ACTIVELY COOLED VACUUM ISOLATION VALVE
A cooled isolation valve includes a valve body, a stationary element coupled to the valve body, and a movable closure element movable with respect to the stationary element between a closed position in which the movable closure element and the stationary element are brought together and an open position. One of the movable closure element and the stationary element includes a sealing element. In the closed position of the movable closure element, the sealing element provides a seal between the movable closure element and the stationary element. A fluid channel is formed in contact with the movable closure element and movable with the movable closure element with respect to the stationary element, such that a fluid in the fluid channel effects heat transfer in the movable closure element. A bellows of the isolation valve can include a metallic substrate with a ceramic coating.
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The present disclosure is related to vacuum isolation valves and, in particular, to vacuum isolation valves with active cooling.
2. Discussion of Related ArtBellows-sealed, poppet vacuum isolation valves are commonly used in semiconductor processing systems. The valves are commonly heated to a specific temperature from the outside in order to prevent byproducts from the chemical vapor deposition (CVD) process being performed from condensing in the valves.
A challenging application for an isolation valve is isolating a flow of reactive gas. Atomic fluorine, for example, is commonly used for chamber cleaning, and is introduced from a remote plasma source. In certain applications, it is useful to place an isolation valve between the remote plasma source and the chamber. It is important that the valve not reduce the atomic fluorine concentration, have high conductance, and be reliable in the application.
There are multiple challenges to the valve in this application. First, the atomic fluorine is extremely reactive, so materials that come in contact with the processing must be carefully selected. Second, the gas temperature inside the remote plasma source, e.g., ASTRON remote plasma source sold by MKS Instruments, Inc., is on the order of 3000K, although at typical pressures of approximately 10 Torr, the heat transported by the gas is moderate.
A significant problem is that when the atomic fluorine collides with a surface, it has an increased probability of recombining into molecular F2. The recombination of atomic fluorine into molecular fluorine is an exothermic reaction that can generate significant heat on the internal components of a vacuum valve. Similarly, oxygen or hydrogen radicals that are produced will have a tendency to recombine and generate heat when colliding with surfaces inside the valve. For example, with 1 slm of NE3 entering the remote plasma source, the heat load on surfaces downstream of the remote plasma source is on the order of 50 mW/cm̂2.
Although the total heat input may be relatively small (on the order of 500 mW-5 W), there is typically high thermal resistance between the moving components of a valve and a cold sink, and therefore the moving components can reach excessive temperatures. The moving part of the valve that forms the seal, commonly the nosepiece, has a very poor conduction path to air at atmosphere where natural convection can occur. The stem and bellows are typically a welded assembly fabricated from stainless steel, which has poor thermal conductivity. In the vacuum space, the pressures are typically on the order of 1-10 Torr, where convection and conduction effects are negligible. Even when the valve is closed, the designs are careful to avoid metal to metal contact between the nosepiece and seat. So, with a moderate power input to the valve internals of several watts, internal temperatures can get extremely high. At temperatures above 250° C., most elastomer or perfluoroelastomer seals will have exceeded their temperature rating. At temperatures above 300° C., most aluminum alloys have lost substantial mechanical strength.
SUMMARYAccording to a first aspect, a cooled isolation valve is provided. The valve includes a valve body, a stationary element coupled to the valve body and stationary with respect to the valve body, and a movable closure element being movable with respect to the stationary element between a closed position in which the movable closure element and the stationary element are brought together and an open position. One of the movable closure element and the stationary element comprises a sealing element. In the closed position of the movable closure element, the sealing element provides a seal between the movable closure element and the stationary element. A fluid channel is formed in contact with the movable closure element and is movable with the movable closure element with respect to the stationary element, such that a fluid in the fluid channel effects heat transfer in the movable closure element.
In some exemplary embodiments, the cooled isolation valve further comprises a sensor for detecting whether the movable closure element is in the open position or the closed position and an actuator for inhibiting flow of the fluid when the sensor detects that the movable closure element is in the closed position.
