Patent Application
20240376877
Certain embodiments of the present invention relate to a cryopump system and a regeneration controller for a cryopump system.
A cryopump is a vacuum pump that captures gas molecules through condensation and adsorption on a cryopanel cooled to a cryogenic temperature and that exhausts the gas molecules. The cryopump is generally used in order to realize a clean vacuum environment which is required for a semiconductor circuit manufacturing process or the like. Since the cryopump is a so-called gas storage type vacuum pump, regeneration to periodically exhaust captured gases to the outside is required.
According to an aspect of the present invention, there is provided a cryopump system including a plurality of cryopumps each of which includes a cryopump container, an exhaust valve that exhausts an exhaust fluid from the cryopump container, and an exhaust purge valve that supplies a purge gas to the exhaust valve or downstream thereof and an exhaust line through which the exhaust fluid is exhausted from the plurality of cryopumps to a treatment device, the exhaust line including a plurality of branch lines and a merging line, the plurality of branch lines each connected to the exhaust valve and the exhaust purge valve of a corresponding cryopump, the merging line connecting the plurality of branch lines to the treatment device.
According to another aspect of the present invention, there is provided a regeneration controller for a cryopump system. The cryopump system includes a plurality of cryopumps, each of which includes a cryopump container, an exhaust valve that exhausts an exhaust fluid from the cryopump container, and an exhaust purge valve that supplies a purge gas to the exhaust valve or downstream thereof, and an exhaust line through which the exhaust fluid is exhausted from the plurality of cryopumps to a treatment device, the exhaust line including a plurality of branch lines and a merging line, the plurality of branch lines each connected to the exhaust valve and the exhaust purge valve of a corresponding cryopump, the merging line connecting the plurality of branch lines with the treatment device. The plurality of cryopumps include a first cryopump and a second cryopump. The regeneration controller is configured to control the first cryopump so that the exhaust fluid is exhausted from the first cryopump to the treatment device and concurrently to control the second cryopump so that the purge gas is supplied from the second cryopump to the merging line of the exhaust line.
According to still another aspect of the present invention, there is provided a cryopump system including a cryopump that includes a cryopump container, an exhaust valve which exhausts an exhaust fluid from the cryopump container, and a first exhaust purge valve which supplies a purge gas to the exhaust valve or downstream thereof and an additional exhaust purge valve that is connected to the exhaust valve and the exhaust purge valve, that is provided at an exhaust line through which the exhaust fluid is exhausted from the cryopump to a treatment device, and that supplies the purge gas to a treatment device side with respect to the first exhaust purge valve.
Any combination of the components described above and a combination obtained by switching the components and expressions of the present invention between methods, devices, systems, and the like are also effective as an embodiment of the present invention.
In the semiconductor manufacturing process, a hazardous gas having various hazards such as explosiveness, corrosiveness, toxicity, and the like is used in some cases. The hazardous gas stored in the cryopump is exhausted from the cryopump through regeneration and is treated to be harmless or to reduce the hazards by a treatment device called an abatement device. In this case, the hazardous gas is diluted by supplying a purge gas to the cryopump, and the concentration of the hazardous gas flowing into the treatment device is decreased, so that safety can be improved.
However, immediately after regeneration start, due to a rise in the temperature of the cryopump, the stored hazardous gas can be rapidly re-vaporized, and a hazardous gas concentration can significantly increase. In order to ensure that the hazardous gas concentration is maintained sufficiently low for safety, a large amount of purge gas is required.
It is desirable to efficiently dilute a hazardous gas that is exhausted from a cryopump and that flows into a treatment device.
Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In the description and drawings, the same or equivalent components, members, and processing will be assigned with the same reference symbols, and redundant description thereof will be omitted as appropriate. The scales and shapes of shown parts are set for convenience in order to make the description easy to understand and are not to be understood as limiting unless stated otherwise. The embodiments are merely examples and do not limit the scope of the present invention. All characteristics and combinations to be described in the embodiments are not necessarily essential to the invention.
The cryopump 10 includes a compressor 12, a cryocooler 14, and a cryopump container 16. The cryopump container 16 includes a cryopump intake port 17. In addition, the cryopump 10 includes a rough valve 18, a body purge valve 20, an exhaust valve 22, and an exhaust purge valve 24, and these are provided at the cryopump container 16.
