Bulletin of the American Physical Society
65th Annual Gaseous Electronics Conference
Volume 57, Number 8
Monday–Friday, October 22–26, 2012; Austin, Texas
Session UF3: Plasma Diagnostics Techniques II |
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Chair: Ed Barnat, Sandia National Laboratories Room: Classroom 202 |
Friday, October 26, 2012 9:00AM - 9:15AM |
UF3.00001: Temperature measurement of substrate with a thin film using low-coherence interference Takayoshi Tsutsumi, Takehiro Hiraoka, Keigo Takeda, Kenji Ishikawa, Hiroki Kondo, Takayuki Ohta, Masafumi Ito, Makoto Sekine, Masaru Hori In plasma etching or plasma CVD, substrate temperature is one of the most important factors which determine the process performances. Non-contact temperature measurement technology is preferred for the fabrication of electric devices because of avoiding contamination and improving reliability. We have developed a highly precise and non-contact temperature monitor using a Fourier domain low-coherence interferometer (FD-LCI) and a super luminescent diode (SLD; center wavelength: 1330 nm, spectral width: 37.6 nm) as a low coherence light source. The temperature is derived from the changes of optical path length in substrate, which occurred by thermal expansion and refractive-index change. We achieved to estimate the Si wafer temperature during a plasma exposure. However, it is necessary to measure a substrate with thin films and/or other material substrate such as sapphire. In this report, we applied the monitor to Si wafer with carbon nanowalls and a sapphire substrate with GaN. While on heating the substrate, the optical path length increased linearly, and it turned out that non-contact measurement of substrate with a thin film could be realized for Si and sapphire substrates. \\[4pt] [1] T. Tsutsumi et al: ISPlasma2011, P1-002A, Nagoya, Japan, (March 2011). [Preview Abstract] |
Friday, October 26, 2012 9:15AM - 9:30AM |
UF3.00002: Significance of self-absorption for emission spectral lines Evgueni Gudimenko, Vladimir Milosavljevic, Stephen Daniels Accurate optical measuring techniques of spectral lines are needed for low pressure plasma semiconductor manufacturing diagnostics. One spectral line broadening problem which has been widely overlooked and its importance neglected is self-absorption. Self-absorption is an effect when a photon emitted by an atom may be absorbed by a different atom before it escapes from the source. In this study the method used to quantify the self-absorption involves changing the optical path length of the measured OES plasma spectral emission. This is achieved by taking OES measurements from two different viewports on the reactive ion etch (RIE) plasma chamber, one directly on top of the plasma chamber and the other on the side of the chamber, both differ in optical length. If the increase in signal intensity changes corresponding to optical length, there is no self-absorption. The experiments are performed in an RIE chamber, 13.56 MHz with maximum RF power of 600 W, Ar - O$_{2}$ mixture. Almost all the measured spectral lines have been affected by self-absorption e.g. the Argon 750 nm spectral line has its intensity affected by up to 40\%. In the case of Actinometry calculation, taking into account Ar and O$_{2}$ emission, correction of self-absorption could change the final result up to 20\%. [Preview Abstract] |
Friday, October 26, 2012 9:30AM - 9:45AM |
UF3.00003: Surface vibrational relaxation of N$_{2}$ studied by infrared titration with time resolved Quantum Cascade Laser diagnostics D. Marinov, O. Guaitella, A. Rousseau, D. Lopatik, M. H\"ubner, J. R\"opcke, Yu Ionikh Relaxation of vibrationally excited nitrogen molecules on reactor walls is the most efficient N$_{2}$(v) loss mechanism in laboratory plasmas at pressures up to few tens of mbars. In the present study a new method for determination of the de-excitation probability $\gamma _{{\rm N}2}$ of vibrationally excited N$_{2}$ on different surfaces has been developed. A short dc discharge pulse was applied to a mixture containing 0.05-1{\%} of CO$_{2}$, N$_{2}$O or CO in N$_{2}$ at 1.3 mbar. Due to a very efficient vibrational coupling between N$_{2}$(v) and CO$_{2}$ (N$_{2}$O, CO), the vibrational excitation of these titrating molecules is an image of the vibrational excitation of N$_{2}$. In the afterglow, the vibrational relaxation was monitored \textit{in-situ} using quantum cascade laser absorption spectroscopy. The measurements were performed in a single discharge pulse without signal accumulation. Experimental results were interpreted in terms of a numerical model of non-equilibrium vibrational kinetics. The value of $\gamma _{{\rm N}2}$ was determined from the best agreement between the measured and calculated relaxation times. Using new technique the relaxation probability of N$_{2}$(v) was measured for SiO$_{2}$, TiO$_{2}$, Al$_{2}$O$_{3,}$ Pyrex and anodized aluminum. [Preview Abstract] |
Friday, October 26, 2012 9:45AM - 10:00AM |
