Fundamentals of wet process interactions of complex metal alloys

For next-generation advanced interconnects, the material properties of Cu render it unreliable for producing ever more performant chips. Various alternative metals, such as ruthenium, rhodium, and molybdenum, have been studied and start to be implemented by the industry to tackle resistive losses due to the small dimensions of the metal structures. 

To further lower the impact of resistivity at even more aggressively scaled dimensions, complex metal alloys are currently being explored. One of the grand challenges to implement these materials at an industrial scale is related to the surface chemistry properties. Even minor changes in the alloy’s composition have a dramatic impact on the resistivity of nanoscale structures. The presence of multiple metals in the alloy results in a deviating stoichiometry of the alloy in the near-surface region, which results in differences in corrosion and wet etch behaviour. Both the underlying chemical and physical processes involved are, to date, not well understood and characterized.

In the project, focus will be on fundamental understanding of wet processes like post patterning cleaning and Chemical Mechanical Planarization (CMP) which can remove material in a controlled way . In the initial phase of the project, the focus will be on characterizing the surface chemistry to check the influence of the wet chemical process (e.g. concentration of oxidizing agent). Also, the focus will be on the study of the alloy’s electrochemistry, e.g. an in-situ set-up on an experimental tool is used allowing us to study the alloy's electrochemistry during CMP on wafer coupon scale. During the entire project, various types of metrology will be used to characterize the material properties (e.g. AFM, XPS, RBS, TEM).