Mechanical strains in pecvd SiN_x:H films for nanophotonic application

Hydrogenated amorphous silicon nitride films (SiN_x:H) are deposited at low temperature by high-frequency plasma-enhanced chemical vapor deposition (HF PECVD). The main effort is to investigate the roles of plasma frequency and plasma power density in determining the film properties particularly in stress. Information about chemical bonds in the films is obtained by Fourier transform infrared spectroscopy (FTIR). The stresses in the SiN_x:H film are determined from substrate curvature measurements. It is shown that plasma frequency plays an important role in controlling the stresses in SiN_x:H films. For silicon nitride layers grown at plasma frequency 40.68 MHz initial tensile stresses are observed to be in a range of 400 MPa–700 MPa. Measurements of the intrinsic stresses of silicon nitride films show that the stress quantity is sufficient for film applications in strained silicon photonics. (paper)