Separation by modular cladding device

Abstract

A process for depositing a multi-layer coating stack onto a flat glass substrate comprising vacuum spraying at least a first layer into a first deposition zone having a first type of atmosphere and at least a second layer into a second deposition zone having a second type of atmosphere that is separated from the first type of atmosphere by a separation zone, wherein the flat glass substrate moves from the first deposition zone to the second deposition zone through the separation zone along a transport path in an uninterrupted manner, characterized in that a gas is injected into the separation zone in the vicinity of the transport path to increase the separation factor between the two types of atmosphere.

Description

Separation by modular cladding device The present invention relates to a process for vacuum depositing a multi-layer coating stack onto a flat glass substrate and a coating apparatus for vacuum depositing multi-layer coating stacks onto large glass substrates, which are, for example, 2, 3, or 4 meters wide, for example, 3.21 meters, continuously. The glass substrates, or glass sheets, are arranged in succession in the coating apparatus with a few centimeters between them; thus, there is a gap between them. This apparatus is a sputtering apparatus and can be a magnetically enhanced sputtering apparatus, also called a magnetron sputtering apparatus. Multilayer coatings may comprise one or more, and in particular three or even four, infrared-reflective silver layers surrounded by dielectric layers, such as metal oxide or metal nitride layers. A glass substrate coated with such a multilayer coating can be used to form a solar control glazing panel or a low-emissivity glazing panel. The coated glass substrate can be assembled with another glass substrate to form an Insulating Glass Unit (IGU) or laminated with another glass substrate to form a vehicle transparency, such as a windshield. The expression "under vacuum" means that the pressure within the deposition zones is reduced to a value significantly lower than normal atmospheric pressure, for example, to a pressure between 0.1 and 99 mTorr (10-3 Torr), preferably, for example, between 0.5 and 15 mTorr. Each layer or group of similar layers (e.g., metal layers) of the coating corresponds to a spray zone, i.e., a deposition zone, comprising one or more positions (a position being a source bay) for the cathode (target) corresponding to the layer to be deposited and in which a particular atmosphere, containing argon alone or together with oxygen or nitrogen or another specific gas, is maintained at a reduced pressure. A module of a modular coating device may generally comprise three (sometimes four) deposition zones associated with three pumping zones to maintain the required low pressure level in the deposition zone.Due to the increased complexity and the growing number of layers in the new coating stacks, especially for coatings that have at least three infrared-reflective layers (silver layer), the number of deposition zones required increases, and the current apparatus is too small. Greater flexibility of the coating devices is also required so that several coatings can be produced on the same line, for example, heat-treatable and non-heat-treatable coatings. This increases the number of positions required. Another requirement is to reduce the time needed to produce the coating. In vacuum coating devices, such as magnetrons, a gas isolation system is necessary between the deposition zones (or chambers) (also called "coating zones") to separate the different processes. For example, in the production of single, double, or triple low-emissivity silver coatings on flat glass, the deposition of metallic silver, which requires injection of pure argon, and the spraying of a dielectric, which requires injection of oxygen (O2) or nitrogen (N2), are adjacent to each other. Without gas isolation zones, the partial pressure of O2 or N2 in the metal spray chamber would be too high to achieve the desired metal properties for the Ag coating. Therefore, these two deposition zones are separated by a section often called the gas separation zone, which preferably has pumping means (also called the pumping section in this case).The design of the insulation between deposition zones depends on the type of coating equipment. The two main suppliers of large-area coatings for the glass industry are AMAT (formerly BOC) and Von Ardenne. For the AMAT modular cladding system, insulation is provided by multiple pumped tunnels. A tunnel is an opening that limits conductance and is attached to the periphery of the chamber. Three tunnels are provided in each gas separation zone. The opening is adjustable to accommodate glass (substrate) of various thicknesses. A pumping space is formed between the openings. Each space is pumped by a dedicated 16" diffusion pump (DP). For a standard design, a total of six DPs are connected to the insulation section. In this case, an additional insulation stage for particularly sensitive claddings can only be achieved by adding a tunnel section with two DPs on each side of the tunnel. The total length of the standard insulation section is approximately 2000 mm. For the Von Ardenne-type cladding device, the gas separation zone is called the "pump section," as opposed to the "cathode sputter section" where the process takes place. The width of the pump section is equivalent to that of the process chamber and is 780 mm. It is equipped with two isolation tunnels. One tunnel is a solid metal plate positioned approximately 25 mm above the pitch line; openings through the upper side wall of the cladding device lead to the adjacent process chamber. The second tunnel is a metal plate with a slit running through its center along the width of the cladding device (perpendicular to the glass transfer direction). Gas pumping in this segment occurs through the slit. Each of the two pump section segments is pumped using one to three Turbo Molecular Pumps (TMPs).The pumps are fixed onto the cover along two parallel lines. Such a type of lining device is described, for example, in WO 2005 / 106069 A1. The performance of the insulation section placed between two spray chambers is called the insulation factor or gas separation factor (SF). It is measured by evacuating the spray chamber to a pressure level below 10⁻⁵ mbar. Argon gas is fed into a deposition zone (zone 