Bulletin of the American Physical Society
72nd Annual Gaseous Electronics Conference
Volume 64, Number 10
Monday–Friday, October 28–November 1 2019; College Station, Texas
Session CT2: Inductively Coupled Plasmas |
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Chair: Alexandre Likhanskii, Applied Materials, Inc. Room: Century II |
Tuesday, October 29, 2019 8:00AM - 8:15AM |
CT2.00001: Student Excellence Award Finalist: Transition to instability-enhanced transport in weakly-ionized magnetized plasmas Romain Lucken, Antoine Tavant, Anne Bourdon, Mike A. Lieberman, Pascal Chabert An inductively coupled plasma column is simulated by an electrostatic particle-in-cell Monte-Carlo method in 2D. The size of the simulated argon discharge is taken to be a few times the ion mean free path and the magnetic field is varied from 0 to 40 mT. The results show that an instability pattern rotating in the direction of the diamagnetic drift develops at magnetic fields greater than 50 mT. This instability is a resistive drift instability triggered by collisions and it greatly enhances the plasma transport from the center to the walls. The linearized fluid transport equations show that it can develop only when the total drift velocity is larger than the Bohm speed. It is observed that the electron drift velocity always remains lower than the electron thermal velocity. This condition yields a maximum Hall parameter and a lower bound for the edge-to-center plasma density ratio of the discharge. The latter yields an effective electron collision frequency proportional to $B^2$. An analytical isothermal fluid model that incorporates the effective collision frequency can correctly reproduce the properties of the plasma transport at high magnetic field. The transition to this regime seems to appear when the classical electron mobility becomes lower than the ion mobility. [Preview Abstract] |
Tuesday, October 29, 2019 8:15AM - 8:30AM |
CT2.00002: Electromagnetic approach to a novel microwave driven ICP plasma jet Michael Klute, Horia-Eugen Porteanu, Ilija Stefanovic, Nikita Bibinov, Wolfgang Heinrich, Peter Awakowicz, Ralf Peter Brinkmann Plasmas jets are usually Microwave or Radio frequency driven and operated in a capacitive mode. This mode, however, couples considerable power to ions which limits the plasma density and the efficiency. Inductive coupling eliminates these disadvantages. A novel small scale, microwave driven plasma jet has been proposed by \textit{Porteanu et al.}. It is operated as an inductive discharge and that has been recently characterized using optical emission spectroscopy (OES) by \textit{Stefanovic et al.}. In this work the proposed plasma jet is examined theoretically. An electromagnetic model is presented based on a series representation of the electromagnetic field in the resonator. An infinite number of modes is found ordered by an azimuthal wave number m. By equating the volume-integrated electromagnetic power that is absorbed by the plasma with the loss power, stable operating points and hysteresis effects are found. All results will be compared to the results of the OES measurements and imagines obtained from CCD-imaging. The relation between the electric field strength and emitted light intensity will be used to compare the spatially resolved calculated field to the measurements. [Preview Abstract] |
Tuesday, October 29, 2019 8:30AM - 8:45AM |
CT2.00003: Computational Investigation of Pulsed Inductively Coupled Plasmas for STI Etching Wei Tian, JC Wang, S Rauf, S Sadighi, J Kenney As critical dimensions continue to shrink, etching of high aspect ratio Si structures, such as those used for shallow trench isolation (STI), is becoming challenging. Pulsed plasma processing has gained a lot of attention due to its advantages, such as better control of flux and energy, over continuous wave (CW) plasmas processing. Pulsed plasma provides us with extra knobs to tailor the etching process. In this talk, an inductively coupled plasma (ICP) at a few mTorr with pulsed source (W$_{\mathrm{s}}$) and RF bias (W$_{\mathrm{b}}$) has been computationally studied for STI etching. Three pulsing schemes are investigated: source pulsing (pulsed source W$_{\mathrm{s}}$ + CW bias W$_{\mathrm{b}}$), bias pulsing (pulsed bias W$_{\mathrm{b}}$ + CW source W$_{\mathrm{s}}$), and their synchronized pulsing. It is found that when the source power is pulsed (pulsed W$_{\mathrm{s}}$ + CW W$_{\mathrm{b}}$), plasma extinguishes during the pulse-off period, higher sheath voltage up to a few kV is produced as a result of lower electron density. When the bias power is pulsed (pulsed W$_{\mathrm{b}}$ + CW W$_{\mathrm{s}}$), plasma density is slightly modulated by the bias power, while sheath voltage increases up to the kV level during the pulse-on period. When the source and bias powers are synchronized, the ion angular and energy distribution function (IAEDF) is sensitive to the phase between powers. [Preview Abstract] |
Tuesday, October 29, 2019 8:45AM - 9:00AM |
CT2.00004: Experimental and numerical investigations on characteristics of electron density in pulsed inductively coupled O$_{\mathrm{2}}$/Ar plasmas Wei Liu, Xiao-Kun Wang, Sha-Sha Song, Yong-Xin Liu, Fei Gao, You-Nian Wang, Yong-Tao Zhao The characteristics of electron density ($n_{\mathrm{e}})$ in pulsed inductively coupled O$_{\mathrm{2}}$/Ar plasmas have been investigated by means of a time-resolved hairpin probe and a two-dimensional (2D) hybrid model. A decrease of $n_{\mathrm{e}}$ has been found at the beginning of active-glow in the discharges with high pulse frequencies. By means of the 2D hybird model, the decrease of $n_{\mathrm{e}}$ can be attributed to two reasons: one is the large consumption rate of electrons at the probe position and another one is the axial electron flux toward the coils at the very beginning of active-glow. Besides, the high energy electrons which formed near the coils can hardly arrive at the probe position due to their short electron energy relaxation length (smaller than the reactor length L $=$ 10 cm). Thus the electron generation via ionization processes becomes unimportant at probe position and the increase of $n_{\mathrm{e}}$ after its minimum is dominated by the axial electron flux (toward the substrate). However, the temporal variation of $n_{\mathrm{e}}$ at P2 (close to the coils) has tremendous difference than that at probe position. This is because the ionization processes dominate the electron generation during the active-glow. [Preview Abstract] |
Tuesday, October 29, 2019 9:00AM - 9:15AM |
CT2.00005: Finite skin depth consideration in the inductive transformer matrix model: implications for external circuit design and pulsed power operation Carl Smith, Joel Brandon, Kristopher Ford, David Peterson, Steven Shannon, Sang-Ki Nam The most commonly employed transformer matrix model for an inductively coupled plasma uses a thin skin depth approximation to obtain the relationship between coil geometry, plasma conditions, and the equivalent circuit elements that make up the transformer matrix equivalent circuit for an RF driven ICP source. A generalized skin depth dependent form of the transformer matrix elements $L_{12}$ {\&} $L_{22}$ was derived and is presented in this work. This model, along with experimental comparison, suggests that these skin depth effects can be especially impactful at low density and during pulsed power operation. Compared to experimental results, prior global models have had difficulty capturing transients in $n_{e}$ in the early power-on cycle. Generalization of skin depth dependence in $L_{12}$ particularly exuberates impedance mismatch in the early on cycle and better accounts for \textit{dn}$_{e}$\textit{/dt} at low n$_{\mathrm{e}}$ where the thin skin depth approximation does not capture the transformer matrix terms. Steady state and time resolved pulsed results were obtained using hairpin data from a cylindrical ICP system with Ar at pressures below 50 mTorr and powers between 5 W and 50 W and were compared to a global equivalent circuit model of the plasma. [Preview Abstract] |
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