Low Temperature Copper Direct Bonding by Laser–Assisted Sintering

Abstract

Wide bandgap semiconductors such as SiC, GaN, and GaO require advanced bonding methods to meet demands to realize high performance and reliability of these devices. Sinter bonding by copper nanoparticles has major challenge to suppress the oxidation during bonding process. We introduced porous sintered copper layer formed by printing copper nanoparticles paste on a copper substrate, and irradiating a scanning blue laser beam. It was solid–phase bonded to copper chip by vertical excitation of ultrasonic waves. As results, porous sintered copper layer prepared with high laser power condition changed continuous and solid, and was densified after ultrasonic bonding. Under moderate laser power condition (3.6W), cohesive failure appeared in the bond region on both sides of the chip and the substrate, showing ductile fracture. It was suggested that the densification of the copper nanoparticles sintered layer and the low–temperature bonding of copper were achieved simultaneously in a short time due to the extremely high compressive deformability of the porous sintered copper layer worked effectively within the bonding layer and at the bonding interface.