JP3713355B2 - Position measuring device - Google Patents

Position measuring device Download PDF

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Publication number
JP3713355B2
JP3713355B2 JP06867097A JP6867097A JP3713355B2 JP 3713355 B2 JP3713355 B2 JP 3713355B2 JP 06867097 A JP06867097 A JP 06867097A JP 6867097 A JP6867097 A JP 6867097A JP 3713355 B2 JP3713355 B2 JP 3713355B2
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JP
Japan
Prior art keywords
light
measurement
illumination
normal direction
plane
Prior art date
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Expired - Fee Related
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JP06867097A
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Japanese (ja)
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JPH10267614A (en
Inventor
真也 渡邉
等 鈴木
和夫 阿部
晋 斎藤
徹 東條
亮一 平野
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Toshiba Corp
Topcon Corp
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Toshiba Corp
Topcon Corp
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  • Length Measuring Devices By Optical Means (AREA)
  • Optical Transform (AREA)
  • Exposure And Positioning Against Photoresist Photosensitive Materials (AREA)
  • Electron Beam Exposure (AREA)

Description

【0001】
【発明の属する技術分野】
本発明は、加工対象物の表面を加工する加工機や測定対象物の表面状態等を測定する測定機械において、対象物の位置を制御する等の目的に利用される位置測定装置に関する。
また、本発明は位置測定装置を適用した電子線描画装置に関する。
【0002】
【従来の技術】
従来、半導体露光装置では、あらかじめ作成された原画パターン(レチクル又はマスク)上の所望の回路パターンを、ウエハ上の露光領域に位置合わせした後、転写を行ってきた。この転写装置は高精度な縮小露光投影装置であり、転写される側のウエハ全面に露光できるように、ウエハ側は高精度なXYステージに固定されている。このウエハ光学系に対し、ステップ&リピートするための掲記転写装置はステッパと呼ばれている。
近年のLSIの高集積化により、半導体装置に要求される回路線幅は益々狭くなってきている。ステッパの縮小率は、従来1/5が主流であったが、これまでの波長限界から1μm以下のパターンは解像できないと言われてきた。しかし、光学系・照明系の改良やレチクル上での光の位相を調整する位相シフトマスク等の出現により、サブμmオーダーのパターンを解像するに至っている。解像度の向上に伴って、縮小レンズの焦点深度は浅くなり、また、あらかじめ作成された原画パターンをウエハ上に転写する精度は、いっそう厳しい値が要求されるようになってきている。このため、ステッパのアライメント光学系に対して、試料の試料面方向及び焦点方向の位置を高精度に検出することが要求されている。
【0003】
位相シフトマスクは前記原画パターン上の露光光透過部を通過する光の位相即ち透過部の光路長を、基板の厚さをエッチングすることにより減少させ、あるいは、屈折率の異なる材料を付加する等の手法で変化させるものである。したがって、位相シフトマスクの作製には、特定の光透過部の基板を厚さ方向に掘り込み、選択的に光路長を変化させる方法や、または、あらかじめパターンが描かれた基板に再度レジストを塗付し、光透過部の位相を部分的に変化させるための材料を付加した後不要部分のエッチングを行う方法が採られる。いずれの場合においても、前記パターン描画装置を用いて、所定の位置のレジストを高精度に感光させる必要がある。
【0004】
【発明が解決しようとする課題】
マスク上の位置合わせマークの検出に先立って、露光ビームの位置はステージ上に設けられたマーク等を用いて測定されかつ校正される。ステージの位置はレーザー干渉計により高精度にモニターされるので、レーザー干渉計の座標系を基準としてビームの位置及び変位を測定することが可能となる。
ところが、電子線露光装置では、鏡筒内部に汚れが付着すると、チャージアップのために電子ビームにドリフトが生じ、測定値が変動する。マスク上のマーク位置の測定はステージ上のマークを介した間接測定であるため、測定値に変動が生じた場合には、その原因はビームドリフトであるのか、或いは、マークそのものが変位しているためであるのかを区別することが出来ないという課題があった。
【0005】
電子ビーム描画装置やステッパにおいて、ドリフトによる影響を受けずにマーク位置を精度良く測定するための手段として、レーザー光を用いた測定光学系を設けた装置を用いる方法が考えられる。
ここで、電子ビーム描画装置やステッパで描画する通常のマスクの基板やレジストの厚さは数十nm〜数百nmのオーダーであるから、Z検出分解能もこのオーダーが要求される。
位相シフトマスクでは、露光〜エッチングの工程を終えた第一層の上にさらに第二層、第三層の工程を行うので、ある層から次の層の工程に移る際、マスクは一旦露光装置からはずされ、次の層のための準備を施されてから再び露光装置に取り付けられる。このとき、取りはずされる前のマスクの位置を正確に再現しなければならないので、要求されるZ検出範囲(ストローク)は数百μmである。
【0006】
したがって、Z検出は数十nm〜数百nmの分解能で、数百μmのストロークが必要である。
分解能は検出ストロークを電気処理系における分割数(サンプル数)で割った値で決められる。例えば検出ストロークが50μm、サンプル数が2000のときの分解能は、
50μm/2000=25nm
となる。前述のようにZ検出では数百μmのストロークが必要であるが、例えば200μmのストロークで同じ25nmの分解能を得るためには、
200μm/25nm=8000
と4倍のサンプル数が必要となる。サンプル数が増大すると電気処理系に負担を掛け、処理時間も増大するという課題がある。
【0007】
従って、小型で高精度な位置測定装置に対する要求があり、また、小型で高精度な位置測定装置を適用した電子線描画装置に対する要求がある。
【0008】
【発明の目的】
そこで、本発明の目的は、
(1)少なくとも3本のレーザー光束を対象物面において異なる角度で照射して、それらの干渉光を用いて測定範囲(ダイナミックレンジ)の広い法線方向の位置測定を行う位置測定装置を提供することにある。
(2)測定範囲を拡大した法線方向の位置測定に加えて、さらに、平面方向の位置測定のための第1平面方向位置測定用照明光束と第2平面方向位置測定用照明光束とを形成照射して平面方向の測定も行う測定装置を提供することにある。
(3)第3照明光束の入射角度を変化させ、測定範囲を変更できる構成の位置測定装置を提供することにある。
(4)照射光学系中に対象物に照射する光束の照射位置を調整する光束シフト部を設けた位置測定装置を提供することにある。
(5)照射光学系中に対象物に照射する光束の集光位置を調整する集光位置変化部を設けた位置測定装置を提供することにある。
(6)対象物の位置を正確に測定することができる位置測定装置を備えた小型で高精度な電子線描画装置を提供することにある。
【0009】
【課題を解決するための手段】
本発明の位置測定装置は、コヒーレント光を発する光源部と、この光源部からの光束を、法線方向基準照明光束として第1入射角により、第1法線方向測定用照明光束として第2入射角により、また前記第2法線方向測定用照明光束として第1入射角及び第2入射角とは異なる第3入射角で、位置の測定をすべき対象物に設けられている2次元パターンへ照射する照射光学系と、2次元パターンからの反射光を受光する受光光学系と、受光光学系で受光した反射光の内で、法線方向基準照明光束と第1法線方向測定用照明光束とを干渉させて第1法線方向測定用干渉信号を形成し、法線方向基準照明光束又は第1法線方向測定用照明光束と第2法線方向測定用照明光束とを干渉させて第2法線方向測定用干渉信号を形成する受光部と、第1法線方向測定用干渉信号及び前記第2法線方向測定用干渉信号の位相に基づき対象物の法線方向の位置測定を行う信号処理部とを有する構成である。
【0010】
このような構成により、測定範囲の広い法線方向の位置測定を行うことができる小型で高精度な位置測定装置を実現することができる。
本発明の位置測定装置の信号処理部は第1法線方向測定用干渉信号と第2法線方向測定用干渉信号との位相差に基づいて前記対象物の法線方向の位置の測定を行う信号処理部を有するのが好ましい。
このような構成により、効率的な信号の処理を行うことができ、小型で高精度な位置測定装置を実現することができる。
また、本発明の位置測定装置の光源部は、この光源部からの光束を周波数が異なる光束として射出する周波数シフター部を更に備え、上記光源部は、この光源部から生じる第1周波数のコヒーレント光を、法線方向基準照明光束とし、周波数シフター部から射出される前記法線方向基準照明光束と周波数が異なる第2周波数の光束を第1法線方向測定用照明光束とし、法線方向基準照明光束又は第1法線方向測定用照明光束のいずれか一つから分離させて第2法線方向測定用照明光束を形成する光束分離部を更に備えているのが好ましい。
【0011】
このような構成により、小型で高精度な位置測定装置の光源を実現することができる。
また、本発明の位置測定装置の光源部は、第1平面方向測定用照明光束となる第1周波数のコヒーレント光を発する光源と、この第1平面方向測定用照明光束と周波数が異なる第2周波数の第2平面方向測定用照明光束を形成する周波数シフターとを有し、照射光学系は、第1平面方向測定用照明光束と第2平面方向測定用照明光束を第1入射角で入射させ、受光部は、受光光学系で受光した第1平面方向測定用照明光束と第2平面方向測定用照明光束の回折光の内で、2次元パターンによる高次回折光と0次回折光の組み合わせ及び高次回折光同士の組み合わせのいずれか一つの周波数が異なる回折光の組み合わせから対象物の2次元パターンを設けた平面内での平面位置測定用干渉信号を形成し、信号処理部は、平面位置測定用干渉信号の位相に基づき対象物の2次元パターンを設けた平面内での位置を求める信号処理部とを有するのが好ましい。
【0012】
このような構成により、小型で高精度な位置測定装置を実現することができる。
また、本発明の位置測定装置の受光部は、第1平面位置測定用照明光束と第2平面位置測定用照明光束の2次元パターンによる0次回折光同士の異なる周波数の回折光の組み合わせからX位置測定用干渉基準信号を形成し、第1平面位置測定用照明光束の0次回折光と第2平面位置測定用照明光束の高次回折光の組合せ又は、第1平面位置測定用照明光束の高次回折光と第2平面位置測定用照明光束の0次回折光の組合せからY位置測定用干渉基準信号を形成し、信号処理部は、X位置測定用干渉測定信号とX位置測定用干渉基準信号との位相差に基づき対象物のX方向の位置を求め、Y位置測定用干渉測定信号とY位置測定用干渉基準信号との位相差に基づき対象物のY方向の位置を求めるように構成するのが好ましい。
【0013】
このような構成により、確実に回折光を受光して、効率的な信号の処理を行うことができ、小型で高精度な位置測定装置を実現することができる。
また、本発明の位置測定装置の光源部は、第1平面方向測定用照明光束と法線方向基準照明光束とを共通の光束とするように構成されているのが好ましい。
このような構成により、小型で高精度な位置測定装置を実現することができる。
また、本発明の位置測定装置の照射光学系での第1法線方向位置測定用照明光束又は第2法線方向位置測定用照明光束の光路中に、その照明光束が前記2次元パターンに照射する入射角度を変化させる入射角度変化部材が配置されているのが好ましい。
【0014】
このような構成により、測定範囲を変更できる小型で高精度な位置測定装置を実現することができる。
また、本発明の位置測定装置の入射角度変化部材は、第1法線方向位置測定用照明光束又は第2法線方向位置測定用照明光束の入射角度を変化させるように、その光路中に光軸と直交方向に回転軸を有する平行平面板として構成されているのが好ましい。
このような構成により、測定範囲を変更できる小型で高精度な位置測定装置を実現することができる。
更に、本発明は、電子線描画装置において、電子線描画装置の構成部品の取付け位置及びそれらの最大作動範囲をさけるように配置されている上記の本発明の位置測定装置を備え、位置測定装置は対象物の位置を測定するための位置測定用光束を照射するための照明側光学部材と、対象物からの反射回折光を受光して対象物の位置を測定するための受光側光学部材とを有し、照明側光学部材から照射して受光側光学部材に入射される光束が、電子線描画装置の構成部品の取付け位置及びそれらの最大作動範囲をさけて透過することができるように、照明側光学部材及び受光側光学部材が電子線描画装置に配置されている構成とした。
【0015】
この構成により、加工すべき対象物の位置を精確に測定することができ、電子線描画装置により極めて高い精度で加工対象物を加工することができる。
【0016】
【発明の実施の形態】
以下、本発明の実施の形態を図面により説明する。
本発明の位置測定装置は、図1に示すように、照明光学系100と、補正光学系200と、照射光学系300と、受光光学系400とを備える。
〔1〕 照明光学系100
図1及び図1の部分拡大図である図16から図18を参照すると、光源1は照明光束となるコヒーレント光を発する光源であり、波長λ=633nmのHe−Neレーザー光源である。光源1から照射される干渉性の強いコヒーレントであるレーザー光は、リレーレンズ102を介してビームスプリッター103で、第1照明光束104と第2照明光束105とに分岐される。
【0017】
第1照明光束104はリレーレンズ106を介して第1周波数シフター108に導かれ、第1周波数シフター108は第1照明光束104を変調して第1測定用照明光束110を形成する。第2照明光束105はリレーレンズ107を介して第2周波数シフター109に導かれ、第2周波数シフター109は第2照明光束105を変調して第2測定用照明光束111を形成する。
音響光学素子(AOM)を周波数シフターとして用いるのが好ましい。第1測定用照明光束110の周波数シフターによる変調周波数は80.05MHzであり、第2測定用照明光束111の周波数シフターによる変調周波数は80.0625MHzである。周波数シフター108、109により、周波数が互いに僅かに異なる第1測定用照明光束110及び第2測定用照明光束111が形成される。この場合に、第1測定用照明光束110と第2測定用照明光束111の周波数の差Δfは12.5KHzとなる。第1測定用照明光束110と第2測定用照明光束111を互いに重ね合わせて、干渉させると、その干渉結果の強度は、周波数Δfのうなり(ビート信号)になる。
【0018】
ビームスプリッター112は、第1測定用照明光束110を第1平面位置測定用照明光束114と第1法線方向測定用照明光束115とに分岐させる。
ビームスプリッター113は、第2測定用照明光束111を第2平面位置測定用照明光束116と第2法線方向測定用照明光束117とに分岐させる。
第1平面位置測定用照明光束114、第1法線方向測定用照明光束115、第2平面位置測定用照明光束116、第2法線方向測定用照明光束117は、それぞれリレーレンズ118、119、120、121を介して調整光学系200に、その光軸に対して互いに平行な光束として導かれる。
但し、第1法線方向測定用照明光束115及び第2法線方向測定用照明光束117は、それぞれ第1平面位置測定用照明光束114及び第2平面位置測定用照明光束116とは別個の測定用照明光束から分岐させることも可能である。
【0019】
ここで、照明光学系100において、リレーレンズ102、106、107により光源1と第1周波数シフター108及び第2周波数シフター109は共役関係となる。
〔2〕 調整光学系200
調整光学系200は、図2から図4に示すように、第1平面位置測定用照明光束114、第1法線方向測定用照明光束115、第2平面位置測定用照明光束116及び第2法線方向測定用照明光束117を、所定の照射条件に適合するように補正を施す光学系である。その補正には、第1法線方向測定用照明光束115及び第2法線方向測定用照明光束117の照射角度を第1平面位置測定用照明光束114及び第2平面位置測定用照明光束116に対して調整を行う照射角度調整、これら4本の照明光束114〜117が照射する対象物上の平面位置を調整する平面位置調整、及び、これら4本の照明光束114〜117のビームウエスト位置が対象物10上に来るように調整するビームウエスト位置調整の3種類がある。
