STMicroelectronics and USound deliver MEMS microspeakers

Semiconductor supplier STMicroelectronics and audio company USound have delivered a range of MEMS silicon microspeakers, following their technology collaboration announced last year.

High-performing MEMS (microelectromechanical systems) motion sensors, pressure sensors and microphones built on silicon chips are the critical enablers for context sensing, navigation, tracking and other features that mobile users now rely on every day. With MEMS advancements now coming to speakers, designers can further miniaturise the audio subsystem, reduce power consumption and create innovative features like 3D sound. Industry analyst Yole Développement values the overall microspeakers market at $8.7 billion currently and expects MEMS manufacturers to capture share with silicon-based devices.

The MEMS microspeakers feature a piezoelectric actuator that deflects in response to analog audio signals. The microspeakers are fabricated completely on silicon and are therefore simpler, more reliable and more economical in high volumes than conventional electromechanical speakers, according to the partners. They also eliminate the usual trade-offs between magnet size, air volume and sound quality that complicate both the design and integration of traditional electromechanical miniature speakers that contain a magnet and balanced-armature mechanism.

USound’s concept for the speakers leverages piezoelectric material properties to drive the speaker membrane, which eliminates the complex signal processing required in other types of MEMS micro speakers. The piezo actuator allows a small speaker footprint and low profile, with good power efficiency and fast response for high acoustic performance. ST’s MEMS device-design competencies and manufacturing capabilities, meanwhile, enable the speakers to be produced in high volumes and at high yield on silicon wafers, leveraging well-characterised processes that are closely related to CMOS (complementary metal-oxide-semiconductor) chip fabrication.

Expected to be the thinnest speakers in the world and less than half the weight of conventional speakers, the microspeakers enable wearable tech such as earphones, over-the-ear headphones or augmented-reality/virtual-reality (AR/VR) headgear to become even more compact and comfortable. Their low power consumption saves extra weight and size by allowing smaller batteries, and they generate negligible heat.

“This successful project combines USound’s design flair and ST’s extensive investment in MEMS expertise and processes, including our advanced thin-film piezo technology PεTra (Piezo-electric Transducer),” said Anton Hofmeister, vice president and GM of MEMS Microactuators Division, STMicroelectronics. “Together, we are winning the race to commercialise MEMS microspeakers by delivering a more highly miniaturised, efficient and better-performing solution leveraging the advantages of piezo-actuation.”

“ST has provided the production expertise and manufacturing muscle to realise our original concept as a pace-setting, advanced product ready for consumer-market opportunities,” said Ferruccio Bottoni, CEO of USound. “These tiny speakers are now poised to change the design of audio and hearable products, and open up new opportunities to develop creative audio functionalities.”

In addition to applications in mobiles, audio accessories and wearables, the piezo-actuated silicon speakers support innovation in a wide variety of hearable electronics, including home digital assistants, media players and IoT devices.

Engineering samples are now with lead customers. Trade demonstrations also took place during CES 2018, held last week in Las Vegas, leveraging the speakers’ ultrathin form factor, low weight and high sound quality as well as advanced features such as beam forming for private audio.