Chi-Wen Liu

Effect of plating current density and annealing on impurities in electroplated Cu film

This study uses secondary-ion-mass spectrometry to examine the effects of plating current density and annealing temperature on the nature of electroplated copper (Cu) films. The experimental results reveal that high levels of impurities, such as C, O, S, and Cl, are incorporated into Cu deposits at the lower current density region while superfilling occurs. The C and O impurities can be released from the plated films by thermal annealing, while S and Cl cannot. This work proposes a possible mechanism based on bond strength to explain the phenomena. Rapid C and O desorption is observed when the films are first cycled to 220°C immediately after electroplating. The activation energy of C desorption is found to be approximately 9.8kJ∕mol. For Cu electroplating, this investigation suggests that high plating current density and an adequate annealing temperature are required to reduce impurities.

Effects of wetting ability of plating electrolyte on Cu seed layer for electroplated copper film

This work examines the impact of the wetting ability of a plating electrolyte on the Cu seed layer on copper electroplating performance. The contact angle of the electrolyte on the Cu seed is highly sensitive to additive decomposition in the electrolyte, as well as being sensitive to Cu seed self-annealing. The contact angle of the electrolyte decreases in the presence of polyethylene glycol (PEG), which forms complexes with chloride ions and is absorbed on the Cu surface during plating. However, the consumption of the additives, particularly that of chloride ions, degrades this adsorption. Additionally, the increase in Cu-seed surface roughness owing to self-annealing also reduces electrolyte wettability, compared to the as-received Cu-seed layer. The poor wettability can be improved with additional rinsing. The x-ray photoelectron spectroscopy (XPS) spectrum demonstrates that the Cu surface was covered with a native cupric-hydroxide layer after rinsing, which was hydrophilic (as in the aqueous-plating b...