Design Approaches of MEMS Microphones for Enhanced Performance

Abstract

This paper reports a review about microelectromechanical system (MEMS) microphones. The focus of this review is to identify the issues in MEMS microphone designs and thoroughly discuss the state-of-the-art solutions that have been presented by the researchers to improve performance. Considerable research work has been carried out in capacitive MEMS microphones, and this field has attracted the research community because these designs have high sensitivity, flat frequency response, and low noise level. A detailed overview of the omnidirectional microphones used in the applications of an audio frequency range has been presented. Since the microphone membrane is made of a thin film, it has residual stress that degrades the microphone performance. An in-depth detailed review of research articles containing solutions to relieve these stresses has been presented. The comparative analysis of fabrication processes of single- and dual-chip omnidirectional microphones, in which the membranes are made up of single-crystal silicon, polysilicon, and silicon nitride, has been done, and articles containing the improved performance in these two fabrication processes have been explained. This review will serve as a starting guide for new researchers in the field of capacitive MEMS microphones.

Development Trends and Perspectives of Future Sensors and MEMS/NEMS

“…MEMS acoustic sensor in which operation frequency ranges from 20-20,000 Hz is much higher than the typical MEMS physical sensor takes a big amount of MEMS market, especially its application in consumer electronics such as smartphones and smart speakers. The conventional MEMS acoustic sensor with working frequency in the audio range, aka microphone, consists of a flexible membrane and a back-plate with a bias voltage using a capacitive sensing mechanism as shown in Figure 4a [62]. Due to the limits of maximum signal level and sensitivity to environmental conditions, more sensing mechanisms have been investigated to improve acoustic sensor performance [63][64][65][66][67][68], which includes using back-plate-less design to minimize air damping, using piezoelectric sensing to achieve low power directional detection and using optical sensing to work at extreme environmental conditions, etc.…”

Low-Cost Sensors for Urban Noise Monitoring Networks—A Literature Review

“…In practice, experiments described in the literature mention noise levels between 20 and 30 dB, depending on the frequency [76]. However, recent works on the development of new generation MEMS microphones suggest the possibility of developing noise sensors with high acoustic performance [77], which makes it the ideal component in the future for the development of noise high-performance sensors.…”

A Review of MEMS Capacitive Microphones

“…We will not discuss that specific type of MEMS microphone in this review. In 2019, Shah et al [32] presented a wide review of MEMS microphones, covering different types of transduction mechanisms and using data from academic The perforated backplate is shown as a dashed line in Figure 1, of which the dashes represent acoustic holes. They enable air to stream in and out of the air gap when the diaphragm vibrates.…”

“…We will not discuss that specific type of MEMS microphone in this review. In 2019, Shah et al [32] presented a wide review of MEMS microphones, covering different types of transduction mechanisms and using data from academic papers and commercial products. In this paper, we offer a focused review on the MEMS capacitive microphone.…”