PORTLAND, Ore.—NXP Semiconductors NV legitimized the silicon oscillator market by demonstrating a resonator it claims is higher-frequency, lower noise and more stable than conventional MEMS resonators. Using a unique micro-cavity structure that can be fabricated on a standard CMOS line, NXP's worldwide manufacturing, distribution and marketing muscle will likely accelerate a mass migration from quartz-crystal-based to MEMS-based oscillators.
Quartz crystals, which ship in the billions of units per year for everything electronic—from tiny thumb drives to supercomputers—have already been one-upped technologically by smaller MEMS oscillators from SiTime, Discrea, IDT and Silicon Labs. However electronics market penetration is still scant. The reputation of NXP, on the other hand, could raise a tide that floats all boats in a mass migration from traditional quartz crystals to silicon-based MEMS timing solutions.
"NXP's ultra-compact, high-precision MEMS-based frequency synthesizer presents a compelling alternative to quartz crystal-based timing devices," said Joost van Beek, senior principal scientist and program manager for MEMS at NXP. "Today we can fit over 100,000 of these tiny MEMS resonators on a standard 200 millimeter [8-inch] wafer, but that is only the beginning since they can be shrunk and scaled down like any other CMOS chip."
The dog-bone shaped silicon resonator (center) is suspended in the middle while vibrating at 50MHz.
The result of a five-year development effort, the tiny silicon die (500-by-700-by-150 microns) is claimed to be 20-times smaller than the smallest quartz crystals available today. The micro-cavity resonator was fabricated with single-crystal silicon using standard CMOS fabs plus an added release tool which NXP is qualifying at multiple foundries. Extensive testing of the resonator has demonstrated that it can be produced with high yields and shows near-zero fatigue even during accelerated aging tests.
"We will be sampling the part to multiple customers in 2012," said Mike Bruno, senior director of sales and marketing of advanced technologies at NXP. "And a full family of MEMS timing solutions based on our resonator will follow, bringing to bear NXP's large customer and manufacturing base in automotive, identification, wireless infrastructure, lighting, industrial, mobile, consumer and computing applications."
NXP claims its MEMS oscillator has higher frequency stability, lower timing jitter, and lower temperature drift than its competitor's parts. Due to its very low motion damping, the NXP resonator maintains an ultra-high quality factor (Q exceeds 40,000) allowing the part to oscillate at frequencies that are 10-times higher than existing MEMS resonators (50MHz compared to 5MHz).
"Today we are achieving frequencies greater than 50-MHz, which we expect to double or even triple to over 100MHz in the future," said van Beek.
By depositing the single-crystal silicon for the resonator structure under very low atmospheric pressures, then hermetically sealing the cavity, NXP claims its resonator shows no significant aging even after accelerated lifetime tests including HTOL (high temperature operating life), HAST (highly accelerated stress testing) and extended temperature cycling.
NXP's claim of lower jitter is derived from its use of a piezo-resistive material to sense the resonator's motion, thereby overcoming the weak electro-mechanical coupling that confines other silicon resonators to lower frequencies.
NXP also claims 10-times less temperature drift compared to existing MEMS resonators, achieving precisions that rivals the best quartz-crystal tuning forks (frequency stability of about two parts-per-million). The key to its low temperature drift, according to NXP, is a special proprietary material with a countering temperature coefficient that coats the silicon resonator, thereby passively compensating for changes in temperature without consuming any extra power. In a YouTube video, NXP demonstrates its oscillator's superior temperature stability by mounting it alongside MEMS oscillators from competitors, then showing how blowing a hair dryer on them causes the others to drift whereas its specially compensated resonator stays rock-solid on-frequency.
NXP's first integrated circuit based on its MEMS resonator will mount the die on top of an application specific integrated circuit (ASIC) realizing a programmable oscillator. The frequency synthesizer will operate between 25-and-200 MHz. NXP expects its initial customers to use the part in communications applications including Gigabit Ethernet, USB, PCI-Express and S-ATA, as well as for processor-, memory- and control-timing in consumer electronics devices. EE Times Confidential is working on a MEMS Sector Profile and Database and if you would be interested in being advised when copies are available send an email to email@example.com
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