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Servo Integrated Patterned Media by Hybrid Directed Self-Assembly Shuaigang Xiao, Xiaomin Yang, Philip Steiner, Yautzong Hsu, Kim Lee, Koichi Wago, and David Kuo ACS Nano, Just Accepted Manuscript • DOI: 10.1021/nn505630t • Publication Date (Web): 07 Nov 2014 Downloaded from http://pubs.acs.org on November 11, 2014
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Servo Integrated Patterned Media by Hybrid Directed Self-Assembly Shuaigang Xiao,* Xiaomin Yang, Philip Steiner, Yautzong Hsu, Kim Lee, Koichi Wago, and David Kuo
Seagate Technology, Media Research Center, 47010 Kato Road, Fremont, California 94538, United States
*Address correspondence to
[email protected].
ABSTRACT A hybrid directed self-assembly approach is developed to fabricate unprecedented servo-integrated bit-patterned media templates, by combining sphere-forming block copolymers with 5 teradot/in2 resolution capability, nanoimprint and optical lithography with overlay control. Nanoimprint generates prepatterns with different dimensions in data field and servo field respectively, and optical lithography controls selective self-assembly process in either field. Two distinct directed self-assembly techniques, low-topography graphoepitaxy and high-topography graphoepitaxy, are elegantly integrated to create bit-patterned templates with flexible embedded servo information. Spinstand magnetic test at 1 teradot/in2 shows a low bit error rate of 10-2.43, indicating fully functioning bit-patterned media and great potential of this approach for fabricating future ultrahigh density magnetic storage media.
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KEYWORDS: block copolymer, directed self-assembly, overlay, servo integration, spinstand, bit-patterned media
In response to continuing digital data explosion, data storage media with ultrahigh density and low cost are thirsted for by enormous data centers nowadays. As a major supplier of storage solution, hard disk drive industry, is heavily investing several next-generation magnetic recording technologies beyond conventional perpendicular magnetic recording (PMR), such as heat-assisted magnetic recording (HAMR)1 and bit-patterned media (BPM).2 Both HAMR and BPM help retarding the appearance of an ultimate physic limit called as the superparamagnetic limit,3 relying on the improvement of recording media’s thermal stability via increasing either the anisotropy field or the effective volume of each magnetic grain. The first hurdle of obtaining high-density BPM is the generation of a master nanoimprint template, called as a BPM template in this paper, via lithography for high-volume manufacture of bit-patterned disks afterwards. The BPM template needs to start with a pattern density of 1 teradot/in2 (Tdpsi) at least so as to be competitive with PMR or HAMR, which is not trivial for current nanolithography society. Directed self-assembly (DSA), based on block copolymer materials, is deemed as one of the alternative nanolithography techniques for potential applications in nanoelectronics,4,5 nanophotonics,6 nanosensors7 and nanofluidics.8 In DSA, the combination of a high-χ (χ is the Flory-Huggins interaction parameter) block copolymer and commensurate prepatterns ensures both high resolution and good addressability, which is critical for applications with stringent requirements on pattern uniformity and feature placement accuracy, such as BPM. Depending on the driving force, DSA has been typically divided into three categories: chemoepitaxy,9-11 hightopography
graphoepitaxy
(HTG),12-15
and
low-topography
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graphoepitaxy
(LTG).16-18
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Chemoepitaxy is based on a prepattern with high chemical contrast mainly plus low topography contrast, i.e. the topography or feature height in the prepattern h
