Patent Document

RELATED APPLICATIONS 
       [0001]    The present application claims priority from U.S. Provisional Patent Application Ser. No. 60/868,720 entitled “MULTIPLE INLET ABATEMENT SYSTEM,” filed Dec. 5, 2006, which is hereby incorporated by reference herein in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to electronic device manufacturing, and more specifically to hazardous compound abatement systems having multiple inlets with inlet clog detection capabilities. 
       BACKGROUND OF THE INVENTION 
       [0003]    Gaseous effluents from the manufacturing of electronic materials and devices may include a wide variety of chemical compounds which are used and/or produced during manufacturing. During processing (e.g. physical vapor deposition, diffusion, etch PFC processes, epitaxy, etc.), some processes may produce undesirable byproducts including, for example, perfluorocompounds (PFCs) or byproducts that may decompose to form PFCs. PFCs are recognized to be strong contributors to global warming. These compounds may be harmful to human beings and/or the environment (hereinafter referred to as “harmful compounds”). The harmful compounds must be removed from the gaseous effluent before the gaseous effluent is vented into the atmosphere. 
         [0004]    Harmful compounds may be removed from the effluents or converted into non-harmful compounds via a process known as abatement. During an abatement process, the harmful compounds used and/or produced by electronic device manufacturing processes may be destroyed or converted to less harmful or non-harmful compounds (abated) which may be further treated or emitted to the atmosphere. 
         [0005]    It is known that effluent may be abated in a thermal abatement reactor which heats and burns, or oxidizes, the effluent, thereby converting the harmful compounds into less harmful or non-harmful compounds. The thermal reactor may include a pilot device, a fuel supply, an oxidant supply, burner jets, effluent inlets and abated effluent outlets. 
         [0006]    Thermal abatement units typically have the capacity to abate the effluent from several process chambers. For example, some thermal abatement units have multiple inlets, and each may be connected to a different process chamber. During operation of the thermal abatement unit, it is possible for solids, e.g., abatement reaction products, to build up in an inlet, and impede the effluent from the process chamber which feeds that inlet from freely entering the thermal abatement unit, causing the effluent pressure at the inlet to build. This may negatively impact the process tool. 
         [0007]    Conventional methods and apparatus for monitoring such pressure build up are expensive and complex. As such, a need exists for improved methods and apparatus for monitoring inlet pressure of an abatement system. 
       SUMMARY OF THE INVENTION 
       [0008]    In some embodiments, a method of operating an electronic device manufacturing thermal abatement system is provided, including: flowing a gaseous effluent through an inlet into a thermal abatement reaction chamber; abating the effluent; flowing the abated effluent through an outlet out of the thermal abatement reaction chamber; using a pressure sensor to measure an inlet pressure of the inlet; using the same pressure sensor to measure an outlet pressure of the outlet; wherein the pressure sensor sequentially measures the inlet pressure and the outlet pressure; determining a difference between the inlet pressure and the outlet pressure; and if the difference between the inlet pressure and the outlet pressure exceeds a pre-determined pressure, diverting the flow of effluent away from the inlet. 
         [0009]    In other embodiments a thermal abatement reactor inlet and outlet pressure measurement system is provided, including: one or more gas inlets, each gas inlet having a pressure port; one or more gas outlets, each gas outlet having a pressure port; and a pressure sensor selectively connected with more than one of the pressure ports. 
         [0010]    In still other embodiments an electronic device manufacturing gaseous effluent abatement system is provided, including: one or more process chambers; a thermal abatement reactor having one or more effluent inlets and one or more outlets, the one or more inlets coupled to the one or more process chambers and adapted to receive effluent from the one or more process chambers, wherein each inlet and each outlet comprises a pressure port; and a pressure sensor selectively connected to more than one pressure port; wherein each process chamber is adapted to flow gaseous effluent through a reaction chamber inlet into the thermal abatement reactor. Numerous other aspects are provided. 
         [0011]    Other features and aspects of the present invention will become more fully apparent from the following detailed description, the appended claims and the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a schematic view of a thermal abatement system including a inlet clog detection system. 
           [0013]      FIG. 2  is a schematic view of the inlet clog detection system. 
