Enhanced Ferroelectric Properties and Insulator–Metal Transition-Induced Shift of Polarization-Voltage Hysteresis Loop in VO_x-Capped Hf_0.5Zr_0.5O₂ Thin Films

Abstract

A capping layer is known to be critical for stabilizing the ferroelectric (FE) orthorhombic phase (o-phase) in a HfO 2based thin film. Here, vanadium oxide (VO x ), a functional oxide exhibiting the insulator−metal transition, is used as a novel type of a capping layer for the Hf 0.5 Zr 0.5 O 2 (HZO) thin film. It is demonstrated that the VO x capping layer (VCL) can enhance the FE properties of the HZO thin film comprehensively. Specifically, the HZO thin film with a VCL shows large remanent polarization (2P r ≈36.9 μC/cm 2 ), relatively small coercive field (E c ≈1.09 MV/ cm), high endurance (up to 10 9 cycles), and long retention (>10 5 seconds). The enhanced FE properties may be attributed to the VCL-induced stabilization of the FE o-phase and suppression of oxygen vacancies at the interface. Furthermore, the HZO thin film with a VCL exhibits a successive rightward shift of polarizationvoltage (P-V) hysteresis loop as the temperature increases. This is well correlated with the insulator−metal transition in a VCL, which can modulate the interfacial built-in field and thus cause the P-V loop shift. It is therefore demonstrated that a VCL not only enhances the FE properties of HZO thin films but also provides a temperature degree of freedom to modulate the FE properties, which may open up a new pathway to develop HfO 2 -based FE memories with high performance and novel functionalities.

Novel Approach to High κ (∼59) and Low EOT (∼3.8 Å) near the Morphotrophic Phase Boundary with AFE/FE (ZrO2/HZO) Bilayer Heterostructures and High-Pressure Annealing

“…Zhang et al reported a temperature-dependent study on oxygen vacancies capped in HZO films, in which the leakage current is mainly affected by the creation and suppression of oxygen vacancies and the increase of those vacancies at the interface region. Also, they observed a change of conduction behavior with increasing measurement temperature . Thus, we believe that formation of oxygen vacancies at the interfaces (HZO/TiN and TiN/ZrO 2 ) of the bilayer films leads to suppression of those oxygen vacancies with increase of measurement temperatures and hence reduced leakage current densities in the bilayer films.…”

“…Also, they observed a change of conduction behavior with increasing measurement temperature. 44 Thus, we believe that formation of oxygen vacancies at the interfaces (HZO/ TiN and TiN/ZrO 2 ) of the bilayer films leads to suppression of those oxygen vacancies with increase of measurement temperatures and hence reduced leakage current densities in the bilayer films. Note that the current density is decreased to 1 order of magnitude at lower measurement temperatures when compared to room temperature measurements.…”

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

“…4(a)), exhibiting the enhanced ophase amount from transitioned t-phase. Meanwhile, the coercive voltage (Vc) shows an increment as the temperature decreases [20]. Besides, the C-V hysteresis remain the same with two peaks, indicating ferroelectric dominance during cooling (Fig.…”

HfO2-based Ferroelectric Field-Effect-Transistor with Large Memory Window and Good Synaptic Behavior

“…22 Fortunately, many methods have been proposed to improve the endurance characteristic in previous literatures. [27][28][29] Finally, retention measurements were performed to evaluate the stability of the memory state. Figure 6c shows the conductance of FeFET retention characteristics after a program pulse (−4V/500 μs) and an erase pulse (+6 V/500 μs).…”