Hybrid bonding for 3D stacked image sensors: impact of pitch shrinkage on interconnect robustness

Hybrid bonding is a high-density technology for 3D integration but further interconnect scaling down could jeopardize electrical and reliability performance. A study of the influence of hybrid bonding pitch shrinkage on a 3D stacked backside illuminated CMOS image sensor was performed from a process, device performance and robustness perspectives, from $8.8\ \mu\mathrm{m}$ down to $1.44\ \mu \mathrm{m}$ bonding pitches. As a result no defect related to smaller bonding pads was evidenced neither by thermal cycling nor by electromigration, thus validating fine-pitch hybrid bonding robustness and introduction for next generation image sensors.