Simulation and Optimization of Defects in Si Wet Etching

Potassium hydroxide (KOH)-based anisotropic wet etching is widely used in MEMS device fabrication due to its low cost, high etching rate, and minimal wafer damage. However, improper process parameters can lead to defects such as V-shaped notches and asymmetric sidewalls, especially in etching (110) Si wafers. These defects reduce pattern fidelity and bring dimensional errors in MEMS devices. This work presents wet etching experiments with COMSOL Multiphysics modeling to elucidate the influence of$\mathbf{K O H}$concentration and solution temperature on (110) Si etch profile evolution. The findings demonstrate that etching with$\mathbf{1 0} \mathbf{~ w t \% ~} \mathbf{K O H}$at$\mathbf{7 0}^{\circ} \mathrm{C}$can yield optimal trench geometries with near-vertical sidewalls ($<89.5^{\circ}$) and negligible basal undercutting. These results provide practical guidelines for achieving submicron-scale dimension control in MEMS fabrication.