Method for making a master mold with high bit-aspect-ratio for nanoimprinting patterned magnetic recording disks, master mold made by the method, and disk imprinted by the master mold
View Patent ↗A method for making a master mold to be used for nanoimprinting patterned-media magnetic recording disks results in a master mold having topographic pillars arranged in a pattern of annular bands of concentric rings. The ratio of circumferential density of the pillars to the radial density of the concentric rings in a band is greater than 1. The method uses sidewall lithography to first form a pattern of generally radially-directed pairs of parallel lines on the master mold substrate, with the lines being grouped into annular zones or bands. The sidewall lithography process can be repeated, resulting in a doubling of the number of lines each time the process is repeated. Conventional lithography is used to form concentric rings over the radially-directed pairs of parallel lines. After etching and resist removal, the master mold has pillars arranged in circular rings, with the rings grouped into annular bands. The master mold may be used to nanoimprint the disks, resulting in disks having a BAR greater than 1, wherein BAR is the ratio of data track spacing in the radial direction to the data island spacing in the circumferential direction.
1. A patterned-media magnetic recording disk comprising:
a substrate having a plurality of magnetic islands arranged about a center point, the islands being arranged into a plurality of annular bands of concentric circular tracks about said center point, the islands in each band being arranged into a plurality of generally radially-directed non-parallel pairs of parallel lines wherein the islands in the parallel lines in each pair are equally circumferentially spaced in all tracks of a band, the pairs of lines being generally equally angularly spaced about said center point, wherein the ratio of radial spacing of the concentric tracks to the circumferential spacing of the islands is the bit-aspect-ratio (BAR) and is greater than 1.
2. The disk of claim 1 wherein the islands in a circular track generally at the middle of each band are generally equally angularly spaced about said track.
3. The disk of claim 1 wherein the radially inner ends of the pairs of lines have the same equal angular spacing about said center as the radially outer ends of the pairs of lines.
4. The disk of claim 1 wherein each pair of lines is aligned along a radius from said center.
5. The disk of claim 1 wherein each pair of lines has a generally arcuate shape.