Self-assembled PS-PMMA nanodot array pattern arranged in a parallelogram guide
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0901-Ra05-05-Rb05-05.1
Self-assembled PS-PMMA nanodot array pattern arranged in a parallelogram guide Kaori Kimura and Masatoshi Sakurai Corporate Research & Development Center, Toshiba Corporation 1, Komukai Toshiba-cho, Saiwai-ku, Kawasaki 210-8582, Japan [email protected] Tel: +81-44-549-2381, Fax: +81-44-520-1802
ABSTRACT Mask patterns for XY-type magnetic patterned media using phase separation of polystyrene-polymethylmethacrylate (PS-PMMA) block copolymer were fabricated. Parallelogram guides molded by the nanoimprint lithography controlled the PS-PMMA self-assembling pattern that formed in the guide area. 45nm-pitch defect-free PS-PMMA dot patterns were obtained within a 1µm x 1µm area by optimizing the PS-PMMA film thickness.
INTRODUCTION Recording density of the hard disc drive is required to reach 1 Tera bit per square inch (Tbpsi). Patterned media has attracted much interest as a candidate for high-density recording media [1-4]. When the recording density surpasses 1Tbpsi, the size of each recording bit should be less than 27nm. Several patterning methods for fabricating such a small magnetic pattern has been presented using anodized alumina substrate [5], polystyrene particle masks [6], and block copolymers mask [7,8,12]. We proposed an Artificially Assisted Self-Assembling (AASA) method as an alternative low-cost and large-area nanopatterning method for the patterned media [9, 10]. In this method, self-assembled dot pattern made by a phase separation of PS-PMMA block copolymer was aligned in circular groove guides which was molded on the resist layer by nanoimprint lithography [12]. The block copolymer dot pattern was used as a mask for etching magnetic thin film. We also demonstrated a mask pattern for an XY type patterned media with rectangular and triangle guides. Fabrication process is shown in figure 1 [13, 14]. (a)
(b)
(c)
Figure 1. Fabrication process of patterned media by AASA method. (a) Imprint the guide groove on the resist layer. (b) Form the separated structure of block copolymer in the groove guide. (c) Etch magnetic film into nanodots etched using block copolymer dots as an etching mask.
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In our previous report, self-assembling dot patterns were controlled by simple groove guides [9, 10]. However these patterns were not suitable for the etching mask of patterned media, because several defects appeared in the relatively long groove guides. Read/write heads can access every dot accurately if the dots are self-assembled in a complete positioned arrangement without any defect along to the suitable guide structure [13-14]. In this report, parallelogram guides with 60º and 120º corners are applied for obtaining single domain self-assembled mask pattern of block copolymer dots.
EXPERIMENTAL Block copolymer of polystyrene-polymethylmethacrylate (PS-PMMA) with a molecular weight of 89,300(PS: 74,300 and PMMA: 15,000) was used for self-assembling periodic mask material. Figure 2 shows AFM phase image of the surface of phase separated PS-PMMA film on flat Si
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