Analysis and Design of FeFET Synapse With Stacked-Nanosheet Architecture Considering Cycle-to-Cycle Variations for Neuromorphic Applications

Using extensive Monte-Carlo simulations with a nucleation-limited-switching (NLS) ferroelectric model and considering cycle-to-cycle variations, this paper constructs and analyzes the intrinsic conductance (G_DS) response of stacked-nanosheet FeFET synapses with emphasis on the challenging identical-pulse stimulation. Our study indicates that the interlayer oxide thickness of the FeFET and the saturation polarization of the ferroelectric are crucial to the linearity and symmetry of the intrinsic G_DS response. With the stacked-nanosheet architecture, the maximum-to-minimum conductance ratio in the G_DS response can be boosted by increasing the number of channel tiers without footprint penalty. For a stacked-nanosheet FeFET synapse with an area ratio effect, the G_DS response can be further engineered by varying the tier number. In addition, the immunity to cycle-to-cycle variations and the noise margin for each state in the G_DS response can also be improved by increasing the number of tiers. Our study may provide insights for future FeFET synapse design for analog computing.