Investigation of cell stability and write ability of finfet subthreshold SRAM using analytical SNM model
Journal
IEEE Transactions on Electron Devices
Journal Volume
57
Journal Issue
6
Pages
1375-1381
Date Issued
2010
Author(s)
Abstract
In this paper, the static noise margin (SNM) of FinFET static random access memory (SRAM) cells operating in the subthreshold region was investigated using an analytical solution of 3-D Poisson's equation. An analytical SNM model for subthreshold FinFET SRAM was demonstrated and validated by 3-D technology computer-aided design (TCAD) mixed-mode simulations. When compared with bulk SRAM, the standard 6T FinFET cell showed larger nominal READ SNM (RSNM), better variability immunity, and lesser temperature sensitivity of cell stability. Furthermore, examination of the stabilities of several novel independently controlled gate FinFET SRAM cells by using the proposed SNM model showed significant nominal RSNM improvements in these novel cells. However, the write ability is found to be degraded, which thus becomes an important concern for certain configurations in the subthreshold region. The result obtained indicates that the READ/WRITE word line voltage control technique is more effective than transistor sizing in improving the stability and write ability of the FinFET subthreshold SRAM. Furthermore, the impacts of process-induced variations on cell stability were also assessed. When compared with RSNM, it was found that WRITE SNM is more susceptible to process variations. While 6T is not a viable candidate for subthreshold SRAM, and 8T/10T cells must be used in bulk CMOS, the present analysis established the potential of 6T FinFET cells for subthreshold SRAM applications. © 2010 IEEE.
Subjects
FinFET; Poisson's equation; Static noise margin (SNM); Subthreshold SRAM
Other Subjects
Analytical solutions; Bulk CMOS; Cell stability; Control techniques; Line voltage; Mixed mode simulation; Poisson's equation; Process Variation; Process-induced variation; SRAM applications; SRAM Cell; Static noise margin; Static random access memory; Subthreshold; Subthreshold region; Technology computer aided design; Temperature sensitivity; Transistor sizing; Cells; Computer aided design; Electric potential; Poisson equation; Stability; Three dimensional; Voltage regulators; Static random access storage
Type
journal article