JP7404217B2 - A method for cleaning a vacuum system used in the manufacture of an OLED device, a method for vacuum deposition on a substrate for manufacturing an OLED device, and a vacuum on a substrate for manufacturing an OLED device. equipment for deposition - Google Patents

Description

Embodiments of the present disclosure relate to a method for cleaning a vacuum system, a method for vacuum deposition on a substrate, and an apparatus for vacuum deposition on a substrate. Embodiments of the present disclosure particularly relate to methods and apparatus used in manufacturing organic light emitting diode (OLED) devices.

Techniques for depositing layers on a substrate include, for example, thermal evaporation, physical vapor deposition (PVD), and chemical vapor deposition (CVD). Coated substrates can be used in a variety of applications and technical fields. For example, the coated substrate can be used in the field of organic light emitting diode (OLED) devices. OLEDs can be used to make things such as television screens, computer monitors, cell phones, and other portable devices for displaying information. OLED devices, such as OLED displays, may include one or more layers of organic material located between two electrodes, all deposited on a substrate.

OLED devices can include, for example, a stack of several organic materials that are evaporated in a vacuum chamber of a processing device. Organic material is subsequently deposited onto the substrate through the shadow mask using an evaporation source. The vacuum conditions inside the vacuum chamber are important to the quality of the deposited material layers and the OLED devices manufactured using these material layers.

Therefore, there is a need for a method and apparatus that can improve the vacuum conditions inside a vacuum chamber. The present disclosure is particularly aimed at improving vacuum conditions so that the quality of the layer of organic material deposited on the substrate can be improved.

In view of the above, there is provided a method for cleaning a vacuum system used in the manufacture of OLED devices, a method for vacuum deposition on a substrate for manufacturing an OLED device, and a method for cleaning a vacuum system on a substrate for manufacturing an OLED device. An apparatus is provided for vacuum deposition on. Further aspects, advantages, and features of the disclosure will become apparent from the claims, the specification, and the accompanying drawings.

According to aspects of the present disclosure, a method is provided for cleaning a vacuum system used in the manufacture of OLED devices. The method includes performing a pre-clean to clean at least a portion of the vacuum system and performing the plasma cleaning using a remote plasma source.

According to another aspect of the disclosure, a method is provided for cleaning a vacuum system used in the manufacture of OLED devices. The method includes performing plasma cleaning of at least a portion of the vacuum system as a final cleaning procedure using a remote plasma source.

According to yet another aspect of the present disclosure, a method is provided for vacuum deposition on a substrate to fabricate an OLED device. The method includes performing a pre-clean to clean at least a portion of the vacuum system; performing a plasma clean to clean at least a portion of the vacuum system using a remote plasma source; depositing one or more layers of on the substrate.

According to further aspects of the present disclosure, an apparatus for vacuum deposition on a substrate for manufacturing OLED devices is provided. The apparatus includes a vacuum chamber, a remote plasma source coupled to the vacuum chamber, and a controller coupled to the remote plasma source for performing plasma cleaning as a final cleaning procedure.

Embodiments are also directed to apparatus for performing the disclosed methods, including apparatus portions for performing aspects of each method described. Aspects of these methods may be performed using hardware components, using a computer programmed with appropriate software, by any combination of the two, or in any other manner. . Furthermore, embodiments according to the present disclosure are also directed to methods of operating the described apparatus. The method of operating the described device includes method aspects for performing any function of the device.

In order that the above features of the disclosure may be understood in detail, a more specific description of the disclosure briefly outlined above can be obtained by reference to the embodiments. The accompanying drawings relate to embodiments of the disclosure and are described below.

1 shows a flowchart of a method for cleaning a vacuum system used in the manufacture of OLED devices, according to embodiments described herein. 1 shows a flowchart of a method for vacuum deposition on a substrate to fabricate an OLED device, according to embodiments described herein. 1 shows a schematic diagram of an apparatus for vacuum deposition on a substrate for manufacturing OLED devices, according to embodiments described herein; FIG. 1 shows a schematic diagram of a system for manufacturing devices with organic materials, according to embodiments described herein. FIG.

