Effect of gravitational strength on nucleation phenomena of electrodeposited copper onto a TiN substrate

Cu2+ ion was electrodeposited potentiostatically in 0.05 M CuSO4 aqueous solutions onto a foreign substrate of TiN film sputtered on a stainless steel sheet. The amount of electricity was limited to 31.8 mC cm−2, which corresponds to a 10 nm thick film, deposited uniformly without any void formation. Two different electrolytic cell configurations were designed in order to discuss quantitatively the effect of gravitational strength on the nucleation and growth of metal electrodeposition in detail: (a) a horizontal cathode surface facing downward over an anode (C/A) and (2) an anode over cathode (A/C). SEM pictures show that the nucleus number density varies from 107 to 1010 cm−2 depending on the negative overpotential and that the A/C configuration introduces more number of nuclei than the case of C/A at a constant overpotential. The gravitational level certainly influences the initial stage of electrodeposition of Cu2+ ion in CuSO4 aqueous solution. Image analysis techniques further demonstrate that copper metal does not nucleate randomly over the TiN substrate, but the presence of a nucleation inhibition or exclusion zone was suggested. Thus, the growth rate of the inhibited zone should be influenced by the gravitational field vector.