JP3690819B2 - Projection optical system, exposure apparatus using the same, and exposure method - Google Patents

Projection optical system, exposure apparatus using the same, and exposure method Download PDF

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Publication number
JP3690819B2
JP3690819B2 JP01627593A JP1627593A JP3690819B2 JP 3690819 B2 JP3690819 B2 JP 3690819B2 JP 01627593 A JP01627593 A JP 01627593A JP 1627593 A JP1627593 A JP 1627593A JP 3690819 B2 JP3690819 B2 JP 3690819B2
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optical system
aperture stop
light beam
partial
partial optical
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JPH06230287A (en
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敏朗 石山
豊 末永
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Nikon Corp
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Nikon Corp
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    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03FPHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/70Microphotolithographic exposure; Apparatus therefor
    • G03F7/70216Mask projection systems
    • G03F7/70225Optical aspects of catadioptric systems, i.e. comprising reflective and refractive elements

Description

【0001】
【産業上の利用分野】
本発明は、マスク上の回路パターンを感光基板上に投影転写するために好適な反射屈折光学系に関するものである。
【0002】
【従来の技術】
従来、LSI等の集積回路を製造する際にウェハ上のフォトレジストにマスクパターンを投影露光するために好適な光学系が例えば特開昭61-203419 号公報に開示されている。この特開昭61-203419 号公報のものは、図7に示す如く、反射面M1 〜M3 を有し物体Oの1次像I1 を形成する第1の部分光学系K1 と、反射面M4 を有し、1次像I1 からの光により縮小像(2次像)I2 を形成する第2の部分光学系K2 とを有するように構成される。
【0003】
そして、このような反射屈折光学系においても、光学系の開口数の設定及び入射瞳及び射出瞳位置の設定のために、光学系内の光路を通過する光束の周縁部を制限する開口絞りを設ける必要がある。ここで、図7に示す反射屈折光学系においては、反射面M2,M4 の位置が開口絞りとなる、即ち、主光線が反射面M2,M4 にて光軸Axと交わるように構成されている。
【0004】
【発明が解決しようとする課題】
しかしながら、反射面M2,M4 の位置に開口絞りを設けることは、反射屈折光学系の光学設計の自由度を著しく損なう問題点があった。例えば、テレセントリック性を維持するにあたっては、入射瞳位置と射出瞳位置とを無限遠に設定するように屈折力配置を定めるが、上述の如く開口絞り位置があらかじめ定められていると、屈折力配置が一義的に定まり、良好な結像性能となる光学設計を行うことができない恐れがある。
【0005】
また、反射面以外の位置に開口絞りを設けることも考えられるが、反射屈折光学系においては、反射面によって光路が折り返されているため、開口絞り位置にて光束が重なり合うことが多い。このとき、単一の開口絞りにて光束の全ての周縁部を制限すると、他の光束(反射面にて折り返された光束)を遮光してしまう問題点がある。
【0006】
そこで、本発明は、光学設計上の自由度の高い投影光学系を提供することを第1の目的とする。また、本発明は、複数の光路が重なる位置に開口絞りを配置できる投影光学系を提供することを第2の目的とする。さらに、これらの投影光学系を使った露光装置および方法を提供することを第3の目的とする。
【0007】
【課題を解決するための手段】
上述の目的を達成するために、本発明による投影光学系は、以下の構成を有する。例えば図1に示すごとく、物体側から順に、正の屈折力を持ち物体Oの1次像I1を形成する第1部分光学系K1と、正の屈折力を持ち1次像からの光により2次像I2を形成する第2部分光学系K2とを有する投影光学系は、第1部分光学系の光路内に少なくとも1つの開口絞りS1を設けると共に、第2部分光学系の光路内に少なくとも1つの開口絞りS2を設けるように構成される。
第2発明による投影光学系は、第1位置に配置され物体面Maからの光束の一部を制限する第1開口絞りS1と、第1位置とは異なる第2位置に配置され第1開口絞りS1で制限されなかった光束を制限する第2開口絞りS2とを有するように構成される。
また、第3発明による露光装置は、マスクパターンPAを感光基板に露光する露光装置において、マスクパターンPAと感光基板との間の光路中に配置され正の屈折力を持ちマスクパターンPAの1次像I1を形成する第1部分光学系K1と、第1部分光学系K1と感光基板との間の光路中に配置され正の屈折力を持ち1次像I1からの光により2次像I2を形成する第2部分光学系K2と、第1、第2部分光学系の少なくとも一方に配置された反射鏡と、第1部分光学系K1の光路内に設けられ光束を制限する第1開口絞りS1と、第2部分光学系K2の光路内に設けられ前記光束を制限する第2開口絞りS2とで構成される。
また、第4発明による露光装置は、第1位置に配置されマスクパターンPAからの光束の一部を制限する第1開口絞りS1と、第1位置とは異なる第2位置に配置され第1開口絞りS1で制限されなかった光束を制限する第2開口絞りS2とで構成される。
【0008】
【作用】
上述の如き構成により、投影光学系の光路の物理的な配置の自由度がある箇所に開口絞りを配置して光束の一部を制限し、前記開口絞りとは異なる開口絞りを別の位置に配置して、前記開口絞りにて制限されなかった光束の残りを部分的に制限することにより、配置の制約なしに、投影光学系全体として開口絞りの作用を達成することができる。これにより、投影光学系の光学設計上の自由度が上がるばかりか、この投影光学系を製作する上での空間的な余裕を持たせることができる。