           [0014]      FIG. 3  is a schematic view of an alternate embodiment of the clog detection system. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    As stated, thermal abatement units typically have the capacity to abate the effluent from several process chambers. For example, some thermal abatement units have up to six inlets, and each may be connected to a different process chamber. During operation of the thermal abatement unit, it is possible for solids, e.g., abatement reaction products, to build up in an inlet, and impede the effluent from the process chamber which feeds that inlet from freely entering the thermal abatement unit, causing the effluent pressure at the inlet to build. This may negatively impact the process tool. When this happens the inlet needs to be shut down and the effluent from the process chamber stopped or diverted to another abatement inlet. 
         [0016]    It is known to monitor inlet clogging by comparing the inlet pressure at each inlet to the outlet pressure of the thermal abatement unit. When the difference in pressure between an inlet and the outlet of the thermal abatement unit exceeds a predetermined pressure, the operator or system may determine that that inlet is clogged and appropriate action may be taken. Typically, pressure sensors may be located at each inlet and the outlet of the thermal abatement unit. Thus, in a six inlet thermal abatement unit, there may be seven pressure sensors. Pressure sensors are expensive, however, and so a need exists for an apparatus and method that provides at least the same functionality as the multiple pressure sensor apparatus but at lower cost. 
         [0017]    The present invention provides an improved thermal abatement system which can abate process gases from one or more process tools. More specifically, the present invention reduces the capital cost of a thermal abatement reactor and at the same time provides an inlet clog detection system. In addition a method and apparatus for determining if the detection system has suffered a failure is provided. 
         [0018]    As stated, a modern thermal abatement reactor may have six inlets. A conventional clog detection system used with such a reactor may include seven pressure sensors, one for each reactor inlet and one for the reactor outlet. Each pressure sensor adds to the expense and complexity of the thermal abatement system and is a part which may fail. In some embodiments, the present invention reduces the number of pressure sensors required in such a thermal abatement system to as few as one pressure sensor. For example, each inlet and the outlet to the thermal abatement unit may be selectively connected to a single pressure sensor through a pressure port on each inlet/outlet, and conduits which connect each pressure port with the pressure sensor. The selectivity of the fluid connection may be accomplished by locating valves between each inlet/outlet and the pressure sensor. To measure the pressure of a particular inlet/outlet, the valve between the sensor and the inlet/outlet may be opened, while all the other valves are kept closed. This process may be repeated for each inlet/outlet in sequence, thus providing a pressure measurement of each inlet/outlet using a single pressure sensor. The pressure measurements obtained in this fashion may be used in at least the same ways as the pressure measurements obtained by conventional multi-pressure sensor inlet clog detection systems. 
         [0019]    In these and other embodiments, the single, or first, pressure sensor may be supplemented by a second pressure sensor which may be in fluid communication with the first pressure sensor so that when an inlet/outlet is selectively connected to one pressure sensor, it is also connected to the second pressure sensor. Connected thus, the pressure sensors should report the same measurement. If one pressure sensor fails, the pressure sensors may begin to report different measurements. In this scenario, one or both sensors may be replaced without shutting down the thermal abatement unit, and with the continued operation of the inlet clog detection system. 
       Thermal Abatement System 
       [0020]      FIG. 1  is a schematic depiction of an improved thermal abatement system  100  of the present invention. 
         [0021]    Process tools  102   a,b  each may have three process chambers  104   a - f . Each process chamber  104   a - f  may exhaust process gases through conduits  106   a - f , into inlets  108   a - f  of thermal abatement reactor  110 , wherein the process gases may be thermally abated, such as, for example, by being oxidized. Following abatement, the abated process gases may be exhausted from outlet  112  and through conduit  114 , where the abated gases may be further treated, passed to a house exhaust system or otherwise released to the atmosphere. Fewer or more process tools, process chambers per process tool, exhaust conduits, inlets and/or outlets may be used. 
         [0022]    Thermal abatement system  100  may also include an inlet clog detection system  116 , which is in fluid communication with inlets  108   a - f  and outlet  112 . The inlet clog detection system  116  may measure an inlet pressure of each inlet  108   a - f  and an outlet pressure of outlet  112 , and report the measurements to controller  118  by information communication means  120 . Controller  118  may be a microprocessor, a microcontroller, a dedicated hardware circuit, software, a combination of the same, or the like. In one embodiment, the controller  118  may be a programmable logic controller. Communication means  120  may be a wire, wireless, fiber or other suitable connection. Although controller  118  is depicted in  FIG. 1  as being separate from the inlet clog detection system  116 , for ease of description it may be considered and described as a part of and/or may be part of the inlet clog detection system  116 , despite the fact that it may perform functions in addition to clog detection. 
