Applications of carrier de‐smearing of photoluminescence images on silicon wafers

Abstract

AbstractLateral carrier diffusion can lead to significant smearing in photoluminescence (PL) images of silicon wafers with high lifetime or localised recombination centres. A method to de‐smear the PL image by applying the continuity equation in two dimensions has been proposed previously and demonstrated on a virtual wafer with simulated carrier diffusion and artificial random Gaussian noise. This work will demonstrate the de‐smearing method experimentally by using a partially shaded monocrystalline silicon wafer. A criterion for determining the noise filter parameters is also proposed based on the convergence of multiple images measured under the same settings and filtered and de‐smeared in parallel. The results show that the de‐smearing method is effective across most of the wafer, with the exception of regions very close to the shaded edge where the signal to noise ratio is poor. The de‐smearing method was also applied to PL images on a high lifetime n‐type multicrystalline wafer and for Fe imaging of p‐type multicrystalline silicon. De‐smearing of the PL images suggests that the intra grain lifetime of the n‐type multicrystalline silicon can reach up to 800 µs, but is limited by recombination in the grain boundaries. The application of de‐smearing for Fe imaging results in a sharper Fe profile near the grain boundaries. Copyright © 2016 John Wiley & Sons, Ltd.