Large-area Production Coatings for Webs/Plasma Cleaning and Pretreatment of Large Surfaces

Tuesday, April 11, 2000 8:30 AM in Room Town & Country

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8:30 AM G5-1 Principles of Pulsed Power Discharges for Plasma Processing
M.A. Lieberman (University of California, Berkeley)
Pulse-power modulated high density discharges are under active consideration for materials processing applications. It has been claimed that such discharges can increase SiO2/Si etch selectivity, reduce aspect ratio dependent etch effects, eliminate notching and charge build-up damage of gate oxide, increase etch uniformity, increase etch and deposition rates, reduce the heat flux to the substrate, extend discharge pressure and power operating regimes, and reduce particulate formation. These discharges have a history going back to World War II. Global (volume-averaged) models of high density, low pressure discharges can provide considerable insight into the dynamics for both continuous wave (cw) and pulsed-power excitation. Chlorine and oxygen discharges are treated as benchmark examples of electronegative process gases. The particle and energy balance equations are applied to determine the charged particle and neutral dynamics. The time-average electron density can be considerably higher than that for cw discharges for the same time-average power. For chlorine, a cw discharge is highly dissociated and the negative ion density is lower than the electron density. A pulsed discharge can have the same neutral radical (Cl) flux to the walls for a reduced average power. Similar phenomenon are observed for oxygen. The analytical models are compared to more complete global model numerical solutions, to particle-in-cell computer simulations, and to experimental observations.
9:10 AM G5-3 Emergent Technologies for Large Area PVD Coating
V. Kirchhoff (FhG-FEP Dresden, Germany)
PVD-coatings on large sheets, metal strips and plastic webs are discussed and used since many years. Recently developed technologies, especially plasma activated processes, opened a fresh ground to think about new applications. The new layer stacks produced by PVD represent an outstanding supplement to existing products. It could be verified that the deposition cost are low enough in comparison to competitive technologies. Evaporation, especially by EB, is the most useful PVD process for low cost coating onto large areas. The combination of evaporation with a powerful plasma is a efficient possibility to influence the layer properties in a wide range. In the paper an overview about such emergent PVD technologies will be presented. The influence of the plasma on the layer properties will be demonstrated with some examples and applications. The high level of reactive pulsed magnetron sputtering is also a useful process for large area coating. An adapted substrate pretreatment in vacuum is essential for PVD coating. This process step includes a lot more than mere substrate cleaning. The new process technologies and available equipment’s are depicted.
9:50 AM G5-5 Design of a Magnetic Pole Enhanced Inductively Coupled Plasma Source
T. Meziani, P. Colpo, F. Rossi (European Commission Joint Research Centre, ITALY)
In the last decade, the ICs size shrinking has led to the development of a new generation of plasma source, enabling the generation of high plasma density with low ion energy: the Inductively Coupled Plasma sources (ICPs). ICP sources are widely used in semiconductor industry for their simple design, process flexibility and their high throughput. At present, the new challenge to be addressed is the scaling up of the plasma sources to enable large area specimen processing. Indeed, the semiconductor industry is now experiencing the transition from 200 to 300 mm wafer technology and plans the transition to 450 mm for 2010. On the other hand, the interest of the FPDs industry for larger area treatments is obvious for the flat video screen fabrication. The paper presents the design of a novel plasma source, enabling large area plasma treatment: the magnetic pole enhanced ICP (Ma-ICP). The plasma source consists of a special arrangement comprising a special inductor embedded in a magnetic pole to create a concentrated and homogeneous magnetic field over large areas. We demonstrated that the plasma uniformity at laboratory scale (30cm) is better than 5%, i.e. 2 times better than the uniformity obtained with the classical ICP source on the same area. Furthermore, the obtained plasma characteristics (i.e. high densities of reactive species, low and controllable ion energy, wide pressure range) make the new source extremely promising for a whole range of processes such as large scale deposition, etching and plasma treatments.
