JPH0574686A - Scanning type position detector - Google Patents

Abstract

PURPOSE:To obtain a scanning type position detector which can produce two slit-like beams having the same optical path length and intersecting each other at right angles with a simple constitution by providing first reflecting means which reflect a beam in a first optical path by an even number of times and second reflecting means which reflect a beam in a second optical path by an odd number of times. CONSTITUTION:A lighting means is provided with a first splitter 2 which branches a luminous flux from a light source 1 to a first and second optical paths (c) and (d), second beam splitter 7 which again combines the two optical paths into one optical path, and beam transforming member which transforms the two luminous fluxes into slit-like beams. Then, by respectively providing first reflecting means M1 and M2 which reflect a beam by an even number of times and second reflecting means 3, 4d, and 5d which reflect a beam by an odd number of times in the first and second optical paths (c) and (d), the two slit-like beams intersecting each other at right angles are formed by making the optical path lengths of the first and second optical paths (c) and (d) the same. Therefore, the optical system of this scanning type position detector can be easily designed and, at the same time, the cost of the detector can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning type position detecting device used for precise alignment of, for example, a semiconductor manufacturing device.

[0002]

2. Description of the Related Art Conventionally, alignment of an object to be inspected, such as a mask or a plate substrate, is previously provided on the object to be inspected with alignment marks in which rectangular dots m are arranged in a cross shape as shown in FIG. The position is detected by this. The size and interval of the dots m are set so that the diffracted light can be sufficiently separated and observed when the alignment light is irradiated.

In order to perform positioning with respect to this alignment mark, two slit-shaped beams A and B elongated by the illumination optical system in directions orthogonal to the position scanning directions X and Y, respectively.
Are formed and are scanned on the surface of the object to be inspected. When the slit-shaped beams A and B overlap the alignment mark,
Diffracted light is generated because the alignment mark acts as a diffraction grating. By detecting this diffracted light, it can be detected that the slit-shaped beams A and B overlap the alignment mark.

The configuration of the alignment optical system is shown in FIG. 7 with respect to the axis in one direction. The beam emitted from the laser L is reflected by the vibrating mirror V and guided to the illumination system, and on the focal plane thereof by the cylindrical lens C. To form an elongated slit-shaped beam in the non-scanning direction (perpendicular to the scanning direction). Further, the first objective lens ob1 and the second objective lens ob2 are arranged so that the test surface is conjugate with this focal plane.

The slit-shaped beam is applied to the alignment mark on the surface to be inspected by the illumination system. When the slit-shaped beam overlaps the alignment mark, it is diffracted to generate diffracted light (only the first-order diffracted light is shown in the figure). The diffracted light is condensed again by the first objective lens ob1, and is guided to the detection system by the beam splitter bs3 arranged between the first objective lens ob1 and the second objective lens ob2.

Since these diffracted lights travel in the non-scanning direction at an angle with the specularly reflected light (0th order light), the first objective lens o
Each spot is connected on the pupil of b1. This spot is further relayed onto the spatial filter F by the pupil relay lens ob3. The specularly reflected light (0th order light) is cut by the spatial filter F and made incident on the photodetector D, so that the diffracted light generated there is felt by the photodetector D only when the slit-shaped beam hits the alignment mark. To

Further, the slit-shaped beam scans the surface to be inspected at a constant cycle by vibrating the vibrating mirror V. Here, when the alignment mark m ′ is at the center of the vibration width 1 of the beam, the diffracted light detection signal S has a time of exactly T / 2 with respect to the vibration cycle T of the vibration mirror V, as shown in FIG. Detected at intervals. However, FIG. 8 (b)
The alignment mark is displaced from the vibration center (d
1), the signal S is detected with a deviation from the T / 2 time interval.

At this time, the direction and distance of the deviation of the alignment mark from the vibration center of the beam are calculated by the signal processing system from the deviation of the vibration direction of the mirror and the time at which the signal appears. Based on this information, the stage (not shown) on which the object to be inspected is placed can be driven to dispose the object to be inspected at a predetermined position.

