JPH1019513A - Position measurement device and pattern measurement device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a position measurement device and a pattern measurement device wherein measurement error due to heat is reduced. SOLUTION: A reference reflection member 24 having a reflection surface in the first plane containing an optical axis of an optical system 14 is used. The reference reflection member 24 is held with a holding member held at a position crossing with the first plane on the outer periphery of optical systems 14 and 14a. The light for measurement is projected to a measurement reflection member fixed to sample objects 20 and 10 and the reference reflection member 24 and a measurement reflection member, and with the light reflected on the reflection surfaces of the reference reflection member 24 and the measurement reflection member, a relative position displacement amount between the optical axis of the optical system 14 and the sample objects 20 and 10 is measured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position measuring device for measuring a relative position displacement of a measurement object with respect to an optical axis of a predetermined optical system, and a pattern of a substrate mounted on a movable stage. The present invention relates to a pattern measuring device that measures

[0002]

2. Description of the Related Art As a method for optically measuring the position of an object to be measured, an interferometer is currently widely used. In the interferometer, for example, one light beam for measurement is split into two light beams, the split light beams are guided in different directions, and the light beams reflected by the two reflecting mirrors are combined again. And these 2
By detecting interference fringes generated by combining the light of the book, it is possible to measure the displacement of the relative position between the members provided with the two reflecting mirrors. Such an interferometer system is frequently used in semiconductor device manufacturing and inspection processes. In the exposure step of transferring the pattern formed on the mask onto the photosensitive substrate, prior to the exposure operation, the coordinates of the pattern formed on the mask are measured by a pattern measuring device. In such a pattern measuring apparatus, a mask to be measured is placed on a movable stage, and the pattern on the mask is scanned by light emitted from an optical system such as an objective lens to thereby position the pattern ( (Coordinates). At this time, the position of the mask moving in the two-dimensional plane is accurately measured by the interferometer.

In the above-described pattern measuring apparatus, a reference mirror is installed on the outer periphery of a lens barrel of an objective lens, and a moving mirror is installed on a stage on which a substrate such as a mask is mounted. Then, the laser light for measurement is set to 2 in the interferometer.
The light is divided into books, and the divided light is projected onto a reference mirror fixed to an objective lens barrel and a movable mirror on a stage. Then, the light reflected by the two reflecting mirrors is combined again in the interferometer, and the position of the substrate is measured by detecting interference fringes generated by the combination of these two lights. To be exact,
The displacement of the relative position between the optical axis of the objective lens and the substrate on the stage is measured.

FIG. 7 shows a schematic configuration of a conventional pattern measuring apparatus. This device measures the position (coordinates) of a pattern 110a formed on a substrate 110, and includes an optical device 112 that emits a laser beam for pattern measurement;
An objective lens 114 for projecting a laser beam emitted from the optical device 112 as a spot on the substrate 110,
Light receiving elements 116a and 116b for receiving scattered light generated at the edge of the ten patterns 110a are provided. The substrate 110 is mounted on a stage 118 movable in a plane perpendicular to the plane of the drawing. A movable mirror 122 that reflects laser light emitted from the interferometer main body 120 is fixed to an end on the stage 118. Further, a reference mirror 124 that reflects a laser beam 123 emitted from the interferometer main body 120 is fixed to an outer periphery of a lens barrel 114 a surrounding the objective lens 114.

[0005] In the pattern measuring apparatus having the above-described configuration, by driving the stage 118, the laser spot irradiated through the objective lens 114 is applied to the substrate 1.
Scanning is performed using ten patterns 110a. Then, the scattered light generated at the edge portion of the pattern 110a is reflected by the light receiving element 116.
a and 116b. At this time, since the position of the substrate 110 is monitored by the interferometer main body 120, the position of the pattern 110a is automatically measured from the signals of the scattered light received by the light receiving elements 116a and 116b.

