Cryopump

Abstract

The cryopump includes a vessel having an open front, the open front including an inlet to the vessel, a radiation shield, and a two-stage refrigerator extending into the vessel, the first stage of the refrigerator being thermally coupled to the radiation shield. A first-stage array is disposed within the vessel and is also thermally coupled to the first-stage refrigerator. A cryopanel structure is coupled to the second stage of the refrigerator. The first-stage array includes a plurality of elements arranged at increasing distances from the inlet, with the elements closest to the inlet being between the cryopanel structure and the inlet, and the elements furthest from the inlet having a passageway through their centers. The elements closest to the inlet have smaller perimeters than the elements furthest from the inlet.

Description

Technical Field

[0001] The field of the present invention relates to cryopumps, and more particularly to a two-stage cryopump having a first stage at a temperature for capturing type I gases such as water vapor, and a second stage at a low temperature for capturing type II gases such as nitrogen and, in some embodiments, cryo-adsorbing type III gases such as hydrogen.

Background Art

[0002] The two-stage cryopump is formed of a low-temperature second-stage cryopanel array operating in the range of 4 to 25 K, which can be coated with a capture material such as charcoal. This cryopanel array functions as a primary pump surface, operates in the temperature range of 40 to 130 K, provides a radiation shield for the low-temperature array, and is surrounded by a first-stage radiation shield that shields from type I gases such as water vapor by capturing these gas molecules where they contact the shield.

[0003] The radiation shield is within the pump housing and is normally closed except for an inlet located between the cryopanel array and the exhaust chamber. This inlet is partially hidden by the front cryopanel of the first stage, and the cryopanel is thermally coupled to the radiation shield and functions as a pumping site for high-boiling-point type I gases such as water vapor.

[0004] During operation, when gas enters the pump vessel through the inlet, at least a portion of the type I gas such as water vapor condenses on the front array. The low-boiling-point gas passes through the front array and enters the interior of the radiation shield. On the other hand, type III gases having a significant vapor pressure at 4 K, such as hydrogen, helium, neon, etc., are adsorbed by adsorbents such as activated carbon, zeolite, molecular sieve, etc., covering the cryopanel of the second stage.

[0005] In this way, the gas flowing from the exhaust chamber into the pump is captured, and a vacuum is created inside the pump vessel. One problem with cryopumps is that during operation, the gas molecules reach a saturation point at the capture surface, reducing the capture capacity. Therefore, cryopumps need to be regenerated periodically to release the captured gas molecules.

[0006] When designing a cryopump, there are competing factors to consider. High gas conductivity to the pump improves pump speed, but it is desirable to have some shielding of the second-stage cryopump from thermal radiation and type I gas to reduce the thermal load on the cryopump. Type I gas that reaches the cryopump condenses on the cryopump, preventing type III gas from being cryo-adsorbed. Furthermore, some type I gases, such as long-chain hydrocarbons, do not leave the array surface during regeneration, leading to a decrease in pump performance throughout the pump's remaining lifespan. However, shielding of the cryopump from gas molecules results in reduced conductivity.

[0007] International Publication No. 2019 / 099728 discloses a two-stage cryopump in which some of these factors are addressed by an igloo-shaped front array that provides shielding for the cryopumper. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] International Publication No. 2019 / 099728 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] It would be desirable to provide a two-stage cryopump that has high conductivity to type II and / or type III gases, and further has effective shielding of the second-stage surface from type I gases. [Means for solving the problem]

[0010] A first embodiment provides a cryopump comprising: a vessel including a front open region, the front open region including an inlet to the vessel; a radiation shield; a two-stage refrigerator extending into the side wall of the vessel at a point in the side wall away from the inlet, the side wall portion being closer to the closed end of the vessel than the inlet; the first stage of the refrigerator being thermally coupled to the radiation shield; a first stage array disposed within the vessel and thermally coupled to the first stage of the refrigerator; and a cryopanel structure coupled to a second stage of the refrigerator, the first stage array comprising a plurality of elements arranged such that their distance from the inlet increases, the element closest to the inlet being located between the inlet and the cryopanel structure and having a smaller outer circumference than the elements furthest from the inlet, each of the elements furthest from the inlet having a passage through its center.

