Cryopump and control system

Abstract

Adapt the cryopump to the radiation environment. [Solution] The cryopump 10 comprises a cold head motor 16a, an inverter 32b located remotely from the cold head motor 16a and configured to output a PWM voltage capable of driving the cold head motor 16a at a determined operating frequency, and at least one converter 34 connected between the inverter 32b and the cold head motor 16a. The converter 34 is configured to receive a PWM voltage from the inverter 32b, convert the PWM voltage into a cold head motor drive voltage that drives the cold head motor 16a at a determined operating frequency, and output the cold head motor drive voltage to the cold head motor 16a. The cold head motor drive voltage has a waveform with reduced high-frequency components compared to the PWM voltage.

Description

Technical Field

[0001] The present invention relates to a cryopump and a control device.

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. A cryopump is installed, for example, in a vacuum vessel of a vacuum process apparatus or other vacuum device, and provides a vacuum environment in the vacuum vessel.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] A cryopump may be mounted on a vacuum device that can generate radiation, such as an accelerator. Radiation can have adverse effects on a cryopump, for example, its control equipment, such as malfunction or damage.

[0005] One exemplary object of certain aspects of the present invention is to adapt a cryopump to a radiation environment.

Means for Solving the Problems

[0007] According to one aspect of the present invention, the control device comprises an inverter located remotely from the cold head motor and configured to output a PWM voltage capable of driving the cold head motor at a determined operating frequency, and at least one converter connected between the inverter and the cold head motor. The converter is configured to receive the PWM voltage from the inverter, convert the PWM voltage into a cold head motor drive voltage that drives the cold head motor at a determined operating frequency, and output the cold head motor drive voltage to the cold head motor. The cold head motor drive voltage has a waveform in which the high-frequency components are reduced compared to the PWM voltage. [Effects of the Invention]

[0008] According to the present invention, a cryopump can be adapted to a radiation environment. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram showing a cryopump according to an embodiment. [Figure 2] This figure schematically shows an example of a control output from an inverter to a cold head motor according to an embodiment. [Figure 3]This diagram schematically shows a part of the control device for a cryopump according to an embodiment. [Figure 4] This diagram schematically shows a part of the control device for a cryopump according to an embodiment. [Modes for carrying out the invention]

[0010] 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.

[0011] Figure 1 is a schematic diagram showing a cryopump 10 according to an embodiment. Figure 1 shows a vacuum device 100 on which the cryopump 10 is mounted, along with the cryopump 10.

[0012] The vacuum apparatus 100 comprises a vacuum vessel 102 and a host controller 104 that controls the vacuum apparatus 100. The vacuum apparatus 100 may also include an accelerator capable of generating radiation (e.g., proton beams, neutron beams, etc.) or it may be a radiation therapy device.

[0013] The cryopump 10 comprises a cryopump body 12 and a cryogenic refrigerator 14. The cryogenic refrigerator 14 comprises a cold head 16 and a compressor 18. The cold head 16 is equipped with a cold head motor 16a that drives the cold head 16.

[0014] The cryopump body 12 is attached to the vacuum chamber 102 of the vacuum apparatus 100 and is used to raise the vacuum level of the vacuum chamber 102 to the level required for the desired vacuum process. The cryopump body 12 contains an extremely cold surface (not shown), also called a cryopanel. Gas entering from the intake port of the cryopump body 12 is captured by condensation or adsorption on this extremely cold surface. The configuration of the cryopump body 12, including the arrangement and shape of the cryopanel, can be appropriately adopted from various known configurations, so it will not be described in detail here.

[0015] The compressor 18 of the cryogenic refrigerator 14 is configured to recover the working gas of the cryogenic refrigerator 14 from the cold head 16, pressurize the recovered working gas, and supply the working gas back to the cold head 16. The working gas is usually helium gas, but other suitable gases may be used.

[0016] The cryogenic refrigerator 14 includes a high-pressure line 20a and a low-pressure line 20b. The high-pressure line 20a connects the compressor 18 to the cold head 16 to supply high-pressure working gas, which has been compressed by the compressor 18, from the compressor 18 to the cold head 16. The low-pressure line 20b connects the compressor 18 to the cold head 16 to recover low-pressure working gas, which has been reduced in pressure by expansion in the cold head 16, from the cold head 16 to the compressor 18. The cold head 16 is also called the expander of the cryogenic refrigerator 14.

