METHOD AND APPARATUS FOR REDUCING PRESSURE AT A VACUUM PUMP EXHAUST

Abstract

An ejector device (100) configured to reduce pressure at a vacuum pump exhaust (110) by introducing a gas flow into a process gas exhaust flow between the vacuum pump exhaust and a gas treatment system for treating the process gas is disclosed. The ejector device comprises: an inlet portion including an inlet for coupling to the vacuum pump exhaust; an outlet for coupling to a conduit providing a fluid communication path to the gas treatment system; a reduced-diameter throttling portion for accelerating a gas flow from the inlet to the outlet; and a gas flow injector for introducing an injection gas flow into the reduced-diameter throttling section. Abstract figure: Figure 3

Description

Title of the invention: METHOD AND APPARATUS FOR REDUCING PRESSURE AT THE LEVEL OF A VACUUM PUMP EXHAUST FIELD OF INVENTION

[0001] The field of the invention relates to a method and apparatus for reducing the pressure at the level of a vacuum pump exhaust. BACKGROUND

[0002] Vacuum pumps can be used to evacuate vacuum chambers, such as those used in semiconductor processing. Semiconductor processing can generate gaseous byproducts, some of which can condense readily and are particularly prone to condense when pressure increases toward the vacuum pump exhaust and / or in the piping connecting the vacuum pump to a gas treatment system. This can lead to condensation and particle buildup on the pump walls, connecting piping, and / or at the inlet of the gas treatment system. This can cause the pump to seize and, in some cases, trigger a high-pressure exhaust alarm. This can result in increased energy consumption, a higher frequency of high-pressure alarm activation, and / or more frequent maintenance requirements. SUMMARY

[0003] According to one aspect, an ejector device is proposed configured to reduce a pressure at the level of a vacuum pump exhaust by introducing a gas flow into a process gas exhaust flow between said vacuum pump exhaust and a gas processing system intended to process said process gas, said ejector device comprising: an inlet part comprising an inlet intended to be coupled to said vacuum pump exhaust; an outlet intended to be coupled to a conduit providing a fluid communication path to said gas processing system; a reduced diameter throttling part (at the level of a throttling) intended to accelerate a gas flow from said inlet to said outlet; and a gas flow injector intended to introduce an injection gas flow into the reduced diameter throttling section.

[0004] It is accepted that one way to reduce condensation at the exhaust of a vacuum pump evacuating a process gas flow such as that generated by semiconductor processing can consist of reducing the pressure at the of the exhaust. It is also accepted that an ejector device can be used to reduce pressure and that this would have the advantage of having no moving parts and therefore requiring little maintenance. Although ejectors are known to reduce pressure in the field of internal combustion engines, for example, by injecting a fluid into the flow, there is a technical prejudice against introducing an additional gas flow into the exhaust of a vacuum pump pumping a process gas, as this results in an increase in the amount of gas to be processed. Furthermore, the leakage requirements for many semiconductor process gases are stringent, so adding additional devices to the exhaust flow can be complex.

[0005] In certain embodiments, said ejector device includes an outer wall forming a flow path between said inlet and said outlet, said gas flow injector including a conduit extending in said flow path and including a nozzle designed to deliver said injection gas flow at the outlet into a central region of said flow path.

[0006] The ejector can be configured such that the gas flow injector is formed by a conduit extending into the flow path to deliver the gas flow substantially axially to the central region of the flow path. This allows for the efficient addition of gas without inducing excessive turbulence, since the additional gas flow is substantially in the same direction as the exhaust gas flow. It also allows the injected gas to be directed toward the central region of the flow path where the gas flow is faster. In some embodiments, the conduit extends through the outer wall. The outer wall can be an outer annular wall.

[0007] In certain embodiments, said gas flow injector conduit extends through an outer wall of said inlet part and is configured such that said nozzle is located in a region of decreasing diameter, between said inlet part and said constriction.

