JPH11241909A - Alignment method and apparatus for exposure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the precision of positioning of a stage by almost simultaneously measuring the curving degrees of reflecting faces of both plane mirrors by using especially installed two θ interferometers, computing the difference of both measured values, and carrying out correction. SOLUTION: Two θ interferometers XθI, YθI are installed for finding the inclination of a local part of reflecting faces to respective plane mirrors for the x-direction and the y-direction and the yawing of the respective plane mirrors (that is stages ST) is measured by simultaneously using these two θinterferometers. Consequently, when the stage ST is moved in one dimension in the x-direction or the y-direction, the addition degree of the curved degree of the plane mirror itself and the yawing degree of the stage is measured by one θ interferometer and only the yawing degree is measured by the other θ interferometer. The curved degree of the plane mirror itself is obtained by calculating the measured value of the two θ interferometers. The obtained curved degree of the plane mirror is stored in a memory and the coordinate position of the stage ST detected in measuring the position or positioning is corrected corresponding to the curved degree, so that the precision as high as that obtained in the case of using an ideal reflecting plane as a plane mirror can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring the position of a stage which moves two-dimensionally in a plane, and more particularly to a method and an apparatus for placing an object on a stage and positioning it two-dimensionally. In particular, measurement that requires extremely high accuracy, such as processing and inspection of semiconductor devices,
Related to positioning technology.

[0002]

2. Description of the Related Art Various exposure apparatuses (steppers and the like) used for pattern transfer of VLSI, drawing apparatuses for transfer masks,
In a mask pattern position coordinate measuring apparatus or other positioning apparatus, an XY stage that holds an object and moves precisely in two orthogonal (X, Y axis) directions is used. To measure the position coordinates of the XY stage,
An optical interferometer (laser interferometer) using a He-Ne frequency-stabilized laser that continuously oscillates at a wavelength of 633 nm as a light source is used. As a commercially available interferometer, Hewle
The products of tPackard, Excel and Zaigo are known. Since a laser interferometer can essentially only perform one-dimensional measurement, two identical laser interferometers are prepared for two-dimensional coordinate measurement. And on the XY stage,
By fixing two plane mirrors whose reflecting surfaces are substantially orthogonal to each other, projecting a beam from a laser interferometer on each of the two plane mirrors and measuring the vertical distance change of each reflecting surface, the two-dimensional stage A coordinate position is determined. Each reflecting surface of the two plane mirrors extends in the x direction and the y direction in accordance with the required movement stroke of the stage. Since such a plane mirror serves as a reference for coordinate measurement, its reflecting surface is required to have extremely high flatness.

The measurement resolution of a laser interferometer is 0.01 μm
The length of the reflecting surface of the plane mirror needs to be about 250 mm in the case of a stage on which a 6-inch semiconductor wafer is mounted. That is, when the 250 mm reflecting surface is totally inclined, partially curved, or has local irregularities, if the amount is 0.01 μm or more, it is measured by the laser interferometer. It means being taken in. Therefore, assuming that the plane mirror is bent by 0.05 μm, the position measurement or positioning of the stage is performed according to a curved (or oblique) coordinate system bent from an ideal rectangular coordinate system by 0.05 μm.
For this reason, the plane mirror is manufactured to be as flat as possible, but irregularities of about 0.02 μm remain due to manufacturing errors. In this way, the total of 0.2 mm for the entire reflecting surface of 250 mm.
The accuracy of having only the unevenness of 02 μm means that the yarn horizontally stretched between two points 100 km apart is only 0.2 mm in the middle.
It is only about 8 cm.

[0004] Of course, depending on the processing method of the plane mirror, etc., it is possible to obtain a higher precision, but the manufacturing cost is significantly increased, and the distortion when actually fixed to the two-dimensional moving stage, Due to subsequent changes over time,
It is impossible to maintain a flatness of 0.02 μm or less. Therefore, it is conceivable to measure the bending (concavity and convexity) of the plane mirror fixed on the moving stage by using a reference plane mirror serving as a reference (a prototype). In this case, a reference plane mirror having substantially the same shape as the plane mirror to be measured is placed on the stage substantially parallel to the plane mirror to be measured, and the beam from the interferometer is vertically projected on each of the plane mirror to be measured and the plane mirror to be measured. That is, the amount of bending of the measured plane mirror with respect to the reference plane mirror is determined from the distance change value obtained by causing the reflected beam to interfere.

[0005]

In the method using such a reference plane mirror, first, the production of the reference plane mirror requires labor and cost. Even if a highly accurate reference plane mirror is made, it is difficult to temporarily set it on the stage, and it takes a long time. In particular, when the reference plane mirror is mounted on the stage, it is necessary to prevent the position of the reference plane mirror from being displaced by the movement of the stage and not to apply a stress that gives a distortion to the optical block of the reference plane mirror.

