Etch characteristics of cobalt thin films using high density plasma of CH3COCH3/Ar gas mixture

Abstract

Co thin films masked with SiO₂/Si₃N₄ layers were etched using a high-density plasma of a CH₃COCH₃/Ar gas mixture. As the concentration of CH₃COCH₃ increased, the etch rate of the Co thin films and etch selectivity decreased. Optimal etch profiles of the Co films without redeposition were achieved owing to the formation of Co compounds and a passivation layer, which facilitated a high degree of anisotropy. Moreover, the etch characteristics of the Co films were examined using the ICP RF power, dc-bias voltage to the substrate, and process pressure. The active species in plasmas and Co compounds formed during etching were investigated using optical emission spectroscopy and X-ray photoelectron spectroscopy. Finally, the Co thin films patterned with 300 nm lines were etched using a CH₃COCH₃/Ar gas mixture under optimized etch conditions. The findings suggest that a CH₃COCH₃/Ar gas mixture can serve as an effective etch gas for fabricating dry-etched Co thin films.