Patent Publication Number: US-2017350014-A1

Title: Plasma processing apparatus and plasma processing method

Description:
TECHNICAL FIELD 
     Various aspects and embodiments of the present disclosure relate to a plasma processing apparatus and a plasma processing method. 
     BACKGROUND 
     There is a plasma processing apparatus using excitation of process gas by microwaves. This plasma processing apparatus radiates microwaves for plasma excitation into a processing container using an antenna, and dissociates gas inside the processing container so as to generate plasma. In addition, the plasma processing apparatus supplies the microwaves to the antenna by a coaxial waveguide. 
     However, in the plasma processing apparatus, in order to maintain uniformity of plasma density inside the processing container, it is required to maintain uniformity of distribution of the microwaves radiated from the antenna. In this regard, there has been suggested a technology which regulates the distribution of the microwaves radiated from the antenna by inserting a plurality of stubs into the coaxial waveguide, and individually controlling an insertion amount of the plurality of stubs with respect to the coaxial waveguide. 
     PRIOR ART DOCUMENT 
     Patent Document 
     Patent Document 1: Japanese Patent Publication No. 5440604 
     DISCLOSURE OF THE INVENTION 
     Problems to be Solved 
     However, the conventional technology does not even consider automatically regulating the distribution of the microwaves according to the distribution of the plasma density inside the processing container. 
     Means to Solve the Problems 
     A plasma processing apparatus disclosed herein, in an exemplary embodiment, includes: a processing container that defines a plasma processing space; a holder that is provided inside the processing container to hold a substrate to be processed; a gas supply unit that supplies gas into the plasma processing space; an antenna that radiates microwaves for generating plasma of the gas supplied into the plasma processing space, to the plasma processing space; a coaxial waveguide that supplies the microwaves to the antenna; a plurality of stubs that are inserted into the coaxial waveguide and regulate distribution of the microwaves radiated from the antenna according to an insertion amount; a measuring unit that measures density of the plasma generated in the plasma processing space by the microwaves radiated from the antenna or a parameter having a correlation with the density of the plasma along a circumferential direction of the substrate to be processed; and a controller that individually controls an insertion amount of each of the plurality of stubs used for regulating the distribution of the microwaves, based on the density of the plasma or the parameter. 
     Effect of the Invention 
     According to one aspect of the plasma processing apparatus described herein, it is possible to achieve an effect in which the distribution of the microwaves may be automatically regulated according to the distribution of the plasma density. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional view schematically illustrating a principle part of a plasma processing apparatus according to an exemplary embodiment. 
         FIG. 2  is an enlarged sectional view schematically illustrating the vicinity of a coaxial waveguide provided in the plasma processing apparatus illustrated in  FIG. 1 . 
         FIG. 3  is a view illustrating a slot antenna plate provided in the plasma processing apparatus illustrated in  FIG. 1  when viewed in the direction of arrow III in  FIG. 1 . 
         FIG. 4  is a sectional view illustrating the coaxial waveguide provided in the plasma processing apparatus illustrated in  FIG. 1  which is taken along IV-IV in  FIG. 2 . 
         FIG. 5  is a view illustrating exemplary experimental results for a relationship of distribution of microwaves with an insertion amount and a material of a stub member. 
         FIG. 6  is a flow chart illustrating an exemplary plasma processing method using the plasma processing apparatus according to the exemplary embodiment. 
         FIG. 7  is an enlarged sectional view schematically illustrating the vicinity of a coaxial waveguide provided in a plasma processing apparatus according to another example embodiment. 
         FIG. 8  is a sectional view schematically illustrating a main part of a plasma processing apparatus according to still another exemplary embodiment. 
         FIG. 9  is a sectional view schematically illustrating the vicinity of the coaxial waveguide provided in the plasma processing apparatus illustrated in  FIG. 8 . 
     
    
    
     DETAILED DESCRIPTION TO EXECUTE THE INVENTION 
     A plasma processing apparatus disclosed herein, in an exemplary embodiment, includes a processing container that defines a plasma processing space; a holder that is provided inside the processing container to hold a substrate to be processed; a gas supply unit that supplies gas into the plasma processing space; an antenna that radiates microwaves for generating plasma of the gas supplied into the plasma processing space, to the plasma processing space; a coaxial waveguide that supplies the microwaves to the antenna; a plurality of stubs that are inserted into the coaxial waveguide and regulate distribution of the microwaves radiated from the antenna according to an insertion amount; a measuring unit that measures density of the plasma generated in the plasma processing space by the microwaves radiated from the antenna or a parameter having a correlation with the density of the plasma along a circumferential direction of the substrate to be processed; and a controller that individually controls an insertion amount of each of the plurality of stubs used for regulating the distribution of the microwaves, based on the density of the plasma or the parameter. 
     Further, in the disclosed plasma processing apparatus, in an exemplary embodiment, the controller individually controls the insertion amount of each of the plurality of stubs so as to make the distribution of the density of the plasma or the distribution of the parameter become uniform distribution along the circumferential direction of the substrate to be processed. 
     Further, in the disclosed plasma processing apparatus, in an exemplary embodiment, the controller individually controls the insertion amount of each of the plurality of stubs so as to make the distribution of the density of the plasma or the distribution of the parameter become predeteimined ununiform distribution along the circumferential direction of the substrate to be processed. 
     Further, in the disclosed plasma processing apparatus, in an exemplary embodiment, the controller individually controls the insertion amount of each of the plurality of stubs so as to make the distribution of the density of the plasma or the distribution of the parameter become predetermined distribution obtained by reversing distribution of a film thickness, based on the distribution of the density of the plasma or the distribution of the parameter, and distribution of a film thickness on the substrate plasma-processed in the plasma processing space. 