10:10 AM G5-6 Improving the Durability of Optical Coatings Through Pulsed Magnetron Sputtering
P.J. Kelly, P.S. Henderson, R.D. Arnell (University of Salford, United Kingdom)
The reactive magnetron sputtering of optical coatings, such as low-E coatings, onto glass for automotive and architectural applications is a well-established technique. However, these coatings can be prone to damage by abrasive particles encountered during service. Consequently, it is often necessary to use either a double-glazed product, where the coating is on an internal surface, or a laminated product, where the coated surface is encapsulated. Improving the durability of the functional film would remove the need to protect the film, and offer the potential to develop lighter, cheaper, less complex products. @paragraph@ To address the above problem, a study has been carried out in which films of alumina, titania and silica have been deposited and characterised in terms of structure, hardness, adhesion and wear resistance. The coatings were deposited by both DC and pulsed DC reactive magnetron sputtering. Using a range of different power delivery systems, it was possible to vary a number of deposition parameters, including pulse frequency (over the range 20-350kHz); duty factor (1-0.5); and reverse voltage (10-20%). Coating properties were analysed using nanoindentation, scratch adhesion and pin-on-disc wear testing techniques. Generally, the pulsed DC coatings exhibited a marked superiority over the DC coatings in terms of their structures and properties. For example, the critical loads of titania films deposited by pulsed DC were found to be some 30% higher than the values obtained for similar DC films. Optimum operating conditions for improved film properties have been identified through a systematic study of the pulsed DC deposition process
10:30 AM G5-7 The Pulsed-plasma Activated Treatment (PAT) Process - Fundamentals and Applications
F.-H. Roegner, J. Faber, B. Scheffel (FhG-FEP Dresden, Germany)
Metallic strips and sheets are covered with contamination's like working layers, oxides and residuals of oil, water and gas. For further PVD processing like Electron Beam High Rate Deposition (EBHD) an in-line vacuum pre-treatment without vacuum interruption is required to get rid of hindering contamination layers. To take the advantage of the low costs of EBHD due to the very high deposition rate, the pre-treatment must be adapted to the necessary high substrate speed. The Pulsed-plasma Activated Treatment (PAT) process is a very flexible, easily adaptable and extremely fast tool for cleaning and preparing a metal surface for PVD coating processes. By using a pulsed gas discharge in the medium frequency range the process is very stable and suitable for removing even insolating layers like oil films and thick oxide layers with high rates. In connection with an optical plasma monitoring system the process can be quickly controlled and optimized. For special purposes the additional usage of reactive gases like oxygen or hydrogen is possible, without disturbing the gas discharge stability. One of our applications is the pre-treatment of strip steel for the EBHD. The magnet field enhanced PAT arrangement can be infinitely variable adopted to a wide range of strip widths and thickness. The pre-treatment process can be monitored and controlled in-situ by an optical monitoring system. Several investigations have been carried out to characterize and to optimize the PAT arrangement and parameters.
10:50 AM G5-8 Comparison of Microstructure and Properties of SiO@sub 2@ Coatings Deposited by Reactive Pulsed Magnetron Sputtering (PMS) and by Hollow Cathode Activated EB-Evaporation (HAD)
O. Zywitzki (Fraunhofer Institut Elektronenstrahl- und Plasmatechnik, Germany); H. Sahm (Fraunhofer Institut Elektronenstrahl- und Plasmatechnik FEP, Germany); M. Krug, H. Morgner, M. Neumann (Fraunhofer Institut Elektronenstrahl- und Plasmatechnik, Germany)
SiO@sub 2@ is widely used as a coating material due to its interesting properties like low refractive index, relative high hardness, high resistance against abrasion wear and good barrier properties. The presented paper gives a comparison of microstructure and layer properties between SiO@sub 2@ coatings deposited by reactive pulsed magnetron sputtering (PMS) and by hollow cathode activated EB evaporation (HAD). The specific advantages and drawbacks of both process types in respect of microstructure, layer properties and last but not least productivity of the coating process are discussed.@paragraph@ SiO@sub 2@ coatings deposited by HAD process at high deposition rates of about 600 nm/s have a relative low hardness of about 1,7-4,1 GPa, a Young's Modulus between 15 and 42 GPa and a low intrinsic stress. These results correspond to the comparable low packing density of the coatings. A substantial advantage of the HAD process is the relative low specific thermal load of the substrate which allows the coating of temperature sensitive plastic materials with some micrometers thick abrasion resistant layers. The Taber Abraser test shows remarkable good results for SiO@sub 2@ coatings on plastic substrates. Probably, the porosity is a reason for a favorable abrasion mechanism, leading to a higher dispersion of crack energy. The liability of cracking under mechanical load can be further reduced by introduction of hexamethyldisiloxane (HMDSO) in the plasma activated deposition process.@paragraph@ In contrast the SiO@sub 2@ coatings deposited by pulsed magnetron sputtering at deposition rates of about 5 nm/s have a much higher hardness of 8 GPa, a Young's Modulus of 70 GPa and more glass like properties. The high density of the coatings is the reason for the excellent environmental stability in the case of thin layers in optical applications. According to the high energy of condensing particles a higher specific thermal load of substrate and higher intrinsic stresses in the coatings have to be taken into account.
