Investigation into Nano-Stereolithography Process for Developing Next Generation Three-dimensional Nano/Micro-Devices

A nano-stereolithography (NSL) apparatus has been developed for fabrication of microstructures with the resolution of approximately 100 nm. In the NSL process, a complicated 3D structure can be fabricated by building layer by layer, so it does not require any sacrificial layer or any supporting structure. A laminated layer was fabricated by means of solidifying liquid-state monomers using twophoton absorption (TPA) which was induced by a femtosecond laser. When the fabrication of a 3D laminated structure was finished, unsolidified liquid-stage resins were removed to develop the fabricated structures by dropping several droplets of solvent, then the polymerized structure was only left on the glass substrate. A microstructure is fabricated by vector scanning method to save the fabrication time. The shell thickness of a structure is very thin around 180 nm, when it is fabricated by a single contour scanning (SCS) path. So, a fabricated structure can be deformed easily in the developing process. In this work, a double contour scanning (DCS) method was proposed to reinforce the strength of a shell typed structure. A beam-expanding technique has been applied to enlarge a working area and to fabricate precise microstructures, and subregion slicing method has been proposed to reduce the process time. Through this work, micro-Thinker, human bust, micro-cup etc. were fabricated to estimate the stability of the developed system. Many applications on NEMS, MEMS, and optical devices using the NSL process will be come forth.