The compressor 12 is configured to collect a refrigerant gas from the cryocooler 14, to pressurize the collected refrigerant gas, and to supply the refrigerant gas to the cryocooler 14 again. The cryocooler 14 is also referred to as an expander or a cold head and constitutes a cryogenic refrigerator together with the compressor 12. A thermodynamic cycle, through which chill is generated, is configured by performing circulation of the refrigerant gas between the compressor 12 and the cryocooler 14 with an appropriate combination of pressure fluctuations and volume fluctuations of the refrigerant gas in the cryocooler 14, and thereby the cryocooler 14 can provide cryogenic temperature cooling. Although the refrigerant gas is typically a helium gas, other appropriate gases may be used. In order to facilitate understanding, a direction in which the refrigerant gas flows is indicated with arrows in
As shown in
The first cylinder 28 connects the first cooling stage 30 to the room temperature portion 26, and accordingly, the first cooling stage 30 is structurally supported by the room temperature portion 26. The second cylinder 32 connects the second cooling stage 34 to the first cooling stage 30, and accordingly, the second cooling stage 34 is structurally supported by the first cooling stage 30. The first cylinder 28 and the second cylinder 32 coaxially extend along a radial direction, and the room temperature portion 26, the first cylinder 28, the first cooling stage 30, the second cylinder 32, and the second cooling stage 34 are linearly arranged in a line in this order.
In a case where the cryocooler 14 is a two-stage GM cryocooler, a first displacer and a second displacer (not shown) are disposed to be reciprocal inside the first cylinder 28 and the second cylinder 32, respectively. A first regenerator and a second regenerator (not shown) are incorporated into the first displacer and the second displacer, respectively. In addition, the room temperature portion 26 includes a drive mechanism (not shown) such as a motor for reciprocating the first displacer and the second displacer. The drive mechanism includes a flow path switching mechanism that switches between flow paths for a working gas (for example, helium) to periodically repeat supply and exhaust of the working gas to and from the cryocooler 14.
In addition, the cryopump 10 includes a radiation shield 36 and a cryopanel 38. In order to provide a cryogenic temperature surface for protecting the cryopanel 38 from radiant heat from the outside of the cryopump 10 or the cryopump container 16, the radiation shield 36 is thermally coupled to the first cooling stage 30 and is cooled to the first cooling temperature.
The radiation shield 36 has, for example, a tubular shape and is disposed to surround the cryopanel 38 and the second cooling stage 34. An end portion of the radiation shield 36 on a cryopump intake port 17 side is opened, and a gas that enters through the cryopump intake port 17 from the outside of the cryopump 10 can be received in the radiation shield 36. An end portion of the radiation shield 36 on an opposite side to the cryopump intake port 17 is closed, or may include an opening and be opened. There is a gap between the radiation shield 36 and the cryopanel 38, and the radiation shield 36 is not in contact with the cryopanel 38. The radiation shield 36 is also not in contact with the cryopump container 16.
An inlet baffle 37 may be provided at the cryopump intake port 17 or between the cryopump intake port 17 and the cryopanel 38 in order to protect the cryopanel 38 from radiant heat from an external heat source of the cryopump 10 (for example, a heat source in the vacuum chamber to which the cryopump 10 is attached). The inlet baffle 37 may be fixed to an open end of the radiation shield 36 and be thermally coupled to the first cooling stage 30 of the cryocooler 14 via the radiation shield 36. Alternatively, the inlet baffle 37 may be attached to the first cooling stage 30. The inlet baffle 37 is cooled to the same temperature as the radiation shield 36 and can condense a so-called type 1 gas (a gas that condenses at a relatively high temperature, such as steam) on a surface thereof.
In order to provide a cryogenic surface that condenses a type 2 gas (for example, a gas that condenses at a relatively low temperature, such as argon and nitrogen), the cryopanel 38 is thermally coupled to the second cooling stage 34 and is cooled to the second cooling temperature. In addition, in order to adsorb a type 3 gas (for example, a non-condensable gas, such as hydrogen), for example, activated carbon or other adsorbents are disposed on at least a part of a surface (for example, a surface on the opposite side to the cryopump intake port 17) of the cryopanel 38. A gas that enters the radiation shield 36 from the outside of the cryopump 10 through the cryopump intake port 17 is captured on the cryopanel 38 through condensation or adsorption. Since various known configurations can be adopted as appropriate as forms that can be taken, such as the disposition and shape of the radiation shield 36 or the cryopanel 38, description thereof will not be made in detail herein.
The cryopump container 16 includes a container body 16a and a cryocooler accommodating tube 16b. The cryopump container 16 is a vacuum chamber designed to maintain vacuum during a vacuum exhaust operation of the cryopump 10 and to withstand the pressure of an ambient environment (for example, the atmospheric pressure). The container body 16a has a tubular shape of which one end includes the cryopump intake port 17 and the other end is closed. The radiation shield 36 is accommodated in the container body 16a, and the cryopanel 38 is accommodated in the radiation shield 36 together with the second cooling stage 34 as described above. The cryocooler accommodating tube 16b includes one end coupled to the container body 16a and the other end fixed to the room temperature portion 26 of the cryocooler 14. The cryocooler 14 is inserted into the cryocooler accommodating tube 16b, and the first cylinder 28 is accommodated in the cryocooler accommodating tube 16b.
