The thermal stability of two sputter-deposited Schottky contact metallizations incorporating Ta-Si-N amorphous diffusion barriers and Au overlayers are compared using depth profiling by backscattering spectrometry and secondary ion mass spectrometry as well as current-voltage measurements. A [6H-SiC]/TaSi2/Ta20Si40N40/Au metallization changes its Schottky barrier height from 0.71 to 0.62 eV upon annealing at 600 degreesC for 30 min, while its ideality factor improves from an initial value of 1.55 to 1.16. Both Schottky barrier height and ideality factor remain stable upon successive annealing of the sample at 700 degreesC for 30 min and for an additional 90 min. The observed stability is attributed to the thermal stability of TaSi2 with SiC and to the effectiveness of the Ta-Si-N diffusion barrier evidenced in backscattering depth profiles. On the other hand, a [6H-SiC]/Ta36Si14N40/Au metallization that does not include the silicide contacting layer becomes ohmic after vacuum annealing at 600 degreesC for 30 min, while no signs of metallurgical interaction are observed in its backscattering spectra. Using secondary ion mass spectrometry, diffusion of nitrogen is observed from the Ta-Si-N layer into the 6H-SiC substrate. It is tentatively suggested that nitrogen penetrates the substrate through defects, induced in the sputter-deposition process.