Technology of ferroelectric thin-film formation with large coercive field on amorphous SiO2 by ion-bombardment-assisted sputtering and oxygen radical treatment for future scaling down of ferroelectric gate field-effect transistor memory device

Ichirou Takahashi, Masaki Hirayama, Shigetoshi Sugawa, Tadahiro Ohmi

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

Sr2(Ta1-x,Nbx)2O7 (perovskite STN; x = 0.3) is one of the most practical candidates for one-transistor-type ferroelectric memory devices, because it has a low dielectric constant. However, in the application to metal-ferroelectric- insulator-Si field-effect transistor (MFIS-FET) memory devices, the fabrication of STN on an amorphous insulator, such as SiO2, is difficult. In particular, in the case of STN, because its crystallization annealing temperature is 950°C, the metal elements of STN and Si react with each other during crystallization annealing. As a result, perovskite STN cannot be fabricated. To overcome this problem, we have developed an ion-bombardment- assisted sputtering method. Furthermore, to obtain universal conditions for forming perovskite STN based on plasma physics, plasma parameters such as ion bombardment energy and ion flux, were measured. Perovskite STN was obtained when the ion bombardment energy was 38 eV and the normalized Kr ion flux was 78 [ions/atom.]. An IrO2/STN (140nm)/STN seed layer (10nm)/Si device whose STN was fabricated under these plasma conditions, shows square hysteresis curves and a memory window of 1.7 V under an 8 V writing operation. This value corresponds to a coercive field ot 55 kV/cm.

Original languageEnglish
Pages (from-to)2205-2210
Number of pages6
JournalJapanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers
Volume46
Issue number4 B
DOIs
Publication statusPublished - 2007 Apr 24

Keywords

  • Developing materials with improved coercive fields
  • Ferroelectric crystallization on amorphous insulator
  • Ion-bombardment-assisted sputtering
  • Sr(Ta,Nb)O (STN)

ASJC Scopus subject areas

  • Engineering(all)
  • Physics and Astronomy(all)

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