JPH05272912A - Interferometer - Google Patents

Abstract

PURPOSE:To reduce the length measuring errors caused by Abbe's errors. CONSTITUTION:An optical beam LB from a coherent light source 1 is guided into a half mirror 2 through a parallel planar plate 3. The first beam LB1, which has passed through the half mirror 2, is cast into a mirror 4-2. The second beam LB2, which is reflected from the half mirror 2, is cast into a mirror 4-1. The first beam LB1, which is reflected from the mirror 4-2, and the second beam LB2, which is reflected from the mirror 4-1, are received with a photodetector 16. The slant angle of the parallel planar plate 3 is adjusted, and the position of the second beam LB2 is aligned with the height of a surface to be measured 5a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is suitable for application when measuring the coordinates of a pattern on a photomask which is an original plate when a semiconductor device, a liquid crystal display device or the like is manufactured by using a photolithography technique. Regarding the interferometer.

[0002]

2. Description of the Related Art A laser interferometer is known as a device capable of measuring a relative distance change amount between a first point and a second point with high accuracy. The laser interferometer includes an optical path length of the first laser beam reflected by the reflecting means at the first point and
The change of the interference fringes or the change of the beat signal when the difference between the optical path length of the second laser beam reflected from the reflection means of the point and the change of the beat signal is converted into a counting pulse or the like. By integrating and counting, the relative distance between the two can be obtained.

As an example of an object to be measured by using a laser interferometer, there is a pattern on a photomask which becomes an original plate when a semiconductor element, a liquid crystal display element or the like is manufactured by a photolithography technique. In order to measure the coordinates of the pattern of such a photomask, the photomask is placed on a stage that can be moved two-dimensionally, and the photomask is observed with, for example, a microscope for edge detection. Further, a fixed reflecting mirror is attached to the side of the edge detecting microscope, and a moving reflecting mirror is attached to the side of the stage. The fixed reflecting mirror and the moving reflecting mirror reflect the first laser beam and the second laser beam, respectively. By interfering these two laser beams after the reflection, the relative movement amount between the stage and the microscope for edge detection can be measured with high accuracy.

Then, after detecting a certain reference pattern of the photomask with a microscope for edge detection, the pattern to be detected is detected and the amount of movement of the stage at that time is measured to determine the coordinates of the pattern in the measuring direction. Can be measured. In this case, the optical system of the conventional interferometer is fixed except the moving reflecting mirror on the stage, and the height of the second laser beam incident on the moving reflecting mirror in the optical axis direction of the microscope for detecting the edge thereof is high. That is, the measurement position in the thickness direction of the photomask is also fixed. The measurement position in the thickness direction of the photomask is fixed to the height of the measurement surface of a standard photomask, for example.

[0005]

However, in the conventional interferometer, when, for example, photomasks having different thicknesses are placed on the stage, the measurement surface of the photomask and the incident position of the second laser beam. There is a disadvantage that a so-called Abbe error occurs due to the pitching of the stage, etc. In addition, when measuring the dimensions of a sample using a laser interferometer other than a photomask, a measurement error due to Abbe error will occur unless the measurement part of the sample and the laser beam are on the same straight line. To do.

In view of the above point, the present invention has an object to provide an interferometer capable of reducing a measurement error due to an Abbe error.

[0007]

A first interferometer according to the present invention is, for example, as shown in FIG. 1, a light source (1) for generating a coherent light beam and the light beam for the first beam L.
A light beam splitting means (2) for splitting into B1 and a second beam LB2, a first reflecting means (4-2) fixed to the first member (11) for reflecting the first beam LB1, and a measuring direction (X). A second reflecting means (4-) fixed to a second member (8) movably supported in the direction) and reflecting the second beam LB2.
1) and a light receiving means (2, 16) for mixing and photoelectrically converting the first beam reflected by the first reflecting means and the second beam reflected by the second reflecting means, In the interferometer for detecting the relative displacement between the first member (11) and the second member (8), the second beam LB2 between the light source (1) and the second reflecting means (4-1). Is provided with an adjusting means (3) for laterally shifting the object in a direction (Z direction) perpendicular to the measurement direction, and the measurement target portion (5) of the second member (8) is provided.
The position of the second beam LB2 is adjusted in accordance with the position of (a) in the direction (Z direction) perpendicular to the measurement direction.

