Characteristics of amorphous Bi2Ti2O7 thin films grown by atomic layer deposition for memory capacitor applications

Bi2Ti2O7 films were deposited on sputtered Ru/SiO2/Si substrates by atomic layer deposition using tris (1-methoxy-2-methyl-2-propoxy-2)bismuth [Bi(mmp)(3)], titanium tetraisopropoxide as Bi and Ti precursors, and H2O as oxidant, respectively. The wafer temperature was varied from 225 to 300 degrees C. The growth rates decreased from 0.075 nm/cycle at 225 degrees C C to 0.055 nm/cycle at 300 degrees C. The Bi concentration in the film decreased with increasing growth temperature and it could be controlled within a certain range by changing the Bi feeding at a given temperature. The as-grown Bi2Ti2O7 films were amorphous but contained metallic Bi at high growth temperatures and high Bi concentrations. Bi and Ti piled-up on the film surface and the Ru interface, respectively. The electrical leakage property of the Bi2Ti2O7 thin film became worse with increasing deposition temperature and Bi concentration due to the metallic Bi formation. The dielectric constant at the optimum deposition condition (225 degrees C) was similar to 40, and the leakage current level was < 10(-7) A/cm(2) at 1.0 MV/cm at a film thickness of similar to 15 nm. Reasonable conformal film thickness and cation composition over contact holes with a diameter of 0.15 mu m and a depth of 1.1 mu m were obtained. (c) 2005 The Electrochemical Society.