The mechanism of N-H bond decomposition in silicon nitride films

Abstract

Thin dielectric films produced by the ammonolysis of monosilane in the temperature range 750–900 °C have 5–30% of their nitrogen atoms and 0.5–5% of their silicon atoms chemically bonded with hydrogen. We investigated the process of N-H bond decomposition under heat treatment at 900–1100 °C in vacuum and in different ambient gases by means of multiple internal reflection spectroscopy in the IR. It was found that in vacuum or in an inert gas ambient the activation energy of the process is 65 ± 2 kcal mol −1, which is close to the N-H bond dissociation energy. When hydrogen or ammonia are added to the inert gas the activation energy of the process increases; pureammonia ( P NH 3 = 1.01 × 10 3 hPa) or hydrogen ( P h 2 = 1.01 × 10 3 hPa) suppress the decomposition entirely. The mechanism of the process and some features of the degradation of MNOS memory devices are discussed.