From Electrical to Physical-Chemical Characterization of the Cu/SiO₂ Hybrid-Bonding Interface—A Cu₂O-Layer as a Cu Diffusion Barrier?
S. Moreau, Hervé Manzanarez, Nicolas Bernier, J. Jourdon, S. Lhostis, H. Frémont
Abstract
This letter discusses copper (Cu) diffusion in the framework of the development of future 3D stacked devices by means of hybrid bonding-based interconnects. Indeed, at the bonding interface, due to the bonding tool accuracy, an inherent misalignment exists between top and bottom tiers leading to a direct contact between copper and neighboring dielectrics. Our experimental studies do not evidence any copper diffusion for the analyzed hybrid bonding-based test structures. Indeed, BTS/TVS (Bias Temperature Stress/Triangular Voltage Sweep) electrical characterization does not evidence any mobile ions diffusion. Our Electron Energy Loss Spectroscopy (EELS) analysis reveals the presence of a thin layer (~3 nm) of cuprous oxide (Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O) at the copper/dielectric interface that most probably acts as a diffusion barrier to copper.