Bulletin of the American Physical Society
61st Annual Gaseous Electronics Conference
Volume 53, Number 10
Monday–Friday, October 13–17, 2008; Dallas, Texas
Session DT1: Plasma-Surface Interactions |
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Chair: CW Chung, Hanyang University, Korea Room: Salon E |
Tuesday, October 14, 2008 1:30PM - 2:00PM |
DT1.00001: Study of elementary processes of plasma-wall interaction in fusion devices by means of an inductively coupled hydrogen plasma in interaction with graphite surfaces Invited Speaker: In controlled fusion devices, the interaction of hydrogen plasma with graphite like walls leads to carbon erosion and hydrocarbon redeposition. When using tritium, which is a radioactive element, hydrocarbon redeposition in the reactor becomes a real safety issue. Therefore carbon erosion must be understood and limited. Our aim is to better understand fundamental mechanisms of hydrogen interaction with graphite. In this aim, we use an ultra-high vacuum set-up equipped with hydrogen guns (atomic and ionic species), with a versatile ICP source working as a plasma source or as an atomic source, and with two mains surface diagnostics: High Resolution Electron Energy Loss Spectroscopy and Scanning Tunneling Microscopy. We will present a model for H adsorption process on graphite surface, and particularly will compare ``hot'' and ``cold'' H atom adsorption. We will deal with H(D) abstraction by D(H) atoms. Finally, we will examine ion interaction with graphite both in beams and in plasmas in order to better understand ion-neutral synergetic effects. [Preview Abstract] |
Tuesday, October 14, 2008 2:00PM - 2:15PM |
DT1.00002: Manipulation of the bombarding ion energy distribution in fluorocarbon plasma etching Amy Wendt, Frank Buzzi, Yuk-Hong Ting Ion bombardment is a key element of plasma etching for microelectronics fabrication and other materials processing applications. A sinusoidal voltage waveform typically produces a broad ``bimodal'' ion energy distribution (IED) at the substrate, with two ion flux maxima, at respective energies considerably above and below the average. In order to deconvolve the effect of ions of multiple energies bombarding the substrate simultaneously, we have manipulated the waveform of the bias voltage to produce two ion flux maxima. By systematically tailoring the shape of the waveform, the energies and relative fluxes of the two IED peaks are varied independently over a 100 to 500 eV range in a fluorocarbon-based helicon plasma, while silicon dioxide and photoresist etch rates are monitored. Two experiments were conducted in which a 100 eV IED peak was combined with a higher energy peak, while the energy and relative flux of the high energy peak were respectively varied. In both cases, a relatively small contribution of high energy ions leads to etch rate enhancement higher than predicted by a linear combination of single peak etch rates at the two energies. We speculate that high energy ion bombardment suppresses fluorocarbon deposition, enabling lower energy ions to more effectively contribute to etching reactions. [Preview Abstract] |
Tuesday, October 14, 2008 2:15PM - 2:30PM |
DT1.00003: Atomic-scale cellular model and profile simulation of Si etching in chlorine- and bromine-containing plasmas: Effects of surface oxidation on evolution of feature profiles Hirotaka Tsuda, Shoki Irie, Masahito Mori, Hiroaki Ohta, Koji Eriguchi, Kouichi Ono Profile simulation is indispensable for understanding the effects of complex surface reaction processes that occur during plasma etching, to achieve the nanometer-scale control of etched profiles and critical dimensions and their microscopic uniformity. This paper presents an atomic-scale model for feature profile evolution during Si etching in chlorine- and bromine-containing plasmas, with emphasis being placed on the effects of surface oxidation arising from impurity as well as added oxygen. The model incorporated an atomic-scale cellular model for surface reaction multilayers and the Monte Carlo calculation for the trajectory of ions and neutrals onto feature surfaces, taking into account chemical etching, ion-enhanced etching, deposition of etch products and by-products, and surface oxidation. The profile simulation was performed to reproduce experimental observations in Si etching at increased O$_{2}$ concentration in Cl$_{2}$/O$_{2}$ and HBr/O$_{2}$ plasmas; e.g., reduced profile anomalies near the feature bottom such as footing and microtrenching, increased thickness of passivation layers on feature sidewalls, increased sidewall tapering, enhanced inverse RIE lag, increased roughness of bottom surfaces, and residue or micropillar and etch stop that occur. [Preview Abstract] |
