Bit patterned media

Fig. 34—Bit pattern media (BPM) or self-ordered magnetic arrays.

Conventional Granular Media E Bit Patterned Media m Single-Grain -Per-Bit Patterned Media... 

Figure 13. FePt SOMA structure with 6.4 nm particles (from Fig. 9) and different media application scenarios. Case 1 conventional media the particles are randomly placed in relation to the bit transition case 2 bit-patterned media with several particles per bit allowing for bit-aspect ratio > 1 the bit transition is pre-located into the transition line between rows of particles case 3 single-particle-per-bit patterned media recording as case 2 but with bit-aspect ratio = 1. For 6.4 nm particle size a maximum density of 9 Tbit/in2 is estimated. If the particle size is reduced to 3 nm, 40-50 Tbit/in2 could be possible.

Nishida, T., Matsumoto, T., Akagi, F., Hieda, H., Kikitsu, A, Naito, K. (2007). Hybrid recording on bit-patterned media using a near-field optical head. Journal of Nanophotonics, Vol. 1, 011597,2007... 

Xb in this case is always less than one and the conclusion expressed by Eq. (9) is straightforward. The typical system that does show this behavior is AuCu alloy. However, the systems that obey a nonideal solution model are more common, and the typical examples of these alloys are CoPt, FePt, CoPd, and FePd. Because of their high magnetic anisotropy introduced by incorporation of Pt, or Pd in to Co hep or Fe bcc lattice and ordering (LIO phase ) these alloys are studied intensively in the past several years as possible candidates for the bit pattern media application as well as MEMS and NEMS technologies. 

Finally, some other companies (Toshiba, Hitachi) have reported the fabrication of UV-NILtools, but for internal use and especially developed for microelectronic or bit-patterned media applications [36, 37]. 

Directed self-assembly shows promise in advanced lithography and a variety of other applications that have less complex requirements. For example, directed self-assembly could be used for enhancing etch selectivity, placing dopants in ordered arrays, or generating high-density, close-packed electrodes in capacitor arrays [6]. Additionally, the assembled nanostructures could be used for fabricating densely packed porous templates [12-14] or membranes [15, 16] at the nanoscale. Other potential applications of assembled block copolymer thin films include the fabrication of MOSFETs (metal-oxide-semiconductor field-effect transistors) [17], quantum dots [18], high surface area devices [19, 20], photovoltaic devices [21], and bit patterned media [22-24]. 

As discussed previously, vertically oriented cylinders are preferred for many applications in lithography, such as the patterning of vias, contact holes, or bit-patterned media. If neither block in the block copolymer is preferentially attracted to the substrate, the microdomains... 

There are of course some problems associated with the use of block copolymers for bit-patterned media. The first lies with the traditionally used block copolymer for most studies to date, PS-fc-PMMA. The relatively weak segregation strength of PS-( -PMMA (x = 0.06) (Russell etfll., 1990) means that an Lq of 20nm (Mn 30000g/mol) is the smallest critical dimension possible before the polymer will fail the condition > 10.5, meaning the polymer... 

There are also compatibility issues between the lattice geometries of block copolymers and the magnetic arrays that are typically used for bit-patterned media. Considerable amounts of money in the semiconductor industry have been spent on circuit design software and fabrication... 

Yang, X., Wan, L. et al. (2010) Directed block copolymer assembly versus electron beam lithography for bit-patterned media with areal density of 1 terabit/inch and beyond. ACS Nano, 3,1844. 

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