Über die Autorin bzw. den Autor

Klaus Wetzig is Director of the Leibniz Institute of Solid State and Materials Research, Dresden. His research interests include materials analysis and microstructures, especially electron microscopy of functional materials, characterization of thin films for electronics, and nanostructural features in general.

Claus Michael Schneider is Director at the Institute of Solid State Research of the Research Center Jülich (IFF-IEE). His research interests include solid state physics, thin film systems and surface magnetism as well as the physics of nanostructures.

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This up-to-date handbook covers the main topics of preparation, characterization and properties of complex metal-based layer systems. The authors discuss advanced methods for structure, chemical and electronic state characterization with reference to the properties of thin functional layers, such as metallization and barrier layers for microelectronics, magnetoresistive layers for GMR and TMR, sensor and resistance layers.
This second edition is completely revised and updated and complemented by a chapter on photovoltaic.

"Through its focus on practical aspects and its didactic approach, the book is designed especially for practitioners. It can be highly recommended to materials engineers, physicists or process engineers who work or plan to work in the still exciting field of micro electronics."
Vakuum in Forschung und Praxis

A perfect introduction to the field - for professionals and students."
Angewandte Chemie 11/2004


Klaus Wetzig is Director of the Leibniz Institute of Solid State and Materials Research, Dresden. His research interests include materials analysis and microstructures, especially electron microscopy of functional materials, characterization of thin films for electronics, and nanostructural features in general.

Claus Michael Schneider is Director at the Institute of Solid State Research of the Research Center Jülich (IFF-IEE). His research interests include solid state physics, thin film systems and surface magnetism as well as the physics of nanostructures.

Aus dem Klappentext

This up-to-date handbook covers the main topics of preparation, characterization and properties of complex metal-based layer systems. The authors discuss advanced methods for structure, chemical and electronic state characterization with reference to the properties of thin functional layers, such as metallization and barrier layers for microelectronics, magnetoresistive layers for GMR and TMR, sensor and resistance layers.
This second edition is completely revised and updated and complemented by a chapter on photovoltaic.

"Through its focus on practical aspects and its didactic approach, the book is designed especially for practitioners. It can be highly recommended to materials engineers, physicists or process engineers who work or plan to work in the still exciting field of micro electronics."
Vakuum in Forschung und Praxis

A perfect introduction to the field - for professionals and students."
Angewandte Chemie 11/2004


Klaus Wetzig is Director of the Leibniz Institute of Solid State and Materials Research, Dresden. His research interests include materials analysis and microstructures, especially electron microscopy of functional materials, characterization of thin films for electronics, and nanostructural features in general.

Claus Michael Schneider is Director at the Institute of Solid State Research of the Research Center Jülich (IFF-IEE). His research interests include solid state physics, thin film systems and surface magnetism as well as the physics of nanostructures.

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Metal Based Thin Films for Electronics

John Wiley & Sons

Chapter One

1.1 Prologue

Electronic devices have found widespread use in our everyday lives. The applications cover many areas such as consumer electronics, information technology, engineering, automotive application, transportation, medical diagnostics and treatments, etc. The construction of these devices and their building blocks involves elaborate fabrication processes which are based on a thorough understanding of materials science and solid state physics. The device functionality may involve conventional microelectronic, acoustoelectronic, optoelectronic, or future spinelectronic elements, or a combination of these (Fig. 1.1). The functionality is achieved by a carefully engineered and complex combination of metallic, semiconducting, and insulating layers. These layers are often micro- and nanostructured by sophisticated lithography techniques in order to achieve the desired properties. Sometimes, as in the case of microprocessors, the structuring involves several levels. The individual feature sizes created by the structuring processes may be as small as 100 nm and are expected to become even smaller in the future in leading edge applications.

The fabrication of these electronic devices requires a very good control of the materials properties. This concerns not only the physical material parameters, but also the film structure and morphology. The latter are largely determined by the details of the deposition process and postgrowth processing procedures. In addition, the interfaces between different materials and material classes are also becoming of crucial importance. In this situation, a wide variety of analysis tools must be used to ensure a reliable process control and - if necessary - a precise failure analysis. These tools include not only different real space (microscopy) and reciprocal space (diffraction) techniques, but also spectroscopic techniques, electrical transport measurements, stress and strain analyses, migration investigations, etc.

