HIGH-PRECISION FILM THICKNESS DETERMINATION USING A LASER-BASED ULTRASONIC TECHNIQUE

A noncontact and nondestructive laser-based acoustic technique called impulsive stimulated thermal scattering (ISTS) is used to measure thic knesses of metal films including Cu, Ta, W, Al, Ti, and others in sing le-layer and multilayer assemblies on silicon substrates. Other opaque film materials and substrates have also been examined. Thicknesses ar e determined with a repeatability of a few angstroms with data acquisi tion times of about 1 s. ISTS and conventional measurements (scanning electron microscopy, profilometry, and four-point electrical sheet res istance) are made on the same samples and the results are found to com pare favorably. (C) 1998 American Institute of Physics.