Characteristic Study of Silicon Nitride Films Deposited by LPCVD and PECVD

This paper analyzes and compares the characteristics of silicon nitride films deposited by low pressure chemical vapor deposition (LPCVD) and plasma enhanced chemical vapor deposition (PECVD), with special attention to the hydrogenation and chemical composition of silicon nitride films. Three different LPCVD processes at various DCS and NH3 gas flow rates and deposition temperatures, together with PECVD using SiH4 and NH3 and ICP CVD using SiH4 and N-2, were compared. The silicon nitride film deposition rate decreases with an increasing NH3/DCS ratio in LPCVD, which also leads to an increase in the refractive index and a decrease in the residual stress in the film. There is nearly no hydrogen incorporated in the LPCVD films, which differs from PECVD and ICP CVD that show significant Si-H and N-H bonds. The chemical composition of silicon nitride films is mostly Si-rich, except for the LPCVD process at high NH3/DCS ratio with near stoichiometric chemistry.