Influence of oxygen transfer in Hf-based high-k dielectrics on flatband voltage shift

Toshihide Nabatame, Masayuki Kimura, Hiroyuki Yamada, Akihiko Ohi, Tomoji Ohishi, Toyohiro Chikyow

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

We investigated flatband voltage (Vfb) behavior for several Hf-based high-k dielectrics, including HfO 2, Mg-, and La-incorporated HfO 2, HfSiO x, and Mg-, La-, and N-incorporated HfSiO x, during the reduction (forming gas annealing: FGA) and oxidation annealing (ODA) processes. A negative Vfb shift appeared in all high-k dielectrics as the FGA temperature increased. In contrast, a positive Vfb shift was observed after the introduction of additional oxygen into the high-k layer during ODA. The oxygen diffusion coefficient (D) values of all samples were estimated using Fick's law. The results showed that the D value of the HfO 2 dielectric was five times as large as that of the HfSiO x dielectric in ODA at 400°C. Furthermore, the Mg-, La-, and N- incorporated high-k dielectrics exhibited a larger D value compared with the pure high-k dielectrics. These results strongly suggest that the ionicity of high-k dielectrics, which we attribute to a large positive Vfb shift, enhances oxygen diffusion in the high-k layer.

Original languageEnglish
Pages (from-to)3387-3391
Number of pages5
JournalThin Solid Films
Volume520
Issue number8
DOIs
Publication statusPublished - 2012 Feb 1

Keywords

  • Flatband voltage shift
  • Gate stack structure
  • Hf-based high-k
  • Ionicity
  • Oxygen diffusion

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films
  • Metals and Alloys
  • Materials Chemistry

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