High-speed optical three dimensional measurement method for micro bump inspection in 3D LSI chip stacking technology

Abstract

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 beam microscope. It is not suitable for a mass production inspection test. We have proposed a new optical three dimensional structure measurement technique using optical microscopes with image sensors or line sensors. We developed recently a high-speed optical three dimensional measurement system using specially manufactured optical microscopes with high-speed 8192-pixel line sensors, which can be used for a mass-production process line. Blue laser diffused illumination was equipped to obtain a high resolution. The cone shape bump height measurement with standard deviation less than 0.3 μm was confirmed. The high-speed wafer measurement was demonstrated using 10 μm diameter Cu pillar bumps.