Exhaust gas emission reduction system

Abstract

The invention provides a waste gas emission reduction system for semiconductor processing. The system includes a vacuum pump having an exhaust outlet, a water injector coupled to the exhaust outlet of the vacuum pump, and a separator coupled to the water injector. The system also includes an exhaust emission reduction device coupled to the gaseous exhaust outlet of the separator. Wherein the system is configured such that, in use, an exhaust stream from the exhaust outlet of the vacuum pump is delivered to the separator via the water injector, and wherein, in use, the separator is configured to separate a gaseous component of the exhaust stream from a non-gaseous component of the exhaust stream.

Description

Technical Field

[0001] The present invention relates to an exhaust gas abatement system for semiconductor processing, a method for abatement of exhaust gas from a semiconductor processing chamber, and the use of a water ejector and a separator in an exhaust gas abatement system for semiconductor production. Background Art

[0002] Semiconductor products are produced by processing single crystal silicon wafers through many photolithography, deposition and etching steps. When performing these steps, various precursor chemical vapors are used, and these steps are usually performed under high vacuum. Typically, the efficiency of using the chemical vapors in the manufacture of semiconductor devices is quite low. It is estimated that in some cases, more than 50 percent of the precursor chemical vapors leave the semiconductor processing chamber through the outlet (i.e., vacuum foreline) connected to the vacuum pump. Subsequently, the precursor chemical vapor can be transported through the vacuum pump in the form of an exhaust stream.

[0003] When the exhaust stream leaves the exhaust port of the vacuum pump, it is typically diluted with nitrogen to reduce the possibility of chemical vapor condensation. Nitrogen also helps reduce the flammability of the resulting mixture, thereby improving safety. In addition, the pump exhaust line is typically heated to reduce the possibility of condensation of volatile chemical vapors. The nitrogen-diluted chemical vapor mixture is delivered to an abatement system for destruction using high temperatures generated by either combustion (e.g., methane gas) or by arc discharge.

[0004] The length of the vacuum pump exhaust line is typically from about 15 feet (4.572 meters) to about 40 feet (12.192 meters). The vacuum pump exhaust line connects the vacuum pump to the abatement system.

[0005] The presence of precursor chemical vapors in the vacuum pump exhaust line can cause many different problems depending on the chemical vapor and conditions.

[0006] For example, titanium tetrachloride, when reacted with ammonia, is used in chemical vapor deposition of titanium nitride thin films. Titanium tetrachloride is a liquid at room temperature and is highly reactive with water. When titanium tetrachloride is used in semiconductor processing, the vacuum pump exhaust composition may contain unreacted titanium tetrachloride and ammonia in nitrogen. Any "cold spots" along the exhaust line may cause titanium tetrachloride to condense. This can lead to hazardous conditions because the accumulation of liquid chemicals may undergo subsequent reactions and cause localized corrosion in the pump exhaust line. This can be particularly dangerous in the presence of water condensation during semiconductor processing or routine maintenance.

[0007] Tungsten hexafluoride has a boiling point of 17°C, reacts with water, and is widely used in semiconductor processing. Diluting the vacuum pump exhaust stream containing tungsten hexafluoride with nitrogen and heating the vacuum pump exhaust line are critical for safe and continuous operation.

[0008] Ammonium nitrate is a product of various chemical vapor reactions that can occur in semiconductor processing chambers or along the vacuum foreline. Ammonium nitrate has a melting point of 169.6°C and a boiling point of 210°C. If the pump exhaust line is not heated to at least 250°C, the ammonium nitrate may condense and deposit. The accumulation of ammonium nitrate in the vacuum pump exhaust line may produce local deposits that can explode in reaction with the pump exhaust or due to friction / vibration of the exhaust line, such as during maintenance schedules.

[0009] Advanced semiconductor processing by atomic layer deposition (ALD) often employs vapors of chemical precursors, such as trimethylaluminum (TMA). Trimethylaluminum has a boiling point of approximately 125°C to 130°C and reacts violently with water. During the atomic layer deposition process, the vacuum pump exhaust line must be heated uniformly along its length to a temperature of at least 200°C. Any cold spots in the vacuum exhaust line may cause trimethylaluminum to condense, requiring removal via extremely dangerous and expensive maintenance procedures. Condensation of trimethylaluminum at the inlet of exhaust abatement systems has been widely reported. As a result, this may require increased maintenance frequency under potentially hazardous conditions.

[0010] In other thin film processes, a tetrakis(dimethylamino)titanium precursor may be used. The exhaust gas stream generated by using this precursor may lead to a large amount of particulate deposition in the vacuum pump exhaust line. This may clog the input nozzle of the abatement system, resulting in frequent downtime and high production costs.

[0011] It would therefore be desirable to provide an improved exhaust abatement system to reduce deposition of chemical precursors, thereby reducing the frequency of maintenance required and the risks associated therewith.

[0012] The present invention is directed to at least partially addressing these and other problems associated with the prior art.The embodiments described in further detail below seek to provide an improved exhaust abatement system for semiconductor processing. Summary of the invention

[0013] The invention is defined in the appended claims.

[0014] In a first aspect, the present invention provides an exhaust abatement system for semiconductor processing. The system comprises a vacuum pump and a water ejector, the vacuum pump comprising an exhaust outlet, and the water ejector coupled to the exhaust outlet of the vacuum pump. The system further comprises a separator coupled to the water ejector. The system further comprises an exhaust abatement device, preferably an abatement furnace, coupled to the gaseous exhaust outlet of the separator. The system is configured such that, in use, an exhaust flow from the exhaust outlet of the vacuum pump is delivered to the separator via the water ejector. The separator is configured to separate, in use, a gaseous component of the exhaust flow and a non-gaseous component of the exhaust flow.

