Printed membrane electrostatic MEMS microspeakers

Publication Type:

Conference Paper

Source:

2016 IEEE 29th International Conference on Micro Electro Mechanical Systems (MEMS), IEEE, Shanghai, China (2016)

URL:

http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=7421831&isnumber=7421533

Abstract:

We report the fabrication and broadband actuation of capacitive electrostatic MEMS microspeakers formed by the contact-transfer printing of suspended 125-nm-thick gold membranes over cavities in a 430-nm-thick silicon dioxide (SiO2) spacer layer on a conducting substrate. The membranes deflect repeatedly to produce sound upon electrostatic actuation with a time-varying signal. The microspeaker has a flat acoustic frequency response that is devoid of any resonance peaks. Its output sound pressure level (SPL) increases at 40 dB/decade with increasing frequency, in the 3 highest octaves of the human audio range, for constant excitation voltage autospectral density. The microspeaker consumes 24 W of real electric power under broadband actuation in free field. It outputs 35 dB (SPL/VoltRMS) of acoustic pressure at 20 kHz drive. The microspeaker operates at a 10Vdc bias, thus enabling the use of electrostatic sound sources in portable audio applications such as hearing aids and earphones. The diaphragm-forcing Vbias-Vrms product is reduced to 19 V2. The total thickness of the microspeakers is dominated by the silicon wafer substrate, with an active device thickness of less than 700 nm.