Active anti-vibration apparatus and exposure apparatus

Details Active anti-vibration apparatus and exposure apparatus Active anti-vibration apparatus and exposure apparatus

2001-02-07

2004-01-27

Picard, Leo (Department: 2125)

Data processing: generic control systems or specific application

Specific application, apparatus or process

Mechanical control system

C248S550000, C318S651000

Reexamination Certificate

active

06684132

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATIONS
This application is related to U.S. application Ser. No. 09/035,982 entitled “Anti-vibration apparatus and anti-vibration method thereof” filed on Mar. 6, 1998 and issued as U.S. Pat. No. 6,170,622 on Jan. 9, 2001 naming Shinji Wakui, Takehiko Mayama and Hiroaki Kato as inventors and assigned to the assignee of this application.
FIELD OF THE INVENTION
The present invention relates to an active anti-vibration apparatus suitably used in a semiconductor manufacturing exposure apparatus or electron microscope which prints a pattern on a reticle onto a semiconductor wafer, or a liquid crystal substrate manufacturing exposure apparatus or electron microscope which prints a pattern on a reticle onto a glass substrate or the like, and an exposure apparatus using the same.
More specifically, the present invention relates to an active anti-vibration apparatus which can suppress an external vibration transmitted to an anti-vibration table and positively cancel a vibration generated by a precision machine itself mounted on the anti-vibration table, and can correct the inclination of the anti-vibration table produced by the moving load of a stage mounted on the anti-vibration table, and an exposure apparatus using this active anti-vibration apparatus.
BACKGROUND OF THE INVENTION
In an electron microscope using an electron beam, or an exposure apparatus represented by a stepper, a wafer stage is mounted on an anti-vibration apparatus. The anti-vibration apparatus has a function of damping vibrations by a vibration absorbing means such as a pneumatic spring, coil spring, anti-vibration rubber member, and the like.
In a passive anti-vibration apparatus with the vibration absorbing means as described above, although a vibration transmitted to it from a floor or the like can be damped to a certain degree, a vibration produced by a wafer stage itself mounted on the anti-vibration apparatus cannot effectively be damped. In other words, a reaction force produced by high-speed motion of the wafer stage itself vibrates the anti-vibration apparatus to considerably interfere with the positioning settling performance of the wafer stage.
In the passive anti-vibration apparatus, insulation (anti-vibration) of a vibration transmitted to it from the floor or the like and a vibration suppressing (vibration control) performance for a vibration generated by high-speed movement of the wafer stage itself trade off each other.
In order to solve these problems, in recent years, an active anti-vibration apparatus tends to be used. The active anti-vibration apparatus can eliminate the trade-off between anti-vibration and vibration control within a range that can be adjusted by an adjusting mechanism. Above all, when the anti-vibration apparatus adopts feed-forward control, it can realize a performance that cannot be achieved by a passive anti-vibration apparatus.
Not only in the passive anti-vibration apparatus but also in the active anti-vibration apparatus, when the wafer stage mounted on the anti-vibration table performs step and repeat or step and scan operation, the center of its gravity changes due to the movement of the wafer stage to accordingly incline the anti-vibration table. As a sufficiently long period of time elapses, this inclination is naturally corrected and the anti-vibration table is restored to the horizontal state. However, since step and repeat or step and scan operation is performed at a high speed, the position restoring movement of the anti-vibration table cannot catch up with the wafer stage, and the anti-vibration table is consequently inclined.
Although this inclination is a natural physical phenomenon, it incurs a serious disadvantage to an exposure apparatus such as a semiconductor exposure apparatus. For example, a functional unit provided to the main body structure vibrates undesirably due to the inclination of the main body structure, so a predetermined performance cannot be obtained. As a countermeasure for this, a response to the disturbance may be suppressed by increasing the eigenfrequency of the anti-vibration table, i.e., by making the anti-vibration table solid. In this case, however, a vibration of the floor or the like becomes easily transmitted to the anti-vibration table, leading to degradation in anti-vibration characteristics. A technique for correcting the inclination of the main body structure without impairing the anti-vibration characteristics is therefore sought for.
For the sake of further detailed understanding, the above contents will be described with reference to the mechanical arrangement of an active anti-vibration apparatus in which a wafer stage is mounted on an anti-vibration table.
FIG. 2
is a perspective view showing an example of the mechanical arrangement of the active anti-vibration apparatus. In
FIG. 2
, a wafer stage
21
is mounted on an anti-vibration table
22
, and active support legs
23
-
1
,
23
-
2
, and
23
-
3
support the anti-vibration table
22
. Each active support leg
23
(
23
-
1
,
23
-
2
, or
23
-
3
) incorporates acceleration sensors AC-xx, position sensors PO-xx, pressure sensors PR-xx, servo valves SV-xx, and pneumatic spring actuators AS-xx necessary for controlling the motion in the two axes, i.e., the vertical and horizontal axes. Suffixes xx attached to AC, PO, and the like indicate the directions in the coordinate system in FIG.
2
and the positions of the active support legs
23
. For example, Y2 denotes a component incorporated in the active support leg
23
-
2
located in the Y direction and on the left side.
A phenomenon wherein the Y stage of the wafer stage
21
has moved for a certain distance in the Y direction shown in FIG.
2
and stopped. The movement of the Y stage in the Y direction corresponds to a change in center of gravity of the entire anti-vibration table for the active support leg
23
. A thrust which is necessary for maintaining the horizontal posture of the anti-vibration table
22
regardless of the change in center of gravity and should be generated by a vertical actuator in each active support leg
23
is uniquely determined. When the Y stage moves and is set in a steady state, after a lapse of a sufficiently long period of time, because of position control, the active support leg
23
generates a thrust that matches the change in center of gravity, and the anti-vibration table
22
is restored to the horizontal state.
The situation changes when the Y stage continuously performs step and repeat or step and scan operation. As the Y stage moves continuously, the position of the center of gravity also changes continuously. Thus, the active support legs
23
cannot be returned to the preset positions in time, and the anti-vibration table
22
inclines gradually. When the X stage performs step and repeat or step and scan operation, it generates rotation (inclination) about the Y-axis due to the same reason. The inclination of the anti-vibration table
22
degrades the measuring precision of a measuring unit (not shown) or the positioning settling performance of the stage itself, partly impairing the productivity of the semiconductor exposure apparatus. Therefore, a technique for correcting the inclination of the anti-vibration table which is caused by a change in center of gravity upon movement of the stage has been sought for.
In order to solve the above problem, Japanese Patent Laid-Open No. 9-134876 (Anti-Vibration Apparatus and Exposure Apparatus) is known as a prior art. According to this reference, the inclination of an anti-vibration table caused by a change in center of gravity upon movement of a stage is predicted on the basis of an output from the position detecting means (laser interferometer) of the stage, and a feed-forward command value for correcting this inclination is input to the vibration control system of the anti-vibration apparatus. The actuator is a voice coil motor (VCM), to which a steady current for correcting the inclination of the anti-vibration table caused upon movement of the stage is supplied. As is easily understood, drawba

Affiliated with

Also associated with

Rating

Active anti-vibration apparatus and exposure apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Active anti-vibration apparatus and exposure apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Active anti-vibration apparatus and exposure apparatus will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3248043