A laser scan technique for electronic materials surface evaluation

A technique utilizing a scanning laser beam has been implemented to examine the surfaces of materials that are used in the form of flat plates or thin deposited films in the field of microelectronics. Unwanted holes in opaque films deposited onto transparent substrates can be detected by sensing the light transmitted through the holes or defects on a reflective surface can be detected by virtue of their light scattering properties. A typical application is the inspection of silicon wafers that have been highly polished preparatory to film deposition for the planar technology of semiconductor device building. Defects as small as one micron can be detected. An entire wafer 5 cm in diameter can be scanned in 40 seconds to give: 1) a total defect count, and 2) a map of defect locations displayed on an oscilloscope screen.