Characterization of Nickel-related Defects in Thin SOI Substrates after Thermal Treatment

Abstract

By means of thermal treatment of blanket wafers, the impact of nickel contamination (applied on the wafer surface) on defect formation in Silicon on Isolator (SOI)-material during oxidation has been studied. Methods like determination of defect density by microscopic control after extended vapor phase decomposition and preferential etching, minority carrier lifetime measurements and vapor phase decomposition - Inductively Coupled Plasma Mass Spectrometry were used to characterize the effect and the redistribution of nickel through the handle wafer after oxidation. It is shown that with the same nickel concentration at the wafer surface the highest defect density is caused in the thinnest SOI-layer after oxidation not dependent from the thermal budget. Furthermore, it is found that nickel diffuses through the buried oxide and might relax the allowable limits nickel at the wafer frontside before oxidation, because it is after oxidation dissolved in the handle wafer. However, the backside contamination with nickel becomes more critical because by the reverse diffusion nickel can reach the frontside and form defects