JP2005123255A - Positioning device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that, in a positioning device, a low-order elastic mode must be reduced without using any notch filter for realizing a high servo-band. <P>SOLUTION: The positioning device which positions a moving body is provided with a position measuring means which measures the positional information of the moving body in the X- and Y-directions and at least four driving mechanisms which drive the moving body in the Z-direction. The positioning device drives the moving body by selecting three out of the four driving mechanisms based on the output of the position measuring means. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a positioning device for positioning a moving body, preferably a positioning device used for an exposure apparatus, a machine tool, an OA machine, or the like.

  An exposure apparatus used in a process of manufacturing a device such as a semiconductor device or a liquid crystal display device is an original substrate such as a mask or a reticle, or a substrate to be exposed such as a semiconductor wafer or a glass substrate (hereinafter collectively referred to as a substrate). A positioning device for positioning;

  As a positioning device (stage device) for an exposure apparatus, for example, there is one as shown in Patent Document 1. In this stage apparatus, the wafer is held on a stage top plate via a wafer chuck, and an XY slider on which the stage top plate is mounted moves in the X and Y directions by the X and Y beams. Here, the X beam and the Y beam are each driven by a linear motor.

  FIG. 5 is a schematic view of the back surface of the stage top plate 111 in the above-described stage apparatus. The motion of the XY slider 231 is transmitted to the stage top plate 111 in a non-contact manner through an electromagnetic coupling 131 having an electromagnet. Between the stage top plate 111 and the XY slider 231, linear motors 141a and 141b that generate force in the X direction, linear motors 142a and 142b that generate force in the Y direction, and linear motors 151a to 151a that generate force in the Z direction. 151c. With these linear motors, the stage top plate 111 is in six directions in the X, Y, and Z directions and θx (rotation around the X axis), θy (rotation around the Y axis), and θz (rotation around the Z axis). (6 degrees of freedom) can be driven.

  Measurement mirrors 121a and 121b are mounted on the stage top plate 111, and the positions of the stage top plate in the six-axis directions are measured by laser interferometers 311a to 311c, 312a, 312b and 313. The stage top plate 111 is configured with a position servo system with six degrees of freedom based on the measured position information in the six-axis directions. That is, the command values to the linear motors 141 a, 141 b, 142 a, 142 b, 151 a to 151 c arranged on the back surface of the stage top plate 111 are 6-axis directions measured by the laser interferometers 311 a to 311 c, 312 a, 312 b and 313. Is calculated and controlled by a compensator based on the position information. Here, three linear motors driven in the Z direction are provided to prevent over-restraint.

Further, for example, Patent Document 2 discloses a configuration in which four linear motors that generate force in the Z direction are arranged in the stage device in order to increase the rigidity of the stage. In Patent Document 2, in the drive control of the positioning actuator of the stage, it is described that four or more actuators are driven to prevent vibration, and three of those actuators are switched to a mode that prevents deformation. ing.
JP 2003-022960 A Japanese Patent Registration No. 2902225

  In a positioning apparatus (stage apparatus) for a semiconductor exposure apparatus, since the resolution of the line width to be exposed is high, high positioning accuracy is required. In addition, the semiconductor exposure apparatus is a production facility, and is required to have high throughput from the viewpoint of productivity. In order to satisfy these requirements, the stage position servo system must have high responsiveness and the stage must be able to move at high speed. However, even if the gain of the position servo system of the stage is set high, the upper limit is limited by the oscillation of the position servo system. There are various factors that limit the servo band, and vibration due to the elastic mode of the control target is one of the factors.

  FIG. 3 shows a mode analysis result of the wafer stage top plate 111. Here, the elastic modes from the first order to the fourth order are shown. Since such a thin plate has low Z-direction rigidity, vibration due to elastic deformation such as bending or twisting occurs. FIG. 4 shows an open loop transmission characteristic of the stage top plate 111 around the Y axis (θy). It can be seen that a high peak appears in the resonance frequency of the elastic mode. In such a system, for example, when the gain of the position servo system for rotation about the Y axis (θy) is increased, the elastic mode is excited at the resonance frequency, thereby deteriorating the positioning accuracy of the stage. When the gain of the position servo system is low to some extent, the vibration due to the elastic mode only appears greatly. However, when the gain is further increased, the position servo system becomes unstable and enters an oscillation state.

