Two Axis stage with arcuate surface bearings

Details Two Axis stage with arcuate surface bearings Two Axis stage with arcuate surface bearings

2000-09-18

2001-10-16

Hannon, Thomas R. (Department: 3682)

Bearings

Linear bearing

With temperature, electrical, or orthogonal feature

C074S490090, C108S137000, C248S913000, C384S002000, C384S007000, C384S036000

Reexamination Certificate

active

06302585

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to precision motion devices and more particularly to an X-Y stage.
BACKGROUND
X-Y stages are well known; they are typically used in machine tools and other applications where two dimensional precise movement is needed to position an object supported on the stage. An application of X-Y stages is in lithography equipment e.g. for semiconductor wafer processing. In this case, a stage is typically used in a lithography tool to position, in two dimensions, the reticle (mask). A separate stage is sometimes provided to position the semiconductor wafer or other workpiece. Mechanical and thermal disturbances are problematic since they reduce the resolution, positioning accuracy and useful positioning speed of the stage and the lithography process. Hence there is a need for improved stages. Increasingly there is also a need for stages which can operate in a vacuum, e.g. for use in electron beam lithography.
SUMMARY
In accordance with this invention, a novel bearing system supports the weight of an X-Y stage on an underlying support surface (the “Z base plate”). It is to be understood that the X-Y stage may be relatively large and heavy. Conventionally such stages are supported on a base e.g. by air bearings or mechanical bearings. In accordance with the invention, a special kind of arcuate bearing is used in which the bearings each have an arcuate (e.g. spherical or cylindrical) distal surface which bears on a generally flat facing surface of the base plate. In one embodiment only three or four such bearings support the entire stage assembly.
These arcuate surfaces and bearings are not continuously constrained in a cage, unlike a conventional ball bearing, but instead each moves freely relative to the stage around a joint (coupling) mounted at the center of curvature of the spherical or cylindrical distal surface, and the underlying facing support surface of the generally planar horizontally mounted base plate. Therefore the associated bearing joint mountings on the x-y stage plate may encompass a small area. Further, the bearings of this invention eliminate the hoses, pumps and any scavenging baffles required to protect for instance an electron beam high vacuum environment (e.g. 10
−7
Torr) from air leakage caused by a pressurized air bearing support. Moreover these bearings are likely to have less mechanical vibration associated with them than conventional ball bearings. Moreover, they will likely require little or no lubrication, thereby eliminating another potential problem in vacuum applications.
A two-axis stage according to the invention includes a generally planar horizontally mounted base plate; a stage plate generally parallel to the base plate, the stage plate having a first axis and a second orthogonal axis in the plane of the plate; and a series of spaced bearings depending from a bottom surface of aid stage plate, the bearings each having an arcuate bottom surface in rocking contact with a facing support surface of the base plate. A joint (coupling) is attached to the bottom surface of the stage plate which pivotally mounts each bearing such that movement of the stage plate rotates the bearing arcuate distal surfaces with respect to the facing support surface of the base plate. The coupling is positioned at the center of curvature of the arcuate bottom surface. The arcuate bottom surfaces are e.g. a segment of a sphere or a segment of a cylinder. In the cylindrical case, two such surfaces are “stacked” to allow two dimensional movement.


REFERENCES:
patent: 4438983 (1984-03-01), Davis
patent: 5152488 (1992-10-01), Richardson
patent: 5366297 (1994-11-01), Wolverton et al.
patent: 5466068 (1995-11-01), Andrä et al.

Affiliated with

Also associated with

Rating

Two Axis stage with arcuate surface bearings does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Two Axis stage with arcuate surface bearings, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Two Axis stage with arcuate surface bearings will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2551239