NOVEL INSITU DOPED POLYSILICON EMITTER PROCESS WITH BURIED DIFFUSION SOURCE (BDS)

An in-situ doped polysilicon emitter process for very shallow and narrow emitter formation and minimum emitter resistance is presented. An in-situ doped film has been imbedded between two undoped poly spacer layers as a buried diffusion source (BDS) to reduce the emitter resistance and to form a high-quality poly/monosilicon interface. Transistors with an emitter area of 0.25 x 0.25-mu-m2 and with nearly ideal I-V characteristics were fabricated. A very high cutoff frequency of 53 GHz and a minimum ECL gate delay of 26 ps have been achieved using BDS-poly emitter transistors with an emitter area of 0.35 x 4.0-mu-m2.