Sputtered tungsten films on polyimide, an application for X-ray masks

Among processes of lithography for submicron technologies, X-ray lithograph y shows the great advantage of high resolution. In the fabrication of X-ray masks, tungsten (W) is one of the alternative absorber materials that can be used instead of gold, but it requires a low stress film with high densit y. Tungsten films were deposited on Kapton and Upilex polyimides using a tr iode discharge system. The dependence of thin W films properties on the wor king argon pressure is reported. X-ray diffraction, AFM and curvature radiu s measurements were used to characterize the coatings in terms of microstru cture and mechanical properties. Average stress and density were found to b e significantly dependent on the argon pressure. Microstructural analysis i ndicated that the grain size and the proportion of metastable phase, beta-W , could vary in a wide range. The adhesion of W to polyimide verified with the scratch testing technique seemed very acceptable. (C) 1999 Elsevier Sci ence Ltd. All rights reserved.