The sol-gel spin-coating technique is increasingly being used for the fabrication of thin-films with diverse applications in areas that include advanced optics, microelectronics and sensors. The performance quality of the thin film devices is affected by the thickness and homogenity of the film, which are in turn controlled by parameters such as substrate surface quality, viscoelastic properties of the sol, and the spin coating parameters. Processing high quality thin-films is simpler when the desired thickness can be achieved by a single-step coating of sol-gel film. We report on the fabrication of TiO₂ thin films by single-step spin-coating of a well characterised sol on a single crystal Si substrate. By monitoring the viscoelasticity of a titanium alkoxide sol, the thickness of the coated film can be controlled and with proper calibration, the viscoelasticity of the sol can be used as a parameter to fabricate a quality film with desired thickness. The thickness of the spin coated sol-gel films and that of the processed TiO₂ films was evaluated using SEM and ellipsometry. The optical interference phenomenon of Newton's colours, which are obtained for the thin transparent films on reflecting surfaces, can be used to estimate the thickness of the TiO₂ thin-films. This presentation provides details on how this concept can be applied to estimate the thickness of the TiO₂ thin-films in the range of 50 to 200nm. The value determined using this method was comparable to that obtained through ellipsometric and SEM measurements.

Date Published: 13 November 2002
PDF: 8 pages
Proc. SPIE 4934, Smart Materials II, (13 November 2002); doi: 10.1117/12.471967

Published in SPIE Proceedings Vol. 4934:
Smart Materials II
Alan R. Wilson, Editor(s)