JP5460644B2 - Cryopump - Google Patents

Description

  The present invention relates to a cryopump and a manufacturing method thereof.

  The cryopump is a vacuum pump that traps and exhausts gas molecules by condensation or adsorption onto a cryopanel cooled to a very low temperature. The cryopump is generally used to realize a clean vacuum environment required for a semiconductor circuit manufacturing process or the like. One application of a cryopump is when a non-condensable gas such as hydrogen occupies most of the gas to be evacuated, such as in an ion implantation process. A non-condensable gas can be exhausted only by adsorbing it in an adsorption region cooled to a very low temperature.

JP-A-1-92591 Japanese Patent Laid-Open No. 60-13992 Special table 2008-514849 gazette JP 2009-162074 A

  One exemplary objective of certain aspects of the present invention is to provide a cryopump for high-speed pumping of non-condensable gases such as hydrogen, and a method for manufacturing such a cryopump.

  A cryopump according to an aspect of the present invention provides a first cooling stage for providing a first cooling temperature, and a second cooling temperature lower than the first cooling temperature and used for adsorption of a noncondensable gas. A radiant shield that includes a refrigerator that includes a front end of a shield that forms an opening for receiving gas, is thermally connected to the first cooling stage, and surrounds the second cooling stage; A cryopanel assembly thermally connected to a cooling stage, wherein an open space to the opening is formed between an outer periphery of the cryopanel and a radiation shield, and at least part of the cryopanel is visible from the front end of the shield An assembly. The cryopanel assembly includes a top panel that faces the opening, and an intermediate panel that includes the front surface of the panel that faces the opening and is disposed on the opposite side of the opening to the top panel. An open portion that continues to the open space is formed between the adjacent cryopanel and the front surface of the panel, and the open portion has a depth greater than the distance between the adjacent cryopanel and the front surface of the panel, The intermediate panel has an adsorption region for a non-condensable gas on the front surface of the panel, and the adsorption region has a boundary determined by the intersection of the line of sight from the front end of the shield to the end of the adjacent cryopanel and the front surface of the panel. It is formed inside.

  A cryopump according to an aspect of the present invention includes a radiation shield, a plurality of front surfaces arranged in the radiation shield from the front to the back, each of which faces the opening of the radiation shield, and a back surface facing the opposite side of the opening. And a cryopanel assembly that forms an open space to the opening between the outer periphery of the plurality of cryopanels and the radiation shield. In the cryopanel assembly, at least 70% of the total area of the front and back surfaces of the plurality of cryopanels is covered with an adsorbent capable of adsorbing hydrogen, and the cryopump has a hydrogen capture probability of at least 30%. The adsorbent is accommodated between the back surface of each of the plurality of cryopanels and the front surface of the cryopanel adjacent to the back of the cryopanel, and the adsorbent with respect to the total adsorbent area of the plurality of cryopanels. The adsorbent visible rate, which is the ratio of the adsorbent area visible from the opening, is less than 7%.

  A cryopump according to an aspect of the present invention includes an arrangement of a plurality of cryosorption panels surrounded by a cryopump internal open space that is open to a cryopump opening, and a radiation shield that surrounds the cryopump internal open space; . At least one of the plurality of cryosorption panels includes a panel end protruding into the cryopump internal open space and directed toward the radiation shield, the panel end having an adsorbent deficient area.

  Another aspect of the present invention is a method for manufacturing a cryopump. This method includes masking the substrate of the cryopanel and adhering an adsorbent to the surface of the substrate that is not masked.

  According to the present invention, a cryopump for high-speed exhaust of non-condensable gas such as hydrogen and a method for manufacturing such a cryopump are provided.

It is a figure which shows typically the ion implantation apparatus and cryopump which concern on one Embodiment of this invention. It is sectional drawing which shows typically the cryopump which concerns on one Embodiment of this invention. It is a top view which shows typically the cryopump which concerns on preferable one Embodiment. It is sectional drawing which shows typically the cryopump which concerns on preferable one Embodiment. It is a figure for demonstrating the adsorption | suction area | region formed in a cryopanel regarding the cryopump shown in FIG. It is a top view which shows the panel front surface of a cryopanel regarding the cryopump shown in FIG.4 and FIG.5. It is a figure which shows the back surface of the cryopanel shown in FIG. It is a table which shows an example of the adsorbent omission ratio or the coverage of the cryopanel assembly which concerns on one Embodiment of this invention. It is a table which shows an example of the adsorbent omission ratio or the coverage of the cryopanel assembly which concerns on one Embodiment of this invention. It is a figure which shows hydrogen discharge speed change of the cryopump through regeneration based on one Embodiment of this invention. It is a flowchart for demonstrating the manufacturing method of the cryopump which concerns on one Embodiment of this invention. It is a flowchart for demonstrating the method for manufacturing the cryopump which concerns on one Embodiment of this invention.

  A cryopump according to an aspect of the present invention includes an exposed cryosorption panel arrangement. The panel arrangement has areas lacking adsorbent, such as activated carbon, at sites that are visible from the cryopump opening or elsewhere. Most panel surfaces and adsorbents thereon are configured to be covered by adjacent panels so that they are not directly visible from the cryopump opening, and the rate of adsorbent visibility from the cryopump opening is zero or slight. The adsorbent is exposed in an open space surrounding the panel array. The adsorbent missing area is formed on the same plane as the adsorbent existing area, and the boundary of the adsorbent missing area is defined by the adsorbent. That is, the adsorbent missing area and the existing area divide the common panel surface.

  Such a hybrid configuration of exposure and non-exposure helps to achieve both high-speed exhaust of non-condensable gas and protection of the adsorbent from hardly regenerated gas. This leads to maintaining stable exhaust performance through repeated regeneration processes. In addition, the reduction in the visible rate due to the lack of adsorbent from the sorption panel contributes to the improvement of the exhaust efficiency of the non-condensable gas and the provision of a cryopump that is excellent in energy saving.

  In one typical application of a cryopump, the gases to be evacuated include a condensable gas and a small amount of non-condensable gas. In order to avoid the non-condensable gas adsorption performance being hindered by the condensation gas ice layer deposition, cryopumps for these typical applications are cryosorption by cryocondensation panels or condensation panels. The panel or adsorption panel is hidden. A typical cryosorption panel is formed by covering an entire area of a certain surface with activated carbon.

  For example, one cryopanel structure has a double structure having a condensation panel for capturing condensable gas on the outside and a sorption panel for capturing noncondensable gas on the inside. Other cryopanel structures have a cryocondensation surface on the surface facing the cryopump opening and a cryosorption surface on the back surface thereof. For example, when the panel has a bent portion at its end, for example, the entire area of one side of the panel excluding the surface of the bent portion separated by the folding line is covered with activated carbon, or the entire area including the surface of the bent portion is covered. Covered with activated carbon.

  In general, both the condensation panel and the sorption panel are cooled to a common cooling temperature, for example, an extremely low temperature of 10K to 20K. Condensation panels and sorption panels are surrounded by a radiation shield or radiation shield to protect them from radiant heat. The radiation shield is cooled to a cooling temperature higher than that of the condensation panel and the sorption panel, for example, a cryogenic temperature of 80K to 100K. The radiation shield can also be regarded as a cryopanel that provides a relatively high temperature cryogenic surface.

  Depending on the application of the cryopump, condensation of condensable gas on the cryogenic surface may not be a problem. An example is a cryopump for an ion implantation apparatus. In this application, the amount of gas condensed in the low-temperature cryopanel is small, and the main purpose of the cryopump is to exhaust non-condensable gas (for example, hydrogen). Therefore, it is desirable to make the non-condensable gas easily reachable by exposing the sorption panel toward the cryopump opening. As a result, a high exhaust speed can be realized.

  The improvement in the exhaust speed by exposure contributes to the reduction of the sorption panel area for realizing a certain required exhaust speed. This is because the flow of gas to the adsorbent is improved by the exposure, and the exhaust speed per panel unit area is increased. As a result, the required panel area is reduced and the weight of the cryopanel structure is also reduced.

  Reduction of the panel weight shortens the time required for the regeneration process of the cryopump. Since the cryopump is a so-called built-in vacuum pump, a regeneration process for discharging the gas accumulated inside to the outside at an appropriate frequency is executed. For regeneration, the temperature of the cryopanel is raised to a temperature higher than the operating temperature of the cryopanel (for example, room temperature), the gas condensed or adsorbed on the panel surface is re-released and discharged to the outside, and the operating temperature of the cryopanel again. This is a process of cooling. One major factor that determines the regeneration time is the time required for recooling. The recooling time correlates with the panel structure weight. The recooling time is shortened by reducing the weight of the panel structure, and as a result, the regeneration time is also shortened.

  The gas accumulated in the cryopump is normally exhausted substantially completely by the regeneration process, and when the regeneration is completed, the cryopump is restored to the specified exhaust performance. However, a part of the accumulated gas has a relatively high ratio of remaining in the adsorbent even after the regeneration process.

  For example, in a cryopump installed for evacuation of an ion implantation apparatus, it was observed that a sticky substance adheres to activated carbon as an adsorbent. It was difficult to completely remove the adhesive substance even after the regeneration treatment. This adhesive substance is considered to be caused by organic outgas discharged from the photoresist coated on the substrate to be processed. Alternatively, it may be caused by a toxic gas used as a dopant gas, that is, a raw material gas in the ion implantation process. There is a possibility that it may be caused by other by-product gas in the ion implantation process. There is a possibility that these gases are combined to produce an adhesive substance.

  In the ion implantation process, most of the gas exhausted from the cryopump can be hydrogen gas. The hydrogen gas is discharged to the outside substantially completely by regeneration. If the amount of the hardly regenerating gas is small, the influence of the hardly regenerating gas on the exhaust performance of the cryopump in one cryopumping process is slight. However, as the cryopumping process and the regeneration process are repeated, the difficult-to-regenerate gas is gradually accumulated in the adsorbent, which may reduce the exhaust performance. When the exhaust performance falls below the allowable range, maintenance work including, for example, replacement of the adsorbent or the cryopanel together with it, or chemical removal of the difficult regeneration gas to the adsorbent is required.

