Cryopumps and methods for operating cryopumps

Abstract

To provide a cryopump which can ease overshoot of a cryopanel temperature which may occur during cross-over.SOLUTION: A cryopump 10 may be attached to a vacuum chamber through a gate valve 102. The cryopump 10 includes: a freezing machine 14; and a controller 60 configured to detect whether or not the gate valve 102 is closed and control the freezing machine 14 so that the freezing capacity of the freezing machine 14 when the gate valve 102 is closed increases, compared to the freezing capacity when the gate valve 102 is open.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a cryopump and a method for operating a cryopump.

Background Art

[0002] A cryopump is a vacuum pump that captures gas molecules by condensation or adsorption on a cryopanel cooled to an extremely low temperature and exhausts them. Cryopumps are generally used to achieve a clean vacuum environment required in semiconductor circuit manufacturing processes and the like.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As preparation for starting a vacuum process in a vacuum chamber of a vacuum process apparatus, the vacuum chamber is first rough-pumped and then switched to vacuum exhaust by a cryopump. During rough pumping of the vacuum chamber, a gate valve provided between the vacuum chamber and the cryopump is closed and opened to start vacuum exhaust by the cryopump. At this time, the ultimate pressure in the cryopump is already considerably lower than the rough pumping pressure of the vacuum chamber. Therefore, a large amount of gas temporarily flows from the vacuum chamber into the cryopump, which becomes a heat load on a refrigerator that cools the cryopump and may cause an overshoot in the cryopanel temperature. Such a temperature rise is also called a crossover. The temperature rise of the cryopanel may, in some cases, have an undesirable effect on the exhaust performance of the cryopump.

[0005] Furthermore, vacuum process equipment may have its own unique settings, such as a predetermined tolerance range for the cryopanel temperature. If the overshoot described above results in the temperature exceeding this tolerance range, the vacuum process equipment may take safety actions, such as issuing an alert or emergency closing of the gate valve. The vacuum process equipment will then wait until the cryopanel temperature returns to the tolerance range, delaying the start of the vacuum process.

[0006] One exemplary object of a certain aspect of the present invention is to provide a cryopump that can mitigate the overshoot of the cryopanel temperature that may occur during crossover. [Means for solving the problem]

[0007] According to one aspect of the present invention, a cryopump that can be mounted in a vacuum chamber via a gate valve is provided. The cryopump comprises a refrigerator and a controller configured to detect whether the gate valve is closed or not and to control the refrigerator so that the cooling capacity of the refrigerator when the gate valve is closed is increased compared to when the gate valve is open.

[0008] According to one aspect of the present invention, a method for operating a cryopump is provided. The cryopump is mountable in a vacuum chamber via a gate valve and comprises a refrigerator. The method comprises detecting whether the gate valve is closed or not, and increasing the cooling capacity of the refrigerator when the gate valve is closed compared to when the gate valve is open.

[0009] According to one aspect of the present invention, the cryopump comprises a refrigerator and a controller that detects whether or not the regeneration of the cryopump is complete and controls the refrigerator to temporarily increase the cooling capacity of the refrigerator following the completion of regeneration.

[0010] According to one aspect of the present invention, a method for operating a cryopump is provided. The cryopump comprises a refrigerator. The method comprises detecting whether the regeneration of the cryopump is complete, and temporarily increasing the cooling capacity of the refrigerator following the completion of regeneration.

[0011] Furthermore, any combination of the above components, or any substitution of components or expressions of the present invention between methods, apparatus, systems, etc., is also valid as an embodiment of the present invention. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a cryopump that can mitigate the overshoot of the cryopanel temperature that may occur during crossover. [Brief explanation of the drawing]

[0013] [Figure 1] This is a schematic diagram showing a cryopump according to an embodiment. [Figure 2] This is a block diagram schematically showing the configuration of the control device for the cryopump according to the embodiment. [Figure 3] This flowchart shows an example of how to operate a cryopump according to an embodiment. [Figure 4] Figure 4(a) shows the operation of a cryopump according to a comparative example, and Figure 4(b) shows the operation of a cryopump according to an embodiment. [Figure 5] This flowchart shows another example of how to operate the cryopump according to the embodiment. [Figure 6] This is a block diagram schematically showing the configuration of a control device for a cryopump according to another embodiment. [Modes for carrying out the invention]

[0014] The embodiments for carrying out the present invention will be described in detail below with reference to the drawings. In the description and drawings, identical or equivalent components, members, and processes are denoted by the same reference numerals, and redundant descriptions will be omitted as appropriate. The scale and shape of the illustrated parts are set for convenience to facilitate the explanation and are not to be interpreted restrictively unless otherwise specified. The embodiments are illustrative and do not limit the scope of the present invention in any way. Not all features or combinations thereof described in the embodiments are necessarily essential to the invention.

[0015] Figure 1 is a schematic diagram showing a cryopump 10 according to an embodiment. Figure 2 is a schematic block diagram showing the configuration of the control device for the cryopump 10 according to an embodiment.

[0016] The cryopump 10 can be mounted via a gate valve 102 to a vacuum chamber 100 of, for example, an ion implantation apparatus, a sputtering apparatus, a deposition apparatus, or other vacuum process apparatus. Figure 1 shows a portion of the vacuum chamber 100 and gate valve 102 together with the cryopump 10.

