Copper Electroplating with Polyethylene Glycol and Chloride: Modeling, Experimental Analysis and Parameter Determination

Abstract

Additives play an important role in electrochemical deposition and understanding their working mechanism is a great challenge. In cyclic voltammetry measurements of copper deposition, a complex hysteresis behavior is ubiquitously observed. In previous models a common assumption to explain the hysteresis is the consumption of additives during copper deposition. However, second-ion mass spectrometry measurements often detected comparatively low levels of impurities in deposits. We proposed recently an alternative mechanism for explaining hysteresis without invoking additive consumption. By assuming for instance a conformation change in the adsorbed PEG layer and an additional activation of additive desorption by copper deposition, the new model can reproduce characteristic features of cyclic voltammograms measured under vastly different conditions and exhibiting pronounced hysteresis. In parallel to that, we examined experimentally the process behavior of the additives PEG (polyethylene glycol) and chloride ions over a wide range of parameters relevant for production-like conditions. Moreover, we fitted crucial parameters of our model from the experimental data. The quantitative agreement of performed simulations of CV scans with the measured scans demonstrates the quantitative predicting power of the proposed model. Equipped with the determined parameter set, the model may help to optimize the copper plating process in industrial applications.