A mixture of tetramethylsilane/CF4/H-2 is used for depositing fluorinated amorphous silicon carbide thin films at room temperature under heavy ion bombardment in a 13.56 MHz RF powered, asymmetric plasma reactor. An optical emission spectrometer and a quadrupole mass spectrometer are used to measure the concentrations of chemical species in the plasma phase while the bonding structure of the deposited films is analyzed by Fourier transform infrared spectroscopy (FTIR). The results indicate that the density and the optical properties of the films obtained at room temperature are as good as those deposited at much higher temperatures. The fluorination results in elimination of the bound hydrogen in the deposited film, decreases in the refractive index and extinction coefficient, an increase in the optical bandgap, and a decrease in the intrinsic stress of the film. Based on the gas-phase concentration measurements and the film bonding structures observed, growth mechanisms of the deposition are suggested.