JP2006042502A - Drift control unit for stage - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress drift of a stage, after the stage has come to a stop, when the stage is moved in a one-dimensional direction by an ultrasonic motor. <P>SOLUTION: A contact member 3 that can be brought into contact with the stage 2 that is set movable in a one-dimensional direction or a base material 9a connected thereto is used as one electrode. Other fixed electrodes 13 and 14 are made to face in the forward or the backward positions in the one-dimensional direction to form two capacitors. Alternating-current voltage is applied to the two capacitors, and a signal based on change in the capacitance of the capacitors is extracted. Based on this change signal, control is carried out so as to stop the stage 2 at a predetermined stop position. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a stage for controlling a drift amount generated at a stop position of a one-dimensional moving body (hereinafter referred to as “stage”) in a precision processing machine, a precision measuring apparatus, a semiconductor manufacturing apparatus, a length measuring SEM (scanning electron microscope), and the like. The present invention relates to a drift control device.

In a structure in which a guide member such as a cross roller guide is provided on the base and a stage that can linearly reciprocate is installed on the guide member, an ultrasonic motor is used as a drive source for moving the stage. (USM) is used.
In the ultrasonic motor, a piezoelectric element is attached to a vibrating body, a part of the vibrating body is brought into contact with the side surface of the stage while being pressed, and an alternating voltage is applied to the piezoelectric element to move the vibrating body. This motion is transmitted to the stage with frictional force, and moves the stage in a one-dimensional direction. When the stage moves to a predetermined position, the driving of the ultrasonic motor is turned off to stop the stage.

FIG. 8 is a plan view showing the structure of the ultrasonic motor. The ultrasonic motor includes three fixing portions 4, 5, and 6 fixed to the base. A vibrating body 8 is attached to the front fixed portion 4 via a parallel hinge 7. The parallel hinge 7 is formed of an elastic member to such an extent that the vibrating body 8 can vibrate left and right due to its deflection.
A first piezoelectric element portion 9 that generates vibration in a direction perpendicular to the moving direction A of the stage 2 is provided at the tip of the vibrating body 8. Further, the second and third piezoelectric element portions 10 and 11 that generate movement in the direction parallel to the moving direction A of the stage 2 between the left and right side surfaces of the vibrating body 8 and the left and right fixing portions 5 and 6. Is provided. A base material 9a is bonded to the tip of the first piezoelectric element portion 9, and a contact member 3 for moving the stage 2 by frictional force while contacting the stage 2 is provided on the tip surface of the base material 9a. It is attached.

  AC vibrations having opposite phases are applied to the second and third piezoelectric element portions 10 and 11, and the first and second piezoelectric element portions 10 and 11 are applied to the first piezoelectric element portion 9 and the second piezoelectric element portions 10 and 11, respectively. The contact member is elliptically vibrated by applying an AC signal to be applied and an AC signal delayed or advanced in phase by 90 degrees. Here, “reverse phase” refers to a phase relationship in which the third piezoelectric element unit 11 moves in the same direction when the second piezoelectric element unit 10 moves in one direction. The elliptical vibration is transmitted to the stage 2 by the frictional force between the contact member 3 and the stage 2, whereby the stage 2 can be moved in an arbitrary direction.

  When the stage 2 is stopped, the application of voltage to the piezoelectric element portions 9, 10, and 11 is stopped. By stopping the application of voltage, the vibrating body 8 is not subjected to the force from the second and third piezoelectric element portions 10 and 11, and the vibrating body 8 is caused by the restoring force of the parallel hinge 7. The stationary position with respect to the front fixing part 4 is maintained. In addition, since the application of voltage to the first piezoelectric element portion 9 in the vibrating body 8 is also stopped, the first piezoelectric element portion 9 and the contact member 3 fixed to the tip of the first piezoelectric element portion 9 are also fixed to the vibrating body 8. It keeps still while maintaining the positional relationship. As a result, the contact member 3 is stationary while holding a predetermined position with respect to the base 1. Since a static frictional force is acting between the contact member 3 and the stage 2 due to the contact therebetween, the stage 2 can be stopped at a predetermined position of the base 1 by the frictional force.

