High growth rate and high wet etch resistance silicon nitride grown by low temperature plasma enhanced atomic layer deposition with a novel silylamine precursor†
Trisilylamine (TSA), an exemplary chlorine and carbon-free commercial silylamine precursor, is well-known to induce improvements in the process and properties of silicon nitride (SiNx) thin films grown using atomic layer deposition (ALD). Herein, we report a TSA homolog, tris(disilanyl)amine (TDSA), as a novel chlorine and carbon-free precursor for the deposition of highly etch resistant SiNx thin films having a high growth rate at a low temperature (<300 °C) using plasma enhanced ALD (PEALD) with hollow cathode plasma (HCP). These improvements in PEALD SiNx using TDSA may be attributed to higher surface reactivity of the molecule enabled by weaker Si–N bonds, higher molecular polarity and the existence of reactive Si–Si bonds in the molecule. The performance of PEALD SiNx grown by TDSA has been compared with that of TSA, aminosilanes and chlorosilanes, and explained with the structure–property relationship of the molecule. TDSA grows SiNx film faster than TSA. Furthermore, the TDSA precursor produces SiNx films that have lower wet etch rate (WER) when compared to other silylamine precursors like TSA, or other types of silane precursors such as aminosilanes and chlorosilanes. We believe that the result, that TDSA-grown SiNx films exhibit lower WER than TSA-grown SiNx films, can be attributed to the abundance of Si in SiNx films, which thereby offers high resistance to a wet etch.