Thermal Atomic Layer Etching of Cobalt Using Sulfuryl-chloride and Hexafluoroacetylacetone

Thermal atomic layer etching (ALE) of cobalt was demonstrated using sulfuryl chloride (SO 2 Cl 2 ) for chlorination and hexafluoroacetylacetone (hfacH) for ligand exchange. This etching chemistry is effective because CoCl 2 has a low vapor pressure, whereas CoCl 2 (hfac) is volatile, facilitating efficient removal. Both the chlorination and ligand-exchange steps were self-limiting, yielding an etch per cycle (EPC) of 0.15 nm cycle −1 , approximately two-thirds of a Co monolayer thickness at 180 °C. The EPC exhibited a temperature dependence of 0.11–0.17 nm cycle −1 in the 160 °C–190 °C range. This process offers a viable route for precise and selective thermal ALE of cobalt in advanced device fabrication.