Bulletin of the American Physical Society
61st Annual Gaseous Electronics Conference
Volume 53, Number 10
Monday–Friday, October 13–17, 2008; Dallas, Texas
Session WF1: Plasma Diagnostics II |
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Chair: M. Goeckner, The University of Texas at Dallas Room: Salon E |
Friday, October 17, 2008 10:00AM - 10:15AM |
WF1.00001: Origin of electrical changes at plasma etching endpoints Mark Sobolewski, David Lahr Electrical signals are often used for endpoint detection in plasma etching, but the origins of the electrical changes observed at endpoint are not well understood. Such changes may indicate a difference in plasma electron density caused by changes in the gas-phase densities of etch products and reactants. Alternatively, changes in substrate electrical properties or surface properties (such as work function or secondary electron yields) may be involved. Investigation of these effects was carried out in an inductively coupled reactor equipped with rf bias and a wave cutoff probe, which allows small changes in plasma electron density to be measured with good accuracy and resolution. Simultaneous cutoff probe and electrical measurements were made during CF$_{4}$/Ar etches of SiO$_{2}$ films on Si substrates. Changes observed in the voltage, current, impedance and phase components at the rf bias frequency were related to, and fully explained by, changes in electron density. The dc self-bias voltage and harmonic signals showed more complicated behavior. The results allow several conclusions to be drawn about the relative reliability of endpoints obtained from different electrical signals. [Preview Abstract] |
Friday, October 17, 2008 10:15AM - 10:30AM |
WF1.00002: Photon-assisted Beam Probes for Low Temperature Plasmas Alvaro Garcia de Gorordo, Gary A. Hallock The Heavy Ion Beam Probe (HIBP) diagnostic has successfully measured the electric potential in a number of major plasma devices in the fusion community. In contrast to a Langmuir probe, the HIBP measures the exact electric potential rather than the floating potential. It is also has the advantage of being a very nonperturbing diagnostic. We propose a new photon-assisted beam probe technique that would extend the HIBP type of diagnostics into the low temperature plasma regime. We expect this method to probe plasmas colder than 10 eV. The novelty of the proposed diagnostic is a VUV laser that ionizes the probing particle. Excimer lasers produce the pulsed VUV radiation needed. These new photo-ionization techniques can take an instantaneous one-dimensional potential measurement of a plasma and are ideal for nonmagnitized plasmas where continuous time resolution is not required, as in plasma processing of semiconductors. It should be noted that the variation of plasma conditions over a wafer surface causes a very problematic non uniformity in the resulting chips. [Preview Abstract] |
Friday, October 17, 2008 10:30AM - 10:45AM |
WF1.00003: Negative Ion Densities and EEDFs in BCl$_{3}$/N$_{2}$ and BCl$_{3}$/SF$_{6}$ CCP Plasmas Bogdan Pathak, John Alexander, Karen Nordheden Previous work has shown that the addition of N$_{2}$ or SF$_{6}$ to BCl$_{3}$ plasmas results in an enhancement of the etch rate of GaAs. Langmuir probe measurements were performed to further investigate this enhancement. The energy distribution functions revealed an increase in negative ion density as N$_{2}$ or SF$_{6}$ were added to BCl$_{3}$. The negative ion density reaches a maximum near 55{\%} BCl$_{3}$ for N$_{2}$ mixtures and 40{\%} BCl$_{3}$ for SF$_{6}$ mixtures. This increase is most likely due to dissociative attachment. The shape of the electron energy distribution function in BCl$_{3}$/N$_{2}$ mixtures remains relatively unchanged and there is a decrease in the average electron energy with increasing N$_{2}$ percentage. Energy transfer from nitrogen metastables appears to be responsible for the increased dissociation in BCl$_{3}$/N$_{2}$ mixtures. This contrasts with BCl$_{3}$/SF$_{6}$ mixtures in which the electron density rapidly decreases and the average electron energy sharply increases at low SF$_{6}$ percentages, indicating that electron attachment heating is responsible for the enhanced dissociation. [Preview Abstract] |
Friday, October 17, 2008 10:45AM - 11:00AM |