As shown in FIG. 8, the reference mirror 124 is held by a U-shaped holding member 126 with the reflecting surface 124a parallel to a plane including the optical axis A of the objective lens. That is, the laser light 123 emitted from the interferometer 120 is perpendicularly incident on the reflection surface 124a of the reference mirror 124. Both ends of the holding member 126 are fixed to the outer periphery of the lens barrel 114a.

In the interferometer main body 120, one laser beam is split into two beams by a beam splitter (not shown), and the two split laser beams are applied to the moving mirror 122 and the reference mirror 124, respectively. Then, the light reflected by the movable mirror 122 and the reference mirror 124 is combined again, and the interference fringes of the combined light are observed, whereby the substrate stage 118
The position of is measured. That is, based on the relative displacement between the distance from the interferometer main body 120 to the reference mirror 124 and the distance from the interferometer main body 120 to the movable mirror 122, the pattern 110a on the optical axis A of the objective lens 114 is Measure the position. Thus, the substrate 110
Since the position of (pattern 110a) is measured based on the relative displacement of the objective lens 114 with respect to the optical axis A, in order to perform accurate measurement, the reflection surface 124a of the reference mirror 124 is required.
It is important to keep the distance between the object and the optical axis A of the objective lens 114 constant.

[0008]

However, according to the above-described conventional method, when the temperature of the lens barrel 114a changes due to some influence, the reference of the lens barrel 114a and the reference mirror 124 is caused by thermal expansion or contraction. Mirror 124
The distance between the reflecting surface 124a and the optical axis A of the objective lens 114 changes.

For example, as shown in FIG.
The radius of 14a is R, the angle of the position where the end of the holding member 126 contacts the lens barrel 114a is 2θ, and the lens barrel 114 is
Assuming that the coefficient of thermal expansion of a is K1 and the amount of temperature change is T, the reference mirror 1 caused by the thermal expansion or contraction of the lens barrel 114a
The displacement ΔX1 in the direction of the 24 laser beams 123 is as follows. ΔX1 = R · K1 · T · cos θ

On the other hand, the distance from the reflecting surface 124a of the reference mirror 124 to the mounting position of the holding member 126 to the lens barrel 114a is L, the thermal expansion coefficient of the holding member 126 is K2,
Assuming that the temperature change amount is T, the thermal displacement amount ΔX2 of the reference mirror 124 (reflection surface 124a) due to the thermal expansion or thermal contraction of the holding member 126 is as follows. △ X2 = L ・ K2 ・ T

Therefore, the total displacement ΔX between the optical axis A of the projection lens 114 and the reflecting surface 124a of the reference mirror 124
Is as follows. ΔX = (R · K1 · T · cos θ) + (L · K2 · T)

Since the shape of the holding member 126 is relatively simple and does not require high precision, the holding member 126 can be formed using a material having a low coefficient of thermal expansion, which is a difficult-to-process material. . For this reason, the amount of displacement △ X2 (= LK2T) of the reflecting surface 124a of the reference mirror 124 due to the thermal displacement of the holding member 126 can be reduced to some extent. However, it is difficult to mold the lens barrel 114a (objective lens 114) from a material having a low coefficient of thermal expansion, which is a difficult-to-process material. Therefore, the displacement amount of the reference mirror 124 due to the thermal displacement of the lens barrel 114a ΔX1 (= R ·
In order to reduce K1 · T · cos θ), it is necessary to minimize the temperature change amount T. For example, when the radius R of the lens barrel 114a is 20 mm, the thermal expansion coefficient K1 of the lens barrel 114a is 15 × 10 ⁻⁶ , and θ is 15 °,
Displacement amount of reference mirror 124 (reflection surface 124a) △ X2 (= R
(K1 · T · cos θ) needs to be controlled to an accuracy of about 0.0017 ° C. or less to make the temperature change T 0.005 μm or less. In measurement performed at room temperature, such accurate temperature control is practically impossible.

When the distance between the reflecting surface 124a of the reference mirror 124 and the optical axis A of the objective lens 114 changes, the interferometer 120
This causes an error in the position of the pattern 110a measured by the measurement.

