Cryopump

Abstract

A cryopump is disclosed that includes a pump inlet, a two-stage refrigerator, a first stage array thermally coupled to the first stage of the two-stage refrigerator, and a cryopanel structure coupled to the second stage of the two-stage refrigerator. The cryopanel structure includes at least three planar panels. The first stage array is mounted between the pump inlet and the cryopanel structure and includes a plurality of slats, each of the plurality of slats mounted such that a side of each of the plurality of slats closest to the cryopanel structure is substantially aligned and offset longitudinally relative to a corresponding one of the at least three planar panels.

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 of temperature for capturing type I gases such as water vapor and a second stage of low temperature for capturing type II gases such as nitrogen and in some embodiments for 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 - 25K, which can be coated with a capture material such as charcoal. This cryopanel array functions as a primary pump surface, operates in a high-temperature range such as 40 - 130K, 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] During operation, when gas enters the pump vessel from the inlet, at least a portion of type I gases such as water vapor condenses on the front array that forms part of the first-stage radiation shield. The low-boiling-point gas passes through the front array and enters the volume within the radiation shield. On the other hand, type III gases having a significant vapor pressure at 4K, such as hydrogen, helium, neon, etc., are adsorbed by adsorbents such as activated carbon, zeolite, molecular sieves, etc., covering the cryopanels of the second stage.

[0004] In this way, the gas flowing from the chamber into the pump is captured, and a vacuum is generated within the pump vessel. One problem with cryopumps is that during operation, gas molecules saturate the capture surface, reducing the capture capacity. Therefore, cryopumps need to be regenerated periodically to release the captured gas molecules.

[0005] There are competing factors to consider when designing a cryopump. High gas conductivity into the pump improves pump speed, but it is advantageous to provide some shielding of the second stage cryopanel from thermal radiation and from type I gas to reduce the thermal load on the cryopanel. Type I gas reaching the cryopanel condenses on the cryopanel and prevents type III gas from being cryo-adsorbed. Further, some type I gases, such as long chain hydrocarbons, do not desorb from the array surface during regeneration and cause a degradation of pump performance over the remaining life of the pump. However, shielding the cryopanel from gas molecules reduces conductivity.

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0006] It would be desirable to provide an improved two-stage cryopump.

MEANS FOR SOLVING THE PROBLEMS

[0007] A first aspect provides a cryopump, the cryopump comprising a pump inlet, a two-stage refrigerator, a first stage array thermally coupled to a first stage of the two-stage refrigerator, and a cryopanel structure coupled to a second stage of the two-stage refrigerator, the cryopanel structure comprising at least three planar panels, the first stage array being mounted between the pump inlet and the cryopanel structure and comprising a plurality of slats, each of the plurality of slats being mounted such that sides of each of the plurality of slats closest to the cryopanel structure are longitudinally substantially aligned with and offset from a corresponding one of the at least three planar panels.

[0008] When designing a cryopump, it is desirable to provide a cryopanel structure having a large surface area for capturing gas molecules, and a first stage or front array that provides some shielding of the cryopanel structure from thermal radiation and from any gas molecules entering the pump from the inlet. The cryopump inlet has conventionally been circular in cross-section, and the cryopanel structure generally has a similar configuration and is probably formed of coaxial cylinders. Such a configuration has the advantages of symmetry and good alignment with the outlet of the vacuum chamber, but can be difficult to manufacture and assemble. Providing a planar second stage cryopanel array formed of planar panels, together with a first stage array formed of linear slats aligned with at least a portion of the planar panels and longitudinally offset with respect to the planar panels, enables a configuration that is easy to manufacture and assemble. Further, having the slats substantially aligned with the planar panels provides effective and focused shielding of the planar panels. Also, this configuration can provide a very high hydrogen pumping speed.

[0009] In some embodiments, each of the plurality of planar panels has corresponding slats that are longitudinally aligned with and offset with respect to it.

[0010] In some embodiments, the plurality of slats are attached so as to extend at an angle between 110° and 160° with respect to the planar panels towards the pump inlet.

[0011] Angling the slats so as to be inclined towards the pump inlet and the adjacent panel enables effective shielding of the cryopanel structure.

[0012] In some embodiments, the plurality of slats are attached such that at least a portion of the slats shields one surface of an adjacent planar panel of the cryopanel structure from gas molecules entering the pump through the pump inlet.

[0013] The slats can be arranged to shield the surface of the adjacent panel from direct collisions from gas molecules entering the pump. Although gas molecules may bounce off other surfaces and collide with the panel, the panel is shielded so as not to be the first surface to be collided with. This enables specific types of gas molecules, such as type-I gas molecules, to be captured before reaching this surface. Each panel can have inclined slats longitudinally aligned and arranged thereon. Alternatively, each panel except for one end panel of the array can have corresponding slats associated therewith. The end panel is at the end in the direction in which the panel slopes away from the edge close to the cryopanel structure. Since the slats provide shielding against the adjacent panel to which it is angled, such slats are provided if there is no subsequent panel.

