Methodology for bipolar process diagnosis and its application to advanced self-aligned bipolar transistors

A methodology for bipolar process diagnosis is developed to evaluate advanced shallow profile bipolar technologies. In this method, the emitter-base leakage current (IEBO) is used as an indicative parameter for the degree of the intrinsic and extrinsic base overlap. By plotting the emitter-base leakage current (IEBO) site-by-site against other device parameters, such as the emitter-collector punchthrough current (ICEO), the collector saturation current density (JCS), and the current gain β, the influence of processing conditions on the device characteristics can be disclosed. An advanced "double-poly" self-aligned bipolar technology is used as an example to demonstrate the application of this method. The effects of the extrinsic base drive-in and the polysilicon emitter junction depth on the device characteristics are studied.