Thermoelastic influence on the performance of film bulk acoustic wave resonators
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Film Bulk Acoustic wave Resonators (FBAR’s) are a promising new technology for high performance resonators in the GHz-range. FBAR’s can provide higher Q-factors and higher coupling efficency than the typical high performance resonators, such as SAW-resonators and similar technologies. To achieve the highest possible performance for these devices, the losses needs to be minimalized. At such high frequencies, the loss effects can have a huge influence on the total performance, and it is very useful to gain better knowledge about these loss effects. This thesis’ main goal is to investigate the thermoelastic loss effects in the metal contacts on the FBAR structure. Due to this metallization of the FBAR’s, thermal losses can occur in the metal layer which can cause a degrading of the performance. An analytical model will be developed for both thermal and non-thermal influence. The model will then be realized in Matlab, in order to quantify the performance of the FBAR with the different contact materials. The Qfactor and effective coupling factor are important parameters which will be used to compare the performance. Due to finding an important error in the Matlab code, most of the results has proven to be wrong. Unfortunately, the lack of time at the end of the project didn’t give me any chance to reproduce all the plots. Nevertheless I’ve done calculations on Aluminium at 5 GHz, aluminium is widely used as a contact material in RF-Mems. The correct results will be shown at the presentation of the thesis.