Diffusion and Self-Gettering of Nickel in Float Zone Silicon Wafers

Abstract

ABSTRACTExternal gettering techniques trap removed impurities in regions of a semiconductor which contain defects or in which the solubility is enhanced like in phosphorus diffused layers or in Al-Si alloy. If a fast diffuser like nickel is used in place of Al to obtain an alloy or a compound close to the surface, contamination and decontamination can occur resulting of the indiffusion and removal of nickel atoms. P type FZ samples were partly covered by nickel (nickel òn part 1 and not on part 2) and then annealed at 950°C for 1h.As expected, after nickel indiffusion the diffusion length of minority carriers decreases but the values are always higher in part 1 than in part 2. Scanning infrared microscopy detects precipitates in part 2 and not in part 1. The results are explained assuming that the nickel-silicon compound formed at the surface serves as a diffusion source as well as an external self-gettering region.