JPS63232916A - Precise positioning device - Google Patents

Abstract

PURPOSE:To improve micro feed precision, by a method wherein a motor stator is rotatably and axially immovably mounted to a fixing bed, a micro rotation mechanism is situated between a stator and the fixing bed, and a brake is secured to the motor stator to fix an output shaft. CONSTITUTION:A table 11 is slid over a fixing bed 12 by means of a ball screw mechanism 14. A ball screw shaft 14a is coupled to the output shaft of a motor 16. A brake 17 is integrally mounted to the stator of the motor 16, and a flange 18 is secured to the motor stator, and a flange 18 is secured to the motor stator. The stator of the motor 16 and the flange 18 are rotatably mounted in an axially constrained state to a bracket 19 mounted to the fixing table 12 through a bearing. A piezo-element 20 has the one end secured to the bracket 19 and the other end secured to the protrusion of the piezo-element 20 pressed through the force of a spring 21. After a ball screw shaft 14a and a whole motor are roughly positioned by means of a ball screw mechanism, the ball screw shaft and the whole motor are integrally rotated by means of the piezo-element, and a stable precise feed is practicable.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION The present invention relates to a precision positioning device for semiconductor manufacturing equipment and the like.

BACKGROUND OF THE INVENTION In recent years, the need for microfabrication has been increasing in the manufacture of semiconductors, etc.9, and the accuracy of positioning devices used for these processes is moving from microns to submicrons and even nanometers.

Such a positioning device has a precision positioning ability of 9
Instead, the ability to move at high speed and over a wide range is often required to improve production. In order to satisfy these conflicting performances, two types of transport systems have been developed: one uses a pole screw and motor, which can move at high speed and over a wide range, but has poor precision, and the other uses a piezo element, which has high precision but has a narrow movement range. A precision positioning device with a mechanism is used.

Figure 3 shows a conventional precision positioning device, where 1 is a table, 2
is a fixed base, 3a is a linear orbit bearing, 3b is a linear orbit guide, 4 is a motor, 6a is a pole screw shaft, and sb is a pole screw nut.Table 1 is coarsely positioned at high speed and over a wide range by motor 4 and ball screw ε. It will be done. 6 is a piezo element, 7 is a pole screw nut retainer, 8 is a pole nut 7, and a spring that presses and fixes the piezo element 6 to the table 1. After rough positioning is completed, the current position of the table is measured and the position is compared with the target position. By changing the voltage supplied to the piezo element 6 according to the error, the length of the piezo element 6 is minutely changed to perform precise positioning.

Problems to be Solved by the Invention However, in the conventional example described above, it was impossible to realize precise positioning that exceeds the feeding accuracy of the piezo element.

Furthermore, the elasticity of the piezo element 6 and the spring 8 reduces the rigidity of the drive system, resulting in deterioration of the acceleration/deceleration dynamic characteristics during rough positioning of the table 1 and a reduction in the load capacity that the table can carry. Furthermore, when the piezo element 6 moves minutely, the ball screw shaft 5b rotates due to the reaction force of the table 1 and the load, making it difficult to perform stable minute feeding.

Means for Solving the Problems In view of the above-mentioned drawbacks, the present invention supports a motor stator so as to be rotatable with respect to a fixed base and not move in the axial direction, and between the motor stator and the fixed base, for example, a piezo The motor is characterized in that it is provided with a minute rotation mechanism that generates a relatively minute rotational movement using an element, and is provided with a brake fixed to the motor stator that locks the motor output shaft.

Operation In the above configuration, the pole screw shaft is fixed to the motor stator by the brake after rough positioning is completed. Thereafter, the minute rotation mechanism operates according to the error from the target position, and the entire pole screw shaft and motor are rotated integrally to perform minute feeding. At this time, since the pole screw has the function of converting rotational motion into linear motion and at the same time decelerating it, more precise positioning is possible than in the conventional example. In addition, the rigidity of the drive system is improved compared to conventional systems because the elasticity of the minute rotation mechanism is apparently reduced by the deceleration function of the ball screw, and the acceleration/deceleration dynamic characteristics and load capacity during rough positioning are improved compared to conventional systems. improves.

Furthermore, since the ball screw shaft is fixed to the motor stator using a brake, the ball screw does not rotate relative to the motor stator during minute feed due to the inertial force of the table and load.

EXAMPLE Hereinafter, a precision positioning device according to an example of the present invention will be described with reference to the drawings.

1 and 2, 11 is a table, 12 is a fixed base, 13a is a linear track bearing, 13b is a linear track guide,
14a is a ball screw shaft, via a coupling 16,
It is connected to the output shaft of the motor 16. 14b is fixed to the table 11 with a pole screw nut. 17 is a brake provided integrally with the stator of the motor 16; 18;
is a 7-lunge fixed to the stator of the motor 1e, and the stator of the motor 16 and the 7-lunge 18 are rotatably and axially attached to a bracket 19 attached to the fixed base 12 via a bearing (not shown). It is installed in a restrained state.

