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

Abstract

• A novel and effective method of ceramic/metal bonding was developed. • The laser-induced Si 3 N 4 surface and the Si 3 N 4 /Cu heterogenous interface were characterized. • The growth mechanism of laser-induced layer on the Si 3 N 4 surface was discussed. • The mechanism of Si 3 N 4 /Cu bonding was discussed based on the diffusion-reaction by laser-induced ceramic degradation. 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-Si 3 N 4 ceramic, the Si microcrystalline layer with stacked α-Si 3 N 4 nanocrystals was prepared first. The face-centered cubic (fcc) Si and hexagonal close-packed (hcp) β-Si 3 N 4 substrate take the coherent orientation relations of [001] fcc ║[0001] hcp and (220) fcc ║( 10 1 ¯ 0 ) hcp . Then, the defect-free Si 3 N 4 /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.