Patent Publication Number: US-2023149841-A1

Title: Liquid filter apparatus with thermal shield

Description:
This is related to U.S. application Ser. No. 16/893,504, which was filed on Jun. 5, 2020 and which is hereby incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD AND BACKGROUND OF THE INVENTION 
     In general, the fabrication of semiconductor devices employs the conversion via oxidation, for example, at modest to highly elevated silicon wafer temperatures of certain chemicals to form the desired thin films that make up the circuit layers of semiconductor devices. For example, in a chemical vapor deposition (CVD) process silicon dioxide thin film deposited on a silicon wafer is formed by the oxidation of silane with oxygen at a wafer temperature of approximately 400 degrees centigrade and at processing chamber pressure of around 300 mTorr. Silicon dioxide thin films are also deposited by the oxidation of vapor tetraethysiloxane, TOES, with oxygen and ozone at nearly similar processing conditions. Silicon oxide films are also deposited at lower temperatures using low-pressure gas phase plasma enhancement (PECVD). In another process, silane is reacted with ammonia to form silicon nitride at low pressures and moderate wafer temperatures. In these and nearly all other CVD reactions, such as the formation of tungsten and tungsten silicide thin films, nearly 75% of the gaseous feed reactants into the processing chamber pass through the process chamber unconverted. 
     The exhaust of a typical semiconductor processing chamber is a gaseous stream that is at low pressure and consists of unconverted feed reactants, reaction byproducts, diluent nitrogen carrier gas and particles. These particles are a byproducts of gas phase reactions of the heated reactants in the gas phase, which continue to form and grow in quantity along the fore-line that spans the distance between the processing chamber and the vacuum pump, which could be up to 60 feet in typical fabrication facilities.  FIG.  1    is a schematic diagram of a typical CVD or PECVD system that consists of processing chamber connected via a fore-line to a vacuum pump. The vacuum pump is connected via an exhaust line to a typical gas exhaust abatement system that uses natural gas flame to destroy the unreacted process gases followed by a gas/water absorption column to remove acidic gaseous byproducts. The outputs of such abatement systems consist of an acidic waste water stream that normally is neutralized and discharged and a gas stream that is laden with fine particles that are emitted to the atmosphere after passing through large surface area mechanical particle filters. 
     Particles coat all the connection lines between the processing chamber, the vacuum pumps and the abatement systems and often fill up and plug these lines causing significant maintenance down times at significant added cost of operations. In many cases, the vacuum pumps have to be shut down due to high particle depositions rendering them inoperative. Routinely vacuum pumps are removed and replaced from such lines at extremely high material and labor costs. In few processes, mechanical filters are placed in the vacuum fore-lines trapping these particles to extend the life time of the vacuum pumps. In many cases both the fore-lines and the pump exhaust lines are heated to prevent the condensation of unconverted condensable reactants, which subsequently help to absorb and agglomerate gas-laden particles and create a liquid/solid plugs that are very challenging and costly to clean. 
     Particles separation from gas-laden particle streams is best achieved using a liquid medium. For example, particles can be separated from large gas flow rates by passing the gas-laden particle stream through a very high flow rate water shower. High particle separation into the water stream can be achieved by proper sizing of the vessel volume and water flow rate. While such separation processes are effective and economical using water they cannot be used in semiconductor processing due to potential adverse water chemical reactions with the reactants in the gas stream and the very high water vapor pressure in low pressure fore-line. In vacuum CVD and PECVD semiconductor processes molecular water present in the fore-line would diffuse backward to the processing chamber itself and degrades the chemical composition of the semiconductor thin films being processed. 
     In some applications, there is a need to remove particles from a very hot gas stream within the fore-line of a semiconductor processing system. For example, the effluent gas within the fore-line could be hot gases flowing in the fore-line, which have a temperature at about 100 C to 200 C. In some applications there is a need to remove particles immediately post a fore-line plasma abatement system operating at very low vacuum. In both cases the liquid filter may need to be modified to ensure that the very hot gas or plasma exhaust does not impinge directly into the fluid. 
     SUMMARY 
     Accordingly, a liquid filter apparatus is provided that uses a liquid as a medium to separate particles from gas-laden particle streams in low pressure fore-line in CVD and PECVD semiconductor processes. 
     In one form, a liquid filter apparatus for semiconductor process waste separation from a semiconductor process includes a housing having a filter chamber, a process waste inlet, a process waste outlet, and a feed tube in communication with the process waste inlet and which has a feed tube outlet in communication with the filter chamber. The filter chamber forms a liquid reservoir holding a filter liquid therein, and the process waste outlet is in communication with the filter chamber. A deflecting surface is interposed between the filter liquid and the feed tube outlet, which deflects the process waste to prevent direct impingement of the process waste flowing from the feed tube outlet with the filter liquid and further absorbs heat from the process waste. 
     In one aspect, the deflecting surface is formed by a plate, such as stainless steel to absorb heat from the process waste and thereby form a heat sink. For example, the plate may be imperforate. 
     In another form, a liquid filter apparatus for semiconductor process waste separation from a semiconductor process includes a housing having a filter chamber, a process waste inlet, a process waste outlet, and a feed tube in communication with the process waste inlet and which has a feed tube outlet in communication with the filter chamber. The filter chamber forms a liquid reservoir holding a filter liquid therein, and the process waste outlet is in communication with the filter chamber. A heat sink is located adjacent the feed tube, which absorbs heat from the process waste to cool the process waste before it impinges the filter liquid. For example, the heat sink may form a deflecting surface to prevent direct impingement of the process waste flowing from the feed tube outlet with the filter liquid. 
     In any of the above, the feed tube includes an open distal end, which forms the feed tube outlet. 
     In any of the above, the housing includes an exhaust chamber between the liquid reservoir and the process waste outlet to direct the flow of filtered process waste from the liquid reservoir to the process waste outlet. 
