Modeling Electrical Resistance Drift with Ultrafast Saturation of OTS Selectors

TL;DR

This paper presents a time and temperature dependent model for OTS selectors that predicts their electrical resistance drift, including an ultrafast saturation phenomenon, aiding in the design of reliable crossbar memory arrays.

Contribution

The authors develop a novel Poole-Frenkel conduction-based model that captures the temporal evolution and saturation of threshold voltage drift in OTS selectors.

Findings

Model accurately predicts resistance drift at 8 nm technology node.

Ultrafast saturation of drift occurs within approximately 10^3 seconds.

Model aligns well with experimental data at different temperatures.

Abstract

Crossbar array architecture is an essential design element for densely connected Non-Volatile Memory(NVM) applications. To overcome intrinsic sneak current problem of crossbar arrays, each memory unit is serially attached to a selector unit with highly nonlinear current-voltage (I-V) characteristics. Recently, Ovonic Threshold Switching (OTS) materials are preferred as selectors due to their fabrication compatibility with PRAM, MRAM or ReRAM technologies; however, OTS selectors suffer from the temporal drift of its threshold voltage. First, based on Poole-Frenkel conduction, we present time and temperature dependent model that predicts temporally evolving I-V characteristics,including threshold voltage of OTS selectors. Second, we report an ultrafast saturation ($\sim 10^3$ seconds) of the drift and extend the model to predict the time of drift saturation. Our model shows excellent agreement with OTS devices fabricated with 8 nm technology node at 25{\deg}C and 85{\deg}C ambient temperatures. The proposed model plays a significant role in understanding OTS device internals and the development of reliable threshold voltage jump table.