[0017] The cryopump 10 is mounted to the vacuum chamber 100 via a gate valve 102 and is used to raise the vacuum level inside the vacuum chamber 100 to the level required for the desired vacuum process. The cryopump 10 has a cryopump intake port (hereinafter also simply referred to as the "intake port") 12 for receiving the gas to be exhausted from the vacuum chamber 100. The gas enters the internal space of the cryopump 10 from the vacuum chamber 100 through the gate valve 102 and the intake port 12.

[0018] In the following, the terms "axial direction" and "radial direction" may be used to clearly represent the positional relationship of the components of the cryopump 10. The axial direction of the cryopump 10 represents the direction passing through the intake port 12 (that is, the direction along the central axis of the cryopump 10, which is the vertical direction in the figure), and the radial direction represents the direction along the intake port 12 (the direction perpendicular to the central axis of the cryopump 10, which is the left-right direction in the figure). For the sake of convenience, being relatively close to the intake port 12 in the axial direction may be called "up", and being relatively far may be called "down". That is, being relatively far from the bottom of the cryopump 10 may be called "up", and being relatively close may be called "down". Regarding the radial direction, being close to the center of the intake port 12 may be called "in", and being close to the periphery of the intake port 12 may be called "out". Note that such expressions have nothing to do with the arrangement when the cryopump 10 is attached to the vacuum chamber 100. For example, the cryopump 10 may be attached to the vacuum chamber 100 with the intake port 12 facing downward in the vertical direction.

[0019] Also, the direction surrounding the axial direction may be called the "circumferential direction". The circumferential direction is the second direction along the intake port 12 and is the tangential direction perpendicular to the radial direction.

[0020] The cryopump 10 includes a refrigerator 14, a cryopump container 16, a first-stage cryopanel 18, and a cryopanel unit 20. The first-stage cryopanel 18 may also be referred to as a high-temperature cryopanel section or a 100K section, etc. The cryopanel unit 20 is a second-stage cryopanel and may also be referred to as a low-temperature cryopanel section or a 10K section, etc.

[0021] The refrigerator 14 is a cryogenic refrigerator, such as a Gifford-McMahon type refrigerator (a so-called GM refrigerator). The refrigerator 14 is a two-stage refrigerator and comprises a first cooling stage 22 and a second cooling stage 24. The refrigerator 14 is configured to cool the first cooling stage 22 to a first cooling temperature and 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 to 120K, preferably 80K to 100K, and the second cooling stage 24 is cooled to about 10K to 20K. The first cooling stage 22 and the second cooling stage 24 may also be called a high-temperature cooling stage and a low-temperature cooling stage, respectively.

[0022] Furthermore, the refrigerator 14 includes a refrigerator structure 21 that structurally supports the second cooling stage 24 in relation to the first cooling stage 22, and structurally supports the first cooling stage 22 in relation to the room temperature section 26 of the refrigerator 14. Therefore, the refrigerator structure 21 includes a first cylinder 23 and a second cylinder 25 that extend coaxially along the radial direction. The first cylinder 23 connects the room temperature section 26 of the refrigerator 14 to the first cooling stage 22. The second cylinder 25 connects the first cooling stage 22 to the second cooling stage 24. Typically, the first cooling stage 22 and the second cooling stage 24 are made of a highly thermally conductive metal material such as copper (e.g., pure copper), while the first cylinder 23 and the second cylinder 25 are made of other metal materials such as stainless steel. The room temperature section 26, the first cylinder 23, the first cooling stage 22, the second cylinder 25, and the second cooling stage 24 are arranged in a straight line in this order.

[0023] A first displacer and a second displacer (not shown) are reciprocally mounted inside the first cylinder 23 and the second cylinder 25, respectively. A first regenerator and a second regenerator (not shown) are incorporated into the first and second displacers, respectively. The room temperature section 26 also has a drive mechanism (not shown) for reciprocating the first and second displacers. The drive mechanism includes a refrigerator motor 50, which will be described later. The drive mechanism also includes a flow path switching mechanism that switches the flow path of the working gas (e.g., helium) to periodically supply and discharge the working gas into and out of the refrigerator 14.

[0024] The chiller 14 is connected to a compressor (not shown) for the working gas. The chiller 14 cools the first cooling stage 22 and the second cooling stage 24 by expanding the working gas, which has been pressurized by the compressor, inside. The expanded working gas is collected by the compressor and pressurized again. The chiller 14 generates cold by repeating a thermal cycle that includes the supply and discharge of working gas and the reciprocating motion of the first and second displacers synchronized therewith.

[0025] The illustrated cryopump 10 is a so-called horizontal cryopump. A horizontal cryopump is generally a cryopump in which the refrigerator 14 is arranged to intersect (usually perpendicular to) the central axis of the cryopump 10. The present invention can also be similarly applied to a so-called vertical cryopump. A vertical cryopump is a cryopump in which the refrigerator is arranged along the axial direction of the cryopump.

[0026] The cryopump container 16 is the housing of the cryopump 10, which contains the refrigerator 14, the first stage cryopanel 18, and the cryopanel unit 20, and is configured to maintain the airtightness of the internal space of the cryopump 10. The cryopump container 16 has an intake flange 16a that extends radially outward from its front end around its entire circumference. The intake flange 16a defines an intake port 12 radially inward. The cryopump container 16 also has a container body 16b that extends axially from the intake flange 16a, a container bottom 16c that closes the container body 16b on the opposite side of the intake port 12, and a refrigerator housing cylinder 16d that extends laterally between the intake flange 16a and the container bottom 16c.

