JPH0718699B2 - Surface displacement detecting device - Google Patents

Surface displacement detecting device

Info

Publication number
JPH0718699B2
JPH0718699B2 JP11188987A JP11188987A JPH0718699B2 JP H0718699 B2 JPH0718699 B2 JP H0718699B2 JP 11188987 A JP11188987 A JP 11188987A JP 11188987 A JP11188987 A JP 11188987A JP H0718699 B2 JPH0718699 B2 JP H0718699B2
Authority
JP
Grant status
Grant
Patent type
Prior art keywords
light
surface
detection
reflected
position
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
JP11188987A
Other languages
Japanese (ja)
Other versions
JPS63275912A (en )
Inventor
英夫 水谷
Original Assignee
株式会社ニコン
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Grant date

Links

Classifications

    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ELECTROGRAPHY; HOLOGRAPHY
    • G03FPHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F9/00Registration or positioning of originals, masks, frames, photographic sheets or textured or patterned surfaces, e.g. automatically
    • G03F9/70Registration or positioning of originals, masks, frames, photographic sheets or textured or patterned surfaces, e.g. automatically for microlithography
    • G03F9/7065Production of alignment light, e.g. light source, control of coherence, polarization, pulse length, wavelength
    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ELECTROGRAPHY; HOLOGRAPHY
    • G03FPHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F9/00Registration or positioning of originals, masks, frames, photographic sheets or textured or patterned surfaces, e.g. automatically
    • G03F9/70Registration or positioning of originals, masks, frames, photographic sheets or textured or patterned surfaces, e.g. automatically for microlithography
    • G03F9/7003Alignment type or strategy, e.g. leveling, global alignment
    • G03F9/7023Aligning or positioning in direction perpendicular to substrate surface
    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ELECTROGRAPHY; HOLOGRAPHY
    • G03FPHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F9/00Registration or positioning of originals, masks, frames, photographic sheets or textured or patterned surfaces, e.g. automatically
    • G03F9/70Registration or positioning of originals, masks, frames, photographic sheets or textured or patterned surfaces, e.g. automatically for microlithography
    • G03F9/7073Alignment marks and their environment
    • G03F9/7076Mark details, e.g. phase grating mark, temporary mark

Description

【発明の詳細な説明】 〔発明の目的〕 (産業上の利用分野) 本発明は、被検面の変位を検出するための表面変位検出装置に関し、特に、例えば半導体製造装置における焦点位置検出装置に適用して好適な表面変位検出装置に関する。 DETAILED DESCRIPTION OF THE INVENTION The present [OBJECT OF THE INVENTION] (relates) invention relates to surface displacement detecting device for detecting the displacement of the test surface, in particular, for example, a semiconductor manufacturing apparatus focal position detection apparatus in of the preferred surface displacement detecting device is applied to.

(従来の技術) 半導体製造装置における焦点位置検出装置としては、従来、撮影レンズによってマスクパターンが転写される位置に設けられた半導体ウェハに対して、斜めに入射光を照射し、その半導体ウェハの表面から斜めに反射する反射光を検出して、その表面位置を検出する斜め入射型焦点位置検出装置が多く用いられ、例えば特開昭56−4220 The focal position detection device in the (prior art) semiconductor manufacturing device, conventionally, the semiconductor wafer which is provided at a position where the mask pattern is transferred by the taking lens, and irradiates the incident light obliquely, the semiconductor wafer by detecting the reflected light reflected from the surface at an angle, it is often used an oblique incidence type focus position detecting device for detecting the surface position, for example, JP 56-4220
5号公報などによって開示されている。 It disclosed by like 5 JP.

この公知の焦点位置検出装置は、半導体ウェハの表面を被検出面として、その被検出面に投射光束を斜めに投射してスリット状の光像を被検出面上に結像させ、その反射光を受光部に設けられた光電変換素子で構成された検出部上に再結像させることにより、その反射光像の検出部上での入射位置を検知するように構成されている。 This known focus position detection apparatus, the surface of the semiconductor wafer as the sensed surface, is imaged on the detection surface of the slit-like light image by projecting projection light beam obliquely to the surface to be detected, the reflected light by re-imaged onto a detector which is constituted by a photoelectric conversion element provided on the light receiving portion, it is configured to detect an incident position on the detector of the reflected light image. 従って、被検出面の半導体ウェハ表面が上下方向に変位(投影レンズ光軸に沿って移動)すると、その上下方向の変位に対応して、検出部に入射する反射光像がその入射方向に対して直交する方向に横ずれする。 Therefore, displacement in the semiconductor wafer surface vertical direction of the detection surface (moves along the projection lens optical axis), the corresponding displacement of the vertical direction, the reflected light image incident on the detector unit with respect to the incident direction the lateral displacement in a direction perpendicular to Te. この横ずれ量を検出することによって半導体ウェハの表面が投影レンズに対して合焦位置にあるか否かを判定可能である。 The surface of the semiconductor wafer can be determined whether the in-focus position with respect to the projection lens by detecting the lateral deviation amount.

(発明が解決しようとする問題点) しかしながら、上記のように構成された斜入射型焦点位置検出装置を用いて半導体ウェハの表面位置を実際に検出する場合、その位置検出精度には、ある一定の限界があることが判明した。 (Trying invention solve that problem) However, if actually detects the surface position of the semiconductor wafer using a grazing incidence focus position detecting apparatus constructed as described above, in that position detection accuracy, a certain it has been found that there is a limit. その原因を種々検討したところ、 Were various studies the causes,
半導体ウェハの表面部分には、シリコンなどの半導体基板上にフォトレジストのような薄膜が付着している場合が多く、その薄膜の膜厚が1〜2μm程度になったとき、薄膜の表面で反射した反射光と、その薄膜の表面を透過して半導体基板の表面で反射した光とによって干渉が生じ、その為、検出部に入射する合成反射光の検出光学系光軸に対して垂直方向における光強度分布に狂いを生じるものと考えられる。 On the surface portion of the semiconductor wafer, often thin film such as photoresist on a semiconductor substrate such as silicon is adhered, when the film thickness of the thin film becomes approximately 1 to 2 [mu] m, reflected on the surface of the thin film and reflected light, transmitted through the surface of the thin film interference is caused by the light reflected from the surface of the semiconductor substrate, in that order, a direction perpendicular to the detection optical system optical axis of the composite reflected light incident on the detector considered as causing a deviation in the light intensity distribution. 因に、フォトレジストなどのように有機物質で構成されている材料の光線透過率は、 In this connection, the light transmittance of the material is composed of organic material, such as photoresist,
一般に、感光波長より長い波長(例えば赤色光)では比較的良好で、その表面からの反射光と、裏面からの反射光とが顕著に干渉し易く、誤差が生じ易いという問題点があった。 In general, the relatively good wavelengths longer than photosensitive wavelength (e.g. red light), and light reflected from the surface, easier and reflected light significantly interference from the back side, the error is disadvantageously likely to occur.

本発明は、上記従来装置において生じる恐れのある反射光の干渉による影響を考慮し、反射光の位置検出結果の精度を、従来装置の限界を超えて一段と改善し得る表面変位検出装置を比較的簡単な構成にて実現することを目的とする。 The present invention takes into account the influence of the interference of the reflected light that may occur in the conventional apparatus, the accuracy of the position detection result of the reflected light, the surface displacement detecting device capable of further improvement beyond the limits of conventional apparatus relatively and to realize with a simple configuration.

〔発明の構成〕 [Configuration of the Invention

(問題点を解決する為の手段) 上記の問題点を解決するために本発明においては、光透過性の薄膜を有する被検面上に光源から検出光を斜めに入射させ、その被検出面からの反射光を検出面上に光スポツトあるいはスリット状に再結像させ、その再結像された像の位置から、被検出面の位置を検出する斜入射型位置検出装置において、その光源から被検出面を介し前記の検出面に至る間の検出光路上の所定の位置に、前記被検出面に入射する検出光の入射面に平行なP偏光成分と垂直なS偏光成分の強度を前記検出面上で任意に変える偏光光学手段を設けることを問題解決の手段とするものである。 In the present invention in order to solve the above problems (means for solving the problem), the detection light is incident obliquely from the light source onto the test surface with light transmissivity of the thin film, the detected face thereof reimaged to image the optical Supotsuto or slit shape on the detection surface of the light reflected from the position of the re-imaging is image, the oblique incidence type position detecting device for detecting a position of the detected surface, from the light source in place of the detection light path between reaching the detection surface of the via the detected surface, wherein the intensity of the detected light perpendicular S-polarized light component parallel to the P-polarized component to the incident surface of the incident on the detected surface it is an unit of solving the problem by providing a polarization optical means for arbitrarily changing over the detection surface.

