JPH10274507A - Positioning method and apparatus using diffraction grating - Google Patents

Abstract

(57) Abstract: In an alignment apparatus or method using a diffraction grating, a semiconductor laser can be easily and quickly exchanged. An optical fiber is applied to laser light transmission from a laser light source to a spatial lens system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to an exposure apparatus for manufacturing a semiconductor IC or an LSI by printing a mask pattern on a wafer after aligning a mask with a wafer and a pattern evaluation apparatus for measuring a pattern position. Further, the present invention relates to a positioning method based on optical heterodyne interferometry using a suitable diffraction grating and a positioning device used for implementing the method.

[0002]

2. Description of the Related Art In an apparatus for exposing and transferring a mask pattern onto a wafer with the miniaturization of semiconductor IC and LSI patterns,
Advances in technology for aligning a mask and a wafer with high precision have become indispensable. In the optical heterodyne interferometry, a heterodyne signal is obtained by causing two laser beams having slightly different frequencies to interfere with each other, a phase difference between a reference heterodyne signal (reference signal) and a measured heterodyne signal is determined, and the position of the mask and the wafer is determined. It performs alignment and position detection.

[0003] Conventionally, as an apparatus for performing minute displacement measurement or precise alignment using optical heterodyne interferometry using a diffraction grating, there is an apparatus applied to an X-ray exposure apparatus as shown in FIG. Japanese Patent Application No. 6-175260). Third
In the figure, reference numeral 20 denotes a transverse Zeeman effect type two-frequency orthogonally polarized laser light source (light source of wavelength λ1) which emits light of two wavelengths whose frequencies are slightly different from each other and whose polarization planes are orthogonal to each other; Frequency orthogonally polarized laser light source (light source of wavelength λ2), 11, 11 ′, 11 ″, 2
1, 21 ', 21 ", 21'" are mirrors, and among these mirrors, mirrors 11 ', 11 ", 21', 21".
Are angle adjustable (incident angle adjusting means). 2
2, 22 'is a cylindrical lens, 23, 23' is a polarizing beam splitter, 24 is a prism mirror, 1, 1 'is a dielectric multilayer mirror, 3, 3', 25, 25 'is a condensing lens, 4, 4 ′, 26, 26 ′ are photoelectric detectors (first to fourth
, 6 is a signal processing controller (signal processing controller), 28 and 29 are respectively a mask stage and a wafer stage (relative moving mechanism), 30 is a mask (first object), and 31 is a wafer (second , 32 is a mask diffraction grating (first diffraction grating), 33 is a monochromatic light incident / diffraction light extraction window, 34 is a wafer diffraction grating (second diffraction grating),
22 ', 44 and 44' are polarizing plates. Here, the monochromatic light incident / diffraction light extraction window 33 is an opening provided in the mask 30, and the incident light can directly enter the diffraction grating 34 through the window 33, and the diffraction light from the diffraction grating 34 Light can be extracted directly. Also,
The mask stage 28 and the wafer stage 29 constitute a moving mechanism for relatively moving the mask 30 and the wafer 31.

The transverse Zeeman effect type two-frequency orthogonally polarized laser light sources 20 and 20 'which emit light of two wavelengths whose frequencies are slightly different from each other and whose polarization planes are orthogonal to each other emit monochromatic lights of center wavelengths λ1 and λ2, respectively. It is preferable that these wavelengths are not close to each other. These laser beams are totally reflected mirrors 21 and 11, cylindrical lenses 22 and 2.
The beam becomes an elliptical beam through 2 ′, and the beam is split by the polarizing beam splitters 23 and 23 ′ into light of two wavelengths, each of which is a linearly polarized light having only a horizontal component or a vertical component, and whose frequencies are slightly different from each other. The reflected lights are mirrors 21 'and 21 ", respectively, and 1
The light enters the diffraction grating 32 and the diffraction grating 34 at desired angles of incidence via 1 ′ and 11 ″, respectively.
Numerals 4 deviate in the grating line direction, and are arranged in the same elliptical beam of incident light of two wavelengths. The diffraction grating pitches of the diffraction gratings 32 and 34 are made equal. When using the n-th order diffracted light from the diffraction grating 32 and the diffraction grating 34, a desired incident angle θni of the diffraction grating is used.
Is the pitch P of the diffraction grating and the wavelength λ of the laser light of the light source.
It is obtained from the following equation by i.

