Abstract:
A compact torch for use in semiconductor processing which may be used both to produce steam and to perform wet or dry dichlorethylene (DCE) oxidation at varying concentrations with no reconfiguration of the torch, providing full temperature of control of the oxidation product gases, with redundancy to provide automatic backup of heating and ignition elements, and with non-mechanical flow control of the oxidation product gases.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to torches for use in semiconductor processing. 
     BACKGROUND OF THE INVENTION 
     A number of the processes in semiconductor production require introduction of particular chemical substances in an ultrapure state into the process chamber or furnace. For example, wet processes require steam and dry processes require hydrogen chloride (HCl). Both of these are typically produced by oxidation in a torch chamber which feeds the oxidation products into the processing chamber. Known torches are Pyrogenic External Torches (PET) which typically include an external ignition element, a quartz hydrogen/oxygen injector, a quartz torch chamber, a safety shield, and an electronic controller for safety interlocks and operation communications with a main computer controller. Heated streams of hydrogen and oxygen are injected via a nozzle into the torch chamber, in which they ignite, thereby producing steam. These torches may also be configured for HCl production, but they then require additional heaters to maintain HCI oxidation. Existing torches in both cases tend to produce more heat than is needed by the semiconductor processing and are subject to expensive downtime when changing the input gases or in cases of heater failure. A further disadvantage is that flow control of the oxidation products is achieved by mechanical valves, which may introduce contaminants into the gas flow being controlled, especially in the case of hot and/or chemically reactive flows as in semiconductor production. 
     An indication of the state of the art is the torch assembly disclosed in U.S. Pat. No. 5,257,926 issued to the same assignee as the present application, the contents of which are incorporated herein by reference. 
     SUMMARY OF THE INVENTION 
     The present invention seeks to provide a compact torch for use in semiconductor processing which may be used to produce both steam and wet or dry Hydrogen Chloride at varying concentrations with no reconfiguration of the torch, providing full temperature of control of the oxidation product gases, with redundancy to provide automatic backup of heating and ignition elements, and with non-mechanical flow control of the oxidation product gases. 
     There is thus provided, in accordance with a preferred embodiment of the present invention, for use with a reactor chamber for semiconductor processing, a torch assembly for both combustion and flameless oxidation processes including: 
     a quartz chamber for sustaining therein combustion and flameless oxidation processes with a longitudinal axis and an open end to allow exit of gaseous oxidation products; 
     a gas injection subassembly mounted either integrally or removably with sealing apparatus at the other end of the quartz chamber with nozzles and supply conduits for first and second gases; 
     a starter unit which includes a radiant energy emitter and at least one radiant energy absorber to provide at least one hot spot to initiate oxidation of the gases in a preselected zone of the quartz chamber; 
     at least one heater mounted within the chamber and generally parallel to the chamber axis for heating the gases to a temperature sufficient to sustain oxidation thereof in the preselected zone of the chamber; 
     a cooling arrangement in heat exchange association with a wall portion of the chamber; and 
     a controller associated with the torch assembly for controlling operation thereof. 
     Additionally in accordance with a preferred embodiment of the present invention, the chamber wall portion is a double wall portion with inner and outer leaves defining an interspace and the cooling arrangement includes apparatus for directing a flowable cooling medium via the interspace to be in heat exchange contact with the inner leaf of the wall portion of the chamber, the interspace further having ridges for defining a generally helical flow path for the flowable cooling medium. 
     Further in accordance with a preferred embodiment of the present invention, the radiant energy emitter includes at least one lamp, which may be a quartz-halogen lamp with a tungsten filament, and the at least one radiant energy absorber includes at least one blackbody member, which may be made of silicon carbide which may be quartz-encapsulated and evacuated, positioned at a predetermined distance from the lamp. 
     Still further in accordance with a preferred embodiment of the present invention, the at least one heater is at least two heaters each of which is operable alone to heat the gases to a temperature sufficient to sustain oxidation thereof in the preselected zone of the chamber, and wherein the controller is operative, in the case of a failure of at least one of the heaters, to cause a non-failing heater to operate alone so as to heat the gases to a temperature sufficient to sustain oxidation thereof in the preselected zone of the chamber. 
