A wake-up free Hf0.5Zr0.5O2 (HZO) ferroelectric film with the highest remnant polarization (Pr) value to-date was achieved through tuning of the ozone pulse duration, the annealing process, and the metal/insulator interface. The ozone dosage during the atomic layer deposition of HZO films appears to be a crucial parameter in suppressing the mechanisms driving the wake-up effect. A tungsten capping electrode with a relatively low thermal expansion coefficient enables the induction of an in-plane tensile strain, which increases the formation of the orthorhombic phase while decreasing the formation of the monoclinic phase during the cooling step of the annealing process. Therefore, increasing the annealing temperature TA followed by rapid cooling to room temperature resulted in a substantial increase in the 2Pr value (≈ 64 µC/cm 2 ). However, the leakage current increased considerably, which can affect the performance of metal-insulator-metal (MIM) devices. To reduce the leakage current while maintaining the mechanical stress during thermal annealing, a 10 nm Pt layer was inserted between the W/HZO bottom interface. This resulted in a ~ 20-fold decrease in the leakage current while the 2Pr value remained almost constant (~ 60 µC/cm 2 ). The increase in barrier height at the Pt/HZO interface compared to that of the W/HZO interface coupled with the suppression of the formation of interfacial oxides (WOx) by the introduction of a Pt/HZO interface serves to decrease the leakage current.

Wake‐up effect is still an obstacle in the commercialization of hafnia‐based ferroelectric thin films. Herein, the effect of defects, controlled by ozone dosage, on the field cycling behavior of the atomic layer deposited Hf0.5Zr0.5O2 (HZO) films is investigated. A nearly wake‐up free device is achieved after reduction of carbon contamination and oxygen defects by increasing the ozone dosage. The sample which is grown at 30 s ozone pulse duration shows about 97% of the woken‐up Pr at the pristine state whereas that grown below 5 s ozone pulse time shows a pinched hysteresis loop, that underwent a large wake‐up effect. This behavior is attributed to the increase in oxygen vacancy and carbon concentration in the films deposited at insufficient O3 dosage, which is confirmed by X‐ray photoelectron spectroscopy (XPS). The X‐ray diffraction (XRD) scan shows that the increase in ozone pulse time yields the reduction of tetragonal phase; therefore, the dielectric constant reduces. The I–V measurements reveal the increase in current density as the ozone dosage decreases, which might be due to the generation of oxygen vacancies in the deposited film. Finally, the dynamics of wake‐up effect is investigated, and it appears to be explained well by the Johnson–Mehl–Avrami–Kolmogoroff model, which is based on structural phase transformation.

Hafnium oxide (HfO2) is one of the mature high‐k dielectrics that has been standing strong in the memory arena over the last two decades. Its dielectric properties have been researched rigorously for the development of flash memory devices. In this review, the application of HfO2 in two main emerging nonvolatile memory technologies is surveyed, namely resistive random access memory and ferroelectric memory. How the properties of HfO2 equip the former to achieve superlative performance with high‐speed reliable switching, excellent endurance, and retention is discussed. The parameters to control HfO2 domains are further discussed, which can unleash the ferroelectric properties in memory applications. Finally, the prospect of HfO2 materials in emerging applications, such as high‐density memory and neuromorphic devices are examined, and the various challenges of HfO2‐based resistive random access memory and ferroelectric memory devices are addressed with a future outlook.

In this study, we investigate the effects of various electrodes on the ferroelectric properties of ultrathin HfZrOx (HZO) films. The ferroelectric polarization is totally suppressed in the HZO films with TiN and W bottom electrodes when the film thickness is below 5 nm. These results can be attributed to the formation of a dead layer at the bottom electrode/HZO interface during the atomic layer deposition (ALD) and annealing processes. On the other hand, the HZO film with a Pt bottom electrode shows an excellent P–E loop with a very high switchable polarization (2Pr) of 42.5 μC/cm2 even at a film thickness of 2.5 nm. Through the short pulse switching technique, we confirm the formation of a thick dead layer in the HZO films with TiN and W electrodes, which inhibits the formation of the orthorhombic phase in these ultrathin HZO films. This implies that the ferroelectric property of ultrathin HZO films can be improved by choosing an appropriate electrode material capable of suppress ing the formation of a dead layer.

