ＳＲＡＭセルにおけるばらつきの影響とその抑制方法

• Project/Area Number: 15J09095
• Research Category: Grant-in-Aid for JSPS Fellows
• Allocation Type: Single-year Grants
• Section: 国内
• Research Field: Electron device/Electronic equipment
• Research Institution: The University of Tokyo
• Research Fellow: QIU HAO 東京大学, 生産技術研究所, 特別研究員(PD)
• Project Period (FY): 2015-04-24 – 2017-03-31
• Project Status: Completed (Fiscal Year 2016)
• Budget Amount: ¥2,300,000 (Direct Cost: ¥2,300,000); Fiscal Year 2016: ¥1,100,000 (Direct Cost: ¥1,100,000); Fiscal Year 2015: ¥1,200,000 (Direct Cost: ¥1,200,000)
• Keywords: SRAM / variability / write stability / low voltage / write butterfly curve / reliability

Outline of Annual Research Achievements

We have gained further understanding of two write stability methods (write butterfly curve and write N-curve).

Firstly, the reason why write noise margin (WNM) in write N-curve deviates from a normal distribution at low VDD is clarified. Two modes are found in WNM's distribution. And the new mode is ascribed to cell transistor's sub-Vth operation.

Secondly, a new write stability method based on write butterfly curve is proposed. By extending the voltage sweeping range of two internal nodes in SRAM, the extended write butterfly curve can be obtained. It is found that the extended WNM (E-WNM) follows a normal distribution even at low VDD. In addition, good correlation between E-WNM and WNM of bit-line method is obtained. Thus, the proposed one is a good candidate for low-VDD yield estimation.

Research Progress Status

28年度が最終年度であるため、記入しない。

Strategy for Future Research Activity

28年度が最終年度であるため、記入しない。

Research Products

• [Journal Article] Statistical Write Stability Characterization in SRAM Cells at Low Supply Voltage (2016)
  • Author(s): Hao Qiu, Tomoko Mizutani, Yoshiki Yamamoto, Hideki Makiyama, Tomohiro Yamashita, Hidekazu Oda, Shiro Kamohara, Nobuyuki Sugii, Takuya Saraya, Masaharu Kobayashi, Toshiro Hiramoto
  • Journal Title: IEEE Transactions on Electron Devices Volume: 63 Pages: 4302-4308
  • DOI: 10.1109/ted.2016.2612678
  • Peer Reviewed / Acknowledgement Compliant
• [Journal Article] Comparison and statistical analysis of four write stability metrics in bulk CMOS static random access memory cells (2015)
  • Author(s): Hao Qiu, Tomoko Mizutani, Takuya Saraya, Toshiro Hiramoto
  • Journal Title: Japanese Journal of Applied Physics Volume: 54 Issue: 4S Pages: 04DC09-04DC09
  • DOI: 10.7567/jjap.54.04dc09
  • NAID: 210000144966
  • ISSN: 0021-4922, 1347-4065
  • Peer Reviewed / Acknowledgement Compliant
• [Presentation] A New Write Stability Metric for Yield Estimation in SRAM Cells at Low Supply Voltage (2016)
  • Author(s): Hao Qiu, Kiyoshi Takeuchi, Tomoko Mizutani, Takuya Saraya, Masaharu Kobayashi, Toshiro Hiramoto
  • Organizer: JSAP Autumn Meeting
  • Place of Presentation: TOKI MESSE Niigata Convention Center, Niigata
  • Year and Date: 2016-09-13
• [Presentation] A New Write Stability Metric Using Extended Write Butterfly Curve for Yield Estimation in SRAM Cells at Low Supply Voltage (2016)
  • Author(s): Hao Qiu, Kiyoshi Takeuchi, Tomoko Mizutani, Takuya Saraya, Masaharu Kobayashi, Toshiro Hiramoto
  • Organizer: IEEE International Conference on Microelectronic Test Structures (ICMTS)
  • Place of Presentation: Mielparque Yokohama, Yokohama
  • Year and Date: 2016-03-28
  • Int'l Joint Research
• [Presentation] Impact of Random Telegraph Noise (RTN) on Write Stability in Silicon-on-thin-BOX (SOTB) SRAM Cells in Sub-0.4V Regime (2015)
  • Author(s): Hao Qiu, Tomoko Mizutani, Yoshiki Yamamoto, Hideki Makiyama, Tomohiro Yamashita, Hidekazu Oda, Shiro Kamohara, Nobuyuki Sugii, Takuya Saraya, Masaharu Kobayashi, Toshiro Hiramoto
  • Organizer: JSAP Autumn Meeting
  • Place of Presentation: Nagoya Congress Center, Nagoya
  • Year and Date: 2015-09-13
• [Presentation] Impact of Random Telegraph Noise on Write Stability in Silicon-on-Thin-BOX (SOTB) SRAM Cells at Low Supply Voltage in Sub-0.4V Regime (2015)
  • Author(s): Hao Qiu, Tomoko Mizutani, Yoshiki Yamamoto, Hideki Makiyama, Tomohiro Yamashita, Hidekazu Oda, Shiro Kamohara, Nobuyuki Sugii, Takuya Saraya, Masaharu Kobayashi, Toshiro Hiramoto
  • Organizer: IEEE Symposium on VLSI Technology
  • Place of Presentation: Rihga Royal Hotel Kyoto, Kyoto
  • Year and Date: 2015-06-16
  • Int'l Joint Research