Evaluation of Polymer Materials for Hybrid Bonding Application

With the advancement in the fine-pitch packaging < 10µm and the requirement of heterogeneous integration, chip-to-wafer (C2W) hybrid bonding is widely explored for future needs. Hybrid bonding is widely explored for stacking of multiple dies vertically. For C2W bonding, there is a need to select a proper dielectric material to have a good bond interface. There are broadly two types of dielectric materials explored by the research community, i.e., inorganic such as oxide/SiCN and organics such as polyimides/polymer. This article explored different polymer materials for the hybrid bonding of bottom substrate and top chip with polymer dielectrics. Such a combination of dielectric materials is required for stacking of dies vertically. Initially, four different polymer materials were considered, i.e., #A, #B, #C, and #D, from different suppliers with different curing temperatures and curing times. However, due to the low shear strength of polymer #A and the toxic nature of polymer #C, only polymer #B and #D were further investigated. After the blanket coating and curing, the CMP process was optimized to obtain uniform polymer thickness and required surface roughness < 5 nm with reduced scratches. After the bonding process, the shear strength of the polymers was measured using the die shear test.