Bulletin of the American Physical Society
67th Annual Gaseous Electronics Conference
Volume 59, Number 16
Sunday–Friday, November 2–7, 2014; Raleigh, North Carolina
Session KW1: Plasma Diagnostics II |
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Chair: Hiroshi Akatsuka, Tokyo Institute of Technology Room: State EF |
Wednesday, November 5, 2014 1:30PM - 2:00PM |
KW1.00001: Diagnostics of plasma-surface interactions in plasma processes Invited Speaker: Kenji Ishikawa Low temperature plasma including electrons, ions, radicals and photons can be applied because only high temperature of electron but for background gases. Recently plasma applications in biology and medicine have grown significantly. For complexity of mechanisms, it is needed to understand comprehensively the plasma-surface interactions. To diagnose the interactions comprises of three areas; (1) incident species generated in plasmas toward the surface, (2) surface reactions such as scission and bond of chemical bonds, and (3) products after the reactions. Considered with non-linearity of the chemical reactions as changed by an initial state, we have focused and developed to observe dangling bonds in situ at real time by electron spin resonance (ESR). Moreover, individual contribution and simultaneous irradiation of each species such as radicals and photons have been studied in utilization of light shades and windows in similar manner of the pellets for plasma process evaluation (PAPE) [1]. As exampled, the interaction of polymeric materials [2], fungal spores[3] and edible meats with plasmas were studied on the basis of the real time in situ observations of dangling bonds or surface radicals formation.\\[4pt] [1] S. Uchida et al., J. Appl. Phys. 103, 073303 (2008);\\[0pt] [2] K. Ishikawa et al., J. Phys. Chem. Lett. 2, 1278 (2011).\\[0pt] [3] K. Ishikawa et al., Appl. Phys. Lett. 101, 013704 (2012). [Preview Abstract] |
Wednesday, November 5, 2014 2:00PM - 2:15PM |
KW1.00002: Phase-modulated dispersion interferometry for electron-density determination of high-pressure plasma Keiichiro Urabe, Tsuyoshi Akiyama, Kazuo Terashima Phase-modulated dispersion interferometry (PMDI) is a laser interferometry technique that was first developed for measurement of electron density in large fusion reactors [1]. PMDI can eliminate the effect of nondispersive components in the refractive-index variation on the measured signals; therefore, it is mostly free from vibration of optical devices during the measurement. Also, configuration of the laser beam axis in PMDI is simpler than that in heterodyne interferometry. In this paper, we demonstrate the potential of PMDI for the diagnostics of low-temperature plasmas generated at high pressures. Most of the variation of the refractive index induced by the variation of gas density was eliminated by signal processing, and it contributed to accurate electron-density determination in high-pressure plasmas [2]. The measurement results for a pulsed-dc microdischarge in an atmospheric-pressure helium gas flow revealed that the electron density in the microdischarge was in the range between 4x10$^{13}$ and 1.4x10$^{14}$ cm$^{-3}$, and our PMDI system had a temporal resolution of 110 $\mu $s and a sensitivity of the line-integrated electron density of 7x10$^{11}$ cm$^{-2}$ respectively. \\[4pt] [1] T. Akiyama \textit{et al.}, Plasma Fusion Res. \textbf{5}, (2010) S1041. \newline [2] K. Urabe \textit{et al.}, J. Phys. D \textbf{47}, (2014) 262001. [Preview Abstract] |
Wednesday, November 5, 2014 2:15PM - 2:30PM |
KW1.00003: In-situ diagnostics and characterization of etch by-product deposition on chamber walls during halogen etching of silicon Neema Rastgar, Saravanapriyan Sriraman, Ricky Marsh, Alex Paterson Plasma etching is a critical technology for nanoelectronics fabrication, but the use of a vacuum chamber limits the number of in-situ, real-time diagnostics measurements that can be performed during an etch process. Byproduct deposition on chamber walls during etching can affect the run-to-run performance of an etch process if there is build-up or change of wall characteristics with time. Knowledge of chamber wall evolution and the composition of wall-deposited films are critical to understanding the performance of plasma etch processes, and an in-situ diagnostics measurement is useful for monitoring the chamber walls in real time. We report the use of attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) to perform in-situ diagnostics of a vacuum chamber's walls during plasma etching. Using ATR-FTIR, we are able to monitor the relative thickness and makeup of chamber wall deposits in real time. We then use this information to develop a chamber wall cleaning process in order to maintain reproducible etching conditions from wafer to wafer. In particular, we report mid-IR (4000-650 cm$^{\mathrm{-1}})$ absorption spectra of chamber wall-deposited silicon byproducts formed during halogen etching of silicon wafers. [Preview Abstract] |
(Author Not Attending)
