Ohmic effects in BAW-resonators

Bulk acoustic wave (BAW) filters owe their performance advantages particularly to the excellent Q-values of the acoustic resonators. As these devices achieve very low impedances in the series resonance condition, the ohmic conductivity of the electrodes is expected to affect the device performance significantly. This paper presents a comprehensive analysis of ohmic effects including a discussion of the associated power dissipation as well as the interaction of ohmic and acoustic effects. The analysis is based on two combined techniques: first, the potential and current distribution on the electrodes and the resulting ohmic power dissipation are derived from surface vibration measured by laser interferometry and an inverse calculation of local charge distribution. The second technique is finite element modeling that has been extended by including ohmic conductivity, thus enabling a consistent electro-acoustic analysis