WO2009030374A1

WO2009030374A1 - Method for producing a metal rear contact of a semiconductor element, particularly a solar cell

Info

Publication number: WO2009030374A1
Application number: PCT/EP2008/006861
Authority: WO
Inventors: Roland Trassl; Stephan Wieder; Jian Liu; Jürgen Heinrich; Gerhard Rist
Original assignee: Applied Materials, Inc.
Priority date: 2007-08-30
Filing date: 2008-08-20
Publication date: 2009-03-12
Also published as: CN101689569B; KR20100046163A; CN101689569A; TW200917502A

Abstract

The present invention relates to a method for producing a rear contact (21) of a semiconductor element, particularly a solar cell (20), comprising a metal layer (24) on the rear of a substrate (22) in a vacuum treatment chamber, and to the use of a vacuum treatment system for carrying out said method. Particularly solar cells (20) based on silicon can be easily equipped with a rear contact (21) by means of said method and the use thereof in a continuous process control, wherein the process control may be conducted in a particularly efficient and cost-effective manner, since no handling systems are required for rotating the substrate (22) and in particular the screen printing steps can be omitted.

Description

Method for producing a metallic back contact of a semiconductor component, in particular a solar cell

The present invention relates to a method for producing a back contact of a semiconductor component, in particular a solar cell, according to the preamble of claim I and the use of a vacuum treatment system for carrying out this method according to the preamble of claim 16.

The photovoltaic is given great attention, since it is attributed to the desire of a fossil fuel-independent energy supply even more important in the future. Despite the recent investigation of thin-film solar cell technology, it is still the silicon technology on the basis of which the largest turnovers are achieved. This is not only because this technology is the most mature, but so far the most efficient solar cells can be produced with it.

To produce a silicon solar cell, the following steps have hitherto been carried out. In a first step, a damage removal and texturing of the silicon wafer takes place. In a second step, the emitter is made by Einduffision a doping, for example, the donor phosphor, which attaches about 0.5 microns below the surface of the silicon wafer and forms an emitter layer. Simultaneously with the emitter production, SiO _{2 is formed} , which is removed again by etching in a third step. Thereafter, a SiN: H antireflection layer is applied, which is effected by (PE) CVD (plasma enhanced chemical vapor deposition) or by a reactive sputtering process. The SiN: H layer serves as a passivation layer in that the hydrogen diffuses into the silicon wafer or the emitter layer in a subsequent firing step and passes defects. In a fourth step, contacts are screen-printed on the front and back sides of the wafer by using a silver paste on the front side (emitter layer side) and an aluminum paste as a recessed metal layer on the back side Silver paste is introduced as a solderable layer. In a subsequent fifth step, a heating is performed (firing step), by which the contacts are cured. In this case, on the front side, the silver in the areas in which it was applied to the SiN: H layer, through the SiN: H layer pressed on the silicon wafer and contacts it so. As already stated above, this simultaneously leads to a passivation of the front defects by hydrogen diffusion and attachment to the defects. On the back of the fire step, a BSF (back surface field) is formed, which also causes a passivation, namely the back defects. This is done by diffusing into the silicon wafer aluminum, thereby forming an Al-Si eutectic. Finally, an edge insulation can be effected to avoid leakage currents, for example by breaking the wafer.

As stated above, the back contact of such a silicon solar cell usually consists of a metallic layer and may also comprise a barrier layer and a solderable layer. By default, the metallic layers of the back contacts have previously been produced by screen printing. As a result, however, it is necessary for large-scale applications in vacuum treatment plants with continuous lines, which first enable the economic efficiency of the production of such solar cells and in which several substrates are coated simultaneously, to provide each individual substrate separately with such a back contact. That that a separate screen printing step must be carried out for each individual substrate. As a result, the throughput of such a vacuum treatment plant is limited. In addition, special handling systems are required to rotate the substrates, thereby increasing the cost of such equipment and further reducing throughput.

