JPS62150106A - Apparatus for detecting position - Google Patents

Abstract

PURPOSE:To enable the detection of a position with high accuracy, by mounting a synthesizing optical system for synthesizing luminous flux returned from a reference reflective member through a movable reflective member and luminous flux returned from a fixed mirror on the same light path to allow both luminous fluxes to interfere with each other. CONSTITUTION:Because an equilateral triangle having three points, that is, a center point OS and points theta1, Y1 as apexes is determined so that the distance from the center point OS to the point theta1 is equal to that from the center point OS to the point Y1, the displacement of the point theta1 and that of the point Y1 in an XB-axis direction are directed reversely to each other and equal in magnitude. The displacement quantity detected by the receiver 36 of a theta-axis interferometer comes only to the movement quantity DELTAya on the line l1 of the point theta1 and the displacement quantity detected by the receiver 37 of a Y-axis interferometer comes only to the movement quantity DELTAyb on the line l2 of the point Y1 and the displacement quantity detected by the receiver 38 of an X-axis interferometer comes only to the movement quantity DELTAx on the line l3 of a point X1. In thus constituted interferometers of three axes, the displacement quantities of the points theta1, Y1 in a YB-axis direction and the displacement quantity of the point X1 in the XB-axis direction can be accurately measured, independently.

Description

Detailed Description of the Invention (Technical Field of the Invention) The present invention relates to a mask ( Reticle) or wafer position detection device.

(Background of the Invention) In recent years, the degree of integration and miniaturization of semiconductor devices (particularly VLSI) have improved dramatically, and the functions and precision required of exposure equipment for manufacturing these devices have become stricter year by year. There is. In particular, reduction (or equal magnification) projection exposure equipment uses a projection lens to focus an image of a circuit pattern formed on an original plate called a reticle onto a local area on a photosensitive substrate (a wafer coated with photoresist) for exposure. It is something.

In this case, if the area of the image that can be transferred in one exposure is small compared to the size of the entire surface of the wafer, the wafer may be placed and
A wafer stage that moves dimensionally is provided, and the wafer stage is moved in a step-and-repeat method to transfer a circuit pattern image on a reticle. Generally, in the manufacture of semiconductor devices, patterns of several to more than ten layers are accurately overlaid and exposed on a wafer.
In the step-and-repeat method, relative alignment with the circuit pattern image is achieved for each area to be exposed on the wafer, so uniform overlay accuracy can be obtained over the entire wafer. At this time, alignment after stepping between the circuit pattern already formed on the wafer and the circuit pattern image on the reticle is performed by adjusting the position of the wafer stage using a high-resolution (for example, 0.02 μm) laser beam interferometer If the wafer stage is detected using an interferometer, this can be done by slightly moving the position of the wafer stage. Alternatively, after stepping, the reticle can be aligned by slightly moving the position of the reticle stage holding the reticle. In either method, the X-axis direction and y-axis direction of the orthogonal coordinate system defined by the laser interferometer on the wafer stage side
Alignment is performed in the axial direction with the resolution of an interferometer, but in particular, in the method of finely moving the reticle, by slightly rotating the reticle, it is possible to eliminate relative rotation errors between the exposed area on the wafer and the circuit pattern image. Highly accurate correction can be made for each exposure shot.

Micro-movement of the reticle stage is achieved by detecting the relative amount of deviation between the alignment mark on the reticle and the alignment mark on the wafer, and moving the reticle stage by that amount of deviation. This method can be roughly divided into a so-called close control method in which the reticle stage is servo driven based on a corresponding signal. In either case, a sensor is required to read the position of the reticle stage, but a highly accurate sensor is especially essential for open control. It is conceivable to use a laser interferometer as this sensor in the same way as for detecting the position of the wafer stage. In this case, if a movable mirror with reflective surfaces extending in the X direction and the X direction is placed above the reticle stage in the same way as the wafer stage, highly accurate position detection of the reticle stage is immediately possible.

