Bulletin of the American Physical Society
61st Annual Gaseous Electronics Conference
Volume 53, Number 10
Monday–Friday, October 13–17, 2008; Dallas, Texas
Session CT3: Magnetically-Enhanced and Related Plasmas |
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Chair: Pascal Chabert, CNRS-Ecole Polytechnique, France Room: Addison Room |
Tuesday, October 14, 2008 10:00AM - 10:15AM |
CT3.00001: Investigations of Magnetically Enhanced RIE Reactors with Rotating Magnetic Fields Natalia Yu. Babaeva, Mark J. Kushner In Magnetically Enhanced Reactive Ion Etching (MERIE) reactors, a magnetic field parallel to the substrate enables higher plasma densities and control of ion energy distributions. Since it is difficult to make the B-field uniform across the wafer, the B-field is often azimuthally rotated at a few Hz to average out non-uniformities. The rotation is slow enough that the plasma is in quasi-equilibrium with the instantaneous B-field. For the pressures (10's mTorr or less) and B-fields (10's - 100's G) of interest, electrons are magnetized whereas ions are usually not. The orientation and intersection of the B-field with the wafer are important, as intersecting field lines provide a low resistance path for electron current to the substrate. We report on a modeling study of plasma properties in MERIE reactors having rotating B-fields by investigating a series of quasi-steady states of B-field profiles. To resolve side-to-side variations, computations are performed in Cartesian coordinates. The model, \textit{nonPDPSIM}, was improved with full tensor conductivities in the fluid portions of the code and v $\times $ B forces in the kinetic portions. Results are discussed while varying the orientation and strength of the B-field for electropositive (argon) and electronegative (Ar/C$_{x}$F$_{y}$, Ar/Cl$_{2})$ gas mixtures. [Preview Abstract] |
Tuesday, October 14, 2008 10:15AM - 10:30AM |
CT3.00002: ABSTRACT WITHDRAWN |
Tuesday, October 14, 2008 10:30AM - 11:00AM |
CT3.00003: On the Plasma Parameters in the High Power Impulse Magnetron Sputtering Discharge (HiPIMS) Invited Speaker: The development of ionized physical vapor deposition (IPVD) was mainly driven by the formation of metal and nitride thin films into deep, narrow trenches and vias that are essential in modern microelectronics. More recently, the control of the ion energy and direction of the deposition species has proved to be an important physical tool in the growth process of new materials and new structures. Over the past few years, various ionized sputtering techniques have appeared that show a high degree of ionization of the sputtered atoms, in the range 50 -- 90\% \footnote{U. Helmersson, M. Latteman, J. Bohlmark, A. P. Ehiasarian, and J. T. Gudmundsson, Thin Solid Films {\bf 513}(2006) 1-24}. This is often achieved by the application of a secondary discharge to a magnetron sputtering discharge, either inductively coupled plasma source (ICP-MS) or a microwave amplified magnetron sputtering. High power impulse magnetron sputtering (HiPIMS) is a more recent sputtering technique that utilizes ionized physical vapor deposition (IPVD) \footnote{U. Helmersson, M. Lattemann, J. Alami, J. Bohlmark, A.P. Ehiasarian, and J.T. Gudmundsson, Proceedings of the 48th Annual Technical Conference of the Society of Vacuum Coaters, April 23-28, 2005, Denver, CO, USA, p.458}. High density plasma is created by applying a high power pulses to a conventional planar magnetron sputtering discharge. The pulse power density is in the range 1 -- 3 kW/cm$^2$, the pulse frequency 50 -- 500 Hz and pulse length 50 -- 500 $\mu$s. Measurements of the temporal and spatial behavior of the plasma parameters indicate peak electron density of the order of 10$^{19}$ m$^{-3}$, that expands from the target with a fixed velocity that depends on the gas pressure \footnote{J.T. Gudmundsson, J. Alami, and U. Helmersson, Surf. Coat. Technol. {\bf 161} (2002) 249 - 256}. The high electron density results in a high degree of ionization of the deposition material. Fractional ionization of the sputtered material has been measured to be over 90\% \footnote{J. Bohlmark, J. Alami, C. Christou, A. P. Ehiasarian and U. Helmersson, J. Vac. Sci. Technol. {\bf 23} (2005), 18-22}. This is important since ions are controllable with respect to energy and direction as they arrive to the growth surface. The spatial and temporal variation of the plasma parameters, electron density, plasma potential, and electron and ion energy, in a HiPIMS discharge are explored. The plasma physics of the HiPIMS will be discussed as well as some of the applications of the HiPIMS technique. [Preview Abstract] |
