Tunable (Ba, Sr)TiO3 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 TiO2 thin film buffer layer is suggested. TiO2 as buffer layer is grown onto Si substrate by atomic layer deposition and the coplanar IDC on BaxSr1-xTiO3(500 nm)/TiO2(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/TiO2/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/TiO2/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. (C) 2007 Wiley Periodicals, Inc.