Gettering of Dissolved and Segregated Impurities in Multicrystalline Silicon Wafers

Abstract

ABSTRACTPhosphorus gettering by diffusion from a POCl3 source was applied to matched wafers cut out of the same region of a cast ingot. Light Beam Induced Current mappings with wavelengths in the range between 840 and 980 nm lead to follow the variation of minority carrier diffusion length after gettering at 900°C for 120 and 240 mn, especially near extended crystallographic defects like dislocations and grain boundaries.The mappings show that after the gettering treatments, the local values of L increase due to the reduction of the recombination strength of extended defects and to the improvement of the homogeneous regions of the grains.As SIMS analyses indicate that Fe, Cu and Ni atoms are gettered, it is reasonable to assume that these impurities were initially dissolved in the grains and also segregated at the extended defects.