Plenary Speakers

Patterning with Polymers and Plasmons

Jillian Buriak, Ph.D.

The semiconductor industry uses the term directed self-assembly, or DSA, in the International Technology Roadmap for Semiconductors (ITRS) to describe the use of self-assembly of block copolymers to generate nanopatterns on semiconductor surfaces as a cost-effective approach for nanolithography on silicon. Typically, the various approaches to nanopatterning of surfaces, including silicon, are broken into two major classes: top-down methods such as photolithography, e-beam lithography and scanning force microscopy variants, and bottom-up synthetic techniques, including self-assembly. Since lithography is the single most expensive step in computer chip manufacturing, the use of self-assembled block copolymers (BCPs) templates on surfaces via DSA is being seriously considered for the patterning of sub-20 nm features on a semiconductor surface. Here, we will describe the remarkable versatility of using BCPs, polymers that contain sufficient chemical information to form highly ordered templates over large areas. These templates, which range from arrays of parallel lines, to dots, to much more complex Moir√© superlattice patterns, can be converted into functional materials, such as metal nanostructures, molecules-on-graphene, and plasmonic stamps. Here we will show how BCP nanopatterns can be converted into plasmonically active ‘stamps’ that drive chemical reactions on a silicon surface. Gold nanopatterns derived from self-assembled BCPs were incorporated into flexible and optically transparent stamps, and coated with a molecular ‘ink’. Upon illumination of the stamp with low intensity light that corresponds to the absorption maximum of the gold plasmons, a dramatic increase of the local electric field of the localized surface plasmon resonance of the gold embedded within the stamp generates electron-hole pairs in the nearby silicon, driving surface reactivity (the ‘stamping’ step). In this case, the chemistry is hydrosilylation between an alkene/alkyne and surface silicon-hydride bonds, leading to nanopatterned attachment of organic molecules on the silicon surface.