Understanding the Memory Window Overestimation of 2D Materials Based Floating Gate Type Memory Devices by Measuring Floating Gate Voltage

TL;DR

This study reveals that the memory window of 2D material-based floating gate memory devices is overestimated when using round sweep transfer curves, due to capacitive coupling effects, and proposes a measurement method for accurate evaluation.

Contribution

It introduces a floating gate voltage measurement method to accurately assess the memory window of 2D NVM devices, correcting overestimations from traditional measurement techniques.

Findings

Memory window overestimation occurs with round sweep curves.

Floating gate voltage measurement clarifies charge and capacitive effects.

Proper evaluation of 2D NVM potential is enabled.

Abstract

The memory window of floating gate (FG) type non-volatile memory (NVM) devices is a fundamental figure of merit used not only to evaluate the performance, such as retention and endurance, but also to discuss the feasibility of advanced functional memory devices. However, the memory window of two dimensional (2D) materials based NVM devices is historically determined from round sweep transfer curves, while that of conventional Si NVM devices is determined from high and low threshold voltages (Vths), which are measured by single sweep transfer curves. Here, it is elucidated that the memory window of 2D NVM devices determined from round sweep transfer curves is overestimated compared with that determined from single sweep transfer curves. The floating gate voltage measurement proposed in this study clarifies that the Vths in round sweep are controlled not only by the number of charges stored in floating gate but also by capacitive coupling between floating gate and back gate. The present finding on the overestimation of memory window enables to appropriately evaluate the potential of 2D NVM devices.