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 (I
EBO
) is used as an indicative parameter for the degree of the intrinsic and extrinsic base overlap. By plotting the emitter-base leakage current (I
EBO
) site-by-site against other device parameters, such as the emitter-collector punchthrough current (I
CEO
), the collector saturation current density (J
CS
), 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.