ICMCTF2003 Session G5: Large Area Production Coatings for Webs; Plasma Cleaning and Pretreatment of Large Surfaces
Tuesday, April 29, 2003 8:30 AM in Sunrise
G5-1 Glow Discharge Pretreatment Tools for Vacuum Web Coating
M. Geisler, G. Hoffmann, R. Ludwig, G. Steiniger (Applied Films Deutschland GmbH & Co KG, Germany)
In the last few years plasma-pretreatment has been established as a powerful tool to increase the quality in vacuum web coating. Whereas the effect of web pretreatment under atmospheric conditions is declining due to several reasons, glow discharge assisted in line - in vacuo pretreatment is much more reliable. Two tools for plasma pretreatment are presented herein. All are easily scalable as to comply with the needs of large area web coating with typical coating width of over 2 m, and they operate in a pressure range that is compatible with sputtering and evaporation processes taking place in the same vacuum system. The effect of the glow discharge on polymeric web depends on electron temperature (typically a few eV), electron density (ranging typically from 10@super -9@ to 10@super -11@ cm@super -3@), ion energy, and chemical composition. The mentioned electron density range is indispensable to meet the demands of satisfactory production speeds, in particular with evaporation. By means of the so called Treatmag an abnormal glow discharge enhanced by a closed loop tunnel shaped magnetic field is generated in the 10@super -3@ mbar pressure range. This tool is widely used for the improvement of metallic coatings on polymeric web. The ion energies typically range well below about 70 eV. Like others, this pretreatment method exhibits the well-known characteristic occurrence of an optimum dose. The so called RF Hollow Anode described herein next is comprising a capacitively coupled, asymmetric 13.56 MHz radio frequency glow discharge driven in a hollow life electrode, operated in the 10@super -2@ mbar pressure range. The Rf HollowAnode, easily scaleable along the coating width, is dedicated for the dynamic pretreatment or coating of either dielectric or metal web (or rigid sheet), and can be used in conjunction either with sputtering or, at line speeds of typical 5 m/sec, with evaporation processes. The Rf HollowAnode renders ion fluxes of up to 1 mA/cm@super 2@ at energies between 100 and several hundred eV. In so far it complements the Treatmag@super (R)@ which yields ions with considerable lower energies. The adhesion improvement by the Rf HollowAnode we attribute to a pronounced increase of the cross link density (amorphization) in the near surface region of in plane oriented polymeric web commonly used. Ex situ XPS spectra taken three days after venting from PET samples treated at high web speeds, are given. It is mentioned that industrial application of the Rf HollowAnode is based on the surface modification as yielded in-situ/in-vacuo almost immediately after treatment. In case the Rf HollowAnode is operated with hydrocarbon, silane or other gases, it can also be employed for thin base-coatings or top-coatings on web material.
G5-3 New Trends and Developments in Large Area PVD Coating of Metal Strips in Europe
Chr. Metzner (Fraunhofer FEP, Germany)
PVD-coatings on metal strips 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 powerful plasma is an 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. The paper gives an overview about new trends and developments in large area PVD coating of metal strips in Europe.
G5-5 Magnetron Sputter Etching Process for Large-area Pretreatment of Metal Sheets and Strips
B. Scheffel, Chr. Metzner, F.-H. Roegner (Fraunhofer FEP, Germany)
The high-rate coating of metal sheets and strips demands an adapted large area pre-treatment. An etching module based on magnetron sputtering was designed for pre-treatment of metallic sheets and strips with a maximum width of 500 mm. The effectiveness of the process was proved with a model layer system that was prepared by physical vapor deposition of copper in the thickness range of 10 - 100 nm. The layers were stepwise removed by magnetron sputter etching afterwards. Investigations on etching rate and power consumption will be presented. Thin insulating layers like oxides could be removed using pulsed power supply in the medium frequency range (10 - 100 kHz). It is demonstrated that a good long-term stability of the plasma discharge with a power up to 20 kW could be reached for metal strip etching.
G5-6 Substrate Biasing in Dual-anode Magnetron Sputtering
A. Belkind (Stevens Institute of Technology); Z.W. Zhao (Nanyang Technological University, Singapore); R Scholl (Advanced Energy Industries)
This work describes the development of a Dual-anode Reactive Magnetron Sputtering system. The above configuration creates a self-cleaning regime for both anodes, and provides dynamically cleaned and sustainable anodes. The substrate holder is connected to the magnetron through a resistor and/or additional floating power supply to provide biasing. Variation of the resistor value allows one to control the fluxes of total energy, and the ion-bombardment energy, delivered to the growing film, during deposition. Optimization of alumina films optical properties has been done by using a combination of closed-loop process control for high deposition rates, and control of ion-bombardment. Analysis of the substrate conditions during the deposition, including the time-resolved plasma properties near it, is presented.
G5-7 Substrate Biasing in Pulsed DC Reactive Sputtering of Dielectrics
A. Freilich, A. Belkind, K. Becker, J. Lopez (Stevens Institute of Technology)
DC reactive sputter deposition of dielectric can be done using dc power pulsed in the range of 5-350 kHz. Although pulsed dc reactive sputtering (PDRS) does not solve disappearing anode problem, it provides a deposition process without arcing. Pulsing plasma creates unusual conditions at the substrates, and requires special approach to biasing. In this work, plasma properties under various biasing conditions were investigated, by using average and time-resolved electrical, optical and calorimetric measurements. Deposition of alumina is used as an example of PDRS.
G5-8 Large Area Magnetron Sputtering of ZnO:Al Films
B. Szyszka, V. Sittinger, X. Jiang, A. Pflug, R. Hong, W. Werner (Fraunhofer IST, Germany); M. Ruske, A. Lopp (Applied Films, Germany)
A new coating technology has been developed for large area deposition of transparent and conductive ZnO:Al films. Reactive AC magnetron sputtering from metallic Zn:Al has been performed at low substrate temperature below 200@super o@C using the new CleanMag technology based on moving magnetic units for layers with low defect density. Process stabilization at non-stable process conditions in transition mode has been performed using closed loop control of discharge power according to fast oxygen partial pressure measurements taken by a lambda probe. Films with film thickness of 800 to 1000 nm deposited with dynamic deposition rate of a > 80 nm m/min exhibit resistivity lower than 270 mikco Ohm and small absorption (k < 0.002) in the visible range. The homogeneity of sheet resistance on 500 mm x 900 mm float glass substrates is better than 6 %. Film properties such as etching characteristics and haze can be modified due to control of total pressure and substrate temperature for large are a-Si:H thin film photovoltaic applications. The optical, electrical and structural properties of these films have been investigated by means of optical spectroscopy (UV-IR), variable angle spectroscopic ellipsometry, X-ray diffraction, atomic force microscopy, Hall mobility and conductivity measurements. Electron probe micro analysis and secondary ion mass spectroscopy has been used for chemical characterization. Detailed results on process technology, film properties and patterning processes will be shown.
G5-9 Time-resolved Investigation of Reactive Sputtering of Dielectrics
J. Lopez, A. Belkind, K. Becker, A. Freilich (Stevens Institute of Technology); D. Sanders, J. Wolfe (Lawrence Livermore National Laboratory)
DC reactive sputter deposition of dielectrics can be done using dc power pulsed in the range of 5-350 kHz. Although pulsed dc reactive sputtering (PDRS) does not solve disappearing anode problem, it provides a deposition process without arcing. Using duty cycles, which could be varied between 90% and 50%, and total pressure in the range of 0.02-1 Pa, plasma dynamics was studied. The relationship of plasma characteristics with various deposition process parameters were studied using time-resolved electrical and optical measurement techniques.