INTERFEROMETRIC RESOLUTION EXAMINED BY MEANS OF ELECTROMAGNETIC THEORY

Interferometric methods are widely used in surface metrology. A questi on that arises is how much information about the surface can be extrac ted from a given interferogram. For examination of the resolution limi t of interferometry with coherent monochromatic light, interferograms of several surface relief gratings calculated with the use of approxim ate and rigorous theories are presented. The limits of the usefulness of scalar theory based on the use of the Fourier transform are indicat ed. Interferograms of dielectric and metallic structures are examined, including simple lamellar gratings and gratings made up of trapezoida l steps with varying slopes and depths. In all cases TE illumination i s assumed. The effects of changing numerical aperture and defocus on t he interferograms are also examined.