JPH0660808B2 - Minute displacement measuring method and minute displacement measuring device - Google Patents

Minute displacement measuring method and minute displacement measuring device

Info

Publication number
JPH0660808B2
JPH0660808B2 JP18134586A JP18134586A JPH0660808B2 JP H0660808 B2 JPH0660808 B2 JP H0660808B2 JP 18134586 A JP18134586 A JP 18134586A JP 18134586 A JP18134586 A JP 18134586A JP H0660808 B2 JPH0660808 B2 JP H0660808B2
Authority
JP
Japan
Prior art keywords
diffraction grating
light
beat signal
phase difference
optical heterodyne
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 - Fee Related
Application number
JP18134586A
Other languages
Japanese (ja)
Other versions
JPS6338102A (en
Inventor
雅則 鈴木
真 猪城
篤▲のぶ▼ 宇根
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nippon Telegraph and Telephone Corp
Original Assignee
Nippon Telegraph and Telephone Corp
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
Application filed by Nippon Telegraph and Telephone Corp filed Critical Nippon Telegraph and Telephone Corp
Priority to JP18134586A priority Critical patent/JPH0660808B2/en
Priority to FR878706393A priority patent/FR2598797B1/en
Priority to DE3715864A priority patent/DE3715864C2/en
Publication of JPS6338102A publication Critical patent/JPS6338102A/en
Priority to US07/492,259 priority patent/US5000573A/en
Publication of JPH0660808B2 publication Critical patent/JPH0660808B2/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

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Classifications

    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03FPHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • 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
    • G03F9/7049Technique, e.g. interferometric
    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03FPHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • 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

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Length Measuring Devices By Optical Means (AREA)
  • Optical Transform (AREA)

Description

【発明の詳細な説明】 〔産業上の利用分野〕 本発明は、回折格子を用いて物体の微小な変位測定を行
なう方法およびそのための装置に関するものである。
Description: TECHNICAL FIELD The present invention relates to a method for measuring a minute displacement of an object using a diffraction grating and an apparatus therefor.

〔従来の技術〕[Conventional technology]

LSIの高集積化に伴い、微細化する集積回路パタンを
高精度で露光,転写する紫外線またはX線露光装置、あ
るいは高精度でパタン描画する電子ビーム露光装置等に
おいては、ステージの精密位置検出ならびに位置決めを
行なう移動量(変位)測定技術の進展は不可欠のものと
なっている。
With the high integration of LSI, in the ultraviolet or X-ray exposure device for exposing and transferring the integrated circuit pattern which becomes finer with high accuracy, or the electron beam exposure device for pattern drawing with high accuracy, etc. Advances in moving amount (displacement) measurement technology for positioning are indispensable.

従来より回析格子を用いて微小な変位測定を行なう方法
として、光ヘテロダイン干渉を利用するものが提案され
ており、第5図にそのような回折格子と光ヘテロダイン
干渉とを組み合わせた微小変位測定装置の一例を示す。
第5図において符号1は、周波数が互いにわずかに異な
り、かつ偏光面が互いに直交する2波長の単色光を発す
る2波長直交偏光レーザ光源、2はビームスプリッタ
ー、3a,3bは集光レンズ、4a,4bは偏光板、5
a,5bは光検出器、6a,6bはプレアンプ、7a,
7b,7c,7dは平面ミラー、8は偏光ビームスプリ
ッター、9は反射型回折格子、10は移動ステージ、1
1はステージ駆動部、12は検出信号処理部、13は変
位表示部、14,15は入射光、16は合成回折光であ
る。
Conventionally, as a method for measuring a minute displacement using a diffraction grating, a method utilizing optical heterodyne interference has been proposed. FIG. 5 shows a minute displacement measurement combining such a diffraction grating and optical heterodyne interference. An example of an apparatus is shown.
In FIG. 5, reference numeral 1 is a two-wavelength orthogonal polarization laser light source which emits monochromatic light of two wavelengths whose frequencies are slightly different from each other and whose polarization planes are orthogonal to each other, 2 is a beam splitter, 3a and 3b are condenser lenses, 4a. , 4b are polarizing plates, 5
a, 5b are photodetectors, 6a, 6b are preamplifiers, 7a,
7b, 7c and 7d are plane mirrors, 8 is a polarization beam splitter, 9 is a reflection type diffraction grating, 10 is a moving stage, 1
Reference numeral 1 is a stage drive unit, 12 is a detection signal processing unit, 13 is a displacement display unit, 14 and 15 are incident lights, and 16 is synthetic diffracted light.

この装置においては、2波長直交偏光レーザ光源1から
発したレーザ光の一部をビームスプリッター2を介して
取り出し、集光レンズ3aでレーザ光を集光し、偏光板
4aを用いて光ヘテロダイン干渉させ、光検出器5aで
検出してプレアンプ6aを通し、基準ビート信号として
検出信号処理部12に入力する。一方、2波長直交偏光
レーザ光源1から発した光の一部は、ビームスプリッタ
ー2,平面ミラー7aを介して偏光ビームスプリッター
8に入る。偏光ビームスプリッター8により偏光面が互
いに直交し周波数がわずかに異なる二つの単色光、すな
わちP偏光の入射光14とS偏光の入射光15に分割
し、これらを平面ミラー7b,7cを介して後述する所
定の入射角で反射型回折格子9に入射する。回折格子9
から得られる2波長の回折光を光学的に合成し、合成回
折光16として平面ミラー7d,集光レンズ3b,偏光
板4bを通し、光ヘテロダイン干渉させて光検出器5b
で検出し、回折光ビート信号としてプレアンプ6bを通
して上記の検出信号処理部12に入力する。検出信号処
理部12では、回折格子9の変位に対応した基準ビート
信号と回折光ビート信号との位相差を検出し、その位相
差を変位量に換算して変位表示部13で回折格子9の変
位量を表示する。また、位相差があらかじめ設定した任
意の値で一定となるように、検出信号処理部12よりス
テージ駆動部11に制御信号を送り、回折格子9を定め
られた位置にサーボ制御することもできる。
In this device, a part of the laser light emitted from the two-wavelength orthogonal polarization laser light source 1 is extracted through the beam splitter 2, the laser light is condensed by the condenser lens 3a, and the optical heterodyne interference is generated by using the polarizing plate 4a. Then, it is detected by the photodetector 5a, passes through the preamplifier 6a, and is input to the detection signal processing unit 12 as a reference beat signal. On the other hand, a part of the light emitted from the two-wavelength orthogonal polarization laser light source 1 enters the polarization beam splitter 8 via the beam splitter 2 and the plane mirror 7a. The polarization beam splitter 8 splits the two monochromatic lights whose polarization planes are orthogonal to each other and whose frequencies are slightly different from each other, that is, P-polarized incident light 14 and S-polarized incident light 15, which are described later via plane mirrors 7b and 7c. Is incident on the reflection type diffraction grating 9 at a predetermined incident angle. Diffraction grating 9
The two-wavelength diffracted lights obtained from the above are optically combined, and the combined diffracted light 16 is passed through the plane mirror 7d, the condenser lens 3b, and the polarizing plate 4b, and optical heterodyne interference is caused to cause photodetector 5b.
And is input to the detection signal processing unit 12 through the preamplifier 6b as a diffracted light beat signal. The detection signal processing unit 12 detects the phase difference between the reference beat signal and the diffracted light beat signal corresponding to the displacement of the diffraction grating 9, converts the phase difference into a displacement amount, and the displacement display unit 13 displays the phase difference of the diffraction grating 9. Display the amount of displacement. Further, a control signal may be sent from the detection signal processing unit 12 to the stage driving unit 11 so that the phase difference becomes constant at a preset arbitrary value, and the diffraction grating 9 may be servo-controlled to a predetermined position.

ここで、回折格子9の変位量ΔXと、基準ビート信号お
よび回折光ビート信号の位相差Δφとの関係について第
6図を参照して説明する。第6図において符号17は反
射型回折格子、18a,18bは波長λの入射光、1
9a,19bは波長λの入射光、20a,20bは合
成回折光である。
Here, the relationship between the displacement amount ΔX of the diffraction grating 9 and the phase difference Δφ between the reference beat signal and the diffracted light beat signal will be described with reference to FIG. In FIG. 6, reference numeral 17 is a reflection type diffraction grating, 18a and 18b are incident light of wavelength λ 1 , 1
Reference numerals 9a and 19b denote incident light of wavelength λ 2 , and 20a and 20b denote combined diffracted light.

