Intermediate Oxide Formation in Double-Polysilicon Gate MOS Structure

Hideo Sunami, Mitsumasa Koyanagi, Norikazu Hashimoto

Research output: Contribution to journalArticlepeer-review

22 Citations (Scopus)


An intermediate insulator formation technique is realized using the concentration-dependent oxidation (CDO) of the phosphorus-doped first polysilicon gate. Utilizing the CDO effect, that is, heavily doped Si is oxidized faster than lightly doped Si, a thick intermediate oxide is formed to cover the first gate with its own oxide and a substrate surface to form the second gate oxide with simultaneous wet oxidation at 700°-900°C. Electrical properties of the intermediate insulator are discussed in terms of the formation conditions and topographical structures of the overlapped region. It is found that oxidation temperatures of around 900°C and moderate oxide thicknesses produce superior electrical properties and preferable geometries. In response to these requirements a dry-wet-dry oxidation (D-W-D) technique is successfully developed. A 5-17-5 min D-W-D oxidation at 900°C causes a 50 nm oxide to be formed on single crystal (100) silicon and a 210 nm oxide on the phosphorusdoped polysilicon. The autodoping effect of phosphorus atoms incorporated in the polysilicon gate is also discussed. It gives rise to harmful threshold voltage lowerings for the second gate n-channel transistors.

Original languageEnglish
Pages (from-to)2499-2506
Number of pages8
JournalJournal of the Electrochemical Society
Issue number11
Publication statusPublished - 1980 Nov


  • autodoping effect
  • concentration-dependent oxidation
  • dielectric breakdown
  • double polysilicon

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Renewable Energy, Sustainability and the Environment
  • Surfaces, Coatings and Films
  • Electrochemistry
  • Materials Chemistry


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