Thermal characterization of Surface Acoustic Wave devices

Reliability of micro-electronic devices is one of the most important issues in mobile communication systems and is significantly influenced by the thermal behavior of the components. This study presents different schemes for thermal characterization of a half-section ladder-type Surface Acoustic Wave (SAW) filter which is acoustically passivated with a thick SiO₂ layer. Unitarity violation quantifies the entire power loss in the device but is unfeasible regarding correlation to each resonator. The Temperature Coefficient of Frequency (TCF) characterizes thermally induced frequency shifts and has the potential to investigate the resonators´ temperatures separately in first order. However, uncertainties arise using this indirect approach as soon as other effects causing a frequency shift play a role. Thermographic techniques such as Infrared Thermography (IRT) and Liquid Crystal Thermography (LCT) serve as direct measurement schemes eliminating inaccuracies inherent to TCF based evaluations and show good agreement with simulation results. Moreover, LCT and IRT provide spatially resolved temperature measurements of the component.