Patent Publication Number: US-2023136707-A1

Title: Apparatus for treating substrate and method for treating substrate

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     A claim for priority under 35 U.S.C. § 119 is made to Korean Patent Application No. 10-2021-0148452 filed on Nov. 2, 2021, in the Korean Intellectual Property Office, the entire contents of which are hereby incorporated by reference. 
     BACKGROUND 
     Embodiments of the inventive concept described herein relate to a substrate treating apparatus and a substrate treating method, more specifically, a substrate treating apparatus and a method for treating a substrate with a plasma. 
     A plasma refers to an ionized gas state composed of ions, radicals, and electrons. The plasma is produced by a very high temperatures, a strong electric field, or a high frequency electromagnetic field (RF electromagnetic field). A semiconductor device manufacturing process may include an etching process of removing a thin film or by-products formed on a substrate such as a wafer using the plasma. The etching process is performed by colliding ions and/or radicals of the plasma with the thin film on the substrate or reacting with the thin film. 
     In a process of treating the substrate, it is important that characteristics of the plasma are kept constant. If the characteristics of the plasma are changed, it is difficult to satisfy process treatment conditions required for the substrate. This causes a process defect of the substrate and leads to a problem of lowering a process efficiency 
     In general, an observation window is installed on a side wall of the chamber to observe plasma characteristics such as a color of the plasma and a distribution of the plasma. The observation window is contaminated by particles, process by-products, etc. generated while performing the process, thereby interfering with an observation of plasma characteristics. Furthermore, a method of monitoring high-frequency voltages or high-frequency currents to observe the properties of the plasma do not provide an accurate information about the plasma distributed over a wide range. In addition, in a process of using multiple plasma with different characteristics in multiple areas inside the chamber, a plurality of observation equipment is required to observe each plasma. This makes an apparatus structurally complex and reduces a spatial efficiency of by the apparatus. 
     SUMMARY 
     Embodiments of the inventive concept provide a substrate treating apparatus and a substrate treating method for observing characteristics of a plasma. 
     Embodiments of the inventive concept provide a substrate treating apparatus and a substrate treating method for observing characteristics of each plasma using one observing equipment which can observe a plural number of plasmas having different characteristics. 
     Embodiments of the inventive concept provide a substrate treating apparatus and a substrate treating method for observing characteristics of a plasma without an additional structure change of an apparatus. 
     The technical objectives of the inventive concept are not limited to the above-mentioned ones, and the other unmentioned technical objects will become apparent to those skilled in the art from the following description. 
     The inventive concept provides a substrate treating apparatus. The substrate treating apparatus includes a housing having an inner space; a plate separating the inner space into a first space which is above and a second space which is below and having a plurality of through holes; a first gas supply unit configured to supply a first gas to the first space; a plasma source for generating a plasma at the first space or the second space; and a monitoring unit installed at the plate and configured to monitor a characteristic of the plasma generated at the first space or the second space. 
     In an embodiment, an optical path connecting the first space or the second space, and the monitoring unit is formed at the plate. 
     In an embodiment, the plasma source includes: a first electrode applied with a first high frequency power and generating a first plasma at the first space; and a second electrode applied with a second high frequency power and generating a second plasma at the second space, and wherein the optical path has a first path which penetrates the plate in an up/down direction and a second path which connects to the first path and extends in a direction toward a side wall of the plate. 
     In an embodiment, the monitoring unit includes a polarizing plate installed at a position at which the first path and the second path intersect, and which has a polarization direction in a first direction, the light includes a first polarization which vibrates in the first direction and a second polarization which vibrates in a second direction which is different from the first direction, and the polarization plate is formed inclined with respect to the first path so the second polarization among the light incident to the first path is reflected from the polarizing plate to face a direction parallel to the second path. 
     In an embodiment, the monitoring unit further includes: a receiving member installed at a side of the second path which is adjacent to the side wall and which receives the light; and a refraction member installed at the other side facing a side of the second path and which changes a characteristic of the second polarization so the second polarization which is reflected from the polarizing plate vibrates in the first direction. 
     In an embodiment, the monitoring unit further includes a reflective member installed on the first path and which reflects the light which is incident from the first path to the second path. 
     In an embodiment, a transparent cover is further installed at each of an end and the other end of the first path at the monitoring unit. 
     In an embodiment, the plate is grounded and captures ions included in a plasma generated in the first space to supply radicals to the second space. 
     The inventive concept provides a substrate treating apparatus. The substrate treating apparatus includes a housing having a plasma region and a substrate treating region; a plate separating the plasma region and the substrate treating region and having a plurality of through holes; a first gas supply unit configured to supply a gas to the plasma region; a plasma source for generating a plasma at the plasma region; and a monitoring unit installed at the plate and configured to monitor a characteristic of the plasma generated at the plasma region. 
     In an embodiment, an optical path is formed connecting the plasma region or the substrate treating region, and the monitoring unit at the plate. 
     In an embodiment, the optical path has a first path which penetrates the plate in an up/down direction and a second path which connects to the first path and extends in a direction toward a side wall of the plate. 
     In an embodiment, the monitoring unit includes a polarizing plate installed at a position at which the first path and the second path intersect, and which has a polarization direction in a first direction, the light includes a first polarization which vibrates in the first direction and a second polarization which vibrates in a second direction which is different from the first direction, and the polarization plate is formed inclined with respect to the first path so the second polarization among the light incident to the first path is reflected from the polarizing plate to face a direction parallel to the second path. 
     In an embodiment, the monitoring unit includes a reflective member plate installed at a position at which the first path and the second path intersect, and which reflects the light incident to the first path in a direction of the second path. 
     In an embodiment, a transparent cover is further installed at each of an end and the other end of the first path at the monitoring unit. 
     The inventive concept provides a substrate treating apparatus. The substrate treating apparatus includes a housing having a treating space; an ion blocker dividing the treating space and a plasma space and which is grounded; a first gas supply unit configured to supply a first gas to the treating space; a second gas supply unit configured to supply a second gas to the plasma space; a top electrode positioned above the ion blocker and facing the ion blocker, which connects with a top source to be applied with a high frequency power, and which excites a first gas to generate a first plasma at a plasma space; a bottom electrode positioned below the ion blocker and facing the ion blocker, which excites the second gas to generate a second plasma at the treating space; and a monitoring unit configured to monitor a characteristic of the first plasma generated at the treating space and/or the second plasma generated at the plasma space, and wherein the monitoring unit is installed at the ion blocker, an optical path which connects the treating space or the plasma space, and the monitoring unit is formed at the ion blocker, and the optical path has a first path which penetrates the ion blocker in an up/down direction and a second path which connects to the first path and extends in a direction toward a side wall of the ion blocker. 
