Light scattering particle detector for wafer processing equipmen

Details Light scattering particle detector for wafer processing equipmen Light scattering particle detector for wafer processing equipmen

1988-10-25

1990-05-08

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Optical or pre-photocell system

250575, 356338, G01N 1506, G01N 1507, G01N 2149

Patent

active

RE0332135

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.

REFERENCES:
patent: 3431424 (1969-03-01), Allen
patent: 3578867 (1971-05-01), Barrington
patent: 3622796 (1971-11-01), Harris
patent: 3704951 (1972-12-01), Chupp
patent: 3772525 (1973-11-01), Goodwin
patent: 3994603 (1976-11-01), Paschedag
patent: 4221485 (1980-09-01), Schulze
patent: 4299489 (1981-11-01), Thery et al.
patent: 4473296 (1984-09-01), Schofner et al.

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