Atomic layer deposition of Ti-HfO2 dielectrics

Titanium-doped hafnium oxide films, TixHf1-xO 2-δ, have been deposited with a Ti content of x = 0.1 and x = 0.5, by atomic layer deposition. The TixHf1-xO 2-δ growth rate is lower compared with the growth rates of the individual binary oxides; however, the composition of the films is unaffected by the reduced growth rate. An 850 °C spike anneal and a 500 °C 30 min furnace anneal were performed, and the resulting film composition and structure was determined using medium energy ion scattering, x-ray diffraction, and transmission electron microscopy. The Ti0.1Hf0.9O 2-δ films readily crystallize into a monoclinic phase during both types of annealing. By contrast, the Ti0.5Hf0.5O 2-δ films remain amorphous during both annealing processes. Electrical characterization of the as-deposited Ti0.1Hf 0.9O2-δ films yielded a dielectric constant of 20, which is slightly higher than undoped HfO2 films. The as-deposited Ti0.5Hf0.5O2-δ films showed a significant increase in dielectric constant up to 35. After a 500 °C 30 min anneal, the dielectric constant reduced slightly to 27. The leakage current density of the amorphous film remains relatively unaffected at 8.7×10-7 A/cm2 at -1 MV/cm, suggesting this composition/heat treatment is a candidate for future device dielectrics. © 2013 American Vacuum Society.