IN-SITU STUDY OF ATOMIC LAYER EPITAXY GROWTH OF TANTALUM OXIDE THIN-FILMS FROM TA(OC2H5)(5) AND H2O

Ta2O5 thin films have been deposited in atomic layer epitaxy process f rom Ta(OC2H5)(5) and H2O. A quartz crystalline mass-sensor was exploit ed to detect the adsorption processes at the gas-solid interface durin g the film growth. It is suggested that Ta(OC2H5)(5) reacts with surfa ce hydroxyls producing intermediate surface species (-O)(n)Ta(OC2H5)(5 -n) where n varies with the reactor temperature. During the subsequent water pulse these species react further converting the surface back t o the hydroxyl-terminated one. The uncontrolled deposition due to the temperature-induced decomposition of tantalum ethoxide with the activa tion energy of 100 +/- 6 kJ/mol contributes to the film growth above 2 75 degrees C. The value of the diffusion coefficient D = 0.0075 m(2)/s for gas-phase Ta(OC2H5)(5) has been calculated at 250 degrees C. Esti mated sticking coefficient of Ta(OC2H5)(5) is about one order of magni tude higher than that of H2O and nearly one order of magnitude lower t han that of TaCl5.