偏光面が互いに直交し、かつ周波数が互いにわずかにず
れている波長λ,波長λの入射光18a,19a
が、回折格子17の格子面の法線方向に対してそれぞれ
n次回折角θn,θnで回折格子17の例えばA点
に入射した場合、回折格子17のA点から格子面の法線
方向に入射光18a,19aのn次回折光それぞれが出
射する。それらのn次回折光は、格子面の法線方向にお
いて光学的に合成されて合成回折光20aとなり、光ヘ
テロダイン干渉ビート信号検出が可能となる。ここで、
回折格子17が格子ラインに直交する方向に変位量ΔX
移動してA点がA′点に変位した場合、同様に入射光1
8b,19bに対してそれぞれのn次回折光が出射し、
それらが光学的に合成されて合成回折光20bとなる。
回折格子17の格子ピッチをPとすると、n次回折角θ
,θn、波長λ,λの間にはsin θn=n・λ/P(nは正の整数)……(1)sin θn=n・λ/P( 〃 )……(2) の関係がある。回折格子17がΔXだけ変位することに
より、入射光18aと18bとにはΔX・sinθn
入射光19aと19bとには−ΔX・sinθnの光路
長差がそれぞれ生じる。したがって、合成回折光20a
と20bとから得られる光ヘテロダイン干渉ビート信号
には、位相差Δφが生じ、このΔφは、 Δφ=(2π・ΔX・sinθn/λ) +(2π・ΔX・sinθn/λ)…(3) となる。(3)式に(1),(2)式を代入すると、 となり、位相差Δφは、回折格子17の変位ΔXに対し
P/2nを周期として変化する。
Incident lights 18a and 19a having wavelengths λ 1 and λ 2 whose polarization planes are orthogonal to each other and whose frequencies are slightly different from each other.
When incident on the diffraction grating 17 at, for example, point A at the n-th order diffraction angles θn 1 and θn 2 with respect to the normal direction of the diffraction grating 17, the normal direction of the diffraction surface from the point A of the diffraction grating 17 The nth-order diffracted lights of the incident lights 18a and 19a are emitted respectively. The n-th order diffracted lights are optically combined in the normal direction of the grating surface to form a combined diffracted light 20a, which enables optical heterodyne interference beat signal detection. here,
Displacement amount ΔX in the direction in which the diffraction grating 17 is orthogonal to the grating line
If point A moves to point A ', the incident light 1
The n-th order diffracted light is emitted to 8b and 19b,
They are optically combined to form combined diffracted light 20b.
When the grating pitch of the diffraction grating 17 is P, the nth-order diffraction angle θ
Between n 1 and θn 2 and wavelengths λ 1 and λ 2 , sin θn 1 = n · λ 1 / P (n is a positive integer) (1) sin θn 2 = n · λ 2 / P (〃 ) ... (2) Due to the displacement of the diffraction grating 17 by ΔX, the incident lights 18a and 18b have ΔX · sin θn 1 ,
An optical path length difference of −ΔX · sin θn 2 occurs between the incident lights 19a and 19b. Therefore, the synthetic diffracted light 20a
And 20b, the optical heterodyne interference beat signal has a phase difference Δφ, and this Δφ is Δφ = (2π · ΔX · sin θn 1 / λ 1 ) + (2π · ΔX · sin θn 2 / λ 2 ) ... (3) Substituting equations (1) and (2) into equation (3), Therefore, the phase difference Δφ changes with a period of P / 2n with respect to the displacement ΔX of the diffraction grating 17.

すなわち、前記第5図における回折格子9からの合成回
折光16が入射光14,15のn次回折光の合成回折光
である場合、前記光検出器6a,6bで検出される基準
ビート信号と回折光ビート信号との位相差Δφは、回折
格子9の格子ピッチをPとすると、回折格子9の変位量
P/2nを1周期として変化する。したがって、検出信
号処理部12において例えば位相検波し、位相差をDC
信号に変換し、例えば位相差0゜ごとにDC信号からパ
ルス信号を生成し、そのパルス信号をカウントすること
によって、分解能P/2nの精度で回折格子9の変位測
定が可能である。さらに、位相差0゜から360゜まで
のDC信号変化を例えば1/360に補間して位相差の
検出分解能を1゜に設定し、前記パルス間の回折格子の
変位を位相差検出することにより、回折格子9の変位を
分解能P/(2n・360)で検出することができる。
なお、回折格子9の変位の方向は、基準ビート信号に対
する回折光ビート信号の位相差の正負を弁別することに
より容易に判定することができる。
That is, when the synthetic diffracted light 16 from the diffraction grating 9 in FIG. 5 is a synthetic diffracted light of the nth-order diffracted light of the incident light 14 and 15, the reference beat signal detected by the photodetectors 6a and 6b and the diffracted light When the grating pitch of the diffraction grating 9 is P, the phase difference Δφ with the optical beat signal changes with the displacement amount P / 2n of the diffraction grating 9 as one cycle. Therefore, in the detection signal processing unit 12, for example, phase detection is performed and the phase difference is DC.
The displacement of the diffraction grating 9 can be measured with an accuracy of resolution P / 2n by converting the signal into a signal, generating a pulse signal from the DC signal for each 0 ° phase difference, and counting the pulse signal. Furthermore, by interpolating a DC signal change from 0 ° to 360 ° in phase difference to, for example, 1/360 and setting the detection resolution of the phase difference to 1 °, the displacement of the diffraction grating between the pulses is detected by the phase difference. , The displacement of the diffraction grating 9 can be detected with the resolution P / (2n · 360).
The direction of displacement of the diffraction grating 9 can be easily determined by discriminating whether the phase difference between the diffracted light beat signal and the reference beat signal is positive or negative.

〔発明が解決しようとする問題点〕[Problems to be solved by the invention]

ところが、上記従来の微小変位測定装置においては、回
折格子面の法線方向についての微小変位を検出できない
という欠点があった。
However, the conventional small displacement measuring device described above has a drawback that it cannot detect a small displacement in the normal direction of the diffraction grating surface.

このことについて、第7図を参照して説明する。第7図
において符号21は反射型回折格子、22a,22bは
波長λの入射光、23a,23bは波長λの入射
光、24a,24bは合成回折光である。波長λ,λ
のレーザー光の入射角はそれぞれn次回折角θn
θnである。
This will be described with reference to FIG. In FIG. 7, reference numeral 21 is a reflection type diffraction grating, 22a and 22b are incident lights of wavelength λ 1 , 23a and 23b are incident lights of wavelength λ 2 , and 24a and 24b are synthetic diffracted lights. Wavelength λ 1 , λ
The incident angle of the second laser beam is the nth diffraction angle θn 1 ,
θn 2 .

入射光22a,23aが回折格子21のB点に入射した
場合、格子面の法線方向に入射光22a,23aのn次
回折光がそれぞれ出射し、それらが光学的に合成されて
合成回折光24aとなる。ここで、回折格子21が法線
方向に変位量ΔZ移動してB点がB′点に変位した場
合、同様に入射光22b,23bに対してn次回折光が
それぞれ出射して合成回折光24bとなる。入射光22
aと22bとには−ΔZ(1+cos θn),入射光2
3aと23bとには−ΔZ(1+cos θn)の光路長
差がそれぞれ生じるので、合成回折光24aと24bと
から得られる光ヘテロダイン干渉ビート信号には位相差
Δφが生じ、このΔφは、 Δφ={2π・ΔZ(1+cos θn)/λ} −{2π・ΔZ(1+cos θn)/λ} =2π・ΔZ・{(λ−λ) +(λcos θn−λcos θn)} /λλ ……(5) となる。
When the incident lights 22a and 23a are incident on the point B of the diffraction grating 21, the nth-order diffracted lights of the incident lights 22a and 23a are respectively emitted in the normal direction of the grating surface, and they are optically combined to be the combined diffracted light 24a. Becomes Here, when the diffraction grating 21 moves by the displacement amount ΔZ in the normal direction and the point B is displaced to the point B ′, similarly, the n-th order diffracted light is emitted to the incident lights 22b and 23b, respectively, and the combined diffracted light 24b is emitted. Becomes Incident light 22
-ΔZ (1 + cos θn 1 ), incident light 2 in a and 22 b
Since an optical path length difference of −ΔZ (1 + cos θn 2 ) is generated between 3a and 23b, a phase difference Δφ occurs in the optical heterodyne interference beat signal obtained from the combined diffracted lights 24a and 24b, and this Δφ is Δφ. = {2π · ΔZ (1 + cos θn 2 ) / λ 2 }-{2π · ΔZ (1 + cos θn 1 ) / λ 1 } = 2π · ΔZ · {(λ 1 −λ 2 ) + (λ 1 cos θn 2 −λ 2 cos θn 1 )} / λ 1 λ 2 (5)

ところが、波長λ,λのレーザ光の周波数差Δfす
なわちビート信号の周波数は、例えば数十KHz〜数M
Hz程度であって光の周波数に比べて非常に小さく、 |λ−λ|=(Δf/C)・λ・λ ≒0 (Cは光速) ……(6) となり、λ≒λ,θn≒θnとなって、(5)
式の位相差ΔφはΔZの値に関係なく常に0となってし
まう。
However, the frequency difference Δf of the laser light having the wavelengths λ 1 and λ 2 , that is, the frequency of the beat signal is, for example, several tens KHz to several M.
It is about Hz, which is much smaller than the frequency of light, and | λ 1 −λ 2 | = (Δf / C) · λ 1 · λ 2 ≈0 (C is the speed of light) (6), and λ 1 ≈ λ 2 , θn 1 ≈ θn 2, and (5)
The phase difference Δφ in the equation is always 0 regardless of the value of ΔZ.