In the embodiment, the cryopump 10 is a so-called horizontal cryopump in which the cryocooler 14 is provided at a side portion of the container body 16a. A cryocooler insertion opening is provided in the side portion of the container body 16a, and the cryocooler accommodating tube 16b is coupled to the side portion of the container body 16a at the cryocooler insertion opening. Similarly, a hole through which the cryocooler 14 passes is also provided in a side portion of the radiation shield 36 adjacent to the cryocooler insertion opening of the container body 16a. The second cylinder 32 and the second cooling stage 34 of the cryocooler 14 are inserted into the radiation shield 36 through the hole, and the radiation shield 36 is thermally coupled to the first cooling stage 30 around the hole of the side portion.
The cryopump can be provided at a site where the cryopump is to be used in various postures. For example, the cryopump 10 can be provided in a shown horizontal posture, that is, a posture in which the cryopump intake port 17 faces upward. In this case, a bottom portion of the container body 16a is positioned below the cryopump intake port 17, and the cryocooler 14 extends in a horizontal direction.
The cryopump 10 includes a first temperature sensor 40 for measuring the temperature of the first cooling stage 30 and a second temperature sensor 42 for measuring the temperature of the second cooling stage 34. The first temperature sensor 40 is attached to the first cooling stage 30. The second temperature sensor 42 is attached to the second cooling stage 34. The first temperature sensor 40 can measure the temperature of the radiation shield 36 and output a first measured temperature signal indicating the measured temperature of the radiation shield 36. The second temperature sensor 42 can measure the temperature of the cryopanel 38 and output a second measured temperature signal indicating the measured temperature of the cryopanel 38. In addition, a pressure sensor 44 is provided inside the cryopump container 16. The pressure sensor 44 is provided in, for example, the cryocooler accommodating tube 16b, can measure the internal pressure of the cryopump container 16, and can output a measured pressure signal indicating the measured pressure.
In addition, the cryopump 10 includes a controller 46 that controls the cryopump 10. The controller 46 may be provided integrally with the cryopump 10 or may be configured as a control device separate from the cryopump 10.
The controller 46 may control the cryocooler 14 based on a cooling temperature of the radiation shield 36 and/or the cryopanel 38 in a vacuum exhaust operation of the cryopump 10. The controller 46 may be connected to the first temperature sensor 40 to receive a first measured temperature signal from the first temperature sensor 40 and may be connected to the second temperature sensor 42 to receive a second measured temperature signal from the second temperature sensor 42.
In addition, the controller 46 can operate as a regeneration controller of the cryopump 10. In a regeneration operation of the cryopump 10, the controller 46 may control the cryocooler 14, the rough valve 18, the body purge valve 20, the exhaust valve 22, and the exhaust purge valve 24 based on a pressure in the cryopump container 16 (or, as necessary, based on the temperature of the cryopanel 38 and the pressure in the cryopump container 16). The controller 46 may be connected to the pressure sensor 44 to receive a measured pressure signal from the pressure sensor 44.
An internal configuration of the controller 46 is realized by an element or a circuit including a CPU and a memory of a computer as a hardware configuration and is realized by a computer program or the like as a software configuration, but is shown in the drawings as a functional block realized in cooperation therewith as appropriate. It is clear for those skilled in the art that the functional blocks can be realized in various manners in combination with hardware and software.
For example, the controller 46 can be mounted in combination with a processor (hardware), such as a central processing unit (CPU) and a microcomputer, and a software program executed by the processor (hardware). The software program may be a computer program for causing the controller 46 to execute regeneration of the cryopump 10.
The rough valve 18 is provided at the cryopump container 16, for example, the cryocooler accommodating tube 16b. The rough valve 18 is connected to a rough pump (not shown) provided outside the cryopump 10. The rough pump is a vacuum pump for evacuating the cryopump 10 to an operation start pressure thereof. When the rough valve 18 is opened through control of the controller 46, the cryopump container 16 communicates with the rough pump, and when the rough valve 18 is closed, the cryopump container 16 is blocked from the rough pump. The cryopump 10 can be depressurized by opening the rough valve 18 and operating the rough pump.
The body purge valve 20 is provided at the cryopump container 16, for example, the container body 16a. The body purge valve 20 is connected to a purge gas source 48 or a purge gas supply device provided outside the cryopump 10. When the body purge valve 20 is opened through control of the controller 46, a purge gas is supplied from the purge gas source 48 to the cryopump container 16, and when the body purge valve 20 is closed, purge gas supply to the cryopump container 16 is blocked. By opening the body purge valve 20 and introducing the purge gas into the cryopump container 16, the cryopump 10 can be pressurized. In addition, the temperature of the cryopump 10 can be increased from a cryogenic temperature to the room temperature or a temperature higher than the room temperature.
A purge gas may be, for example, a nitrogen gas or other dry gases, and the temperature of the purge gas may be adjusted to, for example, a room temperature (higher than 0° C., for example, 15° C. to 30° C.) or may be heated to a temperature higher than the room temperature (for example, 50° C. or lower or 80° C. or lower).
