Study on the Step Coverage of Metallorganic Chemical Vapor Deposited TiO[sub 2] and SrTiO[sub 3] Thin Films

The growth behavior and step coverage of TiO 2 thin films deposited by liquid-delivery metallorganic chemical vapor deposition (MOCVD) at temperatures ranging from 410 to 490°C were investigated. The film growth rates were controlled by the gas phase thermal decomposition reaction of the precursors, and the reaction shows an apparent activation energy of ∼ 90 kJ ∕ mol . The gas phase thermal decomposition produced several intermediate precursor molecules with different sticking coefficients. The intermediate precursors played a crucial role in the film growth and step coverage change. As the growth rate decreases, the step coverage degrades, which can be explained by Langmuir’s isothermal adsorption model of the precursors with the assumption of the various intermediate molecular structures of the precursors. The bulkier intermediate molecular structure of the precursor increases the steric hindrance between the previously adsorbed molecules and the impinging molecules so that the step coverage improves. The unusual step coverage of an MOCVD SrTiO 3 film previously observed for a low precursor injection rate was successfully explained using the results derived from the TiO 2 MOCVD and nonsticking property of the Ti-precursor molecules on the SrO surface.