Influence of additives on electroplated copper films and their solder joints

• Published in: Materials characterization 2019-01, Vol.147, p.57-63
• Main Authors: Lee, Hsuan, Tsai, Shan-Ting, Wu, Ping-Heng, Dow, Wei-Ping, Chen, Chih-Ming
• Format: Article
• Language: English
• Subjects: Copper; Electroplating; Impurity; Intermetallic compounds
• ISSN: 1044-5803; 1873-4189
• DOI: 10.1016/j.matchar.2018.10.029

An organosulfide, 3‑(2‑benzthiazolylthio)‑1‑propanesulfonsäure (ZPS), is used as an accelerator and formulated with a suppressor (polyethylene glycol, PEG) and chloride ions (Cl−) in the copper plating solution containing electrolytes (Cu sulfate and sulfuric acid) to prepare the Cu films. Microstructural characterization using focus ion beam (FIB), scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD) reveals that an increase of the ZPS concentration accelerates the grain growth of the electroplated Cu films. Impurity examination based on time-of-flight secondary ion mass spectrometer (TOF-SIMS) shows that such microstructural evolution effectively suppresses the impurity incorporation in the electroplated Cu films. The suppression effect on impurity incorporation by using a high level of ZPS concentration plays an important role in retaining the microstructural stability and integrity of the electroplated Cu solder joints subjected to thermal aging. •An organosulfide, ZPS, is used as an accelerator for Cu electroplating.•The ZPS concentration has a significant effect on the electroplated Cu film.•An increase of the ZPS concentration coarsens the grain size of Cu.•An increase of the ZPS concentration suppresses the impurity incorporation in Cu.•Impurity suppression retains the microstructural stability of the Cu solder joint.