Profiles of a high-aspect-ratio grating determined by spectroscopic scatterometry and atomic-force microscopy

The new and fast scatterometry method called optical diffraction microscopy is compared with atomic-force microscopy by use of cross-section scanning-electron microscope images as references. The sample is a high-aspect-ratio grating with a period of (almost equal)1000 nm. To allow the atomic-force microscope to track all parts of the grating profile, the grating is investigated at different tilt angles. The measured quantities of the profile include sidewall angle (gamma) ((almost equal)90°), groove height h ((almost equal)2000 nm), and degree of filling f ((almost equal)40%). The two methods, which respond to quite different material properties, give consistent results within standard uncertainties of u((gamma))<=0.8°, u(h)<=15 nm, and u(f)<=1%.