このように、従来の微小変位測定装置においては回折格
子面の法線方向についての微小変位ΔZを検出できない
ものであった。したがって紫外線露光装置における焦点
合わせ、あるいはX線露光装置におけるマスク・ウエハ
間のギャップ設定等のウエハ面の法線方向の制御が必要
不可欠な場合には、上記のような従来の装置は適用でき
ないものであった。このため従来においては、2方向の
変位を測定するためには他の測定装置を用いなければな
らず、装置が大型化,複雑化するという問題を有してい
た。
As described above, the conventional micro-displacement measuring device cannot detect the micro-displacement ΔZ in the normal direction of the diffraction grating surface. Therefore, when it is indispensable to control the normal direction of the wafer surface such as the focus adjustment in the ultraviolet exposure apparatus or the mask-wafer gap setting in the X-ray exposure apparatus, the conventional apparatus described above cannot be applied. Met. For this reason, in the past, another measuring device had to be used to measure the displacement in two directions, and there was a problem that the device became large and complicated.

本発明は上記の事情に鑑みてなされたもので、回折格子
面の法線方向の微小変位についても測定することのでき
る方法およびそのための装置を提供することを目的とし
ている。
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method and an apparatus therefor capable of measuring a minute displacement of a diffraction grating surface in a normal direction.

〔問題点を解決するための手段〕[Means for solving problems]

この発明の微小変位測定方法は、周波数が互いにわずか
に異なる2波長の単色光を合成し光ヘテロダイン干渉さ
せて基準ビート信号を生成するとともに、前記2波長の
単色光のいずれか一方を分光してそれら分光した単色光
をそれぞれ互いに異なる方向から物体上に固定した回折
格子に対して入射させ、かつ前記2波長の単色光の他方
を前記回折格子に対して入射させて前記一方の単色光の
それぞれの分光の回折光と前記他方の単色光の回折光と
をそれぞれ合成して第1および第2の光ヘテロダイン干
渉ビート信号を生成し、前記基準ビート信号と前記第1
の光ヘテロダイン干渉ビート信号との位相差、および前
記基準ビート信号と前記第2の光ヘテロダイン干渉ビー
ト信号との位相差をそれぞれ検出することによって、そ
れら位相差から前記物体の前記回折格子の格子ラインに
直交する方向の微小変位およびその回折格子の法線方向
の微小変位をそれぞれ測定することを特徴としている。
The micro-displacement measuring method of the present invention synthesizes monochromatic lights of two wavelengths whose frequencies are slightly different from each other and causes optical heterodyne interference to generate a reference beat signal, and also disperses one of the monochromatic lights of the two wavelengths. The separated monochromatic lights are made to enter the diffraction grating fixed on the object from different directions respectively, and the other of the monochromatic lights of the two wavelengths are made incident on the diffraction grating to make each of the one monochromatic lights. And the diffracted light of the other monochromatic light are respectively combined to generate first and second optical heterodyne interference beat signals, and the reference beat signal and the first beat signal are generated.
By detecting the phase difference between the optical heterodyne interference beat signal and the phase difference between the reference beat signal and the second optical heterodyne interference beat signal, the grating line of the diffraction grating of the object from these phase differences. It is characterized by measuring a small displacement in a direction orthogonal to the direction and a small displacement in the normal direction of the diffraction grating.

また、この発明の微小変位測定装置は、物体上に固定さ
れた回折格子と、周波数が互いにわずかに異なる2波長
の単色光を発生する光源と、その光源から発せられた2
波長の単色光を合成し光ヘテロダイン干渉させて基準ビ
ート信号を生成する第1の光合成検出手段と、前記光源
から発せられた2波長の単色光のいずれか一方を分光す
る分光手段と、前記分光されたそれぞれの単色光および
前記他方の単色光を前記回折格子に所定の角度を有した
方向からそれぞれ入射させる入射角調整手段と、前記一
方の単色光のそれぞれの分光の回折光と前記他方の単色
光の回折光とをそれぞれ合成して第1、第2の光ヘテロ
ダイン干渉ビート信号を生成する第2、第3の光合成検
出手段と、前記第1および第2の光合成検出手段によっ
てそれぞれ生成された基準ビート信号および第1の光ヘ
テロダイン干渉ビート信号とから第1の位相差信号を算
出処理して前記物体の前記回折格子の格子ラインに直交
する方向の変位量に換算する第1の信号処理装置と、そ
の第1の信号処理装置によって算出処理された第1の位
相差信号および前記第1、第3の光合成検出手段によっ
てそれぞれ生成された基準ビート信号、第2の光ヘテロ
ダイン干渉ビート信号とから第2の位相差信号を算出処
理して前記物体の前記回折格子の法線方向の変位量に換
算する第2の信号処理装置とを具備してなることを特徴
としている。
Further, the micro-displacement measuring device of the present invention includes a diffraction grating fixed on an object, a light source for generating monochromatic light of two wavelengths whose frequencies are slightly different from each other, and a light source for emitting light from the light source.
First photosynthesis detecting means for synthesizing monochromatic light of wavelengths and causing optical heterodyne interference to generate a reference beat signal; spectroscopic means for spectrally splitting one of the monochromatic light of two wavelengths emitted from the light source; Incident angle adjusting means for respectively injecting the respective monochromatic light and the other monochromatic light into the diffraction grating from a direction having a predetermined angle, and diffracted light of each of the one monochromatic light spectrum and the other Generated by the second and third photosynthesis detecting means for respectively synthesizing the diffracted light of the monochromatic light to generate the first and second optical heterodyne interference beat signals, and the first and second photosynthesis detecting means, respectively. A displacement amount of the object in a direction orthogonal to the grating line of the diffraction grating by calculating a first phase difference signal from the reference beat signal and the first optical heterodyne interference beat signal. A first signal processing device for conversion, a first phase difference signal calculated and processed by the first signal processing device, and reference beat signals respectively generated by the first and third photosynthesis detecting means, a second And a second signal processing device for calculating a second phase difference signal from the optical heterodyne interference beat signal and converting it into a displacement amount of the object in the normal direction of the diffraction grating. I am trying.

〔作用〕[Action]

本発明では、2波長の単色光の一方を分光することによ
って合計3本の単色光を回折格子に対して入射させ、そ
れらの回折光から第1、第2の光ヘテロダイン干渉ビー
ト信号を生成する。そして、それら第1、第2の光ヘテ
ロダイン干渉ビート信号と基準ビート信号に基づいて、
回折格子の微小変位を2方向すなわち回折格子の格子ラ
インに直交する方向と回折格子の法線方向の双方に対し
て検出する。
In the present invention, a total of three monochromatic lights are made incident on the diffraction grating by dispersing one of the monochromatic lights of two wavelengths, and the first and second optical heterodyne interference beat signals are generated from the diffracted lights. . Then, based on the first and second optical heterodyne interference beat signals and the reference beat signal,
The minute displacement of the diffraction grating is detected in two directions, that is, both the direction orthogonal to the grating line of the diffraction grating and the normal direction of the diffraction grating.

〔実施例〕〔Example〕

以下、本発明の実施例を第1図ないし第4図を参照して
説明する。
An embodiment of the present invention will be described below with reference to FIGS. 1 to 4.

第1図は本発明に係る微小変位測定装置の第1実施例を
示す。第1図において符号25は2波長直交偏光レーザ
光源(光源)、26a,26bはビームスプリッター、
27は偏光ビームスプリッター、28a,28b,28
c,33a,33b,34a,34b,34c,34d
は平面ミラー、29a,29b,29cは集光レンズ、
30a,30b,30cは偏光板、31a,31b,3
1cは光検出器、32a,32b,32cはプレアン
プ、35は反射型回折格子、36はZ移動ステージ、3
7はXY移動ステージ、38はX変位検出信号処理部
(第1の信号処理装置)、39はZ変位検出信号処理部
(第2の信号処理装置)、40はX変位表示部、41は
Z変位表示部、42はZステージ駆動部、43はXYス
テージ駆動部、44,45,46は入射光、47,48
は合成回折光である。
FIG. 1 shows a first embodiment of a small displacement measuring device according to the present invention. In FIG. 1, reference numeral 25 is a two-wavelength orthogonal polarization laser light source (light source), 26a and 26b are beam splitters,
27 is a polarization beam splitter, 28a, 28b, 28
c, 33a, 33b, 34a, 34b, 34c, 34d
Is a plane mirror, 29a, 29b and 29c are condenser lenses,
30a, 30b and 30c are polarizing plates, 31a, 31b and 3
1c is a photodetector, 32a, 32b and 32c are preamplifiers, 35 is a reflection type diffraction grating, 36 is a Z moving stage, 3
7 is an XY moving stage, 38 is an X displacement detection signal processing unit (first signal processing device), 39 is a Z displacement detection signal processing unit (second signal processing device), 40 is an X displacement display unit, and 41 is Z. Displacement display unit, 42 Z stage drive unit, 43 XY stage drive unit, 44, 45, 46 incident light, 47, 48
Is a synthetic diffracted light.

