First Demonstration of 25-nm Quad Interface p-MTJ Device With Low Resistance-Area Product MgO and Ten Years Retention for High Reliable STT-MRAM

Abstract

We successfully developed 25-nm quad CoFeB/MgO-interfaces perpendicular magnetic tunnel junction (quad-MTJ) with enough thermal stability. To fabricate the quad-MTJ, a physical vapor deposition (PVD) process for depositing novel free layer and low resistance-area (<italic>RA</italic>) product MgO layer and low-damage fabrication processes were developed. The developed quad-MTJ technology and advanced process bring better tunnel magneto resistance (TMR) ratio and <italic>RA</italic> to quad-MTJ than those of double-interface MTJ (double-MTJ), even though quad-MTJ has an additional MgO layer. Scaling down the MTJ size to 25 nm, we demonstrated the advantages of quad-MTJ compared with double-MTJ as follows: 1) two times larger thermal stability factor (<inline-formula> <tex-math notation= LaTeX >$\\Delta $ </tex-math></inline-formula>), which results in over ten years retention; 2) superiority of large <inline-formula> <tex-math notation= LaTeX >$\\Delta $ </tex-math></inline-formula> in the measuring temperature range up to 200 °C; 3) ~1.5 times higher write efficiency; 4) lower write current at short write pulse regions at less than 100 ns; and e) excellent endurance of over 10¹¹ thanks to higher write efficiency, which results from the reduced voltage owing to low <italic>RA</italic> and the low damage integration process technology. As a result, the developed quad-MTJ technologies will open the way for the realization of high-density STT-MRAM with low power, high speed, high reliability, and excellent scalability down to <inline-formula> <tex-math notation= LaTeX >$2\\times $ </tex-math></inline-formula> nm node.