EP4469615A1

EP4469615A1 - Method of operating a coating system, controller for operating a coating system, electron catching apparatus, and coating system

Info

Publication number: EP4469615A1
Application number: EP22708373.0A
Authority: EP
Inventors: Torsten Bruno Dieter; Andreas JENDRZEY; Markus KLIEMT; Steffen BRAUNGER
Original assignee: Applied Materials Inc
Current assignee: Elevated Materials Germany GmbH
Priority date: 2022-01-27
Filing date: 2022-01-27
Publication date: 2024-12-04
Also published as: CN118742668A; WO2023143719A1

Abstract

A method of operating a coating system provided in a vacuum chamber is described. The coating system includes a coating drum for transporting a substrate, at least one electron beam gun for evaporating a coating material, and an electron catcher. The electron catcher includes an anode for collecting free electrons in the vacuum chamber. The anode is heatable via a heating current. The electron catcher is configured such that the heating current passes through the anode or the electron catcher includes a resistive heater thermally coupled with the anode, with the electron catcher being configured such that the heating current passes through the resistive heater. The method includes: an automatic adjustment of at least one parameter selected from a group consisting of: the heating current, a DC bias voltage of the anode, a position of the anode, and a pressure in the vacuum chamber. The automatic adjustment includes a measurement of an electron collection current passing through the anode.

Description

METHOD OF OPERATING A COATING SYSTEM, CONTROLLER FOR OPERATING A COATING SYSTEM, ELECTRON CATCHING APPARATUS, AND COATING SYSTEM

TECHNICAL FIELD

[0001] Embodiments of the present disclosure relate to the operation of a coating system in a vacuum chamber, the coating system including an electron catcher. The electron catcher includes an anode for collecting free electrons in the vacuum chamber.

BACKGROUND

[0002] Electron-beam physical vapor deposition (EBPVD) is a vacuum deposition method used to produce thin films and coatings in various technical fields. Examples include the semiconductor industry, the aerospace industry, and optics. A target of the coating material is bombarded with an electron beam, leading to evaporation of coating material. A thin film can then be formed on a substrate by condensation. Roll-to-roll (R2R) processing is a method where a flexible material taken from an unwinder roll is coated and subsequently re-reeled on a rewinder roll. R2R processing can be used to create electronic devices on flexible plastic, metal foil, or flexible glass substrates.

[0003] In a R2R electron-beam vacuum coating process, EBPVD is applied to a film substrate. In such a process, electrons of the electron beam and secondary electrons emitted by the coating material may fly to the film substrate from the bombarded coating material. The substrate thus gets electrostatically charged. A high charge build-up can occur for example at a rewinder roll of the coating system, particularly if the film is coated with insulating materials like for example SiOx or AlOx. As the roll grows with each additional layer of the film substrate, the electric charge increases. A highly charged film can negatively influence the winding quality. Further, a highly charged film is prone to picking up particles and dust, leading to a decrease in product quality. A negative impact on downstream material processing can ensue. Moreover, handling of a highly charged roll carries the danger of electrical shock to operators.

[0004] By using an electron catcher, electrons can be collected before they reach the substrate. Static charge on the substrate can be reduced significantly. A typical electron catcher includes a conductive wire for collecting electrons. The conductive wire is subjected to a bias voltage and functions as an anode. By collecting free electrons via the conductive wire, the electrons are prevented from reaching the substrate. An increase in the substrate’s charge can be prevented. The collection rate of an electron catcher depends on various parameters of the electron catcher and the coating system. Setting up a coating system such that the collection rate is high requires arduous tests and adjustments. The resulting collection rate can still be lower than desired.

[0005] In view of the above, it is beneficial to provide improved methods of operating an electron catcher.

SUMMARY

[0006] Aspects of the present disclosure provide a method of operating a coating system provided in a vacuum chamber. The coating system includes a coating drum for transporting a substrate, at least one electron beam gun for evaporating a coating material, and an electron catcher. The electron catcher includes an anode for collecting free electrons in the vacuum chamber. The anode is heatable via a heating current. The electron catcher is configured such that the heating current passes through the anode or the electron catcher includes a resistive heater thermally coupled with the anode, with the electron catcher being configured such that the heating current passes through the resistive heater. The method includes: an automatic adjustment of at least one parameter selected from a group consisting of: the heating current, a DC bias voltage of the anode, a position of the anode, and a pressure in the vacuum chamber. The automatic adjustment includes a measurement of an electron collection current passing through the anode.

