Bumpless interconnect of 6-m-pitch Cu electrodes was realized at room temperature with the surface activated bonding (SAB) method. In this study, we propose a novel bumpless structure, where the electrodes and a surrounding Cu frame are fabricated with the same height to increase bond strength and demonstrate the feasibility of a sealing interconnection between Cu surfaces. The damascene process, assisted by the reactive ion beam etching (RIE), was used to fabricate the Cu structures. 923 521 electrodes placed inside the frame were arranged into a spiral chain to enable the detection of the positions with insufficient interconnection by electrical resistance measurements. Using the SAB conditions optimized with simple chemo-mechanical polishing (CMP)-Cu film samples, we found that 744 769 electrodes were successfully interconnected, except some specific lines near the frame, which might be due to sample preparation error rather than a bond defect. The mean contact resistance was below 0.08 ; a sealing effect was achieved at the frame structure because there was little increase in the contact resistance in high temperature storage testing performed at 150 C for 1000 h, in ambient air.Index Terms-Bumpless interconnect, Cu frame, room temperature, sealing, surface activated bonding (SAB).

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Plastic package cracking during reflow soldering is an important problem for the reliability of plastic encapsulated semiconductor devices. This paper describes a simplified method of package cracking estimation obtained by introducing a material property for resin A which is the coefficient between the relative humidity of storage and the saturated moisture content. The consequent process of package expansion during reflow soldering was measured. The individual processes were fitted by calculation and provided a precise mechanism of package cracking.

A synthetic criterion to provide guidance for the high-reliability structure design for the level-1 crackfree package is introduced. The criterion reflects a consideration of both delamination and package cracking. According to the criterion, to prevent delamination is the most effective means to realize the level-1 crack-free package for large chips (ex.15" square). Therefore, a new package structure, a chip side support (CSS) structure which eliminates a die-pad is proposed and reliability tests are carried out. The CSS package realizes the level-1 crack-free package without moisture-proof packing.