The physical and electrical characteristics of Ta2O5 and physical vapor deposited ru in metal-insulator-metal capacitors

We fabricated a tantalum pentoxide (Ta2O5) capacitor with physical vapor deposition (PVD) ruthenium (Ru) as a bottom electrode and PVD TiN as a top electrode. The physical properties of PVD Ru film and thermal stability of the multilayer were evaluated. The electrical property of the capacitor was measured in terms of leakage current density. We found that RuO2 was formed during the post heat-treatment of Ta2O5 at 800degreesC in oxygen ambient. The oxygen content in Ru increased as annealing temperature was raised to 750degreesC even though Ru was not oxidized yet. In nitrogen ambient, however, RuO2 was not formed after heat-treatment. We confirmed that Ru keeps its pure metallic phase after annealing by X-ray analysis (Cu Kalpha(1), lambda = 1.5405 Angstrom). When the film is annealed Ru grains rotate and (002) faces come off from the film surface less than 20.075degrees. Those grains are not detected by the low incident angle mode because their incident angle becomes less than 21.075degrees when the angle between incident beam and film surface is 1degrees. Consequently, peak intensity rapidly decreases in low incident angle mode. The increase of peak intensity in 2theta/theta mode is due to the enhancement of preferred orientation by rotation of grains and partially due to grain growth. High relative permittivity of 50 was obtained after annealing at 800degreesC by rapid thermal process. We also obtained low leakage current of 6 x10(-9) A/cm(2) at +/-1 V bias with 13 nm thick Ta2O5 film in as-deposited condition and after annealing at 600degreesC by furnace annealing. For obtaining a TiN-Ta2O5-Ru capacitor with high permittivity and low leakage current, we need more research. (C) 2002 The Electrochemical Society.