Gas Purge Valve

Abstract

The valve (100) comprises a housing (102) having at least one inlet (104a) and at least one outlet (104b), and a valve member (108) disposed within the housing (102) and movable between different positions in use to control the flow of fluid from the inlet (104a) to the outlet (104b) of the valve (100), the valve (100) further comprising at least two spaced apart valve seats (110a, 110b) against which the valve member (108) rests to provide a fluid flow between the valve seats (110a, 110b) and the valve member (108). The valve member (108) includes at least two spaced apart valve seats (110a, 110b) that define a cavity (112) bounded by an outer surface of the valve member (108) and an inner surface of the housing (102), a first conduit (118) extending between the exterior of the housing (102) and the cavity (112), and a second conduit (125) extending between the cavity (112) and a bore (114) of the valve member (108), through which a purge gas can be introduced into the cavity (112) and the bore (114) during use. Preferably, the purge gas is pressurized and optionally heated using a cartridge heater (126) to inhibit escape of process gas and condensate, respectively.

Description

[Technical field]

[0001] The present invention relates to valves, particularly but not exclusively to gas purge valves that substantially reduce or eliminate the release of corrosive, toxic, pyrophoric and / or harmful gases into the surrounding environment upon valve failure. The present invention also relates to systems including vacuum pumps, gas abatement systems and gas purge valves according to the present invention. [Background technology]

[0002] The manufacture of semiconductor devices, flat panel displays, and solar panels includes various process steps (e.g., etching, deposition, and cleaning) that are typically performed under vacuum conditions. To achieve such conditions, one or more vacuum pumps are connected to the outlet of each process chamber. During operation, the vacuum pumps receive unused process gases and / or by-products exhausted from the process chamber. The unused gases and by-products are typically corrosive, toxic, pyrophoric, and / or harmful gases that cannot be directly released into the environment. Therefore, each vacuum pump exhausts to one or more gas abatement systems. Manufacturers typically install two abatement systems in parallel, with one system operating in an "online" mode and the other operating in an "offline" mode. The use of the two systems together can improve uptime in the event of an abatement system failure or when preventive maintenance is required. During such failure or maintenance, an isolation valve isolates the offline system from the online system. Each inlet line of each abatement system includes an isolation valve that alternates between the online and offline abatement systems. As unused process gases and by-products flow to the isolation valve, the valve's O-ring seal or valve seat may fail. Such a failure may allow pressurized gas to continue to flow to the offline abatement system even after the isolation valve has "closed." Thus, corrosive, toxic, pyrophoric and / or harmful gases may be released into the environment while technicians are servicing the offline system, potentially causing detrimental effects to nearby people and property.

[0003] To minimize gas release, manufacturers often include a second manually operated isolation valve on both the on-line and off-line abatement system inlet lines. Before servicing the off-line abatement system, a technician must also close the manual valve so that pressurized gas no longer flows into the system. However, technicians can forget to close or reopen the manual valve. Thus, adding a manual valve can have several disadvantages. First, adding a second valve adds cost to the system. Second, even with a second manual valve, there is still a small risk of accidental exposure if the ball or seal of the manual valve becomes damaged. Third, if a technician forgets to reopen the manual valve, for example, a catastrophic failure will occur in the process system when the primary system goes off-line and switches to the secondary system.

[0004] Thus, there is a need for a single, reliable isolation valve that can isolate an offline abatement system from an online abatement system and substantially reduce or eliminate the release of corrosive, toxic, pyrophoric and / or hazardous gases. Similarly, there is a need for a treatment system that provides cost-effective redundancy and enhanced safety. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] U.S. Patent No. 7,494,633 [Patent Document 2] U.S. Pat. No. 5,538,702 [Patent Document 3] US Patent Publication No. 2005 / 0217732A1 Summary of the Invention

[0006] According to a first aspect of the present invention there is provided a valve comprising: a housing having at least one inlet and at least one outlet; a valve member disposed within the housing and movable between different positions in use to control fluid flow from the inlet to the outlet of the valve, the valve further comprising at least two spaced apart valve seats against which the valve member seats to define a cavity bounded by the valve seat, an outer surface of the valve member and an inner surface of the housing; a first conduit extending between an exterior of the housing and the cavity; and a second conduit extending between the cavity and a bore of the valve member, wherein a purge gas can be introduced into the cavity and the bore in use through the first and second conduits.

