Cleaning method for vacuum exhaust systems and vacuum pumps

Abstract

To provide an evacuation system that can easily bring about a return from a shutdown condition in which restarting is disabled because a deposition portion blocks a gas passage of a vacuum pump after a dry pump is shut down, the vacuum pump, and a cleaning method for the vacuum pump.SOLUTION: An evacuation system includes: a vacuum pump for discharging a process gas including a condensable gas or oxide dust; a first inert gas introduction unit that expands a gas passage so that the vacuum pump can be restarted, by introducing a high-temperature inert gas for increasing a temperature to a temperature approximately equal to a temperature during normal operation of the vacuum pump, into the gas passage of the vacuum pump put into a shutdown condition due to accumulation of deposited material of the process gas; and a cleaning material introduction unit that removes the deposited material by introducing a cleaning material into the gas passage.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a vacuum exhaust system, a vacuum pump, and a cleaning method for a vacuum pump.

Background Art

[0002] For example, in a semiconductor manufacturing process, CVD (Chemical Vapor Deposition) or dry etching processes are performed to deposit semiconductors, insulators, metal films, etc. on a semiconductor wafer and form a film using a chemical vapor reaction. In a process chamber, various gases such as silane (SiH4) gas are used. The used gas discharged from the process chamber is sucked by a dry pump or the like and further introduced into a detoxification device through a gas exhaust pipe, and the detoxification treatment is performed in the detoxification device (see, for example, Patent Document 1).

[0003] The dry pump known from Patent Document 1 will be described using the reference numerals used in Patent Document 1. It has a pump casing 23 having a plurality of pump chambers 22a, 22b, 22c, 22d, 22e, 22f, rotors 24a, 24b, 24c, 24d, 24e, 24f respectively disposed in the pump chambers 22a to 22f, a pair of rotating shafts 25a, 25b to which these rotors 24a to 24f are integrally fixed and which rotate these rotors 24a to 24f integrally, a pair of gears 26a, 26b for synchronously rotating this pair of rotating shafts 25a, 25b, a motor 27 as a rotation drive mechanism for rotating the rotating shafts 25a, 25b via this pair of gears 26a, 26b, and bearings 28a, 28a, 28b, 28b for pivotally supporting the rotating shafts 25a, 25b on the pump casing 23, respectively.

[0004] In such a dry pump, the gas remaining inside the dry pump solidifies as a film or powder and becomes a deposit (mainly SiO2: silica), and this deposit adheres to the inside of the dry pump in a short period (2 to 3 months), causing an operation failure.

[0005] Furthermore, if the dry pump is temporarily stopped for maintenance or other reasons, the rotors 24a to 24f may lock up, making restart impossible. This is related to the fact that during operation, the pump chambers 22a to 22f become hot, causing them to expand, and the rotating shaft is displaced in the thrust direction. Anticipating these factors, the design ensures that when the pump is stopped, the gap between the sides of the rotor and the inner surfaces of both sides of the pump chamber widens on one side (left) and narrows on the other side (right). The gap on one side when stopped is designed to be approximately several tens to several hundreds of micrometers. Therefore, when the dry pump is stopped, the thrust displacement by the rotating shaft ceases, and the pump, which was in a hot state, cools down. This narrows the gap between the sides of the rotor and the inner surfaces of both sides of the pump chamber, causing accumulated deposits to clog and solidify, preventing the restart of rotors 24a to 24f. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Patent No. 6418838 [Overview of the project] [Problems that the invention aims to solve]

[0007] As mentioned above, conventional dry pumps had a problem in that some of the gas remaining inside the dry pump solidified as a film or powder, forming deposits that adhered to the inside of the dry pump and causing operational malfunctions.

[0008] Furthermore, there was a problem where the rotor would frequently lock up and become impossible to restart if the dry pump was temporarily stopped for maintenance or other reasons. As a result, an overhaul (e.g., disassembly, cleaning, and internal cleaning) was required at short intervals (e.g., every 2-3 months), which was one of the factors that reduced productivity. In addition, once the rotor locked up, it took a long time to release the lock, which was a problem in terms of work efficiency.

[0009] Therefore, a vacuum evacuation system that can easily recover from a stopped state where the dry pump has stopped and the accumulated material has blocked the gas passage of the vacuum pump, making it impossible to restart. Mu and Technical challenges arise that need to be solved in order to provide a cleaning method for vacuum pumps, and the present invention aims to solve these challenges. [Means for solving the problem]

[0010] The present invention was proposed to achieve the above objective, and the invention described in claim 1 provides a vacuum exhaust system comprising: a vacuum pump for exhausting a process gas containing condensable gas or oxidizing dust; a first inert gas introduction unit for introducing a high-temperature inert gas to raise the temperature of the vacuum pump to approximately the same temperature as the normal operating temperature of the vacuum pump, thereby expanding the gas flow path so that the vacuum pump can be started, into which deposits of the process gas have accumulated and the vacuum pump is stopped; and a cleaning material introduction unit for introducing a cleaning material into the gas flow path to remove the deposits.

[0011] In this configuration, when the vacuum pump rotor locks up due to process gas deposits and the vacuum pump cannot be restarted, a high-temperature inert gas is introduced into the vacuum pump's gas flow path to raise the vacuum pump's temperature to approximately the same as its normal operating temperature. The introduction of the high-temperature inert gas returns the temperature inside the vacuum pump to approximately the same as its normal operating temperature, melting the deposits adhering to the inside of the vacuum pump with the increased heat and releasing the rotor lock. Once the rotor is released and can rotate, a cleaning material that reacts with the process gas is introduced into the gas flow path to remove the deposits in the gas flow path, allowing for faster and cleaner removal of the deposits inside the vacuum pump. This enables maintenance to be completed quickly and cleanly, and allows for restart. The temperature approximately the same as the normal operating temperature here refers to the temperature range in which deposits adhering to the inside of the vacuum pump can be melted and the rotor lock released.

