Phase Shift Mask Fabrication by Laser Microlens Array Lithography for Periodic Nanostructures Patterning

Laser microlens array (MLA) lithography was used to fabricate arbitrary periodic array of patterns on photoresist. Reactive ion etching (RIE) was then utilized to etch and transfer the patterns down to the fused silica substrate. By controlling the etching process, the etched surface was 180° out of phase with the unetched surface. Subsequently, the patterns were used as a phase shift mask for UV exposure. Destructive interference occurred at the edges of the phase shift structures, resulting in regions of low light intensities at the edges. It formed periodic array of smaller patterns on the unexposed photoresist, with feature sizes around 290 nm. Simulation verified the experimental result.