Sodium Diffusion in Plasma-Deposited Amorphous Oxygen-Doped Silicon Nitride (a-SiONiH) Films

The dependence of sup 22 Na diffusivity in a-SiH:H and a-SiON:H films on hydrogen content, N/Si ratio, oxygen content and temperature was determined. Measurements were made at 350, 375, and 400 C. The diffusion profiles for silicon in a-SiN:H films have two regions; a short Gaussian region, and shallow linear region. We have interpreted these results using a structural model which describes the film as a two- phase mixture of a highly ordered Si sub 3 N sub 4 -like phase and a highly disordered phase. Using this model we argue that the Gaussian region of the diffusion profile is due to "bulk" diffusion through the Si sub 3 N sub 4 -like phase and the shallow linear region is due to "fast" diffusion through the interfacial region. At 400 C the "fast" diffusivity is on the order of 10 sup 3 times larger than the "bulk" diffusivity. However, at 80 C the "fast" diffusion is approximately 10 sup 5 times smaller than the bulk diffusivity.