Bond Strength Measurement for Wafer-Level and Chip-Level Hybrid Bonding
Junya Fuse, Yuki Yoshihara, Marie Sano, Fumihiro Inoue
Abstract
Regardless of wafer level or die level integration, “hybrid bonding” is gaining high interest for multi-tier stacking. One of the challenges for hybrid bonding is the precise measurement of bond strength, essential for process qualification. The robust and reliable bond strength measurement method has not yet been established for both Wafer-to-Wafer and Die-to-Wafer bonding. The Double-Cantilever-beam test is a commonly used measurement method for wafer bonding, however, the variation caused by water stress corrosion is not deeply discussed. The method is also only applicable at wafer edge, which cause limitation to estimate bond strength uniformity across the wafer. In addition, the Double-Cantilever-Beam test is not applicable for Die-to-Wafer bonding. Using the nanoindentation method, which was devised to overcome the problems of Double-Cantilever-Beam test, we aim to make progress in elucidating the mechanism of variation in bond strength within the wafer surface and by measuring the bond strength of Die-to-Wafer bonding. In this study, the bond strength data generated by Double-Cantilever-Beam and nanoindentation have been deeply compared. The within wafer uniformity in bond strength with wafer-to-wafer bonding was investigated by using nanoindentation test. The bond strength of Die-to-Wafer samples have also been measured by nanoindentation test. The difference of the bond strength due to the difference between the Wafer-to-Wafer process and the Die-to-Wafer process will be discussed.