Phase and microstructure analysis by electron diffraction in semiconductor failure analysis

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.