[0007] Preferably, pressurized or purge gas can be optionally, but preferably, introduced into the cavity to ensure that the process gas cannot escape from the housing. In certain circumstances, this can include providing a continuous flow of purge gas into the cavity or bore to maintain a positive pressure in the cavity or to inhibit backflow or leakage of the process gas out of the housing through any apertures.

[0008] One envisaged advantage of the present invention is that it can provide protection to people and the environment surrounding the valve in the event of malfunction or failure. This can be achieved by providing a method of purging potentially harmful gases from the valve and replacing them with (preferably) an inert or non-hazardous purge gas, so that in the event of a valve leak, failure or incorrect operation, it is more likely that the inert or non-hazardous purge gas will escape rather than the potentially harmful process gas. This is achieved in practice by surrounding the movable valve member with a continuous supply of purge gas and allowing the purge gas to enter the bore of the valve member.

[0009] Advantageously, the second conduit extending between the cavity and the bore of the valve member allows the purge gas to enter the cavity and the bore of the valve member in the first ("on") position, i.e. when the bore is aligned with the inlet and outlet of the valve. Thus, the risk of process gas escaping from the housing can be reduced while the valve is in the first position. This is because the purge gas can flow from the passage into the cavity, from where it can flow through the second conduit into the bore of the valve member, where it can combine with the process gas before exiting the valve. The purge gas can be supplied at a pressure higher than the normal maximum pressure of the process gas, so that the purge gas can flow into the process gas stream.

[0010] The valve may be an isolation valve or a diverter valve, such as may be used in a vacuum system having a redundant gas abatement system. In the case of an isolation valve, the valve member may include a bore such that when moved or rotated to a first position, the bore is aligned with the inlet and outlet of the valve, and / or when moved or rotated to a second position, the bore is not aligned with either the inlet or outlet. Of course, when the valve member is moved to the second ("off") position, it may deadhead the purge gas.

[0011] In the case of a diversion valve, the valve member may be movable or rotatable between a first position and a second position such that in the first position the bore is aligned with the inlet and the first outlet, and in the second position the bore is aligned with the inlet and the second outlet.

[0012] To inhibit or prevent the backflow of purge gas from the housing, an anti-return valve is preferably provided, which may include a spring whose tension can be adjusted, preferably made from an alloy having a high nickel content, such as a mnemonic (or "shape memory") alloy (such as Nitinal™).

[0013] To facilitate the introduction of purge gas to the valve, a manifold may be provided that allows the purge gas to be introduced into the purge gas conduit from outside the housing.

[0014] A heater, such as a suitably defined cartridge heater, can be provided to heat the purge gas within the manifold before it enters the manifold and thus the cavity. Such an arrangement can reduce or prevent condensation within any part of the manifold or valve.

[0015] The manifold, if provided, can function as a heat exchanger to transfer heat from the heater or cartridge heater to the purge gas therein. To maximize the efficiency of the heat exchange, the manifold is preferably fabricated from a highly thermally conductive material, such as copper or aluminum alloy. Heat transfer from the heater or cartridge heater can be maximized by designing the flow path of the purge gas in the manifold such that the flow path has a large surface area and follows a non-linear path. Thus, the flow path of the purge gas through the manifold is preferably disturbed, which can be achieved by increasing the turbulence of the purge gas therethrough, a tortuous flow path of the purge gas through the manifold, appropriate use of baffles and packing materials in the flow path.

[0016] In most practical situations, there is preferably a purge gas supply connected to the inlet of the manifold.

