Structural control of nonequilibrium WSi2.6 thin films by external stress

Abstract

The influence of external stresses on a crystallization and a precipitation process for amorphous WSi2.6 films has been studied. An as-deposited amorphous WSi2.6 has crystallized as a hexagonal WSi2 by annealing at 400 °C for 1 h, and excess Si has precipitated to the WSi2/substrate interface. To verify whether the driving force of the precipitation to the interface is a stress relaxation, calculations of the volume change by a crystallization, precipitations (in the film and to the interface), and the stress measurement were performed. It was revealed that as-deposited film had a tensile stress, and it increased by precipitation of excess Si to the interface. That is, the driving force of the precipitation to the interface is not the stress relaxation. Then we tried to apply larger stress (compression and tension) to make clear an effect of stress on the structural change. By annealing at 350 °C under external tensile stress,the Si precipitated at the interface was not observed. On the other hand, by annealing under external compressive stress, a greater amount of Si has precipitated than that without external stress. These phenomena seem to be related to the stress-assisted diffusion similar to Nabarro–Herring creep.