In this case, a position detecting means (12) for detecting the position of the measurement object portion (5a) of the second member (8) in the direction (Z direction) perpendicular to the measuring direction is provided, and this position detecting means is used. It is desirable to adjust the position of the second beam LB2 to the detected position via the adjusting means (3). Further, an optical path length correcting means (which is also used by the adjusting means (3)) for correcting the optical path length of the first beam LB1 is provided, and the second beam LB when the adjusting means (3) is operated.
It is desirable to change the optical path length of the first beam LB1 by an amount equal to the change amount of the optical path length of 2.

The second interferometer according to the present invention is, for example, as shown in FIG. 1, a light source (1) for generating a coherent light beam, and the light beam as a first beam LB1 and a second beam LB1.
A beam splitting means (2) for splitting into a beam LB2 and a first reflecting means (4-2) for reflecting the first beam LB1.
And a second member which is fixed to the moving member (8) on which the measurement sample (5) is placed and which moves in a substantially plane and which reflects the second beam LB2 thereof.
A reflecting means (4-1), a light receiving means (2, 16) for photoelectrically converting the first beam reflected by the first reflecting means and the second beam reflected by the second reflecting means by mixing them. In the interferometer for detecting the amount of movement of the moving member (8), the second beam L at the measurement point of the measurement sample (5)
Position detecting means (12) for detecting the position in the direction (Z direction) perpendicular to the traveling direction of B2 is provided, and this position detecting means (1
An optical path adjusting means (3) for laterally shifting the optical path of the second beam LB2 in accordance with the position detected in 2) is arranged on the optical path of the light beam incident on the second reflecting means (4-1). It is a thing.

[0010]

According to the first interferometer of the present invention, when the second member (8) moves in the measuring direction, the second reflecting means (4-
Since the optical path length of the second beam reflected in 1) changes and the photoelectric conversion signal of the light flux obtained by causing the first beam LB1 and the second beam LB2 to interfere in the light receiving means changes, The amount of movement of the member with respect to the first member can be detected. In this case, when the position of the measurement target portion (5a) of the second member (8) in the direction perpendicular to the measurement direction (Z direction) changes, the second beam LB is adjusted by the adjusting means (3).
By aligning the position of 2 with the position of the measurement target part (5a), the second beam LB2 and the measurement target part (5a)
And can be set on the same straight line. Therefore, the second
Even if pitching or the like occurs when the member (8) moves, Abbe error does not occur, and the relative displacement between the first member (11) and the second member (8) is detected with high accuracy. be able to.

When the position detecting means (12) for detecting the position of the measurement target portion of the second member (8) in the direction perpendicular to the measurement direction is provided, for example, the measurement target portion of the second member (8) is provided. When the height of (5a) changes, the position detecting means (12) detects the height. Then, by aligning the position of the second beam LB2 with the detected position,
The second beam LB2 and the measurement target portion (5a) of the second member (8) can be automatically set on the same straight line.

Further, when the adjusting means (3) for laterally shifting the second beam LB2 in the direction perpendicular to the measuring direction is, for example, a plane parallel plate, the lateral shift amount is changed by changing the inclination angle of the plane parallel plate. Then, the optical path length of the second beam LB2 changes, and the light receiving means (2, 16) detects a photoelectric conversion signal similar to that when the second member (8) is displaced. On the other hand, when the optical path length correcting means (3) changes the optical path length of the first beam LB1 by an amount equal to the amount of change in the optical path length of the second beam LB2, the optical path length caused by the adjusting means (3) is changed. Can compensate for changes.

