Effects and prevention of source/drain ion implantation into the polysilicon in a BiCMOS technology

The implantation of source/drain dopants into the polysilicon for FET gates and the bipolar emitter has a profound effect on the operation of the devices. Although the collector current is only slightly affected, the base current increases by as much as a factor of three, with the emitter resistance doubled. The effect of altering the gate doping is evident in the FET devices as well. This paper describes the above device processes necessary to add a silicon nitride blocking layer