【0020】
第1法線方向測定用照明光束115及び第2法線方向測定用照明光束117の照射角度調整は、それぞれの光路に挿入されている平行平面板201、202を光軸と直交する回転軸を中心に回転させることにより行われる。第1法線方向測定用照明光束115及び第2法線方向測定用照明光束117は、平行平面板201、202の回転により鉛直方向に平行移動し、その結果、後述する投影レンズによる照射角度が変化する。ここで、「鉛直方向」とは、4本の照明光束114〜117を含むような面に対して垂直な方向をいう。
4本の測定用照明光束114〜117は、それぞれの光路で2つのミラー(図示せず)により光束の間隔を狭くされ、頂角の等しい一組のウエッジプリズム203、204に入射する。
【0021】
4本の測定用照明光束114〜117の平面位置の調整は、水平方向を調整のための中心軸として、ウエッジプリズム203、204の交差角度の調整及び交差中心方向の調整により行われる。
調整前の位置からの距離は、ウエッジプリズム203、204の交差角度を調整することによって決定される。又、調整前からの変化の方向はウエッジプリズム203、204が交差する中心方向を調整することにより決定される。このようにして調整を行うことにより、4本の測定用照明光束114〜117の平面位置の調整を上下左右の任意の方向で行うことができる。
4本の測定用照明光束114〜117は、ウエッジプリズム203、204で平面位置調整を行った後、フォーカスレンズ205、206に入射する。
【0022】
フォーカスレンズ205、206は、その間隔が変化することにより、各光束が光軸と平行であるという条件を維持しつつ、各光束と光軸との間隔を変更できるように構成されており、4本の測定用照明光束114〜117のビームウエストが対象物10上に来るように、ビームウエストの位置を光軸方向に調整することができる。
本発明の実施の形態では、光源側にある調整レンズ205は平凸レンズで形成され、対象物側の調整レンズ206は平凹レンズ206で形成されている。
従って、フォーカスレンズ205と206との間の間隔を広げると、ビームウエストの位置が光源側に近づくように変化する。
但し、光源1のある側のフォーカスレンズ205を平凹レンズ206で形成し、対象物10のある側のフォーカスレンズ206を平凸レンズで形成することも可能である。
【0023】
このように、光軸付近に第1平面位置測定用照明光束114及び第2平面位置測定用照明光束116を配置し、これらを基準として照射角度の調整を行う第1法線方向測定用照明光束115及び第2法線方向測定用照明光束117を周辺に(両脇に)配置することにより、照射角度調整を行う光学素子である平行平面板201、202をそれらの光路中に配置しかつ光軸と直交する回転軸を中心に回転可能とする機構を組み込みやすくすることができる。
【0024】
〔2−1〕 マニュアル調整
上述した調整光学系200のビームの調整方法について説明する。以下では、位置を優先した調整方法について説明する。
初期状態では、ウエッジプリズム203、204は180度回転されたように反対方向を向いて配置され、見掛け上、プリズムのパワーがない状態とされている。また、調整レンズ205と206は両者の間隔が略ゼロとなるように配置され、パワーがない状態であることとする。
この位置を優先した調整方法においては、ウエッジプリズム203、204を用いて初期状態でのビームの照射位置を本来照射したいマーク12上に移動させ、次に調整レンズ205及び206を用いて、4本の測定用照明光束114〜117のビームウエストが対象物10上に来るようにビームウエスト位置を調整する。
具体的にいえば、ビームの移動方向は、ウエッジプリズム203、204の交叉角度の2等分線方向と一致するので、初期状態におけるビーム照射位置を基準として、ビームを照射したいマーク12の方向とウエッジプリズム203、204の交叉角度の2等分線方向が一致するように両プリズムを回転させる。
次に、ビームの移動距離は、ウエッジプリズム203、204の交叉角度が180度から0度に近づくにつれてビームの移動距離が大きくなるので、ウエッジプリズム203、204の交叉角度の2等分線方向を維持したまま互いのウエッジプリズム203、204の交叉角度を調整することにより、対象物10上の2次元パターン12上を照射するように調整することができる。
このように、4本の測定用照明光束114〜117のビーム位置を対象物10上の2次元パターン12上に来るように調整したあと、干渉信号の強度が最大となるなどの影響要素に基づき、ビームウエスト位置を対象物10上の2次元パターン12上になるように調整レンズ205と206との間の間隔を調整する。
本発明の実施の形態では、光源1のある側の調整レンズ205を平凸レンズで形成し、対象物10のある側の調整レンズ206を平凹レンズ206で形成したので、調整レンズ205と調整レンズ206との間の間隔を広げるにつれて、ビームウエスト位置は光源側に近づく。
【0025】
〔3〕 照射光学系300
照射光学系300は、図2から図4に示すように、折り返しミラー301、302及び照射レンズ303を備え、第1平面位置測定用照明光束114、第2平面位置測定用照明光束116、第1法線方向測定用照明光束115及び第2法線方向測定用照明光束117の4本の光束を対象物10上の2次元パターン12上に一点に照射する。
【0026】
このとき照射光学系300は、上記補正光学系200によって所定の補正がされた結果、第1平面位置測定用照明光束114、第2平面位置測定用照明光束116をいっしょに、対象物10を含む平面の法線に対して入射角θ1で照射し、第1法線方向測定用照明光束115を入射角θ1とは異なる入射角θ2で照射し、第2法線方向測定用照明光束117をθ1及びθ2とは異なる入射角θ3で照射する。
照射レンズ303を含む照射光学系300は、ビームウエスト位置調整用の調整レンズ205及び調整レンズ206が作用しない状態で、すなわち、調整レンズ205と調整レンズ206とが互いに接触した状態で、ビームウエスト位置がビームウエスト位置調整範囲の最遠点となるように設定されている。
【0027】
ビームウエスト位置調整用の調整レンズ205と調整レンズ206との間の間隔を適当に定めることにより、対象物10上に測定照明光束のビームウエストが来るように調整することができる。種々の調整が終了した時点で、光源1、周波数シフター108、109及び対象物10はすべて共役関係を形成する。
対象物10上の2次元回折パターン12は市松格子より形成される。この市松格子はX方向及びY方向に、それぞれ等しいピッチdを持つ。
対象物10上の市松格子に入射した4本の測定用照明光束は、この市松格子により反射し、回折する。
今、第1平面位置測定用照明光束114のみに注目すると、入射角θと1次光回折光のX方向の回折角θx及びY方向の回折角θyとの関係は次式で与えられる。
【0028】
sinθx=±λ/d (1)
sinθy=sinθ±λ/d (2)
(1)式及び(2)式を満たす第1平面位置測定用照明光束の正反射光(回折0次光)、回折1次光のマッピングを、図5及び図6に示す。(2次以上の高次に関しては省略してある。)
図5は対象物10上の2次元パターン12に第1平面位置測定用照明光束114が、2次元パターン12の法線12Tに対して角度θで入射した状態を示す。図6は対象物10上の2次元パターン12に4本の測定用照明光束114〜117が入射した状態を示す。
図7及び図8に示すように、第1平面位置測定用照明光束114、第2平面位置測定用照明光束116、第1法線方向測定用照明光束115及び第2法線方向測定用照明光束117は、対象物面法線を軸とし互いに僅かな角度+α回転させた方向から入射されているので、それぞれの0次光、回折1次光は、他の測定用照明光束の0次光、回折1次光と重ならずに、分離して単独に取り出すことが可能である。
【0029】
また入射角に関しては、図8に示すように、第1平面位置測定用照明光束114及び第2平面位置測定用照明光束116は入射角θ1で、第1法線方向測定用照明光束115は入射角θ2で、第2法線方向測定用照明光束117は入射角θ3で、それぞれ対象物10上の2次元回折パターン12に照射される。
図9は、第1平面位置測定用照明光束114及び第2平面位置測定用照明光束116の0次光及び回折1次光と第1法線方向測定用照明光束115及び第2法線方向測定用照明光束117の0次光のマッピングである。
本発明の実施の形態においては、図5、図6及び図9に示すように、回折光マッピングが反射回折となっているため、X軸の正方向は図中で左方向であり、Y軸の正方向は図中で下方向であって、一般の座標系とは異なっている。
【0030】
受光光学系400は、図10、図11及び図19に示すように、前記2次元パターン上の反射点から拡がる回折光を受光するように配置される。しかし、電子ビーム描画装置やステッパなどでは描画光学系や投影光学系などの装置の部材710がスペースの大半を占めており、受光光学系のためのスペースは限られることが多い。
従って、受光光学系全体の大きさを決める回折角が小さくでき、かつ受光部での各回折光の分岐、重ね合わせが容易になるよう互いに適度な間隔が保たれている配置が要求される。また、照射光学系側も受光光学系側と同様に、装置の部材によりそのスペースは限られている。
受光光学系側で0次光のY方向回折角は入射角と同じくθである。1次回折光のY方向回折角θyについて(2)式を参照すると、複合のマイナスの式を満たすθyはθよりも小さい値になる。つまり、−1次回折光は0次光に対し描画光学系や投影光学系など装置の部材側に現れるため、それらの部材により遮られる傾向がある。
【0031】
この場合には、受光光学系側と照射光学系側での光束の通過位置は非対称となり、−1次光が装置本来の部材に遮られないように設定すると、入射側により入射角θを大きくとりデットゾーンを設けることとなる。
また、入射角θを大きくすると反射回折光の各偏光成分(S偏光、P偏光)の回折効率の差も大きくなり、受光部での重ね合わせ干渉性に影響を及ぼす。ところが(2)式の複合のプラスの式を満たすθyはθよりも大きく、+1次回折光は0次光に対し対象物側に現れる。
したがって0次光が部材に遮られていなければ、+1次光も装置の部材710にさえぎられることは無い。よって+1次光を用いれば入射角θは部材に遮られない範囲で最小の値にでき、偏光成分による回折効率の差を小さくできる。
【0032】
(2)式の複合のプラスの式と(1)式を同時に満たす1次回折光は、X方向に+1次、Y方向に+1次の回折光とX方向に−1次、Y方向に+1次の回折光である。これらは互いに隣り合う象限((X、Y)象限及び(−X、Y)象限)に含まれており、これらの光線を用いることで受光側光学系の省スペース化にも貢献できる。
図14は、位置合わせマークで回折された回折光のうち、X、Y、Z方向の測定に用いる回折光マッピングを示す。
ここで、f1(0)は第1平面位置測定用照明光束114が位置合わせマークで回折されたあとの0次の回折光であり、f2(0)は第2平面位置測定用照明光束116が位置合わせマークで回折されたあとの0次の回折光である。
【0033】
f1(X,Y)は第1平面位置測定用照明光束114が位置合わせマークで回折されたあとのX方向が+1次でY方向が+1次の回折光である。
f1(−X,Y)は第1平面位置測定用照明光束114が位置合わせマークで回折されたあとのX方向が−1次でY方向が+1次の回折光である。
f2(X,Y)は第2平面位置測定用照明光束116が位置合わせマークで回折されたあとのX方向が+1次でY方向が+1次の回折光である。
f2(−X,Y)は第2平面位置測定用照明光束116が位置合わせマークで回折されたあとのX方向が−1次でY方向が+1次の回折光である。
f1’(0)は第1法線方向測定用照明光束115が位置合わせマークで回折されたあとの0次の回折光である。
【0034】
f2’(0)は第2法線方向測定用照明光束117が位置合わせマークで回折されたあとの0次の回折光である。
受光光学系を小さくするためのもう一つの方法は、対物レンズ410の径を小さくすることである。レンズ径を小さくするためには、0次光と1次光の回折角の差を小さくすればよい。回折角の差を小さくする方法として、(1)式、(2)式より2次元回折パターンのピッチを大きくする、または光源波長λを小さくすることが挙げられる。
通常回折パターンのピッチは数μm〜数十μm程度である。このときλ=633nmのHe−Neレーザー光源を用いると、回折角を十分小さくすることができる。また対象物面上にはレジストが塗布されていることが多いが、この波長はレジストを感光しない程度に十分長い波長である。
【0035】
さらに対物レンズ401の光軸と対象物の法線との成す角βを、第1照明光束の0次光と対象物の法線との成す角をθ、第1照明光束の+1次回折光のY方向の回折角をθyとして次式で与えられるようにする。
β=(θ+θy)/2
これは0次光と回折1次光の中間の角度で、この光軸を取ることにより対象物から遠い位置に配置しても、レンズ径を小さくできる。また対象物上の反射点から対物レンズまでの距離が長いほど各回折光の間隔が広くなり、受光部での各回折光の分岐、重ね合わせ干渉が容易になるという利点もある。
図10は、投光光学系及び受光光学系の例で、波長λ=633nm、第1平面位置測定用照明光束114及び第2平面位置測定用照明光束116の入射角θ=70°、回折格子ピッチd=20μm、照射レンズ303の焦点距離は133mm、受光側対物レンズの焦点距離は220mmである。
【0036】
照射レンズ303に入射する4本の照明光束は互いに平行で間隔が3mmであるから、この間隔は受光側対物レンズ401を通過した後に約5mmとなる。
また、1次光の回折角に関しては、(1)式及び(2)式を用いて、θx=1.8°、θy=76.25°となる。受光側対物レンズ401の光軸の角度βは73°で、このときレンズ径はφ40mmとなり、4本の照明光束を部材710に衝突することなく透過させることができる。
受光側対物レンズ401は、対象物10上の反射点から1焦点距離分の位置に配置され、対象物10上の反射点から拡がる多数の反射回折光を互いに平行にする役割を担う。受光側対物レンズ401により互いに平行にされた各回折光は、折り返しミラー402、403により受光部に導かれ、さらに折り返しミラー404、405により、0次光及び1次光は同一平面内に納められる。
【0037】
次に、受光部500の構成の詳細を図12に示す。受光部は前記受光光学系400で受光した回折光の内で、隣り合う象限、ここでは(+X、+Y)象限及び(−X、+Y)象限に含まれる第1平面位置測定用照明光束114と第2平面位置測定用照明光束116の前記2次元パターンによる高次回折光と0次光の組み合わせ及び高次回折光同士の組合せのいずれか一つの異なる周波数の回折光の組み合わせから、対象物を含む平面内での位置測定用干渉測定信号を形成する。
対象物を含む平面内のX方向の位置測定用干渉測定信号は、第1平面位置測定用照明光束114の前記2次元パターンによる回折光の内で、X方向に−1次、Y方向に+1次の回折光512と、第2平面位置測定用照明光束116の前記2次元パターンによる回折光の内、X方向に+1次、Y方向に+1次の回折光514をビームスプリッター530で重ね合わせて形成する。X位置測定用干渉信号をフォトセンサ550で受光する。
【0038】
対象物を含む平面内のY方向の位置測定用干渉測定信号は、第1平面位置測定用照明光束114の前記2次元パターンによる回折光の内で、X方向に+1次、Y方向に+1次の回折光511と、ビームスプリッター531で第2平面位置測定用照明光束116の0次光513から分岐された光線を、ビームスプリッター532で重ね合わせ形成する。Y位置測定用干渉測定信号はフォトセンサ551で受光する。
対象物を含む平面の法線方向、即ちZ方向を照射角度θ2で照射した際に得られる第1Z方向位置測定用干渉測定信号は、第2平面位置測定用照明光束116の0次光513からビームスプリッター533で分岐された光線と、第1法線方向測定用照明光束115の0次光517をビームスプリッター534で重ね合わせ形成する。Z位置測定用干渉信号はフォトセンサ552で受光する。
【0039】
対象物を含む平面の法線方向、即ちZ方向を照射角度θ3で照射した際に得られる第2Z方向位置測定用干渉測定信号は、第1平面位置測定用照明光束116の0次光510からビームスプリッター535で分岐された光線と、第2法線方向測定用照明光束115の0次光516をビームスプリッター536で重ね合わせて形成する。Z位置測定用干渉信号はフォトセンサ553で受光する。
受光部ではさらに、第1平面位置測定用照明光束114の0次光510と第2平面位置測定用照明光束の0次光513をミラー537を介してビームスプリッター538で重ね合わせて、X位置測定用干渉基準信号兼Z位置測定用基準信号を形成する。X位置測定用干渉基準信号兼Z位置測定用干渉基準信号は、フォトセンサ554で受光する。
【0040】
また、第1平面位置測定用照明光束114の0次光510からビームスプリッター539で分岐された光線と、第2平面位置測定用照明光束116の2次元パターンによる回折光の内で、X方向に−1次、Y方向に+1次の回折光515をビームスプリッター540で重ね合わせ、Y位置測定用干渉基準信号を形成する。Y位置測定用干渉基準信はフォトセンサ555で受光する。