Next, in the second interferometer of the present invention, as compared with the above-mentioned first interferometer, not the relative movement amount between the two members but the measurement sample (5) is mounted. The difference is that the amount of movement of the placed moving member (8) is measured. Also,
Since the position detecting means (12) and the optical path adjusting means (3) are provided, the second reflecting means (4) is provided via the optical path adjusting means (3) according to the position detected by the position detecting means (12).
By laterally shifting the position of the light beam incident on -1), it is possible to prevent a measurement error due to an Abbe error.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the interferometer according to the present invention will be described below with reference to FIGS. In this embodiment, the present invention is applied to a length measuring system of a photomask pattern coordinate measuring apparatus. FIG. 1 shows the measuring apparatus of the present embodiment. In FIG. 1, 1 is a coherent light source composed of a laser light source. The laser beam LB emitted from the coherent light source 1 is divided into two light beams by the half mirror 2 after passing through the plane-parallel plate 3. Of these light beams, the first beam LB1 transmitted through the half mirror 2 is directed to the reference system mirror 4-2, and the second beam LB2 reflected by the half mirror 2 is passed through the optical path bending mirror 4 and then measured. Head towards the mirror 4-1. The second beam LB2 directed to the mirror 4-1 of the measurement system and the first beam LB1 directed to the mirror 4-2 of the reference system are parallel to each other, and the X axis is parallel to these two parallel beams.

Of the first beam LB1 reflected by the mirror 4-2 of the reference system, the light beam reflected by the half mirror 2 enters the photodetector 16, is reflected by the mirror 4-1 of the measurement system, and is reflected by the mirror 4. Of the reflected second beam LB2, the light beam that has passed through the half mirror 2 is also incident on the photodetector 16. Photo detector 16
Outputs an interference signal obtained by photoelectrically converting a light beam (interference light) obtained by the interference of two light beams. From the change in the interference light, the relative displacement in the X direction between the reference system mirror 4-2 and the measurement system mirror 4-1 can be measured.

Reference numeral 5 denotes a sample composed of a photomask on which a pattern to be measured is formed. The sample 5 is held on a holder 6, and the holder 6 is fixed on a rotatable θ stage 7.
The θ stage 7 is fixed on the sample table 8. A measurement system mirror 4-1 is attached to one end of the sample table 8. Further, the sample stage 8 is fixed on an X stage 9 which can move in the X direction, and
The stage 9 is placed on a Y stage 10 that can move in the Y direction perpendicular to the X direction (direction perpendicular to the plane of FIG. 1). Therefore, the sample table 8 can be moved to any position in the XY plane.

Reference numeral 11 denotes an objective lens, which supports the objective lens 11 above the sample 5 so as to be movable in the Z direction perpendicular to the XY plane. The position sensor 12 constantly detects the position of the objective lens 11 in the Z direction, and the position information output from the position sensor 12 is supplied to the control unit 13. The control unit 13 rotates the plane-parallel plate 3 via the drive unit 14 according to the position of the objective lens 11 in the Z-axis direction about an axis perpendicular to the plane of FIG. For example, when the plane parallel plate 3 is rotated clockwise to the position 3A from the state of FIG. 1, the laser beam LB after passing through the plane parallel plate 3 laterally shifts to the position T1 in the direction parallel to the paper surface of FIG. 1 (Z direction). The second beam LB2 reflected by the half mirror 2 and the mirror 4 and incident on the mirror 4-1 of the measurement system is also laterally displaced to the position T2 in the Z direction. In this embodiment, the first incident on the reference mirror 4-2
The position of the beam LB1 is also laterally displaced in the Z direction by the same amount.

That is, in this example, the position of the second beam LB2 incident on the mirror 4-1 of the measurement system in the Z direction can be adjusted by adjusting the rotation angle of the plane-parallel plate 3. Moreover, since the plane-parallel plate 3 acts in common on the first beam LB1 and the second beam LB2, the plane-parallel plate 3
Even if the rotation angle of the first beam LB1 changes, the difference between the optical path length of the first beam LB1 and the optical path length of the second beam LB2 does not change. Therefore,
Adjust the rotation angle of the plane-parallel plate 3 to adjust the Z of the second beam LB2.
Even if the position in the direction is changed, the state of the interference light received by the photodetector 16 does not change.
Then, it is possible to accurately detect only the relative displacement between the objective lens 11 and the sample table 8 (and thus the sample 5).

