JP2006041389A - Method of adjusting image-formation optical system - Google Patents

Method of adjusting image-formation optical system Download PDF

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JP2006041389A
JP2006041389A JP2004222331A JP2004222331A JP2006041389A JP 2006041389 A JP2006041389 A JP 2006041389A JP 2004222331 A JP2004222331 A JP 2004222331A JP 2004222331 A JP2004222331 A JP 2004222331A JP 2006041389 A JP2006041389 A JP 2006041389A
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mark
optical system
imaging optical
image
wavelength band
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JP4691922B2 (en
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Tatsuo Fukui
達雄 福井
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Nikon Corp
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Abstract

<P>PROBLEM TO BE SOLVED: To fine-adjust the arrangement of an optical element for adjustment with proper sensitivity. <P>SOLUTION: A method of adjusting an image-formation optical system comprises steps of irradiating a lighting light in a predetermined wavelength band to adjusting marks including plural first marks arranged at a first pitch, and plural second marks arranged at a second pitch different from the first pitch (S5, S6); capturing images, based on lights that have passed through an aperture stop and reached the image surface of an image-forming optical system out of diffraction lights produced from the adjusting marks (S5, S6); calculating the positional deviation amount between the first marks and the second marks, by coupling with the symmetry/asymmetry of brightness information concerning the first marks and the second marks out of brightness information on the images of the adjusting marks (S5, S6); changing the wavelength band of the lighting light (S5, S6); and fine-adjusting the optical element for adjustment, disposed between a pupil surface of the image-formation optical system and an aperture stop surface, based on the respective positional deviation amount, when the wavelength bands of the lighting light are different to correct an image-formation positional deviation of a pupil image at the aperture stop surface (S8, S9). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

本発明は、物体の像を形成する結像光学系の調整方法に関し、特に、半導体素子や液晶表示素子などの製造工程において基板（半導体ウエハや液晶基板など）に形成されたマークの位置を高精度に検出する装置に好適な結像光学系の調整方法に関する。   The present invention relates to a method for adjusting an imaging optical system that forms an image of an object, and in particular, increases the position of a mark formed on a substrate (such as a semiconductor wafer or a liquid crystal substrate) in a manufacturing process of a semiconductor element or a liquid crystal display element. The present invention relates to a method for adjusting an imaging optical system suitable for an apparatus for detecting with high accuracy.

半導体素子や液晶表示素子などの製造工程では、周知のリソグラフィ工程を経てレジスト層に回路パターンが転写され、このレジストパターンを介してエッチングなどの加工処理を行うことにより、所定の材料膜に回路パターンが転写される(パターン形成工程)。そして、このパターン形成工程を何回も繰り返し実行することにより、様々な材料膜の回路パターンが基板（半導体ウエハや液晶基板）の上に積層され、半導体素子や液晶表示素子の回路が形成される。   In manufacturing processes such as semiconductor elements and liquid crystal display elements, a circuit pattern is transferred to a resist layer through a well-known lithography process, and a circuit pattern is formed on a predetermined material film by performing processing such as etching through the resist pattern. Is transferred (pattern forming step). By repeating this pattern forming process many times, circuit patterns of various material films are stacked on a substrate (semiconductor wafer or liquid crystal substrate), and a circuit of a semiconductor element or a liquid crystal display element is formed. .

さらに、上記の製造工程では、様々な材料膜の回路パターンを精度よく重ね合わせるため（製品の歩留まり向上を図るため）、各々のパターン形成工程のうち、リソグラフィ工程の前に、基板のアライメントを行い、リソグラフィ工程の後でかつ加工工程の前に、基板上のレジストパターンの重ね合わせ検査を行っている。なお、基板のアライメントには、１つ前のパターン形成工程で下地層に形成されたアライメントマークが用いられる。レジストパターンの重ね合わせ検査には、現在のパターン形成工程でレジスト層に形成された重ね合わせマークと、１つ前のパターン形成工程で下地層に形成された重ね合わせマークとが用いられる。   Furthermore, in the manufacturing process described above, in order to accurately overlay circuit patterns of various material films (in order to improve product yield), the substrate is aligned before the lithography process in each pattern forming process. The registration inspection of the resist pattern on the substrate is performed after the lithography process and before the processing process. For alignment of the substrate, an alignment mark formed on the underlying layer in the previous pattern formation step is used. For overlay inspection of the resist pattern, the overlay mark formed on the resist layer in the current pattern forming process and the overlay mark formed on the underlying layer in the previous pattern forming process are used.

また、基板のアライメントを行う装置や、基板上のレジストパターンの重ね合わせ検査を行う装置には、上記のアライメントマークや重ね合わせマーク（総じて単に「マーク」という）の位置を検出する装置が組み込まれている。位置検出装置では、検出対象のマークに対して照明光を照射し、マークからの光（例えば反射光）に基づく画像をＣＣＤカメラなどの撮像素子によって取り込み、その画像に対して所定の画像処理を施すことにより、マークの位置検出を行う。照明光の波長帯域は、多種多様なマークの構造に対して安定した反射強度を得るため、可視光帯域から赤外光近傍帯域までの広帯域な範囲とすることが多い。   Also, a device for detecting the position of the alignment mark or overlay mark (generally simply referred to as “mark”) is incorporated in a device for aligning the substrate or a device for performing overlay inspection of a resist pattern on the substrate. ing. In the position detection device, illumination light is irradiated to a mark to be detected, an image based on light from the mark (for example, reflected light) is captured by an image sensor such as a CCD camera, and predetermined image processing is performed on the image. As a result, the position of the mark is detected. The wavelength band of the illumination light is often in a wide range from the visible light band to the near infrared light band in order to obtain a stable reflection intensity with respect to various mark structures.

さらに、位置検出装置では、その検出精度を高めるために、例えば特許文献１に開示されている方法を利用して、結像光学系(マークの像を形成する光学系)の開口絞りや対物レンズの配置をシフト方向に微調整し、装置起因の誤差成分（ＴＩＳ値：Tool Induced Shift）を低減するようにしている。
特開２０００−７７２９５号公報 Further, in the position detection device, in order to improve the detection accuracy, an aperture stop or an objective lens of an imaging optical system (an optical system for forming an image of a mark) is used by using a method disclosed in Patent Document 1, for example. Is finely adjusted in the shift direction to reduce an error component (TIS value: Tool Induced Shift) caused by the apparatus.
JP 2000-77295 A

しかしながら、上記した結像光学系の調整方法では、結像光学系の各光学部品を配置する際の製造誤差（光学部品の偏心誤差）などに起因して、結像光学系の開口絞り面における瞳像の結像位置が波長帯域に応じて異なった場合、装置起因の誤差成分(ＴＩＳ値)を良好に低減することができない。
そこで、本発明者は、結像光学系の瞳面と開口絞り面との間に調整用の光学素子を新たに配置して、この光学素子の配置を上記の特許文献１に開示した方法を利用して微調整し、開口絞り面における瞳像の波長帯域に応じた結像位置ずれを補正することを提案した（特願２００３−５４０５８号）。しかし、上記の特許文献１に開示した方法では、光学素子の配置を微調整する際の感度が低く、その調整誤差を小さくすることが難しかった。このため、装置起因の誤差成分(ＴＩＳ値)を十分に低減できるとは限らず、検出精度の向上にも限界があった。 However, in the above-described adjustment method of the imaging optical system, due to a manufacturing error (decentration error of the optical component) at the time of arranging each optical component of the imaging optical system, the aperture stop surface of the imaging optical system When the imaging position of the pupil image differs depending on the wavelength band, the error component (TIS value) caused by the apparatus cannot be reduced satisfactorily.
Therefore, the present inventor newly arranges an optical element for adjustment between the pupil plane and the aperture stop surface of the imaging optical system, and uses the method disclosed in Patent Document 1 for the arrangement of this optical element. It has been proposed to make fine adjustments using the correction and to correct the image formation position shift corresponding to the wavelength band of the pupil image on the aperture stop surface (Japanese Patent Application No. 2003-54058). However, in the method disclosed in Patent Document 1, the sensitivity when finely adjusting the arrangement of the optical elements is low, and it is difficult to reduce the adjustment error. For this reason, the error component (TIS value) caused by the apparatus cannot be sufficiently reduced, and there is a limit to the improvement of detection accuracy.

本発明の目的は、調整用の光学素子の配置を感度良く微調整することが可能な結像光学系の調整方法を提供することにある。   An object of the present invention is to provide a method for adjusting an imaging optical system capable of finely adjusting the arrangement of optical elements for adjustment with high sensitivity.

請求項１に記載の発明は、結像光学系の物体面に、所定の波長帯の落射照明光による±１次回折光束が前記結像光学系の瞳領域に内接するようなピッチ以上の第１のピッチで配列された第１のマークと、前記第１のピッチより小さい第２のピッチを有して配列された第２のマークとを、それぞれ前記結像光学系の視野中心に対して対称に配設し、
前記結像光学系で形成された前記第１のマークの像と前記第２のマークの像との相対位置に基づいて、前記結像光学系の瞳面と開口絞り面との間に配設された光学素子の位置を調整するものである。 According to the first aspect of the present invention, on the object plane of the imaging optical system, the first or higher order diffracted light beam by the incident illumination light of a predetermined wavelength band is not less than a pitch that is inscribed in the pupil region of the imaging optical system. A first mark arranged at a pitch of 1 and a second mark arranged at a second pitch smaller than the first pitch with respect to the field center of the imaging optical system, respectively. Arranged symmetrically,
Based on the relative position between the image of the first mark and the image of the second mark formed by the imaging optical system, it is arranged between the pupil plane and the aperture stop plane of the imaging optical system. The position of the optical element thus adjusted is adjusted.

請求項２に記載の発明は、請求項１に記載の結像光学系の調整方法において、前記第１のピッチをＰ１(μｍ)、前記第２のピッチをＰ２(μｍ)、前記結像光学系の開口数をＮＡima、前記照明光の照射に用いた光学系の開口数をＮＡill、前記照明光の中心波長をλ(μｍ)とするとき、次の条件式を満足するものである。
ＮＡima ＞ ＮＡill
ＮＡima−ＮＡill ＞ λ/Ｐ１
ＮＡima＋ＮＡill/２ ≦ λ/Ｐ２
請求項３に記載の発明は、請求項１または請求項２に記載の結像光学系の調整方法において、前記調整用マークを前記視野中心に対して１８０°回転させる前後の状態の各々で前記結像光学系で形成された像における前記第１のマークと前記第２のマークとの距離を測定し、測定された２つの距離から装置起因の誤差成分量を算出して、前記誤差成分量に基づいて前記光学素子の位置を調整するものである。 According to a second aspect of the present invention, in the method for adjusting an imaging optical system according to the first aspect, the first pitch is P1 (μm), the second pitch is P2 (μm), and the imaging optical system When the numerical aperture of the system is NAima, the numerical aperture of the optical system used for irradiation of the illumination light is NAill, and the center wavelength of the illumination light is λ (μm), the following conditional expression is satisfied.
NAima> NAill
NAima-NAill> λ / P1
NAima + NAill / 2 ≤ λ / P2
According to a third aspect of the present invention, in the method for adjusting an imaging optical system according to the first or second aspect, the adjustment mark is rotated in a state before and after the adjustment mark is rotated by 180 degrees with respect to the center of the visual field. The distance between the first mark and the second mark in the image formed by the imaging optical system is measured, and the error component amount derived from the apparatus is calculated from the two measured distances, and the error component amount Based on the above, the position of the optical element is adjusted.

請求項４に記載の発明は、請求項１から請求項３の何れか１項に記載の結像光学系の調整方法において、前記照明光の波長帯域を変えて、波長ごとに前記第１のマークと前記第２のマークとの相対位置を求め、波長帯域ごとに求められた前記相対位置に基づいて、前記光学素子の位置を調整するものである。
請求項５に記載の発明は、請求項４に記載の結像光学系の調整方法において、前記照明光の波長帯域ごとに算出した前記第１のマークと前記第２のマークとの距離同１士の差分、または前記照明光の波長帯域ごとに算出した前記装置起因の誤差成分量同士の差分を指標として、前記光学素子の位置を調整するものである。 According to a fourth aspect of the present invention, in the method for adjusting an imaging optical system according to any one of the first to third aspects, the wavelength band of the illumination light is changed, and the first optical system is changed for each wavelength. The relative position between the mark and the second mark is obtained, and the position of the optical element is adjusted based on the relative position obtained for each wavelength band.
According to a fifth aspect of the present invention, in the imaging optical system adjusting method according to the fourth aspect, the distance between the first mark and the second mark calculated for each wavelength band of the illumination light is the same. The position of the optical element is adjusted using as an index the difference between the elements or the difference between the error component amounts derived from the apparatus calculated for each wavelength band of the illumination light.

請求項６に記載の発明は、請求項１から請求項５の何れか１項に記載の結像光学系の調整方法において、前記光学素子は平行平面板であり、前記光学素子の配置の調整は、前記平行平面板の位置を傾ける方向に調整するものである。   According to a sixth aspect of the present invention, in the method for adjusting an imaging optical system according to any one of the first to fifth aspects, the optical element is a plane-parallel plate, and the arrangement of the optical elements is adjusted. Adjusts the position of the plane parallel plate in the direction of tilting.

本発明の結像光学系の調整方法によれば、調整用の光学素子の配置を感度良く微調整することができる。   According to the adjustment method of the imaging optical system of the present invention, the arrangement of the adjustment optical elements can be finely adjusted with high sensitivity.