Reference will now be made in detail to various embodiments of the disclosure, one or more examples of which are illustrated. In the following description of the drawings, like reference numbers refer to like elements. In general, only differences with respect to the individual embodiments will be discussed. The examples are provided to illustrate the disclosure and are not intended to limit the disclosure. Furthermore, features illustrated or described as part of one embodiment can be used on or in conjunction with other embodiments to yield a further embodiment. It is possible. It is intended that this description include such modifications and variations.

The vacuum conditions inside the vacuum chamber can be important to the quality of the material layer deposited on the substrate. Especially for mass production of OLEDs, the cleanability of all vacuum components is essential. Even electropolished surfaces may still be too unsanitary for OLED device manufacturing. The present disclosure uses a remote plasma source after a pre-cleaning procedure, for example, as a final cleaning procedure for a vacuum system. Plasma cleaning can be used to treat parts or components of vacuum chambers and/or vacuum systems. By way of example, plasma cleaning can be performed in vacuum before process start-up or before production starts to improve the cleaning level. The treatment can be carried out for a period of time with a remote plasma, for example pure oxygen or a mixture of oxygen with nitrogen or argon. The cleaning level can be significantly increased and the quality of the layers deposited on the substrate can be improved.

FIG. 1 shows a flowchart of a method 100 for cleaning a vacuum system used in the manufacture of OLED devices, according to embodiments described herein.

Method 100 includes performing a pre-clean to clean at least a portion of the vacuum system (block 110) and performing the plasma cleaning using a remote plasma source (block 120). Plasma cleaning can be, for example, a final cleaning step before operating a vacuum system to deposit one or more layers of organic material onto a substrate. The term "final" is to be understood in the sense that no further cleaning steps are performed after the plasma cleaning.

In remote plasma sources, the gas is typically activated in a remote chamber separate from the vacuum chamber in which the cleaning process is performed. Such activation may be performed, for example, within a remote plasma source. Examples of remote plasmas used in embodiments of the present disclosure include, but are not limited to, remote plasmas of pure oxygen or mixtures of oxygen with nitrogen or argon.

Plasma cleaning as a final cleaning procedure can significantly improve the cleaning level of vacuum systems. The inventors have shown that plasma cleaning as a final cleaning step resulted in a cleansing range of less than ^10-9 grams/ ^cm2 , as measured using standard GCMS (gas chromatography-mass spectrometry) procedures. We realized that we could provide a level of cleaning for items. Therefore, the vacuum conditions and also the quality of the layer of organic material deposited on the substrate can be improved.

According to some embodiments that can be combined with other embodiments described herein, plasma cleaning can be performed for a predetermined period of time. A cleaning level of 10 ⁻⁸ grams/cm ² or less, particularly 10 ⁻⁹ grams/cm ² or less, more specifically 10 ⁻¹⁰ grams/cm ² or less (measured using standard GCMS procedures) is provided. You can select a predetermined time to A cleaning level may be defined as grams of one or more selected contaminants ^{per cm2} of surface area of the portion of the vacuum system being cleaned, such as the surface of an inner chamber wall of a vacuum chamber of the vacuum system.

Pre-cleaning to clean at least a portion of the vacuum system and plasma cleaning to clean at least a portion of the vacuum system using a remote plasma source may be used for various components of the vacuum system. Can be done. In some embodiments, the preclean and plasma clean each include cleaning the vacuum chamber. By way of example, precleaning and plasma cleaning each include cleaning one or more interior walls of a vacuum chamber. The inner wall or walls can be pre-cleaned, for example using a wet chemical cleaning process, and then plasma cleaned to improve the level of cleaning.

Additionally or alternatively, pre-cleaning and plasma cleaning each include cleaning one or more components inside a vacuum chamber of a vacuum system. The one or more components can be selected from the group consisting of mechanical components, movable components, actuators, valves, and any combination thereof. By way of example, a mechanical component can be any component provided inside a vacuum chamber, such as a movable component used to operate a vacuum system. Exemplary movable components include, but are not limited to, valves such as gate valves. Drives include drives used for transporting substrates and/or carriers within the vacuum system, drives or actuators for alignment of substrates and/or masks, gates separating adjacent vacuum regions or chambers. It may include a drive device for a valve, such as a valve.