Furthermore, it is disadvantageous in the back contacts produced in this way that the screen printing pastes used are expensive and the contact that forms is poor, since the hardened layer is porous and thus there is only a punctual contact. It is necessary for the metallic layer about 30 microns layer thickness, which can bend through thin wafers. This influence is becoming increasingly important, since the aim is to reduce the wafer thickness. The wafer thickness is determined in a voltage ratio of cost and efficiency, with very thick wafers are expensive due to the necessary material, very thin wafers are expensive due to the complicated production and efficiency on the one hand from a sufficiently large layer thickness for absorbing the light and others from such a small layer thickness that losses due to charge carrier recombination are kept low. Currently, wafer thicknesses of 200 .mu.m to 250 .mu.m are preferred, with sagging already having a negative effect. The object of the present invention is to increase the efficiency of vacuum treatment plants in the production of solar cells with metallic back contacts and in particular to make a screen printing step superfluous. The production should be cost-effective, in particular commercially applicable, and with higher throughput than previously possible.

This object is achieved by a method according to claim 1 and the use of a vacuum coating system for carrying out this method according to claim 16. Advantageous developments of this subject are contained in the respective dependent claims.

The inventive method for producing a back contact of a solar cell with a metallic layer on the back of a substrate is characterized in that the metallic layer is deposited by sputtering from a target or by vapor deposition in an in-line vacuum coating system, before or after Applying the metallic layer at least one further layer on the front and / or the back of the substrate is applied.

Although the application of metallic layers in vacuum has already been proposed for small series of silicon solar cells (US Pat. No. 7,071,018 B2). However, not in an in-line vacuum coating system and exclusively for producing a BSF (back surface field), wherein initially a metallic layer of aluminum is deposited by vapor deposition or sputtering, which is then sintered and doped with a group V element. These three process steps must be carried out in three separate plants. Also, this coating method is therefore not economically feasible in vacuum coating systems with in-line lines and also the actual metallic back contact must continue to be applied by screen printing.

It is furthermore known from US Pat. No. 7,071,018 B2 that silicon solar cells have been produced on a laboratory scale, an aluminum layer having a layer thickness of greater than or equal to 2 μm being applied by means of PVD to a thin dielectric SiO ₂ or SiN layer. The SiO ₂ or SiN layer, on the one hand, promotes the structure of the BSF and, on the other hand, prevents doping diffusion. However, this method is not suitable for commercial, low-cost production because it requires silicon wafers made in the floating zone process.

By the method according to the invention a screen printing step for applying the back contacts is no longer required and there is no interruption of the vacuum, so that an undesirable oxide formation and therefore the step of a subsequent cleaning can be avoided.

When the coating tools for applying the back contact with respect to the line guide are arranged opposite to the coating tools for applying the layers on the front side of the substrate, no complicated handling systems for rotating the substrate are necessary. The substrate therefore no longer needs to be turned, but can be coated in from both sides. Thus, the majority of the manufacturing process of a silicon solar cell can in principle be carried out continuously in an in-line vacuum coating plant.

To avoid shading of the substrate by the carrier is expediently provided that the substrate rests in the carrier on substantially punctiform supports.

Preferably, the substrate is guided substantially horizontally past the coating tools. In this way, installations in which the coating tools are vertically aligned with respect to their coating direction and in which a horizontal substrate transport takes place, are used, whereby the handling of the substrate during transport simplified, since this can now be performed for example via transport rollers.

In a particularly advantageous embodiment of the method, the metallic layer comprises a material from the group aluminum, silver, molybdenum and / or nickel or a mixture of one or more of the above materials. These metals have due to their electrical conductivity very good properties as a contact. Preferably, however, aluminum should be used, since this material is inexpensive. The metallic layer should in particular be deposited with a thickness of 0.1 .mu.m to 10 .mu.m, preferably 2 .mu.m. Such thin layers are sufficient since the contacting is much better than with metallic layers which have been screen-printed. the. With these thin layers, there are also no problems with respect to wafer deflection, even with thin substrates.