     In an embodiment, the monitoring unit includes a polarizing plate installed at a position at which the first path and the second path intersect, and which has a polarization direction in a first direction, the light includes a first polarization which vibrates in the first direction and a second polarization which vibrates in a second direction which is different from the first direction, and the polarization plate is formed inclined with respect to the first path so the second polarization among the light incident to the first path is reflected from the polarizing plate to face a direction parallel to the second path. 
     In an embodiment, the monitoring unit further includes: a receiving member installed at a side of the second path which is adjacent to the side wall and which receives the light; and a refraction member installed at the other side facing a side of the second path and which changes a characteristic of the second polarization so the second polarization which is reflected from the polarizing plate vibrates in the first direction. 
     In an embodiment, the monitoring unit further includes a reflective member installed on the first path and which reflects the light which is incident from the first path to the second path. 
     The inventive concept provides a substrate treating method for treating a substrate at a process chamber having a first space and a second space which is divided from the first space. The substrate treating method includes a treating using a first plasma in a state at which ions are removed at a second space, while the first space and the second space is divided by a plate and a first plasma which includes an ion formed at the first space flows from the first space to the second plate, and a monitoring of a characteristic of a first plasma which is generated at the first space by a monitoring unit installed at the plate. 
     In an embodiment, an optical path is formed at the monitoring unit connecting the first space or the second space, and the monitoring unit, and the optical path has a first path which penetrates the plate in an up/down direction and a second path which connects to the first path and extends in a direction toward a side wall of the plate. 
     In an embodiment, at the treating using the first plasma, the light emitted from the first plasma at the first space is incident to above the first path, a portion of the light incident to the first path passes the polarizing plate installed on the first path to reach the second space, and the other portion of the light incident to the first path is reflected from the polarizing plate and incident to the second path. 
     In an embodiment, the substrate treating method further includes a treating using a second plasma including ions formed at the second space. 
     In an embodiment, at the treating using the second plasma, the light emitted from the second plasma is incident to below the first path, a portion of the light incident to the first path passes a polarizing plate installed on the first path to reach the first space, another portion of the light incident to the first path is reflected from the polarizing plate and then reflected again from a refractive member which changes a characteristic of a polarization to change a characteristic of the polarization, and the light having a changed characteristic passes the polarizing plate to be incident to the second path. 
     In an embodiment, at the treating using the first plasma, the light emitted from the first plasma is incident to above the first path, the light incident to the first path is reflected by a reflective member installed on the first path to be incident to the second path, and at the treating using the second plasma, the light emitted from the second plasma is incident to below the first path, and the light incident to the first path is reflected from the reflective member installed on the first path to be incident to the second path. 
     According to an embodiment of the inventive concept, characteristics of a plasma may be effectively observed. 
     According to an embodiment of the inventive concept, characteristics of each plasma may be observed using one observing equipment which can observe a plural number of plasmas having different characteristics. 
     According to an embodiment of the inventive concept, characteristics of a plasma may be observed without an additional structure change of an apparatus. 
     The effects of the inventive concept are not limited to the above-mentioned ones, and the other unmentioned effects will become apparent to those skilled in the art from the following description. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The above and other objects and features will become apparent from the following description with reference to the following figures, wherein like reference numerals refer to like parts throughout the various figures unless otherwise specified, and wherein: 
         FIG.  1    schematically illustrates a substrate treating apparatus according to an embodiment of the inventive concept. 
         FIG.  2    schematically illustrates an embodiment of a process chamber of  FIG.  1   . 
         FIG.  3    schematically illustrates an embodiment of a monitoring unit of  FIG.  2   . 
         FIG.  4    schematically illustrates another embodiment of the monitoring unit of  FIG.  2   . 
         FIG.  5    schematically illustrates a first plasma treating step in the substrate treating method according to an embodiment of the inventive concept. 
         FIG.  6    illustrates a state in which a light emitted from a first plasma is incident on an optical path in the first plasma treating step of  FIG.  5   . 
         FIG.  7    schematically illustrates a state in which the light incident on the optical path of  FIG.  6    flows inside the optical path. 
         FIG.  8    schematically illustrates a second plasma treating step in the substrate treating method according to an embodiment of the inventive concept. 
         FIG.  9    illustrates a state in which a light emitted from a second plasma is incident on an optical path in the second plasma treating step of  FIG.  8   . 
         FIG.  10    schematically illustrates a state in which a light incident on the optical path of  FIG.  9    flows inside the optical path. 
         FIG.  11    schematically illustrates a shape of the light flowing in the second path by changing a direction of a polarization and the optical path by a refractive member among the light flowing in the optical path of  FIG.  10   . 
         FIG.  12    schematically illustrates a state in which the light emitted from the first plasma by the monitoring unit of  FIG.  4    flows inside the optical path. 
         FIG.  13    schematically illustrates a state in which the light emitted from the second plasma by the monitoring unit of  FIG.  4    flows inside the optical path. 
     
    
    
     DETAILED DESCRIPTION 
     The inventive concept may be variously modified and may have various forms, and specific embodiments thereof will be illustrated in the drawings and described in detail. However, the embodiments according to the concept of the inventive concept are not intended to limit the specific disclosed forms, and it should be understood that the present inventive concept includes all transforms, equivalents, and replacements included in the spirit and technical scope of the inventive concept. In a description of the inventive concept, a detailed description of related known technologies may be omitted when it may make the essence of the inventive concept unclear. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the inventive concept. 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” and/or “comprising,” 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. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Also, the term “exemplary” is intended to refer to an example or illustration. 
     It will be understood that, although the terms “first”, “second”, “third”, etc., may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the inventive concept. 
     Hereinafter, an embodiment of the inventive concept will be described in detail with reference to  FIG.  1    to  FIG.  13   . 
       FIG.  1    schematically illustrates a substrate treating apparatus according to an embodiment of the inventive concept. Referring to  FIG.  1   , the substrate treating apparatus  1  according to an embodiment of the inventive concept may include a load port  10 , an atmospheric pressure transfer module  20 , a vacuum transfer module  30 , a load lock chamber  40 , and a process chamber  50 . 
