Analytical Study of the Characteristics of Cu(I) Species for the Via-Filling Electroplating Using a RRDE

The rotating ring-disk electrode (RRDE) technique was used for investigating the characteristics of the cuprous ion species, which plays an important role in via-filling copper electroplating and is generated in the reaction of copper with the accelerator bis-(3-sulfopropyl) disulfide (SPS) or chloride. species generated during the electrochemical reactions could be detected as a current on a glassy carbon ring electrode. The curves of vs (disk potential) had a peak at a specific potential independent of the various additive concentrations in the bath. The peak height changed with the additive concentrations and the ring potential. It seemed that the peak indicates the amount of species generated on both the cathode and the anode and transported to the neighborhood of the cathode. When HS-(CH2)3-SO3H (MPS) was added as an alternative to SPS, the peak appeared at (V vs saturated calomel electrode, SCE) but disappeared at (V vs SCE). It was suggested that the MPS does not form the same complexes as SPS with ions. The kind of complex as the intermediate of copper electroplating should not be single. Furthermore, the filling test applied to small trenches was done with different SPS concentrations in order to compare with the amount obtained from the ring-disk measurement. It was found that a higher amount of is not necessary for a better filling capability. This indicates that there is an optimum amount which accelerates only inside the via holes.