However, with this method, if the reticle stage rotates slightly, the laser beam from the interferometer may not return along the predetermined optical path (
Therefore, position detection becomes impossible. Therefore, we added some innovation to the structure of the reticle stage, and installed a θ table that rotates minutely on the XY stage that moves in parallel only in the X direction and the X direction.
Another possible method is to measure the position of the stage with an interferometer and measure the amount of rotation of the θ table with another rotary encoder or the like. However, such a configuration requires an XY stage and a θ table, making the structure complicated. Further, the amount of rotation of the θ table is only measured based on the XY stage, and is not the amount of rotation with respect to the absolute coordinate system of the apparatus. Therefore, even if the XY stage itself rotates by a minute amount with respect to the absolute system, it is impossible to detect the rotation.

(Objective of the Invention) It is an object of the present invention to solve the above-mentioned drawbacks and to obtain a position detection device capable of detecting the absolute position of a substrate such as a reticle, including rotation, using a light wave interferometer.

(Summary of the Invention) The configuration of the present invention for achieving the above object is as follows. A movable reflecting member (perpendicular mirror 21:23
:25). This movable reflective member has two reflective surfaces (21a, 21b: 23a, 2
3b: 25a, 25b) are formed, and the two reflecting surfaces thereof are formed at right angles. One reflective surface of this movable reflective member and a fixed mirror (2
A light transmitting optical system (laser light source 18, beam splitter 30.3) that makes a coherent parallel light flux (laser light fluxes LB, , LB, LB3) incident on the
1.42, mirror 26.32.33.34),
A reference reflecting member (beam splitter 20
Reflective surface 2+b formed in a part of :22:24:22b
:24b), a light beam returning from the reference reflecting member via the movable reflecting member, and a light beam returning from the fixed mirror into the same optical path and interfering with each other. 22:24 split surfaces 20a:22a:24a) are provided.

Then, by receiving the emitted light beam from the combining optical system with an interferometer receiver, the change in the position of the intersection point (θ+ : Y+ : It was configured to be able to detect only the direction.

(Embodiment) FIG. 2 is a perspective view showing a schematic configuration of a projection exposure apparatus according to a first embodiment of the present invention.

In Figure 2, a light wave interference length measuring device (hereinafter referred to as an interferometer)
Only the basic systems necessary for this are shown. The reticle stage 1 places the reticle R in parallel within a predetermined orthogonal coordinate system XA, YA, and moves it two-dimensionally (X direction, Y direction, and rotational direction). A circuit pattern, etc. on the reticle R is illuminated with illumination light from an illumination optical system (not shown), and the pattern is imaged and projected onto the wafer W by the projection lens 2. Wafer W
is placed on the wafer stage 3, and the orthogonal coordinate system XA.

Moved two-dimensionally within YA.

A movable mirror 4a with a reflective surface extending in the X direction and a movable mirror 4b with a reflective surface extending in the Y direction are fixed to two sides of the wafer stage 3. After the parallel laser beam from the laser light source 5 is split into two, each beam splitter 6.
7. Beam splitter 6 splits the laser beam into 2
One is incident perpendicularly to the reflective surface of the movable mirror 4a,
The other laser beam is perpendicularly incident on the reflecting surface of a fixed mirror 8 fixed to the lower end of the lens barrel of the projection lens 2 (at a position close to the wafer stage 3). The reflected light flux from the movable mirror 4a and the reflected light flux from the fixed mirror 8 enter the beam splitter 6 again, and the two reflected light fluxes are combined coaxially and enter the receiver 9 of the interferometer. The receiver 9 photoelectrically detects changes in interference fringes. Similarly, the beam splitter 7 splits the laser beam into two parts, one of which is perpendicularly incident on the reflective surface of the movable mirror 4b, and the other laser beam is incident on the fixed mirror 10 fixed to the lower end of the lens barrel of the projection lens 2. It is incident perpendicularly to the reflecting surface. The reflected light flux from the movable mirror 4b and the reflected light flux from the fixed mirror 10 enter the beam splinter again, and the two reflected light fluxes are combined coaxially and enter the receiver 11 of the interferometer. The receiver 9 detects a change in the position of the stage 3 in the YA direction, and its measurement axis (for example, the center line of the laser beam) is arranged to be perpendicular to the optical axis AX of the projection lens 2. Further, the receiver 11 is for detecting a change in the position of the stage 3 in the XA force direction, and its measurement axis is similarly arranged to be orthogonal to the optical axis AX.

Further, it is arranged so that a plane including the two measurement axes substantially coincides with the projection image plane of the projection lens 2. The two measurement axes are perpendicular to each other on the optical axis AX and constitute a coordinate system XA, YA.

