Abstract
Aluminum oxide thin films were deposited by r.f. sputtering on ferrite, glass, and graphite substrates in a vacuum system deliberately contaminated with water vapor and ArO 2 mixtures. The films were analyzed for thickness, etch rate, chemical composition and microstructure using transmission electron microscopy (TEM). The presence of water vapor or oxygen in the vacuum chamber during deposition decreased the film deposition rates, and the etch rate of the films in hot H 3PO 4 was also drastically reduced. TEM micrographs and selected area electron diffraction patterns of films deposited in water vapor and ArO 2 environments showed the existence of a crystalline γ-Al 2O 3 phase in the film at the substrate-film interface. The γ-Al 2O 3 structure depended on the abundance of oxygen or water vapor in the vacuum. The formation of the γ-Al 2O 3 phase at the interface is the cause of reluctant etchability because γ-Al 2O 3 is much less soluble in phosphoric acid etchants than is amorphous Al 2O 3.
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