EXPLANATION OF SPURIOUS FEATURES IN TUNGSTEN DEPOSITION USING AN ATOMIC MOMENTUM MODEL

Adequate uniformity of thin film coverage is necessary in very large s cale integration. Recently, cross-sectional scanning electron microsco pe micrographs of thin films deposited by sputter systems producing hi ghly directional flux have exhibited unusual growth features. A model based on the momenta of the incident sputter flux and resultant asymme tric diffusion has been developed to explain the effects and has been incorporated into simulation of ballistic deposition, a Monte Carlo si mulation package. Experimental growth of tungsten films deposited over VLSI topography is presented illustrating the unique features of the deposited films which necessitated the use of the momentum model. The model reflects a general effect for thin film growth in sputtering sys tems that is more apparent for directional deposition, for example, tu ngsten deposition at low pressure or when using a collimated system. E xperimental results of tungsten films deposited over high aspect ratio contact cuts are carefully compared to simulations incorporating the atomic momentum model. (C) 1995 American Institute of Physics.