JP2010157395A - Device for positioning stage - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stage movement device capable of positioning a stage in nm order across the entire movable range thereof, relating to a stage positioning device which is movably engaged with a guide. <P>SOLUTION: The device includes a feeding nut (nut member) 8 provided to an X stage 13, a ball screw 7 threaded into the feeding nut 8, and an ultrasonic linear motor 37 for rotating the ball screw 7. It further includes a preliminary pressure generating means for generating a preliminary pressure between the nut 8 and a screw shaft 7a of the ball screw 7. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a stage positioning apparatus that is movably engaged with a guide, and more particularly to a stage positioning apparatus used in an observation apparatus such as a scanning electron microscope, a precision processing apparatus using a charged particle beam, and the like.

FIG. 16 shows a cross section including a sample stage of a scanning electron microscope. The scanning electron microscope 1 is provided with a sample stage 3 for positioning the observation sample 2.
The sample stage 3 is provided on the Z stage 11 that moves linearly in the Z-axis direction, the Z stage 11, the T stage 12 that rotates about the X axis with respect to the Z stage 11, and the T stage 12. An X stage 13 that linearly moves in the X-axis direction with respect to the stage 12, a Y stage 14 that is linearly moved in the Y-axis direction with respect to the X stage 13, and a Y stage 14 that is provided in the Y stage 14 It comprises an R stage 15 that rotates about the Z axis with respect to the stage 14 and on which the observation sample 2 is placed.

The sample stage 3 is provided in a vacuum chamber 9 kept in vacuum in order to prevent attenuation of an electron beam used for observation.
Here, a positioning device for the X stage 13 will be described as an example of a positioning device for each stage.

  The X stage 13 engages with a guide (not shown) provided on the T stage 12 and is movable in the X direction. Further, a ball screw 7 is arranged on the T stage 12 along the guide (not shown). One end side of the screw shaft 7 a of the ball screw 7 is rotatably supported using a pair of angular bearings 10.

The X stage 13 is provided with a feed nut (nut member) 8 that is screwed onto the screw shaft 7 a of the ball screw 7.
A stepping motor 4 is provided outside the vacuum chamber 9 (atmosphere side). The output shaft 4a of the stepping motor 4 is introduced into the vacuum chamber 9 using a magnetic fluid seal (not shown).

  The rotation of the stepping motor 4 transmits only the universal joint 5 provided between the output shaft 4a and the one end side of the screw shaft 7a of the ball screw 7 and a slider capable of expanding and contracting in the axial direction. 6 is transmitted to the ball screw 7 via 6.

  The reason why the stepping motor 4 is arranged on the atmosphere side is to avoid the influence of the magnetic field and electromagnetic wave from the stepping motor 4 on the electron beam trajectory, and the heat generated from the stepping motor 4 is applied to both stages 3. This is to prevent positional drift due to thermal expansion.

  The operation of the above configuration will be described. When the stepping motor 4 is driven to rotate, the screw shaft 7 a of the ball screw 7 rotates through the slider 6 and the universal joint 5. Since the feed nut 8 is prohibited from rotating, the X stage 13 moves linearly along a guide (not shown).

  However, when the stepping motor 4 is rotated and the X stage 13 is positioned, backlash due to backlash of each part or hysteresis due to deflection of each part occurs. In particular, during high-magnification observation of several hundred thousand times or more, these effects appear greatly, and positioning of the observation sample 2 is difficult.

Accordingly, it has been proposed to directly drive the stage with an ultrasonic linear motor that eliminates these driving elements and does not generate magnetic fields and electromagnetic waves, as shown in FIG.
FIG. 17 is an overhead view of a single-axis ultrasonic linear motor stage that moves linearly in the X direction.

  The X stage 21 is engaged with the linear guide 22 and is movable in the X axis direction. A plate 23 is provided on the X stage 21 along the X-axis direction. An ultrasonic motor 24 is provided at a place other than the X stage 21, and a movable element 24 a of the ultrasonic motor 24 is pressed against the plate 23. The ultrasonic motor 24 is a resonance type ultrasonic motor with a large feed amount, and is movable even in a non-resonant mode with a small feed amount.

