Patent ID: 12215888

DETAILED DESCRIPTION OF THE DRAWINGS

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.

FIG.1shows a first simplified embodiment of a air flow treatment system1aaccording to the invention. Said system consist of a single photooxidation zone2. The air flow to be treated3comprises one or more vapour phase components and when said air flow is passed through the photooxidation zone2, 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 zone2is arranged such that the concentration of the vapour phase compound is reduced below a predefined threshold.

In the photooxidation zone a number of UV-lamps4are 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-lamps4may alternatively (or in addition) be excimer lamps arranged for emitting a wavelength of about172nm, 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.

Thus, in this first embodiment the photooxidation zone2eliminate the at least one vapour phase compound from the treated air flow5, such that the treated air flow5safely can be introduced into the semiconductor clean room.

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 flow3may in a second embodiment1b,shown inFIG.2be subjected to several consecutively arranged photooxidation steps2,2′,2″, such that decomposition products generated in a first photooxidation2zone is further decomposed in a subsequent photooxidation2′ zone, etc., until the only decomposition products remaining is carbon dioxide and water.

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/zone7e.g. a condensation zone, located after the last photooxidation zone2″, i.e. immediately before the treated air flow5enters the semi-conductor clean room. Such an optionally second treatment zone is show in dotted line inFIG.2.

In a third embodiment1cshown inFIG.3the system according to the invention further comprises a catalytic zone9in which the air flow3first is passed over a catalytic unit10comprising a deNOx-catalyst and an oxidation catalyst. The air flow11exiting the catalytic zone9is then passed though a photooxidation zone2, arranged after the catalytic zone9, and in which the first treated air stream11is subjected to a photooxidation step, as already discussed in relation toFIGS.1and2. The treated air flow5from the photooxidation zone2, can then be passed into the clean room.

The system and method shown inFIG.3is unique in that when the air flow3is passed over the catalytic zone9, any amines present in said air flow is substantially completely removed. Thus, in the catalytic zone9the 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 zone2. Alternatively, the concentration of amine may be reduced, and the remaining concentration of said amine is completely removed/decomposed in the photooxidation zone2.

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 zone9will be significantly reduced, with the risk that amines are left in the air flow11.

Since the catalyst unit10comprises a deNOx-catalyst and an oxidation catalyst a significant portion of the VOCs in the air flow3will also be removed in the catalytic zone9. However, the “pre-treatment” of the air flow in the catalytic zone9in which the amines are removed, ensures that the subsequent photooxidation process works optimally.

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.

FIG.4shows a forth embodiment1dof the system according to the invention. Said embodiment adds further details to the embodiment shown inFIGS.1,2and3, and for like parts the same reference numbers are used.

In this embodiment the air flow3passes through a temperature conditioning zone12before it enters the catalytic zone9. Said conditioning zone12is arranged for providing a conditioned air flow13, 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 flow13enters the catalytic zone9, the conditions for oxidation and accordingly amine and VOC removal are optimal.

In order to ensure that sufficient oxidant is present in the catalytic unit10, additional oxidant14may optionally be added to the catalytic zone9. 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 zone9and/or use smaller catalytic units10due to the strong oxidation capabilities of ozone.

Said additional oxidant14may also be added to the air flow just prior to the catalytic zone9, e.g. provided in a second gas line connected to an air flow line/pipe.

In order to ensure that the UV-lamps operate at highest efficiency, a water spray system (not shown) may be installed in the photooxidation zone2to increase the relative humidity and/or absolute water content of the first treated gas stream to at least above 90%.

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 zone15, 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 inFIG.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.

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 zone15may 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.

In order to ensure that the amine is complete removed from the air flow3before said air flow is introduced into the semiconductor clean room, the air flow may pass though more than one catalytic zone9before entering the photooxidation zone2, and/or the air flow3may pass though more than one photooxidation zone2in order to ensure that any residues of the amine is not introduced into the semiconductor clean room.

In the embodiment shown inFIG.5the air treatment system le comprises three catalytic zones,9a,9b,9cand the air flow3passes all three before entering the photooxidation zone2. Thus, if the concentration of the amine is not reduced sufficiently in a first catalytic zone9a,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 flows3′,3″ can be further reduced in the two subsequent catalytic zones9band9c,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).

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.

The number of catalytic zones9a,9b,9cthe air flow3passes 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 steam5is 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.

A further embodiment if according to the invention is shown inFIG.6, where the photooxidation zone2is arranged before the catalytic zone9. Said catalytic zone may e.g. be arranged for removing ozone generated in the photooxidation step. The catalytic zone9is 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 flow3neither has to be heated nor cooled, thereby providing a highly energy effective system and method according to the invention.

The number of photooxidation zones2and catalytic zones9can 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 zones9, 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.

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.

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