JPS6224929A - Xy stage - Google Patents

Abstract

PURPOSE:To enable positioning to be performed in a high speed further with high accuracy, by interposing a pressure switching means, which variably sets a supply air pressure to a pneumatic bearing in a moving stage in accordance with it performs positioning action and when it performs fine moving action, in an air supply line to the moving stage. CONSTITUTION:Compressed air from a compressor 28 is fed with air of pressure P1 always to each pneumatic bearing 5, 6 in movable guides 2, 3 via filter 29, high pressure use pressure reducing valve 30 and a low pressure use pressure regulating valve 31 while with air selectively to a pneumatic bearing 7 of a moving stage 4 through a solenoid valve 32. And the air is respectively supplied to the pneumatic bearing 7 in the moving stage 4 with air of pressure P1 directly through the solenoid valve 32 when the moving stage 4 performs positioning action while with air of lower pressure P2 through a regulator 33 when the moving stage 4 performs fine moving action. In this way, high accurate positioning can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to an XY stage having an ultra-precise positioning function that is applied to precision measuring instruments, precision processing machines, semiconductor manufacturing equipment, and the like.

<Summary of the Invention> The present invention provides an XY stage in which a movable guide and a moving stage are supported on a table via an air bearing, and the moving stage can be moved at high speed by variably setting the supply pressure of compressed air to the moving stage. It also enables highly accurate positioning.

<Background of the Invention> Conventionally, this type of XY stage has movable guides 2.3 arranged vertically and horizontally on a horizontal table 1, as shown in FIG.
A moving stage 4 is placed at the intersection. Each movable guide 2゜3 and moving stage 4 are supported in a floating state by air bearings 5, 6.7, and compressed air is supplied to the air bearings 5, 6.7 through air tubes 8, 9゜10, respectively. sent.

FIG. 5 shows an example of air piping in this conventional example, in which the compressed air emitted from the compressor 11 is transferred to the air clean unit 12. High pressure air regulator 13. While passing through the low pressure air regulator 14, the pressure is P-, Po, P+
The structure is such that compressed air having a final pressure P that changes sequentially with P is uniformly supplied to the movable guide 2.3 and the moving stage 4.

By the way, in this type of XY stage, the current position of the moving stage 4 is observed by the laser length measuring device 15, and from this current position to the target position, the linear motor 1 is operated while controlling the speed.
6 and 17, and near the target position, speed control is switched to position control to position the moving stage 4 with high precision. This series of control operations is performed by a control system including a position feedback loop 18 and a velocity feedback loop 19 as shown in FIG. In the figure, a speed pattern generation circuit 20 is a circuit for generating a target speed pattern for speed control, and an integral/phase advance gain compensation element 21 is used to provide compensation for improving control characteristics during position control to a speed feedback loop 19. On the other hand, the circuit to provide, the phase lead gain compensation element 22 is a linear motor 16,
17 and the XY stage 23 (movable guides 2, 3 and moving stage 4) to provide compensation for improving control characteristics, and switching from speed control to position control is performed by switch 24. In the figure, XR is current position data, VR is current speed data, and X.

represents the target position data, and S is the Laplace operator.

In the above control system, the XY stage 23 which is the controlled object
Since this constitutes a spring system supported by an air bearing, the resonant frequency f0 shown in FIG. 7 exists in this controlled object. In order to control such a controlled object at high speed, it is necessary to increase this resonance frequency f0. Resonant frequency f0
is given by the following equation, where M is the mass of the controlled object and K is the spring constant (bearing stiffness value here). Therefore, in order to increase the resonance frequency f0, the bearing stiffness value K should be increased ( (See Figure 8).

On the other hand, when finely moving the moving stage using a fine movement mechanism (not shown) built into the movable guides 2 and 3, -axis (
For example, the degree of influence (this is called "inter-axis interference") on other axes (for example, Y-axis) when moving the X-axis) becomes a problem.

Reducing this inter-axis interference leads to improved fine tuning characteristics, but in order to achieve this improved characteristics, it is necessary to
All you have to do is weaken the bearing rigidity between the and movable guide 2.3 (
(See Figure 9).

The above bearing stiffness value is proportional to the supply pressure of compressed air to the moving stage 4, as shown in the 10th page.
It is desirable that this bearing stiffness value be large from the viewpoint of increasing the speed of positioning control, and on the other hand, it is desirable that it be small from the viewpoint of improving the inclination characteristics. However, the conventional XY
In the stage, the air pressure supplied to the moving stage 4 was constant, and it was impossible to satisfy both of the above conditions.

