Directed Self‐Assembly of Block Copolymer for Bit Patterned Media with Areal Density of 1.5 Teradot/Inch² and Beyond

Abstract

Directed self-assembly (DSA) of block copolymer (BCP) holds great promise for many applications in nanolithography, including the next generation magnetic recording. In this work, directed self-assembly of block copolymer technique has been combined with rotary stage electron beam mastering to fabricate a circular full track nanoimprint template for bit patterned media (BPM) fabrication. In order to meet specific requirements in pattern structure and format between the data and the servo zone in a servo-integrated template, three types of lithographically defined prepatterns, (1) two-dimensional chemical pre-pattern, (2) twodimensional low-topographic pre-pattern, and (3) one-dimensional high-topographic pre-pattern, have been explored for DSA process with two types of commercially available BCP thin film materials: cylinder-forming poly(styrene-b-methyl methacrylate) (PS-b-PMMA) and sphere-forming poly(styrene-b-dimethylsiloxane) (PS-b-PDMS). All guided BCP patterns exhibit highly ordered hexagonal close-packed (hcp) structures with high pattern quality. Using these BCP patterns, two polarities of dots-array templates (hole-tone and pillar-tone) with integrated servo patterns have been fabricated on a fused silica substrate at a density greater than 1.0 Td/in 2. Furthermore, the fabricated master template has been used for UV-cure nanoimprint lithography process development on 2.5 inch disk size media. Good pattern uniformity in imprint resist has been achieved over an entire 2.4 mm wide band area. The imprint resist patterns have been further transferred into underlying CoCrPt media by ion beam etching. Evidently, for the first time, the patterned CoCrPt alloy dots (hcp pattern) have successfully been demonstrated at a high density of 1.5 Td/in 2 (pitch = 22.3 nm) for a guided media (≅ 7 kOe) and 3.2 Td/in 2 (pitch = 15.2 nm) for an unguided media (≅ 5 kOe).

Fabrication of servo-integrated template for 1.5 Teradot/inch2bit patterned media with block copolymer directed assembly

“…14, 16 Once the first DSA process in the data zone is completed, the BCP patterns are subsequently transferred into the underlying quartz substrate through a Cr hard mask layer to form pillar-tone quartz dots in the data zone. A similar processing flow can be applied to the servo zone.…”

“…One approach is to form hexagonal BPM by using either cylinder-forming PS-b-PMMA (Refs. [10][11][12][13] or sphere-forming PS-b-PDMS, [14][15][16][17] and the other approach is to form rectangular BPM by using lamellae-forming PS-b-PMMA. 18,19 However, most of these fabrication works previously reported focused on the data zone demonstration, including an all-dots template fabrication, imprint lithography, and magnetic dots formation.…”

Writing Field Analysis for Shingled Bit-Patterned Magnetic Recording

“…And the media characteristics should be considered due to the increasing complexity of the microstructure of the BPM. Research efforts focusing on writing heads [12][13][14][15] or BPM [16][17][18] have been extensive. However, their interdependence and the resulting effects on the writing performance, especially considering the magnetic field distribution around the shingled writing corner, have hardly been addressed, partly due to the complex nature of the problem.…”

Large‐Area Resonance‐Tuned Metasurfaces for On‐Demand Enhanced Spectroscopy

“…NIL has been employed for nanofabrication of electronic and photonic structures [15] and for parallel production of a large number of functional elements [16]. Even high-density nanostructures more than a teradot/inch 2 have been successfully produced [17,18].…”