Evolution of etch profile of copper thin films in high density plasmas of alcohol-based gases

Abstract Dry etching of copper thin films patterned with SiO 2 masks was performed using inductively coupled plasmas of CH 3 OH/Ar, C 2 H 5 OH/Ar, and O 2 /C 2 H 5 OH gases. The etch rates of copper films in CH 3 OH/Ar plasma were slightly faster than those in C 2 H 5 OH/Ar plasma while the etch profiles in C 2 H 5 OH/Ar plasma were better than those in CH 3 OH/Ar plasma. Upon varying the etch parameters, high coil RF power, high dc-bias voltage to substrate, and low process pressure were found to cause increased redeposition of the etched materials on the copper sidewalls and increased etch slopes. Optical emission spectroscopy, energy dispersive X-ray spectroscopy, and the evolution of the etch profiles revealed the etch mechanism of copper films in C 2 H 5 OH/Ar gas. X-ray photoelectron spectroscopy confirmed that the etching of copper films by C 2 H 5 OH/Ar takes place via a chemical mechanism involving the formation of copper compounds and a sputtering mechanism by the ions, depending on the C 2 H 5 OH concentration. Good etch profiles of copper films without the redeposition were achieved using the optimized O 2 /C 2 H 5 OH gas.