     The load port  10  may be disposed on a side of the atmospheric pressure transfer module  20  to be described later. One or more load ports  10  may be provided. The number of load ports  10  may increase or decrease according to a process efficiency, foot print conditions, and the like. A container F according to an embodiment of the inventive concept may be placed in the load port  10 . The container F may be loaded onto or unloaded from the load port  10  by a transfer means (not shown) such as an overhead transfer apparatus (OHT), an overhead conveyor, or an automatic guided vehicle, or by an operator. The container F may include various types of containers according to a type of an article to be stored. As the container F, an airtight container such as a front opening integrated pod (FOUP) may be used. 
     The atmospheric pressure transfer module  20  and the vacuum transfer module  30  may be arranged in a first direction  2 . Hereinafter, when viewed from above, a direction perpendicular to the first direction  2  is defined as a second direction  4 . In addition, a direction perpendicular to a plane including both the first direction  2  and the second direction  4  is defined as a third direction  6 . Here, the third direction  6  is a direction perpendicular to the ground. 
     The atmospheric pressure transfer module  20  may selectively transfer the substrate W between the container F and the load lock chamber  40  to be described later. For example, the atmospheric pressure transfer module  20  may take out the substrate W from the container F and transfer the substrate W to the load lock chamber  40 , or may take out the substrate W from the load lock chamber  40  and transfer the substrate W to the container F. The atmospheric pressure transfer module  20  may include a transfer frame  220  and a first transfer robot  240 . The transfer frame  220  may be provided between the load port  10  and the load lock chamber  40 . That is, the load port  10  may be connected to the transfer frame  220 . The transfer frame  220  may be provided with an atmospheric pressure therein. An inside of the transfer frame  220  may be maintained in an atmospheric pressure atmosphere. 
     The transfer frame  220  may be provided with a first transfer robot  240 . The first transfer robot  240  may selectively transfer the substrate W between the container F seated on the load port  10  and the load lock chamber  40  to be described later. 
     The first transfer robot  240  may move in a up/down direction. The first transfer robot  240  may have a first transfer hand  242  that moves forwardly, backwardly, or rotates on a horizontal plane. One or a plurality of first transfer hands  242  of the first transfer robot  240  may be provided. The substrate W may be placed on the first transfer hand  242 . 
     The vacuum transfer module  30  may be disposed between a load lock chamber  40  to be described later and a process chamber  50  to be described later. The vacuum transfer module  30  may include a transfer chamber  320  and a second transfer robot  340 . 
     The transfer chamber  320  may maintain an inner atmosphere as a vacuum pressure atmosphere. The transfer chamber  320  may be provided with a second transfer robot  340 . In an embodiment, the second transfer robot  340  may be located in a central region of the transfer chamber  320 . The second transfer robot  340  may selectively transfer the substrate W between the load lock chamber  40  and the process chamber  50 . Selectively, the vacuum transfer module  30  may transfer the substrate W between the process chambers  50 . The second transfer robot  340  may move in a horizontal and vertical direction. The second transfer robot  340  may have a second transfer hand  342  that moves forwardly, backwardly, or rotates on a horizontal plane. At least one second transfer hand  342  of the second transfer robot  340  may be provided. 
     At least one process chamber  50  to be described later may be connected to the transfer chamber  320 . The transfer chamber  320  may be provided in a polygonal shape. A load lock chamber  40  and a process chamber  50  may be disposed around the transfer chamber  320 . In an embodiment, as shown in  FIG.  1   , a hexagonal shaped transfer chamber  320  may be disposed at a central region of the vacuum transfer module  30 , and a load lock chamber  40  and a process chamber  50  may be disposed around the transfer chamber  320 . However, a shape of the transfer chamber  320  and the number of process chambers may be variously modified and provided according to the needs of a user. 
     The load lock chamber  40  may be disposed between the transfer frame  220  and the transfer chamber  320 . The load lock chamber  40  provides a buffer space B in which the substrate W or the ring member R is exchanged between the transfer frame  220  and the transfer chamber  320 . 
     As mentioned above, an inner atmosphere of the transfer frame  220  may be maintained in an atmospheric pressure atmosphere, and the inner atmosphere of the transfer chamber  320  may be maintained in a vacuum pressure atmosphere. The load lock chamber  40  is disposed between the transfer frame  220  and the transfer chamber  320 , so that an inner atmosphere thereof may be converted between the atmospheric pressure atmosphere and a vacuum pressure atmosphere. 
     In an embodiment of the inventive concept, the process chamber  50  performs a process on the substrate W. The process chamber  50  treats the substrate W using a plasma. For example, the process chamber  50  may be a chamber performing an etching process of removing a thin film on the substrate W using the plasma, an ashing process of removing a photoresist film, a deposition process of forming a thin film on the substrate W, or a dry cleaning process. However, the inventive concept is not limited thereto, and a plasma treatment process performed at the substrate treating apparatus  10  may be variously modified to a known plasma treatment process. 
       FIG.  2    schematically illustrates an embodiment of the process chamber of  FIG.  1   . Referring to  FIG.  2   , the process chamber  50  includes a housing  510 , a chuck  520 , a plate  530 , a top electrode  540 , a gas supply unit  550 , an exhaust unit  560 , and a monitoring unit  600 . 
     The housing  100  may have an inner space. The inner space of the housing  100  may be divided into a top plasma space A 1  and a bottom treating space A 2  by the plate  530  to be described later. The plasma space A 1  may be defined as a first space. The treating space A 2  may be defined as a second space. 
     The plasma space A 1  may be defined as a space in which the top electrode  540  and the plate  530  are combined with each other, which will be described later. The plasma space A 1  may be provided as a space at which a first plasma P 1  is generated. Specifically, the plasma space A 1  may be provided as a space for exciting a first gas G 1  supplied from the first gas supply unit  551 , which will be described later, into the first plasma P 1 . 
     The treating space A 2  may be defined as a space in which the plate  530  and the bottom electrode  528  are combined with each other, which will be described later. The treating space A 2  may be provided as a space in which the substrate W is treated. Specifically, the treating space A 2  may be provided as a space in which a radical from which ions included in the first plasma P 1  have been removed and a second gas G 2  supplied from a second gas supply unit  555 , which will be described later, act on the substrate W. In addition, the treating space A 2  may be provided as a space for exciting the second gas G 2  supplied from the second gas supply unit  555  to the second plasma P 2 . 
