WO2006082367A1

WO2006082367A1 - Trap device

Info

Publication number: WO2006082367A1
Application number: PCT/GB2006/000230
Authority: WO
Inventors: David Engerran
Original assignee: Edwards Limited
Priority date: 2005-02-02
Filing date: 2006-01-25
Publication date: 2006-08-10
Also published as: TWI368533B; TW200631643A; GB0502148D0

Abstract

A trap device (18) is described for removing particulates from a gas stream drawn from an enclosure by a vacuum pump. The trap comprises a casing (28) having an inlet (16) connectable to the enclosure for receiving the gas stream therefrom and an outlet (20) connectable to the vacuum pump for exhausting the gas stream from the casing. A cartridge (36) removably insertable into the casing (28) has an inlet through which the gas stream enters the cartridge and an outlet through which the gas stream leaves the cartridge, the cartridge housing at least one filter element for removing particulates from the gas stream passing through the cartridge.

Description

TRAP DEVICE

The present invention relates to a trap device, and in particular to a trap device for removing particulates from a gas stream drawn from an enclosure by a vacuum pump.

During processes such as chemical vapour deposition processing, deposition gases are supplied to a process chamber to form a deposition layer on the surface of a substrate, and are subsequently pumped from the process chamber using a pumping arrangement comprising one or more vacuum pumps. A trap device is typically provided between the outlet from the process chamber and the pumping arrangement to remove particulates from the gas stream drawn from the process chamber. If allowed to freely pass to the inlet of a vacuum pump, such particulates can accumulate within the pump and effectively fill the vacant running clearance between the rotor and stator elements of the pump, leading to a loss of pumping performance and ultimately pump failure.

Such an inlet trap device requires a balance between efficiency (that is, the proportion of powder entering the trap which is retained therein) and the service interval for the trap. Existing designs for inlet trap devices are either inefficient and thus allow an undesirably large amount of powder to enter the pump, or block too quickly and thus require frequent servicing. For example, a cyclone design is relatively inefficient as fine powder remains entrained within the gas stream and is therefore carried into the vacuum pump. In contrast, designs including standard filter elements through which the gas stream passes tend to block quickly to cause a significant reduction in pump performance and thus require frequent cleaning.

It is an aim of at least a preferred embodiment of the invention to provide a trap device connectable to the inlet of a vacuum pump which can efficiently trap particulates within a gas stream passing through the trap and which does not significantly reduce performance of the vacuum pump as a filter element of the trap becomes blocked. In a first aspect, the present invention provides a trap device for removing particulates from a gas stream drawn from an enclosure by a vacuum pump, the trap comprising a casing having an inlet for receiving the gas stream and an outlet for exhausting the gas stream from the casing, and a cartridge removably insertable into the casing and comprising at least one filter element having surfaces defining therebetween a tortuous flow passage for a gas stream passing through the device, whereby particulates in the gas stream are urged into contact with the filter element.

By arranging the filter element(s) to define a tortuous passage, for example, a spiral or sinusoidal passage, for a gas stream passing through the trap, the gas stream is forced to repeatedly change direction as it passes from the inlet towards the outlet of the casing. Each time the gas stream changes direction, particulates within the gas stream are thrown outwards from the gas stream and trapped by a filter element. The filter element(s) thus become progressively blocked from the inlet to the outlet of the casing. In the event that the filter element(s) become completely blocked, the gas stream is still able to flow through the casing to a downstream vacuum pump, albeit without any filtering of the particulates contained within, and so that pumping performance is not lost.

Furthermore, by providing the filter element within a cartridge that can be readily removed from the casing of the trap for cleaning or replacement, the speed and ease at which the trap is periodically serviced can be markedly improved, and the level of user exposure to the particulates retained by the filter element during servicing can be minimised. For example, the particulates can be conveniently tipped out from the cartridge and the cartridge replaced without requiring intricate or prolonged cleaning by the user.

