AN AIR TREATMENT METHOD AND A SYSTEM ARRANGED FOR TREATING AIR IN A CLEAN ROOM

Abstract

The present invention relates to an air treatment method and a system (1a-1f) arranged for treating an air flow (3) to be entered into a semiconductor clean room. Said air flow (3) comprises at least one vapour phase compound, and wherein the air flow (3) is subjected to at least one first treatment process arranged for reducing the concentration of the at least one vapour phase compound in the treated air flow below a predefined threshold, and wherein said first treatment process comprises subjecting the air flow to at least one photooxidation step.

Claims

1-27. (canceled)

28. An air treatment method arranged for treating an air flow (3) to be entered into a semiconductor clean room, said air flow comprises at least one vapour phase compound, and wherein the air flow is subjected to at least one first treatment process arranged for reducing the concentration of the at least one vapour phase compound in the treated air flow below a predefined threshold, and wherein the first treatment process comprises the steps of: passing the air flow (3) through at least one catalytic zone (2), and subjecting the air flow to at least one photooxidation step, and wherein the air flow (3) is passed through the at least one catalytic zone (2) before entering the at least one photooxidation step.

29. The air treatment method according to claim 28, wherein the threshold for the at least one vapour phase compound in the air flow is below 500 ppt, preferably below 300 ppt, and even more preferred below 100 ppt.

30. The air treatment method according to 28, wherein decomposition of the at least one vapour phase compound provides one or more decomposition compounds, and wherein the treatment process comprises several consecutively arranged photooxidation steps, such that decomposition products generated in a first photooxidation steps is further decomposed in one or more subsequent photooxidation steps, until the only decomposition products remaining in the air flow is carbon dioxide and water.

31. The air treatment method according to any of the 28, wherein the treatment process comprises one or more second treatment processes arranged for removing one or more decomposition compounds, e.g. water, from the air flow before said air flow enters into the semiconductor clean room.

32. The air treatment method according 28, wherein the at least one first vapour phase compound is an organic compound selected from VOC's, amines, silanes, phospates, siloxanes, halocarbons and organometallic compounds.

33. The air treatment method according to 28, wherein the least one vapour phase compound is an amine and the catalytic zone (2) comprises a deNO.sub.x-catalyst and an oxidation catalyst.

34. The method according to 28, wherein the photooxidation step comprises an UV-O.sub.3 photooxidation process.

35. A semiconductor clean room air treatment system (1a-1f), said system comprises at least one photooxidation zone (6) and at least one catalytic zone (2), whereby the air treatment system is arranged such that the concentration of the at least one vapour phase compound in an air flow is reduced below a predefined threshold, and wherein the at least one catalytic zone (2) is arranged before the at least one photooxidation zone (6), seen in the flow direction.

36. The system (1a-1f) according to claim 35, wherein the predefined threshold of the at least one vapour phase compound in the air flow is below 500 ppt, preferably below 300 ppt, and even more preferred below 100 ppt.

37. The system (1a-1f) according to claim 35, wherein said system comprises several consecutively arranged photooxidation zones.

38. The system (1a-1f) according to claim 35, wherein said system comprises one or more second treatment zones arranged for removing one or more by-products and/or particle contamination from the air flow, before said air flow enters the semiconductor clean room.

39. The system (1c-1f) according to 35, wherein the catalytic zone (2) comprises a deNO.sub.x-catalyst and an oxidation catalyst and wherein the air flow to be treated comprises at least one amine.

40. The system (1c-1f) according to 35, wherein the catalytic zone (2) is operated at a temperature between 80° C. and 225° C.

41. The system (1d) according to claim 40, wherein the system further comprises a conditioning zone arranged before the catalytic zone (2), and wherein said conditioning zone comprises a heating unit arranged for heating the air flow (3) to and/or maintaining the air flow (3) at a temperature of between 80° C. and 225° C.

