HOLLOWING OF AL-AU NANOPARTICLES BY INTERMETALLIC PHASE FORMATION

The Al-Au couples are widely employed in the microelectronic industry in various wire bonding assemblies. During the high temperature working conditions the interdiffusion in the contact zone leads to the formation of intermetallic phases. Formation of such phases has strong implication over the properties and may lead to the bond failure due to void formation. Here we show that voids form in sub-micron Al-Au core-shell particles even at relatively low temperature.

We study the intermetallic phase formation in Al-Au particles. First, we produced an array of Al particles employing the solid state dewetting process of Al film deposited on sapphire substrate in the molecular beam epitaxy tool, followed by in situ annealing. Then, Au layer was deposited on the particles followed by annealing at low homological temperature. During the latter annealing, the intermetallic phases formed in the particle, which resulted in formation of larger irregularly-shaped internal hole. The hollowing process and its kinetics were studied by X ray diffraction, and a combination of scanning and transmission electron microscopies.