Atomic Layer Deposition of Oxide Films – Growth, Characterisation and Reaction Mechanism Studies

Raija Matero
Abstract & Cover

Atomic layer deposition was used to grow Al2O3, TiO2 and ZrO2 thin films. The mechanism of film growth was studied with a quadrupole mass spectrometer (QMS) and a quartz crystal microbalance (QCM). A brief literature review on the ALD growth of binary oxides and on in situ studies on selected oxide processes is presented as background. The effect of water dose on the growth of Al2O3, TiO2, ZrO2 and Ta2O5 was studied. The increased water dose increased the growth rate in all cases. According to the analysis data, it did not seem to affect the film properties. Al2O3 and TiO2 films were deposited for corrosion protection studies. Although ALD grown Al2O3 is amorphous and there should not be any pinholes, it did not work as a protective coating against corrosive media. TiO2 films are crystalline, and the corrosive media was able to penetrate through the coating and cause corrosion of the underlying substrate. The good characteristics of both materials were combined as Al2O3 – TiO2 multilayer structures, which resisted corrosion better than the single oxides. The reaction mechanism studies on Me2AlCl–D2O and TiCl4–D2O ALD processes were carried out using a combination of QMS and QCM integrated to the ALD reactor. QMS gives information about the gaseous products formed in the surface reactions involved in the film growth. QCM, in turn, monitors changes in the film mass. ZrO2 films were deposited using water and new alkoxide precursors: Zr(dmae)4, Zr(dmae)2(OtBu)2 and Zr(dmae)2(OiPr)2. The reaction mechanism was studied using QMS–QCM. The precursors seem to decompose, so the growth can not be regarded as ideal ALD. 

Source of Information
FinALD40 exhibition material,
University of Helsinki, Department of Chemistry, Laboratory of Inorganic Chemistry
(Helsinki, Finland)
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