Patent Publication Number: US-2016220942-A1

Title: Facility for purifying harmful gas

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority under 35 U.S.C. §119 to Korean Patent Application No. 10-2015-0015996, filed on Feb. 02, 2015, in the Korean Intellectual Property Office, the entire contents of which are incorporated herein by reference. 
     BACKGROUND 
     The present invention relates to a facility for purifying harmful gas, and more particularly, to a facility for removing harmful gas by decomposing noxious substances in the harmful gas generated during various processes. 
     Various raw materials are injected into a process chamber of low pressure, and processes such as ashing, evaporation, etching, photolithographic process, cleaning, nitration, and so on, are performed in the process of manufacturing semiconductors or displays. Harmful gas including noxious substances which are the restriction for the use of certain hazardous substances for environment including various volatile organic compounds, acids, odor generating gas, ignition material and non-CO 2  greenhouse gas is generated during the processes. Thus, the process chamber is required to be vacuum status to remove the harmful gas by a vacuum pump and to discharge the harmful gas into the air after purifying process. 
       FIG. 1  shows a conventional facility for disposing harmful gas, which includes a process chamber  10 , a plasma reactor  30  below the process chamber  10  for removing noxious substances in harmful gas, and a vacuum pump  50  below the plasma reactor  30 . The process chamber  10  and the plasma reactor  30  are connected by a pipe  20 , so too the plasma reactor  30  and the vacuum pump  50 . 
     The conventional plasma reactor  30  installed in such the facility for disposing harmful gas applies methods of radio frequency and inductively coupled plasma which may have low discharging stability, thereby requiring additional apparatuses for stabilizing discharging. The Korean patent registrations No. 10-1278682 and No. 10-1063515 disclosed a new plasma reactor to overcome the above problem of the conventional plasma reactor. The developed plasma reactor applies a method of Alternating Current (AC) discharge, thus, the use of electricity may be large, and the intensity of plasma in the center part of a conduit may be decreased due to large amount of harmful gas flow, which results in decline of decomposition performance of harmful gas. Due to the above problem, undecomposed noxious substances inside the harmful gas may flow through the vacuum pump, as a result, they cause malfunction of the vacuum pump when accumulated inside the vacuum pump or environment pollution when released to the air. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Technical Problem of the Invention 
     The present invention provides a facility for purifying harmful gas for removing noxious substances or particles in the harmful gas generated during the semiconductor process, display process, etc. by decomposing the same. 
     Technical Solution of the Invention 
     A facility for purifying harmful gas according to an exemplary embodiment of inventive concept includes a vacuum pump discharging harmful gas generated in a process chamber, a preprocessing apparatus which is provided with buffer gas for plasma discharge together with the harmful gas discharged from the process chamber and performing preprocess for activation of noxious substances in the harmful gas and the buffer gas by irradiating microwave, and a plasma reactor which is provided with harmful gas including the activated noxious substances and activated buffer gas from the preprocessing apparatus and decomposes the activated noxious substances by generating plasma discharge. 
     A facility for purifying harmful gas according to another exemplary embodiment of inventive concept includes a vacuum pump discharging harmful gas generated in the process chamber, a plasma reactor installed between the process chamber and the vacuum pump for decomposing noxious substances in the harmful gas discharged from the process chamber with plasma, and a preprocessing apparatus preprocessing the harmful gas such that noxious substances in the harmful gas may be activated by irradiating microwave to the harmful gas discharged from the process chamber. 
     EFFECTS OF THE INVENTION 
     A facility for purifying harmful gas according to embodiments of the present invention applies microwave by irradiating the same to harmful gas in a preprocessing apparatus before decomposing the harmful gas in a plasma reactor. 
     Accordingly, noxious substances in the harmful gas become activated to have increased kinetic energy during the above process such that the noxious substances may be decomposed and removed well by plasma discharge in the plasma reactor, which is increase in decomposition performance. 
     Especially, buffer gas provided by the preprocessing apparatus may contribute to the activation of noxious substances to maintain the increased decomposition performance in the plasma reactor, in case that vitalizing noxious substances is not successful or the degree of activation is weak only with the microwave. 
