Patent Publication Number: US-2022223382-A1

Title: Substrate processing apparatus and cleaning method

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority to and incorporates by reference the entire contents of Japanese Patent Application No. 2021-002526 filed in Japan on Jan. 12, 2021, the entire contents of which are incorporated herein by reference. 
     FIELD 
     The present disclosure relates to a substrate processing apparatus and a cleaning method. 
     BACKGROUND 
     United States Patent Application Publication No. 2019/0218663 discloses an approach to form a film on a surface of a component and remove the film so as to execute cleaning thereof. 
     The present disclosure provides a technique that removes a deposition substance in an exhaust space efficiently. 
     SUMMARY 
     According to an aspect of a present disclosure, a substrate processing apparatus includes: a chamber where a stage that places a substrate that is provided as a target for substrate processing is provided in an inside thereof and an exhaust port that discharges a gas in an inside thereof is formed at a position that is lower than that of the stage around the stage; a baffle plate that is provided around the stage and divides an inside of the chamber into a processing space where substrate processing is executed for the substrate and an exhaust space that includes the exhaust port; an ejection port that is arranged to eject a gas to the exhaust space; and a gas supply unit that supplies a cleaning gas that reacts with a product that is produced in the exhaust space to the ejection port. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram that illustrates an example of schematic configuration of a plasma processing apparatus according to an embodiment. 
         FIG. 2  is a diagram that illustrates an example of arrangement of gas ejection ports according to an embodiment. 
         FIG. 3  is a diagram that illustrates an example of a flow of a cleaning gas according to an embodiment. 
         FIG. 4  is a diagram that illustrates another example of arrangement of gas ejection ports according to an embodiment. 
         FIG. 5A  is a diagram that illustrates another example of arrangement of gas ejection ports according to an embodiment. 
         FIG. 5B  is a diagram that illustrates another example of arrangement of gas ejection ports according to an embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments of a substrate processing apparatus and a cleaning method as disclosed in the present application will be explained in detail with reference to the drawings. Additionally, a substrate processing apparatus and a cleaning method as disclosed therein are not limited by the present embodiments. 
     A substrate processing apparatus has been known that depressurizes an inside of a chamber thereof and executes substrate processing such as plasma processing for a substrate. A substrate processing apparatus is frequently provided in such a manner that a stage that places a substrate thereon is provided at a center of a chamber and an exhaust port is formed near an end of a bottom surface of the chamber, in view of a space limitation and/or a maintenance characteristic. In such a substrate processing apparatus, in a case where a gas is discharged from an exhaust port so as to depressurize an inside of a chamber, a deviation of an exhaust characteristic is caused. Hence, in a plasma processing apparatus, a baffle plate is provided around a stage so as to homogenize an exhaust characteristic. 
     Meanwhile, in a substrate processing apparatus, a deposition substance is deposited in a chamber. For example, in a plasma processing apparatus, a deposition substance is deposited in a processing space where substrate processing is executed in a chamber, where such a deposition substance is also readily deposited in an exhaust space that is provided on a side of an exhaust port relative to a baffle plate in the chamber. For a technique that removes such a deposition substance, in Patent Literature 1, a film is formed on a surface of a component and such a film is removed so as to execute cleaning. However, formation of a film and removal of the film have to be executed for cleaning, and further, it is impossible to remove a deposition substance in an exhaust space efficiently. 
     Hence, a technique that removes a deposition substance in an exhaust space efficiently is expected. 
     EMBODIMENTS 
     Apparatus Configuration 
     An example of a substrate processing apparatus in the present disclosure will be explained. In an embodiment, a case where a substrate processing apparatus in the present disclosure is provided as a plasma processing apparatus that executes plasma processing such as plasma etching will be explained as an example.  FIG. 1  is a diagram that illustrates an example of a schematic configuration of a plasma processing apparatus  1  according to an embodiment. 
