ICMCTF2005 Session G5: Large Area Production Coatings for Webs, Plasma Cleaning and Pretreatment of Large Surfaces
Tuesday, May 3, 2005 8:30 AM in Room Royal Palm 1-3
G5-1 Plasma and Ion Sources in Large Area Coatings: A Review
A. Anders (Lawrence Berkeley National Laboratory)
The efficient deposition of high-quality coatings often requires controlled application of excited or ionized particles. These particles are either condensing (film-forming) or assisting by providing energy and momentum to the film growth process, resulting in densification, sputtering/etching (often preferential), stress modification etc. In this review, the technical means are surveyed enabling large area application of charged and/or excited particles. Characteristics and differences between plasma and ion sources are explained and a number of examples are given, including linear closed-drift anode-layer sources and hollow-cathode sources. Of great interest are uniformity issues, contamination control and reduction, and the interaction between these sources and other components of the deposition system, like magnetron sputter sources. The review is concluded by considering pulsed plasma and pulsed bias techniques, and in particular large-area plasma immersion techniques. Although substrates are commonly insulating, plasma immersion techniques can be used for large-area surface preparation and deposition, e.g. of hydrogenated diamond-like carbon (a-C:H). @paragraph@ This work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Building Technology, Department of Energy under Contract No. DE-AC03-76SF00098.
G5-3 Flexible Displays and Stable High Efficiency Four Terminal Solar Cells using Thin Film Silicon Technology
A. Madan (MV Systems Inc. and Colorado School of Mines)
Amorphous silicon (a-Si:H) materials are used in diverse applications such as in active matrix displays, solar cells etc.. These types of devices are constructed as multi-layers in a multi-chamber(or cluster tool)system to avoid cross contamination. In this, each process chamber is separated from others via gate valves leading to optimal performance of an electronic device. The planar substrate, such as glass, is transported via a robotic arm from one chamber to another.@paragraph@We present a new type of system architecture to manufacture electronic devices (thin film silicon transistor and solar cells) on flexible substrates and propose a reel-to-reel cassette suitable for use in a cluster tool system. In this, a cassette housing a flexible material is moved to the appropriate location over the process (eg. PECVD) zone. The cassette is engaged for movement of the flexible material from one reel to another. At the end of deposition, the flexible material is returned to its original reel and locked into position and disengaged for transport; after processing in one chamber, the entire cassette is transported to the next chamber in a similar fashion to that for a rigid substrate (i.e using a robotic arm). Hence cross contamination can be eliminated and high performance devices be achieved. @paragraph@We report on the development of stable amorphous Si and nano-crystalline Silicon (nc-Si) tandem junction solar cell constructed as a four-terminal(4-T)device,in which the current matching constraint is released from each constituent cell. We report that by merely joining two cells constructed on separate pieces of glass, we have achieved conversion efficiency,@eta@@>=@9%. We show that by constructing the 4-T device on either side of the glass,@eta@@>=@12% can be achieved. Lastly we discuss the use of pulsed PECVD technique which should be able to improve the properties of nc-Si material thus providing a road map to @eta@@>=@16% on rigid and flexible substrates.
G5-5 Properties of Ag-Based Low-E Films Deposited by High Power Pulse Magnetron Sputtering
A. Pflug, F. Ruske, M. Siemers, W. Wemer, B. Szyszka (Fraunhofer Institute for Surface Engineering and Thin Films, Germany); D.J. Christie (Advanced Energy Industries, Inc.); M. Geisler (Applied Films GmbH & Co.KG, Germany)
The high power pulse magnetron sputtering (HPPMS) is a novel process technology for large area magnetron sputtering. HPPMS allows for a high fraction of ionized target material and thus for growth conditions similar to pulsed laser deposition and filtered arc deposition. This paper is on the influence of HPPMS process conditions on the properties of thin Ag films for insulator-metal-insulator Low-E films. Ag films with film thickness in the range of 1 ... 10 nm have been deposited on ZnO coated substrates by HPPMS in-line magnetron sputtering using a cathode of 750 mm length and 88 mm width for different peak power up to approx. 600 W/cm@super 2@. For high ionization of the sputtered material, we observe percolation characteristics of the Ag film similar to findings by E. Byon et al., Applied Physics Letters 82 (2003) 1634 for the comparison of Ag percolation by filtered arc and conventional magnetron sputtering. We report on the characterization of these films and of the full low-E stack by optical spectroscopy and conductivity measurements as well as by X-ray reflectometry and X-ray diffraction.
G5-6 Plasma Treatment of Metallurgical Surfaces
E.S. Senokosov (AOZT Klaster, Russia); G. Naumann (GFD Innovation und Plasmatechnik, Russia); H. Hartmann (FQZ Brandenburg GmbH, Germany); A.E. Senokosov (GFD Innovation und Plasmatechnik, Russia)
The surface quality of metallic materials with its technical functionality and aesthetic feature to a considerable degree determines the expected product characteristics by the customer. Therefore a multiplicity of different chemical-physical cleaning procedures of the surface is applied during the manufacturing process. For the removal of normal surface impurities and defects traditionally mechanical or thermal procedures as well as chemical and electro-chemical methods are in application. Although the plasma technology represents already an established procedure for the fine surface cleaning of materials, its practical application is limited yet to the surface finishing. The technological benefits of low pressure plasma cleaning process concerning the different metallic substrates, the constant cleaning quality, the low energy consumption and the ecological advantages were the starting point for investigations to adapt this process to the harsh production conditions of metallurgical products. The investigations were carried out on a plasma cleaning pilot line and covered the cleaning of different steel grades as well as non ferrous materials in the state as hot and as cold rolled. The results of the experimental trails show that the configuration of the plasma treatment device can be adapted to the different cleaning tasks, allowing the complete removal of heavy scale and oxides even in case of high alloyed Ni and Cr-Ni steels including inter grain oxidation. The plasma cleaning process has an impact on the characteristics of the surface and near surface area with changes of the surface roughness, the mechanical properties and chemical composition. Beneficial influence of intensive plasma treatment on corrosion resistance, adhesion and some other properties of metallurgical products was observed.
