BASE-PROFILE OPTIMIZATION FOR MINIMUM NOISE-FIGURE IN ADVANCED UHV CVD SIGE HBTS/

We investigate the base-profile design issues associated with optimizi ng ultrahigh vacuum/chemical vapor deposition (UHV/CVD) silicon-german ium (SiGe) heterojuction bipolar transistors (HBT's) for minimum broad -band noise. Using the simulator for cryogenic research and SiGe bipol ar device optimization (SCORPIO), the impact of Ge profile, base dopin g level, and base thickness on minimum noise figure (NFmin) are quanti tatively examined across the -55 degrees C-125 degrees C temperature r ange, We introduce a novel Ge profile for optimum NFmin, which allows independent control of current gain (beta) and achieves maximum f(T) w hile maintaining thermodynamic stability, Simulations show that this p rofile can achieve a beta of similar to 200, a peak f(T) > 50 GHz, a p eak f(max) > 60 GHz, and an NFmin < 0.5 dB at 2 GHz and <1 dB at 10 GH z using a conservative base width of similar to 90 nm, We predict that a 45-nm base-width/0.5-mu m emitter-width device with a thermodynamic ally stable flat Ge profile, manufacturable using an UHV/CVD growth te chnique, should be able to achieve an NFmin < 0.4 dB at 2 GHz and simi lar to 0.8 dB at 10 GHz along with a beta of similar to 300, a peak f( T) > 70 GHz, and a peak f(max) > 90 GHz, These 300-K performance value s improve as the temperature is reduced.