Tunable (Ba, Sr)TiO 3 interdigital capacitor onto Si wafer for reconfigurable radio

In this article, the potential feasibility of integrating BST films into Si wafer by adopting tunable interdigital capacitor (IDC) with TiO 2 thin film buffer layer is suggested. TiO 2 as buffer layer is grown onto Si substrate by atomic layer deposition and the coplanar IDC on Ba x Sr 1−x TiO 3 (500 nm)/TiO 2 (50 nm)/high resistivity Si (HR‐Si) is fabricated. BST interdigital tunable capacitors integrated on HR‐Si substrate with high tunability and low loss tangent are characterized for their microwave performances. BST/HR‐Si and BST/TiO 2 /HR‐Si IDCs show much enhanced tunability values of 31% and 40%, respectively as compared to the value of 21% obtained with BST film on MgO single crystal substrate at the bias of 5 kV/cm. BST/TiO 2 /HR‐Si structure shows much improved figure of merit of 504.4 as compared to 418.53 and 101.68 of BST/MgO and BST/HR‐Si structure, respectively. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2144–2148, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22657