  To prevent such oscillation, there is a method of adding a notch filter that removes the frequency component that excites the elastic mode to the position servo system of the compensator. However, the notch filter delays the phase of the position servo system. This makes the position servo system unstable. In particular, when a notch filter is used for a low-order elastic mode close to the servo band, the phase of the position servo system is significantly delayed. Therefore, in order to improve the responsiveness of the position servo system, it is necessary to reduce the low-order elastic mode to be controlled without using a notch filter.

  The present invention has been made in view of such circumstances, and an object of the present invention is to reduce low-order elastic modes without significantly reducing the quick response.

  For the purpose described above, in the present invention, in a positioning device for positioning a moving body (control target), position measuring means for measuring position information of the moving body in the XY directions, and at least driving the moving body in the Z direction. And a control unit that selects and drives three of the drive mechanisms based on the output of the position measuring means.

  Preferably, the position measuring means is a laser interferometer, and further, three of the drive mechanisms are selected according to the position of the intersection of the X measurement axis and the Y measurement axis of the laser interferometer with respect to the moving body. It is preferable to drive. Here, the intersection of the X measurement axis and the Y measurement axis may be, for example, two midpoints when there are two X measurement axes (or Y measurement axes) and the average is taken. There is no need to have.

  Further, it is preferable that the three selected driving mechanisms are switched based on the output of the position measuring means.

  In addition, when the intersection of the X measurement axis and the Y measurement axis of the laser interferometer is in a triangular region composed of two sides having the first and second mirrors and one diagonal line, the first of the moving body And three drive mechanisms in a triangular area consisting of two sides and one diagonal line not having the second mirror, and the intersection point being two sides and one diagonal line not having the first and second mirrors The three moving mechanisms in the triangular area consisting of two sides having the first and second mirrors and one diagonal line of the moving body may be selected and positioned. preferable.

  Moreover, it is preferable that the control unit includes a filter that reduces a frequency component that excites a higher-order elastic mode from the output of the position measuring unit.

  Moreover, it is preferable that the positioning device performs positioning in six axis directions.

  The exposure apparatus preferably positions the substrate by the positioning device.

  Moreover, it is preferable that a device is manufactured by the exposure apparatus.

  Here, the “elastic mode” refers to vibration due to elastic deformation such as bending or twisting, and can be represented by a mode as shown in FIG. 3, which is expressed as a peak value as shown in FIG. is there. Hereinafter, “low order” and “high order” refer to the components shown in FIGS. 3 and 4, and “low order” refers to the primary and / or secondary components, and “high order” refers to 3 The following and / or the fourth order shall be said.

  According to the present invention, a low-order elastic mode can be reduced in a positioning device that positions a moving body without significantly reducing the quick response.

  According to the invention described in claim 4, the elastic mode can be effectively removed each time the moving body moves.

  According to the eighth aspect of the present invention, the frequency component that excites the higher-order elastic mode that is less affected by the deterioration in positioning response is removed by the filter, so that the low-order to the higher-order can be obtained without greatly reducing the quick response. The elastic mode can be reduced up to.

(Example 1)
FIG. 6 is a schematic diagram of the wafer stage, and FIG. 1 is a schematic diagram of the back side of the stage top plate 111 as a control target (moving body) in the first embodiment. In FIG. 6, a wafer 113 is mounted on a stage top plate 111 via a wafer chuck (not shown). The stage top plate 111 is mounted on the XY slider 231, which will be described later. The XY slider 231 has a Y beam 221 penetrating in the X direction and an X beam 211 penetrating in the Y direction, and each beam is supported in a non-contact manner with the XY slider 231 by, for example, a hydrostatic bearing (not shown). Yes.

