Abstract:
A plasma abatement process for abating effluent containing a PFC gas from a processing chamber is described. A plasma abatement process takes gaseous foreline effluent from a processing chamber, such as an etch chamber, and reacts with the effluent within a plasma chamber placed in the foreline path. The plasma dissociates the PFC gases and reacts them with a reagent, converting the effluent into compounds that are non-global warming and which may be easily removed by traditional facility water scrubbing technology. This disclosure explains methods to control the reagent hydrogen to oxygen ratio such that in addition to PFC destruction, the abated compounds have modified composition to enable extension of the maintenance interval for downstream supporting equipment.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims benefit of U.S. Provisional Patent Application Ser. No. 62/092,581 (APPM/22539USL), filed Dec. 16, 2014, and of U.S. Provisional Patent Application Ser. No. 62/135,449 (APPM/22539USL02), filed Mar. 19, 2015, which are herein incorporated by reference. 
     
    
     BACKGROUND 
       [0002]    1. Field 
         [0003]    Implementations of the present disclosure generally relate to abatement for semiconductor processing equipment. More particularly, implementations of the present disclosure relate to techniques for abating compounds present in the effluent. 
         [0004]    2. Description of the Related Art 
         [0005]    Effluent produced during semiconductor manufacturing processes includes many compounds which must be abated or treated before disposal, due to regulatory requirements and environmental and safety concerns. Among these compounds are perfluorocarbons (PFCs), which are used, for example, in etching processes. 
         [0006]    PFCs, such as CF 4 , C 2 F 6 , NF 3  and SF 6 , are commonly used in the semiconductor and flat panel display manufacturing industries, for example, in dielectric layer etching and chamber cleaning. Following the manufacturing or cleaning process there is typically a residual PFC content in the effluent gas stream pumped from the process tool. PFCs are difficult to remove from the effluent stream, and their release into the environment is undesirable because they are known to have relatively high greenhouse activity. Remote plasma sources (RPS) or in-line plasma sources (IPS) have been used for abatement of PFCs and global warming gases. 
         [0007]    The design of current abatement technology for abating PFC&#39;s utilizes either water vapor, as a source of hydrogen and oxygen as a reagent or oxygen only. These provide excellent destruction capability for PFC gases, but it has been identified that further improvements may be made that also have additional benefit of maintaining cleanliness and reliability of downstream vacuum equipment for extending interval between maintenance. 
       SUMMARY 
       [0008]    Implementations disclosed herein include method and systems of abating effluent from a processing chamber. These include methods to specifically control the ratio of hydrogen to oxygen reagent composition to maintain effective PFC abatement performance and also enable improvements to support equipment maintenance interval. 
         [0009]    In one implementation, a method of processing effluent can include flowing an effluent from a processing chamber into a plasma source, wherein the effluent comprises a PFC gas; delivering an abating reagent to the plasma source, the abating reagent comprising a hydrogen to oxygen ratio of at least 2.5:1; and activating the effluent and the abating reagent in the presence of a plasma to convert the PFC gas to an abated material. 
         [0010]    In another implementation, a method for abating an effluent gas can include flowing an abating reagent into a plasma chamber; flowing an effluent gas into the plasma chamber, the effluent gas comprising a PFC gas such that the gas to be abated reacts with the plasma, wherein the hydrogen to halogen ratio is about 1:1 and the oxygen to PFC gas ratio is about 2:1; and generating a plasma in the plasma chamber from the abating reagent. 
         [0011]    In another implementation, a method of processing effluent can include flowing an effluent comprising PFC gas from a processing chamber into a plasma source; delivering an abating reagent to the plasma source, the abating reagent comprising H 2  and H 2 O, the H 2  and H 2 O being delivered at a hydrogen to oxygen ratio of at least 3:1, wherein the H 2  is formed by H 2 O electrolysis; and forming an inductively coupled plasma from the effluent and the abating reagent creating an abated material, wherein the abated material is gaseous at operating temperatures and pressures. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to implementations, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical implementations of this disclosure and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective implementations. 
           [0013]      FIG. 1  depicts a schematic diagram of a substrate processing system in accordance with some implementations. 
           [0014]      FIG. 2  is a flow diagram illustrating one implementation of a method for abating effluent exiting a processing chamber. 
       
    
    
       [0015]    To facilitate understanding, identical reference numerals have been used, wherever possible, to designate identical elements that are common to the Figures. Additionally, elements of one implementation may be advantageously adapted for utilization in other implementations described herein. 
