NOBLE GAS RECOVERY SYSTEM

A system comprising a pumping system configured to pump respective exhaust gases from each of a plurality of chemical etching process chambers and to combine the exhaust gases to provide a combined exhaust gas, and a noble gas recovery system configured to process the combined exhaust gas to remove one or more noble gases therefrom.

FIELD OF THE INVENTION

The present invention relates to a noble gas recovery system.

BACKGROUND

Argon and Xenon are used in known etch processes. Whilst Argon is a relatively common air gas, xenon is relatively rare.

Systems for recovering noble gases, such as xenon, from dry etch processes are known. Such systems recover gas from a single etch chamber and return it to the same gas chamber in a closed loop system.

SUMMARY OF THE INVENTION

Etch processes that utilize Krypton are under development. The viability of such processes may depend on the ability to recover krypton.

The inventors have realised that vacuum and abatement systems may be used to pump gas from multiple gas chambers simultaneously using a common pump and, optionally, abatement system.

The inventors have realised that vacuum (and optionally abatement) systems that pump gas from multiple gas chambers simultaneously using a common pump may be used to recover krypton from multiple gas chambers, thereby improving efficiency and cost-effectiveness.

The present inventors have realised that an open loop system where the krypton is pumped to a collection vessel and stored at a pressure until there is sufficient to run through a final purification process may improve efficiency and cost-effectiveness.

The present inventors have realised that, with a closed loop system, there may need to be redundancy at each stage. An open loop system may reduce such a need.

In a first aspect, there is provided a system comprising a pumping system configured to pump respective exhaust gases from each of a plurality of chemical etching process chambers and to combine the exhaust gases to provide a combined exhaust gas, and a noble gas recovery system configured to process the combined exhaust gas to remove one or more noble gases (such as argon, xenon, or krypton, or any combination, mixture or blend thereof) therefrom.

In a further aspect, there is provided a system comprising a noble gas supply, a plurality of process chambers, a pumping system, and a noble gas recovery system. Each process chamber is configured to operate alongside (for example, contemporaneously, concurrently asynchronously, or simultaneously) with the other process chambers to receive a respective supply of one or more noble gases from the noble gas supply, perform an etching process using said respective supply of one or more noble gases, and output a respective exhaust gas. The pumping system is configured to pump the respective exhaust gases from the plurality of process chambers, combine the exhaust gases to provide a combined exhaust gas, and to pump said combined exhaust gas to the noble gas recovery system. The noble gas recovery system is configured to process the received combined exhaust gas to remove one or more noble gases therefrom.

In any aspect, the pumping system may comprise a common pump configured to pump the respective exhaust gases from the plurality of process chambers.

In any aspect, the pumping system may comprise a plurality of pumps (for example turbo pumps), each pump in the plurality of pumps configured to pump the exhaust gas from a respective one of the plurality of process chambers.

In any aspect, the noble gas recovery system may comprise a purification module configured to purify the combined exhaust gas. The purification module may be configured to remove gases from the combined exhaust gas using an absorber.

In any aspect, the noble gas recovery system may comprise a polishing module configured to perform a polishing process on the combined exhaust gas.

In any aspect, the noble gas recovery system may comprise a separation module configured to separate noble gas from the other components of the combined exhaust gas. The separation module may be configured to use at least gas chromatography to separate noble gases from a wide variety of other gases in the combined exhaust gas.

In any aspect, the noble gas recovery system may further comprise: a compression module configured to compress the separated one or more noble gases output by the separation module; and a storage module configured to store the compressed separated one or more noble gases. The storage module may be configured to output its contents responsive to its contents reaching a threshold level.

In any aspect, the noble gas recovery system may further comprise a distribution module configured to distribute, to the plurality of process chambers, the separated one or more noble gases output by the separation module. The noble gas recovery system may further comprise a plurality of blender boxes. Each blender box may be configured to: receive a respective first supply of one or more noble gases from the distribution module; receive a respective second supply of one or more noble gases from a further supply; mix the received first and second supplies of one or more noble gases; and supply the mixture to a respective process chamber.

In a further aspect, there is provided a method comprising: simultaneously providing to each process chamber of a plurality of process chambers, from a noble gas supply, a respective supply of one or more noble gases; simultaneously performing, by each process chamber, an etching process using said respective supply of one or more noble gases; simultaneously outputting, by each process chamber, a respective exhaust gas; pumping, by a pumping system, the respective exhaust gases from the plurality of process chambers; combining, by the pumping system, the exhaust gases to provide a combined exhaust gas; pumping, by the pumping system, said combined exhaust gas to a noble gas recovery system; and processing, by the noble gas recovery system, the received combined exhaust gas to remove one or more noble gases therefrom.

The processing may comprise separating, by a separation module, the one or more noble gases from the other components of the combined exhaust gas.

The method may further comprise: compressing, by a compression module, the separated one or more noble gases; storing, by a storage module, the compressed separated one or more noble gases; and, responsive to contents of the storage module reaching a threshold level, extracting, from the storage module, the contents of the storage module.

The method may further comprise distributing, by a distribution module, the separated one or more noble gases to the plurality of process chambers.

The combined exhaust gases may be combined, mixed, or blended with a purge gas.

The pumping system may be configured to receive a purge gas and combine the exhaust gases with the purge gas. The system may further comprise a vacuum pressure swing adsorption module configured to separate the purge gas from the combined exhaust gas. The purge gas may be nitrogen. The vacuum pressure swing adsorption module may be configured to provide the separated purge gas to the pumping system.

The noble gas recovery system may comprise a gas chromatography separation module configured to separate one or more noble gases from the other components of the combined exhaust gas using a gas chromatography process. The gas chromatography separation module may be configured to receive a carrier gas for use in transfer of the combined exhaust gas through the gas chromatography separation module. The noble gas recovery system may comprise a separation module to separate the one or more noble gases from the carrier gas. The gas chromatography separation module may be configured to receive a carrier gas for use in transfer of the combined exhaust gas through the gas chromatography separation module. The noble gas recovery system may comprise a further separation module to separate the other components of the combined exhaust gas from the carrier gas. The carrier gas may be recycled/re-used by the gas chromatography separation module. The carrier gas may be helium.

