TABLE OF CONTENTS Reactions between separate phases or layers in thin films may be classified as heterogeneous, and those that occur within a single layer or on the surface between adatoms or admolecules may be classified as homogeneous. In integrated circuit technology, the products of these reactions make up elements of circuitry, such as gate oxides, or metallic junction elements, such as silicides. Sometimes the reactions between adjacent thin film layers are undesired, as in superlattices. It is thus useful to attempt to summarize the knowledge that has been gained from studies of these various reactions in thin films.
Given monocrystalline layers having different composition as the elements of the diffusion junction. Usually, even though the two layers have the same crystal structure, given that they are completely miscible, they do not have the same lattice parameter. Thus, there will usually be misfit dislocations in the two layers to minimize the free energy of the two-layer structure. As diffusion proceeds to develop a concentration gradient, the misfit dislocations will move to accommodate the difference in lattice parameters along this gradient. One possible result of such diffusion is the formation of new grains whose lattices are curved to adjust for the difference in lattice parameters that exists along the direction of the concentration gradient.1 ,2 The boundaries that separate the curved grains from the matrix are made up of dislocations which once accommodated the misfit in the areas occupied by the curved...
