A Si bipolar transistor with f/sub max/ of 40 GHz and its application to a 35 GHz 1/16 dynamic frequency divider

The development of a Si bipolar transistor with f/sub max/ (maximum frequency of oscillation) of 40 GHz by employing a process which independently optimizes the cutoff frequency (f/sub T/) and the base resistance (r/sub b/) is discussed. By using a A-BSA (advanced BSG self-aligned) technology, the resistance of the link region, the intermediate base region between the intrinsic and extrinsic ones, is controlled by the rediffusion from the BSG side wall to the link region. This process does not degrade f/sub T/. As a result, f/sub max/ of 40 GHz and f/sub T/ of 43 GHz are realized simultaneously. Using this transistor of 1/16 dynamic frequency divider that operates up to 35 GHz has been constructed. The application of Si bipolar transistors will extend to the millimeter-wave frequency region. >