In-Situ Cleaning and Passivation of Oxidized Cu Surfaces by Alkanethiols and Its Application to Wire Bonding

摘要

The treatment of oxidized Cu surfaces using an alkanethiol as a reducing agent has been investigated.Exposure to a dilute solution of 1-decanethiol resulted in the complete removal and/or conversion of CuO and subsequent formation of a passivating thiolate film,a so-called self-assembled monolayer(SAM),on the underlying Cu/Cu_2O surface as evidenced by x-ray photoelec-tron spectroscopy(XPS)analysis.Morphological changes,monitored by scanning electron microscopy(SEM)and atomic force microscopy(AFM),revealed transformation of the rough,porous CuO layer into a comparatively smooth Cu/Cu_2O surface.Experiments performed on integrated circuit back-end-of-line(BEOL)die structures,comprising Cu/SiO_2 bond pads used as substrates for Cu wire bonding,demonstrate the potential application of a thiol-based in-situ cleaning-passivation procedure in microelectronics.