[0017] As mentioned above, it is possible to check the integrity of the valve by monitoring the pressure or flow of the purge gas in any one or more of the group including the cavity, the first and second conduits, the manifold, and the purge gas supply. This can be achieved in certain circumstances by using a pressure transducer or a flow transducer. In the most preferred embodiment of the present invention, the pressure transducer is located in the purge gas supply, and a valve and a pressure regulator are provided upstream of the pressure transducer along with a valve for isolating the purge gas in the cavity and the manifold, and the pressure transducer is adapted to monitor the pressure of the separated purge gas.

[0018] To be compatible with the manufacturing processes described above, the wetted components are preferably selected to be compatible with the process gases flowing through the valve, such as fluorine, chlorine, hydrogen bromide, etc. Similarly, the valve seats are also preferably manufactured from materials that are resistant to chemical and physical attack by the process gases, such as, for example, stainless steel, Hastelloy™, Viton™, Karez™, etc.

[0019] A second aspect of the present invention provides a system comprising a vacuum pump having an exhaust port, a pair of abatement systems connected in a T-shape to the exhaust port, and a valve as described herein disposed upstream of each of the abatement systems.

[0020] Preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0021] [Figure 1] FIG. 2 is a schematic diagram of a gas purged ball valve according to the present invention. [Figure 2a] FIG. 2 is a side view of a gas purged ball valve according to the present invention (shown in an open position). [Figure 2b] FIG. 2 is an end view of a gas purged ball valve according to the present invention (shown in a closed position). [Figure 2c] FIG. 2 is a side view of a gas purged ball valve according to the present invention (shown in a closed position). [Figure 3a] FIG. 2 is a schematic diagram of a gas purge ball valve with purge gas pressure sensing in accordance with the present invention. [Figure 3b] FIG. 2 is a schematic diagram of a gas purged ball valve with flow purge gas detection in accordance with the present invention. [Figure 4a] FIG. 2 is a cross-sectional view of a flow diverter valve according to the present invention. [Figure 4b] FIG. 2 is a diagram of a manifold coupled to a flow diverter valve in accordance with the present invention. [Diagram 5] FIG. 2 is a plan view of a flow diverter valve according to the present invention. [Figure 6a] FIG. 1 is a schematic diagram of a system having a pair of gas purged ball valves in accordance with the present invention. [Figure 6b] FIG. 1 is a schematic diagram of a system having a gas purge diverter valve according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] The isolation valve of the present invention can be a ball valve or a diverter valve. Figure 1 shows one embodiment of a gas purged ball valve of the present invention. The ball valve 100 has a housing 102 with an inlet 104a and an outlet 104b. The valve 100 further includes a rotating ball 108 seated between a pair of valve seats 110a, 110b. The valve seats 110a, 110b are located at the inlet 104a and outlet 104b of the valve 100, respectively.

[0023] The ball 108 has a bore 114 therethrough, and the ball 108 can rotate between a first position and a second position. In a first position, the bore 114 is aligned with the inlet 104a and outlet 104b (see FIG. 2a) and in a second position, the bore 114 is misaligned with or perpendicular to the inlet 104a and outlet 104b (see FIGS. 2b-2c). Aligning the bore 114 with the inlet 104a and outlet 104b creates an "open" process flow path through the valve 100. The ball 108 is spaced apart from the inner surface of the housing 102 to form a cavity 112 therein, as shown in FIG. 1 and more particularly in FIGS. 2a-2c. The cavity 112, or "air gap," between the valve seats 110a, 110b and the housing 102 is purged with an inert gas, as described in more detail below. 2b, the ball 108 further includes a key slot 123 that engages with a drive dog 119 of the valve 100. A small opening 125 in the ball 108 adjacent the key slot 123 allows the bore 114 to be in fluid communication with the cavity 112.

[0024] Closely coupled to the housing 102 is a manifold 116 having a flow passage 118 with an inlet 120a and an outlet 120b. A source 124 of pressurized inert gas (e.g., nitrogen, argon, or helium) is connected to the manifold inlet 120a. The outlet 120b of the manifold 116 is in fluid communication with a port 122 in the housing 102, as shown in FIG. 2b. The port 122 passes through the housing 102 and into the cavity 112, thus connecting the flow passage 118 with the cavity 112. In this manner, the manifold 116 allows the cavity 112 to be filled with an inert purge gas. The manifold 116 can be constructed of a variety of solid materials, but is preferably constructed of a material having a high thermal conductivity, such as an aluminum alloy or copper.

