Lowering the effective work function via oxygen vacancy formation on the GeO2/Ge interface

Tae In Lee, Yujin Seo, Jungmin Moon, Hyun Jun Ahn, Hyun-Yong Yu, Wan Sik Hwang, Byung Jin Cho

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

The use of a GeO2 interfacial layer (IL) between a high-k dielectric and a Ge substrate helps to reduce the interface state density in Ge MOS devices. We report that the presence of the GeO2 IL changes the effective work function (eWF) of the gate stack when annealed after high-k dielectric deposition. The eWF is reduced from 4.31 eV to 3.98 eV for TaN and from 5.00 eV to 4.44 eV for Ni. Consequently, the threshold voltage (Vth) decreases from 0.69 V to 0.21 V for Ni after post deposition annealing. Our investigation confirms that the generation of oxygen vacancies in the GeO2 IL near the Ge substrate is the main cause of the eWF modulation. In addition, the reliability of the GeO2 IL is investigated via the conductance method and a constant-current stress test.

Original languageEnglish
Pages (from-to)57-62
Number of pages6
JournalSolid-State Electronics
Volume130
DOIs
Publication statusPublished - 2017 Apr 1

Keywords

  • Effective work function
  • GeO
  • Germanium
  • MOSFET
  • Oxygen vacancy
  • Threshold voltage

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Materials Chemistry
  • Electrical and Electronic Engineering

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