Bulletin of the American Physical Society
2005 58th Gaseous Electronics Conference
Sunday–Thursday, October 16–20, 2005; San Jose, California
Session DM2: Plasma Chemistry and Plasma-Surface Interactions |
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Chair: Zoran Petrovic, Institute of Physics, Belgrade Room: Doubletree Hotel Cedar |
Monday, October 17, 2005 1:30PM - 2:00PM |
DM2.00001: Plasma-surface interaction: in situ and real time studies during plasma processing of materials Invited Speaker: In this talk I will review our approach to study in situ and in real time the surface kinetic processes occurring during plasma deposition and etching. We have chosen for a photon-in-photon-out approach and have developed novel ultra sensitive techniques to unravel the radical- and ion-surface interactions. I will discuss specifically the techniques of evanescent wave cavity ring down spectroscopy, second harmonic generation and spectroscopic ellipsometry which in combination with gas phase diagnostics such as cavity ring down spectroscopy and threshold ionization mass spectrometry provide an unique possibility to understand the surface kinetic processes. These studies enable the manipulation of the plasma properties to obtain specific material applications. Examples include the understanding of the plasma oxidation of ultra-thin aluminum films for magnetic tunnel junctions, the deposition of dense barrier layers for plastic electronics applications and the high rate deposition of surface and bulk passivating films for multi-crystalline solar cells. [Preview Abstract] |
Monday, October 17, 2005 2:00PM - 2:15PM |
DM2.00002: FTIR characterization of the gas phase chemistry in pulsed 1,3-butadiene discharges in a Gaseous Electronics Conference (GEC) Cell Ashish Jindal, Lawrence Overzet, Matthew Goeckner FTIR Spectroscopy is used to characterize the gas phase chemistry of various pulsed regimes in a 1,3-butadiene (H$_{2}$C=CHCH=CH$_{2})$ discharge in an inductively coupled GEC reactor. Characterization is done as a function of the plasma on to off time at both constant and varying duty cycles. The power delivered during the on time is adjusted such that the time averaged power for all runs is maintained at a constant 10 W (13.56 MHz). The dissociation mechanisms for the observed chemical densities are investigated. For example, it appears that only the $\pi $ bond of the C=C bond is cleaved for the shorter on times. At longer on times the remaining $\sigma $ bond is also broken and a sizable fraction of the gas becomes free CH$_{2}$. This bond destruction has a profound impact on film growth and thus a link between the gas and surface phase processes will also be examined. [Preview Abstract] |
Monday, October 17, 2005 2:15PM - 2:30PM |
DM2.00003: Influence of chamber scaling on different level polymerizing processing gases Sanket Sant, Eric Joseph, Baosuo Zhou, Lawrence Overzet, Matthew Goeckner We have previously examined influence of chamber scaling (both diameter and source to chuck gap) on fluorocarbon film deposition/etch for CF$_{4}$ plasmas$^{1, 2}$. In this paper, we extend those studies to more polymerizing fluorocarbon chemistry, C$_{4}$F$_{8}$. In CF$_{4} $ discharges, film growth on unbiased substrates go from deposition to etch as the source to chuck gap increases. In C$_{4}$F$_{8}$ discharges film growth occurs for all gaps and chamber diameters examined. It is found that ions play an important role in deposition with CF$_{4}$ but not with C$_{4} $F$_{8}$. This difference may be attributed to the structures of the parent gases. Dissociation of a C-C bond in C$_{4}$F$_{8}$ may result in an `unwrapping' of the cyclic structure. When this radical fills an open bond site on a surface, a new site is created. On the other hand, CF$_{3}$ will cap bond sites in CF$_{4}$ plasmas. Thus ion impact is required for site formation in CF$_{4}$ plasmas but not in C$_{4}$F$_{8}$ plasmas. \newline \newline $^{1)}$ EA Joseph, \textit{et al}., J. Vac. Sci. Technol. A 22 (3), May/Jun 2004 \newline $^{2) }$BS Zhou, et al., J. Vac. Sci. Technol. (submitted) [Preview Abstract] |
Monday, October 17, 2005 2:30PM - 2:45PM |
