Vacuum coating system with separation device in the residual gas stream and method for operating a vacuum coating system

Abstract

Vacuum coating system, in particular CVD system (1) with at least one coating station at which at least one layer is deposited from the gas phase of a process gas onto a hollow substrate (3) and at least one vacuum pump (12) with which process gas residues are pumped out, wherein at least one energy source (8) for coupling energy into the process gas residues is arranged between the coating station and the vacuum pump (12), characterized in that the vacuum coating system is designed for depositing an adhesion promoter layer and a barrier layer onto the hollow substrate (3).

Description

Field of invention The invention relates to a vacuum coating system, in particular a CVD system, and a method for operating a vacuum coating system. The vacuum coating system is designed to deposit an adhesion promoter layer and a barrier layer onto a hollow substrate. Background of the invention Vacuum coating systems are known. These are primarily CVD (Chemical Vapor Deposition) systems, in which a coating is deposited onto a substrate to be coated from a precursor gas. The unrelated German patent DE 696 17 858 T2 discloses a device and a method for the chemical deposition, for example, of a silicon nitride film, from the vapor phase onto wafers. In this process, the undesired deposition of components from residual gases in exhaust pipes and vacuum pumps is reduced or eliminated by plasma activation of the residual gases downstream of the reaction chamber. The unrelated EP 0 861 683 A2 describes a “substrate processing system” with an “effluent gas abatement system” for reducing a first compound of the exhaust gas, wherein the “abatement unit” or “abatement device” has an “energy source” that supplies the exhaust gas with energy. The unrelated patent US 6 255 222 B1 discloses a “CVD apparatus 10” comprising a “wafer support pedestal 26”, a “vacuum pump 35”, and a “downstream plasma apparatus” (DPA) with a “plasma generation system”. In this apparatus, a “deposition gas” is introduced into a “substrate processing chamber”, resulting in the deposition of a layer, and exhaust gases are routed from the “chamber” to a “downstream plasma apparatus” where a plasma is generated. The patent discloses only the prior cleaning and activation of the underlying substrate surface with a hydrogen plasma to improve the adhesion of a TMS / ozone layer. The unrelated EP 0 839 930 A1 patent describes "semiconductor processing devices," such as a "chemical vapor deposition machine," for coating wafers with, for example, a "silicon nitride layer." A "downstream plasma cleaning apparatus" is connected to the "CVD apparatus," in which a plasma is generated during the cleaning cycle and which prevents the formation of particles in the "foreline." Particularly well-known are PICVD (Plasma Impulse Chemical Vapor Deposition) systems, in which a plasma is ignited by coupling in energy in the form of pulsed electromagnetic radiation (RF or microwave radiation), from which a coating is deposited. The process times for such coating processes are very short. Often, several layers are deposited sequentially; in particular, an adhesion promoter layer is initially deposited to increase the adhesion of a further layer, for example, a barrier layer for plastic bottles. Such a generic coating system is described, for example, in the applicant's German patent application DE 102 53 512 A1, which shows a so-called rotary coating system in which plastic hollow bodies go through various process steps one after the other in stations on a rotary machine. The coating processes take place in a vacuum, especially in the fine vacuum range. Vacuum pumps, especially high-performance vacuum pumps operating according to the Roots principle, are used to generate the vacuum. It has been found that even with plasma-assisted coating, not only is a coating deposited within the coating chamber, but that when the residual gas is pumped out, precipitates of coating material or even layers are deposited on components of the system behind the recipient. A particularly disadvantageous aspect has been the formation of deposits on the components of the vacuum pump, especially on the pistons. Over time, the accumulating layers can cause the pistons of the vacuum pump to come into contact, which can completely destroy the vacuum pump. Object of the invention In contrast, the invention is based on the objective of reducing the aforementioned disadvantages of the prior art. In particular, it is an object of the invention to reduce the formation of deposits and precipitates in the exhaust stream of a vacuum system. Another objective of the invention is to extend the service life of vacuum pumps installed in vacuum coating systems of the generic type. Summary of the invention The object of the invention is already achieved by a vacuum coating system and by a method for operating a vacuum coating system according to one of the independent claims. The vacuum coating system is to be designed for depositing an adhesion promoter layer and a barrier layer onto a hollow substrate. Preferred embodiments and further developments of the invention can be found in the respective dependent claims. The invention relates to a vacuum coating system, in particular a CVD system with at least one coating station at which at least one layer is deposited onto a substrate from the gas phase of a process gas. The vacuum coating system further comprises a vacuum pump with which at least residual process gas is pumped out. Preferably, the vacuum pump is also designed to evacuate