JPH05312513A - Aligner for sample stage - Google Patents

Abstract

PURPOSE:To simplify the optical system in an interferometer 5y alignining a sample stage based on positional detection through an optical alignment system disposed on the sample stage side and focusing the reflected light of parallel beam, projected obliquely onto the surface of a sample, onto a light receiving means. CONSTITUTION:The aligner for sample stage comprises a light source 24 for projecting light obliquely onto the measuring face of a sample 11 mounted on a sample stage 10, a lens 25 for converting the light projected from the light source 24 into a parallel beam, a lens 26 for focusing the light reflected on the surface of the sample 11, and a light receiving means 27 for detecting the focus position of reflected light. Alignment mechanism is adjusted such that the light impinges on a reference position of the light receiving means 27.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sample table for supporting a sample in an interferometer or the like, and for adjusting the sample table to a predetermined angle so that the measurement surface of the sample is perpendicular to the measurement optical axis. The present invention relates to an alignment device.

[0002]

2. Description of the Related Art Conventionally, for example, in an interferometer for inspecting the surface shape of an object such as an optical element and a mirror, a technique for measuring unevenness of the object by contour line interference fringes by utilizing the coherence of laser light. That is, the reflected light from the high precision plane of the optical reference plate and the reflected light from the surface of the subject are caused to interfere with each other, and the interference fringes generated according to the deviation of the flatness between the two are measured.

That is, a coherent laser beam is collimated into a wide parallel light beam and divided, and one light beam is applied to a standard plate which is a highly accurate flat surface, and the reflected light is used as a reference light, and the other is applied to a subject. It illuminates the object light. When these two lights are combined, an interference fringe is generated, which becomes a contour line interference fringe of the shape of the subject, and is a technique for obtaining the fine surface shape of the subject from the number of the contour lines.

Further, the interval of contour line interference fringes obtained by the above interferometer is half the wavelength of the light wave used,
The He-Ne laser light source usually used has a very small size of 0.3164 μm.

The interferometer is capable of measuring fine irregularities, but since the measurement is a comparative measurement with a standard called a reference plate, the object and the reference plate are highly accurate in the order of microns with respect to the optical axis. Therefore, the parallel adjustment must be made in advance, that is, the object and the reference plate must be parallel to each other with high accuracy in order to generate interference fringes, and the mechanism for obtaining this parallelism is It is provided.

For example, as shown in FIG. 5, the laser light from the light source 41 is condensed by the diverger lens 42 and becomes a point light source, and then the spread light is converted into parallel light by the collimator lens 43 and the reference plate 44. , Is reflected by the subject 45, travels in the reverse direction along the incident optical path, is focused by the collimator lens 43, is focused on the original point light source, and is reflected by the first half mirror 46, and is focused by the imaging lens 47 on the TV camera. An image is formed on 48 and interference fringes are observed. On the other hand, the light reflected by the reference plate 44 and the subject 45 is condensed on O ₁ by the second half mirror 49, and this is imaged again on O ₂ of the screen 51 by the imaging lens 50. The image formation point on the screen 51 is the reference plate 44 and the subject 45.
When tilted, they move, and when they are parallel, they form an image at the same point.

Based on the above characteristics, the angle of the subject 45 is adjusted so that the point image reflected from the subject 45 and formed on the screen 51 overlaps the spot formed by the light reflected from the reference plate 44. A technique is known in which the angle is adjusted by operating the angle adjusting mechanism 52 to obtain parallelism between the two.

[0008]

However, the angle adjustment of the measurement surface of the subject in the above-described conventional interferometer or the like is performed by the alignment optical system utilizing the measurement optical system of the interferometer. Therefore, the optical system of the interferometer becomes large, the optical system becomes complicated as a whole, and it becomes difficult to ensure its accuracy.In addition, the range of alignment adjustment is expanded and the work becomes complicated. I have a problem.

That is, in the optical system of the interferometer provided with an alignment optical system, a method of constantly performing alignment by branching a part of light from the optical system as the interferometer, and switching to the alignment optical system at the time of alignment. There is a method, but in any case, it is an optical system which is not necessary when interference fringes are observed on a CRT, for example. That is, if the interference fringes are visible, the alignment can be performed by increasing or decreasing the interference fringes, and the volume of the interferometer may be significantly increased by attaching the alignment optical system to the interferometer.

