Bulletin of the American Physical Society
65th Annual Gaseous Electronics Conference
Volume 57, Number 8
Monday–Friday, October 22–26, 2012; Austin, Texas
Session CT2: Plasma Surface Interactions |
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Chair: Vince Donnelly, University of Houston Room: Classroom 203 |
Tuesday, October 23, 2012 8:00AM - 8:15AM |
CT2.00001: MD simulations of hydrogen plasma interaction with graphene surfaces David Graves, Emilie Despiau-Pujo, Alexandra Davydova, Gilles Cunge, Laurence Magaud Development of graphene-based technologies relies on the capability to grow and integrate this new material into sophisticated devices but the nm-scale control of graphene processing challenges current processing technology. Plasma-graphene interactions must be carefully controlled to avoid damage to the active layers of graphene-based nanoelectronic devices. Pulsed plasmas will minimize surface damage from ions, and help control neutral chemistry, but they must be better understood. We applied molecular dynamics (MD) simulations, coupled with experiments, to better understand and control the plasma-graphene surface interaction. The influence of graphene temperature and incident species energy on adsorption, reflection and penetration mechanisms is presented. Except for impacts at graphene nanoribbon edges or at defects location, H species are shown to experience a repulsive force due to delocalized $\pi$-electrons which prevents any species with less than $\sim$ 0.6eV to adsorb on the graphene surface. Bonding of H to C requires a local rehybridization from sp2 to sp3 resulting in structural changes of the graphene sample. Energetic H+ bombardment of stacked multilayer graphene sheets are analyzed and the possibility to store hydrogen between adjacent layers is discussed. [Preview Abstract] |
Tuesday, October 23, 2012 8:15AM - 8:30AM |
CT2.00002: Atomic Hydrogen Measurements in a Fusion-Relevant Plasma Cameron Samuell, Cormac Corr Critical to the success of large-scale fusion reactors is the development of new materials that can withstand the extreme conditions at the plasma-surface boundary. The materials required for plasma-facing components will need to withstand a very aggressive environment that is characterized by both a high heat load and high ion flux produced by the hydrogen isotope plasma. As such, investigating the ways in which hydrogen plasmas interact with a range of materials is an important area for research and development and is vital to the future success of fusion. A new experimental reactor, the MAGnetized Plasma Interaction Experiment (MAGPIE), has been constructed at the Australian National University to help resolve some of the critical issues surrounding the choice of fusion reactor materials. MAGPIE is a linear system with a 2.5kW, 13.56MHz helicon source that operates in a magnetic hill configuration with field strengths up to 0.19T. Densities up to 10$^{19}$m$^{-3}$ at temperatures $<$ 5eV have been achieved. The focus of this presentation is the interaction between a magnetized hydrogen plasma and tungsten and graphite targets in MAGPIE. Results from two-photon absorption laser induced fluorescence (TALIF), optical emission spectroscopy (OES) and probe diagnostics will be presented. [Preview Abstract] |
Tuesday, October 23, 2012 8:30AM - 8:45AM |
CT2.00003: Comparison of CF$_{4}$, CHF$_{3}$ and CH$_{2}$F$_{2}$ plasmas used for wafer processing Stefan Tinck, Alexey Milenin, Annemie Bogaerts Fluorocarbon-based plasmas are widely used in the microelectronics industry for the fabrication of computer chips, i.e. in plasma etching of silicon. One such process is the etching of nanoscale trenches in the Si substrate with CH$_{x}$F$_{y}$ plasmas as applied in shallow trench isolation (STI). By carefully altering the ratio between gases such as CF$_{4}$, CHF$_{3}$ and CH$_{2}$F$_{2}$, the overall etching process can be controlled in terms of chemical etching, sputtering and sidewall passivation. Therefore, we wish to obtain a more fundamental understanding of these plasmas and their surface processes. The plasma behavior will be simulated by a hybrid model for addressing the various plasma species, while the surface interactions of the plasma will be described by additional Monte Carlo simulations, allowing a detailed insight in the nanoscale trench etching process. Bulk plasma properties such as species densities, temperatures and fluxes towards the walls will be discussed under typical wafer processing conditions as well as surface properties including etch rate and chemical composition of the surface during trench etching. The etch rate and microscopic etch profiles will be compared with experimental data. [Preview Abstract] |
