UC Santa Barbara

At microwave frequencies, conductor losses due to the bottom electrode resistance severely limit the performance of metal-insulator-metal capacitors that employ tunable dielectric thin films. Here we demonstrate that a novel tunable dielectric, bismuth zinc niobate (BZN), can be integrated directly with low-resistivity Au bottom electrodes. The favorable crystallization kinetics of the BZN pyrochlore structure allowed for a low thermal budget process compatible with Au electrodes. BZN thin films on Au bottom electrodes showed very low dielectric loss tangents of ~ 0.0005 and high dielectric tunabilities of ~ 50%. The Au/BZN interface was abrupt and free of reaction phases. At high frequencies (>1 MHz) the total Au/BZN capacitor device loss was significantly reduced compared to capacitors with Pt bottom electrodes. The low device losses of Au/BZN capacitors revealed an additional, device geometry-dependent loss mechanism that contributed significantly to the device loss at high frequencies.