Liquid filter device equipped with a heat shield

Abstract

The liquid filter apparatus for gas / solids separation includes a housing with a filter chamber, a semiconductor process gas inlet, and a process gas outlet. The filter chamber forms a liquid tank, and the semiconductor process gas inlet and the process gas outlet are in communication with the filter chamber. The housing further includes a filter liquid inlet and a filter liquid outlet that are in communication with the liquid tank for delivering filter liquid to the liquid tank and removing filter liquid from the liquid tank, respectively.

Description

Technical Field

[0001] (Related Application) The present invention relates to U.S. Application No. 16 / 893,504, filed on June 5, 2020, the entire disclosure of which is incorporated herein by reference.

Background Art

[0002] Typically, the manufacture of semiconductor devices utilizes the conversion of certain chemical substances by oxidation at a silicon wafer temperature ranging from a moderate temperature to a high temperature in order to form the desired thin films that make up the circuit layers of the semiconductor device. For example, in a chemical vapor deposition (CVD) process, a silicon dioxide film deposited on a silicon wafer is formed by the oxidation of silane with oxygen at a wafer temperature of about 400°C and a process chamber pressure of about 300 mTorr. Also, a silicon dioxide film is formed by oxidizing vapor tetraethylsiloxane, TEOS, with oxygen and ozone under substantially similar processing conditions. Further, a silicon dioxide film is formed at a lower temperature by a low-pressure vapor phase plasma-enhanced method (PECVD). In another process, silane is reacted with ammonia to form silicon nitride at low pressure and a moderate wafer temperature. In almost all other CVD reactions, such as the formation of tungsten and tungsten silicide thin films, approximately 75% of the gas feed reactants supplied to the process chamber pass through the process chamber without being converted.

[0003] The typical semiconductor processing chamber discharge is a gaseous stream, which is low-pressure and consists of unconverted feed reactants, reaction byproducts, diluent nitrogen carrier gas, and particles. These particles are byproducts of gas-phase reactants of reactants heated in the gas phase and continue to form along a foreline extending over the distance between the processing chamber and the vacuum pump, increasing in volume. Figure 1 is a schematic diagram of a typical CVD or PECVD system comprising a processing chamber connected to a vacuum pump via a foreline. The vacuum pump is connected via a discharge line to a typical gas discharge abatement system, which uses a natural gas flame to break down unreacted process gases and then removes acidic gaseous byproducts in a gas / water absorption column. The products of such abatement system consist of an acidic wastewater stream, which is usually neutralized and discharged, and a gaseous stream containing particulate matter, which is released into the atmosphere after passing through a large-surface-area mechanical particle filter.

[0004] Particles cover all connection lines between the processing chamber, vacuum pump, and abatement system, frequently clogging and blocking these lines, resulting in significant maintenance downtime and substantial additional operating costs. Often, vacuum pumps become inoperable due to high levels of particle buildup, forcing shutdown. Vacuum pumps are periodically removed and replaced from such lines at very high material and labor costs. In some processes, mechanical filters are placed in the vacuum foreline to capture these particles and extend the life of the vacuum pump. Often, both the foreline and pump discharge line are heated to prevent condensation of unconverted condensable reactants, which then help absorb and agglomerate gas-containing particles, resulting in liquid / solid clumps that are very difficult to remove and costly.

[0005] The best way to achieve particle separation from a gas-containing particle stream is to use a liquid medium. For example, particles can be separated from a large gas flow by passing the gas-containing particle stream through a high-flow water shower. High-level particle separation into a water stream can be achieved by appropriately sizing the tank volume and water discharge rate. While such a separation process is effective and economical when using water, it cannot be used in semiconductor processes due to the possibility of harmful chemical reactions between reactants in the gas stream and water, and the extremely high water vapor pressure in low-pressure forelines. In vacuum CVD and PECVD semiconductor processes, molecular water present in the foreline diffuses backward into the processing chamber itself, degrading the chemical composition of the semiconductor thin film being processed. [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] In some applications, it is necessary to remove particles from extremely hot gas flows within the foreline of a semiconductor processing system. For example, the exhaust gas in the foreline may be a hot gas flowing through the foreline with temperatures of approximately 100°C to 200°C. In some applications, it is necessary to remove particles immediately after a foreline plasma abatement system operating at a very low vacuum. In either case, the liquid filter may need to be modified to ensure that extremely hot gas or plasma exhaust does not directly collide with the fluid. [Means for solving the problem]

[0007] Therefore, low-pressure forelines in CVD and PECVD semiconductor processes are equipped with liquid filter devices that use a liquid as a medium to separate particles from a gas-containing particle stream.

[0008] In one embodiment, a liquid filter apparatus for separating semiconductor process waste from a semiconductor process includes a housing having a filter chamber, a process waste inlet, a process waste outlet, and a feed pipe communicating with the process waste inlet and a feed pipe outlet communicating with the filter chamber. The filter chamber forms a liquid tank that holds the filter liquid inside, and the process waste outlet communicates with the filter chamber. A deflection surface is positioned between the filter liquid and the feed pipe outlet to deflect the process waste so as not to cause the process waste flowing from the feed pipe outlet to directly collide with the filter liquid, and further to absorb heat from the process waste.

[0009] In one embodiment, the deflection surface is formed of a plate such as stainless steel, which absorbs heat from process waste and thus forms a heat sink. For example, the plate can be non-porous.

[0010] In another embodiment, a liquid filter apparatus for separating semiconductor process waste from a semiconductor process includes a housing having a filter chamber, a process waste inlet, a process waste outlet, and a feed pipe communicating with the process waste inlet and a feed pipe outlet communicating with the filter chamber. The filter chamber forms a liquid tank that holds the filter liquid inside, and the process waste outlet communicates with the filter chamber. A heat sink is positioned adjacent to the feed pipe to absorb heat from the process waste and cool the process waste before it collides with the filter liquid. For example, the heat sink may have a deflection surface to prevent the process waste flowing from the feed pipe outlet from directly colliding with the filter liquid.

[0011] In all of the above, the supply pipe includes an open distal end that forms the outlet of the supply pipe.

[0012] In any of the above, the housing includes a discharge chamber between the liquid tank and the process waste outlet for guiding the filtered process waste flow from the liquid tank to the process waste outlet.

[0013] In all of the above cases, the supply pipe outlet has an outer diameter, the deflection surface has an outer circumference, and the outer circumference of the deflection surface is larger than the outer diameter of the supply pipe outlet.

