ｌは算出されている。Ｄ_Ｌ＝２ｆが常に成立するように折り返しミラー５をＸ方向に駆動することにより、厚さが部位によって異なるようなプリント基板であっても、マスク４上に形成されたパターンをプリント基板Ｂ上に結像させることができる。
【００９９】
【発明の効果】
以上のように、本発明の投影露光装置によれば、マスクの像を主走査方向と副走査方向で異なる伸縮率で露光可能であり、さらに露光される線状の像のエッジ部分を著しく不鮮明なものとすることがない。
【図面の簡単な説明】
【図１】本発明の実施の形態による投影露光装置を模式的に示した概略図である。
【図２】図１に記載の投影露光装置の一部を示したものである。
【図３】本発明の実施の形態のマスクの概略図である。
【図４】本発明の実施の形態のプリント基板の概略図である。
【図５】本発明の実施の形態の別例の、マスク、プリント基板の概略図である。
【図６】従来の投影露光装置において、プリント基板Ｂの主走査方向の伸縮率Ｒ_ｘと副走査方向の伸縮率Ｒ_ｙが等しい場合の露光手順を示したものである。
【図７】従来の投影露光装置において、プリント基板Ｂの主走査方向の伸縮率Ｒ_ｘと副走査方向の伸縮率Ｒ_ｙが異なる場合の露光手順を示したものである。
【図８】図７に示した手順によって露光されたプリント基板の状態を示したものである。
【図９】本発明の実施の形態のプリント基板基板高さ検出機構の概略図である。
【図１０】本発明の実施の形態の投影露光装置のピント合わせ機構を模式的に示した概略図である。
【図１１】本発明の実施の形態の投影露光装置の、レンズユニットおよびダハミラーをＺ軸正の方向から見た概略図である。
【図１２】本発明の実施の形態の投影露光装置の、マスク、折り返しミラー、レンズユニット、ダハミラー、およびプリント基板をＹ軸負の方向から見たものである。
【図１３】本発明の実施の形態において、Ｙシフト操作を行う前の結像状態を模式的に示したものである。
【図１４】本発明の実施の形態の投影露光装置の、マスク、折り返しミラー、レンズユニット、ダハミラー、およびプリント基板をＺ軸正の方向から見たものである。
【図１５】本発明の実施の形態において、Ｙシフト操作を行った後の投影露光装置の、マスク、折り返しミラー、レンズユニット、ダハミラー、およびプリント基板をＺ軸正の方向から見たものである。
【図１６】本発明の実施の形態において、Ｙシフト操作を行った後の結像状態を模式的に示したものである。
【符合の説明】
１ 投影露光装置
２ 光源
３ コリメータレンズ
４ マスク
５ 折り返しミラー
６ レンズユニット
７ ダハミラー
８ 基板ホルダ
１０ コントローラ
１４ マスク駆動機構
１５ 折り返しミラー駆動機構
１７ ダハミラー駆動機構
１８ 基板ホルダ駆動機構
２４ マスク位置検出手段
２８ 基板位置検出手段
３８ 基板高さ検出機構
Ｂ プリント基板[0001]
BACKGROUND OF THE INVENTION
The present invention performs scanning by driving the mask and the printed wiring board in the main scanning direction while transferring an image of the mask in which the predetermined pattern is formed on the printed wiring board by a light source fixed at a predetermined position. The present invention relates to a projection exposure apparatus that forms the predetermined pattern on the printed wiring board.
[0002]
[Patent Document 1]
JP 2000-187332 A
[Prior art]
As a method for drawing a wiring pattern of a printed wiring board, a transparent thin film electrode of a liquid crystal panel, and the like, a projection exposure apparatus has been conventionally used. The projection exposure apparatus projects a light beam emitted from a high-output light source such as an ultra-high pressure mercury lamp onto a mask having a predetermined pattern, and this light beam is further printed on a printed wiring board coated with a photosensitive agent or integrated by an imaging optical system. An image is formed on an object to be exposed such as a circuit or a liquid crystal panel, and a mask pattern is transferred to the object to be exposed.
[0003]
In order to reduce the size of the projection exposure apparatus, a light source for exposure is fixed at a predetermined position, and a scanning projection exposure apparatus that drives a mask and a printed wiring board in a predetermined direction (main scanning direction) is used. Yes.
[0004]
In general, a printed wiring board is formed with a through-hole, copper-plated, and then subjected to surface treatment to remove an oxide film on the copper surface, and finally a photosensitive agent is applied. The printed wiring board expands and contracts by a maximum of about 0.2% by this surface treatment, temperature change, and lamination process. Since the position of the through hole varies as the printed wiring board expands and contracts, such a projection exposure apparatus can set the expansion / contraction rate of the image of the mask pattern formed on the printed wiring board.
[0005]
However, since the surface treatment is performed by means such as polishing a printed wiring board conveyed in a direction such as a conveyor with a polishing material such as a brush, the board depends on the polishing direction (usually the longitudinal direction of the printed wiring board). It is greatly stretched. That is, the expansion / contraction rate of the printed wiring board is different between the longitudinal direction and the lateral direction.
[0006]
For this reason, as in the projection exposure apparatus described in Patent Document 1, for example, the expansion / contraction ratio of the imaging optical system is set to the expansion / contraction ratio of the printed wiring board in the sub-scanning direction, and the drive speed ratio of the printed wiring board to the mask is printed. The expansion / contraction rate in the main scanning direction of the wiring board is used. By using such a configuration, it is possible to perform exposure without misalignment even when performing exposure on a printed circuit board in which the expansion / contraction ratio in the main scanning direction and the expansion / contraction ratio in the sub-scanning direction are different. It has become.
[0007]
However, when the expansion / contraction ratio of the imaging optical system is different from the drive speed ratio of the printed wiring board to the mask, the edge of the exposed image becomes unclear and the size of the fully exposed area is smaller than the design value. There is a problem of becoming. For example, when a linear image is exposed in the form of a printed wiring board, there is a problem that the line width is extremely small.
[0008]
[Problems to be solved by the invention]
The present invention provides a projection exposure apparatus that can expose an image of a mask with different expansion / contraction ratios in the main scanning direction and the sub-scanning direction, and that does not have a markedly blurred region at the edge portion of the exposed linear image. The purpose is to do.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the projection exposure apparatus of the present invention controls the expansion / contraction rate setting means and the drive mechanism, and compares the expansion / contraction rate of the projection optical system with the ratio of the driving speed of the printed wiring board to the driving speed of the mask. Control means is provided so that the difference is within an allowable value determined by a line width exposed on the printed wiring board.