The exhaust valve 22 is provided at the cryopump container 16, for example, the cryocooler accommodating tube 16b. The exhaust valve 22 is provided as an outlet of the cryopump container 16 in order to exhaust a fluid from the inside to the outside of the cryopump 10. The exhaust valve 22 is also an inlet to an exhaust line 50 to be described later. When the exhaust valve 22 is opened through control of the controller 46, the fluid is exhausted from the cryopump container 16, and when the exhaust valve 22 is closed, fluid exhaust from the cryopump container 16 is blocked. The fluid exhausted from the exhaust valve 22 is basically a gas, but may be a liquid or a mixture of a gas and a liquid. The exhaust valve 22 may be, for example, a normally closed type control valve. In addition, the exhaust valve 22 may function as a vent valve or a safety valve or may be configured to be mechanically opened when a predetermined differential pressure acts. In this case, the exhaust valve 22 is mechanically opened without requiring control when a pressure inside the cryopump becomes high for some reason. Accordingly, the high pressure inside can be released to the exhaust line 50.
The exhaust purge valve 24 is provided in order to supply a purge gas to the exhaust line 50. The exhaust valve 22 and the exhaust purge valve 24 may be separately provided, and the exhaust purge valve 24 may be connected by a pipe downstream of the exhaust valve 22. Alternatively, the exhaust purge valve 24 may be provided integrally with the exhaust valve 22 to supply the purge gas to the exhaust valve 22 or downstream thereof. The exhaust purge valve 24 may be provided at the cryopump container 16, for example, the cryocooler accommodating tube 16b. The exhaust purge valve 24 is connected to the purge gas source 48 or another purge gas source. When the exhaust purge valve 24 is opened through control of the controller 46, the purge gas is supplied from the purge gas source 48 to the exhaust line 50, and when the exhaust purge valve 24 is closed, purge gas supply to the exhaust line 50 is blocked.
The exhaust line 50 is provided in order to exhaust an exhaust fluid from the cryopump 10 to a treatment device 60, is connected to the exhaust valve 22 and the exhaust purge valve 24 at an upstream end thereof, and is connected to the treatment device 60 at a downstream end thereof.
The treatment device 60 may be, for example, an abatement device that treats a hazardous gas (for example, a hydrogen gas, other gases having explosiveness, or other gases having corrosiveness or toxicity) contained in an exhaust fluid to generate a harmless gas or may be a treatment device that treats the hazardous gas to reduce a hazard thereof. Since a known abatement device or treatment device can be adopted as appropriate as the treatment device 60, details thereof will not be described herein.
The exhaust line 50 includes an (additional) purge gas receiving port 52 on a treatment device 60 side with respect to the exhaust purge valve 24. The purge gas receiving port 52 is at the downstream end of the exhaust line 50 and is connected to the treatment device 60. As shown, the purge gas receiving port 52 may be adjacent to the treatment device 60. Alternatively, the purge gas receiving port 52 and the treatment device 60 may not be adjacent to each other, and the purge gas receiving port 52 may be connected to the treatment device 60 via other devices included in the exhaust line 50.
An additional exhaust purge valve 54 may be connected to the purge gas receiving port 52. The additional exhaust purge valve 54 may be connected to the purge gas source 48 or another purge gas source. The exhaust purge valve 54 may constitute a part of the cryopump 10 and may be controlled by the controller 46. When the exhaust purge valve 54 is opened, a purge gas is supplied from the purge gas source 48 to the exhaust line 50, and when the exhaust purge valve 54 is closed, purge gas supply to the exhaust line 50 is blocked.
Therefore, the exhaust purge valve 24 supplies a purge gas to the exhaust line 50 on an upstream side (exhaust valve 22 side) of the exhaust line 50, and the additional exhaust purge valve 54 supplies the purge gas to the exhaust line 50 on a downstream side (treatment device 60 side) of the exhaust line 50. The body purge valve 20 enables “body purge” in which the purge gas is supplied to the container body 16a of the cryopump container 16, the exhaust purge valve 24 enables “upstream purge” in which the purge gas is supplied to the upstream end of the exhaust line 50, and the additional exhaust purge valve 54 enables “downstream purge” in which the purge gas is supplied to the downstream end of the exhaust line 50.
The flow rate of each of body purge, upstream purge, and downstream purge may be selected from, for example, a range of 20 L/min to 100 L/min. The flow rates of the body purge, the upstream purge, and the downstream purge may be equal to each other or may be different from each other. As will be described later, the flow rate of the downstream purge may be great compared to the flow rate of the upstream purge (or the body purge).
As will be described later, the exhaust valve 22 and the exhaust purge valve 24 of another cryopump 10 may be connected to the purge gas receiving port 52, and downstream purge of the exhaust line 50 may be performed by supply of a purge gas from another cryopump 10.