Advantageously, a passivation layer made of a material of the group SiN: H, SiC: H, SiO ₂ : H or a-Si: H, preferably of SiN: H, is applied between the substrate and the metallic contact layer. Furthermore, it may expediently be provided a barrier layer, for example of WTi. In order to improve the solderability of the metallic contact layer, a solderable layer is advantageously applied to this layer. This may comprise one or more layers of materials of the group silver (Ag), nickel (Ni), nickel vanadium alloy (NiV), nickel chromium alloy (NiCr) and chromium (Cr). Layers or layers in this context also include formations in which there is no closed surface layer. For example, the solderable layer can also be patterned, ie only partially covering the surface.

These additional layers are then also each applied by the method according to the invention, both vapor deposition as well as sputtering is possible, but sputtering is preferred.

In an advantageous development, the contacting of the metallic layer on the back of the substrate with the substrate by partial melting by means of an intense laser beam, so that a laser-fired contact (LFC) results. This method can advantageously also be used in the presence of a passivation layer on the back between the substrate and the metallic layer.

During the application of at least one layer on the back side of the substrate, it is particularly preferred to apply at least one layer to the front side of the substrate. For this purpose, opposing coating tools are arranged in at least one vacuum treatment chamber of the vacuum treatment plant, wherein the substrate is passed between the coating tools. Through the substrate so two of each other chamber areas are given. As a result, the spatial expansion and thus the costs of such a vacuum treatment plant can be reduced while at the same time the throughput can be increased since two layers are applied simultaneously to a substrate. Of course, in this embodiment, it must be ensured that the deposition processes do not interfere or hinder each other. Thus, for example, then simultaneously several metals are vapor-deposited, if the metals do not influence each other. The same layers can also be sputtered on, since then the process gases and the layer materials do not influence each other. However, it is not possible to coat and sputter layers at the same time, since the process gas pressures of 10 ^"4 mbar and 10 ^{" 3} mbar are too different.

With regard to the present invention, an "in-line process management" does not necessarily mean a physical transport of the substrate from one vacuum chamber to the next in order to apply different layers, but also a passage through individual process steps without physical transport of the substrate, in this case the simultaneous application In other words, "in-line" also means that the substrate in the vacuum treatment plant is transported into a vacuum treatment chamber, where it remains in one position and after having been coated on the front and back of the vacuum chamber and optionally also leaves the vacuum system again. Of course, the substrate can also be transported during the coating process.

The throughput can be additionally increased if a plurality of substrates, which are arranged in particular in a common carrier, are provided simultaneously with the metallic layer.

In order to simplify the maintenance of the system, at least one coating tool can be provided in a drawer-like manner in a vacuum treatment chamber. "Drawer-like" in this context means that after removal of the drawer in question no interruption of the process control vacuum takes place, but furthermore substrates can be transported in a vacuum through the relevant vacuum chamber be separated.

If the one layer of the metallic layer is vapor-deposited, the metal can advantageously be supplied as a wire through a vacuum feedthrough to the evaporator. On the other hand, the vapor deposition of the metal can also proceed as follows: vaporizers of the metal are provided in two subsequent vacuum treatment chambers and the metal is evaporated in the one vacuum treatment chamber until the metal in the first evaporator located therein has been used up. When the metal in the first evaporator is used up, the metal in the other vacuum processing chamber is evaporated with a second evaporator without interruption of the vapor deposition. In this case, in particular, at the same time, the first evaporator, if it is provided like a drawer, can be maintained and subsequently further evaporated after the second evaporator has been consumed by the first evaporator, and so on. This increases the throughput, as this metal can be evaporated without interrupting the coating process.

