Thickness measurement for Cu and Ta thin films using optoacoustics

New all-optical, nondestructive metrology instruments for metal film thickness measurement have been developed using the opto-acoustic technique impulsive stimulated thermal scattering (ISTS). The technique uses lasers to initiate and detect acoustic waves in the sample film. In this study, a commercial ISTS-based instrument is evaluated for measuring Cu and Ta thin films, and the results are compared with 4-point probe, SEM, TEM, and GIXR. We also show that ISTS can be used in conjunction with 4-point-probe to determine resistivity for thin PVD Cu films.