[0015] For purposes of the present invention, semiconductor processing may include processing silicon wafers through one or more lithography, deposition and etching steps.Semiconductor processing may include, for example, one or more physical vapor deposition, chemical vapor deposition, electrochemical deposition, molecular beam epitaxy and / or atomic layer deposition steps.

[0016] The exhaust stream from the semiconductor processing step may include precursor chemical vapors. Typically, the exhaust stream may be diluted with nitrogen. Preferably, the exhaust gas may be diluted with nitrogen at the exhaust port of the vacuum pump. Advantageously, this may reduce the risk of precursor chemical vapor condensation and may reduce the flammability of the exhaust stream. Nitrogen may be introduced into the exhaust stream at a flow rate of from about 20 slm to about 150 slm.

[0017] In use, the vacuum pump can be configured to evacuate a chamber in which semiconductor processing is performed. During use, the vacuum pump can be connected to an exhaust outlet of the semiconductor processing chamber. An exhaust flow from the semiconductor processing chamber can be conveyed by the vacuum pump and exits via the vacuum pump exhaust outlet. The exhaust flow can be primarily gaseous, but can also include non-gaseous materials (e.g., solid and / or liquid components). During operation, the pressure at the pump outlet is typically about 1 atmosphere.

[0018] Those skilled in the art will appreciate that the present invention can be applied to various types of vacuum pumps and will be able to select a suitable vacuum pump according to the requirements of a specific application. The vacuum pump may be, for example, a turbomolecular pump and / or a multi-stage Roots pump. For example, the vacuum pump may be an iGX dry pump produced by Edwards Ltd.

[0019] The water ejector may preferably be arranged at or adjacent to the exhaust outlet of the vacuum pump. In the water ejector, the exhaust stream including any chemical precursors may be mixed with water. The relatively high flow rate of the water injected into the water ejector may facilitate this mixing. Chemical substances in the exhaust stream that react with water may react with the water in the water ejector and / or dissolve in the water and thereby be removed from the gaseous components of the exhaust stream.

[0020] Additionally or alternatively, the water ejector can remove solid components from the exhaust stream. For example, solid deposits and / or aerosol particles formed at the exhaust outlet of the vacuum pump can be dissolved when mixed with water in the water ejector. Advantageously, positioning the water ejector adjacent to the exhaust outlet of the vacuum pump can reduce the likelihood of chemical vapors condensing in the vacuum pump exhaust line prior to the water ejector.

[0021] The separator may preferably be arranged at or adjacent to the outlet of the water ejector. Preferably, the inlet of the separator is directly connected to the outlet of the water ejector. The exhaust gas flow from the water ejector may flow directly into the inlet of the separator. Advantageously, conveying the exhaust gas flow through the separator may separate the gaseous components of the exhaust gas flow from the non-gaseous components of the exhaust gas flow.

[0022] The exhaust abatement device may be configured to process the gaseous components of the exhaust stream from the separator. The processing may include, for example, abatement in a gas (e.g., natural gas or methane) burner or an arc burner. Preferably, the exhaust abatement device is an abatement furnace. For example, the exhaust abatement device may include an inwardly fired burner, a plasma chamber, and / or an arc discharge chamber. For example, the exhaust abatement device may be an Atlas manufactured by Edwards Ltd. TM .

[0023] The exhaust abatement device may be coupled to the gaseous exhaust outlet of the separator. Typically, the exhaust abatement device may be coupled to the gaseous exhaust outlet of the separator via an exhaust line. The exhaust line may be heated to a temperature of at least 100°C, preferably a temperature of at least 200°C.

[0024] In a typical system of the prior art, the vacuum pump exhaust outlet is fluidly connected to the exhaust abatement device via a vacuum pump exhaust line. The length of the vacuum pump exhaust line can be up to about 40 feet (i.e., 12.192 meters). It has been found that condensation of precursor chemical vapors in the vacuum pump exhaust line is particularly common in prior art systems. However, in the present invention, the conveyance of the exhaust stream through a water ejector and a separator between the vacuum pump exhaust outlet and the abatement device can remove precursor chemical vapors that react with water from the exhaust stream. Therefore, the possibility of condensation of precursor chemical vapors in the exhaust line can be reduced.

[0025] Advantageously, the present invention can remove precursor chemical vapors that react with water from the exhaust stream, as well as solid deposits in the vacuum pump or the vacuum pump exhaust line. In addition, inorganic acids present in the exhaust stream can also be dissolved in the water jet. This can reduce the formation of deposits in the vacuum pump exhaust line and / or the exhaust abatement equipment. In particular, this can reduce the possibility of condensation of precursor chemical vapors at the vacuum pump exhaust outlet and / or the inlet of the exhaust abatement equipment. Therefore, the frequency of maintenance can be reduced and the safety of the system can be improved.

[0026] Typically, the water ejector may include an inlet coupled to the exhaust outlet of the vacuum pump. The water ejector may include a nozzle configured to inject water. The water ejector may further include a mixing throat. In use, the exhaust flow from the vacuum pump may be mixed with the injected water in the mixing throat. The water ejector may further include an expander diffuser coupled to the mixing throat. The expander diffuser may be defined by a chamber having an increasing cross-sectional area in the direction of the water ejector outlet.

[0027] The inlet of the water ejector may be directly connected to the exhaust outlet of the vacuum pump. Alternatively, the inlet of the water ejector may be coupled to the exhaust outlet of the vacuum pump via an exhaust line (e.g., a tube). In use, the water ejector may create a vacuum at the exhaust inlet. Advantageously, this may draw gas through the exhaust outlet of the vacuum pump and / or may reduce backflow of gas through the exhaust outlet.

