Abrasive-free chemical-mechanical planarization (CMP) of gold for thin film nano-patterning

Despite high demand for gold film nanostructuring, patterning gold at the nanoscale still presents considerable challenges for current foundry-compatible processes. Here, we present a method based on abrasive-free chemical mechanical planarization (CMP) to planarize nanostructured gold surfaces with high selectivity against SiO₂. The method is efficient in a damascene process and industry-compatible. Investigations into the material removal mechanism explore the effects of CMP parameters and show that the material removal rate is highly tunable with changes in slurry composition. Millimeter-scale arrays of gold nanostructures embedded in SiO₂ were fabricated and the planarization dynamics were monitored over time, leading to the identification of distinct planarization phases and their correlation with the material removal mechanism. Finally, plasmonic cavities of gold nanostructure arrays over a gold mirror were fabricated. The cavities exhibited efficient plasmonic resonance in the visible range, aligning well with simulation results.