Method and device for reducing exposure to vapors and / or dusts in vacuum-based coating processes

Abstract

Method for reducing exposure to vapors and / or dusts from equipment (1) for vacuum-based coating processes, wherein an operating vacuum is generated in the equipment (1), wherein the equipment (1) has a first, second and third vacuum chamber (2, 2', 2"), wherein the vacuum chambers (2, 2', 2") are connected in series, wherein the second vacuum chamber (2') is arranged between the first and third vacuum chambers (2, 2") and is designed as a process chamber, wherein - in a first process step of the apparatus (1) a gas is supplied, wherein - in a second process step the gas is removed from the second vacuum chamber (2'), whereby - in a third process step, the gas removed from the second vacuum chamber (2') is purified and made available again for feeding into the first and third vacuum chambers (2, 2"), wherein the first process step, the second process step and the third process step are carried out cyclically one after the other, characterized in that at least one rotary lobe pump (7) is used for the first and second process steps, which removes the gas from the second vacuum chamber (2') and supplies it to the first and third vacuum chambers (2, 2").

Description

State of the art

[0001] The present invention relates to a system for operating a vacuum-based coating process. Vacuum-based coating processes such as physical vapor deposition (PVD) and chemical vapor deposition (CVD) are widely used in industry and research. In both PVD and CVD, a gas phase is deposited from a solid by a physical or chemical process, respectively. This occurs under vacuum in a vacuum chamber. The gas phase spreads within the vacuum chamber, which also contains the object to be coated. The coating of the object is achieved either through a chemical reaction (CVD) of the gas phase on the surface of the object or through condensation (PVD) on the surface of the object.

[0002] These processes can generate fumes and dust. If these spread, it can lead to problems. Vacuum chambers and their components, such as vacuum measuring tubes or quartz crystals used to determine the thickness of applied layers, can become clogged. Furthermore, the surfaces of the objects being coated can be contaminated before, during, or after the coating process. The fumes and dust form scattered layers that can flake off, leading to quality problems in the final product.

[0003] A known solution to these problems involves the targeted injection of inert protective gases, which oppose the flow of vapors and gases and prevent their propagation. This approach is described in patent applications JP 2002 081 857 A, US 2008 / 0072822 A1, EP 2 915 901 A1 and DE 10 2012 110 287 A1.

[0004] However, this approach has significant drawbacks. For example, the consumption of protective gases is very high. Furthermore, vacuum pumps with high pumping capacity must be installed to maintain the operating vacuum required for the coating process. Depending on the operating vacuum, very high flow rates of the protective gas are needed to counteract the thermal diffusion of vapors and dust, despite the low probability of impact. Disclosure of the invention

[0005] It is therefore an object of the present invention to provide a method to prevent vapors and dusts from spreading in vacuum chambers of a system for vacuum-based coating processes, which offers extremely high flow velocities of a protective gas with very low protective gas consumption.

[0006] This task is accomplished by a method for reducing exposure to fumes and / or dust from equipment for vacuum-based coating processes, wherein an operating vacuum is generated in the equipment, wherein - in a first process step of the facility a gas is supplied, whereby - in a second process step the gas is removed from the facility, whereby - in a third process step, the gas removed from the facility is purified and made available again for feeding into the facility, whereby The first, second, and third process steps are cyclically executed sequentially. This creates a gas cycle that allows the extracted gas to be reused for re-feeding into the system instead of being discarded. The flow of the supplied gas is directed opposite to the propagation direction of the vapors and particles. Collisions between the gas molecules and the vapors and / or dust transfer momentum from the gas molecules to the vapors and / or dust, thus preventing the vapors and / or dust from spreading. To maintain the operating vacuum, the gas is supplied at a very low pressure, comparable to the target operating vacuum pressure. The operating vacuum pressure is preferably less than 200 mbar, and particularly preferably less than 50 mbar.To transfer a sufficiently high momentum in the desired direction to the vapors and / or dusts, the supplied gas is introduced at a high flow velocity. It is conceivable that the direction of the gas flow is controlled by adjustable vanes. This would allow the momentum transferred to the vapors and / or dusts to be adjusted and corrected. Preferably, the gas flow is directed through a constriction between process steps one and two to further accelerate it in a targeted manner and simultaneously reduce the diffusion cross-section available to the vapors and / or dusts at this point. The momentum transfer from the supplied gas to the vapors and / or dusts occurs in the direction in which the gas is discharged. Thus, the vapors and / or dusts are also removed along with the discharged gas.To prevent these substances from being reintroduced into the system with the extracted gas, the gas is cleaned of vapors and / or dust. It is conceivable to analyze the vapors and / or particles separated from the gas for their chemical composition, particle size, and quantity. This would allow conclusions to be drawn about the atmospheric conditions and the process taking place within the system.

