Evaluation of silicon tetrahalide precursors for low-temperature thermal atomic layer deposition of silicon nitride

Abstract

The development of atomic layer deposition (ALD) processes adaptable to a wide temperature range requires a detailed assessment of the chemical reactivity of the precursors. Theoretical approaches, such as density functional theory (DFT) calculations, can help accelerate and elaborate on the chemistry of ALD. In this paper, the reactivity of silicon tetrahalide precursors (SiCl4, SiBr4, and SiI4) toward a low-temperature thermal ALD of silicon nitride (SixNy) thin films using NH3 as the counter-reactant was evaluated using DFT calculations and supplementary experiments. The enthalpy of reaction, as well as the Gibbs free energy of the reaction, shows a periodic trend, such that the reactions of SiI4 are the most favorable at low deposition temperatures. Also, thermal ALD of SixNy using SiI4 and NH3 at a relatively low temperature of 350 °C was conducted, validating the computational results.