[0008] The gas flow injection nozzle can be arranged in the decreasing diameter region of the inlet portion of the ejector device upstream of the constriction section. Arranging the nozzle in the decreasing diameter region is beneficial for process efficiency, as the inlet gas flow is concentrated in a region that promotes fluid acceleration.

[0009] In certain embodiments, said ejector device comprises an outer annular wall forming a flow path between said inlet and said outlet. In certain embodiments, said inlet and said outlet are axially aligned such that a central region of the inlet and the central region of the outlet are connected by a straight line. The fluid can thus flow substantially in a straight line, which reduces eddy currents that can form in the corners and cause condensation.

[0010] In certain embodiments, a wall of said portion with decreasing diameter is inclined and forms an obtuse angle with a wall of said inlet portion. The angle is chosen so as to avoid abrupt changes in direction of the wall containing the flow path and to ensure a smooth transition zone in order to reduce pressure loss and prevent powder accumulation.

[0011] In certain embodiments, the outlet of the nozzle is directed towards the constriction. This again allows the injected gas to be in the direction of the fluid flow, which reduces energy dissipation and increases efficiency.

[0012] In certain embodiments, said ejector includes an adapter for coupling said vacuum pump exhaust and said ejector inlet. In certain embodiments, said adapter is frustoconical with an increasing diameter between said exhaust and said ejector device inlet.

[0013] The vacuum pump exhaust can be of standard size and have a smaller cross-section than would be desirable in an ejector device. Therefore, a frustoconical adapter with an increasing diameter between its inlet and the ejector device can be used to couple the two components together.

[0014] In some embodiments, said nozzle is a circular or multilobed nozzle. In some embodiments, said nozzle has a diameter of between 1 and 5 mm. The diameter, position, and distance between the nozzle and the constriction are chosen to meet the required differential pressure. The nozzle diameter size allows for rapid flow of injection gas into the process gas flow path.

[0015] In certain embodiments, the gas flow injector is mounted such that the nozzle is oriented towards an axis of the ejector device, which is close to the center of a cross-section, within 20%, preferably within 5% of the diameter length from the center point. By mounting the nozzle in the gas flow towards the axis, the gas is injected into the faster-flowing region of the fluid flow, thereby improving flow symmetry and increasing efficiency.

[0016] In certain embodiments, said gas flow injector is mounted on a support frame comprising an outer annular wall for mounting in said inlet portion and spacers extending from said outer annular wall and configured to support said conduit such that said nozzle is located in said central region of said gas flow path.

[0017] When the ejector device is mounted in the fluid flow, and particularly when there is a significant fluid flow, it may be desirable to mount the ejector device conduit on a support frame in order to hold it stably in a central position away from the walls.

[0018] In some embodiments, the duct is mounted on a support frame comprising T-shaped spacers, i.e., a straight spacer extending over the diameter of the annular outer wall and a central spacer extending perpendicularly from the midpoint of the straight spacer and attaching to and supporting the duct. In other embodiments, Y-shaped spacers are proposed, i.e., three spacers extending from the outer wall, with a central spacer extending perpendicularly from the midpoint and supporting the duct. The Y-shaped spacers provide stronger support, but there is a risk of additional powder deposition, which can lead to increased blockages.

[0019] In certain embodiments, the ejector device further comprises a diffuser part between said reduced diameter constriction part and said gas flow outlet, said diffuser part having a diameter increasing from a diameter of said reduced diameter part up to a diameter of said gas outlet.

[0020] The ejector device may include a diffuser part in which the injection gas and the treatment gas flow expand and mix, which makes it possible to reduce the speed of the gas and to bring the pressure of the gas flow back to a pressure close to ambient pressure, but slightly lower than it.

[0021] In some embodiments, the ejector device includes a flow regulator for regulating a flow of said injection gas introduced into said ejector device.