[0007] Advantageous embodiments and further developments of the invention can be found in the dependent claims and in the description with reference to the drawings.

[0008] According to a preferred embodiment of the present invention, it is provided that the gas discharged from the device is purified during the third process step.

[0009] According to a further preferred embodiment of the present invention, the gas discharged from the device is purified during the third process step using a cyclone separator and / or an electrostatic precipitator and / or a cloth filter and / or a liquid-based filter. By using a cyclone separator, an electrostatic precipitator, a cloth filter, a liquid-based filter, or a combination of these filters, it is possible to effectively filter the vapors and / or dusts from the gas. Based on the nature of the vapors and / or dusts present, the combination of filters for filtering the gas is selected to be particularly effective for the existing vapors and / or dusts.It is conceivable to use a combination of filters based on different filter mechanisms, as well as a combination of filters based on the same filter mechanism but designed for different particle sizes of vapors and / or dusts.

[0010] According to a further preferred embodiment of the present invention, the gas discharged from the device is passed through a condenser during the third process step to liquefy condensable gases. This condenser can, for example, have a large surface area cooled to a temperature below the condensation point of the gas to be condensed. A tube or tube bundle through which liquid nitrogen flows would be conceivable. A condensable gas, such as water vapor, oxygen, fluorine, chlorine, or argon, would condense on the condenser and thus be removed from the device. This also constitutes an additional virtual vacuum pump, which contributes to the overall pumping capacity of all the vacuum pumps used.

[0011] According to a further preferred embodiment of the present invention, an inert protective gas is used. The use of an inert protective gas advantageously prevents the supplied gas from chemically reacting with the objects to be coated in the device, the objects coated in the device, or with components of the device. This protects the device against increased wear and the object to be coated or the coated object against unwanted changes. Furthermore, it prevents a chemical reaction between the vapors and / or dusts and the gas. As a result, the gas is discharged from the device with the same chemical composition as when it was introduced and is thus available for re-introduction.

[0012] According to the invention, at least one rotary lobe pump is used for the first process step and for the second process step. Due to the lack of internal compression, a rotary lobe pump, also known as a Roots pump, can only generate very small pressure differentials (typically 80 mbar). However, it can pump large volumes. This allows extremely high flow velocities to be generated when supplying and removing gas to and from the device, thus effectively controlling the dispersion of vapors and / or dust. It is conceivable that a combination of rotary lobe pumps connected in series could be used to increase the generated pressure differential. Rotary lobe pumps can also be operated in parallel to increase the flow velocity or provide redundancy for the device or system.Additionally, depending on the operating state, it is possible to control their speed using frequency converters.

[0013] According to a further preferred embodiment of the present invention, the gas supplied to the device is examined for contamination. Examining the gas supplied to the device serves to monitor the function of the components present in the gas circuit, in particular the function of a pump in the gas circuit and the function of a filter. For example, it is conceivable that the pump releases oil into the gas during operation. This would lead to contamination of the device and would thus be detected. Furthermore, the failure of filters in the gas circuit could be detected by detecting contamination of the supplied gas. Monitoring the pressure and flow rate of the supplied gas is also conceivable. Both would allow conclusions to be drawn about the function of a pump used in the gas circuit.

[0014] According to a further preferred embodiment of the present invention, the gas discharged from the device is examined for contamination. An examination of the discharged gas for contamination allows conclusions to be drawn about the atmospheric conditions within the device. For example, a chemical analysis of the contamination in the discharged gas provides information about the chemical composition of the vapors and / or dusts discharged with the gas. Furthermore, the ratio of discharged contamination to discharged gas is an indicator of the effectiveness of the vapor and / or dust removal from the device, or an indicator of the quantity of vapors and / or dusts present in the device, and thus of the process itself being carried out in the device or system. Monitoring the pressure and flow rate of the discharged gas is also conceivable.Both would allow conclusions to be drawn about the function of a pump used in the gas circuit.

[0015] According to a further preferred embodiment of the present invention, at least one vacuum pump is controlled to maintain the operating vacuum and / or to extract portions of the gas introduced into the device. This ensures that the correct operating vacuum is set for the coating process. This could be a backing pump present for generating the operating vacuum, such as a rotary vane pump, a liquid ring pump, or a diaphragm pump, or a turbomolecular pump present for generating the operating vacuum. It would also be conceivable to isolate the pumps present for generating the operating vacuum and to use an additional vacuum pump. A control loop between the vacuum pump and a vacuum gauge in the device would also be conceivable.

