Intrinsic switching in Si-doped HfO2: A study of Curie–Weiss law and its implications for negative capacitance field-effect transistor

Abstract

HfO2-based ferroelectrics are considered a promising class of materials for logic and memory applications due to their CMOS compatibility and ferroelectric figures of merit. A steep-slope field-effect-transistor (FET) switch is a device for logic applications in which a ferroelectric gate stack exploits a stabilized negative capacitance regime capable to differentially amplify the surface potential in a metal–oxide–semiconductor FET structure, resulting in the improvement of the subthreshold swing and overdrive. In a number of relevant studies of negative capacitance, intrinsic (thermodynamic) switching is assumed, since alternative switching scenarios predict undesirable hysteretic responses in logic devices. However, there is little support from the experimental data showing that the polarization reversal in HfO2-based ferroelectrics is really driven by the intrinsic switching mechanism. In this work, polarization hysteresis loops are measured over wide temperature ranges on polycrystalline Si-doped HfO2 (Si:HfO2) capacitors. The analysis herein, which is based on the classic Landau–Ginzburg–Devonshire theory, yields the temperature-dependent dielectric susceptibility values, which fit the Curie–Weiss law. The extrapolated Curie temperature value is in line with the data obtained for other HfO2-based ferroelectrics using different techniques. The work also illustrates a method to evaluate the ferroelectric equivalent negative capacitance value and range of voltages, aiming at study and optimization of a stabilized negative capacitance FET. This study indicates that the intrinsic switching provides an adequate description of the polarization hysteresis in Si:HfO2 films. This confirms the usability of hafnia-based ferroelectrics for negative capacitance logic devices, and the important role that the intrinsic mechanism plays in the dielectric response of these materials.

Impact of non-ferroelectric phases on switching dynamics in epitaxial ferroelectric Hf0.5Zr0.5O2 films

“…37 In contrast and counterintuitively, the increase in the number of defects results in the decrease of the switching time. 26 At the local level, microscopic characterization performed in ferroelectric HfO 2 polycrystalline films indicates that thermodynamic switching can occur, 38,39 in addition to giving hints on the intriguing dependence of the coercive electric field dependence on thickness. 40 Despite the fact that several works (some of them contradictory) have investigated domain dynamics in polycrystalline ferroelectric hafnium oxide, further investigation is needed to fully understand switching dynamics.…”

Effect of Film Microstructure on Domain Nucleation and Intrinsic Switching in Ferroelectric Y:HfO2 Thin Film Capacitors

“…[9][10][11][12][13][14] Since functionality of the FE-based devices in most cases depends on the electrical switching of the spontaneous polarization, increasing application of the HfO 2 -based FE films calls for a better understanding of the mechanism of polarization reversal in these materials, which is far from being understood. [15][16][17][18] For example, hysteresisfree negative capacitance can only occur if the polarization switches intrinsically, i.e., without domain nucleation and growth. [19,20] Does it mean that the "S"shaped polarization-electric field (P-E) curve -a signature of the negative capacitance effect -experimentally demonstrated in the Hf 0.5 Zr 0.5 O 2 (HZO) heterostructures [7] is also an indicator of the intrinsic switching?…”

Improved Ferroelectricity in Cryogenic Phase Transition of Hf0.5Zr0.5O2

“…Based on Landau-Ginzburg-Devonshire theory, intrinsic switching is applied to explain the temperature-dependent phase transition [21]. The thermodynamic free energy (G) is an expansion of the polynomial of polarization (P) up to the sixth order,…”