ABSTRACT
“Extreme environment” electronics represents an important niche market in the trillion dollar global electronics industry, and spans the operation of electronic circuits and systems in surroundings lying outside the domain of conventional commercial or military environmental specifications. Extreme environments might include, for instance, (1) operation down to very low temperatures (e.g., to 77 K or even 4.2 K or below); (2) operation up to very high temperatures (e.g., to 200°C or even 300°C or higher); (3) operation across very wide and/or cyclic temperature swings (e.g., −230°C to +120°C night to day, as found on the lunar surface); and (4) operation in a radiation environment (e.g., in space while orbiting the Earth or traveling to an outer planet), or at worst case even all four simultaneously. The unique bandgap-engineered features of silicon–germanium (SiGe) heterojunction bipolar transistors (HBTs) offer considerable potential for simultaneously being able to cope with all four of these extreme environments, potentially with little or no process modifications, ultimately providing compelling advantages at the integrated circuit and system level with respect to size, weight, and power (SWaP) constraints, across a wide class of envisioned commercial and defense applications [1–10]. Such an “environmentally invariant” (i.e., the circuitry can operate unattended and without protection in any environment in which it finds themselves) electronics technology platform would allow mission designers and vehicle architects to reimagine how space systems could and should be designed and operated, and thus SiGe represents a candidate “game-changer” in this important field. In this chapter, we examine the operation of SiGe HBTs at cryogenic temperatures, at elevated temperatures, and in a radiation environment.* We note, parenthetically, that because SiGe technology is inevitably practiced as a BiCMOS platform (SiGe HBT + Si CMOS), there are legitimate questions to be addressed regarding how the CMOS devices within the BiCMOS platform also behave in these extreme environments, and these topics are addressed separately in Chapters 15 through 17.