この第1実施例の装置においては、2波長直交偏光レー
ザ光源25から発したレーザ光の一部をビームスプリッ
ター26a,平面ミラー28a,集光レンズ29a,偏
光板30aを介して光検出器31a(第1の光合成検出
手段)で検出し、光ヘテロダイン干渉の基準ビート信号
としてプレアンプ32aを通してX変位検出信号処理部
38、およびZ変位検出信号処理部39に入力する。一
方、2波長直交偏光レーザ光源25から発したレーザ光
は、ビームスプリッター26aを介して偏光ビームスプ
リッター27に入り、ここでP偏光,S偏光の2つのレ
ーザ光に分離され、P偏光成分は平面ミラー33a,3
4bを介して後述する所定の入射角で入射光44として
反射型回折格子35に入射する。S偏光成分はビームス
プリッター26b(分光手段)によりさらに分割され、
平面ミラー34cを介して入射光45として、また平面
ミラー33b,34aを介して入射光46として、それ
ぞれ反射型回折格子35に入射する。入射光44,45
により回折格子35から得られる合成回折光47を平面
ミラー28b,集光レンズ29b,偏光板30bを介し
て光検出器31b(第2の光合成検出手段)で検出し、
第1の光ヘテロダイン干渉ビート信号としてプレアンプ
32bを通してX変位検出信号処理部38に入力する。
さらに、入射光44,46により回折格子35から得ら
れる合成回折光48を平面ミラー34d,28c,集光
レンズ29c,偏光板30cを介して光検出器31c
(第3の光合成検出手段)で検出し、第2の光ヘテロダ
イン干渉ビート信号としてプレアンプ32cを通してZ
変位検出信号処理部39に入力する。X変位検出信号処
理部38では、回折格子面内で格子ライン方向に直交す
る方向(第1図において左右方向。以後X方向という)
についての回折格子35の変位に対応した基準ビート信
号と第1の光ヘテロダイン干渉ビート信号との位相差を
検出し、その位相差を変位量に換算し、X変位表示部4
0で変位量を表示する。Z変位検出信号処理部39で
は、基準ビート信号と第2の光ヘテロダイン干渉ビート
信号との位相差を検出し、さらにX変位検出信号処理部
38より基準ビート信号と第1の光ヘテロダイン干渉ビ
ート信号との位相差信号(第1の位相差信号)を入力し
て加算処理することにより、回折格子面の法線方向(第
1図において上下方向。以後Z方向という)についての
回折格子35の変位に対応した位相差信号(第2の位相
差信号)を生成し、その位相差を変位量に換算してZ変
位表示部41で表示する。また、位相差があらかじめ設
定した任意の値で一定となるように、XおよびZ変位検
出信号処理部38,39よりZおよびXYステージ駆動
部42,43に制御信号を送り、回折格子35を定めら
れた位置にサーボ制御する。
In the apparatus of the first embodiment, a part of the laser light emitted from the two-wavelength orthogonal polarization laser light source 25 is passed through the beam splitter 26a, the plane mirror 28a, the condenser lens 29a, and the polarizing plate 30a, and the photodetector 31a ( It is detected by the first photosynthesis detecting means) and inputted to the X displacement detection signal processing unit 38 and the Z displacement detection signal processing unit 39 as the reference beat signal of the optical heterodyne interference through the preamplifier 32a. On the other hand, the laser light emitted from the two-wavelength orthogonal polarization laser light source 25 enters the polarization beam splitter 27 via the beam splitter 26a, and is separated into two laser lights of P polarization and S polarization, and the P polarization component is a plane. Mirrors 33a, 3
The incident light 44 is incident on the reflection type diffraction grating 35 at a predetermined incident angle described later via 4b. The S-polarized component is further divided by the beam splitter 26b (spectroscopic means),
The light enters the reflection type diffraction grating 35 as incident light 45 via the plane mirror 34c and as incident light 46 via the plane mirrors 33b and 34a. Incident light 44, 45
The composite diffracted light 47 obtained from the diffraction grating 35 is detected by the photodetector 31b (second photosynthesis detection means) via the plane mirror 28b, the condenser lens 29b, and the polarizing plate 30b.
The first optical heterodyne interference beat signal is input to the X displacement detection signal processing unit 38 through the preamplifier 32b.
Further, the synthetic diffracted light 48 obtained from the diffraction grating 35 by the incident lights 44 and 46 is passed through the plane mirrors 34d and 28c, the condenser lens 29c, and the polarizing plate 30c, and the photodetector 31c.
(Third photosynthesis detecting means), and Z as a second optical heterodyne interference beat signal through the preamplifier 32c.
It is input to the displacement detection signal processing unit 39. In the X displacement detection signal processing unit 38, a direction orthogonal to the grating line direction in the diffraction grating plane (the horizontal direction in FIG. 1, hereinafter referred to as the X direction).
The phase difference between the reference beat signal corresponding to the displacement of the diffraction grating 35 and the first optical heterodyne interference beat signal is detected, the phase difference is converted into the displacement amount, and the X displacement display unit 4
A displacement amount of 0 is displayed. The Z displacement detection signal processing unit 39 detects the phase difference between the reference beat signal and the second optical heterodyne interference beat signal, and the X displacement detection signal processing unit 38 further detects the phase difference between the reference beat signal and the first optical heterodyne interference beat signal. By inputting a phase difference signal (first phase difference signal) with and adding processing, the displacement of the diffraction grating 35 in the normal direction of the diffraction grating surface (vertical direction in FIG. 1, hereinafter referred to as Z direction). A phase difference signal (second phase difference signal) corresponding to is generated, the phase difference is converted into a displacement amount and displayed on the Z displacement display unit 41. Further, a control signal is sent from the X and Z displacement detection signal processing units 38 and 39 to the Z and XY stage drive units 42 and 43 so that the phase difference becomes constant at a preset arbitrary value, and the diffraction grating 35 is determined. Servo control to the specified position.

この装置では、入射光44,45をZ方向に対してそれ
ぞれn次回折角で入射した場合、回折格子35のX方向
の変位量ΔXと、基準ビート信号と第1の光ヘテロダイ
ン干渉ビート信号との位相差Δφxとの関係は、第6図
および第7図で説明した従来の装置による場合と同様
に、 となり、また、Z方向の変位量ΔZに対して位相差は変
化せず一定となる。
In this device, when the incident lights 44 and 45 are respectively incident at the nth diffraction angle in the Z direction, the displacement amount ΔX of the diffraction grating 35 in the X direction, the reference beat signal, and the first optical heterodyne interference beat signal are The relationship with the phase difference Δφx is the same as in the case of the conventional apparatus described in FIGS. 6 and 7, In addition, the phase difference does not change with respect to the displacement amount ΔZ in the Z direction and remains constant.

一方、回折格子35の変位量ΔX,ΔZと、基準ビート
信号および第2の光ヘテロダイン干渉ビート信号との位
相差Δφzxとは次のような関係にあり、それについて
第2図および第3図を参照して説明する。第2図におい
て符号49は反射型回折格子、50a,50bは波長λ
の入射光、51a,51bは波長λの入射光、52
a,52bは合成回折光である。
On the other hand, the displacements ΔX and ΔZ of the diffraction grating 35 and the phase difference Δφzx between the reference beat signal and the second optical heterodyne interference beat signal have the following relationship, which is shown in FIGS. 2 and 3. It will be described with reference to FIG. In FIG. 2, reference numeral 49 is a reflection type diffraction grating, and 50a and 50b are wavelengths λ.
1 incident light, 51a and 51b are incident light of wavelength λ 2 , 52
Reference numerals a and 52b are synthetic diffracted lights.

偏光面が互いに直交し周波数が互いにわずかにずれた波
長λ,λの入射光50a,51aが、Z方向に対し
てそれぞれn次回折角θn、n次回折角の3倍の角度
3θnで回折格子49の例えばA点に入射した場合、
回折格子49のA点からZ方向に対してn次回折角の2
倍の角度2θnの方向に入射光50aの+n次回折
光、入射光51aの−n次回折光がそれぞれ出射する。
上述したように、式(6)よりθn≒θnとなり、
入射光50a,51aのそれぞれ+n次,−n次回折光
は光学的に合成されて合成回折光52aとなり、光ヘテ
ロダイン干渉ビート信号検出が可能となる。
Incident lights 50a and 51a having wavelengths λ 1 and λ 2 whose polarization planes are orthogonal to each other and whose frequencies are slightly deviated from each other have an n-th order diffraction angle θn 1 and an angle 3θn 2 that is three times the n-th order diffraction angle with respect to the Z direction. When the light enters the diffraction grating 49 at point A, for example,
From the point A of the diffraction grating 49 to the Z direction, the nth-order diffraction angle is 2
The + nth-order diffracted light of the incident light 50a and the −nth-order diffracted light of the incident light 51a are emitted in the direction of the double angle 2θn 1 .
As described above, according to the equation (6), θn 1 ≈θn 2 , and
The + nth-order and -nth-order diffracted lights of the incident lights 50a and 51a are optically combined into a combined diffracted light 52a, which enables optical heterodyne interference beat signal detection.

