A method for modeling diffraction includes constructing a theoretical model of
the subject. A numerical method is then used to predict the output field that is
created when an incident field is diffracted by the subject. The numerical method
begins by computing the output field at the upper boundary of the substrate and
then iterates upward through each of the subject's layers. Structurally simple
layers are evaluated directly. More complex layers are discretized into slices.
A finite difference scheme is performed for these layers using a recursive expansion
of the field-current ratio that starts (or has a base case) at the lowermost slice.
The combined evaluation, through all layers, creates a scattering matrix that is
evaluated to determine the output field for the subject.
