Photolithography system with liquid crystal display as active gray-tone mask for 3D structuring of photoresist

Layer manufacturing is generally utilized for the development of micro electromechanical systems (MEMS) and micro total analysis systems (μTAS). However, the preparation of multiple masks and repetitive exposure procedure prevents the rapid fabrication of 3D microstructures. An active mask fabrication by using a liquid crystal display (LCD) as an electrically controllable photomask can simplify the layer manufacturing process. In addition, the gray-tone photolithography is available by using LCD lithography system, since the exposure distribution is easily controlled by an LCD. We have developed the LCD mask exposure system by using UV light source. Firstly, the patterning characteristics of the UV photoresist by exposing line and space patterns are evaluated, and then, a fundamental step shape is produced in order to verify the feasibility of gray-tone UV photolithography by using LCD. A shape with a different height can be fabricated without any repetitive exposure and development procedures. Finally, we confirmed the high patterning resolution such as 11 μm using check patterns and fabricated 3D step shapes by using the LCD as a gray-scale photomask.