Contamination of silicon dioxide films by aqueous zirconium and hafnium species

Zirconium and hafnium oxides and silicates have emerged as potential replacements for Si O2 as gate dielectric material. Patterning of these materials by wet etching in fabrication areas originally designed for Si O2 gates may give rise to contamination of Si O2 by aqueous zirconium and hafnium species. This paper summarizes the work carried out to characterize the adsorption behavior of aqueous zirconium and hafnium species onto thermally grown silicon dioxide. Electrokinetic and adsorption measurements were carried out to understand the extent and nature of interaction. The adsorption of both Zr and Hf species showed a maximum at pH 5.5. Significant reduction in the adsorption of both Zr and Hf occurred upon addition of fluoride ions to the solution. Using appropriate speciation diagrams, an adsorption model has been developed to explain the experimental data.