On the other hand, the two-dimensional position (including rotation) of the reticle stage 1 is also detected by the laser interferometer.

The parallel laser beam from the laser light source 18 is first split into two, and one of the laser beams is sent to the beam splitter 2.
0, and the other laser beam is further divided into two. One of the divided laser beams enters the beam splitter 22, and the other laser beam undergoes a predetermined optical path routing and enters the beam splitter 24. The laser beam incident on the beam splitter 20 is divided into two parts; one laser beam is incident on a right-angle mirror 21 fixed to the reticle stage l, and the other laser beam is incident on a prism mirror 26 parallel to the optical axis AX. After being reflected, the light beam is bent horizontally again and is perpendicularly incident on the reflection surface of a fixed mirror 27 provided at the upper end of the lens barrel of the projection lens 2 (a position close to the reticle stage 1). Further, the laser beam incident on the beam splitter 22 is divided into two parts, one laser beam is incident on a right angle mirror 23 fixed to the reticle stage 1, and the other laser beam is parallel to the optical axis AX by a prism mirror 26. After being reflected, the light is bent horizontally again and enters the reflection surface of the fixed mirror 27 perpendicularly. Furthermore, the laser beam incident on the beam splitter 24 is also divided into two,
One laser beam enters a right-angle mirror 25 fixed to the reticle stage 1, and the other laser beam is bent so as to be parallel to the optical axis AX, then horizontally, and then bent at the upper end of the lens barrel. The light is incident perpendicularly to the reflecting surface of a fixed mirror 28 fixed to the fixed mirror 28 . Note that the reflective surface of the fixed mirror 27 and the reflective surface of the fixed mirror 28 are determined to be orthogonal to each other, and the reflective surface of the fixed mirror 27 is aligned with the XA axis of the coordinate system XA, YA and the optical axis AX.
The reflecting surface of the fixed mirror 28 is parallel to the plane containing YA
It is parallel to the plane containing the axis and the optical axis AX.

Here, the configuration of the interferometer around the reticle stage 1 will be explained in more detail using FIG.

In FIG. 1, quarter wavelength plates and the like necessary for interference are omitted. FIG. 1 shows a state in which the reticle R is placed on the reticle stage 1 with slight rotation.
It is assumed that is not rotated within the orthogonal coordinate system XA, YA. In Figure 1, 30.31 is a beam splitter, 32.33.34 is a mirror, and 36.
．． 37 and 38 are receivers (photoelectric detection units) for interferometers, respectively. Here, set the center point of reticle stage 1 to O8
Then, when the reticle stage 1 is in the neutral position with respect to the XA force direction and the YA force direction, the optical axis AX is determined to pass through the center point O8. In addition, in Figure 1, there are two alignment marks R+ on the reticle R.
Rz are provided at known intervals. This mark R...
The marks W, , W, corresponding to R2 are provided within one exposed area on the wafer W, and are located on the projection lens 2.
It is assumed that the image is back-projected onto the reticle R side via the .

Now, the laser beam LB reflected by the beam splitter 30
, are incident on the split surface 20a of the beam splinter 20 as a combining optical system in parallel to the coordinate system XA and YAOYA axes defined by the measurement axes of the interferometer on the wafer stage 3 side. The laser beam transmitted through the splitting surface 20a is reflected at a substantially right angle by the first reflecting surface 21a of the right-angle mirror 21, and then further reflected by the second reflecting surface 21b. incident on . The reflective surface 20b is arranged to intersect perpendicularly to the laser beam LB. Furthermore, the angle formed by the first reflecting surface 21a and the second reflecting surface 21b of the right-angle mirror 21 is exactly 9.
0', and constitutes a so-called corner reflector. The intersection of the reflecting surfaces 21a and 21b is set at O1.