Actually, the movement amount of the stage 2 or the stop position is determined by measuring the movement amount of the stage 2 with a linear scale and a laser interferometer, and feedback-controlling the measurement result to the driving device of the ultrasonic motor. It is done by doing.
Such an ultrasonic motor has the feature that the minimum controllable amount of movement is on the order of nanometers, and the position of the stage can be precisely controlled.

Therefore, recently, it is suitably used as a one-dimensional motion system driving device such as a precision processing machine, a precision measuring device, and a semiconductor manufacturing device.
JP 2002-341248 A JP 2003-369123 A Japanese Patent Laid-Open No. 2-60474

In the stage movement control system using the ultrasonic motor, after the stage is positioned, the stop position after positioning may fluctuate with time due to a change in temperature, a change in elasticity of the driving force transmission means, or the like. . This is called “drift”.
FIG. 9 is a graph showing the amount of drift that occurs after the stage 2 is stopped. The horizontal axis represents time, and the vertical axis represents the drift amount. The drift amount is measured by the laser interferometer described above. As shown in this graph, the generated drift amount becomes 10 nm or more after several tens of seconds have passed.

Recently, the precision of precision machines and the degree of integration of semiconductor circuits have increased, and the precision of the order of 1 nanometer is required. Therefore, there is a desire to suppress the occurrence of such a drift.
Although it is conceivable to precisely control the stop position of the stage using the linear scale and the laser interferometer described above, the entire control device is heavy, large, and expensive.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a stage drift control device that can suppress the drift amount of the stage with a simple configuration.

  The stage drift control apparatus according to the present invention includes a stage that moves in a one-dimensional direction, a contact member that can contact the stage, a drive unit that moves the contact member, and the contact member or a substrate connected thereto. As electrodes, a capacitor formed by facing another fixed electrode at a position before or after the one-dimensional direction, and an AC voltage is applied to the capacitor to generate a signal based on a change in capacitance of the capacitor. A signal processing unit to be extracted and a stop position control unit that controls the driving unit to stop the stage at a predetermined stop position based on a signal output from the signal processing unit.

  According to this configuration, a member that contacts the stage or a substrate connected thereto is used as one electrode, and a capacitor is formed with another fixed electrode facing the front or rear position in the one-dimensional direction. It is possible to take out a signal based on the change in the electrostatic capacity and control the stop position so as to stop the stage at a predetermined stop position based on this signal. Therefore, the drift amount of the stage can be accurately controlled with a simple configuration.

When the contact member is a member that moves in a one-dimensional direction by moving in contact with the stage, the stage is moved and the stop position of the stage is controlled using the same member. be able to. Therefore, it is possible to control the stop position of the stage with a compact structure without separately preparing a measurement system such as a laser interferometer.
The capacitor may be composed of a single capacitance, but the contact member or the base material connected to the contact member is used as one electrode, and other electrodes are respectively fixed at the front and rear positions in the one-dimensional direction. If the two capacitances are formed, the differential signal of the capacitances of both capacitances can be taken out, so that the sensitivity of position detection can be increased.

The contact member may move the stage by a frictional force that contacts the stage.
The stage may be driven by an ultrasonic motor. In this case, the driving means is a piezoelectric element, and the contact member is attached to the piezoelectric element, and the stage is moved by a frictional force that contacts the stage while moving.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a block diagram showing the overall configuration of a drift control device that performs stage stop position control using the capacitance of the present invention. This drift control device is provided as a part of a stage moving device that controls the movement of the stage in a precision processing machine, a precision measuring device, a semiconductor manufacturing device, or the like.

This drift control device is provided with an ultrasonic motor M for moving the stage.
FIG. 2 is a plan view showing the structure of the ultrasonic motor M.
The ultrasonic motor M is disposed on a base 1 that is installed so that the stage 2 can move in a one-dimensional direction (x direction). A contact member 3 is interposed at a portion of the ultrasonic motor M that contacts the stage 2. A total of three fixing portions are provided behind the stage 2 on the side opposite to the contact member 3 and on the upstream side before the stage moving direction and the downstream side after the stage moving direction. These fixed portions are referred to as a back fixed portion 4, a left fixed portion 5, and a right fixed portion 6. Each fixing part 4, 5, 6 is fixed to the base 1.

