Cryogenic RF CMOS on 22nm FDSOI Platform with Record f_T=495GHz and f_MAX=497GHz

Cryogenic DRAM at 77K is a promising high bandwidth memory option to complement cryogenic superconducting (SC) processors at 4K [1]. CMOS mixed-signal interface circuits with ultra-high gain-bandwidth product (~THz) is needed to bridge the three-order-of-magnitude voltage gap between SC logic (~25mV) and cryo-DRAM (~0.8-1V). In this work, we demonstrate high-frequency operation of 18nm gate length (LG) FDSOI NMOS and PMOS from 300K to 5.5K operating temperature (T). We show record unity current-gain cutoff frequency (fT) of 495/337 GHz (35%/25% gain over 300K) and maximum oscillation frequency (f_MAX) of 497/372 GHz (30%/30% gain) for NMOS/PMOS at 5.5 K. A small-signal equivalent circuit model is developed to identify the T-dependent and T-invariant components of the extrinsic and intrinsic FET. Cryo-RF CMOS on 22 nm FDSOI platform enables access to Terahertz analog regime, while providing Giga-scale digital density at the same time.