Berggren, team beat microchip size barrier with novel self-assembly design

August 15, 2008

Berggren and team make self-assembly possible of a thin film of a spherical-morphology block copolymer is templated using an array of nanoscale topographical elements that act as surrogates for the minority domains of the block copolymer.

As reported by the MIT News Office, and in the journal Science, Karl Berggren, the Emmanuel E. Landsman Associate Professor of Electrical Engineering in MIT's Department of Electrical Engineering and Computer Science and principal investigator in the Research Laboratory of Electronics, working with Edwin L. Thomas, Morris Cohen Professor of Materials Science and Engineering and head of that department, have developed a novel system based on molecules that can assemble themselves into precise patterns to significantly improve data-storage media and electronic microchip capacities.

The self-assembling molecular systems, called block copolymers, have been around for years, but the well-ordered patterns they produced covered only small areas. Berggren and his colleagues found a way to combine the copolymer self-assembly with conventional lithographic chip-making technology such that the lighographic patterns act as 'anchors' to hold the structure in place, while the self-assembling molecules fill in an ordered way around these pillars. Variablity in placement of the pillars on the chip surface will make it possible to control the size and spacing. The pillars themselves are placed on the surface using advanced high-resolution electron-beam lithography, methods that have also been developed at MIT.

Caroline Ross, Toyota Professor in MIT's Department of Materials Science and Engineering and the third MIT faculty member involved in the project described how the molecules, made from a pair of polymer chains that are chemically different and unable to mix with each other, form patterns of tiny balls, roughly 20 nanometers across when spread on a surface. The shorter the molecular chains used, the smaller the possible resulting structures can be made.

Berggren projects, "Ultimately, this is a technology that is very high-resolution and very scalable." In the future, entire computer chips and a complete self-assembling chip structure can be made using this technology. It could also be used for other kinds of devices, including energy technology applications such as electrodes for fuel cells.

The original inspiration for the litho-pillars came from MIT graduate student Ion Bita, now working for Qualcomm in California. Two current MIT graduate students, Joel Yang and Yeon Sik Jung also worked on the project. Funding came from the National Science Foundation, the Semiconductor Research Corp., the Nanoelectronics Research Initiative, King Abdulaziz City for Science and Technology and Alfaisal University, and the Singapore-MIT Alliance.