Characterization of interconnect interfacial adhesion by cross-sectional nanoindentation

The technique of cross-sectional nanoindentation (CSN), as applied to thin films used in microelectronic devices, is reviewed. The technique was developed to characterize interfacial adhesion of interconnect thin films. A Berkovich diamond indenter is used to initiate fracture in a silicon substrate on which multilayer thin film structures are deposited. The cracks propagate to the weakest interface in the system. Both dielectric-dielectric and metal-dielectric interfaces are studied. The technique produces a qualitative measure of interfacial adhesion for blanket and patterned thin films. Quantitative results are obtained for blanket thin films through the application of analytic and finite element modeling. Fracture energy release rates obtained with CSN are in good agreement with results obtained with the four-point bending technique.