Ge₂Sb₂Te₅ Confined Structures and Integration of 64 Mb Phase-Change Random Access Memory

Abstract

Phase-change random access memory is considered a potential challenger for conventional memories, such as dynamic random access memory and flash memory due to its numerous advantages. Nevertheless, high reset current is the ultimate problem in developing high-density phase-change random access memory (PRAM). We focus on the adoption of Ge 2 Sb 2 Te 5 confined structures to achieve lower reset currents. By changing from a normal to a GST confined structure, the reset current drops to as low as 0.8 mA. Eventually, our integrated 64 Mb PRAM based on 0.18 µm CMOS technology offers a large sensing margin: R reset ∼200 kΩ and R set ∼2 kΩ, as well as reasonable reliability: an endurance of 1.0×10 9 cycles and a retention time of 2 years at 85°C.