In Situ Real-Time Characterization of Thin Films

Abstract

The application of thin film materials in advanced technologies is increasing as new generations of complex electronic, optical and magnetic devices are developed. The dynamics of the growth of thin and ultra-thin films and their evolving, dimensionally dependent, properties are of crucial importance in understanding their performance in particular devices. Anyone who has been concerned with the fabrication of thin films and their associated properties will understand the need to have knowledge of their many physical properties and how these are related to the growth mechanisms and environment in which films are deposited. This book provides a reasonably comprehensive overview of several in situ characterization techniques that, in some cases, are capable of following the developing properties of thin films and surfaces in real time. Several techniques are described including those involving ion- and electron-beam scattering, photoemission electron microscopy, a variety of photometric and ellipsometric optical methods, x-ray reflectivity and curvature-based methods of real-time stress monitoring. The various chapters in this book have been written by a variety of authors and therefore it is inevitable that each topic reflects the style and particular interests of individuals. Nevertheless, for newcomers to the field of thin film technology, such as graduate scientists and postdoctoral researchers, the contents provide a means of rapidly assimilating the basics of some of the in situ methods that have been used in the past for characterizing thin films. From this point of view the book is successful, and many references are given for further reading for those who wish to pursue a particular topic in greater detail. As is often the case, specific examples illustrating the techniques tend to be limited and are often chosen to demonstrate the effectiveness of the methods. Whilst this is understandable, it is often the case that a potential user wishes to explore some system or film-thickness regime that will respond poorly to such probe methodologies and a greater discussion of the limitations of the techniques would have been useful, particularly for the beginner. In the chapter on ellipsometry for example, only thick films are dealt with and examples confined to systems that work particularly well (e.g. SiO2 on Si). Likewise, various effective medium models are discussed in relation to non-planar (rough) surfaces. However, the limitations of such models are not dealt with, nor are those of ellipsometry for dealing with more problematic systems such as ultra-thin films and multilayers. A disappointing aspect of the book is that no specific chapter is devoted to magnetic materials and their properties, currently of considerable interest to the information storage industry. Despite these minor drawbacks the book is very commendable, generally well written and a worthy addition to any library on thin film growth and characterization. It is particularly valuable because of the very real need to understand the dynamically developing properties of thin and ultra-thin films and surfaces, and because it provides readable descriptions of some of the more important instrumental techniques that are used to study the evolution of thin-film characteristics in real time. R Atkinson