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In this Letter, the robust ferroelectric properties of low-temperature (350 °C) Hf0.5Zr0.5O2 (HZO) films are investigated. We demonstrate that the lower crystallization temperature of HZO films originates from a densified film deposition with an anhydrous H2O2 oxidant in the atomic layer deposition process. As a consequence of this densification, H2O2-based HZO films showed completely crystallinity with fewer defects at a lower annealing temperature of 350 °C. This reduction in the crystallization temperature additionally suppresses the oxidation of TiN electrodes, thereby improving device reliability. The low-temperature crystallization process produces an H2O2-based HZO capacitor with a high remanent polarization (Pr), reduced leakage current, high breakdown voltage, and better endurance. Furthermore, while an O3-based HZO capacitor requires wake-up cycling to achieve stable Pr, the H2O2-based HZO capacitor demonstrates a significantly reduced wake-up nature. Anhydrous H2O2 oxidant enables the fabrication of a more reliable ferroelectric HZO device using a low process thermal budget (350 °C). [ABSTRACT FROM AUTHOR]

A novel precursor, 1,1,1-tris(dimethylamino)disilane {TADS, [(H3C)2N]3Si2H3}, is used to deposit silicon dioxide (SiO2) films in a temperature range of 115–480 °C by thermal atomic layer deposition (tALD) and plasma-enhanced atomic layer deposition (PEALD) techniques. Compared to tris(dimethylamino)silane (TDMAS), the additional Si-Si bond in TADS is expected to enhance the reactivity of the molecule due to the polarization of the bond. In the tALD process, TADS gives a growth rate of 0.06 nm/cycle, which is approximately 20% higher than that of TDMAS, and an excellent conformality (>95% step coverage) in high aspect ratio nanotrenches (6:1). In the case of the PEALD process, TADS leads to not only a higher or at least comparable growth rates (0.11 nm/cycle), but also a higher bulk film density (∼2.38 g/cm3). As a result, the PEALD SiO2 films of TADS show a wet-etch rate down to 1.6 nm/min in 200:1 HF, which is comparable to that of the thermal oxide. Analyzed with Fourier-Transform Infrared (FTIR), the SiO2 films contain predominant Si−O bonds and a low level of Si−H and O−H bonds, consistent with the observed high wet-etch resistance. Furthermore, the PEALD SiO2 films deposited at 310 °C have at least 75% step coverage in high aspect ratio nanotrenches, suggesting that TADS is applicable for forming high-quality SiO2 films on both planar and patterned surfaces. [ABSTRACT FROM AUTHOR]

In this Letter, a high-pressure annealing (HPA) process is proposed as a way to reduce the thermal budget of Hf0.5Zr0.5O2 (HZO) thin films with ferroelectric behaviors. The low-thermal-budget process is essential for integrating ferroelectric devices in the back-end-of-line to provide more functionalities and effective memory area. For the HZO film annealed at 300 °C using the HPA process, an orthorhombic phase responsible for ferroelectric behavior was formed with a decrease in film thickness, resulting in a remanent polarization (Pr) of ∼13 μC/cm2 (i.e., 2Pr of ∼26 μC/cm2). Meanwhile, when only the annealing time was increased at 300 °C without applying pressure, the HZO film did not crystallize and exhibited linear dielectric properties. Consequently, the HZO films (<10 nm) can be crystallized by applying pressure (15 atm) even at low temperatures of 300 °C, thereby obtaining ferroelectric properties. [ABSTRACT FROM AUTHOR]

In this work, a nano-polycrystalline Ag-doped ZnO-based threshold switching (TS) selector via a facile co-sputtering technique is investigated without using an Ag active metal layer. The effects of the Ag concentration with respect to OFF-state leakage current (Ioff) were studied, and the results demonstrate that by regulating the Ag doping concentration in the switching layer (SL), an electroforming-free switching with an Ion/Ioff ratio of ∼108 could be achieved, having an extremely low Ioff value of ∼10−13 A. Furthermore, cycling endurance can also be improved as the formation of a laterally thick and stable filament does not happen promptly with consequent measurements when there is a limited amount of Ag in the SL. The selector device performance enhancement is attributed to the doping-based polycrystalline structure that facilitates enhanced control on filament formation due to the restricted availability and anisotropic diffusion of Ag ions in the polycrystalline ZnO SL, thereby trimming down the overall stochasticity during metallic filament growth. The present study demonstrates that a doping-based polycrystalline SL structure can be implemented in a selector device to augment TS characteristics, i.e., device variances and cycling endurance for adoption in ultra-high density memory applications. [ABSTRACT FROM AUTHOR]

