Three-dimensional integration technology for sensor application using 5-µm-pitch au cone bump connections

This paper presents the experimental results of a pixel detector device fabricated with 3-μmφ gold cone bump connections using adhesive injections. The as-deposited cone bump consists of gold nanoparticles and is easier to deform than plating gold. Consequently, the collapsibility of the gold cone bump allows for low-stress bonding, resulting in a compliant and reliable junction. The size of the bump is determined by photoresist patterning, and its connections do not protrude significantly during junction formation, in contrast with melting-type bump connections. In addition, the shrink ratio of the volume is larger than that of the surface area. The bump resistance of an easily oxidized metal with a diameter of a few microns is affected by the bonding atmosphere. In contrast, bonding with a micro gold cone bump does not adversely affect the electrical characteristics because gold is an oxidation-resistant material. The resistance per bump is approximately 6 Ω with a robust junction formed. The influence of the stress caused by the bump junction on the MOS characteristics is also investigated.