Polarization Conversion from Highly Conducting, Asymmetric Trapezoidal Gratings

The differences in the curves of the zeroth-order cross-polarization reflection coefficients (p (longrightarrow) s and s (longrightarrow p ) versus angle of incidence have remarkable potential for application in scatterometry because, if the differences are larger than the measurement error, they could contribute to a reliable nondestructive technique for detecting asymmetries in grating profiles. The cross-polarization efficiencies of highly conducting metallic gratings with asymmetric trapezoidal profiles are investigated theoretically by means of a rigorous electromagnetic code. The results show that the differences between p (longrightarrow) s and s (longrightarrow) p conversion tend to be undetectable for highly conducting materials, a fact that limits, in principle, the application of this potential detection technique.