Thermal-cyclic atomic layer etching of cobalt with smooth etched surface by plasma oxidation and organometallization
Sumiko Fujisaki, Y. Yamaguchi, Hiroyuki Kobayashi, Kazunori Shinoda, Masaki Yamada, Hirotaka Hamamura, Kohei Kawamura, Masaru Izawa
Abstract
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.