TWI846332B - Cryogenic pump and method for operating the same - Google Patents

Abstract

The present invention provides a cryogenic pump that can mitigate the overshoot of the cryogenic plate temperature that may occur during the crossover. The cryogenic pump (10) can be installed in a vacuum chamber via a gate valve (102). The cryogenic pump (10) has: a freezer (14); and a controller (60) configured to detect whether the gate valve (102) is closed, and control the freezer (14) so that the freezing capacity of the freezer (14) when the gate valve (102) is closed is increased compared to when the gate valve (102) is opened.

Description

Cryogenic pump and method for operating the same

The present invention relates to a cryogenic pump and an operating method of the cryogenic pump.

A cryogenic pump is a vacuum pump that captures gas molecules on a cryogenic plate cooled to an extremely low temperature by condensation or adsorption and exhausts the gas. Cryogenic pumps are generally used to achieve a clean vacuum environment required in semiconductor circuit manufacturing processes, etc. [Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Application Publication No. 2012-237293

[The problem the invention is trying to solve]

In order to fully increase the vacuum degree of the vacuum chamber as a preparation for starting the vacuum process in the vacuum chamber of the vacuum process device, the vacuum chamber is first roughly pumped, and then switched to vacuum exhaust based on the cryogenic pump. When the vacuum chamber is roughly pumped, the gate valve set between the vacuum chamber and the cryogenic pump is closed, and the gate valve is opened to start the vacuum exhaust based on the cryogenic pump. At this time, the arrival pressure in the cryogenic pump is much lower than the rough pumping pressure of the vacuum chamber. Therefore, a large amount of gas flows from the vacuum chamber into the cryogenic pump at once, which becomes a heat load on the freezer that cools the cryogenic pump, and may cause the temperature of the cryogenic plate to overshoot. Such a temperature rise is also called crossover. The temperature rise of the cryoplate may in some cases have a negative impact on the exhaust performance of the cryo pump.

In addition, as a unique setting in the vacuum sequencer, the allowable range of the low temperature plate temperature may be pre-set. If the above-mentioned overshoot is detected to exceed the allowable temperature range, the vacuum sequencer may perform actions to ensure safety, such as issuing an alarm or emergency closing of the gate valve. The vacuum sequencer will be in standby until the low temperature plate temperature returns to the allowable range, and the start of the vacuum sequence will be delayed accordingly.

One of the exemplary purposes of an embodiment of the present invention is to provide a low-temperature pump that can mitigate the overshoot of the low-temperature plate temperature that may occur during the crossover. [Technical means for solving the problem]

According to one embodiment of the present invention, a cryogenic pump capable of being installed in a vacuum chamber via a gate valve is provided. The cryogenic pump comprises: a freezer; and a controller configured to detect whether the gate valve is closed and control the freezer so that the freezing capacity of the freezer when the gate valve is closed is increased compared to when the gate valve is open.

According to an embodiment of the present invention, a method for operating a cryogenic pump is provided. The cryogenic pump can be installed in a vacuum chamber via a gate valve and is provided with a freezer. The method comprises the following steps: a step of detecting whether the gate valve is closed; and a step of increasing the freezing capacity of the freezer when the gate valve is closed compared to when the gate valve is open.

According to one embodiment of the present invention, a cryogenic pump is provided with: a refrigerator; and a controller for detecting whether the regeneration of the cryogenic pump is completed and controlling the refrigerator to temporarily increase the refrigeration capacity of the refrigerator after the regeneration is completed.

According to an embodiment of the present invention, a method for operating a cryogenic pump is provided. The cryogenic pump is provided with a refrigerator. The method comprises the following steps: a step of detecting whether the regeneration of the cryogenic pump is completed; and a step of temporarily increasing the refrigeration capacity of the refrigerator after the regeneration is completed.

Furthermore, any combination of the above constituent elements or replacement of the constituent elements or expressions of the present invention between methods, devices, systems, etc. are also valid as implementation modes of the present invention. [Effects of the invention]

According to the present invention, a low temperature pump can be provided, which can alleviate the overshoot of the low temperature plate temperature that may occur during the crossover.

Hereinafter, the method for implementing 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 processes are marked with the same element symbols, and repeated descriptions are omitted as appropriate. The scale or shape of each part shown in the figure is simply set for the convenience of explanation, and unless otherwise specifically stated, it is not interpreted in a limiting sense. The implementation method is an example and does not limit the scope of the present invention in any way. All features or combinations thereof recorded in the implementation method are not necessarily the essence of the invention.

Fig. 1 is a diagram schematically showing a cryogenic pump 10 according to an embodiment. Fig. 2 is a block diagram schematically showing a structure of a control device of the cryogenic pump 10 according to an embodiment.

The cryogenic pump 10 can be installed in a vacuum chamber 100 of an ion implantation apparatus, a sputtering apparatus, an evaporation apparatus, or other vacuum process apparatuses via a gate valve 102. FIG1 shows a portion of the vacuum chamber 100 and the gate valve 102 together with the cryogenic pump 10.

The cryogenic pump 10 is installed in the vacuum chamber 100 via the gate valve 102 to increase the vacuum degree inside the vacuum chamber 100 to the level required by the desired vacuum process. The cryogenic pump 10 has a cryogenic pump air intake port (hereinafter also referred to as "air intake port") 12 for receiving the gas to be exhausted from the vacuum chamber 100. The gas enters the internal space of the cryogenic pump 10 from the vacuum chamber 100 through the gate valve 102 and the air intake port 12.