11:10 AM G5-9 Deposition of Oxide Films for Optical Applications by Reactive Gas Flow Sputtering (RGFS)
Th. Jung, M. Höfer (Fraunhofer-Institut für Schicht- und Oberflächentechnik (IST), Germany); A. Jung, H.-U. Kricheldorf, C. Steinberg ()
For some important oxide film materials - widely used especially in optical applications - conventional magnetron sputtering suffers from low deposition rates and difficult process controlling. The recently developed technique of Reactive Gas Flow Sputtering (RGFS) is able to circumvent both the rate and the stability problem owing to it's unique principle of operation. An additional advantage of RGFS is it's excellent target utilization of >60%. @paragraph@ For the large area deposition of high quality oxide films (Al@sub 2@O@sub 3@, TiO@sub 2@, ZrO@sub 2@, ITO, ...) a new generation of linear RGFS sputter sources has been developed. A target length of 1000 mm (39.4'') has been realized and further upscale of the process is easily attainable. Above an input power threshold which depends on material and geometry of the targets the hollow cathode glow discharge becomes distributed uniformly over about 90% of the length of the sputter source. A smooth decrease of the discharge occurs only at the ends of the target gap due to an increased loss of charge carriers. The homogeneity of the film thickness is mainly determined by the proper design of the gas flow system. A contamination of the films by residual gases can be effectively suppressed by an optimized gas flow guiding and an appropriate heat control of the housing and the surrounding of the sputter source. Due to the low argon content of the layers (<0.01%) the density and the refractive index of the oxide films are close to the values of the corresponding bulk materials. Indium tin oxide (ITO) films with high electrical conductivity (10...150 @ohm@ per square) and excellent transparency have been deposited even at low substrate temperatures (T<80 deg. Celsius).
11:30 AM G5-10 PVD Coatings onto Metallic Sheets and Strips - New Developments and Results
Ch. Metzner, B. Scheffel, F.-H. Roegner (FhG-FEP Dresden, Germany)
PVD coatings of metallic sheets and strips, especially produced by electron beam high-rate deposition (EBHD), are well known since many years. But up to now the application on an industrial scale is very limited. One of the reasons are the costs and the progress of conventional processes like ECD or hot dipping in the last ten years. New fields of application have been opened by a combination of the EBHD with additional dense plasmas. On this ground we developed some new PVD processes and layer stacks-based e.g. at titanium, stainless steel, aluminum, silicon oxide, iron and magnesium-onto metallic sheets and strips. The paper presents some examples for new layer stacks their properties and applications. We investigated the new processes under industrial like conditions concerning the most important deposition parameters like the deposition rate. The coating of metallic sheets and strips works usually in an in-line equipment. Also in the case of PVD in-line coating is preferred. It is a sophisticated task to upscale the different processes like pre-treatment, EBHD, plasma activation and after treatment for in-line running. FEP has now the possibility to produce coatings under industrial like conditions in a new in-line deposition equipment for metallic strips and sheets with a width up to 500 mm and a substrate speed up to 1 meter per second.
11:50 AM G5-11 Coatings on Glass
G. Wallace, R.J. Hill (BOC Coating Technology)
A brief history of glass coating brings the technology up to date. The equipment used to coat glass substrates as large as 6 x 3.2 meters continuously with less than a one-minute cycle time is described indicating the controlling factors involved. The composition and properties of low-E architectural layers and also anti-reflective stacks used for flat panel and CRT display uses are presented. Finally, on going developments against future needs are reviewed.