42. The system (1a-1f) according to claim 35, wherein the at least one photooxidation zone (6) comprises at least one UV-lamp operating in an UV-spectrum arranged for generate ozone, and at least one UV-lamp operating in an UV-spectrum arranged generating hydroxylradicals.

43. The system (1a-1f) according to claim 35, wherein said photooxidation zone (6) comprises at least one excimer lamp arranged for emitting a wavelength in the range between 126 nm and 240 nm, preferably about 172 nm.

44. The system (1a-1f) according to claim 43, wherein the photooxidation zone (6) is arranged such that at least 90% of the air flow (5) will be exposed to irradiation in said photooxidation zone (6).

45. An air filtering system for use in a semiconductor clean room, said filtering system comprises a semiconductor clean room air treatment system (1a-1f) claim 35 and a second treatment unit (12) arranged for removing particle contamination from said air flow (3) and/or by-products from the air flow (3).

46. A semiconductor clean room comprising the semiconductor clean room air treatment system (1a-1f) according claim 35 and/or the air filtering system.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0112] FIG. 1 shows schematically a first embodiment of an air flow treatment system according to the present invention,

[0113] FIG. 2 shows schematically a second embodiment of an air flow treatment system according to the present invention, and

[0114] FIG. 3 shows schematically a third embodiment of an air flow treatment system according to the present invention.

[0115] FIG. 4 shows schematically a forth embodiment of an air flow treatment system according to the present invention.

[0116] FIG. 5 shows schematically a fifth embodiment of an air flow treatment system according to the present invention.

[0117] FIG. 6 shows schematically a fifth embodiment of an air flow treatment system according to the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

[0118] The invention will be described below with the assumption that the air flow is collected from a semiconductor clean room comprising at least one vapour phase component, e.g. diphenylamine, and that said air flow has to be treated before it is reintroduced into said clean room. However, the origin of the air flow is immaterial to the method and system of the present invention.

[0119] FIG. 1 shows a first simplified embodiment of a air flow treatment system 1a according to the invention. Said system consist of a single photooxidation zone 2. The air flow to be treated 3 comprises one or more vapour phase components and when said air flow is passed through the photooxidation zone 2, the air flow will subjected to a photooxidation step, in which the at least one vapour phase compound are converted/decomposed into carbon dioxide and water, i.e. the photooxidation zone 2 is arranged such that the concentration of the vapour phase compound is reduced below a predefined threshold.

[0120] In the photooxidation zone a number of UV-lamps 4 are installed. Said lamps may e.g. be arranged for either operating in an UV-spectrum which produces ozone, and/or arranged for producing OH-radicals. However said UV-lamps 4 may alternatively (or in addition) be excimer lamps arranged for emitting a wavelength of about 172 nm, as said wavelength is capable of removing substantially all organic compounds e.g. VOC's by means of photolysis. Furthermore said wavelength will also produce the oxidant ozone, that will proceed to oxidise organic contaminants present in the air.

[0121] Thus, in this first embodiment the photooxidation zone 2 eliminate the at least one vapour phase compound from the treated air flow 5, such that the treated air flow 5 safely can be introduced into the semiconductor clean room.

[0122] However, if the decomposition of the at least one vapour phase component in the photooxidation zone results in decomposition products (by-products) other than water and carbon dioxide, the air flow 3 may in a second embodiment 1b, shown in FIG. 2 be subjected to several consecutively arranged photooxidation steps 2, 2′, 2″, such that decomposition products generated in a first photooxidation 2 zone is further decomposed in a subsequent photooxidation 2′ zone, etc., until the only decomposition products remaining is carbon dioxide and water.

[0123] It should be noted that carbon dioxide safely can be submitted into the semiconductor clean room, and if the humidity in the air exceeds the thresholds for a semiconductor clean room, the water can easily be removed from the air flow, e.g. in an second treatment step/zone 7 e.g. a condensation zone, located after the last photooxidation zone 2″, i.e. immediately before the treated air flow 5 enters the semi-conductor clean room. Such an optionally second treatment zone is show in dotted line in FIG. 2.

