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Offering Aging Mitigation Technique for SRAM based on Chip Memories

Karimi, Maryam | 2016

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 48990 (19)
  4. University: Sharif University of Technology
  5. Department: Computer Engineering
  6. Advisor(s): Miremadi, Ghassem
  7. Abstract:
  8. Bias Temperature Instability (BTI) is known as one serious reliability concern in nanoscale technology sizes. BTI gradually degrades threshold voltage (Vth) of MOS transistors. The main consequence of Vth degradation in SRAM cell transistors is the Static Noise Margin (SNM) degradation that makes SRAM cells susceptible against soft errors. SNM degradation in SRAM cells results in bit-flip occurrences and should be monitored accurately before resulting in permanent failures. This work proposes a sensor called Current-based BTI Sensor (CBS) to assess the aging state of SRAM cells. CBS measures BTI-induced SNM degradation of SRAM cells by monitoring the write current shifts due to BTI. The observations show that the current consumption shifts during write operation is proportional to the threshold voltage shifts of the SRAM cell transistors and is an effective identifier to measure Vth and SNM degradation of the SRAM cells. The granularity of BTI assessment of one cell up to a row of memory can be achieved by writing special bit patterns on the memory block during the test phase. We evaluated the circuit-level design of sensor through SPICE-level simulations in 32nm technology. The precision of the proposed BTI sensor is about ±0.75mV (±2% error). One sensor is enough for the entire SRAM memory block with negligible area/power overhead; less than 1%. The effects of process variation and temperature shifts on CBS are investigated in detail
  9. Keywords:
  10. Reliability ; Sensors ; Reliability ; Static Random Access Memory (SRAM)Cell ; Static Nois Margin (SNM) ; Bias Temperature Instability (BTI)

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