R&D: High-Stability Van Der Waals Structures of GeTe/Sb2Te3 Superlattices for 100× Increased Durability Phase-Change Memory by Low-Temperature Atomic Layer Deposition

Advanced Functional Materials has published an article written by Rong-Jiang Zhu, Rui-Zhe Zhao, Ke Gao, Zhuo-Ran Zhang, School of Integrated Circuits, Huazhong University of Science and Technology, Wuhan, 430074 China, Qiang He, Hao Tong, and Xiang-Shui Miao, School of Integrated Circuits, Huazhong University of Science and Technology, Wuhan, 430074 China, and Hubei Yangtze Memory Laboratories, Wuhan, 430205 China.

Abstract: “The superlattices phase-change memory (SL-PCM), based on GeTe/Sb₂Te₃ superlattices (SLs), garners considerable attention within the academic community owing to its exceptional electrical properties. While the exact mechanism remains a topic of ongoing debate, researchers widely acknowledge that the presence of van der Waals (vdW) gap structures within SLs plays a pivotal role. However, the formation of vertical nanoparticles (VNPs) from the random orientation of Sb₂Te₃ and the substantial intermixing between GeTe and Sb₂Te₃ due to high-temperature fabrication processes leads to pronounced elemental intermixing during electrical operations, causing a loss of SLs properties. This investigation uses atomic layer deposition techniques, specifically Sb-atomic seed layer and periodic quintuple layers stacking, to address issues from random orientation Sb₂Te₃ grains and anomalous VNPs. This approach yields Sb₂Te₃ crystalline films with a high-stability vdW gap structures. By leveraging these films, SLs with a preferred crystallographic orientation at a notable low temperature of 90 °C are successfully fabricated. The optimized SLs exhibit remarkable structural stability and mitigate alloy phase emergence during electrical operations, resulting in a 100-fold enhancement in device durability. This work advances reliable SL-PCM understanding and implementation, propelling this memory technology into the next generation.“