KINETICS OF SIC CVD - SURFACE DECOMPOSITION OF SILACYCLOBUTANE AND METHYLSILANE

Silicon carbide thin films have been deposited on Si(100) from the single-source reagents silacyclobutane (SCB, C-C3H6SiH2) and methylsilane (MeSiH3). Thermal decomposition kinetics were studied in a low-pressure (50 mTorr), cold-wall CVD reactor over the temperature range 600-1150-degrees-C. Partial pressure analyses based on mass spectrometry indicate the dominant decomposition channels for SCB and MeSiH3 are consistent with the formation of the isomeric intermediates H2Si=CH2 and HSiCH3, respectively. Deposition rates using the two reagents were comparable at all temperatures, reaching 80 angstrom/s at 1050-degrees-C. It is apparent from the lattice vibrational spectrum and X-ray diffraction data that SiC deposited from MeSiH3 is more crystalline. These structural differences suggest a distinct difference in the surface reaction mechanism which is inconsistent with isomeric equilibration. SCB deposits carbon-rich material (C/Si = 1.1), becoming stoichiometric above 1000-degrees-C, while that deposited from MeSiH3 is Si-rich (C/Si = 0.8) at all temperatures. The hydrogen content of SCB films decreased from 6 to 1 atom % with increasing temperature. Results were similar with MeSiH3, but with half as much hydrogen. Modeling of heat and mass transfer at the substrate shows that decomposition occurs exclusively at the surface, allowing surface reaction probabilities to be measured as a function of temperature. Activation energies for SCB and MeSiH3 decomposition are 41 and 53 kcal/mol, respectively. A mechanism for SiC/CVD is proposed that is consistent with the observed kinetics and products of SCB and MeSiH3 decomposition.