JP2004111494A - Illumination device and exposure device - Google Patents

Abstract

[Object] To reduce the intensity of concentric interference fringes on a surface to be illuminated to a level that does not affect imaging performance even when a transmission optical flat plate for correcting illuminance distribution is introduced, and to reduce illuminance within an effective illumination range. Provided is a lighting device capable of making the distribution more uniform.
An illumination device for illuminating a surface to be illuminated using coherent illumination light emitted from a light source, wherein an optical path length from an incident surface to an emission surface is equal to or less than half the coherence length of the illumination light. And a transmissive optical flat plate in which the product of the reflectance (%) of the incident surface and the reflectance (%) of the exit surface when the illumination light enters is 0.01 or more, When the angle between the entrance surface and the exit surface is θ, the wavelength of the illumination light from the light source is λ, the minimum width of the illumination light is W, and the refractive index from the entrance surface to the exit surface is n, Provided is a lighting device that satisfies 2nWtan θ ≧ λ or θ ≧ 3 seconds.
[Selection diagram] Fig. 1

Description

【００１２】
露光装置に光源として使用するエキシマレーザーの場合、波長はλ＝０．１５７ｎｍ乃至０．２４８ｎｍ程度、スペクトル半値幅は一般的にΔλ＝０．２ｐｍ乃至０．６ｐｍ程度であるから、この場合、可干渉距離はＳ＝４１．１ｍｍ乃至３０７．５ｍｍとなる。
【００１３】
平行平面板の媒質の屈折率をｎ、平行平面板の厚さをｄとした時、平行平面板の入射面から射出面までの光路長はｎｄである。エキシマレーザーを光源に利用する露光装置に用いられる透過性光学平面板の材質は石英か蛍石が一般的であり、ｎ＝１．４〜１．６程度である。ｎｄ≦Ｓ／２となった場合、顕著な干渉縞が発生するので、フィルタ１２００の厚みを大きくして干渉性を無くすためには、１０ｍｍ〜１００ｍｍ程度の厚みが必要となる。最近の露光装置では、要求するスペクトル半値幅はより狭くなってきており、フィルタ１２００の厚みとしては最低でも数十ｍｍ程度必要となってしまう。従来の投影露光装置においては、一般的に、数ｍｍ程度の平行平面板をフィルタに用いるため、かかるフィルタをオプティカルインテグレータの射出側に用いると、ウェハ面上に無視できないレベルの光強度の同心円状の干渉縞を形成する可能性が高い。
【００１４】
フィルタ１２００の硝材内部透過率を１００％、誘電体多層膜の吸収を０％として、入射面１２００ａの反射率をＲ１［％］、射出面１２００ｂの反射率をＲ２［％］とした時、初期透過光線Ａの透過率Ｔ［Ａ］及び入射面１２００ａ及び射出面１２００ｂで反射した後の透過光線Ｂの透過率Ｔ［Ｂ］は以下の数式２で表される。
【００１５】
【数２】

【００１６】
例えば、入射面１２００ａの反射率Ｒが０．２％で、射出面１２００ｂの反射率が１０％の場合、初期透過光線Ａの透過率Ｔ［Ａ］は８９．８２％で、入射面１２００ａ及び射出面１２００ｂで反射した後の透過光線Ｂの透過率Ｔ［Ｂ］は０．０１８％になるから、初期透過光線Ａの強度を１００％に規格化すれば、入射面１２００ａ及び射出面１２００ｂで反射した後の透過光線Ｂの透過率は０．０２％になる。従って、初期透過光線Ａの振幅を１０とすると、入射面１２００ａ及び射出面１２００ｂで反射した後の透過光線Ｂの振幅は０．１４１となる。よって、完全干渉の場合の強度は、最大値で１０２．８４、最小値で９７．２０となるから、干渉縞のビジビリティは±２．８％となる。近年の投影露光装置による微細化パターン結像においては、露光光の照度ムラは±０．２％以下を要求されている。従って、入射光の光強度を１００％とした時の入射面１２００ａの反射率Ｒ１［％］と射出面１２００ｂの反射率Ｒ２［％］の積が０．０１以上の時に、この干渉縞現象が問題となる。
【００１７】
通常、フィルタ１２００のような薄い平行平面板を製作する場合、両面ラップ研磨によってその平行度が保証され、目標を完全な平行とした場合には、０．５秒以内の角度精度で加工され得る。この場合、図１０に示す初期透過光線Ａの光路長差と入射面１２００ａ及び射出面１２００ｂで反射した後の透過光線Ｂの光路長差との差分は、任意の２つの微小レンズ間において波長の４分の１以下になり、２つの光路長が殆ど揃ってしまう状態になる。従って、ウェハ上には同心円状の干渉縞が顕著に発生する。照明光の開口数が投影光学系のそれよりもかなり小さい小コヒーレンシーσ照明や極端な変形照明のように、オプティカルインテグレータを構成する各微小レンズのうち少ない個数で照明するような場合には、この現象がより顕著になり、レチクルパターンをウェハ上に結像する結像性能を劣化させる。
【００１８】
そこで、本発明は、照度分布補正のための透過型光学平面板を導入した場合でも、被照明面における同心円状の干渉縞の強度を結像性能に影響の無いレベルに軽減させ、有効照明範囲内の照度分布をより均一にすることができる照明装置を提供することを例示的目的とする。
【００１９】
また、本発明は、被照明面を均一で照明する照明装置を使用して高品質の半導体、ＬＣＤ、ＣＣＤ、薄膜磁気ヘッドなどのデバイスを所望のスループットで露光する露光装置を提供することを別の例示的目的とする。
【００２０】
【課題を解決するための手段】
上記目的を達成するために、本発明の一側面としての照明装置は、光源から射出した可干渉性を有する照明光を用いて被照明面を照明する照明装置であって、入射面から射出面までの光路長が前記照明光の可干渉距離の半分以下、且つ、前記照明光が入射する際の前記入射面の反射率（％）と前記射出面の反射率（％）との積が０．０１以上となる透過型光学平面板を有し、前記入射面と前記射出面との成す角度をθ、前記光源からの照明光の波長をλ、前記照明光の最小幅をＷ、前記入射面から前記射出面までの屈折率をｎとする時、２ｎＷｔａｎθ≧λ、又は、θ≧３秒、を満足する。かかる照明装置によれば、可干渉性を有する照明光を用いても、透過型光学平面板の両面（即ち、入射面と射出面）での多重反射により被照明面に発生する干渉縞の光強度を小さくすることができる。前記光源と前記照明面との間に配置され、前記照明光から複数の光源を形成する複数光源形成手段を更に有し、前記透過型光学平面板は、前記複数光源形成手段と前記被照明面との間に配置されてもよい。この場合、前記照明光の最小幅Ｗは、前記複数光源形成手段を構成する任意の微小レンズから射出される各微小レンズ射出面での光束の最小幅である。前記干渉距離をＳ、前記照明光のスペクトル半値幅をΔλとした時、Ｓ＝λ×λ／Δλ、である。前記光源から射出される前記照明光は、エキシマレーザーであってもよい。前記透過型光学平面板は、前記被照明面上における照明範囲内の照度分布を補正する照度分布補正面を有する。前記入射面と前記射出面との成す角度θは、３０分以下であることが望ましい。前記透過型光学平面板は、光軸に垂直な平面に対して傾け可能である。前記透過型光学平面板は、光軸の周りに回転可能である。
【００２１】
本発明の別の側面としての露光装置は、上述の照明装置と、レチクル又はマスクに形成されたパターンを被処理体に投影する光学系とを有する。かかる露光装置によれば、上述した照明装置を構成要素の一部に有し、被処理体上に形成される干渉縞を低減し、優れた結像性能を発揮することができる。
【００２２】
本発明の更に別の側面としてのデバイス製造方法は、上述の露光装置を用いて被処理体を投影露光するステップと、前記投影露光された被処理体に所定のプロセスを行うステップとを有する。上述の露光装置の作用と同様の作用を奏するデバイス製造方法の請求項は、中間及び最終結果物であるデバイス自体にもその効力が及ぶ。また、かかるデバイスは、例えば、ＬＳＩやＶＬＳＩなどの半導体チップ、ＣＣＤ、ＬＣＤ、磁気センサー、薄膜磁気ヘッドなどを含む。
【００２３】
本発明の更なる目的又はその他の特徴は、以下添付図面を参照して説明される好ましい実施例によって明らかにされるであろう。
【００２４】
【発明の実施の形態】
以下、添付図面を参照して、本発明の一側面としての照明装置１００及び露光装置２００について説明する。但し、本発明は、これらの実施例に限定するものではなく、本発明の目的が達成される範囲において、各構成要素が代替的に置換されてもよい。例えば、本発明の照明装置１００及び露光装置２００は、光源にエキシマレーザーを使用しているが、必ずしもこれに限定する必要はなく、水銀ランプやキセノンランプなどのランプも使用可能である。なお、各図において、同一の部材については同一の参照番号を付し、重複する説明は省略する。
【００２５】
ここで、図１は、本発明の一側面としての露光装置２００の例示的一形態を示す概略ブロック図である。露光装置２００は、図１に示すように、回路パターンが形成されたレチクル２１０を照明する照明装置１００と、照明されたマスクパターンから生じる回折光をプレート２３０に投影する投影光学系２２０とを有する。
【００２６】
露光装置２００は、例えば、ステップ・アンド・リピート方式やステップ・アンド・スキャン方式でレチクル２１０に形成された回路パターンをプレート２３０に露光する投影露光装置である。かかる露光装置は、サブミクロンやクオーターミクロン以下のリソグラフィー工程に好適であり、以下、本実施形態ではステップ・アンド・スキャン方式の露光装置（「スキャナー」とも呼ばれる）を例に説明する。ここで、「ステップ・アンド・スキャン方式」は、マスクに対してウェハを連続的にスキャンしてマスクパターンをウェハに露光すると共に、１ショットの露光終了後ウェハをステップ移動して、次の露光領域に移動する露光方法である。「ステップ・アンド・リピート方式」は、ウェハのショットの一括露光ごとにウェハをステップ移動して次のショットの露光領域に移動する露光方法であり、もちろん「ステップ・アンド・リピート方式」の露光装置に本発明を適用してもよい。
【００２７】
照明装置１００は、転写用パターンが形成されたレチクル２１０を照明し、光源部１１０と、照明光学系１２０とを有する。照明装置１００は、オプティカルインテグレータ１２２を構成する微小レンズ１２２ａからの射出光束の最小幅Ｗと、照度分布補正のための透過型光学平面板１３０の入射面と射出面との成す角度θ及び材質の屈折率ｎに関して適切な関係で設定して、透過型光学平面板１３０を導入している。
【００２８】
光源部１１０は、光源としてレーザーを使用する。レーザーは、波長約１９３ｎｍのＡｒＦエキシマレーザー、波長約２４８ｎｍのＫｒＦエキシマレーザーなどを使用することができるが、レーザーの種類はエキシマレーザーに限定さえず、例えば、ＹＡＧレーザーを使用してもよいし、そのレーザーの個数も限定されない。
【００２９】
照明光学系１２０は、レチクル２１０を照明する光学系であり、ビーム整形光学系１２１と、オプティカルインテグレータ１２２と、第１の光学系１２３と、マスキングブレード１２４と、第２の光学系１２５と、透過型光学平面板１３０とを有する。
【００３０】
ビーム整形光学系１２１は、例えば、複数のシリンドリカルレンズを備えるビームエクスパンダ等を使用することができ、光源部１１０からの光束の断面形状の寸法の縦横比率を所望の値に変換する（例えば、断面形状を長方形から正方形にするなど）ことによりビーム形状を所望のものに成形する。ビーム整形光学系１２１は、後述するオプティカルインテグレータ１２２を照明するのに必要な大きさと発散角を持つ光束を形成する。
【００３１】
オプティカルインテグレータ１２２は、光源１１０と被照明面（即ち、レチクル２１０面）との間に配置され、レチクル２１０に照明される照明光を均一化する。オプティカルインテグレータ１２２は、本実施形態では、任意の微小レンズから構成され、ビーム整形光学系１２１から射出した光束を多数の部分光束に分割し複数の有効光源（２次光源）を形成する複数光源形成手段として機能する。微小レンズは、例えば、透明光学部材の両側を平面とシリンドリカル面で構成したものを組み合わせている。
【００３２】
第１の光学系１２３は、オプティカルインテグレータ１２２射出面近傍に形成された２次光源像をマスキングブレード１２４に重畳照射してその面を均一に照明する。
【００３３】
マスキングブレード１２４は、被照明面（即ち、レチクル２１０面）の照明範囲を画定する。マスキングブレード１２４は、例えば、開口形状を可変とするスリットであって（視野絞りと称する場合もある）、第１の光学系１２３の集点を含み、光軸に直交する平面の近傍に配置される。
【００３４】
第２の光学系１２５は、例えば、コンデンサーレンズなどの結像レンズで構成され、マスキングブレード１２４の開口形状をレチクル２１０面に転写し、レチクル２１０面上の必要な領域を均一に照明する。
【００３５】
照明装置１００において、光源部１１０から射出した照射光は、ビーム整形光学系１２１を介して所定のビーム形状に整形された後、複数の微小レンズを二次元的に配列させた複数光源形成手段としてのオプティカルインテグレータ１２２に入射する。オプティカルインテグレータ１２２からの照射光は、第１の光学系１２３により集光される。第１の光学系１２３からの照射光は、マスキングブレード１２４を介して第２の光学系１２５により、レチクル２１０のパターン面を照射する。
【００３６】
以下、本発明による、可干渉性を有する光であるエキシマレーザーを用いる照明装置１００において、照明光学系１２０内のオプティカルインテグレータ１２２と第１の光学系１２３との間に配置される照度分布補正のための透過型光学平面板１３０について説明する。
【００３７】
図２は、オプティカルインテグレータ１２２から射出する光束のうち、射出角αと射出角α´の２つの光束に対応する被照明面上の照明位置との関係を示す概略模式図である。図２を参照するに、射出角αと射出角α´の時の光束は被照明面Ｔの光軸を通る位置から距離ＹとＹ´の位置を照明する。ここでαが小さい時に、以下の数式３で表わされる近似式が成立している。
【００３８】
【数３】