[0022] The amount of gas injected into the ejector device required to prevent condensation may vary depending on the pumped process gas, and it may therefore be desirable to have a flow regulator to control the flow rate. In this regard, when used at the exhaust of a vacuum pump evacuating a semiconductor processing chamber, as the process inside the chamber changes, the quantity and type of gas generated may change, and consequently, the required amount of injection gas may also change.

[0023] In certain embodiments, said flow regulator includes a throttling valve such as an adjustable opening valve, a proportional valve or a needle valve.

[0024] In certain embodiments, said flow regulator is configured to receive signals from a pressure sensor detecting a pressure indicating an exhaust pressure of said vacuum pump, and to regulate said flow of injection gas in response to said signals.

[0025] In some embodiments, there may be feedback regulation of the injection gas, such that the flow of injected gas is regulated according to the pressure detected at or near the exhaust, which makes it possible to maintain the pressure at a desired value selected to prevent condensation, or at a value close to it.

[0026] The pressure sensor may be part of the pump or ejector, or be a separate unit. In some cases, the pressure sensor may include a display unit for showing the measured pressure, and flow regulation may be performed manually by an operator who adjusts the variable opening valve to modify the flow rate so as to maintain the pressure at or near a desired value.

[0027] In certain embodiments, said ejector device is configured for a differential pressure between said inlet and said outlet greater than 1000 Pa and for a nitrogen injection gas flow rate of less than 100 standard liters per minute. In certain embodiments, the treatment gas flow rate is less than 130 liters / min.

[0028] In some embodiments, the nitrogen injection rate is less than 100 standard liters per minute. Excessive gas flow rates are difficult to manage for many purification systems, so a lower injection gas flow rate can be applied, preferably less than 100 liters / min. The nozzle shape, diameter, position, and distance between the nozzle and the throttling are designed to meet the required differential pressure.

[0029] In certain embodiments, said ejector device has a length of less than 500 mm and a maximum diameter of less than 100 mm, and said section forming a reduced diameter constriction has a diameter greater than 20 mm.

[0030] In some embodiments, the section forming a constriction of reduced diameter has a diameter between 20 and 35 mm with a length between 90 and 110 mm.

[0031] In some embodiments, the constriction section is formed by a straight pipe that provides a space allowing the process gas and the injection gas to meet and mix, such that during the mixing process, the process gas receives energy from the injection gas and the injection gas loses energy. The velocity of the injection gas when it enters the process gas flow is greater than that of the process gas flow. In some embodiments, it is more than five times greater. The velocity of the injection gas can, in some cases, be between 180 and 220 m / s, while the velocity of the process gas before the injection of the injection gas can be between 8 and 12 m / s. The diameter of the constriction influences the gas mixing and the performance of the ejector. If the constriction is too narrow, the gas flow rate is primarily limited. The pipe's conductance restricts the amount of gas flow that can pass through the constriction, increasing pressure. If the diameter is too large, the high-velocity effect of the injection flow dissipates over a short distance. To effectively prevent powder buildup in the pumped exhaust gases from semiconductor processing, the constriction should be between 20 and 35 mm. The length of the constriction also influences ejector performance and should preferably be between 90 and 110 mm.

[0032] In certain embodiments, said ejector device is configured with a leakage rate of less than 5.4 x 105 mbarl / s.

[0033] When the ejector device is used in a vacuum pump and scrubber system to remove semiconductor processing gases, it may be important to keep the leakage rate very low, as the gases evacuated from the semiconductor processing chamber can be hazardous, flammable, and / or explosive. Such a leakage rate requires careful design and precludes the use of conventional ejector devices.

[0034] In some embodiments, the ejector device comprises an outer wall forming a flow channel including the inlet portion, the restrictor portion, and the diffuser, the outer wall being formed in one piece, with the gas injection conduit passing through an opening in the outer wall and being sealed to it. This makes it possible to maintain the leakage rate at a low level.