       DETAILED DESCRIPTION 
       [0016]    Implementations disclosed herein include a plasma abatement process for materials present in an effluent exiting a processing chamber. A plasma abatement process takes foreline effluent from a processing chamber, such as a deposition chamber, an etch chamber or other vacuum processing chamber, and reacts the effluent with an abating reagent within a plasma chamber placed in the foreline path. The plasma energizes the materials present in the effluent as well as the abating reagent, making conversion of the material into a more benign form more efficient. In some implementations, the plasma may at least partially dissociate the materials present within the effluent and the abating reagent, which increases the efficiency of the conversion of the materials within the effluent into more benign forms. An abating reagent, such as water, may assist in the abating of the materials present within the effluent. 
         [0017]    In implementations described herein, excess hydrogen can be added to the water vapor in the abating reagent, creating a hydrogen to oxygen ratio of at least 2.5:1. The addition of hydrogen to the water vapor maintains the inherent safety of water vapor addition while controlling reactive oxygen available after reaction with effluent perfluorocompounds (PFC) gases. In methods and systems described herein, hydrogen generation by electrolysis of deionized water may be employed. Implementations disclosed herein are more clearly described with reference to the figures below. 
         [0018]      FIG. 1  depicts a schematic diagram of a processing system  100  in accordance with the implementations disclosed herein. As shown in  FIG. 1 , a foreline  102  couples a processing chamber  101  with an abatement system  111 . The processing chamber  101  may be, for example, a processing chamber for carrying out a deposition process, an etching process, annealing or a cleaning process, among others. Representative chambers for carrying out a deposition process include deposition chambers, such as, for example, plasma enhanced chemical vapor deposition (PECVD) chambers, chemical vapor deposition (CVD) chambers, or physical vapor deposition (PVD) chambers. In some implementations, the deposition process may be one that deposits dielectrics, such as silicon dioxide, (SiO 2 ), silicon nitride (SiN x ), silicon oxynitride (SiON), crystalline silicon, a-Si, doped a-Si, fluorinated glass (FSG), phosphorous doped glass (PSG), boron-phosphorous doped glass (BPSG), carbon-doped glass, and other low-k dielectrics, such as polyimides and organosiloxanes. In other implementations, the deposition process may be one that deposits metals, metal oxides, or metal nitrides, such as, for example, titanium, titanium dioxide, tungsten, tungsten nitride, tantalum, tantalum nitride, tantalum carbide, aluminum, aluminum oxide, aluminum nitride, ruthenium, or cobalt. In addition, metal alloys may be deposited, such as lithium-phosphorous-oxynitride, lithium-cobalt, and many others. 
         [0019]    Foreline  102  serves as a conduit that routes effluent leaving the processing chamber  101  to the abatement system  111 . The effluent may contain material which is undesirable for release into the atmosphere or may damage downstream equipment, such as vacuum pumps. For example, the effluent may contain compounds from a dielectric deposition process or from a metal deposition process. 
         [0020]    Examples of silicon-containing materials which may be present in the effluent include, for example, silicon dioxide (SiO 2 ), silane (SiH 4 ), disilane, silicon tetrachloride (SiCl 4 ), silicon nitride (SiN x ), dichlorosilane (SiH 2 Cl 2 ), hexachlorodisilane (Si 2 Cl 6 ), bis(t-butyl amino)silane, trisilylamine, disilylmethane, trisilylmethane, tetrasilylmethane, and tetraethyl orthosilicate (TEOS) (Si(OEt) 4 ). Other examples of silicon-containing materials include disiloxanes, such as disiloxane (SiH 3 OSiH 3 ), trisiloxane (SiH 3 OSiH 2 OSiH 3 ), tetrasiloxane (SiH 3 OSiH 2 OSiH 2 OSiH 3 ), and cyclotrisiloxane (—SiH 2 OSiH 2 OSiH 2 O—). Examples of other materials which may be present in the effluent include stibine (SbH 3 ), germane (GH 4 ), hydrogen telluride, and carbon-containing compounds, such as CH 4  and higher order alkanes. 
         [0021]    One abatement system  111  that may be modified to benefit from the implementation is a ZFP2™ abatement system available from Applied Materials, located in Santa Clara, Calif., among other suitable systems. As shown, the abatement system  111  includes a plasma source  104 , a reagent delivery system  106 , a foreline gas injection kit  108 , a controller  118 , and a vacuum source  120 . Foreline  102  provides effluent leaving the processing chamber  101  to the plasma source  104 . The plasma source  104  may be any plasma source coupled to the foreline  102  suitable for generating a plasma therein. For example, the plasma source  104  may be a remote plasma source, an in-line plasma source, or other suitable plasma source for generating a plasma within the foreline  102  or proximate the foreline  102  for introducing reactive species into the foreline  102 . The plasma source  104  may be, for example, an inductively coupled plasma source, a capacitively coupled plasma source, a direct current plasma source, or a microwave plasma source. The plasma source  104  may further be a magnetically enhanced plasma source of any kind described above. 