     The housing  510  may be made of a metal material. The housing  510  is grounded. The housing  510  may be provided in a substantially cylindrical shape. A top electrode  540  to be described later may be disposed above the inner space of the housing  510 . A chuck  520  to be described later may be disposed below the inner space of the housing  510 . An exhaust hole  511  is formed on a bottom surface of the housing  510 . An exhaust unit  560  to be described later may be connected to the exhaust hole  511 . 
     On a side of the housing  510 , the substrate W may be taken into the treating space A 2 , or an inlet (not shown) through which the substrate W is taken out from the treating space A 2  may be formed. The inlet (not shown) may be selectively opened and closed by a door (not shown). A view port  515  may be installed on the other side of the housing  510 . The view port  515  may observe a light incident from the monitoring unit  600  to be described later. The view port  515  communicates with an optical path D to be described later. For example, the view port  515  may communicate with a second path D 2  to be described later. 
     The chuck  520  is located in the inner space of the housing  510 . The chuck  520  supports the substrate W in the treating space A 2 . The chuck  520  may heat the substrate W. In addition, the chuck  520  may be an ESC capable of chucking the substrate W using an electrostatic force. The chuck  520  may include a support plate  522 , an electrostatic electrode  524 , a heater  526 , and a bottom electrode  528 . 
     The support plate  522  supports the substrate W. The support plate  522  has a support surface for supporting the substrate W. The substrate W is placed on the top surface of the support plate  522 . The support plate  522  may be provided as a dielectric substrate. The support plate  522  may be provided as a dielectric having a disk shape. In an embodiment, the dielectric plate  520  may be made of a ceramic material. An electrostatic electrode  524  and a heater  546  may be buried in the support plate  522 . 
     The electrostatic electrode  524  may be provided at a position overlapping the substrate W when viewed from above. The electrostatic electrode  524  may be disposed above the heater  546 . The electrostatic electrode  524  is electrically connected to the first power source  524   a . The first power source  524   a  may include a DC power. A first switch  524   b  is installed between the electrostatic electrode  524  and the first power source  524   a . The electrostatic electrode  524  may be electrically connected to the first power source  524   a  by turning on/off of the first switch  524   b . If the first switch  524   b  is turned on, a DC current is applied to the electrostatic electrode  524 . 
     If a current is applied to the electrostatic electrode  524 , an electric field by an electrostatic force capable of chucking the substrate W may be formed in the electrostatic electrode  524 . The electric field may transmit a force chucked in a direction in which the substrate W faces the support plate  522 . Accordingly, the substrate W is sucked to the support plate  522 . In addition, the electric field may allow ions described later to flow straight toward the substrate W. That is, the electric field may allow the ions to have an anisotropy. 
     The heater  526  heats the substrate W. The heater  526  heats the substrate W by increasing a temperature of the support plate  522 . The heater  526  is electrically connected to the second power source  526   a . A second switch  526   b  is installed between the heater  526  and the second power supply  526   a . The heater  526  may be electrically connected to the second power source  526   a  by turning on/off the second switch  526   b . The heater  526  generates a heat by resisting a current applied from the second power source  526   a . The generated heat is transferred to the substrate W through the support plate  522 . The substrate W may be maintained at a predetermined temperature by the heat generated by the heater  526 . 
     According to an embodiment, a plurality of heaters  526  may be provided as spiral coils. The heaters  526  may be provided in different regions of the support plate  522 , respectively. For example, a heater  526  for heating a central region of the support plate  522  and a heater  526  for heating the edge region of the support plate  522  may be respectively provided, and these heaters  526  may independently adjust a degree of a heat generation. The heater  526  may be a heating element such as a tungsten. 
     In the above-described example, it has been described that the heater  526  is provided in the support plate  522 , but the inventive concept is not limited thereto. The heater  526  may not be provided in the support plate  522 . 
     The bottom electrode  528  may have a plate shape. In an embodiment, the bottom electrode  528  may be provided in a disk shape. 
     The bottom electrode  528  may be connected to a bottom power supply  528   a . The bottom power supply  528   a  may apply a high frequency current to the bottom electrode  528 . In an embodiment, the bottom power supply  528   a  may apply a second high frequency current to the bottom electrode  528 . The bottom power supply  528   a  is provided as an RF source. In addition, a bottom impedance match (not shown) may be provided between the bottom electrode  528  and the bottom power supply  528   a.    
     The bottom electrode  528  may be an electrode facing the plate  530  to be described later. The bottom electrode  528  may generate a plasma in the treating space A 2 . If a power is applied to the bottom electrode  528 , the bottom electrode  528  forms an electric field in the treating space A 2 . The electric field formed in the treating space A 2  may generate the second plasma P 2  by exciting the second gas G 2  supplied (inflowed) into the treating space A 2 . Accordingly, the bottom electrode  528  functions as a plasma source together with the top electrode  540  and the plate  530  to be described later. 
     The plate  530  may be disposed above the housing  510 . The plate  530  may be disposed below the top electrode  540  to face the top electrode  540 , which will be described later. The plate  530  is disposed between the chuck  520  and the top electrode  540 . For example, the plate  530  may be disposed between the treating space A 2  and the top electrode  540 . 
     The plate  530  may be formed in a plate shape. The plate  530  may be connected to a sidewall of the housing  510 . The plate  530  divides the inner space of the housing  510 . The plate  530  divides the inner space of the housing  510  into a top plasma space A 1  and a bottom treating space A 2 . 
     A plurality of through holes  532  may be formed in the plate  530 . The plurality of through holes  532  may be formed as through holes vertically extending from a top end to a bottom end of the plate  530 . The plurality of through holes  532  may fluidly communicate the top plasma space A 1  to the bottom treating space A 2 . 
     The plate  530  may be grounded. The plate  530  may be grounded and function as an electrode facing each other with a top electrode  540  to be described later. The plate  530  and the top electrode  540  may form the first plasma P 1  in the plasma space A 1  by exciting the first gas G 1  supplied from the first gas supply unit  551  to be described later. Accordingly, the plate  530  and the top electrode  540  may function as a first plasma source. 
     In addition, the plate  530  may be grounded and function as an electrode facing the bottom electrode  528 . The plate  530  and the bottom electrode  528  may form a second plasma P 2  in the treating space A 2  by exciting the second gas G 2  supplied from a second gas supply unit  555  to be described later. Accordingly, the plate  530  and the bottom electrode  528  may function as a second plasma source. 
