R&D: Enhancing Performance of Phase Change Memory for Embedded Applications

PSS@RRL (Physica Status Solidi Rapid Research Letters) has published an article written by Xi Li, Houpeng Chen, Chenchen Xie, Daolin Cai, Sannian Song, Yifeng Chen, Yu Lei, Min Zhu, and ZhiTang Song, State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Micro‐system and Information Technology, Chinese Academy of Sciences, Shanghai, 200050 China.

Abstract: “Focusing on meeting the requirements for embedded applications of faster switching and sensing, lower‐power consumption, higher reliability, longer cycling endurance, and higher temperature retention, a lot of progress in the phase change memory (PCM) field has been made, including materials improvement, process optimization, new circuits design, and better operation algorithms. Finally, a 128MB embedded PCM chip has been demonstrated in 40nm node. Using carbon‐doped Ge₂Sb₂Te₅ phase change material and 3 nm thick heating bottom electrode contact (BEC) with nitride coating, a resistance ratio of more than two orders of magnitude has been achieved in Reset and Set states. Combined with the parasitic matched sensing circuit, optimized ramp‐down SET pulses, adaptive pre‐read and write‐verify methods, and automatic configure and test procedures, the chip exhibits excellent data retention and endurance characteristics with minimum program time of 200ns, and the Reset/Set resistance ratio becomes even larger after 260°C soldering test. The estimated data retention time is ten years at 128°C, and in a 128MB full integrated chip the endurance over 10⁹ cycles is achieved. It is confirmed that this PCM technology is suitable for embedded applications, especially for those with crucial requirements of high access speed, high thermal stability, and cycling endurance.“