Linear ion sources by Gencoa are a robust and flexible means of pre-cleaning polymer and glass substrates prior to thin film deposition. The plasma jets generated impact the substrate to burn-off hydrocarbons and activate the surface to promote adhesion of the deposited film.
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The intense plasma jets are generated by a combination of the magnetic and electrical field across a narrow gap through which the gas or gases pass. DC power modes can be applied with typical voltages in the 1.5-3kV range to provide a ‘high’ impact plasma pre-treatment. A higher strength version with pulsed DC power can generate plasma jets at sub 1kV for lower ‘damage’ type plasma treatment.The use of pure argon gas generates the most effective plasma cleaning, but any combination of gases can be used.The plasma can also be used for deposition and polymerisation via the gas phase.
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The robust and easy to service design is available in any length and a variety of internal, external or cantilever mounts.A unique feature is the internal graphite anode that is simple to replace and very long in life due to the very low sputter yield of carbon. Under normal operating conditions the anode should have a life of around 6 months before replacement.The IM series are not recommended for metallic substrates or very high speed web movements. Gencoa provide a range of different customised solutions based upon high power magnetically enhanced plasma generation electrodes.
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Principle and advantages
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The device is based upon the inverted magnetron principle; also know as Hall effect or anode layer ion sources, but with some key differences. They use all the same skills required for magnetron design and are hence a natural area of activity for Gencoa. The Gencoa linear ion source has been developed to work in collimated mode at any discharge voltage. Usually a high discharge voltage in the kV range is required to attain the collimated type operation, but the ion optics in the Gencoa source allow this type of operation down to 250 volts. A low voltage is preferable for ion assisted and plasma deposition since less damage is imparted to the growing film. Equally the source can operate at high voltages if required. Also, the anode sputters at a very low rate which allows the possibility of using high discharge currents, whilst still maintaining a long anode lifetime. The sources come packaged together with the power supply.
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The beam aperture is 75mm wide as standard, but by parametric 3D computer aided design of the GENCOA IM Source, any length can be manufactured quickly to suit specific process requirements. In addition, a wide range of mounting styles are available such as; internal, external, cantilever, sliding and angular adjustment. (insert pic, beam).
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The linear ion source has advantages over other methods in that it has a very wide range of operating pressures, there are no filaments, and it is largely maintenance free, industrially robust and low cost.
Applications
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Background
Ion guns based on inverse magnetrons were developed by Russian scientists towards the middle of the last century mainly for deep space propulsion. During the last 10 years these devices have increasingly been used in plasma surface engineering, especially in areas such as substrate pre-cleaning, coating, ion assistance and plasma deposition.
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Much work is now being carried out to explore the usefulness of linear ion beams and recent results show that substrate pre-cleaning with the ion source prior to coating improve many of the coating characteristics. The established areas of web coating and glass coating are obvious examples of where these ion sources can be used, but also a next generation of polymer based coating systems can be generated by PECVD based methods via the linear ion source. As an example of other potential uses, the IM source is currently being used by Gencoa's R&D team to produce plasmapolmerised layers for gas separation membranes in proton exchange membrane fuel cells. (insert plasma polym pic/graph)
Currently, the main application of linear ion sources is in substrate cleaning, especially for surfaces that cannot be biased by any other method. This can be achieved in two ways, either by etching, or by outgassing the surface. Other applications include plasma polymerization, surface modification to promote or discourage adhesion, control of film chemistry by adding functional groups to a particular coating and contamination reduction.
The addition of the IM series complements GENCOA’s other products giving customers a one-stop-shop for all your source and gas control needs.
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SVC 2005