[0012] The invention described in claim 2 provides a vacuum evacuation system in which, in the configuration described in claim 1, the first inert gas introduction unit introduces the inert gas approximately in the middle of the gas flow path.

[0013] In this configuration, a high-temperature inert gas capable of raising the vacuum pump to a temperature approximately equal to its normal operating temperature is introduced approximately midway through the gas flow path. This is because if the inert gas were introduced from the inlet at the very end of the gas flow path towards the outlet at the very end, the pump chamber at the inlet side would quickly rise to its normal operating temperature due to the heat of the high-temperature inert gas. However, by the time the inert gas reaches the pump chamber at the outlet side, which is furthest from the inlet, it would cool down, and it would take time to raise it to its normal operating temperature. By introducing the gas from approximately midway through the gas flow path, the heat of the inert gas is transferred from the midpoint to both the inlet and outlet sides, allowing both pump chambers to be simultaneously raised to approximately the same temperature. This allows for faster and cleaner removal of deposits inside the vacuum pump, enabling maintenance work to be completed more efficiently.

[0014] The invention described in claim 3 provides a vacuum exhaust system comprising, in the configuration described in claim 1 or 2, a second inert gas introduction unit for introducing an inert gas into the gas flow path to protect the seal portion of the vacuum pump, wherein the position at which the first inert gas introduction unit introduces the inert gas and the position at which the second inert gas introduction unit introduces the gas into the gas flow path are the same.

[0015] With this configuration, the first inert gas introduction unit introduces high-temperature inert gas into the gas flow path using the inlet through which the second inert gas introduction unit introduces sealing inert gas. This eliminates the need for the first inert gas introduction unit to provide a new inlet for introducing high-temperature inert gas into the gas flow path, thus simplifying the structure.

[0016] The invention described in claim 4 is the configuration described in any one of claims 1 to 3, wherein the vacuum pump is a positive displacement vacuum pump. Exhaust system To provide.

[0017] This configuration makes it possible to create a positive displacement vacuum pump that can remove deposits inside the pump more quickly and cleanly, thus completing maintenance work more efficiently.

[0018] The invention described in claim 5 provides a method for cleaning a vacuum pump that exhausts a process gas containing condensable gas or oxidizing dust, comprising the steps of: introducing a high-temperature inert gas to raise the temperature of the vacuum pump to approximately the temperature during normal operation of the vacuum pump, thereby expanding the gas passage so that the pump can be started, into the gas passage of the vacuum pump, which has accumulated deposits of the process gas and is in a stopped state, to which the temperature has been raised; and introducing a cleaning material into the gas passage to remove the deposits.

[0019] According to this method, when a vacuum pump rotor is locked due to process gas deposits and the vacuum pump cannot be restarted after stopping, a high-temperature inert gas is introduced into the gas flow path of the vacuum pump to raise the temperature to approximately the same as the normal operating temperature. Then, the temperature inside the vacuum pump is returned to approximately the same as the normal operating temperature by introducing the high-temperature inert gas, and the heat from the increased temperature melts the deposits adhering inside the vacuum pump, releasing the rotor lock. With the rotor able to rotate, a cleaning material that reacts with the process gas is introduced into the gas flow path to remove the deposits, allowing for faster and cleaner removal of deposits inside the vacuum pump and completing maintenance. The temperature approximately the same as the normal operating temperature here refers to the temperature range in which deposits adhering inside the vacuum pump can be melted and the rotor lock released.

[0020] The invention described in claim 6 is a method for cleaning a vacuum pump that exhausts a process gas containing condensable gas or oxidizing dust, wherein during the operation of the vacuum pump, Without introducing cleaning material into the gas flow path within the vacuum pump, The steps include determining whether the deposits from the process gas have accumulated in the vacuum pump above a predetermined standard, and if it is determined that the deposits have accumulated in the vacuum pump above a predetermined standard, before stopping the vacuum pump, Record The step includes introducing cleaning material into the flow path and removing deposits with the process gas. In the step of determining whether the deposit has accumulated in the vacuum pump above a predetermined standard, the rotational speeds of the vacuum pump and its booster pump, as well as the current value of the vacuum pump, are monitored over a predetermined period of time. If, within the predetermined period, the rotational speed of the vacuum pump falls below the rotational speed of the booster pump at least twice and the current value of the vacuum pump exceeds a predetermined threshold at least twice, it is determined that the deposit has accumulated in the vacuum pump above a predetermined standard. This provides a method for cleaning vacuum pumps.

[0021] This method involves introducing a cleaning material that reacts with the process gas into the vacuum pump's gas flow path before the vacuum pump stops, thereby pre-removing deposits inside the vacuum pump. This allows for quick and thorough removal of deposits inside the vacuum pump without stopping its operation. Therefore, this vacuum pump cleaning method contributes to improved productivity by allowing for the removal of deposits inside the vacuum pump without stopping it. [Effects of the Invention]

[0022] According to the present invention, when the rotor of the vacuum pump is locked due to the deposition part of the process gas and the vacuum pump cannot be restarted from the stopped state, an inert gas at a high temperature capable of raising the temperature of the gas flow path of the vacuum pump to a temperature substantially equal to the temperature during normal operation is introduced into the gas flow path of the vacuum pump to return the temperature inside the vacuum pump to the temperature during normal operation, melt the deposits adhering inside the vacuum pump with the high-temperature heat to release the lock of the rotor, and in a state where the rotor can rotate, a cleaning material that reacts with the process gas is introduced into the gas flow path to remove the deposits inside the gas flow path. Therefore, the deposits inside the vacuum pump can be removed more quickly and cleanly. As a result, maintenance and the like can be completed neatly in a short time.