[0016] According to a further preferred embodiment of the present invention, additional gas is continuously introduced into the device during the cyclical execution of the first, second, and third process steps. This advantageously allows the quantity of gas present in the gas circuit to be maintained even in the event of a leak in the gas circuit. Gas can be removed from the gas circuit, for example, through leaks in the gas circuit, by filtering the gas, or by pumping the gas out of the gas circuit. Alternatively, the inert gas can become contaminated with foreign gases, which are not captured by the filter system, due to leaks or from the process itself.If gas is continuously supplied to the gas circuit in the same quantity as gas is withdrawn from it, this advantageously prevents gas contamination over time. Furthermore, a control loop is conceivable that regulates leakage in the gas circuit and the supply of new gas based on the contamination of the supplied gas.

[0017] A further object of the present invention for solving the problem stated at the outset is a device for carrying out vacuum-based coating processes, comprising a unit, one or more vacuum chambers, one or more gas inlets, one or more gas outlets, one or more gas supply lines, and one or more gas return lines, wherein the gas supply lines together with the vacuum chambers and the gas return lines form a gas circuit. The device makes it possible to carry out a vacuum-based coating process and thereby circulate gas through the unit via a gas circuit, so that the dispersion of vapors and / or dusts within the unit can be controlled. The gas circuit is designed such that the vapors and / or dusts generated in a process chamber of the unit are discharged from the unit by a gas that is circulated through the gas circuit.Preferably, the gas circuit includes a pump for transporting the gas through the gas circuit.

[0018] According to a preferred embodiment of the present invention, the vacuum chambers are connected in series with one or more further airlock chambers. This makes it possible to mount or pretreat an object to be coated, for example, on a sample tray or conveyor belt in a first vacuum chamber and then transport it to a second vacuum chamber. According to the invention, the second vacuum chamber is a process chamber in which the coating process takes place. After coating, the coated object can be transported to a third vacuum chamber for further treatment. The vacuum is not broken during this process. This advantageously reduces contamination of the object to be coated.

[0019] According to a preferred embodiment of the present invention, the vacuum chambers are connected to the vacuum chambers via vacuum flanges, and the optional airlock chambers are connected to the vacuum chambers via vacuum flanges. This enables a safe and stable design, but above all, it increases flow resistance to the thermal diffusion of vapors and / or dusts during an increased and directed gas flow. It is conceivable that the vacuum flanges could be extended to further enhance the effect described above.

[0020] According to a preferred embodiment of the present invention, the vacuum chambers can be sealed off from each other in a vacuum-tight manner. This makes it possible, for example for maintenance purposes, to break the vacuum in one vacuum chamber while another vacuum chamber remains evacuated.

[0021] According to a further preferred embodiment of the present invention, it is provided that lock chambers are connected on both sides of the vacuum chambers, so that ribbon-shaped material can be continuously guided through the device or system as the object to be coated.

[0022] According to the invention, at least one rotary lobe pump is installed in the gas circuit. Rotary lobe pumps, also known as Roots pumps, can only generate very small pressure differentials (typically 80 mbar) due to the lack of internal compression. However, they can pump large volumes. This allows rotary lobe pumps to generate extremely high flow velocities when supplying and removing gas to and from the device, thus effectively influencing the dispersion of vapors and / or dust. It is conceivable that a combination of rotary lobe pumps connected in series could be installed in the gas circuit to increase the generated pressure differential. Rotary lobe pumps can also be operated in parallel to increase the flow velocity or provide redundancy for the device or system. Additionally, their speed can be controlled by frequency converters, depending on the operating conditions.

[0023] According to a preferred embodiment of the present invention, a cyclone separator and / or an electrostatic precipitator and / or a cloth filter and / or a liquid-based filter is installed on the gas return line for passing a gas through it. The use of a cyclone separator, an electrostatic precipitator, a cloth filter, a liquid-based filter, or a combination of these filters enables the effective filtering of vapors and / or dust from the gas. It is conceivable that a combination of filters, selected based on the nature of the vapors and / or dust present, is installed to filter the gas. This could include a combination of filters based on different filter mechanisms, as well as a combination of filters based on the same filter mechanism but designed for different particle sizes of the vapors and dust.

