Jang Hojung, Kashir Alireza, Schenk Tony, Habibi Mostafa, Schuster Martin, Oh Seungyeol, Müeller Stefan, Hwang Hyunsang
Center for Single Atom-based Semiconductor Device and the Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang 37673, Korea.
Ferroelectric Memory GmbH, Charlotte-Bühler-Str. 12, 01099 Dresden, Germany.
ACS Appl Mater Interfaces. 2024 Oct 3. doi: 10.1021/acsami.4c08641.
Hafnia thin films are known to demonstrate excellent performance with strong ferroelectricity and high scalability, making them promising candidates for CMOS-compatible materials. However, the reliability of ferroelectric devices must be further improved. This study developed a HfZrO ferroelectric capacitor with a nanolaminate structure that operated at remarkably low voltages, demonstrating excellent retention (>10 years/85 °C) and endurance (>10 cycles). The exceptional performance is attributed to the presence of thin tetragonal phase layers within the thick ferroelectric layers, which decreased the switching barrier in the nanolaminate films. Further, we verified phase crystallization via a detailed analysis of high-resolution transmission electron microscopy images. The improved switching propagation in the nanolaminate films was confirmed through switching speed measurements and theoretical models. Furthermore, we addressed pinching issues by precisely controlling the Hf/Zr ratio and O treatment. The initial imprint and retention characteristics were improved by interfacial engineering. Moreover, by reducing the thickness, we have achieved reliable operation at 1.0 V with a 5.5 nm-thick device while maintaining high retention and endurance. This study is a significant step toward the realization of the longstanding problem of ferroelectric random access memory operation voltage with respect to endurance and retention characteristics.
已知氧化铪薄膜具有优异的性能，具有强铁电性和高可扩展性，使其成为CMOS兼容材料的有前途的候选者。然而，铁电器件的可靠性必须进一步提高。本研究开发了一种具有纳米层状结构的HfZrO铁电电容器，该电容器在极低电压下工作，表现出优异的保持性（>10年/85°C）和耐久性（>10次循环）。这种优异的性能归因于厚铁电层中存在薄的四方相层，这降低了纳米层状薄膜中的开关势垒。此外，我们通过对高分辨率透射电子显微镜图像的详细分析验证了相结晶。通过开关速度测量和理论模型证实了纳米层状薄膜中开关传播的改善。此外，我们通过精确控制Hf/Zr比和O处理解决了夹断问题。通过界面工程改善了初始印记和保持特性。此外，通过减小厚度，我们在厚度为5.5nm的器件上实现了1.0V的可靠操作，同时保持了高保持性和耐久性。这项研究朝着解决铁电随机存取存储器在耐久性和保持特性方面长期存在的操作电压问题迈出了重要一步。
