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Simulation of Magnetically Confined Inductively Coupled Plasma" (2017)

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Simulation of Magnetically Confined Inductively Coupled Plasma South Dakota State University Open PRAIRIE: Open Public Research Access Institutional Repository and Information Exchange Theses and Dissertations 2017 Simulation of Magnetically Confined nducI tively Coupled Plasma Sina Javadpour South Dakota State University Follow this and additional works at: http://openprairie.sdstate.edu/etd Part of the Electrical and Computer Engineering Commons, Mechanical Engineering Commons, and the Physics Commons Recommended Citation Javadpour, Sina, "Simulation of Magnetically Confined Inductively Coupled Plasma" (2017). Theses and Dissertations. 1147. http://openprairie.sdstate.edu/etd/1147 This Thesis - Open Access is brought to you for free and open access by Open PRAIRIE: Open Public Research Access Institutional Repository and Information Exchange. It has been accepted for inclusion in Theses and Dissertations by an authorized administrator of Open PRAIRIE: Open Public Research Access Institutional Repository and Information Exchange. For more information, please contact [email protected]. SIMULATION OF MAGNETICALLY CONFINED INDUCTIVELY COUPLED PLASMA BY SINA JAVADPOUR A thesis submitted in partial fulfillment of the requirements for the Master of Science Major in Mechanical Engineering South Dakota State University 2017 iii ACKNOWLEDGEMENTS I would like to thank Dr. Delfanian, Director of METLAB, for his help and support throughout my 2.5 years at SDSU and Dr. Hu, for giving me the chance to get acquainted with Dr. Delfanian and Dr. Fan and his supervision. My sincere gratitude goes to Dr. Fan for introducing material processing plasma to me and trusting me with this research project. Furthermore, I am greatly in debt of Dr. Letcher for involving me in various research projects and Ms. Jane Boggs, Secretary of ME Department, for helping me get acquainted with Dr. Hu and Dr. Delfanian and receive the graduate research assistantship, which made it possible for me to attend SDSU to study for my master’s degree. This research was supported by the National Science Foundation under awards #1462389 and #1536209. Also acknowledged are South Dakota State University and Fraunhofer USA Center for Coatings and Diamond Technologies. iv CONTENTS ABBREVIATIONS………………………..…………………………………..…….…....v LIST OF FIGURES………………………..…………………………….…..…….…….vii LIST OF TABLES………………………..…………………………………..…….….....ix ABSTRACT………………………………..………………………………….…….….....x INTRODUCTION……….………………………………………………………………..1 MATERIALS AND METHODS……………………………………………………….....6 RESULTS AND DISCUSSIONS………………………………………………………..16 CONCLUSION………..…………………………………………………………………27 LITERATURE CITED………………………………………………………….……….28 v ABBREVIATIONS K Kelvin A Ampere V Volt Ω Ohm 2D 2 Dimensional 3D 3 Dimensional mm millimeter cm centimeter eV Electron Volt RF Radio Frequency CCP Capacitively Coupled Plasma ICP Inductively Coupled Plasma EEDF Electron Energy Distribution Function mTorr Milli Torr Rad Radian S Simens vi F Farad Hz Hertz N Newton C Coulomb T Tesla s Second PVD Physical Vapor Deposition EBPVD Electron Beam Physical Vapor Deposition CVD Chemical Vapor Deposition HDPCVD High Density Plasma Chemical Vapor Deposition PECVD Plasma Enhanced Chemical Vapor Deposition vii LIST OF FIGURES Figure 1. Front, side, and bottom views of the half-toroidal coil…………………………8 Figure 2. Front, side, and top view of the single cylindrical coil…………………………9 Figure 3. 3D view of single cylindrical and half-toroidal coils……………………….…..9 Figure 4. ICP simulation models with single cylindrical and half-toroidal antennas……10 Figure 5. Cut-plane depicted in red, passing through the middle section of the simulation models and used to plot the main plasma variables………………………….…………..16 Figure 6. Electron density cross-section plots for cylindrical and half toroidal coil designs……………………………………………………………………………..……..17 Figure 7. Electron density volume histogram plots for cylindrical and half toroidal coil designs…………………………………………………………………………………....18 Figure 8. Electron temperature cross-section plots for cylindrical and half toroidal coil designs……………………………………………………………………………..……..19 Figure 9. Electron temperature volume histogram plots for cylindrical and half toroidal coil designs………………………………………………………………………….……20 Figure 10. Argon ion density cross-section plots for cylindrical and half toroidal coil designs…………………………………………………………………………………....21 Figure 11. Argon ion density volume histogram plots for cylindrical and half toroidal coil designs……………………………………………………………………………….…...22 viii Figure 12. Excited argon density cross-section plots for cylindrical and half toroidal coil designs…………………………………………………………………………………....23 Figure 13. Excited argon density volume histogram plots for cylindrical and half toroidal coil designs……………………………………………………………………………….24 Figure 14. Electric potential cross-section plots for cylindrical and half toroidal coil designs……………………………………………………………………………….