Dry etching of palladium thin films in high density plasmas of CH3OH/Ar, C2H5OH/Ar, CH4/Ar, and CH4/O2/Ar gas mixtures

High density plasma etching of Pd thin films masked with TiN films was performed using CH3OH/Ar, C2H5OH/Ar, CH4/Ar, and CH4/O2/Ar gas mixtures. The etch rates of the Pd films and TiN masks in all the gas mixtures decreased whereas the etch selectivities increased. The etch profiles of the Pd films etched under C2H5OH/Ar gas were better than those obtained with CH3OH/Ar gas. Addition of O2 gas to the CH4/Ar gas mixture considerably improved the etch profiles of the Pd films. CH4, Ar, and O2 were found to play a critical role in obtaining a vertical etch profile with smooth sidewalls. Energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy revealed the formation of polymeric layers and PdOx compounds on the sidewalls and the film surface. Good etch profiles with a high degree of anisotropy were achieved with the use of C2H5OH/Ar and CH4/O2/Ar gas mixtures.