JP4051473B2 - Illumination optical apparatus and exposure apparatus provided with the illumination optical apparatus - Google Patents

Description

また、輪帯状の二次光源の外径φo は、次の式（７）で表される。
φo ＝２ｙ＋ｂ＝ｆｒ｛２ sin( α／ｍ）＋ａ／ｆ１｝ （７）
【００４０】
式（７）を変形すると、次の式（８）に示す関係が得られる。
ｆｒ＝φo ／｛２ sin( α／ｍ）＋ａ／ｆ１｝ （８）
こうして、式（３）および（４）を参照すると、ズームレンズ７の焦点距離ｆｒが変化することなくアフォーカルズームレンズ５の倍率ｍだけが変化すると、輪帯状の二次光源の幅ｂが変化することなくその高さｙだけが変化することがわかる。すなわち、アフォーカルズームレンズ５の倍率ｍだけを変化させることにより、輪帯状の二次光源の幅ｂを変化させることなくその大きさ（外径φo ）およびその形状（輪帯比Ａ）をともに変更することができる。
【００４１】
また、式（４）および（５）を参照すると、アフォーカルズームレンズ５の倍率ｍが変化することなくズームレンズ７の焦点距離ｆｒだけが変化すると、輪帯状の二次光源の幅ｂおよびその高さｙがともに焦点距離ｆｒに比例して変化することがわかる。すなわち、ズームレンズ７の焦点距離ｆｒだけを変化させることにより、輪帯状の二次光源の形状（輪帯比Ａ）を変化させることなくその大きさ（外径φo ）だけを変更することができる。
さらに、式（６）および（８）を参照すると、一定の大きさの外径φo に対して式（８）の関係を満たすようにアフォーカルズームレンズ５の倍率ｍとズームレンズ７の焦点距離ｆｒとを変化させることにより、輪帯状の二次光源の大きさ（外径φo ）を変化させることなくその形状（輪帯比Ａ）だけを変更することができることがわかる。
【００４２】
以下、具体的な数値例にしたがって、輪帯状の二次光源の大きさ（外径φo ）を変化させることなくその形状（輪帯比Ａ）だけを変更する場合のアフォーカルズームレンズ５の倍率ｍとズームレンズ７の焦点距離ｆｒとの変化について説明する。
この第１数値例では、円錐プリズム４による偏向角度αを７度とし、第１フライアイレンズ６の各レンズエレメントのサイズａを２．５ｍｍとし、各レンズエレメントの焦点距離ｆ１を５０ｍｍとしている。そして、輪帯状の二次光源の外径φo を９６ｍｍで一定に保持しながらその輪帯比Ａを約０．２４〜約０．９５まで変化させるのに必要なアフォーカルズームレンズ５の倍率ｍおよびズームレンズ７の焦点距離ｆｒをそれぞれ求めている。次の表（１）には、第１数値例におけるアフォーカルズームレンズ５の倍率ｍと、輪帯状の二次光源の輪帯比Ａと、ズームレンズ７の焦点距離ｆｒとの対応関係を示している。
【００４３】
【表１】

【００４４】
表（１）を参照すると、第１数値例では、輪帯比Ａを約０．５から約０．６９まで変化させるには、アフォーカルズームレンズ５の倍率ｍを約０．９から約１．６まで変化させるとともに、ズームレンズ７の焦点距離ｆｒを約４７４ｍｍから約３００ｍｍまでさせればよいことがわかる。
前述したように、円錐プリズム４は、照明光路に対して挿脱自在に構成され、且つ角錐プリズム４ａと切り換え可能に構成されている。以下、円錐プリズム４に代えて角錐プリズム４ａを照明光路中に設定した場合、および円錐プリズム４を照明光路から退避させた場合について説明する。
【００４５】
角錐プリズム４ａでは、マスク側の面が光軸ＡＸに垂直な平面状に形成されている。また、角錐プリズム４ａの光源側の面は、４つの屈折面からなり、光源側に向かって全体的に角錐凹面状に形成されている。さらに詳細には、４つの屈折面は、光軸ＡＸ上の一点を頂点し且つＸ軸およびＺ軸に沿って４つの稜線を有する正四角錐の角錐面（底面を除く側面）に相当している。すなわち、４つの屈折面は、光軸ＡＸに関して対称な正四角錐の角錐面に相当している。なお、円錐プリズム４の場合と同様に、角錐凹面がマスク側を向くように角錐プリズム４ａを配置してもよい。
【００４６】
したがって、制御系２１の指令に基づいて光束形状変更部材駆動系２２の作用により円錐プリズム４に代えて角錐プリズム４ａを照明光路中に位置決めした場合、角錐プリズム４ａに入射した光束は、光軸ＡＸを中心として等角度で特定の４つの方向に沿って偏向された後、アフォーカルズームレンズ５に入射する。このように、角錐プリズム４ａは、光源１からの光束を光軸ＡＸに対して偏心した４つの光束に変換するための光束形状変更部材を構成している。アフォーカルズームレンズ５に入射した光束は、その瞳面に４つの点状の光源像を形成する。この場合、４つの点状の光源像を結ぶ四角形は、光軸ＡＸを中心としてＸ軸およびＺ軸に平行な辺を有する正方形となる。４つの点状光源像からの光は、ほぼ平行な光束となってアフォーカルズームレンズ５から射出され、第１フライアイレンズ６に入射する。ここで、第１フライアイレンズ６の入射面には、光軸ＡＸに対してほぼ対称に斜め方向から光束が入射する。さらに詳細には、光軸ＡＸを中心として等角度で特定の４つの方向に沿って光束が斜め入射する。
【００４７】
したがって、第１フライアイレンズ６の各レンズエレメントの後側焦点面にはそれぞれ４つの点状の光源像が形成される。第１フライアイレンズ６の後側焦点面に形成された多数の点状光源像からの光束は、ズームレンズ７を介した後、第２フライアイレンズ８を重畳的に照明する。したがって、第２フライアイレンズ８の入射面には、第１フライアイレンズ６の各レンズエレメントの断面形状に相似な正方形状の照野を光軸ＡＸから４つの対称放射方向に沿って等距離だけ偏心（平行移動）した４つの照野、すなわち光軸ＡＸを中心とした４極状の照野が形成される。その結果、第２フライアイレンズ８の後側焦点面にも、図６（ａ）に示すように、入射面に形成された照野と同じ４極状の二次光源（図６（ａ）中斜線で示す部分）が形成される。
【００４８】
なお、円錐プリズム４から角錐プリズム４ａへの切り換えに対応して、輪帯開口絞り９から開口絞り９ａへの切り換えが行われる。開口絞り９ａは、３つの４極開口絞り４０２、４０４および４０６から選択された１つの４極開口絞りである。４極開口絞り９ａには、図６（ｂ）に示すように、４極状の二次光源を構成する４つの正方形状の光源にほぼ内接するような大きさを有する４つの円形開口部（図６（ｂ）中白抜きで示す部分）が形成されている。また、開口絞り９ａとして、図６（ｃ）に示すような１／４円状の４つの開口部（図６（ｃ）中白抜きで示す部分）を有する４極開口絞りを用いることもできる。
このように、光束形状変更部材として角錐プリズム４ａを用いる場合も、光源１からの光束に基づいてほとんど光量損失することなく４極状の二次光源を形成することができ、その結果二次光源からの光束を制限する開口絞り９ａにおける光量損失を良好に抑えつつ４極変形照明を行うことができる。
【００４９】
そして、アフォーカルズームレンズ５の倍率ｍだけを変化させることにより、４極状の二次光源を構成する４つの正方形状の光源の光量重心の位置を変更することができる。換言すると、４極状の二次光源の幅を変化させることなくその大きさおよびその形状をともに変更することができる。ここで、図６（ａ）において破線で示すように、４極状の二次光源の大きさおよび形状を輪帯状の二次光源と同様に定義することができる。すなわち、４極状の二次光源を構成する４つの正方形状の光源に内接する４つの円を想定する。そして、４つの円が外接する小円の直径φi と４つの円が内接する大円の直径φo との比率φi ／φo に基づいて４極状の二次光源の形状すなわち輪帯比を規定し、大円の直径φo に基づいて４極状の二次光源の大きさを規定することができる。この場合、４極状の二次光源の幅ｂは、大円の直径φo と小円の直径φi との差の１／２として規定される。
また、ズームレンズ７の焦点距離ｆｒだけを変化させることにより、４極状の二次光源の形状（輪帯比）を変化させることなくその大きさだけを変更することができる。さらに、所定の関係を満たすようにアフォーカルズームレンズ５の倍率ｍとズームレンズ７の焦点距離ｆｒとを変化させることにより、４極状の二次光源の大きさを変化させることなくその形状だけを変更することができる。
【００５０】
一方、円錐プリズム４を照明光路から退避させた場合、アフォーカルズームレンズ５には光軸ＡＸに沿って正方形状の断面を有する光束が入射する。アフォーカルズームレンズ５に入射した光束は、その倍率に応じて拡大または縮小され、正方形状の断面を有する光束のまま光軸ＡＸに沿ってアフォーカルズームレンズ５から射出され、第１フライアイレンズ６に入射する。したがって、第１フライアイレンズ６の各レンズエレメントの後側焦点面にはそれぞれ１つの点状の光源像が形成される。また、第２フライアイレンズ８の入射面には、第１フライアイレンズ６の各レンズエレメントの断面形状に相似な正方形状の照野が光軸ＡＸを中心として形成される。その結果、第２フライアイレンズ８の後側焦点面にも、光軸ＡＸを中心とした正方形状の二次光源が形成される。
【００５１】
なお、円錐プリズム４の照明光路からの退避に対応して、輪帯開口絞り９から円形開口絞り９ｂへの切り換えが行われる。円形開口絞り９ｂは、２つの円形開口絞り４０７および４０８から選択された１つの円形開口絞りであり、正方形状の二次光源にほぼ内接するような大きさの開口部を有する。
このように、円錐プリズム４を照明光路から退避させることにより、光源１からの光束に基づいてほとんど光量損失することなく正方形状の二次光源を形成し、二次光源からの光束を制限する開口絞りにおける光量損失を良好に抑えつつ通常円形照明を行うことができる。
この場合、アフォーカルズームレンズ５の倍率ｍまたはズームレンズ７の焦点距離ｆｒを変化させることにより、正方形状の二次光源の大きさを適宜変更することができる。
【００５２】
以下、第１実施例における光束形状変更部材および開口絞りの切り換え動作などについて具体的に説明する。
まず、ステップ・アンド・リピート方式またはステップ・アンド・スキャン方式にしたがって順次露光すべき各種のマスクに関する情報などが、キーボードなどの入力手段２０を介して制御系２１に入力される。制御系２１は、各種のマスクに関する最適な線幅（解像度）、焦点深度等の情報を内部のメモリー部に記憶しており、入力手段２０からの入力に応答して光束形状変更部材駆動系２２、変倍駆動系２３、変倍駆動系２４およびターレット駆動系２５に適当な制御信号を供給する。
【００５３】
すなわち、最適な解像度および焦点深度のもとで輪帯変形照明する場合、光束形状変更部材駆動系２２は制御系２１からの指令に基づいて円錐プリズム４を照明光路中に位置決めする。そして、第２フライアイレンズ８の後側焦点面において所望の大きさおよび輪帯比を有する輪帯状の二次光源を得るために、変倍駆動系２３は制御系２１からの指令に基づいてアフォーカルズームレンズ５の倍率を設定し、変倍駆動系２４は制御系２１からの指令に基づいてズームレンズ７の焦点距離を設定する。また、光量損失を良好に抑えた状態で輪帯状の二次光源を制限するために、ターレット駆動系２５は制御系２１からの指令に基づいてターレットを回転させ、所望の輪帯開口絞りを照明光路中に位置決めする。
こうして、光源１からの光束に基づいてほとんど光量損失することなく輪帯状の二次光源を形成することができ、その結果二次光源からの光束を制限する開口絞りにおいてほとんど光量損失することなく輪帯変形照明を行うことができる。
【００５４】
さらに、必要に応じて、変倍駆動系２３によりアフォーカルズームレンズ５の倍率を変化させたり、変倍駆動系２４によりズームレンズ７の焦点距離を変化させることにより、第２フライアイレンズ８の後側焦点面に形成される輪帯状の二次光源の大きさおよび輪帯比を適宜変更することができる。この場合、輪帯状の二次光源の大きさおよび輪帯比の変化に応じてターレットが回転し、所望の大きさおよび輪帯比を有する輪帯開口絞りが選択されて照明光路中に位置決めされる。
こうして、輪帯状の二次光源の形成およびその制限においてほとんど光量損失することなく、輪帯状の二次光源の大きさおよび輪帯比を適宜変化させて多様な輪帯変形照明を行うことができる。
【００５５】
