Research On Nanoimprint And Fabrication Of MEMS Bionic Functional Surfaces

Due to the restrictions of light wavelength and numerical aperture, conventional lithography is difficult to obtain sub-100 nm patterns. Nanoimprint lithography (NIL) is based on mechanical deformation of the resist shape with a mold pressing into the resist film cast on a substrate, and therefore its resolution is independent of many factors that restrict the resolution of conventional lithography, such as wave diffraction and scattering, therefore it can break the resolution limit of conventional photo-lithography. In addition, it can replicate nanoscale patterns repeatedly in a large area with reasonable uniformity. As a result, NIL is a promising next generation lithography technology to obtain sub-100nm structures with low cost and high throughput, and has potential applications in obtaining nanostructures and fabricating micro-electromechanical systems (MEMS). The main research coentents and creative points in this dissertation are as follows:Rheological property of resists for nanoimprint is investigated, models for calculating process parameters such as imprint pressure, velocity and time are established, and nanoimprint process is simulated by finite element method. These are significant to understand nanoimprint mechanism in depth, and to optimize process parameters and mold structures in order to obtain high-quality replicas.After analysis of nanoimprint movement, a prototype nanoimprint tool with a high - precision alignment system based on moire′fringe technique and image matching, and an orientation stage based on flexure members is developed. Aignment accuracy of the tool within the working range of 150mm×150mm is better than 20nm, thus it can meet the demands to imprint 4 inch silicon wafer and fabricate 3-D nanostructures.A few micro-optical devices such as nanoscale gratings and microlens arrays are imprinted using the prototype tool. Process parameters such as tempertature, pressure and initial resist height are studied, from which histories of the temperature and pressure of the imprint process are deduced, and replicas with high-fidelity are obtained.Nanoimprint is applied to fabricate MEMS bionic functional surfaces with dual microstructures. Lotus effect is proposed to apply to MEMS devices for the purpose of anti-stiction and friction reduction, and the mechanism of lotus effect application in MEMS is investigated by means of molecular dynamics and micro-tribology. This provides a new approach for MEMS functional surface texturing and property modification.A new method to obtain bionic MEMS functional surfaces by nanoimprint is proposed, and some preliminary experiments of fabricating bionic functional surfaces for plastic microfluidic devices and MEMS devices with silicon substrate are preformed, and the micro- tribological properties of the fabricated surfaces are tested.The dissertation aims at providing an alternative nanofabrication method with high resolution, high throughput and low cost, and a novel approach to obtain MEMS bionic functional surfaces to improve their micro- tribological properties, and promote the research and industrialization of nano devices such as nano optical devices, nano electronic devices, nano optoelectronic devices, nano magnetic memory devices, MEMS and so on.