the recipient and / or a hollow substrate. The vacuum coating system is designed to deposit an adhesion promoter layer and a barrier layer onto the hollow substrate. According to the invention, at least one energy source for coupling energy into the process gas residues is arranged between the coating station and the vacuum pump. An energy source is located in the exhaust system of the vacuum coating system, specifically upstream of the vacuum pump's intake side. The exhaust system refers to the section of the system located downstream of the coating station. This section includes components such as pipes, filters, and at least one vacuum pump. The coating station is evacuated via the exhaust system; in particular, residual gases remaining in the coating station after coating are also pumped out via the exhaust system. The inventors have discovered that a kind of afterburning can be carried out using an energy source in the exhaust stream, in which, for example, plasma ignition leads to further precipitation that can be captured in a controlled manner, or the residual gases are converted in such a way that further formation of layers is reduced or even largely avoided. In particular, this reduces or even prevents the formation of layers on the pistons of a vacuum pump, thus significantly increasing the service life of the pump. The energy source preferably comprises a high-frequency (10 kHz to 300 MHz) or microwave source (300 MHz to GHz). In a preferred embodiment of the invention, a magnetron is used as the energy source. Such magnetrons can be provided as relatively inexpensive purchased components. Alternatively or in combination, a simple plate capacitor can also be used, which is connected to an RF voltage source. The energy source is preferably designed such that plasma ignition occurs at least intermittently in the residual process gases. This results in a more complete conversion of the process gases and thus in precipitation and deposition. The growth of coatings in the downstream area of ​​the system is thereby reduced or prevented. In a further development of the invention, the vacuum coating system is configured for the deposition of at least two coatings, the residual process gases of which are combined before the energy source. The two different coatings are applied, for example, using different precursor gases, different precursor gas compositions, and / or different process parameters (pressure, energy input, frequency, duration, etc.). During the discharge process, the residual gases from the two different coating processes are combined. The inventors discovered that combining the various residual process gases can lead to increased reactivity of the gas mixture. This results in increased deposition and precipitation, even without the addition of energy. By combining the residual process gases before the energy source, it is possible to further treat the process gas mixture and undergo a further conversion. Preferably, the vacuum coating system comprises at least two lines through which residual process gases from various coating processes are pumped out. These lines are combined upstream of the energy source. In a further development of the invention, a deposition area is preferably arranged behind the energy source. The deposition area can also extend into the energy source. The process gas or process gas plasma excited by the energy source thus forms layers in the deposition area. The separation area is preferably filled with packing material to increase the surface area. In particular, so-called Raschig rings can be used as packing material. The coating material that accumulates in the separation area, which remains either as deposits on the surface of the packing material or as precipitates, can be removed from time to time by replacing or cleaning the separation area or the packing material. The vacuum coating system is preferably designed as a PICVD rotary system. In this system, the substrates, which according to the invention are designed as hollow bodies, successively pass through various process steps on a rotary unit. In most such systems, the lines for evacuating the recipients or the hollow bodies are combined, so that only one or a few vacuum pumps are required. For the purposes of this invention, a vacuum pump also includes a multi-stage vacuum pump. The invention further relates to a method for operating a vacuum coating system. The vacuum coating system is designed to deposit an adhesion promoter layer and a barrier layer onto the hollow substrate. According to the method, a process gas is introduced into a process chamber or into a hollow substrate to be coated. A coating is produced from the process gas by deposition, and in a further step, the residual gas is pumped out. According to the invention, energy is coupled into the residual gas, i.e., the gas that has left the coating chamber. Preferably, at least two different coatings are produced, the residual gases from the two coating processes are combined, and energy, preferably in the form of RF or microwaves, is coupled into the combined residual gas. The injected energy can ignite a plasma, causing particles to precipitate or detach, or converting the residual gas into components that are essentially non-layer-forming. Components that are essentially non-layer-forming are defined as residual process gases whose ability to form layers independently is reduced compared to the untreated residual gas. At least one process gas preferably comprises a hexamethylsilazane (HMDS), in particular HMDSO and / or HMDSN. Furthermore, the process gas preferably includes oxygen. According to the invention, at least