In a scanning type position detecting device having such a position detecting means, a conventional illuminating system for forming two slit-shaped beams for scanning on a surface to be inspected and whose longitudinal directions are orthogonal to each other is shown in FIG. It was like that.

In FIG. 5, the laser beam emitted from the light source is reflected by the vibrating mirrors M1 and M2, passes through the cylindrical lens R, is converted into a sheet-like beam, and then is incident on the first beam splitter bs3. First
It is branched into an optical path and a second optical path. The beam of the first optical path is reflected by the mirror M3 and the mirror M4 and enters the second beam splitter bs4.

On the other hand, the beam of the second optical path enters the beam splitter bs4 via the image raw data IR. The two beam paths are combined again by the second beam splitter bs4. Here, the longitudinal direction of the slit image of the slit beam from the second beam path and the longitudinal direction of the slit beam from the first beam path are orthogonal to each other. Thus, the image raw data IR on the second optical path is designed.

The two slit-shaped beams, which are formed orthogonally to each other in this way, pass through the objective lens ob2, the half mirror M5, and the objective lens ob1 and are applied to the surface to be inspected. Scan in a direction orthogonal to the direction. The light reflected, scattered, or diffracted from the surface to be inspected passes through the objective lens ob1 and passes through the half mirror M.
The beam is reflected by the objective lens ob3, is condensed by the objective lens ob3, is branched again to the two light speeds by the beam spreader bs5, and is detected by the detectors D1 and D2 for the respective lights.

[0013]

However, in the conventional technique, one beam passes the image raw data but the other beam does not pass, so that an optical path length difference occurs. Therefore, there is a problem that the focus position of the slit-shaped beam is different. Furthermore, it takes time and effort to design and manufacture image raw data, and it is difficult to reduce the cost.

It is an object of the present invention to obtain a scanning type position detecting device having a simple structure and producing two slit-shaped beams having the same optical path length and orthogonal to each other.

[0015]

In order to achieve the above object, in a scanning type position detecting device according to a first aspect of the present invention, two slits which are orthogonal to each other are formed on a surface of an object having a position detecting mark. Means for forming a circular beam and scanning each of the beams in a direction orthogonal to the longitudinal direction of the two slit-shaped beams, and an object to be inspected by detecting reflected light from the position detecting mark by the illuminating means. In a scanning type position detecting device having a detecting means for detecting the position of
The illumination means includes a light source, a first beam splitter that splits a light beam from the light source into a first optical path and a second optical path, a second beam splitter that combines the first and second optical paths, and the second beam splitter. 1 1 between the optical path between the beam splitter and the light source
Or a beam converting member arranged in each of the first optical path and the second optical path to convert a light beam into a slit-shaped beam, and make the optical path lengths of the first optical path and the second optical path the same. However, the plane of incidence of the slit-shaped beam from the first optical path with respect to the combined surface of the second beam splitter is made orthogonal to the longitudinal direction of the beam, and the slit from the second optical path with respect to the combined surface of the second beam splitter is formed. A first reflecting means for reflecting the beam in the first optical path an even number of times and a beam for reflecting the beam an odd number of times in the second optical path in order to make the incident surface of the circular beam parallel to the longitudinal direction of the beam. Two reflecting means were provided.

[0016]

According to the present invention, the illuminating means in the scanning type position detecting device includes a first beam splitter for splitting a light beam from a light source into a first optical path and a second optical path, and a first beam splitter for combining the first and second optical paths again. A two-beam splitter and a beam conversion member for converting the two light beams into a slit-shaped beam, first reflecting means for reflecting the beam an even number of times in the first optical path, and odd-numbered beams for the second optical path. By providing the second reflecting means for reflecting the light twice, two slit-shaped beams orthogonal to each other are formed while the optical path lengths of the first and second optical paths are the same.

The operation of the present invention will be described with reference to FIG. As shown in the figure, the beam splitter and the mirror are arranged at the vertices of a cube in the part where the images are orthogonalized. When an image in the y-axis direction enters the first beam splitter bs1 that splits the light beam from the light source, the beam splitter b
The light transmitted through s1 goes to the first optical path a, and the reflected light goes to the second optical path a.
Proceed to optical path b.