[0024] According to a preferred embodiment of the present invention, a condenser for liquefying condensable gases is provided for passing a gas through it on the gas return line. This condenser can, for example, have a large surface area which is cooled to a temperature below the condensation point of the gas to be condensed. Alternatively, a tube or tube bundle through which liquid nitrogen flows could be used. A condensable gas condenses on the condenser and is thus removed from the device. For continuous operation, the condensate can preferably be pumped out either in liquid form or cleaned cyclically in solid form, e.g., by alternating the operation of two condensers.

[0025] Further details, features, and advantages of the invention will become apparent from the drawing and from the following description of preferred embodiments with reference to the drawing. The drawing merely illustrates exemplary embodiments of the invention, which do not restrict the essential concept of the invention. Brief description of the drawing Fig. Figure 1 shows the basic principle of the method for filtering out vapors and / or dusts from equipment for vacuum-based coating processes according to an exemplary embodiment of the present invention and Fig. Figure 2 shows the basic principle of the method for filtering out vapors and / or dusts from equipment for vacuum-based coating processes according to a further exemplary embodiment of the present invention. Embodiments of the invention

[0026] In the various figures, identical parts are always marked with the same reference symbols and are therefore usually only named or mentioned once.

[0027] In Fig. Figure 1 schematically illustrates the basic principle of a method for filtering vapors and / or dust from equipment for vacuum-based coating processes according to an exemplary embodiment of the present invention. An equipment 1, comprising three vacuum chambers 2, 2', 2" connected to one another by vacuum flanges 3, is suitable for converting a solid into the gas phase and condensing it onto an object to be coated using a physical process. For this purpose, the vacuum chambers 2, 2', 2" are evacuated. The object to be coated is mounted on a slide under vacuum in a first vacuum chamber 2'. The object is then transported from the first vacuum chamber to a second vacuum chamber 2, which serves as a process chamber in which the deposition of the gas phase and its condensation onto the object to be coated—i.e., the coating process—take place.After coating, the coated object is transported to a third vacuum chamber 2, where it is removed from the slide. During the coating process, vapors and / or dust are generated, which can negatively affect the function of the device 1 or the quality of the coating on the object. A rotary lobe pump 7 supplies an inert protective gas to the device 1 via two gas supply lines 4 and two gas inlets 8. The protective gas flows through the device 1 at high velocity and exits through the gas outlet 9. The gas flow prevents the vapors and / or dust from spreading and carries them away through the gas outlet 9. From the gas outlet 9, the protective gas, along with the carried-away vapors and / or dust, flows through a gas return line 5 into a filter 6.Filter 6 is designed as a combination of a cyclone separator, an electrostatic precipitator, a cloth filter, a liquid-based filter, and a condenser for liquefying condensable gases. Here, the protective gas is cleaned of vapors and / or dust. Furthermore, gases other than the protective gas are separated at the condenser. This relieves the vacuum system (not shown) of the unit 1. The cleaned protective gas flows via the gas return 5 to a rotary lobe pump 7, from where it is fed back into the unit 1 via the gas supply 4. At the gas inlet 8 and the gas outlet 9, the protective gas is checked for contamination, flow velocity, and pressure. This verifies the functionality of the vapor and / or dust removal from the unit 1.

[0028] In Fig. Figure 2 schematically illustrates the basic principle of a method for filtering vapors and / or dusts from equipment for vacuum-based strip coating processes according to a further exemplary embodiment of the present invention. The device 1 was additionally described according to Fig.The system is supplemented by two airlock chambers 10, which contain belt airlocks (air-to-air belt airlocks) suitable for continuously feeding strip-shaped material, for example, steel belts, from the ambient atmosphere into the process and then releasing it back into the atmosphere without increasing the pressure in vacuum chamber 2 or negatively affecting the process there. These chambers can be divided into different compartments, each with a belt airlock module, and / or consist of several airlock chambers, each connected by vacuum flanges 3, 3'. The individual compartments and / or vacuum chambers 10 are evacuated by combinations of vacuum pumps (not shown) and thus kept under vacuum to prevent minor, typical leaks. In this case, vacuum chambers 2' and 2" serve as the final separation stage between the atmosphere and the process.The gas supply through the gas inlet 8 and the resulting gas flow according to the invention through 3 to 2 also prevents vapors and / or dust from entering the airlock chambers 10, where they could condense on the sealing devices. Damage, leaks, or quality problems with the processed ribbon material are thus prevented. According to the invention, the pressure in the vacuum chambers 2' and 2" can be controlled by a continuous supply of fresh protective gas to the circuit and / or the vacuum chambers 2' and 2" such that, in addition to the gas flow towards the vacuum chamber 2, there is also a flow towards the airlock chambers 10. There, gas quantities are typically drawn through the first sealing device into the pumps of the airlock stages. According to the invention, these are now a mixture of primarily purified circulating protective gas and fresh protective gas.In addition to the lock stages, the pumps of the vacuum locks are also no longer exposed to vapors and / or dust according to the invention. The resulting flow, directed against the atmosphere, prevents the ingress of harmful, e.g., oxidizing, components from the ambient atmosphere. The lock chambers 10 are in turn connected to the vacuum chambers 2' and 2" respectively by vacuum flanges 3'. Reference symbol list 1. Facility 2 vacuum chamber 2' vacuum chamber 2" vacuum chamber 3 vacuum flange 3' vacuum flange 4 Gas supply 5 Gas return 6 filters 7 Rotary piston pump 8 Gas inlet 9 Gas outlet 10 Lock chamber