[0010]
According to the present invention, the expansion / contraction ratio in the main scanning direction of the mask image actually transferred to the printed wiring board is the ratio of the driving speed of the printed wiring board to the driving speed of the mask, while the expansion / contraction ratio in the sub-scanning direction is expansion / contraction. The expansion / contraction rate set by the rate setting means. Therefore, the expansion / contraction ratios in the main scanning direction and the sub-scanning direction can be set to different values. Furthermore, since the size of the unsharp portion of the exposed image edge in the main scanning direction is determined by the difference between the expansion / contraction ratio of the projection optical system and the ratio of the driving speed of the printed circuit board to the driving speed of the mask, this difference is allowed. By suppressing the value within the range, the size of the blurred portion of the edge of the exposed linear image can be sufficiently reduced.
[0011]
Preferably, the projection exposure apparatus includes an expansion / contraction ratio measuring unit capable of measuring the expansion / contraction ratio of the printed circuit board in the main scanning direction and the sub-scanning direction perpendicular to the main scanning direction. The tolerance of the difference is A, and the expansion / contraction rate of the printed wiring board in the main scanning direction and the sub-scanning direction is R, respectively._x, R_yThen,
(R_x-R_y)> A, the ratio SR and the predetermined expansion / contraction rate Mgn_pIs an expression,
SR = (R_x+ R_y+ A) / 2, and
Mgn_p= (R_x+ R_y-A) / 2,
｜ R_x-R_yWhen | ≦ A, the ratio SR and the predetermined expansion / contraction rate Mgn_pIs an expression
SR = R_x,Mgn_p= R_yThe filling
(R_x-R_y) <-A, the ratio SR and the predetermined expansion / contraction rate Mgn_pIs an expression,
SR = (R_x+ R_y-A) / 2, and
Mgn_p= (R_x+ R_y+ A) / 2.
[0012]
The ratio SR and a predetermined expansion / contraction rate Mgn so as to satisfy the above formula_pBy setting this, the size of the unclear portion of the edge of the linear image to be exposed can be made sufficiently small, and the shift amount in the main scanning direction and the shift amount in the sub-scanning direction can be minimized.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 schematically shows the projection exposure apparatus according to the present embodiment. In the following description, the main scanning direction (direction in which the mask and the printed circuit board are driven) is defined as the X axis, the sub scanning direction is defined as the Y axis, and the direction in which the light beam enters the printed circuit board is defined as the Z axis. Further, the direction from the lower left to the upper right in FIG. 1 is positive for the X axis, the direction from the lower right to the upper left in FIG. 1 is positive for the Y axis, and the direction from the lower to the upper side in FIG.
[0014]
The projection exposure apparatus 1 of this embodiment includes a plurality of light sources 2, a plurality of collimator lenses 3, a slit 40, a mask 4, a plurality of folding mirrors 5, a plurality of lens units 6, a plurality of roof mirrors 7, and a substrate holder 8. Although FIG. 1 shows only three sets of an optical system composed of a collimator lens 3, a folding mirror 5, a lens unit 6, and a roof mirror 7, and a light source 2, an actual projection exposure apparatus has a Y-axis direction. A plurality of light sources and a projection optical system are arranged on the substrate, and the entire printed circuit board can be exposed without reciprocating the mask and the printed circuit board. The slit 40 is disposed between the collimator lens 3 and the mask 4 and makes the cross-sectional shape of the light beam incident on the mask 4 rectangular. By making the cross-sectional shape of the light beam rectangular, the light beams from each of the plurality of light sources 2 are arranged without gaps and overlapping in the Y-axis direction in the figure.
[0015]
FIG. 2 shows a part of the projection exposure apparatus 1 shown in FIG. In FIG. 1, a plurality (three sets) of optical systems and light sources 2 including the collimator lens 3, the folding mirror 5, the lens unit 6, and the roof mirror 7 are shown. In FIG. Only one set of each is shown for purposes of illustration. Since the behavior of each optical system of the projection exposure apparatus 1 is the same, the following description will be made with reference to a drawing showing only a single optical system and a light source as shown in FIG.
[0016]
The light source 2 is a light source having a wavelength and an output sufficient for exposing a photosensitive agent applied to a printed circuit board, such as an ultrahigh pressure mercury lamp. The light beam emitted from the light source 2 and directed in the negative Z-axis direction is illuminated by the collimator lens 3 and the slit 40 so as to have a rectangular shape on the mask 4 and then enters the folding mirror 5.
[0017]
The folding mirror 5 is a triangular prism-shaped member having a right isosceles triangular section, and the height direction thereof is parallel to the Y axis. Further, the side surface of the isosceles part of the folding mirror 5 is a reflecting surface, and the normal lines of the reflecting surface are both at an angle of 45 degrees with the X axis. The folding mirror 5 reflects the light beam that has passed through the mask 4, bends it in the positive X-axis direction, enters the lens unit 6, and projects it from the lens unit 6 to the folding mirror 5 in the negative X-axis direction. The light beam is reflected, bent so as to go in the negative direction of the Z axis, and incident on the printed circuit board B fixed to the substrate holder 8. The light beam incident on the printed circuit board B forms an image on the printed circuit board B. That is, an image of the mask 4 is formed on the printed circuit board B, and this image is transferred onto the printed circuit board B by the photosensitive agent applied on the printed circuit board B.
[0018]
The lens unit 6 is a unit in which a plurality of optical members are arranged in the X-axis direction, and functions as a whole as a convex lens.
[0019]
The roof mirror 7 is a mirror configured such that the two reflecting surfaces face inward at an angle of 90 degrees on the XY plane. The roof mirror 7 is disposed near the focal position of the lens unit 6. With this configuration, the pattern of the mask 4 is transferred in the same direction on the substrate B without reversal in the XY directions.
[0020]
The mask 4 and the substrate holder 8 are respectively driven by a mask driving mechanism 14 and a substrate holder driving mechanism 18 and are movable in the X-axis direction. Similarly, the folding mirror 5 is driven by the folding mirror drive mechanism 15 and is movable in the X-axis direction and the Z-axis direction. The roof mirror 7 can be moved in the X-axis direction and the Y-axis direction by the roof mirror drive mechanism 17.
[0021]
Each projection optical system of the projection exposure apparatus 1 includes a mask position detection unit 24 and a substrate position detection unit 28. Each of the mask position detection means 24 and the substrate position detection means 28 includes a lamp having a wavelength region and intensity that does not react with the photosensitive agent applied to the printed circuit board B, and a CCD camera. The mask position detecting means 24 irradiates the mask 4 with a lamp, and acquires an entire image of the mask 4 with a CCD camera. Similarly, the substrate position detection means 28 irradiates the printed circuit board B with a lamp, and acquires an entire image of the printed circuit board B with a CCD camera. Marks for alignment are provided at the four corners of the mask 4 and the printed circuit board B, respectively. The controller 10 detects the mask 4 and the printed circuit board B obtained by the CCD cameras of the mask position detecting means 24 and the substrate position detecting means 28, respectively. By performing image processing on the entire image, the distance between each of the alignment marks and the incident position of the light beam emitted from the light source 2 can be calculated for each of the mask 4 and the printed board B. Further, the controller 10 can calculate the distance between the alignment marks for each of the mask 4 and the printed board B, and compares the distance between the marks on the mask 4 with the distance between the marks on the printed board B. Thus, the magnification for transferring the image of the mask 4 onto the printed circuit board B is determined.
