Coating chamber for carrying out a vacuum-supported coating process, as well as coating processes

Description

[0001] The invention relates to a coating chamber for carrying out a vacuum-assisted coating process and a coating process according to the preamble of independent claims 1 and 13.

[0002] Vacuum-assisted coating systems for coating or refining the surfaces of various parts of all kinds, such as tools, housings for technical or non-technical equipment, or other parts with functional layers, especially using plasma-assisted PVD and CVD processes, often for applying hard layers comprising nitrides, carbides, borides, oxides and their mixtures, DLC, or for applying other layers, must be designed in such a way that they can achieve high productivity at low cost while simultaneously offering the greatest possible flexibility in the processes that can be implemented with regard to the resulting part temperature during industrial coating.Boundary conditions include, among others, vacuum-related requirements regarding the necessary pumping times to achieve a sufficiently low starting pressure in the coating chamber of the coating system, fast and reliable cleaning of the interior of the coating chamber from unavoidable parasitic coatings, but also ensuring sufficiently high coating rates at a given maximum part temperature, which must not be exceeded under any circumstances, as well as setting a minimum temperature, which should not be undercut, must always be reliably guaranteed during the coating process.

[0003] In state-of-the-art coating chambers, optimized cooling is often achieved with double walls, or alternatively, with single walls and cooling elements in critical areas, such as flanges for coating sources. A well-known method for achieving short pumping times involves smooth chamber walls to minimize the desorption rate of unavoidable gas buildup upon contact with ambient air when the chamber is open. Simplified cleaning is typically achieved using replaceable films applied to the chamber wall and / or replaceable metal sheets mounted to the chamber wall.

[0004] A disadvantage of these prior art arrangements, however, is that the design of the coating chamber is inherently very limited with regard to flexible use across different temperature ranges at sufficiently high coating rates, particularly when maintaining minimum or maximum part temperatures. Furthermore, the aforementioned interchangeable films must be regularly exchanged or replaced, which incurs additional costs.

[0005] The coating processes usually also include process steps that either intentionally or unintentionally introduce heat into the parts due to the process, which can, for example, lead to an increase in the substrate temperature.

[0006] Prominent examples of such process steps include: When pumping and heating the substrates, a targeted heat input is generated by heating, e.g. using radiant heaters or electron heaters, until a minimum starting temperature and a sufficiently low residual gas pressure are reached.

[0007] In contrast, during ion cleaning of the parts surfaces, an otherwise unwanted heat input can occur as a side effect of the plasma processes, for example through accelerated ions for ion cleaning at the substrates and plasma sources, but also through thermal radiation or electron processes.

[0008] Even during the actual coating of the substrate surfaces, an undesirable heat input usually occurs as a side effect of the plasma processes (coating material) at the substrates and plasma sources (e.g. through thermal radiation, electron processes).

[0009] In all three relevant process steps mentioned, heat is introduced into the substrates, whether desired or undesired. In practice, the substrates are usually arranged on rotating substrate holders within the coating chamber. These holders can perform, for example, a single, double, or triple rotation during operation to achieve sufficiently homogeneous coating results. Due to the low process pressures, heat dissipation is essentially only possible through thermal radiation between the substrates and the colder surfaces, which during a process step are usually represented exclusively by the chamber wall.

[0010] For practical reasons, experts typically distinguish between two temperature ranges in common coating processes, which are mentioned below for reference and further clarified. 1. Low-temperature coating (NTB): Tsu ≤ 250 °C

[0011] The industrially typical range for low-temperature coating (NTB) is 150 °C to 250 °C, with a maximum part temperature Tmax. However, significantly lower temperatures are required when using electroplated plastics as substrate material. Since this is an exceptional case, it will not be discussed further here, and the reader is referred to the relevant literature.

[0012] To ensure reliable coating and prevent substrate damage, the substrate start temperatures (Tsu) must not exceed, or at most only briefly exceed, the maximum permissible part temperature (Tmax), which is defined by the part materials to be coated or by the required coating properties. For productivity reasons alone, the processes (heating, ion cleaning, coating) are managed to keep the process time as short as possible, i.e., close to the permissible thermal stress of the substrates or the permissible coating temperature.

[0013] Various processes, material properties, or coating quality requirements can determine the maximum temperature (Tmax). For example, exceeding the maximum part temperature (Tmax) for a sufficiently long period generally leads to a negative impact on the substrate material, such as retained austenite transformation in ball bearing steels, which can cause dimensional changes, or even hardening (case-hardened steels).

[0014] However, the desired layer properties can also determine the Tmax limit. It is known that with certain layers, such as DLC layers, and especially with hard, hydrogen-free carbon layers of the ta-C type, the properties change negatively when a maximum temperature is exceeded. For example, more sp² < C-C bonding states can form compared to sp³ < C-C bonding states. 2. High-temperature coating (HTB): Tmin ≤ 400 °C

[0015] The industrially typical range for high-temperature coating (HTB) is usually between 400 °C and 600 °C, with a minimum part temperature (Tmin). The substrate start temperature (Tsu) must not fall below the minimum required part temperature (Tmin) due to the necessary coating-substrate system properties, or at most, only for very short periods. Depending on the substrate material, an upper temperature limit must also be observed.

[0016] For example, with steels (e.g., secondary hardened steels, HSS), a minimum part temperature Tmin of 400°C to 500°C is usually targeted. For hard metals, temperatures up to 700°C are also commonly achieved.

[0017] It goes without saying that in practice, coating tasks also arise that must be carried out in the temperature range between the NTB and HTB. This is the case, for example, with brazed parts. However, this intermediate range need not be discussed in detail here, as this temperature range between NTB and HTB is merely a special case of HTB.

[0018] From US 6 046 439 A a coating chamber is known which includes a heat shield which has two sides with different heat exchange coefficients and from JP2015-000994 a vacuum chamber with a sheet which is coated with aluminium oxide or nickel.