[0014] In a further embodiment, the housing includes an internal conduit that is in fluid communication with a liquid tank and a discharge chamber, and guides the flow of filtered process waste from the liquid tank to the discharge chamber.

[0015] In any of the above, the liquid filter device further includes a filter fluid control system for controlling the inflow into and outflow of the filter fluid from the liquid tank. For example, the filter fluid control system may include a control device and a fluid circuit, the control device controlling the fluid circuit to regulate the flow of the filter fluid into and out of the liquid tank.

[0016] In any of the above, the liquid filter device may further include a support that supports the deflection surface above the filter liquid in the liquid tank.

[0017] In any of the above, the liquid filter device further includes a heat shield. In one embodiment, the heat shield includes a cup-shaped body that forms a deflection surface and / or heat sink and forms a first volume into which process waste flows from the feed pipe. For example, the cup-shaped body may have a cylindrical wall spaced apart from the feed pipe.

[0018] In a further embodiment, the heat shield includes a second cup-shaped body. The first cup-shaped body is positioned within the second cup-shaped body, which forms a second volume through which process waste flows from the first cup-shaped body and to a process waste outlet.

[0019] Optionally, the heat shield may include a third cup-shaped body, which is positioned within the second cup-shaped body at a distance from the first cup-shaped body, forming a third volume through which process waste flows and to a process waste outlet.

[0020] For example, one or more cup-shaped bodies can be made of stainless steel in order to absorb heat from the waste discharge before it collides with the filter liquid.

[0021] In another aspect, a method of separating solids from process waste in a semiconductor processing system using a liquid filter includes providing a liquid filter having a supply pipe, a filter chamber, and a discharge outlet. The method further includes forming a liquid tank within the filter chamber, holding a filter liquid within the liquid tank, and providing a secondary pre-filter fluid path from the supply pipe outlet to the liquid tank. The process waste is then directed from the supply pipe to the secondary pre-filter fluid path of the filter chamber and then to the liquid tank of the filter chamber.

[0022] In one aspect, directing the process waste to the secondary pre-filter fluid path includes absorbing energy from the process waste before directing the process waste to the liquid tank.

[0023] In another or further aspect, the process waste is directed to the secondary pre-filter fluid path by providing a deflection surface spaced from the supply pipe outlet such that the deflection surface directs the process waste to the secondary pre-filter fluid path.

[0024] In a further aspect, the deflection surface is of a dimension larger than the diameter of the supply pipe outlet.

[0025] Optionally, the deflection surface is supported above the filter liquid within the liquid tank.

[0026] In addition, the filter liquid within the liquid tank is maintained at a liquid level below the deflection surface.

[0027] In another aspect, the filter liquid is circulated through the tank so that the filter liquid filled with particles is removed. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] [Figure 1] A schematic diagram of a prior art CVD or PECVD system composed of a processing chamber connected to a vacuum pump via a foreline. [Figure 2] A schematic diagram of a liquid filter device for separating solids from a semiconductor process gas. [Figure 3] A schematic diagram of a liquid filter device having a modified gas flow path. [Figure 4] A schematic diagram of a liquid filter device having a venturi. <--Removed extra newline-->A schematic diagram of a liquid filter device having a thermal shield. [Figure 6] A schematic diagram of a liquid filter device for stirring a filter liquid. [Figure 6A] A figure similar to FIG. 6 showing a sequence of valve openings. [Figure 6B] A figure similar to FIG. 6 showing a sequence of valve openings [Figure 6C] A figure similar to FIG. 6 showing a sequence of valve openings [Figure 6D] A figure similar to FIG. 6 showing a sequence of valve openings [Figure 7] A schematic diagram of a liquid filter device showing a liquid filter device installed in a semiconductor processing system. [Figure 8] A schematic diagram showing a liquid filter device forming a plurality of chamber facilities for a semiconductor processing system.

Embodiments for Carrying Out the Invention

[0029] Referring to Figure 2, the number 10 shows a liquid filter device that can be positioned in a foreline having a semiconductor process chamber outlet, the liquid filter device being configured to filter solids or particles from the semiconductor process gas, which is discharged from the semiconductor process chamber and typically contains solids or particles as byproducts of gas-phase reactions during the semiconductor process. Various modifications can be made to the liquid filter device to address various process parameters, including when processing very high-temperature semiconductor process gases and / or plasma, which are often referred to herein as semiconductor process waste or process waste, as will be described in detail below.

[0030] Referring again to Figure 2, the filter device 10 includes a housing 12 which has a process gas inlet 14 for receiving the inflow of semiconductor process gas from a semiconductor processing chamber, which typically contains solids and / or particles, and a gas outlet 16 for discharging the filtered process gas after the filtration process. The housing 12 is made of an inert material such as aluminum, quartz, polymer, or stainless steel alloy and includes a filter chamber 18 which receives the process gas from the semiconductor processing chamber through the inlet 14, from which the filtered gas is discharged through the outlet 16. The filter chamber 18 forms a liquid tank 20 which holds a filter liquid for filtering solids and / or particles from the process gas flowing into the filter device.

[0031] Suitable filtrates for removing or filtering solids or particles from semiconductor process gases without chemically reacting with reactants in the process gas stream are known to include chemically inert liquids with a vapor pressure of less than approximately 10⁻⁷ Torr. Suitable liquids include those usable in a temperature range from -58°C to +257°C and in which gas emissions are negligible. Suitable liquids include electrically nonconductive liquids with a dielectric strength in the range of 15.7 MV / m.

[0032] In addition, suitable liquids have a higher kinematic viscosity than water (for reference, water has a kinematic viscosity of 1 cSt), and for example, have a kinematic viscosity in the range of 38 cSt to 1830 cSt. Suitable liquids include commercially available foaming liquid or perfluoropolyether (PFPE). PFPE has a vapor pressure of about 6 × 10⁻⁸ Torr or less and is chemically inert. PFPE can be used in a temperature range of -58 degrees Celsius to +257 degrees Celsius and emits very little gas. Although PFPE has a dielectric strength of about 15.7 MV / m, is chemically inert, can be used in a temperature range of -58 degrees Celsius to +257 degrees Celsius and emits very little gas, as will be discussed later, when processing very hot process gases or plasmas, direct collision and immersion of the process gas into the filter liquid can be minimized or avoided to improve cooling efficiency and separation of particles from the gas phase. PFPE filter fluids can be formulated with kinematic viscosity ranging, for example, from 38 cSt to 1830 cSt. However, since PFPE is an expensive liquid, the PFPE liquid containing extracted particles can be recycled by sending it to a commercially available purifier.