Means may be provided for monitoring the amount of particulates removed from the gas stream by said at least one filter element. In the preferred embodiment, the monitoring means comprises a load cell or other device for monitoring the weight of the cartridge. An output from the load cell may be received by a controller for generates an alert depending on the output from the load cell. The load cell may be conveniently located within the casing, so that the cartridge is located on the load cell when it is fully inserted into the casing.

The cartridge preferably comprises a casing housing said at least one filter element, the cartridge casing preferably having a removable lid. At least one filter element may be mounted on the lid so, as the lid is removed from the cartridge, the filter element is exposed to facilitate cleaning thereof. The cartridge casing preferably comprises a substantially cylindrical outer wall or sidewall, which preferably comprises an inlet for receiving the gas stream from the inlet of the casing. A base of the cartridge casing preferably comprises an outlet for conveying the gas stream from the cartridge to the outlet of the casing.

In one embodiment, said at least one filter element comprises a plurality of substantially concentric, cylindrical filter elements defining a sinusoidal flow passage. Therefore, in a second aspect the present invention provides a trap device for removing particulates from a gas stream drawn from an enclosure by a vacuum pump, the device comprising a casing having an inlet for receiving.the gas, stream and an outlet for exhausting the gas stream from the casing, and a cartridge removably insertable into the casing and comprising a plurality of substantially concentric, cylindrical filter elements defining a sinusoidal flow passage for a gas stream passing through the device, whereby particulates in the gas stream are urged into contact with the filter elements.

In a third aspect the present invention provides a trap device for removing particulates from a gas stream drawn from an enclosure by a vacuum pump, the device comprising a casing having an inlet for receiving the gas stream and an outlet for exhausting the gas stream from the casing, and a cartridge removably insertable into the casing, the cartridge having an inlet through which the gas stream enters the cartridge and an outlet through which the gas stream leaves the cartridge, the cartridge housing at least one filter element for removing particulates from the gas stream passing through the cartridge.

The present invention also provides a vacuum pumping arrangement comprising a vacuum pump having an inlet for receiving a gas stream and an outlet for exhausting a pumped gas stream, and a trap device according to one of the aforementioned aspects of the invention having an outlet connected to the inlet of the vacuum pump.

Features described above in connection with the first aspect of the invention are equally applicable to the second and third aspects, and vice versa.

Preferred features of the present invention will now be described with reference to the accompanying drawing, in which

Figure 1 illustrates schematically an example of a processing system;

Figure 2 is a perspective view of first embodiment of a trap device suitable for use in the system of Figured , with part of the casing removed to reveal the cartridge;

Figure 3 is a side view of the cartridge shown in Figure 2;

Figure 4 is a cross-section taken along line A-A of Figure 3;

Figure 5 is a cross-section taken along line B-B in Figure 4;

Figure 6 is a perspective view of a second embodiment of a trap device suitable for use in the system of Figure 1 , with part of the casing removed to reveal the cartridge;

Figure 7 is a side view of the cartridge shown in Figure 6; Figure 8 is a cross-section taken along line A-A of Figure 7;

Figure 9 is a simplified cross-section illustrating the casing of the trap device of Figure 2 or Figure 6 mounted on a vacuum pump; and

Figure 10 is a similar view to Figure 9, with a cartridge inserted into the casing.

With reference to Figure 1 , a processing system, for example for semiconductors or flat panel display devices, comprises a process chamber 10 having at least one inlet for receiving one or more process gases, and an outlet 12 for exhausting unconsumed process gases containing by-products from the process conducted within the process chamber 10. The outlet 12 from the process chamber 10 is connected by conduit 14 to the inlet 16 of a trap device 18 for removing particulates from the gas stream exhaust from the process chamber 10. The trap 18 has an outlet 20 connected to the inlet 22 of a vacuum pump 24 for drawing the gas stream from the process chamber 10. The vacuum pump 24 has an exhaust 26 connected to the inlet of a backing pump or to the inlet of a scrubbing device as required.