[0011] The inventors recognized that there are competing requirements for cryopumps, specifically that Type II and / or Type III gases must reach the second-stage cryopanel with good conductivity in order to effectively capture them. However, these cryopanels need to be effectively shielded from both thermal radiation and Type I gas in order to maintain an optimal temperature for an extended period and to protect them from being overloaded with Type I gas, which reduces their effectiveness. Conventionally, a front array has been placed at the pump inlet to prevent Type I gas from reaching the cryopanel, and such a conventional front array has openings for introducing gas molecules into the pump, and these openings are arranged in a chevron pattern. Gas molecules arriving at the inlet are either captured at the surface by passing directly through the openings of the front array, deflected towards the radiation shield of the pump sidewall and captured, or deflected back towards the exhaust chamber. One drawback of such arrays is that, for at least a portion of the inlet surface area, there is a direct line-of-sight path through the front array to the cryopanel for molecules moving perpendicular to the inlet plane, meaning that Type I gases with suitable trajectories may travel directly to the cryopanel. Furthermore, the deflection of gas molecules by the array at the inlet results in some Type II and Type III gas molecules being pushed away from the pump inlet, failing to enter the pump, and instead reaching the second-stage array, reducing their conductivity and the pumping speed.

[0012] The inventors solve these problems by forming the first stage array with multiple elements located at different distances from the inlet, providing a barrier for at least some molecules that travel perpendicular to the inlet plane, and providing a through-path for some molecules that have components parallel to the inlet plane, such as molecules deflected by the side walls.

[0013] Furthermore, the chiller is positioned away from the cryopump inlet, which reduces the possibility of gas molecules colliding with the chiller element and being deflected towards the inlet. This arrangement also prevents the chiller element from shielding a large portion of the upper part of the cryopanel structure, increasing the area encountered by type II and type III gases and improving the uniformity of capture of these gases by the cryopanel structure.

[0014] In this way, effective, targeted shielding is provided that allows for high-speed pumping while protecting the cryopanel from the direct influence of Type I gas. In practice, the first-stage array consists of elements at different distances from the inlet, with suitable gas channels between them for molecules reflected from the vessel's radiation shield, but with direct line-of-sight paths blocked. The first-stage array is a good way to enable a high capture rate of hydrogen gas while shielding the second-stage cryopanel and cryo-adsorbent material. Furthermore, by positioning the refrigerator away from the inlet, unnecessary shielding of the cryopanel structure from hydrogen gas is reduced.

[0015] These ideas, working together, enable both effective shielding and increased rates. In some embodiments, the pumping rate can be increased to hydrogen rates of 15,000 L / s or more while the cryo-adsorption array remains shielded from unwanted gases.

[0016] In some embodiments, the cryopanel structure has a diameter at its widest point that is less than 70%, preferably less than 55%, of the diameter of the container.

[0017] Cryopanel structures can be made narrower or longer than conventional cryopanel structures. This increases the likelihood that gas molecules will reach the bottom of the cryopanel structure, thereby improving the uniformity of molecules captured by the cryopanel structure and increasing its effectiveness.

[0018] In some embodiments, the refrigerator extends into the container in a portion of the side wall that is at a distance of 60% or more of the container's length from the inlet.

[0019] To improve gas conductivity and reduce resistance to gas flow that may be introduced by the refrigerator extending into the container, this is the half of the container furthest from the inlet, preferably 60% or more inside the container. 60% or more inside the container means 60% or more along an axis perpendicular to the inlet plane and extending from the inlet to the bottom or closed end of the container. By positioning the refrigerator element deep within the container, the likelihood of type II or III particles impacting the refrigerator element being deflected outside the container or away from the cryopanel is reduced. Furthermore, the first stage array can be mounted above the refrigerator element, and the cryopanel can be mounted such that the majority of the structure is above the refrigerator and therefore not shielded by it.

