Chemical Vapor Deposition Equipment

Abstract

The present disclosure relates to a chemical vapor deposition apparatus for providing a surface of a substrate with a layer, the apparatus comprising a reactor having a chamber for accommodating at least one substrate, and a pressure unit configured to generate a first predetermined pressure in an interior portion of the chamber, the pressure unit including a first pumping stage having at least one liquid ring vacuum pump and a second pumping stage having at least one dry screw vacuum pump.

Description

[Technical field]

[0001] The present disclosure relates to a chemical vapor deposition apparatus for providing a surface of a substrate with a layer. [Background technology]

[0002] The term "chemical vapor deposition" (hereinafter CVD) relates to the provision of layers, especially thin layers, on the surface of other materials (substrates), such as workpieces for metalworking (e.g. cutting plates, saw blades, etc.). CVD methods and devices usually rely on the chemical reaction of chemical compounds contained in a process gas, whereby the desired main product of the chemical reaction is deposited on the surface of the substrate to form a coating or overlay. Known CVD devices are described for example in EP 2 304 075 A1.

[0003] Known CVD equipment is typically tailored to a specific application, such as a particular substrate / coating combination. Different applications in turn utilize different process parameters. However, a CVD equipment tailored to a first application may not be suitable for a second application. Thus, there is a need to promote flexibility in CVD equipment.

[0004] Furthermore, it has been observed that the process gas flow patterns in known CVD apparatus may be spatially non-uniformly distributed. Such non-uniform distribution may in turn lead to a first portion of the substrate to be coated having a higher amount and / or concentration of process gas than a second portion of the substrate to be coated. As a result, the quality of the coating may be negatively affected. Examples of coatings with reduced quality include coatings with varying thicknesses and / or coatings with non-uniform physical and mechanical properties.

[0005] Similar considerations apply to process gas pressure curves, particularly those viewed over time: it has been observed that changes in the process gas pressure curve can negatively affect coating quality.

[0006] Similarly, changes in the pressure curve may progress with a slow rise in the coating. The aforementioned drawbacks may therefore progress to the detriment of the coating quality as well as to the high costs. Summary of the Invention

[0007] The aim of the present disclosure is to overcome at least one of the above mentioned drawbacks in a simple yet effective manner.

[0008] A chemical vapor deposition apparatus according to the present disclosure is defined in claim 1. The dependent claims relate to embodiments.

[0009] A chemical vapor deposition apparatus according to the present disclosure is an apparatus for providing a surface of a substrate with a layer. The apparatus includes a reactor having a chamber for housing at least one substrate and a pressure unit configured to generate a first predetermined pressure in an interior portion of the chamber. The pressure unit includes a first pumping stage having at least one liquid ring vacuum pump and a second pumping stage having at least one dry screw vacuum pump.

[0010] The CVD apparatus as described above may be associated with the technical effect of facilitating flexibility and increasing the pressure operating range of the reactor chamber to 0.1 kPa (1 mbar). That is, the pressure unit comprises a first pumping stage with at least one liquid ring vacuum pump and a second pumping stage with at least one dry screw vacuum pump, so that the pressure unit can operate in a wide pressure range with the liquid ring vacuum pump of the first pumping stage having a low delivery capacity and the dry screw vacuum pump of the second pumping stage having a high delivery capacity. The combination of the liquid ring vacuum pump and the dry screw vacuum pump significantly improves the ability to reliably and finely regulate the pressure in the reactor chamber, which leads to improved coating quality. Furthermore, the CVD apparatus may be associated with the technical effect of having high reliability and increased robustness. The dry screw vacuum pump, like the other pressure units of the CVD apparatus, aspirates the exhaust gases from the reactor. In other words, the dry screw vacuum pump is connected to the outlet of the reactor and aspirates the used gases of the CVD process. Compared to other pump types used in CVD equipment, such as dry root vacuum pumps, the larger gap between the screws of the dry screw vacuum pump makes this particular type of pump less likely to block with by-products contained in the exhaust gas during the CVD process and therefore less likely to malfunction. The relatively large gap of the dry screw vacuum pump greatly improves the cleaning process, which is usually carried out with water or a water-based solution and is carried out after the CVD process is finished. In this way, the residues of the CVD process deposited in the pump can be removed more efficiently and at the same time more thoroughly, which can result in an improved pump life and reduced costs.