【0009】
また、互いに異なる開口径を有する開口絞りをそれぞれ交換可能に設けるか、開口径を変化させる構成にすれば、投影光学系の開口数を変化させることができる。また、かかる投影光学系を使った露光装置、方法では、投影性能が向上しているため回路パターンを正確に感光基板に露光できる。
【0010】
【実施例】
以下、図面を参照して、本発明による実施例を説明する。図1は、本発明による反射屈折光学系を投影露光装置の投影光学系に適用した例の構成と光路とを示す図である。なお、図1において、物体面Oを照明するための照明光学系は図示省略している。そして、図2に示す如く、物体面OとしてのマスクMaには、所定の回路パターン領域PAが形成されており、このマスクMaと、図示なき照明光学系による円弧形状の照明領域LAとを走査方向に相対的に移動させて照明する。このとき、図1の2次像I2 には、円弧形状の2次像が形成され、この2次像が形成される位置に、走査方向に可動な感光基板を設ければ、走査露光、いわゆるステップ・アンド・スキャン方式の投影露光を実現することができる。
【0011】
ここで、図2に戻って、円弧形状の照明領域LAは、反射屈折光学系の光軸(光軸Ax1 )を中心とする所定の半径rの円弧と、光軸Ax1 から所定の幅a(スリット幅a)だけずれた点Ax1'を中心とする半径rの円弧と、間隔b(スリット長b)の直線とで囲まれる領域となる。なお、円弧状の照明領域としては、光軸Ax1 を中心とする同心円状の領域も考えられるが、スキャン露光する際の露光量が光軸Ax3 と軸外とで異なるため望ましくない。
【0012】
図1に戻って、上述の如き照明領域にて照明されたマスク面(物体面O)からの光は、光軸Ax1 に沿って配置されたレンズ成分L1 〜L3 を介して、平面反射鏡MP1 にて略45°偏向され、光軸Ax1 と垂直な光軸Ax2 に沿って配置され凹面を光線の入射側に向けた第1凹面反射鏡M1 にて反射される。そして、第1凹面反射鏡M1 の反射側に、物体面Oの1次像I1 を形成する。ここで、レンズ成分L1 〜L3 と第1凹面反射鏡M1 とが第1部分光学系K1 を構成している。
【0013】
そして、1次像I1 からの光は、光軸Ax2 に沿って配置されたレンズ成分L4 〜L6 を介して、平面反射鏡MP2 にて略45°偏向される。この平面反射鏡MP2 の反射側(光の射出側)には、光軸Ax2 と垂直な(光軸Ax1 と平行な)光軸Ax3 に沿って、レンズ成分L7 と第2凹面反射鏡M2 とが配置されており、平面反射鏡MP2 から射出した光は、レンズ成分L7 を介して第2凹面反射鏡M2 にて反射された後、再びレンズ成分L7 を介してレンズ成分L8 〜L14へ向かう。このレンズ成分L8 〜L14は、全体として正の屈折力を有しており、レンズ成分L7 からの光によって、1次像I1 の縮小像である2次像I2 を基板上に形成する。ここで、レンズ成分L4 〜L6 、レンズ成分L7 、第2凹面反射鏡M2 及びレンズ成分L8 〜L14が第2部分光学系K2 を構成している。
【0014】
さて、円弧形状の照明領域にて照明された物体面Oからの光束LB1 がレンズ成分L1 〜L3 及び平面反射鏡MP1 を介して開口絞りS1 に達すると、その光束断面は、図3(a) に示す如くほぼ円形状となる。ここで、開口絞りS1 の位置にて光束を円形状となる如く遮光することが望ましいが、この位置においては、上述の如き光束LB1 が通過する他に、第1凹面反射鏡M1 から1次像I1 へ向かう光束LB2 が通過する。このため、円形開口部を持つ従来の開口絞りでは、光束LB2 を遮ることなく、効果的に光束LB1 を遮光することができない。
【0015】
また、第2部分光学系K2 中の第7レンズ成分L7 から第8レンズ成分L8 へ向かう光束LB3 が開口絞りS2 の位置を通過する際に、その光束断面形状はほぼ円形状となる。ここで、開口絞りS2 の位置に、円形状の開口部を持つ遮光枠を配置することも考えられるが、図3(b) に示す如く、この位置の近傍には平面反射鏡MP2 が配置されており、空間の余裕がないため、円形状の開口部を持つ遮光枠を設けることはできない。
【0016】
そこで、本実施例においては、反射屈折光学系の光路内の2ヶ所に、互いに異なる2つの開口絞りS1,S2 を配置するように構成している。具体的には、図4(a) の如きほぼ半円形状の開口部を有する開口絞りS1 を第1部分光学系K1 の瞳面近傍に配置し、図4(b) の如きほぼ半円形状の開口部を有する開口絞りS2 を第2部分光学系K2 の瞳面近傍に配置している。
【0017】
即ち、図4(a) の如く、開口絞りS1 によって、光束LB1 の周縁部のうち、図中破線にて示す光束LB2 と重ならない領域が遮光(制限)される。この一部制限された光束LB1 が開口絞りS2 の位置に達すると光束LB3 となる。そして、図4(b) に破線にて示す如き光束LB3 の制限されない領域は、開口絞りS2 のほぼ半円形状の開口部によって遮光(制限)される。
【0018】
なお、開口絞りS1 により制限される領域と、開口絞りS2 により制限される領域とは、多少重なることが望ましい。
ここで、本実施例における開口絞りS1,S2 は、反射屈折光学系の物体高(光軸Ax1 からの距離)100mm における開口数が0.45となり、かつ両側テレセントリックが達成される如く設けられている。
【0019】
このように、本実施例によると、第1部分光学系K1 に設けられた開口絞りS1 と、第2部分光学系K2 に設けられた開口絞りS2 とによって、反射屈折光学系を通過する光束を有効に制限しているので、これらの開口絞りS1,S2 の配置に何ら制約はない。
また、テレセントリック性を維持するための開口絞り位置に開口絞りを配置することが物理的に困難である場合でも、本実施例による反射屈折光学系においては、開口絞り位置の自由度が多いので、良好にテレセントリック性が維持できる光学設計ができる。
【0020】
次に、図5を参照して、本発明による第2実施例を説明する。図5は、本実施例の構成及び光路を示す図である。そして、本実施例は、本発明を適用するために、米国特許4,747,678 号公報の第2実施例に開示された反射屈折光学系の光路の取り回しを変更したものである。
この図5において、物体面Oからの光束は、光軸Ax1 に沿って配置されたレンズ成分L1,L2 を介して、光軸Ax1 に対して45°で斜設された平面反射鏡MP1 にて偏向され、光軸Ax1 と垂直な光軸Ax2 に曲率中心を持ち光の入射側に凹面を向けた凹面反射鏡M1 にて反射される。この凹面反射鏡M1 の反射側には、レンズ成分L3 と、入射側に凸面を向けた凸面反射鏡M2 とが配置されており、凹面反射鏡M1 からの光束は、レンズ成分L3 を介して凸面反射鏡M2 にて反射され、再びレンズ成分L3 を介して、光軸Ax2 に沿って配置され光の入射側に凹面を向けた凹面反射鏡M3 に向かう。ここで、凸面反射鏡M2 の近傍には、開口絞りS1 が配置されており、凸面反射鏡M2 から凹面反射鏡M3 へ向かう光束LB1 の開口絞りS1 側の周縁部を遮光(制限)している。そして、開口絞りS1 を通過する光束LB1 は、凹面反射鏡M3 にて反射され、再び開口絞りS1 近傍を通過する光束LB2 となる。従って、開口絞りS1 近傍には、開口絞りS1 の位置の光束断面を示す図6の如く、ほぼ円形状の光束断面の光束LB1 と、円弧形状の光束LB2 とが位置する。ここで、開口絞りS1 は、円周のほぼ2/3にわたる部分円形状の開口部を有しており、光束LB2 を遮光することなく光束LB1 の最周縁部を部分的に制限している。