2o is a piezo element, one end of which is fixed to the bracket 19, and the other end fixed to a rod-shaped projection projecting from the 72-inch 18 in the radial direction. 21 also goes to the bracket at one end 19
This spring corrects the backlash of the fastening part by pressing the spring stopper and the rod-shaped projection of the 7 flange 18 at the other end. 22 is a linear encoder that measures the position of the table 11.

Next, the operation of this embodiment will be explained. First, a target value is given to the control device. The control device first drives the motor 16 according to the error between the current position information obtained from the linear encoder 22 and the target position, converts rotational movement into linear movement using the pole screw mechanism 14, moves the table 11, and roughly moves the table 11. Start positioning. When the error between the target position and the current position becomes less than the permissible limit for rough positioning, the motor 16 is stopped, and at the same time the brake 17 is operated to lock the ball screw shaft 14a to complete the rough positioning. Next, shift to precision positioning, change the voltage applied to the piezo element 2o according to the error between the target position and the current position, minutely change the length of the piezo element 20, and
The 4a1 motor 16, brake 17, and flange 18 are integrally rotated minutely. The ball screw nut 14b moves slightly in the axial direction, and therefore the table 11 also moves slightly in the axial direction. At this time, the amount of change in the length of the piezo element 20 is set to Δx1
If the amount of movement of the table 11 is Δλ, the distance from the mounting position of the piezo element 2o to the 7 flange 18 to the shaft center of the motor 6 is R, and the lead of the ball screw shaft 14a is L, then Δλ=□−ΔX 2πR, and the piezo element It can be seen that the movement of 2o is decelerated by the ball screw 14. After the tilt pull 11 moves from the target position to within the tolerance range for precise positioning, the series of positioning operations ends.

In this manner, according to this embodiment, the movement of the piezo element 20 is decelerated by the ball screw mechanism 14, so that positioning can be performed with higher precision than in the conventional method. Also,
Conversely, the rigidity of the entire drive system is determined by the piezo element 20 and the spring 21.
The elasticity of the ball screw is apparently reduced by the deceleration function of the ball screw, which improves the acceleration and deceleration dynamic characteristics of the table 11 for rough positioning.
1's load capacity also increases. i! In addition, the ball screw shaft 14a
Since the ball screw shaft 14a is locked by the brake 17, the ball screw shaft 14a does not rotate relative to the motor 16 due to the reaction of the inertia of the table 11 during minute positioning, and stable minute feed can always be performed.

In this embodiment, a piezo element is used as the micro-rotation mechanism, but other elements may also be used, and the point is that the ball screw shaft only needs to be slightly rotated by the micro-rotation mechanism. Further, in this embodiment, a motor and a ball screw mechanism are used as the rotary actuator that drives the table and the screw mechanism directly connected thereto, but the present invention is not limited thereto.

Effects of the Invention As described above, according to the present invention, since the movement of the micro-rotation mechanism is decelerated by the ball screw, highly accurate positioning is possible. In addition, since the elasticity of micro-rotation mechanisms such as piezo elements and springs is apparently reduced by the ball screw, the rigidity of the drive system is less reduced than in conventional systems.
The acceleration/deceleration dynamic characteristics and load capacity of the table during rough positioning are improved compared to conventional ones. Furthermore, during precision positioning, the ball screw shaft is fixed to the motor stator by the brake, so the ball screw shaft does not rotate relative to the motor stator due to the inertial force of the table, load, etc., and the ball screw shaft is always stable. It can perform minute feeds and has great industrial value.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partially cutaway perspective view of an embodiment of the present invention, FIG. 2 is an enlarged view of the same portion, and FIG. 3 is a longitudinal sectional view of a conventional example. 11...Table, 12...Fixed stand,
13a...Linear orbit bearing, 13b...Linear orbit guide, 14a...Ball screw shaft, 14b
...Ball screw nut, 15...Coupling, 16...Motor, 17...
Brake, 18...Flange, 19...
・Bracket, 2o...-Piezo element, 21...
... Spring, 22 ... Linear encoder. Name of agent: Patent attorney Toshio Nakao and 1 other person H-
--Table 14-m-2 [Te-no Otsu + Lee F! Jyo(ni1C--
-Motor 2f-, failed

Claims (2)

[Claims] (1) A table, a fixed base that supports the table so as to be movable back and forth via a guide mechanism, a rotary actuator that drives the table, a screw mechanism directly connected to the table, and a stator of the rotary actuator that means for rotatably supporting a fixed base; means for slightly rotationally driving a stator of the rotary actuator with respect to the fixed base; and means for rotating the rotor of the rotary actuator relative to the stator of the rotary actuator. Precision positioning device consisting of means for fixing to prevent rotation. (2) The precision positioning device according to claim 1, wherein the minute rotational drive means is a piezo element.