If sputtering takes place instead of vapor deposition, the metallic contact layer can preferably be sputtered on with at least one rotatable cathode. With such a rotatable cathode permanently much more consistent coating conditions are achieved than with, for example, static planar cathodes. In particular, the coating in a DC sputtering process, wherein also pulsed DC sputtering or MF sputtering (mid-frequency sputtering of at least two targets) is possible, and in particular dynamically, i. carried out with simultaneous substrate transport.

In an advantageous development, the number of cathodes is selected as a function of the sputtering yield of the cathodes, the thickness of the metallic layer to be achieved and the throughput of the vacuum treatment system to be achieved. That that for a given layer thickness, sputter yield and throughput, the number of cathodes is adjusted. Of course, at the same time by setting the sputtering conditions, the sputtering yield o- / / and by adjusting the transport speed of the throughput can be adjusted.

The barrier layer and the solderable layer can also be applied using these vapor deposition or sputtering techniques. The passivation layer, however, is applied only with sputtering.

Independent protection is claimed for the use of a vacuum treatment plant with at least one vacuum treatment chamber, wherein the vacuum treatment plant comprises at least two coating tools, for carrying out the method described above.

It is preferred if the vacuum treatment plant has a substantially horizontal line, wherein the coating direction of the coating tools is vertically aligned. In question here come, for example, vacuum coating systems, as described in DE 103 52 143 Al and DE 103 52 144 Al, in which sense, these documents and the vacuum treatment plants shown therein are fully included in the Offenbahrungsgehalts the present invention.

It is particularly advantageous if the vacuum treatment system has at least one push-in element which can be pushed into or pulled out of the interior space of at least one vacuum treatment chamber, the coating tools being arranged on the push-in elements. In this way, a modular system is provided for the method, are minimized in the life by the fact that the coating tools can be exchanged or maintained in a particularly simple manner. In particular, if, for example, for the vapor deposition, as described above, two evaporators are operated alternately, which are arranged in successive vacuum treatment chambers in such insertion elements, life with respect to this coating tool can be completely prevented.

Corresponding vacuum treatment plants are known from EP 1 698 715 A1, in which sense this document and the vacuum treatment plants indicated therein are included in full in the Offenbahrungsgehalts of the present invention.

Particularly preferably, at least one vacuum treatment chamber of the system comprises at least two coating tools, wherein of the coating tools a first on the front and a second on the back of one or more substrates to be coated in the vacuum treatment plant has substrates. In this way, as described above, the length of the system and thus their cost and throughput can be optimized. In this case, at least one insertion element advantageously has two coating tools, each facing the front and the back of the substrates. This allows the system length to be shortened even more and both coating tools can be removed and maintained simultaneously by means of the one insert element. For a particularly simple handling can be provided that the vacuum treatment plant has transport rollers on which the substrate or a substrate or a carrier for a plurality of substrates is transported through the vacuum treatment plant.

The present invention will now be explained in more detail with reference to two exemplary embodiments in conjunction with the drawing. Show

Fig. 1 is an in-line vacuum coating system for carrying out the invention

Method and Fig. 2 shows a solar cell produced by the method according to the invention.

FIG. 1 shows purely schematically a horizontal in-line vacuum coating system 1. This plant 1 is subdivided into a plurality of vacuum coating chambers 2, 3, 4, 5, 6, 7, 8 and a loading and unloading area 10 and has a horizontal transport arranged substrate transport (not shown), which is realized via transport rollers, which are mechanically driven to convey substrates (not shown) located on the transport rollers into carriers (not shown) along the lines of Appendix 1 through the individual successive vacuum chambers 2, 3, 4, 5, 6, 7, 8.

The vacuum chambers 4, 5, 6 provided for coating have insertion elements 1 1, 12, 13, on which the coating tools 14, 15, 16 assigned to a chamber are arranged. Furthermore, each vacuum chamber own vacuum pumps (not shown), usually turbomolecular pumps assigned. Sputtering sources, such as sputtering cathodes and magnetrons, but also thermal evaporators and the like are particularly suitable as coating tools. The provision of such insertion elements 1 1, 12, 13 allows quick maintenance and a speedy replacement of the corresponding coating tools.