[0007] Aspects of the present disclosure provide a controller for operating a coating system provided in a vacuum chamber. The controller includes a central processing unit and an interface for exchanging signals with at least one component of the coating system or the vacuum chamber. The controller is configured to carry out a method according to aspects described herein.

[0008] According to an embodiment, an electron catching apparatus is provided. The electron catching apparatus includes an electron catcher and a first actuator. The electron catcher includes an anode configured for collecting free electrons in a vacuum chamber. The anode is heatable via a heating current. The electron catcher is configured such that the heating current passes through the anode or the electron catcher includes a resistive heater thermally coupled with the anode with the electron catcher being configured such that the heating current passes through the resistive heater. The first actuator is configured to move the anode in a first direction, the first direction having at least a component perpendicular to a main extension direction of the anode.

[0009] According to an embodiment, a coating system is provided. The coating system includes a coating drum for transporting a substrate, at least one electron beam gun for evaporating a coating material, a controller according to aspects described herein, and an electron catcher. The electron catcher includes an anode configured for collecting free electrons in a vacuum chamber. The anode is heatable via a heating current. The electron catcher is configured such that the heating current passes through the anode or the electron catcher includes a resistive heater thermally coupled with the anode, with the electron catcher being configured such that the heating current passes through the resistive heater. [0010] The present disclosure is to be understood as encompassing apparatuses and systems for carrying out the disclosed methods, including apparatus parts for performing each described method aspect. Method aspects may be performed for example by hardware components, by a computer programmed by appropriate software or by any combination of the two. The present disclosure is also to be understood as encompassing methods for operating described apparatuses and systems. Methods for operating the described apparatuses and systems include method aspects for carrying out every function of the respective apparatus or system.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] So that the features recited above can be understood in detail, a more particular description of the subject matter briefly summarized above may be provided below by reference to embodiments. The accompanying drawings relate to embodiments and are described in the following:

Figs, la-c are schematic, cross-sectional views of electron catching apparatuses according to embodiments described herein;

Fig. 2a-b are schematic, cross-sectional views of a coating system according to embodiments described herein; and

Fig. 3 is a chart illustrating a method of operating an electron catcher placed in a vacuum chamber, according to aspects described herein.

DETAILED DESCRIPTION OF EMBODIMENTS

[0012] Reference will now be made in detail to the various embodiments, wherein one or more examples of the embodiments are illustrated in the figures. Within the following description of the drawings, the same reference numbers refer to same components. Generally, only the differences with respect to individual embodiments are described. Each example is provided as an explanation and is not meant as a limitation. Further, features illustrated or described as part of one embodiment can be used on or in conjunction with other embodiments to yield yet a further embodiment. It is intended that the description includes such modifications and variations.

[0013] Figs, la-c are schematic, cross-sectional views of electron catching apparatuses, according to embodiments described herein. The electron catching apparatus 100 includes an electron catcher 110 and a first actuator 120. The electron catcher 110 includes an anode 112 configured for collecting free electrons in a vacuum chamber. In particular, a positive voltage can be applied to the anode for collecting free electrons in a vacuum chamber. The anode 112 may be for example a wire, a tube, or a rod. In particular, the anode includes a conductive material, particularly a metal. The anode may include for example tungsten or molybdenum. The cross-sectional planes depicted in Figs, la-c are perpendicular to a main direction of extension of the respective anode.

[0014] The anode is heatable via a heating current. The heating current may be an alternating current (AC). In embodiments, the electron catcher 110 is configured such that the heating current passes through the anode 112. The anode 112 may be a resistively heatable wire. Alternatively, the electron catcher includes a resistive heater thermally coupled with the anode, the electron catcher being configured such that the heating current passes through the resistive heater. The heating current may be regulated via a power supply connected to the anode or the resistive heater. In the context of the present disclosure, thermally coupled is particularly to be understood as “in direct physical contact or coupled via a thermally conducting material”. For example, the electron catcher 110 of the embodiment shown in Fig. lb includes a resistive heater 116 provided between an anode holder 114 and the anode 112. In particular, the anode 112 is heatable by the resistive heater 116. [0015] The first actuator 120 is configured to move the anode 112 in a first direction, the first direction having at least a component perpendicular to a main extension direction of the anode 112. The anode 112 may be attached to the first actuator 120 via the anode holder 114.

