MEMS Microphone and Speakers

The advent of MEMS technology has paved the way for the production of inexpensive and miniature sensors that power consumer electronics. One type of sensor which has benefited from this technology is the MEMS microphone which has been available commercially for over a decade.

 

The main component in a MEMS microphone is the suspended diaphragm. The deformation of the diaphragm due to incident pressure (sound) waves is sensed either by piezoelectric, piezoresistive, or capacitive means. Our work focuses on the design and fabrication of microphones which use a capacitive sensing mechanism.

 

Unlike MEMS microphones, MEMS speakers are still making their way into the market. Most of the conventional speakers used in consumer electronic devices are coil-based and, when used in certain devices such as mobile phones, they can consume up to a quarter of the total available energy. Development of MEMS speakers with a high acoustic output and power efficiency is desirable for the rapidly growing MEMS acoustic device market. Although efforts are being made to create piezoelectric- and capacitive-driven microspeakers, they are large (15 mm) compared to other sensors such as microphones, accelerometers, and gyroscopes. As such, there is clearly a need for continued research to develop MEMS speakers which are both efficient and small in size.

 

Our work aims to develop a MEMS capacitive microphone and MEMS capacitive speaker using a single wafer process. Due to the nature of the sensor, the main challenge in designing these devices is mitigating squeeze film effects.