Impact of Random Variations on Cell Stability and Write-Ability of Low-Voltage SRAMs Using Monolayer and Bilayer Transition Metal Dichalcogenide (TMD) MOSFETs

Chang Hung Yu, Pin Su*, Ching Te Chuang

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

This letter evaluates and analyzes the impacts of random variations on cell stability and write-ability of low-voltage SRAMs using monolayer and bilayer transition metal dichalcogenide (TMD) devices based on ITRS 2028 (5.9 nm) node with the aid of atomistic TCAD mixed-mode simulations. Our study indicates that, for 6T SRAM, the monolayer/bilayer TMD devices may fail to provide the 6σ yield requirement for read static noise margin (RSNM) due to severe metal-gate work function variation in spite of their excellent electrostatics, and hence circuit techniques, such as bootstrapped dynamic power rails or the standard 8T cell, are needed. Besides, RSD as a major concern of TMDs should be less of an issue for near-/sub-threshold SRAMs for ultra low-power applications. For the standard 8T cell structure, the RSNMs of both monolayer and bilayer 8T SRAMs improve significantly, and the bilayer 8T SRAM exhibits better write static noise margin (WSNM). In addition, write-assist techniques (including negative bit-line, boosted word-line, and lower cell supply) for improving WSNM are examined and shown to be more effective for monolayer 8T SRAMs than the bilayer counterparts.

Original languageEnglish
Article number7466773
Pages (from-to)928-931
Number of pages4
JournalIEEE Electron Device Letters
Volume37
Issue number7
DOIs
StatePublished - 1 Jul 2016

Keywords

  • SRAM
  • Variations
  • bilayer
  • cell stability
  • monolayer
  • transition metal dichalcogenide (TMD)
  • write-ability

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