Etch Characteristics Of Copper Thin Films In Inductively Coupled Plasma Of Piperidine/Ethanol/Ar Gas Mixture

High density plasma reactive ion etching of copper thin films patterned with SiO2 masks was performed via piperidine/ethanol/Ar gas mixture. The etch characteristics of the copper thin films were examined as functions of the gas concentrations in piperidine/Ar and piperidine/ethanol/Ar mixtures. As the piperidine concentration increased, the etch rates of the copper films decreased whereas the etch selectivities of the copper films to SiO2 mask increased and the etch profiles improved. Optical emission spectroscopy studies showed that the major active species in the plasmas of piperidine/Ar and piperidine/ethanol/Ar were CH and CN, which were responsible for the good etch profiles. Further, X-ray photoelectron spectroscopy revealed the formation of CuCN, copper compounds, and polymer layers. Finally, dry etching of copper thin films was successfully accomplished with the optimized piperidine/ethanol/Ar gas mixture, thereby obtaining good etch profiles with high degrees of anisotropy.