[0025] A one-way (non-return) valve 128 is disposed at port 122 to allow inert gas to flow from manifold 116 to cavity 112, but not in the reverse direction. In one embodiment, a spring (not shown) is disposed at port 122 between a ball (not shown) of non-return valve 128 and ball 108 of isolation valve 100. The spring establishes the minimum pressure at which purge gas must enter port 122 and cavity 112.

[0026] Certain process steps require heat to prevent the formation of solid by-products in piping and components downstream from the process tool (e.g., valves, vacuum pumps, etc.). For example, aluminum chloride (Al2Cl6), a condensable solid, is a by-product of an aluminum etching step. In another example, ammonium hexafluorosilicate ((NH4)2SiF6) is a condensation by-product of a silicon nitride chemical vapor deposition process using a fluorine-based chamber clean. Thus, the purge gas supplied to the cavity 112 is preferably heated to minimize condensation within the ball 108 and housing 102 of the valve 100.

[0027] As shown in Figures 2b and 2c, the manifold 116 includes a heater 126 (e.g., a cartridge heater) sized to maintain the temperature of the purge gas so as to minimize condensation within the ball 108 and housing 102 of the valve 100. The heater 126 should maintain the temperature of the purge gas at about 90°C or higher, and preferably at about 120°C or higher. If the manifold 116 is constructed of a material with high thermal conductivity, such as an aluminum alloy or copper, the heater 126 can be located in any convenient location within the manifold 116. However, preferably, the heater 126 is located closer to the manifold outlet 120b than to the manifold inlet 120a. As shown in Figures 2b and 2c, the heater 126 is located within the manifold 116 in close proximity to the flow passage 118 and the manifold outlet 120b.

[0028] In addition, the flow paths 118 preferably optimize heat transfer from the heater 126 to the purge gas flowing through the manifold 116. Thus, in one embodiment, the flow paths 118 are serpentine, where the purge gas must flow back and forth within the manifold 116 before exiting at the port 122. In another embodiment, the flow paths 118 may include baffles to increase turbulence or may be a packed bed to enhance heat transfer.

[0029] As mentioned above, the isolation ball valve 100 has a first position and a second position. FIG. 2a shows the valve 100 in a first "open" position, and FIG. 2b and FIG. 2c show the valve 100 in a second "closed" position. When the valve 100 is "open", process gas enters the valve 100 through the valve inlet 104a, through the bore 114 of the ball 108, and exits through the valve outlet 104b. See FIG. 2a. While process gas flows through the "open" valve 100, heated purge gas flows from the passage 118 of the manifold 116 into the cavity 112, thus heating the ball 108 and the housing 102. From the cavity 112, the heated purge gas flows through the opening 125 into the bore 114 of the ball 108, where the heated purge gas merges with the process gas before exiting the valve 100. Preferably, the pressure of the heated inert gas supplied to cavity 112 is greater than the normal maximum pressure of the process gas stream so that the inert gas can enter the process gas stream.

[0030] 2b and 2c, when the ball valve 100 is "closed" and there are no leaks within the valve 100, heated purge gas will continue to flow into the cavity 112 and bore 114 until the pressure of the purge gas within the valve 100 reaches the pressure of the inert gas source 124. Thus, under normal circumstances, the purge gas will be "dead-headed" by the "closed" valve 100. However, if the isolation valve 100 becomes damaged, for example from a scratched ball or a corroded valve seat and / or O-ring, harmless inert gas will leak out of the cavity 112 through the damaged area, rather than harmful process gas.

