Reliability of Capacitive Read in Arrays of Ferroelectric Capacitors

TL;DR

This paper investigates the reliability of capacitive readout in ferroelectric capacitor arrays, addressing device variability challenges and proposing design strategies to improve robustness and security in low-power, scalable memory systems.

Contribution

It introduces a digital read macro for HfO₂ ferroelectric capacitors, backed by a physics-based model and Monte Carlo simulations, along with design guidelines to mitigate variability effects.

Findings

Device variability limits read reliability

Design-technology co-optimization improves robustness

Potential security applications identified

Abstract

The non-destructive capacitance read-out of ferroelectric capacitors (FeCaps) based on doped HfO$_2$ metal-ferroelectric-metal (MFM) structures offers the potential for low-power and highly scalable crossbar arrays. This is due to a number of factors, including the selector-less design, the absence of sneak paths, the power-efficient charge-based read operation, and the reduced IR drop. Nevertheless, a reliable capacitive readout presents certain challenges, particularly in regard to device variability and the trade-off between read yield and read disturbances, which can ultimately result in bit-flips. This paper presents a digital read macro for HfO$_2$ FeCaps and provides design guidelines for capacitive readout of HfO$_2$ FeCaps, taking device-centric reliability and yield challenges into account. An experimentally calibrated physics-based compact model of HfO$_2$ FeCaps is employed to investigate the reliability of the read-out operation of the FeCap macro through Monte Carlo simulations. Based on this analysis, we identify limitations posed by the device variability and propose potential mitigation strategies through design-technology co-optimization (DTCO) of the FeCap device characteristics and the CMOS circuit design. Finally, we examine the potential applications of the FeCap macro in the context of secure hardware. We identify potential security threats and propose strategies to enhance the robustness of the system.