(作用) 光源から被検出面の薄膜に入射してその被検出面で反射する反射光のうち、その薄膜の表面で反射する表面反射光と薄膜を透過して薄膜裏面にて反射してさらに薄膜の表面を透過する内部反射光は、薄膜の厚さに応じて干渉し、検出面において干渉縞を作る。 (Effect) of the reflected light reflected by the detected surface from the light source is incident on a thin film of the detected surface, and further reflected by the thin film back surface passes through the surface reflection light and the thin film that reflects at the surface of the thin film internally reflected light transmitted through the surface of the thin film interferes according to the thickness of the film, making the interference fringes in the detection plane. この干渉縞を作る反射光の入射面に垂直なS偏光による干渉縞と入射面に平行なP偏光による干渉縞とは、入射角がブリュースター角を超えて大きくなると位相が180°ずれる。 The interference fringes due to parallel P-polarized light incident surface and interference fringes due to the vertical S-polarized light on the incident surface of the reflected light to make the interference fringes, the phase is shifted 180 ° when the incident angle is increased beyond the Brewster angle. 従って、 Therefore,
この互いに位相が反転したS偏光成分の干渉光とP偏光成分の干渉光が合成されて得られる光強度の変化は膜厚に比例せず、大きく乱れを生じる。 Changes in light intensity interference light is obtained by combining the interference light and P-polarized light component of the S-polarized component whose phases are mutually inverted are not proportional to the film thickness, resulting in greater turbulence. 従って、これに応じて検出される被検出面上での見掛けの表面からのずれ量が極めて大きいものとなる。 Therefore, the deviation amount from the apparent surface on the detected surface to be detected is extremely high accordingly. そこで、上記のP偏光成分とS偏光成分との比を変化させるために偏光光学手段が、検出光路上の適当な位置に設けられ、前記のP偏光成分とS偏光成分との180°のずれを利用して、その偏光光学手段を適当に回転調整することにより、その両偏光成分の強度を適当に変化させると、被検出面での見掛けの表面のずれ量が少なくなり、検出誤差を改善することができる。 Therefore, a polarization optical means for changing the ratio between the P-polarized component and S-polarized light component is provided at a suitable position of the detecting light path, 180 ° out of the P-polarized component and S-polarized light component utilizing, by appropriately rotating adjusting the polarizing optical means and to the appropriately vary the intensity of the two polarized components, the less the amount of deviation of the surface of apparent at the detection surface, improve the detection error can do.

(実施例) 次に、本発明の実施例を添付の図面に基づいて詳しく説明する。 (Example) Next will be described in detail with reference to the embodiment accompanying drawings of the present invention.

第1図は本発明の実施例を示す斜入射型の表面変位検出装置の光学系概略構成図である。 Figure 1 is an optical system schematic diagram of an oblique incidence type of surface displacement detecting system according to an embodiment of the present invention. なお、実線にて示す光線の経路は、スリット像の共役関係を示し、破線にて示す光線の経路は、光源像の共役関係を示す。 Note that the path of the rays shown by the solid line, shows the conjugate relationship of the slit image, the path of the light beam indicated by a broken line indicates the conjugate relationship of the light source images.

第1図において、発光ダイオード(LED)やハロゲンランプ等のように、特定の偏光方向を有しない、いわゆるランダム偏光の光を発する光源1からの検出光はフィールドレンズ2を介して投光スリット3を照射する。 In FIG. 1, as such as a light emitting diode (LED) or a halogen lamp, no specific polarization direction, the light projecting slit 3 detection light from the light source 1 via a field lens 2 which emits light of a so-called random polarization irradiated with. この投光スリット3は紙面に対して垂直方向に長いスリット開口3Aを有し、このスリット開口3Aを通して投射される検出光L 0は、送光側対物レンズ4Aによって集光され、半導体ウェハ5の表面5A上に光スリット像が結像される。 The light projecting slit 3 has a long slit aperture 3A in the direction perpendicular to the paper surface, the detection light L 0 is projected through the slit opening. 3A, the sending-side objective lens 4A is condensed, the semiconductor wafer 5 light slit image is formed on the surface 5A.
半導体ウェハ5の表面5Aから反射する反射光L 1は、受光側対物レンズ4Bによって集束され、受光スリット6上に光スリット像が再結像される。 Reflected light L 1 reflected from the surface 5A of the semiconductor wafer 5 is converged by the light receiving side objective lens 4B, the light slit image is re-imaged on the light receiving slit 6. また、受光スリット6に設けられたスリット開口6Aを通過した反射光L 1は、検出光L 3としてコレクタレンズ7により光電変換素子のような受光素子8上に集光される。 Further, the reflected light L 1 having passed through the slit opening 6A provided in the receiving slit 6 is focused on the light receiving element 8, such as a photoelectric conversion element by the collector lens 7 as the detection light L 3. なお、受光スリット6、 In addition, the light-receiving slit 6,
コレクタレンズ7及び受光素子8をもって光電検出器9 Photoelectric detector 9 with the collector lens 7 and the light receiving element 8
が構成される。 But composed.

受光スリット6に設けられたスリット開口6Aの長手方向は、投光スリット3のスリット開口3Aと同様に紙面に垂直な方向に設定されている。 Longitudinal direction of the slit opening 6A provided in the receiving slit 6 is set in a direction perpendicular to the paper surface as with the slit opening 3A of the light projecting slit 3. また、受光スリット6は、 In addition, the light-receiving slit 6,
そのスリット開口6Aの長手方向に対して直交する方向、 Direction orthogonal to the longitudinal direction of the slit opening 6A,
すなわちスリット開口6Aの幅方向(第1図中で矢印aにて示す方向)に所定の振幅をもって振動するように構成されている。 That is configured to vibrate with a predetermined amplitude (the direction indicated by arrow a in FIG. 1) width of the slit opening 6A. これにより、受光スリット6上に再結像された光スリット像はスリット開口6Aにて走査され、受光素子8からの検出信号が最大となったときのスリット開口6Aの基準位置からの偏位量から、被検出面5Aの基準面(焦点面)からの偏位が検出されるように構成されている。 Thus, the light slit image that is re-imaged on the light receiving slit 6 is scanned by the slit aperture 6A, deviation amount from the reference position of the slit aperture 6A when the detection signal from the light receiving element 8 is maximized from is configured such that deviations from the reference surface of the detecting surface 5A (focal plane) is detected.

受光側対物レンズ4Bと受光スリット6との間の光路上には、本発明の要部をなす検出誤差補正光学系10が光軸を中心に回転可能に配設されている。 On the optical path between the light-receiving-side objective lens 4B and the light receiving slit 6, the detection error correction optical system 10 that forms an essential part of the present invention is rotatably disposed about the optical axis. この検出誤差補正光学系10については後で詳しく述べる。 Described in more detail later this detection error correction optical system 10.

第2図は、半導体ウェハ5の被検出面5Aが投影レンズ光軸Zに沿って変位した場合における受光スリット6上での光スリット像の変位量を示す説明図である。 Figure 2 is an explanatory view showing a displacement amount of the optical slit image on the light receiving slit 6 in the case where the detected face 5A of the semiconductor wafer 5 is displaced along the projection lens optical axis Z. 検出光(入射光)L 0が入射角θをもって、基準位置Z 0に在る被検出面5Aに入射すると、Q 0点に結像された光スリット像は受光側対物レンズ4Bによって受光スリット6上の基準位置P 0に再結像される。 The detection light (incident light) L 0 with the incident angle theta, when incident on the detection surface 5A located at the reference position Z 0, received by the light slit image formed on the Q 0 points receiving side objective lens 4B slit 6 It is re-imaged reference position P 0 above. 被検出面5Aが鎖線5Sで示す位置までΔZだけ光軸Z方向に変位すると、検出光L 0はQ 1点で反射し、光スリット像を形成する反射主光線L Sは受光側対物レンズ4Bを介して、受光スリット6上のP 1点に達し、そこに光スリット像が再結像される。 When displaced in the direction of the optical axis Z ΔZ to the position where the detected face 5A is indicated by a chain line 5S, the detection light L 0 is reflected at one point Q, the reflected principal ray L S for forming a light slit image light-receiving-side objective lens 4B through, reaching P 1 point on the light receiving slit 6, wherein the optical slit image is re-imaged. この場合、受光スリット6上での基準位置P 0からP 1点までの光スリット像の変位量をΔy、受光側対物レンズ4Bの結像倍率をβとすると、被検出面5Aの変位量ΔZは ΔZ=Δy/(2βsinθ)………(1) で与えられる。 In this case, when the displacement amount of the optical slit image from the reference position P 0 of the on receiving slit 6 to P 1 point [Delta] y, and the imaging magnification of the light-receiving-side objective lens 4B beta, the amount of displacement of the detection surface 5A [Delta] Z is given by ΔZ = Δy / (2βsinθ) ......... (1).

