Modulating Silane Monolayer Grafting on Nanopatterned Silicon: Insights from Infrared-Spectroscopy-Based Air-Trapping Monitoring

Silane-based self-assembled monolayers (SAMs) are widely used to passivate semiconductor surfaces, yet their coverage on nanopatterned, high-aspect-ratio (HAR) structures remains unclear. This study explored how dilute hydrofluoric acid (dHF) pretreatment and deposition time influence the silane SAM density on flat and nanopillar-patterned silicon. To probe differences in surface chemistry and wettability, water contact angle (WCA) and grazing-angle attenuated total reflectance (GATR)-Fourier transform infrared (FTIR) spectroscopy were used. However, these conventional techniques lack the resolution required to assess SAM coverage on nanopatterned surfaces. To address this limitation, a custom-built ATR setup was used to reveal the nanoscale air-trapping behavior, providing insights into SAM coverage. The results also highlight how process optimization can modulate SAM coverage and influence the wetting state on HAR patterned surfaces.