各干渉測定信号及び干渉基準信号は僅かに異なる周波数のを持つ二つの光線の重ね合わせ干渉、即ちヘテロダイン干渉によるうなり(ビート信号)である。第1平面位置測定用照明光束及び第1法線方向測定用照明光束(両者を以下「第1測定光束」という)の周波数をf1、第2平面位置測定用照明光束及び第2法線方向測定用照明光束の周波数(両者を以下「第2測定光束」という)をf2とする。
【0041】
各光束の2次元回折パターンによる多数の回折光の内、ある回折光の複素振幅を、それぞれ、
a1=A1*exp[−i(2πf1t+φ1)]
a2=A2*exp[−i(2πf2t+φ2)]
で表すとする。ただしφ1は第1照明光束の初期位相、φ2は第2照明光束の初期位相、tは時間である。
これらの光線を重ね合わせた強度信号は、

Figure 0003713355
となる。ただしΔf=f1−f2である。
これは周波数がΔfのビート信号で、その位相成分は、
φ1−φ2 (3)
である。
【0042】
第1照明光束または第2照明光束の対象物上の2次元パターンによる多数の高次回折光の内、X方向に+1次、Y方向に+1次の回折光に注目する。2次元回折パターンを含む対象物がX方向にΔX、Y方向にΔY変位したときこの回折光の位相は、第1照明光束及び第2照明光束のいずれの場合においても、
2π(ΔX+ΔY)/d=φx+φy
だけ変化する。ここでdは2次元回折パターンのピッチである。また対象物のZ方向の移動に対しても位相は変化するので、その値をφzとする。
【0043】
したがって、対象物がX方向、Y方向、Z方向に変化したときの、この回折光の位相変化量は、
φx+φy+φz (4)
である。
X方向に−1次、Y方向に+1次の回折光の場合はφxの符号が変わり、対象物のX方向、Y方向、Z方向の変位に対する位相変化量は、
−φx+φy+φz (5)
となる。
0次光は対象物のX方向、Y方向の変位に対しては位相は変化せず、Z方向の変位に対してのみ位相変化する。ただし、第1照明光束及び第2照明光束のうち法線方向測定用照明光束は、入射角の違いから対象物のZ方向の変位ΔZ対しての位相変化量が異なる。
【0044】
対象物のZ方向の変位に対する第1照明光束の位相変化量φz及び対象物のZ方向の変位に対する第2照明光束の位相変化量φz’は、
φz =4πΔZ/λ*cosθ1 (6)
φz’=4πΔZ/λ*cosθ2 (7)
で与えられる。
X位置測定用干渉測定信号の位相成分は、(3)式のφ1に(4)式を代入し、φ2に(5)式を代入して、
(φx+φy+φz)−(−φx+φy+φz)=2φx (8)
となる。
X位置測定用干渉基準信号の位相成分は、(3)式のφ1、φ2に(6)式を代入して、
φz−φz=0 (9)
となる。
【0045】
したがって、X位置測定用干渉測定信号の(8)式とX位置測定用干渉基準信号の(9)式はY方向の位置情報を等しく含み(この場合0)、(8)式と(9)式の差をとれば2φxとして、対象物を含む平面内のX方向の位置情報が得られる。
Y位置測定用干渉測定信号の位相成分は、(4)式及び(6)式より、
(φx+φy+φz)−φz=φx+φy (10)
である。
Y位置測定用干渉基準信号の位相成分は、(5)式及び(6)式より、
φz−(−φx+φy+φz) =φx−φy (11)
である。
【0046】
したがって、Y位置測定用干渉測定信号の(9)式とY位置測定用干渉基準信号の(10)式は、X方向の位置情報を等しく含み、(9)式と(10)式の差をとれば2φyとして、対象物を含む平面内のY方向の位置情報が得られる。
また、第1Z位置測定用干渉測定信号の位相成分は、(6)式及び(7)式より、
φz’−φz=4π(cosθ2−cosθ1)/λ*ΔZ (12)
となり、また、第2Z位置測定用干渉測定信号の位相成分は、(6)式及び(7)式より、
φz’−φz=4π(cosθ3−cosθ1)/λ*ΔZ (13)
となり、これはΔZに比例した値である。
【0047】
Z位置測定用干渉基準信号(兼X位置測定用干渉基準信号)の位相成分は、式 (9)より0である。
したがって、 (12)式と (9)式の差をとれば、Z方向 (対象物を含む平面の法線方向)の位置情報がそのまま (12)式として得られる。
第1Z位置測定用干渉信号とZ位置測定用干渉基準信号との位相差Φz1(ΔZ)及び第2Z位置測定用干渉信号とZ位置測定用干渉基準信号との位相差Φz2(ΔZ)は、(12)式及び(13)式より、それぞれ、
Φz1(ΔZ)=4π(cosθ1−cosθ2)/λ*ΔZ
Φz2(ΔZ)=4π(cosθ1−cosθ3)/λ*ΔZ
で与えられる。ここでは、Z位置測定用干渉基準信号からZ位置測定用干渉信号を引くこととする(つまり括弧の中の符号が反転する)。
【0048】
いま、第1Z位置測定用干渉信号の検出ストロークをZ1、第2Z位置測定用干渉信号の検出ストロークをZ2とする(Z1>Z2)。
ΔZ=Z1で、Φz1(ΔZ)=2π、
ΔZ=Z2で、Φz2(ΔZ)=2π
となるから、
Φz1(ΔZ)=2π/Z1*ΔZ (a)
Φz2(ΔZ)=2π/Z2*ΔZ (b)
と表せられる。図13の左側の波形中、実線は(a)式の信号を示し、点線は(b)式の信号を示している。
Φz2(ΔZ)とΦz1(ΔZ)の差、つまり(b)式と(a)式の差をとると、
Figure 0003713355
となる。
【0049】
(a)式、(b)式と(c)式の形を見比べると、(c)式は検出ストロークがZ1*Z2/(Z1−Z2)のZ位置測定用干渉信号を表していると考えることができる。この(c)式の信号は、図13右側の波形として示してある。
式よりθ2=70.39°、θ3=70.48°とすれば、Z1= 50μm、Z2=40μmとなる。これらを(c)式に代入すると、
ΔΦ(ΔZ)=2π/200μm*ΔZ
となる。したがってストロークが200μmのZ位置測定用干渉信号が得られる。このときサンプル数は、ストロークが50μmで分解能が25nmのときの2000に等しい。つまり、分解能が25nm、サンプル数2000のまま検出ストローク、すなわち検出可能な範囲を200μmに拡大することができる。
【0050】
いま、各方向の位置測定用干渉基準信号を便宜上、X方向が式(9)式、Y方向が(11)式、Z方向が(9)式としたが、これをX方向が(8)式、Y方向が(10)式、Z方向が(12)式としても符号が反転するだけで、各方向の位置情報を得ることができる。
(13)式より、所望のZ検出ストロークを得るための第1法線方向測定照明光束の入射角θ2が求まる。
例えば、(12)式において50μmの検出ストロークが得たい場合、左辺に2π、右辺のΔZに50μmを代入する。
ただし、θ2の値はθ1よりも大きく、つまり、第1照明光束よりも対象物側にとりたいので、第2Z位置測定用干渉基準信号から第1Z位置測定用干渉基準信号を引くと、
2π=4π(cos70°−cosθ2)/633nm×50μm
これより、θ2=70.39°を得る。
【0051】
信号処理部600は、位置測定用干渉測定信号の位相に基づき対象物を含む平面内及び対象物を含む平面の法線方向の位置を求める。X方向の位置測定用干渉測定信号はフォトセンサ550で受光し、X位置測定用干渉基準信号はフォトセンサ554で受光する。フォトセンサ550とフォトセンサ554で受光した信号の位相差を位相計610で測定する。
Y位置測定用干渉測定信号はフォトセンサ551で受光し、Y位置測定用干渉基準信号はフォトセンサ555で受光する。フォトセンサ551とフォトセンサ555で受光した信号との位相差を位相計611で測定する。
第1Z方向位置測定用干渉測定信号は、フォトセンサ552で受光し、Z位置測定用基準信号はフォトセンサ554で受光する。
【0052】
フォトセンサ552で受光した信号とフォトセンサ554で受光した信号との位相差を位相計612で測定する。
第2Z方向位置測定用信号は、フォトセンサ553で受光し、Z方向位置測定用基準信号はフォトセンサ554で受光する。
フォトセンサ553で受光した信号とフォトセンサ554で受光した信号との位相差を位相計613で測定する。
演算処理部620は、位相計610の位相差に基づき対象物を含む平面内のX方向の位置を求め、位相計611の位相差に基づき対象物を含む平面内のY方向の位置を求め、そして、位相計612及び613の位相差に基づき対象物を含む平面内のZ方向の位置を求める。演算処理部620で、対象物のXYZ変位に対し、各方向の変位成分を独立に測定することが可能となり、これにより、対象物の位置合わせを初めとする種々の制御を行うことができる。
〔4〕 本発明の位置測定装置の適用
本発明の位置測定装置は、例えば、電子線描画装置のような荷電粒子線装置、及び、半導体露光装置などの対象物の位置合わせを正確に行うことを必要とする装置に適用することができる。
【0053】
ここで、電子線描画装置を一例にとって説明する。図15を参照すると、電子線描画装置は、電子線を発生する電子銃、電子ビームの向きを変更するX方向走査電極及びY方向走査電極などを内蔵した電子光学系730と、使用の際において真空状態とされるチャンバー内に配置される描画対象物732を載置可能とし、その水平面内のX、Y方向及び法線方向であるZ方向に移動可能とするステージ734とを備える。
そして、本発明の位置測定装置の照明光学系100、補正光学系200及び照射光学系300を含む照明側光学筐体740と、受光光学系400を含む受光側光学筐体742をステージ734の両側に配置する。照明側光学筐体740及び受光側光学筐体742は、電子光学系730等の電子線描画装置の各構成部品の取付け位置及びそれらの最大作動範囲をさけるように配置されている。そして、照明側光学筐体740から照射して受光側光学筐体742に入射される光束が、電子光学系730等の電子線描画装置の各構成部品の取付け位置及びそれらの最大作動範囲をさけて透過することができるように、照明側光学筐体740及び受光側光学筐体742は配置されている。
【0054】
電子線描画装置は、制御回路からの種々の信号に応じて、電子光学系及びステージが所定の動作を行い描画対象物となるマスクやウエハなどに所定のパターンを電子線によって形成するものである。
具体的には、本発明の位置測定装置を適用した電子線描画装置により、エンコーダのパターン、位相シフトマスク等の半導体製造用マスクを加工することができる。
また、本発明の位置測定装置を適用した半導体露光装置により、半導体ウェハ、半導体製造用マスクを加工することができる。
【0055】
【発明の効果】
(1)本発明により、少なくとも3本のレーザー光束を対象物面において異なる角度で照射して、それらの干渉光を用いてダイナミックレンジの広い法線方向の位置測定を行うために、ストロークの異なる2本のZ位置測定用干渉信号の位相差をとることができ、同じ分解能のままサンプル数を増やすことなく(電気処理系への負担、処理時間を増大させることなく)検出ストロークを拡大することが可能となる。
(2)本発明により、小型で高性能な位置測定装置を適用した半導体露光装置を実現することができる。
【図面の簡単な説明】
【図1】本発明の位置測定装置の実施の形態の光学系を示す概略図である。
【図2】本発明の位置測定装置の実施の形態の調整光学系及び照射光学系を示す斜視図である。
【図3】本発明の位置測定装置の実施の形態の調整光学系及び照射光学系を示す平面図である。
【図4】本発明の位置測定装置の実施の形態の調整光学系及び照射光学系を示す側面図である。
【図5】本発明の位置測定装置の実施の形態における対象物上の2次元回折パターンによる第1平面位置測定用照明光束の回折光マッピングである。
【図6】本発明の位置測定装置の実施の形態における対象物上の2次元回折パターンに測定用照明光束が入射した状態を示す斜視図である。
【図7】本発明の位置測定装置の実施の形態における対象物上の2次元回折パターンに測定用照明光束が入射した状態を示す平面図である。
【図8】本発明の位置測定装置の実施の形態における対象物上の2次元回折パターンに測定用照明光束が入射した状態を示す側面図である。
【図9】本発明の位置測定装置の実施の形態における対象物上の2次元回折パターンによる平面位置測定用照明光束と法線方向測定用照明光束の回折光マッピングである。
【図10】本発明の位置測定装置の実施の形態における平面位置測定用照明光束と法線方向測定用照明光束及びその回折光との装置部材との位置関係を示す側面図である。
【図11】本発明の位置測定装置の実施の形態における平面位置測定用照明光束と法線方向測定用照明光束及びその回折光との装置部材との位置関係を示す平面図である。
【図12】本発明の位置測定装置の実施の形態の受光光学系の構成を示す概略ブロック線図である。
【図13】本発明の位置測定装置の実施の形態の信号波形図である。
【図14】本発明の位置測定装置の実施の形態における位置合わせマークで回折された回折光のうち、X、Y、Z方向の測定に用いる回折光マッピングである。
【図15】本発明の位置測定装置を適用した電子線描画装置の実施の形態の概略部分断面図である。
【図16】本発明の位置測定装置の実施の形態の図1の照明光学系の部分の部分拡大図である。
【図17】本発明の位置測定装置の実施の形態の図1の対象物の部分の部分拡大図である。
【図18】本発明の位置測定装置の実施の形態の図1の受光光学系の部分の部分拡大図である。
【図19】本発明の位置測定装置の実施の形態の図11の対象物の部分の部分拡大図である。
【符号の説明】
1 光源
10 対象物
12 2次元回折パターン
100 照明光学系
102 リレーレンズ
103 ビームスプリッター
104 第1照明光束
105 第2照明光束
106、107 リレーレンズ
108 第1周波数シフター
109 第2周波数シフター
110 第1測定用照明光束
111 第2測定用照明光束
112、113 ビームスプリッター
114 第1平面位置測定用照明光束
115 第1法線方向測定用照明光束
116 第2平面位置測定用照明光束
117 第2法線方向測定用照明光束
200 補正光学系
201、202 平行平面板
203、204 ウエッジプリズム
205、206 フォーカスレンズ
300 照射光学系
301、302 折り返しミラー
303 照射レンズ
400 受光光学系
401 受光側対物レンズ
402〜405 折り返しミラー
500 受光部
512 第1平面位置測定用照明光束の(−1、+1)次回折光
514 第2平面位置測定用照明光束の(+1、+1)次回折光
515 第2平面位置測定用照明光束の(−1、+1)次回折光
511 第1平面位置測定用照明光束の(+1、+1)次回折光
510 第1平面位置測定用照明光束の0次光
513 第2平面位置測定用照明光束の0次光
517 第1法線方向測定用照明光束の0次光
516 第2法線方向測定用照明光束の0次光
550〜555 フォトセンサ
600 信号処理部
610 位相計(X)
611 位相計(Y)
612 位相計(Z1)
613 位相計(Z2)
620 演算処理部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a position measuring device used for the purpose of controlling the position of an object in a processing machine for processing the surface of the object to be processed and a measuring machine for measuring the surface state of the object to be measured.
The present invention also relates to an electron beam drawing apparatus to which a position measuring device is applied.
[0002]
[Prior art]
Conventionally, in a semiconductor exposure apparatus, a desired circuit pattern on an original pattern (reticle or mask) prepared in advance is aligned with an exposure area on a wafer and then transferred. This transfer apparatus is a high-precision reduction exposure projection apparatus, and the wafer side is fixed to a high-precision XY stage so that the entire surface of the transfer-side wafer can be exposed. A post transfer apparatus for stepping and repeating the wafer optical system is called a stepper.
