METAL MOLD FABRICATION BY PROTON BEAM WRITING AND ITS APPLICATIONS

Abstract

Metal molds (with micro- and nanostructures) have been used in many areas such as advanced printed circuit board, polymer microlens replication and some other optical device for many years. However, most of the applications are either based on high aspect ratios (can be over 20) feature metal molds with large structure sizes (several µm) or high resolution (sub-100 nm) metal molds with low aspect ratio (typically less than 2). Metal molds with high aspect ratio and high resolution structures are still hard to achieve. In our research, the fabricated Ni mold has the ability to fill this gap. Firstly, an advanced technology named proton beam writing was used in our research. Proton beam writing (PBW) is a mask-less, 3D fabrication lithographic technique which is developed at the Center for Ion Beam Applications (CIBA), Department of Physics, National University of Singapore. It uses a fine focused beam of high energy e.g. MeV protons or H2+ to pattern resist and silicon materials with nanometer scale details. Because of the inherent properties of protons, this technique has many advantages over conventional optical lithography and various next generation lithography techniques. This technique can fulfill high aspect ratio and high resolution structures with vertical and smooth sidewalls. The applications of the technique can be applied in optics, micro- and nano-fluidic devices and biochips fabrication. Secondly, although many photoresists have already been tested with PBW, most of them are not suitable to make high aspect ratio and high resolution Ni mold. This requires us to investigate new photoresists. A lot of new photoresists were explored in our research. Thirdly, the fabricated high resolution and high aspect ratio Ni molds were used in nanoimprinting and injection molding to realize mass production of plastic micro- and nanostructures. The Ni molds can be used for many times without damage. One of fabricated plastic structures has proved to be a good microfluidic device. Overall, our work provides a method to produce a high aspect ratio and high resolution Ni mold. The mold has a promising prospect on mass production of plastic micro- and nanostructures which can be used in microfluidics.