Low-Power MEMS-Based Pierce Oscillator Using a 61-MHz Capacitive-Gap Disk Resonator

Abstract

A 61-MHz Pierce oscillator constructed in 0.35-µm CMOS technology and referenced to a polysilicon surface-micromachined capacitive-gap-transduced wineglass disk resonator has achieved phase noise marks of −119 dBc/Hz at 1-kHz offset and −139 dBc/Hz at far-fromcarrier offsets. When divided down to 13 MHz, this corresponds to −132 dBc/Hz at 1-kHz offset from the carrier and −152 dBc/Hz far-from-carrier, sufficient for mobile phone reference oscillator applications, using a single MEMS resonator, i.e., without the need to array multiple resonators. Key to achieving these marks is a Pierce-based circuit design that harnesses a MEMS-enabled input-to-output shunt capacitance more than 100× smaller than exhibited by macroscopic quartz crystals to enable enough negative resistance to instigate and sustain oscillation while consuming only 78 µW of power-a reduction of ∼4.5× over previous work. Increasing the bias voltage of the resonator by 1.25 V further reduces power consumption to 43 µW at the cost of only a few decibels in far-from-carrier phase noise. This oscillator achieves a 1-kHz-offset figure of merit (FOM) of −231 dB, which is now the best among published chipscale oscillators to date. A complete linear circuit analysis quantifies the influence of resonator input-to-output shunt capacitance on power consumption and predicts further reductions in power consumption via reduction of electrode-to-resonator transducer gaps and bond pad sizes. The demonstrated phase noise and power consumption posted by this tiny MEMS-based oscillator are attractive as potential enablers for low-power "set-and-forget" autonomous sensor networks and embedded radios.

Influence of a Tailored Oxide Interface on the Quality Factor of Microelectromechanical Resonators

“…Piezoelectric materials have been widely used to facilitate efficient electromechanical transductions in a variety of important applications ranging from energy harvesting, [1][2][3] signal processing, [4][5][6] health, [7][8][9] automotive, [10,11] robotics, [12,13] to defense and aerospace environments. [14,15] When compared to other common microelectromechanical systems (MEMS) transduction methods such as thermal/piezoresistive, [16][17][18] capacitive, [19][20][21][22] and electrostatic [23][24][25] schemes, piezoelectric materials have a higher energy density, better frequency scaling, lower power configurations, and are easier to characterize and content) and it does not require a post-deposition poling step. [47] Furthermore, AlN can be doped with scandium to increase electromechanical coupling while maintaining a high quality (Q) factor [53] or to add ferroelectric behavior.…”

Effects of Gamma Ray Radiation on the Performance of Microelectromechanical Resonators

“…[ 11,13–22 ] Compared to alternative transduction methods like thermal/piezoresistive, capacitive, and electrostatic schemes, piezoelectric materials offer advantages such as higher energy density, superior frequency scaling, lower power configurations, and easier characterization and integration. [ 23–33 ] Incorporating additives into piezoelectric materials enhances material constants and aging characteristics. [ 34 ] Particularly, microscale resonant devices utilizing piezoelectric transduction, known as piezo‐MEMS resonators, find extensive utility in inertial sensing, radio frequency (RF) signal processing, and environmental monitoring applications.…”

“…[11,[13][14][15][16][17][18][19][20][21][22] Compared to alternative transduction methods like thermal/piezoresistive, capacitive, and electrostatic schemes, piezoelectric materials offer advantages such as higher energy density, superior frequency scaling, lower power configurations, and easier characterization and integration. [23][24][25][26][27][28][29][30][31][32][33] Incorporating additives into piezoelectric materials enhances material constants and aging characteristics. [34] Particularly, microscale resonant devices…”

Impact of Silicon Ion Irradiation on Aluminum Nitride‐Transduced Microelectromechanical Resonators

“…[25] In general, MEMS sensors and filters have very low mass, power consumption, and smaller footprint than their bulk circuit component equivalents. [26,27] Aluminum nitride (AlN) is especially attractive as a transduction material for MEMS resonators. AlN can be integrated into the complementary metal-oxide-semiconductor (CMOS) fabrication process, maintaining the majority of its bulk physical, thermal, and electrical properties even as a thin film.…”