[0020] In some embodiments, the cryopanel structure has a length greater than 70% of the length of the container.

[0021] Providing a cryopanel structure with a length that extends across most of the pump vessel's length provides a large surface area for particles to collide with and be captured, thereby improving the effectiveness and lifespan of the cryopanel structure during regeneration.

[0022] In some embodiments, the first stage array is attached to mounting elements, which are formed of a thermally conductive material bonded to the first stage refrigerator and each of the multiple elements of the first stage array.

[0023] The first-stage array is cooled to the temperature of the first stage of the refrigerator, which is suitable for trapping type-I gas. In some embodiments, this cooling is effectively provided by attaching the first-stage array within the container to a thermally conductive element extending from the first stage of the refrigerator to each element of the first-stage array, thereby maintaining the array at the temperature of the first-stage refrigerator or near thereto. In other embodiments, the first-stage array can be attached to a radiation shield that is itself thermally coupled to the first-stage refrigerator. In such an arrangement, the first-stage array may not be consistently maintained near the temperature of the first-stage refrigerator as when attached to a thermally conductive mounting element.

[0024] Elements other than the element closest to the inlet have passages passing through a central portion and may, in some cases, have an annular or ring-like form. The element closest to the inlet, located between the cryopanel structure and the inlet, can have a solid cross-section rather than an annular form and can provide shielding of the cryopanel structure from both thermal radiation and at least some gas molecules moving directly from the inlet towards the cryopanel structure. Alternatively, it can have several openings defining passages through the element, and the openings can be at least partially covered by an inclined flap-type surface for deflecting the molecules towards the sidewalls.

[0025] In some embodiments, one end of the cryopanel structure extends into the first-stage array and at least one of the elements further surrounds the outer periphery of the one end of the cryopanel structure from the inlet.

[0026] Having a first stage array formed of a plurality of elements located at different distances from the inlet means that it is not a flat structure, whereby the cryopanel structure can extend into the array, leading to an improvement in the shielding of that part of the cryopanel structure. This is the part closest to the inlet of the cryopanel array, and this part has conventionally received the highest proportion of gas molecules. By providing improved shielding at this part compared to the part of the cryopanel structure further away from the inlet, gas molecules can be captured more uniformly along the length of the cryopanel structure.

[0027] In some embodiments, adjacent elements of the first stage array are configured such that for at least some of the elements closest to the inlet, the outer perimeter of one element is substantially equal to or smaller than the inner perimeter of a subsequent element located further away from the pump inlet.

[0028] The arrangement of the elements can be such that the outer perimeter of one element is substantially the same as the inner perimeter of a subsequent element further away from the inlet. Such an arrangement provides a substantially solid surface when viewed vertically through the inlet, and the substantially solid surface has the dimensions of the outer perimeter of the element furthest from the inlet. This provides a structure that is optically gapless when viewed from the inlet, which is advantageous and provides effective shielding of the cryopanel. In practice, the elements provide a substantially solid surface when viewed vertically, and when these elements are located within the pump at a predetermined distance from the inlet, they shield the cryopanel from a further angle around the perpendicular when viewed from the inlet.

[0029] In this context, the element of the first stage array closest to the inlet can be at a predetermined distance within the pump such that molecules colliding with this surface are less likely to have already passed the pump inlet and be deflected back into the exhaust chamber. In other embodiments, the element of the first stage array closest to the inlet can be located adjacent to the inlet.

[0030] In some embodiments, the outer circumference of one element is slightly smaller than the inner circumference of a subsequent element, providing a gap for molecules moving perpendicular to the inlet plane. In such cases, the difference between the inner and outer circumferences is generally small, about 10% or less, allowing a small number of molecules moving perpendicular to the array's inlet to pass through the array.

[0031] When viewed vertically, creating some gap between elements increases conductivity, which is advantageous for pumping Type III gases, but it has some adverse effects on the increased heat load of the second stage due to contamination of the cryopanel by Type I gases and a decrease in thermal shielding.