Reference numeral 15 denotes a focus and pattern detection system. A predetermined laser beam is supplied from the focus and pattern detection system 15 to the objective lens 11, and the laser beam emitted from the objective lens 11 is on the measurement surface 5a of the sample 5. Be focused on. In this case, the focus and pattern detection system 15 is reflected by the measurement surface 5a and the objective lens 1
The objective lens 1 using the laser light returned via 1
The defocus of the measurement surface 5a from the best focus surface (focal surface) of No. 1 is detected, and the objective lens 11 is moved up and down in the Z direction by using a drive mechanism (not shown).
Should always be located in the focal plane of the objective lens 11.
The position of the objective lens 11 in the Z direction in this case is detected by the position sensor 12. Further, the focus and pattern detection system 15 detects the pattern of the measurement surface 5a by detecting, for example, laser light scattered from the edge portion of the pattern formed on the measurement surface 5a,
The detection information of this pattern is supplied to the pattern coordinate detection unit 18.

Further, the interference signal output from the photodetector 16 is supplied to the interferometer coordinate measuring unit 17, which interrelates the reference system mirror 4-2 and the measuring system mirror 4-1. Displacement, that is, sample stage 8 and objective lens 1
The relative displacement in the X direction with respect to 1 is obtained. The displacement thus obtained is determined by the objective lens 11 on the measurement surface 5a of the sample 5.
It can be considered as a coordinate value in the X direction at the focal position of. Although not shown, in the present embodiment, an interferometer for measuring the relative displacement between the sample stage 8 and the objective lens 11 in the Y direction perpendicular to the paper surface of FIG. 1 is also provided. The interference signal detected by the interferometer for use with is also supplied to the interferometer coordinate measuring unit 17. Therefore, the interferometer coordinate measurement unit 17 calculates the coordinate values in the X direction and the Y direction at the focal position of the objective lens 11 on the measurement surface 5 a, and supplies this coordinate value to the pattern coordinate detection unit 18. The pattern coordinate detection unit 18 measures the X-direction and Y-direction coordinates of each pattern on the measurement surface 5a.

Next, in this embodiment, the measurement surface 5 of the sample 5 is
The operation when measuring the coordinates of the pattern a will be described. First, in order to accurately detect the pattern on the measurement surface 5a, the best focus surface (focal plane) of the objective lens 11 is obtained by the focus and pattern detection system 15, and the height of the objective lens 11 in the Z direction is determined by the drive mechanism. By adjusting, the focal plane of the objective lens 11 is matched with the measurement surface 5a of the sample 5. With the focus on the measurement surface 5a, the X stage 9 and the Y stage 10 are driven to move the sample stage 8 in the XY plane, while the focus and pattern detection system 15 moves the pattern on the measurement surface 5a. Are sequentially detected. The XY coordinates of the pattern detected in this manner are accurately obtained by the pattern coordinate detection unit 18 to which the coordinate information is supplied from the interferometer coordinate measurement unit 17.

Next, the usefulness of the plane parallel plate 3 will be described in detail with reference to FIG. Figure 2 shows the measurement system mirror 4-
The relationship between 1 and the measurement surface 5a of the sample 5 is shown in a simplified manner. In FIG. 2, the current measurement point of the measurement surface 5a is point P. Further, as indicated by the solid line, it is assumed that the second beam LB2 and the measurement surface 5a are displaced by ΔZ in the Z direction. In this state, when the sample stage 8 rotates about the measurement point P by an angle φ due to the pitching, rolling, etc. of the stage, the measurement system mirror 4-1 also rotates by the angle φ.
Just rotate. In this case, the position in the X direction at which the second beam LB2 is incident on the mirror 4-1 of the measurement system changes by δ,
Under the condition that the angle φ is small, δ is almost ΔZ · sinφ
It is represented by. This means that a minute rotation of the sample table 8 causes a measurement error due to an Abbe error.