In the first optical path a, the image reflected by the mirror M ₁₁ is in the x-axis direction, and further reflected by the mirror M ₁₂ and the image remains in the x-axis direction, the second beam splitter bs for optical path combination.
It is incident on 2 and is reflected to obtain an image in the z-axis direction. on the other hand,
In the second optical path, the light reflected by the first beam splitter bs1 is reflected by the mirror M ₂₀ , but the image direction remains the y-axis direction.

Further, although it is reflected by the mirror M ₂₁ to form an image in the x-axis direction, when reflected by the mirror M ₂₂ , it becomes an image in the Y-axis direction again and enters the second beam splitter bs2 and is transmitted therethrough. Here, two images which are orthogonal to each other are obtained in the Z-axis direction image from the first optical path and the Y-axis direction image from the second optical path.

That is, two mutually orthogonal images are formed by the mirror M ₁₂ , the mirror M _22, and the bending surface of the second beam splitter bs2 for combination, and the bending angle of the optical path by each mirror is 90 °. The first optical path from the first beam splitter to the second beam splitter and the second optical path
The optical path lengths of the optical paths are equal.

Since the present invention is provided with the illumination system having the above-mentioned structure including the beam splitter and the mirror, the scanning system is orthogonal to each other with a simple structure that does not require a special optical element. It becomes possible to form two slit-shaped beams. Further, since the optical path lengths of the first optical path and the second optical path are the same, it is possible to solve the problem of the shift of the focus positions of the two slit-shaped beams based on the optical path length difference.

[0022]

EXAMPLES Examples of the present invention will be described below. Figure 1
It is a schematic structure figure explaining the 1st example of the present invention. The configuration of the illumination system of the present embodiment has a first beam splitter 2 that splits a beam from the light source 1 into a first optical path c and a second optical path d.
And a second beam splitter 7 that combines the two optical paths, and a vibrating mirror Ac and a mirror 5 in the first optical path c.
c, the cylinder lens 6c, the mirror 3, the vibrating mirror 4d, the mirror 5d, and the cylinder lens 6 in the second optical path d.
d is installed.

The light emitted from the light source 1 is reflected by the mirror M1,
The light reflected by the mirror M2 and incident on the beam splitter 2 is transmitted to the first optical path c, and the reflected light is guided to the second optical path d. In the first optical path c, the light reflected by the vibrating mirror 4c becomes light that vibrates in the x-axis direction, is further reflected by the mirror 5c, and enters the cylinder lens 6c with the vibrating direction being the x-axis.

By passing through the cylinder lens 6c, a slit-shaped beam whose longitudinal direction of the slit image is the y-axis direction is formed. This slit-shaped beam is reflected by the beam splitter 7 and becomes a slit-shaped beam whose longitudinal direction vibrating in the z-axis direction is the y-axis direction.

On the other hand, in the second optical path d, the light reflected by the mirror 3 becomes light that is reflected by the vibrating mirror 4d and vibrates in the x-axis direction, but is reflected by the mirror 5d again in the y-axis direction. The light oscillates into the cylinder lens 6d. By passing through the cylinder lens 6c, a slit-shaped beam whose longitudinal direction in the slit image is the z-axis direction is formed and is transmitted through the beam splitter 7.

The slit-shaped beam which has passed through the beam splitter 7 and which oscillates in the y-axis direction with the z-axis as the longitudinal direction is again combined with the first optical path c. In this way, the lights of the two optical paths combined by the beam splitter 7 have their vibration directions orthogonal to each other and also the longitudinal directions of the slit images.

The two slit-shaped beams that are combined and orthogonal to each other pass through the objective lens 8, the half mirror 9, and the objective lens 10 and are irradiated onto the surface 11 to be inspected. The two slit-shaped beams are oscillating mirror 4c and oscillating mirror 4d.
The vibration of scans the surface to be inspected in a direction orthogonal to the longitudinal direction of the slit image.

