THE EFFECT OF ION ENERGY ON THE FORMATION OF THE SILICON-CARBIDE INTERFACE OF HYDROGENATED AMORPHOUS-CARBON FILMS GROWN ON SILICON BY PLASMA ASSISTED CHEMICAL VAPOR-DEPOSITION

The interface of hydrogenated amorphous carbon films grown on single crystal silicon by plasma assisted chemical vapor deposition from methane was studied by angle-resolved X-ray photoelectron spectroscopy. The effect of varying RF power for films grown on a RF-powered electrode was investigated, as well as the effect of varying pulse height for films grown under high voltage pulsed biasing on a non-RF-powered electrode. The spectra of the films deposited at the powered electrode revealed the presence of an approximately stoichiometric silicon carbide layer at the interface. In contrast, the interfacial carbide for films formed at the pulsed biased electrode was found to be nonstoichiometric and silicon rich, which could be ascribed to the relatively much smaller high-energy ion flux to the substrate. The effective thickness of the interfacial layer, as determined from the angle-resolved spectra, however, correlated well with the kinetic energy of plasma ions impinging on the silicon substrate, regardless of the average stoichiometry. The thickness varied from approximately 4 to 12 angstrom for kinetic energies ranging from approximately 150 to 1100 eV. The results indicate that the thickness of the interfacial carbide is determined by the average penetration depth of plasma ions into the silicon substrate, as controlled by their kinetic energy.