A novel method for pre-treating and recovering noble gases from gas contaminant streams exiting an etching chamber.

Abstract

A novel method is disclosed for pre-treating a noble gas-containing stream exiting an etching chamber and subsequently recovering the noble gas from the pre-treated noble gas-containing stream. More particularly, the present invention relates to the pre-treatment and recovery of noble gases, such as xenon or krypton, from nitrogen-based exhaust streams containing certain gaseous impurities generated during etching processes performed as part of semiconductor manufacturing processes.

Description

[Technical field]

[0001] The present invention relates to a novel method for pre-treating a noble gas-containing stream exiting an etching chamber and subsequently recovering the noble gas from the pre-treated noble gas-containing stream, and more particularly to the pre-treatment and recovery of noble gases, such as xenon or krypton, from nitrogen-based exhaust streams containing certain gaseous impurities generated during etching processes performed as part of semiconductor manufacturing processes. [Background technology]

[0002] Xenon is a stable noble gas element due to its closed shell electronic structure. The favorable physical properties of xenon include its ionization potential, atomic mass, and electronic structure, which make it suitable for an increasing number of applications. Demand for xenon is growing in core and emerging applications. Of particular importance is the use of xenon in semiconductor etchant processes. Xenon is increasingly being used in dry etching processes to fabricate semiconductor devices, especially for memory chips such as 3D NAND, DRAM, and logic chips. Fluorocarbons (e.g., C), which are used to etch silicon oxide during semiconductor manufacturing, are also used in the manufacture of fluorocarbons. 4 F 6 ) The addition of xenon to the plasma improves the anisotropy of the etch profile. Xenon also improves the etch selectivity, allowing the etch rate of silicon oxide to be much higher than the photoresist used to pattern the silicon oxide film.

[0003] Xenon is a relatively high-cost material. Because it is a trace component of the atmosphere (87 ppb), 11 million litres of air are required to obtain 1 litre of xenon by air separation. Furthermore, the price of xenon is highly volatile, as its supply is controlled by air separation units (ASUs).

[0004] Given the high cost and scarce supply, etchant processes attempt to reuse xenon. However, while reuse of xenon for such etchant processes is recognized as desirable, existing processes are unable to effectively achieve xenon recovery and reuse for a variety of reasons. For example, xenon-containing exhaust streams are complex exhaust effluent mixtures that contain many difficult-to-handle contaminants. Furthermore, the concentration of xenon in xenon-containing exhaust is typically relatively low, on the order of less than 0.5% by volume, thereby making its recovery technically challenging and potentially capital intensive. As a result of these design challenges, many fab users have been left with no choice but to release xenon after only one use through their respective etch processes.

[0005] As a high value product, and with the predicted shortage of xenon, there is a growing unmet need to recover xenon from contaminant-containing gas streams for reuse as part of the etchant in semiconductor processes. Summary of the Invention

[0006] In a first aspect of the invention, there is provided a method for pre-treating a noble gas-containing nitrogen-based exhaust stream exiting an etching chamber prior to recovering noble gas from the noble gas-containing nitrogen-based exhaust stream, the method comprising the steps of receiving a noble gas-containing nitrogen-based exhaust stream from an etching chamber, the noble gas-containing nitrogen-based exhaust stream having a composition of gaseous species including (a) a noble gas, (b) gaseous impurities, and (c) nitrogen (N), the noble gas being in an amount greater than 0 mol % to about 0.5 mol %, the gaseous impurities being comprised of (i) hydrofluorocarbons represented by the general formula CxHyFz, where x, y, and z are each independently selected from the group consisting of fluorocarbons, ... (ii) perfluorocarbons represented by the general formula CxFy, where x can have any integer value from 2 to 5, and y-2x=-2, 0, or 2; (iii) carbon monoxide (CO); (iv) hydrogen fluoride (HF); (v) silicon fluoride (SiF4); and (vi) carbon tetrafluoride (CF4), where each of the gaseous impurities CxHyFz, CxFy, CO, SiF4, and CF4 is greater than 0 mol %. and (b) removing substantially all of the HF and SiF in the scrubber and (c) removing substantially all of the HF and SiF in the scrubber and (d) removing substantially all of the HF and SiF in the adsorbent. adsorbing essentially all of the CO2 and H2O onto an adsorbent to produce a pretreated, diluted rare gas-containing nitrogen-based exhaust stream; and withdrawing the pretreated, diluted rare gas-containing nitrogen-based exhaust stream from an outlet of the adsorber of the pretreatment system, the pretreated, diluted rare gas-containing nitrogen-based exhaust stream having a composition including a rare gas, gaseous impurities, and N2, the rare gas being in an amount greater than 0 mol% and less than about 0.05 mol%, and the gaseous impurities remaining after the pretreatment step being oxygen (O2) in an amount greater than 0.01 mol% and less than about 2 mol%, and the gaseous impurities being greater than 0 mol% and less than about 0.5 mol%, and the gaseous impurities remaining after the pretreatment step being oxygen (O2) in an amount greater than 0.01 mol% and less than about 0.5 mol%, and the gaseous impurities remaining after the pretreatment step being ...and comprising CF4 in an amount up to about 0.01 mol% and CO2 in an amount ranging from about 0.00001 mol% to about 0.0005 mol%.

[0007] In a second aspect of the invention, a method for pre-treating and recovering xenon from a nitrogen-based exhaust stream exiting an etching chamber includes the steps of receiving a xenon-containing nitrogen-based exhaust stream from the etching chamber, the xenon-containing nitrogen-based exhaust stream having a composition of gaseous species including xenon, gaseous impurities and nitrogen, wherein xenon is in an amount of greater than 0 mol % to about 0.5 mol %, the gaseous impurities including hydrofluorocarbons, perfluorocarbons, carbon monoxide (CO), hydrogen fluoride, silicon fluoride and carbon tetrafluoride, each of the hydrofluorocarbon, perfluorocarbon, carbon monoxide, silicon fluoride and carbon tetrafluoride gaseous impurities being in an amount of greater than 0 mol % to about 1 mol %, and further wherein hydrogen fluoride is in an amount of greater than 0 mol % to about 2 mol %, and pre-treating the xenon-containing nitrogen-based exhaust stream by introducing the xenon-containing nitrogen-based exhaust stream into a pre-treatment system, the pre-treatment system including a burner, a scrubber and a filter. (x) combusting a substantial portion of the hydrofluorocarbons, perfluorocarbons, and carbon monoxide into combustion products including carbon dioxide and water vapor to produce a diluted xenon-containing nitrogen-based exhaust stream; (y) removing substantially all of the hydrogen fluoride and silicon fluorides in a scrubber; and (z) adsorbing substantially all of the carbon dioxide and water vapor onto an adsorbent in an adsorber to produce a pretreated, diluted xenon-containing nitrogen-based exhaust stream. and removing a pretreated and diluted xenon-containing nitrogen-based exhaust stream from an outlet of the adsorber, the pretreated and diluted xenon-containing nitrogen-based exhaust stream having a composition including xenon, gaseous impurities, and nitrogen, the xenon being in an amount greater than 0 mol % and less than about 0.05 mol %, and the gaseous impurities remaining after pretreatment being oxygen in an amount greater than 0.01 mol % and up to about 2 mol %, carbon tetrafluoride in an amount greater than 0 mol % and up to about 0.01 mol %, and nitrogen in an amount greater than 0.00001 mol % and up to about 0.0005 mol % of carbon dioxide; cooling the pretreated, diluted xenon-containing nitrogen-based exhaust stream to a first non-cryogenic temperature, followed by introducing the pretreated, diluted xenon-containing nitrogen-based exhaust stream into a temperature swing adsorption apparatus (TSA) containing an adsorbent bed therein, the adsorbent bed comprising an AgX adsorbent; and adsorbing the xenon onto the AgX adsorbent preferentially over gaseous impurities in the pretreated, diluted xenon-containing nitrogen-based exhaust stream remaining after the pretreatment step.

[0008] In a third aspect, a method for pre-treating and recovering a noble gas from a nitrogen-based exhaust stream exiting an etching chamber and recovering a noble gas from a nitrogen-based exhaust stream exiting an etching chamber includes the steps of receiving a noble gas-containing nitrogen-based exhaust stream from an etching chamber, the noble gas-containing nitrogen-based exhaust stream having a composition of gaseous species including a noble gas, gaseous impurities, and nitrogen, the noble gas being in an amount greater than 0 mol % to about 0.5 mol %, and the gaseous impurities being selected from the group consisting of: (i) hydrofluorocarbons represented by the general formula CxHyFz, where x, y, and z each have an integer value ranging from 1 to 5; (ii) perfluorocarbons represented by the general formula CxFy, where x can have any integer value from 2 to 5, and y-2x=-2, 0, or 2; (iii) carbon monoxide (CO); (iv) hydrogen fluoride (HF); (v) silicon fluoride (SiF4); and (vi) carbon tetrafluoride (CF4), where each of the gaseous impurities CxHyFz, CxFy, CO, SiF4, and CF4 is in an amount greater than 0 mole % to about 1 mole %, and H and (f) pretreating the noble gas-containing nitrogen-based exhaust stream by introducing the noble gas-containing nitrogen-based exhaust stream into a pretreatment system, the pretreatment system comprising a burner, a scrubber and an adsorber, the pretreatment system (x) combusting a substantial portion of CxHyFz and CxFy into combustion products comprising carbon dioxide (CO2) and water vapor (HO) to produce a diluted noble gas-containing nitrogen-based exhaust stream, (y) removing substantially all of the HF and SiF4 in the scrubber, and (z) removing substantially all of the CO2 and HO from the nitrogen-based exhaust stream by adsorption in the adsorber. 0.00001 mol%〜2 mol%。 Adsorbing the rare gas on a nitrogen-based exhaust gas adsorbent to produce a pretreated, diluted rare gas-containing nitrogen-based exhaust stream; and removing the pretreated, diluted rare gas-containing nitrogen-based exhaust stream from an outlet of the adsorber, the pretreated, diluted rare gas-containing nitrogen-based exhaust stream having a composition including a rare gas, gaseous impurities, and nitrogen, the rare gas being in an amount of xenon greater than 0 mol% and less than about 0.05 mol%, the gaseous impurities remaining after pretreatment being oxygen (O2) in an amount of greater than 0 mol% and less than about 2 mol%, CF4 in an amount of greater than 0 mol% and less than about 0.01 mol%, and CF4 in an amount of greater than 0 mol% and less than about 0.00001 mol%.0005 mol % CO2, cooling the pre-treated, diluted noble gas-containing nitrogen-based exhaust stream to a first non-cryogenic temperature, followed by introducing the pre-treated, diluted noble gas-containing nitrogen-based exhaust stream into a noble gas recovery unit, and recovering the noble gas from the diluted noble gas-containing nitrogen-based exhaust stream.

[0009] In a fourth aspect, a pretreatment system for pretreatment of a noble gas-containing nitrogen-based exhaust stream exiting an etching chamber prior to recovering a noble gas from the noble gas-containing nitrogen-based exhaust stream includes a collection manifold having an inlet operably connected to an upstream etching chamber and an outlet operably connected to the pretreatment system, the collection manifold configured to receive a signal from each of the upstream etching chambers indicative of the presence or absence of a noble gas in the exhaust stream generated from a corresponding one of the upstream etching chambers, and configured to receive the noble gas-containing nitrogen-based exhaust stream in response to the signal, and in response to the signal: a collection manifold configured to exclude receiving a non-rare gas nitrogen-based exhaust stream that does not contain rare gases; and a pretreatment system comprising a burner, a scrubber, and an adsorber, the pretreatment system configured to (i) combust a substantial portion of the carbon monoxide, hydrofluorocarbon and perfluorocarbon impurities into carbon dioxide and water vapor, (ii) remove a substantial portion of the hydrogen fluoride and silicon tetrafluoride impurities in the scrubber, and (iii) adsorb substantially all of the carbon dioxide and water vapor onto an adsorbent in the adsorber to produce a pretreated, diluted rare gas-containing nitrogen-based exhaust stream.

