Patent ID: 9054149
Filing Date: 2015-06-09
Classification: H01L

Abstract:
1. A method of fabricating a bipolar transistor comprising emitter and base regions having first and second conductivity types, respectively, the method comprising: forming an isolation region at a surface of a semiconductor substrate, the isolation region having an edge that defines a boundary of an active area of the emitter region; and implanting dopant of the second conductivity type through respective portions of the isolation region and the active area defined by a mask opening to form the base region in the semiconductor substrate, the mask opening spanning the edge of the isolation region such that the dopant passing through the isolation region forms a first section of the base region with a shallower lower boundary than a second section of the base region formed by the dopant not passing through the isolation region to establish a variable depth contour of the base region; wherein the shallower lower boundary of the first section of the base region defines a base-collector boundary.