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

What is it about?

Co film is etched digitally using dry etching apparatus with precision at atomic level. In the first step, plasma oxidation of Co is carried out at low temperature of 25°C to obtain a smooth Co oxide layer. In the second step, the Co oxide is reacted with vaporized acetylacetone and forms Co(acac)2. Co(acac)2 disorbs at 210°C. One cycle consists of these two steps. The plasma oxidation of Co at low temperature has saturability, so oxidation amount of 0.6 nm equals to etching amount at one cycle. Number of cycle determines etching amount.

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Photo by jesse orrico on Unsplash

Photo by jesse orrico on Unsplash

Why is it important?

Atomically smooth etched surface: Root-mean-square(RMS) roughness after 20-cycle etching is 0.53 nm. Acetylacetone(acacH) is liquid at RT, so a liquid vaporizing system is connected to the dry etching apparatus and acacH vapor is introduced into the dry etching apparatus without condensation. Low temperature oxidation produces a smooth sureface, a saturated amount of oxidation. That realizes self-limiting and digital etching.