[0005]

## EQU1 ## Here, assuming that the incident angle in the present embodiment is incident from the ± 1st diffraction angle,

## EQU1 ## is expressed as follows.

[0006]

## EQU2 ## Accordingly, the incident angles of the monochromatic lights of the laser lights λ1 and λ2 are respectively set as θ11 = sin−1 (λ1 / P), θ1
By setting 2 = sin-1 (λ2 / P), the first-order diffracted lights of the monochromatic lights of the laser lights λ1 and λ2 are respectively emitted in the same direction.

The optical heterodyne interference diffraction light obtained from the diffraction grating 32 and the optical heterodyne interference diffraction light obtained from the diffraction grating 34 through the monochromatic light incident / diffraction light extraction window 33 are respectively transmitted to the prism mirror 24 via the mirror 21 '". As a result, the light is separated into optical heterodyne interference diffraction light on the mask side and optical heterodyne interference diffraction light on the wafer side.
The separated optical heterodyne interference diffraction light is separated into optical heterodyne interference diffraction lights of wavelengths λ1 and λ2 by the dielectric multilayer mirrors 1 and 1 ′, respectively. The optical heterodyne interference diffraction light separated on the mask side and the wafer side and further separated by wavelengths λ1 and λ2 are
4 ′, 2 and 2 ′, and condensing lenses 25 and 25 ′, and 3 and 3 ′, and are guided to photodetectors 26 and 26 ′ and 4 and 4 ′, and as a diffracted light beat signal, a signal optimization processing control unit 6 is processed.

[0008] In the signal optimization processing control unit 6, the diffraction grating 3
From the beat signal of the optical heterodyne interference diffracted light obtained from 2, 34, the most stable signal (high signal strength or good S / N ratio) is selected for each wavelength, and the mask side for the selected wavelength is selected. The phase difference between the two beat signals is detected using either one of the beat signals of the optical heterodyne interference diffraction light obtained from the wafer side as a reference beat signal, and the mask stage is set so that the phase difference becomes a predetermined value. 28 or the wafer stage 29 is relatively moved so that precise alignment between the mask 30 and the wafer 31 is performed so that the pattern on the mask surface can be accurately overlapped with a predetermined position on the wafer surface for exposure. Have been. However, in the above-described conventional apparatus, it is difficult to reduce the size of the transverse Zeeman effect type two-frequency orthogonally polarized laser light source that generates laser light of two wavelengths. When a light source having a wavelength of? Is used, there is a problem that the entire optical system becomes large. In addition, since the replacement of the light source due to the life of the light source, failure, or the like is also made up of various types of optical heterodyne interference optical systems, there has been a problem that the adjustment of the optical system becomes complicated.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art. The first to third aspects of the present invention separate an optical heterodyne interference optical system from a two-wavelength light source. By coupling using optical fiber,
It is an object of the present invention to provide an alignment method that can reduce the size of an optical system for position detection, and can easily replace a light source by cutting off a joint portion of an optical fiber. According to another aspect of the present invention, the optical heterodyne interference optical system and the two-wavelength light source are separated and coupled using an optical fiber, so that the optical system for position detection can be reduced in size and the light source can be replaced. It is another object of the present invention to provide an alignment device which can be easily formed by cutting off a joint portion of an optical fiber.

[0010]

In order to achieve the above object, according to the first aspect of the present invention, a first diffraction grating provided on a first object and a diffraction grating provided on a second object are provided. And a plurality of light sources that generate a plurality of sets of monochromatic lights of two wavelengths whose frequencies are slightly different from each other, and are generated from the plurality of light sources. A set of two wavelength monochromatic lights is made incident on an optical fiber,
Light emitted from the optical fiber is incident on each of the first and second diffraction gratings at a predetermined incident angle, and a plurality of optical heterodyne interferences corresponding to the set of monochromatic light generated from the first diffraction grating. Diffracted light is independently separated and detected to form a first set of beat signals, and a plurality of optical heterodyne interference diffraction lights are independently separated and detected corresponding to the set of monochromatic light generated from the second diffraction grating. A plurality of independent phase difference signals corresponding to each light source are calculated from the first and second sets of beat signals, and one of the plurality of phase difference signals is calculated. A basic feature is a method of performing relative positioning by moving the first and second objects based on one or two or more phase difference signals.

According to a second aspect of the present invention, a set of monochromatic light of two wavelengths shifted in frequency by using a set of acousto-optic elements is used as a light source. Characteristic is the alignment method described in the item.