Furthermore, in the following, in order to easily understand the positional relationship of the components of the cryogenic pump 10, there will be cases where the terms "axial" and "radial" are used. The axial direction of the cryogenic pump 10 represents the direction through the air intake port 12 (that is, the direction along the central axis of the cryogenic pump 10, which is the up and down direction in the figure), and the radial direction represents the direction along the air intake port 12 (the direction perpendicular to the central axis of the cryogenic pump 10, which is the left and right direction in the figure). For the sake of convenience, there will be a situation where the position relatively close to the air intake port 12 in the axial direction is called "up" and the position relatively far from the air intake port 12 is called "down". That is, there will be a situation where the position relatively far from the bottom of the cryogenic pump 10 is called "up" and the position relatively close to the bottom of the cryogenic pump 10 is called "down". Regarding the radial direction, the position near the center of the air inlet 12 may be referred to as "inside" and the position near the periphery of the air inlet 12 may be referred to as "outside". Furthermore, such a description has nothing to do with the configuration when the cryopump 10 is installed in the vacuum chamber 100. For example, the cryopump 10 may be installed in the vacuum chamber 100 in such a manner that the air inlet 12 faces downward in the vertical direction.

In addition, the direction surrounding the axial direction may be referred to as the “circumferential direction.” The circumferential direction is the second direction along the air intake port 12 and is the tangent direction orthogonal to the radial direction.

The cryopump 10 includes a freezer 14, a cryopump container 16, a first-stage cryopanel 18, and a cryopanel unit 20. The first-stage cryopanel 18 can also be referred to as a high-temperature cryopanel unit or a 100K unit. The cryopanel unit 20 is a second-stage cryopanel unit and can also be referred to as a low-temperature cryopanel unit or a 10K unit.

The freezer 14 is, for example, an ultra-low temperature freezer such as a Gifford-McMahon freezer (so-called GM freezer). The freezer 14 is a two-stage freezer and has a first cooling stage 22 and a second cooling stage 24. The freezer 14 is configured to cool the first cooling stage 22 to a first cooling temperature and cool the second cooling stage 24 to a second cooling temperature. The second cooling temperature is lower than the first cooling temperature. For example, the first cooling stage 22 is cooled to about 60K~120K, preferably 80K~100K, and the second cooling stage 24 is cooled to about 10K~20K. The first cooling stage 22 and the second cooling stage 24 may also be referred to as a high temperature cooling stage and a low temperature cooling stage, respectively.

In addition, the freezer 14 includes a freezer structure 21, and the freezer structure 21 structurally supports the second cooling stage 24 by the first cooling stage 22, and structurally supports the first cooling stage 22 by the room temperature portion 26 of the freezer 14. Therefore, the freezer structure 21 includes a first cylinder 23 and a second cylinder 25 extending coaxially in the radial direction. The first cylinder 23 connects the room temperature portion 26 of the freezer 14 with the first cooling stage 22. The second cylinder 25 connects the first cooling stage 22 with the second cooling stage 24. Typically, the first cooling stage 22 and the second cooling stage 24 are formed of a high thermal conductivity metal material such as copper (e.g., pure copper), and the first cylinder 23 and the second cylinder 25 are formed of other metal materials such as stainless steel. The room temperature portion 26, the first cylinder 23, the first cooling stage 22, the second cylinder 25, and the second cooling stage 24 are sequentially arranged in a straight line.

A first displacer and a second displacer (not shown) are disposed inside each of the first cylinder 23 and the second cylinder 25 in a manner capable of reciprocating movement. A first cold storage device and a second cold storage device (not shown) are respectively assembled on the first displacer and the second displacer. Furthermore, the room temperature portion 26 has a driving mechanism (not shown) for reciprocating the first displacer and the second displacer. The driving mechanism includes the refrigerator motor 50 described later. Furthermore, the driving mechanism includes a flow path switching mechanism that switches the flow path of the working gas in a manner that cyclically repeats the supply and discharge of the working gas (e.g., helium) inside the refrigerator 14.

The refrigerator 14 is connected to a compressor (not shown) for the working gas. The refrigerator 14 expands the working gas compressed by the compressor inside, thereby cooling the first cooling stage 22 and the second cooling stage 24. The expanded working gas is recovered by the compressor and compressed again. The refrigerator 14 generates refrigeration by repeating a heat cycle, which includes the supply and discharge of the working gas and the reciprocating movement of the first displacer and the second displacer in synchronization therewith.

The cryogenic pump 10 shown in the figure is a so-called horizontal cryogenic pump. A horizontal cryogenic pump is usually a cryogenic pump arranged in such a way that the central axis of the freezer 14 and the cryogenic pump 10 intersect (usually orthogonal). Furthermore, the present invention can also be similarly applied to a so-called vertical cryogenic pump. A vertical cryogenic pump is a cryogenic pump arranged in the freezer along the axis of the cryogenic pump.

The cryogenic pump container 16 is a shell of the cryogenic pump 10 that accommodates the freezer 14, the first-stage cryogenic plate 18, and the cryogenic plate unit 20, and is configured to maintain the airtightness of the internal space of the cryogenic pump 10. The cryogenic pump container 16 has an air intake flange 16a that extends radially outward from its front end throughout the entire circumference. The air intake port 12 is defined radially inward by the air intake flange 16a. In addition, the cryogenic pump container 16 has: a container body 16b that extends axially from the air intake flange 16a; a container bottom 16c that closes the container body 16b on the side opposite to the air intake port 12; and a freezer storage cylinder 16d that extends laterally between the air intake flange 16a and the container bottom 16c.

The end of the freezer storage cylinder 16d is mounted on the room temperature portion 26 of the freezer 14 on the side opposite to the container body 16b, whereby the low temperature portion of the freezer 14 (i.e., the first cylinder 23, the first cooling stage 22, the second cylinder 25, and the second cooling stage 24) is arranged in a non-contact manner in the low temperature pump container 16. The first cylinder 23 is arranged in the freezer storage cylinder 16d, and the first cooling stage 22, the second cylinder 25, and the second cooling stage 24 are arranged in the container body 16b. The first stage low temperature plate 18 and the low temperature plate unit 20 are also arranged in the container body 16b.

