Spectroscopic Diagnostics for Low Temperature Industrial Plasmas

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National Science FoundationNSF/DOE Partnership in Basic Plasma Science and EngineeringProposal Number: CBET-0714600Principal Investigator: Wendt, Amy E. Affiliation: University of Wisconsin-MadisonProposal Title: Spectroscopic Diagnostics for Low Temperature Industrial Plasmas New diagnostic strategies for industrial plasmas will be developed and tested, based on sophisticated use of non-invasive and relatively straightforward optical emission spectra (OES) measurements. To that end, a new, cross-disciplinary team has been assembled, combining laboratory expertise in both atomic physics and plasma processing. The new techniques in this work are enabled by recent measurements of cross sections for electron impact excitation in rare gases made in the laboratory of co-PI Prof. Chun Lin. The ability to measure many cross sections rapidly will allow the PIs to identify special combinations of wavelengths for which the ratio of emitted light intensities can be used to determine plasma properties directly. The new methods will first be evaluated on a test plasma system by comparing results with more established diagnostics and then will be implemented on a more chemically complex processing plasma. The central idea used is that all plasmas radiate a characteristic glow ("optical emission"), and the spectrum of the emitted light carries information about the properties of the plasma from which it comes. Scientific insights and data from this project will thus benefit the extraordinary range of processes using plasmas. Plasma processing is most widely known as being vital to computer-chip manufacturing, but plasma usage extends to such varied applications as electric propulsion for long-range space missions, plasma display televisions and plasma-based surgical tools. Understanding and characterization of plasma conditions is essential to the predictive capability needed as processes become more refined and applications more varied. Unfortunately, many other diagnostics have been applied to industrial plasmas with mixed success. They are often difficult to implement or interpret, they may perturb or contaminate the plasma, or they may require highly specialized training, rendering them impractical in an industrial environment.Work from this project will thus add not only to impact on science but also on diverse important technologies and to education. In particular, basic knowledge from these studies is likely to aid effective use and development of plasma-processing tools. Furthermore, the results will be incorporated into courses at Wisconsin, undergraduate and graduate students will have valuable training in research skills. The project is also likely to have important influences on raising under-represented populations in engineering and science, especially in female participation as the lead PI has a strong track record in attracting female graduate-student participation.