Bit Patterned Media at 1 Tdot/in2 and Beyond

Bit patterned media (BPM) provide an alternative to conventional granular thin film recording media, circumventing the challenges of managing grain size and its associated noise and thermal stability issues in granular media. A viable fabrication strategy involves creation of a master pattern by rotary-stage e-beam lithography and directed self-assembly of block copolymers, followed by pattern replication via UV-cure nanoimprint lithography and pattern transfer to a magnetic thin film by ion beam etching. These steps have been demonstrated for 150 Gdot/cm² (1 Tdot/in²) hcp patterns, achieving a dot placement tolerance of 1.2 nm 1σ and a defect rate of <; 10^-3. Media samples fabricated in this manner from continuous CoCrPt alloy films have achieved a 1σ switching field distribution of 4% of H_c. A 2T medium SNR of nearly 14 dB and a write bit error rate of 2 × 10^-3 have been shown using a static tester with a conventional product read/write head. Modeling and experiment suggest that higher recording density can be achieved using BPM with a bit aspect ratio (BAR) >; 1. A master pattern generation generation strategy for BAR>; 1 with rectangular islands is shown using intersecting lines generated by directed self-assembly of lamellar block copolymers in combination with spacer-defined line doubling.