  An air pad is provided on the bottom surface of the XY slider 231 and is supported by a hydrostatic bearing so as to be movable with respect to the wafer surface plate 201. Similarly, the X beam 211 and the Y beam 221 have air pads 214 and 224 between the wafer surface plate 201 and are supported so as to be movable on the wafer surface plate 201. Both ends of the X beam 211 are provided with linear motor movable elements 212 (only one end is shown), and both ends of the Y beam 221 are provided with linear motor movable elements 222 (only one end is shown). , 223 generate a driving force in the X and Y directions. With such a mechanism, the X beam 211 is driven in the X direction to transmit an X direction force to the XY slider 231, and the Y beam 221 is driven in the Y direction to cause the XY slider 231 to have a Y direction force. Then, the XY slider 231 is driven in the XY direction.

  On the stage top plate 111, a measurement mirror 121a is attached to one side perpendicular to the X direction, and a measurement mirror 121b is attached to one side perpendicular to the Y direction. Here, the measurement mirror 121a has a surface perpendicular to the X direction and a surface perpendicular to the Z direction, and the measurement mirror 121b has a surface perpendicular to the Y direction and a surface perpendicular to the Z direction. Laser interferometers 311a to 311c are attached to a barrel surface plate 301 as a reference surface, and the measurement mirror 121a is irradiated with measurement light to displace the stage top plate 111 in the X direction (X) and rotate around the Y axis. The angle (θy) and the rotation angle around the Z axis (θz) are measured. The laser interferometers 312a and 312b are attached to the lens barrel surface plate 301 serving as a reference surface. The measurement mirror 121b is irradiated with measurement light to displace the stage top plate 111 in the Y direction (Y) and rotate around the X axis. The angle (θx) is measured. The laser interferometer 313 measures the displacement (Z) of the stage top plate 111 in the Z direction by irradiating the measurement mirror 121a with measurement light. With such a mechanism, position information of the stage top plate 111 in the 6-axis directions (6 degrees of freedom) is measured.

  In FIG. 1, linear motors 151a to 151d are provided at four corners of the stage top plate 111 as driving means in the Z-axis direction. Here, the reason why four linear motors are provided is to improve the rigidity of the stage top plate 111. The linear motors 151a to 151d position the stage top plate 111 in the Z direction (Z) and around the X and Y axes (θx, θy). The forces generated by the driving units 151a to 151d are calculated by the compensator 110 as a control unit using the measured values of the laser interferometers 311a to 311c, 312a, 312b, and 313. Here, a PID controller is used as a compensator.

  When the stage top plate 111 is regarded as a rigid body, the displacement (Z) of the stage top plate 111 in the Z-axis direction and the rotation about the X and Y axes (θx, θy) are caused by three Z-direction linear motors. Can be controlled. If there are four or more linear motors in the Z direction, it is over-constrained, so it is necessary to select three linear motors in the Z direction. Here, as a condition for selecting three linear motors, the measurement positions of the laser interferometers 311 and 312 with respect to the stage top plate are used. Hereinafter, conditions for selecting the three linear motors to be used will be described. In FIG. 2, a measurement position 9 is a point where one of the laser interferometers 311 a to 311 c intersects with the measurement light from the laser interferometer 312 a or 312 b extended. Here, the intersection of the X measurement axis and the Y measurement axis may be, for example, two middle points when the X measurement axis (or Y measurement axis) takes an average, and it is necessary to actually have a laser axis. Absent. The region 10 is a region indicated by a triangle determined by two sides to which the measurement mirrors 121a and 121b of the stage top plate 111 are attached and a vertex at which the two sides intersect. The region 11 is a region indicated by a triangle determined by two sides of the stage top plate 111 where the measurement mirrors 121a and 121b are not attached and a vertex at which the two sides intersect. When the measurement position 9 is within the area 10, three linear motors excluding the linear motor 151c closest to the apex at which the two sides to which the mirrors 121a and 121b are attached meet among the linear motors 151a to 151d in the Z direction. 151a, 151b, and 151d are used to control the displacement (Z) of the stage top plate 111 in the Z direction and the rotation about the X and Y axes (θx, θy). When the measurement point 9 is in the area 11, three of the linear motors 151a to 151d in the Z-axis direction except for the linear motor 151a closest to the apex at which two sides to which the measurement mirrors 121a and 121b are not attached intersect. The linear motors 151b to 151d are used to control the displacement (Z) of the stage top plate 111 in the Z-axis direction and the rotation around the X and Y axes (θx, θy). FIG. 12 shows a schematic flow.

