Anchor Losses in AlN Contour Mode Resonators

Abstract

In this paper, we analyze possible sources of dissipation in aluminium nitride (AlN) contour mode resonators for three different resonance frequency devices (f r ) (220 MHz, 370 MHz, and 1.05 GHz). For this purpose, anchors of different widths (W a ) and lengths (L a ) proportional to the acoustic wavelength (λ) are designed as supports for resonators in which the dimensions of the vibrating body are kept fixed. The Q extracted experimentally confirms that anchor losses are the dominant source of damping for most anchor designs when f r is equal to 220 and 370 MHz. For specific anchor dimensions (W a /λ is in the range of 1/4-1/2) that mitigate energy leakage through the supports, a temperature-dependent dissipation mechanism dominates as seen in higher f r resonators operating close to 1.05 GHz. To describe the Q due to anchor losses, we use a finite-element method with absorbing boundary conditions. We also propose a simple analytical formulation for describing the dependence of the temperature-dependent damping mechanism on frequency. In this way, we are able to quantitatively predict Q due to anchor losses and qualitatively describe the trends observed experimentally.[ 2014-0232]Index Terms-AlN contour mode resonators, quality factor, anchor losses, temperature dependent dissipation, finite element analysis, perfectly matched layer. 1057-7157

Application of optimally-shaped phononic crystals to reduce anchor losses of MEMS resonators

“…3 are reported. The Q-factor for anchor losses only in the absence of PnC is 344, the matching between the numerical result and the experimental testing can be found in [1]. The first comment on the results of Tab.…”

“…3d) is adopted. In order to confirm these numerical predictions a proper experimental campaign must be conducted, nevertheless it must be noticed that the three-dimensional finite element solver used for the anchor losses calculation has been already validated in a previous work [1].…”

“…At low frequency (i.e. 200MHz) and up to room temperature or at low temperature in general, the Q-factor is dominated by is anchor losses [1]. A valid provision to reduce anchor losses is the application of phononic crystals (PnCs), which show complete band gaps in the transmission of elastic waves, therefore they can be considered as highly efficient acoustic reflectors, which can be used in order to confine the elastic energy.…”

Graphene–aluminum nitride NEMS resonant infrared detector

“…However, the physical and electrical properties of the device metal electrodes fundamentally limit the volume scaling of such resonators. In fact, the bulky metal electrodes attached to the piezoelectric resonant body of the device have been confirmed as a source of mechanical loading and energy loss 19,20 , which reduces the resonance frequency, f 0 , and the quality factor, Q, of the device. Although metal electrodes much thinner than the piezoelectric plate are highly desirable, owing to the requirement of high-electrical conductivity, the thickness of such metal layers can hardly be scaled proportionally to that of the piezoelectric vibrating body of the device using current microfabrication techniques.…”

Green’s Function for the Evaluation of Anchor Losses in Mems

“…Moreover, recent experimental results indicate the presence of additional temperature dependent dissipation mechanisms which are not yet fully understood (see e.g. [2,12]). In a resonating structure the quality factor Q is defined as:…”