【００３９】
従って、オプティカルインテグレータ１２２からの射出光側に、透過率において光入射角度依存性のある照度分布補正のための透過型光学平面板１３０を配置させれば、被照明面Ｔ上において像高依存性のある照度分布を付加することが出来る。即ち、被照明面Ｔの中央部と周辺部について相対的に光強度を調整することができる。
【００４０】
本実施形態において、照度分布補正のための透過型光学平面板１３０は、例えば、照度分布補正面１３２には、研磨面に透過率において光入射角度依存性のある誘電体多層膜を施し、垂直方向からの入射光の反射率は１０％で透過率は９０％、そして、垂直方向より１０°の角度を成す入射光の反射率は９％で透過率は９１％にしている。
【００４１】
更に、透過型光学平面板１３０の反射防止面１３４には、研磨面において一般的な反射防止膜を施し、垂直方向からの入射光の反射率は０．２％で透過率は９９．８％にしている。従って、透過型光学平面板１３０への垂直方向からの入射光の透過率と垂直方向より１０°の角度を成す入射光の透過率とは１％の透過率差がある。かかる透過型光学平面板１３０により、周辺照度低下１％の場合の照度分布補正を行うことができる。
【００４２】
反射防止面１３４と照度分布補正面１３２は、どちらの面が光線入射側となっても構わない。
【００４３】
ところが、このような透過型光学平面板１３０が照明光学系１２０内にある場合、照度分布補正面１３２の反射率（％）と反射防止面１３４の反射率（％）との積は、軸上で２．０そして軸外で１．８となる。従って、上述したように、初期透過光線と入射面１３０ａと射出面１３０ｂの両面で反射した後の透過光線の光路長差が揃う場合には、プレート２３０面上において同心円状の干渉縞を形成させる。
【００４４】
ここで、図３を参照して、オプティカルインテグレータ１２２の中央部の微小レンズ１２２ａからの射出光の干渉性について考える。図３は、オプティカルインテグレータ１２２の微小レンズ１２２ａと透過型光学平面板１３０における光線状況を示す概略断面図である。オプティカルインテグレータ１２２の中央部の微小レンズ１２２ａからの出射光束のうち、上側の最軸外主光線Ｃと、下側の最軸外主光線Ｄについて、各光線が透過型光学平面板１３０に入射してから以降の透過光線を初期透過光線Ｃ１及びＤ１とする。そして、各光線が透過型光学平面板１３０に入射してから射出面１３０ｂと入射面１３０ａを反射した後に透過型光学平面板１３０を透過していく光線を、両面反射後の透過光線Ｃ２及びＤ２とする。
【００４５】
ここで、初期透過光線Ｃ１と両面反射後の透過光線Ｃ２、及び初期透過光線Ｄ１と両面反射後の透過光線Ｄ２の光路長差をそれぞれＡ及びＢとし、上述した同心円状の干渉縞の強度は、Ａ＝Ｂの時に最大で、｜Ａ−Ｂ｜の値が大きくなるにつれて徐々に小さくなる傾向があり、ｍを自然数とした時、｜Ａ−Ｂ｜＝ｍλの時に極小、｜Ａ−Ｂ｜＝（ｍ＋１／２）λの近傍で極大となり、極大値の絶対値を小さくさせながら極大と極小を繰り返す。この時の、光路長差の差分｜Ａ−Ｂ｜と干渉縞の相対強度の関係を図４に示す。同図は、横軸に光路長差の差分を、縦軸に干渉縞の相対強度を採用している。
【００４６】
図４を参照するに、光路長差の差分｜Ａ−Ｂ｜の値がλ以上であれば、干渉縞の強度を最悪でも４分の１以下にすることができる。従って、本実施形態の透過型光学平面板１３０を、オプティカルインテグレータ１２２の射出光側に配置させた時に、プレート２３０上に生じる同心円状の干渉縞の強度を、４分の１以下程度に軽減させるためには、以下の数式４で表わされる条件を満足させていれば良い。
【００４７】
【数４】

【００４８】
オプティカルインテグレータ１２２を構成する１つの微小レンズ１２２ａからの射出光束の、上側の最軸外主光線Ｃと下側の最軸外主光線Ｄとの間隔を、微小レンズ１２２ａからの射出光束の最小幅Ｗとして、透過型光学平面板１３０の屈折率をｎ、照度分布補正面１３２と反射防止面１３４との成す角をθとすれば、初期透過光線Ｃ１の光路長Ｌ［Ｃ１］、初期透過光線Ｄ１の光路長Ｌ［Ｄ１］、透過型光学平面板１３０の両面反射後の透過光線Ｃ２の光路長Ｌ［Ｃ２］、及び、両面反射後の透過光線Ｄ２の光路長Ｌ［Ｄ２］は、それぞれ以下の数式５で表わされる。
【００４９】
【数５】

【００５０】
よって、初期透過光線Ｃ１と両面反射後の透過光線Ｃ２の光路長差Ａ及び初期透過光線Ｄ１と両面反射後の透過光線Ｄ２の光路長差Ｂは、それぞれ以下の数式６で表わされる。
【００５１】
【数６】

【００５２】
ゆえに、光路長差の差分｜Ａ−Ｂ｜は、以下の数式７で表わされる近似式となる。
【００５３】
【数７】

【００５４】
但し、数式７は、有効数字を上２桁として、ｔａｎθｔａｎ２θ≦０．０１の時、即ち、θ≦４°の時に成立する。
【００５５】
従って、かかる数式７と上述した数式４より、以下に示す数式８を満足していれば、本発明の目的を達成させることができる。
【００５６】
【数８】