With the recent high integration of LSIs, circuit line widths required for semiconductor devices are becoming increasingly narrow. Conventionally, the reduction ratio of the stepper has been 1/5, but it has been said that a pattern of 1 μm or less cannot be resolved from the wavelength limit so far. However, the improvement of optical systems and illumination systems and the appearance of phase shift masks for adjusting the phase of light on the reticle have led to the resolution of sub-μm order patterns. As the resolution is improved, the depth of focus of the reduction lens becomes shallower, and the accuracy of transferring a previously created original image pattern onto a wafer is required to be more severe. For this reason, it is required for the alignment optical system of the stepper to detect the position of the sample in the sample surface direction and the focal direction with high accuracy.
[0003]
The phase shift mask reduces the phase of light passing through the exposure light transmission part on the original pattern, that is, the optical path length of the transmission part by etching the thickness of the substrate, or adding a material having a different refractive index. It is something that is changed by the method of. Therefore, for the production of the phase shift mask, the substrate of a specific light transmission part is dug in the thickness direction, and the optical path length is selectively changed, or the resist is applied again to the substrate on which the pattern is drawn in advance. In addition, a method for etching unnecessary portions after adding a material for partially changing the phase of the light transmitting portion is employed. In either case, it is necessary to expose the resist at a predetermined position with high accuracy using the pattern drawing apparatus.
[0004]
[Problems to be solved by the invention]
Prior to detection of the alignment mark on the mask, the position of the exposure beam is measured and calibrated using a mark or the like provided on the stage. Since the position of the stage is monitored with high accuracy by the laser interferometer, the position and displacement of the beam can be measured with reference to the coordinate system of the laser interferometer.
However, in the electron beam exposure apparatus, if dirt adheres to the inside of the lens barrel, the electron beam drifts due to charge up, and the measured value fluctuates. Since the measurement of the mark position on the mask is an indirect measurement through the mark on the stage, if the measurement value fluctuates, the cause is a beam drift or the mark itself is displaced. For this reason, there was a problem that it was not possible to distinguish between the two.
[0005]
In an electron beam drawing apparatus or a stepper, as a means for accurately measuring the mark position without being affected by drift, a method using an apparatus provided with a measurement optical system using laser light can be considered.
Here, since the thickness of the substrate or resist of a normal mask drawn by an electron beam drawing apparatus or a stepper is on the order of several tens of nm to several hundreds of nm, this order is also required for the Z detection resolution.
In the phase shift mask, the steps of the second layer and the third layer are further performed on the first layer after the steps of exposure to etching, so that when moving from one layer to the next layer, the mask is once an exposure device. And is prepared for the next layer before being attached to the exposure apparatus again. At this time, since the position of the mask before being removed must be accurately reproduced, the required Z detection range (stroke) is several hundred μm.
[0006]
Therefore, Z detection requires a stroke of several hundred μm with a resolution of several tens of nm to several hundreds of nm.
The resolution is determined by a value obtained by dividing the detection stroke by the number of divisions (number of samples) in the electric processing system. For example, when the detection stroke is 50 μm and the number of samples is 2000, the resolution is
50 μm / 2000 = 25 nm
It becomes. As described above, Z detection requires a stroke of several hundred μm. For example, in order to obtain the same resolution of 25 nm with a stroke of 200 μm,
200 μm / 25 nm = 8000
4 times as many samples are required. When the number of samples increases, there is a problem that the electric processing system is burdened and the processing time increases.
[0007]
Therefore, there is a demand for a small and highly accurate position measuring device, and there is a need for an electron beam drawing apparatus to which a small and highly accurate position measuring device is applied.
[0008]
OBJECT OF THE INVENTION
Therefore, the object of the present invention is to
(1) Provided is a position measurement device that irradiates at least three laser light beams at different angles on a target surface and performs position measurement in a normal direction with a wide measurement range (dynamic range) using the interference light. There is.
(2) In addition to position measurement in the normal direction in which the measurement range is expanded, a first plane direction position measurement illumination beam and a second plane direction position measurement illumination beam for measuring the plane direction position are further formed. An object of the present invention is to provide a measuring apparatus that performs irradiation and measures in a plane direction.
(3) To provide a position measuring device having a configuration capable of changing the measurement range by changing the incident angle of the third illumination light beam.
(4) To provide a position measuring device provided with a light beam shift unit for adjusting an irradiation position of a light beam applied to an object in an irradiation optical system.
(5) To provide a position measuring device provided with a condensing position changing unit for adjusting a condensing position of a light beam irradiated to an object in an irradiation optical system.
(6) To provide a small and highly accurate electron beam drawing apparatus including a position measuring device capable of accurately measuring the position of an object.
[0009]
[Means for Solving the Problems]
The position measuring device of the present invention includes a light source unit that emits coherent light, and a light beam from the light source unit as a normal direction reference illumination light beam at a first incident angle and a second incident light as a first normal direction measurement illumination light beam. To the two-dimensional pattern provided on the object whose position is to be measured, depending on the angle and at the third incident angle different from the first incident angle and the second incident angle as the illumination beam for measuring the second normal direction. The normal direction reference illumination light beam and the first normal direction measurement illumination light beam among the irradiation optical system for irradiation, the light receiving optical system for receiving the reflected light from the two-dimensional pattern, and the reflected light received by the light receiving optical system To generate a first normal direction measurement interference signal, and cause the normal direction reference illumination beam or the first normal direction measurement illumination beam to interfere with the second normal direction measurement illumination beam. A light receiving portion for forming an interference signal for measuring two normal directions, and a first method; A configuration and a signal processing unit which performs position measurement in the normal direction of the object based on the phase of the interference signal direction measurement and the second normal direction measuring interference signal.
