In this work, electron diffraction techniques were employed for the physical failure analysis of two fab issues. Together with other TEM imaging and microanalysis techniques, electron diffraction techniques enabled us to successfully characterize the phase and microstructures of the defective structures. For the first issue, the identification of tungsten oxide by selected-area electron diffraction analysis revealed the issue with the oxidation of N + W contact due to the galvanic corrosion effects during CMP processes. For the second one, power MOS Vramp issue, STEM-NBD (nanobeam electron diffraction) line scan analysis showed the evidence of defective microstructure in the abnormal active region, which was further verified by HRTEM analysis. The dislocation arrays in the abnormal active may account for the early breakdown the failed device.
In this paper, we describe automated FIB for TEM sample preparation using iFast software on a Helios 450HP dual-beam system. A robust iFast automation recipe needs to consider as many variables as possible in order to ensure consistent sample quality and high success rate. Variations mainly come from samples of different materials, structures, surface patterns, surface topography and surface charging. The recipe also needs to be user-friendly and provide high flexibility by allowing users to choose preferable working parameters for specific types of samples, such as: grounding, protective layer coating, milling steps, and final TEM lamella thickness/width. In addition to the iFast recipe, other practical factors affecting automation success rate are also discussed and highlighted.
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