[0019] The coating chambers known from the prior art are either designed in such a way that, in practice, they can only be operated with satisfactory coating results within a predetermined temperature range, e.g., within the NTB, HTB, or intermediate ranges defined above. Alternatively, modifying the coating chamber is disproportionately complex and therefore uneconomical overall. Due to the limitation to specific temperature ranges, these known coating systems are, as explained above, also limited to specific substrate materials.The types of layers, layer compositions, or properties of the coating that can be produced are limited, which means that several different coating chambers often have to be kept available in one and the same production plant for the different substrate and coating types, or at least a costly conversion of the coating chambers has to be accepted when it is necessary to switch from one substrate type or from one coating type to another.

[0020] The object of the invention is therefore to provide an improved coating chamber with which a wide variety of substrates and coatings or layer systems can be produced in one and the same coating chamber under different temperature conditions, whereby the highest possible flexibility of the coating systems with regard to part temperature should be achieved with the shortest possible process times. In particular, it should not only be possible to flexibly adapt the coating chamber to a required temperature range with very simple measures. Furthermore, special design variants of coating chambers should be provided which, compared to the prior art, have a significantly larger usable temperature range, so that a large number of different substrates can be processed in one and the same coating chamber.A large number of different coating types can be produced without the need for costly modifications when switching to a different coating application. A further object of the invention is to provide a new coating process for implementation in a coating chamber according to the invention.

[0021] The invention further aims to provide a solution that allows the heat dissipation in a coating chamber to be regulated in such a way that the coating temperature does not rise uncontrollably due to an increase in heat input, but can be kept at the desired operating point.

[0022] The subject matter of the invention that solves these problems is characterized by the features of independent claims 1 and 13.

[0023] The respective dependent claims relate to particularly advantageous embodiments of the invention.

[0024] The invention thus relates to a coating chamber for carrying out a vacuum-assisted coating process, in particular a PVD or CVD or arc coating chamber or hybrid coating chamber according to claim 1.

[0025] It should be noted at this point that the physical quantity referred to as the "heat exchange coefficient" in this application is also known to the skilled person, for example, under the terms "emissivity" or "emissivity ratio" and can be measured according to methods known to the skilled person.

[0026] Additionally, the heat shield can comprise a shielding shield with a first shielding surface directed towards the chamber wall and a second shielding surface facing away from the chamber wall, wherein the first shielding surface and / or the second shielding surface each has a glossy reflective surface with a processing condition according to DIN EN10088 of at least 2D, preferably a processing condition according to DIN EN10088 of at least 2R.

[0027] Before discussing specific embodiments of the invention in detail below, the essential basic features of the invention will first be discussed.

[0028] In practice, a coating chamber according to the invention is preferably a double-walled chamber which can be operated with either cold or warm water for heat dissipation, and under certain circumstances also with an oil or another temperature control fluid. In special exceptional cases, a coating chamber according to the invention can also function without temperature control using a temperature control fluid such as water or oil, for example, when the process requires so little heat to be dissipated to the outside that heat dissipation via the outer surfaces of the coating chamber or additional heat dissipation elements is sufficient.

[0029] Inside the chamber, shield holders are provided on the chamber walls, which preferably can accommodate shield components that are essentially geometrically identical but thermally different, in the form of individual sheets as a single layer or as a stack of sheets, thus forming the heat shield.

[0030] Preferably, at least one heat shield for low-temperature coating (LTC) or, in the case of high-temperature coating (HTC), a modular sheet metal assembly is mounted as a heat shield to the inner chamber wall, which additionally includes at least one shielding shield. The essential functional principles of the heat shield and the shielding shield can be summarized as follows: The heat shield is preferably provided in the form of a sheet metal component on the inner chamber wall and is easily removable or replaceable, particularly for cleaning purposes. The heat shield thus fulfills a dual function, serving on the one hand as protection of the chamber wall against parasitic coatings and on the other hand enabling sufficient heat dissipation to the chamber wall by means of thermal radiation.

[0031] Specifically, the chamber wall can also be conditioned in such a way as to enable sufficient heat exchange through thermal radiation between the radiation shield and the chamber wall. The radiation properties, especially the heat exchange coefficients of the chamber wall and the radiation shield, are particularly preferred for optimal heat exchange.

[0032] The shielding plate also serves a dual function. In practice, it is often designed as a sheet metal plate attached to or in front of the chamber wall, which is also easily removable for cleaning purposes. Thus, the shielding plate also provides protection for the chamber wall against parasitic coatings and, unlike the radiation shield, minimizes heat emission through thermal radiation towards the chamber wall or from another sheet metal stack located towards or in front of the chamber wall.

[0033] The chamber wall could be conditioned to minimize heat exchange through thermal radiation between the first sheet of the heat shield stack (the one closest to the chamber) and the chamber wall. However, this is more or less incompatible with the requirements of the low-temperature coating (NTB), for which a heat shield is to be used. Therefore, in such cases, the chamber wall is preferably conditioned to maximize heat transfer through thermal radiation to the chamber wall.

[0034] The following are some calculation examples to demonstrate the dominant importance of the coating of the radiation shield. As is generally known, the maximum possible radiation exchange for a blackbody is given by a heat exchange coefficient of εSch = 1. This means that if both the chamber wall and the radiation shield have a heat exchange coefficient of 1, the maximum possible radiation exchange between the radiation shield and the chamber wall is achieved. The values ​​given below are the fractions achieved in measurements compared to the state of an ideal blackbody. The calculation examples clearly demonstrate the necessity of high values ​​for the heat exchange coefficient of the radiation surfaces involved in the case of the low-temperature coating NTB.