Individual or several silicon substrates accommodated in a carrier are now introduced successively on the transport rollers and conveyed continuously through the individual chambers 2, 3, 4, 5, 6, 7, 8 and subsequently provided with the layers necessary for a solar cell. Of course, a discontinuous transport is possible if the substrates are not transported during the coating. In this case, the coating takes place with those layers which are to be located on the front side of a substrate by means of coating tools, which are arranged above the lines of the substrates, which therefore point vertically downwards. If these layers are applied by means of sputtering, this coating thus takes place in the so-called "sputter-down" mode (the system example according to Fig. 1, however, shows only the production of the back contact.) The metallic layer for the back contact of the solar cell is in turn is applied by means of coating tools 14, 15, 16 which are arranged below the lines of the substrates, that is, which point vertically upwards. If these layers are applied by means of sputtering, this coating thus takes place in the so-called "sputter-up" mode.

In order to reduce the longitudinal extent of the system and to increase the throughput at the same time, it can be provided that in those chambers in which coating tools for the coating of the back contact are provided, simultaneously coating tools for the application of layers are arranged on the front side of the substrate ( Not shown). However, as already stated, it must be ensured here that the two coating processes do not influence or hinder each other. For example, the generation of the SiN: H layers on the front and back sides of a substrate could be done together. Both coating tools of such a chamber are then each arranged on an insertion element and can be exchanged and maintained. If, in turn, sputtering sources are provided as coating tools, then a "sputter-down" as well as a "sputter-up" process is simultaneously performed in a chamber. For continuous substrate transport, the coating rates of the two coating tools must be set such that the respective desired layer thickness is set dynamically on both sides on the transport rollers in relation to the set transport speed of the substrates. Similarly, the coating rates of the coating tools of the other chambers are adapted so that the substrate or the substrates along the entire transport path within the system can be constantly transported. This setting of the coating rates is not necessary in the case of discontinuous transport.

The coating process of a silicon substrate introduced into the system with respect to the back contact now proceeds in the course of the production of a silicon solar cell such that in the "Sputter-Up" process each one or more rotary cathodes 14, 15, 16 in successive chambers 4, 5, 6 a passivation layer, the metallic contact layer, optionally a barrier layer (not shown) and finally to improve the solderability of the back contact a solderable The number of spin cathodes 14, 15, 16 per coating chamber depends on the coating rate, the desired layer thickness and the desired throughput, ie the transport speed of the system 1.

In an alternative embodiment (not shown), the plant is constructed substantially as in the first embodiment, wherein the coating tool for applying the metallic layer and / or the barrier layer and / or the solderable layer is not a sputtering source but a thermal evaporator. This thermal evaporator is arranged in a push-in element and ensures a coating of the substrate back. In this case, the metal can be supplied to the evaporator either in wire form from the atmosphere via vacuum feedthroughs or, which is preferred, in each case two evaporators are provided in successive chambers in each case a push-in element. If the material of an evaporator is consumed, which usually takes place after approximately 24 hours of operation, a horizontal valve is moved over the corresponding insertion element, which separates it from the transport volume in which the substrate moves. At the same time, the coating process starts with the other evaporator in the adjacent chamber. The plug-in element separated by the valve can now be ventilated and removed, so that the empty evaporator arranged therein can be equipped with new material.

The passivation layer is in turn applied via one or more rotary cathodes in the sputter-up process, and the barrier layer and the solderable layer can also be sputtered on instead of being evaporated, so that only the metallic layer is vapor-deposited.

