Browsing by Author "Su, Zhong-Cheng"

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Device and circuit level suppression techniques for random-dopant-induced static noise margin fluctuation in 16-nm-gate SRAM cell
(2010-05-01)
Lee, Kuo-Fu
;
Li, Yiming
;
Li, Tien-Yen
;
Su, Zhong-Cheng
;
Hwang, Chin-Hong
In this study, a three-dimensional "atomistic" coupled device-circuit simulation is performed to explore the impact of process-variation-effect (PVE) and random-dopant-fluctuation (RDF) on static noise margin (SNM) of 16-nm complementary metal-oxide-semiconductor (CMOS) static random access memory (SRAM) cells. Fluctuation suppression approaches, based on circuit and device viewpoints, are further implemented to examine the associated characteristics in 16-nm-gate SRAM cells. From the circuit viewpoint, the SNM of 8T planar SRAM is enlarged to 230 mV and the variation of SNM (sigma(SNM)) is reduced to 22 mV at a cost of 30% extra chip area. As for device level improvement, silicon-on-insulator (SOI) FinFETs replaced the planar MOSFETs in 6T SRAM is further examined. The SNM of 6T SOI FinFETs SRAM is 125 mV and the sigma(SNM) is suppressed significantly to 5.4 mV. However, development of fabrication process for SOI FinFET SRAM is crucial for sub-22 nm technology era. (C) 2010 Elsevier Ltd. All rights reserved.
Statistical Simulation of Metal-Gate Work-function Fluctuation in High-kappa/Metal-Gate Devices
(2010)
Yu, Chia-Hui
;
Han, Ming-Hung
;
Cheng, Hui-Wen
;
Su, Zhong-Cheng
;
Li, Yiming
In this work, we statistically examine the emerging high-kappa / metal gate work-function fluctuation (WKF) induced threshold voltage (V(th)) fluctuations in 16-nm-gate MOSFET devices. Our Monte-Carlo model extensively evaluates the impact of WKF for different technology node, metal grain size, and gate material. This model provides us to identify suitable materials and fabrication processes that can significantly reduce the impact of Vth fluctuation owing to WKF. First, four kinds of gate material are examined and TiN possesses the smallest Vth fluctuation. For fabrication process, a fast deposition of metal at lower temperature prevents the metal grain not to grow to large size result in a smaller variation. In addition, an idea of modeling multilayer metal gate WKF is also presented and discussed, in which the first layer plays the most important role, compared with other layers, for the fluctuation suppression.