[0022]
When high-precision alignment and magnification correction are required, there is a method of detecting by increasing the magnification by arranging CCD cameras 24 and 28 at the mark positions at the four corners of the mask 4 and the printed circuit board B, respectively. In this case, each CCD camera position with respect to the incident position of the light beam can be recognized, and the interval between the CCD cameras can be calculated from this CCD camera position. Therefore, it is possible to more accurately measure the distance between each of the alignment marks and the incident position of the light beam emitted from the light source 2 from the interval between the CCD cameras and the coordinates of the marks in the captured image of each CCD camera. Is possible.
[0023]
Further, the projection exposure apparatus 1 has a substrate height detection mechanism 38. The controller 10 can detect the position of the exposure surface of the printed board B in the Z-axis direction by controlling the board height detection mechanism 38. A specific configuration of the substrate height detection mechanism 38 will be described later.
[0024]
A method for exposing the image of the mask 4 to the printed circuit board B by the projection exposure apparatus 1 configured as described above will be described below with reference to the drawings.
[0025]
First, the position (Z-axis direction) of the exposure surface of the printed circuit board B and the expansion / contraction ratio of the image of the mask 4 formed on the printed circuit board B are obtained.
[0026]
FIG. 3 is a schematic view of the mask 4 as viewed from the positive direction of the Z axis. The mask 4 is a rectangular plate member whose four sides are parallel to the X axis or the Y axis. A mask portion 4 a on which a printed wiring pattern is formed is formed at the center of the mask 4, and a wiring pattern is not applied on the peripheral portion 4 b of the mask 4.
[0027]
Position detection marks M1a, M1b, M1c, and M1d are patterned at the four corners of the peripheral edge 4b of the mask 4. Each of the marks M1a, M1b, M1c, and M1d is at the four vertices of a substantially rectangular-like quadrangle whose four sides are substantially parallel to the X-axis or Y-axis, and the mask portion 4a is all included in the quadrangle. ing. The controller 10 controls the mask position detecting means 24 so that the distance l between the marks M1a and M1b._11xAnd the distance l between the marks M1c and M1d_12xAnd the distance l between the marks M1b and M1c_11yAnd the distance l between the marks M1a and M1d_12yAnd calculate. Then l_11xAnd l_12xAverage value of_1xAnd l_11yAnd l_12yAverage value of_1yAnd ask.
[0028]
FIG. 4 is a schematic view of the printed circuit board B viewed from the positive direction of the Z axis. Similar to the mask 4, there is a pattern portion B1 to which a printed wiring pattern is transferred at the center of the printed circuit board B. There are position detection marks or holes at the four corners of the peripheral edge B2 of the printed circuit board B, which are designated as M2a, M2b, M2c, and M2d, respectively. M2a, M2b, M2c, and M2d are located at the four vertices of a substantially rectangular-like quadrangle whose four sides are substantially parallel to the X-axis or Y-axis, and all the pattern portions B1 are included in the quadrangle. ing. The controller 10 controls the substrate position detecting means 28 so that the distance l between the marks M2a and M2b._21xAnd the distance l between the marks M2c and M2d_22xAnd the distance l between the marks M2b and M2c_21yAnd the distance l between the marks M2a and M2d_22yAnd calculate. Then l_21xAnd l_22xAverage value of_2xAnd l_21yAnd l_22yAverage value of_2yAnd ask.
[0029]
As described above, l_1x, L_2x, L_1y, L_2yIt is possible to calculate how much the printed circuit board B is expanded and contracted compared to the mask 4 in each of the X-axis direction and the Y-axis direction. Since the printed circuit board B expands and contracts due to the leveling process, temperature change, and lamination process, the expansion / contraction rate differs in the X and Y directions.
[0030]
The projection exposure apparatus 1 of the present embodiment can set the magnification when the image of the mask 4 is formed on the printed circuit board B. The magnification in the Y-axis direction is equal to the magnification of the projection optical system. On the other hand, the magnification in the X-axis direction is determined by the drive speed ratio of the printed circuit board B to the drive speed of the mask 4. The expansion and contraction rates of the printed circuit board B in the X-axis direction and the Y-axis direction are R_x, R_yThen, the magnification Mgn of the projection optical system_pThe drive speed ratio SR of the printed circuit board B to the drive speed of the mask 4 is R_x, R_yIs calculated using
[0031]
In this embodiment, l_1x, L_2x, L_1y, L_2yAnd then the formula R_x= L_2x/ L_1x, R_y= L_2y/ L_1yUsing R_x, R_yIs calculated.
[0032]
Alternatively, as shown in FIG. 5, the mask 4 has a plurality of (two in the drawing) portions 4a.₁4a₂A plurality of (two in the figure) B1 corresponding to the printed circuit board B._a, B1_bAre formed in each part of the mask 4, and marks M2a, M2b, M2c, M2d are formed at the four corners of the printed circuit board B. A mask position detecting unit 24 is arranged for each portion of the mask 4, and a substrate position detecting unit 28 is arranged for each portion of the printed circuit board B.
[0033]
In such a configuration, l for each detection means._1x, L_2x, L_1y, L_2yAnd the average value of each_1xm, L_2xm, L_1ym, L_2ymTo calculate the formula R_x= L_2xm/ L_1xm, R_y= L_{2 y m}/ L_{1 y m}Using R_x, R_yIs calculated. By adopting such a configuration, a more appropriate expansion / contraction rate R_x, R_yCan be obtained.
[0034]
The stretch rate R calculated above_x, R_yUse the appropriate magnification Mgn_pThe procedure for calculating the drive speed ratio SR will be described below.
[0035]
FIG. 6 shows an expansion / contraction ratio R in the main scanning direction of the printed circuit board B in a conventional projection exposure apparatus._xAnd expansion / contraction ratio R in the sub-scanning direction_yThe exposure procedure in the case where they are equal is shown. Note that PO in FIGS. 6 and 7 is a projection optical system corresponding to the folding mirror 5, the lens unit 6, and the roof mirror 7 of the present embodiment. The mask 4 and the printed board B are driven from left to right in FIG.
[0036]
In the procedure shown in FIG. 6, the patterns 50, 52, and 54 formed on the mask 4 from the right to the left in the figure at regular intervals in the main scanning direction are respectively exposed on the printed circuit board B. . The expansion / contraction ratio of the printed circuit board B in the main scanning direction is R_xTherefore, the drive speed ratio SR is R_xbe equivalent to. Further, the magnification Mgn by the projection optical system PO_pIs R_ybe equivalent to. Therefore, SR and Mgn_pAre equal. The interval between the patterns 50 and 52 is assumed to be lpm. Note that the size of the opening of the slit 40 is doubled by lpm.
