Phase Change Memory Cell With Reconfigured Electrode for Lower RESET Voltage

Shaolin Zhou,Kezhou Li,Honglin Zhang,Mansun Chan,Yihan Chen,Shaowei Liao

doi:10.1109/jeds.2019.2948254

Abstract

To reduce the reset voltage and thus leakage current of the cross-point architecture of phase change memory (PCM), a type of 1S1R cell hierarchy with reconfigured electrode capping around the phase change material is explored in this paper. The electro-thermal behavior during the RESET phase transition is mimicked using a finite element model. Results indicate that the temperature distribution, potential drop and current density across the active region can be reshaped. Especially, the process of temperature evolution for phase transition is accelerated and thus the PCM cell can be reset under a lower voltage, e.g., from 2.2 V to 1.2 V for our typical configuration with a GST width of 40 nm and heater width of 20 nm . As a result, the lower RESET voltage decreases the leakage current and power consumption, potentially leading to an increased integration level for cross-point PCM.

Highlights

Phase change memory (PCM) is currently one of the most promising candidates for the generation of nonvolatile memories, due to its advantages of fast data shuttling, good scalability, long endurance etc. [1]–[3]
Different from the current control of MOSFETs or BJTs, the two-terminal selectors work in series with storage elements by voltage control [6], [7], enabling ample RESET current for the PCM cell
The V/2 or V/3 scheme for voltage control in the promising 1S1R architecture [8] suffers from inherent leakage current, which becomes a key challenge for the large-scale integration of PCM, and in return, puts stringent requirements on the nonlinear behavior of the selector

Summary

INTRODUCTION

Phase change memory (PCM) is currently one of the most promising candidates for the generation of nonvolatile memories, due to its advantages of fast data shuttling, good scalability, long endurance etc. [1]–[3]. The capping electrode in the PCM cell architecture is reconfigured for a lower RESET voltage, which potentially reduces the current leakage and eases the burden on selectors. The reconfigured metal electrode is used to directly wrap around the storage element of the phase change material to lower the operation voltage with further condensed potential distribution and current density. Results validate that the wrapping electrode architecture potentially accelerates the thermal evolution with higher temperatures across the active region compared to those by the ordinary planar electrode, leading to lower RESET voltage and reduced leakage current, as well as the increased integration density for the cross-point PCM architecture

SCHEME AND ANALYSIS MODEL

DISCUSSIONS ON THERMAL CONDUCTION

CONCLUSION