When the ultrasonic motor 24 is driven, the X stage 21 is moved in the X-axis direction along the linear guide 22 by the movement of the movable element 24a, and the non-resonant mode is used, thereby obtaining positioning accuracy on the order of nm. (For example, refer to Patent Document 1).
JP 2004-31537 A

  However, in the stage positioning apparatus having the configuration shown in FIG. 17, the feed amount in the resonance mode of the ultrasonic motor 24 is about 100 nm, and the positioning is too rough for the sample stage of the electron microscope. Therefore, switching to the non-resonant mode (fine positioning mode based on piezoelectric strain) is performed for positioning on the order of nm, but there is a problem that the range in which the stage can be continuously moved in the non-resonant mode is narrow.

  The present invention has been made in view of the above problems, and an object thereof is to provide a stage moving apparatus capable of positioning in the order of nm over the entire movable range of the stage.

  The invention according to claim 1, which solves the above problem, is a positioning device for a stage that is movably engaged with a guide, a nut member provided on the stage, a ball screw that is screwed to the nut member, and the ball screw It is a stage positioning apparatus characterized by comprising an ultrasonic motor that rotationally drives the motor.

  The invention according to claim 2 is characterized in that a preload generating means is provided so that a preload is generated between the nut member and a screw shaft of the ball screw. It is.

  The stage positioning device according to claim 2, wherein the preload generating means is an oversized ball disposed between a screw shaft of the ball screw and the nut member. It is.

  In the invention according to claim 4, the support of the screw shaft of the ball screw is arranged on the side where the guide is provided, and a first angular bearing that rotatably supports one end side of the screw shaft; It is arranged on the side where the guide is provided, is loaded with a thrust load having the same size as the first angular bearing, and a direction different from the direction of the thrust load loaded by the first angular bearing, A second angular bearing that rotatably supports the end side, and a straight line connecting a contact point between the ball of the first angular bearing and the inner ring / outer ring; and a ball of the second angular bearing and the inner ring / outer ring The first angular bearing and the second angular bearer so that a straight line connecting the contact point with the first angular bearing intersects at a point O on the rotation axis of the screw shaft of the ball screw. Preparative a positioning device of a stage according to any one of claims 1 to 3, characterized in that is provided.

  According to a fifth aspect of the present invention, the rotational driving force of the ultrasonic motor acts on a plane including the point O perpendicular to the rotational axis of the screw shaft with respect to the screw shaft of the ball screw. The stage positioning device according to claim 4, wherein the stage positioning device is provided.

  According to a sixth aspect of the present invention, the guide is provided on a plane parallel to the plane of movement of the stage, a first guide provided on a plane parallel to the plane of movement of the stage, and the first guide 6. The ball screw according to claim 1, further comprising a second guide provided in parallel, wherein the screw shaft of the ball screw is disposed at an intermediate position between the first guide and the second guide. This is a stage positioning apparatus.

  The invention according to claim 7 is a position detection means for detecting the position of the stage, a PID control control means for performing position control of the stage by PID control, and the ultrasonic wave according to a position control signal of the PID control means. A deviation amount between a driver for driving a motor, a high-pass filter provided between the PID control means and the driver, a set target position of the stage and the position of the stage detected by the detection means is an allowable deviation. When the amount falls within the range, the control amount of the PID control means is supplied to the driver via the high-pass filter, and the deviation between the set target position of the stage and the position of the stage detected by the detection means Switch means for supplying the control amount of the PID control means to the driver without passing through the high-pass filter when the amount is greater than or equal to the allowable deviation amount A positioning device of a stage according to any one of claims 1 to 6, wherein a.

  According to the first to fifth aspects of the present invention, the ball comprises: a nut member provided on the stage; a ball screw screwed to the nut member; and an ultrasonic motor that rotationally drives the ball screw. By appropriately setting the screw pitches of the screws and nut members, it is possible to position in the order of nm over the entire movable range of the stage even in the resonance mode of the ultrasonic motor.