A solar cell 20 produced by the method according to the invention has, according to FIG. 2, a back contact 21, which is constructed as a layer system on the substrate rear side of a silicon substrate 22, and has the sequence of passivation layer 23, metallic contact layer 24 and solderable layer 25. The passivation layer consists of SiN: H, SiC: H, SiO ₂ : H or a-Si: H. The metallic layer comprises a material from the group aluminum, silver, molybdenum and / or nickel and is preferably made of aluminum. Before- The passivation layer 23 consists of SiN: H and the metallic layer 24 consists of aluminum. Optionally, between the solderable layer 25 and the metallic layer 24, a barrier layer may additionally be provided (not shown), which consists for example of WTi. The solderable layer comprises one or more layers of materials from the group Ag, Ni, NiV, NiCr and Cr, for example a layer sequence of Ag / NiV and is preferably made of silver. After the application of the metallic layer 24, an LFC step may be provided, in which the metallic layer 24 is contacted selectively with the substrate 22 by laser-induced melting and thus forms a laser-fired contact.

Whether the metallic contact layer 24 is vapor-deposited or sputtered from aluminum depends on the actual required layer thicknesses and the application rates of the coating tools. If, for example, LFC contacts (LASER fired contact) are to be produced, layer thicknesses of a few μm are required, for which vapor deposition is used. For thinner layers of less than 1 μm, on the other hand, sputtering is used. Therefore, the barrier layer and the solderable layer 25 are preferably sputtered on, since they have a thickness of less than 1 micron.

Furthermore, the solar cell 20 has an emitter layer 26, which was produced by in-diffusion of donors, for example phosphorus, a SiN: H passivation layer 27 and bar-like front contacts 28 made of silver. The application of these layers could also be integrated into the process management of the in-line vacuum coating system 1.

As a result of the above explanations, it has become clear that, with the aid of the method according to the invention and the use of a vacuum treatment system according to the invention, silicon-based solar cells can be provided in a simple manner with a metallic layer for back contact, the process control being particularly efficient (high throughput) and cost-effective can, as can be dispensed with screen printing steps and so no interruption of the vacuum is required. In addition, the wafer break rate is lowered because wafer handling is reduced.

Although the invention has been described in detail only for a solar cell, it is clear that it can also be advantageously used for backside contacts in other semiconductor devices.

Claims

claims

1 . Method for producing a back contact (21) of a semiconductor component, preferably a solar cell, in particular a silicon-based solar cell (20), wherein the back contact (21) comprises a metallic layer (24) on the rear side of a substrate (22) and the semiconductor component (20) optionally further layers (23, 25, 27, 28) on the front and / or the back of the substrate (22) and the layers (23, 24, 25, 27, 28) by means of coating tools (14, 15, 16) applied are, characterized in that the metallic layer (24) by sputtering from a target (15) or by vapor deposition in an in-line vacuum coating system (1) is applied and before or after the application of the metallic layer (24) at least one further Layer (23, 25, 27, 28) in the in-line vacuum coating system (1) without interruption of the vacuum is applied.

2. The method according to claim 1, characterized in that the coating tools (14, 15, 16) are provided so that the coating tools (14, 15, 16) for applying the layers (23, 24, 25) on the back of the substrate (22) with respect to the lines of the vacuum coating system (1) opposite to the coating tools for applying the layers (27, 28) on the front side of the substrate (22) are arranged, wherein the substrate (22) in particular punctiform Supports a carrier rests in order to avoid shading of the substrate (22) by the carrier largely.

3. The method according to claim 1 or 2, characterized in that the substrate (22) substantially in a horizontal line on the coating tools (14, 15, 16) is guided past, so that the coating direction is vertical.

4. The method according to any one of claims 1 to 3, characterized in that the metallic layer (24) comprises a material or a material mixture from the group aluminum, silver, molybdenum and / or nickel and preferably consists of aluminum, wherein the metallic layer in particular with a thickness of 0, 1 .mu.m to 10 .mu.m, preferably 2 microns is deposited.

5. The method according to any one of the preceding claims, characterized in that prior to the step of applying the metallic layer (24) a passivation layer (23) made of a material of the group SiN: H, SiC: H, SiC> ₂ : H or a-Si: H, preferably SiN: H is applied.

