A Study of Gettering Efficiency and Stability in Czochralski Silicon

Abstract

AbstractGettering efficiencies and stabilities of internal gettering sites for metallic impurities in high and low carbon doped silicon have been compared with ramped and standard two-step pre-annealing conditions. This study was intended to compare two proposed techniques to shorten the long low temperature nucleation step in the standard Hi-Lo-Hi internal gettering site formation treatment. Specifically, we compare the affect of carbon and a ramped annealing sequence on oxygen precipitate formation and gettering effectiveness. Our results show both techniques accelerate oxygen precipitation, however, only the low carbon ramped materials produced efficient and stable gettering sites. The high carbon materials did not with either annealing treatment. This disparity in performance is due to a difference in the oxygen precipitate’s strain field. The precipitates in the low carbon material possessed a high strain field with strain-induced defects while in the high carbon material they were strain-free with no defects. These results indicate the strain stabilizes the gettered impurity such that the gettering rate is increased and stability is enhanced.