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- Title
Toward a Better Understanding of the Effect of Cu Electroplating Process Parameters on CuSn Voiding.
- Authors
Yin, Liang; Wafula, Fred; Dimitrov, Nikolay; Borgesen, Peter
- Abstract
'Kirkendall voiding' in the interfacial CuSn intermetallic compound is often observed in solder joints made between Sn-containing alloys and Cu interconnect pads, during extended thermal aging or electromigration testing. It is commonly believed that voids arise from the Kirkendall effect, i.e., the imbalance of diffusion fluxes of Cu and Sn atoms in CuSn. However, recent studies have demonstrated that the propensity for voiding is greatly affected by the amount of organic impurities incorporated during Cu electroplating. The level of impurities was shown to depend on various electroplating parameters, such as current density, bath temperature, bath age, etc. In this study, a general picture is proposed to provide a better understanding of the effect of electroplating process parameters on CuSn voiding. The picture correlates the level of impurity incorporation to (1) the applied electroplating overpotential, and (2) the crystallographic orientation of the Cu deposit. As a first-order approximation, the picture is supported by a variety of electroplating experiments, secondary-ion mass spectroscopy (SIMS), and x-ray diffraction (XRD) analysis.
- Subjects
ELECTROPLATING; COPPER; TIN; KIRKENDALL effect; INTERMETALLIC compounds; INTEGRATED circuit interconnections; CURRENT density (Electromagnetism); SECONDARY ion mass spectrometry
- Publication
Journal of Electronic Materials, 2012, Vol 41, Issue 2, p302
- ISSN
0361-5235
- Publication type
Article
- DOI
10.1007/s11664-011-1764-0