一方、半導体ウェハ5の被検出面5Aが、第3図に示すように半導体基板5B上に塗られた例えばフォトレジストでなる薄膜5Cの表面で構成されている場合には、薄膜5Cの表面5Aの点Q 0に入射した検出光L0の一部が反射光L1Aとして反射されるのみならず、薄膜5C内を透過して半導体基板5Bの表面で反射する反射光L2が生じ、この反射光L2 On the other hand, the detected face 5A of the semiconductor wafer 5, if it is constituted by the surface of the third consisting of a for example a photoresist is painted on a semiconductor substrate 5B as shown in FIG film 5C, the surface 5A of the thin film 5C part of the detection light L0 incident on the Q 0 point not only is reflected as reflected light L1A, resulting reflected light L2 reflected by the surface of the semiconductor substrate 5B passes through the inside film 5C, the reflected light L2
が表面5Aを透過して第2の反射光L2Aとして表面5Aから出射する。 There emitted from the second surface 5A as reflected light L2A is transmitted through the surface 5A. 以下同様にして反射光L2のうち表面5Aを透過し切れずに表面5Aで内面反射される反射光L3に基づいて、第3、第4……の反射光L3A、L4A……が発生し、これが第1の反射光L1Aに複合して受光スリット6に到達すると考えられる。 Below based on the reflected light L3 that is internally reflected by the surface 5A not completely through the face 5A of the reflected light L2 in the same manner, the third, fourth ...... reflected light L3A, L4A ...... occurs, This is considered complex to reach the light receiving slit 6 in the first reflected light L1A.

この複合反射光について検討してみると、薄膜5Cの内部で1回反射した第2の反射光L2Aは、見掛け上表面5Aから距離δだけ深い位置で反射したものと考えることができるので、受光スリット6上では、正規の反射光L1の受光スリット6上への入射位置P 0を基準にして ε=2・β・sinθ・δ ………(2) で表されるずれ量εだけ横にずれて結像することになる。 Looking studied this complex reflected light, second reflected light L2A reflected once within the thin film. 5C, so can be considered as reflected by the distance δ just deep position from the apparent surface 5A, the light receiving on the slit 6, the horizontal shifted amount epsilon represented by the incident position P 0 of the receiving slit 6 on the reflected light L1 of the normal with respect ε = 2 · β · sinθ · δ ......... (2) It will be imaged deviates. ここで、表面5Aの見掛け上のずれ量δは Here, the deviation amount of the apparent surface 5A [delta] is として求めることができる。 It can be obtained as. (3)式においてdは薄膜 (3) d In equation film
5Cの厚み、nは薄膜5Cの屈折率である。 5C thickness, n is a refractive index of the thin film 5C. (2)式及び(3)式は薄膜5C内部で1回だけ反射した反射光L2Aによる場合の位置ずれ量であるが、2回、3回……m回反射して得られる反射光L3A、L4A……L(m+1)Aについても同様にして2ε、3ε……mεだけ位置がずれることになる。 (2) and (3) is a positional deviation amount in the case by only the reflected light reflected L2A 1 once inside thin 5C, 2 times, 3 times ...... m times reflected obtained reflected light L3A, L4A ...... L (m + 1) 2ε in the same for a, so that the 3ε ...... mε only position shifts.

このような複合光が受光スリット6に入射すると、光学系の条件や、薄膜5Cの厚さdに基づいて各複合光が互いに干渉性をもつようになり、その結果、受光スリット6 When such a composite light enters the light receiving slit 6, and conditions of the optical system, will have a thickness of each composite beam mutually coherent based on the d of the thin film 5C, as a result, the light receiving slit 6
上に結像される像の形が変形することにより、光電検出器9によって検出される光量重心がずれる結果を生じ、 By the shape of the image formed on deforms, resulting results quantity centroid detected by the photoelectric detector 9 is shifted,
これにより正規の反射光L1に基づく位置ずれ量Δy(第2図参照)の検出結果に誤差を生じる。 Thereby causing an error in the detection result of the positional deviation based on the regular reflected light L1 amount [Delta] y (see Figure 2).

この現象を定性的に検討すれば、第4図のようになる。 If qualitatively examine this phenomenon is as Figure 4.

先ず第1反射光L1Aだけが受光スリット6に到来したとき、光電検出器9がこの光量重心位置をy 0と判定し、薄膜5Cの内部を1回反射した第2反射光L2Aについて、光電検出器9がその光量重心を位置ずれ量ε((2)式) When only first first reflected light L1A has come to receiving slit 6, the photoelectric detector 9 determines the amount of light centroid position and y 0, the second reflected light L2A reflected once inside the thin 5C, the photoelectric detection vessel 9 that the light intensity gravity center position deviation amount epsilon ((2) formula)
だけずれた位置y 01にあると判定したとする。 And it was determined to be in a position y 01 shifted by. この場合第4図(A)に示すように反射光L1Aの光強度が正規化した値2であるとすれば、1回反射の第2反射光L2Aの光強度はこれより弱く、ほぼ0.5程度になる。 In this case the light intensity of the reflected light L1A as illustrated in FIG. 4 (A) is a value 2 normalized once the light intensity of the second reflected light L2A reflections weaker than this, the order of 0.5 become.

ところで、薄膜5Cの厚さdが十分厚く、また、光源1からの検出光L 0が可干渉性の低いものであれば、第1反射光L1Aと1回反射の第2反射光L2Aとでは干渉が生じない。 Incidentally, the thickness d is sufficiently thick to thin 5C, also, as long as the detection light L 0 from the light source 1 is low coherence, the second reflected light L2A of the first reflected light L1A and one reflector interference does not occur. 従って、受光スリット6上に結像された光スリット像の光強度は、第4図(B)に示すように、第4図(A)において実線図示の反射光L1Aの光強度の分布と、破線図示の1回反射の第2反射光L2Aの光強度の分布との和で表される光強度の分布を呈する。 Accordingly, the light intensity of the light slit image formed on the light-receiving slit 6, a fourth as shown in Figure (B), the light intensity of the reflected light L1A of solid shown in FIG. 4 (A) distribution, exhibit a distribution of light intensity represented by the sum of the distribution of light intensity of the second reflected light L2A single reflection dashed illustration. その結果受光スリット6上に結像された光スリット像の光強度分布の光量重心は、反射光L1Aの光強度分布の重心y 0 (第4 Consequently quantity centroid of light intensity distribution of the light slit image formed on the light-receiving slit 6, the centroid of a light intensity distribution of the reflected light L1A y 0 (Fourth
図(A))に対して僅かなずれ量Δy 1だけずれた位置y 1 Figure (A)) position y 1 that is offset by a small shift amount [Delta] y 1 with respect to
に生ずることになる。 It will cause it to. ただし、そのずれ量Δy 1は膜厚d However, the shift amount [Delta] y 1 is the film thickness d
に比例して変化する。 Changes in proportion to.

