Title :
Investigation of Proximity Effects in a 6T SRAM Cell Using Three-Dimensional TCAD Simulations
Author :
Simeonov, Simeon D. ; Avci, Ibrahim ; Balasingam, Pratheep ; Johnson, Mark D. ; Kucherov, Andrey ; Lyumkis, Eugeny ; Von Matt, Urs ; El Sayed, Karim ; Saha, Arup R. ; Tan, Zhiqiang ; Tian, Shiyang ; Villablanca, Luis ; Polsky, Boris
Author_Institution :
Synopsys, Inc., Mountain View, CA, USA
fDate :
4/1/2011 12:00:00 AM
Abstract :
In this paper, we study the impacts of proximity effects on the electrical characteristics Id-Vg and the static noise margin of a six-transistor (6T) bulk complementary metal-oxide-semiconductor (MOS) static random access memory (SRAM) cell using 3-D process and device technology computer-aided design (TCAD) simulations. We show that when a 6T SRAM cell is simulated as a single continuous 3-D structure, effective stresses in channels are reduced due to close proximity of n-channel and p-channel MOS transistors in the cell with respect to simulations of transistors as discrete 3-D structures. Furthermore, we find that doping in channels of SRAM transistors is reduced by well proximity and implant shadowing. Stress and doping proximity effects have opposite contributions to device performance. We estimate the influence of proximity effects for typical 32-nm technology to be more than 10% for certain electrical cell characteristics. We thus conclude that, to accurately predict electrical cell behavior via TCAD simulations, the 6T SRAM cell should be a single continuous 3-D structure, instead of a set of six discrete transistors, which are simulated as individual 3-D devices and connected via a netlist.
Keywords :
CMOS memory circuits; MOSFET; SRAM chips; proximity effect (lithography); technology CAD (electronics); bulk complementary metal-oxide-semiconductor; implant shadowing; n-channel MOS transistor; p-channel MOS transistor; proximity effect; single continuous 3-D structure; six-transistor static random access memory cell; size 32 nm; static noise margin; three-dimensional technology computer-aided design simulation; MOS devices; Proximity effect; Random access memory; Semiconductor device modeling; Semiconductor process modeling; Stress; Transistors; Device; dopant; process; simulation; static random access memory (SRAM); stress; technology computer-aided design (TCAD);
Journal_Title :
Electron Devices, IEEE Transactions on
DOI :
10.1109/TED.2011.2109003