[0010] In a fifth aspect, a system for pre-treating a xenon-containing nitrogen-based exhaust stream exiting an etching chamber to recover xenon includes a collection manifold having an inlet operably connected to an upstream etching chamber and an outlet operably connected to a pre-treatment system, the collection manifold configured to receive a signal from each of the upstream etching chambers, the signal indicating the presence or absence of xenon in the exhaust stream generated from a corresponding one of the upstream etching chambers, configured to receive the xenon-containing nitrogen-based exhaust stream in response to the signal, and configured to exclude receipt of a non-xenon-containing nitrogen-based exhaust stream in response to the signal, the pre-treatment system comprising a burner, a scrubber, and an adsorber, and configured to: (i) remove a first impurity comprising carbon monoxide, hydrofluorocarbons, and perfluorocarbons; a collection manifold configured to (i) combust a substantial portion of the first impurity comprising hydrogen fluoride and silicon tetrafluoride in a scrubber to produce a pretreated, diluted xenon-containing nitrogen-based exhaust stream, (ii) remove a substantial portion of the second impurities comprising hydrogen fluoride and silicon tetrafluoride in the scrubber, and (iii) adsorb a substantial portion of the third impurities comprising carbon dioxide and water vapor onto an adsorbent in the adsorber to produce a pretreated, diluted xenon-containing nitrogen-based exhaust stream; and a temperature swing adsorber (TSA) comprising an adsorbent bed comprising an AgX adsorbent therein, the TSA having an inlet operably connected to an outlet of the adsorber, the TSA being configured to receive the pretreated, diluted xenon-containing nitrogen-based exhaust stream from the outlet of the adsorber to preferentially recover substantially all of the xenon in the xenon-containing nitrogen-based exhaust stream over the first, second and third impurities.

[0011] In a sixth aspect, a system for pre-treating and recovering a noble gas from a noble gas-containing nitrogen-based exhaust stream exiting an etching chamber includes a collection manifold having an inlet operably connected to an upstream etching chamber and an outlet operably connected to a pre-treatment system, the collection manifold configured to receive a signal from each of the upstream etching chambers, the signal indicating the presence or absence of a noble gas in the exhaust stream generated from a corresponding one of the upstream etching chambers, the collection manifold configured to receive the noble gas-containing nitrogen-based exhaust stream in response to the signal, and the collection manifold configured to reject receipt of a non-noble gas-containing nitrogen-based exhaust stream in response to the signal. a rare gas recovery unit configured to receive the pretreated diluted rare gas-containing nitrogen-based exhaust stream from an outlet of the adsorber and recover substantially all of the rare gas from the rare gas-containing nitrogen-based exhaust stream in preference to the first, second and third impurities, the rare gas recovery unit being configured to: (i) combust a substantial portion of a first impurity comprising carbon monoxide, hydrofluorocarbon and perfluorocarbon impurities into carbon dioxide and water vapor; (ii) remove a substantial portion of a second impurity comprising hydrogen fluoride and silicon tetrafluoride in the scrubber; and (iii) adsorb a substantial portion of a third impurity comprising carbon dioxide and water vapor onto an adsorbent in the adsorber to generate a pretreated diluted rare gas-containing nitrogen-based exhaust stream;

[0012] In a seventh aspect, there is provided a method for pre-treating a noble gas-containing nitrogen-based exhaust stream exiting an etching chamber prior to recovering the noble gas from the noble gas-containing nitrogen-based exhaust stream, the method comprising: providing a noble gas-containing nitrogen-based exhaust stream having a composition of gaseous species including (a) a noble gas, (b) gaseous impurities, and (c) nitrogen (N2), wherein the noble gas is in an amount greater than 0 mol % to about 0.5 mol %, and the gaseous impurities are selected from the group consisting of: (i) hydrofluorocarbons, (ii) perfluorocarbons, (iii) carbon monoxide (CO), (iv) hydrogen fluoride (HF), (v) silicon fluoride (SiF4), and (vi) receiving a noble gas-containing nitrogen-based exhaust stream from the etching chamber, the noble gas-containing nitrogen-based exhaust stream comprising carbon tetrafluoride (CF4), wherein each of the gaseous impurities of hydrofluorocarbons, perfluorocarbons, CO, SiF4, and CF4 is in an amount greater than 0 mol % to about 1 mol %, and HF is in an amount greater than 0 mol % to about 2 mol %, and pre-treating the noble gas-containing nitrogen-based exhaust stream by introducing the noble gas-containing nitrogen-based exhaust stream into a pre-treatment system, the pre-treatment system including a burner, a scrubber, and an aspirator. The pretreatment system includes an adsorber, the pretreatment step including: (x) combusting a substantial portion of the CO, hydrofluorocarbons, and perfluorocarbons into combustion products including carbon dioxide (CO) and water vapor (H2O) to produce a diluted rare gas-containing nitrogen-based exhaust stream; (y) removing substantially all of the HF and SiF4 in a scrubber; and (z) adsorbing substantially all of the CO2 and H2O onto an adsorbent to produce a pretreated, diluted rare gas-containing nitrogen-based exhaust stream. and removing a pretreated and diluted noble gas-containing nitrogen-based exhaust stream, the pretreated and diluted noble gas-containing nitrogen-based exhaust stream having a composition including a noble gas, gaseous impurities, and N2, the pre-gas being in an amount greater than 0 mol% and less than about 0.05 mol%, and the gaseous impurities remaining after the pretreatment step being oxygen (O2) in an amount greater than 0.01 mol% to about 2 mol%, CF4 in an amount greater than 0 mol% to about 0.01 mol%, and CO2 in an amount ranging from 0.00001 mol% to about 0.0005 mol%.

[0013] In an eighth aspect, a method of pretreating a noble gas-containing nitrogen-based exhaust stream from an etching chamber includes introducing the noble gas-containing nitrogen-based exhaust stream into a pretreatment system; and pretreating the noble gas-containing nitrogen-based exhaust stream by (x) combusting a substantial portion of combustible gaseous impurities into combustion products including carbon dioxide (CO2) and water vapor (HO) to generate a diluted noble gas-containing nitrogen-based exhaust stream, (y) removing a substantial portion of corrosive fluorides, and (z) adsorbing substantially all of the CO2 and HO onto a sorbent to generate a pretreated, diluted noble gas-containing nitrogen-based exhaust stream.

[0014] The present invention may include any of the aspects in the various combinations and embodiments disclosed herein. [Brief description of the drawings]

[0015] The objects and advantages of the present invention will be better understood from the following detailed description of preferred embodiments thereof when taken in conjunction with the accompanying drawings in which like numerals refer to like features throughout. [Figure 1] 1 shows a process schematic of an embodiment of a xenon pre-treatment and recovery process according to the principles of the present invention. [Diagram 2] 1 shows a block flow diagram of an embodiment of a xenon pre-treatment and recovery process according to the principles of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The advantages of the present invention will be better understood from the following detailed description of relevant embodiments thereof. The present disclosure is described herein in various embodiments and with reference to various aspects and features of the present invention. It will be understood that the specific noble gas pretreatment and recovery methods and systems are shown by way of example and not by way of limitation of the present invention. The principles and features of the present invention can be used in various permutations and combinations in numerous and varied embodiments without departing from the scope of the present invention. The present disclosure may be further specified as comprising, consisting of, or consisting essentially of any of such combinations and permutations of these specific features, aspects, and embodiments, or selected one or more of them.

[0017] All percentages are expressed herein as mole percentages unless otherwise specified.

[0018] As used herein and throughout the specification, "removal efficiency" or "RE" is expressed as follows: (inflow flux of target species-outflow flux of target species) / (inflow flux of target species), where flux=concentration * RE quantifies the removal efficiency of various impurities in a nitrogen-based exhaust stream containing noble gases that are removed in accordance with the principles of the present invention.

[0019] Where a range of values ​​is expressed as a parameter, all subranges, point values, and endpoints within or defining that range are expressly disclosed therein, unless expressly disclosed otherwise. All physical properties, dimensions, and ratio ranges and subranges between those property, dimensional, and ratio range endpoints (including the endpoints) are considered to be expressly disclosed herein, unless expressly disclosed otherwise.

[0020] A "conduit," as used herein and throughout, refers to any type of tubular-like structure of any shape, including, by way of example, a tube, pipe, channel, duct, or trough.

[0021] As used herein, "connected" or "operably connected" means a direct or indirect connection between two or more components, such as conventional piping and assemblies, including, but not limited to, valves and conduits, and unless otherwise specified, allowing for fluid, mechanical, chemical and / or electrical communication between the two or more components.

[0022] As used herein and throughout, a "nitrogen-based exhaust stream" refers to an exhaust stream in which nitrogen is the predominant species contained in the exhaust stream and thus comprises 50 mole % or more, based on the total moles of the exhaust stream.

[0023] As used herein and throughout, a "noble gas-containing nitrogen-based exhaust stream from an etch chamber" refers to a composition of gaseous species including a noble gas, gaseous impurities, and nitrogen, where the noble gas is in an amount greater than 0 mole % to about 0.5 mole %, and the gaseous impurities are selected from the group consisting of: (i) hydrofluorocarbons represented by the general formula CxHyFz, where each of x, y, and z can have any integer value ranging from 1 to 5, with the proviso that when x=1, then y+z=4, and when x=2 to 5, then y+z-2x=-2, 0, or 2; (ii) perfluorocarbons represented by the general formula CxFy, where x can have any integer value from 2 to 5, and y-2x=-2, 0, or 2; (iii) carbon monoxide (CO); (iv) hydrogen fluoride (HF); (v) silicon fluoride (SiF4); and (vi) carbon tetrafluoride (CF4), with each of the gaseous impurities CxHyFz, CxFy, CO, SiF4, and CF4 being in an amount of greater than 0 mol % to about 1 mol %, and further with HF being in an amount of greater than 0 mol % to about 2 mol %. Alternatively, a "noble gas-containing nitrogen-based exhaust stream from an etch chamber," as used throughout this specification, may be characterized as having a composition of gaseous species including: (a) a noble gas; (b) gaseous impurities; and (c) nitrogen (N2); the noble gas is in an amount from greater than 0 mol% to about 0.5 mol%; and the gaseous impurities include: (i) hydrofluorocarbons; (ii) perfluorocarbons; (iii) carbon monoxide (CO); (iv) hydrogen fluoride (HF); (v) silicon fluoride (SiF4); and (vi) carbon tetrafluoride (CF4); each of the hydrofluorocarbon, perfluorocarbon, CO, SiF4, and CF4 gaseous impurities is in an amount from greater than 0 mol% to about 1 mol%, and further, HF is in an amount from greater than 0 mol% to about 2 mol%.

[0024] As used in this specification and throughout, "signal" means any suitable control signal, such as a wireless or wired signal, that can be transmitted to or from a programmable logic controller.