1) at a pressure level of 5 x 10⁻³ mbar (filling pressure). In the deposition zone (zone 2) on the other side of the gas separation zone, the pressure (test pressure) is measured. The test is then repeated by introducing Argon gas into zone 2, measuring the pressure in zone 1. The average gas separation factor (SF) is calculated as: 0.5 ((zone 1 filling pressure / zone 2 test pressure) + (zone 2 filling pressure / zone 1 test pressure)). For this calculation, no glass is present in the tunnel.In fact, since there is a space between the substrates during the deposition process, there are regularly times without a glass substrate, so the separation must be effective without a glass substrate and the separation factor must be evaluated without a glass substrate. In existing industrial lines, the separation factor has been measured. The values ​​for an isolation zone for the AMAT modular lining device design range from 25 to 50. The values ​​for a single Von Ardenne-type pump section range from 30 to 200, depending on the number of pumps and the tunnel slab height. This factor increases to 400 when two pump sections are side-by-side. In conclusion, it can be observed that all the separation zones are based on the same principle: a long zone (between 780 and 2000 mm) between two deposition zones where the conductance is reduced by adjusting the distance between the flow line and the tunnel (metal plate). The zone is more or less open with openings next to which the pumping equipment is installed. This can be described as a fairly static design. Prior art coating devices are designed with static gas isolation between the deposition zones or spray chambers. This configuration provides a minimum gas separation factor of 30 according to specifications, but actual measured values ​​in coating devices are around 400 in the best-case scenario. The objective of the invention is to improve the gas separation between two deposition zones in a coating device. The invention relates to a process for depositing a multi-layer coating stack onto a flat glass substrate comprising vacuum depositing at least a first layer in a first deposition zone having a first atmosphere type and at least a second layer in a second deposition zone having a second atmosphere type that is separated from the first atmosphere type by a separation zone, wherein the flat glass substrate moves from the first deposition zone to the second deposition zone through the separation zone along a transport path, characterized in that a gas is injected into the separation zone in the vicinity of the transport path to increase the separation factor between the two atmosphere types. The expression "in the vicinity of" means a distance of approximately 1 mm to approximately 500 mm. Gas injection is introduced as an adjustable gas flow that can be easily adjusted to the current deposition process and configuration. Regulating the injected gas flow allows for dynamic adjustment of the separation factor. Preferably, the gas from the atmosphere within the separation zone is drawn in by pumping. This increases the separation factor. The invention also relates to a modular coating device for vacuum thin-layer deposition on a flat substrate having at least two deposition zones with a gas separation zone between them and having a transport path for the glass substrate that passes through openings from one deposition zone to the other deposition zone through the separation zone, characterized in that the gas separation zone comprises at least one gas injector in the vicinity of the transport path. Preferably, the gas separation zone includes additional pumping means for drawing the gas out of the gas separation zone. This is a convenient means of increasing the separation factor. Preferably, the covering media are arranged above the transport path to define a tunnel along with the transport path within the gas separation zone when a glass substrate is transported over it, and because at least one gas injector is arranged within this tunnel. This is convenient for achieving good gas injection efficiency. In the embodiment in which the coating device is a sputtering apparatus such as a magnetron, the deposition zones are the sputtering zones that have one or more cathode bays. Preferably, the injector(s) are positioned between the transport path and a ceiling wall located 5 to 50 mm from the transport path to define a tunnel section with the substrate moving along the transport path. Preferably, the gas injector(s) are positioned between 10 mm and 100 mm, ideally between 15 mm and 50 mm, for example, approximately 20 mm, from the transport path. The gas is injected above the transport path, but it can also be injected below it, in addition to being injected above. The invention provides a dynamic way to modify gas separation by injecting an adjustable gas flow into the low-conductance tunnel separating the two deposition zones. The gas injected to improve separation can preferably be pumped by ideally connecting the pumps at the top of the tunnel; this limits the pressure increase in the deposition zone. It is quite surprising that injecting gas into the gas separation zone improves the separation factor. Conversely, one might think it would disrupt the deposition process in the deposition zones. We have found that, surprisingly, the invention offers the possibility of achieving higher separation factors, between 2 and up to 20 times better. This improvement can also be combined with a reduction in costs due to two main factors: a reduced length of the gas separation zone and a reduced number of turbomolecular pumps. Another advantage of the invention is that this gas injection makes the separation factor easily adjustable and the achievable performance is so high that the dimensions can be significantly reduced. This increase in the separation factor provides a flexible way to adjust the separation efficiency between deposition zones and is called dynamic separation tunneling. Other advantages of the invention are that: - the separation factor is significantly higher than in the design of the previous technique; - the separation factor can be adjusted by modifying the amount of gas injected; - the separation factor range can vary from 1 to 10000; - the space required for the separation equivalent to the design of the previous technique is shorter; - The pressure in the deposition chamber can be controlled by the pumping