LOCAL STUDY OF THIN-FILM ADHESION BY SURFACE ACOUSTIC-WAVES AND SUBSURFACE ACOUSTIC MICROSCOPY IMAGING

Four thin-film adhesion characterization methods are proposed. Two of them are surface acoustic wave based and the two others emphasize the complementary nature between acoustic microscopy, scratch test and ten sile experiments. A continuous wave scanning acoustic microscope was u sed to propagate surface modes in the specimen and to measure the surf ace acoustic wave velocity as a function of the frequency. Characteris tic equations have been calculated for generalized Lamb wave and gener alized surface skimming compressional wave modes as a function of inte rface boundary conditions and frequency. Experimental surface acoustic wave velocity dispersion curves and numerically evaluated ones have b een compared in shape and absolute position. It has been shown that th is comparison allows one to characterize the interface preparation qua lity or adhesion property of thin films deposited by Physical Vapour D eposition (PVD). Two original coupling techniques were developed to in crease the comprehension of intermediate adhesion states and thin-film delamination initiation and propagation characteristics. The first ap plies tensile stress to thin-film specimens directly under the microsc ope and the other creates a typical scratch at the top of the layered sample before surface and interface acoustic microscopy observations.