Vacuum exhaust system

Abstract

A vacuum exhaust system is provided that enables miniaturization of pumps and valves, reduces piping diameter, and provides highly efficient exhaust from high vacuum to high flow rate, leveraging the pump's exhaust characteristics. The process gas used in the vacuum chamber (5) passes through an adjusting valve (7) to a branch pipe (29). The flow path on the side indicated by A in the diagram of the branch pipe (29) is connected to the intake port of the second pump. On the other hand, a bypass valve (23) is provided on the flow path on the side indicated by B in the diagram of the branch pipe (29). Furthermore, the first pump is connected downstream of the exhaust port of the second pump and downstream of the bypass valve (23) via a branch pipe (27). In the low-to-medium vacuum region (for high-flow exhaust), the bypass valve (23) is opened. At this time, gas is exhausted using both flow path A and flow path B of the second pump. Then, when exhausting under lower-to-medium vacuum conditions, the bypass valve (23) is closed, and exhaust is performed using flow path A. This allows the piping of flow path B to be made thinner.

Description

Technical Field

[0001] This invention relates to vacuum exhaust systems, and more particularly to vacuum exhaust systems that enable miniaturization of pumps and valves and reduction of piping diameter, and that can efficiently exhaust from high vacuum to high flow rate ranges while leveraging the exhaust characteristics of the pump. Background Technology

[0002] With the development of electronics in recent years, the demand for semiconductors such as memory and integrated circuits has increased dramatically. These semiconductors are manufactured by doping impurities into a semiconductor substrate with very high purity to impart electrical properties, or by forming fine circuit patterns on the semiconductor substrate and stacking them up.

[0003] Furthermore, to avoid the influence of dust and other contaminants in the air, these operations need to be performed in a high-vacuum chamber. The exhaust from this vacuum chamber utilizes a vacuum exhaust system employing a pump device, typically consisting of a volumetric transfer vacuum pump or a momentum transfer vacuum pump.

[0004] Furthermore, in semiconductor manufacturing processes, there are numerous steps involving the application of various process gases to the semiconductor substrate. Vacuum exhaust systems are used not only to create a vacuum within the vacuum chamber but also to remove these process gases from the vacuum chamber (see, for example, Patent Document 1). Moreover, in equipment such as electron microscopes, vacuum exhaust systems are used to create a high-vacuum environment within the vacuum chamber of the electron microscope or similar device to prevent electron beam refraction caused by dust or other contaminants. Figure 3 The diagram shows the structure of this conventional vacuum exhaust system.

[0005] exist Figure 3 In this process, the process gas supplied from the gas cylinder 1 is regulated by a gas flow controller 3 and then introduced into the vacuum chamber 5. The process gas already used in the vacuum chamber 5 is then ejected from the vacuum chamber 5, passes through a regulating valve 7 to adjust the gas flow rate, and reaches the distribution pipe 9. The flow path on the side indicated by A in the diagram of the distribution pipe 9 is connected to the suction port (not shown) of the second pump via a flow path switching valve 11. On the other hand, a flow path switching valve 13 is provided on the side of the distribution pipe 9 indicated by B in the diagram.

[0006] Furthermore, a flow path switching valve 15 is provided at the exhaust port of the second pump (not shown), and the first pump is connected downstream of the flow path switching valve 15 and downstream of the flow path switching valve 13 via a branch pipe 17.

[0007] In this structure, the conditions for processes that require a high gas flow rate in the low-to-medium vacuum region and processes that require a lower pressure condition in the vacuum chamber 5 will be explained.

[0008] In this case, in processes with relatively high gas flow rates in the low-to-medium vacuum range, flow path switching valves 11 and 15 are closed, while flow path switching valve 13 is opened, and exhaust is performed via flow path B. On the other hand, in processes requiring lower pressure conditions in the medium-to-high vacuum range, flow path switching valve 13 is closed, while flow path switching valves 11 and 15 are switched to open, and exhaust is performed via flow path A.

[0009] Existing technical documents

[0010] Patent documents

[0011] Patent Document 1: Japanese Patent Application Publication No. 8-74737 Summary of the Invention

[0012] The problem that the invention aims to solve

[0013] However, in this vacuum exhaust system, in order to reduce the pressure in the vacuum chamber 5 during high-flow exhaust, the piping of flow path B and the diameter of the flow path switching valve 13 need to be increased. Therefore, it is possible that the vacuum exhaust system will be larger, making it more difficult to ensure the installation space or increasing the cost.

[0014] Furthermore, when the process gas flowing from vacuum chamber 5 is at a high flow rate, there are also cases like... Figure 4 As shown, in the case where the vacuum chamber 5 is directly connected to the bypass pipe 21, as mentioned above, the vacuum exhaust system may become larger, making it more difficult to ensure installation space or increasing costs. Additionally, in Figure 4 In China, for the sake of Figure 3 The same elements are given the same reference numerals and the descriptions are omitted (the same applies below).