capacity and can remain within acceptable values ​​for the spraying process (0.1 to 99 mTorr, preferably 0.5 to 15 mTorr); - Two or more dynamic separation tunnels can be installed side by side for special applications where a very high separation factor is required; - Two deposition zones separated by the gas separation zone according to the invention can operate at different pressure levels. The transport path could be an air cushion conveyor. Preferably, in practice, the transport path is a roller conveyor. Using a roller conveyor to transport a succession of glass substrates prevents the use of a narrow opening for entering and exiting the separation zone. Furthermore, the glass substrates may have different thicknesses between various production runs; this must also be taken into account when sizing the openings. The following figures are provided for illustrative purposes only, but cannot limit the scope of the present invention: Figure 1 relates to a first embodiment of the invention showing two deposition zones with a separation zone between them; Figure 2 refers to a second embodiment of the invention showing two deposition zones with a separation zone between them. Figures 1 and 2 schematically show a module comprising two chambers forming the first and second deposition zones (A) with a separation zone or chamber (B) between them. The optional pumping means for the deposition zones are not shown. The separation zone comprises two compartments (D) above the conveying path. Each compartment (D) includes at least one pumping means (C) at the top, which may or may not be activated, to maintain a low pressure level inside the compartment and adjust the separation factor. The transport path (H) is created by the roller conveyor (F) within the separation chamber. Between the first deposition zone (A) and the separation zone (B), there is an opening (G) to allow the passage of the glass substrate. Similarly, there is an opening (G) between the separation zone (B) and the second deposition zone (A). Each pumping compartment (D) is sealed below by a plate-shaped cover located approximately 10 to 50 mm above the transport path, thus forming a tunnel path with the substrate, when present, above the transport path between the two deposition zones. Each plate has a slit (K) that allows the pumping means to extract gas from the tunnel path. A gas injector (E) is positioned near the entrance and exit of the tunnel path and is fixed to the plate covering the tunnel path. Each gas injector is a perforated pipe with holes so that the gas is injected in the direction of the transport path, approximately 20 mm above it. In Figure 2, there is also a side opening (J) between each deposition zone (A) and the pumping compartment (D) to allow gas to be drawn from the deposition zone through the pumping compartment. The gas isolation factor, or gas separation factor (SF), can be further increased by adjusting and / or combining different parameters. These include dimensions of the gas separation zone, such as the opening (see reference G in Fig. 1) above the flow line (H), the length of the isolation tunnel (B), the width of the lining device, and the presence of pumps (C). Modifying the dimensions and adding pumping capacity are common ways to achieve separation, known as static separation. Reducing the length of the separation chamber (zone) by a factor of three can reduce the gas separation factor by approximately 50%. Dividing the pumping capacity by two can reduce the separation factor by 10%, all other parameters being equal. To verify the effect of the invention compared to the prior art, we have performed the following tests. To demonstrate the impact of a simple injection without additional pumping in the separation zone, we added an injection of a neutral gas, such as argon, to the separation chamber. The experiment shows that an injected quantity of 2000 sccm (Standard Cubic Centimeters per Minute, i.e., a measurement of gas flow) can multiply the separation factors by approximately 2.5. An injected quantity of 10,000 sccm can multiply the separation factors by approximately 20. This demonstrates the high degree of flexibility in the separation factor that can be achieved with the invention. These results can be improved by adding pumping capacity to the separation zone. If we consider a pumping capacity similar to that found in the existing design, the improvement in both gas flow injection and pumping capacity in the separation zone represents a multiplicative factor of the separation factor from 3.75 to 30. A modification of the design of the pumping section in the separation zone, which consists of closing the side openings at the top of the pumping chamber (fig.2 J), can improve the separation factor value by 40%. The invention opens the possibility of achieving separation factor values ​​equivalent to the standard separation factor value with a shorter tunnel length, or of achieving better separation factor values ​​with a standard separation zone length. The invention allows for adjusting the separation factor, which is impossible in the existing design without venting the lining device. The pressure level within the lining device is advantageously controlled by turbomolecular pumps, ensuring a pressure level compatible with the process. The desired separation factor is modulated by varying the amount of injected gas. The gas is injected into the separation zone by means of an injector or injectors and the gas can come from the separation zone itself or from neighboring deposition zones. The most suitable gas injection system is made from a perforated pipe with holes fixed along the width of the chamber (perpendicular to the transfer direction). Preferably, there is a gas injector near each of the two deposition zones. The gas flow from the holes can be directed toward and perpendicular to the transport path or it can be directed toward the openings of the corresponding deposition zone. In one embodiment, the injector or injectors are metal tubes approximately 20 mm in diameter with holes distributed along their length, the tube being arranged along the width of the transport path at a distance of 20 mm from the transport path. Any other method of injecting gas into the separation zone is suitable for the current application, regardless of the size or geometry of the injection device. The injected flow is controlled by a regulator such as a mass flow