JPH10260009A - Coordinate measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coordinate measuring device which can avoid influence from shape of a moving mirror reliably. SOLUTION: The device is equipped with shape measuring interferometers 13, 14 which detect the relative position between two points by irradiating two points on a moving mirror 2X with laser beam, and rotational angle detecting interferometers 21, 22 which detect the rotational angle of a stage 1 based on the relative position between two points when the laser beam is irradiated to the two points on the stage 1. The shape of the moving mirror 2X is determined by combining plural relative position data which are detected by the shape measuring interferometer 13, 14 when the stage 1 is moved along the moving mirror 2X, and by correcting relative position data based on rotational angle data which are detected by the rotational angle interferometers 21, 22. Coordinates on measuring point are corrected based on the determined shape of the moving mirror 2X.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coordinate measuring device for measuring the coordinates of a measurement point on an object to be measured via a position of a stage for moving the object.

[0002]

2. Description of the Related Art There is known a coordinate measuring apparatus in which a plane movable mirror is mounted on a stage on which an object to be measured is mounted, and the position of the stage is measured by irradiating the movable mirror with laser light. As shown in FIG. 10, two movable mirrors 2X
And the mirror surface of the movable mirror 2Y is mounted orthogonally to the X axis and the Y axis, respectively, and a laser beam in the X-axis direction from the interferometer 40X is applied to the movable mirror 2X, and the interferometer 40
The XY coordinates of the stage 101 can be measured by irradiating and reflecting the laser beams from Y to the Y-axis direction and measuring the reciprocating optical path length of the laser light. The stage 101 is moved so that the measurement point on the object is positioned at a predetermined position.
By moving the stage 101 and measuring the position of the stage 101 as described above, the coordinates of the measurement point can be measured via the position of the stage 101.

[0003]

However, when the flatness (straightness) accuracy of the movable mirrors 2X and 2Y attached to the stage 101 of the coordinate measuring device is poor, the difference in the optical path difference of the laser light depends on the irradiation position of the laser light. Therefore, an error is mixed in the coordinate measurement data. If the shape of the ideal lattice-like mask pattern 102 is measured when the flatness of the movable mirrors 2X and 2Y is poor, as shown in FIG.
Distortion inverted from 2Y distortion appears in the measurement data. Therefore, such a movable mirror 2 is used in the coordinate measuring device.
Unless the X and 2Y distortions are corrected, the true shape (coordinates) cannot be obtained.

FIG. 1 shows a method for correcting the distortion of a moving mirror.
As shown in FIG. 1, a method is conceivable in which the same mask pattern 103 is shape-measured at 0 ° and 180 ° rotation postures, and a curved component of the pattern is removed from two coordinate measurement results. However, in this method, only the line-symmetric components (even-order components) of the distortion of the movable mirrors 2X and 2Y can be measured (FIG. 11).
(A)), a point-symmetric distortion (odd-order component) cannot be measured. For example, as shown in FIG. 11B, even if the distortion of the S-shape, which is a point-symmetric shape, is rotated by 180 degrees, the S-shape has the same shape, so that no difference can be measured at all and the movable mirror 2X, 2Y distortion cannot be corrected.

An object of the present invention is to provide a coordinate measuring device capable of reliably eliminating the influence of the shape of a movable mirror.

[0006]

