BST tunability study at DC and microwave frequencies by using IDC and MIM capacitors

This paper reports the DC and Radio Frequency (RF) characterization of Ba_0.6S_0.4TiO₃ thin films using three different components. For DC characterization, two single circle patch MIM capacitors of different radii are fabricated over Pt/Ti/SiO₂/Si substrate covered with a 350 nm BST film. The measurement results show a tunability range of 61% for 0V to 20V biasing voltage. For higher frequency characterization, another MIM structures consisting of two imbricate circle patches are fabricated on the same substrate, where BST intrinsic parameters are extracted using a differential method. Results show that BST dielectric constant is nearly frequency independent; giving a tunability of 53% up to 20 GHz. On the other hand, a reflection IDC fabricated on BST/Al₂O₃ substrate is investigated. The IDC exhibits a capacitance tunability of 20% at 18 GHz.