The change in the interplanar spacing (d-spacing) including the ferroelectric orthorhombic (O) phase in the low-temperature fabricated HfxZr1−xO2 (HZO) films was studied using synchrotron grazing-incidence wide-angle x-ray scattering analysis. The 10-nm-thick HZO films were fabricated by thermal and plasma-enhanced atomic layer deposition (TH- and PE-ALD) methods using H2O gas and O2 plasma as oxidants, respectively, and a post-metallization annealing (PMA) was performed at 300–400 °C. The d-spacing of the mixture of (111)-, (101)-, and (111)-planes of O, tetragonal (T), and cubic (C) phases, respectively, for the TH- and PE-ALD HZO films increased up to 2.99 Å with an increase in PMA temperature, while the d-spacing estimated by conventional x-ray diffraction was 2.92 Å regardless of the PMA temperature. The remanent polarization (2Pr= Pr+ − Pr−) of the HZO films increased as the PMA temperature increased. It is clear that the 2Pr value satisfied a linear relationship as a function of the d-spacing of O(111)/T(101)/C(111) phases. Furthermore, the wake-up effect was found to depend on the ferroelectric O phase formation. The wake-up effect was significantly reduced in both the TH- and PE-ALD HZO films after the PMA at 400 °C due to the increase in the ferroelectric O phase formation. The leakage current density (J)–electric field properties of the PE-ALD HZO film with the lowest d-spacing were divided into three steps, such as low, middle, and large J values, in the wake-up (103 cycles), pristine (100 cycle), and fatigue (107 cycles) states, respectively. Therefore, an analysis of the ferroelectric O phase is very important for understanding the ferroelectricity including endurance. [ABSTRACT FROM AUTHOR]

The ferroelectricity of metal–ferroelectric–metal capacitors with a ferroelectric HfxZr1−xO2/ZrO2 (HZO/ZO) bilayer thicker than 20 nm formed by atomic layer deposition and postdeposition annealing at 600 °C was investigated. The HZO/ZO capacitors exhibited a higher remanent polarization (2Pr = Pr+ − Pr−) and breakdown voltage (Vbd) than capacitors with a HfxZr1−xO2 (HZO) single layer. In particular, a HZO (15 nm)/ZO(10 nm) (HZ15Z10) capacitor exhibited excellent Vbd and 2Pr values of 6.7 V and 14 μC/cm2, respectively, which are much higher than those (4.3 V and 10 μC/cm2, respectively) for a HZO (15 nm) (HZ15) capacitor. The HZ15Z10 capacitor also exhibited higher endurance, a smaller wake-up effect (∼5%), and superior fatigue properties up to 108 switching cycles, compared to a HZ15 capacitor, which exhibited a large wake-up effect (∼15%) and large 2Pr degradation at 108 cycles. The wake-up behavior is attributed to domain depinning mainly related to the redistribution of oxygen vacancies and transformation from the nonferroelectric phase to the ferroelectric orthorhombic (O) phase during field cycling. The HZO/ZO bilayer grew a larger grain size with the ZO nucleation layer, which is twice as large as that of the HZO single layer, and the former structure exhibited more stable bulk-like ferroelectricity. Although the ferroelectric O phase in HZO decreased with increasing HZO thickness, the HZO/ZO structure had a larger fraction of the O phase than the HZO structure. Considering the manufacturing process of ferroelectric devices, these thick HZO/ZO bilayers are promising ferroelectric materials. [ABSTRACT FROM AUTHOR]

The ferroelectric (FE) properties of 10-nm-thick Hf0.5Zr0.5O2 (HZO) films deposited by an atomic layer deposition technique were improved by adopting O3 as an oxygen source instead of H2O. All HZO films were annealed at 400 °C for 1 min in an N2 atmosphere after TiN top electrode deposition. Regardless of the oxygen source, the HZO films exhibited the formation of a noncentrosymmetric orthorhombic phase, which is responsible for FE behavior with the suppression of the monoclinic phase. However, compared to the O3-based HZO film, it was confirmed that the H2O-based HZO film was more incorporated with hydrogen derived from H2O, thereby degrading FE polarization and leakage behavior. The results indicate that the strategy of using O3 as the oxygen source is useful for the fabrication and integration of FE HZO films for next-generation memory applications. [ABSTRACT FROM AUTHOR]

In this letter, the ferroelectric (FE) properties of 5-nm-thick Hf0.5Zr0.5O2 (HZO) films deposited by atomic layer deposition have been investigated. By reducing the HZO film thickness to 5 nm, low-voltage operation (1.0 V) of the HZO-based capacitor was achieved while maintaining a remnant polarization (Pr) of about 10 μC/cm2 (i.e., 2Pr of 20 μC/cm2). Meanwhile, in order to form an orthorhombic phase, which is responsible for FE properties, a rapid thermal annealing process was performed after TiN top electrode deposition. The FE properties were realized after low temperature annealing (450 °C for 1 min), making them compatible with the back-end of the line. In addition, the low operating voltage and the suppression of an additional monoclinic phase formation by stress-induced crystallization induced a robust endurance (>1010 cycles at 1.2 V) of the 5-nm-thick HZO sample. [ABSTRACT FROM AUTHOR]

We report on atomic layer deposited Hf0.5Zr0.5O2 (HZO)-based capacitors which exhibit excellent ferroelectric (FE) characteristics featuring a large switching polarization (45 μC/cm2) and a low FE saturation voltage (~1.5V) as extracted from pulse write/read measurements. The large FE polarization in HZO is achieved by the formation of a non-centrosymmetric orthorhombic phase, which is enabled by the TiN top electrode (TE) having a thickness of at least 90 nm. The TiN films are deposited at room temperature and annealed at 400 ºC in an inert environment for at least 1 min in a rapid thermal annealing system. The room-temperature deposited TiN TE acts as a tensile stressor on the HZO film during the annealing process. The stress-inducing TiN TE is shown to inhibit the formation of the monoclinic phase during HZO crystallization, forming an orthorhombic phase that generates a large FE polarization, even at low process temperatures. [ABSTRACT FROM AUTHOR]