Method and system of using a scanning electron microscope in semiconductor wafer inspection with Z-stage focus
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United States of America Patent
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Sep 14, 2004
Grant Date -
Sep 25, 2003
app pub date -
Mar 21, 2002
filing date -
Mar 21, 2002
priority date (Note) -
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Abstract
A method for inspecting a semiconductor wafer using an SEM having a nominal focal plane and operable for guiding a beam. The SEM having a stage movable in each of an X-, Y-, and Z-direction, including moving the SEM stage in the XY-direction to a first location for inspection, optically sensing the location of the top surface of an area in relation to the focal plane of the stage, adjusting the position of the stage in the Z-direction so that the top surface of the area is substantially at the focal plane, inspecting the areas, and moving the stage in the XY-direction to the next location such that the next area is under the SEM beam for inspection. The Z-stage using a non-contact optical sensor to provide feedback to drive a plurality of piezoelectric actuator to move the wafer to the focal plane.
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