EFFECTS OF POSTANNEALING TEMPERATURES AND AMBIENT ATMOSPHERES ON THE ELECTRICAL-PROPERTIES OF ULTRATHIN (BA,SR)TIO3 CAPACITORS

Ultrathin (Ba,Sr)TiO3 (BST) film capacitors with a Pt/Ba0.5Sr0.5TiO3(3 0 nm)/Pt/TiN/Si structure were fabricated. To investigate the effects of annealing temperatures, capacitors were annealed in Bowing Ar or O- 2 at temperatures ranging from 400 degrees C to 600 degrees C for 30 m in. The electrical properties of the annealed samples were strongly de pendent on the annealing temperatures. In the capacitors annealed at 5 00 degrees C (in Ar and O-2) and 550 degrees C (in O-2), the leakage c urrent decreased to a level of 10(-8) A/cm(2) when the bias voltage wa s +/-1.5 V. In the as-deposited sample, the maximum capacitance appear ed at a bias voltage of -1 V. However, the maximum capacitance increas ed and appeared at the zero bias voltage after annealing. These phenom ena are believed to be defect-related (due to oxygen vacancies). The a nnealing atmospheres were also found to have an effect on preserving t he morphology of the Pt electrodes.