A multi-purpose wafer scanning system for PV inspection

This paper describes a PV wafer scanning system that can perform multiple measurements on one platform. The scanning system consists of two probes (a Kelvin probe and a fiber optic probe), a light source, and a monochromator. The Kelvin probe is used to measure the surface potential at different illumination conditions. Surface uniformity and defects, particularly shunting, can be identified from various types of surface potential maps. A monochromator is incorporated with the Kelvin probe to yield the spectral response of solar cells. The fiber optic probe is used to measure the crystalline orientation - related reflectivity and stress-induced wafer curvature. Applications for the scanning system in PV wafer and cell inspections are discussed.