【0021】
図5に戻って、上記開口絞りS1 の近傍を通過した光束LB2 は、光軸Ax2 に沿って配置されたレンズ成分L4,L5 から射出して、同じく光軸Ax2 に沿って配置されたレンズ成分L6 の近傍に物体の1次像I1 を形成する。ここで、レンズ成分L1,L2 、凹面反射鏡M1 、レンズ成分L3 、凸面反射鏡M2 、凹面反射鏡M3 及びレンズ成分L4,L5 が第1部分光学系K1 を構成する。
【0022】
そして、上記1次像I1 からの光束は、レンズ成分L6 〜L8 を介して、光軸Ax2 に対して45°で斜設された平面反射鏡MP2 にて偏向され、この光軸Ax2 と垂直な光軸Ax3 に沿って配置された凹面反射鏡M4 へ向かう如き光束LB3 となる。そして、光束LB3 は、凹面反射鏡M4 にて反射されて光束LB4 となる。ここで、光束LB4 の進行方向(凹面反射鏡M4 の反射側)には、開口絞りS2 が配置されており、凹面反射鏡M4 からレンズ成分L9 へ向かう光束LB4 の開口絞りS2 側の周縁部を制限している。ここで、図6の如く、開口絞りS2 の近傍を通過する光束LB3 は、光束LB4 の周囲を覆うような円弧形状の光束断面を有している。従って、開口絞りS2 は、光束LB3 を遮光することなく光束LB4 を制限するために、円周のほぼ1/3にわたる部分円形状の開口部を有する如く構成されている。これにより、光束LB4 の最周縁部の略1/3に渡る領域、すなわち開口絞りS1 にて制限されなかった領域を制限している。
【0023】
そして、図5に戻って、開口絞りS2 を介した光束は、光軸Ax3 に沿って配置されたレンズ成分L9 〜L11を介して、その射出側に物体の1次像I1 の縮小像である2次像I2 を形成する。ここで、レンズ成分L6 〜L8 、凹面反射鏡M4 及びレンズ成分L9 〜L11が第2部分光学系K2 を形成する。
このように、反射屈折光学系から射出する光束は、開口絞りS1 と開口絞りS2 とによる結果として、全ての周縁部が制限されている。従って、反射屈折光学系においては、所望の開口数を得ること及び両側テレセントリックを維持することが達成できる。なお、本実施例における開口数は、物体高79mmにおいて、0.35である。
【0024】
このように、本発明による反射屈折光学系は、どのような光路の取り回しであっても開口絞りを配置することができる。これにより、反射屈折光学系内を通過する光束を制限することで、所望の開口数を得ると同時に、テレセントリック性の維持をも達成している。
また、第1及び第2実施例において、開口絞りS1,S2 の開口部の径が可動となる如く構成すれば、反射屈折光学系の開口数を可変とすることができる。例えば、図4(a),(b) に示す如き開口絞りS1,S2 を図中矢印方向(光束断面に沿った方向)に可動となる如く設ける。そして、開口絞りS1,S2 の開口部を通過する光束の径が変化するように、それぞれの開口絞りS1,S2 を移動させれば、反射屈折光学系全体の開口数を変化させることができる。また、開口数を変化させるにあたって、互いに異なる開口径を持つ複数の開口絞りを交換可能に設けても良い。
【0025】
なお、上述の各実施例において、開口絞りS1,S2 の開口部の形状は、部分円形状であれば良い。このとき、結果として光束の周縁部の全周が制限されていれば良いため、各実施例の如き半円状の開口部や1/3と2/3との部分円形状の開口部に限られることはない。
また、本実施例においては、各部分光学系K1,K2 内に2組の開口絞りS1,S2 を配置したが、2組以上の開口絞りを設けても良いことは言うまでもない。例えば、物体の1次像を作る部分光学系と、この1次像をリレーして2次像を作る部分光学系と、2次像をリレーして3次像を作る部分光学系とを有する反射屈折光学系においては、各部分光学系内に開口絞りを配置できる。このとき、各部分光学系内の開口絞りの開口部の形状は、部分円形状であれば良い。
【0026】
【発明の効果】
上述の如き本発明によると、開口絞り位置の自由度が多くなるため、光学設計上の制約が非常に少ない反射屈折光学系を得ることができる。さらに、複数の光路が重なる位置でも光路を遮ることなく開口絞りを配置できる。これにより、所望の開口数を得ることができ、テレセントリック性の維持をも達成できる反射屈折光学系を提供できる。
【図面の簡単な説明】
【図1】本発明による第1実施例の構成及び光路を示す図。
【図2】物体面上の照明領域を示す平面図。
【図3】本発明による反射屈折光学系の開口絞りにおける光束断面を示す図。
【図4】開口絞りの形状を示す平面図。
【図5】本発明による第2実施例の構成と光路とを示す図。
【図6】第2実施例における光束断面と開口絞りとを示す平面図。
【図7】従来の反射屈折光学系を示す図。
【符号の説明】
1 ‥‥ 第1部分光学系、
2 ‥‥ 第2部分光学系、
O ‥‥ 物体面、
1 ‥‥ 物体の1次像、
2 ‥‥ 物体の2次像、
[0001]
[Industrial application fields]
The present invention relates to a catadioptric optical system suitable for projecting and transferring a circuit pattern on a mask onto a photosensitive substrate.
[0002]
[Prior art]
Conventionally, an optical system suitable for projecting and exposing a mask pattern onto a photoresist on a wafer when manufacturing an integrated circuit such as an LSI is disclosed in, for example, Japanese Patent Application Laid-Open No. 61-203419. As shown in FIG. 7, Japanese Patent Laid-Open No. 61-203419 discloses a first partial optical system K 1 having reflecting surfaces M 1 to M 3 and forming a primary image I 1 of an object O; The second partial optical system K 2 has a reflecting surface M 4 and forms a reduced image (secondary image) I 2 by light from the primary image I 1 .
[0003]