     In any of the above, the feed tube outlet has an outer diameter, and the deflecting surface has an outer perimeter, with the outer perimeter of the deflecting surface being greater than the outer diameter of the feed tube outlet. 
     According to a further aspect, the housing includes an internal conduit in fluid communication with the liquid reservoir and the exhaust chamber to direct the flow of filtered process waste from the liquid reservoir to the exhaust chamber. 
     In any of the above, the liquid filter apparatus further includes a filter liquid control system for controlling the filter liquid flow into and out of the liquid reservoir. For example, the filter liquid control system may include a controller and a fluid circuit, with the controller controlling the fluid circuit to regulate the flow of filter liquid into and out of the liquid reservoir. 
     In any of the above, the liquid filter apparatus may further include a support to support the deflecting surface above the filter liquid in the liquid reservoir. 
     In any of the above, the liquid filter apparatus further includes a thermal shield. In one aspect, the thermal shield includes a cup-shaped body, which forms the deflecting surface and/or the heat sink and forms a first volume into which the process waste flows from the feed tube. For example, the cup-shaped body may have a cylindrical wall spaced from the feed tube. 
     In further aspects, the thermal shield includes a second cup-shaped body. The first cup-shaped body is located in the second cup-shaped body, which forms a second volume into which the process waste flows from the first cup-shaped body and from which the process waste flows to the process waste outlet. 
     Optionally, the thermal shield may include a third cup-shaped body, which is located in the second cup-shaped body spaced from the first cup-shaped body and which forms a third volume into which the process waste flows and from which the process waste flows to the process waste outlet. 
     For example, one or more of the cup-shaped bodies may be stainless steel bodies to absorb heat from the waste exhaust before it impinges the filter liquid. 
     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 with a feed tube, a filter chamber, and exhaust outlet. The method further includes forming a liquid reservoir in the filter chamber and holding a filter liquid in the liquid reservoir, and further providing an indirect pre-filter fluid pathway from the feed tube outlet to the liquid reservoir. The process waste is then directed the into the indirect pre-filter fluid pathway of the filter chamber from the feed tube and thereafter directed into the liquid reservoir of the filter chamber. 
     In one aspect, the directing the process waste into the indirect pre-filter fluid pathway includes absorbing energy from the process waste prior to the directing the process waste into the liquid reservoir. 
     In another or further aspect, the process waste is directed into the indirect pre-filter fluid pathway by providing a deflecting surface and spacing the deflecting surface from the feed tube outlet so the deflecting surface directs the process waste into the indirect pre-filter fluid pathway. 
     In a further aspect, the deflecting surface is sized greater than the diameter of the feed tube outlet. 
     Optionally, the deflecting surface is supported above the filter liquid in the liquid reservoir. 
     In addition, the filter liquid in the liquid reservoir is maintained at a liquid level below the deflecting surface. 
     In another aspect, the filter liquid is circulated through the reservoir to thereby remove the particle filled filter fluid. 
    
    
     
       DETAILED DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic drawing of a prior art CVD or PECVD system that consists of processing chamber connected via a fore-line to a vacuum pump; 
         FIG.  2    is a schematic drawing of a liquid filter apparatus for separating solid from a semiconductor process gas; 
         FIG.  3    is a schematic drawing of a liquid filter apparatus with a modified flow path for the gas; and 
         FIG.  4    is a schematic drawing of a liquid filter apparatus with a venturi; 
         FIG.  5    is a schematic drawing of a liquid filter apparatus with a thermal shield; 
         FIG.  6    is a schematic drawing of a liquid filter apparatus that stirs the filter liquid; 
         FIG.  6 A  is a similar view to  FIG.  6    showing the sequence of valve openings; 
         FIG.  6 B  is a similar view to  FIG.  6    showing the sequence of valve openings; 
         FIG.  6 C  is a similar view to  FIG.  6    showing the sequence of valve openings; 
         FIG.  6 D  is a similar view to  FIG.  6    showing the sequence of valve openings; 
         FIG.  7    is a schematic drawing of a liquid filter apparatus illustrating the liquid filter apparatus installed in a semiconductor processing system; and 
         FIG.  8    is a schematic drawing of a liquid filter apparatus illustrating the liquid filter apparatus forming a multiple chamber installation for a semiconductor processing system. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG.  2   , the numeral  10  generally designates a liquid filter apparatus that can be placed in the fore-line with a semiconductor process chamber exhaust and is configured to filter solids or particles from the semiconductor process gas, which is exhausted from the semiconductor process chamber and typically laden with solids or particles as a byproduct of gas phase reactions during the semiconductor process. As will be more fully described below, various modifications can be made to the liquid filter apparatus to address different process parameters, including when processing very high temperature semiconductor process gases and/or plasma, which in some cases will be alternately referred herein to semiconductor process waste or process waste. 
     Referring again to  FIG.  2   , filter apparatus  10  includes a housing  12  with a process gas inlet  14  for receiving the semiconductor process gas inflow from a semiconductor processing chamber, which is typically laden with solids and/or particles, and a gas outlet  16 , which discharges the filtered process gas after the filtering process. Housing  12  is formed form an inert material, such as aluminum, quartz, polymers, or a stainless steel alloy, and includes a filter chamber  18  that receives the process gas from a semiconductor processing chamber through inlet  14  and from which filtered gas is discharged through outlet  16 . Filter chamber  18  forms a liquid reservoir  20  to hold a filter liquid that filters solids and/or particles from the process gas flowing into the filter apparatus. 
     It has been found that suitable filter liquids to remove or filter out solids or particles from semiconductor process gases but which do not create chemical reactions with the reactants in the process gas stream include liquids with a vapor pressure below approximately 10 −7  Torr and that are chemically inert. Suitable liquids include liquids that can be used in temperatures ranging from −58 degrees centigrade and up to +257 degrees centigrade and that have negligible outgassing. Suitable liquids include liquids that are electrically non-conductive with a dielectric strength of in a range of 15.7 MV/m. 