[0011] Preferably, such a CVD apparatus may be configured to provide the surface of the substrate with a layer without using a plasma. Such a plasma may be used for dissociation of the molecules of the process gas. Instead of using a plasma for dissociation, the reactor may be heated to a high temperature of 1200° C. and thermal energy may be used for dissociation of the molecules of the process gas. Not using a plasma brings the advantage that a device for generating plasma can be omitted, reducing costs and that the pressure range required for such a CVD apparatus using thermal energy as reaction activation energy can be very well matched with the performance of the pump system described in this application.

[0012] According to some embodiments, the first pumping stage and the second pumping stage of the chemical vapor deposition apparatus are connected in series.

[0013] The CVD apparatus as described above may be associated with the technical effect of improving performance: the series connection of the first pumping stage and the second pumping stage increases the achievable vacuum.

[0014] According to some embodiments, in the chemical vapor deposition apparatus, an inlet side of a second pumping stage is connected to the reactor chamber and an outlet side of the second pumping stage is connected to the inlet side of the first pumping stage.

[0015] This configuration allows the vacuum generated in the reactor chamber to be further increased, since the dry screw vacuum pump of the second pumping stage has a higher delivery capacity than the liquid ring vacuum pump of the first pumping stage. In this way, both the amount of process gas flowing through the reactor chamber and the vacuum can be increased simultaneously. This results in a lower residence time of the process gas chemicals in the reactor and an improved distribution of the process gas. This can further enhance the performance of the CVD apparatus. This configuration also allows the pressure variations in the chamber to be reduced, thereby reducing the variations in the quality of the coating on the substrate.

[0016] According to some embodiments, the first pumping stage includes a first liquid ring vacuum pump and a second liquid ring vacuum pump connected in parallel.

[0017] A first pumping stage with two liquid ring vacuum pumps connected in parallel allows the size of the liquid ring vacuum pump of the type used in the first pumping stage to be reduced, since the displacements of the first and second parallel connected liquid ring vacuum pumps are added together, thus allowing the use of smaller pumps with less power, reducing the cost of the first pumping stage and allowing for more flexible use of the installation space of the CVD apparatus.

[0018] According to some embodiments, the apparatus further includes a pressure regulation unit configured to control the first predetermined pressure generated by the pressure unit, the first predetermined pressure being adjustable in a full range covering 0.1 kPa (1 mbar) to 90 kPa (900 mbar).

[0019] A CVD apparatus as described above may be associated with the technical effect of increased flexibility and reliability on the coating quality. With a pressure unit configured to generate an adjustable pressure in the full range covering 0.1 kPa (1 mbar) to 90 kPa (900 mbar) in the inner part of the chamber and a pressure regulation unit configured to control this pressure, the CVD apparatus may be used for example for coating processes that depend on pressures between 0.1 kPa (1 mbar) and 40 kPa (400 mbar) and also for coating processes that depend on pressures between 40 kPa (400 mbar) and 90 kPa (900 mbar). The extension of the generated vacuum and its lack of variation has a significant positive impact on the coating quality.

[0020] According to some aspects, the pressure regulating unit is configured to control the first predetermined pressure by at least varying a rotational speed of the dry screw vacuum pump.

[0021] As outlined in the description part of this application, changes in the pressure curve of the process gas can have a negative effect on the quality of the coating. Moreover, changes in the pressure curve can progress with slower coating build-up. The vacuum generated by the dry screw vacuum pump depends on its rotation speed. A pressure regulating unit configured to vary the rotation speed of the dry screw vacuum pump allows the pressure generated in the reactor chamber to be adjusted in fine steps and maintained with relatively small changes.

[0022] According to some embodiments, the chemical vapor deposition apparatus further comprises at least one valve configured to reduce crossover of at least one connection to the chamber, optionally with the opening of the valve controlled by the pressure regulating unit.

