Schottky barrier diodes with self-aligned floating guard rings

Schottky barrier diodes with self-aligned guard rings are described. Two device structures compatible with the self-aligned bipolar transistor process [1] are considered. For the first structure, the diffused guard ring is in physical contact with the anode of the Schottky diode as in conventional guard ring structures. For the second structure, the guard ring is separated from the anode by a sidewall oxide of thickness less than 0.3 µm, allowing independent access to the guard ring. Near-ideal I-V characteristics are obtained for both structures. It is shown that for the latter structure the guard ring can be left floating without degrading the I-V and leakage characteristics of the Schottky diode. In this mode of operation, the advantage of the guard ring is maintained while the depletion capacitance and charge storage due to injection from the p⁺-n junction which reduce the effectiveness of the Schottky diode as an antisaturation device are eliminated.