     In addition, suitable liquids have kinematic viscosities greater than water (for reference, water has a kinematic viscosity of 1 cSt), for example, kinematic viscosities ranging from 38 to 1830 cSt. For example, suitable liquids include the commercially available Fomblin liquid, or perfluoropolyethers (PFPE). PFPEs have a vapor pressures of approximately 6×10 −8  Torr or below, and are chemically inert. PFPEs can be used in temperatures ranging from −58 degrees centigrade and up to +257 degrees centigrade and have negligible outgassing. PFPEs have a dielectric strength of approximately 15.7 MV/m, are chemically inert, and can be used in temperatures ranging from −58 degrees centigrade and up to +257 degrees centigrade and have negligible outgassing, though as described below, when processing very high temperature processes gases or plasmas, direct impingement and immersion of the process gas into the filter liquid may be minimized or avoided to improve cooling efficiency and separation of the particles from the gas phase. The PFPE filter fluids can be formulated with kinematic viscosities, for example, ranging from 38 to 1830 cSt. However, PFPE are expensive liquids and thus the particle-laden PFPE liquids withdrawn may be sent to commercial purifiers and recycled. 
     As will be more fully described below, the level of the liquid in the liquid reservoir  20  may be maintained by a control system to assure in some applications immersion of the process gas in the filter liquid, as described more fully below. For example, the height of the liquid in reservoir  20  may fall in a range of 3 inches to 8 inches, or 1 inch to 3 inches, or typically 2 inches to 6 inches depending on the configuration of the filter apparatus. Though as noted, in some when dealing with very high temperature process gases or plasma, the level in the reservoir may be adjusted. The filter size and PFPE volume hold up varies depending on the specific semiconductor process and chemistry. 
     The filter liquid is delivered to and discharged from liquid reservoir  20  through a filter liquid inlet  22  and a filter liquid outlet  24 , which are in communication with the liquid reservoir through conduits, such as tubing, that couple to a common port  26  on housing  12  for delivering and removing filter fluid to and from the liquid reservoir, respectively. Further, as will be more fully described below, in one embodiment, the filter liquid may be circulated through the apparatus  10  to increase the interaction between the filter liquid and the process gas. 
     Referring again to  FIG.  2   , apparatus  10  further includes a feed tube  30 , which is in communication with the process gas inlet  14  and extends into the filter liquid in the liquid reservoir  20  to directly inject the process gas flowing through the process gas inlet into the filter liquid in the liquid reservoir. Alternately, as described below, the process fee tube may terminate above the filter liquid to indirectly, for example, after cooling, 
     Feed tube  30  is formed from an inert material, such as aluminum, quartz, polymers, and typically a stainless steel alloy. Optionally, the feed tube  30  includes a plurality of perforations  32  at its distal end portion  30   a , with its distal end being closed to direct all the flow of the process gas through the perforations  32 , which generate a bubbling effect with the process gas in the liter fluid. The size and number and locations of the perforations  32  may vary, but may fall in a range of 0.125 inch in diameter to 0.5 inch or larger, or about 0.25 inch diameter. The purpose of the holes is to efficiently disperse the particle-laden gas stream and intimately mix it with the filter liquid. The gas bubbles created by the gas flowing from the perforations  32  mixes with the filter liquid, and the particles are separated from the gas stream and adsorbed into the filter liquid without imparting any harmful back-streaming to the semiconductor processing chamber. Alternately, as described in reference to  FIG.  5   , the end of the feed tube may be open to direct the process gas or plasma toward the filter fluid, though with higher temperatures, a thermal shield may be interposed between the open end of the feed tube and the filter fluid, as will be more fully described below. 
     As noted above, the liquid filter apparatus  10  may include a filter liquid control system  50  for controlling the filter liquid flow into and out of the liquid reservoir  20 . For example, the filter liquid control system  50  may include a controller  50   a , such as a microprocessor, and a fluid circuit  28 , with the controller  50   a  controlling the fluid circuit via electrically controlled valves  28   a ,  28   b  and a pump (not shown, such as a centrifugal or magnetically couple pump), to regulate the flow of filter liquid thorough inlet  22  and outlet  24  and into and out of the liquid reservoir  20 . Filter liquid control system  50  may also be configured to maintain the filter liquid at a liquid height in the liquid reservoir, as noted above. In this manner, the filter liquid may be exchanged with new filter liquid when the liquid is “spent” meaning that it has reached a certain level of absorption. For example, when the filter liquid is empirically deemed saturated with particles, it may be desirable to circulate fresh filter liquid in to the reservoir or it may be desirable to circulate the fluid regardless of how much it has absorbed of the particles. 
     In one embodiment, the control system  50  includes one or more sensors  52 . Sensors  52  may be used to detect the level of the filter liquid or measure the opacity or other characteristic of the liquid, which may be used to indicate that the liquid has reached a certain level of particle absorption. For example, determining when the liquid has reached a certain level of particle absorption may be based on another characteristic of the liquid, such as the viscosity. Or both types of sensors may be used—one measuring the filter liquid height and the other measuring the characteristic of the liquid to indicate when the liquid has reached a desired level of particle absorption. In either or both cases, the control system  50  may be used to adjust the flow of filter fluid into and out of liquid reservoir  20  based on the one or more sensors to accommodate the output of the semiconductor chamber and/or to optimize the filtering process. 
     Optionally, apparatus  10  may include one or more optical windows  40  for viewing the chamber  18 . For example, the widows or window  40  may be formed from PYREX or a quartz material and extend into and through the wall of housing  12 . Windows may be located beneath the desired filter liquid height so that the liquid can be observed manually for its height and/or opacity or other characteristic to offer manual control over the filter apparatus if desired. Windows  40  may comprise manual or automated optical windows and can be used to assess empirically the entrained solid content within the filter liquid and trigger a manual or automatic withdrawal of certain liquid volume and the addition of fresh filter liquid via valve  28   a ,  28   b  for continuous dynamic filter operation without the interruption of the process chamber or production. For example, the valving (e.g. valves  28   a ,  28   b ) noted above may provide manual control, including manual override control, over the electrically operated valves so that an operator may manually control apparatus  10 . 