[0035] In some embodiments, the ejector device is made of metal (all or part of the ejector device may be made of metal). Metal is a robust material with high thermal conductivity. Furthermore, the exhaust of a vacuum pump and the ducts of a purification system may also be made of metal, allowing the ejector device to seal effectively against them.

[0036] In some embodiments, the ejector device is made of stainless steel, preferably 306 or 316 stainless steel.

[0037] In certain embodiments, said ejector device further includes a temperature control means for heating said ejector device to a predetermined temperature.

[0038] An ejector device is used to reduce the pressure at the exhaust of a vacuum pump pumping process gases in order to reduce the condensation of these gases. To reduce the condensation of these gases inside the ejector device itself, it may be advantageous to provide some temperature regulation / control function for the ejector device. The controlled temperature may depend on the pumped gases. In this regard, semiconductor processing can generate different by-products at different stages of the process and, consequently, the gases The pumped condensates will vary depending on their condensation temperatures. Therefore, the preferred operating temperature for the ejector may also vary. In some cases, the predetermined temperature may be between 100 and 250 °C.

[0039] The ejector device may include / be supplied with an inert gas, in some cases nitrogen.

[0040] According to another aspect, a vacuum pump for evacuating a treatment gas chamber is proposed, said vacuum pump comprising an ejector device according to one aspect (in particular of the type defined above), connected to an exhaust portion of said vacuum pump.

[0041] According to yet another aspect, a vacuum system comprising at least one vacuum pump and a gas treatment system is proposed, said vacuum system further comprising an ejector device (according to an aspect / of the type mentioned above), configured to receive a treatment gas evacuated from a treatment chamber by said at least one vacuum pump and to deliver said treatment gas and an injection gas to said gas treatment system.

[0042] According to yet another aspect, a method for reducing the exhaust pressure of a vacuum pump evacuating a semiconductor processing chamber is proposed, said method consisting of: fixing an ejector device according to one aspect (device such as that defined above) between an exhaust of said vacuum pump and an inlet of a gas processing system.

[0043] In some embodiments, said gas treatment system includes a gas scrubber.

[0044] In certain embodiments, said gas treatment system includes a purification system. When a device feature is described as serving to perform a function, it should be understood that it is a device feature that performs that function or is designed or configured to perform that function. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Embodiments of the present invention will now be described in more detail, with reference to the accompanying drawings, where: Fig. 1 schematically shows a vacuum pump with condensed particles; Fig. 2 schematically shows a vacuum pump, an ejector device and a gas treatment system according to one embodiment; Figure [Fig. 3] schematically shows an ejector device coupled to a vacuum pump exhaust according to one embodiment; Figure [Fig. 4] schematically shows part of an ejector device according to one embodiment; Figure [Fig. 5] schematically shows a gas flow through an ejector device according to one embodiment; Figure [Fig. 6A] schematically shows an input adapter according to one embodiment; Figure [Fig. 6B] schematically shows a conduit support according to one embodiment; Figure 6C schematically shows a conduit support according to another embodiment; and Figure 7 schematically shows an organizational chart illustrating the steps of a process according to one embodiment. DESCRIPTION OF IMPLEMENTATION METHODS

[0046] Before examining the embodiments in more detail, it is appropriate to give an overview.

[0047] Ejectors can be used to introduce a low-pressure zone into a fluid flow by injecting a fluid into the fluid flow and causing acceleration by passing it through a venturi, so as to reduce the pressure in the flow without using moving parts.

[0048] Vacuum pumps, particularly dry vacuum pumps that discharge process gases intended for treatment by a gas treatment device such as a scrubber, can suffer from particle condensation when the pressure increases inside the pump towards the exhaust. This can lead to pump seizure (as shown in [Fig. 1]) and / or a high exhaust pressure alarm. The high exhaust pressure alarm can be caused by one or more of the following: high outlet pressure; and / or a pressure fluctuation at the inlet of a gas treatment device such as a scrubber or within a connecting pipe to such a device, and can be triggered by the condensation of byproducts towards the pump exhaust. When the pump is a multi-stage pump, this can occur in the final stage.

