Effects of Deposition Method on the Properties of Silicon Nitride and Silicon Oxynitride Films

Abstract

The compositional properties of silicon nitride (SiN) and silicon oxynitride (SiON) films prepared by electron cyclotron resonance plasma CVD (ECR P-CVD) and conventional plasma CVD (P-CVD) methods have been investigated and compared. SiH4-N2 gas was used for SiN depositions in both methods. O2 gas and N2O gas were added to SiH4-N2 gas for SiON film formations in ECR and P-CVD depositions, respectively. SiN films with the N/Si ratio in excess of a stoichiometric value and predominantly with N-H bonds are more easily obtained by the ECR P-CVD method than by the P-CVD method. Hydrogen concentrations were found to be nearly the same in the SiN films deposited by both methods in the microwave powers and rf power of 150-500 W. The addition of O2 and N2O gases to the SiH4-N2 resulted in an increase in the deposition rates of SiON films of about 1.5 times that of SiN films. A slight addition of O2 and N2O gases resulted in a decrease in the absorption due to Si-H bonds and an increase in the absorption due to N-H bonds. Additions of more than a certain amount of O2 or N2O gases resulted in the disappearance of Si-H and N-H bonds. However, hydrogen atoms were found to be still contained in SiON films, although the concentration is a little low in comparison with those in SiN films. The excited states of oxygen are considered to have great influence on such film compositions.