     In the illustrated embodiment, process gas inlet  14  and gas outlet  16  are located at the top and side of housing  12  so that they have a generally ninety degree (right angle) orientation; however, as will be described in reference to the second embodiment, the gas inlet  14  and gas outlet  16  may be rearranged so that they are generally in-line. 
     In operation, the process gas flow enters at the top of apparatus  10 , as shown, and goes through feed tube  30 , bubbles through the filter liquid in reservoir  20 , where sheds off its particles and leaves the filter liquid reservoir  20 . The filtered gas then exits apparatus  10  at the side through gas outlet  16 . 
     Referring to  FIG.  3   , the numeral  110  generally designates another or second embodiment of a liquid filter apparatus that can be placed in the fore-line with a semiconductor process chamber exhaust and is configured to filter solids or particles from the semiconductor process gas, which is exhausted from the semiconductor process chamber. Similar to the previous embodiment, filter apparatus  110  includes a housing  112  with a process gas inlet  114  for receiving the semiconductor process gas inflow from a semiconductor processing chamber, which is typically laden with solids or particles, and a gas outlet  116 , which discharges the filtered process gas after the filtering process described below. For details of the suitable materials for the housing construction reference is made to the first embodiment. 
     As best seen in  FIG.  3   , housing  112  also includes a filter chamber  118  that receives the process gas through process gas inlet  114  and from which the filtered gas is discharged through gas outlet  116 . Filter chamber  118  forms a liquid reservoir  120  to hold a filter liquid that filters solids or particles from the process gas flowing into the filter apparatus. For examples of suitable liquid characteristics and suitable liquids that can filter solids or particles from semiconductor process gases, reference is made to the first embodiment. 
     In the illustrated embodiment, process gas inlet  114  and gas outlet  116  are generally in-line. To that end, housing  120  includes an exhaust chamber  138  between liquid reservoir  120  and gas outlet  116  to allow the filter gas to be exhausted from the filter chamber internally prior to being discharged through gas outlet  116 . In-line filter apparatuses may be used in certain locations where the right-angle filter apparatus of the first embodiment may not fit the existing fore-line geometry. 
     To form exhaust chamber  138 , housing  112  includes a solid plate  136  that divides in the internal space in housing  112  between filter chamber  118  and exhaust chamber  130  and further includes an internal conduit  134 , which includes a first open end  134   a  located above the height of the filter liquid and a second open end  134   b , which is extended through plate  136  for discharge into exhaust chamber  130 . Although illustrated as terminating at plate  136 , it should be understood that internal conduit  134  may extend through the plate into the exhaust chamber  138 . A suitable conduit includes a tube or tubing that is formed from an inert material, such as aluminum, quartz, polymers and typically a stainless steel alloy. 
     Similar to the previous embodiment, housing  110  includes a feed tube  130  that is in fluid communication with inlet  114  and extends into liquid reservoir  120  to inject the process gas into the filter fluid in a similar manner as described above. Further details of the feed tube  130  reference is made to feed tube  30 . 
     Also similar to previous embodiment, the level of the liquid in the liquid reservoir  120  may be maintained by a control system to assure immersion of the process gas in the filter liquid, as described above. 
     Apparatus  110  operates in a similar manner to apparatus  10 . Process gases flows into inlet  114  and is injected into the filter liquid in reservoir  120  via feed tube  130 . Due to the presence of the perforations  132  in the feed tube  130 , the process gas is bubbled into the filter liquid, where the solids or particles are removed from the process gas as they are absorbed by the filter liquid. The filtered gas is then exhausted from the filter chamber  118  through internal conduit  134 , which directs the filtered gas into exhaust chamber  138 , which then discharges the filtered gas through gas outlet  116 . 
     In a similar manner to the previous embodiment, the filter liquid may be circulated through the apparatus  110  via fluid circuit  128 , which includes an inlet valve  128   a  (which is in fluid communication with liquid inlet  122 ) and an outlet valve  128 , which in fluid communication with liquid inlet  124 ), and various conduits and a pump (not shown, such as a centrifugal or magnetically couple pump), to direct the flow of filter liquid to and from the liquid reservoir  120  through a common port  126 , as noted above, to circulate the filter liquid or simply replace the filter liquid. 
     Apparatus  110  may also include optical windows  140  for viewing the chamber  118 . For example, the widows or window  40  extend into and through the wall of housing  12  and may be located beneath the desired filter liquid height so that the liquid can be observed manually for its height and/or opacity or other characteristic to offer manual control over the filter apparatus if desired. 
     As stated above, in operation, the particle-laden process gas flow enters at the top of apparatus  110 , as shown, and goes through the internal feed tube  130 , bubbles through the filter in reservoir  120 , and enters the internal conduit  134  after it is filtered and sheds off its particles and leaves the filter liquid reservoir  120 . The filtered gas then enters exhaust chamber  138  and exits apparatus  110  at the bottom and in in-line with the top process gas input. 
     Referring to  FIG.  4   , the numeral  210  generally designates another or third embodiment of a liquid filter apparatus that can be placed in the fore-line with a semiconductor process chamber exhaust and is configured to filter solids or particles from the semiconductor process gas, which is exhausted from the semiconductor process chamber. Similar to the previous embodiment, filter apparatus  210  includes a housing  212  with a process gas inlet  214  for receiving the semiconductor process gas inflow from a semiconductor processing chamber, which is typically laden with solids or particles, and a gas outlet  216 , which discharges the filtered process gas after the filtering process described above. For details of the suitable materials for the housing construction reference is made to the first embodiment. 
