edfas.org ELECTRONIC DEVICE FAILURE ANALYSIS | VOLUME 27 NO. 1 38 The second topic of the user group was on scan diagnosis. Jayant D’Souza from Siemens presented on “Bridging Design, Test, Diagnosis, and Fault Isolation.” D’Souza showed the evolution of design for test (DFT) strategies from compression, through hierarchical DFT, to modern techniques like streaming scan network (SSN). As DFT has evolved, it’s become more challenging for FA, which is now very obvious in the lack of 1:1 correlation between the tester cycles and the scan state. Siemens has worked to close this gap by adding information to the patterns to enable easy mapping to failing cores. They have worked with the ATE companies to allow looping on the pattern of interest. Discussion from the audience focused on the areas of improvement needed for DFT to continue to support FA needs. The need to make the DFT tools more accessible to FA engineers is important, but also DFT should focus on expanding the tests to provide more diagnosability rather than just screening. For both diagnosability and power consumption, one attendee suggested that a separate test program for screening and another for diagnosis might be the answer. The diagnosis results are limited in resolution by equivalencies, and D’Souza referred to the paper being presented at ISTFA as one example where chain diagnosis results can be improved. Another attendee raised a concern about the challenge of delivering the DFT collateral, which has become more complex. The situation could be improved by more support in the tool for collateral delivery. The 2024 Optical Fault isolation User Group offered a good discussion of topics related to issues that FA engineers are seeing today, and those issues that will be seen in the lab soon. ISTFA 2024 SAMPLE PREP USER GROUP Chair/Co-Chairs: Jim Colvin, Cecile Bonifacio, Rosine Coq Germanicus, Bryan Tracy, and Nathan Bakken jim@fainstruments.com, cs_bonifacio@fischione.com, rosine.germanicus@unicaen.fr, bryan.tracy@ibssgroup.com, nathan.j.bakken@intel.com Sample Prep User Group presenters and co-chairs. The ISTFA 2024 Sample Prep User Group session highlighted cuttingedge methods and key challenges in preparing microelectronics devices for analysis. Thanks are due to our sponsor, ULTRA TEC Manufacturing Inc., for their ongoing support. This year’s session was once again well attended by well over 50 attendees, providing a spirited discussion of the sample prep methodologies. Pawel Nowakowski, Fischione Instruments, opened the discussion by emphasizing the importance of measuring strain in Cu-to-Cu devices using electron backscatter diffraction (EBSD). He shared practical techniques for careful sample preparation, like incrementally removing a heat spreader lid to avoid stressing the device and using a combination of mechanical polishing and argon milling. Audience members contributed various suggestions, including scalpel use and notching package corners, while Nowakowski reiterated that improper handling can lead to strain in the region of interest. Cheryl Hartfield, Carl Zeiss Microscopy, shifted the focus to 3D x-ray analysis, emphasizing its nondestructive nature and challenges such as balancing sample size and resolution. She explained how downsizing the sample and managing beam hardening artifacts by removing BGA balls and stiffeners can enhance image quality. The discussion expanded to advanced tools like femtosecond lasers for precise material removal and techniques for maintaining sample integrity during geometry reduction.
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