         [0023]    Controller  118  may further be connected to a system (not shown) for diverting the flow of effluent away from any particular inlet to either another inlet of the same thermal abatement reactor, or to an inlet of a second thermal abatement reactor. 
       Inlet Clog Detection System 
       [0024]      FIG. 2  is a schematic drawing of at least one embodiment of the inlet clog detection system  116  of  FIG. 1 . In this embodiment, inlets  108   a - f  may include pressure ports  122   a - f , and outlet  112  may include pressure port  124 . Pressure ports  122   a - f  and  124  may be connected to valves  126   a - g  by conduits  128   a - f  and  130 , respectively. Valves  126   a - g  may be connected to optional plenum  132  by conduits  134   a - g . Plenum  132  may be in fluid communication with a pressure sensor  136  through conduit  138 . Instead of a plenum, a simple pipe (not shown) may connect conduits  134   a - g  to conduit  138 . These ports, conduits and valves enable the pressure sensor  136  to be remote from, yet selectively in fluid communication with, the inlets  108   a - f  and outlet  112 , as will be described in more detail below. Any suitable pressure sensor may be employed, such as a Sentra low pressure sensor or similar sensor. In some embodiments, an analog or other operating voltage may be supplied to pressure sensor  136  to excite operation of the pressure sensor. 
         [0025]    In some embodiments, valves  126   a - g  may be operated to selectively enable pressure sensor  136  to measure the pressure of any one inlet/outlet at a time. For example, when valve  126   a  is open and valves  126   b - g  are closed, inlet  108   a  may be in fluid communication with remote pressure sensor  136 , enabling the sensor  136  to measure the pressure of the fluid within inlet  108   a . After the pressure sensor  136  measures the pressure of the fluid within inlet  108   a , valve  126   a  may be closed, and inlet  108   a  may no longer be in fluid connection with pressure sensor  136 . Another valve may then be opened and the process repeated, until the pressure of each inlet/outlet has been measured. This process may be repeated continuously or periodically. 
         [0026]    Controller  118  may be connected to pressure sensor  136  through communication means  120 , over which the pressures measured by the pressure sensor  136  may be reported to controller  118 . Controller  118  may be connected to valves  126   a - g  by communication channel  140 , through which controller  118  may command valves  126   a - g  individually to open or close. In an alternate embodiment, a separate controller may be used to command valves  126   a - g  to open or close. The communication channel  140  may include a wired, wireless, fiber or other communication channel. 
         [0027]      FIG. 3  is a schematic representation of inlet clog detection system  116   a  which may be similar to the inlet clog detection system  116  of  FIG. 2 , with the addition of a second pressure sensor  136   b  connected to plenum  132  by conduit  138   b , and to controller  118  by communication means  120   b . The second pressure sensor  136   b  may be used by controller  118  together with first pressure sensor  136   a  to detect a failure of one of the pressure sensors  136   a,b . In addition to failure detection, dual pressure sensors  136   a,b  may be used as a back-up system, whereby the thermal abatement system  100  may continue to be operated with one failed pressure sensor. In additional embodiments, the thermal abatement system  100  may continue to be operated using one operational pressure sensor, during replacement of a failed pressure sensor. 
       Operation of the Thermal Abatement System 
       [0028]    With reference to  FIG. 1 , process effluent from process chambers  104   a - f  may be directed through conduits  106   a - f  into thermal abatement reactor inlets  108   a - f . The process effluent may be thermally abated in thermal abatement reactor  110  and then exhausted through outlet  112  into conduit  114 , which may carry the effluent to further abatement processes or to the house scrubber or exhaust system, etc. Inlet clog detection system  116  may, either continuously or periodically, measure the pressure at each inlet  108   a - f  and the outlet  112 , in order to detect the clogging of any inlet  108   a - f . The inlet clog detection system  116  may report the measured pressures to controller  118 . In some embodiments, controller  118  may be programmed with a normal pressure range in which a non-clogged inlet will operate. Thus, for example, if during operation of the thermal abatement system  100  the pressure of inlet  108   a  rises above its normal pressure range, controller  118  may determine that inlet  108   a  is becoming or has become clogged. The response to this determination may be that the process chamber  104   a  which is supplying effluent to inlet  108   a  is shut down or that the effluent from process chamber  104   a  is diverted through a system of conduits (not shown) to an inlet other than inlet  108   a  or to a different thermal abatement reactor (not shown). The thermal abatement system  100  may continue to be operated, for example, until such time as a predetermined number of additional inlets are determined to be becoming clogged or to have become clogged and are taken off line. At that time, maintenance may be performed on the system  100  to clean the inlets  108   a - f.    
