Impact of threshold voltage fluctuation due to random telegraph noise on scaled-down SRAM

Abstract

The impact of a random telegraph noise (RTN) on a scaled-down SRAM is shown for the first time. To estimate the impact on SRAM, we statistically analyzed a threshold voltage fluctuation (ΔV <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</inf> ) of n-and p-MOSFETs. It is revealed that ΔV <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</inf> of the p-MOSFET is larger than that of the n-MOSFET. This difference can be explained by considering the followings: (i) number- and mobility-fluctuation models of RTN (ii) the difference in the capture cross section between electron and hole. In addition, based on these results, SRAM margin enclosed by read / write V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</inf> curves with or without RTN was simulated. We consequently found that V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</inf> margin comes close to V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</inf> window of the SRAM by considering the effect of RTN on ΔV <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</inf> , even at hp 65. Moreover, ΔV <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</inf> due to RTN of the p-MOSFET is comparable with ΔV <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</inf> due to the random dopant fluctuation (RDF) at hp 45 because ΔV <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</inf> due to the RDF is inversely proportional to square root of the gate area (S), while ΔV <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</inf> due to RTN is inversely proportional to S.