<Object of the invention> This invention is intended to solve the above problems,
It is an object of the present invention to provide an XY stage that can realize high-speed and highly accurate positioning.

<Structure and Effects of the Invention> In order to achieve the above object, in the present invention, the air pressure supplied to the air bearing is adjusted in the air supply path for sending compressed air to the moving stage during positioning operation and during slight movement. The settings can be changed depending on the situation.

According to this invention, when positioning the moving stage, the resonant frequency of the XY stage can be increased by increasing the supply pressure of compressed air to the moving stage and increasing the bearing stiffness value. High-speed control of the XY stage can be achieved.Also, when making fine movements of the moving stage, good fine movement characteristics can be obtained by lowering the supply pressure of compressed air and weakening the bearing stiffness value, achieving highly accurate positioning, etc. , it achieves the remarkable effect of achieving the purpose of the invention.

<Description of Embodiments> FIG. 1 shows an XY stage according to this invention, and FIG. 2 shows an example of its air piping.

The XY stage shown in FIG. 1 has the same configuration as the one shown in FIG.
Moving stage 4, air bearings 5, 6, 7, linear motor 1
6, 17, a laser length measuring device 15, etc. Air tube 2 is attached to the air bearing 5.6 of each movable guide 2.3.
5.26, and compressed air at a predetermined supply pressure is fed into the air bearing 7 of the moving stage 4 through the air tube 27, respectively.

Compressed air is emitted from the compressor 28 and sent to the air clean unit 29, high pressure regulator 30, and low pressure regulator 31 in order, and the pressures are also Ps, Po, Pt.
and will change sequentially.

Then, the compressed air with pressure P is transmitted to the movable guides 2 and 3.
It is constantly fed to each air bearing 5,6 of the moving stage 4, and selectively fed to the air bearing 7 of the moving stage 4 via a solenoid valve 32.

That is, in the illustrated example, in the air supply path to the moving stage 4, the supply pressure to the air bearing 7 is set to P.

and Pt (where Pz<P,), and a pressure switching unit 34 including a solenoid valve 32 for switching and setting the pressure P and Pt, and a regulator 33 for reducing the pressure to P and Pt.
Compressed air at pressure P is used to position the moving stage 4, and pressure P is used to move the moving stage 4 slightly.
2 compressed air is applied to the air bearing 7 of the moving stage 4, respectively.
The control circuit 35 controls the switching operation of the solenoid valve 32 so that the electric current is supplied to the electromagnetic valve 32.

FIG. 3 shows another example of air piping. In the figure, 38 is a compressor, 39 is an air clean unit, 40 is a regulator, and in the case of this embodiment, movable guides 2, 3
A pressure switching unit 34 including an air regulator 36 and a solenoid valve 37 is provided in a common air supply path to the moving stage 4.

Thus, when positioning the moving stage 4, compressed air at a pressure P0 is used, and when moving the moving stage 4 slightly, compressed air at a reduced pressure P1 (p+<po) is used.
They are supplied simultaneously to all air bearings 5, 6.7, respectively.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of the configuration of the XY stage according to the present invention, FIG. 2 is a diagram showing an example of its air piping, FIG. 3 is a diagram showing an example of air piping of another embodiment, and FIG. 4 is a diagram showing a conventional example. Fig. 5 is a diagram showing an example of the conventional air piping, Fig. 6 is a block diagram showing the control system of the XY stage, and Figs.
FIG. 0 is a diagram for explaining the characteristics of the XY stage. 1...Table 2.3...Movable guide 4.
...Movement stage 5.6.7...Air bearing 28.38...Compressor 34...Pressure switching unit Patent Applicant: Juishi Electric 3M Co., Ltd.

Claims (1)

[Scope of Claims] In the XY stage, movable guides that intersect vertically and horizontally on the table and a moving stage are provided at the intersection points thereof, and each movable guide and the moving stage are supported in a floating state by air bearings, the above-mentioned An air supply means is provided for supplying compressed air to each air bearing of the movable guide and the moving stage, and a pressure switching means is provided in the air supply path to the moving stage for variably setting the supply pressure to the air bearing. XY stage made up of intervening devices.