JP3158544B2 - Scanning position detector - Google Patents

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 a test object such as a mask or a plate substrate is performed by previously providing an alignment mark in which rectangular dots m are arranged in a cross shape as shown in FIG. Thus, the position is detected. The size and interval of the dot m are set so that the diffracted light can be sufficiently separated and observed when the alignment light is irradiated.

In order to position the alignment mark, two slit-like beams A and B elongated in a direction orthogonal to the position scanning directions X and Y by an illumination optical system.
Is formed, and is scanned on the surface of the test object. When the slit beams A and B overlap the alignment mark,
Diffraction light is generated because the alignment mark serves as a diffraction grating. By detecting the diffracted light, it is possible to detect that the slit beams A and B overlap the alignment mark.

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

The illumination beam irradiates the alignment mark on the surface to be inspected with the slit beam. When the slit beam overlaps the alignment mark, it undergoes diffraction to generate diffracted light (only the first-order diffracted light is shown in the figure). This diffracted light is condensed again by the first objective lens ob1, and 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 at an angle to the specularly reflected light (zero-order light) in the non-scanning direction, the first objective lens o
Each spot is connected on the pupil of b1. This spot is further relayed on the spatial filter F by the pupil relay lens ob3. By cutting the specular reflected light (zero-order light) with the spatial filter F and making it incident on the photodetector D, the diffracted light generated there is felt by the photodetector D only when the slit beam hits the alignment mark. To

Further, the slit beam scans the surface to be inspected at a constant period by vibrating the vibrating mirror V. Here, when the alignment mark m ′ is at the center of the beam oscillation width 1, the diffracted light detection signal S takes a time period of T / 2 with respect to the oscillation period T of the oscillation mirror V as shown in FIG. Detected at intervals. However, FIG.
As shown in the figure, the alignment mark is shifted from the center of vibration (d
1) In such a case, the signal S is detected to be shifted from the time interval of T / 2.

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 between the vibration direction of the mirror and the time when the signal appears. Based on this information, by driving a stage (not shown) on which the test object is mounted, the test object can be arranged at a predetermined position.

FIG. 5 shows a conventional illumination system which forms two slit-shaped beams which scan the surface to be inspected and which are orthogonal to each other in a scanning type position detecting device having such position detecting means. It was something like

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

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

The two orthogonal slit beams thus formed are irradiated on the surface to be inspected through the objective lens ob2, the half mirror M5, and the objective lens ob1, and each of the beams is elongated by the vibration of the mirror M1. Scan in the direction orthogonal to the direction. The light reflected, scattered and diffracted from the test surface passes through the objective lens ob1 and passes through the half mirror M
The light is reflected by an objective lens ob3, is condensed by an objective lens ob3, is split into two light speeds again by a beam splitter bs5, and is detected by detectors D1 and D2 for each light.

[0013]

However, in the prior art, one beam passes through 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 beam is different. Furthermore, it takes time and effort to design and manufacture image raw data and the like, and it is difficult to reduce costs.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a scanning type position detecting device which has two light beams having the same optical path length and orthogonal to each other with a simple structure.

[0015]

According to a first aspect of the present invention, there is provided a scanning type position detecting apparatus comprising two slits orthogonal to each other on a surface of a test object having a position detecting mark. Means for forming a shaped beam and scanning each beam in a direction orthogonal to the longitudinal direction of the two slit-shaped beams, and detecting the reflected light from the position detection mark by the lighting means to detect an object. Scanning type position detecting device having a detecting means for detecting the position of
The illuminating means, 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, 1 between the optical path between one beam splitter and the light source
Or a beam converting 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, wherein the first optical path and the second optical path have the same optical path length. While making the plane of incidence of the slit beam from the first optical path with respect to the combined plane of the second beam splitter orthogonal to the longitudinal direction of the beam, the slit from the second optical path with respect to the combined plane of the second beam splitter is First reflecting means for reflecting the beam in the first optical path an even number of times in order to make the plane of incidence of the shaped 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 re-combines the first and second optical paths with the first beam splitter for splitting the light beam from the light source into the first optical path and the second optical path. It has a two-beam splitter and a beam converting member for converting the two light beams into a slit-like beam, a first reflecting means for reflecting the beam even number of times in the first optical path, and an odd number of the beam in the second optical path. By providing the second reflection 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 cuboid in a portion where the image is orthogonal. When the 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.

[0018] In the first optical path a, the second beam splitter bs of is image reflected by image further mirror M ₁₂ becomes the x-axis direction reflected by the mirror M ₁₁ for combining optical paths remain in the x-axis direction
2 and is reflected and an image in the z-axis direction is obtained. on the other hand,
In the second optical path, the light reflected by the first beam splitter bs1, the direction of the the but the image reflected by the mirror M ₂₀ remains in the y-axis direction.

