Chemistry: electrical and wave energy – Processes and products – Vacuum arc discharge coating
Reexamination Certificate
1999-01-12
2002-01-15
McDonald, Rodney G. (Department: 1753)
Chemistry: electrical and wave energy
Processes and products
Vacuum arc discharge coating
C204S298250, C204S298260, C204S298410, C118S719000, C118S7230VE, C118S7230MP, C118S726000, C118S727000, C118S733000, C427S569000, C427S572000, C427S580000, C427S586000, C427S596000, C427S597000
Reexamination Certificate
active
06338778
ABSTRACT:
The invention relates to a vacuum coating system having a coating chamber, which can be evacuated, for a substrate to be coated, and having at least one source chamber connected therewith for a material source for the coating material. With respect to the known prior art—particularly with respect to advantageous further developments of the invention—reference is made to German Patent Document DD 279 695 A1, which is used as an example.
In the case of the vacuum coating systems known so far, the substrate to be coated as well as a material source for the coating material are essentially in a common space which can be evacuated and which, only by means of a so-called screen provided for the targeted guiding of the vaporous coating material, is virtually divided into a so-called coating chamber in which the substrate is situated and a so-called source chamber in which the material source for the coating material is situated. These two chambers of the space, which in the known prior art is a single space, are jointly evacuated in order to generate the vacuum required for the coating operation, but are also jointly ventilated when the substrate to be coated is removed from the vacuum coating system after the conclusion of the coating operation. However, this is a disadvantage because, in the process, the material source for the coating material comes in contact with ambient air and may be contaminated thereby, for example, by the precipitation of air humidity, which will be explained in detail below.
Another disadvantage of the joint arrangement of the substrate to be coated as well as of the material source essentially in a common space which can be evacuated will occur when there are disturbances on the material source for the coating material during the coating process. It may, for example, be required to exchange this material source although the coating process has not been completely concluded. Then the vacuum coating system must necessarily be opened and therefore ventilated, whereby the already started coating process is disturbed and the substrate, which has only been partially coated by this point in time, therefore becomes useless.
However, the known prior art is particularly disadvantageous in connection with the deposition of multiple layers, that is, of several layers of different materials on a substrate to be coated, in which case different material sources are also required.
For this deposition of multiple layers in combination with amorphous carbon layers, a laser-induced vacuum arc discharge evaporator is known from German Patent Document DE 279 695 A1, in the case of which the materials to be evaporated are applied in disk shape to a rotating roller-shaped cathode which is arranged at any point in relationship to the substrate to be coated in the vacuum recipient.
It is a disadvantage of this arrangement that the cathode consisting of different materials is situated in the common space or in the coating chamber and, despite appropriate shielding devices, it can therefore not be prevented that the passive materials of the roller-shaped cathode are contaminated such that the purity of the deposited layers or layer sequences cannot be ensured.
Another disadvantage is the fact that, as the result of the different abrasion of the individual cathode materials, the cathode-anode spacing is altered so non-uniformly that no constantly stable ignition conditions can be ensured in the case of any materials for long-lasting coating cycles under realistic, particularly series-production conditions. For ensuring these ignition conditions, a high-expenditure mechanical turning-off of the cathode roller is required, which considerably reduces the degree of utilization of the cathode material.
Another disadvantage is the result of the limited deflection possibilities of a laser beam under which the focal plane can be ensured on a target (this concerns the cathode or the material source for the coating material). This determines the length of a target (cathode) so that, in the case of a cathode constructed of different materials, no conditions can be ensured for the homogeneous deposition of these materials on large-surface substrates without additional high-expenditures substrate movements.
Another disadvantage of the cathode arrangement in the common space or in the coating chamber is caused by required ventilating cycles during the exchange of the substrate. As the result of the fact that the cathode material comes in contact with the ambient atmosphere, particularly water (air humidity) may precipitate on the cathode surface. This is particularly dramatic in the case of graphite because of its porosity (−8%) in comparison to metals because, analogous to activated carbon, for example, water is embedded and stored in the case of graphite. Thus, no constant layer quality of high-grade amorphous carbon layers can be ensured since, particularly at the start of the coating process, hydrogen and oxygen are released and are included in the deposited layer. It was proven that the hardness of amorphous carbon layers is reduced by the embedding of hydrogen. For preventing such an embedding of hydrogen into the layer, an additional heating of the cathode is required before the start of the deposition. The reason is that, in principle, water should be avoided in the case of the low-temperature coating (<100° C.) because it has been proven to be the cause of an insufficient adhesion and resulting layer detachments.
It is therefore an object of the invention to provide a vacuum coating system which is improved with respect to the above and in the case of which there is no occurrence of at least the most serious above-indicated disadvantages. For achieving this object, it is provided that the coating chamber can be separated in a vacuum-tight manner from the source chamber which can be evacuated by itself. This means that the coating chamber can be evacuated or may remain when the source chamber is ventilated or—as explained in detail below—is exchanged for another source chamber.
Within the scope of advantageous further developments, which are indicated in the subclaims, it is an object of the invention to implement an arrangement for a laser-induced vacuum arc evaporator by means of which, under the conditions of a series production, on large-surface components (substrates) to be coated, homogeneous multiple layers consisting of at least two different material can be deposited in an effective manner.
Therefore, by means of a suitable device and arrangement of a laser-induced vacuum arc evaporator, it is to be possible to effectively deposit homogeneous multiple layers on large-surface components (substrates), in which case, a high operational safety of the evaporator is to be ensured while the utilization of the cathode material is good.
As indicated, according to the invention, the coating chamber in which the substrate to be coated is situated can be separated in a vacuum-tight manner from the source chamber which can be evacuated by itself and in which the material source for the coating material is situated. This means that either the coating chamber is accessible without any ventilation of the source chamber, or the source chamber is accessible without any ventilation of the coating chamber. This is possible in that one separate chamber respectively is provided for the substrate to be coated as well as for the material source for the coating material, in which case the connection between these two chambers required for the coating process can be interrupted. Naturally, it is necessary in this context to construct each chamber so that it can be evacuated separately; that is, a vacuum can in each case be generated separately in the coating chamber as well as in the source chamber. For the removal of the substrate as well as for the exchange of the material source in the coating chamber, these two chambers can therefore be separated from one another, for example, by means of a conventional plate valve which, in particular, has the shape of a separating wall.
However, this const
Giersch Daniela
Mielsch Goetz
Schalausky Robert
Scheibe Hans-Joachim
Bayerische Motoren Werke Aktiengesellschaft
Crowell & Moring LLP
McDonald Rodney G.
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