[0033] As will be described in detail below, the liquid level in the liquid tank 20 can be maintained by a control system to ensure immersion of the process gas in the filter liquid in some applications. For example, the liquid level in tank 20 can be in the range of 3 to 8 inches, or 1 to 3 inches, or typically 2 to 6 inches, depending on the configuration of the filter device. However, as mentioned above, when dealing with very high-temperature process gases or plasmas, the level in the tank can be adjusted. The filter size and PFPE storage volume can vary depending on the specific semiconductor process and chemical properties.

[0034] The filter fluid is supplied to and discharged from the liquid tank 20 via a filter fluid inlet 22 and a filter fluid outlet 24, which communicate with the liquid tank via conduits such as pipes, which are connected to a common port 26 on the housing 12 for supplying and removing the filter flow to and from the liquid tank, respectively. Furthermore, as will be described in detail below, in one embodiment the filter fluid can be circulated through the apparatus 10 to enhance the interaction between the filter fluid and the process gas.

[0035] Referring again to Figure 2, the apparatus 10 further includes a supply pipe 30 that communicates with the process gas inlet 14 and extends into the filter liquid in the liquid tank 20, directly injecting the process gas flowing through the process gas inlet into the filter liquid in the liquid tank. Alternatively, as will be described later, the process supply pipe may be terminated indirectly on the upper side of the filter liquid after cooling, for example.

[0036] The feed tube 30 is formed from an inert material such as aluminum, quartz, polymer, and typically stainless steel alloy. Optionally, the feed tube 30 includes a plurality of perforations 32 at its distal end 30a, which is closed to guide all the process gas flow through the perforations 32, thereby generating a bubbling effect by the process gas in the liter fluid. The size, number, and location of the perforations 32 can vary, but can range in diameter from 0.125 inches to 0.5 inches or larger, or approximately 0.25 inches in diameter. The purpose of these holes is to efficiently disperse the particle-containing gas flow and mix it with the filter liquid. The bubbles generated by the gas flowing through the perforations 32 mix with the filter liquid, and the particles are separated from the gas flow and absorbed into the filter liquid without causing any harmful backflow into the semiconductor processing chamber. Alternatively, as illustrated with reference to Figure 5, the end of the feed tube may be opened to direct the process gas or plasma towards the filter flow, but at higher temperatures, a thermal shield may be placed between the open end of the feed tube and the filter flow, as will be described in detail below.

[0037] As described above, the liquid filter device 10 may include a filter fluid control system 50 for controlling the inflow of filter fluid into the liquid tank 20 and the outflow of filter fluid from the liquid tank 20. For example, the filter fluid control system 50 may include a control device 50a such as a microprocessor and a fluid circuit 28, the control device 50a controlling the fluid circuit by electrically controlled valves 28a, 28b and a pump (such as a centrifugal pump or magnetic coupling pump, not shown) to regulate the flow of filter fluid into and out of the liquid tank 20 through the inlet 22 and outlet 24. Also, as described above, the filter fluid control system 50 may be configured to maintain the filter fluid at the liquid level in the liquid tank. In this way, the filter fluid can be replaced with new filter fluid when it becomes "used," meaning that the liquid has reached a certain absorption level. For example, it may be desirable to circulate new filter fluid in the tank when the filter fluid is considered experimentally saturated with particles, or it may be desirable to circulate the liquid regardless of how many particles it has absorbed.

[0038] In one embodiment, the control system 50 includes one or more sensors 52. The sensors 52 can be used to detect the level of the filter liquid or to measure the opacity or other properties of the liquid, which can be used to indicate that the liquid has reached a predetermined level of particle absorption. For example, determining when the liquid has reached a predetermined level of particle absorption may be based on another property of the liquid, such as viscosity. Alternatively, both types of sensors can be used, one of which is a sensor that measures the level of the filter liquid and the other is a sensor that measures a property of the liquid that indicates when the liquid has reached a desired level of particle absorption. In either or both cases, the control system 50 can be used for the purpose of regulating the flow of the filter stream into and out of the liquid tank 20 based on one or more sensors to accommodate the products of the semiconductor chamber and / or to optimize the filtration process.

[0039] Optionally, the apparatus 10 may include one or more visual windows 40 for observing the chamber 18. For example, one or more windows 40 may be formed from PYREX® or quartz material and may extend into and through the wall of the housing 12. The windows may be positioned below a desired level of filter fluid, and the filter fluid may be manually observed for its level and / or opacity or other properties to provide manual control of the filtering apparatus if necessary. The windows 40 may include manual or automatic visual windows to experimentally evaluate solids entrained in the filter fluid and may be used by valves 28a, 28b to cause manual or automatic withdrawal of a specific amount of fluid and addition of new filter fluid for continuous dynamic filtering operation without interfering with the process chamber or production. For example, the valves described above (e.g., control valves 28a, 28b) may enable manual control, including manual override control by electrically operated valves, so that an operator can manually control the apparatus 10.

[0040] In the illustrated embodiment, the process gas inlet 14 and gas outlet 16 are positioned on the top and side of the housing 12 so as to be generally oriented at a 90-degree (right-angle) angle, but as will be described with reference to the second embodiment, the gas inlet 14 and gas outlet 16 can be rearranged so as to be generally in line.

[0041] During operation, the process gas flow enters from the top of the apparatus 10 as shown in the figure, passes through the supply pipe 30, and bubbles up as it passes through the filter liquid in the tank 20, removing the particles before exiting the filter liquid tank 20. The filtered gas then flows out from the side of the apparatus 10 through the gas outlet 16.

[0042] Referring to Figure 3, the number 110 represents another or second embodiment of the liquid filter device as a whole, which has a semiconductor process chamber outlet and can be positioned in the foreline, and is configured to filter solids or particles from semiconductor process gases discharged from a semiconductor process chamber. Similar to the embodiments described above, the filter device 110 includes a housing 112 having a process gas inlet 114 for receiving inflows of semiconductor process gases from a semiconductor processing chamber, which typically contain solids or particles, and a gas outlet 116 for discharging the filtered process gases after a filtration process described later. For details on materials suitable for the housing structure, please refer to the first embodiment.

