Breakthrough in Cu to Cu Pillar-Concave Bonding on Silicon Substrate with Polymer Layer for Advanced Packaging, 3D, and Heterogeneous Integration

In this paper, finite element method (FEM) simulations are carried out with pillar-concave structure using silicon substrate, silicon substrate with polyimide (PI) and with polybenzoxazole (PBO) for realization of Cu-Cu bonding at low temperature. Parameters of bonding temperature, pillar diameter, concave sidewall angle, and multilayer of concave structure are all considered in simulation. In addition, pillarconcave bonding is successfully demonstrated on silicon substrates with bonding temperatures ranging from 60 degrees C to 100 degrees C. Simulation and fabrication results of concept show potential impacts on current semiconductor packaging method with advantages such as high adhesive strength of polymer on various types of substrates, simplified manufacturing process, solder free interconnect and packaging process, Cu-Cu direct bonding at temperature lower than 100 degrees C, and high tolerance in surface roughness.