In-situ characterization of thermomechanical behavior of copper nano-interconnect for 3D integration

Abstract

Hybrid bonding is a very promising 3D packaging technology which allows extremely high interconnect density between electronic chips. In its most advanced interconnect pitch, Cu pads as small as 300 nm may be used. Successful bonding relies directly on the thermomechanical displacement of Cu above the oxide matrix. Hence, the control of this technology relies on a profound understanding of the thermomechanical behavior of 300 nm Cu pads. To achieve this goal, X-ray synchrotron Laue micro-diffraction is used to monitor the strain state and orientation of individual Cu pads in situ during heat treatment. The experimental findings are completed with Finite Element Modeling simulations including elastic anisotropy and plastic behavior. The 300 nm Cu pads are found monocrystalline with random lattice orientations. The thermomechanical behavior of each pad is found highly driven by its crystal orientation in accordance with the elastic and plastic anisotropy of copper. Very good agreement is found with simulations offering profound understanding of the single nanocrystalline Cu grains properties and providing solid conclusions for a successful hybrid bonding at sub-micrometric pitch level.