UF3.00004: Fine structure of Balmer-$\alpha$ line of atomic hydrogen measured by saturation spectroscopy Shusuke Nishiyama, Goto Motoshi, Koichi Sasaki Saturation spectroscopy is a widely used technique to obtain Doppler-free resolution in fundamental spectroscopy. This technique, however, is not used commonly for plasma diagnostics. In this work, we developed a system of saturation spectroscopy at the Balmer-$\alpha$ line of atomic hydrogen with the intention of applying it to diagnostics of the Large Helical Device at the National Institute for Fusion Science. A weak probe beam and a intense pump beam were injected into a linear magnetized plasma source on the chord of the cylindrical axis of the plasma from the counter directions. The frequency of the probe and pump beams was scanned simultaneously over the whole range of the Doppler-broadened Balmer-$\alpha$ line. In the condition of a weak magnetic field (60 Gauss), we obtained a saturation spectrum with many obvious peaks without Zeeman splitting. Most of the other peaks were assigned to fine-structure components of the Balmer-$\alpha$ line and their cross-over signals, which arose at the midpoint frequency of two transition peaks with a common lower or upper level. We also found anomalous cross-over signals at the midpoint of the peaks which had $2s$ and $2p$ as their lower levels. These signals suggest that the populations of $2s$ and $2p$ are exchanged significantly. [Preview Abstract] |
Friday, October 26, 2012 10:00AM - 10:15AM |
UF3.00005: Measurement of activated species generated by 60 Hz excited atmospheric pressure Ar plasma in atmospheric gas Keigo Takeda, Jerome Jolibois, Kenji Ishikawa, Hiromasa Tanaka, Hiroyuki Kano, Makoto Sekine, Masaru Hori Atmospheric pressure plasmas have a wide field of applications. To improve the performance, it needs to diagnose the behaviors of activated species generated by plasma discharge and to study about the gas-phase reactions in atmospheric pressure. Moreover, plasma treatments are frequently carried out under atmospheric condition without purge gases. In this study, behaviors of activated species generated by the atmospheric pressure plasma under atmospheric condition have been measured by using LIF spectroscopy. Firstly, concentration of the grand state nitrogen monoxide (NO) was measured. The wavelength of laser light for the excitation of NO was 226.3 nm. The fluorescence was observed on A-X(0, 2) band around 247 nm. The AC excited atmospheric pressure plasma with pure Ar gas was generated under atmospheric condition. The flow rate of Ar gas was fixed at 3 slm. The atmospheric condition was the humidity of 40{\%} and ambient temperature of 25 $^{\circ}$C. Concentration of NO has been measured as a function of distance from a jet slit of plasma head. The length of plasma jet was around 10 mm. The results show that the concentration of NO has a maximum at 10 mm from plasma head, and then decreases. This means that the influence of ambient gases was largest in the edge region of plasma. [Preview Abstract] |
Friday, October 26, 2012 10:15AM - 10:30AM |
UF3.00006: Plasma Parameters of SRF Cavities for Radio-Frequency Discharge Processing Janardan Upadhyay, Svetozar Popovic, Lepsha Vuskovic, Anne-Marie Valente-Feliciano, Larry Phillips Superconducting radio frequency (SRF) cavities of bulk Niobium are accelerating field-generating components of particle accelerators. Cavities are designed to support TM modes at a resonant frequency, which usually serve as their identifier. RF plasma surface modification dry-etching technology as an alternative to the currently existing wet etching technology requires a different RF coupling regime. The choice of power generator frequency greatly affects the field and plasma parameters distribution over the cavity. These are adjusted by a coaxial centerline antenna to provide for optimum level of plasma sheath uniformity. In the search for best etching conditions, we are opting for radio frequency (13.56 MHz, 100 MHz) and microwave frequency plasma (2.45 GHz) in Ar/Cl$_{2}$ gas mixture. We have developed five optical probes for simultaneous spectroscopic measurements of the plasma properties at five points inside the cavity. The electron temperature and density measurement at the same set of points will be also measured with a Langmuir probe. The measurement of plasma parameters at different pressure and power for the chosen frequency set with varying chlorine content will be presented. [Preview Abstract] |
Friday, October 26, 2012 10:30AM - 10:45AM |
UF3.00007: Convection-Diffusion Model for Atmospheric Pressure Plasma Jets: Obtaining Off-Axis Data from On-Axis Measurements Ansgar Schmidt-Bleker, Mario D\"unnbier, J\"orn Winter, Klaus-Dieter Weltmann, Stephan Reuter An analytical convection-diffusion model for atmospheric pressure plasma jets is presented. The model can be applied both for ambient air species diffusion and for heat transfer into a jets effluent. Using on-axis data from experiments as input, the model can be used to extrapolate the measured quantities to the complete domain for laminar flows and near-axis region for turbulent flows. The method is applied to experimental data obtained from molecular beam mass spectrometry as well as from a VUV absorption spectrometry method using the plasma jet itself as a VUV emitter. The measurements are conducted on a turbulent atmospheric pressure argon plasma jet with a protective gas nozzle, allowing for the creation of a shielding gas curtain around the plasma jets effluent. The results obtained from the hybrid analytical-experimental method are compared to computational fluid dynamics simulations. [Preview Abstract] |
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