以下、図面を用いて本発明の実施形態を詳細に説明する。
ここでは、本実施形態の結像光学系の調整方法について、図１に示す重ね合わせ測定装置１０を例に説明する。重ね合わせ測定装置１０は、半導体素子や液晶表示素子などの製造工程において、基板１１のレジストパターン(不図示)の重ね合わせ検査を行う装置である。重ね合わせ検査では、基板１１の下地層に形成された回路パターン（以下「下地パターン」という）に対するレジストパターンの位置ずれ量の測定が行われる。 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Here, the adjustment method of the imaging optical system of the present embodiment will be described using the overlay measurement apparatus 10 shown in FIG. 1 as an example. The overlay measurement apparatus 10 is an apparatus that performs overlay inspection of a resist pattern (not shown) of the substrate 11 in a manufacturing process of a semiconductor element, a liquid crystal display element, or the like. In the overlay inspection, the amount of displacement of the resist pattern with respect to a circuit pattern (hereinafter referred to as “underground pattern”) formed on the underlayer of the substrate 11 is measured.

重ね合わせ測定装置１０には、図１(ａ)に示す通り、基板１１または後述の調整用基板３０（図２）を支持するステージ１２と、照明光学系(１３〜１９)と、結像光学系(１９〜２４)と、ＣＣＤ撮像素子２５と、画像処理部２６と、焦点検出部(４１〜４８)と、ステージ制御部２７とが設けられる。
ステージ１２は、図示省略したが、基板１１または後述の調整用基板３０（図２）を水平状態に保って支持するホルダと、このホルダを水平方向(ＸＹ方向)に駆動するＸＹ駆動部と、ホルダを鉛直方向(Ｚ方向)に駆動するＺ駆動部とで構成されている。そして、ＸＹ駆動部とＺ駆動部は、ステージ制御部２７に接続されている。 As shown in FIG. 1A, the overlay measuring apparatus 10 includes a stage 12 that supports a substrate 11 or an adjustment substrate 30 (FIG. 2) described later, an illumination optical system (13 to 19), and imaging optics. A system (19-24), a CCD image pickup device 25, an image processing unit 26, a focus detection unit (41-48), and a stage control unit 27 are provided.
Although not shown, the stage 12 includes a holder that supports the substrate 11 or an adjustment substrate 30 (FIG. 2), which will be described later, in a horizontal state, an XY drive unit that drives the holder in the horizontal direction (XY direction), It is comprised with the Z drive part which drives a holder to a perpendicular direction (Z direction). The XY drive unit and the Z drive unit are connected to the stage control unit 27.

ここで、基板１１は、半導体ウエハや液晶基板などの一般的な製品基板であり、レジスト層に対する露光・現像後で、所定の材料膜に対する加工前の状態にある。製品基板には、重ね合わせ検査のために多数の測定点が用意されている。測定点の位置は、各ショット領域の四隅などである。各測定点には、レジストパターンの基準位置を示すレジストマークと下地パターンの基準位置を示す下地マークとが形成されている。以下の説明では、レジストマークと下地マークとを総じて「重ね合わせマーク１１Ａ」という。   Here, the substrate 11 is a general product substrate such as a semiconductor wafer or a liquid crystal substrate, and is in a state after exposure / development of the resist layer and before processing of a predetermined material film. Many measurement points are prepared on the product substrate for overlay inspection. The positions of the measurement points are the four corners of each shot area. At each measurement point, a resist mark indicating the reference position of the resist pattern and a base mark indicating the reference position of the base pattern are formed. In the following description, the registration mark and the base mark are collectively referred to as “overlapping mark 11A”.

また、調整用基板３０（図２）は、結像光学系(１９〜２４)を調整する際の指標を求めるために設計されたものである。この調整用基板３０には、外マーク３１と内マーク３２とを含む調整用マーク３０Ａが設けられている。調整用マーク３０Ａは、BAR in BAR タイプの２重マークであり、シリコンウエハなどをエッチング処理することにより作成される。調整用マーク３０Ａの段差ｈは、例えば８３ｎｍである。図２(ａ)は平面図、図２(ｂ)は断面図である。   The adjustment substrate 30 (FIG. 2) is designed for obtaining an index for adjusting the imaging optical system (19 to 24). The adjustment substrate 30 is provided with an adjustment mark 30 </ b> A including an outer mark 31 and an inner mark 32. The adjustment mark 30A is a double mark of BAR in BAR type, and is created by etching a silicon wafer or the like. The step h of the adjustment mark 30A is, for example, 83 nm. 2A is a plan view, and FIG. 2B is a cross-sectional view.

外マーク３１は、Ｘ方向に細長い４本のバーマーク１Ａと、Ｙ方向に細長い４本のバーマーク１Ｂとで構成され、２本ずつが１組となって内マーク３２の周囲に四辺状に配置されている。また、４本のバーマーク１Ａは、各組ごとに、ピッチＰ１で配列されている。同様に、４本のバーマーク１Ｂも、各組ごとに、ピッチＰ１で配列されている。ピッチＰ１は、例えば３.８μｍであり、請求項の「第１ピッチ」に対応する。   The outer mark 31 is composed of four bar marks 1A elongated in the X direction and four bar marks 1B elongated in the Y direction, and each of the two marks forms a quadrilateral around the inner mark 32. Has been placed. The four bar marks 1A are arranged at a pitch P1 for each group. Similarly, the four bar marks 1B are also arranged at a pitch P1 for each group. The pitch P1 is, for example, 3.8 μm, and corresponds to the “first pitch” in the claims.

内マーク３２は、Ｘ方向に細長い４本のバーマーク２Ａと、Ｙ方向に細長い４本のバーマーク２Ｂとで構成され、２本ずつが１組となって外マーク３１の内側に四辺状に配置されている。また、４本のバーマーク２Ａは、各組ごとに、上記ピッチＰ１とは異なるピッチＰ２で配列されている。同様に、４本のバーマーク２Ｂも、各組ごとに、ピッチＰ２で配列されている。ピッチＰ２は、例えば１μｍであり、請求項の「第２ピッチ」に対応する。   The inner mark 32 is composed of four bar marks 2A elongated in the X direction and four bar marks 2B elongated in the Y direction. Each of the inner marks 32 forms a quadrilateral shape inside the outer mark 31. Has been placed. Further, the four bar marks 2A are arranged with a pitch P2 different from the pitch P1 for each group. Similarly, four bar marks 2B are arranged at a pitch P2 for each group. The pitch P2 is 1 μm, for example, and corresponds to the “second pitch” in the claims.

上記の基板１１（または調整用基板３０）がステージ１２のホルダに支持された状態で、ステージ制御部２７は、ステージ１２のＸＹ駆動部を制御し、ホルダをＸＹ方向に移動させて、基板１１上の重ね合わせマーク１１Ａ（または調整用基板３０上の調整用マーク３０Ａ）を視野領域内に位置決めする。また、焦点検出部(４１〜４８)から出力される後述のフォーカス信号に基づいて、ステージ１２のＺ駆動部を制御し、ホルダをＺ方向に上下移動させる。このフォーカス調整により、基板１１（または調整用基板３０）をＣＣＤ撮像素子２５の撮像面に対して合焦させることができる。このとき、基板１１上の重ね合わせマーク１１Ａ（または調整用基板３０上の調整用マーク３０Ａ）は、結像光学系(１９〜２４)の物体面に配置される。   In a state where the substrate 11 (or the adjustment substrate 30) is supported by the holder of the stage 12, the stage control unit 27 controls the XY drive unit of the stage 12 and moves the holder in the XY direction to The upper overlay mark 11A (or the adjustment mark 30A on the adjustment substrate 30) is positioned in the visual field region. Further, based on a focus signal (described later) output from the focus detection unit (41 to 48), the Z drive unit of the stage 12 is controlled to move the holder up and down in the Z direction. By this focus adjustment, the substrate 11 (or the adjustment substrate 30) can be focused on the imaging surface of the CCD image sensor 25. At this time, the overlay mark 11A on the substrate 11 (or the adjustment mark 30A on the adjustment substrate 30) is arranged on the object plane of the imaging optical system (19 to 24).

照明光学系(１３〜１９)は、光源部１３と、光軸Ｏ１に沿って順に配置された照明開口絞り１４とコンデンサーレンズ１５と視野絞り１６と照明リレーレンズ１７とビームスプリッタ１８と、光軸Ｏ２上に配置された第１対物レンズ１９とで構成されている。ビームスプリッタ１８は、反射透過面が光軸Ｏ１に対して略４５°傾けられ、光軸Ｏ２上にも配置されている。照明光学系(１３〜１９)の光軸Ｏ１は、結像光学系(１９〜２４)の光軸Ｏ２に垂直である。   The illumination optical system (13 to 19) includes a light source unit 13, an illumination aperture stop 14, a condenser lens 15, a field stop 16, an illumination relay lens 17, a beam splitter 18, an optical axis, which are arranged in order along the optical axis O1. And a first objective lens 19 disposed on O2. The beam splitter 18 has a reflection / transmission surface inclined by about 45 ° with respect to the optical axis O1, and is also disposed on the optical axis O2. The optical axis O1 of the illumination optical system (13-19) is perpendicular to the optical axis O2 of the imaging optical system (19-24).

また、光源部１３は、光源３Ａとコレクタレンズ３Ｂと光学リレーレンズ３Ｃと波長切替機構３Ｄとライトガイドファイバ３Ｅとで構成される。光源３Ａは、波長帯域の広い光（例えば白色光）を射出する。波長切替機構３Ｄには、透過特性の異なる複数の光学フィルタが設けられる。光学フィルタを切り替えて照明光路に挿入することで、光源３Ａから射出された光の波長帯域のうち、広帯域（例えば本実施形態では波長幅が２７０ｎｍ程度）、長波長帯域、短波長帯域の何れかを選択することができる。   The light source unit 13 includes a light source 3A, a collector lens 3B, an optical relay lens 3C, a wavelength switching mechanism 3D, and a light guide fiber 3E. The light source 3A emits light having a wide wavelength band (for example, white light). The wavelength switching mechanism 3D is provided with a plurality of optical filters having different transmission characteristics. By switching the optical filter and inserting it into the illumination optical path, the wavelength band of the light emitted from the light source 3A is any one of a wide band (for example, a wavelength width of about 270 nm in this embodiment), a long wavelength band, and a short wavelength band. Can be selected.

上記の光源部１３において、光源３Ａから射出された広帯域波長の光は、コレクタレンズ３Ｂを介して波長切替機構３Ｄの光学フィルタに入射し、その透過特性に応じた波長帯域（つまり広帯域または長波長帯域または短波長帯域）の光となる。その後、光学リレーレンズ３Ｃとライトガイドファイバ３Ｅとを介して、照明開口絞り１４に導かれる。
照明開口絞り１４は、その中心が光軸Ｏ１上に位置し、光源部１３から射出された光の径を特定の径に制限する。コンデンサーレンズ１５は、照明開口絞り１４からの光を集光する。視野絞り１６は、重ね合わせ測定装置１０の視野領域を制限する光学素子であり、図１(ｂ)に示すように、矩形状の開口である１つのスリット１６ａを有する。照明リレーレンズ１７は、視野絞り１６のスリット１６ａからの光をコリメートする。ビームスプリッタ１８は、照明リレーレンズ１７からの光を下向きに反射する。 In the light source unit 13, the light having a wide wavelength emitted from the light source 3A is incident on the optical filter of the wavelength switching mechanism 3D via the collector lens 3B, and the wavelength band corresponding to the transmission characteristic (that is, the broadband or long wavelength). Band or short wavelength band). Thereafter, the light is guided to the illumination aperture stop 14 via the optical relay lens 3C and the light guide fiber 3E.
The center of the illumination aperture stop 14 is located on the optical axis O1, and limits the diameter of the light emitted from the light source unit 13 to a specific diameter. The condenser lens 15 condenses the light from the illumination aperture stop 14. The field stop 16 is an optical element that limits the field of view of the overlay measurement apparatus 10, and has one slit 16a that is a rectangular opening as shown in FIG. The illumination relay lens 17 collimates the light from the slit 16 a of the field stop 16. The beam splitter 18 reflects light from the illumination relay lens 17 downward.

上記の構成において、光源部１３から射出された光は、照明開口絞り１４とコンデンサーレンズ１５とを介して、視野絞り１６を均一に照明する。そして、視野絞り１６のスリット１６ａを通過した光は、照明リレーレンズ１７を介してビームスプリッタ１８に導かれ、その反射透過面で反射した後（照明光Ｌ１）、光軸Ｏ２上の第１対物レンズ１９に導かれる。   In the above configuration, the light emitted from the light source unit 13 uniformly illuminates the field stop 16 via the illumination aperture stop 14 and the condenser lens 15. Then, the light that has passed through the slit 16a of the field stop 16 is guided to the beam splitter 18 through the illumination relay lens 17, reflected by its reflection / transmission surface (illumination light L1), and then the first objective on the optical axis O2. Guided to the lens 19.

第１対物レンズ１９は、ビームスプリッタ１８からの照明光Ｌ１を入射して集光する。これにより、ステージ１２上の基板１１（または調整用基板３０）は、第１対物レンズ１９を透過した所定の波長帯域の照明光Ｌ１によって垂直に照明される（落射照明）。
なお、基板１１（または調整用基板３０）に入射するときの照明光Ｌ１の入射角度は、照明開口絞り１４の中心と光軸Ｏ１との位置関係によって決まる。また、基板１１（または調整用基板３０）の各点における照明光Ｌ１の入射角度範囲は、照明開口絞り１４の絞り径によって決まる。照明開口絞り１４が第１対物レンズ１９の仮想瞳面１９Ａと共役な位置関係にあるからである。 The first objective lens 19 receives and collects the illumination light L1 from the beam splitter 18. As a result, the substrate 11 (or the adjustment substrate 30) on the stage 12 is vertically illuminated by the illumination light L1 having a predetermined wavelength band transmitted through the first objective lens 19 (epi-illumination).
The incident angle of the illumination light L1 when entering the substrate 11 (or the adjustment substrate 30) is determined by the positional relationship between the center of the illumination aperture stop 14 and the optical axis O1. Further, the incident angle range of the illumination light L1 at each point of the substrate 11 (or the adjustment substrate 30) is determined by the aperture diameter of the illumination aperture stop 14. This is because the illumination aperture stop 14 has a conjugate positional relationship with the virtual pupil plane 19A of the first objective lens 19.