     A facility for purifying harmful gas according to embodiments of the present invention may prevent damages on a conduit in the plasma reactor caused by decomposition of noxious substances, because the activated noxious substances is decomposed and removed by plasma discharge of low energy generated in the plasma reactor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the inventive concept will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a schematic view of a conventional facility for purifying harmful gas; 
         FIG. 2  is a schematic view of a facility for purifying harmful gas according to an exemplary embodiment of the present inventive concept; 
         FIGS. 3 and 4  are cross-sectional views showing exemplary embodiments of a preprocessing apparatus in the facility for purifying harmful gas of  FIG. 2 ; 
         FIG. 5  is a cross-sectional view of a plasma reactor in the facility for purifying harmful gas of  FIG. 3 . 
         FIG. 6  is a schematic view of a facility for purifying harmful gas according to another exemplary embodiment of the present inventive concept; and 
         FIG. 7  is a cross-sectional view of a preprocessing apparatus in the facility for purifying harmful gas of  FIG. 6 . 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     Various example embodiments will be described more fully hereinafter with reference to the accompanying drawings, in which some example embodiments are shown. Inventive concepts may, however, be embodied in many different forms and should not be construed as limited to the example embodiments set forth herein. Rather, example embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of inventive concepts to those skilled in the art. In the drawings, the sizes and relative sizes of layers and areas may be exaggerated for clarity. Like numerals refer to like elements throughout. 
     It will be understood that, although the terms first, second, third etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are used to distinguish one element from another. Thus, a first element discussed below could be termed a second element without departing from the teachings of the inventive concepts. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     It will be understood that when an element is referred to as being “connected” or “coupled” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being “directly connected” or “directly coupled” to another element, there are no intervening elements present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacently” versus “directly adjacently,” etc.). 
     The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the inventive concepts. As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes,” and/or “including,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which inventive concepts belong. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
       FIGS. 2 through 7  show a facility for purifying harmful gas according to exemplary embodiments of the inventive concept. First of all, the facility for purifying harmful gas according to an exemplary embodiment of the inventive concept is described referring to  FIGS. 2 through 5 . 
     Referring to  FIG. 2 , the facility for purifying harmful gas according to an exemplary embodiment of the inventive concept includes a process chamber  110 , a preprocessing apparatus  130 , a plasma reactor  150 , a vacuum pump  170 , and a scrubber  190 . The process chamber  110  is a chamber in which various operations of semiconductor or display process such as ashing, evaporation, etching, photolithography, cleaning, nitration, and so on, are performed. 
     The exemplary embodiment takes the example of etching for the process in the process chamber  110 . Various kinds of process gas and buffer gas are provided during the etching process, and the process gas used for the etching process generates noxious by-products such as CF 4  and NF 3 . The vacuum pump  170  makes the insides of the process chamber  110 , pipes  121 ,  123 ,  125  which will be described later, the preprocessing apparatus  130 , and the plasma reactor  150 , to be vacuum state of lower pressure than the air pressure and performs discharging remaining harmful gas from the process chamber  110  after the etching process. 
     Meanwhile, the vacuum pump  170  includes an exhaust pipe (not shown) at the latter end such that the harmful gas may be discharged to the air through the exhaust pipe. Or the scrubber  190  may be further installed as shown in  FIG. 2 . For example, the scrubber  190  may be a wet scrubbing apparatus. 
     The harmful gas generated during the etching process in the process chamber  110  includes unreacted material and by-products during the process as noxious substances. Thus, the plasma reactor  150  is installed between the process chamber  110  and the vacuum pump  170  to remove the noxious substances in the harmful gas, and the preprocessing apparatus  130  is installed between the process chamber  110  and the plasma reactor  150  to boost decomposing noxious substances in the harmful gas in the plasma reactor so as the noxious substances to be removed. 
     More specifically, the preprocessing apparatus  130  is installed between a first pipe  121  in which the harmful gas discharged from the process chamber  110  flows and a second pipe  123  in which the harmful gas preprocessed in the preprocessing apparatus  130  flows to the plasma reactor  150 . The preprocessing apparatus  130  emits microwave to the harmful gas flows to the first pipe  121  from the process chamber  110  so as noxious substances in the harmful gas to be activated. 
     The preprocessing apparatus  130  includes a microwave generator  131  and a microwave reflection chamber  133 . The microwave generator  131  includes a magnetron (not shown) and a wave guide (not shown). The microwave generator  131  generates the microwave and provides the same to the microwave reflection chamber  133 . 