two coatings are applied to a substrate. The first coating preferably has a higher carbon content than the second coating. The carbon-containing layer preferably forms an adhesion promoter layer, which increases the adhesion of a further layer. The adhesion promoter layer is preferably thinner than the further layer. In a preferred embodiment, the further layer is designed as a barrier layer, in particular as a silicon oxide-containing barrier layer. Preferably, the coatings are applied using a PICVD process. Brief description of the drawings The invention will be explained in more detail below with reference to the drawings Fig. 1, Fig. 2 to Fig. 3. Fig. 1 shows a schematic block diagram of a CVD system, Fig. 2 shows a schematic diagram of a PICVD rotary system, and Fig. 3 shows a schematic perspective view of a power source. Figure 1 schematically depicts a CVD system 1. The CVD system 1 comprises a receiver 2 in which a substrate 3 to be coated can be arranged. The receiver 2 can be evacuated via a vacuum pump 12. The evacuation can be controlled or regulated via the valve 7. CVD system 1 further comprises a container for a first precursor gas 4 and a container for a second precursor gas 5. The two precursor gases can be introduced into the recipient via valves 6 and 7. By using different precursor gases or by selecting different process parameters, 3 different coatings can be applied to the substrate. To form a coating, a plasma is ignited in the recipient by coupling in microwaves (not shown) and a layer is formed at least on the inside of the substrate 3. The residual gases remaining after coating are also pumped out using vacuum pump 12. To protect the vacuum pump 12 from contamination, the CVD system 1 includes an energy source 8 with which a type of afterburning of the residual gases is carried out. Afterburning refers to a further conversion of the residual gases to reduce their tendency to form coatings on their own. This does not necessarily have to be an exothermic oxidation reaction. In this embodiment, the energy source 8 is designed as a plate capacitor connected to a high-frequency voltage source 9. Downstream of the energy source is a separator 10, in which residual gases excited by the energy source 8 can precipitate. A filter 11 is arranged downstream of the separator 10 for further separation of precipitates. This largely protects the vacuum pump 12, preferably designed as a Roots pump, from the growth of layers on the piston (not shown). Referring to Fig. 2, the operating principle of a PICVD rotary system 20 will be explained in more detail schematically. The PICVD rotary system 20 comprises a rotary unit 36 ​​with a plurality of stations 21 to 28 for receiving a substrate, in particular a hollow substrate (not shown). The stations 21 to 28 comprise a receiver in which the substrate successively passes through the various process stages. There is a pumping station 21 in which the recipient or the hollow body substrate (not shown) is evacuated. The circular unit 36 ​​then rotates to the next station. At station 22, the first precursor gas is introduced. In station 23, a plasma is then ignited by means of coupled high-frequency or microwave radiation, so that a first layer is deposited on the substrate. Then, the remaining residual gas is pumped out at pumping station 24. A second precursor gas is introduced at station 25. The composition of the second precursor gas may be identical to that of the first. In station 26, a plasma is ignited by coupling in high-frequency or microwaves, and a second layer is deposited on the substrate. Remaining residual gases are pumped out at pumping station 27. Finally, the recipient and / or the hollow substrate is vented in station 28, i.e., the station is brought to atmospheric pressure. The substrate has now completed all process steps and is removed from the system. The rotary system 20 has a vacuum pump 12 for evacuation. The lines 29, 30 of the first and second pumping stations 24, 27 are joined before an energy source 8. The energy source 8 further reacts the residual process gases, which may have a higher reactivity due to the merging. Precipitations collect in a separator 10. This reduces or largely prevents deposits on components of the vacuum pump 12. It is understood that the vacuum pump 12 is also connected to other stations via further lines (not shown). Preferably, the lines of several stations or all stations are combined to reduce the number of pumps. Fig. 3 shows a schematic perspective view of an energy source 8 for installation in a CVD system. The energy source 8 comprises two flanges 31, 32, with which it can be inserted into an exhaust stream of a vacuum system (not shown). For this purpose, the energy source 8 is mounted on two rails 34. The energy source also includes an inspection hatch 33, through which the energy source can be cleaned or serviced, and a cooler 35 with a fan. By using such an energy source in the exhaust stream, the service life of the vacuum pumps installed in PICVD systems could be significantly increased. Reference symbol list 01 CVD system 02 Recipient 03 Substrate 04 Container for first precursor gas 05 Container for second precursor gas 06 Valve 07 Valve 08 Power source 09 High-frequency voltage source 10 Separator 11 Filter 12 Vacuum pump 20 Rotary PECVD system 21 Pump-off station 22 Station for introducing a first precursor gas 23 Station for generating a plasma 24 Pump-off station 25 Station for introducing a second precursor gas 26 Station for generating a plasma 27 Pump-off station 28 Aeration station 29 Line 30 Line 31 Flange 32 Flange 33 Inspection hatch 34 Rail 35 Cooler 36 Rotary