     A second gas channel  539  may be formed on the plate  530 . The second gas channel  539  may be connected to a second gas line  556  to be described later. The second gas channel  539  may supply the second gas G 2  toward the treating space A 2 . A monitoring unit  600  to be described later may be provided on a side of the plate  530 . An optical path D to be described later may be formed on a side of the plate  530 . 
     The plate  530  may perform a function of an ion blocker. If the first plasma P 1  generated in the plasma space A 1  flows into the treating space A 2 , the plate  530  is grounded to remove ions contained in the first plasma P 1 . Specifically, the first gas G 1  supplied to the plasma space A 1  is decomposed into ions, electrons, and radicals as it is transferred to the first plasma state. As the first plasma passes through the plate  530 , ions and electrons in the components of the first plasma are absorbed. That is, the plate  530  may function as a block ion blocker that blocks a passage of ions. Accordingly, only a radical among components included in the first plasma passes through the plate  530  and moves to the treating space A 2 . 
     The top electrode  540  may have a plate shape. In an embodiment, the top electrode  540  may have an area smaller than that of the plate  530  when viewed from above. However, the inventive concept is not limited thereto, and the top electrode  540  may have an area corresponding to that of the plate  530 . The top electrode  540  may be positioned above the inner space of the housing  510 . The top electrode  540  may be positioned above the plate  530 . The top electrode  540  may be disposed to face the plate  530 . 
     A top power source  542  may be connected to the top electrode  540 . The top power source  542  may apply a high frequency current to the top electrode  540 . In an embodiment, the top power source  542  may apply a first high frequency current to the top electrode  540 . The top power source  542  is provided as an RF source. In addition, a top impedance match (not shown) may be provided between the top electrode  540  and the top power source  542 . 
     The top electrode  540  may generate a plasma in the plasma space A 1 . The top electrode  540  may function as a plasma source. The top electrode  540  may be an electrode facing the plate  530 . For example, the top electrode  540  may function as a first plasma source which generates a first plasma together with the plate  530 . In an embodiment, if the power is applied to the top electrode  540 , the top electrode  540  forms an electric field in the plasma space A 1 . An electric field formed in the plasma space A 1  may generate the first plasma P 1  by exciting the first gas G 1  supplied (inflowed) into the plasma space A 1 . 
     A first gas inlet  549  may be formed in the top electrode  540 . At least one first gas channel  549  may be provided. The first gas channel  549  may be connected to a first gas line  552  to be described later. The first gas channel  549  may supply the first gas G 1  toward the plasma space A 1 . 
     The gas supply unit  550  supplies the first gas G 1  and the second gas G 2  to the inner space of the housing  510 . The gas supply unit  550  may include a first gas supply unit  551  and a second gas supply unit  555 . 
     The first gas supply unit  551  may supply the first gas G 1  to the plasma space A 1 . For example, the first gas supply unit  551  may supply the first gas G 1  to a space between the plate  530  and the top electrode  540 . The first gas supply unit  551  may include a first gas line  552  and a first gas supply source  553 . 
     The first gas line  552  connects the first gas channel  549  and the first gas supply source  553  to each other. An end of the first gas line  552  is connected to a plurality of first gas channels  549 , and the other end of the first gas line  552  is connected to the first gas supply source  553 . The first gas supply source  553  supplies the first gas G 1  to the plasma space A 1  through the first gas line  552 . In an embodiment, the first gas G 1  may be an NH 3 . Optionally, the first gas G 1  may further include one or more of an Ar or an He, or a multiple more. 
     The second gas supply unit  555  may supply the second gas G 2  to the treating space A 2 . For example, the second gas supply unit  555  may supply the second gas G 2  to a space between the plate  530  and the bottom electrode  528 . The second gas supply unit  555  may include a second gas line  556  and a second gas supply source  557 . 
     The second gas line  556  connects the second gas channel  539  and the second gas supply source  557  to each other. An end of the second gas line  556  is connected to a plurality of second gas channels  539 , and the other end of the second gas line  556  is connected to the second gas supply source  557 . The second gas supply source  557  supplies the second gas G 2  to the treating space A 2  through the second gas line  556 . In an embodiment, the second gas G 2  may be an H 2  or/and an NH 3 . 
     The exhaust unit  560  may discharge a gas, process by-products, or the like flowing through the treating space A 2 . The exhaust unit  560  may adjust a pressure of the treating space A 2 . The exhaust unit  560  may include an exhaust line  562  and a depressurizing member  564 . An end of the exhaust line  562  may be connected to the exhaust hole  511 , and the other end of the exhaust line  562  may be connected to the depressurizing member  564 . The depressurizing member  564  may be a pump. However, the inventive concept is not limited thereto, and may be variously modified and provided as a known device for providing a depressurizing. 
     The insulating member  570  may be disposed between the plate  530  and the top electrode  540 . The insulating member  570  is provided with an insulating material. The insulating member  570  may have a ring shape when viewed from the top. The insulating member  570  may electrically insulate the plate  530  from the top electrode  540 . A heating member (not shown) may be provided inside the insulating member  570  to transfer a heat to the plasma space A 1 . However, the inventive concept is not limited thereto, and a heating member (not shown) may not be provided inside the insulating member  570 . 
       FIG.  3    schematically illustrates an embodiment of the monitoring unit of  FIG.  2   . Hereinafter, a monitoring unit according to an embodiment of the inventive concept will be described in detail with reference to  FIG.  2    and  FIG.  3   . 
     The monitoring unit  600  observes characteristics of the plasma. In an embodiment, the monitoring unit  600  may analyze a light emitted from the plasma to observe the characteristics of the plasma. The monitoring unit  600  observes characteristics of the first plasma P 1  generated in the plasma space A 1 . In addition, the monitoring unit  600  observes the characteristics of the second plasma P 2  generated in the treating space A 2 . 
     The monitoring unit  600  is installed on the plate  830 . The monitoring unit  600  may be installed outside the plate  830 . In an embodiment, the monitoring unit  600  may be installed in a region far from a center of the plate  830  having a relatively low influence of an electric field by the plasma. The monitoring unit  600  is installed on the optical path D formed on the plate  830 . The monitoring unit  600  is installed at a position which does not overlap the through hole  532  formed in the plate  830 . In addition, the optical path D is formed not to overlap the through hole  532 . 