     As best seen in  FIG.  4   , housing  212  also includes a filter chamber  218  that receives the process gas through process gas inlet  214  and from which the filtered gas is discharged through gas outlet  216 . Filter chamber  218  forms a liquid reservoir  220  to hold a filter liquid that filters solids or particles from the process gas flowing into the filter apparatus. For examples of suitable liquid characteristics and suitable liquids that can filter solids or particles from semiconductor process gases, reference is made to the first embodiment. 
     In the illustrated embodiment, process gas inlet  214  and gas outlet  216  are generally in line similar to the second embodiment. To that end, housing  220  also includes an exhaust chamber  238  between liquid reservoir  220  and gas outlet  216  to allow the filter gas to be exhausted from the filter chamber internally prior to being discharged through gas outlet  216 . For further details of exhaust chamber  238  reference is made to the previous embodiment. 
     Similar to the previous embodiment, housing  210  includes a feed tube  230  that is in fluid communication with inlet  214  but extends into chamber  218  and optionally terminates above the filter fluid. Feed tube  230  is also formed from an inert material, such as aluminum, quartz, polymers and typically a stainless steel alloy 
     In the illustrated embodiment, feed tube  230  includes a restriction  230   a  to form a venturi tube and an inlet  222  for the filter fluid to flow into the feed tube  230  and to generate the pressure differential to draw in the process gas into feed tube  230  through inlet  214  where it mixes with the filter liquid and thereafter is discharged into the filter chamber  218  via feed tube  230 . The filter liquid is also discharged into the liquid reservoir  220  from feed tube  230 . 
     In a similar manner as described above, the filter fluid may be circulated through apparatus  210  by way of a fluid circuit  228  (e.g. controlled by a controller, such as described above, which includes, in addition to valves  228   a  and  228   b , a pump  228   c  (such as a centrifugal or magnetically coupled pump), which circulates the filter fluid though apparatus  210  by way of various conduits  228   d.    
     In the illustrated embodiment, as noted, the liquid inlet  222  is formed in the feed tube  230 , while the liquid outlet  224  is located in the liquid reservoir beneath the liquid level. 
     Apparatus  210  operates in a similar manner to apparatus  110 . Process gases flows into inlet  214  but whose flow is enhanced by the venturi effect of the filter liquid flowing through feed tube  230 . The process gas mixes with the filter liquid and is then filtered and injected into the filter chamber  118  via feed tube  230 . The filtered gas is then exhausted from the filter chamber  218  through internal conduit  234 , which directs the filtered gas into exhaust chamber  238 , which then discharges the filtered gas through gas outlet  216 . 
     In a similar manner to the previous embodiment, the filter liquid may be circulated through the apparatus  210  via a fluid circuit  228 , which as noted includes an inlet valve  228   a  (which is in fluid communication with liquid inlet  222 ), an outlet valve  228   b  (which in fluid communication with liquid inlet  224 ), and various conduits to direct the flow of filter liquid trough apparatus  210 . Fluid circuit  228  may also be configured to replace the filter liquid after a given time period or after the filter liquid has reached a desired level of particle saturation, as described above. 
     Apparatus  210  may also include optical windows  240  for viewing the chamber  218 , similar to the second embodiment. 
     Referring to  FIG.  5   , the numeral  410  generally also designates a liquid filter apparatus for filtering solids and/or particles from semiconductor waste in semiconductor. Similar to the previous embodiments, filter apparatus  410  includes a housing  412  with a process waste inlet  414  for receiving the semiconductor process waste, such as semiconductor process waste gas and/or plasma, inflow from a semiconductor processing chamber, which is typically laden with solids or particles, and a filtered waste outlet  416 , which discharges the filtered process waste after the filtering process described below. For details of the suitable materials for the housing construction reference is made to the first embodiment. 
     As best seen in  FIG.  5   , housing  412  similarly includes a filter chamber  418  that receives the process waste through waste inlet  414  and from which the filtered waste is discharged through filtered waste outlet  416 . Filter chamber  418  forms a liquid reservoir  420  to hold a filter liquid that filters solids or particles from the process waste flowing into the filter apparatus. For examples of suitable liquid characteristics and suitable liquids that can filter solids or particles from semiconductor process gases, reference is made to the first embodiment. 
     In the illustrated embodiment, process waste inlet  414  and waste outlet  416  are generally in line similar to the second embodiment. Similar to the previous embodiment, housing  410  includes a feed tube  430  that is in fluid communication with inlet  414  but extends into chamber  418  and optionally terminates above the filter fluid. Feed tube  430  is also formed from an inert material, such as aluminum, quartz, polymers, or a stainless steel. 
     However, housing  420  is configured to provide an indirect pre-filter fluid pathway for the process waste from the feed tube outlet  430   a  to the liquid reservoir  420  to reduce the energy, for example, when filtering very hot process waste, such as gases and/or plasma, with a temperature in a range of 200-600 degrees C. or higher. Further, as will more fully described below, the housing  420  is configured to cool the process waste before it impinges the filter liquid. 
     To direct the waste into the indirect pre-filter fluid pathway, liquid filter apparatus  410  includes a deflecting surface  450  that is located adjacent the feed tube outlet  430   a . In this manner, the waste does not directly impinge the filter fluid and, instead, is directed to the indirect pre-filter fluid pathway. In addition, as will be more fully described below, the deflecting surface is formed from a material that absorbs heat to thereby form a heat sink. By impinging on this deflecting surface, much of the initial thermal energy is therefore absorbed, thus creating a thermal shield that can absorb the ionic and high electron energy when, for example, a plasma exhaust is injected into the filter apparatus, helping to rapidly quench the exited electrons and ions and cooling the hot gases. 
     Depending on its construction, the thermal shield can also significantly increase the heat exchange surface area and the gas-liquid interfacial area leading to efficient cooling and particles separation from the gas phase. This novel fluid filter has been tested to show 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 well below any potential chemical reaction and fluid properties degradation while significantly increasing particle separation from the gas phase. 
