Appliance and method for checking surface of object - directs strip light beam on to surface of object with sensor to detect light scatter caused by impurities on surface.

: Grimme, R.; Klumpp, B.

Abstract
The appliance (1) has a light source (2,3) projecting a light beam (5,6) on to the surface (8) of the object and a light sensor (4) to detect light scattered from foreign bodies (impurities) on the surface. The light beam is directed as strip light on to the surface. Foreign bodies on the surface cause scattering of the light beam but otherwise the light is subjected to no or only insignificant change. The light sensor is located so that at least part of the scattered light is detected. The light beam can be directed approximately in parallel to the surface. USE/ADVANTAGE - For detecting irregularities on the surface of silicon wafers. Suitable for wafers with smooth or uneven surfaces as only impurities (foreign bodies) scatter strip light and not uneven surfaces, can be used in series production of wafers.