Monograin Defect in Polysilicon Gates

Soft electrical failures caused by monograin defects can have a significant impact on yield in technology nodes below 40 nm. Moreover, the failures are hard to identify and the defects give very few signatures during localization testing. In this article, the authors explain how they used nanobeam diffraction with automated crystal orientation and phase mapping to pinpoint a single grain orientation causing the problem and, as a result, are now able to recognize the symptoms of this type of failure, observe the defect, and limit the impact on electrical timing margins through both design and process corrections.