meter or any other device capable of controlling gas flow. The applicable flow range is between 0 and 10,000 sccm (standard cubic centimeters), achieved by controlling either the flow or the pressure. The gas ejection angle or the orientation of the orifices in the pipe can vary according to geometric limitations. If two or more injectors are used, the flow can be distributed uniformly or unevenly between the different injector pipes. For example, if two pipes are used as shown in Figure 1, and the total flow is 2,000 sccm, the flow in one pipe could be 1,000 sccm and 1,000 sccm in the second, but it could also be 500 sccm and 1,500 sccm, or any other distribution. The principle of gas injection to separate two deposition zones is valid for any type of gas, but the expert knows that the selection of the gas will depend on the atmosphere of the deposition process to be separated. The most suitable pumping means to combine with gas injection according to the invention consists of four Turbo Molecular Pumps (TMPs) with a nominal pumping capacity of 2300 l / s, mounted on the lid of the separation chamber. The process pressure range for which the invention is most beneficial is preferably between 0.1 and 15 mTorr. The number of pumps can vary from zero to the maximum number determined by the available space around the chamber. The pumping capacity of the TMPs must be designed to accommodate the pressure range. Gas injection into a separation zone according to the invention, while pumping to further improve the separation factor between two deposition zones, is not limited to the magnetron sputtering process pressure.The process, which operates at a higher pressure of up to approximately 100 mTorr, can be isolated from the other components by means of a dynamic tunnel equipped with crude vacuum pumps, such as mechanical or root pumps. In this case, the injected gas flow rate is much higher than that described above. Other types of pumps such as diffusion pumps, mechanical pumps or any type of pump that allows reaching the working pressure are suitable. The most suitable geometry is based on the separation zone (B) divided into two compartments (D). Each compartment is pumped by two pumps (C) located in the lid of the separation zone. The bottom of the compartment is a plate with a slit (K) for pumping above the conveying path. The size of the slit (K) can vary from 0 (no pumping) to the full length of the compartment (fully open). The slit opening is not necessarily located in the center of the tunnel, as shown in Figures 1 and 2. Gas injection (E) is placed in the separation chamber above the conveyor (F), between the deposition chamber and the pumping slit (K). The tunnel length can vary from 100 to 2000 mm. The opening (G) of the dynamic tunnel depends on the substrate thickness and can vary from 1 to 100 mm above the conveying path (H).The openings (G) can differ between the first and second deposition zones (A). Ideally, the compartments (D) do not have a direct opening (Figure 2J) to the deposition zone (A), but the performance of a pump section design in an existing lining device could be improved by injecting gas into the tunnel and pumping it using the current configuration (opening on the side of the pump section, Figure 2J). The dynamic tunnel width ideally corresponds to the width of the lining device. The width depends on the application and the size of the substrates. It is known that homogeneous pumping is achieved if the slit is fully open in the width direction. However, reducing the slit width (K) will only modify the pumping capacity. Example 1. This example shows the influence of gas injection flow on the separation factor. Starting from a standard prior art design based on a static pumping isolation system, we measured a gas separation factor (SF), according to the above description. These values ​​were compared with the values ​​obtained after modifications to the design according to the invention. The reference design consisted of a 1000 mm long separation tunnel without pumping between two deposition zones. A flow of 1000 sccm of Ar was injected into each deposition chamber adjacent to the separation tunnel. A flow of 40 sccm of O2 was injected into one deposition chamber, and the partial pressure of O2 was measured in the other deposition chamber. According to the invention, Ar gas was injected at two different flow rates into the separation zone within the tunnel (see Fig. 1). Table 1 below summarizes the measured results for the increasing Ar flow rates injected into the separation tunnel. The SF is calculated relative to the reference design without gas injection (0 sccm of Ar). Table 1. Comparative example 1. Comparative example 1 shows the influence of pumping alone (without gas injection) from the tunnel on the SF. Here, the reference design consisted of a 300 mm long separation tunnel without pumping, compared to a total pumping capacity of 9000 and 18000 l / s. A flow of 1000 sccm of Ar was injected into each deposition chamber adjacent to the tunnel. A flow of 40 sccm of O2 was injected into one deposition chamber, and the partial pressure of O2 was measured in the other deposition chamber. Table 2 below summarizes the measured results for increasing the pumping capacity in the dynamic tunnel. The SF was calculated relative to the reference design (without pumping). Table 2. Example 2. Example 2 shows a comparison of a prior art standard lining device of the Von Ardenne type design with a dynamic separation tunnel design according to the invention. The design of the prior art Von Ardenne-type lining device is described above. The length of the separation tunnel is 780 mm. There are four pumps, each with a capacity of 2300 l / s. Table 3 below provides the experimental absolute separation factor for both cases. Table 3. The invention can be implemented in all existing magnetron coating devices. It can also be used for any process (PECVD) requiring efficient separation, regardless of the process pressure (from approximately 0.1 mTorr to 100 mTorr). The main advantage is that the invention allows for a good separation factor in confined spaces. Therefore, it is a compact system that can be used in the design of compact coating devices to limit investment costs, and also to combine different processes, such as magnetron coating in one deposition chamber and PECVD (Plasma Enhanced Chemical Vapor Deposition) in an adjacent chamber.

