Effect of N2 Gas Flow Ratio in Plasma-Enhanced Chemical Vapor Deposition with SiH4-NH3-N2-He Gas Mixture on Stress Relaxation of Silicon Nitride

The effects of N-2 gas flow ratios in silicon nitride deposition with SiH4-NH3-N-2-He gas mixtures at a temperature of 275 degrees C on stress relaxation have been investigated We have demonstrated that film stress can be controlled in the range from -692 MPa (compression) to 170 MPa (tension) by increasing N-2 gas flow ratio From the evaluation of the composition ratio of N/St, film density, and bonding structure, the relationships between film stress and these properties are investigated The amount of nitrogen incorporated into the film as N-H bonds increased with increasing N-2 flow ratio, resulting in a higher composition ratio of N/Si At a higher N-2 gas flow ratio, excess N-2 gas in the plasma may disturb the ion bombardment of ionized species on the film surface, resulting in a decrease in the film density The higher N-2 gas flow ratio leads to the generation of a Si-N bonding structure with a larger bond angle at the nitrogen atom site due to bond-strain relaxation, leading to a higher frequency of Si-N stretching vibration Therefore, a nitrogen-richer SiN film with many N-H bonds and a lower film density exhibits bonding structures with a lower bond strain, leading to the relief of film stress (C) 2010 The Japan Society of Applied Physics