Nanometer-scale etching of copper thin films in high-density plasma of an ethylenediamine/acetic acid/argon gas mixture

Dry etching of the copper thin films patterned with sub-100 nm was performed using the high-density plasma of an ethylenediamine (EDA)/CH3COOH/Ar gas mixture. The etch rates and etch selectivities of copper films patterned with 80 nm line array were significantly improved by adding CH3COOH to the EDA/Ar gas mixture, resulting in a high degree of anisotropy in etch profiles. The optimal ratio of EDA to CH3COOH was found to be 4:1, and a good etch profile was obtained at approximately 60% (EDA/CH3COOH) in EDA/CH3COOH/Ar. Optical emission spectroscopy demonstrated that the maximum [CN] and [H] intensities in the (EDA/CH3COOH)/Ar plasma were measured at approximately 50%-75% (EDA/CH3COOH). X-ray photoelectron spectroscopy confirmed the formation of compounds containing CuCN and C-C/C-H during the etching process, meaning that this etch chemistry was effective. Transmission electron microscopy confirmed that there was neither redeposition nor etch residue on the sidewalls of the etched copper films.