According to some embodiments that can be combined with other embodiments described herein, pre-cleaning and plasma cleaning each include one or more mask devices, such as shadow masks, used during the deposition process. including cleaning. In particular, the mask can be treated with a remote plasma before being used in a manufacturing process. In some implementations, one or more mask devices can be plasma cleaned for a period of time in a load lock chamber or a chamber dedicated for this purpose, such as a cleaning chamber. Precleaning and plasma cleaning can be performed with one or more mask devices located in the same location, such as a load lock chamber or a cleaning chamber. In another example, pre-cleaning and plasma cleaning can be performed at different locations. As an example, pre-cleaning can be performed outside the vacuum system. After the pre-cleaning, one or more mask devices can be moved into a load lock chamber or a cleaning chamber, for example, and plasma cleaning can be performed using a remote plasma source.

According to some embodiments that can be combined with other embodiments described herein, method 100 is performed after a maintenance procedure for a vacuum system or a portion of a vacuum system. In particular, wet cleaning after maintenance may be insufficient to reach a cleaning level suitable for mass production of OLEDs. After the first cleaning procedure, i.e. pre-cleaning, the second cleaning procedure, i.e. plasma cleaning, provides a cleaning level capable of improving the quality of the layer of organic material deposited during a deposition process, such as a thermal evaporation process. can be guaranteed.

The term "maintenance procedure" can be understood to mean that the vacuum system is not operated in order to be able to perform various tasks such as servicing and/or initialization of the vacuum system or parts of the vacuum system. . Maintenance procedures may be performed periodically, for example at predetermined service intervals. Method 100 can be a method for basic cleaning of a vacuum system or a portion of a vacuum system after a maintenance procedure is completed.

In some embodiments, plasma cleaning is performed using one or more vacuum systems selected from the group consisting of a load lock chamber, a cleaning chamber, a vacuum deposition chamber, a vacuum processing chamber, a transfer chamber, a routing module, and any combination thereof. Performed in multiple (vacuum) chambers. Pre-cleaning can be performed in the same chamber where plasma cleaning is performed. Alternatively, pre-cleaning can be performed at a different location, such as in a different chamber or outside the vacuum system. According to some embodiments, pre-cleaning is performed under atmospheric air and plasma cleaning is performed under vacuum.

According to some embodiments, which may be combined with other embodiments described herein, the pressure in the vacuum chamber is less than or equal to 10 mbar, more particularly less than or equal to 10 ⁻¹ mbar, for the plasma cleaning process. In general, it drops to 10 ⁻² mbar or less. In order to establish a technical vacuum, the pressure can be reduced after pre-cleaning. By way of example, the pressure within the vacuum chamber may range from 10 ⁻² mbar to 10 mbar, in particular from 10 ⁻¹ mbar to 2 mbar, more particularly from 10 ⁻¹ mbar to 1.5 mbar. . One or more vacuum pumps, such as turbo pumps and/or cryopumps, can be provided coupled to the vacuum chamber to generate a technical vacuum inside the vacuum chamber.

Method 100 includes pre-cleaning, which may include one or more pre-cleaning procedures. A pre-clean can be performed before reducing the pressure within the vacuum chamber to perform plasma cleaning. The one or more pre-cleaning procedures can include, for example, a wet chemical cleaning process.

Below, a method according to the present disclosure using a remote plasma source is described. First, the vacuum system or part of the vacuum system can be pre-cleaned, for example using wet chemical cleaning. A vacuum pressure of, for example, about 0.1 mbar to about 5 mbar is then established inside the vacuum chamber by pumping. A remote plasma source is then turned on and plasma cleaning is performed to provide an improved cleaning level.

FIG. 2 shows a flowchart of a method 200 of vacuum deposition on a substrate to fabricate an OLED device. Method 200 can include aspects of a method for cleaning a vacuum system used in manufacturing OLED devices in accordance with the present disclosure.

Method 200 includes performing a pre-clean to clean at least a portion of the vacuum system (block 110) and performing plasma cleaning using a remote plasma source to clean at least a portion of the vacuum system. (Block 120) and depositing one or more layers of organic material onto the substrate (Block 230).

Plasma cleaning as a final cleaning procedure can significantly improve the cleaning level of vacuum systems. Plasma cleaning as a final cleaning step results in cleaning levels of cleaned items within the range of less than 10 ⁻⁹ grams/cm ² as measured using standard GCMS (Gas Chromatography-Mass Spectrometry) procedures. can be provided. Therefore, the vacuum conditions and also the quality of the layer of organic material deposited on the substrate can be improved.

