Three-beam interferometric profilometer

A noncontact optical technique for the measurement of thin-film thickness and surface roughness with 25-Å and 2-μm vertical and horizontal resolutions, respectively, has been described. It is based on a common-path three-beam shearing interferometer, in which the outer beams act as a reference while the middle beam scans the surface. The results of this technique are comparable with the ones obtained with a stylus instrument.