Light scattering particle detector for wafer processing equipment
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United States of America Patent
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-
Apr 19, 1988
Issued Date -
N/A
app pub date -
Sep 16, 1986
filing date -
Dec 11, 1985
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
A particle detector includes a laser, a beam shaping lens, and a pair of mirrors which reflect the shaped laser beam back and forth between the mirrors a selected number of times in order to create a sheet of light or light net between the mirrors. The path of the beam is terminated by a beam stop which contains a photodiode to monitor beam intensity and thereby system alignment. Light scattered by a particle falling through the sheet of light is gathered and transmitted to a photodiode. A peak detector provides a measure of the peak intensity of light scattered by such a particle to a microprocessor, which counts the number of particles falling through the light net in a selected time interval. The microprocessor also uses the peak intensity to estimate the size of the particle.
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