According to a third aspect of the present invention, a set of two-wavelength monochromatic light whose frequency is shifted by using a set of acousto-optic elements as a light source is incident on separate optical fibers. The alignment method according to claim 2 is characterized.

According to a fourth aspect of the present invention, there is provided the first aspect.
A first diffraction grating provided on a second object, a second diffraction grating provided on a second object, a moving mechanism for relatively moving the first and second objects, and frequencies slightly different from each other 2
A plurality of light sources for generating a plurality of sets of monochromatic lights of wavelengths, an optical fiber incident optical system for causing a set of monochromatic lights of two wavelengths generated from the plurality of light sources to enter an optical fiber, and a set of monochromatic lights emitted from the optical fibers. A plurality of incident angle adjusting means for entering each of the first and second diffraction gratings at a predetermined incident angle; and a plurality of optical heterodyne corresponding to the set of the monochromatic light generated from the first diffraction grating. A plurality of first detecting means for independently separating and detecting the interference diffraction light to generate a plurality of first beat signals; and a plurality of lights corresponding to the set of the monochromatic light generated from the second diffraction grating. A plurality of second detecting means for independently separating and detecting the heterodyne interference diffraction light to generate a plurality of second beat signals; and a plurality of first detecting means generated by the plurality of first and second detecting means. And the second bee Phase difference detecting means for independently detecting a plurality of phase difference signals from the signal corresponding to each light source, and the first and second beat signals among the phase difference detection signals obtained by the phase difference detecting means. A control signal is sent to the moving mechanism based on a phase difference signal obtained from a detection signal having the best intensity or S / N ratio, and the first and second objects are relatively moved and aligned. This is a device basically including signal processing control means.

According to a fifth aspect of the present invention, a set of monochromatic light of two wavelengths shifted in frequency using a set of acousto-optic elements is used as a light source. The alignment device according to the item is characterized.

According to a sixth aspect of the present invention, a set of two-color monochromatic lights whose frequency is shifted by using a set of acousto-optical elements as light sources is incident on separate optical fibers. The alignment method according to claim 5 is characterized.

The light source according to any one of the first to sixth aspects of the present invention is not limited to a laser beam such as a transverse Zeeman laser beam which emits coherent light having two frequency components slightly different from each other on an orthogonal polarization plane, and a frequency shift by an acousto-optic element or the like. A set of laser beams may be used.

As for the method of incidence on an optical fiber, other than a method of injecting coherent light of two frequency components slightly different from each other on an orthogonal polarization plane, such as a transverse Zeeman laser beam, into one optical fiber, the wavelength is slightly different. 2
A method may be used in which laser beams having different wavelengths are separated and made incident on different optical fibers. Also, in the case of using an acousto-optic element, the laser light whose frequency has been shifted may be respectively incident on another optical fiber, or laser light of two wavelengths having slightly different wavelengths may be combined and incident. Similar effects can be obtained.

Further, laser beams having desired wavelengths emitted from a plurality of light sources are respectively made incident on the optical fiber, and the light emitted from the optical fiber is made incident on the same diffraction grating at a predetermined incident angle, and each of the laser beams corresponds to each wavelength. And independently detects misregistration information.
The light source and the optical heterodyne interference optical system can be divided by the optical fiber by performing the alignment by selectively using a signal having a good N ratio, so that the optical system can be downsized and the light source can be easily exchanged and adjusted. Become.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 shows a first embodiment of an alignment method and apparatus according to the first to sixth aspects of the present invention.
It schematically shows an alignment method of an optical heterodyne interference system used for alignment between a mask and a wafer of an X-ray exposure apparatus for manufacturing a semiconductor IC and an LSI, and an outline of a device configuration. The moving mechanism is almost the same as that in FIG. In FIG. 1, 50, 50 'are beam shapers, 51, 51' are fiber connectors,
2, 52 ', 52 ", 52'" are optical fibers, 5
3, 53 'is a fiber incident optical system.