FIG. 1 shows an embodiment of the present invention.
Explaining with reference to FIG. 8, the invention according to claim 1 includes a stage 1 for moving an object 5 and a stage 1.
A movable mirror 2X attached to the mirror, an interferometer 41X for coordinate measurement for measuring the position of the stage 1 by irradiating the movable mirror 2X with a laser beam, and a measurement point on the DUT 5 are detected. The present invention is applied to a coordinate measuring device that measures the position of the stage 1 when the detector 3 detects a measurement point by the coordinate measuring interferometer 41X to measure the coordinates of the measurement point. And moving mirror 2X
Shape measuring interferometers 13 and 14 for detecting the relative positional relationship between the two points by irradiating the two points with a laser beam;
Rotation angle detection interferometers 21 and 22 for detecting the rotation angle of stage 1 based on the relative positional relationship between the two points of another mirror 2Y provided on stage 1 when the two points are irradiated with a laser beam.
When the stage 1 is moved along the movable mirror 2X, a plurality of pieces of relative positional relationship data detected by the shape measuring interferometers 13 and 14 are joined together, and detected by the rotation angle detecting interferometers 21 and 22. The shape of the moving mirror 2X is measured by correcting the relative positional relationship data based on the measured rotation angle data, and the coordinates of the measurement point are corrected based on the measured shape of the moving mirror 2X. According to a second aspect of the present invention, in the coordinate measuring apparatus according to the first aspect, a second movable mirror 2Y provided orthogonal to the movable mirror 2X.
And a second coordinate measuring interferometer 41Y for irradiating a laser beam toward the second movable mirror 2Y, and the stage 1 is moved in the normal direction of the second movable mirror 2Y when measuring the shape of the movable mirror 2X. And the rotation angle detecting interferometer 2
Numerals 1 and 22 irradiate a laser beam toward the second movable mirror 2Y. The third aspect of the present invention is the first aspect.
Or the parallel measuring device according to (2), further comprising a parallel flat plate 30 (31) inserted into the optical axis of the laser beam emitted from the shape measuring interferometers 13 and 14;
By tilting 1) with respect to the optical axis, the laser beam is shifted laterally. According to a fourth aspect of the present invention, there is provided the coordinate measuring apparatus according to any one of the first to third aspects, wherein the shape measuring interferometer 13 and
The attitude of the stage 1 is measured using the interferometers 14 or 22 for detecting the rotation angle, and the coordinates of the measurement points are corrected based on the measured attitude of the stage 1.

In the section of the means for solving the above-mentioned problems, which explains the configuration of the present invention, the drawings of the embodiments of the present invention are used to make the present invention easy to understand. However, the present invention is not limited to this.

[0008]

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

In FIG. 1, reference numeral 1 denotes an XY stage provided so as to be movable in an XY plane; 2X, a movable mirror attached to the XY stage 1 so that a normal line of the mirror surface faces the X-axis direction;
Reference numeral 2Y denotes a movable mirror attached to the XY stage 1 so that the normal line of the mirror surface is directed to the Y-axis direction. Reference numeral 3 denotes an objective lens for detecting a pattern of the DUT 5 mounted on the XY stage 1.
Is an optical system for measuring the X coordinate of the XY stage 1;
Y is an optical system for measuring the Y coordinate of the XY stage 1.

As shown in FIG. 1, a laser beam 6 emitted from a light source (not shown) is branched and guided to an optical system 4X and an optical system 4Y. One of the two pairs of laser beams emitted from the optical system 4X is the movable mirror 2
X, the other laser beam pair is irradiated on a fixed mirror 7X attached to the objective lens such that the normal of the mirror surface is directed to the X-axis direction, and each laser beam pair is reflected by the movable mirror 2X and the fixed mirror 7X. Is done. The optical system 4X is an interferometer 4
1X (FIG. 3), and the X coordinate of the stage 1 is measured based on the optical path length difference between the optical path to the movable mirror 2X and the optical path to the fixed mirror 7X.

[0011] Of the two pairs of laser beams emitted from the optical system 4Y, one of the laser beam pairs is directed to the movable mirror 2Y, and the other laser beam pair is directed to the objective lens 3 so that the normal of the mirror surface faces the Y-axis direction. Are respectively radiated to the fixed mirror 7Y attached to the moving mirror 2Y and reflected by the movable mirror 2Y and the fixed mirror 7Y. The optical system 4Y is connected to an interferometer 41Y (FIG. 3), and the Y coordinate of the stage 1 is measured based on the difference between the optical path to the movable mirror 2Y and the optical path to the fixed mirror 7Y.

The object 5 placed on the XY stage 1 is captured by the objective lens 3, and the measurement point of the object 5 is set at a predetermined position (for example, at the center of the field of view of the objective lens 3).
By measuring the coordinates of the XY stage 1 at this time by the above-described method, the XY coordinates of the measurement point can be obtained.
However, as will be described later, in the coordinate measuring device according to the present embodiment, the coordinates are corrected based on the mirror surface shapes of the moving mirror 2X and the moving mirror 2Y.

