Damping in Aluminum Nitride Contour Mode MEMS Resonators

This work compiles the efforts made to determine and model the main damping mechanisms in Aluminum Nitride (AlN) Contour Mode Resonators (CMRs). Experiments have proved that there are two main sources of damping dominating the AlN CMR quality factor (Q) at very and ultra high frequency (V/UHF): thermoelastic damping (TED) in the metal electrodes (Q(ted)) and anchor losses (Q(anc)). A semi-analytical 1D approach that treats the electrodes as standard anelastic solids exhibiting thermoelastic coupling has been followed to qualitatively estimate Q(ted). Instead, a finite element method (FEM) that imposes fixed-constraints (FC) at the edge of the released substrate and computes the energy lost as the total acoustic energy transferred to the substrate has been developed to quantitatively predict Q(anc). As an example of the experiments run to demonstrate the impact of Q(ted) and Q(anc), we look, in this work, at the temperature dependence of Q displayed by resonators having different electrodes materials.