     A configuration example of a capacitively coupled plasma processing apparatus as an example of the plasma processing apparatus  1  will be explained below. A capacitively coupled plasma processing apparatus  1  includes a plasma processing chamber  10 , a gas supply unit  20 , a power source  30 , and an exhaust system  40 . Furthermore, the plasma processing apparatus  1  includes a substrate supporting unit  11  and a gas introduction unit. The gas introduction unit is configured to introduce at least one processing gas into the plasma processing chamber  10 . The gas introduction unit includes a shower head  13 . The substrate supporting unit  11  is arranged inside the plasma processing chamber  10 . The shower head  13  is arranged above the substrate supporting unit  11 . In an embodiment, the shower head  13  composes at least a part of a top part (ceiling) of the plasma processing chamber  10 . The plasma processing chamber  10  has a plasma processing space  10   s  that is defined by the shower head  13 , a side wall  10   a  of the plasma processing chamber  10 , and the substrate supporting unit  11 . The side wall  10   a  is grounded. The shower head  13  and the substrate supporting unit  11  are electrically insulated from a housing of the plasma processing chamber  10 . 
     The substrate supporting unit  11  includes a body unit  111  and a ring assembly  112 . The body unit  111  has a central area (substrate supporting surface)  111   a  for supporting a substrate (wafer) W and a ring area (ring supporting surface)  111   b  for supporting the ring assembly  112 . The ring area  111   b  of the body unit  111  surrounds the central area  111   a  of the body unit  111  in a plan view. A substrate W is arranged on the central area  111   a  of the body unit  111  and the ring assembly  112  is arranged on the ring area  111   b  of the body unit  111  so as to surround such a substrate W on the central area  111   a  of the body unit  111 . In an embodiment, the body unit  111  includes a base and an electrostatic chuck. The base includes a conductive member. The conductive member of the base functions as a lower electrode. The electrostatic chuck is arranged on the base. An upper surface of the electrostatic chuck has the substrate supporting surface  111   a . The ring assembly  112  includes one or more ring members. At least one of the one or more ring members is an edge ring. Furthermore, the substrate supporting unit  11  may include a temperature regulation module that is configured to regulate at least one of the electrostatic chuck, the ring assembly  112 , and a substrate at a target temperature, although illustration thereof is omitted. The temperature regulation module may include a heater, a heat transfer medium, a flow channel, or a combination thereof. A heat transfer fluid such as brine and/or a gas flows through the flow channel. Furthermore, the substrate supporting unit  11  may include a heat transfer gas supply unit that is configured to supply a heat transfer gas between a back surface of a substrate W and the substrate supporting surface  111   a.    
     The shower head  13  is configured to introduce at least one processing gas from the gas supply unit  20  into the plasma processing space  10   s . The shower head  13  has at least one gas supply port  13   a , at least one gas diffusion room  13   b , and a plurality of gas introduction ports  13   c . A processing gas that is supplied to a gas supply port  13   a  passes through a gas diffusion room  13   b  and is introduced from the plurality of gas introduction ports  13   c  into the plasma processing space  10   s . Furthermore, the shower head  13  includes a conductive member. The conductive member of the shower head  13  functions as an upper electrode. Additionally, the gas introduction unit may include one or more side gas injection units (SGI: Side Gas Injector) that are attached to one or more openings that are formed on the side wall  10   a , in addition to the shower head  13 . 
     The gas supply unit  20  may include at least one gas source  21  and at least one flow volume controller  22 . In an embodiment, the gas supply unit  20  is configured to supply at least one processing gas from a gas source  21  that corresponds thereto to the shower head  13  through a flow volume controller  22  that corresponds thereto. Each flow volume controller  22  may include, for example, a mass flow controller or a pressure control type flow volume controller. Moreover, the gas supply unit  20  may include at least one flow volume modulation device that modulates, or provides pulses of, a flow volume of at least one processing gas. 
     The power source  30  includes an RF power source  31  that is coupled to the plasma processing chamber  10  through at least one impedance matching circuit. The RF power source  31  is configured to supply at least one RF signal (RF power) such as a source RF signal and a bias RF signal to the conductive member of the substrate supporting unit  11  and/or the conductive member of the shower head  13 . Thereby, plasma is formed from at least one processing gas that is supplied to the plasma processing space  10   s . Therefore, it is possible for the RF power source  31  to function as at least a part of a plasma production unit  12 . Furthermore, a bias potential is generated at a substrate W by supplying a bias RF signal to the conductive member of the substrate supporting unit  11 , so that it is possible to attract an ionic component in formed plasma to such a substrate W. 
