METHOD FOR ACHIEVING IDEAL IMPURITY BASE PROFILE IN A TRANSISTOR.

摘要

A method for making a transistor having base, collector, and emitter regions, where the impurity doping profile of the intrinsic (32) and extrinsic (22) base regions can closely approximate that which is ideal for the transistor. The extrinsic (22) and intrinsic (32) base regions are formed in separate steps, where the extrinsic base region (22) is formed first, followed by formation of the intrinsic base region (32). The portion of the extrinsic base region located over the area where the intrinsic base region is to be formed is removed, leaving an opening (26) through which both the emitter (30) and the intrinsic base regions (32) are formed. Thus, the effect of the step in which the extrinsic base region is formed is removed prior to formation of the intrinsic base region. Furthermore, the extrinsic base region is protected during formation of the intrinsic base region. This technique can be applied to processes using either ion implantation or diffusion to form the emitter and base regions of the transistor.