  Positioning of the stage top plate 111 in the X direction (X) and around the Z axis (θz) is performed using linear motors 141a and 141b in the X direction. Command values to the linear motors 141a and 141b are calculated by the compensator 110 as a control unit based on the measured values of the laser interferometers 311a to 311c. Similarly, the positioning of the stage top plate 111 in the Y direction (Y) is calculated by the compensator 110 based on the measurement values of the laser interferometers 312a and 312b.

  7A shows an open loop transmission characteristic around the Y axis of the stage top plate 111, and FIG. 7B shows a closed loop transmission characteristic around the Y axis of the stage top plate 111. FIG. 7 (a) and 7 (b), the dotted line is the transfer characteristic of the prior art in which three linear motors in the Z direction are arranged on the stage top plate 111, and the broken line is the notch filter indicating the elastic mode excited in the prior art. This is the transfer characteristic when reduced, and the solid line is the transfer characteristic when Example 1 is applied. Here, it should be noted that the first embodiment does not use a notch filter or the like for the frequency component for exciting the low-order elastic mode. In the broken line in FIG. 7A, the first and fourth order elastic modes are reduced by the notch filter, the servo band of the stage top plate 111 is 390 [Hz], and the solid line in FIG. In Example 1), the second-order and fourth-order elastic modes are reduced, and the servo band is 470 [Hz]. In the solid line, a notch filter or the like is not used in the low-order elastic mode, so that the servo band is higher than that of the broken line, which indicates that the quick response is good. Here, the “servo band” is determined not by the speed response scale defined on the closed loop frequency characteristic but by the cross frequency (frequency at which the open loop gain characteristic cuts the gain of 0 [dB]).

  It can be seen from the closed-loop transfer characteristic of Example 1 (solid line in FIG. 7B) that the low-order elastic mode is reduced without using a notch filter. That is, in the first embodiment, the low-order elastic mode is not excited, and it is not necessary to use a notch filter for the frequency component that excites the low-order elastic mode. Therefore, the servo control band is improved by not delaying the phase. Can do.

  However, in the first embodiment, a notch filter is used to remove frequency components that excite higher-order elastic modes in order to reduce higher-order elastic modes. The same effect can be obtained by using a low-pass filter instead of the notch filter. In the higher-order elastic mode, even if a notch filter is used, there is no problem because the influence of the phase delay is small.

(Example 2)
In the first embodiment, a notch filter or a low-pass filter is used to reduce higher-order elastic modes. However, higher-order elastic modes can be reduced using an elastic vibration reducing mechanism. Next, the elastic vibration reducing mechanism disposed on the back surface of the stage top plate 111 will be described.

  FIG. 8 shows the back surface of the stage top plate 111. On the back surface of the stage top plate 111, a direction (hereinafter referred to as “pair”) that is substantially parallel to a line segment connecting two non-adjacent vertices of a polygon (rectangular in the case of FIG. 8) formed by the outline of the stage top plate 111. Measuring instruments 1007a to 1007d for measuring elastic vibration generated in the “angular direction”) are arranged. The elastic vibration may include a position component, a velocity component, and an acceleration component. Further, on the back surface of the stage top plate 111, drivers 1008a to 1008d that apply force to predetermined portions of the stage top plate 111 so as to reduce the elastic vibration of the stage top plate 111 based on the outputs of the measuring instruments 1007a to 1007d; And compensators 1009a to 1009d for controlling the drivers 1008a to 1008d. Specifically, drivers 1008a to 1008d that apply a force in a diagonal direction on the stage top plate 111 are arranged close to or superimposed on the measuring devices 1007a to 1007d, respectively. As the measuring instruments 1007a to 1007d and / or the drivers 1008a to 1008d, for example, piezoelectric elements or the like are used. The compensators 1009a to 1009d control the force applied by the drivers 1008a to 1008d to predetermined locations on the stage top plate 111 so as to reduce the elastic vibration based on the measurement information measured by the measuring devices 1007a to 1007d, respectively. . As the compensators 1009a to 1009d, for example, PID compensators and gain compensators are used.

