S. Furst, N. Miller
Smart Material Solutions, Inc.,
Keywords: nanopatterning, roll-to-roll imprinting. drum mold, mastering, nanophotonics, metamaterials, plasmonics
Summary:This paper presents a new, high-speed method to fabricate nanopatterned master molds for roll-to-roll or plate-to-plate nano-imprint lithography. The patented process, known as “nanocoining,” uses mechanical indenting to create vast arrays of sub-wavelength features seamlessly into the outer diameter of a metal drum, with a coverage rate of more than 1 square inch per minute – 500x faster than e-beam lithography. Such nanostructured surfaces can have unique optical and wetting properties to be applied to a variety of commercial products including OLEDs, biosensors, wire-grid polarizers, solar panels, and AR/VR optics. Nanocoining is a two-step process. First, a focused ion beam (FIB) mills the nanofeatures into the flattened tip of a single crystal diamond die over a ~200 μm2 area. Then, the die is mounted to an ultrasonic resonant beam actuator that indents the nanostructured die into a rotating metal drum 45,000 times per second. Presently, the nanocoining process is able to replicate nanofeatures down to 150 nm pitch, microfeatures up to several microns, and hierarchical features (nanofeatures on top of microfeatures). Patterns can be generated on a periodic, arbitrary, and stochastic grid. Smart Material Solutions’ (SMS’s) current pilot line is capable of making molds up to 150 mm in diameter and 150 mm long from materials including nickel-phosphorous, electro-formed copper, 110 copper, brass, and aluminum. The design, fabrication, and most recent results SMS’s new nanocoining pilot system will be presented. The pilot system, designed by SMS and fabricated in partnership with Aerotech, Inc. and Professional Instruments, Inc., is a multifunctional diamond-turning lathe and indenting that is capable of producing seamless cylindrical drum molds for roll-to-roll processes or foil shims that can be flattened or wrapped around a drum. The work also addresses recent developments in the nanofabrication of the diamond dies that are used as indenting tools in the process. Improved FIB milling of diamond has resulted in nanopillars with pitches as small as 150 nm and gratings with spacings as small as 140 nm. Finally, SMS will present preliminary results of plastic films replicated from the indented metal molds, showing a broadband increase in transmission caused by the motheye effect.