Figure 2 is a perspective view of a first embodiment of the trap 18. The trap 18 comprises a cylindrical casing 28 having a flanged inlet 16 formed in a sidewall 30 of the casing 28 for connection to the conduit 14, and a flanged outlet 20 formed in an end wall 32 of the casing 28 for connection to the conduit 21. The casing 28 has a mouth 34 for receiving a cartridge 36 removably insertable into the casing 28 for trapping particulates contained in a gas stream passing through the trap 18.

With reference to Figures 3 to 5, the cartridge 36 comprises a cartridge casing, or body, 38 having a cylindrical sidewall 40 and a base 42. A gas inlet 44 to the cartridge 36 is formed in the sidewall 40 of the body 38, and a gas outlet 46 from the cartridge 36 is formed in the base 42 of the body 38. In the embodiment shown in Figures 3 to 5, the gas inlet 44 is in the form of an elongate slot formed in the side wall 40, the slot extending substantially parallel to the longitudinal axis 48 of the cartridge 36 and extending about the longitudinal axis 48 by an angle θ, where θ is preferably between 10° and 30°. In the illustrated example, θ is 20°. The gas outlet 46 is substantially co-axial with the longitudinal axis 48 of the casing 38, and is positioned such that when the cartridge 36 is inserted in the casing 28, the gas outlet 46 from the cartridge 36 is aligned with, preferably coaxial with, the outlet 20 from the casing 28.

The body 38 of the cartridge 36 is selectively closed by a lid 50. In this embodiment the lid 50 is mounted on the body 38 by the insertion of pins 52 located on the lid 50 into hook-shaped slots 54 formed in the body 38.

Alternatively, the lid 50 may be hinged to the body 38 of the cartridge 36 or otherwise attached to the body 38 so that the lid 50 is moveable relative to the body 38, or the lid 50 may be attached to the casing 28.

The cartridge 36 contains at least one filter element 54 for removing particulates from the gas stream passing through the trap 18. In this first embodiment, the cartridge contains a single filter element 54 mounted in the body 38 of the cartridge 36 and in the form of a spiral defining a tortuous flow passage 56 between the convoluted surfaces 58, 60 of the filter element 54 for the gas stream entering the cartridge 36. Alternatively, the flow passage 56 may be defined by a plurality of substantially semi-circular filter elements 54 of respective radii. In this case, some of the filter elements 54 may be mounted on the base 42 of the body, and some of the filter elements 54 may be mounted on the inner surface 62 of the lid 50 of the cartridge 36. The, or each, filter element 54 may be formed from any suitable material, for example porous stainless steel, or pleated or corrugated filter media, again preferably formed from stainless steel, and preferably comprises a plurality of layers each of a respective mesh size. In the illustrated example, the inner surface 58 of the filter element 54 is provided by a layer having a relatively large mesh size (for example, 80 mesh) to allow particulates to enter the filter element 54 and become trapped therein, and the outer surface 60 of the filter element is provided by a layer having a relatively small mesh size (for example 40 mesh) to prevent smaller particulates from passing through the filter element 54 to another part of the flow passage 56.

In use, a gas stream, which is drawn from the process chamber 10 by the vacuum pump 24, enters the trap 18 through the inlet 16 formed in the casing 28. The gas stream passes around the trap 18 between the sidewall 30 of the casing 28 and the sidewall 40 of the cartridge 36, and enters the body 38 of the cartridge 36 through the inlet 44. Within the body 38 of the cartridge 36, the gas stream is conveyed along the spiral flow passage 56 defined by the filter element 54 to the outlet 46 of the cartridge 36, from which the gas stream passes through the outlet 20 of the casing 28 towards the inlet 22 of the vacuum pump 24.

As the gas stream passes along the flow passage 56 within the cartridge 36, it is forced to continually change direction by the filter element 54 as it spirals inwardly towards the outlet 46. Particulates within the gas stream are thrown outwardly from the gas stream and enter the filter element 54, wherein they become trapped and unable to return to the gas stream. During use, the filter element 54 will become increasingly blocked from the end 64 of the filter element 54 proximate the inlet 44 of the cartridge 36 to the end 66 of the filter element 54 proximate the outlet 46 of the cartridge 36. Even when the filter element 54 has become fully blocked, the gas passage 56 remains unrestricted, and so there is no loss of performance of the vacuum pump 24.