The light reflected, scattered, or diffracted from the surface 11 to be inspected passes again through the objective lens 10, is reflected by the half mirror 9, is condensed by the objective lens 12, is branched again by the beam splitter 13, and is detected for each light. Bowl 14
c, detected by the detector 14d.

Here, the cylinder lens 6c and the cylinder lens 6d may be arranged so that the focal position is the focal plane of the objective lens 8 and is closer to the light source than the beam splitter 7. If the optical path lengths from the respective cylinder lenses to the second beam splitter 7 are set to be equal, the configuration of the optical system becomes easier. In addition, this embodiment has a feature that the vibration frequency of the vibrating mirror can be set independently. In this case, it is possible to use one detector by using a filter having a selection characteristic depending on the frequency. Further, since the vibration axes of the two vibrating mirrors are parallel to each other, it is possible to use the same mirror shape and drive system. Therefore, there is also a feature that the scan stability can be made equal to each axis.

Under the above-mentioned cylinder lens arrangement conditions, the cylinder lens may be arranged closer to the light source than the first beam splitter 2. In this case, only one cylinder lens is required. A case where only one cylinder lens is used is shown in FIG. 2 as a second embodiment.

The configuration of the illumination system of this embodiment is such that the first beam splitter 2 is used instead of the two cylinder lenses 6c and 6d on the first and second optical paths in the first embodiment.
Place one cylinder lens 23 on the light source side from 4,
In addition, the two vibrating lenses 4 on the first optical path and the second optical path
Mirrors are arranged instead of c and 4d, and one oscillating mirror 22 is arranged closer to the light source side than the first beam splitter 24, and the others are the same as in the first embodiment.

In FIG. 2, the light emitted from the light source 21 becomes light that is reflected by the mirror M1 and the vibrating mirror 22 and vibrates in the y-axis direction, and passes through the cylinder lens 23 and the longitudinal direction of the slit image is in the z-axis direction. It becomes a slit-shaped beam that vibrates in the y-axis direction. This slit-shaped beam enters the first beam splitter 24 and is split into a first optical path e and a second optical path f.

In the first optical path e, the beam splitter 2
The slit-shaped beam of the longitudinal axis that oscillates in the y-axis direction that has passed through 4 is reflected by the mirror 26e, the mirror 27e, and the second beam splitter 28, and becomes a slit-shaped beam of the longitudinal y-axis that vibrates in the z-axis direction. ..

On the other hand, in the second optical path f, the slit-shaped beam reflected by the beam splitter 24 is reflected by the mirror 2
5, reflected by the mirror 26f and the mirror 27f, transmitted through the beam splitter 28, and becomes a slit-shaped beam in the longitudinal z-axis that vibrates in the y-axis direction and is combined with the beam from the first optical path e. The vibration directions of the two slit-shaped beams combined here and the longitudinal direction of the slit image are orthogonal to each other.

The two slit-shaped beams, which are orthogonal to each other, pass through the objective lens 29, the half mirror 30, and the objective lens 31 and are irradiated onto the surface 32 to be inspected, and scan in the vibration directions orthogonal to the longitudinal direction. Reflected or scattered from the surface to be inspected,
The diffracted light passes through the objective lens 31 and the half mirror 3
The light is reflected by 0, is condensed by the objective lens 33, and is then branched again by the beam splitter 34, and the respective lights are detected by the detectors 35e and 35f.

In the present embodiment, since only one oscillating mirror is arranged, it is used when it is desired to make the scanning periods of the two beams the same. Further, here, the vibrating mirror 22 is arranged on the light source side of the cylinder lens 23, but either one may be arranged on the light source side.

Next, FIG. 3 shows an illumination system of the third embodiment using polarized light. The configuration of this embodiment includes a vibrating mirror, a cylinder lens, a mirror, a beam splitter, an objective lens,
The detector has the same arrangement as in the second embodiment, and in addition to this, a polarizer is arranged on the optical path.