Brief Description of Drawings

[0023] [Figure 1] It is a block diagram showing a schematic overall configuration of an exhaust gas treatment apparatus in a semiconductor manufacturing process as a first embodiment according to an embodiment of the present invention. [Figure 2] It is a schematic side cross-sectional view schematically showing an internal structure of a dry pump in the exhaust gas treatment apparatus of the same type. [Figure 3] It is a cross-sectional view taken along line A-A of FIG. 2. [Figure 4] It is a diagram of an example of one data showing how solid SiO2 changes to gaseous SiF4 by plasma of NF3 and is discharged from the dry pump. [Figure 5] It is a schematic side cross-sectional view schematically showing an internal structure of another dry pump in the exhaust gas treatment apparatus of the same type as a second embodiment. [Figure 6] It is a cross-sectional view taken along line B-B of FIG. 5. [Figure 7] It is a diagram showing an example of a maintenance determination criterion in the control device.

Modes for Carrying Out the Invention

[0024] The present invention aims to provide a vacuum exhaust system, a vacuum pump, and a vacuum pump cleaning method that can easily recover from a stopped state in which a dry pump has stopped and an accumulation has blocked the gas passage of the vacuum pump, making it impossible to restart. This is achieved by providing a vacuum pump that exhausts process gas containing condensable gas or oxidizing dust; a first inert gas introduction unit that introduces a high-temperature inert gas, approximately equal to the temperature inside the gas passage during normal operation of the vacuum pump, into the gas passage of the vacuum pump in a stopped state in which the process gas accumulation has blocked the gas passage of the vacuum pump, thereby expanding the gas passage so that the vacuum pump can be started; and a cleaning material introduction unit that introduces a cleaning material that reacts with the process gas into the gas passage to remove the accumulation. [Examples]

[0025] Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. In the following embodiments, when referring to the number, numerical values, quantities, ranges, etc., of the components, unless specifically indicated or clearly limited in principle to a particular number, the number is not limited to that particular number, and may be greater than or less than that number.

[0026] Furthermore, when referring to the shape, positional relationship, etc. of constituent elements, unless otherwise explicitly stated or it is clearly considered not to be so in principle, this includes things that are substantially similar or alike to those shapes, etc.

[0027] Furthermore, drawings may exaggerate features by enlarging characteristic parts to make them easier to understand, and the dimensional ratios of components may not be the same as in reality. Also, in cross-sectional views, hatching may be omitted for some components to make the cross-sectional structure of the components easier to understand.

[0028] Furthermore, in the following description, expressions indicating directions such as up and down or left and right are not absolute. They are appropriate when describing the orientation of each part of the vacuum exhaust system of the present invention, but should be interpreted differently if the orientation changes. Also, the same reference numerals are used for the same elements throughout the description of the embodiments.

[0029] Figures 1 to 3 show an exhaust gas treatment apparatus in a semiconductor manufacturing process as one embodiment of the present invention. Figure 1 is a block diagram showing the schematic overall configuration of the exhaust gas treatment apparatus, Figure 2 is a schematic side cross-sectional view showing the internal structure of the dry pump 17 in the exhaust gas treatment apparatus, and Figure 3 is a cross-sectional view taken along line AA in Figure 2.

[0030] First, the overall configuration of the exhaust gas treatment system will be explained, mainly using Figure 1. The internal structure of the dry pump 17 will also be explained using parts of Figures 2 and 3. As shown in Figure 1, the exhaust gas treatment system is controlled according to a predetermined procedure by a program in the control device 10. A semiconductor wafer 12 is housed inside the process chamber 11, and process gas for process processing and cleaning gas for cleaning processing are supplied through the gas supply pipe 13. A dry pump 17, which acts as a vacuum pump, is connected to the process chamber 11 via the gas pipe 14, and the process chamber 11 is reduced to a high vacuum by the operation of the dry pump 17.

[0031] In other words, the process gas containing condensable gas or oxidizing dust that has been processed inside the process chamber 11, such as silane (SiH4) gas and cleaning gases such as ClF3 (chlorine trifluoride), NF3 (nitrogen trifluoride), and HCl (hydrogen chloride) (hereinafter, these process gases and cleaning gases are collectively referred to as "used gas G1"), is introduced into the downstream dry pump 17 through the gas piping 14.

[0032] The internal structure of the dry pump 17 is shown in Figures 2 and 3. The dry pump 17 draws in used gas G1 from the process chamber 11 through the gas inlet 17a and gradually pressurizes the used gas G1 inside the dry pump 17 in six stages, namely passing it through the first stage pump chamber 22a, the second stage pump chamber 22b, the third stage pump chamber 22c, the fourth stage pump chamber 22d, the fifth stage pump chamber 22e, and the sixth stage pump chamber 22f in that order, gradually pressurizing it.

[0033] Furthermore, as shown in Figure 1, the used gas G1, which has been pressurized to near atmospheric pressure in the dry pump 17, is discharged from the gas outlet 17b into the gas exhaust pipe 18, and from the gas exhaust pipe 18 is sent to the abatement device 19, where it is rendered harmless before being discharged into the atmosphere. Therefore, one end of the gas exhaust pipe 18 is connected to the gas outlet 17b of the dry pump 17, and the other end is connected to the gas inlet 19a of the abatement device 19.

[0034] Furthermore, the dry pump 17 is connected to a restart material supply pipe 21a that introduces a high-temperature (e.g., 400°C) inert gas G2 (such as hot N2) which can raise the temperature inside the dry pump 17 to approximately the same temperature as during normal operation (100°C to 190°C) when the rotors (24a to 24f) shown in Figure 2 become locked after the dry pump 17 has stopped, for example, due to residual gas or attached deposits (mainly SiO2) inside the dry pump 17, making it impossible to restart the dry pump 17. This restart material supply pipe 21a introduces a high-temperature (e.g., 400°C) inert gas G2 (such as hot N2) which can raise the temperature inside the dry pump 17 to approximately the same temperature as during normal operation (100°C to 190°C). The plasma supply pipe 21b introduces NF3 plasma, which is the cleaning material G4, after restarting.