         [0022]    A reagent delivery system  106  may also be coupled with the foreline  102 . The reagent delivery system  106  delivers one or more reagents, such as abating reagents, to the foreline  102  upstream of the plasma source  104 . In an alternative implementation, the reagent delivery system  106  may be coupled directly to the plasma source  104  for delivering reagents directly into the plasma source  104 . The reagent delivery system  106  may include a reagent source  105  (or multiple reagent sources (not shown)) coupled to the foreline  102  (or the plasma source  104 ) via one or more valves. For example, in some implementations, a valve scheme may include a two-way control valve  103 , which functions as an on/off switch for controlling the flow the one or more reagents from the reagent source  105  into the foreline  102 , and a flow control device  107 , which controls the flow rates of the one or more reagents into the foreline  102 . The flow control device  107  may be disposed between the foreline  102  and the control valve  103 . The control valve  103  may be any suitable control valve, such as a solenoid valve, pneumatic valve or the like. The flow control device  107  may be any suitable active or passive flow control device, such as a fixed orifice, mass flow controller, needle valve or the like. 
         [0023]    A representative volatizing abating reagent that may be delivered by the reagent delivery system  106  includes, for example, H 2 O. H 2 O may be used when abating effluent containing, for example, CF 4  and/or other materials. A hydrogen-containing gas may be used in conjunction with H 2 O in one or more implementations. Representative hydrogen-containing gases includes ammonia (NH 3 ) and H 2 . In some implementations, the volatilizing abating reagents may be consumed by the compounds of the effluent, and therefore, may not be considered catalytic. 
         [0024]    A foreline gas injection kit  108  may also be coupled to the foreline  102  upstream or downstream of the plasma source  104  (downstream depicted in  FIG. 1 ). The foreline gas injection kit  108  may controllably provide a foreline gas, such as nitrogen (N 2 ), argon (Ar), or clean dry air, into the foreline  102  to control the pressure within the foreline  102 . The foreline gas injection kit  108  may include a foreline gas source  109  followed by a pressure regulator  110 , further followed by a control valve  112 , and even further followed by a flow control device  114 . The pressure regulator  110  sets the gas delivery pressure set point. The control valve  112  turns on and off the gas flow. The control valve  112  may be any suitable control valve, such as discussed above for control valve  103 . The flow control device  114  provides the flow of gas specified by the set point of pressure regulator  110 . The flow control device  114  may be any suitable flow control device, such as discussed above for flow control device  107 . 
         [0025]    In some implementations the foreline gas injection kit  108  may further include a pressure gauge  116 . The pressure gauge  116  may be disposed between the pressure regulator  110  and the flow control device  114 . The pressure gauge  116  may be used to measure pressure in the kit  108  upstream of the flow control device  114 . The measured pressure at the pressure gauge  116  may be utilized by a control device, such as a controller  118 , discussed below, to set the pressure upstream of the flow control device  114  by controlling the pressure regulator  110 . 
         [0026]    In some implementations, the control valve  112  may be controlled by the controller  118  to only turn gas on when the reagent from the reagent delivery system  106  is flowing, such that usage of gas is minimized. For example, as illustrated by the dotted line between control valve  103  of the reagent delivery system  106  and the control valve  112  of the kit  108 , the control valve  112  may turn on (or off) in response to the control valve  103  being turned on (or off). 
         [0027]    The foreline  102  may be coupled to a vacuum source  120  or other suitable pumping apparatus. The vacuum source  120  pumps the effluent from the processing chamber  101  to appropriate downstream effluent handling equipment, such as to a scrubber, incinerator or the like. In some implementations, the vacuum source  120  may be a backing pump, such as a dry mechanical pump or the like. The vacuum source  120  may have a variable pumping capacity with can be set at a desired level, for example, to control or provide additional control of pressure in the foreline  102 . 
         [0028]    The controller  118  may be coupled to various components of the substrate processing system  100  to control the operation thereof. For example, the controller may monitor and/or control the foreline gas injection kit  108 , the reagent delivery system  106 , and/or the plasma source  104  in accordance with the teachings disclosed herein. 
         [0029]    The implementations of  FIG. 1  are schematically represented and some components have been omitted for simplicity. For example, a high speed vacuum pump, such as a turbo molecular pump or the like, may be disposed between the processing chamber  101  and the foreline  102  for removing effluent gases from the processing chamber  101 . Additionally, other variants of components may be provided to supply the foreline gas, the reagent, and/or the plasma. 