  Therefore, a cryopump according to an aspect of the present invention includes an exposed cryosorption panel array, and an adsorbent such as activated carbon is omitted from a part thereof. The exposed cryosorption panel array has a cryopump internal open space that is opened to the cryopump opening. This internal open space is surrounded by a radiation shield. The opened local space is defined by the adjacent sorption panels in the cryosorption panel arrangement, and the local space is opened to the cryopump external space through the cryopump internal open space. The openness of the cryosorption panel facilitates the arrival of gas to the panel surface and supports the realization of high-speed exhaust of non-condensable gas such as hydrogen by the cryopump.

  In one embodiment, the missing part of the adsorbent is set in a region of the cryosorption panel that is visually recognized from the outside of the cryopump through the cryopump opening. The adsorbent missing part may be provided at the end of the sorption panel that protrudes into the open space inside the cryopump and faces the radiation shield. The missing part can be used as a cryocondensation panel.

  Thus, by avoiding direct exposure of the adsorbent to the cryopump opening, or by reducing the rate at which the adsorbent can be seen from the cryopump opening, the adsorbent by the hardly regenerated gas contained in the gas entering the cryopump. The action of is prevented or reduced. The hardly regenerating gas is accumulated in the condensation panel, and the accumulation of sticky substances in the adsorbent is reduced. In this way, both high-speed exhaust of non-condensable gas and protection of the adsorbent from the difficult-to-regenerate gas can be achieved.

  A cryopump according to a specific example of this technical idea is a cryopump suitable for use in an evacuation system of an ion implantation apparatus. Another example is a cryopump suitable for use in a vacuum exhaust system of a substrate processing apparatus. For example, the substrate processing apparatus processes a substrate coated with a resist with a process gas.

  Here, the difficult-to-regenerate gas is, for example, a gas that has not been completely discharged to the outside of the pump when the discharge of the predetermined gas (for example, hydrogen) to the outside of the cryopump is substantially completed in the predetermined regeneration process. . Moreover, even if it passes through the regeneration process adjusted so that predetermined | prescribed gas may be discharged | emitted completely out of a cryopump, it can be said that the gas whose residue in an adsorbent exceeds a reference | standard is a difficult regeneration gas. For example, organic outgas from a resist or other coating applied to the wafer surface may also have a high residual ratio in the adsorbent during the regeneration process. In addition, a toxic dopant gas used in the ion implantation process can also be a difficult-to-regenerate gas.

  The resist is, for example, an organic resist made of an organic material. The process gas may be a reactive process gas that chemically reacts directly with the processing target (for example, the substrate) or the resist on the surface thereof. Alternatively, the process gas may be a gas for assisting the introduction of the reactive gas into the processing target. When the substrate processing apparatus is a sputtering apparatus, the process gas is an inert gas such as argon. When the substrate processing apparatus is an ion implantation apparatus, the process gas is, for example, hydrogen gas or dopant gas. An organic gas can be released from the resist by the interaction between the process gas and the resist during the process. Further, outgas can be released from the resist by a vacuum environment even when not in process. This organic gas can include, for example, aromatics, straight chain hydrocarbons, alcohols, ketones, ethers, and the like.

  The difficult-to-regenerate gas is not limited to the organic gas from the resist and the dopant gas used for the ion implantation process. For example, depending on the process, the process gas itself may be a hardly regenerating gas. In addition, the gas released from the coating other than the resist on the substrate may be a difficult-to-regenerate gas.

  A cryopump according to an embodiment provides a first cooling stage for providing a first cooling temperature, and a second cooling temperature that is lower than the first cooling temperature and used for adsorption of a noncondensable gas. A radiant shield that includes a refrigerator including the second cooling stage, a shield front end that forms an opening for receiving gas, is thermally connected to the first cooling stage, and surrounds the second cooling stage; A cryopanel assembly thermally connected to a stage, wherein an open space to the opening is formed between an outer periphery of the cryopanel assembly and a radiation shield, and at least part of the cryopanel assembly is visible from the front end of the shield And may be provided.

  The cryopanel assembly may include a top panel that faces the shield opening, and an intermediate panel that includes the front surface of the panel that faces the shield opening and is disposed on the opposite side of the top panel from the shield opening. An open portion continuous to the open space may be formed between the adjacent cryopanel facing the front surface of the intermediate panel and the front surface of the panel. An open portion continuous to the open space may be formed between the adjacent cryopanel facing the front surface of the intermediate panel and the front surface of the panel. The open portion may have a depth greater than the distance between the adjacent cryopanel and the front surface of the panel.

  The intermediate panel may have an adsorption region for non-condensable gas on the front of the panel. The suction region may be formed inside a boundary determined by an intersection of a line of sight from the front end of the shield to the end of the adjacent cryopanel and the front surface of the panel. The adsorption region may occupy an area inside the boundary on the front surface of the panel.

  The intermediate panel may have a condensing region for condensable gas on its surface. The condensation region may include an area outside the boundary on the front surface of the panel.

  The outer peripheral part of the intermediate panel may extend parallel to the top panel and closer to the radiation shield than the outer peripheral part of the top panel. The intermediate panel may include a plurality of plates each including a front surface facing the shield opening and a back surface facing the opening opposite to each other and arranged in parallel with each other.

  The cryopanel assembly may include a lower panel disposed on the opposite side of the intermediate panel from the shield opening. The outer peripheral portion of the lower panel may extend parallel to the intermediate panel and to a position closer to the radiation shield than the outer peripheral portion of the intermediate panel.

  The cryopump may include a louver that is thermally connected to the radiation shield and disposed in the shield opening. The louver may have an intermediate size between the top panel and the intermediate panel, and an open region may be formed between the outer periphery of the louver and the radiation shield.

  The intermediate panel is covered with an adsorbent at least 70% of the surface area, the adsorbent is capable of adsorbing hydrogen, and the cryopump may have a hydrogen capture probability of at least 30%. The adsorbent is accommodated in the open portion, and the adsorbent visible ratio, which is the ratio of the adsorbent area visible from the shield opening to the total area of the adsorbent, may be less than 7%.

  A cryopump according to an embodiment includes a radiation shield, a plurality of front surfaces arranged in the radiation shield from the front to the back, each having a front surface facing the opening of the radiation shield and a rear surface facing the opposite side of the opening. A cryopanel assembly including an array of cryopanels and forming an open space to the opening between an outer peripheral portion of the plurality of cryopanels and the radiation shield may be provided. In the cryopanel assembly, at least 70% of the total area of the front and back surfaces of the plurality of cryopanels is covered with an adsorbent capable of adsorbing hydrogen, and the cryopump may have a hydrogen capture probability of at least 30%. . The adsorbent is accommodated between the back surface of each of the plurality of cryopanels and the front surface of the cryopanel adjacent to the back of the cryopanel, and is visible from the shield opening for the total adsorbent area of the plurality of cryopanels. The adsorbent visible rate, which is the ratio of the adsorbent area, may be less than 7%.

  In the arrangement of the plurality of cryopanels, at least a part of the back cryopanel is shielded from the opening by the front cryopanel, and the adsorbent is shielded from the shield opening so that the adsorbent is not visible. It may be provided at the site.

  The total adsorbent area may be 90% or less of the total area of the front and back surfaces of the plurality of cryopanels.

  At least 90% of the adsorbent may be exposed to the radiation shield or shield opening.

  The cryopump according to one embodiment includes an array of a plurality of cryosorption panels surrounded by a cryopump internal open space opened to a cryopump opening, a radiation shield surrounding the cryopump internal open space, May be provided. At least one of the plurality of cryosorption panels may include a panel end projecting into the cryopump internal open space and directed toward the radiation shield, the panel end having an adsorbent deficient area.

  The adsorbent missing area may be formed on the same surface as the adsorbent existing area. In the adsorbent missing area, the surface of the cryopanel substrate may be exposed for cryocondensation. The adsorbent deficient area may be in a peripherally exposed part that is visually recognized through the cryopump opening.

  The method for manufacturing a cryopump according to an embodiment may include masking a base material of a cryopanel and adhering an adsorbent to the surface of the base material that is not masked. Masking may include masking an exposed portion of the substrate that is not shielded by another cryopanel. This method determines the outside of the boundary defined by the line of sight from the front end of the radiation shield to the end of the cryopanel adjacent to the cryopanel and the crossing of the cryopanel for each cryopanel in the arrangement of a plurality of cryopanels as a masking region. May include.

  A cryopump according to an embodiment provides a first cooling stage for providing a first cooling temperature, and a second cooling temperature that is lower than the first cooling temperature and used for adsorption of a noncondensable gas. A radiant shield that includes a refrigerator including the second cooling stage, a shield front end that forms an opening for receiving gas, is thermally connected to the first cooling stage, and surrounds the second cooling stage; A cryopanel assembly thermally connected to the stage, wherein an open space to the shield opening is formed between the outer edge and the radiation shield, and at least part of the cryopanel assembly is visible from the front end of the shield; , May be provided.

  The cryopanel assembly may include a top panel that faces the shield opening, and an intermediate panel that includes the front surface of the panel that faces the shield opening and is disposed on the opposite side of the top panel from the shield opening. The outer peripheral part of the adjacent cryopanel facing the panel front of the intermediate panel and the part of the panel front facing the outer peripheral part extend in parallel toward the radiation shield in the open space, and the front of the panel is not condensed. It may be divided into an adsorption region for a reactive gas and a condensation region for a condensable gas. The outer peripheral part of the front surface of the panel may be divided into an adsorption region for non-condensable gas and a condensation region for condensable gas.

  The adjacent cryopanel may be a top panel, and the outer peripheral portion of the intermediate panel may extend to a position closer to the radiation shield than the outer peripheral portion of the top panel. Each of the top panel and the intermediate panel includes a plurality of plates, each including a front surface facing the shield opening and a back surface facing the opening, and arranged in parallel to each other. It may be larger than the plate.

