Numerical identification of geometric parameters from dynamic measurement of grinded membranes on wafer level

In the paper a new, nondestructive quality testing methods for MEMS will be presented that can be applied on wafer level in early stage of the manufacturing process. The approach was applied to determine the thickness of KOH etched membranes from measured eigenfrequencies. The dynamic measurements of test specimen were performed by Laser Doppler Vibrometry. A Fineite Element (FE) model was created to identify the membrane thickness from the measured eigenfrequency values. A good agreement between the measured thicknesses and the calculated thicknesses of membranes was found. Furthermore, a stochastic model was created to describe the influence of different parameters on the calculated thickness of membrane.