[0043] As best seen in Figure 3, the housing 112 includes a filter chamber 118 that receives process gas through a process gas inlet 114, from which the filtered gas is discharged through a gas outlet 116. The filter chamber 118 forms a liquid tank 120 that holds a filter liquid for filtering solids or particles from the process gas flowing into the filtering device. For suitable liquid properties and examples of suitable liquids that can filter solids or particles from semiconductor process gases, please refer to the first embodiment.

[0044] In the illustrated embodiment, the process gas inlet 114 and gas outlet 116 are generally inline. To this end, the housing 120 includes a discharge chamber 138 between the liquid tank 120 and the gas outlet 116, allowing the filter gas to be discharged internally from the filter chamber before being discharged through the gas outlet 116. The inline filter system can be used in certain locations where the right-angle filter system of the first embodiment may not fit existing foreline shapes.

[0045] To form the discharge chamber 138, the housing 112 includes a solid plate 136 that partitions the internal space of the housing 112 between the filter chamber 118 and the discharge chamber 130, and further includes an internal conduit 134, which includes a first open end 134a positioned above the filter fluid level and a second open end 134b that extends through the plate 136 for discharge into the discharge chamber 130. Although the internal conduit 134 is shown to terminate at the plate 136, it should be understood that it can extend through the plate into the discharge chamber 138. Suitable conduits include tubular bodies or tubing formed from inert materials such as aluminum, quartz, polymers, and typically stainless steel alloys.

[0046] Similar to the embodiments described above, the housing 110 includes a supply pipe 130 that is in fluid communication with the inlet 114, extends into the liquid tank 120, and injects the process gas into the filter fluid in the same manner as described above. For further details of the supply pipe 130, see supply pipe 30.

[0047] Furthermore, similar to the embodiments described above, the liquid level in the liquid tank 120 can be maintained by the control system to ensure immersion of the process gas in the filter liquid, as described above.

[0048] Apparatus 110 operates in a similar manner to apparatus 10. Process gas flows into the inlet 114 and is injected into the filter liquid in tank 120 via the supply pipe 130. Due to the presence of perforations 132 in the supply pipe 130, the process gas bubbles up in the filter liquid, and solids or particles are removed from the process gas as they are absorbed into the filter liquid. The filtered gas is then discharged from the filter chamber 118 through the internal conduit 134, which leads the filtered gas into the discharge chamber 138, which then discharges the filtered gas through the gas outlet 116.

[0049] In a manner similar to that of the embodiments described above, the filter fluid can be circulated through the apparatus 110 by a fluid circuit 128, which includes an inlet valve 128a (fluidly communicating with the liquid inlet 122) and an outlet valve 128 (fluidly communicating with the liquid inlet 124), and various conduits and pumps (such as a centrifugal pump or magnetic coupling pump, not shown), which, as described above, direct the flow of the filter fluid into or from the liquid tank 120 through a common port 126 for circulating the filter fluid or simply replacing the filter fluid.

[0050] The apparatus 110 may also include a visual window 140 for observing the chamber 118. For example, one or more windows 40 may extend into and through the wall of the housing 12, and the window may be positioned below a desired filter fluid level, allowing the filter fluid level and / or opacity or other characteristics to be manually observed, if necessary, to provide manual control of the filtering apparatus.

[0051] As described above, during operation, the particle-containing process gas flow enters from the top of the apparatus 110 as shown in the figure, passes through the internal supply pipe 130, is aerated through the filter in the tank 120, and after the particles are filtered and removed, enters the internal conduit 134 and flows out from the filtered liquid tank 120. The filtered gas then enters the discharge chamber 138 and flows out from the top process gas inlet and inline bottom of the apparatus 110.

[0052] Referring to Figure 4, the number 210 represents another or third embodiment of the liquid filter device as a whole, which can be positioned in a foreline having a semiconductor process chamber outlet and is configured to filter solids or particles from semiconductor process gases discharged from the semiconductor process chamber. Similar to the embodiments described above, the filter device 210 includes a housing 212 having a process gas inlet 214 for receiving inflows of semiconductor process gases from a semiconductor processing chamber, which typically contain solids or particles, and a gas outlet 216 for discharging the filtered process gases after the filtration process described above. For details on materials suitable for the housing structure, please refer to the first embodiment.

[0053] As best seen in Figure 4, the housing 212 includes a filter chamber 218 that receives process gas through a process gas inlet 214, from which the filtered gas is discharged through a gas outlet 216. The filter chamber 218 forms a liquid tank 220 that holds a filter liquid for filtering solids or particles from the process gas flowing into the filtering device. For preferred liquid properties and examples of preferred liquids that can filter solids or particles from semiconductor process gases, please refer to the first embodiment.

[0054] In the illustrated embodiment, the process gas inlet 214 and gas outlet 216 are generally inline, similar to the second embodiment. To this end, the housing 220 also includes a discharge chamber 238 between the liquid tank 220 and the gas outlet 216, allowing the filter gas to be discharged internally from the filter chamber before being discharged through the gas outlet 216. For further details of the discharge chamber 238, please refer to the embodiments described above.

[0055] Similar to the embodiments described above, the housing 210 is in fluid communication with the inlet 214 but includes a supply pipe 230 that extends into the chamber 218 and optionally terminates above the filtered fluid. The supply pipe 230 is also formed from an inert material such as aluminum, quartz, polymer, or typically a stainless steel alloy.

[0056] In the illustrated embodiment, the supply pipe 230 includes a limiting section 230a for forming a venturi tube and an inlet 222 for the filter flow to enter the supply pipe 230, generating a pressure difference to draw process gas into the supply pipe 230 through the inlet 214, where the process gas mixes with the filter liquid and is then discharged through the supply pipe 230 into the filter chamber 218. The filter liquid is then discharged from the supply pipe 230 into the liquid tank 220.

[0057] In the same manner as described above, the filter fluid can be circulated through the device 210 by a fluid circuit 228, which is controlled, for example, by a control device as described above, and the fluid circuit 228 includes a pump 228c (such as a centrifugal pump or a magnetic coupling pump) in addition to control valves 228a and 228b, and the pump 228c circulates the filter fluid through the device 210 via various conduits 228d.

[0058] In the illustrated embodiment, as described above, the liquid inlet 222 is formed in the supply pipe 230, while the liquid outlet 224 is located in the liquid tank below the liquid level.

