Origin of Fermi level pinning in high-k gate stack structures studied by operando hard x-ray photoelectron spectroscopy

Yoshiyuki Yamashita, Toyohiro Chikyow

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)

Abstract

To clarify the Fermi level pinning observed in Hf based gate structures, we employed two types of Hf based gate structures and investigated their bias-dependent potential distribution in the structures using operando hard x-ray photoelectron spectroscopy. In the case of the Pt/HfSiO2/SiO2/p-Si(100) structure, the Si substrate and SiO2 peaks in Si 1 s were shifted when a bias voltage was applied to the structure, indicating that Si substrate was mostly biased. Thus the Pt/HfSiO2/SiO2/p-Si(100) structure had an ideal metal oxide semiconductor structure. On the other hand, applying a bias voltage in the case of the Pt/HfO2/SiO2/p-Si(100) structure shifted HfO2 in Hf 3d, SiO2, and the substrate in Si 1 s, suggesting that a potential drop occurred at the Pt/HfO2 interface. Thus the Fermi level pinning was occurred at the Pt/HfO2 interface. In order to clarify the Fermi level pinning, angle-resolve O1 s photoelectron spectroscopy (PES) was performed at the Pt/HfO2 interface. Analysis of the O1 s PES revealed the formation of a SiO2 layer at the Pt/HfO2 interface, which could be the origin of the Fermi level pinning observed in Hf based gate structures.

Original languageEnglish
Article number146890
JournalJournal of Electron Spectroscopy and Related Phenomena
Volume238
DOIs
Publication statusPublished - 2020 Jan
Externally publishedYes

Keywords

  • Fermi level pinning
  • Hard x-ray photoelectron spectroscopy
  • High-k
  • Operando

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Radiation
  • Atomic and Molecular Physics, and Optics
  • Condensed Matter Physics
  • Spectroscopy
  • Physical and Theoretical Chemistry

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