[0016] An advantage of the electron catching apparatus including at least one actuator is that in situ control of the electron catcher’s position can be enabled. Accordingly, the electron catcher’s position can be modified without a need for manual adjustments performed by a person. The electron catcher’s position can be modified within a vacuum chamber in an evacuated state. In particular, the electron catcher’s position can be modified while components of a coating system provided in the vacuum chamber are running. A further advantage is that a concerted automatic adjustment of a plurality of parameters including the electron catcher’s position but also other parameters associated with a coating system can be facilitated.

[0017] The term “vacuum”, as used herein, can be understood in the sense of a technical vacuum having a vacuum pressure of less than, for example, 10 mbar. Typically, the pressure in a vacuum chamber as described herein may be between 10'⁵ mbar and about 10'⁸ mbar, more typically between 10'⁵ mbar and 10" ⁷ mbar, and even more typically between about 10'⁶ mbar and about 10'⁷ mbar.

[0018] In embodiments, the electron catching apparatus 100 includes a second actuator configured to move the anode in a second direction, the second direction having at least a component perpendicular to the first direction and to the main extension direction of the anode. The position of the electron catcher may be adjusted more precisely.

[0019] Any of the first or the second actuator may be an electric actuator, particularly an electromechanical actuator or a linear motor. Any of the first or the second actuator may be a rotary actuator, particularly an electric rotary actuator. [0020] In embodiments, for example as shown in Fig. 1c, the first actuator 120 is configured to move the anode 112 along at least a section of a circular path. In particular, the first actuator 120 is a rotary actuator.

[0021] Fig. 2a is a schematic, cross-sectional view of a coating system according to embodiments described herein. The coating system 200 includes a coating drum 204 for transporting a substrate 214 and at least one electron beam gun 208 for evaporating a coating material 212. In particular, the evaporated coating material 212 is to be deposited on the substrate 214 by condensation. The substrate 214 may be partly in contact with the coating drum 204. The coating drum 204 may be configured to move the substrate 214 by rotation around an axis. The substrate 214 may be a flexible substrate, particularly a flexible plastic substrate.

[0022] In the present disclosure, a “flexible substrate” can be understood as a bendable substrate. For instance, the “flexible substrate” can be a “foil” or a “web”. In the present disclosure, the term “flexible substrate” and the term “substrate” may be synonymously used. For example, the flexible substrate as described herein may include materials like BOPP, CPP, HOPE, LDPE, PA (Nylon), PET, PVC, particularly unplasticized PVC, PE, PI, PU, TaC, OPP, one or more metals, paper, combinations thereof, or any other material suitable to be coated using evaporation. Further, it is to be noted that also already-coated substrates may be used. Typically, the substrate thickness T_s can be 1 pm < T_s < 200 pm, particularly 5 pm < T_s < 100 pm, more particularly 5 pm < T_s < 50 pm. The substrate length L_s can be L_s > 500 m, particularly L_s > 10000 m, more particularly L_s > 20000 m, even more particularly L_s > 25000 m. The substrate width W_s can be 0.5 m < W_s < 5 m, particularly 1 m < W_s < 3 m.

[0023] In the present disclosure, a “coating drum” can be understood as a drum or a roll having a substrate support surface for contacting the flexible substrate during processing. The coating drum may include a substrate guiding region. Typically, the substrate guiding region is a curved substrate support surface, e.g. a cylindrically symmetric surface, of the coating drum. The curved substrate support surface of the coating drum may be adapted to be (at least partly) in contact with the flexible substrate during operation. The substrate guiding region may be defined as an angular range of the roll in which the substrate is in contact with the curved substrate support surface during the guiding of the substrate, and may correspond to the enlacement angle of the roll. For instance, the enlacement angle of the roll may be 120° or more, particularly 180° or more, or even 270° or more. According to some embodiments, which can be combined with other embodiments described herein, the coating drum is cylindrical and has a length L of 0.5 m < L < 8.5 m. Further, the coating drum may have a diameter D of 1.0 m < D < 3.0 m. Accordingly, beneficially the coating drum is configured for guiding and transporting flexible substrates having a large width.