[0017] The cold head 16, the compressor 18, and the high-pressure line 20a and low-pressure line 20b connecting them constitute a working gas circulation circuit, i.e., the refrigeration cycle of the cryogenic refrigerator 14, thereby cooling the cooling stage of the cold head 16. A cryopanel is attached to the cooling stage of the cold head 16, and the cooling of the cold head 16 also cools the cryopanel. The cryogenic refrigerator 14 is, for example, a two-stage Gifford-McMahon (GM) refrigerator, but other types of cryogenic refrigerators may also be used.

[0018] The cryopump 10 also includes a control device including a cryopump controller 30, an input / output device (hereinafter also referred to as an I / O device 32), and a converter 34.

[0019] The cryopump controller 30 is configured to control the cryopump 10 based on a command received from the host controller 104 or autonomously. The cryopump controller 30 is also configured to transmit information regarding the cryopump 10 to the host controller 104. The cryopump controller 30 is connected to communicate with the cryopump main body 12 via the I / O device 32 and is directly connected to communicate with the compressor 18.

[0020] The I / O device 32 may be, for example, an I / O module or a remote I / O unit, and includes an I / O circuit 32a. The I / O circuit 32a is connected between the cryopump main body 12 and the cryopump controller 30 and is configured to aggregate the transmission and reception between the cryopump main body 12 and the cryopump controller 30. The I / O circuit 32a is connected to these various electrical components (for example, temperature sensors, pressure sensors, valves, etc.) provided in the cryopump main body 12, such as the cold head motor 16a, to transmit and receive signals.

[0021] In addition, the I / O device 32 includes an inverter 32b that controls the cold head motor 16a. The cold head motor 16a is powered from a power source 40 such as a commercial power supply (three-phase AC power supply) via the inverter 32b. The cold head motor 16a may be an electric motor whose operating frequency (i.e., the rotational speed of the cold head motor 16a) is variable, and can operate at an operating frequency corresponding to the output frequency of the inverter 32b. The operating frequency of the cold head motor 16a determines the number of times per unit time of the heat cycle (when the cryopump 14 is a GM cryocooler, the GM cycle) performed in the cold head 16, that is, the frequency of the heat cycle. As an example, the output frequency of the inverter 32b (i.e., the operating frequency of the cold head motor 16a) can vary in the range of 30 Hz to 100 Hz, or in the range of 40 Hz to 70 Hz.

[0022] FIG. 2 is a diagram schematically showing an example of the control output from the inverter 32b to the cold head motor 16a according to the embodiment. The inverter 32b is configured to generate a PWM (Pulse Width Modulation) voltage from the input voltage from the power source 40 by PWM control and output it to the cold head motor 16a. A known PWM control may be implemented in the inverter 32b.

[0023] In the waveform of the PWM voltage output from the inverter 32b, as shown in FIG. 2, the duty ratio of each pulse of the PWM voltage waveform is adjusted by the inverter 32b so that the time-average voltage of the PWM voltage has a sinusoidal waveform with the operating frequency determined by the cryopump controller 30. Therefore, when the PWM voltage is input from the inverter 32b to the cold head motor 16a, the cold head motor 16a can be driven at the operating frequency determined by the cryopump controller 30.

[0024] The cryopump controller 30 may determine the operating frequency of the cold head motor 16a so that the cooling temperature of the cryo panel inside the cryopump body 12 follows a target temperature value, and control the inverter 32b to operate the cold head motor 16a at the determined operating frequency.

[0025] For example, the cooling temperature of the cryopump may be measured by a temperature sensor provided on the cryopump body 12, and the cryopump controller 30 may acquire a measured temperature signal indicating the measured temperature from the temperature sensor via the I / O circuit 32a. The cryopump controller 30 may determine the output frequency of the inverter 32b by feedback control to minimize the deviation between the measured temperature and the target temperature value. The cryopump controller 30 may determine the output frequency of the inverter 32b as a function of the deviation between the measured temperature and the target temperature value (for example, by PID control). The cryopump controller 30 may transmit a motor control signal representing the determined output frequency of the inverter 32b to the I / O device 32. The inverter 32b may generate a PWM voltage according to the motor control signal and output it to the cold head motor 16a.

[0026] The internal configuration of the cryopump controller 30 and I / O device 32 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. However, in the diagram, they are 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.

