JP5103229B2 - Cryopump - Google Patents

Description

  The present invention relates to a cryopump and a vacuum exhaust method.

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. For example, Patent Document 1 discloses a cryopump in which a first cryopanel having a baffle is coupled to a first heat stage, and a second cryopanel is coupled to a second heat stage that is housed in the first cryopanel. . This baffle is provided over the entire opening of the first cryopanel.
JP-A-2-308985

  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. Non-condensable gas can only be exhausted by adsorbing it on an adsorbent cooled to a very low temperature. In this case, in order to improve the exhaust speed, a sufficient gas inflow path to the adsorbent should be ensured. Therefore, for example, the area occupied by the baffle at the opening of the radiation shield may be reduced to widen the opening. However, if it does so, the radiation heat incidence from the outside through an opening part will increase, and it will become easy to raise the temperature of adsorption agent and the low-temperature cryopanel holding this. Thus, conventionally, it has been considered that the exhaust speed of the low-temperature cryopanel and the cooling arrival temperature are in a trade-off relationship with respect to the size of the baffle. That is, if a large baffle with a small opening is used, the exhaust speed decreases, and conversely, if a small baffle is used, it becomes difficult to reach a low cooling temperature. In addition, the adjustment work to determine the dimensions of the baffle so that both the exhaust speed and the cooling temperature meet the required specifications requires that a plurality of baffles with different dimensions be actually manufactured and verified. , It took a lot of work.

  Accordingly, an object of the present invention is to provide a highly practical cryopump and a vacuum evacuation method that can easily achieve both an exhaust performance and a cooling temperature that meet the required specifications.

  A cryopump according to an aspect of the present invention includes a shield inner surface that defines an internal space having a central axis, and a shield end that defines an opening that connects the internal space to an external volume to be exhausted. A radiation shield that is cooled to a temperature level, and has an outer peripheral edge, is thermally connected to the radiation shield and cooled to a first temperature level, and between the outer peripheral edge and the shield inner surface in a radial direction from the central axis A first cryopanel disposed with an open area formed therein, and a layout inside the first space inside the first cryopanel and surrounding the central axis, the temperature being lower than the first temperature level And a second cryopanel cooled to a second temperature level. In the first cryopanel, the open region is formed corresponding to the required exhaust velocity, and the second line is formed just before the straight line intersecting the central axis from the shield end through the outer peripheral end intersects the central axis. The inner space is disposed inside the shield end so as to pass through the cryopanel.

  According to this aspect, there is provided a highly practical cryopump that achieves both the achievement of the required exhaust speed and the reduction of radiant heat from the outside to the low-temperature second cryopanel. The required exhaust speed is, for example, an exhaust speed determined as a design specification for the gas selectively exhausted by the second cryopanel. By appropriately setting the gap between the first cryopanel and the inner surface of the radiation shield, a sufficient gas entry path from the outside to the second cryopanel can be secured and the required exhaust velocity can be realized. Further, by disposing the first cryopanel substantially inside the shield end, at least a part of the radiant heat directed to the second cryopanel is shielded through the gap between the first cryopanel and the shield inner surface. Can do.

  A panel mounting structure for fixing the first cryopanel to the radiation shield, the panel mounting portion provided on the shield inner surface at the shield end, and the shield mounting provided on the outer peripheral end of the first cryopanel And a mounting member that extends in the central axis direction and has one end attached to the panel attaching portion and the other end attached to the shield attaching portion.

  If it does in this way, the 1st cryopanel can be arranged in the optimal offset position by using the adjusted attachment member. Further, since the radiation shield and the first cryopanel can use existing ones, the parts can be shared and the manufacturing cost can be reduced.

  The second cryopanel may be disposed with a gap narrower than the open area between the second cryopanel and the inner surface of the shield in the radial direction from the central axis.

  The second cryopanel has a tip portion that protrudes toward the first cryopanel and is exposed when viewed from the first cryopanel, and a straight line that intersects the central axis from the shield end through the outer peripheral end. You may arrange | position so that this front-end | tip part may be passed.

  The first cryopanel may be exposed when viewed from the opening, and the second cryopanel may be exposed when viewed from the first cryopanel.

  Another embodiment of the present invention is also a cryopump. The cryopump defines a interior space and has a radiation shield having an open end connecting the interior space to an external volume to be exhausted and thermally connected to the radiation shield to cool the radiation shield to a first temperature level. A refrigeration machine including a first cooling stage, a second cooling stage disposed in the internal space and providing a second temperature level that is lower than the first temperature level, and a radiation shield An open region, which is thermally connected and cooled to a first temperature level and has an area set corresponding to a required exhaust speed, is disposed between the radiation shield and a second region from the open end. A first cryopanel disposed on the inner side of the opening end in the internal space so as to shield radiant heat toward the cooling stage.

  Yet another embodiment of the present invention is also a cryopump. The cryopump is attached to the panel mounting portion and includes a radiation inner surface that defines a shield inner surface that defines an internal space and a panel mounting portion provided on the shield inner surface. An attachment member extending from the panel attachment portion to an offset position separated by an offset amount; and a cryopanel disposed at the offset position by the attachment member.

  The cryopump includes a first cooling stage that is thermally connected to the radiation shield and cools the radiation shield, and a second cooling stage that is disposed in the internal space and provides a lower cooling temperature level than the first cooling stage; , May further include a refrigerator. The radiation shield further includes a shield end that defines an opening that connects the internal space to the external volume to be exhausted, and the panel mounting portion is provided on the inner surface of the shield at the shield end, and the mounting member is mounted on the panel in a direction away from the opening. The offset position is selected from an offset range in which the cooling temperature level is lower than when the cryopanel is disposed in the opening, and the cryopanel is disposed substantially inside the opening in the internal space. May be.

  Yet another embodiment of the present invention is also a cryopump. The cryopump has an open end that connects the internal space to an external volume to be exhausted, and the radiation shield that is cooled to the first temperature level and the radiation shield in the internal space are arranged in a non-contact manner, and the first A low-temperature cryopanel that is cooled to a second temperature level that is lower than the first temperature level; and a cooling plate that is thermally connected to the radiation shield and cooled to the first temperature level; And a high-temperature cryopanel disposed at an offset position that makes the interval substantially equal to each other.

  Yet another embodiment of the present invention is a vacuum exhaust method. This method includes a radiation shield having an opening through which a gas to be exhausted enters, a low-temperature cryopanel surrounded by the radiation shield and cooled to a lower temperature than the radiation shield, and a low-temperature cryopanel thermally connected to the radiation shield. A high-temperature cryopanel disposed in front of the cryopanel, and a vacuum pumping method using a cryopump, the inner surface of the radiation shield corresponding to a required pumping speed for a gas to be exhausted by the low-temperature cryopanel Set a gap with the high-temperature cryopanel and place the high-temperature cryopanel at a position offset from the opening so that the cooling temperature of the low-temperature cryopanel is lower than when the high-temperature cryopanel is placed in the opening. The gas to be exhausted is exhausted at the required exhaust speed.

