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Ferroelectric materials, characterized by their polarization switching capabilities, have emerged as promising candidates for non-volatile memory applications due to their fast operation speeds, low switching energies, and remarkable scalability. Among these, hafnia-based ferroelectrics are particularly noted for their compatibility with complementary metal-oxide-semiconductor (CMOS) technology. However, the development of high-quality ferroelectricity in ultra-thin films, essential for low-voltage operations and high-density integrations, remains challenging. This study introduces a novel low-damage metallization process designed to fabricate ultra-thin (sub-5 nm) ferroelectric films exhibiting exceptional ferroelectric properties and reliability. The process, compatible with standard CMOS techniques, achieves a significant remnant polarization (Pr) of 40 µC cm−2 and low leakage currents, alongside enhanced retention characteristics. Crucially, it substantially mitigates the wake-up effect, often attributed to oxygen vacancy redistribution at the interface. Through comprehensive analyses utilizing electron energy loss spectroscopy (EELS), geometric phase analysis (GPA) and X-ray photoelectron spectroscopy (XPS), we demonstrate that our process effectively reduces oxygen vacancies and dislocations at the top interface of the ferroelectric film. The enhanced reliability of ferroelectric random-access memory (FeRAM), evidenced by improved sensing margins and consistency in ferroelectric properties, marks a substantial improvement over the conventional method. To precisely measure reliability characteristics, we propose a new retention model that considers charge screening over time. Moreover, circuit-level simulations via non-volatile memory simulator (NVSim) validate the process's integration potential with existing CMOS technologies, affirming its suitability for advanced, high-density memory configurations without compromising performance or energy efficiency. The findings from this study pave the way for broader applications of nanoscale high-quality dielectric thin films, extending beyond ferroelectric materials to various technological domains requiring advanced material solutions. [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]

We present herewith a novel approach of equally thick AFE/FE (ZrO 2 /HZO) bilayer stack heterostructure films for achieving an equivalent oxide thickness (EOT) of 4.1 Å with a dielectric constant (κ) of 56 in complementary metal-oxide semiconductor (CMOS) compatible metal-ferroelectric-metal (MFM) capacitors using a high-pressure annealing (HPA) technique. The low EOT and high κ values were achieved by careful optimization of AFE/FE film thicknesses and HPA conditions near the morphotropic phase boundary (MPB) after field cycling effects. Stable leakage current density ( J < 10 -7 A/cm 2 at ±0.8 V) was found at 3/3 nm bilayer stack films (κ = 56 and EOT = 4.1 Å) measured at room temperature. In comparison with previous work, our remarkable achievement stems from the interfacial coupling between FE and AFE films as well as a high-quality crystalline structure formed by HPA. Kinetically stabilized hafnia films result in a small grain size in bilayer films, leading to reducing the leakage current density. Further, a higher κ value of 59 and lower EOT of 3.4 Å were found at 333 K. However, stable leakage current density was found at 273 K with a high κ value of 53 and EOT of 3.85 Å with J < 10 -7 A/cm 2 . This is the lowest recorded EOT employing hafnia and TiN electrodes that are compatible with CMOS, and it has important implications for future dynamic random access memory (DRAM) technology.