Electron backscatter diffraction characterization of blind hole fillings by electrolytic Cu deposition

• Blind hole (BH) filling by electrolytic Cu deposition
• Surface Cu deposition obeys Faraday's first law.
• The Cu deposition rate is strongly time dependent in the BH filling.
• [111] and [101] are preferred crystal directions in electrolytic Cu deposition.
• Numerous high angle grain boundaries with strong coincidence site lattices (CSLs).

Blind hole (BH) filling by electrolytic Cu deposition is widely used in high density interconnection technology for printed circuit boards. In this study, we investigated Cu deposition behavior in a BH structure using optical microscopy and field-emission scanning electron microscopy in combination with electron backscatter diffraction (EBSD). According to the deposition morphology/rate, the BH filling process was divided into three distinct regimes: (1) the initial deposition regime (t = 20–25 min), (2) the bottom up deposition regime (t = 25–35 min), and (3) the final deposition regime (t = 35–80 min). EBSD analyses showed that the Cu grains were predominantly in the [111]||TD (TD: transverse direction) orientation in the first regime. The [111] Cu grains were predominantly oriented with a takeoff angle of ~ 20° in the bottom up deposition regime. In the final deposition regime, the [111]||RD (RD: rolling direction) and [101]||RD orientations became dominant in the BH fillings. In addition, we characterized the grain boundaries in the Cu deposits with respect to t. The microstructural/crystallographic information presented in this study will improve the understanding of how the electrolytic Cu filling process occurs in a BH structure.