[0028] For purposes of the present invention, water may be defined as water, distilled water, or an aqueous solution. In some embodiments, the water injected through the nozzle of the water injector may include recycled wastewater from an acid tank of an exhaust abatement device, and / or recycled wastewater from elsewhere in the semiconductor processing machinery. The composition of the water or aqueous solution may depend on the composition of the exhaust gas stream and the specific semiconductor process being performed.

[0029] The water may be supplied to the nozzle by a pump. The pump may be part of the exhaust abatement device, or may be a separate component. The water may provide what may be referred to as a motive fluid for the water injector. The water injector is typically a venturi injector. Typically, during use, the velocity of the water injected through the nozzle may be greater than the velocity of the exhaust gas flow through the water injector inlet. Advantageously, this may improve mixing of the exhaust gas flow and the water.

[0030] The cross-sectional area of ​​the water injector may be reduced at the mixing throat. Advantageously, this may promote mixing of the water and exhaust gas flow in the mixing throat.

[0031] The expander diffuser may be directly connected to the outlet of the mixing throat. The cross-sectional area of ​​the chamber defining the expander diffuser may increase substantially continuously in the outlet direction of the water ejector. The chamber defining the expander diffuser may have a first (e.g., proximal) cross-sectional area adjacent to the mixing throat. The chamber defining the expander diffuser may have a second (e.g., distal) cross-sectional area adjacent to the outlet of the water ejector. The first cross-sectional area may be smaller than the second cross-sectional area. The cross-sectional area of ​​the chamber defining the expander diffuser may increase substantially continuously between the first cross-sectional area and the second cross-sectional area. The chamber defining the expander diffuser may be substantially frustoconical.

[0032] Water can be injected through the nozzle under pressure. As the water passes through the nozzle, the velocity of the water can increase. According to Bernoulli's principle, this can cause the water pressure to decrease. The water can then mix with the exhaust flow from the vacuum pump exhaust outlet in the mixing throat and transfer kinetic energy to it. As the exhaust and water mixture leaves the mixing throat and travels through the expander diffuser, the cross-sectional area of ​​the chamber defining the expander diffuser increases. Therefore, the velocity of the exhaust and water mixture can be reduced, and the pressure can be increased. This can generate a pressure difference between the outlet of the water ejector and the exhaust inlet, resulting in the generation of a vacuum at the inlet of the water ejector via the Venturi effect.

[0033] The water ejector may comprise a valve configured to enable control of the flow rate of water injection through the nozzle. Preferably, the valve is a fluid shut-off valve.

[0034] Advantageously, the water ejector may enable a vacuum to be generated at the inlet of the water ejector. For the purposes of the present invention, the vacuum generated by the water ejector may be defined as a relatively low pressure compared to the pressure at the exhaust outlet of the vacuum pump. The pressure at the exhaust outlet of the vacuum pump is typically about 1 atmosphere. Although the water ejector has no mechanically moving parts, a vacuum may be generated. The vacuum generated may vary depending on the size of the water ejector, the components selected (e.g., nozzle), the water flow rate, and the water pressure. The water ejector may also beneficially allow mixing of a three-phase exhaust flow (i.e., the exhaust flow includes gas, liquid, and / or solid components). In addition, the water ejector provides a low-maintenance solution to the problems associated with prior art systems.

[0035] Typically, the separator may include an inlet coupled to the water ejector outlet. The separator may further include a first chamber including a first liquid outlet and a gaseous exhaust outlet. In use, the first chamber may be configured to be partially filled with a liquid (e.g., water) such that the uppermost surface of the liquid defines a fill line. The first liquid outlet will typically be arranged below the fill line, and the gaseous exhaust outlet will typically be arranged above the fill line. The gaseous exhaust outlet may be connected to an exhaust abatement device.

[0036] Preferably, the separator may further include a second chamber, the second chamber including a liquid inlet that is in fluid communication with the first liquid outlet of the first chamber. The second chamber may further include another (i.e. second) liquid outlet. The second chamber may be arranged so that in use, the liquid flows through the second chamber in a direction substantially opposite to the direction in which the liquid flows through the first chamber. In use, the second chamber may be located below the first chamber so that any gas in the liquid is biased upwards towards the gas outlet.

[0037] The separator may be configured to separate, in use, gaseous components of the exhaust stream from non-gaseous components of the exhaust stream. The gaseous components of the exhaust stream may include gases that are insoluble in water and / or any gaseous byproducts of a reaction between a precursor chemical vapor and water. For example, the gaseous components may include nitrogen, oxygen, argon, ozone, nitrogen trifluoride, hydrogen and / or methane, etc. The non-gaseous components may include water or an aqueous solution, any chemical species dissolved therein, and any solid deposits carried by the water.

[0038] Typically, the separator may be a horizontal separator.

[0039] In use, the exhaust gas flow entering the first chamber of the separator may be directed towards the inlet diverter and / or the wall of the chamber. This may reduce the velocity of the exhaust gas flow. Non-gaseous components of the exhaust gas flow may fall into the liquid contained in the first chamber.

[0040] In use, the flow rate of water injected through the nozzle of the water injector can be controlled to be substantially consistent with the flow rate of the liquid flowing out of the separator, or vice versa. The amount of liquid in the first chamber can be maintained so that the gaseous exhaust outlet is arranged above the fill line and the first liquid outlet is arranged below the fill line. This can increase the probability that the gaseous components of the exhaust flow can leave the separator via the gaseous exhaust outlet, and can reduce the probability that the gaseous components of the exhaust flow can leave the separator via the first liquid outlet.

