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August 15, 2008

Self-assembling polymer arrays improve data storage potential

In a collaborative effort between academic and industry, chemical and biological engineering professors Nealey and Juan de Pablo and other colleagues from the UW-Madison NSEC partnered with researchers from Hitachi Global Storage Technologies to test a promising new twist on the traditional computer memory and storage methods. In the Aug. 15 issue of the journal Science, the team demonstrates a patterning technology that may revolutionize the field, offering performance improvements over existing methods even while reducing the time and cost of manufacturing.

The technique has been used in a demonstration of terabit per square inch hard drives

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. The method could commercialized in a year or two for computer hardrives and higher densities are possible.

The method builds on existing approaches by combining the lithography techniques traditionally used to pattern microelectronics with novel self-assembling materials called block copolymers. When added to a lithographically patterned surface, the copolymers' long molecular chains spontaneously assemble into the designated arrangements.

"There's information encoded in the molecules that results in getting certain size and spacing of features with certain desirable properties," Nealey explains. "Thermodynamic driving forces make the structures more uniform in size and higher density than you can obtain with the traditional materials."




The block copolymers pattern the resulting array down to the molecular level, offering a precision unattainable by traditional lithography-based methods alone and even correcting irregularities in the underlying chemical pattern. Such nanoscale control also allows the researchers to create higher-resolution arrays capable of holding more information than those produced today.

In addition, the self-assembling block copolymers only need one-fourth as much patterning information as traditional materials to form the desired molecular architecture, making the process more efficient, Nealey says. "If you only have to pattern every fourth spot, you can write those patterns at a fraction of the time and expense," he says.

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