Direct laser writing: virtual mask optimization for optical quality control artefact

Greyscale lithography is a way to fabricate 3D microstructures in the fields of micro-electro-mechanical systems (MEMS) and micro-optics. We use direct laser writing (DLW) to create a layered staircase sample for bio-microscopy use. To minimize the number of experiments necessary to determine the laser system parameters necessary to have the specified structure we used Design of Experiment (DOE) together with a 3D profiler using scanning white light interferometry (SWLI). A gray-scale mask with varying intensities was developed and used to pattern a thick positive tone photoresist. We employed a Microtech LW405 laser writer with a 405 nm GaN laser. Our results show the potential of the SWLI-DOE approach as a tool to optimize (precision, speed and structure) greyscale DLW lithography for the herein reported use. This work is a step towards replacing slow SEM and AFM devices for quality control in 3D MEMS production.