JPH07332954A - Method and apparatus for measuring displacement and inclination - Google Patents

Abstract

PURPOSE:To measure the displacement and inclination of a surface to be measured quickly at the same time without requirement for a complicated constitution. CONSTITUTION:Two light beams from the different directions of light sources 2a and 2b irradiate the measuring point on a fine moving stage 1. The light beams reflected from the fine moving stage 1 in this way are detected by two-dimensional optical sensors 3a and 3b, respectively. The amount of the displacement and the amount of the inclination of the fine moving stage 1 can be measured by an operating part 4 at the same time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a displacement inclination measuring method and apparatus for simultaneously measuring displacement and inclination of a moving stage such as a stepper.

[0002]

2. Description of the Related Art In an optical apparatus such as a reduction projection exposure apparatus (stepper), it is important to know the displacement and inclination states of a wafer stage on which a substrate is placed and a minute position control is performed. . As a method for simultaneously measuring the displacement and the inclination of the surface to be measured in real time, an interferometer has been conventionally used.
A measurement method is known in which a capacitance displacement meter, a differential transformer, and the like are arranged in multiple axes with respect to a moving surface of a measurement target. Another method for measuring the inclination is an autocollimator. There is also a measuring method using a divided photodiode capable of measuring displacement or inclination.

[0003]

The conventional interferometer has the advantage that it has a large stroke, but it requires expensive components such as optical components used for each axis and electric systems such as counters. Further, in the capacitance displacement meter and the differential transformer, it is necessary to bring the sensor section close to the section to be measured, and the electric system must perform complex detection such as complex detection. Further, although the autocollimator and the conventional split photodiode can be easily configured at low cost, there is a problem that displacement and inclination cannot be separately detected simultaneously.

The present invention has been made in order to solve the above problems, and it is possible to quickly measure the displacement and inclination of the surface to be measured simultaneously without requiring a complicated structure. The purpose is to do.

[0005]

According to a displacement inclination measuring method of the present invention, first, a measurement surface obtained by irradiating a predetermined position on the measurement surface with a first light from a predetermined angle is measured. The reflected first reflected light is received by the first light receiving surface arranged at the first distance from the predetermined position, and the second light is emitted at the predetermined position from the predetermined angle with respect to the measurement surface. The second reflected light reflected by the measurement surface obtained by the irradiation is received by the second light receiving surface arranged at the second distance from the predetermined position. Then, the first and second distances, the locus of the optical path to the predetermined position of the first light projected on the measurement surface, and the locus of the optical path of the second light projected to the predetermined position on the measurement surface. The angle of projection of the measurement surface is determined by the projection angle, the moving amount of the light receiving position of the first reflected light on the first light receiving surface, and the moving amount of the light receiving position of the second reflected light on the second light receiving surface. The feature is that the amount of displacement in the line direction is calculated at the same time.

Further, according to the displacement inclination measuring device of the present invention, the displacement inclination measuring device is located at a predetermined position on the measuring surface and is at a predetermined angle with respect to the measuring surface.
The first light source for irradiating the first light source and the second light source at a predetermined position from a different direction from the first light source at a predetermined angle with respect to the measurement surface.
Second light source for irradiating the second light source, a first light sensor for receiving the reflected light from the measurement surface by the first light source, and outputting a first light receiving position signal corresponding to the light receiving position, A second optical sensor for receiving the reflected light from the measurement surface by the light source and outputting a second light receiving position signal corresponding to the light receiving position. Then, the inclination of the measurement surface is determined by the change amounts of the first and second light receiving position signals and the respective projection angles formed when the first light line and the second light line are projected on the measurement surface. And an arithmetic processing means for simultaneously calculating the amount and the displacement amount in the normal direction.

[0007]

When the measurement surface is tilted or moved up and down, this change amount changes the optical paths of the first and second reflected lights. Then, the amount of inclination of the measurement surface and the amount of displacement in the normal direction are calculated from the change in the optical path.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. Embodiment 1 FIG. 1 is a configuration diagram showing a configuration of a displacement inclination measuring device according to a first embodiment of the present invention, in which 1 is a fine movement stage for performing minute position control, 2a and 2b are light sources, 3a, Reference numeral 3b is a two-dimensional optical sensor that receives light from the light sources 2a and 2b reflected by the fine movement stage 1, and reference numeral 4 is a two-dimensional optical sensor 3.
It is an arithmetic processing unit for calculating the displacement amount and the inclination amount of the fine movement stage 1 from the signals obtained from a and 3b. The two-dimensional photosensors 3a and 3b output a signal corresponding to the position of the incident light on the light receiving surface, and include, for example, a CCD image sensor and a four-division diode.