Therefore, the laser beam from the beam splitter 20 is perpendicularly incident on the reflecting surface 20b due to the minute rotation of the right-angle mirror 21 due to the rotational displacement of the reticle stage 1, and returns along the original optical path. And reflective surfaces 20b, 21b, 21a
The laser beam that has been reflected and returned in the order of
6. On the other hand, the laser beam is LB, of which the laser beam reflected by the splint surface 20a travels through the beam splitter 20, enters the fixed mirror 27 via the prism mirror 26 as shown in FIG. It is reflected and returns to the prism mirror 26 again, and the beam splitter 20
The light passes through the split surface 20a and enters the receiver 36. In this way, the return light beam from the right-angle mirror 21 as a movable reflecting member fixed to the reticle stage 1 and the return light beam from the fixed mirror 27 are coaxially combined and incident on the receiver 36. Interference fringes are generated on the surface, which flicker as the right-angle mirror 21 moves. The length measurement amount detected by this receiver 36 is the position θ
1 laser beam LB, in the light transmission axis direction, that is, the coordinate system X
A, the amount of movement only in the YAOYA axis direction.

Similarly, the laser beam LB reflected by the beam splinter 31 passes through the split surface 22a of the beam splinter 22, and then passes through the first reflection surface 23a and the second reflection surface 23a of the right-angle mirror 23.
The light is reflected by the reflective surface 23b and enters the reflective surface 22b formed on a part of the beam splitter 22. Laser beam L
B2 is also parallel to the YA axis, and the reflective surface 22b is arranged perpendicular to the optical path axis of the laser beam LB. The angle formed by the reflecting surfaces 23a and 23b of the right-angle mirror 23 is formed to be exactly 90', and the intersection thereof is determined at the position Y1. Therefore, regardless of the slight rotation of the right-angle mirror 23, the laser beam enters the reflecting surface 22b perpendicularly and returns along the original optical path. Therefore, the reflected light beam from the fixed mirror 27 is incident on the receiver 37 via the prism mirror 26 and the split surface 22a, and the reflected light beam from the reflection surface 22b is also incident thereon. The length measurement amount that is 1 by this receiver 37 is the amount of movement of the position Y1 only in the YA axis direction.

Further, the position θ1 and the position Y1 are in the coordinate system XA when the reticle stage 1 is not rotating.

It is determined at a point that is equally divided into two in the X direction by the YAOYA axis. The measurement axis of the θ-axis interferometer composed of the beam splinter 20 and the receiver 36 is the center line of the laser beam LBI, or a line passing through the position θ1 and parallel to the laser beam LB, which corresponds to the coordinate system XA, YAOYA axis. is parallel to Furthermore, the measurement axis of the Y-axis interference needle composed of the beam splitter 22 and the receiver 37 is a line that passes through the center line of the laser beam L B t or the position Y and is parallel to the laser beam LB, which is also the YA axis. parallel. What is important in this embodiment is that the Y-direction measurement axis virtually exists at the center of the measurement axis of the θ-axis interferometer and the measurement axis of the Y-axis interference needle. This virtual measurement axis is reticle stage 1.
Cartesian coordinate system X defined by an interferometer for position detection of
This is the YB axis of B, YB.

Of the laser beams from the laser beam 418, the laser beam LBs that is reflected by the mirrors 32 and 33 and enters the beam splitter 24 is in the coordinate system XA.

It is parallel to the YAOXA axis. The laser beam transmitted through the split surface 24a of the beam splitter 24 is directed to the right angle mirror 2.
reflected by the first reflective surface 25a and the second reflective surface 25b of 5,
Reflection surface 24b formed in a part of beam splitter 24
is incident perpendicularly to The intersection between the reflective surfaces 25a and 25b is determined at a position X1, and this position X1 is determined to coincide with the XB axis of the coordinate system XB, YB. The laser beam LB reflected by the splitting surface 24a of the beam splitter 24 is reflected downward by the mirror 34 and is directed toward the fixed mirror 28. The reflected light flux from the fixed mirror 28 is returned to the mirror 3.
4, and is transmitted through the split surface 24a and enters the receiver 38. At the same time, the laser beam vertically reflected by the reflective surface 24b is reflected by the reflective surfaces 25b and 25a, further reflected by the splint surface 24.3, and enters the receiver 38.

This receiver 38 detects position X and the amount of movement only in the OXB axis direction. The beam splitter 24 and receiver 38
The measurement axis of the X-axis interference needle is a line parallel to the laser beam LB passing through the position X, which is the coordinate system XB.
, the XYOXB axes.