         [0029]    In an alternate embodiment, controller  118  may compare inlet pressures to the outlet pressure. A baseline pressure differential may be established for each inlet  108   a - f , and if the pressure differential for any inlet increases beyond the baseline pressure differential by a predetermined amount, controller  118  may determine that the inlet is clogged or becoming clogged and may take any appropriate action, such as the actions described above. 
       Operation of the Inlet Clog Detection System 
       [0030]    The inlet clog detection system  116 , see  FIG. 2 , may be operated so that the pressure of individual inlets  108   a - f  and the outlet  112  may be measured individually and in any desired sequence. In some embodiments, each inlet pressure may be measured, one after the other, and then the outlet pressure may be measured. In other embodiments, the outlet pressure may be measured between measurements taken of each inlet pressure. Any desired measurement pattern may be used. 
         [0031]    In some embodiments, each inlet  108   a - f  and outlet  112  may selectively be in fluid communication with pressure sensor  136  through a series of pressure ports  122   a - f  and  124 , conduits  128   a - f ,  124  and  134   a - g , valves  126   a - g  and optionally a plenum  132 . Valves  126   a - g  may be, for example, gate valves and may be located such that a fluid communication path from each inlet  108   a - f  and the outlet  112  to pressure sensor  136  may be selectively opened (the inlet or outlet engaged) or closed (the inlet or outlet disengaged). When an inlet or outlet is engaged, pressure sensor  136  may sense the inlet&#39;s or outlet&#39;s pressure. 
         [0032]    In order to measure the pressure of a particular inlet or outlet, all of valves  126   a - g  may be closed except for one valve, which is located between the pressure sensor  136  and the inlet or outlet to be measured. Pressure sensor  136  may then sense the pressure of the particular inlet or outlet. Once a pressure measurement has been made by pressure sensor  136 , the inlet clog detection system  116  may reconfigure valves  126   a - g  to measure the pressure of a different inlet or outlet. This reconfiguration may include closing the open valve, and opening one of the closed valves. The inlet clog detection system  116  may use controller  118  to operate valves  126   a - g  through communication channel  140 . A controller, such as a microprocessor, a microcontroller, a dedicated hardware circuit, software, a combination of the same, a programmable logic controller, etc., will be used to control valves  126   a - g  in the following illustrations, but it will be recognized that valves  126   a - g  may be operated manually. 
         [0033]    When controller  118  configures valves  126   a - g  to measure a first inlet or outlet pressure, and then reconfigures valves  126   a - g  to measure a second inlet or outlet pressure, controller  118  may close a first valve completely before it opens a second valve. Alternatively, controller  118  may begin opening the second valve while it is closing the first valve. This alternative method may reduce pressure surges and oscillations at pressure sensor  136 . 
         [0034]    Pressure sensor  136  may be configured to report inlet and outlet pressure measurements to controller  118  through information communication means  120 . Controller  118  may be configured to compare a reported pressure for each inlet to a pressure expected for the inlet, (e.g., the expected pressure may have been programmed into controller  118  or be available to controller  118  in a database or through some other suitable means). Controller  118  may be further configured to respond to a reported pressure which is outside of an expected pressure range for an inlet. For example, if the measured pressure for a first inlet is greater than the range of pressures expected for the first inlet, controller  118  may be configured to determine that the first inlet is clogged or becoming clogged. Upon making such a determination, controller  118  may be configured to command the diversion of effluent flowing to the first inlet to a second inlet or to a different thermal abatement reactor. Alternatively, controller  118  may be configured to command a shutdown of a process chamber which is feeding effluent to the first inlet. In the event that the measured pressure for the first inlet is less than the range of pressures expected for the first inlet, controller  118  may be configured to issue an alarm if the pressure is below a first level and/or shut down the system if the pressure is below a second level. 