In some exemplary embodiments, the cooled isolation valve further comprises a pneumatic actuation device for controlling movement of the movable closure element and a bellows for isolating the pneumatic actuation device from an environment within the valve body. In these embodiments, the bellows are disposed adjacent to the pneumatic actuation device radially from a longitudinal axis of the valve and at least partially overlapping the pneumatic actuation device along the longitudinal axis.
In some exemplary embodiments, the sealing element comprises an O-ring. In some exemplary embodiments, the valve further comprises a groove in one of the stationary element and the movable closure element, the O-ring being disposed in the groove and a surface of the O-ring protruding from the groove. A protrusion in a surface of the other of the stationary element and the movable closure element contacts a portion of the protruding surface of the O-ring when the movable closure element is in the closed position, such that the O-ring is free to expand and contract.
In some exemplary embodiments, the sealing element comprises an O-ring. In some exemplary embodiments, the valve further comprises a groove in one of the stationary element and the movable closure element, the O-ring being disposed in the groove and a surface of the O-ring protruding from the groove. A concave feature in a surface of the other of the stationary element and the movable closure element contacts a portion of the protruding surface of the O-ring when the movable closure element is in the closed position, such that the O-ring is free to expand and contract.
In some exemplary embodiments, the valve is a poppet valve. In these embodiments, the movable closure element can comprise a nosepiece of the poppet valve. The stationary element can comprise a valve seat of the poppet valve. At least a portion of the cooling channel can be formed in the nosepiece. The nosepiece can be coupled to a movable stem of the cooled isolation valve. At least a portion of the cooling channel can be formed in the stem. The sealing element can comprise an O-ring in a groove, the groove being formed in a nosepiece of the poppet valve.
In some exemplary embodiments, the valve is a gate valve. In these embodiments, the movable closure element can comprise a gate movable between the closed position and the open position and a shaft fixedly attached to the gate, rotation of the shaft causing movement of the gate between the open and closed positions. The stationary element can comprise a valve seat. At least a portion of the cooling channel can be formed in the gate. At least a portion of the cooling channel can be formed in the shaft. The sealing element can comprise an O-ring in a groove, the groove being formed in the gate.
In some exemplary embodiments, the valve is a butterfly valve. In these embodiments, the movable closure element can comprise a flapper movable between the closed position and the open position and a shaft fixedly attached to the flapper, rotation of the shaft causing movement of the flapper between the open and closed positions. The stationary element can comprises walls of an opening through the valve. At least a portion of the cooling channel can be formed in the flapper. At least a portion of the cooling channel can be formed in the shaft.
In some exemplary embodiments, the fluid can comprise a gas or a liquid. For example, the fluid can comprise air, nitrogen (N2), water, a heat transfer fluid, or some combination of these fluids.
According to another aspect, a method of forming a bellows for an isolation valve is provided. According to the method, a metallic bellows substrate is provided. The metallic bellows substrate is configured to one of a compressed state and an elongated state. While maintained in that state, a first layer of a ceramic coating is applied to the metallic bellows substrate. The metallic bellows substrate is transitioned to the other of the compressed state and the elongated state. While maintained in that state, a second layer of the ceramic coating is applied.
In some exemplary embodiments, the metallic bellows substrate is formed of stainless steel.
In some exemplary embodiments, the ceramic coating comprises aluminum oxide.
In some exemplary embodiments, a ratio of thickness of the metallic bellows substrate to thickness of the ceramic coating is greater than 100:1.
According to another aspect, a bellows for a vacuum isolation valve is provided. The bellows includes a metallic substrate and a coating of ceramic material formed over the metallic substrate.
In some exemplary embodiments, the metallic bellows substrate is formed of stainless steel.
In some exemplary embodiments, the ceramic coating comprises aluminum oxide.
In some exemplary embodiments, a ratio of thickness of the metallic bellows substrate to thickness of the ceramic coating is greater than 100:1.
The present disclosure is further described in the detailed description which follows, in reference to the noted plurality of drawings by way of non-limiting examples of embodiments of the present disclosure, in which like reference numerals represent similar parts throughout the several views of the drawings.
