Bulletin of the American Physical Society
2005 58th Gaseous Electronics Conference
Sunday–Thursday, October 16–20, 2005; San Jose, California
Session RW1: Capacitively Coupled Plasmas |
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Chair: P. Chabert, Ecole Polytechnique, France Room: Doubletree Hotel Pine |
Wednesday, October 19, 2005 1:30PM - 1:45PM |
RW1.00001: Breakdown in dual frequency capacitive discharges Miles M. Turner There are two classical mechanisms of breakdown. At low frequencies, an ion-controlled Townsend mechanism prevails, and at high frequencies, there is an electron-controlled breakdown. Among other points, these mechanisms differ in the character of the particle orbits. At low frequency, no particle orbits close within the plasma volume. At high frequency, nearly all particle orbits do so. In this paper we show that there is a third breakdown mechanism at intermediate frequency, where ion orbits are mainly closed and electron orbits are mainly open. In this regime, the dominant ionization mechanism is via electrons produced by fast neutral impacts on the electrodes. We will show that this intermediate frequency mechanism is likely the dominant breakdown process in dual frequency discharges, with the surprising implication that the discharge is initiated by the lower frequency in typical cases. [Preview Abstract] |
Wednesday, October 19, 2005 1:45PM - 2:00PM |
RW1.00002: Phase resolved optical emission spectroscopy on a dual frequency capacitively coupled rf discharge Timo Gans, Julian Schulze, Uwe Czarnetzki, Miles M. Turner Dual frequency capacitively coupled rf discharges are frequently used in technological applications. The principle of these discharges is to allow separate control of the ion energy and ion flux impinging on the substrate surface. The ion flux is mainly controlled by the high frequency component while the ion energy is predominantly determined by the low frequency voltage. We present experimental investigations on a confined industrial discharge (Exelan, Lam Research Inc.) operated with two frequencies, 1.94 MHz and 27.12 MHz, applied simultaneously to one electrode. Phase resolved optical emission spectroscopy (PROES), resolving both the high and low rf frequencies, gives insight into the electron impact excitation dynamics. Measurements reveal a strong coupling of both frequencies. The discharge is well confined resulting in similar excitation mechanisms in front of the powered and grounded electrodes. [Preview Abstract] |
Wednesday, October 19, 2005 2:00PM - 2:15PM |
RW1.00003: Frequency dependent spatial distributions of the electrons in a 300 mm diameter VHF capacitively coupled plasmas Greg Hebner, E. Barnat, P. Miller, A. Paterson, J. Holland, T. Lill The characteristics of VHF capacitively coupled Argon plasmas produced in a modified 300 mm diameter chamber have been investigated. The chamber had a 14-inch diameter upper electrode (source) that was driven at 10 to 196 MHz. The spatial distribution of the electrons is observed to change with the frequency of the applied rf drive. As the frequency was increased, the electron spatial distribution went from approximately uniform across the electrode diameter to peaked in the center. These results will be compared with our previous measurements of the line integrated electron density obtained from microwave interferometry and Abel inverted optical emission measurements. Scaling of the plasma parameters with frequency, power and pressure, and implications to energy deposition models will be discussed. This work was supported by Applied Materials and Sandia National Laboratories, a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04- 94AL85000. [Preview Abstract] |
Wednesday, October 19, 2005 2:15PM - 2:30PM |
RW1.00004: $E$ to $H$ transition in very high frequency capacitive discharges. Pierre Levif, Pascal Chabert, Jean-Luc Raimbault, Jean-Marcel Rax, Michael A. Lieberman Large area capacitive discharges driven at frequency higher than the usual industrial frequency of $13.56$\,MHz have attracted recent interest for materials etching and thin film deposition on large area substrates. However, electromagnetic effects, become significant if the excitation wavelength $\lambda$ and the plasma skin depth $\delta$ are not infinite and can be important limitations for plasma processing uniformity. A self-consistent electromagnetic-transmission line model valid in the entire range of $\lambda$ and $\delta$ of practical interest is solved. We find that the plasma may either be sustained by the usual capacitive ($E$) field or by an inductive ($H$) field, and that the discharge experiences $E$ to $H$ transitions as the voltage and frequency between the electrodes are raised. At low pressure, the transition is global whereas at high pressure the transition is local, the centre is in the $E$ mode while the edges are in the $H$ mode. [Preview Abstract] |
Wednesday, October 19, 2005 2:30PM - 3:00PM |
RW1.00005: PIC and fluid simulations of capacitively coupled plasmas for dielectric etchers and microplasmas Invited Speaker: Fluid, particle-in-cell and hybrid models are the numerical simulation techniques are overviewed. The three modelling techniques are benchmarked by comparing simulation results in different plasma systems (plasma display panels [1], capacitively coupled plasmas [2]) with experimentally measured data. The potential profile and the electron kinetic information such as electron energy distribution and temperature are important for understanding the PDP striation phenomena. Kinetic 1d particle-in-cell/Monte-Carlo-collision modeling of the single- and dual-frequency capacitively coupled plasma (CCP) sources was also carried out in the wide parameter range. In particular, as the low- frequency current increases for the fixed high-frequency current in low-pressure dual radio-frequency argon discharges, the electron energy distribution function (EEDF) changes from Druyvesteyn to bi-Maxwellian type, along with the significant drop in the effective electron temperature. The EEDF evolution was shown to be attributed to the transition of the electron heating mode from collisional to collisionless heating in dual-frequency CCP [2]. *In collaboration with HC Kim (now at UC Berkeley), N Babaeva (now at Iowa State Univ.), F Iza, SS Yang, SJ Kim, M Radmilovic-Radjenovic, HJ Lee (Pusan National Univ.) \newline \newline [1] Plasma Display Review, J.K. Lee and J. Verboncoeur, in Low Temperature Plasma Phys. ed. by R. Hippler et al., p. 367 (\textit{Wiley- VCH 2001}). \newline [2] Mode Transition Induced by Low-frequency Current in Dual- frequency Capacitive Discharges, H.C. Kim and J.K. Lee, \textit{Phys. Rev. Lett}. 93, 085003 (2004). [Preview Abstract] |
Wednesday, October 19, 2005 3:00PM - 3:30PM |
RW1.00006: Analysis of Triple-Frequency Capacitive Systems for Plasma Processing Invited Speaker: Dual- and triple-frequency capacitive systems are becoming more common among dielectric plasma etch systems in the industry today. Frequencies range from $<$1MHz to $\sim $200 MHz. The choice of frequencies is governed primarily by the relative effects desired with respect to density creation, average ion energy, and ion energy spread. At frequencies below 15 MHz, the dominant effect of mixing capacitive systems is seen in changes in ion energy and spread, with density affected to a lesser degree. At frequencies between 15 and 100 MHz, a trade-off exists between density creation and energy spread, particularly when these frequencies are combined with one or more frequencies below 15 MHz. When frequencies exceed 100 MHz, density formation dominates, with changes in ion energy getting progressively smaller at higher frequencies. In this paper, we explore practical density, energy, and spreads achievable for various combinations of frequencies using a physics DOE based on RF measurements of a triple-frequency system, and transform the results into process parameters proportional to density, energy, and spread. [Preview Abstract] |
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