     Further, in the disclosed plasma processing apparatus, in an exemplary embodiment, the parameter is at least one of a temperature of a side wall of the processing container, a temperature of the antenna, light emission intensity of the plasma processing space, and an object attached to the side wall of the processing container. 
     Further, in the disclosed plasma processing apparatus, in an exemplary embodiment, when a plurality of processes for plasma-processing the substrate to be processed in the plasma processing space are continuously performed, the measuring unit measures the density of the plasma or the parameter along the circumferential direction of the substrate to be processed at a timing when each of the plurality of processes is switched. 
     Further, in the disclosed plasma processing apparatus, in an exemplary embodiment, the coaxial waveguide includes an inner conductor and an outer conductor provided outside the inner conductor while having a gap from the inner conductor, the stubs are inserted into the gap, and a material of a portion inserted into the gap is a dielectric or a conductor. 
     Further, a plasma processing method disclosed herein, in an exemplary embodiment, performs a plasma processing in a plasma processing apparatus which includes: a processing container that defines a plasma processing space; a holder that is provided inside the processing container to hold a substrate to be processed; a gas supply unit that supplies gas into the plasma processing space; an antenna that radiates microwaves for generating plasma of the gas supplied into the plasma processing space, to the plasma processing space; a coaxial waveguide that supplies the microwaves to the antenna; a plurality of stubs that are inserted into the coaxial waveguide and regulate distribution of the microwaves radiated from the antenna according to an insertion amount; a measuring unit that measures density of the plasma generated in the plasma processing space by the microwaves radiated from the antenna or a parameter having a correlation with the density of the plasma along a circumferential direction of the substrate to be processed; and a controller that individually controls an insertion amount of each of the plurality of stubs used for regulating the distribution of the microwaves, based on the density of the plasma or the parameter. The plasma processing method includes: measuring density of plasma generated in the plasma processing space by the microwaves radiated from the antenna or a parameter having a correlation with the density of the plasma along a circumferential direction of the substrate to be processed; and individually controlling an insertion amount of each of the plurality of stubs used for regulating the distribution of the microwaves, based on the density of the plasma or the parameter. 
     Hereinafter, various exemplary embodiments will be described in detail with reference to the drawings. Further, in the respective drawings, identical or equivalent parts will be denoted by common reference numerals. 
       FIG. 1  is a sectional view schematically illustrating a principle part of a plasma processing apparatus according to an exemplary embodiment.  FIG. 2  is an enlarged sectional view illustrating the vicinity of a coaxial waveguide provided in the plasma processing apparatus illustrated in  FIG. 1 .  FIG. 3  is a view illustrating a slot antenna plate provided in the plasma processing apparatus illustrated in  FIG. 1  when viewed in the direction of arrow III in  FIG. 1 .  FIG. 4  is a sectional view illustrating the coaxial waveguide provided in the plasma processing apparatus illustrated in  FIG. 1  which is taken along IV-IV in  FIG. 2 . Further, the vertical direction in the paper of each of  FIGS. 1 and 2  will be regarded as the vertical direction of the apparatus. Further, in the specification of the present disclosure, the radial direction indicates the direction oriented from an inner conductor to an outer conductor which are included in a coaxial waveguide. 
     A plasma processing apparatus  11  illustrated in  FIGS. 1 and 2  includes a processing container  12 , a holding table  14 , a gas supply unit  13 , a microwave generator  15 , a dielectric plate  16 , an antenna  20 , and a coaxial waveguide  31 . 
     The processing container  12  is opened at the top side thereof, and defines a processing space S for performing a plasma processing on a target substrate W therein. The processing container  12  includes a bottom portion  21  positioned below the holding table  14 , and a side wall  22  extending upwardly from the outer periphery of the bottom portion  21 . The side wall  22  has a cylindrical shape. An exhaust hole  23  for exhausting gas is provided at the central side of the bottom portion  21  of the processing container  12  in the radial direction. The top side of the processing container  12  is opened, and the processing container  12  is configured to be sealed by a dielectric plate  16  disposed on the top side of the processing container  12  and an O-ring  24  as a seal member interposed between the dielectric plate  16  and the processing container  12 . The surface  25  of the bottom side of the dielectric plate  16  is flat. A material of the dielectric plate  16  is a dielectric. A specific material of the dielectric plate  16  is, for example, quartz or alumina. 
     The gas supply unit  13  supplies gas for plasma excitation and gas for plasma processing into the processing container  12 . The gas supply unit  13  is provided to be partially embedded in the side wall  22 , and supplies gas into the processing space S inside the processing container  12  from the outside of the processing container  12 . 
     The holding table  14  is disposed inside the processing container  12 , and holds the target substrate W. 
     The microwave generator  15  is disposed outside the processing container  12 , and generates microwaves for plasma excitation. Further, in an exemplary embodiment, the plasma processing apparatus  11  includes a waveguide  39  of which one end  38  is connected to the microwave generator  15 , and a mode converter  40  that converts a mode of microwaves. The waveguide  39  is provided to extend horizontally, specifically, in the left-and-right direction in the paper of  FIG. 1 . In addition, as the waveguide  39 , a waveguide having a circular or rectangular sectional surface is used. 
     The antenna  20  is provided on the top surface of the dielectric plate  16 , and radiates microwaves for plasma generation into the processing space S through the dielectric plate  16  based on the microwaves generated by the microwave generator  15 . The antenna  20  has a slot antenna plate  18  and a slow wave plate  19 . 
