Quantitative study of EOT lowering in negative capacitance HfO2-ZrO2 superlattice gate stacks

Recent demonstrations [1] show that superlattice, mixed ferroelectric-antiferroelectric, fluorite-structure gate oxides with negative capacitance (NC) can go beyond state-of-the-art high-kappa HfO2 based equivalent oxide thickness (EOT) scaling [1-3]. However, the physical origin of NC in such gate stacks, especially a quantitative understanding of the gate capacitance, needs more detailed investigation. Here we present a comprehensive study of these gate stacks by combining pulsed-voltage and impedance measurements with compact modeling and 2D phase field simulations. We show that (i) a quantitative agreement between experiment and model can be reached and (ii) 2D effects play a critical role in determining what EOT can be attained. Our experimentally calibrated model provides insight into how substantially larger EOT scaling could be achieved.