Small Pitch Micro-Bumping and Experimental Investigation for Under Filling 3D Stacking

摘要

Although 3D-IC integration is largely acknowledged as most promising technology to push further the scaling concept ofMoore’s law, a few important uncertainties are delaying high volume production. Among these uncertainties, thereliability of 3D-IC stacked components is the most important. A key element in 3D stacking reliability is the choice ofthe correct UF to integrate in the assembly processing: die stacking and final packaging. In this paper we report the recentresults coming from the UF screening and 3D stacking activities. These activities are performed at Imec in the frame ofthe 3D Imec Industrial Affiliation Program (3D-IIAP).After describing the test vehicle used in this work, we introduce some of the requirements in term of processimprovement and stacking accuracy to enable 3D stacking in case of small pitch micro-bumps. We then present recentresults coming from the UF screening activity and report on the electrical characterization of the 3D stacks. Thischaracterization is done by measuring the electrical resistance of the daisy chains connections between top/bottom diesbumps. The stacks are done with thermo-compression bonding and using die-to-die approach. The stacks are latelyexposed to thermo-cycling processing followed by further characterization.