     The slot antenna plate  18  is a thin plate shaped member that is disposed above the dielectric plate  16  to radiate microwaves to the dielectric plate  16 . Each of the opposite surfaces of the slot antenna plate  18  in the plate thickness direction is flat. On the slot antenna plate  18 , as illustrated in  FIG. 3 , a plurality of slot holes  17  are provided to penetrate the slot antenna plate  18  in the plate thickness direction. The slot holes  17  are configured such that two rectangular openings constitute one pair and are arranged in a substantially T shape. The provided slot holes  17  are classified into an inner circumferential side slot hole group  26   a  that is arranged at the inner circumferential side, and an outer circumferential side slot hole group  26   b  that is arranged at the outer circumferential side. The inner circumferential side slot hole group  26   a  includes eight slot holes  17  provided within the range surrounded by a dashed line in  FIG. 3 . The outer circumferential side slot hole group  26   b  includes sixteen slot holes  17  provided within the range surrounded by alternate long and short dashed lines in  FIG. 3 . In the inner circumferential side slot hole group  26   a , the eight slot holes  17  are arranged annularly at equal intervals. In the outer circumferential side slot hole group  26   b , the sixteen slot holes  17  are arranged annularly at equal intervals. The slot antenna plate  18  has rotational symmetry based on the center  28  in the radial direction, and has the same shape, for example, even when the slot antenna plate  18  is rotated by 45° around the center  28 . 
     The slow wave plate  19  is disposed above the slot antenna plate  18 , and propagates microwaves in the radial direction. At the center of the slow wave plate  19 , an opening is provided to dispose therein an inner conductor  32  provided in the coaxial waveguide  31  to be described later. The end of the inner diameter side of the slow wave plate  19  that forms the periphery of the opening protrudes in the plate thickness direction. That is, the slow wave plate  19  has a ring shaped slow wave plate protrusion  27  that protrudes from the end of the inner diameter side in the plate thickness direction. The slow wave plate  19  is attached such that the slow wave plate protrusion  27  faces upward. A material of the slow wave plate  19  is a dielectric. A specific material of the slow wave plate  19  is, for example, quartz or alumina. The wavelength of the microwaves propagated inside the slow wave plate  19  becomes shorter than the wavelength of microwaves propagated in the air. 
     All the dielectric plate  16 , the slot antenna plate  18 , and the slow wave plate  19  have a disc shape. When manufacturing the plasma processing apparatus  11 , the center of the dielectric plate  16  in the radial direction, the center of the slot antenna plate  18  in the radial direction, and the center of the slow wave plate  19  in the radial direction are made coincide with each other. Accordingly, in the microwaves propagated from the central side toward the outer diameter side, the propagation degree of the microwaves in the circumferential direction is kept the same so as to ensure the uniformity of plasma, in the circumferential direction, that is to be generated below the dielectric plate  16 . In addition, here, the center  28  of the slot antenna plate  18  in the radial direction is taken as a reference. 
     The coaxial waveguide  31  is a waveguide that supplies microwaves to the antenna  20 . The coaxial waveguide  31  includes the inner conductor  32  and the outer conductor  33 . The inner conductor  32  is formed in a substantially round rod shape. One end  35  of the inner conductor  32  is connected to the center  28  of the slot antenna plate  18 . The outer conductor  33  is provided at the outer diameter side of the inner conductor  32  while having a gap  34  from the inner conductor  32  in the radial direction. The outer conductor  33  is formed in a substantially cylindrical shape. That is, the coaxial waveguide  31  is configured by combining the inner conductor  32  and the outer conductor  33  such that the outer circumferential surface  36  of the inner conductor  32  and the inner circumferential surface  37  of the outer conductor  33  face each other. The coaxial waveguide  31  is provided to extend in the vertical direction in the paper of  FIG. 1 . The inner conductor  32  and the outer conductor  33  are manufactured as separate members. Then, the center of the inner conductor  32  in the radial direction and the center of the outer conductor  33  in the radial direction are combined to coincide with each other. 
     The microwaves generated by the microwave generator  15  are propagated to the antenna  20  through the waveguide  39  and the coaxial waveguide  31 . As the frequency of the microwaves generated by the microwave generator  15 , for example, 2.45 GHz is selected. 
     For example, microwaves of a TE mode generated by the microwave generator  15  are propagated inside the waveguide  39  in the paper left direction indicated by arrow A 1  in  FIG. 1 , and converted into a TEM mode by the mode converter  40 . Then, the microwaves that have been converted into the TEM mode are propagated inside the coaxial waveguide  31  in the paper downward direction indicated by arrow A 2  in  FIG. 1 . Specifically, the microwaves are propagated in the space between the inner conductor  32  and the outer conductor  33  where the gap  34  is formed, and the space between the inner conductor  32  and a cooling plate protrusion  47 . The microwaves that have been propagated through the coaxial waveguide  31  are propagated inside the slow wave plate  19  in the radial direction, and radiated to the dielectric plate  16  from the plurality of slot holes  17  provided on the slot antenna plate  18 . The microwaves that have penetrated the dielectric plate  16  generate an electric field directly under the dielectric plate  16 , thereby generating plasma inside the processing container  12 . 
