Superconformal Cu electrodeposition using DPS; A substitutive accelerator for SPS

Abstract

3-N,N-Dimethylaminodithiocarbamoyl-1-propanesulfonic acid ~DPS! was applied as an accelerator in damascene Cu electrodeposition. When DPS was used with a one-step electrodeposition method, it was incapable of superfilling in damascene structure. Superfilling, however, could be accomplished with two-step electrodeposition method or derivitization method. The differences in the Cu profiles depending on the deposition methods, were associated with the concentration-dependent behaviors of DPS. The acceleration effect of DPS was proportional to its concentration at low concentrations below 50 mM on nonpatterned wafer, but not at higher concentrations. Through the electrochemical analyses, the critical DPS concentration was determined at 50 mM where the acceleration effect of DPS changed. The DPS reaction mechanism was proposed based on the concentration dependency of the acceleration effect. This is strongly related to the change in molecular structure according to concentration. Furthermore, it was found that even with one-step electrodeposition, the Cu filling profile was considerably improved by controlling DPS concentration.