In-situ chemical beam exposures of CBr4 and SiBr4 have been employed for the removal of native surface oxygen on n-type 6H-SiC. Low temperature grown AlN has been grown using metal organic molecular beam epitaxy (MOMBE). Dimethylethylamine alane (DMEAA) was used as the Al precursor, and group V nitrogen atoms were generated by radio-frequency plasma. The growth temperature was 425degreesC. Reflection high energy electron diffraction (RHEED) showed an enhancement of the diffraction pattern as the SiC substrate was chemically treated at 650degreesC. Auger electron spectroscopy has shown that oxygen is significantly reduced by a combined CBr4/SiBr4 exposure. The AlN films were nanocrystalline, having an rms roughness of 0.5Angstrom. This treatment is of particular interest as a low temperature atomic layer etch process for SiC substrates, and for the development of AIN dielectrics with high breakdown fields and low density of interface states.