     Further, the plasma processing apparatus  11  includes a dielectric plate pressing ring  41  that is disposed above the upper end of the opening side of the side wall  22  to press the dielectric plate  16  from the upper side, an antenna press  42  that is disposed above the dielectric plate pressing ring  41  to press, for example, the slot antenna plate  18  from the upper side, a cooling plate  43  that is disposed above the slow wave plate  19  to cool, for example, the slow wave plate  19 , an electromagnetic shielding elastic member  44  that is interposed between the antenna press  42  and the cooling plate  43  to shield an electromagnetic field inside and outside the processing container  12 , an outer periphery fixing ring  45  that fixes the outer peripheral portion of the slot antenna plate  18 , and a center fixing plate  46  that fixes the center of the slot antenna plate  18 . 
     At the center of the cooling plate  43 , an opening is provided to dispose therein the coaxial waveguide  31  as illustrated in  FIG. 2 . The end of the inner diameter side of the cooling plate  43  that forms the periphery of the opening protrudes in the plate thickness direction. That is, the cooling plate  43  has the ring shaped cooling plate protrusion  47  that protrudes from the end of the inner diameter side toward the plate thickness direction. The cooling plate  43  is attached such that the cooling plate protrusion  47  faces upward. 
     The cylindrical outer conductor  33  is disposed above the cooling plate protrusion  47 . The upper end of the cooling plate protrusion  47  and the lower end of the outer conductor  33  are in contact with each other. In this case, the inner circumferential surface  37  of the outer conductor  33  and the inner circumferential surface  50  of the cooling plate protrusion  47  are continuous to each other, such that the distance in the radial direction between the outer circumferential surface  36  of the inner conductor  32  and the inner circumferential surface  37  of the outer conductor  33 , and the distance in the radial direction between the outer circumferential surface  36  of the inner conductor  32  and the inner circumferential surface  50  of the cooling plate protrusion  47  become the same. Further, the inner circumferential surface  37  of the outer conductor  33  and the inner circumferential surface  50  of the cooling plate protrusion  47  are continuous to each other, such that the cooling plate protrusion  47  is configured as a part of the coaxial waveguide  31 . In addition, the gap  34  formed between the inner conductor  32  and the outer conductor  33  is positioned above the above-described slow wave plate  27 . 
     In addition, a slow wave plate positioning unit  48  is provided on the outer peripheral portion of the cooling plate  43  to protrude in a ring shape toward the side of the dielectric plate  16 . The slow wave plate  19  is positioned in the radial direction by the slow wave plate positioning unit  48 . The outer periphery fixing ring  45  fixes the slot antenna plate  18  at the position in the radial direction where the slow wave plate positioning unit  48  is provided. 
     In addition, an accommodating recess  49  is provided at the center of the top surface of the dielectric plate  16  in the radial direction to be recessed by reducing the plate thickness from the top surface of the dielectric plate  16  so as to accommodate the center fixing plate  46 . 
     Further, as illustrated in  FIGS. 2 and 4 , the plasma processing apparatus  11  includes a plurality of stub members  51  that are extendable from the side of the outer conductor  33  toward the side of the inner conductor  32 , as a changing unit that changes the distance in the radial direction between a part of the outer circumferential surface  36  of the inner conductor  32  and a facing portion that faces the part of the outer circumferential surface  36  of the inner conductor  32  in the radial direction. Further, in the present exemplary embodiment, the facing portion that faces the part of the outer circumferential surface  36  of the inner conductor  32  in the radial direction corresponds to the cooling plate protrusion  47 . 
     Each stub member  51  includes a rod shaped portion  52  that is supported at the side of the outer conductor  33  to extend in the radial direction, and a screw portion  53  as a movement amount regulation member that regulates a movement amount of the rod shaped portion  52  in the radial direction. The screw portion  53  is provided at the end of the outer diameter side of the rod shaped portion  52 . 
     The stub member  51  is inserted into the cooling plate protrusion  47 . Specifically, the cooling plate protrusion  47  is provided with a screw hole  54  that extends straightly in the radial direction to penetrate the cooling plate protrusion  47 , and the screw hole  54  and the screw portion  53  are screw-connected to each other such that the stub member  51  is inserted into the cooling plate protrusion  47 . That is, the stub member  51  is supported at the side of the outer conductor  33  by the screw portion  53  screw-connected to the screw hole  54  provided in the cooling plate protrusion  47 . 
     By rotating the screw portion  53 , the entire stub member  51  including the rod shaped portion  52  may be moved in the radial direction. In  FIG. 2 , the stub member  51  is movable in the left-and-right direction of the paper. In addition, the movement amount is regulated by a rotation amount of the screw portion  53 . 
     A plurality of stub members  51  (six in  FIG. 4 ) are provided in the cooling plate protrusion  47  around the inner conductor  32  to be substantially equally arranged in the circumferential direction. For example, when six stub members  51  are provided, the six stub members  51  are arranged to be spaced apart from each other such that an angle between adjacent stub members in the circumferential direction is 60°. 
     Each of the plurality of stub members  51  may independently move in the radial direction. The movement of each of the stub members  51  is performed using a driving mechanism (not illustrated). By rotating the screw portion  53  of each of the stub members  51 , it is possible to individually control the insertion amount of each of the stub members  51  (the rod shaped portions  52 ) into the gap  34  provided between the outer circumferential surface  36  of the inner conductor  32  and the inner circumferential surface  50  of the cooling plate protrusion  47 . The plurality of stub members  51  regulate the distribution of the microwaves radiated from the antenna  20  according to the individually controlled insertion amount. Further, the control of the insertion amount of each of the stub members  51  is performed by a controller  70  to be described later. 
     A material of at least the portion of each stub member  51  that is inserted into the gap  34  is a dielectric or a conductor. The dielectric is, for example, quartz or alumina. The conductor is, for example, metal. 