     In an embodiment, the RF power source  31  includes a first RF production unit  31   a  and a second RF production unit  31   b . The first RF production unit  31   a  is configured to be coupled to the conductive member of the substrate supporting unit  11  and/or the conductive member of the shower head  13  through the at least one impedance matching circuit and produce a source RF signal (source RF power) for plasma production. In an embodiment, a source RF signal has a frequency within a range of 13 MHz to 150 MHz. In an embodiment, the first RF production unit  31   a  may be configured to produce a plurality of source RF signals that have different frequencies. One or more produced source RF signals are supplied to the conductive member of the substrate supporting unit  11  and/or the conductive member of the shower head  13 . The second RF production unit  31   b  is configured to be coupled to the conductive member of the substrate supporting unit  11  through the at least one impedance matching circuit and produce a bias RF signal (bias RF power). In an embodiment, a bias RF signal has a frequency that is lower than that of a source RF signal. In an embodiment, a bias RF signal has a frequency within a range of 400 kHz to 13.56 MHz. In an embodiment, the second RF production unit  31   b  may be configured to produce a plurality of bias RF signals that have different frequencies. One or more produced bias RF signals are supplied to the conductive member of the substrate supporting unit  11 . Furthermore, in a variety of embodiments, pulses of at least one of a source RF signal and a bias RF signal may be provided. 
     Furthermore, the power source  30  may include a DC power source  32  that is coupled to the plasma processing chamber  10 . The DC power source  32  includes a first DC production unit  32   a  and a second DC production unit  32   b . In an embodiment, the first DC production unit  32   a  is configured to be connected to the conductive member of the substrate supporting unit  11  and produce a first DC signal. A produced first DC signal is applied to the conductive member of the substrate supporting unit  11 . In an embodiment, a first DC signal may be applied to another electrode such as an electrode in the electrostatic chuck. In an embodiment, the second DC production unit  32   b  is configured to be connected to the conductive member of the shower head  13  and produce a second DC signal. A produced second DC signal is applied to the conductive member of the shower head  13 . In a variety of embodiments, pulses of first and second DC signals may be provided. Additionally, the first and second DC production units  32   a ,  32   b  may be provided in addition to the RF power source  31  or the first DC production unit  32   a  may be provided instead of the second RF production unit  31   b.    
     The plasma processing chamber  10  is formed into a hollow cylindrical shape where a space is formed in an inside thereof and the substrate supporting unit  11  as described above is arranged at a center of an inside thereof. A substrate W that is formed into a solid cylindrical shape and provided as a target for substrate processing is placed on the substrate supporting unit  11 . Furthermore, a gas discharge port  10   e  that discharges a gas in an inside thereof is formed on the plasma processing chamber  10  at a position that is lower than that of the substrate supporting unit  11  around the substrate supporting unit  11 . In the plasma processing apparatus  1  according to an embodiment, the gas discharge port  10   e  is formed on a bottom part of the plasma processing chamber  10 . 
     It is possible to provide, for example, the exhaust system  40  that is connected to the gas discharge port  10   e  that is provided on a bottom part of the plasma processing chamber  10 . The exhaust system  40  may include a pressure regulation valve and a vacuum pump. A pressure in the plasma processing space  10   s  is regulated by the pressure regulation valve. The vacuum pump may include a turbo-molecular pump, a dry pump, or a combination thereof. 
     In the plasma processing chamber  10 , a baffle plate  14  is provided around the substrate supporting unit  11 . The baffle plate  14  is provided with a flat ring shape. In the baffle plate  14  according to an embodiment, flat planar surfaces are formed on an inner peripheral side and an outer peripheral side thereof and a step is formed in such a manner that the outer peripheral side is higher than the inner peripheral side. Additionally, the baffle plate  14  may be formed of a planar surface with no step. The baffle plate  14  is arranged so as to surround a periphery of the substrate supporting unit  11 . In the baffle plate  14 , the inner peripheral side is fixed on the substrate supporting unit  11  and the outer peripheral side is fixed on an inner side wall of the plasma processing chamber  10 . Multiple slits and/or holes are formed on the baffle plate  14 , so that a gas is capable of passing therethrough. The baffle plate  14  divides an inside of the plasma processing chamber  10  into the plasma processing space  10   s  that is a processing space where substrate processing is executed for a substrate W and an exhaust space  10   t  that includes the gas discharge port  10   e . The plasma processing space  10   s  is a space on an upstream side of the baffle plate  14  relative to a flow of an exhaust gas to the gas discharge port  10   e . The exhaust space  10   t  is a space on a downstream side of the baffle plate  14  relative to a flow of an exhaust gas to the gas discharge port  10   e.    
