Phase Change Memory and paradigm shift to in-system programming

摘要

Phase Change Memory (PCM) has recently gained momentum in the semiconductor industry as a viable alternative to flash memory due to the fact that flash (NOR and NAND) and DRAM memory technologies are expected to encounter scaling difficulties as chip lithography shrinks, and various unique properties PCM offers[1,2]. The PCM cell has been shown to scale down below 10nm as it uses the unique properties of Chalcogenide glass which can be reversibly “switched” between crystalline (low resistance) and amorphous (high resistance) states with application of heat[3]. This unique temperature property, however, will impose a paradigm shift from off-board pre-programming to in-system programming (ISP) in the manufacturing flow. Any code needed to be stored in the PCM has to be programmed after the surface mount technology (SMT) process. There are several methods already employed in the industry that will facilitate this paradigm shift to in-system programming. This paper attempts to consolidate and describe these methods.