Patent Application
20250223954
This application claims the benefit of Japanese Priority Patent Application JP 2024-001946 filed Jan. 10, 2024, the entire contents of which are incorporated herein by reference.
The present invention relates to a refrigerator and a cryopump.
In cryogenic environments, oil seals cannot be used in refrigerators because lubricating oils become solid at low temperature. For that reason, organic fluorine compounds may be used as seal materials. The organic fluorine compound contacts with another material in a lubrication-free environment, has lubricating properties even when a certain surface pressure is applied thereto, and has excellent wear resistance.
For example, in cryopumps including refrigerators, a refrigerator cylinder and a second-stage displacer are formed of the same material, and stainless steel is employed as the material, for example. A predetermined clearance is provided between the refrigerator cylinder and the second-stage displacer so as to maintain a small conductance from room temperature to low temperature. If the refrigerator cylinder and the second-stage displacer, which are separated from each other with a narrow clearance therebetween, are formed of stainless steel, this results in poor sliding properties. Thus, the displacer surface is coated with an organic fluorine compound such as ethylene/tetrafluoroethylene copolymer (ETFE) or fluororesin, which has excellent wear resistance (see, for example, Japanese Patent Application Laid-open No. 2004-144461).
In the refrigerator described above, since the refrigerator cylinder and the second-stage displacer are disposed with a narrow clearance therebetween, there is a need to form a coating layer with better wear resistance on the displacer surface.
In view of the circumstances as described above, it is desirable to provide a refrigerator in which a coating layer with better wear resistance is formed on a displacer surface, and a cryopump including the refrigerator.
According to an embodiment of the present invention, there is provided a refrigerator including:
A non-fluorine coating layer is formed on an outer circumferential surface of the second-stage displacer.
A clearance is provided between the coating layer and the second-stage cylinder.
According to such a refrigerator, a refrigerator in which a coating layer having better wear resistance is formed on a displacer surface is provided.
In the refrigerator, the coating layer may include at least one of a diamond-like carbon (DLC), titanium nitride, titanium carbide, ceramics, polyimide (PI), or polyetheretherketone (PEEK).
According to such a refrigerator, a refrigerator in which a coating layer having better wear resistance is formed on a displacer surface is provided.
According to an embodiment of the present invention, there is provided a cryopump that evacuates gas inside a vacuum chamber, the cryopump including:
According to such a cryopump, a cryopump including a refrigerator in which a coating layer having better wear resistance is formed on a displacer surface is provided.
As described above, according to the present invention, a refrigerator in which a coating layer having better wear resistance is formed on a displacer surface, and a cryopump including the refrigerator are provided.
These and other objects, features and advantages of the present disclosure will become more apparent in light of the following detailed description of best mode embodiments thereof, as illustrated in the accompanying drawings.
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Further, the same reference symbols may be provided to the same members or the members having the same functions, and after those members are described, the description may be omitted as appropriate. In addition, the numerical values to be shown below are examples and are not limited to those examples.
A vacuum treatment apparatus 60 includes a vacuum chamber 66. An evaporation source (deposition source) 68 is disposed inside the vacuum chamber 66, and a substrate placement device (substrate holder) 63 is disposed above the evaporation source 68.
The vacuum treatment apparatus 60 is, for example, a sputtering apparatus or an etching apparatus. A refrigerator 30 is a refrigerator including a displacer and a cold storage device. The refrigerator 30 is, for example, a refrigerator in which the displacer reciprocates inside a refrigerator cylinder.
The vacuum chamber 66 is connected with a vacuum pump 69 and a cryopump 61. The vacuum chamber 66 is evacuated in advance by the vacuum pump 69. The bottom surface of the vacuum chamber 66 has an exhaust port 88. When the vacuum chamber 66 has a pressure reduced to a predetermined pressure, the cryopump 61 operates to reduce the internal pressure of the vacuum chamber 66 to a high vacuum atmosphere.
The vacuum chamber 66 is connected to a transport chamber 97. The transport chamber 97 is connected with another vacuum treatment apparatus 90. For example, a substrate 62 is transported into the vacuum chamber 66 from the vacuum treatment apparatus 90 via the transport chamber 97 while maintaining a vacuum atmosphere.
