Reaction mechanism of trilevel resist etching in O2/SO2 plasma:: controlling factors for sidewall passivation

In the investigation of resist etching in O-2/SO2 plasma, it was found that the addition of a small amount of SO2 to oxygen plasma resulted in the maximum value of resist etch rate and CO* emission peak intensity and the activation energy was 311 cal/mol which was much higher than that of O-2/N-2 (31 cal/mol) or O-2/CO (103 cal/mol) plasma. Compared to pure N-2 and CO plasmas, pure SO2 plasma showed a much higher resist etch rate under the same etch conditions and besides C and O, a sulfur peak was detected on the etched resist surface by XPS analysis. Using the O-2/SO2 plasma, 0.15 mu m features were successfully defined at high SO2 flow rate ratio, high pressure and low electrode temperature, where the effective sidewall passivation by C-S and C-S-O bond formation occurs. (C) 1998 Elsevier Science Ltd. AII rights reserved.