Co/Pd multilayered films with perpendicular magnetic anisotropy were patterned using block copolymer templating. Two methods of achieving phase separation of the block copolymer were compared. A matrix study of etch time and etch angle was carried out for each phase separation method, and their effects on the magnetic properties were studied. It was found that ion milling at 45° and 3.5 minutes for the heptane annealing method yielded the highest coercivity, 3.2 kOe, a 246% increase over that of an unpatterned film.

We have studied the use of self-assembled block copolymers to pattern multilayers of Co and Pd on silicon wafers. Stacks ranging from four to twelve bilayers of Co (0.3 nm)/Pd (0.8 nm) were sputtered onto Ta/Pd seed layers and capped with 3 nm of Ta and were found to have perpendicular magnetic anisotropy as-deposited. The block copolymer polystyrene- block-poly(ferrocenyl dimethylsilane) (PS-b-PFS) was dissolved in toluene and spun onto the wafers. The polymers were phase-separated by heat treatment, leaving self-assembled PFS spheres embedded in PS, which was removed by oxygen-plasma ashing. The PFS spheres were then used as masks to ion-mill the Co/Pd multilayers into nanopillars. To study the effect of etch time and etch angle on the coercivity distribution, we synthesized samples in a Design of Experiments-(DoE)- in these two factors. Scanning electron micrographs showed nanopillars ranging from 15 to 30 nm in diameter, depending primarily on etch time. M-H loops measured on both patterned and unpatterned wafers showed an increase of up to 130% in overall coercivity upon patterning. First Order Reversal Curves (FORC) were measured, and the resulting FORC distributions displayed using a smoothing program (FORCinel) and one that can display the raw data without smoothing (FORC+). We find that FORC+ reveals information about fine-scale structure and switching mechanism that cannot be seen in the smoothed display.

The (111) orientation preferred L10 FePtB has been obtained by post-deposition annealing sputtered FeB/Pt multilayers on thermally oxidized silicon substrates. Block copolymer templating was employed to pattern FeBPt film. A matrix study of etch time and etch angle showed that ion-milling at 75° for 3 min yielded the highest coercivity. Reannealing after patterning process was found to improve the crystalline structure and coercivity significantly. These results suggested (111) orientation preferred L10 FePt patterned by block copolymer templating may be promising for tilted media and bit patterned media.

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