Low resistance tunnel junctions with remote plasma underoxidized thick barriers

Low resistance tunnel junctions suitable for >200 Gb/inch2 read heads require RxA<1 Ωμm2 and TMR>10%, usually achieved by natural oxidation with tAl<0.7 nm barriers. This paper shows that as-deposited junctions with competitive electrical and magnetic properties can be produced starting from 0.9 nm Al barriers and remote plasma oxidation in ion beam-deposited stacks using Co73.8Fe16.2B10 electrodes. TMR∼20% for RxA∼2-15 Ωμm2 is obtained, while in the RxA∼40-140 Ωμm2 range TMR can reach 40%-45%, in as-deposited samples. A limited number of junctions exhibits considerably lower RxA values with respect to the average while keeping similar MR (down to 0.44 Ωμm2 with 20% and down to 2.2 Ωμm2 with 51%)