Coating processes – Electrical product produced – Integrated circuit – printed circuit – or circuit board
Patent
1987-02-02
1989-09-05
Morgenstern, Norman
Coating processes
Electrical product produced
Integrated circuit, printed circuit, or circuit board
427 40, 427 41, 427 47, 118718, 118723, B05D 306, B05D 314, C23C 1650, C23C 1654
Patent
active
048637564
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method for coating continuously moving substrates by the deposition of compounds from the gas phase by means of a plasma discharge produced by an electrode with a chemical reaction, a system of magnets for the generation of a magnetic trap to constrict the plasma being disposed on one side of the substrate
A field of use is the coating of films and foils with polymers, which are deposited from polymerizable monomers from the gas phase. For this purpose, it is necessary to supply appropriately reactive monomers to the plasma or the corona discharge. A further field of use is the deposition of inorganic compounds. From the German Offenlegungsschrift 2,608,415 (corresponding to U.S. Pat. No. 4,013,532), a coating method of the initially described class is known, with which for example, layers of Polystyrene are to be produced. Two electrodes lie opposite each other in a parallel position at a distance of about 4 cm, and the substrate is passed in the middle between these electrodes. On the side of each electrode, facing away from the substrate position, there is a magnet system for the generation of a magnetic trap to constrict the plasma. The plasma, moreover, burns in the immediate vicinity of each electrode surface and at some distance from the substrate, so that the polymer is deposited on the electrode surfaces. It has also been reported that the cathode vaporizing rate of the electrode material is observed to be much lower than that of the material deposited on the electrode. The known method is based on the hope that the polymer is first of all produced from the gas phase on the electrodes and vaporized once again from there in the direction of the substrate. The occurrence of the effect described is based on the fact that a plasma is maintained between the substrate that is to be coated and the electrode facing this surface and this, in turn is possible only because the distance between the substrate and electrode surfaces is several times as large as dark space distance that arises under the given process conditions. Disregarding the substrate thickness the actual distance present is about 20 mm, while the dark-space distance, arising under the process conditions, is of the order of 3 mm at most. With the known method, not only the electrodes but also other parts of the interior facilities of the evacuatable reaction chamber are coated and contaminated. From the paper by Morosoff, Newton and Yasuda, " Plasma Polymerization of Ethylene by Magnetron Discharge", published in the J. Vac. Sci. Technol., 15(6), Nov./Dec. 1978, pages 1815 to 1822, a very similar method and very similar equipment are known, in which the clear distance between the electrode plates is 7.6 cm. Here also, it is a matter of supplying monomer vapors to the plasma, which deposit as polymers on the substrate. It is also a matter here of depositing the polymer initially on the aluminum electrode plates and of vaporizing it from there in the direction of the substrate.
From the paper by Kaganowicz, Ban and Robinson, "Spatial Effects in Plasma Deposition of SiO.sub.x Using Magnetically Enhanced Glow Discharge" published in the ISPC-6 Montreal, July 1983, Number C-7-6, a once again comparable method and comparable equipment are known for the production of silane layers from silicon compounds In the equipment described there two magnetron cathode also lie opposite one another in mirror symmetrical fashion and the clear distance between the electrode plates is 5 cm. The authors report the observation that the layer composition is highly dependent on the spatial distance from the electrodes and that coating material deposits even in the vicinity of the outlet of the reaction chamber far removed from the electrodes. The dependence of the layer composition on the distance from the electrodes has the disadvantage especially when moving substrates are being passed continuously between the electrodes, that rather inhomogeneous layers are formed. In this connection, one must realize that the construction of the layer c
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Dietrich Anton
Hartig Klaus
Bueker Margaret
Leybold Aktiengesellschaft
Morgenstern Norman
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