[0031] The pressure decay of the heated inert purge gas can be monitored to detect leakage or damage to the isolation valve 100. In one embodiment, as shown in FIG. 3a, a solenoid valve 130 is installed in the inert gas source line 135 upstream from the manifold inlet 120a along with a pressure regulator 132 to regulate the pressure to the manifold 116. A pressure transducer 134 is also placed in the inert gas source line between the manifold inlet 120a and the solenoid valve 130 to monitor the pressure in the manifold 116. A heater 126 is placed in the manifold 116 upstream of a check valve 138. Under normal operating conditions, the pressure of the inert gas should be maintained at a constant, predetermined value.

[0032] As mentioned above, the pressure of the heated inert gas in the cavity 112 is preferably higher than the maximum operating pressure of the process gas stream. The maximum pressure of the process gas stream is dictated by the characteristics of the equipment, such as the abatement system, located downstream of the process chamber. For example, if the abatement system is a burner (see, e.g., U.S. Pat. No. 7,494,633 to Stanton et al. and assigned to Edwards Limited) or a wet scrubber, the pressure of the process gas stream can be about ±5 inH2O (or about ±0.181 psi, or 0.012 Bar). However, if the abatement system is a gas reactor (see, e.g., U.S. Pat. No. 5,538,702 to Smith et al. and U.S. Publication No. 2005 / 0217732 A1 by Martin Ernst Tollner), the pressure of the process gas stream can be as high as about 3.5 psi (i.e., about 0.24 Bar). Therefore, in the former example, the pressure of the purge gas supplied to the valve 100 is about 1 to about 5 psi (i.e., about 0.07 to 0.34 Bar), and in the latter example, the pressure of the purge gas supplied to the valve 100 is about 5 to about 15 psi (i.e., about 0.34 to about 1.03 Bar).

[0033] In operation, the isolation (ball) valve 100 is rotated to the second "closed" position, and shortly after the pressure of the heated inert gas within the valve 100 has had a chance to dead head, the solenoid valve 130 is also "closed." The cavity 112 is then filled with inert gas at a constant pressure, as described in the previous paragraph. Thus, if the valve is leak-free, the pressure of the inert gas measured by the pressure transducer 134 will remain constant. However, if the pressure transducer 134 measures a decay (or decrease) in the pressure of the inert gas, such decay is an indication that the isolation valve 100 is leaking.

[0034] In another embodiment, as shown in FIG. 3b, a flow transducer 136 is disposed in the purge gas line 135 to monitor the flow rate of the purge gas. A pressure regulator 132 is also disposed in the purge gas line 135 upstream of the flow transducer 136. A heater 126 is disposed in the manifold 116 upstream of the check valve 138. Under normal circumstances, the purge gas is deadheaded in the cavity 112, as described above with respect to measuring pressure decay. However, if the flow transducer 136 detects a flow of purge gas, such flow is an indication of a leak in the isolation valve 100. Of note, both the flow rate and pressure decay of the purge gas line 135 can be monitored to detect a failure of the isolation valve 100. To accomplish this, the flow transducer 136 can be installed between the pressure transducer 134 and the manifold inlet 120a.

[0035] In another embodiment, the isolation valve is a diverter valve 200, as shown in FIG. 4a. In this embodiment, the diverter valve 200 has a housing 202 with an inlet 204a (shown in FIG. 5) and two outlets 204b and 204c. The diverter valve 200 also has a rotating ball 208 seated between valve seats 210a, 210b, 210c, and 210d. The valve seats 210a, 210b, 210c, and 210d are centered about the ball 208, as shown in FIG.

[0036] The ball 208 has a bore with two rims 214a, 214b arranged to form a single "L" configuration, as shown in Figure 5. Of note, the bores 214a, 214b are arranged in a plane represented by the horizontal dashed line in Figure 4a. However, the axis of rotation of the ball 208, represented by the vertical dashed line in Figure 4a, is perpendicular to this plane. This perpendicular configuration is necessary to isolate the cavity 212 (described below) from the process fluid flow path through the bores 214a, 214b of the valve 200.

