Structural evolution and mechanical properties of nitrogen doped hydrogenated amorphous silicon thin films

Nitrogen doped hydrogenated amorphous silicon thin films, also recorded as silicon rich hydrogenated amorphous silicon nitride thin films, were deposited by plasma enhanced chemical vapor deposition. The structural evolution and mechanical properties of the films with different nitrogen contents were studied by Fourier transform infrared spectroscopy, Raman scattering spectroscopy, and the density and stress measurement system, respectively. The results showed that with the increase in ammonia gas flow rate from 0.5 SCCM to 20 SCCM, the tensile stress and the density of the films decreased from 600 MPa to 280 MPa and from 2.31 g/cm3 to 2.08 g/cm3, respectively. The hydrogen bonding configurations, hydrogen content, and structural ordering evolution were investigated to reveal the relationship between the structural and mechanical properties of the films. A qualitative model was proposed to explain the role of nitrogen and hydrogen atoms during the film growth.