[0032] In some embodiments, the first stage array has a substantially igloo shape, with elements arranged concentrically, the element closest to the entrance having the smallest circumference, and subsequent elements having circumferences that increase in size with increasing distance from the entrance.

[0033] The first stage ray may have a substantially igloo shape in which the size of the concentric elements increases. In some cases, the elements may increase in size from the element closest to the entrance to the element furthest from the entrance, and in other embodiments, the size of multiple elements closest to the entrance may increase, allowing elements of the same size to be used at a particular location.

[0034] In some embodiments, the elements are substantially flat, with the element closest to the entrance being a disk and the subsequent elements being rings.

[0035] The elements can take many forms, for example, they can have angular outer perimeters, and it may be advantageous for them to consist of disks and rings. This provides symmetry in cross-section and is particularly advantageous when the radiation shield has a substantially cylindrical form.

[0036] In some embodiments, the disk has a solid cross-section, and in other embodiments, the disk has several openings that provide several through-passages through the disk. These openings can be at least partially obscured by inclined surfaces positioned to deflect colliding molecules toward a radiation shield.

[0037] In some embodiments, the surfaces of elements facing the entrance are at an angle between 0 and 30 degrees with respect to the entrance plane, and are either parallel to the plane or inclined so that the surface closest to the entrance faces the radiation shield. In some embodiments, if some of the elements are angled, the element closest to the entrance is at a 0-degree angle, and the remaining elements may be inclined.

[0038] In some cases, it is advantageous to tilt the surface of an element so that particles impacting the surface are deflected toward the radiation shield, and in other embodiments, the surface of an element facing the inlet is substantially parallel to the inlet plane. While tilting the element provides better shielding of the cryopanel structure, it reduces conductivity, so whether flat or slightly tilted elements are preferred depends on the pump requirements. In either case, because the first stage array is inside the pump, even a vertically deflecting flat element may still retain molecules that have reached the pump perpendicularly, as such deflected molecules may collide with other molecules before reaching the inlet.

[0039] In some embodiments, the elements of the first stage array furthest from the inlet are mounted closest to the first stage of the refrigerator, while the elements of the first stage array closest to the inlet are positioned between 5 and 15 percent inside the container.

[0040] In some embodiments, the first stage array extends from a point between 5 and 15 percent into the container to a point between 25 and 40 percent into the container.

[0041] As described above, the first-stage array is not a flat array, but rather spreads longitudinally within the pump, sometimes along a length of 10 to 35 percent of the vessel's length. This longitudinal spread of the array provides effective shielding of the cryopanel structure along a significant portion of its length, leading to a more uniform distribution of captured molecules on the surface of the cryopanel structure.

[0042] In some embodiments, the cryopanel structure comprises a plurality of panels having a substantially cylindrical outer skin extending from a central axis and having at least one tapered end, one of which extends into a first stage inlet array.

[0043] Cryopanel structures can take many forms, but a favorable form is one having multiple panels extending from a central axis, with the outer skin of the structure having a substantially cylindrical shape that matches, but is smaller than, the shape of a cylindrical radiation shield. The structure may have at least one tapered end extending to the first stage array, and in some embodiments, both ends may be tapered.

[0044] Such an integrated structure has multiple cryopanels with adsorbents such as charcoal on both sides when a type III gas, such as hydrogen, is captured. This structure allows the number of panels to be changed according to the rate and volume of type II or type III gas required for a particular application, providing a flexible design that can be optimized for specific applications. In some implant applications, the number of panels depends on the rate and volume of hydrogen.

[0045] In some embodiments, a portion of the cryopanel structure extending into the first stage array constitutes at least 20%, preferably at least 30%, of the cryopanel structure.

[0046] In some embodiments, the radiation shield is substantially cylindrical and includes a flat portion that extends into the cylinder for coupling with the refrigerator, the flat portion extending into the cylinder by less than 8%, preferably less than 6%, of the cylinder's diameter.