[0037] The ball 208 is rotatable between a first position and a second position. In the first position, the bore 214a is aligned with the inlet 204a and the bore 214b is aligned with the outlet 204b. In this first position, process gas flows from the inlet 204a through the outlet 204b. In the second position, as shown in FIG. 4a, the ball 208 is rotated such that the bore 214b is aligned with the inlet 204a and the bore 214a is aligned with the outlet 204c. In this second position, process gas flows from the inlet 204a through the outlet 204c.

[0038] The ball 208 is spaced apart from the inner surface of the housing, as shown in FIG. 4a, forming a cavity 212 therein. The cavity 212 is purged with an inert gas, as described in more detail below. As shown in FIG. 4a, the ball 208 includes a key slot 223 that engages with the drive dog 219 of the valve 200. A small opening 225 in the ball 208 adjacent the key slot 223 allows the cavity 212 to be in fluid communication with the bores 214a, 214b. The small opening 225 must be sized to provide the necessary pressure drop, thus allowing the cavity 212 to operate at a higher pressure than the process fluid stream.

[0039] As shown in Figures 4a and 4b, closely coupled to the housing 202 is a manifold 216 having a flow passage 218 with an inlet 220a and an outlet 220b. A pressurized source 224 of an inert gas, such as nitrogen, argon, or helium, is connected to the manifold inlet 220a. The outlet 220b of the manifold 216 is in fluid communication with a port 222 in the housing 202, as shown in Figure 4. The port 222 passes through the valve housing 202 into the cavity 212, thus connecting the flow passage 218 with the cavity 212. The manifold 216 thus allows the cavity 212 to be filled with pressurized inert purge gas. The manifold 216 can be constructed of a variety of solid materials, but is preferably constructed of a material with high thermal conductivity, such as an aluminum alloy or copper.

[0040] A one-way (non-return) valve 228 is disposed at port 222 to allow inert gas to flow from manifold 216 to cavity 212, but not in the reverse direction. In one embodiment, a spring (not shown) is disposed at port 222 between ball 229 of non-return valve 228 and ball 208 of isolation valve 200. The spring establishes the minimum pressure at which purge gas must enter port 222 and cavity 212.

[0041] As shown in FIG. 4b, the manifold 216 preferably includes a heater 226, such as a cartridge heater, sized to maintain the temperature of the purge gas so as to minimize condensation within the ball 208 and housing 202 of the valve 200. The heater 226 should maintain the temperature of the purge gas at about 90° C. or higher, and preferably at about 120° C. or higher. If the manifold 216 is constructed of a material having a high thermal conductivity, such as an aluminum alloy or copper, the heater 226 can be located in any convenient location within the manifold 216. However, preferably, the heater 226 is located closer to the manifold outlet 220b than to the manifold inlet 220a. As shown in FIG. 4b, the heater 226 is located within the manifold 216 in close proximity to the flow passage 218 and the manifold outlet 220b.

[0042] In addition, the flow passages 218 preferably optimize heat transfer from the heater 226 to the purge gas flowing through the manifold 216. Thus, in one embodiment, the flow passages 218 are serpentine, as shown in Figure 4a, such that the purge gas must flow back and forth within the manifold 216 before exiting at the port 222. In another embodiment, the flow passages 218 can include baffles to increase turbulence, or may be a packed bed to enhance heat transfer.

[0043] As described above, the isolation diverter valve 200 has a first position and a second position. When the bores 214a, 214b are aligned with the inlet 204a and outlet 204b, respectively, process gas enters the valve 200 through the inlet 204a, passes through the bores 214a, 214b in the ball 208, and exits through the outlet 204b. While the process gas flows through the bores 214a, 214b, heated purge gas flows from the passages 218 in the manifold 216 into the cavity 212, thus heating the ball 208 and the housing 202. From the cavity 212, the heated purge gas flows through the openings 225 into the bores 214a, 214b in the ball 208 where the heated purge gas meets with the process fluid before exiting the valve 200. Preferably, the pressure of the heated inert gas supplied to cavity 212 is greater than the normal maximum pressure of the process gas stream so that the inert gas can enter the process gas stream.

