Frequency response in pulsed DC reactive sputtering processes

By simple arguments as well as results from a recently developed computer s imulation model we have found out that for high frequency pulsed DC reactiv e sputtering the target poisoning does not reflect the periodicity of the p ulsed DC power supply. The degree of target poisoning does not change marke dly during a single duty cycle. The degree of poisoning essentially exhibit s the same continuous time independent behavior as observed for the convent ional continuous reactive sputtering process. Furthermore, it is shown that the distribution width of the transit times for sputtered atoms by far exc eeds the period time for pulsed DC frequencies higher than 5-10 kHz. This c auses a large overlap between sputter eroded material between consecutive p ulses during processing resulting in an essentially continuous arrival rate of sputtered atoms to the substrate surface. This implies also that the de position rate will be constant and will not follow the pulsed sputter erosi on variation from the target. These findings show that, with respect to fil m stoichiometry and homogeneity, the high frequency pulsed DC reactive sput tering process behaves identically as the continuous reactive sputtering pr ocess. No chemical reaction effects or gas gettering variations will follow the periodicity of the pulsed DC power supply at high frequencies. (C) 200 0 Elsevier Science S.A. All rights reserved.