Stage counter mass system
First Claim
1. A method for maintaining a center of gravity for a stage and a countermass system in a fixed location comprising at least one moving stage and at least two countermasses, the method comprising the steps of:
- calculating a target position for said at least two countermasses according to a position of said at least one stage; and
pushing said at least two countermasses towards said target position based on said calculating step.
2 Assignments
0 Petitions
Accused Products
Abstract
A wafer stage countermass assembly generally includes a base supporting one or more stages and first and second countermasses. The first and second stages move in one or more degrees of freedom. The countermasses move in at least one degree of freedom and, under ideal conditions, move to counter the movement of the stages in operation and thus preserve the systems center of gravity to avoid unwanted body motion. However, under actual conditions the countermasses may under travel or over travel their ideal trajectory. To more closely track the ideal trajectory, a controller actuates trim motors to apply small forces to the countermasses to push them towards a reference position in the Y direction. A second embodiment also takes into account the X position the stage(s) to cancel torque.
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Citations
31 Claims
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1. A method for maintaining a center of gravity for a stage and a countermass system in a fixed location comprising at least one moving stage and at least two countermasses, the method comprising the steps of:
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calculating a target position for said at least two countermasses according to a position of said at least one stage; and
pushing said at least two countermasses towards said target position based on said calculating step. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A control method for maintaining a center of gravity for a stage and a countermass system comprising a moving stage and at least two countermasses having different target positions, the method comprising the steps of:
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calculating the target positions for said at least two countermasses according to a position of said stage, said calculating step allowing for a weight factor to trade off torque cancellation for reduced countermass stroke; and
pushing said at least two countermasses towards said different target positions. - View Dependent Claims (13, 14, 15, 16)
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17. A system for maintaining a center of gravity for a stage and a countermass system in a fixed location comprising at least one moving stage and at least two countermasses, the system comprising:
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a controller that calculates a target position for said at least two countermasses according to a position of said at least one stage; and
a motor that pushes said at least two countermasses towards said target position based on said calculating. - View Dependent Claims (18, 19, 20, 21, 22)
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23. A control system for maintaining a center of gravity for a stage and a countermass system comprising a moving stage and at least two countermasses having different target positions, the system comprising:
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a controller that calculates the target positions for said at least two countermasses according to a position of said stage, said calculating step allowing for a weight factor to trade off torque cancellation for reduced countermass stroke; and
a motor that pushes said at least two countermasses towards said two different target positions. - View Dependent Claims (24, 25, 26)
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27. A system for maintaining a center of gravity for a stage and a countermass system in a fixed location comprising at least one moving stage and at least two countermasses, the system comprising:
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means for calculating a target position for said at least two countermasses according to a position of said at least one stage; and
means for pushing said at least two countermasses towards said target position based on said calculating step.
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28. A system for maintaining a center of gravity for a stage and a countermass system in a fixed location, comprising:
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at least two countermasses;
at least one guide bar having at least one stage disposed thereon, respectively, said at least one guide bar being mounted to the at least two countermasses;
a controller that calculates a target position for said at least two countermasses according to a position of said at least one stage; and
a motor that pushes said at least two countermasses toward said target positions.
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29. An exposure apparatus, comprising:
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an illumination system that projects radiant energy through a mask pattern on a reticle R; and
a system that reduces a stroke of at least two countermasses in an assembly comprising at least one moving stage and the at least two countermasses, the radiant energy being projected on a wafer positioned on the at least one moving stage, the system comprising;
a controller that calculates a target position for said at least two countermasses according to a position of said at least one stage; and
a motor that pushes said at least two countermasses towards said target position based on said calculating. - View Dependent Claims (30, 31)
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Specification