また、最適な解像度および焦点深度のもとで４極変形照明する場合、光束形状変更部材駆動系２２は制御系２１からの指令に基づいて角錐プリズム４ａを照明光路中に位置決めする。そして、第２フライアイレンズ８の後側焦点面において所望の大きさおよび形状（輪帯比）を有する４極状の二次光源を得るために、変倍駆動系２３は制御系２１からの指令に基づいてアフォーカルズームレンズ５の倍率を設定し、変倍駆動系２４は制御系２１からの指令に基づいてズームレンズ７の焦点距離を設定する。また、光量損失を良好に抑えた状態で４極状の二次光源を制限するために、ターレット駆動系２５は制御系２１からの指令に基づいてターレットを回転させ、所望の４極開口絞りを照明光路中に位置決めする。
こうして、光源１からの光束に基づいてほとんど光量損失することなく４極状の二次光源を形成することができ、その結果二次光源からの光束を制限する開口絞りにおいて光量損失を良好に抑えつつ４極変形照明を行うことができる。
【００５６】
さらに、必要に応じて、変倍駆動系２３によりアフォーカルズームレンズ５の倍率を変化させたり、変倍駆動系２４によりズームレンズ７の焦点距離を変化させることにより、第２フライアイレンズ８の後側焦点面に形成される４極状の二次光源の大きさおよび形状を適宜変更することができる。この場合、４極状の二次光源の大きさおよび形状の変化に応じてターレットが回転し、所望の大きさおよび形状を有する４極開口絞りが選択されて照明光路中に位置決めされる。
こうして、４極状の二次光源の形成およびその制限において光量損失を良好に抑えた状態で、４極状の二次光源の大きさおよび形状を適宜変化させて多様な４極変形照明を行うことができる。
【００５７】
さらに、最適な解像度および焦点深度のもとで通常の円形照明をする場合、光束形状変更部材駆動系２２は制御系２１からの指令に基づいて円錐プリズム４または角錐プリズム４ａを照明光路から退避させる。そして、第２フライアイレンズ８の後側焦点面において所望の大きさを有する正方形状の二次光源を得るために、変倍駆動系２３が制御系２１からの指令に基づいてアフォーカルズームレンズ５の倍率を設定するか、あるいは変倍駆動系２４が制御系２１からの指令に基づいてズームレンズ７の焦点距離を設定する。また、光量損失を良好に抑えた状態で正方形状の二次光源を制限するために、ターレット駆動系２５は制御系２１からの指令に基づいてターレットを回転させ、所望の円形開口絞りを照明光路中に位置決めする。
こうして、光源１からの光束に基づいてほとんど光量損失することなく形成された二次光源からの光束を制限する開口絞りにおいて光量損失を良好に抑えつつ通常円形照明を行うことができる。
【００５８】
さらに、必要に応じて、変倍駆動系２３によりアフォーカルズームレンズ５の倍率を変化させたり、変倍駆動系２４によりズームレンズ７の焦点距離を変化させることにより、第２フライアイレンズ８の後側焦点面に形成される正方形状の二次光源の大きさを適宜変更することができる。この場合、正方形状の二次光源の大きさの変化に応じてターレットが回転し、所望の大きさの開口部を有する円形開口絞りが選択されて照明光路中に位置決めされる。
こうして、正方形状の二次光源の形成およびその制限において光量損失を良好に抑えつつ、σ値を適宜変化させて多様な通常円形照明を行うことができる。
【００５９】
図７は、本発明の第２実施例にかかる照明光学装置を備えた露光装置の構成を概略的に示す図である。また、図８および図９は、第２実施例における回折光学素子の作用を具体的に説明する図である。ただし、以下の実施例および変形例に関する図（図７、図１１および図１２）において、入力手段２０、制御系２１、光束形状変更部材駆動系２２、変倍駆動系２３および２４、並びにターレット駆動系２５（図１２では存在しない）の図示を省略している。
第２実施例は、第１実施例と類似の構成を有する。しかしながら、第１実施例では光束形状変更部材として円錐プリズムや角錐プリズムを用いているが、第２実施例では光束形状変更部材として回折光学素子を用いていることだけが基本的に相違している。したがって、図７において、第１実施例の構成要素と同様の機能を有する要素には図１と同じ参照符号を付している。以下、第１実施例との相違点に着目して第２実施例を説明する。
【００６０】
第２実施例において、整形光学系としてのビームエキスパンダー２を介した光束は、折り曲げミラー３でＹ方向に偏向された後、回折光学素子４ｂに入射する。回折光学素子４ｂは、ガラス基板に露光光（照明光）の波長程度のピッチを有する段差を形成することによって構成され、入射ビームを所望の角度に回折する作用を有する。具体的には、図８（ａ）に示すように、回折光学素子４ｂに光軸ＡＸに沿って垂直入射した細いビームは、光軸ＡＸを中心として等角度であらゆる方向に沿って回折され、リング状のビームとなる。したがって、この回折光学素子４ｂに光軸ＡＸに沿って正方形断面の平行ビームが入射すると、図８（ｂ）に示すように輪帯状のビームとなる。このように、回折光学素子４ｂは、光源１からの光束を実質的に輪帯状の光束に変換するための光束形状変更部材を構成している。
【００６１】
すなわち、回折光学素子４ｂは、光軸ＡＸに沿って垂直入射したビームを光軸ＡＸを中心として等角度であらゆる方向に沿って偏向させるという点で第１実施例における円錐プリズム４と同等の作用をする。しかしながら、第１実施例における円錐プリズム４では入射光束の全体を光軸ＡＸを中心として等角度であらゆる方向に沿って偏向させるのに対し、第２実施例の回折光学素子４ｂでは入射光束を構成する各ビームをその入射軸線（光軸ＡＸに平行）を中心として等角度であらゆる方向に沿って偏向させる。したがって、第２実施例では、アフォーカルズームレンズ５は、回折光学素子４ｂと第１フライアイレンズ６の入射面とを光学的にほぼ共役に結ぶように構成されている。
【００６２】
こうして、第２実施例においても第１実施例と同様に、アフォーカルズームレンズ５の瞳面には、リング状の光源像が形成される。そして、アフォーカルズームレンズ５から射出されたほぼ平行な光束は、第１フライアイレンズ６の入射面に光軸ＡＸを中心として等角度であらゆる方向に沿って斜め入射する。その結果、第２フライアイレンズ８の後側焦点面には、光源１からの光束に基づいて、ほとんど光量損失することなく輪帯状の二次光源が形成される。また、第２フライアイレンズ８の後側焦点面の近傍に配置された開口絞り９においても光量損失はほとんど発生しない。さらに、アフォーカルズームレンズ５の倍率ｍやズームレンズ７の焦点距離ｆｒを適宜変化させることにより、輪帯状の二次光源の大きさや形状（輪帯比）を変更することができる点は第１実施例と同様である。
【００６３】
なお、第２実施例では、回折光学素子４ｂは、照明光路に対して挿脱自在に構成され、且つ他の回折光学素子４ｃと切り換え可能に構成されている。回折光学素子４ｂを照明光路から退避させた場合、第１実施例において円錐プリズムや角錐プリズムを退避させた場合と同様に通常の円形照明を行うことができる。以下、回折光学素子４ｂに代えて回折光学素子４ｃを照明光路中に設定した場合について説明する。
【００６４】
光束形状変更部材として回折光学素子４ｃを用いる場合、図９（ａ）に示すように、光軸ＡＸに沿って垂直入射した細いビームは光軸ＡＸを中心として等角度で特定の４つの方向に沿って回折され、４つの細いビームとなる。したがって、この回折光学素子４ｂに光軸ＡＸに沿って正方形断面の平行ビームが入射すると、図９（ｂ）に示すように４極状のビームとなる。このように、回折光学素子４ｃは、光源１からの光束を光軸ＡＸに対して偏心した４つの光束に変換するための光束形状変更部材を構成している。したがって、アフォーカルズームレンズ５の瞳面には、第１実施例で角錐プリズム４ａを用いた場合と同様に、４つの点状の光源像が形成される。
【００６５】
そして、アフォーカルズームレンズ５から射出されたほぼ平行な光束は、第１フライアイレンズ６の入射面に光軸ＡＸを中心として等角度で特定の４つの方向に沿って斜め入射する。その結果、第２フライアイレンズ８の後側焦点面には、光源１からの光束に基づいて、ほとんど光量損失することなく４極状の二次光源が形成される。また、この４極状の二次光源は、第２フライアイレンズ８の後側焦点面の近傍に配置された開口絞り９ａによって光量損失を良好に抑えつつ制限される。さらに、アフォーカルズームレンズ５の倍率ｍやズームレンズ７の焦点距離ｆｒを適宜変化させることにより、４極状の二次光源の大きさや形状を変更することができる。
【００６６】
図１０は、第２実施例の第１変形例にかかる照明光学装置の要部構成を概略的に示す図であって、（ｂ）は（ａ）の状態よりもアフォーカルズームレンズ５の倍率を拡大した状態を示している。
第１変形例では、第１オプティカルインテグレータとしてマイクロレンズアレイを用いている点だけが第２実施例と相違しており、他の構成は第２実施例と同じである。
【００６７】
図１０に示す第１変形例では、第１フライアイレンズ６に代えてマイクロレンズアレイ６ａを用いている。マイクロレンズアレイ６ａは、縦横に配列された多数のマイクロレンズ（微小レンズ）からなる光学素子であり、たとえば平行平面ガラス板にエッチング処理を施して微小レンズ群を形成することによって構成される。したがって、各マイクロレンズはフライアイレンズを構成する各レンズエレメントよりも微小であるが、正屈折力を有するレンズエレメントが縦横に配置されている点でフライアイレンズと同じである。したがって、マイクロレンズアレイ６ａは、第１フライアイレンズ６と同様の作用を奏する。
【００６８】
以下、回折光学素子４ｂおよびマイクロレンズアレイ６ａを用いた第１変形例において、輪帯状の二次光源の大きさ（外径φo ）を変化させることなくその形状（輪帯比Ａ）だけを変更する場合のアフォーカルズームレンズ５の倍率ｍとズームレンズ７の焦点距離ｆｒとの変化について具体的な数値例にしたがって説明する。
この第２数値例では、回折光学素子４ｂによる回折角度（偏向角度）αを７度とし、マイクロレンズアレイ６ａの各マイクロレンズのサイズａを０．５ｍｍとし、各マイクロレンズの焦点距離ｆ１を１０ｍｍとしている。そして、輪帯状の二次光源の外径φo を９６ｍｍで一定に保持しながらその輪帯比Ａを約０．２４〜約０．９５まで変化させるのに必要なアフォーカルズームレンズ５の倍率ｍおよびズームレンズ７の焦点距離ｆｒをそれぞれ求めている。次の表（２）には、第２数値例におけるアフォーカルズームレンズ５の倍率ｍと、輪帯状の二次光源の輪帯比Ａと、ズームレンズ７の焦点距離ｆｒとの対応関係を示している。
【００６９】
【表２】

【００７０】
表（１）と表（２）とを比較参照すると、アフォーカルズームレンズ５の倍率ｍと輪帯比Ａとズームレンズ７の焦点距離ｆｒとの対応関係が第１数値例と第２数値例とで一致していることがわかる。これは、第１フライアイレンズ６に代えてマイクロレンズアレイ６ａを用いる場合、各マイクロレンズのサイズａおよび焦点距離ｆ１を適当に設定することにより、第１フライアイレンズ６と数値的にも同等の作用を発揮させることが可能をあることを示している。
【００７１】
図１１は、第２実施例の第２変形例にかかる照明光学装置を備えた露光装置の構成を概略的に示す図である。
第２変形例では、アフォーカルズームレンズ５を取り除き回折光学素子４ｂと第１フライアイレンズ６の入射面とを近接配置している点だけが第２実施例と相違しており、他の構成は第２実施例と同じである。したがって、図１１において、第２実施例の構成要素と同様の機能を有する要素には図７と同じ参照符号を付している。以下、第２実施例との相違点に着目して第２変形例を説明する。
【００７２】
前述したように、第２実施例において、アフォーカルズームレンズ５は、回折光学素子４ｂと第１フライアイレンズ６の入射面とを光学的にほぼ共役に結んでおり、第１フライアイレンズ６の入射面への入射光束の角度を変化させる機能を有する。したがって、アフォーカルズームレンズ５を照明光路から取り除いて、回折光学素子４ｂと第１フライアイレンズ６の入射面とを近接配置しても、第１フライアイレンズ６の入射面への入射光束の角度が回折光学素子４ｂの回折角度によって固定的に規定されるだけである。したがって、第２変形例では、ズームレンズ７の焦点距離を変化させることによって、第２フライアイレンズ８の後側焦点面に形成される輪帯状の二次光源の大きさを変更することはできるが、その輪帯比を変更することはできない。