[0027] On the opposite side of the container body 16b, the end of the refrigerator housing cylinder 16d is attached to the room temperature section 26 of the refrigerator 14, thereby positioning the low-temperature section of the refrigerator 14 (i.e., the first cylinder 23, the first cooling stage 22, the second cylinder 25, and the second cooling stage 24) within the cryopump container 16 in non-contact with the cryopump container 16. The first cylinder 23 is located in the refrigerator housing cylinder 16d, and the first cooling stage 22, the second cylinder 25, and the second cooling stage 24 are located in the container body 16b. The first stage cryo panel 18 and the cryo panel unit 20 are also located in the container body 16b.

[0028] The first-stage cryopanel 18, comprising a radiation shield 30 and an inlet cryopanel 32, surrounds the cryopanel unit 20. The first-stage cryopanel 18 provides a cryogenic surface to protect the cryopanel unit 20 from radiant heat from outside the cryopump 10 or from the cryopump vessel 16. The first-stage cryopanel 18 is thermally coupled to the first cooling stage 22 and cooled to a first cooling temperature. The first-stage cryopanel 18 has a gap between it and the cryopanel unit 20, and the first-stage cryopanel 18 does not come into contact with the cryopanel unit 20. The first-stage cryopanel 18 also does not come into contact with the cryopump vessel 16.

[0029] The radiation shield 30 is provided to protect the cryopump container 16 from radiant heat from the cryopump container 16. The radiation shield 30 extends axially in a cylindrical shape (e.g., cylindrical) within the cryopump container 16 from the air intake 12 toward the bottom 16c of the container. The radiation shield 30 is open on the air intake 12 side and closed on the bottom 16c side of the container. The radiation shield 30 is located between the cryopump container 16 and the cryopump container 20 and surrounds the cryopump container 20. The radiation shield 30 has a diameter slightly smaller than the cryopump container 16, and an outer shield gap 31 is formed between the radiation shield 30 and the cryopump container 16. Therefore, the radiation shield 30 does not come into contact with the cryopump container 16.

[0030] The first cooling stage 22 of the refrigerator 14 is directly attached to the outer side surface of the radiant shield 30. In this way, the radiant shield 30 is thermally coupled to the first cooling stage 22 and is therefore cooled to the first cooling temperature. The radiant shield 30 may also be attached to the first cooling stage 22 via an appropriate heat transfer member. In addition, the second cooling stage 24 and the second cylinder 25 of the refrigerator 14 are inserted into the radiant shield 30 from its side.

[0031] The inlet cryopanel 32 is provided at the intake port 12 to protect the cryopanel unit 20 from radiant heat from an external heat source of the cryopump 10 (for example, a heat source inside the vacuum chamber in which the cryopump 10 is installed). The inlet cryopanel 32 is thermally coupled to the first cooling stage 22 via the radiant shield 30 and is cooled to a first cooling temperature, similar to the radiant shield 30. As a result, gases (e.g., water) that condense at the first cooling temperature are trapped on its surface.

[0032] The cryopanel unit 20 comprises a plurality of cryopanels, each thermally coupled to the second cooling stage 24 and cooled to a second cooling temperature lower than the first cooling temperature. These cryopanels may be arranged axially from the air intake 12 toward the bottom 16c of the container, as shown in the figure. At least some of the surfaces of the cryopanels may be provided with an adsorbent (e.g., activated carbon) to capture non-condensable gases (e.g., hydrogen) by adsorption. The cryopanel unit 20 is positioned below the inlet cryopanel 32 within the cryopump container 16, surrounded by the radiation shield 30. The cryopanel unit 20 is not in contact with the radiation shield 30 or the inlet cryopanel 32. The configuration of the cryopanel unit 20, including the arrangement and shape of the cryopanels, can be appropriately adopted from various known configurations, and will not be described in detail here.

[0033] The gate valve 102 is installed between the cryopump 10 and the vacuum chamber 100. The gate valve 102 comprises a valve housing 104 and a valve plate 106. The valve housing 104 forms a passage connecting the opening of the vacuum chamber 100 to the intake port 12 of the cryopump 10. The valve housing 104 has flange portions on each side of this passage, with one flange portion attached to the flange portion of the vacuum chamber 100 surrounding the opening of the vacuum chamber 100, and the other flange portion attached to the intake port flange 16a.

[0034] The gate valve 102 is closed as needed, such as when performing maintenance on the vacuum chamber 100 or the cryopump 10. The flange portion of the valve housing 104 on the intake flange 16a side also acts as the valve seat portion of the gate valve 102, and the valve plate 106, which acts as the valve body, makes tight contact with this valve seat portion, thereby closing the gate valve 102. At this time, the gas flow from the vacuum chamber 100 to the cryopump 10 through the intake port 12 is blocked. The cryopump 10 is isolated from the vacuum chamber 100, and the internal space of the cryopump 10 is kept airtight.

[0035] The gate valve 102 is opened to allow the cryopump 10 to evacuate the vacuum chamber 100. The valve housing 104 is provided with a valve plate housing 108, and the gate valve 102 opens when the valve plate 106 separates from the valve seat of the valve housing 104 and is housed in the valve plate housing 108, as shown by the dashed line in Figure 1. Gas can enter the internal space of the cryopump 10 from the vacuum chamber 100 through the gate valve 102 and the intake port 12. In this way, the vacuum chamber 100 can be evacuated by the cryopump 10 in order to perform the desired vacuum process within the vacuum chamber 100.