しかし、実際には膜厚dが1〜2μm程度に薄い為、その反射光は干渉する可能性が高く、多くの場合、受光スリット上に光スリット像を形成する反射光L1AとL2Aが干渉し、両者は第4図(C)のように互いに強め合うか、 However, in practice since the film thickness d is thin at about 1~2μm, the reflected light is likely interfere often reflected light L1A and L2A to form an optical slit image interferes with the receiving slit , or both reinforce each other as in the FIG. 4 (C),
あるいは第4図(d)に示すように互いに弱め合う結果となる。 Or resulting in weaken each other as shown in FIG. 4 (d). 従って、受光スリット6上に結像された合成像の形が崩れる現象が生じ、これにより受光スリット6上に結像された合成像の光量重心が、反射光L1Aの光量重心y 0から大きくずれることになる。 Therefore, the phenomenon that the shape of the composite image formed on the light receiving slit 6 collapses occur, thereby the light quantity gravity center of the composite image formed on the light receiving slit 6, deviates significantly from the amount centroid y 0 of the reflected light L1A It will be.

例えば、反射光L1Aに対する反射光L2Aの干渉光強度が最大になった場合には、第4図(C)に示すように、干渉部分L1A+L2Aの光強度が極端に大きくなる(この実施例の場合反射光L1Aの光強度が2であるのに対して4.5になる)。 For example, when the interference light intensity of the reflected light L2A to the reflection light L1A is maximized, as shown in FIG. 4 (C), interference portion L1A + light intensity of L2A becomes extremely large (in this embodiment light intensity of the reflected light L1A is 2 of 4.5 whereas). 従って受光スリット6上に結像された像の光量重心は、第4図(B)の場合より多い位置ずれ量Δy 2だけずれた位置y 2に移動する結果になる。 Therefore the light quantity gravity center of the image imaged on the light-receiving slit 6 will FIG. 4 (B) result is moved from the position y 2 shifted by more positional deviation amount [Delta] y 2 cases.

これに対して干渉光強度が最小の場合には、第4図(D)に示すように、反射光L2Aと、正規の反射光L1とが重なり合う範囲において、反射光L1AとL2Aとが互いに打ち消し合い、その結果受光スリット6上に結像された合成像の光量重心が、反射光L1Aの光量重心y 0と比較して極端に大きな位置ずれ量Δy 3で、しかも第4図Cとは反対側にずれた位置y 3に移動する結果になる。 When the interference light intensity is minimum contrast, as shown in FIG. 4 (D), and the reflected light L2A, to the extent that the reflected light L1 overlaps regular, canceling the reflected light L1A and the L2A each other fit, resulting quantity centroid of the composite image formed on the light-receiving slit 6, at a light quantity gravity center y 0 and extremely large positional displacement amount [Delta] y 3 in comparison of the reflected light L1A, yet contrary to the Figure 4 C result of moving to a position y 3 shifted to the side. 特に干渉効果によって反射光L1AとL2Aとが打ち消し合う第4図(D)の場合には、受光スリット6上での光量重心の位置ずれ量Δy 3が大きいため、この位置ずれ量Δy 3が薄膜表面5Aを基準とする被検出面側での見掛けの検出位置に非常に大きな誤差を生じさせる要因となる。 Especially in the case of FIG. 4 cancel each other out and the reflected light L1A and L2A (D) by the interference effect due to the large positional displacement amount [Delta] y 3 of the light quantity gravity center of on the light receiving slit 6, this position deviation amount [Delta] y 3 thin a reference surface 5A becomes a factor causing a very large error in the detected position of apparent at the detection side. 第5図は、 Fig. 5,
上記のような反射光の干渉が被検出面側での検出位置に及ぼす影響を模式的に示す線図で、横軸は薄膜の厚さd、縦軸は薄膜表面5Aを基準とする被検出面側での見掛けの検出位置のずれ量を示す。 The effect of interference above-described reflected light on the detection position at the detection surface side diagram schematically showing the horizontal axis is the thickness d of the thin film and the ordinate detection object relative to the thin film surface 5A It shows the amount of deviation of the detected position of the apparent by side. ただし、一点鎖線にて示す直線K3は薄膜5Cがコートされた半導体基板5Bの上面の位置を示す。 However, the straight line K3 shown by one-dot chain line indicates the position of the upper surface of the semiconductor substrate 5B which thin 5C is coated.

第3図において、仮に反射光が互いに干渉を起こさないものとすると、薄膜表面5Aと半導体基板表面5Dからの反射光の光強度は、それぞれ反射面での反射率によって定まり一定である。 In FIG. 3, when if the reflected light is assumed that do not interfere with each other, the light intensity of the reflected light from the film surface 5A and the semiconductor substrate surface 5D is a constant determined by the reflectivity of each reflecting surface. しかし、半導体基板表面5Dでの反射光 However, light reflected by the semiconductor substrate surface 5D
L2A、L3A……は、薄膜5の膜厚dに比例して薄膜表面5A L2A, L3A ...... a thin film surface 5A in proportion to the thickness d of the thin film 5
からの反射光L1Aに対してずれる。 It deviates from the reflected light L1A from. そのため、受光スリット6上での光スリット像の重心位置は、膜厚dに比例して受光スリット上での検出基準位置P 0からずれることになる。 Therefore, the center of gravity of the light slit image on the light receiving slit 6 would in proportion to the film thickness d deviates from the detected reference position P 0 on the receiving slit. 従って、被検出面側では、薄膜表面5Aの位置Z 0 Thus, at the detection surface, the position Z 0 of the thin film surface 5A
を基準として第5図中で実線K 1にて示す如く膜厚dに比例した直線的なずれを示す。 The shows a linear displacement which is proportional to the film thickness d as shown by a solid line K 1 in FIG. 5 as a reference.

ところが前述の如く、薄膜5Cで干渉現象が起ると、曲線(破線)K 2にて示すように、干渉の影響により実線K 1に沿いながら大きく波を打つような膜厚dには比例しないずれが生じる。 However as described above, the interference when the phenomenon occurs in thin 5C, as shown by curve (dashed line) K 2, not proportional to the thickness d like putting a large wave while along the solid line K 1 due to the influence of interference deviation occurs. 特に、第4図(D)において説明したように、反射光が互いに打ち消し合う状態の膜厚の付近では、鋭く尖った刺状の極端なずれが生じる。 In particular, as described in FIG. 4 (D), in the vicinity of the film thickness in a state in which the reflected light cancel each other, the extreme displacement of sharply pointed barbs occurs. このような状況の下では、例えば薄膜5Cの膜厚dが第5図で示す如く、製造工程においてW 1からW 2の範囲(W 1 〜W 2 =ΔW) Under such circumstances, for example, the thickness d of the thin film. 5C as shown in FIG. 5, the range of W 1 in the manufacturing process of W 2 (W 1 ~W 2 = ΔW)
でばらついているものとすると、反射光が非干渉の場合(実線K 1 )には、わずかにΔX 1だけ検出位置の検出結果にばらつきが有るのみであるが、反射光が干渉を起す曲線K 2の場合には、検出位置の検出結果が最大ΔX 2の範囲で大きくばらつくことになり、これが焦点位置検出の際の検出誤差となる。 Assuming that varies, in the case reflected light incoherent (solid line K 1), but is only slightly variation is in a detection result of the detection position by [Delta] X 1, curve K the reflected light causes interference in the case of 2, will be the detection result of the detection position varies greatly in the range of up to [Delta] X 2, which is a detection error in the focus position detection.

ところで、第4図における干渉の影響の説明では、第1 Incidentally, in the description of the effect of interference in FIG. 4, the first
反射光L1Aと第2反射光L2Aについてのみ定性的に説明したが、実際には第3図に示すように無限回反射となり極めて複雑である。 It reflected light L1A and described only qualitatively for the second reflected light L2A, but actually a extremely complicated and infinite reflection as shown in Figure 3. しかし、第1反射光L1Aと第2反射光L However, the first reflected light L1A and the second reflected light L
2Aに比して、他の反射光L3A、L4A……の光強度は弱いので、上記の反射光L1A、L2Aのみで干渉の影響を代表させても大きく狂うことは無い。 Compared to 2A, the other reflected light L3A, since the light intensity of L4A ...... weak, never mad larger as a representative said reflected light L1A, the influence of only the interference L2A.

