Optimization techniques for grayscale photolithography

With the ongoing development of thick photoresists, promising possibilities have emerged to use these transparent and flexible layers for micro-structures and micropatterns directly and not exclusively as a sacrificial layer in the processing. These 3D polymer microstructures have many potential applications in the field of MEMS: including micro-sensors and actuators, micro-optics and micro-fluidics. Using modern 3D exposure techniques, it is possible to vary the dissolution rate of thick photo resists locally and create complex relief-type three-dimensional structures in just one exposure and development cycle. Unfortunately, realizing the proper exposure conditions needed for a specific 3D micro pattern is complicated, because of the non-linear and smoothing nature of the physical processes. Nowadays, the most widely used approach is based on trial-and-error designed exposure conditions. In this research a systematic approach is developed, based on computational process simulation, associated adjoint sensitivity analysis and optimization techniques.