Electromagnetic field modeling for defect detection in 7 nm node patterned wafers

By 2017, the critical dimension in patterned wafers will shrink down to 7 nm, which brings great challenges to optics-based defect inspection techniques, due to the ever-decreasing signal to noise ratio with respect to defect size. To continue pushing forward the optics-based metrology technique, it is of great importance to analyze the full characteristics of the scattering field of a wafer with a defect and then to find the most sensitive signal type. In this article, the vector boundary element method is firstly introduced to calculate the scattering field of a patterned wafer at a specific objective plane, after which a vector imaging theory is introduced to calculate the field at an image plane for an imaging system with a high numerical aperture objective lens. The above methods enable the effective modeling of the image for an arbitrary vectorial scattering electromagnetic field coming from the defect pattern of the wafer.

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