[0036] As shown in Figure 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 cryopanel 18, and the second temperature sensor 42 is mounted on the second cooling stage 24 or the cryopanel unit 20. Thus, the first temperature sensor 40 can measure the temperature of the first stage cryopanel 18 and output a first measured temperature signal T1 indicating the measured temperature of the first stage cryopanel 18. The second temperature sensor 42 can measure the temperature of the cryopanel unit 20 and output a second measured temperature signal T2 indicating the measured temperature of the cryopanel unit 20.

[0037] The refrigerator 14 includes a refrigerator motor 50 that drives the refrigerator 14 and a refrigerator inverter 52 that controls the operating frequency of the refrigerator 14. The operating frequency (also called the operating speed) of the refrigerator 14 refers to the operating frequency or rotational speed of the refrigerator motor 50, the operating frequency of the refrigerator inverter 52, the thermal cycle frequency, or any of these. The thermal cycle frequency is the number of thermal cycles performed in the refrigerator 14 per unit time.

[0038] Furthermore, the cryopump 10 includes a controller 60 that controls the cryopump 10. The controller 60 may be integrated with the cryopump 10, or it may be configured as a separate control device from the cryopump 10.

[0039] The controller 60 may be connected to the first temperature sensor 40 to receive a first measured temperature signal T1 from the first temperature sensor 40, and may also be connected to the second temperature sensor 42 to receive a second measured temperature signal T2 from the second temperature sensor 42. The above-mentioned refrigerator inverter 52 may be provided in the controller 60.

[0040] The controller 60 may be configured to control the refrigerator 14 based on the cooling temperature of the first stage cryopanel 18 or the cooling temperature of the cryopanel unit 20 during the vacuum evacuation operation of the cryopump 10. For example, the controller 60 may control the operating frequency of the refrigerator 14 by feedback control to minimize the deviation between the target temperature of the first cooling stage 22 and the temperature measured by the first temperature sensor 40.

[0041] 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 specified, for example, according to the process performed in the vacuum chamber 100 in which the cryopump 10 is installed. During operation of the cryopump 10, the target temperature may be changed as needed.

[0042] The controller 60 may determine the operating frequency F of the chiller motor 50 as a function of the deviation between the measured temperature and the target temperature (for example, by PID control). The operating frequency F of the chiller motor 50 is determined within a predetermined operating frequency range. The operating frequency range is defined by predetermined upper and lower limits of the operating frequency. The controller 60 outputs the determined operating frequency F to the chiller inverter 52.

[0043] The refrigeration inverter 52 is configured to provide variable frequency control of the refrigeration motor 50. The refrigeration inverter 52 converts the input power to have an operating frequency F input from the controller 60. The input power to the refrigeration inverter 52 is supplied from a refrigeration power supply (not shown). The refrigeration power supply may be a commercial power supply. The refrigeration inverter 52 outputs the converted power to the refrigeration motor 50. Thus, the refrigeration motor 50 is driven at the operating frequency F determined by the controller 60 and output from the refrigeration inverter 52.

[0044] When the heat load on the cryopump 10 increases, the temperature of the first cooling stage 22 may rise. If the temperature measured by the first temperature sensor 40 is higher than the target temperature, the controller 60 increases the operating frequency of the refrigerator 14. As a result, the frequency of the thermal cycle in the refrigerator 14 also increases, and the first stage cryopanel 18 and the first cooling stage 22 are cooled toward the target temperature. Conversely, if the temperature measured by the first temperature sensor 40 is lower than the target temperature, the operating frequency of the refrigerator 14 is reduced, and the first cooling stage 22 is heated toward the target temperature. In this way, the temperature of the first stage cryopanel 18 can be kept within a temperature range near the target temperature. Since the operating frequency of the refrigerator 14 can be appropriately adjusted according to the heat load, this control helps to reduce the power consumption of the cryopump 10.

[0045] Controlling the temperature of the first cooling stage 22 according to the target temperature using the refrigerator 14 may be referred to as "single-stage temperature control" below. In single-stage temperature control, the second-stage cooling temperature is not directly controlled. In other words, as a result of single-stage temperature control, the second cooling stage 24 and the cryopanel unit 20 are cooled to a temperature determined by the two-stage cooling capacity of the refrigerator 14 and the heat load from the outside onto the second cooling stage 24.

[0046] Similarly, the controller 60 can perform a so-called "two-stage temperature control," controlling the refrigerator 14 to bring the temperature of the second cooling stage 24 to a target temperature. In this case, the controller 60 may control the operating frequency of the refrigerator 14 by feedback control to minimize the deviation between the target temperature of the second cooling stage 24 and the temperature measured by the second temperature sensor 42. This allows the temperature of the cryopanel unit 20 to follow the target temperature. In two-stage temperature control, the first-stage cooling temperature is not directly controlled. In two-stage temperature control, the first-stage cooling temperature is determined by the cooling capacity of the first stage of the refrigerator 14 and the heat load from the outside to the first cooling stage 22.

[0047] The controller 60 may be configured to control not only the cryopump 10 but also the gate valve 102. The controller 60 may generate a command signal to open or close the gate valve 102 and transmit it to the gate valve 102. The gate valve 102 may receive this command signal and open or close according to the command signal. The gate valve 102 may generate a gate valve signal S indicating its open or closed state and transmit it to the controller 60. The controller 60 may receive the gate valve signal S from the gate valve 102 and detect whether the gate valve 102 is closed or not based on the gate valve signal S.

