Recent Technology Insights on STT-MRAM: Structure, Materials, and Process Integration
Jeong-Dong Choe
Abstract
Emerging memory products such as STT-MRAM, PCRAM, ReRAM, FeRAM, and XPoint Memory have been successfully commercialized on market for more than a decade, especially for DDR, SCM (storage-class memory), and embedded cache applications. Among them, STT-MRAM technology is now popular for cache memory replacing eSRAM, eFLASH, and eDRAM. Semiconductor foundries and IDMs are focusing more on MRAM with stand-alone type or embedded devices. They’re developing, producing, and scaling down the MRAM cell design to 22 nm and beyond. Further, the MTJ structure is quite complicated and complex due to multilayers such as synthetic antiferro-magnetics, ferromagnetic, and even they use a dual tunnel barrier structure, and multi-layered diffusion barriers, spacers, and coupling layers added into the structure for high performance and structural stability. We review and discuss the structure, materials, design, and process technology of STTMRAM products up to date, and challenges as well.