Capacitance Matching for Stabilizing Negative Capacitance Effect in MOS Gate Stack Based on HfxZr1-xO2 Ferroelectric Thin Film

Abstract

Although advancements in process technology have been addressing effectively the challenges accompanied with the continuous scaling of semiconductor integrated circuits, more disruptive approaches are necessary to overcome the physical limitations of conventional metal-oxide-semiconductor field-effect transistor (MOSFET).[1] One of them is to utilize the negative capacitance (NC) effect which can lower the dynamic voltage through the so-called gate voltage boosting. The NC effect in ferroelectric materials has been theoretically described by the negative curvature of the Landau-Ginzburg free energy.[2] Since the NC state in a standalone ferroelectric layer is unstable, it is essential to construct a stack including both ferroelectric and dielectric layers to secure the stability of NC state with the appropriate capacitance matching between the two layers. In this study, we demonstrate experimentally the ferroelectric/dielectric stack structure showing the potential to reveal the NC effect when it is incorporated into the gate-stack of MOSFET. The stack is composed of HfxZr1-xO2 (HZO) and non-ferroelectric oxide layers, and its Landau-Ginzburg parameters are extracted from the P-E hysteresis curves measured in the form of metal/ferroelectric-dielectric/metal capacitor. By altering the thicknesses of ferroelectric and dielectric layers and their stacking combination, we find out the stack structures revealing the preferable shapes of Landau-Ginzburg curve for the NC effect. Then, we evaluate the NC performance of each preferable structure by fabricating a metal-oxide-semiconductor capacitor and measuring its C-V characteristics, intended to find the practical guide for achieving the capacitance matching to maximize the NC effect and its stability.

References [1] M. T. Bohr et al., IEEE Micro (Volume:37), 4241347 (2017). [2] K. M. Rabe et al., Physics of Ferroelectrics: A Modern Perspective, Springer, New York (2007).