The first section cryogenic plate 18 has a radiation shield 30 and an inlet cryogenic plate 32, and surrounds the cryogenic plate unit 20. The first section cryogenic plate 18 provides an extremely low temperature surface for protecting the cryogenic plate unit 20 from the influence of radiation heat from the outside of the cryogenic pump 10 or from the cryogenic pump container 16. The first section cryogenic plate 18 is thermally coupled to the first cooling stage 22 and is cooled to a first cooling temperature. There is a gap between the first section cryogenic plate 18 and the cryogenic plate unit 20, and the first section cryogenic plate 18 is not in contact with the cryogenic plate unit 20. The first section cryogenic plate 18 is also not in contact with the cryogenic pump container 16.

The radiation shielding member 30 is provided to protect the cryogenic plate unit 20 from the influence of the radiation heat of the cryogenic pump container 16. The radiation shielding member 30 extends axially in a cylindrical shape (for example, a cylindrical shape) from the air intake port 12 toward the container bottom 16c in the cryogenic pump container 16. The radiation shielding member 30 is open on the air intake port 12 side and is closed on the container bottom 16c side. The radiation shielding member 30 is located between the cryogenic pump container 16 and the cryogenic plate unit 20 and surrounds the cryogenic plate unit 20. The radiation shielding member 30 has a diameter slightly smaller than that of the cryogenic pump container 16, and an outer shielding member gap 31 is formed between the radiation shielding member 30 and the cryogenic pump container 16. Therefore, the radiation shielding member 30 does not contact the cryogenic pump container 16.

The first cooling stage 22 of the freezer 14 is directly mounted on the outer surface of the side of the radiation shielding member 30. In this way, the radiation shielding member 30 is thermally coupled to the first cooling stage 22, and is therefore cooled to the first cooling temperature. Furthermore, the radiation shielding member 30 may also be mounted on the first cooling stage 22 via an appropriate heat conducting member. In addition, the second cooling stage 24 and the second cylinder 25 of the freezer 14 are inserted into the radiation shielding member 30 from the side of the radiation shielding member 30.

In order to protect the cryo plate unit 20 from the influence of radiation heat from the heat source outside the cryopump 10 (for example, the heat source in the vacuum chamber where the cryopump 10 is installed), the inlet cryo plate 32 is provided on the air intake port 12. The inlet cryo plate 32 is thermally coupled to the first cooling stage 22 via the radiation shield 30, and is cooled to the first cooling temperature similarly to the radiation shield 30. Therefore, the gas (for example, moisture) condensed at the first cooling temperature is captured on its surface.

The low temperature plate unit 20 has a plurality of low temperature plates, which are thermally coupled to the second cooling stage 24 and cooled to a second cooling temperature lower than the first cooling temperature. As shown in the figure, the low temperature plates can be arranged axially from the air intake port 12 toward the bottom 16c of the container. An adsorbent material (e.g., activated carbon) can be provided on the surface of at least a portion of the low temperature plate to capture non-condensable gases (e.g., hydrogen) by adsorption. The low temperature plate unit 20 is arranged below the inlet low temperature plate 32 in a manner surrounded by the radiation shield 30 in the low temperature pump container 16. The low temperature plate unit 20 does not contact the radiation shield 30 and the inlet low temperature plate 32. Furthermore, regarding the structure of the low-temperature plate unit 20, such as the configuration and shape of the low-temperature plate, various known structures can be appropriately adopted, so the detailed description is omitted here.

The gate valve 102 is provided between the cryogenic pump 10 and the vacuum chamber 100. The gate valve 102 includes a valve housing 104 and a valve plate 106. The valve housing 104 forms a connecting passage connecting the opening of the vacuum chamber 100 and the air inlet 12 of the cryogenic pump 10. The valve housing 104 has flanges on both sides of the connecting passage, one side of the flange is mounted on the flange of the vacuum chamber 100 surrounding the opening of the vacuum chamber 100, and the other side of the flange is mounted on the air inlet flange 16a.

The gate valve 102 is closed as needed when performing maintenance on the vacuum chamber 100 or the cryogenic pump 10. The flange portion on the side of the air intake flange 16a of the valve housing 104 also functions as a valve seat portion of the gate valve 102, so that the valve plate 106 as the valve body fits tightly against the valve seat portion, thereby closing the gate valve 102. At this time, the flow of gas from the vacuum chamber 100 through the air intake port 12 to the cryogenic pump 10 is blocked. The cryogenic pump 10 is isolated from the vacuum chamber 100, and the internal space of the cryogenic pump 10 is kept airtight.

The gate valve 102 is opened to perform vacuum exhaust of the vacuum chamber 100 by the cryogenic pump 10. A valve plate storage portion 108 is provided on the valve housing 104. As shown by a dotted chain in FIG. 1 , when the valve plate 106 leaves the valve seat portion of the valve housing 104 and is stored in the valve plate storage portion 108, the gate valve 102 is opened. Gas can enter the internal space of the cryogenic pump 10 from the vacuum chamber 100 through the gate valve 102 and the air inlet 12. In this way, in order to perform a desired vacuum process in the vacuum chamber 100, the vacuum chamber 100 can be vacuum exhausted by the cryogenic pump 10.

As shown in FIG. 2 , the cryopump 10 may include: a first temperature sensor 40 for measuring the temperature of the first cooling stage 22; and a second temperature sensor 42 for measuring the temperature of the second cooling stage 24. The first temperature sensor 40 is mounted on the first cooling stage 22 or the first stage low temperature plate 18, and the second temperature sensor 42 is mounted on the second cooling stage 24 or the low temperature plate unit 20. Therefore, the first temperature sensor 40 can measure the temperature of the first stage low temperature plate 18 and output a first measured temperature signal T1 indicating the measured temperature of the first stage low temperature plate 18. The second temperature sensor 42 can measure the temperature of the low temperature plate unit 20 and output a second measured temperature signal T2 indicating the measured temperature of the low temperature plate unit 20.

