Mechanisms for reactive DC magnetron sputtering of elements with different atomic masses: large area coatings of Al oxide and W oxide

Abstract

Stoichiometric Al and W oxide films are prepared with high stability from the metallic state of the cathodes using conventional reactive DC magnetron sputtering on an industrial prototype scale. While for the Al, increased target power is a trivial way to increase growth rates, W oxide sputtering of optically functional films with sufficiently amorphous structure is severely limited by the effect of gas rarefaction at high powers. Choosing an appropriate working gas pressure and a source-to-substrate distance, which facilitates the gas scattering allows the deposition of homogeneous stoichiometric tungsten oxide films in a stable condition with a relatively high discharge current. Optimization of the process parameters with respect to film properties and efficiency of the deposition process is discussed.