The exhaust line 50 includes a buffer volume 56, and an exhaust fluid from the cryopump container 16 flows from the exhaust valve 22 into the treatment device 60 by passing through the buffer volume 56. The exhaust purge valve 24 supplies a purge gas to the upstream side of the exhaust line 50 with respect to the buffer volume 56, and the additional exhaust purge valve 54 supplies the purge gas to the downstream side of the exhaust line 50 with respect to the buffer volume 56.
It is advantageous to provide the buffer volume 56 at the exhaust line 50 in suppressing a concentration peak of a hazardous gas in the exhaust line 50 as will be described later. The buffer volume 56 may be, for example, 1 liter (L) or larger or 3 L or larger. From a perspective of space saving, the buffer volume 56 may have, for example, a volume of 30 L or less or 10 L or less. The buffer volume 56 may be a volume of a pipe constituting the exhaust line 50, that is, a pipe connecting the exhaust valve 22 to the treatment device 60. Alternatively, in a case where a large volume is desired for the buffer volume 56, the buffer volume 56 may be configured by a pipe constituting the exhaust line 50 and a buffer tank connected to the pipe. The pipe may be a flexible pipe or a rigid pipe.
A gas is accumulated in the cryopump 10 as a vacuum exhaust operation of the cryopump 10 is continued. Regeneration of the cryopump 10 is performed in order to exhaust the accumulated gas to the outside. The regeneration of the cryopump 10 generally includes a temperature raising process, an exhaust process, and a cool-down process.
A temperature raising process includes raising the temperature of the cryopump 10 to a melting point of a hazardous gas or a temperature exceeding the melting point among gases captured in the cryopump 10 and further raising the temperature of the cryopump 10 to a regeneration temperature. The hazardous gas is typically, for example, a type 2 gas or a type 3 gas, and the melting point of the hazardous gas is, for example, 100 K or less. The regeneration temperature is, for example, a room temperature or a temperature higher than the room temperature. Accordingly, in many cases, the hazardous gas is re-vaporized in a first half of the temperature raising process, particularly immediately after the start and is exhausted from the cryopump 10 to be flowed into the treatment device 60. The hazardous gas is removed from the cryopump 10 in the temperature raising process.
A heat source for raising the temperature is, for example, the cryocooler 14. The cryocooler 14 enables a temperature raising operation (a so-called reverse temperature rise). That is, the cryocooler 14 is configured such that adiabatic compression occurs in a working gas when the drive mechanism provided at the room temperature portion 26 operates in a direction opposite to a direction in a cooling operation. The cryocooler 14 heats the first cooling stage 30 and the second cooling stage 34 with compression heat obtained in such a manner. The radiation shield 36 and the cryopanel 38 are heated with the first cooling stage 30 and the second cooling stage 34 as heat sources, respectively. In addition, also a purge gas supplied from the body purge valve 20 into the cryopump container 16 also contributes to a temperature rise of the cryopump 10. Alternatively, the cryopump 10 may be provided with, for example, a heating device such as an electric heater. For example, the electric heater that can be controlled independently of the operation of the cryocooler 14 may be mounted on the first cooling stage 30 and/or the second cooling stage 34 of the cryocooler 14.
In an exhaust process, a gas captured in the cryopump 10 is re-vaporized or liquefied and is exhausted through the exhaust line 50 or the rough valve 18 as a gas, a liquid, or a mixture of a gas and a liquid. Since a type 2 gas and a type 3 gas can already be easily exhausted from the cryopump 10 in a temperature raising process, the exhaust process is a process of mainly exhausting a type 1 gas. When the exhaust process is completed, a cooldown process is started. In the cool-down process, the cryopump 10 is re-cooled to a cryogenic temperature for a vacuum exhaust operation. In such a manner, when regeneration is completed, the cryopump 10 can start a vacuum exhaust operation again.
One main application of the cryopump 10 is vacuum exhaust of the ion implanter. In this case, a hydrogen gas is stored in the cryopump 10. The hydrogen gas captured in the cryopanel 38 can be re-vaporized at once during regeneration, particularly immediately after the start of the regeneration (temperature raising process). Although the hydrogen gas is diluted through body purge in the cryopump container 16, an exhaust fluid flowing from the cryopump container 16 to the treatment device 60 through the exhaust line 50 can temporarily contain the hydrogen gas at a considerably high concentration. Since the high-concentration hydrogen gas has a risk of explosion or combustion, it is desired to suppress a concentration peak of the hydrogen gas in the exhaust fluid as low as possible for safety management of the cryopump 10 and the exhaust line 50.
