INVESTIGATIONS ON MICROSTRUCTURE, SURFACE-TOPOGRAPHY, AND GROWTH-PROCESS OF SPUTTERED MOLYBDENUM SHOWING TEXTURE TURNOVER

The microstructure and surface topography of molybdenum films prepared by magnetron sputtering at a low rats of about 1 Angstrom/s was inves tigated by electron microscopy (SEM and TEM) and atomic force microsco py (AFM). Films of 3 mu m thickness exhibit a columnar microstructure visible by TEM and SEM. Low pressure deposited films consist of densel y packed columns, whereas high pressure films consist of free standing columns with inter-columnar spacing of the order of 100 Angstrom. In the early state of growth (23 nm film thickness) the development of do me-like structures on the surface of the dense films is observed by AF M. These structures, whose number (and to a lesser extent Size) increa ses with film thickness, form the top of the microcolumns. No evidence for a relationship between microstructure and the evolution of a spec ial kind of texture has been found. An estimate is given for the energ y flux from the target and for the energy loss of the sputter-ejected Mo and reflected Ar atoms in dependence on the traveled distance-press ure product. Reflected argon neutrals give the far superior contributi on (80 to 90%) to the energy impinging the growing film. These calcula tions explain the strong influence of the argon pressure on the densit y and microstructure of the films. The pressure-dependent deposition r ate is well described by an existing model. A different meaning of the so-called ''thermalization distance'' being a key parameter of the mo del is suggested. The appearance of the texture turnover in the Mo fil ms is explained by the minimization on the film surface energy under p article bombardment.