The freezer 14 has a freezer motor 50 for driving the freezer 14 and a freezer inverter 52 for controlling the operating frequency of the freezer 14. The operating frequency (also referred to as operating speed) of the freezer 14 represents the operating frequency or rotation speed of the freezer motor 50, the operating frequency of the freezer inverter 52, the frequency of the thermal cycle, or any one of the above. The frequency of the thermal cycle is the number of times the thermal cycle is performed in the freezer 14 per unit time.

Furthermore, the cryogenic pump 10 includes a controller 60 for controlling the cryogenic pump 10. The controller 60 may be provided integrally with the cryogenic pump 10, or may be configured as a control device separate from the cryogenic pump 10.

The controller 60 may be connected to the first temperature sensor 40 to receive the first measured temperature signal T1 from the first temperature sensor 40, and may be connected to the second temperature sensor 42 to receive the second measured temperature signal T2 from the second temperature sensor 42. The refrigerator inverter 52 may be disposed in the controller 60.

The controller 60 may be configured to control the freezer 14 according to the cooling temperature of the first stage cryogenic plate 18 or the cooling temperature of the cryogenic plate unit 20 during the vacuum exhaust operation of the cryogenic pump 10. For example, the controller 60 may control the operating frequency of the freezer 14 by feedback control so as to minimize the deviation between the target temperature of the first cooling stage 22 and the measured temperature of the first temperature sensor 40.

The target temperature of the first cooling stage 22 is usually set to a constant value. The target temperature of the first cooling stage 22 is determined, for example, according to the process performed in the vacuum chamber 100 in which the cryopump 10 is installed. The target temperature can be changed as needed when the cryopump 10 is running.

The controller 60 can determine the operating frequency F of the freezer motor 50 according to a function of the deviation between the measured temperature and the target temperature (for example, by PID control). The operating frequency F of the freezer motor 50 is determined within a preset operating frequency range. The operating frequency range is defined by the upper and lower limits of the preset operating frequency. The controller 60 outputs the determined operating frequency F to the freezer inverter 52.

The freezer inverter 52 is configured to provide variable frequency control of the freezer motor 50. The freezer inverter 52 converts input power into an operating frequency F input from the controller 60. The input power to the freezer inverter 52 is supplied from a freezer power source (not shown). The freezer power source may be a commercial power source. The freezer inverter 52 outputs the converted power to the freezer motor 50. In this way, the freezer motor 50 is driven by the operating frequency F determined by the controller 60 and output from the freezer inverter 52.

When the heat load on the cryogenic pump 10 increases, the temperature of the first cooling stage 22 may increase. When the temperature measured by the first temperature sensor 40 is higher than the target temperature, the controller 60 increases the operating frequency of the freezer 14. As a result, the frequency of the heat cycle in the freezer 14 also increases, and the first stage low temperature plate 18 and the first cooling stage 22 are cooled to the target temperature. Conversely, when the temperature measured by the first temperature sensor 40 is lower than the target temperature, the operating frequency of the freezer 14 is reduced and the first cooling stage 22 is heated to the target temperature. In this way, the temperature of the first stage low temperature plate 18 can be maintained in a temperature range near the target temperature. Such control helps to reduce the power consumption of the cryogenic pump 10 because the operating frequency of the refrigerator 14 can be appropriately adjusted according to the heat load.

In the following, the case where the freezer 14 is controlled so that the temperature of the first cooling stage 22 follows the target temperature is referred to as "one-stage temperature control". In the one-stage temperature control, the two-stage cooling temperature is not directly controlled. That is, as a result of the one-stage temperature control, the second cooling stage 24 and the low temperature plate unit 20 are cooled to a temperature determined by the two-stage cooling capacity of the freezer 14 and the heat load on the second cooling stage 24 from the outside.

Similarly, the controller 60 can also perform the so-called "two-stage temperature control" in which the freezer 14 is controlled so that the temperature of the second cooling stage 24 follows the target temperature. At this time, the controller 60 can control the operating frequency of the freezer 14 by feedback control so as to minimize the deviation between the target temperature of the second cooling stage 24 and the measured temperature of the second temperature sensor 42. In this way, the temperature of the low-temperature plate unit 20 can follow the target temperature. In the two-stage temperature control, the first-stage cooling temperature is not directly controlled. In the two-stage temperature control, the first-stage cooling temperature is determined by the first-stage cooling capacity of the freezer 14 and the heat load on the first cooling stage 22 from the outside.

The controller 60 may be configured to control not only the cryogenic pump 10 but also the gate valve 102. The controller 60 may generate a command signal for opening and closing the gate valve 102 and send it to the gate valve 102. The gate valve 102 may receive the command signal and open or close according to the command signal. The gate valve 102 may generate a gate signal S indicating an open and closed state and send it to the controller 60. The controller 60 may receive the gate signal S from the gate valve 102 and detect whether the gate valve 102 is closed according to the gate signal S.

Furthermore, the gate valve 102 may also be controlled by a controller different from the controller 60 (for example, a higher-level controller than the controller 60 that controls the vacuum process device). In this case, the controller 60 may receive the gate valve signal S from the controller that controls the gate valve 102.

The internal structure of the controller 60 is realized as a hardware structure by components or circuits represented by a CPU or memory of a computer, and as a software structure by computer programs, etc., but is appropriately drawn in the figure as a functional block realized by their cooperation. Those skilled in the art should understand that these functional blocks can be realized in various forms by a combination of hardware and software.

For example, the controller 60 can be realized by a combination of a processor (hardware) such as a CPU (Central Processing Unit) or a microcomputer and a software program executed by the processor (hardware). The software program may be a computer program for causing the controller 60 to execute the operation method of the cryogenic pump 10 .