[0035] The restart material supply pipe 21a is connected at one end to the first inert gas introduction unit 20a and at the other end to the restart material inlet 17c via an on-off valve 31a. As shown in Figure 2, the restart material inlet 17c is provided in the pump casing 23, corresponding to one of the multiple (six in this embodiment) pump chambers 22a to 22f, specifically the third stage pump chamber 22c in this embodiment. From the restart material supply pipe 21a, high-temperature (e.g., 400°C) inert gas G2 (hot N2, etc.) sent from the first inert gas introduction unit 20a is introduced into the dry pump 17 by opening and closing the on-off valve 31a. The opening and closing of the on-off valve 31a is controlled by the control device 10. That is, when the on-off valve 31a is open, high-temperature inert gas G2 enters the pump casing 23 from the restart material inlet 17c. Then, when high-temperature inert gas G2 is sent into the pump casing 23 from the restart material inlet 17c for a certain period of time (for example, about 2 hours), the inside of the pump casing 23 reaches a temperature that is almost the same as when the dry pump 17 is in operation. This widens the gap between the sides of the rotors 24a to 24f and the inner surfaces of both sides of the pump chambers 22a to 22f, releasing the lock on the rotors 24a to 24f and enabling the dry pump 17 to be restarted.

[0036] Next, we will describe the cleaning method for the inside of the pump casing 23 while the dry pump 17 is in operation. As shown in Figure 1, one end of the plasma supply pipe 21b is connected to the gas inlet 17a of the pump casing 23 via an on-off valve 31b and gas pipe 14, and the other end is connected to the cleaning material supply unit 30. The cleaning material supply unit 30 is configured to supply NF3 plasma (F radicals), which is the cleaning material G4 used to clean the inside of the dry pump 17, into the pump casing 23 through the gas inlet 17a via an on-off valve 31b that is opened after the dry pump 17 is restarted. In addition to NF3 plasma (F radicals), the cleaning material G4 also includes plasma (F radicals) HF (hydrogen fluoride), water vapor, silicon chloride, etc. The opening and closing of the on-off valve 31b is controlled by the control device 10. That is, when the on-off valve 31b is open, the cleaning material G4 from the cleaning material supply unit 30 enters the pump casing 23 through the gas inlet 17a.

[0037] The cleaning material G4 is introduced into the pump casing 23 after the dry pump 17 has been restarted. When the cleaning material G4, which is NF3 plasma, is introduced into the pump casing 23, the products react with F radicals in the plasma and are released as a gas, almost completely eliminating the deposits inside the dry pump 17. The deposits released as a gas from the dry pump 17 are then introduced into the gas exhaust piping 18 from the gas outlet 17b and sent into the abatement device 19.

[0038] Next, the internal structure of the dry pump 17 will be further explained using Figures 2 and 3. The dry pump 17 shown in Figures 2 and 3 is a positive displacement vacuum pump and consists of a pump casing 23 having multiple (six in this embodiment) pump chambers, namely the first stage pump chamber 22a, the second stage pump chamber 22b, the third stage pump chamber 22c, the fourth stage pump chamber 22d, the fifth stage pump chamber 22e, and the sixth stage pump chamber 22f, and rotors 24a, 24b, 24c, 24d, 24e, and 24f disposed within the pump chambers 22a to 22f, respectively, and these rotors 24a The rotors 24a to 24f are integrally fixed, and the pump casing 23 has bearings 28a, 28a, 28b, 28b that support the rotors 25a to 25b together, a pair of rotating shafts 25a and 24f each rotating together, a pair of gears 26a and 26b that rotate the pair of rotating shafts 25a and 25b together, a motor 27 that serves as a rotational drive mechanism to rotate the rotating shafts 25a and 25b via the pair of gears 26a and 26b, and a pump casing 23 that supports the rotating shafts 25a and 25b respectively.

[0039] Furthermore, although not shown in the figure, the pump casing 23 is formed by stacking multiple stators 23a sequentially in the axial direction, taking into consideration ease of assembly. In addition, as shown in Figure 3, the pump casing 23 is formed in a roughly rectangular shape when cross-sectioned perpendicular to the rotation axes 25a and 25b.

[0040] Next, the operation of the exhaust gas treatment device configured in this way will be explained. First, when the dry pump 17 is activated by a start command from the control device 10, the motor 27 is also driven, and the motor 27 rotates the rotating shaft 25a. At this time, the rotating shaft 25b, which is arranged parallel to the rotating shaft 25a, rotates synchronously due to the meshing of gears 26a and 26b, and the rotating shaft 25b rotates in the opposite direction to the rotating shaft 25a.

[0041] Furthermore, the rotation of the rotating shafts 25a and 25b causes the rotors 24a to 24f, which are integrally fixed to the rotating shaft 25a, and the rotors 24a to 24f, which are integrally fixed to the rotating shaft 25b, to rotate in opposite directions within the pump chambers 22a to 22f. Although not shown in the figures, the rotors 24a to 24f attached to the rotating shafts 25a and 25b in this embodiment are cocoon-shaped roots rotors, which rotate synchronously with a 90° phase difference while maintaining a minute gap between them without contact.

