Temperature stable Pd ohmic contacts to p-type 4H-SiC formed at low temperatures

The formation of low resistivity Pd-based ohmic contacts to p-type 4H-SiC b elow 750 degrees C are reported herein, The electrical properties of the co ntacts were examined using I-V measurements and the transmission-line model (TLM) technique. Contact resistivity as a function of annealing was invest igated over the temperature range of 600 degrees C-700 degrees C, The lowes t contact resistivity (5.5 x 10(-5) Ohm cm(2)) was obtained after annealing at 700 degrees C for 5 min, Atomic force microscopy of the as-deposited Pd layer showed a root-mean squ are roughness of similar to 8 nm, while after annealing at 700 degrees C, a gglomeration occurred, increasing the roughness to 111 nm, Auger electron s pectroscopy depth profiles revealed that with annealing, interdiffusion had resulted in the formation of Pd-rich silicides. However, X-ray diffraction and Rutherford backscattering showed that the majority of the film was sti ll (unreacted) Pd. The thermal stability and reliability of the Pd contacts were examined by a ging and temperature dependence electrical tests, The contacts annealed at 700 OC were stable at prolonged heating at a constant temperature of 500 de grees C and they showed thermal stability in air at operating temperatures up to 450 degrees C, This stability was not found for contacts formed at lo wer temperatures of 600 degrees C or 650 degrees C.