[0024] According to embodiments which can be combined with any other embodiments described herein, the substrate support surface of the coating drum has a coating including an electronegative polymer. An “electronegative polymer” may be understood as a polymer having electronegative properties. Typically, the coating is provided on the complete support surface. In particular, the coating has a constant thickness, e.g. a thickness T selected from the range of 2.5 pm < T < 15 pm. Providing a coating having a thickness T selected from the range of 2.5 pm < T < 15 pm can be beneficial to ensure sufficient capacitance to ensure a sufficient pinning force between the flexible substrate and the coated support surface of the coating drum.

[0025] According to some embodiments, which can be combined with other embodiments described herein, the coating provided on the substrate support surface of the coating drum has triboelectric properties. In other words, the electronegative polymer can be configured to generate static charge through fictional contact with the flexible substrate. In particular, the electronegative polymer (e.g. a fluoropolymer) can be configured to create a mirror charge on the flexible substrate surface during guiding through the triboelectric effect. The triboelectric effect (also known as triboelectric charging) is a type of contact electrification on which certain materials become electrically charged after coming into fictional contact with a different material. In other words, the triboelectric effect can be described as the transfer of charge (electrons) from one material to another following friction or sliding contact. The total charge transfer between two materials is defined by the difference of charge affinity between the two contacting material surfaces.

[0026] Accordingly, providing a coating comprising an electronegative polymer on the support surface of the coating drum configured for creating a mirror charge on the flexible substrate surface being in contact with the coating drum during substrate guiding, beneficially provides for improving the adhesion of the flexible substrates to the coating drum. In other words, providing a coating having triboelectric properties on the support surface of the coating drum, beneficially provides for a charge transfer between the coating and the flexible substrate, such that a constant and homogenous contact force (also referred to as pinning force or clamping force) between the flexible substrate and the coating drum can be ensured. Further, exploiting the triboelectric effect beneficially provides for a slip reduction between the flexible substrate and the coating provided on the support surface of the coating drum.

[0027] For instance, substrate materials as described herein have a charge affinity CA of - 90 nC/J < CA < - 40 nC/J. For instance, PET has a charge affinity CA of CA ~ - 40 nC/J, BOPP has a charge affinity CA of CA ~ - 85 nC/J, and LDEP, HDPE and PP have charge affinities CA of CA ~ - 90 nC/J. The coating comprising an electronegative polymer as described herein, particularly comprising or consisting of a fluoropolymer, particularly comprising or consisting of PTFE and/or PF A, has a charge affinity CA of CA ~ - 190 nC/J.

[0028] Accordingly, beneficially the coating provided on the support surface of the coating drum as described herein ensures that the coated coating drum is negatively charged compared to the substrate, even in the absence of an externally applied electric field. Accordingly, it is to be understood that according to embodiments which can be combined with other embodiments herein, the coating on the support surface of the coating drum can be configured to provide for a charge affinity difference ACA with respect to the flexible substrate to be guided by the coating drum. In particular, the charge affinity difference ACA between the coating and the substrate can be 50 nC/J < ACA < 200 nC/J, particularly 100 nC/J < ACA < 150 nC/J.

[0029] According to embodiments, which can be combined with any other embodiments described herein, the electronegative polymer can be dielectric. In particular, the electronegative polymer can be an electrical insulating material which can be polarized. For instance, the electronegative polymer can be a fluoropolymer, particularly an elastomeric fluoropolymer, e.g. comprising perfluoralkoxy-polymer (PF A) and/or a polytetrafluorethylen (PTFE). In particular, the fluoropolymer may consist of PFA or PTFE. A coating comprising or consisting of a fluoropolymer, such as PFA or PTFE, beneficially provides for a coating having a very high dielectric breakdown strength. Further, a coating comprising or consisting of a fluoropolymer, such as PFA or PTFE, beneficially provides for a low friction coefficient, particularly an ultra-low friction coefficient. Accordingly, beneficially low wear rates of the coating, e.g. comparable to steels, can be provided ensuring coating longevity. In other words, a fluoropolymer coating providing a fluorinated polymer coating surface beneficially provides for an excellent low frictional performance level reducing effective coating wear.

