Interface controlled thermal properties of ultra-thin chalcogenide-based phase change memory devices

TL;DR

This study explores how interface engineering in ultra-thin chalcogenide PCM devices can significantly alter thermal properties, leading to reduced reset currents and improved energy efficiency in memory applications.

Contribution

It introduces a novel approach to control thermal transport in PCM devices by manipulating interfacial thermal resistance without extra insulating layers.

Findings

Thermal boundary resistance varies with GST phase and tungsten contact thickness.

Interfacial resistance reduction can lower reset current by up to 50%.

Effective thermal conductivity can be decreased by a factor of four.

Abstract

Phase change memory (PCM) is a rapidly growing technology that not only offers advancements in storage-class memories but also enables in-memory data storage and processing towards overcoming the von Neumann bottleneck. In PCMs, the primary mechanism for data storage is thermal excitation. However, there is a limited body of research regarding the thermal properties of PCMs at length scales close to the memory cell dimension and, thus, the impact of interfaces on PCM operation is unknown. Our work presents a new paradigm to manage thermal transport in memory cells by manipulating the interfacial thermal resistance between the phase change unit and the electrodes without incorporating additional insulating layers. Experimental measurements show a substantial change in thermal boundary resistance as GST transitions from one crystallographic structure (cubic) to another (hexagonal) and as the thickness of tungsten contacts is reduced from five to two nanometers. Simulations reveal that interfacial resistance between the phase change unit and its adjacent layer can reduce the reset current for 20 and 120 nm diameter devices by up to ~40% and ~50%, respectively. The resultant phase-dependent and geometric effects on thermal boundary resistance dictate that the effective thermal conductivity of the phase change unit can be reduced by a factor of four, presenting a new opportunity to reduce operating currents in PCMs.