In order to form ultrathin insulating layer in magnetic tunnel junctions (MTJs), two surface flatting processes of metal films are investigated. Oxygen-additive sputter-deposition process was applied to the bottom Cu electrode and the Al layer to be nitrided. Dry-etching process was applied for the surface treatment of lower Co-Fe layer. As a result, the surface roughness of stacked ultrathin Al layer to be nitrided is reduced from 3.2Å to 1.7Å, and the tunnel magnetoresistance (TMR) ratio of the MTJs increases from 1% to 26% while maintaining resistance-area product (R×A) less than 5× 102 ω μ m2 in the Co-FeAl (6A) -NCo-Fe MTJs. We conclude that the decrease of the surface roughness of Al layer is one of the key factors to realize high performance MTJs with low R×A and high TMR ratio.
ASJC Scopus subject areas
- Physics and Astronomy(all)