Automatic detector for microscopic dust on large-area, optically unpolished surfaces
US4402607A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 16, 1980 |
| Grant date | Sep 6, 1983 |
| Priority date | — |
| Expiry date | May 16, 2000 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N21/94
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A system for automatically detecting dust or other minute particles on a large-area, optically unpolished surface such as a face of a glass reticle plate used in the production of microelectronic circuits. The system irradiates the surface with a narrow, high intensity beam of monochromatic radiation at a grazing angle, typically 1/2 degree with respect to the surface. An oscillating mirror scans the beam across the moving surface in a direction generally perpendicular to the direction of plate advance. A beam splitter provides separate inspecting beams for each surface of the plate. Optical systems characterized by a high numerical aperture are positioned on opposite sides of the plate to collect radiation which is scattered from the particles. The optical systems are oriented to accept scattered radiation, and typically have their optical axes at an angle in the range of 60.degree. to 160.degree. measured from the direction of advance. They each utilize a multiplet of cylindrical lenses characterized by excellent resolution and a large numerical aperture, preferably in the range of 0.15 to 0.20. A fiber optic concentrator transmits the scattered radiation from the image plane of …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.