On the other hand, when the amount of rotation of the plane parallel plate 3 of FIG. 1 is adjusted and the height of the second beam LB2 in the Z direction is set to the position T3 on the extension of the measurement surface 5a in FIG.
Even if the sample table 8 is tilted, the measurement error is negligible. In addition, for example, since the sample 5 made of a photomask has various thicknesses, the rotation angle of the plane parallel plate 3 is adjusted with respect to a certain sample 5 to adjust the position of the second beam LB2 in the Z direction. Even if the height of the measuring surface 5a is adjusted, the plane-parallel plate 3
If the rotation angle is fixed, the second beam LB2 and the measurement surface will deviate for another sample having a different thickness.

Considering, for example, a glass reticle for semiconductor manufacturing as a sample, there is a change in thickness of several mm depending on the type. As shown in FIG. 2, when the rotation angle φ due to the pitching of the stage is 1 second and the height difference ΔZ between the measurement surface 5a and the second beam LB2 is 2 mm, the measurement error δ due to the Abbe error is about 0.0097 μm. Becomes This corresponds to a shift of about 2 counts when one count of the interferometer is 0.005 μm. This means that it is necessary to correct the height of the second beam LB2 of the interferometer when exchanging the sample. However, when the height difference (concavo-convex) in the measurement surface 5a of the sample 5 is large, when the pitching or rolling is large, or when the measurement needs to be performed with higher accuracy, the measurement surface 5a of the sample 5 is It is necessary to correct the height of the second beam LB2 at the measurement point.

Therefore, in this embodiment, the objective lens 11
Moves in the Z direction to a position where the measurement surface of each sample is focused,
The position of the objective lens 11 at the time of focusing is detected by the position sensor 12, and the rotation angle of the plane parallel plate 3 is adjusted according to the detection result. Therefore, for samples of various thicknesses, even if the thickness varies within the sample, the second beam LB2 is automatically extended on the extension of each measurement point of the sample in the X direction.
Is located, and it is possible to prevent a measurement error due to an Abbe error.

Further, as shown in FIG. 1, the mirror 4-2 of the reference system is fixed to the objective lens 11 to cope with the change in the height of the measurement surface 5a in the Z direction due to the change in the thickness of the sample 5. Then, the height of the objective lens 11 in the Z direction also changes by the same amount. Then, since the incident position of the first beam LB1 on the reference system mirror 4-2 changes by the same amount as the movement amount of the objective lens 11 in the Z direction, the first beam LB1 moves on the reference system mirror 4-2. It always hits a fixed position. Therefore, even if the objective lens 11 moves in the Z direction when the mirror 4-2 of the reference system is not perpendicular to the X direction, there is an advantage that no measurement error occurs.

In the case of performing the measurement by the heterodyne method in the example of FIG. 1, the coherent light source 1 has a frequency f2, for example, a first beam polarized in a direction parallel to the plane of FIG. 1 and a frequency f2 (f2> f1). Then, a two-frequency laser light source that emits a second beam polarized in a direction perpendicular to the paper surface of FIG. 1 is used. Further, a polarization beam splitter is used instead of the half mirror 2, and a 1/4 is provided between the polarization beam splitter and the reference system mirror 4-2 and between the polarization beam splitter and the measurement system mirror 4-1. Place the wave plate. With this arrangement, the first beam of frequency f1 is incident on the mirror 4-2 of the reference system, the second beam of frequency f2 is incident on the mirror 4-1 of the measurement system, and the fundamental frequency is emitted from the photodetector 16. But (f2-
At f1), a beat signal whose frequency is modulated according to the relative moving speed of both mirrors 4-1 and 4-2 is output.

Next, a second embodiment of the present invention will be described with reference to FIG. The present embodiment is an example in which the first beam LB1 and the second beam in the example of FIG. 1 are laterally shifted independently, and in FIG. 3, parts corresponding to those in FIG. Omit it. FIG. 3 shows the measuring apparatus of this example, and in this FIG.
The laser beam LB emitted in the X direction is split by the half mirror 2 into a first beam LB1 as a transmitted light and a second beam LB2 as a reflected light. Then, the first beam LB1 is guided to the reference system mirror 4-2 through the reference system parallel plane plate 3-2, and the second beam LB2 is guided to the optical path bending mirror 4 and the measurement system parallel plane plate 3-1. It is guided to the mirror 4-1 of the measurement system via.

