  Wide attention has been focused on cryogenic CMOS (Cryo-CMOS) operation
because of its wide application and the improvement of CMOS performance.
However, hot carrier degradation (HCD) becomes worsening at cryogenic
temperature, which affects the reliability of Cryo-CMOS. Therefore, this
article investigates HCD in 0.18 um bulk CMOS at cryogenic temperature down to
4.2 K. Particularly, the relationship between HCD and the current overshoot
phenomenon and the influence of substrate bias on HCD are discussed. Besides,
we predict the lifetime of the device at 77 K and 4.2 K. It is concluded that
cryogenic NMOS cannot reach the ten years' commercial standard lifetime at
standard drain voltage (VDD). And it is predicted that the reliability
requirements can be reached when VDD<1.768V/1.734V at 77K/4.2K. Differently,
the lifetime of PMOS is long enough even at low temperatures.
