Bulletin of the American Physical Society
66th Annual Gaseous Electronics Conference
Volume 58, Number 8
Monday–Friday, September 30–October 4 2013; Princeton, New Jersey
Session PR2: Capacitively Coupled Plasmas I |
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Chair: Kallol Bera, Applied Materials Inc. Room: Ballroom II |
Thursday, October 3, 2013 1:30PM - 1:45PM |
PR2.00001: IEDF Skew Control Using Phase Locked Dual Frequency RF Drive Hamilton Clark, Theresa Kummerer, David Coumou, Steven Shannon The distribution of ion energies incident on plasma facing surfaces can have a significant impact on process characteristics. Non-sinusoidal [1] and multi-frequency [2] bias drives have demonstrated both the control of IEDF shape and process enhancement brought about by this level of control. In this work, we will present an extension of multi-frequency drive for IEDF control where multiple frequencies that differ by integer multiples are used to drive an RF sheath for ion energy control. By varying the relative voltages and the phase between these independent drives, the distribution skew can be controlled such that the traditional two peak distribution obtained from an RF sheath can be weighted to the low energy peak or the high energy peak with a reasonable level of control. An analytical sheath model is presented to explain this phenomena; experimental measurement of IEDF's using a gridded energy analyzer are also presented, further demonstrating this configuration's ability to control IEDF shape and validating the analytical model used to introduce these concepts.\\[4pt] [1] Buzzi, Ting, Wendt; PSST 18 025009 (2009)\\[0pt] [2] Shannon, Hoffman, Yang, Patterson, Holland; JAP 97, 103304 (2005) [Preview Abstract] |
Thursday, October 3, 2013 1:45PM - 2:00PM |
PR2.00002: Evaluation of Equivalent Circuit Models for Plasma Bulk Characterization by Comparing IEDF Predictions with those of a Spatially Resolved CCP Model Schabnam Naggary, Mohammed Shihab, Frank Atteln, Mustafa Megahed, Ralf Peter Brinkmann Capacitively coupled radio frequency discharges are widely used in the semiconductor processing industry for thin film deposition and etching. Thus the evaluation of the ion energy distribution function (IEDF) is of paramount importance for industrial applications. Spatially and temporally resolved CCP models are generally computationally expensive leading to reduced applicability of these models for industrial optimization. In order to reduce the simulation time, as an alternative method, we use equivalent circuits based on a global model to characterize the plasma bulk and provide the needed input parameters for a hybrid sheath model $[1,2,3]$. The overall computational time to obtain time averaged IEDFs lies within seconds, hence the concept is very attractive for industrial scanning and optimization. In order to assess the applicability of this novel approach the results are compared with those of commercial multi-physics software CFD-ACE+ in 2 and 3 dimensions. Our investigation demonstrates the feasibility of the compromise between short simulation times and accurate calculation of spatially resolved IEDF.\\[4pt] [1] M Kratzer {\it J. Appl. Phys.}{\bf 90} (2001).\\[0pt] [2] M Shihab {\it J. Phys. D: Appl. Phys.}{\bf 45} (2012).\\[0pt] [3] A E Elgendy arXiv:1306.1664v1 (2013) [Preview Abstract] |
Thursday, October 3, 2013 2:00PM - 2:15PM |
PR2.00003: A particle-in-cell/Monte Carlo simulation of a capacitively coupled chlorine discharge Jon T. Gudmundsson, Shuo Huang We demonstrate the oopd1 (object oriented plasma device for one dimension) particle-in-cell/Monte Carlo simulation tool for the capacitively coupled chlorine discharge with a comprehensive reaction set. The simulation results are compared with available experimental measurements and good agreement is achieved. We explore a typical capacitively coupled chlorine discharge operated at both single frequency and dual frequency using oopd1 and obtain key plasma parameters, including particle density, effective electron temperature, electron energy probability function and ion energy and angular distributions for both Cl$^+$ and Cl$^+_2$ ions. The dependence of the plasma parameters on the discharge pressure is systematically investigated. As the pressure increases from 5 mTorr to 100 mTorr, the heating mechanism evolves from both stochastic and ohmic heating to predominantly ohmic heating and the electron heating outweighs the ion heating at high pressure. The creation of Cl$^+$ ions in the sheath region is mainly due to conversion from Cl$^+_2$ ions to Cl$^+$ ions through non-resonant charge exchange, while in the bulk region the creation of Cl+ ions is mainly ascribed to electron impact ionization processes. [Preview Abstract] |