[0030] According to embodiments, which can be combined with any other embodiments described herein, the coating provided on the support surface of the coating drum can have a friction coefficient p of p < 0.1, particularly a friction coefficient p of p < 0.05. More specifically, a non-lubricated fluoropolymer friction coefficient p can be p < 0.1, particularly p < 0.05. It is to be noted that partial wear from coating asperities can provide highly hydrophobic hydrodynamic boundary lubrication, beneficially further reducing the friction coefficient by a factor F of approximately F = 10. Accordingly, beneficially an effective coating material wear rate approaching the intrinsic wear rate level of steel can be achieved. [0031] For instance, according to embodiments, which can be combined with any other embodiments described herein, the coating provided on the support surface of the coating drum may have a wear-rate constant ka of 0.4 x 10-7 MPa-1 < ka < 2.0 x 10- 6 MPa-1. In other words, the coating may be configured to have a wear-rate constant ka selected from the range of 0.4 x 10-7 MPa-1 < ka < 2.0 x 10-6 MPa-1. The wear rate constant ka is the dimensionless wear rate constant k divided by the hardness [MPa], i.e. ka [MPa- 1] = k / hardness [MPa],

[0032] According to some embodiments, which can be combined with other embodiments described herein, the coating provided on the support surface of the coating drum has a breakdown field strength BFS of 2.0 MV/cm < BFS < 30 MV/cm. For instance, a coating of PFA having a thickness T of T = 5 pm has a BFS of 2.0 MV/cm when an electrical field of 300V is applied. A coating of PTFE having a thickness T of T = 10 pm has a BFS of 24 MV/cm when an electrical field of 300V is applied.

[0033] Providing the coating drum with a coating including an electronegative polymer as described herein beneficially provides for an improved contact of the flexible substrate with the coating drum during substrate transportation. Accordingly, with the coating drum as described herein, a substantially constant and homogenous contact force between the flexible substrate and the coating drum can be achieved such that clamping or adhesion of the flexible substrate to the coating drum can be improved. The contact force may also be referred to as a clamping force. Further, by employing a coating drum having a coating as described herein, the heat transfer from the flexible substrate to the coating drum can be improved, which can be beneficial for processing heat sensitive flexible substrates, particularly thin polymeric flexible substrates. The improved heat transfer results from the fact that when guiding the flexible substrate with the coating drum of the present disclosure, a direct contact of the substrate with the coated support surface can be provided for substantially the complete contact surface. In other words, areas with gaps (down to the microscopic scale) between the flexible substrate and the coated support surface can be reduced or substantially be eliminated. [0034] The coating system 200 may further include an unwinder roll 202 and a rewinder roll 206. The substrate 214 may be partly wound around any of the unwinder roll 202 and the rewinder roll 206. The coating system 200 may be configured to move a part of the substrate 214 from the unwinder roll 202 to the coating drum 204. The coating system 200 may further be configured to move a part of the substrate 214 from the coating drum 204 to the rewinder roll 206.

[0035] In the present disclosure, an “unwinder roll” can be understood as a roll on which the flexible substrate to be processed is stored. Accordingly, a “rewinder roll” as described herein may be understood as a roll adapted for receiving the processed flexible substrate. According to embodiments which can be combined with any other embodiments described herein, the unwinder roll and the rewinder roll are active rolls. An active roll may be understood as a roll that is provided with a drive or a motor for actively moving or rotating the respective roll. Typically, an active roll is controllable to provide a predetermined torque and/or a predetermined rotational speed. For example, an AC-drive can be coupled to an active roll as described herein. The AC-drives of the active rolls as described herein can be synchronized. It is to be understood that the torque and/or rotational speed of the active rollers can be controllable such that variable torques and/or speeds may be provided. Typically, the coating drum is an active roll as described herein.

