Magnetically Actuated Test Method for Interfacial Fracture Reliability Assessment

The interfacial strength of different thin film layers is critical for the reliability of electronic devices. With the continuing trend of decreasing dimensions of various features and layers in microelectronics, the limitations of the methods used to test their mechanical behavior are becoming apparent. Smaller microelectronic device dimensions require the fabrication and attachment of smaller fixtures to the device samples to apply mechanical loads, and at such small length scales, fabrication and attachment of appropriately small fixtures have become difficult. Additionally, testing of smaller devices requires similarly small, but accurate, control and measurement of forces and the resulting displacements. Thus, novel test methods are needed for mechanical reliability testing of next-generation microelectronic devices. In this paper, a magnetically actuated method to mechanically test features and layers in microelectronics is presented and examined. This method uses magnetic forces to initiate and propagate mechanical failures in the interfaces of a microelectronic structure using a fixtureless and contactless technique. In the test, a permanent magnet is attached to the surface of the tested microelectronic structure. The tested sample with the permanent magnet is then placed in an external electromagnetic field which applies a localized force to be able to initiate and propagate interfacial delamination. Different loading magnitudes and profiles can be created by adjusting the applied voltage of the external electromagnetic field. Thus, both monotonic and fatigue loading conditions can be achieved using the proposed test technique. Furthermore, tensile, shear, and mixed loading conditions can be facilitated by changing the location and orientation of the externally applied electromagnetic field. Numerical simulations, in combination with experiments, are used to determine the forces induced on the die pads through the external electromagnetic field on the permanent magnet. The force on the permanent magnet is then used to examine interfacial crack propagation between different layers, and to demonstrate the viability of the proposed test technique.