[0014] In some embodiments, the surfaces of the plurality of planar panels comprise a coated portion coated with an adsorbent and a further portion not coated with an adsorbent.

[0015] Type-III gas does not condense at the temperature of the first-stage or second-stage refrigerator, so an adsorbent is required to capture these molecules. In a cryopump, coating the second-stage array with an adsorbent can not only capture type-II gas but also adsorb these type-III gases. The inventors of the present invention recognize that the problem with the adsorbent-coated surface in a cryopump is that gas molecules are adsorbed over time, reducing the effectiveness. The adsorbent is provided to capture type-III gas, and it is important that these gases come into contact with these surfaces and are captured. However, in order to lengthen the time between regeneration cycles, it would be desirable to suppress the capture of other gases that may condense on other surfaces by the adsorbent. For example, photoresist is a gas that may be present when evacuating a semiconductor process chamber using a cryopump, and this is adsorbed onto the adsorbent surface by collisions, shortening the time between regeneration cycles.

[0016] The inventor of the present invention has recognized that when a part of the surface of the second-stage cryopanel is not coated and a gas such as photoresist first collides with these surfaces, it condenses on the uncoated surface before reaching the adsorbent-coated surface, resulting in an extended life of the adsorbent-coated surface.

[0017] Therefore, by providing an uncoated surface on the pump, gases that are not of type III collide with and condense on the uncoated surface, and type III gases bounce back when they collide with the uncoated surface and are adsorbed. In this way, the adsorbent surface mainly adsorbs type III gases, its effect is enhanced, the time between regenerations is extended, and a substantially stable pumping speed can be maintained for a longer time. In practice, by enabling at least a part of the gas to collide with the uncoated surface, a part of the gas such as photoresist does not reach the coated surface, the coated surface is protected from these gases, and type III gases bouncing back from the uncoated surface can be almost invariably used as a pump, providing a pump with an extended regeneration time and a pumping speed that does not excessively decrease over time.

[0018] In some embodiments, one surface of at least a part of the panel is coated with an adsorbent and the other surface is not coated.

[0019] Coating only one surface provides a system that is easy to manufacture. Regarding some coating techniques where an adhesion coating such as epoxy is provided and the adsorbent is adhered thereto, coating a single surface by bringing the epoxy-coated surface into contact with the adsorbent is much simpler than coating both surfaces.

[0020] In some embodiments, the coated surface is a surface shielded by one of the adjacent ones of the plurality of slats.

[0021] By arranging the slats so that the coating surface is shielded by the slats, the coating surface and the adsorbent thereon can be shielded from gases other than type III gases such as photoresist that first collide with and are captured by other surfaces. This increases the lifespan of the adsorbent. The planar geometry provides an effective system for capturing type III gases on one side while shielding one surface.

[0022] Furthermore, by leaving the surface that is not shielded as effectively by the first-stage array without an adsorbent, it is possible to avoid or at least suppress the situation where over time one surface of the pump becomes contaminated and the adsorption characteristics are lost at a higher rate than the other surface. Such a situation leads to a change in the pumping speed of the pump over time, requiring recalibration of the system, which is generally undesirable.

[0023] In some embodiments, the plurality of slats are arranged substantially parallel to each other, and the plurality of planar panels are arranged substantially parallel to each other.

[0024] A planar arrangement where the panels and slats are substantially parallel to each other provides an apparatus that is easy to manufacture and has a more predictable flow.

[0025] In some embodiments, the plurality of slats are inclined in the same direction relative to each other. In some embodiments, there are the same number of slats as there are panels.

[0026] In some embodiments, the panels and slats are arranged equidistantly from each other within the pump. This results in flow channels of substantially the same size between the panels and slats, enabling a more homogeneous flow and absorption by the slats.

[0027] In some embodiments, the plurality of planar panels are arranged to extend substantially parallel to the longitudinal axis of the pump.

[0028] The planar panels can be arranged substantially parallel to the longitudinal axis of the pump such that each panel receives an equal amount of gas molecules and one panel does not overly shield another panel from the gas molecules entering the pump.

[0029] In some embodiments, the plurality of slats and the plurality of planar panels are substantially rectangular.

[0030] The slats and planar panels can be of many different shapes and in some cases they are rectangular. Rectangular panels are easy to manufacture, install, and coat and provide an effective surface.

