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C. Glacer, A. Dehé, D. Tumpold, R. Laur:
"Silicon Microspeaker with out-of-plane Displacement";
Talk: The 9th IEEE international conference on Nano/Micro Engineered and Molecular Systems, Waiki Beach, Hawaii, USA; 2014-04-13 - 2014-04-16; in: "IEEE-NEMS 2014", (2014), 1 - 5.

In this paper a new way of increasing the enclosed air
volume between the stator and the membrane of an electrostatic
loudspeaker is introduced. Instead of using a thicker sacrificial
layer, a stress-induced self-raising of the stator is utilized. Corrugation grooves in combination with highly tensile silicon nitride
rings are causing a deflection of the stator after the release etch.
For a stator diameter of 1 mm an out of plane deflection of up to
59 m could be measured. On the electrical side, a pull-in voltage
between 4 V and 16 V for the membrane and 27 V to 67 V for
different stator variants was detected. In the free-field, a sound
pressure level of 50 dB SPL at 10 kHz in 10 cm distance was
measured for a small array. Variations of design and layout as
well as technology parameters were varied to determine the ideal
system with regard to maximum deflection, displaced volume and
mechanical stability.