【００５７】
本実施形態では、発振波長λが２４８ｎｍのエキシマレーザーを光源に用い、透過型光学平面板１３０の材質を石英としているので、透過型光学平面板１３０の屈折率ｎは１．５１である。ここで、オプティカルインテグレータ１２２を構成する１つの微小レンズ１２２ａからの出射光束の最小幅Ｗが１ｍｍである時、θ≧１．２°にすれば、数式８を満足し、干渉縞の強度を小さくすることが出来る。
【００５８】
次に、照明装置１００の変形例である照明装置１００Ａを説明する。照明装置１００Ａは、オプティカルインテグレータ１２２の射出側に開口絞り１２６を配置し、かかる開口絞り１２６の最小径と、照度分布補正のための透過型光学平面板１３０Ａの入射面と射出面との成す角度θ、及び透過型光学平面板１３０Ａの材質の屈折率ｎに関して適切な関係で設定する。更に、照明装置１００Ａは、照度分布補正のための透過型光学平面板１３０Ａの入射面と射出面の傾斜方向と、オプティカルインテグレータ１２２を構成する複数の微小レンズ１２２ａの配列方向との成す角度を適切に設定する透過型光学平面板１３０Ａを導入している。本実施形態は、開口絞り１２６のより小さな小コヒーレンシーσ照明モードで使用される場合に最適な条件にした例である。
【００５９】
光源部１１０に用いるエキシマレーザーの発振波長λを２４８ｎｍ、透過型光学平面板１３０Ａの材質は石英に選べば、透過型光学平面板１３０Ａの屈折率ｎは１．５１である。また、オプティカルインテグレータ１２２の後段にある開口絞り１２６の最大径を１５０ｍｍ程度以内、最小径Φは３０ｍｍ程度で使用するのが一般的である。
【００６０】
従って、透過型光学平面板１３０Ａの照度分布補正面１３２と反射防止面１３４の成す角度θを３秒以上に設定して、最小径Φが３０ｍｍの間隔で離れている２つの微小レンズからの照射光について、光路長差の差分２ｎΦｔａｎθを計算すれば以下の数式９に表わされる。
【００６１】
【数９】

【００６２】
従って、照度分布補正面１３２ａと反射防止面１３２ｂの成す角度θを３秒以上に設定すれば、全てのコヒーレンシーσ値の照明モードで、より効果的に本発明の目的を達成させることができる。
【００６３】
ところで、図５に示すように、オプティカルインテグレータ１２２を構成する複数の微小レンズ１２２ａは格子状に配列されている。図５は、照明装置１００Ａの要部概略図であって、オプティカルインテグレータ１２２と開口絞り１２６の関係を示す概略平面図である。従って、２ｎΦｔａｎθ≧λ、となる場合でも、開口絞り１２６の最小径１２６ａの中心を通り、Ｅ方向に沿って配列する微小レンズ１２２ａの中心１２２ｂのうち、隣接する２つの中心を通る光線において、照明装置１００で説明した光路長差の差分｜Ａ−Ｂ｜が全て（ｍ＋１／２）λとなり干渉縞を打ち消し合わない場合がある。
【００６４】
このような場合には、照度分布補正のための透過型光学平面板１３０を図５に示すＦの方向に光軸周りに回転させて設定すれば、隣接する２つの微小レンズ１２２ａにおける中心１２２ｂ間の光路長差の差分を、（ｍ＋１／２）λから外すことができる。そうすれば、干渉縞の強度を弱めることができる。
【００６５】
以上に説明したように、光軸に垂直な方向から見た時に、オプティカルインテグレータ１２２を構成する複数の微小レンズ１２２ａの配列方向と、透過型光学平面板１３０Ａの入射面に対する射出面の傾斜方向とを適切な角度で設定すれば、更に効果的に本発明の目的を達成させることができる。
【００６６】
次に、照明装置１００の更に別の変形例である照明装置１００Ｂを説明する。照明装置１００Ｂは、照度分布補正のために、４つの平面で構成される透過型光学平面板１３０Ｂを用いる。本実施形態の透過型光学平面板１３０Ｂは、図６に示すように、共に両平面の成す角度θが等しい第１の透過型光学平面板１３６と第２の透過型光学平面板１３８で構成している。図６は、照明装置１００の更に別の変形例である照明装置１００Ｂを構成する透過型光学平面板１３０Ｂを示す概略断面図である。
【００６７】
第１の透過型光学平面板１３６は、入射光側において上述した反射防止面１３６ｂ、射出光側において照度分布補正面１３６ａを、両面の傾角θで光軸に対してほぼ垂直に配置している。
【００６８】
そして、第２の透過型光学平面板１３８の両面は、共に上述した反射防止面１３８ｂとし、第１の透過型光学平面板１３６の射出光側に、照度分布補正面１３６ａを挟む２つの反射防止面１３８ｂがその延長上で交差し、各透過型光学平面板１３６及び１３８の入射面と射出面との成す角度と等しい傾角θで対向するように第２の透過性光学平面板１３８を配置させている。
【００６９】
以上のような構成により、照明装置１００Ｂは、第１の透過型光学平面板１３６により発生したメリジオナル光線に対するサジタル光線の平行度の崩れを、第２の透過型光学平面板１３８によりキャンセルさせることができる。従って、照度分布補正のための透過型光学平面板１３６及び１３８を用いたことによって、第１の光学系１２３による照射光において、有効光源の歪みを新たに発生させることが無いという効果がある。
【００７０】
ここで、発振波長λが１５７ｎｍのエキシマレーザーを光源部１１０に用い、透過型光学平面板１３６及び１３８の入射面と射出面との成す角度を３０分にする。また、透過型光学平面板１３６及び１３８の材質を蛍石とすれば、その屈折率ｎは１．５６である。更に、オプティカルインテグレータ１２２を構成する微小レンズ１２２ａの配列のピッチＨを３ｍｍ、各微小レンズ１２２ａからの射出光束の最小幅Ｗを２ｍｍ程度としている。
【００７１】
従って、第１の透過型光学平面板１３６の両面からの反射による干渉の程度を調べるには、上述した光路長差の差分｜Ａ−Ｂ｜を計算してみればよい。上述の数式７より｜Ａ−Ｂ｜は以下に示す数式１０の値になる。
【００７２】
【数１０】

【００７３】
従って、数式１０に示す｜Ａ−Ｂ｜は、上述した数式８を満足している。
【００７４】
次に、第１の透過型光学平面板１３６の射出面と第２の透過型光学平面板１３８の入射面の両面反射による干渉の程度を調べる。第１の透過性光学平面板１３６と第２の透過型光学平面板１３８に挟まれた媒質は空気であるから、その屈折率ｎは１である。従って、光路長差の差分｜Ａ−Ｂ｜は、上述の数式７より以下に示す数式１１の値になる。
【００７５】
【数１１】

