May_EDFA_Digital

edfas.org 37 ELECTRONIC DEV ICE FA I LURE ANALYSIS | VOLUME 23 NO . 2 The group agreed that the challenge stemmed from the package stresses and the resulting die warpage. A mix of solutions were suggested including milling at high tem- perature to reduce thewarpage, filling the chip-interposer topology with epoxy to support the interposer and FIB to expose interposer wiring for probing. PEMwas suggested using a tester to stimulate the interconnect and check the top chip, leading to the next presentation. Dodie Sampang’s talk was on dynamic lock-in ther- mography (LIT) toanalyze interconnect fails onEMIBbased 2.5Dpackages. This dynamic LIT approach uses a tester to stimulate the interconnects. A case study was presented where dynamic LITwas used to isolate an interconnect fail to the GPU top chip. Discussions revolved around taking this approach further by isolating fails within buried or stacked portions of the EMIB or other SOP packages. Sampang recommended further studies into LIT would be needed. The same applied for applications where an open circuit is present in the interconnect which could causeupor down streamthermal signals insteadof signals located at the defect. Dr. Susan Li presented a case study of an open I/O pin failure on a FCBGA interposer module mounted on a systemboard. TDR analysis at the board level was used to predict that the open was near the interposer. However, shepointedout theneed for partial stack samples fromthe customer as a reference for TDR analysis. The case study revealed a defect in the package and she demonstrated the need for plasma cleaning to clean up the mechanical cross-section surface for an artifact free viewof the defect. This analysis prompted an earlier question about using magnetic field imaging to isolate the open. However, there was little experience between the panelists on the subject. We would love to hear from analysts with such experience to comment on the SOP User Group forum on ASM Connect. In the latter part of the session Kevin Distelhurst described various underfill removal techniques and their pros and cons. He presented different options such as use of CF 4 & CF 4 -free O 2 plasmas, acid-based wet etches, or mechanical removal techniques. The tradeoffs are cer- tainly important dependingon theendgoal of theanalysis. He further described a CF 4 -free O 2 plasma enabled probe- based fault isolation. The discussion concludedwith a brief reviewof the top five concerns from the EDFAS FA Technology Roadmap on 3D Device FA. It was felt that die repackaging would be a good topic for future SOP user group discussion. Many thanks to the guest speakers, toDanBockelman for gener- ously volunteering to be a scribe, and everyone else who contributed to making this event a success. 2021 ESREF The 32nd European Symposium on Reliability of Electron Devices, Failure Physics and Analysis (ESREF 2021) will be held as a virtual event, October 4-8. The conference will be hosted by the IMS laboratory, University of Bordeaux in collaboration with LAAS_CNRS, University of Toulouse. This international symposium continues to focus on recent developments and future directions in failure analysis, quality and reliability of materials, and devices and circuits for micro, nano, and optoelectronics. It provides the leading European forum for developing all aspects of reliability management and innovative analysis techniques for present and emerging semiconductor applications. For more information, visit esref2021.sciencesconf.org. NOTEWORTHY NEWS 2021 IPFA The 28th International Symposium on the Physical and Failure Analysis of Integrated Circuits (IPFA 2021) will be held virtually in September. IPFA will continue to focus on the fundamental understanding of the electrical and physical characterization techniques and associated technologies that assist in probing the nature of wear-out and failure in conventional and new CMOS devices, in turn resulting in improved knowhow of the physics of device/circuit/module failure that serves as critical input for future design for reliability. For more information and updates on the dates and times of the virtual sessions, visit the IPFA website at ipfa-ieee.org.