In-process gap reduction of capacitive transducers

This paper presents a MEMS fabrication technique for reducing the trench width of microstructures below the technological limitations of the deep reactive ion etching (DRIE) process, in order to increase the aspect ratio of the sensing electrode gap of capacitive transducers. The in-process trench width reduction is based on the displacement of a substructure actuated by a buckling beam mechanism. Compressive stress causes a longitudinal force in the acting beams which results in the buckling to a predefined direction. This way, the capacitive sensitivity and hence the signal to area ratio of a transverse comb structure could be increased by a factor of 5.