Superconformal Cu Electrodeposition from Cu(II)-EDTA Complexed Alkaline Electrolyte
Daniel Josell, Thomas P. Moffat
This paper details superconformal filling of submicrometer trenches with bright, dense copper from alkaline cupric ethylenediaminetetraacetic acid (EDTA) electrolyte of pH 12. Enhanced deposition from the bottom corners of the trenches and overfill bumps accompany superconformal deposition within the trenches when micromolar concentrations of KSeCN are added. Cyclic voltammograms using a rotating disk electrode (RDE) indicate that metal deposition from the EDTA complexed electrolyte is kinetically hindered. The SeCN- additive induces positive feedback evident as concentration-dependent depolarization in cyclic voltammograms and rising chronoamperometric transients. The feature filling and electrochemical measurements are discussed in the context of existing models for superconformal feature filling. The acceleration of Cu deposition observed electroanalytically and the geometrical evolution observed during feature filling are consistent with the Curvature Enhanced Accelerator Coverage mechanism of feature superfilling.