[0047] The radiation shield is cylindrical, and therefore, in order to couple the shield to the flange of the refrigerator when the flange is flat, the radiation shield has a flat portion that corresponds to the shape of the flange extending into the vessel. This results in a protruding surface extending from the radiation shield above the refrigerator element. This provides a surface to which the gas collides and is deflected back toward the inlet. Recognizing the potential problems of this arrangement, the inventors have provided a design that keeps the flat portion as small as possible for good coupling, and also reduces the size of the extension of this portion into the cylinder, and therefore the protruding surface, thereby improving conductivity.

[0048] The chiller extends into the part of the cryopanel structure furthest from the entrance.

[0049] By attaching the cryopanel structure to the refrigerator in such a way that the refrigerator extends into the cryopanel structure at a distance from the inlet, the possibility of the refrigerator structure being affected by gas molecules can be reduced. Furthermore, since the majority of the cryopanel structure is above the refrigerator, a considerable length of the structure is not obstructed at all by the refrigerator, thereby improving conductivity. The refrigerator extends into the half of the cryopanel structure furthest from the inlet.

[0050] In some embodiments, the cryopanel is coated with carbon to adsorb certain type III gases, such as hydrogen.

[0051] Further specific and preferred embodiments are described in the independent and dependent claims. Features of the dependent claims may be combined with features of the independent claims as appropriate, or in combinations other than those expressly provided in the claims.

[0052] When a feature of a device is described as being operable to provide a certain function, it should be understood that this includes features of the device that provide, or are adapted or configured to provide, that function. Embodiments of the present invention will be further described below with reference to the accompanying drawings. [Brief explanation of the drawing]

[0053] [Figure 1] A first stage array according to one embodiment is shown. [Figure 2] This shows a second-stage cryopanel structure, which is attached to a refrigerator element and extends to a first-stage array, according to one embodiment. [Figure 3] This shows a cryopump according to one embodiment. [Figure 4] This shows a cross-section of a cryopump according to one embodiment. [Figure 5] A further cross-section is shown through a cryopump according to one embodiment. [Modes for carrying out the invention]

[0054] Before describing the embodiments in detail, let's first give an overview. As new implantation processes are developed and more consistent vacuum environments are required to maintain the vacuum state of the process, the demands on cryopumps are becoming more stringent.

[0055] The inventors recognize that the array geometry of the cryopump is important for improving the vacuum conditions that the cryopump provides. Taking the “implant” process as an example, the cryopump is often used to generate the required high vacuum, hydrogen is the main gas component, and contamination from photoresist is a major problem. Embodiments provide contamination resistance and increased hydrogen pumping rate by providing one or more of three main design improvements.

[0056] 1) Cryopanel Optimization: The shape of the second-stage array has been redesigned to be more elongated than before, improving hydrogen pumping performance. The second-stage array is protected from gas contamination and radiation by the "Igloo" first-stage array. The cryopanel structure and the Igloo array are geometrically designed to complement each other, working to improve Type III gas conductivity while enhancing thermal and Type I gas shielding.

[0057] 2) The geometric design of the first stage or "igloo" inlet baffle results in high hydrogen performance and excellent resistance to gas contamination in the second stage array.

[0058] 3) Refrigerator position: Compared to conventional designs, the refrigerator is strategically positioned lower within the vessel, enabling good gas conductivity and creating a longer array pumping path with fewer initial strikes of contaminants. In addition to being low within the vessel, the refrigerator has a smaller penetration cross-sectional area, improving conductivity.

[0059] The above design changes aim to achieve, in particular, an increase in the pumping speed of Type III gas, reduced contamination of the second-stage array, lower the radiant load on the second stage, and lower the temperature of the first-stage or igloo-type array, all of which contribute to a more stable vacuum pump.

[0060] Positioning the refrigerator near the bottom of the vacuum vessel is one way to improve the overall performance of the pump. 1) Good conductivity: There is less shielding of Type II or Type III gases such as hydrogen entering the pump, allowing more gas to reach the cryopanel.