         [0030]    In an exemplary implementation of the method disclosed herein, effluent containing undesirable material exiting from the processing chamber  101  enters the plasma source  104 . The effluent can include a PFC gas which can be a carbon-containing gas, a nitrogen containing gas or a sulfur containing gas. In one implementation, the PFC is a gas selected from the group comprising or consisting of CF 4 , CH 3 F, CH 2 F 2 , CH 4 , C 2 F 6 , C 3 F 8 , C 4 F 10 , CHF 3 , SF 6 , and NF 3 . Combinations of the above described PFC gases may be present in the effluent. An abating reagent with a hydrogen to oxygen ratio of at least a 2.5:1, such as a water vapor and hydrogen containing gas, enters the plasma source  104 . A plasma is generated from the abating reagent within the plasma source  104 , thereby energizing the abating reagent, and in some implementations, also energizing the effluent. In some implementations, at least some of the abating reagent and/or material entrained in the effluent are at least partially disassociated. The identity of the abating reagent, the flow rate of the abating reagent, the foreline gas injection parameters, and the plasma generation conditions may be determined based on the composition of the material entrained in the effluent and may be controlled by the controller  118 . In an implementation where the plasma source  104  is an inductively coupled plasma source, dissociation may require several kW of power. 
         [0031]      FIG. 2  is a flow diagram illustrating one implementation of a volatilizing method  200  for abating a target material in an effluent exiting a processing chamber. The method  200  begins by flowing an effluent from a processing chamber, such as processing chamber  101 , into a plasma source, such as plasma source  104 , wherein the effluent comprises a PFC, at  202 ; delivering an abating reagent to the plasma source, the abating reagent comprising a hydrogen to oxygen ratio of at least 2.5:1, at  204 ; and activating the effluent and the abating reagent in the presence of a plasma to convert the PFC in the effluent and the abating reagent to an abated material, at  306 . In some implementations, at least some of the abating reagent and/or material entrained in the effluent are at least partially disassociated. The target material in the effluent is converted to an abated material in the presence of the plasma including the abating reagent formed in the plasma source. The material in the effluent may then exit the plasma source and flow into the vacuum source, such as vacuum source  120 , and/or be further treated. 
         [0032]    The method  200  begins by flowing an effluent from a processing chamber into a plasma source, wherein the effluent comprises a PFC, at  202 . Effluent containing materials desired for abatement, such as PFC compounds, is flowed into the plasma source  104 . In one example, the exhaust gas may have originated at the process chamber  101  and resulted from performing any of a number of processes, such as etching, deposition, cleaning, or the like. The reagent gas may be injected into the foreline  102 , for example, by the reagent delivery system  106 . 
         [0033]    An abating reagent can be delivered to the plasma source, at  204 . In a representative abatement process using H 2 O, H 2 O from the reagent delivery system  106  is flowed into the plasma source  104 . The H 2 O can be delivered with a hydrogen containing reagent. Hydrogen containing reagents can include H 2 , ammonia (NH 3 ), methane (CH 4 ) or combinations thereof. In one implementation, H 2  is delivered simultaneously with H 2 O. The abating reagent has a hydrogen to oxygen ratio of at least 2.5:1, such as a hydrogen to oxygen ratio of at least 3:1. In one implementation, the hydrogen to oxygen ratio is from about 3:1 to about 10:1. In another implementation, the abating reagent includes at least one of H 2 , H 2 O, ammonia, or methane. The abating reagent can further include combinations of gases to achieve the desired hydrogen to oxygen ratio. 
         [0034]    The effluent and the abating reagent can be activated using a plasma to convert the PFC gas to an abated material, at  206 . A plasma is generated within the plasma source  104 , and thereby converting the PFC compounds into hydrogen halide compounds and oxide compounds. The hydrogen halide compounds and oxide compounds are volatile and more benign to human health and downstream effluent handling components than the unabated effluent. The plasma can be generated using plasma generation methods known in the art, such as microwave plasma, inductively coupled plasma or capacitively coupled plasma. In one implementation, the plasma is inductively coupled plasma. The resulting abated material will be gaseous at operating temperatures and pressures. 
         [0035]    The previously described implementations have many advantages. For example, the techniques disclosed herein can convert volatile, toxic, and/or explosive effluent into much more benign chemicals that can be more safely handled. The plasma abatement process is beneficial to human health in terms of acute exposure to the effluent by workers and by conversion of pyrophoric or toxic materials into more environmentally friendly and stable materials. The plasma abatement process also protects semiconductor processing equipment, such as, for example, vacuum pumps, from excessive wear and premature failure by removing particulates and/or other corrosive materials from the effluent stream. Moreover, performing the abatement technique on the vacuum foreline adds additional safety to workers and equipment. If an equipment leak occurs during the abatement process, the low pressure of the effluent relative to the outside environment prevents the effluent from escaping the abatement equipment. Additionally, many of the abating reagents disclosed herein are low-cost and versatile. For example, H 2 O and H 2 , as used in the abatement of PFC gases, are both versatile and low-cost. The aforementioned advantages are illustrative and not limiting. It is not necessary for all implementations to have all the advantages. 
         [0036]    While the foregoing is directed to implementations of the disclosed devices, methods and systems, other and further implementations of the disclosed devices, methods and systems may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.