Reduction of Slow Trap Density in Al2O3/GeOxNy/n-Ge MOS Interfaces by PPN-PPO Process

Mengnan Ke, Mitsuru Takenaka, Shinichi Takagi

Research output: Contribution to journalArticle


The realization of high-k/IL/GeMOS interfaces with thin equivalent oxide thickness (EOT), low interface state density (Dit), and high reliability is strongly needed for realizing Ge metal-oxide-semiconductor field-effect transistors (MOSFETs). In this article, we examine the properties of the slow trap areal density (Nst) and Dit in Al2O3/GeOxNy/n-Ge MOS interfaces formed by atomic layer deposition (ALD) Al2O3 films with plasma post nitridation (PPN) and plasma post oxidation (PPO). Here, the process order and process time of PPN and PPO are systematically changed to optimize the Al2O3/GeOxNy/n-Ge MOS interface properties. It is found that N atoms induced into GeOx can suppress slow electron trapping. An Al2O3/n-Ge structure with 1-min PPN before PPO can reduce Nst by 34% in a weak electric field, whereas PPN after PPO increase Nst. Also, the sufficient time PPO process after PPN can decrease Dit to a similar level as that at the Al2O3/GeOx/n-Ge MOS interfaces. The temperature dependence of electron trapping properties is also experimentally evaluated. The slow electron trapping is expected to be more suppressed for the GeOxNy interfaces at real device operation temperature.

Original languageEnglish
Article number8891713
Pages (from-to)5060-5064
Number of pages5
JournalIEEE Transactions on Electron Devices
Issue number12
Publication statusPublished - Dec 2019



  • Ge
  • MOS interfaces
  • plasma nitridation
  • reliability
  • slow trap density

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