Multiple-bit-upset and single-bit-upset resilient 8T SRAM bitcell layout with divided wordline structure

S. Yoshimoto, T. Amashita, D. Kozuwa, T. Takata, M. Yoshimura, Y. Matsunaga, H. Yasuura, H. Kawaguchi, M. Yoshimoto

Research output: Chapter in Book/Report/Conference proceedingConference contribution

10 Citations (Scopus)

Abstract

This paper presents a new 8T (8-transistor) SRAM cell layout mitigating multiple-bit upset (MBU) in a divided wordline structure. Because bitlines along unselected columns are not activated, the divided wordline structure eliminates a half-select problem and achieves low-power operation, which is often preferred for low-power / low-voltage applications. However, the conventional 8T SRAM with the divided wordline structure engenders MBUs because all bits in the same word are physically adjoining. Consequently, error correction coding (ECC) techniques are difficult to apply. This paper presents a new 8T cell layout pattern that separates internal latches in SRAM cells using both an n-well and a p-substrate. We investigated an SEU cross section of nMOS that is 3.5-4.5 times higher than that of pMOS. Using an iRoC TFIT simulator, we confirmed that the proposed 8T cell has better neutron-induced MBU tolerance. The MBU in the proposed 8T SRAM is improved by 90.70% and the MBU soft error rate (SER) is decreased to 3.46 FIT at 0.9 V when ECC is implemented. Additionally, we conducted Synopsys 3-D TCAD simulation, which indicates that the LET threshold (LETth) in single-event upset (SEU) is also improved by 66.47% in the proposed 8T SRAM by a common-mode effect.

Original languageEnglish
Title of host publicationProceedings of the 2011 IEEE 17th International On-Line Testing Symposium, IOLTS 2011
Pages151-156
Number of pages6
DOIs
Publication statusPublished - 2011
Event2011 IEEE 17th International On-Line Testing Symposium, IOLTS 2011 - Athens, Greece
Duration: Jul 13 2011Jul 15 2011

Publication series

NameProceedings of the 2011 IEEE 17th International On-Line Testing Symposium, IOLTS 2011

Other

Other2011 IEEE 17th International On-Line Testing Symposium, IOLTS 2011
CountryGreece
CityAthens
Period7/13/117/15/11

All Science Journal Classification (ASJC) codes

  • Electrical and Electronic Engineering

Fingerprint Dive into the research topics of 'Multiple-bit-upset and single-bit-upset resilient 8T SRAM bitcell layout with divided wordline structure'. Together they form a unique fingerprint.

Cite this