The effect of unequal bilayer thickness on stress in WSi2/Si multilayers for multilayer Laue Lens structures

Stress in multilayer Laue lenses can be reduced by choosing unequal thicknesses for the two layers comprising a bilayer in the zone plate structure. We demonstrate this with the wafer curvature measured in-operando for sputter deposition of WSi2/Si bilayers. The curvature measurements showed that the compressive stress built in the multilayers during the deposition process bent the substrate wafers where these multilayers were coated onto it. Within equal thickness WSi2/Si bilayers, the Si layers contribute more compressive stress than the WSi2 layers at a 4 mTorr Argon environment. Reducing the ratio of Si’s thickness in the WSi2/Si bilayer decreased the total stress.