     The microwave reflection chamber  133  includes interior space reflecting the microwave. The microwave reflection chamber  133  includes an inlet  133 a and an outlet  133   b  each connected to the first pipe  121  and the second pipe  123 . Once the harmful gas is input through the inlet  133   a , the microwave generated from the microwave generator  131  is emitted to the harmful gas such that noxious substances in the harmful gas may be activated and then be discharged through the outlet  133   b.    
     The microwave reflection chamber  133  may be various structures such as a rectangular parallelepiped, cylinder, and so on. The exemplary embodiment takes the example of a rectangular parallelepiped structure. The one side of the microwave reflection chamber  133  includes the inlet  133   a  connected to the first pipe  121 , and the opposite side of the microwave reflection chamber  133  includes the outlet  133   b  connected to the second pipe  122 . 
     The microwave reflection chamber  133  includes interior space with a structure reflecting the microwave provided by the microwave generator  131 . That is, the interior space of the microwave reflection chamber  133  is formed of a conductive material and is sealed in the remaining parts except the inlet  133   a  and the outlet  133   b.    
     The microwave provided by the microwave generator  131  may not leak to the outside and be reflected only in the microwave reflection chamber  133  infinitely, because the interior space is made of a conductive material and sealed. But, the microwave loses its energy by collision with substances and then dissipates itself, and the microwave in this embodiment collides with noxious substances in the harmful gas to lose its energy and then dissipates itself. 
     That is, the noxious substances are activated with increased kinetic energy by absorbing energy from the microwave. At this time, the temperature inside the microwave reflection chamber  133  is confirmed to be increased. Kinetic energy of an object is proportional to the temperature, accordingly, the temperature increases when the noxious substances have increased kinetic energy by absorbing energy from the microwave, resulting the temperature increase in the interior space of the microwave reflection chamber  133 . Thus, the activation of the noxious substances in the harmful gas may be confirmed by measuring temperature inside the microwave reflection chamber  133  with a temperature sensor. 
     Meanwhile, although not shown in the drawings, buffer gas may be further provided into the microwave reflection chamber  133  along with the harmful gas. The buffer gas may be one of H 2 O, gas, or liquid. The noxious substances in the harmful gas are so various that activation only by the microwave may not be successful. Accordingly, the buffer gas provided into the microwave reflection chamber  133  is activated by the microwave and then flows to the plasma reactor  150  along with the harmful gas, as a result, the buffer gas decomposes the noxious substances in the harmful gas together with the plasma discharge because the buffer gas in the state of being activated may be dissociated by the plasma discharge sooner than the harmful gas. Like this, the decomposition function for noxious substances in the harmful gas may be increased with the assistance of buffer gas. 
     As described above, the microwave reflection chamber  133  includes the inlet  133   a  and the outlet  133   b . At this time, the microwave may leak through the inlet  133   a  and the outlet  133   b  if the inlet  133  and the outlet  133   b  are maintained to be open. Accordingly, mesh  135  is prepared on the inlet  133   a  and the outlet  133   b , respectively, to avoid the above. 
     The mesh  135  includes plurality of holes (not shown) through which only the harmful gas may be input or discharged, but not the microwave. The microwave may be reflected. 
     The microwave may not pass through the hole smaller than a fourth of its wavelength size. Thus, the microwave may not pass through the mesh  135  and may be reflected continuously within the microwave reflection chamber  133 , when the size of each hole of the plurality of holes on the mesh  135  is formed to be smaller than a fourth of the microwave wavelength. 
       FIGS. 3 and 4  show different exemplary embodiments of the above preprocessing apparatus. The identical compositions with the preprocessing apparatus  130  in the preprocessing apparatus in  FIGS. 3 and 4  are referred to as the same drawing reference numbers, and descriptions of those will be omitted. 
     Referring to  FIG. 3 , a preprocessing apparatus  130 ′ according to another exemplary embodiment of the inventive concept includes a plurality of baffles  137  inside the microwave reflection chamber  133 . The baffles  137  are arranged to face each other while being separated by the predetermined space in alternation with each other. The harmful gas input to the microwave reflection chamber  133  flows through the path set by the baffles  137  while changing the flow direction by the plural times. 
