Imprint lithography template technology for bit patterned media (BPM)

Abstract

Bit patterned media (BPM) for magnetic recording has emerged as a promising technology to deliver thermally stable magnetic storage at densities beyond 1Tb/in 2 . Insertion of BPM into hard disk drives will require the introduction of nanoimprint lithography and other nanofabrication processes for the first time. In this work, we focus on nanoimprint and nanofabrication challenges that are being overcome in order to produce patterned media.Patterned media has created the need for new tools and processes, such as an advanced rotary e-beam lithography tool and block copolymer integration. The integration of block copolymer is through the use of a chemical contrast pattern on the substrate which guides the alignment of di-block copolymers.Most of the work on directed self assembly for patterned media applications has, until recently, concentrated on the formation of circular dot patterns in a hexagonal close packed lattice. However, interactions between the read head and media favor a bit aspect ratio (BAR) greater than one. This design constraint has motivated new approaches for using self-assembly to create suitable high-BAR master patterns and has implications for template fabrication.

Thin Film Self-Assembly of Poly(trimethylsilylstyrene-b-d,l-lactide) with Sub-10 nm Domains

“…The fundamental resolution limit of 193 nm optical immersion lithography has been reached that has driven a large, worldwide effort directed toward development of new technologies that enable patterning of sub-32 nm features . Several candidates, including extreme ultraviolet (EUV) lithography, electron beam lithography, nanoimprint lithography, and others, are being pursued, but no single solution has emerged. An attractive hybrid approach for achieving sub-32 nm patterning extends conventional lithography limits by using larger patterns, resolved by conventional lithography, as guides for directed self-assembly (DSA) , of block copolymers, thereby multiplying the pitch of gratings or shrinking the size of contact holes …”

Nanoimprint lithography: 2D or not 2D? A review

“…Many of the NIL applications which were first published were essentially 2D, i.e., applications which could have also been performed by other photon or electron-based lithography, but needed cost-effective solutions for which other current high-resolution lithography would not have been reasonable. The manufacturing of such devices, patterned magnetic media [123][124][125][126], wire grid polarizers [127][128][129][130] and high-brightness light emitting diodes (LED)…”

Transfer of self-aligned spacer patterns for single-digit nanofabrication

“…Lithographically directed self-assembly (DSA) of block copolymers (BCPs), in which the BCPs multiply feature density of and rectify defects in lithographically defined topographical [4,5] and chemical surface patterns [6][7][8][9], is a promising method to fabricate nanoimprint lithography master templates with the registered, highly uniform, sub-10 nm feature dimensions demanded by BPM. While considerable effort has been devoted to the creation of hexagonally packed 'dot' patterns for BPM using BCPs exhibiting cylindrical or spherical self-assembled morphologies [1,7,10], rectangular bit islands are more closely aligned with traditional servo system implementation and may be more compatible with wider read or write heads [11][12][13]. Previously, we demonstrated the creation of rectangular bit island master templates through a sequential double-imprint 'line-cutting' process involving two submaster templates with lines patterned using rotary-stage electron beam lithography and DSA of lamellae-forming polystyrene-b-poly(methyl methacrylate) (PS-PMMA) along circumferential and radial directions, respectively [14].…”