Vertical Profile Optimization of Very High Frequency Epitaxial Si- and SiGe-Base Bipolar Transistors

Bipolar transistors with phosphorus-doped emitters and sub-50nm epitaxial bases have been fabricated in a low thermal-cycle process to explore the trade-offs between cutoff frequency, breakdown voltage and Early voltage. Record peak fTs of 73 GHz for a Si BJT and 113 GHz for a SiGe HBT with respective βVA products of 630 and 48,400 V were obtained for intrinsic base sheet resistances of 26 and 7 kΩ/□.