Chemical vapor deposition apparatus

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 having layers.

Background Art

[0002] The term "chemical vapor deposition" (hereinafter CVD) relates to providing a layer, particularly a thin layer, on the surface of another material (substrate), such as a workpiece for metal processing (e.g., cutting plate, saw blade, etc.). CVD methods and apparatuses typically rely on chemical reactions of chemical compounds contained in process gases, and the desired main product of the chemical reaction is deposited on the surface of the substrate so as to form a coating or overlay. Known CVD apparatuses are described, for example, in EP2304075A1.

[0003] Known CVD apparatuses are generally adjusted for specific applications, such as a specific combination of substrate / coating. Different applications sequentially utilize different process parameters. However, a CVD apparatus adapted for a first application may not be suitable for a second application. Therefore, it is necessary to promote the flexibility of CVD apparatuses.

[0004] Furthermore, it has been observed that the process gas flow pattern in known CVD apparatuses may be spatially non-uniformly distributed. Such non-uniform distribution can in turn lead to a situation where the first part of the substrate to be coated has a higher amount and / or concentration of process gas than the second part 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 having varying thicknesses and / or coatings having non-uniform physical and mechanical properties.

[0005] Similar considerations apply to the pressure curve of the process gas, particularly the pressure curve of the process gas as seen over time. That is, it has been observed that changes in the pressure curve of the process gas can have a negative impact on the quality of the coating.

[0006] Similarly, changes in the pressure curve may occur along with the slow rise of the coating. The aforementioned drawbacks, therefore, can not only impair the quality of the coating but also be compounded by high costs. [Overview of the Initiative]

[0007] The purpose of this disclosure is to overcome at least one of the above-mentioned shortcomings in a simple but effective manner.

[0008] The chemical vapor deposition apparatus according to this disclosure is defined in claim 1. Dependent claims relate to embodiments.

[0009] The chemical vapor deposition apparatus according to the present disclosure is an apparatus for providing a layered surface on a substrate. The apparatus comprises a reactor having a chamber for housing at least one substrate and a pressure unit configured to generate a first predetermined pressure in the inner 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 described above may offer technical benefits such as increased flexibility and an increased pressure operating range of the reactor chamber down to 0.1 kPa (1 mbar). Specifically, since 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, the pressure unit can operate over a wide pressure range with the liquid ring vacuum pump of the first pumping stage having a low discharge capacity and the dry screw vacuum pump of the second pumping stage having a high discharge capacity. The combination of the liquid ring vacuum pump and the dry screw vacuum pump significantly improves the ability to reliably and precisely adjust the pressure within the reactor chamber, leading to improved coating quality. Furthermore, this CVD apparatus may offer technical benefits such as increased reliability and robustness. The dry screw vacuum pump, like other pressure units in the CVD apparatus, draws in exhaust gas from the reactor. In other words, the dry screw vacuum pump is connected to the reactor outlet and draws in used gas from the CVD process. Compared to other pump types used in CVD equipment, such as dry-route vacuum pumps, dry-screw vacuum pumps have a larger gap between the screws. This makes them less likely to clog with by-products in the exhaust gas during the CVD process, and therefore less prone to malfunction. The relatively large gap in dry-screw vacuum pumps greatly improves the cleaning process, which is typically performed using water or a water-based solution after the CVD process is complete. In this way, CVD process residues accumulated inside the pump can be removed more efficiently and thoroughly, resulting in improved pump life and reduced costs.

[0011] Preferably, the CVD apparatus described above may be configured to provide a layered substrate surface without using plasma. Such plasma would be used for the dissociation of process gas molecules. Instead of using plasma for dissociation, the reactor can be heated to a high temperature of 1200°C, and thermal energy can be used for the dissociation of process gas molecules. Not using plasma has the advantage of eliminating the equipment for generating plasma, reducing costs, and allowing the pressure range required for such a CVD apparatus that uses thermal energy as reaction activation energy to 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 described above may be related to technical effects that improve performance. The series connection of the first and second pumping stages increases the achievable vacuum level.

[0014] In some embodiments, the suction side of the second pumping stage is connected to the chamber of the reactor, and the discharge side of the second pumping stage is connected to the suction side of the first pumping stage.

[0015] This configuration allows the dry screw vacuum pump in the second pumping stage to have a higher delivery capacity than the liquid ring vacuum pump in the first pumping stage, thereby further increasing the vacuum generated within the reactor chamber. In this way, both the amount of process gas flowing through the reactor chamber and the vacuum can be increased simultaneously. This results in lower residence times for chemicals in the process gas within the reactor and an improved distribution of the process gas. This further enhances the performance of the CVD apparatus. Furthermore, this configuration reduces pressure fluctuations within the chamber, thereby reducing variations in the quality of the substrate coating.