     In the plasma processing chamber  10 , a gas ejection port  15  is provided in the exhaust space  10   t . In an embodiment, the gas ejection port  15  is provided on an upstream side of the exhaust space  10   t  relative to a flow of an exhaust gas to the gas discharge port  10   e . For example, the gas ejection port  15  is provided on an inner side wall of the plasma processing chamber  10  below the baffle plate  14 . A plurality of gas ejection ports  15  are provided on an inner side wall of the plasma processing chamber  10  so as to be oriented in a peripheral direction thereof. 
       FIG. 2  is a diagram that illustrates an example of arrangement of gas ejection ports  15  according to an embodiment.  FIG. 2  is a top view of an inside of a plasma processing chamber  10 . A substrate supporting unit  11  with a circular shape is arranged at a center of an inside of the plasma processing chamber  10 . A plurality of gas ejection ports  15  are provided on an inner side wall of the plasma processing chamber  10  at a predetermined intervals so as to be oriented in a peripheral direction thereof. Additionally, each gas ejection port  15  is oriented in a certain direction. Furthermore, as an orientation thereof in a certain direction is attained, such a direction is not limiting where a clockwise direction may be provided as illustrated in  FIG. 2  or a counterclockwise direction may be provided in an opposite manner. 
       FIG. 1  is returned to. Each gas ejection port  15  is connected to the gas supply unit  20 . The gas supply unit  20  supplies a gas to each gas ejection port  15 . For example, the gas supply unit  20  supplies a cleaning gas for cleaning to each gas ejection port  15 . The gas supply unit  20  is provided so as to be capable of controlling a flow volume of a gas that is supplied to each gas ejection port  15 . In an embodiment, the gas supply unit  20  is connected to respective gas ejection ports  15  separately by respective pipes  24 . Flow volume controllers  25  are respectively provided on the respective pipes  24 . The gas supply unit  20  is configured to supply a cleaning gas from respective corresponding gas sources  21  to the respective gas ejection ports  15  through respective corresponding flow volume controllers  25 . The gas supply unit  20  controls a flow volume of a gas by the flow volume controllers  25 , so that it is possible to control a flow volume of a gas that is supplied to each gas ejection port  15 . Additionally, a structure may be provided in such a manner that a flow volume of a gas is controlled by one flow volume controller  25  and the gas is distributed to the respective pipes  24  separately. Furthermore, a structure may be provided in such a manner that a gas is delivered from one flow volume controller  25  through one pipe  24  and the gas is distributed just in front of the respective gas ejection ports  15 . 
     Meanwhile, in the plasma processing apparatus  1 , although a deposition substance is deposited in the plasma processing space  10   s  where substrate processing is executed in the plasma processing chamber  10  as described above, a deposition substance is also readily deposited in the exhaust space  10   t  that is provided on a side of the gas discharge port  10   e  of the baffle plate  14  in the plasma processing chamber  10 . Such a deposition substance includes a product that is produced by plasma processing, ash that is provided by heat, or the like. 
     Hence, a deposition substance in the exhaust space  10   t  is removed by a cleaning process in a cleaning method according to an embodiment. The plasma processing apparatus  1  according to an embodiment executes a cleaning process that removes a deposition substance in the exhaust space  10   t . A timing when a cleaning process is executed may be any timing during substrate processing. For example, the plasma processing apparatus  1  may execute a cleaning process simultaneously with plasma processing such as plasma etching. Furthermore, the plasma processing apparatus  1  may execute substrate processing for a certain number of a substrates W and subsequently execute a process that recovers a state of an inside of the plasma processing chamber  10  by dry cleaning or the like. For example, the plasma processing apparatus  1  executes dry cleaning that cleans the plasma processing space  10   s  on an upstream side of the baffle plate  14 . The plasma processing apparatus  1  may execute a cleaning process in a cleaning method according to an embodiment during dry cleaning for the plasma processing space  10   s  or subsequent to such dry cleaning. Furthermore, the plasma processing apparatus  1  may alternately execute dry cleaning for the plasma processing space  10   s  and a cleaning process in a cleaning method according to an embodiment multiple times. 
