Novel oxygen showering process (OSP) for extreme damage suppression of sub-20nm high density p-MTJ array without IBE treatment

A novel damage recovery scheme using the oxygen showering post-treatment (OSP) is proposed to recover patterning damages and to improve electric and magnetic properties of p-MTJs, and its array yield. By applying our OSP to 25nm p-MTJs cell array, the MR was increased from 99% to 116% and the Isw was decreased from 41.1uA to 28.7uA. Moreover, electric short fails of MTJs array due to metallic by-products reduced dramatically by the selective oxidation of the damaged layer and its isolation from damage-less area. The OSP process makes the switching efficiency of 25nm patterned MTJs to be improved more than 30% compared with IBE treatment process. The mechanism of this enhancement is that spin directions of damaged area is changed from perpendicular to in-plane and, by this change, the energy barrier of damaged area is reduced. By the OSP treatment, we could develop the robust patterning process for sub-20nm STT-MRAM.