In-situ curvature and stress analyses for sputtered tungsten silicide/silicon multilayer thin films on silicon wafers.

摘要

Multilayered thin films with layer thicknesses of a few nanometers can be used to focus x-rays (e.g., Multilayer-Laue Lenses). Stress develops layer-by-layer during deposition; high stress from the multilayers can give adverse effects like delamination. This project studies the wafer curvature of dc magnetron sputtered amorphous WSi2/Si bilayers on Si wafers. Sputtering was interrupted and wafer curvature was measured in-situ five times per layer with a laser-based optical system. The variables studied were: substrate orientation, wafer rotation with respect to the wafer flat, and Ar plasma pressure in the deposition chamber. Results show that layers grown at lower pressures were in compression while layers at higher pressures were in tension. Similarly to other sputter deposited materials, there is a quick transition between compressive and tensile stress as the plasma pressure is increased. It is found that during deposition the sputtered Si layer was more stressed than the WSi2 layer.