BaSrTiO3 thin films for integrated high frequency capacitors

The complex oxide dielectric Ba_1-xSr_xTiO₃ (BST) has recently been studied intensively for DRAM applications. Another significant nearer term application for which BST may be suited is replacement of discrete capacitors now attached to advanced IC´s. Specific devices include bypass, decoupling, and switched filter capacitors, often operated at high frequencies. With current SiO₂ based dielectrics such integrated capacitors may take up from 20% to 50% of the device area; use of higher dielectric constant BST could reduce this by at least a factor of 10. We will discuss properties of MOCVD-grown BST which relate to these capacitor applications, including second order dielectric nonlinearity and leakage currents at useful device operating voltages (3 V). Dielectric constant, nonlinearity and breakdown voltages are found to have a strong dependence on deposition temperature of BST films, so optimum processing conditions will depend on the end device application