Horizontally supported planar surfaces – Plural related horizontal surfaces – Terraced
Reexamination Certificate
1999-10-08
2001-08-28
Chen, Jose V. (Department: 3636)
Horizontally supported planar surfaces
Plural related horizontal surfaces
Terraced
C108S022000
Reexamination Certificate
active
06279490
ABSTRACT:
BACKGROUND
1. Field of the Invention
This invention relates to movable stages and other precision location mechanisms and more particularly to a stage with multiple rotating tables on air bearings.
2. Description of Related Art
Movable stage systems are typically used in many applications where precise two-dimensional movement is required to position an object supported on a stage, e.g., in high resolution lithography applications. Such movable stages typically progress linearly on linear races and bearings and are conventionally driven along both the X and Y axes. Typically this is accomplished by linear motors or actuators; a first set of linear actuators providing the X direction motion and a second set of linear actuators providing the orthogonal Y direction motion. For instance, the stage powered by linear motors may be moved back and forth in the Y direction on a mechanical guide beam which in turn is moved and powered by linear motors in the X direction along guide rails. This provides the desired independent two direction motion.
Such a stage supports, for instance, a mask blank or other workpiece so that the workpiece is precisely positioned for lithography. Similar arrangements are used in other lithographic applications, for instance, for defining conductive patterns on a laminate workpiece which is a substrate for a printed circuit board. Typically, a chuck is located on a stage or other holding mechanism arrangement for holding the workpiece. Conventional stages used for electron beam lithographic applications present several problems because they typically require the use of bellows, thin gap seals, or other mechanisms operating inside a vacuum to enclose the electron beam. Some of these problems include limited stage travel, vibration from the bellows, and poor positioning resolution partly due to thermal expansion of materials such as the guide rails or holding mechanisms heated up by the motors. Therefore, there is a need for a movable stage having minimal vibration with smooth and large effective travel, useful but not limited to electron beam lithography applications.
SUMMARY
In accordance with the invention, the above problems are overcome by a movable stage assembly which has three preferably circular stages rotating independently of one another. Because certain applications such as electron beam lithography also require precise positioning resolution, the stage travel also needs to be smooth with minimal vibration. The present stage assembly includes a base and a rotatable table mounted on the base. This table has a second smaller table which is eccentrically mounted within the first table and rotates independently. This second table also has a smaller third table eccentrically mounted and independently rotatable within the second table.
All three tables, in one embodiment, rotate on air or conventional bearings but are used in a vacuum chamber. Atmospheric air, or the air within the air bearings, is prevented from entering the vacuum by ferrofluidic seals which allow the rotation of all the tables. These ferrofluidic seals are further maintained by differential pumpouts which are attached to all three seals around all three tables. Alternatively, air can be kept out of the vacuum chamber by using, e.g., a thin gap differentially pumped seal. Additionally, the three tables are driven by axial servo motors which are mounted beneath the tables. Edge capstan drives, built-in motors, or other suitable drives may be used instead of the axial motors. An alternative embodiment of the stage assembly includes an additional fourth and fifth table which are mounted within the first table and coplanar to second and third tables. The fourth table is mounted within the first table, and the fifth table is mounted within the fourth table and operates similarly to the second and third tables.
The stage assembly presents several distinct advantages. One advantage is the ability of the stage assembly to move workpieces within the vacuum chamber while keeping all the relevant mechanisms, e.g., motors, races, bearings, hoses, etc., outside the vacuum and in atmosphere without requiring bellows. This eliminates friction problems, generation of debris, and simplifies heat dissipation from guides, motors, and bellows life problems. Another advantage relates to the stage assembly's compact size. Non-vacuum applications enable the stage to be made thinner and with less material in resisting stresses and deflections from atmospheric pressure. This results in a more compact design than conventional stages or robotic arms. In such conventional stages and robotic mechanisms, individual axis controls are typically stacked one on top of the other; however, in the present assembly, the different axes are coplanar. Finally, the compact design gives rise to the possibility of using a single stage assembly to move several workpieces within a chamber. This is an advantage if utilizing multiple electron beam columns in the same chamber.
REFERENCES:
patent: 434414 (1890-08-01), Culp
patent: 1254983 (1918-01-01), Chadwick
patent: 1472348 (1923-10-01), Whittemore
patent: 2103175 (1937-12-01), Prins
patent: 2181021 (1939-11-01), Lockwood et al.
patent: 2324343 (1943-07-01), Wjarton
patent: 3245545 (1966-04-01), Lortie
patent: 3897063 (1975-07-01), Lehwalder
patent: 4653408 (1987-03-01), Nagashima et al.
patent: 4656951 (1987-04-01), Kimura et al.
patent: 4694213 (1987-09-01), Gowda et al.
patent: 5109989 (1992-05-01), Kremmin et al.
patent: 5163651 (1992-11-01), Matsumoto
patent: 5456134 (1995-10-01), Bouwer et al.
patent: 0 492 992 A2 (1992-07-01), None
patent: 62043145 (1987-02-01), None
patent: 534398 (1993-12-01), None
patent: 7138757 (1995-05-01), None
Chen José V.
Etec Systems, Inc.
Leitich Greg
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