ところで、第1図に示すように被検出面5Aに検出光L 0が入射すると、第3図に示すようにその一部は反射し、残りは被検出面5Aを透過して屈折する。 Incidentally, the detection light L 0 to the detected surface 5A as shown in Figure 1 is incident, is a part, as shown in FIG. 3 reflects the remainder refracted through the sensed surface 5A. この場合、一般に反射光中には入射面(被検出面5Aに垂直)に平行なP偏光と入射面に垂直なS偏光とを含み、光の振幅、位相について、次のフレネルの式が成立する。 In this case, generally includes a reflection plane of incidence in the light perpendicular S polarized light incident surface parallel to P-polarized light (perpendicular to the detected surface 5A), the optical amplitude, the phase, the formula for a Fresnel satisfied to. いま、入射角をθ 、屈折角をθ 、P偏光の振幅をR P 、S偏光の振幅をR Sとすると、 R P =−tan(θ −θ )/tan(θ +θ ) ……(4) R S =−sin(θ −θ )/sin(θ +θ ) ……(5) ここで、入射角がブリュースター角(θ +θ =90 Now, the incident angle theta i, the amplitude of the refractive angle theta t, P-polarized R P, when the amplitude of the S-polarized light and R S, R P = -tan ( θ i -θ t) / tan (θ i + θ t) ...... (4) R S = -sin (θ i -θ t) / sin (θ i + θ t) ...... (5) in this case, the incident angle is Brewster's angle (θ i + θ r = 90
°)に等しいときは、tan(θ +θ )=∞.sin(θ When equals °) is, tan (θ i + θ t ) = ∞.sin (θ
+θ )=1となる。 i + θ t) = 1 to become. 従って、S偏光の振幅R Sは薄膜の屈折率に応じた値となるが、P偏光の振幅R Pは零(ゼロ)となり、反射することなく全部被検出面5Aを透過する。 Therefore, the amplitude R S of the S-polarized light is a value corresponding to the refractive index of the thin film, P amplitude R P polarized light is zero (zero), and transmits the sensed surface 5A all without reflection. また、 Also, ならば、0<sin(θ +θ )<1となり、従って(5)式におけるS偏光の振幅R Sの符号は変らないが、 If, 0 <sin (θ i + θ t) <1 , and the thus (5) code does not change the amplitude R S of the S-polarized light in the formula,
tan(θ +θ )0となり、従って(4)式におけるP偏光の振幅R Pの付符号は逆転する。 tan (θ i + θ t) 0 , and the thus (4) with the sign of the amplitude R P of the P-polarized light in the equation is reversed.

第6図は、P偏光とS偏光とで干渉光の位相がほぼ180 FIG. 6 is, P-polarized light and S-polarized light and the interference light phase almost 180
°ずれることを説明するための断面説明図である。 ° is a cross-sectional view for explaining that the shift. 先ず、検出光L 0の試料面5Aへの入射角θ がブリュースター角より小さい場合(θ +θ <90°)は、第6図(A)に示すように、反射光L1Aと試料面5Aを透過した後、薄膜5C内で一回反射した後試料面5Aを透過する反射光L2Aについて、P偏光(紙面に平行な矢印p 1 、p 2 )とS偏光(紙面に垂直なX印S 1 、S 2 )とは共に同方向で位相のずれは無い。 First, when the incident angle theta i of the sample surface 5A of the detection light L 0 is smaller than the Brewster angle (θ i + θ t <90 °) , as shown in FIG. 6 (A), the reflected light L1A and the sample after passing through the surface 5A, the reflected light L2A transmitted through the sample surface 5A after being reflected once in a thin film 5C, P-polarized light (arrow p 1 parallel to the plane, p 2) and S-polarized light (perpendicular to the paper surface X mark S 1, S 2) phase shift is not together in the same direction and. しかし、入射角θ がブリュースター角より大きい場合(θ +θ >90°)の場合には、第6図(B)に示すようにS偏光については不変であるが、P偏光については反射光L1AのP偏光が第6図(A)の場合とは異なり、180°だけ逆転していることを示している。 However, in the case where the incident angle theta i is greater than the Brewster angle (θ i + θ t> 90 °) is the S-polarized light, as shown in FIG. 6 (B) is unchanged, the P-polarized light P-polarized light of the reflected light L1A is unlike in FIG. 6 (a), which indicates that reversed by 180 °. すなわち、反射光L1A中のP偏光は、入射角θ がブリュースター角を境として位相が逆転することを示している。 That, P polarized in reflected light L1A is the incident angle theta i indicates that the phase is reversed as boundary Brewster angle.

第3図に示す多数回反射光L3A、L4A……についても一回反射光L2Aと同様に、反射光L1Aに対してP偏光が180° Multiple reflected light L3A shown in Figure 3, like the once reflected light L2A also L4A ......, P-polarized light is 180 ° with respect to the reflected light L1A
逆転するものと考えられる。 It is considered to be reversed. 基板5Bは通常シリコンやアルミニウム等で形成されており、これらの物質からの反射光も入射角が大きい場合には位相ずれを起す。 Substrate 5B is formed in a conventional silicon, aluminum, or the like, it causes a phase shift in the case the incident angle the reflected light from these materials is high. しかし、薄膜(レジスト)5C内では入射角θ がブリュースター角より小さくなるので、殆んど位相ずれを起すこと無く、その結果、試料面5Aへの入射角θ がブリュースター角より大きい場合、P偏光はS偏光に対しても180 However, larger the incident angle theta a is smaller than the Brewster angle, without causing a phase shift almost, as a result, Brewster angle is an incident angle theta i of the sample surface 5A is a thin film (resist) in 5C If, even for P-polarized S-polarized light 180
°位相のずれたものとなる。 ° becomes phase-shifted.

第7図は、第3図における多数回反射光L3A、L4A……まで考慮した、P偏光の干渉光とS偏光の干渉光とのシュミレーションの例を示す線図で、第7図(A)は薄膜の膜厚tの変化に対する干渉光の強度変化を示す線図で、 Figure 7 is a multiple reflected light L3A in Figure 3, L4A considering to ..., diagrammatically illustrating an example of a simulation of the interference light of the P polarized light and S-polarized light of the interference light, FIG. 7 (A) diagrammatically showing the intensity change of the interference light with respect to changes in the thickness t of the thin film,
第7図(B)はその干渉光の重心位置に基づく、試料面 Figure 7 (B) is based on the gravity center position of the interference light, the sample surface
5A側での見掛けの表面ずれ量を示す線図である。 It is a diagram showing a surface deviation amount of apparent at 5A side. 実線はP偏光による曲線、破線はS偏光による曲線を示す。 The solid line curve by the P-polarized light, the broken line indicates a curve by S-polarized light. この場合、光源1からの検出光L 0を波長λ=740μmの単色光とし、シリコン基板(複素屈折率n S =3.71+0.01 In this case, the detection light L 0 from the light source 1 and monochromatic light of wavelength λ = 740μm, the silicon substrate (complex refractive index n S = 3.71 + 0.01
i)の表面にアルミニウム層(複素屈折率n AL =1.44+5. aluminum layer on the surface of the i) (complex refractive index n AL = 1.44 + 5.
2i)を厚さ1μmに付着し、その上にフォトレジスト(複素数n R =1.64+0.002i)を付着させて成る半導体ウェハ5の表面5Aに対して、入射角θ=70°で開口数NA= Attaching a 2i) to a thickness of 1 [mu] m, the photoresist (complex n R = 1.64 + 0.002i) surface 5A of the semiconductor wafer 5 made by adhering thereon, the numerical aperture NA at the incident angle theta = 70 ° =
0.1の対物レンズ4A、4Bを用いて前記の検出光L 0を投射するものと仮定してある。 0.1 of the objective lens 4A, are assumed for projecting detection light L 0 of the using 4B.

第7図(A)から明らかなようにP偏光(実線)とS偏光(破線)とでは、干渉効果による光の強弱の周期がほぼ半周期(180°)だけずれており、それに伴って、その光強度が弱くなるときに、第7図(B)に示すようにレジストの遥か下方(表面からのずれ量が大きい)位置を検出することになり、検出誤差が大きいことを示している。 In Figure 7 and as is apparent P-polarized light from the (A) (solid line) S-polarized light (dashed line), the period of the intensity of light due to interference effects are offset substantially by the half-period (180 °), with it, as when the light intensity is weak, will be detected (shift amount is large from the surface) position far below the resist as shown in FIG. 7 (B), shows that the detection error is large. 例えば、膜厚1.2μmにおける干渉光の強度(第7図(A)参照)及び検出誤差(第7図(B)参照)を見ると、P偏光(実線)では強度が最大で、しかも検出誤差(表面からのずれ量)が少なく、第4図(C)の状態にあることを示している。 For example, looking the intensity of the interference light in the film thickness 1.2 [mu] m (FIG. 7 (A) refer) and the detection error (Figure 7 (B) refer) to, as P-polarized light (solid line) in intensity maximum, yet detection error less (amount of deviation from the surface), shows that in the state of FIG. 4 (C). しかし、S偏光については逆に干渉光の強度が最小付近となり、検出誤差が大きく、第4図(D)の状態となる。 However, the intensity of the interference light is minimum near the opposite for S-polarized light, detection error is large, a state of FIG. 4 (D). そこで、この2つのP Therefore, the two P
偏光とS偏光とを合成すると、第4図中で(C)と(D)の光量分布をインコヒーレントに加えることになり、その光量重心は光強度の強い方(例えば第4図(C)の方向)へ引き戻される。 When combining the polarized light and S polarized light, it will be added in the fourth figure (C) and the light intensity distribution (D) incoherently, stronger (e.g. Figure 4 of that quantity centroid intensity (C) It is pulled back to the direction).