In such a catadioptric optical system, an aperture stop that restricts the peripheral edge of the light beam passing through the optical path in the optical system is used for setting the numerical aperture of the optical system and setting the entrance pupil and exit pupil positions. It is necessary to provide it. Here, in the catadioptric optical system shown in FIG. 7, the positions of the reflecting surfaces M 2 and M 4 serve as an aperture stop, that is, the principal ray intersects the optical axis Ax at the reflecting surfaces M 2 and M 4 . It is configured.
[0004]
[Problems to be solved by the invention]
However, providing an aperture stop at the positions of the reflecting surfaces M 2 and M 4 has a problem that the degree of freedom in the optical design of the catadioptric optical system is significantly impaired. For example, in maintaining telecentricity, the refractive power arrangement is determined so that the entrance pupil position and the exit pupil position are set to infinity, but if the aperture stop position is predetermined as described above, the refractive power arrangement Is unambiguously determined, and there is a possibility that optical design with good imaging performance cannot be performed.
[0005]
Although it is conceivable to provide an aperture stop at a position other than the reflecting surface, in the catadioptric optical system, since the optical path is folded back by the reflecting surface, the light beams often overlap at the aperture stop position. At this time, if all the peripheral portions of the light beam are limited by a single aperture stop, there is a problem in that other light beams (light beams folded at the reflecting surface) are shielded.
[0006]
Therefore, a first object of the present invention is to provide a projection optical system having a high degree of freedom in optical design. A second object of the present invention is to provide a projection optical system capable of disposing an aperture stop at a position where a plurality of optical paths overlap. It is a third object of the present invention to provide an exposure apparatus and method using these projection optical systems.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, a projection optical system according to the present invention has the following arrangement. For example, as shown in FIG. 1, in order from the object side, a first partial optical system K 1 that has a positive refractive power and forms a primary image I 1 of the object O, and light from the primary image that has a positive refractive power. by the projection optical system and a second partial optical system K 2 for forming a secondary image I 2, together with at least one providing the aperture stop S 1 to the first partial optical system in the optical path, the second partial optical system configured such that at least one of an opening diaphragm S 2, which in the light path.
The projection optical system according to the second aspect of the present invention is arranged at the first position, the first aperture stop S 1 that restricts a part of the light beam from the object surface Ma, and the first aperture that is arranged at a second position different from the first position. The second aperture stop S 2 is configured to limit the light beam that is not limited by the stop S 1 .