Novel device technologies are often closely linked to the use of new materials or material classes. One recent example is the replacement of the conventional Al interconnects in microprocessors by Cu ones. This step not only involves new fabrication procedures, such as the "damascene" technique, but also requires new barrier layers to avoid the mixing of Cu and Si. Another example is the emerging technology of magneto- or spinelectronics. In its present state it employs complex magnetic units composed of metal or metal/insulator layer stacks. In addition to the electrical properties, the layers must also provide a distinct magnetic functionality. Since all of the classical ferromagnets Fe, Co, Ni and many antiferromagnets used in magnetoelectronics are metals, this adds another and very exciting facet to the application of metal-based films in electronics.

From the above considerations follows quite clearly that metal-based thin films play a central role in the different steps of the fabrication and for the specific functionality of electronic devices. The most evident use concerns conducting lines and interconnects. Less obvious is their employment as barrier layers against interdiffusion and segregation. Also very important are metallization layers, for example, in acoustoelectronic devices. In chemically complex systems, the physical properties can be conveniently changed by the chemical composition. This is particularly true for the conductivity and is exploited in silicides for thermoelectric applications. Metal-based films are also very important for X-ray optical techniques used to fabricate (X-ray lithography) and analyze (X-ray diffraction and spectroscopy) electronic device structures.

Since metal-based films have such a widespread use in the different areas of microelectronics, knowledge of the respective properties and phenomena is distributed over various fields of physics and materials science. As a consequence, one usually has to consult many different sources in order to get the desired piece of information or a broader overview of a specific issue. Considering the importance of metal-based films in the field of electronics it is thus justified to describe and discuss these systems, the associated effects and phenomena, and their applications in one place.

1.2 Organization, Aim and Content of This Book

The main purpose of this book is two-fold. On the one hand, it is meant to serve as a compendium for metal-based thin film systems and their usage in electronics technology. As such, it addresses both the scientist and the research engineer. On the other hand, the book also includes a more tutorial part which is intended to bridge the gap between fundamental phenomena and their technological applications. It may therefore also serve as a textbook for advanced students in solid state physics, materials science, and electronics engineering.

The book is organized into several chapters covering the range from principal aspects and phenomena over contemporary challenges in materials science to actual device concepts and applications. We thereby mainly concentrate on the relevant fields of interconnects, acoustoelectronics, thermoelectrics, magnetoelectronics, and X-ray optics.

In Chapter 2 we review the various fundamental aspects of metal and metal-based films with respect to the individual fields and applications addressed in this book. This chapter is mainly intended to convey background information for the advanced student in a more tutorial form. It forms a basis for the discussion of the future challenges and the device-related topics in the subsequent chapters. The first section is devoted to a key aspect in microelectronics, namely the means to transfer and distribute information and power in a microelectronic device, for example, in a microprocessor. This is achieved by means of metallic interconnects which are usually arranged in very complicated and delicate three-dimensional networks. The contribution discusses both Al and Cu-based technologies for interconnects and highlights the specific implications and problems associated with each technology. A somewhat less familiar, though not less eminent area of microelectronics is acoustoelectronics. Acoustoelectronic devices are based on the exploitation of phenomena involving the generation, transport, and filtering of surface acoustic waves. Their functionality is largely determined by the interaction between a piezoelectric substrate and a metallic film serving as an electrode. Surface acoustic wave devices play a strategic role in telecommunication and other high frequency applications. A rather novel facet of microelectronics is called magnetoelectronics or "spintronics" which is the topic of the third section of Chapter 2. Spintronics is still an emerging technology which is based on the transport of spins and charges, rather than just charges. It thus combines magnetic functionalities and materials with established microelectronics concepts. Current spintronics applications concern read heads in hard disk drives, magnetocouplers, or nonvolatile magnetic random access memories (MRAM). In the long run, reprogrammable magnetic logic circuits or active magnetoelectronic devices, such as a spin transistor, may be expected. The section reviews the fundamental aspects of spin-dependent transport and magnetic coupling phenomena in thin films and layer stacks. It also discusses the basic thin film arrangements and their specific properties with...