WF1.00004: Application of an RF Biased Langmuir Probe to Etch Reactor Chamber Matching, Fault Detection and Process Control Douglas Keil, Jean-Paul Booth, Neil Benjamin, Chris Thorgrimsson, Mitchell Brooks, Mikio Nagai, Luc Albarede, Jung Kim Semiconductor device manufacturing typically occurs in an environment of both increasing equipment costs and per unit sale price shrinkage. Profitability in such a conflicted economic environment depends critically on yield, throughput and cost-of-ownership. This has resulted in increasing interest in improved fault detection, process diagnosis, and advanced process control. Achieving advances in these areas requires an integrated understanding of the basic physical principles driving the processes of interest and the realities of commercial manufacturing. Following this trend, this work examines the usefulness of an RF-biased planar Langmuir probe$^{1}$. This method delivers precise real-time (10 Hz) measurements of ion flux and tail weighted electron temperature. However, it is also mechanically non-intrusive, reliable and insensitive to contamination and deposition on the probe. Since the measured parameters are closely related to physical processes occurring at the wafer-plasma interface, significant improvements in process control, chamber matching and fault detection are achieved. Examples illustrating the improvements possible will be given. $^{1}$J.P. Booth, N. St. J. Braithwaite, A. Goodyear and P. Barroy, Rev.Sci.Inst., Vol.71, No.7, July 2000, pgs. 2722-2727. [Preview Abstract] |
Friday, October 17, 2008 11:00AM - 11:15AM |
WF1.00005: Simultaneous determination of electron density and electron temperature in low-pressure plasmas using the Multipole Resonance Probe Martin Lapke, Thomas Mussenbrock, Ralf Peter Brinkmann Plasma diagnostics is a highly developed science. In this contribution a diagnostic concept is proposed which enables simultaneous determination of electron density and electron temperature in low-pressure gas discharges, suitable for an industrial setting. The proposed method is robust, calibration free, and economical, and can be used for ideal and reactive plasmas alike. The diagnostic tool -- the Multipole Resonance Probe [1] -- is a radio-frequency driven probe of particular spherical design which is immersed in the plasma to excite a family of spatially bounded surface resonances. An analysis of the measured absorption spectrum provides information on the distribution of the plasma in the probe's vicinity, from which the values of electron density and electron temperature can be inferred. For an idealized case, the probe consists of two dielectrically shielded, conducting hemispheres which are symmetrically driven by an rf source. The excited resonances can be classified as multipole fields, which allows the analytical evaluation of the measured signal. [1] M. Lapke et al., submitted to Appl. Phys. Lett. (2008) [Preview Abstract] |
Friday, October 17, 2008 11:15AM - 11:30AM |
WF1.00006: A direct measurement of the energy flux density in plasma surface interaction Remi Dussart, Anne-Lise Thomann, Nadjib Semmar, Laurianne Pichon, Larbi Bedra, Jacky Mathias, Yves Tessier, Philippe Lefaucheux The energy flux transferred from a plasma to a surface is a key issue for materials processing (sputtering, etching{\ldots}). We present direct measurements made with a Heat Flux Microsensor (HFM) in an Ar plasma interacting with the surface of the sensor. The HFM is a thermopile of about one thousand metal couples mounted in parallel. An Inductively Coupled Plasma in Argon was used to make the experiments. Langmuir probe and tuneable laser diode absorption measurements were carried out to estimate the contribution of ions, neutrals (conduction) and metastables. In order to evaluate the ability of the HFM to measure the part due to chemical reactions, a Si surface in contact with the HFM was submitted to an SF$_{6}$ plasma. The direct measurements are in good agreement with the estimation we made knowing the etch rate and the enthalpy of the reaction. Finally, tests were performed on a sputtering reactor. Additional energy flux provided by condensing atoms (Pt) was also measured. [Preview Abstract] |
Friday, October 17, 2008 11:30AM - 11:45AM |
WF1.00007: Development of a compact, high energy electron beam source Scott Walton, Richard Fernsler, Robert Meger The US Naval Research Laboratory is developing a compact, high-energy electron beam source for welding and metal forming applications. The delivery of 1-2 kW over a small surface area is typically sufficient to melt thin metal rods. Thus, beam energies and currents in the range of 25 keV and 50 mA, with a spot size of about 3 mm, are required to deliver this level of power. In this work, we discuss the development of the electron beam source, which operates by extracting electrons from a discharge and then accelerating them to the required energy. To date, we have used a hollow cathode discharge to produce the electrons and a high-voltage wire mesh to accelerate them. We discuss the key attributes of operation and also the possibilities in using different sources and configurations to achieve the desired beam characteristics. This work was supported by the Office of Naval Research and NASA. [Preview Abstract] |
Friday, October 17, 2008 11:45AM - 12:00PM |
WF1.00008: ABSTRACT WITHDRAWN |
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