The present invention has been made in view of the above situation, and has as its object to provide a position measuring device and a pattern measuring device in which a measurement error due to heat is reduced.

[0015]

In order to solve the above-mentioned problems, the present invention measures a relative displacement of a measurement object (10) with respect to an optical axis (A) of a predetermined optical system (14). The optical axis (A) of the optical system (14)
A reference reflecting member (24) having a reflecting surface (24a) in a first plane (Pa) including: an optical system (14, 14);
a) a holding member (44) supported at a position intersecting with the first plane (Pa) on the outer periphery of (a) and holding the reference reflecting member (24) with respect to the optical system (14); (2
The measurement reflection member (28) fixed to the reference reflection member (24) and the reference reflection member (24) and the measurement reflection member (28). )
The optical axis of the optical system (14) and the object to be measured (20, 10) are determined by using the light reflected by the reflecting surface of the measuring reflecting member (28).
Measuring means (32) for measuring the relative positional displacement with respect to. In the position measuring device as described above, it is desirable that a portion of the holding member (44) which is in contact with the outer periphery of the optical system (14, 14a) is formed in a shape symmetrical with respect to the first plane (Pa).

The reference reflecting member (24) includes a first reference mirror (24) and a second reference mirror disposed at symmetric positions with the optical system (14) therebetween in the first plane (Pa). (58)
May be included. At this time, the measuring means (53, 55) projects the measuring light onto the first and second reference mirrors (24, 58), and the first and second reference mirrors (24, 58). Interferometer (66, 68, 70, 72, 74, 76, 78,
80). In addition, the measuring means includes a first
And the distance from the optical axis of the measurement light projected to the second reference mirror (24, 58) is set equal to each other.

Further, another aspect of the present invention uses a first light irradiated through an objective lens (14), and uses a first light on a substrate (10) mounted on a movable stage (20). In a pattern measuring apparatus for measuring a position of a pattern, a first plane (P) including an optical axis (A) of an objective lens (14) is used.
Reference reflective member (2) having a reflective surface (24a) in a)
4) and; supported at a position intersecting the first plane (Pa) on the outer periphery of the objective lens (14, 14a), and holding the reference reflecting member (24) with respect to the objective lens (14, 14a). A holding member (44); a measuring reflecting member (28) fixed to the substrate (10); and a measuring light (Bx, B) with respect to the reference reflecting member (24) and the measuring reflecting member (28).
xm), and using the light reflected on the reference reflecting member (24) and the reflecting surface (24a, 28a) of the measuring reflecting member (28), the optical axis (A) of the objective lens (14) is adjusted. A measuring unit (32) for measuring a relative displacement amount with respect to the substrate (10);

[0018]

According to the present invention as described above, the reference reflecting member (24) is provided with the reflecting surface (24a) of the optical system (14).
Are arranged so as to coincide with the first plane (Pa) including the optical axis (A), and are supported at positions intersecting with the first plane (Pa) on the outer periphery of the optical system (14a). Even when the optical system (14, 14a) thermally expands or contracts, deviation of the reflection surface (24a) in the measurement direction can be minimized. That is, when the optical system (14, 14a) thermally expands, the expansion propagates substantially uniformly in the radial direction around the optical axis (A). It will be displaced along a plane (Pa) including the axis (A). Therefore, in the present invention, the optical system (1)
The thermal displacement of (4, 14a) is propagated only in a direction parallel to the reflecting surface (24a) of the reference reflecting member (24). In other words, there is almost no displacement of the reflection surface (24a) of the reference reflection member (24) in the measurement direction (XL, YL).
Measurement means (3) by thermal deformation of (14, 14a) of the optical system
A decrease in measurement accuracy due to 2) can be suppressed.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the following examples. In the present embodiment, the present invention is applied to a pattern position measuring device that measures coordinates of a pattern formed on a substrate such as a reticle.

