PORTLAND, Ore. A demonstration of terabit-per-square-inch densities for hard-disk media used self-assembling block co-polymers to perform "density multiplication."
The technique, demonstrated by researchers from Hitachi Global Storage Technologies (San Jose, Calif.) and the University of Wisconsin in Madison, used current lithographic tools to pattern magnetic domains for a 250-megabit disk. A self-assembling block co-polymer was then added to divide each track into fourths, resulting in terabit-per-inch2 densities.
"The demonstration that we've done so far is at a terabit per inch squared. But the really revolutionary aspect of the work is that you don't have to pattern every domain, you only have to pattern every fouth one," said UW professor Paul Nealey, director of its Nanoscale Science and Engineering Center (NSEC). "We call it 'interpolation,' or 'density multiplication'."
According to Nealey, the block co-polymer not only multiplies lithographically-patterned densities by a factor of four, it also cleans up defects that plague current high-resolution lithography, including line roughness and uniformity.
The technique combines the best aspects of lithography with self-assembling materials, said Nealey. "There is information encoded in the [block co-polymer] materials themselves that yields lower lineage roughness, greater uniformity in the features that are assembled and enhanced resolution."
Next, the researchers will assemble and test hard-disk media at Hitachi that will be patterned at 1 terabit per inch2. They will also seek to expand capacity beyond that benchmark.
The University of Wisconsin researchers also plan to use similar block co-polymer materials to perform density multiplication in the patterning of memory arrays and other periodic structures on semiconductors.
Funding for the joint research was provided by the NSEC, the National Science Foundation, Hitachi Global Storage Technologies and Semiconductor Research Corp.
Other researchers are also experimenting with block co-polymers to pattern more complicated structures compared to the concentric circles of hard-disk media. For instance, the Massachusetts Institute of Technology is using electron-beam lithography to etch patterns that act as templates. In this approach, self-assembling block co-polymer fill in the finest details.