N-type 4H-SiC Ni Schottky barrier diodes are fabricated with various annealing temperatures during the annealing for the activation of implanted atoms in the guard rings, and the one after patterning Schottky electrodes. The leakage currents show a tendency to increase with temperature up to 1700degreesC during the activation anneals, and to decrease with temperature up to 600degreesC during the Schottky metal anneals. The diodes are analyzed using optical beam induced current (OBIC) measurements, and bright spots of OBIC are observed at the Schottky interfaces only in the case of high leakage currents. Some of die bright spots of OBIC coincide with scratch lines and etch pits. The bright spots of OBIC are analyzed using cross sectional transmission electron microscopy (TEM), and the dark regions beneath the Ni Schottky electrode are found, which are due to the inappropriate lattice sites of SiC atoms.