At the measurement point on the fine movement stage 1, the light source 2
Two lights from different directions a and 2b are emitted. At this time, one light source may be divided into two, or two light sources may be used. Each of the light reflected from the fine movement stage 1 is detected by the two two-dimensional optical sensors 3a and 3b,
By performing the above calculation by the calculation processing unit 4, the displacement amount and the inclination amount of the fine movement stage 1 can be simultaneously measured. In addition, here
Two-dimensional optical sensors 3a, 3 from the measurement point on the fine movement stage 1
Both distances to b are L.

The two-dimensional photosensors 3a and 3b are arranged so as to be able to measure changes in the direction of the line of intersection with the incident surface of the light beam and the direction orthogonal to the line of intersection. This measurement includes the incident angle (θ) of the light ray on the measurement point, the distance from the measurement point to the light receiving surface of the two-dimensional optical sensor 3a, 3b (L), the angle between the two light rays on the xy plane (Φ), and the reflection. The sensitivity and the dynamic range change depending on the spot diameter on the light receiving surface of the two-dimensional optical sensor 3a, 3b. Further, as the reflection surface of the fine movement stage 1 is optically flat, the spot shape is less deformed and the reflection intensity is increased, so that the sensitivity is improved. Therefore, even if the fine movement stage 1 is a rough surface, the reflection surface should be a mirror surface. Sensitivity increases by attaching.

The calculation of the displacement amount and the inclination amount of the fine movement stage 1 by the displacement inclination measuring method of the present invention will be described in detail below. Here, in order to simplify the calculation formula,
As shown in FIG. 1, the coordinates are set so that the optical axis from the light source 2a has the yz plane as the incident plane, and the angle between the optical axis from the light source 2a and the optical axis from the light source 2b in the xy plane is Φ. And Further, the angle between the two light rays and the xy plane is θ.
That is, the light beams from the light sources 2a and 2b and the minute stage 1
The angle formed by and is θ.

Here, consider a case where the minute stage 1 is slightly displaced by δz in the z-axis direction and is minutely rotated (tilted) by δθ ₁ about the x-axis and δθ ₂ about the y-axis. The displacement / tilt amount of the micro stage 1 is very small, and this change can be regarded as linear within the measurement range.
The movement amounts S ₁ and S ₂ on the three-dimensional photosensors 3a and 3b are represented by a two-dimensional vector and are represented by the following equations 1 and 2.

S ₁ (ξ ₁ , η ₁ ) = {2Lδθ ₂ , Aδz-2Lδθ ₁ } (1)

S ₂ (ξ ₂ , η ₂ ) = {2Lδθ ₂ (sinΦ + cosΦ), Aδz + 2Lθ ₁ (sinΦ−cosΦ)} (2)

In the above equation, S ₁ is the coordinates of the spot formed on the light receiving surface of the two-dimensional optical sensor 3a by the light having the yz plane emitted from the light source 2a as the incident surface, and its coordinate system is (ξ ₁ , η ₁ )
Indicated by. Further, S ₂ is the light from the other light source 2b,
The coordinates of a spot formed on the light receiving surface of the two-dimensional optical sensor 3b are represented by (ξ ₂ , η ₂ ). A is a constant determined by the incident angle of light on the measurement surface, and ξ is parallel to the incident surface and η is perpendicular to the incident surface.

Here, B (Φ) = (sinΦ + cosΦ), C
By defining (Φ) = (sinΦ−cosΦ), the above expression 2 can be organized as shown in the following expression 3.

S ₂ (ξ ₂ , η ₂ ) = {2LB (Φ) δθ ₂ , Aδz + 2LC (Φ) θ ₁ } (3)

Since L and Φ can be measured in advance and are known, it is possible to separately obtain the respective variations by solving the above equations 1 and 3 (equation 2), and the stage displacement amount (δz). , The inclination amounts (Δθ ₁ , Δθ ₂ ) are as follows.

