Thermal Stability of Neodymium Aluminates High-κDielectric Deposited by Liquid Injection MOCVD Using Single-Source Heterometallic Alkoxide Precursors

P Taechakumput,Susu Chen,C Z Zhao,P R Chalker,M Werner,J M Gaskell,S Taylor,H C Aspinall,A C Jones

doi:10.1155/2012/891079

Abstract

Thin films of neodymium aluminate (NdAlOx) have been deposited by liquid injection metalorganic chemical vapor deposition (MOCVD) using the bimetallic alkoxide precursor [NdAl(OPri)6(PriOH)]2. The effects of high-temperature postdeposition annealing on NdAlOxthin films are reported. The as-deposited thin films are amorphous in nature. X-ray diffraction (XRD) and medium energy ion scattering (MEIS) show, respectively, no crystallization or interdiffusion of metal ions into the substrate after annealing at 950°C. The capacitance-voltage (C-V) and current-voltage (I-V) characteristics of the thin films exhibited good electrical integrity following annealing. The dielectric permittivity (κ) of the annealed NdAlOxwas 12, and a density of interface states at flatband (Dit) of4.01×1011 cm−2 eV−1was measured. The deposited NdAlOxthin films are shown to be able to endure high-temperature stress and capable of maintaining excellent dielectric properties.

Highlights

IntroductionThe lanthanide aluminates are promising high-κ candidates as they combine the advantages of the high permittivity of the lanthanide oxide with the chemical and thermal stability of Al2O3
Considerable effort has been exerted in developing high-κ rare earth oxide, M2O3 (M = La, Pr, Nd, etc.), as a replacement of the conventional SiO2-based gate dielectric material [1]
Near stoichiometric NdAlOx thin films (Nd/Al = 0.87) were deposited on n-type silicon (100) substrates by liquid injection metalorganic chemical vapor deposition (MOCVD) at 450◦C on an Aixtron AIX 200FE AVD reactor fitted with the “TriJet”TM liquid injector system [12], utilizing the single-source precursor [NdAl(OPri)6(PriOH)]2

Summary

Introduction

The lanthanide aluminates are promising high-κ candidates as they combine the advantages of the high permittivity of the lanthanide oxide with the chemical and thermal stability of Al2O3. They remain amorphous up to high temperatures, leading to a large reduction in leakage current relative to polycrystalline M2O3 films during CMOS processing [5, 6]. Little is still known about the physical and electronic characteristics of NdAlOx due to a lack of suitable precursors with appropriate stability, volatility, and decomposition characteristics This has motivated us to further exploit these perovskite thin films. The effects of high-temperature postdeposition annealing (PDA) on the properties of the NdAlOx thin films, deposited by metalorganic chemical vapor deposition (MOCVD) using single-source precursor, were studied

Experimental

Results and Discussion

Conclusions