[0037]
At the time of FIG. 6A, the pattern 50 is located at the center of the opening of the slit 40. Further, the pattern 52 is located at the left end of the slit 40 in the drawing. Further, the light beam passing through the center of the slit 40 is configured to pass through the optical axis of the projection optical system PO. At the time of FIG. 6A, the image of the pattern 50 is projected onto the position 51 on the printed circuit board B located on the extension line of the optical axis of the projection optical system PO. The image of the pattern 52 is a distance Mgn from the position 51 to the left in the figure._pProjected at a position 53 shifted by lpm.
[0038]
FIG. 6B shows a state when the mask 4 is moved to the right in the drawing by a distance lpm from the state of FIG. In the state of FIG. 6B, the pattern 52 is located at the center of the opening of the slit 40. The patterns 50 and 54 are located at the right and left ends of the slit 40 in the drawing.
[0039]
At this time, the printed circuit board B has moved to the right in the drawing by a distance SR × lpm from the state of FIG. In this example, SR = Mgn_pTherefore, at the time of FIG. 6B, on the extension line of the optical axis of the projection optical system PO, the distance SR × lpm (= Mgn) from the position 51 to the left in the figure._pXlpm) There is a shifted position 53. That is, the image of the pattern 52 is projected onto the position 53 at the time of FIG. The image of the pattern 50 is a distance Mgn from the position 53 to the right in the figure._pProjected at a position 51 which is a position shifted by 1 lpm. The image of the pattern 54 is a distance Mgn from the position 53 to the left in the figure._pProjected at a position 55 shifted by lpm.
[0040]
FIG. 6C shows a state when the mask 4 is moved to the right in the drawing by a distance lpm from the state of FIG. 6B. In the state of FIG. 6C, the pattern 54 is located at the center of the opening of the slit 40. The pattern 52 is located at the right end of the slit 40 in the drawing.
[0041]
At this time, the printed circuit board B has moved to the right in the drawing by a distance SR × lpm from the state of FIG. Therefore, at the time of FIG. 6C, it is located on the extension line of the optical axis of the projection optical system PO, and the distance SR × lpm (= Mgn) from the position 53 to the left in the figure._pXlpm) The image of the pattern 54 is projected on the shifted position 55. The image of the pattern 52 is a distance Mgn from the position 55 to the right in the figure._pProjected at a position 53 that is a position shifted by 1 lpm.
[0042]
Therefore, the image of the pattern 52 continues to be projected on the position 53 at all the time points shown in FIGS. In other words, R_x= R_yIn this case, the image of the pattern is exposed on a predetermined position on the printed circuit board only during the time when the pattern passes through the opening of the slit, and the image of the pattern is clearly transferred onto the substrate.
[0043]
On the other hand, FIG. 7 shows an expansion / contraction ratio R in the main scanning direction of the printed circuit board B in the conventional projection exposure apparatus._xAnd expansion / contraction ratio R in the sub-scanning direction_yIs different (R_y> R_x) Shows the exposure procedure. Also in the example of FIG. 7, the mask 4 and the printed circuit board B are driven from left to right in FIG.
[0044]
In the procedure shown in FIG. 7, the patterns 50, 52, and 54 formed on the mask 4 and arranged from the right to the left in the drawing at regular intervals in the main scanning direction are respectively exposed on the printed circuit board B. . The expansion / contraction ratio of the printed circuit board B in the main scanning direction is R_xTherefore, the drive speed ratio SR is R_xbe equivalent to. Further, the magnification Mgn by the projection optical system PO_pIs R_ybe equivalent to. Therefore, SR <Mgn_pIt becomes. The interval between the patterns 50 and 52 is assumed to be lpm. Note that the size of the opening of the slit 40 is doubled by lpm.
[0045]
At the time of FIG. 7A, the pattern 50 is located at the center of the opening of the slit 40. Further, the pattern 52 is located at the left end of the slit 40 in the drawing. Further, the light beam passing through the center of the slit 40 is configured to pass through the optical axis of the projection optical system PO. At the time of FIG. 7A, the image of the pattern 50 is projected onto the position 51 on the printed circuit board B located on the extension line of the optical axis of the projection optical system PO. The image of the pattern 52 is a distance Mgn from the position 51 to the left in the figure._pProjected at a position 53 'shifted by lpm.
[0046]
FIG. 7B shows a state when the mask 4 is moved to the right in the drawing by a distance lpm from the state of FIG. In the state of FIG. 7B, the pattern 52 is located at the center of the opening of the slit 40. The patterns 50 and 54 are located at the right and left ends of the slit 40 in the drawing.
[0047]
At this time, the printed circuit board B has moved to the right in the drawing by a distance SR × lpm from the state of FIG. In this example, at the time of FIG. 7B, a position 53 is located on the extension line of the optical axis of the projection optical system PO at a position shifted by a distance SR × lpm from the position 51 to the left in the drawing. That is, the image of the pattern 52 is projected on the position 53 at the time of FIG. The image of the pattern 50 is a distance Mgn from the position 53 to the right in the figure._pProjected at a position 51 ″ which is a position shifted by × lpm. The image of the pattern 54 is a distance Mgn from the position 53 to the left in the figure._pProjected at a position 55 'shifted by lpm.
[0048]
FIG. 7C shows a state when the mask 4 is moved to the right in the drawing by a distance lpm from the state of FIG. 7B. In the state of FIG. 7C, the pattern 54 is located at the center of the opening of the slit 40. The pattern 52 is located at the right end of the slit 40 in the drawing.
[0049]
At this time, the printed circuit board B has moved to the right in the drawing by a distance SR × lpm from the state of FIG. Therefore, at the time of FIG. 7C, the pattern 54 is positioned on the position 55 that is located on the extension line of the optical axis of the projection optical system PO and is shifted from the position 53 to the left in the figure by the distance SR × lpm. The image is projected. The image of the pattern 52 is a distance Mgn from the position 55 to the right in the figure._pProjected to a position 53 ″ which is a position shifted by 1 lpm.
[0050]
Accordingly, the image of the pattern 52 is projected at the position 53 ′ at the time of FIG. 7A, projected at the position 53 at the time of FIG. 7B, and at the position 53 ″ at the time of FIG. 7C. Projected. The position 53 'is a distance (Mgn from the position 53 to the left in the figure)._p−SR) × lpm, and the position 53 ″ is a distance (Mgn) from the position 53 to the right in the figure._p-SR) is a position shifted by lpm. In other words, R_x<R_yIn this case, the projected position of the image of the pattern continues to move while the pattern passes through the slit opening. Therefore, the image of the pattern exposed on the printed circuit board becomes unclear.
[0051]
For example, it is assumed that the pattern is a linear pattern having a certain width w extending from the front to the back in FIG. An exposure state when such a pattern is exposed on the printed circuit board B is shown in FIG. When the mask pattern is a straight line as described above, it is desirable that the printed circuit board B is exposed to a straight line having a width (SR × w) for a time during which the pattern passes through the opening of the slit. However, what is actually exposed is as shown in FIG. 8, and the pattern continues to be exposed only for the time passing through the opening of the slit, and is a straight line having a width smaller than (SR × w). Only the portion 60a. Width b = (ls × | Mgm) before and after this straight line portion_pThe section 60b of -SR |) is an unclear area where the pattern is exposed only for a shorter time than the time when it passes through the opening of the slit. Note that ls is an opening dimension of the slit 40.
