FinFET SRAM Optimization With Fin Thickness and Surface Orientation

In this paper, the design space, including fin thickness
$(T_{\rm fin})$
, fin height
$(H_{\rm fin})$
, fin ratio of bit-cell transistors, and surface orientation, is researched to optimize the stability, leakage current, array dynamic energy, and read/write delay of the FinFET SRAM under layout area constraints. The simulation results, which consider the variations of both
$T_{\rm fin}$
and threshold voltage
$(V_{\rm th})$
, show that most FinFET SRAM configurations achieve a superior read/write noise margin when compared with planar SRAMs. However, when two fins are used as pass gate transistors (PG) in FinFET SRAMs, enormous array dynamic energy is required due to the increased effective gate and drain capacitance. On the other hand, a FinFET SRAM with a one-fin PG in the (110) plane shows a smaller write noise margin than the planar SRAM. Thus, the one-fin PG in the (100) plane is suitable for FinFET SRAM design. The one-fin PG FinFET SRAM with
$T_{\rm fin} = \hbox{10}\ \hbox{nm}$
and
$H_{\rm fin} = \hbox{40}\ \hbox{nm}$
in the (100) plane achieves a three times larger noise margin when compared with the planar SRAM and consumes a 17% smaller bit-line toggling array energy at a cost of a 22% larger word-line toggling energy. It also achieves a 2.3 times smaller read delay and a 30% smaller write delay when compared with the planar SRAM.