Effects of gas pressure and substrate temperature on the etching of parylene-N using a remote microwave oxygen plasma

The effects of temperature and pressure on the rate of etching of parylene-N in a downstream oxygen plasma created with a microwave source have been determined. Etch rate increases with increasing substrate temperature, with an apparent activation energy of 6.6-8.0 kcal/mol over the 373-523 K temperature range. The etch rate goes through a maximum between 0.6 and 0.8 Torr as pressure is increased from 0.4 to 1.0 Torr. The observed maxima are more pronounced as substrate temperature increases. Analyses of x-ray photoelectron spectra for unetched and etched films reveal that exposure to the plasma afterglow decreases the relative amount of aromatic carbon and creates carboxylic acid groups in the film. Residual gas analysis of the reactor effluent during etching indicates that the only volatile etch products are H2O, CO2 and CO. Likely reactions that may lead to the formation of the observed etch products are presented and discussed. (C) 2001 American Vacuum Society.