Dielectric Materials Characterization for Hybrid Bonding

Abstract

Wide range of choices are available for dielectric materials selection for hybrid bonding, which include: thermal oxide, PECVD TEOS SiO2, SiN, SiCN and commercial polymer dielectrics. Among the polymer dielectrics, two types: high-temperature curable (350°C) and low-temperature curable (250°C) are investigated. Conclusion of bond strength characterization of different dielectric materials are as follows: Polymer > SiCN > TEOS SiO2 > SiN. Bonding energy >2.5 J/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and die shear strength ≥ 50 MPa, which is higher than the Si yield strength could only be achieved through polymer dielectrics. Dielectric delamination during post-bond annealing for enhancing Cu-Cu diffusion bonding is a major challenge frequently encountered for SiO2 dielectric. Peeling stress generation is the root cause for such delamination. It is confirmed that polymer dielectrics with low Young's Modulus will mitigate such peeling stress generation. However, polymer dielectrics too have their own challenges. Fine scratches generation during chemical-mechanical polishing (CMP) is yet to be fully resolved. SiCN is identified to be the ideal candidate from CMP perspective. Replacing Cu with Cu/Sn solder was also explored for catering low T hybrid process flow. Pros and Cons of different dielectric materials in the process integration of Cu/dielectric hybrid bonding are discussed.