Philip J. Stephanou

Piezoelectric Aluminum Nitride Vibrating Contour-Mode MEMS Resonators

This paper reports theoretical analysis and experimental results on a new class of rectangular plate and ring-shaped contour-mode piezoelectric aluminum nitride radio-frequency microelectromechanical systems resonators that span a frequency range from 19 to 656 MHz showing high-quality factors in air (Qmax=4300 at 229.9 MHz), low motional resistance (ranging from 50 to 700 Omega), and center frequencies that are lithographically defined. These resonators achieve the lowest value of motional resistance ever reported for contour-mode resonators and combine it with high Q factors, therefore enabling the fabrication of arrays of high-performance microresonators with different frequencies on a single chip. Uncompensated temperature coefficients of frequency of approximately -25 ppm/degC were also recorded for these resonators. Initial discussions on mass loading mechanisms induced by metal electrodes and energy loss phenomenon are provided

Single-Chip Multiple-Frequency ALN MEMS Filters Based on Contour-Mode Piezoelectric Resonators

This paper reports experimental results on a new class of single-chip multiple-frequency (up to 236 MHz) filters that are based on low motional resistance contour-mode aluminum nitride piezoelectric micromechanical resonators. Rectangular plates and rings are made out of an aluminum nitride layer sandwiched between a bottom platinum electrode and a top aluminum electrode. For the first time, these devices have been electrically cascaded to yield high performance, low insertion loss (as low as 4 dB at 93MHz), and large rejection (27 dB at 236 MHz) micromechanical bandpass filters. This novel technology could revolutionize wireless communication systems by allowing cofabrication of multiple frequency filters on the same chip, potentially reducing form factors and manufacturing costs. In addition, these filters require terminations (1 kOmega termination is used at 236 MHz) that can be realized with on-chip inductors and capacitors, enabling their direct interface with standard 50-Omega systems

Low motional resistance ring-shaped contour-mode aluminum nitride piezoelectric micromechanical resonators for UHF applications

This paper reports experimental results on a new class of ring-shaped, contour-mode aluminum nitride piezoelectric resonators that span a frequency range from 223 MHz to 656 MHz showing high quality factors in air (Q/sub max/=2,900 at 472.7 MHz), low motional resistance (ranging from 56 to 205 /spl Omega/), and center frequencies that can be lithographically tuned. These resonators achieve the lowest value of motional resistance ever reported for contour-mode resonators and combine it with high Q factors, therefore truly enabling the fabrication of arrays of microresonators with different frequencies on a single chip. Uncompensated temperature coefficients of frequency of only approximately -25 ppm//spl deg/C were also recorded for these resonators.

PS-4 GHZ Contour Extensional Mode Aluminum Nitride MEMS Resonators

This work presents higher-order contour mode piezoelectric AlN MEMS resonators with lithographically defined GHz operating frequencies. By selectively patterning the transduction electrodes and routing the electrical excitation waveform, the resonant frequency of the device is uncoupled from the overall dimensions of the AlN plate and spurious electrical responses are suppressed over a wide frequency range. Resonators employing either parallel or coplanar ground and signal electrode pairs have been developed. The design has been validated by demonstrating a 1.28 GHz resonator with a 231 Omega motional resistance and a Q factor over 1,400 when tested in air

Single-chip multiple-frequency filters based on contour-mode aluminum nitride piezoelectric micromechanical resonators

This paper reports experimental results on a new class of single-chip multiple-frequency (up to 236 MHz) filters that are based on low motional resistance contour-mode aluminum nitride piezoelectric micromechanical resonators. For the first time, aluminum nitride rectangular plates and rings have been electrically cascaded to yield high performance, low insertion loss (as low as 4dB at 93 MHz) micromechanical band pass filters. This novel technology could revolutionize wireless communication systems by allowing the co-fabrication of multiple frequency filters (IF and RF) on the same chip, therefore reducing form factors and manufacturing costs. In addition, these filters require terminations on the order of k/spl Omega/, thereby making possible their direct interface with standard 50 /spl Omega/ systems.

