RF-PECVD deposition and optical properties of hydrogenated amorphous silicon carbide thin films

Hydrogenated amorphous silicon carbide (a-SiCx:H) thin films were deposited using a radio frequency plasma enhanced chemical vapor deposition (RF-PECVD) system with methane (CH4) and silane (SiH4) as reactive precursor gases and H2 as a carrier and dilution gas. The effects of RF-PECVD deposition conditions on the optical properties and microstructural characteristics of a-SiCx:H thin films were systematically investigated. When the RF power density, deposition pressure (P) and temperature (Ts) were fixed, the refractive index (n) and the growth rate of a-SiCx:H thin films decreased with the CH4/SiH4 flow rate ratio (R), while their optical band gap (Eg) increased with R. The a-SiCx:H thin film grown at higher R was found to be smoother than that grown at lower R. When the RF power density, P and R were fixed, the growth rate of a-SiCx:H thin films decreased with Ts, while their n increased with Ts. It was found that Eg slightly increased with Ts, and the film became rough at higher Ts. When Ts, P and R were fixed, the growth rate of a-SiCx:H thin films increased with the RF power density, while their n only slightly increased and Eg slightly decreased with the RF power density. It was found that the RF power density had a large impact on the roughness of a-SiCx:H thin films.