The operation of the cryogenic pump 10 of the above structure is described below. When the cryogenic pump 10 is working, first, before the operation, the vacuum chamber 100 is roughly pumped to a predetermined pressure (for example, about 100Pa or about 10Pa) by using other appropriate rough pumps. When the vacuum chamber 100 is roughly pumped, the gate valve 102 is closed. Thereafter (or in parallel with the rough pumping of the vacuum chamber 100), the cryogenic pump 10 is operated. By driving the freezer 14, the first cooling stage 22 and the second cooling stage 24 are cooled to the first cooling temperature and the second cooling temperature, respectively. Therefore, the first low temperature plate unit and the second low temperature plate unit thermally coupled thereto are also cooled to the first cooling temperature and the second cooling temperature, respectively. The gate valve 102 is opened, and vacuum exhaust of the vacuum chamber 100 based on the cryopump 10 begins.

The inlet low temperature plate 32 cools the gas flying from the vacuum chamber toward the cryogenic pump 10. The gas whose vapor pressure is sufficiently low (for example, below 10 ^{- 8} Pa) at the first cooling temperature condenses on the surface of the inlet low temperature plate 32. This gas can be called the first type of gas. The first type of gas is, for example, water vapor. In this way, the inlet low temperature plate 32 can discharge the first type of gas. A portion of the gas whose vapor pressure is not low enough at the first cooling temperature enters the cryogenic pump 10 from the air intake port 12. Alternatively, another portion of the gas is reflected by the inlet low temperature plate 32 and returns to the vacuum chamber 100 without entering the cryogenic pump 10.

The gas entering the cryogenic pump 10 is cooled by the cryogenic plate unit 20. At the second cooling temperature, the gas with a sufficiently low vapor pressure (e.g., below 10 ^-8 Pa) condenses on the surface of the cryogenic plate unit 20. This gas can be referred to as the second gas. The second gas is, for example, argon. In this way, the cryogenic plate unit 20 can discharge the second gas.

The gas whose vapor pressure is not low enough at the second cooling temperature is adsorbed on the adsorption material of the low temperature plate unit 20. This gas can be called the third gas. The third gas is, for example, hydrogen. In this way, the low temperature plate unit 20 can discharge the third gas. Therefore, the low temperature pump 10 can discharge various gases by condensation or adsorption so that the vacuum degree of the vacuum chamber reaches the desired level.

By continuing the vacuum exhaust operation of the cryopump 10, gas is accumulated in the cryopump 10. In order to discharge the accumulated gas to the outside, the cryopump 10 is regenerated. The regeneration of the cryopump 10 generally includes a heating process, a discharge process, and a cooling process. In the heating process, the cryopump 10 is heated from the extremely low temperature used for the vacuum exhaust operation to the regeneration temperature (for example, room temperature). The gas captured in the cryopump 10 is vaporized. The second gas and the third gas can be easily discharged from the cryopump 10 in the heating process. In the discharge process, the first gas is mainly discharged. If the discharge process is completed, the cooling process begins. In the cooling process, the cryopump 10 is cooled again to the extremely low temperature used for the vacuum exhaust operation. In this way, if the regeneration is completed, the cryopump 10 can start the vacuum exhaust operation again.

During the regeneration of the cryogenic pump 10, the gate valve 102 is closed. After the regeneration is completed, the gate valve 102 is opened again. However, the gate valve 102 may not be opened immediately at the time of the completion of the regeneration (i.e., the end of the cooling process). After the regeneration is completed, the cryogenic pump 10 can also be cooled to an extremely low temperature in a standby state with the gate valve 102 closed. By opening the gate valve 102, the cryogenic pump 10 in the standby state can immediately start the vacuum exhaust of the vacuum chamber 100.

As described above, by opening the gate valve 102, a large amount of gas flows from the vacuum chamber 100 into the cryogenic pump 10 at once, which becomes a heat load on the freezer 14 and may cause the temperature of the cryogenic plate to overshoot. Due to various reasons, the temperature overshoot is more likely to occur on the second-stage low-temperature plate than on the first-stage low-temperature plate. This is simply because the temperature of the second stage is low, and the temperature difference with the room temperature gas flowing in is large. In addition, in most cases, the heat capacity of the second stage is smaller than that of the first stage (large parts such as the radiation shielding part 30 are installed on the first stage, so the mass and heat capacity are mostly large). The second gas such as nitrogen, which is the main gas flowing in, does not condense on the first stage but condenses on the second stage. The latent heat generated by the phase change of the gas may increase the temperature of the second stage. The temperature rise of the cryo plate may have a negative impact on the exhaust performance of the cryo pump in some cases.

In the conventional cryopump control, when the gate valve 102 is closed to reduce the heat load from the vacuum chamber 100 to the cryopump 10, the refrigeration capacity of the freezer 14 is often suppressed for energy saving. Under such control, it is effective to maintain the second stage temperature at a relatively high level. As a result, the second stage temperature at the time of the occurrence of the crossover tends to be high, and there is a possibility that the temperature overshoot may easily occur.

In addition, as a unique setting in the vacuum sequencer, the allowable range of the low temperature plate temperature may be pre-set. If the result of the above-mentioned overshoot is detected to exceed the allowable temperature range, the vacuum sequencer may perform actions to ensure safety, such as issuing an alarm or emergency closing of the gate valve 102. The vacuum sequencer becomes standby until the low temperature plate temperature returns to the allowable range, and the start of the vacuum sequence is delayed accordingly.

Therefore, in the present embodiment, in order to mitigate the overshoot of the low temperature plate temperature that may occur during the crossover, the controller 60 is configured to detect whether the gate valve 102 is closed, and control the freezer 14 so that the freezing capacity of the freezer 14 when the gate valve 102 is closed is increased compared to when the gate valve 102 is open.