The transverse Zeeman effect type two-frequency orthogonally polarized laser light sources 20 and 20 ′ which emit light of two wavelengths whose frequencies are slightly different from each other and whose polarization planes are orthogonal to each other emit monochromatic lights of center wavelengths λ 1 and λ 2 respectively. It is preferable that these wavelengths are not close to each other. These laser beams are incident on the optical fibers 52 ″, 52 ″ ″ by the fiber incident optical systems 53, 53 ′. As shown in FIG. 2, a set of monochromatic light of two wavelengths, which is frequency-shifted using a set of acousto-optic elements, can be used as these light sources. The optical fibers 52 ″ and 52 ′ ″ are connected to the optical fiber 5 via fiber connectors 51 and 51 ′.
2, 52 '. The laser light emitted from the optical fiber is shaped into a desired shape by the beam shapers 50 and 50 ′, and is linearly polarized light having only a horizontal component or a vertical component, respectively, by the polarization beam splitters 23 and 23 ′. The light is split into two different wavelengths of light, and the split light is
And 21 ", and 11 'and 11", respectively, and enter the diffraction grating 32 and the diffraction grating 34 at desired angles of incidence.

The method of detecting the diffracted light from the diffraction grating and processing the beat signal is the same as that of FIG. 3 except that the optical heterodyne interference diffraction light obtained from the diffraction grating 32 and the monochromatic light incident / diffraction light extraction window 33 are used. The optical heterodyne interference diffraction light obtained from 34 is separated into optical heterodyne interference diffraction light on the mask side and optical heterodyne interference diffraction light on the wafer side by the prism-shaped mirror 24 via the mirror 21 ′ ″, respectively. The interference diffraction light is separated into optical heterodyne interference diffraction lights of wavelengths λ1 and λ2 by the dielectric multilayer mirrors 1 and 1 ′, respectively.The optical heterodyne separated on the mask side and the wafer side, and further separated by the wavelengths λ1 and λ2. The interference diffracted light is divided into polarizing plates 44 and 44 ', 2 and 2', and condensing lenses 25 and 2 respectively.
The light is guided to photodetectors 26 and 26 ', 4 and 4' via 5 ', 3 and 3', and is processed as a diffracted light beat signal by the signal optimization processing control unit 6.

In the signal optimization processing control unit 6, the diffraction grating 3
From the beat signal of the optical heterodyne interference diffracted light obtained from 2, 34, the most stable signal (high signal strength or good S / N ratio) is selected for each wavelength, and the mask side for the selected wavelength is selected. The phase difference between the two beat signals is detected using either one of the beat signals of the optical heterodyne interference diffraction light obtained from the wafer side as a reference beat signal, and the mask stage is set so that the phase difference becomes a predetermined value. 28 or the wafer stage 29 is relatively moved so that precise alignment between the mask 30 and the wafer 31 is performed so that the pattern on the mask surface can be accurately overlapped with a predetermined position on the wafer surface for exposure. Have been.

FIG. 2 shows a second embodiment of the alignment method and apparatus according to the first to sixth aspects of the present invention. As a light source, a set of two-wavelength monochromatic light that is frequency-shifted using a set of acousto-optic elements is used, and components other than the light source, such as an optical system, a mechanical system, and a circuit system, are the first embodiment Is similar to

In FIG. 2, reference numerals 12 and 12 'denote laser light sources (12 is a wavelength λ1, 12' is a wavelength λ2), 13, 1
3 'is a mirror, 14, 14' is a beam splitter, 1
6, 16 ′, 16 ″, 16 ′ ″ are acousto-optical elements, 1
7, 17 ', 17 ", 17"' are mirrors, 18 is an acousto-optical element driving unit, 54, 54 ', 54 ", 54 are fiber incident optical systems, 55, 55', 55", 55 '". Is an optical fiber, 56, 56 ', 56 ", 56"' is a fiber connector, 57, 57 ', 57 ", 57"'.
Is an optical fiber, and 58, 58 ', 58 "and 58"' are beam shapers.

The monochromatic lights of the center wavelengths λ 1 and λ 2 emitted from the laser light sources 12 and 12 ′ are
14 ′, the beam is split into two beams, respectively, and acousto-optic devices 16, 1 are transmitted through total reflection mirrors 13, 13 ′.
6 ′, 16 ″, 16 ′ ″. Acousto-optic element 1
6, 16 ', 16 ", and 16'" shift the frequency of the transmitted laser light according to the signal from the acousto-optic element driving unit 18. The two laser lights having the wavelength λ1 are used as the acousto-optic elements 16, 16. ′, The frequencies are shifted by frequencies f1 and f2, respectively, which are slightly different from each other.
The frequency is shifted by 6 ″ and 16 ′ ″ by slightly different frequencies f3 and f4, respectively. These frequency-shifted laser beams are respectively incident on an optical fiber by a fiber incident optical system. The optical fiber is connected to the optical fiber by a fiber connector, and the light emitted from the optical fiber is shaped into a desired shape by a beam shaper, and the mirrors 17 and 1 are respectively provided.
The light is incident on the diffraction grating 32 and the diffraction grating 34 at desired angles of incidence through 7 'and 17 "and 17'", respectively.

