Improved leakage current properties of ZrO2/(Ta/Nb)Ox-Al2O3/ZrO2 nanolaminate insulating stacks for dynamic random access memory capacitors

Takashi Onaya, Toshihide Nabatame, Tomomi Sawada, Kazunori Kurishima, Naomi Sawamoto, Akihiko Ohi, Toyohiro Chikyow, Atsushi Ogura

Research output: Contribution to journalArticlepeer-review

9 Citations (Scopus)


The influence of amorphous high-k interlayers, such as Al2O3, (Ta/Nb)Ox (TN), and (Ta/Nb)Ox-Al2O3 (TNA), on the leakage current (J) and dielectric constant (k) for metal-insulator-metal capacitors with ZrO2/high-k/ZrO2 nanolaminate insulating films and TiN electrodes was investigated. The insulating films were prepared by atomic layer deposition followed by post-deposition annealing at 600 °C. The capacitance equivalent thickness (CET) of the capacitors increased in the order ZrO2/(Ta/Nb)Ox/ZrO2 (ZTNZ) < ZrO2/(Ta/Nb)Ox-Al2O3/ZrO2 (ZTNAZ) < ZrO2/Al2O3/ZrO2 (ZAZ), owing to the k values for Al2O3 (~6), TNA (~9), and TN (~11). The J values at 0.6 V for capacitors with a CET of 1.1 nm increased in the order ZTNAZ < ZAZ ZTNZ. The effect of a high-k interlayer on the J characteristics appeared above a thickness of 0.4 nm in the case of Al2O3 and TNA, while a 0.8-nm-thick TN maintained high J values. Based on these results, there are three important factors as a high-k interlayer to reduce J value, such as a band gap larger than that for TN (4.4 eV), a thickness of ≥0.4 nm, and an amorphous structure. Therefore, to achieve the low J and CET, TNA is a promising candidate material for a high-k interlayer for future dynamic random access memory.

Original languageEnglish
Pages (from-to)48-53
Number of pages6
JournalThin Solid Films
Publication statusPublished - 2018 Jun 1


  • (Ta/Nb)O
  • AlO
  • Atomic layer deposition (ALD)
  • Dynamic random access memory (DRAM)
  • High-k material
  • Metal-insulator-metal capacitor
  • ZrO

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films
  • Metals and Alloys
  • Materials Chemistry

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