Sum frequency spectroscopy studies of adsorption of additives on metal/electrolyte interfaces

Abstract

Summary form only given.Copper is rapidly being introduced into chip interconnection technology as a replacement for aluminum. Copper electrodeposition has an advantage over aluminum physical deposition in its ability to allow superconformal deposition and 'superfilling' of trenches and vias in the Damascene process when additives (inhibitors, accelerators) are present in the plating bath. An additive formulation that has been shown to exhibit superfill contains NaCl, 3-mercapto-1propanesulfonate (MPSA), and polyethylene glycol (PEG). However, although it is recognized that copper inhibition is essential to achieve superfill, the overall mechanism and role of each additive in achieving superfill is still under debate due to the lack of understanding these processes on the molecular level. Detailed analysis of vibrational spectra can provide information on the local order of the surface species and their orientation. We measured ex situ vibrationally resonant sum frequency generation (VR-SFG) spectra of MPSA self-assembled from a perchloric acid solution on both gold and copper substrates. Five resonant features between 2800 and 2950 cm/sup -1/ can be attributed to the CH/sub 2/ group of MPSA.