[0059] Apparatus 210 operates in a similar manner to apparatus 110. Process gas flows into inlet 214, but its flow is enhanced by the Venturi effect of the filter liquid flowing through supply pipe 230. The process gas mixes with the filter liquid, is then filtered, and injected into filter chamber 118 through supply pipe 230. The filtered gas is discharged from filter chamber 218 through internal conduit 234, which leads the filtered gas to discharge chamber 238, which then discharges the filtered gas through gas outlet 216.

[0060] In a manner similar to that of the embodiments described above, the filter fluid can be circulated through the apparatus 210 by a fluid circuit 228, which includes, as described above, an inlet valve 228a (which is in fluid communication with the liquid inlet 222) and an outlet valve 228b (which is in fluid communication with the liquid inlet 224), and various conduits for guiding the flow of the filter fluid through the apparatus 210. The fluid circuit 228 can also be configured, as described above, to replace the filter fluid after a given period of time or after the filter fluid has reached a desired level of particle saturation.

[0061] Furthermore, the apparatus 210 may also include a visual window 240 for observing the chamber 218, similar to the second embodiment.

[0062] Referring to Figure 5, the number 410 represents a liquid filter device for filtering solids and / or particles from semiconductor waste in a semiconductor. Similar to the embodiments described above, the filter device 410 typically includes a housing 412 comprising a process waste inlet 414 for receiving semiconductor process waste such as semiconductor process waste gases and / or plasma from a semiconductor processing chamber containing solids or particles, and a filtered waste outlet 416 for discharging the filtered process waste after a filtration process described later. For details on materials suitable for the housing structure, please refer to the first embodiment.

[0063] As best seen in Figure 5, the housing 412 also includes a filter chamber 418 that receives process waste through a waste inlet 414, from which the filtered waste is discharged through a filtered waste outlet 416. The filter chamber 418 forms a liquid tank 420 that holds a filter liquid for filtering solids or particles from the process waste flowing into the filtering device. For preferred liquid properties and examples of preferred liquids that can filter solids or particles from semiconductor process gases, see the first embodiment.

[0064] In the illustrated embodiment, the process waste inlet 414 and waste outlet 416 are generally inline, as in the second embodiment. Similar to the embodiments described above, the housing 410 includes a feed pipe 430 that is in fluid communication with the inlet 414 but extends into the chamber 418 and optionally terminates above the filtered flow. The feed pipe 430 is also formed from an inert material such as aluminum, quartz, polymer, or stainless steel.

[0065] However, the housing 420 is configured to provide a secondary pre-filter fluid path for process waste from the supply pipe outlet 430a to the liquid tank 420 in order to reduce energy consumption when filtering very hot process waste, such as gases and / or plasmas having temperatures in the range of 200-600°C or higher. Furthermore, as will be described in detail below, the housing 420 is configured to cool the process waste before it strikes the filter fluid.

[0066] To guide waste into a secondary pre-filter fluid path, the liquid filter device 410 includes a deflection surface 450 positioned adjacent to the supply pipe outlet 430a. In this way, the waste does not directly collide with the filter fluid, but is instead guided into a secondary pre-filter fluid path. In addition, as will be described in detail below, the deflection surface is formed from a heat-absorbing material and thus forms a heat sink. By colliding with this deflection surface, much of the initial thermal energy is absorbed, so it generates a heat shield that can absorb ions and high electron energy, for example, when plasma emissions are injected into the filter device, which helps to rapidly cool the emitted electrons and ions and cool the hot gas.

[0067] The thermal shield, through its structure, can also significantly increase the heat exchange surface area and gas-liquid interface area, resulting in efficient cooling and particle separation from the gas phase. This novel fluid filter has been tested and shown that when the input gas or plasma has a temperature in the range of 400°C to 600°C or higher, the fluid temperature is maintained at a low temperature in the range of 45°C to 70°C, far below any potential chemical reactions and degradation of fluid properties, while significantly improving particle separation from the gas phase.

[0068] The first deflection surface can be formed by a plate. Optionally, the plate is provided by a cup-shaped body 452 having side walls 452a, such as cylindrical side walls, extending upward from a bottom wall 452b, which can form a plate such as a non-porous plate. The body 452 can be a single unit and can be formed by molding or welding. Optionally, the cup-shaped body can be supported so as to straddle and surround the end of the supply pipe 430, but at a distance from it, such that the bottom wall 452b, which can form the first deflection surface as described above, is positioned at a distance from the supply pipe outlet 430a of the supply pipe 430. In this way, the outer circumference of the deflection surface can be larger than the outer diameter of the supply pipe outlet.

[0069] Secondary pre-filter fluid paths can be formed by additional orientation or deflection surfaces. For example, additional deflection surfaces can be formed by separate structures, including separate structures that are assembled or joined together during their formation process or subsequent formation processes, such as by welding. For example, a second deflection surface 452c can be formed by the inner surface of the side wall 452a of the cup-shaped body 452, which, together with the first deflection surface 450, can form a space 452d of a first capacity through which waste flows when it flows out of the supply pipe outlet 430a.

[0070] A third deflection surface 454 can be provided by a second cup-shaped body 460, which supports the first cup-shaped body 452 therein and is supported on the lower wall 412a of the housing 412 by one or more supports 464. Optionally, the second cup-shaped body 460 is supported on the lower wall 412a of the housing 412 above the filter liquid level, and the filter liquid level can be controlled by a control system in the same manner as described above.

[0071] Furthermore, the second cup-shaped body 460 extends upward from the bottom wall 460b and includes a side wall 460a, such as a cylindrical side wall, that is higher than the side wall 452a of the cup-shaped body 452, so that when waste flows out of the first volume 452d, the waste flows into the second volume 460d formed above the cup-shaped body 452 by the second cup-shaped body 460 between it and the cup-shaped body 452. Thus, the inner surface 460c of the side wall 460a forms a third deflection surface that guides the flow of waste along the secondary pre-filter fluid path through the housing 412.

[0072] Thus, when waste flows into the second volume, it flows upward, over the top of the side wall 460a, and flows down into the filter liquid in the liquid tank 420 directly below the second cup-shaped body 460. Some of the waste flows between the two side walls 452a and 460a and emerges from below the first cup-shaped body (as shown by the green arrow in Figure 5), then flows upward and can then flow down into the filter liquid in the liquid tank 420.

[0073] In either case, the deflection surface is formed from a heat-absorbing material such as stainless steel, and thus a heat sink can be formed.

