JP4263785B2 - Tilt stage - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to wafer flatness measurement in which wafer flatness is measured by using Fizeau-type interference, and the interference fringes are received by a CCD camera and image analysis is performed based on a set minute angle. The present invention relates to a tilt stage used in an inspection apparatus or the like.
[0002]
[Prior art]
Conventionally, as shown in FIGS. 6 and 7, this type of tilt stage has cylindrical surfaces in the X and Y directions, is driven by a pulse motor independently in the X and Y directions, and is controlled in an open loop. In FIG. 6, 1 is a rotation drive mechanism, 2 is a Y-axis rotation unit, 3 is a Y-axis drive motor, 4 is a drive shaft that rotates the Y-axis, and 5 is a Y-axis power drive that applies a rotational force to the Y-axis rotation unit 2. A piece 6 is a Y-axis roller guide for sliding the Y-axis rotating unit 2. Reference numeral 13 denotes a wafer stage mounting plate for mounting the wafer stage 16; 16 a wafer stage for vacuum-sucking the wafer; 17 a wafer; 18 a control mechanism; 19 a center of the wafer surface; In FIG. 7, 7 is an X-axis base plate on the Y-axis rotating unit 2, 8 is an X-axis rotating unit, 9 is an X-axis driving motor, 10 is a driving shaft for rotating the X-axis, and 11 is an X-axis rotating unit 8 Reference numeral 12 denotes an X-axis roller guide portion that slides the X-axis base plate 7 and the X-axis rotating portion 8.
[0003]
In general, this type of stage is designed so that the center of rotation is at the center 19 of the wafer surface. Accordingly, the curvatures of the Y-axis roller guide portion 6 and the X-axis roller guide portion 12 are formed with a curvature centering on the center 19 of the wafer surface, and the X-axis is on the Y-axis.
[0004]
In order to operate this, a pulse is sent from the control mechanism 18 to the Y-axis drive motor 3 or the X-axis drive motor 9 to drive the drive motor, via the X and Y axis drive shafts 4 and 10. The X and Y axis driving pieces 5 and 11 are moved by the rotational force, and the X and Y rotating parts 2 and 8 are rotated along the roller guide parts 6 and 12 to obtain the rotation angles α and β. ing. Further, the magnitudes of the rotation angles α and β are set by the number of rotations of the drive motors 3 and 9, and are controlled in an open loop. Therefore, when the drive motors (pulse motors) 3 and 9 lose their pulses, the rotation angle α or β has a possibility of becoming an angle different from the set value. In order to improve the missing pulse, a method of monitoring the missing pulse by installing an encoder on the shaft of the drive motor is also employed. However, even if the rotation angle on the stage has a structure that is set with relatively high accuracy in the drive motor unit, there are several connection parts in the drive system, and due to the backlash of the connection part or screw part, At present, the rotation angle of the drive motor is not an accurate rotation angle on the wafer stage 16. In particular, with a precision tilt stage with a rotation angle of 0.05 degrees or less, it is currently impossible to achieve accuracy with open loop control.
[0005]
[Problems to be solved by the invention]
The conventional tilt stage is configured as described above, and the rotation of the drive motor is transmitted via screws or gears and controlled by an open loop. Therefore, the tilt stage is affected by a slight gap between the screws and gears. As a result, the power of the drive motor cannot be accurately transmitted onto the stage, and as a result, an accurate angle setting cannot be performed.
[0006]
The present invention has been made to solve the above-described problems, and an object of the present invention is to set an angle with high accuracy and high resolution with the center of the wafer surface on the wafer stage as the center of rotation.
[0007]
[Means for Solving the Problems]
In order to solve the above-described problem, the tilt stage of the present invention has a rotation center of rotation angles α and β that rotate around the X axis and the Y axis with respect to the XY plane constituting the wafer surface on the tilt stage base. A tilt stage having a rotation drive mechanism set to be on the wafer surface, a wafer stage mounting plate on the rotation drive mechanism, and a wafer stage on which the wafer is sucked and fixed. It is fixed on the tilt stage base by a linear scale support rod, and is attached in contact with the wafer stage mounting plate while being tilted in a tangential direction of a rotation circle centered on the rotation center at a position below the wafer surface. X-axis of the rotary drive mechanism Te, the rotation angle about the Y-axis alpha, has a linear scale for measuring β respectively, the rotation angle alpha, on the basis of the measured values of β And having a control mechanism for controlling the rotation drive mechanism.