Thursday, October 3, 2013 2:15PM - 2:30PM |
PR2.00004: Numerical Confirmation of the Feasibility to Generate Uniform Large-Area VHF Plasmas by Launching a Travelling Wave Hsin-Liang Chen, Yen-Cheng Tu, Cheng-Chang Hsieh, Wen-Fa Tsai, Chi-Fong Ai, Keh-Chyang Leou Large-area VHF (very high frequency) PECVD has been demonstrated to be an effective approach to improve the throughput of thin film silicon solar cell industry because it could increase the deposition rate without deteriorating the film quality. An innovative approach, i.e., creating a traveling wave in the discharge region by simultaneously launching two specific standing waves, is proposed to generate uniform large area VHF plasmas. The feasibility of this approach has been successfully verified by numerical simulation in this study. The spatial distribution of electric field for each standing wave is separately controlled by the phase difference ($\varphi )$ between the corresponding two feeding points placed on opposite sides of electrode and designated to produce a specific standing wave pattern. The simulation results indicate that the standing wave patterns obtained with $\varphi $ equal to 0$^{\mathrm{o}}$ and 180$^{\mathrm{o}}$ waves are spatially out of phase by 90$^{\mathrm{o}}$ and the corresponding standing patterns are consistent with various experimental works. By launching these two standing waves at the same time, a traveling wave can be generated once the conditions that these two standing waves must possess the same amplitude and be 90$^{\mathrm{o}}$ out of phase in terms of time are also fulfilled. To provide useful information for diagnostics, how the deviations from the necessary conditions would affect discharge patterns are discussed in details. [Preview Abstract] |
Thursday, October 3, 2013 2:30PM - 2:45PM |
PR2.00005: Higher harmonic waves and a center-peaked plasma density profile in VHF-CCP reactors Ikuo Sawada, Barton Lane, Peter Ventzek, Rochan Upadhay, Laxminarayan Raja Measurements of electron density profile and higher harmonic waves were performed in a very high frequency parallel-plate capacitively coupled plasma test-bench reactor. An Argon plasma was generated with a single frequency feed from the upper electrode at pressures of 20 to 100mTorr. The driving frequencies were 60 or 100MHz with electron densities ranging from 2e16 to 2e17[1/m3]. With increasing power, a center peak in the density profile becomes prominent. At higher densities, over 5e16[1/m3], a very sharp and localized center-peaked density profile is observed. On the contrary, a broad center peak is observed at lower densities. In order to elucidate the mechanism leading to center-peaked profiles, both experimental measurement and numerical calculation of higher harmonic spectrum were performed. A relationship between higher harmonics waves over 400 MHz and a very sharp center-peaked density profile was found and is described. [Preview Abstract] |
Thursday, October 3, 2013 2:45PM - 3:00PM |
PR2.00006: Observation of an abrupt electron heating mode transition in capacitive single radio frequency discharges Sebastian Wilczek, Jan Trieschmann, Julian Schulze, Ralf Peter Brinkmann, Thomas Mussenbrock, Aranka Derzsi, Ihor Korolov, Zoltan Donk\'o The electron heating in capacitive discharges at very low pressures ($\approx$1 Pa) is dominated by stochastic heating. In this regime electrons are accelerated by the oscillating sheaths, traverse through the plasma bulk and interact with the opposite sheath. By varying the driving frequency or the gap size of the discharge, energetic electrons reach the sheath edge at different temporal phases, i.e., the collapsing or expanding phase, or the moment of minimum sheath width. This work reports numerical experiments based on Particle-In-Cell simulations which show that at certain frequencies the discharge switches abruptly from a low density mode in a high density mode. The inverse transition is also abrupt, but shows a significant hysteresis. This behavior is explained by the complex interaction of the bulk and the sheath. [Preview Abstract] |
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