High-temperature oxidation resistance of Ta-Si-N films with a high Si content

The high-temperature oxidation resistance of ternary Ta-Si-N films with a high (≥ 20 at.%) Si content deposited by reactive dc magnetron sputtering on silicon substrates was systematically investigated by means of a symmetrical high-resolution thermogravimetry in a flowing air up to an annealing temperature of 1300 °C. Additional analyses including optical microscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD) and the microhardness measurement were carried out as well. The obtained results showed an excellent high-temperature oxidation resistance Ta₁₂Si₂₆N₆₂ films up to 1300 °C. A slight oxidation starts just above 800 °C and stops approximately at 1080 °C due to the formation of a thin barrier oxide layer composed dominantly of orthorhombic Ta₂ O₅ phase. The thickness of the oxide layer is almost constant with the annealing from 1080-1300 °C (h_oxide/ h_film ≈ 18%), however, the crystallinity is much improved. The microhardness decreases from 25 to 16 GPa with increasing annealing temperature due to the formation of the oxide layer of a lower microhardness. The microhardness and the oxide layer thickness almost do not change with increasing annealing time up to 1 h at a constant annealing temperature of 1300 °C.