An exposure apparatus according to a third aspect of the present invention is an exposure apparatus that exposes a mask pattern PA onto a photosensitive substrate. The exposure apparatus is disposed in an optical path between the mask pattern PA and the photosensitive substrate and has a positive refractive power and has a primary refractive power. the first partial optical system K 1 for forming an image I 1, the light from the primary image I 1 has a positive refractive power arranged in an optical path between the first partial optical system K 1 and the photosensitive substrate 2 a second partial optical system K 2 for forming a primary image I 2, first, a reflecting mirror disposed on at least one of the second partial optical system, a light beam is provided in the first part the optical path of the optical system K 1 The first aperture stop S 1 for limiting and the second aperture stop S 2 for limiting the luminous flux provided in the optical path of the second partial optical system K 2 are configured.
The exposure apparatus according to the fourth aspect of the present invention is arranged at a first position, which is arranged at a first position and is arranged at a second position different from the first position, and a first aperture stop S 1 that restricts a part of the light beam from the mask pattern PA. It is composed of a second aperture stop S 2 that limits a light beam that is not limited by the aperture stop S 1 .
[0008]
[Action]
With the configuration as described above, an aperture stop is arranged at a place where there is a degree of freedom in physical arrangement of the optical path of the projection optical system to limit a part of the light beam, and an aperture stop different from the aperture stop is placed at another position. By arranging and partially limiting the remainder of the light beam that was not restricted by the aperture stop, the function of the aperture stop can be achieved as a whole of the projection optical system without restrictions on the arrangement. As a result, the degree of freedom in the optical design of the projection optical system is increased, and a spatial margin can be provided for manufacturing the projection optical system.
[0009]
Further, if the aperture stops having different aperture diameters are provided interchangeably or the aperture diameter is changed, the numerical aperture of the projection optical system can be changed. Further, in the exposure apparatus and method using such a projection optical system, since the projection performance is improved, the circuit pattern can be accurately exposed on the photosensitive substrate.
[0010]
【Example】
Embodiments according to the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a configuration and an optical path of an example in which a catadioptric optical system according to the present invention is applied to a projection optical system of a projection exposure apparatus. In FIG. 1, an illumination optical system for illuminating the object plane O is not shown. As shown in FIG. 2, a predetermined circuit pattern area PA is formed on the mask Ma as the object plane O, and this mask Ma and an arc-shaped illumination area LA by an illumination optical system (not shown) are scanned. Move relative to the direction and illuminate. At this time, an arc-shaped secondary image is formed in the secondary image I 2 in FIG. 1, and if a photosensitive substrate movable in the scanning direction is provided at a position where the secondary image is formed, scanning exposure, A so-called step-and-scan projection exposure can be realized.
[0011]
Here, referring back to FIG. 2, the arc-shaped illumination area LA has an arc with a predetermined radius r centered on the optical axis (optical axis Ax 1 ) of the catadioptric optical system and a predetermined width from the optical axis Ax 1. This is a region surrounded by a circular arc having a radius r centered on a point Ax 1 ′ shifted by a (slit width a) and a straight line having an interval b (slit length b). As the arcuate illumination area, a concentric area centered on the optical axis Ax 1 is also conceivable, but it is not desirable because the exposure amount at the time of scanning exposure differs between the optical axis Ax 3 and the off-axis.
[0012]
Returning to FIG. 1, the light from the mask surface (object plane O) illuminated in the illumination area as described above passes through the lens components L 1 to L 3 arranged along the optical axis Ax 1. The light is deflected by approximately 45 ° by the reflecting mirror MP 1 and is reflected by the first concave reflecting mirror M 1 which is disposed along the optical axis Ax 2 perpendicular to the optical axis Ax 1 and whose concave surface faces the light incident side. Then, a primary image I 1 of the object plane O is formed on the reflection side of the first concave reflecting mirror M 1 . Here, the lens components L 1 to L 3 and the first concave reflecting mirror M 1 constitute a first partial optical system K 1 .
[0013]
Then, the light from the primary image I 1 is deflected by about 45 ° by the plane reflecting mirror MP 2 through the lens components L 4 to L 6 arranged along the optical axis Ax 2 . On the reflection side (light emission side) of the plane reflecting mirror MP 2 , the lens component L 7 and the second concave surface along the optical axis Ax 3 perpendicular to the optical axis Ax 2 (parallel to the optical axis Ax 1 ). a reflecting mirror M 2 is disposed, light emitted from the plane reflecting mirror MP 2 is reflected by the second concave reflecting mirror M 2 via the lens component L 7, through a lens component L 7 again Te toward the lens component L 8 ~L 14. The lens components L 8 to L 14 have a positive refractive power as a whole, and a secondary image I 2 that is a reduced image of the primary image I 1 is formed on the substrate by the light from the lens component L 7. Form. Here, the lens components L 4 to L 6 , the lens component L 7 , the second concave reflecting mirror M 2 and the lens components L 8 to L 14 constitute the second partial optical system K 2 .
[0014]
Now, when the light beam LB 1 from the object plane O illuminated in the arc-shaped illumination area reaches the aperture stop S 1 via the lens components L 1 to L 3 and the plane reflecting mirror MP 1 , the light beam cross section becomes: As shown in FIG. 3 (a), it is almost circular. Here, it is desirable to shield the light beam so as to be circular at the position of the aperture stop S 1 , but at this position, in addition to the passage of the light beam LB 1 as described above, the first concave reflecting mirror M 1 A light beam LB 2 traveling toward the primary image I 1 passes through. Therefore, a diaphragm conventional openings having a circular opening, without blocking the light beam LB 2, it is impossible to shield effectively the light beam LB 1.