A λ / 2 plate 44 is provided between the first beam splitter 45 and the cylinder lens 43, and λ / is provided on the first optical path g.
2 plate 46g, λ / 2 plate 46h on the second optical path h, and λ / 2 between the second beam splitter 50 and the objective lens 52.
The plate 51 has a λ / 2 plate 58 placed in and out of the objective lens 57 and the beam splitter 59, or rotatably arranged, and a λ / 4 plate 54 placed in and out of the beam splitter 53 and the objective lens 55. It is rotatably arranged. The beam splitter used in this embodiment is a polarization beam splitter.

In FIG. 3A, the light from the laser light source 41 is reflected by the mirror M1 and the oscillating mirror 42, passes through the cylinder lens 43, and becomes a slit-shaped beam whose longitudinal direction oscillates in the y-axis direction. .. Here, the light from the light source 41 is linearly polarized light parallel to the paper surface and orthogonal to the optical axis (hereinafter,
It is referred to as P-polarized light).

The slit-shaped beam emitted from the cylinder lens 43 becomes linearly polarized light (hereinafter referred to as S-polarized light) whose polarization direction is rotated by 90 ° by the λ / 2 plate 44, enters the first polarization beam splitter 45, and is reflected. 2 is guided to the optical path h.
At this time, S-polarized light does not pass through the first optical path g due to the polarization characteristics of the polarization beam splitter 45.

In the second optical path h, the S-polarized light is rotated again by the λ / 2 plate 46h to become P-polarized light, which is reflected by the mirror 47, the mirror 48h, and the mirror 49h.
Of the polarization beam splitter 50. Here, the P-polarized light vibrates in the y-axis direction to obtain a slit-shaped beam in the longitudinal z-axis.

This P-polarized slit-shaped beam is either extracted from the optical path or passed through the λ / 2 plate 51 whose axis is aligned with the direction in which the polarization direction is not rotated, and is transmitted through the objective lens 52 and the polarization beam splitter 53. Then λ /
It is made into circularly polarized light by the four plate 54, passes through the objective lens 55, and is irradiated onto the surface 56 to be inspected.

The light reflected, scattered or diffracted by the surface 56 to be inspected passes through the objective lens 55 again to be S-polarized by the λ / 4 plate 54, is reflected by the polarization beam splitter 53 and is condensed by the objective lens 57. .. Here, the λ / 2 plate 58 is rotated or pulled out. Therefore, the S-polarized light enters the polarization beam splitter 59 as it is, is reflected, and is detected by the detector 60h. In this way, position detection is performed using one slit-shaped beam.

The position detection by the other slit-shaped beam is performed by rotating the λ / 2 plate 44 by 90 ° or by pulling it out. As a result, the P-polarized slit-shaped beam from the light source passes through the polarizing beam splitter 45 as it is and is guided to the first optical path g.
At this time, the P-polarized light is not reflected to the second optical path h due to the polarization characteristics of the polarization beam splitter 45.

In the first optical path g, the P-polarized slit-shaped beam transmitted through the polarization beam splitter 45 is converted into S-polarized light by the λ / 2 plate 46g, and the mirror 48g and the mirror 4
9 g, which is reflected by the second polarization beam splitter 50. Here, an S-polarized slit-shaped beam oscillating in the z-axis direction and in the longitudinal y-axis is obtained.

This S-polarized slit-shaped beam is now P-polarized by the λ / 2 plate 51 whose polarization direction is rotated by 90 °, passes through the objective lens 52 and the polarization beam splitter 53, and then becomes λ. It becomes circularly polarized light by the / 4 plate 54, passes through the objective lens 55, and is irradiated onto the surface 56 to be inspected.

The light reflected, scattered or diffracted by the surface to be inspected 56 passes through the objective lens 55 again to be S-polarized by the λ / 4 plate 54, is reflected by the polarization beam splitter 53 and passes through the objective lens 57, and this time. It is converted into P-polarized light by the λ / 2 plate 58, transmitted through the polarization beam splitter 59, and then detected by the detector 60g.