[0020]

FIG. 1 shows the overall configuration of a pattern position measuring apparatus according to this embodiment. The pattern position measuring apparatus according to the present embodiment measures the position (coordinates) of a pattern formed of chromium or the like on the substrate 10, and includes an illumination system (12, 14) for irradiating measurement light, and a substrate. Light receiving system (16a, 16b, 18a, 18b) for receiving scattered light from 10
A stage driving device 22 for driving the stage 20 on which the substrate 10 is mounted, and an interferometer system (24, 26, 28, 30, 30) for measuring the position of the stage 20 (substrate 10).
32, 34), a main control device 40 for controlling the entire pattern measuring device, and a display device 42 for displaying a measurement result by the device.

The illumination system (12, 14) includes an optical device 12 for outputting a laser beam for measurement, and an objective lens 14 for guiding the laser beam emitted from the optical device 12 as a spot onto the substrate 10. I have. The objective lens 14 is arranged in a lens barrel 14a.

The substrate 10 to be measured can be, for example, a mask such as a reticle used in a semiconductor exposure process, or a photosensitive substrate such as a wafer having the mask pattern exposed. The stage 20 on which the substrate 10 is placed is configured to be movable in an XY two-dimensional plane by a stage driving device 22 controlled by a main controller 40. And, by the movement of the stage 20,
The laser spot emitted from the objective lens 14 is
The scanning is performed on the zero surface.

The light receiving system (16a, 16b, 18a, 18b) for receiving the scattered light from the substrate 10 is arranged so as to look obliquely from above the substrate 10, and performs relative scanning between the laser light and the substrate 10. Thereby, scattered light or diffracted light generated at the pattern edge on the substrate 10 is received. Then, the main controller 4 outputs an electric signal corresponding to the intensity of the received light.
0 is supplied.

The interferometer system (24, 26,
28, 30, 32, and 34) are two-axis interferometer systems that measure the position of the substrate 10 in the X-axis direction.
4, 28, 32) and a system (26, 30, 34) for measuring the position in the Y-axis direction. The interferometer system (24, 28, 32) for measuring the position in the X-axis direction includes a reference mirror 24 fixed on the outer periphery of the lens barrel 14a by a mounting member 44 (see FIG. 2) and an end on the stage 20. It comprises a long movable mirror 28 fixed to the section and an interferometer main body 32. A laser light source (not shown) is provided in the interferometer main body 32. The laser light emitted from the laser light source is separated by a spectroscope (not shown) such as a beam splitter.
The light is split into two lights (Bx, Bxm), and the split light is projected onto the reference mirror 24 and the moving mirror 28. And reference mirror 2
4 and the laser light reflected by the movable mirror 28 are again interferometer main body 3
2, the relative position change of the reference mirror 24 and the movable mirror 28, that is, the amount of movement of the stage 20 in the X direction is measured based on the interference fringes of the combined light. More precisely, the X coordinate of the pattern on the substrate 10 existing on the optical axis A (see FIG. 2) of the objective lens 14 is measured based on the relative displacement of the reference mirror 24 and the movable mirror 28. I do.

On the other hand, the interferometer systems (26, 30, 34) for measuring the position in the Y-axis direction are also mounted on the outer periphery of the lens barrel 14a by the mounting members 46 (see FIG. 2), similarly to the systems in the X-axis direction. It comprises a fixed reference mirror 26, a long moving mirror 30 fixed to an end on the stage 20, and an interferometer main body 34. The interferometer body 34 is
Similarly to the interferometer 32, a laser light source (not shown) is provided inside, and the laser light emitted from the laser light source is separated by a spectroscope (not shown) such as a beam splitter.
The light is split into two lights (By, Bym), and the split light is projected onto the reference mirror 26 and the movable mirror 30. And reference mirror 2
6 and the laser light reflected by the movable mirror 30 are recombined in the interferometer body 34, and based on the interference fringes of the combined light, the relative displacement of the reference mirror 26 and the movable mirror 30, ie, the stage 20 Is measured in the Y direction. More precisely, the Y coordinate of the pattern on the substrate 10 existing on the optical axis A of the objective lens 14 is measured based on the relative displacement of the reference mirror 26 and the movable mirror 30.

