Thermal-cyclic atomic layer etching of cobalt with smooth etched surface by plasma oxidation and organometallization

Thermal-cyclic atomic layer etching of a Co film and a fine pattern with a smooth etched surface by plasma oxidation and organometallization is demonstrated. One cycle of the etching process consists of a two-temperature process. In the first step, plasma oxidation of Co is carried out at a low temperature of 25 °C to obtain a smooth Co oxide layer. In the second step, the Co oxide is organometallized with acetylacetone and desorbs at a high temperature of 210 °C that is suitable for organometallization and desorption. The etched amount per cycle is 0.6 nm, which is the same as the saturation amount of oxidation. A smooth etched surface is obtained after 20 cycles with a root mean square roughness of 0.53 nm, which is only slightly higher than the initial value of 0.34 nm. High etching selectivity over barrier metal of titanium-nitride was obtained. The two-step temperature cycle is crucial to achieve favorable etching with smooth etched surfaces.