As shown in FIG. 2, the coordinate measuring apparatus according to the present embodiment has an optical system 4X, an interferometer 41X, an optical system 4Y and an interferometer 41Y for measuring the distance to the movable mirror 2X separately from the interferometer 41Y. A total of 11 to 14 and interferometers 21 to 24 for measuring a distance to the movable mirror 2Y are provided around the XY stage 1. Interferometers 11 to 14 and 21 to 2
Reference numeral 4 denotes a so-called heterodyne laser interferometer system which is capable of measuring the distance to the movable mirror 2X and the movable mirror 2Y at four points.

Interferometers 11 to 14 and interferometers 21 to 24
Is for measuring the mirror surface shapes of the movable mirror 2X and the movable mirror 2Y. In the coordinate measuring device of the present embodiment, data of coordinate measurement is based on the measured mirror surface shapes of the movable mirror 2X and the movable mirror 2Y. Correction is performed.

In FIG. 3, 1X denotes XY stage 1
A driving device that moves in the axial direction, 1Y moves the XY stage 1 to Y
A driving device that moves in the axial direction, C is a control device, and 8 is a storage device. The coordinate values of the XY stage 1 obtained by the interferometers 41X and 41Y and the interferometers 11 to 14,
The measurement data of 21 to 24 is input to the control device C, and the drive device 1X and the drive device 1Y are controlled by the control device C. The control device C calculates the mirror surface shapes of the movable mirror 2X and the movable mirror 2Y, stores the shapes in the storage device 8, and performs an operation of correcting the coordinates of the XY stage 1 based on the shape data stored in the storage device 8. Do.

Next, the operation for measuring the mirror shapes of the movable mirror 2X and the movable mirror 2Y will be described.

FIG. 4 shows a four-axis interferometer arrangement for measuring the mirror surface shape of the movable mirror 2X. When measuring the mirror surface shape of the movable mirror 2X, the XY stage 1 is moved in the Y direction at a constant pitch, and the coordinate values measured by the interferometers 13 and 14 at each stop position are taken. .

The moving mirror 2 is integrated by integrating the coordinate values.
Although the mirror surface shape f (y) of X can be obtained, the rotation error component e _P (y) and the translation error e _X (y) of the XY stage 1 always occur with the movement of the XY stage 1 in the Y direction. . Unless these errors are eliminated, the mirror surface shape cannot be accurately measured. However, the apparatus of the present embodiment eliminates the errors by using the interferometer 21 and the interferometer 22. Strictly, there is a translation error in the Z direction, but when measuring the mirror surface shape of the movable mirror 2X, the influence is small, and therefore, the description is ignored here.

The measured values of the interferometer 13, the interferometer 14, the interferometer 21, and the interferometer 22 are respectively m _x1 (y),
_{Let mx2} (y), _my1 (y) and _my2 (y).
As shown in FIG. 5, the Y coordinate of the measurement position at each stop position is y, and the distance from y to the optical axis of the interferometer 13 is d _A , y
The distance to the optical axis of the interferometer 14 When d _B from the measured value m _x2 of the interferometer 13 the measurement value m _x1 (y) and the interferometer 14 (y) are as follows.

[Number 1] _{m x1 (y) = f (} y-d A) + e X (y) -d A · e P (y) ··· formula (1)

[Number 2] _{m x2 (y) = f (} y + d B) + e X (y) + d B · e P (y) ··· (2)

When the equation (1) is subtracted from the equation (2), a translation error e _X (y) is obtained, and the following equation is obtained.

[Number 3] _{m x2 (y) -m x1 (} y) = f (y + d B) -f (y-d A) + (d A + d B) · e P (y) ··· (3)

If the distance between the optical axis of the interferometer 13 and the optical axis of the interferometer 14 is L (= d _A + d _B ), and the distance between the optical axis of the interferometer 21 and the optical axis of the interferometer 22 is D, Rotation error component e _P
(Y) is obtained from the difference between the measured value _my1 (y) of the interferometer 21 and the measured value _my2 (y) of the interferometer 22, and is given by the following equation.

E _P (y) = − arctan {(my ₁ (y) _{−my 2} (y)) / D} (4)

Therefore, the larger D is, the more accurately the rotation error component e _P (y) can be obtained. By substituting equation (4) into equation (3),

Equation 5] _{m x2 (y) -m x1 (} y) = f (y + d B) -f (y-d A) -L · arctan {(m y1 (y) -m y2 (y)) / D} ... Formula (5) is obtained. Since the obtained equation (5) is the slope of a straight line connecting the two measurement points by the interferometer 13 and the interferometer 14,
By integrating this, a value proportional to f (y) multiplied by the slope coefficient is obtained. By multiplying this value by the slope coefficient and removing the offset, the mirror surface shape of the movable mirror 2X is obtained.