[0023] It has been found that in a CVD apparatus, the use of a pressure unit comprising a first pumping stage with a liquid ring vacuum pump and a second pumping stage with a dry screw vacuum pump allows the operating pressure range to be extended to 0.1 kPa (1 mbar) with a fairly stable pressure curve (i.e. a pressure curve with a rather low amplitude of changes). However, especially at pressures as low as 0.1 kPa, the vacuum generated in the reactor chamber can still be subject to certain pressure changes. A CVD apparatus as described above allows for a precise control of the pressure in the chamber by means of at least one valve, preferably a throttle valve, configured to reduce the crossing of one connection from the dry screw vacuum pump to the chamber, preferably to the outlet of the chamber. Also, the pressure changes in the reactor chamber can be further reduced or completely eliminated. Moreover, by controlling both the rotation speed of the at least one valve and of the at least one pump, the pressure in the chamber can be controlled even more precisely. By these measures, the quality of the coating, i.e. the homogeneity and thickness of the coating, can be precisely adjusted.

[0024] According to some embodiments, the chemical vapor deposition apparatus further includes a second valve configured to reduce crossover of at least one connection to the chamber. The second valve has a different size than the at least one valve and is connected in parallel to the at least one valve. An opening of the second valve and an opening of the at least one valve are simultaneously controlled by the pressure regulating unit.

[0025] By using two valves connected in parallel and of different sizes, meaning that the valves have different crossings and are designed for different mass flow rates, the pressure changes occurring in the chamber can be more effectively suppressed. This is because the pressure regulating unit may control these valves with different control strategies. For example, by controlling the opening of the larger valve, larger changes in the generated pressure can be compensated or eliminated, and by controlling the opening of the smaller valve, finer changes in the generated pressure can be controlled.

[0026] According to some embodiments, the at least one dry screw vacuum pump has a liquid cooling system configured to transfer heat between a liquid and the at least one dry screw vacuum pump.

[0027] Compared to CVD apparatuses known from the prior art, this configuration of a dry screw vacuum pump in combination with a liquid cooling system allows the CVD process to be sustained substantially longer without overheating the dry screw vacuum pump. In particular, when using nitrogen (N2) and / or argon (Ar) as carrier gas or when using high gas flows of hydrogen (H2), it is often necessary to operate the pump of the second pumping stage at high rotational speeds, which causes the pump of the second pumping stage to heat up. When operating the pump for a certain period of time under such conditions, the pump tends to overheat if the heat inside the pump cannot be sufficiently dissipated. This effect occurs in particular with dry root vacuum pumps. According to the present invention, this negative effect can be efficiently avoided when combining a dry screw vacuum pump with a relatively large clearance between the screw and the liquid cooling system.

[0028] Further advantages and features of the present disclosure, which may be realized by themselves or in combination with one or more of the features described above, provided that the features do not interfere with each other, will become apparent from the following description of working examples and / or any of the aspects and / or embodiments. The specification is provided with reference to the accompanying drawings. [Brief description of the drawings]

[0029] [Figure 1a] FIG. 1 a is a schematic diagram showing a pressure unit 6 comprising a single stage pumping system with a single liquid ring vacuum pump 601 connected to a reactor 1 . [Figure 1b] FIG. 1 b is a schematic diagram showing a pressure unit 6 comprising a single stage pumping system having two liquid ring vacuum pumps 601 connected in parallel and connected to a reactor 1 . [Diagram 2] FIG. 2 is a schematic diagram showing a pressure unit 6 having a first pumping stage 60, a second pumping stage 61 and a third pumping stage 62, where the first pumping stage comprises two liquid ring vacuum pumps 601 connected in parallel, the second pumping stage 61 comprises a dry root vacuum pump 612, the third pumping stage 62 comprises a second dry root vacuum pump, and the two dry root vacuum pumps 612 of the second and third pumping stages are connected in series, and the pressure unit 6 is connected to a reactor 1. [Diagram 3] FIG. 3 is a schematic diagram showing a pressure unit 6 having a first pumping stage 60 and a second pumping stage 61, the first pumping stage comprising two liquid ring vacuum pumps 601 connected in parallel and the second pumping stage 61 comprising one dry screw vacuum pump 611, the first and second pumping stages being connected in series, and the pressure unit 6 being connected to a reactor 1. [Figure 4]FIG. 4 is a chart showing the pressure in mbar in the reactor chamber generated by a pressure unit of a representative configuration, as a function of the mass flow rate of hydrogen (H2) in normal liters per minute (Nl / min), in a preferred embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] Embodiments of the devices, uses and methods according to the present disclosure are described in detail below, by way of limiting example only, and with reference to the accompanying drawings, in which: like reference characters appearing in different figures, unless otherwise indicated, indicate identical, corresponding or functionally similar elements, in which:

[0031] The pressure unit 6 is configured to generate a first predetermined pressure in the inner part of the chamber 10, said first predetermined pressure being adjustable in a full range covering 0.1 kPa (1 mbar) to 90 kPa (900 mbar).

[0032] As shown diagrammatically in FIG. 3, the pressure unit 6 comprises a liquid ring vacuum pump 601. The use of a liquid ring vacuum pump is associated with the technical effect that a liquid is used to generate a vacuum. When using a solution of NaOH in such a pump, the exhaust gases can already be neutralized inside the pump respectively. This also promotes the life of the pump and reduces corrosion as the acidic exhaust gases are at least partially neutralized. The liquid in the liquid ring vacuum pump 601 also flushes out the residues of the acidic exhaust gases inside the pump.

[0033] Providing two liquid ring vacuum pumps 601 connected in parallel as shown in FIG. 3 is associated with the technical effect of increasing the efficiency of the CVD apparatus. If the chemical vapor deposition process requires a higher gas flow and / or a higher vacuum, a second liquid ring vacuum pump 601 is used in addition to the first one. In this way, the first and second liquid ring vacuum pumps 601 can each be of smaller dimensions. If the process requires a lower gas flow and / or a lower vacuum, one of the liquid ring vacuum pumps 601 can be switched off again. In this way, the CVD apparatus can be operated more economically as if only one large liquid ring vacuum pump 601 were provided. Likewise, the demand for resources required to operate the pump, such as liquid solution (NaOH), power consumption, etc., can be reduced. Such pressure units 6 are typically associated with generating pressures as low as 5 kPa (50 mbar). Known CVD apparatuses have a single stage pressure unit 6 with one or two liquid ring vacuum pumps 601, as shown in FIGS. 1a and 1b.

[0034] According to the present disclosure, however, the pressure unit 6 includes a first pumping stage and a second pumping stage. Each pumping stage may comprise one or more pumps.

[0035] The second pumping stage 61 of the pressure unit 6 preferably comprises a dry screw vacuum pump. The second pumping stage 61 is preferably connected in series to the first pumping stage 60 as shown in FIG.

[0036] In the second pumping stage, the use of vacuum pumps often leads to the pumps being prone to overheating. This is because the pumps in the second pumping stage often need to be operated at high rotational speeds when using nitrogen (N2) and / or argon (Ar) as carrier gases or when using high gas flows of hydrogen (H2). Due to the relatively small gaps between the rotating parts, e.g. the screws, dry root vacuum pumps generate a lot of heat during operation, which results in relatively quick overheating of the dry root vacuum pump. If the pump overheats, the CVD process must be paused to avoid damage to the pump.

[0037] In this respect, the use of a dry screw vacuum pump in the second pumping stage has proven to be advantageous. When used in the second pumping stage, the dry screw vacuum pump is less prone to overheating. Probably due to the relatively large gap between the rotating parts such as the screws, the dry screw vacuum pump generates less heat during operation. This minimizes the risk that the CVD process must be stopped to prevent damage to the pump, thus increasing productivity. This effect can be significantly increased by providing a liquid cooling system for the dry screw vacuum pump, since the generated heat can be dissipated more effectively.