[0048] The gate valve 102 may be controlled by a controller other than the controller 60 (for example, a controller higher than the controller 60 that controls the vacuum process equipment). In this case, the controller 60 may receive a gate valve signal S from the controller that controls the gate valve 102.

[0049] The internal configuration of the controller 60 is realized in hardware form by components and circuits such as the CPU and memory of a computer, and in software form by computer programs, etc., but in the diagram, it is depicted as functional blocks realized through the coordination of these components as appropriate. It will be understood by those skilled in the art that these functional blocks can be realized in various forms by combinations of hardware and software.

[0050] For example, the controller 60 can be implemented as a combination of a processor (hardware) such as a CPU (Central Processing Unit) or microcontroller, and a software program executed by the processor (hardware). The software program may be a computer program that instructs the controller 60 to execute the operation method of the cryopump 10.

[0051] The operation of the cryopump 10 with the above configuration is described below. Before operating the cryopump 10, the vacuum chamber 100 is first roughly pumped to a predetermined pressure (for example, about 100 Pa or about 10 Pa) using another suitable rough pump. During the rough pumping of the vacuum chamber 100, the gate valve 102 is closed. After that (or in parallel with the rough pumping of the vacuum chamber 100), the cryopump 10 is operated. The first cooling stage 22 and the second cooling stage 24 are cooled to the first cooling temperature and the second cooling temperature, respectively, by the operation of the refrigerator 14. As a result, the first cryopreel unit and the second cryopreel unit, which are thermally coupled to these stages, are also cooled to the first cooling temperature and the second cooling temperature, respectively. The gate valve 102 is opened, and the vacuum evacuation of the vacuum chamber 100 by the cryopump 10 begins.

[0052] The inlet cryopreel 32 cools the gas flying from the vacuum chamber toward the cryopreel 10. The surface of the inlet cryopreel 32 is coated with a first cooling temperature at which the vapor pressure is sufficiently low (e.g., 10 -8Gases (below Pa) condense. This gas may be called a first-class gas. A first-class gas is, for example, water vapor. Thus, the inlet cryopanel 32 can exhaust the first-class gas. Some of the gas whose vapor pressure is not sufficiently low at the first cooling temperature enters the cryopump 10 through the intake port 12. Alternatively, other portions of the gas are reflected by the inlet cryopanel 32 and return to the vacuum chamber 100 without entering the cryopump 10.

[0053] The gas that enters the cryopump 10 is cooled by the cryopane unit 20. The surface of the cryopane unit 20 is coated with a gas whose vapor pressure is sufficiently low at the second cooling temperature (for example, 10 -8 The gas (below Pa) condenses. This gas may also be called a Type 2 gas. A Type 2 gas is, for example, argon. In this way, the cryopanel unit 20 can exhaust the Type 2 gas.

[0054] Gases whose vapor pressure is not sufficiently low at the second cooling temperature are adsorbed by the adsorbent of the cryopanel unit 20. This gas may be referred to as a third-type gas. A third-type gas is, for example, hydrogen. In this way, the cryopanel unit 20 can exhaust the third-type gas. Therefore, the cryopump 10 can exhaust various gases by condensation or adsorption and bring the vacuum level of the vacuum chamber to a desired level.

[0055] As the cryopump 10 continues to operate under vacuum, gas accumulates in the cryopump 10. 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 cool-down process. In the heating process, the cryopump 10 is heated from the cryogenic temperature required for vacuum operation to the regeneration temperature (e.g., room temperature). The gas trapped inside the cryopump 10 is vaporized. Type 2 and Type 3 gases can be easily discharged from the cryopump 10 during the heating process. In the discharge process, mainly Type 1 gas is discharged. Once the discharge process is complete, the cool-down process begins. In the cool-down process, the cryopump 10 is recooled to the cryogenic temperature required for vacuum operation. Once regeneration is complete, the cryopump 10 can start vacuum operation again.

[0056] During the regeneration of the cryopump 10, the gate valve 102 is closed. After regeneration is complete, the gate valve 102 is opened again. However, the gate valve 102 does not have to be opened immediately upon completion of regeneration (i.e., upon completion of the cool-down process). After regeneration is complete, the cryopump 10 can enter a standby state where it is cooled to an extremely low temperature with the gate valve 102 closed. In the standby state, the cryopump 10 can immediately begin vacuuming the vacuum chamber 100 by opening the gate valve 102.

[0057] As described above, opening the gate valve 102 temporarily allows a large amount of gas to flow from the vacuum chamber 100 into the cryopump 10, which can become a heat load on the refrigerator 14 and cause an overshoot in the cryopanel temperature. Due to various factors, temperature overshoot may occur more easily in the second-stage cryopanel than in the first-stage cryopanel. This is simply because the second stage is at a lower temperature, resulting in a larger temperature difference with the incoming room-temperature gas. Also, in most cases, the second stage has a smaller heat capacity than the first stage (the first stage often has a larger mass and therefore a larger heat capacity due to the attachment of large components such as the radiation shield 30). The incoming main gas, such as nitrogen, does not condense in the first stage but does condense in the second stage. The latent heat generated by the phase change of the gas can raise the temperature of the second stage. The rise in the temperature of the cryopanel may, in some cases, have an undesirable effect on the exhaust performance of the cryopump.