Fig. 3 is a flow chart showing an example of a method for operating the cryogenic pump 10 according to the embodiment. The controller 60 may periodically execute this process when the cryogenic pump 10 is operating.

As shown in FIG3 , when the present process is started, it is first determined whether the gate valve 102 is closed (S10). As an example, the controller 60 may be configured to receive a gate signal S indicating the open and closed states of the gate valve 102, and detect whether the gate valve 102 is closed based on the gate signal S. As described above, the controller 60 may receive the gate signal S from the gate valve 102 or from another controller.

As another method, the controller 60 may be configured to obtain the heat load on the freezer 14 and detect whether the gate valve 102 is closed based on the obtained heat load. The heat load on the freezer 14 mainly enters the freezer 14 from the vacuum chamber 100 through the gate valve 102. Therefore, it is expected that the heat load on the freezer 14 when the gate valve 102 is closed will be smaller than the heat load on the freezer 14 when the gate valve 102 is open. Therefore, when the heat load on the refrigerator 14 is lower than the heat load threshold, the gate valve 102 can be detected to be closed, and when the heat load on the refrigerator 14 exceeds the heat load threshold, the gate valve 102 can be detected to be opened. The heat load threshold can be obtained in advance based on the experience of the designer of the cryogenic pump 10 or experiments or simulation experiments conducted by the designer, and stored in the controller 60 in advance.

The controller 60 may be configured to refer to a map showing the relationship between the heat load on the freezer 14, the operating frequency of the freezer 14, and the low temperature plate temperature, and obtain the heat load on the freezer 14 according to the current operating frequency of the freezer 14 and the measured low temperature plate temperature. Such a map is also called a roadmap, which can be obtained in advance based on the experience and insights of the designer of the cryogenic pump 10 or experiments or simulation experiments conducted by the designer, and stored in the controller 60 in advance.

For example, the first roadmap shows the relationship between the heat load on the first and second sections of the refrigerator 14, the operating frequency of the refrigerator 14 under the first-stage temperature control, and the temperature of the second-stage low-temperature plate. The controller 60 can refer to the first roadmap when performing the first-stage temperature control, and obtain the heat load on the first and second sections of the refrigerator 14 according to the current operating frequency of the refrigerator 14 and the measured second-stage low-temperature plate temperature. The second-stage low-temperature plate temperature can be measured by the second temperature sensor 42.

Alternatively, a second roadmap may be used that shows the relationship between the heat load on each of the first and second stages of the refrigerator 14, the operating frequency of the refrigerator 14 under the two-stage temperature control, and the temperature of the first stage low temperature plate. The controller 60 may refer to the second roadmap when performing the two-stage temperature control, and obtain the heat load on each of the first and second stages of the refrigerator 14 based on the current operating frequency of the refrigerator 14 and the measured temperature of the first stage low temperature plate. The temperature of the first stage low temperature plate may be measured by the first temperature sensor 40.

Furthermore, the controller 60 can be configured to switch and execute 1-stage temperature control and 2-stage temperature control as needed. When the cryogenic pump 10 performs vacuum exhaust operation, 1-stage temperature control is usually performed. The controller 60 can perform 2-stage temperature control in the standby state of the cryogenic pump 10, switch from 2-stage temperature control to 1-stage temperature control at the time of crossover, and perform 1-stage temperature control during vacuum exhaust operation. Alternatively, the controller 60 can detect whether the gate valve 102 is open, and perform 1-stage temperature control when the gate valve 102 is open, and perform 2-stage temperature control when the gate valve 102 is closed.

As shown in FIG. 3 , when the gate valve 102 is detected to be closed (“Yes” in S10), the controller 60 controls the freezer 14 so that the refrigeration capacity of the freezer 14 is increased compared to when the gate valve 102 is opened (S12). On the other hand, when the gate valve 102 is detected to be opened (“No” in S10), the refrigeration capacity is not increased.

As an example of control for increasing the refrigeration capacity of the freezer 14, the controller 60 may be configured to operate the freezer 14 at an operating frequency greater than the first lower limit when the gate valve 102 is open, and to operate the freezer 14 at an operating frequency greater than the second lower limit greater than the first lower limit when the gate valve 102 is closed. In this way, if the gate valve 102 is closed when the freezer 14 is operating at an operating frequency less than the second lower limit, the operating frequency of the freezer 14 is increased to the second lower limit. If the value of the operating frequency determined by the one-stage temperature control or the two-stage temperature control is greater than the second lower limit, the operating frequency of the freezer 14 is increased to the value. In this way, the refrigeration capacity of the freezer 14 when the gate valve 102 is closed can be increased compared to when the gate valve 102 is opened.

Furthermore, the second lower limit of the operating frequency may be the upper limit of the operating frequency range allowed by the freezer 14 or a predetermined value slightly smaller than the upper limit (e.g., greater than 80% or 90% of the upper limit). In this way, the refrigeration capacity of the freezer 14 when the gate valve 102 is closed can be increased more than when the gate valve 102 is opened.

As another example of control for increasing the refrigeration capacity of the freezer 14, the controller 60 may be configured to determine the operating frequency of the freezer 14 in such a manner that the cooling temperature measured by the temperature sensor is consistent with the first target temperature when the gate valve 102 is opened, and to determine the operating frequency of the freezer 14 in such a manner that the cooling temperature measured by the temperature sensor is consistent with the second target temperature lower than the first target temperature when the gate valve 102 is closed, and to operate the freezer 14 at the determined operating frequency. In this way, the freezer 14 can also be controlled so that the operating frequency of the freezer 14 when the gate valve 102 is closed is increased compared to when the gate valve 102 is opened.

For example, when performing the first stage temperature control, the controller 60 can determine the operating frequency of the freezer 14 in such a manner that the cooling temperature measured by the first temperature sensor 40 is consistent with the first target temperature when the gate valve 102 is opened, and determine the operating frequency of the freezer 14 in such a manner that the cooling temperature measured by the first temperature sensor 40 is consistent with the second target temperature lower than the first target temperature when the gate valve 102 is closed. At this time, the first target temperature can be selected, for example, from a range of 80K to 120K. The second target temperature can be selected, for example, from a temperature above 60K.