[0015] Furthermore, in Figure 5 The example shown is an instance where the second pump is connected in series with the first pump, provided that the second pump can also operate in the medium vacuum region.

[0016] However, in this situation, the exhaust efficiency of the second pump may decrease in the medium vacuum region, leading to a decline in the system's exhaust performance. Figure 6 The value in the figure represents the condition where the exhaust characteristics of the second pump decrease in the intermediate vacuum region. That is, it is known that the effective exhaust velocity of the second pump gradually decreases as the pressure increases in the intermediate vacuum region with a pressure higher than 0.1 [Pa].

[0017] To compensate for this, the second pump needs to be enlarged, or the piping and valve sizes need to be increased, and the vacuum exhaust system needs to be enlarged. Therefore, as mentioned above, ensuring the installation space may become more difficult or the cost may increase.

[0018] The present invention was made in view of such prior problems, and the object is to provide a vacuum exhaust system that enables miniaturization of pumps and valves and reduction of piping diameter, and enables highly efficient exhaust of pump exhaust characteristics from high vacuum to large flow range.

[0019] Methods used to solve problems

[0020] Therefore, the present invention (technical solution 1) is a vacuum exhaust system comprising: a first pump for vacuum exhaust from atmospheric pressure in a vacuum region; a second pump connected in series with the first pump and reaching a pressure lower than that of the first pump; and a bypass valve configured in parallel with the second pump via a pipe communicating with the intake and exhaust ports of the second pump; characterized in that exhaust gas from the vacuum chamber is discharged via both the flow path of the second pump and the flow path of the bypass valve.

[0021] In addition to the suction from the first pump, exhaust gas from the vacuum chamber is also discharged through the flow path of the second pump and the flow path of the bypass valve. Therefore, compared to the case where suction is performed by switching the flow path of the second pump and the flow path of the bypass valve, or by connecting the first and second pumps in series, this vacuum exhaust system allows for vacuum exhaust that utilizes the exhaust characteristics of both the second and first pumps without increasing the size of the second pump. The bypass valve and piping diameter can also be made smaller.

[0022] Furthermore, the present invention (technical solution 2) is characterized in that, in the low and medium vacuum region, the aforementioned first pump and the aforementioned second pump are operated and the aforementioned bypass valve is opened, and in the medium and high vacuum region, the aforementioned first pump and the aforementioned second pump are operated and the aforementioned bypass valve is closed.

[0023] This enables the miniaturization of the second pump, bypass valve, and piping diameter, and allows for highly efficient exhaust from high vacuum to high flow rate, leveraging the exhaust characteristics of both the first and second pumps.

[0024] Furthermore, the present invention (technical solution 3) comprises the following mechanisms: a flow meter measuring mechanism for measuring the flow rate of the aforementioned waste gas flowing in the aforementioned vacuum chamber; and an opening and closing control mechanism for opening or closing the aforementioned bypass valve based on the flow rate measured by the flow meter measuring mechanism.

[0025] Based on the flow rate measured by the flow meter, the bypass valve is opened or closed. This allows for efficient control by switching between a high flow rate of waste gas flowing in the vacuum chamber and a low flow rate (or zero flow rate) required for high vacuum in the vacuum chamber.

[0026] Furthermore, the present invention (technical solution 4) is characterized by having an opening control mechanism for controlling the opening degree of the aforementioned bypass valve; the opening degree is controlled by the opening control mechanism based on at least one of the flow rate of the aforementioned waste gas flowing in the aforementioned vacuum chamber and the pressure in the exhaust system.

[0027] By controlling the opening of the bypass valve, the pressure load acting on the pump can be reduced, thus ensuring stable pump operation. Furthermore, it prevents changes in process conditions due to exhaust pulsation, or positional shifts in the workpiece within the vacuum chamber caused by pressure fluctuations or vibrations.

[0028] Furthermore, the present invention (technical solution 5) is characterized in that the aforementioned first pump is a volumetric transfer vacuum pump with a high exhaust velocity in the medium vacuum region.

[0029] Furthermore, the present invention (technical solution 6) is characterized in that the aforementioned second pump is a momentum transfer type vacuum pump with a high exhaust velocity in the high vacuum region and an arrival pressure that reaches or is lower than the high vacuum.

[0030] Invention Effects

[0031] As explained above, according to the present invention, since the exhaust gas from the vacuum chamber is discharged via both the flow path of the second pump and the flow path of the bypass valve, in addition to the suction of the first pump, vacuum exhaust can be performed in this vacuum exhaust system while utilizing the exhaust characteristics of both the second pump and the first pump without increasing the size of the second pump. The bypass valve and piping diameter can also be made smaller. Attached Figure Description

[0032] Figure 1 This is a structural diagram of a vacuum exhaust system as an embodiment of the present invention.

