Effects of plasma prenitridation and postdeposition annealing on the structural and dielectric characteristics of the Ta2O5/Si system

Yi Sheng Lai, Kuan Jen Chen, Jen S. Chen

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6 Citations (Scopus)

Abstract

Material and dielectric properties of Ta2O5 layers grown on bare Si, as well as N2O and NH3 plasma nitrided Si substrates, before and after postdeposition annealing in oxygen, were investigated. X-ray photoelectron spectroscopy reveals that NH3 and N2O plasma nitridation on Si at 450°C formed a nitrogen-rich and an oxygen-rich SiOxNy layer, respectively. Capacitance-voltage (C-V) measurements show that Ta2O5 layers deposited on the prenitrided Si exhibit a higher relative dielectric constant and contain a lower density of charge trapping sites (Nh), as compared to the one on bare Si. In contrast, the interface state density (Dit) near the midgap is ∼1013 cm-2 eV-1 for non-nitrided and NH3 nitrided samples, but it is ∼1012 cm-2 eV-1 for the N2O nitrided sample. Postdeposition annealing at 650 or 800°C leads to an increment of Nh, except to a lesser extent for the N2O nitrided sample, and reduces all Dit to ∼1012 cm-2 eV-1. Concurrently, crystallization of the Ta2O5 layer and depletion of nitrogen in the SiOxNy interlayer formed by NH3 plasma nitridation are observed after annealing at 800°C. As for current-voltage (I-V) characteristics, all as-deposited samples exhibit large leakage currents, regardless of the prenitridation process. Postdeposition annealing will significantly lower the leakage currents, and the annealed Ta2O5 deposited on N2O nitrided Si exhibits better I-V character than the others at high electric field. Effects of various prenitridation and postannealing processes on the structural and electrical characteristics of Ta2O5/Si systems are discussed.

Original languageEnglish
Pages (from-to)F63-F68
JournalJournal of the Electrochemical Society
Volume149
Issue number7
DOIs
Publication statusPublished - 2002 Jul 1

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Renewable Energy, Sustainability and the Environment
  • Surfaces, Coatings and Films
  • Electrochemistry
  • Materials Chemistry

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