A Novel High-SNR Full Bandwidth Piezoelectric MEMS Microphone Based on a Fully Clamped Aluminum Nitride Corrugated Membrane

We present an innovative design and the related fabrication method for a high-SNR piezoelectric MEMS microphone based on fully clamped corrugated aluminum nitride (AlN) membrane. The corrugations allow for effective intrinsic stress relaxation and additionally enable differential signal generation by exploiting a pseudo-bimorph effect. Two distinct designs are compared against a state-of-the-art commercial cantilever-based piezoelectric MEMS microphone of same die and similar package size. We show that, in contrast to the commercial microphone, a resonance-free system response up to 20 kHz can be achieved and the low-frequency-roll-off (LFRO) is tightly defined by lithography and independent of intrinsic stress variation. Finally, albeit higher system resonance, the new concept shows superior signal-to-noise ratio (SNR) values with a maximum of 62.61 dB(A) and a sensitivity of -47.11 dBV/Pa.