[0015]
When the light beam LB 3 from the seventh lens component L 7 to the eighth lens component L 8 in the second partial optical system K 2 passes through the position of the aperture stop S 2 , the cross-sectional shape of the light beam is substantially circular. It becomes. Here, the position of the aperture stop S 2, it is conceivable to arrange the light shielding frame having a circular opening, as shown in FIG. 3 (b), in the vicinity of this position plane reflecting mirror MP 2 Since it is arranged and there is no space, it is not possible to provide a light-shielding frame having a circular opening.
[0016]
Therefore, in this embodiment, two different aperture stops S 1 and S 2 are arranged at two locations in the optical path of the catadioptric optical system. Specifically, an aperture stop S 1 having a substantially semicircular aperture as shown in FIG. 4A is arranged in the vicinity of the pupil plane of the first partial optical system K 1 , and substantially half as shown in FIG. 4B. An aperture stop S 2 having a circular opening is disposed in the vicinity of the pupil plane of the second partial optical system K 2 .
[0017]
That is, as shown in FIG. 4A, the aperture stop S 1 blocks (limits) a region of the peripheral portion of the light beam LB 1 that does not overlap with the light beam LB 2 indicated by a broken line in the drawing. When this partially restricted light beam LB 1 reaches the position of the aperture stop S 2 , it becomes a light beam LB 3 . Then, an unrestricted region of the light beam LB 3 as indicated by a broken line in FIG. 4B is shielded (limited) by the substantially semicircular opening of the aperture stop S 2 .
[0018]
Note that it is desirable that the area limited by the aperture stop S 1 and the area limited by the aperture stop S 2 overlap slightly.
Here, the aperture stops S 1 and S 2 in the present embodiment are provided such that the numerical aperture at the object height (distance from the optical axis Ax 1 ) of 100 mm of the catadioptric optical system is 0.45 and the telecentricity on both sides is achieved. ing.
[0019]
Thus, according to this embodiment, an aperture stop S 1 provided in the first partial optical system K 1, by the aperture diaphragm S 2, which provided in the second partial optical system K 2, the catadioptric optical system Since the passing light beam is effectively limited, there is no restriction on the arrangement of these aperture stops S 1 and S 2 .
Even when it is physically difficult to arrange the aperture stop at the aperture stop position for maintaining telecentricity, the catadioptric optical system according to the present embodiment has a large degree of freedom in the aperture stop position. Optical design that can maintain good telecentricity can be achieved.
[0020]
Next, a second embodiment according to the present invention will be described with reference to FIG. FIG. 5 is a diagram illustrating the configuration and the optical path of the present embodiment. In this embodiment, in order to apply the present invention, the optical path handling of the catadioptric optical system disclosed in the second embodiment of US Pat. No. 4,747,678 is changed.
In FIG. 5, the light beam from the object plane O through the lens component disposed along the optical axis Ax 1 L 1, L 2, a plane reflection is obliquely disposed at 45 ° with respect to the optical axis Ax 1 The light is deflected by the mirror MP 1 and reflected by the concave reflecting mirror M 1 having a center of curvature on the optical axis Ax 2 perpendicular to the optical axis Ax 1 and having a concave surface facing the light incident side. The reflective side of the concave reflecting mirror M 1, the lens component L 3, and convex reflecting mirror M 2 with a convex surface facing the incident side is disposed, the light beam from the concave reflecting mirror M 1 is a lens component L 3 is reflected by the convex reflecting mirror M 2 , and again passes through the lens component L 3 toward the concave reflecting mirror M 3 disposed along the optical axis Ax 2 and having the concave surface facing the light incident side. Here, in the vicinity of the convex reflector M 2, and the aperture stop S 1 is disposed, shielding a peripheral portion of the aperture stop S 1 side light beam LB 1 directed from the convex reflector M 2 to the concave reflecting mirror M 3 (Restricted). The light beam LB 1 passing through the aperture stop S 1 is reflected by the concave reflecting mirror M 3 and becomes the light beam LB 2 passing through the vicinity of the aperture stop S 1 again. Therefore, in the vicinity of the aperture stop S 1, as shown in FIG. 6 showing the light beam cross-section of the position of the aperture stop S 1, almost the light beam LB 1 of circular light flux cross-section, and the light beam LB 2 arcuate located. Here, the aperture stop S 1 has a partial circular opening that covers approximately 2/3 of the circumference, and partially restricts the outermost peripheral portion of the light beam LB 1 without shielding the light beam LB 2. ing.
[0021]
Returning to FIG. 5, the light beam LB 2 that has passed through the vicinity of the aperture stop S 1 is emitted from the lens components L 4, L 5, which is disposed along the optical axis Ax 2, likewise along the optical axis Ax 2 The primary image I 1 of the object is formed in the vicinity of the lens component L 6 arranged in the above manner. Here, the lens components L 1 and L 2 , the concave reflecting mirror M 1 , the lens component L 3 , the convex reflecting mirror M 2 , the concave reflecting mirror M 3 and the lens components L 4 and L 5 form the first partial optical system K 1 . Constitute.
