VARIATION IN STRESS WITH BACKGROUND PRESSURE IN SPUTTERED MO SI MULTILAYER FILMS/

We have measured the stress in Mo/Si multilayer films deposited by mag netron sputtering, using the wafer-curvature technique, and find a str ong dependence on background pressure. We find that for multilayers co ntaining 40 bilayers of similar to 4.3 nm Si layers and similar to 2.6 nm Mo layers, the stress increases from approximately -280 MPa (compr essive) to -450 MPa as the background pressure in the deposition chamb er (i.e., measured just prior to deposition) decreases from 1.O X 10(- 5) to 6.0 x 10(-8) Torr. For multilayers of the same period but with t hicker Mo layers, the dependence on background pressure is even strong er. X-ray (lambda = 0.154 nm) diffraction measurements reveal only a s light increase in interfacial roughness for films deposited at high ba ckground pressure, but no evidence was found for any differences in th e microstructure of the polycrystalline Mo layers that comprise these structures. The peak soft x-ray (lambda = 13 nm) reflectance, which-is sensitive to interfacial roughness at longer spatial wavelengths, als o shows no correlation with background pressure or stress. Atomic conc entrations of incorporated oxygen and carbon, measured with Auger elec tron spectroscopy, were found to be less than similar to 0.5 at. % for all samples. However, the average hydrogen concentration, as determin ed from forward-recoil-scattering measurements made using a 2.6 MeV He beam, was found to increase linearly with background pressure. We dis cuss possible mechanisms for the observed dependence of film stress on background pressure, including gas incorporation and the affect of re sidual gas atoms on adatom mobility. (C) 1995 American Institute of Ph ysics.