MEMS timing device cracks cellphone market

November 04, 2013 //By R. Colin Johnson, EE Times
Micro-electromechanical system (MEMS) chipmaker Sand 9 Inc., of Cambridge, Massachusetts, claims to have finally cracked the multibillion unit mobile phone and Internet of Things market with a piezo-electric design that provides the performance lacking in traditional MEMS timing chips. More than five years in the making, Sand 9 has finally announced its first piezo-electric timing chips, for which it already has mobile phone customers lined up.

“We started from the mobile market and its requirements, and worked our way backwards to find out that our MEMS chips needed to be piezoelectric,” said senior director of marketing Todd Borkowski.

The key to its success in cracking the mobile phone market, Sand 9 claims, is its piezo-electric materials that give its MEMS timing chips better electro-mechanical coupling than conventional electro-static capacitive designs, resulting in ultra-stable higher-frequency operation in a tiny size and with low-power requirements.

“The piezoelectric MEMS technology we invented has 100 times better electromechanical coupling than electro-static,” said Borkowski. “Basically it gets us the performance we need in a small size and at power-consumption levels on par with quartz.”

From its founding in 2007 as a Boston University spinoff by co-founders Pritiraj Mohanty (inventor of its MEMS technology) and Matt Crowley (vice president of business development) Sand 9’s aim has been to produce timing chips that offered a better price/performance ratio than quartz in the core markets for cellular phones and the high-speed communications chips inside Internet of Things devices.

“These are the very first MEMS timing devices in the world capable of accurately clocking what people refer to as the Internet of Things devices as well as high-speed transceivers and conductivity ICs,” said Borkowski.

Sand 9 has filed more than 80 patents — with 35 granted so far — covering not only its MEMS technology itself, but also the circuits, systems, and process innovations that make its piezo-electric timing chips unique. In particular, Sand 9’s piezo-electric resonator uses an interdigitated design that creates a standing wave at the desired frequency. The resonator itself is constructed from a silicon film with two layers of silicon dioxide, one above and one below, topped by the aluminum nitride piezo-electric material. Since higher temperatures affect silicon and silicon dioxide in an opposite manner — softening silicon but stiffening silicon dioxide — the MEMS resonator achieves 200 parts-per-million frequency stability

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