Heat-depolymerizable polycarbonates as electron beam patternable sacrificial layers for nanofluidics

This research investigates a heat-depolymerizable polycarbonate (HDP) for use as a sacrificial layer in fabricating nanofluidic devices by electron beam lithography. When solid HDP films are heated to 300 degreesC, the monomer units separate into a nontoxic vapor. This property suggests that a patterned HDP film may be used as a temporary support for another film which is stable at the depolymerization temperature. Heating the structure removes the HDP, leaving a network of nanofluidic tubes without the use of solvents or other chemicals as required in most other sacrificial layer processes. We found that HDP films may be patterned directly by electron beam lithography, followed by immersion in isopropanol to remove HDP from the exposed areas. The patterns are then sputter coated with silicon dioxide at low temperature, provided with access holes for venting, heated to clear out HDP remaining inside the tubes, and injected with fluorescent dye for observation. Tube dimensions of 140 nm height, 1 mum width, and 1 mm length are reported, and fabrication of other structures is discussed. (C) 2001 American Vacuum Society.