Scatterometric analysis of a plasmonic test structure

Traditional ellipsometric measurements of copper gratings are limited to Angstrom resolution and are rather insensitive to changes in the critical dimension (CD) or pitch of the structure. By adding another grating per- pendicular and with larger CD and pitch, sensitivity is greatly enhanced. The spectra of one dimensional grat- ings is largely featureless over a wide range of CDs while crossed-gratings exhibit large minima which shift with changing CDs of less than an Angstrom. This improvement is due to plasmonic activity in the crossed-grating, demonstrated in detail here. Mueller matrix element analysis under azimuthal rotation provides information about cross-polarization and plasmon coupling conditions.