Low‐temperature low‐stress silicon nitride for optoelectronic Applications prepared by electron cyclotron resonance plasma Chemical‐vapor deposition

Silicon nitride films have been deposited with a single‐magnet electron‐resonance deposition system using nitrogen and silane as the reaction gases at substrate temperatures of 110°C and 300°C. The films are slightly nitrogen‐rich with no measurable Si‐H bonds measurable by Fourier Transform infrared spectroscopy and the concentration of hydrogen present as N‐H bonds increases with increasing SiH4/N2. The stress levels in the films can be controlled from tensile to compressive by decreasing the SiH4/N2 flow ratio and very low stress can be obtained with N‐H bond concentrations of 4 at. %. The optical bandgap for the layer with the lowest stress value (‐11.5 MPa), deposited at 300°C was 4.9 eV, as determined from a taue plot, and the waveguide loss at 632.8 nm was 2.3 dB/cm for 500 nm thick film deposited on fused silica.