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-ideal characteristics are obtained. It is shown that the guard ring can be left floating without degrading the 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 minority-carrier injection from the p⁺-n junction which reduce the effectiveness of the Schottky diode as an antisaturation device are eliminated.