Stability optimization of monolithic 3-D MoS2-n/WSe2-p SRAM cells for superthreshold and near-/sub-threshold applications

2-D transition metal dichalcogenides (TMDs) such as MoS₂ and WSe₂ (Fig. 1(a)) are very attractive for future ultimately scaled low-power CMOS devices owing to their atomic-scale thickness, adequate band-gap, and pristine surface (without dangling bonds) [1-3]. Our previous study [4] has evaluated the stability of MoS₂-n/WSe₂-p SRAMs with planar technology. However, the process complexity of heterogeneous integration of distinct materials for n/p-FETs can become a concern. Monolithic 3-D integration [5] offers the possibility to independently optimize the n-FETs and p-FETs at distinct tiers. It has also been envisioned [6] that monolithic 3-D integration combined with the extremely scaled TMD devices may offer the ultimate solution for future ultra-high density ICs and SRAMs (Fig. 1(c)).