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Vibrating polysilicon micromechanical ring-resonator structure operating in a compound mode is proposed. Results suggest the achievement of higher frequency and lower impedance.

Substantial reductions in vibrating micromechanical resonator series motional resistance [R.sub.x] have been attained by mechanically coupling and exciting a parallel array of corner-coupled polysilicon square plate resonators. Using this technique with seven resonators, an effective [R.sub.x] of 480 [OMEGA] has been attained at 70 MHz, which is more than 5.9X smaller than the 2.82 k[OMEGA] exhibited by a stand-alone transverse-mode corner-supported square resonator, and all this achieved while still maintaining an effective Q > 9000. This method for [R.sub.x]-reduction is superior to methods based on brute force scaling of electrode-to-resonator gaps or dc-bias increases, because it allows a reduction in [R.sub.x] without sacrificing linearity, and thereby breaks the [R.sub.x] versus dynamic range tradeoff often seen when scaling. This paper also compares two types of anchoring schemes for transverse-mode square micromechanical resonators and models the effect of support beam parameters on resonance frequency. Index Terms--Array, impedance, mechanical coupling, micromechanical resonator, motional resistance, quality factor, resonator, radio frequency (RF) microelectromechanical systems (MEMS), square plate.

A micromechanical, laterally vibrating disk resonator, fabricated via a technology combining polysilicon surface-micromachining and metal electroplating to attain submicron lateral capacitive gaps, has been demonstrated at frequencies as high as 829 MHz and with Q's as high as 23000 at 193 MHz. Furthermore, the resonators have been demonstrated operating in the first three radial contour modes, allowing a significant frequency increase without scaling the device, and a 193 MHz resonator has been shown operating at atmospheric pressure with a Q of 8,880, evidence that vacuum packaging is not necessary for many applications. These results represent an important step toward reaching the frequencies required by the RF front-ends in wireless transceivers. The geometric dimensions necessary to reach a given frequency are larger for this contour-mode than for the flexural-modes used by previous resonators. This, coupled with its unprecedented Q value, makes this disk resonator a choice candidate for use in the IF and RF stages of future miniaturized transceivers. Finally, a number of measurement techniques are demonstrated, including two electromechanical mixing techniques, and evaluated for their ability to measure the performance of sub-optimal (e.g., insufficiently small capacitive gap, limited dc-bias), high-frequency, high-Q micromechanical resonators under conditions where parasitic effects could otherwise mask motional output currents. Index Terms--Electromechanical coupling, microelectromechanical systems (MEMS), microelectromechanical devices, microresonator, quality factor, resonator, UHF, VHF.

A new fabrication methodology that allows self-alignment of a micromechanical structure to its anchor is used to achieve vibrating raidal-contour mode polysilicon micromechanical disk resonators with resonance frequencies up to 1.156 GHz. An equivalent electrical circuit model is formulated that accurately predicts the performance of disk resonators, and provides details on the fabrication process, testing techniques, and experimental results.

A device comprised of interlinked micromechanical resonators with capacitive mixer transducers has been demonstrated to perform both frequency translation (i.e., mixing) and highly selective low-loss filtering of applied electrical input signals. In particular, successful downconversion of a 200-MHz radio frequency (RF) signal down to a 37-MHz intermediate frequency (IF) and subsequent high-Q bandpass filtering at the IF are demonstrated using this single, passive, micromechanical device, all with less than 13 dB of combined mixing conversion and filter insertion loss. The mixer-filter (or 'mixler') RF-to-IF voltage transfer function is shown to depend upon a ratio of local oscillator amplitude and applied bias voltages. [796] Index Terms--Bandpass filter, electromechanical coupling, IF, intermediate frequency, microelectromechanical systems (MEMS), microelectromechanical devices, mixer, quality factor, resonator, VHF.

A glass vacuum package based on localized aluminum/silicon-to-glass bonding has been successfully demonstrated. A constant heat flux model shows that heating can be confined locally in the dielectric layer underneath a microheater as long as the width of the microheater and the thickness of silicon substrate are much smaller than the die size and a good heat sink is placed underneath the silicon substrate. With 3.4 W heating power, ~ 0.2 MPa applied contact pressure and 90 min wait time before bonding, vacuum encapsulation at 25 mtorr (~ 3.33 Pa) can be achieved. Folded-beam comb drive [micro]-resonators are encapsulated and used as pressure monitors. Long-term testing of vacuum-packaged [micro]-resonators with a Quality Factor (Q) of 2500 has demonstrated stable operation after 69 weeks. A [micro]-resonator with a Q factor of ~ 9600 has been vacuum encapsulated and shown to be stable after 56 weeks. [686] Index Terms--Localized heating, MEMS packaging, microresonators, vacuum encapsulation, wafer level packaging.

Free-free-beam flexural-mode micromechanical resonators utilizing nonintrusive supports to achieve measured Qs as high as 8400 at VHF frequencies from 30 to 90 MHz are demonstrated in a polysilicon surface micromachining technology. The microresonators feature torsional-mode support springs that effectively isolate the resonator beam from its anchors via quarter-wavelength impedance transformations, minimizing anchor dissipation and allowing these resonators to achieve high-Q with high stiffness in the VHF frequency range. The free-free-beam micromechanical resonators of this paper are shown to have an order of magnitude higher Q than clamped-clamped-beam versions with comparable stiffnesses. [499] Index Terms--Anchor loss, electromechanical coupling, IF filter, MEMS, microelectromechanical devices, motional resistance, quality factor, resonator, VHF.

Third-order, high-Q, micromechanical bandpass filters comprised of three ratioed folded-beam resonators coupled by flexural mode springs are demonstrated using an integrated circuit compatible, doped polycrystalline silicon surface-micromachining technology. A complete design procedure for multiresonator micromechanical filters is presented and solidified via an example design. The use of quarter-wavelength coupling beams attached to resonators at velocity-controllable locations is shown to suppress passband distortion due to finite-mass and process mismatch nonidealities, which become increasingly important on this microscale. In addition, low-velocity coupling methods are shown to greatly alleviate the lithographic resolution required to achieve a given percent bandwidth. Ratioed folded-beam micromechanical resonators are introduced as the key impedance transforming components that enable the needed low-velocity coupling. Using these design techniques, balanced three-resonator microscale mechanical filters with passband frequencies centered around 340 kHz are demonstrated with percent bandwidths of 0.1%, associated insertion losses as small as 0.1 dB, 20-dB shape factors as low as 1.5, and stopband rejections greater than 64 dB. Measurement and theory are rigorously compared and important limitations, such as thermal susceptibility, the need for passband tuning, and inadequate electromechanical coupling, are addressed. [470] Index Terms--Circuit modeling, fabrication, electromechanical coupling, filters, high-Q, insertion loss, MEMS, microelectromechanical devices, micromachining, micromechanical, passband tuning, percent bandwidth, quarter-wavelength, resonators.