Stress-induced positive charge in Hf-based gate dielectrics: Impact on device performance and a framework for the defect

Ce Z. Zhao, Jian F. Zhang, Mo Huai Chang, A. R. Peaker, Stephen Hall, Guido Groeseneken, Luigi Pantisano, Stefan De Gendt, Marc Heyns

    Research output: Contribution to journalArticlepeer-review


    A Hf-based dielectric has been selected to replace SiON for CMOS technologies. When compared with SiON, Hf dielectrics can suffer from higher instability. Previous attentions were focused on electron trapping, and positive charging received less attention. The objective of this paper is to study the impact of positive charging on device performance and to provide a framework for the defect. Three components of threshold voltage instability Δ Vth are unambiguously identified for pMOSFETs, i.e., loop, loop-shift, and up-loop. The loop dominates Δ Vth at a relatively short time (<1 s). After stressing for a longer time, the whole loop is shifted in the negative direction. Unlike the loop, the up-loop cannot readily be recharged after recovery. In addition to the generated interface states, three different types of positive charges are formed in the Hf-based stacks, i.e., cyclic positive charges (CPC), antineutralization positive charges (ANPC), and as-grown hole trapping (AHT). Each type of defect has its unique signatures and properties. CPC can repeatedly be charged and discharged by alternating the gate bias polarity. ANPC is more difficult to neutralize, whereas AHT is harder to charge. Both the generated interface states and the AHT saturate at longer stress time, but ANPC does not. ANPC reduces at higher measurement temperature, but CPC is insensitive to temperature. The relation between each type of defect and each component of Δ Vth is clarified. © 2008 IEEE.
    Original languageEnglish
    Pages (from-to)1647-1656
    Number of pages9
    JournalIEEE Transactions on Electron Devices
    Issue number7
    Publication statusPublished - Jul 2008


    • Degradation
    • Gate stacks
    • HfO2 hf-silicates
    • Negative bias temperature instability (NBTI)
    • Positive charges
    • Traps


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