The two-way interferometer system (3
2, 34), the coordinate value on the XY plane of the pattern on the laser spot projected from the objective lens 14 is obtained.

FIG. 2 shows the positional relationship among the lens barrel 14a, the reference mirrors 24 and 26, and the mounting members (44, 46) according to the first embodiment of the present invention. The reference mirror 24 used for position measurement in the X-axis direction is fixed to the outer periphery of the lens barrel 14a by the mounting member 44 such that the reflection surface 24a thereof coincides with a plane Pa passing through the optical axis A of the objective lens 14. I have. Mounting member 44 and lens barrel 14
The contact position (mounting position) with a is set on the plane Pa, and the distances Dx1 and Dx2 in the X direction from the plane Pa (reflection surface 24a) to each mounting position are arranged to be equal. With this arrangement, when the lens barrel 14a thermally expands or contracts, its displacement becomes X
It propagates only in the Y-axis direction perpendicular to the axis. In other words, care is taken to prevent the mounting member 44 from rotating due to the thermal displacement of the lens barrel 14a and displacing the reflecting surface 24a of the reference mirror 24 in the X-axis direction. For the same reason, it is desirable that the contact area between each mounting member 44 and the lens barrel 14a be as small as possible.

On the other hand, a reference mirror 26 for position measurement in the Y-axis direction
Is fixed to the outer periphery of the lens barrel 14a by a mounting member 46 such that its reflection surface 26a coincides with a plane Pb (a plane orthogonal to the plane Pa) passing through the optical axis A of the objective lens 14. The contact position (attachment position) between the attachment member 46 and the lens barrel 14a is set on the plane Pb, and distances Dy1 and Dy2 in the Y direction from the plane Pb (reflection surface 26a) to each attachment position are set. They are arranged to be equal.

Next, the overall operation of the pattern position measuring apparatus having the above configuration will be described. Before starting the pattern measurement, the optical axis A of the objective lens 14 is first aligned with a certain reference point on the substrate 10, and the so-called calibration is performed in which the measured values by the interferometer bodies 32 and 34 at that time are set to zero. Do. Thereafter, the stage 20 is moved to the driving device 22.
By scanning in the XY directions, the laser spot output from the optical device 12 via the objective lens 14 is scanned on the surface of the substrate 10. When the laser spot is scanned by the pattern on the substrate, scattered light (or diffracted light) is generated at the edge of the pattern, and the scattered light is received by the light receiving elements 16a, 16b, 18a, and 18b. The interferometer bodies 32 and 34 measure the relative displacement of the substrate 10 (moving mirrors 28 and 30) and the objective lens 14 (reference mirrors 24 and 26) in the X and Y directions, and supply the measured values to the main controller 40. I do. In the main controller 40, the position information supplied from the interferometer main bodies 32 and 34 and the light receiving elements 16a, 16b and 18 are used.
The distance between the patterns on the substrate 10 is determined based on the detection signals from the signals a and 18b and displayed on the display device.

In this embodiment as described above, the reference mirror 24 is arranged so that its reflection surface 24a coincides with the plane Pa including the optical axis A of the objective lens 14, and this is placed on the outer periphery of the lens barrel 14a. Since the lens barrel 14a is supported at a position that intersects the upper plane Pa, even if the lens barrel 14a thermally expands or contracts, it is possible to minimize the deviation of the reflection surface 24a in the measurement direction. That is, when the lens barrel 14a thermally expands, the expansion propagates substantially uniformly in the radial direction around the optical axis A. Therefore, the outer peripheral portion of the lens barrel 14a extends along the plane Pa including the optical axis A. Will be displaced. Therefore, the thermal displacement of the lens barrel 14a is
Is propagated only in a direction parallel to the reflection surface 24a. In other words, there is almost no displacement of the reflection surface 24a of the reference mirror 24 in the measurement direction (X-axis direction). Thereby, the lens barrel 14
A decrease in the measurement accuracy of the interferometer 32 due to the thermal deformation of “a” is suppressed.

