Ta-Si contacts to n-SiC for high temperatures devices

The properties of Ta-Si contact to n-SiC have been investigated by complementary use of 2 MeV He+ Rutherford backscattering spectroscopy and X-ray diffraction measurements. Electrical properties were characterized by current-voltage characteristics and specific contact resistance. Contact metallization was deposited on 4H- and 6H-SiC (0 0 0 1) wafers by RF magnetron sputtering the 100 nm thick Ta silicide film. The Ni(100 nm) film was sputtered on reference wafers for comparative studies electrical characteristics of the contacts. The I-V characteristics of Ta-Si and Ni contact are linear after rapid thermal annealing (RTA) at 850 and 750 °C, for 3 min, respectively. The specific contact resistance of 4 × 10−5 Ω cm2 for Ta-Si contact annealed at 950 °C is achieved on the 4H-SiC with donor concentration of (6-8) × 1018 cm−3. For the reference contact, the contact resistivity is 2 × 10−5 Ω cm2. The amorphous microstructure of Ta-Si contacts is stable up to 900 °C and no significant reaction at SiC/Ta-Si interface is observed at this temperature. After annealing at 1000 °C a reaction at the interface is revealed but limited to very narrow region. The phases of Ta5Si3, Ta, β-Ta, Ta2C and Ta(O) are detected in amorphous matrix of the film. Surface morphology of the Ta-Si contact is stable up to 1000 °C, therefore, this kind of contact has great advantage over Ni-silicides contacts. Even at 1100 °C, Ta-Si contact has still abrupt interface with SiC and featureless surface.