Alternatively, when performing two-stage temperature control, the controller 60 may determine the operating frequency of the freezer 14 in such a manner that the cooling temperature measured by the second temperature sensor 42 is consistent with the first target temperature when the gate valve 102 is opened, and determine the operating frequency of the freezer 14 in such a manner that the cooling temperature measured by the second temperature sensor 42 is consistent with the second target temperature lower than the first target temperature when the gate valve 102 is closed. At this time, the first target temperature may be selected, for example, from the range of 12K to 20K. The second target temperature may be selected, for example, from the range of 10K to 12K.

Furthermore, when executing the control of increasing the refrigeration capacity of the freezer 14, the controller 60 can detect whether the gate valve 102 is opened, and when the gate valve 102 is opened, the increase of the refrigeration capacity of the freezer 14 is terminated. In this way, the refrigeration capacity of the freezer 14 can be restored to its original state when the gate valve 102 is opened.

FIG4(a) is a diagram showing the operation of a cryogenic pump in a comparative example. As described above, in existing cryogenic pumps, in most cases, the heat load on the cryogenic pump's freezer from the vacuum chamber is reduced by closing the gate valve, so the freezer is controlled to suppress the freezer's refrigeration capacity. Therefore, as shown in FIG4(a), the operating frequency of the freezer decreases during the period when the gate valve is closed. At this time, the heat load on the freezer also decreases, so the low-temperature plate temperature (for example, the second-stage low-temperature plate temperature) is maintained at the target temperature Ta. However, when the gate valve is opened, the situation changes. Since the heat load on the freezer increases with the crossover, the low-temperature plate temperature may temporarily rise significantly. That is, the low temperature plate temperature overshoots. As a result, the low temperature plate temperature deviates from the target temperature Ta, and the operating frequency of the freezer increases, and then the low temperature plate temperature gradually returns to the target temperature Ta.

FIG4(b) is a diagram showing the operation of the cryogenic pump of the implementation method. According to the implementation method, the refrigeration capacity of the freezer 14 when the gate valve 102 is closed can be increased compared to when the gate valve 102 is opened. As shown in FIG4(b), during the period when the gate valve is closed, the operating frequency of the freezer 14 increases. At this time, the heat load on the freezer 14 becomes smaller, so the temperature of the cryogenic plate decreases. Thereafter, since the gate valve 102 is opened, the heat load on the freezer 14 increases, and the temperature of the cryogenic plate rises. However, since the temperature of the cryogenic plate is sufficiently lowered in advance when the gate valve 102 is closed, it is expected that the temperature of the cryogenic plate follows the target temperature Ta without significantly exceeding the target temperature Ta. Thus, according to the implementation, the overshoot of the low temperature board temperature that may occur during the crossover can be mitigated.

Most of the total operation time of the cryogenic pump 10 is the vacuum exhaust operation of the vacuum chamber 100, during which the gate valve 102 is open. The proportion of the total operation time of the cryogenic pump 10 that the gate valve 102 is closed should be very small. Therefore, in the cryogenic pump 10 of the embodiment, the power consumption when the gate valve 102 is closed may increase slightly, but it is estimated that the time is very short and therefore will not cause much impact.

FIG5 is a flow chart showing another example of the operation method of the cryogenic pump 10 of the embodiment. Instead of detecting the opening and closing of the gate valve 102, it is possible to detect whether the regeneration of the cryogenic pump 10 is completed. Therefore, the controller 60 can detect whether the regeneration of the cryogenic pump 10 is completed, and control the refrigerator 14 to temporarily increase the refrigeration capacity of the refrigerator 14 after the regeneration is completed. In this way, as in the above-mentioned embodiment, the overshoot of the cryogenic plate temperature that may occur at the time of the crossover can be alleviated.

As shown in FIG5 , it is determined whether the regeneration of the cryopump 10 is completed (S20). The controller 60 can obtain the measured temperature from the first temperature sensor 40 and the second temperature sensor 42 in the cooling process of the regeneration, compare the measured temperature of the first temperature sensor 40 with the target cooling temperature of the first stage cryopanel 18 for vacuum exhaust operation, and compare the measured temperature of the second temperature sensor 42 with the target cooling temperature of the second stage cryopanel unit 20 for vacuum exhaust operation. The controller 60 can continue the cooling process when any of the measured temperatures of the first temperature sensor 40 and the second temperature sensor 42 does not reach the target cooling temperature, and when the measured temperatures of the first temperature sensor 40 and the second temperature sensor 42 respectively reach the target cooling temperature, it is determined that the cooling process, that is, the regeneration of the low-temperature pump 10 is completed.

When the regeneration of the cryogenic pump 10 is completed ("Yes" in S20), the controller 60 controls the refrigerator 14 to increase the refrigeration capacity of the refrigerator 14 (S22). As in the above-mentioned embodiment, the increase in the refrigeration capacity of the refrigerator 14 can be achieved by increasing the operating frequency of the refrigerator 14, by lowering the target temperature under the 1st stage temperature control, or by lowering the target temperature under the 2nd stage temperature control. On the other hand, when it is detected that the regeneration of the cryogenic pump 10 is not completed ("No" in S20), the increase in the refrigeration capacity is not performed.

The control to increase the refrigeration capacity of the freezer 14 may be performed until the gate valve 102 is opened. At this time, the controller 60 may control the freezer 14 to increase the refrigeration capacity of the freezer 14 when the cryogenic pump 10 is in the standby state. Alternatively, the control to increase the refrigeration capacity of the freezer 14 may also be performed within a predetermined time.

