Estimating Verticality Parameters in Deep Reactive Ion Etching using MEMS Oscillators

In view of characterizing a vertical profile of deep reactive ion etching (DRIE) without making a cross section, we propose a method to estimate representative parameters, namely, the underetched cross-section area and the second moment of area. The test structure consists of a series of MEMS oscillators, the resonance frequency of which was plotted for varied spring stiffness and fitted to a physical model derived from geometry. The estimation from oscillation measurement was compared to the actual profile parameters obtained from visual observation, showing correlation R²=0.556 and 0.913 for the underetch area and the second moment of area, respectively.