[0031] In some embodiments, the plurality of slats are configured to overlap when viewed in a direction parallel to the planar panels through the pump inlet.

[0032] The plurality of slats can be configured to overlap when viewed through the pump inlet along the longitudinal axis such that there is no line of sight between the pump inlet and the planar panels such that gas molecules will collide with another surface before generally colliding with the surface of the cryopanel structure. In this regard, gas molecules moving substantially parallel to the angle of the slats can directly collide with one surface of the panel, which in some embodiments is the surface not coated with the adsorbent of the panel. In this way, the surface of the panel coated with the adsorbent is protected from direct collisions from gas molecules.

[0033] In some embodiments, the plurality of planar panels are all substantially the same size.

[0034] In other embodiments, the slats and panels at both ends of the array may be smaller than those in the center. In this regard, it may be advantageous for the pump inlet to have a circular cross-section and increase the panel size towards the center of the pump with a larger diameter. However, having panels and slats of different sizes results in a more complex manufacturing process, and in some instances, it may be desirable to make them all the same size.

[0035] In some embodiments, the adsorbent is configured to adsorb type III gases such as hydrogen, helium, and neon.

[0036] In some embodiments, the adsorbent consists of a molecular sieve that coats the coating surface.

[0037] In some embodiments, the adsorbent consists of one of charcoal, activated carbon, zeolite, or a porous metal surface.

[0038] Further specific and preferred aspects are set forth in the independent and dependent claims. The features of the dependent claims can be combined with the features of the independent claims as appropriate, or in combinations other than those explicitly defined in the claims.

[0039] When a feature of a device is described as being operable to provide a certain function, it is to be understood that this includes features of the device that provide, or are adapted or configured to provide, that function.

[0040] Embodiments of the present invention are further described below with reference to the accompanying drawings.

Brief Description of the Drawings

[0041]

Figure 1

Figure 2

Best Mode for Carrying Out the Invention

[0042] Before explaining the embodiments in detail, first, an overview will be described.

[0043] A cryopump having a planar front array with panels or slats inclined in parallel can align a second-stage structure, which is also a planar structure, with the front array. This can result in a very high hydrogen pumping speed. The drawback is that the entire area of the inlet may not be effectively utilized compared to the case of a circular configuration.

[0044] The second-stage array panel is placed across the pump and aligned perpendicular to the longitudinal axis of the pump. The first-stage array is provided with an inclined panel or slat between the second-stage array and the pump inlet, arranged such that the edge closest to the second-stage array is aligned with one of the corresponding ones of the second-stage panels. The slats are inclined such that their surfaces are inclined towards the pump inlet. In some embodiments, one side surface of the second-stage panel is coated with charcoal, and this side surface is completely blocked by the front array at a higher temperature (about 80K approximately) against direct collisions by gas molecules entering the pump. The gas condensed at the temperature of the front panel will collide with the front panel and not proceed further, and some will collide with the surface of the second-stage panel that is not coated with charcoal and not proceed further. Type-III gases such as hydrogen will bounce off these surfaces and be adsorbed when they collide with the surface coated with charcoal. Thus, the surface coated with the adsorbent will almost invariably pump Type-III gases, and the other surfaces will collect other gases.

[0045] In some embodiments, when viewed along the longitudinal axis perpendicular to the cross-section of the pump inlet, the slats of the front array overlap. The amount of overlap determines the pumping speed and also determines how well the panels of the second stage array are shielded from the initial collisions by the gas molecules entering the pump inlet. This embodiment of the pump is effective for pumping vacuum chambers for implant applications and semiconductor processing such as PVD (Physical Vapor Deposition) processes.

[0046] Figures 1 and 2 show an embodiment of a cryopump having a planar array in the form of a planar element. FIG. 1 shows parallel planar elements 25 of a second stage cryopanel structure within a pump having an inlet 5. The front array of the first stage is not shown. The second stage cryopanel structure has parallel panels 25 arranged in a row and equally spaced from each other. There is a front array (not shown) having a set of inclined slats, the lower surface of the slats being aligned with the corresponding panels. The front array is longitudinally offset from the second stage array to thermally separate the two arrays to some extent and is located between the second stage array and the pump inlet 5.

[0047] In some embodiments, one side of the panel 25 is coated with an adsorbent and the opposite side is not coated. The inclined elements of the front array protect the coated surface from the initial collisions by the molecules entering from the pump inlet.

[0048] FIG. 2 schematically shows the second stage array element 25 and the front array element 12 with respect to the pump inlet 5. As shown, the slats 12 are attached between the pump inlet 5 and the cryopanel structure of the second stage array. The slats are inclined so as to overlap when viewed from the pump inlet 5. The angle θ between the slats 12 and the panel 25 is between 110° and 160°, and the slats are inclined towards the adjacent panels to shield the panels from the gas molecules entering the pump inlet. There is a gap between the panels 12 to allow gas molecules to enter the pump.

