Novel Quad-Interface MTJ Technology and its First Demonstration With High Thermal Stability Factor and Switching Efficiency for STT-MRAM Beyond 2X nm

We have proposed a novel quad-interface magnetic tunnel junction (MTJ) technology which brings forth an increase of both thermal stability factor Δ and switching efficiency defined as the ratio of Δ to intrinsic critical current IC0(Δ/IC0) by a factor of 1.5-2 compared with the conventional double-interface MTJ technology. The free layer of the developed quad interface consists of bottom-MgO/FL1/middle-MgO/FL2/top-MgOstack structure. We successfully fabricated the quad-interface MTJ using a 300-mm process based on a novel low-damage integration process including physical vapor deposition (PVD), reactive ion etching (RIE), and so on. By developing the quadinterface MTJ, we have achieved about two times larger Δ and Δ/IC0at the same time. Moreover, we have achieved about two times larger tunnel magnetoresistance (TMR) ratio at the same resistance area (RA) product by developing the FL1, bottom-MgO, and middle-MgO. The developed quad-interface MTJ technology considered as post-double-interface MTJ technology will become an essential technology for the scaling of the spin-transfer-torque magnetoresistive random access memory (STT-MRAM) beyond 20 nm.