Now, FIG. 3 is a sectional view of the device shown in FIG. 2 taken along a plane including the optical axis AX and the XA axis (or XB axis). The reticle stage 1 is mounted on a bearing 4 on an interferometer holding column 40.
1 and is movable in all directions in the horizontal plane. The holding column 40 has each optical member (
(including the receiver) are fixed. In FIG. 3, the beam splitter 24 and mirror 32 are shown as representatives. A motor drive section 42 is located below the interferometer mounting section of the holding column 40.
is fixed, and its drive is converted into reciprocating motion of the threaded part,
It is transmitted to the reticle stage 1 via the connecting rod 43.

Three motor drive units are arranged independently corresponding to each of the three axes of interferometers, and their drive points are at positions θ, , Y, , and X in this embodiment.

, and gives the reticle stage l movement in the direction of the measurement axis of the interferometer for each axis. Note that the position of this driving point is not particularly limited.

Now, the projection lens 2 is held on a pedestal 45a of a lens holding column 45 constructed on a base plate 44. A flange portion 2a is formed around the lens barrel of the projection lens 2 to be placed on a pedestal 45a. The wafer stage 3 is placed on the base plate 44 so as to be movable in two dimensions. The above-described interferometer holding column 40 is placed on top of the holding column 45 with a washer 46 interposed therebetween. This washer 46 is used to adjust the distance between the reticle R and the wafer W to the projection lens 2.
This is to adjust it accordingly. Also washer 46
are provided at multiple locations around the projection lens 2, and by delicately adjusting the thickness of each washer, the projection image plane of the projection lens 2 and the surface of the wafer W can be made precisely parallel. In Fig. 3, the laser beam L B s
Although only the laser beams LB, , LB2 are shown,
, and LB3 are both located in the same horizontal plane perpendicular to the optical axis AX, and this horizontal plane is determined to coincide as much as possible with the pattern surface of the reticle R, that is, the reticle mounting surface of the reticle stage 1. When detecting marks R, R2, etc. formed on the pattern surface of the reticle R with an alignment microscope (not shown), the marks R+, R2, etc. are made to satisfy Abbe's principle for the pattern surface. This is to reduce the Atsube error to zero when detecting the position of Rg.

It should be noted that each of the three-axis interferometer systems on the reticle side shown in FIGS. 1, 2, etc. is a double-pass system that can obtain higher resolution than a so-called single-pass system.

In addition, the beam splitter 20.22 as a combining optical system
．． 24 has reflective surfaces 20b and 22b as reference reflective members.
, 24b are integrally formed to ensure long-term stability of the optical system.

Furthermore, beam splitters 20 and 22 may be constructed from the same material. By doing this, the Y axis between the θ-axis interferometer and the Y-axis interference needle
Relative position adjustment in the B force direction is not required, making manufacturing easier.

Next, the operation of this embodiment will be described. However, since the operation of the interferometer on the wafer stage side is well known, the explanation will be omitted, and the operation of the interferometer on the reticle stage side will be explained only.

First, when the reticle stage 1 is in the neutral position (a state in which there is no positional shift in the X direction, the X direction, and the rotational direction) as shown in FIG.
The situation when moving only in the direction of the XB axis of YB will be described. In this case, since the position X4, that is, the right angle mirror 25 moves in the XB axis direction, the optical path length of the laser beam from the splitting surface 24a of the beam splitter 24 to the reflecting surface 24b naturally changes. This amount of change is determined by the receiver 38
It is detected as the amount of directional movement. On the other hand, for the right angle mirrors 21 and 23, the laser beams LB+ and LBz
Therefore, from the optical properties of the right-angle mirrors 21 and 23, the optical path length from the split surface 20a to the reflective surface 20b and the optical path length from the splint surface 22a to the reflective surface 22b are both Unchanging. Therefore, the amount of displacement in the YB axis direction of the position θ1 detected by the receiver 36 and the YB axis direction of the position Y1 detected by the receiver 37 are
Both displacement amounts in the B-axis direction are zero.

Furthermore, when the reticle stage 1 moves only in the YB-axis direction, the amount of movement detected by the receiver 38 is zero due to the optical properties of the right-angle mirror 25, and the amount of movement detected by the receivers 36 and 37 is zero. Both have the same value.