     Additionally in accordance with a preferred embodiment of the present invention, the gas injection nozzles provide streams of the gases with at least minimum predetermined exit velocities and at predetermined angles each in the range of 5°-90° with respect to the chamber axis, thereby to mix the gases and produce a mixed stream generally parallel to the chamber axis. The nozzles each further have one or more orifices which may be of different diameters; and the supply conduits selectably supply the respective gases to their respective orifices so that the gas outflows will have the minimum predetermined exit velocities. The gas injection subassembly may further have a single emitting surface with all the orifices thereon, wherein the gas streams are emitted at predetermined angles each in the range of 5°-90° with respect to the emitting surface, or two emitting surfaces, one for each gas and its respective orifices, wherein the gas streams are generally perpendicular to the respective emitting surfaces. The gas conduits further include branching and mixing conduits to supply mixtures at preselected concentrations of the gases, where the first gas may be oxygen or a mixture at a preselected concentration of oxygen and dichlorethylene (DCE) vapor suspended at predetermined concentrations in nitrogen and the second gas is hydrogen, which is supplied when steam production is required. The torch assembly may also include a flame detector and a number of temperature sensors associated with the controller. 
     In accordance with an additional preferred embodiment of the present invention, the torch assembly further includes a flow divertor situated between the open end of the quartz chamber and a reactor chamber for semiconductor production for controlling the flow of the gaseous oxidation products. The flow divertor has: 
     a primary conduit for conducting gaseous oxidation products from the quartz chamber to the reaction chamber, which may include an auxiliary input conduit for adding preselected auxiliary chemical substances to the gaseous oxidation products flowing in the primary conduit; 
     a secondary conduit intersecting with and communicating with the primary conduit via an outlet formed in a side wall thereof at a location upstream of the reactor chamber; and 
     apparatus for selectably applying a pressure drop across the primary conduit and the secondary conduit, employing a flow of a carrier fluid or gas, which may be controlled by valves, to produce a Venturi effect in the secondary conduit, thereby causing the gaseous oxidation products in the primary conduit to flow into the secondary conduit, thus to prevent the gaseous oxidation products from reaching the reactor chamber. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be more fully understood and appreciated from the following detailed description, taken in conjunction with the drawings, in which: 
     FIG. 1A is a schematic representation of a torch assembly, constructed and operative in accordance with an embodiment of the present invention; 
     FIG. 1B is a block diagram of a semiconductor processing system employing the torch assembly of the present invention; 
     FIGS. 2A and 2B are two side-sectional views, taken perpendicular to one another, of the quartz chamber of a preferred embodiment of the present invention; 
     FIG. 3 is a cross-sectional view of the quartz chamber of FIG. 2A, taken along line  3 — 3  therein; 
     FIGS. 4 and 5 are two side-sectional views, taken perpendicular to one another, of a gas injection subassembly of a torch assembly in accordance with an alternative embodiment of the present invention; 
     FIGS. 6 and 7 are two side-sectional views, taken perpendicular to one another, of a gas injection subassembly of a torch assembly in accordance with a further alternative embodiment of the present invention; 
     FIG. 8 is a transverse view of a gas injection subassembly of a torch assembly in accordance with a preferred embodiment of the present invention; 
     FIGS. 9A and 9B are detailed views of gas injection nozzles of the gas injection subassembly of FIG. 8; and 
     FIGS. 10A and 10B are detail schematic block diagrams of a flow divertor in a semiconductor processing system employing the torch assembly of a further embodiment of the present invention, in which oxidation gases are seen to be permitted and to be prevented, respectively, to reach the semiconductor reactor chamber. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to FIG. 1A, there is shown a schematic representation of a torch assembly, referred to generally as  10 , constructed and operative in accordance with an embodiment of the present invention. Torch assembly  10  includes a quartz chamber  110 , wherein oxidation of gases takes place, that defines a longitudinal axis  180  for torch assembly  10 . As shown in the drawing, left end  12  of quartz chamber  110  is open and is typically configured for connection with a semiconductor processing furnace (not shown) so that gaseous products of oxidation, for example, ultrapure steam or hydrogen chloride gas, within torch assembly  10  can exit therefrom and be received as input gases by the semiconductor processing furnace. Quartz chamber  110  typically has in association therewith a cooling arrangement (not shown) to prevent excess heating which may result when there is combustion taking place therein. 
