Impurity segregation to sink layer during phosphorus gettering

During phosphorus gettering, metal impurities segregate to a sink layer where they are captured. There is some uncertainty concerning which mechanisms are responsible of segregation. We bring some experimental evidence that suggests that, at least in some cases, two mechanisms apply in different ranges of temperature: at high temperatures metals are segregated to a different phase, that can be composed by a liquid phosphosilicate, where they are more soluble than in the Si matrix, while at low temperatures metals are segregated to traps present in a solid sink layer. Experiments have been carried out in previously contaminated high resistivity float zone wafers, that have passed through a phosphorus gettering step to recover its bulk quality. Characterization of the segregation process comes by means of lifetime measurements. The relation between segregation coefficient and carrier lifetime is clearly shown in the paper.