Plasma-assisted thermal atomic layer etching of Al2O3

In this paper, we report on plasma assisted thermal Atomic Layer Etching (ALE) of Al2O3. The surface was modified via a fluorine containing plasma without bias power. The removal was accomplished by a thermal reaction step using tin-(II) acetylacetonate Sn(acac)2. After a few cycles, material removal stopped and growth of a Sn-containing layer was observed. Insertion of a hydrogen plasma step was found to remove the Sn layer and a continuous material removal of 0.5 A/cycle was measured. The results show that plasma assistance can be used to realize thermal ALE of Al2O3. Specifically, plasma can be used both in the fluorination step and to keep the surface free from contaminations.