[0058] In existing cryopump control systems, the cooling capacity of the refrigerator 14 is often suppressed to conserve energy while the gate valve 102 is closed, reducing the heat load from the vacuum chamber 100 to the cryopump 10. Under such control, it is effective to maintain a relatively high second-stage temperature. As a result, the second-stage temperature tends to be high at the time of crossover, raising concerns that temperature overshoot may easily occur.

[0059] Furthermore, a unique setting in the vacuum process equipment may be a predetermined tolerance range for the cryopanel temperature. If the overshoot described above detects that the temperature has exceeded this tolerance range, the vacuum process equipment may take safety actions such as issuing an alert or emergency closing of the gate valve 102. The vacuum process equipment will then wait until the cryopanel temperature returns to the tolerance range, delaying the start of the vacuum process.

[0060] Therefore, in this embodiment, in order to mitigate the overshoot of the cryopanel temperature that may occur during crossover, the controller 60 is configured to detect whether or not the gate valve 102 is closed and to control the refrigerator 14 so that the cooling capacity of the refrigerator 14 when the gate valve 102 is closed is increased compared to when the gate valve 102 is open.

[0061] Figure 3 is a flowchart illustrating an example of how to operate the cryopump 10 according to this embodiment. The controller 60 may periodically execute this process while the cryopump 10 is in operation.

[0062] As shown in Figure 3, when this process is started, it is first determined whether the gate valve 102 is closed or not (S10). For example, the controller 60 may be configured to receive a gate valve signal S indicating the open / closed state of the gate valve 102 and to detect whether the gate valve 102 is closed or not based on the gate valve signal S. As described above, the controller 60 can receive the gate valve signal S from the gate valve 102 or from another controller.

[0063] Alternatively, the controller 60 may be configured to acquire the heat load to the chiller 14 and detect whether the gate valve 102 is closed based on the acquired heat load. The heat load to the chiller 14 mainly enters the chiller 14 from the vacuum chamber 100 through the gate valve 102. Therefore, the heat load to the chiller 14 when the gate valve 102 is closed is expected to be smaller than the heat load to the chiller 14 when the gate valve 102 is open. Thus, if the heat load to the chiller 14 falls below the heat load threshold, it can be detected that the gate valve 102 is closed, and if the heat load to the chiller 14 exceeds the heat load threshold, it can be detected that the gate valve 102 is open. The heat load threshold may be acquired in advance based on the empirical knowledge of the designer of the cryopump 10 or experiments and simulations conducted by the designer, and stored in the controller 60 beforehand.

[0064] The controller 60 may refer to a map showing the relationship between the heat load to the chiller 14, the operating frequency of the chiller 14, and the cryopanel temperature, and may be configured to acquire the heat load to the chiller 14 based on the current operating frequency of the chiller 14 and the measured cryopanel temperature. Such a map, also called a road map, may be acquired in advance based on the empirical knowledge of the designer of the cryopump 10 or experiments and simulations conducted by the designer, and may be pre-stored in the controller 60.

[0065] For example, the first roadmap represents the relationship between the heat load on the first and second stages of the chiller 14, the operating frequency of the chiller 14 under single-stage temperature control, and the cryo-panel temperature of the second stage. The controller 60 may refer to the first roadmap while performing single-stage temperature control and obtain the heat load on the first and second stages of the chiller 14 based on the current operating frequency of the chiller 14 and the measured cryo-panel temperature of the second stage. The cryo-panel temperature of the second stage may be measured by a second temperature sensor 42.

[0066] Alternatively, a second roadmap may be used that represents the relationship between the heat load on the first and second stages of the chiller 14, the operating frequency of the chiller 14 under two-stage temperature control, and the cryo-panel temperature of the first stage. The controller 60 may refer to the second roadmap while performing two-stage temperature control and obtain the heat load on the first and second stages of the chiller 14 based on the current operating frequency of the chiller 14 and the measured cryo-panel temperature of the first stage. The cryo-panel temperature of the first stage may be measured by a first temperature sensor 40.

[0067] The controller 60 may be configured to switch between single-stage and two-stage temperature control as needed. Normally, single-stage temperature control is performed when the cryopump 10 is in vacuum evacuation operation. The controller 60 may perform two-stage temperature control when the cryopump 10 is in standby mode, switch from two-stage to single-stage temperature control at the crossover, and perform single-stage temperature control during vacuum evacuation operation. Alternatively, the controller 60 may detect whether the gate valve 102 is open or closed, perform single-stage temperature control when the gate valve 102 is open, and perform two-stage temperature control when the gate valve 102 is closed.

[0068] As shown in Figure 3, if the gate valve 102 is detected to be closed (Y in S10), the controller 60 controls the chiller 14 to increase its cooling capacity compared to when the gate valve 102 is open (S12). On the other hand, if the gate valve 102 is detected to be open (N in S10), no such increase in cooling capacity is made.

[0069] As an example of control to increase the cooling capacity of the chiller 14, the controller 60 may be configured to operate the chiller 14 at an operating frequency of a first lower limit or higher when the gate valve 102 is open, and to operate the chiller 14 at an operating frequency of a second lower limit or higher than the first lower limit when the gate valve 102 is closed. In this way, if the gate valve 102 is closed while the chiller 14 is operating at an operating frequency lower than the second lower limit, the operating frequency of the chiller 14 will increase to this second lower limit. If the value of the operating frequency determined by the one-stage temperature control or two-stage temperature control is greater than the second lower limit, the operating frequency of the chiller 14 will increase to that value. In this way, the cooling capacity of the chiller 14 when the gate valve 102 is closed can be increased compared to when the gate valve 102 is open.