  The cryopanel assembly may further include a lower panel disposed on the opposite side of the intermediate panel from the shield opening. The outer peripheral portion of the lower panel may extend parallel to the intermediate panel and to a position closer to the radiation shield than the outer peripheral portion of the intermediate panel. The lower panel includes a plurality of plates, each including a front surface facing the shield opening and a back surface facing the opening, arranged in parallel to each other, the plates being larger than the plates of the intermediate panel. May be.

  An open portion continuous to the open space is formed between the portion of the front panel of the intermediate panel and the outer peripheral portion of the adjacent cryopanel, and the open portion has a depth that is close to the adjacent cryopanel and the front surface of the panel. It may be larger than the interval.

  The cryopump may include a louver that is thermally connected to the radiation shield and disposed in the shield opening. The louver may have an intermediate size between the top panel and the intermediate panel, and an open region may be formed between the outer periphery of the louver and the radiation shield.

  The cryopump has a hydrogen capture probability of at least 30%, and the intermediate panel includes a cryopanel substrate for supporting an adsorbent capable of adsorbing hydrogen on the surface, and has a large total surface area of the cryopanel substrate. In both cases, by removing the adsorbent from 30%, the hydrogen pumping efficiency, which is the ratio between the hydrogen pumping speed of the cryopump and the adsorbent area, is increased compared to the case where the entire surface of the cryopanel substrate is covered with the adsorbent. Also good.

  A cryopump according to an embodiment includes a radiation shield and a plurality of cryopanels arranged from the front to the back in the radiation shield, and includes a shield opening between an outer peripheral portion of the plurality of cryopanels and the radiation shield. And a cryopump assembly having an open space with a cryopump having a hydrogen capture probability of at least 30%. Each of the plurality of cryopanels includes a cryopanel substrate for supporting an adsorbent capable of adsorbing hydrogen on the surface, and by removing the adsorbent from at most 30% of the total surface area of the cryopanel substrate. The hydrogen pumping efficiency, which is the ratio between the hydrogen pumping speed of the cryopump and the adsorbent area, may be made higher than when the entire surface of the cryopanel substrate is covered with the adsorbent.

The hydrogen exhaust efficiency may be 5 × 10 ⁻² L / s · mm ² or more. At least 10% of the total surface area of the cryopanel substrate may be an adsorbent missing area. At least 90% of the adsorbent may be exposed to the radiation shield or shield opening.

  The method according to an embodiment includes a value of a panel structure parameter that gives a maximum hydrogen pumping speed when the panel structure parameter is changed under a condition that the adsorbent is missing from a part of the surface of the cryosorption panel. Determining the configuration of the cryosorption panel arrangement based on the value of the panel structure parameter. Panel structure parameters may include the dimensions of the cryosorption panel.

  FIG. 1 is a diagram schematically showing an ion implantation apparatus 1 and a cryopump 10 according to an embodiment of the present invention. An ion implantation apparatus 1 as an example of a beam irradiation apparatus for irradiating a target with a beam includes an ion source unit 2, a mass analyzer 3, a beam line unit 4, and an end station unit 5.

  The ion source unit 2 is configured to ionize an element to be implanted into the substrate surface and extract it as an ion beam. The mass analyzer 3 is provided downstream of the ion source unit 2 and is configured to select necessary ions from the ion beam.

  The beam line unit 4 is provided downstream of the mass analyzer 3 and includes a lens system that shapes the ion beam and a scanning system that scans the substrate with the ion beam. The end station unit 5 is provided downstream of the beam line unit 4, and a substrate holder (not shown) that holds a substrate 8 to be subjected to ion implantation processing, that is, an irradiation target, and the substrate 8 with respect to the ion beam. A drive system for driving is included. A beam path 9 in the beam line unit 4 and the end station unit 5 is schematically indicated by broken arrows.

Further, the ion implantation apparatus 1 is provided with a vacuum exhaust system 6. The evacuation system 6 is provided to maintain a desired high vacuum (for example, a high vacuum of about 10 ⁻⁵ Pa) from the ion source unit 2 to the end station unit 5. The vacuum exhaust system 6 includes cryopumps 10a, 10b, and 10c.

  For example, the cryopumps 10 a and 10 b are attached to the cryopump mounting opening on the vacuum chamber wall surface of the beam line unit 4 for evacuating the vacuum chamber of the beam line unit 4. The cryopump 10 c is attached to a cryopump mounting opening in the vacuum chamber wall surface of the end station unit 5 for evacuating the vacuum chamber of the end station unit 5. The beam line unit 4 and the end station unit 5 may each be configured with an evacuation system 6 so as to be evacuated by one cryopump 10. Further, the vacuum exhaust system 6 may be configured such that the beam line unit 4 and the end station unit 5 are exhausted by a plurality of cryopumps 10 respectively.

  The cryopumps 10a and 10b are attached to the beam line unit 4 via gate valves 7a and 7b, respectively. The cryopump 10c is attached to the end station unit 5 through a gate valve 7c. Hereinafter, the cryopumps 10a, 10b, and 10c are collectively referred to as the cryopump 10 and the gate valves 7a, 7b, and 7c are collectively referred to as the gate valve 7 as appropriate. During the operation of the ion implantation apparatus 1, the gate valve 7 is opened, and the cryopump 10 evacuates. When regenerating the cryopump 10, the gate valve 7 is closed.

  The evacuation system 6 may further include a turbo molecular pump and a dry pump for making the ion source unit 2 high vacuum. Further, the vacuum exhaust system 6 may include a roughing pump for exhausting the beam line unit 4 and the end station unit 5 from the atmospheric pressure to the operation start pressure of the cryopump 10 in parallel with the cryopump 10.

  The gas present in the beam line unit 4 and the end station unit 5 and the introduced gas are exhausted by the cryopump 10. Most of the exhausted gas is usually hydrogen gas. Using the cryopanel of the cryopump 10, exhausted gas including hydrogen gas is exhausted from the beam path 9. Note that the exhausted gas may include a gas released from the resist applied to the substrate, a dopant gas, or a by-product gas in the ion implantation process.

  The ion implantation apparatus 1 includes a main controller 11 for controlling the apparatus. The cryopump 10 is provided with a cryopump controller (hereinafter referred to as a “CP controller” for simplicity) 100 for controlling the cryopump 10. It can be said that the main controller 11 is an upper controller that supervises the cryopump 10 via the CP controller 100. Each of the main controller 11 and the CP controller 100 includes a CPU that executes various arithmetic processes, a ROM that stores various control programs, a RAM that is used as a work area for data storage and program execution, an input / output interface, a memory, and the like. . The main controller 11 and the CP controller 100 are communicably connected to each other.

  The CP controller 100 is provided separately from the cryopump 10 and controls each of the plurality of cryopumps 10. Each cryopump 10a, 10b, 10c may be provided with an IO module (not shown) for processing input / output communicating with the CP controller 100. Note that the CP controller 100 may be individually provided in each of the cryopumps 10a, 10b, and 10c.

  The cryopump 10 for the ion implantation apparatus 1 mainly exhausts hydrogen gas as described above. In order to increase the throughput of the ion implantation process of the ion implantation apparatus 1, a cryopump 10 that can exhaust hydrogen gas at high speed is required. In addition, there is a demand for a cryopump that is excellent in improving the exhaust efficiency of hydrogen and thus excellent in energy saving. Therefore, the cryopump 10 includes an adsorption region for a non-condensable gas that is substantially unexposed in the exposed cryosorption panel array 14.

  FIG. 2 is a cross-sectional view schematically showing the cryopump 10 according to the embodiment of the present invention. FIG. 3 is a top view of the cryopump 10 according to a preferred embodiment. FIG. 4 is a cross-sectional view schematically showing a cryopump 10 according to a preferred embodiment.

  The exposed cryopanel array 14 forms a cryopump internal open space 30 that is opened to the cryopump opening 31 between the outer peripheral portion and the radiation shield 16. An open local space 54 is defined by the adjacent cryopanels 50 of the cryopanel array 14, and the local space 54 is continuous to the cryopump internal open space 30. The adsorption region is formed on the surface of the cryopanel 50 surrounding the local space 54. Such openness of the local space 54 facilitates the arrival of gas to the adsorption region, and supports the realization of high-speed exhaust of non-condensable gas such as hydrogen by the cryopump 10.

  At least a part of the open local space 54 is shielded from the cryopump opening 31 by the adjacent cryopanel 50, and the adsorption region is accommodated in the local space 54. By avoiding direct exposure of the adsorption region to the cryopump opening 31, the adsorption region is protected from the hardly regenerated gas contained in the gas entering the cryopump 10. In this way, both high-speed exhaust of non-condensable gas and protection of the adsorption region from hardly regenerated gas can be achieved.

The cryopump 10 includes: a first cryopanel that is cooled to a first cooling temperature level; and a second cryopanel that is cooled to a second cooling temperature level lower than the first cooling temperature level. Prepare. The first cryopanel captures a gas having a low vapor pressure at the first cooling temperature level by condensation. For example, a gas having a vapor pressure lower than a reference vapor pressure (for example, 10 ⁻⁸ Pa) is exhausted.

  The second cryopanel is a sorption panel that traps non-condensable gas that does not condense even at the second temperature level by adsorption due to its high vapor pressure. Therefore, the entire or most part of the panel surface is an adsorption region. The adsorption region is formed, for example, by providing an adsorbent on the panel surface. The adsorbent is, for example, activated carbon. The adsorption region may use, for example, an adsorbent such as zeolite formed so as to selectively adsorb specific gas molecules, and is a porous surface layer formed on the panel substrate. Also good. The non-condensable gas is adsorbed in the adsorption region cooled to the second temperature level and exhausted. The non-condensable gas contains hydrogen. If a gas with a low vapor pressure is present in the atmosphere at the second cooling temperature level, it is trapped by condensation on the sorption panel adsorbent or on the non-adsorbent surface.