[0041] Typically, the separator may further include a third chamber having a liquid inlet and another (i.e., the third) liquid outlet that is fluidly connected to the second liquid outlet. The third chamber may be arranged so that liquid flows through the third chamber in a direction substantially opposite to the direction in which the liquid flows through the second chamber. Typically, in use, the third chamber may be located below the second chamber.

[0042] Typically, the liquid exiting the separator may be conveyed to an acid waste processing machine. The acid waste processing machine may be part of an exhaust gas abatement plant.

[0043] Advantageously, the third chamber may further prevent gaseous components of the exhaust flow from leaving the separator via the third liquid outlet. Instead, the gaseous components of the exhaust flow may be biased towards leaving via the gaseous exhaust outlet. Those skilled in the art will appreciate that one or more further chambers may be present after the third chamber and are typically arranged so that liquid flows through the chamber in a direction substantially opposite to the direction of liquid flow in the previous chamber.

[0044] The separator may include an inlet diverter.The inlet diverter may be configured to direct non-gaseous components of the exhaust gas flow towards the liquid in the first chamber.

[0045] The separator may include a moisture extractor. The moisture extractor may be configured to substantially prevent non-gaseous components of the exhaust flow from passing through the gaseous exhaust outlet. Preferably, the moisture extractor may provide a physical barrier for solids and / or liquids to pass through the gaseous exhaust outlet. The moisture extractor may cause droplets carried by the gaseous components of the exhaust flow to coalesce and be directed back into the first chamber. The moisture extractor may be arranged at or towards the gas exhaust outlet. The moisture extractor may include a wire mesh and / or a plurality of blades.

[0046] Additionally or alternatively, the separator may include a liquid level sensor in the first chamber. The liquid level sensor may be operably connected to the controller. The controller may be configured to adjust the flow rate and / or pressure of water entering the water ejector. The liquid level sensor and the controller may maintain the water level (fill line) in the first chamber at a preferred level, such as below the gaseous exhaust outlet and / or above the first liquid outlet.

[0047] Typically, the water ejector may be configured to substantially prevent gas from flowing back through the exhaust outlet of the vacuum pump. Additionally or alternatively, the water ejector may be configured to produce a flow rate of nitrogen of at least 40 slm through the exhaust inlet. Preferably, the water ejector may be configured to produce a flow rate of nitrogen of at least 100 slm through the exhaust inlet. The water ejector may be configured to produce a flow rate at least equal to the flow rate of nitrogen introduced into the exhaust flow. Advantageously, this may substantially prevent gas from flowing back into the vacuum pump through the exhaust outlet when in use, thereby facilitating pumping performance.

[0048] Typically, at a pressure of 5 psi (i.e., 34.4738 kPa), the water flow rate through the nozzle of the water ejector may be at least 0.5 gallons per minute (i.e., 2.27304 liters per minute). Preferably, at a pressure of 50 psi (i.e., 344.738 kPa), the water flow rate through the nozzle of the water ejector may be at least 5 gallons per minute (i.e., 22.7304 liters per minute). Advantageously, controlling the pressure and flow rate of water through the nozzle of the water ejector may enable control of the vacuum created at the inlet of the water ejector.

[0049] In some embodiments, the water jet may have a length of less than about 200 mm, preferably less than about 160 mm. The water jet may have a height of less than about 150 mm, preferably less than about 100 mm. The water jet may have a width of less than about 50 mm, preferably less than about 30 mm.

[0050] Additionally or alternatively, the separator may have a length of less than about 250 mm, preferably less than about 160 mm. The separator may have a height of less than about 150 mm, preferably less than about 100 mm. The separator may have a width of less than about 150 mm, preferably less than about 100 mm.

[0051] Advantageously, the compact design of the water ejector and / or separator can enable them to be installed in an exhaust abatement system where space is limited. In addition, the compact design can allow the water ejector and separator to be positioned closer to the vacuum pump exhaust outlet, thereby reducing the likelihood of precursor chemical vapors condensing before reaching the water ejector.

[0052] Typically, the water ejector may be configured to be heated to a temperature of at least 100°C during operation. Preferably, the water ejector may be configured to be heated to a temperature of at least 200°C during operation. For some applications, the temperature of the vacuum pump exhaust stream may be from about 100°C to about 200°C, or higher. In this case, the water ejector may be heated to reduce the likelihood of condensation of the precursor chemical vapor upon entering the water ejector due to the temperature drop. The water ejector may include a heating element, such as a heating tape, configured to maintain the water ejector at a selected temperature.

[0053] Typically, the water ejector may be made of a polymer material and / or a metal-containing material. Preferably, the water ejector may consist of a single material. The material selected may depend on the application.

[0054] For example, in embodiments where the water ejector comprises a polymer material, the material of the water ejector may be selected from a list comprising polypropylene, chlorinated polyvinyl chloride (CPVC), or Teflon. In embodiments where the water ejector is made of a metal-containing material, the material of the water ejector may be selected from a list comprising stainless steel, acid-resistant Hastelloy, copper, or brass.

[0055] For applications where the water ejector is heated when in use, the water ejector may preferably be made from a metal-containing material. For example, the water ejector may comprise stainless steel.

[0056] For applications where the exhaust gas stream from the vacuum pump contains mineral acids (such as hydrofluoric acid or hydrochloric acid), the water ejector may preferably comprise Hastelloy steel.

[0057] Advantageously, selecting a particular material for a water ejector may increase component life, and / or reduce cost, depending on the application.

