ION-ASSISTED SPUTTER-DEPOSITION OF MOLYBDENUM SILICON MULTILAYERS

X-ray multilayer (ML) structures that are fabricated by the use of mag netron-sputter deposition exhibit a degradation in structural quality as the deposition pressure is increased. The observed change in morpho logy is attributed to a reduced mobility of surface adsorbed atoms, wh ich inhibits the formation of smooth, continuous layers. The applicati on of a negative substrate bias produces ion bombardment of the growin g film surface by sputtering gas ions extracted from the plasma and pe rmits direct control of the energy density supplied to the film surfac e during thin-film growth. The technique supplements the energy lost t o thermalization in high-pressure deposition and permits the fabricati on of high-quality ML structures at elevated processing pressures. A t hreefold improvement in the soft-x-ray normal-incidence reflectance at 130 angstrom results for substrate bias voltages of the order of appr oximately -150 V for Mo-Si ML's deposited at 10-mTorr Ar.