  The cryopump 10 includes a refrigerator 12. The refrigerator 12 generates cold by a heat cycle in which working gas is sucked, expanded inside and discharged. The refrigerator 12 is a Gifford McMahon refrigerator (so-called GM refrigerator). The refrigerator 12 is a two-stage refrigerator, and includes a first stage cylinder 18, a second stage cylinder 20, a first cooling stage 22, a second cooling stage 24, and a refrigerator motor 26. The first-stage cylinder 18 and the second-stage cylinder 20 are connected in series, and a first-stage displacer and a second-stage displacer (not shown) that are connected to each other are incorporated therein. A regenerator material is incorporated inside the first stage displacer and the second stage displacer. The refrigerator 12 may be a refrigerator other than the two-stage GM refrigerator, for example, a single-stage GM refrigerator, or a pulse tube refrigerator or a Solvay refrigerator.

  The refrigerator 12 includes a flow path switching mechanism that periodically switches the flow path of the working gas in order to periodically suck and discharge the working gas. The flow path switching mechanism includes, for example, a valve unit and a drive unit that drives the valve unit. The valve unit is a rotary valve, for example, and the drive unit is a motor for rotating the rotary valve. The motor may be an AC motor or a DC motor, for example. The flow path switching mechanism may be a direct acting mechanism driven by a linear motor.

  A refrigerator motor 26 is provided at one end of the first stage cylinder 18. The refrigerator motor 26 is provided inside a motor housing 27 formed at the end of the first stage cylinder 18. The refrigerator motor 26 is connected to the first stage displacer and the second stage displacer so that the first stage displacer and the second stage displacer can reciprocate inside the first stage cylinder 18 and the second stage cylinder 20, respectively. Is done. The refrigerator motor 26 is connected to the movable valve (not shown) provided in the motor housing 27 so as to be able to rotate forward and reverse.

  The first cooling stage 22 is provided at an end portion of the first stage cylinder 18 on the second stage cylinder 20 side, that is, a connecting portion between the first stage cylinder 18 and the second stage cylinder 20. The second cooling stage 24 is provided at the end of the second stage cylinder 20. The first cooling stage 22 and the second cooling stage 24 are fixed to the first stage cylinder 18 and the second stage cylinder 20 by brazing, for example.

  The refrigerator 12 is connected to the compressor 102 through a gas supply port 42 and a gas discharge port 44 provided outside the motor housing 27. The refrigerator 12 expands a high-pressure working gas (for example, helium) supplied from the compressor 102 to generate cold in the first cooling stage 22 and the second cooling stage 24. The compressor 102 collects the working gas expanded in the refrigerator 12, pressurizes it again, and supplies it to the refrigerator 12.

  Specifically, first, high-pressure working gas is supplied from the compressor 102 to the refrigerator 12. At this time, the refrigerator motor 26 drives the movable valve inside the motor housing 27 so that the gas supply port 42 communicates with the internal space of the refrigerator 12. When the internal space of the refrigerator 12 is filled with high-pressure working gas, the movable valve is switched by the refrigerator motor 26 and the internal space of the refrigerator 12 is communicated with the gas discharge port 44. As a result, the working gas expands and is recovered into the compressor 102. In synchronization with the operation of the movable valve, the first stage displacer and the second stage displacer reciprocate inside the first stage cylinder 18 and the second stage cylinder 20, respectively. The refrigerator 12 generates cold in the first cooling stage 22 and the second cooling stage 24 by repeating such a heat cycle.

  The second cooling stage 24 is cooled to a lower temperature than the first cooling stage 22. The second cooling stage 24 is cooled to about 10K to 20K, for example, and the first cooling stage 22 is cooled to about 80K to 100K, for example. A first temperature sensor 23 for measuring the temperature of the first cooling stage 22 is attached to the first cooling stage 22, and a second temperature stage for measuring the temperature of the second cooling stage 24 is attached to the second cooling stage 24. A two-temperature sensor 25 is attached.

  The radiation shield 16 is fixed to the first cooling stage 22 of the refrigerator 12 in a thermally connected state, and the cryopanel assembly 14 is thermally connected to the second cooling stage 24 of the refrigerator 12. It is fixed. Therefore, the radiation shield 16 is cooled to the same temperature as the first cooling stage 22, and the cryopanel assembly 14 is cooled to the same temperature as the second cooling stage 24.

  The CP controller 100 (see FIG. 1) determines a control output based on the sensor output signal. For example, the CP controller 100 determines the voltage and frequency to be supplied to the refrigerator motor 26. The CP controller 100 controls an inverter (not shown) attached to the refrigerator motor 26. The inverter of the refrigerator motor adjusts the power of a specified voltage and frequency supplied from an external power source, for example, a commercial power source, according to a command from the CP controller 100 and supplies the adjusted power to the refrigerator motor 26.

  For example, the CP controller 100 controls the refrigerator 12 based on the temperature of the cryopanel. The CP controller 100 gives an operation command to the refrigerator 12 so that the actual temperature of the cryopanel follows the target temperature. For example, the CP controller 100 controls the operating frequency of the refrigerator motor 26 by feedback control so as to minimize the deviation between the target temperature of the first cryopanel and the temperature measured by the first temperature sensor 23. The frequency of the thermal cycle of the refrigerator 12 is determined according to the operating frequency of the refrigerator motor 26. The target temperature of the first cryopanel is determined as a specification according to the process performed in the vacuum chamber 80, for example. In this case, the second cooling stage 24 and the cryopanel assembly 14 of the refrigerator 12 are cooled to a temperature determined by the specifications of the refrigerator 12 and the external heat load.

  If the measured temperature of the first temperature sensor 23 is higher than the target temperature, the CP controller 100 outputs a command value so as to increase the operating frequency of the refrigerator motor 26. The frequency of the heat cycle in the refrigerator 12 is increased in conjunction with the increase in the motor operating frequency, and the first cooling stage 22 of the refrigerator 12 is cooled toward the target temperature. Conversely, when the temperature measured by the first temperature sensor 23 is lower than the target temperature, the operating frequency of the refrigerator motor 26 is decreased and the first cooling stage 22 of the refrigerator 12 is raised toward the target temperature. Is done.

  Normally, the target temperature of the first cooling stage 22 is set to a constant value. Therefore, the CP controller 100 outputs a command value so as to increase the operating frequency of the refrigerator motor 26 when the thermal load on the cryopump 10 increases, and freezes when the thermal load on the cryopump 10 decreases. A command value is output so as to reduce the operating frequency of the machine motor 26. Note that the target temperature may be appropriately changed. For example, the target temperature of the cryopanel may be sequentially set so that the target atmospheric pressure is realized in the exhaust target volume (for example, the vacuum chamber 80). The CP controller 100 may control the operation frequency of the refrigerator motor 26 so that the actual temperature of the second cryopanel matches the target temperature.

  In a typical cryopump, the frequency of the thermal cycle is always constant. It is set to operate at a relatively high frequency so as to enable rapid cooling from normal temperature to the pump operating temperature. When the external heat load is small, the temperature of the cryopanel is adjusted by heating with a heater. Therefore, power consumption increases. On the other hand, in this embodiment, since the thermal cycle frequency is controlled according to the thermal load on the cryopump 10, a cryopump excellent in energy saving can be realized. Further, it is not necessary to provide a heater, which contributes to reduction of power consumption.

  The cryopump 10 includes a cryopanel assembly or a cryopanel structure 14. The cryopanel assembly 14 includes a plurality of cryopanels that are cooled by the second cooling stage 24 of the refrigerator 12. These panels are arranged in the radiation shield 16 from the front, that is, from the opening side to the back. Each cryopanel has a front surface facing the shield opening 31 and a back surface facing the shield opening 31, that is, the back surface facing the closing portion 28. The cryopanel assembly 14 may include a cryopanel that faces the side of the radiation shield 16 or a cryopanel (not shown) that is oriented in another direction. A cryogenic surface for trapping and exhausting gas by condensation or adsorption is formed on the panel surface. An adsorbent such as activated carbon for adsorbing gas is usually provided on the surface of the cryopanel.

  The cryopanel assembly 14 forms an internal space 30 opened to the shield opening 31 between the outer peripheral portion and the radiation shield 16. At least part of the cryopanel assembly 14, for example, the outer peripheral portion, can be visually recognized from the shield front end 33. The cryopump 10 shown in FIG. 2 differs from the cryopump 10 shown in FIGS. 3 and 4 in the specific form of the cryopanel assembly 14. Details of the configuration of each cryopanel assembly 14 will be described later.

  The cryopump 10 includes a radiation shield 16. The radiation shield 16 is provided to protect the cryopanel assembly 14 from ambient radiant heat. The radiation shield 16 is formed in a bottomed cylindrical shape having a shield opening 31 at one end. The shield opening 31 is defined by the shield front end 33 of the radiation shield 16, for example, the inner surface of the end of the cylindrical side surface. The shield front end 33 forms an opening for receiving gas from the vacuum chamber 80 to the cryopanel assembly 14.

  On the other hand, a closing portion 28 is formed on the opposite side of the radiation shield 16 from the shield opening 31, that is, on the other end on the pump bottom side. The blocking portion 28 is formed by a flange portion extending radially inward at the end portion on the pump bottom side of the cylindrical side surface of the radiation shield 16. Since the cryopump 10 shown in FIG. 2 is a so-called vertical cryopump, the flange portion is attached to the first cooling stage 22 of the refrigerator 12. The refrigerator 12 projects into the internal space 30 along the central axis of the radiation shield 16, and the second cooling stage 24 is inserted into the internal space 30.

  The so-called horizontal cryopump shown in FIG. 4 is a second cooling stage 24 of the refrigerator in a direction crossing the axial direction of the radiation shield 16 (usually in the orthogonal direction, from the back to the front in FIG. 4). Is inserted and placed. In the case of the horizontal type, the closing portion 28 is normally completely closed. The refrigerator 12 is disposed so as to protrude into the internal space 30 along a direction orthogonal to the central axis of the radiation shield 16 from the opening for attaching the refrigerator formed on the side surface of the radiation shield 16. The first cooling stage 22 of the refrigerator 12 is attached to the opening for attaching the refrigerator of the radiation shield 16, and the second cooling stage 24 of the refrigerator 12 is disposed in the internal space 30. The cryopanel assembly 14 is attached to the second cooling stage 24. Thus, the cryopanel assembly 14 is disposed in the internal space 30 of the radiation shield 16.