The noble gas recovery system may comprise an acid gas removal module configured to remove acidic gases from the combined exhaust gas.

The noble gas recovery system comprises a wet scrubber configured to perform a scrubbing process on the combined exhaust gas. The noble gas recovery system may comprise a drier configured to perform a drying process on a gas stream output from the wet scrubber.

The pumping system may comprise: a plurality of pumps, each pump in the plurality of pumps configured to pump the exhaust gas from a respective one of the plurality of process chambers; and a plurality of perfluorocompound (PFC) removal or conversion modules configured to remove PFCs from gas streams output by the plurality of pumps or to convert the PFCs into other compounds, each one or the plurality of PFC removal or conversion modules being coupled to a respective one of the plurality of pumps. One or more of the PFC removal or conversion modules may comprise a burners, a plasma reactors, a combined plasma catalysis (CPC) modules, and/or abatements apparatus.

The noble gas recovery system may comprise a getter module comprising a getter. The getter may be titanium.

The pumping system may be configured to receive a purge gas and combine the exhaust gases with the purge gas; and the noble gas recovery system may comprise: an acid gas removal module coupled to the pumping system and configured to remove acidic gases from the combined exhaust gas received from the pumping system; a vacuum pressure swing adsorption module configured receive a gas stream from the acid gas removal module and to separate the purge gas from the received gas stream; and a gas chromatography separation module configured to receive a gas stream from the vacuum pressure swing adsorption module, to separate one or more noble gases from the other components of the gas stream received from the vacuum pressure swing adsorption module using a gas chromatography process, and to output the separated one or more noble gases.

The pumping system may comprise: a plurality of pumps, each pump in the plurality of pumps configured to pump the exhaust gas from a respective one of the plurality of process chambers; and a plurality of perfluorocompound (PFC) removal or conversion modules configured to remove PFCs from gas streams output by the plurality of pumps or to convert the PFCs into other compounds, each one or the plurality of PFC removal or conversion modules being coupled to a respective one of the plurality of pumps; and the noble gas recovery system may comprise: a wet scrubber configured to perform a scrubbing process on the combined exhaust gas; and a drier configured to perform a drying process on a gas stream output from the wet scrubber. The noble gas recovery system may further comprise: a gas chromatography separation module configured to receive a gas stream from the drier, to separate one or more noble gases from the other components of the gas stream received from the drier using a gas chromatography process, and to output the separated one or more noble gases.

The pumping system may be configured to receive a purge gas and a further purge gas, and combine the exhaust gases with the purge gas and the further purge gas; and the noble gas recovery system may comprise: a vacuum pressure swing adsorption module configured receive a gas stream from the pumping system and to separate the purge gas from the received gas stream; a getter module comprising a getter, the getter module configured to receive a gas stream from the vacuum pressure swing adsorption module, and to remove a gas from the gas stream received from the vacuum pressure swing adsorption module; and a separation module configured to receive a gas stream from the getter module and to separate the one or more noble gases in the received gas stream from the further purge gas in the received gas stream, and to output the separated one or more noble gases.

DETAILED DESCRIPTION

FIG. 1is a schematic illustration (not to scale) of a microfabrication system100and an open loop exhaust gas processing system102, in accordance with an embodiment.

The microfabrication system100comprises a krypton supply104and a plurality of process chambers106.

The krypton supply104is configured to supply krypton gas to each of the plurality of process chambers106.

Each of the process chambers106is configured to, using the received krypton gas, perform an etch process to chemically remove layers from surfaces of wafers located therein.

The exhaust gas processing system102is operably coupled to the microfabrication system100. The exhaust gas processing system102is configured to recover the krypton used for etching by the microfabrication system100.

The exhaust gas processing system102comprises a pumping system108and a krypton recovery system110.

The pumping system108is configured to pump (e.g. at about atmospheric pressure) exhaust gas from the plurality of process chambers106to the krypton recovery system110.

The pumping system108comprises a plurality of turbo pumps112and a pumping module114.

Each turbo pump112is coupled to a respective process chamber106. Each turbo pump112is configured to pump exhaust gases from the process chamber106to which it is coupled to the pumping module114.

The pumping module114comprises a pump. The pumping module114is configured to pump exhaust gases from the turbo pumps112to the krypton recovery system110. In operation, the pumping module114receives respective flows of exhaust gas from the turbo pumps112. The pumping module114combines the received flows of exhaust gas into a single combined flow of gas. The pumping module114pumps the combined flow of gas to the krypton recovery system110.

In some embodiments, the pumping module114is further configured to receive (e.g. to pump) a further gas, which is a purge gas. The pumping module114may be configured to blend or mix the pumped exhaust gases with the pumped purge gas. This mixture or combination of exhaust gases and purge gas may then be pumped to the krypton recovery system110. Advantageously, the addition of this purge gas tends to extend the operational lifetime of the pumping module114.

The quantity and composition of the purge gas may be application dependent, and selected based on system requirements and/or operation. The quantity and composition of the purge gas may be selected to facilitate downstream separation of one or more noble gases (i.e. krypton in this embodiment) from other constituents of the gas mixture. In some embodiments, it may be beneficial if the purge gas is specifically selected such that it is easy to separate from krypton, by one or other means, in the separation module120of a krypton recovery system110. In some embodiments, the purge gas may comprise, wholly or in part, gas that would otherwise be rejected from the separation module120, after having been separated from krypton. This tends to have the effect of simplifying the separation process. In addition, this tends to increase efficiency and reduce the cost of ownership of the system as a whole, since additional gases are typically consumed within the separation module, and may be re-used if recirculated via the pump purge.

The krypton recovery system110comprises a control module116, a purification module118, a separation module120, a polishing module122, a compression module124, and a storage module126.