[0022]
The light beam from the primary image I 1 is deflected by the plane reflecting mirror MP 2 inclined at 45 ° with respect to the optical axis Ax 2 via the lens components L 6 to L 8 , and this light. The light beam LB 3 is directed to the concave reflecting mirror M 4 arranged along the optical axis Ax 3 perpendicular to the axis Ax 2 . Then, the light beam LB 3 is a light beam LB 4 is reflected by the concave reflecting mirror M 4. Here, an aperture stop S 2 is arranged in the traveling direction of the light beam LB 4 (the reflection side of the concave reflecting mirror M 4 ), and the aperture stop of the light beam LB 4 going from the concave reflecting mirror M 4 to the lens component L 9 . limiting the periphery of S 2 side. Here, as shown in FIG. 6, the light beam LB 3 passing in the vicinity of the aperture stop S 2 has an arc-shaped light beam cross section that covers the periphery of the light beam LB 4 . Accordingly, the aperture stop S 2 is configured to have a partially circular opening that extends over approximately 1/3 of the circumference in order to limit the light beam LB 4 without blocking the light beam LB 3 . As a result, a region over approximately one third of the outermost peripheral portion of the light beam LB 4 , that is, a region that is not limited by the aperture stop S 1 is limited.
[0023]
Returning to FIG. 5, the light beam that has passed through the aperture stop S 2 passes through the lens components L 9 to L 11 arranged along the optical axis Ax 3 , and the primary image I 1 of the object on the exit side. A secondary image I 2 is formed. Here, the lens components L 6 to L 8 , the concave reflecting mirror M 4 and the lens components L 9 to L 11 form the second partial optical system K 2 .
As described above, all the peripheral portions of the light beam emitted from the catadioptric optical system are limited as a result of the aperture stop S 1 and the aperture stop S 2 . Accordingly, in the catadioptric optical system, it is possible to obtain a desired numerical aperture and maintain bilateral telecentricity. The numerical aperture in this example is 0.35 at an object height of 79 mm.
[0024]
Thus, the catadioptric optical system according to the present invention can arrange an aperture stop regardless of the optical path. Thus, by limiting the light beam passing through the catadioptric optical system, a desired numerical aperture can be obtained and at the same time, telecentricity can be maintained.
In the first and second embodiments, if the aperture diameters of the aperture stops S 1 and S 2 are configured to be movable, the numerical aperture of the catadioptric optical system can be made variable. For example, aperture stops S 1 and S 2 as shown in FIGS. 4 (a) and 4 (b) are provided so as to be movable in the direction of the arrow (direction along the beam cross section). If the aperture stops S 1 and S 2 are moved so that the diameters of the light beams passing through the apertures of the aperture stops S 1 and S 2 are changed, the numerical aperture of the entire catadioptric optical system is changed. be able to. Further, when changing the numerical aperture, a plurality of aperture stops having different aperture diameters may be provided interchangeably.
[0025]
In each of the embodiments described above, the shape of the openings of the aperture stops S 1 and S 2 may be a partial circular shape. At this time, as a result, the entire circumference of the peripheral edge of the light beam only needs to be limited. Therefore, it is limited to a semicircular opening as in each embodiment or a partial circular opening of 1/3 and 2/3. It will never be done.
In this embodiment, two sets of aperture stops S 1 and S 2 are disposed in each of the partial optical systems K 1 and K 2. Needless to say, two or more sets of aperture stops may be provided. For example, a partial optical system that creates a primary image of an object, a partial optical system that relays the primary image to create a secondary image, and a partial optical system that relays the secondary image to create a tertiary image In the catadioptric optical system, an aperture stop can be disposed in each partial optical system. At this time, the shape of the aperture of the aperture stop in each partial optical system may be a partial circular shape.
[0026]
【The invention's effect】
According to the present invention as described above, since the degree of freedom of the aperture stop position increases, it is possible to obtain a catadioptric optical system with very few restrictions on optical design. Furthermore, the aperture stop can be arranged without blocking the optical path even at a position where a plurality of optical paths overlap. Thereby, it is possible to provide a catadioptric optical system that can obtain a desired numerical aperture and can also maintain telecentricity.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration and an optical path of a first embodiment according to the present invention.
FIG. 2 is a plan view showing an illumination area on an object plane.
FIG. 3 is a diagram showing a light beam cross section in an aperture stop of a catadioptric optical system according to the present invention.
FIG. 4 is a plan view showing the shape of an aperture stop.
FIG. 5 is a diagram showing a configuration and an optical path of a second embodiment according to the present invention.
FIG. 6 is a plan view showing a beam cross section and an aperture stop in the second embodiment.
FIG. 7 is a diagram showing a conventional catadioptric optical system.
[Explanation of symbols]
K 1 ... 1st partial optical system,
K 2 ... the second partial optical system,
O ... Object surface,
I 1 ... Primary image of the object
I 2 ... Secondary image of the object

Claims (9)

物体側から順に、正の屈折力を持ち前記物体の1次像を形成する第1部分光学系と、正の屈折力を持ち前記1次像からの光により2次像を形成する第2部分光学系とを有する投影光学系において、
前記第1、第2部分光学系の少なくとも一方に配置された反射鏡と、
前記第1部分光学系の光路内に設けられ、光束の一部を制限する第1開口絞りと、
前記第2部分光学系の光路内に設けられ、前記第1開口絞りにて制限されなかった光束の残りを部分的に制限する第2開口絞りとを有することを特徴とする投影光学系。
In order from the object side, a first partial optical system that has positive refractive power and forms a primary image of the object, and a second portion that has positive refractive power and forms a secondary image by light from the primary image In a projection optical system having an optical system,
A reflecting mirror disposed on at least one of the first and second partial optical systems;
A first aperture stop provided in the optical path of the first partial optical system, for limiting a part of the light beam;
A projection optical system comprising: a second aperture stop provided in an optical path of the second partial optical system, and partially limiting a remainder of the light beam that was not limited by the first aperture stop.
