Laser ablation ICP-MS for impurity analysis in multicrystalline silicon wafers

Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICPMS) is an important characterization technique for elemental analysis of solid samples. It has been extensively used for analysing geological and forensic samples, but its use for silicon photovoltaics has been limited. In the last four decades, detailed studies have shown that the presence of metallic impurities in silicon wafers is detrimental for cell performance and reliability. In this study, we explore the potential of LA-ICPMS to provide a fast, accurate and sensitive measurement technique for measuring metallic contamination in industrially manufactured multicrystalline silicon (multi-Si) wafers. A quick scan using a LA-ICPMS system is used to measure the gettering effectiveness of a phosphorus diffusion process. We observe that transition elements are more concentrated at the grain boundaries than within the grains of high-performance multi-Si wafers. Thus, LA-ICPMS could be used to monitor wafer quality during manufacturing. We also study the elemental compositions of regions of a multi-Si wafer that degrade to different extents during light elevated temperature induced degradation and observe that there is a positive correlation between the extent of degradation and spatial concentration of certain transition elements.