Low Loss Tungsten-Based Electrode Technology for Microwave Frequency BST Varactors

Abstract

Composite metallization stacks consisting of 1.5 µm W layers and 0.1 µm Ir layers have been developed for low series resistance electrode applications. These hybrid metallization layers are compatible with barium strontium titanate deposition and standard patterning/etching procedures. The multilayer stacks were prepared for use as bottom electrodes in microwave varactors based upon the electrically tunable dielectric barium strontium titanate. These low resistivity layers are critical for realizing low insertion loss devices, and overcome difficulties associated with delamination or hillocking in traditional noble metal layers. Controlling the oxygen content during BST deposition was necessary to achieve high-quality BST and a stable electrode stack. Using these metallization stacks and optimized deposition conditions, BST films with tan δ values below 0.007 and tunabilities of 2:1 were realized. These properties are comparable to those measured on typical Pt/BST/Pt/SiO 2 /Si capacitors. Finally, a combination of reactive ion and wet chemical etching were used to demonstrate that the thick hybrid metallization layers are patternable using routine and manufacturable process methods.

Influence of sputter deposition parameters on the properties of tunable barium strontium titanate thin films for microwave applications

“…33 To compare the properties of the ferroelectric film without simplification we further use the Qfactor to illustrate the BST film loss-factor. …”

Electronic Beam Steering Metamaterial Antenna with Dual-Tuned Mode of Liquid Crystal Material

“…Moreover, electronic beam-steering CRLH metamaterial antennas integrated tunable components or materials have the ability to beam steer in a fixed frequency and increase the frequency reuse ratio and the spectrum utilization [20][21][22]. Familiar modulation methods, including varactor [23], ferrite [24], BST [25], MEMS [26] and mechanical tuning, are broadly applied in microwave and millimeter wave components. Compared with the forenamed tuning methods, LC features a wide application frequency range, convenient feeding and continuous linear tuning [27,28].…”

Electrode metallization for high permittivity oxide RF thin film capacitors

“…6 The use of W for electrode metallization can be found in literature. 7 Additionally, conducting oxides like RuO 2 and IrO 2 have been investigated, but mostly for memory applications. 8 This paper will focus on stable electrode metallization structures for RF high permittivity thin film devices.…”