Experimental characterization and modeling of most advanced Silicon-Germanium HBT technologies from 4 K to 423 K

• Applicant: Professor Dr.-Ing. Michael Schröter
• Subject Area: Electronic Semiconductors, Components and Circuits, Integrated Systems, Sensor Technology, Theoretical Electrical Engineering
• Term: since 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 377861290

Recent technology development of silicon-germanium-carbon (SiGeC) heterojunction bipolar transistors (HBTs) has led to maximum operating frequencies of 500 GHz and beyond at 1.6 V breakdown voltage (BVCEO) even for industry prototyping processes. BiCMOS technology, resulting from combining high-speed HBT circuits with moderate-cost digital CMOS, has enabled a large variety of commercial and emerging mm- and sub-mm-wave applications, such as broadband wireless communications, imaging and sensing. SiGeC HBTs have increasingly also found their way into applications operating under extreme conditions in terms of bias and temperatures. Many explorations in space, material physics, chemistry, and technology development benefit from operating electronic circuits and devices at cryogenic temperatures. In particular, SiGeC HBTs have been shown to operate at 4 K with significantly improved performance which has made them attractive for emerging applications such as quantum computing, where speed can be traded for lower noise and energy efficiency. Unfortunately, models for the design of cryogenic high-frequency (HF) circuits do presently not exist. In the first phase of this project the suitability of the existing HBT compact model was experimentally demonstrated for the temperature range of 150 K to 423 K, and first low-temperature measurements revealed serious model deficiencies in the range of 4 K to 150 K. The main objectives of this second phase of the project thus address both these deficiencies and the increasing need for accurate models for emerging low-temperature applications: (1) Theory development for and simulator implementation of a physics-based geometry scalable non-linear compact model for SiGeC HBTs that accurately captures the operation at low (including cryogenic) temperatures from 4 K to 150 K with special emphasis on the saturation region for extremely low-power mm-wave applications. (2) Design and fabrication of test chips with HBTs and passive devices (relevant to mm-wave circuits) for model parameter determination as well as with selected circuit building blocks for cryogenic applications and model verification. (3) Experimental DC and HF characterization of high-speed and high-voltage SiGeC HBTs, fabricated with different advanced process technologies, versus bias, frequency, and geometry in the temperature range of 4 K to 150 K for compact model verification and parameter extraction. The results of this project enable mm- and sub-mm-wave circuit and system design for emerging applications operating at low and, in particular, cryogenic temperatures. The developed model will be used, among others, by IHP customers, such as Google and MIT, for designing circuits for quantum computing.

• DFG Programme: Research Grants