  Further, since the mover of the ultrasonic motor having low shear rigidity does not directly contact the stage, the stage rigidity is increased, and even if there is an environmental disturbance (for example, floor vibration), there is no problem in the observation image.

  According to the second and third aspects of the invention, by providing the preload generating means so as to generate a preload between the nut member and the screw shaft of the ball screw, backlash is eliminated and high accuracy is achieved. Positioning is possible.

  According to the invention of claim 4, the support of the screw shaft of the ball screw is disposed on the side where the guide is provided, and the first angular bearing that rotatably supports one end side of the screw shaft. A thrust load in a direction different from a thrust load applied by the first angular bearing, and rotatably supports one end side of the screw shaft. A straight line connecting the contact point between the ball of the first angular bearing and the inner ring / outer ring and a straight line connecting the contact point of the ball of the second angular bearing with the inner ring / outer ring. The first angular bearing and the second angular bearing are provided so as to intersect at a point O on the rotation axis of the screw shaft of the ball screw. Since the moment rigidity of the first angular bearing and the second angular bearing is the lowest, the screw shaft of the ball screw is a plane perpendicular to the central axis of the screw shaft within a minute angle with respect to the feed direction. It can move with a light force against the inside. That is, the first angular bearing and the second angular bearing are virtual spherical bearings centered on the point O in a minute range. Therefore, even if the ball screw screw shaft is slightly swung around due to processing accuracy or assembly accuracy, or when the parallelism between the ball screw screw shaft and the guide is not very good, the nut member or stage The axial force perpendicular to the central axis of the screw shaft exerted can be kept small, and almost no force other than the moving direction acts on the stage.

  According to the fifth aspect of the invention, the rotational driving force of the ultrasonic motor acts on the screw shaft of the ball screw on a plane that is orthogonal to the rotational axis of the screw shaft and includes the point O. Thus, that is, the driving force acting on the screw shaft is positioned on a plane passing through the rotation center of the spherical bearing, so that no bending moment is generated on the screw shaft, and the stage can be moved smoothly.

  According to the invention of claim 6, the guide is provided on a plane parallel to the moving plane of the stage, the first guide provided on a plane parallel to the moving plane of the stage, and the first The ball screw includes a second guide provided in parallel with the guide, and the screw shaft of the ball screw is disposed at an intermediate position between the first guide and the second guide so that the first is moved when the stage is moving. The moment due to friction generated in the guide and the second guide is balanced. For this reason, even when the stage driving direction is reversed, it is possible to prevent the stage from rotating in the stage moving plane due to the moment imbalance.

  According to the invention of claim 7, position detection means for detecting the position of the stage, PID control control means for performing position control of the stage by PID control, and the position control signal according to the position control signal of the PID control means A deviation amount between a driver for driving an ultrasonic motor, a high-pass filter provided between the PID control means and the driver, a set target position of the stage and the position of the stage detected by the detection means When the deviation is within the allowable deviation amount, the control amount of the PID control means is supplied to the driver via the high-pass filter, and the set target position of the stage and the position of the stage detected by the detection means If the deviation amount of the PID is greater than the allowable deviation amount, the switch for supplying the control amount of the PID control means to the driver without passing through the high-pass filter. And a means. If an integration operation (I operation) is combined to reduce the residual deviation, a limit cycle (hunting) due to stick-slip generated by friction cannot be avoided. Since the limit cycle has a relatively long period, when the deviation amount between the set target position of the stage and the position of the stage detected by the detection means is within the allowable deviation amount, the control of the PID control means is performed. By supplying quantity to the driver via the high pass filter, limit cycles can be prevented.

  Further, the control amount of the ultrasonic motor after positioning is attenuated exponentially to 0, and the ultrasonic motor stops. Therefore, the vibration of the stage due to the operation of the ultrasonic motor is eliminated, and the heat generation of the ultrasonic motor can be suppressed.