The center portion of the substrate placement device 63 is perforated. When a deposition material is released from the evaporation source 68, the deposition material passes through the through-hole and reaches the substrate 62. As a result, a thin film is formed on the substrate 62. A mask member may be disposed between the substrate 62 and the evaporation source 68 if necessary.
The cryopump 61 evacuates the gas inside the vacuum chamber 66. The cryopump 61 includes a pump main body 71 and the refrigerator 30. The refrigerator 30 includes a motor portion 53 and a refrigeration portion 54.
The pump main body 71 includes a low-temperature baffle 87 and a low-temperature shield 82 inside a pump case 83 (vacuum exhaust chamber) that can maintain vacuum airtightness. The low-temperature baffle 87 is cooled to 80 K (Kelvin), and the low-temperature shield 82 is cooled to 80 K. The low-temperature baffle 87 and the low-temperature shield 82 can absorb most of the radiant heat that flows in from the vacuum treatment apparatus 60. A cryopanel 76 (cryogenic plate) that is cooled to a cryogenic temperature of 15 K is disposed inside the pump main body 71. The low-temperature baffle 87, the low-temperature shield 82 and the cryopanel 76 are collectively referred to as a cooling plate that is cooled by the refrigerator 30 and that condenses or adsorbs the gas within the vacuum chamber 66 to remove the gas.
The motor portion 53 is disposed outside the vacuum atmosphere of the cryopump 61. The motor portion 53 includes a motor that is driven by an alternating-current (AC) power supply.
The refrigeration portion 54 is disposed in an adiabatic vacuum atmosphere so as not to be affected by heat input due to radiation or by heat input due to heat conduction.
The refrigeration portion 54 includes a cylindrical body 91 on the pump case 83 side, a flange 92 on the pump case side, a bellows 93, a flange 99 on the motor portion side, and a refrigeration case 95. All parts constituting the refrigeration portion 54 can maintain airtightness by welding or elastic bodies. The space surrounding the refrigeration portion 54 is in a vacuum state similar to the inside of the cryopump.
The flange 92 on the pump case side and the flange 99 on the motor portion side are fixed to each other via an anti-vibration device 55. An extendable bellows 93 is disposed between the flange 92 on the pump case side and the flange 99 on the motor portion side.
A first-stage cylinder 3 is disposed inside the refrigeration case 95. A second-stage cylinder 5 is disposed inside the pump case 83. The first-stage cylinder 3 and the second-stage cylinder 5 are airtightly connected to each other and form a refrigerator cylinder 100 into which helium gas is introduced.
One end of the refrigerator cylinder 100 (left end in
Among the gases that enter an cryopump intake 89 from the vacuum chamber 66 via the exhaust port 88, gases with low vapor pressure, such as H2O, are condensed by the low-temperature baffle 87 and the low-temperature shield 82, which are cooled (e.g., 80 K) by the first stage of the refrigerator cylinder 100. Further, of those gases, the gases with high vapor pressure other than water, such as N2, O2, Ar, and H2, pass through the low-temperature baffle 87 and are condensed or adsorbed on the cryopanel 76, which is cooled (e.g., below 15 K) by the second stage of the refrigerator cylinder 100. The cryopanel 76 is connected to the tip portion of the refrigerator cylinder 100 via an attachment member 84.
The motor portion 53 is fixed to the flange 99 on the motor portion side by the refrigeration case 95. The flange 99 on the motor portion side is fixed to the flange 92 on the pump case side by the anti-vibration device 55.
The flange 92 on the pump case side is fixed to the pump case 83 by the cylindrical body 91 on the pump case 83 side. The cryopanel 76, the refrigeration portion 54, the refrigerator cylinder 100 disposed therein, and the motor portion 53 are supported by the pump case 83 via the anti-vibration device 55.