[0033] Figure 2 yes Figure 1 The exhaust characteristics diagram of the vacuum exhaust system in the structure.

[0034] Figure 3 This is a structural diagram of a conventional vacuum exhaust system (Figure 1).

[0035] Figure 4 This is a structural diagram of a conventional vacuum exhaust system (Figure 2).

[0036] Figure 5 This is a structural diagram of a previous vacuum exhaust system (Figure 3).

[0037] Figure 6 This is a diagram showing the condition when the exhaust characteristics of the second pump decrease in the medium vacuum region. Detailed Implementation

[0038] The embodiments of the present invention will be described below. Figure 1 The diagram shows the structure of a vacuum exhaust system as an embodiment of the present invention.

[0039] exist Figure 1 In the process gas already used in the vacuum chamber 5, the gas reaches the branch pipe 29 via the regulating valve 7. The flow path on the side of the branch pipe 29 indicated by A in the diagram is connected to the suction port of the second pump (not shown). On the other hand, a bypass valve 23 is provided on the flow path on the side of the branch pipe 29 indicated by B in the diagram.

[0040] Furthermore, downstream of the exhaust port of the second pump (not shown) and downstream of the bypass valve 23, the first pump is connected via a branch pipe 27.

[0041] In this structure, a volumetric transfer vacuum pump, such as a Roots type, screw type, or claw type, is used as the first pump. A pump with characteristics suitable for large-volume gas discharge in the mid-vacuum range is preferred. Furthermore, to obtain even higher discharge velocities, multiple stages can be used. Because the first pump has a larger size, it can also be installed outside the cleanroom.

[0042] On the other hand, as a second pump, a momentum transfer type vacuum pump, such as a turbomolecular pump or a molecular pump (a drag pump, such as a grooved pump, Siegbahn pump, or Gaede pump), is used. Preferably, the pump is one that, as a second pump, has the characteristics of a high exhaust velocity in the high vacuum region and reaches a pressure equal to or lower than high vacuum. Momentum transfer type vacuum pumps, because they generally operate at high speeds to effectively impart momentum to gas molecules, are unsuitable for exhausting large volumes of gas in the intermediate vacuum region due to heat generation and the need for significant electrical power. Furthermore, according to the exhaust principle, the exhaust velocity decreases in the intermediate vacuum region.

[0043] In addition, the second pump is preferably located near the vacuum chamber 5 in order to obtain high vacuum performance.

[0044] Next, the operation of the embodiments of the present invention will be explained.

[0045] exist Figure 1In the low-to-medium vacuum region (during high-flow exhaust), the bypass valve 23 is opened. At this time, the gas is exhausted using both flow path A and flow path B, which pass through the second pump. Then, when exhausting under lower-to-medium vacuum conditions, the bypass valve 23 is closed, and exhaust is performed using flow path A.

[0046] exist Figure 2 The middle indicates that Figure 1 The exhaust characteristics diagram of the vacuum exhaust system in the structure. Figure 1 The flow path B is compared to Figures 3-5 The situation involves fine piping. Therefore, as in... Figure 2 As indicated by solid lines in the middle, and Figure 6 Compared to the hump characteristics of the first pump, the hump height of the exhaust characteristics of flow path B is lower. However, since gas is discharged using both flow path A and flow path B, the confluence point of flow path A and flow path B... Figure 1 The exhaust velocity at point C is approximately the sum of the exhaust velocities of flow path A and flow path B. Therefore, the exhaust characteristics of the low-to-medium vacuum region at point C, as shown in... Figure 2 The mountain shape represented by dots and lines becomes a symbol with... Figures 3-4 The structure is the same as the shape of the exhaust flow in the flow path switching valve 13, which has the same height.

[0047] Because gas is discharged using both flow path A and flow path B, the system's exhaust characteristics will affect the performance of the gas in the low and medium vacuum regions. Figure 2 The exhaust characteristics, represented by the dotted line, exhibit a mountain-shaped pattern. The effective exhaust velocity decreases in the low-to-medium vacuum region on the A side of the flow path, while becoming flat in the high vacuum region. Figure 2 It is synthesized in the same way as the continuous transition part represented by "a" in Chinese.

[0048] Then, because in Figure 2 The position of "b" in the diagram transitions from operation in the low-to-medium vacuum region to operation in the medium-to-high vacuum region, so the bypass valve 23 is switched from open to closed. As a result, the bypass valve 23 connected to the intake and exhaust ports of the second pump is shut off, allowing the second pump to achieve its high-vacuum compression performance.