In the closed state of valve 10 illustrated in
Valve 10 is typically controlled pneumatically via a pneumatic air inlet 20. High-pressure air introduced at air inlet 20 causes actuator 22 to move pneumatic piston 24 upwardly, carrying the fixedly attached stem 26 in the upward direction, sliding within stem guide 28 and stem bushings 30. Pneumatic seals 40 seal the pneumatic chamber to maintain elevated air pressure needed to actuate pneumatic piston 24. Nosepiece 32 is fixedly attached to the end of stem 26 and is forced upwardly against the bias force of spring 34 away from seat 38 to open valve 10, such that valve inlet and outlet communicate across internal chamber 18. This allows, for example, reactive gases to flow from the reactive gas source to the processing chamber. A spring bushing 48 can be used as a stroke stop by interfering with the travel of nosepiece 32.
Internal chamber 18 is sealed at the top by bonnet plate 42 and bonnet seal 44 between bonnet plate 42 and the interior wall of valve body 12. Internal valve components such as stem 26 and nosepiece 32 are isolated from internal chamber 18 by bellows 46. The interior of bellows 46 is vented to atmosphere via bellows vent 50. Bellows 46 is fixedly mounted to the interior wall of valve body 12 at bellows flange 52.
Referring to
In the closed state of valve 100 illustrated in
Valve 100 can be controlled pneumatically via a pneumatic air inlet 120. High-pressure air introduced at air inlet 120 causes pneumatic piston 124 to move upwardly, carrying the fixedly attached stem 126 in the upward direction. Pneumatic seals 140 seal the pneumatic chamber to maintain elevated air pressure needed to actuate pneumatic piston 124. Nosepiece 132 is fixedly attached to the end of stem 126 and is forced upwardly against the bias force of spring 134 away from seat 138 to open valve 100, such that valve inlet and outlet communicate across internal chamber 118. This allows, for example, reactive gases to flow from the reactive gas source to the processing chamber. A spring bushing 148 can be used as a stroke stop by interfering with the travel of nosepiece 132.
Internal chamber 118 is sealed at the top by bonnet plate or flange 142 and bonnet seal 144 between bonnet plate or flange 142 and the interior wall of valve body 112. Internal valve components such as stem 126 and nosepiece 132 are isolated from internal chamber 118 by bellows 146.
Referring to
Exposure of bellows 146 to process gas can be harmful to bellows 146 and, as a result, to valve 100. In the embodiments illustrated in
Similar to embodiments described above, valve 200 can be controlled pneumatically via pressurized air entering pneumatic chamber 227 via air inlet 220. In this case, when pneumatic chamber 227 is pressurized, stem 226 is forced upwardly against spring 234 to open valve 200 by moving nosepiece 232 and nosepiece seals 236 out of their seal with valve seat 238. When open, devices such as a processing chamber and a source of reactive gas can communication with each other via connections at flanges 214 and 216 across interior chamber 218. With reference to
In another embodiment, a closed-loop temperature controller is utilized. In this embodiment, a thermocouple is attached to a key component inside the valve, such as the nosepiece or bonnet flange, for example. The thermocouple is the sensor of a temperature control system, where the actuator of the control system is a pilot valve that modulates the flow of cooling fluid. A temperature set point can be applied to the temperature control system that causes the system to operate when the set point is reached.
The implementations illustrated and described in detail above are bellows-sealed poppet isolation valves. However, the same techniques could be applied to a valve that uses dynamic sliding shaft seals rather than a bellows. A shaft-sealed valve will also be subjected to thermal loads on the nosepiece and stem and will have a thermal dissipation path with high resistance. According to exemplary embodiments, active cooling of the stem and nosepiece can be implemented in a similar manner as shown in
According to some exemplary embodiments, the active cooling techniques described herein can also be applied to pendulum/gate isolation valves.
