Development of micro bump joints fabrication process using cone shape Au bumps for 3D LSI chip stacking

3D LSI chip stacking technology have been developed using cone shape Au micro bumps fabricated by nanoparticle deposition method. The cone shape bumps with less than 10 um diameter are suitable for a thermocompression bump joint process with low temperature and low load force. High yield micro bump joints can be obtained. In this study, the property evaluation of the cone shape bumps, and the cone shape bump joints were investigated in details. The collapsed bump height and the electrical resistance can be controlled by compression force. The low resistance (average 8.6 mΩ) bump joint with a 10 μm diameter cone shape Au bump was successfully achieved.