In view of the above circumstances, the present invention provides an alignment device for a sample table, which can easily perform alignment of the measurement surface of a subject placed on the sample table separately from the optical system for measurement. The purpose is to do.

[0011]

In order to achieve the above object, an alignment apparatus for a sample stage according to the present invention comprises a light source that emits light obliquely onto a measurement surface of a subject placed on the sample stage.
The light receiving unit includes an emitting lens for converting the light of the light source into parallel rays, an image forming lens for forming an image of the light reflected on the surface of the subject, and a light receiving unit for detecting the image forming position of the reflected light. The alignment mechanism is adjusted so that the incident light is at the reference position.

[0012]

In the alignment apparatus as described above, the light from the light source is obliquely incident on the surface of the subject on the sample stage as parallel light through the emission lens, and the light obliquely reflected on the opposite side is reflected by the imaging lens. An image is formed on the light receiving means, and when the image forming position is at a preset reference position due to the arrangement of the alignment optical system, the measurement surface of the subject is set to be perpendicular to the measurement optical axis, for example. If the tilt angle of the sample stage is adjusted by the alignment mechanism, the image forming position moves. By adjusting the angle of the sample stage so that the image forming position coincides with the reference position. The alignment is performed so that the measurement surface of the subject has a predetermined angle.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of a sample table equipped with an alignment apparatus of one embodiment. The sample table supports a subject of an interferometer typified by, for example, a Fizeau interferometer, and an auto alignment device is installed.

The sample table 10 is provided with a flat plate-shaped table 15 on which the subject 11 is mounted. The table 15 is installed on a table 17 via an alignment mechanism 20 so that the tilt angle can be adjusted. There is.
As shown in the layout diagram of FIG. 2, this alignment mechanism 20 has a spherical joint 18 provided on the bottom surface of one corner of the stage 15, and in any direction with respect to the platform 17 with the joint 18 as a fulcrum. Is also pivotally supported so that it can be tilted, and linear actuators 21 and 22 are installed at the other two corners that intersect at right angles. The linear actuators 21 and 22 are such that the projecting amounts of the telescopic rods 21a and 22a are adjusted according to an input signal.
The tip end of 22a is engaged with the bottom surface of the stage 15, and the tilt angle of the stage 15 in the X and Y directions can be adjusted by the expansion and contraction operation. The bottom portion of the stage 15 that engages with the tips of the telescopic rods 21a, 22a is the spherical joint 18
It is formed in the shape of a V groove extending in the direction of, and is configured to correspond to the movement of the engagement point according to the change of the inclination angle of the stage 15.

On the other hand, columns 12 and 13 are provided upright on a platform 17 on both sides of the above-described object platform 15, and an alignment optical system 30 is arranged on the columns 12 and 13. This alignment optics 30
Is a light source 24 and an emission lens 25 arranged on one of the light-projecting-side columns 12 (right side in the drawing), and an imaging lens 26 and a light-receiving lens disposed on the other light-receiving side column 13 (left side in the drawing). Means 27 (position sensor).

The light source 24 is provided by utilizing a directional LED or the like, and an emission lens 25 arranged in front of the light source 24.
Is to convert the light emitted from the light source 24 into parallel light, and irradiate the parallel light obliquely onto the measurement surface 11a of the subject 11 on the object table 15. On the other hand, the imaging lens 26 installed at the incident position of the reflected light from the measurement surface 11a of the subject 11 receives this reflected light at the light receiving means 27 behind it.
It forms an image on top. Further, the light receiving means 27 is composed of, for example, a CCD, and detects the position of the spot light made incident by the imaging lens 26.

The relative positional relationship of the optical system 30 is such that when the measurement surface 11a of the subject 11 on the stage 15 is orthogonal to the measurement optical axis from above, the reference position of the light receiving means 27 is set. The position where the spot light is incident on the light receiving means 27 changes in response to the change in the angle of the measurement surface 11a. It should be noted that even if there is some displacement in the thickness direction of the measurement surface 11a, the image formation position does not change, and adjustment for this variation is unnecessary.

Further, the detection signal of the light receiving means 27 is stored in the frame memory 33 in the control means 32, and the signal of the frame memory 33 is inputted to the arithmetic processing unit 34 (CPU) and the spot light P (see FIG. 3). Based on the position, the driving signal is output to both the linear actuators 21 and 22 via the driver 35, and the alignment is automatically adjusted so that the spot light P overlaps the reference position R.