Claims

Vacuum coating system, in particular CVD system (1) with at least one coating station at which at least one layer is deposited from the gas phase of a process gas onto a hollow substrate (3) and at least one vacuum pump (12) with which process gas residues are pumped out, wherein at least one energy source (8) for coupling energy into the process gas residues is arranged between the coating station and the vacuum pump (12), characterized in that the vacuum coating system is designed for depositing an adhesion promoter layer and a barrier layer onto the hollow substrate (3). Vacuum coating system according to the preceding claim, characterized in that the energy source (8) comprises an RF and / or microwave source. Vacuum coating system according to one of the preceding claims, characterized in that the energy source (8) comprises a magnetron. Vacuum coating system according to one of the preceding claims, characterized in that the energy source (8) is designed to ignite a plasma in the process gas residues at least temporarily. Vacuum coating system according to one of the preceding claims, characterized in that the vacuum coating system is designed for the deposition of at least two coatings, the process gas residues of which are combined before the energy source. Vacuum coating system according to one of the preceding claims, characterized in that the vacuum coating system comprises at least two strands through which process gas residues from various coating processes can be pumped out, wherein the at least two strands are brought together before the energy source (8). Vacuum coating system according to one of the preceding claims, characterized in that a deposition area (10) is preferably arranged behind the energy source (8). Vacuum coating system according to the preceding claim, characterized in that the separation area (10) is filled with packing materials to increase the surface area. Vacuum coating system according to the preceding claim, characterized in that the filler elements comprise Raschig rings. Vacuum coating system according to one of the preceding claims, characterized in that the vacuum coating system is designed as a PICVD system. Vacuum coating system according to one of the preceding claims, characterized in that the vacuum coating system is designed as a rotary system. Method for operating a vacuum coating system, in particular a vacuum coating system according to one of the preceding claims, comprising the steps of: supplying a process gas into a process chamber and a hollow substrate (3) to be coated; producing a coating by deposits from the process gas; and pumping out the residual gas, whereby energy is coupled into the residual gas, characterized in that an adhesion promoter layer and a barrier layer are applied to the hollow substrate (3). Method for operating a vacuum coating system according to claim 12, characterized in that at least two different coatings are produced, the residual gases of these two coating processes are combined and the energy is coupled into the combined residual gas. Method for operating a vacuum coating system according to claim 12 or 13, characterized in that the energy is coupled in the form of RF and / or microwaves. Method for operating a vacuum coating system according to one of claims 12 to 14, characterized in that a plasma is ignited by the energy. Method for operating a vacuum coating system according to one of claims 12 to 15, characterized in that the process gas comprises a hexamethylsilazane (HMDS), in particular HMDSO and / or HMDSN. Method for operating a vacuum coating system according to one of claims 12 to 16, characterized in that the process gas comprises oxygen. Method for operating a vacuum coating system according to one of claims 12 to 17, characterized in that at least two coatings are applied successively to a substrate, wherein the first coating has a higher carbon content than the second coating. Method for operating a vacuum coating system according to one of claims 12 to 18, characterized in that at least one, preferably all coatings are applied using a PICVD process.

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