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Sand 9 MEMS cracks cell phone market

Sand 9 MEMS cracks cell phone market

Technology News |
By eeNews Europe



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 in an interview with EE Times.

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 electro-mechanical 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 spin-off by co-founders Pritiraj Mohanty (co-founder and 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's interdigitated piezo-electric resonator (center) is the world's first MEMS timing solution for cellular phones, due to its electro-mechanical coupling that is 100 times better than traditional MEMS.
(Source: Sand 9)

Sand 9’s interdigitated piezo-electric resonator (center) is the world’s first MEMS timing solution for cellular phones, due to its electro-mechanical coupling that is 100 times better than traditional MEMS.
(Source: Sand 9)

Sand 9 has filed over 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 with no external compensation.

Sand 9 is targeting the wireless applications market being served by high-end quartz temperature compensated crystals (TCXO), especially those used by a mobile phone’s cellular transceivers, power management ICs, GPS, WiFi, FM, Bluetooth, and accessories using the low-power version called Bluetooth Smart.

Its first two timing chips will be the TM061 MEMS resonator (MR) and TM361 temperature-sensing MEMS resonator (TSMR). Both devices use a sub-millimeter package size (0.76-by-0.84-by-0.5 millimeters) which Sand 9 claims is 50 percent smaller than the smallest quartz crystal in the industry and 10-times more resistant to shock.

The 48-MHz TM061, which targets Bluetooth Smart applications, is a resonator with a dummy cap instead of an ASIC, making it the ultra-low-cost solution. The 76.8-MHz TM361 also uses a dummy cap, but includes within the material stack a temperature sensor (thermistor) and heater for sophisticated compensation and calibration of the resonator. Integrating the thermistor into the MEMS resonator gives it 10 times better thermal coupling than quartz, which must use an external thermistor. The heater allows the TM361 to be quickly calibrated by the original equipment manufacturer (OEM). For the future, Sand 9 plans a follow-on device which integrates the phase-locked-loop (PLL) needed for a complete piezo-electric MEMS oscillator.

"Our future road map includes a temperature-sensing MEMS oscillator (TSMO), which integrates the oscillator circuitry into the silicon cap," said Borkowski.

Sand 9’s chips will be manufactured in two foundries — GlobalFoundries for the MEMS portion and IBM for the application-specific integrated circuit (ASIC) — after which the two chips will use wafer-scale bonding, so that the ASIC carrying the electronics serves double duty by also capping the MEMS chip to prevent environmental contamination.

Sand 9's chip-scale design can be flipped and over-molded into the customer's package, along with the device for which it is providing the timing signals.
(Source: Sand 9)

Sand 9’s chip-scale design can be flipped and over-molded into the customer’s package, along with the device for which it is providing the timing signals.
(Source: Sand 9)

The big surprise is that, unlike quartz, Sand 9’s MEMS resonators and oscillators can be over-molded into the same package as the device for which they are providing timing signals. In fact, Sand 9’s business model is to sell only die in wafer-level chip-scale packages that can be flipped and over-molded into the customer’s package, thus reclaiming the board-space dedicated to multiple bulky quartz crystals today.

Besides its venture capital backers — Commonwealth Capital Ventures, Vulcan Capital, Flybridge Capital Partners, General Catalyst Partners, and Khosla Ventures — Sand 9 has also assembled a stellar cast of technology partners, including Ericsson, Intel, Analog Devices, and CSR (formerly Cambridge Silicon Radio).

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