Adsorption and thermal behaviors of methyl chloride on Si(100)-2x1 have been studied by low energy electron diffraction(LEED), Auger electron spectroscopy (AES) and thermal desorption spectroscopy (TDS). The dissociative adsorption of the methyl chloride on Si(100) takes place without breaking of silicon dimers with high efficiency. For the adsorption at room temperature, the existence of a precursor state is confirmed by the change of the sticking probability depending on the coverage and temperature. From Clausis-Clapeyron equation, the determined activation barrier of adsorption $(\deltaH_{ads})$ is -28.4 KJ/mol. It indicates that the adsorption process is a non- activated process. The adsorption of $CH_3Cl$ on the sputtered and H- passivated surfaces is also investigated. Prebombarding the Si surface with $Ar^+$ ions significantly enhances the adsorption of methyl chloride while the H- passivation suppresses it. Thermal heating of $CH_3Cl$ adsorbed on Si(100) leads to decomposition of the $CH_3$ groups on Si(100) and simultaneous desorption of molecular hydrogen. The carbon Auger line shape shows the formation of silicon carbide due to the diffusion of carbon into the bulk.