Morphotropic phase boundaries (MPBs) show substantial piezoelectric and dielectric responses, which have practical applications. The predicted existence of MPB in HfO 2 -ZrO 2 solid solution thin film has provided a new way to increase the dielectric properties of a silicon-compatible device. Here, we present a new fabrication design by which the density of MPB r MPB and consequently the dielectric constant ò r of HfO 2 -ZrO 2 thin film was considerably increased. The r MPB was controlled by fabrication of a 10 nm [1 nm Hf 0.5 Zr 0.5 O 2 (ferroelectric)/1 nm ZrO 2 (antiferroelectric)] nanolaminate followed by an appropriate annealing process. The coexistence of orthorhombic and tetragonal structures, which are the origins of ferroelectric (FE) and antiferroelectric (AFE) behaviors, respectively, was structurally confirmed, and a double hysteresis loop that originates from AFE ordering, with some remnant polarization that originates from FE ordering, was observed in P-E curve. A remarkable increase in ò r compared to the conventional HfO 2 -ZrO 2 thin film was achieved by controlling the FE-AFE ratio. The fabrication process was performed at low temperature (250 °C) and the device is compatible with silicon technology, so the new design yields a device that has possible applications in near-future electronics.

The formation of an interfacial layer is believed to affect the ferroelectric properties in HfO2 based ferroelectric devices. The atomic layer deposited devices continue suffering from a poor bottom interfacial condition, since the formation of bottom interface is severely affected by atomic layer deposition and annealing process. Herein, the formation of bottom interfacial layer was controlled through deposition of different bottom electrodes (BE) in device structure W/HZO/BE. The transmission electron microscopy (TEM) and x-ray photoelectron spectroscopy analyses done on devices W/HZO/W and W/HZO/IrO x suggest the strong effect of IrO x in controlling bottom interfacial layer formation while W/HZO/W badly suffers from interfacial layer formation. W/HZO/IrO x devices show high remnant polarization (2P r) ∼ 53 μC cm−2, wake-up free endurance cycling characteristics, low leakage current with demonstration of low annealing temperature requirement as low as 350 °C, valuable for back-end-of-line integration. Further, sub-5 nm HZO thicknesses-based W/HZO/IrO x devices demonstrate high 2P r and wake-up free ferroelectric characteristics, which can be promising for low power and high-density memory applications. 2.2 nm, 3 nm, and 4 nm HZO based W/HZO/IrO x devices show 2P r values 13.54, 22.4, 38.23 μC cm−2 at 4 MV cm−1 and 19.96, 30.17, 48.34 μC cm−2 at 5 MV cm−1, respectively, with demonstration of wake-up free ferroelectric characteristics.

The existence of morphotropic phase boundary (MPB) inside HfO2-ZrO2 solid solution thin films has been predicted; if it exists, it provides up a new path toward an ideal silicon-compatible dielectric....

In this paper, we propose a method to improve the performance of TiN/Hf0.5Zr0.5O2 (HZO)/TiN Nano-capacitors used in memory devices. Instead of direct fabrication of the TiN/HZO/TiN device, our method involves an intermediate step in which W metal is used as a capping material to induce a large in-plane tensile strain during rapid thermal annealing, resulting in a total suppression of the monoclinic phase and the appearance of the ferroelectric phase. Consequently, after removing the W capping electrode through an etching process and the post-deposition of a TiN top electrode at room temperature, a high remnant polarization of approximately 40 μC cm−2 and a 65% increase of coercive field were obtained. Moreover, the leakage current was reduced by an order of magnitude compared to the normal TiN/HZO/TiN capacitor; this result is attributed to the presence (absence) of the W/HZO (TiN/HZO) top interface during thermal annealing. The formation of a TiO x interfacial layer at elevated temperatures, which pulls oxygen from the HZO layer, resulting in the formation of oxygen vacancies, is the main cause of the high leakage current through the TiN/HZO/TiN stacks. It was confirmed that the re-capped TiN/HZO/TiN capacitor has a comparable endurance to a normal capacitor. Our results offer the re-capping process as a promising approach to fabricating HfO2-based ferroelectric memory devices with various electrode materials.