Particle detection method and apparatus
US5317380A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Dec 31, 1991 |
| Grant date | May 31, 1994 |
| Priority date | — |
| Expiry date | Dec 31, 2011 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N2021/4742
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A method and apparatus for detecting particles on a surface of an object, such as a virgin or patterned semiconductor wafer, ceramic tile, or the like. In one embodiment, an apparatus is provided in which a scanning beam of laser light is brought to focus as an arcuate scan line on a surface of the object at a grazing angle of incidence using an off-axis hypertelecentric mirror. A pair of light detectors are positioned at a meridional angle of about 30 degrees and at an azimuthal angle of about 4 degrees to measure forward scattered light from the surface. The object is then moved translationally so that the beam can scan another line of the surface. A light trap is provided to trap light that is reflected by the surface, and a series of masks are provided to mask light which is scattered by the hypertelecentric mirror and, in the case of patterned objects, light which is diffracted by the pattern imprinted on the object.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.