Next, reticle stage 1 is in the neutral position and the center point O
The case of rotation by Δθ about 8 will be explained with reference to FIG. FIG. 4 is a plan view showing changes in the optical path of each three-axis interferometer. Reticle stage 1 is in the coordinate system
It is assumed that the rotation is made in the counterclockwise direction by Δθ within B and YB. 1" represents the position of the reticle stage when there is no rotation. As is clear from FIG. 3, the position θ.

(hereinafter referred to as point θ1) is X with respect to the neutral position
While being displaced in the positive direction of the B axis and the positive direction of the YB axis, the right angle mirror 21 is also displaced as if rotated counterclockwise by Δθ around point θ1. The position Y (hereinafter referred to as point Y) is displaced in the positive direction of the XB axis and the negative direction of the YB axis, and the right-angle mirror 23 is displaced by Δ around point Y.
Displaced as if rotated counterclockwise by θ. At position XI (hereinafter referred to as point X), the right angle mirror 2 is displaced in the positive direction of the XB axis and the negative direction of the YB axis.
5 is displaced as if rotated counterclockwise by Δθ around point XI. In this example, the distance from center point O8 to point θ1 is equal to the distance from center point O3 to point Y1, which is defined as an isosceles triangle whose vertices are center point O8, point θ1, and Yl. Therefore, the displacements of points θ and Y in the XB axis direction are the same in direction and magnitude, and the displacements in the YB axis direction are opposite to each other and have the same magnitude. Here point θ.

Let the line passing through point Y and parallel to the YB axis (or laser beam LB+) be l, the line passing through point Y and parallel to the YB axis (or laser beam LB) be ρ2, and the line passing through point
If a line parallel to the B-axis (or the laser beam LB3) is l, then the amount of displacement detected by the receiver 36 of the θ-axis interferometer is only the amount of movement Δya of the point θ1 on the line 7!1, The amount of displacement detected by the receiver 37 of the interference needle is only the amount of movement Δyb on the line 12 of the point Y, and the amount of displacement detected by the receiver 38 of the X-axis interference needle is the amount of displacement Δyb at the point Y,
The only amount of movement ΔX (not shown in FIG. 4 as it is a minute amount) is on the line 23. In this example, Δya and Δyb
and have the same size.

Further, as shown in Fig. 4, when the reticle stage 1 moves in parallel to the XB force direction and the YB force direction while rotating by Δθ, θ
The difference between the measured value of the axis interferometer and the measured value of the Y-axis interference needle does not change.

As described above, in the three-axis interferometer configured as in this embodiment, the amount of displacement of points θ1 and Yl in the YB axis direction and the amount of displacement of point
The amount of displacement in the B-axis direction can be accurately measured independently. Therefore, the point θ+ required to correct the rotation of 80
, '1'+, and the moving direction and amount of XI are uniquely determined. In other words, the point θ is equal to the amount measured by each interferometer.
For 1 and Y, it is sufficient to give movement in the YB force direction,
Point Xl only needs to be moved in the XB force direction, and the moving direction of each point θ+, YI, and XI may always be constant regardless of the amount of rotation Δθ. Furthermore, if the YB force direction position of points θ1 and Y and the XB force direction position of point LB+, L
Since the arrangement relationship between Bz and LB3 remains unchanged, the required amount of rotation of the reticle stage 1, that is, the point θ+
, Y1% The coordinate values of the position where Xl should exist can be determined by simple calculation on the order of the resolution of the interferometer (for example, 0.02 μm).

Note that due to the optical properties of the right-angle mirrors 21, 23, and 25, even if each right-angle mirror rotates around points θ1, YI, and Xl, the optical path length of the laser beam does not change at all. Further, while each right-angle mirror continues to rotate, lines 21, 12 .
23, the optical path length does not change at all.

By the way, as shown in FIG. 1, the mark W on the wafer Wl
1. The two-dimensional deviation of the marks R+ and Rz on the reticle R with respect to W2 is the XB force direction ΔX, the YB force direction Δy,
Then, if ε rotated by Δθ in the rotation direction is found using an alignment HJm mirror (not shown), mark R3
The alignment of overlapping the marks R2 and W1 and the marks R2 and W2 can be performed at high speed based only on the measured amounts of the three-axis interferometers. Or the amount of deviation ΔX and Δ
y may be corrected by the wafer stage 3, and only the rotation of the reticle R may be corrected by the reticle stage l. In this case, it is only necessary to provide two axes: a θ-axis interferometer and a Y-axis interference needle.

