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 FT2: Capacitive Discharges - Computational |
Hide Abstracts |
Chair: Uwe Czarnetzki, Ruhr-Universität Bochum Room: State C |
Tuesday, November 4, 2014 3:30PM - 3:45PM |
FT2.00001: Tailoring plasma properties through the non-linear frequency coupling of odd harmonics Andrew Gibson, Arthur Greb, William Graham, Timo Gans Multiple frequency plasma sources are commonplace in plasma based nano-fabrication. However the control of plasma properties in these discharges is often limited by a poor understanding of the non-linear coupling between the frequencies. Thus investigations of this non-linear coupling are crucial for achieving better control of plasma processes and optimising process outcomes. Presented here is a study of plasma excitation by two coupled odd harmonics (13.56 and 40.68 MHz) using a 1D fluid model of a symmetric capacitively coupled plasma. Non-linear frequency coupling is found to minimise the average plasma potential when both frequencies contribute equally to the voltage waveform. Furthermore, varying the phase between the frequencies can further decrease the average plasma potential, without having a significant effect on the ion density. This effect allows for control of the sheath potential at both electrodes simultaneously, independent of the ion density. As such the use of odd harmonics offers a novel method of plasma control that maintains the symmetry of the discharge. This is in contrast to plasma control techniques utilising the electrical asymmetry effect where the sheath potential is decreased at one electrode by increasing it at the opposing electrode. [Preview Abstract] |
Tuesday, November 4, 2014 3:45PM - 4:00PM |
FT2.00002: Particle-in-cell Monte Carlo collision simulation of a capacitively coupled discharge in oxygen Jon Tomas Gudmundsson, Michael A. Lieberman The oopd1 particle-in-cell Monte Carlo collision (PIC-MCC) code is used to simulate a capacitively coupled discharge in oxygen. oopd1 is a one-dimensional object-oriented PIC-MCC code in which the model system has one spatial dimension and three velocity components [1]. The oxygen model includes, in addition to electrons, the oxygen molecule in the ground state, the oxygen atom in the ground state, the negative ion O$^-$, the positive ions O$^+$ and O$_2^+$, and the metastable states O$(^1$D) and O$_2(a^1\Delta_g)$. We explore the electron energy distribution function (EEDF), the electron temperature profile, the density profiles of charged particles and electron heating rates for a capacitively coupled oxygen discharge. We explore the influence of the metastables on the plasma parameters and in particular the influence of detachment by the metastable O$_2(a^1\Delta_g)$ molecule on the electron heating mechanism in the discharge. \\[4pt] [1] J. T. Gudmundsson, E. Kawamura and M. A. Lieberman, A benchmark study of a capacitively coupled oxygen discharge of the oopd1 particle-in-cell Monte Carlo code, Plasma Sources Science and Technology 22(3) (2013) 035011 [Preview Abstract] |
Tuesday, November 4, 2014 4:00PM - 4:15PM |
FT2.00003: Electron beam formation and resonance phenomena in low pressure capacitive rf plasmas Sebastian Wilczek, Jan Trieschmann, Ralf Peter Brinkmann, Thomas Mussenbrock, Edmund Sch\"ungel, Julian Schulze, Aranka Derzsi, Ihor Korolov, Zolt\'an Donk\'o In capacitively coupled radio frequency discharges the expansion of the modulated plasma sheaths accelerates a fraction of electrons. This consequently leads to various kinds of electron beam formations; one or likely multiple beams are triggered and start propagating. Especially at low pressures, these electrons traverse through the plasma bulk with high kinetic energy and ionize the neutral background gas to sustain the plasma. Under distinct discharge conditions a violation of the quasi-neutrality of the plasma bulk is indicated by a local accumulation of charge density. Consequently, strong electric fields exist even in the center of the discharge. In this work, the electron beam formations are investigated in conjunction with resonance behavior of the discharge by means of 1d3v Particle-In-Cell simulations. It is shown that the driving frequency or higher harmonics of the driving frequency match the local electron plasma frequency, particularly in the bulk region. This is an indication of local resonance phenomena in conjunction with the establishing of distinct electron beam modes being formed. Moreover, this is connected to a change of the local electric field. [Preview Abstract] |
Tuesday, November 4, 2014 4:15PM - 4:30PM |
FT2.00004: Efficient Modelling of Pulsing CCP Reactors Schabnam Naggary, Frank Atteln, Ralf Peter Brinkmann, Mustafa Megahed Pulsed multi-frequency CCP reactors provide additional means to manipulate the plasma characteristics and in particular the ion energy distribution. The interaction of the plasma with the pulse duty cycle and frequency is not fully understood yet, due to complex excitation and de-excitation of the rf and pulsing signals. Numerical models were demonstrated to accurately capture the transient behavior of the pulsed plasma. The high computational effort, however, makes these models very inaccessible to the community and do not allow for systematic study of the different parameters of interest to system designers. This work presents an efficient model that allows the characterization of the ``main'' plasma properties including the ion energy distribution functions within seconds. The zero dimensional model allows the analysis of the reactor operation parameter space and it provides the boundary conditions for more detailed, spatially resolved models that are used to fine tune the design including the resolution of wafer edge and wave effects. [Preview Abstract] |