FIG6 is a block diagram schematically showing the structure of the control device of the cryogenic pump 10 of another embodiment. In order to adjust the refrigeration capacity of the freezer 14, the freezer 14 may be provided with a heating device 62 such as an electric heater. The heating device 62 may be provided on the first cooling stage 22, or on the second cooling stage 24, or on both the first cooling stage 22 and the second cooling stage 24. The controller 60 may be configured to switch the heating device 62 on and off and/or control the output of the heating device 62.

The controller 60 may be configured to operate the heating device 62 at a first output when the gate valve 102 is open, and operate the heating device 62 at a second output lower than the first output or to not operate the heating device 62 when the gate valve 102 is closed. By reducing the output of the heating device 62, the refrigeration capacity of the freezer 14 when the gate valve 102 is closed can be increased compared to when the gate valve 102 is open.

Furthermore, in the embodiment of FIG. 6 , similarly to the embodiment of FIG. 2 , the freezer 14 may be configured to have a freezer inverter 52 and to make the operating frequency variable. In this case, for example, the operating frequency of the freezer 14 may be controlled by a one-stage temperature control or a two-stage temperature control, and the heating device 62 may be used to adjust the refrigeration capacity. Alternatively, in the embodiment of FIG. 6 , the freezer 14 may be driven at a certain operating frequency, or may not have the freezer inverter 52.

The present invention has been described above based on the embodiments. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and various design changes and modifications are possible, and such modifications are also within the scope of the present invention. This application claims priority based on Japanese Patent Application No. 2022-024015 filed on February 18, 2022. The entire contents of the Japanese application are incorporated by reference in this specification.

10: Low temperature pump 14: Refrigerator 60: Controller 100: Vacuum chamber 102: Gate valve

[Figure 1] is a diagram schematically showing a cryogenic pump of an embodiment. [Figure 2] is a block diagram schematically showing the structure of a control device of a cryogenic pump of an embodiment. [Figure 3] is a flow chart showing an example of an operation method of a cryogenic pump of an embodiment. In [Figure 4], Figure 4(a) is a diagram showing the operation of a cryogenic pump of a comparative example, and Figure 4(b) is a diagram showing the operation of a cryogenic pump of an embodiment. [Figure 5] is a flow chart showing another example of an operation method of a cryogenic pump of an embodiment. [Figure 6] is a block diagram schematically showing the structure of a control device of a cryogenic pump of another embodiment.

10: Low temperature pump

14: Freezer

40: 1st temperature sensor

42: Second temperature sensor

50: Freezer motor

52: Freezer inverter

60: Controller

102: Gate valve

F: Operating frequency

T1: 1st measured temperature signal

T2: Second measured temperature signal

S: Gate signal

Claims (9)

A cryogenic pump capable of being installed in a vacuum chamber via a gate valve comprises: a freezer; and a controller configured to detect whether the gate valve is closed and control the freezer so that the freezing capacity of the freezer when the gate valve is closed is increased compared to when the gate valve is open. A cryogenic pump as described in claim 1, wherein the controller is configured to receive a gate signal indicating the open and closed state of the gate, and detect whether the gate is closed based on the gate signal. A cryogenic pump as described in claim 1, wherein the controller is configured to obtain a heat load on the refrigerator and detect whether the gate valve is closed based on the obtained heat load. A cryogenic pump as described in any one of claim 1 to claim 3, wherein the refrigeration machine is configured to make the operating frequency variable, and the controller is configured to operate the refrigeration machine at an operating frequency greater than a first lower limit value when the gate valve is opened, and to operate the refrigeration machine at an operating frequency greater than a second lower limit value greater than the first lower limit value when the gate valve is closed. A cryogenic pump as described in any one of claim 1 to claim 3, wherein the refrigerator is configured to have a variable operating frequency, and the cryogenic pump further comprises a temperature sensor for measuring the cooling temperature of the refrigerator, and the controller is configured to determine the operating frequency of the refrigerator in a manner such that the cooling temperature measured by the temperature sensor is consistent with a first target temperature when the gate valve is opened, and to determine the operating frequency of the refrigerator in a manner such that the cooling temperature measured by the temperature sensor is consistent with a second target temperature lower than the first target temperature when the gate valve is closed, and to operate the refrigerator at the determined operating frequency. A cryogenic pump as described in any one of claim 1 to claim 3, wherein the refrigerator is provided with a heating device, and the controller is configured to operate the heating device at a first output when the gate valve is opened, and to operate the heating device at a second output lower than the first output or to not operate the heating device when the gate valve is closed. A method for operating a cryogenic pump, wherein the cryogenic pump can be installed in a vacuum chamber via a gate valve and is equipped with a freezer, the method comprising the following steps: a step of detecting whether the gate valve is closed; and a step of increasing the freezing capacity of the freezer when the gate valve is closed compared to when the gate valve is open. A cryogenic pump comprises: a refrigerator; and a controller, which detects whether the regeneration of the cryogenic pump is completed, and controls the refrigerator to temporarily increase the refrigeration capacity of the refrigerator after the regeneration is completed; the regeneration includes: a heating process from an extremely low temperature for vacuum exhaust operation to a regeneration temperature, a discharge process for mainly discharging a first gas from the cryogenic pump, and a cooling process for cooling the cryogenic pump to the extremely low temperature for vacuum exhaust operation. A method for operating a cryogenic pump, wherein the cryogenic pump is equipped with a refrigerator, and the method comprises the following steps: a step of detecting whether the regeneration of the cryogenic pump is completed; and a step of temporarily increasing the refrigeration capacity of the refrigerator after the regeneration is completed; the regeneration comprises: a heating process of heating from an extremely low temperature for vacuum exhaust operation to a regeneration temperature, a discharge process of mainly discharging a first gas from the cryogenic pump, and a cooling process of cooling the cryogenic pump to the extremely low temperature for vacuum exhaust operation.

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