The hard disk industry has done a remarkable job over the past 50 years increasing the areal density by an average of over 40% per year while maintaining extraordinarily low costs. This has been accomplished by reducing the grain size and the size of the thin film read/write head. As grain size continued to shrink, bits begin to randomly “flip” as a consequence of temperature; this is known as the superparamagnetic effect.
The practical limitations of the superparamagnetic effect can be avoided by patterning the boundaries between the magnetic domains; hence the term “patterned media”. Patterning the magnetic material creates magnetic switching volumes with highly uniform size and shape, which can greatly facilitate the reading and writing of bits. Because the magnetic switching volume is defined lithographically – and not by the random grain structure of the deposited film – it is possible to robustly address the magnetization of a single magnetic grain.
The introduction of patterned media technology into manufacturing is expected to enable the next generation of hard disk drives with storage density exceeding ten trillion bits per square inch (1 Tb/in2). Realization of this technology transition requires industrial-scale lithography at unprecedented levels of feature resolution, pattern precision, and cost efficiency.
