Stress evolution in ion assisted thin metal film deposition

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Abstract
Thermal atom deposited thin films are usually under dense, voided and in a state of tensile stress. Simultaneous ion bombardment during film growth can increase density, modify tensile stress and even generate compressive stress. The present analysis evaluates a number of collisionally motivated densification processes and predicts the dependence of tensile stress evolution, in each case, upon the parameters of ion flux density and ion energy and atomic deposition rate. A further set of models for the development of compressive stress, associated with dislocation loop and dislocation formation either by direct interstitial loop punching from collision cascades or by agglomeration and capture of freely migrating interstitials, are also considered. More complex dependences upon processing parameters and possible dependence upon film thickness are deduced.