Layer-by-Layer Interference Lithography of Three-dimensional Microstructures in SU-8

A method for rapid and large area fabrication of 2D, 2.5D, and 3D-planar periodic structures with micrometer scale features as well as a non-periodic vertical symmetry using a layer-by-layer interference patterning approach, was demonstrated. The experiment employed the photoresist SU-8 mixed with a liquid UV absorber of the hydroxyphenyl benzotriazole class, and were conducted in an ambient UV-light free room using a high-power pulsed Nd:YAG laser. The results show that the absorption depth for the unmodified photoresist is about 19 μm, and indicated that for the fabrication of 3D structures with good layer-to-layer bonding, a photopolymerizable material with an absorption depth. The experiment was able to control the absorption depth of the material and thus to obtain true 3D structures, where controlled compositions of the photoresist and exposure parameters demonstrates versatile and rapid fabrication.