Δθ ₁ = (η ₂ −η ₁ ) / (2LC (Φ) + 2L) (4)

Δθ ₂ = ξ ₁ / (2L) (5)

Δz = η ₁ + 2Lδθ ₁ (6)

Two two-dimensional optical sensors 3 are provided for the convenience of design.
Even if it is not possible to match θ and L, which are the arrangements of a and 3b, respectively, for example, for either δθ or δz, the amplifier gain is set so that the differential output per unit beam deflection of both light receiving surfaces becomes equal. Adjust it.
As a result, the displacement amount and the inclination amount of the fine movement stage 1 can be simultaneously calculated by a linear calculation of post-processing of the signals obtained from the two two-dimensional optical sensors 3a and 3b.

Example 2. In the above embodiment, 2
Although the two-dimensional optical sensor is used, the present invention is not limited to this. It is also possible to use four one-dimensional photosensors that output a signal corresponding to the position of the incident light in the one-dimensional direction. As shown in FIG. 2, one light 22 reflected by the measurement surface 21 is divided into two by a beam splitter 23 or the like, and one-dimensional sensors 24a, 24b are arranged so as to receive the two lights 22a, 22b. And the light 2 split into two
One-dimensional optical sensor 24a, 24b for receiving 2a, 22b
Need only be arranged so that their light receiving portions are orthogonal to each other, and the same effect as that of the first embodiment is obtained.

[0024]

As described above, according to the present invention, the first and second lights when the measuring surface is inclined or moved up and down by irradiating the measuring surface with the first and second lights from different directions. The amount of inclination of the measurement surface and the amount of displacement in the normal direction were calculated by changing the optical path of the reflected light. Therefore, there is an effect that the displacement and the inclination of the measurement target surface can be simultaneously measured quickly without requiring a complicated configuration.

For example, the moving stage of the stepper is displaced with respect to the image plane formed by the reduction projection lens system.
If there is an inclination, it causes a focus error during exposure. However, according to the present invention, since the in-plane movement is not detected with respect to the parallel movement due to the stepping operation of the moving stage which is the measurement surface, the focus position at the measurement point when the moving stage moves in parallel and It is possible to know the error characteristics such as inclination.

[Brief description of drawings]

FIG. 1 is a perspective view showing a configuration of a displacement inclination measuring device according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing a second embodiment of the present invention.

[Explanation of symbols]

1 ... Fine movement stage, 2a, 2b ... Light source, 3a, 3b ... 2
Dimensional optical sensor, 4 ... Calculation processing unit.

Claims (2)

[Claims] 1. A displacement inclination measuring method for measuring an amount of displacement of a flat measuring surface in a direction of a normal line and an amount of inclination of the measuring surface, wherein the measuring method is provided at a predetermined position of the measuring surface with respect to the measuring surface. The first reflected light reflected by the measurement surface obtained by irradiating the first light from the angle of is received by the first light receiving surface arranged at the first distance from the predetermined position, The second reflected light reflected by the measurement surface obtained by irradiating the measurement surface with the second light from the predetermined angle at a position is arranged at a second distance from the predetermined position. Light received by two light receiving surfaces, the first and second distances, the trajectory of the optical path of the first light to the predetermined position projected onto the measurement surface, and the predetermined position of the second light A projection angle formed by a trajectory obtained by projecting an optical path up to the measurement surface, the first opposite surface of the first light receiving surface. The inclination amount of the measurement surface and the displacement amount in the normal direction are calculated at the same time based on the movement amount of the light receiving position of the light and the movement amount of the light receiving position of the second reflected light of the second light receiving surface. Displacement tilt measurement method. 2. A displacement tilt measuring device for measuring a displacement amount of a flat measurement surface in a normal direction and a tilt amount of the measurement surface, wherein the displacement tilt measuring device is arranged at a predetermined position on the measurement surface with respect to the measurement surface. A first light source for irradiating the first light from a predetermined angle, and a second light source for irradiating the measurement surface with a second light at a predetermined angle from a direction different from that of the first light source at the predetermined position. Light source, a first optical sensor that receives reflected light from the measurement surface by the first light source, and outputs a first light receiving position signal corresponding to the light receiving position, and the second light source A second optical sensor for receiving the reflected light from the measurement surface and outputting a second light receiving position signal corresponding to the light receiving position; a change amount of the first and second light receiving position signals; Angle of projection when the line of light and the line of second light are projected onto the measurement surface. Displacement gradient measuring device is characterized in that an arithmetic processing means for calculating the inclination amount and the normal direction of displacement of the measurement surface simultaneously by.