  As shown in FIGS. 2 to 4, a baffle or louver 32 that is thermally connected to the radiation shield 16 is provided in the shield opening 31 of the radiation shield 16. The louver 32 and the radiation shield 16 are arranged coaxially, and an annular open region 35 is formed between the outer periphery of the louver 32 and the radiation shield 16. The louver 32 is spaced from the cryopanel assembly 14 in the central axis direction of the radiation shield 16. A gate valve 7 (see FIG. 1) is provided between the louver 32 and the vacuum chamber 80.

  As shown in FIG. 3, the louver 32 is attached to the radiation shield 16 by an attachment structure 37. For example, the attachment structure 37 is provided at four positions every 90 degrees. The attachment structure 37 mechanically fixes the louver 32 to the radiation shield 16 and also functions as a heat transfer path from the radiation shield 16 to the louver 32.

  The louver 32 is formed of a plurality of blades 38, and each blade 38 is formed in the shape of the side surface of a truncated cone having a different diameter and arranged concentrically. In FIG. 3, there is a gap between the blades 38, but the blades 38 may be arranged closely so that there is no gap when adjacent blades 38 overlap each other when viewed from above. Each slat 38 is attached to a cross-shaped support member 39, and this support member 39 is attached to an attachment structure 37. The louver 32 may be formed, for example, concentrically when viewed from the vacuum chamber 80 side, or may be formed in another shape such as a lattice shape.

  The area of the open region 35 is set so that the hydrogen pumping speed by the cryopump 10 realizes the required specification. Specifically, for example, the area of the open region 35 can be adjusted by changing the number of louvers 38 of the louver 32 to change the diameter of the louver 32. An exposed portion of the cryopanel assembly 14 that is not shielded by the louver 32, for example, a peripheral portion, is visually recognized from the outside through the open region 35.

  The cryopump 10 is attached to the vacuum chamber 80 by a pump case 34. The vacuum chamber 80 is a vacuum chamber of the beam line unit 4 or the end station unit 5 (see FIG. 1), for example. The cryopump 10 is airtightly fixed to the exhaust opening of the vacuum chamber 80 via the flange portion 36 of the pump case 34, and an airtight space integrated with the internal space of the vacuum chamber 80 is formed.

  The pump case 34 accommodates the radiation shield 16, the louver 32, the cryopanel assembly 14, and the first cooling stage 22 and the second cooling stage 24 of the refrigerator 12. Both the pump case 34 and the radiation shield 16 are formed in a cylindrical shape, and are arranged coaxially. Since the inner diameter of the pump case 34 is slightly larger than the outer diameter of the radiation shield 16, the radiation shield 16 is disposed with a slight gap between the inner surface of the pump case 34.

  The pump case 34 is formed by connecting two cylinders having different diameters in series. The large-diameter cylindrical side end of the pump case 34 is opened, and a flange portion 36 for connection to the vacuum chamber 80 is formed extending outward in the radial direction. Thus, the large-diameter end of the pump case 34 defines a cryopump opening 31 for receiving gas from outside the cryopump, for example from the vacuum chamber 80. A small cylindrical end portion of the pump case 34 is fixed to the motor housing 27 of the refrigerator 12.

  The cryopanel assembly 14 is disposed in the internal space 30 of the radiation shield 16. The cryopanel assembly 14 includes a plurality of cryopanels 50 and a panel mounting member 52. The cryopanel assembly 14 includes a combination of atypical or different diameter cryopanels.

  The panel attachment member 52 is an element that constitutes a heat transfer path from the second cooling stage 24 of the refrigerator 12 to each of the cryopanels 50 in a fixed arrangement according to the designed panel layout. The panel attachment member 52 is, for example, a member having a bottom surface for attachment to the second cooling stage 24 and a side surface for fixing the plurality of cryopanels 50. The panel mounting member 52 has a bottom surface directed toward the pump opening side and a side surface surrounding the second cooling stage 24.

  The plurality of cryopanels 50 are arranged from the near side to the back side near the shield opening 31. Each cryopanel 50 extends parallel to each other toward the side surface of the radiation shield 16. The cryopanels 50 are arranged evenly with equal intervals between adjacent cryopanels. The plurality of cryopanels 50 include a plurality of large cryopanels and a plurality of small cryopanels. The embodiment shown in FIGS. 3 and 4 includes a plurality of larger cryopanels. The small cryopanel has a shape included in the outer shape of the large cryopanel. The outer peripheral edge of the cryopanel protrudes radially from the shield central axis toward the open space 30. An open space 30 extends between the outer peripheral edge of the cryopanel and the side surface of the radiation shield 16, and the open space 30 continues directly to the open area 35 around the louver 32.

  Hereinafter, the cryopanel facing the cryopump opening 31 may be referred to as a top panel. That is, the cryopanel closest to the cryopump opening 31 is the top panel. Although the top panel is a large cryopanel in FIG. 2, the top panel may be a small cryopanel as shown in FIG. Further, the top panel may be a single cryopanel, or may be a collective term for several cryopanels closest to the cryopump opening 31.

  In the embodiment shown in FIG. 2, large cryopanels and small cryopanels are alternately arranged with a space therebetween. That is, a small cryopanel is adjacent to a large cryopanel, and the next large cryopanel is adjacent to the small cryopanel. The outer peripheral end of the large cryopanel extends to a position closer to the radiation shield 16 than the outer peripheral end of the small cryopanel. Louver 32 may have an intermediate size between a large cryopanel and a small cryopanel.

  On the other hand, in a preferred embodiment shown in FIGS. 3 and 4, the plurality of cryopanels 50 of the cryopanel assembly 14 are divided into a plurality of groups according to their dimensions, and the groups are arranged from the front side to the back side of the radiation shield 16. Has been.

  In the present embodiment, the first to third groups are divided in order from the side closer to the shield opening 31, and the larger the group is, the larger the group is. Therefore, the first group cryopanel is a top panel or small cryopanel 60, the second group cryopanel is an intermediate panel or medium cryopanel 62, and the third group cryopanel is a lower panel or large cryopanel 64. Hereinafter, it will be referred to as appropriate. Although the cryopanel assembly 14 may include two groups in the present embodiment, the cryopanel assembly 14 may include two groups or more than three groups.

  Each group includes at least one cryopanel, and preferably each group includes a plurality of cryopanels. In one embodiment, each group has 2 to 5 cryosorption panels, and the cryopanel assembly 14 has a total of 8 to 14 cryosorption panels. In FIG. 4, there are three, four, and three small cryopanels 60, medium cryopanels 62, and large cryopanels 64, respectively.

  The medium cryopanel 62 is disposed on the side opposite to the shield opening 31 with respect to the small cryopanel 60. The large cryopanel 64 is disposed on the side opposite to the shield opening 31 with respect to the medium cryopanel 62. The outer periphery of the medium cryopanel 62 extends in parallel to the small cryopanel 60 and to a position closer to the radiation shield 16 than the outer periphery of the small cryopanel 60. The outer periphery of the large cryopanel 64 extends in parallel with the medium cryopanel 62 and to a position closer to the radiation shield 16 than the outer periphery of the medium cryopanel 62. As shown in FIG. 3, the louver 32 may have an intermediate size between the small cryopanel 60 (shown by a broken line in FIG. 3) and the medium cryopanel 62.

  In one embodiment, each cryopanel 50 has a disk shape. In this case, the plurality of cryopanels 50 include a large-diameter disk panel, a small-diameter disk panel, and an intermediate-diameter disk panel. The louver 32 may be a disk-shaped louver having an intermediate diameter between an intermediate-diameter disk panel and a small-diameter disk panel. In the embodiment shown in FIG. 2, the louver 32 may be a disk-shaped louver having an intermediate diameter between a large-diameter disk panel and a small-diameter disk panel.

  Each of the plurality of cryosorption panels 50 is, for example, a metal plate including a front surface facing the shield opening 31 or the louver 32 and a back surface facing the closing portion 28 on the opposite side. Activated carbon is adhered to the surface of the plate to form an adsorption region. For example, at least 50% of the total area of the front surface and the back surface is an adsorption region, and the remaining 50% is a non-adsorption region. The non-adsorption region is an adsorbent missing area where the metal surface of the plate on which no adsorbent is provided is exposed. Such an adsorbent missing area can function as a condensation area.

  The entire rear surface of each cryopanel 50 may be an adsorption region, and at least a part of the front surface of the cryopanel 50 may also be an adsorption region. Only the back surface of the uppermost cryopanel may have an adsorption region. In one embodiment shown in FIG. 2, for example, at least the front surface of the large cryopanel among the lower cryopanels 50 excluding the uppermost cryopanel is an adsorption region at the center, and the outside is a non-adsorption region or a condensation region. There may be. The entire front surface of the small cryopanel among the cryopanels 50 below may be an adsorption region. The entire front surface of some large cryopanels at the bottom may be an adsorption region.

  The boundary between the adsorption area and the non-adsorption area, in other words, the boundary between the adsorbent missing area and the existence area may be determined by the locus of the line of sight projected on the front surface of the cryopanel. This line of sight is a straight line drawn from the shield front end 33 to the outer peripheral end of the immediately preceding cryopanel. That is, the line where the line of sight intersects with the front surface of the panel is the boundary line. An adsorption region is formed inside the boundary line, and preferably, the adsorption region occupies the inside of the boundary. In addition, the condensation region includes a region outside the boundary, and is preferably limited to the outside of the boundary. In this way, the outer peripheral portion of the front surface of the cryopanel 50 is divided into the adsorption region and the condensation region.

  FIG. 5 is a view for explaining an adsorption region formed on the cryopanel 50 with respect to the cryopump shown in FIG. In FIG. 5, the first line of sight 70 and the second line of sight 72 from the shield front end 33 are illustrated for the sake of explanation by dashed arrows. The first line of sight 70 is a line of sight to the outer end of the small cryopanel 60 farthest from the shield opening 31 or the shield front end 33. The second line of sight 72 is a line of sight to the outer end of the medium-sized cryopanel 62 closest to the shield opening 31 or the shield front end 33. As described above, the small cryopanel 60 farthest from the shield opening 31 and the medium cryopanel 62 closest to the shield opening 31 are adjacent to each other.