A vibrating body 8 is attached to the back fixing portion 4 via a parallel hinge 7. The parallel hinge 7 is formed in such a shape as to be elastic enough to allow the vibrating body 8 to vibrate in the x direction due to its deflection.
The vibrating body 8 has a bottomed concave portion, and a first piezoelectric element portion 9 that generates vibration along the y direction perpendicular to the x direction is fixed to the bottom surface of the concave portion. Further, between the left and right side surfaces of the vibrating body 8 and the left and right fixing portions 5 and 6, second and third piezoelectric element portions 10 and 11 that generate vibration along the x direction are fixed.

  In addition, a cylindrical base material 9a made of a material such as copper is coupled to the distal end portion of the first piezoelectric element portion 9, and a frictional force is applied to the distal end surface of the cylindrical base material 9a while being in contact with the stage 2. The contact member 3 for moving the stage 2 is attached. The contact member 3 is made of alumina, zirconia, or Altic which is a composite material of alumina and titanium carbide.

PZT, barium titanate or the like is used as the piezoelectric material constituting the piezoelectric element portions 9, 10, and 11.
An AC signal having an opposite phase is applied to the second and third piezoelectric element portions 10 and 11 from a stage moving device (not shown), and the second and third piezoelectric element portions 9 are applied to the second and third piezoelectric element portions 9 and 11. The contact member 3 is elliptically vibrated in the xy plane by applying an AC signal applied to the third piezoelectric element portions 10 and 11 and an AC signal delayed or advanced in phase by 90 degrees. Thereby, the stage 2 can be moved in the + x direction or the −x direction using the frictional force with the contact member 3. The moving speed of the stage 2 can be arbitrarily set by adjusting the frequency of the AC signal.

The structure of the capacitor, which is a feature of the present invention, will be described below.
The side surface of the cylindrical base material 9a is coated with a metal film such as titanium nitride or titanium carbide. The cylindrical base material 9a itself may be formed of a metal material.
And the fixed electrode body 12 is being fixed to the base 1 in the state surrounding the circumference | surroundings of the said cylindrical base material 9a. As shown in FIG. 3, the fixed electrode body 12 has a hole 12 a that is drawn out in a cylindrical shape.

The fixed electrode body 12 is formed of an insulator such as ceramics or synthetic resin, but the inside of the hole 12a formed by pulling out is made of titanium nitride, titanium carbide or the like in a state of being separated into left and right two poles. It is coated with a metal film. These metal film coatings are indicated by “13, 14” in FIG.
Instead of coating the metal film, it is also possible to form the main body of the fixed electrode body 12 by two separated metal members. In this case, the left and right separated metal members constitute the electrodes of the capacitor.

The cylindrical base material 9 a passes through the drawing hole 12 a of the fixed electrode body 12. The inner diameter of the drawing hole 12a of the fixed electrode body 12 is slightly larger than the radius of the column of the columnar substrate 9a, and therefore there is a gap between the columnar substrate 9a and the metal films 13 and 14. . An electrostatic capacity is formed by this gap.
In this way, two capacitors are formed between the cylindrical base material 9a and the fixed electrode body 12. Here, the capacitance of the cylindrical base material 9a and the metal film 13 of the fixed electrode body 12 on the + x side is C1, and the cylindrical base material 9a and the metal film 14 of the fixed electrode body 12 on the -x side thereof. Is expressed as C2.

The difference in capacitance (C1−C2) is proportional to the amount of movement of the cylindrical base material 9a of the first piezoelectric element portion 9 in the + x direction or the −x direction. That is, the difference in capacitance (C1-C2) increases in the positive direction if the first piezoelectric element portion 9 moves in the + x direction, and if the first piezoelectric element portion 9 moves in the -x direction, Increase in the negative direction.
As shown in FIG. 1, the drift control device of the present invention forms a bridge circuit by the capacitances C1 and C2 and the capacitances C3 and C4 of a fixed capacitor such as a chip capacitor mounted on the substrate 20. ing. A high frequency signal is applied to the bridge circuit from the oscillator 21, and a difference signal corresponding to the difference (C1−C2) between the capacitances C1 and C2 is extracted from the bridge circuit.