[0124] In a third embodiment 1c shown in FIG. 3 the system according to the invention further comprises a catalytic zone 9 in which the air flow 3 first is passed over a catalytic unit 10 comprising a deNO.sub.x-catalyst and an oxidation catalyst. The air flow 11 exiting the catalytic zone 9 is then passed though a photooxidation zone 2, arranged after the catalytic zone 9, and in which the first treated air stream 11 is subjected to a photooxidation step, as already discussed in relation to FIGS. 1 and 2. The treated air flow 5 from the photooxidation zone 2, can then be passed into the clean room.

[0125] The system and method shown in FIG. 3 is unique in that when the air flow 3 is passed over the catalytic zone 9, any amines present in said air flow is substantially completely removed. Thus, in the catalytic zone 9 the amine may be either partly or completely converted/decomposed into one or more hydrocarbons e.g. a VOC, that easily can be removed/decomposed in the subsequent photooxidation zone 2. Alternatively, the concentration of amine may be reduced, and the remaining concentration of said amine is completely removed/decomposed in the photooxidation zone 2.

[0126] The catalytic zone is operated at temperatures between 100-225° C., preferably between 125° C. and 200° C. whereby a very effective amine removal is provided. If the temperature is raised above 250° C. the efficiency of the catalytic zone 9 will be significantly reduced, with the risk that amines are left in the air flow 11.

[0127] Since the catalyst unit 10 comprises a deNO.sub.x-catalyst and an oxidation catalyst a significant portion of the VOCs in the air flow 3 will also be removed in the catalytic zone 9. However, the “pre-treatment” of the air flow in the catalytic zone 9 in which the amines are removed, ensures that the subsequent photooxidation process works optimally.

[0128] The method and system according to the present invention thereby provides a very simplified air flow treatment method and system. The system has a compact structure, and can easily can be added to existing workplaces. The system and method further have the advantage that the pressure drop over the system is small and that said system uses much less energy for the removal process compared to the traditional amine/VOC removal systems and methods.

[0129] FIG. 4 shows a forth embodiment 1d of the system according to the invention. Said embodiment adds further details to the embodiment shown in FIGS. 1, 2 and 3, and for like parts the same reference numbers are used.

[0130] In this embodiment the air flow 3 passes through a temperature conditioning zone 12 before it enters the catalytic zone 9. Said conditioning zone 12 is arranged for providing a conditioned air flow 13, i.e. an air flow having a temperature between 80° C. and 225° C., preferably between 125° C. and 200° C., such that when the air flow 13 enters the catalytic zone 9, the conditions for oxidation and accordingly amine and VOC removal are optimal.

[0131] In order to ensure that sufficient oxidant is present in the catalytic unit 10, additional oxidant 14 may optionally be added to the catalytic zone 9. Said oxidant may be secondary air or oxygen. It is however preferred that said oxidant is ozone, since it is possible to shorten the retention time in the catalytic zone 9 and/or use smaller catalytic units 10 due to the strong oxidation capabilities of ozone.

[0132] Said additional oxidant 14 may also be added to the air flow just prior to the catalytic zone 9, e.g. provided in a second gas line connected to an air flow line/pipe.

[0133] In order to ensure that the UV-lamps operate at highest efficiency, a water spray system (not shown) may be installed in the photooxidation zone 2 to increase the relative humidity and/or absolute water content of the first treated gas stream to at least above 90%.

[0134] Even though the residuals from the photooxidation process consist mainly of carbon dioxide and water, it may in some situations, depending on the compounds/compounds in the air flow, be advantageously to subject the air flow exiting the photooxidation process, to a second treatment zone 15, e.g. arranged for removing particle contamination and/or one or more by-product. The second treatment zones may accordingly be a condensation zone and/or a scrubber, and/or an electrostatic precipitation, mechanical filtration (HEPA, ULPA etc), non-thermal plasma processes etc. or other conventional means for removing particular matters from an air flow. A person skilled in the art, will understand that there may be more than one second treatment zone. Even though the second treatment zone is located after the photooxidation zone in FIG. 4, said means for removing e.g. particular matters from the air flow could also be placed before the catalytic zone, or both before and after.

