Insertion bonding: A novel Cu-Cu bonding approach for 3D integration

A novel low temperature Cu-Cu bonding approach called the insertion bonding technique has been developed. This technique leverages on the initiation of high shear stresses at metal-metal contact interface, thus resulting in high plastic deformation, which is essential for strong bond formation. Through finite element studies, it is observed that the insertion bonding technique result in significantly larger plastic deformation in comparison to the conventional bonding technique under the same bonding conditions. Experimental studies of the insertion bonding technique were performed and it is observed that a seamless bond interface is achieved, even at a low bonding temperature of 100°C. Bonding at room temperature (RT) in the presence of a surface cleaning agent resulted in an improved bond interface. Resistance measurement of the samples bonded at 100°C revealed that an electrical contact is achieved between the stacked dies. This shows that the insertion bonding techniques holds much promise for low temperature Cu-Cu bonding.