Furthermore, although is reflected by the mirror M ₂₁ in the x-axis direction of the image, incident transmitted as a difference is again Y-axis direction of the image reflected by the mirror M ₂₂ to the second beam splitter bs2. Here, two images that are orthogonal to the image in the Z-axis direction from the first optical path and the image in the Y-axis direction from the second optical path are obtained.

[0020] That is, the image orthogonal two mutually are formed by bent surface of the second beam splitter bs2 for the synthesis mirror M ₁₂ and the mirror M _22, bending angle of the optical path by each mirror is 90 °, A first optical path from the first beam splitter to the second beam splitter;
The optical path lengths are equal.

Since the present invention is provided with the illumination system having the above-described configuration including the beam splitter and the mirror, it is orthogonal to each other for scanning with a simple configuration that does not require a special optical element. It is possible to form two slit beams. In addition, since the first optical path and the second optical path have the same optical path length, it is possible to solve the problem that the focus positions of the two slit beams are deviated based on the optical path length difference.

[0022]

Embodiments of the present invention will be described below. FIG.
FIG. 1 is a schematic configuration diagram illustrating a first embodiment of the present invention. The configuration of the illumination system according to the present embodiment includes a first beam splitter 2 that splits a beam from a light source 1 into a first optical path c and a second optical path d.
And a second beam splitter 7 for synthesizing the two optical paths, and a vibrating mirror Ac and a mirror 5 are provided in the first optical path c.
c, a cylinder lens 6c is provided in the second optical path d in the mirror 3, the vibration mirror 4d, the mirror 5d, the cylinder lens 6
d is installed.

The light emitted from the light source 1 is 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 oscillating mirror 4c becomes light oscillating in the x-axis direction, is further reflected by the mirror 5c, and enters the cylinder lens 6c with the oscillating direction being the x-axis.

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

On the other hand, in the second optical path d, the light reflected by the mirror 3 is reflected by the oscillating mirror 4d to become light that oscillates in the x-axis direction. The light oscillates to enter the cylinder lens 6d. By passing through the cylinder lens 6c, a slit-like beam whose longitudinal direction of the slit image is in the z-axis direction is formed and transmitted through the beam splitter 7.

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

The two slit beams thus synthesized and orthogonal to each other are irradiated on the surface 11 to be measured through the objective lens 8, the half mirror 9, and the objective lens 10. The two slit beams are divided into a vibrating mirror 4c and a vibrating mirror 4d.
The vibration is caused to scan the surface to be inspected in a direction orthogonal to the longitudinal direction of the slit image.

The light reflected, scattered, and diffracted from the surface 11 to be measured passes through the objective lens 10 again, 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. Table 14
c, detected by the detector 14d.

Here, the arrangement of the cylinder lenses 6c and 6d may be such 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 length from each cylinder lens to the second beam splitter 7 is set to be equal, the configuration of the optical system becomes easier. Further, this embodiment is characterized in that the vibration frequency of the vibration mirror can be set independently. In this case, if a filter having a selection characteristic based on frequency is used, it is possible to use one detector. Further, since the vibration axes of the two vibration mirrors are parallel, a common mirror shape and drive system can be used. For this reason, there is a feature that the scanning stability can be made equal to each axis.

Under the above-described cylinder lens arrangement conditions, a 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. FIG. 2 shows a second embodiment in which only one cylinder lens is used.

The configuration of the illumination system of this embodiment is different from that of the first embodiment in that the first beam splitter 2 is used instead of the two cylinder lenses 6c and 6d on the first optical path and the second optical path.
One cylinder lens 23 is arranged on the light source side from 4,
Also, 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 than the first beam splitter 24, and the other is the same as the first embodiment.

In FIG. 2, the light emitted from the light source 21 is reflected by the mirror M1 and the vibrating mirror 22, and becomes light vibrating in the y-axis direction. A slit beam vibrates in the y-axis direction. The slit 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
4 is reflected by the mirror 26e, the mirror 27e, and the second beam splitter 28 to vibrate in the y-axis direction, and becomes a slit beam in the y-axis direction vibrating in the z-axis direction. .

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

The two mutually orthogonal slit beams pass through the objective lens 29, the half mirror 30, and the objective lens 31 and irradiate on the surface 32 to be inspected, and scan in a vibration direction orthogonal to the longitudinal direction. Reflection or scattering from the test surface,
The diffracted light passes through the objective lens 31 and the half mirror 3
After being reflected at 0 and condensed by the objective lens 33, it is split again by the beam splitter 34, and each light is detected by the detectors 35e and 35f.

In this embodiment, since only one oscillating mirror is provided, it is used when it is desired to make the scanning cycle by two beams the same. Further, here, the vibration mirror 22 is arranged on the light source side with respect to the cylinder lens 23, but either one may be arranged on the light source side.