[0035] The following assumptions underlie this: A) Optimal vacuum-technical condition of the surfaces for low desorption rates. The chamber wall (heat exchange coefficient = εk) and the directly adjacent radiation plate (heat exchange coefficient = εplate) are made of stainless steel and largely polished to a mirror finish. The following heat exchange coefficients are then obtained: ε k = ε Blech : 0,1 + / − 0,05 and thus for the effective total exchange coefficient εges = 0.053. B) Frequent case in industrial manufacturing. Matted, scratched surfaces of the chamber wall and directly adjacent radiation plate made of stainless steel, largely smooth: ε k = ε Blech : 0,2 + / − 0,1 and thus for the effective total exchange coefficient εges = 0.111. C) Blasting treatment to create rough surfaces: Chamber wall and directly adjacent blasting plate made of stainless steel, rough blasted: ε k = ε Blech : 0,4 + / − 0,1 and thus for the effective total heat exchange coefficient εges = 0.25. D) Chamber wall made of rough-blasted stainless steel, directly adjacent radiation plate made of rough-blasted stainless steel and coating with a high heat exchange coefficient εplate: ε k = 0,4 + / − 0,1 ε sheet metal = 0.85 + / - 0.15, thus for the effective total exchange coefficient ε ges = 0,374 . E) Chamber wall made of rough-blasted stainless steel with a coating of high heat exchange coefficient ε k, directly adjacent radiation plate made of rough-blasted stainless steel with a coating of high heat exchange coefficient ε plate: ε k = 0,85 + / − 0,1 ε sheet metal = 0.85 + / - 0.15, thus for the effective total exchange coefficient ε ges = 0,74 . F) Ideal blackbody radiator ε k = ε sheet : 1 and thus for the effective total exchange coefficient ε ges = 1 .

[0036] Naturally, the chamber temperature, or rather the temperature of the chamber wall, also influences the heat dissipation of the radiation shield, since radiative heat exchange is known to follow the fourth power of the temperature. Therefore, for low-temperature coating (NTB), the lowest possible wall temperature should be set, for example, a cooling water temperature of 20°C or lower for a double-walled coating chamber. To demonstrate this influence, let's consider, for example, an experimentally measured temperature of 150°C for a radiation shield used in NTB. If the chamber walls are not cooled with cold water, a temperature of 50°C or even higher often occurs during operation. The heat flux to the chamber wall at a temperature of 20°C is calculated to be 1.16 times higher than that to the chamber wall at 50°C.

[0037] Chamber cooling also provides an additional cooling effect on the components. Since the chamber lining with radiation shields is not electrically sealed between the plasma and the plasma sources, electrons often flow directly to the grounded chamber wall, thereby increasing its temperature inside the chamber if cooling is insufficient. Another portion of the electrons can directly contribute to heating the radiation shields, even if they are at chamber potential.

[0038] Thus, both the chamber walls and the radiation shields can be heated by two different components of the total heat input. One component is due to thermal radiation from the heated parts to be coated, and the other component is determined by an electron flow originating from the plasma and / or plasma sources. This effect is particularly pronounced in the cathodic vacuum arc evaporation method, where, when using multiple evaporators, total currents of several hundred to several thousand amps are often employed. Even with optimized magnetic fields for guiding the arc and anode structures around the evaporators, electrons flow to the grounded radiation shields. This electron effect is especially pronounced when no anode structures are used around the evaporator, and the chamber wall acts as the sole anode.To prevent heating, a good solution is to electrically separate the radiation shields from the chamber wall using an insulating element, so that the electrons flow to the cooled chamber wall and not to the radiation shields.

[0039] As already explained, a key insight of the present invention is that the surface properties of the radiation shield, the shielding shield, and the chamber wall are of central importance. According to the invention, this results in a suitable conditioning or coating of one or more of the aforementioned components.

[0040] Due to its design, the radiation shield according to the invention is a dual-function radiation shield with two differently designed sides in terms of radiation technology; the side facing the chamber wall and the side facing the parts to be coated.

[0041] In a specific embodiment of the invention, the side facing the chamber is subjected to blasting treatment with suitable blasting media known to those skilled in the art (corundum, SiC, and others), sufficient blasting pressures, sufficient angle of incidence, and sufficient duration to achieve the roughest possible (gray) surface condition. The arithmetic mean roughness values ​​(Ra values) should be around 1 µm ± 0.2 µm or greater, up to 10 µm ± 2 µm. The mean roughness values ​​(Rz values) should be around 10 µm ± 2 µm or greater, up to 100 µm ± 20 µm. The side facing the chamber is then coated with a suitable, preferably black, layer to create an adhesive, black, and preferably scratch-resistant coating. The layers can be PVD layers, e.g. Al x Ti y N, preferably Al 66 Ti 33 N but also AlCrN, preferably with the same composition but also other black PVD layers.The layers are deposited with optical density. A layer thickness of 500 nm is usually sufficient. However, the layer thicknesses can also be greater, e.g., up to a few µm. Another option is coating with suitable DLC layers, e.g., aC, aC:H, aC:H:X, aC:H:Me.

[0042] The side facing the parts to be coated, as well as the side facing the chamber wall, is roughened by blasting. However, the epsilon value of the heat exchange coefficient is usually subject to change over the process time, since, depending on the coating process and the layers to be applied to the parts, unavoidable variations in the presence of parasitic coatings occur. Ideally, for heat transfer to the chamber wall, black layers are formed, as in DLC coating processes; however, in other cases, metallic gray layers, as in CrN coating, or gold-colored layers, as in TiN coatings using cathodic vacuum arc coating, are formed. A key insight of the invention, however, is that the rough surface ensures the best possible radiative heat exchange between the parts to be coated and the cold chamber wall, regardless of the parasitic coatings.The blasting shield undergoes re-blasting after each cycle or if excessive parasitic layers are deposited. Therefore, the coated side facing the chamber wall requires a highly abrasion-resistant layer to prevent damage during this reconditioning process. AlTiN coatings deposited using cathodic vacuum arc evaporation are particularly well-suited for this purpose.