Claims

[1] Method for reducing exposure to vapors and / or dusts from equipment (1) for vacuum-based coating processes, wherein an operating vacuum is generated in the equipment (1), wherein the equipment (1) has a first, second and third vacuum chamber (2, 2', 2"), wherein the vacuum chambers (2, 2', 2") are connected in series, wherein the second vacuum chamber (2') is arranged between the first and third vacuum chambers (2, 2") and is designed as a process chamber, wherein - in a first process step of the apparatus (1) a gas is supplied, wherein - in a second process step the gas is removed from the second vacuum chamber (2'), whereby - in a third process step, the gas removed from the second vacuum chamber (2') is purified and made available again for feeding into the first and third vacuum chambers (2, 2"), wherein the first process step, the second process step and the third process step are carried out cyclically one after the other, characterized by , that for the first and second process steps at least one rotary lobe pump (7) is used, which removes the gas from the second vacuum chamber (2') and supplies it to the first and third vacuum chambers (2, 2"). [2] Method according to claim 1, wherein the gas discharged from the apparatus is cleaned during the third method step using a cyclone separator (6) and / or an electrostatic precipitator (6) and / or a cloth filter (6) and / or a liquid-based filter (6). [3] Method according to one of the preceding claims, wherein the gas discharged from the apparatus is passed through a condenser for liquefaction of condensable gases during the third method step. [4] Method according to one of the preceding claims, wherein an inert protective gas is used. [5] Method according to any of the preceding claims, wherein the gas supplied to the apparatus (1) is examined for contamination. [6] Method according to any of the preceding claims, wherein the gas discharged from the device (1) is examined for contamination. [7] Method according to any of the preceding claims, wherein at least one vacuum pump is controlled to maintain the operating vacuum and / or to extract parts of the gas introduced into the device (1). [8] Method according to one of the preceding claims, wherein additional gas is introduced into the device (1) during the cyclical execution of the first process step, the second process step and the third process step. [9] Device for carrying out vacuum-based coating processes, comprising a device (1) with a first, second and third vacuum chamber (2, 2', 2"), one or more gas inlets (8), one or more gas outlets (9), two gas inlets (4) and a gas return (5), wherein the vacuum chambers (2, 2', 2") are connected in series, wherein the second vacuum chamber (2') is arranged between the first and third vacuum chambers (2, 2") and is designed as a process chamber, wherein the gas inlets (4) together with the vacuum chambers (2, 2', 2") and the gas returns (5) form a gas circuit, characterized by, that at least one rotary lobe pump (7) is installed in the gas circuit, which is configured to discharge a gas from the second vacuum chamber (2') via the gas return (5) and to supply it to the first and third vacuum chambers (2, 2") via the gas supply lines (4). [10] Device according to claim 9, wherein the vacuum chambers (2, 2', 2") are connected in series with one or more further lock chambers (10). [11] Device according to one of claims 9 or 10, wherein the vacuum chambers (2, 2', 2") are connected to vacuum flanges (3) and the optional airlock chambers (10) are connected to the vacuum chambers (2', 2") with vacuum flanges (3'). [12] Device according to one of claims 9 to 11, wherein lock chambers (10) are connected on both sides of the vacuum chambers (2', 2"), so that ribbon-shaped material can be continuously guided through the device as the object to be coated. [13] Device according to one of claims 9 to 12, wherein the vacuum chambers (2, 2', 2") can be sealed against each other in a vacuum-tight manner. [14] Device according to one of claims 9 to 13, wherein a cyclone separator (6) and / or an electrostatic precipitator (6) and / or a cloth filter (6) and / or a liquid-based filter (6) for passing a gas is attached to the gas return (5). [15] Device according to one of claims 9 to 13, wherein a condenser for liquefying condensable gases for passing a gas is attached to the gas return (5).

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