     The baffle  137  may be formed of a material through which the microwave may pass or reflecting the microwave. The baffles  137  installed inside the microwave reflection chamber  133  block the straight flow path of the harmful gas to the outlet  133   b  while altering the flow direction by the plural times, accordingly, the harmful gas may stay longer inside the microwave reflection chamber  133  such that more noxious substances in the harmful gas may be activated. 
     Referring to  FIG. 4 , a preprocessing apparatus  130 ″ according to yet another exemplary embodiment of the inventive concept includes a duct  137 ″ inside the microwave reflection chamber  133 . The duct  137 ′&#39; connects connects the inlet  133   a  and the outlet  133   b  and forms a flow path of the harmful gas input through the inlet  133   a.    
     The duct  137 ″ is bended by the plural times with forms of “S” and alters the flow direction of the harmful gas by the plural times like the baffles  137  in the above embodiment. But, the harmful gas flows inside the duct  137 ″, accordingly, the duct  137 ″ is required to be made of a material transmitting the microwave. 
     The harmful gas flowing through the duct  137 ″ stays long inside the microwave reflection chamber  133  while flowing inside the microwave reflection chamber  133  from the inlet  133   a  and to the outlet  133   b  due to the structure of the duct  137 ″ altering the flow direction by the plural times. More amount of the noxious substances may be activated by the microwave in the duct  137 ″ of the microwave reflection chamber  133  while staying long as the duct  137 ″ is made of a material transmitting the microwave. 
     After the noxious substances in the harmful gas are activated by the apparatus for preprocessing the harmful gas  130 ,  130 ′,  130 ″, the harmful gas is discharged through the outlet  133   b  and input to the plasma reactor  150  through the second pipe  123 . The plasma reactor  150  decomposes noxious substances in the preprocessed harmful gas undergone the preprocess in the preprocessing apparatus  130  with reaction to the plasma discharge. 
     The plasma reactor  150  uses a radio frequency (RF) source for an energy source. The plasma reactor  150  includes a conduit  151 , a coil unit  153  winding the outer surface of the conduit  151  in a spiral, flanges  155 , and an outer pipe  157 . The conduit  151  is a flow path of the harmful gas, which has a cylinder form with a longitudinal through hole. The conduit  151  is made of high-k dielectric such as alumina, zirconia (ZrO 2 ), yttria (Y 2 O 3 ), sapphire, quartz, glass, or the like. Especially, using mixed powder of alumina and yttria with pressed and coating the alumina tube with sputtering resistant yttria spraying may increase etch resistant feature. The conduit  151  and the coil unit  153  winding the same are protected by the outer pipe  157 . That is, the plasma reactor  150  is formed of a double pipe by arranging the conduit  151  and the coil unit  153  inside the outer layer pipe  157 . The double pipe form prevents electromagnetic waves generated by the coil unit  153  from releasing to the outside of the plasma reactor  150 . 
     The double pipe form also prevents gas leakage in the plasma reactor  150  caused by cracks or damage on the conduit  151 . The conduit  151  may have cracks and damage by itself during the plasma discharge in a vacuum status of high temperature, accordingly, the connection of the conduit  151  to the surrounding pipe may have cracks. 
     The coil unit  153  decomposes noxious substances in the harmful gas flowing inside the conduit  151  by generating RF plasma discharge from the coil unit  153  with appliance of electricity from outside. The conduit  151  is made of dielectrics so as to be protected from damage caused by RF plasma discharge generated from the coil unit  153  and protect the coil unit  153 . 
     The flanges  155  are located at both ends of the conduit  151  and connect the conduit  151 , the second pipe  123 , and the third pipe  125 . The flanges  155  are also made of dielectrics like the conduit  151  such that the second pipe  123  and the third pipe  125  may be protected from damage caused by RF plasma discharge generated from the coil unit  153 . Meanwhile, although the plasma discharge is generated by the RF power source in the plasma reactor  150  in the exemplary embodiments of the inventive concept, the embodiments are not restricted thereto, and plasma discharge may be generated by an AC power source, a DC power source, and microwave. 
