The deposition behavior of SiO2-TiO2 thin film by metalorganic chemical vapor deposition methods

Abstract

SiO2-TiO2 thin films were deposited by metalorganic chemical vapor deposition using an alkoxide source. At 680 degrees C, the deposition rate curve showed parabolic behavior and the refractive index increased linearly from 1.45 to 2.35 with increasing titanium tetraisopropoxide: Ti(OC3H7)(4)(TTIP) ratio. Each oxide component in the film was separated analytically and its effective deposition rate, in the composite thin film, was calculated to analyze the deposition mechanism of the mixed sources. A Lorentz-Lorenz model was used to attain the composition of the film for each component separation. Effective SiO2 deposition from tetraethylorthosilicate: Si(OC2H5)(4)(TEOS) showed parabolic behavior with increasing TTIP ratio, while the effective TiO2 deposition did not. In addition, TTIP lowered the apparent activation energy of SiO2 deposition significantly from similar to 40 to similar to 10 Kcal/mol. From this, it was concluded that TTIP enhanced the TEOS decomposition, which results in the anomalous deposition behavior in composite films. A more reactive TTIP molecule acting as a "free radical reaction initiator'' was suggested as a mechanism for enhancement of the process. (C) 2000 American Vacuum Society. [S0734-2101(00)05505-6].