Magnetron sputtering is a widely used technique to deposit thin films. Adding a reactive gas to the discharge allows one to deposit stoichiometric compound films from a metallic (or substoichiometric) target at a high deposition rate. However, the addition of this reactive gas makes the control of the deposition process a complex task. Huge efforts are going into the understanding of the fundamental phenomena of this reactive sputter process and into the simulation of the deposition process by e.g. PIC/MC. However, one of the most uncertain parameters in this reactive sputtering process is the incorporation coefficient of the reactive gas on the growing layer, i.e. the real-time sticking coefficient during deposition. In this work, mass spectrometry is used to deliver more insights on this complex matter.

A method has been developed to determine the incorporation coefficient of the reactive gas onto the growing metal film, using mass spectrometry combined with thin film analysis. This method delivers a global, realistic incorporation coefficient and hence a correct parameter to be used in the models for the reactive sputtering process. We have determined the sticking coefficient of O₂ and N₂ on several metals during reactive magnetron sputtering, and relate these to the material properties of the different metals.

The growth of Ag thin films deposited at 300 K on amorphized Si surfaces under ultra high vacuum conditions is investigated by in situ scanning tunneling microscopy (STM). The analysis of the film morphology as a function of film thickness together with additional annealing or low temperature experiments allow one to obtain a quite complete picture of the film formation processes. It is shown that the large kinetic stability of the trenches separating Ag islands strongly influences all the structural features during the initial growth stages, i. e., island density, grain size, roughness and texture evolution. Specifically it becomes understandable, why abnormal grain growth is initiated only when continuous films develop facets. Finally it is shown, how texture evolution and grain structure can be manipulated in ion assisted growth by using a grazing incidence ion beam.

The contributions to this work by Celia Polop, Christian Rosiepen, Daniel Förster and Se bastian Bleikamp are acknowledged.

Due to their inherent physical and mechanical properties transition metal (TM) nitride thin films are commonly used in various applications, such as contact layers in microelectronics or protective hard coatings on cutting tools.¹ Extensive studies have been carried out in binary compounds (TiN, ZrN or TaN) to relate deposition conditions, stress, microstructure and preferred orientation to films' properties. In particular, it is important to understand stress development during growth to tailor thin films with reduced stress levels to enhance device's lifetime and reliability.

Current efforts are now made to synthesize functional and adaptative layers based on multicomponents TM-based systems. Among these, the TiN-ZrN and TiN-TaN systems arouse an increasing interest due to the possibility to stabilize ternary nitride solid solutions with enhanced properties. For example, conducting Ti_1-xTa_xN thin films (02 However, stress development during growth in these multinary systems remains unexplored.

In the present work, we investigated the stress evolution during reactive magnetron cosputtering of TiTaN and TiZrN thin films using a real time wafer curvature measurement technique. Samples were grown at 300°C on Si wafers under an Ar/N₂ atmosphere. The influence of substrate bias voltage, deposition rate, N₂ and Ar partial pressures on stress buildup was studied. The obtained data showed the presence of stress gradients over film thickness, as a result of two competing stress producing mechanisms: atomic peening inducing compressive stress and void formation inducing tensile stress.³ Complimentary ex situ techniques using X-ray diffraction and atomic force microscopy were performed to correlate stress evolution with texture formation and film morphology. A comparison will also be made with thin films grown by pulsed laser deposition.

¹G. Abadias, Surf. Coat. Technol. 202, 2223 (2008)

²L. E. Koutsokeras, G. Abadias, Ch. E. Lekka,G. M. Matenoglou, D. F. Anagnostopoulos, G. A. Evangelakis and P. Patsalas, Appl. Phys. Lett. 93, 011904 (2008)

³G. Abadias and Ph. Guerin, Appl. Phys. Lett. 93, 111908 (2008).

Sputter-deposited, exothermic multilayer films and foils have generated a great deal of interest recently, because they exhibit rapid, high-temperature, self-sustained reactions characterized by tailorable average propagation speeds.¹ These multilayers often consist of two or more reactant layers (typically dissimilar metals) characterized by a large negative heat of formation. Layer thicknesses range from 5-300 nm and coatings may consist of thousands of individual layers. Despite much interest, a great deal of research is required to fully understand the behavior and performance of these materials. In this presentation, we describe the dynamics of reaction front propagation as these depend on multilayer design and composition. Using high-speed photography (1E5 frames per second with 5 um spatial resolution) and high-speed thermal imaging devices we show direct evidence for steady and unsteady modes. A few multilayer systems (e.g., those consisting of Al/Pt) exhibit a steady reaction mode with no evidence for unsteady behaviors. Co/Al, Ni/Ti and other lower-enthalpy metal-metal pairs exhibit various, unsteady modes - particularly when bilayer thickness is made large. We further show how reaction mode and flame morphology depends on the total thickness of a given multilayer system (varied in this study from 150 nm to 50 micrometers). In addition, the relationship of reaction mode to final foil microstructure and morphology is presented. Complimentary finite difference and finite element heat transport models explain some of the observed macroscopic behaviors.

1 U.S. Patent 5,538,795 T.W. Barbee, Jr. and T. Weihs.