Reduction of Thermal Stress in Copper TSV due to Annealing by Low TEC Copper

Copper through-silicon via (TSV) is the key technology used in 3D packaging. During the fabrication process, copper TSV is exposed to a high temperature between 400 degrees C and 600 degrees C. For conventional copper TSV, we observed the cracks at the bottom of TSV after annealing at 500 degrees C and a very high copper extrusion height, which destroys the overlying layers above the TSV. We also succeeded to prevent cracks at the bottom of the TSV and reduce the copper extrusion height by using the low thermal expansion coefficient (TEC) copper.