[0010]
With such a configuration, it is possible to realize a small and highly accurate position measuring apparatus that can perform position measurement in the normal direction with a wide measurement range.
The signal processing unit of the position measurement apparatus of the present invention measures the position of the object in the normal direction based on the phase difference between the first normal direction measurement interference signal and the second normal direction measurement interference signal. It is preferable to have a signal processing unit.
With such a configuration, efficient signal processing can be performed, and a small and highly accurate position measuring device can be realized.
The light source unit of the position measuring apparatus of the present invention further includes a frequency shifter unit that emits a light beam from the light source unit as a light beam having a different frequency, and the light source unit has a first frequency coherent light generated from the light source unit. Is a normal direction reference illumination light beam, and a second frequency light beam having a frequency different from that of the normal direction reference illumination light beam emitted from the frequency shifter is used as a first normal direction measurement illumination light beam. It is preferable to further include a light beam separation unit that forms a second normal direction measurement illumination light beam by separating it from either the light beam or the first normal direction measurement illumination light beam.
[0011]
With such a configuration, a light source of a small and highly accurate position measuring device can be realized.
Further, the light source unit of the position measuring apparatus of the present invention includes a light source that emits coherent light having a first frequency serving as a first planar direction measurement illumination beam, and a second frequency that is different in frequency from the first planar direction measurement illumination beam. A frequency shifter for forming the second plane direction measurement illumination beam, and the irradiation optical system causes the first plane direction measurement illumination beam and the second plane direction measurement illumination beam to enter at a first incident angle, The light receiving unit includes a combination of high-order diffracted light and zero-order diffracted light in a two-dimensional pattern among the diffracted lights of the first planar direction measuring illumination light beam and the second planar direction measuring illumination light beam received by the light receiving optical system, and the next time An interference signal for plane position measurement in a plane provided with a two-dimensional pattern of an object is formed from a combination of diffracted lights having different frequencies in any one of the combinations of the folded light, and the signal processing unit performs interference for plane position measurement. signal Preferably, a signal processing unit for determining the position in a plane in which a two-dimensional pattern of the object based on the phase.
[0012]
With such a configuration, a small and highly accurate position measuring device can be realized.
In addition, the light receiving unit of the position measuring device of the present invention can detect the X position from the combination of the diffracted lights having different frequencies of the 0th order diffracted lights by the two-dimensional pattern of the first planar position measuring illumination light beam and the second planar position measuring illumination light beam. A measurement interference reference signal is formed, and a combination of the 0th-order diffracted light of the first plane position measurement illumination beam and the higher-order diffracted light of the second plane position measurement illumination beam, or the higher-order diffracted light of the first plane position measurement illumination beam And an interference reference signal for Y position measurement from the combination of the zeroth order diffracted light of the illumination light beam for second plane position measurement, and the signal processing unit calculates the position of the interference measurement signal for X position measurement and the interference reference signal for X position measurement. It is preferable that the position in the X direction of the object is obtained based on the phase difference, and the position in the Y direction of the object is obtained based on the phase difference between the interference measurement signal for Y position measurement and the interference reference signal for Y position measurement. .
[0013]
With such a configuration, it is possible to reliably receive diffracted light and perform efficient signal processing, and to realize a small and highly accurate position measuring device.
Moreover, it is preferable that the light source unit of the position measuring apparatus of the present invention is configured so that the first planar direction measurement illumination light beam and the normal direction reference illumination light beam are a common light beam.
With such a configuration, a small and highly accurate position measuring device can be realized.
Further, the illumination light beam irradiates the two-dimensional pattern in the optical path of the first normal direction position measurement illumination light beam or the second normal direction position measurement illumination light beam in the irradiation optical system of the position measuring apparatus of the present invention. It is preferable that an incident angle changing member for changing the incident angle is arranged.
[0014]
With such a configuration, a small and highly accurate position measuring device capable of changing the measurement range can be realized.
Further, the incident angle changing member of the position measuring apparatus of the present invention is configured so that the incident angle of the first normal direction position measuring illumination light beam or the second normal direction position measuring illumination light beam is changed in the optical path thereof. It is preferably configured as a plane parallel plate having a rotation axis in a direction orthogonal to the axis.
With such a configuration, a small and highly accurate position measuring device capable of changing the measurement range can be realized.
Furthermore, the present invention is an electron beam drawing apparatus comprising the above-described position measuring device of the present invention arranged so as to avoid the mounting positions of the components of the electron beam drawing apparatus and their maximum operating range. Includes an illumination-side optical member for irradiating a position-measuring light beam for measuring the position of the object, a light-receiving-side optical member for receiving the reflected diffracted light from the object and measuring the position of the object So that the light beam irradiated from the illumination side optical member and incident on the light reception side optical member can pass through the mounting positions of the component parts of the electron beam drawing apparatus and their maximum operating range. It was set as the structure by which the illumination side optical member and the light reception side optical member are arrange | positioned at the electron beam drawing apparatus.
[0015]
With this configuration, the position of the object to be processed can be accurately measured, and the object to be processed can be processed with extremely high accuracy by the electron beam drawing apparatus.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the position measuring apparatus of the present invention includes an illumination optical system 100, a correction optical system 200, an irradiation optical system 300, and a light receiving optical system 400.
[1] Illumination optical system 100
Referring to FIGS. 16 to 18 which are partially enlarged views of FIGS. 1 and 1, the light source 1 is a light source that emits coherent light as an illumination light beam, and is a He—Ne laser light source having a wavelength λ = 633 nm. The coherent laser beam emitted from the light source 1 is branched into the first illumination light beam 104 and the second illumination light beam 105 by the beam splitter 103 via the relay lens 102.
[0017]
The first illumination light beam 104 is guided to the first frequency shifter 108 via the relay lens 106, and the first frequency shifter 108 modulates the first illumination light beam 104 to form a first measurement illumination light beam 110. The second illumination light beam 105 is guided to the second frequency shifter 109 via the relay lens 107, and the second frequency shifter 109 modulates the second illumination light beam 105 to form a second measurement illumination light beam 111.
An acousto-optic element (AOM) is preferably used as a frequency shifter. The modulation frequency by the frequency shifter of the first measurement illumination light beam 110 is 80.05 MHz, and the modulation frequency by the frequency shifter of the second measurement illumination light beam 111 is 80.0625 MHz. The frequency shifters 108 and 109 form a first measurement illumination light beam 110 and a second measurement illumination light beam 111 having slightly different frequencies. In this case, the frequency difference Δf between the first measurement illumination light beam 110 and the second measurement illumination light beam 111 is 12.5 KHz. When the first measurement illumination light beam 110 and the second measurement illumination light beam 111 are overlapped with each other and caused to interfere with each other, the intensity of the interference result becomes a beat (beat signal) of the frequency Δf.
[0018]
The beam splitter 112 splits the first measurement illumination light beam 110 into a first plane position measurement illumination light beam 114 and a first normal direction measurement illumination light beam 115.
The beam splitter 113 splits the second measurement illumination light beam 111 into a second plane position measurement illumination light beam 116 and a second normal direction measurement illumination light beam 117.
The first plane position measurement illumination beam 114, the first normal direction measurement illumination beam 115, the second plane position measurement illumination beam 116, and the second normal direction measurement illumination beam 117 are relay lenses 118, 119, respectively. The light beams are guided to the adjusting optical system 200 through 120 and 121 as light beams parallel to the optical axis.
However, the first normal direction measurement illumination beam 115 and the second normal direction measurement illumination beam 117 are measured separately from the first plane position measurement illumination beam 114 and the second plane position measurement illumination beam 116, respectively. It is also possible to diverge from the illumination light beam.
[0019]
Here, in the illumination optical system 100, the light source 1, the first frequency shifter 108, and the second frequency shifter 109 are in a conjugate relationship by the relay lenses 102, 106, and 107.
[2] Adjustment optical system 200
As shown in FIGS. 2 to 4, the adjustment optical system 200 includes a first plane position measurement illumination beam 114, a first normal direction measurement illumination beam 115, a second plane position measurement illumination beam 116, and a second method. This is an optical system that corrects the illumination light beam 117 for measuring the linear direction so as to meet a predetermined irradiation condition. For the correction, the irradiation angles of the first normal direction measurement illumination beam 115 and the second normal direction measurement illumination beam 117 are changed to the first plane position measurement illumination beam 114 and the second plane position measurement illumination beam 116, respectively. Irradiation angle adjustment for adjustment, planar position adjustment for adjusting the plane position on the object irradiated by these four illumination light beams 114 to 117, and beam waist positions of these four illumination light beams 114 to 117 There are three types of beam waist position adjustments that are adjusted to be on the object 10.
[0020]
The irradiation angle adjustment of the first normal direction measurement illumination beam 115 and the second normal direction measurement illumination beam 117 is performed by rotating the parallel plane plates 201 and 202 inserted in the respective optical paths with a rotation axis orthogonal to the optical axis. This is done by rotating to the center. The first normal direction measurement illumination light beam 115 and the second normal direction measurement illumination light beam 117 are translated in the vertical direction by the rotation of the plane parallel plates 201 and 202. As a result, the irradiation angle by the projection lens described later is increased. Change. Here, the “vertical direction” refers to a direction perpendicular to a plane including the four illumination light beams 114 to 117.
The four measurement illumination light beams 114 to 117 are narrowed by two mirrors (not shown) in the respective optical paths, and enter the pair of wedge prisms 203 and 204 having the same apex angle.
[0021]
The adjustment of the planar positions of the four measurement illumination light beams 114 to 117 is performed by adjusting the crossing angle and adjusting the crossing center direction of the wedge prisms 203 and 204 with the horizontal direction as the central axis for adjustment.
The distance from the position before adjustment is determined by adjusting the intersection angle of the wedge prisms 203 and 204. Further, the direction of change from before the adjustment is determined by adjusting the central direction where the wedge prisms 203 and 204 intersect. By performing the adjustment in this way, it is possible to adjust the plane positions of the four measurement illumination light beams 114 to 117 in any direction, up, down, left, and right.
The four measurement illumination light beams 114 to 117 are incident on the focus lenses 205 and 206 after the plane position is adjusted by the wedge prisms 203 and 204.
[0022]
The focus lenses 205 and 206 are configured to change the distance between each light beam and the optical axis while maintaining the condition that each light beam is parallel to the optical axis by changing the distance between the focus lenses 205 and 206. The position of the beam waist can be adjusted in the optical axis direction so that the beam waists of the measurement illumination light beams 114 to 117 are on the object 10.
In the embodiment of the present invention, the adjustment lens 205 on the light source side is formed by a plano-convex lens, and the adjustment lens 206 on the object side is formed by a plano-concave lens 206.
Accordingly, when the interval between the focus lenses 205 and 206 is increased, the position of the beam waist changes so as to approach the light source side.
However, it is also possible to form the focus lens 205 on the side with the light source 1 with a plano-concave lens 206 and form the focus lens 206 on the side with the object 10 with a plano-convex lens.
[0023]
In this way, the first plane position measurement illumination beam 114 and the second plane position measurement illumination beam 116 are arranged in the vicinity of the optical axis, and the illumination angle is adjusted with reference to these, the first normal direction measurement illumination beam. 115 and the second normal direction measuring illumination light beam 117 are arranged in the vicinity (on both sides), so that parallel plane plates 201 and 202 which are optical elements for adjusting the irradiation angle are arranged in their optical paths and light. A mechanism that can rotate around a rotation axis orthogonal to the axis can be easily incorporated.
[0024]
[2-1] Manual adjustment
A beam adjustment method of the adjustment optical system 200 described above will be described. Hereinafter, an adjustment method giving priority to the position will be described.
In the initial state, the wedge prisms 203 and 204 are arranged to face in opposite directions as if rotated 180 degrees, and apparently have no prism power. The adjustment lenses 205 and 206 are arranged so that the distance between them is substantially zero, and there is no power.
In the adjustment method giving priority to this position, the irradiation position of the beam in the initial state is moved onto the mark 12 to be originally irradiated using the wedge prisms 203 and 204, and then the four lenses are adjusted using the adjustment lenses 205 and 206. The beam waist position is adjusted so that the beam waists of the measurement illumination light beams 114 to 117 are on the object 10.
More specifically, the moving direction of the beam coincides with the bisector direction of the crossing angle of the wedge prisms 203 and 204, and therefore, the direction of the mark 12 to be irradiated with the beam with reference to the beam irradiation position in the initial state. Both prisms are rotated so that the bisector directions of the intersecting angles of the wedge prisms 203 and 204 coincide.
Next, the moving distance of the beam becomes larger as the crossing angle of the wedge prisms 203 and 204 approaches 180 degrees from 0 degrees, so that the bisecting direction of the crossing angle of the wedge prisms 203 and 204 is changed. The two-dimensional pattern 12 on the object 10 can be adjusted to be irradiated by adjusting the crossing angle of the wedge prisms 203 and 204 while maintaining the same.
In this way, after adjusting the beam positions of the four measurement illumination light beams 114 to 117 so as to be on the two-dimensional pattern 12 on the object 10, based on the influence factors such as the maximum intensity of the interference signal. The interval between the adjustment lenses 205 and 206 is adjusted so that the beam waist position is on the two-dimensional pattern 12 on the object 10.
