Electrochemical properties of Cu deposition from methanesulphonate electrolytes for ULSI and MEMS applications

Methanesulphonic acid (MSA) is an alternative to sulphuric acid electrolytes. The electrochemical nucleation and growth of Cu on a glassy carbon (GC) electrode was studied from the methanesulphonate and sulphate baths. The overpotential for Cu deposition was much smaller in the MSA bath compared to the traditional sulphuric acid bath. 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. The UV-Vis 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 found to be photoresist compatible with no void formation. 1D Cu nanorods were also deposited through AAO template on a Ni evaporated seed layer substrate showing potential applications as interconnects in ULSI and MEMS.