Revealing the effects of particle shape and distribution on the direct wafer-to-wafer bonding dynamics

Particle contamination control is one of the most critical challenges in wafer-to-wafer (W2W) hybrid bonding technology. Particles induce voids at the bonding interface, thereby compromising the bonding quality and reliability. However, the effects of particle shape and distribution on the W2W pre-bonding process have not yet been investigated. In this work, three-dimensional (3D) W2W hybrid bonding analysis involving particles was conducted. The influence of particle on bonding front propagation was analyzed. Besides, the effects of particle shape and position on bonding time, interfacial void size, and upper wafer von Mises stress were quantitatively evaluated. The results show that the presence of particle leads to the split of the bonding front and a pronounced delay in bonding time. Compared with the cylindrical particle, the square particle results in a longer bonding delay (4.4 s vs 3.1 s) and produces a larger void height (17.1 μm vs 11.1 μm). Moreover, it is found that particle contamination significantly amplifies the void defects. Particle position is found to have a non-monotonic influence on bonding dynamics. As the particle location gradually moves away from the wafer center, the area and height of void, as well as the total bonding time exhibit a trend of first increasing and then decreasing. Specifically, a cylindrical particle located at 70–80 mm from wafer center generates the largest void area (up to 2350 mm2), the highest void height (14.8 μm), and the longest bonding time (3.6 s). This study offers a quantitative guidance for contamination control in 3D heterogeneous integration technology.