[0061] 2) This enables an integrated design of the cryopanel / mount in the second stage. The symmetry of the cryopanel improves the uniformity of pumping type II / type III gases across the entire cryopanel surface. This uniformity is crucial for the rate and volume of type II / type III gases, ensuring that all panels are available to deliver these gases more uniformly, preventing any panel from being overwhelmed by the gas. If the cryopanel design is not uniform and localized saturation occurs, these panels become unusable when more molecules flow in. This increases the load on the remaining cryopanels, causing the cryopump pressure to rise faster than expected and resulting in an unbalanced pumping state where the pumping rate of type III gases drops sharply.

[0062] 3) The chiller cylinder is located low within the pump and works in conjunction with the reinforced igloo inlet array to shield the cryopanel from unwanted radiation and photoresist contamination from many initial strikes. The inlet array design is mounted on a thermally conductive element extending from the first stage of the chiller, allowing it to be maintained at lower temperatures than a typical inlet array configuration coupled to a radiation shield.

[0063] Figure 1 shows an igloo-type first-stage array 10 according to one embodiment. The array is formed of a plurality of elements 12, 14 arranged so that the distance from the inlet to the pump increases. The element closest to the pump is the disk 12, and the larger elements 14 are arranged so as to increase the distance from the inlet to the pump. This igloo-type inlet baffle or array is attached to the first stage of the refrigeration element via a thermal conductive member 36 (see Figure 2). This thermal conductive member allows the igloo to be maintained at a temperature close to the temperature of the first-stage refrigeration element, reducing hot spots on the igloo surface and allowing the surface to be held at a reduced temperature, thereby providing improved capture of type I gas. Additionally, the radiant shield can reach a lower temperature compared to a conventional radiant shield coupled to a first-stage array extending across the inlet, and therefore, similarly, can result in improved capture of type I gas. In this embodiment, the disk 12 is a solid disk, while in other embodiments, the disk 12 may have openings in the disk to allow the passage of some molecules. In some cases, these openings can be partially shielded by flaps that extend partially across the openings and are angled to deflect molecules toward the radiation shield.

[0064] Figure 2 shows the first stage array 10, which extends to the side wall of the pump vessel and is coupled to the refrigerator element 30 that supports the second stage cryopanel structure 20. The second stage cryopanel structure 20 extends into the first stage array 10 such that the elements of the first stage array 10 surround the portion of the second stage cryopanel structure 20 closest to the entrance. This improves the shielding of this portion of the cryopanel structure, reduces the probability of gas molecules coming into contact with the higher portion, improves the uniformity of molecular capture along the length of the cryopanel structure, and thereby extends the lifespan and increases the effectiveness of the cryopanel structure.

[0065] The refrigerator element 30 extends into the container and constitutes the first stage refrigerator element at the temperature of the first stage, and is coupled to the first stage array 10 via a thermal conductive mount 36, enabling the first stage array to be maintained at or near the temperature of the first stage refrigerator element in a uniform and effective manner. The thermal conductive mount 36 extends around the first stage array and contacts each element at two points, providing effective cooling for this array.

[0066] The second-stage cryopanel structure is attached to the second-stage refrigerator element and is therefore cooled to the temperature of the second stage. The refrigerator element 30 extends into the lower part of the pump vessel away from the inlet and supports the lower half of the cryopanel structure, and this support does not obscure the upper half of the cryopanel structure from gas molecules entering the pump. This also leads to a better distribution of gas molecules on the cryopanel structure.

[0067] The cryopanel structure 20 is longer and thinner than conventional cryopanel structures, which improves conductivity and the uniformity of type II and type III gas capture, and allows for better access to the bottom of the cryopanel. Furthermore, the lower position of the refrigerator relative to the pump inlet improves conductivity and increases the pump speed.

