The effect of hydrogen on programmed threshold-voltage distribution in NAND flash memories

Yung Yueh Chiu, Cheng Han Lin, Jhih Siang Yang, Bo Jun Yang, Minoru Aoki, Toshiaki Takeshita, Masaru Yano, Riichiro Shirota*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


This paper, for the first time, presents a comprehensive study into the effect of hydrogen concentration in the forming gas on the reliability of NAND Flash memories. It is newly observed that a higher hydrogen concentration leads to broaden the threshold-voltage (V T) distribution after programming. This suggests that a higher hydrogen concentration makes a larger amount of ionized hydrogens (H+) exist in the shallow trench isolation (STI), which results in the fluctuation of the Fowler-Nordheim tunneling current during programming. It is also found that the V T distribution width difference between higher and lower hydrogen concentration turns out to be smaller after the program/erase cycling. This could be explained by the neutralization of H+ due to the capture of the tunneling electrons at the STI edge. On the other hand, the higher hydrogen concentration proves to be able to provide better retention characteristics. Thus, the programming and retention characteristics are the tradeoff relationship. Therefore, optimization of the hydrogen concentration is crucial for the NAND Flash process integration.

Original languageEnglish
Article number081002
JournalJapanese Journal of Applied Physics
Issue number8
StatePublished - 1 Aug 2019

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