Fabrication Process Study of Silicon Nitride Passivation Layer on GaAs Substrate at Low Temperature

Abstract

In order to obtain the excellent silicon nitride (SiN) films in AlGaAs laser, SiN films with different deposition parameters are fabricated on GaAs substrate by plasma enhanced chemical vapor deposition (PECVD) at low temperature. The residual stress, surface morphology and refractive index of these films are investigated comprehensively by means of refractometer, atomic force microscope (AFM) and Fourier transform infrared spectroscopy (FTIR). The results show that residual stress of SiN films increases with the deposition power. An ultra low stress (6 MPa) is obtained at the pressure of 200 Pa. The AFM results show that the surface roughness increases with the deposition power, while decreases with the deposition pressure. Both the deposition power and the pressure have a weak effect on the refractive index. The refractive index of all these films are 2.0~2.2. The FTIR results show that the H element exists in the film with the N-H bond. SiN films with ultra low stress and good surface morphology can be obtained by selecting proper power and pressure at low temperature.