Degradation of perpendicular magnetic anisotropy in CoFeB film after H2 plasma irradiation

The degradation of the perpendicular magnetic anisotropy (PMA) of a Ta cap/MgO/CoFeB stack film after H2 plasma irradiation was investigated to clarify the magnetic damage induced during the hydrogen-containing plasma etching (e.g., CO/NH3 or CH3OH plasma etching). When the CoFeB layer thickness was 1.2 nm, the out-of-plane coercivity decreased from 1.0 to 0.15 mT after H2 plasma irradiation, and the perpendicular anisotropy field also decreased, from 220 to 90 mT. The dependence of the reduction in the PMA on the CoFeB thickness revealed that the interfacial anisotropy energy was reduced from 0.98 to 0.79 mJ/cm2 after H2 plasma irradiation. These results clearly indicate that hydrogen-containing plasma etching has the potential to degrade the PMA during MgO/CoFeB film patterning.