The control module116is configured to control operation of the other modules of the krypton recovery system110. I.e. the control module116controls operation of the purification module118, the separation module120, the polishing module122, the compression module124, and the storage module126.

The purification module118is configured to receive the combined flow of gas from the pumping module114. The purification module118is configured to purify the received combined flow of gas, thereby to provide a purified gas stream. The purification module118may be configured to remove toxic and corrosive gases from the combined flow of gas, for example, by facilitating a chemical or physical reaction between certain gases and one or more solid materials, at ambient or elevated temperature. In some embodiments, an absorber may be implemented. The purification module118is configured to provide the purified gas stream to the separation module120.

The separation module120is configured to receive the purified gas stream from the purification module118. The separation module120is configured to separate the krypton from the other components of the purified gas stream, thereby to provide a gas flow comprising separated krypton. The separation module120may be configured to use gas chromatography to separate the large, heavy and therefore slow krypton molecules from the lighter inert gases. The separation module120is configured to provide the separated krypton to the polishing module122.

The polishing module122is configured to receive the separated krypton from the separation module120. The polishing module122is configured to perform a polishing process on the gas flow comprising separated krypton, thereby to provide a polished gas flow. The term “polishing” may be understood to refer to removal of trace contaminants excluding noble gases. The polishing process may be performed using chemical means, or physical means, or more preferably a combination of chemical and physical means. The polishing module122is configured to provide the polished gas flow to the compression module124.

In some embodiments, the polishing module122is omitted from the open loop system ofFIG. 1. In such embodiments, polishing may be performed at a later stage, for example on contents retrieved from the storage module126, and may, for example, be performed at a location or other facility that is remote from the system100.

In this embodiment, the polishing module122is connected between the separation module120and the compression module124. However, in other embodiments, the polishing module122is connected between a different pair of modules. For example, in some embodiments, the polishing module122is connected between the compression module124and the storage module126instead of between the separation module120and the compression module124. In such other embodiments, the polishing module122is arranged to perform the polishing process on a compressed gas flow received from the compression module124, and to output the polished, compressed gas to the storage module126.

The compression module124comprises a compressor. In this embodiment, the compression module124is configured to receive the polished gas flow from the polishing module122. The compression module124is configured to compress the polished gas flow, thereby to provide a compressed gas flow. The compressed gas flow has a high pressure, i.e. greater than atmospheric pressure. The pressure of the compressed gas flow may be application dependent, and may be selected to ensure that a threshold amount of gas can be stored at a given volume. The compression module124is configured to provide the compressed gas flow to the storage module126.

The storage module126is configured to receive the compressed gas flow from the compression module124. The storage module126is configured to store the received compressed gas.

The storage module126may continue to receive and store the krypton-containing gas until the amount of gas and/or the amount of krypton stored therein reaches a threshold level. Once the amount of gas and/or the amount of krypton stored in the storage module126reaches said threshold level, a further (e.g. final) purification process may be performed on the stored gas to recover the krypton therein. The krypton stored in the storage module may be returned to the krypton supply104or used for a different purpose (e.g. after performance of the further purification process in some embodiments).

Thus, a microfabrication system100and open loop exhaust gas processing system102is provided.

FIG. 2is a schematic illustration (not to scale) of a microfabrication system200and a closed loop exhaust gas processing system202, in accordance with an embodiment.

The microfabrication system200comprises a krypton supply204, a plurality of blender boxes205, and a plurality of process chambers206.

The krypton supply204is configured to supply krypton gas to each of the plurality of blender boxes205.

Each of the blender boxes205is configured to receive a respective supply of krypton from the krypton supply204. Each of the blender boxes205is further configured to receive a respective supply of krypton from a distribution module228of the exhaust gas processing system202, the function of which is described in more detail later below. Each of the blender boxes205is further configured to mix or blend the krypton received from the krypton supply204and the distribution module228to form a respective blended supply of krypton.

Each of the blender boxes205is coupled to a respective process chamber206. Each of the blender boxes205is further configured to supply its respective blended supply of krypton to the respective process chamber206to which it is coupled. The blending or mixing performed by each blender box205may be such that each process chamber206is supplied with a desired or required amount of krypton. The blending or mixing performed by each blender box205may be performed to adjust the purity of the gas sent to the process chambers206, for example in cases where the krypton from the supply204and distribution module228may have different levels of trace impurities.

Each of the process chambers206is configured to, using the received krypton gas, perform an etch process to chemically remove layers from surfaces of wafers located therein.

The exhaust gas processing system202is operably coupled to the microfabrication system200. The exhaust gas processing system202is configured to recover the krypton used for etching by the microfabrication system200.

The exhaust gas processing system202comprises a pumping system208and a krypton recovery system210.

The pumping system208is configured to pump (e.g. at about atmospheric pressure) exhaust gas from the plurality of process chambers206to the krypton recovery system210.

The pumping system208comprises a plurality of turbo pumps212and a pumping module214.

Each turbo pump212is coupled to a respective process chamber206. Each turbo pump212is configured to pump exhaust gas from the process chamber206to which it is coupled to the pumping module214.

The pumping module214comprises a pump. The pumping module214is configured to pump exhaust gas from the turbo pumps212to the krypton recovery system210. In operation, the pumping module214receives respective flows of exhaust gas from the turbo pumps212. The pumping module214combines the received flows of exhaust gas into a single combined flow of gas. The pumping module214pumps the combined flow of gas to the krypton recovery system210.

In some embodiments, the pumping module214is further configured to receive (e.g. to pump) a further gas, which is a purge gas. The pumping module214may be configured to blend or mix the pumped exhaust gases with the pumped purge gas. This mixture or combination of exhaust gases and purge gas may then be pumped to the krypton recovery system210. Advantageously, the addition of this purge gas tends to extend the operational lifetime of the pumping module214.

