Study on TSV-Cu protrusion under different annealing conditions and optimization

With the rapid development of three-dimensional (3D) integration technology, the through silicon via (TSV) approach has become the main trend of study. However the protrusion of cooper in TSV (TSV-Cu) due to the thermal mismatch of different materials in TSV structure imposes serious reliability problems. In this paper therefore focuses on the TSV-Cu protrusion effect under different annealing conditions including annealing temperature, heating rate and duration time. Furthermore, to simulate the actual thermal process that TSV underwent, a consequent second annealing was conducted to study the relationship between the annealing times and TSV-Cu protrusion. It is found that the protrusion of TSV-Cu increases with annealing temperature in the first annealing, especially after 300°C, and also an obvious grain growth is observed at 300°C. The Cu protrusion height is accumulated with the annealing times, and mainly determined by the highest annealing temperature of those thermal treatments while the amount of protrusion becomes less if the second annealing temperature is lower than that of the first annealing.