[0049] High exhaust pressure will result in increased power consumption and trigger warnings or alarms from the dry pump system. Typically, an exhaust pressure sensor is installed on the pump to read the pump's exhaust pressure and send a signal to the main pump control device to protect its mechanism.

[0050] Fig. 1 schematically shows the condensation of by-products 32 in the final stage of a multi-stage pump where the pressure is highest, the condensation causing the pump mechanism to seize.

[0051] For example, when a vacuum pump evacuates a vacuum chamber used in an ACL etching process, byproducts such as -[CS]n- and H2SO4 are formed, and -[CS]n- is very sticky and condenses easily. H2SO4 can also be generated and cause corrosion of the pump. This can lead to pump seizure and triggering an alarm.

[0052] ACL(a-CxHy)+O2+COS->CO2+-[CS]n-+C(s, graphite)+C2(g)

[0053] -[CS]n-+H2O->H2SO4

[0054] An ejector according to one embodiment can be used to reduce local pressure and solve this problem. The ejector device is configured to reduce pressure in a defined region, such that, with appropriate positioning, it can be used to effectively reduce the pump's exhaust pressure and indirectly reduce the pressure of the last stage in a multi-stage pump. Furthermore, installing the ejector at the pump outlet, or between the pump and the gas treatment unit, closer to the pump than to the gas treatment unit, can make the dry pump's exhaust pressure substantially independent of the piping and the gas treatment unit, such as a scrubber, connected to it. This is because the ejector device ensures pressure regulation and dampens pressure variations.In addition, the partial pressure of the by-products will decrease as the total pressure to the pump exhaust decreases, and the by-products will not condense easily, thus mitigating condensation and associated problems such as pump seizing.

[0055] However, it is difficult to propose a suitable ejector with the properties required for use at the exhaust of a dry pump. Since conventional ejectors can be made of plastic, they are prone to failure. Their leakage rates are also generally too high to meet the requirements of use in semiconductor processing. They can also be bulky and difficult to install on the exhaust lines of a vacuum system, especially in the confined space of a sub-plant, and may have configurations such as angles in the flow path that make them unsuitable for the requirements of semiconductor processing gases with solid by-products.Furthermore, the quantity of injected gas used in the ejectors of the embodiments must be limited, as a large quantity of injected gas flow is difficult for a gas processing device such as a scrubber to handle.

[0056] The embodiments propose an ejector design that solves these problems and is suitable for use with a dry pump. The embodiments propose an ejector made of 304 or 316 stainless steel, which makes it robust and difficult to damage. In addition, the use of stainless steel allows a better connection between the ejector and the associated device and piping, which can also be made of stainless steel, which in turn helps to reduce the leakage rate.

[0057] The embodiments provide a compact ejector that is small and short. For example, the dimensions include a diameter of less than 100 mm and a length of less than 500 mm, making it easy to install and remove. The diameter of the constriction can be greater than or equal to 20 mm.

[0058] The quantity of injection gas flow is relatively low for an ejector device, which allows it to be processed by the scrubber without excessively affecting its operation. Generally, this quantity is kept below 100 standard liters per minute.

[0059] Indeed, the ejector is specifically designed to reduce the pump's exhaust pressure and internal pump pressure in order to facilitate the exit of the process gas from the pump, and one or more parameters among its material, length, injection gas flow, throttling diameter, operating pressure and temperature regulation and other local dimensions, are developed to make it usable in the exhaust flow of a vacuum pump of a semiconductor processing system.

[0060] Figure 2 shows a possible arrangement of an ejector device 100 according to one embodiment. The ejector device 100 is located in a conduit between the vacuum pump 10 and the gas scrubber 20. The ejector device 100 is significantly closer to the vacuum pump 10 than to the scrubber 20.

