Amorphous Indium Oxide Channel FEFETs With Write Voltage of 0.9 V and Endurance >1012 for Refresh-Free Embedded Memory

Abstract

This work presents, for the first time, a back-end-of-the-line (BEOL)-compatible W-doped indium oxide (IWO) ferroelectric field-effect transistor (FEFET) with a record-low operating voltage below 0.9 V and a write speed of 20 ns while achieving a transient read current window (CW) ratio ( ${I}_{\text {LVT}}/{I}_{\text {HVT}}$ ) greater than ${10}^{{4}}$ . The device also exhibits exceptional reliability characteristics such as: 1) measured bipolar write endurance up to ${10}^{{12}}$ cycles; 2) a fast read speed of 50 ns; 3) read endurance surpassing ${10}^{{12}}$ cycles; and 4) retention exceeding ${10}^{{4}}$ s at $85~^{\circ } $ C. Furthermore, a physics-based numerical model has been developed to investigate the nanoscale characteristics of BEOL FEFET devices, leveraging nucleation-limited switching in HfO2 ferroelectrics and dc characterization to extract material and channel parameters for accurate device simulation. The simulation uncovers the stochastic switching behavior of BEOL amorphous oxide semiconductor (AOS) FEFETs and demonstrates an intrinsic switching time as low as 1 ps, highlighting the potential of BEOL AOS FEFETs for ultrafast memory applications. These results establish AOS FEFETs as a compelling candidate for high-density embedded memory applications for last-level cache (LLC) (L4) in advanced CMOS technology nodes.