BARRIER LAYERS FOR REALIZATION OF HIGH CAPACITANCE DENSITY IN SRTIO3 THIN-FILM CAPACITOR ON SILICON

High dielectric constant SrTiO3 thin films were sputter deposited on barrier layers/Si substrate to fabricate a capacitor for dynamic random access memories. Dielectric constant (εr) values of 140-210 were achieved for the 150-nm-thick SrTiO3 films using a Pt/Ti or Pt/Ta double-layer barrier. In the Pt(50 nm)/Ti(10 nm), Pt(50 nm)/Ti(50 nm), and Pt(50 nm)/Ta(10 nm) barrier, effective εr decreased by annealing in the temperature range between 450 and 550°C, where the interdiffusion of Pt and Si was confirmed by x-ray diffraction analysis and cross-sectional transmission electron microscopy. In the Pt(50 nm)/Ta barrier, increase of the Ta thickness from 10 to 50 nm brought out a remarkable improvement of endurance to high-temperature annealing. That is, in the Pt(50 nm)/Ta(50 nm) barrier, large εr value (∼200) was maintained even with annealing at up to 700°C.