Low-loss, tunable bismuth zinc niobate films deposited by rf magnetron sputtering

Abstract

Near-stoichiometric ${\mathrm{Bi}}_{\text{1.5}}{\mathrm{Zn}}_{\text{1.0}}{\mathrm{Nb}}_{\text{1.5}}{\mathrm{O}}_7$ (BZN) films were deposited by rf magnetron sputtering. The relative permittivity and dielectric loss of BZN films were measured with frequencies up to 100 MHz using planar ${\mathrm{Al}}_2{\mathrm{O}}_3/\mathrm{Pt/BZN/Pt}$ and ${\mathrm{Si/SiO}}_2/\mathrm{Pt/BZN/Pt}$ capacitor structures. BZN films with thicknesses in the range of 160 to 170 nm exhibited electric field tunable permittivities up to 220, and dielectric loss tangents less than 0.0005. A maximum applied bias field of 2.4 MV/cm resulted in a $\text{∼55\%}$ tunability of the dielectric constant. The permittivity was independent of the measurement frequency over a wide frequency range (10 kHz–100 MHz). Above 1 MHz, losses were increasingly dominated by conductor losses of the Pt bottom electrode. Their excellent dielectric properties make BZN films attractive candidates for low-loss, medium-permittivity integrated device applications.