[0027] If the vacuum device 100 may emit radiation from the vacuum vessel 102 during operation, the vacuum vessel 102 is placed in the radiation controlled area 106. The cryopump body 12 is also placed in the radiation controlled area 106 along with the vacuum vessel 102 of the vacuum device 100. The cold head motor 16a is part of the cryopump body 12 and is therefore placed in the radiation controlled area 106. The radiation controlled area 106 is pre-defined around the vacuum vessel 102 as an area where radiation doses exceeding a standard may occur, and access to this area is restricted, at least while the vacuum device 100 is operating. To prevent radiation that may be generated in the vacuum vessel 102 from leaking out, the radiation controlled area 106 may be surrounded by relatively thick radiation shielding walls 108, such as concrete walls or lead walls, and separated from the safety area outside.

[0028] Incidentally, some existing cryopumps have a design in which at least part of the control device of the cryopump 10 is directly attached to the cryopump body 12, such as by screwing the housing of the cryopump controller 30 and / or the housing of the I / O device 32 to the outside of the cold head 16. In this case, the control device of the cryopump 10 is located in the radiation controlled area 106 together with the cryopump body 12 and may be exposed to radiation doses exceeding the standard during the operation of the vacuum device 100. Radiation can have adverse effects on the control device, such as malfunction or damage.

[0029] To protect against radiation that may be generated in the vacuum chamber 102, the control device for the cryopump 10 may be located remotely from the cryopump body 12, preferably outside the radiation controlled area 106. The cryopump controller 30 and I / O device 32 may also be located outside the radiation controlled area 106. The compressor 18 may also be located outside the radiation controlled area 106. The host controller 104 of the vacuum device 100 may also be located outside the radiation controlled area 106.

[0030] In this way, the inverter 32b may be located remotely from the cold head motor 16a and outside the radiation controlled area 106. The inverter 32b may be connected to the cold head motor 16a by a power cable 36. The power cable 36 may have a power-transmitting core wire and an electromagnetic shield surrounding the core wire, and the electromagnetic shield may be grounded.

[0031] The power cable 36 may have a length of, for example, 1 m or more, 5 m or more, or 10 m or more. Alternatively, the power cable 36 may have a length of, for example, 100 m or less, 50 m or less, or 20 m or less. In this way, the power cable 36 can be long enough to connect the inverter 32b and the cold head motor 16a, which are separated by the radiation shielding wall 108 and located at a relatively long distance.

[0032] However, the inventors have experimentally found that if the inverter 32b is simply placed remotely from the cold head motor 16a and connected by a power cable 36, undesirable phenomena may occur, such as the cold head motor 16a not being able to operate at the determined operating frequency, or the cold head motor 16a not moving at all.

[0033] One possible reason is that the adverse effects of leakage current become too significant to ignore. Leakage current can occur, for example, in the electromagnetic shield of the power cable 36. The leakage current can disrupt the waveform of the PWM voltage transmitted through the power cable 36, potentially resulting in a waveform that is not as expected when input to the cold head motor 16a.

[0034] Alternatively, the cause could be based on the specifications of inverter 32b. Inverter 32b may be configured to detect the normal operation of the cold head motor 16a (i.e., operation at a determined operating frequency). Inverter 32b may be configured to increase the current supplied to the cold head motor 16a until normal operation of the cold head motor 16a is detected. In this case, if the cold head motor 16a does not operate normally, it could lead to the shutdown of inverter 32b and cold head motor 16a due to overcurrent.

[0035] Therefore, in this embodiment, as shown in Figure 1, the converter 34 is connected between the inverter 32b and the cold head motor 16a. The converter 34, like the I / O device 32, is located outside the radiation controlled area 106. The converter 34 is connected to the cold head motor 16a by the power cable 36 described above.

[0036] The converter 34 is positioned closer to the inverter 32b than to the cold head motor 16a. The converter 34 and inverter 32b may be connected by a power cable 38 that is shorter than the power cable 36. Alternatively, the converter 34 may be integrated into the I / O device 32 and constitute part of the I / O device 32. The close proximity of the converter 34 and inverter 32b can suppress distortion of the PWM voltage waveform between the inverter 32b and the converter 34.