  ADVANTAGE OF THE INVENTION According to this invention, the cryopump and the vacuum exhaust method which are excellent in practical use which can implement | achieve high pumping speed and low cooling temperature are provided.

  First, the outline | summary of embodiment which concerns on this invention demonstrated below is demonstrated. In one embodiment, the cryopanel is disposed at a position offset inward from the radiation shield opening. When viewed from the radiation shield opening, this cryopanel is provided in front of the cooler cryopanel, and is hereinafter also referred to as a baffle as appropriate. This offset baffle is thermally connected to the radiation shield. On the other hand, the low-temperature cryopanel disposed at the rear stage of the baffle is surrounded by the radiation shield and disposed in a non-contact manner. The present inventor effectively reduces the radiant heat to the low-temperature cryopanel while maintaining the exhaust speed of the low-temperature cryopanel at a desired level by this offset arrangement type baffle, and lowers the exhaust speed to the low-temperature cryopanel to a desired exhaust speed. It was found experimentally that the cooling ultimate temperature can be realized.

  The radiation shield and the baffle are cooled to a first cooling temperature level, and the low temperature cryopanel is cooled to a second cooling temperature level that is lower than the first cooling temperature level. Therefore, the radiation shield and the low-temperature cryopanel may be thermally connected to the first cooling stage and the second cooling stage of the two-stage refrigerator, respectively. The first and second cooling stages provide first and second cooling temperature levels, respectively. Hereinafter, the baffle is also referred to as a first cryopanel, and the low-temperature cryopanel is also referred to as a second cryopanel.

In the first cryopanel, a gas having a low vapor pressure at the first cooling temperature level is captured by condensation and exhausted. For example, a gas having a vapor pressure lower than a reference vapor pressure (for example, 10 ⁻⁸ Pa) is exhausted. In the second cryopanel, gas having a low vapor pressure at the second cooling temperature level is captured by condensation and exhausted. An adsorption region is formed on the surface of the second cryopanel in order to capture non-condensable gas such as hydrogen that does not condense even at the second temperature level due to high vapor pressure. The adsorption region is formed, for example, by providing an adsorbent on the panel surface. The non-condensable gas is adsorbed in the adsorption region cooled to the second temperature level and exhausted.

  In a typical cryopump, the baffle is disposed in the shield opening, while the low-temperature cryopanel is attached to a second cooling stage disposed in the center of the shield. The arrangement is merely determined independently of each other. There is no technical idea here that harmonizes the positional relationship between the exhaust speed and the cooling ultimate temperature from the viewpoint of coexistence or optimization. The optimization of the exhaust speed and the ultimate cooling temperature is typically based on, for example, adjusting the outer diameter of the baffle. In this case, there is a trade-off relationship between the exhaust speed and the cooling arrival temperature. If a large-diameter baffle is used, the exhaust speed decreases, and if a small-diameter baffle is used, it becomes difficult to reach a low cooling temperature.

  On the other hand, in one embodiment of the present invention, the baffle and the low-temperature cryopanel are regarded as one unit from the viewpoint of optimizing the exhaust speed and the cooling arrival temperature, and the distance between the baffle and the low-temperature cryopanel, that is, from the shield opening. Adjust the offset amount. This is based on a new finding that even if the offset amount of the baffle from the shield opening is varied, the influence on the exhaust speed of the low-temperature cryopanel is small.

  For example, first, a low-temperature cryopanel is designed so as to obtain a desired gas storage amount. For example, the layout of the low-temperature cryopanel, the area of the adsorption region, the type and shape of the adsorbent used are determined so as to satisfy the required gas storage capacity. And the ratio and baffle shape which a baffle occupies a shield opening are defined so that the required exhaust speed may be implement | achieved by a low-temperature cryopanel. That is, the area of the open region formed between the inner surface of the radiation shield and the baffle is set in accordance with the required exhaust speed for the gas to be exhausted by the low-temperature cryopanel. When the baffle is a louver, for example, the diameter of the louver is determined. Further, the amount of offset from the opening is determined so that the temperature at which the cryogenic cryopanel reaches the cooling temperature is lower than when the baffle is disposed in the shield opening. Preferably, the offset position of the baffle is selected from an offset range in which the temperature at which the low temperature cryopanel is cooled is lower than the required cooling temperature.

  In this way, the exhaust speed and the ultimate temperature can be specified in a sequential procedure by setting the baffle dimensions and shape according to the required exhaust speed and then setting the baffle offset amount according to the required cooling temperature. Can be adapted. Both can be easily optimized without considering the trade-off between the exhaust speed and the ultimate temperature.

  As a result, in one embodiment, a straight line that intersects the central axis of the radiation shield internal space from the shield end through the outer peripheral end of the first cryopanel passes through the second cryopanel just before intersecting the central axis. In addition, the first cryopanel is disposed inside the shield end. Further, the first cryopanel may be disposed inside the opening in the radiation shield internal space so as to shield the radiant heat from the radiation shield opening end toward the second cooling stage of the refrigerator.

  Alternatively, the first cryopanel is disposed at an offset position selected from an offset range in which the cooling temperature level of the second cryopanel is substantially lower than when the first cryopanel is disposed in the radiation shield opening. Also good. Preferably, the first cryopanel is arranged at an offset position selected from an offset range in which the cooling temperature level of the second cryopanel is lower than the required cooling temperature. Further, the first cryopanel may be disposed at an offset position at which the distance from the radiation shield opening and the distance from the low-temperature cryopanel are substantially equal.

  The mounting structure for arranging the baffle at the offset position includes, for example, a baffle mounting portion provided at the radiation shield opening, a shield mounting portion formed at the outer periphery of the baffle, and an extension direction. And an attachment member for connecting the baffle attachment portion and the shield attachment portion.

  FIG. 1 is a diagram schematically showing a part of a cryopump 100 according to the first embodiment of the present invention. The cryopump 100 includes a pump container 102, a radiation shield 104, and a first cryopanel 112. The first cryopanel 112 is an offset arrangement type baffle. In FIG. 1, the pump container 102, the radiation shield 104, and the first cryopanel 112 are mainly illustrated for simplicity.

  The first cryopanel 112 is attached to the radiation shield 104 via a panel attachment structure (not shown). A second cryopanel is provided in the second panel installation space 114. In the figure, the second panel installation space 114 is indicated by a broken line. The radiation shield 104 and the second cryopanel are attached to first and second cooling stages of a refrigerator (not shown), respectively. The radiation shield 104 and the first cryopanel 112 are cooled to 80 to 100K, for example, and the second cryopanel is cooled to 10 to 20K, for example.

  The radiation shield 104 is formed in a bottomed cylindrical shape with the straight line A as the central axis, one end being opened and the other end being closed. The inner surface of the radiation shield 104 defines a cylindrical interior space 106 having a central axis A. In addition, the pump container 102 is disposed with a gap between the outer surface of the radiation shield 104. An end of the radiation shield 104 on the open side (hereinafter referred to as “shield end” where appropriate) 110 defines a radiation shield opening (hereinafter referred to as “shield opening” where appropriate) 108. Since the radiation shield 104 is cylindrical, the shield opening 108 is circular.