さらに、視野絞り１６と基板１１（または調整用基板３０）とは共役な位置関係にあるため、基板１１（または調整用基板３０）の表面のうち、視野絞り１６のスリット１６ａに対応する領域が照明光Ｌ１によって照明される。つまり、基板１１（または調整用基板３０）の表面には、照明リレーレンズ１７と第１対物レンズ１９の作用によって、スリット１６ａの像が投影される。   Furthermore, since the field stop 16 and the substrate 11 (or the adjustment substrate 30) are in a conjugate positional relationship, a region corresponding to the slit 16a of the field stop 16 on the surface of the substrate 11 (or the adjustment substrate 30) is present. Illuminated by the illumination light L1. That is, the image of the slit 16 a is projected on the surface of the substrate 11 (or the adjustment substrate 30) by the action of the illumination relay lens 17 and the first objective lens 19.

そして、上記した所定の波長帯域の照明光Ｌ１が照射された基板１１（または調整用基板３０）の領域から、回折光Ｌ２が発生する。回折光Ｌ２には、０次回折光（つまり反射光）や、±１次回折光などが含まれる。回折光Ｌ２の波長特性は、調整用基板３０の場合、調整用マーク３０Ａの外マーク３１と内マーク３２とで等しく、照明光Ｌ１の波長特性とも略等しい。また、基板１１（一般的な製品基板）の場合、重ね合わせマーク１１Ａのレジストマークと下地マークの構造や物性に応じて異なる。これは、マークの反射特性が、マークの構造や物性に応じて変化するからである。基板１１（または調整用基板３０）からの回折光Ｌ２は、後述の結像光学系(１９〜２４)に導かれる。   Then, diffracted light L2 is generated from the region of the substrate 11 (or the adjustment substrate 30) irradiated with the illumination light L1 having the predetermined wavelength band described above. The diffracted light L2 includes 0th order diffracted light (that is, reflected light), ± 1st order diffracted light, and the like. In the case of the adjustment substrate 30, the wavelength characteristic of the diffracted light L2 is the same for the outer mark 31 and the inner mark 32 of the adjustment mark 30A, and is substantially the same as the wavelength characteristic of the illumination light L1. Further, in the case of the substrate 11 (general product substrate), it differs depending on the structure and physical properties of the registration mark and the base mark of the overlay mark 11A. This is because the reflection characteristics of the mark change according to the structure and physical properties of the mark. The diffracted light L2 from the substrate 11 (or the adjustment substrate 30) is guided to an imaging optical system (19 to 24) described later.

結像光学系(１９〜２４)は、光軸Ｏ２に沿って順に配置された第１対物レンズ１９と第２対物レンズ２０と第１結像リレーレンズ２１と平行平面板２２と結像開口絞り２３と第２結像リレーレンズ２４とで構成されている。結像光学系(１９〜２４)の光軸Ｏ２は、Ｚ方向に平行である。なお、第１対物レンズ１９と第２対物レンズ２０との間には、照明光学系(１３〜１９)のビームスプリッタ１８が配置され、第２対物レンズ２０と第１結像リレーレンズ２１との間には、焦点検出部(４１〜４８)のビームスプリッタ４１が配置されている。ビームスプリッタ１８,４１は、光の振幅分離を行うハーフプリズムである。   The imaging optical system (19-24) includes a first objective lens 19, a second objective lens 20, a first imaging relay lens 21, a parallel plane plate 22, and an imaging aperture stop arranged in order along the optical axis O2. 23 and a second imaging relay lens 24. The optical axis O2 of the imaging optical system (19 to 24) is parallel to the Z direction. A beam splitter 18 of the illumination optical system (13 to 19) is disposed between the first objective lens 19 and the second objective lens 20, and the second objective lens 20 and the first imaging relay lens 21 are connected to each other. Between them, the beam splitter 41 of the focus detection units (41 to 48) is arranged. The beam splitters 18 and 41 are half prisms that perform light amplitude separation.

そして、第１対物レンズ１９は、基板１１（または調整用基板３０）からの回折光Ｌ２をコリメートする。第１対物レンズ１９でコリメートされた回折光Ｌ２は、上記のビームスプリッタ１８を透過して第２対物レンズ２０に入射する。第２対物レンズ２０は、ビームスプリッタ１８からの回折光Ｌ２を１次結像面１０ａ上に集光する。
１次結像面１０ａの後段に配置された焦点検出部(４１〜４８)のビームスプリッタ４１は、焦点検出部(４１〜４８)の光軸Ｏ３と結像光学系(１８〜２４)の光軸Ｏ２に対して、反射透過面が略４５°傾けられている。そして、ビームスプリッタ４１は、第２対物レンズ２０からの回折光Ｌ２の一部（Ｌ３）を透過すると共に、残りの一部（Ｌ４）を反射する。ビームスプリッタ４１を透過した一部の光Ｌ３は、結像光学系(１８〜２４)の第１結像リレーレンズ２１に導かれる。第１結像リレーレンズ２１は、ビームスプリッタ４１からの光Ｌ３をコリメートする。 The first objective lens 19 collimates the diffracted light L2 from the substrate 11 (or the adjustment substrate 30). The diffracted light L 2 collimated by the first objective lens 19 passes through the beam splitter 18 and enters the second objective lens 20. The second objective lens 20 condenses the diffracted light L2 from the beam splitter 18 on the primary imaging surface 10a.
The beam splitter 41 of the focus detection unit (41 to 48) disposed at the subsequent stage of the primary image formation surface 10a includes the optical axis O3 of the focus detection unit (41 to 48) and the light of the imaging optical system (18 to 24). The reflection / transmission surface is inclined by approximately 45 ° with respect to the axis O2. The beam splitter 41 transmits a part (L3) of the diffracted light L2 from the second objective lens 20 and reflects the remaining part (L4). A part of the light L3 transmitted through the beam splitter 41 is guided to the first imaging relay lens 21 of the imaging optical system (18 to 24). The first imaging relay lens 21 collimates the light L3 from the beam splitter 41.

平行平面板２２は、光軸Ｏ２に垂直な２つの軸（それぞれＸ軸とＹ軸に平行）を中心として、数度程度の範囲内でチルト可能である。つまり、平行平面板２２の配置は、チルト方向に微調整可能である。Ｘ軸と平行な軸を中心としたチルト方向の微調整について示すと図３のようになる。図３に示す通り、平行平面板２２の光軸２２ａ（厚さ方向に平行な軸）を光軸Ｏ２に対して傾斜させる方向が「チルト方向」に対応する。平行平面板２２の配置のチルト方向の微調整とは、平行平面板２２のチルト角θの微調整に対応する。   The plane parallel plate 22 can be tilted within a range of several degrees around two axes perpendicular to the optical axis O2 (each parallel to the X axis and the Y axis). That is, the arrangement of the plane parallel plate 22 can be finely adjusted in the tilt direction. FIG. 3 shows the fine adjustment of the tilt direction around the axis parallel to the X axis. As shown in FIG. 3, the direction in which the optical axis 22a (axis parallel to the thickness direction) of the plane-parallel plate 22 is tilted with respect to the optical axis O2 corresponds to the “tilt direction”. The fine adjustment of the tilt direction of the arrangement of the plane parallel plate 22 corresponds to the fine adjustment of the tilt angle θ of the plane parallel plate 22.

上記のように、平行平面板２２は、その配置をチルト方向に微調整可能であり（詳細は後述）、第１結像リレーレンズ２１からの光を透過する。結像開口絞り２３は、第１対物レンズ１９の仮想瞳面１９Ａと共役な面に配置され、平行平面板２２からの光の径を特定の径に制限する。第２結像リレーレンズ２４は、結像開口絞り２３からの光をＣＣＤ撮像素子２５の撮像面(２次結像面)上に再結像する。   As described above, the arrangement of the plane parallel plate 22 can be finely adjusted in the tilt direction (details will be described later), and the light from the first imaging relay lens 21 is transmitted. The imaging aperture stop 23 is disposed on a plane conjugate with the virtual pupil plane 19A of the first objective lens 19, and limits the diameter of light from the parallel plane plate 22 to a specific diameter. The second imaging relay lens 24 re-images the light from the imaging aperture stop 23 on the imaging surface (secondary imaging surface) of the CCD image sensor 25.

上記の結像光学系(１８〜２４)では、視野領域内に基板１１上の重ね合わせマーク１１Ａ（または調整用基板３０上の調整用マーク３０Ａ）が位置決めされているとき、そのマークの像をＣＣＤ撮像素子２５の撮像面に形成する。さらに、第１対物レンズ１９の仮想瞳面１９Ａと、結像開口絞り２３の配置面（以下「開口絞り面２３Ａ」）との間に配置された平行平面板２２は、その配置をチルト方向に微調整可能であり、平行平面板２２を用いて結像光学系(１８〜２４)の調整が行われる（詳細は後述）。平行平面板２２は、請求項の「調整用の光学素子」に対応する。   In the imaging optical system (18 to 24), when the overlay mark 11A on the substrate 11 (or the adjustment mark 30A on the adjustment substrate 30) is positioned in the visual field region, an image of the mark is displayed. It is formed on the imaging surface of the CCD imaging device 25. Further, the plane parallel plate 22 arranged between the virtual pupil plane 19A of the first objective lens 19 and the arrangement plane of the imaging aperture stop 23 (hereinafter referred to as “aperture stop plane 23A”) is arranged in the tilt direction. Fine adjustment is possible, and the imaging optical system (18 to 24) is adjusted using the plane parallel plate 22 (details will be described later). The plane parallel plate 22 corresponds to “an optical element for adjustment” in the claims.

ＣＣＤ撮像素子２５は、その撮像面が結像光学系(１８〜２４)の像面と一致するように配置される。ＣＣＤ撮像素子２５は、複数の画素が２次元配列されたエリアセンサであり、基板１１上の重ね合わせマーク１１Ａ（または調整用基板３０上の調整用マーク３０Ａ）の像を撮像して、画像信号を画像処理部２６に出力する。画像信号は、ＣＣＤ撮像素子２５の撮像面における各画素ごとの輝度値に関する分布（輝度分布）を表している。   The CCD image pickup device 25 is arranged such that its image pickup surface coincides with the image surface of the imaging optical system (18 to 24). The CCD image pickup element 25 is an area sensor in which a plurality of pixels are two-dimensionally arranged, picks up an image of the overlay mark 11A on the substrate 11 (or the adjustment mark 30A on the adjustment substrate 30), and outputs an image signal. Is output to the image processing unit 26. The image signal represents a distribution (luminance distribution) related to the luminance value for each pixel on the imaging surface of the CCD imaging device 25.

画像処理部２６は、ＣＣＤ撮像素子２５からの画像信号に基づいて、基板１１上の重ね合わせマーク１１Ａ（または調整用基板３０上の調整用マーク３０Ａ）の画像を取り込み、その画像に対して所定の画像処理を施す。ちなみに、重ね合わせマーク１１Ａの画像に対しては、重ね合わせ検査用の画像処理を施す。調整用マーク３０Ａの画像に対しては、平行平面板２２の配置をチルト方向に微調整する際の指標を求めるために、所定の画像処理（後述）を施す。なお、画像処理部２６を介して、不図示のテレビモニタよる目視観察も可能である。   The image processing unit 26 captures an image of the overlay mark 11A on the substrate 11 (or the adjustment mark 30A on the adjustment substrate 30) based on the image signal from the CCD image pickup device 25, and performs a predetermined process on the image. The image processing is performed. Incidentally, the image of the overlay mark 11A is subjected to image processing for overlay inspection. The image of the adjustment mark 30A is subjected to predetermined image processing (described later) in order to obtain an index when finely adjusting the arrangement of the plane-parallel plate 22 in the tilt direction. Note that visual observation with a television monitor (not shown) is also possible via the image processing unit 26.

次に、焦点検出部(４１〜４８)の説明を行う。焦点検出部(４１〜４８)は、ステージ１２上の基板１１（または調整用基板３０）がＣＣＤ撮像素子２５の撮像面に対して合焦状態にあるか否かを検出するものである。
焦点検出部(４１〜４８)は、光軸Ｏ３に沿って順に配置されたビームスプリッタ４１とＡＦ第１リレーレンズ４２と平行平面板４３と瞳分割ミラー４４とＡＦ第２リレーレンズ４５とシリンドリカルレンズ４６とからなる光学系と、ＡＦセンサ４７と、信号処理部４８とで構成されている。ＡＦセンサ４７はラインセンサであり、その撮像面４７ａには複数の画素が１次元配列されている。シリンドリカルレンズ４６は、ＡＦセンサ４７の撮像面４７ａにおける画素の配列方向（図中Ａ方向）に対して垂直な方向の屈折力を持つ。 Next, the focus detection units (41 to 48) will be described. The focus detection units (41 to 48) detect whether or not the substrate 11 (or the adjustment substrate 30) on the stage 12 is in focus with respect to the imaging surface of the CCD image sensor 25.
The focus detection units (41 to 48) include a beam splitter 41, an AF first relay lens 42, a parallel plane plate 43, a pupil division mirror 44, an AF second relay lens 45, and a cylindrical lens arranged in order along the optical axis O3. 46, an AF sensor 47, and a signal processing unit 48. The AF sensor 47 is a line sensor, and a plurality of pixels are arranged one-dimensionally on the imaging surface 47a. The cylindrical lens 46 has a refractive power in a direction perpendicular to the pixel arrangement direction (A direction in the figure) on the imaging surface 47 a of the AF sensor 47.

