Effect of Y-Doping on the Dielectric Properties of BatiO3 Films Deposited in Reducing Atmospheres Using Pulsed Laser Deposition

BaTiO3-based multilayer capacitors with Ni electrodes are fired at low Po2 to prevent the oxidation of Ni. Amphoteric dopants such as Y, Ho and Dy are used to prevent electrical degradation due to oxygen vacancy migration. This paper describes use of this approach in preparing thin film BaTiO3 capacitors. Tolerance of reducing atmospheres is particularly important in films which are co-processed with resistors such as TaN for integrated resistor-capacitor networks. To assess this approach, films with and without Y-doping were grown in pure N2 atmospheres by pulsed laser deposition from undoped and 0.2wt% Y2O3 doped BaTiO3 targets, respectively. Films were deposited onto Pt/Ti/SiO2/Si substrates using a 5∼10Hz laser repetition rate, an energy density of 4.2J/cm2 and a working pressure of 100mTorr. It was found that polycrystalline perovskite films could be grown at 700°C and that Y-doped films had better crystallinity than the undoped ones. The dielectric constants of films without and with Y-doping are ∼1100 and ∼1300 at lkHz, respectively. The dielectric losses of Y-doped films were lower than for undoped films, possibly because the concentration of mobile charges including oxygen vacancies was decreased. Y-doped films also have a smaller coercive field (25kV/cm) and higher maximum polarization (∼20μC/cm2) than undoped films. The defect chemistry of the system is also discussed.