As in other embodiments, the quantity and composition of the purge gas may be application dependent, and selected based on system requirements and/or operation. The quantity and composition of the purge gas may be selected to facilitate downstream separation of the krypton from other constituents of the gas mixture. In some embodiments, it may be beneficial if the purge gas is specifically selected such that it is easy to separate from krypton, by one or other means, in the separation module220of the krypton recovery system210. In some embodiments, the purge gas may comprise, wholly or in part, gas that would otherwise be rejected from the separation module220, after having been separated from krypton. This tends to have the effect of simplifying the separation process. In addition, this tends to increase efficiency and reduce the cost of ownership of the system as a whole, since additional gases are typically consumed within the separation module, and may be re-used if recirculated via the pump purge.

The krypton recovery system210comprises a control module216, a purification module218, a separation module220, a polishing module222, a storage module226, and a distribution module228.

The control module216is configured to control operation of the other modules of the krypton recovery system210. I.e. the control module216controls operation of the purification module218, the separation module220, the polishing module222, the storage module226, and the distribution module228.

The purification module218is configured to receive the combined flow of gas from the pumping module214. The purification module218is configured to purify the received combined flow of gas, thereby to provide a purified gas stream. The purification module218may be configured to remove toxic and corrosive gases from the combined flow of gas using an absorber such as a GRC column. The purification module218is configured to provide the purified gas stream to the separation module220. In this closed loop system, the purification module218advantageously tends to ensure no unwanted contaminants are returned to the process chambers206.

The separation module220is configured to receive the purified gas stream from the purification module218. The separation module220is configured to separate the krypton from the other components of the purified gas stream, thereby to provide a gas flow comprising separated krypton. The separation module220may be configured to use gas chromatography to separate the large, heavy and therefore slow krypton molecules from the lighter inert gases. The separation module220is configured to provide the gas flow comprising separated krypton to the polishing module222.

The polishing module222is configured to receive the separated krypton from the separation module220. The polishing module222is configured to perform a polishing process on the separated krypton, thereby to provide a polished gas flow. The polishing module222is configured to provide the polished gas flow to the storage module226.

In this embodiment, the polishing module222is connected between the separation module220and the storage module226. However, in other embodiments, the polishing module222is connected between a different pair of modules. For example, in some embodiments, the closed loop system comprises a compression module (such as that described in more detail earlier above with reference toFIG. 1). The polishing module222may be preceded by a compression module. The polishing module222is arranged to perform the polishing process on a compressed gas flow received from the compression module, and to output the polished, compressed gas to the storage module226. In some embodiments, the polishing module222is connected to a compression module that is downstream of the polishing module222, and the polishing module222outputs a polished gas flow to the compression module.

In some embodiments, the polishing module222is omitted from the closed loop system ofFIG. 2.

The storage module226is configured to receive the polished gas flow from the polishing module222. The storage module226is configured to store the received polished gas. The storage module226is configured to provide the stored krypton-containing gas to the distribution module228. In some embodiments, this storage module226may be omitted.

The distribution module228is configured to receive the krypton-containing gas from the storage module226. The distribution module228is configured to distribute the received krypton-containing gas between the blender boxes205coupled thereto. The distribution module228is configured to split or separate a flow of krypton-containing gas received from the storage module226into a plurality of separate gas flows, and to provide each of those separate gas flow to a respective blender box205. Thus, krypton is recovered and recycled.

An advantage provided by the above-described systems is that the cost and the physical footprint of the krypton recovery system is shared across multiple process chambers, thereby increasing efficiency (e.g. in terms of physical size) per processing chamber.

In the above embodiments, the pump of the pumping module114,214may be considered to be a common pump, i.e. a pump that is common to all of the process chambers106,208.

Further details of krypton recovery systems that may be implemented with the open loop exhaust gas processing system102described in more detail above with respect toFIG. 1and/or the closed loop exhaust gas processing system202described in more detail above with respect toFIG. 2will now be described with reference toFIGS. 3 to 5.

FIG. 3is a schematic illustration (not to scale) showing further details of a portion of a microfabrication system300.

The portion of the microfabrication system300shown inFIG. 3comprises a process chamber306, a turbo pump312, a pumping module314, and a krypton recovery system310.

The process chamber306may be the same as or similar to one or more of the process chambers106,206described in more detail earlier above with reference toFIGS. 1 and/or 2. Although only a single process chamber306is shown inFIG. 3, it will be appreciated that in practice, in this embodiment, there are in fact a plurality of process chambers306.

The turbo pump312may be the same as or similar to one or more of the turbo pumps112,212described in more detail earlier above with reference toFIGS. 1 and/or 2. Although only a single turbo pump312is shown inFIG. 3, it will be appreciated that in practice, in this embodiment, there are in fact a plurality of turbo pumps312. Each turbopump312is coupled to a respective process chamber306and is configured to pump exhaust gas from the respective process chamber306.

The pumping module314may be the same as or similar to one or both of the pumping modules114,214described in more detail earlier above with reference toFIGS. 1 and/or 2. The pumping module314comprises a pump, which may be a dry pump. The pumping module314is configured to pump exhaust gases from each of the turbo pumps312, via a manifold330, to the krypton recovery system310. The pumping module314combines the received flows of exhaust gas into a single combined flow of gas and pumps the combined flow of gas to the krypton recovery system310.

In this embodiment, the pumping module314is further configured to receive (e.g. to pump) a purge gas. The flow of the purge gas into the pumping module314and/or manifold is indicated inFIG. 3by arrows and a reference numeral340. The pumping module314is configured to blend or mix the pumped exhaust gases with the pumped purge gas. This mixture or combination of exhaust gases and purge gas is then pumped to the krypton recovery system310. Advantageously, the addition of this purge gas tends to extend the operational lifetime of the pumping module314.

In this embodiment, the purge gas is nitrogen.

The quantity and composition of the purge gas may be application dependent, and selected based on system requirements and/or operation. The quantity and composition of the purge gas may be selected to facilitate downstream separation of one or more noble gases (i.e. krypton in this embodiment) from other constituents of the gas mixture.

