Radiation Tolerance and Charge Trapping Enhancement of ALD HfO2/Al2O3 Nanolaminated Dielectrics.

Dencho Spassov,Todor Stanchev,Elżbieta Guziewicz,Srboljub Stanković,Albena Paskaleva,Ninoslav Stojadinović,Vojkan Davidović,Tzvetan Ivanov,Snežana Djorić-Veljković

doi:10.3390/ma14040849

Abstract

High-k dielectric stacks are regarded as a promising information storage media in the Charge Trapping Non-Volatile Memories, which are the most viable alternative to the standard floating gate memory technology. The implementation of high-k materials in real devices requires (among the other investigations) estimation of their radiation hardness. Here we report the effect of gamma radiation (60Co source, doses of 10 and 10 kGy) on dielectric properties, memory windows, leakage currents and retention characteristics of nanolaminated HfO2/Al2O3 stacks obtained by atomic layer deposition and its relationship with post-deposition annealing in oxygen and nitrogen ambient. The results reveal that depending on the dose, either increase or reduction of all kinds of electrically active defects (i.e., initial oxide charge, fast and slow interface states) can be observed. Radiation generates oxide charges with a different sign in O2 and N2 annealed stacks. The results clearly demonstrate a substantial increase in memory windows of the as-grown and oxygen treated stacks resulting from enhancement of the electron trapping. The leakage currents and the retention times of O2 annealed stacks are not deteriorated by irradiation, hence these stacks have high radiation tolerance.

Highlights

The charge trapping in thin dielectric films has been intensively investigated recently in order to employ this phenomenon in the non-volatile memories as a replacement of the existing floating gate technology [1,2,3,4,5,6,7]
We demonstrated the excellent application capability of Al2 O3 /HfO2 stacks obtained by atomic layer deposition technique (ALD) as charge trapping media in CTMbased non-volatile memory devices
Nanolaminated Al2 O3 /HfO2 stacks were deposited on p-type (100) Si wafers with resistivity of 6 Ω cm by atomic layer deposition (ALD)

Summary

Introduction

The charge trapping in thin dielectric films has been intensively investigated recently in order to employ this phenomenon in the non-volatile memories as a replacement of the existing floating gate technology [1,2,3,4,5,6,7]. The charge trapping memory (CTM) design has a lot in common with the floating gate design. The introduction of high-k dielectrics in microelectronic technology boosted CTM development as these dielectrics have been proven to possess large densities of traps whose parameters could be tailored by the fabrication processes and consequent treatments. The trap densities available in HfO2 are adequate for CTM applications [8] but its potential for charge storage media can be further enhanced by its doping/mixing with other metals/oxides. It has been reported that by doping HfO2 with Al very promising charge trapping layers can be obtained, the reasons for the substantial improvements in charge trapping parameters are not clear yet [9,10,11]

Methods

Results

Conclusion