This EArly-concept Grants for Exploratory Research (EAGER) grant provides funding for the development of a novel electrochemical film deposition process for metallic alloys, of potential use in the manufacturing of microelectronic, microsensors and information storage devices. This process exploits the energy of formation of the alloy to induce the deposition of the more reactive element under conditions where deposition of the pure element would otherwise not occur. At low deposition rates, i.e. in the thermodynamic limit, the deposition process will be dominated by the alloy energetics, making it insensitive to the reactor geometry and enhancing uniformity. This work will focus on the synthesis of platinum based binary and ternary alloys with the objective to demonstrate the viability of the process for manufacturing purposes, as well as to produce novel materials for information storage. Manufacturing issues to be explored include composition and thickness uniformity in blanket films and lithographic patterns and limits in the achievable deposition rates. Finally, the possibility to produce ordered structures and alloys including highly reactive elements will be investigated.
If successful, this research will validate the proposed deposition method as a viable manufacturing process. In particular, this work will determine the relative importance of thermodynamic predictions and growth rate in controlling alloy composition and uniformity, establishing optimal processing variables to achieve the required material properties in a predetermined device geometry. Additionally, novel materials could be manufactured by electrochemical methods, widening the materials palette available for microfabrication processes. This will lead in turn to innovation in electrodeposition practice, and will pave the way to a variety of novel device designs and functionalities.
Alloys are metals made by combining two or more metallic elements; their purpose is to provide improved properties over those of pure metals, such as greater strength or extended stability over time. Alloys have shaped our civilization in the past, enabling bridges, skyscrapers and airplanes. Today on the other hand microchips and microsystems shape the way we live and interact. Their operation is made possible by using semiconductors and few metals; a more widespread use of alloys in the design of these systems has the potential to immensely enhance their performance and widen their functionality. This project investigates a novel method of forming alloy coatings that would be compatible with conventional semiconductor microfabrication processes and at the same time capable of precise control over the composition, metallurgical characteristics and properties of the finished product. The method consists in applying a precisely defined voltage to a chip immersed in a solution containing ions of the metals to be deposited; the applied voltage determines the alloy composition as well as its structure and can be predicted by taking into account the energy needed to combine atoms in the crystallographic configuration being sought. In a first step, gold-copper alloys were used as a model system to test the validity of the underpinning theoretical framework; by using different process conditions it was confirmed that alloy composition and structure could be predicted solely on the basis of the atomistic interactions within the alloys, while the metallurgical properties of the coatings varied with process parameters as predicted by existing theories. This method was then applied to form alloys of iron and platinum of equiatomic composition; post-processing of these materials resulted in outstanding permanent magnet properties that could be used to implement motion in microsystems with high force and large stroke, while using low power. Even milder post-processing conditions have been achieved by combining layers of iron-platinum alloys with different composition. The fundamental understanding achieved in this project has opened interesting opportunities for a wider use of metallic materials in microchip design. In order to raise awareness of the advantages of this method, the theoretical and applied aspects of this novel process are being taught to students and presented at various academic and conference venues, as well in industrial settings.
