Comparison of differential and large-signal sensing scheme for subthreshold/superthreshold FinFET SRAM considering variability

Ming Long Fan*, Vita Pi Ho Hu, Yin Nien Chen, Pin Su, Ching Te Chuang

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

2 Scopus citations

Abstract

This paper investigates the viability and compares the merits of small-signal differential sensing and large-signal single-ended sensing scheme for FinFET SRAM under fin Line-Edge-Roughness (fin LER) and Work-Function- Variation (WFV). The local random variation of selected cell, leakage (and its variation) from unselected cells on the selected Bit-Line (BL), and variation of sense amplifier offset voltage (for differential sensing) and trip voltage (for large-signal sensing) are considered simultaneously at subthreshold (V dd=0.4V) and superthreshold (V dd=1.0V) regions. For differential sensing, the subthreshold sensing margin is severely degraded by the variation in Bitline voltage and sufficient time before enabling the sense amplifier is required to improve the limited margin. For large-signal sensing scheme, we show that there is large disparity between the sense "0" margin and sense "1" margin with the significantly worse sense "0" margin limiting the affordable number of cells per Bitline. The possibility of using double-fin PFET in large-signal sensing inverter to improve the sense "0" margin is examined, and shown to be of limited benefit, especially for operation in subthreshold region. Compared with BULK CMOS, the superior electrostatic integrity and variability of FinFET enhances/enables the feasibility of differential sensing in subthreshold/superthreshold SRAM applications.

Original languageEnglish
Title of host publication2012 International Symposium on VLSI Technology, Systems and Applications, VLSI-TSA 2012 - Proceedings of Technical Papers
DOIs
StatePublished - 16 Jul 2012
Event2012 International Symposium on VLSI Technology, Systems and Applications, VLSI-TSA 2012 - Hsinchu, Taiwan
Duration: 23 Apr 201225 Apr 2012

Publication series

NameInternational Symposium on VLSI Technology, Systems, and Applications, Proceedings
ISSN (Print)1930-8868

Conference

Conference2012 International Symposium on VLSI Technology, Systems and Applications, VLSI-TSA 2012
CountryTaiwan
CityHsinchu
Period23/04/1225/04/12

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