[0036] The coating system 200 includes an electron catching apparatus 100 according to embodiments described herein, particularly as described with regard to Figs. la-c. The coating system may also include at least one further electron catching apparatus according to embodiments described herein.

[0037] The coating material 212 may be held by a material holder 210. In particular, the material holder 210 is positioned such that electrons emitted by the electron beam gun 208 can impinge on the coating material 212. The material holder 210 may be for example a crucible, a plate, or a socket. A crucible is particularly suitable when the coating material is provided in the form of an ingot. A socket is particularly suitable when the coating material is provided in the form of a rod. [0038] The coating system 200 may include a controller 220 for operating the coating system. The controller may be configured to carry out a method according to aspects described herein. The controller particularly includes an interface for exchanging signals with at least one component of the coating system or the vacuum chamber. Exemplary components include a vacuum pump, a power supply, and a vacuum control valve. The at least one component may particularly include a power supply for providing a heating current to the anode or to the resistive heater of the electron catcher. The at least one component may include a power supply for providing a DC bias voltage to the anode of the electron catcher. According to one aspect, the at least one component may include at least one of a first or a second actuator of an electron catching apparatus as described herein.

[0039] In particular, the controller is configured to automatically adjust at least one parameter selected from a group consisting of: the heating current, a DC bias voltage of the anode, a position of the anode, and a pressure in the vacuum chamber. A highly effective collection of free electrons can be achieved. The controller may be configured to automatically adjust 2, 3, or all 4 parameters selected from the group. The effectiveness of electron collection can thus be further increased.

[0040] A high effectiveness of electron collection decreases static charge on the substrate leading to reduced particle creation on the substrate. The quality of a final product of a roll-to-roll electron-beam vacuum coating process can thus be improved.

[0041 ] The automatic adjustment of the at least one parameter includes measuring an electron collection current passing through the anode. In the context of the present disclosure, an electron collection current may be understood as the total direct current passing through the anode as a result of a DC bias voltage applied to the anode. The DC bias voltage may be regulated via a power supply connected to the anode.

[0042] The controller may include a central processing unit (CPU), a memory and, for example, support circuits. To facilitate control of the system, the CPU may be one of any form of general-purpose computer processor that can be used in an industrial setting for controlling various components and sub-processors. The memory is coupled to the CPU. The memory, or a computer readable medium, may be one or more readily available memory devices such as random-access memory, read only memory, a floppy disk, a hard disk, or any other form of digital storage either local or remote. The support circuits may be coupled to the CPU for supporting the processor in a conventional manner. These circuits include cache, power supplies, clock circuits, input/output circuitry and related subsystems, and the like.

[0043] Control instructions are generally stored in the memory as a software routine or program. The software routine or program may also be stored and/or executed by a second CPU that is remotely located from the hardware being controlled by the CPU. The software routine or program, when executed by the CPU, transforms the general-purpose computer into a specific purpose computer (controller) that controls a system for depositing a material, according to any of the embodiments of the present disclosure.

[0044] Methods according to the present disclosure may be implemented as a software routine or program. At least some of the method operations disclosed herein may be performed via hardware as well as by a software controller. As such, the embodiments may be implemented in software as executed upon a computer system, and hardware as an application specific integrated circuit or another type of hardware implementation, or a combination of software and hardware. The controller may execute or perform a method of depositing a material on a substrate, according to embodiments of the present disclosure. Methods described herein can be conducted using computer programs, software, computer software products and interrelated controllers, which can have a CPU, a memory, a user interface, and input and output devices being in communication with corresponding components of the system for depositing a material. [0045] In embodiments, a coating system according to the present disclosure may include at least one additional electron catching apparatus. An electron collection effectiveness may be further improved. The coating system may include for example two or three electron catching apparatuses. In this regard, an electron collection current is particularly to be understood as a sum calculated with respect to all electron catchers in operation. Fig. 2b shows an exemplary coating system 200 including an electron catching apparatus 100 and an additional electron catching apparatus 230. The remaining features may be the same as described above with regard to Fig. 2a. The additional electron catching apparatus 230 can be an electron catching apparatus as described with regard to Figs. la-c.