FIG. 3 shows an apparatus 300 for vacuum deposition on a substrate to fabricate OLED devices, according to embodiments described herein.

Apparatus 300 includes a vacuum chamber 310, a remote plasma source 320 coupled to vacuum chamber 310, and a controller 330 coupled to remote plasma source 320 to perform plasma cleaning as a final cleaning procedure. Among other things, controller 330 can be configured to implement a method for cleaning a vacuum system used in manufacturing OLED devices of the present disclosure.

Vacuum chamber 310 can be selected from the group consisting of a load lock chamber, a cleaning chamber, a vacuum deposition chamber, a vacuum processing chamber, a transfer chamber, a routing module, and any combination thereof. As an example, vacuum chamber 310 can be a vacuum processing chamber used for depositing organic materials onto a substrate.

One or more vacuum pumps 340 , such as turbo pumps and/or cryopumps, are connected to the vacuum chamber 310 , such as via one or more tubes, such as bellows tubes, for creating a technical vacuum within the vacuum chamber 310 . Can be combined. Controller 330 can be further configured to control one or more vacuum pumps 340 to reduce the pressure within vacuum chamber 310, such as prior to a plasma cleaning procedure.

The term "vacuum" as used throughout this specification can be understood to mean a technical vacuum, for example with a vacuum pressure of less than 10 mbar. The pressure within the vacuum chamber may be from 10 ⁻⁵ mbar to about 10 ⁻⁸ mbar, in particular from 10 ⁻⁵ mbar to 10 ⁻⁷ mbar, more particularly from about 10 ⁻⁶ mbar to about 10 ⁻⁷ mbar.

A remote plasma source 320 is coupled to the vacuum chamber 310 at a gas injection point 322. By way of example, remote plasma source 320 can be vacuum-tightly coupled to vacuum chamber 310 using, for example, a flange. In some implementations, a gas injection manifold, such as a showerhead, can be provided at the gas injection point 322, for example within the vacuum chamber 310. The gas injection manifold can be configured to evenly distribute the (reactive) gas inside the vacuum chamber 310. The gas injection manifold can provide a uniform cleaning process inside the vacuum chamber 310.

According to some embodiments, apparatus 300 can be included in a vacuum processing system for the manufacture of devices having organic materials therein, such as OLED devices. By way of example, apparatus 300 can include one or more material deposition sources, such as an evaporation source, within a vacuum chamber configured to deposit one or more organic materials onto a substrate.

The vacuum processing system, and in particular the apparatus, may include a transport device 350 configured to transport a carrier, such as a substrate carrier and/or mask carrier 360, within the vacuum chamber 310 without contact. By way of example, plasma cleaning of mask 20 can be performed within vacuum chamber 310, which can be a vacuum processing chamber or a separate cleaning chamber, with mask 20 held by mask carrier 360.

In some embodiments, the vacuum processing system includes one or more material deposition sources (not shown), such as one or more evaporation sources, within the vacuum chamber 310. The vacuum processing system can be configured to evaporate organic materials, such as for making OLED devices, for example. In some embodiments, the one or more material deposition sources are evaporation sources, and in particular evaporation sources for depositing one or more organic materials onto a substrate to form layers of an OLED device. Can be done. For example, during a layer deposition process, the mask carrier 360, which may be further configured to support the substrate 10, is transported into and through the vacuum chamber 310 along a transport path, such as a linear transport path. In particular, it can be conveyed through a deposition area.

As shown in FIG. 3, additional chambers can be provided adjacent to vacuum chamber 310. A valve having a valve housing 304 and a valve unit 306 can isolate the vacuum chamber 310 from adjacent chambers. After the carrier with the mask 20 and/or the substrate thereon is inserted into the vacuum chamber 310, as indicated by the arrow, the valve unit 306 can be closed. The atmosphere in the vacuum chamber 310 can be individually controlled, for example, by creating a technical vacuum, such as by coupling a vacuum pump to the vacuum chamber 310, prior to plasma cleaning.

In some implementations, the vacuum processing system can include one or more transport paths extending through the vacuum chamber 310. The carrier can be configured for transport along one or more transport paths, eg, past one or more material deposition sources. Although one transport path is exemplarily shown by an arrow, it should be understood that the present disclosure is not so limited and that more than one transport path can be provided. By way of example, at least two transport paths can be arranged substantially parallel to each other for respective carrier transport. One or more material deposition sources can be positioned between the two transport paths.