FIG. 3 shows a modification (second embodiment) of the embodiment shown in FIG.
Embodiment), and a lens barrel 14a of a reference mirror 48 for position measurement in the Y-axis direction and a reference mirror 50 for position measurement in the X-axis direction
The positions of the upper attachment members 52 and 54 are changed. That is, in this example, the reference mirrors 48 and 50 each reflection surface 48
The laser beams Bx and By incident on the laser beams a and 50a cross each other. Other configurations, arrangements and the like are the same as those of the embodiment shown in FIG.

FIG. 4 shows a lens barrel 14a and reference mirrors (24, 26, 56, 58) according to a third embodiment of the present invention.
And the positional relationship between the mounting members (44, 46, 60, 62). In this embodiment, reference mirrors 56 and 58 are further provided in addition to the reference mirrors 24 and 26 of the first embodiment shown in FIG. The interferometer system (53, 55) of the present embodiment is a two-beam interferometer, and has two measurement laser beams (Bx1, Bx2) and (Bx1, Bx2) in each of the X-axis direction and the Y-axis direction. By1, By2) are used. The reference mirror 56 is arranged by the mounting member 60 such that the reflection surface 56a thereof coincides with the plane Pb. The reference mirror 56 and the reference mirror 26 are arranged at symmetrical positions with respect to the optical axis A of the objective lens 14. That is, the distance Lx1 from the optical axis A of the objective lens 14 to the incident position of the laser beam By1 on the reflecting surface 26a of the reference mirror 26, and the distance Lx2 from the optical axis A of the reflecting surface 56a of the reference mirror 56 to the incident position of the laser beam By2 on the reflecting surface 56a. Are set to be equal.

On the other hand, the reference mirror 58 is arranged by the mounting member 62 such that the reflection surface 58a thereof coincides with the plane Pa. Similarly to the reference mirror 56, the reference mirror 58 is disposed at a position symmetrical to the reference mirror 24 with respect to the optical axis A of the objective lens 14. That is, the objective lens 14
From the optical axis A to the position where the laser beam Bx1 is incident on the reflection surface 24a of the reference mirror 24, and the reference mirror 58.
Are set so that the distance Ly2 to the position where the laser beam Bx2 is incident on the reflection surface 58a is equal. If the distances Ly1 and Ly2 and the distances Lx1 and Lx2 cannot be made equal, it is desirable to arrange the distances as close as possible.

FIGS. 5 and 6 schematically show the structure of the optical system of the two-beam interferometer 53. FIG. Since the interferometer 55 has the same configuration, a duplicate description will be omitted. The two-beam interferometer 53 is a so-called Michelson type interferometer, and the detection accuracy is improved as compared with an interferometer using a single beam. The two-line beam interferometer 53 includes a laser oscillator 66 that outputs a laser beam Bo, and reference mirrors 24 and 58.
Reflection surfaces 24a and 58a and the reflection surface 28a of the movable mirror 28
A detector 68 for receiving and detecting the light returned from the light source, a polarizing beam splitter 70, and four λ / 4 plates 72, 74, 76, 78 through which light emitted from the polarizing beam splitter 70 or transmitted therethrough is transmitted. Have. λ / 4 plate 7
Reference numerals 2 and 74 are arranged in the Y direction so that the reference beams Bx2 and Bx1 respectively pass therethrough. Also, λ
The quarter plates 76 and 78 are λ / 4 plates 72 and 7 for the reference beam.
4, the measurement beams Bxm2 and Bxm1 are arranged side by side in the Y direction so as to pass therethrough.

In the figure, the laser beam Bo emitted from the laser oscillator 66 has a polarized light component (P-polarized light component) parallel to the paper of FIG. 5 and a polarized light component (S-polarized light component) perpendicular to the paper of FIG. The laser beam Bo output from the laser oscillator 66 is applied to the polarization splitting surface 8 of the beam splitter 70.
2 (see FIG. 6), the light is polarized and separated into two beams, and one S-polarized light component is reflected by its polarization separation surface 82 to become a reference beam Bx2.

