Low-loss tunable capacitors fabricated directly on gold bottom electrodes

Abstract

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 (>1MHz) 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.

Parallel-Plate Capacitors

“…2, the quality factors for all sizes of devices are grossly frequency dependent, and smaller area devices have higher . Area-dependent quality factors have also been observed in similarly sized cubic pyrochlore bismuth-zinc-niobate parallel-plate capacitors [12], [13]. Thus, we believe that this behavior may be common to other small-geometry high-permittivity devices.…”

“…Our pathway can be modeled as a short-circuit terminated transmission line of length . Thus, the input admittance of the parasitic pathway is (11) The conductance correction is (12) and the capacitance correction is (13) For most of the devices in our set, is very large, thus,…”

“…In our measurements, we find the series resistance of all of the devices in this geometry series to be approximately 1 . Additionally, in [13], bismuth-zinc-niobate parallel-plate capacitors fabricated on gold and platinum bottom electrodes were compared. The gold bottom electrodes were found to improve device , but not affect the additional series resistance term.…”

Effect of deposition pressure on the dielectric properties of bismuth magnesium niobium titanium thin films prepared by RF magnetron sputtering

“…However, the high dielectric loss limits their further practical application [7]. Recently, it was reported that the bismuth-based material with cubic pyrochlore structure was the potential candidate for its low loss and large tunability [8][9][10][11][12]. The Bi 1.5 ZnNb 1.5 O 7 (BZN) material with cubic pyrochlore structure, was reported to exhibit excellent tunability and low loss [8,9].…”

Effect of rf power on the dielectric properties of bismuth magnesium niobium titanium thin films deposited by RF magnetron sputtering

“…Recently, the bismuth-based materials with cubic pyrochlore structure came into the vision of researchers [9][10][11]. It was reported that the Bi 1.5 MgNb 1.5 O 7 (BMN) thin films exhibited impressive tunable properties and low dielectric loss [12,13].…”