AVS 49th International Symposium
    Plasma Science Tuesday Sessions
       Session PS2-TuA

Paper PS2-TuA5
Direct Detection of Radical and Stable Species Impacting and Desorbing from Surfaces

Tuesday, November 5, 2002, 3:20 pm, Room C-105

Session: Plasma Surface Interactions I
Presenter: Y. Kimura, University of California, Berkeley
Authors: Y. Kimura, University of California, Berkeley
J.W. Coburn, University of California, Berkeley
D. Fraser, University of California, Berkeley
D.B. Graves, University of California, Berkeley
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We present results from a new vacuum beam apparatus that has been designed to measure directly the radical and stable species fluxes impacting surfaces and the products that form as a result of these interactions under high vacuum conditions. The Radical- and Ion-Surface Interaction Analysis System (RISIAS) is equipped with an external plasma source that creates a beam of radicals, and a threshold ionization quadrupole mass spectrometer (TIQMS) that is aligned with the beam's line of sight. This setup allows us to measure all the radical and stable species in the beam. The TIQMS is vertically translatable to allow a horizontal insertion of a sample surface into the beam path via a load lock. With the sample surface in place, all species desorbing from the surface can also be detected with the TIQMS through a separate aperture. Choppers are used for background subtraction, allowing a direct measurement of the incident beam and product components. The addition of ion bombardment from a separate ion source on the chamber before or during radical beam exposure allows us to simulate processes with substrates in direct contact with a plasma. We demonstrate operation of RISIAS with O, N, NH, and F radicals impacting a variety of surfaces. In particular, we report the etch product composition for a nanoporous silica film (hydrogen silsesquioxane, or HSQ) etched with fluorine. The products include SiF@sub 4@, SiH@sub 4@, O@sub 2@ and a variety of carbon-containing species, apparently due to carbon contamination in the film.