Calculation conditions are as follows. The volume of the cryopump 10 (that is, the cryopump container 16) is set to 30 L, and an initial concentration of a hydrogen gas in the cryopump container 16 is set to 60% (corresponding to a maximum storage capacity of the hydrogen gas of the cryopump 10). In addition, the flow rate of body purge (the flow rate of a purge gas supplied from the body purge valve 20 to the cryopump container 16) is set to 20 L/min, the flow rate of upstream purge (the flow rate of the purge gas supplied upstream of the exhaust line 50 from the exhaust purge valve 24) is set to 20 L/min, and the flow rate of downstream purge is set to 0 L/min (that is, the downstream purge is not performed). The conditions are common to the calculation of
When regeneration (temperature raising process) is started, the body purge valve 20, the exhaust valve 22, and the exhaust purge valve 24 are simultaneously opened by the controller 46. At a regeneration start time point, a hydrogen gas concentration at the purge gas receiving port 52 is 0%, as shown. By transporting an exhaust fluid downstream of the exhaust line 50 from the cryopump container 16 together with body purge and upstream purge, the hydrogen gas concentration at the purge gas receiving port 52 temporarily increases, and the concentration reaches a peak. After then, as the exhaust fluid flows into the treatment device 60, the hydrogen gas concentration at the purge gas receiving port 52 gradually decreases again to 0%. Such a tendency of a concentration change is common regardless of the size of the buffer volume 56, as shown in
Due to an effect of upstream purge having the same flow rate as in body purge, a hydrogen gas concentration peak of an exhaust fluid upstream of the buffer volume 56 is estimated to be half (that is, 30%) of the initial concentration. From there, as the exhaust fluid flowing into the buffer volume 56 and a purge gas that initially fills the buffer volume 56 are mixed, it is expected that the hydrogen gas concentration peak downstream of the buffer volume 56, that is, at the purge gas receiving port 52 is further lowered to some extent according to the volume of the buffer volume 56.
By comparing the hydrogen gas concentration peaks shown in
Calculation conditions are as follows. The volume of the cryopump 10 (that is, the cryopump container 16) is set to 30 L, and an initial concentration of a hydrogen gas in the cryopump container 16 is set to 60%. In addition, the buffer volume 56 is set to 30 L. The conditions are common to the calculation of
When regeneration (temperature raising process) is started, the body purge valve 20, the exhaust valve 22, the exhaust purge valve 24, and the additional exhaust purge valve 54 (in a case where downstream purge is performed) are simultaneously opened by the controller 46. The tendency of a change in a hydrogen gas concentration at the purge gas receiving port 52 is that the concentration is initially 0% and temporarily increases to reach a concentration peak, and then gradually decreases to 0% again. This is common to
By comparing the hydrogen gas concentration peaks shown in
As shown in
As shown in
Next, a flow rate ratio of body purge, upstream purge, and downstream purge will be focused on. According to the study of the inventor, when a cryopump volume and the buffer volume are set to be constant, a hydrogen gas concentration peak at the purge gas receiving port 52 is determined by the flow rate ratio of the body purge, the upstream purge, and the downstream purge. The magnitudes of the flow rates of the body purge, the upstream purge, and the downstream purge itself affect a time required for exhaust (a time until the hydrogen gas concentration becomes 0% again from the regeneration start), but do not affect the hydrogen gas concentration peak at the purge gas receiving port 52.
In view of this, increasing the flow rate of downstream purge compared to the flow rate of body purge (or upstream purge) is effective in order to suppress a peak of a hydrogen gas concentration in an exhaust fluid at the purge gas receiving port 52 of the exhaust line 50, that is, the exhaust fluid flowing into the treatment device 60. In addition, the flow rate of the downstream purge may be great compared to a total flow rate of the body purge and the upstream purge. Even in this manner, the peak of the hydrogen gas concentration in the exhaust fluid flowing into the treatment device 60 can be suppressed.
As is known, in a case where a hydrogen gas concentration is 4% or less, a hydrogen gas does not combust. Accordingly, it is beneficial in terms of safety to suppress a hydrogen gas concentration peak at the purge gas receiving port 52 to be 4% or less.
Thus when exemplary conditions in which a hydrogen gas concentration peak is set to 4% or less are considered, for example, under the conditions of
An increase in the amount of a hydrogen gas stored in the cryopump 10 is suppressed, so that a hydrogen gas concentration peak at the time of regeneration can be suppressed. For example, when a hydrogen gas initial concentration is set to 13% (when a hydrogen gas storage capacity of the cryopump 10 is set to a maximum value of 22% (=13/60*100)) under the conditions of
Therefore, in a case where the buffer volume 56 is relatively small (less than 10 L, for example, 3 L), the flow rate of downstream purge may be selected from a range of 1 time to 11 times the flow rate of body purge (or upstream purge). On the other hand, in a case where the buffer volume 56 is relatively large (for example, 10 L or more and 30 L or less), the flow rate of the downstream purge may be selected from a range of 1 time to 6 times the flow rate of the body purge (or the upstream purge). In this manner, it is expected that a hydrogen gas concentration peak at the purge gas receiving port 52 can be suppressed to approximately 4% or less.