Mechanically Coupled Contour Mode Piezoelectric Aluminum Nitride MEMS Filters

A new class of mechanically coupled contour mode MEMS filters is demonstrated using a thin film piezoelectric aluminum nitride (AlN) process. The use of contour modes, whose frequencies are set by lithographically defined dimensions, permits the co-fabrication of multiple filters at arbitrary frequencies on the same chip. The stronger electromechnical coupling of the thin film piezoelectric structural material vis-à-vis electrostatically transduced devices results in lower insertion losses (as low as 1.5 dB) with termination values of 1 to 2.5 kΩ. Finally, filters synthesized using mechanically coupled resonators are fundamentally capable of wider bandwidths than electrically coupled ladder filters without requiring external tuning elements. Two designs for bandpass filters are analyzed, fabricated, and tested. The filters have center frequencies of 40 and 100 MHz.

GHZ higher order contour mode ALN annular resonators

This work introduces a new class of low motional resistance piezoelectric aluminum nitride (AlN) MEMS ring resonators that operate in GHz contour modes of vibration. The resonators are based on an annular thin film AlN structural layer sandwiched between two or more pairs of concentric transduction electrodes whose design effectively uncouples the resonant frequency of the device from its transduction area (and consequently its motional resistance) at the layout level. The devices under test exhibit lithographically-defined fundamental series resonant frequencies from 1.03 to 1.60 GHz, motional resistances from 57 to 130 Omega, a resonator figure of merit (FOM = kt 2Q) of 6.4 to 7.4, and no coherent spurious responses from DC to 5 GHz.

AlN Contour-Mode Vibrating RF MEMS for Next Generation Wireless Communications

AlN contour-mode vibrating RF MEMS resonator technology is described as capable of low-loss filtering and frequency synthesis for next generation wireless devices. Contour-mode piezoelectric resonators can span frequencies from 10 MHz up to few GHz on the same silicon chip offering high quality factors in air (1,000-4,000) and low motional resistance (25-700 Omega). Low loss (<- 1.5 dB) electrically and mechanically coupled filters and low phase noise oscillators can be easily implemented using this resonator technology. Low power transceiver architectures based on frequency hopping, multi-band filtering and direct frequency synthesis are presented as next generation wireless solutions that will be enabled by this new class of AIN contour-mode resonators

Single-chip multiple-frequency RF microresonators based on aluminum nitride contour-mode and FBAR technologies

This work reports experimental results on a new class of multiple-frequency contour-mode bulk acoustic wave aluminum nitride resonators that were co-fabricated on the same silicon chip with suspended thin film bulk acoustic resonators (FBAR). The novel contour-mode technology combined with FBAR resonators permit the fabrication of integrated single-chip RF platforms that can cover IF and RF frequencies of particular interest to the handset market. High Q ranging from 2,000 to 4,000 were demonstrated for rectangular and ring shaped contour-mode resonators in air at frequencies as high as 473 MHz. FBAR resonators with Q of 2,000 at 1.75 GHz were fabricated on the same substrate. To further prove the contour-mode technology, ladder filters at 93 and 236 MHz were demonstrated with insertion losses of 4 and 8 dB, respectively, 3 dB bandwidth of 0.3 % and high out-of-band rejection (larger than 26 dB). In addition a low phase noise (less than - 110 dBc/Hz at 10 kHz offset) oscillator was realized using a 224 MHz ring resonator in a standard pierce design.

Piezoelectric Thin Film AlN Annular Dual Contour Mode Bandpass Filter

The following work presents the analytical, numerical and experimental characterization of a novel piezoelectric Aluminum Nitride MEMS bandpass filter. In contrast to multipole filters employing distinct mechanically or electrically coupled resonator building blocks, the passband of the device in the present work is defined by the proximity of two natural contour modes of vibration in a single annular resonator. The proposed implementation, albeit currently limited to dual -pole filters, results in smaller form factors and reduces device sensitivity to across wafer fabrication tolerances.