In situ tuning of a MEMS microphone using electrodeposited nanostructures

This paper presents a new method for in situ tuning of acoustic sensitivity in micro-electro-mechanical-system (MEMS) microphones using silver metallic nano-electrodeposits. The nano-electrodeposits are electrochemically formed using an external dc bias under low power and at room temperature on an Ag-doped Ge₃₀Se₇₀ solid electrolyte film integrated with the microphone diaphragm. The growth/retraction mechanism generates mass/stress redistribution on the diaphragm and this effect is used to manipulate microphone sensitivity to incoming acoustic waves. Acoustic measurements with a reference microspeaker demonstrate that the microphone can achieve a tuning range of 0.6 dB (7.2%). This technique is useful for a variety of microdevice applications, including sensitivity matching for directional microphones (e.g., in hearing aids), post-package trimming and resonant frequency tuning.