[0025] The inventors have recognized that xenon-containing nitrogen-based exhaust streams from etch chambers are highly corrosive, reactive and hazardous, thereby making recovery of the xenon potentially dangerous and difficult, but that careful pre-treatment systems and processes utilizing burners, scrubbers and adsorption systems can produce an exhaust stream composition suitable for recovery in a xenon gas recovery unit located downstream of the pre-treatment system. The present invention has the ability to pre-treat and recover xenon from xenon-containing nitrogen-based exhaust streams exiting one or more etch chambers in connection with fab operations.

[0026] According to one aspect of the present invention, a pre-treatment process is provided to ensure effective recovery of xenon in a downstream xenon recovery unit. FIG. 1 shows a process schematic of a xenon pre-treatment and recovery system 90. The system 90 is designed to have a modular structure that can be assembled on-site at a semiconductor manufacturing facility 10 (hereinafter referred to as a "fab"). Additionally, the pre-treatment and recovery system 90 can be constructed to be portable and operated as needed within the premises of the fab 10. The pre-treatment and recovery system 90 includes a pre-treatment system 100 and a recovery system 107. The pre-treatment system 100 includes an exhaust collection manifold 101, a burner 104, a scrubber 105, and a pressure swing adsorber 106. The pre-treatment system 100 removes certain gaseous impurities, some or all of which are generated during the etching process, to enable downstream recovery of xenon from the contaminant-laden nitrogen-based exhaust stream, as described below.

[0027] The recovery system 107 is a xenon recovery unit 107. The xenon recovery unit 107 is a temperature swing adsorption unit that includes an AgX adsorbent that can selectively adsorb xenon over nitrogen and other impurities, as described in more detail below.

[0028] The pre-treatment and recovery system 90 is connected to the etching tool 15 as shown in FIG. 2. FIG. 2 illustrates an example of an etching tool 15 connected to the system 90 by way of example and not limitation. The etching tool 15 is comprised of a plurality of etching systems 120. A total of 22 etching systems 120 are shown (i.e., designated as 1 through 22 etching systems 120). The etching systems 120 are connected to the xenon pre-treatment and recovery system 90. Each etching system 120 includes six etching chambers 103 configured in a parallel relationship to one another. Each of the etching systems 120 can have any number of etching chambers 103. In the example of FIG. 2, in which embodiments herein are described, each etching system 120 has six etching chambers 103 (i.e., designated as 1-6 etching chambers 103), resulting in a total of 132 etching chambers 103 (i.e., designated as 1-132 etching chambers 103) provided in the etching tool 15, with each of the 1-132 etching chambers 103 having a dedicated conduit 140 connecting the etching chamber 103 located in the particular etching system 120 to the inlet of the collection manifold 101. A total of 132 etching conduits 140 are shown in FIG. 2 (i.e., designated as 1-132 conduits 140). It should be understood that FIG. 2 represents one possible configuration of the etching tool 15, and embodiments herein are described therewith. Other flow networks are contemplated. Any number of etching systems 120 may be utilized, and any number of etching chambers 103 in the etching systems 120 may be utilized. The number of etching chambers 103 in the etching system 120 may be the same for each of the 1 to 22 etching systems 120. Alternatively, the number of etching chambers 103 may vary from one etching system 120 to another.

[0029] Each of the etch chambers 103 includes a turbomolecular pump and a roughing pump, which in combination can draw the necessary vacuum within the etch chambers 103 to perform the etch process. Any portion of the 1-132 etch chambers 103 or all of the 1-132 etch chambers 103 in a particular 1-22 etch system 120 can be operationally active. The exact number of operationally active 1-132 etch chambers 103 depends at least in part on the manufacturing requirements of the fab 10.

[0030] 2, a xenon-containing nitrogen-based gas flow is utilized to perform an etchant operation in one or more of the etchant chambers 103, 1-132. As a result of the etchant operation, certain gaseous impurities specific to the etchant process are generated. A large amount of nitrogen is introduced into the etchant system 120 and utilized to dilute the concentration of gaseous impurities, more specifically, etchants, in the etchant exhaust gas stream 22. As a result, the xenon-containing etchant exhaust stream 22 is nitrogen-based. The etchant gas stream 22 exits a corresponding etchant chamber 103 in the etchant system 120. As an example, a xenon-containing nitrogen-based etchant stream 22 having a flow rate of 45 slpm emerges from an etchant chamber 103 of the etchant system 120. Another xenon-containing nitrogen-based etchant stream 22 emerges from another etchant chamber 103 of the etchant system 120. In this manner, multiple etchant streams 22 can exit a particular etchant system 120, depending on how operationally active the etchant chambers 103 are in the etchant system 120. FIG. 2 shows that each xenon-containing nitrogen-based exhaust stream corresponds to an etching chamber 103 .

[0031] Any flow rate is contemplated for each of the etching streams 22. In one example, there are six etching streams 22, each exiting a dedicated 1-6 etching chamber 103 of the etching system 120 at a flow rate of about 45 slpm. As a result, a maximum of about 270 slpm can emerge from a single etching system 120. The fab 10 of FIG. 2 includes a total of 22 etching systems 120 such that a maximum of 5940 slpm can enter the pre-treatment system 100. It should be understood that the pre-treatment and recovery system 90 can be sized to handle any volume of the xenon-containing nitrogen-based exhaust gas stream 22 exiting each etching system 120 in the etching tool 15.

[0032] Some of the 1-22 etching systems 120 may be partially idle, such that some of the etch chambers 103 in the etching systems 120 are not operationally active; a fully idle state, in which all of the 1-6 etching chambers 103 in the etching systems 120 are idle; i.e., all of the 1-6 etching chambers 103 in the etching systems 120 are operational. Based on the particular conditions, the amount of xenon-containing gas flowing out of a particular etching system 120 may vary from 0 (all six etching chambers 103 are idle) to 270 slpm (assuming all six etching chambers 103 are operationally active, thereby causing each etching stream 22 to have a flow rate of 45 slpm exiting each of the 1-6 etching chambers 103). Alternatively, some of the 1-6 etching chambers 103 may be in an idle mode, resulting in intermediate flow rates of between 0 and 270 slpm of xenon-containing gas flowing out of a particular etching system 120. Applicants have considered a wide range of operating conditions for multiple 1-22 etching systems 120 to minimize the load on the pretreatment and recovery system 90, thereby improving xenon recovery, by designing the collection manifold 101 to allow only the xenon-containing nitrogen-based exhaust stream 22 to enter the collection manifold 101 and not allow non-xenon-containing streams to enter the collection manifold 101, as described below.

[0033] A number of means are contemplated for ensuring that the exhaust collection manifold 101 only allows the xenon-containing nitrogen-based exhaust stream 22 to enter the collection manifold 101 of the pretreatment system 100. In one example, a xenon mass flow controller located upstream of a particular 1-132 etching chamber 103 sends a source signal to a dedicated three-way control valve located on the collection manifold 101. When the xenon mass flow controller detects the flow of xenon therethrough, a source signal is sent from the xenon mass flow controller to the dedicated three-way control valve, which causes the three-way control valve to move from a closed position to an open position relative to the collection manifold 101, thereby allowing the xenon-containing nitrogen-based exhaust stream 22 exiting the particular 1-132 etching chamber 103 to enter the collection manifold 101 and then on to the pretreatment system 100. The three-way control valve is in a closed position relative to the abatement system, thereby blocking the flow of the xenon-containing nitrogen-based exhaust stream 22 to the downstream abatement system.

[0034] Conversely, if the xenon mass flow controller has a zero set point and does not detect a nitrogen-based exhaust gas flow through it, a source signal can be sent from the mass flow controller to the three-way control valve, which will remain in a closed position relative to the collection manifold 101 and in an open position relative to the abatement system, thereby directing the non-xenon-containing nitrogen-based exhaust gas flow to the abatement system.

[0035] Alternatively, when the xenon mass flow controller does not detect exhaust gas flow therethrough, a source signal may not be sent from the xenon mass flow controller to the three-way control valve, causing the three-way control valve to remain in a closed position relative to the collection manifold 101. Thus, the default configuration of the three-way control valve is to remain in a closed position relative to the collection manifold 101 when no signal is relayed to the three-way control valve. In this scenario, the absence of exhaust gas flow from a corresponding 1-132 etching chamber 103 can indicate that the particular 1-132 etching chamber 103 is idle, resulting in no signal being sent to the three-way control valve.

[0036] In another embodiment, a sensing device may be utilized in place of the xenon mass flow controller. The sensing device is disposed in a conduit 140 extending between a particular etching chamber 103 and the collection manifold 101. In a first scenario, when the sensing device detects the presence of xenon flowing through the conduit 140, the sensing device may send a signal to a three-way control valve disposed on the collection manifold 101, which may open the control valve to allow the xenon-containing nitrogen-based exhaust stream 22 present in the corresponding etching chamber 103 to pass to the collection manifold 101 while blocking flow to the abatement system. In a second scenario, when the sensing device does not detect xenon flowing therethrough, no signal may be sent to the three-way control valve, thereby maintaining the three-way control valve in a closed position relative to the collection manifold 101 and diverting the non-xenon nitrogen-based exhaust stream to the abatement system. In a third scenario, when the sensing device does not detect exhaust gas flow from the corresponding etching chamber 103, the system recognizes that the particular etching chamber 103 may be idle, and as a result, no signal is sent to the three-way control valve, thereby maintaining the three-way control valve in a closed position relative to the collection manifold 101.

[0037] It should be understood that, as known in the art, other measurement, analysis, and detection systems can be utilized to determine the presence of xenon in the exhaust stream and ensure that only the xenon-containing nitrogen-based exhaust stream 22 from the etching chamber 103 enters the collection manifold 101.

[0038] The above-described embodiments represent so-called "smart switching" techniques that reduce, mitigate or eliminate the introduction of non-xenon-containing nitrogen-based exhaust streams to the collection manifold 101 and pretreatment system 100. In this manner, by selectively rejecting and / or diverting non-xenon-containing nitrogen-based exhaust streams to the abatement system, the pretreatment and recovery system 90 is not unnecessarily overloaded with large amounts of exhaust gas. Furthermore, recovery of xenon from the xenon-containing nitrogen-based exhaust stream 22 can be accomplished without encountering the adverse effects of dilution that may occur from non-xenon-containing nitrogen-based exhaust streams entering the pretreatment system 100. Furthermore, by utilizing an exhaust collection manifold 101 that collects only xenon-containing nitrogen-based exhaust streams 22 from the various etching systems 120, variations in xenon concentration in the xenon-containing nitrogen-based exhaust stream 22 received from the etching chambers 120 can be minimized. The net effect in all cases is improved recovery of xenon from the xenon gas recovery unit 107 without overloading the pretreatment and recovery system 90.

[0039] In this manner, the collection manifold 101 is configured to selectively receive only the xenon-containing nitrogen-based exhaust stream 22 from the exhaust stream 22 exiting the etching chamber 103 of the corresponding etching system 120 of the etching tool 15 in the fab 10 by the aforementioned "smart switching" feature. In addition, the collection manifold 101 is characterized by a sufficient volume that can reduce, mitigate, or eliminate back pressure to the corresponding etching chamber 103, so that no interruption is caused to any of the etching systems 120. The collection manifold 101 may have multiple inlets, each of which is operably connected to a particular upstream etching chamber 103 by a dedicated conduit 140. In other words, each 1-132 etching chamber 103 may have a dedicated 1-132 conduit 140 that connects to a dedicated inlet of the collection / recovery manifold 101.

