Bipolar Transistor With Pedestal Subcollector Regions Self-Aligned Underneath Field Oxide Regions
Original Publication Date: 1988-Aug-01
Included in the Prior Art Database: 2005-Feb-15
This article describes a technique for fabricating bipolar transistors to minimize charge storage in the epitaxial (epi) region under the field oxide and provide better p-to-p isolation. In conventional no-recessed oxide (ROX) structures, such as in advanced self-aligned bipolar circuit technology, the epi regions which are doped only to approximately 1016 cm-3 underneath the field oxide, store minority carriers (holes). Also, p-region-to-p-region isolation may not be adequate because of the light n-type doping, as illustrated in Fig. 1. The n-epi region underneath the field oxide can store minority carriers (holes) when holes are injected into those regions. The ideal field oxide which solves the problems mentioned above is the shallow trenches which reach all the way down to the n+ subcollector layer, as illustrated in Fig.