ここで、回折格子49が変位量ΔX移動してA点がA′
点に変位した場合、同様に入射光50b,51bに対し
てそれぞれの+n次,−n次回折光が光学的に合成され
合成回折光52bとなる。回折格子49がΔX変位する
ことにより、入射光50aと50bとにはΔX・(sin
θnsin2θn),入射光51aと51bとには
ΔX・(sin3θnsin2θn)の光路長差がそれ
ぞれ生じる。したがって合成回折光52aと52bとか
ら得られる光ヘテロダイン干渉ビート信号には、位相差
Δφ′zxが生じ、このΔφ′zxは Δφ′zx=2π・ΔX・{(sinθnsin2θn)/λ−(sin3θnsin2θn)/λ} ……(8) となる。ここでθn≒θnsin3θn≒3sinθ
,λ≒λであるから(8)式は、 となり、ΔXに対する基準ビート信号と第2の光ヘテロ
ダイン干渉ビート信号との位相差Δφ′zxは、式
(7)で示されている基準ビート信号と第1の光ヘテロ
ダイン干渉ビート信号との位相差Δφxと位相のずれ方
向が反対となる。
Here, the diffraction grating 49 moves by the displacement amount ΔX and the point A becomes A ′.
When displaced to a point, similarly, the + n-order diffracted light and the −n-order diffracted diffracted light are optically combined with the incident lights 50b and 51b to become combined diffracted light 52b. Due to the displacement of the diffraction grating 49 by ΔX, the incident lights 50a and 50b have ΔX · ( sin
θn 1 - sin 2θn 1), ΔX · in the incident light 51a and 51b (sin 3θn 2 - optical path length difference between the sin 2θn 2) occurs, respectively. Thus the optical heterodyne interference beat signal obtained from the synthesis diffracted light 52a and 52 b, resulting phase difference Derutafai'zx, this Derutafai'zx is Δφ'zx = 2π · ΔX · {( sin θn 1 - sin 2θn 1) / lambda 1 - a / λ 2} ...... (8) - (sin 2θn 2 sin 3θn 2). Where θn 1 ≈ θn 2 , sin 3 θn 2 ≈ 3 sin θ
Since n 2 , λ 1 ≈λ 2 , the equation (8) is Therefore, the phase difference Δφ′zx between the reference beat signal and the second optical heterodyne interference beat signal with respect to ΔX is the phase difference between the reference beat signal and the first optical heterodyne interference beat signal shown in equation (7). The phase shift direction is opposite to Δφx.

一方、第3図において符号53は反射型回折格子、54
a,54bは波長λの入射光、55a,55bは波長
λの入射光、56a,56bは合成回折光である。波
長λ,λの入射光54a,55aがZ方向に対して
それぞれn次回折角θn、n次回折角の3倍の角度3
θnで回折格子53の例えばB点に入射した場合、Z
方向に対してn次回折角の2倍の角度2θnの方向に
入射光54aの+n次回折光、入射光55aの−n次回
折光が出射して合成回折光56aとなり、光ヘテロダイ
ン干渉ビート信号が検出可能となる。ここで、回折格子
53が変位量ΔZ移動してB点がB′点に変位した場
合、同様に入射光54b,55bに対してそれぞれ+n
次,−n次回折光が光学的に合成されて合成回折光56
bとなる。回折格子53がΔZ変位することにより、入
射光54aと54bとには−ΔZ・(cos θn+cos
2θn),入射光55aと55bとには−ΔZ・(co
s 3θn+cos 2θn)の光路長差がそれぞれ生じ
る。したがって、合成回折光56aと56bとから得ら
れる光ヘテロダイン干渉ビート信号には、位相差Δφ″
zxが生じ、 Δφ″zx=2π・ΔZ{(cos 3θn +cos 2θn)/λ−(cos θn −cos 2θn)/λ} ……(10) となる。λ≒λ,θn≒θnを考慮すると、 Δφ″zx≒2π・ΔZ・(cos 3θn −cos θn)/λ ……(11) となり、 ΔZ=λ/(cos 3θn−cos θn) の周期で位相が変化することがわかる。
On the other hand, in FIG. 3, reference numeral 53 is a reflection type diffraction grating, 54
Reference numerals a and 54b are incident lights of wavelength λ 1 , 55a and 55b are incident lights of wavelength λ 2 , and 56a and 56b are synthetic diffracted lights. Incident light beams 54a and 55a having wavelengths λ 1 and λ 2 respectively have an n-th diffraction angle θn 1 and an angle 3 which is three times the n-th diffraction angle with respect to the Z direction.
When incident on the diffraction grating 53, for example, at point B at θn 2 , Z
The + nth-order diffracted light of the incident light 54a and the −nth-order diffracted light of the incident light 55a are emitted in the direction of an angle 2θn 1 which is twice the nth-order diffracted angle with respect to the direction to become the combined diffracted light 56a, and the optical heterodyne interference beat signal is detected. It will be possible. Here, when the diffraction grating 53 moves by the displacement amount ΔZ and the point B is displaced to the point B ′, similarly, the incident light beams 54b and 55b are respectively + n.
And the -nth order diffracted light are optically combined to form a combined diffracted light 56.
b. Due to the displacement of the diffraction grating 53 by ΔZ, −ΔZ · (cos θn 1 + cos is generated between the incident lights 54a and 54b.
2θn 1 ) and −ΔZ · (co
An optical path length difference of s 3θn 2 + cos 2θn 2 ) occurs. Therefore, the optical heterodyne interference beat signal obtained from the combined diffracted lights 56a and 56b has a phase difference Δφ ″.
zx occurs, Δφ "zx = 2π · ΔZ {(cos 3θn 2 + cos 2θn 2) / λ 2 - (cos θn 1 -cos 2θn 1) / λ 1} ...... becomes (10) .λ 1 ≒ λ 2 , θn 1 considering the ≒ θn 2, Δφ "zx ≒ 2π · ΔZ · (cos 3θn 1 -cos θn 1) / λ 1 ...... (11) next, ΔZ = λ 1 / (cos 3θn 1 -cos θn 1 It can be seen that the phase changes in the cycle of.

したがって、式(9),(11)より、前記回折格子3
5(第1図参照)の微小変位ΔX,ΔZに対して、基準
ビート信号と第2の光ヘテロダイン干渉ビート信号との
位相差Δφzxは、 Δφzx=Δφ′zx+Δφ″zx =−Δφx+2π・ΔZ・ (cos 3θn−cos θn)/λ……(12) となる。すなわち、前記Z変位検出信号処理部39にお
いて、基準ビート信号と第2の光ヘテロダイン干渉ビー
ト信号との位相差Δφzxを検出し、前記X変位検出信
号処理部38において検出した基準ビート信号と第1の
光ヘテロダイン干渉ビート信号との位相差Δφxとの加
算処理を行なうことにより、次式(13)に示すよう
に、回折格子35の微小変位ΔZに対応した位相差信号
Δφzを検出することができる。
Therefore, from the equations (9) and (11), the diffraction grating 3
The phase difference Δφzx between the reference beat signal and the second optical heterodyne interference beat signal with respect to the small displacements ΔX and ΔZ of 5 (see FIG. 1) is Δφzx = Δφ′zx + Δφ ″ zx = −Δφx + 2π · ΔZ · ( cos 3θn 1 −cos θn 1 ) / λ 1 (12) That is, the Z displacement detection signal processing unit 39 detects the phase difference Δφzx between the reference beat signal and the second optical heterodyne interference beat signal. Then, by adding the phase difference Δφx between the reference beat signal detected by the X displacement detection signal processing unit 38 and the first optical heterodyne interference beat signal, as shown in the following equation (13), The phase difference signal Δφz corresponding to the minute displacement ΔZ of the grating 35 can be detected.

Δφz=Δφzx+Δφx=2π・ΔZ・ (cos 3θn−cos θn)/λ……(13) したがって、検出信号処理部38,39において、例え
ば位相検波し、位相差信号Δφx,ΔφzをDC信号に
変換し、例えば位相差0゜ごとにDC信号からパルス信
号を生成し、そのパルス信号をカウントすることによ
り、分解能P/2n,λ/(cos 3θn−cos θn
)でそれぞれ回折格子35のX方向,Z方向の変位測
定が可能である。さらに、位相差0゜から360゜まで
のDC信号変化を例えば1/360に補完して位相差の
検出分解能を1゜に設定し、前記パルス間に回折格子3
5の変位を位相差検出することにより、回折格子35の
X方向,Z方向の変位をそれぞれ分解能,P/2n・3
60,λ/(cos 3θn−cos θn)・360で
検出することができる。なお、X方向,Z方向の変位の
方向は、基準ビート信号に対する第1あるいは第2の光
ヘテロダイン干渉ビート信号の位相差の正負を弁別する
ことにより容易に判定することができる。
Δφz = Δφzx + Δφx = 2π · ΔZ · (cos 3θn 1 −cos θn 1 ) / λ 1 (13) Therefore, in the detection signal processing units 38 and 39, for example, phase detection is performed and the phase difference signals Δφx and Δφz are DC signals. To a pulse signal from the DC signal at every phase difference of 0 °, and counting the pulse signal, the resolution P / 2n, λ 1 / (cos 3θn 1 −cos θn
In 1 ), the displacement measurement of the diffraction grating 35 in the X direction and the Z direction can be performed. Further, the DC signal change from the phase difference of 0 ° to 360 ° is complemented with, for example, 1/360 to set the detection resolution of the phase difference to 1 °, and the diffraction grating 3 is provided between the pulses.
By detecting the displacement of No. 5 by the phase difference, the displacements of the diffraction grating 35 in the X direction and the Z direction are resolved to P / 2n.3, respectively.
60, can be detected at λ 1 / (cos 3θn 1 -cos θn 1) · 360. The directions of displacement in the X and Z directions can be easily determined by discriminating between the positive and negative phase differences of the first or second optical heterodyne interference beat signal with respect to the reference beat signal.