【００７３】
図１２は、本発明の第３実施例にかかる照明光学装置を備えた露光装置の構成を概略的に示す図である。
第３実施例は、第１実施例と類似の構成を有する。しかしながら、第１実施例では第２オプティカルインテグレータとしてフライアイレンズを用いているが、第２実施例では第２オプティカルインテグレータとしてロッド型のオプティカルインテグレータ（以下、単に「ロッド型インテグレータ」という）を用いていることだけが基本的に相違している。したがって、図１２において、第１実施例の構成要素と同様の機能を有する要素には図１と同じ参照符号を付している。以下、第１実施例との相違点に着目して第３実施例を説明する。
【００７４】
第３実施例では、第２フライアイレンズ８に代えてロッド型インテグレータ８ａを用いることに対応して、ズームレンズ７とロッド型インテグレータ８ａとの間の光路中にコンデンサーレンズ７ａを付設し、コンデンサー光学系１０に代えて結像光学系１０ａを設置するとともに、二次光源の制限のための開口絞りを取り除いている。ここで、ズームレンズ７とコンデンサーレンズ７ａとからなる合成光学系は、第１フライアイレンズ６の後側焦点面とロッド型インテグレータ８ａの入射面とを光学的にほぼ共役に結んでいる。また、結像光学系１０ａは、ロッド型インテグレータ８ａの射出面とマスク１１とを光学的にほぼ共役に結んでいる。
【００７５】
ロッド型インテグレータ８ａは、石英ガラスや蛍石のような硝子材料からなる内面反射型のガラスロッドであり、内部と外部との境界面すなわち内面での全反射を利用して集光点を通りロッド入射面に平行な面に沿って内面反射数に応じた数の光源像を形成する。ここで、形成される光源像のほとんどは虚像であるが、中心（集光点）の光源像のみが実像となる。すなわち、ロッド型インテグレータ８ａに入射した光束は、内面反射により角度方向に分割され、集光点を通りその入射面に平行な面に沿って多数の光源像からなる二次光源が形成される。第３実施例の場合、光束形状変更部材として円錐プリズム４が用いられているときには輪帯状の二次光源が形成され、角錐プリズム４ａが用いられているときには４極状の二次光源が形成される。
【００７６】
ロッド型インテグレータ８ａによりその入射側に形成された二次光源からの光束は、その射出面において重畳された後、結像光学系１０ａを介して所定のパターンが形成されたマスク１１を均一照明する。上述したように、結像光学系１０ａは、ロッド型インテグレータ８ａの射出面とマスク１１（ひいてはウエハ１３）とを光学的にほぼ共役に結んでいる。したがって、マスク１１上には、ロッド型インテグレータ８ａの断面形状と相似な矩形状の照野が形成される。
【００７７】
このように、第３実施例においても第１実施例と同様に光量損失を良好に抑えつつ、光束形状変更部材として円錐プリズム４を用いることにより輪帯変形照明を行うことができ、光束形状変更部材として角錐プリズム４ａを用いることにより４極変形照明を行うことができ、光束形状変更部材を照明光路から退避させることにより通常の円形照明を行うことができる。また、アフォーカルズームレンズ５の倍率ｍやズームレンズ７の焦点距離ｆｒを適宜変化させることにより、二次光源の大きさや形状を変更することができる。
【００７８】
以上のように、上述の実施例および変形例では、二次光源を制限するための開口絞りにおける光量損失を良好に抑えつつ、輪帯変形照明や４極変形照明のような変形照明および通常円形照明を行うことができる。加えて、簡単な変倍操作により、開口絞りでの光量損失を良好に抑えつつ変形照明のパラメータを変化させることができる。したがって、変形照明の種類およびパラメータを適宜変化させて、露光投影すべき微細パターンに適した投影光学系の解像度および焦点深度を得ることができる。その結果、高い露光照度および良好な露光条件のもとで、スループットの高い良好な投影露光を行うことができる。
【００７９】
各実施例および変形例の露光装置による露光の工程（フォトリソグラフィ工程）を経たウエハは、現像する工程を経てから、現像したレジスト以外の部分を除去するエッチングの工程、エッチングの工程後の不要なレジストを除去するレジスト除去の工程等を経てウエハプロセスが終了する。そして、ウエハプロセスが終了すると、実際の組立工程にて、焼き付けられた回路毎にウエハを切断してチップ化するダイシング、各チップに配線等を付与するボンディング、各チップ毎にパッケージングするパッケージング等の各工程を経て、最終的にデバイスとしての半導体装置（ＬＳＩ等）が製造される。
【００８０】
なお、以上の説明では、投影露光装置を用いたウエハプロセスでのフォトリソグラフィ工程により半導体素子を製造する例を示したが、露光装置を用いたフォトリソグラフィ工程によって、半導体デバイスとして、液晶表示素子、薄膜磁気ヘッド、撮像素子（ＣＣＤ等）を製造することができる。
こうして、本発明の照明光学装置を用いて半導体デバイスを製造する露光方法の場合、良好な露光条件のもとで投影露光を行うことができるので、良好な半導体デバイスを製造することができる。
【００８１】
なお、上述の実施例および変形例において円形開口照明を行うにあたっては、光束形状変更部材を照明光路中から退避させることが望ましい。光束形状変更部材（４、４ａ、４ｂ）を退避させることにより、特開昭５８−１４７７０８号公報に記載されているような、いわゆるダブルフライアイシステムの構成とすることができる。
この際、図１、図７および図１２に例示したような構成の装置においては、アフォーカルズームレンズ５を同時に退避させてもよい。また、図１１に例示したような構成の装置においては、第１フライアイレンズ６を同時に退避させ、かわりに照明条件に対して適切な別のフライアイレンズを第１フライアイレンズとして照明光路中に挿入してもよい。
また、上述の実施例および変形例では、円錐プリズムとして円錐凹面を有するプリズムを用いているが、円錐凸面を有するプリズムを用いることもできる。角錐プリズムについても同様に、角錐凸面を有するプリズムを用いることもできる。
【００８２】
また、上述の実施例および変形例では、照明光学装置を備えた投影露光装置を例にとって本発明を説明したが、マスク以外の被照射面を均一照明するための一般的な照明光学装置に本発明を適用することができることは明らかである。
さらに、以上の実施例および変形例では、２４８ｎｍの波長光を供給するＫｒＦエキシマレーザや１９３ｎｍの波長光を供給するＡｒＦエキシマレーザ等を光源として用いた例を示したが、これ以外の光源を備えた装置にも本発明を適用できることは言うまでもない。例えば、１５７ｎｍの波長光を供給するＦ₂ レーザ等のレーザ光源、あるいは所定の波長の光を供給するレーザ光源とそのレーザ光源からの光を２００ｎｍ以下の短波長の光に変換する非線型光学素子との組合せ等からなる光源ユニット等を本発明の光源手段として用いることも可能である。
【００８３】
【発明の効果】
以上説明したように、本発明の照明光学装置では、二次光源を制限するための開口絞りにおける光量損失を良好に抑えつつ、輪帯変形照明や４極変形照明のような変形照明および通常円形照明を行うことができる。加えて、簡単な変倍操作により、開口絞りでの光量損失を良好に抑えつつ変形照明のパラメータを変化させることができる。
【００８４】
したがって、本発明の照明光学装置を組み込んだ露光装置では、変形照明の種類およびパラメータを適宜変化させて、露光投影すべき微細パターンに適した投影光学系の解像度および焦点深度を得ることができる。その結果、高い露光照度および良好な露光条件のもとで、スループットの高い良好な投影露光を行うことができる。また、本発明の照明光学装置を用いて被照射面上に配置されたマスクのパターンを感光性基板上に露光する露光方法では、良好な露光条件のもとで投影露光を行うことができるので、良好な半導体デバイスを製造することができる。
【図面の簡単な説明】
【図１】本発明の第１実施例にかかる照明光学装置を備えた露光装置の構成を概略的に示す図である。
【図２】複数の開口絞りが円周状に配置されたターレットの構成を概略的に示す図である。
【図３】円錐プリズム４から第１フライアイレンズ６の入射面までの構成を概略的に示す図であって、アフォーカルズームレンズ５の作用を説明する図である。
【図４】第１フライアイレンズ６から開口絞り９までの構成を概略的に示す図であって、第１フライアイレンズ６の入射面に斜め入射した光束が第２フライアイレンズ８の入射面に輪帯状の照野を形成する様子を示す図である。
【図５】円錐プリズム４から第２フライアイレンズ８の入射面までの構成を概略的に示す図であって、アフォーカルズームレンズ５の倍率およびズームレンズ７の焦点距離と第２フライアイレンズ８の入射面に形成される輪帯状の照野の大きさおよび形状との関係を説明する図である。
【図６】第２フライアイレンズ８の後側焦点面に形成される４極状の二次光源およびその近傍に配置される４極開口絞りの構成を示す図である。
【図７】本発明の第２実施例にかかる照明光学装置を備えた露光装置の構成を概略的に示す図である。
【図８】第２実施例における回折光学素子４ｂの作用を具体的に説明する図である。
【図９】第２実施例における回折光学素子４ｃの作用を具体的に説明する図である。
【図１０】第２実施例の第１変形例にかかる照明光学装置の要部構成を概略的に示す図であって、（ｂ）は（ａ）の状態よりもアフォーカルズームレンズ５の倍率を拡大した状態を示している。
【図１１】第２実施例の第２変形例にかかる照明光学装置を備えた露光装置の構成を概略的に示す図である。
【図１２】本発明の第３実施例にかかる照明光学装置を備えた露光装置の構成を概略的に示す図である。
【符号の説明】
１ 光源
２ ビームエキスパンダー
３ 折り曲げミラー
４ 円錐プリズム
４ａ 角錐プリズム
４ｂ、４ｃ 回折光学素子
５ アフォーカルズームレンズ
６ 第１フライアイレンズ
６ａ マイクロレンズアレイ
７ ズームレンズ
７ａ コンデンサーレンズ
８ 第２フライアイレンズ
８ａ ロッド型インテグレータ
９ 開口絞り
１０ コンデンサー光学系
１０ａ 結像光学系
１１ マスク
１２ 投影光学系
１３ ウエハ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an illumination optical apparatus and an exposure apparatus provided with the illumination optical apparatus, and more particularly to an illumination optical apparatus suitable for an exposure apparatus for manufacturing a semiconductor device or the like by a lithography process.
[0002]
[Prior art]
In this type of exposure apparatus, the light beam emitted from the light source enters the fly-eye lens, and forms a secondary light source composed of a large number of light source images on the rear focal plane. The light beam from the secondary light source is limited through an aperture stop disposed in the vicinity of the rear focal plane of the fly-eye lens, and then enters the condenser lens. The aperture stop limits the shape or size of the secondary light source to a desired shape or size depending on the desired illumination conditions (exposure conditions).