When the filter element 54 becomes fully blocked, more preferably a period of time before the filter element 54 becomes fully blocked, the cartridge 36 is removed from the casing 28 and the lid 50 removed to allow the cartridge 3β to be emptied of particulates, for example, by agitating the cartridge 36 to dislodge the particulates from the filter element 54 and tipping the dislodged particulates from the cartridge 36. The filter element 54 may be replaced by a fresh filter element during this servicing interval. The lid 50 is then replaced on the thus-emptied cartridge 36, which is subsequently re-inserted into the casing 28 for re-use. Figure 6 is a perspective view of a second embodiment of the trap 118. The casing 28 of the trap 118 is the same as the casing 28 of the trap 18 illustrated in Figure 2, and therefore will not be described in detail with reference to Figure 6. With reference also to Figures 7 and 8, the cartridge 136 of the trap 118 of Figure 6 comprises a cartridge casing, or body, 138 having a cylindrical sidewall 140 and a base 142. A gas inlet 144 to the cartridge 136 is formed in the sidewall 140 of the body 138, and a gas outlet 146 from the cartridge 136 is formed in the base 142 of the body 138. In this second embodiment, the gas inlet 144 is in the form of an elongate slot formed in the sidewall 140, the slot extending about the longitudinal axis 148 of the cartridge 136 by an angle θ, where θ is preferably between 70° and 110°. In the illustrated example, θ is 90°. Similar to the first embodiment, the gas outlet 146 is substantially co-axial with the longitudinal axis 148 of the casing 138, and is positioned such that when the cartridge 136 is inserted in the casing 28, the gas outlet 146 from the cartridge 136 is aligned with, preferably co-axial with, the outlet 20 from the casing 28.

Similar to the first embodiment, the body 138 of the cartridge 136 is selectively closed by a lid 150. In this embodiment the lid 150 is also mounted on the body 138 by the insertion of pins located on the lid.,,150 into- hook-shaped slots formed in the body 138.

The cartridge 136 contains a plurality of filter elements for removing particulates from the gas stream passing through the trap 118. In this second embodiment, as illustrated the cartridge contains five cylindrical, substantially concentric filter elements 154, 156, 158, 160, 162 having different respective diameters, although any suitable number of filter elements may be provided. The cylindrical filter elements may be formed from any suitable material, for example one or more layers of porous stainless steel. Alternatively, each cylindrical filter element may be formed from pleated or corrugated filter media, again preferably formed from stainless steel. This filter media may comprise a plurality of layers, with the internal layer having a larger mesh size (for example 80 mesh) than the outer layer (having, for example, a mesh size of 40). Where pleated filter media is used, the ends of the cylinders may be locally strengthened, for example by a metal ring spot welded to the filter media. An advantage associated with pleated filter elements is a greater surface area for the capture of particulates.

In this second embodiment, a number of the filter elements are mounted on the base 142 of the cartridge 136, and a number are mounted on the lid 150 of the cartridge. Alternatively, all of the filter elements may be mounted on one of the base 142 and the lid 150 of the cartridge 136 as desired. In the illustrated embodiment, the filter elements 154, 158, 162 are mounted in the base 142 of the cartridge 136. The outermost filter element 154 is provided with an aperture 163 of substantially the same size and shape as the inlet 144 of the cartridge 136, the outermost filter element 154 being mounted on the base 142 so that this aperture 163 is aligned with the inlet 144. Alternatively, the outer filter element 154 may be welded to the sidewall 140 of the cartridge 136.

