Capacitive microphone with a surface micromachined backplate using electroplating technology

Author

Bergqvist, J. ; Gobet, J.

Author_Institution

Centre Suisse d´´Electronique et de Microtechnique SA, Neuchatel, Switzerland

Volume

3

Issue

2

fYear

1994

fDate

6/1/1994 12:00:00 AM

Firstpage

69

Lastpage

75

Abstract

A technology for surface micromachining of free-standing metal microstructures using metal electrodeposition on a sacrificial photoresist layer has been applied to a condenser microphone. Electroplating technology has been used to implement a suspended and perforated 15-μm-thick microstructure in copper, which serves as backplate electrode in the condenser microphone. The 1.8×1.8 mm ² large microphone diaphragm is in monocrystalline silicon and is fabricated with anisotropic etching of the substrate wafer. The realized prototypes have a measured sensitivity of 1.4 mV/Pa using a bias voltage of 28 V. The bandwidth is limited by an anti-resonance at 14 kHz which is due to the semi-rigid backplate. The resonance behavior of the backplate structure has been analyzed with finite element modeling with results in good agreement with measured data

Keywords

electric sensing devices; electroplating; etching; finite element analysis; micromechanical devices; microphones; 15 micron; 28 V; anisotropic etching; anti-resonance; bias voltage; capacitive microphone; condenser microphone; electroplating technology; finite element modeling; metal electrodeposition; microphone diaphragm; sacrificial photoresist layer; semi-rigid backplate; surface micromachined backplate; Anisotropic magnetoresistance; Copper; Electrodes; Etching; Micromachining; Microphones; Microstructure; Prototypes; Resists; Silicon;

fLanguage

English

Journal_Title

Microelectromechanical Systems, Journal of

Publisher

ieee

ISSN

1057-7157

Type

jour

DOI

10.1109/84.294323

Filename

294323