Mechanism of AlCu Film Corrosion

Abstract
We report corrosion of an Al–Cu film treated by O2/CF4 downflow. Corrosion occurs on the Al–Cu surface in the case of a P-SiN film deposited on a TiN/Al–Cu film, but does not occur in the case of deposition of a P-SiO2 film or no film on TiN. In ion-chromatography analysis, the NH4 + concentration of the sample treated by O2/CF4 downflow was more than twice that for a sample not treated by O2/CF4 downflow. In TDS analysis, the peak signal of NH3 from a P-SiN film treated by O2/CF4 downflow was observed at around 150° C. These results indicate that NH3 molecules desorbed from the P-SiN film adsorb on the Al–Cu surface, and corrosion of the Al–Cu film is induced by chemical reaction between NH3 and Al–Cu. We also investigated the reducing effect of corrosion by O2 downflow treatment and DI water rinsing. The NH3 concentration on the wafer decreases to about half the initial value following these treatments. Consequently, the outbreak of corrosion is reduced.

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