Masaru Hori

(Invited) Thermal Cyclic Atomic-Level Etching of Nitride Films: A Novel Way for Atomic-Scale Nanofabrication

A highly selective, rapid thermal-cyclic atomic-level etching (ALE) process for SiNx film has been developed. The first step of this process is exposing SiNx to hydrofluorocarbon plasma to form an (NH4)2SiF6 layer on the SiNx surface. The second step is rapid thermal annealing with an infrared (IR) irradiation to decompose and sublimate the (NH4)2SiF6 layer. Etching of SiNx was observed after the (NH4)2SiF6 layer was removed by thermal annealing. Cyclic etching tests were carried out by repeated plasma exposure and IR irradiation. It was found that the cyclic process is self-limiting because etching depth depends only on the cycle number and not on the plasma exposure time. A high selectivity over SiO2 and poly Si was confirmed. This paper reviews the novel isotropic ALE for nitride films focusing on the surface reaction mechanism investigated by x-ray photoelectron spectroscopy (XPS) and thermal desorption spectroscopy (TDS). Isotropic ALE of TiN was also demonstrated using the same approach.