A Schottky-barrier diode with self-aligned floating guard ring

A Schottky-barrier diode with self-aligned floating guard ring is described. The device structure requires no additional mask or process step in an advanced bipolar LSI technology featuring polysilicon base contact and self-aligned emitter region [1]. In contrast to conventional guard ring structures, 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-idealI-Vcharacteristics are obtained. It is shown that the guard ring can be left floating without degrading theI-Vcharacteristics 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 minority-carrier injection from the p+-n junction which reduce the effectiveness of the Schottky diode as an antisaturation device are eliminated.