Low temperature fusion wafer bonding quality investigation for failure mode analysis

In this paper, a brief summary of potential defect formation and failure characteristics for low temperature plasma-assisted Si wafer bonding in correlation to different influencing factors is given. In terms of a failure catalogue classification, these defects are related to incoming material quality variation, wafer bonding equipment and bonding tools issues, or to the choice of inappropriate post-bonding process parameters. To attribute experimentally detected bond defects to its specific root cause requires applying appropriate failure analysis methods, such as e.g. atomic force microscopy, scanning acoustic microscopy, transmission electron microscopy and surface analysis but also strength testing. Practical failure analysis application examples together with new and upcoming methodical developments are presented briefly that support process and technology optimization for future wafer bonded 3D integrated electronic systems.