     Opposite open end  12  of quartz chamber  110  is gas injection subassembly, referred to generally as  120 , which provides the gases for oxidation to torch assembly  10  which may be mounted either integrally or removably on quartz chamber  110 , provided that it be sealed thereon. Gas injection subassembly  120  includes nozzles  13  for oxidation gases configured to produce a mixed flow thereof generally along axis  180 . Gas injection subassembly  120  further includes a system of conduits and valves  130 , schematically indicated by box V, to supply preselected oxidation gases to nozzles  13 . 
     Combustion of the mixed flow of gases in torch assembly  10  is initiated by an ignition unit including radiant energy source  14  and blackbody radiant energy absorbing member  15 . In accordance with a preferred embodiment of the present invention, radiant energy source  14  is one or more quartz-halogen lamps with tungsten filaments and blackbody radiant energy absorbing member  15  is one or more evacuated, quartz-encapsulated, granular silicon-carbide capsules. As described in U.S. Pat. No. 5,257,926, included herein by reference, when lamp  14  is activated, its radiant energy is rapidly absorbed by blackbody member  15 , in times typically less than one minute, raising the temperature of blackbody member  15  to the required ignition temperature of the gases in chamber  110 . Blackbody member  15  is located close enough to the mixed flow of oxidation gases to provide a hot spot for ignition thereof. For example, when torch assembly  10  is to be used to produce ultrapure steam, hydrogen and oxygen gases are the oxidation gases and blackbody member  15  rises to 760° C., which, according to the safety standards of the semiconductor industry, is a safe ignition temperature therefor. 
     While combustion in torch assembly  10  could be maintained by the lamp  14  and backbody  15  arrangement described above, as will be understood by persons skilled in the art, tungsten-halogen lamps will have a relatively short lifetime if they are continuously used in such an application. Therefore, in accordance with a preferred embodiment of the present invention, torch assembly  10  includes two or more electric heaters  16  in wells  17  extending into quartz chamber  110  to heat the gases to sustain combustion. As will be described in conjunction with FIGS. 2A and 2B hereinbelow, two or more heaters  16  are employed to provide redundancy and backup capability so that torch operation, and hence, semiconductor processing, can be maintained without interruption even in a case of heater failure. Heaters  16  could also be employed as an ignition device for the combustion gases, but they reach the required temperature somewhat more slowly than the lamp-blackbody arrangement described above. 
     Torch assembly  10  further includes a flame detector and a number of temperature sensors, typically thermocouples, not shown, positioned at a number of predetermined locations in the assembly. These sensor devices are connected with controller  140 , which allow it to monitor the assembly for desired operation. Controller  140  is also connected to electrical devices such as lamp  14  and heater  16  and the valves in V  130  allowing it to control all aspects of torch operation, typically in connection with the controller of the semiconductor processing system to which torch assembly  10  is connected. 
     Referring briefly to FIG. 1B, there is shown a block diagram of a semiconductor processing system employing a torch assembly  10  constructed and operative in accordance with an alternative embodiment of the present invention. Processing furnace or tube  115  receives as input gases, for example, ultrapure steam or hydrogen chloride gas, which are oxidation products of torch  111 , which is controlled by controller  140 , which interfaces directly with the control system  116  of process furnace  115 . Gas flow from torch  111  to process furnace  115  is controlled by flow divertor  118 . 
     Referring now to FIGS. 2A and 2B, there are shown two side-sectional views, taken perpendicular to one another, along the longitudinal axis  280  of a quartz chamber, referred to generally by reference number  20 , of a torch assembly constructed in accordance with a preferred embodiment of the present invention, wherein FIG. 2B is along line B—B in FIG.  2 A and FIG. 2A is along line A—A in FIG.  2 B. 
     In accordance with a preferred embodiment of the present invention, quartz chamber  20  is a double-walled enclosure with inner and outer walls,  21  and  22  respectively, enclosing the zone  230  wherein torch oxidation occurs. The space between inner and outer walls  21  and  22  has an inlet tube  23  and an outlet tube  24  to direct a flow of a cooling fluid therethrough to cool, by heat exchange, primarily inner wall  21  to a temperature within a desired temperature range while the torch is operating and hence, producing excess heat. The cooling fluid may be gaseous, such as compressed air, or liquid, such as water. In a preferred embodiment of the present invention, there are formed, on one or both of the mutually facing surfaces of inner and outer walls  21  and  22  helical ridges  25  which direct the flow of the cooling medium in a helical fashion, to provide for more efficient heat exchange between the fluid and the chamber walls. There is also a thin, tubular enclosure  26  extending into the space between inner and outer walls  21  and  22  to house a temperature sensor, such as a thermocouple, to allow monitoring of the temperature by the torch controller  140  (FIG.  1 A). 