焦点検出部(４１〜４８)において、ビームスプリッタ４１で反射した一部の光Ｌ４（以下「ＡＦ光」という）は、ＡＦ第１リレーレンズ４２によってコリメートされ、平行平面板４３を透過して、瞳分割ミラー４４に入射する。瞳分割ミラー４４上には、照明光学系(１３〜１９)の照明開口絞り１４の像が形成される。平行平面板４３は、照明開口絞り１４の像を瞳分割ミラー４４の中心に位置調整するための光学素子であり、チルト調整が可能な機構になっている。   In the focus detection unit (41 to 48), a part of the light L4 reflected by the beam splitter 41 (hereinafter referred to as “AF light”) is collimated by the AF first relay lens 42, passes through the parallel plane plate 43, and The light enters the pupil division mirror 44. On the pupil division mirror 44, an image of the illumination aperture stop 14 of the illumination optical system (13 to 19) is formed. The plane parallel plate 43 is an optical element for adjusting the position of the image of the illumination aperture stop 14 at the center of the pupil division mirror 44, and has a mechanism capable of tilt adjustment.

瞳分割ミラー４４に入射したＡＦ光は、そこで２方向の光に振幅分離された後、ＡＦ第２リレーレンズ４５とシリンドリカルレンズ４６を介して、ＡＦセンサ４７の撮像面４７ａの近傍に集光される。このとき、撮像面４７ａには、画素の配列方向（図中Ａ方向）に沿って離れた位置に、計測方向に対して２つの視野絞り１６の像が形成される。
そして、ＡＦセンサ４７は、撮像面４７ａに形成された２つの像の結像中心に関する受光信号を信号処理部４８に出力する。信号処理部４８は、ＡＦセンサ４７からの出力に基づいて、計測方向について２つの視野絞り１６の像の結像中心の距離を算出し、予め記憶している合焦状態での距離との差を求め、フォーカス信号をステージ制御部２７に出力する。このような瞳分割方式のＡＦ動作の詳細は、例えば特開２００２−４０３２２号公報に記載されている。 The AF light incident on the pupil division mirror 44 is separated into light in two directions there, and then condensed in the vicinity of the imaging surface 47a of the AF sensor 47 via the AF second relay lens 45 and the cylindrical lens 46. The At this time, on the imaging surface 47a, images of the two field stops 16 are formed in the measurement direction at positions separated along the pixel arrangement direction (A direction in the figure).
Then, the AF sensor 47 outputs a light reception signal regarding the imaging center of the two images formed on the imaging surface 47 a to the signal processing unit 48. Based on the output from the AF sensor 47, the signal processing unit 48 calculates the distance between the imaging centers of the images of the two field stops 16 in the measurement direction, and the difference from the distance in the in-focus state stored in advance. And a focus signal is output to the stage control unit 27. Details of such an AF operation of the pupil division method are described in, for example, JP-A-2002-40322.

ところで、上記のように構成された重ね合わせ測定装置１０（図１）において、結像光学系(１８〜２４)の各光学部品を配置する際には、各光学部品を金物で固定し、そのブロックをコリメータなどの器具により調整しながら光軸Ｏ２に対して平行に配置していく。しかし、ブロックの加工精度や調整誤差などに起因して、各光学部品が偏心誤差を持つことがある。   By the way, in the overlay measuring apparatus 10 (FIG. 1) configured as described above, when the optical components of the imaging optical system (18 to 24) are arranged, the optical components are fixed with hardware. The blocks are arranged in parallel to the optical axis O2 while being adjusted with a tool such as a collimator. However, each optical component may have an eccentric error due to block processing accuracy or adjustment error.

光学部品の偏心誤差が、結像光学系(１８〜２４)の仮想瞳面１９Ａと開口絞り面２３Ａとの間に発生した場合、その偏心誤差に起因して、開口絞り面２３Ａにおける瞳像の結像位置が波長帯域に応じて異なってしまう。このような場合の瞳像の位置関係を模式的に示すと、図４のようになる。図４には、照明光Ｌ１の中心波長帯域に相当する瞳像ＨGと、短波長帯域に相当する瞳像ＨBと、長波長帯域に相当する瞳像ＨRとの位置関係を示す。図４の瞳像ＨR,ＨG,ＨBは、結像開口絞り２３Ａに入射する回折光Ｌ３のうち、同じ回折次数の成分（例えば０次回折成分）である。 When an eccentric error of the optical component occurs between the virtual pupil surface 19A of the imaging optical system (18 to 24) and the aperture stop surface 23A, the pupil image of the aperture stop surface 23A is caused by the eccentric error. The imaging position varies depending on the wavelength band. FIG. 4 schematically shows the positional relationship of the pupil image in such a case. FIG. 4 shows the pupil image H G corresponding to the center wavelength band of the illumination light L1, and the pupil image H B corresponding to the short wavelength band, the positional relationship between the pupil image H R corresponding to the long wavelength band. The pupil images H R , H G , and H B in FIG. 4 are components of the same diffraction order (for example, a 0th-order diffraction component) in the diffracted light L3 incident on the imaging aperture stop 23A.

また、開口絞り面２３Ａにおける瞳像ＨR,ＨG,ＨBの結像位置ずれ（図４）を引き起こす場合の一例として、図５に示すようなビームスプリッタ１８の偏心誤差（チルト誤差）が考えられる。図５では、光軸Ｏ２上の光学部品のうちビームスプリッタ４１の図示を省略し、平行平面板２２のチルト角θ＝０（図３(ａ)と同様）とした。また、図５には、回折光Ｌ３のうち、短波長帯域の回折光ＬBの光路と、長波長帯域の回折光ＬRの光路とを分けて示した。 In addition, as an example of causing an imaging position shift (FIG. 4) of the pupil images H R , H G , H B on the aperture stop surface 23A, an eccentric error (tilt error) of the beam splitter 18 as shown in FIG. Conceivable. In FIG. 5, the illustration of the beam splitter 41 among the optical components on the optical axis O2 is omitted, and the tilt angle θ = 0 of the parallel flat plate 22 (similar to FIG. 3A). Further, in FIG. 5, in the diffracted light L3, the optical path of the diffracted light L B of the short wavelength band, showing separately the optical path of the diffracted light L R of the long wavelength band.

図５から分かるように、例えばビームスプリッタ１８が偏心誤差を持つ場合、平行平面板２２の微調整を行わないと（つまりチルト角θ＝０に設定すると）、短波長帯域の回折光ＬBと長波長帯域の回折光ＬRとが位置ずれした状態のまま開口絞り面２３Ａに入射し、開口絞り面２３Ａにおける瞳像ＨR,ＨG,ＨBの結像位置ずれ（図４）が起きる。なお、ビームスプリッタ１８に限らず、第２対物レンズ２０やビームスプリッタ４１や第１結像リレーレンズ２１が偏心誤差を持つ場合も同様である。 As can be seen from FIG. 5, for example when the beam splitter 18 has an eccentric error, not to perform fine adjustment of the parallel flat plate 22 (that is set to the tilt angle theta = 0), and the diffracted light L B of the short wavelength band The long-wavelength band diffracted light L R is incident on the aperture stop surface 23A while being shifted in position, and image formation position shifts of the pupil images H R , H G , H B on the aperture stop surface 23A occur (FIG. 4). . The same applies to the case where the second objective lens 20, the beam splitter 41, and the first imaging relay lens 21 are not limited to the beam splitter 18, but have an eccentric error.

そして、開口絞り面２３Ａにおける瞳像ＨR,ＨG,ＨBの結像位置が波長帯域に応じて異なると（図４）、そこに配置されている結像開口絞り２３を各波長帯域の回折光Ｌ３が通過する際、波長帯域ごとにケラレの対称/非対称性が異なることになる。例えば、中心波長帯域のケラレが対称な場合には、短波長帯域のケラレも長波長帯域のケラレも非対称となってしまう。 If the imaging positions of the pupil images H R , H G , and H B on the aperture stop surface 23A differ depending on the wavelength band (FIG. 4), the imaging aperture stop 23 arranged there is moved to each wavelength band. When the diffracted light L3 passes, the symmetry / asymmetric property of vignetting differs for each wavelength band. For example, when the vignetting in the central wavelength band is symmetric, the vignetting in the short wavelength band and the vignetting in the long wavelength band are asymmetric.

ケラレが非対称な場合とは、図６(ａ)に示す通り、結像開口絞り２３の中心Ｃ23に対して、瞳像Ｈの中心ＣHの位置がずれている場合である。図６(ａ)では、瞳像Ｈの０次回折成分と±１次回折成分とを例示した。図６(ａ)の場合、瞳像Ｈのうち、＋１次回折成分の一部（点ハッチング部）は、結像開口絞り２３により遮られてケラレとなっているが、−１次回折成分は、結像開口絞り２３による制限を受けない。このため、瞳像Ｈの中心ＣHに関して、ケラレが非対称となる。 And if vignetting is asymmetric is the case as shown in FIG. 6 (a), that with respect to the center C 23 of the imaging aperture stop 23, are out of position of the center C H of the pupil image H. FIG. 6A illustrates the 0th-order diffraction component and the ± 1st-order diffraction component of the pupil image H. In the case of FIG. 6A, a part (point hatched portion) of the + 1st order diffraction component of the pupil image H is blocked by the image forming aperture stop 23, but the -1st order diffraction component is The image forming aperture stop 23 is not limited. For this reason, the vignetting is asymmetric with respect to the center C H of the pupil image H.

これに対し、ケラレが対称な場合とは、図７(ａ)に示す通り、瞳像Ｈの中心ＣHの位置が結像開口絞り２３の中心Ｃ23に一致している場合である。図７(ａ)でも、瞳像Ｈの０次回折成分と±１次回折成分とを例示した。図７(ａ)の場合には、瞳像Ｈのうち、＋１次回折成分と−１次回折成分の一部（点ハッチング部）が、同じ量だけ、結像開口絞り２３により遮られてケラレとなっている。このため、瞳像Ｈの中心ＣHに関して、ケラレが対称となる。 In contrast, in the case vignetting is symmetric is the case as shown in FIG. 7 (a), the position of the center C H of the pupil image H is coincident with the center C 23 of the imaging aperture stop 23. FIG. 7A also illustrates the 0th-order diffraction component and the ± 1st-order diffraction component of the pupil image H. In the case of FIG. 7A, a part of the + 1st order diffracted component and the −1st order diffracted component (point hatched portion) of the pupil image H are blocked by the imaging aperture stop 23 by the same amount and vignetted. It has become. Therefore, with respect to the center C H of the pupil image H, vignetting is symmetrical.

また、ケラレが非対称な場合（図６(ａ)）、結像開口絞り２３を通過した後の回折光Ｌ３を考えると、０次回折成分と−１次回折成分の光量は変化しないが、＋１次回折成分の光量は低下することになる。すなわち、−１次回折成分と比べて＋１次回折成分の光量が少なくなる。これは、そもそも、結像光学系(１９〜２４)の物体面に配置された図６(ｂ)のような凹凸構造のマークから回折光Ｌ２が発生するとき、−１次回折成分よりも＋１次回折成分の光量が少なくなり、左右のエッジ像に関する結像状態に差が現れる。   Further, when the vignetting is asymmetric (FIG. 6A), considering the diffracted light L3 after passing through the imaging aperture stop 23, the light amounts of the 0th-order diffraction component and the −1st-order diffraction component do not change, but +1 The light amount of the next diffraction component will decrease. That is, the light amount of the + 1st order diffraction component is smaller than that of the −1st order diffraction component. In the first place, when the diffracted light L2 is generated from the concavo-convex structure mark as shown in FIG. 6B arranged on the object plane of the imaging optical system (19 to 24), it is +1 from the −1st order diffraction component. The light amount of the next diffraction component is reduced, and a difference appears in the imaging state regarding the left and right edge images.

さらに、上記のような回折光Ｌ２の非対称性が起きると、図６(ｂ)に示すマークの２つのエッジＥ１,Ｅ２の見え方が異なってしまう。そのため、結像光学系(１８〜２４)を介してＣＣＤ撮像素子２５の撮像面に形成されたエッジＥ１,Ｅ２の像の強度プロファイルは、図６(ｃ)のような歪み（左右のアンバランス）を含むことになる。この場合、ＣＣＤ撮像素子２５からの画像信号に基づいて、図６(ｂ)に示すマークの位置を検出すると、検出結果には、左右のエッジ像のアンバランスに応じた誤差成分（ＴＩＳ値）が含まれてしまう。   Further, when the asymmetry of the diffracted light L2 as described above occurs, the appearance of the two edges E1 and E2 of the mark shown in FIG. Therefore, the intensity profile of the images of the edges E1 and E2 formed on the imaging surface of the CCD imaging device 25 via the imaging optical system (18 to 24) is distorted as shown in FIG. ) Will be included. In this case, when the position of the mark shown in FIG. 6B is detected based on the image signal from the CCD image sensor 25, the detection result includes an error component (TIS value) corresponding to the imbalance between the left and right edge images. Will be included.

