Chemical vapor cleaning of 6H-SiC surfaces

The techniques (temperature range of study) of in situ thermal desorption (500-1100 °C) and chemical vapor cleaning (CVC) via exposure to SiH₄ and/or C₂H₄ (750-1100 °C) have been investigated for preparing 6H SiC [(0001)_Si, (0001̄)_C (112̄0), and (101̄0)] surfaces suitable for epitaxial growth of SiC and III-nitride films, and are compared with regard to surface purity, stoichiometry, and structural order. Oxide removal below the detection limits of Auger electron spectroscopy was achieved for all orientations via annealing in 200 L SiH₄ at 850-900 °C or ≈200° lower than necessary by thermal desorption. No non-SiC carbon was detected on the surface by X-ray photoelectron spectroscopy. An approximately one-tenth of a monolayer of oxygen coverage and significant quantities of non-SiC carbon were detected for all 6H-SiC surfaces prepared by thermal desorption. In contrast to the predominantly non-SiC carbon-rich surfaces prepared by thermal desorption, the stoichiometry of the SiC surfaces prepared by CVC could be manipulated from Si-rich to C-rich without non-SiC carbon formation by either extending the SiH₄ exposures or by following with C₂H₄ exposure. The latter surfaces also had lower concentrations of both oxygen and non-SiC carbon and increased surface order.