[0040] Each of the xenon-containing nitrogen-based exhaust streams 22 that may enter a particular inlet of the collection manifold 101 may enter therein at any flow rate. In one example, each of the selected etching flows 22 may have an input flow rate between 0 and 100 slpm, with the total flow rate of all the selected etching flows 22 being between 0 and 13,200 slpm. In another example, each of the selected etching flows 22 may have an input flow rate between 10 and 80 slpm, with the total flow rate of all the selected etching flows being between 1320 and 10,560 slpm. In yet another example, each of the selected etching flows 22 may have an input flow rate between 30 and 60 slpm, with the total flow rate of all the selected etching flows being between 3960 and 7920 slpm.

[0041] FIG. 2 shows that the collection manifold 101 is connected to a booster pump that can be utilized to pressurize the xenon-containing nitrogen-based exhaust stream 22. The outlet of the booster pump is operably connected to downstream burner 104 and scrubber 105 units. It should be understood that while FIG. 2 shows the burner 104 and scrubber 105 as single units, the operation of each will be described separately to more clearly explain how the burner 104 and scrubber 105 each combust and remove certain impurities. The xenon-containing nitrogen-based exhaust stream 22 can exit the collection manifold 101 as stream 95 and then enter the booster pump where it is pressurized to a pressure suitable for entering the downstream burner 104. The pressurized stream (FIG. 2) exits the booster pump as stream 91. In one example, stream 91 is pressurized to about 10 psig. Stream 91 may have a representative composition characterized by: (i) hydrofluorocarbons having the general formula CxHyFz, where each of x, y, and z may have any value greater than 0; (ii) perfluorocarbons represented by the general formula CxFy, where x may have any value greater than 1 and y may have any value greater than 0; (iii) carbon monoxide (CO); (iv) hydrogen fluoride (HF); and (v) silicon fluorides represented by the general formula SixFy, where each of x and y may have any value greater than 0 and carbon tetrafluoride (CF4). Each of such gaseous impurities CxHyFz, CxFy, CO, SixFy, and CF4 may be in an amount of from greater than 0 to about 1 mol%, alternatively from greater than 0.0001 mol% to about 1 mol%, and further alternatively from greater than 0.0001 mol% to about 0.3 mol%. HF may be in an amount from greater than 0 to about 2 mol %, alternatively from greater than 0.0001 to about 2 mol %, and further alternatively from greater than 0.0001 to about 0.5 mol %.

[0042] Stream 91 having the above-mentioned composition is directed to a pretreatment system 100 including a burner 104, a scrubber 105, and a pressure swing adsorber 106. As shown in FIG. 2, by way of non-limiting example, stream 91 may contain about 600 ppm xenon. The xenon-containing nitrogen-based exhaust stream 91 enters burner 104. Excess oxygen or oxygen-enriched air may be provided to burner 104 in an amount to ensure that a substantial portion of the one or more hydrocarbons and one or more hydrofluorocarbons are combusted to carbon dioxide and water vapor to produce a diluted xenon-containing nitrogen-based exhaust stream. In one example, the excess oxygen or oxygen-enriched air is introduced to burner 101 in an amount effective to dilute the xenon contained in stream 91 by no more than a factor of about 2-3 times the amount of xenon in stream 91. Burner 104 is preferably operated at a temperature greater than 1120° C. Burner 104 (i) allows for nearly 100% or complete combustion of combustible contaminants, and (ii) does not unnecessarily introduce excess oxygen or excess oxygen-enriched air that would cause dilution of the xenon contained in stream 91 by a factor of more than about 2-3 times the amount of xenon in stream 91. In other words, the dilution of the xenon is controlled to allow recovery of the xenon by ensuring that the xenon is not diluted by more than 2-3 times the initial amount of xenon contained in stream 91 entering burner 104. Balancing these competing design considerations for burner 104 is possible with the present invention. Conventional xenon gas recovery units do not implement burner systems in the manner utilized by the present invention because combustion tends to cause excessive dilution of the xenon and is unable to consistently control the level of dilution of the xenon exiting the burner, thereby making recovery of the diluted xenon impossible.

[0043] With respect to the present invention, despite the dilution of xenon, which is expected to be no more than about 2-3 times the amount of xenon contained in stream 91, Applicants have determined that the combustible impurities are CO 2 and H 2We have found that the burner 104 is robust to pretreatment setups because xenon is converted to easier to handle components such as O, which can be more easily removed in subsequent purification operations. The burner 104 can handle changes in the compositional makeup of the gaseous impurities contained in the etching stream 22. Despite the dilution of xenon that occurs in the burner 104, when the burner 104 is combined with an adsorption process using an adsorbent that is highly selective for xenon, the integrated approach of the present invention is economically viable and effective for xenon recovery, even when stream 91 has a xenon concentration of 500-600 ppm or less.

[0044] The diluted xenon-containing nitrogen-based exhaust stream has a composition that exits the burner 104 that includes HF, SixFy, and CF, as well as the combustion products of CO2 and HO from the burner 104. The diluted xenon-containing nitrogen-based exhaust stream exits the burner 104 and flows to an inlet of a wet scrubber 105 where it can remove substantially all of the corrosives, consisting essentially of hydrogen fluoride and silicon tetrafluoride (collectively referred to as "fluorides").

[0045] The diluted xenon-containing N-based exhaust stream may be contacted with a suitable aqueous medium, such as potassium hydroxide (KOH), aluminum nitrate nonahydrate (ANN), monobasic aluminum nitrate (monoban) or caustic alkali (NaOH). The aqueous medium removes substantially all of the scrubbable fluorides from the diluted xenon-containing nitrogen-based exhaust stream. A sufficient flow rate of the incoming diluted xenon-containing nitrogen-based exhaust stream is provided. In one example, the scrubber 105 may include a single vertical packed tower with a liquid injection manifold at the top of the packed tower and a demister pad or other demisting means thereon. The scrubber 105 may be supplied with any suitable aqueous scrubbing medium that may be cooled or at a suitable temperature relative to the diluted xenon-containing nitrogen-based exhaust stream from the burner 104, and may optionally be subjected to quenching or pre-cooling upstream of the scrubber 105. Sufficient contact between the aqueous scrubbing medium and the diluted xenon-containing nitrogen-based exhaust stream occurs to allow at least a substantial portion of the scrubbable fluorides to be absorbed into the aqueous scrubbing medium.

[0046] Additionally, the scrubber may incorporate a cooler located adjacent to the scrubber tower and capable of pre-cooling the wash water or other aqueous scrubbing medium. Instead of using demister pads or similar mechanical means to minimize or remove residual mist (small size water droplets), the scrubber unit in the practice of the present invention may be constructed to hydrodynamically minimize or substantially remove such mist components by contacting the gas stream with a water "knockdown" spray of larger droplets to remove the mist components from the gas stream.

[0047] The use of cold water in washing is desirable to cool the effluent gas stream below ambient temperature, thereby reducing the amount of water vapor below ambient relative humidity conditions prevailing in the environment of a semiconductor manufacturing operation, for example, when the effluent gas stream is derived from a semiconductor manufacturing tool. The use of cold water is also desirable to introduce thermophoretic effects to enhance acid gas absorption and particulate absorption in the packed tower.

[0048] As described for the example of Figure 2, a typical composition of stream 92 exiting scrubber 105 may include xenon in an amount less than about 0.05%, CO2 in an amount of about 5-10%, O2 in an amount of about 0.1-5%, H2O in an amount of greater than 0% to about 4%, and CF4 in an amount of greater than 0% to about 0.1%. Figure 2 generally illustrates the types of contaminants that are partially or completely removed from burner 104 and scrubber 105: CO, CF4, CxHyFz, CxFy, HF, SixFy.

[0049] The diluted xenon-containing nitrogen-based exhaust stream 92, with reduced corrosives, hydrocarbons and hydrofluorocarbons, exits the outlet of the scrubber 105 and is sent to a pressure swing adsorber (PSA) 106. Stream 92 is preferably elevated in pressure to at least about 50 psi, but not more than about 250 psi, to enable effective adsorption of H2O and CO2 in the PSA 106. The adsorption beds of the PSA 106 adsorb moisture and CO2 with at least 90% xenon recovery. 2 Pressure swing adsorption processes can be operated using one or more adsorbent beds. The adsorbent beds contain CO 2 and H 2 The PSA 106 may be packed with one or more layers of adsorbents purposely designed to be selective for the impurities to be removed, such as, but not limited to, O, but with minimal selectivity for adsorption of xenon, such as alumina, silica gel and / or zeolites. The pressure drop in the PSA 106 is proportional to the amount of CO 2 and H 2 10 and 11. The PSA 106 is then cooled to room temperature to allow desorption of the CO and H2O impurities, thereby allowing regeneration of the bed for subsequent use. Substantially all of the CO2 and H2O are adsorbed onto the adsorbent within the PSA 106, thereby producing intermediate stream 93.

[0050] The removal efficiency (RE) of each of the gaseous impurities contained in stream 91 that are subsequently removed by pretreatment system 100 is greater than 99%. The removal of the gaseous impurities by pretreatment system 100 produces a partially purified intermediate stream 93.

[0051] The intermediate stream 93 exiting the PSA 106 may be characterized as a pretreated diluted xenon-containing nitrogen-based exhaust stream having a composition including xenon, gaseous impurities, and balance N2, where the xenon is diluted and in an amount greater than 0 mol% and less than about 0.05 mol%, and the gaseous impurities remaining after the pretreatment steps in the burner 104 and scrubber 105 include oxygen (O2) in an amount greater than 0.01 mol% to about 2 mol%, CF4 in an amount greater than 0 mol% to about 0.01 mol%, and CO2 in an amount ranging from 0.00001 mol% to about 0.0005 mol%. The intermediate stream 93 may be characterized as a gaseous intermediate product that has undergone partial purification from the PSA 106 and subsequently cooled to a non-cryogenic temperature below 300 K, preferably below about 250 K, and more preferably below about 200 K. Cooling to non-cryogenics is done so as not to liquefy the intermediate stream 93, but to create a sufficiently cold temperature that favors adsorption of xenon onto the adsorbent in the TSA 107, as opposed to nitrogen or other gaseous impurities in the intermediate stream 93. The TSA 107 bed is indirectly cooled from high temperature to ambient temperature with air. Cooling to the desired non-cryogenic temperature of less than 300 K from ambient temperature is done by direct cooling with substantially contaminant free N2. An optional guard bed, as shown in FIG. 3, located upstream of the TSA 107 may also be used to remove other impurities that may adversely affect the ability of the TSA 107 to selectively adsorb xenon within the temperature swing adsorption unit (TSA) 107.

[0052] The pressure of intermediate stream 93 entering PSA 106 is substantially similar to the pressure of stream 93 exiting PSA 106 as a result of minimizing pressure drop losses along the flow network extending between the outlet of PSA 106 and the inlet of TSA 107.

[0053] The intermediate stream 93 enters the inlet of the TSA 107 and contacts the adsorbent. The xenon in the intermediate stream 93 is preferentially and selectively adsorbed on the adsorbent designed to selectively adsorb xenon over nitrogen and other gaseous impurities in the intermediate stream 93. The adsorbent bed can be packed with an adsorbent selective for the desired noble gas xenon, such as silver ion-exchanged zeolite of type X, a low silica variant of type X zeolite, where the ion exchange level is at least 80% Ag on an equivalents basis. In a preferred embodiment, the adsorbent in the TSA 107 is AgX. Further details of AgX and other suitable adsorbents for xenon are described in U.S. Pat. No. 10,295,255, which is incorporated herein by reference in its entirety for all purposes.

