Polysilicon Encapsulation Gettering with Electric-Field-Enhanced Isothermal Annealing for Copper Impurities in Bulk Silicon

Enhanced gettering of iron impurities in bulk silicon by using external direct current electric field

“…This is in sharp contrast to that observed for copper impurities, which showed more significant diffusive flow of the copper interstitials, as was reported in our previous work. 25 The low level of Fe concentrations could well be due to the accumulation of the positively charged Fe ϩ i interstitials at the polysilicon layer, which eventually built up to the extent that they could oppose the continual diffusion of the Fe ϩ i interstitials, and thus saturation of the gettered Fe concentrations was expected in sample B. When an external electric field was applied across the thickness of the sample, as in sample A, the gettering process for Fe accelerated.…”

“…The detailed description of the system is published elsewhere. 25 A high voltage power supply was used to provide a parallel external direct current electric field strength of 4.3 kV/cm across the thickness of sample A between the two electrodes. Although the actual redistribution of the electric field within the test sample is not known, the internal field strength is thought to be smaller than that of the external electric field due to the larger dielectric constant of silicon, relative to that of the space gap between the electrodes.…”