Comprehensive evaluation of grayscale laser lithography build accuracy via benchmark artefacts

Grayscale laser lithography is capable of producing continuous-relief (2.5D) structures down to the micro- and nanoscale for applications such as micro-optics, micro-electromechanical systems and functional surfaces. The present work evaluates build accuracy by employing benchmark artefacts having an active area of up to 1 mm × 1 mm and a structure depth of up to 50 μm with a resolution of 1 μm as models for the production of 2.5D structures with a wide range of representative features in terms of elevation, slope, curvature, aspect ratio and area density. The topography of manufactured samples is determined via laser scanning confocal microscopy and 3D optical microscopy based on white light interferometry, with alignment algorithms developed within MATLAB employed to evaluate local build error over the entire surface. Further to the incident laser energy density within each region, the applied energy in adjacent regions is found to influence build accuracy due to the laser intensity distribution, light scattering and photochemical reaction effects, with the area density and aspect ratio of model features found to be of strong influence on outcomes. The results imply that greater build accuracy can be achieved by basing process parameters on not only the local model height but also that within adjacent regions. The present work was performed within the Horizon Europe project “Automated Maskless Laser Lithography Platform for First Time Right Mixed Scale Patterning” (OPTIMAL, Grant Agreement No. 101057029), with the aim of facilitating automated approaches for error correction and accuracy optimization.