Chemical-Vapor-Deposited Graphene as Charge Storage Layer in Flash Memory Device

W J Liu,S J Ding,H L Lu,P Zhou,Q Q Sun,L Chen,David W Zhang

doi:10.1155/2016/6751497

Abstract

We demonstrated a flash memory device with chemical-vapor-deposited graphene as a charge trapping layer. It was found that the average RMS roughness of block oxide on graphene storage layer can be significantly reduced from 5.9 nm to 0.5 nm by inserting a seed metal layer, which was verified by AFM measurements. The memory window is 5.6 V for a dual sweep of ±12 V at room temperature. Moreover, a reduced hysteresis at the low temperature was observed, indicative of water molecules or −OH groups between graphene and dielectric playing an important role in memory windows.

Highlights

Flash memory has been highly demanded for mobile phone, digital camera, communication system, and data storage owing to its small size, high density, and low power
Graphene oxide (GO) was incorporated into TANOS as a trapping layer, while it suffers the reliability issues since the charge storage capability will significantly degrade at high temperatures [23]
In contrast to graphene flash memory cell, only a small hysteresis of ∼40 mV at the dual sweep of ±12 V remains for the control cell at room temperature; see Figure 4(b)

Summary

Introduction

Flash memory has been highly demanded for mobile phone, digital camera, communication system, and data storage owing to its small size, high density, and low power. The charge storage capability in floating gates will degrade because of reduced density of state of poly-Si under such continuous scaling along the thickness direction [4]. There are additional advantages for multilayer graphene as a floating gate, for example, (1) being compatible with conventional planar CMOS process line; (2) suppression of the ballistic current along the thickness direction because of reduced conductivity between layers; (3) large DOS; and (4) high work function which can increase the capability for storage and long-term data retention [5, 15]. Graphene oxide (GO) was incorporated into TANOS as a trapping layer, while it suffers the reliability issues since the charge storage capability will significantly degrade at high temperatures [23]. We observed a reduced hysteresis at low temperature, indicative of −OH or water molecules between graphene and dielectric playing an important role in memory windows

Experimental Details

Results and Discussion

Conclusion