       FIG. 5  is a view illustrating exemplary experimental results for a relationship of the distribution of the microwaves with the insertion amount and the material of the stub member in an exemplary embodiment. In  FIG. 5 , “Center Stub” represents the respective experimental results. In the experimental results, “Dummy” represents an experimental result for a case where no stub member  51  is provided. Further, “Ceramic-1-5” represents experimental results for a case where the material of the stub member  51  is a dielectric, the distance between the tip end of the rod shaped portion  52  of the stub member  51  and the inner conductor  32  (hereinafter, referred to as a “stub gap”) is 1 mm, and an insertion direction of the stub member  51  with respect to a reference direction is the direction of 5 o&#39;clock. Further, “Metal-3-5” represents experimental results for a case where the material of the stub member  51  is a conductor, the stub gap is 3 mm, and the insertion direction of the stub member  51  with respect to the reference direction is the direction of 5 o&#39;clock. Further, “Metal-2-5” represents experimental results for a case where the material of the stub member  51  is a conductor, the stub gap is 2 mm, and the insertion direction of the stub member  51  with respect to the reference direction is the direction of 5 o&#39;clock. 
     In addition, in  FIG. 5 , “Mapping of thickness” represents distribution of a film thickness on the target substrate W, as an experimental result. Further, in  FIG. 5 , “Mapping of Difference (Comparing with Dummy)” represents distribution of a film thickness difference based on the film thickness on the target substrate W when no stub member  51  is provided. Further, in  FIG. 5 , “Max. Difference [A]” represents a maximum value of the film thickness difference, and “Min. Difference [A]” represents a minimum value of the film thickness difference. Further, the example of  FIG. 5  represents that, as an absolute value of the maximum value of the film thickness difference and an absolute value of the minimum value of the film thickness difference are large, the regulation range of the distribution of the microwaves (the distribution of the electric field intensity) radiated from the antenna  20  is large. 
     As is clear from the experimental results of  FIG. 5 , the distribution of the microwaves radiated from the antenna  20  may be regulated by changing the stub gap. That is, it is found that the distribution of the microwaves radiated from the antenna  20  may be regulated by controlling the insertion amount of the stub member  51 . As a result of further conducting intensive study, the inventors have found that, as the stub gap is small, the regulation range of the distribution of the microwaves radiated from the antenna  20  is large. Further, from the experimental results of  FIG. 5 , it is found that, when the material of the stub member  51  is a conductor, the regulation range of the distribution of the microwaves radiated from the antenna  20  is large, as compared with the case where the material of the stub member  51  is a dielectric. 
     In addition, as illustrated in  FIG. 1 , the plasma processing apparatus  11  further includes a measuring unit  60 . The measuring unit  60  measures the density of plasma (hereinafter, referred to as “plasma density”) generated in the processing space S by the microwaves radiated from the antenna  20  along the circumferential direction of the target substrate W. For example, the measuring unit  60  is provided at each of a plurality of positions on the inner circumferential surface of the side wall  22  of the processing container  12  along the circumferential direction of the target substrate W, and measures the plasma density from each of the positions. 
     When a plurality of processes for plasma-processing the target substrate W in the processing space S are continuously performed, the measuring unit  60  measures the plasma density along the circumferential direction of the target substrate W at a timing when each of the plurality of processes is switched. 
     Further, as illustrated in  FIG. 1 , the plasma processing apparatus  11  includes the controller  70  that controls each component of the plasma processing apparatus  11 . The controller  70  may be a computer provided with a control device such as, for example, a central processing unit (CPU), a storage device such as, for example, a memory, an input/output device and others. The controller  70  controls each component of the plasma processing apparatus  11  when the CPU operates according to a control program stored in the memory. 
     For example, the controller  70  measures the plasma density along the circumferential direction of the target substrate W by using the measuring unit  60 , and individually controls the insertion amount of each of the plurality of stub members  51  that is used for regulating the distribution of the microwaves, based on the measured plasma density. Hereinafter, examples of a stub insertion amount control process by the controller  70  will be described. 
     First Example 
     First, a first example of the stub insertion amount control process will be described. In the first example, the controller  70  individually controls the insertion amount of each of the plurality of stub members  51  so as to make the distribution of the plasma density become uniform distribution along the circumferential direction of the target substrate W. For example, the controller  70  individually controls the insertion amount of each of the plurality of stub members  51 , while monitoring the plasma density measured by the measuring unit  60 , until a measurement value of the plasma density is equalized to a predetermined reference value. Further, for example, while monitoring the plasma density measured by the measuring unit  60 , the controller  70  calculates an average value of measurement values of the plasma density, and individually controls the insertion amount of each of the plurality of stub members  51  until the measurement values of the plasma density reach the calculated average value. 
     As described above, according to the first example, since the insertion amount of each of the plurality of stub members  51  is individually controlled so as to make the distribution of the plasma density become uniform distribution along the circumferential direction of the target substrate W, a uniform plasma processing may be performed on the to-be-processed surface of the target substrate W. 
     Second Example 
     Subsequently, a second example of the stub insertion amount control process will be described. In the second example, the controller  70  individually controls the insertion amount of each of the plurality of stub members  51  so as to make the distribution of the plasma density become predetermined ununiform distribution along the circumferential direction of the target substrate W. For example, the controller  70  individually controls the insertion amount of each of the plurality of stub members  51  so as to make the distribution of the plasma density become predetermined distribution obtained by reversing distribution of a film thickness, based on the distribution of the plasma density measured by the measuring unit  60  and the distribution of the film thickness on the target substrate W plasma-processed in the processing space S. 