     Referring now to FIG. 2B, there are shown two large cylindrical wells  27  preferably parallel to axis  280  of chamber  20 . As shown in FIG. 2A, wells  27  extend longitudinally along the length of and below oxidation zone  230  but still within chamber  20 . Wells  27  accommodate a pair of heaters (not shown) which heat the oxidation gases to a temperature sufficient to sustain oxidation thereof, once oxidation has started. In accordance with a preferred embodiment of the present invention, the heaters are high-output electrical resistance coil heaters. 
     Under normal functioning of the torch, the heaters operate together, each at an intermediate power level, to heat the oxidation gases to the required temperature. In accordance with a preferred embodiment of the present invention, each heater is operable alone to produce enough heat to sustain oxidation in the torch. In case of failure or significant power output reduction of one of the heaters, the controller  140  (FIG. 1A) will immediately raise the power in the functioning heater to continue the current semiconductor processing step or sequence of steps through completion without a need to replace the defective heater. It will be appreciated by persons skilled in the art that this capability to maintain uninterrupted operation provided by the redundancy and backup arrangement of the heaters in the present invention is very useful in semiconductor production and a significant improvement over prior art. Further, it should be noted that similar redundancy and backup arrangements employing more than two heaters is also included within the scope of the present invention. 
     As is known by persons skilled in the art, existing torches in semiconductor production heat the oxidation zone by means of heating elements externally placed on the chamber walls which inevitably heat the entire chamber. They take longer than the present invention to reach the desired temperature and run the risk of devitrification as a result of excess heating of the chamber walls. The present invention is operable in a desired temperature range which is hot enough to preclude condensation of the steam produced therein, but cool enough to protect against damage to the torch and devitrification thereof and of quartz chamber  20 . This is due both to the compact size of the torch of the present invention, and to the internal location of the heaters in heater wells  27  within chamber  20 ; both factors allow a lower power requirement to heat the entire oxidation zone  230 . Referring briefly to FIG. 3, there is shown a cross-sectional view of quartz chamber  20  of FIG. 2A, taken along line  3 — 3  therein, which shows the positions of heater wells  32  within the chamber. Also shown in the drawing is a thin well  29  (also in FIG. 2A) for housing a temperature sensor, such as a thermocouple, to allow monitoring of the temperature near the oxidation zone  230  by the torch controller  140  (FIG.  1 A). 
     As shown in FIGS. 2A and 2B, left end  260  of chamber  20  along its longitudinal axis  280  is open. The torch assembly is typically connected to a semiconductor processing system by this open end  260 , as shown in FIG. 1B, thereby allowing gaseous oxidation products, for example ultrapure steam or hydrogen chloride gas, to exit the torch assembly and enter the semiconductor processing furnace. In a further preferred embodiment of the present invention, a flow divertor ( 118  in FIG.  1 B), which is discussed hereinbelow in conjunction with FIGS. 10A and 10B, may be included between the torch assembly and the semiconductor processing furnace. Again as shown in FIGS. 2A and 2B, mounted on right end  270  of chamber  20  along its longitudinal axis  280  is gas injection subassembly  220  of the burner of the torch assembly. In the present embodiment, gas injection subassembly  220  is thermally welded to chamber  20  to provide an integral construction for the torch assembly, enabling fast and easy assembly and disassembly. In an alternative embodiment of the present invention, gas injection subassembly  220  may be removably but sealingly mounted to chamber  20 . The present embodiment, as shown in FIG. 2A, has three conduits for gas input: two hydrogen conduits  221 , one for high-flow and one for low-flow hydrogen; and an oxygen or other gas conduit  223  with a “tee”  224  for introducing an additional gas such as DCE vapor. 
     Referring now to FIGS. 4 through 9B, there are shown a number of views of gas injection subassemblies constructed and operative in accordance with alternative embodiments of the present invention. Common to all gas injection subassemblies constructed and operative in accordance with the present invention are an emitting surface having formed thereon orifices for the combustible gases, and gas routing apparatus connecting the orifices to supplies of the gases. The orifices are of a size and orientation to direct the gas flows, for desired predetermined gas flow rates, to a predetermined zone of intersection and mixing wherein oxidation is to take place, that is far enough from the emitting surface and with sufficient velocity to preclude exposure thereof to the combustion flame, thereby preventing risk of devitrification or damage to the surface and to its orifices. The mixed gas flow and, hence the combustion flame, further will be generally parallel to longitudinal axis  280  of quartz chamber  20  (FIG.  2 A). 
