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The ferroelectric NAND flash memory devices have garnered interest because of their rapid switching speed, low operating voltage, and superior reliability in comparison to conventional charge-trap flash memory. In particular, hafnia-based ferroelectrics have been intensively studied thanks to their relatively low crystallization temperature, CMOS compatibility, and excellent scaling characteristics. However, when processing the 3D integration, FeNAND devices based on hafnia encounter thermal instability issues due to the high process temperature required for both deposition and annealing of the poly-Si channel. Furthermore, FeNAND devices suffer from the read/pass disturbance and narrow memory window (MW) stems from the sub-loop characteristics and intrinsic small coercive field of hafnia ferroelectrics. To address these issues, we propose oxide channel dual-port FeNAND devices with additional gate dielectric and gate metal on the opposite side of the ferroelectrics from the channel layer. The thermal stability and disturbance issues are resolved with the low-temperature process oxide channel (<300 °C) and an extra gate stack. We experimentally verified that our devices show a broad MW range of 10 V, operate using quad-level-cell technology, and exhibit excellent levels of reliability. In addition, considering the findings from the experiments, we propose a 3D process integration strategy and evaluate the characteristics of dual-port 3D FeNAND devices using TCAD modeling. [ABSTRACT FROM AUTHOR]

The need for novel memory devices with low energy usage, strong reliability, and multi-level capacity is growing significantly nowadays. Among one of the promising candidates, hafnia (HfO2)-based ferroelectric devices with a coercive field (Ec) designed for a multi-peak profile are known to provide stable multi-level capabilities in terms of suppressed device-to-device variations. In this study, a novel approach was demonstrated using a fixed charge method to realize a six-level ferroelectric cell. Using the Landau–Khalatnikov model, it is verified that the fixed charge in the ferroelectric device generated a bidirectional imprint field leading to separate Ec peaks. For experimental demonstration, tantalum oxide (TaO) and hafnium zirconium oxide (HZO) were employed as a fixed charge source and ferroelectric layer, respectively, to fabricate a HZO/TaO/HZO/TaO/HZO device. The imprint field created by positively charged oxygen vacancies at TaO/HZO interfaces shifted the switching properties of HZO layers, allowing the device to exhibit three distinct switching behaviors from the HZO layers. Therefore, the overall device showed a triple-peak Ec profile and corresponding six polarization states. Moreover, because of the preferential polarization switching within the shifted HZO layers, polarization states were well maintained over time. The findings of this work may provide a hint toward a scalable path for future memory solutions. [ABSTRACT FROM AUTHOR]

The morphotropic phase boundary (MPB), which arises from the combination of antiferroelectric and ferroelectric phases, demonstrates the highest dielectric constant (κ) compared to other phases. This emphasizes its potential as a leading contender for dielectric films in future dynamic random access memory (DRAM) capacitors. MPB‐based high‐κ materials using hafnia have shown a trade‐off between equivalent oxide thickness (EOT) and leakage current density (Jleak) when the crystallization temperature increases with scaling the thickness. Herein, a microwave annealing (MWA) method that can achieve low‐temperature crystallization below 350 °C is employed. The purpose of this method is to mitigate the trade‐off relationships and achieve the strict criteria of current DRAM capacitors. These criteria include low EOT (less than 4 Å) and Jleak (less than 10−7 A cm−2 at 0.8 V) characteristics. The MWA is capable of relatively low‐temperature annealing by supplying energy to the films through both thermal energy and dipole vibration energy. As a result, a record‐low EOT of 3.76 Å and a low leakage current characteristic of 4.2 × 10−8 A cm−2 at 0.8 V are achieved concurrently. It is confident that the research can be important in addressing the challenges associated with reducing the size of next‐generation DRAM capacitors. [ABSTRACT FROM AUTHOR]

