Nucleation behavior during the first stages of SiC growth on different substrates

SiC films were deposited on bare Si(001), on MBE carbonized Si(001) and on thermally oxidized (300 nm thick) Si(001) to investigate the effect of the substrate surface on the nucleation behaviour and the subsequent SiC growth mode. The SiC film depositions were performed in a conventional hot-wall L PCVD reactor at temperatures around 1150 degrees C. The precursor gas used was tetramethylsilane (TMS) mixed with H-2. Extensive morphological and str uctural characterization was carried out by AFM, SEM, XRD (rocking curves a nd texture measurements), WDS and TEM. The influence of the different nucle ation surfaces on the quality of the grown film and its microstructure is d iscussed. On both bare Si and MBE carbonized substrates, a very thin film c overs the substrate surface even after very short times. The presence of vo ids and hillocks on these samples is associated to Si-outdiffusion during t he SiC growth. The resulting thick layers grown for longer times are single -crystalline 3C-SiC. On the contrary, SiC growth on thick SiO2 proceeds via the formation of hexagonal pyramidal islands, which coalesce after very lo ng deposition times.