【００７６】
よって、本実施形態の透過型光学平面板において、第１の透過型光学平面板１３６の照度分布補正面１３６ａと反射防止面１３６ｂ、及び第１の透過型光学平面板１３６の射出面と第２の透過型光学平面板１３８の入射面に関わる多重反射光は、発明の目的を達成するための、上述した数式８を満足させている。
【００７７】
従って、本実施形態で説明したように、２つの透過型光学平面板１３６及び１３８を照明装置１００Ｂに適切な構成で配置させれば、第１の透過型光学平面板１３６を形成する２つの面の成す角θを大きく設定しても、照射光における有効光源に歪みを生じさせること無く、良好な照度分布補正を行わせることができる。
【００７８】
上記実施例（図６）では、第１の透過型光学平面板１３６の射出面と、第２の透過型光学平面板１３８の射出面を共に光軸に垂直としている例を示しているが、必ずしもその必要はなく、第１の透過型光学平面板１３６、第２の透過型光学平面板１３８のそれぞれの入射面、射出面の相対傾角がほぼ同一であり、その傾き方向が光軸に対して互いに１８０度回転した位置であれば構わない。もちろんその際にも、初期透過光線Ａと、照度分布補正面１３６ａとその他の面により反射して照射面に向かう透過光線Ｂの光路長差が、各位置において揃わないことが重要である。
【００７９】
本発明の照明装置１００及び照明装置１００Ａに用いた照度分布補正のための透過型光学平面板１３０及び透過型光学平面板１３０Ａは、装置に取り付ける時に、楔角による照射領域のシフト量を少なくしておく方が望ましい。そのためには、入射面と射出面との成す角度を３０分以下に設定すると良い。
【００８０】
更に、取り付け角度設定誤差による透過率の角度依存効果の非対称性を調整するために、照度分布補正のための透過型光学平面板１３０、透過型光学平面板１３０Ａ及び透過型光学平面板１３０Ｂは、光軸に垂直な面に対して傾け可能であることがより望ましい。
【００８１】
また、本発明の照明装置１００及び照明装置１００Ａに用いた照度分布補正のための透過型光学平面板１３０及び透過型光学平面板１３０Ａは、装置に取り付ける時に、楔角の方向の違いによって生じる照射領域のシフト方向を一方向に揃える方が望ましい。そのためには、照度分布補正のための１３０及び透過型光学平面板１３０Ａは、光軸の周りに回転可能にしておくと良い。
【００８２】
なお、照度分布補正のための透過型光学平面板１３０、透過型光学平面板１３０Ａ及び透過型光学平面板１３０Ｂの入射面および射出面は、何れも平面で説明しているが、入射面と射出面がゆるい曲率を持つ同Ｒのメニスカスレンズ形状の場合にも適用することができる。
【００８３】
また、本発明に係る照度分布補正のための透過型光学平面板は従来例で説明した絞り付きフィルタ１０６０ａのように絞りと一体でも良いし、別に絞りを設けて構成しても良い。
【００８４】
また、上記複数の実施例においては、照度分布補正面と反射防止面の反射について記載したが、必ずしもこの限りではなく、可干渉距離の１／２以内の間隔で配置された２つの面の相対角度が上記実施例の条件を満たしていれば良い。
【００８５】
また、２つの面が可干渉距離の１／２以内の間隔で配置され、オプティカルインテグレータ各点から同一角度で射出された光線の初期透過光線Ａと透過光線Ｂの光路長差のばらつきが、被照射面に形成される干渉縞を打ち消し合わないレベルであっても、２面の反射率の積が０．０１以下になる構成とすれば良い。
【００８６】
再び、図１に戻って、レチクル２１０は、例えば、石英製で、その上には転写されるべき回路パターン（又は像）が形成され、図示しないレチクルステージに支持及び駆動される。レチクル２１０から発せられた回折光は投影光学系２２０を通りプレート２３０上に投影される。プレート２３０は被処理体でありレジストが塗布されている。レチクル２１０とプレート２３０とは共役の関係に配置される。露光装置２００は、ステップ・アンド・スキャン方式の露光装置であるため、レチクル２１０とプレート２３０を走査することによりマスクパターンをプレート２３０上に縮小投影する。
【００８７】
投影光学系２２０は、複数のレンズ素子のみからなる光学系、複数のレンズ素子と少なくとも一枚の凹面鏡とを有する光学系（カタディオプトリック光学系）、複数のレンズ素子と少なくとも一枚のキノフォームなどの回折光学素子とを有する光学系、全ミラー型の光学系等を使用することができる。色収差の補正の必要な場合には、互いに分散値（アッベ値）の異なるガラス材からなる複数のレンズ素子を使用したり、回折光学素子をレンズ素子と逆方向の分散が生じるように構成したりする。
【００８８】
プレート２３０は、本実施形態ではウェハであるが、液晶基板その他の被処理体（被露光体）を広く含む。プレート２３０には、フォトレジストが塗布されている。フォトレジスト塗布工程は、前処理と、密着性向上剤塗布処理と、フォトレジスト塗布処理と、プリベーク処理とを含む。前処理は洗浄、乾燥などを含む。密着性向上剤塗布処理は、フォトレジストと下地との密着性を高めるための表面改質（即ち、界面活性剤塗布による疎水性化）処理であり、ＨＭＤＳ（Ｈｅｘａｍｅｔｈｙｌ−ｄｉｓｉｌａｚａｎｅ）などの有機膜をコート又は蒸気処理する。プリベークはベーキング（焼成）工程であるが現像後のそれよりもソフトであり、溶剤を除去する。
【００８９】
プレートステージ２３５は、プレート２３０を支持する。プレートステージ２３５は、当業界で周知のいかなる構成をも適用することができるので、ここでは詳しい構造及び動作の説明は省略する。例えば、プレートステージ２３５はリニアモータを利用してＸＹ方向にプレート２３０を移動することができる。レチクル２１０とプレート２３０は、例えば、同期走査され、プレートステージ２３５と図示しないレチクルステージの位置は、例えば、レーザー干渉計などにより監視され、両者は一定の速度比率で駆動される。プレートステージ２３５は、例えば、ダンパを介して床等の上に支持されるステージ定盤上に設けられ、レチクルステージ及び投影光学系２２０は、例えば、鏡筒定盤は床等に載置されたベースフレーム上にダンパ等を介して支持される図示しない鏡筒定盤上に設けられる。
【００９０】
露光において、光源部１１０から発せられた光束は、照明光学系１２０によりレチクル２１０をケーラー照明により均一に照明する。レチクル２１０を通過して回路パターンを反映する光は投影光学系２２０によりプレート２３０に結像される。
【００９１】
照明装置１００を使用する露光装置２００は、被照明面における同心円状の干渉縞の強度を結像性能に影響の無いレベルに軽減させ、有効照明範囲内の照度分布をより均一にすることができるため、レジストへのパターン転写を高精度に行って高品位なデバイス（半導体素子、ＬＣＤ素子、撮像素子（ＣＣＤなど）、薄膜磁気ヘッドなど）を提供することができる。
【００９２】
次に、図７及び図８を参照して、露光装置２００を利用したデバイス製造方法の実施例を説明する。図７は、デバイス（ＩＣやＬＳＩなどの半導体チップ、ＬＣＤ、ＣＣＤ等）の製造を説明するためのフローチャートである。ここでは、半導体チップの製造を例に説明する。ステップ１（回路設計）では、デバイスの回路設計を行う。ステップ２（マスク製作）では、設計した回路パターンを形成したマスクを製作する。ステップ３（ウェハ製造）では、シリコンなどの材料を用いてウェハを製造する。ステップ４（ウェハプロセス）は前工程と呼ばれ、マスクとウェハを用いてリソグラフィー技術によってウェハ上に実際の回路を形成する。ステップ５（組み立て）は後工程と呼ばれ、ステップ４によって作成されたウェハを用いて半導体チップ化する工程であり、アッセンブリ工程（ダイシング、ボンディング）、パッケージング工程（チップ封入）等の工程を含む。ステップ６（検査）では、ステップ５で作成された半導体デバイスの動作確認テスト、耐久性テストなどの検査を行う。そうした工程を経て半導体デバイスが完成し、これが出荷（ステップ７）される。
【００９３】
図８は、ステップ４のウェハプロセスの詳細なフローチャートである。ステップ１１（酸化）では、ウェハの表面を酸化させる。ステップ１２（ＣＶＤ）では、ウェハの表面に絶縁膜を形成する。ステップ１３（電極形成）では、ウェハ上に電極を蒸着などによって形成する。ステップ１４（イオン打ち込み）では、ウェハにイオンを打ち込む。ステップ１５（レジスト処理）では、ウェハに感光剤を塗布する。ステップ１６（露光）では、露光装置２００によってマスクの回路パターンをウェハに露光する。ステップ１７（現像）では、露光したウェハを現像する。ステップ１８（エッチング）では、現像したレジスト像以外の部分を削り取る。ステップ１９（レジスト剥離）では、エッチングが済んで不要となったレジストを取り除く。これらのステップを繰り返し行うことによってウェハ上に多重に回路パターンが形成される。かかるデバイス製造方法によれば、従来よりも高品位のデバイスを製造することができる。このように、露光装置２００を使用するデバイス製造方法、並びに結果物としてのデバイスも本発明の一側面を構成する。
【００９４】
以上、本発明の好ましい実施例を説明したが、本発明はこれらに限定されずその要旨の範囲内で様々な変形や変更が可能である。
【００９５】
【発明の効果】
本発明の照明装置によれば、照明光学系に導入するオプティカルインテグレータと透過型光学平面板において、諸条件を適切に設定することにより、エキシマレーザーのように可干渉性のある照射光を発光する光源を利用し、照明光学系の中に照度分布補正のための透過型光学平面板を導入しても、被照明面上の照射光に有害な干渉縞を発生させること無く、有効照明範囲内の照度分布を均一にすることができる。従って、レチクル上の回路パターンがより微細化しても、縮小投影パターンの相似性をより維持しながら被処理体上に焼付露光することのできる投影露光装置を提供できる。
【図面の簡単な説明】
【図１】本発明の一側面としての露光装置の例示的一形態を示す概略ブロック図である。
【図２】図１に示すオプティカルインテグレータから射出する射出角の異なる２つの光束に対応する被照明面上の照明位置との関係を示す概略模式図である。
【図３】図１に示すオプティカルインテグレータの微小レンズと透過型光学平面板における光線状況を示す概略断面図である。
【図４】光路長差の差分と干渉縞の相対強度の関係を示すグラフである。
【図５】図１に示す照明装置の変形例である照明装置の要部を示す概略平面図である。
【図６】図１に示す照明装置の更に別の変形例である照明装置を構成する透過型光学平面板を示す概略断面図である。
【図７】デバイス（ＩＣやＬＳＩなどの半導体チップ、ＬＣＤ、ＣＣＤ等）の製造を説明するためのフローチャートである。
【図８】図７に示すステップ４のウェハプロセスの詳細なフローチャートである。
【図９】従来の投影露光装置の概略構成図である。
【図１０】図９に示すフィルタにおける多重反射を示す概略模式図である。
【符号の説明】
１００　　　　　　　照明装置
１１０　　　　　　　光源部
１２０　　　　　　　照明光学系
１２１　　　　　　　ビーム整形光学系
１２２　　　　　　　オプティカルインテグレータ
１２３　　　　　　　第１の光学系
１２４　　　　　　　マスキングブレード
１２５　　　　　　　第２の光学系
１３０　　　　　　　透過型光学平面板
２００　　　　　　　露光装置
２１０　　　　　　　レチクル
２２０　　　　　　　投影光学系
２３０　　　　　　　プレート[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention generally relates to an illumination optical system, and more particularly, to an illumination apparatus of an illumination optical system used for exposing an object to be processed such as a single crystal substrate for a semiconductor wafer and a glass substrate for a liquid crystal display (LCD). , And an exposure apparatus. The present invention is suitable, for example, for an illumination device for an exposure apparatus that exposes a single crystal substrate for a semiconductor wafer by a step-and-scan projection method in a photolithography process. However, the application of the illumination device of the present invention is not limited to an exposure device, and can be widely applied to optical equipment such as photolithography, projection inspection, a projector, and a projector.
[0002]
[Prior art]
In a manufacturing process of a semiconductor element formed from an extremely fine pattern such as an LSI or a super LSI, a reticle or a mask (in the present application, these terms are used interchangeably) as an exposure apparatus capable of achieving high resolution and high throughput. 2. Description of the Related Art A reduction projection exposure apparatus has been conventionally used in which a circuit pattern drawn on a wafer is reduced and projected by a projection optical system onto a wafer or the like to which a photosensitive agent has been applied, and the circuit pattern is printed.
[0003]
With the recent increase in packaging density of semiconductor devices, further miniaturization of patterns is required, and with the development of resist processes, projection exposure apparatuses are also required to respond to miniaturization. Therefore, in general, a method of increasing the numerical aperture (NA) of the projection optical system or changing the exposure wavelength from an ultra-high pressure mercury lamp (g-line, i-line) to an excimer laser (for example, a KrF excimer laser or an ArF excimer laser). The resolution of a projection exposure apparatus has been improved by a method of shortening the wavelength.
[0004]
Since the actual process of manufacturing a semiconductor element may or may not require a high resolution of the pattern, in general, the numerical aperture of the illumination light and the projection optical system may be adjusted by using apertures having different aperture diameters. Controlling the numerical aperture has been performed. In a conventional projection exposure apparatus, when the numerical aperture of illumination light is changed in the illumination system, the illuminance distribution on the reticle surface tends to change. In order to solve this problem, a projection exposure apparatus in which a filter for correcting the illuminance distribution is installed downstream of the optical integrator is proposed in Japanese Patent Application Laid-Open No. 66121/1995.
[0005]
FIG. 9 is a schematic configuration diagram of a projection exposure apparatus 1000 proposed in Japanese Patent Application Laid-Open No. 66121/1995. The projection exposure apparatus 1000 has a high-luminance light-emitting portion that emits ultraviolet light, far ultraviolet light, and the like in a light-emitting tube 1010 as a light source, and arranges the light-emitting portion near the first focal point of the elliptical mirror 1020. Most of the emitted light from the light emitting unit is reflected by the cold mirror 1030 to the optical system 1040 and condensed on the incident surface of the optical integrator 1050. The illumination light from the optical integrator 1050 is condensed by a condenser lens 1080, the optical path is turned back by a mirror 1090, the reticle 1110 is illuminated by the imaging lens 1100, and the pattern on the reticle 1110 is projected by the projection optical system 1120. To form an image on the wafer 1130.
[0006]
Here, the projection exposure apparatus 1000 is provided with a filter mechanism with aperture 1060 in which a plurality of filters with aperture 1060a are arranged in a turret type on the emission side of the optical integrator 1050. The filter with a stop 1060a is configured by integrating a stop with an optical element coated so that the transmittance varies depending on the incident angle. The filter mechanism 1060 with a diaphragm is rotated by the arcuator 1070 so that an arbitrary filter 1060a with a diaphragm is located in the optical path.
[0007]
The projection exposure apparatus 1000 controls the illuminance distribution of the illumination light on the wafer 1130 by optimizing the illuminance distribution on the wafer 1130 by changing the light flux incident on the condenser lens 1080 by using such a filter mechanism 1060 with a diaphragm. ing.
[0008]
[Problems to be solved by the invention]
In a projection exposure apparatus using a light source that emits illumination light with little coherence or a short coherence distance (for example, a mercury lamp as shown in FIG. 9), a flat plate whose entrance surface and exit surface are strictly parallel There is no particular problem even if a filter made of glass is used. However, in a projection exposure apparatus that uses a light source that emits coherent illumination light such as an excimer laser, a filter composed of flat glass whose entrance surface and exit surface are strictly parallel to the exit side of the optical integrator is used. When used, the following problems occur.
[0009]
A filter 1200 provided with an anti-reflection film on the entrance surface 1200a and a dielectric multilayer film having a certain reflectance on the exit surface 1200b is arranged on the exit side of the optical integrator 1050 in order to control the transmittance. As shown in FIG. 10, the illumination light from the optical integrator 1050 causes multiple reflections on the entrance surface 1200a and the exit surface 1200b of the filter 1200. Here, the optical path length difference between the initial transmitted light beam A and the transmitted light beam B after being reflected on the incident surface 1200a and the exit surface 1200b of the filter 1200 is smaller than the coherent distance, that is, the optical path length of the filter 1200 is smaller than the coherent distance. In the case where the distance is not more than half and is almost completely parallel, the optical path length difference between the initial transmitted light beam A and the transmitted light beam B emitted at the same angle from the positions of the microlenses constituting the optical integrator 1050 is uniform. The two luminous fluxes of the initial transmitted light beam A and the transmitted light beam B emitted from each point on the emission surface of the optical integrator 1050 have slightly different wavefront curvatures on the surface to be irradiated, and concentric interference fringes on the wafer surface. Is formed. Normally, in the case of an exposure system illumination system, light beams emitted from the optical integrator 1050 at the same angle are radiated to almost the same position on the surface to be irradiated, so that the initial transmitted light A and the transmitted light B from each point of the optical integrator 1050 are emitted. If the optical path length differences are uniform, the interference fringes will not cancel each other. Such interference fringes cause deterioration of pattern imaging performance. Here, FIG. 10 is a schematic diagram illustrating multiple reflection in the filter 1200.
[0010]
The coherence length S is generally represented by the following equation 1, where λ is the wavelength of the illumination light and Δλ is the spectral half width of the illumination light.
[0011]
(Equation 1)