[0061] Figure 3 shows an ejector device attached to an exhaust 110 of a vacuum pump via an inlet adapter 115. In this embodiment, the vacuum pump exhaust includes a pressure sensor 170 for measuring the pressure of the gas flow exiting the vacuum pump. In other embodiments, the pressure sensor may be located on a process gas inlet of the ejector device, the process gas inlet possibly having the same diameter as the pump exhaust.

[0062] The ejector device 100 comprises a gas inlet or treatment portion 125, a narrow constriction portion 120, and an intermediate portion 126 between the inlet portion 125 and the constriction portion 120. The intermediate portion 126 is frustoconical in shape and decreases in diameter between the inlet portion and the constriction portion. A diffuser portion 150 is then located where the flow channel widens from the constriction portion 120 and where the mixing of the treatment and injection gases occurs. The inlet portion 125, the intermediate portion 126, the constriction portion 120, and the diffuser 150 are formed from a single piece of stainless steel that forms a flow path between the inlet and outlet of the ejector device. This The flow path has a central axis that lies at the center of the inlet and outlet, such that a line of sight is present between the inlet and outlet of the gas flow, although the channel width varies with the outer wall diameter as it moves from the inlet to the reduced section constriction and then to the diffuser.

[0063] The size of the ejector can vary depending on the application. The inlet portion or the gas treatment chamber of the ejector may have an inlet with a diameter chosen according to the particular process to be evacuated. An inlet adapter is provided to connect the inlet portion to the pump's exhaust pipe. The size of the inlet adapter is dictated by the pump's exhaust pipe and the inlet portion or the gas treatment chamber of the ejector. Connection methods may be threaded or flanged, but are not limited to these two examples.

[0064] The diameter and length of the constriction section 120 can be chosen according to the required differential pressure and the process to be evacuated. If the required differential pressure is high, the diameter can be smaller. Otherwise, the size can be larger to provide more space to prevent powder accumulation. Generally, the diameter of the constriction section is greater than 20 mm.

[0065] The length of the diffuser portion 150 can also be chosen according to the system and installation constraints. The inlet and outlet diameters must correspond to those of the exhaust pump and the pipe connected to the purification system.

[0066] Inside the inlet section is a conduit 130 that supplies the free-flowing process gas from the vacuum pump with injection gas, namely an inert gas such as nitrogen or argon. This conduit extends through the outer wall and is sealed to it. The conduit may be made of metal and, in some cases, of stainless steel matching that of the outer wall. The flow of injection gas can be regulated by means of a variable-opening valve or a throttling valve 160 provided for this purpose. A nozzle 140 is provided to deliver the injection gas to the ejector device just upstream of the throttling valve in the intermediate section 126. The flow rate can be adjusted to a higher rate when a high differential pressure is required and to a lower rate to reduce energy consumption when a lower differential pressure is acceptable.Several types of throttle valves can be chosen to regulate gas flow, for example a proportional valve or a needle valve.

[0067] In this embodiment, a flow regulator 180 receives signals from a pressure sensor 170 and transmits a control signal to the variable opening valve 160, so as to regulate the flow of the injection gas in the ejector 100. In other embodiments, this regulation can be carried out manually and the display unit on the pressure sensor 170 can be used to determine the pressure and an operator can regulate the valve himself according to the reading.

[0068] Figure 4 schematically shows the conduit 130 extending into the inlet portion 125 and the position of the nozzle 140 in the intermediate portion 126 of the ejector device. As shown in the figure, the nozzle is upstream of the constriction, and the angle between the inlet portion and the intermediate portion is an obtuse angle greater than 90°. This angle and this intermediate section help to create a smooth transition zone to reduce pressure loss and prevent powder buildup.

