New optical three dimensional structure measurement method of cone shape micro bumps used for 3D LSI chip stacking

3D LSI chip stacking technology has been developed in AIST using cone shape micro bumps fabricated by nanoparticle deposition method. The cone shape bumps are suitable for a thermocompression bump joint process with low temperature and low load force, where the bumps are easy to collapse with loading due to the pointed structure. High yield micro bump joints can be obtained. The three dimensional measurement of the cone shape bumps can be done using laser scanning microscope or scanning electron (ion) beam microscope (SEM, SIM). It takes much long time to get the precise three dimensional measurement data. It is not suitable for a mass production inspection test. The highly efficient measurement technique is required for this purpose. We propose a new optical three dimensional structure measurement technique using optical microscopes with CCD cameras or line sensors. In this technique, the dimensional measurement of bumps is done by image processing with three images captured by three microscopes, where one microscope is for a top view and the other two are for slanting views from two directionals which counter.