Development Of DMD-based Micro-lithography System And Adapted To Photo-patterning In Liquid Crystal Alignments

We design and develop a DMD-based micro lithography system with optical design theory. We obtain arbitrary patterns with high resolution on photoresist by applying this system to the exposure process.Exist mask photo-lithography (μL) techniques, including contact-lithography and step projection-lithography, are limited from the high cost of the mask, and difficult to fabricate the stero structure. Conventional scanning lithography doesn’t need a mask and can reach a high resolution but lack of efficiency. The rapid development of MEMS (Micro-Electro-Mechanical System) enables the DMD based micro-lithography technique, which offers a novel approach to fabricate arbitrary structures and has the capability for complex3D micro structure fabrication.In this work, a projection lens with a double-telecentric structure is designed with ZEMAXTM software. To develop DMD-based projection μL system, the design for the optical system is accomplished by dividing an illumination and image-formation part. The key component of this system is a dynamic mask which can generate arbitrary pattern according to the computer code. Using a projection lens, the mask pattern is minisized and focused on the substrate. The using of dynamic mask generator greatly simplifies the mask changing and eliminates the registration problem between each mask. To characterize the developed system, experiment on the photoresist film is carried out. Results show the low optical error and high resolution of1.5μm of our system.Besides, we also implement this technique for arbitrary pattern fabrication in liquid crystal (LC) alignments and local polarization control for light wavefront. Arbitrary micro-images generated by the DMD are focused on photoalignment layers and further guides the LC molecule orientations. Besides normal phase gratings, more complex2D patterns such as quasicrystal and chequerboard structures are demonstrated. To characterize the optical performances of the fabricated structures, the electro-optically tunable diffraction patterns and efficiencies are demonstrated in several1D/2D phase gratings. Compared to other techniques, our method enables the arbitrary and instant manipulation of LC alignments and light polarization states, facilitating wide applications in display and photonic fields.