In this embodiment, the krypton recovery system310comprises an acid gas removal module350, a first compressor352, a vacuum pressure swing adsorption (VPSA) module354, a second compressor355, a plurality of first storage modules356, a gas chromatography module358, a separation module360, a carrier gas supply364, a thermal conductivity detector (TCD)366, a third compressor368, a purification module370, and a krypton storage module326.

The acid gas removal module350is coupled to the pumping module314. The acid gas removal module350is configured to receive the combined flow of gas from the pumping module314. The acid gas removal module350is configured to remove toxic, corrosive and/or acidic compounds, e.g. toxic, corrosive and/or acidic gases, from the received combined flow of gas. The acid gas removal module350may be a gas reactor column (GRC). The acid gas removal module350is configured to provide the gas stream (after removal of the toxic, corrosive and/or acidic compounds) to the first compressor352.

The first compressor352is configured to receive the gas stream output by the acid gas removal module350. The first compressor352is configured to compress the received gas stream, thereby to provide a compressed gas stream. The first compressor352is configured to provide the compressed gas stream to the VPSA module354.

The VPSA module354is configured to receive the compressed gas stream from the first compressor352. The VPSA module354is configured to separate the purge gas (and optionally other gas species) from a mixture of gases in the compressed gas stream. The VPSA module354separates gases under pressure according to the species' molecular characteristics and affinity for an adsorbent material used in the VPSA module354. Preferably, the VPSA module354separates a maximum amount of the purge gas, i.e. nitrogen in this embodiment, from the compressed gas stream. In practice, the VPSA module354may remove/separate, for example, approximately 95% of the nitrogen present in the compressed gas stream.

The VPSA module354is coupled to the pumping module314such that the separated purge gas is returned to the pumping module314for purging processes, i.e. the nitrogen purge gas is re-used or recycled.

The VPSA module354is coupled to the second compressor355such that the other gas species (i.e. other than the nitrogen purge gas) separated by the VPSA module354are sent to the second compressor355.

The second compressor355is configured to receive the gas stream output by the VPSA module354. The second compressor355is configured to compress the received gas stream, thereby to provide a compressed gas stream. The second compressor355is configured to provide the compressed gas stream to the first storage modules356.

The second compressor355is coupled to the first storage modules356via a first valve380. The first valve380is a two-way valve. The first valve380is configured to be controlled (e.g. by a control module such as control module116or control module216described in more detail above with reference toFIGS. 1 and 2) to control the flow of gas between the second compressor355and the first storage modules356.

The first storage modules356are configured to receive and store the gas received from the VPSA module354. The gas stream received by the first storage modules356may be a compressed stream, i.e. under pressure. Thus, in this embodiment, the first storage modules356receive and store a gas stream that has had at least some toxic, corrosive and/or acidic compounds, and at least a portion of the purge gas removed.

Each first storage module356is coupled to the gas chromatography module358such that gas stored in the first storage module356may be supplied to the gas chromatography module358.

Each first storage module356is coupled to the gas chromatography module358via a second valve382. The second valve382is a three-way valve. The second valve382is configured to be controlled (e.g. by a control module such as control module116or control module216described in more detail above with reference toFIGS. 1 and 2) to control the flow of gas between the first storage modules356and the gas chromatography module358.

The gas chromatography module358is configured to receive, at its inlet, a gas stream from the first storage modules356. The gas chromatography module358may comprise a gas chromatography column. Although only one gas chromatography module358(i.e. gas chromatography column) is shown inFIG. 3, it will be appreciated that, in practice, there may be a plurality of gas chromatography module/columns358. The plurality of gas chromatography module/columns358may be arranged to operate in parallel, or in series.

The gas chromatography module358is configured to separate the krypton from the other components of the received gas stream using gas chromatography. In this embodiment, in operation, lighter gases exit the gas chromatography module358first, and then heavier gases (i.e. krypton in this embodiment) exit the gas chromatography module358afterwards (i.e. at a later time).

In this embodiment, the inlet of the gas chromatography module358is coupled to a carrier gas supply364such that the gas chromatography module358receives a carrier gas from the carrier gas supply364. In this embodiment, the carrier gas is helium. The carrier gas is used by the gas chromatography module358to assist in separation of the krypton from other gas species in the received gas stream. In particular, the carrier gas is used to transfer, or carry, the received gas stream through the gas chromatography module358.

The gas chromatography module358is coupled to the carrier gas supply364via a third valve384and a fourth valve386. The third valve384is a two-way valve. The third valve384is configured to be controlled (e.g. by a control module such as control module116or control module216described in more detail above with reference toFIGS. 1 and 2) to control the flow of the carrier gas between the carrier gas supply364and the gas chromatography module358. The fourth valve386is a non-return valve.

The gas chromatography module358is coupled, at its outlet, to the TCD366.

The TCD366is configured to sense changes in the thermal conductivity of the gases exiting the gas chromatography module358to detect when different species of gases (e.g. krypton) are being output. The TCD366may compare pure helium against the gas coming out of the gas chromatography module358over time and may be calibrated to detect when the krypton is eluted from the gas chromatography module358.

The outlet of the chromatography module358is coupled, via the TCD366, to the carrier gas supply364, a system outlet367, and the separation module360.

The outlet of the chromatography module358is coupled to the carrier gas supply364via a fifth valve388. The fifth valve388is a two-way valve. The fifth valve388is configured to be controlled (e.g. by a control module such as control module116or control module216described in more detail above with reference toFIGS. 1 and 2) to control the flow of a gas output by the gas chromatography module358to the carrier gas supply364.

The output of the chromatography module358is coupled to the system outlet367via a sixth valve390. The sixth valve390is a two-way valve. The sixth valve390is configured to be controlled (e.g. by a control module such as control module116or control module216described in more detail above with reference toFIGS. 1 and 2) to control the flow of a gas output by the gas chromatography module358to the system outlet367.

