Nanoporous membrane production via block copolymer lithography for high heat dissipation systems

We demonstrate the first steps towards realizing a highly effective hardmask fabrication technique for producing cheap low defect nanoporous membranes, which can be incorporated as fluidic wicking structures for use in evaporative cooling solutions integrated at device level. Next-generation cooling solutions are becoming necessary to dissipate increasing heat fluxes and maintain acceptable junction temperatures in high-speed electronics. The proposed pumpless two-phase evaporation-based heat sink device relies on a supported nanoporous membrane (SNM) as the driving mechanism for generating the requisite capillarity for pumping low surface tension refrigerants. Molecular self-assembling block copolymers (BCPs), specifically cylindrical forming poly(styrene)-block-poly(4-vinyl-pyridine) (PS-b-P4VP) are ideal as a cost effective hardmask fabrication route for patterning sub 80 nm pores when compared to the high cost of ownership of state of the art immersion photolithography. We report on the pattern formation of the phase segregated BCP with optimization of the annealing parameters. The work addresses defect elimination in the BCP template by developing a custom solvothermal annealing chamber which achieves excellent phase segregation of the BCP, limits processing defects and prevents polymer dewetting on a microscale level. The chamber is capable of processing up to 4 inch wafers and allows for in-situ monitoring of a solvent annealing cycle by monitoring film swelling via optical reflectometry.