Modification of Thin Film Properties by Sputtered Particles

Irrespective of thin film preparation methods such as PVD and CVD, the thin film process comprises three elementary stages including decomposition, transport, and nucleation and growth mechanisms. Fig. 1 shows the flow chart of the thin film process, where starting materials are successively modified to the resulting films. In the first stage, starting materials in the form of gas, liquid or solid are decomposed into various fragments of neutrals or ions in the form of atoms, molecules, clusters or powders by the external powers of plasma, laser, ion, microwave and thermal energies. The decomposed fragments thus formed will travel through the medium of gas or liquid and approach to the substrate. This phase is referred to as the transport stage in the thin film process. The Monte Carlo simulation technique is helpful in understanding the mechanism of the transport stage. The chemical reaction between the transport medium and the decomposed fragments is also important in the reactive process of thin film formation. The decomposed fragments land on the substrate for nucleation and growth, which result in the formation of functional films. Thin film properties are strongly influenced at this final stage, because the energy of the decomposed fragments is dissipated in the very shallow surface region of the substrate. This dissipation of the energy of the decomposed fragments may enhance the surface migration of ad atoms, chemical reaction between landing fragments and adsorbed molecules, and finally reconstruction into the structures of the resulting films. Consequently, we have possibi l i t ies of