The output of the chromatography module358is coupled to the separation module360via seventh and eighth valves391,392. The seventh valve391is a three-way valve. The eight valve392is a two-way valve. The seventh and eighth valves391,392are each configured to be controlled (e.g.

by a control module such as control module116or control module216described in more detail above with reference toFIGS. 1 and 2) to control the flow of a gas output by the gas chromatography module358to the separation module360.

In this embodiment, responsive to the TCD366detecting helium (i.e. the carrier gas) being output from the gas chromatography module358, the valves388,390,391,392are controlled to route the gas (i.e. the helium) output from the chromatography module358to the carrier gas supply364. Thus, the helium carrier gas can be re-used/recycled.

Also, responsive to the TCD366detecting waste gasses (which may, for example, be heavier than helium but lighter than krypton) being output from the gas chromatography module358, the valves388,390,391,392are controlled to route the gases (i.e. the waste gases mixed with helium) output from the chromatography module358to the system outlet367. These waste gasses may be abated and disposed of. The waste gases may include, but are not limited to argon, nitrogen, and/or oxygen gases which may be mixed with the helium carrier.

Also, responsive to the TCD366detecting krypton being output from the gas chromatography module358, the valves388,390,391,392are controlled to switch to routing the output gas (i.e. the krypton mixed with helium) output from the chromatography module358to the first separation module360.

In other embodiments, a different arrangement of valves to that shown inFIG. 3may be implemented to route the gases exiting the gas chromatography module358. Also, in other embodiments, a different technology for detecting which species of gases are present in the output gases may be implemented, instead of or in addition to the TCD366.

In operation, the separation module360receives from the gas chromatography module358a gas stream comprising a mixture of krypton and the helium carrier. The separation module360is configured to process this gas stream to separate the krypton from the helium carrier gas. Any appropriate gas separation technique may be used by the separation module360. For example, the separation module360may comprise a membrane, a filter, or a metal-organic framework (MOF) to separate the krypton from the helium carrier.

The separation module360is further configured to output the separated krypton, for example, to the krypton storage module326as shown inFIG. 3, or a distribution module228such as that shown inFIG. 2and described in more detail earlier above. The krypton storage module326may be similar to or the same as the storage module126described in more detail earlier above with reference toFIG. 1. In this embodiment the separation module360is coupled to the krypton storage module326via the third compressor368and the purification module370, which compress and purify the krypton, respectively, prior to it being stored in the krypton storage module326. In some embodiments, the third compressor368and/or the purification module370is omitted.

The purification module370is configured to receive the krypton output by the separation module360. The purification module370is configured to purify the received krypton. Any appropriate purification process may be performed, for example pressure swing adsorption purification or cryogenic purification.

The separation module360is further configured to output the separated helium carrier gas, and to send the helium carrier gas back to the second compressor355, whereby the helium may be re-used/recycled. A ninth valve394may regulate flow of helium back to the second compressor355from the separation module360. The ninth valve394is a two-way valve. The ninth valve394is configured to be controlled (e.g. by a control module such as control module116or control module216described in more detail above with reference toFIGS. 1 and 2).

In some embodiments, separation module360is further configured to output the separated helium carrier gas, and to send the helium carrier gas back to the carrier gas supply364.

Thus, an embodiment of a krypton recovery system is provided.

FIG. 4is a schematic illustration (not to scale) showing further details of a portion of a microfabrication system400.

Elements that are common to the embodiments shown inFIGS. 3 and 4are indicated using the same reference numerals.

The portion of the microfabrication system400shown inFIG. 4comprises a plurality of process chambers306, a plurality of turbo pumps312, a manifold330, a pumping module314, and a krypton recovery system410.

The process chambers306, the turbo pumps312, the manifold330, and the pumping module314are as described in more detail above with reference toFIG. 3, and will not be described again for the sake of brevity.

In this embodiment, the portion of the microfabrication system400further comprises a plurality of perfluorocompound (PFC) removal or conversion modules, hereinafter referred to as “PFC removal modules”402. Each PFC removal module402is coupled between a respective turbo pump312and the manifold330.

The PFC removal modules402are configured to remove PFCs from gas streams output by the turbo pumps312, or to convert the PFCs into other compounds. The PFC removal modules402may implement any appropriate PFC removal process. The PFC removal modules402may include, but are not limited to, burners, plasma reactors, combined plasma catalysis (CPC) modules, abatements modules, and the like.

In some embodiments, the krypton recovery system410may be the same as the krypton recovery system310shown inFIG. 3and described in more detail earlier above. In some embodiments, the krypton recovery system410may be the same as the krypton recovery system310, except with the acid gas removal module replaced by a wet scrubber (such as that described below). In some embodiments, the krypton recovery system410may be the same as the krypton recovery system310, except with the VPSA module354omitted. In some embodiments, the krypton recovery system410may be the same as the krypton recovery system310, except with the acid gas removal module replaced by a wet scrubber (such as that described below) and with the VPSA module354omitted.

In this embodiment, the krypton recovery system410comprises a scrubber420, a first compressor352, a first storage module356, a gas chromatography module358, the separation module360, a further separation module460, a carrier gas supply364, a second storage module466, a fourth compressor468, and (optionally) a purification module370. The krypton recovery system410further comprises the first valve380, the second valve382, a tenth valve484, an eleventh valve486, a twelfth valve488, a thirteenth valve490, a fourteenth valve492, and a fifteenth valve494. The first compressor352, the first storage module356, the gas chromatography module358, the separation module360, the carrier gas supply364, and the valves380-382are as described in more detail above with reference toFIG. 3, and will not be described again for the sake of brevity.

