Microstructure optimization and optical and interfacial properties modulation of sputtering-derived HfO2 thin films by TiO2 incorporation

• Published in: Journal of alloys and compounds Vol. 611; pp. 253 - 259
• Main Authors: Zhang, J.W., He, G., Zhou, L., Chen, H.S., Chen, X.S., Chen, X.F., Deng, B., Lv, J.G., Sun, Z.Q.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 25.10.2014; Elsevier
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; High-k gate dielectrics; Optical constant; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of specific thin films; Physics; RF sputtering; Structure and morphology; thickness; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Thin film structure and morphology; TiO2-doped HfO2; TiO2-doped HfO2; RF sputtering; High-k gate dielectrics; Optical constant; Spectroscopic ellipsometry; Doping; Hafnium oxide; XRD; Thin films; Interface properties; Dielectric thin films; doped HfO; Chemical composition; Urbach rule; TiO; Microstructure; Titanium oxide; Optical constants; Radiofrequency sputtering; X-ray photoelectron spectra
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2014.05.074

•Sputtering-derived Hf1−xTixO2 gate dielectrics have been deposited on Si substrates.•Increase in crystallization temperature and reduction in Eg have been observed.•Formation of silicate layer for 9% TiO2-doped HfO2/Si sample has been detected. TiO2-doped HfO2 gate dielectric thin films have been deposited on Si(100) substrates by RF sputtering. The component, morphology, structure, optical and interfacial properties of Hf1−xTixO2 films related to TiO2 concentration are systematically investigated by atomic force microscope (AFM), X-ray diffraction (XRD), spectroscopic ellipsometry (SE), X-ray photoelectron spectroscopy (XPS), and Fourier transformation infrared (FTIR). By employing Cauchy–Urbach model, the optical constants, such as refractive index (n), extinction coefficient (k), absorption coefficient (α), and optical band gap (Eg) have been determined precisely. Measurements from XRD have confirmed that TiO2 incorporating into HfO2 films leads to the increase of the crystallization temperature of HfO2 films with increasing the TiO2 concentration. SE analyses have indicated that reduction in band gap and refractive index has been observed with increasing the TiO2 component in Hf1−xTixO2 films. The increase in Urbach parameter EU with the increase of TiO2 concentration also suggests the rise in disorder for Hf1−xTixO2 films. FTIR measurements for Hf1−xTixO2/Si gate stack indicate the existence of the interfacial layer regardless of the TiO2 concentration. For the 9% TiO2-doped HfO2 samples, the shift in FTIR characteristic peak suggests the formation of the silicate layer, which leads to the suppressed interfacial layer growth during deposition. As a result, it can be conclude that the TiO2 component in Hf1−xTixO2 films should be controlled precisely to guarantee interfacial properties of Hf1−xTixO2/Si gate stacks.