[0054] Before intermediate stream 93 enters TSA 107, stream 93 and the AgX adsorber are cooled to the same non-cryogenic temperature described above to ensure optimal selectivity of Xe over N2 and other gaseous impurities in intermediate stream 93. In one preferred method of operation, the temperature of the AgX is reduced to about 200K. As a result of the selectivity of the AgX adsorbent for xenon, substantially all of the xenon contained in intermediate stream 93 is preferentially adsorbed onto the AgX, while nitrogen and gaseous impurities are not adsorbed onto the AgX, but instead flow freely through the outlet of TSA 107. In one embodiment, to ensure that all of the available active sites on the AgX adsorbent for xenon adsorption are utilized, the feed of intermediate stream 93 to the TSA can be maintained until the xenon concentration in the outlet product stream 96 is equal to or greater than 5% of the xenon feed concentration contained in intermediate stream 93. However, it should be understood that the duration of adsorption can continue longer or shorter than the time required to reach a 5% xenon breakthrough. In contrast to U.S. Pat. No. 10,295,255, the adsorption bed as utilized by the present invention does not need to be operated to near complete breakthrough with xenon to allow deep elimination of other gaseous impurities contained in the intermediate stream 93 before regeneration. The present invention can be operated in a more flexible manner than the method described in U.S. Pat. No. 10,295,255, whereby xenon adsorption may leave some adsorption capacity or active sites on the AgX for other impurities (e.g., CF4) and nitrogen in the intermediate stream 93, but the present invention incorporates a robust burner and scrubber process to remove many of the problematic contaminants (e.g., hydrocarbons, perfluorocarbons, HF, SixFy, and reduced levels of CF4) that would otherwise cause problems for the AgX selectivity of xenon over other gaseous impurities and nitrogen in the intermediate stream 93. By pre-treating the problematic contaminants as described herein, the present invention can utilize timely and effective xenon recovery without the need to operate to a level of breakthrough of xenon at the outlet of the TSA 107. Because concerns regarding deep removal of contaminants from the AgX are eliminated, excess amounts of xenon do not leak out, thereby improving the amount of xenon recovered by the AgX.Thus, the present invention operates to reduce the loss of xenon through the adsorbent bed of TSA 107, thereby allowing a greater portion of the xenon contained in exhaust stream 22 to be recovered at acceptable product purity levels.

[0055] The choice of adsorption temperature when operating the TSA 107 is in the range of 150 K to 300 K, preferentially below 250 K, for example about 200 K. The intermediate stream 93 is in the gas phase.

[0056] Recovery of the purified xenon product is accomplished by regeneration of the AgX adsorbent bed to produce a product stream 96 of xenon. Regeneration requires raising the temperature of the AgX adsorbent bed to at least 350 K, and up to about 550 K. Heating of the bed can be accomplished in a variety of ways, such as indirect heating. Alternatively, or in addition, a purge gas having a sufficiently elevated temperature can be utilized to improve the amount of xenon desorbed as product stream 96. The purge gas can include nitrogen and / or argon or mixtures thereof. However, to obtain the highest achievable concentration of xenon in product stream 96, N is preferably used. 2 And / or excessive amounts of warm purge gas such as Ar or mixtures thereof are preferably avoided if a purge gas is used to assist in the desorption of xenon.

[0057] Heating the bed causes the xenon to desorb from the AgX as a xenon-containing product stream 96. Product stream 96 has a composition including greater than about 10 mol % xenon, up to 0.5 mol % carbon dioxide, less than about 2 mol % oxygen, and less than about 1 mol % carbon tetrafluoride. Xenon product stream 96 preferably has at least 20 times the xenon concentration contained in exhaust stream 22 entering collection manifold 101.

[0058] The xenon product stream 96 may be compressed into the cylinder of FIG. 2 and then sent to further purification (e.g., a refinery) to remove problematic contaminants, after which the xenon product will have an electronic grade purity suitable for reuse as an etching gas in the etching tool 15. If the purity is determined to be acceptable (e.g., electronics purity grade), the product stream 96 may be reused on-site as an etching gas for the etching tool 15 without the need for further processing and purification. Measurement equipment known in the art may be used to determine the purity level of xenon in the cylinder either before, during, or after filling the cylinder with the xenon product stream 96 exiting the TSA 107.

[0059] After the xenon is recovered in product stream 96, the AgX bed is cooled with a cryogenic fluid, preferably below 250 K, which is substantially free of noble gases and other adsorbable components. The cooling fluid includes nitrogen gas and / or liquid.

[0060] The feed, adsorption and desorption steps are performed in a cyclical fashion. The TSA 107 may be used in conjunction with other adsorbents and / or processes that may help remove deleterious impurities from the feed stream that may affect the xenon adsorption capacity of the xenon recovery adsorbent material, such as the optional guard beds shown in FIG. 2. In addition, it should be understood that the TSA 107 may be operated using one or more adsorbent beds. When the invention is practiced with two or more adsorbent beds, the phasing of the operation of the beds may be modified such that the on-line period of the first bed begins when the second bed goes off-line to minimize output fluctuations. Alternatively, the cycle may be adjusted such that there is an overlap between the on-line period of the first adsorbent bed and the on-line period of the second adsorbent bed.

[0061] It should be noted that the pretreatment step of the present invention is characterized by the absence of catalytic or catalytic plasma decomposition. Although catalytic based decomposition methods can reduce the decomposition temperature with less energy consumption and sufficient RE of gaseous impurities, such processes are sensitive to changes in exhaust composition and subject to fouling or poisoning. Catalyst replacement due to fouling or poisoning is costly and requires significant downstream of the fab system.

[0062] Furthermore, the pretreatment step of the present invention does not use non-equilibrium or thermal plasmas. Non-equilibrium plasmas produce lower REs of gaseous impurities generated during the etching process. Thermal plasmas require high temperatures, exceeding 2500° C., to generate the plasma. As a result, the hardware is susceptible to thermal damage and degradation, which can shorten the plasma operating life, even when additional cooling gases are utilized. Generally, plasma systems are limited to small volume use sites. Plasma torch life and capacity can be an issue in fab-wide pretreatment and recovery operations. As a result, for these reasons, the inventors of the present invention have recognized that plasma processes are not robust enough for use in large pretreatment systems where the exhaust stream is an etching stream containing corrosive and reactive species.

[0063] Alternative embodiments are contemplated by the present invention. In particular, although the present invention has been described with respect to a xenon-containing nitrogen-based exhaust stream, the pretreatment system of the present invention can be utilized with other noble gases. As an example, the noble gas includes krypton and the recovery gas unit for krypton is a cryogenic distillation column instead of a TSA. The composition of a noble gas-containing nitrogen-based exhaust stream, where the noble gas is krypton or xenon or another noble gas, can generally be expressed as a composition of gaseous species including (a) the noble gas, (b) gaseous impurities, and (c) nitrogen (N2), where the noble gas is in an amount greater than 0 mole % to about 0.5 mole %, and the gaseous impurities are (i) hydrochloric acid represented by the general formula CxHyFz, where each of x, y, and z is an integer in the range of 1 to 5, with the proviso that when x=1, y+z=4, and when x=2 to 5, y+z-2x=-2, 0, or 2. (ii) a perfluorocarbon represented by the general formula CxFy, where x can have any integer value from 2 to 5, and y-2x=-2, 0, or 2; (iii) carbon monoxide (CO); (iv) hydrogen fluoride (HF); (v) silicon fluoride (SiF4); and (vi) carbon tetrafluoride (CF4), wherein each of the gaseous impurities CxHyFz, CxFy, CO, SiF4, and CF4 is in an amount of greater than 0 mol% to less than about 1 mol%, and HF is in an amount of greater than 0 mol% to less than about 2 mol%.

[0064] The lower level for each of the aforementioned gaseous impurities in stream 22 may be 0.0001 mole percent or less, or 0.0001 mole percent or more.

[0065] The above description represents only one possible arrangement of the burner 104 and scrubber 105. It will be understood that a wide variety of other burners and scrubbers may be utilized as part of the pretreatment system 100, and that the construction, arrangement, and operation of the burner 104 and scrubber 105 may be widely varied to treat gases exhausted from the tools and manufacturing operations of the upstream fab 10. Other designs of scrubbers may be used.

[0066] Another scrubber unit includes a falling film acid absorber with cold water fed to the shell side of the absorber. With such a scrubber unit, the liquid from the pretreatment unit, the quencher, and the scrubber unit can be directed to discharge to a common reservoir on the bottom of the scrubber tower. In this way, the used liquid streams from the effluent gas treatment system are combined, and such a reservoir may be arranged for its gravity-fed operation.

[0067] Alternatively, cleaning fluid and other liquid flows from the constituent process units of the effluent gas treatment system may be pressurized or pumped out of the system by suitable pumping means, such as centrifugal pumps, peristaltic pumps, air-driven pumps, water-fed eductors, or other suitable liquid-driven driver means.

[0068] It is understood that the PSA as part of the pretreatment system can be replaced with a TSA as known in the art, whereby the TSA has an adsorbent bed of alumina, molecular sieve, carbon, or combinations thereof, for the purpose of removing CO2 and HO as well as trace contaminants that may interfere with downstream rare gas recovery. Other suitable adsorption systems are also contemplated.

[0069] Additionally, although the present invention has been described with respect to a nitrogen-based exhaust stream, other inert-based exhaust streams other than nitrogen are contemplated. For example, an argon-based exhaust stream may be utilized.

[0070] While what are considered to be particular embodiments of the invention have been shown and described, it will of course be understood that various modifications and changes in form or detail can be readily made without departing from the spirit and scope of the invention. It is therefore intended that the invention not be limited to the exact forms and details shown and described herein, nor be limited to anything less than the full scope of the invention disclosed herein and claimed below. Note that the following [1] to

