Ferroelectricity of Hf_xZr_1−xO₂ Thin Films Fabricated Using TiN Stressor and ZrO₂ Nucleation Techniques

Abstract

We studied the ferroelectricity and the leakage current (J) properties of two types of the MFM capacitors such as the TiN/ZrO2/HfxZr1−xO2/ZrO2/TiN capacitor (D-ZrO2) with the ZrO2 nucleation layers, comparing to the TiN/HfxZr1−xO2/TiN capacitor (D-TiN) with the TiN stressor layers. The larger ferroelectric phase ratio was achieved by the epitaxial like grain growth of the HfxZr1−xO2 film on the surface of the top- and bottom-ZrO2 nucleation layers. Thus, the larger remanent polarization (2P r = 29 µC/cm2) of D-ZrO2 was obtained compared to that (24 µC/cm2) of D-TiN. Moreover, the J value of D-ZrO2 was approximately one order of magnitude lower than that of D-TiN. Therefore, these results suggest that the superior ferroelectricity of HZO film can be obtained using the ZrO2 nucleation technique instead of the TiN stressor technique.

Enhanced Ferroelectric Properties and Insulator–Metal Transition-Induced Shift of Polarization-Voltage Hysteresis Loop in VOx-Capped Hf0.5Zr0.5O2 Thin Films

“…(a) P-V hysteresis loops at 300 K of different HZO samples, (b) comparison of FE performance between the HZO/VO x -1.67 sample and previous HZO-based capacitors (note: data are obtained from refs − and plotted by the authors). In panel (b), capping layer materials are indicated at the corresponding data points, while the bottom electrode and seed layer materials are represented by the colors of the data points that are illustrated in the right of the panel.…”

“…Solutions to these scaling and integration issues may lie in the recently emerging HfO 2 -based FE materials. − Ferroelectricity in HfO 2 -based FE materials originates from a noncentrosymmetric orthorhombic phase (o-phase; space group: P ca 2 1 ). − Theoretically, this o-phase can exhibit a remnant polarization ( P r ) as high as 50 μC/cm 2 . However, the experimental P r values of HfO 2 -based FE materials reported in recent years were limited to the range of ∼10–20 μC/cm 2 , − well below the theoretical value. In addition, the coercive field ( E c ) values of HfO 2 -based FE materials were typically 1–2 MV/cm, − about one order of magnitude higher than those of traditional FE materials.…”

“…For example, metallic capping layers, such as TiN, − Ru, , Au, Ta, W, Pt, , Pd, Ni, , TaN, and ITO, can act as top electrodes. In addition, some oxide capping layers, such as Al 2 O 3 , and ZrO 2 , can reduce the leakage current. Other oxide capping layers, like RuO 2 , can reduce the number of oxygen vacancies at the interface, thus suppressing the wake-up effect and improving the endurance and retention properties.…”

Toward Low-Thermal-Budget Hafnia-Based Ferroelectrics via Atomic Layer Deposition

“…This concept is based on the superior characteristics of ZrO 2 films processed via the low-temperature ALD process at 300 °C (e.g., good crystallinity and predominantly o/t/c-phases). The HZO-based MFM capacitors with a ZrO 2 nucleation layer exhibited the improvement of their ferroelectricity, while those with an amorphous Al 2 O 3 layer showed smaller 2 P r compared to the conventional HZO-based MFM capacitors. − ,− Here, the effect of the ZrO 2 layer on the ferroelectricity of the MFS structure was investigated. Figure a,b shows cross-sectional TEM images of MFS capacitors without ZrO 2 (w/o) and ZrO 2 -10 nm following the PMA process at 300 °C.…”

Improvement in nonvolatile memory operations for metal–ferroelectric–insulator–semiconductor capacitors using HfZrO2 and ZrO2 thin films as ferroelectric and insulator layers

“…In this work, atomic-layer deposited (ALD) ZrO 2 thin films were introduced as ILs with sufficiently good interface between the Si and good leakage current characteristics without any introduction of additional SiO 2 interfacial layer for the MFIS capacitors using ferroelectric HZO layers. The ZrO 2 thin films have been employed as seed layers for expediting the crystallization process of the ferroelectric HZO layers for the metal-ferroelectric-metal (MFM) and MFIS capacitors [22,23]. Xiao et al demonstrated the ferroelectric MW as wide as 2.8 V for the capacitors with TaN/HZO/ZrO 2 /SiO 2 /Si structure [24], but in-depth discussions on the detailed design schemes to optimize the device performance were not provided.…”