Grain-orientation induced work function variation in nanoscale metal-gate transistors - Part I: Modeling, analysis, and experimental validation

Hamed F. Dadgour, Kazuhiko Endo, Vivek K. De, Kaustav Banerjee

Research output: Contribution to journalArticlepeer-review

132 Citations (Scopus)

Abstract

This paper highlights and experimentally verifies a new source of random threshold-voltage (Vth) fluctuation in emerging metal-gate transistors and proposes a statistical framework to investigate its device and circuit-level implications. The new source of variability, christened work-function (WF) variation (WFV), is caused by the dependence of metal WF on the orientation of its grains. The experimentally measured data reported in this paper confirm the existence of such variations in both planar and nonplanar high-k metal-gate transistors. As a result of WFV, the WFs of metal gates are statistical distributions instead of deterministic values. In this paper, the key parameters of such WF distributions are analytically modeled by identifying the physical dimensions of the devices and properties of materials used in the fabrication. It is shown that WFV can be modeled by a multinomial distribution where the key parameters of its probability distribution function can be calculated in terms of the aforementioned parameters. The analysis reveals that WFV will contribute a key source of Vth variability in emerging generations of metal-gate devices. Using the proposed framework, one can investigate the implications of WFV for process, device, and circuit design, which are discussed in Part II.

Original languageEnglish
Article number5575410
Pages (from-to)2504-2514
Number of pages11
JournalIEEE Transactions on Electron Devices
Volume57
Issue number10
DOIs
Publication statusPublished - 2010 Oct
Externally publishedYes

Keywords

  • Grain orientation
  • VLSI design
  • metal-gate devices
  • random variations
  • reliability
  • subthreshold leakage
  • threshold voltage
  • work-function (WF) variation (WFV)

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Electrical and Electronic Engineering

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