[0008]
In the present invention, it is composed of a rotation mechanism that gives rotation angles α and β in the X and Y directions, respectively, and a linear scale that reads the rotation angle, and controls the rotation drive mechanism while directly measuring the rotation angle. A rotation angle is obtained.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
[Example 1]
An embodiment of the present invention is shown in FIG. A linear scale is installed on a conventional swivel stage (see FIGS. 6 and 7). 1 is a rotation drive mechanism, 2 is a Y-axis rotation unit, 3 is a Y-axis rotation motor, and 4 is a Y-axis rotation. A drive shaft, 5 is a Y-axis power drive piece that applies a rotational force to the Y-axis rotation unit 2, and 6 is a Y-axis roller guide unit that slides the Y-axis rotation unit 2. Reference numeral 22 denotes a Y-axis linear scale, 13 denotes a wafer stage mounting plate to which the wafer stage 16 is attached, 15 denotes a Y-axis linear scale support rod to which the linear scale is attached, 16 denotes a wafer stage for vacuum-sucking the wafer, 17 denotes a wafer, 18 denotes A control mechanism 19 is a tilt rotation center at the center of the wafer surface. The curvature of the roller guide 6 is set so that the center of rotation is at the center 19 of the wafer surface. The same applies to the X-axis direction except that the X-axis base plate 7 is on the Y-axis rotating portion. The X-axis linear scale 21 ′ is supported by an X-axis linear scale support bar.
[0010]
In order to operate this, the Y-axis rotating motor 3 is driven according to the angle set by the control mechanism 18 to rotate the wafer stage 16 and the wafer 17 on the Y-axis. At this time, the amount of movement by the motor is constantly measured by the Y-axis linear scale 22, and the rotation of the Y-axis drive motor 3 is stopped when the measured value reaches the set value. Thus, since the rotation angle β is constantly monitored by the linear scale 22, a tilt stage with high resolution can be obtained. The same applies when operating the rotation angle α in the X direction. The angle setting accuracy is determined by the resolution of the drive motors 3 and 9 and the linear scales 22 and 22 '. Therefore, when a tilt stage with high accuracy is required, it is necessary to use a motor with high resolution as the drive motors 3 and 9, and to use linear scales 22 and 22 'with accuracy of 1 μm or less. Of course, the same effect can be obtained even if a laser length measuring device is used as the measuring means.
[0011]
[Example 2]
FIG. 2 shows another embodiment, in which 22 is a Y-axis linear scale, 15 is a Y-axis linear scale support rod to which the linear scale is attached, 28 is a rotation circle about the center 19 of the wafer surface, and 14 and 14 'are rotations. This is the point where the circle 28 intersects the surface of the wafer 17. As an example, the Y direction will be described. In the tilt stage, it is difficult to vertically install the Y-axis linear scale 22 so as to be in contact with the point 14 due to the structure. Therefore, as shown in FIG. 1, the Y-axis linear scale 22 must be attached at a position below the wafer surface. In this case, since the axis of the Y-axis linear scale 22 is not in the tangential direction of the rotation circle 28, when the rotation angle β is relatively large, a deviation occurs between the contact surfaces of the Y-axis linear scale 22 and the wafer stage mounting plate 13. There is a possibility of rotation error.
[0012]
In this embodiment, in order to prevent this, the Y-axis linear scale 22 is inclined and installed in the tangential direction of the rotation circle 28 centering on the center 19 of the wafer surface. By installing the rotating circle 28 at an angle in the tangential direction in this way, the deviation between the contact surfaces of the Y-axis linear scale 22 and the wafer stage mounting plate 13 can be reduced.
[0013]
For a relatively large angle of 0.5 degrees used when the rotation angle is used as an optical measuring instrument, the lateral displacement on the contact surface of the Y-axis linear scale 22 is 0.02 μm or less, minimizing the error. be able to. The same applies to the X direction. Of course, when a laser length measuring device or the like is used as the measuring means, the measurement direction should be aligned with the tangential direction, and the same effect can be expected.