一方、ケラレが対称な場合（図７(ａ)）、結像開口絞り２３を通過した後の回折光Ｌ３を考えると、０次回折成分の光量は変化しないが、−１次回折成分と＋１次回折成分の光量は同じ量だけ低下する。
さらに、上記のような回折光Ｌ２の対称性が保たれると、図７(ｂ)に示すマークの２つのエッジＥ１,Ｅ２の見え方が同じになる。つまり、一方のエッジＥ１は−１次回折成分の光量確保によって良く見え、他方のエッジＥ２は＋１次回折成分の光量確保によって良く見えることになる。そのため、結像光学系(１８〜２４)を介してＣＣＤ撮像素子２５の撮像面に形成されたエッジＥ１,Ｅ２の像の強度プロファイルは、図７(ｃ)のように、左右で等しくなる（バランスする）ことになる。この場合、ＣＣＤ撮像素子２５からの画像信号に基づいて、図７(ｂ)に示すマークの位置を検出すると、誤差成分（ＴＩＳ値）を含まない正確な検出結果を得ることができる。 On the other hand, when the vignetting is symmetric (FIG. 7A), considering the diffracted light L3 after passing through the imaging aperture stop 23, the light amount of the 0th-order diffraction component does not change, but the −1st-order diffraction component and +1 The light amount of the next diffraction component decreases by the same amount.
Further, when the symmetry of the diffracted light L2 as described above is maintained, the two edges E1 and E2 of the mark shown in FIG. That is, one edge E1 looks good by securing the light amount of the −1st order diffraction component, and the other edge E2 looks good by securing the light amount of the + 1st order diffraction component. Therefore, the intensity profiles of the images of the edges E1 and E2 formed on the imaging surface of the CCD image sensor 25 via the imaging optical system (18 to 24) are equal on the left and right as shown in FIG. Balance). In this case, when the position of the mark shown in FIG. 7B is detected based on the image signal from the CCD image sensor 25, an accurate detection result that does not include an error component (TIS value) can be obtained.

したがって、既に説明した通り、開口絞り面２３Ａにおける瞳像ＨR,ＨG,ＨBの結像位置が波長帯域に応じて異なると（図４）、波長帯域ごとにケラレの対称/非対称性が異なるため（図６(ａ),図７(ａ)）、同じマーク（図６(ｂ),図７(ｂ)）のエッジＥ１,Ｅ２の像であっても、その強度プロファイル（図６(ｃ),図７(ｃ)）は波長帯域ごとに左右のバランス/アンバランスが異なってしまう。例えば、中心波長帯域のケラレが対称で、長波長帯域や短波長帯域のケラレが非対称な場合、前者のエッジ像の強度プロファイルは図７(ｃ)のようになり、後者のエッジ像の強度プロファイルは図６(ｃ)のようになる。 Therefore, as described above, if the imaging positions of the pupil images H R , H G , and H B on the aperture stop surface 23A differ depending on the wavelength band (FIG. 4), the vignetting symmetry / asymmetric property is different for each wavelength band. Since they are different (FIGS. 6A and 7A), even the images of the edges E1 and E2 of the same mark (FIGS. 6B and 7B) have their intensity profiles (FIG. In FIG. 7 (c)), the left / right balance / unbalance differs for each wavelength band. For example, when the vignetting in the center wavelength band is symmetric and the vignetting in the long wavelength band or short wavelength band is asymmetric, the intensity profile of the former edge image is as shown in FIG. 7C, and the intensity profile of the latter edge image. Is as shown in FIG.

その結果、ケラレの対称な中心波長帯域では、マーク位置の正確な検出結果を得ることができるのに対し、ケラレの非対称な長波長帯域や短波長帯域では、マーク位置の検出結果が誤差成分（ＴＩＳ値）を含む不正確なものとなってしまう。
ちなみに、長波長帯域におけるケラレの非対称性が図６(ａ)のような方向特性を持つ場合、短波長帯域におけるケラレの非対称性は、図８(ａ)のような反転した方向特性を持つことになる。そして、マークから発生する回折光Ｌ２の各成分の光量と、エッジＥ１,Ｅ２の像の強度プロファイルは、図８(ｂ),(ｃ)のようになる。このため、短波長帯域におけるマーク位置の検出結果の誤差成分（ＴＩＳ値）は、長波長帯域におけるマーク位置の検出結果の誤差成分（ＴＩＳ値）とは反転した方向特性を持つことになる。 As a result, an accurate detection result of the mark position can be obtained in the symmetric center wavelength band of the vignetting, whereas the detection result of the mark position is an error component (in the asymmetrical long wavelength band and short wavelength band of the vignetting. Inaccurate data including TIS value.
Incidentally, when the vignetting asymmetry in the long wavelength band has a directional characteristic as shown in FIG. 6A, the vignetting asymmetry in the short wavelength band has an inverted directional characteristic as shown in FIG. become. The light intensity of each component of the diffracted light L2 generated from the mark and the intensity profiles of the images of the edges E1 and E2 are as shown in FIGS. For this reason, the error component (TIS value) of the mark position detection result in the short wavelength band has a directional characteristic that is reversed from the error component (TIS value) of the mark position detection result in the long wavelength band.

次に、本実施形態の結像光学系(１８〜２４)の調整方法について説明する。結像光学系(１８〜２４)の調整は、開口絞り面２３Ａにおける瞳像ＨR,ＨG,ＨBの波長帯域に応じた結像位置ずれ（図４）を補正し、波長帯域に拘わらず同一の結像位置（例えば図７の位置）に瞳像ＨR,ＨG,ＨBを形成するために行われる。この調整には、図２に示す調整用基板３０と、結像光学系(１８〜２４)の仮想瞳面１９Ａと開口絞り面２３Ａとの間に配置された平行平面板２２とが用いられる。 Next, a method for adjusting the imaging optical system (18 to 24) of this embodiment will be described. The adjustment of the imaging optical system (18 to 24) corrects an imaging position shift (FIG. 4) corresponding to the wavelength bands of the pupil images H R , H G , and H B on the aperture stop surface 23A, and depends on the wavelength band. This is performed to form pupil images H R , H G , and H B at the same imaging position (for example, the position in FIG. 7). For this adjustment, the adjustment substrate 30 shown in FIG. 2 and the plane parallel plate 22 disposed between the virtual pupil plane 19A of the imaging optical system (18 to 24) and the aperture stop plane 23A are used.

調整用基板３０（図２）に設けられている調整用マーク３０Ａは、既に説明した通り、外マーク３１と内マーク３２とで構成され、外マーク３１のピッチＰ１が例えば３.８μｍであり、内マーク３２のピッチＰ２が例えば１μｍである。このようなピッチＰ１,Ｐ２は、照明光学系(１３〜１９)の開口数をＮＡill、結像光学系(１９〜２４)の開口数をＮＡima、照明光Ｌ１の中心波長をλ(μｍ)とするとき、次の条件式(１)〜(３)を満足する。   As described above, the adjustment mark 30A provided on the adjustment substrate 30 (FIG. 2) is composed of the outer mark 31 and the inner mark 32, and the pitch P1 of the outer mark 31 is, for example, 3.8 μm. The pitch P2 of the inner marks 32 is 1 μm, for example. With such pitches P1 and P2, the numerical aperture of the illumination optical system (13 to 19) is NAill, the numerical aperture of the imaging optical system (19 to 24) is NAima, and the center wavelength of the illumination light L1 is λ (μm). The following conditional expressions (1) to (3) are satisfied.

ＮＡima ＞ ＮＡill …(１)
ＮＡima−１.２×ＮＡill ＝ λ/Ｐ１ …(２)
ＮＡima＋ＮＡill/２ ＝ λ/Ｐ２ …(３)
条件式(１)を満足する場合、結像光学系(１９〜２４)の開口絞り面２３Ａにおける瞳像Ｈ（図６〜図８参照）の大きさは、各成分ごとに結像開口絞り２３より小さくなる。 NAima> NAill (1)
NAima-1.2 × NAill = λ / P1 (2)
NAima + NAill / 2 = λ / P2 (3)
When the conditional expression (1) is satisfied, the size of the pupil image H (see FIGS. 6 to 8) on the aperture stop surface 23A of the image forming optical system (19 to 24) is the image forming aperture stop 23 for each component. Smaller.

条件式(２)は、調整用マーク３０Ａの外マーク３１に関する。条件式(２)を満足する場合、開口絞り面２３Ａにおける外マーク３１の波長λの瞳像Ｈ31は、図９(ａ)に示す通り、０次回折成分と±１次回折成分との全てが結像開口絞り２３の内側に余裕を持って入射する。図９(ａ)には、瞳像Ｈ31の中心ＣHの位置が結像開口絞り２３の中心Ｃ23に一致しているときの位置関係を示した。 Conditional expression (2) relates to the outer mark 31 of the adjustment mark 30A. When the conditional expression (2) is satisfied, the pupil image H 31 of the wavelength λ of the outer mark 31 on the aperture stop surface 23A is all of the 0th-order diffraction component and the ± 1st-order diffraction component as shown in FIG. Is incident on the inside of the imaging aperture stop 23 with a margin. FIG. 9A shows the positional relationship when the position of the center C H of the pupil image H 31 coincides with the center C 23 of the imaging aperture stop 23.

また、条件式(２)を満足する場合、図４に示す波長帯域ごとの瞳像ＨR,ＨG,ＨBの結像位置ずれがあっても、波長帯域に拘わらず０次回折成分と±１次回折成分との全てを結像開口絞り２３の内側に入射させることができる。つまり、外マーク３１では、照明光Ｌ１の中心波長λだけでなく、長波長帯域と短波長帯域との何れにおいても、ケラレの対称性を保つことができる（図７参照）。 Further, when the conditional expression (2) is satisfied, even if there is an image formation position shift of the pupil images H R , H G , H B for each wavelength band shown in FIG. All of the ± first-order diffraction components can be incident on the inside of the imaging aperture stop 23. That is, the outer mark 31 can maintain vignetting symmetry not only in the center wavelength λ of the illumination light L1, but also in both the long wavelength band and the short wavelength band (see FIG. 7).

一方、条件式(３)は、調整用マーク３０Ａの内マーク３２に関する。条件式(３)を満足する場合、開口絞り面２３Ａにおける内マーク３２の波長λの瞳像Ｈ32は、図９(ｂ)に示す通り、０次回折成分が結像開口絞り２３の内側に入射し、±１次回折成分が結像開口絞り２３の外側に入射する。図９(ｂ)には、瞳像Ｈ32の中心ＣHの位置が結像開口絞り２３の中心Ｃ23に一致しているときの位置関係を示した。この場合、ケラレの対称性が保たれている。 On the other hand, the conditional expression (3) relates to the inner mark 32 of the adjustment mark 30A. When the conditional expression (3) is satisfied, the pupil image H 32 of the wavelength λ of the inner mark 32 on the aperture stop surface 23A has a 0th-order diffraction component inside the imaging aperture stop 23 as shown in FIG. Incidently, ± 1st order diffraction components are incident outside the imaging aperture stop 23. FIG. 9B shows a positional relationship when the position of the center C H of the pupil image H 32 coincides with the center C 23 of the imaging aperture stop 23. In this case, the vignetting symmetry is maintained.

また、条件式(３)を満足する場合、図４に示す波長帯域ごとの瞳像ＨR,ＨG,ＨBの結像位置ずれがあると、長波長帯域では瞳像Ｈ32の中心ＣHが結像開口絞り２３の中心Ｃ23よりも図中左方にシフトし（図６参照）、短波長帯域では反対に瞳像Ｈ32の中心ＣHが結像開口絞り２３の中心Ｃ23よりも図中右方にシフトする（図８参照）ため、ケラレの対称性が崩れて非対称となる。 Further, when the conditional expression (3) is satisfied, if there is an imaging position shift of the pupil images H R , H G , H B for each wavelength band shown in FIG. 4, the center C of the pupil image H 32 in the long wavelength band. H is shifted to the left in the figure from the center C 23 of the imaging aperture stop 23 (see FIG. 6), the center C 23 of the center C H is imaging aperture stop 23 of the pupil image H 32 as opposed to the short wavelength band Since it shifts to the right in the figure (see FIG. 8), the symmetry of the vignetting is broken and becomes asymmetric.

本実施形態の結像光学系(１８〜２４)の調整方法では、上記のような内マーク３２における波長帯域ごとのケラレの対称/非対称性を加味して、結像光学系(１９〜２４)を調整する際の指標を求め、その指標に基づいて平行平面板２２の配置をチルト方向に微調整する（図３参照）。結像光学系(１８〜２４)の調整は、図１０のフローチャートの手順にしたがって行われる。   In the adjustment method of the imaging optical system (18 to 24) of the present embodiment, the imaging optical system (19 to 24) is added in consideration of the vignetting symmetry / asymmetry for each wavelength band in the inner mark 32 as described above. An index for adjusting is obtained, and the arrangement of the plane-parallel plate 22 is finely adjusted in the tilt direction based on the index (see FIG. 3). Adjustment of the imaging optical system (18 to 24) is performed according to the procedure of the flowchart of FIG.

ステップＳ１では、ステージ１２のホルダに調整用基板３０を載置し、重ね合わせ測定装置１０の視野領域内に調整用マーク３０Ａを位置決めする。この位置決め後、焦点検出部(４１〜４８)からのフォーカス信号に基づいてＡＦ動作を行い、調整用マーク３０ＡをＣＣＤ撮像素子２５の撮像面に対して合焦させる。つまり、結像光学系(１９〜２４)の物体面に調整用マーク３０Ａを配置する。   In step S <b> 1, the adjustment substrate 30 is placed on the holder of the stage 12, and the adjustment mark 30 </ b> A is positioned in the visual field region of the overlay measurement apparatus 10. After this positioning, an AF operation is performed based on the focus signal from the focus detectors (41 to 48), and the adjustment mark 30A is focused on the imaging surface of the CCD image sensor 25. That is, the adjustment mark 30A is arranged on the object plane of the imaging optical system (19 to 24).