  As illustrated, the first cryopanel 112 may be, for example, a disk-shaped baffle, a louver shape formed concentrically, or a chevron shape. The first cryopanel 112 is disposed so as to form an open region with the radiation shield 104. As shown in the figure, the open area is an annular gap having a width B, for example. The area of the open region is set so that the exhaust speed of the second cryopanel satisfies the required specifications. Further, the first cryopanel 112 is disposed in the internal space 106 so as to be separated from the shield opening 108 by an offset amount C. The offset amount C is set so that the cooling arrival temperature of the second cryopanel satisfies the required specification.

  The second panel installation space 114 is a part of the shield internal space 106 and is a space that includes the second cryopanel. The second panel installation space 114 is, for example, a cylindrical space having the straight line A as the central axis. The second panel installation space 114 is surrounded by the first cryopanel 112 and the radiation shield 104. As a result, the second cryopanel is arranged at the rear stage of the first cryopanel 112 when viewed from the shield opening 108. The second cryopanel can be arranged in an arbitrary layout inside the second panel installation space. For example, the second cryopanel is arranged in a layout that surrounds the central axis of the radiation shield 18.

  2 and 3 are views for explaining the shielding effect of radiant heat by the offset arrangement type cryopanel. As shown in FIG. 2, among the radiant heat that enters the shield internal space 106 through the shield end 110 from the outside, for example, the radiant heat that passes through the range of the angle α from the opening surface 108 is shielded by the first cryopanel 112. Is done. That is, the radiant heat a traveling from the shield end 110 toward the central axis A through the outer periphery of the first cryopanel 112 enters the second panel installation space 114, but the radiant heat b incident from the shield end 110 at a shallower angle, c is included in the range of the angle α and is shielded by the first cryopanel 112.

  In addition, as shown in FIG. 3, the offset arrangement type cryopanel 112 is incident on the shield internal space 106 from the heat source P outside the cryopump as compared with the case where the first cryopanel 112 is provided in the shield opening 108. Radiant heat is also shielded more. When the first cryopanel 112 is provided in the shield opening 108, it only shields radiant heat having an incident angle shallower than that of the radiant heat e, but the first cryopanel 112 is arranged offset inward by an offset amount C. Thus, it is possible to shield radiant heat having an incident angle shallower than radiant heat d traveling from the external heat source P toward the central axis A through the outer peripheral edge of the first cryopanel 112. Compared with the case where the first cryopanel 112 is provided in the shield opening 108, when the offset amount C is given, the radiant heat in the range of the angle β can be further shielded.

  As shown in FIG. 3, when the heat source P is located outside the first cryopanel 112 in the radial direction from the central axis A, the radiant heat enters the second panel installation space by the offset arrangement type cryopanel 112. Is reduced. However, when there is a radiant heat source inside the first cryopanel 112 in the radiation direction from the central axis A, the first cryopanel 112 is offset into the radiation shield 104 to enter the shield internal space 106. Radiant heat will increase. However, the influence of this radiant heat on the second cryopanel is small. Radiant heat from the radiation heat source on the inner side in the radial direction is first shielded by the first cryopanel 112. Furthermore, most of the radiant heat that has entered the shield internal space 106 through the open region between the radiation shield 104 and the first cryopanel 112 is incident on the inner surface of the radiation shield 104. That is, the radiant heat from the radiant heat source on the inner side in the radial direction basically does not directly enter the second cryopanel. Therefore, the radiant heat entering the second panel installation space 114 is effectively reduced by the offset first cryopanel 112.

  The inner surface of the radiation shield 104 is preferably subjected to a treatment for increasing the absorption rate of the radiant heat, for example, a black surface treatment so as to absorb the incident radiant heat. Then, the radiant heat reflected by the inner surface of the radiation shield 104 and incident on the second cryopanel can be suppressed.

  In addition, depending on the control method of the refrigerator that cools the first and second cryopanels, an increase in heat input to the inner surface of the radiation shield 104 may be rather useful for lowering the cooling ultimate temperature of the second cryopanel. is there. For example, when the operating gas intake / exhaust cycle of the refrigerator is controlled so that the temperature of the first cooling stage of the refrigerator matches the target temperature, an increase in heat input to the inner surface of the radiation shield 104 increases the second cryopanel. Cooling attainment temperature can be lowered more. In this case, the intake / exhaust cycle of the refrigerator is increased against the increase in the thermal load on the first cooling stage to maintain the target temperature, and the temperature of the second cooling stage is lowered in conjunction with this. Therefore, in one Example, you may provide the control part which controls the working gas intake / exhaust cycle of a refrigerator so that the temperature of the 1st cooling stage of a refrigerator may correspond with target temperature. For example, the control unit may include a temperature sensor that measures the temperature of the first cooling stage of the refrigerator, and a controller that controls a working gas intake / exhaust cycle of the refrigerator based on a measurement value of the temperature sensor. .

  The offset amount of the first cryopanel 112 is preferably selected from the offset range D shown in FIG. As shown in FIG. 4, the minimum offset amount C1 of the offset range D is such that a straight line that intersects the central axis A of the shield internal space 106 from the shield end 110 through the outer peripheral end of the first cryopanel 112 is It is set so as to pass through the intersection point Q with the second panel installation space 114. The maximum offset amount C2 of the offset range D is set so as to have a gap between the first cryopanel 112 and the second cryopanel so that they do not contact each other. This air gap may be set in consideration of substantially eliminating the influence of heat exchange due to radiation between the first cryopanel 112 and the second cryopanel.

  By selecting the offset amount of the first cryopanel 112 from the offset range D set in this way, as shown in FIG. 2, the first cryopanel 112 has an outer periphery of the first cryopanel 112 from the shield end 110. A straight line that intersects the central axis A of the shield internal space 106 through the end is disposed inside the shield end 110 so as to pass through the second panel installation space 114 before crossing the central axis A. In this way, it is possible to achieve both the achievement of the required exhaust speed and the reduction of radiant heat to the second cryopanel.

  FIG. 5 is a diagram schematically showing a part of the cryopump 10 according to the second embodiment of the present invention. In the second embodiment, the first cryopanel is a louver 23, and the second cryopanel is suspended from the refrigerator 14, exposed to the shield opening 20, and protruded from the cryopanel 24. It is.

  The cryopump 10 includes a pump container 12, a refrigerator 14, a panel structure 16, and a radiation shield 18. The cryopump 10 shown in FIG. 5 is a so-called horizontal cryopump. In the horizontal cryopump 10, the second cooling stage 22 of the refrigerator 14 is generally inserted into the radiation shield 18 along a direction (usually an orthogonal direction) intersecting the central axis direction of the cylindrical radiation shield 18. The cryopump 10 is arranged. The present invention can be similarly applied to a so-called vertical cryopump. The vertical cryopump is a cryopump in which the refrigerator 14 is inserted along the central axis direction of the radiation shield 18.