Referring to
As noted above, valve 400 is actively cooled. In some exemplary embodiments, active cooling is effected by circulation of a cooling fluid, such as air, nitrogen (N2), water, or other such fluid, through cooling channel 418 formed in gate 426. The fluid enters cooling channel 418 at fluid inlet 420, circulated through gate 426 in cooling channel 418, and exits cooling channel 418 through fluid outlet 422, thus carrying heat away from gate 426 and valve 400.
According to some exemplary embodiments, the active cooling techniques described herein can also be applied to butterfly pressure control valves.
According to exemplary embodiments, a vacuum valve has a seat and a movable plate. The movable plate provides a seal against the seat when the valve is in the closed position. The movable plate moves away from the seat in order to allow process fluid to pass through the valve when the valve is in the open position. The movable plate includes a separate and isolated internal cooling path that allows an independent cooling fluid to remove heat from the movable plate.
In some embodiments, the separate and isolated cooling path includes movable and non-movable components of the valve. In some embodiments, the valve includes a bellows to isolate the process fluid from the outside environment. In some embodiments, the bellows separates part of the cooling path from the process fluid. In some embodiments, the valve includes dynamic seals between components with relative motion in order to isolate the process fluid from the outside environment. In some embodiments, the flow of cooling fluid is switched off when the valve is in the closed position.
In some embodiments, the vacuum valve includes a temperature sensor measuring the temperature of the valve and a pilot valve that modules the flow of the cooling fluid in order to regulate the temperature of the valve as measured by the temperature sensor. In some embodiments, the vacuum valve includes a shield attached to the moving part of the valve to shield the external surface of the bellows from direct exposure to the process fluid. In some embodiments, the vacuum valve includes a secondary fixed shield in close proximity or adjacent to the moving shield. In some embodiments, the process gas is a reactive gas.
It is noted that, in the embodiments of poppet isolation valves 100, 200 illustrated in
Referring to
In the closed state of valve 300 illustrated in
Valve 300 can be controlled pneumatically via a pneumatic air inlet 320. High-pressure air introduced at air inlet 320 causes pneumatic piston 324 to move downwardly, carrying the fixedly attached stem 326 in the downward direction. Pneumatic seals 340 seal the pneumatic chamber to maintain elevated air pressure needed to actuate pneumatic piston 324. Actively cooled nosepiece 332 is fixedly attached to the end of stem 326 and is forced downwardly toward seat 338 where nosepiece seals 336 contact and seal against seat 338 to close valve 300, such that valve inlet and outlet ports are isolated from each other and cannot communicate across internal chamber 318. This prevents, for example, reactive gases from flowing from the reactive gas source to the processing chamber.
When high-pressure air is not being introduced at air inlet 320, valve 300 is controlled to transition to and remain in the open state. In the open state, as illustrated in
As noted above valve 300 includes active cooling which is analogous to the active cooling described above in detail in connection with
As illustrated in particular in
In the various embodiments of isolation valves described in detail above, O-ring seals such as, for example, nosepiece O-ring seals 136, 236, 336, are used to seal nosepieces 132, 232 and 332 to valve seats 138, 238 and 338, respectively. O-rings are typically disposed and retained within a groove or gland, such as, for example, groove or gland 137 illustrated in
Continuing to refer to
In alternative embodiments, another approach to reducing O-ring stress includes maintaining the nosepiece and the seat at similar and relatively constant temperature. This can be accomplished by active fluid cooling both the nosepiece as illustrated and described in detail herein and the seat. By cooling both the seat and the nosepiece, the O-ring will see relatively constant temperature, regardless of the heat load present, and regardless of whether the O-ring is compresses or uncompressed. For example, if under all circumstances the nosepiece and seat have temperature excursions of less than, for example, 10 degrees C., stress to the O-ring will be relatively low. In contrast, if the O-ring experiences temperature gradients or excursions on the order of 100 degrees C., stresses in the O-ring will be much higher.
