The Impact of Annealing on the Corrosion Mechanism of Copper Films

Abstract

AbstractWe investigated the corrosion mechanism of copper films. Based on our results regarding the morphology of the Cu surface, examined by scanning electron microscopy (SEM) and focused ion beam (FIB), it is shown that with an inorganic acid-based model CMP solution corrosion is initiated at the grain boundaries. In contrast, for an organic acid-based solution, corrosion starts with no preferential location. Some of the samples received an additional anneal after the CMP process was completed to monitor the influence of annealing on the corrosion mechanism by the acid solutions. Presence of facets especially after treatment with the inorganic acid-based model CMP solution suggests that a different mechanism governs the initiation and the evolution of corrosion. Desorption of the impurities during annealing, which is monitored by Atmospheric Pressure Ionized Mass Spectrometry (APIMS) revealed desorbing species from the copper films that could originate from the additives used in the Cu plating bath.