  FIG. 5 is a diagram schematically showing a cross section by a plane including the central axis A of the pump container 12 and the radiation shield 18 and orthogonal to the central axis of the refrigerator 14. In FIG. 5, an arrow E indicates a gas entering direction from a vacuum chamber, which is an exhaust target volume outside the pump, into the cryopump. FIG. 6 is a diagram illustrating a modification of the second embodiment. FIG. 7 is a diagram schematically showing the louver 23 when viewed from the gas entry direction E. FIG. FIG. 8 is a diagram schematically showing the panel structure 16 when viewed from the gas entry direction E. FIG.

  It should be understood that the gas entry direction E is a direction from the outside to the inside of the cryopump. In the drawing, the gas entry direction E is parallel to the central axis A of the radiation shield 18 only for the sake of convenience. Of course, the actual entry direction of gas molecules entering the cryopump in the cryopumping process does not exactly coincide with the illustrated gas entry direction E, but rather intersects the gas entry direction E. Is normal.

  The pump container 12 has a portion formed in a cylindrical shape having an opening at one end and the other end closed. A panel structure 16 and a radiation shield 18 are disposed inside the pump container 12. The opening of the pump container 12 is provided as an intake port through which gas to be exhausted enters, and is defined by the inner surface of the upper end portion of the cylindrical side surface of the pump container 12. A mounting flange 30 extends radially outward from the upper end of the pump container 12. The cryopump 10 is attached using a mounting flange 30 to a vacuum chamber such as an ion implantation apparatus that is an exhaust target volume. The cross section of the pump container 12 is not limited to a circular shape, and may be another shape such as an elliptical shape or a polygonal shape.

  The refrigerator 14 is, for example, a Gifford McMahon refrigerator (so-called GM refrigerator). The refrigerator 14 is a two-stage refrigerator and includes a first cooling stage (not shown) and a second cooling stage 22. The second cooling stage 22 is surrounded by the pump container 12 and the radiation shield 18, and is disposed at the center of the internal space of the pump container 12 and the radiation shield 18. The first cooling stage is cooled to the first cooling temperature level, and the second cooling stage 22 is cooled to the second cooling temperature level lower than the first cooling temperature level. The second cooling stage 22 is cooled to about 10K to 20K, for example, and the first cooling stage is cooled to about 80K to 100K, for example.

  The radiation shield 18 is fixed in a state where it is thermally connected to the first cooling stage of the refrigerator 14 and is cooled to a temperature similar to that of the first cooling stage. The radiation shield 18 is provided as a radiation shield that protects the panel structure 16 and the second cooling stage 22 from ambient radiation heat. Similarly to the pump container 12, the radiation shield 18 is also formed in a cylindrical shape having a shield opening 20 at one end and closed at the other end. The radiation shield 18 is formed in a cup shape. Both the pump container 12 and the radiation shield 18 are formed in a substantially cylindrical shape, and are arranged coaxially. The inner diameter of the pump container 12 is slightly larger than the outer diameter of the radiation shield 18, and the radiation shield 18 is disposed in a non-contact state with the pump container 12 with a slight gap between the inner surface of the pump container 12. In the embodiment shown in FIG. 5, the closed portion of the radiation shield 18 is formed in a dome shape so as to be away from the shield opening 20 as it approaches the central axis A. Similarly, the closed portion of the pump container 12 is curved in a dome shape.

  A second cooling stage 22 of the refrigerator 14 is disposed in the center of the internal space of the radiation shield 18. The refrigerator 14 is inserted from the opening on the side surface of the radiation shield 18, and the first cooling stage is attached to the opening. In this manner, the second cooling stage 22 of the refrigerator 14 is disposed between the shield opening 20 and the deepest portion on the central axis of the radiation shield 18.

  The shape of the radiation shield 18 is not limited to a cylindrical shape, and may be a cylindrical shape having any cross section such as a rectangular cylindrical shape or an elliptical cylindrical shape. Typically, the shape of the radiation shield 18 is similar to the shape of the inner surface of the pump container 12. Further, the radiation shield 18 may not be configured as an integral cylindrical shape as illustrated, and may be configured so as to form a cylindrical shape as a whole by a plurality of parts. The plurality of parts may be arranged with a gap therebetween.

  In addition, a louver 23 is disposed with a substantial offset from the opening 20 of the radiation shield 18. The louver 23 is provided at a distance from the panel structure 16 in the central axis direction of the radiation shield 18. The interval between the louver 23 and the panel structure 16 may be wider or narrower than the interval between the shield opening 20 and the louver 23. Further, the interval between the louver 23 and the panel structure 16 may be substantially equal to the interval between the shield opening 20 and the louver 23. In the embodiment shown in FIG. 5, the offset amount of the louver 23 is set to be relatively large, and the distance from the shield opening 20 to the upper end of the louver 23 is from the lower end of the louver 23 to the upper end of the distal end portion 34 of the cryopanel 24. It is wider than the interval. A gate valve (not shown) may be provided between the louver 23 and the vacuum chamber. This gate valve is closed when, for example, the cryopump 10 is regenerated, and is opened when the vacuum chamber is evacuated by the cryopump 10.

  The offset amount of the louver 23 is set so that a straight line F that intersects the central axis A from the opening end of the radiation shield 18 through the outer peripheral end 50 of the louver 23 passes through the cryopanel 24 just before intersecting the central axis A. . The straight line F is indicated by a broken line in FIG. Further, preferably, the offset amount of the louver 23 may be set so that the straight line F passes between the outermost part and the innermost part of the distal end portion 34 of the cryopanel 24. As will be described later, in order to reduce the temperature at which the cryopanel 24 reaches the cooling state, it is more preferable that the louver 23 is not extremely close to the cryopanel 24 but has a certain distance from the cryopanel 24. This is because it has been experimentally confirmed.

  Further, the offset amount of the louver 23 may be set so that at least a part of the radiant heat from the opening end of the radiation shield 18 toward the second cooling stage 22 of the refrigerator 14 is shielded. Preferably, the offset amount of the louver 23 may be set so that radiant heat from the opening end of the radiation shield 18 toward the second cooling stage 22 of the refrigerator 14 is completely shielded. In this way, direct incidence of radiant heat to the second cooling stage 22 that is a cooling source is suppressed, which is considered to contribute to a decrease in the cooling temperature of the cryopanel 24. For example, as shown in FIG. 6, by bringing the louver 23 relatively close to the cryopanel 24, a straight line G that intersects the central axis A from the opening end of the radiation shield 18 through the outer peripheral end 50 of the louver 23 becomes a refrigerator 14. The second cooling stage 22 passes below. As a result, it is possible to prevent the radiant heat entering from the gap between the radiation shield 18 and the louver 23 from entering the second cooling stage 22.