[37] are all embodiments or aspects of the present invention. [1] 1. A method for pre-treating a noble gas-containing nitrogen-based exhaust stream exiting an etching chamber prior to recovering the noble gas from the noble gas-containing nitrogen-based exhaust stream, the method comprising: receiving the nitrogen-based exhaust stream containing a noble gas from the etch chamber, the nitrogen-based exhaust stream containing a noble gas having a composition of gaseous species including (a) the noble gas, (b) gaseous impurities, and (c) nitrogen (N2), the noble gas being in an amount greater than 0 mol % to about 0.5 mol %, the gaseous impurities being (i) a hydrofluoric acid represented by the general formula CxHyFz, where each of x, y, and z is an integer in the range of 1 to 5, with the proviso that when x=1, y+z=4, and when x=2 to 5, y+z-2x=-2, 0, or 2; (ii) a perfluorocarbon represented by the general formula CxFy, where x can have any integer value from 2 to 5, and y-2x=-2, 0, or 2; (iii) carbon monoxide (CO); (iv) hydrogen fluoride (HF); (v) silicon fluoride (SiF4); and (vi) carbon tetrafluoride (CF4), wherein each of said gaseous impurities CxHyFz, CxFy, CO, SiF4, and CF4 is in an amount of greater than 0 mol% to about 1 mol%, and HF is in an amount of greater than 0 mol% to about 2 mol%. pre-treating the noble gas-containing nitrogen-based exhaust stream by introducing the noble gas-containing nitrogen-based exhaust stream into a pre-treatment system, the pre-treatment system comprising a burner, a scrubber and an adsorber, (x) combusting a substantial portion of the CO, CxHyFz and CxFy into combustion products comprising carbon dioxide (CO2) and water vapor (HO) to generate a diluted noble gas-containing nitrogen-based exhaust stream, (y) removing substantially all of the HF and SiF4 in the scrubber, and (z) adsorbing substantially all of the CO2 and HO onto an adsorbent to generate a pre-treated diluted noble gas-containing nitrogen-based exhaust stream; and removing the pretreated, diluted noble gas-containing nitrogen-based exhaust stream from an outlet of the adsorber of the pretreatment system, the pretreated, diluted noble gas-containing nitrogen-based exhaust stream having a composition including the noble gas, the gaseous impurities, and the N2, the noble gas being in an amount greater than 0 mol% and less than about 0.05 mol%, and the gaseous impurities remaining after the pretreatment include oxygen (O2) in an amount greater than 0.01 mol% to about 2 mol%, CF4 in an amount greater than 0 mol% to about 0.01 mol%, and CO2 in an amount ranging from 0.00001 mol% to about 0.0005 mol%. [2] The method according to [1], wherein the pretreatment is characterized by the absence of a plasma decomposition step, a catalytic decomposition step and a catalytic plasma decomposition step. [3] The method of claim 1, wherein the pre-treatment step comprises a process sequence of introducing the rare gas-containing nitrogen-based exhaust stream to an inlet of the burner, followed by an inlet of the scrubber, and then to an inlet of the adsorber, the scrubber being characterized as a wet scrubber. [4] receiving the noble gas-containing nitrogen-based exhaust gas flow from the etching chamber; collecting one or more of the noble gas-containing nitrogen-based exhaust gas streams from a corresponding noble gas-containing etching chamber, while excluding collecting one or more gas streams from the corresponding etching chamber, each of which does not contain a noble gas; and directing the one or more of the noble gas-containing nitrogen-based exhaust gas streams into the inlet of the burner of the pre-treatment system. [5] 2. The method of claim 1, wherein the burning step further comprises introducing oxygen-enriched air or excess oxygen into the burner in an amount effective to dilute the rare gas exiting the pretreatment system by about 2 to 3 times the amount of the rare gas entering the pretreatment system. [6] 2. The method of claim 1, further comprising pressurizing the diluted rare gas-containing nitrogen-based exhaust stream after exiting the scrubber to a pressure suitable for feeding the stream to the adsorber. [7] 2. The method of claim 1, wherein the amounts of each of CxHyFz, CxFy, CO, HF, SiF4, and CF4 in the noble gas-containing nitrogen-based exhaust stream received from the etching chamber have a lower limit that is at least 0.0001 mol %. [8] 2. The method of claim 1, wherein the pretreated and diluted noble gas-containing nitrogen-based exhaust stream enters a noble gas recovery unit at a first non-cryogenic temperature in the range of about 200 K to about 300 K, and further wherein the noble gas comprises xenon. [9] 13. The method of claim 1, wherein each of the gaseous impurities is removed with a removal efficiency (RE) of greater than about 99%.

[10] 2. The method of claim 1, further comprising sending the pre-treated, diluted rare gas-containing nitrogen-based exhaust stream to a rare gas recovery unit.

[11] 1. A method for pre-treating and recovering xenon from a nitrogen-based exhaust stream exiting an etch chamber, comprising: receiving a xenon-containing nitrogen-based exhaust stream from an etch chamber, the xenon-containing nitrogen-based exhaust stream having a composition of gas species including the xenon, gaseous impurities, and nitrogen, the xenon being in an amount of greater than 0 mol % to about 0.5 mol %, the gaseous impurities including hydrofluorocarbons, perfluorocarbons, carbon monoxide (CO), hydrogen fluoride, silicon fluoride, and carbon tetrafluoride, each of the gaseous impurities of hydrofluorocarbons, perfluorocarbons, carbon monoxide, silicon fluoride, and carbon tetrafluoride being in an amount of greater than 0 mol % to about 1 mol %, and further the hydrogen fluoride being in an amount of greater than 0 mol % to about 2 mol %; pre-treating the xenon-containing nitrogen-based exhaust stream by introducing the xenon-containing nitrogen-based exhaust stream into a pre-treatment system, the pre-treatment system comprising a burner, a scrubber and an adsorber, (x) combusting a substantial portion of the hydrofluorocarbons, perfluorocarbons and carbon monoxide into combustion products comprising carbon dioxide and water vapor to produce a diluted xenon-containing nitrogen-based exhaust stream, (y) removing substantially all of the hydrogen fluoride and silicon fluorides in the scrubber, and (z) adsorbing substantially all of the carbon dioxide and the water vapor onto an adsorbent in the adsorber to produce a pre-treated diluted xenon-containing nitrogen-based exhaust stream; removing the pre-treated, diluted xenon-containing nitrogen-based exhaust stream from an outlet of the adsorber, the pre-treated, diluted xenon-containing nitrogen-based exhaust stream having a composition including the xenon, the gaseous impurities, and the nitrogen, the xenon being in an amount greater than 0 mol % and less than about 0.05 mol %, and the gaseous impurities remaining after the pre-treatment including oxygen in an amount greater than 0.01 mol % and up to about 2 mol %, carbon tetrafluoride in an amount greater than 0 mol % and up to about 0.01 mol %, and carbon dioxide in an amount ranging from 0.00001 mol % to about 0.0005 mol %; cooling the pretreated, diluted xenon-containing nitrogen-based exhaust stream to a first non-cryogenic temperature; and introducing the pretreated, diluted xenon-containing nitrogen-based exhaust stream into a temperature swing adsorber (TSA) containing therein an adsorbent bed comprising an AgX adsorbent; and adsorbing said xenon onto said AgX adsorbent preferentially over said gaseous impurities in said pretreated, diluted, xenon-containing nitrogen-based exhaust stream remaining after said pretreatment step.

[12] 12. The method of claim 11, further comprising, prior to performing the pretreatment step, directing the pretreated, diluted xenon-containing nitrogen-based exhaust stream through a guard bed to remove impurities.

[13] (i) maintaining the step of introducing the pretreated diluted xenon-containing nitrogen-based exhaust stream into a TSA containing AgX adsorbent therein for a predetermined period of time; (ii) increasing the temperature of the AgX sorbent with an optional purge gas to a temperature effective to desorb the xenon from the AgX sorbent in the adsorbent bed to produce a product stream; (iii) cooling the adsorption bed with a purge fluid that is substantially free of xenon and other impurities that may be adsorbed on the AgX adsorbent.

[14] 13. The method of claim 12, wherein the composition of the product stream comprises xenon in an amount greater than about 10 mol%, carbon dioxide in an amount up to 0.5 mol%, oxygen in an amount less than about 2 mol%, and carbon tetrafluoride in an amount less than about 1 mol%.

[15] collecting the xenon desorbed from the AgX adsorbent;

[13] The method of claim 13, further comprising: filling the xenon under pressure into a cylinder.

[16] The method of claim 13, further comprising periodically repeating steps (i), (ii) and (iii).

[17] 12. The method of claim 11, wherein each of the gaseous impurities is removed in the pretreatment system with a removal efficiency (RE) of greater than 99%.

[18] 1. A method for pre-treating and recovering a noble gas from a nitrogen-based exhaust stream exiting an etching chamber, comprising: receiving a nitrogen-based exhaust stream containing a noble gas from an etch chamber, the nitrogen-based exhaust stream having a composition of gaseous species including the noble gas, the gaseous impurities, and nitrogen, the noble gas being in an amount greater than 0 mol % to about 0.5 mol %, the gaseous impurities being: (i) a hydrofluorocarbon represented by the general formula CxHyFz, where each of x, y, and z can have any integer value ranging from 1 to 5, with the proviso that if x=1, then y+z=4, and if x=2 to 5, then y+z-2x=-2, 0, or 2; (ii) perfluorocarbons represented by the general formula CxFy, where x can have any integer value from 2 to 5, and y-2x=-2, 0, or 2; (iii) carbon monoxide (CO); (iv) hydrogen fluoride (HF); (v) silicon fluoride (SiF4); and (vi) carbon tetrafluoride (CF4), wherein each of said gaseous impurities CxHyFz, CxFy, CO, SiF4, and CF4 is in an amount of greater than 0 mol % to about 1 mol %, and HF is in an amount of greater than 0 mol % to about 2 mol %; pre-treating the noble gas-containing nitrogen-based exhaust stream by introducing the noble gas-containing nitrogen-based exhaust stream into a pre-treatment system, the pre-treatment system comprising a burner, a scrubber and an adsorber, (x) combusting a substantial portion of the CxHyFz and CxFy into combustion products comprising carbon dioxide (CO2) and water vapor (HO) to generate a diluted noble gas-containing nitrogen-based exhaust stream, (y) removing substantially all of the HF and the SiF4 in the scrubber, and (z) adsorbing substantially all of the CO2 and HO onto an adsorbent in an adsorber to generate a pre-treated diluted noble gas-containing nitrogen-based exhaust stream; removing the pre-treated diluted noble gas-containing nitrogen-based exhaust stream from an outlet of the adsorber, the pre-treated diluted noble gas-containing nitrogen-based exhaust stream having a composition including the noble gas, the gaseous impurities, and the nitrogen, the noble gas being in an amount of xenon greater than 0 mol % and less than about 0.05 mol %, and the gaseous impurities remaining after the pre-treatment including oxygen (O2) in an amount greater than 0.01 mol % to about 2 mol %, CF4 in an amount greater than 0 mol % to about 0.01 mol %, and CO2 in an amount ranging from 0.00001 mol % to about 0.0005 mol %; cooling the pretreated diluted noble gas-containing nitrogen-based exhaust stream to a first non-cryogenic temperature; and introducing the pretreated and diluted rare gas-containing nitrogen-based exhaust stream into a rare gas recovery unit; and recovering the noble gas from the diluted noble gas-containing nitrogen-based exhaust stream.

[19] 18. The method of claim 17, wherein (i) the stripping gas unit is a temperature swing adsorption (TSA) unit when the rare gas comprises xenon, and (ii) the stripping gas unit is a cryogenic distillation column when the rare gas comprises krypton.

[20] 19. The method of claim 18, wherein the noble gas is xenon, further comprising adsorbing the xenon onto the AgX adsorbent in preference to the gaseous impurities in the pretreated, diluted, xenon-containing, nitrogen-based exhaust stream remaining after the pretreatment step.

[21] 1. A pre-treatment system for pre-treating a noble gas-containing nitrogen-based exhaust stream exiting an etching chamber prior to recovering the noble gas from the noble gas-containing nitrogen-based exhaust stream, the pre-treatment system comprising: a collection manifold having an inlet operably connected to an upstream etching chamber and an outlet operably connected to a pre-treatment system, said collection manifold configured to receive a signal from each of said upstream etching chambers, said signal indicative of the presence or absence of said noble gas in an exhaust stream generated from one of said corresponding upstream etching chambers, said collection manifold configured to receive said noble gas-containing nitrogen-based exhaust stream in response to said signal, said collection manifold configured to exclude receiving a non-noble gas nitrogen-based exhaust stream not including said noble gas; The pretreatment system includes a burner, a scrubber, and an adsorber, the pretreatment system being configured to: (i) combust a substantial portion of carbon monoxide, hydrofluorocarbon, and perfluorocarbon impurities into carbon dioxide and water vapor; (ii) remove a substantial portion of hydrogen fluoride and silicon tetrafluoride impurities in the scrubber; and (iii) adsorb substantially all of the carbon dioxide and the water vapor onto an adsorbent in the adsorber to produce a pretreated, diluted rare gas-containing nitrogen-based exhaust stream.

