Particle detection method and apparatus
US4655592A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Dec 30, 1983 |
| Grant date | Apr 7, 1987 |
| Priority date | — |
| Expiry date | Dec 30, 2003 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N21/47
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
An apparatus and method are disclosed for detecting the presence of particles on the surface of a material, such as a semiconductor wafer, using the principle of scattered light. Light from a mercury arc lamp is collimated by a Cassegrain mirror collimator. The collimated beam of light is deflected by an annular shaped 45.degree. mirror toward a truncated annular shaped inverted parabolic mirror. Light striking the parabolic mirror is reflected outward in all directions as a converging beam of light toward a ring mirror. Light striking the ring mirror is reflected inward and strikes the surface from all directions at an angle of about 78.degree. to 86.degree. from normal incidence as a small spot. An objective lens located a distance directly above the area on the surface illuminated by the spot of light and mounted at one end of a light tight tube collects light scattered by any particles on the surface, but not light reflected by the surface, and forms an image of the light so collected on the light sensitive surface of a photodetector mounted at the other end of the tube. The wafer is mounted on a holder which is movable rotationally and translationally relative to the impinging…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.