Characterization of flatband voltage roll-off and roll-up behavior in La2O3/silicate gate dielectric

K. Kakushima*, T. Koyanagi, K. Tachi, J. Song, P. Ahmet, K. Tsutsui, N. Sugii, T. Hattori, H. Iwai

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

20 Scopus citations

Abstract

The roll-off and roll-up behavior of flatband voltage (Vfb) on equivalent oxide thickness (EOT) of La2O3/silicate capacitors have been characterized by X-ray photoelectron spectroscopy and modeled by the fixed charges. It has been revealed that the thickness of the reactively formed silicate layer is dependent on the La2O3 thickness initially deposited on the wafer. When the La2O 3 thickness is over 3 nm, the silicate layer has been found to be formed with a constant thickness of 1.6 nm. However, while decreasing the La2O3 thickness to 1 nm, the thickness of silicate layer decreases due to the reduction of radical oxygen atoms originated from the La2O3 layer, resulting in the formation of La-rich silicate. The Vfb roll-off behavior can be attributed to the enhanced generation of positive fixed charges induced by the diffusion of metal atoms from the gate electrode into the silicate layer. On the other hand, the V fb roll-up behavior can be explained when the initially deposited La2O3 layer has been all converted into silicate.

Original languageEnglish
Pages (from-to)720-723
Number of pages4
JournalSolid-State Electronics
Volume54
Issue number7
DOIs
StatePublished - Jul 2010

Keywords

  • Hard X-ray photoelectron spectroscopy
  • High-k gate dielectric
  • Lanthanum oxide
  • Silicate

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