     The optical path D may be connected to the plasma space A 1 . The optical path D may be connected to the treating space D 2 . The optical path D may be connected to the monitoring unit  600 . The optical path D may be formed to penetrate a sidewall of the housing  510 . The optical path D may be connected to a view port  515  installed on a side wall of the housing  510 . 
     The optical path D may include a first path D 1  and a second path D 2 . The first path D 1  may be formed to penetrate the plate  830  in the vertical direction. For example, the first path D 1  may be formed in a vertical direction penetrating a top end and a bottom end of the plate  830 . The second path D 2  extends from the first path D 1 . The second path D 2  may extend from the first path D 1  to be connected to the view port  515 . For example, the second path D 2  may be formed to be horizontal with respect to the first path D 1 . Unlike the above-described example, path directions of the first path D 1  and the second path D 2  may be formed by being modified into various paths. 
     The monitoring unit  600  may include a transparent cover  620 , a polarizing plate  640 , a refracting member  660 , and a light receiving member  680 . 
     The transparent cover  620  is installed in the first path D 1 . The transparent cover  620  may be installed at a top end and a bottom end of the first path D 1 , respectively. The transparent cover  620  may be installed above the first path D 1  closest to the plasma space A 1  among the first paths D 1 . The transparent cover  620  may be installed below the first path D 1  closest to the treating space A 2  among the first paths D 1 . A first light L 1  emitted from the first plasma P 1  generated in the plasma space A 1  is incident on the transparent cover  620  installed at the top end of the first path D 1 . A second light L 2  emitted from the second plasma P 2  generated in the treating space A 2  is incident on the transparent cover  620  installed at the bottom end of the first path D 1 . The transparent cover  620  may be made of a transparent material so that the light may be incident. 
     The transparent cover  620  vacuum-shields an inside of the optical path D. The transparent cover  620  may be made of a material capable of minimizing an influence of ions. In addition, the transparent cover  620  may be made of a material capable of minimizing a chemical reaction. According to an embodiment, the transparent cover  620  may be made of a material made of a Y 2 O 3 . Accordingly, the transparent cover  620  protects the monitoring unit  600  provided inside the optical path D from the plasma space A 1  and the treating space A 2 . 
     The polarizing plate  640  is installed inside the optical path D. The polarizing plate  640  is installed at a position where the first path D 1  and the second path D 2  intersect. The polarizing plate  640  has a polarization direction formed in a first direction. The polarizing plate  640  may pass a first polarization having a polarization in the first direction among polarization components of the light emitted from the plasma. The polarizing plate  640  may reflect second polarizations having a second direction different from the first direction among polarization components of light emitted from the plasma. 
     The polarizing plate  640  may be disposed to be inclined. The polarizing plate  640  is formed to be inclined with respect to the first path D 1  at an angle capable of reflecting a second polarization having a second direction in a direction horizontal to the second path D 2 . 
     The refractive member  660  is installed inside the optical path D. The refractive member  660  is formed on a side of the second path D 2  inside the optical path D. The refractive member  660  is installed at a point at which the first path D 1  and the second path D 2  cross each other. The refractive member  660  may be disposed adjacent to the first path D 1  of the first path D 1  and the second path D 2  at a point at which the first path D 1  and the second path D 2  meet. In an embodiment, the refractive member  660  may be disposed on the first path D 1  and on a virtual straight line connecting a path direction of the second path D 2 , farther from the second path D 2  than the polarizing plate  640 . That is, inside the optical path D, the refractive member  660 , the polarizing plate  640 , and the light receiving member  680  to be described later may be sequentially disposed in a direction away from the center of the plate  530 . 
     The refractive member  660  reflects the light flowing inside the optical path D. For example, the refractive member  660  may reflect the light flowing in the optical path D in a direction toward the second path D 2 . In addition, the refractive member  660  may change the polarization component of the light flowing in the optical path D. For example, if the light incident on the refractive member  660  is assumed to be a second polarization having a second direction, a characteristic of the second polarization may be changed to correspond to the first direction of the first polarization through the refractive member  660 . Accordingly, the light reflected from the refractive member  660  may pass through the polarizing plate  640  having the first direction and move toward the second path D 2 . A detailed mechanism for this will be described later with reference to  FIG.  5    to  FIG.  11   . 
     The light receiving member  680  receives the light flowing inside the optical path D. The light receiving member  680  receives the light passing through the second path D 2 . The light receiving member  680  is installed inside the optical path D. The light receiving member  680  is installed inside the optical path D on the other side opposite to a side of the second path D 2  in which the refractive member  660  is installed. For example, the light receiving member  680  is installed in the second path D 2  at a position adjacent to a sidewall of the housing  510 . The light received from the light receiving member  680  moves to the view port  515 . 
       FIG.  4    schematically illustrates another embodiment of the monitoring unit of  FIG.  2   . The monitoring unit according to an embodiment of the inventive concept will be described in detail with reference to  FIG.  4   . Since the monitoring unit described below is mostly provided similar to the monitoring unit described with reference to  FIG.  2    and  FIG.  3   , redundant descriptions will be omitted to prevent an overlapping of contents. 
     Referring to  FIG.  4   , the monitoring unit  600  may include a transparent cover  620 , a light receiving member  680 , and a reflective member  690 . Since the transparent cover  620  and the light receiving member  680  are provided similarly to the configurations described with reference to  FIG.  2    and  FIG.  3   , the reflective member  690  will be described in detail below. 
     The reflective member  690  is installed inside the optical path D. The reflective member  690  is provided with a material that reflects the light. The reflective member  690  may be installed in the first path D 1 . The reflective member  690  may be installed at a point at which the first path D 1  and the second path D 2  meet. For example, the reflective member  690  may be installed on a side of the first path D 1  at a point at which the first path D 1  and the second path D 2  meet. 
     The reflective member  690  reflects the light incident into the first path D 1  through the transparent cover  620  toward the second path D 2 . The reflective member  690  may be formed so that a top end and a bottom end are generally inclined. The top end of the reflective member  690  may be formed to be downwardly inclined toward the second path D 2 . An inclination of an inner part of the reflective member  690  adjacent to a side of the first path D 1  may be greater than an inclination of the other side of the reflective member  690 . Accordingly, the light emitted from the first plasma P 1  incident above the first path D 1  may flow to the view port  515  through the second path D 2  by the reflective member  690 . 