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KW1.00004: Accurate characterization of RF antennas for low-temperature plasma discharges with non-uniform magneto-static fields Davide Melazzi, Vito Lancellotti, Alessandro Cardinali, Marco Manente, Daniele Pavarin The analysis of Radio Frequency Helicon plasma sources appears to have focused on the absorption of electromagnetic energy, but not much on the role played by the antenna driving the plasma discharge. In fact, most approaches assume (i) the induced current density on the antenna a priori, and (ii) a uniform magneto-static field aligned with the plasma column. To determine the antenna current self-consistently and to consider non-uniform magneto-static fields we have developed two codes: ADAMANT and RAYWh. The former implements a full-wave approach to evaluate the current distribution on the antenna and the antenna impedance, which is crucial for the design of the feeding network. RAYWh solves the 3D Maxwell-Vlasov model equations by a WKB asymptotic expansion, and is capable of predicting the occurrence of mode transitions. We report on a comparative study of various antennas working in the 1-30 MHz range commonly used in Helicon sources. The current distribution on the antenna, power deposition, and wave propagation phenomena have been investigated for various density profiles, magneto-static field configurations, neutral pressure, electron temperature. [Preview Abstract] |
Wednesday, November 5, 2014 2:45PM - 3:00PM |
KW1.00005: Electron Density Measurement of Argon Containing Plasmas by Saturation Spectroscopy S. Nishiyama, H. Wang, S. Tomioka, K. Sasaki Langmuir probes are widely used for electron density measurements in plasmas. However, the use of a conventional probe should be avoided in a plasma which needs high purity because of the possibility of contamination. Optical measurements are suitable for these plasmas. In this work, we applied saturation spectroscopy to the electron density measurement. The peak height of the saturation spectrum is affected by the relaxation frequency of the related energy levels. In the case of the metastable levels of argon, the electron impact quenching rate, which is proportional to the electron density, is the dominant factor. In our experiments, an inductively coupled plasma source and a tunable cw diode laser were used. The frequency of the laser was scanned over the Doppler width of the $\rm 4s[3/2]^o_2-4p[3/2]_2$ (763.51 nm) transition. The experimental saturation spectrum was composed of a sharp Lorentzian peak and a broad base component, which was caused by velocity changing collisions. We deduced a new relationship between the saturation parameter and the measured saturated absorption spectrum with considering velocity changing collisions. We confirmed a linear relationship, which was expected theoretically, between the inverse of the saturation parameter and the electron density. [Preview Abstract] |
Wednesday, November 5, 2014 3:00PM - 3:15PM |
KW1.00006: OH(A,X) radicals in microwave plasma-assisted combustion of methane/air Wei Wu, Che Fuh, Chuji Wang A novel microwave plasma-assisted combustion (PAC) system, which consists of a microwave plasma-assisted combustor, a gas flow control manifold, and a set of optical diagnostic systems, was developed as a new test platform to study plasma enhancement of combustion. Using this system, we studied the state-resolved OH(A,X) radicals in the plasma-assisted combustion and ignition of a methane/air mixture. Experimental results identified three reaction zones in the plasma-assisted combustor: the plasma zone, the hybrid plasma-flame zone, and the flame zone. The OH(A) radicals in the three distinct zones were characterized using optical emission spectroscopy (OES). Results showed a surge of OH(A) radicals in the hybrid zone compared to the plasma zone and the flame zone. The OH(X) radicals in the flame zone were measured using cavity ringdown spectroscopy (CRDS), and the absolute number density distribution of OH(X) was quantified in two-dimension. The effect of microwave argon plasma on combustion was studied with two different fuel/oxidizer injection patterns, namely the premixed methane/air injection and the nonpremixed (separate) methane/air injection. Parameters investigated included the flame geometry, the lean flammability limit, the emission spectra, and rotational temperature. State-resolved OH(A,X) radicals in the PAC of both injection patterns were also compared. [Preview Abstract] |
Wednesday, November 5, 2014 3:15PM - 3:30PM |
KW1.00007: Ion Flux and Energy Virtual Sensor for Measuring Ion Flux and Energy Distribution at a RF Biased Electrode in ICP Reactor (RIE-MODE) Maria Bogdanova, Dmitriy Lopaev, Sergey Zyryanov The modern technology of micro- and nanoelectronics involves a great number of steps, e.g. pattern transfer, where Reactive Ion Etching (RIE) in rf plasma reactors is widely used. RIE is carried out placing samples on the surface of rf biased electrode, as rule in an asymmetric rf low-pressure discharge. In an effort to control the etching process, ion flux and energy distribution should be controlled precisely as much as possible. However, measurements of them during the process in the real-time operation mode are impossible. Nevertheless, if virtual sensor of ion flux and energy can be developed, such a sensor would allow monitoring ion energy spectrum without direct measurements during plasma processing. This virtual plasma diagnostics should include calculation of ion energy spectrum based on the simple physical model of ion motion in collisionless rf sheath. In addition the modeling has to be fulfilled in the real-time operation mode by using the set of external measurable parameters. This paper is just devoted to creation of such ion energy distribution virtual diagnostics. [Preview Abstract] |
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