  As shown in FIG. 5, the diameter of the outer peripheral end 50 of the louver 23 is preferably smaller than the outermost diameter of the cryopanel 24. That is, the distance between the cryopanel 24 and the inner surface of the radiation shield 18 in the radiation direction from the central axis A is preferably smaller than the distance between the outer peripheral end 50 of the louver 23 and the inner surface of the radiation shield 18. Considering the radiant heat to the cryopanel 24, the diameter of the outer peripheral end 50 of the louver 23 is preferably 75% to 100% of the outermost diameter of the cryopanel 24, and more preferably 85% to 95%. . By making the louver 23 relatively small, the flowability of gas into the shield can be improved and the exhaust speed can be increased. Further, a relatively large panel area can be secured by reducing the distance between the cryopanel 24 and the radiation shield 18. This also contributes to improvement of exhaust performance.

  The louver 23 is exposed when viewed from the shield opening 20, and the cryopanel 24 is exposed when viewed from the louver 23. That is, only a space is formed in the upper part of the louver 23, and no obstacles that obstruct the gas flow are provided. Further, only a space is formed between the louver 23 and the cryopanel 24, and no obstacles that obstruct the gas flow are provided. With such a simple configuration, a good exhaust speed is realized without excessively hindering the gas flow.

  The louver 23 is attached to the radiation shield 18 by a panel attachment structure 40. The panel mounting structure 40 is discretely provided at a plurality of locations in the radial direction with respect to the central axis A, and is provided at, for example, four locations every 90 degrees (see FIG. 7). The panel mounting structure 40 mechanically fixes the louver 23 to the radiation shield 18 and thermally connects the radiation shield 18 and the louver 23. As a result, the panel mounting structure 40 also functions as a heat transfer path from the radiation shield 18 to the louver 23, and the louver 23 is cooled to the same temperature as the radiation shield 18.

  As shown in FIG. 5, the panel attachment structure 40 includes a panel attachment portion 42, a first attachment member 44, a second attachment member 46, and a shield attachment portion 48. The panel attachment portion 42 is a protrusion that is erected vertically from the inner surface of the radiation shield 18 toward the central axis A in the vicinity of the shield opening 20. The first attachment member 44 is a rod-shaped member for connecting the panel attachment portion 42 and the second attachment member 46, one end is attached to the panel attachment portion 42, and the other end is attached to the second attachment member 46. . The panel attachment part 42 and the second attachment member 46 are attached to the first attachment member 44 by attachment means such as bolts, for example. In the mounted state, the first mounting member 44 is disposed so as to extend in parallel with the shield opening 20 from the panel mounting portion 42 toward the central axis A.

  The second attachment member 46 is a rod-like member for connecting the first attachment member 44 and the shield attachment portion 48, one end is attached to the first attachment member 44, and the other end is attached to the shield attachment portion 48. . The first attachment member 44 and the shield attachment portion 48 are attached to the second attachment member 46 by attachment means such as bolts, for example. The shield attachment portion 48 is a rod-shaped portion extending from the outer peripheral end 50 of the louver 23 toward the radially outer side. In the mounted state, the second mounting member 46 is disposed so as to extend from the first mounting member 44 along the central axis A into the radiation shield 18. The second mounting member 46 extends from the first mounting member 44 in a direction along the shield inner surface and in a direction away from the shield opening 20. For this reason, the offset amount of the louver 23 is realized by the second mounting member 46. Therefore, a desired offset amount can be realized by adjusting the length of the second mounting member 46.

  In addition, you may make it form the connection part with the shield attachment part 48 in the multiple places of the axial direction of the 2nd attachment member 46. FIG. In this way, the offset amount of the louver 23 can be changed by selecting one of the plurality of connecting portions. Further, the second attachment member 46 may incorporate a length adjustment mechanism. In this way, the offset amount of the louver 23 can be arbitrarily adjusted on-site.

  The first attachment member 44 is configured to be attached not only to the second attachment member 46 but also to the shield attachment portion 48. For example, the second mounting member 46 and the shield mounting portion 48 have bolt holes with a common diameter. For this reason, it is also possible to directly attach the shield attachment portion 48 to the first attachment member 44. In this case, similarly to a typical cryopump, the louver 23 is disposed at the same position as the panel mounting portion 42 in the direction along the central axis A. That is, the louver 23 is disposed in the vicinity of the shield opening 20 and an offset from the shield opening 20 is not substantially formed. If it does in this way, offset can be given to louver 23 by adding the 2nd attachment member 46 as needed. Since the radiation shield 18 and the louver 23 can be shared regardless of the presence or absence of an offset, the cost can be reduced when providing the cryopump 10 with an offset and the cryopump without an offset as a product series.

  As shown in FIG. 7, the louver 23 is formed of a plurality of slats 52, and each slat 52 is formed in the shape of a side surface of a truncated cone having a different diameter and arranged concentrically. In FIG. 7, the gaps 54 are arranged so as to be formed between the blades 52 when viewed from above, but the gaps 54 are not formed when the adjacent blades 52 overlap each other and viewed from above. In this way, the slats 52 may be densely arranged. Each slat 52 is attached to a cross-shaped support member 56. A shield mounting portion 48 is formed at the radial end of the support member 56. The louver 23 may be formed in other shapes such as a lattice shape.

  The louver 23 is arranged coaxially with the radiation shield 18. In FIG. 7, the inner surface of the radiation shield 18 and the first mounting member 44 of the panel mounting structure 40 are indicated by broken lines. As illustrated, an annular open region 58 is formed between the inner surface of the radiation shield 18 and the outer peripheral end 50 of the louver 23. The area of the open region 58 is set so that the hydrogen exhaust speed by the cryopanel 24 shown in FIG. Specifically, for example, the area of the open region 58 can be adjusted by changing the number of the louvers 52 of the louver 23 to change the diameter of the louver 23.

  As shown in FIG. 5, the panel structure 16 is fixed in a state of being thermally connected to the second cooling stage 22 of the refrigerator 14, and is cooled to the same temperature as the second cooling stage 22. The The panel structure 16 includes a plurality of cryopanels 24, a connection member 26, and an intermediate member 28. A connection member 26 is attached to the second cooling stage 22 of the refrigerator 14, an intermediate member 28 is attached to the connection member 26, and a plurality of cryopanels 24 are attached to the intermediate member 28. The cryopanel 24, the connection member 26, and the intermediate member 28 are all formed of a material such as copper. You may use what plated the surface with nickel by using copper as a base material. Further, the cryopanel 24 or the like may be formed of aluminum instead of copper. Copper may be used when emphasizing thermal conductivity, and aluminum may be used when emphasizing weight reduction and thus shortening the regeneration time.

  The connection member 26 is provided as a connection member for thermally connecting and mechanically supporting the panel structure 16 to the second cooling stage 22. The intermediate member 28 is provided as a panel support member that thermally connects the plurality of cryopanels 24 to the second cooling stage 22 via the connection member 26 and supports the cryopanel 24. Further, the connecting member 26 and the intermediate member 28 can be regarded as a panel support member. The connection member 26 and the intermediate member 28 may be formed as separate members, or may be formed integrally. The cryopanel 24 is thermally connected to the second cooling stage 22 of the refrigerator 14 via the intermediate member 28 and the connecting member 26, and is cooled to the same temperature as the second cooling stage 22. Similarly, the intermediate member 28 and the connecting member 26 are cooled to a temperature similar to that of the second cooling stage 22.