This differential signal is input to the low-pass filter 24 through the differential amplifier 22 and the amplifier 23. The low-pass filter 24 removes high-frequency noise that enters the control circuit from a power line or the like, induction noise that is transmitted through the air, or noise that is generated in the semiconductor circuit. As a result, a differential signal without noise is output from the low-pass filter 24.
The difference signal output from the low-pass filter 24 is input to the adder 25. On the other hand, a capacitance difference target value is input to the adder 25. These difference signals are input to the analog PID device 26 and processed by analog signals. Then, a signal proportional to the difference between the two signals is output, and a drive signal for the ultrasonic motor M is generated in the DC driver 27.

  In the above description, a bridge circuit is formed by the capacitances C1 and C2 and the capacitances C3 and C4 of the fixed capacitors, and a difference signal corresponding to the difference between the capacitances C1 and C2 (C1−C2). However, the present invention is not limited to this. For example, even if a single variable capacitance capacitor is formed by the cylindrical base material 9a and one side of the fixed electrode body 12, and a bridge circuit is formed by three other fixed capacitance capacitors mounted on the substrate 20, A signal based on the change in capacitance can be extracted.

  Next, based on the drive signal of the ultrasonic motor M, voltages V having opposite signs are applied to the second and third piezoelectric element portions 10 and 11. By this application, the contact member is moved in the + x direction or the −x direction. The amount of movement in the x direction is much smaller than the amount of movement when the stage moving device moves the stage 2 to a predetermined stop position. By this movement, the stop position of the stage 2 to be stopped can be finely adjusted, and the stage 2 can be accurately stopped at a desired position.

  It has been described that “the voltages V having opposite signs are applied to the second and third piezoelectric element portions 10 and 11”, but the voltage V only needs to be able to correct the drift amount of the stage 2. The waveform is not limited at all. Specifically, it may be a rectangular pulse that lasts for a short time as shown in FIG. Alternatively, a pulse having a smooth shape as shown in FIG. The number of pulses is not limited to one. Further, since the movement amount of the second and third piezoelectric element portions 10 and 11 is determined according to an integral value obtained by integrating the voltage V with time, the voltage V does not necessarily have to be a direct current. As shown in FIG. 4C, it may be an alternating signal that attenuates continuously for one or more cycles.

FIG. 5 is a flowchart for explaining the entire stage movement control including the stop position control in the drift control apparatus described so far.
First, with the stage 2 stopped (step S1), the stage moving device receives a stage moving instruction from a parent control device such as a precision processing machine, a precision measuring device, or a semiconductor manufacturing device (step S2). The stage moving device performs the elliptical vibration, moves the stage 2 while using the laser interferometer, and starts positioning control to the target value (step S3). If it is determined that the stage 2 has moved to a predetermined position (OK in step S4), the drift control device waits for an instruction to start drift control from the stage moving device (step S5).

When the drift control device receives an instruction signal for drift control (step S6), the drift control device starts drift control (step S7).
The drift control device performs the above-described drift control over a predetermined time. As a result, the difference between the stage stop position and the capacitance difference target value falls within a predetermined range. If the drift control device receives the drift control end instruction of the present invention from the stage moving device (step S8), the drift control device ends the drift control (step S9).

With the above procedure, the stage 2 can be stopped at a desired position by finely adjusting the stop position of the stage to be stopped.
Although the embodiments of the present invention have been described above, the embodiments of the present invention are not limited to the above-described embodiments. For example, the shape of the columnar base material 9a and the fixed electrode body 12 surrounding the periphery of the columnar base material 9a may not be cylindrical, and a shape capable of forming a capacitance between the columnar base material 9a and the fixed electrode body 12. Any shape can be used. Moreover, this electrostatic capacitance is not limited to the case where two cylindrical base materials 9a and the metal films 13 and 14 on both sides thereof are formed. As described above, only one cylindrical base material 9a and the metal film 13 or 14 on one side thereof may be formed. Moreover, although one electrode which forms an electrostatic capacitance is formed by the cylindrical base material 9a, the present invention is not limited to this, and the electrode may be formed by the contact member 3 connected to the cylindrical base material 9a. In this case, a wear-resistant conductive material such as cermet, carbide, high carbon chrome steel, or martensite may be used as the material of the contact member 3. In addition, various modifications can be made within the scope of the present invention.