     Dry cleaning may be executed by placing a dummy substrate on the substrate supporting unit  11  in order to protect a surface of the substrate supporting unit  11 . Even in a cleaning process in a cleaning method according to an embodiment, particles that flows back above the baffle plate  14  are present more than slightly, so that it is desirable to place a dummy substrate on the substrate supporting unit  11  and execute it. 
     In a case where a cleaning process in a cleaning method according to an embodiment is executed, the plasma processing apparatus  1  controls the gas supply unit  20  so as to supply a cleaning gas from the gas supply unit  20  to the plurality of gas ejection ports  15  and eject such a cleaning gas from the gas ejection ports  15 . 
     A cleaning gas may be provided as plasma and ejected from a gas ejection port  15 . For example, a plasma generation unit such as a plasma source that provides a gas as plasma may be provided on a pipe  24  so as to provide a cleaning gas as plasma and eject an active species of a cleaning gas provided as plasma from a gas ejection port  15 . A cleaning gas may be provided as plasma in the plasma processing chamber  10 . For example, a parallel plate type electrode for plasma generation and/or an antenna coil for inductively-coupled-type plasma may be installed below the baffle plate  14  so as to provide a cleaning gas that is ejected from a gas ejection port  15  as plasma in the plasma processing chamber  10 . 
     A cleaning gas may be any gas species that is capable of removing a deposition substance. For example, in a case where a deposition substance is an organic product that is produced from an etching gas at a time of an etching process for a substrate W, it is possible to provide an oxygen-containing gas such as O 2 , O 3 , CO, or CO 2  as a cleaning gas. An O 3  gas) is a gas with a high reactivity even if plasma is not used. Furthermore, in a case where a deposition substance is an organic film that includes a metal such as W (tungsten) or Ti (titanium), it is possible to provide an oxygen-containing gas such as O 2 , CO, O 3 , or CO 2 , a gas where a halogen-containing gas such as CF 4  or Cl 2  is added to an oxygen-containing gas, an F 2  gas, and/or a ClF 2  gas as a cleaning gas. An F 2  gas or a ClF 2  gas is a gas with a high reactivity even if plasma is not used. Furthermore, a deposition substance is a deposition substance in metal etching such as Ru (ruthenium), cobalt (Co), or iron (Fe), it is possible to provide a methanol (CH 3 OH) gas as a cleaning gas. Furthermore, multiple types of gasses may be switched and supplied as cleaning gasses. In a case where a deposition substance is a laminated film of a plurality of products and/or organic films, it is sufficient to select a gas species depending on a type of a film that is exposed to an outermost surface of a laminated film and supply it as a cleaning gas. In a case where a cleaning process is executed simultaneously with a plasma process where a plurality of step processes where reaction products that are provided as deposition substances are different are executed, cleaning gasses may be switched for each step process. 
     Each gas ejection port  15  is provided on an inner side wall of the plasma processing chamber  10  so as to be oriented in a peripheral direction thereof. Each gas ejection port  15  ejects a cleaning gas toward a peripheral direction of the plasma processing chamber  10 .  FIG. 3  is a diagram that illustrates an example of a flow of a cleaning gas according to an embodiment. A cleaning gas that is ejected from each gas ejection port  15  swirls along an inner wall of a plasma processing chamber  10  in a peripheral direction thereof. Thus, a cleaning gas swirls along an inner wall of the plasma processing chamber  10  so as to increase a period of time when such a cleaning gas contacts the inner wall of the plasma processing chamber  10 , so that it is possible to remove a deposition substance in an exhaust space efficiently. Furthermore, a cleaning gas is ejected from each gas ejection port  15 , so that it is possible to generate a swirling flow that is a fast flow along an inner wall of the plasma processing chamber  10  and it is possible to remove a deposition substance that is attached to the inner wall of the plasma processing chamber  10  by such a swirling flow efficiently. 
