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.