         [0035]    In yet other embodiments, controller  118  may be configured to calculate a pressure differential for each inlet  108   a - f . This pressure differential may be the difference between the pressure reported for the inlet  108   a - f  and the pressure reported for the outlet  112 . Controller  118  may be further configured to compare the pressure differential calculated for an inlet  108   a - f  with the pressure differential expected for that inlet (e.g., the expected pressure differential may be programmed into controller  118  or be available to controller  118  in a database or by some other suitable means). Controller  118  may be still further configured to respond to an inlet&#39;s calculated inlet/outlet pressure differential which falls outside of the expected range for that inlet. For example, if the calculated pressure differential for an inlet is above an expected range for that inlet, controller  118  may be configured to determine that the inlet is clogged or becoming clogged. Controller  118  may be further configured to respond to such a determination in the ways which were described above. If the pressure differential is below the expected range, controller  118  may be configured to issue an alarm if the pressure is below a first level and/or shut down the system if the pressure is below a second level. 
         [0036]    In yet other embodiments, controller  118  may keep a record of some or all of the preceding pressure measurements for each inlet  108   a - f . The record retention may begin when the thermal abatement system  100  is first brought on line, for example after maintenance, and a baseline pressure for each inlet  108   a - f  may be established at that time. Thereafter the inlet clog detection system  116  of this embodiment may operate similarly to any of the embodiments previously described, except that instead of comparing reported pressures to expected pressures which have been either programmed into controller  118  or provided to controller  118  from a database, the reported pressures are compared to the baseline pressures developed by controller  118 . Controller  118 &#39;s response to unexpected pressures, whether greater or less than the expected, may be similar to that described above in other embodiments under similar circumstances. 
       Operation of the Failure Detection and Backup Inlet Clog Detection System 
       [0037]    In some additional embodiments, the inlet clog detection system  116   a  of  FIG. 3  is similar to the inlet clog detection system  116  of  FIG. 2 , with the exception that instead of a single pressure sensor  136 , redundant pressure sensors  136   a,b  are provided. Inlet clog detection system  116   a  may include all of the functionality of inlet clog detection system  116  described with respect to  FIG. 2  above. In addition, controller  118  may receive reported pressure measurements from pressure sensors  136   a,b  via communication means  120   a,b . Controller  118  may be configured to compare some or all reported pressure measurements received from the two pressure sensors  136   a,b . Over time, if neither pressure sensor  136   a,b  has failed, the difference, if any, in the pressures reported by pressure sensor  136   a  and pressure sensor  136   b  for a particular inlet or outlet may not change substantially. If, however, one of the pressure sensors does fail, the two pressure sensors may begin reporting different pressures for a particular inlet or outlet. Controller  118  may be configured to provide a warning alert in such a case and/or may be configured to shut down the thermal abatement system  100 . 
         [0038]    In some of these and other embodiments, controller  118  may be configured to determine which pressure sensor has failed. In such a case, the failed sensor may be replaced, with or without shutting down the thermal abatement system  100 . For example, if the pressure sensors  136   a,b  begin to provide diverging pressure measurements, the measurements from one of the pressure sensors  136   a,b  may continue to indicate that all of the inlets  108   a - f  are operating nominally, while the pressure measurements provided by the other pressure sensor may indicate that one or more of the inlets  108   a - f  is operating at a lower or higher pressure than the inlet&#39;s expected pressure. Controller  118  may be further configured to determine that a pressure sensor has failed if the pressure sensor reports that all of the pressures measured by the sensor are drifting higher or lower, while the other pressure sensor is reporting steady pressures. 
         [0039]    The foregoing description discloses only exemplary embodiments of the invention. Modifications of the above disclosed apparatus and methods which fall within the scope of the invention will be readily apparent to those of ordinary skill in the art. For instance, the pressure at the outlet of the abatement reactor, scrubber or other location may be compared to the pressure of an inlet. 
         [0040]    Accordingly, while the present invention has been disclosed in connection with exemplary embodiments thereof, it should be understood that other embodiments may fall within the spirit and scope of the invention, as defined by the following claims.

Technology Category: g