Mechanistic analysis on low temperature thermal atomic layer deposition of nitrides utilizing H2S

Atomic layer deposition (ALD) enables the deposition of thin films with excellent step coverage and conformality that are required for nanoscale semiconductor devices. For ALD of nitrides, the high thermal budget required to eliminate impurities in the deposited films is often an issue. Recently, an alternative three-step recipe for thermal ALD of nitrides is reported to simultaneously decrease both the deposition temperature and the impurity contamination, by introducing H2S between chloride precursors and NH3 reactants. In this study, a theoretical analysis is conducted on comparing direct versus three-step alternative reaction paths for thermal ALD of nitrides using density functional theory calculations. The introduction of H2S would enhance the ligand-exchange reaction for nitrides of Al, Ti, and Zr by modifying the reaction scheme to involve a greater number of steps for each lower activation energy required. However, SiN ALD is expected to be hindered by H2S. Our study may be utilized for the development of a new efficient method for ALD of nitride thin films at lower process temperatures.