Grooves may be provided on the upper surface 164 of the base 142 to facilitate correct location of these filter elements 154, 158, 162. The filter elements 156, 160 are mounted in the lid 150 of the cartridge 136. Grooves may also be provided on the lower surface 166 of a mounting ring 168 attached to the lower surface 170 of the lid 150 to facilitate correct location of these filter elements 156, 160. The length of the filter elements is such that, when the lid 150 is mounted on the body 138 of the cartridge 136, the filter elements define a tortuous, serpentine gas flow passage 172 extending from the inlet 144 to the outlet 146 of the cartridge 136 and between the surfaces of the filter elements.

In use, a gas stream, which is drawn from the process chamber 10 by the vacuum pump 24, enters the trap 118 through the inlet 16 formed in the casing 28. The gas stream passes around the trap 118 between the sidewall 30 of the casing 28 and the sidewall 140 of the cartridge 136, and enters the body 138 of the cartridge 136 through the inlet 144 and aperture 163. Within the body 138 of the cartridge 136, the gas stream is conveyed along the serpentine flow passage 172 to the outlet 146 of the cartridge 136, from which the gas stream passes through the outlet 20 of the casing 28 towards the inlet 22 of the vacuum pump 24. As the gas stream passes along the flow passage 172 within the cartridge 136, it is forced to continually change direction by the filter elements 154, 156, 158, 160,162 as it moves radially inwardly towards the outlet 146. Particulates within the gas stream are thrown outwardly from the gas stream and enter the filter elements, wherein they become trapped and unable to return to the gas stream. Similar to the first embodiment, during use the filter elements will become increasingly blocked from the inlet 144 of the cartridge 136 to the outlet 146 of the cartridge 136, and even when the filter elements have become fully blocked, the flow passage 172 remains unrestricted, and so there is no loss of performance of the vacuum pump 24.

Again, when the filter elements become fully blocked, more preferably a period of time before the filter elements become fully blocked, the cartridge 136 is removed from the casing 28 and the lid 150 removed to allow the cartridge 136 to be emptied of particulates, for example, by agitating the cartridge 136 to dislodge the particulates from the filter elements 154, 158, 162 and tipping the dislodged particulates from the cartridge 36. The filter elements 156, 160 mounted on the lid 150 may be readily cleaned during this servicing, and any of the filter elements ■■■ may be replaced by a fresh filter element. The lid 150 is.then replaced on the thus-emptied cartridge 136, which is subsequently re-inserted into the casing 28 for re-use.

The servicing of a trap 18 (or 118) may be timed according to the processes taking place in the process chamber 10 so as not to disrupt the processing within the chamber. For example, the servicing of the trap may coincide with servicing of the process chamber 10, or otherwise performed when no gases are being drawn from the process chamber 10 by the vacuum pump 24. Alternatively, the servicing of the trap may be time according to the amount of particulates removed from the gas stream by the trap. For example, as illustrated in Figures 9 and 10, a load cell 200 may be provided within the casing 28 such that, when the cartridge 36 is fully inserted in the casing 20, the cartridge 36 rests upon the load cell 200. A controller (not shown) may be provided to monitor signals output from the load cell 200 indicative of the increase in weight of the cartridge 36 (due to the trapping thereby of particulates within a gas stream passing therethrough) and to generate an alert when the cartridge 36 needs to be emptied.

Claims

1. A trap device for removing particulates from a gas stream drawn from an enclosure by a vacuum pump, the device comprising a casing having an inlet for receiving the gas stream and an outlet for exhausting the gas stream from the casing, and a cartridge removably insertable into the casing and comprising at least one filter element having surfaces defining therebetween a tortuous flow passage for a gas stream passing through the device, whereby particulates in the gas stream are urged into contact with the filter element.

2. A trap device according to Claim 1 , comprising means for monitoring the amount of particulates removed from the gas stream by said at least one filter element.

3. A trap device according to Claim 2, wherein the monitoring means comprises means for monitoring the weight of the cartridge.

4. A trap device according to Claim 3, wherein the monitoring means comprises a load cell.

5. A trap device according to any of Claims 2 to 4, wherein the monitoring means is located within the casing.

6. A trap device according to any preceding claim, wherein the cartridge comprises a cartridge casing housing said at least one filter element.

