Blind hole (BH) filling by electrolytic Cu deposition iswidely 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]parallel to TD (TD: transverse direction) orientation in the first regime. The [111] Cu grains were predominantly oriented with a takeoff angle of similar to 20 degrees in the bottom up deposition regime. In the final deposition regime, the [111]parallel to RD (RD: rolling direction) and [101]parallel to 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. (C) 2014 Elsevier B. V. All rights reserved.