  The panel structure 16 as a whole has a configuration that is suspended from the second cooling stage 22 of the refrigerator 14 by the connection member 26 downward or toward the deep part of the radiation shield 18. The connection member 26 is a suspension member that suspends and supports the panel structure 16 on the refrigerator 14. For this reason, the panel structure 16 can be arranged away from the shield opening 20. As a result, since the distance between the external heat source and the panel structure 16 can be increased, the influence of external radiant heat can be reduced. In addition, the space between the panel structure 16 and the shield opening 20 can be used to relatively increase the cryopanel area, which contributes to the improvement of the exhaust performance of the cryopump.

  The connection member 26 suspends and supports the intermediate member 28 on the second cooling stage 22. The intermediate member 28 is disposed at a position farther from the shield opening 20 with respect to the gas entry direction E than the second cooling stage 22. The intermediate member 28 supports the end portions of the plurality of cryopanels 24. The cryopanel 24 projects and extends upward from the intermediate member 28 or toward the shield opening 20.

  Therefore, the heat transfer path from the second cooling stage 22 of the refrigerator 14 to the tip of the cryopanel 24 meanders inside the radiation shield 18. In other words, the heat transfer path from the refrigerator 14 to the tip of the cryopanel 24 extends from the second cooling stage 22 to the deep part of the radiation shield 18, and turns back toward the opening 20 of the radiation shield 18. The heat transfer path is folded back at the intermediate member 28. By making the panel structure 16 have such a folded structure, the cryopanel area can be increased. This makes it possible to achieve high exhaust performance in the cryopump 10.

  An adsorbent installation surface for installing an adsorbent for adsorbing gas is formed on at least a part of the cryopanel surface. In the present embodiment, the entire area of both surfaces of the cryopanel 24 is the adsorbent installation surface. In the present embodiment, the adsorbent 25 is bonded to the entire area of both surfaces of the cryopanel 24 so that the entire surface is an adsorption area. The adsorbent 25 is, for example, granular activated carbon. All adsorbent installation surfaces are exposed in the opening 20.

  The reflectivity of the adsorbent surface is generally lower than the reflectivity of the surface of the cryopanel 24 itself, and it is considered that the influence of radiant heat through the adsorbent is large. This is because the cryopanel 24 is usually made of metal, whereas the adsorbent is black if it is activated carbon, for example. Therefore, as shown in FIG. 5, it is preferable to set the straight line F so as to pass through the adsorbent installation region of the cryopanel 24. Then, at least a part of the adsorbent installation area can be shielded by the louver 23. Accordingly, it is possible to suppress radiant heat from entering through the adsorbent.

  The cryopanel 24 includes a connection part 32 that is a terminal part connected to the intermediate member 28, a tip part 34 that is closest to the opening 20, and an intermediate part 36 that connects the connection part 32 and the tip part 34. In this embodiment, the connection part 32, the front-end | tip part 34, and the intermediate part 36 are formed with one plate. The connection part 32, the tip part 34, and the intermediate part 36 may be formed separately and connected to each other to form a single cryopanel 24. The cryopanel 24 has a connection portion 32 attached to the intermediate member 28. For example, a flange is formed at the end of the connection portion 32, and the flange is attached to the intermediate member 28 by appropriate fixing means such as a bolt and a nut. The cryopanel 24 and the intermediate member 28 may be formed as an integral member.

  Since the intermediate member 28 is disposed at a position farther from the opening 20 with respect to the gas entry direction E than the second cooling stage 22, the connection portion 32 of the cryopanel 24 is also farther from the opening 20 than the second cooling stage 22. Placed in a different position. The cryopanel 24 extends from the connection portion 32 toward the opening 20. The tip 34 of the cryopanel 24 is disposed at a position closer to the opening 20 with respect to the gas entry direction E than the center of the radiation shield 18 and the second cooling stage 22. The cryopanel 24 extends along the gas entry direction E from the connection portion 32 to the tip portion 34 beyond the central portion of the internal space of the radiation shield 18. As described above, the cryopanel 24 extending beyond the central portion of the radiation shield 18 in the gas entry direction E can increase the area of the cryopanel arranged along the gas entry direction E. This makes it possible to achieve high exhaust performance in the cryopump 10.

  The cryopanel 24 may have the tip 34 disposed below or deeper than the radiation shield 18 or the center of the pump container 12. Similarly, the tip 34 of the cryopanel 24 may be disposed below the second cooling stage 22 of the refrigerator 14. In this case, the cryopanel 24 may have a folded structure at the distal end portion 34 and extend again downward below the cryopump. That is, the cryopanel 24 may be formed so as to extend from the connection portion 32 to the distal end portion 34 and be folded back toward the lower portion of the cryopump at the distal end portion 34. In this way, the panel area can be increased while suppressing the length of the cryopanel 24 in the gas entry direction E. Further, it is possible to provide the panel structure 16 compactly at the bottom of the pump so as to avoid radiant heat. The position, shape, and the like of the distal end portion 34 of the cryopanel 24 may be determined in consideration of, for example, the required exhaust performance to the cryopump 10 and the influence of external radiant heat.

  In the cryopanel 24, at least the connection portion 32 is exposed toward the opening 20. In the present embodiment, the distal end portion 34 and the intermediate portion 36 of the cryopanel 24 are also exposed toward the opening 20. For this reason, the entire cryopanel 24 is exposed toward the opening 20. Therefore, the cryopanel 24 can directly receive the gas molecules that have entered the internal space of the radiation shield 18 from the outside over the entire surface. The entire adsorbent installation surface of the cryopanel 24 can directly receive gas molecules. Therefore, unlike the configuration in which the adsorbent 25 is shielded from the opening 20, the gas can be processed efficiently. In the present embodiment, since the entire surface of the cryopanel 24 is an adsorption region, a non-condensable gas such as hydrogen can be efficiently exhausted. Such a panel configuration is preferable as a cryopump for, for example, an ion implantation apparatus using a non-condensable gas as a main exhaust gas.

  The cryopanel 24 is disposed in parallel to the central axis A. In the present embodiment, the cryopanel 24 is erected vertically on the intermediate member 28. Therefore, the cryopanel 24 is disposed perpendicular to the opening 20. Since both sides of the cryopanel 24 can be used evenly for exhaust, the gas can be exhausted efficiently. However, the cryopanel 24 may be inclined and arranged so as to intersect the central axis A in consideration of the gas flowability and the external radiant heat.

  The cryopanel 24 has a trapezoidal shape whose width is continuously expanded from the connection portion 32 toward the tip end portion 34. A side end portion on the outer peripheral side of the cryopanel 24 is parallel to the central axis A, and a side end portion on the inner peripheral side extends in a direction intersecting the central axis A. The shape of the cryopanel 24 is not limited to the trapezoidal shape shown in FIG. 5, and may be a rectangular shape or other shapes. Further, the shapes of the cryopanels 24 may be different from each other. For example, a plurality of types of cryopanels may be mixed. For example, a large cryopanel and a small cryopanel may be mixed and arranged.