ステップＳ２では、調整用マーク３０Ａに対して広帯域の照明光Ｌ１（例えば波長幅が２７０ｎｍ程度）を照射し、このとき調整用マーク３０Ａから発生する広帯域の回折光Ｌ２に基づいて、マーク画像を取り込む。マーク画像の取り込みは、調整用マーク３０Ａを１８０度回転させる前後の状態の各々で行う。そして、２つのマーク画像の輝度情報に基づいて、各々、外マーク３１と内マーク３２との位置ずれ量を算出する。   In step S2, the adjustment mark 30A is irradiated with broadband illumination light L1 (for example, a wavelength width of about 270 nm), and a mark image is captured based on the broadband diffracted light L2 generated from the adjustment mark 30A at this time. . The mark image is captured in each of the states before and after the adjustment mark 30A is rotated 180 degrees. Then, based on the luminance information of the two mark images, the amount of positional deviation between the outer mark 31 and the inner mark 32 is calculated.

さらに、次の式(４)にしたがって、０度方向（初期状態）での位置ずれ量Ｌ0と、１８０度方向での位置ずれ量Ｌ180との平均値を、ＴＩＳ値として算出する。このＴＩＳ値は、開口絞り面２３Ａにおける広帯域の瞳像（図９に示す中心波長λの瞳像Ｈ31や瞳像Ｈ32の他、長波長帯域や短波長帯域の瞳像を含む）の中心波長λの中心ＣHと、結像開口絞り２３の中心Ｃ23との位置ずれを表している。 Further, according to the following equation (4), the positional deviation amount L 0 at the 0-degree direction (initial state), the average value of the positional deviation amount L 180 in the direction of 180 degrees, is calculated as a TIS value. This TIS value is the center of a wide-band pupil image (including the pupil image H 31 and pupil image H 32 of the center wavelength λ shown in FIG. 9 as well as the pupil image of the long wavelength band and the short wavelength band) shown in FIG. it represents the center C H wavelength lambda, the positional deviation between the center C 23 of the imaging aperture stop 23.

ＴＩＳ＝（Ｌ0＋Ｌ180）/２ …(４)
ステップＳ３では、ステップＳ２で算出したＴＩＳ値（つまり瞳像の中心波長λの中心ＣHの位置ずれ）を、予め定めた閾値と比較する。閾値は、十分に小さい規格値である。そして、ＴＩＳ値が閾値より大きい場合（Ｓ３がＮｏ）、このＴＩＳ値を指標として、結像開口絞り２３の配置をシフト方向に微調整する（ステップＳ４）。その後、ステップＳ２の処理に戻る。上記したステップＳ２〜Ｓ４の処理は、ＴＩＳ値（つまり瞳像の中心波長λの中心ＣHの位置ずれ）が閾値より小さくなる（Ｓ３がＹｅｓとなる）まで繰り返し行われる。 TIS = (L 0 + L 180 ) / 2 (4)
In step S3, the calculated TIS value in step S2 (that positional deviation of the center C H of the center wavelength λ of the pupil image), is compared with a predetermined threshold value. The threshold value is a sufficiently small standard value. If the TIS value is larger than the threshold (S3 is No), the arrangement of the imaging aperture stop 23 is finely adjusted in the shift direction using the TIS value as an index (step S4). Thereafter, the process returns to step S2. Process of step S2~S4 described above are, TIS value (i.e. positional deviation of the center C H of the center wavelength λ of the pupil image) is smaller than the threshold value (S3 becomes Yes) is repeated until.

ステップＳ２で算出したＴＩＳ値が閾値より小さくなったとき、瞳像の中心波長λの中心ＣHと結像開口絞り２３の中心Ｃ23とは、図９(ａ),(ｂ)に示す通り、互いに略一致したことになる。この場合、中心波長λにおけるケラレは、調整用マーク３０Ａの外マーク３も内マーク３２も対称となる。外マーク３１のケラレの対称性は、瞳像Ｈ31の±１次回折成分の全てが結像開口絞り２３の内側に入射したことによる。また、内マーク３２のケラレの対称性は、瞳像Ｈ32の±１次回折成分の全てが結像開口絞り２３の外側に入射したことによる。 When the TIS value calculated in step S2 is smaller than the threshold value, the center C H of the center wavelength λ of the pupil image and the center C 23 of the imaging aperture stop 23 are as shown in FIGS. 9 (a) and 9 (b). , They are almost identical to each other. In this case, the vignetting at the center wavelength λ is symmetrical for both the outer mark 3 and the inner mark 32 of the adjustment mark 30A. The vignetting symmetry of the outer mark 31 is due to the fact that all ± first-order diffraction components of the pupil image H 31 are incident on the inside of the imaging aperture stop 23. Further, the vignetting symmetry of the inner mark 32 is due to the fact that all ± first-order diffraction components of the pupil image H 32 are incident on the outside of the imaging aperture stop 23.

次のステップＳ５では、照明光Ｌ１の波長帯域を変更し、調整用マーク３０Ａに対して短波長帯域の照明光Ｌ１を照射し、このとき調整用マーク３０Ａから発生する短波長帯域の回折光Ｌ２に基づいて、マーク画像を取り込む。短波長帯域の回折光Ｌ２には、外マーク３１のピッチＰ１に応じた広がり角で発生した光と、内マーク３２のピッチＰ２に応じた広がり角で発生した光とが含まれる。そして、この回折光Ｌ２のうち、結像開口絞り２３を通過して結像光学系(１９〜２４)の像面に到達した光に基づいて、マーク画像の取り込みが行われる。   In the next step S5, the wavelength band of the illumination light L1 is changed, and the adjustment mark 30A is irradiated with the short wavelength band illumination light L1, and at this time, the short wavelength band diffracted light L2 generated from the adjustment mark 30A. Based on the above, a mark image is captured. The diffracted light L2 in the short wavelength band includes light generated at a spread angle corresponding to the pitch P1 of the outer mark 31 and light generated at a spread angle corresponding to the pitch P2 of the inner mark 32. Of the diffracted light L2, the mark image is captured based on the light that has passed through the imaging aperture stop 23 and has reached the image plane of the imaging optical system (19 to 24).

図４に示す波長帯域ごとの瞳像ＨR,ＨG,ＨBの結像位置ずれがある場合、短波長帯域の回折光Ｌ２による外マーク３１の瞳像は、図９(ａ)に示す中心波長λの瞳像Ｈ31よりも図中右方にシフトするが、上記の条件式(２)を満足するため、−１次回折成分が結像開口絞り２３の外側にはみ出すことはない。したがって、外マーク３１では、短波長帯域でもケラレの対称性を保つことができる。この場合、マーク画像の外マーク３１の輝度情報は、その強度プロファイルが左右で等しくなる（図７(ｃ)参照）。 When there is an imaging position shift of the pupil images H R , H G , H B for each wavelength band shown in FIG. 4, the pupil image of the outer mark 31 by the diffracted light L2 in the short wavelength band is shown in FIG. Although it shifts to the right in the figure with respect to the pupil image H 31 having the center wavelength λ, since the conditional expression (2) is satisfied, the −1st order diffraction component does not protrude outside the imaging aperture stop 23. Therefore, the outer mark 31 can maintain vignetting symmetry even in a short wavelength band. In this case, the intensity information of the outer mark 31 of the mark image has the same intensity profile on the left and right (see FIG. 7C).

一方、内マーク３２の場合には上記の条件式(３)を満足するため、短波長帯域の回折光Ｌ２による瞳像は、図９(ｂ)に示す中心波長λの瞳像Ｈ32よりも図中右方にシフトして、＋１次回折成分の一部が結像開口絞り２３の内側に入射する。つまり、＋１次回折成分のケラレ量が減少し、−１次回折成分のケラレ量は変化しない。したがって、内マーク３２では、短波長帯域においてケラレが非対称となってしまう。この場合、マーク画像の内マーク３２の輝度情報は、その強度プロファイルが歪み（左右のアンバランス）を含むことになる（図６(ｃ)参照）。 On the other hand, in the case of the inner mark 32 which satisfies the above conditional expression (3), the pupil image by the diffracted light L2 of the short wavelength band, than pupil image H 32 of center wavelength λ shown in FIG. 9 (b) Shifting to the right in the figure, a part of the + 1st order diffraction component is incident on the inside of the imaging aperture stop 23. That is, the amount of vignetting of the + 1st order diffraction component decreases, and the amount of vignetting of the −1st order diffraction component does not change. Therefore, in the inner mark 32, the vignetting becomes asymmetric in the short wavelength band. In this case, the intensity information of the inner mark 32 in the mark image includes distortion (left and right imbalance) in the intensity profile (see FIG. 6C).

短波長帯域の照明光Ｌ１を用いたマーク画像の取り込みも、調整用マーク３０Ａを１８０度回転させる前後の状態の各々で行う。そして、２つのマーク画像の輝度情報に基づいて、外マーク３１に関わる輝度情報の対称/非対称性を加味すると共に、内マーク３２に関わる輝度情報の対称/非対称性を加味して、各々、外マーク３１と内マーク３２との位置ずれ量を算出する。さらに、上記式(４)にしたがって、０度方向での位置ずれ量Ｌ0と、１８０度方向での位置ずれ量Ｌ180との平均値を、ＴＩＳ値として算出する。このＴＩＳ値は、開口絞り面２３Ａにおける短波長帯域の瞳像の中心ＣHと、結像開口絞り２３の中心Ｃ23との位置ずれを表している。 Capture of the mark image using the illumination light L1 in the short wavelength band is also performed in each of the states before and after the adjustment mark 30A is rotated 180 degrees. Based on the luminance information of the two mark images, the symmetry / asymmetric property of the luminance information related to the outer mark 31 is taken into account, and the symmetry / asymmetric property of the luminance information related to the inner mark 32 is taken into account, respectively. The amount of positional deviation between the mark 31 and the inner mark 32 is calculated. Further, according to the above equation (4), an average value of the positional deviation amount L 0 in the 0 degree direction and the positional deviation amount L 180 in the 180 degree direction is calculated as a TIS value. This TIS value represents a positional deviation between the center C H of the pupil image in the short wavelength band on the aperture stop surface 23A and the center C 23 of the imaging aperture stop 23.

さらに、ステップＳ６では、照明光Ｌ１の波長帯域を変更し、調整用マーク３０Ａに対して長波長帯域の照明光Ｌ１を照射し、このとき調整用マーク３０Ａから発生する長波長帯域の回折光Ｌ２に基づいて、マーク画像を取り込む。長波長帯域の回折光Ｌ２には、外マーク３１のピッチＰ１に応じた広がり角で発生した光と、内マーク３２のピッチＰ２に応じた広がり角で発生した光とが含まれる。そして、この回折光Ｌ２のうち、結像開口絞り２３を通過して結像光学系(１９〜２４)の像面に到達した光に基づいて、マーク画像の取り込みが行われる。   Further, in step S6, the wavelength band of the illumination light L1 is changed, and the adjustment mark 30A is irradiated with the long wavelength band illumination light L1, and at this time, the long wavelength band diffracted light L2 generated from the adjustment mark 30A. Based on the above, a mark image is captured. The diffracted light L2 in the long wavelength band includes light generated at a spread angle corresponding to the pitch P1 of the outer mark 31 and light generated at a spread angle corresponding to the pitch P2 of the inner mark 32. Of the diffracted light L2, the mark image is captured based on the light that has passed through the imaging aperture stop 23 and has reached the image plane of the imaging optical system (19 to 24).

図４に示す波長帯域ごとの瞳像ＨR,ＨG,ＨBの結像位置ずれがある場合、長波長帯域の回折光Ｌ２による外マーク３１の瞳像は、図９(ａ)に示す中心波長λの瞳像Ｈ31よりも図中左方にシフトするが、上記の条件式(２)を満足するため、＋１次回折成分が結像開口絞り２３の外側にはみ出すことはない。したがって、外マーク３１では、長波長帯域でもケラレの対称性を保つことができる。この場合、マーク画像の外マーク３１の輝度情報は、その強度プロファイルが左右で等しくなる（図７(ｃ)参照）。 When there is an imaging position shift of the pupil images H R , H G , H B for each wavelength band shown in FIG. 4, the pupil image of the outer mark 31 by the diffracted light L2 in the long wavelength band is shown in FIG. Although it shifts to the left in the figure from the pupil image H 31 of the center wavelength λ, the above-mentioned conditional expression (2) is satisfied, so that the + 1st order diffraction component does not protrude outside the imaging aperture stop 23. Therefore, the outer mark 31 can maintain vignetting symmetry even in a long wavelength band. In this case, the intensity information of the outer mark 31 of the mark image has the same intensity profile on the left and right (see FIG. 7C).

一方、内マーク３２の場合には上記の条件式(３)を満足するため、長波長帯域の回折光Ｌ２による瞳像は、図９(ｂ)に示す中心波長λの瞳像Ｈ32よりも図中左方にシフトして、−１次回折成分の一部が結像開口絞り２３の内側に入射する。つまり、−１次回折成分のケラレ量が減少し、＋１次回折成分のケラレ量は変化しない。したがって、内マーク３２では、長波長帯域においてケラレが非対称となってしまう。この場合、マーク画像の内マーク３２の輝度情報は、その強度プロファイルが歪み（左右のアンバランス）を含むことになる（図８(ｃ)参照）。 On the other hand, in the case of the inner mark 32 which satisfies the above conditional expression (3), the pupil image by the diffracted light L2 in a long wavelength band, than pupil image H 32 of center wavelength λ shown in FIG. 9 (b) Shifting to the left in the figure, a part of the −1st order diffraction component is incident on the inside of the imaging aperture stop 23. That is, the amount of vignetting of the −1st order diffraction component decreases, and the amount of vignetting of the + 1st order diffraction component does not change. Therefore, in the inner mark 32, vignetting becomes asymmetric in the long wavelength band. In this case, the intensity information of the inner mark 32 of the mark image includes distortion (left and right imbalance) in the intensity profile (see FIG. 8C).