[0003]
The light beam condensed by the condenser lens illuminates the mask on which a predetermined pattern is formed in a superimposed manner. The light transmitted through the mask pattern forms an image on the wafer via the projection optical system. Thus, the mask pattern is projected and exposed (transferred) onto the wafer. The pattern formed on the mask is highly integrated, and it is essential to obtain a uniform illuminance distribution on the wafer in order to accurately transfer this fine pattern onto the wafer.
[0004]
In recent years, the size of the secondary light source formed by the fly-eye lens can be changed by changing the size of the aperture of the aperture stop arranged on the exit side of the fly-eye lens, so that the coherency of illumination can be improved. A technique for changing σ (σ = aperture stop diameter / pupil diameter of the projection optical system) has attracted attention. In addition, by setting the shape of the aperture of the aperture stop arranged on the exit side of the fly-eye lens to be an annular shape or a four-hole shape, the shape of the secondary light source formed by the fly-eye lens is an annular shape or a four-hole shape. A technology that improves the depth of focus and resolution of the projection optical system by limiting the shape to a hole is drawing attention.
[0005]
[Problems to be solved by the invention]
As described above, in the prior art, the shape of the secondary light source is limited to an annular shape or a four-hole shape to perform deformed illumination (annular deformation illumination or quadrupole deformed illumination). The light beam from the relatively large secondary light source formed in the above is limited by an aperture stop having an annular or four-hole opening. In other words, in the annular deformation illumination and the quadrupole deformation illumination in the prior art, a substantial part of the light beam from the secondary light source is shielded by the aperture stop and does not contribute to illumination (exposure). As a result, there is an inconvenience that the illuminance on the mask and the wafer is reduced due to the loss of light quantity at the aperture stop, and the throughput of the exposure apparatus is also reduced.
[0006]
The present invention has been made in view of the above-described problems, and an illumination optical device capable of performing modified illumination such as annular illumination or quadrupole illumination while suppressing light loss at the aperture stop well, and the illumination optics An object of the present invention is to provide an exposure apparatus including the apparatus.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, in the first invention of the present invention, a first light source means for forming a first multiple light source comprising a light source means for supplying a light flux and a plurality of light sources based on the light flux from the light source means. A first optical integrator, a second optical integrator for forming a second multiple light source comprising a larger number of light sources based on light beams from the first multiple light source formed by the first optical integrator, and the second optical integrator. In the illumination optical apparatus comprising a condenser optical system for illuminating the irradiated surface by condensing light beams from the second multiple light sources formed by
In order to form a ring-shaped light source or a plurality of light sources decentered from the reference optical axis as the second multiple light sources, the light beam from the light source means is substantially symmetrical with respect to the reference optical axis from the oblique direction. An illumination optical device is provided, characterized in that oblique light beam forming means for converting into a light beam incident on an integrator is arranged.
[0008]
According to a preferred aspect of the first invention, the oblique light beam forming means converts the light flux from the light source means into a substantially annular light flux or a plurality of light fluxes decentered with respect to the reference optical axis. A shape changing member and a shape changed by the light beam shape changing member so that the light beam changed in shape by the light beam shape changing member is incident on the first optical integrator in a superimposed manner from an oblique direction substantially symmetrically with respect to the reference optical axis. And a condensing optical system for condensing the changed light flux. In this case, it is preferable that the light beam shape changing member includes a plurality of prism members or a plurality of diffractive optical elements configured to be detachable with respect to the illumination optical path.
[0009]
According to a preferred aspect of the first invention, the condensing optical system includes an annular ratio of an annular light source formed as the second multiple light source or a plurality of light sources formed as the second multiple light source. In order to change the position of the center of gravity of each light amount, the first variable magnification optical system having a variable magnification is provided. Further, in the optical path between the first optical integrator and the second optical integrator, the light beam from the first multiple light source formed by the first optical integrator is condensed and guided to the second optical integrator. In order to change the size of the second multiple light source, the relay optical system preferably includes a second variable magnification optical system having a variable magnification.
[0010]
According to a second aspect of the present invention, there is provided the illumination optical apparatus according to the first aspect of the present invention and a projection optical system for projecting and exposing a mask pattern disposed on the irradiated surface onto a photosensitive substrate. An exposure apparatus characterized by the above is provided.
Furthermore, in the third invention, there is provided an exposure method characterized in that a pattern of a mask arranged on the irradiated surface is exposed on a photosensitive substrate using the illumination optical apparatus of the first invention.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, the oblique light beam forming means is disposed in the optical path between the light source means and the first optical integrator. The oblique light beam forming unit converts the light beam from the light source unit into a light beam that is incident on the first optical integrator from an oblique direction substantially symmetrically with respect to the reference optical axis. Specifically, the oblique light beam forming means includes a light beam shape changing member such as a conical prism or a pyramid prism and a condensing optical system such as an afocal optical system.
[0012]
The light beam from the light source means is converted into a substantially annular light beam or a plurality of light beams decentered with respect to the reference optical axis through the light beam shape changing member. In this case, when a conical prism is used as the light beam shape changing member, it is converted into a substantially annular light beam, and when a pyramid prism is used, it is converted into a plurality of light beams that are decentered with respect to the reference optical axis. Note that a diffractive optical element having the same function can be used instead of the conical prism or the pyramid prism.
[0013]
The light beam whose shape has been changed by the light beam shape changing member is condensed through the condensing optical system, and is incident on the first optical integrator in a superimposed manner from an oblique direction almost symmetrically with respect to the reference optical axis. In this way, the first multiple light sources are formed by the first optical integrator. The light flux from the first multiple light source is condensed via the relay optical system and guided to the second optical integrator. As a result, a ring-shaped light source or a plurality of light sources decentered from the reference optical axis can be formed as the second multiple light sources, that is, secondary light sources by the second optical integrator.
[0014]
Here, when a conical prism is used as the light beam shape changing member, an annular light source is formed, and when a pyramid prism is used, a plurality of light sources decentered from the reference optical axis are formed. In particular, when a quadrangular pyramid prism (hereinafter simply referred to as “pyramidal prism”) is used as the pyramidal prism, a secondary light source composed of four light sources symmetrically decentered from the reference optical axis, that is, a quadrupole secondary light source is formed. Is done. The luminous flux from the annular or quadrupolar secondary light source formed by the second optical integrator in this manner is irradiated after being limited by an aperture stop having an opening according to the size and shape of the secondary light source. Illuminate the surface.
[0015]
As described above, in the present invention, an annular or quadrupolar secondary light source can be formed with almost no light loss based on the light flux from the light source means. As a result, it is possible to perform annular deformation illumination or quadrupole deformation illumination while satisfactorily suppressing light loss at the aperture stop that restricts the luminous flux from the secondary light source. Needless to say, normal circular illumination can be performed while the loss of light quantity is suppressed satisfactorily by retracting the oblique light beam forming means from the illumination optical path.
[0016]
Further, in the present invention, the condensing optical system is configured as a variable magnification optical system having a variable magnification, and a ring-shaped light source ring formed as a second multiple light source by changing the magnification of the variable magnification optical system. The band ratio or the position of the center of light quantity of each of the plurality of light sources formed as the second multiple light sources can be changed. Furthermore, the relay optical system arranged in the optical path between the first optical integrator and the second optical integrator is configured as a variable magnification optical system with variable magnification, and by changing the magnification of the variable magnification optical system, The size of the second multiple light source can be changed.
[0017]
As described above, the illumination optical device according to the present invention performs modified illumination such as annular deformation illumination and quadrupole deformation illumination, and usually circular illumination while favorably suppressing light loss at the aperture stop that restricts the secondary light source. be able to. In addition, it is possible to change the parameters of the modified illumination (the size and shape of the limited secondary light source) while satisfactorily suppressing the light loss at the aperture stop by a simple zooming operation. Therefore, in the exposure apparatus incorporating the illumination optical apparatus of the present invention, the resolution and depth of focus of the projection optical system suitable for the fine pattern to be exposed and projected can be obtained by appropriately changing the type and parameters of the modified illumination. As a result, good projection exposure with high throughput can be performed under high exposure illuminance and good exposure conditions. In the exposure method in which the mask pattern arranged on the irradiated surface is exposed on the photosensitive substrate using the illumination optical device of the present invention, projection exposure can be performed under good exposure conditions. A good semiconductor device can be manufactured.
[0018]
Embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a drawing schematically showing a configuration of an exposure apparatus provided with an illumination optical apparatus according to the first embodiment of the present invention.
In FIG. 1, the Z-axis is along the normal direction of the wafer 13 which is a photosensitive substrate, the Y-axis is parallel to the paper surface of FIG. 1 in the wafer surface, and the wafer surface is perpendicular to the paper surface of FIG. The X axis is set for each direction.
[0019]
The exposure apparatus of FIG. 1 includes an excimer laser light source that supplies light having a wavelength of 248 nm or 193 nm, for example, as the light source 1 for supplying exposure light (illumination light). A substantially parallel light beam emitted from the light source 1 along the Z direction has a rectangular cross section extending along the X direction, and enters a beam expander 2 including a pair of cylindrical lenses 2a and 2b. Each cylindrical lens 2a and 2b has a negative refracting power and a positive refracting power in the plane of FIG. 1 (in the YZ plane), and is in a plane orthogonal to the plane of the paper (in the XZ plane) including the optical axis AX. Functions as a plane parallel plate. Therefore, the light beam incident on the beam expander 2 is expanded in the plane of FIG. 1 and shaped into a light beam having a predetermined cross section, for example, a light beam having a square cross section.
[0020]
The light beam that has passed through the beam expander 2 as the shaping optical system is deflected in the Y direction by the bending mirror 3 and then enters the conical prism 4. The mask side surface (the right side surface in the figure) of the conical prism 4 is formed in a planar shape perpendicular to the optical axis AX. Further, the light source side surface (the left surface in the figure) of the conical prism 4 is formed in a conical concave surface toward the light source side. More specifically, the refracting surface on the light source side of the conical prism 4 corresponds to a conical surface (a side surface excluding the bottom surface) that is symmetrical with respect to the optical axis AX. Therefore, the light beam incident on the conical prism 4 is deflected along all directions at an equal angle with the optical axis AX as the center, and then enters the afocal zoom lens 5. Thus, the conical prism 4 constitutes a light beam shape changing member for converting the light beam from the light source means into a substantially annular light beam.
[0021]
In FIG. 1, the conical concave surface of the conical prism 4 faces the light source side, but the conical prism 4 may be arranged so that the conical concave surface faces the mask side. The conical prism 4 is configured to be detachable with respect to the illumination optical path, and is configured to be switchable with a pyramid prism 4a as another light beam shape changing member. The configuration and operation of the pyramid prism 4a will be described later.
The afocal zoom lens 5 is configured to continuously change the magnification within a predetermined range while maintaining an afocal system (non-focus optical system).
Here, switching between the conical prism 4 and the pyramid prism 4a and withdrawal from the illumination optical path are performed by a light beam shape changing member drive system 22 that operates based on a command from the control system 21. Further, the magnification change of the afocal zoom lens 5 is performed by a variable power drive system 23 that operates based on a command from the control system 21.
[0022]
The light beam incident on the afocal zoom lens 5 forms a ring-shaped (annular) light source image on the pupil plane. Light from the ring-shaped light source image is emitted from the afocal zoom lens 5 as a substantially parallel light beam, and is incident on a first fly-eye lens 6 as a first optical integrator. At this time, the light beam enters the incident surface of the first fly-eye lens 6 from an oblique direction almost symmetrically with respect to the optical axis AX. In other words, the light flux is obliquely incident along all directions at an equal angle around the optical axis AX.
The first fly-eye lens 6 is configured, for example, by arranging a large number of lens elements having a square cross section and having a positive refractive power along the optical axis AX. The surface on the incident side of each lens element is formed in a spherical shape with a convex surface facing the incident side, and the surface on the exit side is formed in a flat shape.
