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“Chemical analysis of imperfect sample surfaces of two metal layers sandwiching a 5 μm-gap, which is filled with infrared absorbing matters, would have been very difficult to accomplish with either conventional FTIR nor Raman microscopy.”
Reporting in the 2022 IEEE International Symposium on Physical and Failure Analysis of Integrated Circuits, researchers at Advanced Micro Devices demonstrate how optical photothermal infrared (O-PTIR) spectroscopy revolutionizes failure analysis of semiconductor components.
Traditional infrared spectroscopy faces severe limitations with spatial resolution constraints of 5-20 μm, making meaningful analysis impossible for features smaller than 30 μm. Additionally, rough sample surfaces from cross-sectioning and chemomechanical polishing introduce significant spectral artifacts that compromise identification accuracy.
The research presents two compelling case studies showcasing O-PTIR’s superior analytical capabilities. In electrolytic chip capacitor failure analysis, O-PTIR successfully identified different polymer compositions in cracked versus non-cracked capacitors, revealing that Brand A contained poly(phenylene) derivatives with graphite, while the failed Brand B showed polyethylene glycol derivatives and PEDOT:PSS. These chemical differences directly correlated with the observed failure rates during temperature and humidity reliability testing, providing crucial insights for quality improvement.
For underfill creep analysis in lidded packages, O-PTIR demonstrated exceptional performance in characterizing a challenging 5 μm gap between metal layers filled with infrared-absorbing materials.
The technique successfully resolved two chemically distinct layers: an upper epoxy layer consistent with underfill material and a lower layer containing carboxylates from pyrolyzed cellulosic origin. This level of detail would have been impossible to achieve with conventional FTIR due to the narrow gap width and highly scattering sample features.
The study establishes O-PTIR as a breakthrough analytical tool that overcomes traditional limitations through its unique detection mechanism. With submicron spatial resolution, 65 femtogram mass sensitivity, and freedom from spectral artifacts, O-PTIR enables precise chemical identification from small flat areas within rough, poorly reflecting samples.
The technique’s ability to simultaneously collect both infrared and Raman spectra provides comprehensive analytical coverage, making it an invaluable tool for semiconductor failure analysis where conventional methods fall short.
Authors: Syahirah Zulkifli1, Bernice Zee1, Michael K. F. Lo2
- Advanced Micro Devices (Singapore) Pte Ltd
- Photothermal Spectroscopy Corp.
DOI: 10.1109/IPFA55383.2022.9915774
