Published papers

The local interfacial strength is a key factor in designing and fabricating advanced three-dimensional large-scale integration interconnect structures. In this paper, both local fracture tests and three-dimensional elastic–plastic crack propagation analysis for a 10 μm × 10 μm specimen were performed, and the local interfacial adhesion between a Cu interconnect and a SiN cap layer were evaluated. The three-dimensional elastic–plastic crack propagation simulation was developed to evaluate the interfacial adhesion that eliminated the effect of progressive plastic dissipation energy during crack propagation. The results show that the average interfacial adhesion for Cu/SiN is 4.46 ± 0.17 J/m2. The crack propagation behavior and fracture pattern depend on the interfacial adhesion, and these differences are due to the plastic yielding of the side edge of the specimen. The critical interfacial adhesion for the onset of shear fracture is 4.92 J/m^2, which is the upper bound of the interfacial adhesion evaluation for the 10 μm × 10 μm specimen.

The authors investigate the overall structural balance of stiffness from the viewpoint of load transfer and load paths. The concept of load transfer balance is examined and graphically expressed using U*. Index U* is a new concept introduced by the authors to express load transfer in structures. The load transfer balance is calculated for an automotive body structure under conditions of vertical loading on the front suspension. The load transfer balance of a body affects the drivability of an automobile. Through the use of figures showing the U* distribution along load transfer paths, the balance of load transfer is clearly expressed. From these figures, it is shown that frontal load is mainly transferred to the lower structure rather than to the upper structure in the vehicle body used in this study. Diagrams and histograms for U*sum, which is the summation of two kinds of U*s, are presented in this study to show the load transfer balance more precisely. These figures show that the transition of load transfer balance to the lower structure is caused by the stiffened support effect near the rear supporting points.