[0038] As can be seen from the graph of the preferred embodiment in FIG. 4, when using the dry screw vacuum pump 611 in the second pumping stage 61 and using hydrogen (H2) as the carrier gas, it is difficult to operate the CVD process at a carrier gas flow rate below 30 normal liters per minute (Nl / m). This is due to the larger gap between the rotating screws, for example, compared to the dry root vacuum pump 610. But at the same time, surprisingly, the use of the dry screw vacuum pump 611 in the second pumping stage 61 of the pressure unit 6 leads to various advantageous effects. For example, in contrast to the use of the dry root vacuum pump 610 in the second pumping stage 61, the use of the dry screw vacuum pump 611 benefits from the higher compression coefficient of the dry screw vacuum pump 611, which improves the delivery capacity of the pressure unit 6. Thus, the slightly lower performance of providing a vacuum inside the chamber at very low gas flow rates compared to the exemplary configurations discussed below can be ignored, and the system is perfectly suitable for working at high gas flow rates and achieving large vacuums. This results in a lower residence time of the process gas chemicals in the reactor and an improved distribution of the process gas, as further outlined above. This allows the number of pumping stages in the pressure unit 6 to be reduced, or fewer pumps to be used in each stage, reducing costs. If a dry root vacuum pump 610 were used in the second pumping stage 61 instead of the dry screw vacuum pump 611, another dry root vacuum pump 610 connected in series forming the third pumping stage 62 would normally be required due to the lower compression factor of the dry root vacuum pump 610. Such an arrangement is shown in FIG. 2. Thus, the use of the dry screw vacuum pump 611 can simplify the design of the pressure unit 6. For example, in contrast to the dry root vacuum pump 610, the dry screw vacuum pump 611 has a larger clearance between the rotating parts, such as the screw. Thus, when used in a CVD apparatus, the dry screw vacuum pump 611 is less likely to become clogged or blocked by the by-products of the CVD process.This can improve the reliability of the CVD tool. Also, the larger gap compared to dry root pumps can improve the process of cleaning the pump, for example with water, after the CVD process is finished. The pump can be cleaned more easily and thoroughly.

[0039] The normal liter (Nl), sometimes referred to as the standard liter, is a commonly used unit of volume used to compare amounts of gas present at different pressures and temperatures. As used in this description, the normal liter refers to the volume of gas at standard conditions, i.e., a standard pressure of 101,325 Pa and a standard temperature of 0 °C.

[0040] In a preferred embodiment, the pressure unit 6 comprises a first pumping stage 60 and a second pumping stage 61, the first pumping stage 60 having one liquid ring vacuum pump 601 and the second pumping stage 61 having one dry screw vacuum pump 611. The liquid ring vacuum pump 601 of the first pumping stage 60 has a flow rate of about 250 to 650 m. 3 / h (cubic meters per hour), while the dry screw vacuum pump 611 of the second pumping stage 61 may have a relatively low specified delivery capacity of approximately 8000 m / h.

[0041] An exemplary pressure unit 6, in which a dry root vacuum pump 610 is used instead of a dry screw vacuum pump 611, includes a first pumping stage 60, a second pumping stage 61 and a third pumping stage 62, the pumping stages being connected in series. The first pumping stage 60 has two liquid ring vacuum pumps 601 connected in parallel, the second pumping stage 61 has one dry root vacuum pump 610 and the third pumping stage has a second dry root vacuum pump 610. Such a configuration is shown in FIG. 2. Since the first pumping stage 60 has two liquid ring vacuum pumps 601, the first pumping stage 60 has a flow rate of about 250 to 650 m. 3The second pumping stage 61 with one dry route vacuum pump may have a specific delivery capacity of about 1000-2000 m 3 The third pumping stage 62 with one dry route vacuum pump may have a specific delivery capacity of about 2000 to 6000 m3 / h. 3 / h. Delivery capacity refers to the delivery capacity specified by the pump manufacturer.