     The first deflecting surface may be formed by a plate. Optionally, the plate is provided by a cup-shaped body  452 , with a side wall  452   a , such as a cylindrical side wall, that extends upwardly from a base wall  452   b , which may form the plate, such as an imperforate plate. Body  452  may be a unitary body and be formed by molding or welding. Optionally, the cup-shaped body may be supported so that it straddles and surrounds the end of feed tube  430 , but is spaced therefrom so that base wall  452   b , which as noted may form the initial deflecting surface, is spaced from the feed tube outlet  430   a  of feed tube  430 . In this manner, the outer perimeter of the deflecting surface may be greater than the outer diameter of the feed tube outlet. 
     The indirect pre-filter fluid pathway may be formed by additional directing or deflecting surfaces. For example, the additional deflecting surfaces may be formed by discrete structures, including discrete structures assembled or joined together, for example, during their forming process or post forming process, such as by welding. For example, a second deflecting surface  452   c  may be formed by the inside surface of the side wall  452   a  of the cup-shaped body  452 , which together with the first deflecting surface  450  may form a first volume of space  452   d  into which the waste flows once it has exited the feed tube outlet  430   a.    
     A third deflecting surface  454  may be provide by a second cup-shaped body  460 , which supports first cup-shaped body  452  therein and which is supported on the lower wall  412   a  of housing  412  by one or more supports  464 . Optionally, second cup-shaped body  460  is supported on the lower wall  412   a  of housing  412  above the filter liquid level, which may be controlled by a control system in a similar manner as described above. 
     Second cup-shaped body  460  also includes a side wall  460   a , such as a cylindrical side wall, that extends upwardly from a base wall  460   b  and which is taller than the side wall  452   a  of cup-shaped body  452  so that when waste flows from the first volume  452   d  it will flow into a second volume  460   d  formed by second cup-shaped body  460  above and between cup shaped body  452 . Inner surface  460   c  of side wall  460   a  will, therefore, form the third deflecting surface to direct the flow of waste along the indirect pre-filter fluid pathway through housing  412 . 
     In this manner, as the waste flows into the second volume it flows up and over the top of side wall  460   a  and down to the filter liquid in the liquid reservoir  420  beneath second cup-shaped body  460 . Some waste may flow between the two side walls  452   a  and  460   a  emerge from under the first cup-shaped body (as shown by the green arrow in  FIG.  5   ) and thereafter flow upwardly and then down to the filter liquid in the liquid reservoir  420 . 
     In each case the deflecting surfaces may be formed from material that absorbs heat, such as stainless steel, to thereby form heat sinks. 
     Apparatus  410  operates in a similar manner to apparatuses  210  and  110 . Process waste (gases and/or plasma) flows into inlet  414  and then after cooling mixes with the filter liquid. The filtered waste is then exhausted from the filter chamber  418  through an internal conduit  434 , which extends through base wall  460   b  of second-cup-shaped body  460 . Internal conduit  434  then directs the filtered waste into exhaust chamber  438 , which then discharges the filtered waste through waste outlet  416 . 
     The flow of filtered waste may be directed to internal conduit  434  through another cylindrical side wall  470 , which is also supported in second cup-shaped body  460  and is coaxial with and spaced from internal conduit  434 . Additionally, cylindrical side wall  470  is spaced from first cup-shaped body  452  and further extends above both cup-shaped bodies  452  and  460 . Hence the outer surface  470   a  of cylindrical wall  470  also forms a deflecting surface (and hence forms part of the indirect pre-filter fluid pathway) to direct the flow of waste upwardly over the top edge of second cup-shaped body  460 , as best understood from  FIG.  5   . Additionally, the inside surface  470   b  of cylindrical wall  470  forms a post filter pathway that allows the filtered waste to flow upwardly and into internal conduit  434 . 
     In a similar manner to the previous embodiment, the filter liquid may be circulated through the apparatus  410  via a fluid circuit. The fluid circuit may also be configured to replace the filter liquid after a given time period or after the filter liquid has reached a desired level of particle saturation, as described above. Further, the control system optionally maintains the level of the filter liquid below the second cup-shaped body to thereby form part of the post filter pathway for the filtered waste to flow. 
     Housing  412  also includes an exhaust chamber  438  between liquid reservoir  420  and waste outlet  416  to allow the filter waste to be exhausted from the filter chamber internally prior to being discharged through outlet  416 . For further details of exhaust chamber  438  reference is made to the previous embodiment. 
     Suitable materials for the deflecting surfaces may be stainless steel, which is inert and additionally can absorb heat and, hence, cool the waste, as noted above. 
     The cup-shaped bodies  452  and  460  and cylindrical wall  470  may be a unitary assembly  480  that is joined together by welding or molding or may be discrete components that are assembled to form the indirect pre-filter pathway and post filter pathway for the waste flowing through the apparatus  410 . 
     Accordingly, using a liquid filter the apparatus may be used to separate solids from process waste in a semiconductor processing system. By providing an indirect pre-filter fluid pathway from the feed tube outlet to the filter liquid reservoir, the waste can be cooled prior to imping the filter fluid, which can absorb much of the initial thermal energy. The resulting thermal shield can absorb the ionic and high electron energy when a plasma exhaust is injected into the apparatus to help rapidly quench the exited electrons and ions and cooling the hot gases. The components forming the thermal shield can also significantly increase the heat exchange surface area and the gas-liquid interfacial area leading to efficient cooling and particles separation from the gas phase. 
     Referring to  FIG.  6   , the numeral  310  generally designates a liquid filter apparatus that stirs the filter fluid that can be placed in the fore-line between a semiconductor processing chamber and a processing pump (see  FIGS.  6  and  7   ) and is configured to filter solids or particles from the semiconductor process gas, which is exhausted from the semiconductor process chamber. Further, as will be more fully described below, liquid filter apparatus  310  is configured to be in communication with a fluid circuit ( 328 , described below) in an arrangement that allows for automatic fluid addition and removal of filter fluid to or from chamber ( 318 ) of the fluid apparatus. 
