Fabrication of Si₃N₄/Cu direct-bonded heterogeneous interface assisted by laser irradiation

Joining of ceramic and metal is a key component in microelectronic device manufacturing, in which the integrity of bonded interface is critical in the performance and stability of the devices. Current methods with a problem of thick transition layer at the interface impeded heat flow, which degraded device service life seriously. Herein, we propose a laser-assisted bonding approach to join ceramic to metal directly without any intermediate material. By focusing the laser on the surface of β-Si₃N₄ ceramic, the Si microcrystalline layer with stacked α-Si₃N₄ nanocrystals was prepared first. The face-centered cubic (fcc) Si and hexagonal close-packed (hcp) β-Si₃N₄ substrate take the coherent orientation relations of [001]_fcc║[0001]_hcp and (220)_fcc║(101¯0)_hcp. Then, the defect-free Si₃N₄/Cu bonded interface obtained by the reaction of the formed Si and Cu at elevated temperature in the 805 - 900°C range for 30 min demonstrated a strong and stable joining of ceramic to metal. The introduction of the laser provides a novel approach to join ceramics to metals, and the ceramic/metal component is expected to be a new configuration for package substrate in high-power device applications.