Role of the functional groups of complexing agents in copper slurries

We investigate the role of -NH2 and -COOH functional groups of complexing agents in H2O2-based slurries in controlling copper (Cu) removal rates. Slurries containing complexing agents with two of the same functional groups (succinic acid: HOOC-CH2CH2-COOH, ethylene diamine: H2N-CH2CH2-NH2) and a complexing agent containing one each of the functional groups (beta-alanine: H2N-CH2CH2-COOH), all with the same carbon chain length, were investigated. Along with dissolution and disk polish experiments, potential-pH diagrams were constructed for these three systems in the presence of H2O. The dissolution and polish rates are consistent with the known activity of carboxylic acids (with -COOH groups) at acidic conditions and that of amines (with -NH2 groups) in an alkaline environment. The observed trends in the removal rates with all these slurries are explained using potential-pH diagrams, UV/visible spectra, and electrochemical experiments. When compared to glycine (H2N-CH2-COOH), beta-alanine (H2N-CH2CH2-COOH) produced higher removal rates at acidic pH values and lower removal rates at alkaline pH values. Finally, succinic acid and beta-alanine-based slurries were found to result in lower dissolution rates and higher polish rates compared to glycine-based slurries at pH 4. (c) 2006 The Electrochemical Society.