長波長帯域の照明光Ｌ１を用いたマーク画像の取り込みも、調整用マーク３０Ａを１８０度回転させる前後の状態の各々で行う。そして、２つのマーク画像の輝度情報に基づいて、外マーク３１に関わる輝度情報の対称/非対称性を加味すると共に、内マーク３２に関わる輝度情報の対称/非対称性を加味して、各々、外マーク３１と内マーク３２との位置ずれ量を算出する。さらに、上記式(４)にしたがって、０度方向での位置ずれ量Ｌ0と、１８０度方向での位置ずれ量Ｌ180との平均値を、ＴＩＳ値として算出する。このＴＩＳ値は、開口絞り面２３Ａにおける長波長帯域の瞳像の中心ＣHと、結像開口絞り２３の中心Ｃ23との位置ずれを表している。 Capture of the mark image using the illumination light L1 in the long wavelength band is also performed in each of the states before and after the adjustment mark 30A is rotated 180 degrees. Based on the luminance information of the two mark images, the symmetry / asymmetric property of the luminance information related to the outer mark 31 is taken into account, and the symmetry / asymmetric property of the luminance information related to the inner mark 32 is taken into account, respectively. The amount of positional deviation between the mark 31 and the inner mark 32 is calculated. Further, according to the above equation (4), an average value of the positional deviation amount L 0 in the 0 degree direction and the positional deviation amount L 180 in the 180 degree direction is calculated as a TIS value. This TIS value represents a positional shift between the center C H of the long-wavelength pupil image on the aperture stop surface 23A and the center C 23 of the imaging aperture stop 23.

上記したステップＳ５,Ｓ６の説明から分かるように、短波長帯域におけるケラレの非対称性と長波長帯域におけるケラレの非対称性とは反転した方向特性を持つ。このため、ステップＳ５で算出したＴＩＳ値（短波長帯域の瞳像の中心ＣHの位置ずれ）と、ステップＳ６で算出したＴＩＳ値（長波長帯域の瞳像の中心ＣHの位置ずれ）も、互いに反転した方向特性を持つことになる。 As can be seen from the description of steps S5 and S6 described above, the vignetting asymmetry in the short wavelength band and the vignetting asymmetry in the long wavelength band have inverted directional characteristics. Therefore, the TIS value calculated in step S5 (position shift of the center C H of the short wavelength band pupil image) and the TIS value calculated in step S6 (position shift of the center C H of the long wavelength band pupil image) are also obtained. , The direction characteristics are reversed.

そして、ステップＳ７では、ステップＳ５で算出したＴＩＳ値（短波長帯域の瞳像の中心ＣHの位置ずれ）と、ステップＳ６で算出したＴＩＳ値（長波長帯域の瞳像の中心ＣHの位置ずれ）との差を求める。「ＴＩＳ値の差」は、開口絞り面２３Ａにおける短波長帯域の瞳像の中心ＣHと長波長帯域の瞳像の中心ＣHと位置ずれを表している。
ステップＳ８では、ステップＳ７で算出した「ＴＩＳ値の差」を、予め定めた閾値（十分に小さい規格値）と比較する。そして、「ＴＩＳ値の差」が閾値より大きい場合（Ｓ８がＮｏ）、「ＴＩＳ値の差」を指標として、平行平面板２２の配置をチルト方向に微調整する（ステップＳ４）。その後、ステップＳ５の処理に戻る。上記したステップＳ５〜Ｓ９の処理は、「ＴＩＳ値の差」が閾値より小さくなる（Ｓ８がＹｅｓとなる）まで繰り返し行われる。 In step S7, the TIS value calculated in step S5 (position shift of the center C H of the short wavelength band pupil image) and the TIS value calculated in step S6 (position of the center C H of the long wavelength band pupil image). Find the difference from the deviation. The “difference in TIS value” represents a positional deviation between the center C H of the short wavelength band pupil image and the center C H of the long wavelength band pupil image on the aperture stop surface 23A.
In step S8, the “TIS value difference” calculated in step S7 is compared with a predetermined threshold value (a sufficiently small standard value). When the “TIS value difference” is larger than the threshold (No in S8), the arrangement of the plane parallel plates 22 is finely adjusted in the tilt direction using the “TIS value difference” as an index (step S4). Thereafter, the process returns to step S5. The processes in steps S5 to S9 described above are repeated until the “TIS value difference” becomes smaller than the threshold value (S8 becomes Yes).

なお、調整用マーク３０Ａの外マーク３１と内マーク３２との位置ずれ量（０度方向での位置ずれ量Ｌ0と１８０度方向での位置ずれ量Ｌ180）は、結像開口絞り２３と瞳像Ｈとの相対的な位置関係によって敏感に変化する。また、調整用マーク３０ＡのＴＩＳ値を測定した場合、波長帯域ごとに、内マーク３２の特性が反転するため、ＴＩＳ値の変化が大きい。これは「ＴＩＳ値の差」が波長帯域によって感度良く変化する指標となることを意味している。 The positional shift amount of the outer mark 31 and the inner mark 32 of the adjustment mark 30A (position shift amount of 0 degree direction L 0 and the position deviation amount L 180 in the direction of 180 degrees) has an imaging aperture stop 23 It changes sensitively depending on the relative positional relationship with the pupil image H. Further, when the TIS value of the adjustment mark 30A is measured, the characteristic of the inner mark 32 is inverted for each wavelength band, so that the change of the TIS value is large. This means that the “difference in TIS value” is an index that changes with high sensitivity depending on the wavelength band.

ステップＳ７で算出した「ＴＩＳ値の差」が閾値より小さくなったとき（Ｓ８がＹｅｓのとき）、開口絞り面２３Ａにおける短波長帯域の瞳像の中心ＣHと長波長帯域の瞳像の中心ＣHとは、互いに略一致したことになる。この場合、中心波長λの瞳像Ｈ31の中心ＣHも、短波長帯域や長波長帯域の中心ＣHと略一致する。ただし、この時点でステップＳ２のＴＩＳ値を再び算出すると、閾値から外れている（Ｓ３がＮｏとなる）可能性がある。 When the “difference in TIS value” calculated in step S7 is smaller than the threshold value (when S8 is Yes), the center C H of the short wavelength band pupil image and the center of the long wavelength band pupil image on the aperture stop surface 23A C H substantially coincides with each other. In this case, the center C H of the pupil image H 31 of center wavelength λ also substantially coincides with the center C H of the short wavelength band and a long wavelength band. However, if the TIS value in step S2 is calculated again at this time, there is a possibility that it is out of the threshold (S3 becomes No).

したがって、ステップＳ２〜Ｓ９の処理を繰り返し行い、ステップＳ２のＴＩＳ値と、ステップＳ７の「ＴＩＳ値の差」とが、各々の閾値より小さくなるように追い込む。ステップＳ２のＴＩＳ値とステップＳ７の「ＴＩＳ値の差」との双方が規格値以内（ステップＳ１０がＮｏ）となった時点で、本実施形態の結像光学系(１９〜２４)の調整処理を終了する。   Accordingly, the processes in steps S2 to S9 are repeated, and the TIS value in step S2 and the “difference in TIS value” in step S7 are driven to be smaller than the respective threshold values. Adjustment processing of the imaging optical system (19 to 24) of the present embodiment when both the TIS value in step S2 and the “difference in TIS value” in step S7 are within the standard values (No in step S10). Exit.

このとき、開口絞り面２３Ａにおける瞳像ＨR,ＨG,ＨBの波長帯域に応じた結像位置ずれ（図４）が補正され、波長帯域に拘わらず同一の結像位置（例えば図７の位置）に瞳像ＨR,ＨG,ＨBを形成することができる。また、波長帯域に拘わらず、開口絞り面２３Ａにおけるケラレを対称な状態（図７）に保つことができる。
上記したように、本実施形態の結像光学系(１９〜２４)の調整方法では、調整用基板３０の調整用マーク３０Ａの画像から指標（ＴＩＳ値の差）を求め、この指標に基づいて平行平面板２２の配置をチルト方向に微調整するため、平行平面板２２の配置を感度良く微調整することができる。したがって、平行平面板２２の調整誤差（チルト角θの誤差）を確実に小さくすることができ、装置起因の誤差成分（ＴＩＳ値）を良好に低減できる。 At this time, the imaging position shift (FIG. 4) corresponding to the wavelength bands of the pupil images H R , H G , H B on the aperture stop surface 23A is corrected, and the same imaging position (for example, FIG. 7) regardless of the wavelength band. ), Pupil images H R , H G , H B can be formed. Further, the vignetting on the aperture stop surface 23A can be maintained in a symmetric state (FIG. 7) regardless of the wavelength band.
As described above, in the adjustment method of the imaging optical system (19 to 24) of the present embodiment, an index (difference in TIS value) is obtained from the image of the adjustment mark 30A on the adjustment substrate 30, and based on this index. Since the arrangement of the plane parallel plate 22 is finely adjusted in the tilt direction, the arrangement of the plane parallel plate 22 can be finely adjusted with high sensitivity. Therefore, the adjustment error (tilt angle θ error) of the plane parallel plate 22 can be reliably reduced, and the error component (TIS value) caused by the apparatus can be reduced satisfactorily.

さらに、ステップＳ５における照明波長の設定を光源３Ａの最も短波側とし、ステップＳ６における照明波長の設定を光源３Ｂの最も長波側とすることにより、可視光帯域から赤外光近傍帯域までの広帯域な範囲（例えば波長幅が２７０ｎｍ程度の範囲）で、装置起因の誤差成分（ＴＩＳ値）を良好に低減できる。
その結果、重ね合わせ測定装置１０における基板１１（一般的な製品基板）の重ね合わせ検査の際に、重ね合わせマーク１１Ａのレジストマークと下地マークの構造や物性に応じて回折光Ｌ２の波長特性が異なる場合でも、それぞれのマーク位置の検出結果として誤差成分（ＴＩＳ値）を含まない正確な値を求めることができ、検出精度が向上する。さらに、レジストマークと下地マークとの位置ずれ量も正確に求めることができ、高精度な重ね合わせ検査が可能となる。
（変形例）
なお、上記した実施形態では、調整用マーク３０Ａの外マーク３１のピッチＰ１が条件式(２)を満足する例で説明したが、本発明はこれに限定されない。次の条件式(４)を満足する場合にも、本発明を適用できる。 Furthermore, the setting of the illumination wavelength in step S5 is the shortest wave side of the light source 3A, and the setting of the illumination wavelength in step S6 is the longest wave side of the light source 3B, so that a wide band from the visible light band to the near infrared light band can be obtained. In a range (for example, a range where the wavelength width is about 270 nm), an error component (TIS value) caused by the apparatus can be reduced satisfactorily.
As a result, at the time of overlay inspection of the substrate 11 (general product substrate) in the overlay measurement apparatus 10, the wavelength characteristic of the diffracted light L2 depends on the structure and physical properties of the registration mark and the base mark of the overlay mark 11A. Even if they are different, it is possible to obtain an accurate value that does not include an error component (TIS value) as the detection result of each mark position, and the detection accuracy is improved. Furthermore, the amount of misalignment between the registration mark and the base mark can be obtained accurately, and high-precision overlay inspection can be performed.
(Modification)
In the above-described embodiment, the example in which the pitch P1 of the outer mark 31 of the adjustment mark 30A satisfies the conditional expression (2) has been described, but the present invention is not limited to this. The present invention can also be applied when the following conditional expression (4) is satisfied.

ＮＡima−ＮＡill ＞ λ/Ｐ１ …(４)
さらに、上記した実施形態では、調整用マーク３０Ａの内マーク３２のピッチＰ２が条件式(３)を満足する例で説明したが、本発明はこれに限定されない。次の条件式(５)を満足する場合にも、本発明を適用できる。
ＮＡima＋ＮＡill/２ ≦ λ/Ｐ２ …(５)
また、上記した実施形態では、外マーク３１のピッチＰ１を内マーク３２のピッチＰ２より大きくしたが、本発明はこれに限定されない。外マーク３１と内マーク３２のピッチＰ１,Ｐ２が異なっていれば、ピッチＰ１,Ｐ２の大小関係が逆であっても、本発明を適用できる。 NAima-NAill> λ / P1 (4)
Further, in the above-described embodiment, the example in which the pitch P2 of the inner mark 32 of the adjustment mark 30A satisfies the conditional expression (3) has been described, but the present invention is not limited to this. The present invention can also be applied when the following conditional expression (5) is satisfied.
NAima + NAill / 2 ≤ λ / P2 (5)
In the above-described embodiment, the pitch P1 of the outer mark 31 is larger than the pitch P2 of the inner mark 32, but the present invention is not limited to this. As long as the pitches P1, P2 of the outer mark 31 and the inner mark 32 are different, the present invention can be applied even if the magnitude relationship between the pitches P1, P2 is reversed.