     As described above, according to the second example, since the insertion amount of each of the plurality of stub members  51  is individually controlled so as to make the distribution of the plasma density become predetermined ununiform distribution along the circumferential direction of the target substrate W, a desired plasma processing may be performed on the to-be-processed surface of the target substrate W. 
     Further, according to the second example, since the insertion amount of each of the plurality of stub members  51  is individually controlled so as to make the distribution of the plasma density become predetermined distribution obtained by reversing the distribution of the film thickness, the microwaves from the antenna  20  may be intensively radiated to an area of the to-be-processed surface of the target substrate W where the film thickness is smaller than a predetermined value. 
     Further, in the first and second examples, the example where the controller  70  continuously controls the insertion amount of each of the plurality of stub members  51  is described. However, the present disclosure is not limited thereto. For example, when a plurality of processes for plasma-processing the target substrate W in the processing space S are continuously performed, the controller  70  may reset the insertion amount of each of the stub members  51  at a timing when each of the plurality of processes is switched. 
     Next, descriptions will be made on an exemplary flow of a plasma processing method using the plasma processing apparatus  11  according to an exemplary embodiment.  FIG. 6  is a flow chart illustrating an exemplary flow of the plasma processing method using the plasma processing apparatus according to an exemplary embodiment. 
     As illustrated in  FIG. 6 , the controller  70  of the plasma processing apparatus  11  measures the plasma density along the circumferential direction of the target substrate W by using the measuring unit  60  (step S 101 ). Subsequently, based on the measured plasma density, the controller  70  individually controls the insertion amount of each of the plurality of stub members  51  that is used for regulating the distribution of the microwaves (step S 102 ). 
     As described above, in the plasma processing apparatus  11  according to an exemplary embodiment, the plasma density is measured along the circumferential direction of the target substrate W, and based on the measured plasma density, the insertion amount of each of the plurality of stub members  51  that is used for regulating the distribution of the microwaves is individually controlled. As a result, according to the exemplary embodiment, the distribution of the microwaves may be automatically regulated according to the distribution of the plasma density. 
     Further, in the above-described exemplary embodiment, descriptions have been made on the example where the plasma processing apparatus  11  individually controls the insertion amount of each of the plurality of stub members  51  that is used for regulating the distribution of the microwaves, based on the plasma density. However, the present disclosure is not limited thereto. For example, the plasma processing apparatus  11  may individually control the insertion amount of each of the plurality of stub members  51  based on a parameter having a correlation with the plasma density, instead of the plasma density. In this case, the measuring unit  60  of the plasma processing apparatus  11  measures the parameter having a correlation with the plasma density, instead of the plasma density. The parameter having a correlation with the plasma density is at least one of a temperature of the side wall  22  of the processing container  12 , a temperature of the antenna  20 , light emission intensity of the processing space S, and a thickness of an object attached to the side wall  22  of the processing container  12 . Then, the controller  70  individually controls the insertion amount of each of the plurality of stub members  51  based on the parameter having a correlation with the plasma density. Accordingly, the distribution of the microwaves may be automatically regulated according to the distribution of the parameter having a correlation of the plasma density. 
     Further, in the above-described exemplary embodiment, the example where the extending direction of the stub members is the horizontal direction, that is, the stub members extend straightly in the radial direction has been described. However, as illustrated in  FIG. 7 , the extending direction of the stub members may be an obliquely downward direction.  FIG. 7  is an enlarged sectional view schematically illustrating the vicinity of the coaxial waveguide of the plasma processing apparatus in this case, and corresponds to  FIG. 2 . Referring to  FIG. 7 , on a cooling plate protrusion  83  of a cooling plate  82  provided in a plasma processing apparatus  81  according to another exemplary embodiment, a plurality of screw holes  84  are provided to penetrate a part of the cooling plate protrusion  83  so as to extend obliquely downward when the inner diameter side is regarded as the downward side. Then, stub members  85  are attached to the respective screw holes  84  to extend obliquely downward. With this configuration, the point at which each stub member  85  acts, specifically, the tip end of each stub member  85  may be made approach the slow wave plate  19 . In order to suppress the electromagnetic field distribution from being biased in the circumferential direction, it is required that the electromagnetic field distribution be regulated at a position as close as possible to the slow wave plate  19 . Accordingly, by providing the stub members  85  to extend obliquely downward, the regulation of the electromagnetic field distribution in the circumferential direction may be more effectively performed. 
     Further, in the above-described exemplary embodiment, the stub members are supported in the cooling plate protrusion. However, the present disclosure is not limited thereto, and the stub members may be configured to be supported in the outer conductor. Specifically, a screw hole is provided on the outer conductor to penetrate the outer conductor in the radial direction, and a stub member is attached by screw-connecting the screw hole and the screw portion to each other. In this case, the facing portion that faces a part of the outer circumferential surface of the inner conductor becomes a part of the inner circumferential surface of the outer conductor. 
     Further, in the above-described exemplary embodiment, the stub members are arranged at equal intervals to have the rotational symmetry. However, the stub members may not be arranged at equal intervals as long as the stub members have the rotational symmetry. 
     Further, in the above-described exemplary embodiment, total six stub members are provided in the circumferential direction. However, the number of the stub members is not limited thereto, and an arbitrary number of stub members, for example, four or eight stub members may be provided according to necessity. 