When the XY stage 1 is 500 mm square, the distance L between the optical axes of the interferometers 13 and 14 is, for example, 3 m.
It is set to about m to 15 mm. Further, if the optical axis interval D between the interferometer 21 and the interferometer 22 is determined so that the optical axes are located at both ends of the movable mirror 2Y, it is advantageous in terms of measurement accuracy.

In general, according to the sampling theorem in electrical processing, the optical axis interval between the interferometers 13 and 14 is L
In the case of (1), there is a disadvantage that the periodic undulation of a shape having a length of L / 2 or more cannot be measured. As long as the optical axis interval L is a finite value, there is a region of such a periodic undulation that cannot be measured. For example, as shown in FIG. 6, when there is a periodic waviness having the same period as the optical axis interval L, the optical axis lengths of the interferometers 13 and 14 change at the same timing even if the XY stage 1 moves. Therefore, it is clear that the periodic waviness cannot be measured.

In order to cope with such a drawback, in the present embodiment, the parallel plate 30 as shown in FIG.
To the optical axis of the interferometer 30 by changing the rotation angle of the parallel plate 30 to an arbitrary distance Δ in the Y-axis direction.
It is possible to move by d. Thereby, while acquiring the measured values before and after the change when the optical axis interval L is changed in the direction of narrowing, the undulation in a short cycle can be measured by integrating the measured values. However, it is necessary that the parallel plate 30 has a uniform or isotropic refractive index and has no thickness unevenness or a known thickness unevenness.

As shown in FIG. 9, when the thickness of the parallel plate 30 is d and the parallel plate 30 is inclined by an angle i ₁ with respect to the optical axis, the shift width Δd of the optical axis becomes:

Δd = {d · sin (i ₁ −i ₂ )} / cos ₂ (6) Since Δd is calculated based on the rotation angle of the parallel plate 30, Δd can be calculated.

In measuring the mirror surface shape of the movable mirror 2X,
To compensate for the roughness of the moving pitch of the XY stage 1, FIG.
As shown in (1), a parallel flat plate 31 may be inserted so as to hang on both the optical axis of the interferometer 13 and the optical axis of the interferometer 14.
In this case, by changing the rotation angle of the parallel plate 31, the two optical axes can be moved by an arbitrary distance Δd in the Y-axis direction without changing the optical axis interval, so that the moving pitch of the XY stage 1 is coarse. Even when a small amount of movement is impossible, the measurement position y can be finely (continuously) shifted.

The case where the mirror surface shape of the movable mirror 2X is measured has been described above. When the mirror surface shape of the movable mirror 2Y is measured, the interferometers 23 and 24 are moved while moving the XY stage in the X-axis direction. What is necessary is just to integrate the optical path length difference measured by. In this case, the rotation error component can be detected by the interferometer 11 and the interferometer 12.

The moving mirror 2X measured by the above method
The mirror shape of the movable mirror 2Y is stored in the storage device 8, and the coordinate value is corrected based on the measured value stored at the time of measuring the coordinates of the DUT 5. Thereby, the moving mirror 2X
In addition, since the influence of the mirror surface shape of the movable mirror 2Y can be eliminated, accurate coordinate measurement can be performed.

When performing coordinate measurement, for example, the interferometers 11 to
14. The attitude of the XY stage 1 such as the rotation angle in the XY plane may be measured using any two or more of the interferometers 21 to 24. XY measured
By correcting the measurement value of the coordinate measurement using the attitude data of the stage 1, the accuracy of the coordinate measurement can be further improved. For example, while the XY stage 1 is driven for coordinate measurement, the rotation angle of the XY stage 1 in the XY plane can be determined by detecting the optical path length difference between the interferometer 11 and the interferometer 14, thereby obtaining the coordinate measurement value. Can be corrected.