[0023]
Therefore, the light beam incident on the first fly-eye lens 6 is two-dimensionally divided by a large number of lens elements, and one ring-shaped light source image is formed on the rear focal plane of each lens element. Light beams from a large number of ring-shaped light source images formed on the rear focal plane of the first fly-eye lens 6 pass through the zoom lens 7 and then superimpose on the second fly-eye lens 8 as a second optical integrator. Illuminate. The zoom lens 7 is a relay optical system capable of continuously changing the focal length within a predetermined range, and the rear focal plane of the first fly-eye lens 6 and the rear side of the second fly-eye lens 8. The focal plane is optically almost conjugate. The zoom lens 7 constitutes a telecentric optical system on the rear side. In order to satisfy the above conjugate relationship and telecentricity, the zoom lens 7 is configured as a multi-group zoom lens in which at least three lens groups can move independently. The change of the focal length of the zoom lens 7 is performed by a zoom drive system 24 that operates based on a command from the control system 21.
[0024]
Accordingly, an infinite number of square illumination fields similar to the cross-sectional shapes of the lens elements of the first fly-eye lens 6 are arranged on the incident surface of the second fly-eye lens 8 at an equal distance from the optical axis AX. The illumination field having the above-described shape, that is, an annular illumination field centering on the optical axis AX is formed.
Similar to the first fly-eye lens 6, the second fly-eye lens 8 is configured by vertically and horizontally arranging a large number of lens elements having positive refractive power along the optical axis AX. However, each lens element constituting the second fly-eye lens 8 has a rectangular cross section similar to the shape of the illumination field to be formed on the mask (and thus the shape of the exposure region to be formed on the wafer). The incident-side surface of each lens element constituting the second fly's eye lens 8 is formed in a spherical shape with a convex surface facing the incident side, and the exit-side surface is formed in a spherical shape with the convex surface facing the exit side. ing.
[0025]
Accordingly, the light beam incident on the second fly-eye lens 8 is two-dimensionally divided by a large number of lens elements, and the number of lens elements of the first fly-eye lens 6 is on the rear focal plane of each lens element on which the light beam is incident. A number of light source images are respectively formed. In this way, on the rear focal plane of the second fly-eye lens 8, there are a large number of annular light sources (hereinafter referred to as “secondary light sources”) that are the same as the illumination field formed by the light flux incident on the second fly-eye lens 8. It is formed.
The light flux from the annular secondary light source formed on the rear focal plane of the second fly-eye lens 8 is incident on the aperture stop 9 disposed in the vicinity thereof. The aperture stop 9 is supported on a turret (rotary plate: not shown in FIG. 1) that can rotate around a predetermined axis parallel to the optical axis AX.
[0026]
FIG. 2 is a diagram schematically showing a configuration of a turret in which a plurality of aperture stops are arranged in a circumferential shape.
As shown in FIG. 2, the turret substrate 400 is provided with eight aperture stops along the circumferential direction having a light transmission region indicated by hatching in the drawing. The turret substrate 400 is configured to be rotatable about an axis passing through the center point O and parallel to the optical axis AX. Therefore, by rotating the turret substrate 400, one aperture stop selected from the eight aperture stops can be positioned in the illumination optical path. The turret substrate 400 is rotated by the turret drive system 25 that operates based on a command from the control system 21.
[0027]
The turret substrate 400 is formed with three annular aperture stops 401, 403, and 405 having different annular ratios. Here, the annular aperture stop 401 has an annular transmission region having an annular ratio of r11 / r21. The annular aperture stop 403 has an annular transmission region having an annular ratio of r12 / r22. The annular aperture stop 405 has an annular transmission region having an annular ratio of r13 / r21.
[0028]
The turret substrate 400 is formed with three quadrupole aperture stops 402, 404, and 406 having different annular ratios. Here, the quadrupole aperture stop 402 has four eccentric circular transmission regions in an annular region having an annular ratio of r11 / r21. The quadrupole aperture stop 404 has four eccentric circular transmission regions in the annular region having an annular ratio of r12 / r22. The quadrupole aperture stop 406 has four eccentric circular transmission regions in the annular region having an annular ratio of r13 / r21.
Further, two circular aperture stops 407 and 408 having different sizes (diameters) are formed on the turret substrate 400. Here, the circular aperture stop 407 has a circular transmission region having a size of 2r22, and the circular aperture stop 408 has a circular transmission region having a size of 2r21.
[0029]
Therefore, by selecting one of the three annular aperture stops 401, 403 and 405 and positioning it in the illumination optical path, the annular luminous flux having three different annular ratios is accurately limited. (Regulation), three types of annular deformation illumination with different annular ratios can be performed. In addition, by selecting one of the three quadrupole aperture stops 402, 404, and 406 and positioning it in the illumination optical path, four eccentric beams having three different annular ratios can be accurately obtained. By limiting, three types of quadrupole deformation illumination with different zone ratios can be performed. Furthermore, by selecting one of the two circular aperture stops 407 and 408 and positioning it in the illumination optical path, two types of normal circular illuminations having different σ values can be performed.
[0030]
In FIG. 1, an annular secondary light source is formed on the rear focal plane of the second fly's eye lens 8, so that one aperture selected from the three annular aperture stops 401, 403, and 405 as the aperture stop 9. A band aperture stop is used. However, the configuration of the turret shown in FIG. 2 is exemplary, and the type and number of aperture stops to be arranged are not limited to this. Further, the aperture stop is not limited to the turret type aperture stop, and an aperture stop capable of appropriately changing the size and shape of the light transmission region may be fixedly installed in the illumination optical path.
[0031]
The light from the secondary light source through the aperture stop 9 having a ring-shaped opening (light transmitting portion) is subjected to the condensing action of the condenser optical system 10 and then superimposed on the mask 11 on which a predetermined pattern is formed. Uniform illumination. The light flux that has passed through the pattern of the mask 11 forms an image of the mask pattern on the wafer 13 that is a photosensitive substrate via the projection optical system 12. In this way, by performing batch exposure or scan exposure while driving and controlling the wafer 13 two-dimensionally in a plane (XY plane) orthogonal to the optical axis AX of the projection optical system 12, each exposure region of the wafer 13 is masked. Eleven patterns are sequentially exposed.
[0032]
In the batch exposure, the mask pattern is collectively exposed to each exposure region of the wafer in accordance with a so-called step-and-repeat method. In this case, the shape of the illumination area on the mask 11 is a rectangular shape close to a square, and the cross-sectional shape of each lens element of the second optical integrator is also a rectangular shape close to a square.
On the other hand, in scan exposure, according to a so-called step-and-scan method, a mask pattern is scan-exposed to each exposure region of the wafer while moving the mask and wafer relative to the projection optical system. In this case, the shape of the illumination area on the mask 11 is a rectangular shape in which the ratio of the short side to the long side is, for example, 1: 3, and the cross-sectional shape of each lens element of the second optical integrator is a similar rectangular shape. It becomes.
[0033]
FIG. 3 is a diagram schematically illustrating a configuration from the conical prism 4 to the incident surface of the first fly-eye lens 6, and is a diagram illustrating the operation of the afocal zoom lens 5.
As shown in FIG. 3A, the light beam deflected along the conical prism 4 along all directions at an equal angle α around the optical axis AX passes through the afocal zoom lens 5 having a magnification m1, The first fly-eye lens 6 is incident obliquely along all directions at an equal angle of θ1 with the optical axis AX as the center. At this time, the size of the illumination field formed on the incident surface of the first fly-eye lens 6 is d1.
Here, as shown in FIG. 3B, when the magnification of the afocal zoom lens 5 is changed from m1 to m2, the conical prism 4 is centered on the optical axis AX and along all directions at an equal angle α. The deflected light beam passes through the afocal zoom lens 5 having the magnification m2, and then obliquely enters the incident surface of the first fly-eye lens 6 along all directions at an equal angle of the angle θ2 around the optical axis AX. At this time, the size of the illumination field formed on the incident surface of the first fly-eye lens 6 is d2.
[0034]
Here, the incident angles θ1 and θ2 of the light flux on the incident surface of the first fly-eye lens 6, the sizes d1 and d2 of illumination fields formed on the incident surface of the first fly-eye lens 6, and the afocal zoom lens The relationship shown in the following expressions (1) and (2) is established between the magnifications m1 and m2 of 5.
θ2 = (m1 / m2) · θ1 (1)
d2 = (m2 / m1) · d1 (2)
Referring to Equation (1), the incident angle θ of the light beam on the incident surface of the first fly-eye lens 6 can be continuously changed by continuously changing the magnification m of the afocal zoom lens 5. I understand.
[0035]
FIG. 4 is a diagram schematically showing a configuration from the first fly-eye lens 6 to the aperture stop 9, and a light beam obliquely incident on the incident surface of the first fly-eye lens 6 is incident on the second fly-eye lens 8. It is a figure which shows a mode that a ring-shaped illumination field is formed in a surface.
As indicated by a solid line in FIG. 4A, the light beam obliquely incident on the incident surface of the first fly-eye lens 6 at a predetermined angle from a predetermined direction remains at an angle after being imaged through each lens element. Is incident obliquely on the zoom lens 7 and an illumination field having a predetermined width is formed at a position eccentric from the optical axis AX by a predetermined distance on the incident surface of the second fly-eye lens 8.
[0036]
Actually, as indicated by a broken line in FIG. 4A, a light beam enters the incident surface of the first fly-eye lens 6 from an oblique direction almost symmetrically with respect to the optical axis AX. In other words, the light flux is obliquely incident along all directions at an equal angle around the optical axis AX. Therefore, as shown in FIG. 4B, a ring-shaped illumination field centered on the optical axis AX is formed on the incident surface of the second fly-eye lens 8. In addition, a secondary light source having an annular shape similar to the illumination field formed on the incident surface is formed on the rear focal plane of the second fly-eye lens 8. On the other hand, as described above, the annular aperture stop 9 disposed in the vicinity of the rear focal plane of the second fly-eye lens 8 has an annular aperture corresponding to the annular secondary light source (FIG. 4 ( c) A hollow portion) is formed.
Thus, when the conical prism 4 is used as the light beam shape changing member, an annular secondary light source can be formed with almost no light loss based on the light beam from the light source 1, and as a result, the light beam from the secondary light source can be changed. The annular deformation illumination can be performed with almost no light loss at the aperture stop 9 to be restricted.
[0037]
FIG. 5 is a diagram schematically showing a configuration from the conical prism 4 to the incident surface of the second fly-eye lens 8, and the magnification of the afocal zoom lens 5, the focal length of the zoom lens 7, and the second fly-eye lens. It is a figure explaining the relationship with the magnitude | size and shape of an annular illumination field formed in 8 entrance planes.
In FIG. 5, the central ray of the light beam emitted from the conical prism 4 about the optical axis AX at the angle α passes through the afocal zoom lens 5 having the magnification m, and then the first light at the angle θ with respect to the optical axis AX. The light enters the fly eye lens 6. The first fly-eye lens 6 is composed of a lens element having a size of a and a focal length of f1. The central ray emitted from the lens element of the first fly-eye lens 6 at an angle θ reaches the incident surface of the second fly-eye lens 8 via the zoom lens 7 having a focal length fr. At this time, the incident range of the light flux on the incident surface of the second fly's eye lens 8 is a range having a width b with the height from the optical axis AX as the center. That is, as shown in FIG. 4B, the illumination field formed on the incident surface of the second fly's eye lens 8 and the secondary light source formed on the rear focal plane of the second fly's eye lens 8 are light It has a height y from the axis AX and a width b.
[0038]
Here, the relationship represented by the following expression (3) is established between the exit angle α from the conical prism 4 and the incident angle θ to the first fly-eye lens 6.
θ = (1 / m) · α (3)
Further, the height y and the width b of the annular secondary light source are expressed by the following equations (4) and (5), respectively.
y = fr · sinθ (4)
b = (fr / f1) · a (5)
[0039]
Therefore, the annular ratio A defined by the ratio between the inner diameter φi and the outer diameter φo of the annular secondary light source is expressed by the following equation (6).
[Expression 1]

Further, the outer diameter φo of the annular secondary light source is expressed by the following equation (7).