Tuesday, October 14, 2008 11:00AM - 11:15AM |
CT3.00004: \textit{IPD} -The Use of Impulse Plasma in Surface Engineering Krzysztof Zdunek It is evident that impulse plasma ensures both the highest level of nonequilibrity and highest level of vapour ionisation. These conditions seemed to be especially suitable for synthetizing the phases with high energetic barrier of nucleation process. In our methods, called by us as the \textbf{\textit{I}}mpulse \textbf{\textit{P}}lasma \textbf{\textit{D}}eposition (\textbf{\textit{IPD}}) the impulse plasma is generated and accelerated in a coaxial accelerator. The only source of electric energy in the plasma process is condenser battery charged to the voltage of order of kVs. During the discharge of condensers individual plasmoids are being accelerated in the coaxial generator by the Ampere force to the speed of the order of 10$^{4}$ ms$^{-1}$ and directed to the non-heated substrate. The most characteristic feature of the is that the synthesis proceeds in the impulse plasma itself, with the participation of ions. The crystallization on ions (ionization degree of the impulse plasma is equal to 100{\%}) makes individual plasmoids to be strongly enriched rather in clusters or particles agglomerates with dimensions of order of single nms than the atoms. Because of the very short life time of plasmoids (approx. 10$^{-4}$ sec each) the surface coalescence of particles delivered to the substrate has a limited character. As a consequence the material of the layer has nanocrystalline, globular morphology. [Preview Abstract] |
Tuesday, October 14, 2008 11:15AM - 11:30AM |
CT3.00005: Practical helicon sources using permanent magnets Francis F. Chen Helicon sources are known for efficient conversion of RF energy into plasma density, but the need for a large electromagnet has impeded commercial acceptance. A novel use of permanent magnets, in which the plasma is placed below, rather than inside, a ring magnet allow the plasma to be ejected toward the substrate. The dimensions of a single source and its magnet have been optimized by computation and tested experimentally. For large area coverage, a multiple-source array has been designed and tested. In this case, RF circuitry and coupling present problems that have been solved. Measurements show that an 8-tube module should produce 10$^{12}$/cm$^3$ density 7'' below a source only 6'' in height with 2-3{\%} uniformity. Stacked modules can cover arbitrarily large substrates with this new paradigm. [Preview Abstract] |
Tuesday, October 14, 2008 11:30AM - 11:45AM |
CT3.00006: Time and space-resolved measurements of the neutral gas density in a helicon reactor by TALIF Laurent Liard, Ane Aanesland, Jacques Jolly, Jean-Luc Raimbault, Pascal Chabert Contemporary plasma reactors used for plasma processing or space plasma propulsion (Inductively Coupled or Helicon plasmas for instance) are characterized by a high electronic density. In these reactors, the electronic pressure can be as high as the neutral pressure, resulting in neutral depletion effects in the centre of the discharge. This phenomenon has been recently studied both theoretically (using fluid models\footnote{J.-L. Raimbault \textit{et al}, \textbf{PoP}, 2007$, 14$, 013503} and experimentally.\footnote{A. Aanesland \textit{et al}, \textbf{Appl. Phys. Lett.}$, $2007$, 91$, 121502}$^,$\footnote{D. O'Connell \textit{et al}, \textbf{J. Phys. D}$, $2008$, 41$, 035208} In this presentation, we are interested in the dynamics of this phenomenon. By using a two photon laser induced fluorescence (TALIF) diagnostic in Xenon gas, radial measurements of the Xenon ground state density at different times are performed. We have studied both the ignition phase, and the afterglow relaxation. It appears, as expected, that the depletion in the centre occurs in a short time-scale, typically in the millisecond range. However, a longer timescale effect has also been observed, due to a change in the pumping speed. [Preview Abstract] |
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