Impact of titanium addition on film characteristics of HfO2 gate dielectrics deposited by atomic layer deposition

• Published in: Journal of applied physics 2005-09, Vol.98 (5)
• Main Authors: Triyoso, D. H., Hegde, R. I., Zollner, S., Ramon, M. E., Kalpat, S., Gregory, R., Wang, X.-D., Jiang, J., Raymond, M., Rai, R., Werho, D., Roan, D., White, B. E., Tobin, P. J.
• Format: Article
• Language: English
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.2030407

The impact of 8-to45-at.% Ti on physical and electrical characteristics of atomic-layer-deposited and annealed hafnium dioxide was studied using vacuum-ultraviolet spectroscopic ellipsometry, secondary ion mass spectroscopy, transmission electron microscopy, atomic force microscopy, x-ray diffraction, Rutherford backscattering spectroscopy, x-ray photoelectron spectroscopy, and x-ray reflectometry. The role of Ti addition on the electrical performance is investigated using molybdenum (Mo)-gated capacitors. The film density decreases with increasing Ti addition. Ti addition stabilizes the amorphous phase of HfO2, resulting in amorphous films as deposited. After a high-temperature annealing, the films transition from an amorphous to a polycrystalline phase. Orthorhombic Hf–Ti–O peaks are detected in polycrystalline films containing 33-at.% or higher Ti content. As Ti content is decreased, monoclinic HfO2 becomes the predominant microstructure. No TiSi is formed at the dielectric/Si interface, indicating films with good thermal stability. The band gap of Hf–Ti–O was found to be lower than that of HfO2. Well-behaved capacitance-voltage and leakage current density-voltage characteristics were obtained for Hf–Ti–O. However, an increased leakage current density was observed with Ti addition. The data from capacitance-voltage stressing indicate a smaller flatband voltage (Vfb) shift in the HfO2 films with low Ti content when compared with the HfO2 films. This indicates less charge trapping with a small amount of Ti addition.