[0037] The converter 34 is configured to receive a PWM voltage from the inverter 32b, convert the PWM voltage into a cold head motor drive voltage, and output the cold head motor drive voltage to the cold head motor 16a. The cold head motor drive voltage is configured to drive the cold head motor 16a at a determined operating frequency (i.e., the operating frequency of the cold head motor 16a represented by the PWM voltage). Therefore, when the cold head motor drive voltage is input to the cold head motor 16a from the converter 34, the cold head motor 16a can be driven at the determined operating frequency.

[0038] However, the cold head motor drive voltage has a waveform with reduced high-frequency components compared to the PWM voltage. Therefore, the converter 34 may include a low-pass filter that removes or reduces high-frequency components from the PWM voltage. The reduced high-frequency components may be, for example, frequency components exceeding the operating frequency of the cold head motor 16a determined by the cryopump controller 30, or frequency components exceeding twice the determined operating frequency of the cold head motor 16a, or frequency components exceeding five times the determined operating frequency of the cold head motor 16a.

[0039] As an exemplary configuration, the converter 34 may include a sine wave filter. The sine wave filter converts the PWM voltage to a cold head motor drive voltage such that the cold head motor drive voltage has a sinusoidal waveform with a determined operating frequency. In other words, the sine wave filter converts the PWM voltage to a time-averaged voltage as shown in Figure 2, and outputs this time-averaged voltage to the cold head motor 16a as the cold head drive voltage. The sine wave filter may be a known sine wave filter having, for example, an LC circuit or an LCR circuit.

[0040] The aforementioned leakage current is thought to become more pronounced as the PWM voltage contains more high-frequency components. According to the embodiment, since the cold head motor drive voltage has a waveform with reduced high-frequency components compared to the PWM voltage, the effect of leakage current is reduced or can be ignored. Therefore, the above-mentioned problem can be addressed and the cold head motor 16a can be operated at a determined operating frequency. The control device of the cryopump 10 can be placed outside the radiation controlled area 106, and the adverse effects of radiation on the control device are also reduced or prevented. In this way, the cryopump 10 can be adapted to a radiation environment.

[0041] Figure 3 is a schematic diagram illustrating a part of the control device of the cryopump 10 according to an embodiment. The cryopump 10 may further include at least one noise reduction component 42 provided between the inverter 32b and the power supply 40 of the inverter 32b. Various known noise reduction components can be used for the noise reduction component 42. For example, the noise reduction component 42 may include a noise filter 42a such as an LC filter, or a line noise filter such as a radio noise filter 42b. The noise reduction component 42 may also include a ferrite core 42c. In this way, noise such as common-mode noise can be reduced, and the control devices of the cryopump 10, such as the I / O device 32, can be operated stably.

[0042] Figure 4 is a schematic diagram illustrating a part of the control device of the cryopump 10 according to an embodiment. The converter 34 may comprise a first converter 34a and a second converter 34b. The first converter 34a may be positioned close to the inverter 32b, and the second converter 34b may be positioned close to the cold head motor 16a. The first converter 34a and the second converter 34b may be connected by the power cable 36 described above. The first converter 34a and the inverter 32b may be connected by a power cable 38 that is shorter than the power cable 36, and the second converter 34b and the cold head motor 16a may be connected by a power cable 39 that is shorter than the power cable 36.

[0043] The first converter 34a is configured to receive a PWM voltage from the inverter 32b and convert the PWM voltage to an intermediate voltage. The intermediate voltage has a waveform with reduced high-frequency components compared to the PWM voltage. The second converter 34b is configured to receive the intermediate voltage from the first converter 34a, convert the intermediate voltage to a cold head motor drive voltage, and output the cold head motor drive voltage to the cold head motor 16a. For example, the intermediate voltage may be a DC voltage, the first converter 34a may be an AC-DC converter that converts the PWM voltage to an intermediate voltage (DC voltage), and the second converter 34b may be a DC-AC converter that converts the intermediate voltage (DC voltage) to an AC voltage that drives the cold head motor 16a. In this way, the cold head motor 16a can be operated at a determined operating frequency, similar to the embodiment described with reference to Figure 1.

[0044] 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. Various features described in relation to one embodiment are applicable to other embodiments. New embodiments resulting from combinations will possess the combined effects of each of the embodiments combined.

[0045] In the above-described embodiment, the case in which the cryopump 10 has one cryopump body 12 is explained as an example, but the cryopump 10 may have multiple cryopump bodies 12, for example, several to more than ten or even more cryopump bodies 12. In addition, the cryopump 10 may be provided with multiple compressors 18 in order to supply and discharge refrigerant gas to and from the cold heads 16 of these cryopump bodies 12.

