Bulletin of the American Physical Society
61st Annual Gaseous Electronics Conference
Volume 53, Number 10
Monday–Friday, October 13–17, 2008; Dallas, Texas
Session XF2: Capacitively-Coupled Plasmas |
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Chair: D. O'Connell, Queen's University Belfast Room: Salon A-D |
Friday, October 17, 2008 1:30PM - 2:00PM |
XF2.00001: Nonlinear Effects on Heating in Capacitive Discharges Invited Speaker: In low-pressure capacitive RF discharges two mechanisms of electron heating are dominant: i) Ohmic heating due to electron-neutral collisions and ii) stochastic heating due to momentum transfer from the oscillating sheath. Numerous models have been proposed in order to study electron heating phenomena. However, these models do not account for non-sinusoidal RF currents due to self-excitation of the plasma series resonance. Recently, analytical and numerical calculations of both enhanced Ohmic electron heating and enhanced stochastic electron heating due to nonlinear series resonance excitation have been described. This paper discusses the phenomenon of resonance excitation induced by nonlinear plasma-sheath interaction in capacitive discharges and its effect on electron heating. [Preview Abstract] |
Friday, October 17, 2008 2:00PM - 2:15PM |
XF2.00002: The RF Sheath, Nonlinearity and Stochastic heating: An extended analytical approach Michael Klick For both proper modeling of RF discharges and model-based plasma diagnostics in RF discharges the analysis of the electron heating process is very important. At least at lower pressure, which now more used now in many industrial processes as in the semiconductor manufacturing, the stochastic heating is the dominant electron heating mechanism. The analytic model for the nonlinearity of the RF sheath is based on a series expansion of the RF potential in the sheath which provides an parametric approach for the description of ion density distribution within the RF sheath. In contrast to established, analytical models, it is not restricted to a sinusoidal RF current. The electron dynamics is described by using the first three moments of the Boltzmann equation. In order to include also here nonlinear effects, harmonics in the RF current are considered as well. Finally the analytic results are discussed in comparison to experimental results of the electron collision rate for momentum transfer in RF discharges. For the comparison, the boundary condition of a sinusoidal RF voltage at the driven electrode is used. [Preview Abstract] |
Friday, October 17, 2008 2:15PM - 2:30PM |
XF2.00003: Effects of Magnetic Field on Very High Frequency Capacitively Coupled Plasma Kallol Bera, Shahid Rauf, Ken Collins Both electromagnetic and electrostatic effects play important roles in determining the spatial plasma profile in very high frequency (VHF) plasma sources. We investigated the effect of magnetic field on plasma profile for different electromagnet coil configurations, pressure and plasma electronegativity. Our plasma model includes the full set of Maxwell equations. The equations governing the vector potential, \textbf{\textit{A}}, are solved in the frequency domain for multiple harmonics. The tensor electron transport coefficients depend on the magnetic field. The coupled set of equations governing the scalar potential, and charged species are solved implicitly in time. Plasma simulation results show that radial component of magnetic field inhibits electron transport to the top and bottom electrodes, and modifies electron power deposition. The electron density increases near the wafer edge and decreases near the chamber center as the magnetic field is increased. The plasma current near the chamber center decreases reducing electromagnetic power deposition. The effects of magnetic field on the ion flux and energy have also been investigated. [Preview Abstract] |
Friday, October 17, 2008 2:30PM - 2:45PM |
XF2.00004: Resonance heating of dual frequency capacitive discharges Dennis Ziegler, Thomas Mussenbrock, Ralf Peter Brinkmann The dynamics of dual frequency capacitively coupled plasmas (2f-CCPs) is investigated using an approach that integrates theoretical insight and experimental data. Basis of the analysis is an extended version of a recently published model which casts the high frequency behavior of asymmetric 2f-CCPs in terms of a nonlinear second-order differential equation, or equivalently, a lumped element equivalent circuit [1]. The current work bases the choice of its model parameters on the data obtained by an actual 2f-CCP experiment conducted by Semmler et al. [2]. The analysis shows that the system is governed by a nonlinear interaction of the applied RF with the inner dynamics of the discharge, particularly with the collective oscillation mode known as the plasma series resonance (PSR). With respect to the power dissipation, two distinct paths can be identified which contribute in approximately equal parts. The first path is non-resonant and corresponds to the traditional picture of 2f-CCPs; the second path is resonant and identical with the mechanism of nonlinear electron resonance heating (NERH) proposed in [1,3]. [1] T. Mussenbrock, D. Ziegler, and R.P. Brinkmann, Phys. Plasmas 13, 083501 (2006) [2] E. Semmler, P. Awakowicz, and A. von Keudell, Plasma Sources Sci. Technol. 16, 839 (2007) [3] T.Mussenbrock and R.P. Brinkmann, Appl. Phys. Lett. 88, 151503 (2006) [Preview Abstract] |