Even if such a difficult problem can be solved, there is a problem that a complicated calculation is required for measuring the amount of bending, and the measurement cannot be easily performed. recent years,
The positioning accuracy of an exposure apparatus incorporating this type of stage has a submicron resolution line width (0.8 to 0.4 μm).
As a result, it is becoming more and more severe, and it is entering an area where the influence of the bending of the plane mirror cannot be ignored.

The present invention has been made in view of such a conventional problem, and can easily and accurately measure the bending of a plane mirror mounted on a stage without using a reference plane mirror or the like. Accordingly, an object of the present invention is to improve the accuracy of stage position measurement and positioning.

[0008]

According to the present invention, the stage (S
For each of two orthogonal plane mirrors (MX, MY) provided on the stage for detecting the coordinate position of T) with the light wave interferometers (XI, YI), the local bending amount of the reflecting surface Interferometer (XθI, Y
θI). The two θ interferometers (Xθ
I, YθI), the bending amounts of the reflecting surfaces of the two plane mirrors are measured almost simultaneously, and the difference between the two measured values is obtained, whereby the true bending amount of the reflecting surface that offsets the error in the straightness of the stage Ask for. Then, the position measured by the light wave interferometer for coordinate measurement is corrected by an amount corresponding to the true bending amount.

[0009]

According to the present invention, a .theta. Interferometer for determining the inclination of the local portion of the reflecting surface is arranged for each of the plane mirrors for the x and y directions, and each of the plane mirrors (that is, the stage) is used by using these two .theta. Of yaw. Therefore, when the stage is moved in one dimension in the x direction or y direction, one θ interferometer measures the sum of the bending amount of the plane mirror itself and the yawing amount of the stage, and the other θ interferometer Only the yawing amount is measured. So two θ
When the difference between the measurement values of the interferometer is obtained, it becomes the bending amount of the plane mirror itself. By storing the amount of bending of this plane mirror, the coordinate position of the stage detected at the time of position measurement or positioning is calculated.
If the correction is made according to the amount of bending, the same accuracy as that obtained by using a plane mirror having an ideal reflection plane can be obtained.

[0010]

FIG. 1 is a perspective view showing a configuration in which a position measuring device according to a first embodiment of the present invention is applied to a stepper, and FIG. 2 is a plan view showing an arrangement of a stage portion. In FIG. 1, a reticle R having a circuit pattern and the like
Is precisely positioned with respect to the optical axis AX of the projection lens PL using the reticle alignment systems 32X, 32Y, 32θ. The projection lens PL has a pattern image P of the reticle R.
I is projected so as to overlap one of a plurality of local regions (shot regions) on the wafer W.

The wafer W is fixed on a stage ST, and the stage ST is moved in parallel in the x and y directions by motors 30X and 30Y. A reference mark plate FM for calibration of an alignment system or the like is fixedly mounted on the stage ST at substantially the same height position as the wafer W. Further, a moving mirror (plane mirror) having a reflecting surface extending in the y direction is provided on each of two sides of the stage ST orthogonal to each other.
MX and a moving mirror (plane mirror) MY having a reflecting surface extending in the x direction
Are fixed so as not to shift on the stage ST.
As shown in FIG. 2, a laser beam BX from an interferometer XI for detecting a position (distance change) in the x direction is vertically projected on the moving mirror MX, and a position in the y direction is detected on the moving mirror MY. The laser beam BY from the interferometer YI is vertically projected. The center line of the beam BX is parallel to the x-axis, and its extension line intersects with the origin O through which the optical axis AX of the projection lens PL passes. The center line of the beam BY is parallel to the y-axis, and its extension line intersects at the origin O. Two beams BXθ1 and BXθ2 from the X-axis θ interferometer XθI are vertically projected on the moving mirror MX, and the X-axis θ interferometer XθI is divided into beams BXθ1 and BX
Measure the optical path difference of θ2.

Two beams BYθ1 and BYθ2 from the Y-axis θ interferometer YθI are vertically projected onto the moving mirror MY,
The axis θ interferometer YθI measures the optical path difference between the beams BYθ1 and BYθ2. The two θ interferometers XθI and YθI correspond to the bending amount measuring means of the present invention, and the rotation amount of the moving mirror MX and the two rotation amounts within the range defined by the interval between the two beams BXθ1 and BXθ2 in the y direction. Beams BYθ1 and B
The rotation amount of the movable mirror MX is measured in a range defined by the interval in the x direction of Yθ2.

