A Study on the Effects of Release Area on the Quality Factor of Contour-Mode Resonators by Laser Doppler Vibrometry

Through the use of a laser Doppler vibrometer, it is shown that a 31% variation in quality factor can occur due to the effect of undercutting of the device layers outside of the anchors of a 220-MHz aluminum nitride contour-mode resonator. This undercutting is a result of the isotropic etch process used to release the device from the substrate. This paper shows that the variation in <inline-formula> <tex-math notation="LaTeX">$Q$ </tex-math></inline-formula> is a function of the release distance, <inline-formula> <tex-math notation="LaTeX">$L$ </tex-math></inline-formula>, between the active region of the resonator and the edge of this released region. This paper also determined a design modification that eliminated this issue and achieved a <inline-formula> <tex-math notation="LaTeX">$Q$ </tex-math></inline-formula> of 3048, which is independent of <inline-formula> <tex-math notation="LaTeX">$L$ </tex-math></inline-formula>.

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