Measurement of antiresonant frequency during DC bias voltage application for analysis of second harmonic response of ScAlN on SMR

Second harmonic generation (H2) is not desirable for BAW filter applications. Recent BAW filter requires reduction of H2 to achieve high receiver sensitivity. In order to reduce H2, nonlinear parameters of AlN and ScAlN are important because it is widely used in BAW filters. Irieda et al. indicated that second order nonlinear piezoelectric coefficients chi{11}{}-{mathrm{T}} and dielectric chi{02}{}-{mathrm{E}} are dominant for H2 [1], [2]. They showed these nonlinear coefficients chi{11}{}-{mathrm{T}} and chi{02}{}-{mathrm{E}} can be approximately estimated from the change of parallel resonant frequency f{mathrm{p}} and inverse dielectric constant beta-{mathrm{S}} during a DC bias voltage application. In this study, AlN and ScAlN films were grown on Al bottom electrode/Ta2O5/SiO2 Bragg reflector (SMR) by RF magnetron sputtering. f{mathrm{p}} and beta-{mathrm{S}} of AlN/SMR and ScAlN/SMR as a function of the DC bias voltage were measured. Nonlinear parameter chi{11}{}-{mathrm{T}} and chi{02}{}-{mathrm{E}} of films were estimated. chi{11}{}-{mathrm{T}} was decreased with increasing of Sc concentration.