[0069] Figure 5 schematically illustrates the gas flow through an ejector device 100 according to one embodiment. The process gas enters the device at the process gas inlet 40 and flows through the process gas section or forming inlet via the injection gas duct. The injection gas is introduced through the injection gas inlet 60 and exits into the process gas flow through the nozzle 140. The mixed gases then flow through the throttling section and into the diffuser, and then exit at the mixed gas outlet 50 to a purification system. In some embodiments, the ejector device 100 includes a temperature control system or a heating element 190 which is configured to provide heat to the external surface of the ejector device and prevent any condensation of the gases inside the device.

[0070] The temperature management system 190 is generally a heating system and is particularly advantageous for processes that generate a large amount of easily condensable by-products. Its heating element can be a resistive wire or other types of heating. It may include a display unit to show the temperature and allow an operator to regulate the temperature in an open-loop system. In one variant, it may also be an automatic closed-loop system that uses a temperature sensor to help maintain the required temperature. Such a heating device is optional and can operate effectively when the external surface of the ejector device is made of metal, for example, 304 or 316 stainless steel.

[0071] Fig. 6A shows the truncated conical inlet adapter 115.

[0072] Figures 6B and 6C show two embodiments of the support frame 135, which is an optional feature for supporting the gas injection conduit in position. The support frame can be a Y-shaped structure, such as that illustrated in [Fig. 6B], or a T-shaped structure, such as that illustrated in [Fig. 6C]. The Y-shaped structure of [Fig. 6B] can be used for the processes that require a large flow of gas and that require a solid frame to support the conduit. The T-shaped structure of [Fig.6C] can be used when handling powder is problematic and many solid by-products condense, which can lead to blockage of the pipeline, so this structure is preferable to the Y-shaped structure of [Fig.0B].

[0073] Figure 7 schematically shows a flowchart illustrating the steps of a process according to one embodiment. In step S10, an inlet adapter is attached to the exhaust of a vacuum pump. In the additional step S20, the inlet of the ejector device is coupled to an outlet of the inlet adapter. In step S30, the diffuser of the ejector device is coupled to a conduit providing a fluid flow path to a gas scrubber. These steps can be carried out in any order. In step S40, the injection gas conduit is connected to an inert gas supply.When the injection gas flow control is a closed-loop control system, then in step S50 the flow control valve on the injection gas line is coupled to a feedback controller that receives signals from a pressure sensor detecting the pressure at or near the vacuum pump exhaust and regulates the opening size of the control valve. In step S60, when the ejector device includes a temperature management system such as a heating element, the temperature management system or the heating element can be connected to an electrical supply to heat the ejector device as required.

[0074] In summary, the structure of the ejector embodiments may include a process gas inlet, a pressure sensor or pressure transducer, an inlet adapter, a support frame for the injection gas flow line, an injection gas flow line, a flow regulator, a restrictor, a diffuser, and a temperature control system. The inner and outer surfaces of the ejector may be coated with a corrosion-resistant coating, such as a polymer or zinc. The ejector may be coupled to a purge flow line and / or a grid to remove by-product powder. It may be formed as a monolithic structure or may be formed from component parts sealed together.Monolithic structures can be more integrated, reduce leakage, and be less expensive to manufacture, while component structures offer greater ease of parts replacement.

[0075] In operation, the process gas flow enters the ejector through a process gas inlet orifice, and the injection gas flow enters the system through an injection orifice. The gases mix together in the throttling. and exit the ejector via the ejector diffuser to the gas outlet. The ejector's performance can be evaluated by determining the differential pressure between the inlet and outlet. Typically, the differential pressure between the inlet and outlet of this ejector's process gas is greater than 1000 Pa when the process gas flow rate is less than 130 L / min and the injection gas flow rate is less than 100 L / min.