<First embodiment>
A first embodiment of the stage positioning device will be described with reference to FIGS. 1 is a cross-sectional view of a sample stage of a scanning electron microscope to which the first embodiment is applied, FIG. 2 is a top view of FIG. 1, and FIG. 3 is an enlarged view of a pair of angular bearings in FIG. The present embodiment is applied to the sample stage of the scanning electron microscope shown in FIG. 16. In FIGS. 1 to 3, the same parts as those in FIG. The stage positioning apparatus of this embodiment is applied to the Z stage 11, the X stage X13, and the Y stage 14, and the configuration is the same. Therefore, description will be made with the stage positioning device of the X stage 13, and description of other stages will be omitted.

  As shown in FIG. 1, the X stage 13 engages with a guide (not shown) provided on the T stage 12 and is movable in the X direction. Further, a ball screw 7 is arranged on the T stage 12 along the guide (not shown). One end side of the screw shaft 7 a of the ball screw 7 is provided on the T stage 12, and is rotatably supported using a pair of angular bearings including a first angular bearing 31 and a second angular bearing 33.

  As shown in FIG. 3, the second angular bearing 33 is a bearing having the same size as the first angular bearing, and a direction (a left direction in FIG. 3) different from the direction of the thrust load applied by the first angular bearing 31 ( It is provided so as to apply a thrust load in the right direction in the figure.

  Furthermore, a straight line L1 connecting the contact points of the balls 31a of the first angular bearing 31 with the inner ring 31b / outer ring 31c, and a straight line L2 connecting the contact points of the balls 33a of the second angular bearing 33 with the inner ring 33b / outer ring 33c are formed. A first angular bearing 31 and a second angular bearing 33 are provided so as to intersect at a point O on the rotation axis of the screw shaft 7 a of the ball screw 7.

Further, a pulley 35 is fixed to an intermediate position between the first angular bearing 31 and the second angular bearing 33 on the screw shaft 7 a of the ball screw 7.
The T stage 12 has a movable element 39 that contacts the peripheral surface of the pulley 35, and is provided with an ultrasonic motor that rotationally drives the pulley 35, in this embodiment, a resonance type ultrasonic linear motor 37. Accordingly, the rotational driving force of the ultrasonic linear motor 37 acts on the screw shaft 7a of the ball screw 7 on a plane that is orthogonal to the rotation shaft of the screw shaft 7a and includes the point O.

The X stage 13 is provided with a feed nut (nut member) 8 that is screwed onto the screw shaft 7 a of the ball screw 7.
A preload generating means is provided so that a preload is generated between the feed nut 8 and the threaded rod 7a of the ball screw 7. The preload generating means of this embodiment is configured so that the preload is generated by using a ball disposed between the screw shaft 7a of the ball screw 7 and the feed nut 8 as a slightly larger diameter ball (oversize ball). As other preload generating means, there is a structure in which two feed nuts are formed and preload is formed therebetween, and the X stage 13 is urged in the axial direction of the screw shaft 7 a of the ball screw 7.

  In FIG. 2, a first guide 41 for guiding the X stage 13 in the X-axis direction and a first guide 41 provided in parallel to the first guide 41 are provided on a plane parallel to the movement plane of the X stage 13 of the T stage 12. 2 guides 42 are provided.

The screw shaft 7 a of the ball screw 7 is disposed at an intermediate position between the first guide 41 and the second guide 42.
In FIG. 2, reference numeral 43 denotes a guide provided on the X stage 13 for guiding the Y stage 14 in the Y-axis direction.

Next, an electrical configuration for controlling the position of the X stage 13 will be described with reference to FIG. FIG. 4 is a block diagram showing an electrical configuration for controlling the position of the X stage.
In FIG. 4, the position of the X stage 13 driven by the ultrasonic linear motor 37 is detected by a rotary encoder (position detection means) 51. The position detecting means may be a linear encoder.

The position of the X stage 13 detected by the rotary encoder 51 and the set target value are input to the differentiator 52. The deviation output from the differentiator 52 is input to the PID control means 53.
The PID control unit 53 includes a proportional calculation unit 55 that performs a proportional calculation from a deviation, an integration calculation unit 57 that performs an integral calculation from the deviation, and a differential calculation unit 59 that performs a differential calculation from the deviation.