     Referring now to FIGS. 4 and 5, there are shown two side-sectional views, taken perpendicular to one another, of a gas injection subassembly, referred to generally as  60 , according to an alternative embodiment of the present invention. The body of gas injection subassembly  60  is the conduit for one combustible gas via gas inlet  62 , and a conduit  63  for a second combustible gas via inlet  64  passes therethrough. Gas injection subassembly  60  has a faceplate  65  thermally welded to body of subassembly  60  and conduit  63  with orifices  68  and  69  formed thereon, preferably by laser drilling therethrough, to allow emission of flows of the gases at predetermined angles with respect to the faceplate surface and each other. Second combustible gas conduit  63  is welded to the back of faceplate  65  so as to surround one orifice  69 . In the present embodiment, orifices  68  and  69  are oriented with respect to emitting surface  67  so that the gas flows therefrom are at an angle in the range 10°-170° with diameters in the range 0.2-1.8 mm. Gas injection subassembly  60  may optionally further include a mounting portion  61  for sealingly mounting gas injection subassembly  60  to quartz chamber  20  (FIG.  2 A). 
     Referring now to FIGS. 6 and 7, there are shown two side-sectional views, taken perpendicular to one another, of a gas injection subassembly, referred to generally as  70 , according to a further alternative embodiment of the present invention. The present embodiment differs from the previous embodiment, shown in FIG. 4 in that it includes an extra internal conduit  73  with an extra associated orifice  77  on faceplate  75  and its own second gas inlet. This allows a single torch assembly to provide a choice or a sequence of two second oxidation gases, for example: oxygen for steam production, and DCE and oxygen for HCl production, the flow of which is entirely under control of gas flow control valves external to the torch itself. 
     Referring now to FIG. 8, there is shown a transverse view of a gas injection subassembly, referred to generally as  80 , according to a preferred embodiment of the present invention. Gas injection subassembly  80  has a solid gas emitting head  85  with separate emitting surfaces  86  and  87  for each of the two oxidation gases with a predetermined angle, in the present embodiment in the range 10°-180°, therebetween. Emitting surfaces  86  and  87  each have formed thereon two orifices  83  and  84  for gas flow emission. As opposed to the previous embodiments (FIGS.  6  and  7 ), the orifices  83  and  84  and the gas flow are substantially perpendicular to the emitting surfaces  86  and  87 , due to the angle of emitting surfaces. This has been shown to be an advantage in the present embodiment, since this perpendicular gas flow is less likely to become turbulent as it emerges, thereby providing a faster gas flow that is less likely to broaden. As in the previous embodiment shown in FIGS. 6 and 7, each of the two second gas orifices has its own gas conduit, while the two first gas orifices are fed by a single gas conduit. In the present embodiment, first gas orifices  83  have diameters in the range 0.5-2.0 mm, and two second gas orifices  84  have diameters in the range 0.1-0.8 mm and 0.5-1.5 mm, as shown in FIG.  9 B. As will be understood by those familiar with the art, the smaller orifices will provide faster gas flows, which will, when combustion takes place, produce a longer flame, which, for the case of lower gas flow rates, will be more readily detectable by a flame detector (not shown) associated with controller  140  (FIG.  1 A), thereby providing better control of the operation of torch assembly  10 . 
     Referring briefly again to FIG. 1B, there is shown a block diagram of a semiconductor processing system employing a torch assembly  10  constructed and operative in accordance with an alternative embodiment of the present invention. The embodiment in the diagram includes flow divertor  118  to control the flow of combustion gases from torch  111  to process furnace  115 . Referring now to FIGS. 10A and 10B, there are shown detail schematic block diagrams of a flow divertor, referred to generally as  510  in a semiconductor processing system employing the torch assembly of the present invention. Flow divertor  510  is used to selectably prevent oxidation product gases produced by torch  512  from reaching reactor chamber  514 . 
     The flow divertor of the present embodiment is particularly suited for use with wet oxidation processes, used for rapid oxidation of silicon, in the semiconductor industry. The particular suitability of the present embodiment in wet oxidation processes will be appreciated from the fact that, unlike prior art systems, it has no moving parts which come into contact with the oxidation products, and thus no contaminant particles can be released into the process fluid stream, by the apparatus of the present embodiment. 
     It will be appreciated, however, that the present invention may also be suitable for use in other technological applications, and it is thus not intended to limit the present invention solely to use in the semiconductor industry. 