φo = 2y + b = fr {2 sin (α / m) + a / f1} (7)
[0040]
When the equation (7) is transformed, the relationship shown in the following equation (8) is obtained.
fr = φo / {2 sin (α / m) + a / f1} (8)
Thus, referring to equations (3) and (4), if only the magnification m of the afocal zoom lens 5 changes without changing the focal length fr of the zoom lens 7, the width b of the annular secondary light source changes. It can be seen that only the height y changes without. That is, by changing only the magnification m of the afocal zoom lens 5, the size (outer diameter φo) and the shape (annular ratio A) are both changed without changing the width b of the annular light source. Can be changed.
[0041]
Further, referring to equations (4) and (5), if only the focal length fr of the zoom lens 7 changes without changing the magnification m of the afocal zoom lens 5, the width b of the annular secondary light source and its It can be seen that both the height y changes in proportion to the focal length fr. That is, by changing only the focal length fr of the zoom lens 7, only the size (outer diameter φo) can be changed without changing the shape of the annular light source (annular ratio A). .
Further, referring to the equations (6) and (8), the magnification m of the afocal zoom lens 5 and the focal length of the zoom lens 7 so as to satisfy the relationship of the equation (8) with respect to the outer diameter φo of a certain size. It can be seen that by changing fr, only the shape (annular ratio A) can be changed without changing the size (outer diameter φo) of the annular secondary light source.
[0042]
Hereinafter, according to a specific numerical example, the magnification of the afocal zoom lens 5 when only the shape (annular ratio A) is changed without changing the size (outer diameter φo) of the annular secondary light source. A change in m and the focal length fr of the zoom lens 7 will be described.
In this first numerical example, the deflection angle α by the conical prism 4 is 7 degrees, the size a of each lens element of the first fly-eye lens 6 is 2.5 mm, and the focal length f1 of each lens element is 50 mm. The magnification m of the afocal zoom lens 5 necessary to change the annular ratio A from about 0.24 to about 0.95 while keeping the outer diameter φo of the annular secondary light source constant at 96 mm. The focal length fr of the zoom lens 7 is obtained. The following table (1) shows the correspondence between the magnification m of the afocal zoom lens 5 in the first numerical example, the annular ratio A of the annular secondary light source, and the focal length fr of the zoom lens 7. ing.
[0043]
[Table 1]

[0044]
Referring to Table (1), in the first numerical example, the magnification m of the afocal zoom lens 5 is changed from about 0.9 to about 1 in order to change the zone ratio A from about 0.5 to about 0.69. 6 and the focal length fr of the zoom lens 7 may be changed from about 474 mm to about 300 mm.
As described above, the conical prism 4 is configured to be detachable with respect to the illumination optical path, and is configured to be switchable with the pyramid prism 4a. Hereinafter, a case where the pyramid prism 4a is set in the illumination optical path instead of the cone prism 4 and a case where the cone prism 4 is retracted from the illumination optical path will be described.
[0045]
In the pyramid prism 4a, the mask side surface is formed in a planar shape perpendicular to the optical axis AX. The surface on the light source side of the pyramid prism 4a is composed of four refracting surfaces, and is formed in a generally pyramidal concave shape toward the light source side. More specifically, the four refracting surfaces correspond to a pyramid surface (a side surface excluding the bottom surface) of a regular quadrangular pyramid having one point on the optical axis AX and having four ridge lines along the X axis and the Z axis. . That is, the four refracting surfaces correspond to the pyramid surfaces of a regular quadrangular pyramid that is symmetric about the optical axis AX. As in the case of the conical prism 4, the pyramid prism 4a may be arranged so that the concave surface of the pyramid faces the mask side.
[0046]
Therefore, when the pyramid prism 4a is positioned in the illumination optical path in place of the conical prism 4 by the action of the light beam shape changing member drive system 22 based on the command of the control system 21, the light beam incident on the pyramid prism 4a has the optical axis AX. Is incident along the four specific directions at equal angles with respect to the center, and then enters the afocal zoom lens 5. Thus, the pyramid prism 4a constitutes a light beam shape changing member for converting the light beam from the light source 1 into four light beams decentered with respect to the optical axis AX. The light beam incident on the afocal zoom lens 5 forms four point-like light source images on the pupil plane. In this case, a quadrilateral connecting the four point-like light source images is a square having sides parallel to the X axis and the Z axis with the optical axis AX as the center. Lights from the four point light source images are emitted from the afocal zoom lens 5 as substantially parallel light beams and enter the first fly-eye lens 6. Here, the light flux enters the incident surface of the first fly-eye lens 6 from an oblique direction almost symmetrically with respect to the optical axis AX. More specifically, light beams are incident obliquely along four specific directions at equal angles with the optical axis AX as the center.
[0047]
Accordingly, four point-like light source images are formed on the rear focal plane of each lens element of the first fly-eye lens 6. Light beams from a number of point light source images formed on the rear focal plane of the first fly-eye lens 6 pass through the zoom lens 7 and then illuminate the second fly-eye lens 8 in a superimposed manner. Accordingly, a square illumination field similar to the cross-sectional shape of each lens element of the first fly-eye lens 6 is equidistant from the optical axis AX along the four symmetric radiation directions on the incident surface of the second fly-eye lens 8. Only four illumination fields that are decentered (translated), that is, a quadrupole illumination field centered on the optical axis AX are formed. As a result, as shown in FIG. 6 (a), the same quadrupole secondary light source as the illumination field formed on the incident surface is also formed on the rear focal plane of the second fly-eye lens 8 (FIG. 6 (a)). A portion indicated by a middle oblique line) is formed.
[0048]
In response to switching from the conical prism 4 to the pyramid prism 4a, switching from the annular aperture stop 9 to the aperture stop 9a is performed. The aperture stop 9a is one 4-pole aperture stop selected from three 4-pole aperture stops 402, 404 and 406. In the quadrupole aperture stop 9a, as shown in FIG. 6 (b), four circular apertures having a size almost inscribed in the four square light sources constituting the quadrupole secondary light source ( A portion indicated by white in FIG. 6B is formed. Further, as the aperture stop 9a, a quadrupole aperture stop having four quarter-circle openings (portions shown in white in FIG. 6C) as shown in FIG. 6C can also be used. .
Thus, even when the pyramid prism 4a is used as the light beam shape changing member, a quadrupole secondary light source can be formed with almost no light loss based on the light beam from the light source 1, and as a result, the secondary light source. 4 pole deformation illumination can be performed while suppressing the light quantity loss in the aperture stop 9a that restricts the luminous flux from the light.
[0049]
Then, by changing only the magnification m of the afocal zoom lens 5, the positions of the light intensity centroids of the four square light sources constituting the quadrupole secondary light source can be changed. In other words, both the size and the shape of the quadrupole secondary light source can be changed without changing the width. Here, as indicated by a broken line in FIG. 6A, the size and shape of the quadrupole secondary light source can be defined in the same manner as the annular secondary light source. That is, four circles inscribed in the four square light sources constituting the quadrupole secondary light source are assumed. Then, the shape of the quadrupolar secondary light source, that is, the zonal ratio, is defined based on the ratio φi / φo between the diameter φi of the small circle circumscribed by the four circles and the diameter φo of the large circle circumscribed by the four circles. The size of the quadrupole secondary light source can be defined based on the diameter φo of the great circle. In this case, the width b of the quadrupole secondary light source is defined as ½ of the difference between the diameter φo of the great circle and the diameter φi of the small circle.
Further, by changing only the focal length fr of the zoom lens 7, only the size of the quadrupole secondary light source can be changed without changing the shape (ring zone ratio). Further, by changing the magnification m of the afocal zoom lens 5 and the focal length fr of the zoom lens 7 so as to satisfy a predetermined relationship, only the shape of the quadrupolar secondary light source is not changed. Can be changed.
[0050]
On the other hand, when the conical prism 4 is retracted from the illumination optical path, a light beam having a square cross section enters the afocal zoom lens 5 along the optical axis AX. The light beam incident on the afocal zoom lens 5 is enlarged or reduced in accordance with the magnification, and is emitted from the afocal zoom lens 5 along the optical axis AX as a light beam having a square cross section. 6 is incident. Accordingly, one point-like light source image is formed on the rear focal plane of each lens element of the first fly-eye lens 6. Further, a square illumination field similar to the cross-sectional shape of each lens element of the first fly-eye lens 6 is formed on the incident surface of the second fly-eye lens 8 with the optical axis AX as the center. As a result, a square-shaped secondary light source centered on the optical axis AX is also formed on the rear focal plane of the second fly-eye lens 8.
[0051]
In response to the withdrawal of the conical prism 4 from the illumination optical path, switching from the annular aperture stop 9 to the circular aperture stop 9b is performed. The circular aperture stop 9b is one circular aperture stop selected from the two circular aperture stops 407 and 408, and has an opening having a size that is substantially inscribed in the square-shaped secondary light source.
In this way, by retracting the conical prism 4 from the illumination optical path, a square-shaped secondary light source is formed with almost no light loss based on the light beam from the light source 1, and an aperture for limiting the light beam from the secondary light source. Ordinary circular illumination can be performed while satisfactorily suppressing light loss at the stop.
In this case, the size of the square secondary light source can be appropriately changed by changing the magnification m of the afocal zoom lens 5 or the focal length fr of the zoom lens 7.
[0052]
Hereinafter, the switching operation of the light beam shape changing member and the aperture stop in the first embodiment will be specifically described.
First, information on various masks to be sequentially exposed in accordance with the step-and-repeat method or the step-and-scan method is input to the control system 21 via the input means 20 such as a keyboard. The control system 21 stores information such as optimum line width (resolution) and depth of focus on various masks in an internal memory unit, and responds to an input from the input means 20 to a light beam shape changing member drive system 22. Appropriate control signals are supplied to the variable power drive system 23, the variable power drive system 24, and the turret drive system 25.
[0053]
That is, when the annular deformation illumination is performed with the optimum resolution and depth of focus, the light beam shape changing member drive system 22 positions the conical prism 4 in the illumination optical path based on a command from the control system 21. Then, in order to obtain a ring-shaped secondary light source having a desired size and ring ratio at the rear focal plane of the second fly-eye lens 8, the variable power drive system 23 is based on a command from the control system 21. The magnification of the afocal zoom lens 5 is set, and the zoom drive system 24 sets the focal length of the zoom lens 7 based on a command from the control system 21. Further, in order to limit the annular secondary light source in a state where the light loss is well suppressed, the turret drive system 25 rotates the turret based on a command from the control system 21 to illuminate a desired annular aperture stop. Position in the optical path.
In this way, a ring-shaped secondary light source can be formed based on the light flux from the light source 1 with almost no light loss, and as a result, the ring stop with almost no light loss at the aperture stop that restricts the light flux from the secondary light source. Band deformation illumination can be performed.
[0054]
Further, if necessary, the magnification of the afocal zoom lens 5 is changed by the zoom drive system 23, or the focal length of the zoom lens 7 is changed by the zoom drive system 24. The size and annular ratio of the annular secondary light source formed on the rear focal plane can be appropriately changed. In this case, the turret rotates in accordance with the size of the annular secondary light source and the change in the annular ratio, and an annular aperture stop having a desired size and annular ratio is selected and positioned in the illumination optical path. The
In this way, various annular deformation illuminations can be performed by appropriately changing the size of the annular secondary light source and the annular ratio, with almost no light loss in forming and limiting the annular secondary light source. .
[0055]
In addition, when quadrupole deformation illumination is performed with an optimal resolution and depth of focus, the light beam shape changing member drive system 22 positions the pyramid prism 4 a in the illumination optical path based on a command from the control system 21. Then, in order to obtain a quadrupole secondary light source having a desired size and shape (annular ratio) on the rear focal plane of the second fly's eye lens 8, the variable power drive system 23 is supplied from the control system 21. The magnification of the afocal zoom lens 5 is set based on the command, and the variable power drive system 24 sets the focal length of the zoom lens 7 based on the command from the control system 21. Further, in order to limit the quadrupole secondary light source in a state where the light loss is well suppressed, the turret drive system 25 rotates the turret based on a command from the control system 21 to set a desired quadrupole aperture stop. Position in the illumination light path.