[0058] In another aspect, the present invention provides a method for reducing exhaust gas from a semiconductor processing chamber. The method comprises the following steps:

[0059] a. evacuating the exhaust gas from the semiconductor processing chamber by operation of a vacuum pump;

[0060] b. conveying the exhaust gas leaving the vacuum pump through a water ejector so that the exhaust gas is mixed with water;

[0061] c. conveying the exhaust gas and water mixture from the water injector through a separator, thereby separating the gaseous components of the exhaust gas from the non-gaseous components; and

[0062] d. Processing of the gaseous components of the exhaust gas in exhaust gas abatement equipment.

[0063] For the avoidance of doubt, further features of the vacuum pump, water ejector, separator and / or exhaust abatement device may be as defined in the first aspect and elsewhere herein.

[0064] Typically, step (a) may include operation of a vacuum pump to provide a high vacuum or ultra-high vacuum within the semiconductor processing chamber. High vacuum may be defined as a pressure ranging from about 10 -7 mbar to about 10 -3 mbar. Ultrahigh vacuum can be defined as pressure less than about 10 -7 millibar.

[0065] Typically, the exhaust gas can be diluted with nitrogen. Preferably, the exhaust gas can be diluted with nitrogen at the exhaust outlet of the vacuum pump. The exhaust gas can be diluted with nitrogen having a flow rate of about 20 slm to about 150 slm. Advantageously, this can reduce the risk of precursor chemical vapor condensation and can reduce the flammability level.

[0066] Preferably, throughout steps (b) and (c), the water ejector may be heated to a temperature above about 100° C., preferably above about 200° C. Advantageously, this may reduce the likelihood of condensation of the chemical precursor gas upon entering the water ejector, particularly where the vacuum pump exhaust is at an elevated temperature (e.g., a temperature above 100° C.).

[0067] Preferably, throughout step (b), the water ejector may provide a vacuum at the exhaust outlet of the vacuum pump to draw the exhaust flow into the water ejector. Preferably, the water ejector may provide a vacuum at the exhaust outlet of the vacuum pump sufficient to cause a flow rate at least equal to the flow rate of nitrogen dilution. More preferably, the water ejector may provide a vacuum sufficient to cause a flow rate of nitrogen of at least 40 slm through the exhaust inlet of the water ejector. Advantageously, this may substantially prevent backflow of gas through the exhaust outlet of the vacuum pump.

[0068] In another aspect, the present invention provides the use of a water ejector and a separator in an exhaust gas abatement system for semiconductor production, wherein the water ejector and the separator are arranged between a vacuum pump and an exhaust gas abatement device so that exhaust gas from the vacuum pump is conveyed to the separator via the water ejector.

[0069] Preferably, the water ejector and the separator may be arranged directly adjacent to the exhaust outlet of the vacuum pump.The vacuum pump, the water ejector, the separator and the exhaust abatement device may be arranged in series and may be fluidly connected.

[0070] For the avoidance of doubt, further features of the vacuum pump, water ejector, separator and / or exhaust abatement device are as defined in the preceding aspects and elsewhere herein.

[0071] Advantageously, the use of a water ejector and separator according to the present invention can provide a low-cost and efficient mechanism for removing chemical precursor gases that react with water from semiconductor processing exhaust gas streams. As a result, condensation of the chemical precursor gases within the exhaust line can be reduced, and the mean time between failures of the exhaust abatement system can be increased. This can result in safer and less scheduled maintenance.

[0072] For the avoidance of doubt, all aspects and embodiments described herein may be combined with necessary modifications. It is also to be understood that the invention is not limited to the embodiments and aspects set forth in the following detailed description or shown in the accompanying drawings. The invention may be implemented in various other embodiments and may be implemented in alternative ways not expressly disclosed herein.

[0073] In addition, it is to be understood that the words and terms used herein are for descriptive purposes and should not be considered limiting. The use of "include" and "comprises" and variations thereof is meant to cover the items listed thereafter and their equivalents as well as additional items and their equivalents. In addition, enumeration can be used in the description of various embodiments. Unless otherwise expressly stated, the use of enumeration should not be interpreted as limiting the present invention to any particular order or number of components. The use of enumeration should also not be interpreted as excluding from the scope of the present invention any additional steps or components that may be combined with or incorporated into the enumerated steps or components. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] Preferred features of the present invention will now be described by way of example with reference to the accompanying drawings, in which:

[0075] Figure 1 A schematic diagram showing a typical semiconductor processing system of the prior art is shown;

[0076] Figure 2 A cross-sectional view showing a water injector suitable for use in an exhaust gas abatement system according to the present invention;

[0077] Figure 3 A cross-sectional view showing a water injector and separator suitable for use in an exhaust gas abatement system according to the present invention;

[0078] Figure 4 A cross-sectional view showing a vacuum pump, a water ejector and a separator suitable for use in an exhaust gas abatement system according to the present invention;

[0079] Figure 5 A flow chart of a method according to the invention is shown. DETAILED DESCRIPTION

[0080] Figure 1 A schematic diagram of a typical semiconductor processing system of the prior art is shown. The system comprises a semiconductor processing chamber (1). In the chamber (1), a single crystal silicon wafer is processed via a plurality of photolithography, deposition and / or etching steps using various precursor chemical vapors. The processing is carried out under high vacuum or ultra-high vacuum. Therefore, the semiconductor processing chamber (1) is connected to a vacuum pump (3) via a foreline (2).

[0081] The vacuum pump (3) may be, for example, a dry vacuum pump. In use, the vacuum pump (3) is configured to evacuate the semiconductor processing chamber (1) to a high vacuum. The exhaust gas flows out of the vacuum pump (3) through the vacuum pump exhaust line (4).

