PORTLAND, Ore.—Integrated Device Technology Inc. (IDT) said Wednesday (Nov. 30) it has developed what it claims is the world's first piezoelectric micro-electro-mechanical system (pMEMS).
IDT (San Jose, Calif.) also claimed its new pMEMS process could produce oscillators that operated at higher-frequencies than traditional MEMS, had higher-stability than quartz oscillators, and could be delivered in the world's smallest waferscale package.
"Our pMEMS oscillator is so small that it is difficult to see with the naked eye," said Harmeet Bhugra, managing director of MEMS at IDT.
IDT, which already has quartz-, SAW-, and CMOS-timer chips, is striving to become a one-stop timing chip solution provider. IDT claims that MEMS oscillators in general is one of the fastest growing segments of the $3 billion timing chip market, prompting it to devote almost five years to developing pMEMS oscillator chips in waferscale packages as small as 0.56-by-0.43 millimeters.
"MEMS is a natural step forward for us, and complements our other oscillators,” said Bhugra.
IDT's new pMEMS process works by layering aluminum-nitride piezoelectrics on top of a single-crystal silicon MEMS resonator beam. The piezoelectric layer both actuates the silicon beam's vibrations, as well as tranduces its bulk-acoustic wave into electrical timing signals. As a result, native frequencies as high as one gigahertz can be achieved with pMEMS, according to IDT.
The central silicon beam is coated with piezoelectric material which transforms the induced bulk acoustic wave (BAW) into an electrical signal at the oscillator's desired frequency.
"Traditional MEMS oscillators are limited to megahertz frequencies, but pMEMS can oscillate at hundreds of megahertz or even gigahertz frequencies," Bhugra said.
The second drawback to traditional silicon MEMS, according to Bhugra, is that quartz has better long-term stability than MEMS. IDT, on the other hand, claims that its pMEMS process solves the stability problem, too, by operating with higher long-term stability even that quartz oscillators.
"Our pMEMS oscillators offer better stable over time than quartz oscillators," Bhugra said. "We recently demonstrated that frequency drift as our pMEMS device's age is comparable to quartz at 25 degrees [Celsius] and significantly better than quartz in 125 degree [C] accelerated tests."
IDT also claims that its pMEMS oscillators are naturally ruggedized, offering superior reliability due to the strong electromechanical coupling between the piezoelectric aluminum nitride layer atop the extremely stable bulk silicon resonator. The result is natural shock and vibration resistance, ultra low jitter, and easy creation of multiple frequency outputs from a single device, according to IDT.
IDT's pMEMS devices can also be delivered in inexpensive plastic packages, and are already available as part of several evaluation boards, with volume delivery of pMEMS chips slated for 2012.
STI offered this ability back in 2007. We tried it on Ethernet devices (15MHz) as a crystal replacement and it worked fine. Plus the drift over the expected lifetime was better than quartz. It was cost that was the hold-up.
Accuracy is not yet specified since actual production devices are not yet announced, but in testing IDT claims drift is just 2 PPM for pMEMS compared with 10 PPM for quartz after 1400 hours at 125 degrees C.
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