[0068] Figure 3 shows the view through the pump inlet 40. As can be seen, the inner surface of the pump vessel is equipped with an inner element 42, which is a radiation shield. Viewed through the inlet, the first stage array effectively shields the second stage array when viewed perpendicularly through the inlet, protecting the process from radiation loads and generated contaminants. The spacing between the elements in the axial direction allows access to the cryopanel by molecules having a velocity component parallel to the inlet, such that it is deflected by the radiation shield 42. Molecules deflected by the radiation shield are mainly type II or type III gases, as the radiation shield traps type I gases. The lower part of the cryopanel structure is not surrounded by the front array, which allows for easy access to this part by molecules moving deep within the pump.

[0069] Figure 4 is a side view of the pump vessel, partially cut out to allow an internal view. For clarity, the chiller 30 extends to the bottom of the pump vessel away from the inlet, and the first stage of the chiller element 34 is thermally coupled to a thermal conductive mount 36 that houses the radiant shield 42 and the first stage array 10.

[0070] The thermally conductive mount 36 extends around the igloo structure, contacting each element at two points 180 degrees opposite each other, providing good thermal coupling between these elements and the first stage of the refrigerator elements. Thus, a good direct thermal path exists from the first stage refrigerator elements to each element of the first stage array, making it possible to maintain the array at a low and uniform temperature.

[0071] The second-stage chiller 32 is coupled to a second-stage cryopanel (not shown) to maintain them at a lower second-stage temperature. The chiller elements 30 are positioned toward the bottom of the pump vessel, thus reducing gas shielding due to the extension of the chiller elements into the pump.

[0072] Figure 5 is a cross-sectional view of the pump showing the first stage array 10, the cryogenic elements 30, and how they are coupled. In particular, it shows how the cryogenic elements are held within the pump vessel and coupled to the radiant shield. The radiant shield is flat at this stage, providing a sealing coupling with the flat flange of the cryogenic elements, and above the coupling, the radiant shield has a projection 44 that reflects this flattened portion and provides a surface from which molecules can collide and be deflected toward the inlet. In this embodiment, the projection is smaller in size compared to conventional cryopumps and is designed to extend into the cylinder by less than 8% of the cylinder diameter, and less than 6% in many embodiments. This reduces obstruction to gas molecules entering the pump and improves the pumping speed.

[0073] Figure 5 shows the temperature difference between different parts of the first stage. The chiller element of the first stage is at its coldest point at approximately 65K, the first stage array is maintained at a temperature of 71-72.5K, and the radiant shield is colder toward the chiller side, but reaches temperatures of over 75K on the opposite side. In a conventional cryopump where the first stage array is adjacent to the inlet, this inlet array is above 75K, reflecting the temperature of the warmer part of the radiant shield. Thus, the embodiment provides a cooler first stage array with a more uniform temperature than conventional cryopumps, improving the capture of type I gases.

[0074] In summary, conventional cryopump designs involve shielding the second-stage array with a planar radiation baffle or front array mounted at the inlet. This baffle is adjacent to the inlet and mounted above the radiation shield. Like a large umbrella, gas molecules are blocked and repelled from the pump before they reach the second-stage array. Additionally, the chiller cylinder and first-stage mount are conventionally located high up in the pump, shielding many type II and III molecules, such as hydrogen, from reaching the second-stage array.

[0075] In contrast, the embodiment provides a second-stage array shielded by an inlet radiation baffle of multiple elements positioned at different distances from the inlet within the pump. This array configuration obstructs fewer molecules at the pump inlet, allowing more molecules to reach positions where they collide with the surface of the second-stage array. This design also improves the shielding of the second-stage array from Type I gas, reducing contamination and radiation exposure of the second stage. The second-stage array is reinforced in a tripartite manner by a combination of the shape of the first-stage array and the arrangement of the lower chiller.

