ABSTRACTIn MEMS packages and silicon devices, the adhesion of interconnects to the substrate is a critical reliability issue. A Precracked Line Scratch Test (PLST) is among one of the available tests to measure the thin line adhesion. In the test, an initial crack is introduced at the interface between the thin line and the substrate. The line is then loaded from the precracked end. The load is recorded continuously while the crack propagates before and after the line buckles. This precracked line scratch test has been applied earlier to tungsten thin lines on silicon wafers [1]. A macroscopic version of the test was also performed to evaluate the analytical model [2]. In the macroscopic tests, polycarbonate lines were bonded to steel substrates with cyanoacrylate.In this paper, finite element analysis is performed for the Precracked Line Scratch Test before line buckling. The energy release rates and phase angles are calculated based on the corresponding load and crack length. The results are then compared to the closed-form solution. Macroscopic experimental model along with the finite element solution has provided a way to derive the interface fracture toughness as a function of the crack length based on the load and crack length history. With the analysis in place, the precracked line scratch test can be used conveniently to study the adhesion of interconnects to passivation layers, MEMS devices and packages on different scales.
Finite Element Analysis on Interfacial Stress of Scratch Test