A porous carbon-rich layer with the thickness in submicron order is found to form at the interface between polycrystalline cubic SiC film and (100) Si substrate during the film growth using a reactive hydrogen plasma sputtering of ceramic SiC target. The appearance of the porous carbon-rich layer at the interface is due to an indiffusion of carbon atoms through the growing SiC film, and is related to the existence of a hollow voids at the interface. The results obtained in the present study suggest that the indiffusion of carbon atoms through the film may result SiC film growth at the interface.