Surface and interface characteristics of Cu films deposited by ionized cluster beam

Abstract

We have deposited Cu films on Si(111) and Si(100) substrates by ionized cluster beam (ICB) technique. The surface and interface characteristics of these films were investigated. When the deposition of ionized and accelerated Cu clusters was made on a Si(111) substrate, the (111) preferential orientation of the film increased and the x-ray line broadening decreased with increasing acceleration voltage Va. In addition, the NH4OH etching of the grain boundaries in the films was reduced with increasing Va. This was due to the enhancement of bonding strength between grain boundaries and/or decreased strain. The interdiffusion between Cu and Si atoms after annealing in vacuum was very small, and it decreased with increasing Va. The diffusion coefficient of Cu at 230 °C was 4×10−14 cm2/s for the case of Va=5 kV; it was smaller than one-tenth in comparison to films prepared by using neutral Cu clusters. When Cu films were prepared on a Si(100) substrate, the films showed the (100) preferential orientation. The interdiffusion between Cu and Si atoms after annealing became small at Va=3 kV, and the dependence of the diffusion coefficient of Cu on the Va corresponded to that of the (100) preferential orientation as well as the x-ray line broadening of the film. The diffusion coefficient obtained at 130 °C was 6.4×10−14 cm2/s for the case of Va=3 kV; it was larger by a factor of 5 than that for the case of Si(111) substrate.