STUDY OF THE INITIAL FORMATION OF SILICON-CARBIDE BY REACTION OF TETRAETHYL SILANE WITH SILICON

The growth of SiC films on Si by reaction with tetraethyl silane (SiEt4) has been studied using Auger and electron energy-loss spectroscopies, low-energy electron diffraction, and external-reflection infrared reflection absorption spectroscopy (IRRAS). IRRAS is used to monitor the chemisorption of the reagent molecule on polycrystalline Si at substrate temperatures below the point where complete dissociation occurs. The electron techniques are used to characterize the structure and composition of SixC1-x (0 less-than-or-equal-to x less-than-or-equal-to 1) layers formed on Si(100) at higher temperatures during dosing with SiEt4. Near room temperature, IRRAS data indicate adsorption of undissociated -C2H5 groups with the C-C bond oriented nearly normal to the surface. Under growth conditions, the relative rates of deposition and indiffusion of C control the stoichiometry of the initial SixC1-x phase. At lower temperatures (approximately 750-1000 K), a partially noncarbidic phase occurs. Annealing this surface or dosing the clean surface at higher temperature leads to formation of a SiC layer which then acts to slow further diffusion. Subsequent layer growth occurs mainly by pyrolysis of the SiEt4 molecule. However, the underlying Si substrate continues to function as either a C sink or a Si source.