Ion-implantation-damage gettering effect in silicon photodiode array camera target

Abstract

The use of ion implantation damage to getter deleterious impurities from diode space-charge regions is studied. Ion implantation into the neutral regions near p-n junctions is shown to cause substantial reduction in the incidence of the type of white video defects (excessive-leakage current diodes) caused by impurity precipitation and often found in a cyclonic pattern. It is found that using doses of 1016 cm−2 phosphorus (50 keV), ≥1015 cm−2 arsenic (150 keV), and ≥3×1015 cm−2 argon (50 keV) can completely eliminate these defects. In addition, the dark currents of the targets which receive ion implantation is equivalent to or lower than control slices receiving regular phosphorus gettering. From curves of the dark current vs target voltage, it is estimated that the surface recombination velocity (S0) of the ion-implanted slices is ∼20% lower than S0 in the control slices, while the Si–SiO2 interface fixed-charge density is not affected by ion implantation. By comparing the gettering efficiency of P+-, As+-, and Ar+-implanted slices, it is concluded that the damage layer rather than the presence of an implanted n+ region is responsible for the observed gettering behavior.