R&D: Atomic Layer Deposition of GeSb2Te4 Thin Films for Reliable Phase Change Memory with High Dynamic Range

IEEE Electron Device Letters has published an article written by Rongjiang Zhu, Ruizhe Zhao, Ke Gao, School of Integrated Circuits, Huazhong University of Science & Technology, China, Hao Tong, and Xiangshui Miao, School of Integrated Circuits, Huazhong University of Science & Technology, China, and Hubei Yangtze Memory Laboratories, Wuhan, China.

Abstract: “With the increase of memory cell density, the structure of phase change memory (PCM) has changed from two-dimensional to three-dimensional, the manufacturing process has become increasingly complex, and the cost of tape-out has risen sharply. In order to optimize device performance and improve yield, improving device reliability has become a primary focus of attention. A high dynamic range can significantly reduce the possibility of device failure or bit errors, thereby improving reliability. In this study, we utilized atomic layer deposition (ALD) to fabricate a crystalline GeSb ₂ Te ₄ film using special precursor pulses. By inducing crystallization through crystal nucleation, the film was able to switch stably between high and low resistance states during device operation without experiencing any intermediate states that may lead to device failure or bit errors. Moreover, the Rhombohedral phase film (~10 ³ Ω) fabricated by ALD resulted in PCM cells with a higher dynamic range (~1000X) compared to physical vapor deposition (PVD) (~10X). The PCM cell’s endurance under a dynamic range of 1000X was able to reach 10 ⁶ cycles, with a low drift coefficient (0.00066) for the low resistance state. This work offers a new approach to improving the reliability of PCM.“