7. A trap device according to Claim 6, wherein the cartridge casing has a removable portion.

8. A trap device according to Claim 7, wherein at least one filter element is mounted on the removable portion.

9. A trap device according to any of Claims 6 to 8, wherein said cartridge casing comprises a substantially cylindrical outer wall.

10. A trap device according to Claim 9, wherein the outer wall of the cartridge casing comprises an inlet for receiving the gas stream from the inlet of the casing.

11. A trap device according to any of Claims 6 to 10, wherein the cartridge casing comprises a base having an outlet for conveying the gas stream from the cartridge to the outlet of the casing.

12. A trap device according to any preceding claim, wherein said at least one filter element defines a spiral flow passage for the gas stream.

13. A trap device according to any of Claims 1 to 11 , wherein said at least one filter element defines a sinusoidal flow passage for the gas stream.

14. A trap device according to Claim 13, wherein said at least one filter element comprises a plurality of substantially concentric, cylindrical filter elements defining said sinusoidal flow passage.

15. A trap device for removing particulates from a gas stream drawn from an enclosure by a vacuum pump, the device comprising a casing having an inlet for receiving the gas stream and an outlet for exhausting the gas stream from the casing, and a cartridge removably insertable into the casing and comprising a plurality of substantially concentric, cylindrical filter elements defining a sinusoidal flow passage for a gas stream passing through the device, whereby particulates in the gas stream are urged into contact with the filter elements.

16. A trap device according to any preceding claim, wherein said at least one filter element comprises a plurality of layers each having a respective mesh size.

17. A trap device according to Claim 16, wherein each layer comprises a pleated or corrugated filter element.

18. A trap device according to any preceding claim, wherein the inlet is located in a side wall of the casing and the outlet is located in an end wall of the casing.

19. A trap device for removing particulates from a gas stream drawn from an enclosure by a vacuum pump, the device comprising a casing having an inlet for receiving the gas stream and an outlet for exhausting the gas stream from the casing, and a cartridge removably insertable into the casing, the cartridge having an inlet - through which the gas stream enters the cartridge and an outlet through which the gas stream leaves the cartridge, the cartridge housing at least one filter element for removing particulates from the gas stream passing through the cartridge.

20. A trap device according to Claim 19, comprising means for monitoring the amount of particulates removed from the gas stream by said at least one filter element.

21. A trap device according to Claim 20, wherein the monitoring means comprises means for monitoring the weight of the cartridge.

22. A trap device according to Claim 21 , wherein the monitoring means comprises a load cell.

23. A trap device according to any of Claims 20 to 22, wherein the monitoring means is located within the casing.

24. A trap device according to any of Claims 19 to 23, wherein the cartridge comprises a cartridge casing housing said at least one filter element.

25. A trap device according to Claim 24, wherein the cartridge casing has a removable portion.

26. A trap device according to Claim 25, wherein at least one filter element is mounted on the removable portion.

27. A trap device according to any of Claims 19 to 26, wherein the inlet is located in a side wall of the casing and the outlet is located in an end wall of the, casing.

28. A trap device according to any of Claims 19 to 27, wherein said at least one filter element has surfaces defining therebetween a tortuous flow passage for a gas stream passing through the device, whereby particulates in the gas stream are urged into contact with said at least one filter element.

29. A trap device according to Claim 28, wherein said at least one filter element defines a spiral flow passage for the gas stream.

30. A trap device according to Claim 28, wherein said at least one filter element defines a sinusoidal flow passage for the gas stream.

31. A trap device according to Claim 30, wherein said at least one filter element comprises a plurality of substantially concentric, cylindrical filter elements defining said sinusoidal flow passage.

32. A vacuum pumping arrangement comprising a vacuum pump having an inlet for receiving a gas stream and an outlet for exhausting a pumped gas stream, and a trap device according to any preceding claim having an outlet connected to the inlet of the vacuum pump.

33. A vacuum pumping arrangement according to Claim 32, wherein the trap device is mounted on the vacuum pump.