<I>In-Situ</I> Ellipsometric Analysis of Formation Process of TiO<SUB>2</SUB> Thin Films in Low-Pressure CVD

The formation process of a TiO2 thin film on a Si(100) substrate by low-pressure CVD with tetraisopropyl titanate (TPT) has been studied by in-situ ellipsometry. Changes in the growth rate and the refractive index of the film obtained from ellipsometry were examined as a function of the substrate temperature, the vaporization temperature of TPT, and the flow rate of O2 reactant gas. The formation process of the film at the substrate temperatures below 569 K can be divided into two regions; the initial region corresponding to the nucleation of TiO2 and the steady state region corresponding to the growth of the TiO2 layer after coalescence of the nuclei. The initial region was undistinguishable at the substrate temperatures higher than 600 K. The growth rate in the steady state region increased with increasing substrate temperature and the refractive index decreased. At a constant substrate temperature of 695 K, both the growth rate and the refractive index increased with increasing vaporization temperature of TPT. A Raman spectroscopic analysis indicated that the film has an anatase structure. An infrared spectroscopic analysis suggested that the more ordered anatase is formed with the higher substrate temperature.