Improved PDMS mold fabrication by direct etch with nanosphere self-assembly mask for Soft UV-NIL subwavelength metasurfaces fabrication

Abstract

With the increased relevance of metasurface for optical applications, a fabrication method that allows for both large surface and 100 nm range dimensions at a low cost is required for their development. Due to its high throughput and small structuration capabilities, Soft Nanoimprint Lithography is a good canditate as fabrication method for these type of devices. But its application for metasurfaces at visible wavelengths has been hindered by the necessity to use low-viscosity PDMS in order to reach the dimensions required, making the final stamp more fragile and the process more expensive. Here we propose a PDMS mold fabrication method which relies on self-assembly masking of the PDMS followed by direct etching of the mold, decorrelating the minimum dimension attainable from the PDMS viscosity. We characterize a metasurface fabricated using a mold obtained with our method validating its use for nanofabrication of large surface devices.