Importance

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Abstract

The deformable wafter chuck system includes a base with a recess having a diameter slightly smaller than the diameter of the wafer to be held. The base may have one or more orifices or channels running therethrough for distributing a vacuum to secure the wafer to the chuck, or it may have a plurality of clips attached at the rim of the chuck for holding the wafer. Attached to the chuck within the recess is a plurality of distortive actuators, such as piezoelectric crystals, which cause the wafer to be selectively deformed to assume arbitrary shapes, cancelling the warpage of the wafer to permit reduced distortion of the projected pattern. An interferometer system is included to combine light reflected from the wafer surface with a portion of incoming light modulated by a mask or reticle, thereby forming an interference pattern. The interference pattern is sued by a computer to determine warpage-induced distortions to activate the actuators to provide realtime correction of wafer flatness and also permits adjustment of depth of focus by varying heights of portions of the wafer.

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First Claim