  The locus of the first line of sight 70 on the front surface of the medium-sized cryopanel 62 closest to the shield opening 31 provides a boundary 84 between the adsorption region 74 and the condensation region 78 on the front surface of the medium-sized cryopanel 62. The locus of the second line of sight 72 on the front surface of the medium cryopanel 62 second closest to the shield opening 31 provides a boundary 86 between the adsorption region 76 and the condensation region 82 on the front surface of the medium cryopanel 62. Similarly, the boundary between the adsorption region and the condensation region can be determined for the remaining medium-sized cryopanel 62, small-sized cryopanel 60, and large-sized cryopanel 64.

  FIG. 6 is a top view showing the front panel of the cryopanel 50 with respect to the cryopump 10 shown in FIGS. 4 and 5. The cryopanel 50 is provided with a notch 88 from a part of the outer periphery to the center for attachment to the panel attachment member 52. FIG. 6 shows a boundary line 86 determined by the second line of sight 72 of FIG. 5 as an example. Corresponding to the fact that the shield opening 31 and the cryopanel 50 are circular, the boundary line 86 also draws a circle on the front surface of the panel. In this case, the boundary line 86 represents the sticking limit radius of the adsorbent. By adsorbing the adsorbent over the entire area inside the sticking limit radius, the most adsorbent can be mounted on the front surface of the panel without exposing the adsorbent as viewed from the shield opening 31.

  FIG. 7 is a view showing the back surface of the cryopanel 50 shown in FIG. As described above, the adsorbent may be adhered to the entire area of the panel rear surface, or the outer peripheral edge of the rear surface may be slightly opened as shown in FIG. Such a narrow adsorbent missing area may be provided to ensure that it is not exposed to the shield opening 31 in view of, for example, the height of the adsorbent to be adhered, such as activated carbon particles.

  In this way, the cryosorption panel 50 has an adsorbent missing area formed on the same surface as the adsorbent existing area. The common surface is, for example, a flat surface, and more specifically, the front surface of the panel or the back surface of the panel. In the adsorbent missing area, the surface of the cryopanel substrate, for example, a metal surface is exposed for cryocondensation. The adsorbent missing area is located at the exposed peripheral portion visually recognized through the cryopump opening 31.

  The activated carbon particles adhered to the cryopanel 50 are formed in a cylindrical shape, for example. A large number of activated carbon particles are adhered in an irregular arrangement in a state of being closely arranged on the surface of the cryopanel 50. The shape of the adsorbent may not be a cylindrical shape, and may be, for example, a spherical shape, other shaped shapes, or an indefinite shape. The arrangement of the adsorbent on the panel may be a regular arrangement or an irregular arrangement.

  2 and 4, at least 60% or at least 70% of the total area of the front and back surfaces of the plurality of cryopanels 50 is covered with the adsorbent. Preferably, at least 90% or at most 80% of the total area of the front surface and the back surface of the plurality of cryopanels 50 is adsorbed by making the adsorbent presence area at least the center (opening side) of the cryopanel 50. Covered with agent. 65 to 85% of the total area of the front and back surfaces of the plurality of cryopanels 50 may be covered with the adsorbent.

  In the embodiment of FIGS. 2 and 4, at most 40% or at most 30% of the total area of the front and back surfaces of the plurality of cryopanels 50 is the area where the adsorbent is missing. Preferably, at least 10% or at least 20% of the total area of the front surface and the back surface of the plurality of cryopanels 50 is missing the adsorbent by making the outer peripheral portion of the cryopanel 50 at the upper side (opening side) at least an adsorbent missing area Is an area. 15 to 35% of the total area of the front surface and the back surface of the plurality of cryopanels 50 may be an adsorbent missing area.

  In particular, in the cryopanel assembly 14 including the medium-sized cryopanel 62, it is preferable that at least 60% or at least 70% of the total surface area of the medium-sized cryopanel 62 is covered with the adsorbent. At least 60% or at least 70% of each surface of each panel of the medium-sized cryopanel 62 may be covered with the adsorbent. At least 60% or at least 70% may be covered with the adsorbent on both sides of each panel or as the sum of multiple panels. Moreover, it is preferable that 90% or less or 80% or less of the total surface area of the medium-sized cryopanel 62 is covered with the adsorbent by making the outer peripheral portion an adsorbent-deficient area. More preferably, the medium-sized cryopanel 62 has an adsorbent coverage of 65 to 85%.

  In this case, the small cryopanel 60 preferably has an adsorbent coverage that is equal to or smaller than that of the medium cryopanel 62. For example, the small cryopanel 60 preferably has an adsorbent coverage of 50 to 65%. The large cryopanel 64 preferably has an adsorbent coverage that is equal to or greater than the medium cryopanel 62. For example, the large cryopanel 64 preferably has an adsorbent coverage of 85 to 100%. The large cryopanel 64 may be covered on both sides with an adsorbent.

  8 and 9 are tables showing an example of an adsorbent missing rate or a coverage rate of the cryopanel assembly 14 according to an embodiment of the present invention. The adsorbent missing rate and coverage rate are shown for each of the small cryopanel 60, the medium cryopanel 62, and the large cryopanel 64. The missing and covered rates are shown for both the individual plates and the group total. FIG. 8 shows each of the front and back surfaces, and FIG. 9 shows the sum of the front and back surfaces.

  In FIGS. 8 and 9, the small cryopanel 60, the medium cryopanel 62, and the large cryopanel 64 are referred to as a first group, a second group, and a third group, respectively. In this embodiment, the first group, the second group, and the third group include three plates, four plates, and three plates, respectively, and a total of 10 plates are included. These plates are arranged in the same manner as the cryopanel assembly 14 shown in FIG. In FIG. 8, plate numbers 1 to 10 are assigned respectively.

  In this embodiment, each plate is a metal, the adsorbent is granular activated carbon, and the activated carbon is bonded to the metal surface with an adhesive. Therefore, the area of the metal part shown in FIG. 8 represents the area of each of the front surface and the back surface of the plate. The area of the activated carbon part is zero when activated carbon is not provided on the surface, and is equal to the area of the metal part when the entire surface is covered with activated carbon, and there is an area where activated carbon is missing. Is an intermediate value between them. The ratio of the area of the activated carbon part to the area of the metal part is the coverage, and the ratio of the remaining area to the area of the metal part is the missing rate.

  Note that the three plates of the small cryopanel 60 all have the same diameter. The top plate (plate number 1) closest to the opening of a group has a larger area than the plate (plate numbers 2 and 3) immediately below it, as shown in FIG. This is because the top plate is not provided. That is, the area of the top plate is larger by the area corresponding to the notch 88.

  As for the front surface of the plate, as in the embodiment shown in FIG. 6, activated carbon is adhered to the inside of the boundary determined by the intersection of the front surface of the plate and the line of sight from the shield front end 33 to the end of the adjacent plate on the near side. . However, activated carbon is not provided on the front surface of the top plate (plate number 1) closest to the opening of the group, and the metal surface is exposed. The plate directly below (plate number 2) is also not exposed to activated carbon on the front surface and has a metal surface exposed. This is because the line of sight from the shield front end 33 does not intersect the plate surface (that is, the entire front surface is visible from the shield front end 33).

  The activated carbon occupies the entire area inside the boundary determined by the line of sight. The plate farthest from the first group (plate number 3), the plate closest to the second group (plate number 4), and the second group 2 The plate closest to the opening (plate number 5), the plate closest to the opening of the third group (plate number 8), and the plate of the third group closest to the opening (plate number 9).

  From the viewpoint of production efficiency, the two lower plates (plate numbers 6 and 7) in the second group are the same as the plates directly above (plate number 5), and the lowermost plates in the third group (plate number 10). Is the same as the plate immediately above (plate number 9). Therefore, these plates have the actual outer periphery of the activated carbon portion slightly inside the boundary determined by the line of sight. Also for these plates, the activated carbon portion may be somewhat widened by matching the boundary determined by the line of sight with the actual outer periphery of the activated carbon portion.

  Regarding the back surface of the plate, unlike the embodiment shown in FIG. 7, the activated carbon is bonded to the entire area without providing the activated carbon missing area at the outer peripheral end. Therefore, the metal part area on the back surface and the activated carbon part area are equal.

  When the subtotal of each group shown in FIG. 9 is seen, the activated carbon coverage is 50% for the first group, 77% for the second group, and 87% for the third group, and increases in stages. In the entire cryopanel assembly 14, the activated carbon coverage is 76%.

  As shown in FIGS. 2 and 4, one back surface and the other front surface of two adjacent cryopanels 50 extend in parallel toward the side surface of the radiation shield 16, and an open portion 54 is formed therebetween. ing. The open part 54 is directed to the radiation shield 16 and is continuous with the open space 30. The outer peripheral side of the open portion 54 is an inlet for a gas continuous to the open space 30, and the inner peripheral side of the open portion 54 is closed by two adjacent cryopanels 50 and a panel mounting member 52.

  The cryopanels 50 are densely arranged in the shield central axis direction so that the depth of the open portion 54 is larger than the interval between two adjacent cryopanels 50. The “depth” of the open portion 54 is the length in the in-plane direction of the cryopanel 50 and is the distance from the outer peripheral edge of the cryopanel to the panel mounting member 52. When the sizes of two adjacent cryopanels 50 are different, the distance from the outer peripheral end of the smaller cryopanel to the panel mounting member 52 is the depth of the open portion 54. With such a dense panel arrangement, more adsorbents can be mounted in a limited space inside the cryopump.

