Relationship between junction radius and reverse leakage of silicide Schottky-barrier diodes

Unguarded Schottky-barrier diodes exhibit excessive leakage current in the reverse-current direction. A portion of this excess current has always been attributed to sharp-edge effects. In this paper, the sharp-edge-related excess reverse current is attributed to the additional barrier lowering that is due to the electric-field enhancement present near the diode edges. Mathematical relationships describing the effect of the edge radius on the I-V characteristics of unguarded diodes are developed. These relationships are then used to model an unguarded Schottky-barrier diode. The correlation between the junction radius and the diode characteristics was found to be strong in the reverse-current direction. In the foward direction, the diode characteristics were not greatly affected, and thus the large diode-quality factors of unguarded diodes cannot be attributed to the sharp-edge effect. A comparison is made between the experimental characteristics of Pd2Si/ nSi and VSi2/nSi diodes and those obtained from modeling.