In the isolation valves of the various embodiments, the bellows are typically exposed to a highly corrosive environment. As a result, stress corrosion cracking of the bellows can occur. In some exemplary embodiments, a very thin coating of aluminum oxide is applied to the bellows. In some particular embodiments, the bellows are approximately 100 μm thick, and the coating of aluminum oxide is approximately 0.5 μm thick. Typically, bellows materials are limited to those that can be welded, for example, stainless steel, Inconel or other such material. However, stainless steel has limited corrosion resistance to the process chemistry. In contrast, aluminum oxide has an advantage of a lower recombination rate for atomic fluorine, as compared to that of Inconel or stainless steel. The reduced recombination rate results in reduced heat load on the bellows and the overall system.
In order to produce a robust coating for a bellows that experiences significant strain, in some exemplary embodiments, the coating thickness is much thinner than the thickness of the substrate of the bellows. For example, in some particular exemplary embodiments, the thickness of the coating is less than one one-hundredth ( 1/100) the thickness of the bellows substrate. According to the exemplary embodiments, this very low thickness ratio between the coating and the bellows substrate enables the use of a ceramic in a flexible bellows, without cracking.
In general, there are two types of bellows, namely, formed bellows and welded bellows.
Referring to
Referring again to
It should be noted that, throughout the foregoing Detailed Description, the various valve embodiments are described as including active cooling. In the exemplary embodiments, this active cooling is achieved by effecting a flow of fluid through some portion of the valve, such as, for example, the movable closure device, i.e., nosepiece, flapper, gate, etc., and, in some exemplary embodiments, at least some portion of the valve body. In any of the embodiments described herein, the cooling fluid can be, for example, clean, dry compressed air, Nitrogen (N2) or other gas, with or without temperature control; water, or other liquid, with or without temperature control. Also, the fluid can be a heat transfer fluid, such as Galden® Heat Transfer Fluid, sold by Kurt J. Lesker Company, 1925 Route 51, Jefferson Hills, Pa. 15025 USA, or other such heat transfer fluid.
While the present inventive concept has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present inventive concept as defined by the following claims.
Claims
1. A cooled isolation valve, comprising:
- a valve body;
- a stationary element coupled to the valve body and stationary with respect to the valve body;
- a movable closure element being movable with respect to the stationary element between a closed position in which the movable closure element and the stationary element are brought together and an open position, one of the movable closure element and the stationary element comprising a sealing element, in the closed position of the movable closure element, the sealing element providing a seal between the movable closure element and the stationary element; and
- a fluid channel formed in contact with the movable closure element and movable with the movable closure element with respect to the stationary element, such that a fluid in the fluid channel effects heat transfer in the movable closure element.
2. The cooled isolation valve of claim 1, further comprising:
- a sensor for detecting whether the movable closure element is in the open position or the closed position; and
- an actuator for inhibiting flow of the fluid when the sensor detects that the movable closure element is in the closed position.
3. The cooled isolation valve of claim 1, further comprising:
- a pneumatic actuation device for controlling movement of the movable closure element; and
- a bellows for isolating the pneumatic actuation device from an environment within the valve body, the bellows being disposed adjacent to the pneumatic actuation device radially from a longitudinal axis of the valve and at least partially overlapping the pneumatic actuation device along the longitudinal axis.
4. The cooled isolation valve of claim 1, wherein the sealing element comprises an O-ring.
5. The cooled isolation valve of claim 4, further comprising:
- a groove in one of the stationary element and the movable closure element, the O-ring being disposed in the groove, and a surface of the O-ring protruding from the groove; and
- a protrusion in a surface of the other of the stationary element and the movable closure element, the protrusion contacting a portion of the protruding surface of the O-ring when the movable closure element is in the closed position, such that the O-ring is free to expand and contract.
6. The cooled isolation valve of claim 4, further comprising:
- a groove in one of the stationary element and the movable closure element, the O-ring being disposed in the groove, and a surface of the O-ring protruding from the groove; and
- a concave feature in a surface of the other of the stationary element and the movable closure element, the concave feature contacting a portion of the protruding surface of the O-ring when the movable closure element is in the closed position, such that the O-ring is free to expand and contract.
