Effects of electric field on polysilicon gettering of iron and copper in highly boron-doped silicon

The polysilicon gettering behavior of iron (Fe) and copper (Cu) in highly boron doped silicon was studied under isothermal annealing with and without the presence of an electric field. Depth profiles of Fe and Cu in the polysilicon were obtained by dynamic secondary ion mass spectrometry. Enhanced gettering as a result of the electric field can be attributed to the drift-behavior of Fe and Cu over thermal diffusion at elevated temperature. While the polysilicon-silicon interfacial segregation acted against the back-diffusion of Cu, the same was not observed for Fe. About 61% of Cu and 35% of Fe were trapped in polysilicon after 2 days owing to strong interfacial segregations.