[0031]

According to the first aspect of the present invention, a plurality of relative positional relationship data detected by the shape measuring interferometer when the stage is moved along the movable mirror are joined together, and the rotational angle is detected. The shape of the moving mirror is measured by correcting the relative positional relationship data based on the rotation angle data detected by the interferometer, and the coordinates of the measurement point are corrected based on the measured shape of the moving mirror. Coordinate measurement can be performed with high accuracy without being affected by the shape. According to the third aspect of the present invention, there is provided a parallel plate inserted into the optical axis of the laser beam emitted from the shape measuring interferometer, and the laser beam is shifted laterally by tilting the parallel plate with respect to the optical axis. Therefore, the irradiation position of the laser beam can be controlled. According to the invention described in claim 4, at the time of measuring the coordinates of the measurement point, the posture of the stage is measured using a shape measurement interferometer or a rotation angle detection interferometer, and the measurement is performed based on the measured stage posture. Since the coordinates of the points are corrected, it is possible to perform the coordinate measurement with high accuracy while eliminating the influence of the posture of the stage.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of a coordinate measuring device according to the present invention.

FIG. 2 is a top view showing the coordinate measuring device according to the embodiment;

FIG. 3 is a block diagram showing a coordinate measuring device according to the embodiment;

FIG. 4 is a diagram showing an interferometer arrangement when measuring a mirror surface shape of a movable mirror.

FIG. 5 is a diagram showing an optical axis interval of an interferometer.

FIG. 6 is a diagram showing a case where a mirror surface of a movable mirror has a periodic undulation.

FIG. 7 is a diagram showing a case where the optical axis interval of a laser beam is reduced by a parallel plate.

FIG. 8 is a diagram showing a case where two irradiation positions of a laser beam are shifted by a parallel plate.

FIG. 9 is a diagram illustrating a shift amount of an optical axis by a parallel flat plate.

FIG. 10 is a diagram showing a conventional coordinate measuring device.

FIG. 11 is a diagram showing a method for detecting a distortion of a moving mirror by inverting a mask pattern and measuring a shape thereof;
(A) is a diagram showing a case where the distortion consists of a line symmetric component,
(B) is a diagram showing a case where the distortion is composed of point symmetric components.

[Explanation of symbols]

 Reference Signs List 1 XY stage 2X moving mirror 2Y moving mirror 3 detector 5 device under test 13 interferometer 14 interferometer 21 interferometer 22 interferometer 30 parallel flat plate 31 parallel flat plate 41X interferometer

Claims (4)

[Claims] 1. A stage for moving an object to be measured, a planar movable mirror attached to the stage, and a coordinate measuring device for measuring a position of the stage by irradiating a laser beam toward the movable mirror. Interferometer, comprising a detector for detecting a measurement point on the object to be measured, by measuring the position of the stage when the detector detects the measurement point by the coordinate measurement interferometer, A coordinate measuring device for measuring coordinates of a measuring point, wherein a shape measuring interferometer for detecting a relative positional relationship between the two points by irradiating a laser beam to two points of the movable mirror; A rotation angle detection interferometer for detecting a rotation angle of the stage based on a relative positional relationship between the two points when the laser beam is irradiated to the two points of the mirror; A plurality of relative position relationship data detected by the shape measurement interferometer when the device is moved, and correcting the relative position relationship data based on the rotation angle data detected by the rotation angle detection interferometer. A coordinate measuring apparatus for measuring the shape of the moving mirror, and correcting the coordinates of the measurement point based on the measured shape of the moving mirror. 2. The apparatus according to claim 1, further comprising: a second movable mirror provided orthogonal to the movable mirror; and a second coordinate measuring interferometer for irradiating the second movable mirror with a laser beam. At the time of measuring the shape of the movable mirror, the stage is moved in a direction normal to the second movable mirror, and the rotation angle detecting interferometer irradiates a laser beam toward the second movable mirror. The coordinate measuring apparatus according to claim 1, wherein: 3. A parallel plate which is inserted into an optical axis of a laser beam emitted from the shape measuring interferometer, wherein the parallel plate is tilted with respect to the optical axis to laterally shift the laser beam. 3. A method according to claim 1, wherein
The coordinate measuring device according to 1. 4. At the time of measuring the coordinates of the measurement point, the posture of the stage is measured using the shape measuring interferometer or the rotation angle detecting interferometer, and the measurement is performed based on the measured posture of the stage. The coordinate measuring device according to any one of claims 1 to 3, wherein the coordinates of the point are corrected.