In this case, the second beam LB2 reflected by the measurement system mirror 4-1 returns to the half mirror 2 via the parallel plane plate 3-1 and the mirror 4 of the measurement system, and the half mirror 2
The light beam that has passed through is incident on the photodetector 16. On the other hand, the first beam LB1 reflected by the mirror 4-2 of the reference system returns to the half mirror 2 via the plane-parallel plate 3-2 of the reference system, and the light beam reflected by the half mirror 2 enters the photodetector 16. In the photo detector 16, the interference light between the beam reflected by the mirror 4-1 and the beam reflected by the mirror 4-2 is photoelectrically converted. Further, the rotation angles of the plane-parallel plates 3-1 and 3-2 are the drive unit 1 respectively.
It is set to the value instructed to the control unit 13 by 4-1 and 14-2. In this embodiment, the plane-parallel plates 3-1 and 3 are used.
-2 has the same thickness, and the inclination angles of both are set to be the same. Other configurations are similar to the example of FIG.

To explain the measuring operation of the embodiment shown in FIG. 3, when the sample 5 to be measured is held by the holder 6, the objective lens 11 is moved to Z by the focus and pattern detection system 15.
Up and down in the direction, the measurement surface 5a of the sample 5 matches the best focus surface of the objective lens 11. The position of the objective lens 11 at this time is detected by the position sensor 12 for the objective lens, and this position information is supplied to the control unit 13. Control unit 1
3 is a drive unit 14- so that the height of the second beam LB2 incident on the mirror 4-1 in the Z direction matches the measurement surface 5a.
The tilt angle of the parallel plane plate 3-1 of the measurement system is adjusted via 1. At the same time, the control unit 13 sets the inclination angle of the parallel plane plate 3-2 of the reference system to be the same as the inclination angle of the parallel plane plate 3-1 of the measurement system via the drive unit 14-2.

Therefore, also in the present embodiment, the height of the second beam LB2 incident on the mirror 4-1 of the measurement system in the Z direction matches the measurement surface 5a of the sample 5, so that the sample table 8 is tilted. However, the measurement error due to the Abbe error can be reduced to a negligible level. Further, the amount of movement of the objective lens 11 in the Z direction and the amount of change in the height of the first beam LB1 incident on the reference system mirror 4-2 in the Z direction are the same, and the amount of change with respect to the reference system mirror 4-2 is the same. The incident position of the first beam LB1 does not change. Therefore, even if the mirror 4-2 is attached so as to be inclined, no measurement error occurs. Furthermore,
Since the plane-parallel plates 3-1 and 3-2 have the same inclination angle, even if the inclination angle changes, the first beam LB1 and the second beam LB1 are not changed.
The difference in optical path length from the beam LB2 does not change. Therefore, it is always possible to accurately detect only the relative displacement between the objective lens 11 and the sample 5.

In the example of FIG. 3, the position in the Z direction is the sample 5
Although the reference system mirror 4-2 is fixed to the objective lens 11 that changes depending on the thickness of the reference lens, the reference system mirror 4-2 may be fixed to a fixed object. When the position of the mirror 4-2 of the reference system in the Z direction is completely fixed in this way, the position of the first beam LB1 of the reference system is displaced by tilting the parallel plane plate 3-2 of the reference system. Therefore, this change in the measurement conditions may cause a measurement error. In such a case, an optical system that changes only the optical path length of the first beam LB1 of the reference system and does not change the position of the first beam LB1 is required.

