Structural and material system design for highly reliable non-metallurgical interconnections

The effect of material properties on non-metallurgical interconnection reliability in several TEG samples was investigated. The experimental results confirmed the validity of the assumed failure mechanism at high temperature; that is, the interconnection reliability deteriorates when the material system causes the large plastic strain in a gold bump during temperature cycling. The failure mechanism at low temperature was also clarified. In particular, when the gold bumps were located on the peripheral of a silicon chip, the compressive contact stress is reduced by bimetallic warpage during the cooling process. The effects of structural and manufacturing-process factors on interconnection reliability were also studied. Especially, the chip thickness is a critical factor in enhancing interconnection reliability at both high and low temperatures. Since the rigidity of the silicon chip rapidly decreases when it is less than roughly 0.1 mm thick, the thermal mismatch between the gold bumps and adhesive film is absorbed by the elastic deformation of the chip. It is thus concluded that system design, i.e., material, structural, and manufacturing-processes, plays a major role in enhancing the non-metallurgical interconnection reliability.