Base-profile optimization for minimum noise figure in advanced UHV/CVD SiGe HBT's

Abstract

We investigate the base-profile design issues associated with optimizing ultrahigh vacuum/chemical vapor deposition (UHV/CVD) silicon-germanium (SiGe) heterojuction bipolar transistors (HBT's) for minimum broad-band noise. Using the simulator for cryogenic research and SiGe bipolar device optimization (SCORPIO), the impact of Ge profile, base doping level, and base thickness on minimum noise figure (NFmin) are quantitatively examined across the 055 C-125 C temperature range.We introduce a novel Ge profile for optimum NFmin, which allows independent control of current gain () and achieves maximum fT while maintaining thermodynamic stability. Simulations show that this profile can achieve a of 200, a peak fT > 50 GHz, a peak fmax > 60 GHz, and an NFmin < 0.5 dB at 2 GHz and <1 dB at 10 GHz using a conservative base width of 90 nm.We predict that a 45-nm base-width/0.5-m emitter-width device with a thermodynamically stable flat Ge profile, manufacturable using an UHV/CVD growth technique, should be able to achieve an NF min < 0.4 dB at 2 GHz and 0.8 dB at 10 GHz along with a of 300, a peak f T > 70 GHz, and a peak f max > 90 GHz.These 300-K performance values improve as the temperature is reduced.

SiGe HBTs for application in BiCMOS technology: I. Stability, reliability and material parameters

“…Errors in the SIMS profile cause large errors in some of the computed characteristics of the HBT. The IBM group [60,61] scale each SIMS doping profile (within 20%) so that the measured characteristic which depends most strongly on the profile shows best agreement with its computed value. The scaled profiles are designated as calibrated profiles.…”

“…The calibrated profiles for a typical HBT [60,61] are shown in figure 12(a). With the calibrated profiles and reliable models for material parameters, the observed Gummel plots and cutoff frequencies agree with the simulated values within 10-20% [1,60,61]. Daimler-Benz AG (DBAG) SIMS profiles are shown in figure 12(b).…”

Noise modeling and SiGe profile design tradeoffs for RF applications [HBTs]

“…For constant film stability, at a given geometry and doping, a higher and higher can only be realized in practice by pushing the edge of the Ge retrograde in the collector significantly closer to the EB junction (surface). The additional Ge can then be used to reduce the effective Gummel number in the neutral base for higher , and increase the Ge grading for higher [14], [15]. We are thus forced to trade highroll-off performance for improved .…”

Noise properties of SiGe heterojunction bipolar transistors

“…Firstly, we report on works of Schumxher et al [I91 which have measured abrupt HBT 30 optimized with respect to the high frequency noise featuring minimum noise figure lower than I dB at I O GHz. Ansley et a1 [20] have also presented works on gradual HBT imcl they have shown that an appropriate base shape can leucl to vcry attractive performance since they report minimum noise figure as low as 0.5 dB at 2 GHz and they state that their technology are able to achieve HBT featuring minimuin noise figure in the 0.8 dB range at I O GHz. The works we present in this paper concerning the SiGe HBT are obtained on SiGe HBT optimized with respect to their L.F noise properties ancl doesn't constitute the state of the art.…”