The refrigerator cylinder 100 included in the refrigerator 30 includes the first-stage cylinder 3, and the second-stage cylinder 5 coupled to the first-stage cylinder 3. The first-stage cylinder 3 and the second-stage cylinder 5 have a cylindrical shape (tubular). The second-stage cylinder 5 is configured to have a smaller inner diameter than the first-stage cylinder 3. One end of the first-stage cylinder 3 is connected to one end of the second-stage cylinder 5. This forms one refrigerator cylinder 100. The connection portion between the first-stage cylinder 3 and the second-stage cylinder 5 is provided with a flange 35. The refrigerator cylinder 100 is made of stainless steel, for example.
If the upper surface of the other end of the first-stage cylinder 3 is defined as a first-stage flange 20, and the bottom surface of the other end of the second-stage cylinder 5 is defined as a second outer bottom plate 37, the inside of the first-stage cylinder 3 and the inside of the second-stage cylinder 5 are made airtight by the first-stage flange 20, the flange 35, and the second outer bottom plate 37. A high-purity helium gas serving as a refrigerant of the refrigerator is sealed inside the first-stage cylinder 3 and the second-stage cylinder 5.
The first-stage flange 20 is provided with a through-hole, into which a rod 31 is inserted airtightly and movably. A tip of the rod 31 is located inside the first-stage cylinder 3. A presser plate (upper cap) 32a is provided at the tip of the rod 31.
A cylindrical first-stage displacer 2 is disposed inside the first-stage cylinder 3. A cylindrical second-stage displacer 4 is disposed inside the second-stage cylinder 5, the second-stage displacer 4 having smaller inner and outer diameters than the first-stage displacer 2 and having an end coupled to the first-stage displacer 2. The first-stage displacer 2 is made of, for example, a thermosetting resin, and the second-stage displacer 4 is made of, for example, stainless steel. A coating layer is formed on the outer circumferential surface of the second-stage displacer 4 (described below).
The first-stage cylinder 3, the second-stage cylinder 5, the first-stage displacer 2, and the second-stage displacer 4 are disposed such that a central axis line 301 of the first and second-stage cylinders 3 and 5 and a central axis line 302 of the first and second-stage displacers 2 and 4 coincide with each other. The central axis line 301 and the central axis line 302 form a central axis line 300 of the refrigerator cylinder 100.
A first-stage cold storage device 8 is disposed in the internal space of the first-stage displacer 2. A second-stage cold storage device 10 is disposed in the internal space of the second-stage displacer 4.
The first-stage displacer 2 includes a small-diameter portion 33 having a cylindrical shape, and a large-diameter portion 34 having a cylindrical shape and a larger diameter than the small-diameter portion 33. The end surface of the large-diameter portion 34, which is opposite from the small-diameter portion 33, is coupled to the upper end portion of the second-stage displacer 4. The rod 31 is inserted airtightly and movably into the through-hole formed in the first-stage flange 20. When the rod 31 reciprocates in the axial direction by the motor portion 53, the presser plate 32a, the first-stage displacer 2, and the second-stage displacer 4 reciprocate together along the central axis line 300 in the space formed by the inside of the first-stage cylinder 3 and the inside of the second-stage cylinder 5.
In other words, the motor portion 53 and the rod 31 form a reciprocating mechanism to reciprocate the first and second-stage cylinders 3 and 5. Thus, in the refrigerator cylinder 100 into which the helium gas as a refrigerant gas is introduced, the reciprocating mechanism reciprocates the first-stage displacer 2 and the second-stage displacer 4 in the direction along the central axis line 300 of the refrigerator cylinder 100.
A first-stage O-ring 1 and an auxiliary ring 13a made of resin and having an annular shape are disposed in the small-diameter portion 33 with their inner circumferences being in contact with the outer circumference of the small-diameter portion 33. The first-stage O-ring 1 is disposed with the inner circumference of a first-stage cap 21 made of resin and having an annular shape being in contact with the outer circumference of the first-stage O-ring 1. The first-stage O-ring 1 and the first-stage cap 21 form a first-stage seal member 22. The outer circumferential surface of the first-stage cap 21 and the outer circumferential surface of the auxiliary ring 13a are in contact with the inner circumferential surface of the first-stage cylinder 3.
The conductance between the second-stage displacer 4 and the second-stage cylinder 5 is reduced by a minute clearance and controls the amount of helium gas that passes therethrough within a time period during which the second-stage displacer 4 reciprocates.
