Highly functional and reliable 8Mb STT-MRAM embedded in 28nm logic

Abstract

We fabricated 8Mb 1T-1MTJ STT-MRAM macro embedded in 28nm CMOS logic platform by developing novel integration/stack/patterning technologies. MTJ memory cell array was successfully embedded into Cu backend without open fail and severe degradation of magnetic property. Advanced perpendicular MTJ stack using MgO/CoFeB was developed to show high TMR value of 180% after full integration. In addition, ion beam etching (IBE) process was optimized with power, angle, and pressure to reduce a short fail below 1 ppm. Through these novel technologies, we demonstrated highly functional and reliable 8Mb eMRAM macro having a wide sensing margin and strong retention property of 85 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sup> C and 10yrs.