Finite element simulation and experimental study on the through-mask electrochemical micromachining (EMM) process

In this work, the influence of electrode surface patterning on shape evolution in through-mask electrochemical micromachining (EMM) process is investigated numerically and experimentally. With finite element method, the anodic dissolution process is predicted and the etching behavioral trends under various parameters involving spacing and opening ratio, mask aspect ratio, and the etched feature aspect ratio have been identified and interpreted in which the etched depth non-uniformity is mostly ascribed to the current aggregate effect due to surface patterning on substrate. The validation experiment is conducted and the procedure of island formation and disappearing gradually along with etching progress in the center of the etched region is observed, which is in good agreement with the numerical calculation prediction. With the combination of experiments and numerical simulation, the optimized electroetching conditions and the formulation of the electrolyte in through-mask EMM are achieved, with which the ordered microstructures with a feature size down to 15 μm and smooth etched surface in large scale are obtained.