Tuesday, October 23, 2012 8:45AM - 9:00AM |
CT2.00004: Effect of cathode cooling efficiency and oxygen plasma gas pressure on the hafnium cathode wall temperature Koustubh Ashtekar, Gregory Diehl, John Hamer The hafnium cathode is widely used in DC plasma arc cutting (PAC) under an oxygen gas environment to cut iron and iron alloys. The hafnium erosion is always a concern which is controlled by the surface temperature. In this study, the effect of cathode cooling efficiency and oxygen gas pressure on the hafnium surface temperature are quantified. The two layer cathode sheath model is applied on the refractive hafnium surface while oxygen species (O2, O, O+, O++, e-) are considered within the thermal dis-equilibrium regime. The system of non-linear equations comprising of current density balance, heat flux balance at both the cathode surface and the sheath-ionization layer is coupled with the plasma gas composition solver. Using cooling heat flux, gas pressure and current density as inputs; the cathode wall temperature, electron temperature, and sheath voltage drop are calculated. Additionally, contribution of emitted electron current (Je) and ions current (Ji) to the total current flux are estimated. Higher gas pressure usually reduces Ji and increases Je that reduces the surface temperature by thermionic cooling. [Preview Abstract] |
Tuesday, October 23, 2012 9:00AM - 9:15AM |
CT2.00005: Ultra low-k dielectrics damage under VUV and EUV radiation Sergey Zyryanov, Oleg Braginsky, Alexander Kovalev, Dmitry Lopaev, Yury Mankelevich, Tatyana Rakhimova, Alexander Rakhimov, Anna Vasilieva, Mikhail Baklanov Low-k dielectric films can be substantially damaged during plasma processing. High energy UV photons emitted by plasma play the key role in damaging the porous low-k films directly or indirectly by stimulating chemical reactions with radicals in plasma. The damage for ultra low-k (ULK, k $<$ 2.2) films with higher porosity and increased pore radius becomes more intense because of the increased penetration depth of UV photons and radicals. Three key wavelength ranges (VUV, DUV and EUV) were studied by exposing the different ULK samples (k: 2.0--2.2, porosity: 30--50{\%}, pore radius: 1--2 nm) to UV radiation at 13.5, 58.3 (mainly effect the Si-O-Si bonds) and 193 nm (mainly effect C-C and C-H bonds) varying the photon dose. ULK damage was studied using FTIR spectroscopy (chemical bond modification), XRF analysis (atom and radical extraction) and ellipsometry (changes in ULK film thickness and dielectric constant). [Preview Abstract] |
Tuesday, October 23, 2012 9:15AM - 9:30AM |
CT2.00006: Plasma surface interaction in hot filament cathode arc discharge used to nitride steel substrates R.P. Dahiya, O. Singh, V. Aggarwal, H.K. Malik, Nisha Kumari Plasma-assisted nitriding process is a well developed technique for increasing the surface hardness. The process is energy efficient, environment friendly and versatile to treat samples of various shapes and sizes. Though the use of this process in industry is established, there are several scientific questions in the basic understanding of the migration of ions, electrons and radicals and plasma surface interaction. We have studied these processes in an experimental system developed with hot cathode arc discharge plasma. A mixture of nitrogen and hydrogen is utilized for plasma generation. Negatively biased steel substrate is nitrided in this plasma. The hot cathode arc discharge plasma source is utilized to independently monitor and optimise the plasma and the work piece parameters. Substrate bias and temperature, which are the important parameters for achieving the desirable surface hardness, are regulated. Hardness depth profile and nitrogen content in the hardened sample are also measured. Transport and diffusion of ions, electrons, radicals and neutrals are considered to explain the results. [Preview Abstract] |
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