Claims

1. A process for depositing a multi-layer coating stack onto a flat glass substrate comprising vacuum spraying at least a first layer into a first deposition zone having a first type of atmosphere and at least a second layer into a second deposition zone having a second type of atmosphere separated from the first type of atmosphere by a separation zone, wherein the flat glass substrate moves from the first deposition zone to the second deposition zone through the separation zone along a continuous transport path, characterized in that a gas is injected into the separation zone in the vicinity of the transport path to increase the separation factor between the two types of atmosphere.

2. A process according to claim 1, characterized in that the gas from the atmosphere within the separation zone is drawn out by pumping. 3.A process according to any one of claims 1 or 2, characterized in that the gas is injected through a perforated pipe.

4. A process according to any one of the preceding claims, characterized in that the gas is injected near each of the two deposition zones.

5. A process according to any one of the preceding claims, characterized in that the gas is injected towards and perpendicular to the transport path.

6. A process according to any one of claims 1 to 4, characterized in that the gas is injected towards the openings of the closed deposition zone.

7. A process according to any one of the preceding claims, characterized in that the gas is injected between 10 mm and 100 mm, preferably between 15 mm and 50 mm, from the transport path. 8.A process according to any of the preceding claims, characterized in that the gas is injected within a defined tunnel path above the substrate.

9. A modular coating device for vacuum spraying thin-layer deposition onto a flat glass substrate having at least two deposition zones with a gas separation zone between them and having a transport path for the glass substrate passing through openings from one deposition zone to the other deposition zone through the separation zone uninterruptedly, characterized in that the gas separation zone comprises at least one gas injector in the vicinity of the transport path.

10. A modular coating device according to claim 9, characterized in that the gas separation zone comprises pumping means for drawing the gas out of the gas separation zone. 11.A modular coating device according to any of claims 9 or 10, characterized in that the coating means are arranged above the transport path to define a tunnel path together with the transport path within the gas separation zone when a glass substrate is transported thereon, and in that at least one gas injector is arranged within said tunnel.

12. A modular coating device according to any of claims 9 to 11, characterized in that the gas injector comprises a perforated pipe with holes positioned along the width of the zone perpendicular to the direction of the transport path.

13. A modular coating device according to any of claims 9 to 12, characterized in that a gas injector is arranged between 10 mm and 100 mm from each of the two deposition zones.

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