In this project funded by the Chemical Synthesis Program of the Chemistry Division, Professor Gregory S. Girolami of the Department of Chemistry of the University of Illinois will explore the synthesis of several classes of molecular precursors for electronic materials. The project involves the synthesis of new compounds, investigations of their chemical reactivities, and studies of their volatilities and utilities as thin film precursors. Some of the specific objectives of the current project are the development of volatile two-coordinate amido complexes of the late transition elements, and mechanistic studies of dealkylation reactions that are relevant both to chemical vapor deposition (CVD) and to the chemistry of dialkylamide ligands. In parallel, investigations of new CVD precursors for both metal borides and metal oxides will be carried out, using a new class of chelating borohydride ligands of the general formula NR2(BH3)2-.

The broader impacts involve training undergraduate students, graduate students, and postdoctoral researchers, and broadening participation through the inclusion of researchers from underrepresented groups on the project. This work could lead to the development of better molecular precursors for chemical vapor deposition (CVD) and atomic layer deposition (ALD) growth of thin films. Such chemistry will have an impact on critical problems in the microelectronics industry, and could lead to faster and more capable microprocessors for computers and other electronic equipment. In addition, this project will provide excellent training of students, from pre-undergraduate to post-doctoral, including those from groups historically underrepresented in the sciences.

Project Report

P.I. Gregory S. Girolami, Professor of Chemistry, University of Illinois at Urbana-Champaign A vital national scientific need is the development of new and better performing materials that will enable the continued miniaturization of integrated circuits. One class of materials that have very attractive properties for such applications is the metal diborides, compounds formed by chemically combining a metal such as titanium with the element boron in a 1:2 ratio. The metal diborides have high melting temperatures near or above 3000 °C, and have very low electrical resistivities that rival those of platinum metals. They are also extremely hard and chemically inert. This combination of properties makes them potentially useful for applications in the manufacturing of integrated circuits. Despite these attractive attributes, transition metal diborides have not been previously used in microelectronics, due principally to the lack of effective methods to make them as high quality films at temperatures compatible with the manufacturing limits for integrated circuits, i.e., below 400 °C. In this completed project, we developed new low temperature methods to grow metal diborides by a technique called chemical vapor deposition, in which chemical compounds (called precursors) are passed over a surface, and a chemical reaction occurs to grow the metal diboride material as a thin film. We also discovered over three dozen new compounds that are currently being tested as precursors for future chemical vapor deposition methods. Specific broader impacts include the education and training of new B.S. and Ph.D. chemists, including multiple students from underrepresented groups. The results have been broadly disseminated by presentations at international conferences, by publication in reputable scientific journals, and by news stories that discuss the work as well as the enabling role of NSF. Interactions with leading companies in microelectronics development, especially IBM and Intel, led to presentation and discussion of the project results with their research and development scientists.

National Science Foundation (NSF)
Division of Chemistry (CHE)
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Tingyu Li
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University of Illinois Urbana-Champaign
United States
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