The reference beam Bx2 is reflected by the reflection surface 84 of the beam splitter 70, passes through the λ / 4 plate 72, and enters the reflection surface 58a of the reference mirror 58. Reference mirror 58
The beam reflected by the reflection surface 58a of the
Through the beam splitter to become a P-polarized light wave,
Incident on. The P-polarized light wave incident on the beam splitter 70 passes through the polarization splitting surface 82 and is incident on the corner cube 80, is reflected twice in the corner cube 80, and is shifted by a distance L in the (-) Y direction in the figure. Thereafter, the process returns to the beam splitter 70. This light that has entered the beam splitter 70 transmits through the polarization splitting surface 82 and is reflected by the reflecting surface 84,
After passing through the λ / 4 plate 74, it is incident on the reflection surface 24 a of the reference mirror 24 as a reference beam Bx1. The reference beam Bx1 reflected by the reflecting surface 24a of the reference mirror 24 again passes through the λ / 4 plate 74 to become an S-polarized light wave, and the beam splitter 7
The light is reflected by the zero reflection surface 84 and the polarization separation surface 82 and enters the photodetector 68.

On the other hand, the P polarization component of the laser beam Bo is
The light passes through the polarization splitting surface 82 of the beam splitter 70 and becomes a measurement beam Bxm2. This length measuring beam Bxm2 is λ
After passing through the / 4 plate 76, reflected by the reflecting surface 28a of the movable mirror 28, and again passing through the λ / 4 plate 76, the light enters the beam splitter 70 as an S-polarized light wave. Beam splitter 7
The S-polarized light wave incident on 0 is reflected on the polarization separation surface 82 and is incident on the corner cube 80. Corner cube 8
The light incident on 0 is reflected twice in the light, and (-) in FIG.
After shifting by the distance L in the Y direction, the beam splitter 7
Return to 0. This light incident on the beam splitter 70 is
After being reflected by the polarization separation surface 82 and passing through the λ / 4 plate 78,
The beam is incident on the reflecting surface 28a of the movable mirror 28 as a measurement beam Bxm1. The measurement beam Bxm1 reflected on the reflection surface 28a of the movable mirror 28 transmits through the λ / 4 plate 78 again, becomes a P-polarized light wave, transmits through the polarization separation surface 82 of the beam splitter 70, and enters the photodetector 68. .

On the photodetector 68, the position of the substrate 10 on the optical axis A of the objective lens 14 in the X-axis direction is measured by detecting the interference fringes of the reference beam Bx1 and the measurement beam Bxm1. Can be. In addition,
In the Y-axis direction, position measurement is performed by the same configuration and operation.

In the two-beam interferometer system described above, as shown in FIG. 4, the distance Ly1 from the optical axis A of the objective lens 14 to the position where the laser beam Bx1 is incident on the reflecting surface 24a of the reference mirror 24 is defined as , The reflecting surface 58a of the reference mirror 58
Distance Ly2 to the position where the laser beam Bx2 is incident thereon
Are set to be equal. Therefore, the so-called Abbe principle can be satisfied, and the measurement accuracy is improved.
For example, when the objective lens 14 (lens barrel 14a) is slightly displaced about the optical axis A due to heat or mechanical error, the distance from the λ / 4 plate 72 to the reflection surface 58a of the reference mirror 58 and λ When one of the distances from the / 4 plate 74 to the reflection surface 24a of the reference mirror 24 decreases, the other increases. For this reason, the two reference mirrors 5 emitted from the laser oscillator 66
The optical path lengths of the beams reflected by the reflecting surfaces 58a and 24a of the light beams 8 and 24 and entering the photodetector 68 do not change. That is, the position of the substrate 10 can be measured based on the distance from the photodetector 68 to the optical axis A of the objective lens 14. Therefore, the measurement reliability is improved as compared with the embodiment shown in FIG.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and does not depart from the gist of the technical idea of the present invention shown in the claims. Various changes are possible within the scope.

