Particle detection on patterned wafers and the like
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United States of America Patent
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Feb 6, 1990
Issued Date -
N/A
app pub date -
Sep 19, 1988
filing date -
Jun 18, 1987
priority date (Note) -
Expired
status (Latency Note)
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Abstract
A particle detection on a periodic patterned surface is achieved in a method and apparatus using a single light beam scanning at a shallow angle over the surface. The surface contains a plurality of identical die with streets between die. The beam scans parallel to a street direction, while a light collection system collects light scattered from the surface with a constant solid angle. The position of the collection system as well as the polarization of the light beam and collected scattered light may be arranged to maximize the particle signal compared to the pattern signal. A detector produces an electrical signal corresponding to the intensity of scattered light that is colelcted. A processor constructs templates from the electrical signal corresponding to individual die and compares the templates to identify particles. A reference template is constantly updated so that comparisons are between adjacent die. In one embodiment, the templates are made up of registered positions where the signal crosses a threshold, and the comparison is between corresponding positions to eliminate periodic pattern features, leaving only positions representing particles.
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