Non-Equilibrium Processing of Block Copolymer Directed Self-Assembled Polymer-Inorganic Hybrid Materials

Transient laser annealing/heating is a process well-established in the microelectronics industry. While initially developed for doping of smaller and smaller nanostructures, in the last decade or so this non-equilibrium approach has seen tremendous growth in areas well beyond this initial application. This is due to the realization that limiting thermal heating to small time scales all the way down to the nanosecond regime allows reaching temperature levels well beyond traditional equilibrium thermal stability limits, in particular for organic/polymeric materials. This talk will report on progress achieved in this area at Cornell over the last decade or so, suggesting substantial possible innovations in directed self-assembly for next generation nanomanufacturing. The first part will discuss achievable increases of thermal stability limits of polymeric materials by hundreds of degrees under transient laser annealing/heating processing conditions. This will set the stage for experiments employing thermal processing windows never-before accessed with such organic materials. Experiments will then be discussed describing the formation of block copolymer self-assembly directed semiconductor and metallic single-crystal homo-and heteroepitaxial nanostructures on silicon substrates. This will be followed by the report on experiments in which two transient laser annealing processes are employed in series. The first generates mesoporous organic/polymeric templates from all-organic block copolymer self-assembly directed hybrids with the help of a CO₂ laser (wavelength: 10.6 microns). After sputtering of amorphous silicon into the pores of the resulting mesoporous thin films, transient laser annealing with nanosecond pulses of an excimer laser (wavelength: 308 nm) allows use of the organic material as a template for liquid silicon (melting temperature above 1000 degrees Celsius!) infiltration and conformal pore space filling. Subsequent removal of the template finally leads to crystalline silicon nanostructures that are the negative of the original organic template structure. The final part of the talk will describe transient laser annealing processes which enable combination of the nanostructure control exemplified in the earlier experiments with additional chemical conversion reactions in various chemical environments. This work suggests entirely new processing paradigms in materials patterning interesting for next-generation semiconductor applications and beyond.