Inductively coupled plasma reactive ion etching of copper thin films using ethylenediamine/butanol/Ar plasma

The dry etching of copper thin films patterned with SiO2 hard masks was performed using an ethylenediamine (EDA)/butanol/Ar gas mixture. Ethylenediamine is an organic chelator that served as the main etching gas and butanol was used as an additive gas. As the concentrations of EDA and butanol in EDA/Ar and butanol/Ar increased, respectively, the etch rate of copper thin films decreased. The etch rate in EDA was less than that in butanol. However, a good etch profile of copper thin films was obtained with high EDA concentration in the EDA/Ar gas mixture, whereas high etch selectivity of copper was achieved from the butanol/Ar gas mixture. In the EDA/butanol/Ar gas mixture, the optimal ratio of EDA to butanol was investigated to increase the etch rate and improve the etch profile. The optical emission spectroscopy indicates that the main species in EDA were [CN] and [H], whereas in butanol, [H] was the main substance. The X-ray photoelectron spectroscopy reveals that copper reacted with [CN], [H], and [0] to form copper compounds that could be desorbed from the film surface by the sputtering of ions. The EDA/butanol/Ar gas mixture can be a good etch gas to dry-etch copper thin films.