[0041]

As described above, according to the present invention,
Even when the optical system (14, 14a) thermally expands or contracts, deviation of the reflection surface (24a) in the measurement direction can be minimized. As a result, it is possible to suppress a decrease in measurement accuracy of the measuring means (32) due to thermal deformation of the optical system (14, 14a).

[Brief description of the drawings]

FIG. 1 is a conceptual diagram (perspective view) showing a configuration of a pattern position measuring apparatus according to a first embodiment of the present invention.

FIG. 2 is an enlarged plan view showing a configuration of a main part (a reference mirror mounting member) of the pattern position measuring device shown in FIG.

FIG. 3 is an enlarged plan view showing a configuration of a main part (a reference mirror mounting member) of a pattern position measuring device according to a second embodiment of the present invention.

FIG. 4 is an enlarged plan view illustrating a configuration of a main part (a reference mirror mounting member) of a pattern position measuring apparatus according to a third embodiment of the present invention.

FIG. 5 is a plan view showing the operation and principle of the embodiment shown in FIG. 4;

FIG. 6 is a side view showing the operation and principle of the embodiment shown in FIG. 4, and corresponds to the plan view of FIG.

FIG. 7 is a schematic diagram (side view) showing a configuration of a conventional pattern position measuring device.

FIG. 8 is an enlarged plan view showing a configuration of a main part (a reference mirror mounting member) of a conventional pattern position measuring device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Substrate 12 ... Optical device 14 ... Objective lens 14a ... Lens barrel 16a, 16b, 18a, 18b ... Light receiving element 20 ... Stage 24, 26, 48, 50, 56 , 58... Reference mirrors 24a, 26a, 48a, 50a, 56a, 58a,.
Reflective surfaces 28, 30 Moving mirrors 32, 34 Interferometer body 44, 46, 52, 54, 60, 62 (reference mirror)
Mounting member 40: Main controller 53, 55: Two-beam interferometer A: Object lens optical axis Pa, Pb: Plane including optical axis A

Claims (6)

[Claims] 1. A position measuring device for measuring a relative displacement of an object to be measured with respect to an optical axis of a predetermined optical system, comprising a reflecting surface in a first plane including the optical axis of the optical system. A reflection member for use; a holding member supported at a position intersecting the first plane on the outer periphery of the optical system, for holding the reference reflection member with respect to the optical system; fixed to the measurement object A reflective member for measurement; and projecting light for measurement to the reflective member for reference and the reflective member for measurement, and using the light reflected by the reflective surfaces of the reflective member for reference and the reflective member for measurement, A position measuring device comprising: a measuring unit that measures a relative position displacement amount between an optical axis of an optical system and the measurement object. 2. The position measuring device according to claim 1, wherein a portion of said holding member which is in contact with an outer periphery of said optical system is formed in a shape symmetric with respect to said first plane. 3. The reference reflecting member includes a first reference mirror and a second reference mirror disposed at symmetric positions with the optical system in the first plane. Item 3. The position measuring device according to item 1 or 2. 4. The measuring means projects the light for measurement onto the first and second reference mirrors, and
4. The position measuring device according to claim 3, wherein the position measuring device is a two-beam interferometer using reflected light from a reference mirror. 5. The apparatus according to claim 4, wherein said measuring means sets the distance from said optical axis of said measuring light projected onto said first and second reference mirrors to be equal to each other.
The position measuring device according to item 1. 6. A pattern measuring apparatus for measuring a position of a pattern on a substrate mounted on a movable stage using first light irradiated through an objective lens, wherein the optical axis of the objective lens A reference reflection member having a reflection surface in a first plane, the reference reflection member being supported at a position intersecting the first plane on the outer periphery of the objective lens, and the reference reflection member being positioned relative to the objective lens. A holding member for holding; a reflection member for measurement fixed to the substrate; and a light beam for measurement projected on the reflection member for reference and the reflection member for measurement.
Measuring means for measuring a relative positional displacement between the optical axis of the objective lens and the substrate by using light reflected by the reflecting surfaces of the reference reflecting member and the measuring reflecting member. And a pattern measuring device.