以上で第1実施例を説明したが、次に第4図を参照して
第2実施例を説明する。
The first embodiment has been described above. Next, the second embodiment will be described with reference to FIG.

第4図は、本発明に係る微小変位測定装置の第2実施例
を示すもので、第4図において符号57は2波長直交偏
光レーザ光源(光源)、58a,58bはビームスプリ
ッター、59a,59b,59c,59d,65a,6
5b,65cは平面ミラー、60a,60b,60cは
集光レンズ、61a,61b,61c,61dは偏光
板、62a,62b,62cは光検出器、63a,63
b,63cはプレアンプ、64は1/2波長板、66は
反射型回折格子、67はZ移動ステージ、68はXY移
動ステージ、69はZステージ駆動部、70はXYステ
ージ駆動部、71はX変位検出信号処理部(第1の信号
処理装置)、72はZ変位検出信号処理部(第2の信号
処理装置)、73はX変位表示部、74はZ変位表示
部、75a,75bは偏光ビームスプリッター、76
a,76bは入射光、77a,77bは回折光である。
FIG. 4 shows a second embodiment of the minute displacement measuring apparatus according to the present invention. In FIG. 4, reference numeral 57 is a two-wavelength orthogonal polarization laser light source (light source), 58a and 58b are beam splitters, and 59a and 59b. , 59c, 59d, 65a, 6
5b and 65c are plane mirrors, 60a, 60b and 60c are condenser lenses, 61a, 61b, 61c and 61d are polarizing plates, 62a, 62b and 62c are photodetectors and 63a and 63.
b and 63c are preamplifiers, 64 is a half-wave plate, 66 is a reflective diffraction grating, 67 is a Z moving stage, 68 is an XY moving stage, 69 is a Z stage driving unit, 70 is an XY stage driving unit, and 71 is an X unit. Displacement detection signal processing unit (first signal processing device), 72 Z displacement detection signal processing unit (second signal processing device), 73 X displacement display unit, 74 Z displacement display unit, and 75a and 75b polarization. Beam splitter, 76
Reference numerals a and 76b denote incident light, and reference numerals 77a and 77b denote diffracted light.

この第2実施例の装置は、第1図で示した第1実施例の
装置とはレーザ−ビームの回折格子66への入射方向が
一部逆となっており、回折格子66には2波長直交偏光
レーザ光がビームスプリッター58a,58bを介して
Z方向から入射光76aとして入射する。回折格子66
からの±n次回折光77a,77bは、それぞれ互いに
直交する偏光面をを有した2波長のP偏光、S偏光から
なる。回折光77aから平面ミラー65b,59c、偏
光ビームスプリッター75aを介してS偏光の単色光を
取り出し、回折光77bから平面ミラー65c、偏光ビ
ームスプリッター75b,75aを介してP偏光の単色
光を取り出し、両偏光の単色光を光学的に合成して平面
ミラー59b、集光レンズ60b、偏光板61bを介し
て光ヘテロダイン干渉させて光検出器(第2の光合成検
出手段)62bにより第1の光ヘテロダイン干渉ビート
信号を検出する。
In the device of the second embodiment, the incident direction of the laser beam on the diffraction grating 66 is partly opposite to that of the device of the first embodiment shown in FIG. 1, and the diffraction grating 66 has two wavelengths. The orthogonally polarized laser light enters as incident light 76a from the Z direction via the beam splitters 58a and 58b. Diffraction grating 66
The ± n-order diffracted lights 77a and 77b from are composed of two-wavelength P-polarized light and S-polarized light having polarization planes orthogonal to each other. S-polarized monochromatic light is extracted from the diffracted light 77a through the plane mirrors 65b and 59c and the polarization beam splitter 75a, and P-polarized monochromatic light is extracted from the diffracted light 77b through the plane mirror 65c and the polarization beam splitters 75b and 75a. The monochromatic lights of both polarizations are optically combined to cause optical heterodyne interference through the plane mirror 59b, the condenser lens 60b, and the polarizing plate 61b, and the photodetector (second photosynthetic detection means) 62b is used to generate the first optical heterodyne. Detects interfering beat signals.

一方、ビームスプリッター58b(分光手段)で分割し
たレーザ光を平面ミラー59d、偏光板61dを介して
P偏光の単色光を取り出し、1/2波長板64により偏
光面を90゜回転させて平面ミラー65aを介し、Z方
向に対してn次回折角の2倍の角度より入射光76bと
して回折格子66に入射させる。入射光76bの−n次
回折光は回折光77bと同一の方向に回折し、入射光7
6aの+n次回折光77bのS偏光の単色光と光ヘテロ
ダイン干渉する。入射光76bの−n次回折光と回折光
77bのS偏光との合成回折光を平面ミラー65c、偏
光ビームスプリッター75bを介して取り出し、集光レ
ンズ60c、偏光板61cを介して光ヘテロダイン干渉
させ、光検出器62c(第3の光合成検出手段)により
第2の光ヘテロダイン干渉ビート信号を検出する。
On the other hand, the laser light split by the beam splitter 58b (spectroscopic means) is extracted as P-polarized monochromatic light through the plane mirror 59d and the polarizing plate 61d, and the plane of polarization is rotated by 90 ° by the ½ wavelength plate 64 to obtain a plane mirror. Incident light 76b is made incident on the diffraction grating 66 at an angle twice the nth diffraction angle with respect to the Z direction via 65a. The -nth order diffracted light of the incident light 76b is diffracted in the same direction as the diffracted light 77b, and the incident light 7b
Optical + heterodyne interference occurs with the + n-order diffracted light 77b of 6a and the S-polarized monochromatic light. The synthetic diffracted light of the -nth-order diffracted light of the incident light 76b and the S-polarized light of the diffracted light 77b is extracted through the plane mirror 65c and the polarization beam splitter 75b, and optical heterodyne interference is performed through the condenser lens 60c and the polarizing plate 61c. The photodetector 62c (third photosynthesis detecting means) detects the second optical heterodyne interference beat signal.

さらに、ビームスプリッター58aによりレーザ光の一
部を取り出し、平面ミラー59a、集光レンズ60a、
偏光板61aを介して光ヘテロダイン干渉させて光検出
器62a(第1の光合成検出手段)より基準ビート信号
を検出する。基準ビート信号、第1および第2の光ヘテ
ロダイン干渉ビート信号をそれぞれプレアンプ63a,
63b,63cを通し、X変位検出信号処理部71へ基
準ビート信号と第1の光ヘテロダイン干渉ビート信号を
入力し、Z変位検出信号処理部72へ基準ビート信号と
第2の光ヘテロダイン干渉ビート信号を入力する。検出
信号処理部71,72では第1実施例の場合と同様に、
それぞれ位相検波して位相差をΔφx,Δφzを回折格
子66の変位量ΔX,ΔZに換算し、変位表示部73,
74により表示する。また位相差が一定となるように検
出信号処理部71,72よりそれぞれステージ駆動部7
0,69に制御信号を送り、回折格子66を定められた
位置にサーボ制御する。
Further, a part of the laser light is extracted by the beam splitter 58a, and the plane mirror 59a, the condenser lens 60a,
Optical heterodyne interference is caused through the polarizing plate 61a, and the reference beat signal is detected by the photodetector 62a (first photosynthesis detecting means). The reference beat signal and the first and second optical heterodyne interference beat signals are respectively fed to the preamplifier 63a,
The reference beat signal and the first optical heterodyne interference beat signal are input to the X displacement detection signal processing unit 71 through 63b and 63c, and the reference beat signal and the second optical heterodyne interference beat signal are input to the Z displacement detection signal processing unit 72. Enter. In the detection signal processing units 71 and 72, as in the case of the first embodiment,
Phase detection is performed respectively to convert the phase difference Δφx and Δφz into displacement amounts ΔX and ΔZ of the diffraction grating 66, and a displacement display unit 73,
Display by 74. In addition, the detection signal processing units 71 and 72 respectively operate the stage driving unit 7 so that the phase difference becomes constant.
A control signal is sent to 0 and 69 to servo-control the diffraction grating 66 to a predetermined position.