Tuesday, November 4, 2014 4:30PM - 5:00PM |
FT2.00005: Capacitively Coupled Plasma Modeling at Low and Moderately High Pressures Invited Speaker: Kallol Bera Capacitively coupled plasmas have been used in both deposition and etching processes in semiconductor industry. The etching processes are typically performed at low pressure (5-500 mT) as directionality and energy of ions are important. The deposition processes are performed at moderately high pressure (1-10 T) to achieve higher process deposition rates with minimal ion bombardment damage. Our plasma model includes the full set of Maxwell equations in their potential formulation. The equations governing the vector potential are solved in the frequency domain after every cycle for multiple harmonics of the driving frequency. Current sources for the vector potential equations are computed using the plasma characteristics from the previous cycle. The coupled set of equations governing the scalar potential and drift-diffusion equations for all charged species are solved implicitly in time. In the low pressure regime, stochastic heating is important. This effect is considered in the model using modified transport parameters. The model was validating using experimental data. At 13 MHz, secondary electron emission is found to play an important role in enhancing ionization through collisions. At higher frequency, the effect of secondary electron emission is less significant. At very high frequency, the electromagnetic standing wave leads to peak in plasma density at the center of the discharge. In the moderately high pressure regime, secondary electrons are important as they participate in bulk plasma heating. At very high frequency, under moderately high pressure, the electromagnetic effect is also found to be important, with the shape of the plasma profile varying according to aspect ratios of reactor structure. In this paper we will present plasma modeling that adequately represents plasmas at low and moderately high pressures at different frequency. [Preview Abstract] |
Tuesday, November 4, 2014 5:00PM - 5:15PM |
FT2.00006: The effect of ambipolar electric fields on the electron heating in capacitive RF plasmas Julian Schulze, Zoltan Donko, Aranka Derzsi, Ihor Korolov, Edmund Schuengel We investigate the electron heating dynamics in argon and helium capacitively coupled RF discharges driven at 13.56 MHz by Particle in Cell simulations and by an analytical model. Electrons are found to be heated by strong ambipolar electric fields outside the sheath during the phase of sheath expansion in addition to classical sheath expansion heating. Moreover, we find that electrons reflected multiple times from the expanding sheath edge within one RF period are the primary sources of ionization. In fact a synergistic combination of different heating events is required to sustain the plasma. The ambipolar electric field outside the sheath is found to be time modulated due to a time modulation of the electron mean energy caused by the presence of sheath expansion heating only during one half of the RF period at a given electrode. This time modulation results in more heating than cooling on time average. If an electric field reversal is present during sheath collapse, this time modulation will be enhanced. This ambipolar electron heating is found to represent an important heating mechanism, which should be included in models of capacitive RF plasmas. [Preview Abstract] |
Tuesday, November 4, 2014 5:15PM - 5:30PM |
FT2.00007: A Simplified Model of The Electrical Asymmetry Effect Douglas L. Keil, Edward Augustyniak, Yukinori Sakiyama, Pavel Ni Dual Frequency Capacitively Coupled Plasmas (DF CCP) have been used extensively in semiconductor processing. One of the most promising methods for extending CCP technology is the application of the Electrical Asymmetry Effect (EAE). Extensive studies of this effect have appeared in the literature and the effect can be claimed to be reasonably well understood [1]. However, the complexity of the available models often makes them unwieldy for resolving engineering issues and for analysis of test data. In this work it is shown that most of the industrially important features of the EAE effect can be captured with a greatly simplified model. Although approximate, this simplified model enables relatively quick design guidance and simplifies analysis of test data. Electrical measurements of the EAE effect from a commercially relevant CCP plasma deposition tool are presented. These results show good agreement with the model and serve to illustrate the basic features of the model.\\[4pt] [1] U Czarnetzki et.al, Plasma Sources Sci. Technol. 20 (2011) 024010. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700