  The stage top plate 111 further includes a measuring instrument that measures elastic vibration generated in a direction substantially parallel to each of the rectangular straight portions formed by the outline of the stage top plate 111 (hereinafter referred to as “side direction”). 1010a to 1010d may be arranged respectively. In this case, the drivers 1011a to 1011d that apply a force in the direction of each side (straight line portion) on the stage top plate 111 are arranged close to or superimposed on the measuring devices 1010a to 1010d, respectively. The compensators 1012a to 1012d control the forces applied by the drivers 1011a to 1011d so as to reduce the elastic vibration based on the measurement information measured by the measuring devices 1010a to 1010d, respectively. As the compensators 1012a to 1012d, for example, a PID compensator, a gain compensator, or the like can be used.

  Such an elastic vibration reducing mechanism is more effective when the elastic mode of the stage top is excited by disturbance (flexible, wiring, floor vibration transmitted through the pipe, etc.) than when using a notch filter. There is an effect that the elastic mode can be attenuated.

  In the present embodiment, the elastic vibration reducing mechanism is configured to suppress both the diagonal and side elastic vibrations (see FIG. 8), but the present invention is not limited to this. For example, the elastic vibration reducing mechanism may be configured to suppress elastic vibration in one of the diagonal direction and the side direction, or may have a configuration other than that.

  The solid line in FIG. 9 indicates that the stage top plate 111 is opened around the Y axis when elastic vibrations generated in the side direction are reduced using the measuring instruments 1010a to 1010d, the drivers 1011a to 1011d, and the compensators 1012a to 1012d. It is a loop transfer characteristic. The dotted line in FIG. 9 is an open loop transmission characteristic when the elastic vibration generated in the side direction is not controlled. It can be seen that the third-order elastic vibration is reduced by using the elastic vibration reducing mechanism.

(Example 3)
FIG. 11 shows an example in which a positioning apparatus similar to the above is used in a semiconductor device manufacturing apparatus (exposure apparatus).

  This exposure apparatus is used for manufacturing a semiconductor device such as a semiconductor integrated circuit or a device in which a fine pattern is formed such as a micromachine or a thin film magnetic head, and is applied on a semiconductor wafer W as a substrate through a reticle as an original plate. Projection lens 503 (exposure light as exposure energy from illumination system unit 501 (this term is a general term for visible light, ultraviolet light, EUV light, X-rays, electron beams, charged particle beams, etc.) as a projection system. This term is a general term for a refractive lens, a reflective lens, a catadioptric lens system, a charged particle lens, etc.), thereby forming a desired pattern on a substrate mounted on the wafer stage 504. . Further, such an exposure apparatus is required to be exposed in a vacuum atmosphere as the exposure light becomes short wavelength light.

  A wafer (object) as a substrate is held on a chuck mounted on a wafer stage 504, and a reticle pattern, which is an original plate mounted on the reticle stage 502, is stepped and repeated in each region on the wafer by an illumination system unit 501. Alternatively, transfer by step and scan. Here, the stage apparatus of the first embodiment is used as the wafer stage 504 or the reticle stage 502.

Example 4
Next, a semiconductor device manufacturing process using this exposure apparatus will be described. FIG. 12 is a diagram showing a flow of an entire manufacturing process of a semiconductor device. In step 1 (circuit design), a semiconductor device circuit is designed. In step 2 (mask fabrication), a mask is fabricated based on the designed circuit pattern.

  On the other hand, in step 3 (wafer manufacture), a wafer is manufactured using a material such as silicon. Step 4 (wafer process) is called a pre-process, and an actual circuit is formed on the wafer by using the above-described exposure apparatus and lithography technology using the above-described mask and wafer. The next step 5 (assembly) is called a post-process, and is a process for forming a semiconductor chip using the wafer produced in step 5, and is an assembly process (dicing, bonding), packaging process (chip encapsulation), etc. Process. In step 6 (inspection), the semiconductor device manufactured in step 5 undergoes inspections such as an operation confirmation test and a durability test. A semiconductor device is completed through these processes, and is shipped in Step 7.