In the embodiment of the present invention, the adjustment lens 205 on the side of the light source 1 is formed of a plano-convex lens, and the adjustment lens 206 on the side of the object 10 is formed of a plano-concave lens 206. As the distance between the two is increased, the beam waist position approaches the light source side.
[0025]
[3] Irradiation optical system 300
As shown in FIGS. 2 to 4, the irradiation optical system 300 includes folding mirrors 301 and 302 and an irradiation lens 303, and includes a first planar position measurement illumination beam 114, a second planar position measurement illumination beam 116, and a first projection beam. Four beams of the normal direction measuring illumination beam 115 and the second normal direction measuring illumination beam 117 are irradiated onto the two-dimensional pattern 12 on the object 10 at one point.
[0026]
At this time, the irradiation optical system 300 includes the object 10 together with the first plane position measurement illumination beam 114 and the second plane position measurement illumination beam 116 as a result of the predetermined correction performed by the correction optical system 200. Irradiation is performed at an incident angle θ1 with respect to the plane normal line, the first normal direction measurement illumination beam 115 is irradiated at an incident angle θ2 different from the incident angle θ1, and the second normal direction measurement illumination beam 117 is θ1. And an incident angle θ3 different from θ2.
The irradiation optical system 300 including the irradiation lens 303 has a beam waist position in a state where the adjustment lens 205 and the adjustment lens 206 for adjusting the beam waist position do not act, that is, in a state where the adjustment lens 205 and the adjustment lens 206 are in contact with each other. Is set to be the farthest point in the beam waist position adjustment range.
[0027]
By appropriately determining the interval between the adjustment lens 205 for adjusting the beam waist position and the adjustment lens 206, the beam waist of the measurement illumination light beam can be adjusted on the object 10. When various adjustments are completed, the light source 1, the frequency shifters 108 and 109, and the object 10 all form a conjugate relationship.
The two-dimensional diffraction pattern 12 on the object 10 is formed from a checkered lattice. This checkered lattice has equal pitches d in the X and Y directions.
The four illumination beams for measurement incident on the checkered lattice on the object 10 are reflected and diffracted by the checkered lattice.
If attention is paid only to the illumination light beam 114 for measuring the first plane position, the relationship between the incident angle θ and the diffraction angle θx in the X direction and the diffraction angle θy in the Y direction of the primary light diffraction light is given by the following equation.
[0028]
sin θx = ± λ / d (1)
sin θy = sin θ ± λ / d (2)
The mapping of the regular reflection light (diffracted zero order light) and the diffracted primary light of the first planar position measurement illumination light beam that satisfies the expressions (1) and (2) is shown in FIGS. (The second and higher orders are omitted.)
FIG. 5 shows a state in which the first planar position measurement illumination light beam 114 is incident on the two-dimensional pattern 12 on the object 10 with respect to the normal 12T of the two-dimensional pattern 12 at an angle θ. FIG. 6 shows a state where four measurement illumination light beams 114 to 117 are incident on the two-dimensional pattern 12 on the object 10.
As shown in FIGS. 7 and 8, the first plane position measurement illumination beam 114, the second plane position measurement illumination beam 116, the first normal direction measurement illumination beam 115, and the second normal direction measurement illumination beam. 117 are incident from directions rotated by a slight angle + α with respect to the object surface normal, and the zero-order light and the diffracted primary light are the zero-order light of other measurement illumination beams, It can be separated and extracted independently without overlapping with the diffracted primary light.
[0029]
As for the incident angle, as shown in FIG. 8, the first plane position measurement illumination beam 114 and the second plane position measurement illumination beam 116 are at the incident angle θ1, and the first normal direction measurement illumination beam 115 is incident. The illumination beam 117 for second normal direction measurement is incident on the two-dimensional diffraction pattern 12 on the object 10 at an angle θ2 and at an incident angle θ3.
FIG. 9 shows the 0th-order light and the diffracted primary light and the first normal direction measurement illumination light beam 115 and the second normal direction measurement of the first plane position measurement illumination beam 114 and the second plane position measurement illumination beam 116. This is a mapping of the 0th-order light of the illumination light beam 117 for use.
In the embodiment of the present invention, as shown in FIGS. 5, 6, and 9, since the diffracted light mapping is reflection diffraction, the positive direction of the X axis is the left direction in the figure, and the Y axis The positive direction of is a downward direction in the figure and is different from a general coordinate system.
[0030]
As shown in FIGS. 10, 11, and 19, the light receiving optical system 400 is arranged so as to receive diffracted light spreading from the reflection point on the two-dimensional pattern. However, in an electron beam drawing apparatus or a stepper, a member 710 of an apparatus such as a drawing optical system or a projection optical system occupies most of the space, and the space for the light receiving optical system is often limited.
Therefore, an arrangement is required in which the diffraction angle that determines the overall size of the light receiving optical system can be reduced, and that the diffracted light at the light receiving portion can be easily branched and superposed at an appropriate interval. Further, the space on the irradiation optical system side is limited by the members of the apparatus, similarly to the light receiving optical system side.
On the light receiving optical system side, the Y-direction diffraction angle of the 0th order light is θ as is the incident angle. Referring to equation (2) for the Y-direction diffraction angle θy of the first-order diffracted light, θy that satisfies the composite negative equation is a value smaller than θ. That is, since the −1st order diffracted light appears on the member side of the apparatus such as the drawing optical system and the projection optical system with respect to the 0th order light, it tends to be blocked by these members.
[0031]
In this case, the light beam passage positions on the light receiving optical system side and the irradiation optical system side are asymmetric, and if the −1st order light is set not to be blocked by the original member of the apparatus, the incident angle θ is increased by the incident side. A dead zone will be provided.
In addition, when the incident angle θ is increased, the difference in diffraction efficiency of each polarization component (S-polarized light, P-polarized light) of the reflected diffracted light also increases, which affects the overlay interference at the light receiving unit. However, θy that satisfies the compound plus expression (2) is larger than θ, and the + 1st order diffracted light appears on the object side with respect to the 0th order light.
Therefore, if the 0th order light is not blocked by the member, the + 1st order light is not blocked by the member 710 of the apparatus. Therefore, if + 1st order light is used, the incident angle θ can be minimized within a range not blocked by the member, and the difference in diffraction efficiency due to the polarization component can be reduced.
[0032]
The first order diffracted light satisfying both the compound plus expression (2) and the expression (1) is + 1st order in the X direction, + 1st order diffracted light in the Y direction, −1st order in the X direction, and + 1st order in the Y direction. Diffracted light. These are included in quadrants adjacent to each other ((X, Y) quadrant and (−X, Y) quadrant), and by using these light beams, it is possible to contribute to space saving of the light receiving side optical system.
FIG. 14 shows diffracted light mapping used for measurement in the X, Y, and Z directions among the diffracted light diffracted by the alignment mark.
Here, f1 (0) is the 0th-order diffracted light after the first plane position measurement illumination beam 114 is diffracted by the alignment mark, and f2 (0) is the second plane position measurement illumination beam 116. This is 0th-order diffracted light after being diffracted by the alignment mark.
[0033]
f1 (X, Y) is the + 1st order diffracted light in the X direction and the + 1st order in the Y direction after the first planar position measurement illumination beam 114 is diffracted by the alignment mark.
f1 (−X, Y) is diffracted light in which the X direction is −1st order and the Y direction is + 1st order after the first planar position measuring illumination beam 114 is diffracted by the alignment mark.
f2 (X, Y) is the + 1st order diffracted light in the X direction and the + 1st order in the Y direction after the second planar position measuring illumination beam 116 is diffracted by the alignment mark.
f2 (−X, Y) is the -1st order diffracted light in the X direction and the + 1st order in the Y direction after the second planar position measuring illumination beam 116 is diffracted by the alignment mark.
f1 ′ (0) is the 0th-order diffracted light after the first normal direction measuring illumination light beam 115 is diffracted by the alignment mark.
[0034]
f2 ′ (0) is the 0th-order diffracted light after the second normal direction measuring illumination beam 117 is diffracted by the alignment mark.
Another method for reducing the light receiving optical system is to reduce the diameter of the objective lens 410. In order to reduce the lens diameter, the difference in diffraction angle between the 0th order light and the 1st order light may be reduced. As a method for reducing the difference in diffraction angle, there are methods of increasing the pitch of the two-dimensional diffraction pattern or reducing the light source wavelength λ from the equations (1) and (2).
Usually, the pitch of the diffraction pattern is about several μm to several tens of μm. At this time, if a He—Ne laser light source of λ = 633 nm is used, the diffraction angle can be made sufficiently small. Also, a resist is often applied on the surface of the object, but this wavelength is long enough to not expose the resist.
[0035]
Furthermore, the angle β formed between the optical axis of the objective lens 401 and the normal line of the object is set to θ, the angle formed between the 0th order light of the first illumination light beam and the normal line of the object is θ, and the + 1st order diffracted light of the first illumination light beam The diffraction angle in the Y direction is given by θy as θy.
β = (θ + θy) / 2
This is an intermediate angle between 0th-order light and diffracted 1st-order light. By taking this optical axis, the lens diameter can be reduced even if it is arranged at a position far from the object. In addition, the longer the distance from the reflection point on the object to the objective lens, the wider the interval between the diffracted lights, and there is an advantage that the diffracted lights at the light receiving unit can be easily branched and overlapped.
FIG. 10 shows an example of a light projecting optical system and a light receiving optical system. The wavelength λ = 633 nm, the incident angle θ of the first plane position measuring illumination beam 114 and the second plane position measuring illumination beam 116 = 70 °, and the diffraction grating. The pitch d = 20 μm, the focal length of the irradiation lens 303 is 133 mm, and the focal length of the light-receiving side objective lens is 220 mm.
[0036]
Since the four illumination light beams incident on the irradiation lens 303 are parallel to each other and have a distance of 3 mm, the distance is about 5 mm after passing through the light-receiving side objective lens 401.
Further, regarding the diffraction angle of the primary light, θx = 1.8 ° and θy = 76.25 ° using the equations (1) and (2). The angle β of the optical axis of the light-receiving-side objective lens 401 is 73 °. At this time, the lens diameter is φ40 mm, and four illumination light beams can be transmitted without colliding with the member 710.
The light-receiving-side objective lens 401 is disposed at a position corresponding to one focal length from the reflection point on the object 10 and plays a role of making a large number of reflected diffracted lights spreading from the reflection point on the object 10 parallel to each other. Respective diffracted lights made parallel to each other by the light receiving side objective lens 401 are guided to the light receiving section by the folding mirrors 402 and 403, and the 0th order light and the first order light are stored in the same plane by the folding mirrors 404 and 405. .
[0037]
Next, details of the configuration of the light receiving unit 500 are shown in FIG. The light receiving unit includes the first planar position measurement illumination light beam 114 included in the adjacent quadrants, here (+ X, + Y) quadrant and (−X, + Y) quadrant, of the diffracted light received by the light receiving optical system 400. A plane including an object from a combination of high-order diffracted light and zero-order light and a combination of high-order diffracted lights of any one of the two-dimensional patterns of the second planar position measurement illumination beam 116. An interferometric signal for position measurement is formed.
The X-direction position measurement interference measurement signal in the plane including the object is −1st order in the X direction and +1 in the Y direction in the diffracted light of the first planar position measurement illumination beam 114 by the two-dimensional pattern. Of the diffracted light of the next diffracted light 512 and the two-dimensional pattern of the illumination light beam 116 for measuring the second plane position, the + 1st order diffracted light 514 in the X direction and the + 1st order diffracted light 514 in the Y direction are superimposed by the beam splitter 530. Form. The photo sensor 550 receives the X position measurement interference signal.
[0038]
The Y-direction position measurement interference measurement signal in the plane including the object is + 1st order in the X direction and + 1st order in the Y direction in the diffracted light by the two-dimensional pattern of the illumination light beam 114 for first plane position measurement. The beam splitter 532 superimposes the diffracted beam 511 and the beam split from the 0th-order beam 513 of the second planar position measurement illumination beam 116 by the beam splitter 531. The Y position measurement interference measurement signal is received by the photosensor 551.
The first Z direction position measurement interference measurement signal obtained when the normal direction of the plane including the object, that is, the Z direction is irradiated at the irradiation angle θ2, is obtained from the 0th-order light 513 of the second plane position measurement illumination beam 116. The beam branched by the beam splitter 533 and the 0th-order light 517 of the illumination beam 115 for first normal direction measurement are superimposed by the beam splitter 534. The Z position measurement interference signal is received by the photosensor 552.
[0039]
The second Z-direction position measurement interference measurement signal obtained when the normal direction of the plane including the object, that is, the Z direction is irradiated at the irradiation angle θ3, is obtained from the 0th-order light 510 of the first plane position measurement illumination beam 116. The light beam branched by the beam splitter 535 and the 0th-order light 516 of the illumination beam 115 for second normal direction measurement are overlapped and formed by the beam splitter 536. The Z position measurement interference signal is received by the photosensor 553.
The light receiving unit further superimposes the zero-order light 510 of the first planar position measurement illumination beam 114 and the zero-order light 513 of the second plane position measurement illumination beam on the beam splitter 538 via the mirror 537 to measure the X position. Interference reference signal and Z position measurement reference signal are formed. The X position measuring interference reference signal and the Z position measuring interference reference signal are received by the photosensor 554.