[0135] Photooxidation is a destruction process and some of the resultant by-products e.g. water, and inert salts, cannot be emitted into the semiconductor clean room. In an alternative embodiment, the second treatment zone 15 may be arranged for removing said by-products from the first and/or second treated air stream. A person skilled in the art will understand that several kinds of further treatment zones may be provided, e.g. both for removing particular matter and/or by-products.

[0136] In order to ensure that the amine is complete removed from the air flow 3 before said air flow is introduced into the semiconductor clean room, the air flow may pass though more than one catalytic zone 9 before entering the photooxidation zone 2, and/or the air flow 3 may pass though more than one photooxidation zone 2 in order to ensure that any residues of the amine is not introduced into the semiconductor clean room.

[0137] In the embodiment shown in FIG. 5 the air treatment system le comprises three catalytic zones, 9a,9b,9c and the air flow 3 passes all three before entering the photooxidation zone 2. Thus, if the concentration of the amine is not reduced sufficiently in a first catalytic zone 9a, i.e. the remaining concentration of said compound can either not be completely removed in the photooxidation process or said compound will still influence the photooxidation process negatively, the concentration of the amine in the air flows 3′, 3″ can be further reduced in the two subsequent catalytic zones 9b and 9c, respectively. At this stage, the concentration of the amine is reduced to an acceptable level, i.e. below a predetermined threshold in which the amine is either completely removed, i.e. converted into one or more hydrocarbons, and/or the concentration of said amine is so low that it can be removed in the subsequent photooxidation step(s).

[0138] The three catalytic zones may either be identical i.e. they are arranged for reducing the concentration of the same vapour phase component (e.g. diphenylamine), and/or the three catalytic zones may be different, i.e. they may be arranged for reducing the concentration of three different compounds (e.g. diphenylamine; tricresyl phosphate and vinyltris(methylethylketoxime)-silane.

[0139] The number of catalytic zones 9a,9b,9c the air flow 3 passes though may vary depending on the content of the relevant air flow and the efficiency of said catalytic zones, but there may be e.g. two, three, four or even higher numbers of catalytic zones if required, the only requirement being that the concentration of the at least one vapour phase compound in the treated air steam 5 is so low that it can be introduced into the semiconductor clean room without compromising the semiconductor clean room, i.e. the criteria's for the semiconductor clean room are meet.

[0140] A further embodiment if according to the invention is shown in FIG. 6, where the photooxidation zone 2 is arranged before the catalytic zone 9. Said catalytic zone may e.g. be arranged for removing ozone generated in the photooxidation step. The catalytic zone 9 is preferably operated at the same temperature as the air in the clean room, e.g. between 15-25° C., preferably around 20-22° C. whereby the air flow 3 neither has to be heated nor cooled, thereby providing a highly energy effective system and method according to the invention.

[0141] The number of photooxidation zones 2 and catalytic zones 9 can be varied, they can be placed in any suitable order, e.g. alternating, having a number of consecutively photooxidation zones and/or a number of catalytic zones 9, the only requirement being that the concentration of the at least one vapour phase compound is reduced below a predefined threshold value, such that the treated air flow can be passed into a semiconductor clean room.

[0142] Accordingly, the air flow treatment systems according to the preset invention can be constructed to meet different demands, depending on the compounds/compounds in the air flow such that several different vapour phase compounds can be removed by passing the air flow though a number of identical and/or different, and e.g. subsequently arranged, catalytic zones and/or photooxidation zones.

[0143] Modifications and combinations of the above principles and designs are foreseen within the scope of the present invention.