[22] The pretreatment system described in

[21] , characterized in that the pretreatment system does not have a plasma decomposition unit, a catalytic decomposition unit, or a catalytic plasma decomposition unit.

[23] The system of

[21] , wherein the pretreatment system comprises the burner upstream of the scrubber and the scrubber located upstream of the adsorber, and further wherein the scrubber is characterized as a wet scrubber.

[24] 1. A system for pre-treating and recovering xenon from a xenon-containing nitrogen-based exhaust stream exiting an etch chamber, comprising: a collection manifold having an inlet operably connected to an upstream etching chamber and an outlet operably connected to a pre-treatment system, said collection manifold configured to receive a signal from each of said upstream etching chambers, said signal indicative of the presence or absence of xenon in an exhaust stream generated from one of said corresponding upstream etching chambers, said collection manifold configured to receive a xenon-containing nitrogen-based exhaust stream in response to said signal, and said collection manifold configured to bypass and exclude receiving a non-xenon-containing nitrogen-based exhaust stream in response to said signal; the pretreatment system includes a burner, a scrubber, and an adsorber, the pretreatment system being configured to: (i) combust a substantial portion of first impurities comprising carbon monoxide, hydrofluorocarbons, and perfluorocarbons into carbon dioxide and water vapor; (ii) remove a substantial portion of second impurities comprising hydrogen fluoride and silicon tetrafluoride in the scrubber; and (iii) adsorb a substantial portion of third impurities comprising the carbon dioxide and water vapor onto an adsorbent in the adsorber to generate a pretreated, diluted xenon-containing nitrogen-based exhaust stream; and a temperature swing adsorber (TSA) containing an adsorbent bed therein comprising an AgX adsorbent, said TSA having an inlet operably connected to an outlet of said adsorber, said TSA configured to receive said pretreated diluted xenon-containing nitrogen-based exhaust stream from said outlet of said adsorber to preferentially recover substantially all of the xenon in said xenon-containing nitrogen-based exhaust stream over said first, second and third impurities.

[25] The system described in

[24] , wherein the TSA has an outlet operably connected to a compression and cylinder filling system.

[26] 24. The system of claim 23, configured to recover a product stream of xenon having a concentration at least 20 times greater than the xenon-containing nitrogen-based exhaust stream exiting the etching chamber.

[27] 2. The system of claim 1, further comprising a guard bed positioned between the adsorber and the TSA.

[28] 2. The system of claim 1, further comprising a compressor located between the adsorber and the TSA.

[29] 1. A system for pre-treating and recovering a noble gas from a noble gas-containing nitrogen-based exhaust stream exiting an etch chamber, comprising: a collection manifold having an inlet operably connected to an upstream etching chamber and an outlet operably connected to a pre-treatment system, said collection manifold configured to receive a signal from each of said upstream etching chambers, said signal indicative of the presence or absence of said noble gas in an exhaust stream generated from one of said corresponding upstream etching chambers, said collection manifold configured to receive a noble gas-containing nitrogen-based exhaust stream in response to said signal, and said collection manifold configured to exclude receipt of a non-noble gas-containing nitrogen-based exhaust stream in response to said signal; a collection manifold configured to: (i) combust a substantial portion of first impurities, including carbon monoxide, hydrofluorocarbon and perfluorocarbon impurities, into carbon dioxide and water vapor; (ii) remove a substantial portion of second impurities, including hydrogen fluoride and silicon tetrafluoride, in the scrubber; and (iii) adsorb a substantial portion of a third impurity, including the carbon dioxide and water vapor, onto an adsorbent in the adsorber to generate a pretreated, diluted rare gas-containing nitrogen-based exhaust stream; a rare gas recovery unit configured to receive the pre-treated diluted rare gas nitrogen-based exhaust stream from the outlet of the adsorber to recover substantially all of the rare gas from the rare gas-containing nitrogen-based exhaust stream in preference to the first, second and third impurities.

[30]

[29] . The system of claim 29, wherein (i) when the noble gas comprises xenon, the noble gas recovery unit is a temperature swing adsorption (TSA) apparatus, the TSA comprising an adsorbent bed therein, the adsorbent bed comprising an AgX adsorbent, and (ii) when the noble gas comprises krypton, the noble gas recovery unit is a cryogenic distillation column.

[31] 30. The system of claim 29, wherein the collection manifold is configured to redirect the non-noble gas-containing nitrogen-based exhaust stream to an abatement system or other system for capture thereof.

[32] 1. A method for pre-treating a noble gas-containing nitrogen-based exhaust stream exiting an etching chamber prior to recovering the noble gas from the noble gas-containing nitrogen-based exhaust stream, the method comprising: receiving the noble gas-containing nitrogen-based exhaust stream from the etch chamber, the noble gas-containing nitrogen-based exhaust stream having a composition of gaseous species including: (a) the noble gas; (b) gaseous impurities; and (c) nitrogen (N2), the noble gas being in an amount of greater than 0 mol% to about 0.5 mol% and the gaseous impurities including: (i) hydrofluorocarbons; (ii) perfluorocarbons; (iii) carbon monoxide (CO); (iv) hydrogen fluoride (HF); (v) silicon fluoride (SiF4); and (vi) carbon tetrafluoride (CF4); each of the gaseous impurities of hydrofluorocarbons, perfluorocarbons, CO, SiF4, and CF4 being in an amount of greater than 0 mol% to about 1 mol% and further HF being in an amount of greater than 0 mol% to about 2 mol%; pre-treating the noble gas-containing nitrogen-based exhaust stream by introducing the noble gas-containing nitrogen-based exhaust stream into a pre-treatment system, the pre-treatment system including a burner, a scrubber, and an adsorber, the pre-treating including: (x) combusting a substantial portion of the CO, the hydrofluorocarbons, and the perfluorocarbons into combustion products including carbon dioxide (CO2) and water vapor (H2O) to generate a diluted noble gas-containing nitrogen-based exhaust stream; (y) removing substantially all of the HF and the SiF4 in the scrubber; and (z) adsorbing substantially all of the CO2 and H2O onto an adsorbent to generate a pre-treated, diluted noble gas-containing nitrogen-based exhaust stream; and removing the pretreated diluted noble gas-containing nitrogen-based exhaust stream from an outlet of the adsorber of the pretreatment system, the pretreated diluted noble gas-containing nitrogen-based exhaust stream having a composition including the noble gas, the gaseous impurities, and the N2, the noble gas being in an amount greater than 0 mol% and less than about 0.05 mol%, and the gaseous impurities remaining after the pretreatment step including oxygen (O2) in an amount greater than 0.01 mol% to about 2 mol%, CF4 in an amount greater than 0 mol% to about 0.01 mol%, and CO2 in an amount ranging from 0.00001 mol% to about 0.0005 mol%.

[33] 1. A method for pre-treating a noble gas-containing nitrogen-based exhaust stream from an etch chamber, comprising: introducing a nitrogen-based exhaust stream containing a noble gas from the etching chamber into a pretreatment system; (x) combusting a substantial portion of combustible gaseous impurities into combustion products comprising carbon dioxide (CO2) and water vapor (HO) to produce a diluted noble gas-containing nitrogen-based exhaust stream; (y) removing a substantial portion of corrosive fluorides; and (z) pretreating the noble gas-containing nitrogen-based exhaust stream by adsorbing substantially all of the CO2 and HO onto a sorbent to produce a pretreated, diluted noble gas-containing nitrogen-based exhaust stream.

[34] directing the pretreated, diluted rare gas-containing nitrogen-based exhaust stream to a rare gas recovery unit; 33. The method of claim 32, further comprising separating the rare gas as a product stream from the pre-treated, diluted rare gas-containing nitrogen-based exhaust stream in the rare gas recovery unit.

[35] 33. The method of claim 32, further comprising collecting a plurality of noble gas-containing nitrogen-based exhaust streams in a collection manifold while excluding one or more non-noble gas-containing nitrogen-based exhaust streams from entering the collection manifold.

[36] 34. The method of claim 34, wherein the composition of the product stream comprises a noble gas in an amount greater than about 10 mol%, carbon dioxide in an amount up to 0.5 mol%, oxygen in an amount less than about 2 mol%, carbon tetrafluoride in an amount less than about 1 mol%, and nitrogen.

[37] 34. The method of claim 33, wherein (i) the rare gas recovery unit is a temperature swing adsorption (TSA) unit when the rare gas comprises xenon, and (ii) the rare gas recovery unit is a cryogenic distillation column when the rare gas comprises krypton.

Claims

1. 1. A method for pre-treating a noble gas-containing nitrogen-based exhaust stream exiting an etching chamber prior to recovering the noble gas from the noble gas-containing nitrogen-based exhaust stream, the method comprising: receiving the noble gas-containing nitrogen-based exhaust stream from the etching chamber, the noble gas-containing nitrogen-based exhaust stream having a composition of gaseous species including (a) the noble gas, (b) gaseous impurities, and (c) nitrogen (N2), the noble gas being in an amount greater than 0 mol % to about 0.5 mol %, the gaseous impurities being (i) a hydrofluoric acid represented by the general formula CxHyFz, where each of x, y, and z is an integer ranging from 1 to 5, with the proviso that when x=1, y+z=4, and when x=2 to 5, y+z-2x=-2, 0, or 2; (ii) a perfluorocarbon represented by the general formula CxFy, where x can have any integer value from 2 to 5, and y-2x=-2, 0, or 2; (iii) carbon monoxide (CO); (iv) hydrogen fluoride (HF); (v) silicon fluoride (SiF4); and (vi) carbon tetrafluoride (CF4), wherein each of said gaseous impurities of CxHyFz, CxFy, CO, SiF4, and CF4 is in an amount of greater than 0 mol % to about 1 mol %, and HF is in an amount of greater than 0 mol % to about 2 mol %; pre-treating the noble gas-containing nitrogen-based exhaust stream by introducing the noble gas-containing nitrogen-based exhaust stream into a pre-treatment system, the pre-treatment system comprising a burner, a scrubber and an adsorber, (x) combusting a substantial portion of the CO, CxHyFz and CxFy into combustion products comprising carbon dioxide (CO2) and water vapor (HO) to produce a diluted noble gas-containing nitrogen-based exhaust stream, (y) removing substantially all of the HF and the SiF4 in the scrubber, and (z) adsorbing substantially all of the CO2 and HO onto an adsorbent to produce a pre-treated diluted noble gas-containing nitrogen-based exhaust stream; and removing the pretreated, diluted noble gas-containing nitrogen-based exhaust stream from an outlet of the adsorber of the pretreatment system, the pretreated, diluted noble gas-containing nitrogen-based exhaust stream having a composition including the noble gas, the gaseous impurities, and the N2, the noble gas being in an amount greater than 0 mol% and less than about 0.05 mol%, and the gaseous impurities remaining after the pretreatment step including oxygen (O2) in an amount greater than 0.01 mol% to about 2 mol%, CF4 in an amount greater than 0 mol% to about 0.01 mol%, and CO2 in an amount ranging from 0.00001 mol% to about 0.0005 mol%.

2. 2. The method of claim 1, wherein the pretreatment is characterized by the absence of a plasma decomposition step, a catalytic decomposition step, and a catalytic plasma decomposition step.