Friday, October 17, 2008 2:45PM - 3:00PM |
XF2.00005: Electrode Impedance Effect on Electron Density in a CCP Reactor Yohei Yamazawa The generation of harmonics is one of the major nonlinear phenomena in a capacitively coupled plasma. Recently, Mussenbrock and Brinkmann proposed nonlinear electron resonance heating (NERH) model that predict the enhanced Ohmic dissipation caused by the harmonics originated from the series resonance of the plasma bulk and the sheath[1]. In our previous study, we experimentally demonstrated the resonantly growth of the harmonics by tuning a variable capacitor attached to the electrode and clearly shows that the electrode reactance must be taking into account in the series resonance condition.[2] Here, we focus on the change in electron density caused by the growth of the harmonics. We observed significant increases in electron density as the amplitude of the harmonics grows. We compared the influence of the growth in 3rd and 4th harmonics and found that 4th harmonic has smaller effect on electron density than that of 3rd harmonic has. \newline [1] T.Mussenbrock and R.P. Brinkmann, Appl. Phys. Lett. 88, 151503, (2006) \newline [2]Y. Yamazawa, M. Nakaya, M. Iwata and A. Shimizu Jpn. J. Appl. Phys 33 (2007) 4335. [Preview Abstract] |
Friday, October 17, 2008 3:00PM - 3:15PM |
XF2.00006: Characteristics of Pulsed Capacitively Coupled Plasma Sources for Plasma Etching Ankur Agarwal, Phillip Stout, Shahid Rauf, Ken Collins Dielectric etching of high aspect ratio features is susceptible to plasma charging damage giving less than ideal profiles. Charging damage occurs due to charge trapping on sidewall polymer. Tapering and twisting of features can also occur due to randomness in ion/radical flux composition as feature dimensions approach only a few tens of nm. While neutral beam etching and UV photon bombardment help mitigate charging damage, pulsing of a multiple frequency capacitively coupled plasma (CCP) may also allow for control of charging damage if negatively charged species can be extracted from the plasma. Pulsed plasma operation of a multiple frequency CCP reactor in electronegative etching gases is computationally investigated using coupled plasma equipment -- feature scale models. Results are compared to continuous plasma operation to assess the consequences on charging of features. Careful tailoring of pulsing at both source and bias frequencies enables negative charge acceleration in the features and helps negate charge buildup. Sustaining a steady pulsed plasma can however be complicated in strongly electronegative gas mixtures as the plasma may not re-ignite after power is turned-off. [Preview Abstract] |
Friday, October 17, 2008 3:15PM - 3:30PM |
XF2.00007: A Parallelized 3D Particle-In-Cell Method With Magnetostatic Field Solver And Its Applications Kuo-Hsien Hsu, Yen-Sen Chen, Men-Zan Bill Wu, Jong-Shinn Wu A parallelized 3D self-consistent electrostatic particle-in-cell finite element (PIC-FEM) code using an unstructured tetrahedral mesh was developed. For simulating some applications with external permanent magnet set, the distribution of the magnetostatic field usually also need to be considered and determined accurately. In this paper, we will firstly present the development of a 3D magnetostatic field solver with an unstructured mesh for the flexibility of modeling objects with complex geometry. The vector Poisson equation for magnetostatic field is formulated using the Galerkin nodal finite element method and the resulting matrix is solved by parallel conjugate gradient method. A parallel adaptive mesh refinement module is coupled to this solver for better resolution. Completed solver is then verified by simulating a permanent magnet array with results comparable to previous experimental observations and simulations. By taking the advantage of the same unstructured grid format of this solver, the developed PIC-FEM code could directly and easily read the magnetostatic field for particle simulation. In the upcoming conference, magnetron is simulated and presented for demonstrating the capability of this code. [Preview Abstract] |
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