As shown in FIG. 1, the alignment marks and the reference marks FM on the wafer W are formed by off-axis type wafer alignment systems WR and WL fixed outside the field of the projection lens PL. The position is detected. As shown in FIG. 2, the respective detection centers of the wafer alignment systems WR and WL are separated by x with respect to the y-axis passing through the origin O.
The distance between the detection centers in the x direction is fixed to a predetermined constant value (a value smaller than the diameter of the wafer W). Note that the wafer alignment system W
L and WR are configured so that the x-direction alignment mark and the y-direction alignment mark on the wafer W can be photoelectrically detected through the same objective lens, that is, two-dimensional displacement detection of the mark can be performed. And

Here, the basic configuration of the interferometer systems XI and YI, θ
The basic configuration of the interferometers XθI and YθI will be briefly described with reference to FIG. The interferometer XI converts the He-Ne laser beam 1X into a measurement beam BX and a reference beam BXr.
The reference beam BXr is vertically projected onto a reference mirror fixed to the lower end of the projection lens PL. The beam splitter 2X, the mirror 6X, the receiver 10X, and the like are divided into two. The receiver 10X coaxially enters the reflected beam from the reference mirror and the reflected beam from the movable mirror MX, and photoelectrically detects a change in fringe due to interference between the two reflected beams. The same is true for the interferometer YI, and the laser beam 1Y
, A mirror 6Y, a receiver 10Y, etc., and the reference beam BYr is projected onto a reference mirror fixed to the projection lens PL. Such interferometers XI and YI may be of any type. Since the detailed description of the format is redundant in describing the present invention, it will be briefly described with reference to FIG.

FIG. 3 shows an example of the configuration of the interferometer XI in xz
It is viewed in a plane and is called a plane mirror interferometer. A He-Ne laser beam 1X having a frequency difference and orthogonally polarized components (P-polarized light and S-polarized light) enters a polarization beam splitter 2X, where the beam (BX) is directed to a moving mirror MX depending on the polarization direction.
And a beam (BXr) directed to the reference mirror 7X fixed to the lens barrel 8 of the projection lens PL via the mirror 6X. Each optical path (BX, BXr) from the polarizing beam splitter 2X to the reference mirror 7X and the moving mirror MX is １ ／.
Wavelength plates (hereinafter referred to as λ / 4 plates) 3A and 3B are arranged,
A corner cube 5 is provided below the polarizing beam splitter 2X.
X is fixed. Of the beam 1X, the beam reflected by the beam splitter 2X is S-polarized, but is converted into circularly polarized light by the λ / 4 plate 3B and projected on the lower half of the reference mirror 7X. Return to At this time, the reflected beam is converted into P-polarized light orthogonal to the transmitted light by passing through the λ / 4 plate 3B, transmitted through the polarization beam splitter 2X, reflected by the corner cube 5X in the opposite direction, and again enters the beam splitter 2X. .

The P-polarized beam passes through the beam splitter 2X and reaches the upper half of the reference mirror 7X again via the mirror 6X and the λ / 4 plate 3B. The reflected beam is λ /
Returning to the order of the four plates and the mirror 6, the light is converted into S-polarized light. Then, the light is reflected by the polarizing beam splitter 2X and is
Incident on. On the other hand, a part (P-polarized light) of the beam 1X transmitted through the beam splitter 2X is projected onto the lower half of the movable mirror MX via the λ / 4 plate 3A, and the reflected beam here passes through the λ / 4 plate 3A. The light is then converted into S-polarized light, reflected by the beam splitter 2X downward, and returned in the opposite direction by the corner cube 5X. The S-polarized beam from the corner cube 5X is again projected on the upper half of the movable mirror MX via the λ / 4 plate 3A, and the reflected beam there is converted to P-polarized light via the λ / 4 plate 3A and the beam splitter 2X. Being receiver 1
It is incident on 0X. The receiver 10X causes the reflected beam from the moving mirror MX and the reflected beam from the reference mirror 7X to interfere with each other by adjusting their polarization directions, and uses the frequency difference due to the difference in the polarization direction of the beam 1X to generate a heterodyne signal. The amount of change in the difference between the two optical paths (BX and BXr) is detected.
Since the structure of the Y-side interferometer YI is completely the same, further description is omitted.

Next, referring to FIG. 1, the θ interferometers XθI, Yθ
The basic configuration of I will be described. The θ interferometer XθI includes a beam splitter 12X that makes a laser beam 11X incident and splits in two directions, and a mirror 13X that reflects a part of the beam reflected by the beam splitter 12X in the direction of the moving mirror MX.
And a receiver 17X and the like. θ interferometer X
The two beams BXθ1 and BXθ2 of θI are parallel to each other, and the interval between them is about 10 mm to several tens mm. The beam BX from the laser interferometer XI is located approximately between the beams BXθ1 and BXθ2. The same applies to the θ interferometer YθI, and a beam splitter 12Y, a mirror 13Y, a receiver 17 and the like are provided in order to project the two beams BYθ1 and BYθ2 at regular intervals substantially perpendicular to the reflection surface of the mirror MY. .