[0043] Suitable conditioning or coating of the chamber wall can be carried out, for example, as follows. The chamber wall is subjected to blasting with suitable abrasives known to those skilled in the art (corundum, SiC, and others) and sufficient blasting pressures to achieve the roughest possible (gray) surface condition. The Raa values ​​should be around 1 µm ± 0.2 µm or greater up to 10 µm ± 2 µm, and the Rz values ​​around 10 µm ± 2 µm or greater up to 100 µm ± 20 µm.

[0044] Alternatively, the chamber wall can be additionally coated with black layers. These should be electrically conductive. Suitable options include black PVD coatings and conductive DLC coatings, as already described for the radiation shield designed as a dual-purpose radiation plate.

[0045] The following are some important remarks regarding the properties of the shielding plates. In practice, these plates are almost always made of a sheet of metal that is as smooth as possible, ideally with a mirror finish, to ensure the lowest possible heat flow. The side facing the chamber has a glossy, reflective surface with a surface finish according to DIN EN 10088 of at least 2D, preferably at least 2R, where roughness measurements exclude unavoidable scratches caused by handling the plates or areas where mounting elements are located. While the side facing the parts to be coated is also smooth when new, the surface roughness and heat exchange coefficient (ε) are modified differently during the coating process, depending on the coating method and the layers applied to the parts.Nevertheless, the set roughness is such that heat transfer to the chamber wall is minimized.

[0046] A preferred embodiment of a coating chamber according to the invention for carrying out a high-temperature coating process (HTB) is briefly outlined below. To reduce heat transfer to the chamber wall, which should be as high as possible for the NTB process and modified for the HTB process by using the radiation shield, which is coated in the direction of the chamber wall and interacts with the rough chamber wall as described, at least one geometrically identical or very similar shielding shield is additionally mounted. The radiation shield then acts as a radiation protection screen. Preferably, further shielding plates are provided between the radiation shield and the shielding shield. If the chamber wall is double-walled, it can then preferably be cooled with warm water of approximately 50°C instead of cold water to minimize heat radiation to the chamber.

[0047] In a particularly preferred embodiment, three drawn sheets of stainless steel (DIN 1.4301) with a thickness of 1 mm are used for the heat shield in the form of a sheet system. The roughness in areas without unavoidable scratches was in the range of Ra = 0.8 µm ± 0.16 µm and Rz = 6 µm ± 1.2 µm. The heat exchange coefficient of these surfaces was determined to be 0.15 ± 0.5. One of the sheets used for the heat shield was shot-blasted using a dry blasting process with corundum. The resulting roughness was Ra = 7 µm ± 1.4 µm and Rz = 60 µm ± 12 µm. This radiation shield was then coated with a black AlTiN using a PVD process (cathodic vacuum arc evaporation) with a layer thickness of 1 µm, employing cathodes of composition Al66Ti34. The heat exchange coefficient of this surface was measured at 0.83 ± 0.5.The double-walled coating chamber used was blasted for the PVD process based on cathodic vacuum arc evaporation inside the chamber. The average roughness was Ra = 5 µm ± 1 µm and Rz = 48 µm ± 9.6 µm. A heat shield in the form of a sheet metal system was constructed for the HTB (heat transfer plate). This system consisted of a heat shield, a shielding plate placed on top of it, and another shielding plate placed on top of that. The required temperature of 500°C for the HTB was achieved even when using a cooling water temperature of 20°C.

[0048] For the NTB process at approximately 200°C, both the shielding plate and the shielding shield were removed. Only the single-sided coated shield remained on the chamber wall. The cooling water temperature was kept at 20°C. This allowed for a continuous coating process at the required low temperatures without interruption.

[0049] In a particularly practical embodiment, the first radiation surface or the second radiation surface is roughened to adjust the first predefinable heat exchange coefficient or the second predefinable heat exchange coefficient of the radiation shield; in particular, a roughness of Ra = 1 µm ± 0.2 µm to 10 µm ± 2 µm or a roughness of Rz = 10 µm ± 2 µm to 100 µm ± 20 µm is provided, which, as already explained, has proven to be the optimal roughness parameter for the desired heat exchange rates.

[0050] In comparison to the blackbody heat exchange coefficient of the blackbody radiator with ε Sch = 1.0, it is particularly advantageous for the first radiating surface to be a black surface or alternatively or simultaneously a surface coating with a high first heat exchange coefficient in the range of 0.1 to 1.0, specifically between 0.5 and 0.95, particularly preferably between 0.7 and 0.9, wherein the first heat exchange coefficient is particularly preferably in the range of approximately 0.85.

[0051] As previously discussed, the first radiation surface and / or the second radiation surface comprises the aforementioned surface coating, which in particular comprises a coating deposited by PVD, specifically an Al x Ti y N, preferably Al 66 Ti 33 N and / or an AlCrN, in particular an Al 66 Cr 33 N coating, and / or a suitable DLC coating, specifically an aC, aC:H, aC.H:X, aC:H:Me coating, wherein the coating is preferably an optically densely deposited coating and / or has a layer thickness of 100 nm to several 1000 nm, specifically between 300 nm and 800 nm and particularly preferably at least 500 nm.

[0052] In particular, for use in low-temperature coating processes up to a maximum part temperature of approximately 250°C, the heat shield can comprise only one radiating shield coated only on the first radiating surface, so that a sufficiently high heat transfer from the parts to be coated inside the coating chamber to the chamber wall is ensured.

[0053] In contrast, particularly when the parts are to be coated at higher temperatures, e.g. in the HTB range or at temperatures between the NTB range and the HTB range, one or more additional radiation shields, in particular up to three additional radiation shields, may be provided between the radiation shield and the shielding shield, which is arranged directly adjacent to the chamber wall.

[0054] For secure mounting on a shield holder, the radiation shield and / or the shielding shield and / or the radiation shield each comprise a mounting area designed such that the corresponding radiation plate can be fixed to the chamber wall using the mounting area on a holding device of a shield holder, preferably all radiation plates simultaneously, by means of one and the same shield holder. The radiation plates can, for example, be screwed to the shield holder, clamped in a groove of the shield holder, or preferably detachably connected to the shield holder in another manner.