     The plasma reactor  150  decomposes noxious substances in the harmful gas flowing inside the conduit  151  with the plasma discharge generated from the coil unit  153 . Especially, the harmful gas undergone the substance activation through the preprocessing apparatus  130  is input to the plasma reactor  150 , accordingly, the reaction of the noxious substances to the plasma discharge improves. Thus, more noxious substances in the harmful gas are decomposed and removed than decomposing through only in the plasma reactor  150  with reaction to the plasma discharge, thereby enhancing the purifying performance with regards to the harmful gas. 
     The purified gas undergone the decomposition of noxious substances by the plasma reactor  150  flows to the vacuum pump  170  and the scrubber  190  to be discharged to the outside. The vacuum pump  170  and the scrubber  190  may not be damaged because the gas is purified, and the purified gas discharged to the outside may not cause air pollution. 
       FIGS. 6 and 7  show a facility for purifying harmful gas  200  according to another exemplary embodiment of the inventive concept. The facility for purifying harmful gas  200  is different from the facility for purifying harmful gas  100  only in a preprocessing apparatus  230 . Thus, just the preprocessing apparatus  230  will be described hereinafter. 
     The preprocessing apparatus  230  includes a microwave transmitting pipe  231 , a magnetron  233 , and a housing  235 . The microwave transmitting pipe  231  is installed between the first pipe  121  in which the harmful gas discharged from the process chamber  110  flows and the second pipe  123  in which the preprocessed harmful gas flows to the plasma reactor  150  with mutually communicated. The microwave transmitting pipe  231  has a through hole for inputting and outputting the harmful gas and is formed of a material transmitting the microwave at least by a portion. 
     The microwave transmitting pipe  231  includes a region surrounded by the housing  235  which is formed of one-layered material transmitting the microwave, and the rest region that is consisted of a first layer of anti-corrosion material and a second layer of conductive material reflecting the microwave. 
     The rest region is formed of multi-layers including the first layer and the second layer, which is for blocking loss of the microwave that a portion of the microwave escapes to the outside. The first layer also helps to prevent the second layer from being damaged by the microwave. But, embodiments may not be restricted thereto, and the rest region may be formed of one layered conductive material that can reflect the microwave. 
     Meanwhile, the microwave transmitting pipe  231  is made of a material transmitting the microwave, such as quartz material, ceramic material, plastic material, and carbon material. Also, the anti-corrosion material is at least one of quartz material, ceramic material, plastic material, and carbon material. 
     The magnetron  233  generates the microwave and provides the same into the inside of the microwave transmitting pipe  231 . The magnetron  233  is installed between the microwave transmitting pipe  231  and the housing  235 , wherein the housing  235  is formed of a material reflecting the microwave. The housing  235  encloses the microwave transmitting pipe  231  so as to have space from the outer circumference surface of the microwave transmitting pipe  231 , and the magnetron  233  is prepared in the space. Although not shown in the drawings, a waveguide (not shown) may be further prepared inside the space. The size of the waveguide may be set by the wavelength of the microwave. 
     The microwave generated from the magnetron  233  passes through the microwave transmitting pipe  233  and collides with noxious substances in the harmful gas floating inside the microwave transmitting pipe  233 . At this time, the microwave energy is absorbed into the noxious substances, which results in increase of kinetic energy of the noxious substances and activation thereof. Meanwhile, the microwave which may not collide with the noxious substances passes through the microwave transmitting pipe  231  to arrive at the housing  235  and may be reflected by the housing  235  again. 
     Meshes (not shown) may be installed at one side of the microwave transmitting pipe  233 , the side of inflow of the harmful gas discharged from the process chamber  110 , the other side of the microwave transmitting pipe  233 , and the side of discharge of the harmful gas including activated noxious substances. The meshes are used to prevent damage to the plasma reactor  150  and to the microwave itself by blocking the microwave from transmitting toward the process chamber  110  or the plasma reactor  150  while allowing free inlet and outlet of the harmful gas. 
     Meanwhile, although not shown in the drawings, the preprocessing apparatus  230  may be connected to the plasma reactor  150  directly. That is, the side of discharging the harmful gas from the preprocessing apparatus  230  is directly connected to the plasma reactor  150 . In case that the preprocessing apparatus  230  and the plasma reactor  150  are connected directly, time for the harmful gas flowing to the plasma reactor  150  may be shortened, thereby increasing treatment efficiency of the activated harmful gas. 
     While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood that various changes in form and details may be made therein without departing from the spirit and scope of the following claims.