さらに、上記した実施形態では、条件式(２),(３)や条件式(４),(５)のように、開口絞り面２３Ａにおける瞳像Ｈの±１次回折成分と結像開口絞り２３との位置関係により、調整用マーク３０ＡのピッチＰ１,Ｐ２を定めたが、本発明はこれに限定されない。±１次回折成分に代えて、±２次回折成分やそれ以上の高次成分と結像開口絞り２３との位置関係を用い、ピッチＰ１,Ｐ２を定めても構わない。   Furthermore, in the above-described embodiment, the ± first-order diffraction components of the pupil image H on the aperture stop surface 23A and the imaging aperture stop are expressed by the conditional expressions (2) and (3) and the conditional expressions (4) and (5). 23, the pitches P1 and P2 of the adjustment mark 30A are determined. However, the present invention is not limited to this. Instead of the ± 1st order diffraction component, the pitches P1 and P2 may be determined using the positional relationship between the ± 2nd order diffraction component or higher order component and the imaging aperture stop 23.

また、上記した実施形態では、２種類のマーク（外マーク３１と内マーク３２）により構成された調整用マーク３０Ａの例を説明したが、本発明はこれに限定されない。調整用マーク３０Ａが、ピッチの異なる３種類以上のマークからなる場合にも、本発明を適用できる。
さらに、上記した実施形態では、調整用マーク３０Ａを構成する複数のマーク（例えば外マーク３１と内マーク３２）をバーマークにより構成したが、本発明はこれに限定されない。他の形状（例えばドット状）とする場合にも、本発明を適用できる。また、調整用マーク３０Ａは、複数のマークを中心が一致するように重ねて配置した２重マーク（設計上の位置ずれ量が０のマーク）に限らず、複数のマークを予め定めた間隔（設計上の位置ずれ量≠０）をあけて並べて配置することもできる。 Further, in the above-described embodiment, the example of the adjustment mark 30A configured by two types of marks (the outer mark 31 and the inner mark 32) has been described, but the present invention is not limited to this. The present invention can also be applied to the case where the adjustment mark 30A includes three or more types of marks having different pitches.
Further, in the above-described embodiment, the plurality of marks (for example, the outer mark 31 and the inner mark 32) constituting the adjustment mark 30A are configured by bar marks, but the present invention is not limited to this. The present invention can also be applied to other shapes (for example, dot shapes). Further, the adjustment mark 30A is not limited to a double mark (a mark whose design positional deviation amount is 0) which is a plurality of marks arranged so that their centers coincide with each other. It is also possible to arrange them side by side with a design displacement amount ≠ 0).

また、上記した実施形態では、照明光Ｌ１の波長帯域が異なるときの誤差成分（ＴＩＳ値）の差を指標として平行平面板２２の配置を微調整する例を説明したが、本発明はこれに限定されない。照明光Ｌ１の波長帯域が異なるときの位置ずれ量に基づいて、平行平面板２２の配置を微調整する場合にも、本発明を適用できる。このとき、例えば位置ずれ量の差を指標とすればよい。   In the above-described embodiment, the example in which the arrangement of the plane-parallel plate 22 is finely adjusted using the difference in the error component (TIS value) when the wavelength band of the illumination light L1 is different as an index has been described. It is not limited. The present invention can also be applied when finely adjusting the arrangement of the plane-parallel plates 22 based on the amount of displacement when the wavelength bands of the illumination light L1 are different. At this time, for example, a difference in positional deviation amount may be used as an index.

さらに、上記した実施形態では、平行平面板２２を用いて結像光学系(１９〜２４)を調整する例を説明したが、本発明はこれに限定されない。調整用の光学素子としては、他に、屈折率の異なる２個の楔形プリズムを用いることが考えられる。この場合、２個の楔形プリズムの斜面どうしを対向させ、光軸Ｏ２に垂直な方向に沿ってスライドさせる（相対位置を変更する）ことによって、平行平面板２２のチルト調整と同等の効果を得ることができる。   Furthermore, in the above-described embodiment, the example in which the imaging optical system (19 to 24) is adjusted using the plane parallel plate 22 has been described, but the present invention is not limited to this. As an adjustment optical element, it is conceivable to use two wedge-shaped prisms having different refractive indexes. In this case, the slopes of the two wedge-shaped prisms face each other and are slid along the direction perpendicular to the optical axis O2 (the relative position is changed), thereby obtaining the same effect as the tilt adjustment of the parallel flat plate 22. be able to.

また、上記した実施形態では、重ね合わせ測定装置１０に組み込まれた結像光学系(１９〜２４)を例にその調整方法を説明したが、本発明はこれに限定されない。物体を観察するための光学装置（例えば光学顕微鏡や外観検査装置など）の結像光学系を調整する場合にも、本発明を適用できる。   In the embodiment described above, the adjustment method has been described by taking the imaging optical system (19 to 24) incorporated in the overlay measurement apparatus 10 as an example, but the present invention is not limited to this. The present invention can also be applied when adjusting an imaging optical system of an optical apparatus (for example, an optical microscope or an appearance inspection apparatus) for observing an object.

重ね合わせ測定装置１０の全体構成を示す図である。1 is a diagram illustrating an overall configuration of an overlay measurement apparatus 10. 調整用基板３０の調整用マーク３０Ａの構成を示す図である。FIG. 5 is a diagram showing a configuration of an adjustment mark 30A on the adjustment substrate 30. 平行平面板２２の配置の微調整を説明する図である。It is a figure explaining the fine adjustment of arrangement | positioning of the plane parallel plate. 開口絞り面２３Ａにおける瞳像ＨR,ＨG,ＨBの波長帯域に応じた結像位置ずれを説明する図である。It is a figure explaining the imaging position shift according to the wavelength band of the pupil images H R , H G , H B on the aperture stop surface 23A. ビームスプリッタ１８の偏心誤差（チルト誤差）による開口絞り面２３Ａでの結像位置ずれを説明する図である。It is a figure explaining the imaging position shift in 23 A of aperture stop surfaces by the eccentric error (tilt error) of the beam splitter 18. FIG. ケラレが非対称な場合（＋１次回折成分のみ光量低下）を説明する図である。It is a figure explaining the case where vignetting is asymmetrical (only the + 1st order diffraction component is reduced in light amount). ケラレが対称な場合を説明する図である。It is a figure explaining the case where vignetting is symmetrical. ケラレが非対称な場合（−１次回折成分のみ光量低下）を説明する図である。It is a figure explaining the case where vignetting is asymmetric (only -1st-order diffracted component decreases in light amount). 結像開口絞り２３と外マーク３１の瞳像Ｈ31との位置関係(ａ)、結像開口絞り２３と内マーク３２の瞳像Ｈ32との位置関係(ｂ)を示す図である。Positional relationship between the pupil image H 31 of the imaging aperture stop 23 and the outer mark 31 (a), a diagram showing positional relationship (b) of the pupil image H 32 of the inner mark 32 and the imaging aperture stop 23. 本実施形態の結像光学系(１９〜２４)の調整手順を示すフローチャートである。It is a flowchart which shows the adjustment procedure of the imaging optical system (19-24) of this embodiment.

符号の説明Explanation of symbols

１０ 重ね合わせ測定装置
１１ 基板
１２ ステージ
１３ 光源部
１４ 照明開口絞り
１５ コンデンサーレンズ
１６ 視野絞り
１７ 照明リレーレンズ
１８，４１ ビームスプリッタ
１９ 第１対物レンズ
２０ 第２対物レンズ
２１ 第１結像リレーレンズ
２２，４３ 平行平面板
２３ 結像開口絞り
２４ 第２結像リレーレンズ
２５ ＣＣＤ撮像素子
２６ 画像処理装置
２７ ステージ制御装置
３０ 調整用基板
３０Ａ 調整用マーク
３１ 外マーク
３２ 内マーク
４２ ＡＦ第１リレーレンズ
４４ 瞳分割ミラー
４５ ＡＦ第２リレーレンズ
４６ シリンドリカルレンズ
４７ ＡＦセンサ
４８ 信号処理部 DESCRIPTION OF SYMBOLS 10 Overlay measuring apparatus 11 Board | substrate 12 Stage 13 Light source part 14 Illumination aperture stop 15 Condenser lens 16 Field stop 17 Illumination relay lens 18, 41 Beam splitter 19 1st objective lens 20 2nd objective lens 21 1st imaging relay lens 22, 43 Parallel plane plate 23 Imaging aperture stop 24 Second imaging relay lens 25 CCD imaging device 26 Image processing device 27 Stage controller 30 Adjustment substrate 30A Adjustment mark 31 Outer mark 32 Inner mark 42 AF first relay lens 44 Pupil Split mirror 45 AF second relay lens 46 Cylindrical lens 47 AF sensor 48 Signal processing unit

Claims (6)

結像光学系の物体面に、所定の波長帯の落射照明光による±１次回折光束が前記結像光学系の瞳領域に内接するようなピッチ以上の第１のピッチで配列された第１のマークと、前記第１のピッチより小さい第２のピッチを有して配列された第２のマークとを、それぞれ前記結像光学系の視野中心に対して対称に配設し、
前記結像光学系で形成された前記第１のマークの像と前記第２のマークの像との相対位置に基づいて、前記結像光学系の瞳面と開口絞り面との間に配設された光学素子の位置を調整する
ことを特徴とする結像光学系の調整方法。 First ± first-order diffracted light beams produced by epi-illumination light in a predetermined wavelength band are arranged on the object plane of the imaging optical system at a first pitch that is greater than or equal to a pitch that is inscribed in the pupil region of the imaging optical system. And the second marks arranged with a second pitch smaller than the first pitch are arranged symmetrically with respect to the field center of the imaging optical system, respectively.
Based on the relative position between the image of the first mark and the image of the second mark formed by the imaging optical system, it is arranged between the pupil plane and the aperture stop plane of the imaging optical system. A method for adjusting an imaging optical system, characterized by adjusting a position of a formed optical element. 請求項１に記載の結像光学系の調整方法において、
前記第１のピッチをＰ１(μｍ)、前記第２のピッチをＰ２(μｍ)、前記結像光学系の開口数をＮＡima、前記照明光の照射に用いた光学系の開口数をＮＡill、前記照明光の中心波長をλ(μｍ)とするとき、次の条件式を満足する
ＮＡima ＞ ＮＡill
ＮＡima−ＮＡill ＞ λ/Ｐ１
ＮＡima＋ＮＡill/２ ≦ λ/Ｐ２
ことを特徴とする結像光学系の調整方法。 In the adjustment method of the imaging optical system according to claim 1,
The first pitch is P1 (μm), the second pitch is P2 (μm), the numerical aperture of the imaging optical system is NAima, the numerical aperture of the optical system used for irradiation of the illumination light is NAill, When the center wavelength of the illumination light is λ (μm), the following conditional expression is satisfied. NAima> NAill
NAima-NAill> λ / P1
NAima + NAill / 2 ≤ λ / P2
An imaging optical system adjustment method characterized by the above. 請求項１または請求項２に記載の結像光学系の調整方法において、
前記調整用マークを前記視野中心に対して１８０°回転させる前後の状態の各々で前記結像光学系で形成された像における前記第１のマークと前記第２のマークとの距離を測定し、測定された２つの距離から装置起因の誤差成分量を算出して、前記誤差成分量に基づいて前記光学素子の位置を調整する
ことを特徴とする結像光学系の調整方法。 In the adjustment method of the imaging optical system according to claim 1 or 2,
Measuring the distance between the first mark and the second mark in the image formed by the imaging optical system in each of the states before and after the adjustment mark is rotated by 180 ° with respect to the center of the visual field; A method for adjusting an imaging optical system, comprising: calculating an error component amount caused by the apparatus from two measured distances, and adjusting a position of the optical element based on the error component amount. 請求項１から請求項３の何れか１項に記載の結像光学系の調整方法において、
前記照明光の波長帯域を変えて、波長ごとに前記第１のマークと前記第２のマークとの相対位置を求め、波長帯域ごとに求められた前記相対位置に基づいて、前記光学素子の位置を調整する
ことを特徴とする結像光学系の調整方法。 In the adjustment method of the imaging optical system of any one of Claims 1-3,
By changing the wavelength band of the illumination light, the relative position between the first mark and the second mark is determined for each wavelength, and the position of the optical element is determined based on the relative position determined for each wavelength band. A method for adjusting an imaging optical system, characterized in that 請求項４に記載の結像光学系の調整方法において、
前記照明光の波長帯域ごとに算出した前記第１のマークと前記第２のマークとの距離同１士の差分、または前記照明光の波長帯域ごとに算出した前記装置起因の誤差成分量同士の差分を指標として、前記光学素子の位置を調整する
ことを特徴とする結像光学系の調整方法。 In the adjustment method of the imaging optical system according to claim 4,
The difference between the distance between the first mark and the second mark calculated for each wavelength band of the illumination light or the error component amount due to the apparatus calculated for each wavelength band of the illumination light. The method of adjusting the imaging optical system, wherein the position of the optical element is adjusted using the difference as an index. 請求項１から請求項５の何れか１項に記載の結像光学系の調整方法において、
前記光学素子は平行平面板であり、
前記光学素子の配置の調整は、前記平行平面板の位置を傾ける方向に調整する
ことを特徴とする結像光学系の調整方法。 In the adjustment method of the imaging optical system of any one of Claims 1-5,
The optical element is a plane parallel plate;
The adjustment of the arrangement of the optical elements is performed by adjusting the position of the plane-parallel plate in a tilting direction.
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TW094117746A TW200609483A (en) 2004-05-28 2005-05-30 Method of adjusting optical imaging system, imaging device, positional deviation detecting device, mark identifying device and edge position detecting device
US11/604,354 US7528954B2 (en) 2004-05-28 2006-11-27 Method of adjusting optical imaging system, positional deviation detecting mark, method of detecting positional deviation, method of detecting position, position detecting device and mark identifying device

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