A base 1 capable of moving the stage 2 in a one-dimensional direction was manufactured. The weight of the stage 2 was 15 kg, and a cross roller guide was used as a guide. The moving distance of the stage 2 was measured by installing a laser interferometer having a wavelength of 633 nm. The resolution of measurement is 0.6 nm.
The moving distance of the stage 2 is 100 mm, and the moving speed is 200 mm / second at the maximum value.
For controlling the stop position of the stage 2, the drift control device of FIG. 1 that measures the difference in capacitance was adopted. In the drift control device, the oscillation frequency of the oscillator 21 is 500 kHz, the capacitances C3 and C4 of the chip capacitor are 100 pF, and the cutoff frequency of the low-pass filter 24 is 2.5 kHz.

FIG. 6 is a graph showing the position change for each time during the movement of the stage 2.
FIG. 7 is an enlarged view showing the drift amount when the stage 2 is stopped. The position of the stage 2 on the vertical axis in FIG. 7 is measured using the laser interferometer.
According to FIG. 7, an overshoot of about 3 nm was observed immediately after the stage 2 stopped, but the subsequent drift of the stop position of the stage 2 is less than 1 nm. Therefore, it can be said that the drift has almost completely converged.

It is a block diagram which shows the whole drift control apparatus which performs the drift control of a stage using the electrostatic capacitance of this invention. 2 is a plan view showing a structure of an ultrasonic motor M. FIG. It is a front view of the ultrasonic motor M seen from the stage side. 4 is a graph showing a waveform of a drift control voltage V applied to second and third piezoelectric element portions 10 and 11. It is a flowchart for demonstrating the whole stage movement control including the stop position control of this invention. It is a graph which shows the position change for every time during a stage movement. It is an enlarged view which shows the drift after a stage stops. 1 is a plan view showing a structure of a general ultrasonic motor M. FIG. It is a graph which showed the amount of drift which occurs after stopping a stage.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Base 2 Stage 3 Contact member 4 Back fixing | fixed part 5 Left fixing | fixed part 6 Right fixing | fixed part 7 Parallel hinge 8 Vibration body 9 1st piezoelectric element part 9a Cylindrical base material 10 2nd piezoelectric element part 11 3rd piezoelectric element Part 12 Fixed electrode body 12a Holes 13 and 14 Metal film coating 20 Substrate 21 Oscillator 22 Differential amplifier 23 Amplifier 24 Low pass filter 25 Adder 26 Analog PID device 27 DC driver M Ultrasonic motor

Claims (5)

A stage that moves in one dimension,
A contact member capable of contacting the stage;
Drive means for moving the contact member;
Capacitor formed by using the contact member or the substrate connected thereto as one electrode, and facing another fixed electrode at the front or rear position in the one-dimensional direction,
A signal processing unit that applies an AC voltage to the capacitor and extracts a signal based on a change in capacitance of the capacitor;
A stage drift control device comprising: a stop position control means for controlling the drive means so as to stop the stage at a predetermined stop position based on a signal output from the signal processing section.   2. The stage drift control apparatus according to claim 1, wherein the contact member moves in a one-dimensional direction by moving in contact with the stage.   The capacitor uses the contact member or a substrate connected thereto as one electrode, and fixes other electrodes at the front and rear positions in the one-dimensional direction to form two capacitances, and the signal 3. The stage drift control apparatus according to claim 1, wherein the signal based on the change in capacitance in the processing unit is a differential signal based on a difference between the two capacitances.   4. The stage drift control device according to claim 1, wherein the contact member moves the stage by a frictional force that contacts the stage.   5. The stage drift control device according to claim 4, wherein the contact member and the driving means are constituent members of an ultrasonic motor.

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