A bottom-inlet type MEMS acoustic sensor with wheel-shaped back-plate anchor

A bottom-inlet type micro-electro-mechanical system (MEMS) acoustic sensor with a wheel-shaped back-plate anchor is presented. Underneath the back-plate, the wheel-shape anchor is newly inserted to be adjusted to a fixed stator on a substrate. The 30 μm;-high back-plate anchor is patterned by deep reactive-ion etching (DRIE) and covered with a thick back-plate of 2.3 μm; thus, it can play an important role in protecting the foundations under the diaphragm anchors from other loads. Furthermore, structure-based equivalent circuit modeling for a capacitive-type MEMS acoustic sensor is implemented with a lumped model, which is subsequently divided into three main areas: acoustic, mechanical, and electrical domains. The acoustic sensor had an open-circuit sensitivity of -43.0 dBV/Pa at 1 kHz with a bias of 10.0 V, while the modeled open-circuit sensitivity was -42.7 dBV/Pa, which shows good agreement in the range from 100 Hz to 18 kHz. This demonstrates the validity of the structure-based equivalent circuit model for the prediction and design of the sensor.