     Similar to the previous embodiment, filter apparatus  310  includes a housing  312 , which forms a filter chamber  318 , with a process gas inlet  314  for receiving the semiconductor process gas inflow from a semiconductor processing chamber into chamber  318  (see  FIG.  6    for example, where filter apparatus  310  is mounted in the fore-line of the processing system, between the semiconductor chamber and the process pump), which is typically laden with solids or particles, and a gas outlet  316 , which discharges the filtered process gas from chamber  318  after the filtering process described below. For details of the suitable materials for the housing construction reference is made to the first embodiment. 
     As best seen in  FIG.  6   , chamber  318  forms a liquid reservoir  320  to hold a filter liquid that filters solids or particles from the process gas flowing into the filter apparatus, and which is then discharged as waste. For examples of suitable liquid characteristics and suitable liquids that can filter solids or particles from semiconductor process gases, reference is made to the first embodiment. In the illustrated embodiment, process gas inlet  314  and gas outlet  316  are generally in line similar to the second embodiment with a right angle arrangement. Also similar to the previous embodiment, housing  310  includes a feed tube  330  that is in fluid communication with inlet  314  and that extends into chamber  318  and optionally terminates at or slightly below the filter fluid in liquid reservoir  320 . Feed tube  330  is also formed from an inert material, such as aluminum, quartz, polymers and typically a stainless steel alloy. 
     In the illustrated embodiment, chamber  318  includes a rotating member  332 , which is driven to rotate by a motor  334 . Motor  334  is mounted external or outside of housing  312  but whose drive shaft  334   a  may extend through a sealed opening provided in housing wall  312   a  to engage rotating member  332  or may not penetrate the housing an instead couple to the rotating member via a magnetic coupling, as noted below. For example, the sealed opening may be formed by a sealed bushing or sealed grommet. The rotating member  332  may be in the form of multiple blades commonly mounted to an annular support, which is rotatably mounted at the bottom portion of housing wall  312   a.    
     In one embodiment, drive shaft  334   a  of motor couples to rotating member  332  by a magnetic coupling through the wall of the housing  312 . For example, shaft  334   a  may include a magnet, and rotating member  332  may also include a magnet, for example, mounted in or about the annular support to provide the magnetic coupling. 
     As noted above, rotating member  332  is located at the bottom portion of housing  312  in liquid reservoir  320  and, when rotated by motor  334 , stirs or rotates the filter fluid in liquid reservoir  320 , optionally in a continuous fashion. This fluid rotation enables the particles of varying densities to thoroughly mix with the filter fluid and thereafter is discharged from the filter chamber  318  via an outlet  312   b  formed in housing wall  312   a . In addition, the rate of rotation will impact the discharge rate of the fluid from chamber via outlet  312   b  and the rate of inflow of the filter fluid into chamber  318  via an inlet  312   c  (also formed in housing wall  312   a ) from the fluid circuit described below. Further, the rate of rotation will determine the depth of the vortex V generated due to fluid rotation. 
     In a similar manner as described above, the filter fluid may be selectively and automatically circulated through apparatus  310  by way of a fluid circuit  328  (e.g. controlled by a controller, such as programmable logic controller, including microprocessor, such as described below). 
     In the illustrated embodiment, fluid circuit  328  includes a conduit  340 , which is in fluid communication with the chamber  318  above the filter fluid, a sliding valve  342 , and a plurality of control valves  328   a  (V1),  328   b  (V2),  328   c  (V3),  328   d  (V4),  328   e  (V5), and  328   f  (V6), which are opened and closed by a controller  350  (such as a microprocessor), to automatically control the flow of fluid through conduit  340  and through valve  342  based on a sequence of valve openings and closings described below. By providing fluid communication between chamber  318  (above the filter fluid) and conduit  340 , conduit  340  is subject to the pressure in chamber  318 , which is under a vacuum (or low or very low pressure) due to the fluid communication between the fore-line and chamber  318  through outlet  316 . This vacuum (or low or very low pressure) is then extended to other parts of circuit  328 , as described below. For example, conduit  340  may comprise a stainless steel tube. 
     As best seen in  FIG.  6   , sliding valve  342  includes a cylinder  342   a  and a sliding piston  342   b , which is moved up and down cylinder  342   a  (as viewed in  FIG.  6   ) by a motor  343 , which is also controlled by controller  350  to open and close communication with the chamber  318  and circuit  328  through valve  342 . 
     Additionally, circuit  328  includes two chambers  344  and  346 , with chamber  344  in selective fluid communication with a make-up fluid supply via valve  328   a  (V1), and with chamber  346  in selective fluid communication with a supply of nitrogen gas via valve  328   c  (V3) and via valve with conduit  340 . Thus, when valve  328   a  (V1) is opened, chamber  344  is filled with make-up fluid. Similarly, when valve  328   e  (V5) is opened, chamber  346  is filled with nitrogen. When valve  328   e  (V5) is closed, and valve  328   d  (V4) is open, the pressure in chamber  346  is then reduced to a low, very low or vacuum pressure. 
     To control the flow of fluid into and out of reservoir  320 , cylinder  342   a  includes a first port (optionally formed by a conduit) in fluid communication with inlet  312   c  of housing  312  and a second port (optionally formed by a conduit) in fluid communication with outlet  312   b  of housing  312 . Further, piston  342   b  includes two transverse passageways  342   c  and  342   d , which when moved by motor  343  can align with the ports of the cylinder  342   a  to allow fluid communication between reservoir  320  and chamber  344  and/or chamber  346 , depending on the open or closed state of valve  328   b  (V2) and valve  328   c  (V3). Valve  328   b  (V2) provides for selective fluid communication between chamber  344  and sliding valve  342  and reservoir  320  depending on the position of the piston  342   b , and valve  328   c  (V3) provides for selective fluid communication between chamber  346  and sliding valve  342  and reservoir  320  depending on the position of the piston  342   b.    