[0049] In some embodiments, both surfaces of panel 25 are coated with an adsorbent, while in other embodiments, one surface 24 of the panel is coated with an adsorbent, but the opposite surface 22 is not coated. Since the only direct path for molecules moving between the slats 12 of the front array leads to the uncoated surface 22 of the cryopanel structure, molecules entering from the pump inlet first collide with the slats 12 or the uncoated surface 22 of the second-stage array. Thus, the first collision of any molecules is not with the coated surface 24, so molecules that condense at the temperature of the first-stage or second-stage refrigerator are trapped on these surfaces. Other type III molecules bounce back from these surfaces towards the coated surface 24 and are trapped by the adsorbent coating upon collision. In this way, the coated surface of the second-stage element is shielded from the first collision by the incoming molecules by the inclined first-stage array slats 12. Uncondensed molecules on the first-stage array or the second-stage array will collide with the coated surface 22 and be trapped by the adsorbent.

[0050] Exemplary embodiments of the present invention are disclosed in detail herein with reference to the accompanying drawings, but the present invention is not limited to the exact embodiments, and it should be understood that various changes and modifications can be made by those skilled in the art without departing from the scope of the present invention as defined by the appended claims and their equivalents.

Description of the Reference Numerals

[0051] 5 Pump inlet 12 Slat 22 Uncoated surface of the panel 24 Coated surface of the panel 25 Second-stage array panel

Claims

Claim 1 A cryopump, comprising: a pump inlet; a two-stage refrigerator; a first-stage array thermally coupled to the first stage of the two-stage refrigerator; a cryopanel structure coupled to the second stage of the two-stage refrigerator; wherein the cryopanel structure comprises at least three planar panels; the first-stage array is mounted between the pump inlet and the cryopanel structure and comprises a plurality of slats, each of the plurality of slats having a corresponding slat disposed adjacent to each of the planar panels and a bottom edge of each of the corresponding slats being parallel to and disposed above an upper edge of the planar panel, the cryopump being mounted such that. Claim 2 The cryopump according to claim 1, wherein the plurality of slats are mounted to extend at an angle between 110° and 160° with respect to the planar panel toward the pump inlet. Claim 3 The cryopump according to claim 1 or 2, wherein at least a portion of the plurality of slats is mounted to shield one surface of an adjacent planar panel of the cryopanel structure from gas molecules entering the pump from the pump inlet. Claim 4 The cryopump according to any one of claims 1 to 3, wherein the surfaces of the plurality of planar panels include a coated portion coated with an adsorbent and a further portion not coated with the adsorbent. Claim 5 The cryopump according to claim 4, wherein one surface of at least a portion of the planar panel is coated with the adsorbent and the other surface is not coated with the adsorbent. Claim 6 The cryopump according to claim 5 when dependent on claim 3, wherein the coated surface is the surface shielded by one of the adjacent ones of the plurality of slats. Claim 7 The cryopump according to any one of claims 1 to 6, wherein the plurality of slats are disposed substantially parallel to each other and the plurality of planar panels are disposed substantially parallel to each other. Claim 8 The cryopump according to any one of claims 1 to 7, wherein the plurality of planar panels are disposed to extend substantially parallel to the longitudinal axis of the pump. Claim 9 The cryopump according to any one of claims 1 to 8, wherein the plurality of slats and the plurality of planar panels are substantially rectangular.

10. The cryopump according to any one of claims 1 to 9, wherein the plurality of slats are configured to overlap when viewed in a direction parallel to the planar panel through the pump inlet.

11. The cryopump according to any one of claims 1 to 10, wherein all of the plurality of planar panels are substantially the same size.

12. The cryopump according to any one of claims 1 to 11, wherein all of the plurality of slats are substantially the same size.

13. The planar panel at the end of the array of the at least three planar panels and the slat at the end of the array of the plurality of slats are smaller than those in the center, according to any one of claims 1 to 10. cryopump described in the section.

14. The cryopump according to any one of claims 4 to 6, or any one of claims 7 to 13 when dependent on claim 4, wherein the adsorbent is configured to adsorb type III gases such as hydrogen, helium, neon.

15. The cryopump according to any one of claims 4 to 6, 14, or any one of claims 7 to 13 when dependent on claim 4, wherein the adsorbent consists of a molecular sieve that coats the coated surface.

16. The cryopump according to any one of claims 4 to 6, 14, or any one of claims 7 to 13 when dependent on claim 4, wherein the adsorbent consists of one of charcoal, activated carbon, zeolite, or a porous metal surface.

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