Fabrication and Characterisation of pnp Polysilicon Emitter Bipolar Transistors

The fabrication of pnp polysilicon emitter bipolar transistors is described for devices both with and without a deliberately grown interfacial oxide layer. SIMS is used as an aid to determine the optimum emitter drive-in conditions, and this is compared with electrical results from actual devices. Precipitation of boron in the polysilicon is shown to occur for devices with high implant doses and low drive-in temperatures. Preliminary modelling of devices with an interfacial oxide layer has been undertaken in terms of the barrier heights to majority and minority carriers.