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We conducted a comprehensive investigation on the influence of TiN thickness and stress on the ferroelectric properties of Hf 0.5 Zr 0.5 O 2 thin films. TiN top electrode layers with varying thicknesses of 2, 5, 10, 30, 50, 75, and 100 nm were deposited and analyzed. It was observed that the in-plane tensile stress in TiN films increased with the thickness of the TiN top electrode. This is expected to elevate the tensile stress in the Hf 0.5 Zr 0.5 O 2 film, consequently leading to an enhancement in ferroelectric polarization. However, the effect of stress on the ferroelectric behavior of Hf 0.5 Zr 0.5 O 2 films exhibited distinct stages: improvement, saturation, and degradation. Our study presents novel findings revealing a saturation and degradation phenomenon of in-plane tensile stress on the ferroelectric properties of polycrystalline Hf 0.5 Zr 0.5 O 2 films, thereby partially resolving the discrepancies between experimental observations and theoretical predictions. The observed phase transformation induced by tensile stress in Hf 0.5 Zr 0.5 O 2 films played a crucial role in these effects. Furthermore, we found that the impact of the TiN top electrode thickness on other factors influencing ferroelectricity, such as grain size and oxygen vacancies, was negligible. These comprehensive results offer valuable insights into the influence of stress and TiN top electrode thickness on the ferroelectric behavior of Hf 0.5 Zr 0.5 O 2 films. [ABSTRACT FROM AUTHOR]

Hf0.5Zr0.5O2 (HZO) is a promising candidate for low-power non-volatile memory due to its nanoscale ferroelectricity and compatibility with silicon-based technologies. Stress and oxygen vacancy (VO) are key factors that impact the ferroelectricity of HZO. However, their combined effects have not been extensively studied. In this study, we investigated the impact of the VO content on HZO thin films' ferroelectricity under different electrode stresses by using TiN and tungsten (W) top electrodes and controlling ozone dose time during HZO deposition. The HZO thin films with W top electrodes exhibit elevated stress levels and a greater abundance of orthorhombic/tetragonal phases, and the HZO thin films with TiN top electrode shows an increase in the monoclinic phase with increasing ozone dose time. The residual polarization (Pr) of the capacitors with TiN and W top electrodes displayed different or even opposing trends with increasing ozone dose time, and the VO content decreases with increasing ozone dose time for both sets of capacitor samples. We propose a model to explain these observations, considering the combined influence of electrode stresses and VO on the free and formation energy of the crystalline phase. Increasing the VO content promotes the transformation of the tetragonal phase to the orthorhombic phase in HZO films with TiN top electrodes, and with W top electrodes, a higher VO content prevents the tetragonal phase from transforming into the orthorhombic/monoclinic phase. Additionally, an alternative explanation is proposed solely from the perspective of stress. These findings provide valuable insights into the regulation of ferroelectricity in HZO thin films. [ABSTRACT FROM AUTHOR]

In the 3D ferroelectric memory fabrication process, the outer Titanium nitride metal electrode and silicon doped hafnium-based ferroelectric layer will produce void defects at the interfaces, causing increased leakage and compromising device performance. These void defects are caused by the volume contraction during the phase transition process, which leads to tension at the outer interface of the 3D ferroelectric capacitor structure. Due to the unavoidable structural stress, it is necessary to optimize the interface bonding energy. First principles simulation revealed insufficient binding energy between titanium nitride and silicon doped hafnium oxide ferroelectric materials, while introducing an amorphous alumina interface layer can effectively improve the binding ability. Experimental verification has confirmed that using an amorphous alumina interface layer as an adhesive layer can successfully solve the interface void defects, thereby improving the ferroelectric properties in three-dimensional structures. [ABSTRACT FROM AUTHOR]

The metal oxide solid electrolyte-based RRAM device is a promising candidate for post-Flash nonvolatile memories. The critical operation of such a device is the reset process, and the reliability study of the reset process and its physical understanding are important to RRAM development. This letter reports the observation of the unstable reset behavior in the \ZrO2-based solid electrolyte RRAM. During the reset process, the LRS resistance (RL) of the device will first reduce and then increase to reach the HRS. It is also seen that V0 (i.e., the voltage at which a decrease of RL takes place) decreases with an increase of RL. This instability might be attributed to the subsequent growth of the filament after the energy barrier is reached to overcome electrochemical reactions during the reset process. Based on these experimental results, a physical model is developed to help explain the dependence of V0 on RL, which provides an important guideline to the optimization of RRAM operations. [ABSTRACT FROM PUBLISHER]

In this letter, the insertion of a Cu nanocrystal (NC) layer between the Pt electrode and \ZrO2 film is proposed as an effective method to improve resistive switching properties in the \ZrO2 -based resistive switching memory. This Cu/\ZrO2:Cu/Cu NC/Pt memory exhibits asymmetric nonpolar resistive switching behavior, low operating voltage ( < 1.2 V), low Reset current (< \50\ \mu\A), and high uniformity of resistance switching. The switching mechanism is believed to be related with the formation and rupture of conductive filament. The NC-induced electrical field enhancement has the benefit to accelerate and control the CF formation process, thus leading to low-switching threshold voltage and high uniformity. [ABSTRACT FROM PUBLISHER]