Cu electrodeposition from methanesulfonate electrolytes for ULSI and MEMS applications

Methanesulfonic acid (MSA) is an alternative to sulfuric acid electrolyte for metal deposition. The electrochemical nucleation and growth of Cu on a glassy carbon electrode in methanesulfonate was compared with sulfate baths. The overpotential for Cu deposition was much smaller in the MSA bath compared to the traditional sulfuric acid bath, and Cu nucleation occurred at a higher rate in the MSA bath. The measured diffusion coefficient value for Cu deposition from the MSA bath was 6.82× 10^-6 cm² /s. UV-visible spectroscopic results confirmed that the coordination of Cu species was the same in both electrolytes. Cu electrodeposition on Ni sputtered Si substrate from the high efficiency MSA bath was photoresist-compatible with no void formation. One-dimensional Cu nanorods were also deposited through an anodized aluminum oxide template on a Ni evaporated seed layer substrate, showing potential applications as electrical interconnects in ultralarge scale integration (ULSI) and microelectromechanical systems (MEMS).