FIG. 4 shows a detailed configuration of the θ interferometer XθI.
However, the configuration shown in FIG. 4 is merely an example, and the point is that the amount of change in the optical path difference between the two beams BXθ1 and BXθ2 may be obtained. Now, in FIG. 4, a laser beam 11 having a certain frequency difference between two orthogonally polarized lights.
X is split into two by a polarizing beam splitter 12X, and S
The polarized beam is projected as a beam BXθ1 perpendicular to one point of the movable mirror MX via the mirror 13X and the λ / 4 plate 14A. The P-polarized beam transmitted through the polarizing beam splitter 12X is projected as a beam BXθ2 perpendicularly to another point of the moving mirror MX via mirrors 15X, 16X and a λ / 4 plate 14B. Here, beams BXθ1 and BXθ2 are X
It is parallel to the axis, and the interval in the Y direction is SX (about 10 mm to several tens mm) on the reflection surface of the moving mirror MX. The polarization beam splitter 12X coaxially combines the reflected beam returning coaxially with the beam BXθ1 and the reflected beam returning coaxially with the beam BXθ2 toward the receiver 17X. Since the detailed configuration of the θ interferometer YθI is completely the same, the description is omitted.

The .theta. Interferometers X.theta.I and Y.theta.I are omitted in FIG. 4, but actually measure the optical path difference at two points of the movable mirror MX with reference to the fixed mirror. By the way, in the configuration of FIG. 1, the receiver 17X of the θ interferometer,
The measurement signal from each of the 17Ys is converted into a digital counter 40 for measuring the amount of rotation (such as yawing and bending).
X, 40Y, and data Dθx, D corresponding to the amount of rotation.
θy is output to the coordinate correction system 42. The correction system 42 includes an arithmetic unit for calculating the difference between the data Dθx and Dθy, and a memory unit and the like for storing the difference in correspondence with the movement position of the stage ST in the x and y directions.

Receiver 1 of interferometer XI for measuring coordinate position
The signal from 0X is converted into a digital coordinate value DXC by a counter circuit (not shown),
The signal from 0Y is converted into a digital coordinate value DYC by a counter circuit (not shown). These coordinate values DXC,
In the DYC, the main control system 50 inputs the coordinate values DXC and DYC, and based on the input of the data (difference) information DRD corresponding to the amount of bending of the movable mirrors MX and MY stored in the correction system 42, the coordinate value DXC , DYC, and a function of outputting commands DSX, DSY for driving the motors 30X, 30Y of the stage ST with respect to the target position.
Of course, other functions for various controls are provided, but since they are not directly related to the present invention, further description is omitted. It should be noted that the correction system 42 sends out, in real time, the data DRD 'of the difference between the bending amounts Dθx and Dθy to the main control system.

Next, with the above configuration, the moving mirror MX,
A method of measuring the curvature of each reflection surface of MY will be described with reference to FIG. 5 using the movable mirror MY as an example. As mentioned earlier,
The θ interferometer is actually a moving mirror MX, M
Although the rotation amount of the reflection surface of Y is measured, here, for the sake of simplicity, the θ interferometer YθI has a movable mirror MY based on a virtually fixed reference line RY as shown in FIG. (The amount of rotation and the amount of bending) are detected. Reference line R
The distance between Y and the movable mirror MY is defined as Ya (a value measured by the interferometer system YI), and the local bending angle of the movable mirror MY at that position is defined as θY (x). θ interferometer YθI has a reference line RY
At the two points separated by SY in the x direction, the difference between the distances yθ1 and yθ2 to the movable mirror MY, ie, Yθ (x), is measured.
That is, the counter circuit 40Y of the θ interferometer YθI outputs a difference Yθ (x) determined by the following equation.

[0022]

(Equation 1)

Here, the counter circuit 40Y includes a moving mirror MY
Is at the reference point Ox in the x direction, that is, the moving mirror MY
Is reset to zero when the beam BY of the Y-axis interferometer YI is incident on a fixed point Ox on the reflecting surface of the Y-axis. It is assumed that the interferometer YI is reset to zero at the reference point Ox. The bending angle θY (x) of the moving mirror is at most 1-2.
It is a small angle of about seconds, and the interval SY is from 10 mm to several tens of meters.
m, the angle θY (x) can be approximated by the following equation.

[0024]

(Equation 2)

On the other hand, the unevenness amount ΔY (x) of the reflecting surface at the position x of the movable mirror MY can be obtained by the following equation with respect to the reference Ox of x.

