Noncontact inspection of opaque film thickness in single layer and multilayer structures and edge-exclusion zones

Abstract

A rapid, noncontact, nondestructive optical measurement method permits determination of the thicknesses of opaque films with angstrom repeatability. The method, called impulsive stimulated thermal scattering (ISTS), can be used on nearly any metal including Cu, Al, Ti, W, and Ti:W. Measurements are made across the entire area of a wafer including the edge-exclusion zone, permitting examination of beveled layer edges. Exposed and buried metal layers can both be measured. Typical data acquisition time is about one second, suitable for in-line measurement of product wafers. Comparisons of ISTS results with those of conventional four-point probe, SEM, and profilometry measurements are favorable.