EOT of 0.62 nm and high electron mobility in La-silicate/Si structure based nMOSFETs achieved by utilizing metal-inserted poly-si stacks and annealing at high temperature

Takamasa Kawanago, Yeonghun Lee, Kuniyuki Kakushima, Parhat Ahmet, Kazuo Tsutsui, Akira Nishiyama, Nobuyuki Sugii, Kenji Natori, Takeo Hattori, Hiroshi Iwai

Research output: Contribution to journalArticlepeer-review

38 Citations (Scopus)

Abstract

This paper reports on the control of the direct-contact La-silicate/Si interface structure with the aim of achieving scaled equivalent oxide thickness (EOT) and small interface state density. The interface state density at the direct-contact La-silicate/Si interface is found to be reduced to 1.6 \times \hbox{10}^{11}\ \hbox{cm}^{-2}\hbox{eV} -1 by annealing at 800 ^̂{C} for 30 min in forming gas ambient, whereas excess silicate reaction concurrently induced a significant increase in EOT. By utilizing metal-inserted poly-Si (MIPS) stacks and their annealing at high temperature, the increase in EOT is drastically suppressed. At the same time, a superior interfacial property is obtained because the Si layer in the MIPS stacks prevents the excess oxygen diffusion from the atmosphere during the annealing process. As a result, the effective electron mobility of 155 cm^{2}/\hbox{V}\cdot{s} at 1 MV/cm and an EOT of 0.62 nm are successfully achieved by utilizing direct-contact La-silicate/Si structure. This result is comparable with the recorded effective electron mobility achieved by utilizing Hf-based oxides/Si structure. This demonstrates the advantage of our proposed method to realize the scaled EOT with a superior interfacial property for state-of-the-art metal-oxide-semiconductor field-effect transistors.

Original languageEnglish
Article number6093743
Pages (from-to)269-276
Number of pages8
JournalIEEE Transactions on Electron Devices
Volume59
Issue number2
DOIs
Publication statusPublished - 2012 Feb
Externally publishedYes

Keywords

  • Direct-contact high-k/Si structure
  • effective mobility
  • equivalent oxide thickness (EOT)
  • high- k gate dielectrics
  • interface state density
  • rare earth oxides
  • silicate

ASJC Scopus subject areas

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

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