[0046] Fig. 3 is a chart illustrating a method of operating a coating system provided in a vacuum chamber, according to aspects described herein. The coating system includes a coating drum for transporting a substrate, at least one electron beam gun for evaporating a coating material, and an electron catcher. The coating material may be placed in a material holder.

[0047] The electron catcher includes an anode for collecting free electrons in the vacuum chamber. The anode is heatable via a heating current. The heating current passes through the anode or the electron catcher comprises a resistive heater thermally coupled with the anode, the heating current passing through the resistive heater. The heating current may be regulated via a power supply connected respectively to the anode or the resistive heater. Generally, the coating system may be for example a coating system as described herein, particularly with regard to Figs. 2a-b.

[0048] The method 300 starts in block 302. The method 300 includes an automatic adjustment 310 of at least one parameter selected from a group consisting of: the heating current, a DC bias voltage of the anode, a position of the anode and a pressure in the vacuum chamber. The method may include an automatic adjustment of 2, 3, or all 4 parameters selected from the group. A particularly effective collection of free electrons can be achieved. The automatic adjustment 310 includes, in block 312, a measurement of an electron collection current passing through the anode.

[0049] The automatic adjustment of the at least one parameter may be performed via closed loop control. Closed loop control is particularly to be understood as a method where process outputs (influenced by process inputs) are measured and the measurement results are used as further input for the process. The automatic adjustment may include calculating a difference between a desired value and a measured value of the electron collection current and applying a correction to the at least one parameter. The correction may be based on at least one of: a proportional, an integral, or a derivative term. The automatic adjustment may be performed for example via a PID controller. A PID controller is particularly to be understood as a controller calculating a difference between a desired value and a measured value of a process variable and applying a correction based on proportional, integral, and derivative terms.

[0050] According to an aspect, the automatic adjustment may be performed by a computational optimization technique, particularly an optimization algorithm, an iterative method, or a heuristic algorithm.

[0051] The position of the anode is particularly to be understood as a position of the anode relative to any of: the coating drum or the material holder. The position may additionally or alternatively be understood as a position relative to the substrate.

[0052] The heating current may be an alternating current (AC). The heating current may be adjusted for example to a value being any of: at least 10 A or at most 80 A.

[0053] The DC bias voltage may be regulated via a power supply connected to the anode. The DC bias voltage may be adjusted for example to a value being any of: at least 30 V or at most 120 V. [0054] The pressure may be regulated for example by a gas inlet provided on the vacuum chamber. The pressure may be adjusted for example to a value being any of: at least 5- 1 O'⁶ mbar or at most 8- 1 O'³ mbar.

[0055] According to an aspect, the coating material may include, particularly be, a non-metallic material. The coating material may include, particularly be, an electrically insulating material. In the present disclosure, an electrically insulating material may be understood as a material having a resistivity higher than for example 10¹⁰, 10¹⁴, or 10¹⁶ Q-m. With electrically insulating coating materials, it is particularly beneficial to avoid impingement of electrons to prevent charge buildup. The coating material may include at least one of SiOx, AlOx, or SiO2.

[0056] The automatic adjustment of the at least one parameter may include maximizing the electron collection current. The number of electrons reaching the substrate and causing electrostatic charging can be reduced or eliminated.

[0057] According to an aspect, the automatic adjustment 310 of the at least one parameter may include, in block 314, comparing the electron collection current with an electron beam gun current. An electron beam gun current is particularly to be understood as the quantity of electric charge per unit of time emitted as an electron beam. In coating systems including more than one electron beam gun, the electron beam gun current is particularly to be understood as a sum calculated with respect to all used electron beam guns.

[0058] The electron collection current may be compared to the electron beam gun current continuously. A particularly precise adjustment of the at least one parameter may be achieved.

[0059] The method may include adjusting the at least one parameter such that the electron collection current is at least for example 80, 90, or 95% of the electron beam gun current. The method may include adjusting the at least one parameter such that the electron collection current is equal to the electron beam gun current. Beneficial values of the at least one parameter can thus be achieved particularly efficiently. Generally, a part of an electron beam’s energy impinging on a coating material may be lost due to any of: secondary electron emission or production of X-rays. Under operating conditions where no secondary electrons are emitted by the coating material, the maximum number of electrons the electron catcher is able to collect is equal to the number of electrons introduced with the electron beam.