The optical heterodyne interference diffraction light obtained from the diffraction grating 32 and the optical heterodyne interference diffraction light obtained from the diffraction grating 34 through the monochromatic light incident / diffracted light extraction window 33 are the same as in the first embodiment. , And is detected as a beat signal, processed by the signal optimization processing control unit 6, and controls the alignment between the mask and the wafer. Here, the beat frequency of the beat signal obtained from the diffracted light of wavelength λ1 is | f1−f2 |, and the beat frequency of the beat signal obtained from the diffracted light of wavelength λ2 is | f3−f4 |.
It is. Further, the two laser lights having the wavelength λ2 are frequency-shifted by the acousto-optic devices 16 ″ and 16 ″ ′ by frequencies f1 and f2 slightly different from each other, and the beat frequency of the beat signal obtained from the diffracted light having the wavelength λ1 Even if it is configured to be the same | f1−f2 |, it is possible to separate into diffracted lights of each wavelength by the dielectric multilayer mirrors 1 and 1 ′.

As described above, in the present embodiment, laser beams having desired wavelengths emitted from a plurality of light sources are respectively made incident on the optical fiber, and the light emitted from the optical fiber is converted into the same diffraction grating at a predetermined incident angle. , And the position shift information is detected independently corresponding to each wavelength, and alignment can be performed by selectively using a signal having a high signal strength or a high S / N ratio. The light source and the optical heterodyne interference optical system can be divided by an optical fiber, so that downsizing of the optical system and facilitation of exchange adjustment of the light source can be realized.

In the first embodiment, two-wavelength orthogonally polarized laser beams having slightly different wavelengths emitted from the respective laser light sources are separated into two by a polarization beam splitter, and each of the laser beams is separated using four optical fibers. The same effect can be obtained even if the laser beam is incident.
Also in the second embodiment, for each of the wavelengths λ1 and λ2, two frequency-shifted laser beams are combined as laser beams orthogonally polarized by a polarization beam splitter, and two laser beams are respectively used by using two optical fibers. The same effect can be obtained even if the laser beam is incident.

Further, in the first and second embodiments, a configuration using a dielectric multilayer mirror as a configuration for independently separating and detecting a plurality of optical heterodyne interference diffraction lights corresponding to a set of monochromatic lights. Although the apparatus is shown, corresponding to the set of monochromatic light, the optical path of the monochromatic light is used to take out only the desired optical heterodyne interference diffraction light using an optical shutter, and by controlling the optical shutter, each monochromatic light is sequentially output. The same effect can be obtained by a configuration in which the beat signal of the optical heterodyne interference diffraction light of light is extracted and the optimum beat signal is selected.

The same effect can be obtained by changing the angle of inclination of the diffraction grating in the direction of the grating line in accordance with the set of monochromatic lights with respect to the incident angle.

Further, in the second embodiment, the difference in beat frequency generated by shifting the frequency by the acousto-optic device corresponding to the set of monochromatic light, | f1−f2 |, |
f3-f4 | may be separated and detected by an electric filter or the like, or a configuration in which only a desired optical heterodyne interference diffraction light is extracted by controlling a drive signal of an acousto-optic element. It goes without saying that the configuration of the invention can be applied.

[0033]

As described above, according to the present invention, the light source and the optical heterodyne interference optical system can be divided by the optical fiber, and the size of the optical system can be reduced and the exchange of the light source can be easily adjusted. The effect is obtained.

[Brief description of the drawings]

FIG. 1 is a first embodiment of the present invention.

FIG. 2 is a second embodiment of the present invention.

FIG. 3 is a schematic configuration diagram of a conventional alignment device using a diffraction grating.

