| 摘要 |
With respect to exposure apparatus, apparatus and methods are disclosed for compensating for lateral shift of a leveling table caused by a tilt (theta) of the leveling table. One embodiment includes a wafer-stage-position loop servo, a leveling-table tilt-position loop servo, and a first feed-forward loop from the leveling-table tilt-position loop servo to the wafer-stage-position loop servo. The first feed-forward loop converts a torque-control signal for the leveling table to a linear-acceleration-control signal for the wafer stage. Thus, the wafer stage moves laterally to compensate for lateral shift of the leveling table. If the exposure apparatus includes a reticle stage controlled by a reticle-stage-position loop servo, then the subject apparatus can include (in addition to or in place of the first feed-forward loop) a second feed-forward loop from the leveling-table tilt-position loop servo to the reticle-stage-position loop servo. The second feed-forward loop converts a positional signal for the leveling table to a position-control signal for the reticle stage, to cause the reticle stage to undergo lateral compensatory motion. The methods and apparatus provide a faster and more accurate compensation for lateral shifts of the leveling table.
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