Impact of nonlinearity in probe contacts on nonlinearity measurement of RF SAW/BAW devices

Abstract Probe-to-wafer contact (PWC) has often been overlooked in on-wafer nonlinearity measurements of radio frequency surface acoustic wave (SAW) and bulk acoustic wave devices, yet the authors’ experience indicates that it can significantly distort the results. This work demonstrates that PWC introduces non-negligible nonlinear products, which are correlated with electrode surface oxidation and contact impedance. To characterize this effect, a nonlinear modified Butterworth–Van Dyke model incorporating PWC nonlinearity is proposed, which well fits the measured second- and third-order harmonic spectra of a temperature-compensated SAW resonator. For the first time, we reveal the critical role of PWC nonlinearity in nonlinear measurement, providing a solid basis for reliable on-wafer nonlinear characterization of acoustic devices.