[0042] As a result, used gas G1 is drawn into the first-stage pump chamber 22a from the gas inlet 17a, which is connected to the space to be vacuumed. After this, the used gas G1 is drawn sequentially from the first-stage pump chamber 22a to the second-stage pump chamber 22b, the third-stage pump chamber 22c, the fourth-stage pump chamber 22d, the fifth-stage pump chamber 22e, and the sixth-stage pump chamber 22f. Finally, the used gas G1 is discharged from the dry pump 17 via the gas exhaust pipe 18, which is connected to the gas outlet 17b of the sixth-stage pump chamber 22f, and the space to be vacuumed becomes a vacuum.

[0043] At this time, the used gas G1 is compressed and discharged in each of the pump chambers 22a, 22b, 22c, 22d, 22e, and 22f, so the temperature of the used gas G1 rises, as does the temperature of the pump casing 23. Of the pump chambers 22a, 22b, 22c, 22d, 22e, and 22f, the temperature of the used gas G1 is highest on the discharge side of the sixth stage pump chamber 22f, where the pressure difference between the suction and discharge sides of the used gas G1 is the largest. The temperature of the used gas G1 here is relatively high, for example, around 150 to 200°C.

[0044] Furthermore, the used gas G1 discharged from the sixth-stage pump room 22f travels through the gas exhaust pipe 18 to the abatement device 19 located several meters away.

[0045] Incidentally, in a dry pump 17 like the one in this embodiment, the gas remaining inside the dry pump 17 solidifies into a film or powder and becomes a deposit (mainly SiO2: silica), and this deposit adheres to the inside of the dry pump in a short period of time (2-3 months), causing operational malfunctions. Also, if the dry pump 17 is temporarily stopped for maintenance or other reasons, the rotors 24a-24f may lock up, making it impossible to restart. As mentioned above, the gap between the rotors 24a-24f and the inner walls of the fixed pump chambers 22a-22f is designed so that when the pump is stopped, the gap between both sides of the rotors 24a-24f and the inner surfaces of both sides of the pump chambers 22a-22f widens on one side (left) and narrows on the other side (right), taking into account that the pump chambers 22a-22f become hot and expand during operation. The gap on one side when stopped is designed to be around several tens to several hundreds of μm.

[0046] Therefore, if, when attempting to stop and restart the dry pump 17, the gap between the rotors 24a-24f and the inner walls of the pump chambers 22a-22f becomes clogged with deposits, causing the rotors 24a-24f to lock up, the control device 10 opens the on-off valve 31a, and the first inert gas introduction unit 20a sends high-temperature inert gas G2 at approximately 400°C into the pump casing 23 through the restart material inlet 17c for approximately several hours (for example, about 2 hours). Here, the restart material inlet 17c is located in the fourth-stage pump chamber 22d, and a high-temperature inert gas G2 of approximately 400°C is introduced into the pump casing 23 from the fourth-stage pump chamber 22d. This gas spreads to the third-stage pump chamber 22c, second-stage pump chamber 22b, first-stage pump chamber 22a, fifth-stage pump chamber 22e, and sixth-stage pump chamber 22f, both towards the gas inlet 17a and gas outlet 17b, rapidly heating the entire inside of the pump casing 23 to a high temperature. This heating brings the temperature inside the pump casing 23 to approximately the same high temperature (approximately 150°C to 200°C) as when the dry pump 17 is operating. This widens the gap between the sides of the rotors 24a to 24f and the inner surfaces of the pump chambers 22a to 22f, melting the deposits and releasing the lock on the rotors 24a to 24f, allowing the dry pump 17 to be restarted. In other words, the process here involves introducing high-temperature inert gas G2 to heat the temperature inside the pump casing 23 to approximately the same temperature as the dry pump 17 during normal operation, thereby expanding the gas flow path so that the dry pump 17 can be started. The inert gas G2 introduced into the pump casing 23 is then flowed through the gas exhaust pipe 18 and sent into the abatement device 19. In this embodiment, the temperature of the inert gas G2 sent into the pump casing 23 is approximately 400°C, taking into account the temperature drop in the supply pipe before it is introduced into the pump casing 23, and the temperature used to heat the pump casing 23 is approximately 150°C to 200°C. However, any other temperature (lower or higher) is acceptable as long as it is the temperature at which the solidified deposits inside the pump casing 23 melt and the rotors 24a to 24 are released.

[0047] Furthermore, once the dry pump 17 can be restarted, the control device 10 opens the on-off valve 31b, and the cleaning material G4, which is NF3 plasma (F radical), is sent from the cleaning material supply unit 30 into the pump casing 23 through the gas inlet 17a, allowing the cleaning material G4 to flow into the pump casing 23. The cleaning process here involves introducing the cleaning material G4 into the gas flow path to remove deposits. The cleaning material G4 that has flowed into the pump casing 23 is then sent from the gas outlet 17b through the gas exhaust pipe 18 into the abatement device 19. As the cleaning material G4 flows through the pump casing 23, the products react with the F radicals in the plasma and are released as gas, almost completely eliminating the deposits in the dry pump 17. The deposits released as gas from the dry pump 17 are then sent from the gas outlet 17b through the gas exhaust pipe 18 along with the cleaning material G4, and further into the abatement device 19.

[0048] Figure 4 shows the data obtained by measuring the concentrations (ppm) of NF3 (nitrogen trifluoride) plasma and SiF4 (silicon tetrafluoride) per unit time discharged from the gas outlet 17b after flowing the cleaning material G4, which is NF3 plasma, from the gas inlet 17a into the pump casing 23. In the figure, the vertical axis represents concentration (ppm), and the horizontal axis represents elapsed time T.

