Patent ID: 7807539

Claim:
A method comprising: providing a substrate, the substrate including (i) a collector layer, (ii) a common base layer formed over the collector layer, and (iii) a top layer formed over the common base layer; forming a plurality of isolation trenches in the top layer to define a plurality of regions in the top layer; forming a first photoresist layer over the top layer; patterning the first photoresist layer to reveal a first portion of the top layer; doping the first portion of the top layer with a first dopant to form a base pick-up region; and subsequent to doping the first portion of the top layer, doping a second portion of the top layer with a second dopant, wherein doping the second portion includes doping the plurality of regions with the second dopant to form a corresponding plurality of emitter regions, and wherein the first dopant is different from the second dopant.