The discovery of ferroelectricity in HfO2 ultrathin films has gathered considerable interest from the microelectronic industry owing to their compatibility with complementary metal oxide semiconductor technology. However, a significant challenge in utilizing HfO2 thin films for commercial devices is the wakeup effect, which is an increase in polarization with the number of electric field cycles in HfO2-based capacitors. Despite efforts to develop wakeup-free HfO2 thin films, the root cause of this effect remains elusive. Some studies attribute it to the tetragonal (T) to orthorhombic (O) phase transformation, while others suggest it is due to the redistribution of oxygen vacancies within the HfO2 layer during electric field cycling. This study investigated the phase transformation dynamics and oxygen vacancy distributions in TiN/Hf0.5Zr0.5O2/TiN capacitors subjected to electric field cycling using in situ grazing incidence synchrotron x-ray diffraction and ex situ x-ray photoelectron spectroscopy. The as-grown HZO films were crystallized in a mixed phase consisting of monoclinic (M), tetragonal, and orthorhombic fractions. The T-phase volume fraction decreased continuously up to 10k electric field cycles. In contrast, the O-phase fraction increased within the first 100 cycles and then stabilized with further cycling. The redistribution of oxygen vacancies occurred continuously throughout the cycling process. The results revealed that continuous oxygen vacancy redistribution during electric field cycling resulted in phase transformation between the T-, O-, and M-phases. The study provides insight into the phase transformation dynamics and oxygen vacancy redistribution in TiN/Hf0.5Zr0.5O2/TiN capacitors during electric field cycling, shedding light on the underlying mechanisms of the wakeup effect. [ABSTRACT FROM AUTHOR]

The development of artificial tactile receptor systems is important in the fields of prosthetic devices, interfaces for the metaverse, and sensors. A pressure sensor and memory device may be used in this system to replicate the tactile detecting capabilities of human skin. The implementation of systems that take into account mass production and miniaturization is still difficult. Here, a flexible artificial tactile receptor built using conventional semiconductor processes that combine a vertically stacked piezoelectric sensor with neuromorphic memory is presented. As a fundamental component for both sensors and memory, hafnium zirconium oxide (HZO) formed by using semiconductor deposition technique is introduced. Due to its exceptional piezoelectric performance, the morphotropic phase boundary of HZO is studied. The entire materials and processes are highly compatible with conventional semiconductor processes, including microwave annealing‐based low‐temperature crystallization. Even after 10,000 times of bending stress, the sensor and memory constructed on a flexible substrate exhibit consistent pressure detection characteristics over a wide range of 2–25 kPa. The feasibility of the approach is further demonstrated by a deep neural network simulation, which reached 90.8% braille recognition accuracy. Wearable electronics and medical devices are two examples of industrial domains that can use these flexible, exceptionally durable devices. [ABSTRACT FROM AUTHOR]

Investigation of the polarization switching mechanism in ferroelectric hafnium zirconium oxide (HZO) film is of great importance for developing high-quality ferroelectric memory devices. Recently, several works have been reported to describe the switching process of polycrystalline HZO film using the inhomogeneous field mechanism (IFM) model. However, no report has recorded the effect of high pressure annealing (HPA) on the polarization switching process. In this paper, we have carried out a careful investigation on the switching properties of HZO capacitors annealed at 600 °C with various high pressure conditions (1, 50, and 200 atm) using the IFM model. As pressure increases to 200 atm, the ferroelectric properties were enhanced in the HZO films, and, as a result, highest remanent polarization (Pr of 24.5 μC/cm2) was observed when compared with 1 and 50 atm. Similarly, as HPA increases, the HZO capacitors showed a decrement of the coercive field, which significantly improved the switching properties. The time consumed for reversing 80% polarization was 113.1, 105.7, and 66.5 ns for the sample annealed at 1, 50, and 200 atm, respectively. From the IFM model, the smallest active field (2.997 MV/cm) and a uniform distribution of the local electric field (0.304) were observed at 200 atm. Furthermore, the characteristic time constant (τ 0) showed a decreasing trend (34.7, 18.1, and 11.7 ps) with increasing HPA. The improved switching properties and detailed findings recorded in this study may be helpful for developing the ferroelectric hafnia based non-volatile memory applications. [ABSTRACT FROM AUTHOR]