  The wafer process in step 4 includes the following steps. An oxidation step for oxidizing the surface of the wafer, a CVD step for forming an insulating film on the wafer surface, an electrode formation step for forming electrodes on the wafer by vapor deposition, an ion implantation step for implanting ions on the wafer, and applying a photosensitive agent to the wafer A resist processing step, an exposure step for transferring the circuit pattern to the wafer after the resist processing step by the above exposure apparatus, a development step for developing the wafer exposed in the exposure step, and an etching step for scraping off portions other than the resist image developed in the development step A resist stripping step that removes the resist that has become unnecessary after etching. By repeating these steps, multiple circuit patterns are formed on the wafer.

It is a figure which shows the back surface of a stage top plate. It is a figure which shows a measurement position. It is a figure which shows the elastic mode of a stage top plate. It is a figure which shows the transmission characteristic of the conventional stage top plate. It is a figure which shows the back surface of the conventional stage top plate. It is the schematic of a wafer stage. It is a figure which shows the transmission characteristic of a stage top plate. It is a figure which shows the back surface of a stage top plate. It is a figure which shows the back surface of a stage top plate. It is a figure which shows the outline of a switching flow. FIG. 10 is a diagram illustrating an exposure apparatus according to the third embodiment. The figure showing the semiconductor manufacturing process concerning Example 4

Explanation of symbols

9 Measuring position 110 Compensator 111 Stage top plate 113 Wafer 121a, 121b Measuring mirror 131 Electromagnetic coupling 141a, 141b Linear motor 142a, 142b Linear motor 151a-151d Linear motor 161a-161c Self-weight compensation magnet 201 Wafer surface plate 202 Air damper 211 X bridge 212 linear motor 213 counter mass 214 air pad 221 Y bridge 222 linear motor 223 counter mass 224 air pad 231 XY slider 301 lens barrel surface plates 311a to 311c laser interferometers 312a and 312b laser interferometers 313 laser interferometers 501 illumination system unit 502 reticle stage 503 Reduction projection lens 504 Wafer stage 505 Exposure apparatus main body 1007a to 1007d Measuring instrument 1 08a~1008d driver 1009a~1009d compensator 1010a~1010d instrument 1011a~1011d driver 1012a~1012d compensator

Claims (11)

In a positioning device for positioning a moving body,
Position measuring means for measuring position information of the moving body in the XY directions;
And at least four drive mechanisms for driving the movable body in the Z direction,
A positioning apparatus comprising: a control unit that selects and drives three of the drive mechanisms based on an output of the position measuring means. The positioning device according to claim 1,
A positioning apparatus wherein the position measuring means is a laser interferometer. The positioning device according to claim 2, wherein
3. A positioning apparatus, wherein three of the drive mechanisms are selected and driven according to the position of the intersection of the X measurement axis and the Y measurement axis of the laser interferometer with respect to the moving body. The positioning device according to any one of claims 1 to 3,
3. A positioning apparatus according to claim 1, wherein the selected three driving mechanisms are switched based on an output of the position measuring means. In the positioning device according to any one of claims 2 to 4,
The positioning apparatus according to claim 1, wherein the movable body has a rectangular shape, and the driving mechanism is disposed at four corners of the rectangular shape. The positioning device according to claim 5, wherein
A positioning apparatus, wherein first and second mirrors are arranged along two orthogonal sides of the rectangle. The positioning device according to claim 6, wherein
The intersection of the X and Y measurement axes of the laser interferometer is
In a triangular area consisting of two sides and one diagonal line of the movable body when the first and second mirrors are located in a triangular area consisting of two sides and one diagonal line. Select the three drive mechanisms in
When the intersection is in a triangular region composed of two sides and one diagonal line not having the first and second mirrors, the movable body is composed of two sides and one diagonal line having the first and second mirrors. A positioning device that selects and positions three drive mechanisms in a triangular region. The positioning device according to any one of claims 1 to 7,
The positioning apparatus comprising: a filter that reduces a frequency component that excites a higher-order elastic mode from the output of the position measuring unit. The positioning device according to claim 1,
The positioning device performs positioning in six axial directions.   An exposure apparatus for positioning a substrate using the positioning apparatus according to claim 1.   A device manufacturing method, wherein a device is manufactured by the exposure apparatus according to claim 10.

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