     Flow divertor  510  includes a secondary conduit  518  which intersects with and communicates with primary conduit  516  via an outlet  520  formed in a side wall  522  of primary conduit  516 , at a location upstream of reactor chamber  514 . There is further provided a tertiary conduit  524  which also intersects with primary conduit  516 . Tertiary conduit  524  has a free end portion  526  which extends through an opening  528  formed opposite the outlet  520  so as to extend across primary conduit  516  and such that it protrudes through outlet  520  into the secondary conduit  518 . As seen, free end portion  526  defines an end constriction  527  having a narrow orifice just inside secondary conduit  518 , the function of which is described below. 
     As seen in the drawings, the free end portion  526  of tertiary conduit  524  has a diameter which is smaller than that of the primary conduit  516  so as not to prevent fluid flow therewithin, and, further, which is also smaller than the diameter of the secondary conduit  518 , so as not to obstruct fluid flow therewithin, of fluid flowing through outlet  520 . Secondary conduit  518  has an outlet valve  530 , which may be of any suitable type, arranged downstream of outlet  520 , and tertiary conduit  524  has an inlet valve  532 , which may be similar to outlet valve  530 , disposed in regulatory association with a carrier fluid supply  538 . 
     When it is sought to permit normal flow of the oxidation products from torch  512  to process chamber  514 , valves  530  and  532  are closed or off, and the flow through primary conduit  516  is uninterrupted. When it is sought to interrupt the flow, however, in a manner which prevents the oxidation products from reaching reactor chamber  514 , but, unlike the prior art, avoids introduction of contaminant particles into the process fluid, valves  530  and  532  are opened, thereby to permit injection of the carrier fluid, via valve  532  and tertiary conduit  524 , into secondary conduit  518 . 
     The outflow of the carrier fluid into secondary conduit  518 , through narrow constriction  527  formed at free end  526  of tertiary conduit  524 , is operative to cause a pressure drop, due to the well-known Venturi effect. The pressure at which the carrier fluid is supplied, combined with the geometry of secondary and tertiary conduits  518  and  524 , are operative to cause a pressure drop between primary and secondary conduits  516  and  518 , such that oxidation products in primary conduit  516  are forced through outlet  520 , into secondary conduit  518 . Subsequent closing of valves  530  and  532  removes the pressure drop, and the oxidation products then resumes their flow along primary conduit  516 , to reactor chamber  514 . 
     As described above, the present embodiment is particularly suitable for use in wet oxidation of silicon, in which case the oxidation product is a steam, and the carrier fluid is an inert gas, such as nitrogen. It is also suitable for DCE oxidation, in which case the oxidation product is HCl. In certain semiconductor processes, it is desirable to introduce auxiliary chemicals into the reactor chamber. In an alternative embodiment of the present invention, primary conduit  516  has an auxiliary input conduit (not shown) for the introduction of these auxiliary chemicals. 
     In this case, the pressure of the steam flowing in primary conduit  516  will be just above atmospheric pressure, and the pressure in secondary conduit  518  required to divert the entire steam flow from the primary conduit  516  will be somewhat below atmospheric, typically in the range 5600-5700 mm Hg. This will be generated by a flow of inert gas supplied at a pressure in the range 510 psi -5100 psi. 
     Furthermore, referring particularly to FIG. 10B, the internal dimensions of primary, secondary and tertiary conduits  516 ,  518 , and  524  will typically be as follows: 
     
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 primary conduit 516 
                 internal diameter D1: 8-520 mm 
               
               
                   
                 secondary conduit 518 
                 internal diameter D2: 6-7 mm 
               
               
                   
                 tertiary conduit 524 
                 internal diameter D3: 5-7 mm 
               
               
                   
                 tertiary conduit 524, 
                 internal diameter d: 1-3 mm 
               
               
                   
                 orifice of end construction 527 
               
               
                   
                   
               
             
          
         
       
     
     It will be appreciated by persons skilled in the art that, the present invention is not limited solely to wet oxidation processes, and may be used in other environments in which it is sought to eliminate direct contact between valves having moving parts, and a process fluid. In these cases, the various pressures required to achieve diversion of a fluid flow from the primary conduit  516 , as described hereinabove, as well as the geometry of the conduits  516 ,  518  and  524 , and of the orifice of end constriction  527 , will be determined in accordance with the nature of the liquids or gases employed, and with the nature of the process. 
     It will further be appreciated by persons skilled in the art that the scope of the present invention is not limited by what has been specifically shown and described hereinabove, merely by way of example. Rather, the scope of the present invention is defined solely by the claims, which follow.