Challenges for the commercialization of acoustic sensors using microfabrication technologies

Abstract

In this paper a review is given of the methods used in the design and realization of acoustic sensors based on microfabrication technologies. It is shown that the most important issues relate to material properties, which must be tightly controlled to achieve acceptable consistency and stability of the devices. In addition, the requirements for successful commercialization of such devices are discussed and a number of critical parameters are identified which include environmental performance, reliability and cost. It is contended that microphones made with this new technology will not provide advances over existing technology in terms of sensitivity and noise performance, and hence the motivation for the use of the technology must be found in the added value of smaller size, increased bandwidth, and better flexibility in terms of device assembly and ruggedness. Based on these considerations a new capacitive microphone design is proposed, which simplifies the fabrication of the so-called free-plate or zero-stress microphone, referring to the lack of tension in the microphone diaphragm. It is further shown that the introduction of flip-chip assembly methods will enhance the repeatability and ruggedness of the microphone package, which so far has received little attention in the development micromachined acoustic sensors.