An Analysis of Local BTI Variation with Ring-Oscillator in Advanced Processes and Its Impact on Logic Circuit and SRAM

Mitsuhiko IGARASHI  Yuuki UCHIDA  Yoshio TAKAZAWA  Makoto YABUUCHI  Yasumasa TSUKAMOTO  Koji SHIBUTANI  Kazutoshi KOBAYASHI  

Publication
IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E104-A    No.11    pp.1536-1545
Publication Date: 2021/11/01
Publicized: 2021/05/25
Online ISSN: 1745-1337
DOI: 10.1587/transfun.2020KEP0017
Type of Manuscript: Special Section PAPER (Special Section on Circuits and Systems)
Category: 
Keyword: 
local BTI variation,  Ring-Oscillator,  7nm FinFET,  SRAM Vmin,  

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Summary: 
In this paper, we present an analysis of local variability of bias temperature instability (BTI) by measuring Ring-Oscillators (RO) on various processes and its impact on logic circuit and SRAM. The evaluation results based on measuring ROs of a test elementary group (TEG) fabricated in 7nm Fin Field Effect Transistor (FinFET) process, 16/14nm generation FinFET processes and a 28nm planer process show that the standard deviations of Negative BTI (NBTI) Vth degradation (σ(ΔVthp)) are proportional to the square root of the mean value (µ(ΔVthp)) at any stress time, Vth flavors and various recovery conditions. While the amount of local BTI variation depends on the gate length, width and number of fins, the amount of local BTI variation at the 7nm FinFET process is slightly larger than other processes. Based on these measurement results, we present an analysis result of its impact on logic circuit considering measured Vth dependency on global NBTI in the 7nm FinFET process. We also analyse its impact on SRAM minimum operation voltage (Vmin) of static noise margin (SNM) based on sensitivity analysis and shows non-negligible Vmin degradation caused by local NBTI.