Realistic CNFET Based SRAM Cell Design for Better Write Stability

Behzad Ebrahimi and Ali Afzali Kusha
University of Tehran


In this paper, a comparison between CNFET and Si-MOSFET SRAM cells at 32nm technology node are presented. The designs are based on predictive technology model (PTM) for the Si-MOSFET cell and CNFET Stanford model for the CNFET cell. For practical reasons, in the CNFET case, the substrate of the entire chip is considered to be one node. The effect of the voltage of this node on improving the overall characteristics of the CNFET cell is described. HSPICE simulation results show that CNFET has better performance compared to Si-MOSFET. Finally, the characteristics of the SRAM cell in the presence of fabrication imperfections of CNFET are studied. The write stability of CNFET SRAM is low because of the same current drive capability for both p- and n-CNFETs. For solving this problem, we weaken the pull up transistors by different channel length and CNT diameter with respect to n type transistors.