63rd Annual Gaseous Electronics Conference and 7th International Conference on Reactive Plasmas
Volume 55, Number 7
Monday–Friday, October 4–8, 2010;
Paris, France
Session NR2: Plasma Surface Interactions II
10:30 AM–12:30 PM,
Thursday, October 7, 2010
Room: 162
Chair: Hirotaka Toyoda, Nagoya University
Abstract ID: BAPS.2010.GEC.NR2.1
Abstract: NR2.00001 : Heterogeneous Reactions in Processing Plasmas*
10:30 AM–11:00 AM
Preview Abstract
Abstract
Author:
Vincent Donnelly
(University of Houston)
This talk will briefly review issues related to reactions of
atoms and small molecules on substrates and chamber walls that
are immersed in a plasma, a relatively unexplored, yet very
important area of plasma science and technology. Emphasis will be
placed on diagnostic methods, and in particular the ``spinning
wall'' technique. With this method, a cylindrical substrate in
the wall of the plasma reactor is rotated, and the surface is
periodically exposed to the plasma and then to a differentially
pumped diagnostics chamber and optionally to a beam of additional
reactants or surface coatings. Reactants impinging on the surface
can stick and react over time
scales that are comparable to the substrate rotation period,
which can be varied from $\sim $0.5 to 40 ms.
Langmuir-Hinshelwood reaction probabilities can be derived from a
measurement of the absolute desorption product yields as a
function of the substrate rotation frequency. Auger electron
spectroscopy allows the plasma-immersed surface to be monitored
during plasma operation. Mass spectrometer cracking patterns are
used to identify simple desorption products. In oxygen or
chlorine plasmas, surfaces become coated with a layer containing
Si, Al, and O, due to slow erosion of the reactor materials, in
addition to Cl in chlorine plasmas. Low recombination
probabilities were found for Cl and O on anodized Al and
stainless steel surfaces, consistent with the similar chemical
composition of the layer that forms on these surfaces after long
exposure to the plasma. Weakly adsorbed Cl$_{2}$ was found to
inhibit Cl recombination, hence the Cl recombination probability
decreases with increasing Cl$_{2}$-to-Cl number density ratios in
chlorine plasmas. In Cl$_{2}$/O$_{2}$ plasmas, Cl and O
recombination occur, but in addition, ClO and ClO$_{2}$ form on
the surface and desorb. These and other results, including a
multi-site model and the catalytic enhancement of O recombination
by monolayer amounts of Cu, will be discussed.
*This work is supported by the National Science Foundation and Lam Research Corp.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2010.GEC.NR2.1