Sand 9 granted core patent for piezoelectric MEMS microphones

Sand 9, Inc., a developer of piezoelectric micro-electromechanical systems (MEMS) timing products for wireless and wired applications, today announced that the United States Patent and Trademark Office has granted the company a core patent based on the use of piezoelectric MEMS for a wafer-level, chip-scale packaged (WLCSP) microphone (US20140084395 A1).

Today, most microphones are condenser microphones, which typically feature a fixed electrode (back plate) in close proximity to a moveable electrode (diaphragm). The back plate is usually rigid and is necessary because condenser microphones use electrostatic (i.e., capacitive) transduction between the diaphragm and the back plate to convert acoustic pressure into an electrical signal.

Condenser microphones typically use a small gap between the respective electrodes to achieve high signal-to-noise ratio (SNR), frequently resulting in reliability challenges such as stiction. Such a small gap can also degrade the thermal-mechanical noise performance by damping the overall mechanical structure. Moreover, a DC bias between the electrodes is normally required to enable capacitive detection of motion, which can be a significant source of power consumption.

In contrast, piezoelectric MEMS microphones offer high electromechanical coupling compared with electrostatic transduction, enabling improved SNR with lower power consumption. Piezoelectric MEMS structures are not susceptible to stiction from particles or other contaminants, resulting in a significantly higher quality product for OEMs. Finally, piezoelectric MEMS can be implemented in WLCSP with through-silicon-vias (TSVs) to support both top and bottom port configurations with matched performance in the smallest package size.

“We are delighted to receive this latest patent,” said Sand 9’s CEO, Vince Graziani. “This brings our total number of issued patents to 52, covering an array of piezoelectric MEMS products including timing devices, microphones, and gyroscopes. It validates our belief that piezoelectric MEMS technology offers significant advantages over traditional electrostatic technology to enable higher levels of performance and quality in an ultra-small form factor.”


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