Characterization of stress in amorphous silicon nitride and implications to c-Si surface passivation

In this work we study stress in amorphous silicon nitride (SiN_x) deposited by semi-remote microwave plasma-enhanced chemical vapor deposition. The film stress, determined from the change in wafer curvature before and after SiN_x deposition, is found to depend on SiN_x stoichiometry irrespective of process conditions. We demonstrate that an increase in stress correlates to a shift of the Si-H stretching vibrational peak to a higher wavenumber and an increase of total bond density of N-related bonds (sum of Si-N and N-H bond densities). We also find that there is no dominant relationship between stress and the effective surface recombination velocity or the interface defect density, but for SiN_x prepared by varying a single process condition such as gas ratio, there does exist correlation between electrical interface properties and stress. These results suggest that the Si-SiN_x interfacial electrical properties are less dependent on stress than they are on other factors such as ion bombardment or hydrogen passivation that can be altered by varying process variables.