As described above, according to the embodiment, as the exhaust line 50 has the buffer volume 56, a hazardous gas that is exhausted from the cryopump 10 and that flows into the treatment device 60 can be efficiently diluted, and a concentration peak of the hazardous gas can be suppressed. In addition, according to the embodiment, as downstream purge is applied to the exhaust line 50, the hazardous gas that flows into the treatment device 60 can be efficiently diluted, and the concentration peak of the hazardous gas can be suppressed. The consumption of a purge gas can be suppressed compared to a case where only body purge (or upstream purge) is used.
In the above description, a hydrogen gas is given as an example, but the hazardous gas is typically a type 2 gas or a type 3 gas, and a concentration change in the exhaust line 50 is the same as that of the hydrogen gas. Therefore, the buffer volume 56 and the downstream purge are also effective for other hazardous gases in efficiently diluting the hazardous gases flowing into the treatment device 60 and suppressing concentration peaks of the hazardous gases.
Each of the cryopumps 10 includes the rough valve 18, the body purge valve 20, the exhaust valve 22, and the exhaust purge valve 24, and these are provided at the cryopump container 16 of each cryopump. The cryopump system is provided with the controller 46 that controls the plurality of cryopumps 10, and the controller 46 can operate as a regeneration controller that controls each of the valves described above of each cryopump 10 during regeneration of the plurality of cryopumps 10. The configuration of the cryopump 10 shown in
The exhaust line 50 is provided in order to exhaust an exhaust fluid from the plurality of cryopumps 10 to the treatment device 60. The exhaust line 50 includes a plurality of branch lines 50a and a merging line 50b that connects the plurality of branch lines 50a to the treatment device 60. Each of the branch lines 50a is connected to the exhaust valve 22 and the exhaust purge valve of the corresponding cryopump 10 at the upstream end and is connected to the merging line 50b at the downstream end.
Each of the branch lines 50a includes the buffer volume 56 that connects the exhaust valve 22 of the corresponding cryopump 10 to the merging line 50b. The buffer volume 56 of each branch line 50a may be in a range of 1 liter to 30 liters as described above. The exhaust purge valve 24 of each cryopump 10 is connected to the branch line 50a on the upstream side (exhaust valve 22 side) with respect to the buffer volume 56. An exhaust fluid from the cryopump container 16 of each of the cryopumps 10 merges in the merging line 50b by passing through the buffer volume 56 of each of the branch lines 50a of the exhaust line 50 from the exhaust valve 22 of each of the cryopumps 10 and flows into the treatment device 60.
The body purge valve 20 of each cryopump 10 enables body purge of the cryopump 10. The exhaust purge valve 24 of each cryopump 10 supplies a purge gas to the upstream side of the exhaust line 50 with respect to the buffer volume 56 and enables upstream purge of the cryopump 10. In addition, the body purge from the body purge valve 20 can also be used as the upstream purge by opening the exhaust valve 22.
The merging line 50b of the exhaust line 50 corresponds to the purge gas receiving port 52 in the embodiment described above. In addition, for a certain cryopump 10 (for example, a first cryopump 10a), the exhaust valve 22 or the exhaust purge valve 24 of another cryopump 10 (for example, a second cryopump 10b or a third cryopump 10c) corresponds to the additional exhaust purge valve 54 in the embodiment described above. Accordingly, downstream purge of the certain cryopump 10 (for example, the first cryopump 10a) is enabled by receiving body purge or upstream purge of another cryopump 10 (for example, the second cryopump 10b or the third cryopump 10c) from the merging line 50b to the branch line 50a of the certain cryopump 10 (for example, the first cryopump 10a).
The cryopump system is provided with a roughing line 58 separately from the exhaust line 50. The roughing line 58 connects the rough valve 18 of each cryopump 10 to a common roughing pump 59. The plurality of cryopumps 10 are roughed by the roughing pump 59 through the rough valve 18 of each cryopump 10 and the roughing line 58.
According to this configuration, while depending on the number of cryopumps 10 included in the cryopump system, it is easy to realize the great flow rate of downstream purge. For example, a total purge gas flow rate from the second cryopump 10b and the third cryopump 10c can be used for the downstream purge of the first cryopump 10a.
However, in this case, it is not desirable that a gas flowing into a certain cryopump 10 (for example, the first cryopump 10a) from another cryopump (for example, the second cryopump 10b or the third cryopump 10c) as downstream purge contains a hazardous gas exhausted from another cryopump.
Thus, in a case where the plurality of cryopumps 10 are regenerated simultaneously, regeneration start of a certain cryopump 10 may be prioritized over the remaining cryopumps 10. In other words, regeneration start of the remaining cryopumps 10 may be delayed with respect to the cryopump 10 that starts the regeneration first. The delay time may be, for example, several minutes (for example, 2 minutes to 10 minutes).
