Chemical mechanism of oxidative etching of ruthenium: Insights into continuous versus self-limiting conditions

Abstract

Ruthenium (Ru) has emerged as a promising material for microelectronic applications that require precise modification and patterning of thin films at the nanoscale. However, the susceptibility of Ru to oxidative etching has raised challenges in achieving the desired profile of Ru thin films. In this study, we investigated the mechanisms and conditions required for oxidative etching of Ru using density functional theory (DFT) calculations. Our calculations examined the thermodynamics and kinetics of several pathways toward the formation of gaseous RuO4, including oxidations of bulk Ru and RuO2, from both surfaces of which surface reactions were considered. Our findings suggest that etching reactions under O3 exposure are more favored on a Ru surface than on RuO2. Experimental results obtained from etching of Ru using O3 further support our computational predictions, indicating that oxide formation leads to a reduction in the etching rate and that quasi-self-limiting etching conditions can be achieved towards oxidative ALE of Ru. Our study may contribute to the fundamental understanding of Ru surface phenomena and provides insights into the development of effective ALE techniques for Ru.