第8図は、上記の第7図に示すP偏光とS偏光とを合成した結果を示す線図で、破線の曲線は膜厚変化に対する干渉光の強度変化を示し、実線の曲線は、試料面側での表面からの見掛けのずれ量(検出誤差)を示す。 Figure 8 is a graph showing the results obtained by combining the P polarized light and S-polarized light shown in FIG. 7 of the above, the dashed curve shows the change in intensity of the interference light with respect to the film thickness change, the solid curve, the sample the amount of deviation of the apparent from the surface of a plane side (detection error) is shown. 第8図を見れば明らかなように、干渉による光強度の変化が少なくなり、検出誤差Δは膜厚1.1μm付近においてなお、0.32μmの範囲の検出誤差を有する。 Obviously if you look at the Figure 8, the change in light intensity due to interference is reduced still in the vicinity of the film thickness 1.1μm detection error delta, having a detection error in the range of 0.32 [mu] m. しかし、次に述べる手段を用いてP偏光とS偏光の強度の比を適当に変えれば、その検出誤差(膜厚の変化による検出誤差の変動、第5図中でΔX 2 )を最小とすることが可能である。 However, if appropriately changing the ratio of the intensity of the P-polarized light and S-polarized light by using a means described below, (variation of the detection error due to variation in the thickness, [Delta] X 2 in FIG. 5) the detection error to minimize the It is possible.

上記の干渉による検出位置の検出誤差を改善するために、第1図に示すように、受光側対物レンズ4Bと受光スリット6との間に検出誤差補正光学系10が設けられている。 To improve the detection error of the detected position by the interference, as shown in FIG. 1, a detection error correction optical system 10 is provided between the light-receiving-side objective lens 4B and the light receiving slit 6. この検出誤差補正光学系10は、第9図に示すような偏光プリズム11にて構成されている。 The detection error correction optical system 10 is constituted by the polarizing prism 11 as shown in Figure 9. 偏光プリズム11の反射面11Rは45°傾斜した合わせ面に誘電体多層膜をコートして成り、第10図の分光透過特性図に示す如く、P The reflecting surface 11R of the polarizing prism 11 is made by coating a dielectric multilayer film on the mating surface inclined by 45 °, as shown in the spectral transmittance characteristic diagram of FIG. 10, P
偏光はほぼ100%透過し、S偏光は50%を透過、残りの5 Polarization is transmitted almost 100% S-polarized transmits 50% remaining 5
0%を反射するように構成されている。 And it is configured to reflect 0%. 従って、この偏光プリズム11を透過する光のうちP偏光はほぼ100%その反射面11Rを透過するがS偏光は約50%に減光され、 Therefore, P-polarized out of the light transmitted through the polarizing prism 11 is transmitted through the substantially 100%, the reflective surface 11R is S-polarized light is dimmed to about 50%,
P偏光とS偏光の強度比を2:1とすることができる。 The intensity ratio of the P polarized light and S-polarized light 2: can be 1. この比率は、薄膜5Cと半導体基板5Bとの間の反射面5D(第6図参照)がアルミニウム膜にて構成されている場合における検出誤差補正に極めて有効である。 This ratio is very effective in the detection error correction when the reflecting surface 5D between the thin 5C and the semiconductor substrate 5B (see FIG. 6) is composed of an aluminum film.

ところで、基板5Bや薄膜5Cの屈折率特性によっては、P Incidentally, the refractive index properties of the substrate 5B and the thin film. 5C, P
偏光とS偏光との比率を上記の値とは異なる値に変えた方がよい場合がある。 The ratio of the polarized light and S-polarized light in some cases it is better to change to a value different from the value of the. この場合は、反射面10Rの特性を変えることにより、P偏光とS偏光との比率を自由に設定でき、更に、この偏光プリズムを入射光軸を中心としてα方向に回動させることによって、検出光L 0の入射面に対するP偏光とS偏光との比を変えることが可能である。 In this case, by changing the characteristics of the reflecting surface 10R, you can freely set the ratio between P polarized light and S-polarized light, further, by rotating the polarizing prism to the α direction around the incident light axis, detection it is possible to vary the ratio of the P-polarized and S-polarized light with respect to the incident surface of the light L 0.

また、検出誤差補正光学系10は、第11図に示すような偏光板12にて代用することも可能である。 The detection error correction optical system 10, can be substituted by the polarizing plate 12 as shown in FIG. 11. この場合、偏光軸をβ方向に回転させることにより、入射光のP偏光とS偏光との比を変えることができる。 In this case, by rotating the polarization axis in the β direction, it is possible to change the ratio of the P-polarized and S-polarized light of the incident light. すなわち、検出光 That is, the detection light
L 0を含み且つ試料面5Aに垂直な入射面に対して偏光軸X Polarization axis X with respect to normal incidence plane and the sample surface 5A includes L 0
がβだけ回転したとすると、P偏光はCos 2 β、S偏光は When but a rotates by beta, P polarized Cos 2 beta, S polarized
Sin 2 βの透過率となり、その角度βを適当に調整することにより所望の比率とすることができる。 Becomes transmittance Sin 2 beta, it can be a desired ratio by adjusting the angle beta appropriately. また、第9図に示す偏光プリズム11のP偏光の透過率T P =100%、S Further, the transmittance of P-polarized T P = 100% of the polarizing prism 11 shown in FIG. 9, S
偏光の透過率をT S =0%になるように構成すれば、前記の偏光板12と全く同様に使うことができ、入射光軸のまわりに回転調整することにより、P偏光とS偏光との比率を変えることができる。 By configuring the transmittance of polarized light such that T S = 0%, the polarizing plate 12 and can be used exactly similar, by rotating adjustment around the incident light axis, P-polarized light and S-polarized light it is possible to change the ratio.

第12図は、第9図の偏光プリズム11や第11図の偏光板12 FIG. 12, the polarizing prism 11 in Fig. 9 and Fig. 11 polarizer 12
の如き検出誤差補正光学系10を第1図に示す検出光路上に回転可能に設けることにより、第7図の場合と同様な光学的条件のもとに、P偏光とS偏光の比率を1:0.35として合成した。 The detection error correction optical system 10, such as by providing rotatably detection light path shown in FIG. 1, under the same optical conditions as in Figure 7, 1 the ratio of the P polarized light and S-polarized light : was synthesized as 0.35. 干渉光の強度の変化と、試料面側での検出位置の検出誤差(表面からのずれ量)を具体的に示したものである。 And changes in the intensity of the interference light is specifically shows the detection error of the detected position of the sample surface (amount of deviation from the surface). この第12図から明らかなように、薄膜5C As apparent from FIG. 12, a thin film 5C
の膜厚が1.1μm付近において検出誤差範囲Δ=0.21μ In the vicinity of the film thickness of 1.1μm detection error range Δ = 0.21μ
mで、第8図に示すΔ=0.32μmに比して精度が向上している。 In m, it has improved accuracy in comparison with the delta = 0.32 [mu] m shown in FIG. 8. すなわち、第7図に示すS偏光を相対的に弱めることにより、そのS偏光による検出誤差を小さくし、 That is, by weakening relative S-polarized light shown in FIG. 7, to reduce the detection error due to the S-polarized light,
精度の向上がはかられている。 Improve the accuracy of are grave. また、干渉光の強度変化も第8図の強度変化(破線)に比して強弱の幅が狭くなり改善されていることが分る。 Further, it can be seen that the width of intensity than the intensity variation of the Figure 8 (broken line) is improved becomes smaller intensity change of the interference light.