[0055] The heat shield and / or the shielding plate and / or the radiation shield are advantageously designed with identical geometry, at least in the mounting area, so that they can be used interchangeably in any mounting device of the shield holder. This allows for flexible adjustment of different heat exchange characteristics between the chamber wall and the heat shield, for example, by simply changing the arrangement of the radiation plates as required.

[0056] As explained above, the radiation shield and / or the shielding shield and / or the radiation shield can be electrically insulated and connected to the chamber wall, so that additional heating by free charge carriers in the coating chamber, e.g. by electrons or ions, is at least significantly reduced or essentially completely avoided.

[0057] In practice, the coating chamber itself usually has a double-walled chamber wall, so that a temperature control fluid, usually simply pre-tempered or non-pre-tempered water, an oil, or another suitable temperature control fluid, can circulate within the double-walled chamber wall for temperature control.

[0058] The inner surface of the chamber wall can also be roughened and, for example, exhibit a roughness in the range of Ra = 1 µm ± 0.2 µm to 10 µm ± 2 µm and / or Rz = 10 µm ± 2 µm to 100 µm ± 20 µm. In comparison to the blackbody heat exchange coefficient of a blackbody radiator with εSch = 1.0, the inner surface can have a black layer with a high chamber heat exchange coefficient in the range of 0.1 to 1.0, specifically between 0.2 and 0.8, particularly preferably between 0.3 and 0.6, and specifically a chamber heat exchange coefficient in the range of approximately 0.4.

[0059] The inside of the chamber wall can also have a chamber coating analogous to the radiation plates, which in particular comprises a coating deposited by PVD, specifically an Al x Ti y N, preferably Al 66 Ti 33 N and / or an AlCrN, in particular an Al 66 Cr 33 N coating, and / or a suitable DLC coating, specifically an aC, aC:H, aC.H:X, aC:H:Me coating, wherein the coating is preferably an optically densely deposited coating and / or has a layer thickness of 100 nm to several 1000 nm, specifically between 300 nm and 800 nm and particularly preferably at least 500 nm.

[0060] The heat shield for a coating chamber according to the present invention is in particular a retrofit part so that an already existing coating chamber can also be retrofitted with a heat shield as described above.

[0061] Furthermore, the invention also relates to a coating method according to claim 13 using a coating chamber according to the described invention, wherein the coating method is a PVD method, in particular a PVD method comprising magnetron sputtering and / or HIPIMS, or a plasma-assisted CVD method, or a cathodic or anodic vacuum arc evaporation method, or a combination method formed from these methods, or another vacuum-assisted coating method, wherein, depending on the coating method used or depending on the specific coating to be applied, a heat shield optimally configured for this purpose is selected and used to set optimal coating temperatures.

[0062] Specifically, the coating process can be a low-temperature coating process, and the coating chamber is heated with a temperature control fluid, in particular water or oil, at a temperature in the range of 10°C to 30°C. Alternatively, the coating process according to the invention can also be a high-temperature coating process, or a coating process carried out in a temperature range between an NTB and an HTB process, wherein the coating chamber is heated with the temperature control fluid, in particular water or oil, at a temperature in the range of 30°C to 80°C, preferably in a temperature range of 40°C to 60°C.

[0063] The invention is explained in more detail below with reference to the schematic drawing. It shows: Fig. 1 schematically shows a coating chamber according to the invention; Fig. 2 shows a coating chamber with only one radiation shield; Fig. 3 shows a coating chamber with a radiation shield, a shielding shield, and a radiation shield for HTB operation. Fig. 4 is a schematic representation of the arrangement of basic elements of a vacuum chamber according to the present invention. Fig. 5 shows the temperature profile of substrates to be treated, each treated in a non-inventive vacuum chamber (dashed line) and an inventive vacuum chamber (solid line).

[0064] In Fig. 1 A first simple embodiment of a coating chamber according to the invention is shown schematically, which can be used particularly advantageously, for example, for carrying out a high-temperature coating process.

[0065] The coating chamber 1 according to the invention for carrying out a vacuum-supported coating process according to Fig. 1 The invention comprises a heat shield 3, 31, 32, 33 arranged on a temperature-controlled chamber wall 2 of the coating chamber 1, which serves to control the exchange of a predefinable amount of thermal radiation between the heat shield 3, 31, 32, 33 and the temperature-controlled chamber wall 2. According to the present invention, the heat shield 3, 31, 32, 33 comprises an interchangeable radiation shield 31 directly adjacent to an inner surface 21 of the chamber wall 2, which has a first radiation surface 311 of the radiation shield 31 directed towards the chamber wall 2 with a first predefinable heat exchange coefficient εD1, wherein a second radiation surface 312 of the radiation shield 31 facing away from the chamber wall 2 has a second predefinable heat exchange coefficient εD2, and the first heat exchange coefficient εD1 is greater than the second heat exchange coefficient εD2. For the sake of clarity, the radiation shield 31 is in Fig. 1Not shown in detail. However, the specific construction of the radiation shield 31 is essentially identical to that shown in Fig. 2a. Fig. 3 , so that for details on the construction of the radiation shield 31 refer to Fig. 2a or Fig. 2a. Fig. 3 can be referred to.

[0066] The coating chamber 1 comprises, in a manner known per se, a heater 6 for preheating the parts to be coated, which, in the operating state, are located, for example, on a rotating part holder within the coating chamber 1 and are not shown here, as well as plasma sources 7 for the coating, which are also known per se in many variations from the prior art. Details such as the heater, the plasma sources, the part holder for the parts to be coated, etc., are hardly relevant for understanding the invention itself.

[0067] Between the radiation shield 31 directly adjacent to the chamber wall 2 and the shielding shield 32, a plurality of further radiation shields 33 are provided between the radiation shield and the shielding shield 32.