The proportional calculation means 55 has an amplifier 55b that outputs a signal obtained by multiplying the deviation by a proportional gain Kp.
The integration calculation means 57 includes an integrator 57a that performs an integration calculation from the deviation, and an amplifier 57b that outputs a signal obtained by multiplying the calculation value of the integrator 57a by an integration gain Ki.

The differential operation means 59 includes a differentiator 59a that performs a differential operation from the deviation, and an amplifier 59b that outputs a signal obtained by multiplying the operation value of the differentiator 59a by a differential gain Kd.
The signal from the proportional calculation means 55, the signal from the integration calculation means 57, and the signal from the differentiation calculation means 59 are added by an adder 61 to become a position control signal for the ultrasonic linear motor 37.

A driver 63 drives the ultrasonic linear motor 37 in accordance with a position control signal from the PID control means 53.
A high pass filter 65 is provided between the PID control means 53 and the driver 63.

  67, when the deviation amount between the set target position of the X stage 13 and the position of the X stage 13 detected by the rotary encoder 51 becomes an allowable deviation amount, the high-pass filter 65 is used to set the 53 control amount of the PID control means. When the deviation amount between the set target position of the X stage 13 and the position of the X stage 13 detected by the rotary encoder 51 is equal to or larger than the allowable deviation amount, the PID is not passed through the high pass filter 65. The switch means supplies the control amount of the control means 53 to the driver 63.

  The switch means 67 takes in the difference from the differentiator 53 and determines whether or not the deviation amount between the set target position of the X stage 13 and the position of the X stage 13 detected by the rotary encoder 51 has become an allowable deviation amount. It consists of an allowable deviation amount determination unit 69 and a switch 71 that operates in accordance with the determination of the allowable deviation amount determination unit 69.

  The operation of the above configuration will be described. When the ultrasonic linear motor 37 is driven, the screw shaft 7 a of the ball screw 7 rotates via the pulley 35. Since the feed nut 8 is prohibited from rotating, the X stage 13 moves linearly along the first guide 41 and the second guide 42.

According to the above configuration, the following effects can be obtained.
(1) By comprising a feed nut (nut member) 8 provided on the X stage 13, a ball screw 7 screwed into the feed nut 8, and an ultrasonic linear motor 37 that rotationally drives the ball screw 8. By appropriately setting the screw pitch of the screw rod 7a of the ball screw 7 and the feed nut 8, even in the resonance mode of the ultrasonic linear motor 37, positioning in the order of nm can be performed over the entire movable range of the X stage 13.

  Further, since the mover 39 of the ultrasonic linear motor 37 having low shear rigidity does not directly contact the X stage 13, the rigidity of the X stage 13 is increased, and even if there is an environmental disturbance (for example, floor vibration), There is no problem in the observed image.

  In the case of this embodiment, when the lead of the screw rod 7a of the ball screw 7 is 1 mm and the outer diameter of the pulley 35 is 14 mm, the reduction ratio thereof, that is, the value obtained by dividing the lead 1 mm by the outer circumference π × 14 mm of the pulley 35. : The spring constant in the X-axis direction increases by an inverse of about 1/44, that is, about 44 times.

 (2) Preload generating means (in this embodiment, between the screw shaft 7a of the ball screw 7 and the feed nut 8 so that a preload is generated between the feed nut 8 and the screw shaft 7a of the ball screw 7. By providing a ball having a slightly larger diameter as a ball (oversize ball) that is arranged so that a preload is generated, backlash is eliminated and highly accurate positioning is possible.

 (3) The second angular bearing 33 is a bearing having the same size as the first angular bearing 31 and has a direction different from the direction of the thrust load (left direction in FIG. 3) applied to the first angular bearing 31 (right in the figure). Direction).

  Furthermore, a straight line L1 connecting the contact points of the balls 31a of the first angular bearing 31 with the inner ring 31b / outer ring 31c, and a straight line L2 connecting the contact points of the balls 33a of the second angular bearing 33 with the inner ring 33b / outer ring 33c are formed. A first angular bearing 31 and a second angular bearing 33 are provided so as to intersect at a point O on the rotation axis of the screw shaft 7 a of the ball screw 7.