上記の実施例では、第1図に示す如く検出誤差補正光学系10を受光側の検出光路上に設けたが、これを送光側つまり第1図中で光源と試料面5Aとの間の検出光路上に設けても同様な補正効果が得られる。 In the above embodiments, is provided with the detection error correction optical system 10 as shown in FIG. 1 to detect light path of the light receiving side, between the light source and the sample surface 5A this with sending side, that the first drawing similar correction effect be provided in the detection beam path is obtained. その際、検出誤差補正光学系10が、偏光プリズム11のような場合には、なるべく平行光束に近い部分の光路上に設けることが望ましい。 At that time, the detection error correction optical system 10, in the case such as the polarizing prism 11 is preferably provided in a portion of the optical path close to the possible parallel beam. しかし、光束の開き角が小さい場合には、P偏光成分とS偏光成分との透過率があまり変化しないので、設置場所を特に限定しなくてもよい。 However, if the opening angle of the light beam is small, since no transmittance change much with the P-polarized component and S-polarized light component, may not be particularly limited installation place.

また、第1図の実施例においては、光源としてランダム偏光のものを用いたが、直線偏光光を発する光源例えば半導体レーザや直線偏光型のレーザを光源1として用いる場合には、その偏光面を検出光の入射面に対して回転調整するために、偏光プリズム11や偏光板12の代りに、 Further, in the embodiment of Figure 1 has been used as a randomly polarized light as a light source, in the case of using a laser light source such as a semiconductor laser or a linear polarization type emits linearly polarized light as the light source 1, the polarization plane to rotational adjustment with respect to the plane of incidence of detected light, instead of the polarizing prism 11 and the polarizing plate 12,
検出誤差補正光学系10として回転可能なλ/2板を用いてもよい。 It may be used a rotatable lambda / 2 plate as a detection error correction optical system 10. また、磁場を制御することにより偏波面(偏光面)を光軸のまわりに回転可能なファラデー素子、あるいは光の旋光性(自然旋光)のある素子、例えば水晶板等を利用して偏光面を回転調整してもよい。 Further, the rotatable Faraday element around the optical axis polarization (polarization plane) by controlling the magnetic field, or optical rotation of light with a (natural optical rotation) elements, for example, the polarization plane by using a quartz plate or the like it may be rotated adjustment. ただし、水晶板の場合には、所定量だけ偏光面を回転させるために、所定の厚さの水晶板を単体または複数個組み合わせて光路中に挿入する。 However, in the case of the quartz plate, to rotate the predetermined amount polarization plane is inserted into the optical path in combination singly or a plurality of predetermined thickness quartz plate.

光源からの偏波面(偏光面)を上記のλ/2板やファラデー素子、水晶板等のような偏光光学手段を用いて、光源の偏波面を入射面に対して傾けることにより、P偏光成分とS偏光成分の強度の相対的な比を変えることが可能である。 The polarization plane of the light source (polarization plane) using the above lambda / 2 plate or Faraday element, the polarizing optical means such as a quartz plate or the like, by tilting with respect to the incident surface of the polarization plane of the light source, P-polarized light component and it is possible to change the relative ratio of the intensity of the S-polarized light component. 例えば、第12図に示す例において、P偏光とS For example, in the example shown in FIG. 12, P-polarized light and S
偏光の強度比を1:0.35にする場合には、反射面(試料面 The intensity ratio of the polarized light 1: When 0.35, the reflective surface (sample surface
5A)と偏波面の角度をθとしてCos 2 θ:Sin 2 θ=1:0.35 5A) and Cos 2 theta angles of polarization as θ: Sin 2 θ = 1: 0.35
にする角度θを選べば、θ=30.6°となる。 If you choose the angle theta to become θ = 30.6 °. このように、光源が偏光している場合には、前述の偏光プリズム Thus, when the light source is polarized in the aforementioned polarizing prism
11や偏光板12のような偏光光学手段によるものよりも光の損失が少ない点で有利である。 Than with polarizing optical means such as 11 and the polarizing plate 12 is advantageous in loss of light is small.

なお、光源1として多波長光源を用い、多色光により反射光の干渉性を少なくさせるようにすれば、更に検出精を向上させることが可能である。 Note that using a multi-wavelength light source as the light source 1, if so as to reduce the interference of the reflected light by polychromatic light, it is possible to further improve the detection accuracy. また、上記第1図の実施例においては、振動する受光スリット6を含む光電検出器9で反射光を検出するように構成されているが、この受光部にCCD型の個体撮像素子やPSD(半導体位置検出素子)あるいは撮像管等の各種検出器を用いて光量重心を検出するように構成してもよい。 Further, in the above-described embodiment of FIG. 1, is configured so as to detect the reflected light at the photoelectric detector 9 comprising receiving slit 6 to vibrate, the CCD type light-receiving unit solid-state imaging device or PSD ( a semiconductor position detecting element) or various detector such as camera tubes may be configured to detect the light quantity gravity center with.

〔発明の効果〕 〔Effect of the invention〕

以上の如く本発明によれば、検出光路上にP偏光成分のS偏光成分との強度を検出面において任意に変えることができる偏光光学手段を設けたので、光透過性の薄膜を有する被検出面に対して、その薄膜によって生じる干渉に起因する表面変位検出誤差を極めて簡単な構成で軽減することができ、さらに、検出先の光強度の変化も小さく、測定精度を向上させることができる利点がある。 According to the present invention as described above, is provided with the polarizing optical means capable of arbitrarily changing the detection surface the intensity of the S-polarized component of the P-polarized light component in the detection light path, the detection having an optical transparency of the film relative to the plane, the surface displacement detection error caused by the interference can be reduced by a very simple construction and caused by the thin film, further, smaller change in the detection target light intensity, the advantage of being able to improve the measurement accuracy there is.

【図面の簡単な説明】 BRIEF DESCRIPTION OF THE DRAWINGS

第1図は本発明の実施例を知す光学系概略構成図、第2 Figure 1 is known to optical system schematic diagram of an embodiment of the present invention, the second
図は、第1図の実施例における、被検出面の位置の変化と検出面における光スポツト像の位置の変化を示す説明図、第3図は第1図の実施例における被検出面上の薄膜にて反射する反射光を示す説明図、第4図は第3図における薄膜による反射光の干渉によって生じる検出面上での光量重心の移動を示す説明図、第5図は干渉によって生じる被検出面側での検出誤差を説明するための線図、 Figure in the embodiment of FIG. 1, explanatory view showing a change in position of the optical Supotsuto image in the change and the detection surface of the position of the detected surface, Figure 3 is on the sensed surface in the embodiment of Figure 1 explanatory view showing a light reflected by the thin film, the Figure 4 is caused by illustration, FIG. 5 is interference showing the movement of a light amount centroid on the detection surface resulting from the interference of the light reflected by the thin film in Figure 3 diagram for explaining a detection error in the detection side,
第6図は検出光の入射角が反射光のP偏光に影響を及ぼすことを説明するための説明図で、(A)は入射角がブリュースター角より小さい場合の断面図、(B)は入射角がブリュースター角より大きい場合の断面図、第7図はP偏光とS偏光のそれぞれの干渉状態における検出結果をシミュレーションで示した線図で(A)は膜厚に対するP偏光とS偏光の光強度分布図、(B)は膜厚に対する被検出面側での見掛ける表面からのずれ量をP偏光とS偏光とについて示す線図、第8図は、第1図の実施例から偏光光学手段を削除した場合の検出結果をシミュレーションで示す線図、第9図は、第1図に示す検出誤差補正光学系としての偏光プリズムを示す斜視図、第10 Figure 6 is a diagram of the incident angle of detection light is described to affect the P-polarized light of the reflected light, (A) a cross-sectional view of when the incident angle is smaller than the Brewster angle, (B) is sectional view of the incident angle is larger than the Brewster angle, Figure 7 is P-polarized light and S-polarized light with respect to the film thickness in the diagram showing the detection result in the simulation (a) is in each state of interference P polarized light and S-polarized light the light intensity distribution diagram, (B) is diagram showing a shift amount from see surface at the detection side with respect to the film thickness for a P-polarized light and S-polarized light, FIG. 8, the polarization from the examples Figure 1 diagram showing the simulation the detection result of deleting the optical means, Figure 9 is a perspective view showing a polarizing prism as a detection error correction optical system shown in FIG. 1, 10
図は第9図の偏光プリズムの光線透過率線図、第11図は検出誤差補正光学系としての偏光板を示す斜視図、第12 Figure light transmittance diagram of a polarization prism Fig. 9, Fig. 11 is a perspective view illustrating a polarizing plate as a detection error correction optical system, 12
図は第1図に示す本発明の検出結果をシミュレーションで示した線図である。 Figure is a diagram illustrating the simulation of the detection result of the present invention shown in Figure 1. (主要部分の符号の説明) 1…光源、3A…送光スリット、4A…送光対物レンズ、4B (Description of main parts of the code) 1 ... light source, 3A ... sending slits, 4A ... light sending objective lens, 4B
…受光対物レンズ、5…半導体ウェハ、5A…半導体ウェハ表面(被検出面)、5B…半導体基板、5C…薄膜、6… ... light receiving objective lens, 5 ... semiconductor wafer, 5A ... semiconductor wafer surface (the detection surface), 5B ... semiconductor substrate, 5C ... film, 6 ...
受光スリット(検出面) 10…検出誤差補正光学系(偏光光学手段) 11…偏光プリズム(偏光光学手段) 12…偏光板(偏光光学手段) Receiving slit (detection surface) 10 ... detection error correction optical system (polarizing optical means) 11 ... polarizing prism (polarization optical means) 12 ... polarizer (polarizing optical means)