[0026]

(Equation 3)

The above measurement is performed while moving the stage ST in the x direction.
Since the yawing of T occurs at the same time, the error due to the yawing amount must be subtracted from the measured value of the equation (3). Therefore, when measuring the flatness of the moving mirror MY for the Y axis, the yaw amount Xθ of the stage ST with respect to the reference point Ox of x is determined by using the θ interferometer XθI on the X axis side.
Find (x). In this case, since the stage ST moves only one-dimensionally in the x direction, the two beams BXθ1 and BXθ2 of the θ interferometer XθI continue to be projected on the same point on the reflection surface of the X-axis moving mirror MX. Since the counter circuit 40X of the θ interferometer XθI has been reset to zero at the reference point Ox, the value of the counter circuit 40X at the position x is the yawing amount Xθ (x) of the stage ST with reference to the origin Ox.

Then, the stage ST is moved in the x direction, the measurement value Xθ (x) measured by the θ interferometer XθI is read at the same time, and a correction operation as shown in the following equation is performed to obtain the movable mirror MY
The true unevenness amount DY (x) of the reflection surface is obtained.

[0029]

(Equation 4)

This unevenness amount DY (x) is obtained and stored at every suitable position interval of the stage ST in the x direction, and thereafter, the measurement value of the Y-axis interferometer YI is corrected according to the position of the stage ST in the x direction. Then, the position measurement in the y direction can be performed with the same accuracy as when there is no bending of the movable mirror MY. Here, the calculations of the equations (2) and (4) and the storage of the true unevenness amount DY (x) are performed by the correction system 42 and are treated as device constants.

The movable mirror MX for the X-axis is also moved in the y-direction by moving the stage ST in the same manner as the true unevenness DX.
(Y) is obtained and stored in the correction system 42. In this case, the measured value of the θ interferometer XθI in the counter circuit 40X is Xθ (y), and the measured value of the θ interferometer XθI in the counter circuit 40Y is Yθ (y).
(Y) is required.

[0032]

(Equation 5)

[0033]

(Equation 6)

The above equations (4) and (6) correspond to sections 0 to x,
Alternatively, the integration is performed in the form of 0 to y, but in practice, the integration may be performed for each local section, for example, for every 5 to 10 mm.
That is, assuming that the length of the local section is ΔL, the integral section in the x direction is (n−1) · ΔL〜, where n is an integer of 1 or more.
After integration in the range of n · ΔL, the position is sequentially shifted to n = n + 1. Therefore, the memory in the correction system 42 contains the interferometer X
The unevenness amount DY corresponding to each ΔL of the measured coordinate values of I and YI
Data of (x) and DX (y) are stored as a table.

As described above, when the measurement of the unevenness amount of the movable mirrors MX and MY is performed only during the manufacture of the stepper or during the regular maintenance, one of the two θ interferometers XI and YI is made detachable, It may be attached to the device only when used. However, when the change over time is large or an error of a very small amount is a problem, the two θ interferometers XI and YI are always attached and the bending of the movable mirrors MX and MY is frequently measured. It is better to do.

In the above embodiments, the present invention has been described as applied to the position measurement and positioning of the stage of the stepper. However, the same applies to a measuring apparatus for measuring the coordinate position of a pattern of a mask or a wafer with high accuracy. Applicable to In the above-described embodiment, the target is merely measurement of the position of the stage. However, in this type of stepper or the like, an alignment operation for detecting an alignment mark on the wafer W and specifying the position of the wafer W in the apparatus coordinate system is indispensable. is there. In this alignment work, if the stage ST is slightly rotated due to yawing, the mark detection position is measured with a lateral shift, so that it is necessary to make correction using the θ interferometer XθI or YθI. Therefore, a second embodiment of the present invention suitable for alignment work will be described below.

As shown in FIGS. 1 and 2, the detection center of the wafer alignment system WL, WR is on the extension line (measurement axis) of the beam BX of the X-axis interferometer XI or the beam BY of the Y-axis interferometer YI. In the case of an arrangement that is not described above, it is necessary to correct an error due to yawing of the stage ST when measuring the position of the mark on the wafer W. However, JP-A-56-102
As disclosed in Japanese Patent No. 823, when the wafer alignment system detects a mark on the measurement axis of the interferometers XI and YI, even if the stage ST has yaw, the position detection result needs to be corrected by the yaw error. There is no.

Unlike the related art, if there is only one set of θ interferometers, the tilt (rotation) of the movable mirror due to yawing of the stage ST and the bending of the reflecting surface cannot be handled separately. When the invention is applied, it can be handled separately. Hereinafter, this embodiment will be described with reference to FIG. FIG. 6 is a diagram for explaining an error that occurs when the position of the mark on the wafer W in the x direction is detected using the wafer alignment system WR provided at the position where the Abbe error occurs. In FIG. 6, the x axis and the y axis are the measurement axes (beams BX and BY) of the interferometers XI and YI, respectively, and the origin O is the projection lens PL.
Is the optical axis AX position. The detection center of the wafer alignment system WR is located at a position ly away from the x axis in the y direction. When the mark on the wafer is detected by the wafer alignment system WR, if the reflecting surface of the moving mirror MX for the X axis is exactly perpendicular to the x axis (parallel to the y axis) like MXa, then the stage ST is fixed. Move in the x direction by the amount lx
By moving by y in the y direction, the measured mark can be matched with the point O, and no error occurs.