[0040]
Also, in the X direction, the light beam branched from the 0th-order light 510 of the first planar position measurement illumination beam 114 by the beam splitter 539 and the diffracted light by the two-dimensional pattern of the second planar position measurement illumination beam 116 The + 1st order diffracted light 515 is overlapped by the beam splitter 540 in the −1st order and Y direction to form an interference reference signal for Y position measurement. The Y position measurement interference reference signal is received by the photosensor 555.
Each interference measurement signal and interference reference signal is a superposition interference of two rays having slightly different frequencies, that is, a beat (beat signal) due to heterodyne interference. The frequency of the first plane position measurement illumination beam and the first normal direction measurement illumination beam (both are hereinafter referred to as “first measurement beam”) is f1, the second plane position measurement illumination beam and the second normal direction measurement. The frequency of the illumination light beam for use (both are hereinafter referred to as “second measurement light beam”) is defined as f2.
[0041]
The complex amplitude of a diffracted light among a number of diffracted lights according to the two-dimensional diffraction pattern of each light beam,
a1 = A1 * exp [−i (2πf1t + φ1)]
a2 = A2 * exp [−i (2πf2t + φ2)]
Suppose that Where φ1 is the initial phase of the first illumination light beam, φ2 is the initial phase of the second illumination light beam, and t is the time.
The intensity signal obtained by superimposing these rays is
Figure 0003713355
It becomes. However, it is (DELTA) f = f1-f2.
This is a beat signal with a frequency of Δf, and its phase component is
φ1-φ2 (3)
It is.
[0042]
Of the many high-order diffracted lights having a two-dimensional pattern on the object of the first illumination light flux or the second illumination light flux, attention is paid to the + 1st order diffracted light in the X direction and the + 1st order in the Y direction. When an object including a two-dimensional diffraction pattern is displaced by ΔX in the X direction and ΔY in the Y direction, the phase of the diffracted light is the same in both cases of the first illumination light beam and the second illumination light beam.
2π (ΔX + ΔY) / d = φx + φy
Only changes. Here, d is the pitch of the two-dimensional diffraction pattern. Further, since the phase also changes with respect to the movement of the object in the Z direction, the value is φz.
[0043]
Therefore, the amount of phase change of the diffracted light when the object changes in the X direction, Y direction, and Z direction is
φx + φy + φz (4)
It is.
In the case of -1st order diffracted light in the X direction and + 1st order diffracted light in the Y direction, the sign of φx changes, and the amount of phase change with respect to displacement of the object in the X direction, Y direction, and Z direction is
-Φx + φy + φz (5)
It becomes.
The zero-order light does not change in phase with respect to the displacement of the object in the X and Y directions, but changes in phase only with respect to the displacement in the Z direction. However, the normal direction measuring illumination light beam among the first illumination light beam and the second illumination light beam has a different amount of phase change with respect to the displacement ΔZ in the Z direction of the object due to a difference in incident angle.
[0044]
The phase change amount φz of the first illumination light beam with respect to the displacement of the object in the Z direction and the phase change amount φz ′ of the second illumination light beam with respect to the displacement of the object in the Z direction are:
φz = 4πΔZ / λ * cos θ1 (6)
φz ′ = 4πΔZ / λ * cos θ2 (7)
Given in.
The phase component of the X position measurement interference measurement signal is obtained by substituting the equation (4) into φ1 in the equation (3) and substituting the equation (5) into φ2.
(Φx + φy + φz) − (− φx + φy + φz) = 2φx (8)
It becomes.
The phase component of the interference reference signal for X position measurement is obtained by substituting Eq. (6) into φ1 and φ2 in Eq. (3),
φz−φz = 0 (9)
It becomes.
[0045]
Therefore, the equation (8) for the X position measurement interference measurement signal and the equation (9) for the X position measurement interference reference signal equally include position information in the Y direction (in this case, 0), and the equations (8) and (9) If the difference between the equations is taken, the position information in the X direction in the plane including the object is obtained as 2φx.
From the equations (4) and (6), the phase component of the Y position measurement interference measurement signal is
(Φx + φy + φz) −φz = φx + φy (10)
It is.
The phase component of the Y position measurement interference reference signal is obtained from the equations (5) and (6):
φz − (− φx + φy + φz) = φx−φy (11)
It is.
[0046]
Therefore, the equation (9) for the Y position measurement interference measurement signal and the equation (10) for the Y position measurement interference reference signal include position information in the X direction equally, and the difference between the equations (9) and (10) is obtained. For example, position information in the Y direction within a plane including the object is obtained as 2φy.
Further, the phase component of the first Z position measurement interference measurement signal is expressed by the following equations (6) and (7):
φz′−φz = 4π (cos θ2−cos θ1) / λ * ΔZ (12)
Further, the phase component of the second Z position measurement interference measurement signal is expressed by the following equations (6) and (7):
φz′−φz = 4π (cos θ3−cos θ1) / λ * ΔZ (13)
This is a value proportional to ΔZ.
[0047]
The phase component of the Z-position measuring interference reference signal (also serving as the X-position measuring interference reference signal) is 0 from Equation (9).
Therefore, if the difference between the equations (12) and (9) is taken, the position information in the Z direction (the normal direction of the plane including the object) can be directly obtained as the equation (12).
The phase difference Φz1 (ΔZ) between the first Z position measurement interference signal and the Z position measurement interference reference signal and the phase difference Φz2 (ΔZ) between the second Z position measurement interference signal and the Z position measurement interference reference signal are: From the equations (12) and (13),
Φz1 (ΔZ) = 4π (cos θ1−cos θ2) / λ * ΔZ
Φz2 (ΔZ) = 4π (cos θ1−cos θ3) / λ * ΔZ
Given in. Here, the Z position measurement interference signal is subtracted from the Z position measurement interference reference signal (that is, the sign in parentheses is inverted).
[0048]
Now, the detection stroke of the first Z position measurement interference signal is Z1, and the detection stroke of the second Z position measurement interference signal is Z2 (Z1> Z2).
ΔZ = Z1, Φz1 (ΔZ) = 2π,
ΔZ = Z2 and Φz2 (ΔZ) = 2π
So,
Φz1 (ΔZ) = 2π / Z1 * ΔZ (a)
Φz2 (ΔZ) = 2π / Z2 * ΔZ (b)
It can be expressed. In the waveform on the left side of FIG. 13, the solid line indicates the signal of equation (a), and the dotted line indicates the signal of equation (b).
Taking the difference between Φz2 (ΔZ) and Φz1 (ΔZ), that is, the difference between equation (b) and equation (a),
Figure 0003713355
It becomes.
[0049]
Comparing the forms of the expressions (a), (b), and (c), the expression (c) is considered to represent a Z position measurement interference signal having a detection stroke of Z1 * Z2 / (Z1-Z2). be able to. The signal of equation (c) is shown as the waveform on the right side of FIG.
If θ2 = 70.39 ° and θ3 = 70.48 ° from the equation, then Z1 = 50 μm and Z2 = 40 μm. Substituting these into equation (c),
ΔΦ (ΔZ) = 2π / 200 μm * ΔZ
It becomes. Therefore, an interference signal for measuring the Z position having a stroke of 200 μm is obtained. At this time, the number of samples is equal to 2000 when the stroke is 50 μm and the resolution is 25 nm. That is, the detection stroke, that is, the detectable range can be expanded to 200 μm while the resolution is 25 nm and the number of samples is 2000.
[0050]
Now, for the sake of convenience, the position measurement interference reference signal in each direction is represented by Equation (9), the Y direction is Equation (11), and the Z direction is Equation (9). Even if the expression, the Y direction is the expression (10), and the Z direction is the expression (12), the position information in each direction can be obtained only by reversing the sign.
From the equation (13), the incident angle θ2 of the first normal direction measurement illumination light beam for obtaining a desired Z detection stroke is obtained.
For example, if it is desired to obtain a detection stroke of 50 μm in equation (12), 2π is substituted for the left side and 50 μm is substituted for ΔZ on the right side.
However, since the value of θ2 is larger than θ1, that is, since it is desired to be closer to the object side than the first illumination light beam, subtracting the first Z position measurement interference reference signal from the second Z position measurement interference reference signal,
2π = 4π (cos 70 ° −cos θ2) / 633 nm × 50 μm
As a result, θ2 = 70.39 ° is obtained.
[0051]
The signal processing unit 600 obtains the position in the normal direction of the plane including the target object and the plane including the target object based on the phase of the position measurement interference measurement signal. The X-direction position measurement interference measurement signal is received by the photosensor 550, and the X-position measurement interference reference signal is received by the photosensor 554. A phase difference between signals received by the photosensor 550 and the photosensor 554 is measured by a phase meter 610.
The Y position measurement interference measurement signal is received by the photosensor 551, and the Y position measurement interference reference signal is received by the photosensor 555. A phase meter 611 measures the phase difference between the photosensor 551 and the signal received by the photosensor 555.
The first Z-direction position measurement interference measurement signal is received by the photosensor 552, and the Z-position measurement reference signal is received by the photosensor 554.
[0052]
The phase difference between the signal received by the photosensor 552 and the signal received by the photosensor 554 is measured by the phase meter 612.
The second Z-direction position measurement signal is received by the photosensor 553, and the Z-direction position measurement reference signal is received by the photosensor 554.
The phase difference between the signal received by the photosensor 553 and the signal received by the photosensor 554 is measured by the phase meter 613.
The arithmetic processing unit 620 determines the position in the X direction in the plane including the object based on the phase difference of the phase meter 610, determines the position in the Y direction in the plane including the object based on the phase difference of the phase meter 611, Then, based on the phase difference between the phase meters 612 and 613, the position in the Z direction within the plane including the object is obtained. The arithmetic processing unit 620 can independently measure the displacement components in each direction with respect to the XYZ displacement of the object, and various controls including alignment of the object can be performed.
[4] Application of the position measuring device of the present invention
The position measurement apparatus of the present invention can be applied to, for example, a charged particle beam apparatus such as an electron beam lithography apparatus and an apparatus that requires accurate alignment of an object such as a semiconductor exposure apparatus. .
[0053]
Here, an electron beam drawing apparatus will be described as an example. Referring to FIG. 15, the electron beam drawing apparatus includes an electron optical system 730 including an electron gun that generates an electron beam, an X direction scanning electrode that changes the direction of an electron beam, a Y direction scanning electrode, and the like. A stage 734 is provided that can place a drawing object 732 placed in a vacuum chamber and can move in the X, Y, and normal directions in the horizontal plane.
Then, the illumination side optical casing 740 including the illumination optical system 100, the correction optical system 200, and the irradiation optical system 300 of the position measurement apparatus of the present invention, and the light reception side optical casing 742 including the light reception optical system 400 are arranged on both sides of the stage 734. To place. The illumination-side optical casing 740 and the light-receiving side optical casing 742 are arranged so as to avoid the mounting positions of the respective components of the electron beam drawing apparatus such as the electron optical system 730 and the maximum operating range thereof. The light beam irradiated from the illumination side optical casing 740 and incident on the light receiving side optical casing 742 avoids the mounting position of each component of the electron beam drawing apparatus such as the electron optical system 730 and the maximum operating range thereof. The illumination-side optical casing 740 and the light-receiving-side optical casing 742 are arranged so that they can be transmitted through.
[0054]
In the electron beam drawing apparatus, the electron optical system and the stage perform a predetermined operation in response to various signals from a control circuit to form a predetermined pattern on the mask, wafer, or the like, which is a drawing target, using the electron beam. .
Specifically, a semiconductor manufacturing mask such as an encoder pattern or a phase shift mask can be processed by an electron beam lithography apparatus to which the position measuring apparatus of the present invention is applied.
Moreover, a semiconductor wafer and a semiconductor manufacturing mask can be processed by a semiconductor exposure apparatus to which the position measuring apparatus of the present invention is applied.
[0055]
【The invention's effect】
(1) According to the present invention, at least three laser light beams are irradiated at different angles on the object surface, and the position of the normal direction with a wide dynamic range is measured using the interference light, so that the strokes are different. The phase difference between the two interference signals for Z position measurement can be taken, and the detection stroke can be expanded without increasing the number of samples with the same resolution (without increasing the burden on the electrical processing system and increasing the processing time). Is possible.
(2) According to the present invention, a semiconductor exposure apparatus to which a small and high-performance position measuring apparatus is applied can be realized.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an optical system according to an embodiment of a position measuring apparatus of the present invention.
FIG. 2 is a perspective view showing an adjustment optical system and an irradiation optical system according to an embodiment of the position measurement apparatus of the present invention.
FIG. 3 is a plan view showing an adjustment optical system and an irradiation optical system according to an embodiment of the position measurement apparatus of the present invention.
FIG. 4 is a side view showing an adjustment optical system and an irradiation optical system according to an embodiment of the position measurement apparatus of the present invention.
FIG. 5 is a diffracted light mapping of the first planar position measuring illumination light beam by a two-dimensional diffraction pattern on the object in the embodiment of the position measuring apparatus of the present invention.
FIG. 6 is a perspective view showing a state in which a measurement illumination light beam is incident on a two-dimensional diffraction pattern on an object in the embodiment of the position measurement apparatus of the present invention.
FIG. 7 is a plan view showing a state in which a measurement illumination light beam is incident on a two-dimensional diffraction pattern on an object in the embodiment of the position measurement apparatus of the present invention.
FIG. 8 is a side view showing a state in which a measurement illumination light beam is incident on a two-dimensional diffraction pattern on an object in the embodiment of the position measurement apparatus of the present invention.