  In this embodiment, as shown in FIG. 8, the cryopanels 24 are arranged so as to surround the central axis of the radiation shield in a radial layout. The cryopanels 24 are arranged at equal intervals except for the part necessary for inserting the refrigerator 14. For example, the cryopanels 24 are arranged at equal angular intervals of 10 degrees to 20 degrees. The cryopanel 24 is provided on the outer peripheral side in the radial direction of the disk-shaped intermediate member 28, and a columnar space surrounded by the panel is formed at the center of the intermediate member 28. The width of the cryopanel 24 is set so as to occupy, for example, from the outermost peripheral portion to a position about half the radius of the intermediate member 28 in the radial direction of the intermediate member 28. In this case, a cylindrical space having a diameter about half the diameter of the intermediate member 28 is formed at the center of the intermediate member 28. Thus, when the cryopanel 24 is arranged radially on the surface of the intermediate member 28, it is preferable that the panel is provided on the outer peripheral side of the surface of the intermediate member and an open space is formed at the center. As a result, it is possible to avoid the denseness of the panel at the center portion, so that the gas flowability can be improved.

  The intermediate member 28 is a flat plate-like member having, for example, a disk shape. The upper surface of the intermediate member 28, that is, the surface facing the opening 20 is the panel mounting surface. The panel mounting surface is a circular plane. The intermediate member 28 may not be a disk-shaped flat plate member, and may be a flat plate member of another shape. Alternatively, the intermediate member 28 may have a curved shape or a bent shape. For example, the intermediate member 28 may have a dome shape that approaches the opening 20 as it approaches the center. In this case, the panel mounting surface is a dome-shaped curved surface.

  A plurality of cryopanels 24 may be attached by forming a panel attachment surface on the lower surface of the intermediate member 28. In this case, a slit for promoting the gas flow may be formed in the intermediate member 28 between adjacent panels. If it does in this way, the gas distribution to the panel currently standing toward the cryopump bottom side can be promoted.

  The connection member 26 is formed so as to surround the second cooling stage 22, for example. The connection member 26 has a refrigerator attachment part attached to the second cooling stage 22 of the refrigerator 14 at one end on the opening 20 side, and a flange for attachment to the intermediate member 28 is formed at the other end on the pump bottom side. Yes. A suspended portion extends from the periphery of the refrigerator attachment portion toward the lower side of the pump, and a flange is formed at the end of the suspended portion. The flange of the connecting member 26 is attached to the intermediate member 28 by appropriate fixing means such as bolts and nuts.

  The connection member 26 and the cryopanel 24 are indirectly connected through an intermediate member 28. However, in order to improve the thermal conductivity to the tip portion 34 of the cryopanel 24, a heat transfer path that directly connects the connection member 26 to the tip portion 34 of the cryopanel 24 may be provided. This heat transfer path is preferably formed so as to minimize the influence on the flowability of the gas, and for example, it is desirable that the heat transfer path is formed of a surface arranged in parallel with the gas ingress direction E.

  In addition, you may employ | adopt the panel arrangement | positioning different from the above-mentioned embodiment. For example, instead of a radial panel arrangement, the panels may be arranged in parallel or arranged in a grid. The intervals between the panels may be the same or different. Alternatively, a cylindrical outer peripheral panel having the same diameter as that of the intermediate member 28 may be provided on the outermost peripheral portion of the intermediate member 28. In addition to the outer peripheral panel, a small-diameter concentric cylindrical panel may be further provided. Further, other known cryopanel arrangements may be adopted instead of the above-described suspension type panel configuration.

  Now, an experimental result will be described that shows that the evacuation speed of the cryopanel 24 and the cooling temperature can be realized by giving an offset to the louver 23. FIG. 9 and FIG. 10 are diagrams showing the exhaust speed and the cooling temperature when the offset amount of the louver 23 is varied in the second embodiment.

  First, FIGS. 9 and 10 show three cases where there is no offset, when a small offset amount is given, and when a large offset amount is given. In either case, the same louver 23 having the same diameter is used. The case where there is no offset is a case where the louver 23 is arranged at the same position as the panel mounting portion 42 in the direction along the central axis A, as in the conventional cryopump. When a small offset amount is given, the louver 23 is disposed at a position where the distance between the shield opening 20 and the louver 23 and the distance between the louver 23 and the cryopanel 24 are substantially equal. When a large offset amount is given, the louver 23 is arranged at a position having an offset amount twice as large as that when a small offset amount is given.

  FIG. 9 is a diagram illustrating the cooling temperature of the cryopanel 24 when the offset amount is varied. 9 indicates the temperature of the second cooling stage 22 of the refrigerator 14, and the horizontal axis indicates the flow rate of hydrogen gas. The temperature of the second cooling stage 22 corresponds to the temperature of the cryopanel 24. As shown in FIG. 9, when there is no offset, the temperature of the cryopanel 24 is approximately 12.5K. On the other hand, when the offset is given, the temperature of the cryopanel 24 is lowered to about 11.5K regardless of the magnitude of the offset amount. What should be noted here is that a lower cooling temperature is reached when a small offset is given than when a large offset is given. This tendency is also confirmed when an experiment is performed using a louver having a diameter different from that in FIG.

  FIG. 10 is a diagram showing the hydrogen exhaust speed of the cryopanel 24 when the offset amount is varied. The vertical axis in FIG. 10 indicates the hydrogen exhaust speed, and the horizontal axis indicates the hydrogen gas pressure. As shown in FIG. 10, it can be seen that the exhaust speed basically does not change greatly regardless of the presence or absence of an offset. However, it should be noted that the best exhaust speed is obtained when a small offset is given, particularly in the low pressure region. This tendency is also confirmed when an experiment is performed using a louver having a diameter different from that in FIG.

  Therefore, when the louver 23 is disposed at a position where the distance between the shield opening 20 and the louver 23 and the distance between the louver 23 and the cryopanel 24 are substantially equal, the hydrogen exhaust speed is the best and the panel cooling temperature is the highest. Can be lowered. It is preferable that the distance between the shield opening 20 and the louver 23 be, for example, about 90% to 110% of the distance between the louver 23 and the cryopanel 24. As described above, the offset position of the louver 23 is preferably selected from an offset range in which the distance from the shield opening 20 and the distance from the cryopanel 24 are substantially equal.

  On the other hand, as a comparative example, FIGS. 11 and 12 show the exhaust speed and the cooling temperature when the diameter of the louver 23 is varied. 11 and 12 show a case where a large diameter louver is used and a case where a small diameter louver is used. The large diameter louver is 22% larger in diameter than the small diameter louver. In either case, no offset is given to the louver.

  FIG. 11 is a diagram showing the cooling temperature of the cryopanel 24 when the louver diameter is varied. The vertical axis in FIG. 11 indicates the temperature of the second cooling stage 22 of the refrigerator 14, and the horizontal axis indicates the flow rate of hydrogen gas. As shown in FIG. 11, the temperature of the cryopanel 24 is slightly lower when a large-diameter louver is used than when a small-diameter louver is used. However, even when a large-diameter louver is used, the amount of temperature decrease is about 0.2K to 0.4K. The cooling temperature of the cryopanel 24 can be greatly lowered when the offset is given as shown in FIG.

