NSF-DFG: Understanding Rough-Surface Humid Adhesion to Unlock Next-Generation Semiconductor Manufacturing

• Applicant: Professor Dr. Lars Pastewka
• Subject Area: Coating and Surface Technology
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 540640170

he main objectives of the present proposal are: (1) to develop fundamental understanding of the combination of chemistry, mechanical properties, and surface topography that controls capillary adhesion of hard interfaces; and (2) to understand changes in humid adhesion over time in high-volume manufacturing and develop strategies to control it. The central hypothesis of the proposed work is that the formation, deformation and percolation of capillary bridges determines adhesive force in humid environments and is controlled by topography at multiple length scales. The research will be conducted using cutting-edge experiments and numerical simulations, to accomplish two Research Aims. Research Aim 1: Determine how multi-scale surface topography, combined with surface chemistry and mechanical properties, controls the capillary adhesion of technology-relevant materials. Three commonly used wear- resistant materials will be investigated, diamond-like carbon and two nanodiamond materials. The materials will be tested and extensively characterized, down to the Å-scale, including after various surface treatments. Complementary simulations will reveal the physical origins of observed behavior. Research Aim 2: Understand and control the feedback loop between surface evolution, chemical evolution, and capillary adhesion that limits the lifetime of key manufacturing equipment. This aim will generate science-guided strategies to modify materials for significantly improved adhesion performance, to enable next-generation technologies in semiconductor manufacturing. The proposed research will establish a paradigm shift in the understanding of capillary adhesion. The existing framework, based on surfaces with well-defined deterministic topography, describes individual liquid bridges. This framework does not apply to manufacturing surfaces that contain random roughness superimposed at many different length scales. The situation is analogous to the prior understanding of non-adhesive or dry-adhesion rough surfaces, where simple single-scale models dominated until the field was disrupted by new models that described multi-scale topography. A similar paradigm shift is needed—but has not yet occurred—in humid-environment adhesion. The fundamental science question at the heart of this proposal is: for real-world surfaces with random multi-scale topography, what features, structures, and properties most strongly impact capillary adhesion? This can only be answered using the proposed first-of-its-kind combination of: (a) all-scale surface measurements; (b) experimental measurements of humid adhesion; (c) accelerated testing to understand changes over time; (d) data- science-based correlation of topography and adhesion; and (e) large-scale numerical simulations of capillary formation. Together, these advances will generate wholly new insights into capillary adhesion.

• DFG Programme: Research Grants
• International Connection: USA
• Partner Organisation: National Science Foundation (NSF)
• Cooperation Partner: Professor Tevis Jacobs, Ph.D.