[0082] In use, the exhaust flow in the vacuum pump exhaust line (4) may be diluted with nitrogen to reduce the possibility of condensation of the exhaust flow in the vacuum pump exhaust line (4).

[0083] The nitrogen diluted exhaust stream can be delivered via a vacuum pump exhaust line (4) to an exhaust abatement device (5) where the exhaust gas is processed. The processing includes exposing the exhaust gas to high temperatures generated by an inwardly burning combustion chamber, a plasma chamber, or an arc discharge. The processed exhaust gas is then allowed to exit the exhaust abatement device (5) through a gas outlet (6).

[0084] It has been found that in such systems, a significant portion of the precursor chemical vapors leave the semiconductor processing chamber (1) in the exhaust gas flow through the foreline (2) and pass through the vacuum pump (3), the vacuum pump exhaust line (4), and into the exhaust abatement equipment (5). This is undesirable because condensation of the precursor chemical vapors can form deposits and react with any water in the system. It has been found that deposit formation can be particularly prevalent in the vacuum pump exhaust line (4), thereby increasing the frequency of maintenance required.

[0085] Figure 2 A cross-sectional view of a water ejector (7) suitable for use in an exhaust gas abatement system according to the present invention is illustrated. The water ejector (7) comprises an inlet (8) configured to be coupled to an exhaust outlet of a vacuum pump (not shown). Preferably, the inlet (8) may be directly connected to the exhaust outlet of the vacuum pump. Alternatively, the inlet (8) may be coupled to the exhaust outlet of the vacuum pump via an exhaust gas line.

[0086] The water ejector (7) further comprises a nozzle (9) configured for injecting water. In use, the injected water may provide a motive fluid for the venturi effect generated by the water ejector (7). In use, pressurized water may be supplied to the nozzle (9) from a pump (not shown). Typically, the water flow rate through the nozzle (9) of the water ejector (7) may be at least 0.5 gallons per minute (i.e. 2.27304 liters per minute) at 5 psi (i.e. 34.4738 kPa), preferably at least 5 gallons per minute (i.e. 22.7304 liters per minute) at 50 psi (i.e. 344.738 kPa).

[0087] The water injector also includes a mixing throat (10). In use, water injected through the nozzle (9) mixes in the mixing throat (10) with the exhaust gas flow entering through the inlet (8). The cross-sectional area of ​​the water injector (7) may be narrowed at the mixing throat (10). This may advantageously improve mixing.

[0088] The water ejector (7) further comprises an expander diffuser (11) coupled to the mixing throat (10). The chamber defining the expander diffuser (11) may have an increasing cross-sectional area in the direction of the outlet (12) of the water ejector (7). The chamber may have a first cross-sectional area adjacent to the mixing throat (10), and a second cross-sectional area adjacent to the outlet (12) of the water ejector (7), wherein the first cross-sectional area is smaller than the second cross-sectional area. The cross-sectional area of ​​the chamber defining the expander diffuser (11) may increase substantially continuously between the first cross-sectional area and the second cross-sectional area. The chamber defining the expander diffuser (11) may be substantially frustoconical. In use, water and exhaust gas flows may be conveyed through the chamber.

[0089] In use, the water ejector (7) may provide a vacuum at the inlet (8) via the Venturi effect. Advantageously, this may draw gas out of the exhaust outlet of the vacuum pump and may reduce backflow of gas through the exhaust outlet.

[0090] In use, the water injector (7) may be heated to a temperature of at least 100°C, preferably at least 200°C. Advantageously, this may reduce the likelihood of condensation of precursor chemical vapors that may be present in the exhaust gas stream. In such an embodiment, the water injector (7) is made of a metal-containing material, such as stainless steel.

[0091] Figure 3 The figure shows a cross-sectional view of a water injector (7) and a separator (13) suitable for use in an exhaust gas reduction system according to the present invention. Figure 2 As shown, corresponding reference numerals will be used and the description of the features will not be repeated.

[0092] The separator (13) comprises an inlet (14) coupled to the outlet (12) of the water ejector (7). The separator (13) further comprises a first chamber (15) comprising a first liquid outlet (16) and a gaseous exhaust outlet (17). The first chamber (15) is configured to be partially filled with liquid in use such that an uppermost surface of the liquid defines a fill line. Figure 4 As shown, in use, the first liquid outlet (16) is arranged below the liquid level and the gaseous exhaust outlet (17) is arranged above the liquid level. The gaseous exhaust outlet (17) is connected to an abatement device (not shown).

[0093] The separator (13) further comprises a second chamber (18) having an inlet fluidically connected to the first liquid outlet (16) of the first chamber (15) and a second liquid outlet (19). Figure 4 As will be shown in Figure 1, the second liquid outlet (19) is arranged so that, in use, liquid flows through the second chamber (18) in a direction substantially opposite to the direction in which liquid flows through the first chamber (15).

[0094] The separator (13) is configured to separate, in use, gaseous components of the exhaust stream from non-gaseous components of the exhaust stream. The gaseous components of the exhaust stream may include any gas that is not dissolved in the water in the water injector (7), and / or gaseous products of a reaction between the exhaust stream and the water. The non-gaseous components may include water, any chemical species dissolved therein, and any solid sediment carried in the water.

[0095] In this embodiment, the separator (13) further comprises a third chamber (20). The third chamber (20) has a liquid inlet fluidically connected to the second liquid outlet (19). The third chamber has a third liquid outlet (21). The third chamber (20) can be arranged so that, in use, liquid flows through the third chamber (20) in a direction substantially opposite to the direction in which the liquid flows through the second chamber (18). In this embodiment, the third liquid outlet (21) provides an outlet for the separator (13).

