GROWTH-MORPHOLOGY OF LOW-PRESSURE METALORGANIC CHEMICAL-VAPOR-DEPOSITION SILICON-CARBIDE ON A-SIO2/SI(100) SUBSTRATES

Silicon carbide films were deposited on Si(100) wafers in the temperature range 950-1150 degrees C, from a mixture of Si(CH3)(4) + H-2 in a hot-wall low-pressure chemical vapor deposition (LPCVD) reactor. A thin a-SiO2 layer of 60 Angstrom was grown on the Si substrate prior to deposition. The total pressure, H-2 flow rate and H-2/Si(CH3)(4) ratio were fixed at 0.65 Torr, 1300 cm(3)/min and 130, respectively. The microstructure of the as-grown films was investigated by X-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) and electron microprobe analysis (EPMA). The deposition reaction of SiC is thermally activated with an apparent activation energy of 150 kJ/mol. It was found that a mixture of micro-crystalline and amorphous phases is formed with an overall C content of 60 at% at the deposition temperature of 950 degrees C. Crystallinity is improved and microstructure becomes columnar as growth proceeds on films deposited at 1000 degrees C. Films grown at temperatures between 1050 and 1105 degrees C are stoichiometric beta-SIC polycrystals, with a columnar morphology and well developed (111) preferential orientation. In agreement with a columnar grains development, surface roughness increases dramatically as deposition temperature changes from 950 to 1150 degrees C. At T = 1105 degrees C cylindrical crystallites with diameters similar to 150 nm are observed in films similar to 20 mu m thickness. Planar defects perpendicular to the axis of the crystallites are microtwins generated by the rapid incorporation of a high number of atoms with low adatom mobilities and are responsible for the fast growth along the [111] direction.