[0012]
In the case of an excimer laser used as a light source in an exposure apparatus, the wavelength is about λ = 0.157 nm to 0.248 nm, and the spectral half width is generally about Δλ = 0.2 pm to 0.6 pm. The interference distance is S = 41.1 mm to 307.5 mm.
[0013]
When the refractive index of the medium of the plane-parallel plate is n and the thickness of the plane-parallel plate is d, the optical path length from the entrance surface to the exit surface of the plane-parallel plate is nd. The material of the transmissive optical flat plate used in the exposure apparatus using the excimer laser as a light source is generally quartz or fluorite, and n is approximately 1.4 to 1.6. When nd ≦ S / 2, noticeable interference fringes are generated. Therefore, in order to increase the thickness of the filter 1200 and eliminate coherence, a thickness of about 10 mm to 100 mm is required. In recent exposure apparatuses, the required spectral half width is becoming narrower, and the filter 1200 needs to have a thickness of at least several tens of mm. In a conventional projection exposure apparatus, a parallel flat plate of about several mm is generally used as a filter. Therefore, when such a filter is used on the exit side of an optical integrator, a concentric circle of light intensity of a level which cannot be ignored on a wafer surface. Is highly likely to form interference fringes.
[0014]
When the internal transmittance of the glass material of the filter 1200 is 100%, the absorption of the dielectric multilayer film is 0%, the reflectance of the entrance surface 1200a is R1 [%], and the reflectance of the exit surface 1200b is R2 [%]. The transmittance T [A] of the transmitted light beam A and the transmittance T [B] of the transmitted light beam B after being reflected by the entrance surface 1200a and the exit surface 1200b are represented by the following Expression 2.
[0015]
(Equation 2)