The scrubber420is coupled to the pumping module314. The scrubber420is configured to receive the combined flow of gas from the pumping module314. The scrubber420is configured to remove certain substances (e.g. toxic, corrosive and/or acidic compounds or gases) from the gas stream flowing through it. In this embodiment, the scrubber420is a wet scrubber configured to introduce a scrubbing liquid, for example water, into the gas stream flowing through the scrubber420. For example, the scrubber420may spray the gas stream with the scrubbing liquid, or may force the gas stream through a reservoir of the scrubbing liquid, or may implement some other contact method. In this embodiment, the scrubber420receives a supply of the scrubbing liquid, for example water, and outputs used scrubbing liquid, as indicated inFIG. 4by arrows and the reference numeral424.

Preferably, a drier is coupled to the outlet of the scrubber420to dry (i.e. remove liquid and/or vapour) from the gas stream output by the scrubber420.

The scrubber420is configured to provide the scrubbed/washed gas stream to the first compressor352.

The gas chromatography module358is coupled to the carrier gas supply364via the eleventh valve486, the second storage module466, the tenth valve484, and the second valve382. The tenth valve484is a four-way valve. The eleventh valve486is a two-way valve. The tenth and eleventh valves484,486are configured to be controlled (e.g. by a control module such as control module116or control module216described in more detail above with reference toFIGS. 1 and 2). The eleventh valve486is controlled to control the flow of the carrier gas between the carrier gas supply364and the second storage module466. The second storage module466is configured to receive and store the carrier gas received from the carrier gas supply364. The second storage module466is configured to provide the carrier gas to the gas chromatography module358for use in the gas chromatography separation process. The second and tenth valves382,484may be controlled to regulate the supply of the carrier gas to the gas chromatography module358.

The gas chromatography module358is coupled to the separation module360and the further separation module460.

An output of the chromatography module358is coupled to the further separation module460via the twelfth valve488. The twelfth valve488is a two-way valve. The twelfth valve488is configured to be controlled (e.g. by a control module such as control module116or control module216described in more detail above with reference toFIGS. 1 and 2) to control the flow of a gas output by the gas chromatography module358to the further separation module460.

Also, an output of the chromatography module358is coupled to the separation module360via a thirteenth valve490. The thirteenth valve490is a two-way valve. The thirteenth valve490is configured to be controlled (e.g. by a control module such as control module116or control module216described in more detail above with reference toFIGS. 1 and 2) to control the flow of a gas output by the gas chromatography module358to the separation module360.

In this embodiment, the valves488and490are controlled such that the relatively lighter gases (mixed with the helium carrier gas) that exit the gas chromatography module358are routed to the further separation module460, whereas the relatively heavier gases, i.e. the krypton, (mixed with the helium carrier gas) that exit the gas chromatography module358are routed to the separation module360. Any appropriate process may be used to detect when krypton is exiting the gas chromatography module358and control the valves488,490to correctly route the output gas. For example, a TCD may be implemented in a similar fashion to that described above with reference toFIG. 3.

In operation, the further separation module460receives from the gas chromatography module358a gas stream comprising a mixture of the relatively lighter gases (which may include, for example, argon, nitrogen, and/or oxygen gases) and the helium carrier. The further separation module460is configured to process this gas stream to separate the relatively lighter gases from the helium carrier gas. Any appropriate gas separation technique may be used by the further separation module460.

The further separation module460is further configured to output the separated relatively lighter gases from the system400. These gases may be output to an abatement system.

The further separation module460is further configured to output the separated helium carrier gas, and to send the helium carrier gas back to the second storage module466, where it is stored and subsequently re-used/recycled. In this embodiment, the further separation module460is coupled to the second storage module466via the fourth compressor468which compresses the helium prior to it being stored in the second storage module466.

In operation, the separation module360receives from the gas chromatography module358a gas stream comprising a mixture of krypton and the helium carrier. The separation module360is configured to process this gas stream to separate the krypton from the helium carrier gas. Any appropriate gas separation technique may be used by the separation module360. For example, the separation module360may comprise a membrane, a filter, or a metal-organic framework (MOF) to separate the krypton from the helium carrier.

The separation module360is further configured to output the separated krypton, for example, to a krypton storage module326as shown inFIG. 4, or a distribution module228such as that shown inFIG. 2and described in more detail earlier above. The krypton storage module326may be similar to or the same as the storage module126described in more detail earlier above with reference toFIG. 1.

The separation module360is further configured to output the separated helium carrier gas, and to send the helium carrier gas back to the second storage module366, where it is stored and subsequently re-used/recycled. In this embodiment, the separation module360is coupled to the second storage module366via the fourth compressor468which compresses the helium prior to it being stored in the second storage module366.

In this embodiment, optionally the input and output of the gas chromatography module358are coupled together via a pipe and fourteenth valve492. The fourteenth valve492is a two-way valve. The fourteenth valve492is configured to be controlled (e.g. by a control module such as control module116or control module216described in more detail above with reference toFIGS. 1 and 2) to control the flow of a gas output by the gas chromatography module358back to the input of the to the gas chromatography module358. Thus, gas output by the gas chromatography module358can be recirculated through the gas chromatography module358to undergo a further gas chromatography separation process.

The optional purification module370is coupled between the separation module360and the krypton storage module326. The krypton storage module326is described in more detail above with reference toFIG. 3, and will not be described again for the sake of brevity.

The purification module370is configured to receive the krypton output by the separation module360. The purification module370is configured to purify the received krypton. Any appropriate purification process may be performed, for example pressure swing adsorption purification or cryogenic purification. The purification module370is configured to output the purified krypton to either the krypton storage module326or to a further krypton storage module426(via an optional polishing module428and/or buffer volume430). The routing of the purified krypton to either the krypton storage module326or the further krypton storage module426is controlled by the fifteenth valve494. The fifteenth valve494is a two-way valve. The fifteenth valve494is configured to be controlled (e.g. by a control module such as control module116or control module216described in more detail above with reference toFIGS. 1 and 2) to control the routing of the purified krypton to either the krypton storage module326or the further krypton storage module426.

The optional polishing module428may be the same as or similar to one or both of the polishing modules122,222described in more detail earlier above with reference toFIGS. 1 and/or 2.

