Determination of Position Jitter and Dot-Size Fluctuations in Patterned Arrays Fabricated by the Directed Self-Assembly of Gold Nanoparticles

The promise of magnetic bit-patterned media (BPM) in the hard disk drive industry hinges on its capability to extend the data storage density beyond that achievable by conventional continuous media. Its success, however, depends strongly on meeting the jitter and throughput requirements of BPM with a suitable fabrication process. In this paper, we report on the directed self-assembly of gold nanoparticles using a topographical template as an approach to fulfill the BPM fabrication requirements. The effects of position jitter and dot-size fluctuations are examined by performing image analysis on scanning electron microscopies of samples fabricated with areal densities of 4.4 Tdot/in². For comparison, we considered three different cases: electron-beam lithography-defined templates, monolayer films of self-assembled nanoparticles on an unpatterned substrate, and nanoparticles directed to assemble within a template. Our analysis provides evidence for the improvements in position jitter of the directed assembly of nanoparticles over those that were left to assemble without a template.

I. Introduction

The continuous evolution of magnetic recording density toward 10 has involved many enabling technologies in hard disk drive (HDD) fabrication, such as perpendicular magnetic recording [1] and heat-assisted magnetic recording [2], to name a few. As we approach the superparamagnetic limit, further increase in the storage density might require the transition from granular continuous media to bit-patterned media (BPM) [3]. The latter consists of periodically ordered arrays of individual magnetic islands physically defined by patterning techniques, where each bit of information will be stored in a single magnetic island [4]. However, the fabrication of BPM faces many challenges: in addition to problems of high cost and low throughput, there are currently few methods that are able to meet the lithographic resolution requirements for patterning at such high densities. Therefore, to keep up with the evolution of the storage density, new patterning approaches are needed.