However, when a mark on a wafer is detected,
The reflecting surface of the moving mirror MX is θX from the y-axis like MXb.
(Y), a point on the reflecting surface MXb away from the x-axis by ly as shown in FIG.
In order to make the mark on the wafer W coincide with the origin O, the feed amount of the stage ST in the x direction is ly with respect to the design distance lx.
(Y) must be corrected.

When the yawing amount θX (y) of the stage ST is measured, an error in the bending of the reflecting surface of the movable mirror is included. However, as in the first embodiment, the movable mirror MX,
The true irregularities DX (y) and DY (x) of MY or local inclination information Yθ (x) and Xθ (y) of the reflecting surface are measured and stored, and the θ interferometers XθI and YθI are measured. Correcting the actual measurement value with the stored data value allows the true yawing amount to be obtained in which the influence of the bending of the reflection surface itself is subtracted.

Such yawing correction at the time of alignment is performed by the main control system 50 and the correction system 42.
As the actual sequence, the wafer alignment system WR
(Or WL), the position of the stage ST when the mark on the wafer is detected is measured by the interferometers XI and YI, and at the same time, the yawing amount at that position is detected by one or both of the θ interferometers XθI and YθI. . The measurement values of the θ interferometers XθI and YθI are corrected in the correction system 42 or the main control system 50 by referring to a table of the amount of unevenness or the amount of local inclination stored in advance, and the true yawing amount is corrected. Desired. 2
When both interferometers XθI and YθI are used, one true yawing amount is obtained by averaging the obtained true yawing amounts.

If the true yawing amount is significantly different between the X-axis side and the Y-axis side, the stage ST
During the movement of, at least one of the movable mirrors MX and MY slightly rotates on the stage ST. In this case, it is desirable to suspend the operation of the apparatus and execute operations such as self-check and calibration. In some cases, it is necessary to rewrite the table in the correction system 42.

As described above, according to the present embodiment, even if the position of the mark on the wafer W is measured using an alignment system that cannot avoid the Abbe error, the error due to yawing can be easily and accurately detected. Since the correction can be performed, a highly accurate wafer alignment system can be achieved as a result. Next, a positioning method (apparatus) according to a third embodiment of the present invention will be described.

In the stepper, the field of view for forming the projection image is 2
There is a dimension, and due to yawing of the stage ST, a rotation error (chip rotation) occurs in the field of view for each exposure shot (each stepping). This chip rotation poses a problem when printing the first layer pattern on the wafer W and when printing the second and subsequent layers repeatedly. In particular, when the requirements for the positioning error and the overlay error become severe, the chip rotation becomes a nonnegligible amount. FIG. 7 shows the tip rotation in an exaggerated manner. Assuming that the rectangular projection image PI of the reticle R does not rotate with respect to the xy coordinates, the shot area CP on the wafer W is yawed by the wafer stage ST. Rotates relative to the image PI. This relative rotation is generated as the tip rotation amount Cθ. Assuming that the rotation amount Cθ is 1 second, a misalignment of about 0.075 μm occurs at the end of the 15 mm square image PI (or the shot area CP).

In order to prevent this error, the true yawing of the stage ST is monitored, and the holder holding the wafer W is slightly rotated in the direction opposite to the yawing direction by the minute amount to be monitored. Should always be constant in the absolute coordinate system. For this purpose, as shown in FIG. 8, a wafer holder WH that rotates by θ on the stage ST is provided, and the motor MT and the control system 60 perform a minute rotation. Part 2 of the holder WH
By fixing two corner reflectors (right angle mirrors) CR1 and CR2 and projecting beams from the θ interferometer WθI mounted on the stage ST to the respective reflectors CR1 and CR2, the amount of rotation of the holder WH on the stage ST can be reduced. Be able to measure accurately. At this time, the control system 60 inputs the true yaw amount corrected in the same manner as in the previous embodiment from the θ interferometer XθI, the correction system 42, and the like, and the yaw amount (based on the origin position of the stage ST as a reference). The motor MT is servo-controlled while monitoring the measurement value of the θ interferometer WθI so that the wafer holder WH rotates in the opposite direction by the amount of rotation).

