Abstract
Current trends in microelectronics focus on three-dimensionally integrating different components to allow for increasing density and functionality of integrated systems. Concepts pursued involve vertical stacking and interconnecting technologies that employ micro bumping, wafer bonding, and through silicon vias (TSVs). Both the increasing complexity and the miniaturization of key elements in three-dimensional (3-D) components lead to new requirements on inspection and metrology tools and techniques as well as for failure analysis methodologies. For metrology and quality assessment in particular, methods operating nondestructively are of major importance. Scanning acoustic microscopy has the ability of illuminating optically opaque materials and, thus, allowing the assessment and imaging of internal structures. Conventional scanning acoustic microscopy (SAM) equipment can be applied to analyze the quality of wafer-bonded interfaces in 3-D integration but may reach its limitations when structures shrink in size and gain complexity. A new concept of acoustic inspection in the gigahertz (GHz) frequency band is explored for its applicability to 3-D integration technologies. Extending the acoustic inspection frequency allows for lateral resolutions in the 1-μm range and also enables the inspection of microbumps and TSVs in addition to wafer bonded interfaces, which exceed the applicability of conventional SAM. Three case studies are presented here ranging from conventional SAM on a full wafer scale to acoustic GHz microscopy on thin films and TSVs.
Highlights
IntroductionTechnologies enabling three-dimensional (3-D) integration of semiconductor devices have rapidly attracted attention
Over the last years, technologies enabling three-dimensional (3-D) integration of semiconductor devices have rapidly attracted attention
Recent developments in the field of scanning acoustic microscopy (SAM) have been focused on inspection and metrology of decreasing structure dimensions, which are of major relevance for the emerging technologies aiming at the 3-D integration in the semiconductor industry and the field of microelectronics, providing applicable equipment with the benefits of acoustic inspection
Summary
Technologies enabling three-dimensional (3-D) integration of semiconductor devices have rapidly attracted attention. The complexity of 3-D high-density integration with respect to novel designs, processes, and materials leads to new challenges for metrology, quality assurance, and failure analysis that have to be met prior to mass manufacturing. Since scanning acoustic microscopy (SAM) is an already well-established methodology for defect analysis of wafer-bonded interfaces of MEMS components, it is rather straightforward to consider SAM techniques as inspection tools for 3-D integration. Novel methodical SAM approaches for defect characterization in 3-D integrated components are shown exemplarily. The potential of these techniques is illustrated for a 3-D-integrated sensor component formed by Si direct bonding with a TSV last process, focusing on the quality of the bonding steps. It will be shown that advanced SAM analysis techniques can significantly contribute to secured and improved quality and reliability properties of complex 3-D devices and systems
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