INTERFACE CHEMISTRY AND ELECTRIC CHARACTERIZATION OF NICKEL METALLIZATION ON 6H-SIC

The interface chemistry and the electrical properties of annealed Ni/6 H-SiC ohmic contacts have been compared using X-ray photoemission spec troscopy, current-voltage and resistance measurements by a four-point probe method. Substrates of n-type SIC wafers (CREE Res) with N-d = 1 x 10(18) cm(-3) have been used. The XP spectra indicate that carbon is in the graphite state and silicon is bonded predominantly to Ni resul ting in NiSi formation which is preceded by decomposition of SiC to si licon and carbon after annealing. One hour annealing leads to a degrad ation of the contact resistance by a factor of 1.5 as compared with th e contacts annealed for 5 min. This seems to be due to an increased gr aphite precipitation in the subsurface region of the contact layer. Cu rrent-voltage characteristics are linear for the contacts annealed abo ve 900 degrees C, while the contact resistance reaches a minimum aroun d 1000 degrees C.