3. 2. The method of claim 1, wherein the pre-treatment step includes a process sequence in which the rare gas-containing nitrogen-based exhaust stream is introduced into an inlet of the burner, followed by an inlet of the scrubber, and then into an inlet of the adsorber, the scrubber being characterized as a wet scrubber.

4. receiving the noble gas-containing nitrogen-based exhaust stream from the etch chamber; collecting one or more of the noble gas-containing nitrogen-based exhaust streams from a corresponding noble gas-containing etching chamber, while excluding collecting one or more gas streams from the corresponding etching chamber, each of which does not contain a noble gas; 2. The method of claim 1, further comprising: directing the one or more of the noble gas-containing nitrogen-based exhaust streams into an inlet of the burner of the pre-treatment system.

5. 2. The method of claim 1, wherein the burning step further comprises introducing oxygen-enriched air or excess oxygen into the burner in an amount effective to dilute the noble gas exiting the pretreatment system by about 2 to 3 times the amount of the noble gas entering the pretreatment system.

6. 10. The method of claim 1, further comprising pressurizing the diluted rare gas-containing nitrogen-based exhaust stream after exiting the scrubber to a pressure suitable for feeding to the adsorber.

7. 2. The method of claim 1, wherein the amounts of each of CxHyFz, CxFy, CO, HF, SiF4, and CF4 in the noble gas-containing nitrogen-based exhaust stream received from the etch chamber have a lower limit that is at least 0.0001 mol %.

8. 2. The method of claim 1, wherein the pretreated, diluted noble gas-containing nitrogen-based exhaust stream enters a noble gas recovery unit at a first non-cryogenic temperature in the range of about 200 K to about 300 K, and further wherein the noble gas comprises xenon.

9. 10. The method of claim 1, wherein each of the gaseous impurities is removed with a removal efficiency (RE) of greater than about 99%.

10. 10. The method of claim 1, further comprising passing the pretreated diluted rare gas-containing nitrogen-based exhaust stream to a rare gas recovery unit.

11. 1. A method for pre-treating and recovering xenon from a nitrogen-based exhaust stream exiting an etch chamber, comprising: receiving a xenon-containing nitrogen-based exhaust stream from an etch chamber, the xenon-containing nitrogen-based exhaust stream having a composition of gas species including the xenon, gaseous impurities, and nitrogen, the xenon being in an amount of greater than 0 mol % to about 0.5 mol %, the gaseous impurities including hydrofluorocarbons, perfluorocarbons, carbon monoxide (CO), hydrogen fluoride, silicon fluoride, and carbon tetrafluoride, each of the gaseous impurities of hydrofluorocarbons, perfluorocarbons, carbon monoxide, silicon fluoride, and carbon tetrafluoride being in an amount of greater than 0 mol % to about 1 mol %, and further the hydrogen fluoride being in an amount of greater than 0 mol % to about 2 mol %; pre-treating the xenon-containing nitrogen-based exhaust stream by introducing the xenon-containing nitrogen-based exhaust stream into a pre-treatment system, the pre-treatment system comprising a burner, a scrubber and an adsorber, (x) combusting a substantial portion of the hydrofluorocarbons, perfluorocarbons and carbon monoxide into combustion products comprising carbon dioxide and water vapor to produce a diluted xenon-containing nitrogen-based exhaust stream, (y) removing substantially all of the hydrogen fluoride and silicon fluorides in the scrubber, and (z) adsorbing substantially all of the carbon dioxide and the water vapor onto an adsorbent in the adsorber to produce a pre-treated, diluted xenon-containing nitrogen-based exhaust stream; removing the pre-treated, diluted xenon-containing nitrogen-based exhaust stream from an outlet of the adsorber, the pre-treated, diluted xenon-containing nitrogen-based exhaust stream having a composition including the xenon, the gaseous impurities, and the nitrogen, the xenon being in an amount greater than 0 mol % and less than about 0.05 mol %, and the gaseous impurities remaining after the pre-treatment including oxygen in an amount greater than 0.01 mol % to about 2 mol %, carbon tetrafluoride in an amount greater than 0 mol % to about 0.01 mol %, and carbon dioxide in an amount ranging from 0.00001 mol % to about 0.0005 mol %; cooling the pretreated, diluted xenon-containing nitrogen-based exhaust stream to a first non-cryogenic temperature; and introducing said pretreated, diluted xenon-containing nitrogen-based exhaust stream into a temperature swing adsorber (TSA) containing therein an adsorbent bed comprising an AgX adsorbent; and adsorbing said xenon onto said AgX adsorbent preferentially over said gaseous impurities in said pretreated, diluted, xenon-containing nitrogen-based exhaust stream remaining after said pretreatment step.

12. 12. The method of claim 11, further comprising directing the pretreated, diluted xenon-containing nitrogen-based exhaust stream through a guard bed to remove impurities prior to performing the pretreatment step.

13. (i) maintaining the step of introducing the pretreated diluted xenon-containing nitrogen-based exhaust stream into a TSA containing AgX adsorbent therein for a predetermined period of time; (ii) increasing the temperature of the AgX adsorbent with an optional purge gas to a temperature effective to desorb the xenon from the AgX adsorbent in the adsorbent bed to produce a product stream; 12. The method of claim 11 further comprising: (iii) cooling the adsorbent bed with a purge fluid that is substantially free of xenon and other impurities that may be adsorbed onto the AgX adsorbent.

14. 14. The method of claim 13, wherein the composition of the product stream comprises xenon in an amount greater than about 10 mol%, carbon dioxide in an amount up to 0.5 mol%, oxygen in an amount less than about 2 mol%, and carbon tetrafluoride in an amount less than about 1 mol%.

15. collecting the xenon desorbed from the AgX adsorbent; 14. The method of claim 13, further comprising: filling the xenon under pressure into a cylinder.

16. 14. The method of claim 13, further comprising repeating steps (i), (ii) and (iii) periodically.

17. 12. The method of claim 11, wherein each of the gaseous impurities is removed in the pretreatment system with a removal efficiency (RE) of greater than 99%.

18. 1. A method for pre-treating and recovering a noble gas from a nitrogen-based exhaust stream exiting an etching chamber, comprising: receiving a noble gas-containing nitrogen-based exhaust stream from an etch chamber, the noble gas-containing nitrogen-based exhaust stream having a composition of gaseous species including the noble gas, gaseous impurities, and nitrogen, the noble gas being in an amount greater than 0 mole % to about 0.5 mole %, the gaseous impurities being selected from the group consisting of (i) hydrofluorocarbons represented by the general formula CxHyFz, where each of x, y, and z can have any integer value ranging from 1 to 5, where x=1, then y+z=4, and where x=2 to 5, then y+z-2x=-2, 0, or 2; (ii) perfluorocarbons represented by the general formula CxFy, where x can have any integer value from 2 to 5, and y-2x=-2, 0, or 2; (iii) carbon monoxide (CO); (iv) hydrogen fluoride (HF); (v) silicon fluoride (SiF4); and (vi) carbon tetrafluoride (CF4), wherein each of said gaseous impurities CxHyFz, CxFy, CO, SiF4, and CF4 is in an amount of greater than 0 to about 1 mol %, and HF is in an amount of greater than 0 to about 2 mol %; pre-treating the noble gas-containing nitrogen-based exhaust stream by introducing the noble gas-containing nitrogen-based exhaust stream into a pre-treatment system, the pre-treatment system comprising a burner, a scrubber and an adsorber, (x) combusting a substantial portion of the CxHyFz and CxFy into combustion products comprising carbon dioxide (CO2) and water vapor (HO) to produce a diluted noble gas-containing nitrogen-based exhaust stream, (y) removing substantially all of the HF and the SiF4 in the scrubber, and (z) adsorbing substantially all of the CO2 and HO onto an adsorbent in an adsorber to produce a pre-treated diluted noble gas-containing nitrogen-based exhaust stream; removing the pre-treated diluted noble gas-containing nitrogen-based exhaust stream from an outlet of the adsorber, the pre-treated diluted noble gas-containing nitrogen-based exhaust stream having a composition including the noble gas, the gaseous impurities, and the nitrogen, the noble gas being in an amount of xenon greater than 0 mol % and less than about 0.05 mol %, and the gaseous impurities remaining after the pre-treatment including oxygen (O2) in an amount greater than 0.01 mol % to about 2 mol %, CF4 in an amount greater than 0 mol % to about 0.01 mol %, and CO2 in an amount ranging from 0.00001 mol % to about 0.0005 mol %; cooling the pretreated diluted noble gas-containing nitrogen-based exhaust stream to a first non-cryogenic temperature; and introducing the pretreated and diluted rare gas-containing nitrogen-based exhaust stream into a rare gas recovery unit; and recovering the noble gas from the diluted noble gas-containing nitrogen-based exhaust stream.

19. 20. The method of claim 18, wherein (i) when the noble gas comprises xenon, the noble gas recovery unit is a temperature swing adsorption (TSA) unit, and (ii) when the noble gas comprises krypton, the noble gas recovery unit is a cryogenic distillation column.

20. 20. The method of claim 18, wherein said noble gas is xenon, further comprising adsorbing said xenon onto an AgX adsorbent in preference to said gaseous impurities in said pretreated, diluted xenon-containing nitrogen-based exhaust stream remaining after said pretreatment step.

21. 1. A method for pre-treating a noble gas-containing nitrogen-based exhaust stream exiting an etching chamber prior to recovering the noble gas from the noble gas-containing nitrogen-based exhaust stream, the method comprising: receiving the noble gas-containing nitrogen-based exhaust stream from the etch chamber, the noble gas-containing nitrogen-based exhaust stream having a composition of gas species including: (a) the noble gas; (b) gaseous impurities; and (c) nitrogen (N2), the noble gas being in an amount from greater than 0 mol % to about 0.5 mol % and the gaseous impurities including: (i) hydrofluorocarbons; (ii) perfluorocarbons; (iii) carbon monoxide (CO); (iv) hydrogen fluoride (HF); (v) silicon fluoride (SiF4); and (vi) carbon tetrafluoride (CF4); each of the gaseous impurities of hydrofluorocarbons, perfluorocarbons, CO, SiF4, and CF4 being in an amount from greater than 0 mol % to about 1 mol %, and HF being in an amount from greater than 0 mol % to about 2 mol %; pre-treating the noble gas-containing nitrogen-based exhaust stream by introducing the noble gas-containing nitrogen-based exhaust stream into a pre-treatment system, the pre-treatment system including a burner, a scrubber, and an adsorber, the pre-treating including: (x) combusting a substantial portion of the CO, the hydrofluorocarbons, and the perfluorocarbons into combustion products including carbon dioxide (CO2) and water vapor (HO) to produce a diluted noble gas-containing nitrogen-based exhaust stream; (y) removing substantially all of the HF and the SiF4 in the scrubber; and (z) adsorbing substantially all of the CO2 and HO onto an adsorbent to produce a pre-treated, diluted noble gas-containing nitrogen-based exhaust stream; and removing the pretreated, diluted noble gas-containing nitrogen-based exhaust stream from an outlet of the adsorber of the pretreatment system, the pretreated, diluted noble gas-containing nitrogen-based exhaust stream having a composition including the noble gas, the gaseous impurities, and the N2, the noble gas being in an amount greater than 0 mol% and less than about 0.05 mol%, and the gaseous impurities remaining after the pretreatment step including oxygen (O2) in an amount greater than 0.01 mol% to about 2 mol%, CF4 in an amount greater than 0 mol% to about 0.01 mol%, and CO2 in an amount ranging from 0.00001 mol% to about 0.0005 mol%.

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