Therefore, the controller 46 may be configured to control a certain cryopump 10 so that an exhaust fluid is exhausted from the certain cryopump 10 to the treatment device 60 and to control another cryopump 10 so that a purge gas is supplied from another cryopump 10 to the merging line 50b of the exhaust line 50. The controller 46 may be configured to open the body purge valve 20 of the certain cryopump 10 in order to exhaust the exhaust fluid from the certain cryopump 10 to the treatment device 60. The controller 46 may be configured to open the exhaust purge valve 24 of the other cryopump 10 in order to supply the purge gas from another cryopump 10 to the merging line 50b of the exhaust line 50.
In this manner, first, regeneration (temperature raising process) of the first cryopump 10a is started, and an exhaust fluid is exhausted from the first cryopump 10a to the exhaust line 50 by using body purge of the first cryopump 10a. The exhaust purge valves 24 of the remaining second cryopump 10b and the third cryopump 10c are opened, and the first cryopump 10a can efficiently dilute the exhaust fluid flowing into the treatment device 60 using a purge gas from the two cryopumps 10b and 10c as downstream purge.
After a hazardous gas is exhausted from the first cryopump 10a in this manner, regeneration (temperature raising process) of any one (for example, the second cryopump 10b) of the remaining cryopumps 10 is started. Body purge and upstream purge of the first cryopump 10a can be used as downstream purge for the second cryopump 10b. The upstream purge of the third cryopump 10c can also be continuously used as the downstream purge for the second cryopump 10b.
Then, after a hazardous gas is exhausted from the second cryopump 10b, regeneration (temperature raising process) of the third cryopump 10c is started. Body purge and upstream purge of the first cryopump 10a and the second cryopump 10b can be used as downstream purge for the third cryopump 10c.
The controller 46 may be configured to open both the body purge valve 20 and the exhaust purge valve 24 of a certain cryopump 10 in order to exhaust an exhaust fluid from the certain cryopump 10 to the treatment device 60. In this manner, the exhaust fluid can be efficiently exhausted from the cryopump 10 to the exhaust line 50 by using body purge and upstream purge.
The controller 46 may be configured to control the cryocooler 14 so that another cryopump 10 is cooled to prevent generation of an exhaust fluid in the cryopump container 16 of another cryopump 10, and to open the exhaust purge valve 24 of another cryopump 10. In this manner, when regeneration (temperature raising process) of the first cryopump 10a is started, the remaining second cryopump 10b and third cryopump 10c can be maintained in a cooling state, and exhaust from the remaining cryopumps 10b and 10c can be reliably blocked. At the same time, the first cryopump 10a can efficiently dilute the exhaust fluid flowing into the treatment device 60 using a purge gas from the two cryopumps 10b and 10c as downstream purge.
The controller 46 may be configured to control a certain cryopump 10 and another cryopump 10 so that the flow rate of a purge gas from another cryopump 10 to the merging line 50b is increased compared to the flow rate of the purge gas from the certain cryopump 10 to the merging line 50b. In this manner, the flow rate of downstream purge can be increased compared to the flow rate of body purge (or upstream purge), which is effective in suppressing a peak of a hazardous gas concentration in an exhaust fluid flowing into the treatment device 60.
Considering exemplary conditions in which a concentration peak of a hydrogen gas is set to 4% or less, for example, when the cryopump volume is set to 30 L, the buffer volume 56 of each of the branch lines 50a of the exhaust line 50 is set to 10 L, the hydrogen gas initial concentration is set to 60%, and the flow rates of body purge and upstream purge of each cryopump 10 are set to 20 L/min and 60 L/min, respectively (in this case, downstream purge corresponds to 160 L/min), a hydrogen gas concentration peak in the merging line 50b of the exhaust line 50 can be set to 4.0%.
In addition, in this example, in a case where a hydrogen gas initial concentration is decreased to 25%, a hydrogen gas concentration peak in the merging line 50b of the exhaust line 50 can be set to less than 4.0% even when the buffer volume 56 of each of the branch lines 50a of the exhaust line 50 is reduced to 3 L and the flow rates of the body purge and the upstream purge of each cryopump 10 are decreased to 20 L/min.
The present invention has been described hereinbefore based on the examples. It is clear for those skilled in the art that the present invention is not limited to the embodiments, various design changes are possible, various modification examples are possible, and such modification examples are also within the scope of the present invention.
The present invention can be used in the field of cryopump systems and regeneration controllers for cryopump systems.
It should be understood that the invention is not limited to the above-described embodiment, but may be modified into various forms on the basis of the spirit of the invention. Additionally, the modifications are included in the scope of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-013219 | Jan 2022 | JP | national |
This is a bypass continuation of International PCT Application No. PCT/JP2022/048620, filed on Dec. 28, 2022, which claims priority to Japanese Patent Application No. 2022-013219, filed on Jan. 31, 2022, which are incorporated by reference herein in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2022/048620 | Dec 2022 | WO |
| Child | 18779408 | US |
