Magnetic Bit Patterned Media Fabrication Using Block Copolymer Directed Assembly

Perpendicular magnetic recording media in excess of 1Tbit/in² faces thermal stability and/or writeability challenges that are currently driving intense research in alternative technologies. Bit patterned media (BPM), in which magnetic bits are lithographically patterned as individual islands, stands as a promising technology for thermally stable, writable media. One of the main challenges of BPM lies in its lithographic specifications which push dimensions beyond those established for the conventional semiconductor industry roadmap. The most promising solution to the lithographic challenge can be found in directed self assembly of block copolymer films which has recently evolved as a viable technique to achieve sub-20nm lithography in time for BPM technology.

The periodic features naturally formed in block copolymer films display superior size uniformity at ultra-high densities, making them ideal lithographic masks to define the highly periodic data bits in the data sectors of hard disk drives for bit patterned media (BPM) technology at densities beyond 1Tbit/in².  Nanofabrication challenges towards bit patterned media, however, reach far beyond pattern formation at small length scales. The challenges faced in the fabrication of templates for BPM have spurred a set of important innovations in nanofabrication techniques such as the formation of geometries that deviate from the typical shapes naturally formed by block copolymers, as well as advances in high-fidelity pattern transfer and progress in scalability towards higher feature densities. In this presentation, we discuss some of these innovations. We demonstrate a process that combines directed self assembly with nanoimprint lithography to achieve rectangular patterns mounted on circular tracks. We will also discuss the impact of the nanofabrication process on the magnetic performance of the magnetic islands and the outlook for BPM technology. We will also explore additional innovations in nanofabrication techniques made possible by block copolymer lithography including opportunities in electroplating using self assembled masks.