     The bottom end of the reflective member  690  may be formed to be upwardly inclined toward the second path D 2 . An inclination of the inner part of the reflective member  690  adjacent to a side of the first path D 1  may be greater than an inclination of the other side of the reflective member  690 . Accordingly, the light emitted from the second plasma P 2  incident from the bottom part of the first path D 1  may flow to the view port  515  through the second path D 2  by the reflective member  690 . 
       FIG.  5    schematically illustrates a first plasma treating step in a substrate treating method according to an embodiment of the inventive concept. Hereinafter, a first plasma treating step according to an embodiment of the inventive concept will be described in detail with reference to  FIG.  5   . The first plasma treating step S 100  to be described below is not related to the second plasma treating step S 200  to be described later. For convenience of description, the first plasma treating step S 100  and the second plasma treating step S 200  may be defined, and the second plasma treating step S 200  may be performed after the first plasma treating step S 100 , the first plasma treating step S 100  may be performed after the second plasma treating step S 200 , or the first plasma treating step S 100  may be performed simultaneously with the first plasma step S 200 . 
     Referring to  FIG.  5   , the substrate treating method according to an embodiment of the inventive concept may perform the first plasma treating step S 100 . The first plasma treating step S 100  is a step of treating the substrate W with a first plasma P 1 . In the first plasma treating step S 100 , the first gas supply unit  551  supplies a first gas G 1  to the plasma space A 1  through the first gas channel  549 . The first gas G 1  supplied to the plasma space A 1  is excited to the first plasma P 1  by the grounded plate  530  and the top electrode  540  to which the first high frequency power is applied. That is, as the first gas G 1  is transferred to the first plasma P 1 , ions, electrons, and radicals are decomposed. 
     The first plasma P 1  flows from the plasma space A 1  to the treating space A 2  through the through hole  532  of the plate  530 . In the first plasma P 1 , ions and electrons in the components of the first plasma P 1  are absorbed in the process of passing through the through hole  532 . Accordingly, only radicals among the components included in the first plasma P 1  flow into the treating space A 2 . 
     In addition, in the first plasma treating step S 100 , the second gas supply unit  555  supplies the second gas G 2  to the treating space A 2 . The radicals moved to the treating space A 2  are mixed with the second gas G 2  supplied to the treating space A 2  to generate a reaction gas in the treating space A 2 . The reaction gas may react with the substrate W positioned in the treating space A 2  to remove a natural oxide layer of the substrate W. In an embodiment, a fluorine radical (F*) moved to the treating space A 2  may be mixed with an NH 3  and/or an H 2 , which is an embodiment of the second gas G 2 , to generate the reaction gas of an NH 4 F.HF (ammonium hydrogen fluoride) and/or an NH 4 F (ammonium fluoride) in the treating space A 2 . 
       FIG.  6    illustrates a state in which the light emitted from the first plasma is incident on the optical path in the first plasma treating step of  FIG.  5   .  FIG.  7    schematically illustrates a state in which the light incident on the optical path of  FIG.  6    flows inside the optical path. Hereinafter, a mechanism in which the light flowing inside an optical path moves to a view port by a monitoring unit will be described in detail with reference to  FIG.  6    and  FIG.  7   . 
     As described above, the first gas G 1  supplied by the first gas supply unit  551  to the plasma space A 1  is excited to generate the first plasma P 1  in the plasma space A 1  by the plate  530  and the top electrode  540 . The light emitted from the first plasma P 1  is incident into the optical path D. Hereinafter, for convenience of description, the light emitted from the first plasma P 1  is defined as a first light L 1 . In addition, the first light L 1  is defined as consisting of a first polarization L 11  vibrating in the first direction and a second polarization L 12  vibrating in the second direction, which is different from the first direction. In addition, the polarizing plate  640  is defined as having the same direction as the first direction, which is a vibration direction of the first polarization L 11 . 
     Referring to  FIGS.  6  and  7   , the first light L 1  is incident into the first path D 1  through the transparent cover  620  installed at a top end of the first path D 1 . The first light L 1  flows through the first path D 1 , and is incident on the polarizing plate  640  at a point at which the first path D 1  and the second path D 2  meet each other. The first light D 1  incident on the polarizing plate  640  passes through the polarizing plate  640  in the first direction according to the polarizing direction in the first direction. Accordingly, the first polarization L 11  flows from the top end to the bottom end of the first path D 1 . The first polarization L 11  passes through the transparent cover  620  installed at the bottom end of the first path D 1  and exits to the treating space A 2 . 
     In addition, among the first light L 1  incident on the polarizing plate  640 , the second polarization L 12  having a component in the second direction is reflected from the polarizing plate  640  according to a polarization direction in the first direction formed on the polarizing plate  640 . Since the polarizing plate  640  is formed to be inclined so that light incident on the first path D 1  is directed toward the second path D 2 , the reflected second polarization L 12  flows toward the second path D 2 . The second polarization L 12  incident on the second path D 2  is incident on the view port  515 , and the operator can observe the characteristics of the first plasma P 1  through the view port  515 . 
       FIG.  8    schematically illustrates a second plasma treating step in the substrate treating method according to an embodiment of the inventive concept. The second plasma treating step S 200  according to an embodiment of the inventive concept is a step of treating the substrate W with the second plasma P 2 . In the second plasma treating step S 200 , the second gas supply unit  555  supplies the second gas G 2  to the treating space A 2  through the second gas channel  539 . The second gas G 2  supplied to the treating space A 2  is excited to the second plasma P 2  by the grounded plate  530  and the bottom electrode  528  to which the second high frequency power is applied. The second plasma P 2  flowing through the treating space A 2  may act on the substrate W. The second plasma P 2  acting on the substrate W may contribute to a surface modification of the substrate. In an embodiment, the H ions included in the second plasma P 2  may weaken a bond between an Si and an O formed in the substrate W. 
       FIG.  9    illustrates a state in which the light emitted from the second plasma is incident on the optical path in the second plasma treating step of  FIG.  8   .  FIG.  10    schematically illustrates a state in which the light incident on the optical path of  FIG.  9    flows inside the optical path.  FIG.  11    is a view schematically showing a shape of light flowing in the second path by changing a direction of polarization and the optical path by a refractive member among the light flowing in the optical path of  FIG.  10   . 