The transport device 350 can be configured for contactless flotation and/or contactless transport of a carrier, such as a mask carrier 360, within the vacuum chamber 310, for example in the transport direction along one or more transport paths. . Contactless flotation and/or transport of the carrier is advantageous in that no particles are generated during transport, for example due to mechanical contact with the guide rail. Since particle generation is minimized when using non-contact flotation and/or transport, improved purity and uniformity of layers deposited on the substrate can be provided.

FIG. 4 shows a schematic diagram of a system 400 for manufacturing devices with organic materials, according to embodiments described herein. System 400 can be cleaned using methods and apparatus according to embodiments described herein.

System 400 includes two or more processing areas and a transport device 460 configured to sequentially transport carrier 401 supporting substrate 10 and optionally a mask to the two or more processing areas. By way of example, the transport device 460 can be configured to transport the carrier 401 along the transport direction 2 through two or more processing zones for substrate processing. In other words, the same carrier is used to transport the substrate 10 through multiple processing areas. In particular, between substrate processing within a processing region and subsequent substrate processing within the processing region, the substrate 10 is never removed from the carrier 401; Stay on top.

As illustratively shown in FIG. 4, the two or more processing regions can include a first deposition region 408 and a second deposition region 412. Optionally, a transfer region 410 can be provided between the first deposition region 408 and the second deposition region 412. Multiple regions can be provided within a single vacuum chamber, such as two or more processing and transfer regions. Alternatively, multiple regions may be provided in different vacuum chambers coupled to each other. As an example, each vacuum chamber may provide one area. In particular, a first vacuum chamber can provide a first deposition region 408, a second vacuum chamber can provide a transfer region 410, and a third vacuum chamber can provide a second deposition region 408. A region 412 may be provided. In some implementations, the first vacuum chamber and the third vacuum chamber can be referred to as "deposition chambers." The second vacuum chamber may be referred to as a "processing chamber." Additional vacuum chambers or regions may be provided adjacent to the region shown in the example of FIG.

A valve with a valve housing 404 and a valve unit 405 allows a vacuum chamber or region to be separated from an adjacent region. After the carrier 401 with the substrate 10 thereon has been inserted into a region, such as the second deposition region 412, the valve unit 405 can be closed. By creating a technical vacuum, e.g. by coupling a vacuum pump to the regions, and/or inserting one or more process gases into the first deposition region 408 and/or the second deposition region 412, e.g. By doing so, the atmosphere within a region can be individually controlled. A transport path, such as a linear transport path, may be provided for transporting the carrier 401 with the substrate 10 thereon into, through, and from the region. The transport path can extend at least partially through two or more processing regions, such as first deposition region 408 and second deposition region 412, and optionally through transfer region 410.

System 400 can include a transfer region 410. In some embodiments, transfer region 410 may be omitted. Transfer region 410 may be provided by a rotating module, a transit module, or a combination thereof. FIG. 4 shows a combination of a rotation module and a transit module. In a rotating module, the track device and the carrier disposed thereon are capable of rotating about an axis of rotation, such as a vertical axis of rotation. As an example, a carrier may be transferred from the left side of system 400 to the right side of system 400, or vice versa. The transit module can include intersecting tracks so that carriers can be transferred through the transit module in different directions, such as directions perpendicular to each other.

One or more deposition sources may be provided within a deposition region, such as first deposition region 408 and second deposition region 412. By way of example, first deposition source 430 may be provided within first deposition region 408 . A second deposition source 450 may be provided within the second deposition region 412. The one or more deposition sources can be an evaporation source configured to deposit one or more organic layers onto the substrate 10 to form an organic layer stack for an OLED device.

The system described herein can be used for evaporation on large area substrates, for example for OLED display manufacturing. In particular, the substrate on which systems according to embodiments described herein are provided is a large area substrate. For example, a large area substrate or carrier has a GEN 4.5, which corresponds to a surface area of approximately 0.67 m ² (0.73 m x 0.92 m), which corresponds to a surface area of approximately 1.4 m ² (1.1 m x 1.3 m). GEN 5, which corresponds to a surface area of approximately 4.29 m ² (1.95 m x 2.2 m), GEN 7.5, which corresponds to a surface area of approximately 5.7 m ² (2.2 m x 2.5 m), or It can even be GEN10, corresponding to a surface area of approximately 8.7 m ² (2.85 m x 3.05 m). Larger substrate generations, such as GEN11 and GEN12, and their corresponding surface areas can be similarly implemented. Half sizes of the GEN generation can also be offered in OLED display manufacturing.