[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] In a first pumping stage where two liquid ring vacuum pumps are connected in parallel, the dimensions of the type of liquid ring vacuum pump used in the first pumping stage can be reduced. This is because the discharge capacities of the first and second liquid ring vacuum pumps connected in parallel are added together. Therefore, a smaller pump can be used with less power, the cost of the first pumping stage can be reduced, and the installation space of the CVD equipment can be used more flexibly.

[0018] According to some embodiments, the apparatus further includes a pressure regulating unit configured to control a first predetermined pressure generated by a pressure unit. The first predetermined pressure is adjustable over the entire range covering 0.1 kPa (1 mbar) to 90 kPa (900 mbar).

[0019] The CVD apparatus described above may offer technical benefits such as improved flexibility and reliability of coating quality. Using a pressure unit configured to generate an adjustable pressure over the entire range covering 0.1 kPa (1 mbar) to 90 kPa (900 mbar) within the inner chamber, and a pressure regulating unit configured to control this pressure, the CVD apparatus may be used, for example, for coating processes dependent on pressures between 0.1 kPa (1 mbar) and 40 kPa (400 mbar), and for coating processes dependent on pressures between 40 kPa (400 mbar) and 90 kPa (900 mbar). The extension of the generated vacuum and the lack of variation have a significant positive impact on coating quality.

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

[0021] As outlined in the descriptive portion of this application, changes in the process gas pressure curve can adversely affect the quality of the coating. Furthermore, changes in the pressure curve may progress with slower coating accumulation. The vacuum generated by a dry screw vacuum pump depends on its rotational speed. A pressure regulating unit configured to change the rotational speed of the dry screw vacuum pump allows for fine-step adjustment of the pressure generated in the reactor chamber, maintaining relatively small changes.

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

[0023] In a CVD apparatus, it has been found that utilizing 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 for an extended operating pressure range down to 0.1 kPa (1 mbar), along with a fairly stable pressure curve (i.e., a pressure curve with rather low amplitude changes). However, especially at low pressures of around 0.1 kPa, the vacuum generated in the reactor chamber can still be subject to certain pressure fluctuations. The CVD apparatus described above allows for precise control of the pressure in the chamber by at least one valve, preferably a throttling valve, configured to reduce the crossing of one connection from the dry screw vacuum pump to the chamber, preferably the chamber outlet. Furthermore, pressure changes in the reactor chamber can be further reduced or eliminated entirely. In addition, the pressure in the chamber can be controlled even more precisely by controlling both the rotational speed of at least one valve and at least one pump. These means allow for precise adjustment of the coating quality, i.e., the homogeneity and thickness of the coating.

[0024] According to some aspects, the chemical vapor deposition apparatus further includes a second valve configured to reduce the intersection of at least one connection to the chamber. The second valve has a size different from that of at least one valve and is connected in parallel to at least one valve. The opening degree of the second valve and the opening degree of at least one valve are simultaneously controlled by a pressure adjustment unit.

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

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

[0027] Compared with the CVD apparatus known from the prior art, in this configuration where a dry screw vacuum pump is used in combination with a liquid cooling device, the CVD process can be maintained substantially longer without overheating of the dry screw vacuum pump. In particular, when nitrogen (N2) and / or argon (Ar) are used as carrier gases, or when a high gas flow rate of hydrogen (H2) is used, the pump in the second pumping stage often needs to be operated at a high rotational speed, so the pump in the second pumping stage is heated. When the pump is operated for a certain period of time under such conditions, if the heat inside the pump cannot be sufficiently dissipated, the pump tends to overheat. This effect occurs particularly in dry root vacuum pumps. According to the present invention, when combining a dry screw vacuum pump with a relatively large gap between the screw and the liquid cooling system, this negative influence can be efficiently avoided.

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

Brief Description of the Drawings

[0029] [Figure 1a] FIG. 1a is a schematic view showing a pressure unit 6 including a single-stage pump system including a single liquid ring vacuum pump 601 and connected to a reactor 1. [Figure 1b] FIG. 1b is a schematic view showing a pressure unit 6 including a single-stage pump system having two liquid ring vacuum pumps 601 connected in parallel and connected to a reactor 1. [Figure 2] FIG. 2 is a schematic view showing a pressure unit 6 having a first pumping stage 60, a second pumping stage 61, and a third pumping stage 62. The first pumping stage includes two liquid ring vacuum pumps 601 connected in parallel. The second pumping stage 61 includes a dry root vacuum pump 612. The third pumping stage 62 includes a second dry root vacuum pump. 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 the reactor 1. [Figure 3] FIG. 3 is a schematic view showing a pressure unit 6 having a first pumping stage 60 and a second pumping stage 61. The first pumping stage includes two liquid ring vacuum pumps 601 connected in parallel. The second pumping stage 61 includes one dry screw vacuum pump 611. The first and second pumping stages are connected in series, and the pressure unit 6 is connected to the reactor 1. [Figure 4]Figure 4 is a chart showing the pressure in the reactor chamber generated by a typical pressure unit configuration in mbar, and a preferred embodiment is shown with the hydrogen mass flow rate (H2) as a function of normal liters per minute (Nl / min). [Modes for carrying out the invention]