[0049] The data in Figure 4 shows how solid SiO2 (silica) is converted to gaseous SiF4 by the NF3 plasma (F ions) and then discharged. Specifically, Figure 4 shows the changes in the amount (concentration) of NF3 plasma and the amount (concentration) of SiF4 discharged from the gas inlet 17a to the pump casing 23 from time T0 to time Tn, respectively, after introducing NF3 plasma into the pump casing 23 from the gas inlet 17a. In the figure, the low concentration of NF3 plasma during the period from time T1 to T2 is due to the ongoing reaction with SiO2. Furthermore, the conversion to SiF4 peaks around time T2, and then gradually decreases thereafter. Therefore, this data also shows that when cleaning material G4, which is NF3 plasma, is flowed into the pump casing 23 from the gas inlet 17a, solid SiO2 is converted to gaseous SiF4 and discharged from the gas outlet 17b, and the deposited SiO2 disappears from inside the pump casing 23.

[0050] Therefore, according to the exhaust gas treatment apparatus of this embodiment, when the rotation of the rotors 24a to 24f of the dry pump 17 is locked due to process gas deposits and the dry pump 17 cannot be restarted from a stopped state, a high-temperature inert gas G2 is introduced into the gas flow path of the dry pump 17 to raise the temperature to approximately the same as the temperature during normal operation of the dry pump 17, thereby returning the temperature inside the dry pump 17 to a temperature close to that during normal operation. By melting the deposits adhering inside the dry pump 17 with high heat, the lock on the rotors 24a to 24f can be released, allowing the rotors 24a to 24f to rotate.

[0051] Furthermore, after the rotors 24a to 24f are ready to rotate, cleaning material G4, which reacts with process gas G1, is introduced into the gas flow path to remove deposits in the gas flow path. This allows for faster and cleaner removal of deposits in the dry pump 17. As a result, maintenance can be completed quickly and efficiently.

[0052] In the first embodiment, the restart material supply piping 21a is configured such that a restart material inlet 17c is provided in the pump casing 23 corresponding to an intermediate pump chamber among the multiple pump chambers 22a to 22f, i.e., the fourth stage pump chamber 22d, and high-temperature inert gas G2 is introduced into the pump casing 23 from the third stage pump chamber 22c. However, this does not necessarily have to be the third stage pump chamber 22c. For example, it could be introduced from the gas inlet 17a and flowed out of the first stage pump chamber 22a. However, the effects of introducing the gas from an intermediate pump chamber instead of the first stage pump chamber 22a are as follows.

[0053] Experiments comparing the flow of high-temperature inert gas G2 into the pump casing 23 from the first-stage pump chamber 22a and from the intermediate third-stage pump chamber 22c (or fourth-stage pump chamber 22d) revealed that the temperature upon reaching the final sixth-stage pump chamber 22f was significantly lower when flowing from the first-stage pump chamber 22a compared to when flowing from the intermediate third-stage pump chamber 22c. Furthermore, the time required for restart was longer when flowing from the first-stage pump chamber 22a compared to when flowing from the third-stage pump chamber 22c. This suggests that when high-temperature inert gas G2 is introduced into the pump casing 23 from the third-stage pump chamber 22c, the temperature of the inert gas G2 is transferred from the third-stage pump chamber 22c to the second-stage pump chamber 22b and the first-stage pump chamber 22a. At the same time, the heat is transferred from the third-stage pump chamber 22c to the fourth-stage pump chamber 22d, the fifth-stage pump chamber 22e, and the sixth-stage pump chamber 22f, spreading from the intermediate positions to both the inlet and outlet sides. This effectively heats the entire inside of the pump casing 23 to approximately the temperature of normal operation. Therefore, it was found that introducing the gas from the third-stage pump chamber 22c or the fourth-stage pump chamber 22d allows for a more rapid increase in temperature (heating) of the entire inside of the pump casing 23 to approximately the temperature of normal operation, thus shortening the time until restart is possible.

[0054] Figures 5 and 6 show a second embodiment of the dry pump in the exhaust gas treatment device shown in Figure 1. Figure 5 is a schematic side cross-sectional view showing the internal structure of the dry pump 32, and Figure 6 is a cross-sectional view taken along line BB in Figure 5.

[0055] In the dry pump 17 shown in Figures 1 to 3, a pump restart material, which is a high-temperature (approximately 400°C) inert gas G2, is flowed into the third-stage pump chamber 22c from the outside of the pump casing 23 through the restart material inlet 17c, allowing the overall temperature of the dry pump 17 to rise to approximately the same high temperature as during operation (approximately 150°C to 200°C). In contrast, the configuration of the dry pump 32 includes on-off valves 39 and 41 for introducing sealing gas G3 and on-off valve 44 for introducing high-temperature inert gas G2 in a sealing gas passage 33 provided in the sealing gas groove 33a of the pump casing 23. By switching between on-off valves 39, 41, and 44, sealing gas G3 to protect the seal and high-temperature inert gas G2 to heat the inside of the pump casing 23 are flowed. Therefore, in the following description, the same components as those in the first embodiment of the dry pump 17 shown in Figures 2 and 3 will be given the same reference numerals and their descriptions will be omitted, and only the parts with different structures will be described.

[0056] In Figures 5 and 6, each of the multiple stators 23a that are stacked in the axial direction to constitute the pump casing 23 has sealing gas grooves 33a formed on opposing surfaces so as to surround the outside of each pump chamber 22d to 22f. When the pump casing 23 is assembled by stacking the stators 23a, the sealing gas grooves 33a face each other in the parts that form each pump chamber 22d to 22f, forming a sealing gas passage 33. The sealing gas passage 33 is described as being formed on both sides of the stator 23a, but the sealing gas grooves 33a may be formed on only one side of the stator 23a. Furthermore, during the assembly of the pump casing 23, in order to maintain airtightness between each pump chamber 22a to 22f and each stator 23a, O-rings 35 are densely arranged in O-ring grooves 34 surrounding the outside of each pump chamber 22d to 22f, as shown in Figure 6. In addition, as shown in Figure 6, the sealing gas passage 33 is provided with gas inlets 42 for introducing sealing gas G3 and high-temperature inert gas G2 into each pump chamber 22d to 22f.

