The gettering behavior of polycrystalline material, and internal gettering during isothermal annealing (600 to 1000C), were systematically investigated, in the presence of Fe contamination, by using deep-level transient spectroscopy. There was a clear dependence of the polycrystalline-material gettering efficiency upon its deposition temperature and upon the annealing temperatures which were used for gettering. The use of lower deposition temperatures and lower gettering temperatures resulted in a higher gettering efficiency. The internal gettering efficiency exhibited a clear dependence upon the size and density of O precipitates. In the case of a bulk micro-defect density of 105/cm2, it was necessary for the platelet O precipitate size to be greater than 200nm, while a polyhedral O precipitate size of 100nm was sufficient to obtain internal gettering effects at an Fe contamination level of 1012/cm3. The gettering efficiency was clearly related to the volume of the O precipitates per unit volume of Si wafer. The results suggested that Fe atoms were gettered within the O precipitates and not in the volumes surrounding them.

S.Ogushi, S.Sadamitsu, K.Marsden, Y.Koike, M.Sano: Japanese Journal of Applied Physics - 1, 1997, 36[11], 6601-6