INVESTIGATION OF A NEW FRACTURE-MECHANICS SPECIMEN FOR THIN-FILM ADHESION MEASUREMENT

We have investigated mechanical probing of a precracked fine line stru cture as a new type of thin film fracture mechanics specimen. An ideal ized mechanics analysis is first presented. Experimentally, two types of precracks are formed. A thin carbon layer to which other layers wea kly adhere creates a ''processed precrack'' by integrated circuit proc essing techniques. An ''indented processed precrack'' is formed by pre cision alignment of a sharp microwedge. The processed precrack is foun d to reduce the critical tangential load by 50% from a non-precracked Line, while the indented processed precrack lowers the load by 200%. F rom this, a reasonable value of adhesion may be directly calculated. C rack path behavior is observed to depend on strength of the interface. In the case of a weak interface, the crack remains in the interface a s it extends. For a strong interface, it kinks into the substrate if t he crack is initially short, but remains in the interface if it is ini tially long. Given the experimental evidence, the mechanics are slight ly modified to quantitatively model the experimental data.