[0014]
[Example 3]
FIG. 3 is a perspective view of still another embodiment, in which 16 is a wafer stage, 17 is a wafer, 18 is a control mechanism, 19 is the center of the wafer surface, 20 is a tilt stage base, and 21 is a linear motion motor for Y-axis rotation. , 22 is a Y-axis linear scale, 23 is a Y-axis rotation base plate, 24 is an X-axis rotation base plate, 25 is a Y-axis center rod connecting the tilt stage base 20 and the Y-axis rotation base plate 23, and 26 is a rotation A ball bearing 27 for smoothing the shaft 27 is a gate pillar that supports the base plate 23 for Y-axis rotation. The ball center of the ball bearing 26 and the wafer surface are set on the same plane, and the rotation center of the rotation angle β is the center 19 of the wafer surface. Similarly, in the X direction, there are an X axis center rod, a ball bearing, and a gate pillar around the Y axis rotation base plate 23, and the wafer stage 16 is configured to rotate independently around the X axis and the Y axis.
[0015]
4A and 4B show the tilt stage of the present embodiment viewed from the Y direction and the X direction, respectively, FIG. 4A shows the case when viewed from the Y direction, and FIG. 4B shows the case viewed from the X direction. In FIG. 4B, 21 ′ is an X-axis rotating linear motor, 22 ′ is an X-axis linear scale, 23 is a Y-axis rotating base plate, 24 is an X-axis rotating base plate, and 25 ′ is a Y-axis rotating. An X-axis center bar connecting the base plate 23 and the X-axis rotation base plate 24, 26 'denotes a ball bearing that makes the rotation smooth, and 27' denotes a gate pillar that supports the X-axis rotation base plate 24. The ball center of the ball bearing 26 ′ and the wafer surface are set on the same plane, and the rotation center of the rotation angle α is the center 19 of the wafer surface.
[0016]
The X-axis and Y-axis rotating mechanisms have independent structures, and the Y-axis rotating linear motion motor 21 and the Y-axis linear scale 22 are fixed to the tilt stage base 20 in the Y direction. Further, the X-axis rotation linear motion motor 21 ′ and the X-axis linear scale 22 ′ are attached to the Y-axis rotation base plate 23, and when the X-axis rotation linear plate 22 ′ is rotated by an angle α around the X-axis, the Y-axis is affected. The structure is such that the X axis is not affected when it is rotated by an angle β around the Y axis. Further, the X-axis rotation linear motion motor 21 ′ and the X-axis linear scale 22 ′, or the Y-axis rotation linear motion motor 21 and the Y-axis linear scale 22 are on the diagonal line of the rotation center 19, and always measure the rotation angle. It has a structure that can be done.
[0017]
These operations will be described in the Y direction as an example. When the rotation angle β is operated, the Y-axis rotation linear motion motor 21 is driven according to the angle set by the control mechanism 18 to rotate the wafer stage 16 and the wafer 17 on the Y-axis. At this time, since the Y-axis linear scale 22 on the diagonal line is configured to constantly measure the movement amount by the motor, the rotation of the motor is stopped when the measured value reaches the set value. The angle setting accuracy is determined by the resolution of the Y-axis rotating linear motion motor 21 and the Y-axis linear scale 22. Similarly, when the rotation angle α in the X direction is operated, the angle setting accuracy is determined by the resolution of the X axis rotating linear motion motor 21 ′ and the Y axis linear scale 22 ′. Therefore, when a highly accurate tilt stage is required, it is necessary to use a motor with high resolution of the linear motion motors 21 and 21 ′ for rotation, and also to use linear scales 22 and 22 ′ having an accuracy of 1 μm or less. There is. Of course, the same effect can be obtained even if a laser length measuring device is used as the measuring means.
[0018]
[Example 4]
FIG. 5 shows still another embodiment, in which FIG. 5A is a view from the Y direction, and FIG. 5B is a view from the X direction. When viewed from the Y direction in FIG. 5A, 28 is a rotation circle on the XZ plane centering on the center 19 of the wafer surface, 14, 14 'are points where the rotation circle 28 and the wafer surface intersect, and 23 is A Y-axis rotation base plate 24 is an X-axis rotation base plate. In FIG. 5B, 28 ′ is a rotation circle on the YZ plane centering on the center 19 of the wafer surface, 21 ′ is an X-axis rotating linear motion motor, and 22 ′ is an X-axis linear scale.
[0019]
In the tilt stage, it is structurally difficult to vertically install the Y-axis rotating linear motion motor 21 and the Y-axis linear scale 22 so as to be in contact with the points 14 and 14 ′. Therefore, as shown in FIG. 4, these must be attached at a position below the wafer surface. In this case, since the axes of the Y-axis rotation linear motion motor 21 and the Y-axis linear scale 22 are not in the tangential direction of the rotation circle 28, if the rotation angle becomes relatively large, the Y-axis rotation linear motion motor 21 and the Y-axis rotation linear motion motor 21 There is a possibility that the shaft rotation base plate 23 and the contact surface between the Y-axis linear scale 22 and the Y-axis rotation base plate 23 are displaced, resulting in a rotation error.
