Overview

Three aspects of grain structure affect properties of thin films: crystallographic texture, grain morphology, and grain size. For example, control of thin film magnetic properties requires control of the film texture; resistance to electro-migration damage is affected by both grain morphology and size.

It is important at the outset to recognize the need to distinguish between two types of film deposition in studying the grain structure of thin films. One class involves deposition in the absence of energetic particle bombardment and the other in its presence. It is further necessary to distinguish between films deposited on epitaxial substrates from those deposited on non-epitaxial substrates. Films deposited on the former substrates have a relation defining a crystallographic plane in the film that is parallel to a crystallographic plane in the substrate and defining parallel directions in these planes. A non-epitaxial substrate is one that does not produce such epitaxy.

Grain morphology has been studied to a greater extent than texture and mechanisms have been suggested to account for the observed morphology. We shall evaluate these mechanisms. The study of crystallographic texture in thin films has not led to a coherent proposal for the origin of the observed textures and an attempt will be made to fill this lacuna in our understanding.

The most extensive study of all these aspects of thin film grain structure has been carried out on films deposited in the absence of energetic particle bombardment. Thus, we will first consider this body of work and use it...