Integrated circuit lateral transistor structure

Abstract

In a monolithic silicon integrated circuit fast diffusing impurities are incorporated into the collectors of the bipolar lateral transistors. The impurity level is controlled, using ion implantation, so that after device processing the lateral transistor collectors extend an additional increment into the base. This increment is doped with the fast diffusing impurity at a level that overcompensates the normal base impurity to the opposite conductivity type and conductivity about equal to that of the base. Thus the collector junction is moved towards the emitter and is symmetrical in terms of conductivity. This means that when the collector is reverse biased the depletion field extends about equally on both sides of the junction. This action greatly relieves the voltage gradient and stress so that collector junction voltage breakdown is enhanced. Since the collector junction is closer to the emitter the transistor current gain and frequency response are enhanced.