[0016]
For example, when the reflectance R of the entrance surface 1200a is 0.2% and the reflectance of the exit surface 1200b is 10%, the transmittance T [A] of the initially transmitted light beam A is 89.82%, and the entrance surfaces 1200a and 1200a Since the transmittance T [B] of the transmitted light B after being reflected by the exit surface 1200b is 0.018%, if the intensity of the initial transmitted light A is normalized to 100%, the incident surface 1200a and the exit surface 1200b have the same transmittance. The transmittance of the transmitted light beam B after the reflection is 0.02%. Therefore, assuming that the amplitude of the initially transmitted light beam A is 10, the amplitude of the transmitted light beam B after being reflected by the incident surface 1200a and the emission surface 1200b is 0.141. Therefore, the intensity in the case of complete interference is 102.84 at the maximum value and 97.20 at the minimum value, and the visibility of interference fringes is ± 2.8%. In miniaturized pattern imaging by a projection exposure apparatus in recent years, illuminance unevenness of exposure light is required to be ± 0.2% or less. Therefore, when the product of the reflectance R1 [%] of the incident surface 1200a and the reflectance R2 [%] of the exit surface 1200b when the light intensity of the incident light is 100% is 0.01 or more, this interference fringe phenomenon occurs. It becomes a problem.
[0017]
Usually, when manufacturing a thin parallel plane plate such as a filter 1200, the parallelism is guaranteed by double-sided lap polishing, and when the target is made completely parallel, it can be processed with an angular accuracy within 0.5 seconds. . In this case, the difference between the optical path length difference of the initial transmitted light beam A shown in FIG. 10 and the optical path length difference of the transmitted light beam B reflected on the entrance surface 1200a and the exit surface 1200b is the wavelength difference between any two microlenses. This is a quarter or less, and the two optical path lengths are almost aligned. Therefore, concentric interference fringes are significantly generated on the wafer. In the case of illuminating with a small number of the minute lenses constituting the optical integrator, such as a small coherency σ illumination or an extremely deformed illumination in which the numerical aperture of the illumination light is considerably smaller than that of the projection optical system, The phenomenon becomes more remarkable, and deteriorates the imaging performance of imaging the reticle pattern on the wafer.
[0018]
Therefore, the present invention reduces the intensity of concentric interference fringes on the surface to be illuminated to a level that does not affect the imaging performance, even when a transmission optical flat plate for correcting the illuminance distribution is introduced. It is an exemplary object to provide an illuminating device capable of making the illuminance distribution in the inside more uniform.
[0019]
The present invention also provides an exposure apparatus for exposing devices such as semiconductors, LCDs, CCDs, thin-film magnetic heads, and the like with a desired throughput by using an illumination apparatus that uniformly illuminates a surface to be illuminated. For illustrative purposes.
[0020]
[Means for Solving the Problems]
In order to achieve the above object, an illuminating device according to one aspect of the present invention is an illuminating device that illuminates a surface to be illuminated using coherent illumination light emitted from a light source. And the product of the reflectance (%) of the incident surface and the reflectance (%) of the exit surface when the illumination light is incident is zero. .01, the angle between the entrance surface and the exit surface is θ, the wavelength of illumination light from the light source is λ, the minimum width of the illumination light is W, Assuming that the refractive index from the surface to the exit surface is n, 2nWtan θ ≧ λ or θ ≧ 3 seconds is satisfied. According to such an illuminating device, even if illumination light having coherence is used, interference fringe light generated on the surface to be illuminated due to multiple reflections on both surfaces (ie, the incident surface and the exit surface) of the transmission optical flat plate. Strength can be reduced. The apparatus further includes a plurality of light source forming units disposed between the light source and the illumination surface and forming a plurality of light sources from the illumination light, wherein the transmission optical flat plate includes the plurality of light source forming units and the illuminated surface. And may be arranged between them. In this case, the minimum width W of the illumination light is the minimum width of a light beam emitted from each of the microlenses constituting the plurality of light source forming means on each microlens exit surface. When the interference distance is S and the spectral half width of the illumination light is Δλ, S = λ × λ / Δλ. The illumination light emitted from the light source may be an excimer laser. The transmission type optical flat plate has an illuminance distribution correction surface for correcting an illuminance distribution within an illumination range on the illumination target surface. The angle θ between the incident surface and the exit surface is desirably 30 minutes or less. The transmission type optical flat plate can be inclined with respect to a plane perpendicular to the optical axis. The transmission type optical flat plate is rotatable around an optical axis.
[0021]
An exposure apparatus as another aspect of the present invention includes the above-described illumination device and an optical system that projects a pattern formed on a reticle or a mask onto a target object. According to such an exposure apparatus, the above-described illumination device is included as a part of the constituent elements, and interference fringes formed on the object to be processed can be reduced, and excellent imaging performance can be exhibited.
[0022]
A device manufacturing method according to still another aspect of the present invention includes a step of projecting and exposing an object to be processed by using the above-described exposure apparatus, and a step of performing a predetermined process on the object that has been subjected to the projection exposure. The claims of the device manufacturing method having the same operation as that of the above-described exposure apparatus extend to the device itself as an intermediate and final product. Such devices include, for example, semiconductor chips such as LSI and VLSI, CCDs, LCDs, magnetic sensors, thin-film magnetic heads, and the like.
[0023]
Further objects and other features of the present invention will become apparent from preferred embodiments described below with reference to the accompanying drawings.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an illumination apparatus 100 and an exposure apparatus 200 according to one aspect of the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited to these embodiments, and each component may be replaced as long as the object of the present invention is achieved. For example, the illumination device 100 and the exposure device 200 of the present invention use an excimer laser as a light source, but the light source is not necessarily limited to this, and a lamp such as a mercury lamp or a xenon lamp can also be used. In the drawings, the same members are denoted by the same reference numerals, and redundant description will be omitted.
[0025]
Here, FIG. 1 is a schematic block diagram showing an exemplary embodiment of an exposure apparatus 200 as one aspect of the present invention. As shown in FIG. 1, the exposure apparatus 200 includes an illumination device 100 that illuminates a reticle 210 on which a circuit pattern is formed, and a projection optical system 220 that projects diffracted light generated from the illuminated mask pattern onto a plate 230. .
[0026]
The exposure apparatus 200 is, for example, a projection exposure apparatus that exposes a circuit pattern formed on the reticle 210 to the plate 230 by a step-and-repeat method or a step-and-scan method. Such an exposure apparatus is suitable for a submicron or quarter-micron lithography process. Hereinafter, in this embodiment, a step-and-scan type exposure apparatus (also referred to as a “scanner”) will be described as an example. Here, in the “step-and-scan method”, the wafer is continuously scanned with respect to a mask to expose a mask pattern onto the wafer, and after one-shot exposure is completed, the wafer is step-moved and the next exposure is performed. This is an exposure method for moving to an area. The "step-and-repeat method" is an exposure method in which a wafer is step-moved for each batch exposure of a wafer shot and is moved to an exposure area of the next shot. Of course, the "step-and-repeat method" exposure apparatus The present invention may be applied to
[0027]
The illumination device 100 illuminates the reticle 210 on which the transfer pattern is formed, and has a light source unit 110 and an illumination optical system 120. The illuminating device 100 includes a minimum width W of a light beam emitted from the minute lens 122a included in the optical integrator 122, an angle θ formed between an incident surface and an exit surface of the transmission optical flat plate 130 for illuminance distribution correction, and a material The transmissive optical flat plate 130 is introduced with an appropriate relationship with respect to the refractive index n.
[0028]
The light source unit 110 uses a laser as a light source. As the laser, an ArF excimer laser having a wavelength of about 193 nm, a KrF excimer laser having a wavelength of about 248 nm can be used, but the type of laser is not limited to an excimer laser. For example, a YAG laser may be used. The number of the lasers is not limited.
[0029]
The illumination optical system 120 is an optical system that illuminates the reticle 210, and includes a beam shaping optical system 121, an optical integrator 122, a first optical system 123, a masking blade 124, a second optical system 125, and a transmission optical system. Optical flat plate 130.
[0030]
The beam shaping optical system 121 can use, for example, a beam expander including a plurality of cylindrical lenses, and converts the aspect ratio of the cross-sectional dimension of the light beam from the light source unit 110 to a desired value (for example, By changing the cross-sectional shape from a rectangle to a square, for example), the beam shape is formed into a desired shape. The beam shaping optical system 121 forms a light beam having a size and a divergence angle necessary for illuminating an optical integrator 122 described later.
[0031]
The optical integrator 122 is disposed between the light source 110 and the surface to be illuminated (that is, the surface of the reticle 210), and makes the illumination light illuminated on the reticle 210 uniform. In the present embodiment, the optical integrator 122 includes an arbitrary minute lens, and forms a plurality of light sources that divides a light beam emitted from the beam shaping optical system 121 into a number of partial light beams and forms a plurality of effective light sources (secondary light sources). Functions as a means. The microlens combines, for example, a transparent optical member having both sides formed of a flat surface and a cylindrical surface.
[0032]
The first optical system 123 irradiates the masking blade 124 with a secondary light source image formed near the exit surface of the optical integrator 122 to irradiate the surface uniformly.
[0033]
The masking blade 124 defines an illumination range of the illuminated surface (that is, the reticle 210 surface). The masking blade 124 is, for example, a slit having a variable opening shape (sometimes referred to as a field stop), and includes a convergence point of the first optical system 123 and is disposed near a plane orthogonal to the optical axis. You.
[0034]
The second optical system 125 is formed of, for example, an imaging lens such as a condenser lens, transfers the opening shape of the masking blade 124 to the surface of the reticle 210, and uniformly illuminates a required area on the surface of the reticle 210.
[0035]
In the illumination device 100, irradiation light emitted from the light source unit 110 is shaped into a predetermined beam shape through a beam shaping optical system 121, and then formed as a plurality of light source forming units in which a plurality of minute lenses are two-dimensionally arranged. To the optical integrator 122. Irradiation light from the optical integrator 122 is collected by the first optical system 123. Irradiation light from the first optical system 123 irradiates the pattern surface of the reticle 210 with the second optical system 125 via the masking blade 124.
[0036]
Hereinafter, in the illuminating device 100 using the excimer laser, which is coherent light, according to the present invention, the illuminance distribution correction between the optical integrator 122 in the illumination optical system 120 and the first optical system 123 is performed. Transmission optical flat plate 130 will be described.
[0037]
FIG. 2 is a schematic diagram showing the relationship between the illuminating positions on the illuminated surface corresponding to two luminous fluxes having an emission angle α and an emission angle α ′ among the luminous fluxes emitted from the optical integrator 122. Referring to FIG. 2, the light beam at the exit angle α and the exit angle α ′ illuminates the positions at distances Y and Y ′ from the position passing through the optical axis of the illumination target surface T. Here, when α is small, an approximate expression represented by the following Expression 3 holds.
[0038]
[Equation 3]

[0039]
Therefore, if the transmission type optical flat plate 130 for correcting the illuminance distribution having the transmittance which is dependent on the light incident angle is arranged on the side of the light emitted from the optical integrator 122, the image height dependency on the illuminated surface T can be improved. Illuminance distribution can be added. That is, the light intensity can be relatively adjusted between the central portion and the peripheral portion of the illumination target surface T.
[0040]
In the present embodiment, the transmission optical flat plate 130 for illuminance distribution correction includes, for example, applying a dielectric multilayer film having a light incident angle dependence on transmittance to a polished surface on the illuminance distribution correction surface 132, The reflectance of the incident light from the direction is 10% and the transmittance is 90%, and the reflectance of the incident light forming an angle of 10 ° from the vertical direction is 9% and the transmittance is 91%.
[0041]
Further, a general antireflection film is applied to the antireflection surface 134 of the transmission type optical flat plate 130 on the polished surface, and the reflectance of incident light from the vertical direction is 0.2% and the transmittance is 99.8%. I have to. Therefore, there is a 1% transmittance difference between the transmittance of the incident light to the transmission optical flat plate 130 from the vertical direction and the transmittance of the incident light forming an angle of 10 ° from the vertical direction. With such a transmission type optical flat plate 130, it is possible to correct the illuminance distribution when the peripheral illuminance is reduced by 1%.
[0042]
Either the antireflection surface 134 or the illuminance distribution correction surface 132 may be on the light incident side.
[0043]
However, when such a transmission type optical flat plate 130 is in the illumination optical system 120, the product of the reflectance (%) of the illuminance distribution correction surface 132 and the reflectance (%) of the antireflection surface 134 is on the axis. At 2.0 and 1.8 off-axis. Therefore, as described above, when the optical path length difference between the initial transmission light beam and the transmission light beam reflected on both the incident surface 130a and the emission surface 130b is equal, concentric interference fringes are formed on the plate 230 surface. .
[0044]
Here, with reference to FIG. 3, the coherence of light emitted from the minute lens 122a at the center of the optical integrator 122 will be considered. FIG. 3 is a schematic cross-sectional view showing the state of light rays on the micro lens 122 a of the optical integrator 122 and the transmission optical flat plate 130. Of the light beams emitted from the micro lens 122a at the center of the optical integrator 122, each of the uppermost off-axis principal ray C and the lowermost off-axis principal ray D enters the transmission optical flat plate 130. The transmitted light after this is referred to as initial transmitted light C1 and D1. Then, light rays which enter the transmission type optical flat plate 130 and then pass through the transmission type optical flat plate 130 after being reflected by the exit surface 130b and the incident surface 130a are transmitted light beams C2 and D2 after both-side reflection. And
[0045]
Here, the optical path length differences between the initial transmitted light beam C1 and the transmitted light beam C2 after both-sided reflection, and the initial transmitted light beam D1 and the transmitted light beam D2 after both-sided reflection are A and B, respectively. , A = B, and tends to gradually decrease as the value of | AB | increases. When m is a natural number, the minimum is obtained when | AB | = mλ, and | AB. The maximum becomes near | = (m + ＝) λ, and the maximum and the minimum are repeated while the absolute value of the maximum value is reduced. FIG. 4 shows the relationship between the difference | AB | of the optical path length difference and the relative intensity of the interference fringe at this time. In the figure, the horizontal axis indicates the difference in the optical path length difference, and the vertical axis indicates the relative intensity of the interference fringes.
[0046]
Referring to FIG. 4, if the value of the difference | A−B | of the optical path length difference is equal to or greater than λ, the intensity of the interference fringes can be reduced to 1/4 or less at worst. Therefore, when the transmission-type optical flat plate 130 of the present embodiment is arranged on the emission light side of the optical integrator 122, the intensity of concentric interference fringes generated on the plate 230 is reduced to about a quarter or less. For this purpose, it suffices that the condition represented by the following Expression 4 is satisfied.
[0047]
(Equation 4)

[0048]
The distance between the uppermost off-axis principal ray C and the lowermost off-axis principal ray D of the luminous flux emitted from one micro lens 122a constituting the optical integrator 122 is determined by the minimum width of the luminous flux emitted from the micro lens 122a. Assuming that W is n, the refractive index of the transmission type optical flat plate 130 is n, and the angle between the illuminance distribution correction surface 132 and the antireflection surface 134 is θ, the optical path length L [C1] of the initial transmitted light beam C1, the initial transmitted light beam The optical path length L [D1] of D1, the optical path length L [C2] of the transmitted light beam C2 after both-side reflection of the transmission type optical flat plate 130, and the optical path length L [D2] of the transmitted light beam D2 after both-side reflection are respectively given. It is represented by the following Equation 5.
[0049]
(Equation 5)

