BASIC: an advanced high-performance bipolar process

A novel high-performance bipolar process suitable for analog applications is described. A self-aligned technology called BASIC (best alignment with sidewall contact) yields a sidewall contacted structure with strongly reduced parasitic capacitances and low base resistance. The base link-up problem, which is of particular importance for analog applications, is eliminated in the BASIC process by the introduction of a well-defined submicron region, into which a link-up base adjustment dose can be implanted. A simple, novel polysilicon planarization method has been used to form sidewall contacted base boosts. The method is based on the controlled diffusion of boron in polysilicon, followed by the selective wet etching of undoped polysilicon. DC and AC characteristics for the npn transistor exhibit a combination of properties that makes this process very suitable for analog applications, featuring a maximum f/sub T/ of 17 GHz and an Early voltage of 80 V. Two-dimensional device simulations indicate that the increase in Early voltage by more than a factor of two for narrow emitters is caused by lateral depletion of the collector region underneath the intrinsic emitter-base region.<>