Growth of titanium silicate thin films by photo-induced chemical vapor deposition

Titanium silicate thin films have been grown on Si substrates by photo-induced chemical vapor deposition using 222-nm ultraviolet excimer lamps. Titanium tetraisopropoxide (TTIP) and tetraethoxysilane (TEOS) were used as precursors. TTIP and TEOS were dissolved together in cyclohexane and introduced into the photochemical reaction chamber through a droplet injector vaporizer. The composition of the film was controlled by changing the ratio of TTIP to TEOS in the precursor solution. High quality titanium silicate films with various Ti/Si ratios and low carbon content have been achieved as revealed by X-ray photoelectron spectroscopy measurements. The atomic percentage of Ti content in the grown silicate films is significantly larger than that in the precursor solution. The films were measured to be 30-80 nm in thickness and 1.91-2.31 in refractive index by ellipsometry. Both the growth rate and refractive index increase with increasing Ti percentage in the silicate films. The evolution of Fourier transform infrared spectra of the silicate films with solution composition shows that the Ti-O-Si absorption at approximately 920 cm-1becomes stronger, while the Ti-O absorption at approximately 430 cm-1becomes weaker with decreasing Ti percentage in the solution. A small feature at ∼1035 cm-1related to Si-O-Si bonds is also observed in the SiO2-rich Ti silicate film. © 2003 Elsevier B.V. All rights reserved.