[0074] Apparatus 410 operates in the same manner as apparatuses 210 and 110. Process waste (gas and / or plasma) flows into the inlet 414 and, after cooling, mixes with the filter liquid. The filtered waste is then discharged from the filter chamber 418 through an internal conduit 434 that extends through the bottom wall 460b of the second cup-shaped body 460. The internal conduit 434 then leads the filtered waste to the discharge chamber 438, which then discharges the filtered waste through the waste outlet 416.

[0075] The filtered waste flow can be guided through another cylindrical sidewall 470 to an internal conduit 434, which is also supported by a second cup-shaped body 460, coaxial with the internal conduit 434, and spaced apart from it. In addition, the cylindrical sidewall 470 is spaced apart from the first cup-shaped body 452 and extends further above the cup-shaped bodies 452 and 460. Thus, as is best understood from Figure 5, the outer surface 470a of the cylindrical sidewall 470 forms a deflection surface for guiding the waste flow upward over the upper end of the second cup-shaped body 460 (thus forming part of a secondary pre-filter fluid path). In addition, the inner surface 470b of the cylindrical sidewall 470 forms a post-filter path that allows the filtered waste to flow upward and into the internal conduit 434.

[0076] In a manner similar to that of the embodiments described above, the filter liquid can be circulated through the apparatus 410 by a fluid circuit. The fluid circuit may also be configured to replace the filter liquid after a given period of time or after the filter liquid reaches a desired particle saturation level, as described above. Furthermore, the control system may optionally maintain the filter liquid level below the second cup-shaped body, thus forming part of a post-filter path for the filtered waste to flow.

[0077] Furthermore, the housing 412 includes a discharge chamber 438 between the liquid tank 420 and the waste outlet 416, allowing the filter waste to be discharged internally from the filter chamber before being discharged through the outlet 416. For further details of the discharge chamber 438, please refer to the embodiments described above.

[0078] A suitable material for the deflection surface can be stainless steel, which is inert and can also absorb heat, thus allowing it to cool the waste as described above.

[0079] The cup-shaped bodies 452 and 460 and the cylindrical wall 470 can be a single assembly 480 joined by welding or molding, or they can be individual components assembled to form secondary pre-filter and post-filter paths for waste flowing through the device 410.

[0080] Therefore, using a liquid filter, the apparatus can be used to separate solids from process waste in semiconductor processing systems. By providing a secondary pre-filter fluid path from the supply pipe outlet to the filter liquid tank, the waste can be cooled before it collides with the filter fluid, absorbing much of the initial thermal energy. The resulting heat shield can absorb the ionic and high-electron energy when plasma emissions are injected into the apparatus, catalyzing the emitted electrons and ions and helping to cool the hot gas. In addition, the components forming the heat shield significantly increase the heat exchange surface area and gas-liquid interface area, resulting in efficient cooling and particle separation from the gas phase.

[0081] Referring to Figure 6, the number 310 schematically represents a liquid filter device for agitating a filter fluid, which can be positioned in a foreline between the semiconductor processing chamber and the processing pump (see Figures 6 and 7). The liquid filter device is configured to filter solids or particles from the semiconductor processing gas discharged from the semiconductor process chamber. Furthermore, as will be described in detail below, the liquid filter device 310 is configured to communicate with a fluid circuit (328, described later) in a manner that allows for the automatic addition and removal of the filter fluid to and from the chamber (318) of the fluid device.

[0082] Similar to the embodiments described above, the filter device 310 includes a housing 312 forming a filter chamber 318 and is equipped with a process gas inlet 314 for receiving semiconductor process gas inflows from the semiconductor processing chamber into the chamber 318 (see, for example, Figure 6, where the filter device 310 is mounted in the foreline of the processing system between the semiconductor chamber and the process pump), the process gas generally containing solids or particles, and a gas outlet 316 discharges the filtered process gas from the chamber 318 after a filtration process described later. For details on materials suitable for the housing structure, please refer to the first embodiment.

[0083] As best seen in Figure 6, the chamber 318 forms a liquid tank 320 for holding the filter fluid, which filters out solids or particles from the process gas flowing into the filter device and is then discharged as waste. Refer to the first embodiment for preferred liquid properties and examples of preferred liquids that can filter solids or particles from semiconductor process gases. In the illustrated embodiment, the process gas inlet 314 and gas outlet 316 are generally inline, as in the second embodiment where they are arranged at right angles. Also, as in the embodiments described above, the housing 310 includes a supply pipe 330 that is in fluid communication with the inlet 314, extends into the chamber 318, and optionally terminates at the location of the filter fluid in the liquid tank 320 or slightly below therein. The supply pipe 330 is similarly formed from an inert material such as aluminum, quartz, polymers, and typically stainless steel alloys.

[0084] In the illustrated embodiment, the chamber 318 includes a rotating member 332 that is rotationally driven by a motor 334. The motor 334 is mounted outside or on the exterior of the housing 312, but its drive shaft 334a may extend through a sealed opening in the housing wall 312a and engage with the rotating member 332, or it may not penetrate the housing and instead be coupled to the rotating member via a magnetic coupling, as described later. For example, the sealed opening may be formed by a sealed bush or a sealed grommet. The rotating member 332 may take the form of a plurality of blades commonly attached to an annular support that is rotatably mounted at the bottom of the housing wall 312a.

[0085] In one embodiment, the motor's drive shaft 334a is coupled to the rotating member 332 by a magnetic coupling via the wall of the housing 312. For example, the drive shaft 334a may include a magnet, and the rotating member 332 may include a magnet mounted, for example, on or around an annular support to provide the magnetic coupling.

[0086] As described above, the rotating member 332 is positioned at the bottom of the housing 312 of the liquid tank 320 and, when rotated by the motor 334, agitates or rotates the filter fluid in the liquid tank 320 in a continuous manner as desired. This rotation of the fluid completely mixes particles of various densities with the filter fluid, and the fluid is then discharged from the filter chamber 318 through the outlet 312b formed in the housing wall 312a. In addition, the rotational speed affects the discharge rate of the fluid from the chamber through the outlet 312b, and the inflow rate of the filter fluid from the fluid circuit (described later) into the chamber 318 through the inlet 312c (similarly formed in the housing wall 312a). Furthermore, the rotational speed determines the depth of the vortex V generated by the rotation of the fluid.