[0068] The coating chamber 1 itself has a double-walled chamber wall 2, so that a temperature control fluid 5, here water, can circulate within the double-walled chamber wall 2 for its temperature control.

[0069] The inner surface 21 of the chamber wall 2 is either only rough blasted and / or provided with a chamber coating 20, which is a coating deposited by means of PVD, e.g. an Al x Ti y N, an AlCrN coating or a suitable DLC coating, wherein the coating is an optically densely deposited coating and has a layer thickness of 100 nm to several 1000 nm.

[0070] Fig. 2a shows a special coating chamber with only one heat shield 31 for NTB operation. The heat shield 3 thus consists of exactly one heat shield 31, coated only on the first radiation surface 311, for use in low-temperature coatings up to a maximum part temperature of approximately 250 °C.

[0071] To adjust the first predefinable heat exchange coefficient ε D1 and the second predefinable heat exchange coefficient ε D2 of the radiation shield 31, the first radiation surface 311 and the second radiation surface 312 are rough and have a roughness of Ra = 1 µm ±0.2 µm to 10 µm ±2 µm or a roughness of R z = 10 µm ±2 µm to 100 µm ±20 µm.

[0072] Furthermore, the first radiating surface 311 is provided with a surface coating 30 which, compared to the black heat exchange coefficient ε Sch of the black radiator with ε Sch = 1.0, has a high first heat exchange coefficient ε D1 in the range of 0.7 to 0.9.

[0073] The surface coating 30 is a coating deposited by means of PVD, specifically an Al x Ti y N, an AlCrN, or a suitable DLC coating, specifically an aC, aC:H, aC.H:X, aC:H:Me coating, wherein the coating is an optically densely deposited coating and has a layer thickness of 100 nm to several 1000 nm, e.g. approximately 500 nm thick.

[0074] The radiation shield 31 is fixed in a mounting area on a holding device 41 of a shield holder 4 by means of a shield holder 4 on the chamber wall 2, wherein the radiation shield 41 is a radiation plate that is simply clamped in a holding device 41 of the shield holder designed as a groove, so that it can be easily and quickly replaced.

[0075] Based on the Fig. 3 Finally, this is a special embodiment of a coating chamber 1 with a radiation shield 31, a shielding shield 32 and a radiation shield 33 arranged between them. This arrangement is particularly well suited for high-temperature operation.

[0076] In a further embodiment, the present invention relates to a vacuum chamber and a coating system with a special design for increasing heat dissipation.

[0077] Conventional coating systems are typically designed to achieve and maintain a predetermined coating temperature within the coating chamber or receiver. Often, the interior surfaces of the coating chamber are made of polished or blasted stainless steel or aluminum. Since the inner walls of the coating chamber can become unintentionally coated during the coating process, shielding is generally used to prevent the buildup of thicker layers on the inner walls. The use of such shielding is particularly helpful when multiple coating processes are to be carried out consecutively without maintenance, as this can lead to the accumulation of multiple layers and subsequent flaking during and after coating.Such shielding is often made of polished or blasted stainless steel or aluminum. This design is usually applied uniformly across the entire receiver, i.e., along the outer surface, the lid, and the base.

[0078] Coating sources, heating and cooling elements are typically distributed as individual components within the coating chamber in such a way that some internal surfaces or chamber wall surfaces remain free of sources and / or elements. Consequently, these "free" surfaces act as heat dissipation elements, or in a similar manner to cooling elements.

[0079] The ratio between heat input (e.g., from heating elements and coating sources) and heat dissipation (e.g., through the surface area of ​​the coating chamber) typically plays a crucial role in setting the system's operating point with regard to coating temperature, especially when both the top and bottom surfaces of the coating chamber are thermally insulated. Thermal insulation of the top and bottom surfaces results in a homogeneous temperature distribution across the coating thickness, even when, for example, heating elements are operated without temperature control.

[0080] Before a coating process can even begin, a specific coating temperature—that is, a specific temperature of the substrate surfaces to be coated—must be reached. To supply heat, at least until the coating process starts, heating elements are often positioned on a chamber wall surface, so that these hot surfaces radiate heat onto the substrate.

[0081] After the start and during the execution of the coating process, the operation of the coating sources generates an additional heat input, which can be particularly high when a large number of arc evaporation sources are operated with high arc currents.

[0082] If one were to coat substrates with a specific coating in a coating system and achieve a higher coating rate, this could be accomplished, for example, by using a greater number of coating sources. However, in this case, a corresponding increase in the heat input to the coating chamber must be expected, which directly leads to an increase in the coating temperature if the heat dissipation is not adjusted or increased accordingly. This problem is particularly pronounced when arc evaporation sources are used.

[0083] The invention therefore further aims to provide a solution that makes it possible to regulate the heat dissipation in a coating chamber in such a way that the coating temperature does not rise uncontrollably due to an increase in heat input, but can be kept at the desired operating point.

[0084] To better understand the facts explained above and the present invention, reference is made to the Figures 4 and 5 Referenced: Fig. 4 Figure 1 shows a schematic representation of the arrangement of basic elements of a vacuum chamber according to the present invention. Fig. 5 shows the temperature profile of substrates to be treated, each treated in a non-inventive vacuum chamber (dashed line) and an inventive vacuum chamber (solid line).

[0085] The present invention basically discloses a vacuum chamber for the treatment of substrates, which comprises at least the following elements: Heat supply elements for supplying heat to a treatment area of ​​the vacuum chamber in which at least one substrate 100 can be treated, a chamber wall 200 through which heat can be dissipated from the treatment area, which comprises an inner and an outer chamber wall side, and a shielding wall 300, which is arranged between the chamber wall 200 and the treatment area, such that a shielding wall side facing away from the treatment area is positioned opposite the inner chamber wall side, and is characterized by the fact that the shielding wall side opposite the inner chamber wall side is at least partially, preferably mostly, provided with a first layer 310 which has an emission coefficient ε ≥ 0.65.