[0096] Figure 4 A cross-sectional view of a vacuum pump (22), a water ejector (7) and a separator (13) suitable for use in an exhaust gas reduction system according to the present invention is shown. The water ejector (7) and the separator (13) are respectively as shown in FIG. Figure 2 and 3 The same will be described herein and corresponding reference numerals will be used.

[0097] In use, a semiconductor processing chamber (not shown) is evacuated by a vacuum pump (22). The exhaust flow from the semiconductor processing chamber and therefore from the vacuum pump (22) may include precursor chemical vapors. A motive flow of water (W1) is injected through a nozzle (9) at a predetermined pressure and flow rate. The exhaust flow (G1) leaves the vacuum pump (22) and is delivered to the water ejector (7) through an inlet (8). The water (W1) mixes with the exhaust gas (G1) in the mixing throat (10) and transfers kinetic energy to it. Most of the components of the exhaust gas flow that react with water can be dissolved in water. Preferably, this can include precursor chemical vapors and / or inorganic acids that react with water present in the exhaust gas flow.

[0098] The exhaust gas flow (W2), i.e. the mixture of exhaust gas and water, then leaves the mixing throat (10) and enters the expander diffuser (11). As the cross-sectional area of ​​the chamber defining the expander diffuser (11) increases in the direction of the outlet (12), the velocity of the exhaust gas flow (W2) decreases and the pressure increases. Thus, due to the generated pressure difference, a vacuum is formed at the inlet (8) to draw the exhaust gas (G1) into the water ejector (7).

[0099] The exhaust gas stream (W2) then leaves the expander diffuser (11) and enters the first chamber (15) of the separator (13) via the inlet (14). In use, the first chamber (15) is partially filled with liquid so that the uppermost surface of the liquid defines a fill line (23). The fill line (23) is maintained so that the first liquid outlet (16) is arranged below the fill line (23) and the gaseous exhaust gas outlet (17) is arranged above the fill line (23).

[0100] The exhaust gas flow (W2) entering the first chamber (15) of the separator (13) is directed toward an inlet diverter or a wall (24) of the first chamber (15). This can reduce the velocity of the exhaust gas flow (W2) and its non-gaseous components can flow into the liquid contained in the first chamber (15). The direction (A) of the liquid flow through the first chamber (15) is towards the liquid outlet (16).

[0101] The liquid then enters the second chamber (18). The direction (B) of the liquid flow through the second chamber (18) is towards the second liquid outlet (19). The direction (B) is substantially opposite to the direction (A) of the liquid flow through the first chamber (15).

[0102] The liquid then enters the third chamber (20). The direction (C) in which the liquid flows through the third chamber (20) is towards the third liquid outlet (21). The direction (C) is substantially opposite to the direction (B) in which the liquid flows through the second chamber (18). The first chamber (15) may be positioned above the second chamber (18). The second chamber may be positioned above the third chamber (20).

[0103] The alternating directions (A, B, C) of the water flow through the first (15), second (18) and third chambers (20), respectively, can reduce the likelihood of the gaseous components of the exhaust flow leaving the separator (13) via the third outlet (21). Instead, the gaseous components (G2) of the exhaust flow are biased to leave the separator (13) through the gaseous exhaust outlet (17).

[0104] Although not shown in this embodiment, a moisture diffuser may be present to reduce the likelihood of liquid droplets passing through the gaseous exhaust outlet (17).

[0105] A water level sensor (not shown) may be present in the first chamber (15). The water level sensor may be coupled to a controller. The controller may be configured to adjust the rate of water through the nozzle (9) to ensure that the fill line (23) is maintained at an appropriate level within the first chamber (15).

[0106] Figure 5 A flow chart of a method according to the invention is shown.For the avoidance of doubt, the features of the vacuum pump, water ejector, separator and exhaust abatement device may be as defined in any other aspect or embodiment described herein.

[0107] The method comprises the step of evacuating exhaust from the semiconductor processing chamber by operation of a vacuum pump (25). This step may comprise operation of the vacuum pump to produce a high vacuum or an ultra-high vacuum in the semiconductor processing chamber. Preferably, when the exhaust leaves the vacuum pump, it may be diluted with nitrogen (26).

[0108] The exhaust gas is then conveyed from the vacuum pump through the water ejector so that the exhaust gas is mixed with water (27). Preferably, the water ejector can provide a vacuum at the exhaust gas outlet of the vacuum pump sufficient to draw the exhaust gas into the water ejector. More preferably, the water ejector can provide a flow rate sufficient to draw at least 40 slm of nitrogen through the exhaust gas inlet. Preferably, the water ejector is heated to a temperature greater than about 100°C, preferably a temperature greater than about 200°C.

[0109] The exhaust gas and water mixture is then conveyed from the water ejector through a separator whereby gaseous components of the exhaust gas are separated from non-gaseous components (28).

[0110] The gaseous components are then processed in the exhaust gas abatement device (29). The non-gaseous components are discharged through the liquid outlet of the separator.

[0111] For the avoidance of doubt, the features of any aspect or embodiment described herein may be combined mutatis mutandis. It will be appreciated that various modifications may be made to the illustrated embodiments without departing from the spirit and scope of the invention as defined by the appended claims, as interpreted by patent law, including the doctrine of equivalents. Any reference to a claim element in the singular, such as using the articles "a," "an," "the," or "said," should not be construed as limiting the element to the singular.