[0044] Similarly, when bores 214a and 214b are aligned with outlet 204c and inlet 204a, respectively, process gas flows into inlet 204a and through outlet 204c. See FIG. 4a. As in the first position, heated inert purge gas flows into bores 214a, 214b and combines with the process fluid. Additionally, the pressure of the inert purge gas is preferably higher than the operating pressure of the process gas.

[0045] Thus, during operation, when the valve 200 is in either the first or second position, heated inert purge gas flows constantly into the cavity and bores 214a, 214b. As described above, the port 222 is sized to allow the pressure of the purge gas to exceed the pressure of the process gas and control the flow of the purge gas into the bores 214a, 214b. Should the valve 200 fail, for example from erosion of the valve seat, the flow rate of the inert purge gas will increase. Thus, using the same configuration as shown in FIG. 3b, a flow transducer can be placed in the purge gas line to monitor the flow rate of the purge gas. If the flow transducer detects an increase in the relative flow rate, this is considered to be an indication of a valve failure.

[0046] The wetted components of the isolation valves 100, 200, such as the housing, balls 108, 208, valve seats 110a, 110b, etc., must be compatible with gases such as fluorine, chlorine, hydrogen bromide, etc., used in the manufacturing processes of semiconductors, flat panel displays, and solar panels. Similarly, the wetted components of the check valves 128, 228, such as the ball 229, springs (not shown), washers (not shown), and sealing rings (not shown), must be compatible with the aforementioned gases. The balls 108, 208, and balls 229 are preferably made of stainless steel (e.g., 304L, 316L, etc.) that are corrosion resistant to the aforementioned gases. The springs (not shown) are preferably made of high nickel content alloys or mnemonic materials such as those manufactured by Incoralloy. The washers and sealing rings (not shown) are preferably made of stainless steel (304L, 316L, etc.), Hastelloy, Viton®, or Karez®. Additionally, the manifold 116 can be made of a relatively inexpensive material such as aluminum.

[0047] Also provided is a system 300 having an isolation valve 100, 200 according to the invention. Figure 6A shows a system 300 according to the invention. The system 300 has redundant abatement systems 302a, 302b for receiving exhaust 304 from one or more vacuum pumps 306 connected to an outlet 307 of a process chamber 308. The exhaust lines 304 tees into each abatement system 302a, 302b, and in the embodiment shown in Figure 6a, an isolation valve 100 is provided in each line of the tee. In another embodiment 301 shown in Figure 6b, a diversion valve 200 according to the invention is provided in the tee upstream of the abatement systems 302a, 302b. In both embodiments 300, 301, the diversion valves 100, 200 are constructed and function as described above.

[0048] The present invention as described above and shown in the embodiments of Figures 1-6b provides cost-effective redundancy and enhanced safety in semiconductor, solar panel and flat panel display processes. It is expected that other embodiments and modifications of the present invention will be readily apparent to those skilled in the art in light of the foregoing description, and such embodiments and modifications are likewise intended to be included within the scope of the present invention as defined in the appended claims. [Explanation of symbols]

[0049] 100 Ball valve 102 Housing 104a Entrance 104b Exit 108 Ball 110a valve seat 110b valve seat 112 Cavity 114 Boa 116 Manifold 118 Channel 119 Driving Dog 120a Manifold inlet 120b Manifold outlet 122 port 123 Key Slot 124 Inert Gas Source 125 Opening 126 Heater 128 One-way valve 130 Solenoid valve 132 Pressure Regulator 134 Pressure Transducer 135 Inert Gas Source Line 136 Flow Transducer 138 Check valve 200 Diverter valve 202 Housing 204a Entrance 204b Exit 204c exit 208 Ball 210a-d Valve seat 212 Cavity 214a Boarlim 214b Boarlim 216 Manifold 218 Channel 219 Driving Dog 220a Entrance 220b exit 222 Port 223 Key Slot 224 Inert Gas Source 225 Opening 226 Heater 228 One-way valve 229 Ball 300 Systems 302a Abatement System 302b Abatement Systems 304 Exhaust port 306 Vacuum Pump 307 Exit 308 Process Chamber

