From electrochemical kinetics to evaluate the through hole thickening throwing power of an acidic copper solution

Abstract

Galvanostatic method based on the convection-dependent adsorption (CDA) model can be effectively utilized to predict the blind via filling performance but failed in evaluating the throwing power (TP) of an acidic copper plating solution for through hole (TH) thickening. In this work, another two factors of copper ions mass transfer and electric field distribution inside the TH are considered for further understanding the thickening mechanism of TH. Considering the copper ions mass transfer, forced convection is necessary to improve the undesirable gradient distribution of copper ions concentration inside the TH for the uniform thickening. Considering the uneven electric field distribution, a simple strategy for evaluating the TP of a plating solution by the electrochemical electrode kinetic parameters measured from linear scanning voltammetry (LSV) test is established. A larger value of Tafel slope (lower value of transfer coefficient) indicates that inside the TH, copper deposition rates at the hole center and hole mouth are more approaching thereby in favor of higher TP. The strategy, which is verified by three copper plating solutions and the finite element simulation, indicates the great reliability and applicability in TH thickening.