Laser direct write system for fabricating seamless roll-to-roll lithography tools

Implementations of roll to roll contact lithography require new approaches towards manufacturing tooling, including stamps for roll to roll nanoimprint lithography (NIL) and soft lithography. Suitable roll based tools must have seamless micro- or nano-scale patterns and must be scalable to roll widths of one meter. The authors have developed a new centrifugal stamp casting process that can produce uniform cylindrical polymer stamps in a scalable manner. The pattern on the resulting polymer tool is replicated against a corresponding master pattern on the inner diameter of a centrifuge drum. This master pattern is created in photoresist using a UV laser direct write system. This paper discusses the design and implementation of a laser direct write system targeting the internal diameter of a rotating drum. The design uses flying optics to focus a laser beam along the axis of the centrifuge drum and to redirect the beam towards the drum surface. Experimental patterning results show uniform coatings of negative photoresist in the centrifuge drum that are effectively patterned with a 405 nm laser diode. Seamless patterns are shown to be replicated in a 50 mm diameter, 60 mm long cylindrical stamp made from polydimethylsiloxane (PDMS). Direct write results show gratings with line widths of 10 microns in negative photoresist. Using an FPGA, the laser can be accurately timed against the centrifuge encoder to create complex patterns.