  FIG. 12 is a diagram showing the hydrogen exhaust speed of the cryopanel 24 when the louver diameter is varied. The vertical axis in FIG. 12 indicates the hydrogen exhaust speed, and the horizontal axis indicates the hydrogen gas pressure. As shown in FIG. 12, it can be seen that the hydrogen exhaust speed is greatly reduced by using a large-diameter louver.

  It can be seen from FIGS. 9 to 12 that the sensitivity of the cryopanel 24 to the hydrogen pumping speed is lower when the louver 23 is offset than when the louver diameter is increased. When the louver diameter is increased, the hydrogen exhaust speed is greatly reduced. However, when an offset is applied, the hydrogen exhaust speed does not change much. Further, even if the louver diameter is increased or the louver 23 is offset, both have a certain effect on the cooling temperature drop of the cryopanel 24. However, if the louver 23 is offset, the temperature can be greatly decreased. it can.

  In the end, when the louver diameter is increased, the hydrogen exhaust speed and the cooling temperature are in a trade-off relationship, so that optimization of both is not easy. Moreover, even if the louver diameter is varied, the amount of decrease in the cooling temperature is not so large, so it may be difficult to adapt both the hydrogen exhaust speed and the cooling temperature to the required specifications. As an example, when the required cryopanel cooling temperature is 12K, it can be reached in this embodiment, but not in the comparative example. Furthermore, it is necessary to manufacture a plurality of louvers having different diameters for the verification test. In particular, when preparing cryopumps with different calibers as a product series, it is necessary to optimize the louver diameter for each caliber, which requires enormous effort. On the other hand, according to the present embodiment, the hydrogen exhaust speed and the cooling temperature can be easily optimized in a sequential procedure by selecting the louver diameter in accordance with the required exhaust speed and adjusting the offset amount. It can be carried out.

  In the operation of the cryopump 10 described above, first, before the operation, another appropriate roughing pump is used to roughly rough the exhaust target volume, for example, the inside of the vacuum chamber of the ion implantation apparatus to about 1 Pa. Thereafter, the cryopump 10 is operated. The first cooling stage and the second cooling stage 22 are cooled by driving the refrigerator 14, and the radiation shield 18, the louver 23, and the panel structure 16 are also cooled to the cooling temperature level of the connected cooling stage. The cryopanel 24 is cooled by the second cooling stage 22 through a meandering heat transfer path including the connection member 26 and the intermediate member 28.

  The cooled louver 23 cools the gas molecules flying from the volume to be exhausted toward the inside of the cryopump 10, and condenses on the surface a gas (for example, moisture) whose vapor pressure is sufficiently low at the cooling temperature. To do. The gas whose vapor pressure does not become sufficiently low at the cooling temperature of the louver 23 passes through the louver 23 or the open region 58 and enters the radiation shield 18. Among the gas molecules that have entered, a gas whose vapor pressure is sufficiently low at the cooling temperature of the panel structure 16 (for example, argon) is condensed on the surface of the panel structure 16 and exhausted. A gas whose vapor pressure does not become sufficiently low even at the cooling temperature (for example, hydrogen) is adsorbed by the adsorbent on the surface of the panel structure 16 and exhausted.

  When the vacuum chamber of the ion implantation apparatus is evacuated, most of the gas is hydrogen. The cryopanel 24 is exposed to the opening surface of the cryopump, and the hydrogen gas is particularly efficiently adsorbed and exhausted by the adsorbent 25. In this manner, the cryopump 10 can reach the desired vacuum level in the vacuum chamber. Further, since the diameter of the louver 23 is set corresponding to the required hydrogen exhaust speed and the offset amount of the louver 23 is set corresponding to the required cooling temperature, the cryopump 10 realizes the required exhaust performance. Can do.

It is a figure which shows typically the cryopump which concerns on the 1st Embodiment of this invention. It is a figure which shows typically the cryopump which concerns on the 1st Embodiment of this invention. It is a figure which shows typically the cryopump which concerns on the 1st Embodiment of this invention. It is a figure which shows typically the cryopump which concerns on the 1st Embodiment of this invention. It is a figure which shows typically the cryopump which concerns on the 2nd Embodiment of this invention. It is a figure which shows typically the cryopump which concerns on the modification of the 2nd Embodiment of this invention. It is a figure which shows typically the louver which concerns on the 2nd Embodiment of this invention. It is a figure which shows typically the panel structure which concerns on the 2nd Embodiment of this invention. It is a figure which shows the cooling temperature of a cryopanel at the time of varying offset amount. It is a figure which shows the hydrogen exhaust speed of a cryopanel at the time of varying offset amount. It is a figure which shows the cooling temperature of a cryopanel at the time of making a louver diameter differ. It is a figure which shows the hydrogen exhaust speed of a cryopanel at the time of changing louver diameter.

Explanation of symbols

  10 cryopump, 12 pump container, 14 refrigerator, 16 panel structure, 18 radiation shield, 20 shield opening, 22 second cooling stage, 23 louver, 24 cryopanel, 25 adsorbent, 26 connecting member, 28 intermediate member, 32 connection part, 34 tip part, 40 panel mounting structure.

Claims (5)

A radiation shield having a shield inner surface defining an interior space having a central axis and a shield end defining an opening connecting the interior space to an external volume to be exhausted and cooled to a first temperature level;
An outer peripheral end, thermally connected to the radiation shield and cooled to the first temperature level, to form an open region between the outer peripheral end and the shield inner surface in a radial direction from the central axis; A first cryopanel arranged
The second cryocooler is disposed in the inner space with the layout surrounding the central axis inside the first cryopanel and cooled to a second temperature level lower than the first temperature level. A panel, and
In the first cryopanel, the open region is formed corresponding to a required exhaust velocity, and a straight line that intersects the central axis from the shield end through the outer peripheral end before the central axis intersects the central axis. A cryopump, wherein the cryopump is disposed inside the shield end in the internal space so as to pass through a second cryopanel.   A panel mounting structure for fixing the first cryopanel to the radiation shield, the panel mounting portion provided on the shield inner surface at the shield end, and the outer peripheral end of the first cryopanel A panel mounting structure including a shield mounting portion provided; and a mounting member extending in the direction of the central axis, having one end attached to the panel mounting portion and the other end attached to the shield mounting portion. The cryopump according to claim 1.   2. The cryopump according to claim 1, wherein the second cryopanel is disposed with a gap narrower than the open region between the second cryopanel and the inner surface of the shield in a radial direction from the central axis. .   The second cryopanel has a tip portion that protrudes toward the first cryopanel and is exposed when viewed from the first cryopanel, and extends from the shield end to the central axis through the outer peripheral end. The cryopump according to claim 1, wherein the intersecting straight line is disposed so as to pass through the tip portion.   The cryopump according to claim 1, wherein the first cryopanel is exposed when viewed from the opening, and the second cryopanel is exposed when viewed from the first cryopanel. .

Images