Thin film bulk acoustic wave devices : performance optimization and modeling

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Perustieteiden korkeakoulu | Doctoral thesis (article-based)
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Date
2011
Major/Subject
Mcode
Degree programme
Language
en
Pages
Verkkokirja (1858 KB, 97 s.)
Series
VTT publications, 756
Abstract
Thin film bulk acoustic wave (BAW) resonators and filters operating in the GHz range are used in mobile phones for the most demanding filtering applications and complement the surface acoustic wave (SAW) based filters. Their main advantages are small size and high performance at frequencies above 2 GHz. This work concentrates on the characterization, performance optimization, and modeling techniques of thin film BAW devices. Laser interferometric vibration measurements together with plate wave dispersion modeling are used to extract the full set of elastic material parameters for sputter deposited ZnO, demonstrating a method for obtaining material data needed for accurate simulation of the devices. The effectiveness of the acoustic interference reflector used to isolate the vibration from the substrate is studied by 1-D modeling, 2-D finite element method and by electrical and laser interferometric measurements. It is found that the Q-value of reflector-based BAW resonators operating at 2 GHz is limited to approximately 2000 by mechanisms other than leakage through the reflector. Suppression of spurious resonances in ZnO resonators is studied in depth by modeling and measurements. It is verified that the approximate mode orthogonality is behind the suppression in boundary frame type ZnO devices operating in the piston mode, but also another narrow band mode suppression mechanism is found. A plate wave dispersion based 2-D simulation scheme for laterally acoustically coupled BAW resonator filters is developed and employed in designing of experimental devices, which show both good agreement with the model predictions and a remarkable 4.9 % relative bandwidth.
Description
Supervising professor
Kaivola, Matti, Prof.
Keywords
thin film, bulk acoustic wave, BAW, AIN, ZnO, resonator, filter, GHz, microacoustic, modeling, interferometric imaging
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Parts
  • [Publication 1]: T. Makkonen, T. Pensala, J. Vartiainen, J.V. Knuuttila, J. Kaitila, and M.M. Salomaa, Estimating Materials Parameters in Thin-Film BAW Resonators Using Measured Dispersion Curves, IEEE Trans. on Ultrasonics, Ferroelectrics and Frequency Control, vol. 51, 2004, pp. 42-51.
  • [Publication 2]: T. Pensala, R. Thalhammer, J. Dekker, and J. Kaitila, Experimental Investigation of Acoustic Substrate Losses in 1850-MHz Thin Film BAW Resonator, IEEE Trans. on Ultrasonics, Ferroelectrics and Frequency Control, vol. 56, 2009, pp. 2544-2552.
  • [Publication 3]: K. Kokkonen, T. Pensala, and M. Kaivola, Dispersion and Mirror Transmission Characteristics of Bulk Acoustic Wave Resonator, IEEE Trans. on Ultrasonics, Ferroelectrics and Frequency Control, vol. 58, 2011, pp. 215-225.
  • [Publication 4]: T. Pensala and M. Ylilammi, Spurious Resonance Suppression in Gigahertz-Range ZnO Thin-Film Bulk Acoustic Wave Resonators by the Boundary Frame Method: Modeling and Experiment, IEEE Trans. on Ultrasonics, Ferroelectrics and Frequency Control, vol. 56, 2009, pp. 1731-1744.
  • [Publication 5]: T. Pensala, J. Meltaus, K. Kokkonen and M. Ylilammi, 2-D Modeling of Laterally Acoustically Coupled Thin Film Bulk Acoustic Wave Resonator Filters, IEEE Trans. on Ultrasonics, Ferroelectrics and Frequency Control, vol. 57, 2010, pp. 2537-2549.
  • [Publication 6]: J. Meltaus, T. Pensala, K. Kokkonen and A. Jansman, Laterally Coupled Solidly Mounted BAW Resonators at 1900 MHz, Proc. IEEE Ultrasonics Symposium, 2009, pp. 847-850.
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