[0049] If the arrival pressure of the first vacuum pump in the high vacuum region does not reach a high vacuum, and the bypass valve 23 is opened, backflow will occur through flow path B. Therefore, the bypass valve 23 is preferably closed. Then, with the help of the second pump, a high vacuum state is achieved through a certain effective exhaust rate.

[0050] Alternatively, it is preferable to link the bypass valve 23 with the gas flow controller 3, so that the bypass valve 23 opens when the flow rate is high and closes when the flow rate required for high vacuum is low (or the gas flow rate is zero). The control of opening or closing the bypass valve 23 is equivalent to an on / off control mechanism.

[0051] Through the above, in this vacuum exhaust system, it is possible to perform vacuum exhaust that utilizes the exhaust characteristics of both the second pump and the first pump without increasing the size of the second pump.

[0052] Furthermore, while the bypass valve 23 has been described as a valve that only performs opening and closing, it can also be made into a valve capable of opening degree control, adjusting the opening degree according to the gas flow rate and the pressure within the exhaust system to smoothly switch between functions. Controlling the opening degree of this bypass valve 23 is equivalent to an opening degree control mechanism. Here, the flow rate is extracted, for example, from the gas flow controller 3, and the pressure is extracted from the vacuum chamber 5.

[0053] This structure can reduce the pressure load on the pump and make the pump operate stably, and can prevent changes in process conditions due to exhaust pulsation, or positional displacement of the workpiece in the vacuum chamber 5 due to pressure changes or vibration.

[0054] Through the above, the second pump, the bypass valve 23, and the piping diameter can be miniaturized, and high-efficiency exhaust can be achieved from high vacuum to large flow range, giving full play to the exhaust characteristics of the first and second pumps.

[0055] Furthermore, in this vacuum exhaust system, the first pump performs vacuum exhaust first, and the second pump starts after the internal pressure becomes suitable for operation. Although not shown in the figure, a maintenance valve can be installed at the intake and exhaust ports of the second pump. Additionally, although not shown in the figure, an exhaust path and valve can be provided to roughly draw air from the atmosphere into the vacuum chamber 5 to a predetermined pressure.

[0056] Furthermore, the present invention can be modified in various ways without departing from its spirit, and the above-described embodiments and variations can be combined in various ways.

[0057] Explanation of reference numerals in the attached figures

[0058] 1. Air pump

[0059] 3. Gas Flow Controller

[0060] 5 Vacuum Chamber

[0061] 7 Adjusting valve

[0062] 9, 17, 27, 29 are sub-controls

[0063] 11, 13, 15 Flow path switching valves

[0064] 23 Bypass valve

Claims

1. A vacuum exhaust system, comprising: The first pump is used for vacuum exhaust in the intermediate vacuum region from atmospheric pressure. It consists of a volumetric transfer vacuum pump with high exhaust velocity and high gas flow rate in the intermediate vacuum region. The second pump, connected in series with the first pump, reaches a lower pressure than the first pump; it is a momentum transfer type vacuum pump with a high exhaust velocity in the high vacuum region and a reaching pressure equal to or lower than high vacuum. A bypass valve is provided in parallel with the aforementioned second pump via a piping that connects to the suction port and exhaust port of the second pump. Its features are, When the aforementioned bypass valve transitions from operation in the low-to-medium vacuum region (from atmospheric pressure to the aforementioned medium vacuum range) to operation in the medium-to-high vacuum region (where pressure is even lower), it switches from open to closed. During the operation of the first pump, exhaust gas from the vacuum chamber is discharged through both the flow path of the second pump and the flow path of the bypass valve, so that the effective exhaust speed does not decrease in the medium vacuum region and the low vacuum region compared with the operation of only the first pump and the second pump.

2. The vacuum exhaust system as described in claim 1, characterized in that, In the low-to-medium vacuum region, the aforementioned first pump and the aforementioned second pump are operated and the aforementioned bypass valve is opened. In the medium-to-high vacuum region, the aforementioned first pump and the aforementioned second pump are operated and the aforementioned bypass valve is closed.

3. The vacuum exhaust system as described in claim 1 or 2, characterized in that, have: A flow meter measuring mechanism measures the flow rate of the aforementioned waste gas flowing in the aforementioned vacuum chamber; and The opening and closing control mechanism opens or closes the aforementioned bypass valve based on the flow rate measured by the flow meter.

4. The vacuum exhaust system as described in claim 1 or 2, characterized in that, It has an opening control mechanism for controlling the opening degree of the aforementioned bypass valve; The opening degree is controlled by the opening control mechanism based on at least one of the flow rate of the aforementioned exhaust gas flowing in the aforementioned vacuum chamber and the pressure in the exhaust system.

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