Rapid Octadecylphosphonic Acid Self-Assembled Monolayer Formation on Cu for Etch Inhibition: Characterizations Using Sum Frequency Generation Vibrational Spectroscopy

Self-assembled monolayers (SAMs) can be used to modify surface properties in a large area, which have wide applications ranging from corrosion inhibition, electronic device fabrication, oil/water separation, to biosensors. In industry, it is required to deposit a monolayer on copper substrate for etch inhibition within a short period of time. This study developed a simple method to satisfy such a need in industry. The SAM was deposited by using octadecylphosphonic acid (ODPA) solution. The quality of the prepared ODPA SAM on copper was compared to that of the SAM prepared using octadecanethiol (ODT) on copper. Sum frequency generation (SFG) vibrational spectroscopy was applied to characterize the deposited SAMs. It was found that ODPA SAMs prepared with 2 min of deposition time using ODPA solutions with concentrations of 0.05%, 0.1%, and 0.2% only have small numbers of gauche defects, with 80% or more methyl surface coverages compared to ODT SAMs. The deduced methyl group orientations of such ODPA SAMs are similar to that of the ODT SAM methyl groups. This study successfully demonstrated the feasibility of preparing relatively good quality ODPA SAMs on copper using a short deposition time.