  For this reason, the moment rigidity of the first angular bearing 31 and the second angular bearing 33 is the lowest around the point O. Therefore, the screw shaft 7a of the ball screw 7 is within a minute angle with respect to the feed direction. It can move with a light force with respect to a plane perpendicular to the central axis of the screw shaft 7a. That is, the first angular bearing 31 and the second angular bearing 33 are virtual spherical bearings centered on the point O in a minute range. Therefore, when the screw shaft 7a of the ball screw 7 is slightly swung around due to processing accuracy or assembly accuracy, or the parallelism between the screw shaft 7a of the ball screw 7 and the first guide 41 and the second guide 42. Even if the condition is not so good, the force in the axial direction perpendicular to the central axis of the screw shaft 7a exerted on the feed nut 8 and the X stage 13 can be kept small, and almost no force other than the moving direction acts on the X stage 13. .

(4) The rotational driving force of the ultrasonic linear motor 37 acts on the screw shaft 7a of the ball screw 7 on a plane that is orthogonal to the rotation shaft of the screw shaft 7a and includes the point O.
That is, when the driving force acting on the screw shaft 7a is located on a plane passing through the rotation center of the spherical bearing constituted by the first angular bearing 31 and the second angular bearing 33, a bending moment is generated in the screw shaft 7a. Smooth stage movement can be obtained.

 (5) The screw shaft 7 a of the ball screw 7 is disposed at an intermediate position between the first guide 41 and the second guide 42. Therefore, when the X stage 13 is moving, the moment caused by the friction generated in the first guide 41 and the second guide 42 is balanced. For this reason, even when the stage drive direction is reversed, it is possible to prevent the X stage 13 from rotating in the stage moving plane due to the moment imbalance.

 (6) A rotary encoder 51 for detecting the position of the X stage 13, a PID control control means for controlling the position of the X stage 13 by PID control, and an ultrasonic linear motor 37 according to the position control signal of the PID control means 53. The deviation amount between the driver 63 to be driven, the high-pass filter 65 provided between the PID control means 53 and the driver 63, the set target position of the X stage 13 and the position of the X stage 13 detected by the rotary encoder 51 is When the deviation is within the allowable deviation amount, the control amount of the PID control means 53 is supplied to the driver 63 via the high-pass filter 65, and the set target position of the X stage 13 and the X stage 13 detected by the rotary encoder 51 are supplied. If the deviation from the position is greater than or equal to the allowable deviation, the control of the PID control means 53 without passing through the high-pass filter 65 And switch means 67 for supplying the amount to the driver 63.

  If an integration operation (I operation) is combined to reduce the residual deviation, a limit cycle (hunting) due to stick-slip generated by friction cannot be avoided. Since the limit cycle has a relatively long cycle, when the deviation amount between the set target position of the X stage 13 and the position of the X stage 13 detected by the rotary encoder 51 is within the allowable deviation amount, the PID control means 53 By supplying this control amount to the driver 63 via the high-pass filter 65, the limit cycle can be prevented.

Further, the control amount of the ultrasonic linear motor 37 after positioning is attenuated exponentially to 0, and the ultrasonic linear motor 37 stops. Therefore, the vibration of the X stage 13 due to the operation of the ultrasonic linear motor 37 is eliminated, and the heat generation of the ultrasonic linear motor 37 can be suppressed.
<Second embodiment>
This will be described with reference to FIG. FIG. 5 is a sectional view of a sample stage of a scanning electron microscope to which the second embodiment is applied. The difference between this embodiment and the first embodiment is the ultrasonic motor, and the other parts are the same. Therefore, the same parts as those in FIG.

  The ultrasonic motor of the present embodiment uses a rotary ultrasonic motor 101, and connects the output shaft 101a of the rotary ultrasonic motor 101 and the screw rod 7a of the ball screw 7 using a backlashless coupling 103. ing.