In this way, a quadrupole secondary light source can be formed with almost no light loss based on the light flux from the light source 1, and as a result, the light loss can be suppressed satisfactorily at the aperture stop that restricts the light flux from the secondary light source. However, quadrupole deformation illumination can be performed.
[0056]
Further, if necessary, the magnification of the afocal zoom lens 5 is changed by the zoom drive system 23, or the focal length of the zoom lens 7 is changed by the zoom drive system 24. The size and shape of the quadrupole secondary light source formed on the rear focal plane can be appropriately changed. In this case, the turret rotates in accordance with changes in the size and shape of the quadrupole secondary light source, and a quadrupole aperture stop having a desired size and shape is selected and positioned in the illumination optical path.
Thus, various quadrupole modified illuminations are performed by appropriately changing the size and shape of the quadrupole secondary light source in a state in which the loss of light quantity is satisfactorily suppressed in the formation and limitation of the quadrupole secondary light source. be able to.
[0057]
Further, when performing normal circular illumination with an optimal resolution and depth of focus, the light beam shape changing member drive system 22 retracts the conical prism 4 or the pyramid prism 4a from the illumination optical path based on a command from the control system 21. . Then, in order to obtain a square-shaped secondary light source having a desired size on the rear focal plane of the second fly-eye lens 8, the variable power drive system 23 is an afocal zoom lens based on a command from the control system 21. 5 is set, or the zoom drive system 24 sets the focal length of the zoom lens 7 based on a command from the control system 21. Further, in order to limit the square-shaped secondary light source in a state in which the light loss is satisfactorily suppressed, the turret drive system 25 rotates the turret based on a command from the control system 21, and sets a desired circular aperture stop to the illumination optical path. Position inside.
In this way, it is possible to perform normal circular illumination while satisfactorily suppressing the light loss at the aperture stop that restricts the light from the secondary light source formed with almost no light loss based on the light from the light source 1.
[0058]
Further, if necessary, the magnification of the afocal zoom lens 5 is changed by the zoom drive system 23, or the focal length of the zoom lens 7 is changed by the zoom drive system 24. The size of the square-shaped secondary light source formed on the rear focal plane can be appropriately changed. In this case, the turret rotates in accordance with the change in the size of the square secondary light source, and a circular aperture stop having an opening of a desired size is selected and positioned in the illumination optical path.
Thus, various ordinary circular illuminations can be performed by appropriately changing the σ value while favorably suppressing the light loss in the formation and limitation of the square secondary light source.
[0059]
FIG. 7 is a drawing schematically showing a configuration of an exposure apparatus provided with the illumination optical apparatus according to the second embodiment of the present invention. 8 and 9 are diagrams for specifically explaining the operation of the diffractive optical element in the second embodiment. However, in the drawings relating to the following embodiments and modifications (FIGS. 7, 11 and 12), the input means 20, the control system 21, the light beam shape changing member drive system 22, the variable power drive systems 23 and 24, and the turret drive. Illustration of the system 25 (not present in FIG. 12) is omitted.
The second embodiment has a configuration similar to that of the first embodiment. However, in the first embodiment, a conical prism or a pyramid prism is used as the light beam shape changing member, but in the second embodiment, the only difference is that a diffractive optical element is used as the light beam shape changing member. . Therefore, in FIG. 7, elements having the same functions as those of the first embodiment are denoted by the same reference numerals as in FIG. Hereinafter, the second embodiment will be described by paying attention to differences from the first embodiment.
[0060]
In the second embodiment, the light beam that has passed through the beam expander 2 as a shaping optical system is deflected in the Y direction by the bending mirror 3 and then enters the diffractive optical element 4b. The diffractive optical element 4b is configured by forming a step having a pitch of about the wavelength of exposure light (illumination light) on a glass substrate, and has a function of diffracting an incident beam to a desired angle. Specifically, as shown in FIG. 8A, the thin beam perpendicularly incident on the diffractive optical element 4b along the optical axis AX is diffracted along all directions at an equal angle around the optical axis AX, It becomes a ring-shaped beam. Therefore, when a parallel beam having a square cross section is incident on the diffractive optical element 4b along the optical axis AX, a zonal beam is formed as shown in FIG. In this way, the diffractive optical element 4b constitutes a light beam shape changing member for converting the light beam from the light source 1 into a substantially annular light beam.
[0061]
That is, the diffractive optical element 4b has the same effect as the conical prism 4 in the first embodiment in that the beam vertically incident along the optical axis AX is deflected along all directions at an equal angle around the optical axis AX. do. However, the conical prism 4 in the first embodiment deflects the entire incident light beam along all directions at an equal angle around the optical axis AX, whereas the diffractive optical element 4b in the second embodiment forms the incident light beam. Each beam is deflected along all directions at an equal angle with its incident axis (parallel to the optical axis AX) as the center. Therefore, in the second embodiment, the afocal zoom lens 5 is configured to optically substantially conjugate the diffractive optical element 4b and the incident surface of the first fly-eye lens 6.
[0062]
Thus, in the second embodiment as well, as in the first embodiment, a ring-shaped light source image is formed on the pupil plane of the afocal zoom lens 5. Then, the substantially parallel light beam emitted from the afocal zoom lens 5 is incident on the incident surface of the first fly-eye lens 6 obliquely along all directions at an equal angle with the optical axis AX as the center. As a result, an annular secondary light source is formed on the rear focal plane of the second fly's eye lens 8 based on the light beam from the light source 1 with almost no light loss. Also, almost no light loss occurs in the aperture stop 9 disposed in the vicinity of the rear focal plane of the second fly-eye lens 8. Furthermore, the first feature is that the size and shape (annular ratio) of the annular secondary light source can be changed by appropriately changing the magnification m of the afocal zoom lens 5 and the focal length fr of the zoom lens 7. It is the same as that of an Example.
[0063]
In the second embodiment, the diffractive optical element 4b is configured to be detachable with respect to the illumination optical path and is configured to be switchable with other diffractive optical elements 4c. When the diffractive optical element 4b is retracted from the illumination optical path, normal circular illumination can be performed as in the case where the conical prism or the pyramid prism is retracted in the first embodiment. Hereinafter, a case where the diffractive optical element 4c is set in the illumination optical path instead of the diffractive optical element 4b will be described.
[0064]
When the diffractive optical element 4c is used as a light beam shape changing member, as shown in FIG. 9A, a thin beam perpendicularly incident along the optical axis AX is in four specific directions at equal angles around the optical axis AX. Diffracted along, resulting in four narrow beams. Therefore, when a parallel beam having a square cross section is incident on the diffractive optical element 4b along the optical axis AX, the beam becomes a quadrupole beam as shown in FIG. 9B. Thus, the diffractive optical element 4c constitutes a light beam shape changing member for converting the light beam from the light source 1 into four light beams decentered with respect to the optical axis AX. Accordingly, four dot-like light source images are formed on the pupil plane of the afocal zoom lens 5 as in the case where the pyramid prism 4a is used in the first embodiment.
[0065]
Then, the substantially parallel light beam emitted from the afocal zoom lens 5 is incident obliquely on the incident surface of the first fly-eye lens 6 along four specific directions at an equal angle with the optical axis AX as the center. As a result, a quadrupole secondary light source is formed on the rear focal plane of the second fly's eye lens 8 based on the light beam from the light source 1 with almost no light loss. Further, the quadrupole secondary light source is limited by the aperture stop 9a disposed in the vicinity of the rear focal plane of the second fly-eye lens 8 while favorably suppressing the light amount loss. Furthermore, by appropriately changing the magnification m of the afocal zoom lens 5 and the focal length fr of the zoom lens 7, the size and shape of the quadrupole secondary light source can be changed.
[0066]
FIG. 10 is a diagram schematically illustrating a main configuration of the illumination optical apparatus according to the first modification example of the second embodiment. FIG. 10B illustrates the magnification of the afocal zoom lens 5 in comparison with the state illustrated in FIG. The enlarged state is shown.
The first modified example is different from the second example only in that a microlens array is used as the first optical integrator, and the other configuration is the same as that of the second example.
[0067]
In the first modification shown in FIG. 10, a microlens array 6 a is used instead of the first fly-eye lens 6. The microlens array 6a is an optical element composed of a large number of microlenses (microlenses) arranged vertically and horizontally, and is configured, for example, by performing etching processing on a parallel flat glass plate to form a microlens group. Accordingly, each microlens is smaller than each lens element constituting the fly-eye lens, but is the same as the fly-eye lens in that lens elements having positive refractive power are arranged vertically and horizontally. Therefore, the microlens array 6a has the same effect as the first fly-eye lens 6.
[0068]
Hereinafter, in the first modification using the diffractive optical element 4b and the microlens array 6a, only the shape (annular ratio A) is changed without changing the size (outer diameter φo) of the annular secondary light source. A change in the magnification m of the afocal zoom lens 5 and the focal length fr of the zoom lens 7 will be described according to specific numerical examples.
In this second numerical example, the diffraction angle (deflection angle) α by the diffractive optical element 4b is 7 degrees, the size a of each microlens of the microlens array 6a is 0.5 mm, and the focal length f1 of each microlens is 10 mm. It is said. The magnification m of the afocal zoom lens 5 necessary to change the annular ratio A from about 0.24 to about 0.95 while keeping the outer diameter φo of the annular secondary light source constant at 96 mm. The focal length fr of the zoom lens 7 is obtained. The following table (2) shows the correspondence relationship between the magnification m of the afocal zoom lens 5, the annular ratio A of the annular secondary light source, and the focal length fr of the zoom lens 7 in the second numerical example. ing.
[0069]
[Table 2]

[0070]
Comparing and referring to Table (1) and Table (2), the correspondence between the magnification m of the afocal zoom lens 5, the zone ratio A, and the focal length fr of the zoom lens 7 is a first numerical example and a second numerical example. You can see that they match. This is because when the microlens array 6a is used in place of the first fly-eye lens 6, it is numerically equivalent to the first fly-eye lens 6 by appropriately setting the size a and the focal length f1 of each microlens. It is shown that it is possible to exert the action of.
[0071]
FIG. 11 is a drawing schematically showing a configuration of an exposure apparatus including an illumination optical apparatus according to a second modification example of the second embodiment.
The second modification is different from the second embodiment only in that the afocal zoom lens 5 is removed and the diffractive optical element 4b and the incident surface of the first fly-eye lens 6 are arranged close to each other. Is the same as in the second embodiment. Therefore, in FIG. 11, the same reference numerals as those in FIG. 7 are given to elements having the same functions as the constituent elements of the second embodiment. Hereinafter, the second modification will be described by paying attention to differences from the second embodiment.
[0072]
As described above, in the second embodiment, the afocal zoom lens 5 optically couples the diffractive optical element 4b and the incident surface of the first fly-eye lens 6 optically in a conjugate manner. Has a function of changing the angle of the incident light beam on the incident surface. Therefore, even if the afocal zoom lens 5 is removed from the illumination optical path and the diffractive optical element 4b and the incident surface of the first fly's eye lens 6 are arranged close to each other, the incident light flux on the incident surface of the first fly's eye lens 6 can be reduced. The angle is only fixedly defined by the diffraction angle of the diffractive optical element 4b. Therefore, in the second modification, the size of the annular secondary light source formed on the rear focal plane of the second fly-eye lens 8 can be changed by changing the focal length of the zoom lens 7. However, the zone ratio cannot be changed.
[0073]
FIG. 12 is a drawing schematically showing a configuration of an exposure apparatus including an illumination optical apparatus according to the third example of the present invention.
The third embodiment has a configuration similar to that of the first embodiment. However, in the first embodiment, a fly-eye lens is used as the second optical integrator, but in the second embodiment, a rod-type optical integrator (hereinafter simply referred to as “rod-type integrator”) is used as the second optical integrator. The only difference is that Therefore, in FIG. 12, the same reference numerals as those in FIG. 1 are given to elements having the same functions as the constituent elements of the first embodiment. Hereinafter, the third embodiment will be described by paying attention to differences from the first embodiment.
