Influence of Deposition Conditions on the Characteristics of Luminescent Silicon Carbonitride Thin Films

The influence of the substrate temperature and argon gas flow on the compositional, structural, optical, and light emission properties of amorphous hydrogenated silicon carbonitride (a-SiCxNy:H) thin films were studied. Thin films were fabricated using electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR PECVD) at a range of substrate temperatures from 120 to 170°C (corresponding to deposition temperatures of 300 to 450°C) in a mixture of SiH4, N2, and CH4 precursors. Variable angle spectroscopic ellipsometer (VASE), elastic recoil detection (ERD), and Rutherford backscattering spectrometry (RBS) verified optical bandgap widening, layer densification, and an increase of the refractive index at higher substrate temperatures. The microstructure of a-SiCxNy:Hz thin films was determined by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy. The substrate temperature strongly affected the binding state of all atoms, and in particular, carbon atoms attached to silicon and nitrogen, as well as hydrogen-terminated bonds. We correlated the films' microstructural changes to a higher species' mobility arriving on the growin layer at higher temperatures. Photoluminescence (PL) measurements showed that the total intensity of visible light emission increased. A systematic blueshift of the centroid of the wide PL peak was observed following the increase of optical gap.