[0086] According to a preferred embodiment of the present invention, the inner chamber wall side is also provided at least partially, preferably at least mostly, with a second layer 210 which has an emissivity ε ≥ 0.65.

[0087] According to a further preferred embodiment of the present invention, the chamber wall 200 comprises an integrated cooling system 150.

[0088] Preferably, the emissivity of the first layer 310 is greater than or equal to 0.80, even more preferably greater than or equal to 0.90.

[0089] Likewise, the emission coefficient of the second layer 210 is preferably greater than or equal to 0.80, even more preferably greater than or equal to 0.90.

[0090] In general, the inventors have observed a particularly significant increase in heat dissipation from ε ≥ 0.8, especially from ε ≥ 0.9. ε close to 1 is even preferred.

[0091] According to a further preferred embodiment of the present invention, the first layer 310 and / or the second layer 210 are deposited at least partially by means of a PVD process and / or a PACVD process (PVD: Physical Vapor Deposition; PACVD: Plasma assisted chemical vapor deposition).

[0092] According to yet another preferred embodiment of the present invention, the first layer 310 and / or the second layer 210 comprises aluminium and / or titanium.

[0093] Preferably, the first layer 310 and / or the second layer 210 comprises nitrogen and / or oxygen.

[0094] The inventors have also found that layers comprising or consisting of titanium aluminum nitride or aluminum titanium nitride are very suitable as the first layer 310 and / or second layer 210 in the context of the present invention.

[0095] Layers comprising or consisting of aluminium oxide may also be well suited as the first layer 310 and / or second layer 210 in the context of the present invention.

[0096] The present invention also discloses a coating system with an inventive vacuum chamber, as described above, as the coating chamber.

[0097] According to a preferred embodiment of an inventive coating system, the coating chamber is designed as a PVD coating chamber.

[0098] Preferably, a shielding wall 300 is provided to reduce or prevent coating of the inner chamber wall side during the execution of a PVD process in the PVD coating chamber.

[0099] Preferably, both the top and bottom surfaces of the PVD coating chamber are thermally insulated to achieve a more homogeneous temperature distribution over the entire coating height (or over the entire height of the treatment area).

[0100] Preferably, the chamber wall 200 or chamber walls 200 are not provided with functional elements such as coating, plasma treatment or heating elements.

[0101] Depending on requirements, all chamber walls 200, on which preferably no such functional elements are arranged, can be provided with a second layer 210 in the inner chamber wall side and equipped with a shielding wall 300 with a first layer 310 according to the present invention.

[0102] It can also be advantageous to equip all these chamber walls 200 with integrated cooling systems 150 if even greater heat dissipation is desired.

[0103] As mentioned above, the Figure 2 The comparison of the substrate temperature profile in the same vacuum chamber, wherein, for the inventive example, shielding walls 300 and chamber walls 200 were provided with corresponding first layers 310 and second layers 210 according to the invention (solid line), and, for the non-inventive example, the same vacuum chamber arrangement was used but without layers 310 and 210 (dashed line). Both examples were carried out with the same heat input into the coating chamber.

[0104] For the above-mentioned inventive example, a PVD-deposited titanium aluminum nitride layer with an emissivity ε of approximately 0.9 was used both as the first layer 310 and as the second layer 210.

[0105] According to a preferred embodiment of the present invention, the inner side of all shielded chamber walls can be coated at least mostly with a corresponding second layer 210 and the side opposite the chamber walls of all shielding walls can be coated at least mostly with a corresponding first layer 310.

[0106] Both layer 210 and layer 310 according to the present invention are to be made of materials suitable for vacuum application. It is also important that these materials are non-magnetic in order to avoid process disruptions during coating.

[0107] Preferably, layers 210 and / or 310 have at least one of the following properties: a layer thickness not greater than 50 µm, a dense layer structure so that outgassing through the layer is possibly not possible, good adhesion to the substrate material so that good heat transfer can be ensured, high temperature stability which allows coating processes to be carried out at elevated temperatures, preferably up to at least 600°C, good wear resistance so that these layers are not worn away quickly in a "harsh production environment".

[0108] Preferably, layers 210 and / or 310 are deposited using PVD techniques, so that they can be applied, for example, to the corresponding chamber wall and shielding wall surfaces in the same coating chamber. In this case, for example, the inner chamber walls can first be coated with layer 210 in a coating process without shielding walls. Subsequently, the shielding walls in the coating chamber can be reversed so that the desired shielding wall surface, which will later be opposite the inner chamber wall surface, can be coated with layer 310. A single application of layers 210 and 310 is sufficient to operate the coating system with a coating chamber equipped according to the invention multiple times.

[0109] For carrying out a PVD coating process for coating substrates in a coating chamber according to the invention, the shielding walls in the coating system are arranged such that the inner chamber walls or the inner side of the chamber walls are shielded in order to minimize or prevent unwanted coating of these walls. In this way, only the shielding wall side without layer 310 is coated during the coating of substrates. Consequently, both the applied layer 310 and the applied layer 210 remain intact after each coating process.

[0110] It is understood that the described embodiments are merely examples and that the scope of protection is not limited to the explicitly described embodiments.

Claims

1. Coating chamber for performing a vacuum-assisted coating process, in particular PVD or CVD or arc coating chamber or a hybrid coating chamber with a heat shield (3, 31, 32, 33), which is arranged on a temperature-controllable chamber wall (2) of the coating chamber and is intended for adjusting an exchange of a predeterminable amount of thermal radiation between the heat shield (3, 31, 32, 33) and the temperature-controllable chamber wall (2), characterized in that the heat shield (3, 31, 32, 33) comprises at least one exchangeable radiating shield (31), which is directly adjacent to an inner side (21) of the chamber wall (2), and a first radiation surface (311) of the radiating shield (31), that is directed towards the chamber wall (2), has a first predeterminable heat exchange coefficient (εD1) and a second radiation surface (312) of the radiating shield (31) being directed away from the chamber wall (2) has a second predeterminable heat exchange coefficient (εD2), wherein the first heat exchange coefficient (εD1) is greater than the second heat exchange coefficient (εD2), wherein the radiating shield (31) comprises an assembly area and can be fixed to a holding device (41) of a shield holder (4) at the chamber wall (2) in the assembly area.