[0087] In a similar manner to that described above, the filter fluid can be selectively and automatically circulated through the device 310 by the fluid circuit 328 (controlled by a control device such as a programmable logic control device including, for example, a microprocessor as described below).

[0088] In the illustrated embodiment, the fluid circuit 328 includes a conduit 340 in fluid communication with the upper chamber 318 of the filter fluid, a slide valve 342, and a plurality of control valves 328a(V1), 328b(V2), 328c(V3), 328d(V4), 328e(V5), and 328f(V6), which are opened and closed by a control device 350 (such as a microprocessor) to automatically control the flow of fluid through the conduit 340 and the slide valve 342 based on the valve opening and closing sequence described below. By providing fluid communication between the chamber 318 (upper side of the filter fluid) and the conduit 340, the conduit 340 is exposed to the pressure in the chamber 318, which is under vacuum (or low or very low pressure) due to the fluid communication between the foreline and the chamber 318 leading to the outlet 316. Next, this vacuum (or low or very low pressure) extends to other components of the circuit 328, as will be described later. For example, the conduit 340 may include a stainless steel tube.

[0089] As is best seen in Figure 6, the slide valve 342 includes a cylinder 342a and a slide piston 342b, the slide piston 342b moves the cylinder 342a up and down by a motor 343 (as seen in Figure 6), and the motor 343 is controlled by a control device 350, which opens and closes the communication between the chamber 318 and the circuit 328 via the valve 342.

[0090] In addition, the circuit 328 includes two chambers 344 and 346, where chamber 344 is selectively fluid-connected to a makeup fluid supply via valve 328a(V1), and chamber 346 is selectively fluid-connected to a nitrogen gas supply via valve 328c(V3) and a valve in conduit 340. Thus, when valve 328a(V1) is opened, chamber 344 is filled with makeup fluid. Similarly, when valve 328e(V5) is opened, chamber 346 is filled with nitrogen. Next, when valve 328e(V5) is closed and valve 328d(V4) is opened, the pressure in chamber 346 drops to low pressure, very low pressure, or vacuum pressure.

[0091] To control the flow of fluid into and out of the tank 320, the cylinder 342a includes a first port (optionally formed by a conduit) in fluid communication with the inlet 312c of the housing 312, and a second port (optionally formed by a conduit) in fluid communication with the outlet 312b of the housing 312. Furthermore, the piston 342b includes two lateral passages 342c and 342d, which, when moved by the motor 343, can align with the ports of the cylinder 342a, enabling fluid communication between the tank 320 and the chambers 344 and / or chambers 346, depending on the open / closed state of 328b(V2) and valve 328c(V3). Valve 328b(V2) allows selective fluid communication between chamber 344, slide valve 342, and tank 320 depending on the position of piston 342b, and valve 328c(V3) allows selective fluid communication between chamber 346, slide valve 342, and tank 320 depending on the position of piston 342b.

[0092] As best understood from Figure 6, when valve 328a(V1) is opened and all other valves (328b(V2), 328c(V3), 328d(V4), 328e(V5), and 328f(V6)) are closed (Step 1, see Figure 6A), the makeup fluid is directed to chamber 344. When valves 328b(V2) and 328c(V3) are opened and the remaining valves (328a(V1), 328d(V4), 328e(V5), and 328f(V6)) are closed (Step 2, see Figure 6B), the motor 343 is driven to move the piston to the lower position (the lateral passages 342c and 342d of piston 342b align with the ports of cylinder 342a as seen in Figure 6), the makeup fluid is sent to tank 320 and the particle-filled fluid is discharged to chamber 346. When valves 328a(V1), 328b(V2), 328c(V3), and 328d(V4) are closed and valves 328f(V6) and 328e(V5) are opened (step 3, see Figure 6C), the fluid is pushed out of chamber 346 by a pre-adjusted nitrogen flow passing through the open valve 328e(V5). After a predetermined time has been given for the fluid to be removed from chamber 346, valves 328a(V1), 328b(V2), 328c(V3), and 328e(V5), as well as 328f(V6), are then closed and valve 328d(V4) is opened (step 4, see Figure 6D), allowing chamber 346 to be evacuated so that the pressure inside chamber 346 is in equilibrium with the foreline pressure. This sequence is repeated by the control device. The timing of the sequence steps can vary, as it depends on the specific process and process settings. Generally, the sequence timing is expected to cycle every 10 to 20 seconds, depending on the fluid particle load. If the particle load of semiconductor process emissions is low, the sequence could be up to 30 to 60 minutes.

[0093] Apparatus 310 operates in a similar manner to apparatus 110, in that process gas flows into the inlet 314, but its flow is enhanced by the vortex effect of the filter liquid flowing around the supply pipe 330. The process gas is mixed with the filter liquid and then injected into the filter chamber 318 via the supply pipe 330, where it is filtered. The filtered gas is then discharged from the filter chamber 318 through the gas outlet 316.

[0094] In the illustrated embodiment, the filter fluid is dynamically circulated through the device 310 by the fluid circuit 328.

[0095] As mentioned above, the fluid circuit 328 may also be configured to replace the filter liquid after a given period of time or after the filter liquid has reached a desired particle saturation level.

[0096] Referring to Figures 7 and 8, the filter device 310 (or any of the other filter devices 410, 210, 110, 10 described herein) can be installed in the foreline between the semiconductor processing chamber C and the processing pump P, and can also be installed in a system comprising multiple chambers (C, C2, C3) and multiple pumps (P, P2, P3), wherein waste fluid from each filter device is optionally directed to a shared waste tank T, and optionally, makeup fluid is supplied from a shared makeup fluid supply tank T.

[0097] In any embodiment, the control system may include one or more sensors (not shown in each embodiment) which can be used to detect the level of the filtered liquid, or to measure the opacity (optical inertness) or other properties of the liquid, which can be used to indicate that the liquid has reached a certain absorption level. Alternatively, both types of sensors can be used, one of which measures the height of the filtered liquid and the other measures the properties of the liquid. In either or both cases, the control system may be used, based on one or more sensors, to regulate the flow of filtered liquid into and out of the apparatus to accommodate the products of the semiconductor chamber and / or to optimize the filtration process.