[0050]
Therefore, the optical path length difference A between the initial transmitted light beam C1 and the transmitted light beam C2 after both-side reflection, and the optical path length difference B between the initial transmitted light beam D1 and the transmitted light beam D2 after both-side reflection are expressed by the following Equations 6, respectively.
[0051]
(Equation 6)

[0052]
Therefore, the difference | AB | of the optical path length difference is an approximate expression represented by the following Expression 7.
[0053]
(Equation 7)

[0054]
However, Equation 7 holds when tanθtan2θ ≦ 0.01, that is, when θ ≦ 4 °, where the significant figures are the first two digits.
[0055]
Therefore, the object of the present invention can be achieved if the following Expression 8 is satisfied from Expression 7 and Expression 4 described above.
[0056]
(Equation 8)

[0057]
In the present embodiment, an excimer laser having an oscillation wavelength λ of 248 nm is used as a light source, and the material of the transmission optical flat plate 130 is quartz. Therefore, the refractive index n of the transmission optical flat plate 130 is 1.51. Here, when the minimum width W of the light beam emitted from one micro lens 122a constituting the optical integrator 122 is 1 mm, if θ ≧ 1.2 °, Expression 8 is satisfied, and the intensity of the interference fringes is reduced. You can do it.
[0058]
Next, a lighting device 100A which is a modification of the lighting device 100 will be described. The illuminating device 100A has an aperture stop 126 disposed on the exit side of the optical integrator 122. The minimum diameter of the aperture stop 126 and the angle formed between the entrance surface and the exit surface of the transmission optical flat plate 130A for illuminance distribution correction. θ and the refractive index n of the material of the transmission optical flat plate 130A are set in an appropriate relationship. Furthermore, the illumination device 100A appropriately adjusts the angle formed by the inclination direction of the entrance surface and the exit surface of the transmission optical flat plate 130A for illuminance distribution correction and the arrangement direction of the plurality of microlenses 122a constituting the optical integrator 122. Is introduced. The present embodiment is an example in which the optimum conditions are used when the aperture stop 126 is used in a smaller coherency σ illumination mode.
[0059]
If the oscillation wavelength λ of the excimer laser used for the light source unit 110 is 248 nm and the material of the transmission optical flat plate 130A is selected to be quartz, the refractive index n of the transmission optical flat plate 130A is 1.51. In general, the aperture stop 126 located downstream of the optical integrator 122 has a maximum diameter of about 150 mm or less and a minimum diameter Φ of about 30 mm.
[0060]
Therefore, the angle θ formed by the illuminance distribution correction surface 132 and the antireflection surface 134 of the transmission optical flat plate 130A is set to 3 seconds or more, and irradiation from two microlenses whose minimum diameter Φ is separated by an interval of 30 mm. When the difference 2nΦtanθ of the optical path length difference is calculated for the light, it is expressed by the following equation (9).
[0061]
(Equation 9)

[0062]
Therefore, if the angle θ formed between the illuminance distribution correction surface 132a and the antireflection surface 132b is set to 3 seconds or more, the object of the present invention can be achieved more effectively in the illumination mode of all coherency σ values.
[0063]
By the way, as shown in FIG. 5, a plurality of micro lenses 122a constituting the optical integrator 122 are arranged in a lattice. FIG. 5 is a schematic diagram of a main part of the illumination device 100A, and is a schematic plan view showing the relationship between the optical integrator 122 and the aperture stop 126. Therefore, even when 2nΦtan θ ≧ λ, the light passing through two adjacent centers among the centers 122b of the microlenses 122a arranged along the direction E through the center of the minimum diameter 126a of the aperture stop 126 is illuminated. In some cases, the difference | AB | of the optical path length difference described in the apparatus 100 becomes (m + 1/2) λ, and the interference fringes cannot be canceled.
[0064]
In such a case, if the transmission optical flat plate 130 for correcting the illuminance distribution is set by rotating the optical flat plate 130 around the optical axis in the direction F shown in FIG. Can be excluded from (m + ／) λ. Then, the intensity of the interference fringes can be reduced.
[0065]
As described above, when viewed from the direction perpendicular to the optical axis, the arrangement direction of the plurality of micro lenses 122a constituting the optical integrator 122 and the inclination direction of the exit surface with respect to the entrance surface of the transmission optical flat plate 130A Is set at an appropriate angle, the object of the present invention can be more effectively achieved.
[0066]
Next, a lighting device 100B, which is still another modified example of the lighting device 100, will be described. The illumination device 100B uses a transmission-type optical flat plate 130B composed of four planes for illuminance distribution correction. As shown in FIG. 6, the transmission type optical flat plate 130B of the present embodiment includes a first transmission type optical flat plate 136 and a second transmission type optical flat plate 138, both of which have the same angle θ. ing. FIG. 6 is a schematic cross-sectional view showing a transmission optical flat plate 130B included in a lighting device 100B which is still another modified example of the lighting device 100.
[0067]
In the first transmission type optical flat plate 136, the above-described antireflection surface 136b on the incident light side and the illuminance distribution correction surface 136a on the emission light side are arranged substantially perpendicular to the optical axis at an inclination angle θ of both surfaces. .
[0068]
Both surfaces of the second transmission-type optical flat plate 138 serve as the above-described anti-reflection surfaces 138b, and two anti-reflection surfaces sandwiching the illuminance distribution correction surface 136a on the emission light side of the first transmission-type optical flat plate 136. The second transmissive optical flat plate 138 is disposed such that the surfaces 138b intersect on the extension thereof and face each other at an inclination angle θ equal to the angle formed between the entrance surface and the exit surface of each of the transmissive optical planar plates 136 and 138. ing.
[0069]
With the above-described configuration, the illumination device 100B can cancel the collapse of the parallelism of the sagittal light beam with respect to the meridional light beam generated by the first transmission optical flat plate 136 by the second transmission optical flat plate 138. it can. Therefore, by using the transmission type optical flat plates 136 and 138 for correcting the illuminance distribution, there is an effect that distortion of the effective light source is not newly generated in the irradiation light by the first optical system 123.
[0070]
Here, an excimer laser having an oscillation wavelength λ of 157 nm is used for the light source unit 110, and the angle formed between the entrance plane and the exit plane of the transmission optical flat plates 136 and 138 is set to 30 minutes. If the material of the transmission type optical flat plates 136 and 138 is fluorite, the refractive index n is 1.56. Further, the pitch H of the arrangement of the minute lenses 122a constituting the optical integrator 122 is set to 3 mm, and the minimum width W of the light beam emitted from each minute lens 122a is set to about 2 mm.
[0071]
Therefore, in order to check the degree of interference due to reflection from both surfaces of the first transmission optical flat plate 136, the above-described difference | AB | of the optical path length difference may be calculated. From the above equation 7, | AB | is the value of equation 10 shown below.
[0072]
(Equation 10)

[0073]
Therefore, | AB | shown in Expression 10 satisfies Expression 8 described above.
[0074]
Next, the degree of interference due to double-sided reflection between the exit surface of the first transmission optical flat plate 136 and the incident surface of the second transmission optical flat plate 138 is examined. Since the medium sandwiched between the first transmissive optical flat plate 136 and the second transmissive optical flat plate 138 is air, the refractive index n is 1. Therefore, the difference | AB | of the optical path length difference is the value of the following expression 11 from the above expression 7.
[0075]
[Equation 11]

