Novel Passivation Dielectrics—The Boron‐ or Phosphorus‐Doped Hydrogenated Amorphaus Silicon Carbide Films

Abstract

Hydrogenated amorphous silicon carbide thin films were prepared and studied in a radio‐frequency glow‐discharge system, using a gas mixture of and one of the following carbon sources: methane , benzene , toluene , σ‐xylene , trichloroethane , trichloroethylene , or carbon tetrachloride . The effect of doping phosphorus and boron into those films on chemical etching rate, electrical dc resistivity, breakdown strength, and optical refractive index have been systematically investigated. Their chemical etching properties were examined by immersing in 49% , buffered , 180°C solutions, or in plasma. It was found that the boron‐doped film possesses five times slower etching rate than the undoped one, while phosphorus‐doped film shows about three times slower. Among those films, the one obtained from a mixture of and benzene shows the best etch‐resistant property, while the ones obtained from a mixture of and chlorine containing carbon sources (e.g., trichloroethylene, trichloroethane, or carbon tetrachloride) shows that they are poor in etching resistance (i.e., the etching rate is higher). By measuring dc resistivity, dielectric breakdown strength, and effective refractive index, it was found that boron‐ or phosphorus‐doped films exhibit much higher dielectric strength and resistivity, but lower etching rate, presumably because of higher density.