[0052]
As described above, SR and Mgn_pAre different from each other in terms of the size ls of the slit 40, SR, and Mgn._pIt can be seen that it depends on the difference between In the present embodiment, SR and Mgn are set so that the size of the blurred region is sufficiently small._pIs set.
[0053]
In this embodiment, SR and Mgn_pSR and Mgn so that the difference between them is within a predetermined value A_pSet. The predetermined value A is an allowable value b for the size b of the blurred area._maxIs a value that is determined by the specification of the printed circuit board B and the like.
[0054]
In this embodiment, (R_x-R_y)> When A, SR and Mgn_pIs set to satisfy Equation 1.
[0055]
[Expression 1]

[0056]
SR and Mgn_pIs set based on Equation 1, the size b of the blurred region is b_maxIt becomes. SR and R_xDifference, and Mgn_pAnd R_yThe greater of these differences is the smallest. An image of a pattern at a position dx away from the center of the mask 4 in the X-axis direction and dy away in the Y-axis direction is R in the X-axis direction from the center of the printed circuit board B._x× dx, R in the Y-axis direction_yIt is desirable to project at a position separated by × dy. SR and Mgn_pIs set based on Equation 1, the size b of the blurred region is set to the allowable value b._maxIt is possible to minimize the amount of deviation of the position at which the pattern is projected from the desired position while keeping it within the range.
[0057]
Also, | R_x-R_yWhen | ≦ A, SR and Mgn_pIs set to satisfy Equation 2.
[0058]
[Expression 2]

[0059]
SR and Mgn_pIs set based on Equation 2, the size b of the blurred region is the allowable value b._maxIt becomes as follows. An image of a pattern at a position dx away from the center of the mask 4 in the X-axis direction and dy away in the Y-axis direction is R in the X-axis direction from the center of the printed circuit board B._x× dx, R in the Y-axis direction_yProjected at a position separated by xdy. Therefore, SR and Mgn_pIs set based on Equation 2, the size b of the blurred area is set to the allowable value b._maxThe amount of deviation of the position where the pattern is projected from the desired position can be reduced to 0, while keeping it within the range.
[0060]
Also, (R_xWhen -Ry) <-A, SR and Mgn_pIs set to satisfy Equation (3).
[0061]
[Equation 3]

[0062]
SR and Mgn_pIs set based on Equation 3, the size b of the blurred area is b_maxIt becomes. SR and R_xDifference, and Mgn_pAnd R_yThe larger of the differences is the smallest. An image of the pattern at a position dx away from the center of the mask 4 in the X-axis direction and dy away in the Y-axis direction is R in the X-axis direction from the center of the printed circuit board B._x× dx, R in the Y-axis direction_yIt is desirable to project at a position separated by × dy. SR and Mgn_pIs set based on Equation 3, the size b of the blurred region is set to the allowable value b._{m ax}It is possible to minimize the amount of deviation of the position at which the pattern is projected from the desired position while keeping it within the range.
[0063]
FIG. 9 is a schematic view of the substrate holder 8 and the printed circuit board B as viewed from the negative Y-axis direction. The substrate height detection mechanism 38 emits a laser light source 38a having a wavelength and intensity that does not react with the photosensitive agent applied on the printed circuit board B in an oblique direction on the XZ plane toward the printed circuit board B, and emitted from the laser light source 38a. A convex lens 38d for condensing the emitted light on the printed circuit board B, a light receiving unit 38b for receiving the laser light LB reflected on the printed circuit board B, and a convex lens 38c. The convex lens 38c is arranged in front of the light receiving surface of the light receiving unit 38b so that its optical axis is parallel to the optical axis of the reflected laser beam LB, and refracts the laser beam LB reflected on the printed circuit board B to receive it. It fits in the light-receiving surface of the part 38b. The reflection position on the printed circuit board B and the light receiving portion 38b are in the conjugate position of the convex lens 38c, and have a relationship of magnification μ. The magnification μ is a ratio Λ2 / Λ1 of a length Λ2 between the convex lens 38c and the light receiving portion 38b in the optical axis direction and a length Λ1 between the reflecting surface on the printed circuit board B and the convex lens 38c in the optical axis direction. When the laser beam LB at the time of reflection on the printed circuit board B is closer to the negative Z-axis direction (that is, closer to the printed circuit board B) than the optical axis of the convex lens 38c, the laser light LB is more than the optical axis of the convex lens 38c. Incident at a position near the positive direction of the Z-axis.
[0064]
The light receiving unit 38b can detect at which position on the light receiving surface of the light receiving unit 38b the laser beam LB is incident, and can detect the height of the printed circuit board B from this incident position.
[0065]
A method for detecting the height of the printed circuit board B using the substrate height detection mechanism 38 will be described in detail below. The substrate height BH when the laser beam LB is incident on the center of the light receiving surface of the light receiving portion 38b (the point where the light receiving surface intersects the optical axis of the convex lens 38c).₀Is previously calculated by experiment.
[0066]
Here, the incident position of the laser beam LB is ΔL from the intersection of the optical axis of the convex lens 38c and the light receiving surface of the light receiving unit 38b._DIf there is a deviation, the substrate height BH at that time is calculated by Equation 4. If the incident position of the laser beam LB is moving away from the printed circuit board B, ΔL_D> 0, ΔL when moving in the direction approaching the printed circuit board B_D<0. Θ is the incident angle of the laser beam LB.
[0067]
[Expression 4]

[0068]
Here, in order to detect BH with higher accuracy, ΔL with respect to a change in BH is determined in advance through experiments or the like._DThere is also a method to measure.
[0069]
The optical path length from the mask 4 to the lens unit 6 and the optical path length from the lens unit 6 to the exposure surface of the printed circuit board B from the height BH of the printed circuit board B calculated by the above method and the position of the folding mirror 5. Sum D_LCan be calculated.
[0070]
In order to form an image in which the pattern formed on the mask 4 is in focus on the printed circuit board B, the mask 4 and the exposed surface of the printed circuit board B have a conjugate relationship with respect to the lens unit 6. Must be arranged so that In the present embodiment, the lens unit 6 is fixed, and the mask 4 and the substrate holder 8 do not move in the Z-axis direction.
[0071]
In the exposure apparatus 1 configured as described above, focusing is performed so that the mask 4 and the exposure surface of the printed circuit board B are in a conjugate relationship by moving the folding mirror 5 in the X-axis direction. When the distance DL is twice the focal length of the lens unit 6, the mask 4 and the exposed surface of the printed circuit board B have a conjugate relationship. Hereinafter, a procedure for forming an image of the pattern formed on the mask 4 by moving the folding mirror 5 on the printed circuit board B will be described with reference to FIG.
