Phase separation and silicide formation in the films of Pd-W alloys on Si

Abstract

Pd-W alloy films are of interest because of their use for contact fabrication in microelectronic devices.In the present work Pd2 5W7 5, Pd4 0W6 0, Pd9 0W1 0 films were sputter deposited on Si(100) and only Pd9 0W1 0 films were polycrystalline.The amorphization of Pd- W films, possibly due to impurities, was not observed previously. The reaction of Pd9 0W1 0 films with a Si substrate begins at 200°C and leads to the formation of Pd2Si in two equivalent epitaxial orientations: A and B.In contrast to Ni-Nb films the presence of the native SiO2 layer under Pd-W alloy does not prevent the diffusion processes and the formation of silicides both on bulk and on plan-view specimens.Amorphous Pd-W films do not react with Si up to∼500°C and their crystallisation begins at T∼575°C.The reaction is also followed by the formation of two types of epitaxially oriented Pd2 Si islands as shown in Figure 1.The crystallisation of the films is accompanied by the formation of W grains.Pd crystals were not observed, that is possibly due to Pd precipitation at W grain boundaries.