Focal mechanism and method for controlling focal point position, and apparatus and method for inspecting semiconductor wafer
Number of patents in Portfolio can not be more than 2000
United States of America Patent
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-
Apr 1, 2003
Grant Date -
N/A
app pub date -
Sep 14, 2000
filing date -
Sep 14, 1999
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
For effecting auto-focussing of an objective lens used for observing a semiconductor wafer, a semiconductor microscopic device includes an inspection stage for supporting a semiconductor wafer and an objective lens for observing the semiconductor wafer. For automatic focussing of the objective lens, a defocussing magnitude of a light spot is detected using a knife edge. A collimator lens is oscillated by a voice coil motor to oscillate the light spot on the wafer. A peak value of the defocussing quantity detected at this time is peak-held to generate a position detection signal. The inspection stage is vertically moved so that this position detection signal will be equal to a pre-set target value.
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