Importance

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Abstract

A non-contact holder including one or more chucks holds a planar workpiece such as a semiconductor wafer, particularly a thin wafer. Each chuck in the holder includes a cavity that opens to a surface adjacent to the workpiece. A tangential orifice introduces a tangential gas flow into the cavity to create a vortex having a central, low-pressure region. A central orifice directs a gas flow into the low-pressure region of the vortex. The combination of gas flows creates a more uniform vacuum attraction holding a workpiece in close proximity to the chuck. The gas exiting from the chuck provides a cushion that prevents contact between wafer and chuck. Small diameter chucks located close to each other help avoid distortion when processing very thin workpieces. In addition to equalizing pressure, the central gas flow increases the angular spread of gas exiting from each chuck and thus simplifies the design of a holder providing a gas flow that inhibits entry of contaminants between the holder and the workpiece.

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First Claim