In the present embodiment, the feed rigidity in the feed direction (X-axis direction) is high as in the first embodiment, and unlike the case of using an electromagnetic motor, the influence of a magnetic field and electromagnetic waves can be avoided.
In the case of the ultrasonic linear motor 37 of the first embodiment, the mover 39 is pressed against the pulley 35 with a relatively strong spring force. Therefore, the rolling resistance of the first angular bearing 31 and the second angular bearing 33 is increased.

On the other hand, in the connection structure between the rotary ultrasonic motor 101 and the screw shaft 7a of this embodiment, the rolling resistance of the first angular bearing 31 and the second angular bearing 33 does not increase, and the X stage 13 moves with a lighter torque. To do.
<Third embodiment>
This will be described with reference to FIGS. FIG. 6 is a partial cross-sectional view of a sample stage of a scanning electron microscope to which the third embodiment is applied, and FIG. 7 is a cross-sectional view taken along a cutting line AA in FIG. The difference between this embodiment and the first embodiment is the ultrasonic motor, and the other parts are the same. Therefore, the same parts as those in FIG.

  In these drawings, between the pulley 35 and the T stage 12, an ultrasonic motor is not an ultrasonic linear motor or a rotary ultrasonic motor with a driving frequency of several tens of kHz. A surface acoustic wave motor 201 that generates a traveling wave having an amplitude of several 10 nm on the surface of the surface and drives by this is disposed.

  The surface acoustic wave motor 201 is provided on a support member 203 whose base end is attached to the T stage 12. A hinge portion 203 a having a reduced thickness is formed at the base portion of the support member 203. For this reason, when the hinge part 203a is elastically deformed, the front end side of the support member 203 is rotatable in the direction of arrow B in FIG. 7 around the hinge part 203a.

  The T stage 12 has a bottomed hole 205 having an opening on the support member 203 side. A steel ball 207 and a spring 209 are disposed in the hole 205 from the opening side. The steel ball 207 causes the surface acoustic wave motor 201 to be connected to the upper periphery of the pulley 35 via the support member 203 by the biasing force of the spring 209. Pressed against the surface.

  According to such a configuration, the surface acoustic wave motor 201 has a small amplitude but a high frequency. Therefore, the surface acoustic wave motor 201 can be driven at a high speed of several m / sec and a smaller minimum step feed. Therefore, high-speed and precise positioning is possible.

For step driving, as shown in FIG. 8, a sine wave burst signal 215 obtained by multiplying a sine wave 211 by a rectangular gate 213 is used.
Since the amplitude of the surface acoustic wave motor 201 is extremely small, it is necessary to avoid the entry of dust into the contact surface with the pulley 35. In this embodiment, as shown in FIGS. 9 and 10, a V-shaped groove 35 a is provided on the circumferential surface of the pulley 35 along the circumferential direction. 9 is a top view of the pulley, and FIG. 10 is a front view of FIG. As a result, minute dust escapes into the V-shaped groove 35a, and the entry of dust into the contact surface between the surface acoustic wave motor 201 and the pulley 35 is eliminated. In FIG. 9, a hatched portion C is a contact surface with the surface acoustic wave motor 201.

  In the surface acoustic wave motor, the driving force increases as the contact area between the surface acoustic wave motor and the peripheral surface of the pulley increases. Therefore, if the driving force is insufficient, another surface acoustic wave motor may be provided. That is, as shown in FIGS. 11 and 12, a surface acoustic wave motor 201 ′ pressed against the lower portion of the pulley 35 is provided. Note that the mechanism for pressing the surface acoustic wave motor 201 ′ against the lower peripheral surface of the pulley 35 is the same as the mechanism for pressing the surface acoustic wave motor 201 against the upper peripheral surface of the pulley 35. ') And repeated description is omitted.

  In FIG. 12, reference numerals 217 and 219 denote power return wirings connecting the two surface acoustic wave motors 201 and 201 '. By using the power return wirings 219 and 217, the two surface acoustic wave motors 201 and 201 'can be driven by one drive circuit.