[0070] Furthermore, the second lower limit of the operating frequency may be the upper limit of the allowable operating frequency range of the chiller 14 or a slightly smaller default value (for example, it may be greater than 80% or 90% of the upper limit). In this way, the cooling capacity of the chiller 14 when the gate valve 102 is closed can be reliably increased compared to when the gate valve 102 is open.

[0071] As another example of control to increase the cooling capacity of the chiller 14, the controller 60 may be configured to determine the operating frequency of the chiller 14 so that the cooling temperature measured by the temperature sensor matches a first target temperature when the gate valve 102 is open, and to determine the operating frequency of the chiller 14 so that the cooling temperature measured by the temperature sensor matches a second target temperature lower than the first target temperature when the gate valve 102 is closed, and to operate the chiller 14 at the determined operating frequency. In this way as well, the chiller 14 can be controlled so that the operating frequency of the chiller 14 when the gate valve 102 is closed is higher than when the gate valve 102 is open.

[0072] For example, during the execution of single-stage temperature control, the controller 60 may determine the operating frequency of the chiller 14 so as to match the cooling temperature measured by the first temperature sensor 40 to a first target temperature when the gate valve 102 is open, and determine the operating frequency of the chiller 14 so as to match the cooling temperature measured by the first temperature sensor 40 to a second target temperature lower than the first target temperature when the gate valve 102 is closed. In this case, the first target temperature may be selected from a range of, for example, 80K to 120K. The second target temperature may be selected from a temperature of, for example, 60K or higher.

[0073] Alternatively, during two-stage temperature control, the controller 60 may determine the operating frequency of the chiller 14 so as to match the cooling temperature measured by the second temperature sensor 42 to the first target temperature when the gate valve 102 is open, and determine the operating frequency of the chiller 14 so as to match the cooling temperature measured by the second temperature sensor 42 to a second target temperature lower than the first target temperature when the gate valve 102 is closed. In this case, the first target temperature may be selected from a range of, for example, 12K to 20K. The second target temperature may be selected from a range of, for example, 10K to 12K.

[0074] Furthermore, while the control to increase the cooling capacity of the chiller 14 is being executed, the controller 60 may detect whether the gate valve 102 is open or not, and may terminate the increase in the cooling capacity of the chiller 14 if the gate valve 102 is open. In this way, the cooling capacity of the chiller 14 can be returned to its original state when the gate valve 102 is opened.

[0075] Figure 4(a) shows the operation of a cryopump in a comparative example. As described above, in most existing cryopumps, closing the gate valve reduces the heat load from the vacuum chamber to the cryopump's chiller, so the chiller is controlled to suppress its cooling capacity. Therefore, as shown in Figure 4(a), the operating frequency of the chiller is reduced while the gate valve is closed. At this time, the heat load on the chiller is also reduced, so the cryopanel temperature (for example, the second stage cryopanel temperature) is maintained at the target temperature Ta. However, the situation changes when the gate valve is opened. Due to the increase in heat load on the chiller associated with the crossover, the cryopanel temperature may temporarily rise significantly. In other words, the cryopanel temperature overshoots. As the cryopanel temperature deviates from the target temperature Ta in this way, the operating frequency of the chiller is increased, and then the cryopanel temperature gradually returns to the target temperature Ta.

[0076] Figure 4(b) shows the operation of the cryopump according to the embodiment. According to the embodiment, the cooling capacity of the refrigerator 14 can be increased when the gate valve 102 is closed compared to when the gate valve 102 is open. As shown in Figure 4(b), the operating frequency of the refrigerator 14 is increased while the gate valve is closed. At this time, the heat load on the refrigerator 14 is small, so the cryopanel temperature decreases. Subsequently, when the gate valve 102 opens, the heat load on the refrigerator 14 increases and the cryopanel temperature rises. However, since the cryopanel temperature has been sufficiently lowered in advance while the gate valve 102 was closed, the cryopanel temperature is expected to follow the target temperature Ta without significantly exceeding the target temperature Ta. In this way, according to the embodiment, it is possible to mitigate the cryopanel temperature overshoot that may occur during crossover.

[0077] The majority of the total operating time of the cryopump 10 is spent in vacuum evacuation operation of the vacuum chamber 100, during which time the gate valve 102 is open. The proportion of the total operating time of the cryopump 10 that the gate valve 102 is closed is considered to be very small. Therefore, in the cryopump 10 according to this embodiment, the power consumption may increase somewhat while the gate valve 102 is closed, but since such a time is expected to be very short, it will not have a significant impact.

[0078] Figure 5 is a flowchart showing another example of how to operate the cryopump 10 according to the embodiment. Instead of detecting the opening and closing of the gate valve 102, it may be detected whether or not the regeneration of the cryopump 10 is complete. Therefore, the controller 60 may detect whether or not the regeneration of the cryopump 10 is complete and control the refrigerator 14 to temporarily increase its cooling capacity following the completion of regeneration. In this way as well, it is possible to mitigate the overshoot of the cryopanel temperature that may occur during crossover, similar to the embodiment described above.