2. Coating chamber according to claim 1, wherein the heat shield (3) comprises at least one protection shield (32), and a first protection surface (321) of the protection shield (32), that is directed towards the chamber wall (2) and a second protection surface (322) of the protection shield (32), that is directed away from the chamber wall (2), each having a shiny reflecting surface with a processing status according to DIN EN10088 of at least 2D, preferred a processing status according to DIN EN10088 of at least 2R.

3. Coating chamber according to claim 1 or 2, wherein the first radiation surface (311) and / or the second radiation surface (312) for adjusting the first predeterminable heat exchange coefficient (εD1) and / or the second predeterminable heat exchange coefficient (εD2) of the radiating shield (31) is rough, in particular having a roughness of Ra = 1 µm ±0.2 µm to 10 µm ± 2µm and / or a roughness of Rz = 10 µm ±2µm to 100 µm ±20µm.

4. Coating chamber according to one of the preceding claims, wherein the first radiation surface (311) has a black surface and / or a surface coating (30) with a high first heat exchange coefficient (εD1) in the range of 0.1 to 1.0, especially between 0.5 and 0.95, in particular preferred between 0.7 and 0.9, especially a first heat exchange coefficient (εD1) in the range of approximately 0.85, compared to the black heat exchange coefficient (εSch) of the black radiator with εSch = 1.0.

5. Coating chamber according to one of the preceding claims, wherein the first radiation surface (311) and / or the second radiation surface (312) comprises the surface coating (30), and the surface coating (30) comprising a coating, in particular deposited by means of PVD, especially an AlxTiyN, preferred Al66Ti33N and / or an AlCrN, in particular a Al66Cr33N coating, and / or comprising a suitable DLC-coating, especially an a-C, a-C:H, a-C.H:X, a-C:H:Me coating, wherein the coating is preferred an optically dense deposited coating and / or has a coating thickness of 100 nm to a few 1000 nm, especially between 300 nm to 800 nm and in particular preferred at least 500 nm.

6. Coating chamber according to claim 5, wherein the heat shield (3, 31, 32, 33) comprises exactly only one radiating shield (31) being coated only on the first radiation surface (311), in particular for applying for low temperature coatings in the range of up to a maximum temperature of parts of 250°C.

7. Coating chamber according to one of the preceding claims, wherein preferably one or a majority of additional radiation shields (33) are provided between the radiating shield (31), which is directly adjacent to the chamber wall (2), and the protection shield (32), especially up to three radiation shields (33) between the radiating shield (31) and the protection shield (32) are provided.

8. Coating chamber according to one of the preceding claims, wherein the radiating shield (31) and / or the protection shield (32) and / or the radiation shield (33) each comprising an assembly area and being fixed to a holding device (41) of a shield holder (4) at the chamber wall (2) in the assembly area, preferred by means of one and the same shield holder (4).

9. Coating chamber according to one of the preceding claims, wherein the radiating shield (31) and / or the protection shield (32) and / or the radiation shield (33) is geometrically designed at least in the assembly area in such an identically manner, that they can be applied interchangeably in each holding device (41) of the shield holder (4), so that different characteristics of the heat exchange can be adjusted flexibly between the chamber wall (2) and the heat shield (3, 31, 32, 33) and / or wherein the radiating shield (31) and / or the protection shield (32) and / or the radiation shield (33) is connected electrically insulated with the chamber wall (2).

10. Coating chamber according to one of the preceding claims, wherein the coating chamber comprises a double-walled designed chamber wall (2), so that a thermostating fluid (5), especially water or an oil, is circulable inside the double-walled chamber wall (2) for thermostating.

11. Coating chamber according to one of the preceding claims, wherein the inner side (21) of the chamber wall (2) has a roughness in the range of Ra = 1 µm ±0.2 µm to 10 µm ±2µm and / or of Rz = 10 µm ±2µm to 100 µm ±20µm and / or wherein the inner side (21) has a black coating with a high chamber exchange coeffizient (εK) in the range of 0.1 to 1.0, especially between 0.2 and 0.8, in particular preferred between 0.3 and 0.6, especially a chamber exchange coefficient (εK) in the range of approximately 0.4, compared to the black heat exchange coefficient of the black radiator with εSch = 1.0.

12. Coating chamber according to one of the preceding claims, wherein the inner side (21) of the chamber wall (2) comprises a chamber coating, and the chamber coating (20) comprising a coating, in particular deposited by means of PVD, especially an AlxTiyN, preferred Al66Ti33N and / or an AlCrN, in particular an Al66Cr33N coating, and / or comprising a suitable DLC-coating, especially an a-C, a-C:H, a-C.H:X, a-C:H:Me chamber coating (20), wherein the chamber coating (20) is preferred an optically dense deposited coating and / or has a coating thickness of 100 nm to a few 1000 nm, especially between 300 nm to 800 nm and in particular preferred at least 500 nm.

13. Coating process using a coating chamber (1) according to one of the claims 1 to 12, wherein the coating process is a PVD process, in particular a PVD process comprising magnetron sputtering and / or HIPIMS, or a plasma-assisted CVD process or a cathodic or an anodic vacuum arc vaporization process or a combination process formed of these processes or another vacuum-assisted coating process.

14. Coating process according to claim 13, wherein the coating process is a low temperature coating process and the coating chamber (2) is thermostated by a thermostating fluid (5), especially water or oil, from a temperature in the range of 10°C to 30°C, and wherein the coating process is a high temperature coating process and the coating chamber (2) is thermostated with the thermostating fluid, in particular water or oil with a temperature in the range of 40°C to 60°C.