Patent ID: 8647955

Claim:
A method for forming an electrostatic discharge protection (ESD) clamp having a predetermined threshold voltage Vt 1 , the method comprising: providing a semiconductor substrate having a first surface; producing at least a first bipolar transistor on the semiconductor substrate comprising a base of a first conductivity type underlying the first surface, a base contact of the first conductivity type extending into the base from the first surface, an emitter of a second, opposite, conductivity type extending into the base from the first surface and laterally separated from the base contact at the first surface by a distance Lbe, and a collector proximate the base; wherein the base is formed to include: a first base portion containing the base contact and the emitter and having a first base dopant concentration; a second base portion located laterally between the first portion and a first boundary and having a second base dopant concentration; and a third base portion of width D located laterally between the boundary and a portion of the collector and having a third base dopant concentration, wherein the threshold Vt 1 is determined at least in part by the width D; wherein the first base dopant concentration is less than the second base dopant concentration; and wherein Lbe is in the range of about 0.7 to 23 micrometers.