Novel recombination lifetime mapping technique through Kelvin probe studies

The Kelvin probe is a very powerful and versatile tool, allowing the extraction of data such as diffusion length, surface photovoltage and impurity concentrations. This paper investigates the extraction of surface recombination velocities (and assuming a bulk lifetime, the surface recombination lifetime) from the I-V type dependence of the sample. By using an X-Y stage, the surface recombination lifetime can be imaged for entire wafers, instead of obtaining an average value of lifetime similar to that obtained from the Sinton WCT-120 lifetime tool. This is useful in determining where further improvements in the surface passivation can be obtained, by observing problem areas in the passivation layer.