Patent attributes
High frequency performance of (e.g., silicon) bipolar devices (100, 100″) is improved by reducing the extrinsic base resistance Rbx. Emitter (160), base (161) and collector (190) are formed in or on a semiconductor substrate (110). The emitter contact (154) has a portion (154′) that overhangs a portion (1293, 293″) of the extrinsic base contact (129), thereby forming a cave-like cavity (181, 181″) between the overhanging portion (154′) of the emitter contact (154) and the underlying regions (1293, 1293″) of the extrinsic base contact (129). When the emitter contact and the extrinsic base contact are silicided, some of the metal atoms forming the silicide penetrate into the cavity (181, 181″) so that the highly conductive silicided extrinsic base contact extends under the edge of the emitter contact (154′) closer to the base (161, 163) itself, thereby reducing Rbx. Smaller Rbx provides transistors with higher fMAX.