この第2実施例においては、上述と同様の解析を行なう
ことにより、回折格子66の変位ΔX,ΔZと位相差信
号Δφx,Δφzとの間には、次のような関係式が成り
立つことは明らかである。
In the second embodiment, it is clear that the following relational expression holds between the displacements ΔX and ΔZ of the diffraction grating 66 and the phase difference signals Δφx and Δφz by performing the same analysis as described above. Is.

Δφz=2π・ΔZ・(cos 2θn−1) (θnはn次回折角)……(15) 以上で本発明の実施例を説明したが、本発明は上記実施
例に限定されるものではない。たとえば、上記第1,第
2実施例においては2波長の単色光光源として2波長直
交偏光レーザ光源を用いたが、2波長の単色光としてブ
ラッグセルなどの音響光学素子を用いて生成した光を用
いても同様の効果を得ることができる。また、第1図に
おいては、偏光板を使用せずに回折格子面において2波
長の単色光の偏光面の方向が一致するように、2波長の
単色光のいずれか一方の光路系に1/2波長板を組み込
むことによっても干渉性のよい光ヘテロダイン干渉ビー
ト信号が得られ、同様の効果を得ることができる。
Δφz = 2π · ΔZ · (cos 2θn 1 −1) (θn 1 is the nth diffraction angle) (15) Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. Absent. For example, in the above-mentioned first and second embodiments, the two-wavelength orthogonal polarization laser light source is used as the two-wavelength monochromatic light source, but the light generated by using the acousto-optic device such as the Bragg cell is used as the two-wavelength monochromatic light. However, the same effect can be obtained. Further, in FIG. 1, the optical path system of either one of the two wavelengths of the monochromatic light is adjusted so that the directions of the polarization planes of the two wavelengths of the monochromatic light coincide with each other on the diffraction grating surface without using the polarizing plate. An optical heterodyne interference beat signal with good coherence can also be obtained by incorporating a two-wave plate, and the same effect can be obtained.

また、上記実施例では、回折格子への入射光の方向およ
び回折格子からの回折光の方向が、回折格子面に垂直な
Z方向を含み格子ラインの方向に垂直な面内にある場合
について述べたが、前記Z方向を含み格子ラインの方向
に垂直な面に対して所定の角度を有した方向から2波長
の単色光を入射して、所定の角度を有した方向において
回折光を検出し、光学的に合成して光ヘテロダイン干渉
ビート信号を生成する方法を用いても同様の効果を得る
ことができる。
Further, in the above embodiment, the case where the direction of the incident light to the diffraction grating and the direction of the diffracted light from the diffraction grating are in the plane including the Z direction perpendicular to the diffraction grating surface and perpendicular to the direction of the grating line is described. However, monochromatic light of two wavelengths is made incident from a direction having a predetermined angle with respect to a plane that includes the Z direction and is perpendicular to the direction of the grating line, and diffracted light is detected in the direction having the predetermined angle. The same effect can be obtained by using a method of optically combining to generate an optical heterodyne interference beat signal.

また、本発明において用いる回折格子としては、吸収型
回折格子,位相型回折格子のいずれを用いてもよく、さ
らにバイナリー回折格子に限定されることなく、正弦波
状回折格子,フレーズ回折格子などの種々の回折格子を
用いることも可能である。また、反射型回折格子の他に
透過型回折格子を用いることも可能である。
The diffraction grating used in the present invention may be either an absorption type diffraction grating or a phase type diffraction grating, and is not limited to a binary diffraction grating, and various types such as a sinusoidal diffraction grating and a phrase diffraction grating may be used. It is also possible to use the diffraction grating of. It is also possible to use a transmissive diffraction grating in addition to the reflective diffraction grating.

さらに、上記実施例では、周波数の異なる2つの波長の
レーザー光のそれぞれの1次回折光どうしが2方向にお
いて合成回折光となるように設定したが、2つの合成回
折光を得る方法としては、高次の回折光、あるいは異な
る次数の回折光の合成回折光を用いても良く、その場合
には位相差信号の周期が変わるだけであり、位相差信号
に応じた検出信号処理を行なうことによってX,Z方向
の変位を検出でき、同様の効果を得ることができる。
Furthermore, in the above embodiment, the first-order diffracted lights of the laser lights of the two wavelengths having different frequencies are set to be the combined diffracted light in the two directions. Next-order diffracted light or a combined diffracted light of diffracted light of different orders may be used. In that case, only the period of the phase difference signal changes, and X is obtained by performing detection signal processing according to the phase difference signal. , Z-direction displacement can be detected, and similar effects can be obtained.

なお、2つの回折格子を用いてそれらの格子ライン方向
が互いに直交するように物体上に設置すれば、互いに直
交するX,Y,Zの3軸について高精度の微小変位測定
を行なうことが可能となる。
If two diffraction gratings are used and installed on an object so that their grating line directions are orthogonal to each other, it is possible to perform highly accurate microdisplacement measurement on three mutually orthogonal X, Y, and Z axes. Becomes

〔発明の効果〕〔The invention's effect〕

以上で詳細に説明したように、本発明の微小変位測定方
法によれば、周波数が互いにわずかに異なる2波長の単
色光のうちいずれか一方を分光して回折格子に入射し、
それらの分光のそれぞれの回折光と他方の単色光の回折
光とをそれぞれ合成することによって第1、第2の光ヘ
テロダイン干渉ビート信号を生成させるようにしたこと
により、回折格子の2方向の微小変位、すなわち回折格
子の格子ラインに直角な方向の微小変位と回折格子の法
線方向の微小変位を、それぞれ第1、第2の光ヘテロダ
イン干渉ビート信号の位相変化として測定できる。しか
も、光源の強度変動や回折格子の回折効率が変動するこ
と等によって回折光強度が変動したような場合であって
も、回折光のビート信号の振幅が変動するのみで位相変
化に影響はないので、位相差検出を高安定かつ高精度で
行うことができる。したがって、物体の2方向の微小変
位をそれぞれ高精度で測定することが可能であるという
効果を奏する。
As described in detail above, according to the micro-displacement measuring method of the present invention, one of the monochromatic lights of two wavelengths whose frequencies are slightly different from each other is split and incident on the diffraction grating,
Since the first and second optical heterodyne interference beat signals are generated by respectively combining the respective diffracted lights of the spectra and the diffracted light of the other monochromatic light, the minute directions in the two directions of the diffraction grating are generated. The displacement, that is, the small displacement in the direction perpendicular to the grating line of the diffraction grating and the small displacement in the normal direction of the diffraction grating can be measured as the phase change of the first and second optical heterodyne interference beat signals, respectively. Moreover, even if the diffracted light intensity fluctuates due to fluctuations in the intensity of the light source or the diffraction efficiency of the diffraction grating, the amplitude of the beat signal of the diffracted light only fluctuates and the phase change is not affected. Therefore, the phase difference detection can be performed with high stability and high accuracy. Therefore, it is possible to measure the minute displacements of the object in the two directions with high accuracy.

また、本発明の微小変位測定装置は、検出光学系を一体
にまとめることにより小型簡便なものと構成できるの
で、上記方法の実施に用いて有効である。
Further, the micro-displacement measuring device of the present invention can be configured to be compact and simple by integrating the detection optical system, and therefore it is effective for use in implementing the above method.

【図面の簡単な説明】[Brief description of drawings]

第1図ないし第4図は本発明の実施例を示す図である。
第1図ないし第3図は第1実施例を示すもので、第1図
はこの第1実施例の装置の概略構成図、第2図および第
3図はそれぞれ回折格子の拡大図である。第4図は第2
実施例の装置の概略構成図である。 第5図ないし第7図は従来の微小変位測定装置を示すも
ので、第5図はこの従来の装置の概略構成図、第6図お
よび第7図はそれぞれ回折格子の拡大図である。 25……2波長直交偏光レーザー光源(光源)、 26b……ビームスプリッター(分光手段)、 31a……光検出器(第1の光合成検出手段)、 31b……光検出器(第2の光合成検出手段)、 31c……光検出器(第3の光合成検出手段)、 33a,33b,34a,34b,34c……平面ミラ
ー(入射角調整手段)、 35,49,53……回折格子、 36……Z移動ステージ(物体)、 37……XY移動ステージ(物体)、 38……X変位検出信号処理部(第1の信号処理装
置)、 39……Z変位検出信号処理部(第2の信号処理装
置)、 57……2波長直交偏光レーザー光源(光源)、 58b……ビームスプリッター(分光手段)、 63a……光検出器(第1の光合成検出手段)、 63b……光検出器(第2の光合成検出手段)、 63c……光検出器(第3の光合成検出手段)、 59d,65a……平面ミラー(入射角調整手段) 66……回折格子、 67……Z移動ステージ(物体)、 68……XY移動ステージ(物体)、 71……X変位検出信号処理部(第1の信号処理装
置)、 72……Z変位検出信号処理部(第2の信号処理装
置)。
1 to 4 are views showing an embodiment of the present invention.
1 to 3 show the first embodiment, FIG. 1 is a schematic configuration diagram of the apparatus of the first embodiment, and FIGS. 2 and 3 are enlarged views of the diffraction grating, respectively. Figure 4 is second
It is a schematic block diagram of the apparatus of an Example. 5 to 7 show a conventional minute displacement measuring apparatus. FIG. 5 is a schematic configuration diagram of this conventional apparatus, and FIGS. 6 and 7 are enlarged views of a diffraction grating, respectively. 25 ... 2-wavelength orthogonal polarization laser light source (light source), 26b ... Beam splitter (spectral means), 31a ... Photodetector (first photosynthesis detection means), 31b ... Photodetector (second photosynthesis detection) Means), 31c ... Photodetector (third photosynthesis detecting means), 33a, 33b, 34a, 34b, 34c ... Plane mirror (incident angle adjusting means), 35, 49, 53 ... Diffraction grating, 36 ... Z movement stage (object), 37 XY movement stage (object), 38 X displacement detection signal processing unit (first signal processing device), 39 Z displacement detection signal processing unit (second signal) Processing device), 57 ... 2-wavelength orthogonal polarization laser light source (light source), 58b ... beam splitter (spectral means), 63a ... photodetector (first photosynthesis detecting means), 63b ... photodetector (first) 2 photosynthesis detection ), 63c ... Photodetector (third photosynthesis detecting means), 59d, 65a ... Planar mirror (incident angle adjusting means) 66 ... Diffraction grating, 67 ... Z moving stage (object), 68 ... XY moving stage (object), 71 ... X displacement detection signal processing unit (first signal processing device), 72 ... Z displacement detection signal processing unit (second signal processing device).

