Find in Library

This study presents the effects of bottom electrode designs on the operation of laterally vibrating aluminum nitride (AlN) contour-mode resonators (CMRs). A total of 160 CMRs were analyzed with varying bottom electrode areas at two resonant frequencies (<i>f</i>₀) of about 230 MHz and 1.1 GHz. Specifically, we analyzed the impact of bottom electrode coverage rates on the resonator quality factor (<i>Q</i>) and electromechanical coupling (<i>k</i>²), which are important parameters for Radio Frequency (RF) and sensing applications. From our experiments, <i>Q</i> exhibited different trends to electrode coverage rates depending on the device resonant frequencies, while <i>k</i>² increased with the coverage rate regardless of <i>f</i>₀. Along with experimental measurements, our finite element analysis (FEA) revealed that the bottom electrode coverage rate determines the active (or vibrating) region of the resonator and, thus, directly impacts <i>Q</i>. Additionally, to alleviate thermoelastic damping (TED) and focus on mechanical damping effects, we analyzed the device performance at 10 K. Our findings indicated that a careful design of bottom electrodes could further improve both <i>Q</i> and <i>k</i>² of AlN CMRs, which ultimately determines the power budget and noise level of the resonator in integrated oscillators and sensor systems.