     As best understood from  FIG.  6   , when valve  328   a  (V1) is open and all the other valves ( 328   b  (V2),  328   c  (V3),  328   d  (V4),  328   e  (V5), and  328   f  (V6)) are closed (step  1 , see  FIG.  6 A ), make-up fluid is directed to chamber  344 . When valve  328   b  (V2) and valve  328   c  (V3) are open and the rest of the valves ( 328   a  (V1),  328   d  (V4),  328   e  (V5), and  328   f  (V6)) are closed (step  2 , see  FIG.  6 B ) and motor  343  is driven to move the piston is in the lower position (as viewed in  FIG.  6   , where the transverse passageways  342   c  and  342   d  of piston  342   b  are aligned with the ports of the cylinder  342   a ), make-up fluid is sent to reservoir  320  and particle-filled fluid is discharged to chamber  346 . When valves  328   a  (V1),  328   b  (V2),  328   c  (V3), and  328   d  (V4) are closed and valves  328   f  (V6) and  328   e  (V5) are opened (step  3 , see  FIG.  6 C ) then fluid is removed from chamber  346 , driven by a pre-set nitrogen flow passing through the open valve  328   e  (V5). Once a given time is allowed so the fluid is removed from chamber  346 , then valves  328   a  (V1),  328   b  (V2),  328   c  (V3), and  328   e  (V5), and  328   f  (V6) are closed and valve is  328   d  (V4) is opened to allow chamber  346  to evacuate so that the pressure in chamber  346  equilibrates with the fore-line pressure (step  4 , see  FIG.  6 D ). And the sequence is repeated by the controller. The timing of the sequence steps can vary because it is based the particular process and settings for the process. On average it is anticipated that the sequence timing could be cycling every 10 to 20 seconds depending on the particle loading of the fluid. If the semiconductor process effluent is of low particle loading the sequence could be up to 30 to 60 minutes. 
     Apparatus  310  operates in a similar manner to apparatus  110  in that process gases flows into inlet  314  but whose flow is then enhanced by the vortex effect of the filter liquid flowing around feed tube  330 . The process gas mixes with the filter liquid and is then filtered after it is injected into the filter chamber  318  via feed tube  330 . The filtered gas is then exhausted from the filter chamber  318  through gas outlet  316 . 
     In the illustrated embodiment, the filter liquid is thus dynamically circulated through the apparatus  310  via fluid circuit  328 . 
     Fluid circuit  328  may also be configured to replace the filter liquid after a given time period or after the filter liquid has reached a desired level of particle saturation, as described above. 
     Referring to  FIGS.  7  and  8   , filter apparatus  310  (or any of the other filter apparatuses  410 ,  210 ,  110 , or  10  described herein) may be installed in the fore-line between a semiconductor processing chamber C and a processing pump P, and further installed in a system with multiple chambers (C, C 2 , C 3 ) and multiple pumps (P, P 2 , P 3 ), with the waste fluid from each of the filter apparatuses optionally directed to a shared waste tank T, and optionally with the make-up fluid supplied from a shared make-up fluid supply tank T. 
     In any of the embodiments, the control system may include one or more sensors (not shown in each embodiment), which may be used to detect the level of the filter liquid or measure the opacity (optical torpidity) or other characteristic of the liquid, which may be used to indicated that the liquid has reached a certain level of absorption. Or both types of sensors may be used—one measuring the filter liquid height and the other measuring the characteristic of the liquid. In either or both cases, the control system may be used to adjust the flow of filter fluid into and out of the apparatus based on the one or more sensors to accommodate the output of the semiconductor chamber and/or to optimize the filtering process. 
     Both the right angle and the in-line filter apparatus configurations may be passive (“passive” means the reservoir has a fixed amount of filter fluid that is periodically manually change and replace with new filter fluid), i.e. they are inserted in line in a semiconductor processing system using the process gas pressure and flow characteristics of the semiconductor processing system or dynamic (“dynamic” means the particle laden filter fluid is dynamically/automatically removed and exchanged with fresh filter fluid, as described above in reference to  FIG.  7   ). As noted, the filter liquids may be removed and added periodically through the valving and optionally pump based on predetermined maintenance periods. As noted, in one configuration, a filter liquid recirculating pump may be added to recirculate the filter liquid as shown in  FIG.  4   . In this embodiment, the recirculating filter liquid can have very high recirculating flow rate and may be mixed more efficiently using the venturi tube as shown and described. Using a venturi tube may achieve very high particle/gas separation and, as noted, creates a localized vacuum pull on the process gases entering the filter thus assisting the process vacuum pump operation and potentially reducing its total energy consumption. 
     Directional terms, such as “vertical,” “horizontal,” “top,” “bottom,” “upper,” “lower,” “inner,” “inwardly,” “outer” and “outwardly,” are used to assist in describing the invention based on the orientation of the embodiments shown in the illustrations. The use of directional terms should not be interpreted to limit the invention to any specific orientation(s). 
     The above description is that of current embodiments of the invention. Various alterations and changes can be made without departing from the spirit and broader aspects of the invention as defined in the appended claims, which are to be interpreted in accordance with the principles of patent law including the doctrine of equivalents. This disclosure is presented for illustrative purposes and should not be interpreted as an exhaustive description of all embodiments of the invention or to limit the scope of the claims to the specific elements illustrated or described in connection with these embodiments. For example, and without limitation, any individual element(s) of the described invention may be replaced by alternative elements that provide substantially similar functionality or otherwise provide adequate operation. This includes, for example, presently known alternative elements, such as those that might be currently known to one skilled in the art, and alternative elements that may be developed in the future, such as those that one skilled in the art might, upon development, recognize as an alternative. The present invention is not limited to only those embodiments that include all of these features or that provide all of the stated benefits, except to the extent otherwise expressly set forth in the issued claims. Any reference to claim elements in the singular, for example, using the articles “a,” “an,” “the” or “said,” is not to be construed as limiting the element to the singular.