[0042] Besides the above mentioned advantageous effects, also from the performance point of view, the pressure unit 6 of the preferred embodiment, which is equipped with only two pumping stages and uses a dry screw vacuum pump 611, has proven to be more advantageous than the representative configuration with two dry root pumps 610 described above. As is evident from the graph of FIG. 4, while maintaining the same pressure inside the chamber 10 of the reactor 1, the pressure unit 6 of the preferred embodiment delivers a higher flow rate of hydrogen (H2) (at standard conditions in normal liters per minute (Nl / min)) than the pressure unit 6 of the representative configuration described above, at a pressure as low as about 0.14 kPa (1.4 mbar). In other words, when delivering the same mass flow rate of hydrogen of 30 Nl / min or more, the pressure unit 6 of the preferred embodiment can create a larger vacuum in the chamber 10 of the reactor 1 than the pressure unit 6 of the representative configuration. It should be noted that the peripheral area of ​​the graph of FIG. 4 represents the extremes of the measurements and is not necessarily the performance limit of the pressure unit.

[0043] The pressure generated by the pressure unit 6 can be controlled by a pressure regulating unit. To control the generated pressure, the pressure regulating unit can vary the rotation speed of the pump of the respective pumping stage. For such control, each pump can be operated with a frequency converter. Control of the rotation speed of the dry screw vacuum pump 611, for example via frequency control, allows a particularly precise control of the generated pressure. Furthermore, the pressure inside the chamber 10 can be controlled by controlling the opening of at least one valve provided at the connection point to the chamber 10. The connection point to the chamber 10 is preferably the gas outlet of the chamber 10.

[0044] While various exemplary embodiments of the apparatus, methods, and / or uses according to the present disclosure have been described above, it should be understood that they have been presented by way of example and not by way of limitation. It will be apparent to those skilled in the art that various changes in form and detail can be made therein. Thus, the present disclosure should not be limited by any of the exemplary embodiments described above, but should be defined only in accordance with the following claims and their equivalents.

[0045] Moreover, it should be understood that certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in a particular combination, and even initially claimed as such, in some cases one or more features from a claimed combination may be excluded from the combination, and the claimed combination may be directed to a subcombination or a variation of the subcombination.

Claims

1. 1. A chemical vapor deposition apparatus for providing a surface of a substrate with a layer, comprising: The chemical vapor deposition apparatus includes: A reactor (1) having a chamber (10) for housing at least one substrate; a pressure unit (6) configured to generate a first predetermined pressure in an inner portion of the chamber (10), The pressure unit (6) a first pumping stage (60) having at least one liquid ring vacuum pump (601); a second pumping stage (61) having at least one dry screw vacuum pump (611).

2. 2. The chemical vapor deposition apparatus of claim 1, wherein the first pumping stage (60) and the second pumping stage (61) are connected in series.

3. 3. The chemical vapor deposition apparatus according to claim 2, characterized in that the suction side of the second pumping stage (61) is connected to the chamber (10) of the reactor (1) and the discharge side of the second pumping stage (61) is connected to the suction side of the first pumping stage (60).

4. 4. The chemical vapor deposition apparatus according to claim 1, wherein the first pumping stage (60) comprises a first liquid ring vacuum pump (601) and a second liquid ring vacuum pump (601) connected in parallel.

5. a pressure regulation unit configured to control the first predetermined pressure generated by the pressure unit (6), 5. The chemical vapor deposition apparatus according to claim 1, wherein the first predetermined pressure is adjustable in a full range covering 0.1 kPa (1 mbar) to 90 kPa (900 mbar).

6. 6. The chemical vapor deposition apparatus of claim 5, wherein the pressure regulating unit is configured to control the first predetermined pressure by at least varying a rotation speed of the dry screw vacuum pump (611).

7. and further comprising at least one valve configured to reduce crossover of at least one connection to said chamber (10); 7. The chemical vapor deposition apparatus according to claim 5 or 6, wherein optionally the opening of said valve is controlled by said pressure regulating unit.

8. a second valve configured to reduce crossover of at least one connection to the chamber; the second valve having a size different from a size of the at least one valve and connected in parallel to the at least one valve; 8. The chemical vapor deposition apparatus according to claim 7, wherein the opening degree of the second valve and the opening degree of the at least one valve are controlled by the pressure regulating unit.

9. 9. The chemical vapor deposition apparatus of claim 1, wherein the at least one dry screw vacuum pump (611) comprises a liquid cooling system configured to transfer heat between a liquid and the at least one dry screw vacuum pump (611).

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