CAREER: Low Temperature Deposition of Thin Metal Films from Supercritical Carbon Dioxide Solution

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Abstract - Watkins - 9734177 The demands of present and future microelectronic and optoelectronic device fabrication place stringent requirements on metal deposition schemes. These include high film purity, low temperatures and rapid, controllable deposition rates. The PI postulates that these objectives can be met via Chemical Fluid Deposition (CFD), a new approach to metal deposition that involves the chemical or thermal reduction of soluble organometallic compounds in supercritical carbon dioxide at low temperatures (40-80oC) to yield continuous films on inorganic or organic substrates. CFD exploits the unique, and adjustable, physicochemical properties of SCF solvents, which lie intermediate to those of liquids and gases, to circumvent the limitations of both vapor and liquid phase techniques. In CFD, precursor transport and reduction occurs in solution at significantly lower temperatures and higher reagent concentrations than those of vapor phase techniques such as chemical vapor deposition (CVD). While CFD is a solution-based process, the "gas-like" transport properties of the SCF and its miscibility with gaseous reducing agents such as hydrogen, render the process unencumbered by issues of poor mass transfer and poor deposition rates associated with liquid phase reductions. Preliminary experiments demonstrate that high-purity, continuous platinum and palladium films can be deposited from SCF solution onto silicon wafers and other inorganic substrates at temperatures up to 170oC below those employed in CVD. The research program will focus on the deposition of thin films from carbon dioxide solution by the hydrogenolysis of dimethylcyclooctadine platinum (II) and the deposition of copper films by reduction of copper(II)bis(hexafluoroacetylacetone) and copper(II)bis(2,2,6,6-tetramethyl-3,5-heptanedionate). The precursors were chosen to facilitate a direct comparison of film quality and reduction kinetics in CFD to those of existing techniques and the potential utility of the m etal deposits in microelectronics copper and catalytic platinum devices. The educational portion of the work are to: (1) train graduate students who will work at the interface of engineering and materials chemistry, (2) provide undergraduates with opportunities for research experience, (3) develop a two-course series in materials processing that addresses the interests of students and is reinforced by the expanding materials research efforts in the Department of Chemical Engineering, and (4) incorporate research problems and active learning principles into the classroom and assist in the implementation of interactive teaching tools across the curriculum.