G5-7 Transparent Abrasion Resistant Layers on Plastic and Metal Substrates by Plasma Activated High Rate Deposition
H. Morgner, O. Zywitzki, F.-H. Roegner, Chr. Metzner (Fraunhofer Institut fuer Elektronenstrahl- und Plasmatechnik Germany)
Plastic and metal materials have different but excellent and valuable properties making them to wide spread materials in large number of applications. But both materials lack high surface hardness in different degree. For spreading to more application harder surface resulting in improved mare resistance without essential changing the optical properties is requested. Transparent oxide layers on large area substrates like plastic films and sheets and metal foils and sheets can be deposited by high rate plasma activated deposition technology with high productivity. Application of HAD (Hollow cathode arc Activated Deposition) process with EB evaporation of silicon dioxide and organic modification of layer material by introduction of monomer in the evaporation process results in excellent adaptation of oxide layers to plastic and metal substrates as well. For plastic substrates like PC or PET the tolerable temperature rise in deposition process is strongly restricted to maximum temperature 80 to 160 @super o@C. Otherwise the glass transition temperature would be exceeded or the mechanical stability of substrate gets lost by drop of elastic modulus. Despite the low condensation temperature, the plasma activation results in amorphous layers with glassy and dense appearance in SEM micrograph. The layer hardness ranges between 2 to 3 GPa measured on layers on plastic substrates. The organic modification results in improved elasticity essential for crack-free performance of layers despite the mismatch in thermal expansion coefficient. Coating of metal substrates gives much more freedom for process parameters. With higher substrate temperature and much higher degree of plasma activation the SiO@sub x@ layer hardness can be improved to 15 GPa overstepping the hardness of bulk SiO@sub 2@. Characteristically, the ratio O to Si in at% decreases to 1,2 for hard layers. A process window exists with absorption coefficient below 0,01 for hard layers.
G5-8 On-Line Process Control by X-Ray Fluorescence
J. Piltz (Amtec GmbH, Germany)
The effective control of coating process requires to ascertain online information on the current coating thickness and the stoichiometry. New instruments for energy dispersive X-ray fluorescence analysis (EDXRF) allow to measure single-, multi- or alloy layers in the thickness range from 20 nm to 50 Âµm on different substrates (metal, plastics). It is necessary to minimize the statistical error for a short measuring period. The X-ray source and the routing of the X-ray beam can be designed with help of a simulation calculation of the coating layer to get a maximum measuring effect. The detection system has to process the high counting rate of fluorescence quanta with a high energy resolution. Automatic measuring of a reference sample allows to self calibrate the system over a long time to get a low drift of parameters of the measuring system. To realize the different measuring tasks some features are available, for instance the possibility to traverse the system for coating profiles and to analyze light elements in very thin layers. The measuring system is protected against the influence of coating process through metal dust, temperature (up to 500°C), electrical and magnetic fields. Some typical measuring jobs will be presented.
G5-9 Properties of TiO@sub 2@ Layers Deposited onto Large Areas by Reactive Plasma-activated High-Rate Electron Beam Evaporation
Chr. Metzner, Th. Modes, B. Scheffel, O. Zywitzki (Fraunhofer Institut fuer Elektronenstrahl- und Plasmatechnik, Germany); E. Reinhold, Chr. Steuer (Von Ardenne Anlagentechnik GmbH Dresden, Germany)
Reactive electron beam evaporation enables the deposition of TiO@sub 2@ layers at high deposition rates. However layers deposited without additional ion bombardment are often characterized by porous columnar microstructure with low refractive index. Another drawback is the hygroscopic behavior under humid conditions which is linked with a drift in optical properties. Ion assisted deposition can be used for improvement of layer properties. The influence of process parameters substrate temperature (between 100 and 400@super o@C) and plasma activation on structure and properties of TiO@sub 2@ layers deposited by reactive electron beam evaporation at high deposition rates between 40 and 70 nm/s onto steel sheets was investigated. For plasma activation a spotless arc discharge (Spotless arc Activated Deposition - SAD-process) was used. XRD investigations have revealed that structure of all layers deposited at substrate temperature below 150@super o@C is amorphous. At a substrate temperature above 200@super o@C layers with crystalline phases were deposited. It could be shown that the degree of substrate ion bombardment controls the formation of anatase or rutile phase. Furthermore a drastic influence of plasma activation on the properties of the layers could be found. For instance the hardness is raised from 2.0 to 6.7 GPa at substrate temperature below 150@super o@C. The formation of the rutile phase in layers deposited with plasma activation is linked with a further increase of hardness up to 12 GPa. With powerful plasma activation a drastic raise of refractive indexes to values between 2.30 and 2.58 can be reached too. Measurements of the contact angle show a promising photoinduced (super) hydrophilicity of anatase layers. Therefore these layers should be well-suited as coatings with self-cleaning or antifogging properties. At substrate temperature below 150°C the plasma activation enables the deposition of dense, high-refractive layers at very high deposition rates for applications as optical layers.