FIG. 4 shows an example of such an optical system. In FIG. 4, the second beam LB2 is a mirror 4 of the measurement system.
Let d be the thickness of the plane-parallel plate 3-1 that passes when entering −1 and θ be the counterclockwise tilt angle. Then, two parallel plane plates 3-having a thickness of d / 2 are provided in the optical path when the first beam LB1 of the reference system is incident on the mirror 4-2 of the reference system.
3 and 3-4 are inserted, one parallel plane plate 3-3 is tilted counterclockwise by an angle θ, and the other plane parallel plate 3-4.
Is tilted clockwise by an angle θ. As a result, the position of the first beam LB1 of the reference system does not change,
First beam LB1 of the reference system and second beam LB2 of the measurement system
It is possible to keep the optical path lengths in the plane parallel plates with and equal to each other.

Next, a third embodiment of the present invention will be described with reference to FIG. This example is a simplification of the example of FIG. 3. In FIG. 5, parts corresponding to those in FIG. 3 are designated by the same reference numerals, and detailed description thereof will be omitted. In FIG. 5, the side surface of the objective lens 11 is mounted on the Z-axis through the support member 19.
Mount the two mirrors 4-3 and 4-4 in parallel with an inclination angle of °. That is, as the objective lens 11 moves in the Z direction, the mirrors 4-3 and 4-4 also move in the Z direction. Further, the mirrors 20 and 21 are attached to a stable base different from the objective lens 11, the mirror 20 is arranged between the mirror 4-3 and the mirror 4-4, and the mirror 21 is arranged in the mirror 4.
-4 above.

Then, the mirror 21 and the objective lens 11 to which the first beam LB1 transmitted through the half mirror 2 is fixed
The second beam LB2 guided to the mirror 4-2 of the reference system fixed to the objective lens 11 via the mirror 4-4 interlocked with, and the second beam LB2 reflected by the half mirror 2 for bending the optical path 4 and the fixed mirror. It is guided to the mirror 4-1 of the measurement system fixed to the sample stage 8 via the mirror 4-3 which is interlocked with 20 and the objective lens 11. In this embodiment, the Z of the objective lens 11 is
There is no need for a sensor for detecting the directional position and a plane-parallel plate with a variable tilt angle. Other configurations are the same as those in the example of FIG.

Also in the example of FIG. 5, the focus and pattern detection system 15 adjusts the Z direction of the objective lens 11 according to the thickness of the sample 5 so that the focal plane of the objective lens 11 matches the measurement surface of the sample 5. The height of is adjusted. In this case, since the two mirrors 4-3 and 4-4 coupled to the objective lens 11 also move in the Z direction in conjunction with the objective lens 11, the second beam LB2 incident on the mirror 4-1 of the measurement system.
The position in the Z direction and the height of the measurement surface of the sample 5 always match. Moreover, since the incident position of the first beam LB1 on the mirror 4-2 of the reference system is also constant, the relative displacement between the objective lens 11 and the sample 5 can always be measured with high accuracy.

In the example of FIG. 5, mirrors 4-3 and 4-
4 always moves in conjunction with the objective lens 11, but by devising the connecting portion between the objective lens 11 and the two mirrors 4-3 and 4-4, for example, the mirror 4-3 and A mechanism for moving 4-4 may be adopted.

Further, in the above-mentioned embodiment, only the positional deviation in the Z direction between the measurement point of the sample 5 and the second beam LB2 for measurement is taken into consideration. For example, the sample is compared with the Y direction perpendicular to the paper surface of FIG. Even if there is a positional deviation between the measurement point 5 and the second measurement beam LB2, an Abbe error occurs due to the yawing of the stage. On the other hand, the Abbe error can be eliminated by disposing an optical system that adjusts the position of the second beam LB2 incident on the mirror 4-1 of the measurement system in the Y direction.

Further, for example, in the example of FIG. 3, the plane-parallel plate 3-1 is rotated around an axis perpendicular to the plane of FIG. 3, but the plane-parallel plate 3-1 is further rotated. By rotating around an axis parallel to the Y axis, the incident position of the second beam LB2 on the mirror 4-1 of the measurement system is changed to YZ.
It can be set at any position in the plane. Further, for example, in the example of FIG. 1, a corner cube or the like may be used instead of the reference system mirror 4-2 and the measurement system mirror 4-1. As described above, the present invention is not limited to the above-described embodiments, and various configurations can be taken without departing from the gist of the present invention.