[0079] As shown in Figure 5, it is determined whether or not the regeneration of the cryopump 10 is complete (S20). The controller 60 may obtain the measured temperatures from the first temperature sensor 40 and the second temperature sensor 42 during the cool-down process of regeneration, compare the measured temperature of the first temperature sensor 40 with the target cooling temperature of the first stage cryo panel 18 for vacuum evacuation operation, and compare the measured temperature of the second temperature sensor 42 with the target cooling temperature of the second stage cryo panel unit 20 for vacuum evacuation operation. If either the measured temperature of the first temperature sensor 40 or the second temperature sensor 42 has not yet reached the target cooling temperature, the controller 60 may continue the cool-down process, and if the measured temperatures of the first temperature sensor 40 and the second temperature sensor 42 have both reached the target cooling temperature, the controller 60 may determine that the cool-down process, i.e., the regeneration of the cryopump 10, is complete.

[0080] If the regeneration of the cryopump 10 is complete (Y in S20), the controller 60 controls the refrigerator 14 to increase its cooling capacity (S22). The increase in the cooling capacity of the refrigerator 14 may be achieved, as in the embodiments described above, by increasing the operating frequency of the refrigerator 14, thereby lowering the target temperature in the first-stage temperature control, or by lowering the target temperature in the second-stage temperature control. On the other hand, if it is detected that the regeneration of the cryopump 10 is not complete (N in S20), no such increase in cooling capacity is performed.

[0081] The control to increase the cooling capacity of the chiller 14 may be performed until the gate valve 102 opens. In this case, the controller 60 may control the chiller 14 to increase its cooling capacity when the cryopump 10 is in standby mode. Alternatively, the control to increase the cooling capacity of the chiller 14 may be performed for a predetermined period of time.

[0082] Figure 6 is a schematic block diagram showing the configuration of a control device for a cryopump 10 according to another embodiment. To adjust the cooling capacity of the refrigerator 14, the refrigerator 14 may be equipped with a heating device 62 such as an electric heater. The heating device 62 may be provided in the first cooling stage 22, or in the second cooling stage 24, or in 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 / or to control the output of the heating device 62.

[0083] The controller 60 may be configured to operate the heating device 62 at a first output when the gate valve 102 is open, and to operate the heating device 62 at a second output lower than the first output or not operate it at all when the gate valve 102 is closed. By reducing the output of the heating device 62, the cooling capacity of the refrigerator 14 when the gate valve 102 is closed can be increased compared to when the gate valve 102 is open.

[0084] In the embodiment shown in Figure 6, as in the embodiment shown in Figure 2, the chiller 14 may be equipped with a chiller inverter 52 and configured to have a variable operating frequency. In this case, for example, the operating frequency of the chiller 14 may be controlled by single-stage temperature control or two-stage temperature control, and the chilling capacity may be adjusted using the heating device 62. Alternatively, in the embodiment shown in Figure 6, the chiller 14 may be driven at a constant operating frequency and may not be equipped with a chiller inverter 52.

[0085] The present invention has been described above based on examples. Those skilled in the art will understand that the present invention is not limited to the above embodiments, that various design changes are possible, and that various modifications are possible, and that such modifications also fall within the scope of the present invention. [Explanation of Symbols]

[0086] 10 cryopumps, 14 refrigerators, 60 controllers, 100 vacuum chambers, 102 gate valves.

Claims

1. A cryopump that can be mounted in a vacuum chamber via a gate valve, A refrigerator and A cryopump comprising: a controller configured to detect whether the gate valve is closed or not, and to control the refrigerator so that the cooling capacity of the refrigerator when the gate valve is closed is increased compared to when the gate valve is open.

2. The cryopump according to claim 1, characterized in that the controller is configured to receive a gate valve signal indicating the open / closed state of the gate valve and to detect whether or not the gate valve is closed based on the gate valve signal.

3. The cryopump according to claim 1, characterized in that the controller is configured to acquire the heat load to the refrigerator and to detect whether or not the gate valve is closed based on the acquired heat load.

4. The aforementioned refrigerator is configured to have a variable operating frequency. The cryopump according to any one of claims 1 to 3, characterized in that the controller is configured to operate the refrigerator at an operating frequency of a first lower limit or higher when the gate valve is open, and to operate the refrigerator at an operating frequency of a second lower limit or higher than the first lower limit when the gate valve is closed.

5. The aforementioned refrigerator is configured to have a variable operating frequency. The cryopump further includes a temperature sensor for measuring the cooling temperature of the refrigerator, The cryopump according to any one of claims 1 to 3, characterized in that the controller is configured to determine the operating frequency of the refrigerator so that the cooling temperature measured by the temperature sensor matches a first target temperature when the gate valve is open, and to determine the operating frequency of the refrigerator so that the cooling temperature measured by the temperature sensor matches 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.

6. The aforementioned refrigerator is equipped with a heating device, The cryopump according to any one of claims 1 to 4, characterized in that the controller is configured to operate the heating device at a first output when the gate valve is open, and to operate the heating device at a second output lower than the first output or not to operate it when the gate valve is closed.

7. A method for operating a cryopump, wherein the cryopump is mountable to a vacuum chamber via a gate valve and is equipped with a refrigerator, and the method is: To detect whether the gate valve is closed or not, A method characterized by increasing the cooling capacity of the refrigerator when the gate valve is closed compared to when the gate valve is open.

8. A refrigerator and A cryopump comprising: a controller that detects whether the regeneration of the cryopump is complete, and controls the refrigerator to temporarily increase its cooling capacity after the completion of the regeneration.

9. A method for operating a cryopump, wherein the cryopump is equipped with a refrigerator, and the method is: To detect whether the regeneration of the cryopump has been completed, A method characterized by comprising temporarily increasing the cooling capacity of the refrigerator after the completion of the aforementioned regeneration.

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