The buffer volume430may be a storage tank or container or the like for storing purified krypton (e.g. temporarily) before it is transferred to the further krypton storage module426.Thus, a further embodiment of a krypton recovery system is provided.

FIG. 5is a schematic illustration (not to scale) showing further details of a portion of a microfabrication system500.

Elements that are common to the embodiments shown inFIGS. 3 to 5are indicated using the same reference numerals.

The portion of the microfabrication system500shown inFIG. 5comprises a process chamber306, a turbo pump312, a manifold330, a pumping module314, and a krypton recovery system510.

The process chambers306, the turbo pumps312, the manifold330, and the pumping module314are as described in more detail above with reference toFIG. 3, and will not be described again for the sake of brevity.

Although only a single process chamber306and only a single turbo pump312is shown inFIG. 5, it will be appreciated that in practice, in this embodiment, there are in fact a plurality of process chambers306and turbo pumps312, each turbopump312being coupled to a respective process chamber306.

In this embodiment, in addition to being configured to receive the purge gas (i.e. nitrogen), as indicated inFIG. 5by arrows and a reference numeral340, the pumping module314is further configured to receive a further gas (which may be considered to be a further purge gas). In this embodiment, this further purge gas in an inert gas such as helium. The flow of the further purge gas into the pumping module314and/or manifold is indicated inFIG. 5by arrows and a reference numeral550. The flow of the further purge gas into the pumping module314may be regulated by a ninth valve552. The ninth valve552is configured to be controlled (e.g. by a control module such as control module116or control module216described in more detail above with reference toFIGS. 1 and 2) to control the flow of the further purge gas to the pumping module314.

The further purge gas may also be supplied to the turbo pump312.

The pumping module314and/or the turbo pump312are configured to blend or mix the pumped exhaust gases with further purge gas (and the purge gas in the case of the pumping module314).

The pumping module314is configured to pump the mixture of gases to the first compressor352of the krypton recovery system510.

In this embodiment, the krypton recovery system510comprises a first compressor352, a VPSA module354, a getter module502, a first pump504, a third separation module506, a second pump508, a first buffer volume509, a second buffer volume512, and a plurality of krypton supplies514. The first compressor352, and the VPSA module354are as described in more detail above with reference toFIG. 3, and will not be described again for the sake of brevity.

The getter module502is configured to receive a gas stream output from the VPSA module354. The getter module502comprises a getter, i.e. a deposit of reactive material placed in the gas flow path. The getter may be a coating applied to a surface within the getter module502. The getter may be a titanium getter, e.g. a hot titanium getter. In operation, when gas molecules strike the getter material, they combine with it chemically or by absorption. Thus, the getter removes amounts of gases from the gas stream. In particular, in this embodiment, the getter is configured to remove one or more gases selected from the group consisting of PFCs, hydrogen, and nitrogen. The getter module502is further configured to provide the gas stream (after removal of gases by the getter) to the first pump504.

The first pump504is configured to receive the gas stream output by the getter module502. The first pump504is configured to pump the received gas stream to the third separation module506.

In operation, the third separation module506receives, from the first pump504, a gas stream comprising a mixture of krypton and helium (and possibly other gases). The third separation module506is configured to process this gas stream to separate the krypton from the helium (and possibly other gases). Any appropriate gas separation technique may be used by the third separation module506. For example, the third separation module506may comprise a membrane, a filter, or a metal-organic framework (MOF) to separate the krypton from the helium.

The third separation module506is further configured to output the separated helium gas, and to send the helium gas to the turbo pump312and/or the pumping module314, to which the helium is supplied as the further purge gas. In this embodiment, the third separation module506provides the separated helium to the turbo pump312and/or the pumping module314via the second pump508(which pumps the helium) and the first buffer volume509, which may temporarily store the helium. Thus, the further purge gas (i.e. the helium) is re-used/recycled.

The third separation module506is further configured to output the separated krypton to, for example, a krypton storage module326, via the second buffer volume512as shown inFIG. 5, or to a distribution module228such as that shown inFIG. 2and described in more detail earlier above. The krypton storage module326may be similar to or the same as the storage module126described in more detail earlier above with reference toFIG. 1.

The second buffer volume512is configured to receive the separated krypton from the third separation module506. The second buffer volume512is further configured to receive additional (e.g. top-up) krypton from the krypton supplies514. The flow of the additional krypton from the krypton supplies514is regulated or controlled by a plurality of sixteenth valves520. The sixteenth valves520are two-way valves. The sixteenth valves520are configured to be controlled (e.g. by a control module such as control module116or control module216described in more detail above with reference toFIGS. 1 and 2) to control the flow of krypton from the krypton supplies514and the second buffer volume512. The second buffer volume512is configured to store a mixture of the separated krypton from the third separation module506and the additional krypton from the krypton supplies514. The second buffer volume512is configured to output stored krypton to the krypton storage module326.

Optionally, an analysis module516is implemented to perform an analysis of the compositions of the mixture stored in the second buffer volume512.

Thus, a further embodiment of a krypton recovery system is provided.

In the above embodiments, krypton is used in the process chambers and recovered by the krypton recovery system. However, in other embodiments, the systems used a different noble gas instead of or in addition to krypton. Examples of other appropriate noble gases include but are not limited to argon and xenon. Blends or mixtures of multiple different noble gases, such as any combination of argon, xenon, and krypton, may be used.

In the above embodiments, there is a plurality of process chambers. However, in other embodiments there is only a single process chamber.

REFERENCE NUMERALS

102—open loop exhaust gas processing system

110—krypton recovery system

202—closed loop exhaust gas processing system

210—krypton recovery system

310—krypton recovery system

340—purge gas flow

350—acid gas removal module

356—first storage module

364—carrier gas supply

326—krypton storage module

402—PFC removal module

424—scrubbing liquid flow

426—further krypton storage module

460—further separation module

466—second storage module

506—third separation module

509—first buffer volume

510—krypton recovery system

512—second buffer volume