     Additionally, although a case where the gas ejection port  15  is provided on an inner side wall of the plasma processing chamber  10  below the baffle plate  14  has been explained as an example in an embodiment as described above, this is not limiting. The gas ejection port  15  may be provided anywhere in the exhaust space  10   t . For example, the gas ejection port  15  may be provided on each of an upstream side and a downstream side of the exhaust space  10   t  relative to a flow of an exhaust gas to the gas discharge port  10   e .  FIG. 4  is a diagram that illustrates another example of arrangement of gas ejection ports  15  according to an embodiment.  FIG. 4  is a side view of an inside of a plasma processing chamber  10 . In  FIG. 4 , a gas ejection port  15  is provided on each of an inner side wall of the plasma processing chamber  10  below a baffle plate  14  and a peripheral part of a bottom surface of the plasma processing chamber  10 . Each gas ejection port  15  is arranged so as to be oriented in a peripheral direction of the plasma processing chamber  10 . Thereby, it is possible to generate a swirling flow of a cleaning gas along an inner wall of the plasma processing chamber  10  on each of an upstream side and a downstream side of an exhaust space  10   t , so that it is possible to remove a deposition substance that is attached to the inner wall of the plasma processing chamber  10  by such a swirling flow efficiently. Furthermore, a cleaning gas may be ejected simultaneously from each of an upstream side and a downstream side of the exhaust space  10   t , a cleaning gas may be ejected from at least one of the upstream side and the downstream side and subsequently be switched to another side, or ejection thereof may be executed alternately therebetween. Furthermore, the gas ejection port  15  may be arranged on one of an upstream side and a downstream side of the exhaust space  10   t  relative to a flow of an exhaust gas to a gas discharge port  10   e.    
     Furthermore, although a case where each gas ejection port  15  is arranged so as to be oriented in a peripheral direction of the plasma processing chamber  10  so as to cause a cleaning gas to swirl along an inner wall of the plasma processing chamber  10  in the peripheral direction thereof has been explained as an example in an embodiment as described above, this is not limiting. Each gas ejection port  15  may be arranged so as to be oriented toward a downstream side relative to a flow of an exhaust gas to the gas discharge port  10   e  along an inner side wall of the plasma processing chamber  10 .  FIG. 5A  and  FIG. 5B  are diagrams that illustrate another example of arrangement of gas ejection ports  15  according to an embodiment.  FIG. 5A  is a side view of an inside of a plasma processing chamber  10 .  FIG. 5B  is a top view of an inside of the plasma processing chamber  10 . In  FIG. 5A  and  FIG. 5B , a gas ejection port  15  is provided on an inner side wall of the plasma processing chamber  10  below a baffle plate  14 . Each gas ejection port  15  is arranged along a peripheral direction of the plasma processing chamber  10 . A cleaning gas that is ejected from each gas ejection port  15  flows in a downward direction along an inner wall of the plasma processing chamber  10 , so that a curtain-like downward flow of such a cleaning gas is generated on the inner wall of the plasma processing chamber  10 . Whereas, in general, in a case where a gas flows in a space, a speed of a gas around an inner wall in the space is less than a speed of a gas that flows at a central part of the space, a cleaning gas is ejected along an inner wall of the plasma processing chamber  10  in a practical example as described above, so that it is possible to generate a flow of a gas that is fast even around the inner wall of the plasma processing chamber  10 . Thereby, it is possible to remove a deposition substance that is attached to an inner wall of the plasma processing chamber  10  efficiently. A curtain-like cleaning gas flows on an inner wall of the plasma processing chamber  10 , so that it is possible to prevent a deposition substance from being readily attached to the inner wall of the plasma processing chamber  10 . Additionally, although each gas ejection port  15  is arranged so as to be oriented toward a downstream side, it does not have to be perpendicular to the gas discharge port  10   e  or may be arranged so as to be oriented obliquely relative to the downstream side. Thereby, it is also possible to generate a swirling flow. 
