Modeling Transient Negative Capacitance in Steep-Slope FeFETs

TL;DR

This paper investigates transient negative capacitance in ferroelectric FETs, explaining steep subthreshold slopes as a transient effect caused by ferroelectric domain switching, challenging the need for stabilized negative capacitance.

Contribution

The study models and experimentally analyzes transient negative capacitance, providing new insights into ferroelectric switching effects and their impact on FET performance.

Findings

Steep subthreshold slope is a transient phenomenon linked to polarization changes.

Transient negative capacitance can be explained without stabilized negative capacitance.

FE polarization switching limits high-performance CMOS applications.

Abstract

We report on measurements and modeling of FE HfZrO/SiO2 Ferroelectric-Dielectric (FE-DE) FETs which indicate that many of the phenomena attributed to Negative Capacitance can be explained by a delayed response of ferroelectric domain switching - referred to as Transient Negative Capacitance (TNC). No traversal of the stabilized negative capacitance branch is required. Modeling is used to correlate the hysteretic properties of the ferroelectric material to the measured transient and subthreshold slope (SS) behavior. It is found that steep SS can be understood as a transient phenomenon, present when significant polarization changes occur. The experimental signature of TNC is investigated, and guidelines for detecting it in measured data are outlined. The technological implications of FE polarization switching are investigated, and it is found that NCFETs relying on it are not suitable for high performance CMOS logic, due to voltage, frequency, and hysteresis limitations. Requirements for experimental evidence of stabilized S-curve behavior are summarized.