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) two‐dimensional 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/in2. 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/in2 (pitch = 22.3 nm) for a guided media (Hc≅7 kOe) and 3.2 Td/in2 (pitch=15.2 nm) for an unguided media (Hc≅5 kOe).
Highlights
An ever-increasing demand for higher capacity information storage is forcing the magnetic storage industry to develop alternative technologies to the currently adopted perpendicular magnetic recording
We have demonstrated several key bit patterned media (BPM) challenging processes based on DAS approach, including the following: (1) fabricating two polarities of block copolymer (BCP) dots-array fused silica templates with servo features integrated; (2) developing the UV-cure nanoimprint lithography process on standard 2.5 inch disk size media; (3) developing the pattern transfer process to form the nanoscale magnetic dots array
Several prepattern approaches for Directed self-assembly (DSA) have been explored for fabrication of the high-density BPM master template
Summary
An ever-increasing demand for higher capacity information storage is forcing the magnetic storage industry to develop alternative technologies to the currently adopted perpendicular magnetic recording. One of the leading technological candidates for extending current perpendicular magnetic recording beyond 1 Teradot per square inch (Td/in2) is the bit patterned media (BPM) technology, in which magnetic nanoarrays are fabricated and each “island” in the array forms a separate recording bit at a sub-25 nm length scale [1–3]. BPM applications present extreme challenges to today’s lithography capability because of the small feature size and the tight spacing tolerance requirements. High-resolution BPM dots-array patterning up to ∼4.5 Td/in[2] has been previously demonstrated using direct e-beam writing [6, 7], it still remains very challenging to achieve a defect-free dense dotsarray pattern over a full disk size area by only using the conventional e-beam lithography approach even for a master template fabrication. Using ZEP520 e-beam resist, it would take more than a week to write a full 2.5 inch master template at a density
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