[0072]
FIG. 10 is a side view of the projection exposure apparatus 1 of FIG. 1 projected in the Y-axis direction. In FIG. 7, the lens unit 6 is described as a single convex lens and the roof mirror 7 is described as a single plane mirror for simplification of the drawing. Controller 10 is distance D_LAnd the focal length f of the lens unit 6 are compared, and the difference ΔD between the exposure surface of the printed circuit board B and the imaging surface of the mask lens unit 6 is compared._L= D_L-2f is obtained. Then ΔD_L> 0 if X axis positive direction, and ΔD_LIf <0, the folding mirror 5 is moved to the distance | ΔD in the negative direction of the X axis._LMove it by | / 2. Here, in FIG. 7, ΔD_L> 0, and the position of the image formation plane by the lens unit 6 is | ΔD in the positive direction of the Z axis with respect to the exposure surface of the printed circuit board B._LThis is a position moved by | (a position indicated by a two-dot chain line in FIG. 10). Distance | ΔD of folding mirror 5 in the positive direction of the X axis_LThe folding mirror 5 when moved by | / 2 is indicated by a broken line, and the optical path at that time is indicated by a one-dot chain line. The sum D of the optical path length from the mask 4 to the lens unit 6 at this time and the optical path length from the lens unit 6 to the exposure surface of the printed circuit board B_LIs the distance D before moving the folding mirror 5_LThan | ΔD_L| Only shortened, D_L= 2f. Accordingly, the mask 4 and the exposed surface of the printed circuit board B have a conjugate relationship, and the pattern formed on the mask 4 forms an image on the printed circuit board B. Therefore, by measuring the height of the printed circuit board B and adjusting the imaging position in the previous process as described above, the projection exposure apparatus 1 can cope with printed circuit boards having different thicknesses.
[0073]
Next, the magnification Mgn obtained by the above calculation is the magnification when the image of the mask 4 is formed on the printed circuit board B._pSet to. To set the magnification, the controller 10 controls the roof mirror driving mechanism 17 to drive the roof mirror 7 in the X-axis direction, and the controller 10 controls the folding mirror driving mechanism 15 to drive the folding mirror 5 in the Z-axis direction. Is done by.
[0074]
The principle of setting the magnification will be described with reference to FIGS. FIG. 11 is a schematic view of the lens unit 6 and the roof mirror 7 as viewed from the positive direction of the Z axis. For simplicity of illustration, the lens unit 6 and the roof mirror 7 are each depicted as one surface. Further, a light beam traveling toward the roof mirror 7 is indicated by a two-dot chain line, and a light beam reflected by the roof mirror 7 is indicated by a broken line.
[0075]
In order to set the magnification, first, the roof mirror 7 is moved ΔL from the focal position 7a of the lens unit 6 in the positive direction of the X axis.₁Move. When the roof mirror 7 is moved in this way, the pupil position when exiting the lens unit 6 is 2ΔL in the positive X-axis direction.₁It will shift. As a result, with respect to the incident light that is a parallel light flux, the reflected light becomes a light flux whose telecentricity has collapsed into a fan shape.
[0076]
However, the size of the image at the substrate-side focal position does not change only by breaking the telecentricity. Therefore, the relative positions of the exposure surface of the mask 4 and the printed circuit board B with respect to the lens unit 6 are optically moved so that the exposure surface of the mask 4 and the printed circuit board B maintains a conjugate state with respect to the lens unit 6. That is, when the exposure surface of the printed circuit board B comes close to the lens unit 6, the mask image formed on the exposure surface of the printed circuit board B is enlarged. On the contrary, if the exposure surface of the printed circuit board B moves away from the lens unit 6, the image of the mask formed on the exposure surface of the printed circuit board B is reduced.
[0077]
In order to optically move the relative positions of the exposure surface of the mask 4 and the printed circuit board B with respect to the lens unit 6 so that the exposure surface of the mask 4 and the printed circuit board B maintains a conjugate state with respect to the lens unit 6. ΔD in the direction of the Z-axis mirror 5₁Move. When the roof mirror 7 is moved in the positive direction of the X axis, when the image is enlarged, the folding mirror 5 is moved in the negative direction of the Z axis, and when the image is reduced, the folding mirror 5 is moved in the positive direction of the Z axis. Move in the direction. Further, when the roof mirror 7 is moved in the negative direction of the X axis, when the image is enlarged, the folding mirror 5 is moved in the positive direction of the Z axis, and when the image is reduced, the folding mirror 5 is moved in the negative direction of the Z axis. Move in the direction.
[0078]
FIG. 12 shows the mask 4, the folding mirror 5, the lens unit 6, the roof mirror 7, and the printed board B as viewed from the negative Y-axis direction. In FIG. 12, the luminous flux before setting the magnification is shown by a two-dot chain line, and the luminous flux after moving the roof mirror 7 and the folding mirror 5 to set the magnification is shown by a broken line. In the example shown in FIG. 12, the magnification Mgn_p<1, and the folding mirror 5 moves in the positive Z-axis direction.
[0079]
As shown in FIGS. 11 and 12, the roof mirror 7 is moved ΔL from the position 7a to 7b in the positive direction of the X axis.₁Move the folding mirror 5 further in the positive direction of the Z-axis by ΔD₁By moving, the light flux that has passed through the mask 4 contracts and forms an image on the printed circuit board B. At this time, ΔL₁And ΔD₁Is set to a value satisfying Equation 5. In this magnification correction, the center position of the optical axis does not change.
[0080]
[Equation 5]

[0081]
FIG. 13 shows the light source 2, the mask 4, and the printed board B after the image enlargement process is performed according to the magnification setting principle, as viewed from the positive direction of the X axis. In the actual projection exposure apparatus, the pattern of the mask 4 is formed on the printed circuit board B via the collimator lens 3, the folding mirror 5, the lens unit 6 and the roof mirror 7, but in FIG. Only the light source 2, the mask 4 and the printed circuit board B are described to clearly show the image state. As shown in FIG. 13, when the image enlargement process is performed, each of the images by the individual light sources 2 is enlarged, but the image formation position in the Y-axis direction of each image does not change. For this reason, images from the respective light sources overlap on the printed circuit board B, and the pattern of the mask 4 is not accurately transferred onto the printed circuit board B. Therefore, Y shift processing is performed to shift the image forming position of each image in the Y axis direction so that the images do not overlap each other.
[0082]
14 and 15 are schematic views of the mask 4, the printed circuit board B, the lens unit 6 and the roof mirror 7 as seen from the positive direction of the Z axis. For simplicity of illustration, the lens units 6 are depicted as one surface, and the folding mirror 5 is omitted, and the positions of the substrate surface and the mask surface are projected on the XY plane.