Next, an illumination system according to a third embodiment using polarized light is shown in FIG. The configuration of this embodiment includes a vibration mirror, a cylinder lens, a mirror, a beam splitter, an objective lens,
The detector has the same arrangement as that of the second embodiment, and additionally, 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 a λ / 2 plate 44 is provided on the first optical path g.
The second plate 46g, the λ / 2 plate 46h on the second optical path h, and the λ / 2 plate 46h between the second beam splitter 50 and the objective lens 52.
The plate 51 is arranged so that a λ / 2 plate 58 can be inserted and removed or rotatable between the objective lens 57 and the beam splitter 59, and a λ / 4 plate 54 can be inserted and removed between the beam splitter 53 and the objective lens 55. It is arranged to be rotatable. The beam splitter used in this embodiment is a polarization beam splitter.

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

The slit beam that has exited the cylinder lens 43 becomes linearly polarized light (hereinafter referred to as S-polarized light) whose polarization direction has been rotated by 90 ° by the λ / 2 plate 44, enters the first polarization beam splitter 45, is reflected and is reflected. It is guided to two optical paths h.
At this time, the 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 again rotated in the polarization direction by the λ / 2 plate 46h to become P-polarized light, and is reflected by the mirror 47, the mirror 48h, and the mirror 49h.
Through the polarizing beam splitter 50. Here, a P-polarized light oscillates in the y-axis direction to obtain a slit-like beam in the longitudinal z-axis.

The P-polarized slit-like beam passes through the objective lens 52 and the polarizing beam splitter 53 either withdrawn from the optical path or passed through a λ / 2 plate 51 whose axis is aligned in a direction in which the polarization direction is not rotated. And λ /
The light is converted into circularly polarized light by the four plates 54, and is irradiated on the surface 56 to be measured through the objective lens 55.

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

The position detection by the other slit beam is performed by rotating or pulling out the λ / 2 plate 44 by 90 °. Thus, the P-polarized slit-like beam from the light source passes through the polarization 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 and directed 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 a λ / 2 plate 46g, and the mirror 48g and the mirror 4
9 g is reflected by the second polarizing beam splitter 50. Here, an S-polarized slit beam oscillating in the z-axis direction and in the longitudinal y-axis direction is obtained.

This S-polarized slit beam is turned into P-polarized light by a λ / 2 plate 51 whose polarization direction is turned by 90 °, and transmitted through an objective lens 52 and a polarization beam splitter 53. The light is converted into circularly polarized light by the / 4 plate 54, and is irradiated on the surface 56 to be measured through the objective lens 55.

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

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

Also, the polarization direction of the light incident on the first polarization beam splitter 45 is linearly polarized in the 45 ° direction 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 becomes simpler, and simultaneous position detection using two slit beams becomes possible. Further, without being limited to this configuration, each of the first and second beam splitters
There may be a case where one of them is a non-polarizing beam splitter.

In the embodiment described above, the cylinder lens is used as the beam converting member. However, the present invention is not limited to this, and can be widely used as long as it can convert a light beam into a slit beam, such as an anamorphic prism. is there.

[0051]

As described above, according to the present invention, two slit beams orthogonal to each other for scanning can be formed with a simple configuration that does not require a special optical element, so that the design of the optical system is easy. Therefore, the cost can be reduced. Further, since the first optical path and the second optical path have the same optical path length, there is an effect that the problem of the shift of the focus position between the two slit beams based on the optical path length difference can be solved. In addition, the present invention can be applied not only to position detection but also to cases where it is desired to obtain mutually orthogonal images.

[Brief description of the 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 a lighting system according to a 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 illustrating an operation of the present invention.

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

FIG. 6 is a plan view illustrating a method of detecting an alignment mark using a slit beam in the scanning type position detecting 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 a position detecting means of the scanning type position detecting device.

[Explanation of symbols]

1,21,41: Light source 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 splitters 7, 28, 50, bs2, bs4: second beam splitters 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

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-235507 (JP, A) JP-A-61-124131 (JP, A) JP-A-60-115225 (JP, A) 241816 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/027 G03F 9/00 G01B 11/00

Claims (1)

(57) [Claims] 1. A slit beam orthogonal to each other is formed on a surface of a test object having a position detection mark.
Illuminating means for scanning each beam in a direction orthogonal to the longitudinal direction of the two slit-shaped beams, and detecting means for detecting the reflected light from the position detection mark by the illuminating means and detecting the position of the test object; In the scanning type position detecting device having the above, the illuminating means combines 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, and combines the first and second optical paths. And a second beam splitter 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, wherein the first optical path and the second optical path have the same optical path length. While
The plane of incidence of the slit beam from the first optical path with respect to the combined plane of the second beam splitter is orthogonal to the longitudinal direction of the beam, and the slit beam from the second optical path with respect to the combined plane of the second beam splitter. In order to make the incident surface of the beam parallel to the longitudinal direction of the beam, first reflecting means for reflecting the beam in the first optical path an even number of times, and second reflecting means for reflecting the beam in the second optical path an odd number of times. A scanning type position detecting device comprising means.