1. Field of the Invention
The present invention refers to a coating device for the deposition of thin films on especially large-area substrates, like architectural glass or display panels. Furthermore, the present invention refers to a method for coating such substrates.
2. Prior Art
Coating devices for coating of especially thin layers on substrates like glass are widely used in industrial applications, e.g. depositing of heat insulation layers on architectural glass or conductive or semiconducting layers on display panels or photovoltaic units.
In order to apply such thin films on large-area substrates, devices and methods are known from prior art. However, a permanent need for improvement exists with respect to an increase of homogeneity of layer thickness or other properties of the deposited layers over the whole coated substrate as well as an enhancement of efficiency of coating.
Since it is always difficult to find an appropriate comprise to achieve these diverging needs, an improvement in this respect is especially valuable.
From prior art sputter processes are known for carrying out coating processes mentioned above.
As can be seen from FIG. 9 showing a prior art apparatus, sputter devices have an electrode arrangement 401, 402 within a process chamber 201, 202 in order to ignite a plasma and accelerate ions of the plasma towards a target in front of a cathode of the electrode arrangement 401, 402. Magnetron cathodes comprise a magnet arrangement, which is disposed behind the target so as to lead to a confinement of electrons in front of the target and thus to a plasma concentration in this area. Thus, a high sputter yield is achieved due to the high concentration of ions impinging on the target. The material of the target is atomized and deposits on the substrate 5, 6 being disposed opposing to the magnetron cathode.
In order to achieve a high through-put of the device, a double-chamber design can be used with two process chambers 201, 202 arranged side by side to each other. Such a double-chamber 200 enables a production of the process chambers with reduced effort and allows a space saving design of the sputter apparatus. According to the embodiment shown in FIG. 9, a buffer chamber 100 for storing the substrates to be coated and a lock section 300 having two locks 301 and 301 for feeding the substrates into both process chambers 201, 202 are additionally provided for.
DE 41 26 236 C2 also describes a device for a sputter process. This device comprises a rotating magnetron cathode having a hollow cylinder target, which rotates in order to use the whole target surface for sputtering.
According to DE 41 26 236 C2 two magnet arrangements are disposed in the hollow cylinder target so as to form two plasma areas on opposing sides of the cylindrical magnetron electrode. One plasma is used for coating the substrate, the second plasma generated by the second magnet arrangement is used for cleaning of the rotating target. However, it is also possible to simultaneously deposit layers on two substrates being located at the opposing sides of the cathode. This device can however only be used for small-area coatings or a dynamic coating process wherein the substrates are passing the single sputter source.
A similar device is disclosed in U.S. Pat. No. 5,158,660. However, instead of a magnet arrangement inside the cylindrical electrode, a magnet arrangement disposed outside the target or cathode is used. However, this device of U.S. Pat. No. 5,158,660 is also a single coating source with small lateral dimensions for small-area coatings or dynamic coating processes.
In order to achieve large-area coatings with homogenous layer thicknesses, EP 15 94 153 A1 suggests to provide a plurality of cathodes in order to allow stationary coating of large-area substrate facing the plurality of cathodes. However, in order to be sure that at the margins of the substrates the same layer thickness is achieved as in the central area, the cathodes of EP 15 93 153 A1 are arranged at a curved surface. Accordingly, it is not possible to use cathodes described in DE 41 26 236 C2 or U.S. Pat. No. 5,158,660 having deposition areas on two sides of the cathodes, since the curved arrangement of the cathode does not allow homogenous twin-deposition from two sides of the cathode.
Other devices, e.g. described in WO 2007/051105 A2 or JP 2004 027 272 A, deal with the above-mentioned problems by providing movable magnet arrangements for magnetron electrodes. Although, this leads to an improved material usage of target material and allows for adapted deposition areas leading to an enhancement of layer homogeneity, improvements with respect to layer homogeneity of large-area depositions and improvements with respect to efficiency are still necessary.