Thin Solid Films, 156 (1988) 351 363 GENERAL FILM BEHAVIOUR 351 SILICIDE FORMATION FROM TERNARY METAL METAL SILICON SYSTEMS M. SETTON Department of Materials Science and Engineering, and Laboratory for Research on the Structure of Matter, University of Pennsylvania, Philadelphia, PA 19104 (U.S.A.) J. VAN DER SPIEGEL Department of Electrical Engineering, and Laboratoryfor Research on the Structure of Matter, University of Pennsylvania, Philadelphia PA 19104 (U.S.A.) (Received July 31, 1987; accepted October 1, 1987) Thin film interactions for ternary systems are presented and compared with those for bulk samples. The various outcomes of the reaction such as solid solution, phase separation or ternary compound formation are analyzed using specific examples in each case. As a possible first step of the reaction, the alloying behavior of the metals is described using Miedema's model. Ternary phases reported in bulk studies are rarely observed for thin film samples possibly because of unlimited supply of silicon, interfacial contamination or stress, and different kinetics or formation temperatures. The use of high temperature equilibrium phase diagrams is therefore limited in explaining the behavior of the system. However, for systems evolving towards a pseudobinary solid solution or complete solid solubility of the silicides, bulk data are valuable guides to predict or analyze the evolution of the structure submitted to thermal processing. I. INTRODUCTION Following the development of silicide thin films for gates, interconnections and contacts in very-large-scale integration (VLSI) technology, the study of other phenomena such as the interaction of two metals with silicon appears as a logical extension of the research. The characterization and understanding of single-metal silicides is only a first step towards the implementation of complex metallization processes involving several metals, either deposited as distinct layers or mixed on a microscopic scale in alloys. As an example of practical significance, a near-noble- refractory metal alloy can provide simultaneously a contact to shallow junctions and an aluminum diffusion barrier, both resulting from phase separation 1. In general, a full knowledge of individual binary systems is insufficient to analyze the product phases since the growth of a ternary compound may now be part of the evolution of the structures. Although the rejection of the refractory metal silicide to the top has been observed for various near-noble and refractory metal couples 2, a recent observation of a ternary phase for the Pt-Ti-Si system 3 indicates the need for further study prior to drawing general conclusions. Four possible outcomes for metal-metal-silicon reactions can be distinguish- 0040-6090/88/$3.50 ~1 Elsevier Sequoia/Printed in The Netherlands