[0074]
In the third embodiment, in response to the use of the rod-type integrator 8a instead of the second fly-eye lens 8, a condenser lens 7a is provided in the optical path between the zoom lens 7 and the rod-type integrator 8a. An imaging optical system 10a is installed instead of the optical system 10, and an aperture stop for limiting the secondary light source is removed. Here, the combining optical system including the zoom lens 7 and the condenser lens 7a optically substantially conjugates the rear focal plane of the first fly-eye lens 6 and the incident surface of the rod integrator 8a. The imaging optical system 10a optically couples the exit surface of the rod integrator 8a and the mask 11 optically in a conjugate manner.
[0075]
The rod-type integrator 8a is an inner surface reflection type glass rod made of a glass material such as quartz glass or fluorite, and passes through a condensing point using total reflection at the boundary surface between the inside and the outside, that is, the inside surface. A number of light source images corresponding to the number of internal reflections is formed along a plane parallel to the incident surface. Here, most of the light source images to be formed are virtual images, but only the light source image at the center (condensing point) is a real image. That is, the light beam incident on the rod-type integrator 8a is divided in the angular direction by internal reflection, and a secondary light source composed of a large number of light source images is formed along a plane parallel to the incident surface through the condensing point. In the case of the third embodiment, an annular secondary light source is formed when the conical prism 4 is used as the light beam shape changing member, and a quadrupolar secondary light source is formed when the pyramid prism 4a is used. The
[0076]
The light beam from the secondary light source formed on the incident side by the rod integrator 8a is superimposed on the exit surface, and then uniformly illuminates the mask 11 on which a predetermined pattern is formed via the imaging optical system 10a. . As described above, the imaging optical system 10a optically couples the exit surface of the rod integrator 8a and the mask 11 (and thus the wafer 13) optically in a conjugate manner. Therefore, a rectangular illumination field similar to the cross-sectional shape of the rod integrator 8a is formed on the mask 11.
[0077]
As described above, in the third embodiment as well, the annular deformation illumination can be performed by using the conical prism 4 as the light beam shape changing member while suppressing the light amount loss as well as the first embodiment. By using the pyramid prism 4a as a member, quadrupole deformation illumination can be performed, and normal circular illumination can be performed by retracting the light beam shape changing member from the illumination optical path. Further, the size and shape of the secondary light source can be changed by appropriately changing the magnification m of the afocal zoom lens 5 and the focal length fr of the zoom lens 7.
[0078]
As described above, in the above-described embodiments and modifications, modified illumination such as annular deformation illumination and quadrupole deformation illumination, and a normal circular shape, while suppressing the light amount loss in the aperture stop for restricting the secondary light source satisfactorily. Lighting can be performed. In addition, it is possible to change the parameters of the modified illumination while satisfactorily suppressing the light loss at the aperture stop by a simple zooming operation. Therefore, the resolution and depth of focus of the projection optical system suitable for the fine pattern to be exposed and projected can be obtained by appropriately changing the type and parameters of the modified illumination. As a result, good projection exposure with high throughput can be performed under high exposure illuminance and good exposure conditions.
[0079]
The wafer that has undergone the exposure process (photolithography process) by the exposure apparatus of each of the embodiments and the modified examples is subjected to a development process and then an etching process that removes portions other than the developed resist, and unnecessary after the etching process. The wafer process is completed through a resist removal process for removing the resist. After the wafer process is completed, in the actual assembly process, the wafer is cut into chips for each burned circuit, dicing is performed to form chips, bonding is applied to each chip, and packaging is performed for each chip. Through these steps, a semiconductor device (LSI or the like) as a device is finally manufactured.
[0080]
In the above description, an example in which a semiconductor element is manufactured by a photolithography process in a wafer process using a projection exposure apparatus has been described. However, a liquid crystal display element, as a semiconductor device, by a photolithography process using an exposure apparatus, A thin film magnetic head and an image sensor (CCD, etc.) can be manufactured.
In this way, in the case of the exposure method for manufacturing a semiconductor device using the illumination optical apparatus of the present invention, projection exposure can be performed under good exposure conditions, and thus a good semiconductor device can be manufactured.
[0081]
In performing the circular aperture illumination in the above-described embodiments and modifications, it is desirable to retract the light beam shape changing member from the illumination optical path. By retracting the light beam shape changing member (4, 4a, 4b), a so-called double fly-eye system configuration as described in JP-A-58-147708 can be obtained.
At this time, in the apparatus configured as illustrated in FIGS. 1, 7, and 12, the afocal zoom lens 5 may be retracted simultaneously. In the apparatus configured as illustrated in FIG. 11, the first fly-eye lens 6 is retracted at the same time, and instead, another fly-eye lens suitable for the illumination condition is used as the first fly-eye lens in the illumination optical path. May be inserted.
In the above-described embodiments and modifications, a prism having a conical concave surface is used as the conical prism, but a prism having a conical convex surface can also be used. Similarly, a prism having a pyramid convex surface can be used for the pyramid prism.
[0082]
In the above-described embodiments and modifications, the present invention has been described by taking the projection exposure apparatus provided with the illumination optical apparatus as an example. However, the present invention is applied to a general illumination optical apparatus for uniformly illuminating the irradiated surface other than the mask. It is clear that the invention can be applied.
Further, in the above-described embodiments and modifications, examples have been shown in which a KrF excimer laser that supplies light with a wavelength of 248 nm, an ArF excimer laser that supplies light with a wavelength of 193 nm, or the like is used as a light source. It goes without saying that the present invention can also be applied to other devices. For example, F that supplies light having a wavelength of 157 nm ₂ A light source unit comprising a combination of a laser light source such as a laser or a laser light source that supplies light of a predetermined wavelength and a non-linear optical element that converts light from the laser light source into light of a short wavelength of 200 nm or less It can also be used as the light source means of the invention.
[0083]
【The invention's effect】
As described above, in the illumination optical device according to the present invention, the deformation illumination such as the annular deformation illumination and the quadrupole deformation illumination, and the normal circular shape, while suppressing the light amount loss in the aperture stop for limiting the secondary light source satisfactorily. Lighting can be performed. In addition, it is possible to change the parameters of the modified illumination while suppressing the light loss at the aperture stop well by a simple zooming operation.
[0084]
Therefore, in the exposure apparatus incorporating the illumination optical apparatus of the present invention, the resolution and depth of focus of the projection optical system suitable for the fine pattern to be exposed and projected can be obtained by appropriately changing the type and parameters of the modified illumination. As a result, good projection exposure with high throughput can be performed under high exposure illuminance and good exposure conditions. In the exposure method in which the mask pattern arranged on the irradiated surface is exposed on the photosensitive substrate using the illumination optical device of the present invention, projection exposure can be performed under good exposure conditions. A good semiconductor device can be manufactured.
[Brief description of the drawings]
FIG. 1 is a drawing schematically showing a configuration of an exposure apparatus provided with an illumination optical apparatus according to a first embodiment of the present invention.
FIG. 2 is a diagram schematically showing a configuration of a turret in which a plurality of aperture stops are arranged in a circumferential shape.
FIG. 3 is a diagram schematically showing a configuration from a conical prism 4 to an incident surface of a first fly-eye lens 6, and is a diagram for explaining the operation of an afocal zoom lens 5. FIG.
4 is a diagram schematically showing a configuration from a first fly-eye lens 6 to an aperture stop 9, and a light beam obliquely incident on an incident surface of the first fly-eye lens 6 is incident on a second fly-eye lens 8. FIG. It is a figure which shows a mode that a ring-shaped illumination field is formed in a surface.
FIG. 5 is a diagram schematically showing a configuration from a conical prism 4 to an incident surface of a second fly's eye lens 8, wherein the magnification of the afocal zoom lens 5, the focal length of the zoom lens 7, and the second fly's eye lens; It is a figure explaining the relationship with the magnitude | size and shape of an annular illumination field formed in 8 entrance planes.
6 is a diagram showing a configuration of a quadrupole secondary light source formed on the rear focal plane of the second fly's eye lens 8 and a quadrupole aperture stop disposed in the vicinity thereof. FIG.
FIG. 7 is a drawing schematically showing a configuration of an exposure apparatus including an illumination optical apparatus according to a second example of the present invention.
FIG. 8 is a diagram for specifically explaining the operation of the diffractive optical element 4b in the second embodiment.
FIG. 9 is a diagram for specifically explaining the operation of the diffractive optical element 4c in the second embodiment.
FIG. 10 is a diagram schematically showing a main configuration of an illumination optical apparatus according to a first modification of the second embodiment, in which (b) shows the magnification of the afocal zoom lens 5 rather than the state (a). The enlarged state is shown.
FIG. 11 is a drawing schematically showing a configuration of an exposure apparatus including an illumination optical apparatus according to a second modification example of the second embodiment.
FIG. 12 is a drawing schematically showing a configuration of an exposure apparatus including an illumination optical apparatus according to a third example of the present invention.
[Explanation of symbols]
1 Light source
2 Beam expander
3 Bending mirror
4 Conical prism
4a Pyramidal prism
4b, 4c diffractive optical element
5 Afocal zoom lens
6 First fly-eye lens
6a Micro lens array
7 Zoom lens
7a Condenser lens
8 Second fly-eye lens
8a Rod type integrator
9 Aperture stop
10 Condenser optics
10a Imaging optical system
11 Mask
12 Projection optical system
13 Wafer

Claims (9)

In the illumination optical device that illuminates the illuminated surface ,
A first optical integrator for forming a first multiple light source comprising a plurality of light sources based on the light flux from the light source means;
A second optical integrator for forming a second multiple light source comprising a larger number of light sources based on the light flux from the first multiple light source formed by the first optical integrator;
A condenser optical system for condensing a light beam from a second multiple light source formed by the second optical integrator to illuminate the irradiated surface;
In order to form a ring-shaped light source or a plurality of light sources decentered from the reference optical axis as the second multiple light sources, the light beam from the light source means is substantially symmetrical with respect to the reference optical axis from the oblique direction. An oblique light beam forming means for converting into a light beam incident on the integrator ,
The oblique light beam forming means includes:
A luminous flux shape changing member for converting the luminous flux from the light source means into a substantially annular luminous flux or a plurality of luminous fluxes decentered with respect to the reference optical axis;
The light beam whose shape has been changed by the light beam shape changing member is incident on the first optical integrator in a superimposed manner from an oblique direction almost symmetrically with respect to the reference optical axis. the illumination optical device according to claim Rukoto which have a a focusing optical system for focusing. The illumination optical apparatus according to claim 1, wherein the light beam shape changing member includes a plurality of prism members or a plurality of diffractive optical elements configured to be detachable with respect to the illumination optical path . In order to change the annular ratio of the annular light source formed as the second multiple light source or the position of the light intensity centroid of each of the plurality of light sources formed as the second multiple light source, the condensing optical system, The illumination optical apparatus according to claim 1, further comprising a first variable power optical system having a variable magnification . In the optical path between the first optical integrator and the second optical integrator, a light beam from a first multiple light source formed by the first optical integrator is condensed and guided to the second optical integrator. A relay optical system,
4. The relay optical system according to claim 1, wherein the relay optical system includes a second variable magnification optical system having a variable magnification in order to change the size of the second multiple light sources. 5. Illumination optical device. 5. The illumination optical apparatus according to claim 3, wherein the first variable magnification optical system is capable of continuously changing the magnification while maintaining a non-focus optical system . 6. The illumination optical apparatus according to claim 1, wherein the condensing optical system connects the light beam shape changing member and the first optical integrator in a conjugate manner. The illumination optical apparatus according to claim 1, and a projection optical system for projecting and exposing a pattern disposed on the irradiated surface onto a photosensitive substrate. Exposure equipment to do. An exposure method, comprising: exposing a pattern disposed on the irradiated surface onto a photosensitive substrate using the illumination optical apparatus according to claim 1. An exposure step of exposing a photosensitive substrate to a pattern disposed on the irradiated surface using the illumination optical apparatus according to any one of claims 1 to 6,
A device manufacturing method comprising: a developing step of developing the exposed photosensitive substrate.

Images