前記投影光学系は、前記物体の円弧形状の領域の2次像を形成することを形成することを特徴とする請求項1記載の投影光学系。  The projection optical system according to claim 1, wherein the projection optical system forms a secondary image of an arc-shaped region of the object. 前記開口絞りは、部分円形状の開口部を有することを特徴とする請求項1又は2記載の投影光学系。  The projection optical system according to claim 1, wherein the aperture stop has a partially circular opening. マスクパターンを感光基板に露光する露光装置において、
前記マスクパターンと前記感光基板との間の光路中に配置され、正の屈折力を持ち前記マスクパターンの1次像を形成する第1部分光学系と、
前記第1部分光学系と前記感光基板との間の光路中に配置され、正の屈折力を持ち前記1次像からの光により2次像を形成する第2部分光学系と、
前記第1、第2部分光学系の少なくとも一方に配置された反射鏡と、
前記第1部分光学系の光路内に設けられ、光束の一部を制限する第1開口絞りと、
前記第2部分光学系の光路内に設けられ、前記第1開口絞りにて制限されなかった光束の残りを部分的に制限する第2開口絞りとを有することを特徴とする露光装置。
In an exposure apparatus that exposes a mask pattern onto a photosensitive substrate,
A first partial optical system disposed in an optical path between the mask pattern and the photosensitive substrate and having a positive refractive power and forming a primary image of the mask pattern;
A second partial optical system disposed in an optical path between the first partial optical system and the photosensitive substrate and having a positive refractive power and forming a secondary image by light from the primary image;
A reflecting mirror disposed on at least one of the first and second partial optical systems;
A first aperture stop provided in the optical path of the first partial optical system, for limiting a part of the light beam;
An exposure apparatus comprising: a second aperture stop that is provided in an optical path of the second partial optical system and that partially limits the remainder of the light beam that is not limited by the first aperture stop.
前記第2部分光学系は、前記物体の円弧形状の領域の2次像を形成することを形成することを特徴とする請求項4記載の露光装置。  5. The exposure apparatus according to claim 4, wherein the second partial optical system forms a secondary image of an arc-shaped region of the object. 前記開口絞りは、部分円形状の開口部を有することを特徴とする請求項4又は5記載の露光装置。  6. The exposure apparatus according to claim 4, wherein the aperture stop has a partial circular opening. 光線を使って、マスクパターンを感光基板に露光する露光方法において、
前記光線が、前記マスクパターンと前記感光基板との間の光路中に配置され、
正の屈折力を持ち前記マスクパターンの1次像を形成すると共に、光路を制限する第1開口絞りを含む第1部分光学系を経由する工程と、
前記第1部分光学系を経由した光線が、前記感光基板と前記第1部分光学系との光路中に配置され、正の屈折力を持ち前記1次像からの光により2次像を形成すると共に、前記光路を前記第1開口絞りにて制限されなかった光束の残りを部分的に制限する第2開口絞りを含む第2部分光学系を経由する工程とを有し、
前記第1、第2部分光学系の少なくとも一方に反射鏡が配置されていることを特徴とする露光方法。
In an exposure method that exposes a mask pattern onto a photosensitive substrate using light rays,
The light beam is disposed in an optical path between the mask pattern and the photosensitive substrate;
A step of forming a primary image of the mask pattern having a positive refractive power and passing through a first partial optical system including a first aperture stop for limiting an optical path;
A light beam passing through the first partial optical system is disposed in an optical path between the photosensitive substrate and the first partial optical system, and has a positive refractive power and forms a secondary image by light from the primary image. And passing through a second partial optical system including a second aperture stop that partially restricts the remainder of the light beam that was not restricted by the first aperture stop.
An exposure method, wherein a reflecting mirror is disposed on at least one of the first and second partial optical systems.
前記マスクパターンと前記感光基板とを相対的に走査方向に移動させることを特徴とする請求項7記載の露光方法。  8. The exposure method according to claim 7, wherein the mask pattern and the photosensitive substrate are relatively moved in a scanning direction. 前記第1、又は第2開口絞りを可変にすることで開口数を可変とする工程を有することを特徴とする請求項7記載の露光方法。  8. The exposure method according to claim 7, further comprising the step of changing the numerical aperture by changing the first or second aperture stop.
JP01627593A 1993-02-03 1993-02-03 Projection optical system, exposure apparatus using the same, and exposure method Expired - Lifetime JP3690819B2 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
JP01627593A JP3690819B2 (en) 1993-02-03 1993-02-03 Projection optical system, exposure apparatus using the same, and exposure method
US08/187,484 US5592329A (en) 1993-02-03 1994-01-28 Catadioptric optical system

Applications Claiming Priority (1)

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JP3690819B2 true JP3690819B2 (en) 2005-08-31

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US6512631B2 (en) * 1996-07-22 2003-01-28 Kla-Tencor Corporation Broad-band deep ultraviolet/vacuum ultraviolet catadioptric imaging system
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JP2001228401A (en) 2000-02-16 2001-08-24 Canon Inc Projection optical system, projection aligner by this projection optical system and method for manufacturing device
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US7085075B2 (en) * 2003-08-12 2006-08-01 Carl Zeiss Smt Ag Projection objectives including a plurality of mirrors with lenses ahead of mirror M3
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