Observation of extended copper passivity in carbonate solutions and its future application in copper CMP

In the present work we report on carbonate-based solutions, which can provide copper passivity in a wide potential range with the capability for producing protective characteristics similar to Al and W. This report focuses mainly on the identification of copper passivity parameters, such as potential range, anodic current limits, current characteristics, and rates of passivation and repassivation subsequent to mechanical damage of copper passivity in carbonate-based solutions. Copper is fully passivated in sulfate solutions containing potassium carbonate. The observed passivity is more pronounced in solutions containing higher carbonate content. On the contrary, increasing the sulfate concentration has the opposite effect on copper passivity than carbonate does. Friction of the passive film by repeated surface abrading resulted in a rapid repassivation of the mechanically activated surface sites. Thus, the use of a carbonate anion as a passivating component in a future chemical mechanical planarization (CMP) slurry design should be considered. (c) 2005 The Electrochemical Society.