[0030] Embodiments of the apparatus, use, and method described herein are described below in detail, merely as limited examples, with reference to the accompanying drawings. Unless otherwise indicated, elements that are identical, corresponding, or functionally similar are indicated, such as reference numerals appearing in different drawings.

[0031] The pressure unit 6 is configured to generate a first predetermined pressure in the inner portion of the chamber 10, and this first predetermined pressure is adjustable over the entire range covering 0.1 kPa (1 mbar) to 90 kPa (900 mbar).

[0032] As schematically shown in Figure 3, the pressure unit 6 is equipped with a liquid ring vacuum pump 601. The use of a liquid ring vacuum pump is related to the technical effect that a liquid is used to generate a vacuum. When a solution of NaOH is used in such a pump, the exhaust gases can each be neutralized within the pump. This also extends the life of the pump and reduces corrosion as the acidic exhaust gases are at least partially neutralized. In addition, the liquid in the liquid ring vacuum pump 601 washes away any residue of acidic exhaust gases inside the pump.

[0033] As shown in Figure 3, providing two liquid ring vacuum pumps 601 connected in parallel is related to the technical effect of increasing the efficiency of the CVD apparatus. When 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 made smaller in size. When the process requires a lower gas flow and / or a vacuum less than that, 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. Similarly, the demand for resources required to operate the pumps, such as liquid solution (NaOH) and power consumption, can be reduced. Such a pressure unit 6 is typically associated with generating low pressures of about 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 Figures 1a and 1b.

[0034] According to this 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 is preferably equipped with a dry screw vacuum pump. The second pumping stage 61 is preferably connected in series with the first pumping stage 60, as shown in Figure 3.

[0036] In the second pumping stage, when using a vacuum pump, the pump often tends to overheat. This is because, when using nitrogen (N2) and / or argon (Ar) as the carrier gas, or when using high gas flow rates of hydrogen (H2), the pump in the second pumping stage often needs to be operated at high rotational speeds. Due to the relatively small gap between rotating parts, such as the screw, dry-root vacuum pumps generate a large amount of heat during operation, resulting in relatively rapid 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 regard, it has been found that using a dry screw vacuum pump in the second pumping stage is advantageous. When used in the second pumping stage, the dry screw vacuum pump is less prone to overheating. This is likely because the gap between the rotating parts, such as the screw, is relatively large, resulting in less heat generation during operation. This minimizes the risk of having to stop the CVD process to prevent pump damage, and thus increases productivity. This effect can be significantly enhanced by providing a liquid cooling system for the dry screw vacuum pump, as the generated heat can be dissipated more effectively.

[0038] As can be seen from the graph of the preferred embodiment in Figure 4, when using a 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 of less than 30 normal liters per minute (Nl / m). This is due to the larger gap between the rotating screws compared, for example, with a dry root vacuum pump 610. However, surprisingly, at the same time, using a 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 a dry root vacuum pump 610 in the second pumping stage 61, the use of a dry screw vacuum pump 611 benefits from the higher compressibility coefficient of the dry screw vacuum pump 611, which improves the delivery capacity of the pressure unit 6. Thus, the slightly lower performance in providing a vacuum inside the chamber at very low gas flow rates compared to the exemplary configuration discussed below can be ignored, and this system is perfectly suited for working at high gas flow rates and achieving large vacuums. This results in lower residence times for chemicals in the process gas within the reactor and an improved distribution of the process gas, as further outlined above. This allows for a reduction in the number of pumping stages in the pressure unit 6 and a reduction in the number of pumps used in each stage, thereby reducing costs. If a dry-root vacuum pump 610 is used in the second pumping stage 61 instead of a dry-screw vacuum pump 611, another dry-root vacuum pump 610 connected in series to form a third pumping stage 62 would typically be required due to the lower compressibility of the dry-root vacuum pump 610. Such a configuration is shown in Figure 2. Thus, the design of the pressure unit 6 can be simplified by using a dry-screw vacuum pump 611. For example, in contrast to a dry-root vacuum pump 610, a dry-screw vacuum pump 611 has larger gaps between rotating parts, such as a screw. Therefore, when used in a CVD apparatus, a dry-screw vacuum pump 611 is less likely to clog or block with by-products of the CVD process.This improves the reliability of the CVD equipment. Furthermore, because the gap is larger compared to dry-root pumps, the process of cleaning the pump after the CVD process, for example with water, can be improved. The pump can be cleaned more easily and thoroughly.

