PROCESS FOR FABRICATION OF HIGH-SPEED RADIATION HARD BIPOLAR SEMICONDUCTOR DEVICES

A thermal oxide is grown on a semiconductor substrate containing single crystal, dielectrically isolated tubs. A silicon nitride layer, serving as a mask for complete self-alignment of collector contacts, bases and emitters is then deposited. After the silicon nitride is patterned, the wafer is reoxidized. The oxide over the emitter and collector contact areas is then etched using the previously patterned silicon nitride film as an alignment mask. The remaining silicon nitride is stripped, a base photoresist pattern is formed and a base impurity ion implant is performed, to define the essential profile of the base. Polysilicon is then deposited and implanted with impurities to form 4000 ohm/square resistors. Silicon dioxide is deposited over the areas of polysilicon which are to become resistors when the polysilicon is patterned, which silicon dioxide masks the polysilicon resistor precursors from the impurities implant conducted for the collector contact, emitter and interconnects. The polysilicon is patterned for resistors, contacts and interconnects. Another photoresist is deposited and patterned to open up contact areas for the formation of schottky barrier diodes and transistor bases. Thereafter, the device is metallized, and processing is completed.