Wafer Bumping and Characterizations of Fine-Pitch Lead-Free Solder Microbumps on 12” (300mm) wafer for 3D IC Integration

In this study, the wafer bumping and characterization of fine-pitch lead-free solder microbumps on 300mm wafer for 3D IC integration are investigated. Emphasis is placed on the Cu-plating solutions (conformal and bottom-up). Also, the amount of Cu and solder (Sn) volumes is examined. Furthermore, characterizations such as shearing test and aging of the microbumps are provided and cross sections/SEM images of the microbumps before and after test are discussed. Finally, the process windows of applying the conventional electroplating wafer bumping method of the ordinary solder bumps to the microbumps are also presented.