Effects of additives on copper electrodeposition in submicrometer trenches

Effects of the conventional bath additives [chloride ions (Cl^-), poly(ethylene glycol) (PEG), bis(3-sulfopropyl)disulfide (SPS), and Janus green B (JGB)] used in the damascene process on the filling of submicrometer trenches with electrodeposited copper were investigated by electrochemical polarization measurement and cross-sectional microscopy. The combination of Cl^- and PEG inhibited copper deposition in the areas of opening of the trenches, while SPS accelerated it at the bottom. Polarization curves showed that the degree of acceleration of copper deposition by SPS increases with the concentration of SPS. This SPS concentration-dependent acceleration accounts for the observed bottom-up growth. The addition of JGB inhibited copper deposition at the later stages of the filling process, leading to the suppression of the overfill phenomenon, although the bottom-up growth was also inhibited at high JGB concentrations. Bath agitation significantly enhanced the inhibition effect of JGB on the overfill phenomenon, without disturbing the bottom-up growth.