On-axis scheme and novel MTJ structure for sub-30nm Gb density STT-MRAM

Feasibility of STT-MRAM (Spin-Transfer Torque Magnetic Random Access Memory) as next generation non-volatile memory has been tested for the replacement of DRAM and NOR Flash. For competition with DRAM, STT-MRAM unit cell size should be reduced to 6 ~ 8F² and switching current density is required to be less than 1 MA/cm². Here, we report that the cell characteristics of on-axis STT-MRAM with 6 ~ 8F² are similar to those of off-axis STT-MRAM with 12 ~ 16F². In addition, we suggest a novel MTJ (Magnetic Tunnel Junction) with the operation current density of 0.8 MA/cm². These results open a way to scale STT-MRAM down to sub- 30 nm technology node using present technology. By further material engineering of ferromagnetic electrode and MTJ structure design, the usage of present technology could be extended down to sub-20 nm node.