The refrigerator 30 includes a compressor (not shown). When the refrigerator 30 is operated, the first and second-stage displacers 2 and 4 are separated from the first-stage flange 20. Inside the first and second-stage cylinders 3 and 5, an introduction space 12 is formed between the first-stage flange 20 and the first-stage displacer 2. An introduction port 23 is provided to the first-stage flange 20. A high-pressure helium gas supplied by the compressor is introduced into the introduction space 12 through the introduction port 23.
After a high-pressure helium gas is introduced into the introduction space 12, the first-stage displacer 2 moves toward the first-stage flange 20 by the movement of the rod 31. Accordingly, a first-stage expansion space 9 is formed inside the first-stage cylinder 3 on the opposite side from the introduction space 12, and a second-stage expansion space 11 is formed inside the second-stage cylinder 5 between the second-stage displacer 4 and the bottom surface of the second-stage cylinder 5. When the first and second-stage expansion spaces 9 and 11 reach their maximum volume, the volume of the introduction space 12 becomes minimum.
The presser plate 32a and the small-diameter portion 33 are provided with a first flow channel 24 that is a through-hole. Further, the first-stage displacer 2 is provided with a second flow channel 25 that connects the space in which the first-stage cold storage device 8 is disposed and the first-stage expansion space 9. The second-stage displacer 4 is provided with a third flow channel 26 that connects the first-stage expansion space 9 and the space in which the second-stage cold storage device 10 is provided, and a fourth flow channel 27 that connects the second-stage expansion space 11 and the space in which the second-stage cold storage device 10 is provided.
When the first and second-stage expansion spaces 9 and 11 are formed, the high-pressure helium gas introduced into the introduction space 12 passes through the first flow channel 24 and flows into the space in which the first-stage cold storage device 8 is disposed. After the high-pressure helium gas is cooled in the first-stage cold storage device 8, the high-pressure helium gas passes through the second flow channel 25 and flows into the first-stage expansion space 9. Further, the high-pressure helium gas flowing into the first-stage expansion space 9 passes through the third flow channel 26 and flows into the space in which the second-stage cold storage device 10 is disposed. The high-pressure helium gas is then cooled in the second-stage cold storage device 10, passes through the fourth flow channel 27, and flows into the second-stage expansion space 11.
When the introduction port 23 is connected to the compressor (not shown) in this state, the high-pressure helium gas, which has flowed into the first and second-stage expansion spaces 9 and 11, flows backwards through the first to fourth flow channels 24 to 27 to flow into the spaces in which the first and second-stage cold storage devices 8 and 10 are disposed while expanding. The high-pressure helium gas then reduces the pressure while cooling the first and second-stage cold storage devices 8 and 10, and moves to the compressor (not shown).
The helium gas that has returned to the compressor (not shown) is compressed while dissipating heat inside the compressor to become a high-pressure helium gas.
In this embodiment, the movement when the first and second-stage expansion spaces 9 and 11 are formed, that is, the movement in the direction in which the first and second-stage displacers 2 and 4 approach the first-stage flange 20, is defined as outward movement. Further, the movement when the introduction space 12 is formed, that is, the movement in the direction in which the first and second-stage displacers 2 and 4 move away from the first-stage flange 20, is defined as return movement. The introduction of the high-pressure helium gas into the introduction space 12, the outward movement, the movement of the high-pressure helium gas, which has moved to the first and second-stage expansion spaces 9 and 11, to the compressor, and the return movement are repeated, so that a temperature gradient is formed within the first and second-stage cold storage devices 8 and 10. Accordingly, the lower ends of the first and second-stage cylinders 3 and 5 are cooled, and the low-temperature baffle 87, the low-temperature shield 82, the cryopanel 76, and the like are cooled.
In the refrigerator 30 of this embodiment, in order to avoid damage to the second-stage displacer 4 when the metal materials of the second-stage displacer 4 and the second-stage cylinder 5 come into contact with each other due to the above operation, a non-fluorine coating layer 41 is formed on the outer circumferential surface 40 of the second-stage displacer 4. The coating layer 41 is formed, for example, by vacuum deposition such as CVD, sputtering, or vapor deposition, or by baking.