[0083]
FIG. 14 shows the state of the mask 4, the printed circuit board B, the lens unit 6 and the roof mirror 7 before the Y shift process. At this time, the mask 4 and the printed circuit board B are both separated from the lens unit 6 by the focal length f of the lens unit 6. The roof mirror 7 has a focal position O of the lens unit 6._MIs arranged. The luminous flux is indicated by a two-dot chain line.
[0084]
At this time, in the figure in which the mask 4 and the printed board B are projected on the XY plane as shown in FIG. 14, the optical paths of the incident light and the reflected light are equal.
[0085]
In the Y shift process, the controller 10 controls the roof mirror driving mechanism 17 to drive the roof mirror 7 in the Y-axis direction, and the controller 10 controls the folding mirror driving mechanism 15 to drive the folding mirror 5 in the Z-axis direction. Is done by.
[0086]
FIG. 15 shows the state of the mask 4, the printed circuit board B, the lens unit 6 and the roof mirror 7 when the image forming position on the printed circuit board B is moved by ΔY in the negative Y-axis direction by performing the Y shift process. It is. In FIG. 15, the light flux before being reflected by the roof mirror 7 is indicated by a two-dot chain line, and the light flux after reflection is indicated by a broken line. As shown in FIG._MIs located at the position, the pupil position of the luminous flux from the lens unit 6 toward the roof mirror 7 is O_MIt is. On the other hand, the Dach mirror 7 is O_MTo the Y-axis positive direction from the distance ΔL₂As shown in FIG. 15, the pupil position is O_MDistance 2ΔL in the positive direction of the Y-axis₂Just move. In addition, the Dach mirror 7 is O_MWhen moving in the negative Y-axis direction, the pupil position is also O_MIs moved in the negative direction of the Y axis by twice the moving distance of the roof mirror 7.
[0087]
As a result, the telecentricity is broken obliquely, but the image forming position on the printed circuit board B does not shift when both the mask 4 and the printed circuit board B are separated from the lens unit 6 by the focal length f of the lens unit 6. Therefore, the folding mirror 5 is set to ΔD in the negative direction of the Z axis.₂The optical path lengths from both lens units 6 are changed so that the mask 4 and the printed circuit board B are kept in a conjugate state by being moved. ΔD in the negative direction of the Z-axis of the folding mirror 5₂By moving, the optical path length from the mask 4 to the lens unit 6 is ΔD.₂The optical path length from the lens unit 6 to the printed circuit board B is ΔD₂Decrease. At this time, ΔL₂And ΔD₂Is set to a value satisfying Equation 6.
[0088]
[Formula 6]

[0089]
Here, ΔD in Formula 5₁, ΔD of Equation 6₂Indicates the amount of movement of the folding mirror 5 in the Z-axis direction.₁= ΔD₂The movement amounts of the other axes in Equations 5 and 6 are obtained in a state where “is satisfied.
[0090]
Note that the number of light sources and projection optical systems used in the projection exposure apparatus 1 is n._LThen, the value of ΔY is obtained using Equation 7.
[0091]
[Expression 7]

[0092]
Here, a is a natural number, a = 1 in the case of the light source closest to the Y-axis, a = 2 in the case of the adjacent light source, and a = 3 in the case of the adjacent light source. In this way, the value of a of the light source adjacent to the light source with a = am on the Y axis positive side is set to be a = am + 1.
[0093]
The constant W is the exposure width of one projection optical system when magnification correction is not performed.
[0094]
FIG. 16 shows the light source 2, the mask 4, and the printed board B after the Y shift processing is viewed from the positive direction of the X axis. As shown in FIG. 16, when the Y shift is performed according to the above procedure, the image by the central light source 2 and the projection optical system is not shifted, and the image by the adjacent light source 2 and the projection optical system is W (Mgn_p-1) is shifted outward, and the image by the light source 2 adjacent to the outer side is 2 W (Mgn), respectively._pShift outward by -1). Therefore, the image forming positions in the Y-axis direction of the respective images are arranged so that the images do not overlap each other, and the pattern of the mask 4 is accurately transferred onto the printed board B.
[0095]
Next, the driving speed of the substrate holder 8 is set. In this embodiment, the driving speed of the mask 4 is a predetermined value V._MIt is fixed to. Driving speed V_BV_B= SR x V_MSet to be.
[0096]
Next, alignment of the mask 4 and the printed circuit board B in the X-axis direction is performed. By this alignment, the light beam that has passed through the center of the mask portion 4a of the mask 4 at the time of exposure enters the center of the pattern portion B1 of the printed circuit board B. By performing the alignment in this way, it is possible to minimize variation in deviation when the pattern of the mask 4 is transferred to the printed board B.
[0097]
After aligning the mask 4 and the printed circuit board B in this way, the light source 2 is turned on, the mask 4 and the printed circuit board B are moved in the X-axis direction, and the pattern written on the mask 4 is applied to the printed circuit board B. Transcript.
[0098]
Even after the movement of the mask 4 and the printed circuit board B is started, the optical path length from the mask 4 to the lens unit 6 and the exposure surface of the printed circuit board B from the mask 4 using the substrate height detection mechanism 38 are reached. Sum D with optical path length_LIs calculated. D_LBy driving the folding mirror 5 in the X direction so that = 2f is always established, the pattern formed on the mask 4 is connected to the printed circuit board B even if the printed circuit board has a different thickness depending on the part. Can be imaged.
[0099]
【The invention's effect】
As described above, according to the projection exposure apparatus of the present invention, the mask image can be exposed at different expansion / contraction ratios in the main scanning direction and the sub-scanning direction, and the edge portion of the exposed linear image is remarkably blurred. There is nothing to do.
[Brief description of the drawings]
FIG. 1 is a schematic view schematically showing a projection exposure apparatus according to an embodiment of the present invention.
FIG. 2 shows a part of the projection exposure apparatus shown in FIG.
FIG. 3 is a schematic view of a mask according to an embodiment of the present invention.
FIG. 4 is a schematic view of a printed circuit board according to an embodiment of the present invention.
FIG. 5 is a schematic view of a mask and a printed circuit board according to another example of the embodiment of the present invention.
FIG. 6 shows an expansion / contraction ratio R in the main scanning direction of the printed circuit board B in the conventional projection exposure apparatus._xAnd expansion / contraction ratio R in the sub-scanning direction_yThe exposure procedure in the case where they are equal is shown.
FIG. 7 shows an expansion / contraction ratio R in the main scanning direction of the printed circuit board B in the conventional projection exposure apparatus._xAnd expansion / contraction ratio R in the sub-scanning direction_yThe exposure procedure in the case where the values are different is shown.
8 shows a state of the printed circuit board exposed by the procedure shown in FIG.
FIG. 9 is a schematic view of a printed circuit board substrate height detection mechanism according to the embodiment of the present invention.
FIG. 10 is a schematic view schematically showing a focusing mechanism of the projection exposure apparatus according to the embodiment of the present invention.
11 is a schematic view of a lens unit and a roof mirror viewed from the positive direction of the Z axis in the projection exposure apparatus according to the embodiment of the present invention. FIG.
