Through glass via (TGV) copper metallization and its microstructure modification

The microstructure and uniformity of Cu metallization in the through glass via (TGV) structure were investigated through electron backscatter diffraction (EBSD) analysis system and finite element analysis (FEA) method. Two different direct current (DC) electroplating methods were employed for the TGV metallization, including single- and multiple-step electroplating methods. We found that the multiple-step electroplating process with appropriate current density (j)/plating time (t) can efficiently enhance the throwing power (TP) value (uniformity) of electroplated Cu in the TGV metallization. Moreover, the Cu electrodeposition via the multiple-step electroplating process possessed larger grain sizes and high fraction of high angle grain boundaries (HAGBs), including twin boundaries (TBs), which are very beneficial to the mechanical and electrical properties of Cu interconnects. Detailed analyses of the uniformity (i.e., TP), crystallographic microstructure (e.g., grain size), and mechanical characteristics (e.g., ductility) of electroplated Cu derived from single- and multiple-step electroplating process were discussed in this paper.