Unique pH Effects on TiN Etching in Nano Confinement with Dilute H2O2 Solutions

Understanding etching behavior in nanoconfined environments is essential for continued scaling of microelectronic devices. In this study, we investigated pH dependent etching characteristics of titanium nitride (TiN) in nano confinement using dilute hydrogen peroxide (H₂O₂) solutions. Etching rate was evaluated under various pH conditions by adjusting concentration of sulfuric acid (H₂SO₄) and ammonium hydroxide (NH₄OH). The results revealed that TiN etching rate decreases in nano confinement compared to blanket samples. This reduction is especially pronounced at pH values above 9. At high pH, overlap of electrostatic double layers (EDLs) causes repulsion of negatively charged HO₂⁻ ions as primary etchant species. As a result, concentration of HO₂⁻ ions in nano confinement are reduced. Furthermore, decrease in etching rate was also observed at pH < 4, despite alleviation of EDLs overlap. This suggests that other mechanisms such as changes in surface reaction sites and species may affect etching under acidic conditions. These results imply complex relationship between surface potential, ion distribution, and surface chemistry, offering insights for designing etching processes in advanced devices.