FIG. 12 shows a mask, a folding mirror, a lens unit, a roof mirror, and a printed circuit board of the projection exposure apparatus according to the embodiment of the present invention as viewed from the negative Y-axis direction.
FIG. 13 schematically shows an imaging state before performing a Y shift operation in the embodiment of the present invention.
FIG. 14 is a view of a mask, a folding mirror, a lens unit, a roof mirror, and a printed circuit board of the projection exposure apparatus according to the embodiment of the present invention as viewed from the positive direction of the Z axis.
FIG. 15 shows a mask, a folding mirror, a lens unit, a roof mirror, and a printed circuit board of the projection exposure apparatus after performing a Y shift operation as viewed from the positive direction of the Z axis in the embodiment of the present invention. .
FIG. 16 schematically illustrates an imaging state after performing a Y shift operation in the embodiment of the present invention.
[Explanation of sign]
1 Projection exposure equipment
2 Light source
3 Collimator lens
4 Mask
5 Folding mirror
6 Lens unit
7 Dach Miller
8 Substrate holder
10 Controller
14 Mask drive mechanism
15 Folding mirror drive mechanism
17 Dach mirror drive mechanism
18 Substrate holder drive mechanism
24 Mask position detection means
28 Substrate position detection means
38 Board height detection mechanism
B Printed circuit board

Claims (8)

The mask and the printed wiring board are driven in the main scanning direction while scanning the mask image on which the predetermined pattern is formed on the printed wiring board by the light source fixed at a predetermined position, and the printing is performed. A projection exposure apparatus for forming the predetermined pattern on a wiring board,
A projection optical system that forms an image of the mask on the printed wiring board;
An expansion / contraction ratio measuring means capable of measuring the expansion / contraction ratio of the printed wiring board in a main scanning direction and a sub-scanning direction perpendicular to the main scanning direction;
An expansion / contraction ratio setting means for setting the expansion / contraction ratio of the projection optical system based on the expansion / contraction ratios of the printed wiring board in the main scanning direction and the sub-scanning direction of the expansion / contraction ratio measuring means;
A drive mechanism for driving the mask and the printed wiring board in a main scanning direction;
The stretch rate setting means and the drive mechanism are controlled, the drive speed ratio of the printed wiring board to the mask is SR, the stretch rate of the projection optical system is Mgn _p , and the line width exposed on the printed circuit board When the determined allowable value is A, and the expansion / contraction ratios of the printed wiring board in the main scanning direction and the sub-scanning direction are R _x and R _y , respectively, when (R _x −R _y )> A, the drive speed ratio SR is The stretch rate Mgn _p satisfies the formulas SR = (R _x + R _y + A) / 2 and Mgn _p = (R _x + R _y −A) / 2, and when | R _x −R _y | ≦ A the drive speed ratio SR and the expansion ratio Mgn _p is the formula _SR = R x, satisfies the _{Mgn p = R y (R x} -R y) <- when a is the stretch ratio Mgn and the drive speed ratio SR _p is the _{formula, SR = (R x + R} y -A) / 2, you Fine _{Mgn p = (R x + R} y + A) / 2, and a control means for so meet,
A projection exposure apparatus comprising:   The expansion / contraction rate measuring means has board observation means for measuring the distance between at least two marks formed on the printed wiring board in the main scanning direction and the sub-scanning direction, respectively. The projection exposure apparatus according to claim 1, wherein an expansion / contraction ratio of the printed circuit board is measured using a measurement result of the substrate observation unit.   The printed wiring board is installed such that its longitudinal direction is parallel to the main scanning direction and its short direction is parallel to the sub-scanning direction, and the mark is formed at four corners of the printed wiring board. It is formed at the position of four vertices of a rectangle as a vertex, and the expansion / contraction rate measuring means obtains the length of the printed circuit board and the length in the short direction by the average value of each two sides of the rectangle on the printed circuit board. The projection exposure apparatus according to claim 2, wherein an expansion / contraction ratio of the printed wiring board is measured based on the length in the longitudinal direction and the short direction.   The board observing means includes a first camera means for photographing the printed wiring board and a distance between marks formed on the printed wiring board by performing image processing on an image photographed by the first camera means. 4. The projection exposure apparatus according to claim 2, further comprising first image processing means for measuring.   The expansion / contraction rate measuring means includes mask observation means for measuring a distance between at least two marks formed in the main scanning direction and the sub-scanning direction on the mask, respectively. 5. The projection exposure according to claim 2, wherein the expansion / contraction ratio of the printed circuit board is measured by comparing the measurement result of the substrate observation unit and the measurement result of the mask observation unit. apparatus.   The mask is installed such that its longitudinal direction is parallel to the main scanning direction and its short direction is parallel to the sub-scanning direction, and the marks are four vertices of a rectangle whose vertices are the four corners of the mask. 6. The projection according to claim 5, wherein the expansion / contraction rate measuring means sets an average value of each two sides of the rectangle of the mask as a length in a longitudinal direction and a lateral direction of the mask. Exposure device.   The mask observing means measures the mark formed on the mask by performing image processing on an image photographed by the second camera means and second camera means for photographing the mask. The projection exposure apparatus according to claim 5, further comprising an image processing unit. While transferring an image of a mask in which a predetermined pattern is formed on a printed wiring board by a plurality of light sources fixed at a predetermined position, the mask and the printed wiring board are driven in a main scanning direction to perform scanning, A projection exposure apparatus for forming the predetermined pattern on the printed wiring board,
A plurality of projection optical systems for forming an image of the mask on the printed wiring board;
An expansion / contraction rate setting means for setting an expansion / contraction rate of the projection optical system;
A drive mechanism for driving the mask and the printed wiring board in a main scanning direction;
The stretch rate setting means and the drive mechanism are controlled, the drive speed ratio of the printed wiring board to the mask is SR, the stretch rate of the projection optical system is Mgn _p , and the line width exposed on the printed circuit board When the determined allowable value is A, and the expansion / contraction ratios of the printed wiring board in the main scanning direction and the sub-scanning direction are R _x and R _y , respectively, when (R _x −R _y )> A, the drive speed ratio SR is The stretch rate Mgn _p satisfies the formulas SR = (R _x + R _y + A) / 2 and Mgn _p = (R _x + R _y −A) / 2, and when | R _x −R _y | ≦ A the drive speed ratio SR and the expansion ratio Mgn _p is the formula _SR = R x, satisfies the _{Mgn p = R y (R x} -R y) <- when a is the stretch ratio Mgn and the drive speed ratio SR _p is the _{formula, SR = (R x + R} y -A) / 2, you Fine _{Mgn p = (R x + R} y + A) / 2, and a control unit to satisfy the,
The projection exposure apparatus characterized in that the image of the mask is formed on the printed wiring board at an expansion / contraction ratio set based on a measurement result of the expansion / contraction ratio measuring means of the plurality of projection optical systems.

Images