…...25 Figure 15. Electric potential volume histogram plots for cylindrical and half toroidal coil designs…………………………………………………………………………………....26 Figure 16. Magnetic field flux plots for cylindrical and half-toroidal coil designs.……………………………………………………………………………….......27 ix LIST OF TABLES Table 1. Collision processes included in the simulated argon discharge.………………..13 Table 2. Average of main plasma variables over the entire chamber volume…….……..26 x ABSTRACT SIMULATION OF MAGNETICALLY CONFINED INDUCTIVELY COUPLED PLASMA SINA JAVADPOUR 2017 In this work, a new parallel coil design was presented to address the need for high density inductively coupled plasmas with enhanced properties and a more uniform and consistent distribution, suitable for large-area material processing. Fluid model simulations of 3D argon inductively coupled plasma (ICP) were performed in COMSOL for the proposed coil and a conventional single cylindrical coil with the same impedance to be used as reference, to compare and evaluate the performance of this new half- toroidal parallel coil design and study its effects on the main variables of the generated plasma. Through different comparisons of the simulations results, it was shown that using the new half-toroidal coil has the advantage of a higher and more uniform power deposition over the conventional cylindrical coil, resulting in a plasma with enhanced main variables and a more even distribution than those generated by the traditional methods. These improvements in the generated plasma provide a larger effective area to be used for material processing, increasing the efficiency of the system. 1 INTRODUCTION Plasma is basically ionized gas composed of unbound positive and negative charges and is considered as the forth state of matter along with solid, liquid, and gas. Although the charges are unbound, they have interactions with each other and when they move they generate electric currents and magnetic fields, which govern their collective behavior with many degrees of freedom and give properties to plasma unlike the other states of matter. Plasma usually possesses equal positive and negative charge densities and hence is electrically neutral. Moreover, it is electrically conductive and has a strong response to electromagnetic fields. Plasma is the most abundant state of matter in the universe and forms 99.9% of its visible mass, excluding the dark matter. All matter goes to plasma state in temperatures exceeding 10000 K. Because of the unique properties of plasma, it is used for different application, some of which are: lights, displays, thrusters, spray coating, and material processing. Main plasma-assisted processes with material processing application include: 1. Physical Vapor Deposition (PVD) processes, such as Electron Beam Physical Vapor Deposition (EBPVD), Magnetron Sputtering, and Ion Sputtering. 2. Chemical Vapor Deposition (CVD) processes, such as High Density Plasma Chemical Vapor Deposition (HDPCVD) and Plasma Enhanced Chemical Vapor Deposition (PECVD). 3. Plasma Etching, such as Microwave Plasma Etching and Hydrogen Plasma Etching. 4. Plasma Cleaning. and 5. Plasma Torches used for welding and cutting parts. Plasma processes, especially CVD processes, are essential to the fabrication of microelectronics. Also, gold sputtering is often used to ground the sample for Scanning Electron Microscope (SEM) imaging. 2 Plasma is generated by the electric field directly or indirectly induced by an electrode which leads to accelerating the free electrons pre-existing in the neutral gas, making them drift and collide with the neutral atoms of the gas and ionize them. The electrons freed from the neutral atoms of the gas through the process of ionization add to the density of the plasma and lead to more ionizing collisions, through which the plasma would be sustained. The increase in the number of electrons as they drift away from one electrode to the other is known as Townsend Discharge or electron avalanche. After the plasma is sustained in a high density, the interactive species, i.e. neutral radicals, ions, and electrons will be delivered to the material being processed through drift, diffusion, and Lorentz forces to add, remove, or modify it. Industrial plasma for material processing has the following main characteristics: 1. Plasma Density, which is the number of electrons and ions per unit volume and typically in the range of 1014 m-3 to 1021 m-3. 2. Electron and Ion Temperatures (Energies). Higher electron temperatures than ion temperatures are usually desired in material processing. Since electrons have higher energies than ions and the neutral gas in material processing plasmas,
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