Also, as is clear from Figure 4, reticle stage 1
Due to the rotation of , the center line that exists parallel between km 6 + and 12 shifts from the YB axis in the XB force direction, and the measurement axis (
YB axis) does not pass through the optical axis AX, but the rotation amount becomes small if the amount of rotation of the reticle stage 1 is small. Furthermore, if the center line existing parallel to the center between the laser beams LB and LB2 is considered as the measurement axis, this always coincides with the YB axis and remains unchanged. However, in both cases, the measurement axes of the θ-axis interferometer and the Y-axis interference needle are always parallel to the XA and YAOYA axes of the coordinate system on the wafer stage 3 side, and the line β3 (measurement axis) of the X-axis interference needle is also It is always parallel to the coordinate system XA and YAOXA axes. That is, the measurement axis of the interferometer on the reticle side is always kept in the same direction as the absolute system (coordinate system XA, YA) regardless of the rotation of the reticle stage 1.

As described above, in this embodiment, it is assumed that the measured values of the coordinate systems XA, YA on the wafer side and the coordinate systems XB, YB on the reticle side are correlated in advance, but the work of correlating them is also easy. For that, there is a mark W on the wafer on the wafer stage 3,
, a fiducial mark with the same shape as WZ is provided, and the reticle mark R is created by running this fiducial mark.
What is necessary is to detect the position of the wafer stage 3 when each of R1 and R2 is superimposed on the reference mark, and compare that position with the measured values of each interferometer of the three axes. Also, when placing the reticle R on the reticle stage 1 and aligning the reticle R with the device, each three-axis interferometer and the reference mark on the wafer stage 3 are used to achieve accuracy determined by the resolution of the interferometer. The positioning of the reticle R is achieved in this step.

Furthermore, in this embodiment, the vertices θI and YI% It's okay. Further, the position of the driving point of the reticle stage 1 does not need to be near the points θ, , Y, , X, either.

For example, the reticle R may be placed on an XY stage similar to the wafer stage 3 via a θ table as in the prior art. In this case, the XY stage has a coordinate system XA, YB (
The θ table is configured to move only in the direction of the coordinate axes (XB, VB), and rotate within the horizontal plane on the XY stage.
The right angle mirrors 21, 23, 25 are fixed to the θ table.

Now, FIG. 5 is a plan view showing the configuration of a position detection device according to a second embodiment of the present invention. This embodiment is applied to detecting the position of a mask in an X-ray exposure apparatus, etc., and the mask is held on a θ table 100 via a leveling stage (not shown). The θ table 100 is provided on an XY stage (not shown) so as to be minutely rotatable. Furthermore, an opening 100a is formed in the θ table 100 so as not to shield the pattern PT on the mask from X-rays.

Coordinate systems XA and YA in FIG. 5 are coordinate systems for movement of the wafer placed under the mask in proximity.

The normal line established at the origin C of the coordinate system XA, YA is
It is determined to pass through the xbi generation point of the X-ray source. The mask also has alignment marks MY, MX, Mθ.
are provided, and marks MY and Mθ are both used for YA force direction alignment, and mark MX is used for XA direction alignment. These marks are originally determined to be located on the XA and YA axes.

Also in this embodiment, three right angle mirrors 21.2
3.25 is provided integrally with the θ table 100. and θ
When the table 100 and the XY stage are in the neutral position, the intersection θ1 of the two reflective surfaces of the right-angle mirror 21
and the intersection point Y, or XA of the two reflective surfaces of the right-angle mirror 23.
It is configured so that it is located on the wheel axis, and the measurement axis of the θ-axis interferometer and Y
Make both the measurement axis of the axis interference needle parallel to the YA axis. In addition, points θ and Y are assumed to be at equal distances from the origin C6.Similarly, the intersection point X of the two reflective surfaces of the right-angle mirror 25 is configured to be located on the YA axis, and the X-axis interference The measurement axis of the needle is parallel to the XA axis. In addition, in FIG. 5, the arrangement of the optical system of the Y-axis interference needle is omitted, and the beam splitter 42
numeral 41 separates the light beam from the laser light source into two, laser light beams LB and LBz, and 41 is a fixed mirror block provided at the fixed part of the device.

