Five-step plasma-enhanced atomic layer etching of silicon nitride with a stable etched amount per cycle
Akiko Hirata, Masanaga Fukasawa, Jomar U. Tercero, Katsuhisa Kugimiya, Yoshiya Hagimoto, Kazuhiro Karahashi, Satoshi Hamaguchi, Hayato Iwamoto
Abstract
Abstract Atomic layer etching is an advanced plasma etching technique that enables the atomic-precision control. In this study, the effects of surface conditions on the stability of the etched amount per cycle (EPC) in silicon nitride (SiN) plasma-enhanced atomic layer etching (PE-ALE) were examined. A single cycle of SiN PE-ALE consisted of two steps: hydrofluorocarbon (HFC) absorption step and argon-ion (Ar + ) desorption step. After a few cycles, an etch-stop of SiN occurred due to the HFC deposition. An oxygen-plasma ashing step was introduced after desorption step, which made three-step SiN PE-ALE. The etch-stop was avoided but the EPC was low due to the surface oxidation of SiN. By combining this three-step SiN PE-ALE with subsequent two-step SiO 2 PE-ALE, which consists of fluorocarbon adsorption step and Ar + desorption step, SiN PE-ALE was achieved with a stable and large EPC. This five-step SiN PE-ALE allows the precise control of SiN etched depth.