Wet Cleaning of Molybdenum for Nano Interconnects

The effect of various chemical solutions on the etch characteristics of molybdenum and on the removal of post-etch residues formed between Mo lines was investigated. In contrast to diluted SC1 mixtures, it was found that diluted HF solution (0.05%) and formulated semi-aqueous alkaline mixtures are highly compatible with Mo. The high etching rate measured for SC1 is attributed to the presence of the oxidizer in the mixture. Post-etch residue removal assessment performed on a semi-damascene structure with metal pitch of 32 nm showed that cleaning using diluted HF did not completely removal the residues. On the contrary, a clean using FOTOPUR R-2403, a semi-aqueous formulated mixture, resulted in efficient removal of the residues. The effect of oxygen in the plasma gas mixture and subsequent wet cleaning on the thickness of Mooxides was also performed on blanket Mo