| Summary: | 碩士 === 國立清華大學 === 化學工程學系 === 92 === Our study is to develop a new diffusion barrier with low resistivity and high thermal stability via electroless deposition, and get a good control of Ni-W-P film composition by adjusting the bath condition and other parameters including bath temperature, [Na2WO4] and pH. The elemental composition of the deposited Ni-W-P films in this report has been determined to be Ni: 83–87 at.%, P:3-16 at.%, W:1-10 at.%. The resistivity of our Ni-W-P film can be as low as 63-92 μΩ-cm. Thus, copper could be directly deposited on this barrier layer and the copper seed layer is eliminated.
No metastable phases are observed in the Ni-W-P coating after heat treatment at 400. We found that the electrical property of Ni-W-P film still remain good after 400℃ heat-treatment for at least 1 hr. From these results, the Ni-W-P films do possess sufficient thermal stability.
Copper interconnection was directly carried on Ni-W-P film without other seed layer. From SIMS depth profile, no significant diffusion can be found in the sample at 400 ℃, implying that Ni-W-P film has a good capacity to prevent Cu and Si inter-diffusion.
Conformal deposition of a barrier layer is a decisive step in producing deep submicron interconnects for high aspect ratio features. Therefore, the investigation of basic mechanism and processes involved in electroless barrier deposition is necessary. The goal of various investigations such as UV, CV and XPS is to study the species present in th electroless solution that could be potential reactants involving in the deposition mechanism. From CV results, the plot is similar to that obtained for the Ni-P system. Just as observed in the induced electrodeposition of W or Mo by transition metals, no separate peaks are present when tungsten is codeposited. No evidence of the formation of some complex containing Ni and W together could be found via UV measurements.The Ni-W-P film contains tungsten in a form of pure tungsten metal as well as tungstate, the latter being the predominant form.
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