Mechanistic considerations of low temperature hydrogen-based plasma etching of Cu

Abstract

A simple plasma-based, low temperature etch process is described, which allows subtractive etching of copper (Cu) films and thereby offers an alternative to damascene technology for microelectronic and integrated circuit device fabrication. Hydrogen (H2)-based plasma etching of blanket and SiO2 masked Cu thin films is performed in an inductively coupled plasma reactor at temperatures below room temperature. This process achieves anisotropic Cu features and an etch rate of ∼13 nm/min. Although Ar and He are more efficient sputter gases, Cu etching in these plasma atmospheres displays lower etch rates than those observed with H2 plasmas. Moreover, anisotropy degraded with enhanced ion bombardment due to mask ablation. Cu etch rate and patterning results are consistent with an etch process that involves both chemical and physical characteristics. Specifically, the combination of ultraviolet photon impingement, ion bombardment, and hydrogen interaction with Cu surfaces appears to be responsible for the efficient removal of Cu in low temperature H2-based plasma environments.