Scanned Surface Photovoltage Detection of Defects in Silicon Wafers

A scanned surface photovoltage (SSP) method is capable of detecting a wide variety of defects in a silicon surface. This method can be used to scan a large area of the silicon surface, which is coupled by a surface channel to a small remote electrode. The resolution obtained, about 2 μm, is explained theoretically in this paper for the case of a differentiated photovoltage signal and a small (0.8 μm diameter) light beam from an optimized optical system. SSP images of a variety of defects, both naturally occurring and induced, were obtained along with images produced by other methods for comparison.