LEAKAGE AND INTERFACE ENGINEERING IN TITANATE THIN-FILMS FOR NONVOLATILE FERROELECTRIC MEMORY AND ULSI DRAMS

The leakage behavior of Pb(Zr,Ti)O-3 PZT and (Ba,Sr)TiO3 (BST) thin fi lms has been studied. The leakage behavior is dependent upon the botto m electrode. PZT films on RuO2 bottom electrodes display a large leaka ge, predominantly ohmic in behavior, which we have shown to be PZT mic rostructure-controlled. The leakage of PZT and BST films on Pt display Schottky emission characteristics which is controlled by the film/ele ctrode interface. In the case of PZT films, we have shown that several methods can be utilized to successfully lower the RuO2/PZT/RuO2 syste m leakage, while retaining the long term performance. These methods in clude pre-annealing of RuO2 bottom electrode prior to PZT film deposit ion; addition of buffer layer between RuO2 and PZT film; and PZT film growth via in-situ ion beam sputter-deposition.