[0020]
In this embodiment, in order to prevent this, the Y-axis rotation linear motion motor 21 and the Y-axis linear scale 22 are inclined and installed in the tangential direction of the rotation circle 28 centered on the center 19 of the wafer surface. In this way, by providing an angle in the tangential direction of the rotating circle 28, the deviation on the contact surface of the Y-axis rotating base plate 23 can be reduced.
[0021]
For a relatively large angle of 0.5 degrees used when the rotation angle is used as an optical measuring instrument, there is no lateral deviation at the contact surface between the Y-axis rotating linear motion motor 21 and the Y-axis linear scale 22. .02 μm or less, and the error can be minimized. The same applies to the X direction in FIG.
[0022]
【The invention's effect】
As described above, the tilt stage according to the present invention has a closed loop structure in which the rotation angle is set by motor drive while constantly measuring the rotation angle with a high-precision and high-resolution linear scale. The influence can be corrected, and the rotation angle can be obtained with high accuracy.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of Embodiment 1 of the present invention.
FIG. 2 is a configuration diagram of Embodiment 2 of the present invention.
FIG. 3 is a configuration diagram of Embodiment 3 of the present invention.
FIGS. 4A and 4B are a diagram viewed from the Y direction and a diagram viewed from the X direction according to the third embodiment of the present invention. FIGS.
FIG. 5 is a configuration diagram of Embodiment 4 of the present invention.
FIG. 6 is a configuration diagram of an example of a tilt stage according to the prior art.
FIGS. 7A and 7B are a diagram viewed from the Y direction and a diagram viewed from the X direction of an example of a tilt stage according to the prior art. FIGS.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Rotation drive mechanism 2 Y-axis rotation part 3 Y-axis drive motor 4 Drive shaft 5 which rotates Y-axis Y-axis power drive piece 6 which gives rotational force to Y-axis rotation part 6 Y-axis base plate and Y-axis rotation part Y-axis roller guide section 7 to be slid X-axis base plate 8 on Y-axis rotation section X-axis rotation section 9 X-axis drive motor 10 X-axis rotation drive shaft 11 X-axis rotation section giving a rotational force X-axis Power drive piece 12 X-axis base plate and X-axis roller guide part 13 for sliding the X-axis rotating part Wafer stage mounting plate 14 for mounting the wafer stage 14, 14 'Point 15 where the rotating circle 28 intersects the wafer surface 15 Y-axis linear scale Support rod 16 Wafer stage 17 Wafer 18 Control mechanism 19 Tilt rotation center at the center of the wafer surface 20 Tilt stage base 21 of the tilt stage Y-axis drive linear motion motor 22 Y-axis Near scale 23 Y-axis rotation base plate 24 X-axis rotation base plate 25 Y-axis center rod 26 connecting the tilt stage base and Y-axis rotation base plate 26 Ball bearing 27 for smooth rotation Supports the Y-axis rotation base plate Gate pole 28 Y-axis rotation circle 21 ′ centered on the center 19 of the wafer surface X-axis drive linear motion motor 22 ′ X-axis linear scale 25 ′ X-axis center connecting the Y-axis rotation base plate and the X-axis rotation base plate Rod 26 ′ Ball bearing 27 ′ for smooth rotation Gate pole 28 ′ for supporting X-axis rotation base plate X-axis rotation circle about center 19 of wafer surface

Claims (2)

A rotation drive mechanism is set on the tilt stage base so that rotation centers of rotation angles α and β that rotate about the X axis and the Y axis are on the wafer surface with respect to the XY plane constituting the wafer surface. a, a wafer stage mounting plate on the rotary drive mechanism, the tilt stage structure having a wafer stage for chucking the wafer thereon, is fixed by the linear scale support rod on said tilt stage base, the wafer Rotation angles about the X and Y axes of the rotational drive mechanism mounted in contact with the wafer stage mounting plate while being tilted in a tangential direction of a rotational circle centered on the rotational center at a position below the surface alpha, having a linear scale for measuring β, respectively, and further comprising a control mechanism for controlling the rotation drive mechanism on the basis of the rotation angle alpha, measured values of β That tilt stage.   2. The tilt stage according to claim 1, wherein the control mechanism controls the rotational drive mechanism by driving an X-axis and Y-axis drive linear motion motor.

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