A Directional Capacitive MEMS Microphone using Nano-Electrodeposits

We present an in-situ non-volatile tuning method for adjusting MEMS microphone sensitivity using integrated nano-electrodeposits to achieve high directionality in hearing aids. Using a DC bias at room temperature, nano-electrodeposits are electrochemically formed on a Ag-Ge-Se solid electrolyte film integrated with a microphone diaphragm. The in-situ growth mechanism generates mass/stress redistribution on the diaphragm, tuning microphone sensitivity to incoming acoustic sources. Acoustic measurements demonstrate the technique can achieve a tuning range of 1.67 dB (24%), corresponding to a 1.17-dB Directivity Index (DI) improvement, which is sufficient to enable acoustic directionality in high accuracy microphone arrays.