[0057] In this embodiment, the O-ring 35 is corroded by the used gas G1. Therefore, in the dry pump 32 of this embodiment, to prevent this corrosion, during operation of the dry pump 32, an inert gas, N2 gas, is introduced into the sealing gas passage 33 as sealing gas G3 from the second inert gas introduction unit 20b. Also, the pressure in each pump chamber 22a to 22f increases towards the downstream stage. Therefore, in the dry pump 32 of this embodiment, sealing gas G3, which is N2 gas, is flowed (introduced) into the fourth, fifth, and sixth pump chambers 22d to 22f, which are the downstream stages. This is because the corrosive used gas G1 is compressed and concentrated in the higher-pressure pump chambers 22d to 22f, which accelerates the corrosion of the O-ring 35 and reduces the seal, thus preventing this and contributing to the seal together with the O-ring 35. However, the pump chamber through which the sealing gas G3 flows may be configured to flow only to the final pump chamber (the sixth stage pump chamber 22f) where the pressure is highest, or, taking into account the heating inside the pump casing 23, sealing gas passages 33 may be provided for all pump chambers 22a to 22f, and high-temperature inert gas G2 may be flowed from all sealing gas passages 33 into all pump chambers 22a to 22f.

[0058] In this second embodiment of the dry pump 32, each stator 23a forming the fourth, fifth, and sixth pump chambers 22d to 22f is provided with a sealing gas groove 33a, a sealing gas inlet 36b for a sealing gas inlet pipe 38, which has a sealing gas inlet 36a on the outer surface of the stator 23a (outer surface 29 of the pump casing 23), and a sealing gas outlet 37b, which has a sealing gas outlet connection port 37a on the outer surface of the stator 23a. Each sealing gas inlet 36a is connected to a sealing gas inlet pipe 38 supplied with sealing gas G3 via an on-off valve 39, and each sealing gas outlet connection port 37a is connected to a sealing gas outlet pipe 40, which discharges sealing gas G3, via an on-off valve 41. The sealing gas outlet pipe 40 is connected to a gas exhaust pipe 18 via a dilution gas inlet 18a. For the on-off valves 39 and 41, it is preferable to use on-off valves that, for example, allow for adjustment of the gas flow rate.

[0059] Furthermore, the first inert gas introduction unit 20a is connected to the sealing gas introduction pipe 38 via the pump restart material supply pipe 43 and the on-off valve 44. The opening and closing of the on-off valve 44 is controlled by the control device 10. That is, when inert gas G2 is to flow, the on-off valve 39 and on-off valve 41 are closed, and the on-off valve 44 is opened. Then, the high-temperature inert gas G2 from the first inert gas introduction unit 20a enters the sealing gas flow path 33 through the sealing gas introduction port 36a from the pump restart material supply pipe 43, and further flows into the fourth, fifth, and sixth stage pump chambers 22d to 22f through the gas intake port 42. This high-temperature inert gas G2 then spreads throughout the pump casing 23, causing the temperature inside the pump casing 23 to rise. After that, it is discharged into the gas exhaust pipe 18 through the gas outlet 17b and sent to the abatement device 19 via the gas exhaust pipe 18.

[0060] Therefore, in the exhaust gas treatment apparatus of this second embodiment, when the rotors 24a to 24f of the dry pump 32 are locked due to the accumulation of process gas and the dry pump 32 cannot be restarted, the temperature inside the dry pump 32 can be raised to approximately the same temperature as the temperature during normal operation (100°C to 190°C) by flowing high-temperature inert gas G2 into the sealing gas passage 33, thereby rapidly returning the temperature inside the dry pump 32 to a temperature close to that during normal operation. Then, the deposits adhering to the inside of the dry pump 17 can be melted by the high temperature, unlocking the rotors 24a to 24f and allowing them to rotate.

[0061] Furthermore, once the dry pump 32 can be restarted, the control device 10 opens the on-off valve 31b, and the cleaning material G4, which is NF3 plasma, is sent into the pump casing 23 from the gas inlet 17a, allowing the cleaning material G4 to flow into the pump casing 23. The cleaning material G4 that has flowed into the pump casing 23 is then sent into the abatement device 19 through the gas exhaust pipe 18 from the gas outlet 17b. As the cleaning material G4 that has been sent into the pump casing 23 flows through the pump casing 23, the products react with F radicals in the plasma and are released as gas, almost completely eliminating the deposits inside the dry pump 17.

[0062] Furthermore, the sediment inside the dry pump 17 that is released as gas is flowed through the gas outlet 17b into the gas exhaust pipe 18 along with the cleaning material G4, and is then sent into the abatement device 19.

[0063] Therefore, according to this embodiment of the exhaust gas treatment device, when the rotors 24a to 24f of the dry pump 32 are locked due to the accumulation of process gas, and the dry pump 17 cannot be restarted after stopping, a high-temperature inert gas G2 is flowed into the sealing gas passage 33 to return the temperature inside the dry pump 17 to a temperature close to that of normal operation. This allows for faster and cleaner removal of deposits inside the dry pump 32. As a result, maintenance and other processes can be completed quickly and cleanly.

[0064] Furthermore, the structures of the first embodiment and the second embodiment can be combined as needed.

[0065] Furthermore, in each embodiment, when the rotors 24a to 24f of dry pump 17 and dry pump 32 are locked and dry pump 17 cannot be restarted after stopping, a high-temperature inert gas G2 is flowed through the gas passage of dry pump 17 to raise the temperature to approximately the same as the temperature during normal operation of dry pump 17, thereby returning the temperature inside dry pump 17 to a temperature close to that during normal operation. After restarting, cleaning material G4 is then flowed into dry pump 17 to eliminate the deposits. However, it is also possible to pre-emptively flow cleaning material G4, which reacts with the process gas, through the gas passages of dry pump 17 and dry pump 32 before stopping dry pump 17 and dry pump 32 to remove deposits (SiO2) caused by the process gas G1.

