High-Throughput Wafer-Scale Wrinkle Patterning: a Single-Step Fabrication Process and Applications for Tunable Optical Transmittance

The engineering of wrinkled surfaces has attracted enormous research interest, especially for optical applications. However, the standard fabrication processes rely on the routine with skin-layer generations and controlled mechanical deformations, which are normally performed separately with dedicated equipment, limiting the possibility for large-scale practical applications. In this work, we have developed an effective fabrication strategy to pattern wafer-scale wrinkles on photoresists. By performing a fluorine-based plasma treatment, skin layers can be generated and thermal stress is induced simultaneously, due to the limited heat dissipation from substrates. Uniform wrinkling across the wafer is achieved with a few seconds of plasma processing, and the morphology of wrinkles has been investigated in terms of the photoresist thickness, ion energies, and process times. The wrinkled resists can be transferred to silica substrates for quasi-random SiO2 gratings, leading to tunable optical transmittances depending on the filling ratio. An application for reversible optical transmittance is also demonstrated, when organic solvents are applied to reduce the scattering losses on the grating surfaces. We believe our technique can pave the way toward high-throughput CMOS-compatible fabrication of wrinkle-based devices, which can be interesting for various fields due to their unique quasi-random surface morphology.