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 V
_T
and the subthreshold swing SS. The significant increase of V
_T
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 T
_c
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 T
_c
. 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.