I describe the development of low-stress W/Cr bilayer films, for use as SCALPEL(R) mask scattering layers. These films are produced by de magnetron sputtering in argon, and consist of 25-50-nm-thick W layers deposited onto 5-10-nm-thick Cr layers. X-ray reflectance analysis is used to measure the thicknesses of the individual W and Cr layers with subangstrom precision; surface and interface roughnesses, film densities, and also the thickness of the tungsten-oxide overlayer which forms after exposure to air are determined by this technique as well. Film stress, which is measured using the wafer curvature technique, is controlled by adjusting the deposition conditions such that the Cr layers are in tension while the W layers are in compression (and thus have high density and low surface roughness), so that the net stress in the bilayer is balanced near zero. I present data that illustrates how the net stress in these films varies with argon pressure, background pressure (i.e., partial pressure of residual gases present in the vacuum chamber), and Cr layer thickness. I also show how the stress depends on the composition of the substrate: i.e., stresses measured in films deposited onto Si wafers are systematically higher (by several hundred MPa) than the stresses measured for the same films deposited onto silicon-nitride-coated Si wafers. I discuss the implication of these results with regard to the production of high-quality SCALPEL(R) mask blanks for sub 0.12 mu m lithography.