  Since an adsorption region is formed on the surface of the cryopanel 50 surrounding the open portion 54, at least 90% of the adsorbent, preferably substantially all of the adsorbent, is exposed towards the radiation shield 16 or the shield opening 31. Has been. The gas molecules flying toward the cryopump 10 pass through the open area 35 around the louver 32 and enter the internal open space 30. Non-condensable gas such as hydrogen is reflected by the shield surface or panel surface, enters the open portion 54, and reaches the adsorbent. The openness inside the cryopump that continues from the open area 35 to the open portion 54 through the open space 30 facilitates the arrival of gas from the outside to the adsorption area. Thus, a cryopump 10 having a high hydrogen capture probability of at least 30% is realized.

  The hydrogen capture probability is given by the ratio of the actual hydrogen pumping speed to the theoretical maximum hydrogen pumping speed in a cryopump having the same diameter as the cryopump 10 (that is, the cryopump opening area is the same). The actual hydrogen pumping speed of the cryopump can be obtained by a known Monte Carlo simulation.

  Also, the theoretical hydrogen pumping speed can be regarded as being equal to the conductance of the molecular flow about the opening. The conductance C (hydrogen) of hydrogen is obtained from the conductance C (20 ° C. air) of 20 ° C. air by the following equation.

Here, T is the temperature (K) of hydrogen gas, and M is the molecular weight of hydrogen (ie, M = 2). The conductance C of 20 ° C. air (20 ° C. air) is proportional to the opening area A (m ² ) and is given by C (20 ° C. air) = 116A. For example, in the case of a cryopump with a diameter of 250 mm, the theoretical hydrogen pumping speed is about 20840 L / s according to the above equation. At this time, a hydrogen capture probability of 30% is equivalent to a hydrogen pumping speed of the cryopump of about 6252 L / s.

  A typical conventional cryopump for high-speed hydrogen pumping is designed based on the idea that the pumping speed is increased by mounting more cryopanels, that is, activated carbon, on the cryopump. Therefore, there is a trade-off relationship between an improvement in the exhaust speed and an increase in the panel weight as well as an increase in the regeneration time (particularly the cool-down time). In order to suppress the increase in cool-down time while increasing the exhaust speed, a refrigerator having a high refrigerating capacity is required. Therefore, energy saving performance can be sacrificed by improving the exhaust speed.

In contrast, an embodiment of the present invention provides a new design concept of optimizing hydrogen exhaust efficiency in a cryopump for high-speed hydrogen exhaust. The present inventor determined the ratio between the hydrogen pumping speed (L / s) of the cryopump and the adsorption area (mm ² ), that is, the pumping speed per unit area of the adsorbent existing area, as the hydrogen pumping efficiency (L / s) of the cryopump. • It is defined as mm ² ). Instead of simply increasing the adsorbent, the exhaust efficiency is increased by reducing the area of the adsorption region somewhat. As described above, the adsorption region area may be reduced at the outer peripheral portion of the cryopanel, or the adsorption region area may be reduced at other portions.

  If the adsorption region area is made somewhat smaller, the hydrogen pumping speed of the cryopump will be made somewhat smaller accordingly. However, it is considered that it is not really a problem in practice. Even if there is a difference in pumping speed between the cryopumps alone, the difference in pumping speed that actually results when the cryopump is actually installed in a vacuum chamber tends to be smaller. This is because the pumping speed performance as seen from the cryopump alone is not necessarily exhibited as it is due to the limitation due to the conductance on the vacuum chamber side.

  According to the inventor's experience and consideration, in the cryopump for high-speed hydrogen pumping, even if there is a difference of 10% in the pumping speed performance of the cryopump alone, the pumping speed when attached to the vacuum chamber There is almost no impact on performance. Therefore, when the allowable reduction range of the hydrogen exhaust speed is set to 10% or less, the advantage of improving the hydrogen exhaust efficiency by reducing the adsorption region area surpasses the disadvantage of reducing the exhaust speed. Therefore, in one embodiment of the present invention, even if the adsorption region area is adjusted to increase the hydrogen exhaust efficiency under the condition of providing an exhaust rate of at least 90% of the hydrogen exhaust rate when the entire cryopanel is covered with the adsorbent. Good.

According to the analysis of the present inventor, for example, a cryopump having a plurality of flat panel arrangements parallel to openings of the type shown in FIGS. It stays at about 2 × 10 ⁻² L / s · mm ² to 4 × 10 ⁻² L / s · mm ² . On the other hand, the hydrogen exhaust efficiency can be increased to 5 × 10 ⁻² L / s · mm ² or more by providing the adsorbent missing portion as in the embodiment shown in FIGS. The hydrogen exhaust efficiency can be increased to 7 × 10 ⁻² L / s · mm ² within the allowable range of decrease in the hydrogen exhaust speed.

  That is, the hydrogen exhaust efficiency is about double. This means that the same level of hydrogen pumping speed is realized in an adsorption region of about half. This can reduce the panel weight by about 1000 to 2000 g. If the panel weight is reduced, the time required for cool-down will be shortened. As a result, the average power consumption during reproduction can be reduced by about 40%.

In order to make the hydrogen exhaust efficiency higher than 7 × 10 ⁻² L / s · mm ^2, a cryopanel assembly of a type that completely exposes the adsorbent (for example, Japanese Patent Application Laid-Open No. 2009-162074). It would be realistic to adopt Japanese Patent Application Laid-Open No. 2009-162074 is incorporated herein by reference in its entirety.

  By the way, the molecules of the condensable gas flying from the outside toward the cryopump 10 pass through the open area 35 around the louver 32 and reach the condensation area around the radiation shield 16 or the cryopanel 50 through a linear path. And are trapped on their surface. The open local space 54 is shielded from the cryopump opening 31 by the upper cryopanel 50 except for the gas inlet on the outer peripheral side, and the adsorption region is accommodated in the shielding part. The hardly regenerating gas is a condensable gas almost without exception. By avoiding direct exposure of the adsorption region to the cryopump opening 31, the adsorption region is protected from the hardly regenerated gas contained in the gas entering the cryopump 10. The hardly regenerating gas is deposited in the condensation region. In this way, both high-speed exhaust of non-condensable gas and protection of the adsorption region from hardly regenerated gas can be achieved.

  In one embodiment of the present invention, the suction region is not visible from the cryopump opening 31 by being accommodated in the shielding part. In other words, the “adsorbent visible rate” which is the ratio of the adsorbent area visible from the cryopump opening 31 to the total adsorbent area of the cryopanel 50 is zero%. However, the cryopump according to the embodiment of the present invention is not limited to the configuration in which the adsorbent visible rate is zero%. When the adsorbent visible rate is less than 7%, it may be evaluated that the adsorbent is substantially invisible from the opening. In one embodiment, the adsorbent visibility rate is preferably less than 7%, less than 5%, or less than 3%. However, if, for example, the content of the difficult-to-regenerate gas is expected to be sufficiently low, or if it is allowed to sacrifice the exposed adsorbent, more than 7% adsorbent may be visible from the opening. Good.

  Compared with the cryopanel 50 close to the cryopump opening 31, gas molecules are less likely to reach the cryopanel 50 inside the radiation shield 16 away from the cryopump opening 31. The cryopanel 50 away from the cryopump opening 31 has a small contribution to the exhaust speed and is less affected by the hardly regenerating gas. Therefore, in one embodiment, the lower large cryopanel 64 may be provided with an adsorbent at the exposed peripheral portion. For example, in the embodiment shown in FIG. 8, when the adsorbent is provided over the entire front surface of the large cryopanel 64, the adsorbent visible rate is about 7%.

  The operation of the cryopump 10 will be described. When the cryopump 10 is operated, first, the vacuum chamber 80 is roughly evacuated to about 1 Pa to 10 Pa using another appropriate roughing pump before the operation. Thereafter, the cryopump 10 is operated. The first cooling stage 22 and the second cooling stage 24 are cooled by driving the refrigerator 12, and the radiation shield 16, the louver 32, and the cryopanel assembly 14 that are thermally connected thereto are also cooled. The first cryopanel includes the radiation shield 16 and the louver 32, and the second cryopanel includes the cryopanel assembly 14.

  The cooled louver 32 cools gas molecules flying from the vacuum chamber 80 toward the inside of the cryopump 10, and exhausts gas (for example, moisture) whose vapor pressure is sufficiently low at the cooling temperature to condense on the surface. To do. A gas whose vapor pressure is not sufficiently low at the cooling temperature of the louver 32 passes through the louver 32 and enters the radiation shield 16. When the gas molecules that have passed through the louver 32 contain a gas (for example, argon) whose vapor pressure is sufficiently low at the cooling temperature of the cryopanel assembly 14, the gas molecules are condensed on the surface of the cryopanel assembly 14 and exhausted. A gas (for example, hydrogen) whose vapor pressure does not become sufficiently low even at the cooling temperature is adsorbed by the adsorbent that is bonded to the surface of the cryopanel assembly 14 and cooled, and then exhausted. In this way, the cryopump 10 can reach the desired degree of vacuum inside the vacuum chamber 80.

  In particular, in the cryopump 10 used in the vacuum exhaust system of the ion implantation apparatus, among the gases that have entered the radiation shield 16, difficult-to-regenerate gases such as organic gases and dopant gases are adsorbed on the outer peripheral portion of the cryopanel 50. It is condensed at the site where the agent is missing. A gas having a relatively small molecular diameter such as hydrogen gas is adsorbed by the adsorbent. In this way, the cryopumping process is performed.

  When the cryopumping process is continuously performed, gas is accumulated inside the cryopump. A regeneration process is performed to discharge the accumulated gas to the outside. First, the cryopump 10 is separated from the vacuum chamber 80 by closing the gate valve 7. Next, the temperature of the cryopanel 50 is raised. The cryopanel 50 is heated to a temperature (for example, room temperature) higher than the cooling temperature in the cryopumping process.

  As the temperature rises, the gas captured by condensation on the cryopanel surface is vaporized, and the gas captured by adsorption is desorbed and re-released into the pump container. The re-released gas is discharged to the outside through a discharge port (not shown) of the cryopump 10 by driving an attached roughing pump, for example. Thereafter, the cryopanel 50 is re-cooled to the operating temperature in the cryopumping process. The regeneration process is completed by re-cooling. The gate valve 7 is opened and the cryopumping process is started again. In this way, the cryopumping process and the reproduction process are alternately performed.