     Further, in the above-described exemplary embodiment, the six stub members are provided at one position in the extending direction of the coaxial waveguide, that is, at the same position in the vertical direction. However, the present disclosure is not limited thereto, and the plurality of stub members may be provided at an interval in the extending direction of the coaxial waveguide. When the stub members are provided as an electromagnetic field regulation unit, a part of the microwaves is reflected upward by the above-described rod shaped portion. This may cause a power loss corresponding to reflectivity represented with a value obtained by dividing the electric field intensity of reflected waves by the electric field intensity of incident waves, and as a result of the influence of the reflected waves, the regulation of the electromagnetic field may become complicated, and it may be difficult to make the electromagnetic field distribution uniform. Thus, by providing the plurality of stub members at an interval in the extending direction of the coaxial waveguide, the influence of the reflected waves caused by the stub members may be greatly reduced, and the regulation of the electromagnetic field is facilitated, so that the electromagnetic field distribution may be made uniform in the circumferential direction. 
     This will be described in detail.  FIG. 8  is a sectional view illustrating a part of a plasma processing apparatus in the case described above, and corresponds to  FIG. 2 . Referring to  FIG. 8 , in a plasma processing apparatus  91  according to still another exemplary embodiment of the present disclosure, two stub member groups  92   a  and  92   b  are provided in the vertical direction in  FIG. 8 . The first stub member group  92   a  provided at the lower side as an electromagnetic field regulation mechanism is provided in the cooling plate protrusion  47  of the cooling plate  43 , as provided in the plasma processing apparatus  11  illustrated in  FIG. 1 . Each stub member of the first stub member group  92   a  has the same configuration as that of each stub member provided in the plasma processing apparatus illustrated in  FIG. 1 . That is, each stub member provided in the first stub member group  92   a  is extendable in the radial direction, and is configured to include a screw portion provided to be screw-connected to the screw hole provided in the cooling plate protrusion  47  to extend straightly in the radial direction, and a rod shaped portion. Meanwhile, the second stub member group  92   b  provided at the upper side as a reflected wave compensation mechanism is provided in the outer conductor  33  of the coaxial waveguide  31 . Each stub member provided in the second stub member group  92   b  also has the same configuration as that of each stub member provided in the first stub member group  92   a . The stub member is extendable in the radial direction and is configured to include a screw portion provided to be screw-connected to a screw hole provided in the outer conductor  33  to extend straightly in the radial direction, and a rod shaped portion. 
     In the first stub member group  92   a  of the two stub member groups, six stub members are substantially equally arranged in the circumferential direction as in the case illustrated in  FIG. 1 . In the second stub member group  92   b  as well, six stub members are substantially equally arranged in the circumferential direction. In addition, the two stub member groups mentioned herein indicate that stub member groups each including the six stub members provided at intervals in the circumferential direction are provided at an interval in the vertical direction. 
     As for the circumferential position where each stub member of the first and second stub member groups  92   a  and  92   b  is provided, each stub member of the first stub member group  92   a  and each stub member of the second stub member group  92   b  are provided at the same position. That is, when viewed from the upper side in  FIG. 8 , the stub members appear as illustrated in  FIG. 4 , and each stub member of the first stub member group  92   a  and each stub member of the second stub member group  92   b  appear to overlap with each other. In addition, the interval in the vertical direction between the first stub member group  92   a  and the second stub member group  92   b , that is, the distance L 4  between the first stub member group  92   a  and the second stub member group  92   b  is ¼ of the in-waveguide wavelength of the coaxial waveguide  31 . The distance L 4  between the first stub member group  92   a  and the second stub member group  92   b  is the distance between the axial direction of the first stub member group  92   a  indicated by an alternate long and short dashed line in  FIG. 8 , that is, the central position of the first stub member group  92   a  in the vertical direction and the central position of the second stub member group  92   b  in the vertical direction. Further, the microwave reflectivity of each stub member provided in the first stub member group  92   a  and the microwave reflectivity of each stub member provided in the second stub member group  92   b  are the same. A material of each stub member provided in the first and second stub member groups  92   a  and  92   b  is, for example, alumina or metal. 
     With this configuration, the electromagnetic field distribution may be more effectively made uniform by the first stub member group  92   a  functioning as an electromagnetic field regulation mechanism and the second stub member group  92   b  functioning as a reflected wave compensation mechanism. In addition, in  FIGS. 8 and 9 , the same configurations as those of the plasma processing apparatus  11  illustrated in  FIGS. 1 and 2  will be denoted by the same reference numerals as used in  FIGS. 1 and 2 , and descriptions thereof will be omitted. 
     Here, the principle of the plasma processing apparatus  91  illustrated in  FIG. 8  will be described.  FIG. 9  is an enlarged sectional view schematically illustrating the vicinity of the coaxial waveguide  31  provided in the plasma processing apparatus  91  illustrated in  FIG. 8 . From the viewpoint of facilitating the understanding,  FIG. 9  schematically illustrates, for example, the configuration of the first and second stub member groups  92   a  and  92   b.    
