This work focuses on Ni ohmic contacts to the C-face (backside) of n-type 4H-SiC substrates. Low-resistive ohmic contacts to the wafer backside are important especially for vertical power devices. Ni contacts were deposited using E-beam evaporation and annealed at different temperatures (700-1050 °C) in RTP to obtain optimum conditions for forming low resistive ohmic contacts. Our results indicate that 1 min annealing at temperatures between 950 and 1000 °C provides high quality ohmic contacts with a contact resistivity of 2.3x10-5 Ωcm2. Also our XRD results show that different Ni silicide phases appear in this annealing temperature range.