Project Abstract:

Although various bonding methods have been developed for flip chip assembly, most of them cannot be applied to ultra-high density interconnections for the next generation. Direct metal bonding is a promising candidate for solving all the above problems. Presently, most direct metal bonding is done by thermosonic methods, where ultrasonic energy is applied to lower the bonding temperature and pressure. Although thermosonic bonding is an attractive choice, there are distinct disadvantages. For example, it is difficult to control the ultrasonic energy transmission. Small deviations from planarity between the bonding tool and the stage can result in non-uniform ultrasonic energy distribution. Another potential problem is silicon cratering, which results from excessive ultrasonic vibration. This project is to develop a direct metal bonding method at low temperatures and low pressures for hybrid integration, build up a model on the interfacial kinetics of bond formation, and carry reliability studies on direct metal direct bonding for fine-pitch flip chip and waferscale 3-d interconnections.