Tuesday, October 14, 2008 2:30PM - 2:45PM |
DT1.00004: Mechanistic model of atomic recombination J.D. Guha, V.M. Donnelly Recently we have started a new approach of studying atomic recombination at the reactor walls, by rapidly rotating a spinning substrate between the plasma and differentially pumped diagnostic chamber, thereby exposing the surface to the plasma, and then analyzing the reaction products few ms thereafter. We have investigated atom recombination in Cl$_{2}$ and O$_{2}$ plasmas with this technique. In a Cl$_{2}$ plasma, Cl$_{2}$ physisorbs and then desorbs over the time scale comparable to that for Cl recombination, thereby competing with Cl adsorption for active sites. With the plasma off, Cl$_{2 }$desorption flux increases nearly linearly with pressure. Cl recombination probabilities, $\gamma _{Cl}$, ranged from 0.01 to 0.1 and were found to increase with increasing n$_{Cl}$/n$_{Cl2}$ number density ratio (from 0.1 to 0.8) in Cl$_{2}$ plasmas. A multi-site adsorption model has been developed to explain the desorption kinetics of physisorbed Cl$_{2}$. The total surface site density of $\sim $ 10$^{15}$ cm$^{-2}$ was distributed with a Gaussian profile over binding energies (B.E) ranging from 7.8 to 19.8 Kcal/mol. For Cl$_{2}$ physisorption, the sites with B.E $<$ 14Kcal/mol are mostly unsaturated, and give rise to the pressure scaling of Cl$_{2}$ desorption flux. For sites with B.E $>$14Kcal/mol, the fractional surface coverage (\textit{$\theta $}$_{i})$ rises sharply with increasing B.E and pressure. The competitive adsorption of Cl$_{2}$ vs Cl at these high B.E sites is likely responsible for the observed dependence of $\gamma _{Cl}$ on n$_{Cl}$/n$_{Cl2}$. [Preview Abstract] |
Tuesday, October 14, 2008 2:45PM - 3:00PM |
DT1.00005: Surface loss rate of H and N radicals in H$_{2}$/N$_{2}$ plasma etching process Chang Sung Moon, Keigo Takeda, Toshio Hayashi, Seigo Takashima, Makoto Sekine, Yuichi Setsuhara, Masaharu Shiratani, Masaru Hori As ULSI devices are down to nano-scale size, there have been many efforts to develop low dielectric constant (low-k) materials and establish the plasma etching technology. Especially, the interaction between the plasma and the surface has an enormous influence on characterizing the etching process. However, the reactions in contact with solid surface such as substrate and wall are very complicated and moreover, at present, there are many interactions unknown and they are not fully understood yet. In this study, surface loss probabilities of H, N radicals on stainless steel and organic low-k film surfaces are investigated by vacuum ultraviolet absorption spectroscopy (VUVAS) technique. The changes of H, N radical densities are quantitatively measured in H$_{2}$/N$_{2}$ plasma afterglow and the loss rates on each surface are evaluated. It is expected that the development of plasma etching process can be advanced by understanding the reaction of radicals with the surface during organic low-k etching process. [Preview Abstract] |
Tuesday, October 14, 2008 3:00PM - 3:15PM |
DT1.00006: ABSTRACT WITHDRAWN |
Tuesday, October 14, 2008 3:15PM - 3:30PM |
DT1.00007: Effects of Remote Plasma Treatment on Surface Defects in ZnO Nanopowders Jorge Paramo, Raul Peters, Yuri Strzhemechny The field of high-tech applications of ZnO nanostructures is rapidly growing. Because of the large surface/volume ratio in these systems, device performance in many cases is determined by surface and near-surface properties of the nanocrystals. The nature of the surface/subsurface defect states in nanosized ZnO is still ambiguous, and only in a small number of recent studies attempts were made to modify these states in a controllable fashion. In our work, we used remote plasma treatment of several commercially available ZnO nanopowders to manipulate their surface and subsurface defects. Temperature-dependent photoluminescence spectroscopy was employed to monitor the effects of nitrogen, hydrogen, and oxygen plasmas on the surface states. We demonstrated that those plasma species induce a variety of changes in the deep defect visible emission as well as in the bound-exciton luminescence, most likely associated with the surface/subsurface states. We also observed significant size-dependent effects of plasma treatment in our nanosystems. [Preview Abstract] |
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