[0098] Both right-angle and in-line filter systems can be configured passively ("passive" meaning the tank has a fixed amount of filter fluid that is periodically changed and replaced manually with new filter fluid), i.e., the filter system is inserted into a line within the semiconductor processing system using the pressure and flow characteristics of the process gas of the semiconductor processing system, or they can be dynamic ("dynamic" meaning the particle-containing filter fluid is dynamically / automatically removed and replaced with fresh filter fluid, as described above with reference to Figure 7). As described above, the filter fluid can be periodically removed and added by valve adjustment and optionally by pumps based on a predetermined maintenance interval. As described above, in one configuration, a filter fluid recirculation pump can be added to recirculate the filter fluid, as shown in Figure 4. In this embodiment, the recirculated filter fluid can have a very high recirculation flow rate and can be mixed more efficiently using a Venturi tube as illustrated and described. By using a Venturi tube, a very high degree of particle / gas separation can be achieved, and as mentioned above, a localized vacuum is created in the process gas entering the filter, which in turn helps the process vacuum pump to operate and potentially reduces its overall energy consumption.

[0099] Terms indicating direction, such as "vertical," "horizontal," "up," "down," "up," "down," "inside," "inside," "outside," and "outside," are used to help describe the invention based on the directions of the embodiments shown in the figures. The use of terms indicating direction should not be interpreted as limiting the invention to any particular direction(s).

[0100] The above description pertains to current embodiments of the invention. Various modifications and alterations can be made without departing from the spirit and broad aspects of the invention as defined in the claims, and these will be interpreted in accordance with the principles of patent law, including the doctrine of equivalents. This disclosure is presented for illustrative purposes only and should not be construed as an exhaustive description of all embodiments of the invention, nor does it limit the claims to any particular element illustrated or described in relation to these embodiments. For example, any individual element(s) of the invention may be replaced by an alternative element that provides substantially similar functionality or otherwise provides appropriate operation. This includes, for example, currently known alternative elements that may be known to those skilled in the art, and alternative elements that may be developed in the future that those skilled in the art may recognize as alternative elements at the time of development. The invention is not limited to embodiments that include all of these features or provide all of the described advantages, except to the extent expressly provided for in the patented claims. For example, any reference to an element of a claim in the singular form using the articles “a,” “an,” “the,” or “said” should not be construed as limiting the element to the singular form. [Explanation of Symbols]

[0101] 10 Filter device 12 Housing 14. Inlet for processed gas 16. Processed gas outlet 18 Filter Chamber 20 liquid tanks 22 Filter liquid inlet 24 Filter liquid outlet 26 Common opening 28 Fluid circuit 28a Electric control valve 28b Electric control valve 30 Supply pipe 30a Distal end 32 perforation 40 Visual Window 50 Filter Fluid Control System 50a Control device 52 sensors

Claims

1. A liquid filter device for semiconductor process waste, A housing having a filter chamber, a process waste inlet, a process waste outlet, and a supply pipe communicating with the process waste inlet and the filter chamber, wherein the supply pipe has a supply pipe outlet, the filter chamber forms a liquid tank for holding filter liquid, and the process waste outlet communicates with the filter chamber, A deflection surface disposed between the filter liquid and the outlet of the supply pipe, wherein the deflection surface deflects the process waste flowing from the supply pipe so as to prevent the process waste from directly colliding with the filter liquid, and further absorbs heat from the process waste, A first cup-shaped body that forms the deflection surface and forms a first volume into which the process waste flows in from the supply pipe, Equipped with, A liquid filter device in which the deflection surface is formed by a stainless steel plate of the first cup-shaped body that absorbs heat from the process waste.

2. The liquid filter device according to claim 1, wherein the stainless steel plate is non-porous.

3. The liquid filter apparatus according to claim 1, wherein the supply pipe includes an open distal end, and the open distal end forms the outlet of the supply pipe.

4. The liquid filter device according to claim 1, wherein the supply pipe outlet has a predetermined diameter, the deflection surface has an outer circumference, and the outer circumference of the deflection surface is larger than the diameter of the supply pipe outlet.

5. The liquid filter apparatus according to claim 1, wherein the housing includes a discharge chamber between the liquid tank and the process waste outlet for guiding the flow of filtered process waste from the liquid tank to the process waste outlet.

6. The liquid filter apparatus according to claim 5, wherein the housing includes an internal conduit that is in fluid communication with the liquid tank and the discharge chamber, and guides the flow of the filtered process waste from the liquid tank to the discharge chamber.

7. The liquid filter apparatus according to claim 1, further comprising a filter liquid control system for controlling the inflow and outflow of the filter liquid into the liquid tank.

8. The liquid filter apparatus according to claim 7, wherein the filter liquid control system comprises a control device and a fluid circuit, and the control device controls the fluid circuit to adjust the flow of filter liquid into and out of the liquid tank.

9. The liquid filter device according to claim 7, further comprising at least one support that supports the deflection surface above the filter liquid in the liquid tank.

10. The liquid filter device according to claim 1, wherein the first cup-shaped body has a cylindrical wall positioned at a distance from the supply pipe.

11. The liquid filter device according to claim 1, further comprising a second cup-shaped body, wherein the first cup-shaped body is positioned within the second cup-shaped body, and the second cup-shaped body forms a second volume through which the process waste flows from the first cup-shaped body and the process waste flows to the process waste outlet.

12. The liquid filter device according to claim 11, wherein at least one of the first cup-shaped body and the second cup-shaped body is made of stainless steel.

13. A method for separating solid materials from process waste in a semiconductor processing system using a liquid filter, A step of providing a liquid filter comprising a supply pipe, a filter chamber, an outlet, and a cup-shaped body, wherein the supply pipe has a supply pipe outlet, the cup-shaped body forms a deflection surface and a volume into which the process waste flows from the supply pipe, and the deflection surface is formed of a stainless steel plate, The steps include forming a liquid tank in the filter chamber, The steps include: holding the filter liquid in the liquid tank below the deflection surface; The steps include providing a secondary pre-filter fluid path from the supply pipe outlet to the liquid tank using the cup-shaped body, A step of introducing the process waste from the supply pipe into the secondary pre-filter fluid path of the filter chamber, wherein the deflecting surface deflects the process waste so as to prevent the process waste flowing in from the supply pipe from directly colliding with the filter fluid, and absorbs heat from the process waste. The steps include: guiding the process waste to the secondary pre-filter fluid path, and then guiding the process waste to the liquid tank of the filter chamber; A method that includes this.

14. The method according to claim 13, further comprising the step of making the deflection surface larger than the diameter of the supply pipe outlet.

15. The method according to claim 13, further comprising the step of supporting the deflection surface above the filter liquid in the liquid tank.

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