In this embodiment, as described above, the beam for position detection can be arbitrarily selected by moving the λ / 2 plate in and out or rotating it. Therefore, it is possible to reduce the light amount loss. It is also possible to adjust the light quantity of the orthogonal slit-shaped beam by rotating the λ / 2 plate 44 and changing the direction of the polarized light incident on the first polarization beam splitter 45.

Further, the polarization direction of the light incident on the first polarization beam splitter 45 is linearly polarized in the direction of 45 ° as shown in FIG. 3B, and the λ / 2 plate and the λ / 4 plate are removed,
If the beam splitter 59 is a non-polarizing beam splitter, the optical system can be simplified and simultaneous position detection by two slit-shaped beams is possible. Further, not limited to this configuration, each of the first and second beam splitters,
A case where either one of them is a non-polarizing beam splitter can be considered.

In the embodiments described above, the cylinder lens is used as the beam conversion member, but the invention is not limited to this, and it can be widely used as long as it can convert a light beam into a slit-shaped beam such as an anamorphic prism. is there.

[0051]

As described above, the present invention makes it possible to form two slit-shaped beams for scanning that are orthogonal to each other with a simple structure that does not require a special optical element, so that the design of the optical system is easy. Therefore, the cost can be reduced. Furthermore, since the optical path lengths of the first optical path and the second optical path are equal, there is an effect that the problem of focus position deviation of the two slit-shaped beams due to the optical path length difference can be solved. Further, the present invention can be applied not only to position detection but also to obtaining images orthogonal to each other.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram illustrating an illumination system according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating the illumination system according to the second embodiment of the present invention.

FIG. 3 is a schematic configuration diagram illustrating an illumination system according to a second embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of an optical system for explaining the operation of the present invention.

FIG. 5 is a schematic configuration diagram illustrating an illumination system of a conventional scanning position detection device.

FIG. 6 is a plan view illustrating an alignment mark detection method using a slit-shaped beam of the scanning position detection device.

FIG. 7 is an optical path diagram of a detection system of the scanning position detection device.

FIG. 8 is an explanatory diagram of position detecting means of the scanning position detecting device.

[Description of Reference Signs] 1,21,41: Light Sources M1, M2, M3, M4, 3, 5c, 5d, 25, 2
6e, 26f, 27e, 27f, 47, 48g, 48
h, 49g, 49h, M ₁₁ , M ₁₂ , M ₂₀ , M ₂₁ , M ₂₂ :
Mirrors 4c, 4d, 22, 42: Vibrating mirrors 2, 24, 45, bs1, bs3: First beam splitter 7, 28, 50, bs2, bs4: Second beam splitter 13, 34, 53, 59: Beam splitter 6c , 6d, 23, 43, c, R: Cylinder lens 8, 10, 12, 29, 31, 33, 52, 55, 5
7, ob12, ob2, ob3: Objective lens 9, 30, M5: Half mirror 11, 32, 56: Surface to be inspected

Claims (1)

[Claims] 1. A slit-shaped beam, which is orthogonal to each other, is formed on a surface of an object having a position detection mark,
Illumination means for scanning each slit-shaped beam in a direction orthogonal to the longitudinal direction, and detection means for detecting the reflected light from the position detection mark by the illumination means to detect the position of the object to be inspected. In the scanning position detecting device having: a light source, the illumination unit combines the light source, a first beam splitter that splits a light flux from the light source into a first optical path and a second optical path, and the first and second optical paths. And a second beam splitter for controlling the optical path between the first beam splitter and the light source.
Or a beam conversion member that is disposed in each of the first optical path and the second optical path and converts a light beam into a slit-shaped beam, and makes the optical path lengths of the first optical path and the second optical path the same. While
A slit-shaped beam from the second optical path with respect to the combined surface of the second beam splitter is formed by making the incident surface of the slit-shaped beam from the first optical path with respect to the combined surface of the second beam splitter orthogonal to the longitudinal direction of the beam. First reflection means for reflecting the beam in the first optical path an even number of times, and second reflection means for reflecting the beam in the second optical path an odd number of times in order to make the incident surface of the beam parallel to the longitudinal direction of the beam. A scanning type position detecting device comprising means.