[0040]

According to the first interferometer of the present invention, since the position of the second beam can be adjusted to the position of the object to be measured by the adjusting means, even if the second member tilts due to the pitching of the stage or the like. There is an advantage that the measurement error due to Abbe error does not occur. Further, when the position detecting means for detecting the position of the measurement target portion of the second member is provided, the second automatically
The position of the beam can be adjusted to the position of the measurement target part. Further, when the optical path length correcting means for correcting the optical path length of the first beam is provided, even if the optical path length of the second beam changes due to the operation of the adjusting means, the optical path length of the first beam changes by the same amount. Therefore, it is always possible to accurately detect only the relative displacement between the first member and the second member.

Also, in the second interferometer of the present invention,
When detecting the moving amount of the moving member, the optical path of the second beam can be automatically adjusted to the position detected by the position detecting means, and the length measurement error due to the Abbe error can be eliminated.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a coordinate measuring apparatus of a first embodiment of an interferometer according to the present invention.

FIG. 2 is a diagram for explaining an Abbe error in the first embodiment.

FIG. 3 is a configuration diagram showing a coordinate measuring device according to a second embodiment of the present invention.

FIG. 4 is a configuration diagram showing a main part of a modified example of the second embodiment.

FIG. 5 is a configuration diagram showing a coordinate measuring device according to a third embodiment of the present invention.

[Explanation of symbols]

 1 Coherent light source 2 Half mirror 3,3-1,3-2 Parallel plane plate 4 Mirror 4-1 Measurement system mirror 4-2 Reference system mirror 4-3,4-4 Mirror 5 Sample 6 Holder 7 θ table 8 Sample stage 9 X stage 10 Y stage 11 Objective lens 12 Position sensor for objective lens 13 Control unit for parallel plane plate 14, 14-1, 14-2 Drive unit for parallel plane plate 15 Focus and pattern detection system 16 Photodetector 17 Interferometer coordinate measuring unit 18 Pattern coordinate detecting unit

Claims (4)

[Claims] 1. A light source for generating a coherent light beam, a light beam splitting device for splitting the light beam into a first beam and a second beam, and a first member fixed to a first member for reflecting the first beam. A reflecting means; a second reflecting means fixed to a second member movably supported in the measuring direction to reflect the second beam; a first beam reflected from the first reflecting means; and a second beam
An interferometer for detecting relative displacement between the first member and the second member, the interferometer comprising: a light receiving unit that performs photoelectric conversion by mixing a second beam reflected from a reflecting unit. Adjustment means for laterally offsetting the second beam in a direction perpendicular to the measurement direction is provided between the second reflection means and the second reflection means, and the adjustment means is provided according to the position of the measurement target portion of the second member in the direction perpendicular to the measurement direction. An interferometer characterized in that the position of the second beam is adjusted. 2. A position detecting means for detecting a position of a measurement target portion of the second member in a direction perpendicular to the measuring direction is provided, and the second position is detected at the position detected by the position detecting means via the adjusting means. The interferometer according to claim 1, wherein the positions of the beams are adjusted. 3. An optical path length correction means for correcting the optical path length of the first beam is provided, and an amount equal to the amount of change in the optical path length of the second beam when the adjusting means is operated is set. The interferometer according to claim 1 or 2, wherein the optical path length is changed. 4. A light source for generating a coherent light beam, a light beam splitting means for splitting the light beam into a first beam and a second beam, a first reflecting means for reflecting the first beam, and a measurement sample. Second reflecting means fixed to a moving member that mounts on and moves on a substantially flat surface, and reflects the second beam; the first beam reflected from the first reflecting means; and the second beam.
An interferometer that has a light receiving unit that mixes a second beam reflected from a reflecting unit and photoelectrically converts the second beam, and advances the second beam at a measurement point of the measurement sample. Position detecting means for detecting a position in a direction perpendicular to the direction is provided, and optical path adjusting means for laterally shifting the optical path of the second beam according to the position detected by the position detecting means is incident on the second reflecting means. An interferometer characterized by being arranged on the optical path of a light beam.