     As described above, the second gas G 2  supplied by the second gas supply unit  555  to the treating space A 2  is excited to generate the second plasma P 2  in the treating space A 2  by the plate  530  and the bottom electrode  528 . The light emitted from the second plasma P 2  is incident into the optical path D. Hereinafter, for convenience of description, the light emitted from the second plasma P 2  is defined as the second light L 2 . In addition, the first light L 2  is defined as consisting of a first polarization L 21  vibrating in the first direction and a second polarization L 22  vibrating in the second direction, which is different from the first direction. In addition, the polarizing plate  640  is defined as having the same direction as the first direction, which is the vibration direction of the first polarization L 21 . 
     Referring to  FIGS.  9  and  10   , the second light L 2  is incident into the first path D 1  through the transparent cover  620  installed at the bottom end of the first path D 1 . The second light L 2  flows through the first path D 1 , and is incident on the polarizing plate  640  at a point at which the first path D 1  and the second path D 2  meet each other. The second light L 2  incident on the polarizing plate  640  passes through the polarizing plate  640  along the polarizing direction in the first direction, and the first polarization L 21  having a component in the first direction passes through the polarizing plate  640 . Accordingly, the first polarization L 21  flows from a bottom end to a top end of the first path D 1 . The first polarization L 21  passes through the transparent cover  620  installed on the top end of the first path D 1  and exits to the plasma space A 1 . 
     Referring to  FIG.  10    and  FIG.  11   , among the second light L 2  incident on the polarizing plate  640 , the second polarization L 22  having a component in the second direction is reflected from the polarizing plate  640  in the first direction. Since the polarizing plate  640  is inclined so that the light incident from the top of the first path D 1  toward the bottom of the second path D 2 , the second polarizing wave L 22  having a second direction component incident from the bottom of the first path D 1  is reflected from the polarizing plate  640  toward the refracting member  660 . The second polarization L 22  incident on the refractive member  660  changes the characteristics of the polarization so as to vibrate in the first direction by the refractive member  660 . The second polarization L 22 ″ in which the characteristics (wavelength or vibration) of the polarization are changed flows from the refractive member  660  toward the second path D 2 . Accordingly, the second polarization L 22 ′ whose polarization characteristics have changed is incident on the view port  515  through the second path D 2 , and the operator can observe the characteristics of the second plasma P 2  through the view port  515 . 
     According to an embodiment of the inventive concept described above, by installing the monitoring unit  600  capable of observing the plasma on the plate  530 , the first plasma P 1  generated above the plate  530  and the second plasma P 2  generated from below the plate  530  may be observed by the monitoring unit  600 . Accordingly, it is possible to realize an effect of observing a plurality of plasma generated at different positions with different characteristics. 
     In addition, according to one embodiment of the inventive concept, by placing the monitoring unit  600  inside the plate  530  which is relatively less affected by the electric field, it is possible to minimize an interference of an observing of the plasma due to a deposition of process by-products or particles on the monitoring unit  600 . In addition, since the optical path D in which the monitoring unit  600  is formed is sealed by the transparent cover  620 , the plasma can be prevented from penetrating the optical path D, thereby forming an environment in which the plasma can be observed efficiently. 
     In addition, according to an embodiment of the inventive concept, by forming the optical path D inside an existing plate  530  and placing the monitoring unit  600  for observing the plasma on the optical path D, multiple plasma having different characteristics can be observed without additional structural changes. Accordingly, it is possible to increase an efficiency of a substrate W treatment due to a change in the characteristics of the plasma. 
     In an embodiment of the inventive concept described above, it has been described that the polarizing plate  640  is formed to be downwardly inclined toward the second path D 2 , but is not limited thereto. In an embodiment, the polarizing plate  640  may be formed to be upwardly inclined toward the second path D 2 . In this case, a mechanism of observing the characteristics of the first plasma P 1  in the mechanism of the monitoring unit  600  may be changed to a mechanism of observing the characteristics of the second plasma P 2 , and the mechanism of the monitoring unit  600  may be changed to a mechanism of observing the characteristics of the first plasma P 1 . 
     In addition, according to an embodiment of the inventive concept described above, the monitoring unit  600  includes a light receiving member  680 , but the light incident on the second path D 2  can immediately move to the view port  515  through the sidewall of the housing  510 . 
       FIG.  12    schematically illustrates a state in which the light emitted from the first plasma flows inside an optical path by the monitoring unit of  FIG.  4   .  FIG.  13    schematically illustrates a state in which the light emitted from the second plasma flows inside the optical path by the monitoring unit of  FIG.  4   . Hereinafter, a plasma observation mechanism by the monitoring unit of  FIG.  4    will be described in detail with reference to  FIG.  12    and  FIG.  13   . 
     Referring to  FIG.  12   , the first light L 1  emitted from the first plasma P 1  in the plasma space A 1  passes through the transparent cover  620  and is incident into the first path D 1 . The first light L 1  incident on the first path D 1  reaches the reflective member  690  provided at a point at which the first path D 1  and the second path D 2  intersect each other. The first light L 1  is incident on a top end of the reflective member  690  and is reflected to the second path D 2 . The first light L 1  reflected by the second path D 2  is incident on the view port  515  through the second path D 2 . Accordingly, the operator may observe the characteristics of the first plasma P 1  generated in the plasma space A 1  from the first light L 1 . 
     Referring to  FIG.  13   , the second light L 2  emitted from the second plasma P 2  in the treating space A 2  is incident into the first path D 1  via the transparent cover  620 . The second light L 2  incident on the second path D 2  reaches the reflective member  690  provided at a point at which the first path D 1  and the second path D 2  intersect each other. The second light L 2  is incident on a bottom end of the reflective member  690  and reflected to the second path D 2 . The second light L 2  reflected by the second path D 2  is incident on the view port  515  through the second path D 2 . Accordingly, the operator may observe the characteristics of the second plasma P 2  generated in the treating space A 2  from the second light L 2 . 
     The effects of the inventive concept are not limited to the above-mentioned effects, and the unmentioned effects can be clearly understood by those skilled in the art to which the inventive concept pertains from the specification and the accompanying drawings. 
     Although the preferred embodiment of the inventive concept has been illustrated and described until now, the inventive concept is not limited to the above-described specific embodiment, and it is noted that an ordinary person in the art, to which the inventive concept pertains, may be variously carry out the inventive concept without departing from the essence of the inventive concept claimed in the claims and the modifications should not be construed separately from the technical spirit or prospect of the inventive concept.