[Description of Signs] 1, 1 'Dielectric multilayer mirror 2, 2', 44, 44 'Polarizer 3, 3', 25, 25 'Condensing lens 4, 4', 26, 26 'Photoelectric detector 6 Signal processing control unit 11, 11 ', 11 "mirror 12, 12' Laser light source (12 is wavelength λ1, 12 '
Is the wavelength λ2) 13, 13 'mirror 14, 14' beam splitter 16, 16 ', 16 ", 16"' acousto-optic device 17, 17 ', 17 ", 17"' mirror 18 acousto-optic device driver 20 Transverse Zeeman effect dual frequency orthogonally polarized laser light source (light source of wavelength λ1) 20 ′ Transverse Zeeman effect dual frequency orthogonally polarized laser light source (light source of wavelength λ2) 21, 21 ′, 21 ″, 21 ′ ″ mirror 22, 22 'Cylindrical lens 23, 23' Polarization beam splitter 24 Prism mirror 28 Mask stage 29 Wafer stage 30 Mask 31 Wafer 32 Mask diffraction grating 33 Monochromatic light incident / diffraction light extraction window 34 Wafer diffraction grating 50, 50 'Beam shaper 51, 51 ′ Fiber connector 52, 52 ′, 52 ″, 52 ′ ″ Optical fiber 53, 53 ′ Fiber incidence optical system 54, 5 ', 54 ", 54'" Fiber incident optics 55, 55 ', 55 ", 55"' Optical fibers 56, 56 ', 56 ", 56'" Fiber connectors 57, 57 ', 57 ", 57''' Optical Fiber 58, 58, 58 ', 58 ", 58"' Beam Shaper

## EQU1 ## (n.λi) / P = sin (θni)

## EQU2 ## λi / P = sin (θ1i)

Claims (6)

[Claims] A first diffraction grating provided on a first object;
A second diffraction grating provided on the second object is arranged at a fixed interval, and a plurality of light sources that generate a plurality of sets of monochromatic lights of two wavelengths whose frequencies are slightly different from each other are used as light sources, A set of monochromatic lights of two wavelengths generated from the plurality of light sources is incident on each of the first and second diffraction gratings at a predetermined incident angle using an optical fiber,
A plurality of optical heterodyne interference diffraction lights corresponding to the set of monochromatic lights generated from the diffraction gratings are independently separated and detected,
And a plurality of optical heterodyne interference diffraction lights are independently separated and detected in correspondence with the set of monochromatic lights generated from the second diffraction grating, to form a second set of beat signals. A plurality of phase difference signals independent of each light source are calculated from the set of the first and second beat signals, and based on one or two or more phase difference signals of the plurality of phase difference signals. An alignment method using a diffraction grating, wherein the alignment is performed by relatively moving the first and second objects. 2. The alignment method according to claim 1, wherein a set of monochromatic light of two wavelengths, which is frequency-shifted using a set of acousto-optic elements, is used as a light source. 3. A two-wavelength monochromatic light set, which is frequency-shifted using a set of acousto-optic elements as a light source, is incident on separate optical fibers.
The alignment method described in the item. 4. A first diffraction grating provided on a first object,
A second diffraction grating provided on a second object, a moving mechanism for relatively moving the first and second objects, and a plurality of sets of monochromatic lights of two wavelengths having slightly different frequencies from each other are generated. A plurality of light sources, an optical fiber incident optical system that causes a set of monochromatic lights of two wavelengths generated from the plurality of light sources to enter an optical fiber, and a set of the monochromatic lights emitted from the optical fiber into the first and second diffraction gratings, respectively. A plurality of incident angle adjusting means for entering the light at a predetermined incident angle, and independently separating and detecting a plurality of optical heterodyne interference diffraction lights corresponding to the set of the monochromatic light generated from the first diffraction grating. A plurality of first detecting means for generating a plurality of first beat signals;
A plurality of second detection means for independently separating and detecting a plurality of optical heterodyne interference diffraction lights corresponding to the set of monochromatic lights generated from the second diffraction grating to generate a plurality of second beat signals; Phase difference detection means for independently detecting a plurality of phase difference signals corresponding to each light source from the plurality of first and second beat signals generated by the plurality of first and second detection means, The moving mechanism based on a phase difference signal obtained from a detection signal having the best intensity or S / N ratio of the first and second beat signals among the phase difference detection signals obtained by the phase difference detection means. Signal processing control means for sending a control signal to the first and second objects to relatively move and align the first and second objects. 5. The alignment device according to claim 4, wherein a set of monochromatic light of two wavelengths shifted in frequency using a set of acousto-optic elements is used as a light source. 6. The apparatus according to claim 5, wherein a set of monochromatic lights of two wavelengths, which are frequency-shifted by using a set of acousto-optic elements as light sources, are incident on separate optical fibers.
The alignment device according to the item.