Low-loss tunable capacitors fabricated directly on gold bottom electrodes

• Published in: Applied physics letters 2006-03, Vol.88 (11), p.112905-112905-3
• Main Authors: Lu, Jiwei, Schmidt, Steffen, Boesch, Damien S., Pervez, Nadia, York, Robert A., Stemmer, Susanne
• Format: Article
• Language: English
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.2186077

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 allowed for a low thermal budget process compatible with Au electrodes. BZN thin films on Au bottom electrodes showed 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 reduced compared to capacitors with Pt bottom electrodes. The low device losses of Au/BZN capacitors revealed a device geometry-dependent loss mechanism that contributed significantly to the device loss at high frequencies.