7. The cooled isolation valve of claim 1, wherein the valve is a poppet valve.
8. The cooled isolation valve of claim 7, wherein the movable closure element comprises a nosepiece of the poppet valve.
9. The cooled isolation valve of claim 8, wherein the stationary element comprises a valve seat of the poppet valve.
10. The cooled isolation valve of claim 8, wherein at least a portion of the cooling channel is formed in the nosepiece.
11. The cooled isolation valve of claim 8, wherein the nosepiece is coupled to a movable stem of the cooled isolation valve.
12. The cooled isolation valve of claim 11, wherein at least a portion of the cooling channel is formed in the stem.
13. The cooled isolation valve of claim 7, wherein the sealing element comprises an O-ring in a groove, the groove being formed in a nosepiece of the poppet valve.
14. The cooled isolation valve of claim 1, wherein:
- the valve is a gate valve; and
- the movable closure element comprises a gate movable between the closed position and the open position and a shaft fixedly attached to the gate, rotation of the shaft causing movement of the gate between the open and closed positions.
15. The cooled isolation valve of claim 14, wherein the stationary element comprises a valve seat.
16. The cooled isolation valve of claim 14, wherein at least a portion of the cooling channel is formed in the gate.
17. The cooled isolation valve of claim 14, wherein at least a portion of the cooling channel is formed in the shaft.
18. The cooled isolation valve of claim 14, wherein the sealing element comprises an O-ring in a groove, the groove being formed in the gate.
19. The cooled isolation valve of claim 1, wherein:
- the valve is a butterfly valve; and
- the movable closure element comprises a flapper movable between the closed position and the open position and a shaft fixedly attached to the flapper, rotation of the shaft causing movement of the flapper between the open and closed positions.
20. The cooled isolation valve of claim 19, wherein the stationary element comprises walls of an opening through the valve.
21. The cooled isolation valve of claim 19, wherein at least a portion of the cooling channel is formed in the flapper.
22. The cooled isolation valve of claim 19, wherein at least a portion of the cooling channel is formed in the shaft.
23. The cooled isolation valve of claim 1, wherein the fluid comprises a gas.
24. The cooled isolation valve of claim 1, wherein the fluid comprises a liquid.
25. The cooled isolation valve of claim 1, wherein the fluid comprises air.
26. The cooled isolation valve of claim 1, wherein the fluid comprises nitrogen (N2).
27. The cooled isolation valve of claim 1, wherein the fluid comprises water.
28. The cooled isolation valve of claim 1, wherein the fluid comprises a heat transfer fluid.
29. A method of forming a bellows for an isolation valve, comprising:
- forming a metallic bellows substrate;
- configuring the metallic bellows substrate to one of a compressed state and an elongated state;
- applying a first layer of a ceramic coating to the metallic bellows substrate while the metallic bellows substrate is maintained in the one of the compressed state and the elongated state;
- transitioning the metallic bellows substrate to the other of the compressed state and the elongated state; and
- applying a second layer of the ceramic coating while the metallic bellows substrate is maintained in the other of the compressed state and the elongated state.
30. The method of claim 29, wherein the metallic bellows substrate is formed of stainless steel.
31. The method of claim 29, wherein the ceramic coating comprises aluminum oxide.
32. The method of claim 29, wherein a ratio of thickness of the metallic bellows substrate to thickness of the ceramic coating is greater than 100:1.
33. A bellows for a vacuum isolation valve, comprising:
- a metallic substrate; and
- a coating of ceramic material formed over the metallic substrate.
34. The bellows of claim 33, wherein the metallic bellows substrate is formed of stainless steel.
35. The bellows of claim 33, wherein the ceramic coating comprises aluminum oxide.
36. The bellows of claim 33, wherein a ratio of thickness of the metallic bellows substrate to thickness of the ceramic coating is greater than 100:1.
Type: Application
Filed: Apr 4, 2017
Publication Date: Oct 12, 2017
Applicant: MKS Instruments, Inc. (Andover, MA)
Inventors: Gordon Hill (Arlington, MA), David F. Broyer (Kingston, NH), David C. Neumeister (Longmont, CO), Bradly Raymond Lefevre (Lakewood, CO)
Application Number: 15/478,623