Bulletin of the American Physical Society
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 |
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Chair: Hirotaka Toyoda, Nagoya University Room: 162 |
Thursday, October 7, 2010 10:30AM - 11:00AM |
NR2.00001: Heterogeneous Reactions in Processing Plasmas Invited Speaker: 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. [Preview Abstract] |
Thursday, October 7, 2010 11:00AM - 11:15AM |
NR2.00002: Reactivity of atoms adsorbed on catalytic surfaces under plasma exposure Daniil Marinov, Olivier Guaitella, Antoine Rousseau, Marko Huebner, Jurgen Roepcke, Vasco Guerra, Carlos Pintassilgo Recently we have demonstrated that reactive atomic species may be adsorbed on different catalytic surfaces (SiO$_{2}$, TiO$_{2}$, pyrex) under low pressure N$_{2}$/O$_{2}$ plasma exposure [1]. Adsorbed N atoms recombine with gas phase O atoms to produce NO when exposed to O$_{2}$ plasma. Adsorbed O atoms initiate surface oxidation/losses of various probe molecules (C$_{2}$H$_{2}$, CO, NO, NO$_{2})$. Using laser absorption measurements of gas phase species as a fingerprint of surface reactions, we investigate the state of the surface after different pretreatment procedures and probe the number of adsorbed atoms as a function of pretreatment parameters (duration, power, wall temperature, pressure, etc.). Stability of adsorbed atoms under Ar plasma exposure is investigated. Comparison between different surfaces and different probe molecules provides information on the nature and binding energies of adsorbed atomic species. [1] D. Marinov, O. Guaitella, A. Rousseau and Y.Ionikh, J. Phys. D: Appl. Phys. \textbf{43 }(2010) 115203 [Preview Abstract] |
Thursday, October 7, 2010 11:15AM - 11:30AM |
NR2.00003: Plasma-Modification of Mineral Surfaces for Optimizing Froth-Flotation Frank May, Volker Br\"{u}ser, Antje Quade, Christian Walter Modifications of mineral surfaces result in changes in their wettability behavior. This is attracting a great deal of interest with regards to separation of mineral mixtures by froth flotation processes. In order to obtain the separation of minerals a number of chemicals, e.g. collectors, depressing reagents, etc., are conventionally used to increase either the hydrophilic or the hydrophobic properties. A new approach is to improve the selectivity of the bonding behaviour between these chemicals and surfaces by plasma pre-treatment of the mineral mixture. Thereby we try to increase the effectiveness of the flotation by reducing the amount of chemicals with a view to save expenses and enhance environmental friendliness. However, this requires the investigation of the physical interactions between mineral surfaces and plasmas. In our experiments we treated sulfidic minerals (FeS$_2$, CuFeS$_2$ and Cu$_2$S) with RF- and MW-plasmas in Ar-O$_2$- and Ar-H$_2$- mixtures under different conditions while the processes were observed by in situ mass spectroscopy. XRD-, XPS- and EDX-measurements were used for surface characterizations. We show that several minerals can be oxidised selectively caused by different reaction velocities. Additionally SO$_4^{2-}$-groups, an aging product which can interrupt the flotation, could be removed by Ar-H$_2$-Plasmas. [Preview Abstract] |
Thursday, October 7, 2010 11:30AM - 11:45AM |
NR2.00004: Mechanism of Si Oxidation in H$_{2}$/O$_{2}$/Ar Surface Wave Plasma Keigo Takeda, Masaru Hori In the plasma oxidation processes for forming dielectric films in ULSIs, the rare and O$_{2}$ mixture surface wave plasma with small amount of H$_{2}$ gas addition has been frequently used in order to obtain the higher oxidation rate. The Si oxidation rate in the SWP is increased at small amount of H$_{2}$ flow rate ratio around 0.2{\%}, and then decreased at the H$_{2}$ gas flow rate ratio over 1{\%}. This oxidation mechanism has never been clarified because the reaction is the very complex process by addition of H$_{2}$ gas. Therefore the effect of H$_{2}$ addition on Si oxidation in a H$_{2}$/O$_{2}$/Ar SWP was investigated on the basis of behaviors of reactive species in gas phase. H atom, the ground ($^{3}$P$_{2})$ and excited ($^{1}$D$_{2})$ O atoms, OH radicals in the H$_{2}$/O$_{2}$/Ar SWP were quantitatively measured by absorption spectroscopy. Electron and positive ions measured by Langmuir single probe and quadrupole mass analyzer. On the basis of these measurement and process results, we have investigated the mechanism of Si oxidation process with the H$_{2}$/O$_{2}$/Ar SWP. From the result, it was found that O($^{1}$D$_{2})$ is a main oxidizing species in the Si oxidation with the SWP. Moreover, it is considered that the behaviors of H atom and positive ions affect the sticking coefficients of O atoms on the wafer. [Preview Abstract] |
Thursday, October 7, 2010 11:45AM - 12:00PM |
NR2.00005: On plasma based species deposition at a Pyrex surface studied by post plasma N$_{x}$O$_{y}$ conversion J. Roepcke, M. Huebner, D. Marinov, O. Guaitella, A. Rousseau, C.D. Pintassilgo, V. Guerra The deposition of atomic species at the inner surface of a Pyrex tube RF plasma reactor was studied by measuring the time dependent conversion of N$_{x}$O$_{y}$ in a post plasma experiment. First the inner surface of the tube was treated by a capacitively coupled RF plasma with different precursors. Then following the plasma phase, after evacuation a gas mixture (1{\%} N$_{x}$O$_{y}$ in N$_{2})$ was filled into the tube. The time evolutions of NO, NO$_{2}$ and N$_{2}$O were measured using a 3 laser QCLAS system. It was found, that only after the usage of oxygen containing precursor gases NO was oxidised into NO$_{2}$. The N$_{2}$O concentration did not show any changes over time. A modelling approach showed good agreement with the experiment. [Preview Abstract] |
Thursday, October 7, 2010 12:00PM - 12:15PM |
NR2.00006: Energy influxes at the substrate in magnetron sputtering processes Pierre-Antoine Cormier, Anne-Lise Thomann, Nadjib Semmar, R\'emi Dussart, Jacky Mathias, Adil Balhamri, Stephanos Konstadinidis, Rony Snyders, Olivier Antonin, Caroline Boisse-Laporte, Tiberiu Minea The study of the energy transfer between plasmas and substrate surfaces is of particular interest in plasma processes of materials. In most works the energy influxes are determined from the surface temperature evolution, which impedes the detection of transient transfers and make difficult to separate all the energetic contributions. We have designed a diagnostic for direct and time resolved measurements. It was successfully used on silicon etching process to determine the energy released by the chemical reaction. In metal thin film deposition by sputtering, the low energy contribution of the condensing atoms was detected and separated from the predominant contribution (plasma effect). In the present contribution we discuss the ability of the energy flux diagnostic to study magnetron sputtering processes, especially when bipolar pulses or high power impulses (HIPIMS) are used. [Preview Abstract] |
Thursday, October 7, 2010 12:15PM - 12:30PM |
NR2.00007: Angular distribution of sputtered platinum particles during argon plasma etching Pierre-Marc Berube, Joelle Margot, Sebastien Delprat, Mohamed Chaker, Luc Stafford The angular distribution of platinum particles sputtered by an argon plasma is measured as a function of both gas pressure and ion energy in an inductively couple plasma reactor. For this purpose, photoresist is first deposited on the platinum sample. An ``inverse T'' profile is further patterned into the resist to enable platinum etching by the plasma followed by redeposition of the sputtered particles on the T-shaped cavity wall. The angular distribution can be determined by measuring the thickness of redeposited platinum with position. At low plasma pressure (0.5 mTorr), the observed angular distribution is in excellent agreement with the distribution calculated by the low-energy regime of the Sigmund theory for ion sputtering. However, at higher pressure (30 mTorr) the spatial dependence of the redeposited platinum thickness can only be explained by considering the interactions between plasma and sputtered species. [Preview Abstract] |
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