     As provided above, a plasma processing apparatus  1  according to an embodiment has a plasma processing chamber  10  (a chamber), a baffle plate  14 , a gas ejection port  15  (an ejection port), and a gas supply unit  20 . In the plasma processing chamber  10 , a substrate supporting unit  11  (a stage) that places a substrate W that is provided as a target for substrate processing is provided in an inside thereof and a gas discharge port  10   e  (an exhaust port) that discharges a gas in an inside thereof is formed at a position that is lower than that of the substrate supporting unit  11  around the substrate supporting unit  11 . The baffle plate  14  is provided around the substrate supporting unit  11  and divides an inside of the plasma processing chamber  10  into a plasma processing space  10   s  (a processing space) where substrate processing is executed for the substrate W and an exhaust space  10   t  that includes the gas discharge port  10   e . The gas ejection port  15  is arranged so as to eject a gas to the exhaust space  10   t . The gas supply unit  20  supplies a cleaning gas that reacts with a product that is produced in the exhaust space  10   t  to the gas ejection port  15 . Thereby, it is possible for the plasma processing apparatus  1  to remove a deposition substance in the exhaust space  10   t  efficiently. 
     Furthermore, the gas ejection port  15  is arranged on at least one of an upstream side and a downstream side of the exhaust space  10   t  relative to a flow of an exhaust gas to the gas discharge port  10   e . Thereby, it is possible for the plasma processing apparatus  1  to remove a deposition substance on each of an upstream side and a downstream side of the exhaust space  10   t  efficiently. 
     Furthermore, the gas ejection port  15  is provided on an inner side wall of the plasma processing chamber  10  below the baffle plate  14 . Thereby, it is possible for the plasma processing apparatus  1  to clean a lower part of the baffle plate  14  where a deposition substance is readily deposited efficiently. 
     Furthermore, a plurality of the gas ejection port  15  are arranged so as to surround a periphery of the substrate supporting unit  11  on an inner side wall of the plasma processing chamber  10  and respectively eject a cleaning gas toward a peripheral direction thereof. Thereby, it is possible for the plasma processing apparatus  1  to generate a swirling flow that is a fast flow along an inner wall of the plasma processing chamber  10 , so that it is possible to remove a deposition substance that is attached to the inner wall of the plasma processing chamber  10  by such a swirling flow efficiently. 
     Furthermore, a plurality of the gas ejection port  15  are arranged so as to surround a periphery of the substrate supporting unit  11  on an inner side wall of the plasma processing chamber  10  and respectively eject a cleaning gas toward a downward direction. Thereby, it is possible for the plasma processing apparatus  1  to generate a curtain-like flow of a cleaning gas on an inner wall of the plasma processing chamber  10 , so that it is possible to remove a deposition substance that is attached to the inner wall of the plasma processing chamber  10  efficiently. 
     Furthermore, the gas supply unit  20  supplies a cleaning gas during dry cleaning in the plasma processing chamber  10  or subsequent to the dry cleaning so as to eject a cleaning gas from the gas ejection port  15 . Thereby, it is possible for the plasma processing apparatus  1  to remove a deposition substance that is attached to an inner wall of the plasma processing chamber  10  at a timing of dry cleaning. 
     Although embodiments have been explained above, it should be considered that embodiments as disclosed herein are not limitative but are illustrative in all aspects. In fact, it is possible to implement embodiments as described above in a variety of forms thereof. Furthermore, embodiments as described above may be omitted, substituted, or modified in a variety of forms thereof, without departing from what is claimed and an essence thereof. 
     For example, although a case where plasma processing is executed for a semiconductor wafer as a substrate W has been explained as an example in an embodiment as described above, this is not limiting. Any substrate W may be provided. 
     Furthermore, although a case where a substrate processing apparatus is provided as the plasma processing apparatus  1  that executes plasma processing has been explained as an example in an embodiment as described above, this is not limiting. A substrate processing apparatus may be any apparatus that executes substrate processing for a substrate W. For example, a substrate processing apparatus may be a film formation apparatus or the like. 
     According to the present disclosure, it is possible to remove a deposition substance in an exhaust space efficiently. 
     Although the invention has been described with respect to specific embodiments for a complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art that fairly fall within the basic teaching herein set forth. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the disclosures. Indeed, the embodiments described herein may be embodied in a variety of other forms. Furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the disclosures. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the disclosures.