FIG. 9 is a diffracted light mapping of a plane position measurement illumination beam and a normal direction measurement illumination beam by a two-dimensional diffraction pattern on an object in an embodiment of the position measurement apparatus of the present invention.
FIG. 10 is a side view showing the positional relationship between the plane position measurement illumination beam, the normal direction measurement illumination beam, and the diffracted beam of the position measurement device according to the embodiment of the present invention.
FIG. 11 is a plan view showing a positional relationship between a plane position measurement illumination beam, a normal direction measurement illumination beam, and a diffracted beam of the position measurement device according to the embodiment of the present invention.
FIG. 12 is a schematic block diagram showing a configuration of a light receiving optical system according to an embodiment of the position measuring apparatus of the present invention.
FIG. 13 is a signal waveform diagram of the embodiment of the position measurement apparatus of the present invention.
FIG. 14 is a diffracted light mapping used for measurement in the X, Y, and Z directions among the diffracted light diffracted by the alignment mark in the embodiment of the position measuring apparatus of the present invention.
FIG. 15 is a schematic partial cross-sectional view of an embodiment of an electron beam lithography apparatus to which the position measuring apparatus of the present invention is applied.
16 is a partially enlarged view of the portion of the illumination optical system of FIG. 1 in the embodiment of the position measuring apparatus of the present invention.
17 is a partially enlarged view of the portion of the object in FIG. 1 of the embodiment of the position measuring device of the present invention.
18 is a partially enlarged view of the portion of the light receiving optical system in FIG. 1 of the embodiment of the position measuring apparatus of the present invention.
FIG. 19 is a partial enlarged view of the portion of the object in FIG. 11 in the embodiment of the position measurement apparatus of the present invention.
[Explanation of symbols]
1 Light source
10 Object
12 Two-dimensional diffraction pattern
100 Illumination optical system
102 Relay lens
103 Beam splitter
104 First illumination beam
105 Second illumination beam
106,107 Relay lens
108 First frequency shifter
109 Second frequency shifter
110 Illumination beam for first measurement
111 Illumination beam for second measurement
112, 113 Beam splitter
114 Illumination beam for first plane position measurement
115 Illumination beam for first normal direction measurement
116 Illumination beam for second plane position measurement
117 Illumination luminous flux for second normal direction measurement
200 Correction optical system
201, 202 parallel plane plate
203, 204 Wedge prism
205,206 Focus lens
300 Irradiation optical system
301, 302 Folding mirror
303 Irradiation lens
400 Receiving optical system
401 Light-receiving-side objective lens
402-405 Folding mirror
500 Light receiver
512 (−1, +1) th order diffracted light of illumination light beam for first plane position measurement
514 (+1, +1) -order diffracted light of illumination light beam for second plane position measurement
515 (−1, + 1) -order diffracted light of illumination light beam for second plane position measurement
511: (+1, +1) -order diffracted light of the first plane position measurement illumination beam
510 0th-order light of the illumination light beam for first plane position measurement
513 Zeroth-order light of the illumination light beam for second plane position measurement
517: 0th-order light of illumination beam for first normal direction measurement
516 0th-order light of the illumination beam for measuring the second normal direction
550-555 photo sensor
600 Signal processor
610 Phase meter (X)
611 Phase meter (Y)
612 Phase meter (Z1)
613 Phase meter (Z2)
620 arithmetic processing unit

Claims (9)

コヒーレント光を発する光源部と、
該光源部からの光束を、法線方向基準照明光束として第1入射角により、第1法線方向測定用照明光束として第2入射角により、また前記第2法線方向測定用照明光束として第1入射角及び第2入射角とは異なる第3入射角で、位置の測定をすべき対象物に設けられている2次元パターンへ照射する照射光学系と、
前記2次元パターンからの反射光を受光する受光光学系と、
前記受光光学系で受光した反射光の内で、法線方向基準照明光束と第1法線方向測定用照明光束とを干渉させて第1法線方向測定用干渉信号を形成し、法線方向基準照明光束又は第1法線方向測定用照明光束と第2法線方向測定用照明光束とを干渉させて第2法線方向測定用干渉信号を形成する受光部と、
前記第1法線方向測定用干渉信号及び前記第2法線方向測定用干渉信号の位相に基づき対象物の法線方向の位置測定を行う信号処理部と、
を有することを特徴とする位置測定装置。
A light source that emits coherent light;
The light beam from the light source is used as a normal direction reference illumination light beam at a first incident angle, as a first normal direction measurement illumination light beam at a second incident angle, and as a second normal direction measurement illumination light beam. An irradiation optical system for irradiating a two-dimensional pattern provided on an object whose position is to be measured at a third incident angle different from the first incident angle and the second incident angle;
A light receiving optical system for receiving reflected light from the two-dimensional pattern;
Of the reflected light received by the light receiving optical system, the normal direction reference illumination light beam and the first normal direction measurement illumination light beam are interfered to form a first normal direction measurement interference signal, and the normal direction A light receiving unit that interferes with the reference illumination light beam or the first normal direction measurement illumination light beam and the second normal direction measurement illumination light beam to form a second normal direction measurement interference signal;
A signal processing unit for measuring the position of the target in the normal direction based on the phases of the first normal direction measurement interference signal and the second normal direction measurement interference signal;
A position measuring device comprising:
前記信号処理部は前記第1法線方向測定用干渉信号と前記第2法線方向測定用干渉信号との位相差に基づいて前記対象物の法線方向の位置の測定を行う信号処理部を有することを特徴とする、請求項1に記載の位置測定装置。The signal processing unit includes a signal processing unit that measures the position of the target in the normal direction based on a phase difference between the first normal direction measurement interference signal and the second normal direction measurement interference signal. The position measuring device according to claim 1, comprising: 前記光源部は、該光源部からの光束を周波数が異なる光束として射出する周波数シフター部を更に備え、
前記光源部は、該光源部から生じる第1周波数のコヒーレント光を、法線方向基準照明光束とし、前記周波数シフター部から射出される前記法線方向基準照明光束と周波数が異なる第2周波数の光束を第1法線方向測定用照明光束とし、法線方向基準照明光束又は第1法線方向測定用照明光束のいずれか一つから分離させて第2法線方向測定用照明光束を形成する光束分離部を更に備えていることを特徴とする、請求項1に記載の位置測定装置。
The light source unit further includes a frequency shifter unit that emits light beams from the light source unit as light beams having different frequencies,
The light source unit uses coherent light having a first frequency generated from the light source unit as a normal direction reference illumination beam, and a second frequency beam having a frequency different from that of the normal direction reference illumination beam emitted from the frequency shifter unit. Is a first normal direction measurement illumination beam, and is separated from either the normal direction reference illumination beam or the first normal direction measurement illumination beam to form a second normal direction measurement illumination beam The position measuring device according to claim 1, further comprising a separation unit.
前記光源部は、第1平面方向測定用照明光束となる第1周波数のコヒーレント光を発する光源と、この第1平面方向測定用照明光束と周波数が異なる第2周波数の第2平面方向測定用照明光束を形成する周波数シフターとを有し、
前記照射光学系は、第1平面方向測定用照明光束と第2平面方向測定用照明光束を第1入射角で入射させ、
前記受光部は、前記受光光学系で受光した第1平面方向測定用照明光束と第2平面方向測定用照明光束の回折光の内で、前記2次元パターンによる高次回折光と0次回折光の組み合わせ及び高次回折光同士の組み合わせのいずれか一つの周波数が異なる回折光の組み合わせから前記対象物の2次元パターンを設けた平面内での平面位置測定用干渉信号を形成し、
前記信号処理部は、平面位置測定用干渉信号の位相に基づき前記対象物の2次元パターンを設けた平面内での位置を求める信号処理部とを有することを特徴とする、請求項1記載の位置測定装置。
The light source unit emits a first frequency coherent light to be a first plane direction measurement illumination beam, and a second plane direction measurement illumination having a second frequency different from the first plane direction measurement beam. A frequency shifter that forms a luminous flux,
The irradiation optical system causes the first plane direction measurement illumination light beam and the second plane direction measurement illumination light beam to be incident at a first incident angle;
The light receiving unit is a combination of high-order diffracted light and zero-order diffracted light according to the two-dimensional pattern among the diffracted light of the first plane direction measuring illumination light beam and the second plane direction measuring illumination light beam received by the light receiving optical system. And an interference signal for measuring a plane position in a plane in which a two-dimensional pattern of the object is provided from a combination of diffracted lights having different frequencies from any one of combinations of higher-order diffracted lights,
2. The signal processing unit according to claim 1, further comprising: a signal processing unit that obtains a position in a plane on which a two-dimensional pattern of the object is provided based on a phase of an interference signal for plane position measurement. Position measuring device.
前記受光部は、第1平面位置測定用照明光束と第2平面位置測定用照明光束の前記2次元パターンによる0次回折光同士の異なる周波数の回折光の組み合わせからX位置測定用干渉基準信号を形成し、第1平面位置測定用照明光束の0次回折光と第2平面位置測定用照明光束の高次回折光の組合せ又は、第1平面位置測定用照明光束の高次回折光と第2平面位置測定用照明光束の0次回折光の組合せからY位置測定用干渉基準信号を形成し、
前記信号処理部は、X位置測定用干渉測定信号とX位置測定用干渉基準信号との位相差に基づき前記対象物のX方向の位置を求め、Y位置測定用干渉測定信号とY位置測定用干渉基準信号との位相差に基づき前記対象物のY方向の位置を求めるように構成されていることを特徴とする、請求項4記載の位置測定装置。
The light receiving unit forms an X-position measurement interference reference signal from a combination of diffracted lights having different frequencies of zero-order diffracted lights according to the two-dimensional pattern of the first planar position measuring illumination light beam and the second planar position measuring illumination light beam. And a combination of the 0th-order diffracted light of the first plane position measurement illumination beam and the higher-order diffracted light of the second plane position measurement illumination beam, or the higher-order diffracted light of the first plane position measurement illumination beam and the second plane position measurement. An interference reference signal for Y position measurement is formed from the combination of the 0th order diffracted light of the illumination light beam,
The signal processing unit obtains the position of the object in the X direction based on the phase difference between the X position measurement interference measurement signal and the X position measurement interference reference signal, and the Y position measurement interference measurement signal and the Y position measurement The position measuring device according to claim 4, wherein the position measuring device is configured to obtain a position in the Y direction of the object based on a phase difference from an interference reference signal.
前記光源部は、前記第1平面方向測定用照明光束と法線方向基準照明光束とを共通の光束とするように構成されていることを特徴とする、請求項4記載の位置測定装置。The position measuring device according to claim 4, wherein the light source unit is configured so that the first planar direction measurement illumination light beam and the normal direction reference illumination light beam are a common light beam. 前記照射光学系での第1法線方向位置測定用照明光束又は第2法線方向位置測定用照明光束の光路中に、その照明光束が前記2次元パターンに照射する入射角度を変化させる入射角度変化部材が配置されていることを特徴とする、請求項1又は請求項4記載の位置測定装置。Incident angle that changes the incident angle of the illumination beam on the two-dimensional pattern in the optical path of the first normal direction position measurement illumination beam or the second normal direction position measurement illumination beam in the irradiation optical system. The position measuring device according to claim 1, wherein a change member is disposed. 前記入射角度変化部材は、第1法線方向位置測定用照明光束又は第2法線方向位置測定用照明光束の入射角度を変化させるように、その光路中に光軸と直交方向に回転軸を有する平行平面板として構成されていることを特徴とする、請求項1又は請求項4記載の位置測定装置。The incident angle changing member has a rotation axis in a direction orthogonal to the optical axis in the optical path so as to change the incident angle of the first normal direction position measurement illumination light beam or the second normal direction position measurement illumination light beam. The position measuring device according to claim 1, wherein the position measuring device is configured as a parallel plane plate. 電子線描画装置において、
該電子線描画装置の構成部品の取付け位置及びそれらの最大作動範囲をさけるように配置されている、請求項1から請求項8のいずれか1項に記載の位置測定装置を備え、
前記位置測定装置は対象物の位置を測定するための位置測定用光束を照射するための照明側光学部材と、前記対象物からの反射回折光を受光して前記対象物の位置を測定するための受光側光学部材とを有し、
前記照明側光学部材から照射して前記受光側光学部材に入射される光束が、前記電子線描画装置の構成部品の取付け位置及びそれらの最大作動範囲をさけて透過することができるように、前記照明側光学部材及び前記受光側光学部材が前記電子線描画装置に配置されていることを特徴とする電子線描画装置。
In an electron beam drawing device,
The position measuring device according to any one of claims 1 to 8, wherein the position measuring device is disposed so as to avoid a mounting position of components of the electron beam drawing apparatus and a maximum operating range thereof.
The position measuring device receives an illumination-side optical member for irradiating a position-measuring light beam for measuring the position of the object, and measures the position of the object by receiving reflected diffracted light from the object. And a light receiving side optical member,
The light beam irradiated from the illumination-side optical member and incident on the light-receiving-side optical member can pass through the mounting positions of the component parts of the electron beam drawing apparatus and the maximum operating range thereof. An electron beam drawing apparatus, wherein the illumination side optical member and the light receiving side optical member are arranged in the electron beam drawing apparatus.
JP06867097A 1997-03-21 1997-03-21 Position measuring device Expired - Fee Related JP3713355B2 (en)

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