DM2.00004: O-atom Recombination on Anodized Aluminum in an Oxygen Plasma, Studied by a New ``Spinning Wall'' Technique. Vincent M. Donnelly, Peter Kurunczi, Joydeep Guha We have developed a new method for studying plasma-surface interactions. A cylinder coated with the material of interest (here, anodized Al) is embedded in the plasma chamber wall. Skimmers and differential pumping allow the plasma chamber to be operated at standard pressures (e.g. 10 mTorr) while the chamber on the opposite side of the cylinder is at high or ultrahigh vacuum, allowing the surface to be studied by line-of-sight mass spectrometer or Auger electron spectroscopy. When the sample is rotated at up to 200,000 rpm, the surface can be examined in as little as 0.2 ms after exposure to the plasma. By varying the rotation frequency the reaction time can be varied, thus allowing the kinetics of atom-surface interactions to be extracted. O$_{2}$ is observed to desorb when the surface is exposed to an oxygen plasma, due to heterogeneous recombination of O. The signal falls off rapidly as a function of decreasing rotation frequency at high frequency, and much more slowly at lower frequencies. This time dependence can be well represented by a multi-site adsorption model with mobile O diffusing from site to vacant site. Supported by ACS/PRF. [Preview Abstract] |
Monday, October 17, 2005 2:45PM - 3:00PM |
DM2.00005: Hyper-Thermal Hydrogen Atoms Produced by Surface Neutralisation Tatiana Babkina, Timo Gans, Uwe Czarnetzki Hyper-thermal neutrals have significant potential for technological applications and can also play an important role in the power balance of plasmas. We present experimental investigations of the energy distribution function of the flux of hyper-thermal hydrogen atoms and compare results with data obtained using a computer simulation (TRIM). Hydrogen ions are produced in a magnetically confined inductively coupled RF plasma. They are accelerated from the plasma bulk towards a biased electrode by the plasma boundary sheath potential in front of the surface. Neutralisation and reflection of impinging ions at the surface result in hyper-thermal atoms. These atoms are investigated by optical emission spectroscopy; and a quantitative analysis of the energy distribution function is carried out using a mass resolved energy analyser. The obtained energy spectra can be explained as a superposition of individual spectra of the various ion species (H$^+$, H$_2$$^+$, H$_3$$^+$). Negative ions created at the electrode surface produce hyper-thermal neutrals with energies exceeding the sheath potential. [Preview Abstract] |
Monday, October 17, 2005 3:00PM - 3:15PM |
DM2.00006: Oxygen Plasma Ion Implantation in MgF2 Anti-Reflection Coatings M. Tuszewski, K. Scarborough Low-energy ($<$ 10 kV) oxygen (O+) plasma ion implantation is performed in the (100-nm-thick) MgF2 anti-reflection coatings of various solar panel coverglasses. O+ implantation could cause MgF2 darkening, and associated degradation of solar array power observed in Global Positioning Satellites (GPS). We irradiate various GPS coverglass samples with O+ doses up to 1015 cm-2, corresponding to a 10 year-exposure in simulated average oxygen environment at GPS orbit (20,000 km altitude). The O+ implants are performed with a low-pressure (0.5 -- 3 mTorr) inductive plasma source and a commercial high-voltage pulser. Negative high-voltage pulses (5 -- 20 microsecond widths, 1 -- 10 kV amplitudes, 0.1 - - 2 kHz repetition rates) are applied to samples mounted on a downstream, water-cooled, electrode. The optical transmission (200 -- 800 nm) of the samples is measured before and after each implant. Preliminary results suggest that the O+ implants indeed cause some optical transmission loss in the MgF2 coatings. The oxygen plasma density profiles, the electron temperatures, and the plasma potentials are measured with Langmuir probes. The oxygen species content are measured with optical and mass spectrometry. These measurements are required to estimate as accurately as possible the incident O+ doses. [Preview Abstract] |
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