[0066] Before stopping the dry pumps 17 and 32, a cleaning material G4 that reacts with the process gas is flowed through the gas passages of the dry pumps 17 and 32 to remove deposits (SiO2) caused by the process gas. An example of this will be explained using Figure 7, specifically in the case of the dry pump 17 shown in Figures 1 to 3.

[0067] In one example shown in Figure 7, the control is performed by a control device 10. The control device 10 receives the booster pump speed 101, the dry pump 17 speed 102, and the dry pump 17 current value 103 as inputs while the dry pump 17 is running, and monitors each of these values ​​for approximately one hour. If, during this one hour, the dry pump 17 speed 102 falls below the booster pump speed 101 several times, and the dry pump 17 current value 103 exceeds a threshold (for example, 45.0 amperes) several times, the control device 10 determines that a certain amount of deposit has accumulated in the dry pump 17. Then, before stopping the dry pump 17, the control device 10 controls the first inert gas introduction unit 20a and the on-off valve 31b to flow cleaning material G4, which reacts with process gas G1, into the pump casing 23 from the gas inlet 17a for a certain period of time, thereby eliminating the deposit accumulated in the pump casing 23. This allows for the removal of deposits adhering to the inside of the dry pump 17 without stopping the dry pump 17.

[0068] Furthermore, the present invention can be modified or combined in various ways without departing from the spirit of the invention, and it goes without saying that the present invention extends to such modified or combined forms. [Explanation of Symbols]

[0069] 10: Control device 11: Process Chamber 12: Semiconductor wafers 13: Gas supply piping 17: Dry pump 17a: Gas inlet 17b: Gas outlet 17c: Restart material inlet 18: Gas exhaust piping 19:Abatement device 20a: First inert gas introduction unit 20b: Second inert gas introduction unit 21a: Restart material supply piping 21b: Plasma supply piping 22a: First stage pump room 22b: Second stage pump room 22c: Third stage pump room 22d: Fourth stage pump room 22e: Fifth stage pump room 22f: 6th stage pump room 23: Pump casing 24a: Rotor 24b: Rotor 24c: Rotor 24d: Rotor 24e: Rotor 24f: Rotor 31a: Shut-off valve 31b: Shut-off valve 32: Dry pump 33: Gas passage for sealing 33a: Gas groove for sealing 36: Gas introduction passage for sealing 36a: Gas inlet for sealing 36b: Gas inlet for sealing 37: Gas discharge passage for sealing 37a: Gas discharge pipe connection port for sealing 37b: Gas outlet for sealing 38: Gas introduction pipe for sealing 39: Shut-off valve 40: Gas discharge pipe for sealing 41: Shut-off valve 42: Gas intake 43: Pump restart, material supply piping 44: Shut-off valve G1: Process gas G2: Inert gas G3: Sealing gas G4: Cleaning materials

Claims

1. A vacuum pump for exhausting process gas containing condensable gas or oxidizing dust, A first inert gas introduction unit expands the gas flow path of a vacuum pump, which is stopped due to the accumulation of process gas deposits, by introducing a high-temperature inert gas to raise the temperature to approximately the same as the temperature during normal operation of the vacuum pump, thereby enabling the vacuum pump to be started. A cleaning material introduction unit that introduces cleaning material into the gas flow path to remove the deposits, A vacuum exhaust system characterized by having the following features.

2. The vacuum exhaust system according to claim 1, characterized in that the first inert gas introduction unit introduces the inert gas approximately in the middle of the gas flow path.

3. The vacuum pump further comprises a second inert gas introduction unit that introduces an inert gas into the gas flow path to protect the seal portion of the vacuum pump, The vacuum exhaust system according to claim 1 or 2, characterized in that the position where the first inert gas introduction unit introduces the inert gas and the position where the second inert gas introduction unit introduces the gas into the gas flow path are the same.

4. The vacuum exhaust system according to any one of claims 1 to 3, characterized in that the vacuum pump is a positive displacement vacuum pump.

5. A method for cleaning a vacuum pump that exhausts process gas containing condensable gas or oxidizing dust, The steps include: introducing a high-temperature inert gas to the gas flow path of the vacuum pump, which is stopped due to the accumulation of the process gas deposits, to raise the temperature to approximately the same as the temperature during normal operation of the vacuum pump, thereby expanding the gas flow path so that the vacuum pump can be started; A step of introducing cleaning material into the gas flow path to remove the deposits, A method for cleaning a vacuum pump, characterized by including [a specific element].

6. A method for cleaning a vacuum pump that exhausts process gas containing condensable gas or oxidizing dust, During the operation of the vacuum pump, a step is made to determine whether or not deposits from the process gas have accumulated in the vacuum pump above a predetermined standard without introducing cleaning material into the gas flow path within the vacuum pump. If it is determined that the deposits in the vacuum pump exceed a predetermined standard, the following steps are taken before stopping the vacuum pump: introducing cleaning material into the gas flow path and removing the deposits with the process gas. In the step of determining whether the deposit has accumulated in the vacuum pump in an amount exceeding a predetermined standard, the rotational speeds of the vacuum pump and its booster pump, as well as the current value of the vacuum pump, are monitored for a predetermined period of time. If, within the predetermined period, the rotational speed of the vacuum pump falls below the rotational speed of the booster pump at least twice and the current value of the vacuum pump exceeds a predetermined threshold at least twice, it is determined that the deposit has accumulated in the vacuum pump in an amount exceeding a predetermined standard. A method for cleaning a vacuum pump, characterized by the following features.

Images