In this embodiment, the relative rotational error between the pattern PT and the pattern on the wafer is detected using an alignment microscope using the marks MY and Mθ. The amount of rotational error is converted into the amount of deviation in the YA force direction between the point Y1 and the point θ1, and the θ table 100 may be rotated about the origin C by the amount of deviation.

Of course, by slightly moving the XY stage, the θ table can be adjusted to 100.
Since the interferometers move together, the measured values of each interferometer on the three axes also change accordingly.

Although two embodiments of the present invention have been described above, the present invention can be similarly implemented in the case of detecting the rotation of the θ table provided on the wafer stage 3.

Further, the present invention allows highly accurate position detection without being affected by the yawing of the stage even when detecting the position of a stage that originally moves only in the -dimensional direction. To do this, in the reticle stage shown in FIG. 1 or 4, an arrangement such as the right-angle mirror 25 may be employed to detect the position of the stage in the XB force direction. If yawing is also to be detected, an arrangement like the right-angle mirrors 21 and 23 shown in Fig. 1 is used.
What is necessary is to detect the position of the stage in the YB force direction. In this case, the one-dimensional movement stroke of the stage can be quite large.

(Effects of the Invention) According to the present invention, a double-pass interferometer system is constructed using a right-angle mirror as a movable mirror that moves together with the stage, so even if the stage is rotated, the direction of the measurement axis remains unchanged. Highly accurate position detection is possible without any change. Furthermore, since the measurement points for detecting the position of the stage are limited to the intersections of the right-angle mirrors in the orthogonal coordinate system, the positioning control of the stage is also facilitated.

Furthermore, according to the embodiment, right-angle mirrors are provided at two different locations on the stage to configure an interferometer system with at least two axes, so rotational errors during alignment between the pattern on the reticle (mask) and the pattern on the wafer are reduced. It has the advantage of being simple and highly accurate in detection, and rotation correction can be controlled quickly and precisely. Therefore, improvements in overlay accuracy and servoput can be achieved at the same time.

[Brief explanation of drawings]

FIG. 1 is a plan view showing the configuration of a light wave interferometer system as a position detection device according to a first embodiment of the present invention, and FIG. 2 is a schematic diagram of a projection exposure apparatus having the light wave interferometer system of FIG. FIG. 3 is a cross-sectional view of the apparatus shown in FIGS. 1 and 2 taken along a plane including the optical axis; FIG. 4 is a plan view illustrating the operation of the optical interferometer system on the reticle stage side. , FIG. 5 is a plan view showing the configuration of a position detection device according to a second embodiment of the present invention. [Explanation of symbols of main parts] 1----Reticle stage, 2-111 projection lens 3---Wafer stage 6.7---Beam splinter 8.10----1 Fixed mirror, 9 .11---Receiver 20.22.24---Beam splitter 21.2
3.25---One right angle mirror 27.28---One fixed mirror

Claims (2)

[Claims] (1) A stage that holds a substrate and moves the substrate two-dimensionally, including rotation, within a predetermined orthogonal coordinate system; and an optical interference length measurement device that detects the amount of displacement of the stage with respect to a predetermined reference position. an apparatus having at least two reflecting surfaces arranged to move integrally with the stage and substantially perpendicular to a coordinate plane according to the orthogonal coordinate system, and an angle formed by the two reflecting surfaces is determined to be a right angle. a movable reflective member;
a light transmitting optical system that makes a coherent parallel light beam enter one reflecting surface of the movable reflecting member substantially parallel to the coordinate plane and also makes it incident on a fixed mirror fixed at a predetermined position of the device; the movable reflecting member a reference reflecting member that reflects the light beam emitted from the other reflecting surface of the movable reflecting member and returns it to the light transmitting optical system via the two reflecting surfaces of the movable reflecting member;
a combining optical system for combining the light beam returning from the reference reflecting member via the movable reflecting member and the light beam returning from the fixed mirror into the same optical path and causing interference; A position detection device that measures length by photoelectrically detecting. (2) The movable reflective member is provided at two different locations on the stage, the reference reflective member and the synthetic optical system are arranged with respect to each of the two movable reflective members, and The present invention is characterized in that two interferometer receivers that separately receive emitted light beams are provided, and the amount of rotational displacement of the stage can be detected based on the measured values of the two interferometer receivers. The device according to scope 1.