Cryo-CMOS Compact Modeling

This paper highlights some of the challenges faced for the modeling of MOSFET devices for operation at cryogenic temperature (CT). A special focus is given on the modeling of the threshold voltage VT and the subthreshold swing SS. The significant increase of VT at CT reduces the available overdrive voltage and therefore needs to be modeled properly. The SS saturates to a constant value below a critical temperature Tc of typically 40 K. This mitigates the current saving that could be expected from reducing the temperature since the transconductance for a given current does not scale inversely with 1/T below Tc. A correct modeling of these two phenomena is therefore key for developing an improved compact model (CM) that scales with T from RT down to CT.