Direct bonding of Ni nanoparticles to a semiconductor Al electrode in air and its form

Abstract

This research group evaluated the bondability of sinter bonding using Ni nanoparticles, which have a high melting point and excellent corrosion resistance, as a new metal nanoparticle bonding material, and found that bonding is possible at bonding temperatures below 400 °C when the particle size is less than 100 nm. Furthermore it was found that Ni nanoparticles can be directly bonded to Al, which is considered difficult to bond directly with solder materials containing tin (Sn) or lead (Pb), and that high bonding strength can be obtained. In addition, the bonding strength of Ni nanoparticles to Al was higher when bonded in air than in a reduction atmosphere of N2+H2 (3%), indicating that there were differences in bonding properties depending on the bonding atmosphere. In this study, we compared the bonding properties to Al in different bonding atmospheres. In the N2+H2 (3%) reducing atmosphere, the bonding strength was not increased even when the bonding temperature was increased. On the other hand, the bonding strength was significantly increased with increasing bonding temperature over 330 °C in air. The failure mode was also rupture in the bonding layer, and good bonding was achieved at the Ni/Al bonding interface. Observation of the bonding interface between Ni nanoparticles and Al using Transmission electron microscope (TEM) showed the presence of an interlayer of oxide film at both bonding interfaces in air and in the N2+H2 (3%) reduction atmosphere. And the oxide layer at the interface bonded in air was thicker, indicating that the structure at the interface between the Ni layer, the oxide layer and the Al layer has changed. It was suggested that the difference in oxide film formation behavior, structure, and thickness affects the bondability due to the difference in the bonding atmosphere.