  FIG. 10 is a diagram illustrating a change in the hydrogen pumping speed of the cryopump through regeneration according to an embodiment of the present invention. FIG. 10 shows a change in the hydrogen exhaust speed of the cryopump 10 according to the embodiment of the present invention. For comparison, a change in the hydrogen pumping speed of a cryopump having a cryopanel assembly that completely exposes the adsorbent described in, for example, Japanese Patent Application Laid-Open No. 2009-162074 is shown. The vertical axis in FIG. 10 indicates the measured value of the hydrogen exhaust speed, and the horizontal axis indicates the number of regenerations. The exhaust velocity measurement value on the solid line is a value immediately before the regeneration process is executed, and the measurement value on the broken line is a value immediately after the regeneration is completed.

  The measured value on the broken line regarding the first regeneration shown in FIG. 10 is a value when the cryopump is operated for the first time. Since the activated carbon is not contaminated by the difficult-to-regenerate gas, the fully exposed type of the comparative example shows a particularly high hydrogen pumping speed.

  The exhaust speed is low just before regeneration and is expected to recover after completion. However, in the comparative example, as shown in the figure, after the third regeneration, such reduction and recovery of the exhaust speed are repeated, but until the second regeneration, the exhaust speed rapidly increases from the initial high exhaust speed. It is falling. It is considered that the exhaust speed continued to decrease until the exposed activated carbon was contaminated to some extent. Subsequent regeneration has not recovered the initial exhaust performance.

  However, in the embodiment, the exhaust speed is repeatedly increased and decreased from the first regeneration to the seventh regeneration. Even if regeneration is repeated, a substantially constant level of hydrogen exhaust speed is maintained as shown by the thick broken line in the figure. The original exhaust performance has been recovered by regeneration. That is, it can be seen that the stable exhaust performance is continuously maintained from the first operation immediately after the cryopump is shipped.

  FIG. 11 is a flowchart for explaining a manufacturing method of the cryopump 10 according to the embodiment of the present invention. This method is performed by an operator or a manufacturing apparatus in the manufacturing process of the cryopump 10. Prior to the masking process, a cryopanel substrate is processed from the base material and molded (S10). As shown in FIG. 11, a masking process is performed on the base material of the cryopanel 50 (S12). The masking process includes masking an exposed portion of the substrate that is not shielded by another cryopanel (for example, an upper cryopanel adjacent when the cryopanel assembly 14 is assembled). The masking process includes, for example, applying a masking tape to such an exposed portion.

  Next, an adsorbent adhesion treatment for adhering the adsorbent to the surface of the substrate that is not masked is performed (S14). This adhesion treatment includes applying an adhesive to the surface of the unmasked substrate and adhering an adsorbent, for example, granular activated carbon, to the adhesive application area. The cryopanel 50 to which the adsorbent is bonded is attached to the panel attachment member 52, and the cryopanel assembly 14 is assembled (S16). The cryopanel assembly 14 is attached to the refrigerator 12 of the cryopump 10 and the cryopump 10 is assembled (S18).

  Prior to the masking process, the outside of the boundary defined by the intersection of the line of sight from the front end of the radiation shield 16 to the end of the cryopanel 50 adjacent to the cryopanel 50 and the cryopanel 50 is masked for each cryopanel 50. Determining as a region may be performed. This determination process may be performed in a design process prior to the manufacturing process.

  FIG. 12 is a flowchart for explaining a method for manufacturing the cryopump 10 according to the embodiment of the present invention. This method is performed, for example, to design the cryopanel assembly 14. First, the value of the cryopanel structure parameter that gives the maximum hydrogen pumping speed when the cryopanel structure parameter is changed under a certain constraint is obtained (S20). The value of the panel structure parameter that gives the maximum hydrogen pumping speed may be obtained by using a known experimental design method with the panel pumping parameter as a variable and the hydrogen pumping speed as an objective function.

  The constraints include removing the adsorbent from a portion of the surface of the cryosorption panel. This adsorbent missing condition is that an adsorption region is formed inside the boundary determined by the line of sight from the front end of the radiation shield 16 to the end of the cryopanel 50 adjacent to the cryopanel 50 and the front of the cryopanel. May be.

  The panel structure parameter includes the dimensions of the cryosorption panel, for example, the panel diameter when the panel is circular. When the cryopanel assembly 14 includes a plurality of types of cryopanels having different shapes, a plurality of parameters for representing the respective shapes may be used. When the cryopanel assembly 14 includes a plurality of types of cryopanels having different diameters, the panel structure parameter may include each diameter. The panel structure parameter may include a distance between the cryopump opening 31 and the top panel. The panel structure parameter may include the diameter of the louver 32. The panel structure parameter may include an interval between adjacent cryopanels.

  The configuration of the cryosorption panel array is determined based on the value of the panel structure parameter thus obtained (S22). For example, a value of a cryopanel dimension, for example, a panel diameter, which gives the maximum hydrogen exhaust speed under the condition that the adsorbent is missing from a part of the surface of the cryosorption panel can be obtained. This value can be used to determine the specific configuration of the cryopanel assembly 14.

  In the above, this invention was demonstrated based on the Example. It will be understood by those skilled in the art that the present invention is not limited to the above-described embodiment, and various design changes are possible, various modifications are possible, and such modifications are within the scope of the present invention. By the way.

  You may employ | adopt the panel arrangement | sequence different from the above-mentioned embodiment. For example, the cryopanel spacing may be the same for all panels or different. For example, each of the plurality of panels 50 may be arranged so that the panel interval becomes narrower as the position of the panel moves away from the opening 31. In this way, it is possible to improve the gas flowability in the region close to the opening 31 and increase the exhaust speed. At the same time, in the region far from the opening 31, the adsorption region can be increased by arranging the panels relatively densely, so that a sufficient gas storage amount can be ensured.

  Further, a cryopanel 50 having a shape and / or orientation different from that of the above-described embodiment may be adopted. For example, the length of the panel 50 in the radial direction may be shortened with increasing distance from the opening 31 or may be equal to each other. The shape when the panel 50 is viewed from the opening 31 may not be circular, and may be other shapes such as a polygonal shape. The panel 50 may have, for example, an upward or downward bent portion at the peripheral edge. The panel 50 may have openings or slits on the surface for promoting gas flow. The orientation of the panel 50 may be inclined so as to be separated from the opening 31 as it extends outward in the radial direction, or may be inclined so as to approach the opening 31 as it extends outward in the radial direction.

  For example, an exposed surface other than the cryopanel 50 in the cryopanel assembly 14 may be used as the adsorbent application surface. For example, the panel attachment member 52 may be used as one of the panels.

  DESCRIPTION OF SYMBOLS 1 Ion implantation apparatus, 10 Cryo pump, 12 Refrigerator, 14 Cryo panel assembly, 16 Radiation shield, 22 1st cooling stage, 24 2nd cooling stage, 30 Cryo pump internal open space, 31 Cryo pump opening, 32 louver, 33 Shield front end, 35 open area, 50 cryopanel, 52 panel mounting member, 54 open part, 60 top panel, 62 middle panel, 64 lower panel, 76 adsorption area, 82 condensing area, 86 boundary, 100 CP controller.

Claims (8)

A first cooling stage for providing a first cooling temperature and a second cooling stage for providing a second cooling temperature lower than the first cooling temperature and used for adsorption of noncondensable gas. A refrigerator,
A radiation shield including a shield front end forming an opening for receiving a gas, thermally connected to the first cooling stage and surrounding the second cooling stage;
A cryopanel assembly thermally connected to the second cooling stage, wherein an open space to the opening is formed between the outer periphery of the cryopanel assembly and the radiation shield, and at least a part of the cryopanel assembly is visible from the front end of the shield. A cryopanel assembly, and
The cryopanel assembly includes a top panel that faces the opening, and an intermediate panel that includes the front surface of the panel that faces the opening and is disposed on the opposite side of the opening to the top panel. An open portion that continues to the open space is formed between the adjacent cryopanel and the front surface of the panel, and the open portion has a depth greater than the distance between the adjacent cryopanel and the front surface of the panel,
The intermediate panel has an adsorption region for a non-condensable gas on the front surface of the panel, and the adsorption region has a boundary determined by the intersection of the line of sight from the front end of the shield to the end of the adjacent cryopanel and the front surface of the panel. A cryopump characterized by being formed inside. The cryopump according to claim 1, wherein the suction region occupies an area inside the boundary on the front surface of the panel. The cryopump according to claim 1, wherein the intermediate panel has a condensing region for condensable gas on a surface thereof, and the condensing region includes an area outside the boundary on the front surface of the panel.   2. The cryopump according to claim 1, wherein an outer peripheral portion of the intermediate panel extends parallel to the top panel and a position closer to the radiation shield than an outer peripheral portion of the top panel.   The cryopanel assembly further includes a lower panel disposed on a side opposite to the opening with respect to the intermediate panel, and an outer peripheral portion of the lower panel is parallel to the intermediate panel and more than an outer peripheral portion of the intermediate panel. The cryopump according to claim 1, wherein the cryopump extends to a position close to the radiation shield.   2. The cryopump according to claim 1, wherein the intermediate panel includes a plurality of plates each including a front surface facing the opening and a back surface facing the opening and arranged in parallel with each other. .   And a louver thermally connected to the radiation shield and disposed in the opening, the louver having an intermediate size between a top panel and an intermediate panel, between the outer periphery of the louver and the radiation shield. The cryopump according to claim 1, wherein an open region is formed in the cryopump. The intermediate panel is covered with an adsorbent at least 70% of the surface area, the adsorbent is capable of adsorbing hydrogen, and the cryopump has a hydrogen capture probability of at least 30%;
The adsorbent is provided on the surface of the cryopanel surrounding the open portion , and the adsorbent visible rate, which is the ratio of the adsorbent area visible from the opening to the total adsorbent area of the cryopanel assembly, is 7 The cryopump according to claim 1, wherein the cryopump is less than%.

Images