Cryogenic Characterization of Ferroelectric Nonvolatile Capacitors

Ferroelectric-based capacitive crossbar arrays have been proposed for energy-efficient in-memory computing in the charge domain. They combat the challenges like sneak paths and high static power faced by resistive crossbar arrays but are susceptible to thermal noise limiting the effective number of bits (ENOBs) for the weighted sum. A direct way to reduce this thermal noise is by lowering the temperature, as thermal noise is proportional to temperature. In this work, we first characterize the nonvolatile capacitors (nvCAPs) on a foundry 28-nm platform at cryogenic temperatures to evaluate the memory window (MW), on state retention as a function of temperature down to 77 K, and then use the calibrated device models to simulate the capacitive crossbar arrays in SPICE at lower temperatures to demonstrate higher ENOB (~5 bits) for <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$128\times 128$</tex-math> </inline-formula> multiply-and-accumulate (MAC) operations.