Stabilization of tungsten and tungsten silicide films by rapid thermal annealing in nitrogen

The effects of N2 and Ar as processing ambients during rapid thermal annealing and silicidation of thin W and amorphous W0.62Si0.38 films on Si substrates have been investigated. The W films were deposited by sputtering, cosputtering, and e-beam evaporation. All of the films reacted with the substrate and transformed to the stable WSi2 phase during high temperature annealing in Ar. Stresses induced in the films by the transformation generally caused delamination from the substrate during the anneal. In contrast, high temperature annealing in N2 was found to stabilize the films and suppress any film/substrate interactions to 1100 degrees C; β-W initially present in the sputtered films transformed into α-W and the cosputtered amorphous films crystallized to W5Si3. No appreciable diffusion of Si into the films was observed. A Rutherford backscattering resonance measurement indicated less than 2.1016 n/cm2 present at the interface, although nitrogen was incorporated in the near surface. The effect of the N2 anneal could not be reproduced by direct nitrogen implantation to the interface followed by annealing in Ar