[0039] The normal liter (Nl), sometimes also referred to as the standard liter, is a commonly used unit of volume used to compare the amount of gas present at different pressures and temperatures. In this explanation, the normal liter refers to the volume of gas under standard conditions, i.e., at a standard pressure of 101325 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 capacity of approximately 250-650 m 3 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 (cubic meters / hour), although it may have a relatively 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 the second dry-root vacuum pump 610. Such a configuration is shown in Figure 2. Since the first pumping stage 60 has two liquid-ring vacuum pumps 601, the first pumping stage 60 has a pressure of approximately 250-650 m 3It may have a specific discharge capacity of / h. The second pumping stage 61, which has one dry-route vacuum pump, has a discharge capacity of approximately 1000-2000m 3 It may have a specific discharge capacity of / h. The third pumping stage 62, which has one dry-route vacuum pump, has a discharge capacity of approximately 2000-6000m 3 It may have a specific discharge capacity of / h. Discharge capacity refers to the discharge capacity specified by the pump manufacturer.

[0042] In addition to the advantageous effects described above, from a performance standpoint, the preferred embodiment of the pressure unit 6, which simply has two pumping stages and uses a dry screw vacuum pump 611, has proven to be more advantageous than the typical configuration with the two dry root pumps 610 described above. As is clear from the graph in Figure 4, while maintaining the same pressure inside the chamber 10 of reactor 1, the preferred embodiment of the pressure unit 6 delivers hydrogen (H2) at a higher flow rate (normal liters per minute (Nl / min) under standard conditions) than the typical configuration of the pressure unit 6, at a lower pressure of about 0.14 kPa (1.4 mbar). In other words, when delivering hydrogen at the same mass flow rate of 30 Nl / min or more, the preferred embodiment of the pressure unit 6 can create a larger vacuum inside the chamber 10 of reactor 1 than the typical configuration of the pressure unit 6. Note that the peripheral region of the graph in Figure 4 represents the edge of measurement and does not necessarily represent the performance limit of the pressure unit.

[0043] The pressure generated by the pressure unit 6 can be controlled by the pressure regulating unit. To control the generated pressure, the pressure regulating unit can change the rotational speed of the pumps in each pumping stage. For such control, each pump can be actuated by a frequency converter. Controlling the rotational speed of the dry screw vacuum pump 611, for example via frequency control, allows for 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 located 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 described herein have been set forth above, it should be understood that they are presented as examples only and not as limitations. It will be apparent to those skilled in the art that various forms and details can be modified therein. Therefore, this disclosure should not be limited by any of the exemplary embodiments described above, but should be defined only by the following claims and their equivalents.

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

Claims

1. A chemical vapor deposition apparatus for providing a substrate surface having layers, The aforementioned chemical vapor deposition apparatus is A reactor (1) having a chamber (10) that accommodates at least one substrate, The chamber (10) is provided with a pressure unit (6) configured to generate a first predetermined pressure, located in the 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) is provided, The aforementioned chemical vapor deposition apparatus is A pressure adjustment unit configured to control the first predetermined pressure generated by the pressure unit (6), The system further comprises a first valve and a second valve, each configured to reduce the crossing of at least one connection to the chamber (10), The second valve has a different size from the first valve and is connected in parallel to the first valve. The pressure adjustment unit is configured to control the rotational speed of at least one of the liquid ring vacuum pump (601) and the dry screw vacuum pump (611), and to control the opening degree of the second valve and the opening degree of the first valve. The first predetermined pressure is adjustable over the entire range covering 0.1 kPa (1 mbar) to 90 kPa (900 mbar). A chemical vapor deposition apparatus characterized by the following features.

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

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. The chemical vapor deposition apparatus according to any one of claims 1 to 3, characterized in that the first pumping stage (60) has a first liquid ring vacuum pump (601) and a second liquid ring vacuum pump (601) connected in parallel.

5. The chemical vapor deposition apparatus according to any one of claims 1 to 4, characterized in that the pressure adjustment unit is configured to control the first predetermined pressure by at least changing the rotational speed of the dry screw vacuum pump (611).

6. The chemical vapor deposition apparatus according to any one of claims 1 to 5, characterized in that the at least one dry screw vacuum pump (611) has a liquid cooling system configured to transfer heat between the liquid and the at least one dry screw vacuum pump (611).

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