FIG. 3 shows an example of the detection position of the spot light P by the frame memory 33. In the case where the spot light P is incident on the coordinates (x, y) with the reference position R as the origin of the coordinates. FIG. 4 shows a flowchart of the arithmetic processing by the arithmetic processing unit 34.

According to FIG. 4, in response to the start of alignment, an image is read from the frame memory 33 in step S1, a reference position R, that is, a target position is read in step S2, and this point is set as the origin, and the origin of this coordinate is set. Based on the above, the position of the spot light P is detected in step S3. Then, in step S4, the x and y values of the position coordinate of the spot light P become smaller, that is, the reference position R.
Linear actuators 21,22 in the direction of approaching the (origin)
Driving amount (step amount) is calculated, and a driving signal is output via the driver 35.

The incident position of the spot light P changes as the linear actuators 21 and 22 are driven. In step S5, it is determined whether or not the coordinates x and y of the spot light P have become 0, and NO. When the judgments do not match, the above steps are repeated to perform feedback control of the linear actuators 21 and 22, and when the YES judgment is made, the alignment adjustment is completed.In this state, the measurement surface 11a of the subject 11 on the stage 15 Is the target angle.

In the above embodiment, the CCD (imaging lens
The spot light is detected by the light receiving means 27 by the TV camera including 26), but the shift between the reference position R and the spot light P is detected by using the light receiving means by another photo detector, a four-divided diode, or the like. You may do so. That is, for example, in the four-divided diode, the light-receiving surface is divided into four vertically and horizontally, and the center position thereof is used as a reference position to adjust the inclination of the alignment mechanism in the X direction according to the difference in the amount of light received in the upper and lower portions, and The automatic alignment can be realized by outputting a drive signal to the actuators 21 and 22 via a comparison circuit so as to adjust the inclination of the alignment mechanism in the Y direction according to the difference in the amount of received light.

Further, the alignment mechanism 20 for adjusting the tilt angle of the stage 15 can also be appropriately designed and changed to a known angle adjusting mechanism in addition to the configuration of the above embodiment. Further, in the above embodiment, the alignment is provided automatically based on the position detection of the spot light by the light receiving means 27, but the light receiving means by the screen is installed at the position of the image forming surface of the spot light. The alignment may be adjusted by the operator by directly observing the spot light or while observing the image of the CCD.

[0024]

In the alignment apparatus for the sample table as described above, in adjusting the measurement surface of the mounted object to a predetermined angle by the alignment mechanism, the light source and the emission lens are used to obliquely light the surface of the object. The alignment mechanism is adjusted so that the reflected light is imaged on the light receiving means by the imaging lens and the imaging position becomes the reference position, which facilitates alignment and automation. Easy to implement. Furthermore, it is not necessary to install an alignment optical system in the internal optical system of the device main body such as an interferometer, and it is possible to make it compact, and it has an effect that the alignment range can be set according to its accuracy. ..

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a sample table equipped with an alignment device according to an embodiment of the present invention.

[Fig. 2] Bottom view of the sample table

FIG. 3 is an explanatory diagram showing an example of an image detected by a light receiving unit.

FIG. 4 is a flow chart for explaining the processing of the control means based on FIG.

FIG. 5 is a schematic configuration diagram of an interferometer including a conventional alignment device.

[Explanation of symbols]

 10 Sample stage 11 Object 11a Measuring surface 15 Mounting stage 20 Alignment mechanism 21,22 Actuator 24 Light source 25 Emitting lens 26 Imaging lens 27 Light receiving means 30 Alignment optical system 32 Control means

Claims (1)

[Claims] 1. An alignment device for adjusting a measurement surface of a subject placed on the sample stage to a predetermined angle in a sample stage provided with an alignment mechanism capable of adjusting an inclination angle. A light source that emits light obliquely to the subject surface, an emission lens that converts the light from the light source into parallel rays, an imaging lens that forms an image of the light reflected on the subject surface, and a reflected light An alignment apparatus for a sample stage, comprising: a light receiving unit that detects an image formation position, and the alignment mechanism is adjusted so that the light incident on the light receiving unit becomes a reference position.