Claims

1. A valve, a housing having at least one inlet and at least one outlet; a valve member disposed within the housing and movable, in use, between a first position and a second position to control fluid flow from an inlet to an outlet of the valve; at least two spaced apart valve seats against which the valve member is seated to define a cavity bounded by the valve seats, an outer surface of the valve member, and an inner surface of the housing; a first conduit extending between an exterior of the housing and the cavity; a second conduit extending between the cavity and the bore of the valve member, such that in use a purge gas can be introduced into the cavity and the bore through the first and second conduits; the valve member is rotatable between the first position and the second position such that in the first position the bore is aligned with the inlet and the outlet and when the valve member is in the second position purge gas is deadheaded. A valve characterized by:

2. A valve, a housing having at least one inlet and at least two outlets; a valve member disposed within the housing and movable in use between a first position and a second position to control fluid flow from an inlet to an outlet of the valve, the valve member being rotatable between the first position and the second position such that in the first position a bore is aligned with the inlet and the first outlet, and in the second position a bore is aligned with the inlet and the second outlet; at least three spaced apart valve seats against which the valve member is seated to define a cavity bounded by the valve seats, an outer surface of the valve member, and an inner surface of the housing; a first conduit extending between an exterior of the housing and the cavity; and a second conduit extending between the cavity and the bore of the valve member, wherein in use a purge gas can be introduced into the cavity and the bore through the first and second conduits.

3. 3. A valve as claimed in claim 1 or claim 2, in which a pressurised purge gas can be introduced into the cavity and the bore.

4. 4. The valve of claim 1, further comprising an anti-return valve for inhibiting or preventing purge gas from exiting the housing through the first conduit, preferably wherein the anti-return valve comprises a spring manufactured from an alloy having a high nickel content.

5. 5. A valve as claimed in any one of claims 1 to 4, further comprising a manifold through which, in use, purge gas is introduced from outside the housing into a purge gas conduit, preferably further comprising a heater to heat the purge gas within the manifold before it enters the cavity, preferably the heater comprising a cartridge heater and / or the heater sized to minimise condensation within the cavity.

6. 6. The valve of claim 5, further comprising a purge gas supply connected to an inlet of the manifold; and / or the manifold comprises a means for increasing turbulence of the purge gas flowing therethrough; and / or the manifold comprises a tortuous path for the purge gas flowing therethrough; and / or the manifold comprises a flow path for the purge gas flowing therethrough, the flow path including a baffle; and / or the manifold comprises a flow path for the purge gas flowing therethrough, the flow path including a filler material; and / or a purge gas supply connected to an inlet of the manifold.

7. 7. A valve as claimed in any one of claims 1 to 6, further comprising means for monitoring the pressure or flow of the purge gas in the cavity and / or in the first conduit and / or in the second conduit and / or in the manifold.

8. 8. The valve of claim 7, further comprising means for monitoring the pressure or flow of the purge gas in the purge gas supply, preferably the means for monitoring the pressure of the purge gas comprises a pressure transducer.

9. 9. The valve of claim 8, wherein the pressure transducer is disposed within the purge gas supply, and a pressure regulator is provided upstream of the pressure transducer along with a valve for isolating purge gas within the cavity and the manifold, and the pressure transducer is adapted to monitor the pressure of the isolated purge gas.

10. A valve as claimed in any one of claims 7 to 9, wherein the means for monitoring the flow of purge gas comprises a flow transducer.

11. The valve of claim 10 , wherein the flow transducer is disposed in the purge gas supply to monitor a flow rate of the purge gas.

12. A valve according to any preceding claim, wherein the wetted components are compatible with a gas selected from the group consisting of fluorine, chlorine and hydrogen bromide.

13. A vacuum pump having an exhaust port and a pair of abatement systems connected to the exhaust port in a T-shape, wherein the valve according to any one of claims 1 to 12 is disposed upstream of each of the abatement systems. A system characterized by:

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