Bulletin of the American Physical Society
65th Annual Gaseous Electronics Conference
Volume 57, Number 8
Monday–Friday, October 22–26, 2012; Austin, Texas
Session UF4: Plasma Deposition and Photovoltaic Applications |
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Chair: Masaharu Shiratani, Kyushu University Room: Salon DE |
Friday, October 26, 2012 9:00AM - 9:30AM |
UF4.00001: Investigation of high power impulse magnetron sputtering (HIPIMS) discharge using fast ICCD camera Invited Speaker: Ante Hecimovic High power impulse magnetron sputtering (HIPIMS) combines impulse glow discharges at power levels up to the MW range with conventional magnetron cathodes to achieve a highly ionised sputtered flux. The dynamics of the HIPIMS discharge was investigated using fast Intensified Charge Coupled Device (ICCD) camera. In the first experiment the HIPIMS plasma was recorded from the side with goal to analyse the plasma intensity using Abel inversion to obtain the emissivity maps of the plasma species. Resulting emissivity maps provide the information on the spatial distribution of Ar and sputtered material and evolution of the plasma chemistry above the cathode. In the second experiment the plasma emission was recorded with camera facing the target. The images show that the HIPIMS plasma develops drift wave type instabilities characterized by well defined regions of high and low plasma emissivity along the racetrack of the magnetron. The instabilities cause periodic shifts in the floating potential. The structures rotate in ExB direction at velocities of 10 kms$^{-1}$ and frequencies up to 200 kHz. The high emissivity regions comprise Ar and metal ion emission with strong Ar and metal neutral emission depletion. A detailed analysis of the temporal evolution of the saturated instabilities using four consequently triggered fast ICCD cameras is presented. Furthermore working gas pressure and discharge current variation showed that the shape and the speed of the instability strongly depend on the working gas and target material combination. In order to better understand the mechanism of the instability, different optical interference band pass filters (of metal and gas atom, and ion lines) were used to observe the spatial distribution of each species within the instability. [Preview Abstract] |
Friday, October 26, 2012 9:30AM - 9:45AM |
UF4.00002: Reactive high power impulse magnetron sputtering J.T. Gudmundsson, F. Magnus, T.K. Tryggvason, O.B. Sveinsson, S. Olafsson Here we discuss reactive high power impulse magnetron sputtering sputtering (HiPIMS) [1] of Ti target in an Ar/N$_2$ and Ar/O$_2$ atmosphere. The discharge current waveform is highly dependent on both the pulse repetition frequency and discharge voltage. The discharge current increases with decreasing frequency or voltage. This we attribute to an increase in the secondary electron emission yield during the self-sputtering phase of the pulse, as nitride [2] or oxide [3] forms on the target. We also discuss the growth of TiN films on SiO$_2$ at temperatures of 22-600 $^{\circ}$C. The HiPIMS process produces denser films at lower growth temperature and the surface is much smoother and have a significantly lower resistivity than dc magnetron sputtered films on SiO$_2$ at all growth temperatures due to reduced grain boundary scattering [4].\\[4pt] [1] J. T. Gudmundsson, N. Brenning, D. Lundin and U. Helmersson, J. Vac. Sci. Technol. A, {\bf 30} 030801 (2012)\\[0pt] [2] F. Magnus, O. B. Sveinsson, S. Olafsson and J. T. Gudmundsson, J. Appl. Phys., {\bf 110} 083306 (2011)\\[0pt] [3] F. Magnus, T. K. Tryggvason, S. Olafsson and J. T. Gudmundsson, J. Vac. Sci. Technol., submitted 2012\\[0pt] [4] F. Magnus, A. S. Ingason, S. Olafsson and J. T. Gudmundsson, IEEE Elec. Dev. Lett., accepted 2012 [Preview Abstract] |
Friday, October 26, 2012 9:45AM - 10:00AM |
UF4.00003: Control Capabilities of Reactive Sputter Deposition Process via ICPs Driven by Low-Inductance Antenna for Large-Area Formation of Thin Film Devices Yuichi Setsuhara, Kosuke Takenaka, Akinori Ebe Novel plasma-enhanced reactive sputter-deposition system has been developed with a new type of low-inductance antenna (inner-type LIA) consisting of an RF antenna conductor with a length much shorter than the RF wavelength, which is embedded in a hall region dug in the chamber wall and the dielectric window plate for insulation. This new type of the reactive sputter-deposition system has been developed for enhancement of sputter discharge and excellent control of reactivity during film growth. The ICP-enhanced sputter system has been applied to film formations of micro-crystalline silicon (intrinsic layer) and transparent amorphous oxide semiconductor, a-InGaZnO4 (a-IGZO), aiming at low-temperature formation of high-quality functional films for development of next-generation flexible devices. The newly developed process can offer independent control of the flux ratio of the reactive species (ions and radicals) to the deposited species sputtered out of the target. With this new method, micro-crystalline silicon films with crystallinity of 74{\%} and a-IGZO films with mobility as high as 18 cm$^{2}$(Vs)$^{-1}$ have been successfully formed without substrate heating. Furthermore, for development of large-area deposition, uniformity control capabilities with a linear rectangular sputter target with 500 mm length have been examined via variation of power deposition profiles with multiple LIAs. [Preview Abstract] |
Friday, October 26, 2012 10:00AM - 10:15AM |
