Light scattering particle detector for wafer processing equipment
US4739177A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Sep 16, 1986 |
| Grant date | Apr 19, 1988 |
| Priority date | — |
| Expiry date | Sep 16, 2006 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N2021/516
- WIPO fieldMeasurement
- WIPO sectorInstruments
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.