Atomic Layer Deposition of TiO2 films at low temperatures using tetrakis-dimethyl-amido-titanium and ozone.

Publication Details
Authors: Kääriäinen Tommi, Kääriäinen Marja-Leena, Gandhiraman Ram Prasad, Cameron David
Publication year: 2007
Language: English
JUFO-Level of this publication:
Open Access: Not an Open Access publication

In the group of oxide semiconductor photocatalysts, TiO2 is mostly used material due to its biological and chemical inertness, strong oxidizing power, non-toxicity and long-term stability against photo corrosion and chemical corrosion. Besides of photocatalytic behavior, TiO2 has also photo-induced super hydrophilicity behavior under UV-VIS light illumination. Polymers are thermally fragile and withstand the temperatures ranking from 50-260°C. In general, the ALD processes are carried at temperatures over 100-250°C, which are too high for polymers. However some previous work on ALD of TiO2/Al2O3 single and multilayer coatings using TiCl4/H2O and Al(CH3)3 / H2O precursors has shown that uniform, conformal, and adherent coatings can be deposited on polymer substrates at temperatures ranging from 80-180 °C [1],[2],[3]. TDMAT (metal-amide compound) has shown to be good candidate for low temperature ALD processes due to its higher reactivity compared to for example TiCl4 (metal-halide compound) [4],[5]. Thermal decomposition of TDMAT occurs at temperatures above 180 ºC causing non-self-limiting growth of the film [6]. This also supports the use of TDMAT at low temperature ALD processes. In previous ALD studies of TiO2 using TDMAT as a metal precursor, the reactants for oxygen used were H2O and H2O2. Efficiency of ozone as an oxidizing agent is well known and it can be assumed that it may be good candidate for oxidizing agent in processes at process temperatures below 100 ºC. Ozone has been used in several ALD oxide processes [7],[8],[9]. In this work sequential exposures of tetrakis(dimethylamido) titanium (TDMAT) and O3 were used to deposit TiO2 at temperatures ranging 55-180 °C on silicon (100), sodalime glass, PMMA and PC substrates.

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