Design and Optimization of Superjunction Collectors for Use in High-Speed SiGe HBTs

After reviewing the various mechanisms causing breakdown in bipolar transistors, we present a novel collector design for silicon-germanium heterojunction bipolar transistors (SiGe HBTs). The design improves the well-known speed/breakdown voltage tradeoff in SiGe HBTs for radio-frequency (RF) and mil...

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Bibliographic Details
Published in:IEEE transactions on electron devices 2011-06, Vol.58 (6), p.1655-1662
Main Authors: Jiahui Yuan, Cressler, J D
Format: Article
Language:English
Subjects:
Accumulators
Applied sciences
Breakdown
Breakdown voltage
Collectors
Compound structure devices
cutoff frequency
Devices
Doping
Electric potential
Electronics
Exact sciences and technology
heterojunction bipolar transistor (HBT)
Heterojunction bipolar transistors
Impact ionization
Junctions
operation speed
Radio frequencies
Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices
Silicon carbide
Silicon germanides
Silicon germanium
superjunction
Thyristors
Transistors
Voltage
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Summary:After reviewing the various mechanisms causing breakdown in bipolar transistors, we present a novel collector design for silicon-germanium heterojunction bipolar transistors (SiGe HBTs). The design improves the well-known speed/breakdown voltage tradeoff in SiGe HBTs for radio-frequency (RF) and millimeter-wave applications. Applying multiple alternating p- and n-type layers (a superjunction) deep in the collector-base (CB) space-charge region (SCR) alters the electric field and electron temperature in the CB junction. Consequently, impact ionization is suppressed, whereas the width of the CB SCR is not increased, and therefore, the breakdown voltages BV CEO and BV CEO are increased, with no degradation in the device speed or RF performance. For a fixed alternating-current performance, BV CEO is improved by 0.33 V, producing a SiGe HBT with f T = 101 GHz, f max = 351 GHz, and BV CEO = 3.0 V, as predicted by calibrated DESSIS technology computer-aided design simulations. Concerns with regard to the influence of thermal cycles associated with fabrication are considered, and a more practical doping profile is proposed to simplify the use of superjunctions. The proposed structure is also contrasted with other approaches from the literature.
ISSN:0018-9383
1557-9646
DOI:10.1109/TED.2011.2128872