[0112] Reference numerals

[0113] 1. Semiconductor processing chamber

[0114] 2. Foreline

[0115] 3. Vacuum pump

[0116] 4. Vacuum pump exhaust pipeline

[0117] 5. Waste gas emission reduction equipment

[0118] 6. Gas outlet

[0119] 7. Water jets

[0120] 8. Entrance

[0121] 9. Nozzle

[0122] 10. Hybrid Throat

[0123] 11. Expander Diffuser

[0124] 12. Export

[0125] 13. Separator

[0126] 14. Entrance

[0127] 15. First Chamber

[0128] 16. First liquid outlet

[0129] 17. Gaseous exhaust outlet

[0130] 18. Second Chamber

[0131] 19. Second liquid outlet

[0132] 20. The third chamber

[0133] 21. Third liquid outlet

[0134] 22. Vacuum pump

[0135] 23. Fill line

[0136] 24.Wall

[0137] 25. Step 1

[0138] 26. Step 2

[0139] 27. Step 3

[0140] 28. Step 4

[0141] 29. Step 5

Claims

1. A waste gas reduction system for semiconductor processing, comprising: a vacuum pump including an exhaust outlet; a water ejector coupled to an exhaust outlet of the vacuum pump; a separator coupled to the water ejector; and an exhaust gas abatement device, preferably an abatement furnace, coupled to the gaseous exhaust gas outlet of the separator; wherein the system is configured such that, in use, an exhaust gas flow from an exhaust gas outlet of the vacuum pump is delivered to the separator via the water ejector, And wherein the separator is configured to separate, in use, a gaseous component of the exhaust gas flow and a non-gaseous component of the exhaust gas flow.

2. The exhaust gas reduction system according to claim 1, wherein: The water ejector comprises: an inlet coupled to an exhaust outlet of the vacuum pump; a nozzle configured to inject water; a mixing throat in which, when in use, the injection water is mixed with an exhaust flow from the vacuum pump; and An expander diffuser is coupled to the mixing throat and is defined by a chamber having an increasing cross-sectional area in an outlet direction of the water ejector.

3. The exhaust gas reduction system according to claim 1 or 2, wherein: The separator comprises: an inlet coupled to an outlet of the water ejector; a first chamber comprising a first liquid outlet and a gaseous exhaust outlet and configured to be partially filled with liquid such that an uppermost surface of the liquid defines a fill line, and wherein the first liquid outlet is arranged below the fill line and the gaseous exhaust outlet is arranged above the fill line; and, preferably, a second chamber comprising a liquid inlet in fluid communication with the first liquid outlet of the first chamber and having a further liquid outlet, wherein the second chamber is arranged such that, in use, liquid flows through the second chamber in a direction substantially opposite to the direction in which liquid flows through the first chamber.

4. The exhaust gas reduction system according to claim 3, wherein: The separator further comprises a third chamber having a liquid inlet fluidly connected to the second liquid outlet and a further liquid outlet, the third chamber being arranged such that liquid flows through the third chamber in a direction substantially opposite to the direction in which liquid flows through the second chamber.

5. The exhaust gas reduction system according to claim 3 or 4, wherein: The separator further comprises an inlet diverter, and / or a moisture extractor, and / or a liquid level sensor in the first chamber.

6. An exhaust gas abatement system according to any preceding claim, wherein: The water ejector is configured to substantially prevent gas from flowing back through the exhaust outlet of the vacuum pump, and / or wherein, The water ejector is configured to generate a flow rate of at least 40 slm of nitrogen through the inlet.

7. An exhaust gas abatement system according to any preceding claim, wherein: The water flow rate through the nozzle of the water ejector is at least 0.5 gallons per minute at 5 psi, and preferably at least 5 gallons per minute at 50 psi.

8. An exhaust gas abatement system according to any preceding claim, wherein: The water jet has a length of less than about 200 mm, preferably less than about 160 mm; a height of less than about 150 mm, preferably less than about 100 mm; and a width of less than about 50 mm, preferably less than about 30 mm.

9. An exhaust gas abatement system according to any preceding claim, wherein: The separator has a length of less than about 250 mm, preferably less than about 160 mm; a height of less than about 150 mm, preferably less than about 100 mm; and a width of less than about 150 mm, preferably less than about 100 mm.

10. An exhaust gas abatement system according to any preceding claim, wherein: The water ejector is configured to be heated to a temperature of at least 100°C, preferably at least 200°C, during operation.

11. An exhaust gas abatement system according to any preceding claim, wherein: The water ejector is made of a polymer material and / or a metal-containing material.

12. A method for reducing exhaust gas from a semiconductor processing chamber, comprising the steps of: a. evacuating the exhaust gas from the semiconductor processing chamber by operation of a vacuum pump; b. The exhaust gas leaving the vacuum pump is conveyed through a water ejector so that the exhaust gas is mixed with water; c. conveying the exhaust gas and water mixture from the water injector through a separator, thereby separating the gaseous components of the exhaust gas from the non-gaseous components; and d. Processing the separated gaseous components of the exhaust gas in an exhaust gas abatement plant.

13. The method according to claim 12, wherein: Throughout steps (b) and (c), the water ejector is heated to a temperature greater than about 100°C, preferably greater than about 200°C.

14. The method according to claim 12 or 13, wherein: Throughout step (b), the water ejector provides a vacuum at the exhaust outlet of the vacuum pump to draw the exhaust gas into the water ejector.

15. Use of a water ejector and a separator in an exhaust gas abatement system for semiconductor production, wherein: The water ejector and the separator are arranged between a vacuum pump and an exhaust gas abatement device such that exhaust gas from the vacuum pump is delivered to the separator via the water ejector.

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