Theoretical an experimental investigation of noise in advanced SiGe BiCMOS process technologies
Final Report Abstract
The demand for high-speed integrated circuits and systems is being driven by the continuous push for higher operating frequencies, such as 60 GHz for wireless communications, 160 Gb/s for fiber-optic data transmission, and 77 GHz for automotive radar. At these frequencies, heterojunction bipolar transistors (HBTs) have inherent advantages with respect to speed and analog characteristics over MOSFETs (i.e. CMOS technology). Silicon-Germanium (SiGe) HBTs presently achieve maximum operating frequencies up to 350 GHz. This together with the tremendous boost in footprint reduction from the integration into advanced CMOS technology makes SiGe HBTs and the associated BiCMOS technology a serious contender for high-speed applications. In the latter, SiGe HBTs are used especially in high-frequency (h.f.) circuit modules, such as low-noise amplifiers (LNAs), voltage-controlled oscillators (VCOs), and mixers, in alio of which noise plays a very important role. Experience has shown that cost and design of such modules represent a significant bottleneck for overall system implementation. Furthermore, considering the exorbitant increase of mask cost beyond SlMio for existing 90nm technology, circuit optimization with respect to yield and reduction in design cycles is of utmost importance. Therefore special models for circuit simulation, so-called compact models (CMs), are required that very accurately capture the device characteristics over a wide bias, frequency, temperature and geometry range as well as non-standard characteristics such as noise and distortion that are of high importance for h.f applications. In this project h.f noise characteristics were investigated for two different types of SiGe HBTs fabricated with existing production technologies: (a) conventional emitter doping HBTs and (b) low-emitter concentration HBTs. The standard HBT compact model HICUM/Level2, which has been available in all commercial circuit simulators and is being supported by the semiconductor industry world-wide, was employed es vehicle for demonstrating the validity of the results. This work focussed on the three directions briefly described below in terms ofthe main results. An improved analytical model for correlated base and collector shot noise was derived and verified with experimental data up to 26 GHz. This analytical model contains all noise relevant circuit elements and allows a fast prediction of noise characteristics. Better understanding of the theory also allowed to identify the often used "delay time" as the first-order time constant in non-quasistatic operation. The analytical description also enabled to include correlated noise in HICUM within SPICE-like circuit simulators using the Verilog-AMS language. As second topic, impact ionization noise was investigated with the additional help of numerical device simulation for gaining an understanding of the underlying device physics. It turned out that the main noise contributor for operation beyond the breakdown voltage is the avalanche current related fluctuation itself. It was further shown that the drift-diffusion based approach can still be used for impact ionization noise modeling in compact models such as HICUM. However, the extracted model parameters appear to be less physical. Finally, the resulting new HICUM/Level2 version 2.23 was verified on both experimental and device simulation data. Excellent agreement has been obtained over the entire relevant bias and frequency range. In particular, the noise characteristics of HICUM have been verified on calibrated hydro-dynamic device simulation up to lOOGHz, which is well beyond the presently existing measurement equipment bandwidth. The new HICUM version is presently being officially released to the Electronic Design Automation (EDA) industry and the circuit design community world-wide.
Publications
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J. Herricht, P. Sakalas, M. Schröter, P. Zampardi, Y. Zimmermann, F. Komdoerfer, A. Simukovic "Verification of Ti-Equivalent Circuit based Microwave Noise Model on AniBy HBTs with Emphasis on HICUM", Digest IEEE MTT-S IMS, Long Beach, CA, pp. 1419-1422, 2005.
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A. Chakravorty, M. Schröter, P. Sakalas, J. Herricht, "Correlated noise modeling - an implementation into HICUM", Proc. 6th HICUM workshop, Heilbronn, Germany, 2006. (Siehe online unter: http://www.iee.et.tu-dresden.de/~schroter/Models/workshop0606/I-b-hicum_ws_noise_0606.pdf)
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J. Herricht, "Beiträge zur verbesserten Modellierung von Rauschen und nichtlinearen Verzerrungen in integrierten Bauelementen und Hochfrequenzschaltungen", Dissertation, Lehrstuhl Elektronische Bauelemente und Integrierte Schatungen, TU Dresden, 2006.
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P. Sakalas, A. Chakravorty, M. Schröter, M. Ramonas, J. Herricht, A. Shimukovitch, C Jungemann, "Modeling of high frequency noise in SiGe HBTs", Digest International Conference on Simulation of Semiconductor Processes and Devices, Monterey, Califomia, USA, 6-8 September, CA, USA, pp.271-274, 2006.
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M. Ramonas, P. Sakalas, C. Jungemann, M. Schröter, A. Shimukovitch, W. Krauss, "Microscopic modeling of Impact-Ionization Noise in SiGe Heterobipolar Transistors", Proc. SPIE Conf Noise and Fluctuations in Circuits and Materials, Florence, Italy, Vol. 66001F, 12 pages, 2007.
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A. Rumiantsev, R. Doemer, P. Sakalas, "Verification of Wafer-Level Calibration Accuracy at Cryogenic Temperatures", Proc. 68th ARTFG Microwave Measurement Conference, Measurement for Emerging Technologies, pp. 137-140, 2006.
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J. Herricht, P. Sakalas, A. Chakravorty, M. Schröter, "Transistor-Kompaktmodell mit korrelierten Rauschquellen für sehr hohe Frequenzen", ITG-Fachbericht ANALOG'06, 196, September, Dresden, pp. 27-29, 2006.
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M. Ramonas, P. Sakalas, C. Jungemann, M. Schröter,W. Kraus, A. Shimukovitch, "Microscopic Modeling of High Frequency Noise in SiGe HBTs", Proc. 37th European Solid State Device Research Conference, Munich, 11-13 September, pp. 183-186, 2007.
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P. Sakalas, J. Herricht, "High Frequency Noise Investigations in HBTs using Compact Model Approach", invited talk at IEEE MTT IMS WMC Workshop 'TMoise in SiGe and III-V HBTs and Circuits: Opportunities and Challenges", San Francisco, CA, USA, June 11, 2006.
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P. Sakalas, J. Herricht, A. Chakravorty, M. Schröter, "Compact Modeling of High Frequency Correlated Noise in HBTs", Proc. 2006 Bipolar/BiCMOS Circuits and Technology Meeting, Maastricht, The Netherlands, pp.279-282, 2006.
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P. Sakalas, M. Schröter, P. Zampardi, "Investigation of shot noise reduction in InGaP HBTs with different base thickness", Proc.of Int. Conf. Noise and Fluctuations, ICNF-2005, ed.T Gonzalez, J. Mateos, D. Pardo, Salamanca, Spain, pp. 151-163, 2005. .