Without secondary electron emission, the electron collection current therefore does not exceed the electron beam gun current. The probability of secondary electron emission is influenced by the energy distribution of the electron beam and binding energies of the coating material’s electrons. [0060] According to an aspect, the automatic adjustment 310 of the position may include: moving the anode in a first direction via a first actuator, the first direction having at least a component perpendicular to a main extension direction of the anode. Moving the anode via an actuator enables configuring the coating system without requiring an operator to perform arduous tests and adjustments. The method concludes in block 320.

[0061] While the foregoing is directed to some embodiments, other and further embodiments may be devised without departing from the basic scope of the disclosure. The scope is determined by the following claims.

Claims

CLAIMS Method of operating a coating system provided in a vacuum chamber, the coating system comprising a coating drum for transporting a substrate, at least one electron beam gun for evaporating a coating material, and an electron catcher, the electron catcher comprising an anode for collecting free electrons in the vacuum chamber, the anode being heatable via a heating current, the electron catcher being configured such that the heating current passes through the anode or the electron catcher comprising a resistive heater thermally coupled with the anode, with the electron catcher being configured such that the heating current passes through the resistive heater; the method comprising an automatic adjustment of at least one parameter selected from a group consisting of: the heating current, a DC bias voltage of the anode, a position of the anode, and a pressure in the vacuum chamber, the automatic adjustment comprising a measurement of an electron collection current passing through the anode. Method according to claim 1, wherein the automatic adjustment comprises maximizing the electron collection current. Method according to any of the preceding claims, wherein the automatic adjustment comprises comparing the electron collection current with an electron beam gun current. Method according to any of the preceding claims, comprising automatic adjustment of the position of the anode, wherein the automatic adjustment of the position comprises: moving the anode in a first direction via a first actuator, the first direction having at least a component perpendicular to a main extension direction of the anode. Method according to any of the preceding claims, wherein the automatic adjustment is performed via closed loop control. Method according to any of the preceding claims, wherein the heating current is adjusted to a value being any of: at least 10 A or at most 80 A. Method according to any of the preceding claims, wherein the DC bias voltage is adjusted to a value being any of: at least 30 V or at most 120 V. Method according to any of the preceding claims, wherein the pressure is adjusted to a value being any of: at least 5-10'⁶ mbar or at most 8-10'³ mbar. Method according to any of the preceding claims, wherein the coating material comprises an electrically insulating material. Controller for operating a coating system provided in a vacuum chamber, the controller comprising a central processing unit and an interface for exchanging signals with at least one component of the coating system or the vacuum chamber, the controller being configured to carry out the method according to any of claims 1 to 9. Electron catching apparatus comprising an electron catcher and a first actuator, the electron catcher comprising an anode configured for collecting free electrons in a vacuum chamber, the anode being heatable via a heating current, the electron catcher being configured such that the heating current passes through the anode or the electron catcher comprising a resistive heater thermally coupled with the anode, with the electron catcher being configured such that the heating current passes through the resistive heater; the first actuator being configured to move the anode in a first direction, the first direction having at least a component perpendicular to a main extension direction of the anode. Electron catching apparatus according to claim 11, comprising a second actuator configured to move the anode in a second direction, the second direction having at least a component perpendicular to the first direction and to the main extension direction of the anode. Electron catching apparatus according to any of claims 11 to 12, wherein the first actuator is configured to move the anode along at least a section of a circular path. Coating system comprising a coating drum for transporting a substrate, at least one electron beam gun for evaporating a coating material, a controller according to claim 10, and an electron catcher, the electron catcher comprising an anode configured for collecting free electrons in a vacuum chamber, the anode being heatable via a heating current, the electron catcher being configured such that the heating current passes through the anode or the electron catcher comprising a resistive heater thermally coupled with the anode, with the electron catcher being configured such that the heating current passes through the resistive heater. Coating system according to claim 14, further comprising a first actuator configured to move the anode in a first direction, the first direction having at least a component perpendicular to a main extension direction of the anode.