[0046] In the above-described embodiment, the case where the vacuum device 100 is a radiation therapy device is explained as an example, but the vacuum device 100 may be a device for other purposes. For example, the vacuum device 100 may be a vacuum process device such as an ion implanter, sputtering device, or deposition device, which is configured to process a workpiece, such as a wafer, in a desired vacuum process in a vacuum environment within a vacuum chamber 102.

[0047] In the embodiments described above, the present invention is explained as being applied to a cryopump as an example, but the present invention may be applied to a cryogenic refrigerator instead of a cryopump. In one embodiment, the cryogenic refrigerator may include a cold head motor, an inverter located remotely from the cold head motor and configured to output a PWM voltage capable of driving the cold head motor at a determined operating frequency, and at least one converter connected between the inverter and the cold head motor. The converter may be configured to receive a PWM voltage from the inverter, convert the PWM voltage to a cold head motor drive voltage that drives the cold head motor at a determined operating frequency, and output the cold head motor drive voltage to the cold head motor. The cold head motor drive voltage may have a waveform in which the high-frequency components are reduced compared to the PWM voltage.

[0048] Although the present invention has been described using specific terms based on the embodiments, the embodiments only illustrate one aspect of the principle and application of the present invention, and many modifications and changes in arrangement are permitted in the embodiments, as long as they do not depart from the spirit of the present invention as defined in the claims. [Explanation of Symbols]

[0049] 10 Cryopump, 12 Cryopump body, 14 Cryogenic refrigerator, 16 Cold head, 16a Cold head motor, 18 Compressor, 30 Cryopump controller, 32 I / O device, 32a I / O circuit, 32b Inverter, 34 Converter, 34a First converter, 34b Second converter, 36 Power cable, 42 Noise reduction component, 100 Vacuum device, 102 Vacuum vessel, 106 Radiation controlled area.

Claims

1. Cold head motor and, An inverter located remotely from the cold head motor, configured to output a PWM voltage capable of driving the cold head motor at a determined operating frequency, At least one converter connected between the inverter and the cold head motor, The PWM voltage is received from the inverter. The PWM voltage is converted to a cold head motor drive voltage that drives the cold head motor at the determined operating frequency. The system includes a converter configured to output the cold head motor drive voltage to the cold head motor, The cryopump is characterized in that the cold head motor drive voltage has a waveform in which high-frequency components are reduced compared to the PWM voltage.

2. The at least one converter includes a sinusoidal filter that converts the PWM voltage to the cold head motor drive voltage, The cryopump according to claim 1, characterized in that the cold head motor drive voltage has a sinusoidal waveform having the determined operating frequency.

3. The cryopump according to claim 2, characterized in that the sine wave filter is positioned closer to the inverter than the cold head motor.

4. The cryopump according to claim 2, characterized in that the sine wave filter is connected to the cold head motor by a power cable having a length of 1 m to 100 m.

5. The aforementioned cold head motor is located in a radiation controlled area. The cryopump according to claim 2, characterized in that the inverter and the sinusoidal filter are located outside the radiation controlled area.

6. The at least one converter is A first converter configured to receive the PWM voltage from the inverter and convert the PWM voltage into an intermediate voltage, The system includes a second converter configured to receive the intermediate voltage from the first converter, convert the intermediate voltage into the cold head motor drive voltage, and output the cold head motor drive voltage to the cold head motor, The cryopump according to claim 1, characterized in that the intermediate voltage has a waveform in which the high-frequency components are reduced compared to the PWM voltage.

7. The cryopump according to claim 6, characterized in that the intermediate voltage is a DC voltage.

8. Cryopump according to any one of claims 1 to 7, further comprising a noise reduction component provided between the inverter and the power supply of the inverter.

9. An inverter located remotely from the cold head motor, configured to output a PWM voltage capable of driving the cold head motor at a determined operating frequency, At least one converter connected between the inverter and the cold head motor, The PWM voltage is received from the inverter. The PWM voltage is converted to a cold head motor drive voltage that drives the cold head motor at the determined operating frequency. The system includes a converter configured to output the cold head motor drive voltage to the cold head motor, The control device is characterized in that the cold head motor drive voltage has a waveform in which the high-frequency components are reduced compared to the PWM voltage.

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