Electron Beam Chemical Vapor Deposition of Platinum and Carbon
Beaulieu, David Cartier
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Electron Beam Chemical Vapor Deposition (EBCVD) is a process by which an electron beam is used to decompose adsorbed reagent molecules to produce a deposit. The primary electrons from the beam, and especially the secondary electrons emitted from the substrate, dissociate the adsorbed molecules. Important factors for the deposition process include the beam parameters and reagent gas composition. Simple structures are fabricated through utilization of the various scanning modes of an SEM. Fibers (pillar-like structures) can be deposited, and lines (wall-like structures) can be deposited easily. This investigation focuses on the process parameters controlling deposition rate and geometry for platinum and carbon fibers and lines in a modified SEM. Platinum deposition was performed using a system with a small diameter needle that supplied a localized flow of gas from an organometallic platinum compound. Carbon deposition was performed in the Environmental mode, in which the microscope chamber is filled with a specified pressure of reagent gas. Statistically designed experiments were performed for platinum fiber and line deposition. Analysis indicated that the beam current and deposition time were dominant factors in determining the deposition rate. The voltage also had a significant effect on fiber deposition. For platinum line deposition, the effects of the dwell time and line time were also studied. The line time had a significant effect on line height deposited per scan. Optimization analysis was performed, and results indicated that high voltage and high beam current led to higher aspect ratios. Medium voltage and low beam current were preferable for depositing minimal width lines (less than 200 nm). Low voltage and high beam current were preferable for maximum deposition rates. EDS and EELS performed for platinum deposits in a TEM indicated amorphous structure with no carbon detected. This differs significantly from previously reported results. Statistically designed experiments were performed for carbon line deposition. The voltage, beam current, and dwell/line time were studied. Increasing line time led to a significant increase in line height/scan and appeared to be a dominant factor. Lower beam currents appeared to favor higher deposition rates. TEM analysis indicated that carbon deposits were mostly amorphous.