This operation is continuously executed after the completion of the wafer alignment (global alignment, EGA, etc.), and the servo control by the motor MT continues to operate during the step-and-repeat exposure operation. Since the rotation center of the wafer holder WH is not at the center of each shot area on the wafer W, the rotation of the wafer holder WH causes the shot area to be slightly shifted in the x and y directions from the position defined by the alignment work. . Therefore, the control system 60
Are x, y of the shot position according to the rotation amount of the holder WH.
The direction shift amount is obtained by calculation, and the information for correcting the stepping position of the stage ST by that amount is output to the control system 50 in FIG.

After correcting the rotation of the wafer holder WH only once at the time of global alignment, while measuring the true yawing amount of the stage ST, correcting the rotation of the reticle stage holding the reticle R in the same direction as the yawing direction. And repeat exposure may be performed. In this case, the center of each shot area on the wafer W may be made coincident with the center of the projection image PI, and there is no need for minute shifts in the x and y directions as when the wafer W is rotated for yawing correction. . In this case, it is desirable that the center of rotation of the reticle stage coincides with the center of the reticle R as much as possible, and a θ interferometer or the like for monitoring the amount of rotation is provided.

Further, a relative rotation error between each shot area on the wafer W and the reticle R is detected by a TTR (through the reticle) or TTL (through the lens) type alignment system, and the error is corrected. A reticle stage or a sequence for minutely rotating the wafer stage ST may be combined with the sequence. As described above, according to the present embodiment, only the pure yawing amount is detected without the influence of the bending of the reflecting surfaces of the movable mirrors MX and MY, and the wafer W or the reticle R is slightly rotated. The chip rotation can be corrected from the shot of the first layer printed by printing, and the occurrence of the chip rotation due to the influence of yawing can be suppressed even in the overlapping exposure of the second and subsequent layers.

As described above, in each embodiment of the present invention, the moving mirror M
The rotation amounts (bending amounts) of X and MY are measured by a θ interferometer using a coherent beam. However, it is not always necessary to use an interferometer. The same effect can be obtained by a configuration in which the light is projected onto the reflecting surface of the movable mirror and the change in the reflection direction of the reflected light beam is photoelectrically detected. In this case, the parallel light beam projected on the movable mirror may have a slit-shaped cross section having a length of about 10 to several tens mm in the direction in which the reflecting surface extends.

As the exposure method, any method such as a proximity method in which the mask and the wafer are brought close to each other, an aligner in which the mask and the wafer are integrally scanned with respect to the projection optical system, or a step-and-scan method can be applied. In addition, the moving mirrors MX and MY for the X axis and the Y axis are
Two perpendicular sides of the ceramic stage may be optically polished, and aluminum or the like may be deposited thereon.

[0051]

As described above, according to the present invention, the bending of a plane mirror can be measured without being affected by yawing and recorded.
Since the bending amount can be corrected and used when measuring the X and Y coordinates, highly accurate two-dimensional coordinate measurement can be performed, which is effective. The use of this coordinate measuring unit improves the measurement accuracy of a two-dimensional coordinate measuring machine, and the use of a pattern transfer device such as a stepper improves the positioning accuracy. Also, when there is a change in the relative angle between the two plane mirrors X and Y as well as the bending of the plane mirror, the amount can be monitored and corrected, so that accurate coordinate measurement can be performed. Further, when the present invention is used for yaw correction in the case of position measurement in an observation system in which an Abbe error occurs, yaw can be accurately corrected, and an error due to yaw can be accurately corrected.

Further, when the present invention is used to correct the chip rotation of a stepper or the like, the true yawing amount can be corrected, so that the chip rotation can be corrected accurately and a good overlay accuracy can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a configuration of a stepper to which a position measuring or positioning device according to a first embodiment of the present invention is applied.

FIG. 2 is a plan view showing a state of stage arrangement in the first embodiment.

FIG. 3 is a diagram illustrating a configuration of an interferometer for measuring a coordinate position.

FIG. 4 is a diagram showing a configuration of a θ interferometer for measuring rotation and bending of a movable mirror (stage).

FIG. 5 is a diagram for explaining how to measure the bending of the movable mirror itself.

FIG. 6 is a diagram illustrating yawing that occurs when positioning is performed using an alignment system, and positioning correction based on the yawing.

FIG. 7 is an exaggerated view of the tip rotation.

FIG. 8 is a plan view showing a structure of a wafer stage suitable for preventing chip rotation (yawing).