A clearance C1 is provided between the coating layer 41 and the second-stage cylinder 5 to avoid contact therebetween as much as possible. This clearance C1 is controlled to be length enough to inhibit the helium gas from passing therethrough in order to provide a temperature difference between the first-stage cylinder 3 and the second-stage cylinder 5. For example, the clearance C1 is configured to be 20 μm or more and 50 μm or less.
Examples of materials for the coating layer 41 include diamond-like carbon (DLC), ceramics such as titanium nitride or titanium carbide, polyimide (PI), and polyetheretherketone (PEEK), which have better wear resistance than organic fluorine compounds. The coating layer 41 includes at least one of diamond-like carbon (DLC), ceramics such as titanium nitride or titanium carbide, polyimide (PI), or polyetheretherketone (PEEK).
For example, if the coating layer 41 is made of a diamond-like carbon layer, the thickness of the diamond-like carbon layer is configured to be 0.3 μm or more and 2 μm or less. If the thickness of the diamond-like carbon layer is smaller than 0.3 μm, the unevenness of the base material appears on the surface after coating, which is not desirable. If the thickness of the diamond-like carbon layer is larger than 2 μm, the degree of adhesion deteriorates and the layer peels easily, which is not desirable.
For example, if the coating layer 41 is made of a titanium nitride layer or titanium carbide layer, the thickness of the titanium nitride layer or titanium carbide layer is configured to be 0.1 μm or more and 5.0 μm or less. If the thickness of the titanium nitride layer or titanium carbide layer is smaller than 0.1 μm, the unevenness of the base material appears on the surface after coating, which is not desirable. If the thickness of the titanium nitride layer or titanium carbide layer is larger than 5.0 μm, the degree of adhesion deteriorates and the layer peels easily, which is not desirable.
For example, if the coating layer 41 is made of a ceramic layer, the thickness of the ceramic layer is configured to be 15 μm or more and 30 μm or less. If the thickness of the ceramic layer is smaller than 15 μm, the base material is exposed due to mottling of the coating, which is not desirable. If the thickness of the ceramic layer is larger than 30 μm, the degree of adhesion deteriorates and the layer peels easily, which is not desirable.
For example, if the coating layer 41 is made of a polyimide layer, the thickness of the polyimide layer is configured to be 20 μm or more and 50 μm or less. If the thickness of the polyimide layer is smaller than 20 μm, the base material is exposed due to mottling of the coating, which is not desirable. If the thickness of the polyimide layer is larger than 50 μm, the adhesion deteriorates and the layer peels easily, which is not desirable.
For example, if the coating layer 41 is made of a polyetheretherketone layer, the thickness of the polyetheretherketone layer is configured to be 20 μm or more and 40 μm or less. If the thickness of the polyetheretherketone layer is smaller than 20 μm, the base material is exposed due to mottling of the coating, which is not desirable. If the thickness of the polyetheretherketone layer is larger than 40 μm, the adhesion deteriorates and the layer peels easily, which is not desirable.
Organic fluorine compounds have conventionally been used as the materials for the coating layer 41, and the above-mentioned materials have not been used. This is based on the reason that the coating of the conventional organic fluorine compounds has sufficient durability for the maintenance interval (e.g., 10,000 hours). In contrast, the maintenance interval can be extended (e.g., 36,000 hours) by employing the materials of this embodiment.
The coating layer 41 is densely formed by vacuum deposition or baking treatment. Thus, the mechanical strength of the coating layer 41 is higher than that of the case using the organic fluorine compound. Forming the coating layer 41 on the outer circumferential surface 40 of the second-stage displacer 4 improves wear resistance in a lubrication-free environment as compared to the case of using the organic fluorine compound. Further, the sliding properties against the second-stage cylinder 5 are more improved. Uneven wear of the coating layer 41 is also less likely to occur. This enhances the reliability of the coating layer 41 in a low-temperature environment.
As shown in
Hereinabove, the embodiment of the present invention has been described, but the present invention is not limited to the embodiment described above, but can of course be modified in various ways. Each embodiment is not necessarily an independent form, but can be combined as much as technically possible.
It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2024-001946 | Jan 2024 | JP | national |