     Referring to  FIGS. 8 and 9 , an incident wave C 1  that is incident downward from the upper side reaches a stub member provided in the first stub member group  92   a  as an electromagnetic field regulation mechanism, and then, a part of the incident wave C 1  is reflected upward as a reflected wave C 2 . Further, an incident wave D 1  reaches a stub member provided in the second stub member group  92   b  as a reflected wave compensating mechanism, and then, a part thereof is reflected upward as a reflected wave D 2 . Here, the reflected wave C 2  that has been delayed in time by the reciprocating length of the distance L 4  between the first stub member group  92   a  and the second stub member group  92   b  interferes with the reflected wave D 2 . In this case, since the distance L 4  between the first stub member group  92   a  and the second stub member group  92   b  is ¼ of the in-waveguide wavelength of the coaxial waveguide  31 , the reciprocating length of the distance between the first stub member group  92   a  and the second stub member group  92   b  becomes ½ of the in-waveguide wavelength of the coaxial waveguide  31 . Then, the phases of the respective reflected waves C 2  and D 2  are deviated from each other by 180 degrees. Here, since the reflectivity of the stub member provided in the first stub member group  92   a  and the reflectivity of the stub member provided in the second stub member group  92   b  are the same, the reflected waves C 2  and D 2  are thoroughly set off so that the electromagnetic field regulation in which the influence of the reflected waves is greatly reduced may be implemented. Accordingly, the electromagnetic field may be more effectively and uniformly supplied. 
     Here, the reflectivity of the stub member provided in the first stub member group  92   a  and the reflectivity of the stub member provided in the second stub member group  92   b  are set to be the same. However, according to a specific exemplary embodiment, each reflectivity may be set to 0.1 to 0.2, and the total of the reflectivities may be set to 0.03 or less. However, strictly speaking, the incident wave C 1  is partially reflected by the stub member provided in the second stub member group  92   b  and becomes small. Thus, in consideration of this influence, the reflectivity of the stub member provided in the first stub member group  92   a  and the reflectivity of the stub member provided in the second stub member group  92   b  may be mutually exchanged. 
     Further, in the exemplary embodiment illustrated in  FIG. 8 , the interval in the vertical direction between the first stub member group and the second stub member group is set to ¼ of the in-waveguide wavelength of the coaxial waveguide. However, the present disclosure is not limited thereto, and the interval may be odd number times ¼ of the in-waveguide wavelength of the coaxial waveguide. Accordingly, the phases of the respective reflected waves may be made deviated from each other by 180 degrees, and thus, the above-described effect may be achieved. Further, the influence of the reflected wave may be reduced even when the interval is somewhat deviated from the odd number times ¼ of the in-guide wavelength of the coaxial waveguide. 
     In the above-described exemplary embodiment illustrated in  FIG. 8 , the circumferential position of each stub member provided in the first stub member group and the circumferential position of each stub member provided in the second stub member group are set to be the same. However, the present disclosure is not limited thereto, and the positions may be slightly deviated from each other in the circumferential direction. Further, the number of the stub members provided in the first stub member group and the number of the stub members provided in the second stub member group may be different from each other. 
     In addition, in the above-described exemplary embodiment illustrated in  FIG. 8 , each stub member provided in the first and second stub member groups is provided to extend straightly in the radial direction. However, the present disclosure is not limited thereto, and the extending direction of each stub member may be the obliquely downward direction. In this case, the extending direction of each stub member provided in one of the first and second stub member groups may be the obliquely downward direction, or the extending direction of each stub member provided in both the first and second stub member groups may be the obliquely downward direction. 
     In addition, in the above-described exemplary embodiment, the stub member is used as a changing unit. However, the present disclosure is not limited thereto, and the changing unit may have another configuration. That is, for example, a protrusion may be provided on the inner circumferential surface of the outer conductor to extend in the radial direction and regulate the extending distance, and this protrusion may be used as the changing unit. Alternatively, the changing unit may be configured such that, by recessing the outer diameter surface of the outer conductor, the distance between the inner circumferential surface of the outer conductor and the outer circumferential surface of the inner conductor is changed according to the recess. 
     In addition, in the above-described exemplary embodiment, the changing unit is provided at the side of the outer conductor. However, the present disclosure is not limited thereto, and the changing unit may be provided at the side of the inner conductor. Specifically, the changing unit may be configured to extend from the outer circumferential surface of the inner conductor toward the outer diameter side, that is, toward the direction in which the gap is formed, and regulate the extending distance. 
     Although the exemplary embodiments of the present disclosure have been described, the present disclosure is not limited thereto. Various modifications or changes may be made to the illustrated exemplary embodiments within the scope identical or equivalent to that of the present disclosure. 
     DESCRIPTION OF SYMBOL 
     
         
         
           
               11 ,  81 ,  91 : plasma processing apparatus 
               12 : processing container 
               13 : gas supply unit 
               14 : holding table 
               15 : microwave generator 
               16 : dielectric plate 
               17 : slot holes 
               18 : slot antenna plate 
               19 : slow wave plate 
               20 : antenna 
               21 : bottom portion 
               22 : side wall 
               23 : exhaust hole 
               24 : O-ring 
               25 : surface 
               26   a : inner circumferential side slot hole group 
               26   b : outer circumferential side slot hole group 
               27 : slow wave protrusion 
               28 : center 
               31 : coaxial waveguide 
               32 : inner conductor 
               33 : outer conductor 
               34 : gap 
               35 ,  38 : end 
               36 : outer circumferential surface 
               37 ,  50 : inner circumferential surface 
               39 : waveguide 
               40 : mode converter 
               41 : dielectric plate pressing ring 
               42 : antenna press 
               43 ,  82 : cooling plate 
               44 : electromagnetic shielding elastic member 
               45 : outer periphery fixing ring 
               46 : center fixing plate 
               47 ,  83 : cooling plate protrusion 
               48 : slow wave plate positioning unit 
               49 : accommodating recess 
               51 ,  85 : stub member 
               52 : rod shaped portion 
               53 : screw portion 
               54 ,  84 : screw hole 
               60 : measuring unit 
               70 : controller 
               92   a : first stub member group 
               92   b : second stub member group