Method and apparatus for detecting particles on a material

Abstract

A method and apparatus for detecting and measuring the number and sizes of impurities on the surface of a material, such as a semiconductor wafer, wherein high intensity collimated light is directed onto the surface, in the absence of any extraneous light, through a collimating mirror, and employing a point source, whereat the particles will scatter the light, and wherein the surface is viewed by a highly light sensitive TV camera which picks up the scattered light and displays same on a viewing screen. The intensity of scattered light will indicate the size of the particles when compared with a calibrated model. Advantageously, a broad range of light waves is employed and thus enables a range of sizes of particles to be detected by the light scattered thereby. Also, advantageously, with the use of ordinarily available equipment, the system can inspect wafer surfaces for particles having sizes as small as 0.3 microns. The system also enables detection and identification of moving particles as distinguished from stationary particles.

Dependencies are inferred from the claim text.