[Description of Signs of Main Parts]

R: reticle, W: wafer, ST: stage, MX, M
Y: movable mirror, XI, YI: interferometer for coordinate position measurement, X
θI, YθI: Interferometer for measuring the amount of rotation, 40X, 40Y
... Counter circuit, 42 ... Correction system, 50 ... Control system

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[Procedure amendment]

[Submission date] December 18, 1998

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Name of invention

[Correction method] Change

[Correction contents]

Patent application title: Alignment method and exposure apparatus

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

Claims (6)

[Claims] 1. A moving part of a stage which moves in parallel in x and y directions substantially orthogonal to each other, is provided with two plane mirrors extending along each of the x and y directions, and a reflection surface of the two plane mirrors. A method of measuring a coordinate change in the x, y directions of the stage by measuring a distance change in a vertical direction with a light wave interferometer, wherein a local bending amount in a direction in which each reflecting surface of the two plane mirrors extends is determined. And measuring the two plane mirrors at substantially the same time and correcting the coordinate position of the stage measured by the light wave interferometer based on both the measured values. 2. A stage that moves in parallel in x and y directions that are substantially orthogonal to each other, and the x and y are fixedly mounted on a part of the stage.
Two plane mirrors each having a reflecting surface extending along each of the directions, and two light wave interferometers for measuring a change in distance in a direction perpendicular to each of the reflecting surfaces of the two plane mirrors. In a measuring device, two measuring means for individually measuring a local bending amount of each of the two plane mirrors in a direction in which each reflecting surface extends, and the stage in one dimension in the x and y directions. When moving, each measured value obtained from the two measuring means is input almost simultaneously, and information corresponding to the difference between the measured values is obtained and stored corresponding to the position of the reflecting surface in the extending direction. Means; and a correction means for correcting the coordinate position of the stage measured by the light wave interferometer in accordance with the information stored in the storage means. 3. A moving part of a stage that moves in parallel in x and y directions that are substantially perpendicular to each other, is provided with two plane mirrors extending along each of the x and y directions, and a reflection surface of the two plane mirrors. Along with measuring the distance change in the vertical direction with the light wave interferometer, a specific mark on the object held on the stage is detected by mark detection means off the length measurement axis of the light wave interferometer, In the method of measuring the coordinate position of the object, a local rotation amount in a direction in which each reflecting surface of the two plane mirrors extends is measured individually for each of the two plane mirrors, and based on both measured values. A position measuring method, wherein a yawing amount of the stage is obtained, and a coordinate position of the mark detected by the mark detecting means is corrected according to the yawing amount. 4. A stage that moves in parallel in x and y directions that are substantially perpendicular to each other, and the x and y are fixed to a part of the stage.
Two plane mirrors having reflecting surfaces extending along respective directions, two light wave interferometers for measuring a distance change in a direction perpendicular to each reflecting surface of the two plane mirrors, and measurement of the two light wave interferometers Mark detection means for detecting a mark of the object on the stage at a predetermined position in a coordinate system defined by an axis, and at a position deviated from the measurement axis, the light wave interferometer and mark detection means, An apparatus for measuring a coordinate position of an object, comprising: two measuring means for individually measuring a local rotation amount of each of the two plane mirrors in a direction in which each reflecting surface of the two plane mirrors extends; The amount of bending of the reflecting surface of the plane mirror is obtained based on the difference between the measured values of the means, and the amount of rotation measured by at least one of the two measuring means is supplemented based on the amount of bending. Correction means for calculating the true yawing amount of the stage; and correcting means for correcting the coordinate position of the mark detected by the mark detecting means based on the yawing amount. Position measuring device. 5. When projecting a pattern having a predetermined outer shape onto a substrate held on a stage that moves in parallel in x and y directions that are substantially perpendicular to each other, a projection surface extending along x and y directions is provided. By projecting a beam from an optical interferometer to each of the two plane mirrors fixed to the stage and measuring a change in distance between the two plane mirrors, the projection pattern and the substrate are brought into a predetermined positional relationship. A true yawing of the stage, in which a local rotation amount of each reflecting surface of the two plane mirrors is individually measured, and an influence of a bending amount of the reflecting surface itself is removed based on the two measured values. A method of calculating the amount of rotation and correcting the rotation error due to yawing by relatively rotating the projection pattern and the substrate according to the true yawing amount. 6. A stage that translates in x and y directions that are substantially orthogonal to each other, projection means for projecting a pattern having a predetermined outer shape on a substrate held on the stage, , Two plane mirrors each having a reflecting surface extending along each of the y-directions, and two light wave interferometers for measuring a change in distance between the two plane mirrors, based on the measurement values of the light wave interferometer. In an apparatus for positioning the stage so that a predetermined area on the substrate is aligned with the projection pattern, a local rotation amount with respect to a direction in which each reflection surface of the two plane mirrors extends is individually determined for each of the two plane mirrors. Two measuring means for measuring; calculating the amount of bending of the reflecting surface of the plane mirror based on a difference between the measured values of the two measuring means; Calculating means for correcting the amount of rotation measured by the direction in accordance with the amount of bending to determine the true yawing amount of the stage; and when positioning the predetermined area on the substrate and the projection pattern, A positioning device comprising: a rotation correcting unit that relatively rotates the substrate and the projection pattern based on a true yawing amount.