Plasma-enhanced atomic layer deposition of tantalum thin films: the growth and film properties

Ta thin films were grown by plasma-enhanced atomic layer deposition (PE-ALD) on Si and SiO2 substrates. The deposition processes and film properties were investigated as a function of various key growth kinetic parameters, including TaCl5 exposure time, atomic hydrogen exposure time, hydrogen flow, and growth temperatures. The growth rate increases with increasing TaCl5 exposure time to saturate at approximately 0.08 Angstrom/cycle. Cl content and resistivity, which are closely related each other, are strong function of H exposure time and growth temperature. Low resistivity and low Cl content films were obtained at a low substrate temperature of 150degreesC. Transmission electron microscopy and X-ray diffraction show that the grown films are amorphous. H and Cl contents decrease with increasing annealing temperature and intermixing of Ta and Si substrates was observed only at high annealing temperature of 900degreesC. The growth mechanisms and thermal stability of PE-ALD Ta thin films are discussed based upon these results. (C) 2003 Elsevier Science B.V. All rights reserved.