[0076] Exemplary embodiments of the present invention are disclosed in detail herein with reference to the accompanying drawings, but it should be understood that the present invention is not limited to the exact embodiments and that various modifications and alterations can be made by those skilled in the art without departing from the scope of the invention as defined by the accompanying claims and equivalents. [Explanation of Symbols]

[0077] 10. First Stage Array 12 disk elements 14 Ring-shaped elements 20 Cryopanel Structure 30 Refrigeration element 32 Second Stage Refrigeration Element 34. First-stage refrigerator element 36. Mount for the first stage array 40 Entrance 42 Radiation Shield 44 Radiation shield protrusion

Claims

1. A cryopump, comprising: A container including a front opening region, the front opening region including an inlet to the container, the container; A radiation shield; A two-stage refrigerator extending into the side wall of the container at a portion of the side wall remote from the inlet, the portion of the side wall being at a point closer to the closed end of the container than the inlet, and a first stage of the refrigerator being thermally coupled to the radiation shield, the two-stage refrigerator; A first stage array disposed within the container and thermally coupled to the first stage of the refrigerator through a mount element extending from the two-stage refrigerator towards the inlet within the radiation shield; A cryopanel structure coupled to the second stage of the refrigerator; Comprising: The first stage array includes a plurality of elements arranged such that the distance from the inlet increases, one of the plurality of elements closest to the inlet being located between the inlet and the cryopanel structure and having an outer circumference smaller than all of the other plurality of elements, each of the plurality of elements other than the element closest to the inlet having a passage therethrough at the central portion of the element, the mount element positioning all of the plurality of elements at a position closer to the inlet than the two-stage refrigerator. A cryopump.

2. The cryopump according to claim 1, wherein the cryopanel structure has a diameter at its widest point of less than 70% of the diameter of the container.

3. The cryopump according to claim 1 or 2, wherein the refrigerator extends into the container at a portion of the side wall at a distance of at least 60% of the length of the container from the inlet.

4. The cryopump according to any one of claims 1 to 3, wherein the cryopanel structure has a length greater than 70% of the length of the container. **Claim 5**: The mounting element is formed of a thermally conductive material coupled to each of the first stage refrigerator and the plurality of elements of the first stage array. The cryopump according to any one of claims 1 to 4. **Claim 6** One end of the cryopanel structure extends into the first stage array, and at least one of the elements further surrounds the outer periphery of the one end of the cryopanel structure from the inlet. The cryopump according to any one of claims 1 to 5. **Claim 7** For at least some of the elements adjacent to the first stage array near the inlet, the outer periphery of one element is configured to be substantially equal to or smaller than the inner periphery of a subsequent element located further away from the pump inlet. The cryopump according to any one of claims 1 to 6. **Claim 8** The first stage array has a substantially igloo shape, the elements are concentric, the element closest to the inlet has the smallest outer periphery, and the plurality of subsequent elements have outer peripheries of increasing size with the distance from the inlet. The cryopump according to any one of claims 1 to 7. **Claim 9** The elements are substantially flat, the element closest to the inlet has a disk shape, and the subsequent elements are rings. The cryopump according to any one of claims 1 to 8. **Claim 10** The surface of the element facing the inlet forms an angle between 0 degrees and 30 degrees with the plane of the inlet, is parallel to the plane, or is inclined such that the surface closest to the inlet faces the radiation shield. The cryopump according to any one of claims 1 to 9. **Claim 11** The element of the first stage array furthest from the inlet is mounted closest to the first stage of the refrigerator, and the surface of the first stage array closest to the inlet enters the container between 5% and 15%. The cryopump according to any one of claims 1 to 10.

12. The first stage array of the cryopump according to claim 11, which extends from a point between 5 and 15% into the container to a point between 25 and 40% into the container.

13. The cryopump according to claim 6, or if dependent on claim 6, according to any one of claims 6 to 12, wherein the cryopanel structure comprises a plurality of panels having a substantially cylindrical outer skin extending from a central axis and having at least one tapered end, and one of the at least one tapered ends extends into the first stage array.

14. The cryopump according to claim 13, wherein a part of the cryopanel structure extending into the first stage array constitutes at least 20% of the cryopanel structure.

15. The cryopump according to any one of claims 1 to 14, wherein the radiation shield is substantially cylindrical and has a flat portion extending into the cylinder for coupling to the refrigerator, and the flat portion extends into the cylinder by less than 8% of the diameter of the cylinder.

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