Claims (2)

    【特許請求の範囲】 [The claims]
  1. 【請求項1】光透過性の薄膜を有する被検出面に光源からの検出光を斜めに入射して所定形状の光像を結像させた後、前記被検出面からの反射光を検出面上に再結像させ、前記被検出面の位置の変化に応じて変位する前記検出面上での光像を検出して前記被検出面の位置を検出する斜入射型位置検出装置において、前記被検出面で反射された後に前記検出面上に入射する検出光の入射面に平行な偏光成分と入射面に垂直な偏光成分との強度を任意に変え得る偏光光学手段を前記光源から前記被検出面を介して前記検出面に至る間の検出光路上の所定の位置に設けたことを特徴とする表面変位検出装置。 [Claim 1] After imaging the optical image of the predetermined shape of the detection light from the light source to the detected face having a light transmittance of the thin film obliquely incident on the detection surface reflected light from the surface to be detected reimaged by image above, the at grazing incidence position detecting device for detecting a position of the detected face and detecting the light image on the detection surface is displaced in response to a change in position of the detected face, the wherein the polarizing optical means may vary arbitrarily strength perpendicular polarization component in the incident plane parallel polarization component to the incident surface of the detecting light incident on the detection surface after being reflected by the detection surface from the light source to be surface displacement detecting device, characterized in that provided in a predetermined position of the detection light path between leading to the detection surface through the detection surface.
  2. 【請求項2】前記偏光光学手段は、偏光プリズム、板状の偏光板、λ/2板または、磁場を制御して光源の偏光面を回転調整可能なファラデー素子または、旋光性のある光学素子であることを特徴とする特許請求の範囲第1項記載の表面変位検出装置。 Wherein said polarizing optical means, polarizing prism, a plate-like polarizing plate, lambda / 2 plate or controls the magnetic field or rotate the adjustable Faraday element the polarization plane of the light source, an optical element having the optical rotation surface displacement detection apparatus claims paragraph 1, wherein a is.
JP11188987A 1987-05-08 1987-05-08 Surface displacement detecting device Expired - Lifetime JPH0718699B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP11188987A JPH0718699B2 (en) 1987-05-08 1987-05-08 Surface displacement detecting device

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP11188987A JPH0718699B2 (en) 1987-05-08 1987-05-08 Surface displacement detecting device
US07189831 US4864123A (en) 1987-05-08 1988-05-03 Apparatus for detecting the level of an object surface

Publications (2)

Publication Number Publication Date
JPS63275912A true JPS63275912A (en) 1988-11-14
JPH0718699B2 true JPH0718699B2 (en) 1995-03-06

Family

ID=14572686

Family Applications (1)

Application Number Title Priority Date Filing Date
JP11188987A Expired - Lifetime JPH0718699B2 (en) 1987-05-08 1987-05-08 Surface displacement detecting device

Country Status (1)

Country Link
JP (1) JPH0718699B2 (en)

Families Citing this family (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0726648Y2 (en) * 1988-03-30 1995-06-14 アンリツ株式会社 Displacement measuring device
NL9100410A (en) * 1991-03-07 1992-10-01 Asm Lithography Bv Display device provided with a focusfout- and / or tilt detection device.
KR101532824B1 (en) 2003-04-09 2015-07-01 가부시키가이샤 니콘 Exposure method and apparatus, and device manufacturing method
EP2660852B1 (en) 2005-05-12 2015-09-02 Nikon Corporation Projection optical system, exposure apparatus and exposure method
US7609373B2 (en) * 2005-05-31 2009-10-27 Kla-Tencor Technologies Corporation Reducing variations in energy reflected from a sample due to thin film interference
CN105204302A (en) 2005-07-08 2015-12-30 株式会社尼康 Surface Position Detection Apparatus, Exposure Apparatus, And Exposure Method
JP5267029B2 (en) 2007-10-12 2013-08-21 株式会社ニコン Illumination optical apparatus, exposure apparatus and device manufacturing method
US8379187B2 (en) 2007-10-24 2013-02-19 Nikon Corporation Optical unit, illumination optical apparatus, exposure apparatus, and device manufacturing method
US9116346B2 (en) 2007-11-06 2015-08-25 Nikon Corporation Illumination apparatus, illumination method, exposure apparatus, and device manufacturing method
JP5084558B2 (en) * 2008-02-28 2012-11-28 キヤノン株式会社 Surface shape measuring apparatus, an exposure apparatus and device manufacturing method
NL2009273A (en) * 2011-08-31 2013-03-04 Asml Netherlands Bv Level sensor arrangement for lithographic apparatus, lithographic apparatus and device manufacturing method.
CN105700296A (en) * 2014-11-26 2016-06-22 上海微电子装备有限公司 Silicon chip surface height and gradient detection apparatus and method thereof

Also Published As

Publication number Publication date Type
JPS63275912A (en) 1988-11-14 application

Similar Documents

Publication Publication Date Title
US5182455A (en) Method of detecting relative positional deviation between two objects
US5602399A (en) Surface position detecting apparatus and method
US5072126A (en) Promixity alignment using polarized illumination and double conjugate projection lens
US5596411A (en) Integrated spectroscopic ellipsometer
US4923301A (en) Alignment of lithographic system
US6417922B1 (en) Alignment device and lithographic apparatus comprising such a device
US6198527B1 (en) Projection exposure apparatus and exposure method
US5995198A (en) Exposure apparatus
US7442908B2 (en) Method for optically detecting deviations of an image plane of an imaging system from the surface of a substrate
US5323207A (en) Projection exposure apparatus
EP1148390A2 (en) Mark independent alignment sensor
US5333050A (en) Measuring method and apparatus for meausring the positional relationship of first and second gratings
US5436761A (en) Projection exposure apparatus and polarizer
US6594012B2 (en) Exposure apparatus
US4999014A (en) Method and apparatus for measuring thickness of thin films
US4952815A (en) Focusing device for projection exposure apparatus
US5184196A (en) Projection exposure apparatus
US4886974A (en) Mark detecting device for detecting the center of a mark by detecting its edges
US6421124B1 (en) Position detecting system and device manufacturing method using the same
US5764361A (en) Interferometer, adjusting method therefor, stage apparatus having the interferometer, and exposure apparatus having the stage apparatus
US5133603A (en) Device for observing alignment marks on a mask and wafer
US5576829A (en) Method and apparatus for inspecting a phase-shifted mask
US5633721A (en) Surface position detection apparatus
US6122058A (en) Interferometer system with two wavelengths, and lithographic apparatus provided with such a system
US5625453A (en) System and method for detecting the relative positional deviation between diffraction gratings and for measuring the width of a line constituting a diffraction grating

Legal Events

Date Code Title Description
EXPY Cancellation because of completion of term
FPAY Renewal fee payment (prs date is renewal date of database)

Free format text: PAYMENT UNTIL: 20080306

Year of fee payment: 13