Stress, Microstructure and Stability of Mo/Si, W/Si, and Mo/C Multilayer Films

The stresses in periodic Mo/Si, W/Si, and Mo/C multilayer films have been determined from wafer-curvature measurements. The layer thickness of each material was varied systematically, and parametric stress contours were generated, showing contours-of-constant-stress in the two-dimensional layer-thickness parameter space. These results illustrate that the net stress in a periodic multilayer is not an intrinsic property of the film, but rather depends strongly on the individual layer thickness. X-ray diffraction measurements show (a) how the lattice spacing in the W and Mo crystallites varies with layer thickness; and (b) in the case of the W/Si films, how the phase composition of the polycrystalline W layers vary with W-layer thickness, i.e., a predominance of beta-phase material is present for W layer thicknesses below ~5 nm.