High-throughput nanoscale metrology of ultrathin inert and functionalized dielectric substrates using plasmonic nanoparticles

Ensuring uniformity in ultrathin dielectric films deposited on large-area bulk substrates-which may include inert oxide layers or those formed through chemical and biological functionalization-presents a significant industrial challenge, particularly when dealing with surfaces of hundreds of square centimetres. Conventional surface assessment techniques, such as ellipsometry, fluorescence and high-resolution microscopy, frequently encounter limitations in resolution, cost, and throughput at this large scale. In this study, we introduce a rapid and cost-effective methodology that provides nanometric accuracy and sub-micrometre optical spatial resolution for evaluating ultrathin dielectric films over substrates of hundreds of square centimetres within a matter of minutes. The technique is based on the deposition of plasmonic gold nanoparticles on dielectric films, followed by the measurement of their spectral properties using our proprietary AVAC optical platform, which is capable of detecting and analysing millions of nanoparticles in a matter of seconds. The approach is validated by the successful detection of nanometric thickness variations in both inert oxide layers and chemically and biologically active layers. As a proof-of-concept quality control application, the methodology was applied to biosensor substrates used in interleukin-6 detection assays leading to a significantly improved limit of quantification and a reduction in the variability among replicate samples. In conclusion, this approach provides a scalable, cost-effective, and high-throughput alternative to conventional thickness characterization techniques, enabling precise surface evaluation of large-area substrates suitable for several industrial applications.