Copper Through-Silicon Via (Cu TSV) is becoming a key technology for three dimensional (3D) packaging and 3D integrated circuit (IC) applications. The microstructure of the Cu TSV is important as it not only affects the electrical properties, but ma y play a role in its reliability such as protrusion. In this study, physical vapor deposition (PVD) and electroplated (ECP) Cu TSV microstructure evolution with Ti and Ta barrier after thermal annealing was investigated. As deposited PVD Cu grain showed a preferred orientation on (111) and transformed into (001) after annealing. On the other hand, ECP Cu grain orientation appears to be random for both samples before and after annealing. The grain size for both PVD and ECP increased substantially after annealing at 410°C 30 min because of grain growth. However, the grain growth was more significant in Ti-barrier Cu TSV sample than the Ta-barrier one.