6. The method according to any one of the preceding claims, characterized in that after the application of the metallic layer (24) for contacting the metallic layer (24) on the substrate back to the substrate (22), the metallic layer (24) partially by means of an intense laser beam is melted, so that forms a laser-fired contact (LFC).

7. The method according to any one of the preceding claims, characterized in that after the step of applying the metallic layer (24), a barrier layer is applied, which preferably consists of WTi.

8. The method according to claim 5 or 7, characterized in that after the step of applying the metallic layer (24) or after the step of applying the barrier layer, a solderable layer (25) is applied, the one or more layers of materials of the group Ag, Ni, NiV, NiCr or Cr.

9. The method according to any one of the preceding claims, characterized in that in a vacuum processing chamber at least two layers are applied, wherein during the application of a layer on the back of the substrate (22) a layer on the front side of the substrate (22) is applied.

10. The method according to any one of the preceding claims, characterized in that a plurality of substrates, which are arranged in particular in a common carrier, are provided simultaneously with the layer or layers.

1 1. A method according to any one of the preceding claims, characterized in that at least one coating tool (14, 15, 16) in a vacuum treatment chamber in a slide-in element (1 1, 12, 13) is provided like a drawer.

12. The method according to any one of the preceding claims, characterized in that at least two coating tools in a vacuum treatment chamber in a common insertion element is provided like a drawer, wherein preferably has a first coating tool on the front and a second on the back of the substrate.

13. The method according to any one of the preceding claims, characterized in that at least one of the layers of metallic layer (24), barrier layer and solderable layer (25) are vapor-deposited, wherein the corresponding materials are fed as a wire through a vacuum feedthrough an evaporator.

14. The method according to any one of claims 1 to 12, characterized in that at least one of the layers of metallic layer (24), barrier layer and solderable layer (25) are vapor-deposited, wherein the respective materials in each case in two subsequent vacuum treatment chambers in a first and a second Evaporators are vaporizable and are each evaporated in the first evaporator until the material is used up in the first evaporator and the Materials are then evaporated without interruption of the vapor deposition in the respective other vacuum treatment chamber with the second evaporator when the respective material is consumed in the respective first evaporator, in particular at the same time the respective first evaporator is maintained.

15. The method according to any one of the preceding claims, characterized in that at least one of the layers (23, 25), each with at least one rotatable cathode (14, 16), preferably in a DC sputtering process for metallic layers or dielectric layers of ceramic sputtering targets or sputtered by means of reactive center frequency sputtering for dielectric layers of metallic sputtering targets.

16. The method according to claim 15, characterized in that the number of cathodes is selected as a function of the sputter yield of the cathodes, the thickness of the layer to be achieved and the throughput of the vacuum treatment plant to be achieved.

17. Use of a vacuum treatment plant (1) having at least one vacuum treatment chamber, wherein the vacuum treatment plant comprises at least two coating tools, for carrying out a method according to one of the preceding claims.

18. Use according to claim 17, characterized in that the vacuum treatment plant (1) has a substantially horizontal lines, wherein the coating direction is vertically aligned.

19. Use according to one of claims 17 or 18, characterized in that the Vakuumbehand treatment plant (1) at least one insertion element (1 1, 1 2, 1 3), in the interior of at least one vacuum treatment chamber (4, 5, 6 ) can be inserted and / or pulled out of this, wherein at the insertion element (1 1, 12, 13) at least one coating tool (14, 15, 16) is arranged.

20. Use according to one of claims 17 to 19, characterized in that at least one vacuum treatment chamber has at least two coating tools, wherein a first coating tool points to the front and a second to the back of one or more substrates to be coated in the vacuum treatment plant.

21. Use according to one of claims 17 to 20, characterized in that the vacuum treatment plant (1) has transport rollers on which the substrate or substrates (22) or a carrier for a plurality of substrates are transported through the vacuum treatment plant (1).