The present disclosure uses a remote plasma source after a pre-cleaning procedure, for example, as a final cleaning procedure for a vacuum system. Plasma cleaning can be used to treat parts or components of vacuum chambers and/or vacuum systems. By way of example, plasma cleaning can be performed in vacuum before process start-up or before production starts to improve the cleaning level. The treatment can be carried out for a period of time with a remote plasma, for example pure oxygen or a mixture of oxygen with nitrogen or argon. The cleaning level can be significantly increased and the quality of the layers deposited on the substrate can be improved.

Although the above description is directed to embodiments of the disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope of the disclosure, and the scope of the disclosure is as follows: defined by the scope of the claims.

Claims (13)

A method for cleaning a vacuum system used in the manufacture of OLED devices, the method comprising:
performing a pre-cleaning to clean at least a portion of the vacuum system;
performing a plasma cleaning to clean at least the portion of the vacuum system using a remote plasma source, the pre-cleaning being performed in a chamber at atmospheric pressure, and the plasma cleaning carried out under vacuum in a chamber, said pre-cleaning being carried out before the pressure in said chamber is reduced to carry out said plasma cleaning, said plasma cleaning using a plasma of pure oxygen or an oxygen mixture; ,Method. 2. The method of claim 1, wherein the plasma cleaning is a final cleaning procedure before operating the vacuum system. 3. The method of claim 1 or 2, wherein the plasma cleaning includes cleaning a vacuum chamber. 4. The method of claim 3, wherein the plasma cleaning includes cleaning one or more interior walls of the vacuum chamber. 5. A method according to any preceding claim, wherein the plasma cleaning comprises cleaning components inside a vacuum chamber of the vacuum system. 6. The method of claim 5, wherein the component is selected from the group consisting of a mechanical component, a movable component, a drive, a valve, and any combination thereof. 7. A method according to any preceding claim, wherein the plasma cleaning comprises cleaning one or more mask devices used during the deposition process. 8. A method according to any preceding claim, carried out after a maintenance procedure of the vacuum system or part of the vacuum system. The plasma cleaning is performed within one or more chambers of the vacuum system selected from the group consisting of a load lock chamber, a cleaning chamber, a vacuum deposition chamber, a vacuum processing chamber, a transfer chamber, a routing module, and any combination thereof. 9. A method according to any one of claims 1 to 8, wherein the method is carried out. 10. A method according to any preceding claim, wherein the pre-cleaning comprises a wet chemical cleaning process. A method for vacuum deposition on a substrate for manufacturing an OLED device, the method comprising:
performing a pre-clean to clean at least a portion of the vacuum system;
performing plasma cleaning to clean at least the portion of the vacuum system using a remote plasma source;
depositing one or more layers of organic material on the substrate, the precleaning being performed in a chamber under atmospheric pressure, the plasma cleaning being performed in the chamber under vacuum, and the plasma cleaning being performed in the chamber under vacuum; The pre-cleaning is performed before the pressure in the chamber is reduced to perform plasma cleaning, the plasma cleaning uses a plasma of pure oxygen or an oxygen mixture , and the depositing is performed in the chamber. The method by which it is carried out . An apparatus for vacuum deposition on a substrate for manufacturing an OLED device, the apparatus comprising:
a vacuum chamber;
a remote plasma source coupled to the vacuum chamber;
a controller coupled to the remote plasma source for performing plasma cleaning as a final cleaning step;
a vacuum pump coupled to the vacuum chamber, wherein a pre-cleaning is performed in the vacuum chamber under atmospheric pressure, and the plasma cleaning is performed in the vacuum chamber under vacuum, before performing the plasma cleaning. wherein the controller is configured to control the vacuum pump to reduce pressure in the vacuum chamber, and wherein the plasma cleaning uses a plasma of pure oxygen or an oxygen mixture. 13. Apparatus according to claim 12, wherein the controller is configured to implement a method according to any one of claims 1 to 11.

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