Effect of NH 3 flow rate on growth, structure and luminescence of amorphous silicon nitride films by electron cyclotron resonance plasma

Abstract

In this paper, hydrogenated amorphous silicon nitride (a-SiN x :H) films have been deposited using an electron cyclotron resonance chemical vapor deposition system. The effect of NH 3 flow rate R on the deposition rate, structure and luminescence were studied using various techniques such as optical emission spectroscopy, Fourier Transform Infrared absorption (FTIR), X-ray photoelectron spectroscopy (XPS) and fluoro-spectroscopy, respectively. Optical emission behavior of SiH 4 + NH 3 plasma shows that atomic Si radical concentration determines the film deposition rate. Structural transition of a-SiN x film from Si-rich one to near-stoichiometric/N-rich one with R was revealed by FTIR and the two phase separation of a-Si and a-Si 3N 4 was also convinced in Si-rich SiN x films by XPS. Either photo- or electroluminescence for all the SiN x films with R > 3 sccm shows a strong light emission in visible light wavelength range. As R < 6 sccm, recombination of electrons and holes in a-Si quantum dots is the main mechanism of photo/electroluminescence for Si-rich SiN x films, however, for photoluminescence, gap states' luminescence is also in competition; as R > 6 sccm, light emission of the SiN x film originates from defect states in its band gap.