Evolution of defect densities with height in a HPMC-Si ingot

In this paper we have used a sequential measurement routine to separate and evaluate the effects of two dominant mechanisms for degradation of the carrier lifetime of silicon wafers: Boron-oxygen related light induced degradation (BO-LID) and light and elevated temperature induced degradation (LeTID). Wafers from different heights in a high performance multicrystalline silicon brick have first been illuminated at room temperature to fully activate the BO-LID process in the wafers, followed by an illuminated annealing to activate the more detrimental recombination sites causing LeTID. By isolating the effects of LeTID in this way we hope to improve the analysis and arrive closer to an understanding of the underlying recombination mechanism. The concentration of LeTID defects was observed to increase with height in the bottom half of the ingot and then decrease towards the top in the upper half.