UF4.00004: Source gas depletion in narrow metal tube during internal DLC coating with microwave-excited high-density near plasma Ryosuke Matsui, Hiroyuki Kosaka, Noritsugu Umehara In internal DLC (Diamond-Like Carbon) coating to mm-sized narrow metal tubes by using MVP (Microwave-sheath Voltage combination Plasma) method, axially uniform distribution of film thickness can be obtained by repeating the depletion and homogenization of source gas in a coated tube during plasma-on time $T_{on}$ and plasma-off time $T_{off}$ of pulsed plasma generation, respectively. DLC was deposited to the inner surface of a stainless-steel tube 4.4 mm in inner diameter and 50 mm in length with small holes of \textit{$\Phi $}=0.4 mm fabricated at every 10 mm, where the flow rates of Ar and methane were controlled to be 14 and 2 sccm, respectively, at a total gas pressure of 80 Pa. A pulsed negative voltage of --200 V was applied to the tube at a pulse frequency of 10 Hz and duty ratio of 3.2{\%}, synchronizing a pulsed injection of 2.45-GHz microwaves at the same pulse frequency ($T_{on}$=3.2 ms and $T_{off}$=96.8 ms). The high-speed camera image showed that the emission (696, 706 nm) from Ar atom was approximately constant during plasma-on time. On the other hand, the emission (468-474 nm) from C$_{2}$ dimer was decreased until $T_{on}$ =1.5 ms, and then converged in a constant value; this is ascribed to the consumption of CH$_{4}$ gas which is considered to be a main source of C$_{2}$ dimer formation. [Preview Abstract] |
Friday, October 26, 2012 10:15AM - 10:30AM |
UF4.00005: Fabrication of graphene-based films using remote plasma CVD Mineo Hiramatsu, Ryosuke Tsukada, Yohei Kashima, Masateru Naito, Hiroki Kondo, Masaru Hori Plasma-enhanced CVD (PECVD) employing methane/hydrogen gases has been used to grow diamond, diamond-like carbon, and carbon nanotubes. In the case of microwave PECVD with methane/hydrogen system without catalyst nanoparticles at temperatures of 700--850 $^{\circ}$C, where the substrate is exposed to the plasma, vertical nano-graphenes and carbon nanoflakes have been easily grown even on Cu substrate due to the ion bombardment and local electric field forces. In this work, we demonstrate the synthesis of planar few-layer graphene-based film using PECVD with remote plasma configuration. In the case using microwave plasma of cylindrical resonant cavity type, by simply installing grounded grid over the substrate plate for obtaining remote plasma configuration, we have successfully fabricated graphene-based films on Cu substrate, which was confirmed by the Raman spectrum and SEM image of deposit. Similar method will be applied to other plasmas such as low-pressure inductively coupled plasma, in order to verify the effectiveness of remote plasma configuration for the growth of planar graphene using PECVD technique. We will discuss the planar graphene growth mechanism in terms of precursors and their surface reaction. [Preview Abstract] |
Friday, October 26, 2012 10:30AM - 10:45AM |
UF4.00006: A plasma-enhanced close-spacing sublimation (PECSS) device for photovoltaic thin-film modification Garrett Metz, Len Mahoney, John Williams, Drew Swanson, Walajabad Sampath A plasma-enhanced, close-spacing sublimation (PECSS) device has been developed for improving CdS deposition on a transparent conductive oxide (TCO)-coated substrate that is part of the plasma production circuit. This unique device and process method makes possible the elimination of pin holes in the CdS transmission layer. In addition the process has been used to incorporate oxygen-dopants within the CdS layer, reducing absorption, and thereby increasing cell efficiency. We review the spatial uniformity of the ion current flux on the TCO-coated substrate when operating with Ar/O$_{2}$ and N$_{2}$/O$_{2}$ by means of in situ surface probes fashioned by laser-scribing strips in the TCO coating. Bulk plasma features of the PECSS device are also reviewed including electron energy and plasma potential. Process utility, modeling, and scaling of the PECSS device are reviewed for pressures of 40-200 mTorr and surface areas of 60 -- 1700 cm$^{2}$. [Preview Abstract] |
Friday, October 26, 2012 10:45AM - 11:00AM |
UF4.00007: Investigations of capacitively coupled radio frequency hydrogen and hydrogen/silane discharges Sebastian Mohr, Edmund Sch\"ungel, Julian Schulze, Uwe Czarnetzki One of the most important challenges in optimizing capacitively coupled radio frequency discharges for applications such as the deposition of thin films is gaining the independent control of flux and energy of ions and reactive species at the surfaces. This independent control can be obtained by using electrically asymmetric discharges which use two consecutive harmonics to excite the plasma; the ion energy can be controlled by the phase between the two frequencies while the flux stays constant. We conduct two-dimensional simulations of such discharges using the simulation tool Hybrid Plasma Equipment Model by Mark Kushner [1]. The focus of our investigations lies on hydrogen and hydrogen/silane plasmas at pressures up to several 100 Pascals as they are used in the production of solar cells. This presentation deals with the question, how characteristics of these discharges such as field reversals influence the independent control of ion energy and flux.\\[4pt] Funded by the German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (0325210B).\\[4pt] [1] M. Kushner 2009 \textit{J. Phys. D} \textbf{42} 194013 [Preview Abstract] |
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