Low cost and high speed molten solder-filling process of through silicon via (TSV) for 3D packaging was investigated. Present filling methods, such as Cu electroplating and chemical vapor deposition (CVD), have some problems like low process speed and complicated process factors. In this study, molten solder was filled into the TSV without voids by using vacuum system. The thickness of wafer was 200 μm and the hole diameters were 20 and 30 μm respectively. TSVs were formed by deep reactive ion etching (DRIE) process. As the wetting layer, Ti and Au was sputtered on the wall of the TSVs. Vacuum pressure was ranged from 0.06 ~ 0.02MPa. In 0.02MPa condition, via was filled perfectly within only few seconds. To evaluate reliability of the filled TSV, thermal cycle test were carried out. And interface between TSV wall and filled Sn alloy was observed by focused ion beam (FIB).