  Further, as a configuration for increasing the contact area between the surface acoustic wave motor and the peripheral surface of the pulley, as shown in FIG. 13, a contact portion with the pulley 35 of the surface acoustic wave motor 201 is formed with a V-shaped groove 201a, or FIG. As shown, the groove 201b having a bottom curved at the same curvature as that of the peripheral surface of the pulley 35 may be formed at the contact portion of the surface acoustic wave motor 201 with the pulley 35. When the configuration of FIGS. 13 and 14 is applied, in order to avoid the ingress of dust into the contact surface between the surface acoustic wave motor 201 and the pulley 35, as shown in FIG. A V-shaped groove 35b may be provided along.

It is sectional drawing of the sample stage of the scanning electron microscope to which the 1st form example is applied. FIG. 2 is a top view of FIG. 1. It is an enlarged view of the angular bearing pair part of FIG. It is a block diagram explaining the electrical structure which performs position control of the X stage of FIG. It is sectional drawing of the sample stage of the scanning electron microscope to which the 2nd example is applied. It is a fragmentary sectional view of the sample stage of the scanning electron microscope to which the third embodiment is applied. It is sectional drawing in the cutting line AA of FIG. It is a figure explaining step drive. It is a top view of the pulley in FIG. FIG. 10 is a front view of FIG. 9. It is a figure explaining the structure which increased the number of Danze surface wave motors in FIG. FIG. 12 is a cross-sectional view taken along a cutting line DD in FIG. 11. It is a figure explaining the other example of a form. It is a figure explaining the other example of a form. It is a figure explaining the other example of a form. It is sectional drawing of the sample stage of a scanning electron microscope. It is the figure which looked down at the 1 axis ultrasonic linear motor stage which moves linearly to a X direction from the upper part.

Explanation of symbols

7 Ball screw 8 Feed nut (nut member)
13 X stage

Claims (7)

In a stage positioning device that is movably engaged with a guide,
A nut member provided on the stage;
A ball screw threadably engaged with the nut member;
A stage positioning apparatus comprising: an ultrasonic motor that rotationally drives the ball screw.   2. The stage positioning apparatus according to claim 1, wherein preload generating means is provided so that a preload is generated between the nut member and a screw shaft of the ball screw. The preload generating means includes
3. The stage positioning device according to claim 2, wherein the stage positioning device is an oversized ball disposed between a screw shaft of the ball screw and the nut member. The support of the screw shaft of the ball screw is
A first angular bearing disposed on the side where the guide is provided and rotatably supporting one end side of the screw shaft;
A thrust load is disposed on the side where the guide is provided, and has the same size as the first angular bearing, and a thrust load in a direction different from the direction of the thrust load applied by the first angular bearing, A second angular bearing that rotatably supports the end side,
Further, a straight line connecting the contact points between the balls of the first angular bearing and the inner ring / outer ring and a straight line connecting the contact points of the balls of the second angular bearing with the inner ring / outer ring are formed on the screw shaft of the ball screw. 4. The stage positioning apparatus according to claim 1, wherein the first angular bearing and the second angular bearing are provided so as to intersect at a point O on the rotation axis.   The rotational driving force of the ultrasonic motor acts on a plane including the point O perpendicular to the rotational axis of the screw shaft with respect to the screw shaft of the ball screw. Stage positioning device. The guide is
A first guide provided on a plane parallel to the moving plane of the stage;
A second guide provided on a plane parallel to the moving plane of the stage, and provided in parallel with the first guide;
6. The stage positioning apparatus according to claim 1, wherein the screw shaft of the ball screw is disposed at an intermediate position between the first guide and the second guide. Position detecting means for detecting the position of the stage;
PID control control means for performing position control of the stage by PID control;
A driver for driving the ultrasonic motor in accordance with a position control signal of the PID control means;
A high-pass filter provided between the PID control means and the driver;
When the deviation amount between the set target position of the stage and the position of the stage detected by the detection means falls within an allowable deviation amount, the control amount of the PID control means is transferred to the driver via the high-pass filter. When the deviation amount between the set target position of the stage and the position of the stage detected by the detection means is greater than or equal to an allowable deviation amount, the control amount of the PID control means is not passed through the high-pass filter. Switch means for supplying to the driver;
The stage positioning device according to claim 1, comprising:

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