The reliability characteristics of SiGe HBTs with 200 GHz fT and 285 GHz fMAX are shown and discussed. We review the degradation from avalanche operation, and it is found that the degradation can be predicted using an empirical model that includes integrated avalanche charge and VCB. The model predicts acceptable lifetime degradation with operation up to 1.5-2×BVCEO. We also present, for the first time, detailed device degradation from accelerated temperature and current stress. The degradation observed compares favorably against other published silicon-based bipolar devices under comparable accelerated current stress.
"Consequently, the bias circuitry is designed to provide a base resistance of 300 at low frequencies, while the matching networks provide the necessary low base impedance at high frequencies. Stress tests for advanced SiGe technologies have shown a slight degradation of forward DC current gain at very low bias currents , . Since the transistors in the PA are biased with a high current density, the operation above will not create a reliability issue. "
[Show abstract][Hide abstract] ABSTRACT: A 77-GHz, +17.5 dBm power amplifier (PA) with fully integrated 50-Omega input and output matching and fabricated in a 0.12-mum SiGe BiCMOS process is presented. The PA achieves a peak power gain of 17 dB and a maximum single-ended output power of 17.5 dBm with 12.8% of power-added efficiency (PAE). It has a 3-dB bandwidth of 15 GHz and draws 165 mA from a 1.8-V supply. Conductor-backed coplanar waveguide (CBCPW) is used as the transmission line structure resulting in large isolation between adjacent lines, enabling integration of the PA in an area of 0.6 mm<sup>2</sup>. By using a separate image-rejection filter incorporated before the PA, the rejection at IF frequency of 25 GHz is improved by 35 dB, helping to keep the PA design wideband
[Show abstract][Hide abstract] ABSTRACT: In this paper, we investigate the behavior of advanced SiGe HBTs operating at very high power densities. Measurement results are presented and explained using a model that considers both impact ionization and self-heating. It is shown that even for small transistors, the temperature difference between the center and the ends of the emitter finger causes a significantly more nonuniform current density than expected solely from impact ionization. This requires special attention because the high temperatures that result from very large current densities can degrade the device lifetime.
Bipolar/BiCMOS Circuits and Technology, 2004. Proceedings of the 2004 Meeting; 10/2004
[Show abstract][Hide abstract] ABSTRACT: It is demonstrated that SiGe bipolar technologies are well suited for voltage-controlled oscillators (VCOs) in 77-GHz automotive radar systems. For this, the design of a VCO with powerful output buffer (with good decoupling capability and high output power), comparatively wide tuning range, and reasonably low phase noise is described. To achieve the required high output power, the potential operating range of the output transistors, limited by high-current effects and avalanche breakdown, respectively, had to be exploited using adequate transistor models. The VCOs need a single supply voltage only and have been fully integrated (including resonant circuit and output buffer) on a single small (1 mm<sup>2</sup>) chip, demonstrating their low-cost potential. Experimental results showed, at a center frequency of around 77 GHz, a usable tuning range of 6.7 GHz and a phase noise of -97 dBc/Hz at 1-MHz offset frequency averaged over this range. In addition, the center oscillation frequency can be coarsely adjusted within a wide range by cutting links in the upper metallization layer. The total signal power delivered by both buffer outputs together is as high as 18.5 dBm at a power consumption of 1.2 W. Simulations let us expect a potential doubling of the output power (for two or four outputs) by extension of the output buffer. To get an impression of the maximum frequency achievable with the circuit concept and technology used, a second VCO (again with buffered output) has been developed. To the best of the authors' knowledge, the measured maximum oscillation frequency of about 100 GHz, at 12.4-dBm total output power (14.3 dBm at 99 GHz), is a record value for SiGe VCOs with buffered output operating at their fundamental frequency. The usable tuning range is still 6.2 GHz.
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