[0076]
Therefore, in the transmission type optical flat plate of the present embodiment, the illuminance distribution correction surface 136a and the antireflection surface 136b of the first transmission type optical flat plate 136, the emission surface of the first transmission type optical flat plate 136, and the second The multiple reflection light relating to the incident surface of the transmission type optical flat plate 138 satisfies the above-described Expression 8 in order to achieve the object of the invention.
[0077]
Therefore, as described in the present embodiment, if the two transmission-type optical flat plates 136 and 138 are disposed in the lighting device 100B in an appropriate configuration, the two surfaces forming the first transmission-type optical flat plate 136 will be described. , The illuminance distribution can be corrected satisfactorily without causing distortion of the effective light source in the irradiation light.
[0078]
The above embodiment (FIG. 6) shows an example in which the exit surface of the first transmission optical flat plate 136 and the exit surface of the second transmission optical flat plate 138 are both perpendicular to the optical axis. This is not always necessary, and the relative angles of incidence and exit of the first transmission type optical flat plate 136 and the second transmission type optical flat plate 138 are substantially the same, and the tilt direction is relative to the optical axis. The position may be any position rotated by 180 degrees. Of course, also at this time, it is important that the difference in optical path length between the initial transmitted light beam A and the transmitted light beam B reflected by the illuminance distribution correction surface 136a and other surfaces toward the irradiation surface is not uniform at each position.
[0079]
The transmissive optical flat plate 130 and the transmissive optical flat plate 130A used for the illuminating device 100 and the illuminating device 100A according to the present invention for correcting the illuminance distribution reduce the shift amount of the irradiation area due to the wedge angle when attached to the device. It is better to keep it. For this purpose, the angle formed between the entrance surface and the exit surface is preferably set to 30 minutes or less.
[0080]
Furthermore, in order to adjust the asymmetry of the angle dependence effect of the transmittance due to the mounting angle setting error, the transmission optical flat plate 130, the transmission optical flat plate 130A, and the transmission optical flat plate 130B for correcting the illuminance distribution include: More desirably, it can be tilted with respect to a plane perpendicular to the optical axis.
[0081]
Further, the transmission optical flat plate 130 and the transmission optical flat plate 130A used for the illumination device 100 and the illumination device 100A for correcting the illuminance distribution used in the illumination device 100 and the illumination device 100A of the present invention are irradiated by the difference in the direction of the wedge angle when attached to the device. It is desirable that the shift directions of the regions are aligned in one direction. For this purpose, it is preferable that the illuminance distribution correction 130 and the transmission type optical flat plate 130A be rotatable around the optical axis.
[0082]
Although the entrance and exit surfaces of the transmission optical plane plate 130, the transmission optical plane plate 130A, and the transmission optical plane plate 130B for correcting the illuminance distribution are all described as planes, the entrance surface and the exit surface The present invention can also be applied to the case of a meniscus lens shape having the same radius of curvature having a gentle curvature.
[0083]
Further, the transmission type optical flat plate for correcting the illuminance distribution according to the present invention may be integrated with the stop like the filter with stop 1060a described in the conventional example, or may be provided with a separate stop.
[0084]
Further, in the above-described embodiments, the reflection of the illuminance distribution correction surface and the reflection of the anti-reflection surface are described. However, the present invention is not limited to this. It is sufficient that the angle satisfies the conditions of the above embodiment.
[0085]
Further, the two surfaces are arranged at an interval within 1/2 of the coherent distance, and the difference in the optical path length difference between the initially transmitted light A and the transmitted light B of the light emitted from each point of the optical integrator at the same angle is affected. Even if the interference fringes formed on the irradiation surface do not cancel each other, the product of the reflectance of the two surfaces may be 0.01 or less.
[0086]
Returning to FIG. 1 again, the reticle 210 is made of, for example, quartz, on which a circuit pattern (or image) to be transferred is formed, and is supported and driven by a reticle stage (not shown). Diffracted light emitted from the reticle 210 passes through the projection optical system 220 and is projected onto the plate 230. The plate 230 is an object to be processed and is coated with a resist. The reticle 210 and the plate 230 are arranged in a conjugate relationship. Since the exposure apparatus 200 is a step-and-scan exposure apparatus, the mask pattern is reduced and projected onto the plate 230 by scanning the reticle 210 and the plate 230.
[0087]
The projection optical system 220 includes an optical system including only a plurality of lens elements, an optical system including a plurality of lens elements and at least one concave mirror (catadioptric optical system), a plurality of lens elements and at least one kinoform. For example, an optical system having a diffractive optical element such as an optical system, an all-mirror optical system, or the like can be used. When it is necessary to correct chromatic aberration, a plurality of lens elements made of glass materials having mutually different dispersion values (Abbe values) may be used, or a diffractive optical element may be configured to cause dispersion in a direction opposite to that of the lens element. I do.
[0088]
The plate 230 is a wafer in the present embodiment, but widely includes a liquid crystal substrate and other objects to be processed (objects to be exposed). The plate 230 is coated with a photoresist. The photoresist application step includes a pretreatment, an adhesion improver application process, a photoresist application process, and a pre-bake process. Pretreatment includes washing, drying and the like. The adhesion improver application treatment is a surface modification treatment (that is, a hydrophobic treatment by applying a surfactant) for increasing the adhesion between the photoresist and the base, and the organic film such as HMDS (Hexamethyl-disilazane) is treated. Coat or steam. Prebaking is a baking (firing) step, but is softer than that after development, and removes the solvent.
[0089]
The plate stage 235 supports the plate 230. As the plate stage 235, any structure known in the art can be applied, and a detailed description of the structure and operation will be omitted. For example, the plate stage 235 can move the plate 230 in the X and Y directions using a linear motor. The reticle 210 and the plate 230 are, for example, synchronously scanned, and the positions of the plate stage 235 and a reticle stage (not shown) are monitored by, for example, a laser interferometer, and both are driven at a constant speed ratio. The plate stage 235 is provided, for example, on a stage base supported on a floor or the like via a damper. The reticle stage and the projection optical system 220 are, for example, a lens barrel base mounted on the floor or the like. It is provided on a lens barrel base (not shown) supported on a base frame via a damper or the like.
[0090]
In the exposure, the light beam emitted from the light source unit 110 uniformly illuminates the reticle 210 by Koehler illumination by the illumination optical system 120. Light passing through the reticle 210 and reflecting the circuit pattern is imaged on the plate 230 by the projection optical system 220.
[0091]
The exposure apparatus 200 using the illumination apparatus 100 can reduce the intensity of concentric interference fringes on the surface to be illuminated to a level that does not affect the imaging performance, and can make the illuminance distribution within the effective illumination range more uniform. Therefore, a high-quality device (semiconductor device, LCD device, imaging device (such as CCD), thin-film magnetic head, etc.) can be provided by performing pattern transfer onto a resist with high precision.
[0092]
Next, an embodiment of a device manufacturing method using the exposure apparatus 200 will be described with reference to FIGS. FIG. 7 is a flowchart for explaining the manufacture of devices (semiconductor chips such as ICs and LSIs, LCDs, CCDs, etc.). Here, the manufacture of a semiconductor chip will be described as an example. In step 1 (circuit design), the circuit of the device is designed. Step 2 (mask fabrication) forms a mask on which the designed circuit pattern is formed. In step 3 (wafer manufacturing), a wafer is manufactured using a material such as silicon. Step 4 (wafer process) is called a preprocess, and an actual circuit is formed on the wafer by lithography using the mask and the wafer. Step 5 (assembly) is called a post-process, and is a process of forming a semiconductor chip using the wafer created in step 4, and includes processes such as an assembly process (dicing and bonding) and a packaging process (chip encapsulation). . In step 6 (inspection), inspections such as an operation check test and a durability test of the semiconductor device created in step 5 are performed. Through these steps, a semiconductor device is completed and shipped (step 7).
[0093]
FIG. 8 is a detailed flowchart of the wafer process in Step 4. Step 11 (oxidation) oxidizes the wafer's surface. Step 12 (CVD) forms an insulating film on the surface of the wafer. Step 13 (electrode formation) forms electrodes on the wafer by vapor deposition or the like. Step 14 (ion implantation) implants ions into the wafer. In step 15 (resist processing), a photosensitive agent is applied to the wafer. Step 16 (exposure) uses the exposure apparatus 200 to expose a circuit pattern on the mask onto the wafer. Step 17 (development) develops the exposed wafer. Step 18 (etching) removes portions other than the developed resist image. Step 19 (resist stripping) removes unnecessary resist after etching. By repeating these steps, multiple circuit patterns are formed on the wafer. According to such a device manufacturing method, it is possible to manufacture a device of higher quality than before. As described above, the device manufacturing method using the exposure apparatus 200 and the resulting device also constitute one aspect of the present invention.
[0094]
Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications and changes can be made within the scope of the gist.
[0095]
【The invention's effect】
According to the illumination device of the present invention, the optical integrator and the transmission optical plane plate introduced into the illumination optical system emit irradiation light having coherence like an excimer laser by appropriately setting various conditions. Even if a light source is used and a transmissive optical flat plate for correcting the illuminance distribution is introduced into the illumination optical system, it does not generate harmful interference fringes in the irradiation light on the illuminated surface and remains within the effective illumination range. Illuminance distribution can be made uniform. Therefore, even if the circuit pattern on the reticle becomes finer, it is possible to provide a projection exposure apparatus capable of performing printing exposure on a target object while maintaining similarity of the reduced projection pattern.
[Brief description of the drawings]
FIG. 1 is a schematic block diagram illustrating an exemplary embodiment of an exposure apparatus according to one aspect of the present invention.
FIG. 2 is a schematic diagram showing a relationship between two light beams emitted from the optical integrator shown in FIG. 1 and having different emission angles and illumination positions on an illumination target surface corresponding to the two light beams.
FIG. 3 is a schematic cross-sectional view showing a state of light rays on a micro lens and a transmission optical flat plate of the optical integrator shown in FIG.
FIG. 4 is a graph showing the relationship between the difference in optical path length difference and the relative intensity of interference fringes.
FIG. 5 is a schematic plan view showing a main part of a lighting device which is a modification of the lighting device shown in FIG.
FIG. 6 is a schematic cross-sectional view showing a transmission optical flat plate constituting an illumination device which is still another modification of the illumination device shown in FIG.
FIG. 7 is a flowchart for explaining the manufacture of devices (semiconductor chips such as ICs and LSIs, LCDs, CCDs, etc.).
FIG. 8 is a detailed flowchart of a wafer process in Step 4 shown in FIG. 7;
FIG. 9 is a schematic configuration diagram of a conventional projection exposure apparatus.
FIG. 10 is a schematic diagram showing multiple reflection in the filter shown in FIG. 9;
[Explanation of symbols]
100 lighting equipment
110 Light source
120 Illumination optical system
121 Beam shaping optical system
122 Optical Integrator
123 First Optical System
124 masking blade
125 second optical system
130 Transmission optical flat plate
200 Exposure equipment
210 reticle
220 Projection optical system
230 plates

Claims (11)

An illumination device that illuminates a surface to be illuminated using coherent illumination light emitted from a light source,
The optical path length from the entrance surface to the exit surface is less than half the coherence distance of the illumination light, and the reflectance (%) of the incident surface and the reflectance (%) of the exit surface when the illumination light enters. Having a transmission type optical flat plate whose product is 0.01 or more,
When the angle between the entrance surface and the exit surface is θ, the wavelength of the illumination light from the light source is λ, the minimum width of the illumination light is W, and the refractive index from the entrance surface to the exit surface is n. An illumination device that satisfies 2nWtan θ ≧ λ or θ ≧ 3 seconds. Further comprising a plurality of light source forming means disposed between the light source and the illumination surface, to form a plurality of light sources from the illumination light,
The lighting device according to claim 1, wherein the transmission optical flat plate is disposed between the plurality of light source forming units and the illuminated surface. The lighting device according to claim 2, wherein the minimum width W of the illumination light is emitted from an arbitrary minute lens included in the multiple light source forming unit. When the interference distance is S, and the spectral half width of the illumination light is Δλ,
S = λ × λ / Δλ
The lighting device according to claim 1, wherein The illumination device according to claim 1, wherein the illumination light emitted from the light source is an excimer laser. The lighting device according to claim 1, wherein the transmission-type optical flat plate has an illuminance distribution correction surface that corrects an illuminance distribution within an illumination range on the illuminated surface. The lighting device according to claim 1, wherein an angle θ between the incident surface and the exit surface is 30 minutes or less. The lighting device according to claim 6, wherein the transmission-type optical flat plate is tiltable with respect to a plane perpendicular to an optical axis. The lighting device according to claim 7, wherein the transmission-type optical flat plate is rotatable around an optical axis. The lighting device according to any one of claims 1 to 9,
An exposure system having an optical system for projecting a pattern formed on a reticle or a mask onto an object to be processed. Projecting and exposing an object to be processed using the exposure apparatus according to claim 10;
Performing a predetermined process on the object subjected to the projection exposure.

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