Particle detection method and apparatus
US5805278A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jun 18, 1996 |
| Grant date | Sep 8, 1998 |
| Priority date | — |
| Expiry date | Jun 18, 2016 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N2201/0675
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
An apparatus and method for detecting particles on a surface of a semiconductor wafer having repetitive patterns includes a laser for illuminating an area on the front surface at grazing angle of incidence with a beam of polarized light. A lens collects light scattered from the area and forms a Fourier diffraction pattern of the area illuminated. A Fourier mask blocks out light collected by the lens at locations in the Fourier diffraction pattern where the intensity is above a predetermined level indicative of background information and leaves in light at locations where the intensity is below the threshold level indicative of possible particle information. The Fourier mask includes an optically addressable spatial light modulator and a polarization discriminator. A camera detects scattered light collected from the area by the lens and not blocked out by the Fourier mask.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.