Grain Pattern Media Recording (GPMR) technology is proposed as a candidate to replace Bit Pattern Media (BPM). GPMR media fabrication process shows great promise to resolve the technical and manufacturing issues associated with conventional BPM. Rather than a highly aggressive subtractive process with thick masking layers to pattern magnetic bits, GPMR employs a bottom-up new approach where thin (2nm) and narrow (3nm) radial line pattern is fabricated on top of the interlayer, then FePt granular alloy is deposited using conventional sputter deposition. This Line pattern acts as nucleation constraints to force the newly deposited FePt grains to grow on the interlayer along the radial direction to ensure alignment of grain edges. Fig. 1 shows a illustration of the GPMR magnetic configuration and radial lines. To ensure grains only grow on the interlayer and no grains grow on top of segregant lines, the segregant lines needs to be controlled to be less than ~3 nm. We proposed to use simple sidewall patterning approach which combines nano-imprint lithography with dry plasma etch technique to create < 3 nm width dielectric segregant lines for fabricating GPMR media. Two sidewall processes with different mandrel materials have been developed to successfully fabricate < 3 nm SiO2 lines on MTO surfaces on the disks. The segreant line width is determined by the deposition thickness of SiO2, whereas the segregant line height of 1-3 nm is determined by the CF4 etch process. Fig. 2A shows the sidewall process flow and the top-down SEM image with inserted TEM cross sectional image of 2.8 nm linewidth radial segregant SiO2 line patterns on MTO (pitch= 32 nm). Fig. 2B shows that TEM image of 2 nm FePt grains was deposited on 3 nm SiO2 lines on MTO at 650C (pitch= 160 nm). This is the first successful experimental demonstration of phase segregation of ordered FePt granular media using this newly invented bottoms up approach to form patterned media.
References:
1 T. R. Albrecht et al., in IEEE Transactions on Magnetics, vol. 51, no. 5, pp. 1-42, May 2015, TMAG.2015
2 D. S. Kuo et al., 2016 International Conference of Asian Union of Magnetics Societies (ICAUMS), 2016, pp. 1-1, 2016.

Fig. 1 The proposed design with single-grain-row-per-line pitch design for GPMR media

Fig. 2(a) The sidewall process and SEM image of 2.8 nm linewidth SiO2 lines on MTO (pitch= 32 nm). Fig. 2(b) shows 2 nm FePt grains deposited on 3 nm SiO2 lines