Ge(2)Sb(2)Te(5) confined structures and integration of 64Mb 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 mu m CMOS technology offers a large sensing margin: R(reset) similar to 200 k Omega and R(set) similar to 2 k Omega, as well as reasonable reliability: an endurance of 1.0 x 10(9) cycles and a retention time of 2 years at 85 degrees C.