Claims (2)

【特許請求の範囲】[Claims] 【請求項1】周波数が互いにわずかに異なる2波長の単
色光を合成し光ヘテロダイン干渉させて基準ビート信号
を生成するとともに、前記2波長の単色光のいずれか一
方を分光してそれら分光した単色光をそれぞれ互いに異
なる方向から物体上に固定した回折格子に対して入射さ
せ、かつ前記2波長の単色光の他方を前記回折格子に対
して入射させて前記一方の単色光のそれぞれの分光の回
折光と前記他方の単色光の回折光とをそれぞれ合成して
第1および第2の光ヘテロダイン干渉ビート信号を生成
し、前記基準ビート信号と前記第1の光ヘテロダイン干
渉ビート信号との位相差、および前記基準ビート信号と
前記第2の光ヘテロダイン干渉ビート信号との位相差を
それぞれ検出することによって、それら位相差から前記
物体の前記回折格子の格子ラインに直交する方向の微小
変位およびその回折格子の法線方向の微小変位をそれぞ
れ測定することを特徴とする微小変位測定方法。
1. A reference beat signal is generated by synthesizing monochromatic lights of two wavelengths whose frequencies are slightly different from each other and causing optical heterodyne interference, and one of the monochromatic lights of the two wavelengths is spectrally dispersed to separate them. Light is incident on the diffraction grating fixed on the object from different directions, and the other of the monochromatic lights of the two wavelengths is incident on the diffraction grating to diffract each of the monochromatic lights of the respective spectra. Light and the diffracted light of the other monochromatic light are respectively combined to generate first and second optical heterodyne interference beat signals, and a phase difference between the reference beat signal and the first optical heterodyne interference beat signal, And a phase difference between the reference beat signal and the second optical heterodyne interference beat signal, respectively, to detect the diffraction pattern of the object from the phase difference. Minute displacement measuring method and measuring in a direction perpendicular to the grating lines small displacement and a normal direction of the minute displacement of the diffraction grating, respectively.
【請求項2】物体上に固定された回折格子と、周波数が
互いにわずかに異なる2波長の単色光を発生する光源
と、その光源から発せられた2波長の単色光を合成し光
ヘテロダイン干渉させて基準ビート信号を生成する第1
の光合成検出手段と、前記光源から発せられた2波長の
単色光のいずれか一方を分光する分光手段と、前記分光
されたそれぞれの単色光および前記他方の単色光を前記
回折格子に所定の角度を有した方向からそれぞれ入射さ
せる入射角調整手段と、前記一方の単色光のそれぞれの
分光の回折光と前記他方の単色光の回折光とをそれぞれ
合成して第1、第2の光ヘテロダイン干渉ビート信号を
生成する第2、第3の光合成検出手段と、前記第1およ
び第2の光合成検出手段によってそれぞれ生成された基
準ビート信号および第1の光ヘテロダイン干渉ビート信
号とから第1の位相差信号を算出処理して前記物体の前
記回折格子の格子ラインに直交する方向の変位量に換算
する第1の信号処理装置と、その第1の信号処理装置に
よって算出処理された第1の位相差信号および前記第
1、第3の光合成検出手段によってそれぞれ生成された
基準ビート信号、第2の光ヘテロダイン干渉ビート信号
とから第2の位相差信号を算出処理して前記物体の前記
回折格子の法線方向の変位量に換算する第2の信号処理
装置とを具備してなることを特徴とする微小変位測定装
置。
2. A diffraction grating fixed on an object, a light source for generating monochromatic light of two wavelengths having frequencies slightly different from each other, and monochromatic light of two wavelengths emitted from the light source are combined to cause optical heterodyne interference. First to generate a reference beat signal
Photosynthesis detecting means, a spectroscopic means for separating one of the two wavelengths of monochromatic light emitted from the light source, and the respective monochromatic light and the other monochromatic light which are split into a predetermined angle to the diffraction grating. Angle of incidence adjusting means for making incident light from different directions, and the first and second optical heterodyne interference by respectively combining the diffracted light of each of the one monochromatic light and the diffracted light of the other monochromatic light. A first phase difference from second and third photosynthesis detecting means for generating beat signals, and a reference beat signal and a first optical heterodyne interference beat signal generated by the first and second photosynthesis detecting means, respectively. A first signal processing device for calculating a signal to convert it into a displacement amount in a direction orthogonal to a grating line of the diffraction grating of the object, and a calculation processing by the first signal processing device. The second phase difference signal is calculated from the first phase difference signal, the reference beat signal respectively generated by the first and third photosynthesis detecting means, and the second optical heterodyne interference beat signal, and the object is calculated. (2) A second signal processing device for converting the displacement amount in the normal direction of the diffraction grating, to a small displacement measuring device.
JP18134586A 1986-05-07 1986-08-01 Minute displacement measuring method and minute displacement measuring device Expired - Fee Related JPH0660808B2 (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
JP18134586A JPH0660808B2 (en) 1986-08-01 1986-08-01 Minute displacement measuring method and minute displacement measuring device
FR878706393A FR2598797B1 (en) 1986-05-07 1987-05-06 METHOD FOR MEASURING AND / OR ADJUSTING THE MOVEMENT OF AN OBJECT AND APPARATUS FOR CARRYING OUT THIS METHOD
DE3715864A DE3715864C2 (en) 1986-05-07 1987-05-07 Method and device for detecting / setting a displacement
US07/492,259 US5000573A (en) 1986-05-07 1990-03-12 Method of alignment with the use of diffraction gratings and an apparatus therefor

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP18134586A JPH0660808B2 (en) 1986-08-01 1986-08-01 Minute displacement measuring method and minute displacement measuring device

Publications (2)

Publication Number Publication Date
JPS6338102A JPS6338102A (en) 1988-02-18
JPH0660808B2 true JPH0660808B2 (en) 1994-08-10

Family

ID=16099076

Family Applications (1)

Application Number Title Priority Date Filing Date
JP18134586A Expired - Fee Related JPH0660808B2 (en) 1986-05-07 1986-08-01 Minute displacement measuring method and minute displacement measuring device

Country Status (1)

Country Link
JP (1) JPH0660808B2 (en)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0323242A3 (en) * 1987-12-28 1989-10-18 Kabushiki Kaisha Toshiba Method and apparatus for aligning two objects, and method and apparatus for providing a desired gap between two objects
JPH05152186A (en) * 1991-05-01 1993-06-18 Canon Inc Measuring apparatus and exposure apparatus and positioning method for exposure apparatus
US5477324A (en) * 1994-08-26 1995-12-19 Georgia Tech Research Corporation Method and apparatus for detecting surface wave vector dynamics using three beams of coherent light
NL1036742A1 (en) * 2008-04-18 2009-10-20 Asml Netherlands Bv Stage system calibration method, stage system and lithographic apparatus including such stage system.
EP2553401B1 (en) 2010-03-30 2015-09-02 Zygo Corporation Interferometric encoder systems
JP5618898B2 (en) * 2010-08-31 2014-11-05 Dmg森精機株式会社 Displacement detector
WO2012106246A2 (en) 2011-02-01 2012-08-09 Zygo Corporation Interferometric heterodyne optical encoder system
JP5862857B2 (en) * 2011-07-15 2016-02-16 株式会社ニコン Encoder device, optical device, and exposure device
WO2013070848A1 (en) * 2011-11-09 2013-05-16 Zygo Corporation Low coherence interferometry using encoder systems
CN111457843B (en) * 2019-04-26 2021-07-30 上海微电子装备(集团)股份有限公司 Displacement measuring device, displacement measuring method and photoetching equipment

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