[0076] Although embodiments of the invention, given by way of example, have been described in detail in the present invention with reference to the accompanying drawings, it should be understood that the invention is not limited to a specific embodiment and that various variations and modifications can be made by a person skilled in the art without departing from the full scope of the invention. REFERENCE SIGNS

[0077] 10 vacuum pump 20 gas scrubber 32 condensed particles 40 process gas flow inlet 50 mixing gas flow outlet 60 Injection gas flow inlet 100 ejector device 110 pump exhaust 115 input adapter 120 strangulation 125 inlet part or process gas 126 intermediate part 130 injection gas duct 135 conduit support 140 nozzle 150 diffuser part 160 throttle valve 170 pressure sensor 180 flow regulator 190 heating element

Claims

Demands

1. Ejector device (100) configured to reduce pressure at a vacuum pump exhaust (110) by introducing a gas flow into a process gas exhaust flow between said vacuum pump exhaust and a gas processing system for processing said process gas, said ejector device comprising: an inlet portion comprising an inlet for coupling to said vacuum pump exhaust; an outlet portion for coupling to a conduit providing a fluid communication path to said gas processing system; a throttling portion, of reduced diameter at a throttling (120), for accelerating a gas flow from said inlet to said outlet; and a gas flow injector for introducing, into a section forming the reduced diameter throttling, an injection gas flow.

2. Ejector device according to claim 1, said ejector device (100) comprising an outer wall forming a flow path between said inlet and said outlet, said gas flow injector comprising a conduit (130) extending in said flow path and comprising a nozzle (140) designed to deliver said injection gas flow at the outlet into a central region of said flow path.

3. Ejector device according to claim 2, said gas flow injector conduit extending through an outer wall of said inlet part and is configured such that said nozzle (140) is located in a region of decreasing diameter, between said inlet part and said constriction (120).

4. Ejector device according to claim 2 or 3, said gas flow injector being mounted on a support frame comprising an outer annular wall for mounting in said inlet portion and spacers extending from said outer annular wall and configured to support said conduit (130) such that said nozzle (140) is located in said central region of said gas flow path.

5. Ejector device according to any one of the preceding claims, further comprising a diffuser part (150) between said reduced diameter constriction part and said gas flow outlet, said diffuser part (150) having a diameter increasing from a diameter of said reduced diameter part up to a diameter of said gas flow outlet.

6. Ejector device according to any one of the preceding claims, comprising a flow regulator (180) for regulating a flow of said injection gas introduced into said ejector device.

7. Ejector device according to claim 6, said flow regulator (180) being configured to receive signals from a pressure sensor detecting a pressure indicating an exhaust pressure of said vacuum pump, and to regulate said flow of injection gas in response to said signals.

8. Ejector device according to any one of the preceding claims, said ejector device (100) being configured for a differential pressure between said inlet and said outlet greater than 1000 Pa and for an injection flow rate of nitrogen gas less than 100 standard liters per minute and a process gas flow rate less than 130 L / min.

9. Ejector device according to any one of the preceding claims, said ejector device (100) having a length less than 500 mm and a maximum diameter less than 100 mm, and said constriction section having a diameter greater than 20 mm.

10. Ejector device according to any one of the preceding claims, said ejector device (100) being configured with a leakage rate of less than 5.4 x 105 mbarl / s.

11. Ejector device according to any one of the preceding claims, said ejector device (100) being formed of a metal.

12. Ejector device according to any one of the preceding claims, said ejector device (100) further comprising a temperature control means for heating said ejector device to a predetermined temperature.

13. Vacuum pump (10) for evacuating a treatment gas chamber, said vacuum pump comprising an ejector device (100) according to any one of the preceding claims, connected to an exhaust port of said vacuum pump.

14. Vacuum system comprising at least one vacuum pump (10) and a gas treatment system, said vacuum system further comprising an ejector device (100) according to any one of claims 1 to 12, configured to receive a treatment gas evacuated from a treatment chamber by said at least one vacuum pump (10) and to deliver said treatment gas and an injection gas to said gas treatment system.

15. Method of reducing the exhaust pressure of a vacuum pump (10) evacuating a semiconductor processing chamber, said method consisting of: fixing an ejector device (100) according to any one of claims 1 to 12 between an exhaust (110) of said vacuum pump (10) and an inlet of a gas processing system.

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